Laminates of films and methods and apparatus for their manufacture

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Laminates of filns and methods and apparatus for their manufacture

Ole-Bendt Rasmussen C. 148978 WO 02/102592 PCT/EP02/07264

Laminates of Films and Methods and Apparatus for their

Manufacture

The present invention relates to a flexible laminateof films from thermoplastic polymer material for 5 applications in which relatively high yield strength andultimate tensile strength is required, and a method andapparatus for its manufacture.

Examples of such applications are: tarpaulins,pondliners, substitute of geotextiles, weather protective 10 laminates, greenhouse film, industrial bags, carrier bagsand self-standing pouches.

For economical reasons there is an increasing need toreduce the thickness or square metre weight of flexiblefilm made from thermoplastic polymer material. The limits 15 are partly set by the required strength properties, andpartly by the required self supporting capability, i.e.stiffness with respect to banding. These needs.have mainlybeen met by selected developments of the thermoplasticpolymer compositions and as far as the strength is 20 concerned also by biaxial orientation, or by cross-lamination of films each of which exhibits a generallymonaxial or unbalanced biaxial orientation.

From strength point of view essential savings can beachieved by such orientation and/or cross-lamination 25 processes.

Thus as an example an industrial bag made fromextruded polyethylene film of the best suited grades anddestined for packing of 25 kg polyethylene granules mustgenerally have a thickness of 0.12-0.15mm in order to 30 satisfy the normal strength requirements, while thisthickness can be brought down to about 0.07mm by use ofoptimized oriented and cross-laminated film from polyethylene. However, when this cross-laminate is made inthe known manner, few available types of machines for 3 5 manufacturing bags from film, and few available types ofmachines for filling the bags, can work adequately withfilm which is so thin and flimsy. WO 02/102592 PCT/EP02/07264 2 A cross-laminate which, besides the improved strengthproperties obtained by the orientation and cross-laminationalso by virtue of its geometrical structure showssignificant improvements in this respect, is described in 5 the inventor's earlier Specification EP-A-0624126.

This is a cross-laminate of a slightly wavedconfiguration in which the material of the curved crests onone or both sides of the laminate is thicker thanelsewhere, the material between these thicker curved crests 10 being generally straightened out. (See Figs. 1 and 2 ofsaid patent publications.) The structure is obtained bystretching between several sets of grooved rollers underspecial conditions. This stretching also impartstransverse orientation. The disclosed wavelengths of the 15 final products are between 2.2 and 3.1mm.

Cross-laminates according to the said patent have been produced industrially since 1995 for manufacture ofindustrial bags from combinations of high molecular weighthigh density polyethylene (HMWHDPE) and linear low density 20 polyethylene (LLDPE) with film weight about 90 gm'2, and theslightly waved shape in combination with the thickenedcrests imparts a stiffness in one direction of the filmwhich has proven to be very important for the performanceof the bag machines with such relatively thin film. 25 However, the film is not adequate for work with the 70 gm'2gauge which satisfies the strength requirements.

Furthermore the corrugated character of the filmsurface makes a particularly fine print (as often required)impossible and also to some extent reduces the friction 3 0 between filled bags in a stack, when the layers of thisstack are built up with the bags in crisscrossingarrangement as usually done. *

As another example an agricultural tarpaulin (e.g. forprotection of crops) made from a 70 gm'2 cross-laminate of > 35 oriented polyethylene films would be a fully adequatesubstitute of a 10 0 gm"2 tarpaulin made from extrusion-coated woven tape, if only objective criteria were applied. WO 02/102592 PCT/EP02/07264 3

However, in actual fact the average customer toagricultural tarpaulins makes his choice to a great extenton the basis of the "handle" and the appearance, and willreject the 70 gm*2 tarpaulin due to its flimsiness, judging 5 that it lacks substance.

The stiffness can of course always be increased by suitable incorporation of a filler, (and the presentinvention includes that as an additional option) but thiswill always more or less be at the expense of puncture and 10 tear propagation resistance, especially under impactactions .

Object of the present invention is to add a "feel ofsubstance" and improve stiffness in laminates of films atleast in one direction, without sacrificing the laminate 1s 15 character of feeling and looking like a generally two-dimensional structure, furthermore without essentiallyharming the puncture and tear propagation resistance, andwhen desired also providing a good printability at least onone side of the laminate. 20 The basic idea behind the present invention is to apply the corrugated paperboard principle to laminates ofthermoplastic films, but in such a way that the flutestructure is made extraordinarily fine ("minifluted") , soas to obtain a laminate which, in spite of the structurally 25 increased stiffness (at least in one direction), can stillsatisfy the above-mentioned conditions.

In itself the application of the corrugated paperboardprinciple to the thermoplastic film is not new, but thefinest flute structure which has been disclosed in patent 30 literature, namely in US-A-4132581 col. 6, In. 66, is 50+/-3 flutes per foot corresponding to a wavelength of about6.0mm. It must also strongly be doubted that a wavelengthlower than this can be achieved by the method disclosed inthe said patent, in which the first bonding process takes 35 place under use of a row of many sealer bars supported andtransported by a belt. WO 02/102592 PCT/EP02/07264 4

The sealer bars are transverse to the direction ofmovement (the machine direction) so the fluting alsobecomes perpendicular to this direction.

The use of the method of the said US patent is stated5 to be manufacture of board material, and the thickness of - the fluted ply is indicated to be about 0.004-0.025 inches(0.10-0.625mm). In the example it is 0.018 inches(0.45mm). Other patents dealing with the use of thecorrugated paperboard principle to thermoplastic film for 10 the making of panels or boards are US-A-3682736, US-A-3833440, US-A-3837973, EP-A-0325780 and WO-A-94/05498.

Japanese Patent Application Hei 02-052732 discloseslaminates consisting of a corrugated thermoplastic filmbonded to a flat thermoplastic film, which on its other 15 side is bonded to paper. (The paper and flat sheet arefirst joined and then the corrugated film is added.) Theflutes, which also in this case are perpendicular to themachine direction are pressed flat and adhesively closed atintervals so that a large number of airtight vesicles are 20 formed. The stated use of this product is for cushionmaterial, sound insulating material, heat- and moisture-insulating material and wall decorative material. Thethickness of the corrugated sheet and flat sheet are notindicated, neither are the wavelength of the fluting and 25 the length of the vesicles, but it is mentioned that thedimensions can be selected depending on the use of thelaminate. However, it must be understood as implied thatthe wavelength in any case will be no lower than the lowestmentioned in the above-mentioned US-A-4132581 (i.e. about 3 0 6mm) . One reason for judging this is that this would not be advantageous for the mentioned purposes, except fordecoration, while another reason is that the disclosed *'«apparatus would not be able to work with a lower wavelength(i.e. a lower pitch of the gear rollers) except for making 35 an extremely shallow and practically useless fluting. Thisis due to the fact that thermoplastic film is resilient andnot permanently formable at ambient temperature which as WO 02/102592 PCT/EPO2/07264 5 implied by the presentation in the drawing is used in thesaid method. If the pitch is low on the gear rollerswhich produce the fluting and the lamination, thecorrugated film will "jump out" of the grooves in the 5 forming and laminating roller during its passage from thelocation where forming of flutes takes place to thelocation where bonding takes place. The patent publicationdoes not mention any means to hold the flutes in shape inthe grooves of the roller. 10 In a conventional corrugator for manufacture of corrugated paperboard there are provided tracks or shieldto hold the fluted paper in the grooves. At ambienttemperature this allows the paper to be more readilypermanently formed. 15 Similar tracks or shields in unmodified form cannot be used with thermoplastic film under production conditionssince friction against the track or shield quickly wouldcreate congestion by heating of the polymer.

An improved, frictionless way of holding of flutes of 20 paper in the grooves of a roller is known from US-A-6139938, namely by maintaining a controlled under pressurewithin the grooves (see Figs. 9 and 10 and col. 7 lines 25-34) . This US patent deals entirely with corrugated paperlaminates having particularly low wavelength while 25 manufacture of corrugated structures from thermoplasticfilms is not mentioned. However, the improved method ofholding the flutes will in fact also, depending on the filmthickness, be applicable to fine flutes in thermoplasticfilm. This was found in connection with the development of 30 the present invention. However as mentioned above, theJapanese patent application does not disclose anyprecautions to hold the flutes in shape in the grooves.

The development of the particularly fine flutestructure, the "miniflutes", which is the object of the 35 present invention has made the corrugated paperboardprinciple applicable to completely different fields of use WO 02/102592 PCT/EPO2/07264 6 such as the fields mentioned at the very beginning of thisspecification.

This has comprised a development of new types ofmachinery based on grooved rollers with a very fine pitch. 5 As it will appear from the example the wavelength in a 90gm'2 "minifluted" 2-ply laminate (each ply about 45 gm"2)has in actual fact been brought down to 1.0mm through aprocess which can be carried out industrially, and aftershrinkage of the flat ply transversely to the flutes it has 10 even been brought down to 0.8mm. Especially by further useof shrinkage it can probably be brought further down e.g.to about 0.5mm. The mentioned 2 x 45 gm'2 corresponds toan average thickness of about 0.074mm (2x0.037mm) if thelaminate were pressed flat. 15 The invention is not limited to pressed-flat thicknesses around this value, but also comprises, verygenerally speaking, minifluted laminates of an averagethickness in compacted form which is roughly about 0.3mm orlower. Thicknesses down to 0.03mm or even lower can be 20 made for special purposes.

Nor is the invention limited to the use in connection with cross-laminates of oriented films. For differentpurposes different combinations of strength properties arerequired. Cross-laminates can, as is known, be produced 25 with suitable combinations of several categories ofstrength properties but for many purposes other types ofstrength laminates may be preferable when the cost of themanufacturing process also is considered, and the presentinvention can also be useful in such other strength 30 laminates as it further shall be specified below.

By making the wavelength as low as 3mm or less, the laminate loses its character of being a board material andgets appearance, handle and bending properties like aflexible film (see the example) . It also gets improved 35 puncture properties, compared to laminates made fromsimilar plies but with longer wavelength, since in thelatter there is a large tendency for the plies to be WO 02/102592 PCT/EPO2/07264 proceed inThereby the ruptured individually instead of cooperating in theresistance against the puncture.

The "minifluted" laminate also has the advantage thatit can receive a fine print on the flat side and a coarse5 print on the corrugated side.

Compared to non-corrugated laminates of the samecomposition and same square metre weight it feels much moresubstantial due to the increased stiffness in one directionand due to the increased volume. 10 In the case of cross-laminates it is well-known that a weak bonding between the plies, or strong bonding orline-bonding, gives much improved tear propagationresistance, since it allows the tear todifferent directions in the different plies. 15 notch effect is reduced. Since a cross-laminate with oneply corrugated will be line-bonded, it will show improvedtear propagation resistance, no matter whether thewavelength is short or long, however "mini-fluting" makesthe tear stop after a very short propagation, which of20 course is very advantageous in most cases.

For the sake of good order, it should be mentionedthat there already have been described "minifluted"laminates in literature, however laminates of which atleast the fluted ply consists of a material which is not a25 thermoplastic film or an assembly of thermoplastic films.

Thus US-A-613 993 8, which has been mentioned above, hasfor its object a 3-ply paper laminate with a corrugatedpaper sheet in the middle and flat paper sheets on eachside, like normal corrugated paper board, however claimed30 to comprise 500-600 flutes per metre corresponding to awavelength of 1.67-2.00mm. This state purpose is toimprove the printability.

Japanese patent publication No. 07-251004 relates toan absorbing product in which a plane thermoplastic 35 synthetic fiber sheet is thermally bonded to a corrugatedsheet mainly consisting of active carbon fibers. Thewavelength of the corrugation is 2.5-20mm. WO 02/102592

PCT/EP02/0726-I 8

Japanese patent publication No. 08-299385 relates toan absorbent laminate consisting of a fluted non-wovenfabric bonded on one side to a plane sheet or film, whichcan be a thermoplastic film. Between these two plies there 5 is nested a water-absorbing material. The wavelength isclaimed to be 3-50mm, and it is stated that there would notbe sufficient space for the absorbing material if it wereless . The product is for diapers and the similar products .

More precisely expressed the present invention10 concerns a laminate comprising at least a monofilm-formedor multifilm-formed ply (A) and another monofilm-formed ormultifilm-form ply (B) both mainly consisting ofthermoplastic polymer material, whereby at least A consistsof cold-orientable material in which A has a waved flute 15 configuration while B is not waved, and B on a first sideis adhesively bonded in bonding zones to the crests on afirst side of A. A characterising feature of the laminateis that the wavelength of the said configuration is no more . than 3mm. The use of cold-orientable material in A is

20 important for the strength of the product. Furthermore itis normally important that the adhesive bonding has beenestablished through a lamination layer, so that melting ofthe main portions of A and B can be avoided during thelamination process, and that either the thickness of A 25 generally is the same within the non-bonded zones as it iswithin the bonded zones, or A exhibits zones which areattenuated in the solid state and extend parallel to theflute direction in such a manner that each bonding zonemainly is located within one of the attenuated zones. 30 These attenuated zones will be referred to as the "firstattenuated zones" since there also may be furtherattenuated zones, as it shall be explained later.

In this connection, an essential attenuation of A inthe non-bonded zones, as compared to the thickness of A in 35 the bonded zones, will of course have a negative influenceon the resistance to bending in the stiff direction (but itis generally easier to make the fluted laminate so) . By WO 02/102592 PCT/EP02/07264 9 contrast this resistance to bending is enhanced, seen inrelation to the average thickness of ply A, when eachbonding zone mainly falls within one of these attenuatedzones. The attenuated zones also facilitate the 5 manufacturing process as it later shall be explained. Itis noted that while attenuation by stretching in the moltenstate reduces the tensile strength, attenuation bystretching in solid state increases the tensile strength inthe direction in which this stretching has taken place. 10 While I here have identified the laminate as comprising the plies A and B, each "ply" can consist of oneor more "films", normally extruded films, and each extrudedfilm can and normally will consist of several co-extruded"layers". Thus the "lamination layer" through which the 15 bonding takes place will normally be a co-extruded layer,however it can also be a thin film applied in aconventional extrusion-lamination process.

While an upper limit of 3mm wavelength has been chosenas a suitable value for distinguishing the product of the 20 invention from corrugated board material, it is generallybetter to keep the wavelength within 2.5mm, preferablywithin 2 mm and more preferably 1.5mm. As alreadymentioned and shown in the example the inventor has beenable to make it 1.0mm and under use of shrinkage after 25 lamination even 0.8mm.

As it appears from the introduction, the use of the present invention is mainly for strength film. This needsnot always mean good strength in all directions; bycontrast there are cases, e.g. in construction of bags,. 3 0 where the focus should be on the strength in one direction, combined with a certain puncture and tear-propagationresistance. As an example a conventional industrial bag offilm thickness 0.160mm made from a blend of 90% LDPE and10% LLDPE will typically in its longitudinal direction show 3 5 a yield force of 20 Ncm-1, i.e. a yield tension of 12.5 MPaand in its transverse direction shows a yield force of 16Ncm'1, i.e. a yield tension of 10.0 MPa. WO 02/102592 PCT/EP02/07264 10

Cross-laminated film material in average thickness0.086mm for heat-sealable bags developed by the inventorand manufactured in accordance with the above-mentioned EP-A-0624126 shows in its strongest direction a yield force of 5 20 Ncm'1, i.e. 23 MPa, and in its weakest direction a yield force of 17 Ncm"1, i.e. a yield tension of 20 MPa.

Since the invention in principle relates to flexiblelaminates for uses where relatively high strength isrequired, although the emphasis of the invention is on 10 stiffness, feel and appearance, the yield tension of thelaminate in its strongest direction should normally be noless than 15 MPa, preferably no less than 25 MPa.Correspondingly the ultimate tensile tension isconveniently about twice the said indicated values, or 15 more. Here the cross section in mm2 is based on the solidmaterial only, not including the air spaces, and it is anaverage, considering that ply A may have attenuated zones.

The yield tensions mentioned here refer to tensiletesting at an extension velocity of 500% per minute. They 20 are established from strain/stress graphs. These graphswill begin linear accordingly to Hook's law, but willnormally soon deviate from linearity although thedeformation still is elastic. In principle the yieldtension should be the tension at which the deformation 25 becomes permanent, but this critical value, which isvelocity dependent, is practically impossible to determine.The way yield tension normally is determined in practice,and also considered determined in connection with thepresent invention, is the following: 30 In case the tension reaches a relative maximum, then remains constant or decreases under continued elongation,later to increase again until break occurs, the relativemaximum of the tension is considered to be the yieldtension. The sample may also break at this point, and then 35 the yield tension equals the ultimate tensile tension. Ifhowever the tension continues to increase with thecontinued elongation, but with much lower increases in WO 02/102592 PCT/EP02/07264 11 tension per percentage elongation, then the strain/stresscurve after yield, and after it practically has become astraight line, is extrapolated backward to intersect withthe line which represents the Hook's-Law-part of the 5 stretching. The tension at the intersection between thetwo lines is the defined yield tension.

An embodiment of the invention is characterised inthat the ply A by the choice of polymer material or by anincorporated filler or by orientation, within the non- 10 bonded zones exhibits an average yield tension parallel tothe direction of fluting, which when it is determined asexplained above, is no less than 30 Nmm"2 (cross-section ofply A alone) , preferably no less than 50 Nmm"2 and stillmore preferably no less than 75 Nmm"2. 15 As already mentioned, A is preferably solid-state- attenuated in zones (the "first attenuated zones") and eachbonding zone is mainly located within a first attenuatedzone. These zones should be understood as delimited by thepositions where the thickness of A is an average between 20 A's lowest thickness within the first attenuated zone andA's highest thickness within the adjacent non-bonded zone.

Another important embodiment of the invention ischaracterised in that A within each non-bonded zone andoutside the first attenuated zone if such zone is present 25 (delimited as mentioned above) is molecularly orientedmainly in a direction parallel to the direction of theflutes or a direction close to the latter as established byshrinkage tests. Such tests are commonly used. In thisconnection, a component of orientation in A perpendicular 30 to the direction of the flutes will not contribute to theyield tension in any direction, but will contribute tocertain other strength properties. A preferable limitation of the extension of each firstattenuated zone - preferable with a view to the stiffness 35 in one direction - is specified in claim 12, and preferablethicknesses of these zones are specified in claim 21. WO 02/102592 PCT/EP02/07264 12

Additionally to the first attenuated zones it can bevery advantageous to have a second solid-state-attenuatedzone (hereinafter the second attenuated zone) between eachpair of adjacent first attenuated zones. These second 5 attenuated zones should be narrower than the first ones -preferably as narrow as possible but also alternated sothat the thickness of A in the zone is as thin as possible- and located on the crests of A on the side opposite tothe bonded zones. They act as "hinges", and if they are 10 made narrow and deep enough they improve the stiffnesssince the cross-section of A becomes zig-zagging instead ofsmoothly waved (as described further in connection withFigure 3) and A and B thereby form triangular structures.They also essentially facilitate the manufacturing process, 15 which is explained below.

In addition to the improvements in stiffness caused by the first and second attenuated zones (improvements seen inrelation to the average thickness of A) each set of zonesalso normally improves the resistance against shock 20 actions, i.e. they normally improve impact strength, shock-puncture resistance and shock-:tear-propagation resistance.This is because there is started a stretching (or furtherstretching if A already was stretched) and this stretchingnormally has a tendency to progress under shock actions, 25 whereby the first and second attenuated zones can act asshock-absorbers.

Normally the wavelength of each flute including anadjacent bonding zone should be no longer than 50 times thehighest thickness of A within the flute, preferably no more 3 0 than 4 0 times and still more preferably no more than 3 0times the said thickness. As an example, if the highestthickness of A is 0.037mm as in the operative examplebelow, the mentioned values correspond to wavelengths of1.85, 1.48 and 1.11mm respectively. 35 In order to "integrate" the plies conveniently with each other in order for strength purposes, the width ofeach bonding zone should normally be no less than 15%, WO 02/102592 PCT/EP02/07264 13 preferably no less that 20% and still more preferably noless than 30% of the wavelength, and in order to achieve asubstantial effect of the fluting, the width of each non-bonded zone of A as measured between the two adjacent 5 bonding zones and measured along its curved surface, shouldpreferably be no less than 10% and preferably no less than20% longer than the corresponding linear distance. This isa measure of the depth of the flutes.

For many purposes, e.g. when increased stiffness10 against bending in all directions is wanted, there can bea non-waved monolayered or multilayered film C on the side of A which is opposite to B as specified in claim 15. A fluted outside surface on a bag has as mentionedabove a disadvantage, namely in connection with printing 15 and stacking of the filled bag. However there are articlesin which the special roughness of a fluted surface can bevery advantageous in use e.g. on mats. For such articlesthere can advantageously be two waved mono- or multilayeredplies (A) and (D) laminated to the two opposing sides of 20 the non-waved mono- or multilayered film (B), as specifiedin claim 16.

The films A, B, C and D will normally consist ofpolyolefin and will normally be produced by a process whichinvolves extrusion. This will normally be a co-extrusion 25 process by which lamination layers and optionally heat-seallayers are joined with the main body of the film.

At least some of the flutes can be flattened atlongitudinally spaced intervals and preferably bondedacross the entire width of each flute at the flattened 30 locations to make the flutes form a row of narrow closedelongated pockets. Preferably the flattened portions of anumber of mutually adjacent flutes or of all flutes form aseries of lines transverse to the longitudinal direction ofthe flutes. This can make the corrugated laminate look and 3 5 feel more textile-like, almost make the impression of awoven structure, and make it more flexible in the directionwhich otherwise is stiff, without losing the feel of bulk WO 02/102592 PCT/EP02/07264 14 and substance. Flattening can also be used to createpreferential locations for bending.

Further description of different embodiments of theproduct and of particular uses will follow after the 5 description of the method.

In accordance which the above characterization of the laminate of the invention, the method of manufacture whichtakes place under use of a grooved roller for formation ofthe flutes, and also under use of a grooved roller for the 10 lamination by heat and pressure (which in certain cases canbe the same grooved roller) is characterised in that thedivision on the roller which produces the lamination is atthe highest 3mm. The new method according to the inventionis as defined in claim 36. New apparatus suitable for 15 carrying out the method is defined in claim 65.

The apparatus can be adapted either to make the flutes generally perpendicular to the machine direction as inconventional manufacture of corrugated laminates, orgenerally parallel to the machine direction. This will be 20 specified below.

Normally the bonding is established through alamination layer (produced by co-extrusion or by anextrusion lamination technique) in order to avoidweakening, and normally the steps of the process are 25 adapted either to avoid any significant attenuation of thezones in A, or alternatively a stretching in solid statebetween a set of grooved rollers is adapted to produce theabove-mentioned "first attenuated zones", whereby thegrooved roller for lamination is coordinated with the set 30 of grooved rollers for stretching in such a way that eachzone of bonding mainly becomes located within a firstattenuated zone.

The "second attenuated zones'·', which have beendescribed above in the description of the product, can be 35 formed by stretching between a further set of groovedrollers suitably coordinated with the grooved rollers whichproduce the first attenuated zones. WO 02/102592 PCT/EP02/07264 15

The advantages of the first and second attenuatedzones in terms of product properties have already beenexplained. For the carrying out of the method, the firstattenuated lines allow increases of velocity and therefore 5 improved economy, since the zones in ply A which are goingto be bonded, have been made thinner and therefore requireless heating time during the application of heat prior tothe bonding. Furthermore the first attenuated zones and inparticular the combination of first and second attenuated 10 zones can be of great help for the process by acting as"hinges" in ply A. In the type of apparatus in which thegrooved roller for lamination has grooves which aregenerally parallel with its axis, these "hinges" make.itpossible to direct even relatively heavy A-ply into fine 15 grooves . In the type of apparatus in which the grooves arecircular or helical, but in any case approximatelyperpendicular to the roller axis, the "hinges" help to keepply A "in track" during its passage from grooved roller togrooved roller, in other works the "hinges" help to 20 coordinate the action of the grooved lamination roller withthe action of the preceding set or sets of grooved rollerswhich form the flute under a simultaneous transversestretching.

While it is essential for normal uses of the invention 25 . for applications as a flexible film that the division onthe grooved roller which produces the lamination on thecrests is no more than 3mm, it is generally recommendableto make it no more than 2.5mm, preferably no more than2.0mm and still more preferably no more than I.5mm. 30 The film or films used for ply A is preferably, prior to forming of the waved configuration and prior to makingof the first and second attenuated zones (if such zones aremade) , supplied with orientation in one or both directions,the resultant main direction of orientation being in the 35 direction which is selected to become the direction offluting. This can be by means of a strong meltorientation, or preferably, alternatively or additionally WO 02/102592 PCT/EP02/07264 16 by known stretching procedures carried out in the solidstate. If the process is adapted to make the flutesgenerally parallel with the machine direction, this will bea generally longitudinal orientation process, which is 5 simple, and if the process is adapted to make the flutesgenerally perpendicular to the machine direction, it willbe a generally transverse orientation process which is muchmore complicated to establish and usually requiresexpensive machinery. It is noted that neither of the two 10 closest references, i.e. US-A-4132581 and Japanese patentapplication Hei 02-052732 have disclosures which indicatethat ply A could be oriented in a direction generallyparallel with the flutes. In these two publications theflutes are formed in the transverse direction, and had 15 there been thought of using transversely oriented film itwould have been natural to mention this, since withoutspecial steps the film is not formed so in the extrusion orcasting process.

As it already has been described in connection with 20 the product, a further non-waved monofilm formed ormultifilm formed ply (C) of thermoplastic polymer materialcan simultaneously with or subsequent to the bonding of Bto A be adhesively bonded to the crests of A on the secondside of A. Another useful possibility is that, in a manner 25 similar to the forming and application of A, there isproduced a second monofilm formed or multifilm formed ply(D) having waved flute configuration with a wavelength ofpreferably no more than 3mm, and the crests on one side ofD are laminated to the second side of B simultaneously with 30 or following the lamination of B with A.

In most applications of the invention the mono- or multifilm formed plies should mainly consist of polyolefin,and should be produced by a process involving extrusion.Furthermore the films constituting the plies should 35 normally be made by co-extrusion in which there is co-extruded surface layers to enable the lamination withoutany melting of the main body of the films. WO 02/102592 PCT/EP02/07264 17

As it also appears from the description of theproduct, some of the flutes at least can be flattened afterthe lamination. This is done at intervals, preferablyunder heat and pressure sufficient to bond all films in the 5 laminate to each other so that the flutes with adjacentfilm material form fine elongated pockets closed at eachend. The flattening can be carried out with bars or cogswhich have their longitudinal direction arrangedtransversely to the flute direction and which each covers 10 a number of flutes, optionally the entire width of thelaminate. A suitably distinct formation of the first attenuatedzones can be established at least in part by giving thecrests on the grooved stretching roller intended- to produce 15 the stripes a temperature which is higher than thetemperature of the crests on the other grooved stretchingroller and/or by giving the crests on the groovedstretching roller intended to produce the stripes a radiusof curvature which is smaller than the radius of curvature 20 of the crests on the matching grooved stretching roller.A significant orientation mainly in the direction nearlyparallel with the fluting, and/or a high co-efficient ofelasticity (B) of ply A are also efficient means to givethe first attenuated zones suitably distinct borders. 25 A good way to make the fluting finer than this can be done by purely mechanical means is by use of shrinkage.Prior to the lamination ply B is supplied with orientationgenerally perpendicular to the direction which becomesdirection of fluting, and after the lamination B is 30 subjected to shrinkage in a direction generallyperpendicular to the direction of fluting.

As it already has been stated the waved flutestructure can be formed in different directions. Thus itcan be established mainly in A's longitudinal direction 35 under a generally transverse orientation process by takingA through a set of driven mutually intermeshing groovedrollers, the grooves of the rollers being circular or being WO 02/102592 PCT/EP02/07264 18 helical and forming an angle of at least 60’ with theroller axis. It is most practical to make this angle about90’ or at least very close to this. This can be arrangedso that A moves directly from its exit from one of the 5 grooved stretching rollers which form the waving on A tothe grooved lamination roller, whereby these two groovedrollers are in close proximity to each other and have thesame pitch, and are mutually adjusted in the axialdirection. The pitch, in this aspect should be measured at 10 the operational temperature of the respective roller.

Alternatively A can move from this exit from one of the grooved stretching rollers which form the waving on Ato the grooved lamination roller over one or a series ofheated, grooved transfer rollers. The grooved rollers in 15 this row start with the grooved stretching rollers and endwith the grooved lamination roller and each is in closeproximity to its neighbour or neighbours. Each of thegrooved rollers in the row has the same pitch (measured atthe operational temperature of the respective roller) and 20 their axial positions are adjustable to each other (seefigs. 7 and 8 and the example).

When the fluting is produced in the longitudinaldirection by means of rollers with circular grooves, plyA's width measured as the direct, linear distance will 25 remain constant from its inlet to the process of thelamination, apart from deviations in very narrow edgeregions, which should be trimmed off. Therefore, the ratiobetween ply A's real width, measured along its curvedextension, and A's linear width, which is the same as B's 30 width, equals the transverse stretch ratio and is relatedto the thickness reductions in the attenuated zones.

However, as it already has been mentioned, the flutescan also be produced in a distinctly transverse direction.In this embodiment, an angle of about 30’ between the 35 grooves and the roller axis is probably about the maximumwhich is practically possible, but it is simplest to workwith grooves which are parallel with the roller axis. WO 02/102592 PCT/EP02/0726-1 19

The embodiment with grooves parallel to the rolleraxis is further defined in claims 56, 57, 58 and 59. Themeans to hold A in fluted form in the grooves from fluteformation to bonding, and adapted to avoid a frictional 5 rubbing on A, can be devices for suction through channelsfrom the inside of the grooved roller - a method which asalready mentioned is known from making of corrugatedpaperboard - or it can be use of tracks or shields whichare adapted from the constructions used in manufacture or 10 corrugated paperboard by being air-lubricated. This meansthat the tracks or shields are supplied with fine channels,or preferably a part of each track or shield is made fromporous, sintered metal, and pressurized air is blownthrough the channels or pores to form an air-film on which 15 the fluted ply can flow.

The means for fine regulation mentioned in claims 58 and 59 are similar to registration means in multicolourprinting technology.

The following sections will describe different 20 selections of the orientation and/or elasticity in thedifferent plies, special utilization of the channels orpockets formed by the flutes, and particular end uses ofthe product of the invention.

It has already been mentioned that, in an important 25 embodiment of the product according to the invention, plyA within each non-bonded zone and outside the firstattenuated zone if such zone is present, is molecularlyoriented mainly in a direction parallel to the direction ofthe flutes or a direction close to the latter. 3 0 With ply A so oriented, there are different preferable options for ply B, depending on the uses of the laminate.One very important option is that B also is molecularlyoriented and B' s orientation within each non-bonded zone ina direction perpendicular to the direction of the flutes is 35 higher than A's average orientation in the same directionwithin the non-bonded zone. The said two components of WO 02/102592 PCT/EP02/07264 20 orientation are also in this case, indicated by shrinkagetests .

This does not necessarily mean that ply B must haveits strongest component of orientation in the transverse 5 direction, in other words the laminate needs notnecessarily be a cross - laminate . Thus, ply B may simply bea highly blown film, which by means of the high blow ratiohas obtained a relatively high transverse melt orientation.The embodiment is further specified in claim 8. 10 As mentioned there are cases, e.g. in bag construction, in which there is a need for a high yieldtension in one direction only, but combined with highpuncture resistance. The laminate according to claim 9 orclaim 10 is designed for this. 15 As it appears from the foregoing the present invention is very useful in connection with cross-laminates, i.e. thelaminate then comprises at least two films each of whichhas a main direction of orientation and which are laminatedso that the said two directions cross each other. 20 Different ways of carrying out this aspect of theinventions appears from product claims 22 to 25, from whichalso the method of making becomes clear.

Suitable methods and apparatus for cross-laminationmay be achieved by combining the information in the above 25 mentioned EP-A-0624126, mainly in its introduction, withthe formation in the inventor's older GB-A-1526722. Thus,with reference to Fig. 4 of the present drawings, B and Cmay each be films, including laminates, which exhibit amain direction of orientation whereby B's main direction of 30 orientation criss-crosses with C's main direction oforientation. One of these directions may be parallel withthe machine direction, the other perpendicular thereto, orboth may from an angle higher than 0’ and lower than 90*,preferably between 2 0* and 70* and more preferably in the 35 range 25* - 65* with the machine direction. In this arrangement the waved A supplies to the laminate stiffnessagainst bending, but at the same time, since it establishes WO 02/102592 PCT/EP02/07264 21 a "dislocated" bonding between B and C, it also hasimportance for the tear propagation resistance. It isknown e.g. from the above-mentioned GB-A-1526722, that thesuperior tear propagation resistance which can be obtained 5 by cross-lamination, depends on having bonding strengthwhich is not too high, since the tear must be allowed todevelop along different 'directions in the different pliesof the cross-laminate. Since on the other hand the cross-laminate should not be prone to accidental delamination 10 during use, as for instance described in the said patent,there can be used a combination of strong bonding in spotsor lines and a weak bonding over the rest. However, the"dislocated" bonding of cross-laminated B and C through thewaved A can provide a better combination of high tear 15 propagation resistance and adequate bonding strength,especially when the coefficient of elasticity E of film Ais lower than the coefficient E for both B and C,preferably by a factor of at least 1.5 and more preferablyat least 2. Furthermore the flutes may be flattened at 20 intervals and bonded across each ones entire width to makethe flute from a row of narrow, closed pockets. Thepurposes of such flattening have been mentioned above.

In the above description there is mentioned the "maindirection of orientation" in the films B and C. If plies 25 B and C each are mono-films, normally with coextrudedsurface layers, this may be a monoaxial or unbalancedbiaxial orientation. However, each of the films B and Cmay also in themselves be cross-laminates, normally 2-plycross-laminates. 30 To clarify this, B may e.g. consist of two plies of equal composition, equal thickness and equal degree oforientation, but one oriented at +30* and the other at -30’to the machine direction. This will result in a maindirection of orientation following the machine direction. 35 Similarly C may consist of two equal plies, one oriented at+60’ and the other at -60’. The resultant direction oforientation then is perpendicular to the machine direction. WO 02/102592 PCT/EPO2/07264 22

Uniaxial or unbalanced orientation in a film can beobtained under use of spiral cutting of a tubular film withmainly longitudinal direction as disclosed in EP-A-0624126and GB-A-1526722, both mentioned above, and disclosed in 5 more detail in EP-A-0426702. The latter also discloses amethod of obtaining a uniaxial or strongly unbalanced melt-orientation which is perpendicular to the machinedirection, namely by twisting of a tubular film coming outof the extrusion die followed by helical cutting under the 10 calculated angle. Another embodiment of the cross-lamination aspect of the present invention is stated inclaim 22. The expression "resultant main direction oforientation" has the same meaning as explained above.

If this laminate is to be used in the construction of 15 bags with heat-seals generally perpendicular to thedirection of the flutes, and if such heat-seals may besubjected to high shock-peel forces then the laminateshould preferably be constructed as stated in claim 61.The fluted softer A-film can then form the inner side for 20 heat-sealing, and the stiffer, smooth B-film can form theouter side of the bag.

Another aspect of the invention ("theencapsulation/canalization aspect") comprises a number ofembodiments which for different practical purposes utilize 25 the interior cavities in the laminate, optionally incombination with suitable perforations, either to canalizea flow of liquid or air, or to encapsulate filling materialin particulate, fibrous, filament or liquid form. Thelatter may e.g. be a preservative for goods packed in the 30 flexible laminate. These different embodiments appear fromproduct claims 27 to 30, 34 and 35. The method of makingthese products will appear from claims 48 to 51, andapparatus suitable for carrying out the method is definedin claims 88 and 89. 35 The embodiment of the present invention in which the fine canals or "pockets" are used to "bury" preservatives,have obvious advantages over the usual method of blending WO 02/102592 PCT/EP02/07264 23 such agents with the polymers to be extruded into filmform. One advantage is that the concentration of thepreservative can be much higher, another that thepreservative needs not be able to withstand the temperature 5 of extrusion. The preservative may reach the object to bepreserved by migration alone, or if the agent is solid itmay gradually evaporate and diffuse through sufficientlyfine perforations or pores.

It is also customary to contain preservative agents in10 small bags which are placed inside a package. Compared tothis method of protection, the present invention has theadvantage that the preservative agent can be distributedalmost homogeneously over the full area of the packing material. 15 The filter material stated in claim 30 has many potential uses, e.g. as a geotextile (claims 34 and 35) butalso for instance for water treatment in the chemicalindustry and in gas face masks.

Although the claims relating to these filter 20 materials, including the weather-protective laminate ofclaim 62, formally depend on claim 1, it should beunderstood that similar products having wavelength somewhathigher than 3mm also have important uses and are consideredinventive new products. Thus in a further aspect of the 25 invention there is provided a laminate comprising at leasta monofilm· formed or multifilm formed ply (A) and anothermonofilm formed or multifilm formed ply (B) both mainlyconsisting of thermoplastic polymer material, whereby atleast A consists of cold-orientable material in which A has 3 0 a waved flute configuration while B is not waved, and B on a first side is adhesively bonded in bonding zones to thecrests on a first side of A in which the adhesive bondinghas been established through a lamination layer, and thateither the thickness of A is generally the same within the 35 non-bonded zones as it is within the bonded zones, or Aexhibits first solid-state-attenuated zones (hereinafterthe first attenuated zones) extending parallel to the flute WO 02/102592 PCT/EP02/07264 24 direction, each bonding zone mainly being located within afirst attenuated zone, the laminate being moistureresistant but air permeable. The laminates are useful forforming raincoats and tarpaulins. Other uses in which an 5 additive is incorporated into the flutes are describedbelow.

Other important uses of the invention are for bags andself-standing pouches. In this connection reference ismade to the product claims 31, 32 and 33. 10 For all uses of the present invention, a very interesting and wear-resistant print can be obtained when,prior to the lamination, A and/or B is supplied with printon the surface to become the inside of the laminate, theprinting process being in register with the flute-forming 15 and lamination processes so as to limit the print generallyto the non-bonded zones. This durable print may form atext, a decorative pattern or simply lines which accentuatethe fluting or the textile-like appearance of the laminate.Special decorative effects can be achieved if the print 20 provides a metallic appearance or a mother-of-pearl effect.

The invention shall now be explained in further detail with references to the drawings.

Figs. 1, 2, 3, 4 and 5 are cross-sections representing four different structures of the laminate of the invention, 25 comprising the minifluted ply A, or plies A and D, and thestraight ply B or plies B and C. The flutes in each ofthese structures can extend longitudinally or transversely,seen in relation to the machine direction of the flute-forming and laminating machinery. 30 Fig. 6 is an enlarged detail of Fig. 1 to illustrate how these plies themselves can be laminates of films, andhow these films can be multilayered as made by co-extrusion, this being done to facilitate bonding andlamination. 35 Fig. 7 is a principal sketch representing the steps from formation of the miniflutes in A to lamination of Awith B in the manufacture of the product shown in Fig. 2, WO 02/102592

PCT/EP02/0726-I 25 the different steps being represented by the cross-sectionsof the films A and B and by the cross-sections through theaxis of the rollers of the surfaces of the rollers.

Fig. 8 is a sketch of the machine line corresponding5 to Fig. 7 with addition of the means to laminate straight film C to A opposite to B.

Figs. 9a, 9b and 9c are sketches illustrating thecross-laminate constructed as stated in claim 22.

Figs. 10a, b and c represent sections parallel to the 10 flutes and through the middle of a non-bonded zone, showingapplications of the invention in which the channels orpockets formed between ply A and ply B are used as mini-containers or to canalize a flow of air or water, namely infig. 10a as mini-containers for a protective agent, in Fig. 15 10b for filtration and in Fig. 10c for weather protection.

Fig. 11 shows a modification of the lamination stationof Fig. 8 in which there are added filling devices to fill particulate material into the flutes before the lamination,and added sealing equipment to form transverse seals after 20 the lamination, thereby making closed pockets which serveas "mini-containers" for the particulate material.

Fig. 12 is a flow-sheet showing a process forproducing the laminate with transverse fluting and with"first" and "second" attenuated zones (as these expressions 25 have been defined).. . .

Fig.13 shows a detail of a grooved lamination rollerfor formation of transverse fluting, air jets being used todirect the ply into the grooves and vacuum being used toretain it there. 3 0 With references to Figs. 1 to 5 it should be mentioned for the sake of clarity, that· the wavelength referred to inthe foregoing and in the claims, is the straight lineardistance from x to z. This distance is preferably 3 mm orlower, and as it appears from the example, the inventor has 3 5 been able to make it as small as 0.8mm, which however needsnot be the ultimate lower limit obtainable and useful. Itis noted that US-A-5441691 (Dobrin et al.) makes embossed WO 02/102592 PCT/EP02/07264 26 film (not heat-bonded laminates) having a generallycircular shape of the bosses, with a spacing from centre tocentre which can be still finer than these 0.8mm, howeverthe bosses of this patent are drawn much thinner than the 5 main body of the film.

In Fig. 1 the thickness of ply A is generally the sameacross the ply. In case of transverse fluting this can beachieved by the process shown in Fig. 12 (without precedingformation of attenuated zones) however there is a limit, 10 which is of practical importance, of how fine thewavelength can be, seen in relation to the thickness of plyA.

In case the flutes are made parallel with the machinedirection, for formation of the flutes and the lamination 15 is preferably carried out generally as shown in Fig. 8.This means there will always be a transverse stretchingbetween intermeshing grooved rollers, and the degree offluting will correspond to the degree of stretching. Whenfilm is stretched between very fine grooved rollers, there 20 will be a strong tendency to localize the stretchingentirely or predominately on and near to the tips of thegrooves. This can be avoided, but with difficulty, byusing film which in a preceding process has beentransversely stretched, and feeding the film unto the 25 roller at a temperature which is higher than thetemperature of the roller.

However, in the laminate structures shown in Figs. 2to 5 the differences of thickness resulting from groovedroller stretching has been utilized in a way which 30 generally is an advantage for the properties of theproduct. By the exact registration between the groovedrollers for stretching, the grooved roller for laminationand a grooved transfer roller therebetween, it is arrangedthat each bonding zone mainly falls within an attenuated 35 zone. As it appears from Fig. 3 there can be two sets ofattenuated zones for each zone of bonding, namely a series (6) of wider ones ("the first attenuated zones") within WO 02/102592 PCT/EP02/07264 27 which the bonding zones fall, and a set of shorter ones(101), the latter referred to as the "second attenuatedzones".

By attenuating ply A at the basis where it is bonded5 to ply B, the thickness of A is minimized at the locationwhere its contribution to stiffness in the stiff directionin any case is insignificant. By introducing the narrow"second attenuated zones" which act as "hinges", the cross-section becomes almost triangular as shown in Fig. 3. This 10 means that the stiffness is further improved. Theseattenuated zones also introduce a tendency in the materialto stretch rather than rupture under impact actions.

To clarify the concepts, each first attenuated zone(6) is per definition delimited by the locations (102) 15 where the thickness of ply A (or ply D) as indicated byarrows is the average between the smallest thickness inthis zone and the highest thickness in the adjacent non-bonded zone.

Structures with "first attenuated zones" as shown in 20 Figs. 2 to 5 and structures with both "first and secondattenuated zones", as shown in Figs. 3 can also be producedwith machinery which make transverse fluting. This shallbe described later.

In Fig. 6 both plies A and B are in themselves 25 laminates, for instance cross-laminates as in claim 22, andeach film from which the plies are produced is co-extruded.Therefore A and B are each formed by a lamination process(the "pre-lamination") prior to the lamination of A to B.Layer (1) is the main layer in each of the two coex films 30 which make A, and layer (2) is the main layer in the twocoex films which make B. Layers (1) and (2) can e.g.consist of high density polyethylene (preferably HMWHDPE)or iso- or syndio-tactic polypropylene (PP) of blends ofone of these polymers with a more flexible polymer, for 35 instance, for HMWHDPE, LLDPE. If stiffness is the mostpreferred property of the minifluted laminate, plainHMWHDPE or plain PP may be chosen, but if tear and puncture WO 02/102592 PCT/EP02/07264 28 properties play a more important role and/or superior heat-seal properties are essential, the mentioned blends may bemore suited.

Layers (3) are coextruded surface layers with the5 function to improve the heat-seal properties of thefinished, minifluted laminate and/or modify its frictionalproperties. Layers (4) are co-extruded surface layers("lamination layers") with the two functions: a) tofacilitate the pre-lamination and b) to control the bonding 10 strength (in cross-laminates the bonding should not be toostrong, otherwise the tear propagation strength suffers).

Similarly, layers (5) are co-extruded surface layersto facilitate the lamination of the entire A to the entireB and control the strength of the bonding between A and B. 15 With reference to Fig. 7 and Fig. 8 the structure shown in Fig. 2 can be formed by passing film (A) firstover the grooved pre-heating roller (6a) which heats itonly along the lines which shall become attenuated, thenover the grooved stretching rollers (7) and (8),. further 20 over grooved transfer and flute-stabilizing roller (9) , andfinally over grooved lamination roller (10) and its rubber-coated counter-rollers (11), while film (B) is passed overthe smooth rollers (12) and (11) . The grooves of all ofthe rollers are circular so that the flutes are formed in 25 the machine direction. If B is transversely oriented andtherefore has a tendency to transverse shrinkage, rollers(12) and (11) are preferably supplied with devices, e.g.belts, to hold the edges (not shown) . All of these rollersare temperature controlled rollers, rollers (9), (10), (11) 30 and (12) being controlled at the lamination temperature,rollers (6a) and (8) at a somewhat lower temperature androller (7) at a temperature about 20 or 3 0°C. (There can be further rollers for preheating of B) . By choice ofsuitable, coextruded surface layers - see (5) in Fig. 6 - 35 the lamination temperature is kept far below the meltingrange of the main layers in (A) and (B). The temperatureof the zones (6) in (A) during the transverse stretching WO 02/102592 PCT/EP02/07264 29 between rollers (7) and (8) is preferably still lower, e.g.in the range of about 50-70‘C and the rest of (A) muchlower, e.g. around room temperature, as it also appearsfrom the mentioned roller temperatures. If the main layers 5 in (A) and (B) consist of plain HDPE or blend of HDPE andLLDPE, the lamination temperature is preferably chosenbetween about 80 and about 110’C, and the coextrudedlamination layers, which can consist of a suitable plain orblended copolymer of ethylene, are chosen to produce 10 lamination at this temperature.

The crests on roller (8) has very small radius of curvature, e.g. about 0.05mm or an extremely narrow "land".The crests on roller 6a which have the function to preheat,may, depending on the film, be similar or somewhat rounder 15 or with a slightly wider land. The crests on rollers (7)and (9) have a higher radius of curvature or a wider land,to avoid transverse stretching on these crests. Suitablevalues for the sizes of the grooves are mentioned below inthe example. 20 The different temperatures on the different grooved rollers cause different thermal expansions, compared to astate where all have room temperature, and this must betaken into consideration when the grooved rollers areconstructed, since they must fit exactly to each other 25 during operation. (10‘C heating of a 10cm long steelroller segment causes about 0.011mm expansion of thissegment) . Reference is again made to values in theexample.

Rollers (7) , (8) and (10) are driven, while rollers 30 (6a), (9), (11) and (12) may be idling.

As it will be understood, the attenuation of A in the zones (6) takes place almost entirely by the ..transverseorientation at a temperature essentially below the meltingrange of the main body of A. This attenuation therefore 35 does not cause any significant weakening of A's transversestrength, contrarily it will normally cause an increase ofthis strength. After the transverse stretching on the WO 02/102592 PCT/EP02/07264 30 crests of roller (8) the width of the "first attenuatedzones" (6) should preferably not exceed (as a rule of thethumb) half the wavelength, but the degree of stretchingshould normally be as high as practically obtainable, while 5 the degree of transverse stretching between the "firstattenuated zones" normally should be as low as practicallyobtainable, with the intended result that ply A in theunbonded zones becomes as thick as the chosen square metreweight of A allows and the flutes become as high as 10 possible. A practical way of achieving that the first attenuatedzones and the zones of bonding match with almost equalwidth is the following: the relatively flat crests on thelaminating roller (10) are made slightly wider than the 15 chosen width of the first attenuated zones, and thetemperature and velocities are adjusted to each other insuch a way that the first attenuated zones (6) becomeheated to a temperature at which the material will laminatewith B, while the thicker A-ply between zones (6) does not 20 reach a temperature at which lamination can take place.

The use of longitudinally oriented A-ply as in claim 6 will impart , a tendency in A to "neck down" and form thinlongitudinal lines when A is stretched transversely.Therefore, longitudinally oriented A-ply will enhance the 25 possibilities of getting a sharp distinction betweenstrongly attenuated zones (6) and non-attenuated ply Abetween these zones.

Theoretically there will always occur some attenuationalso of the B-ply in the zones of bonding, since the 30 bonding is established under pressure, but this attenuationhas no positive effect and should preferably not exceed20%. Due to the presence of lamination layers (see (5) inFig. 6) such attenuation of the B-ply can be madenegligible. 35 In Fig. 8 the minif luted laminate leaving lamination rollers 10 and 11 is marked (B/A), In this figure itproceeds for lamination in conventional manner with the WO 02/102592 PCT/EP02/07264 31 non-waved, mono-/or multilayered film C coming from thesmooth steel roller (13). The lamination takes placebetween the smooth steel rollers (14) and (15) of which atleast roller (14) is heated to a convenient lamination 5 temperature and is. driven. The waved film A is heated tolamination temperature, at least on its free crests, bymeans of hot air from the blower (16). Rollers (14) and(15) are kept at a distance from each other which is smallenough to effect the lamination but big enough to avoid 10 excessive flattening, e.g. between 0.2 and 0.6mm. When A,B and C are very thin films, e.g. each in the range of0.03-0.10mm thick (for A this refers to the non-waved form)such conventional lamination would have been very difficultdue to the floppiness of waved A, but since the flutes now 15 have been consolidated by the bonding to B, the laminationof A to C presents no particular difficulty.

The laminate leaving the lamination rollers (14) and(15) is marked B/A/C. It is cooled, e.g. by air (notshown) and may normally be reeled up or flip-flopped, since 20 it normally is sufficiently flexible material althoughfluted, or it may directly be cut into lengths.

To make the laminate shown in Fig. 5, one option is tomake the A/B laminate shown in Fig. 2, and laminate thisover the rollers (11) and (10) with the fluted ply D 25 leaving roller (9) . This requires exact registrationbetween the rollers which make the A/B laminate and roller(1)) . Alternatively B can consist of e.g. two films BI andB2. Then in two mutually independent processes there aremade an A/Bl laminate and a D/B2 laminate, and the two are 30 bonded together with Bl against B2 in an extrusionlamination process.

With certain modification the line shown in Figs. 7and 8 can also be used to make the laminate of Fig. 3,which has "second attenuated zones". For this purpose 35 roller (6a) should have the same surface profile and thesame low temperature as roller (7) , and it should bepreceded by and in slight engagement with a roller with the WO 02/102592 PCT/EP02/07264 32 same surface profile as roller (8), which roller shouldhave the same higher temperature as roller (8).

In the minifluted "multi-crosslaminate" shown in Figs.9a, 9b and 9c, the two coextruded films (la) and (lb) from 5 which A is made by "pre-lamination", are oriented in criss-crossing directions, which form an angle lower than 45”with the longitudinal direction (the flute direction) assymbolized by the arrows (laa) and (lbb). This gives aresultant main orientation direction for A parallel with 10 the flute direction, symbolized by the arrow marked A' .Similarly the two coextruded films (2a) and (2b) from whichB is made by "pre-lamination", are oriented in criss-crossing directions, which form an angle higher than 45’with the flute direction, as symbolized by the arrows (2aa) 15 and (2bb) . This gives a resultant main orientationdirection of B perpendicular to the flute direction,symbolized by the arrow B'.

In Fig. 10a, which as mentioned shows a longitudinalsection through a flute in ply A, the latter has been 20 flattened and sealed to ply B at intervals (103) to formpockets or "mini-containers", and these mini-containershave been filled with a particulate substance (104) whichhas a purpose for the use of the laminate, e.g. forprotection of material packed or wrapped up in the latter. 25 As one among many options it may be an oxygen scavenger.To enhance the action of the substance the flutes may besupplied with fine perforations on the side towards thepacked product. The substance may also e.g. be a fireretardant material such as CaCl2 with crystal water,. or 30 just fine sand to increase the bulk density of thelaminate.

Fig. 11 which shall be described below, shows how theparticulate substance can be fed into the flutes of ply Aprior to its lamination with ply B, and how the flutes can 35 be closed to pockets by transverse sealing after thelamination, without any essential contamination of thesetransverse seals. WO 02/102592 PCT/EP02/07264 33 A laminate between a fluted thermoplastic film and anon-fluted thermoplastic film with a filling materialbetween is known from Japanese Patent publication No. 07-276547 (Hino Masahito). However, in this case the filling 5 material is a continuous porous sheet (for absorption)which extends from flute to flute without interruptions, sothat there is no direct bonding between the flute and thenon-fluted films. One of the thermoplastic films is firstdirectly extruded unto this porous (e.g. fiberformed) 10 sheet, then the two together are given a fluted shapebetween gear rollers while the thermoplastic film still ismolten, and finally a second thermoplastic film is extrudeddirectly unto this fluted assembly to join with the poroussheet. Hereby the bonding necessarily must be very weak, 15 and the mechanical characteristics must be completelydifferent from those of the present product. Thewavelength of the fluting is not indicated.

In the technical filter material for liquid or gasflows shown in Fig. 10b there is inserted a strand or yarn 20 into each flute - in connection with the description ofFig. 11 it shall be explained how that can be done - andboth sides of each channel formed by fluted ply A and non-fluted ply B is supplied with a row of perforations, (106)in ply A and (107) in ply B. These rows are mutually 25 displaced as shown so that the liquid or gas passing fromone surface of the laminate to the other, is forced tofollow a channel over a distance corresponding to thedisplacement. The fitting between the yarn and the channelmay be improved by shrinkage of A and/or B after the 30 lamination process.

The pocket structure shown in Fig. 10a can also beused for filtration purposes if ply A and ply B aresupplied with mutually displaced holes. Then theparticulate substance (104) can e.g. consist of active 35 charcoal, or an ion-exchange resin, or for simplefiltration purposes fine sand. Also in this case a WO 02/102592 PCT/EP02/07264 34 tightening of the passage by means of shrinkage can beadvantageous or may even be essential.

Practical examples of the use of such filter materialsare for air filtration systems including absorption of 5 poisonous substances, and ion-exchange processes. In bothcases the laminate can have the form of a long web which isslowly advanced transversely, to the flow which passesthrough it.

Another practical use is as a substitute of10 geotextiles e.g. for road constructions. Such textilesmust allow water to penetrate but hold back even fineparticles. The present laminate, e.g. filled with fine sand in the pockets, is suitable for this use.

For such filtration purposes, high puncture strength15 will often be needed, and the laminate then preferably comprises oriented, cross-laminated films.

For the filtration purposes the condition that thewavelength should not exceed 3mm, is often less importantsince appearance and handle may not be a primary concern as 20 it is in the case of laminates for ordinary tarpaulin uses.

The weather protective laminate shown in Fig. 10c, e.g. for raincoats, also has a pocket structure, wherebyply A is heat-sealed to ply B by transverse seals atlocations (103), but there is no particulate substance in 25 the pockets. Like the laminate for filtration, each lineof pockets is supplied with perforations in a displacedsystem, here shown as groups of perforations (109) in A andsimilar groups (110) in B, and these groups are mutuallydisplaced. In this sketch it is considered that ply A is 30 on the side where it rains, and a person, animal or item,which the laminate shall protect, is on the ply B side.(It could be the other way round) . It is also consideredthat the direction shown by arrow (108) is upward. Sincethe perforations (109) are at the bottom of the pockets, 35 and because of the gravity force, only the bottom of thepockets may be filled with rainwater, while in principle nowater will reach the perforations (110) . On the other hand WO 02/102592 PCT/EP02/07264 35 there is free passage of air and transpiration between thehole groups (109) and (110) . Also in this product thewavelength may to some extent exceed 3 mm.

The modification of the Fig. 8 machine-line, which is5 shown in Fig. 11, is adapted to fill a particulatesubstance (104) into the channels formed between A and B.The filling is here shown very schematically. The powder(104) is taken from a hopper (111) and is administered bymeans of an adjustable vibrator (not shown) . It falls into 10 the fluted ply A at the upper side of the groovedlamination roller (10) . At regular time intervals hopper(111) is filled up with the powder (104) . The means forthis are not shown. Other conventional systems foradministering the powder (104) onto ply A on roller (10) 15 may of course be chosen.

Roller (10) vibrates (means not shown) so that the powderis moved from the higher zones, i.e. those which becomebonded zones when A meets B in the nip between (10) and(11), into the lower zones, which become the "channels". 20 Having left the laminating rollers (10) and (11). The A+B- laminate with powder (104) in the channels movestowards the cog-roller (113) - its surface is shown in adetailed part-drawing - and its rubber-coated counter-roller (114) which together flatten and close the channels 25 by making transverse seals. Roller (113) is vibrated inorder to remove powder away from the channel-parts whichbecome flattened and sealed.

Both rollers (113) and (114) are heated to atemperature needed for the sealing, and since the laminate 30 while entering these rollers still is at about atemperature suitable for heat-sealing due to the previoustemperatures, this second heat-seal process needs not causea deceleration of the entire process.

Ply A and/or ply B may be perforated by means of pin- 35 rollers after rollers (10)/(11) and in front or after thepair of rollers (113)/(114). In case mutually displacedrows of perforations are needed (see Figs. 10b and c) and WO 02/102592 PCT/EP02/07264 36 pin-rollers for ply A and ply B must be suitablycoordinated, and in case the perforations should have afixed relation to the transverse seals (see Fig. 10c, thepin-rollers must be coordinated with roller (113). 5 In order to make the product shown in Fig. 10a, rollers (113) and (114) are omitted or taken out offunction, and instead of administering powder into ply A,there is at the same place laid a yarn into each flute.Each yarn is taken from a separate reel. 10 At some stage after rollers (10)/(11), ply A and/or

play B may be subjected to transverse shrinkage. If thisis done with ply A only, it may be sufficient to heat theply A-side of the laminate to an adequate temperature bymeans of hot air or on one or more hot rollers. If ply B 15. should be involved in the shrinkage it may be necessary tohold the laminate at the edges while it shrinks. This may . be done by means of an ordinary tenterframe, but the lattershould be set up to work. " inversely" so that the widthgradually is reduced instead of increased. 20 The methods applied for making pockets from the flutes, fill powder into these flutes, and making suitableperforations, have been explained in connection with thelongitudinally fluted laminate. Analogous methods can beapplied in connection with a transversely fluted laminate 25 (the general method of making such laminate appears fromFig. 12), and in that case the closing of the channels toform pockets may take place by use of a circularly orhelically grooved roller. However, it is not consideredpractically possible to lay down yarn in transverse flutes .30 at industrially acceptable velocities.

The process for. making the transversely fluted laminate, which appears from the flow-sheet Fig. 12 isgenerally analogous to the process which is described inconnection with Figs. 7 and 8, and the profiles of the 35 grooved rollers can also be generally similar, except thatfor the process of Fig. 12 the grooves extend axially,while for the process of Figs. 7 and 8 they are circular. WO 02/102592 PCT/EP02/07264 37

Step 1: Ply A is longitudinally stretched in verynarrow zones localized on the tips of a hot roller whichhas a profile similar to that of roller (8). The groovedcounter-roller, which is cold, has a profile like that of 5 roller (7) .

Step 2: The warm, stretched "second attenuated zones"are cooled on a cold grooved roller which also has aprofile like that of roller (7), and then to form "firstattenuated zones" between the "second", ply A is 10 longitudinally stretched between this cold roller and awarm grooved roller which also has a profile similar tothat of roller (8) . The stretching is localized to thetips of this roller. Similar to the registration inprinting technology, step 2 is brought in registration with 15 step 1 under use of a device which optically detects thestretched zones.

Step 3: The flutes are first formed in the grooves, ofa hot roller with a profile similar to that of roller (10) , e.g. under use of compressed air, and are held in the 20 grooves e.g. under use of a vacuum, all as explained inconnection with Fig. 13, and ply A is then laminated withply. B between the crests of this grooved roller and arubber-coated counter-roller, which also is heated. Ply Bhas been preheated. 25 There can be different after treatments as explained in the foregoing.

In Fig. 13, ply A which has been supplied first withthe very narrow transverse "second attenuated zones" (101) ,and then with the somewhat wider, also transverse "first 30 attenuated zones" (6) , is directed into the grooves (115.)of the heated lamination roller by means of compressed airfrom a row of nozzles of which one (116) is shown. By useof registration means, working on basis of opticaldetection of zones (6) or (101) it is arranged that the 35 first attenuated zones (6) will cover the crests (118) ofthe grooved roller. The two sets of attenuated zones actas hinges so that even a quite heavy ply A may be bent and WO 02/102592 PCT/EPO2/07264 38 form the flutes. The latter are held in shape in thegrooves under use of vacuum applied through channels (117)from the interior of the roller. Thus ply A is moved influte shape to the nip (not shown) between the grooved 5 roller and the rubber-coated counter-roller, wherelamination takes place. The vacuum in the grooves isadjusted so that ply A is held firmly when this is needed,but can be released where that is needed. There can alsobe a valve arrangement inside the grooved roller to 10 eliminate the vacuum during the release.

Example A 2-ply laminate of fluted ply A and non-fluted ply Bwith A longitudinally and B transversely oriented ismanufactured on a pilot-unit constructed as shown in Figs.

15 7 and 8, but terminating after the lamination of A and B have taken place. Both plies consist of one coextruded,cold-stretched 0.037mm thick film consisting of HDPE witha thin layer on one side, consisting of an ethylenecopolymer having a melting range between 95-105’C. This is 20 used as lamination layer in the process. The cold-stretching was carried out near room temperature at a drawratio about 3:1 and was followed by heat stabilization, allby conventional means, and while the film had flat tubularform. The tube was longitudinally cut to form ply A. 25 Processes for continuous manufacture of transversely oriented film are well-known and mentioned in theforegoing, but it would have caused practical complicationsfor the inventor to have such film manufactured accordingto his specifications, and therefore short lengths of the 3 0 ply A-film were glued together edge to edge with a pressure-sensitive adhesive to form a transversely orientedweb.

All of the grooved rollers have the pitch 1.1000mm atthe temperature at which they actually are used, but due to 35 the large temperature differences during thestretching/laminating process, the thermal expansion had tobe taken into consideration when these rollers were WO 02/102592 PCT/EP02/07264 39 machined at 20°C, see the table below. The biggesttemperature difference between the rollers, as it appearsfrom this table, is 85°, and this corresponds to anexpansion of about 0.10mm per 10 cm roller length, while 5 the accumulated error in the fitting between adjacentrollers from end. to end of the rollers must be maintainedlower than 0.15mm to obtain the needed registration.

The table below also indicates the radius of curvature (R) or the roller, as Roller No. length of a seen in the 6a "land" on the crest of each groovedaxial section in Pig. 7. 7 8 9 10 Crest land R= land R= Land mm 0.4 0.2 0.15 0.15 0.7 Temperature °C 70 20 70 105 105 Pitch mm 1,0993 1,1000 1,0993 . 1,0988 1,0988

It is of course not practically possible to achieve 25 such a high accuracy in the pitch seen individually fromgroove to groove, but it is essential that errors in thepitch do not accumulate by more than 0.05mm. This is bestachieved when the surface parts are made from segments andaccumulated errors are eliminated by fine grinding of the 30 segment ends and/or thin shims (foils) are inserted betweenthe segments. In the actual pilot machine the length ofthe grooved part of each roller surface was about 450mm andwas assembled from 3 segments. It is judged that in anindustrial machine the rollers can be made in up to about 3 5 5 m length, but in that case the accuracy from end to end has to be checked with laser measurements and adjustmentsmade as explained. WO 02/102592 PCT/EP02/07264 40

The transverse stretching, which is the basis for theflute-formation and which forms the "first attenuatedzones" - later the zones which become bases, not crests ofthe flutes in the laminate - takes place by the 5 intermeshing between rollers (7) and (8) and becomeslocalized to a zone on and nearby the crests of roller (8) .This is because roller (8) is hot and has a relativelysharp crest, while roller (7) is cold and has a muchrounder crest (higher radius of curvature R) . It is 10 relevant also in this connection that ply A is uniaxiallyoriented in the machine direction and therefore has a hightendency to "neck-down" and form sharply delimitedattenuated zones when it is transversely stretched.

The function of roller (6a) is to preheat the zones 15 which are to be stretched on the tips of roller (8). Inthis example the "land" on the crests of roller (6a) arewider than the "land" on the crests of roller (8). Thishas been chosen in order to counteract the very pronouncedtendency in the film to "neck-down", in other words, to 20 make the limits of the "first attenuated zones" smoother.In other cases e.g. when ply A has a pronounced transverseorientation and therefore no tendency to "necking down" bytransverse stretching, the "land" on the crests of roller(6a) which preheats the film, should be no wider than the 25 "land" on the crests of roller (8).

Between rollers (6a) and (7) there is a slight but almost zero engagement to avoid wrinkles without stretchingthe films.

Having left the transverse stretching roller (8), ply 30 A is taken over by transfer roller (9). This is heated inorder to help the shaping of flutes in the zones which havenot been stretched. At this stage the "first attenuatedzones" are still deeply curved, but when (A) is taken overby the flat 0.4mm wide crests (lands) on the grooved 35 laminating roller (10) the "first attenuated zones" areflattened almost over their entire width except at theirboundaries where the thickness gradually increases, and by 02/102592 PCT/EP02/07264 41 means of the rubber-coated counter-roller, which on itssurface has temperature 80’C, this flat portion islaminated to the transversely oriented ply B.

Prior to the experimental run the axial position ofthe grooved rollers are very carefully adjusted to eachother, and so is the intermeshing between adjacent groovedrollers. The intermeshing between rollers (7) and (8) isset to make the depth of the fluting 0.40mm, as measured inmicroscope on a cross-section of the finished laminate.

When leaving the stretching/laminating apparatus, theminif luted laminted is aircooled and is reeled up on a coreof diameter 250mm. In the test report below this laminateis called "Sample I".

It is noted that although the pitch of each groovedroller in the line is l,1000mm referring to the temperatureat which the roller has been operated, the wavelength ofthe fluting in the final minifluted laminate, due totransverse shrinkage, is only 1.0mm.

As a principal experiment there is out specimens ofthis film, 3 0cm long in the machine direction and 20cm widein the transverse direction, and these specimens aresubjected to further transverse shrinkage by a primitivearrangement which imitates an "inverse" operation of atenter frame. The two 30cm long edges are fixed to twosticks, which are held by hand, and an even shrinkage isarranged by moving the specimen over a roller surface,which is heated to 115°C, with the B film contacting theroller. Hereby the wavelength is reduced from 1.0mm to0.8mm.

Sample II, made for comparison: By a relativelyprimitive arrangement there is made specimens of corrugatedboard material from the same film as used to make "SampleI" (coextruded coldstretched HDPE-film of thickness0.037mm), with all dimensions of sample A, namely asfollows: WO 02/102592 PCT/EP02/07264 42

Sample Wavelength mm Bonded Zones mm Flute-depth mm I 1.0 0.4 0.4 II 5.5 2.2 2.2

It is noted that Il's wavelength, 6.0mm, is slightly 10 less than the minimum mentioned in patent literature namelyin US-A-4.132.581.

In both samples I and II, the direction oforientation in ply A is parallel with the flutes, and thedirection of orientation in B is perpendicular to the 15 flutes.

Sample B is manufactured with a small laboratorymachine constructed as explained in connection with Fig.13, but in this case there has now been any need to make"first attenuated zones" and "second attenuated zones". 20 The flutes become perpendicular to the machine direction.Like the grooved laminating roller (10) used in themanufacture of sample I, this grooved laminating roller isheated to 105°C.

Sample III, made for comparison: The same film 25 (coextruded oriented HDPE, 0.037mm thick) is crosslaminatedwith itself without any fluting being made.

Comparisons between samples I, II and III:

Appearance and handle: (II) looks and feels like a board material, but is 30 instable when bent or compressed between the fingers. (I) has a rather textilis look, can stand a substantial amount of bending and compressionbetween thefingers without changing its character, and it has a feelof "bulk". 35

Bending tests: WO 02/102592 PCT/EP02/07264 43 (I) and (II) are bent over cylindrical bodies ofdifferent diameters, and it is examined how small thatdiameter can be before the flutes begin to collapse in anon-elastic manner, i.e. so that there remain marks in the 5 flutes after the specimen has been straightened out again. (II) can withstand bending down to a diameter of250mm. while (I) can withstand bending down to a diameterof 50mm. 10 Stiffness measurements: 10cm long specimens are cut out from samples (I) ,(II) and (III).

The specimens from sample (I) each comprises 20flutes and at the edges a bonded zone. The width of these 15 specimens is 21mm.

The specimens from sample (II) each comprise 4 flutesand at the edges a bonded zone. The width of thesespecimens is 23mm.

The width of each sample (III) specimen is 21mm. 20 For controlled bending of the specimens there is made a very lightweight support arrangement comprising twosupports with 50mm spacing between. This supportarrangement is placed on the table of a letter balance.The bending is effected by means of a cylinder which has a 25 diameter 50mm and starts pressing at the middle of thesupported sample. This cylinder is assembled on a standand can be moved up and down. Corresponding values of thedepression in mm and the resisting force in grams aremeasured and plotted. Up to a certain limit there is a 30 linear dependence, and from the declination of the line andstiffness is calculated as grams force per mm depression.In order to obtain reliable reading for sample (III), 10specimens are laid one on top of the other. The value ofstiffness is determined for this bunch and divided by 10. 35

Results WO 02/102592 PCT/EP02/07264 44

Surprisingly samples (I) and (II) show the samestiffness, namely 1.6 gram per mm, while sample (III) shows0.13 gram per mm, in other words the present invention hasmagnified the stiffness in one direction by a factor of 5 about 12, as measured by this method.

It should have been expected that sample (III) wouldhave shown higher stiffness than sample (I). When this isnot the case, the explanation probably is that the flutesmay have been pressed relatively flat right from the 10 beginning of the depression, although in elastic manner.

In the characterisation of the product and method ofthe invention, it has been emphasised that the wavelengthof the fluted ply A or the pitch on the grooved laminatingroller should be no more that 3mm in order to give the 15 corrugated laminate the character of a flexible film ratherthan a board material. However; in connection with thedescription of the filter material, in which liquid or gaspasses from holes in one ply to displaced holes in theother ply, and on the way passes a filler, it was 20 nevertheless stated that for such purposes the wavelengthmay exceed the 3mm. Similar is true for the describedweatherprotective corrugated laminate, in which there alsoare displaced holes, but usually no filler, and the gravityforce is used to "filter" the rainwater from the passing 25 air.

Furthermore, the making of "first attenuated zones"and optionally also "second attenuated zones" has beenexplained as useful measures for obtaining the"miniflutes", be it in connection with longitudinally or 30 transversely fluted laminates. Since these zones act as"hinges" - see e.g. Fig. 13 - they enable for a giventhickness of ply A a finer wavelength and/or deeper flutingthen it otherwise could be achieved. In the foregoingthere has also been stated other useful effects of the 35 "fist attenuated zones" and the "second attenuated zones",and it is clear that similar advantages can be achieved WO 02/102592 PCT/EP02/07264 45 when the wavelength of the product or the pitch of thegrooved lamination roller exceeds 3mm.

Therefore the product and the making of the "firstattenuated zones" and optionally and "second attenuatedzones" placed as it has been described in the foregoing, isconsidered an invention independently of the wavelength. 5