Untitled record

(54) Name: Methods of making a segmentally thermally bonded fabric from a fibrous web

The present invention relates to a method of producing a segmentally thermally bonded fabric of a fibrous web with excellent draping and other good properties.

Many methods for the production of bonded sheet fabrics have been proposed, which means that binder is added to a fibrous web or, if the sheet contains thermoplastic materials, adds heat. A particular way is to apply heat under pressure to create bonds on restricted portions of the surface of the web when the fibrous web is passed through the roll nip between two calender rolls, at least one of which is heated and on the roll surface has a pattern of pressure surfaces and depressions. In the places where the web is pressed between the roll surfaces, strong or primary bonds are formed as separate segments in the fiber web, thus forming a segment-bound fabric. Of the roller pairs used as calender rolls, either one roller or both can have patterns of pressure surfaces and depressions, and in the first case the other roller is a smooth unpainted roller. In the first case, the roll, especially when directly heated, tends to cause some less severe bonding over the remaining fabric surface, where it is not pressed into the nip between the rollers. This secondary secondary bonding on one side of the fabric tends to make the fabric stiffer. In the latter case, when both rollers are patterned, the pattern may take the form of circumferential rings or spirals or longitudinal strips which cannot intervene. Calendering with such rolls does not provide secondary bonding over the entire fabric surface but only at the places where one

7504770-4 or other side, of the fabric turned at a printing surface. However, with this limitation of the secondary bonds, the disadvantage comes from the fact that only a small number of patterns of primary bonds can be achieved at the pressure points of the surfaces during the rotation of the rollers.

By calendering a fibrous web between two rollers, each of which has a printing pattern and which corresponds sufficiently closely to one another, one could achieve any desired pattern with both primary and secondary bonds, but maintaining such a careful fit is not practicable, or at best, very costly, when using rolls that are large enough to make wide fabrics and have pressure surfaces that are small enough for the fabrics to have advantageous properties and attractive appearance.

The highest possible physical and visual properties of the bonded fabric are in direct or inverse proportion to the number of bonds, and the properties thus obtained are the result of a compromise. Heretofore, fabrics have not had the best combination of properties for all purposes, in particular this applies to clothing where you want properties that closely resemble conventional woven and knitted fabrics and which have appealing appearance. Known fabrics of this type usually have a geometric regular pattern of primary bonds, which is not aesthetically pleasing.

For example, in US Patent No. 3,542,634 discloses a nonwoven fabric in which the fibers are bonded together in a rhombic pattern by rolling between two rolls, at least one of which is not smooth without a groove pattern row.

It is an object of the present invention to provide a process for producing segmented bond fabrics of irregular or random bond size and shape, which is such that repetition of the pattern is impossible or difficult to detect, the pattern being visually essentially independent of mechanical changes in a calender roll used to depress the segment bindings. It is an advantage of the method that control of the properties of the bonded fabric and the minimization of secondary bonding are made possible with a high degree of flexibility in the regulation.

A new aesthetic appeal in segment-bound fabric and a new method of producing the same have now been worked out, thus overcoming the various problems of excessive secondary bonding, pattern limitation, dull appearance and mechanical engineering difficulties.

The invention thus relates to a method of producing a segmentally thermally bonded fabric by having a fibrous web containing at least one

7504770-4 part distributed therein, thermally bonding material, is passed through the nip between cooperating calender rolls, at least one of which is heated and which rolls have different pattern surfaces, characterized in that a certain irregularity in the bonded pattern is achieved by the surface pattern of the one roller consists of printing surfaces which are continuous and the surface pattern of the other roller consists of printing surfaces which are isolated projections; wherein the center surface of the projections that are simultaneously in the roll nip is located at different distances from the longitudinal axis of the nearest continuous pressure surface, so that pressure surfaces which face each other in the nip overlap to different extents and form bonds of different sizes and shapes.

According to a preferred embodiment of the invention, the insulated projections are arranged in such a way that they form in echelong arranged, overlapping or overlapping rows of adjacent projections, the rows having a direction which deviates from the roll line's nip line. This way of arranging the projections serves to break the regularity of the pattern in a different direction on the fabric surface and, in cases where the printing surfaces are annular or helical, prevent any possibility of sludge as the rollers rotate. When the continuous pressure surfaces are in the form of longitudinal strips, it is not possible to remove the sludge phenomenon, which can only be reduced by reducing the distance between the strips and / or increasing the rolling diameter.

The term continuous printing surface here refers to a printing surface which extends around substantially the entire periphery or along substantially the entire length of the roll. Such pressure surfaces can e.g. take the form of circular or elliptical rings, spirals or longitudinal bands.

The interaction between pressure surfaces on one calender roll and opposite pressure surfaces on the other roll in the pair of rolls is described here, for simplicity's sake, with respect to the roll line's new line. This is of course not a static state as this line is continuously moved during the rotation of the rollers. When the rollers have a diameter of a few centimeters to 30 cm or more, the nip pressure will at any moment be applied over a limited circumferential width of the nip, including several pressure faces in the circumferential direction. In calendering, the interaction between opposing pressure surfaces can be more complicated than that described here for the static situation and a new line without a defined width. Shifts in the relative fit between the rollers due to clearance and other mechanical variations in calender mechanism 7504770-A but result in an increase in overlapping surfaces between opposite pairs and a decrease in overlapping surfaces between other opposing pairs. The changes in the binding pattern caused by these variations will pass substantially unnoticed due to the inherent pattern variation of a product according to the invention.

According to another preferred embodiment of the invention, the distances from the centers of the projections to the longitudinal axis of the continuous pressure surfaces vary from zero to half the width of the gap between adjacent continuous pressure surfaces, whereby the rollers cannot intervene regardless of their mutual fit as a whole. and whereby the pattern of primary bonds in a fabric will consist of partially large bonds resulting from total surface contact between certain printing surfaces and partially very small bonds resulting from only contact between other surfaces. Such a primarily bonded pattern provides a visually very interesting fabric texture, which is visibly not substantially altered by variations in the relative fit between the rollers ·

According to the invention, suitable fiber webs may be cut fibers, continuous fibers or mixtures thereof. Floors of cut fibers are usually produced by carding a cut fiber material, and webs of continuous fibers can be produced by a conventional method whereby an air jet is used to transport the fibers from any source and spread them in a random pattern on a perforated conveyor belt. An electrostatic charge can be applied to the fibers to increase their dispersion before being applied to the conveyor belt. Floral of cut fibers can be made from conventionally wrinkled fibers and sufficiently bonded fabrics can be obtained therefrom. However, it has been found that a bonded product with improved physical properties, especially with respect to tensile and tear strength, can be produced by the method of the invention of a web consisting of non-crimped fibers. The absence of ripples on the cut fibers adversely affects the homogeneity of a web produced only by carding, but this inconvenience can be reduced or overcome by applying the fibers prior to carding to a coating which increases friction between the fibers, e.g., a lubricating mixture containing solid particles. substance such as silicic acid. Alternatively, the web may be produced by carding followed by a propagation by means of air, or by direct propagation by means of air. A suitable machine for propagation using air is a Rando-Webber, manufactured by Curlator Corporation, in which the fibers are twice distributed in an air stream and laid as one. flores on a perforated conveyor belt that sets them apart

7504770-4 air. The final web is essentially anisotropic unlike a carded web in which the fibers exhibit a predominantly orientation in the machine direction.

The thermoplastic material contained in a web according to the present invention may consist of particles distributed in the fibrous web, or it may be in the form of distributed fibers having a lower softening or melting point than the other fibers in the web or, thirdly, the web may be completely or partially consist of two-component fibers in which one component is at least present on the fiber surface and has a lower softening or melting point than the other component. The fibers in a web may be natural or artificial fibers or synthetic fibers spun from linear organic polymeric materials, such as, for example, in the molten state, spinnable polyesters and polyamides as well as copolymers of these types of organic linear polymers.

In the method of the present invention, both of the patterned rollers may be rigid or one or both may have some natural flexibility or limited flexibility to accommodate and equalize minor pressure differentials along the roll, in which case a rigid supporting roll which opposes the flexible roll is required.

The isolated projections forming the printing pattern on one roller of a pair of calender rolls can be formed in different ways, for example, in the form of small points with flat or slightly angular top surfaces and with square, rectangular, circular or otherwise shaped cross sections, whereby at the top has a cross-sectional area of ​​a few tenths or a hundredths frame. The projections can be formed on the roller surface by suitable machining or by etching. The continuous printing surfaces, which can have a width of 0.1-1 mm, are most easily produced by machining in a lathe or milling machine or by grinding. If the gaps between the printing surfaces are different on the two rollers, the varying relative fit between opposing printing surfaces can be achieved by appropriate choice of the size of the insulated projections and the pattern formed by them. If the gaps between the printing surfaces are equal, an oblique position of one pattern relative to the other at a small angle is the easiest way to achieve the divergent relative fit between opposing printing surfaces. This method also has the advantage that the pattern of primary bonds applied to a fabric can be radically changed simply by moving one pattern at a different oblique angle.

7504770-4 ^r By varying the relative fit of the invention between opposing printing surfaces, the fixed or regular specimen of segmental bonding, which is characteristic of prior methods and in which the bonds also have substantially regular size and shape, can be replaced by patterns of bonded surfaces and, above all, of primary bonds without regular bonding. shape and surface, wherein the regular pattern from the printing surfaces of each calender roll is broken up and cannot be discerned in the complete pattern of the bonded fabric produced. As a result, the central portions of the bonded surfaces adjacent to any imaginary straight line across the fabric will vary in distance from this line. Hereby, the variations in the relative fit between opposing surfaces of the rollers are adapted due to clearance in the gear or other mechanical irregularities during rotation, as the resulting bonds are obscured by the final, irregularly bound pattern, and a fabric having a pleasant and attractive appearance is obtained. good feel and good draping properties.

A fabric bonded according to the invention has on both sides patterns of strongly bonded segments, formed where opposing printing surfaces cover each other in the nip, and patterns of comparatively weakly bonded surfaces where the web has come into contact with a heated printing surface on only one roller and the heat has been sufficiently high to achieve a certain fusion between adjacent fiber segments. Such weak bonds are difficult to detect to the naked eye but can easily be seen in a microscope. For simplicity, the heavily bonded segments are referred to as primary bonds and the weakly bonded surfaces are secondary bonds. In addition, there are surfaces in the fabric that are essentially unbound and have not been in contact with a printing surface on any of the rollers. The visual difference between the three different types of surfaces on a bonded fabric can be increased by superficial metallization of the fabric surface.

In order to obtain the best possible properties, especially with respect to the feel and the draping properties, the fabrics after bonding may need light mechanical machining, such as the bending and curvature that occurs when washing or dyeing the fabric. Fabrics made from blends of various fibers, especially blends of two-component and single-component fibers of synthetic polyamides or polyesters, have an excellent feeling immediately after bonding and feel no slight mechanical treatment, and the manufacture of such fabrics can therefore be simplified.

The invention is further illustrated by means of the attached pictures, wherein

Fig. 1 shows a pattern of pressure surfaces on a cage roller, which pattern consists of parallelogram-like insulated projections arranged in a dense echelon Fig. 2 shows a pattern of continuous pressure surfaces on a cage roller, which consists of an evenly spaced rotor around the peripheral rings; 3 shows a pattern of printing surfaces on a calender roll applied by etching, Fig. 4 shows one side of a bonded fabric according to the invention wherein the pattern of primary bonds is formed during passage between a pair of calender rolls, one according to Fig. 1 and the other according to Fig. 2, and one pattern is inclined at an angle of 2 ° with respect to second, Fig. 5 shows a fabric bonded between rollers of Fig. 4, but with an oblique angle of 8 °; Fig. 6 shows one surface of a fabric bonded during passage between a roll of Fig. 2 and a roll of Fig. 3; which patterns are individually applied axially around the periphery of the respective roll, and Fig. 7 shows one side of a fabric bonded between rolls in the same manner as in Fig. 6 but at an angle of 5 °.

In these images, white surfaces in Figures 1-3 represent printing surfaces and in Figures 4-7 represent primary bonds. All images are essentially full scale.

From the primarily bonded patterns shown in Figs. 4 and 5, the tighter breaking of the line pattern in Fig. 2 is evident when a larger oblique angle is used. Figures 4 and 5 also show the varying bonding surfaces along some imaginary nip line (where the machine direction is downward on the paper), achieved by the varying relative fit between opposing pairs of printing surfaces.

Fig. 6 shows a pattern of primary bonds of varying shape on the surfaces, produced by the choice of the respective bonded patterns, but without any oblique position.

Fig. 7 shows the effect when two selected patterns, such as those in Fig. 6, are aligned with one another and at the same time tilted with respect to the other at a small angle.

The invention is further illustrated below by way of example, and the ripple ratio has thereby been calculated as follows;

widespread length - rippled length rippled length

7504770-4 ^r The drape coefficient was measured by the method of Cusick, j. Text. Dep. 1968, 59, T253.

Certain properties were measured in two directions, the longitudinal or machine direction and the transverse or transverse direction, and these are designated as MD and CD respectively in the following examples.

Example 1

As melted spun, fresh fibers, which were made up of two-component fibers with a casing around a core and in which the casing consisted of nylon 6 and the core of nylon 66 in proportions 35:65 parts by weight, were partially pulled and distributed by means of an air ejector on a perforated conveyor belt , which air ejector moved laterally across the conveyor belt to form a randomly laid web having a weight of 70 g / m, in which the fibers had a toughness of 2.5 g / decitex, a crime elongation of 120% and a decitex of 4.

At a rate of 7.5 m / min, the web was then treated with heat under pressure in the nip between 1 m wide calender rolls, both heated to a temperature of 200 ° C and which were combined with a nip pressure of 20 kg / cm, with both rollers had patterns of printing surfaces, one roller continuous and the other roller discontinuous, with depressions in between. The pattern of discontinuous pressure surfaces on one roller was that shown in Fig. 3, with the top surfaces of each printing surface having the center 2.64x0.90 mm and at the top axially and longitudinally separated by a space of 1.28 mm, and the printing surfaces had a height of 1.0 mm. This roller had a diameter of 195 mm. The pattern of continuous printing surfaces was in the form of strips, 0.38 mm wide at the surface and 0.73 mm high and spaced at a distance of 1.42 mm at the surface. The latter roller also had some flexibility so that it could equalize the nip pressure produced by a steel pipe having a wall thickness of 13 mm and an outer diameter of 127 mm. The pattern of discontinuous pressure surfaces on the upper roller was applied axially and around the periphery, and the belts on the lower roller were axially parallel.

The conditions of the roll nip caused the component of the casing around the fibers to adhere, while the component of the core remained unaffected, and upon cooling, bonds between adjacent fibers in a pattern of primary bonds were reminiscent of that in Figure 6. The product had an attractive appearance, excellent draping. washing and the properties given below before and after a simple wash in water at 60 ° C:

7504770-4

<td>Property</td><td>untreated</td><td>After washing</td>

<td>Weight, g / m²</td><td> 73</td><td> 84</td>

<td>Draping coefficient,%</td><td> 73</td><td> 27</td>

<td rowspan="2">Fracture strength, kg / g / cm</td><td>MD 356</td><td> 286</td>

<td>CD 411</td><td> 386</td>

<td>Breakout Increase,%</td><td>MD 61</td><td> 48</td>

<td></td><td>CD 75</td><td> 74</td>

<td rowspan="2">Tear strength, g / g / m²</td><td>MD 36</td><td> 31</td>

<td>CD 29</td><td> 27</td>

MD measured in the machine direction

CD measured across the machine direction

Example 2

Two-component polyester fibers with a core of poly (ethylene terephthalate) having an internal viscosity (IV) of 0.65, IV being measured at 25 ° C in a solution of o-chlorophenol, and a shell of a 15 mole% ethylene isophthalate / terephthalate copolyester (IV 0.55), which components were in a 2: 1 core to casing ratio, spun in molten state, drawn to a decitex of 3.3, mechanically crimped into a chamber crush box to 3.5 ripples / cm with a ripple ratio of 34% and cut into lengths of 50 mm. The thus prepared cut fibers were mixed with the same amount of cut poly (ethylene terephthalate) fibers with IV equal to 0.63, 3.3 deticex, 50 mm length, 3.5 ripples / cm and a ripple ratio of 34%, and formed into a webs weighing 142 g / m by means of a conventional air-conditioning device (Rando-Webber manufactured by Curlator Corporation). The floret was consolidated by light needling with 36 gauge 5 bar needles arranged in a random pattern on a needle board, the needles penetrating the floor to a depth of 4 mm. The floret was allowed to pass through the needle board at a rate of approximately 46 needles per cm.

The floret was then calendered at a rate of 3 m / min between patterned rolls, the same as in Example 1, both heated to a temperature of 195 ° C and which were combined to a nip pressure of 31 kg / cm.

The segment-bound fabric had the following properties in its untreated condition:

<td>Weight, g / m²</td><td></td><td> 142</td>

<td>Draping shoe efficiency,%</td><td></td><td> 79</td>

<td rowspan="2">Fracture strength, g / g / cm</td><td>MD</td><td> 60</td>

<td>CD</td><td> 138</td>

<td>Breakout Increase,%</td><td>MD</td><td> 19</td>

<td></td><td>CD</td><td> 62</td>

<td>Tear strength, g / g / m²</td><td>MD</td><td> 12</td>

<td></td><td>CD</td><td> 11</td>

Example 3

A lightly consolidated web weighing 133 g / m was prepared as described in Example 2 from a mixture of the same amounts of wool and cut two-component polyamide having the composition of Example 1 having a decitex of 3.3, a length of 100 mm, 5.3 ripples per cm and a ripple ratio of 20%.

The floret was calendered at a rate of 3 r / rain between patterned rollers, which were heated to a temperature of 217 ° C and which were combined to a nip pressure of 31 kg / cm. One roll had the pattern of Fig. 3 with insulated print surfaces as described in Example 1, and the other roll had a spiral thread (left threaded) of 5.2 threads per cm, which was essentially square in shape and a width of the print surface of 0.32 mm. The latter roll consisted of a flexible style tube with 127 mm outer and 112.5 mm inner diameter.

The segmented fabric manufactured in segment had the following properties in an untreated state:

Weight, g / ra² 133

Draping coefficient,% 77

Fracture strength, g / g / cm MD 132

CD 67

Break elongation,% MD 27

CD 54

Tear strength, g / g / m² MD 1.5

CD 7.5

Example 4

A lightly consolidated web weighing 122 g / m 2 was prepared as described in Example 2 of nylon 6 cut fibers having a decitex of 6.7, a length of 72.5 mm, 11.6 ripples / cm and a ripple ratio of 24 %.

The floret was then calendered at a rate of 3 m / min between patterned rolls, both of which were heated to a temperature of 200 ° C and pooled at a nip pressure of 31 kg / cm. The lower flexible roll had a pattern of strip according to Example 1, and the upper roll having a diameter of 195 mm had a pattern according to Fig. 1 of dense echelong arranged parallelogram-shaped printing surfaces of the size 3.22x0.84 in the peripheral respectively. the axial direction at a distance of 0.58 mm and 0.71 mm in the peripheral and axial directions, respectively, and the longer dimension of the pressure surfaces extended substantially perpendicular to the roller shaft.

The fabric bound in segment-bound fabric had the following properties in the untreated to:

<td>Weight, g / m</td><td></td><td> 122</td>

<td>Draping coefficient,%</td><td></td><td> 73</td>

<td>Fracture strength, g / g / cm</td><td>MD</td><td> 93</td>

<td></td><td>CD</td><td> 103</td>

<td>Break elongation,%</td><td>MD</td><td> 16</td>

<td></td><td>CD</td><td> 34</td>

<td>Tear strength, g / g / m²</td><td>MD</td><td> 5,2</td>

<td></td><td>CD</td><td> 3,7</td>

Example 5

A lightly consolidated web weighing 129 g / m was prepared as described in Example 2 from a mixture of cut nylon 6 and nylon 66 fibers in equal weight amounts. The fibers of nylon 6 were of the kind described in Example 4, and the fibers of nylon 66 had a decile of 3.3, a length of 51 mm, 5 ripples per cm and a ripple ratio of 18%.

The floret was calendered at a speed of 3 m / min between the patterns of the rollers, the same as in Example 4 and at the same rolling temperature and nip pressure.

The fabric-bound segmented fabric had the following properties in its untreated condition:

<td>Weight, g / m²</td><td></td><td> 129</td>

<td>Draping coefficient,%</td><td></td><td> 79</td>

<td>Fracture strength, g / g / cm</td><td>MD</td><td> 151</td>

<td></td><td>CD</td><td> 211</td>

<td>Break elongation,%</td><td>MD</td><td> 29</td>

<td></td><td>CD</td><td> 34</td>

<td>Tear strength, g / g / m²</td><td>MD</td><td> 12,9</td>

<td></td><td>CD</td><td> 6,9</td>

In the aforementioned experiments, rolls having a length of 1 m are used, but rolls of different length and diameter or two rigid rolls can also be used in the method according to the invention.

The percentage of the surface of the fabric occupied by primary bonds, calculated as the product of the percentage of each roll surface occupied by printing surfaces, is given below, as well as the ratio of the printing surfaces of the rollers.

7504770-4

<td>Example</td><td>Pressure surfaces,%</td><td>Primary bond</td><td>Relationship between pressure surfaces</td>

<td> 1</td><td>25 and 21</td><td> 5,3</td><td> 1,2</td>

<td> 2</td><td>25 and 21</td><td> 5,3</td><td> 1,2</td>

<td> 3</td><td>25 and 18</td><td> 4,5</td><td> 1,4</td>

<td> 4</td><td>46 and 21</td><td> 9,7</td><td> 2,2</td>

<td> 5</td><td>46 and 21</td><td> 9,7</td><td> 2,2</td>

Large bonding areas tend to give stiffer fabrics and small bonding areas tend to give less coherent fabrics. Furthermore, the same primary bonding surface can be provided with rollers having the same printing surfaces or with rollers having different printing surfaces, which provide greater secondary bonding on one side, which increases the rigidity of the fabric, and at the same time provides less secondary bonding on the other side, which decreases the fabric's resistance against abrasion and pitting.

Therefore, it is preferred to use equally large printing surfaces so that fabrics with balanced bonding are obtained on the two sides. However, strict observance of a balanced bond causes an unnecessary restriction on the pattern selection and is not required. Different uses of the fabrics also give different working conditions in fabric manufacture. It is generally advantageous to use pairs of rollers for which the product of the printing surfaces is between 2 and 20%, and more preferably between 5 and 12%, and for which the ratio of the printing surfaces is less than 5-1.

In the method described herein, calender rolls have been utilized to provide patterns of bonded surfaces on a fibrous web. However, the more impractical pressing of a web into sections between plates of a press can also be used without departing from the idea of ​​the invention, but such alternatives are usually slow and cumbersome to carry out.

7504770-4

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