Laminates of ethylene vinyl acetate polymers and polymers of vinylidene chloride

[B] (11) EXPLANATORY STATEMENT «No. 138337

<td>NORWAY</td><td>(51) Intel? C 08 L 27/08 // B 32 B 27/16,</td>

<td>[NO]</td><td>B 65 D 65/40</td>

<td>BOARD</td><td>(21) Patent Application No. 5004/73</td>

FOR THE INDUSTRIAL (22) Enlisted 28.12.73

<td>DEFENSE</td><td>(23) Running day 29.03.72 (62) Divided from application no. 1104/72</td>

(41) Almen! available from 03.10.72 (44) The application laid out, pamphlet published 08.05.78

<td>(30) Priority requested</td><td>30.03.71, United States, No. 129501</td>

<td>(54) Designation of the invention</td><td>Plastic material, especially for the preparation of films by melt extrusion, based on a mixture of two copolymers of vinylidene chloride.</td>

<td>(71) (73) Applicant / Patenlhaver</td><td>WR GRACE &amp; CO., Grace Plaza, 114 Avenue of the Americas, New York, NY 10036, USA.</td>

<td>(72) Inventor</td><td>HARRI JOUNA BRAX, Spartanburg, JOSEPH FREDERICK PORINCHAK, Spartanburg, ALAN STUART WEINBERG, Greenville, SC, USA.</td>

<td>(74) Agent</td><td>A / S Oslo Patent Office Dr. ing. K. 0. Berg, Oslo.</td>

<td>(56) Cited publications</td><td>Norwegian Patent No. 124727 (B 32 B 27/08) British Patent No. 1222398 (B 32 b 31/30) BRD outside. No. 1262018 (39b-22/06), 1536124 (39b⁴-29/22) US Patent Nos. 3509236 (260-876), 3513226 (260-876) Austrian Patent Nos. 3509236 (260-876), 3513226 (260-876), 3549389 (99-174)</td>

The present invention relates to a composition based on vinylidene chloride polymers, as well as films and laminates containing them, and in particular laminates for use as packaging materials.

For many purposes, it is necessary that packaging materials have a high resistance to mechanical stresses in order to withstand reckless transport and handling. When the goods inside the package are not soft or elastic, mechanical stress can also occur from inside the package during transport and handling. An example of materials which can particularly easily cause such mechanical stresses is bone in meat, ie a piece of meat containing bone. Puncture of packaging material will naturally adversely affect the meat.

Another requirement that is often required for such materials is that they must have low oxygen permeability. A polymeric material which is excellent in this respect is a copolymer of vinylidene chloride and at least one other ethylenically unsaturated monomer, the copolymer containing at least 50% by weight of vinylidene chloride derived units. For vinylidene chloride, the abbreviation VDC is used below.

The polymer is preferably a copolymer of VDC and vinyl chloride. It may contain, for example, 70-85% by weight of VDC-derived units and 30% by weight of vinyl chloride-derived units. Other monomers suitable for copolymerization with VDC are many and well-known and therefore should not be mentioned here.

The above-mentioned VDC copolymer does not exhibit sufficiently high mechanical strength for packaging purposes. Therefore, it is proposed to use a laminate comprising a first layer of high mechanical strength, an intermediate layer of VDC copolymer, and a third layer of high mechanical strength. Such a laminate provides protection against damage from both the inside and the outside of the package. The VDC copolymer layer is referred to as a barrier layer, as it acts to prevent the passage of molecular oxygen.

A practical way to prepare a laminate of the type described above would be to melt-extrude a strong substrate film, cool the film to solidify, then melt-extrude a barrier layer of VDC copolymer, solidify barrier layer, or melt-extrude onto the barrier layer. a layer of a strong material, and then stretch this laminate biaxially.

However, in the art, there has been a problem with melt extrusion of VDC copolymers. It is simple and economical to prepare VDC chloride polymer by emulsion polymerization. It has been found that the emulsion polymerized product, hereinafter referred to as emulsion polymer, is sometimes deposited in the extruder. That is, the polymer does not flow sufficiently in the molten state. The present invention solves this problem.

According to the invention, a plastics material is provided, in particular for the preparation of films by melt extrusion, on the basis of a mixture of two copolymers of vinylidene chloride, each containing at least 50% by weight vinylidene chloride units and up to 50% by weight of units of at least one another, ethylenically unsaturated monomer and the characteristic is that it contains 5-40% by weight of suspension polymerized copolymer and 60-95% by weight of emulsion polymerized copolymer.

While it was known to use a mixture of two different VDC / vinyl chloride copolymers for barrier layers in packaging laminates (U.S. Patent No. 3,549,389, column 15, Item G), it was quite unexpected that the above mixture of emulsion 3 and suspension resins may melt-extruded and molded into a good quality biaxially oriented film. Normally, the suspension ion resin is expected to cause gel formation in the emulsion resin extrusion. In the present case, however, the suspension polymer appears to serve as a stabilizer instead of causing gelling. Without adhering to the following assumptions, it is assumed that the suspension polymer melts more slowly in the extrusion cylinder and serves as a scouring agent during passage through the extruder, thereby preventing the accumulation of the polymer. In other words, the emulsion polymer tends to adhere as it melts, and the suspension polymer acts more like a ball bearing that moves it further. But of course, during the passage through the nozzle, the suspension polymer will also be melted.

It has been found that when the suspension polymer content in the polymer mixture exceeds 20%, the orientation of the film becomes difficult. Only with very careful handling is it possible to use a mixture containing up to 40% suspension polymer. The difficulty of orientation is that crystals are formed more quickly in a suspension polymer film. Accordingly, the suspension polymer acts as a contaminant in the emulsion polymer in the sense that the suspension polymer crystallizes too rapidly with respect to sufficient extraction (film thickness reduction) during the orientation step.

We have found it possible to run with extrusion temperatures that are between the temperatures normally used for emulsion and superpower polymers, i.e. usually from 138 to 171 ° C for the most preferred compositions. It was initially believed that the mixed materials would not be compatible in the molten state due to the different melting rates.

The preferred copolymer for VDC is vinyl chloride, preferably 5 to 40% by weight of the copolymer units derived from vinyl chloride.

\ R "·. Λ'γ * -. ~

The preferred mixing ratio in the plastics material according to the invention is 5-15% suspension polymer and 85-95% emulsion polymer. Preferably, the composition also contains 2-10% by weight, especially 4-6% by weight, of an epoxy resin. The preferred material comprises (a) a VDC / vinyl chloride copolymer with 15-30% vinyl chloride-derived units, and (b) 4-6% epoxy resin, the copolymer being a mixture of 5-15% suspension polymer and 85-95% emulsion polymer. All percentages used refer to weight percent unless otherwise indicated.

The invention is particularly useful for providing barrier layers in a three-layer laminate, namely, a mechanically resistant layer, a barrier layer, and a mechanical resistance layer, and the production of such a laminate will be described hereinafter. However, it will be appreciated that the mixture of the emulsion and suspension polymer may also be used to prepare a laminate of only two layers, one of the strong layers being omitted.

The laminates themselves are the subject of Norwegian patent application No. 1104/72.

For wide use in shrink packaging, the polymeric films give a molecular orientation by stretching.

The process for preparing laminates by melt extrusion and orientation of the laminates (in hose form) is known in principle from British Patent No. 1,222,398.

A preferred class of polymers for one or both of the mechanically resistant layers are copolymers of ethylene and vinyl acetate, containing 5% to 20% by weight of units derived from vinyl acetate. Before orienting such polymers, it is best to cross-link them, e.g. by irradiation.

The preferred polymeric material for the first layer (substrate) of the laminate is the copolymer of ethylene with vinyl acetate. The third layer, which is also resistant to stresses, can be exactly the same as the '' · f- · '· · Aiy. .

used for the substrate.

[38337

Examples of the use of the plastic material according to the invention will now be described with reference to the accompanying drawings, in which:

FIG. 1 is a schematic representation of apparatus for use in a preferred method of producing a laminate;

FIG. 2 is a cross-sectional view of a nozzle head forming part of this apparatus;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 2;

FIG. 4 shows a cross section of a laminate.

Referring to FIG. 1 extrude tube 10 downwardly from the nozzle head 11 which is fed from extruder 9. The extruded tube is 250 - 750 µm thick, preferably 375 - 625 µm. After abrupt cooling by means of water shower from cooling ring 12, the tube is clamped by means of clamping rollers 13, and passed through an irradiation sheath 14 surrounded by protection screen 15, where it is irradiated with electrons from an iron core transformer accelerator 16. Other accelerators such as Van de Graaff or resonance transformer may be used. Other ionizing radiation can also be used. The radiation unit RAD is defined as the amount of irradiation whereby 100 energy (measured as absorbed energy) is consumed per day. grams of irradiated material. MRI is one million (loS RAD.

The irradiation time of copolymer tubes 10 should provide a desired degree of cross-linking. It is preferably irradiated at a dose of 2 - 15 MR.

Pipes 10 are passed through irradiation vault 14 by means of drums 17. After irradiation, pipes 10 pass between clamping rollers 18, followed by a gentle inflation by means of a trapped gas bubble 20. The pipe does not extend noticeably longitudinally, since the rollers 18 are driven at about the same speed as rollers 13. The tube is inflated only to a round hose without substantial orientation.

[38337

This hose 10 passes through vacuum chamber 21 to a laminating or coating nozzle 22, which is placed under chamber 21. A second tubular film 23 is melt extruded from coating nozzle 22, thereby obtaining a coating on the hose 10, thereby forming a two-layer laminate 24. The film 23 is preferably a blocking film. It consists of the plastic material which is the subject of the present invention.

Extruder 25, preferably at a cylinder temperature of 93 to 160 ° C, preferably at 121 to 149 ° C, and the extrusion nozzle is preferably operated at a temperature of from 138 to 171 ° C, preferably from 146 to 157 ° C. The extruded tube is 25 - 125 µm thick, preferably 5 - 100 µm.

Extruder 25 is conventional, e.g. a standard 8.2 cm extruder.

The details of the nozzle 22 will be better illustrated with reference to FIG. 2 and 3. The nozzle 22 is a circular crosshead nozzle with a spacer 26 attached thereto which provides, in a preferred form, an 8.9 cm aperture 27 for the gentle inflation of hose 10. Aperture 27 through which the hose 10 has been formed by means of mandrel 28 attached to the nozzle housing 29. The flow path of the molten coating material 23 is indicated by arrows in FIG. 2 and 3. Vacuum chamber 21 causes a smaller vacuum, e.g. up to 6.4 cm of water column, in the nozzle 22, thereby obtaining an attraction or suction force on the extruded film 23 while still being melted, and against the inflated hose 10, thereby avoiding formation of enclosed blisters in laminate 24. Vacuum chamber 22 may simply consist of a cylindrical housing whose inner diameter fully adapts to the outer diameter of the inflated hose. A vacuum can be created through outlet port 30 and by means of a conventional (not shown) vacuum hose.

The two-layer film 24 passes coating or lamination 32, preferably while still warm. In a discontinuous process, it will be possible to cool the hose 24 before passing the secondary coating nozzle 32, but this will usually also require a re-inflation, as well as a reheating of the hose to obtain the best possible bond between the second layer and the first layer.

A third layer is melt extruded from coating nozzle 32, and is coated on tubing 24, thereby forming a three-layer, tubular laminate 34. This last coating 33 is preferably of the same composition as tubular film 10. The coating process at nozzle 32 is the same as with nozzle 32. 22. The vacuum chamber 36 serves the same function as vacuum chamber 21, and is operated in the same manner, whereby the vacuum is produced through outlet conduit 37. The tubular film 33 is 75 to 375 µm thick, preferably 100 to 300 µm.

The three-layer hose-shaped laminate 34 is quenched using water showers from cooler 39. The water is normally approx. 7 ° C. The clamping rollers 40 compress the three-layer hose which is then wound up on winding drum 41. In a continuous process, alternatively, the film will not roll up on winding drum 41, but will be delivered directly to the next step in the subsequent process (stretching).

As shown in FIG. 1, the hose from a dispensing drum 42, previously winding drum 41, is developed via lead roller 43. Laminate 34 is substantially unstretched when passing over lead roller 43. The film passes from lead roller 43 to a bath 44 containing hot water 45 The preferred bath temperature is 70-100 ° C, and preferably 82-96 ° C. The compressed three-layer hose stays in the bath for at least approx. 5 seconds, preferably approx. 20 seconds. The lead rollers 46 and 47 guide the hose through the bath 45.

After reaching a suitable orientation temperature, bubble 54 is blown into the film and the film is stretched in both directions with a tensile ratio of 1: 1.5 - 1: 6, preferably 1: 2 - 1: 4, which corresponds to a biaxial ( spatial) orientation of respectively. 1: 2.25 - 1:36 and 1: 4 - 1:16. Thickness of layers8

<img file="NO138337B_D0001.tif" />

love is reduced largely in the same relationship. The bubble 54 is maintained between the press rollers 48 and 49. The hose is gradually clamped at the rollers 50, and the laminate passes between the clamp rollers 49, passes guide drum 51 and under guide roll 53, and is wound onto drum 52.

In FIG. 4 shows a cross section of the oriented laminate 34. The first applied layer, which is the inner layer of the hose, is layer 10 having a preferred thickness 25 · - 50 µm. The barrier layer is indicated at 23 and has a preferred thickness of 2.5 to 6 microns. The third layer 33, which is the outer protective layer of the tube, is preferably 6 to 25 µm thick. The laminate has a shrinkage stress of usually 14 - 35 kg / cm, preferably 14 - 28 kg / cm, and a free shrinkage of at least 40%, preferably at least 50% at 96 ° C, and a free shrinkage of at least 20%, preferably at least 30%, at 85 ° C.

According to another method of preparing the laminate, the second and third layers can be co-extruded onto the preformed tube from a co-extrusion nozzle. This will give the same laminate as the final product with a somewhat more difficult method.

The tubular film produced from the tubing provides an excellent protective bag, whereby the layer 10 binds to itself at temperatures between 93 and 177 ° C without changing the shape when welding with a thermal impulse welding apparatus.

The layer 10 also provides excellent strength against the permeation of the bag. The thin barrier layer provides the necessary barrier properties with minimal thickness and cost. The outer layer of unirradiated copolymer provides high resistance at low temperatures and improved tear strength.

The above-mentioned laminate is to be used especially as wrapping material for packages containing freshly cut red meat with bone in it.

The bag made is heat shrink-tightened over the meat.

The preferred wood ply laminate has many advantageous properties, of which good shrinkage can be mentioned at a moderate temperature, an elongation before breaking of at least 50%, preferably 100 125%, an oxygen permeability ratio of not more than 70 cm³/ (Ch²/ 24 h / 1 atm) at 22.8 ° C and 0% relative humidity

2 (ASTM D 1434); and usually not more than 25 cm / (1 m / 24 h / 1 atm) at 22.8 ° C and 0% relative humidity (ASTM

D 1434). In a preferred form, the film has a ball burst impact resistance of at least 25 cm-kg, measured with a Ball Burst Tester No. 13-8 using a standard hemispherical head.

The barrier layer can be made as a self-supporting film. The blends have superior extrusion properties whether they are melt extruded as a coating on an already prepared film, or melt extruded into a self-supporting film. To become self-supporting, the VDC polymer film must be at least 50-75 µm thick when extruded as a tube, using normal extrusion technique. In addition, it has been found that the oriented film made from a material according to the invention has unexpectedly high tear and break resistance values ​​compared to conventional films of VDC / vinyl chloride polymers.

In some cases, it is desirable to use a different polymer in the outer layer of the laminate. This is the layer that should be resistant to mechanical stresses. Examples of such polymers are polypropylene, polyamides and polyesters, as well as copolymers or terpolymers of propylene, polyamides and polyesters. Such coating polymers are well known.

The plastic material of the invention and the various layers of the laminates may comprise the usual additives such as stabilizers, pigments, waxes, deodorants, antisatic agents and anti-blocking agents.

This invention will be further illustrated by the following examples.

'η Q η Ο Ι · ι L ci ο ο ο i

Example 1

Using the method shown schematically in FIG. 1, an ethylene / vinyl acetate copolymer, containing 10% vinyl acetate, with a melt index of approx. 2 and a narrow molecular weight distribution fed to the filling funnel of extruder 9. The extruder is an 8.9 cm extruder and operated at the following temperatures: rear zone 121 ° C, center cylinder 132 ° C, front of cylinder 143 ° C, intermediate 149 ° C and the nozzle 166 ° C.

The screw speed is 37 rpm. and the pressure is 267 kg / cm. The nozzle diameter is 8.9 cm and the circumference of the produced pipe is 20.3 cm. The water temperature from cooling 12 is 7 ° C. The clamping rollers 13 are run at a speed of 10.7 m per second. min and the thickness of the clamped tube is approx. 460 pm.

This tube passes through an irradiation unit, which is depicted in FIG. 1, and run at 500 kilo-electron volts, 20 MA and a speed of 10.7 m per second. Min. Four passes are made and the tube receives a dosage amount of approx. 6 megarad.

The irradiated substrate film is then fed to a coating nozzle 22, where it is coated with a barrier material. The barrier material contains a gently softened mixture of copolymers of VDC and vinyl chloride. The copolymer mixture consists of 10% suspension polymerized and 90% emulsion polymerized copolymer. The emulsion polymerized copolymer consists of approx. 70% units obtained from VDC and 30% units obtained from vinyl chloride, and the suspension polymerized copolymer consists of approx. 80% units obtained from VDC and 20% units obtained from vinyl chloride. Other ingredients in the barrier layer are 5% of an epichlorohydrin / bisphenol A (epoxy resin), and approx.

0.5% of a microcrystalline paraffin wax. The three resins were blended into a Prodex-Henschel mixer of the type exhibiting high velocity and high intensity, and the mixture is fed to the filling funnel of extruder 25, the extruder being a 5 cm Prodex extruder operated with a transverse head nozzle of the same. type shown in FIG. 2 and 3. This extruder is operated at the following temperatures: rear zone 99 ° C, center cylinder 127 ° C, front of cylinder 149 ° C, spacer 141 ° C and nozzle 160 ° C. The screw speed is 34 rpm. my. and the pressure is 2

390 kg / cm. The nozzle diameter is 8.9 cm and the circumference of the tube is 20.3 cm. The top drums 18 are run at a speed of 10.7 m per second. and the coating thickness is approx. 75 pm.

A third layer was then prepared using the same resin as the first layer. The resin is extruded through extruder 35, which runs in the same manner as extruder 9, except for the following temperatures: rear zone 121 ° C, center piece 132 ° C, front of cylinder 193 ° C, intermediate piece 227 ° C and nozzle 232 ° C. Coating nozzle 32 is of the same type as coating nozzle 22. Bottom drums 40 are operated at a speed of 11.0 m per second. and the water from cooling 39 has a temperature of 7 ° C. The thickness of the coating is approx. 150 pm.

The biaxial orientation is carried out after heating in water of approx. 88 ° C, as indicated by 44 in FIG. 1, after which the thus heated hose passes between the clamping rollers, which are run at a speed of 5.8 m per minute. my. to the add-on rollers running at a speed of 21.4 m per min., as well as inflating the 10 cm wide tube while making a film having a width of approx. 41 cm and a film thickness of approx. 61 pm. This tubing film is then rolled onto a bearing roller.

Example II

The above procedure was repeated except that the barrier layer was added with 2% 2-ethylhexyldiphenyl phosphate plasticizer and the epoxy resin content was reduced to 3%.

Example III

The procedure of Example I was repeated except that 5% of an epoxidized soybean oil (which should not be confused with epoxy resin) replaced the 5% epoxy resin.

Example IV

The procedure of Example I was repeated except that 4%

2-ethylhexyldiphenyl phosphate plasticizer and 1% magnesium oxide replaced the 5% epoxy resin.

Example V

The procedure of Example I was repeated except that a mixture consisting of polypropylene having 53.3% by weight isotacticity, 33.3% polybutene-1 and 13.3% of an atactic polypropylene was used in the third layer. The atactic and isotactic polypropylene is first added in equal amount to a Banbury mixer and melt blended for approx. 8 min. at 20 ° C, then extrude to a plate which is divided into pellets. These pellets are mixed with polybutene-1 pellets in a rotating cylinder and this mixture is added to the filling funnel of extruder 35. Extruder 35 is run at the following temperatures: rear zone 196 ° C, middle zone 204 ° C, front zone 232 ° C, spacer204 ° C and nozzle 218 ° C.

Example VI

The mixture used in Example II to form the barrier layer was used except that 4% epoxy resin was used and the content of emulsion polymerized VDC resin was reduced by 1%, after which extruded a self-supporting single layer film under the conditions specified in Example II. A coating of propylene glycol was applied to the interior of the tube to prevent adhesion when squeezed prior to the biaxial orientation. In addition, the water bath was maintained at ca. 38 ° C. The thickness of the extruded film was approx. 125 µm, and the thickness of the biaxially oriented film approx. 19 pm, after a total biaxial orientation distance ratio of approx. 12: 1. The film was found to have unexpectedly high tear and breakthrough strength values ​​compared to conventional oriented films of VDC / vinyl chloride copolymers.

Gasket resistance tests

The following procedure was used. All test bags were codified and conditioned 24 hours at 7-10 ° C. Randomly selected bags were used to pack cut rib meat with bones weighing 11.3 - 13.6 kg. The bags were 41 cm wide and 81 cm deep. The gaskets were evacuated and the bags squeezed, shrunk sealed and dried in air flow. The packages were then placed in boxes in wax-coated corrugated containers, three in one container. The containers were then closed with nylon monofilament tape.

During the fall test, each container will fall from a height of 0.91 m from a moving device. In the transport test, the containers were stored at 3 ° C for 24 hours and then shaken for 7.5 min. at 1 g on a LAB Vibration tester, which should simulate a 200 km road transport.

In both experiments, the gaskets were filled with air and immersed in water to determine leakage.

L38337

<img file="NO138337B_D0002.tif" />

<img file="NO138337B_D0003.tif" />

I ζ Μ CQ

I ω ο Ε- &lt;Ζ -

<td>ω η ω</td>

<td>μ α ζ</td>

<td>Η Μ Μ Η</td>

<td>1 ft Η a</td>

<td>aOBQ</td>

<td>fl fa η &lt;</td>

<td>fl ft ω ¢ 4</td>

<td>&lt;aa ω</td>

<td>a ft ft a</td>

I κ Not W &lt;fl

<img file="NO138337B_D0004.tif" />

<img file="NO138337B_D0005.tif" />

<td></td><td colspan="2">lf)</td>

<td>lf)</td><td> 1 0</td><td>LD</td>

<td></td><td></td><td>n</td>

<img file="NO138337B_D0006.tif" />

'Η? σχ &lt;0

<td>v? o \</td><td>x $ OX</td><td></td><td></td><td></td>

<td>CM</td><td>CM</td><td>o</td><td>in</td><td>k0</td>

<td> 00</td><td>σ)</td><td> 00</td><td>kF</td><td>ro</td>

<td>X? 0^s»</td><td>xo σχ</td><td>so 0^s·</td><td>xp ox</td>

<td>m</td><td>co</td><td>cn</td><td>in</td>

<td>r *</td><td>r&gt;</td><td>queue</td><td>CM</td>

χο σχ ω c&gt;

co CM

<img file="NO138337B_D0007.tif" />

Φ σ »io

M 00 m

<td></td><td> 1</td><td></td><td>Ό</td><td></td><td> 1</td><td>Ό</td><td></td><td> 1</td><td></td><td>Ό</td><td></td>

<td></td><td>X&gt;</td><td> 1</td><td>Φ</td><td></td><td>Ό</td><td>1 Φ</td><td></td><td>Ό</td><td> 1</td><td>φ</td><td></td>

<td></td><td>V</td><td>μ</td><td>g</td><td></td><td>Φ</td><td>μ ε</td><td></td><td>Φ</td><td>M</td><td>ε</td><td></td>

<td></td><td> &gt;</td><td>Φ</td><td></td><td></td><td> &gt;</td><td>φ</td><td></td><td> &gt;</td><td>Φ</td><td></td><td></td>

<td></td><td> 0</td><td> &gt;</td><td>Φ</td><td></td><td> 0</td><td>&gt; φ</td><td></td><td> 0</td><td> &gt;</td><td>φ</td><td></td>

<td></td><td>X</td><td> 0</td><td>tn</td><td></td><td>fl</td><td>0 id</td><td></td><td>fl</td><td> 0</td><td>tn</td><td>Η</td>

<td></td><td></td><td></td><td>r-1</td><td>H</td><td></td><td>rd</td><td>H</td><td></td><td></td><td>rh</td><td>Η</td>

<td></td><td> +&gt;</td><td>Ή</td><td>Φ</td><td></td><td> +&gt;</td><td>• rl Ο)</td><td></td><td> 4-&gt;</td><td>• rl</td><td>Φ</td><td></td>

<td></td><td>&lt;u</td><td></td><td>P</td><td>rh</td><td>Φ</td><td>P</td><td>rh</td><td>Φ</td><td></td><td>P</td><td>rh</td>

<td></td><td>X</td><td>O '</td><td>g</td><td>Φ</td><td>fl</td><td>Oi E</td><td>Φ</td><td>fl</td><td>cn</td><td>g</td><td>φ</td>

<td></td><td>μ</td><td>• rl</td><td>Ψ</td><td>ft</td><td>M</td><td>• rl Φ</td><td>ft</td><td>μ</td><td>r |</td><td> 5)</td><td> &amp;</td>

<td></td><td>• rl</td><td>r-1</td><td>X</td><td></td><td>• rl</td><td>rH 4-J</td><td>ε</td><td>rl</td><td>r-1</td><td>4J</td><td>ε</td>

<td>few</td><td> &gt;</td><td>tu</td><td>tn</td><td>Φ</td><td> &gt;</td><td>Φ row</td><td>φ</td><td> &gt;</td><td>Φ</td><td>red Ca</td><td>φ</td>

<td>tn</td><td>r M</td><td>fl</td><td>tn</td><td>tn</td><td>rh</td><td>* 4 Μ</td><td>tn</td><td>rh</td><td>fl</td><td>red Ca</td><td>tn</td>

<td>o</td><td>• rl</td><td> &lt;0</td><td colspan="2">C fl</td><td>• r |</td><td colspan="2">(Ο β fl</td><td>• rl</td><td>nJ</td><td colspan="2">β fl</td>

<td>ft</td><td>Eh</td><td>ID</td><td>Φ</td><td>tu</td><td>Eh</td><td>tn φ</td><td>Φ</td><td>Eh</td><td>m</td><td>φ</td><td>φ</td>

i, i

<td></td><td></td><td>X5</td>

<td></td><td>• rl</td><td>• rl</td>

<td></td><td>in</td><td>μ</td>

<td></td><td> 0 ,</td><td> 0</td>

<td>Ό</td><td>rH * 5)</td><td>X5 η ra</td>

<td>μ</td><td>fl</td><td>μ fl</td>

<td>(Β</td><td>rd μ</td><td>05 η μ</td>

<td>Ό</td><td>ft Φ</td><td>Xi ft Φ</td>

<td>β</td><td>β ε</td><td>g β ε</td>

<td> 05</td><td>• reef £</td><td>05 -l ft</td>

<td>X</td><td>&gt; H</td><td>-P&gt; H</td>

<td>tn</td><td>X 0.</td><td>tn \ 0</td>

<td></td><td>υ a</td><td>υ a</td>

<td> &gt;</td><td>Q 0</td><td>&gt; Q 0</td>

<td colspan="2">&lt;&gt; 'fl-</td><td>et al</td>