JP2974243B2 - Resin composition and multilayer structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an ethylene-vinyl alcohol copolymer which is free from pinholes, cracks, local thickness unevenness, etc., and has excellent transparency and gas barrier properties during heat stretching, especially high-speed heating stretching. Combined (hereinafter EVO)
H)) a resin composition, and a multilayer structure using the same, particularly, a heat-stretched, and further, a high-speed, heat-stretched multilayer structure.

[0002]

2. Description of the Related Art Today, EVOH is used for packaging films for foods and the like, particularly for foods requiring a barrier property against oxygen, odors, flavors, and the like, and other products requiring aroma retention. Has been confirmed to be effective. EVOH is formed by laminating a thermoplastic resin layer such as polyethylene, polypropylene, polystyrene, polyester, polyamide, and polyvinyl chloride, and various adhesive resin layers represented by ionomer, ethylene-vinyl acetate copolymer, and the like. Used in the form of a multilayer structure.

When a multilayer structure (film, sheet, barison, etc.) manufactured by various methods is subjected to secondary processing into a container or the like, particularly when stretch molding is performed at a temperature lower than the melting point of EVOH, small voids and cracks are formed in the EVOH layer. As a result, local uneven wall thickness occurs frequently, and as a result, the oxygen barrier property of the molded container is greatly deteriorated. In particular, recently, appearance and transparency have tended to be regarded as important, and they have been in a situation where they cannot be used as containers for foods and the like.

Therefore, conventionally, EVO generated at the time of heating and stretching is used.
To prevent pinholes and cracks in the H layer,
Addition of various plasticizers to the VOH layer (JP-A-53-8806)
7, JP-A-59-20345), blends of polyamide resins (JP-A-52-141785, JP-A-58-36)
412) has been studied, but it has been found that in any case, the following points are not satisfactory. That is, in the addition system of various plasticizers, it is necessary to add 10 to 20 parts by weight of the plasticizer with respect to 100 parts by weight of the EVOH in order to sufficiently improve the heat-stretching property. There are many problems such as lowering and lowering of the interlayer adhesion strength with the EVOH layer, and it cannot be used.

[0005] On the other hand, a polyamide resin-added system cannot withstand use because of its high chemical reactivity with EVOH, the presence of a large number of gel-like substances in a molded product, and marked coloring. In addition, in the addition system of the polyamide resin having relatively little gel coloring, an apparently good container is obtained, probably because the compatibility between the EVOH and the polyamide is not sufficient. Probably because of the presence of pinholes, the measured values of gas barrier properties varied widely, and the gas barrier container was not reliable and could not be used. However, recently, attempts have been made to blend EVOH with an amorphous gas-barrier nylon such as hexamethylenediamine-iso / terephthalamide to prevent pinholes and cracks in the EVOH layer generated during heating and stretching. However, because of the presence of minute pinholes, the transparency and reliability of the gas barrier container are not reliable, and they cannot be used.

[0006] Therefore, the transparency, high gas barrier properties, and reliability (variation) as a gas barrier container are good. That is, at the time of heating and high-speed stretching, minute pinholes, cracks, and unevenness are formed in the EVOH layer. No meat, etc.
Development of EVOH is one of the important issues.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides an EVOH without deteriorating the excellent gas barrier properties of EVOH.
H E generated when secondary processing of a multilayer structure into a container or the like
An EVOH resin composition that prevents the occurrence of cracks, pinholes, local thickness deviations, and the like in a VOH layer and has transparency, high gas barrier properties, and highly reliable gas barrier properties, and a multilayer structure using the same. In particular, the present invention provides a heat-stretched multilayer structure.

[0008]

The object of the present invention is to provide an EVOH (A) having two or more endothermic peaks in DSC measurement and having an ethylene content of 20 to 60 mol% and a weight of 60 to 95% by weight.
The problem is solved by using an EVOH composition consisting of 40 to 5% by weight of the amorphous polyamide (B).

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present inventors blended various plasticizers and polymers with EVOH to prepare various multilayer sheets comprising an adhesive resin and a thermoplastic resin.
A cup and a bottle were obtained by a stretching operation, and the appearance and gas barrier properties of the container were measured. As a result, EVO
H (A) 60 to 95% by weight of amorphous polyamide (B)
(Hexamethylenediamine-isophthalic acid / terephthalic acid polycondensate, etc.) When a multilayer sheet using a resin composition blended with 40 to 5% by weight is heated and stretched at high speed,
At first glance, it seemed that a good molded product free from the occurrence of cracks, pinholes, and local thickness deviation of the EVOH layer was obtained.

However, low temperature thermoforming (12
(0 to 130 ° C.) The transparency of the container was poor, and local whitening and turbidity were conspicuous, and the measured values of gas barrier properties varied greatly, which was a problem in use. Therefore,
The present inventors have conducted intensive studies, and as a result, surprisingly, EVOH
In DSC measurement, it has two or more endothermic peaks , an ethylene content of 20 to 60 mol%, and a vinylsilane compound content of 0.0001 to 0.
When 5 mol% of EVOH (A) is used, not only the moldability is good, but also the transparency and gas barrier properties are hardly deteriorated. The present inventors have found that a container having a high gas barrier property can be obtained, and have completed the present invention.

In the present invention, EVOH (A) is DS
In the C measurement, it has two or more endothermic peaks, an ethylene content of 20 to 60 mol%, preferably 25 to 50 mol%, and if necessary, a silane content of 0.0001 to
The EVOH is 0.5 mol%, preferably 0.001 to 0.2 mol%, and has a saponification degree of 90% or more, preferably 95% or more. Here, DSC measurement (scanning heating rate 10 ° C.)
/ Min. )), Having two or more endothermic peaks does not necessarily mean that two or more independent endothermic peaks are present, and the peaks may be overlapped shoulder-shaped or hump-shaped peaks. It is effective that the difference from the peak temperature is 5 ° C. or more, preferably 7 ° C. or more. Note that the peak at which the endothermic peak temperature shifts, develops, or disappears due to heat treatment or the like does not correspond to the endothermic peak referred to herein.

An EV having two or more endothermic peaks
OH (A) is defined as two or more EVOH compositions having different ethylene contents, two or more EVOH compositions having the same ethylene content but different saponification degrees, or two or more EVOH compositions having different saponification degrees. More than kind of EVOH
Compositions. As a method of obtaining an EVOH composition in which two or more EVOHs are blended, a method of blending two or more EVOHs having different ethylene contents and / or saponification degrees in a solution state or a molten state, or a method of blending an ethylene content Of ethylene-vinyl acetate copolymers obtained by blending two or more kinds of ethylene-vinyl acetate copolymers having different or different polymerization conditions, and saponifying two or more kinds of ethylene-vinyl acetate copolymers having different ethylene contents or / and saponification degrees. EVO including EVOH
There is a method of obtaining an H composition, and the like.

The difference in ethylene content {(maximum ethylene content) − (minimum ethylene content)} is 5 to 40 mol%, preferably 10 to 35 mol%. The difference in the degree of saponification is 1 to 10%, preferably 2 to 8%. It is more preferable that the EVOH component having a high ethylene content has a low degree of saponification, and the EVOH component having a high ethylene content is 5 to 40% by weight, preferably 10 to 30% by weight, based on the total EVOH. It is.

The ethylene content of two or more different EVOHs is 20 to 60 mol%, preferably 25 to 5 mol%.
It is selected from the range of 0 mol%. If the ethylene content is less than 20 mol%, the melt moldability is poor, and if it is 60 mol% or more, the gas barrier properties are insufficient. Two different types of EVOH
Is selected from the range of 90% or more.
If the degree of saponification is less than 90%, the gas barrier properties and the thermal stability deteriorate.

The EVOH (A) is preferably modified with a vinylsilane compound. The preferred content of the vinylsilane compound is 0.0001 to 0.5 mol%. Here, as the vinylsilane-based compound, compounds represented by the following (I), (II) and (III) are preferable.

[0016]

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[0017]

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[0018]

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[Where n is from 0 to 1 and m is from 0 to
2, R ¹ is a lower alkyl group, an aryl group, or a lower alkyl group having an allyl group, and R ² is a carbon atom having 1 carbon atom.
To 40 alkoxyl groups, and the alkoxyl group may have a substituent containing oxygen. R ³ is hydrogen or methyl, R ⁴ is a divalent organic residue hydrogen atom or a lower alkyl group, R ⁵ is the alkyl group or a chain of carbon atoms bonded to each other to oxygen or nitrogen, R ⁶
Is hydrogen, halogen, a lower alkyl group, an allyl group, or a lower alkyl group having an allyl group; R ⁷ is an alkoxyl group or an acyloxyl group (where the alkoxyl group or the acyloxyl group has a substituent containing oxygen or nitrogen; R ⁸ is hydrogen, halogen, a lower alkyl group, an allyl group or a lower alkyl group having an allyl group, and R ⁹ is a lower alkyl group.] More specifically, R ¹ has 1 to ¹ carbon atoms. 5 lower alkyl groups, allyl groups having 6 to 18 carbon atoms, or lower allyl groups having 1 to 5 carbon atoms having an allyl group having 6 to 18 carbon atoms, R ⁴ is a hydrogen atom or a lower alkyl having 1 to 5 carbon atoms represents a group, R ⁵ represents a divalent organic residue is an alkyl group or a chain of carbon atoms of 1 to 5 carbon atoms bonded to each other to oxygen or nitrogen, R ⁶ is hydrogen, halo Emissions, lower alkyl group of 1 to 5 carbon atoms, an allyl group having 6 to 18 carbon atoms or carbon atoms, 6-1
R ⁷ represents an alkoxyl group or an acyloxyl group (wherein the alkoxyl group or the acyloxyl group may have a substituent containing oxygen or nitrogen; ), R ⁸
Represents hydrogen, halogen, a lower alkyl group having 1 to 5 carbon atoms, an allyl group having 6 to 18 carbon atoms, or a lower alkyl group having 1 to 5 carbon atoms having an allyl group having 6 to 18 carbon atoms;
⁹ represents a lower alkyl group having 1 to 5 carbon atoms. Specific compound names of the vinylsilane compounds (I), (II) and (III) include, for example, vinylmethoxysilane, vinylmethoxysilane, vinyltri (β-methoxy, ethoxy) silane,
γ-methacryloxypropylmethoxysilane. Among them, vinylmethoxysilane and vinylethoxysilane are preferably used.

The EVOH (A) may contain other comonomers [eg, propylene, butylene, unsaturated carboxylic acid or its ester ｛(meth) acrylic acid, and so on as long as the object of the present invention is not impaired. (Meth) acrylic acid ester (methyl, ethyl), etc., and vinylpyrrolidone (N-vinylpyrrolidone, etc.)] can also be copolymerized.

In the present invention, the amorphous polyamide is
It has no endothermic crystal melting peak in the DSC measurement and is mainly a polycondensate of an aliphatic diamine and an aromatic dicarboxylic acid. Examples of the aliphatic diamine include hexamethylenediamine, 2,2,4-trimethylhexamethylenediamine, 2,4,4-trimethylhexamethylenediamine, 2, methylpentanemethylenediamine, and bis- (4-aminohexyl) -methane , 2, 2
-Bis- (4-aminohexyl) -isopropylidine,
1,4 (1,3) -diaminocyclohexane, 1,5-
Diaminopentane, 1,4-diaminobutane, 1,3-
Diaminopropane, 2-ethyldiaminobutane and the like. One or more of these diamines can be used simultaneously. Among them, hexamethylenediamine, 2-methylpentanemethylenediamine, 1,5-diaminopentane, 1,4-diaminobutane, and 1,3-diaminopropane are preferably used.

Examples of the aromatic dicarboxylic acid include isophthalic acid, terephthalic acid, alkyl-substituted isophthalic acid, alkyl-substituted terephthalic acid, naphthalenedicarboxylic acid, and diphenyl ether dicarboxylic acid. One or more of these dicarboxylic acids can be used simultaneously. Among them, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, diphenyl ether dicarboxylic acid and the like are suitable in terms of thermoformability, transparency, gas barrier properties and the like.

Examples of the amorphous polyamide include a polycondensate of hexamethylenediamine-isophthalic acid, a polycondensate of hexamethylenediamine-isophthalic acid / terephthalic acid, 2,2,4-trimethylhexamethylenediamine and 2,2,4-trimethylhexamethylenediamine. And polycondensates of 4,4-trimethylhexamethylenediamine-terephthalic acid. Among them, the molar ratio of isophthalic acid / terephthalic acid is 60 /
Hexamethylenediamine-isophthalic acid in the range of 40-95 / 5, even 65 / 35-90 / 10
Polycondensates of terephthalic acid are preferred.

The compounding ratio of the amorphous polyamide (B) is as follows:
It is 5 to 40% by weight, preferably 7 to 35% by weight, based on the total amount of (A) and (B). If the addition amount is less than 5% by weight, the effect of improving the moldability is not sufficient, and cracks and unevenness tend to occur. On the other hand, if it exceeds 40% by weight, the gas barrier property is greatly reduced, and it cannot be used as a high gas barrier container.

The melt viscosity index [MI (A)] of EVOH (A) at 190 ° C. under a load of 2160 g is 0.1 to 5
0 g / 10 min, preferably 0.3 to 30 g / 10 m
in. It is. The melt viscosity index [MI (B)] of the amorphous polyamide (B) is 0.01 to 50 g / 10 mi.
n. Preferably, 0.05 to 20 g / 10 min. It is. The ratio of MI (A) / MI (B) is preferably 0.1 or more, more preferably 1 or more. If less than 0.1,
In some cases, the transparency during thermoforming is reduced, or the variation in gas barrier properties is increased, so that it may not be usable. And
Regarding the melt viscosity index (MI) of the blend composition of EVOH (A) and amorphous polyamide (B), 0.1 to 5
0 g / 10 min. Preferably, 0.2 to 25 g / 10 m
in. It is. The melt viscosity index of the composition is 0.1 g / 10
min. Less than 50 g / 10 min. In the case described above, a molded article having good appearance may not be obtained, possibly due to uneven thickness of the EVOH composition layer during the production of the multilayer structure. The melt viscosity index [MI (A), MI (B)] is
Those whose melting point is around 190 ° C or higher than 190 ° C
It is a value measured at a plurality of temperatures equal to or higher than the melting point under a load of 160 g, and the reciprocal of the absolute temperature is plotted on the abscissa and the melt viscosity index is plotted on the ordinate (logarithm) in a semilogarithmic graph.

The method of blending the EVOH and the amorphous polyamide is not particularly limited, but the EVOH and the amorphous polyamide are dry-blended and used as they are, or more preferably a Banbury mixer. And a method of pelletizing and drying with a single screw or twin screw extruder. If the blend is non-uniform, or if gels and / or lumps are generated or mixed during the blend pelletizing operation, there is a high possibility that the EVOH composition layer will be broken, cracked, or uneven during the heat-stretch molding. Therefore, it is desirable to use an extruder with a high degree of kneading during the blend pelletizing operation, seal the hopper port with nitrogen, and extrude at a low temperature. When blending and pelletizing, other additives (plasticizer, heat stabilizer, ultraviolet absorber, antioxidant, coloring agent, filler, other resin, etc.) are used within a range that does not impair the purpose of the present invention. You are free to do it. Especially,
As a countermeasure for preventing gel formation, one or more of a hydrotalcite-based compound, a hindered phenol-based, a hindered amine-based heat stabilizer, and a metal salt of a higher aliphatic carboxylic acid (for example, calcium stearate) are added.
It is preferable to add from 01 to 1% by weight.

Next, the case where the EVOH composition of the present invention is used for a multilayer structure, particularly for a heat-stretched multilayer structure, will be described. The thermoplastic resin laminated on at least one surface of the layer made of the EVOH composition of the present invention may be a resin that can be stretch-molded at the following temperature, and may be a polypropylene resin, a polystyrene resin, a polyamide resin, or polyvinyl chloride. Suitable resins include thermoplastic resins and thermoplastic polyester resins. X−10 ° C. ≧ Y ≧ X−110 ° C. Here, X represents the melting point of EVOH {the maximum endothermic peak temperature measured by DSC (scanning speed 10 ° C./min.)}, And Y represents the heating stretching temperature ° C. Y is (X-1
0) When the temperature is higher than 0 ° C., the EVOH is softened and melted during the heat-stretch molding, so that molding can be performed without adding any additives. On the other hand, when Y is lower than (X−110) ° C., the glass transition temperature (Tg) of the thermoplastic resin is equal to or lower than room temperature.
Molded product has poor shape and dimensional stability and cannot be used.

In the present invention, in order to form a multilayer of the EVOH composition and the thermoplastic resin, the adhesive resin used may be one that firmly adheres the EVOH composition layer and the thermoplastic resin layer. For example, the unsaturated carboxylic acid or its anhydride (such as maleic anhydride) may be used as an olefin-based polymer or copolymer [polyethylene ｛low-density polyethylene (LDPE), linear low-density polyethylene, although not particularly limited thereto. (LLDPE), ultra-low density polyethylene (SLDPE)}, ethylene-vinyl acetate copolymer, ethylene- (meth) acrylate (methyl ester or ethyl ester) copolymer] is preferably used. Can be

The EVOH composition of the present invention can be formed into an arbitrary molded product such as a film, a sheet, a bottle, etc. by a well-known melt molding method and compression molding method. Remarkable features are exhibited when used as a single layer of the structure, and this point will be described below.

First, as a method for obtaining a multilayer structure, the EVOH composition and the thermoplastic resin are often extruded via an adhesive resin, by an extrusion lamination method, a dry lamination method, a coextrusion lamination method, a coextrusion sheet molding method, A laminate is obtained by a co-extrusion pipe molding method, a co-injection molding method, a solution coating method, etc., and then the laminate is reheated to a temperature not higher than the melting point of EVOH by vacuum pressure deep drawing, biaxial stretch blow molding, or the like. A stretching method, a method of subjecting the laminate (film or sheet) to a biaxial stretching machine and stretching by heating, and a method of co-injection biaxial stretching blow of an EVOH composition and a thermoplastic resin. can give.

The thickness structure of the multilayer structure is not particularly limited. However, in consideration of moldability and cost, the thickness ratio of the EVOH composition layer to the total thickness is about 2 to 20%. It is suitable. The structure of the multilayer structure is as follows: EVOH composition layer / adhesive resin layer / thermoplastic resin layer, thermoplastic resin layer / adhesive resin layer /
EVOH composition layer, thermoplastic resin layer / adhesive resin layer / E
VOH composition layer / adhesive resin layer / thermoplastic resin layer, thermoplastic resin layer / adhesive resin layer / EVOH composition layer / adhesive resin layer / thermoplastic resin layer / adhesive resin layer / EVOH composition layer It is mentioned as a typical one. When a thermoplastic resin layer is provided on both outer layers, the resins may be different or the same. In addition, scrap such as trim generated during molding can be blended with the thermoplastic resin layer,
In some cases, it may be reused with a separate recovery layer.

In the present invention, the heat-stretched multilayer structure is, as described above, a container or sheet such as a cup or a bottle obtained by heat-stretching, or a film-like material. Any method may be used as long as it is left at a temperature required for stretching for a predetermined time and the multilayer structure is operated so as to be substantially thermally uniform, and is heated and uniformized with various heaters in consideration of operability. The method is preferred.

The heating operation may be performed simultaneously with the stretching or before the stretching. In addition, the stretching operation means an operation of uniformly forming a thermally heated multilayer structure into a container, a cup, a bottle, and a film by using a chuck, a plug, a vacuum force, a pneumatic force, and the like. Any of biaxial stretching (simultaneous or sequential) can be adopted. The stretching ratio and the stretching speed are appropriately selected according to the purpose.
× 10 ⁵ % / min. This means a method of stretching uniformly at a high speed as described above, and the molded article does not necessarily have to be oriented.

In the present invention, the water content of EVOH is not particularly limited, but may be 0.001 to 0.001.
It is preferred that the content be within 10% by weight. In general,
In the step of making a composition of EVOH and amorphous polyamide, or in the step of molding the composition into a multilayer structure,
It is desirable that the water content of EVOH be as low as possible, from 0.001 to 1% by weight. On the other hand, in the thermoforming of the multilayer structure, the water content of the EVOH layer is from 0.01 to 10% by weight,
It is preferable that the water content is high as long as the VOH layer does not foam.

The heat-stretched multilayer structure of the present invention obtained in this manner has no gas holes in the EVOH composition layer, and therefore has very good gas barrier properties and little variation. It is effective for a container for food packaging excellent in quality, or a container required to have a good fragrance retention property. Hereinafter, the present invention will be further described with reference to Examples, but the present invention is not limited thereto.

[0036]

【Example】

Example 1 Ethylene-vinylsilane having an ethylene content of 27 mol% and a trimethoxyvinylsilane content of 0.015 mol%
80 parts by weight of a vinyl acetate copolymer and 20 parts by weight of an ethylene-vinyl acetate copolymer having an ethylene content of 48 mol% were blended in a methanol solution and saponified under an alkali catalyst. As a result of DSC measurement of the obtained EVOH composition, endothermic peak temperatures were found at 190 ° C and 155 ° C. 80 parts by weight of this EVOH (A), amorphous polyamide (B)
(The molar ratio of isophthalic acid / terephthalic acid is 75/2
5, hexamethylenediamine-isophthalic acid /
20 parts by weight of terephthalic acid polycondensate) were placed in a twin screw type, vented 40φ extruder, and in the presence of nitrogen,
Extrusion pelletization was performed at 200 ° C. At this time, the MI of the pellet (at 190 ° C. under a load of 2160 g) was 2.7 g /
It was 10 minutes.

Using the pellets, a three-layer, five-layer coextrusion apparatus was used to form a multilayer sheet (polystyrene resin layer / adhesive resin layer / EVOH composition layer / adhesive resin layer / polystyrene resin layer). The outermost polystyrene resin layer (Asahi Dow Stylon 691) is 800 sheets.
μ, and an adhesive resin layer (Toso- “Mersen M-542”).
0 ", maleic acid-modified ethylene-vinyl acetate copolymer)
Is 50 μm each, and the intermediate layer (EVOH composition layer) is 50 μm.
μ. The obtained sheet is applied to a vacuum pressure air thermoforming machine,
(Stretching speed 9 × 10 ⁵ % / min.) And molding at 130 ° C.

The obtained molded product was free from cracks, unevenness and uneven thickness, and had good appearance and transparency. This container was conditioned at 20 ° C.-65% RH, and the gas barrier property was measured (Mocon 10/50 type). 2
In addition to exhibiting a very good gas barrier property of 0 μ / m ² · 24 hr · atm, the dispersion of measured values (R = maximum value−minimum value) when measuring 20 samples is extremely small at 0.1, It was a highly reliable high gas barrier container.

Example 2 80 parts by weight of an ethylene-trimethoxyvinylsilane-vinyl acetate copolymer having an ethylene content of 27 mol% and an ethylene-vinyl acetate copolymer 20 having an ethylene content of 48 mol%
Parts by weight were blended in a methanol solution and saponified under an alkaline catalyst. Using the obtained EVOH composition (A), the same operation as in Example 1 was performed. The result is
It is shown in Table 1.

Comparative Examples 1 to 7 Except as shown in Table 1, containers were obtained under the same conditions as in Examples 1 and 3, and the results are shown in Table 1.

[0041]

[Table 1]

[0042]

EFFECTS OF THE INVENTION There are no pinholes, cracks, unevenness, local uneven thickness, etc. in the operation of heat stretching, especially high-speed heating operation, and it is excellent in transparency, gas barrier properties and its reliability.
An EVOH resin composition and a heat-stretched multilayer structure using the same can be provided.

Continuation of the front page (51) Int.Cl. ⁶ identification code FI (C08L 29/04 77:00) (58) Investigated field (Int.Cl. ⁶ , DB name) C08L 23/08 C08L 29/04 B32B 27 / 28

Claims (3)

(57) [Claims] In DSC measurement, two or more endothermic peaks are measured.
Has over click an ethylene content of 20 to 60 mole% of ethylene - vinyl alcohol copolymer (A) 60 to 95 wt%
And a resin composition comprising 40 to 5% by weight of an amorphous polyamide (B). 2. A multilayer structure having a thermoplastic resin on at least one surface of a layer comprising the resin composition according to claim 1. 3. The multilayer structure according to claim 3, wherein the multilayer structure is a heat-stretched multilayer structure of a co-extruded multilayer sheet.