JPH03115447A - Ethylene-vinyl alcohol copolymer composition and multilayered structure - Google Patents

Abstract

PURPOSE:To prepare an ethylene-vinyl alcohol copolymer compsn. which has excellent gas barrier properties and which allows neither pinhole nor crack nor local variation in thickness to occur in thermal orientation by compounding two or more specific ethylene-vinyl alcohol copolymers and specifying the ethylene content of the resulting compsn. CONSTITUTION:To prepare the title compsn., 50-95wt.% ethylene-vinyl alcohol copolymer contg. 20-40mol% ethylene and 5-50wt.% ethylene-vinyl alcohol copolymer contg. 61-90mol% ethylene, either or both of the copolymers contg. a specified amt. of a vinylsilane compd. (e.g. vinyltrimethoxysilane) as the comonomer, are compounded in such a manner that the resulting compsn. has an ethylene content of 25-60mol%.

Description

[Detailed Description of the Invention] U-1 The present invention provides gas barrier properties that are free from pinholes, cracks, local thickness unevenness, etc. during heating stretching, especially during heating high-speed stretching operations, and furthermore, scraps can be recovered and reused. excellent in
The present invention relates to an ethylene-vinyl alcohol copolymer (hereinafter referred to as EVOH) composition and a multilayer structure using the same, particularly a multilayer structure that is heated and stretched, and furthermore, a multilayer structure that is heated and stretched at high speed.

L-support double L EVOH is currently being used for packaging films for foods, etc., especially for foods that require barrier properties against oxygen, bromine, flavors, etc., and other products that require aroma retention. Its effectiveness has been recognized in the field of EVOH is made by laminating a thermoplastic resin layer such as polyethylene, polypropylene, polystyrene, polyester, polyamide, vinyl chloride, etc., and various adhesive resin layers typified by ionomer, ethylene-vinyl acetate copolymer, etc. Used in the form of multilayer structures.

By the way, multilayer structures (films,
When secondary processing (notebooks, parisons, etc.) into containers etc., especially when stretch forming is performed below the melting point of EVOH, EV
Small voids, cracks, local thickness unevenness, etc. frequently occur in the OH layer, and as a result, the oxygen barrier properties of the molded container are greatly deteriorated. In addition, the appearance of the container was defective, making it unfit for use as a container for food, etc.

Therefore, in order to prevent pinholes, cracks, etc. in the EVOH layer that occur during heating and stretching, various plasticizers have been added to the EVOH layer (JP-A-5388067, JP-A-5
9-20345), polyamide resin blend (JP-A-52-141785, JP-A-511-36412)
Although these methods have been considered, it has been found that none of them are fully satisfactory in terms of the following points.

In other words, in a system in which various plasticizers are added, in order to sufficiently improve the heat-stretching properties, it is necessary to add 10 to 20 parts by weight of the plasticizer per 100 parts by weight of EVOH, which greatly improves the gas barrier properties. There are many problems such as a decrease in interlayer adhesion strength with the EVOI layer and the EVOI layer, making it unusable.

On the other hand, in the addition system of polyamide resin, EVOH
It is not usable due to the large chemical reactivity with the molded product, the presence of a large number of gel-like substances in the molded product, and the noticeable coloring. Also,
In the case of adding a polyamide resin with relatively little gel coloration, a good-looking container can be obtained, perhaps because the compatibility between EVOH and polyamide is not sufficient, but in particular, the characteristics of overheating and high-speed stretching molding are poor. Possibly due to the presence of pinholes, the measured values of gas barrier properties vary greatly (and the container is unreliable as a gas barrier container and cannot be used).

Also, JP-A-61. -4752, as stated in
At first glance, an EVOH composition prepared by mixing different types of ethylene-vinyl acetate copolymers and saponifying them in a solution appears to yield a container with good appearance. However, when heated at a relatively low temperature (110 to 140°C) and stretched at high speed, the measured values of gas barrier properties vary widely, probably due to the presence of minute pinholes, and the reliability of the container as a gas barrier property deteriorates. do not have. To make matters worse, in order to obtain a composition with high gas barrier properties, the addition rate of the ethylene-vinyl acetate copolymer with a high ethylene content must be reduced to 30% by weight or less, which is outside the scope of the above-mentioned JP-A-Sho. In this case, the variation in the measured values of gas barrier properties becomes even larger, making it unusable as a gas barrier container.

On the other hand, as described in JP-A No. 60-173033, when using a composition containing different types of EVOH and having a predetermined area ratio without independent endothermic peaks measured by differential scanning calorimetry, the appearance It appears that a good container can be obtained. However, relatively low temperatures (110-140
When it was heated and stretched at high speed at a temperature (°C), the measured gas barrier properties varied widely, probably due to the presence of minute pinholes, making it unreliable as a gas barrier container. In particular, as shown in the Examples, when a composition in which two types of EVOH are melted and mixed is used, the measured values of the gas barrier properties vary greatly and the container is unreliable as a gas barrier container.

Furthermore, as described in JP-A No. 63-196645, an EVOH composition made by blending two or more types of EVOH containing silicon and having different ethylene contents can provide a container with a good appearance and a gas barrier. It has good reliability as a plastic container, but when scraps such as trim are collected and used, it may not be possible to obtain a good sheet, probably due to poor compatibility with the base material, which poses problems in terms of productivity and cost. was there.

Therefore, it has good gas barrier properties and reliability (variation) as a gas barrier container. In other words, there are no minute pinholes, cracks, uneven thickness, etc. in the EVOH layer during heating and high speed stretch molding. Of course, one of the important issues is the development of EVOH from which scrap can be recovered and reused.

The present invention, which is strong in C9, eliminates cracks, pinholes, and local deviations in the EVOH layer that occur when secondary processing an EVOH multilayer structure into containers, etc., without impairing the excellent gas barrier properties of EVOH. The present invention provides an EVOH composition that prevents the generation of meat, etc., and has high gas barrier properties and highly reliable gas barrier properties that allow recovery and reuse of scrap, and a multilayer structure using the same. .

D. The above-mentioned problem for solving the problem is that EV with an ethylene content of 20 to 40 mol%
OH(A) 70-95% by weight and ethylene content 61-9
0 mol% of E V OH (B) 5 to 50% by weight, and (A) and/or (B) contain a vinylsilane compound as a copolymerization component, and the following formulas (1) to () to
(IIIf), the average content of ethylene is 25
This is achieved by using ~60 mole % EVOH composition.

0.5 mol%≧5t(A)+31(B)≧0.005
Mol% (1) Sl(A)/SI(B)≦1
(■) [η] (B)≦1
(III)≦1 (■) However, S I (A) and 31 (B) are E V OH (A)
, content of vinylsilane compound (B) (mol%)
shows.

[η](A)/[η](B) is E V OH(^), (
B) shows the solution viscosity of 10% hydrated phenol at 30°C.

The present inventors have added various plasticizers, polymers, etc. to EV OH.
Various multilayer sheets are prepared by blending with adhesive resin and thermoplastic resin, and by reheating and stretching,
Cups and bottles were obtained, and the appearance and gas barrier properties of the containers were measured. As a result, as mentioned above, when a multilayer sheet using a melt-blended composition of two or more types of EVOH with different ethylene contents is heated and stretched at high speed, the E
It was found that a good molded product without the occurrence of VOHWA cracks, pinholes, local thickness unevenness, etc. could be obtained. However, the higher the ethylene content in the EVOH composition, or the higher the ethylene content, the better the molded product can be obtained. The barrier properties deteriorated and were not necessarily sufficient for use. In addition, when a multilayer sheet using a saponified EVOH composition prepared by mixing two or more types of ethylene-vinyl acetate copolymers with different ethylene contents is heated and stretched at high speed, slight racks and pinholes occur in the EVOH layer. Perhaps because of this, there were some cases in which variations were observed in the measured values of gas barrier properties.

In particular, when the heating high-speed stretching temperature was low, there was a problem with the reliability of gas barrier properties. Furthermore, when scraps such as trim are collected and reused, abnormalities such as flow unevenness during film formation of the original fabric sheet often occur, making collection and reuse difficult.

Therefore, as a result of intensive study, the present inventors found that EV OH (A) with an ethylene content of 20 to 40 mol% was 50 to 95%.
EVOH with weight% and ethylene content of 161-90 mol%
(B) 5 to 50% by weight, and (A) and/
Alternatively, (B) is an EVOH composition that contains a vinyl silane compound as a copolymerization component and satisfies formulas (1) to (■). There is little uneven thickness, and there is almost no deterioration or variation in gas barrier properties.
Furthermore, we discovered that it is possible to collect and reuse scraps. As a result of further careful consideration, surprisingly, the E.
Rather than mixing V OH (A) and EVOH (B) in solution or in the melt, E V OH (A), E
Ethylene-vinyl acetate copolymer or ethylene-vinyl acetate-vinylsilane compound copolymer (hereinafter collectively referred to as EVAC), which is the raw material for VOH (B),
That is, E V A C (A), E V A C (B
) in a solution or melt and saponified in solution or under an acid or alkali catalyst. During stretching operation, cracks, pinholes,
We have completed the present invention by discovering that there is less local thickness unevenness, there is almost no deterioration or variation in gas barrier properties, and furthermore, the recovery and reuse of scrap is greatly improved.

EVOH (^), (B,) used in the present invention is
It is a saponified ethylene-vinyl acetate copolymer, and the degree of saponification of each vinyl acetate component is preferably 95% or more, more preferably 97% or more.

For EVOH (A), it is important that the ethylene content is 20 to 40 mol%, and if the ethylene content is less than 20 mol%, even if EVOH (B) is mixed, the moldability improvement effect will be sufficient. It is not demonstrated. On the other hand, when the ethylene content exceeds 40 mol%, gas barrier properties are insufficient.

Further, for EV OH (B), it is important that the ethylene content is 61 to 90 mol%, and preferably 61 to 90 mol%.
It is 2 to 88 mol%.

When the ethylene content of EV OH (B) is 61 mol%, it may be because the softening temperature is higher than the stretching temperature, and not only the moldability improvement effect may not be sufficient, but also the scrap recovery and reusability. Unfavorable in terms of On the other hand, when the ethylene content is 90 mol% or more, the gas barrier properties vary widely and reliability is insufficient, probably because of poor compatibility with EV OH (A).

In the present invention, it is important that the average content of ethylene in the composition consisting of EV OH (A) and (B) is 25 to 60 mol%, preferably 25 to 55 mol%. In addition, the average saponification degree of vinyl acetate component is 95% or more,
It is preferably 97% or more. Ethylene content 25 mol%
If it is less than 60 mol%, the melt moldability is poor, while if it is more than 60 mol%,
Gas barrier properties are insufficient. Moreover, if the degree of saponification is less than 95%, gas barrier properties and thermal stability will deteriorate.

Regarding the mixing ratio of E V OH (A) and (B),
EV OH (A) 5fl ~ 95% by weight, E
It is important that V OH (B) is 5-50% by weight, preferably EVOH (A) 65-95% by weight, E
VOH(B) is 5 to 35% by weight. EVOH(B
) is 50% by weight or more, gas barrier properties are significantly deteriorated. On the other hand, if it is less than 5% by weight, not only the moldability improvement effect is not sufficiently exhibited, but also it is not preferable in terms of scrap recovery and reusability.

When a vinyl silane compound is copolymerized with E V OH (A) and/or (B), the content of the vinyl silane compound (31 (A) + 31 (B)) is the same as in (1) above.
It is important to satisfy the formula, preferably 0008 to 0
．． It is 2 mol%.

If the content of the vinyl silane compound is 0.005 mol% or less, the gas barrier properties may vary widely and the reliability may not be sufficient, probably due to poor compatibility between EV OH (A) and (B). Not only that, but it is also unfavorable in terms of scrap recovery and reusability. On the other hand, when the content of the vinyl silane compound is 0.5 mol% or more, probably due to the poor thermal stability of EVOH, not only gels and bubbles occur during film formation, but also the gas barrier property varies greatly, making reliability unreliable. is not enough.

In addition, the vinyl silane compound content of EVOH (^) and (B) 31 (A), 5t (B) and the solution viscosity [η]
The relationship between (^) and [η] (B) is also the above (II) and (I
It is important to satisfy the formula I[).

Preferably 5t(A)/SI(B)≦0.5, o, ot<
Crt](B)/[η](A)≦0.9. 5
l(A)/5t(B) > 1 or/and [T
I](B)/[η(A)>1, EVOH(A
) and (B), or EVOH and the base material, the gas barrier property varies widely and reliability may not be sufficient. So it's not desirable.

By the way, in the present invention, as a method for obtaining an EVOH composition, ethylene-vinyl acetate copolymer (precursor of A)
When producing ethylene-vinyl acetate copolymer (precursor of B), a vinylsilane compound is used as a copolymerization component to obtain a copolymer, which is separately saponified to produce EVOH.
There is a method of manufacturing these and then blending them in a molten state or a solution state. However, although the E V OH composition obtained by this method has the effect of improving thermoformability and gas barrier properties, it may not always be sufficient. Therefore, the present inventors further determined that tI:At! As a result of the investigation, it was surprisingly found that after copolymerizing the ethylene-vinyl acetate copolymer, which is the precursor of (A) and (B), with a vinylsilane compound in (^) and/or (B), a solution EVOH obtained by mixing in a state and then saponifying
It has been found that the composition provides a container with thermoformability, high gas barrier properties, and high reliability. This is also clear from the examples shown below.

As a method for obtaining two or more types of ethylene-vinyl acetate copolymer compositions having different ethylene contents, ethylene-containing i
A method of blending two or more types of ethylene-vinyl acetate copolymers with different t in solution or melting, or using a two-tank polymerization tank arranged in series or parallel,
Different polymerization conditions in each polymerization tank, such as polymerization temperature, polymerization pressure, polymerization catalyst, polymerization solvent, polymerization time, etc.
By setting different conditions, for example, to obtain an ethylene-vinyl acetate copolymer with a higher ethylene content, the polymerization pressure may be set higher, and if an ethylene-vinyl acetate copolymer with a lower ethylene content is obtained, the polymerization pressure may be set higher. In the case of obtaining the polymerization, there is a method of obtaining the ethylene-vinyl acetate copolymer composition by setting the polymerization pressure lower. Alternatively, there is a method of blending an ethylene-vinyl acetate copolymer and EVOH having different ethylene contents in a solution or melt. Among these, the former method by changing the polymerization conditions is most suitable.

Next, as a method for saponifying the ethylene-vinyl acetate copolymer composition, the ethylene-vinyl acetate copolymer composition is dissolved or dispersed in water, alcohol, or other organic solvent, and then saponified with an acid or alkaline catalyst. There are ways to do that.

However, the E V OH (A) and (B) may be used in combination with other comonomers such as propylene, butylene, unsaturated carboxylic acid or its ester ((meth) ) acrylic acid, (meth)acrylic esters (methyl, ethyl), etc.), vinylpyrrolidone (N-vinylpyrrolidone, etc.), as well as plasticizers, heat stabilizers, ultraviolet absorbers, and antioxidants. , colorants, fillers, and other resins (polyamide, partially saponified ethylene-vinyl acetate copolymer, etc.) may also be blended freely. Further, a suitable melt index (Mr, (190°C, under 2160g load) of EVOH used in the present invention is 0.1-50g/lomin, preferably 0.
5-208/lO width in.

By the way, examples of vinylsilane compounds used as copolymerization components of ethylene-vinyl acetate copolymer include the following 32 (
Compounds represented by ■), (■) and (Vl) are preferred.

II’ R’ R”.

II I CHt-CCN R5-3t-R"., 1...
... (V)Rs R8= 1 [However, n here is O=1. m is O-2, R1 is a lower alkyl group, an allyl group, or a lower alkyl group having an allyl group, R2 is an alkoxyl group having 1 to 40 carbon atoms, and the alkoxyl group has an oxygen-containing substituent. You can leave it there. R3 is hydrogen or a methyl group, R4 is a hydrogen atom or a lower alkyl group, R5 is an alkyl group or a divalent residue in which chain carbon atoms are mutually bonded to oxygen or nitrogen, R6 is hydrogen, halogen, or lower alkyl group, allyl group, or lower alkyl group having an allyl group, R7 is an alkoxyl group or an acyloxyl group (here, the alkoxyl group or acyloxyl group may have a substituent containing nitrogen rather than oxygen), R8 is hydrogen, halogen, a lower alkyl group, an allyl group, or a lower alkyl group having an allyl group, and R9 is a lower alkyl group]a To be more specific, R1 has 1 to 5 carbon atoms.
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; R4 is a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms; R5 represents an alkyl group having 1 to 5 carbon atoms or a divalent organic residue in which chain carbon atoms are mutually bonded to nitrogen, and R6 is hydrogen, halogen, or lower alkyl having 1 to 5 carbon atoms. group, 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, and R7 is an alkoxy group or an acyloxyl group (wherein ), R8 is hydrogen, halogen, carbon number 1~
R9 represents 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, and R9 represents a lower alkyl group having 1 to 5 carbon atoms. show. Vinyl silane compounds (W), (V), (■
) Specific examples of compounds include vinyltrimethoxinelan, vinyltriethoxyquinonelan, vinyltri(β-methoxy,ethquin)silane, and γ-methacryloquinepropylmethquinsilane. Among them,
Vinyltrimethoxysilane and vinyltriethoxysilane are preferably used.

The EVOH composition of the present invention is suitably used for multilayer structures, particularly heat-stretched multilayer structures. The thermoplastic resin to be laminated on at least one side of the layer of the EVOH introduction compound composition of the present invention may be any resin that can be stretch-formed at the following temperatures, such as polypropylene resin, polystyrene resin,
Preferred are polyamide resins, polyvinyl chloride resins, thermoplastic polynystyl resins, and the like.

x-10°C≧Y≧X-110°C, where X represents the melting point of the EVOH composition, and Y represents the heating stretching temperature °C. (However, the melting point of the EVOH composition is D
If Y is higher than (X-1o)'C, E V OH will soften and dissolve during hot stretch forming, so no additives should be added. It is also possible to mold the material. On the other hand, Y is (X-110℃)℃
If lower, the glass transition temperature (Tg) of the thermoplastic
Since the temperature is below room temperature, the shape and dimensional stability of the molded product are poor and it cannot be used.

In the present invention, the adhesive resin used for multilayering the EVOH composition and the thermoplastic resin is E
There is no particular limitation, as long as it firmly adheres the VOHAll composition and the thermoplastic resin layer.
Unsaturated carboxylic acids or their anhydrides (maleic anhydride, etc.) can be used as olefinic polymers or copolymers [polyethylene (low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), ultra-low-density polyethylene (
SLDPE)), ethylene-vinyl acetate copolymer, ethylene-(meth)acrylic acid ester (methyl ester,
or ethyl ester) copolymer] is preferably used.

The EVOH composition of the present invention can be molded into any molded product such as a film, sheet, or bottle by a well-known melt molding method or compression molding method; however, as described above, the molded product can be formed into a multilayer structure. When used as a single layer, remarkable characteristics are exhibited, and this point will be explained below.

First, methods for obtaining a multilayer structure include extrusion lamination, dry lamination, coextrusion lamination, coextrusion sort molding, and coextrusion vibrator, in which the EVOH composition and thermoplastic resin are often bonded via an adhesive resin. A laminate is obtained by a molding method, a co-injection molding method, a solution coating method, etc., and then the laminate is reheated and stretched in a range below the melting point of the EVOH composition by vacuum pressure deep drawing, biaxial stretching blow molding, etc. Alternatively, the laminate (Fnorm or Sort) may be subjected to a biaxial stretching machine and heated and stretched, and furthermore, an EVOH composition and a thermoplastic resin may be co-injected, biaxially stretched and blown. It will be done.

There are no particular limitations on the method for collecting and reusing scraps such as l/rims and defective containers generated during shape shaping. A method of pulverizing the scrap, drying it if it has absorbed moisture, and triblending it with a raw material thermoplastic resin;
There are methods such as a method in which pulverized scrap is pelletized and then triblended with a raw material thermoplastic resin, and a method in which pulverized scrap and raw material thermoplastic resin are blended into pellets.

Regarding the blending ratio of raw thermoplastic resin and scrap, the higher the scrap ratio, the more likely abnormalities such as uneven thickness, unevenness, cracks, and whitening will occur during stretch molding, so it is set depending on the molding conditions, but usually 2~ Blended at a ratio of about 80%. At this time, in order to improve dispersibility and thermal stability and suppress the above abnormalities during container molding, maleic anhydride-modified polyolefins, maleic anhydride-modified polyolefin-borisdyrene copolymers, metal soap, and hydrotalcite are used. It may be preferable to add one or more types of compounds, furan-modified polyolefins, etc.

Furthermore, the thickness of the multilayer structure is not particularly limited, but when considering moldability and cost, the thickness ratio of the EVOH layer to the total thickness is 2 to 20.
% is suitable. Further, the structure of the multilayer structure includes EVOH composition layer/adhesive resin layer/thermoplastic resin layer,
Thermoplastic resin layer/adhesive resin layer/EVOH composition layer/adhesive resin layer/thermoplastic resin layer, EVOH composition layer/adhesive resin layer/recovery layer, EVOH composition layer/adhesive resin layer/ Recovery layer/thermoplastic resin layer, thermoplastic resin layer/recovery layer/adhesive resin layer/EVOH composition layer/adhesive resin layer/thermoplastic resin layer, thermoplastic resin layer/recovery N!I/adhesiveness Resin layer/EVOH composition M/adhesive resin layer/recovery layer/thermoplastic resin layer, recovery layer/adhesive resin layer/E V O
H composition layer/adhesive resin layer/thermoplastic resin layer, recovery layer/
Typical examples include adhesive four-finger FJ/EV OH composition layer/adhesive resin layer/recovery layer. When providing thermoplastic resin layers on both outer layers, the resins may be different or may be the same.

In the present invention, the heat-stretched multilayer structure is, as described above, a container such as a cup or bottle, or a sort or film-like object obtained by heat-stretching, and heating is necessary for heat-stretching the multilayer structure. This refers to an operation in which the multilayer structure is left at a certain temperature for a predetermined period of time to make the multilayer structure almost thermally uniform.
A method of uniformity is preferred.

The heating operation may be performed simultaneously with the stretching, or may be performed before the stretching. In addition, stretching operation refers to a uniformly heated multilayer structure that is pulled by chucks, plugs, vacuum force, etc.
Refers to the operation of uniformly forming containers, cups, bottles, and films using compressed air force, etc. - Axial stretching, biaxial stretching i! (
(simultaneous or sequential) can be adopted. Further, the stretching ratio and the stretching speed can be appropriately selected depending on the purpose, but in the present invention, high-speed stretching means that the stretching speed is 5X 10'% (
It means a method of uniformly stretching at a high speed of at least 100% area magnification (area magnification)/sin, and the molded product does not necessarily have to be oriented.

In addition, in the present invention, regarding the water content of EVOH,
Although not particularly limited, 0.001 to 10% by weight
It is preferable that it be within the range. -For boat fishing, the moisture content of EVOH should be as low as [1,001 to 1% by weight] during melt extrusion molding, while it should be 0.1 to 10% by weight during thermoforming as long as the EVOH layer does not foam. I'm looking forward to it.

The heat-stretched multilayer structure of the present invention obtained in this way has extremely good gas barrier properties, with almost no variation, since no pinholes, cracks, or uneven thicknesses are observed in the EVOH composition layer. It is used for its long-lasting effect in food packaging containers and containers that require aroma retention.

The present invention will be further explained below with reference to Examples, but the present invention is not limited thereto.

Example 1 20 parts by weight of ethylene-vinyl acetate copolymer (A) (hereinafter referred to as EVAC(A)) with an ethylene content of 28 mol%, and vinyl with an ethylene content of 62 mol% EV A c (with a trimethquin silane content of 0.02 mol%
B) 29 parts by weight was dissolved in a methanol solvent, and while boiling at 75°C, a NaOH-methanol solution (0.20 in molar ratio to the vinyl acetate component) was added dropwise, and the by-product (methyl acetate) was chased with methanol vapor. I put it out (EV OH/
i matching steam = l/4 weight ratio). The average content of ethylene in the EVOH obtained was 32 mol%, and the degree of saponification was 99.0.
%, melt index (M [190°C, 2160g weight) was 2.8g/10mln. Also, EVO
The solution viscosity of H(^) and (B) (10% hydrated phenol system, 30°C) is [η](A) = O, lIC, respectively.
/gl[η](B)=0', 08Q/g. (
The solution viscosity of EV OH (A) and (B) is the solution viscosity of EV OH (A) and (B) obtained by separately saponifying copolymers with different degrees of saponification under the same conditions. It is a value. ) This EVOH composition was applied to a three-type, five-layer coextrusion device to create a multilayer sheet. The structure of the sheet is both outermost polystyrene dendritic layers (Idemitsu Petrochemical Idemitsu Styrene E T
-81) was 800 μm each, adhesive resin (Toyo Soda Mersen M-5420) was 50 μm each, and the innermost layer (center) was the EVOH composition layer of 50 μm. The obtained sheet was put into a vacuum-pressure aging machine (stretching speed & 9x lo
'%/mii, ), and molding was carried out at 140°C.

The obtained molded product had no cracks, unevenness, or uneven thickness, and had a good appearance. This container was heated to 20°C and 65% r(H), and its gas barrier properties were measured (Mocon Co., Ltd. 10/
50 type), 0.3cc, 20μ/m''24hr, at
In addition to exhibiting very good gas barrier properties with IN,
When 20 samples were measured, the variation in measured values (R=maximum value - minimum value) was very small at 0.1, indicating that the container had a highly reliable high gas barrier property.

In addition, after tri-blending 40% by weight of crushed scraps such as trim generated during the aging mold with 601% of the crushed polystyrene resin, the pellets were pelletized using an extruder, and the polystyrene resin was replaced with the 315i coextrusion equipment to form a multilayer sheet. It was created. Not only did the sheet have a good appearance, but when it was thermoformed in a vacuum-pressure aging machine, it turned out to be a good container.

Examples 2 to 5, Comparative Examples 1 to 3 U12 was prepared under the same conditions as Example 1 except as shown in Table 1.
According to the present invention, there are no pinholes, cracks, unevenness, local thickness unevenness, etc. during heating stretching, especially during heating high-speed stretching, and it has excellent gas barrier properties and reliability, and is also easy to recover and reuse scraps. It is possible to obtain an EVOH composition and a heat-stretched multilayer structure with excellent properties.

Claims (6)

[Claims] (1) Ethylene-vinyl alcohol copolymer (A) with an ethylene content of 20-40 mol% (A) 50-95% by weight and ethylene-vinyl alcohol copolymer (B) with an ethylene content of 61-90 mol% (5-50% by weight) % by weight, and
(A) and/or (B) is an ethylene-vinyl alcohol copolymer containing a vinylsilane compound as a copolymerization component and satisfying the following formulas (I) to (III) and having an average ethylene content of 25 to 60 mol%. Polymer composition. 0.5 mol%≧SI(A)+SI(B)≧0.005 mol% (I) SI(A)/SI(B)≦1(II) [η](B)/[η](A) ≦1 (III) However, SI (A) and SI (B) are EVOH (A), (B
) shows the content (mol%) of each vinylsilane compound. [η] (A), [η] (B) are EVOH (A), (B)
The viscosity of each solution of 10% hydrated phenol at 30°C is shown. EVOH stands for ethylene-vinyl alcohol copolymer. (2) Ethylene-vinyl acetate copolymer (A) with an ethylene content of 20-40 mol% (A) 50-95% by weight and ethylene-vinyl acetate copolymer (B) with an ethylene content of 61-90 mol% (5-50% by weight) % by weight, and (A) and/or (B) contain a vinylsilane compound as a copolymerization component, and the ethylene-vinyl acetate copolymer composition is further mixed in a solution state and then saponified. The average content of ethylene according to claim 1 obtained by
Mol% ethylene-vinyl alcohol copolymer composition. (3) A multilayer structure having a thermoplastic resin on at least one side of the layer made of the ethylene-vinyl alcohol copolymer composition according to claim 1 or 2. (4) The multilayer structure according to claim 3, wherein the thermoplastic resin can be stretched within the stretching temperature range shown by the following formula. X-10°C≧Y≧X-110°C, where X represents the melting point of the EVOH composition, and Y represents the heating stretching temperature °C. (5) The multilayer structure according to claim 3 or 4, wherein the multilayer structure is a stretched thermoformed product from a coextruded multilayer sheet. (6) The multilayer structure according to claim 3 or 4, wherein the multilayer structure is a stretch molded product from a co-injection molded parison.