JPS59152852A - Laminate and manufacture thereof - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coextruded laminate having excellent gas barrier properties and good adhesive strength between resin layers. More specifically, the saponified resin layer of ethylene-vinyl acetate copolymer and (B
The present invention relates to a laminate in which a polystyrene resin layer (C1) is laminated via an ethylene resin layer that satisfies specific viscoelastic performance, and a method for producing a laminate obtained by coextruding the same at high speed.

Technological innovation in the food packaging industry in recent years has been remarkable.

For example, it is well known that thermoplastic resins such as polystyrene are being used for food packaging for the purpose of reducing weight for hygiene, aesthetic appearance, and reduced transportation costs. However, these polystyrene resins have low resistance to oxygen and carbon gas, making them unsuitable for long-term storage of foods, carbonated drinks, etc. Glass bottles and metal cans are often used, and empty cans are stored on the street. There are many problems such as the pollution caused by throwing bottles and the cost required to collect the bottles, and the development of alternative packaging materials has been delayed.

A saponified ethylene-vinyl acetate copolymer resin with an ethylene content of 20 to 55 mol% has melt moldability, low gas permeability, and high transparency, and is used as a material for food containers and excellent gas barrier properties. It has excellent properties as a packaging material. However, it has drawbacks in other physical properties, such as rigidity and moisture resistance, and is not fully satisfactory.

On the other hand, polystyrene resins, especially impact-resistant polystyrene resins, have a good balance between moldability, impact resistance, and rigidity.
Although it has excellent hygiene properties, it does not have sufficient gas barrier properties against oxygen and carbon dioxide, and food cannot be stored for long periods of time, so its use as food containers and packaging materials is limited.

Therefore, in order to obtain food containers and packaging materials that have the good gas barrier properties of saponified ethylene-vinyl acetate copolymer and the excellent mechanical properties of polystyrene resin, we thought of laminating layers of both resins. It will be done. However, these bipolar resin layers have little affinity with each other, and it is impossible to obtain a laminate by mere thermal bonding.

Polystyrene resin and gas barrier that do not adhere to each other
and an adhesive resin selected from a modified ethylene-vinyl acetate copolymer or an ionomer having an unsaturated carboxylic acid or its acid anhydride component concentration of 0.001 to 10% by weight. A method for producing a resin laminate characterized by the following is known from Japanese Patent Laid-Open No. 54-46281. The publication states that many gas barrier resins such as saponified ethylene-vinyl acetate copolymers, polyamide resins, vinylidene chloride resins, and thermoplastic polyesters can be laminated with polystyrene resins via adhesive resins. It shows. The adhesive resin is a modified ethylene-vinyl acetate copolymer (modified EV
A) Or, by using an ionomer, it is possible to perform melt coextrusion and lamination, demonstrating its superiority. Lamination by long-term pressure and heating using a hot press, or even in coextrusion, when lamination is performed at an extremely low rate of 0.5 nL/min or less for a long time, is disclosed in the publication. However, when carrying out coextrusion lamination at industrial speeds, the method disclosed in the publication does not exhibit sufficient adhesion performance, and the molding Due to the above problems, it is not possible to obtain products with value as products.

In view of these circumstances, the present inventors performed coextrusion based on the relationship between various physical properties of the adhesive resin and coextrusion adhesiveness, based on consideration of the necessary characteristics of the adhesive resin during nose-crossing coextrusion. The inventors discovered that the adhesive had sufficient adhesive performance even when the adhesive was used, leading to the present invention. This can be done simply by laminating a polystyrene resin layer and a saponified ethylene-vinyl acetate copolymer resin layer using a resin having a vinyl acetate component or an acid component, or a resin having both a vinyl acetate component and an acid component. This is completely unexpected from the description in the above-mentioned publication, and is truly surprising.

That is, the present invention has (A) an ethylene component content of 20 to 55
Mol% ml [90 mol% or more of ethylene-vinyl acetate copolymer saponified resin layer, fB) Polystyrene resin layer and fcl Ethylene component - vinyl acetate or (meth)acrylic acid ester component - ethylenically unsaturated carboxylic acid or An adhesive resin which is made of a main body consisting of the carboxylic acid anhydride component and satisfies the following formula (I) in the range where the real part of the complex modulus of elasticity measured at frequency 1101 (Z) is between 20 and 70°C. The present invention is a method for producing a laminate, comprising a laminate consisting of layers (C) and fB), and a laminate comprising co-extruding these layers and drawing them at a rate of 3 B/min or more.

8.0-0.0145T (JogE〈10.0-1],
0286T... (I) The object of the present invention is to have good interlayer adhesion, and to have excellent mechanical properties of polystyrene resin and excellent properties of saponified ethylene-vinyl acetate copolymer resin. The object of the present invention is to industrially obtain a laminate that also has gas barrier properties and is excellent as a food container or packaging material.

The most important feature of the present invention is that the adhesive resin of layer (C) is a polymer consisting of ethylene a component, vinyl acetate or (meth)acrylic acid ester component, and ethylenically unsaturated carboxylic acid or carboxylic acid anhydride component. and the real part of the complex modulus measured at a frequency of 110 Hz is 20 ~
Within the range of 70°C, the following formula (I), preferably (n)
8,0-0,0143T (j?og E<10.0-
0.0286T-・=(I)8.5-0.0214
T(4g E'(9,5-0,0257T --(II
) What is important in the present invention is the discovery that the real part of the complex modulus is an extremely important point for adhesive properties, especially adhesive properties in coextrusion molding, and also that the second-order transition point of saponified ethylene-vinyl acetate copolymer It has been found that the adhesion of coextrusion is greatly affected by the value of the real part of the complex modulus between temperatures near or below the cooling temperature. That is, in the present invention, the adhesive resin is made of a polymer consisting of an ethylene component, a vinyl acetate or (meth)acrylic acid ester component, and an ethylenically unsaturated carboxylic acid or carboxylic acid anhydride component, and the adhesive resin is measured at a frequency of 110 kiz. When the real part of the complex modulus of elasticity is 20 to 70°C, the above (
It has been found that by satisfying formula I), preferably formula (n), the coextrusion adhesiveness can be significantly improved not only by normal speed coextrusion but also by high speed coextrusion.

When the real part of the complex modulus of elasticity is larger than the range of formula (I), perhaps because the stress applied between the layers is not sufficiently relaxed after extrusion until cooling, only a product with low adhesive strength can be obtained;
) If it is smaller than the formula, it may be because the cohesive force of the resin is weak at high temperatures.
This is not recommended as it may have weak adhesive strength or cause trouble during coextrusion molding. This is clear from the Examples and Comparative Examples described below.

In the present invention, it is important that the real part of the complex modulus of elasticity satisfies the above formula (1,) at 20 to 70°C. Here, 20°C corresponds to the temperature of the polymer in the cooling process during coextrusion molding, and 70°C corresponds to the temperature of the polymer in the cooling process during coextrusion molding.
This corresponds to the temperature at or near the second-order transition point of the saponified vinyl acetate co-monomer, and corresponds to the temperature of the polymer at the point where the co-extruder has cooled down somewhat. It is greatly influenced by the value of the real part of the complex modulus of elasticity at 20 to 70°C. In other words, coextrusion adhesion is greatly affected by the value of the real part of the complex modulus during the process of changing the temperature of the polymer (from 70°C to 20°C) when coextruding the polymer and cooling it to obtain a laminate. It is something.

There is no particular restriction on the content of the ethylene component and vinyl acetate or (meth)acrylic acid ester component, but the weight ratio is 90.
A range of 10:1 to 50:50 is good. (Meth)acrylic acid ester components include (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid 2-ethylhexyl ester, (meth)acrylic acid methyl ester, (meth)acrylic acid ethyl ester, (meth)acrylic acid 2-ethylhexyl ester,
Acrylic acid methyl ester and the like are used. The ethylenically unsaturated carboxylic acid or carbonic anhydride component is not particularly limited, but maleic acid, acrylic acid, itaconic acid, maleic anhydride, etc. are used in a range of 0.05 to 5% by weight. Further, these components are introduced by known methods such as copolymerization and graft polymerization. Among these polymers, a copolymer of ethylene and vinyl acetate grafted with an ethylenically unsaturated carboxylic acid anhydride is preferably used.As a method for producing the adhesive resin used as the layer (C), For example, when producing a copolymer of ethylene and vinyl acetate grafted with ethylenically unsaturated carboxylic acid anhydride, the type and amount of initiator used for the grafting, the type and amount of grafting monomer, temperature, and pressure. The model number depends on the temperature dependence of the real part of the complex modulus, such as reaction conditions, type of solvent, amount, etc., type of copolymer of ethylene and vinyl acetate, degree of compaction, content of vinyl acetate component, etc. By appropriately selecting the conditions under which the adhesive resin is subjected to the reaction, the desired adhesive resin can be obtained. A specific method for producing the adhesive resin of the layer (C) is, for example, the method described in the Examples below.9 The temperature dependence of the real part of the complex modulus of elasticity is not clear, but it is introduced. It is presumed that this is determined by the length and structure of the acid group chain, as well as the fine structure of the resin such as branching and crosslinking.

Next, the resin used as the captive layer in the present invention is a saponified ethylene-vinyl acetate copolymer having an ethylene component content of 20 to 55 mol% and a saponification degree of 90 mol% or more. When the content of the ethylene component is less than 20 mol%, it is difficult to melt and mold the resulting saponified resin, and the content is less than 55 mol%7! - The degree of saponification of the vinyl acetate component is undesirable since the gas barrier properties tend to deteriorate if it exceeds 90 mol%.

If it is less than 90 mol%, not only the gas barrier properties will be low, but also physical properties such as heat resistance and water resistance will tend to deteriorate, which is not preferable.

The polystyrene resin used for the layer (B) is a styrene polymer, a com-blended polystyrene resin in which styrene is polymerized in the presence of butadiene-styrene rubber, which is widely known in the industry as impact-resistant polystyrene, and AB8. Acrylonitrile-butadiene-styrene resins widely known in the industry as polystyrene, styrene-butadiene block copolymers with a large styrene component known as transparent impact-resistant polystyrene, and the like are used.

Adhesiveness due to coextrusion cannot be estimated from the results of adhesive strength measurement simply by hot press bonding, and in most cases, coextrusion significantly reduces adhesiveness. The decrease is particularly severe when coextruded and withdrawn at high speed.

This seems to be because the laminate is cooled and stretched within a short time even after passing through the molding machine. However, by using the adhesive resin of the present invention, it exhibits strong adhesion even when coextruded and withdrawn at a speed of 37 TL/min or more in the case of C above, thereby improving productivity. The industrial significance is extremely large.

Here, the take-off speed refers to the take-off speed at a point where the temperature of the polymer drops to 40° C. in the process of coextruding and cooling the polymer.

Although there is no particular restriction on the thickness of each layer of the laminate obtained in this manner, it is preferable that the thickness of the captive layer is 5 to 70 .mu.tcj layer is 5 to 90 .mu.f, and the thickness of B1 layer is 50 to 1000 .mu.f. .

In addition, the resulting laminate has sufficient adhesive strength between each layer, and has both the excellent mechanical properties of polystyrene resin and the excellent barrier performance of saponified ethylene-vinyl acetate copolymer, making it truly excellent. It is useful as food containers (cups, bottles, etc.) and packaging materials.

The (C) layer resin used in the present invention shows excellent effects in extrusion molding using the T-die method or ring die method, but it can also be used in blow molding, etc. to shorten the molding cycle. Its usefulness is outstanding, as it allows for faster molding speed. In this case, the polystyrene resin layer of tB) may be an inner layer,
There is no problem even if it comes to the outer layer. In addition, as a laminate, it is
(c) -(B), prisoner-(c) -(B) -(c)-
It can have a multilayer structure such as Further, if necessary, other resin layers (for example, polyolefin layers such as polyethylene and polypropylene) can be laminated on these laminates.

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

Example 1 EVAFLEX P-2805 (Mitsui Ho!J 'y'
100 parts by weight of ethylene-vinyl acetate copolymer (vinyl acetate content: 28% by weight, manufactured by Michal) and 8 parts by weight of maleic anhydride were dissolved in 500 parts by weight of purified xylene and maintained at 130°C. A solution prepared by dissolving 1 part by weight of benzoyl peroxide in 20 parts of xylene was added dropwise to this solution over 2 hours with stirring F, and stirring was continued for 60 minutes. After cooling, the reaction solution was added to a large amount of purified acetone to precipitate a polymer. The resulting polymer was purified by reprecipitation using purified xylene as a solvent and purified acetone as a non-solvent, and was analyzed by IR and NMR methods to find that it contained 2.8% by weight of maleic anhydride component. was. The obtained polymer was hot pressed to a thickness of 0.0214 cTI, a width of 0.5021 cm,
A sheet with a length of 2,0000 m was prepared, and the temperature dependence of the complex modulus was measured using a direct-connection dynamic viscoelasticity measuring instrument (1) DV-II) manufactured by Toyo Sokki ■. As shown in the figure, the scope of the present invention was satisfied.

The thus obtained adhesive resin is used as layer (C), and is obtained by saponifying 99.5 mol% of the vinyl acetate component of an ethylene vinyl acetate copolymer with a vinyl acetate content of 56 mol%. [η] - 0.096% (phenol/
The inner layer is a saponified ethylene-vinyl acetate copolymer resin (water, = 85715 mixed solution, measured at 60°C), and the fB1 is made of high-impact polystyrene ("Staroin 470" manufactured by Asahi Dow Co., Ltd.).
A layered resin was obtained using the following method.

Equipped with an extruder machine with an inner diameter of 60 Wnφ, an extruder with an inner diameter of 'Sownφ, and an extruder with an inner diameter of 90 mm, the molten material from each extruder is spread by each manifold in one tie. After that, using a flat tie-type three-layer coextrusion device that merges with - in the tie to form a multilayer, the inner layer resin is placed in the extruder ■, and the (C) layer is placed in the extruder ■. The resin was fed into the extruder ■ (B1 layer resin was supplied, the die temperature was 220°C, and the take-up speed was 7 m/min (the take-up speed was measured when the temperature of the resin reached 40°C on the cooling roller). Perform coextrusion and IA/(cl
, / (B) A clean laminate having a three-layer structure without any ripples was obtained. The thickness of each layer is (50μ for AJ layer, 2μ for fB1 layer)
50μ, (Cj layer layered 15μ, peel strength between each layer is 1.9 kg/cm between C/(C), FB+/(C)
It showed good adhesion of 1-6 kg/cm between 1 and 1.

Comparative Example 1 Yuka O 7
After adding 1.0 part by weight of 2,5-dimethylhexane-2,5-sivitro-oxide, it was mixed in a Henschel mixer, extruded at 220°C with an extruder with a diameter of 40φ, and pelletized after cooling with water to obtain 'AkM% A polymer containing anhydrous malemono brewing ingredients was obtained. When the temperature dependence of the complex modulus of elasticity of this material was measured, as shown in FIG. 1, it did not satisfy the scope of the present invention. This is thought to be due to differences in the type of ethylene-vinyl acetate copolymer used, the grafting conditions, the branching state of the obtained polymer (long chain or short chain branched crosslinked structure, molecular weight, molecular weight distribution, etc.). Co-extrusion of three types of laminate/(C1/(B)) was attempted in the same manner as in Example 1 except that the above polymer was used as fC1 layer resin.The extruded laminate was a defective product with ripples. When I selected the best possible place on the laminate and measured the thickness, the inner layer was 40-60μ, and the (B) layer was 2
The thickness of the layer (C) was 40 to 280μ, and the thickness of the (C) layer was 5 to 20μ. Also, its interlayer peel strength is 0.4 kq/cm between C/(C) *
(B) / (Cl) was 0.1 kg/lyn, and both the adhesive strength and appearance were completely unsuitable for practical use.

Example 2 A resinous polymer was obtained in the same manner as in Example 1, except that EVAFLEX-2s o s (manufactured by Mitsui Polychemical Co., Ltd.; engineered tyrene-vinyl acetate copolymer (vinyl acetate content: 25% by weight)) was used. When this product was analyzed by L method and NMR method, it was found to contain 1.9% maleic anhydride component. The temperature dependence of the complex elastic modulus of the polymer satisfies the scope of the present invention as shown in Figure 1. This modified polymer was used as a +01 layer resin and ethylene with a vinyl acetate content of 67 mol% was used. - Obtained by saponifying 99.6 mol% of the vinyl acetate component of the vinyl acetate copolymer [η]: o, 1121/9 ethylene-vinyl acetate copolymer saponified resin was used as (A) # resin. ,
A laminate was obtained using high-impact polystyrene (STYRON 4750, manufactured by Asahi Dow Co., Ltd.) as the +81 layer resin in the following manner.

Extruder 11 with an inner diameter of 60wφ; extruder ■ with an inner diameter of 45wnφ;
Equipped with an extruder (■) with an inner diameter of 90 mm, extruders (■, ■)
In the case of , the molten material is separated into two layers and spread by each manifold in the die, then melted and extruded from the extruder (■), and sequentially merged with the resin layer (2) and (2) spread by the resin layer (2). A type of flat die type three-layer five-layer coextrusion equipment is used. Temperature 220℃, take-up speed 6na/
(The take-up speed is 4 minutes when the temperature of the resin is 4 minutes on the cooling roller.)
Coextrusion was carried out at 0°C (measured when the temperature reached 0°C), and the
A good laminate of five layers of three types (C1/(B)/(C)/(8)) was obtained.

The thickness of each layer is 45μ for the solid layer, 280μ for the C81 layer, (
The C1 layer is 20μ, and the peel strength between each layer is /(C)
1.81(g/an between (Bl / (C)) 'A
kg/cm showed good adhesion.

Comparative Example 2 Evaflex p-5507 (manufactured by Mikata Polychemical Co., Ltd.;
Ethylene-vinyl acetate copolymer (vinyl acetate content 63
(% by weight) ) 100 parts by weight and 7 parts by weight of maleic anhydride were dissolved in 17,700 parts by weight of xylene and maintained at 130°C. A solution prepared by dissolving 10 weight parts of benzoyl peroxide in 20 weight parts of xylene was added dropwise to this solution over 4 hours while stirring, and stirring was continued for 30 minutes. After cooling, the reaction solution was added to a large amount of acetone to precipitate a polymer, thereby obtaining a polymer containing 1.7% by weight of maleic anhydride component. When the temperature dependence of the complex modulus of elasticity of this material was measured, it was found that it did not satisfy the scope of the present invention. This is considered to be due to differences in grafting conditions, branching state (long chain or short chain branching state), crosslinked structure, molecular weight, molecular weight distribution, etc. of the obtained polymer.

The polymer was prepared in the same manner as in Example 2 except that the above polymer was a +01 layer resin.
We attempted coextrusion of A) with three types and five layers. The extruded laminate was of poor quality. When the thickness of the laminate was measured at the best possible location, the solid layer was 30 to 65 μm.
C81 layer is 270-290μ, IC1 layer is 15-27μ
Met. Also, the interlayer peel strength is 0.2 kg/cm between (A) / +Cj, and 0.1 between (B) / IC1.
kg/cIn, which was completely poor.

Comparative Example 3 1: VAF'LEX-P 2505 (Mikataho'!J
100 parts by weight of 'r Mical 1511; ethylene-vinyl acetate copolymer) and 8 parts by weight of maleic anhydride were dissolved in 400 parts by weight of xylene and maintained at 110°C. To this solution, add 10 parts by weight of benzoyl peroxide and 2 parts by weight of xylene.
A solution dissolved in 0.00 parts of a bundle was added dropwise over 1 hour while stirring, and stirring was continued for 1.5 hours. The reaction solution was immediately added to a large amount of 77 tons to precipitate the polymer. The obtained polymer was purified by reprecipitation using xylene as a solvent and acetone as a non-solvent. This product contained 6.2% by weight of maleic anhydride component. When the temperature dependence of the complex modulus of the obtained polymer was measured, as shown in FIG. 1, it did not satisfy the scope of the present invention.

A laminate obtained by coextruding the obtained resin as one IC layer in the same manner as in Example 2 was a defective product. When I selected the best possible part of the laminate and measured its thickness, I found that the number of layers was 6.
The thickness was 5 to 40μ, the C81 layer was 290 to 310μ, and the (C) layer was 16 to 29μ. The delamination strength is (At
/ (C) 0.1 kg/cm s (Bl /
(It was completely poor with μi of 0.3 between c1.

Although the same ethylene-hinyl acetate copolymer (EVAFLEX P 2505) used in Example 2 was used in this example, the peel strength of the coextruded laminate sheet was completely poor as described above.

This means that the performance of the laminate, such as its adhesive strength and appearance, is determined solely by the content of the vinyl acetate component in the copolymer and the type of ethylenically unsaturated carboxylic acid compound used. It clearly shows that it is not.

[Brief explanation of the drawing]

Figure 1 shows the real part (E') of the complex modulus of various adhesive resins.
This is a graph showing the relationship between and temperature (T), and the vertical axis is &g
E', the horizontal axis indicates the temperature T ('C). Patent applicant Rira Shi Co., Ltd. Agent Patent attorney Ken T ('c)

Claims (1)

[Scope of Claims] (1) A saponified ethylene-vinyl acetate copolymer resin layer with an IA ethylene component content of 20 to 55 mol% and a saponification degree of 90 mol% or more, (Bl polystyrene resin layer and (C) ethylene component - vinyl acetate or (meth)acrylic acid ester component - consisting of a polymer consisting of an ethylenically unsaturated carboxylic acid or the carboxylic acid anhydride component,
The adhesive resin layer is made of an adhesive resin layer that satisfies the following formula (I) when the real part of the complex modulus measured at a frequency of 110 is in the range of 20 to 70°C, and fAl and (
A laminate obtained by laminating B). 8.0-0.0143T(j?ogE'(10,0-0
,0286T---(I)(2) The laminate according to claim 1, wherein the real part of the complex modulus of elasticity is expressed by the following formula (II). s, s-0,0214T<log E<9.5-0.
02 syT--(II) (3) Saponified ethylene-vinyl acetate copolymer resin with a content of 20 to 55 mol% of ethylene content and 90 mol% or more of ethylene content, (B) polystyrene resin and (C ) ethylene component - vinyl acetate or (meth)acrylic acid ester component - ethylenically unsaturated carboxylic acid or a polymer consisting of the carboxylic acid anhydride component,
+A) and (Bl) are coextruded through (C) into an adhesive resin whose real part of the complex modulus measured at a frequency of 110H7 satisfies the following formula (I) within the range of 20 to 70°C. A method for manufacturing a laminate, characterized in that the laminate is taken at a speed of , 3 pieces/min or more. 8, o-0,0143T (dog E'(10,0-0
,0286'L"・kawa,, (■) (4) Claim 6 in which the real part of the complex modulus of elasticity satisfies the following formula (II)
2. Method for manufacturing a laminate described in Section 1. 8.5-0.0214T<JOgE'(9,5-0,0
257T・・・・・・・・・(II)