JPH0515185B2 - - Google Patents

Description

[Detailed description of the invention] A. Industrial application field The present invention has no thickness unevenness, no streaks, etc. during coextrusion molding, and no pinholes, cracks, etc. during hot stretching.
This invention relates to a multilayer structure with excellent gas barrier properties without localized thickness deviation.

B. Conventional technology Saponified ethylene-vinyl acetate copolymer (hereinafter referred to as
EVOH) is today used as food packaging film,
It has been found to be of considerable value, particularly in films intended for use on food and other products requiring protection against oxygen. However, single-layer films made of EVOH lack toughness and are brittle, and the films do not exhibit effective barrier properties against water or water vapor. In order to improve these shortcomings,
EVOH resin is typically made of nylon, polyester,
A multilayer film formed by laminating a structural layer containing one or more thermoplastic resins such as polypropylene, polyethylene, and polyvinyl chloride, and various heat sealant layers such as ionomers and ethylene-vinyl acetate copolymers. used in the form

However, due to recent technological advances, multilayer structures containing EVOH are often manufactured by a coextrusion method in which various resins are simultaneously extruded using multiple extruders and a multilayer laminate is obtained using a single die.
Further, in order to increase the strength of the multilayer structure, heating and co-stretching may be performed. However, during such molding processing,
Because it contains EVOH, it has the following problems and is often difficult to use as a food packaging material. In other words, when molding a multilayer structure containing EVOH by coextrusion,
Perhaps because the viscosity properties of EVOH, polypropylene, and polystyrene are vastly different, even if the overall thickness and distribution of the multilayer structure is made uniform, the thickness distribution of the EVOH layer is not uniform, making it difficult to use as a gas barrier food packaging material. EVOH more than necessary to guarantee sex
The layer needs to be thick. Furthermore, due to the non-uniform thickness of the EVOH layer, the gas barrier properties often deteriorated significantly due to cracks and local uneven thickness during heating and stretching. What's worse is that during coextrusion molding, if you run for a long time, the EVOH layer will cause minute streaks,
Not only do bumps occur and the appearance is damaged, but also EVOH cracks and slight thickness unevenness increase during hot stretching.
The gas barrier properties deteriorate and it becomes unusable as a food packaging material.

On the other hand, even if we improve the molding conditions and molding equipment to make the thickness distribution of the EVOH layer as uniform as possible, even if EVOH sheets with uniform thickness are laminated by the dry lamination method, there are still problems during heating stretching. Gas barrier properties are greatly deteriorated due to cracks in the EVOH layer, local thickness unevenness, etc.
There were cases where it was unusable. Conventionally, in order to make the thickness distribution uniform during coextrusion molding, methods have been used to select brands of polypropylene, polystyrene, and adhesive resins whose melt viscosity (melt index; MI) is close to EVOH, and to modify the coextrusion equipment. has been taken, but the former is essentially
EVOH and other resins have different dependence of viscosity on shear rate, so even if the viscosity (melt index) under constant shear rate conditions is combined, it is impossible to significantly improve the thickness distribution. Since the viscosity of polypropylene, polystyrene, and adhesive resin is regulated, there was a problem that the desired food packaging material could not be obtained. On the other hand, a uniform EVOH layer can sometimes be obtained by modifying the coextrusion equipment, but because the operating conditions are very narrow, the thickness distribution changes due to slight fluctuations in the discharge speed and discharge temperature, resulting in stable production. Another major problem is that when changing the brand of resin, it is necessary to make extensive modifications to the equipment itself through trial and error, and it requires a great deal of labor, time, and raw materials to establish the conditions. It was hot.

On the other hand, as a measure to prevent pinholes, cracks, local thickness unevenness, etc. in the EVOH layer that occur during heating and stretching processing, a blend of polyamide resin and aromatic sulfonamide plasticizer is mixed with EVOH (Japanese Patent Laid-Open No. 59-20345 ), and also mixtures of hydroxyl group-containing plasticizers such as glycerin, various glycols, and polyhydric compounds (Japanese Patent Laid-Open No. 53-88067).
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, when polyamide resin is blended with EVOH to obtain a multilayer structure, the polyamide resin and EVOH react, and a large number of gel-like substances (fish eyes) are generated in the molded product, and the product is heavily colored, making it difficult to use. do not have. In addition, when a multilayer structure is made into a container by secondary molding, the content of polyamide resin added to prevent the occurrence of cracks, pinholes, etc. in the EVOH layer is 10 to 30 parts by weight per 100 parts by weight of EVOH. It is necessary to add a large amount. As a result, the gas barrier properties are greatly reduced, and even if the molded containers are good, they cannot be used in the field of food packaging, which is characterized by high gas barrier properties. Further, in the case of a hydroxyl group-containing plasticizer system, the amount added is 10 to 20 parts by weight per 100 parts of EVOH, similar to the polyamide resin, and the gas barrier properties are greatly reduced. Even worse,
Perhaps due to insufficient compatibility with EVOH, plasticity bleeds, and the adhesive strength between the EVOH layer and other resin layers in a multilayer laminated container decreases significantly over time, impairing the shape of the container. In other words, the above additives are unacceptable to use. Therefore, there is no significant drop in gas barrier properties, the thickness of the EVOH layer is uniform when forming a multilayer structure by coextrusion, and the thickness of the EVOH layer is uniform when the multilayer structure is heated and stretched. One of the important issues is the development of EVOH that has good moldability and does not produce pinholes, cracks, or minute thickness deviations.

C. Problems to be Solved by the Invention The present invention provides a modified product that is free from the above-mentioned drawbacks, has no unevenness between products and within a molded product, and therefore has no variation in the above-mentioned properties, and has an extremely high degree of uniformity. The aim is to obtain a coextruded multilayer structure using the silicon-containing EVOH produced by the present invention.

D. Means for Solving the Problems The present invention provides a melt molding material consisting of EVOH obtained by saponifying a copolymer of vinyl acetate, ethylene, and an olefinic unsaturated monomer containing silicon in a specific molecule. By saponifying vinyl acetate, ethylene, and one or more copolymers selected from silicon-containing olefinic unsaturated monomers represented by the following general formulas (), (), and (). The obtained vinyl acetate component has a saponification degree of 95 mol% or more, an ethylene content of 25 to 60 mol%, preferably 25 to 55 mol%, and a silicon content of 0.0005 to 0.2 mol%. Polypropylene is applied on at least one side of the silicon-containing EVOH layer. It is a coextruded multilayer structure having a layer of resin or polystyrene resin.

E Effects of the invention When creating various laminated multilayer structures having a polypropylene and/or polystyrene layer on one or both sides of the EVOH layer via an adhesive resin by coextrusion, the brands of the adhesive resin, polypropylene, and polystyrene are used. The thickness distribution of the EVOH layer in the direction perpendicular to the direction of resin discharged from the coextruder die remains uniform even if the viscosity and viscosity are changed, or the structure and flow rate of the resin flow path of the coextrusion device are changed. It was extremely difficult to do so. As a result, EVOH
There were many problems such as cracks during heating and stretching due to uneven thickness distribution of the layer, and the need to make the EVOH layer thicker than necessary in order to compensate for the deterioration of gas barrier properties due to uneven thickness in some places.

The root cause of the above problem is the shear rate dependence of the viscosity of polypropylene, polystyrene, and adhesive resin.
It was thought that this was because it was different from that of EVOH resin, so
EVOH was modified by using various additives (plasticizers, crosslinking agents, etc.) and by changing the copolymer composition. As a result, although polyhydric alcohol plasticizers, carboxylic acid amide plasticizers, aromatic sulfonic acid plasticizers, etc. have the effect of reducing viscosity, their effect on improving the thickness distribution of the EVOH layer is so small that they are not practical. Additionally, the method of changing the shear rate dependence of viscosity by cross-linking EVOH by adding peroxide was found to be somewhat effective, but it appeared to be unusable due to the appearance of bumps and uneven flow during long-term operation. It was hot. However, surprisingly, compared to EVOH alone and EVOH compositions with other plasticizers, crosslinkers, and additives, silicon-containing EVOH
Not only is the thickness distribution of the EVOH layer uniform,
It was found to be a very good product with almost no bumps, streaks, or uneven flow during long-term operation. Surprisingly, when a multilayer structure having a polypropylene or polystyrene layer in the EVOH layer is heated and stretched, unlike EVOH alone or an EVOH composition containing other plasticizers, pinholes, cracks, and minute defects in the EVOH layer occur. It was found that not only a very good molded product with almost no unevenness in thickness could be obtained, but also that the molded product had excellent gas barrier properties, particularly under high humidity conditions, leading to the present invention. The reason why silicon-containing EVOH has the above-mentioned unexpected moldability improvement effect is not obvious, but the low degree of polymerization containing silicon compounds
Because EVOH is partially and reversibly crosslinked via a silicon compound, it acts as a low molecular weight resin in the high shear rate range and as a high molecular weight resin in the low shear rate range. Because the shear rate dependence of viscosity and the radiation stress characteristics match those of the adhesive resin, it is
This is thought to be due to the fact that the thickness distribution of the EVOH layer can be easily made uniform. It is also the cause of bumps, streaks, and uneven flow that tend to occur during long-term operation.
It seems that the gelation of EVOH is also a characteristic of EVOH with a low degree of polymerization. In other words, although the apparent viscosity shows a certain value due to partial and reversible crosslinking of the silicon compound, it is essentially an aggregate of EVOH with a low polymerization degree, and the lower the polymerization degree resin, the more difficult it is to gel. The observed facts support the above inference (specificity of silicon compounds). Furthermore, the moldability improvement effect in hot stretching processing is due to the partial, reversible crosslinking effect of silicon compounds, as described above.In other words, during high-speed deformation (stretching), it appears to act as a low molecular weight resin and facilitates deformation, while crosslinking This is thought to be due to the fact that the strength of the high molecular weight component is taken into account, and the stretchability is greatly increased.

F. More detailed description of the invention The melt molding material made of EVOH in the present invention has an ethylene content of 25 to 60 mol%, preferably 25 to 60 mol%.
~55 mol%, and the degree of saponification of the vinyl acetate component of the copolymer is preferably 95 mol% or more.If the ethylene content is less than 25 mol%, good melt molding processability is maintained while oxygen etc. It becomes difficult to significantly improve the effect of improving the humidity dependence of the barrier properties of EVOH, and on the other hand, if it exceeds 55 mol%, especially 60 mol%, the barrier properties against oxygen, etc., which are the characteristics of EVOH, and the fragrance retention properties decrease. . Furthermore, if the degree of saponification is less than 95 mol%, the barrier properties and oil resistance will decrease,
Not only will EVOH not be able to maintain its original characteristics,
This makes it difficult to enjoy the effects of the present invention.

The silicon-containing olefinic unsaturated monomer used in the present invention is preferably one or more selected from the compounds represented by the following general formulas (), (), and (). be able to.

[However, here, n is 0 to 1, m is 0 to 2, R ¹ is a lower alkyl group, an aryl group, or a lower alkyl group having an aryl group, and R ² is a linear or branched chain having 1 to 40 carbon atoms. is an alkoxyl group, and the alkoxyl group may have an oxygen-containing substituent. R ³ is a hydrogen atom or a methyl group, R ⁴ is a hydrogen atom or a lower alkyl group, R ⁵ is an alkylene group or a divalent organic residue in which chain carbon atoms are interconnected by oxygen or nitrogen, R ⁶ is a hydrogen atom, a halogen atom, a lower alkyl group, an aryl group, or a lower alkyl group having an aryl group,
R ⁷ is an alkoxyl group or an acyloxyl group (herein, the alkoxyl group or acyloxyl group may have a substituent having oxygen or nitrogen), and R ⁸ is a hydrogen atom, a halogen atom, a lower alkyl group, an aryl group, or , a lower alkyl group having an aryl group, R ⁹ is a lower alkyl group. ] More specifically, R ¹ is a lower alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 18 carbon atoms, or a aryl group having 1 to 18 carbon atoms.
5 represents a lower alkyl group, R ⁴ represents a hydrogen atom or a lower alkyl group having 1 to 5 carbon atoms, and R ⁵ represents an alkylene group having 1 to 5 carbon atoms or a group in which chain carbon atoms are interconnected by oxygen or nitrogen. combined 2
^R6 represents a hydrogen atom, a halogen atom, a lower alkyl group having 1 to 5 carbon atoms, or a valent organic residue having 6 carbon atoms.
~18 aryl group, or a lower alkyl group having 1 to 5 carbon atoms having an aryl group having 6 to 18 carbon atoms, and R ⁷ is an alkoxyl or acyloxyl group having 1 to 40 carbon atoms (here, may have a substituent containing oxygen or nitrogen), and R ⁶ is a hydrogen atom, a halogen atom, a lower alkyl group having 1 to 5 carbon atoms, an aryl group having 6 to 18 carbon atoms, or a carbon number It represents a lower alkyl group having 1 to 5 carbon atoms and having a 6 to 18 aryl group, and ^R9 represents a lower alkyl group having 1 to 5 carbon atoms.

Examples of the silicon-containing olefinic unsaturated monomer represented by the general formula () include vinyltrimethoxysilane, vinylmethyldimethoxysilane, vinyldimethylmethoxysilane, vinyltriethoxylane, vinylmethyldiethoxysilane, vinyldimethylethoxysilane, Allyltrimethoxysilane, allylmethyldimethoxysilane, allyldimethylmethoxysilane, allyltriethoxysilane, allyldimethylethoxysilane, vinyltris(β-methoxyethoxy)silane, vinylisobutyldimethoxysilane, vinylethyldimethoxysilane, vinylmethoxydibutoxysilane, Vinyldimethoxybutoxysilane, vinyltributoxysilane, vinylmethoxydihexyloxysilane, vinyldimethoxyhexyloxysilane, vinyltrihexyloxysilane, vinylmethoxydioctyloxysilane, vinyldimethoxyoctyloxysilane, vinyltrioctyloxysilane, vinylmethoxy Dilauryloxysilane, Vinyldimethoxylauryloxysilane, Vinylmethoxydioleyloxysilane, Vinyldimethoxyoleyloxysilane, General formula Examples include polyethylene glycol derivatives of vinylmethoxysilane represented by (where m is the same as above and x represents 1 to 20), but vinyltrimethoxysilane is preferred from an economic standpoint.

The silicon-containing olefinic unsaturated monomer represented by the general formula () is 3-(meth)acrylamide-propyltrimethoxysilane 3-(meth)acrylamide-propyltriethoxysilane 3-(meth)acrylamide-propyltri(β-methoxyethoxy)silane 3-(meth)acrylamido-propyltri(N-methylaminoethoxy)silane 2-(meth)acrylamide-ethyltrimethoxysilane 1-(meth)acrylamide-methyltrimethoxysilane 2-(meth)acrylamido-2-methylpropyltrimethoxysilane 2-(meth)acrylamide-isopropyltrimethoxysilane (Meth)acrylamide-linear or branched alkyltrialkoxysilane such as (R represents hydrogen or methyl group) N-(2-(meth)acrylamide-ethyl)-
Amidopropyltrimethoxysilane CH ₂ = CRCONHCH ₂ CH ₂ NH(CH ₂ ) ₃ Si(OCH ₃ ) ₃ (3-(meth)acrylamido-propyl)-oxypropyltrimethoxysilane CH ₂ = CRCONH(CH ₂ ) ₃ O ( _meth )acrylamide-nitrogen-containing or nitrogen-containing alkyltrialkoxysilane such as (CH2) _3Si ( _OCH3 ) ₃ (R represents hydrogen or methyl group) 3-(meth)acrylamide-propyltriacetoxysilane CH ₂ = CRCONH(CH ₂ ) ₃ Si(OCOCH ₃ ) ₃ 2-(meth)acrylamide-ethyltriacetoxysilane CH ₂ = CRCONH(CH ₂ ) ₂ Si(OCOCH ₃ ) ₃ 4-(meth)acrylamide-butyltriacetoxy Silane CH ₂ = CRCONH (CH ₂ ) ₄ Si (OCOCH ₃ ) ₃ 3-(meth)acrylamide-propyltripropionyloxysilane CH ₂ = CRCONH (CH ₂ ) ₃ Si (OCOCH ₂ CH ₃ ) ₃ 2-(meth) Acrylamido-2-methylpropyltriacetoxysilane N-( _2- (meth)acrylamido-ethyl)aminopropyltriacetoxysilane _CH2 = _{CRCONHCH2CH2NH} ( _CH2 ) _3Si ( _OCOCH3 ) ₃ (R represents hydrogen or methyl group) ) acrylamide-alkyltriacyloxysilane, 3-(meth)acrylamido-propylisobutyldimethoxysilane 2-(meth)acrylamide-ethyldimethylmethoxysilane 3-(meth)acrylamide-propyloctyldiacetoxysilane 1-(meth)acrylamide-methylphenyldiacetoxysilane 3-(meth)acrylamide-propylbenzyldiethoxysilane 2-(meth)acrylamido-2-methylpropyl monochlorodimethoxysilane 2-(meth)acrylamido-2-methylpropylhydrodienemethoxysilane (Meth)acrylamido-alkyldi- or monoalkoxy or di- or monoacyloxysilane such as (R represents hydrogen or methyl group), 3-(N-methyl(meth)acrylamido)-propyltrimethoxysilane 2-(N-ethyl-(meth)acrylamide)-
Ethyltriacetoxysilane Examples include (N-alkyl-(meth)acrylamido)alkyltrialkoxy or triacetoxysilane such as (R represents hydrogen or a methyl group). Among these, 3-(meth)acrylamide-
Propyltrimethoxysilane and 3-(meth)
Acrylamido-propyltriacetoxysilane is relatively easy and inexpensive to produce industrially, and 2-(meth)acrylamido-2-methylpropyltrimethoxysilane and 2-(meth)acrylamido-2-methylpropyltriacetoxysilane is preferably used because the amide bond is extremely stable against acids or alkalis. Here, the modified silicon-containing EVOH obtained by copolymerizing the silicon-containing polymerizable monomer represented by the general formula () with vinyl acetate and ethylene and saponifying the resulting copolymer is obtained by the following general formula ().
Contains copolymerized units shown in

(Here, R ³ , R ⁴ , R ⁵ , R ⁶ , and m are the same as above.
R ¹⁰ represents a hydroxyl group or a salt of the hydroxyl group represented by the general formula OM (M represents an alkali metal or NH ₄ ). ) As the silicon-containing olefinic unsaturated monomer represented by the general formula (), vinyltriacetoxysilane Vinyltripropionyloxysilane isopropenyltriacetoxysilane Vinylisobutyldiacetoxysilane Vinylmethyldiacetoxysilane Vinyldimethylacetoxysilane vinyl phenyl diacetoxysilane Vinyl monochlorodiacetoxysilane vinyl monohydrodiene diacetoxysilane etc., but vinyltriacetoxysilane is preferred from an economic standpoint.

The copolymerization of the silicon-containing olefinic unsaturated monomer with vinyl acetate and ethylene is preferably carried out by solution polymerization in the presence of alcohol. As for the alcohol, lower alcohols such as methanol and ethanol are usually preferred industrially. Copolymerization can be carried out either batchwise or continuously. The ethylene content of EVOH is mainly determined by the vinyl acetate present in the copolymerization system and the amount of ethylene dissolved in the copolymerization system, and the latter mainly depends on the polymerization ethylene pressure and temperature. In some cases, the silicon content of the modified EVOH is primarily governed by the quantitative relationship between vinyl acetate and silicon-containing olefinically unsaturated monomers present in the system. It is well known that in the case of a batch method, the copolymer composition changes with the polymerization rate depending on the copolymerization reactivity ratio, but one or both monomers are In order to obtain a copolymer having a uniform copolymerization composition, it is more desirable to adopt a so-called semi-batch method of adding . An example of how to calculate the amount added in this case is RJ Hanna (RJ
Industrial and Engineering Chemistry
Engineering Chemistry) vol.49, No.2, 208~
209 (1957). In the case of a continuous system, a completely mixed one-stage flow system reaction system in which the stirring mixing tank is used as a copolymerization reaction tank is most suitable, and in the case of a multi-stage flow system reaction system of two or more stages, the same method as above is used. For this reason, it is more preferable to carry out the reaction while adding monomers to the second and subsequent copolymerization tanks so that the monomer composition in each stage of the copolymerization tank is constant. As a polymerization initiator, 2,2'-azobis(4-methoxy-
2,4-dimethylvaleronitrile), 2,4,4
-Ntriles such as trimethylvaleronitrile, 2,2'-azobisisobutyronitrile, di-n-
Propyl peroxycarbonate, bis-4-t
- Known radical initiators such as carbonates such as butylcyclohexyl peroxydicarbonate and bis-2-ethylhexyl peroxydicarbonate, peroxides such as acetylcyclohexane sulfonyl peroxide, benzoyl peroxide, and lauroyl peroxide. can be used. In particular, polymerization initiators with a shorter half-life are suitable for long-term continuous polymerization operations because they can almost completely or largely suppress the formation of gel-like substances that are insoluble in the polymerization system and are observed over time during copolymerization. used.

The copolymer obtained by polymerization is then subjected to a saponification reaction. The saponification reaction is advantageously carried out in a known manner, for example by using an alkaline catalyst, that is, usually in the form of an alcoholic solution of the copolymer, and the reaction is carried out by alcoholysis. In particular,
The most suitable method is the method disclosed in Japanese Patent No. 575889 and Japanese Patent No. 611557, which uses a tower reactor and removes methyl acetate, which is a by-product during the saponification reaction, from the top of the tower by blowing alcohol vapor into the bottom of the tower. Can be used.

As alkaline catalysts used for saponification reactions,
Alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alcoholates such as sodium methylate and potassium methylate, and the like are used. Among these, sodium hydroxide is industrially and economically advantageous. The saponification temperature is suitably selected from the range of 60 to 175°C. In particular, when using the tower type reactor, a temperature of 100°C or higher is preferable from the viewpoint of shortening the reaction time and the solubility of the silicon-containing EVOH in alcohols, although it is also related to the composition of the copolymer. .

In the saponification reaction, vinyl alkoxysilane units are also partially or highly saponified and converted into vinyl silanol units, their alkali salts, or their intercondensates. However, the general formula ()
The copolymer containing the monomer represented by is kept stable without decomposition of the amide bond of the silicon-containing polymerizable monomer unit in the saponification reaction using an alkaline catalyst. However, during the saponification reaction, the silicon-bonded alkoxyl group, carboxyl group, hydrogen, and halogen of the silicon-containing monomer unit represented by the general formula () are simultaneously partially or highly saponified and converted into hydroxyl groups or alkali salts of hydroxyl groups. Ru. Furthermore, some of these hydroxyl groups are
When drying the modified EVOH molding material obtained after the saponification reaction, these reactive groups may be bonded together to form siloxane bonds depending on the drying conditions.
This modification resulted in the formation of many siloxane bonds.
The thermal meltability of EVOH molding materials sometimes deteriorates, so in such cases, the content of silicon-containing monomers must be adjusted or the silicon-containing polymerizable monomer unit must be extremely stable against alkalis. It is preferable to use a modified EVOH molding material having (meth)acrylamide-branched alkylsilane units with high properties.

After the saponification reaction, known methods can be applied to isolate the modified EVOH molding material.
In particular, the method disclosed in Japanese Patent No. 725520 in which the polymer is precipitated into strands and the polymer is separated is preferably used. The precipitated and isolated EVOH molding material is washed with water by a known method, then subjected to a known heat stabilization treatment such as acid treatment, and dried. During the saponification reaction during the acid treatment, the silicon-bonded alkoxyl group, carboxyl group, hydrogen, and halogen are converted into an alkali salt of the hydroxyl group, resulting in a hydroxyl group.

The modified silicon-containing EVOH according to the present invention is
It is extremely satisfactory from the viewpoint of improving the inherent properties of EVOH resin and imparting properties that are compatible with other resins and processing methods, and the content of silicon-containing monomer in the copolymer is extremely satisfactory. The modified EVOH melt molding material suitable for each case can be obtained by changing it accordingly. For example, as the ethylene content increases, the melt viscosity index of EVOH increases, and when composited with other resins with low melt viscosity indexes, there is a large difference in melt viscosity, and a phenomenon indicating melt viscosity inconsistency has been observed. In such cases, the modified EVOH resin molding material, in which the melt viscosity index of the EVOH resin is lowered by the modification of the present invention while maintaining the composition, is used to improve the melt viscosity. The usefulness of the modified EVOH molding material of the present invention, such as the ability to eliminate alignment, is extremely large due to the uniformity of its modification. If the content of the silicon-containing monomer is too small, the modification effect will not be exhibited, and if it is too large, the degree of crosslinking will increase too much and heat infusibility will develop. The content is selected depending on the purpose, but
A range of 0.0005 to 0.2 mol%, particularly 0.001 to 0.1 mol% is preferred. The silicon content herein refers to the amount (mol %) of the silicon-containing monomer in the silicon-containing monomer-vinyl acetate-ethylene copolymer.

As mentioned above, the modified silicon-containing EVOH of the present invention can be used more satisfactorily for all conventional purposes, but it has new properties derived from its silicon-containing characteristics, such as aluminum It can advantageously improve adhesion to boxes, other resins, etc.

ASTM D of modified EVOH in the present invention
The melt viscosity index measured by -1238-T was at 190℃ and a load of 2160g.
0.05 g/10 minutes or more, more preferably 0.05 to 10 g/10 minutes, and especially 0.1 to 10 g/10 minutes for various uses such as films, sheets, containers, etc., either unstretched or at least uniaxially stretched. It is suitably used.

The silicon-containing EVOH of the present invention is obtained from EVOH having a specific ethylene content and silicon content obtained by saponifying a copolymer of vinyl acetate, ethylene, and the above-mentioned specific silicon-containing olefinic unsaturated monomer. However, the copolymer may contain another third substance as a copolymer component within a range that does not affect its properties. Examples of the third substance include α-olefins having 3 or more carbon atoms, acrylic acid, methacrylic acid, and esters of these acids. Furthermore, ordinary EVOH can be freely blended into this silicon-containing EVOH to the extent that it does not impede the object of the present invention.

As mentioned above, the silicon-containing EVOH of the present invention is used in combination with polypropylene resin or polystyrene resin, but in recent years, with the diversification of properties and higher quality required, various other resins have been used. They are suitably used in combination as a two-layer structure or a multilayer structure of two or more layers. When compounding, a coextrusion method is used, but in this case, EVOH with a desired ethylene content that does not cause melt viscosity mismatch with polypropylene resin or polystyrene resin can be obtained by appropriately selecting the silicon content. . The layer structure of the multilayer structure includes, for example, polypropylene (hereinafter referred to as PP)/adhesive layer/silicon-containing EVOH (hereinafter referred to as Si-EVOH), PP/adhesive layer/Si-EVOH/adhesive layer/PP, PP. /Adhesive layer/Si
-EVOH/adhesive layer/PE, PET/adhesive layer/Si-
EVOH/adhesive layer/PP, polystyrene (hereinafter referred to as PS)/adhesive layer/Si-EVOH, PS/adhesive layer/Si
-EVOH/adhesive layer/PS etc. are exemplified. The adhesive resin used for the adhesive layer varies depending on the type of resin laminated adjacent to the Si-EVOH, but examples include maleic anhydride graft-modified PE, maleic anhydride graft-modified PP, and maleic anhydride graft-modified ethylene. - One or more mixtures selected from ethyl acrylate, ethylene-vinyl acetate copolymer, maleic anhydride graft-modified ethylene-vinyl acetate copolymer, etc., or a blend of these and Si-EVOH, etc. There are several types available, and you can select one from these.

When commercializing the laminated structure into containers etc., it is economically important to reuse the scraps and rejected products of the laminated product produced during molding.
Blends of EVOH and other resins and/or adhesives to be laminated can be used alone or laminated with Si-EVOH or other thermoplastic resins.

In the present invention, as the polypropylene resin, a homopolymer, a copolymer, or a blend of these or with other polymers, which is mainly composed of propylene, is used. Suitable propylene polymers include isotactic polypropylene, crystalline propylene-ethylene copolymers, blends of polypropylene and propylene-ethylene copolymers or polyethylene, and blends of crystalline propylene copolymers and polyethylene. I can list things. The amount of ethylene units contained in the propylene polymer in the form of a copolymer or blend is preferably 20% by weight or less, particularly 10% by weight or less of the total weight.

The polystyrene resin in the present invention is defined as having at least a structural unit represented by the following general formula in the resin.
It is a resin containing 25% by weight or more.

(Here, R is a hydrogen atom or a methyl group, Z is a halogen atom or a methyl group, and p is 0 or 1 to
It is an integer of 3. ) Specifically, polystyrene,
Examples include homopolymers and copolymers of styrene and its derivatives, such as rubber-modified polystyrene, styrene-acrylonitrile copolymer, styrene-butadiene-acrylonitrile copolymer, and the like. Blends of these resins with styrene-conjugated diene block copolymer rubber and water agents thereof are also applicable.

In the present invention, the method for obtaining a multilayer structure is
A method of coextruding Si-EVOH and polypropylene or/or polystyrene resin via an adhesive resin (feedblock method or multi-manifold method), a method of coextrusion lamination, a method of coextrusion and co-stretching, a method of coextrusion and co-stretching, A method of creating an extruded pipe, a method of creating a parison by co-injection molding, or a method of reheating and stretching the laminate obtained in this way by vacuum pressure deep drawing, biaxial stretching molding, biaxial stretching blow molding, etc. There are ways to do this. There are no particular limitations on the thickness structure of the multilayer structure of the present invention, but when considering moldability, cost, etc., the thickness ratio of the EVOH layer to the thickness of all layers is preferably about 2 to 20%. It is. Further, in the present invention, there is no particular restriction on the moisture content of the Si-EVOH layer, which is one component of the multilayer structure pair, during heating and stretching, but it is preferably within 0.01 to 10%.

The thus obtained multilayer structure of the present invention and its heat-stretched product have a uniform thickness of the Si-EVOH layer, are free from streaks and bumps, and are free from pinholes, cracks, and uneven thickness that tend to occur during stretching. The gas barrier properties are extremely good. Therefore, it is useful as a food packaging material, a container, or a container that requires gas barrier properties.

EXAMPLES Hereinafter, the present invention will be further explained with reference to Examples, but the present invention is not limited thereto in any way. (In addition, the middle part of the examples or % indicates parts by weight or weight % unless otherwise specified.) <Thickness distribution measurement of coextruded product> In a feed block type 3 type 5 layer coextrusion device, from a die width of 550 cm PP to be discharged/
AD ₁ EVOH/AD ₁ /PP or PS/AD ₂ /EVOH/
An AD ₂ /PS sheet (see below for brands and thicknesses of PP, AD, and PS) was formed at a take-up speed of 1 m/1 min.

The thickness of the EVOH layer in the center of the above sheet is Aμ,
If the average thickness of 10cm on both sides from the center is Bμ,
The thickness variation rate (X%) of the EVOH layer is X = (B-
A)/A×100 (%).

PS...Polystyrene (Idemitsu styrene ET-61)
450μ PP...Polypropylene (Mitsubishi Yuka Noblen)
MA-6) 450μ AD ₁ ...PP adhesive resin (Mitsui Petrochemical Admer QF-500) 50μ AD ₂ ...PS adhesive resin (Toyo Soda Mersen
5420) 50μ EVOH...Target center thickness of 50μ <Method for measuring moisture in EVOH layer> Peel off the EVO layer on the multilayer structure just before heating and stretching, and leave it in a hot air dryer at 120℃ for 24 hours.
Determine the moisture content of the EVAL layer from the weight loss. This value is expressed as a percentage and is referred to as volatile content.

Example 1 Continuous polymerization was carried out under the following conditions in order to obtain a silicon-containing ethylene-vinyl acetate copolymer in a polymerization tank with a capacity of 10 and equipped with a stirrer and a cooling coil inside.

Vinyl acetate supply rate 480g/hr Methanol supply rate 40g/hr Vinyl-tri-methoxysilane supply rate 355mg/hr 2,2'-azobisisobutyronitrile 33mg/hr Polymerization temperature 77℃ Polymerization tank ethylene pressure 60Kg/cm ² G Average residence time 6hrs The polymerization rate of vinyl acetate was about 50%. The copolymerization reaction liquid was supplied to a purging tower, and unreacted vinyl acetate was removed from the top of the tower by introducing methanol vapor from the bottom of the tower, to obtain a 45% methanol solution of the copolymer. According to the magnetic resonance analysis, the copolymer contains 0.027 mol% of vinyltrimethoxysilane units, 59.5 mol% of vinyl acetate units, and approximately 59.5 mol% of ethylene units.
It was confirmed that the content was 40.5 mol%. A methanol solution of the copolymer was introduced into a tower-type saponification reactor, and sodium hydroxide was further supplied to the reactor at a molar ratio of 0.05 to the vinyl acetate component contained in the copolymer. More methanol vapor is blown into the column, and while removing by-product methyl acetate from the top of the column, a saponification reaction is carried out, and reforming is carried out from the bottom of the column.
A methanol solution of EVOH was obtained. Mixed steam with a weight ratio of methanol/water = 7/3 was blown into the methanol solution to change the solution composition to a water/methanol mixed system, and then discharged in the form of a strand into a 10% methanol aqueous solution at 5°C. The EVOH was isolated as a pellet by coagulation, precipitation, and cutting. After thoroughly washing with water, immerse it in dilute acetic acid water.
Dry at 65°C to 110°C. Saponification degree is 99.3 mol%
It was hot.

The EVOH, polypropylene (Mitsubishi Noblen)
MA-6) and adhesive resin {Mitsui Petrochemical Co., Ltd.'s "Admar QF500" (maleic anhydride grafted polypropylene)} were supplied to a feed block type 3 type 5 layer coextrusion device, and the die temperature was 230°C and the extruder was
PP/AD ₁ /Si− with 1 min sheet pulling device
A sheet of EVOH/AD ₁ /PP composition with a total thickness of about 1 mm was obtained. The thickness of each layer is approximately 450μ for the PP layer, approximately 50μ for each adhesive layer (AD), and approximately 50μ for the EVOH layer. The thickness variation rate (thickness distribution in the direction perpendicular to the discharge direction) of the EVOH layer of this sheet was 7%. In addition, there were hardly any streaks, bumps, or uneven flow.

The obtained sheet was subjected to a vacuum pressure forming machine (FK-0431 manufactured by Asano Laboratory) at a sheet temperature of 150℃.
SPPF molding was performed. (The volatile content of the EVOH layer before molding was 0.14%.) As a result, the transparency of the molded container was good, and no cracks or slight thickness deviations were observed (the deep drawing ratio of the molded container was
1.5).

This drawing-formed container was heated at 20℃−65%RH and at 20℃−
After sufficiently controlling the humidity at 100% RH (for approximately one month), the amount of oxygen permeation was measured using a Mocon oxygen analyzer (manufactured by Mocon). As a result, the amount of oxygen permeation through the EVOH layer was 1.1cc・20μ/ ^m2・24hr・atm (20℃
−65%RH), 13c.c.・20μm ²・24hr・atm (20℃−
100% RH) and showed very good gas barrier properties.

Comparative Example 1 The same procedure as Example 1 was carried out except that vinyltrimethoxysilane was not used, and the ethylene content
EVOH with a saponification degree of 40.7 mol% and a saponification degree of 99.4 mol% was obtained. Melt film formation was carried out in the same manner as in Example 1. the result,
The thickness variation rate of the EVOH layer of the sheet exceeds 100%,
Not only was the film extremely non-uniform, but streaks and spots were noticeable after 2 to 3 hours of film formation, making it difficult to use over the entire width. In addition, we applied SPPE (solid phase pressure forming) to the parts of this sheet with small thickness variations using a vacuum pressure forming machine, but
Many minute cracks were visible to the naked eye on the sides of the molded product, making it unusable. The oxygen permeation rate of this container is 4000c.c.・20μ/ ^m2・24hr・atm (20
℃ - 100% RH), indicating that the EVOH layer was cut. The oxygen permeation rate of the original fabric before vacuum pressure forming is 1.0cc・20μ/m ²・24hr・atm (20
℃-65%RH), 28c.c.・20μ/ ^m2・24hr・atm(20
℃−100%RH).

Comparative Example 2 In order to investigate the cause of cracks that occurred on the side of the molded product during vacuum-pressure molding in Comparative Example 1, the EVOH used in Comparative Example 1 was formed into a film using a 40φ single-layer extruder to form a single layer with a uniform thickness. An EVOH layer was obtained (50μ film, thickness variation rate 5%). After this EVOH film was dry laminated onto a 1000μ polypropylene sheet (Mitsubishi Noprene MA-6) treated with an anchor coat (Toyo Morton AT-335A), SPPF molding was performed using a vacuum-pressure forming machine, but as in Comparative Example 1, A slight crack was observed on the side of the container. Therefore, the abnormalities (cracks) during deep drawing that occurred in Comparative Example 1 are not due to uneven thickness, streaks, or spots in the EVOH layer during sheet creation, but are essentially due to the characteristics of the EVOH used in Comparative Example 1. Something has become clear.

Comparative Example 3 [η] _ph (measured with 15% hydrated phenol at 30°C) of EVOH used in Example 1 was 0.084 (/g), and MI ₁₉₀ (melt index value measured at 190°C with a load of 2160 g) is 2.1 (g/10 min), compared to [η] _ph of EVOH used in Comparative Example 1.
MI ₁₉₀ = 165 (g/10 min) for 0.081 (/g). Since the difference in MI ₁₉₀ may be considered to be the cause of abnormalities in film formability and deep drawability, 0.35 parts by weight of BPO (benzoyl peroxide) was added to 100 parts by weight of EVOH used in Comparative Example 1. 40φ extruder 220
Crosslinking pelletization was carried out at °C. The obtained pellets were dried at 90°C for 16 hours and the MI ₁₉₀ was measured.
It was 1.8g/10 minutes. Using this EVOH, film formation was performed in the same manner as in Example 1. As a result, the thickness variation rate of the EVOH layer of the sheet was 48%, which was lower than Comparative Example 1, but was still not as high as that of Example 1. Further, minute spots were observed in the EVOH layer of this sheet from the beginning of operation, and after 2 to 3 hours, streaks and uneven flow increased, making it difficult to continue operation. Example 1 was applied to a portion with relatively few bumps and streaks and a relatively good thickness distribution at the initial stage of operation.
Vacuum-pressure molding was carried out in the same manner as in the above, but many cracks appeared on the sides of the molded product, making it unusable.

Example 2 Using the same polymerization tank as in Example 1, continuous polymerization was carried out under the conditions shown below.

Vinyl acetate supply rate 440g/hr t-Butanol supply rate 60g/hr 2,2'-azobis-(2,4-dimethylvaleronitrile) 110mg/hr 3-acrylamide-propyltrimethoxysilane 150mg/hr Polymerization temperature 60℃ Average Residence time: 8 hours Polymerization tank ethylene pressure: 46 Kg/cm ² G The polymerization rate of vinyl acetate was approximately 55%. The copolymer was confirmed by nuclear magnetic resonance analysis to contain 0.013 mol% of 3-acrylamide-propyltrimethoxysilane units, 65 mol% of vinyl acetate units, and about 35 mol% of ethylene units.

The product was saponified and isolated in the same manner as in Example 1, post-treated, and then dried to obtain modified EVOH. The degree of saponification was 99.2 mol%, and the MI ₁₉₀ was 0.7 g/10 min.

As in Example 1, PP/AD ₁ /
A sheet of Si-EVOH/AD ₁ /PP composition with a total thickness of about 1 mm was obtained. The thickness variation rate of this sheet was 5%, and even after long-term operation (2 to 3 days or more), there were very few streaks, bumps, and uneven flow.

The obtained sheet was subjected to a biaxial stretching test device (pantograph type, manufactured by Toyo Seiki), and the sheet temperature was 150°C.
Sequential biaxial stretching was carried out by a factor of 5×5. before stretching
The volatility of the EVOH layer was 0.25%. the result,
EVOH layer has no cracks and uniform thickness distribution.
It was also found that a co-stretched film with good transparency could be obtained. The oxygen permeability of this film is 0.5
cc・20μ/m ²・24hr・atm (20℃−65%RH) 20
cc・20μ/m ²・24hr・atm (20°C-100%RH), showing very good gas barrier properties.

Comparative Example 4 The same procedure as Example 2 was carried out except that 3-acrylamide-propylmethoxysilane was not used. Ethylene content was 35 mol%, saponification degree was 99.3 mol%,
MI ₁₉₀ obtained 2.1 g/10 min EVOH. The sheet obtained by coextrusion film formation in the same manner as in Example 2
The EVOH layer had a very poor thickness variation rate of 68% and was not only non-uniform, but also streaks, bumps, and uneven flow became noticeable after 3 to 4 hours of continuous operation. Biaxial stretching was performed in the same manner as in Example 2 at the initial stage of operation and in a portion where the thickness variation and unevenness of the EVOH layer were relatively small. The volatile content of the EVOH layer at this time was 0.28%. This biaxially stretched film had a network of cracks all over its surface and was unusable. The oxygen permeation rate of this co-stretched film is 4000c.c.・20μ/ ^m2・24hr・atm (20℃−
100% RH) or higher, indicating that the EVOH layer was cut. The oxygen permeation rate of the original fabric before vacuum pressure forming is 0.6cc・20μ/m ²・24hr・atm (20℃−65%
RH) 35c.c.・20μ/m ²・24hr・atm (20℃−100%
RH).

Comparative Example 5 N-ethyltoluenesulfonamide 15 was added as a plasticizer to 100 parts by weight of EVOH used in Comparative Example 4.
Place the weight part and set the die temperature using a 40φ extruder.
Pelletization was carried out at 220°C. After drying the pellets at 95°C for 16 hours, coextrusion film formation was carried out in the same manner as in Example 2. The thickness variation rate of the obtained sheet was 21%, which showed a slight tendency to improve, but it was not enough, and to make matters worse, the sheet had many streaks and flow irregularities 20 to 30 minutes after the start of operation, making it difficult to operate for a long time. was difficult. A portion at the beginning of operation and where the thickness distribution was relatively good was sampled and co-stretched in the same manner as in Example 2. As a result, it appeared that a relatively good stretched film with no cracks had been obtained, although there was some unevenness in stretching, but when oxygen permeability was measured, it was found to be 5 c.c.
20μ/m ²・24hr・atm (20℃−65%RH) 98c.c.・
The amount of oxygen permeation is large at 20μ/ ^m2・24hr・atm.
It was found that the material was not fully satisfactory as a food packaging material with gas barrier properties. By adding plasticizer
Although the moldability is improving as the crystallinity of EVOH decreases, it is thought that the gas barrier properties, which are strongly related to the degree of crystallinity, deteriorated due to the decrease in crystallinity.

Example 3 In Example 2, 3-
The procedure was as in Example 2 except that acrylamide-propyltriacetoxysilane was used at 290 mg/hr. It was confirmed by nuclear magnetic resonance analysis that the polymer contained 0.02 mol% of 3-acrylamide-propyltriacetoxysilane units, and had almost the same composition as in Example 2 regarding vinyl acetate and ethylene. The degree of saponification of the modified EVOH is 99.5.
It was mol % and MI ₁₉₀ was 0.3 g/10 min. Applicable
EVOH, polystyrene (Idemitsu styrene ET-
61) and adhesive resin (Toyo Soda "M5420" (maleic anhydride grafted ethylene-vinyl acetate copolymer)) were supplied to a multi-manifold type three-type, five-layer coextrusion device, and the die temperature was 230°C and the extrusion rate was 1 m/min.
PS/AD ₂ /Si-EVOH/
A sheet of AD ₂ /PS composition with a total thickness of about 1 mm was obtained.
The thickness of each layer is 450μ each for the PS layer, 50μ each for the adhesive layer, and
The EVOH layer was about 50μ. EVOH of this sheet
The layer thickness variation rate (thickness distribution in the direction perpendicular to the discharge direction) is 3%, even during long-term operation of 20 to 24 hours.
There were hardly any streaks, bumps, or uneven flow in the EVOH layer. The obtained sheet was applied to a vacuum-pressure forming machine (using a drawing ratio 15 square mold manufactured by Asano Research Institute) and drawn at 120°C, and a good molded product without cracks was obtained. The oxygen permeation rate of this container is 0.6cc・20μ/ ^m2・24hr・atm (20℃−65%
RH), 20c.c.・20μ/ ^m2・24hr・atm (20℃−65%
RH) and showed very good gas barrier properties.

Comparative Example 6 The same procedure as Example 3 was carried out except that 3-acrylamide-propyltriacetoxysilane was not used, and the ethylene content was 34.5 mol% and the degree of saponification was
99.5 mol %, MI ₁₉₀ yielded 1.9 g/10 min of EVOH. Coextrusion film formation was carried out in the same manner as in Example 3. The thickness variation rate of the EVOH layer of the obtained sheet was as large as 65%, and it was not only non-uniform, but also streaks and spots were noticeable after 3 to 4 hours of film formation. Further, when deep drawing was performed in the same manner as in Example 3 on a portion of this sheet where the thickness variation was small, many minute cracks were observed on the side surface of the molded product.
The oxygen permeation rate of this container is 4000c.c.・20μ/m ²・
24hr・atm (20℃－100%RH) or more,
It was found that the EVOH layer was disconnected.

Comparative Example 7 10 parts by weight of diethylene glycol was added as a plasticizer to 100 parts by weight of EVOH used in Comparative Example 6, and pelletization was carried out using a 40φ extruder at a die temperature of 220°C. After drying the pellets at 95° C. for 16 hours, coextrusion film formation was carried out in the same manner as in Example 3. The thickness variation rate of the sheet obtained was 45%, with almost no improvement observed, and to make matters worse, uneven flow, streaks, etc. began to occur frequently after 3 to 4 hours. A portion with relatively uniform thickness distribution was sampled and deep drawing was performed in the same manner as in Example 3.
A crack occurred, albeit slightly. The oxygen permeation rate of this container is 240c.c.・20μ/ ^m2・24hr・atm (20
℃ - 100% RH), making it unsuitable for use as a gas barrier container.

Example 4 In Example 2, the polymer layer ethylene pressure was set to 35 kg/
cm ² G, vinyltriethoxysilane was used as the silicon-containing olefinic unsaturated monomer, and the same procedure was carried out except that the feed rate was 100 mg/hr. The obtained copolymer contained 0.008 mol% of vinyltriethoxysilane units, 72 mol% of vinyl acetate units, and about 28 mol% of ethylene units.
Modified EVOH was obtained according to Example 2. The degree of saponification was 99.4 mol%, and the melt viscosity index MI ₂₁₀ measured at 210° C. and a load of 2160 g was 0.80 g/10 minutes.

The EVOH, polypropylene (Mitsubishi Noblen)
MA-6) and adhesive resin (Mitsui Petrochemical Admar QF500) were supplied to a spiral flow type 3 type 5 layer coextrusion pipe forming machine, and the die temperature was 220℃.
PP/AD ₁ /Si- with 0.6m/min pipe pulling device
A pipe having an EVOH/AD ₁ /PP configuration with a total thickness of 3 m/m and an outer diameter of 30 m/m was obtained. The thickness of each layer is PP
Each layer is approximately 1200μ, AD layer is approximately 150μ each, EVOH
The layer is about 200μ. EVOH of this pipe cross section
The thickness distribution of the layer was uniform as seen under a microscope (100x magnification), and there were virtually no visible streaks, bumps, or flow irregularities in the flow direction of the pipe (approx.
continuous operation). After cutting this pipe and forming the mouth and lower part to create a parison, the pipe was heated to about 150℃.
After heating for 12 minutes, the mixture was passed through a biaxial stretching blower to create a container, and a good bottle with no cracks in appearance was obtained.

Comparative Example 8 The same procedure as Example 4 was carried out except that vinyltriethoxysilane was not used in Example 4, and the ethylene content was 28.3 mol%, the degree of saponification was 99.5 mol%,
MI ₁₉₀ 2.3 g/10 min EVOH was obtained. This EVOH
When a pipe was formed in the same manner as in Example 4 and the cross section of the EVOH layer was observed, several localized thickness irregularities were observed. Also, in the flow direction of the pipe
Streaks and uneven flow in the EVOH layer were observed. When this pipe was stretch-blow molded in the same manner as in Example 4, vertical stripes and cracks were observed on the bottle surface, and streak-like uneven thickness was observed especially in the portion (shoulder) near the mouthpiece.

Example 5 Batch polymerization was carried out under the conditions shown below in order to obtain a silicon-containing ethylene-vinyl acetate copolymer in a polymerization tank with a capacity of 50 mm and equipped with a stirrer and a cooling coil inside.

Vinyl acetate amount 15Kg Methanol amount 5.8Kg Vinyltrimethoxysilane amount 6.4g 2,2'-Azobisisobutyronitrile amount
2.7g Polymerization temperature 60°C Polymerization tank ethylene pressure 33Kg/cm ² G Polymerization time 6.5hr The polymerization rate of vinyl acetate was 31%. It was confirmed by the magnetic resonance analysis that the copolymer contained 0.02 mol% of vinyltrimethoxysilane units, 68 mol% of vinyl acetate units, and 32 mol% of ethylene units. The product was saponified, isolated and post-treated in the same manner as in Example 1, and then dried to obtain modified EVOH.
The degree of saponification was 99.5 mol%, and the MI ₁₉₀ was 0.55 g/10 minutes.

The EVOH, polypropylene (Mitsubishi Noblen)
MA-6) and an adhesive resin (Mitsui Petrochemical Admer QF500) were supplied to a spiral flow type three-type five-layer coextrusion blow molding machine, and a 500 ml bottle was molded at a die temperature of 220°C. The composition of the bottle body is PP/AD ₁ /Si-EVOH/AD ₁ /PP, and the thickness of each layer is 300μ for the PP layer and approximately 300μ for the AD layer.
20μ, and the Si-EVOH layer is about 20μ. The thickness variation rate of the EVOH layer in the circumferential direction of the container {defined as (maximum thickness - minimum thickness)/percentage of average thickness} was 8.9%. In addition, no unevenness or streaks were observed in appearance.

Comparative Example 9 The same procedure as Example 5 was carried out except that vinylmethoxysilane was not used in Example 5, and the ethylene content was 31.8 mol% and the degree of saponification was 99.6 mol%.
MI ₁₉₀ 5.1 g/10 min EVOH was obtained. This EVOH
When blow molding was carried out in the same manner as in Example 5, the appearance of the bottle was reasonably good, but when the cross section of the EVOH layer on the bottle body was observed, it was found that the thickness was highly uneven.

The thickness variation rate of the EVOH layer was measured and was 85%. The oxygen permeation rate of this bottle was measured at 1.8
cc/bottle/24hr/atm (0.5 bottle) showed poor values. The cause of this is probably that the EVOH layer is locally thin due to uneven growth of the EVOH layer and uneven thickness, which deteriorates the gas barrier properties.

Example 6 Using the same polymerization tank as in Example 1, continuous polymerization was carried out under the conditions shown below.

Vinyl acetate supply rate 400g/hr Methanol supply rate 100g/hr Vinyltrimethoxysilane 240mg/hr 2,2'-azobis-(2,4-dimethylvaleronitrile) 170mg/hr Polymerization temperature 60℃ Average residence time 5hr Polymerization tank ethylene Pressure: 46 Kg/cm ² G Polymerization rate of vinyl acetate was approximately 45%. Nuclear magnetic resonance analysis revealed that the copolymer contained 0.023 mol% of vinyltrimethoxysilane units and 0.023 mol% of vinyl acetate units.
It was confirmed that it contained 61 mol% and about 39 mol% of ethylene units.

After saponification, isolation, and post-treatment in the same manner as in Example 1, the product was dried to obtain modified EVOH. The degree of saponification was 99.4 mol%, and the MI ₁₉₀ was 1.5 g/10 min.

The EVOH and polypropylene (Mitsubishi Noblen MA-6) were supplied to a two-type, three-layer co-injection molding machine to produce a multilayer parison. PP/Si-EVOH/PP
The thickness of each layer of the component is 1200μ for each PP layer,
The EVOH layer was 200μ. The cross section of this pipe
The thickness distribution of the Si-EVOH layer was uniform as seen under a microscope (x100 magnification). This parison was heated at 150°C for about 15 minutes, and then placed in a biaxial stretch blow molding machine called Nissei.
When a container was made using ASB, a good bottle with no visible cracks was obtained.

Comparative Example 10 The same procedure as in Example 6 was carried out except that vinyltrimethoxysilane was not used, and the ethylene content was 39 mol%, the degree of saponification was 99.4 mol%,
MI ₁₉₀ 1.5 g/10 min EVOH was obtained. This EVOH
A parison was created in the same manner as in Example 6 using
When stretch blow molding was performed, vertical lines and cracks were observed on the bottle surface, and streak-like uneven thickness was observed particularly in the area near the mouth (shoulder), making it unusable.

Claims (1)

[Claims] 1 Vinyl acetate, ethylene and the following general formula (),
Saponification degree of vinyl acetate component obtained by saponifying one or more copolymers selected from silicon-containing olefinic unsaturated monomers represented by () and (): 95 mol% The above-mentioned copolymer has a polypropylene resin or polystyrene resin layer on at least one side of a layer made of a saponified silicon-containing ethylene-vinyl acetate copolymer having an ethylene content of 25 to 60 mol% and a silicon content of 0.0005 to 0.2 mol%. Extruded multilayer structure. [However, here, n is 0 to 1, m is 0 to 2, R ¹ is a lower alkyl group, an aryl group, or a lower alkyl group having an aryl group, R ² is an alkoxyl group having 1 to 40 carbon atoms, The alkoxyl group may have an oxygen-containing substituent. R ³ is a hydrogen atom or a methyl group, R ⁴ is a hydrogen atom or a lower alkyl group, R ⁵ is an alkylene group or a divalent organic residue in which chain carbon atoms are interconnected by oxygen or nitrogen, R ⁶ is a hydrogen atom, a halogen atom, a lower alkyl group, an aryl group or a ^lower alkyl group having an aryl group; ), R ⁸ is a hydrogen atom, a halogen atom, a lower alkyl group, an aryl group, or a lower alkyl group having an aryl group, R ⁹
is a lower alkyl group. 2. The multilayer structure according to claim 1, wherein the multilayer structure is a heat-stretched multilayer structure.