JP2710854B2 - Resin composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a resin composition, and in particular, has excellent melt moldability, gas barrier properties, and mechanical strength, has no pinholes or cracks, and is used when molded into a container. The present invention relates to a resin composition having excellent heat stretchability without local unevenness in thickness.

[Conventional technology]

Saponified ethylene-vinyl acetate copolymer (hereinafter sometimes abbreviated as EVOH) makes use of its characteristic gas barrier properties, and is particularly effective in shielding oxygen against food packaging materials, cosmetic packaging materials, chemical packaging materials, etc. It is used for packaging materials for packaging necessary foods and medicines.

However, EVOH has the drawback that it is hard and very brittle, easily breaks, and has a hydroxyl group in the molecule, so that it is sensitive to water and water vapor, and the gas barrier property is significantly deteriorated by moisture absorption.

In order to solve this drawback, a multilayer laminate is used in which a polyolefin-based polymer such as polyethylene and polypropylene or one or more polymers such as polyester, polystyrene and polyvinyl chloride are laminated on EVOH.

These laminating methods include extruding and laminating polyolefin, EVOH and their adhesive resin from each extruder, so-called co-extrusion molding, dry lamination molding, extrusion lamination molding, solution coating molding, etc. Obtained in the form of films and bolts.

With respect to the sheet, a secondary process such as vacuum forming or pressure forming is performed on the raw material of the EVOH multilayer laminate to form a packaging container.

In most cases, it is necessary to mold the resin having the lowest melting point among the materials constituting the multilayer laminate under the molding conditions. Therefore, in EVOH having a high melting point, fine voids (so-called voids) and cracks are generated in the layer by secondary processing. In addition, due to the high crystallization speed of EVOH, such voids, cracks, and local uneven thickness occur. In particular, in deep drawing, such a phenomenon tends to occur at corners and the like due to a large drawing ratio, and there is a limit in use.

On the other hand, also in the bolt forming, such a phenomenon is likely to occur when the parison is expanded and formed into a bottle shape.

Further, in a film, a pinhole is easily generated due to a bending motion received in a distribution stage or the like, and the gas barrier property originally provided in EVOH may be significantly impaired.

When such cracks, pinholes, uneven thickness, etc. occur, the oxygen barrier properties are remarkably deteriorated, the appearance is poor, and the interlayer between the adhesive resin and the EVOH is peeled off. was there.

As a method for solving such problems, a method of blending a polyamide resin with EVOH (Japanese Patent Application Laid-Open Nos. 59-20345, 62-106944 and 62-22840), glycerin, various glycols , A method of mixing a hydroxyl group-containing plasticizer (JP-A-53-88067), an EVOH copolymerized with a pyrrolidone ring (JP-A-62-11644), and a method of subjecting EVOH to silane crosslinking (Japanese Patent Laid-Open No. 51-20946
JP, JP-A-60-144304, JP-A-60-170672,
61-290047 and 61-290048), and a method of blending lithium chloride and an aromatic or aliphatic amide or a polyhydric alcohol compound with EVOH (Japanese Patent Application Laid-Open Nos. 61-281147 and 61-283643). JP-A-61-283644) and the like.

However, all of these methods have the following problems and have not been sufficiently satisfactory. That is,
When a polyamide-based resin is blended with EVOH, the polyamide and EVOH react during melt molding to generate gel fisheye, and a special polyamide resin is required to solve these problems, resulting in a problem in cost.

In addition, glycerin, various glycols, and hydroxyl group-containing plasticizers have poor compatibility with EVOH, causing bleeding of these plasticizers with the passage of time, causing the adhesive strength to the adhesive resin layer to decrease over time. was there.

In addition, terpolymers in which a pyrrolidone ring is copolymerized in the molecule are more apt to absorb moisture than EVOH, and the effect of reducing gas barrier properties due to moisture absorption and preventing pinholes, cracks, and uneven thickness are still insufficient. there were. The silane cross-linking method for EVOH makes it difficult to control the cross-linking, and often causes gels and fish eyes during melt molding.

On the other hand, when a lithium chloride compound and an aromatic or aliphatic amide or a polyhydric alcohol compound are blended with EVOH, the lithium chloride compound often causes poor dispersion or a sheet raw material when blended with EVOH. At the time of heating and stretching such as forming a container, and obtaining a stretched film, there is a problem that a portion of the lithium chloride particles generates voids by stretching and conversely causes cracks and pinholes. Was enough.

On the other hand, on the other hand, the ethylene content of EVOH has been increased in order to increase the bending fatigue resistance and mechanical strength.However, according to this method, the gas barrier property is reduced due to the increase in the ethylene content. There were restrictions on use.

Therefore, when thermoforming a container using the EVOH multilayer laminate, an EVOH that is excellent in gas barrier properties without pinholes, cracks and uneven thickness of the EVOH layer has been desired.

[Problems to be solved by the invention]

Although EVOH has extremely excellent gas barrier properties as described above, when molding an EVOH multilayer laminate into a container,
Pinholes, cracks, uneven thickness, etc. occur in the EVOH layer,
As a result, the gas barrier properties inherent to OH were greatly impaired.

Accordingly, an object of the present invention is to prevent pinholes, cracks, and uneven thicknesses generated when a multilayer laminate of EVOH is thermoformed into a container or the like without impairing the gas barrier properties of EVOH, and to have excellent bending fatigue resistance. Another object of the present invention is to provide a resin composition effective for obtaining a stretched EVOH film.

[Means for solving the problem]

(A) 100 parts by weight of saponified olefin-vinyl acetate copolymer (B) Polyvinyl alcohol is at least 10% by weight based on the total amount of polyvinyl alcohol and vinyl acetate monomer
Ethylene content obtained by emulsion polymerization of vinyl acetate monomer and ethylene monomer in the presence of 1
An object of the present invention is to provide a resin composition comprising 5 to 50% by weight of a polyvinyl alcohol copolymer resin in an amount of 5 parts by weight or more.

Olefin which is the component (A) of the resin composition of the present invention
The saponified vinyl acetate copolymer refers to a saponified product of a part or all of a copolymer of various olefins, for example, an olefin such as ethylene, propylene, and butene-1 and vinyl acetate, for example, ethylene-vinyl acetate copolymer. There are a combined saponified product, a saponified product of a propylene-vinyl acetate copolymer and the like, and a saponified ethylene-vinyl acetate copolymer (EVOH) is particularly preferable because of easy polymerization. There are various types of EVOH, with an ethylene content of 15 to 60 mol% and a degree of saponification.
Those having a composition of 90% or more are preferably used. If the ethylene content is less than 15 mol%, the melt moldability is reduced, and if the saponification degree of the vinyl acetate component is less than 90%, the gas barrier properties may be reduced. Particularly preferred ethylene content
EVOH having a concentration of 25 to 50% by mole and a saponification degree of 96% or more.
In addition to ethylene and vinyl acetate (or saponified vinyl alcohol), unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, and maleic acid or alkyl esters thereof, and propylene, butene, α-decene, α
-A small amount of α-olefin such as octadecene may be contained as a comonomer.

Next, the polyvinyl alcohol copolymer resin as the component (B) of the resin composition of the present invention is described in, for example, JP-A-60-96637 and JP-A-63-108016. It can be manufactured by a method or the like.

An example of a method for producing the polyvinyl alcohol-based copolymer resin is obtained by copolymerizing a vinyl acetate monomer and an ethylene monomer using a known catalyst in the presence of polyvinyl alcohol having an average degree of polymerization of 20 to 5000. Can be The polyvinyl alcohol used here may have any degree of hydrolysis, but preferably has an average degree of saponification of 50.
9999%, especially those having an average degree of saponification of 80-99% are optimal. During the copolymerization reaction between the vinyl acetate monomer and the ethylene monomer, the amount of polyvinyl alcohol present in the aqueous emulsion must be at least 10% by weight, based on the total amount of vinyl acetate monomer and polyvinyl alcohol. When the amount is less than 10% by weight, the resulting polyvinyl alcohol-based copolymer resin has poor compatibility with the saponified olefin-vinyl acetate copolymer as the component (A), and as a result, a composition having poor gas barrier properties. And the object of the present invention is not achieved.

Further, the ethylene content in the polyvinyl alcohol-based copolymer resin produced by the above method is 1 to 50% by weight.
And preferably 10 to 45% by weight. Ethylene content is 50
If the content is more than 10% by weight, gas barrier properties and the like are inferior and are not suitable for the purpose of the invention. If it is less than 1% by weight, the melt moldability may be inferior and cannot be used.

In the composition of the present invention, the compounding ratio of the saponified olefin-vinyl acetate copolymer as the component (A) and the polyvinyl alcohol copolymer resin as the component (B) is 100 parts by weight of the component (A). In contrast, component (B) is selected in an amount of 5 parts by weight or more, preferably 10 parts by weight or more. Here, when the component (B) is less than 5 parts by weight, the effect of preventing pinholes, cracks and uneven thickness is not exhibited, and the effect of improving the heat stretchability and the like is not exhibited, so that it cannot be used. The upper limit of the component (B) can be selected depending on the intended use.

The above (B) polyvinyl alcohol copolymer resin is obtained by copolymerizing the following monomer in place of the ethylene monomer, or copolymerizing a monomer having an ethylenic unsaturated bond in addition to a vinyl acetate monomer and an ethylene monomer. can do. Examples of these monomers include unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, and itaconic acid and alkyl esters thereof, acrylonitrile, vinyl chloride, styrene, vinylidene chloride, and propylene, butene. Α-olefins such as, decene and octadecene.

The melting index of the composition of the present invention (MFR, measured at a load of 2.16 kg according to JIS-K6758 at a temperature of 230 ° C.) is not particularly limited and may be appropriately selected according to a molding method. A range of 0.1 to 50 g / 10 minutes is appropriate.

The composition of the present invention basically comprises the above-mentioned components (A) and (B), but may further contain, if necessary, other resins or various additives in an appropriate amount as long as the object of the present invention is not impaired. Can be blended.

Further, the composition of the present invention can be formed into a film, a sheet, a tube, a bottle or the like by a known melt molding method, melt extrusion molding method and compression molding method.

What is formed into a film or sheet from the composition of the present invention can be used as it is, but it is also effective to laminate it with another layer and use it as a multilayer laminate. For example, as such a lamination method, a so-called dry lamination molding method or a lamination method in which a urethane-based or acrylic-based dry laminating adhesive is used and another thermoplastic resin layer is laminated on a single-layer product of the composition of the present invention. Lamination method, or co-extrusion lamination method, co-extrusion method (feed block, multi-manifold method), co-injection molding method, co-extrusion pipe molding method, and solution coat molding method of dissolving and coating the present composition in a solvent There are various methods.

The multilayer laminate thus obtained is further reheated using a vacuum forming machine, a compressed air molding machine, a stretch blow molding machine or the like and subjected to a stretching operation, or the above-described multilayer laminate is uniaxially or biaxially stretched. A heating stretching operation can be performed using a stretching machine.

Other thermoplastic resins to be laminated on the composition of the present invention include polyethylene resin, polypropylene resin, copolymer of ethylene and α-olefin having 3 to 12 carbon atoms, polyolefin resin such as ionomer resin, polystyrene resin, polyethylene Thermoplastic resins such as terephthalate resin, polyvinyl chloride resin, polycarbonate resin, polyamide resin and the like. Here, ethylene and carbon number are 3 ~
The α-olefin copolymer of No. 12 is a modified blend of ethylene-butene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-propylene rubber and the like. polypropylene,
An unsaturated carboxylic acid or its anhydride is grafted to a modified polybutene, a modified poly-4-methylpentene or the above-mentioned polyolefin-based polymer under an organic peroxide or other monomers (for example, methyl methacrylate, ethyl acrylate, etc.). ) And those copolymerized with) are also included.

The layer constitution of the multilayer laminate is such that the composition of the present invention comprises the layer (a),
Adhesive resin layer is layer (b), other thermoplastic resin is (c)
The layers are (a) layer / (b) layer / (c) layer, (c) layer /
(B) layer / (a) layer / (b) layer / (c) layer, (c) layer /
Typical examples are (b) layer / metal foil / (a) layer / (b) layer / (c) layer. Here, the thermoplastic resins of both outer layers may be different or the same resin may be used.

As the adhesive resin layer, a so-called urethane-based, acrylic-based, polyester-based dry laminating adhesive, or an adhesive resin known in a co-extrusion molding method can be used. For example, as such an adhesive resin layer,
There is a resin obtained by grafting or copolymerizing an unsaturated carboxylic acid, an acid anhydride or an ester monomer to a polyolefin resin. The grafting method at this time, a method of melt-grafting a polyolefin resin with an organic peroxide and the above components,
Alternatively, there is a method of dissolving a polyolefin resin in hot xylene and grafting the above components with an organic peroxide. Examples of unsaturated carboxylic acids, acid anhydrides, and ester monomers include methacrylic acid, acrylic acid, ethacrylic acid, glycidyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, diethyl maleate, and monoethyl maleate. Di-n-butyl maleate, maleic acid, maleic anhydride, fumaric acid, fumaric anhydride, itaconic acid, itaconic anhydride, 5-norbornene-
2,3-anhydride, citraconic acid, citraconic anhydride crotonic acid, crotonic anhydride, acrylonitrile, methacrylonitrile, sodium acrylate, calcium acrylate, magnesium acrylate and the like. These graft polymers are described in detail in U.S. Pat. No. 4026967 and U.S. Pat. No. 3,953,655, JP-A-51-98784, JP-B-44-15423, and JP-B-49-4822. Have been.

The blending method for producing the composition of the present invention is not particularly limited, but the components (A) and (B) and other components to be added as necessary may be mixed with a ribbon blender, a high-speed mixer, a kneader, a pelletizer, mixing. It is preferable to supply to a roll or the like, pelletize and dry.
Further, each component may be directly supplied to a molding machine for molding.

For the composition of the present invention, other additives commonly used in thermoplastic resins can be blended. Examples of such additives include 2,5-di-tert-butylhydroquinone; 2,6-di-tert-butyl-p-cresol; 4,4'-
Thiobis- (6-t-butylphenol); 2,2-methylene-bis (4-methyl-6-t-butylphenol);
Octadecyl 3- (3 ', 5'-di-t-butyl-1'-
(Hydroxyphenyl) propinate; 4,4'-thiobis-
(6-butylphenol) and the like as an ultraviolet absorber, ethyl-2-cyano-3,3-diphenylacrylate;
(2'-hydroxy-5-methylphenyl) benzotriazole; dimethyl phthalate as a plasticizer, such as 2-hydroxy-4-octoxybenzophenone; glycerin;
Dipropylene glycol; triethylene glycol; diethyl diethylene glycol phthalate; wax; liquid paraffin; tomonostearate as an antistatic agent such as phosphate; sorbitan monopalmitate; sulfated oleic acid; polyethylene oxide; carbowax; Carbon black as a coloring agent such as bis-stearamide, butyl stearate; phthalocyanine; quinacridone; indoline;
As a filler, there are glass oxide; asbestos; mica; ballastonite; calcium silicate; aluminum silicate; calcium carbonate; Many other high molecular compounds can also be blended to such an extent that the effects of the present invention are not impaired.

[Action]

According to the present invention, a pinhole,
By blending a polyvinyl alcohol-based copolymer resin in a fixed ratio with a saponified olefin-vinyl acetate copolymer, which is liable to generate cracks, uneven thickness, etc., the resulting composition has pinholes, cracks, unevenness during molding. It does not produce meat or the like. In addition, the formed container and the like have excellent barrier properties.

The reason why the conventional problem can be solved in this way is not clear, but the polyvinyl alcohol copolymer resin mixed with the olefin-vinyl acetate copolymer saponified product is rich in flexibility and gas barrier property. It is excellent and has excellent compatibility with the saponified olefin-vinyl acetate copolymer, so that the gas barrier property inherent in the saponified olefin-vinyl acetate copolymer is not impaired, and the defect thereof can be improved. It seems possible.

〔Example〕

 Next, the present invention will be described in more detail with reference to examples.

Examples 1 to 9 and Comparative Examples 1 to 7 (1) (Preparation of polyvinyl alcohol-based copolymer resin) A partially saponified polyvinyl alcohol resin having a polymerization degree of 500 and a saponification degree of 88% was prepared by using an autoclave having a content of 30 l. Using Kuraray Co., Ltd., PVA205 (trade name), while adding ammonium persulfate and sodium metabisulfite as catalysts, the concentration ratio of PVA and vinyl acetate was 5/95, 10/90,
The ratio was changed so as to be 25/75, 50/50 (weight ratio), and then the emulsion polymerization was carried out by changing the pressure of ethylene gas to obtain a polyvinyl alcohol copolymer resin (emulsion). The solids concentration of the polymerized emulsion was about 20-60% by weight. Add this emulsion to -20
The mixture was allowed to stand at 20 ° C. for 20 hours and then freeze-precipitated to obtain a polymer (polyvinyl alcohol-based copolymer resin).

Next, after freeze-crushing and freeze-drying the obtained polymer,
Vacuum dried at a temperature of 80 ° C. The ratio of the ethylene component of the polymer was determined by an alkali saponification method. Table 1 shows the ethylene content of the polyvinyl alcohol copolymer resin thus obtained.

(2) (Mixing of saponified ethylene-vinyl acetate copolymer and polyvinyl alcohol-based copolymer resin) Using a Labo Plastomill ME type manufactured by Toyo Seiki Seisakusho Co., Ltd. at a temperature of 220 ° C., ethylene-vinyl acetate copolymer was used. A resin composition was obtained by mixing the polyvinyl alcohol (PVA) -based copolymer resin obtained in the above (1) at a predetermined ratio with 100 parts by weight of the saponified polymer (EVOH).

The resin composition produced as described above was press-molded at a temperature of 230 ° C. to form a film having a thickness of 100 μm, and this film was manufactured using OXTRAN-10 / 5 manufactured by Modern Control.
The oxygen permeability was measured using 0A, the film impact strength was measured using a pendulum-type film impact tester manufactured by Toyo Seiki Seisaku-sho, Ltd., and the tensile modulus was measured according to ASTM-D638. Table 2 shows the results.

[Effect of the Invention] The composition of the present invention is superior in flexibility, impact strength, and gas barrier properties as compared with a conventional saponified olefin-vinyl acetate copolymer resin. Therefore, it is effective as a food packaging material, a pharmaceutical packaging material, a cosmetic packaging material, or various containers requiring gas barrier properties.

Continued on the front page (72) Inventor Akio Harada 251-1 Ibonaka, Ibocho, Tatsuno City, Hyogo Prefecture Inside Showa Polymer Co., Ltd. Osaka Research Laboratory (72) Inventor Yoji Tanaka 251-1 Ibonaka, Ibocho, Tatsuno City, Hyogo Prefecture (56) References JP-A-2-261847 (JP, A) JP-A-60-161474 (JP, A) JP-A-58-129035 (JP, A)

Claims (3)

(57) [Claims] (1) 100 parts by weight of a saponified olefin-vinyl acetate copolymer, (B) at least 10% by weight of polyvinyl alcohol based on the total amount of polyvinyl alcohol and vinyl acetate monomer.
Ethylene content obtained by emulsion polymerization of vinyl acetate monomer and ethylene monomer in the presence of 1
A resin composition comprising 5 to 50% by weight of a polyvinyl alcohol copolymer resin in an amount of 5 parts by weight or more. 2. The resin composition according to claim 1, wherein the saponified olefin-vinyl acetate copolymer is a saponified ethylene-vinyl acetate copolymer having an ethylene content of 15 to 60 mol% and a saponification degree of 90% or more. 3. The resin composition according to claim 1, wherein the saponified olefin-vinyl acetate copolymer is a saponified ethylene-vinyl acetate copolymer having an ethylene content of 25 to 50 mol% and a saponification degree of 96% or more.