JP3109813B2 - Polyvinyl alcohol resin composition - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyvinyl alcohol-based resin composition, and more particularly, it has excellent melt fluidity and excellent gas barrier properties and mechanical strength, and is particularly suitable for melt extrusion molding. And a polyvinyl alcohol-based resin composition.

[Conventional technology]

Conventionally, since polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) has a very close melting temperature and thermal decomposition temperature, melt extrusion molding has been impossible. Further, the PVA film is flexible and tough under high humidity, but has a problem that it loses flexibility under low humidity and is brittle and easily broken.

As a solution to this problem, a method has been known in which an α-olefin and vinyl acetate are copolymerized and saponified. As a typical example, an ethylene-vinyl alcohol copolymer resin is known.

Although this ethylene-vinyl alcohol copolymer resin can be melt-extruded, it is much more expensive than PVA, and has poor gas barrier properties under low humidity than PVA, so that its use is limited.

Since PVA cannot be melt-extruded, for example, as a method for obtaining a film, Poval P-374: Polymer Publishing Association (19
PVA is dissolved with water and a plasticizer such as glycols and cast through a slit on a drying drum or belt, as disclosed in U.S. Pat.
Casting method of applying film by roll coater, drying water with drum or belt to obtain film, and PV
A method of impregnating A with a plasticizer and an appropriate amount of water to form pellets, and extruding with an extruder having a special dissolving, kneading, and defoaming mechanism is used. This extrusion is BRITISH POLY
As described in MER JOURNAL VOL.20 NO.4, P335 (1988), a PVA solution is continuously formed with a twin-screw extruder, the aqueous solution is guided to a single-screw extruder, and pressure measurement is performed while making the temperature uniform. After filtering, the mixture is extruded from a T-die.

Thus, molding of PVA requires a special molding machine,
It required a filtration step for removing the gel component and a step of drying after forming the water content of the aqueous solution after film formation, which was very complicated.
Therefore, it has been desired that this PVA can be easily melt-molded like a thermoplastic resin.

As a method of making PVA melt-moldable and preventing brittleness, there is known a method of adding a plasticizer such as dipropylene glycol, triethylene glycol, diethylene glycol, and glycerin to PVA to lower the melting point and flow start temperature. Have been. See RKTubbs, J.Po
lymer. Sci, A3, 4181 (1965) and Polymer Chemistry Vol. 26, P118
(1969) and the like.

However, according to this method, although effective in lowering the flow start temperature, the gas barrier property is lowered or the strength is generally lowered, and it tends to be softened by absorbing moisture at high temperatures,
On the other hand, it tends to be hard and brittle at low temperatures. Further, there is a problem that the plasticizer bleeds on the surface of the molded product when stored for a long time.

Also, a method in which a saponified ethylene-vinyl acetate copolymer (hereinafter sometimes abbreviated as EVOH) is mixed with PVA to enable melt molding (Japanese Patent Laid-Open No. 49-33945), a method having 5 to 30 carbon atoms.
A long chain α-olefin-saponified vinyl acetate copolymer,
A method of mixing so-called modified PVA with a polymer excluding polyolefin (JP-A-49-117536).
H is mixed to enable melt molding (JP-A-49-33945), a modified PVA is mixed with bisphenols (JP-A-50-123151), and PVA is grafted with a polyolefin resin. A method in which a graft product is mixed with PVA and a polyolefin resin to enable melt molding (Japanese Patent Application Laid-Open No. 60-1985)
188488) and the like.

All of these methods were inferior in melt moldability, uniform mixing properties, or gas barrier properties.

[Problems to be solved by the invention]

The above conventional techniques have problems such as a decrease in bleeding and gas barrier properties due to a plasticizer, a lack of melt moldability, and a lack of uniform mixing properties.

Therefore, a main object of the present invention is to obtain a PVA-based resin composition having excellent melt moldability and excellent melt fluidity.

[Means for solving the problem]

That is, the present invention provides (A) 5-95% by weight of a polyvinyl alcohol-based resin containing a vinyl alcohol unit and a vinyl acetate unit and having a degree of polymerization of 50 to 2500 and a saponification degree of 50 mol% or more; Polyvinyl alcohol having an ethylene content of 1 to 50% by weight with respect to vinyl acetate, obtained by emulsion polymerization of a vinyl acetate monomer and an ethylene monomer in a state of being present in an amount exceeding 15% by weight based on the total amount of alcohol and vinyl acetate monomer. The present invention provides a polyvinyl alcohol resin composition comprising 95 to 5% by weight of a copolymer resin.

The polyvinyl alcohol resin as the component (A) of the resin composition of the present invention refers to a partially or completely saponified polyvinyl acetate or a modified polyvinyl alcohol resin thereof.

Polyvinyl acetate polymerization methods include bulk polymerization, solution polymerization, emulsion polymerization, and suspension polymerization.

Among them, bulk polymerization has problems such as an increase in viscosity during polymerization, adhesion of the polymer to a polymerization vessel, and difficulty in removing polymerization heat.

Emulsion polymerization uses the emulsion-polymerized liquid as it is as a raw material for adhesives and paints, but is not necessarily suitable as a method for producing polyvinyl acetate.

Suspension polymerization has problems such as difficulty in controlling production conditions.

Therefore, the solution polymerization described below is generally used as a method for producing polyvinyl acetate. In this solution polymerization, a method of diluting a vinyl acetate monomer with a solvent such as methanol, ethanol, or methyl acetate, adding a catalyst, performing polymerization, and removing the heat of polymerization by the heat of evaporation of the solvent is employed.

Solution polymerization has a low viscosity, so that stirring is easy and removal of polymerization heat is also easy. In these polymerizations, a method using an initiator which decomposes by heat is usually used.

Other examples include polymerization by ultraviolet rays, polymerization by radiation such as gamma rays, and low-temperature polymerization by a redox catalyst.

Benzoyl peroxide (BP
O), azobisisobutyronitrile (AIBN) and the like are usually used.

PVA, which is the component (A) of the present invention, can be obtained by subjecting the thus polymerized polyvinyl acetate to a saponification reaction using an alkali catalyst or an acid catalyst.

The modified PVA resin refers to a partially or completely saponified copolymer as described below. For example, vinyl acetate and carbon number 4
Copolymers with olefins Nos. 18 to 18, copolymers of vinyl acetate and vinyl carboxylate (vinyl versatate, vinyl stearate, etc.), copolymers of vinyl acetate and alkyl vinyl ethers (lauryl vinyl ether, methyl vinyl ether, etc.) Copolymer of vinyl acetate and (meth) acrylate (such as methyl methacrylate), copolymer of vinyl acetate and acrylamide (acrylamide; methacrylamide; N, N-dimethylacrylamide, etc.), vinyl acetate and unsaturated carboxylic acid Copolymers of acids or their anhydrides or esters (acrylic acid, crotonic acid, maleic acid, fumaric acid, itaconic acid, etc.), copolymers of vinyl acetate and sulfonic acid monomers (vinyl sulfonic acid, acrylsulfonic acid, etc.) , Vinyl acetate and cationic monomer (dimethylaminoethyl Methacrylate, vinyl imidazole, vinyl pyridine, copolymer of vinyl succinate imide), vinyl acetate and other monomers (vinylene carbonate, allyl alcohol, allyl acetate, etc.)
And the like.

The PVA thus obtained is composed of a vinyl alcohol unit and a vinyl acetate unit, and the degree of polymerization is preferably 50 to 2500, and may be appropriately selected depending on the application and the like within the range. . In particular, those having a degree of polymerization of 200 to 1800 are preferable in consideration of the melt fluidity and the mechanical strength. On the other hand, the saponification degree is preferably 50 mol% or more,
Considering the melt fluidity, those having a saponification degree of 70 to 99.5 mol% are preferred. When the saponification degree is less than 50 mol%, there is a disadvantage that the mechanical strength is poor.

Next, the polyvinyl alcohol copolymer resin as the component (B) of the composition of the present invention is described in, for example,
-96637, JP-A-63-108016, and 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 gas barrier property and the compatibility with the polyvinyl alcohol resin as the component (A) are inferior, and there are inconveniences such as stickiness of the molded product surface, which is not suitable for the purpose of the present invention. It will be.

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, the compatibility with the PVA as the component (A), the gas barrier property, and the like will be poor, which is not suitable for the purpose of the invention. On the other hand, if it is less than 1% by weight, it cannot be used because of poor melt moldability.

The content of the vinyl acetate unit in the polyvinyl alcohol-based copolymer resin is not particularly limited, but is usually preferably 1 to 89% by weight. If the amount is less than 1% by weight, the melt moldability decreases, and if it exceeds 89% by weight, there are problems such as compatibility with PVA and stickiness on the surface of the molded product.

In the polyvinyl alcohol copolymer resin, the following monomers are copolymerized in place of the ethylene monomer,
In addition to the vinyl acetate monomer and the ethylene monomer, a monomer having an ethylenically unsaturated bond can be copolymerized. Examples of these monomers include acrylic acid,
Unsaturated acids such as methacrylic acid, crotonic acid, maleic acid, itaconic acid and alkyl esters thereof, and α- such as propylene, butene, decene and octadecene
Olefin and the like can be given.

In the composition of the present invention, the proportion of PVA as the component (A) to the polyvinyl alcohol-based copolymer resin as the component (B) is 5 to 95% by weight of the PVA, and the polyvinyl alcohol-based copolymer resin is 95 to 95% by weight. 5% by weight, preferably PVA1
5 to 90% by weight, polyvinyl alcohol copolymer resin 85
~ 10% by weight. In addition, when PVA having a low polymerization degree is used in the composition of the present invention, the melt fluidity tends to be improved as the blending ratio of PVA increases.

Here, the blending ratio of the polyvinyl alcohol-based resin is 95
If the content is more than the weight percentage, the melt moldability may be limited due to excessive melt fluidity. On the other hand, if it is less than 5% by weight, melt extrudability will not be exhibited when PVA having a high degree of saponification is mixed, and it will not withstand use.

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 and 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
To α-olefin copolymers of ethylene-butene-1 copolymer, ethylene-4-methylpentene-1 copolymer, ethylene-hexene-1 copolymer and ethylene-
Grafting of unsaturated carboxylic acid or anhydride thereof to a modified polypropylene, modified polybutene, modified poly-4-methylpentene or the above-mentioned polyolefin polymer blended with propylene rubber or the like under an organic peroxide or other monomer Those copolymerized with (for example, methyl methacrylate, ethyl acrylate, etc.) are also included as targets.

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 adhesive for dry lamination, and an adhesive resin known in co-extrusion molding 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 includes a method in which the polyolefin-based resin is melt-grafted with the above component using an organic peroxide or a method in which the polyolefin-based resin is dissolved in hot xylene and the above component is grafted with the organic peroxide. There is. 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. , Maleic acid di-
n-butyl, 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 U.S. Pat. Nos. 4026967 and 3953655, JP-A-51-98784, JP-B-44-15423, and JP-B-49.
It is described in detail in -4822 and the like.

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; Paraffin; tomonostearate as an antistatic agent such as phosphate ester; sorbitan monopalmitate; sulfated oleic acid; polyethylene oxide;
Ethylene bis stearamide, butyl stearate, etc. as a lubricant; carbon black as a coloring agent; phthalocyanine; quinacridone; indoline; azo pigments; titanium oxide; red iron oxide; glass fiber as a filler; asbestos; mica; Calcium; 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, 5 to 95% by weight of a polyvinyl alcohol-based copolymer resin as the component (B) is added to polyvinyl alcohol (PVA) which cannot be melt-extruded conventionally.
By mixing in the range, the obtained composition can be melt-extruded and melt-flowable. Moreover, in the range where the mixing ratio of PVA is large, the cause of the excellent melt fluidity is unknown, but due to the interaction when PVA and the polyvinyl alcohol-based copolymer resin are mixed, the PVA itself becomes melt-flowable and melt-molded. It seems possible.

〔Example〕

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

Examples 1 to 13 and Comparative Examples 1 to 14 (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 using an autoclave having a content of 30. 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 polyvinyl alcohol-based copolymer resin and polyvinyl alcohol-based resin) Using a Labo Plastomill ME type manufactured by Toyo Seiki Seisaku-sho at the temperature of 220 ° C., the polyvinyl alcohol obtained in the above (1) The resin composition shown in Tables 2 and 3 was obtained by mixing the copolymer resin and the polyvinyl alcohol resin.

The resin composition produced as described above, using a melt indexer manufactured by Takara Kogyo, according to JIS-K6758, temperature 23.
The MFR was measured at 0 ° C. The results are shown in Tables 2 and 3. The resin composition was press-molded at a temperature of 230 ° C. to form a film having a thickness of 100 μm, and the extrudability was evaluated by MFR. The oxygen permeability of this film was measured using OXTRAN-10 / 50A manufactured by Modern Control Co., Ltd., and the tensile modulus was measured in accordance with ASTM-D638. The results are shown in Tables 2 and 3.

[Effect of the Invention] The composition of the present invention has extremely good melt moldability, melt extrusion moldability, gas barrier properties, mechanical strength, etc., and is excellent in food packaging materials, pharmaceutical packaging materials, cosmetic packaging materials, and gas barrier properties. Is effective as a required container.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Akio Harada 251-1 Ibonaka, Ibocho, Tatsuno City, Hyogo Prefecture Showa Polymer Co., Ltd. Osaka Research Laboratory (72) Inventor Yoji Tanaka Ibonaka, Ibocho, Tatsuno City, Hyogo Prefecture 251-1 Showa Polymer Co., Ltd. Osaka Research Laboratory (56) References JP-A-3-244650 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08L 29/04 C08L 31 / 04

Claims (2)

(57) [Claims] 1. A method comprising (A) a vinyl alcohol unit and a vinyl acetate unit, having a polymerization degree of 50 to 2500 and a saponification degree of 50 mol%.
Emulsion polymerization of a vinyl acetate monomer and an ethylene monomer in a state where the above-mentioned polyvinyl alcohol resin is present in an amount of 5 to 95% by weight and (B) the polyvinyl alcohol exceeds 15% by weight based on the total amount of the polyvinyl alcohol and the vinyl acetate monomer. A polyvinyl alcohol-based resin composition comprising 95 to 5% by weight of a polyvinyl alcohol-based copolymer resin having an ethylene content of 1 to 50% by weight based on vinyl acetate. 2. A resin composition for melt extrusion molding comprising the polyvinyl alcohol resin composition according to claim 1.