JP2000038489A - Poly(vinyl alcohol)-based resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a poly(vinyl alcohol)-based resin composition scarcely causing gel in being molded, capable of giving film excellent in gas permeability by adding phenol-based and phosphorus-based antioxidants to a blend resin consisting of poly(vinyl alcohol) and polyethylene glycol. SOLUTION: This poly(vinyl alcohol)-based resin composition comprises (A) 100 pts.wt. resin consisting of (i) 55-95 wt.% poly(vinyl alcohol) having 60-95 mol.% degree of saponification and (ii) 5-45 wt.% polyethylene glycol where the total content of both poly(vinyl alcohol) and polyethylene glycol is 100 wt.% and (B) 0.01-5 pts.wt. antioxidants consisting of phenol-based antioxidant and phosphorus-based one. It is pref. that 0.01-5 pts.wt. stabilizer of at least one kind selected from a group consisting of a Ca-Zn-Sn-based stabilizer, an alkali metal salt of hydrogen-including organic polybasic acid and an alkali (or alkaline earth) metal salt of hydrogen-including inorganic phosphoric acid and 5-40 pts.wt. copoly(ethylene/vinyl acetate) saponified product respectively based on 100 pts.wt. ingredient A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a resin composition mainly comprising polyvinyl alcohol (PVA). More specifically, PVA and polyethylene glycol (PEG)
The present invention relates to a resin composition containing a resin consisting of the following and an antioxidant, producing a film with little gel during molding and excellent in gas selective permeability.

[0002]

2. Description of the Related Art Packaging of food which dislikes contact with oxygen and generates carbon dioxide, such as fermented food such as natural cheese, miso, or coffee beans which generate carbon dioxide by breathing, garlic, etc. There is a demand for a packaging material that does not easily transmit oxygen gas but easily transmits carbon dioxide gas.
With the diversification of foods, development of packaging materials having such selective gas permeability is required. Some proposals have already been made on packaging materials mainly composed of PVA and having a large ratio of the permeability of carbon dioxide (PCO ₂ ) to the permeability of oxygen (PO ₂ ) (PCO ₂ / PO ₂ ). JP 5
JP-A-222215 discloses a composition comprising a polymer of PVA and an alkylene glycol having a specific saponification degree, and a saponified ethylene-vinyl acetate copolymer resin (E).
VOH) is described as a melt-extruded product used for food packaging of a composition comprising VOH), and achieves a certain object as a gas selectively permeable membrane material for food packaging. On the other hand, P
Since the VA-based polymer has poor thermal stability, melt molding is extremely difficult. Even if it can be melted, it tends to be significantly colored during thermoforming. Regarding the moldability of a PVA-based polymer, JP-A-7-179709 discloses a PVA having a specific saponification degree.
A resin composition having good moldability comprising (A), a saponified ethylene / vinyl acetate copolymer (B), a thermoplastic resin (C) having a specific softening temperature, and polyethylene glycol (D) is disclosed. Also, JP-A-52-95
No. 4 discloses a method for producing a PVA-based resin having good thermal stability, comprising PVA and a polybasic acid alkali metal salt. However, when producing a gas selectively permeable membrane material (film) mainly composed of PVA, there remains a problem that needs to be solved, such as formation of a gel in the film.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide a resin composition mainly composed of polyvinyl alcohol (hereinafter abbreviated as PVA), which gives a molded product with less generation of a gel during film formation. .

[0004]

Means for Solving the Problems The present inventors added gels during molding by adding phenolic and phosphorus-based antioxidants to a resin composed of PVA and polyethylene glycol (hereinafter abbreviated as PEG). Was found to be able to be suppressed, and the present invention was completed.

That is, the present invention relates to 55 to 95% by mass of PVA having a saponification degree of 60 to 95% by mol and 5 to 45% by mass of PEG.
(Total of 100% by mass of both) and a total of 0.01 to 100 parts by mass of a phenol-based and phosphorus-based antioxidant
And 5 parts by mass. Further, a Ca—Zn—Sn-based stabilizer, an alkali metal salt of a hydrogen-containing organic polybasic acid, and an alkali or alkaline earth metal of a hydrogen-containing inorganic phosphoric acid are added to 100 parts by mass of the resin composed of PVA and PEG of the invention. Provided is a resin composition containing 0.01 to 5 parts by mass of at least one stabilizer selected from salts. The present invention relates to the PV of the resin composition of the present invention.
A saponified ethylene-vinyl acetate copolymer (EVOH) was added to 100 parts by mass of the resin comprising A and PEG.
Provide a resin composition containing 〜40 parts by mass. The phenolic antioxidant of the invention is n-octadecyl-3- (3 ′,
5'-di-tert-butyl-4'-hydroxyphenyl) propionate, wherein the phosphorus antioxidant is tris (2,4
-Di-t-butylphenyl) phosphite. The stabilizer of the invention is Ca-Zn-Sn
Provided is a resin composition which is at least one selected from a system stabilizer, disodium dihydrogen pyrophosphate and calcium dihydrogen pyrophosphate.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the present invention, 100 parts by mass of a resin comprising 55 to 95% by mass of polyvinyl alcohol (PVA) having a saponification degree of 60 to 95% by mol and 5 to 45% by mass of polyethylene glycol (PEG) (total 100% by mass of both) and phenol And the total of 0.01 to 5 parts by mass of the total amount of the system-based and phosphorus-based antioxidants, the resin composition of the present invention has the effect of the present invention, The third component, which has the effect of suppressing the generation of gel as a whole as an additive, may be contained in addition to the phenolic and phosphorus-based antioxidants. This means that the addition of the third component, which has an adverse effect on the effect as compared with the case where no additive is added, is excluded. The effect of suppressing the generation of gel is determined by the gel fraction by the filter paper method described later. The degree of saponification of the PVA used in the present invention is 60 to 95 mol%.
And preferably in the range of 60 to 90 mol%
, More preferably in the range of 60 to 80 mol%. By using a PVA having a degree of saponification of 60 mol% or more, a molded article having a low oxygen permeability can be obtained. On the other hand, by using a substance having a saponification degree of 95 mol% or less, it can be incorporated into the composition of the present invention. This is preferable because the solubility of PVA in PEG can be maintained. That is, PVA dissolves and retains PEG in the composition of the present invention,
This is because the higher the degree of saponification of A, the lower the saturation solubility of PEG. Further, P having a saponification degree of 95 mol% or less
VA is also preferable from this point of view because the difference between the melting point and the thermal decomposition onset temperature, that is, the moldable temperature range is wide. The number average degree of polymerization of PVA is preferably 300 or more in view of the strength of the film, more preferably 3500 or less, and particularly preferably in the range of 500 to 2,000 from the viewpoint of moldability of the resin composition. In addition, the number average degree of polymerization of PVA is a measured value based on JIS-K6726.

The PEG used in the present invention is not particularly limited, but as long as the average molecular weight is in the range of 400 to 2,000, the PEG is evaporated by evaporation when the composition of the present invention is formed into a film in the melt extrusion step. This is preferred because it is difficult to perform and the compatibility with PVA is maintained. In the present invention, PVA
And PEG are blended in an amount of 55 to 95% by mass of PVA, preferably 60 to 90% by mass, and more preferably 70 to 90% by mass.
EG is 5 to 45% by mass, preferably 10 to 40% by mass, and more preferably 10 to 30% by mass (the total of PVA and PEG is 100% by mass).

[0008] EVOH may optionally be used in the composition of the present invention. EVOH from the viewpoint of moldability and oxygen barrier properties
Is used, the melt viscosity η at a shear rate of usually 210 ° C. and 10 ² sec ⁻¹ is 1.0 × 10 ^{3 to} 3.0 × 1.
0 is preferable in the range of ⁴ poise. The ethylene component content is in the range of 20 to 55 mol%, more preferably 2 to 55 mol%.
It is in the range of 0 to 45 mol%. 90 for the degree of saponification
Mol% or more is preferred, and 95 mol% or more is more preferably used. The amount of EVOH used is the PVA
The amount is preferably 5 to 40 parts by mass, and more preferably 5 to 20 parts by mass, based on 100 parts by mass of the resin composed of PEG and PEG.

The phenolic antioxidants used in the present invention include 2,6-di-tert-butyl-4-methylphenol and n-octadecyl-3- (3 ', 5'-di-tert-butyl-4'). -Hydroxyphenyl) propionate, tetrakis- [methylene-3- (3 ', 5'-di-butyl-4-hydroxyphenyl) propionate] methane,
Tris (3,5-di-tert-butyl-4-hydroxybenzyl) isocyanurate, triethylene glycol-bis- [3- (3-tert-butyl-4-hydroxy-5-methylphenyl) propionate], 2,2 '-Methylenebis- (4-methyl-6-t-butylphenol),
4,4'-thiobis- (3-methyl-6-t-butylphenol) and 4,4'-butylidenebis- (3-methyl-6-t-butylphenol) can be exemplified.
Of these, n-octadecyl-3- (3 ′, 5′-
Di-t-butyl-4'-hydroxyphenyl) propionate is preferred from the viewpoint of suppressing gel formation.

The phosphorus antioxidants used in the present invention include:
Trisnonylphenyl phosphite, distearylpentaerythritol diphosphite, tris (2,4-di-t-butylphenyl) phosphite, tetrakis (2,4-di-t-butylphenyl) -4,4′-biphenylene -Di-phosphites. Furthermore, triphenyl phosphite, diphenyl isodecyl phosphite, phenyl diisodecyl phosphite,
4,4'-butylidene-bis (3-methyl-6-t-butylphenylditridecyl) phosphite, cyclic neopentanetetraylbis (octadecylphosphite), tris (nonylphenyl) phosphite, diisodecylpentaerythritol diphosphite Phosphite, 9.1
Phosphite stabilizers such as 0-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide and 2,2'-methylenebis (4,6-di-t-butylphenyl) octyl phosphite Can be mentioned. Of these, when tris (2,4-di-t-butylphenyl) phosphite is used in combination with the phenolic antioxidant tris (2,4-di-t-butylphenyl) phosphite, the generation of gel is suppressed. It is preferable from the viewpoint of doing. It is necessary to use a total of 0.01 to 5 parts by mass of the phenolic antioxidant and the phosphorus antioxidant with respect to 100 parts by mass of the resin composed of PVA and PEG,
Preferably from 0.01 to 3 parts by mass, more preferably from 0.1 to 3 parts by mass.
05 to 3 parts by mass. In the present invention, it is necessary that both the phenolic antioxidant and the phosphorus antioxidant are present, and the weight ratio is preferably 10/90.
~ 95/5, more preferably 30/70 ~ 95 /
5 is used.

The resin composition of the present invention contains the phenolic antioxidant and the phosphorus antioxidant, and further comprises Ca
At least one stabilizer selected from a Zn-Sn-based stabilizer, an alkali metal salt of a hydrogen-containing organic polybasic acid, and an alkali or alkaline earth metal salt of a hydrogen-containing inorganic phosphoric acid; 0.01 to 5 parts by mass, more preferably 0.0 to 5 parts by mass with respect to parts by mass.
It may be contained in an amount of 1 to 1 part by mass. On the other hand, in the present invention, a Ca—Zn-based stabilizer is excluded because no effect is observed. Alkali metals constituting the alkali metal salt of the hydrogen-containing organic polybasic acid include potassium and sodium.Examples of the organic polybasic acid include phthalic acid, isophthalic acid, adipic acid, azelaic acid, citric acid, glutaconic acid, and glutan Acids, succinic acid, suberic acid, pimelic acid, fumaric acid, tartaric acid, maleic acid, malonic acid, malic acid. Among these, alkali metal salts of hydrogen-containing organic polybasic acids include potassium dihydrogen citrate, sodium dihydrogen citrate, sodium monohydrogen succinate,
Sodium dihydrogen phosphate and sodium monohydrogen tartrate. Examples of the alkali metal salt of a hydrogen-containing inorganic phosphoric acid include dipotassium dihydrogen pyrophosphate, dihydrogen pyrophosphate and dihydrogen pyrophosphate.
Metal salts containing at least one hydrogen in the molecule, such as sodium, may be mentioned, and alkaline earth metal salts include calcium hydrogen dihydrogen pyrophosphate. These stabilizers may be used alone and in combination with the antioxidant, or two or more of these stabilizers may be used in combination with the antioxidant. The use amount of these stabilizers is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 1 part by mass, per 100 parts by mass of the resin comprising PVA and PEG. When the stabilizers are used in combination, the amount used can be appropriately set so that the total amount of the stabilizers is 0.01 to 5 parts by mass.

[0012] In addition to the above components, the resin composition of the present invention may further comprise, if necessary, an anti-adhesive agent as long as the effects of the present invention are not impaired.
It may contain a lubricant, a coloring agent, a filler and the like.

A specific example of the method for producing the resin composition of the present invention will be described with respect to an example using EVOH. PVA, EVOH
The method of mixing each component of PEG and PEG is not particularly limited. For example, PEG can be mixed with PV under heating at about 60 ° C.
A, and left for several hours to ripen. Further, a total amount of a phenolic antioxidant and a phosphorus type antioxidant is added in a predetermined amount, and a total amount of a stabilizer is added in a predetermined amount. Dry blending with a mixer, tumbler, mini color or the like is preferred. When PEG is solid at room temperature, it may be dry-blended as it is. Thus, the resin composition of the present invention can be obtained.

This resin composition is formed into a film or the like as described below, but it is preferable to use a composition pelletized by a twin-screw extruder or the like in advance for forming a film or the like. The resulting mixture or pellet is formed into a film, sheet, tray or the like. The molding method is preferably a melt extrusion molding method, but is not particularly limited thereto. A molded article, for example, a film may be unstretched or may be uniaxially or biaxially stretched. As the molding method, for example, a press molding method, an extrusion molding method using a T-die, a co-extrusion molding method using a circular die, a deep drawing molding method, or the like can be used. In particular, when forming a laminated film of the resin composition of the present invention and another thermoplastic resin, an extrusion lamination method, a coextrusion lamination method, a coextrusion inflation method, or the like can be used.

Other thermoplastic resins laminated with the resin composition layer of the present invention include ethylene and ethyl acrylate,
At least one copolymer selected from acrylates such as acrylates such as methyl methacrylate and methacrylate, and their acid-modified products (graft polymers); ethylene-vinyl acetate copolymers; high-pressure low-density polyethylene; Chain low density polyethylene (LLDP)
E), polyolefin resins such as polypropylene and ionomer, and furthermore, polyamide resins. Further, an adhesive resin layer may be used for laminating the core layer and the outer layer. Examples of the adhesive resin include a thermoplastic polymer containing a carboxyl group or a derivative thereof, such as a resin obtained by graft copolymerizing maleic anhydride or the like with a polyolefin, and an adipic acid-based polyester having a urethane bond. Can be.

The thickness of the film differs depending on whether the film obtained from the composition of the present invention is used alone or when it is used as a laminate of a layer obtained from the resin composition of the present invention and another resin film. The layer obtained from the resin composition of the present invention is formed to have a thickness of 3 to 50 μm, preferably 5 to 30 μm. The film obtained using the resin composition obtained in this manner is a film having low gas permeability and low gas permeability, so garlic, kimchi,
It is suitably used as a packaging material for pickles and flowers.

[0017]

EXAMPLES The present invention will now be described specifically with reference to examples, but the present invention is not limited to these examples. The evaluation was performed by the following evaluation method. (Mixing test) Using Labo Plastomill Model 30C150 manufactured by Toyo Seiki Co., Ltd. (PVA + PEG + EVOH)
A kneading test of the system resin was performed to obtain a test sample for gel fraction measurement. The resin composition was 87.5% by mass of PVA and PEG12.
5% by mass of resin was mixed with 100 parts by mass of EVO
H10 parts by weight were added. In other words, the temperature of the mixing zone was set to 210 ° C.
After 44.44 g of the VA and PEG resin powders were charged, a predetermined amount of the additive was immediately charged into the same inlet. afterwards,
After preheating for 3 minutes, the screw was rotated at 25 rpm and kneaded. After a lapse of 10 minutes from the start of kneading, EVOH pellets were charged from the charging port while the screw was rotating. In this state, kneading was performed for 2 hours and 50 minutes. The kneading time was 3 hours in total. After completion of the kneading, the molten resin was taken out, cut into small pieces with scissors, and allowed to cool naturally to obtain a sample.

(Measurement of Gel Fraction) With respect to the finely cut sample resin pieces obtained by the above method, the insolubility in boiling water was determined by the following method, and the gel fraction was determined. 0.2 g of the finely cut test resin piece obtained by the kneading test was placed in a 10 ml test tube, and 6 ml of water was added. This was heated and melted for 3 hours using a test tube heater heated to 105 ° C. Stirring was performed at intervals of 30 minutes, and was performed for 1 minute each time using a test tube stirrer. After the completion of the dissolution for 3 hours, Advantech Co., Ltd. 3 Using a quantitative filter paper, filtration was performed using an aspirator. The filtrate was vacuum-dried at 100 ° C. for 2 hours, and the mass of the dried product was measured. EV from the mass of the dried product after dissolution to the mass obtained by subtracting the mass of EVOH from the mass before dissolution in boiling water
The ratio of the mass obtained by subtracting the mass of OH was expressed as a percentage, and was defined as a gel fraction.

Example 1 PVA (manufactured by Kuraray Co., Ltd.
PVA405, degree of saponification 80%)
EG (manufactured by Sanyo Chemical Co., Ltd., PEG600, average molecular weight 6)
00) 12.5% by mass was added and blended with a Henschel blender to obtain a powdery mixture. 0.075 parts by mass of a phenolic antioxidant (Irganox 1076, manufactured by Asahi Denka Co., Ltd.) and phosphorus antioxidant (Irgafos S, manufactured by Asahi Denka Co., Ltd.) are added to 100 parts by mass of this powdery mixture.
168) and 0.1 part by mass of a Ca-Zn-Sn-based stabilizer (SC-52, manufactured by Asahi Denka Co., Ltd.), and the mixture was charged into the Labo Plastomill and kneaded. The test was performed. EVOH pellets (Nippon Synthetic Chemical Co., Ltd.)
Soarnol D2908, ethylene content 29 mol%, saponification degree 99.4 mol%, 210 ° C., 10 ² sec
The melt viscosity at a shear rate of ^-1 was 1.0 × 10 ⁴ poise).
12.5 parts by mass was added to 100 parts by mass of A and PEG. The total kneading time was 3 hours. The gel fraction was determined by the above measurement method, and the results shown in Table 1 were obtained.

(Example 2) PVA and P used in Example 1
The same phenolic antioxidant and phosphorus antioxidant as used in Example 1 were added to 100 parts by mass of the EG mixed powder in the same amounts as in Example 1, and the mixture was charged into a Labo Plastomill and kneaded for 10 minutes. , And EVOH. The same EVOH as in Example 1 was used. The total kneading time was 3 hours. The gel fraction of this sample was determined in the same manner as in Example 1 and is shown in Table 1.

(Embodiment 3) Ca-Zn-Sn of Embodiment 1
0.1% sodium dihydrogen pyrophosphate in place of the system stabilizer
A kneading test was performed in the same manner as in Example 1 except that the parts by mass were used, and the gel fraction was determined and shown in Table 1.

Comparative Example 1 PVA and P used in Example 1
A kneading test was performed in the same manner as in Example 1 except that no additive was added to the mixed powder of EG, and the gel fraction was determined.
It was shown to. (Comparative Example 2) A kneading test was performed in the same manner as in Example 1 except that 1 part by mass of the Ca-Zn-based stabilizer was used instead of the Ca-Zn-Sn-based stabilizer of Example 1, and the gel fraction was determined. The results are shown in Table 1.

[0023]

[Table 1]

[0024]

According to the kneading test, a resin composition containing PVA, PEG, and optionally, a phenolic and phosphorus-based antioxidant in a resin of EVOH has little gel-like substance. Furthermore, gel generation can also be suppressed by adding a Ca-Zn-Sn-based stabilizer in addition to the phenol-based and phosphorus-based antioxidants. However, Ca-Zn
The system stabilizer has no effect.

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Claims (5)

[Claims] (1) 55 to 95% by mass of polyvinyl alcohol (PVA) having a saponification degree of 60 to 95% by mol and 5 to 45% by mass of polyethylene glycol (PEG) (the total of both is 100%).
(% By mass) and a total of 0.01 to 5 parts by mass of a total of phenolic and phosphorus-based antioxidants. 2. A 100 mass part of said resin comprising PVA and PEG, further comprising a Ca-Zn-Sn-based stabilizer, an alkali metal salt of a hydrogen-containing organic polybasic acid, and an alkali or alkaline earth of a hydrogen-containing inorganic phosphoric acid. 2. The composition according to claim 1, comprising at least one stabilizer selected from metal salts in an amount of 0.01 to 5 parts by mass.
The resin composition as described in the above. 3. The composition according to claim 1, further comprising 5 to 40 parts by mass of a saponified ethylene-vinyl acetate copolymer (EVOH) based on 100 parts by mass of the resin comprising PVA and PEG.
The resin composition as described in the above. 4. The phenolic antioxidant is n-octadecyl-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate, and the phosphorus antioxidant is tris (2,4). The resin composition according to any one of claims 1 to 3, which is -di-t-butylphenyl) phosphite. 5. The method according to claim 2, wherein the stabilizer is at least one selected from a Ca—Zn—Sn-based stabilizer, disodium dihydrogen pyrophosphate, dipotassium dihydrogen pyrophosphate, and calcium dihydrogen pyrophosphate. Resin composition.