JP2001288321A - Polyvinyl alcohol resin composition - Google Patents

Abstract

(57) [Problem] To provide a resin composition capable of producing a molded article excellent in hot melt moldability, moisture resistance, water disintegration property, durability, strength, and form stability. SOLUTION: The degree of polymerization is 200 to 2000, and the degree of saponification is 85.
A resin composition containing 1 to 50 parts by weight of a solid plasticizer with respect to 100 parts by weight of a hot-melt polyvinyl alcohol-based resin at ９９99.5 mol%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a resin composition comprising a polyvinyl alcohol resin. More specifically, hot melt moldability, moisture resistance, water disintegration, durability, strength,
The present invention relates to a resin composition capable of producing a molded article having excellent morphological stability.

[0002]

2. Description of the Related Art Molded articles made of polyvinyl alcohol are excellent in water disintegration, mechanical properties, oil resistance, biodegradability, etc., and are used for agricultural, civil engineering, industrial, medical, packaging, leisure, It is used in a wide range of fields such as toys, miscellaneous goods, daily necessities, containers and parts. However, conventionally, since polyvinyl alcohol has a melting point and a decomposition temperature close to each other, it has been difficult to produce a molded product by hot melt molding. In addition, in the case of a molding method that requires fluidity of a resin, such as injection molding, polyvinyl alcohol has a relatively high melting point and melt viscosity. A product could not be obtained and molding was often extremely difficult. Various studies have been made so far to impart thermal fusibility to polyvinyl alcohol. For example, lowering the degree of saponification, copolymerizing other comonomers, or adding a plasticizer to lower the melting point or melt viscosity to impart heat fusibility, or lowering the degree of polymerization to lower the melt viscosity A method of causing such a situation has been studied.

[0003] However, when the saponification degree is lowered, the thermal stability is lowered, so that acetic acid odor or decomposition odor may be generated at the time of molding, or gels or lumps may be generated on the molded product, which may cause a problem. When the obtained molded product is left under high humidity, the strength and elastic modulus may be greatly reduced or deformed. Also, in the case of copolymerization, the strength and elastic modulus when the obtained molded product is left under high humidity are reduced. Furthermore, even when the melting point or melt viscosity is lowered by adding a liquid plasticizer, the strength and elastic modulus of the obtained molded product when left under high humidity may be reduced or deformed. Alternatively, the plasticizer may ooze out on the surface of the molded product, which often causes a problem. In addition, when the degree of polymerization is lowered, the physical properties of the obtained molded article, particularly the impact resistance, are remarkably reduced, which often causes a problem.

Further, in recent years, it has been required to maintain physical properties and morphological stability under high humidity as described above, that is, to increase water resistance, while maintaining the excellent water solubility of polyvinyl alcohol. In general, when the water resistance of a vinyl alcohol polymer is increased by increasing the degree of saponification, the water solubility decreases, and it has been difficult to impart water resistance while maintaining the water solubility. Although studies have been made by adding a filler, the effects on water resistance, moisture resistance, and form stability were insufficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a molded article excellent in hot-melt moldability, moisture resistance, water disintegration, durability, strength and form stability in such a background. To provide a resin composition that can be used.

[0006]

The object of the present invention is to achieve a polymerization degree of 20.
This is achieved by providing a resin composition having 0 to 2000, a saponification degree of 85 to 99.5 mol%, and 100 parts by weight of a hot-melt polyvinyl alcohol-based resin and 1 to 50 parts by weight of a solid plasticizer.

[0007]

DETAILED DESCRIPTION OF THE INVENTION The polyvinyl alcohol resin used in the present invention is a saponified vinyl ester alone or a vinyl ester copolymer. Here, as the vinyl ester, vinyl acetate may be mentioned as a representative example, and in addition, vinyl esters such as vinyl propionate, vinyl pivalate, vinyl valerate, vinyl caprate, and vinyl benzoate may also be mentioned. These vinyl esters may be used alone or in combination of two or more.

The polyvinyl alcohol used in the present invention is preferably modified with an α-olefin having 4 or less carbon atoms. ethylene as an example of an α-olefin,
Propylene, n-butene, isobutylene and the like can be mentioned, but ethylene is preferable in terms of water resistance, moisture resistance, form stability and the like of the obtained molded article. It is surprising that by copolymerizing a specific amount of α-olefin, particularly ethylene, it is possible to impart heat melting property to the polyvinyl alcohol-based resin without impairing the water resistance and moisture resistance of the obtained molded article, and the shape stability. It is. α-olefin content is 1 to 19 mol%
Is preferable, 2 to 15 mol% is more preferable, and 3 to 12 mol% is particularly preferable. When the content of the α-olefin is less than 1 mol%, the effect of copolymerization is not remarkably exhibited, and the heat fusibility may be reduced. On the other hand, when the content of the α-olefin exceeds 19 mol%, the water disintegrability of the obtained molded product is reduced, which may cause a problem depending on the use.

The polyvinyl alcohol resin used in the present invention may be modified other than α-olefin as long as the effects of the present invention are not impaired. Vinyl monomers copolymerizable with vinyl ester include acrylamide monomers such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide; methacrylamide, N-methylmethacrylamide, N-ethylmethacryl Methacrylamide monomers such as amides and N, N-dimethylmethacrylamide;
Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, i-propyl vinyl ether,
vinyl ether monomers such as t-butyl vinyl ether and dodecyl vinyl ether; allyl alcohol; vinyl trimethoxysilane; N-vinyl-2-pyrrolidone, isopropenyl alcohol, 7-octen-1-ol,
Allyl acetate, isopropenyl acetate and the like can be mentioned.

The degree of polymerization of the polyvinyl alcohol resin used in the present invention needs to be 200 to 2000, preferably 250 to 1500, and 300
It is particularly preferable that the number is from 1,000 to 1,000. 200 degree of polymerization
If it is lower, the physical properties of the obtained molded product, particularly the impact resistance and the mechanical physical properties, decrease. On the other hand, if the degree of polymerization is higher than 2000,
The melt viscosity becomes high, and hot melt molding becomes extremely difficult.

The degree of saponification of the polyvinyl alcohol resin used in the present invention must be 85 to 99.5 mol%, preferably 88 to 99 mol%, and more preferably 90 to 98.5 mol%. Is particularly preferred.
If the degree of saponification is less than 85 mol%, not only the water resistance, moisture resistance, and morphological stability of the obtained molded product are lowered, but also the thermal stability at the time of molding is deteriorated, and an acetic acid odor may be generated. . On the other hand, when the degree of saponification exceeds 99.5 mol%, the water disintegrability of the molded product decreases.

Further, the polyvinyl alcohol-based resin may be used by mixing polyvinyl alcohol-based resins differing in at least one of the kind and amount of these comonomers, the degree of saponification, and the degree of polymerization.

The polyvinyl alcohol resin used in the present invention needs to be heat-fusible. The thermal fusibility means that molding conditions can be set so as not to cause remarkable deterioration or deterioration such as gelation at the time of hot melt molding, and a polyvinyl alcohol resin having a melting point of 170 to 230 ° C is preferable. When the melting point is less than 170 ° C., the thermal stability of the polyvinyl alcohol resin, water resistance, moisture resistance,
Since the morphological stability is reduced, a problem may occur. On the other hand, when the melting point exceeds 230 ° C., the temperature becomes close to the thermal decomposition temperature of the polyvinyl alcohol-based resin, so that molding may be difficult. Further, those having a melt flow index of 0.1 to 500 g / 10 min at a load of 2160 g at any temperature in the range of 190 ° C. to 230 ° C. are generally used.

Further, the present inventors have found that the α-olefin-modified polyvinyl alcohol-based resin used in the present invention comprises:
When the content of the carboxylic acid and the lactone ring is 0.02 to
0.4 mol%, preferably from 0.022 to 0.2 mol%.
It has been found that 37 mol% is preferable, 0.024 to 0.33 mol% is more preferable, and 0.025 to 0.3 mol% is particularly preferable. The carboxylic acid in the present invention includes an alkali metal salt thereof, and examples of the alkali metal include potassium and sodium. When the content of the carboxylic acid and the lactone ring is less than 0.02 mol%, viscosity increase and gelation become remarkable when the polyvinyl alcohol-based resin is hot melt-molded, and the melt moldability and the molding fluidity are reduced. May be. On the other hand, when the content of the carboxylic acid and the lactone ring exceeds 0.4 mol%, not only may the melt moldability be deteriorated due to the thermal decomposition of the polyvinyl alcohol-based resin, but also the water resistance and moisture resistance of the obtained molded product Properties and morphological stability may decrease.

Α- having a carboxylic acid and a lactone ring
As a method for producing an olefin-modified vinyl alcohol resin, a vinyl ester monomer such as vinyl acetate and an α-
A method of saponifying a vinyl ester resin obtained by copolymerizing an olefin with a carboxylic acid and a monomer capable of forming a lactone ring in an alcohol or dimethyl sulfoxide solution, mercaptoacetic acid, 3-mercaptopropionic acid In the presence of a thiol compound containing a carboxylic acid such as, a method of polymerizing an α-olefin and a vinyl ester monomer and then saponifying it, when polymerizing a vinyl ester monomer such as vinyl acetate, A method of causing a chain transfer reaction to a vinyl ester monomer and an alkyl group of a vinyl ester resin to obtain a hyperbranched vinyl ester resin, followed by saponification, a monomer having an epoxy group and a vinyl ester monomer Reacting a co-resin with a thiol compound having a carboxyl group and then saponifying, PVA and And a method by acetalization reaction of an aldehyde having carboxyl group.

The contents of the carboxylic acid and lactone rings of the polyvinyl alcohol resin can be determined from proton NMR peaks. After complete saponification to a degree of saponification of 99.95 mol% or more, washing with methanol was carried out sufficiently, followed by drying at 90 ° C. under reduced pressure for 2 days to prepare PVA for analysis. In the above case, the prepared analytical PVA was DMSO-
D6 and dissolved in 500 MHz proton NMR (JEO
LGX-500) at 60 ° C. Acrylic acid, acrylic acid esters, acrylamide and acrylamide derivative monomers can be synthesized from methacrylic acid, methacrylic esters, methacrylamide and methacrylamide derivatives using the peak (2.0 ppm) derived from the main chain methine. The content of the monomer was calculated by a conventional method using a peak (0.6 to 1.1 ppm) derived from a methyl group directly connected to the main chain. Fumaric acid, maleic acid,
Itaconic acid, monomers having a carboxyl group derived from maleic anhydride or itaconic anhydride and the like, in addition a few drops of lysis after trifluoroacetic acid PVA for analysis created DMSO-D _6, 500 MHz proton NMR (JEOL
GX-500) at 60 ° C. For quantification, the content was calculated by an ordinary method using the methine peak of the lactone ring attributed to 4.6 to 5.2 ppm. In the cases of and, the content was calculated using the peak (2.8 ppm) derived from methylene bonded to the sulfur atom. In the case of the above, the prepared analytical PVA was replaced with methanol-D ₄ / D ₂ O =
Dissolved in 2/8, and 500 MHz proton NMR (JE
OL GX-500) at 80 ° C. The peaks derived from the methylene of the terminal carboxylic acid or an alkali metal salt thereof (the following chemical formulas 1 and 2) belong to 2.2 ppm (integral value A) and 2.3 ppm (integral value B). The derived peak is (Chemical Formula 3 below)
Belongs to 2.6 ppm (integral value C) and the peak derived from methine in the vinyl alcohol unit belongs to 3.5 to 4.15 ppm (integral value D), and the content of carboxylic acid and lactone ring is calculated by the following formula. Here, △ indicates the amount of modification (mol%). Carboxylic acid and lactone ring content (mol%) = 50
× (A + B + C) × (100− △) / (100 × D)

[0017]

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[0018]

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[0019]

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In the case of (1), the prepared analysis PVA is
It was dissolved in O-D6 and proton NMR at 500 MHz (J
EOL GX-500) at 60 ° C. Peak 4.8 to 5.2 derived from methine in the acetal moiety
The content was calculated by the usual method using ppm (the following chemical formula 4).

[0021]

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The resin composition of the present invention must contain 1 to 50 parts by weight of a solid plasticizer based on 100 parts by weight of the polyvinyl alcohol resin, and preferably 3 to 45 parts by weight. Parts, optimally 5 to 40 parts by weight. Here, the solid plasticizer is a substance that acts as a plasticizer of the polyvinyl alcohol resin during melt molding and becomes solid after molding. Specifically, the solid plasticizer is a solid at 20 ° C. and has a melting point of polyvinyl alcohol. At the above temperatures, it is a substance that can be in a liquid state and improve the molding fluidity of the polyvinyl alcohol-based resin, and is preferably a water-dispersible substance, and when melt-kneaded with polyvinyl alcohol, dispersibility, It is more preferable that the substance has good compatibility. Such substances include solid polyhydric alcohols, especially those having 3 to 30 carbon atoms, preferably 5 to 30 carbon atoms.
And sorbitol, mannitol, pentaerythritol, dipentaerythritol and the like.

Known liquid plasticizers such as glycerin, diglycerin and derivatives thereof, polyethylene glycol and water can be used in combination with the resin composition of the present invention as long as the object of the present invention is not impaired. The liquid plasticizer can improve the molding fluidity of the polyvinyl alcohol-based resin composition and the flexibility of the molded product.However, when the added amount is large, the water resistance and the moisture resistance of the molded product are reduced, or the plasticizer is used in the molded product The problem may be caused by oozing on the surface. The amount added is preferably less than 20 parts by weight, more preferably less than 8 parts by weight, based on 100 parts by weight of the polyvinyl alcohol-based resin. Further, other additives (a heat stabilizer, an ultraviolet absorber, an antioxidant, a coloring agent, a lubricant, a release agent, a filler, a filler, a surfactant, and the like) can be used as long as the object of the present invention is not hindered. .

The present inventors have further found that it is preferable to incorporate an elastomer into the resin composition of the present invention. That is, the addition of the solid plasticizer may cause a problem in that the impact resistance and elongation of the molded product are reduced depending on the use. By adding an elastomer, impact resistance and elongation can be improved. Further, unlike the liquid plasticizer, the water resistance and the moisture resistance of the molded product are not reduced, and the plasticizer does not seep out to the surface. If the amount of the added elastomer is small, the effect of improving impact resistance and elongation becomes inconspicuous, and if it is large, water disintegration and strength are reduced. Therefore, the elastomer is usually 1 to 100 parts by weight of the polyvinyl alcohol-based resin.
It is added in the range of 50 parts by weight, preferably 3 to 45 parts by weight, particularly preferably 5 to 40 parts by weight.

Here, the elastomer is a substance capable of improving the impact resistance and elongation of the polyvinyl alcohol-based resin used in the present invention. The elastomer is usually solid at ordinary temperature and is melted and kneaded with the polyvinyl alcohol-based resin. Is preferably excellent in dispersibility and compatibility. Further, as long as it is a substance that can improve the impact resistance and elongation of the polyvinyl alcohol-based resin, the elastomer may or may not be melted when the resin composition is molded. Examples of such materials include rubber polymers, thermoplastic resins such as polyolefins blended with rubber polymers, and polar functional materials such as maleic anhydride, itaconic acid, acrylic acid, or glycidyl (meth) acrylate. And thermoplastic resins such as polyolefin.

The polyvinyl alcohol-based resin composition used in the present invention and a molded product obtained by melt-molding the same are:
Water-disintegrable, biodegradable, other thermoplastic resins such as biodegradable resins and general-purpose resins having photodegradability, blended or laminated as long as the object of the present invention is not hindered, and used. it can. There is no particular limitation on the type of these other thermoplastic resins, and as biodegradable resins, polylactic acid, polyethylene succinate, polybutylene succinate, polycaprolactone, etc. are given as examples, and as general-purpose resins, polyethylene, polypropylene, etc. Polystyrene, polystyrene, ABS resin, nylon, polyester resin and the like.

The molded product of the present invention is produced by hot-melt molding the above resin composition. The shape and size of the molded product are not particularly limited, and can be appropriately selected depending on the application and purpose, such as lump, plate, rod, box, column, cylinder, film, bottle, container, cup, sheet, cap, and the like. Processed into molded products. The type of the hot melt molding method is not particularly limited, and is appropriately selected from known methods depending on the shape and use of the molded product. Examples of the molding method include an injection molding method, an extrusion molding method, a T-die extrusion molding method, an inflation molding method, a press molding method, a hollow molding method, a vacuum molding method, a pressure molding method, and the like.

The polyvinyl alcohol-based resin composition of the present invention is excellent in hot-melt moldability, and various molded articles can be prepared by a desired molding method. Because of its excellent durability, strength, and form stability, it is used for various purposes such as agricultural, civil engineering, industrial, medical, packaging, leisure, toys, sundries, daily necessities, containers, parts, etc. You.

[0029]

The present invention will be described in more detail with reference to the following Examples and Comparative Examples. In the following Examples and Comparative Examples, “parts” and “%” mean on a weight basis unless otherwise specified. The analysis method of polyvinyl alcohol was measured in the following manner.

Analysis method for PVA The analysis method for PVA is JIS-K6 unless otherwise specified.
726. The ethylene modification amount of the present invention is a modified polyvinyl ester, and the content of carboxylic acid and lactone ring is 500 MHz 1H-NMR using PVA (JEOL GX-500).
It was determined from the measurement by the apparatus as described above. PV of the present invention
The melting point of A was measured by using a DSC (Mettler, TA3000) in nitrogen at 250 ° C. at a heating rate of 10 ° C./min, then cooling to room temperature, and again at 250 ° C. at a heating rate of 10 ° C./min.
The temperature at the peak top of the endothermic peak indicating the melting point of PVA when the temperature was raised up to was examined.

Example 1 A degree of polymerization of 450, a degree of saponification of 96.3 mol%, a degree of ethylene modification of 8 mol%, a carboxylic acid and lactone ring content of 0.0
54% ethylene-modified polyvinyl alcohol-based resin 10
0 parts by weight and pentaerythritol 2 as a solid plasticizer
0 parts, thermoplastic elastomer (glycidyl methacrylate-modified ethylene-ethyl acrylate copolymer) ｛trade name “Lexpearl RA3150” (manufactured by Nippon Polyolefin Co., Ltd.) ド ラ イ After dry blending 15 parts, use a twin screw extruder at 225 ° C. The mixture was melt-kneaded to produce pellets. Further, injection molding is performed from the pellets at a cylinder temperature and a nozzle temperature of 230 ° C. and a mold temperature of 40 ° C., and is 5 cm long, 5 cm wide, 1 cm high and 0.8 m thick.
m injection-molded articles having a box shape were prepared. The molding was performed using a mold in which six molded products were formed in one shot. Moldability,
The water disintegrability, impact resistance, form stability, and appearance of the molded product were evaluated according to the following criteria. Tables 1 and 2 show the resin composition and the results.

Evaluation method (1) Moldability The following criteria were used to evaluate the degree of resin filling in the molded article. ：: The resin was completely filled, and there was no molded product with insufficient filling (defective product). ：: Although the resin was almost completely filled, a molded article which was rarely insufficiently filled (defective product) was observed. Δ: A molded product in which the resin was insufficiently filled (defective product) was considerably observed. X: The resin was insufficiently filled in all the molded products, and a completely filled molded product was not obtained at all. (2) Water disintegration property The obtained molded article was immersed in water at 30 ° C for 28 days, and the degree of disintegration was visually observed. ◎: Most of the molded product has collapsed, and the form has not been stopped. ：: A part of the molded product collapsed and swelled considerably (to the extent that it could be crushed with a finger), but the form was kept. Δ: A very small part of the molded product collapsed and swelling was slight (to the extent that it could not be crushed with a finger) ×: The molded article hardly collapsed and swelling was extremely small. Or not swelling at all. (3) Impact resistance A 30 g weight (weight) was attached to the molded product, the temperature was adjusted in a 5 ° C. constant temperature bath for one day, and the product was dropped on a concrete ground from a height of 3 m, and the change in appearance was evaluated according to the following criteria. A: No cracking or chipping, and no change in appearance. ：: No cracking or chipping occurred, but abnormalities such as whitening were observed in the appearance. : A very small part was found or small cracks were observed. ×: The molded product was broken. (4) Morphological stability After leaving the molded article at 20 ° C. and 65% RH for 28 days, the degree of deformation was visually observed and evaluated according to the following criteria. : No deformation was observed. ：: Almost no deformation was observed. Δ: Some deformation is observed. ×: Deformed considerably. (5) Molded product surface appearance After the molded product was left at 20 ° C. and 65% RH for 28 days, the surface of the molded product was visually observed, and the extent to which the solid plasticizer or glycerin oozed out was visually observed. The evaluation was based on the following criteria. : No oozing of the plasticizer was observed on the surface. : Very little seepage of the plasticizer was observed on the surface. X: Exudation of the plasticizer is considerably observed on the surface.

Examples 2 to 4 and Comparative Examples 1 to 3 Injection molded articles were prepared and evaluated in the same manner as in Example 1 except that the amounts of the solid plasticizer and the thermoplastic elastomer were different. Tables 1 and 2 show the resin composition and the results.

Examples 5 to 13 and Comparative Examples 4 to 7 Injection molded articles were prepared in the same manner as in Example 1 except that the degree of polymerization, saponification, degree of ethylene modification, carboxylic acid and lactone ring contents of polyvinyl alcohol were different. And evaluated.
Tables 1 and 2 show the resin composition and the results.

Example 14 A degree of polymerization of 410 and a degree of saponification of 9 were added to polyvinyl alcohol.
An injection molded article was prepared and evaluated in the same manner as in Example 1 except that propylene-modified polyvinyl alcohol having 7.8 mol%, a propylene modification degree of 3 mol%, and a carboxylic acid and lactone ring content of 0.062% was used. did. Tables 1 and 2 show the resin composition and the results.

Examples 15 and 16 Injection molded articles were prepared and evaluated in the same manner as in Example 1 except that glycerin was used in combination as a liquid plasticizer during pelletization. Tables 1 and 2 show the resin composition and the results.

Comparative Example 8 An injection molded article was prepared in the same manner as in Example 2, except that 20 parts of glycerin as a liquid plasticizer was used instead of 20 parts of pentaerythritol. evaluated. Tables 1 and 2 show the resin composition and the results.

[0038]

[Table 1]

[0039]

[Table 2]

[0040]

According to the present invention, there can be provided a resin composition capable of producing a molded article excellent in hot melt moldability, moisture resistance, water disintegration property, durability, strength and shape stability.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) // (C08L 29/04 (C08L 29/04 101: 00) 101: 00) F-term (Reference) 4F071 AA10 AA14 AA14X AA15 AA15X AA29 AA29X AA32 AA32X AA35 AA35X AA78 AC05 AE04 AF01 AF13 AF53 AH01 AH04 AH05 BA01 BB05 BC04 4J002 AC002 BB003 BE021 BE031 BN032 BN052 CD192 EC056 FD026 GA00 GB00 GC00 GG01 GG02 GL00 4J100 AA02Q AA03Q AA04Q AA06Q AD01R AD02P AD03R AE02R AE03R AE04R AE05R AE06R AG10R AJ02R AJ08R AJ09R AK31R AK32R AM15R AM17R AM19R AP16R AQ08R BA11H BA77R BC53H CA03 CA31 DA01 HA08 HA17 HC09 HC69 HC70

Claims (6)

[Claims] 1. A polymerization degree of 200 to 2000 and a saponification degree of 85.
A resin composition containing 1 to 50 parts by weight of a solid plasticizer with respect to 100 parts by weight of a hot-melt polyvinyl alcohol-based resin at ９９99.5 mol%. 2. The resin composition according to claim 1, wherein the polyvinyl alcohol is a polyvinyl alcohol containing 1 to 19 mol of an α-olefin having 4 or less carbon atoms in a main chain. 3. The resin composition according to claim 2, wherein the α-olefin is ethylene. 4. The resin composition according to claim 2, wherein the polyvinyl alcohol-based resin contains 0.02 to 0.4 mol% of a carboxylic acid and a lactone ring. 5. The resin composition according to claim 1, further comprising 1 to 50 parts by weight of an elastomer based on 100 parts by weight of the polyvinyl alcohol-based resin. 6. A molded product obtained by melt-molding the resin composition according to any one of claims 1 to 5.