JPH04258654A - Molded article - Google Patents

Abstract

PURPOSE:To improve melt moldability and shape retention and enable a spontaneous decomposition in a wet environment such as in soil by compounding a specific PVA resin with an inorg. filler and molding the resulting compsn. CONSTITUTION:A polyvinyl ester is hydrolyzed or alcoholyzed to give a PVA resin which contains 20-80mol%, pref. 40-70mol%, vinyl alcohol units, has a viscosity-average mol.wt. of 100-1000, pref. 200-700, and is water-sol. or thermally meltable. The resin is compounded with an inorg. filler having a low reactivity with the resin and a mean particle diameter of 0.1-100mum (e.g. talc), and the resulting compsn. is heated, plasticized, and molded to give a molded article.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded product which can be molded by hot melt molding and which naturally disintegrates and disappears when exposed to an environment containing moisture such as soil.

0002

BACKGROUND OF THE INVENTION Among various molding materials, there are already known polymers that lose their shape when exposed to a moisture-containing environment after being molded into a predetermined shape, that is, have disintegration properties. Water-soluble polymers such as polyvinyl alcohol are well known as these polymers. However, molded products of these water-soluble polymers have generally been molded from aqueous solutions because of the poor hot-melt moldability of water-soluble polymers. However, since this method has low molding accuracy, it has hardly been put to practical use in fields where complex shapes or molding precision are required. To address this drawback of poor hot-melt moldability, various water-soluble polymers have already been proposed that retain water-solubility while imparting hot-meltability. However, molded products made from these water-soluble polymers alone have the disadvantage that when exposed to a moist environment, the polymers that make up the molded product absorb moisture, become plasticized, and easily change shape. was.

0003

[Problems to be Solved by the Invention] The present invention has the characteristics that it has good hot-melt moldability and naturally disintegrates and disappears when exposed to a moisture-containing environment. The purpose of this invention is to provide a molded product that has excellent shape retention even when the polymer constituting the molded product absorbs moisture.

0004

[Means for Solving the Problems] As a result of intensive studies to solve the above problems, the present inventors have found that a specific water-soluble and heat-melting polyvinyl alcohol resin A and an inorganic filler B The molded product has good hot-melt moldability, naturally disintegrates and disappears when exposed to a moisture-containing environment, and is resistant to moisture even if the polymer that makes up the molded product absorbs moisture. The inventors have discovered that the above object of having excellent shape retention can be achieved, and have completed the present invention.

Polyvinyl alcohol resin A used in the present invention is kneaded and molded with filler B, so its melting properties are important, and the presence of a large amount of water may cause the shape of the molded product to collapse. A certain degree of water solubility and water dispersibility is required, and the range of polyvinyl alcohol resin A suitable for the present invention is determined from this viewpoint. The content of vinyl alcohol units in the polyvinyl alcohol resin A of the present invention is 20 to 80 mol%, especially 30 to 75 mol%.
It is preferably mol%, more preferably 40 to 70 mol%. If the content of vinyl alcohol units in the polyvinyl alcohol resin A is greater than 80 mol%, the melting point of the resin A will become high and the moldability of the molded product will deteriorate, so that it cannot be used in the present invention. Furthermore, if the content of vinyl alcohol units is less than 20 mol %, the disintegration properties of the molded product in the presence of water will decrease, and therefore it cannot be used in the present invention. The viscosity average degree of polymerization of the polyvinyl alcohol resin A of the present invention is 10
0-1000, preferably 100-800, 20
0 to 700 is more preferable. If the viscosity average degree of polymerization of the polyvinyl alcohol resin A is less than 100, the shape retention of the obtained molded product will deteriorate, so that it cannot be used in the present invention. Furthermore, if the viscosity average degree of polymerization of polyvinyl alcohol resin A is greater than 1000, the melt viscosity becomes too high and the moldability deteriorates, so that it cannot be used in the present invention. The polyvinyl alcohol resin A of the present invention is produced by hydrolysis or alcoholysis of polyvinyl ester. The polyvinyl ester in the present invention includes homopolymers of vinyl esters, copolymers of vinyl esters, and copolymers of vinyl esters and other ethylenic monomers. The vinyl ester is preferably a vinyl ester of a fatty acid having 1 to 25 carbon atoms, more preferably a vinyl ester of a fatty acid having 1 to 20 carbon atoms,
Among these, vinyl acetate is particularly preferred.

[0006] The polyvinyl ester of the present invention may also be modified at the polymer terminal using a chain transfer agent. The ethylenic monomer to be copolymerized with vinyl ester is not particularly limited as long as it can be copolymerized with vinyl ester, and examples include α-olefins such as ethylene, propylene, n-butene, isobutene, and 1-hexadecene. styrene, styrenes such as α-methylstyrene, halogen-containing monomers such as vinyl chloride, vinylidene chloride, tetrafluoroethylene, (meth)acrylic acid, fumaric acid, itaconic acid, crotonic acid, maleic acid, maleic anhydride Carboxylic acid-containing monomers such as acids and their salts, methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylate 2-ethylhexyl acid, (meth)acrylic esters such as stearyl (meth)acrylate, esters such as dimethyl fumarates, dimethyl itaconate, dimethyl maleate, monomethyl maleate, dimethyl crotonate, methyl vinyl ether, ethyl vinyl ether , vinyl ethers such as butyl vinyl ether, lauryl vinyl ether, stearyl vinyl ether, sulfonic acid group-containing monomers such as vinyl sulfonic acid, allyl sulfonic acid, methalylsulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, and salts thereof. , (meth)acrylamide, N,
Amide group-containing monomers such as N-dimethyl (meth)acrylamide, N-methylol (meth)acrylamide, N-t-butoxy (meth)acrylamide, N-t-octyl (meth)acrylamide, N-vinylpyrrolidone,
Monomers containing amino groups such as dimethylaminoethyl (meth)acrylamide, monomers containing quaternary ammonium salts such as (meth)acrylamide-propyl-trimethylammonium chloride, vinylhydroxysilane, (meth)
Silyl group-containing monomers such as 3-trimethoxysilylpropyl acrylate, hydroxyl group-containing monomers such as allyl alcohol, dimethylallyl alcohol, isopropenyl alcohol, allyl acetate, dimethylallyl acetate, isopropenyl acetate, etc. Examples include monomers containing an acetyl group. Among these, N-vinylpyrrolidone, itaconic acid, allyl alcohol, (meth)acrylamide-propyl-trimethylammonium chloride, allylsulfonate, etc. are particularly preferred because they have the effect of improving the disintegration properties of molded products.

Furthermore, a plasticizer can be used in the polyvinyl alcohol resin A used in the present invention in order to improve its moldability. Examples of the plasticizer include ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol with a molecular weight of 600 or less, trimethylene glycol,
Glycols such as tetramethylene glycol, pentamethylene glycol, hexamethylene glycol, propylene glycol, diols such as glycerin, 1,3-butanediol, 2,3-butanediol, trimethylolpropane, diglycerin, 3-methyl- 1, 3, 5
Examples include, but are not limited to, -pentanetriol, a small amount (10% by weight or less) of water, and the like. Among these plasticizers, particularly preferred ones include glycerin and ethylene glycol. The amount of these plasticizers added is 30 parts or less, preferably 20 parts or less, and more preferably 10 parts or less, based on 100 parts by weight of the polyvinyl alcohol resin A (hereinafter, parts by weight are abbreviated as parts).

[0008] The inorganic filler B of the present invention is selected from substances having low reactivity with the polyvinyl alcohol resin A, such as clay minerals, inorganic salts, and glass.
Specific examples of these inorganic fillers B include kaolin, clay, talc, acid clay, silica, alumina, diatomaceous earth,
Bentonite, montmorillonite, kibushi clay, frog's eye clay, waxite, alumite, china clay, feldspar, asbestos, perlite, calcium carbonate, magnesium hydroxide, carbon black, titanium oxide, mica, shirasu, glass, glass fiber, etc. However, it is not limited to these. The average particle size of the inorganic filler B that can be used in the present invention is not particularly limited, but the average particle size is 0.1 to 100μ.
m is preferable, and 0.5 to 50 μm is more preferable.

[0009] The weight blending ratio of polyvinyl alcohol resin A and inorganic filler B in the present invention is A:B=50:
50-5:95, preferably 50:50-10:
It is 90. If the blending ratio of polyvinyl alcohol resin A is more than 50 parts, the molded product will absorb moisture and become soft even if it is placed under relatively high humidity conditions, resulting in a decrease in shape retention. cannot be used. If the blending ratio of polyvinyl alcohol resin A is less than 5 parts, the moldability will deteriorate, and therefore it cannot be used in the present invention.

[0010] The molded product of the present invention can be easily made into a molded product of any shape by heating and plasticizing a blend of polyvinyl alcohol resin A and inorganic filler B. Methods for blending polyvinyl alcohol resin A and inorganic filler B include a method of blending polyvinyl alcohol resin A and inorganic filler B by melt kneading, a method of powder dry blending, and a method of blending all of inorganic filler B. A method in which a part of polyvinyl alcohol resin A is blended in advance and this is blended with the remaining polyvinyl alcohol resin A, after blending polyvinyl alcohol resin A and inorganic filler B in a solution state. , any method that removes the solvent can be used. Molding methods that can be used in the present invention include press molding, extrusion molding, injection molding, blow molding, and the like. The shapes of the blend used in the present invention include pellets, chips,
Examples include flakes and pulverized particles, but shapes other than these may be used as long as problems such as poor biting do not occur when feeding into a molding machine. Moreover, an antioxidant, an ultraviolet absorber, a lubricant, a coloring agent, a heat stabilizer, etc. can be further added to the polyvinyl alcohol resin A used in the present invention, if necessary. Other polymeric compounds can also be blended to the extent that the effects of the present invention are not inhibited.

[0011]

EXAMPLES The present invention will be explained in more detail with reference to Examples below, but the present invention is not limited to these Examples in any way. In addition, in the following, "part" and "%"
Unless otherwise specified, "parts by weight" and "parts by weight" respectively.
% by weight. In the following Examples and Comparative Examples, mechanical strength, shape retention, and disintegration were measured by the following methods. (1) Mechanical strength A sheet with a thickness of approximately 100 μm was created by melt press molding, conditioned for one week at a temperature of 20°C and a relative humidity of 65%, and using an autograph, the chuck interval was 50 mm,
The evaluation was made by measuring the tensile strength at a tensile speed of 500 mm/min. (2) Shape retention The Young's modulus of the sample whose mechanical strength was measured in (1) above was measured, and it was determined that the larger the Young's modulus, the better the shape retention. (3) A sheet with a thickness of about 500 μm was created by collapsible melt press molding, and was buried in outdoor soil at a depth of 1 m, and after 3 months was dug up and its shape was observed.

Example 1 Content of vinyl alcohol unit: 61 mol%, degree of polymerization: 34
A sample obtained by extruding 40 parts of a polyvinyl alcohol-based resin of No. 0 and 60 parts of commercially available talc (Matsumura Sangyo: High Filler #12), melt-kneading and molding at a temperature of 180°C was used, and the above items (mechanical strength, shape retention , disintegration) were evaluated. The composition is shown in Table 1, and the evaluation results are shown in Table 2. The mechanical strength, shape retention, and disintegration properties of the obtained sample were all good. Example 2 A molded article was created and evaluated in the same manner as in Example 1, except that the talc used in Example 1 was replaced with mica (produced in the People's Republic of China, average particle size 120 μm, aspect ratio 60). Ta. The composition is shown in Table 1, and the evaluation results are shown in Table 2. The mechanical strength, shape retention, and disintegration properties of the obtained sample were all good.

Example 3 A molded article was prepared and evaluated in the same manner as in Example 1, except that the weight mixing ratio of the polyvinyl alcohol resin and talc used in Example 1 was 20:80. . The composition is shown in Table 1, and the evaluation results are shown in Table 2. The mechanical strength, shape retention, and disintegration properties of the obtained sample were all good. Example 4 The polyvinyl alcohol resin used in Example 1 had a vinyl alcohol unit content of 45.3 mol% and a polymerization degree of 45.
A molded product was made and evaluated in the same manner as in Example 1, except that the sample was replaced with a 0. The composition is shown in Table 1, and the evaluation results are shown in Table 2. The mechanical strength, shape retention, and disintegration properties of the obtained sample were all good.

Comparative Example 1 A molded article was prepared in the same manner as in Example 1 using only the polyvinyl alcohol resin used in Example 1, and evaluated. The composition is shown in Table 1, and the evaluation results are shown in Table 2. The obtained molded product did not have good shape retention. Comparative Example 2 Example 1 except that the weight blending ratio of the polyvinyl alcohol resin and talc used in Example 1 was 95:5.
A molded article was prepared and evaluated in the same manner as described above. The composition is shown in Table 1, and the evaluation results are shown in Table 2. The obtained molded product did not have good shape retention.

Comparative Example 3 Same as Example 1 except that the weight mixing ratio of the polyvinyl alcohol resin and talc used in Example 1 was 1:99.
An attempt was made to create a molded product using the same method as above, but the moldability was poor and no molded product could be obtained. The composition is shown in Table 1, and the evaluation results are shown in Table 2. Comparative Example 4 Except that the content of vinyl alcohol units in the polyvinyl alcohol resin used in Example 1 was 98 mol%,
An attempt was made to create a molded article in the same manner as in Example 1, but the moldability was poor and no molded article could be obtained. The composition is shown in Table 1, and the evaluation results are shown in Table 2.

Comparative Example 5 The content of vinyl alcohol units in the polyvinyl alcohol resin used in Example 4 was 18 mol%.
A molded article was created in the same manner as in Example 1 and evaluated. The composition is shown in Table 1, and the evaluation results are shown in Table 2. The resulting molded product had poor disintegration properties. Comparative Example 6 A molded article was prepared and evaluated in the same manner as in Example 1, except that the degree of polymerization of the polyvinyl alcohol resin used in Example 1 was changed to 40. The composition is shown in Table 1, and the evaluation results are shown in Table 2. The obtained molded product did not have good shape retention.

Comparative Example 7 An attempt was made to create a molded product in the same manner as in Example 1 except that the degree of polymerization of the polyvinyl alcohol resin used in Example 1 was changed to 1700, but the moldability was poor and the molded product was not obtained. The composition is shown in Table 1, and the evaluation results are shown in Table 2.

[0018]

Effects of the Invention The collapsible molded product of the present invention has a characteristic that conventional molded products do not have, that is, it quickly disintegrates when it comes into contact with water. Therefore, it can be widely used as water-disintegrating sheets and water-disintegrating molded products (containers, trays, toys, etc.).

[Table 1]

[Table 2]

Claims (1)

[Claims] Claim 1: Content of vinyl alcohol units: 20~
80 mol%, water-soluble and heat-melting polyvinyl alcohol resin A with a viscosity average degree of polymerization of 100 to 1000, and an inorganic filler B, and the weight blending ratio of component A and component B is A:B = 50. :50 to 5:95.