JP2000178396A - Melt-moldable polyvinyl alcohol resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyvinyl alcohol resin composition suppressed in thermal deterioration such as decomposition or gelation and having stabilized PVA melt moldability and giving a molding excellent in impact resistance and shape stability. SOLUTION: This composition comprises (A) a polyvinyl alcohol having a degree of polymerization of 200-1,200, a degree of saponification of 75-99.99 mol%, a melting point of 160-230 deg.C, and having a total content of terminal carboxyl groups and terminal lactone rings of 0.008-0.15 mol% and (B) an alkali metal salt in such amounts that 0.003-1 pt.wt. alkali metal of component B is present per 100 pts.wt. component A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyvinyl alcohol resin composition for melt molding comprising polyvinyl alcohol (hereinafter abbreviated as "PVA") and an alkali metal salt.

[0002]

2. Description of the Related Art PVA is a typical water-soluble resin, and its dissolution rate varies depending on the degree of saponification, but has the property of dissolving in water to lose its shape. Also, PVA is known to be excellent in mechanical strength and a material superior to other resins, and is widely used in fiber sizing agents, films, coating agents for paper, and the like. . Further P
VA is a biodegradable resin, and PV dissolved in water
A does not pollute the environment. By the way, PV
When melt-molding A, thermal stability at a high temperature is very important. Factors that affect thermal stability include the degree of polymerization, degree of saponification, terminal carboxyl group and terminal lactone ring, and the content of alkali metal salts.These factors are complicatedly entangled, resulting in crosslinking gelation and decomposition. Thermal degradation such as coloring occurs. For the terminal carboxyl group and the terminal lactone ring, a chain transfer reaction to the vinyl ester monomer and the alkyl group of the polymer occurs during polymerization,
Then, after a saponification reaction, a carboxyl group is formed at the terminal, and when a part of the carboxyl group is condensed with a hydroxyl group, a lactone ring is formed. For alkali metal salts,
Since the hydroxide is often used as a catalyst for the saponification reaction, in that case, some alkali metals remain as salts in PVA even after washing. However, with respect to these factors, the mechanism by which thermal deterioration is progressing has not been clearly elucidated, and the content thereof has not been controlled.

[0003]

DISCLOSURE OF THE INVENTION The present invention is intended to suppress thermal degradation such as decomposition or gelation and to provide a terminal carboxyl group, a terminal lactone ring, a melting point and an alkali metal salt so that PVA has stable melt moldability. It is an object to limit the content and to supply a molded article having excellent impact resistance and morphological stability by using such PVA.

[0004]

According to the present invention, the degree of polymerization is from 200 to 1200, the degree of saponification is from 75 to 99.99 mol%, the melting point is from 160 to 230 ° C, and the total amount of terminal carboxyl groups and terminal lactone rings is 0.008-0.1
5 mol% of polyvinyl alcohol (A) and alkali metal salt (B), and the blending ratio of alkali metal in component (B) to component (A) is 0.003 to 100 parts by weight.
1 part by weight of a polyvinyl alcohol-based resin composition for melt molding is provided.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. In the composition of the present invention, a heat-meltable PVA-based resin is used as the component (A), which is obtained by saponifying a vinyl ester polymer. Examples of the vinyl ester include vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like. Vinyl acetate, which is industrially produced and is advantageous in cost, is preferable.

The degree of polymerization of the PVA of the present invention is from 200 to 120.
0, preferably from 240 to 1000,
-800 are more preferable, and 300-600 are particularly preferable. A polymer having a degree of polymerization of less than 200 is not practical because the resulting molded product has low mechanical strength and low-temperature impact strength and is easily broken. On the other hand, when the degree of polymerization exceeds 1200, the melt viscosity increases, and the processability deteriorates. The degree of saponification of the PVA of the present invention is 75 to 99.99.
Mol%, preferably 80 to 99.5 mol%,
-99 mol% is more preferable, and 90-98.5 mol% is particularly preferable. If the degree of saponification is less than 75 mol%, the resulting molded article has poor mechanical strength and morphological stability. In addition, thermal stability during melt molding is poor, and decomposition, gelation, and coloring are increased. The PVA of the present invention has a melting point of 160 to 230.
° C, preferably 170-227 ° C, and 175-22
4 ° C is more preferable, and 180 to 220 ° C is particularly preferable. If the melting point is lower than 160 ° C., the crystallinity of PVA is reduced, and a satisfactory molded product cannot be obtained. The melting point is 230 ° C
If the temperature exceeds the above range, the melting temperature becomes high, and it becomes impossible to produce a molded product stably. The melting point of PVA was measured using DSC at 250 ° C. in nitrogen at a rate of 10 ° C./min, cooled to room temperature, and again at 250 ° C. in a nitrogen at a rate of 10 ° C./min.
It means the temperature at the peak top of the endothermic peak indicating the melting point of PVA when the temperature is raised to ° C.

In the present invention, the total amount of terminal carboxyl groups and terminal lactone rings of PVA is 0.008 to 0.1.
5 mol%, preferably 0.01 to 0.145 mol%, more preferably 0.012 to 0.14 mol%, and 0.1 to 0.14 mol%.
014-0.13 mol% is particularly preferred. The carboxyl group of the present invention includes an alkali metal salt thereof, and examples of the alkali metal include potassium and sodium. P
The terminal carboxyl group and the terminal lactone ring of VA are in the range of 0.
If the amount is less than 008 mol%, the gelation of the polymer at the time of melt molding is large, so that the melt moldability is reduced and at the same time the solubility of the molded product in an aqueous solution is reduced. When the terminal carboxyl group and the lactone ring of PVA are more than 0.15 mol%, thermal stability at the time of polymer melt molding is poor, and decomposition,
Great gelling and coloring. The content of the terminal carboxyl group and the terminal lactone ring of the PVA of the present invention was determined by the following measurement. After saponification to a degree of saponification of 99.9 mol% or more, the PVA was thoroughly washed with methanol, and then dried at 90 ° C. under reduced pressure for 2 days to obtain methanol-d ₄ / D ₂ O = 8 /
2 was dissolved in 500 MHz 1H-NMR (JEO
(LGX-5000) apparatus. The methylene-derived peak of the carboxyl group or an alkali metal salt thereof is 2.19 ppm and 2.30 ppm, the methylene-derived peak of the lactone ring is 2.60 ppm, and the methine-derived peak of the vinyl alcohol unit is 3.5 to 4.15.
The content of carboxyl groups and lactone rings was calculated.

[0008] In the composition of the present invention, component (A) 100
The mixing ratio of the alkali metal in the component (B) with respect to parts by weight is 0.003 to 1 part by weight, preferably 0.005 to 0.8 part by weight, more preferably 0.007 to 0.6 part by weight, 0.01 to 0.5 part by weight is particularly preferred. Examples of the alkali metal include potassium and sodium,
They are mainly present as salts of lower fatty acids such as acetic acid and propionic acid, salts of terminal carboxyl groups of PVA, and salts of carboxyl groups and sulfonic acid groups contained in copolymer monomers. The mixing ratio of alkali metal is 0.0
If the amount is less than 03 parts by weight, gelation during polymer melt molding is large, and melt moldability is reduced, and at the same time, solubility of the molded product in an aqueous solution is reduced. When the mixing ratio of the alkali metal is more than 1 part by weight, the thermal stability at the time of polymer melt molding is poor, and decomposition, gelation, and polymer coloring are large. The compounding amount of the alkali metal was measured by an atomic absorption spectrophotometer, and the measurement sample used was one obtained by ashing a sample and dissolving it in an acid.

The PVA used in the present invention preferably contains an α-olefin unit, which has 4 or less carbon atoms, such as ethylene, propylene, 1-butene, isobutene, and 1-hexene. However, ethylene is more preferable in consideration of water resistance and hygroscopicity. α
-The content of the olefin unit is 0.1 to 20 mol%, and when the content is 20 mol% or more, the solubility of the modified PVA in water decreases.

In addition, as long as the effect of the present invention is not impaired, the PVA of the present invention may contain a vinyl alcohol unit,
It may contain a vinyl ester unit and a monomer unit other than α-olefins. Examples of such a unit include unsaturated acids such as acrylic acid, methacrylic acid, crotonic acid, (anhydride) phthalic acid, (anhydride) maleic acid, (anhydride) itaconic acid, or salts thereof, or alkyl esters having 1 to 18 carbon atoms. , Acrylamide, N having 1 to 18 carbon atoms
Acrylamides such as -alkylacrylamide, N, N-dimethylacrylamide, 2-acrylamidopropanesulfonic acid or a salt thereof, acrylamidopropyldimethylamine or an acid salt thereof or a quaternary salt thereof, methacrylamide, N- having 1 to 18 carbon atoms; Methacrylamides such as alkyl methacrylamide, N, N-dimethylmethacrylamide, 2-methacrylamidopropanesulfonic acid or a salt thereof, methacrylamidopropyldimethylamine or an acid salt thereof or a quaternary salt thereof, N-vinylpyrrolidone, N- N-vinylamides such as vinylformamide and N-vinylacetamide, vinyl cyanides such as acrylonitrile and methacrylonitrile, methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl Ether, i-propyl vinyl ether, vinyl ethers such as n-butyl vinyl ether, allyl acetate, propyl allyl ether,
Allyl ethers such as butyl allyl ether and hexyl allyl ether; vinyl halides such as vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, and vinyl bromide; vinylsilanes such as trimethoxyvinylsilane; and oxyalkylene groups. Monomer, isopropenyl acetate, 3-buten-1-ol, 4-pentene-
1-ol, 5-hexen-1-ol, 7-octen-1-ol, 9-decen-1-ol, 3-methyl-
Having a carboxyl group derived from hydroxy group-containing α-olefins such as 3-buten-1-ol, fumaric acid, maleic acid, itaconic acid, maleic anhydride, phthalic anhydride, trimellitic anhydride or itaconic acid; Monomer, monomer having a sulfonic acid group derived from ethylene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, etc., vinyloxyethyltrimethylammonium chloride, vinyloxybutyl Trimethylammonium chloride, vinyloxyethyldimethylamine, vinyloxymethyldiethylamine, N-acrylamidomethyltrimethylammonium chloride, N-acrylamidoethyltrimethylammonium chloride, N-acrylamidodimethylamine, allyl Ammonium chloride, methallyl trimethylammonium chloride, dimethyl allyl amine include monomers having a cationic group derived from the Ariruechiru like. Among these monomers, from the viewpoint of availability, copolymerizability and melt moldability, methyl vinyl ether, ethyl vinyl ether,
vinyl ethers such as n-propyl vinyl ether, i-propyl vinyl ether, n-butyl vinyl ether,
Allyl ethers such as allyl acetate, propyl allyl ether, butyl allyl ether, hexyl allyl ether, monomers having an oxyalkylene group, 3-buten-1-ol, 4-penten-1-ol, 5-hexene-1 Monomers derived from hydroxy group-containing α-olefins such as -ol, 7-octen-1-ol, 9-decene-1-ol, and 3-methyl-3-buten-1-ol are preferred. The content of these monomers is usually 20
Mol% or less, preferably 10 mol% or less. However, for a monomer containing an alkali metal such as a carboxylate or a sulfonate, it is necessary to limit the amount of modification so that the amount of the alkali metal falls within the scope of the claims.

Examples of the polymerization method of the vinyl ester polymer include known methods such as bulk polymerization, solution polymerization, suspension polymerization, and emulsion polymerization. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without a solvent or in a solvent such as an alcohol is usually employed. Examples of the alcohol used as a solvent during the solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol, and propyl alcohol. As the initiator used for the polymerization,
For example, α, α′-azobisisobutyronitrile, 2,2
Known initiators such as azo initiators such as 2'-azobis (2,4-dimethylvaleronitrile, benzoyl peroxide, and n-propyl peroxycarbonate, and peroxide initiators. Although there is no particular limitation, a range of −30 to 150 ° C. is appropriate.

The vinyl ester polymer is saponified by a known method. For example, it is saponified while being dissolved in alcohol. Examples of the alcohol used for the saponification reaction include lower alcohols such as methyl alcohol and ethyl alcohol, and methyl alcohol is particularly preferably used. Alcohol used in the saponification reaction includes
If it is 40% by weight or less, it may contain a solvent such as acetone, methyl acetate, ethyl acetate, and benzene. As a catalyst used for the saponification reaction, an alkali metal hydroxide such as potassium hydroxide or sodium hydroxide, an alkali catalyst such as sodium methylate, or an acid catalyst such as a mineral acid is used. The temperature of the saponification reaction is not particularly limited, but is preferably in the range of 20 to 60 ° C. When a gel-like product precipitates as the saponification reaction proceeds, the PVA polymer of the present invention is obtained by pulverizing the product at that time, washing and drying.

The PVA-based resin composition of the present invention may contain a filler, a plasticizer, another plastic resin, a fragrance, a coloring agent, a foaming agent, and a filler, as long as the object of the present invention is not impaired. Normally used for odorants, extenders, lubricants, release agents, ultraviolet absorbers, antioxidants, processing stabilizers, weathering stabilizers, antistatic agents, flame retardants, release agents, reinforcing materials, fungicides, preservatives, etc. Can be appropriately compounded. The filler is used to further increase the hardness and rigidity, give a sense of weight, adjust the speed of water disintegration and biodegradability, express anti-blocking properties, and provide printability. it can. As the filler, talc, clay, calcium carbonate, silica, mica, alumina, titanium oxide,
Examples include inorganic fillers such as zirconium oxide, boron nitride, and aluminum nitride, and organic fillers such as urea-formalin-based resin and melamine-formalin-based resin. The amount of the filler is not particularly limited, but is preferably 0 to 300 parts by weight, more preferably 0 to 100 parts by weight, based on 100 parts by weight of the PVA-based resin. The plasticizer has the effect of lowering the melting point, improving moldability, and imparting flexibility and toughness to the molded product. The plasticizer is not particularly limited, and those generally used as PVA plasticizers can be used. As this plasticizer,
Polyglycols such as glycerin, diglycerin and diethylene glycol, polyethers such as polyethylene glycol and polypropylene glycol, sorbitol and compounds obtained by adding ethylene oxide to a polyhydric alcohol such as glycerin, sugars, polyethers, bisphenol A, Phenol derivatives such as bisphenol S, other amide compounds such as N-methylpyrrolidone,
Compounds in which about 2 to 4 moles of an alkylene oxide are added to 1 mole of a trihydric or higher polyhydric alcohol, and water, etc. The amount of the plasticizer is not particularly limited, but is preferably 0 to 100 parts by weight, more preferably 1 to 20 parts by weight, based on 100 parts by weight of the PVA-based resin. Further, as the other thermoplastic resin, for example, polyethylene,
General-purpose resins such as polypropylene, ABS resin, and polystyrene are exemplified.

The method for preparing the PVA-based resin composition of the present invention is not particularly limited, and a filler, a plasticizer, an additive, and the like may be simply added to the PVA-based resin. You may. Alternatively, the melt kneader may be kneaded and pelletized while separately charging a PVA-based resin, a filler, a plasticizer, an additive, and the like at a fixed ratio.

The method of melt-molding using the resin composition of the present invention includes a compression molding method, a transfer molding method, a reinforced plastic molding method, an injection molding method, an extrusion molding method, an extrusion film forming method from a T-die, inflation. Film forming method, hollow molding method, blow molding method, calender molding method, foam molding method,
Vacuum forming method and compressed air forming method are mentioned. If desired, another thermoplastic resin may be laminated. As the other thermoplastic resin, the same components as those exemplified above can be exemplified as desired components of the resin composition of the present invention.

[0016]

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 degree of polymerization and the degree of saponification are determined according to JIS.
It was measured by K6726.

Example 1 Polymerization degree 400, saponification degree 97.8 mol%, melting point 218
C., the sodium content (refers to the content based on 100 parts by weight of PVA; the same applies to the following examples).
Pellets were produced by extruding 2 parts by weight of PVA powder having a total amount of terminal carboxyl groups and terminal lactone rings of 0.07 mol% under the following conditions. (Pelletizing conditions) Extruder: Labo Plastomill manufactured by Toyo Seiki Co., Ltd. Screw: Two axes in the same direction, 25 mmφ, L / D = 26 Screw rotation speed: 60 rpm Set temperature (cylinder part): 225 ° C. Set temperature (die part) ): 130 ° C. Discharge rate: 3.2 kg / h These pellets were injection-molded at 225 ° C., and the obtained molded product was evaluated by the following method. Table 2 shows the results. [Moldability] ○: Molded without any problem △: Moldable but problematic in irregular shape, plasticization instability, etc. ×: Not moldable [Heat stability] Heat treated pellets at 220 ° C under nitrogen atmosphere Then, a part of the solution was cooled to room temperature every hour, and the time until gelation occurred was measured by examining whether or not it was dissolved in DMSO. [Flexural modulus] Measured according to JIS K7203.

Examples 2 to 16 Pellets obtained by injection molding in the same manner as in Example 1 except that PVA shown in Table 1 was used. Table 2 shows the evaluation results of the molded articles.

Example 17 After 100 parts of PVA shown in Table 1 were mixed with 20 parts of talc, pelletization and injection molding were performed under the same conditions as in Example 1. Table 2 shows the evaluation results of the molded articles.

Example 18 After 100 parts of PVA shown in Table 1 was mixed with 10 parts of glycerin, pelletization and injection molding were performed under the same conditions as in Example 1. Table 2 shows the evaluation results of the molded articles.

Example 19 After 100 parts of PVA shown in Table 1 was mixed with 10 parts of water, pelletization and injection molding were performed under the same conditions as in Example 1. Table 2 shows the evaluation results of the molded articles.

Comparative Examples 1 to 7 Pellets obtained in the same manner as in Example 1 except that PVA shown in Table 1 was used were injection-molded. Table 2 shows the evaluation results of the molded articles.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

According to the present invention, the degree of polymerization of PVA, the degree of saponification,
By limiting the melting point, the content of the terminal carboxyl group and the terminal lactone ring, and the content of the alkali metal salt, it is possible to suppress thermal decomposition, gelation, and the like during melt molding. Moreover, by using such PVA, a molded article having excellent impact resistance and morphological stability can be stably manufactured.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Toshiyuki Akazawa 1621 Sazu, Kurashiki City, Okayama Prefecture Kuraray Co., Ltd. F-term (reference) 4J002 AA052 BE021 BE031 EG026

Claims (4)

[Claims] 1. A polymerization degree of 200 to 1200 and a saponification degree of 75.
Polyvinyl alcohol (A) and alkali metal salt (B) having a melting point of 160 to 230 ° C. and a total amount of terminal carboxyl groups and terminal lactone rings of 0.008 to 0.15 mol%. Consisting of
(A) A polyvinyl alcohol-based resin composition for melt molding, wherein the mixing ratio of the alkali metal in the component (B) to 100 parts by weight is 0.003 to 1 part by weight. 2. The polyvinyl alcohol resin composition for melt molding according to claim 1, wherein the polyvinyl alcohol (A) is a polyvinyl alcohol containing 0.1 to 20 mol% of α-olefin units having 4 or less carbon atoms. 3. The polyvinyl alcohol resin composition for melt molding according to claim 2, wherein the α-olefin unit having 4 or less carbon atoms is an ethylene unit. 4. A molded article comprising the polyvinyl alcohol-based resin composition according to claim 1.