JPH09272719A - Hot-melt polyvinyl alcohol resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a hot-melt resin composition which shows excellent heat stability during melt molding and can give a molding having good toughness and water solubility and markedly reduced plasticizer migration by mixing a polyvinyl alcohol with a polyhydric alcohol/alkylene oxide adduct. SOLUTION: This composition is prepared by mixing 100 pts.wt. polyvinyl alcohol having a degree of polymerization of above 500 to 5,000 with 3 to below 20 pts.wt. compound (which serves as a plasticizer) prepared by the addition reaction of 1mol of an at least trihydric alcohol with 2-4mol of an alkylene oxide. The polyvinyl alcohol used is a common PVA, i.e., a saponificate of a polyvinyl acetate, desirably a saponificate of a copolymer of a vinyl acetate with at least one monomer selected among α-olefins, ω-hydroxy-α-olefins, long- chain vinyl ethers, unsaturated polyoxyalkylene compounds, etc.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a hot-melt resin composition using a polyvinyl alcohol resin. More specifically, the present invention relates to a heat-meltable resin composition having excellent thermal stability during melt molding, good toughness and water solubility of the obtained molding, and very little plasticizer migration.

[0002]

2. Description of the Related Art Polyvinyl alcohol (hereinafter abbreviated as PVA) resin has a thermal melting start temperature and a thermal decomposition temperature that are very close to each other, and it is practically impossible to continuously mold at a high temperature. there were. In order to operate continuously for a long time under appropriate molding conditions, the degree of polymerization and saponification of PVA should be greatly reduced.
Furthermore, it was necessary to thoroughly remove metal salts such as sodium acetate contained in PVA. Even if it could be molded in this way, if it was continuously operated for a long time, the viscosity increased and the torque increased, and gel was generated, so that a good molded product could not be obtained. Also for the obtained molded product,
Since PVA having a low degree of polymerization and a low degree of saponification is used, there is a drawback that only a molded product lacking mechanical strength, toughness and flexibility can be obtained.

As a method of compensating for these drawbacks, a method of adding a plasticizer such as glycerin or polyethylene glycol, a method of using a modified PVA obtained by copolymerizing various unsaturated compounds with vinyl acetate, a method of preventing thermal decomposition Methods for adding agents and the like are being studied. Glycerin, polyethylene glycol, polypropylene glycol, polyglycerin, mannitol, sorbitol, pentaerythritol, etc. are commonly used as plasticizers for lowering the melting point and melting viscosity of PVA. Of these, glycerin is the most used. Has been done. But,
Glycerin has a large effect of lowering the melting point and melt viscosity,
When pelletizing or melt-molding is performed at a molding temperature of 190 ° C. or higher, the pellets are decomposed and evaporated, and escape to the outside of the system, so pellets of constant quality cannot be obtained. In addition, there is also a problem that migration in the molded product is large, migration occurs to the surface of the molded product, causing blocking, and the molded product becomes partially hard and brittle, and strength and toughness at low temperatures are greatly reduced. ing.
Polyethylene glycol and polypropylene glycol have relatively low evaporation at high temperatures and migration in molded products, but have poor performance as a plasticizer for PVA, and are very often used in order to obtain appropriate melt molding conditions. Since the addition amount is required, the physical properties of the molded product are adversely affected. This tendency also applies to polyglycerin, mannitol, sorbitol, pentaerythritol and the like. A plasticizer that is solid at room temperature, such as sorbitol, has a problem that a white powder is deposited when it migrates to the surface of a molded product. Further, the modified PVA with improved heat melting property can be molded even at high temperature, but without plasticizer, increase in torque due to thickening and generation of gel are unavoidable, and substantially long-time melt molding is not possible. Met. It has been proposed to add phosphoric acid, a phosphate, a radical scavenger, a hydrophobic compound such as wax, etc., as a PVA thermal decomposition inhibitor, but these also do not function as complete decomposition inhibitors.
It could not be operated under stable conditions for a long time.

[0004]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above-mentioned drawbacks and to provide excellent thermal stability during melt molding.
An object of the present invention is to provide a heat-fusible resin composition in which the obtained molded product has good toughness and water solubility and has very little plasticizer migration.

[0005]

[Means for Solving the Problems] The present inventors have made earnest studies in view of the present situation, and as a result, the degree of polymerization exceeds 500 and 50
100 parts by weight of PVA (00 or less) and 3 parts by weight or more and less than 20 parts by weight of a compound (B) obtained by addition reaction of 2 to 4 moles of alkylene oxide to 1 mole of polyhydric alcohol having 3 or more valences. The inventors have found a PVA-based hot-melt resin composition and completed the present invention. When the composition of the present invention is melt-molded, the plasticizer does not decompose by heat, does not evaporate, and does not thicken with time even after continuous molding for a long time.
A molded product free of gel and fish eyes is obtained. The plasticizer (corresponding to the compound (B)) used in the present invention is PVA.
Since it has an excellent plasticizing property against, it is possible to lower the molding temperature in order to lower the melting point of PVA and also lower the melt viscosity of PVA. When this plasticizer is used, PVA with a high degree of saponification that could not be conventionally melt-molded.
However, melt molding becomes possible.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The composition for use in the present invention comprises, in addition to ordinary PVA which is a saponified product of polyvinyl acetate, α-
A modified PVA obtained by copolymerizing an olefin, an ω-hydroxy-α-olefin, a long-chain vinyl ether, a polyoxyalkylene group-containing unsaturated compound, a saturated branched fatty acid vinyl or an unsaturated sulfonate with vinyl acetate and saponifying is also preferable. Although it depends on the modification ratio, good melt molding is possible even with PVA having a saponification degree of 90 mol% or more. Further, the obtained molded product also has a high mechanical strength and impact strength. The molded product obtained from the composition of the present invention gives a uniform molded product without migration of the plasticizer to the surface, blocking and partial decrease in toughness. This property imparts a particularly great feature to thin films and sheets obtained by melt molding. The molded product obtained from the composition of the present invention can be easily dissolved or dispersed in water when immersed in water or washed with water, and the initial shape of the molded product can be lost. Therefore, this molded product is also useful for applications such as a water-soluble film and a core which is removed by dissolving with water after molding.

The compound (B) obtained by addition reaction of 2 to 4 mol of alkylene oxide with respect to 1 mol of polyhydric alcohol having 3 or more valences used in the present invention is a liquid at ordinary temperature, and is a non-modified PVA or modified PVA. On the other hand, it has excellent compatibility and plasticization performance, and has little migration to the surface of the molded product,
Little bleed-out and blocking. Further, this compound (B) gives excellent performance without impeding the water solubility of the obtained molded product.

Hereinafter, the present invention will be described in more detail. As PVA (A) used in the present invention, various P
VA is available. A polymer obtained by polymerizing or copolymerizing a vinyl ester according to a conventional method, and then saponifying. Examples thereof include the following. Saponified polymer of vinyl ester homopolymer, or vinyl ester and α-
One or more copolymers selected from olefins, ω-hydroxy-α-olefins, long-chain vinyl ethers, polyoxyalkylene group-containing unsaturated compounds, saturated branched fatty acid vinyls and unsaturated sulfonates. It is a compound. Here, the vinyl ester includes vinyl acetate, vinyl propionate, vinyl formate, vinyl versatate, vinyl pivalate, and the like. Vinyl acetate that is industrially produced and has a cost advantage is usually used.

Examples of α-olefins include α-olefins having 2 to 30 carbon atoms such as ethylene, propylene, butene, hexene, octene and decene. When the copolymer unit is ethylene, the α-olefin content is 2 to 20 mol%, preferably 4 to 15 mol%.
If the content is less than 2 mol%, the effect of copolymerization is low, and
If it exceeds mol%, the compound (B) used in the present invention
And the water solubility and water dispersibility of the molded product are markedly deteriorated. Further, when the copolymer unit is an α-olefin having 3 to 30 carbon atoms, the content of the α-olefin is appropriately 0.5 to 10 mol%. When the content is less than 0.5 mol%, the effect of copolymerization is low, and when it exceeds 10 mol%, the degree of polymerization of the obtained modified PVA is low, and the strength and toughness of the molded product are small. Water solubility and water dispersibility are significantly deteriorated.

The ω-hydroxy-α-olefin is an α-olefin having a hydroxyl group at the terminal of the molecule, such as 4-hydroxy-1-butene and 5-hydroxy-1.
-Pentene, 6-hydroxy-1-hexene, 7-hydroxy-1-octene and the like are compounds having a hydroxyl group at the molecular end of an α-olefin having 4 to 20 carbon atoms. Of these, 7-hydroxy-1-octene is preferable. The content of ω-hydroxy-α-olefin is 0.5 to 10 mol%. If the content is less than 0.5 mol%, the effect of copolymerization is low, and if it exceeds 10 mol%, the degree of polymerization of the modified PVA obtained is low and the strength and toughness of the molded product are small. PVA is particularly useful because it has excellent thermal stability and is excellent in water solubility and water dispersibility even when the degree of modification is high.

The long-chain vinyl ether has 4 to 4 carbon atoms.
12 alkyl vinyl ether. The content of vinyl ether is 0.5 to 10 mol%. Content is 0.5
If the modified PVA content is less than mol%, the effect of copolymerization is low and 1
Modified PVA exceeding 0 mol% cannot be used because it is substantially difficult to synthesize.

The polyoxyalkylene group-containing unsaturated compound is a polyalkylene (meth) allyl ether such as polyoxyethylene (meth) allyl ether or polyoxypropylene (meth) allyl ether. The repeating unit of the polyoxyalkylene moiety is 3 to 50, preferably 5 to 20. The content of the polyoxyalkylene group-containing unsaturated compound is 0.5 to 10 mol%, preferably 0.1.
It is 5 to 5 mol%. PVA containing a polyoxyalkylene group can be obtained by copolymerizing the above-mentioned unsaturated compound and vinyl acetate, or by polymodifying the polyvinyl acetate obtained by polymerizing vinyl acetate to obtain a polyoxyalkylene group. Incorporated into PVA can also be used.

The saturated branched fatty acid vinyl is a saturated branched fatty acid vinyl having 6 to 16 carbon atoms such as vinyl versatate. It is necessary that the saturated branched fatty acid vinyl is not hydrolyzed during the saponification reaction after being copolymerized with vinyl acetate. Content of saturated branched fatty acid vinyl is 0.5 to 10
Mol%.

The unsaturated sulfonates include acrylamido-2-methylpropanesulfonic acid alkali metal salts, acrylamido-1-methylpropanesulfonic acid alkali metal salts, and methacrylamide-2-methylpropanesulfonic acid alkali metal salts. In addition, metal salts of olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid and methallyl sulfonic acid. Among them,
An alkali metal salt of acrylamido-2-methylpropanesulfonic acid is preferable from the viewpoint of copolymerization reactivity with vinyl ester and stability during saponification. The content of unsaturated sulfonate is 0.2 to 20 mol%, preferably 0.1.
5 to 10 mol%. PVA (A) in the present invention
Is a saponified product of polyvinyl ester or a copolymer of vinyl acetate and one or more monomers selected from the above-mentioned copolymer units, and these are contained alone or in combination of several types. You can do it.

The degree of polymerization of PVA (A) is particularly important in the case of a molded product, and in the case of a molded product, mechanical strength, toughness, flexibility and the like are required, and the viscosity average polymerization degree ( Hereinafter, abbreviated as "degree of polymerization" is an essential condition of more than 500 and 5000 or less. If the degree of polymerization is 500 or less, the strength of the molded product and the impact strength at low temperature are too small to use. In particular, in the case of a film, a sheet, a bottle or the like including a thin portion, PVA having a low degree of polymerization has a problem in strength. The degree of polymerization is more than 500 and 5000 or less, preferably 5
It is 50 to 2000. The degree of polymerization is greater than 5000 P
VA is not preferable because the melt viscosity becomes high and there is a problem in workability. The degree of saponification of PVA (A) is not particularly limited as long as it can be melted by heat, and it can be used in a wide range. The degree of saponification also has a strong influence on the strength and toughness of the molded product. Considering strength, toughness, stiffness, etc., it is usually 40 to 100 mol%, preferably 60 to 100 mol%. In particular, in the PVA obtained by copolymerizing the above-mentioned copolymerized units, the degree of saponification of the vinyl acetate portion is 80 to 100 mol%, more preferably 90 to 100 mol%.

Examples of the trihydric or higher polyhydric alcohol used in the present invention include glycerin, trimethylolpropane,
Included are diglycerin, pentaerythritol, xylose, arabinose, ribulose and sorbitol. Glycerin, pentaerythritol and sorbitol are preferred. The compound (B) of the present invention is obtained by adding 2 to 4 mol of alkylene oxide to 1 mol of the polyhydric alcohol. Here, the alkylene oxide is ethylene oxide or propylene oxide, preferably ethylene oxide. Depending on the case, a mixed addition reaction of ethylene oxide and propylene oxide may be carried out. The number of moles of alkylene oxide added is preferably 2 to 3. When the average number of moles of alkylene oxide added is 1 mol or less, the thermal stability during melt molding is insufficient and the migration of the plasticizer in the obtained molded product is problematic, which is not preferable. Further, if the average number of added moles exceeds 4 moles, the compatibility with PVA deteriorates and the plasticizing performance also deteriorates, which is not preferable. The number of added moles in the present invention is an average number of added moles, and the distribution may match the number of added moles. However, if the number of moles added is 5 or more,
It is not preferable to mix 0 wt% or more.

The compounding amount of the compound (B) with respect to PVA (A) is 3 parts by weight or more and less than 20 parts by weight, preferably 5 to 15 parts by weight, based on 100 parts by weight of PVA (A). If the compounding amount of the compound (B) is less than 3 parts by weight, the thermal stability at the time of molding is insufficient, there is a problem in stable operability for a long time, the strength and toughness of the molded product are insufficient, and the impact resistance at low temperature is low. It is too weak to use. Further, when the compounding amount of the compound (B) is 20 parts by weight or more, the strength of the molded product is deteriorated, the hardness, the stiffness and the morphological stability are lacking, and further problems such as blocking properties occur, which are not preferable.

In the composition of the present invention, the compound (B)
In addition to the above, it is also possible to mix and use those generally used as a plasticizer for PVA (A) within a range that does not impair the characteristics of the present invention. As these plasticizers, polyhydric alcohols such as glycerin, diglycerin and diethylene glycol, polyethers such as polyethylene glycol and polypropylene glycol,
This includes phenol derivatives such as bisphenol A and bisphenol S, amide compounds such as N-methylpyrrolidone, and water. To prepare a composition comprising the PVA (A) and the compound (B) of the present invention, PVA is prepared in advance.
After blending (A) and compound (B), they may be melt-kneaded and pelletized, or they may be pelletized by separately kneading them in a melt-kneading machine at a fixed ratio. The melt molding method using the composition of the present invention is not particularly limited, and T
Any molding method such as a die extrusion method, an inflation molding method, a direct blow molding method, an extrusion molding method such as a hollow molding method, an injection molding method, and a pressure molding method is possible. It may be co-extruded with another resin, or may be laminated by melt extrusion on another material such as paper or film. The composition comprising the PVA (A) and the compound (B) of the present invention is not only molded by itself but also blended or laminated with other general-purpose resins such as polyethylene, polypropylene, ABS resin and polystyrene. You can The molded product thus obtained can impart hydrophilicity to the hydrophobic resin and improve wettability with water. Further, after molding, the PVA resin portion is dissolved and removed with water to form a hollow molded product or a porous molded product. The thing is obtained. The composition of the present invention, if necessary, a filler, a colorant, fibers such as glass fiber and carbon fiber, a fragrance, a foaming agent, a bulking agent, a lubricant, a peeling agent, an ordinary additive such as an ultraviolet absorber. It may be blended appropriately.
Inorganic powder can be added as a filler as a morphological stability, blocking prevention, and hardness imparting agent. For example, talc, calcium carbonate, clay, mica, titanium oxide and the like, and the average particle diameter is preferably 0.2 to 10 μm.
The addition amount of these is 0 to 100 parts by weight with respect to 100 parts by weight of PVA (A).

[0019]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the present invention is limited thereto. Unless otherwise specified, “%” and “parts” in the examples are on a weight basis. [Plasticizer Transferability Measuring Method] The film was made into a 10 × 10 cm bag with a heat sealer, 15 g of diatomaceous earth was packaged and heat sealed. Double-wrap the bag with an aluminum / polyethylene laminate film bag to prevent water and plasticizer from scattering to the outside.
It was left in a constant temperature bath at ℃. After standing for 2 weeks, the amount of plasticizer (corresponding to the compound (B)) of the packaged film was measured. To measure the amount of plasticizer, the film sample was dried in a vacuum dryer at 50 ° C. for 5 hours to remove the water content, and Soxhlet extraction was performed with methanol to measure the amount of plasticizer in the film from the change in weight. A value obtained by dividing the amount of the plasticizer after the standing test by the amount of the plasticizer before the test was shown as "%" as the residual ratio of the plasticizer. [Measuring method of impact strength of film] 40% R film
After conditioning the humidity in an atmosphere of H for 1 week, the impact strength of the film was measured at a temperature of 5 ° C. using a film impact tester.

Example 1 Partially saponified PVA having a degree of polymerization of 750 and a degree of saponification of 80 mol%
100 parts of the powder and 10 parts of a compound obtained by adding 2 mol of ethylene oxide to 1 mol of glycerin were mixed with a planetary mixer, and then pelletized. Pelletizing conditions Toyo Seiki Co., Ltd. Labo Plastomill Biaxial 20 mmφ L / D = 28 Rotational speed 100 rpm Motor 200V Rated 20A Then, pellets were supplied to an extruder equipped with a T die to form a film. Molding conditions Toyo Seiki Co., Ltd. Labo Plastomill Single shaft 25mmφ L / D = 28 Rotation speed 20rpm T die effective width 300mm Lip clearance 0.2mm Motor 200V Rated 20A Pelletization, film forming temperature is 200 ° C
Then, the discharge rate at the time of molding was 1.5 kg / h and the take-up speed was adjusted to form a film having a thickness of 40 μm. Film formation was carried out continuously for 24 hours, and the torque at the start of formation and after 24 hours, and the number of spots in the film (size: 10 × 10 cm) were measured. The results are shown in Table 1. The amount of plasticizer (corresponding to compound (B)) in the obtained film and its migration property were measured by the above method. Also, the impact strength of the film at 5 ° C. for which the migration property was measured was measured. Table 2 shows the results. Even after continuous film formation for 24 hours, the increase in torque was small, and the occurrence of spots was small. The migration of the plasticizer in the film was also small, and the film showed tough physical properties.

Comparative Example 1 Except that the compound (B) of Example 1 was replaced with glycerin,
Pelletization and film molding were performed in the same manner as in Example 1. The results are shown in Tables 1 and 2. During molding, remarkable white smoke was observed and glycerin was scattered. In the molding after 24 hours, an increase in torque and generation of spots were observed.
The obtained film had rough skin, bleeding of the plasticizer on the film surface was large, and blocking property was large. In addition, the plasticizer migration was large, and the film showed poor toughness.

Comparative Example 2 Pelletization and film forming were carried out in the same manner as in Example 1 except that the compound (B) of Example 1 was not added at all. The results are shown in Tables 1 and 2. In the continuous operation of film formation, the rated torque value was exceeded after 20 hours, so the operation was stopped. The film had a large amount of lumps and was poor in toughness.

Comparative Example 3 Ethylene and vinyl acetate were copolymerized and saponified by a conventional method to obtain a polymer having an ethylene unit content of 8 mol%, a vinyl acetate component saponification degree of 98 mol% and a polymerization degree of 1450. 100 parts of this modified PVA containing ethylene units and 12 parts of a compound obtained by adding 1 mol of ethylene oxide to 1 mol of sorbitol were mixed in a planetary mixer, and then pelletized and film-formed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 2 Copolymerization of 7-hydroxy-1-octene and vinyl acetate and saponification by a conventional method, the content of 7-hydroxy-1-octene units was 4.5 mol%, and the degree of saponification of vinyl acetate component. A polymer with 98 mol% and a degree of polymerization of 580 was obtained. This modified PVA100 containing 7-hydroxy-1-octene group
And 10 parts of a compound obtained by adding 2 mol of ethylene oxide to 1 mol of sorbitol were mixed in a planetary mixer, and then pelletized and film-formed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Comparative Example 4 The compound (B) of Example 2 was treated with polyethylene glycol # 4.
Pelletization and film-forming were carried out in the same manner as in Example 2 except that the value of 00 was changed. The results are shown in Tables 1 and 2. It was a film with low impact strength because continuous operation after 24 hours was quite difficult.

Comparative Example 5 Pelletization and film forming were carried out in the same manner as in Example 2 except that the compound (B) in Example 2 was replaced with sorbitol. The results are shown in Tables 1 and 2. The film after the migration test was hard and white powder was deposited on the surface.

Example 3 Copolymerization of octyl vinyl ether and vinyl acetate and saponification by a conventional method, the content of the octyl vinyl ether unit was 2 mol%, the saponification degree of the vinyl acetate component was 94 mol%,
A polymer having a degree of polymerization of 650 was obtained. 100 parts of this modified PVA containing an octyl vinyl ether group and 8 parts of a compound obtained by adding 3 mol of ethylene oxide to 1 mol of pentaerythritol were mixed in a planetary mixer, and then pelletized and film-formed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 4 Polyoxyethylene allyl ether having a condensation degree of ethylene oxide of 10 and vinyl acetate were copolymerized and saponified by a conventional method to give a polyoxyethylene allyl ether unit content of 1.8 mol% and a vinyl acetate component. A polymer having a saponification degree of 95 mol% and a polymerization degree of 550 was obtained. 100 parts of this modified PVA containing a polyoxyethylene allyl ether group and 10 parts of a compound obtained by adding 2 mol of ethylene oxide to 1 mol of sorbitol were mixed in a planetary mixer, and then pelletized and film-formed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

Example 5 Vinyl versatate, acrylamido-2-sodium methylpropanesulfonate and vinyl acetate were terpolymerized and saponified by a conventional method to obtain a vinyl versatate unit content of 3 mol%, acrylamide-2-. A polymer having a sodium methylpropanesulfonate unit content of 1 mol%, a vinyl acetate component saponification degree of 90 mol%, and a polymerization degree of 700 was obtained. 100 parts of this modified PVA containing versatic acid vinyl group and sodium sulfonate group and glycerin 1
2 moles of ethylene oxide and 1 mole of propylene oxide
After mixing 15 parts of the compound to which a mole had been added with a planetary mixer, pelletization and film formation were performed in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0030]

[Table 1]

[0031]

[Table 2]

[0032]

EFFECT OF THE INVENTION The hot-melt resin composition of the present invention is excellent in heat stability during melt molding, has good toughness and water solubility of the obtained molding, and has very little plasticizer migration. .

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display area C08F 220: 58)

Claims (2)

[Claims] 1. A polyvinyl alcohol (A) having a degree of polymerization of more than 500 and not more than 5000 and 100 parts by weight of polyvinyl alcohol (A) and 2 to 4 alkylene oxides per 1 mol of a polyhydric alcohol having 3 or more valences.
A polyvinyl alcohol-based heat-meltable resin composition comprising 3 parts by weight or more and less than 20 parts by weight of a compound (B) which has undergone a mole addition reaction. 2. Polyvinyl alcohol is a saponified product of polyvinyl acetate, or α-olefin, ω-hydroxy-α-olefin, long-chain vinyl ether, polyoxyalkylene group-containing unsaturated compound, saturated branched fatty acid vinyl and unsaturated sulfone. The heat-meltable resin composition according to claim 1, which is a saponified product of a copolymer of vinyl acetate and one or more monomers selected from acid salts.