JPH06344410A - Manufacture of polyvinyl alcohol resin molded product - Google Patents

Abstract

PURPOSE:To carry out a specific quantity-extrusion by a single screw extruder without causing thermal decomposition by a method wherein a polyvinyl alcohol resin having specific physical chemical properties independently or a mixed composition wherein a specific quantity of polyhydric alcohol is added thereto is melt extrusion molded in an anhydrous state. CONSTITUTION:Polyvinyl alcohol resin(PVA) of at least 95wt.%, within a range of 3.5 mesh on cut, and 3.5 to 50 mesh in particle size distribution and 10 deg. to 40 deg. of repose angle, 5.0 to 98.0mol% of saponification degree, and 100 to 600 of polimerization degree is melt extrusion molded in an anhydrous state, or a composition wherein 0.01 to 30 pts.wt. of polyhydric alcohol is mixed in 100 pts.wt. of PVA resin of at least 95wt.% within a range of 3.5 mesh on cut and 3.5 to 50 mesh of particle size distribution and 10 deg. to 40 deg. of repose angle, 5.0 to 98.0mol% of saponification degree, and 100 to 2000 of polymerization degree, is melt extrusion molded in an anhydrous state.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a polyvinyl alcohol resin having a specific particle size distribution and angle of repose (hereinafter referred to as PVA resin), which is quantitatively unmelted by a single-screw extruder without pelletizing. The present invention relates to a method for producing a PVA-based resin molded product which can be melt-extruded in a substantially anhydrous state without causing discoloration due to thermal decomposition.

[0002]

2. Description of the Related Art In general, melt extrusion molding of a PVA resin composition is carried out with a PVA resin alone because its thermal decomposition temperature is lower than its melting point unlike thermoplastic resins such as polyethylene, polypropylene and polyvinyl chloride. Was very difficult. Therefore, conventionally, the melt extrusion molding of the PVA-based resin has been performed by a molding method using water as a plasticizer.

In the conventional casting methods of PVA-based resins, which are casting methods and melt extrusion methods, since water is used as a plasticizer, drying and heat treatment after molding require complicated steps. And Further, in the case of the melt extrusion molding method, resin pelletization is required, and the temperature control in the extruder and the mold must be strictly controlled in order to prevent bubbles and unmelted substances contained in the molded product. As a method of performing melt extrusion molding of a PVA-based resin in an anhydrous state,
Japanese Patent Publication No. 42-26930, Japanese Patent Publication No. 44-28588, Japanese Patent Publication No. 53-24975
Japanese Patent Publication No. 56-49733 and Japanese Patent Publication No. 50-22049 have been proposed, but when melt extrusion molding is performed using a single screw extruder by these methods, the resin forms a bridge in the hopper. As a result, the resin is not smoothly supplied into the single-screw extruder. Therefore, it becomes difficult to quantitatively extrude the resin from the extruder and an unmelted product is generated in the melt-extruded product.

[0004]

Since the PVA resin has a lower thermal decomposition temperature than its melting point, a thermal decomposition product or coloration occurs in the melt extruded product, so that it is used as a general thermoplastic resin. Melt extrusion cannot be performed by the method described above. However, it is known that the flow initiation temperature can be lowered by adding a polyhydric alcohol to the PVA-based resin [Koichi Nagano, Saburo Yamane, Kentaro Toyoshima, Poval, Kobunshi Kobunkai 221-224 (1989)]. Therefore, as a result of diligent study focusing on this point, the present inventors have found that PVA
By adjusting the particle size distribution and angle of repose of the base resin, melt extrusion can be performed in a substantially anhydrous state without pelletizing without unmelting and without causing discoloration due to thermal decomposition without pelletizing. As a result, they have reached the present invention. Therefore, an object of the present invention is to melt-extrude a PVA-based resin in a substantially anhydrous state without pelletizing the PVA-based resin, and in particular, to obtain a PVA-based resin by a thermal decomposition without unmelted matter in a single screw extruder. An object of the present invention is to provide a method for producing a molded product which can be quantitatively extruded without causing discoloration.

[0005]

The inventors of the present invention focused on the relationship between the physical properties of PVA-based resins and the extrusion molding conditions in order to solve such problems, and as a result of continued investigations, the inventors established the optimum conditions. The present invention has been completed successfully, and its gist is (1) particle size distribution of 3.5 mesh on-cut, 3.5-
95% by weight or more in the range of 50 mesh, angle of repose 10-40 degrees,
Polyvinyl alcohol resin having a saponification degree of 5.0 to 98.0 mol% and a polymerization degree of 100 to 600, or (2) a particle size distribution of 3.5 mesh on-cut, 95 to 50% by weight or more in the range of 3.5 to 50 mesh, angle of repose. 10-40 degrees, saponification degree 5.0-
Melt extrusion of a composition containing 0.01 to 30 parts by weight of polyhydric alcohol to 100 parts by weight of polyvinyl alcohol resin having a polymerization degree of 98.0 mol% and a polymerization degree of 100 to 2000 in a substantially anhydrous state. A method for producing a polyvinyl alcohol-based resin molded article characterized by molding, in particular, the composition (2) is obtained by heating the temperature of the polyvinyl alcohol-based resin to 70 to 120 ° C. to impregnate the polyhydric alcohol with the polyhydric alcohol. It should be cooled to room temperature.

The present invention will be described in detail below. The PVA-based resin used in the present invention has a saponification degree of 5.0 to 98.0 mol% and a polymerization degree of 1 obtained by saponifying polyvinyl acetate.
It is in the range of 00 to 2000. When the saponification degree exceeds 98.0 mol%, the resin causes thermal decomposition during melt extrusion molding even when impregnated with a polyhydric alcohol. Saponification degree 5.0 mol%
If it is less than the above range, the properties of PVA are completely lost and it cannot be used. If the degree of polymerization is less than 100, the mechanical strength of the molded product after melt extrusion molding is low, and if the degree of polymerization exceeds 2000, melt extrusion molding does not occur even if impregnated with polyhydric alcohol without causing thermal decomposition of the resin. I can't do it.

The PVA resin supplied to the extruder has a particle size distribution of 3.5 mesh on cut, 3.5 to 50.
The mesh range is 95% by weight or more, and the angle of repose is 10
It is better to use one that is ~ 40 degrees. When the above particle size distribution of the resin is as small as less than 95% by weight, or when the angle of repose exceeds 40 degrees, the resin easily forms a bridge in the hopper of the extruder and the resin is smoothly supplied to the single-screw extruder. Since it is not carried out, it becomes difficult to extrude the resin in a fixed amount, and an unmelted product is produced in the melt extruded product. It is difficult to supply coarse particles of 3.5 mesh on to the extruder, and unmelted material is easily generated. P
Examples of the VA-based resin include, in addition to the above, polyvinyl alcohol derivatives obtained by phosphorylating, sulfating, or etherifying these polyvinyl alcohols, vinyl acetate monomers and aryl alcohols, acrylic acid, crotonic acid, maleic acid, itaconic acid, and the like. A modified polyvinyl alcohol obtained by saponifying a copolymer obtained by copolymerizing an unsaturated carboxylic acid can also be used.

Examples of the polyhydric alcohol used include those generally known as plasticizers for polyvinyl alcohol such as ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol and glycerin. The amount of polyhydric alcohol added varies depending on the degree of polymerization of the PVA resin. Degree of polymerization 100
-600, saponification degree 5.0-98 mol% PVA-based resin, if the water content is within the range inevitable in the production of PVA-based resin, it is necessary to add a polyhydric alcohol because water acts as a plasticizer. There is no. When polyhydric alcohol is added, 0.01 to 30 parts by weight to 100 parts by weight of PVA resin,
It is preferably 1.0 to 20 parts by weight. Especially the degree of polymerization is 600
If it exceeds, the flowability suitable for melt extrusion molding cannot be obtained unless a polyhydric alcohol is added. If the amount of the polyhydric alcohol added exceeds 30 parts by weight, the polyhydric alcohol bleeds from the molded product, which is not practical.

Further, if necessary, thermoplastic resins such as polyethylene and polypropylene, cellulose derivatives such as starch, carboxymethyl cellulose and hydroxyethyl cellulose, polysaccharides such as xanthan gum, carrageenan, chitin and chitosan, stearic acid, phosphate ester, Glycerin fatty acid ester, lubricant such as sorbitan acid fatty acid ester, talc, filler such as calcium carbonate, foaming agent, magnesium sulfate, zinc sulfate or copper sulfate, cobalt sulfate, acetic acid described in JP-B-35-1669 It is also possible to add a coloring inhibitor such as primary lead tin formate and manganese bromide, an organic or inorganic acid, various pigments such as titanium oxide and carbon black, or a reinforcing or coloring substance such as a dye.

Next, a method for producing a molded product will be described. P
When the VA resin is impregnated with the polyhydric alcohol, the temperature of the resin is set within a range of 70 to 120 ° C., preferably 80 to 110 ° C. in a heated mixer, and it is carried out for 30 minutes to 4 hours. Is desirable. If the temperature of the resin is less than 70 ° C, the impregnation of polyhydric alcohol cannot be carried out completely.
If the temperature exceeds 0 ° C, the resin melts and aggregates, which is not preferable. If it is less than 30 minutes, the impregnation of the polyhydric alcohol will be insufficient, and 4 hours or less will be sufficient for practical use. After impregnation, the impregnation mixture is cooled to room temperature for extrusion stabilization. If the polyhydric alcohol is not sufficiently impregnated, the resin becomes extremely sticky and the resins stick to each other, or the resin sticks to the inside of the hopper of the extruder to form a bridge and the resin is smoothly supplied to the single-screw extruder. Therefore, it becomes difficult to perform quantitative extrusion from the extruder. Here, impregnation means a state in which the polyhydric alcohol is incorporated into the gaps in the PVA-based resin particle structure, and the polyhydric alcohol does not cover even a part of the resin particle surface.

As the mixer used for this impregnation,
A Nauta mixer that does not apply shear stress for the purpose of preventing the resin from melting or agglomerating due to shear heat generation during mixing.
A ribbon blender or the like is suitable.
When performing melt extrusion, set the mold temperature at 120 to 200.
℃, it is desirable to set the cylinder temperature of the extruder to 120 ~ 200 ℃. If the mold temperature is less than 120 ° C, the fluidity of the resin will decrease, and if it exceeds 200 ° C, thermal decomposition of the resin will occur. If the cylinder temperature of the extruder is lower than 110 ° C, the resin is not sufficiently melt-kneaded, and if it exceeds 200 ° C, the resin is thermally decomposed, which is not preferable.
In the present invention, the substantially anhydrous state means that water is not added to the PVA-based resin composition after blending the polyhydric alcohol with the PVA-based resin. P obtained as described above
The VA-based resin composition remains in the form of particles, does not need to be pelletized, and is melt-extruded in a substantially anhydrous state using a single-screw extruder without causing quantitative thermal decomposition or discoloration. It can be carried out. Further, even if a multi-screw extruder is used, melt extrusion molding can be performed in the same manner as a single-screw extruder.

Next, as an example of a method for producing a PVA-based resin molded product, a single-screw extruder and a T-die extrusion molding method using a T-die as a mold will be described to form a sheet or film.
After cooling the above-mentioned polyhydric alcohol-impregnated resin composition particles, they are put into the hopper of a single-screw extruder and continuously supplied to the extruder at a cylinder temperature (C _{1 to} C ₄ ) of 120 to 200 ° C. Then, the mixture is melt-kneaded and discharged from a T-die (D _{1 to} D ₃ ) heated to 120 to 200 ° C. to form sheets or films of various thicknesses with the first roll. The PVA-based resin molded product according to the present invention can be applied not only to the T-die extrusion molding method but also to any conventionally known molding method such as an inflation molding method, an injection molding method or a blow molding method.

[0013]

[Action]

(1) According to the manufacturing method of the present invention, P having specific physical properties
The VA-based resin particles can be supplied to the extruder in a substantially anhydrous state, which eliminates the need for pelletizing the PVA-based resin. (2) Since it can be smoothly supplied into the extruder, it is possible to carry out quantitative extrusion even with a single-screw extruder, and it is possible to prevent the generation of unmelted matter. (3) Since melt extrusion molding can be performed without adding water, a drying step after molding is unnecessary, and the manufacturing process can be simplified.

[0014]

EXAMPLES The embodiments of the present invention will be specifically described below with reference to examples, but the present invention is not limited to these. (Example 1) Each PVA-based resin shown in Table 1 had L / D = 28,
Cylinder inner diameter 50mm using a full-flight screw with a compression ratio of 2.5 times is fed to a general-purpose single-screw extruder and melt-kneaded under the conditions shown in Table 2, and under the conditions shown in Table 1
-It was discharged from the die 2 to obtain a sheet and a film of PVA type resin. The fluctuation of the resin pressure during extrusion was less than 5 kg / cm ² , and the resin was quantitatively supplied and extruded. Further, in the obtained PVA-based resin sheet and film, thermal decomposition products, discoloration, unmelted products, etc. were not observed at all.

(Comparative Example 1) The PVA resin shown in Table 1 was
Using the same screw, extruder, and T-die as in Example 1, melt extrusion was performed under the conditions shown in Table 1. Sample number 1
In Nos. 3 to 3, the resin pressure during melt extrusion remarkably fluctuated, and quantitative extrusion was difficult. Further, a large number of unmelted substances were observed in the obtained PVA-based resin sheet and film. Sample No. 4 had a low mechanical strength after molding and could not be molded. Sample No. 5 could not be melt-extruded when the cylinder temperature of the extruder was lower than 215 ° C. On the other hand, when the temperature exceeds 215 ° C, many thermal decomposition products and discoloration were observed in the obtained sheet.

Example 2 Each sample shown in Table 2 consisting of a PVA resin and a polyhydric alcohol was put into a Nauta mixer. After charging, the mixture was stirred under the conditions shown in Table 2. After stirring, the mixture was cooled to room temperature to obtain a PVA-based resin molded product capable of melt extrusion molding in a substantially anhydrous state. In the obtained PVA-based resin molded product, no polyhydric alcohol unimpregnated product, adhesion of resins to each other, or melt agglomeration was not observed at all. The substantially anhydrous meltable PVA-based molded product obtained here was melt-extruded using the same screw, extruder and T-die as in Example 1 under the conditions shown in Table 2. The fluctuation of the resin pressure during extrusion was less than 5 kg / cm ² , and the resin was quantitatively supplied and extruded. Further, in the obtained PVA-based resin sheet and film, thermal decomposition products, discoloration, unmelted products, etc. were not observed at all.

(Comparative Example 2) Each sample shown in Table 3 consisting of a PVA resin and a polyhydric alcohol was put into a Nauta mixer. After the addition, the mixture was stirred under the conditions shown in Table 3. In Sample Nos. 1 and 2, unimpregnated products of polyhydric alcohol and adhesion of resins were observed. In Sample Nos. 3 and 4, the resin was melted and agglomerated. The PVA-based molded product obtained here was melt-extruded using the same screw, extruder, and T-die as in Example 1 under the conditions shown in Table 3. Sample Nos. 1 and 2 have resin sticking in the hopper and forming a tight bridge,
The resin pressure fluctuated drastically, and many unmelted materials were present in the obtained sheet. Sample Nos. 3 and 4 could not be melt-aggregated into the extruder. Therefore, a molded product could not be obtained.

In Sample Nos. 5 to 8, the resin pressure at the time of melt extrusion fluctuated remarkably, and quantitative extrusion was difficult. Also,
Many unmelted materials were found in the obtained sheets and films. Sample No. 9 has an extruder cylinder temperature of 220.
When the temperature was lower than ° C, melt extrusion could not be performed. On the other hand, when the temperature exceeds 220 ° C, many thermal decomposition products and discoloration were observed in the obtained sheet. Sample number 10
Similarly, when the cylinder temperature of the extruder was less than 215 ° C, melt extrusion molding could not be performed, and when it exceeded 215 ° C, many thermal decomposition products and discoloration were observed in the obtained sheet. In Sample Nos. 11, 12 and 13, many thermal decomposition products and discoloration were observed in the obtained film or sheet molded product.

[Note] The temperature measurement positions of the cylinder and the T-die of the single-screw extruder used in the examples and comparative examples of the present invention are as follows. Cylinder C ₁ : 31 cm from the center of the raw material supply port. C _2: the position of the compression unit -C ₁ 25 cm. C _3: Position of 50cm from the compression unit -C _1. C _4: position of 75cm from the metering section -C _1. Mold D ₁ : T-die left side 1/3 as seen from the extruder side,
20 cm from D ₂ . D _2: as viewed from the extruder side T- die center 1/3 position of 0cm from molten resin inlet. D _3: extruder viewed from side T- die right 1/3, D ₂ from 20
The position in cm.

[0020]

[Table 1]

[0021]

[Table 2]

[0022]

[Table 3]

[0023]

EFFECTS OF THE INVENTION According to the present invention, it is possible to quantitatively melt a PVA-based resin in a substantially anhydrous state without adding water to a PVA-based resin and in a substantially anhydrous state by using a single-screw extruder. Extrusion molding can be performed, and a PVA-based resin molded product having no bubbles, unmelted substances, discoloration due to thermal decomposition, etc. can be obtained. Therefore,
Since complex processes such as pelletizing process, drying process and heat treatment process can be omitted from the conventional manufacturing process, productivity is improved, and since melt extrusion molding is possible with a general-purpose single screw extruder, polyethylene, polypropylene It can also be manufactured on a manufacturing line for general-purpose thermoplastic resins such as polyvinyl chloride. In addition, coextrusion with a thermoplastic resin such as polyethylene or polypropylene or polymer blending is possible, and its industrial utility value is extremely high.

Claims (3)

[Claims] (1) Particle size distribution is 3.5 mesh on-cut, 95% by weight or more in the range of 3.5 to 50 mesh, angle of repose
10-40 degrees, saponification degree 5.0-98.0 mol%, degree of polymerization 100-6
Polyvinyl alcohol resin within the range of 00, or (2) 3.5 mesh on cut, 95% by weight or more in the range of 3.5 to 50 mesh, angle of repose 10 to 40 degrees, saponification degree 5.0 to 98.0 mol% , A composition comprising 0.01 to 30 parts by weight of a polyhydric alcohol with respect to 100 parts by weight of a polyvinyl alcohol resin having a polymerization degree of 100 to 2000 is melt-extruded in a substantially anhydrous state. A method for producing a polyvinyl alcohol-based resin molded article, comprising: 2. The polyvinyl composition according to claim 1, wherein the composition (2) comprises a polyvinyl alcohol resin heated to 70 to 120 ° C. for impregnation and then cooled to room temperature. Method for producing alcohol-based resin molded product. 3. A mold temperature of 120 as a melt extrusion molding condition.
The method for producing a polyvinyl alcohol-based resin molded product according to claim 1, wherein the method is carried out at a temperature of ˜200 ° C. and an extruder cylinder temperature of 120˜200 ° C. 3.