JPH08258145A - Production of polyvinyl alcohol resin film - Google Patents

Abstract

PURPOSE: To easily, stably and inexpensively produce a PVA resin film free from coloration or blocking without requiring a drying process. CONSTITUTION: A water-containing polyvinyl alcohol resin prepared by compounding water with a polyvinyl alcohol resin so that an equilibrium moisture absorbing ratio under a 20 deg.C.65%RH condition becomes 50-100wt.% is used to be subjected to inflation molding at a die temp. of 180 deg.C or lower.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a polyvinyl alcohol resin film by inflation molding a polyvinyl alcohol resin.

[0002]

2. Description of the Related Art Polyvinyl alcohol (hereinafter abbreviated as PVA) water-soluble film is widely used for packaging detergents, agricultural chemicals, etc. It is produced by a casting method in which a flat film is formed from a solution obtained by heating and dissolving a resin and an additive such as a plasticizer in water. However,
In the production by this casting method, each step of melting, casting, and drying is required, the equipment becomes complicated, and more energy is required. Therefore, it cannot be said to be an inexpensive and advantageous production method.

On the other hand, an inflation method for forming a tubular film has been developed as a method for producing a PVA-based resin film, and as a packaging film or the like, a flat sheet produced by a casting method or the like is used. Compared to other films
Since the film produced by the inflation molding method has a tubular shape, the process of slitting and sealing can be omitted, so that the bag-making work can be simplified and the processing cost can be reduced. It is desired to establish a method for producing a film by inflation molding of a base resin. In this inflation molding method, melt extrusion molding in which a PVA-based resin is melted and extruded into a tubular shape from an annular die is generally used.
Since the PVA-based resin has a high melting temperature and the melting temperature is very close to the decomposition temperature, coloring occurs due to decomposition during molding, and it is difficult to obtain a practical film.

As a method for solving these problems, PV
A method of blending a large amount of water (20 to 50% by weight with respect to PVA) with an A resin to lower the melting temperature and performing inflation molding is disclosed in JP-B-36-15784. A method of blending a large amount of a plasticizer to lower the melting temperature and performing inflation molding is also known.

However, in the method in which a large amount of water is blended with the PVA resin, the obtained film also contains a large amount of water, and as it is, the surface of the film has high tackiness and is apt to cause blocking. However, it is necessary to post-dry the film in order to put it into a state in which it can be normally used, and the energy required for production becomes enormous. Further, even in the method of adding a large amount of plasticizer to the PVA-based resin, in order to obtain a melt viscosity that is required under normal molding conditions in a temperature range in which decomposition and coloring of the PVA-based resin does not occur, Usually, it is necessary to blend a larger amount of plasticizer than that required for plasticizing the PVA-based resin, and the resulting film absorbs water at high temperature and high humidity, and the tackiness of the surface of the molded product increases. However, there is a problem that the films are easily blocked with each other and the plasticizer bleeds onto the film surface.

[0006]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and makes it possible to easily and stably produce a PVA-based resin film free from coloring and blocking without a drying step. It is intended to provide a method for manufacturing.

[0007]

The method for producing a polyvinyl alcohol-based resin film according to the present invention uses water so that the polyvinyl alcohol-based resin has an equilibrium moisture absorption rate of 50 to 100% by weight at 20 ° C. and 65% RH. Inflation molding is performed at a die temperature of 180 ° C. or lower using a water-containing polyvinyl alcohol-based resin blended with.

The present invention will be specifically described below.
As the PVA resin used in the present invention, those having various degrees of polymerization and saponification can be used. From the viewpoint of mechanical properties and moldability of the film, those having a degree of polymerization of 300 to 2500 and a degree of saponification of 60 mol% or more are particularly preferable.

The PVA-based resin used in the present invention may contain a small amount of other components in the molecule to the extent that the effects of the present invention are not impaired. Examples of the method of introducing such other components include (meth) acrylic acid, maleic acid, maleic anhydride, fumaric acid, crotonic acid, itaconic acid, and other carboxylic acid-containing monomers or salts thereof, and acrylamide-2- Cationic properties such as vinyl sulfonic acid group-containing monomers such as methyl propane sulfonic acid sodium, allyl sulfonic acid sodium and vinyl sulfonic acid sodium, and quaternary ammonium salt-containing monomers such as (meth) acrylamido-propyl-trimethylammonium chloride Monomers, α-olefins such as ethylene and propylene, (meth) acrylic acid esters, acrylamide, dimethylacrylamide, N-methylolacrylamide, amide group-containing monomers such as N-vinyl-2-pyrrolidone, alkyl vinyl ethers, trimethoxy Silyl group such as vinylsilane Monomers, allyl alcohol, dimethyl allyl alcohol, isopropenyl alcohol and other hydroxyl group containing monomers, allyl acetate, dimethyl allyl acetate, isopropenyl allyl acetate and other acetyl group containing monomers, vinyl chloride, vinylidene chloride, etc. There is a method of saponifying a copolymer of vinyl acetate and one or more of the halogen-containing monomer of (1) and aromatic monomer such as styrene.

The amount of water contained in the PVA resin is 50 to 100 which is the equilibrium moisture absorption of the PVA resin at 20 ° C. and 65% RH.
It is in the range of% by weight. If the amount of water is less than 50% by weight of the equilibrium moisture absorption rate at 20 ° C. and 65% RH, the melting temperature becomes high, and the PVA-based resin is decomposed and colored during molding.
On the other hand, when the amount of water is 20 ° C and the equilibrium moisture absorption rate of 65% RH is 10
If the content is more than 0% by weight, foaming may occur at the time of molding and the film may break, a large amount of air bubbles may be contained in the film, or a large amount of water may remain in the obtained film, resulting in fusion due to blocking during winding. Occurs, and it becomes difficult to open it in a tubular shape.

As a method of adjusting the amount of water in the PVA-based resin, it is desirable to add water to the PVA-based resin powder or the like or dry it so as to be within the scope of the present invention.
At that time, it is preferable to sufficiently impregnate the PVA-based resin with water.

In the present invention, a plasticizer may be added in order to further improve the fluidity of the PVA type resin during molding. P
Examples of the plasticizer for VA resin include glycerin, diglycerin, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, sorbitol, polyethylene glycol, trimethylolethane, trimethylolpropane, pentaerythritol,
Examples thereof include polyhydric alcohols such as 2,3-butanediol, 1,3-butanediol and mannitol, amides such as dimethylacetamide, amines such as triethanolamine, and sulfoxides such as dimethylsulfoxide. The blending amount of the plasticizer is preferably 30 parts by weight or less based on 100 parts by weight of the PVA resin. When the amount is more than 30 parts by weight, the obtained film has high tackiness, is easily blocked, and has a problem that the plasticizer bleeds to the surface.

The compounding method of the above-mentioned plasticizer is not particularly limited, but the plasticizer may be mixed in advance with the hydrous PVA resin before molding, or the plasticizer may be absorbed.
The resin and the plasticizer may be separately charged and mixed in a molding machine to be molded.

The PVA-based resin film obtained in the present invention has no risk of blocking, but when a high degree of blocking resistance is required, a slip agent and an antiblocking agent may be further added. By blending these, it is possible to remarkably improve the disadvantage of the PVA-based resin film that blocking is likely to occur under high temperature and high humidity.

The slip agent is blended in order to impart slipperiness to the film obtained by forming irregularities on the film surface, and examples thereof include calcium carbonate, alumina, apulgite, kaolin clay, silicon dioxide, calcium silicate, magnesium oxide. , Calcium carbonate, magnesium carbonate,
Examples thereof include barite, calcium sulfate, titanium dioxide, clay, talc, bentonite, wood flour and starch.
The amount of the slip agent blended is preferably 5 parts by weight or less with respect to 100 parts by weight of the PVA-based resin.

An antiblocking agent is added to prevent adhesion of the film surface after molding and facilitate opening.
What is generally commercially available may be used. For example, hydrocarbons having 12 to 30 carbon atoms, higher fatty acids, oxyfatty acids, fatty acid amides, alkylenebis fatty acid amides, fatty acid polyhydric alcohol esters, fatty acid polyglycol esters, fatty acid fatty alcohol esters, fatty acid glycerin esters, aliphatic alcohols, Metal soap etc. are mentioned. Specific examples are paraffin wax, low-polymerization degree polyethylene, stearic acid, mystic acid, arachidic acid, behenic acid, stearylamide, palmitylamide, oleylamide, methylenebisstearamide, ethylenebisstearamide, butyl. Stearate, hydrogenated castor oil, ethylene glycol monostearate, stearic acid monoglyceride, oleic acid monoglyceride,
Stearyl alcohol, cetyl alcohol, lead stearate, cadmium stearate, barium stearate, calcium stearate, magnesium stearate and the like can be mentioned. The amount of anti-blocking agent added is P
2 parts by weight or less is desirable for 100 parts by weight of the VA resin.

In the present invention, not only the PVA resin alone but also a water-soluble or water-dispersible resin such as polyacrylic acid or a salt thereof, cellulose such as polyacrylamide, hydroxypropylcellulose, hydroxypropylmethylcellulose and methylcellulose is mixed. It is also possible to use a mixture of other thermoplastic resin such as polyolefin such as polyethylene and polypropylene, nylon, polyester, polyvinyl chloride, polystyrene, polyvinyl butyral or ethylene-vinyl acetate copolymer and its saponified product. It is possible.

As an extrusion film-forming machine for the inflation molding of the present invention, a molten resin is continuously extruded into a tube shape from an annular die, and cold air is blown to the outside of the tube to cool and solidify it. An ordinary extrusion film-forming machine for thermoplastic resin, such as blowing a gas from the center of the die to expand the tube diameter and drawing it at a high speed to form a film, can be used, but the temperature of the die is 180 It is an essential condition that the temperature is not higher than ° C. When the temperature of the die is higher than 180 ° C., there are problems that foaming occurs due to boiling of water and the PVA-based resin is thermally decomposed and colored. The temperature of the cylinder part is not particularly limited, but it is preferably adjusted to a temperature 10 to 40 ° C. higher than that of the die part.

The thickness of the film is not particularly limited, but a film having a thickness of 5 to 200 μm is usually preferred. Further, the obtained film can be subjected to plasma treatment.

The film obtained in the present invention utilizes the water solubility of the PVA-based resin to make a detergent, an insecticide, a bleach, a detergent,
As a packaging material for agricultural chemicals, bath salts, toiletry products, etc.
It is also preferably used as a packaging material for laundry bags and gardening seeds.

[0021]

EXAMPLES The present invention will now be described in more detail with reference to examples. Each physical property in the examples is measured by the methods described below. 1. Saponification degree, viscosity average degree of polymerization Measured according to JIS K6726. 2. Equilibrium Moisture Absorption Rate The polyvinyl alcohol resin powder was left in an atmosphere of 20 ° C. and 65% RH for 7 days, and the weight (W ₁ ) was measured. Next, it is dried at 105 ° C. for 3 hours, the weight (W ₂ ) is measured,
The equilibrium moisture absorption rate was calculated according to the following formula. Equilibrium moisture absorption rate (wt%) = _{[(W 1 -W 2) / W} 1 ] × 1
00

3. Coloring The obtained film (50 μm) was visually evaluated. Evaluation Criteria ○: No coloration (colorless and transparent) Δ: Slightly coloration (pale yellow) ×: Significant coloration (yellow) 4. Blocking It was evaluated whether the obtained folded tubular film could be opened with a finger. Evaluation criteria ○: The mouth of the tube can be opened by sliding it with a finger. X: The mouth of the tube cannot be opened by sliding it with a finger.

5. Foaming The frequency of foaming due to boiling of water generated during molding was evaluated. Evaluation criteria ○: No foaming at all △: Occasionally present ×: Existent quite frequently 6. Comprehensive Evaluation The obtained films were comprehensively evaluated. Evaluation criteria ○: Good ×: There is a problem

Example 1 (Preparation of water-containing PVA resin) PVA powder (saponification degree: 88 mo
The water content was 3.0% by weight when the water content was 1%, the viscosity average degree of polymerization was 1000, the average moisture absorption was 9.0% by weight at 20 ° C. and 65% RH. After mixing 1000 g of PVA powder and 66 g of water in a sealed bag, the mixture was left for 4 hours to absorb water, and the equilibrium moisture absorption rate at 20 ° C. and 65% RH was 10%.
A PVA containing 0 wt% water was prepared.

(Production Method of Film) The above-mentioned water-containing polyvinyl alcohol resin was used as an inflation film-forming machine (LCD-50C) manufactured by Placo Co., Ltd. to control the temperature of the cylinder part to 190 ° C. and the temperature of the die part to 155 ° C. Melt extrusion molding, draw ratio MD (take-over direction ratio) 5 times, T
D (blow ratio) is stretched to 3 times and the thickness is 50
A film of μm was obtained. In the melt extrusion molding, molten resin is extruded into a tube shape from an annular die, solidified by blowing cold air from the outside of the tube, while blowing gas from the center of the annular die into the tube to expand the tube diameter. The drawing was carried out at a high speed, and the draw ratio at this time was as follows: the slit diameter of the annular die was 1, the extrusion speed (linear velocity) of the molten resin was v ₁ , the expansion tube diameter was L,
When the take-up speed is v ₂ , the take-up direction magnification is v ₂ /
v ₁ and blow ratio were determined as L / l. The results of evaluating the obtained film are shown in Table 1. A good film could be obtained without coloring, blocking, or foaming.

Example 2 The same PVA as in Example 1 was added with water to obtain a water content of 60% of the equilibrium moisture absorption of the PVA at 20 ° C. and 65% RH.
Using the raw material adjusted to the weight%, the die temperature is 165 ° C.
A film was obtained under the same conditions as in Example 1 except that
Table 1 shows the evaluation results. A good film could be obtained without coloring, blocking, or foaming.

Example 3 The same PVA as in Example 1 was added with water to obtain a water content of 80% of the equilibrium moisture absorption of the PVA at 20 ° C. and 65% RH.
Using the raw material adjusted to the weight%, the die temperature is 165 ° C.
A film was obtained under the same conditions as in Example 1 except that
Table 1 shows the evaluation results. A good film could be obtained without coloring, blocking, or foaming.

Example 4 PVA (saponification degree 70 mol%, viscosity average degree of polymerization 2400,
Using 20% and 65% RH, the average moisture absorption rate of 10.0% by weight) was used to determine the water content of the PVA by the same method as in Example 1.
A film was obtained under the same conditions as in Example 1 except that the raw material adjusted to an equilibrium moisture absorption rate of 0 ° C. and 65% RH was adjusted to 60% by weight and the die temperature was changed to 170 ° C. Table 1 shows the evaluation results. A good film could be obtained without coloring, blocking, or foaming.

Example 5 PVA (saponification degree 70 mol%, viscosity average degree of polymerization 2400,
In the same manner as in Example 1, using 20 ° C. and 65% RH with an average moisture absorption rate of 11.0% by weight, the water content of the PVA was adjusted to 2%.
A film was obtained under the same conditions as in Example 1 except that the raw material adjusted to 100% by weight of the equilibrium moisture absorption rate at 0 ° C. and 65% RH was used and the die temperature was set to 160 ° C. Table 1 shows the evaluation results. A good film could be obtained without coloring, blocking, or foaming.

Example 6 PVA (saponification degree 98 mol%, viscosity average degree of polymerization 500, 2
The average moisture absorption rate at 0 ° C. and 65% RH was 11.0% by weight), and the water content of the PVA was 20% in the same manner as in Example 1.
A film was obtained under the same conditions as in Example 1 except that the raw material adjusted to 60% by weight of the equilibrium moisture absorption rate at 65 ° C and 65% RH was used and the die temperature was set to 160 ° C. The evaluation results are shown in Table 1.
Shown in A good film could be obtained without coloring, blocking, or foaming.

Example 7 PVA (saponification degree 98 mol%, viscosity average degree of polymerization 500, 2
The average moisture absorption rate at 0 ° C. and 65% RH was 8.0% by weight), and the moisture content of the PVA was 20% in the same manner as in Example 1.
A film was obtained under the same conditions as in Example 1 except that the raw material adjusted to 100% by weight of equilibrium moisture absorption at 65 ° C. and 65% RH was used and the die temperature was changed to 150 ° C. Table 1 shows the evaluation results. A good film could be obtained without coloring, blocking, or foaming.

Example 8 15 parts by weight of glycerin (plasticizer) and 3 parts of corn starch (slip agent) were added to the same PVA resin as in Example 1.
Parts by weight, 0.2 parts by weight of Chemistat 1300 (antiblocking agent) manufactured by Sanyo Kasei Co., Ltd. was used as the raw material.
A film was obtained under the same conditions as in Example 1 except that the die temperature was 145 ° C. Table 1 shows the evaluation results. A good film could be obtained without coloring, blocking, or foaming.

Comparative Example 1 Using the same PVA as in Example 1, using a raw material whose moisture content was adjusted to 20 ° C. and 40% by weight of equilibrium moisture absorption of 65% RH, the die temperature was set to 200 ° C. A film was obtained under the same conditions as in Example 1 except for the above. Table 1 shows the evaluation results. Moisture bubbling occurred and the resulting film became quite colored.

Comparative Example 2 Using the same PVA as in Example 1, using a raw material in which the moisture content was adjusted to 20 ° C. and 230% by weight of the equilibrium moisture absorption of 65% RH, the die temperature was set to 110 ° C. A film was obtained under the same conditions as in Example 1 except for the above. Table 1 shows the evaluation results. Moisture bubbling occurred and the resulting film blocked.

Comparative Example 3 Using the same PVA as in Example 4, using a raw material whose moisture content was adjusted to 20 ° C. and 40 wt% of the equilibrium moisture absorption of 65% RH, the die temperature was set to 210 ° C. A film was obtained under the same conditions as in Example 1 except for the above. Table 1 shows the evaluation results. Moisture bubbling occurred and the resulting film became quite colored.

Comparative Example 4 Using the same PVA as in Example 4, using a raw material whose moisture content was adjusted to 20 ° C. and 230 wt% of the equilibrium moisture absorption rate of 65% RH, the die temperature was set to 130 ° C. A film was obtained under the same conditions as in Example 1 except for the above. Table 1 shows the evaluation results. Moisture bubbling occurred and the resulting film blocked.

Comparative Example 5 Using the same PVA as in Example 7, using a raw material in which the moisture content was adjusted to 20 ° C. and 40 wt% of the equilibrium moisture absorption rate of 65% RH, the die temperature was set to 195 ° C. A film was obtained under the same conditions as in Example 1 except for the above. Table 1 shows the evaluation results. Moisture bubbling occurred and the resulting film became quite colored.

Comparative Example 6 Using the same PVA as in Example 7, using a raw material in which the moisture content was adjusted to 20 ° C. and 230 wt% of the equilibrium moisture absorption rate of 65% RH, the die temperature was set to 100 ° C. A film was obtained under the same conditions as in Example 1 except for the above. Table 1 shows the evaluation results. Moisture bubbling occurred and the resulting film blocked.

Comparative Example 7 A film was prepared under the same conditions as in Example 1 except that the raw material prepared by using the same PVA as in Example 1 and having the same moisture content as in Example 1 was used and the die temperature was 190 ° C. Got Table 1 shows the evaluation results. Bubbling of water has occurred.

[0040]

[Table 1]

[0041]

As is apparent from the above description, according to the invention, an inflation-molded film of PVA resin can be stably and easily manufactured at low cost.

Claims (1)

[Claims] 1. A polyvinyl alcohol resin at 20 ° C.
Inflation molding at a die temperature of 180 ° C. or lower using a water-containing polyvinyl alcohol-based resin mixed with water so that the equilibrium moisture absorption at 65% RH becomes 50 to 100% by weight. Manufacturing method.