JPH0977947A - Film readily soluble in cold water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a film readily soluble in cold water and suitable for packaging an acidic or alkaline substance. SOLUTION: This film is composed mainly of a composition obtained by blending 1-100 pts.wt. water-soluble compound containing a sulfonic salt with 100 pts.wt. water-soluble modified polyvinyl alcohol comprising a saponified copolymer of 2-20mol% allyl ester and 98-80mol% vinyl ester.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film easily soluble in cold water. More specifically, it relates to a cold water easily soluble film for packaging acidic or alkaline substances.

[0002]

2. Description of the Related Art In recent years, cold water easily soluble films have been used for various packaging applications such as laundry detergents, insecticide / bactericides, bleaches, herbicides, fertilizers, etc. from the viewpoint of safety, hygiene and labor saving. .

When the cold-water-soluble film is used as a packaging material, the water-soluble film dissolves or disperses in water quickly during use, so that the handling becomes very simple. Since a polyvinyl alcohol (hereinafter abbreviated as PVA) film has excellent features that the film is tough and has good printability, the PVA film is conventionally well known as a water-soluble film. .

However, among the PVA-based films, the completely saponified PVA-based film is difficult to dissolve in cold water, so that the partially saponified PVA-based film is used for easy solubility in cold water. This partial saponification type P
When an acidic or alkaline substance is packaged with a film using VA, the partially saponified PVA is saponified by the acidic or alkaline substance and finally becomes a completely saponified PVA, which dissolves in cold water. There is a problem that it becomes difficult to do.

As a means for solving this problem, we previously proposed a cold water-soluble film composed of a saponified product of a copolymer of allyl ester and vinyl ester (Japanese Patent Laid-Open No. 62-179550).

[0006]

However, the water-soluble film of a cold water-soluble film composed of a saponified product of a copolymer of allyl ester and vinyl ester is considerably improved in water solubility. There was a problem that was not satisfied.

An object of the present invention is to provide an easily soluble cold water film for packaging acidic or alkaline substances which has excellent solubility even in cold water at 5 ° C. or lower.

[0008]

The PVA-based film of the present invention comprises a copolymer-modified polyvinyl alcohol obtained by saponifying a copolymer of 2 to 20 mol% of allyl ester and 98 to 80 mol% of vinyl ester in an amount of 65 mol% or more. And a composition in which 1 to 100 parts by weight of the water-soluble sulfonate-containing compound is mixed with 100 parts by weight of the polyvinyl alcohol as a main component.

Hereinafter, the present invention will be described in detail.

The water-soluble modified PVA used in the present invention comprises 2 to 20 mol% of allyl ester and 98 to 8 of vinyl ester.
It is obtained by saponifying 0 mol% of the copolymer. These manufacturing methods can be performed by known methods.

First, the copolymerization of allyl ester and vinyl ester can be obtained, for example, by copolymerizing allyl ester and vinyl ester in the presence of a polymerization catalyst using a lower alcohol such as methanol as a solvent. The proportion of allyl ester in the obtained copolymer is in the range of 2 to 20 mol%, preferably 5 to 15 mol%. When the allyl ester content is less than 2 mol%, the saponified product which is easily soluble in cold water may be inferior, or the solubility in cold water may be impaired by contact with an acidic or alkaline substance. On the other hand, when the amount of allyl ester exceeds 20 mol%, the strength of the film is lowered and it becomes unsuitable for packaging. The degree of polymerization of the copolymer is not particularly limited, but is preferably 400 or more.

Next, the saponification of the copolymer can be carried out by adding an acid or an alkali to the alcohol solution or the water-containing alcohol solution of the copolymer for saponification.
Examples of the alcohol used here include methanol and ethanol, but methanol is preferably used. As the saponification catalyst, an alkali catalyst such as sodium hydroxide or sodium methylate or an acid catalyst such as sulfuric acid or hydrochloric acid is used. The degree of saponification of the allyl ester component and vinyl ester component of the copolymer is not particularly limited as long as it becomes water-soluble, but preferably 65 mol% or more,
More preferably, it is desirable to increase it to 90 mol% or more. If the saponification degree of the copolymer is too low, the solubility in cold water is poor, or the saponification degree changes greatly due to contact with an acidic or alkaline substance, making it difficult to handle.

The modified PVA of the present invention can be obtained by heating and drying the saponified product of the copolymer obtained as described above according to a conventional method, and crushing it if necessary.

As the allyl ester in the present invention,
For example, allyl formate, allyl acetate, allyl butyrate, and the like, vinyl ester, vinyl formate, vinyl acetate, vinyl propionate, vinyl pivalate, and the like, among them, allyl acetate and vinyl acetate, among others. Industrially preferable. The allyl ester and vinyl ester may be used alone or in combination of two or more.

The copolymer of allyl ester and vinyl ester in the present invention is also a carboxylic acid group-containing unit such as crotonic acid, (meth) acrylic acid, maleic acid, itaconic acid, fumaric acid and their derivatives. Body, acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid, vinylsulfonic acid and sulfonic acid group-containing monomers such as alkali metal salts thereof, vinylpyrrolidone ring group-containing monomers such as vinylpyrrolidone, vinyl pivalate , Bar
Branched fatty acid vinyls such as vinyl succinate, ethylene,
The copolymerizable monomer such as α-olefins such as propylene, (meth) acrylic acid esters, acrylamides, alkyl vinyl ethers, allyl alcohol, vinyl chloride, styrene, etc. can be used as the effect of the present invention. Copolymers may be used as long as they are not impaired.

The water-soluble sulfonate-containing compound used in the present invention is a water-soluble compound containing an alkali metal salt of sulfonic acid in the molecule and may be a low molecular weight compound, a high molecular weight compound, or both. You may use together. For example, sulfonate-containing aliphatics such as allyl sulfonic acid soda and vinyl sulfonic acid soda, propylbenzene sulfonic acid soda
Sulfonate-containing aromatics such as sodium and isopropyl naphthalene sulfonate, polyethylene sulfonate
Examples thereof include, but are not limited to, sulfonic acid-containing polymers such as da, polyallyl sulfonic acid soda, and polystyrene sulfonic acid soda, and copolymers with other monomers.

The compounding amount of the sulfonate-containing compound is in the range of 1 to 100 parts by weight, preferably 5 to 80 parts by weight, based on 100 parts by weight of the modified PVA. If it is less than 1 part by weight, the effect of improving the cold water solubility cannot be sufficiently obtained. On the other hand, if the amount exceeds 100 parts by weight, the mechanical strength of the obtained film is lowered and it becomes unsuitable for packaging.

The cold water-soluble film of the present invention comprises 2 to 20 mol% of allyl ester and 9 vinyl ester as described above.
Water-soluble copolymer-modified PVA saponified with 8-80 mol% of the copolymer and 1-10 with respect to 100 parts by weight of the PVA.
It is obtained by using a composition containing 0 part by weight of a water-soluble sulfonate-containing compound as a film-forming substance.

The mechanism for improving the cold water solubility of the film of the present invention is to dissociate it in water by incorporating a sulfonate-containing compound having a very high degree of ionic dissociation into a nonionic copolymerization-modified PVA film. It is presumed that the repulsion between the ions inhibits the aggregation of PVA molecules, accelerates the swelling speed of the film, and increases the cold water dissolution speed of the film.

As the method for forming the film of the present invention, known methods such as a casting method and a melt extrusion method can be appropriately used. The thickness of the film is arbitrary, but is preferably 10 to 150 μm.

Further, in forming the film, known plasticizers such as polyvalent alcohols such as glycerin, diglycerin, polyethylene glycol and sorbitol may be added, if necessary, to impart flexibility to the film. Agents can also be added. Glycerin and diglycerin are preferred.

Further, the film of the present invention comprises PVA, starch, cellulose, aqueous emulsion / suspension, pigment such as clay and titanium oxide, defoaming agent, antiblocking agent, slip agent, etc. May be appropriately contained.

[0023]

EXAMPLES Next, the present invention will be described more specifically with reference to examples. In addition, "parts" and "%" in the examples mean "parts by weight" and "% by weight" unless otherwise specified.

Reference Example 1 (Synthesis of Copolymer Modified PVA) 1000 parts of vinyl acetate and 2 parts of allyl acetate were placed in a flask equipped with a stirrer, a thermometer, a dropping funnel and a reflux condenser.
After 5 parts were charged and the system was replaced with nitrogen, the internal temperature was adjusted to 60
The temperature was raised to ° C. A solution of 10 parts of 2,2-azobisisobutyronitrile dissolved in 300 parts of methanol was added to this system to initiate polymerization. After initiation of the polymerization, 225 parts of allyl acetate was added dropwise at a constant rate within 5 hours, and the polymerization was stopped within 6 hours. The solid content concentration in the system at the time of termination of the polymerization was 50%, and the polymerization yield was 62% based on all the monomers.
After the unreacted vinyl acetate and allyl acetate were removed under reduced pressure, a 45% methanol solution of the copolymer was obtained. It was confirmed by quantification of unreacted allyl acetate and vinyl acetate that the copolymer contained 85 mol% of vinyl acetate units and 15 mol% of allyl acetate.

While stirring 100 parts of a solution of this copolymer in methanol at 40 ° C., 15 parts of a solution of IN caustic soda in methanol was added thereto, mixed well, and then allowed to stand. . After 30 minutes, the solidified polymer was crushed by a crusher, washed with methanol and dried to obtain a polymer powder. The obtained powder was dissolved in water, and the viscosity was measured at 30 ° C., whereupon the solid content was 4% and it was 8 millipascal · sec. The saponification degree of this powder was 98 mol%.

Reference Example 2 (Synthesis of Copolymer Modified PVA) Using 1000 parts of vinyl acetate and 50 parts of allyl acetate,
After nitrogen substitution and temperature increase to 60 ° C. as in Reference Example 1, a solution of 5 parts of 2,2-azobisisobutyronitrile dissolved in 260 parts of methanol was added to the system to carry out polymerization. Started. The polymerization was stopped 5 hours after the initiation of the polymerization.
When the polymerization was stopped, the solid content concentration in the system was 60%, and the polymerization yield was 60% based on all the monomers. Then, unreacted allyl acetate and vinyl acetate were expelled in the same manner as in Reference Example 1 to obtain a 47% methanol solution of the copolymer. It was confirmed by the same quantitative method as in Reference Example 1 that the copolymer contained 6 mol% of allyl acetate units and 94 mol% of vinyl acetate units.

100 parts of a methanol solution of this copolymer was stirred at 40 ° C. and 13 parts of a 1N caustic soda methanol solution was added in the same manner as in Reference Example 1 to solidify the polymer. Was obtained, pulverized, washed and dried to obtain a polymer powder.
When this powder was dissolved in water and the viscosity was measured at 30 ° C., it was found to be 15 millipascal · s at a solid content concentration of 4%.
The saponification degree of this powder was 94 mol%.

Example 1 A mixture of the powder obtained in Reference Example 1 and soda allylsulfonate in a weight ratio of 100: 5 was dissolved in water to prepare a 10% aqueous solution.

This aqueous solution was cast on a polyester plate having a smooth surface and a horizontal surface using an applicator and dried at room temperature to obtain a transparent and uniform film. The thickness of the obtained film was 50 μm.

A bag having a size of 5 × 5 cm was made from the obtained film, and 29 g of laundry detergent (trade name “Zab” Kao) was put in the bag and heat-sealed. Also, a soot-sealed bag was prepared in the same manner for soda carbonate powder, ammonium sulfate powder or herbicide (trade name "Kitazine P" manufactured by Kumiai Chemical Co., Ltd.). This was left at room temperature for 1 year, 6 months, 1 year later, a 1 × 1 cm film was cut out and immersed in water at 5 ° C. to measure the time required until the film completely dissolved (time required for film dissolution). . Table 1 shows the results. As is clear from Table 1, all showed excellent cold water solubility with little change over time.

Example 2 The powder obtained in Reference Example 1 and polystyrene sulfonate
A mixture of da (trade name "Chemistat SA-9" manufactured by Sanyo Kasei Co., Ltd.) in a weight ratio of 100: 25 was dissolved in water to prepare a film similar to that in Example 1, and the same procedure as in Example 1 was performed to dissolve the film in water. Changes in sex over time were measured. Table 1 shows the results. As is clear from Table 1, all showed excellent cold water solubility with little change over time.

Example 3 The powder obtained in Reference Example 2 and polystyrene sulfonate
A mixture of da (trade name "Chemistat SA-9" manufactured by Sanyo Kasei Co., Ltd.) in a weight ratio of 100: 40 was dissolved in water to form a film similar to that in Example 1, and the same procedure as in Example 1 was performed to dissolve the film in water. Changes in sex over time were measured. Table 1 shows the results. As is clear from Table 1, all showed excellent cold water solubility with little change over time.

Comparative Example 1 A film was prepared in the same manner as in Example 1 except that only the powder obtained in Reference Example 1 was used, and the change with time in water solubility of the film due to the drug was measured. Table 1 shows the results. 5 ℃
The solubility in water was unsatisfactory.

Comparative Example 2 A film was prepared in the same manner as in Example 3 except that only the powder obtained in Reference Example 2 was used, and the daily change in water solubility of the film due to the drug was measured. Table 1 shows the results. 5 ℃
The solubility in water was unsatisfactory.

Comparative Example 3 A film was prepared in the same manner as in Example 1 except that PVA having a degree of polymerization of 1500 and a saponification degree of 88 mol% was used in place of the powder obtained in Reference Example 1, and the water content of the film was changed by a chemical agent. Changes in sex over time were measured. Table 1 shows the results. The water solubility decreased significantly with the number of days left.

Comparative Example 4 The powder obtained in Reference Example 2 and polystyrene sulfonate
A film was made in the same manner as in Example 1 except that a 100: 110 weight ratio mixture of das was used, and the resulting film was opaque and non-uniform, brittle and could be packaged with a drug. There wasn't.

[0037]

[Table 1]

[0038]

EFFECTS OF THE INVENTION As is apparent from the above description, the cold water-soluble film of the present invention shows little change with time in cold water of 5 ° C. or less even when used for packaging acidic substances or alkaline substances. It has excellent solubility.

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Claims (1)

[Claims] 1. A water-soluble modified polyvinyl alcohol obtained by saponifying a copolymer of 2 to 20 mol% of allyl ester and 98 to 80 mol% of vinyl ester, and 1 to 100 parts by weight based on 100 parts by weight of the polyvinyl alcohol. An easily soluble film in cold water, which comprises a composition containing the water-soluble sulfonate-containing compound as a main component.