JPH1060207A - Water-soluble film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject film suitable for a packaging material, etc., slight in change of physical properties to temperature/humidity, capable of suppressing greasiness followed by moisture absorption to the minimum and exceeding in low-temperature solubility, strength and handle, comprising a specific modified polyvinyl alcohol and prescribed fine powder. SOLUTION: This water-soluble film comprises (A) a modified polyvinyl alcohol such as one obtained by subjecting a polyvinyl alcohol having 2.0-40.0mol% modification ratio by an anionic group such as carboxyl group to Michael addition with a vinyl compound such as acrylonitrile or acrylamide and partially or completely hydrolyzing the resulting substance and (B) preferably 2.0-20wt.% (based on the component A) of fine powder such as clay which has <=150μm average particle diameter and is water-insoluble or slightly water- soluble. A water-soluble packing material is obtained from the water-soluble film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold-water fast-dissolving water-soluble film and a water-soluble packaging material, and more particularly, to a cold-water quick-dissolving polyvinyl alcohol-based film having improved tackiness due to moisture absorption, and a water-soluble packaging material comprising the film. About.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol (hereinafter referred to as PVA) can be formed into a film relatively easily and has excellent strength, so that it exhibits water solubility such as packaging of a water-soluble film and a cleaning agent. Widely used as packaging material.

[0003] The PVA used in these compounds has a water solubility of 80 to 80, particularly a low temperature water solubility (low temperature solubility).
90% saponified is common.

[0004]

However, in the conventional PVA film, the P
Even when VA is used as a raw material, the solubility at low temperatures may be insufficient, and thus, in applications that require rapid solubility at low temperatures, satisfactory performance is not necessarily obtained.

[0005] Further, at low temperature and low humidity, the problem of film breakage such as cracking and the like, and the saponification reaction progresses upon contact with an alkaline substance, the solubility in cold water is further reduced, and the packaging of the alkaline substance is difficult. There was a problem that can not be used.

On the other hand, the applicant has previously described modified polyvinyl alcohol having an anionic group introduced into PVA (hereinafter referred to as “modified P
VA ") (Japanese Patent Application No. 7-179064), which is very excellent in cold water rapid dissolution, is deteriorated by alkali, and is damaged under low temperature and low humidity. Can also be prevented. However, when the modification rate is increased to improve the rapid solubility in cold water, the stickiness due to the hygroscopicity of the film increases, so that in the production of the film and the packaging material of the modified PVA, the humidity must be controlled. There is a problem.

An object of the present invention is to provide a PV which has solved the above problems.
A-based water-soluble film, that is, excellent in low-temperature solubility, little change in physical properties with respect to temperature and humidity, no deterioration even in packaging of alkaline substances, and minimizes stickiness due to moisture absorption, as a packaging material P holding strength
An object of the present invention is to provide a VA-based water-soluble film.

[0008]

Means for Solving the Problems In view of the above problems, the present inventors have conducted intensive studies and as a result, have found that a modified PVA having a modification ratio of 2.0 to 40.0 mol% by an anionic group and an average particle size of 2.0 to 40.0 mol%. 1
Films containing water-insoluble or sparingly soluble fine powders of 50 μm or less have faster solubility in cold water than conventional water-soluble PVA films, and change in physical properties with respect to temperature and humidity. It was found that not only the problem of small size, film breakage under low temperature and low humidity, insolubilization by alkali was solved, but also that it was not sticky even when absorbing moisture and that good texture was maintained, and the present invention was completed. .

That is, the water-soluble film of claim 1 is
(A) a modified polyvinyl alcohol having a modification ratio of 2.0 to 40.0 mol% with an anionic group and (B) an average particle size of 1
And a water-insoluble or poorly-soluble fine powder of 50 μm or less.

A second aspect of the present invention is the water-soluble film according to the first aspect, wherein the modified polyvinyl alcohol is a modified polyvinyl alcohol obtained by subjecting a vinyl compound to Michael addition to polyvinyl alcohol and then partially or completely hydrolyzing the same. is there.

According to a third aspect of the present invention, in the water-soluble film of the first aspect, the modified polyvinyl alcohol is obtained by adding acrylonitrile or acrylamide to polyvinyl alcohol with Michael and then partially or completely hydrolyzing the modified polyvinyl alcohol. It is.

[0012] The water-soluble packaging material of the fourth aspect is the first aspect.
3. The water-soluble film according to any one of 3.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a modified PV having an anionic group, which is the component (A) constituting the water-soluble film of the present invention.
A will be described in detail below.

The type of the anionic group of the modified PVA of the component (A) includes a carboxyl group, a sulfone group, a phosphoric acid group and the like, and a carboxyl group and a sulfone group are preferable in view of economy and ease of production. .

The carboxyl group-modified P used in the present invention
As the VA, for example, so-called copolymerized modified PVA obtained by copolymerizing vinyl acetate and itaconic acid or maleic acid and then saponified, and so-called post-modified PVA obtained by directly introducing a carboxyl group into PVA, and the like Is mentioned.

As a method for introducing a carboxyl group into PVA by post-modification, a method of monoesterifying PVA with maleic anhydride or the like, a method of substituting monochloroacetic acid or the like with PVA, a Michael addition reaction of acrylic acid or the like with PVA. Similarly, there is a method in which acrylonitrile, acrylamide or the like is subjected to a Michael addition reaction and then partially or completely hydrolyzed. Among them, a method of adding acrylonitrile or acrylamide with Michael and then hydrolyzing it is preferable from the viewpoint that a high conversion rate and a high modification rate can be obtained.

On the other hand, as a method for introducing a sulfone group into PVA, for example, vinyl acetate and vinyl sulfonic acid, styrene sulfonic acid, allyl sulfonic acid, methallyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid (hereinafter referred to as “vinyl sulfonic acid”) , AMPS) and the like, and saponification, vinyl sulfonic acid or a salt thereof, A
There is a method in which MPS or a salt thereof is added to PVA by Michael. Among them, a method of adding AMPS or a salt thereof to PVA by Michael is preferable in that the conversion is high and a highly modified product is obtained.

Examples of the AMPS salt include a Na salt and a K salt.

Naturally, in the production of anion-modified PVA, two or more of the above-mentioned anionizing agents and modification methods may be used in combination.

The degree of modification by anionic groups is 2.0 to 4
0.0 mol% is preferable, and 4.0 to 30 mol% is more preferable. If the content is less than 2.0 mol%, rapid solubility in cold water is reduced, and the film may be damaged at low temperature and low humidity. On the other hand, those exceeding 40.0 mol% are difficult to produce.

The above-mentioned anion-modified PV used in the present invention
The polymerization degree of A is not particularly limited, but is 200 to 8,000.
Is preferred, and 300 to 4,000 is more preferred. If the degree of polymerization is less than 200, sufficient film strength cannot be obtained. On the other hand, when the degree of polymerization exceeds 8,000, not only does the rapid solubility in cold water decrease, but also the viscosity of the aqueous solution increases, so that it cannot be dissolved at a high concentration, and the productivity decreases.

Next, the water-insoluble or poorly-soluble fine powder of the component (B) will be described in detail.

The average particle size of the water-insoluble or hardly-soluble fine powder used in the present invention is 150 μm or less, preferably 5 μm or less.
0 μm or less.

When the average particle size exceeds 150 μm, the amount required to prevent the film from sticking increases,
As a result, the texture is impaired, and the film strength is also reduced.

The types of fine powders insoluble or hardly soluble in water used in the present invention include clay, kaolin, aluminum hydroxide, calcium carbonate, titanium dioxide, barium sulfate, satin white, talc, silicate, pulp, cellulose and the like. These can be used alone or in combination of two or more, if necessary.

All of these fine powders prevent stickiness due to moisture absorption and minimize the influence on film physical properties, and pulp, cellulose, calcium carbonate, Clay, kaolin.

The addition amount of these fine powders is preferably 0.5 to 40% by weight, more preferably 2.0 to 20%, based on the modified PVA of the component (A). If the amount is less than 0.5% by weight, the effect of the present invention, ie, the prevention of stickiness due to moisture absorption, is not sufficient. On the other hand, if it exceeds 40% by weight, it becomes difficult to obtain film properties suitable as a packaging material.

In forming the modified PVA composition thus obtained into a film, the production method is not particularly limited, and a conventionally known method for producing a PVA film can be applied mutatis mutandis.

For example, after preparing an aqueous solution of these modified PVA-based compositions (the fine powder is suspended and dispersed),
A casting method of casting on a plastic film such as T, release paper or a belt or drum and drying is common.

The thickness of the film of the present invention can be arbitrarily set according to the purpose of use. However, in any of the film forming methods, the finally obtained film has a mechanical strength and a water-soluble property. 10 to 100 μm is preferable,
10 to 70 μm is more preferable.

In the film of the present invention, a plasticizer can be used if necessary in order to impart flexibility. As a plasticizer used for these, a plasticizer used for an ordinary PVA film can be used. In particular, ethylene glycol, glycerin, diglycerin, and low molecular weight polyethylene glycol (molecular weight: 600 or less) are preferable. . Further, within the range not impairing the spirit of the present invention, a coloring agent,
A release agent or the like can be compounded or applied. Further, for the purpose of preventing blocking and improving aesthetic appearance, the film may be subjected to uneven processing such as embossing.

The water-soluble PVA-based film of the present invention obtained as described above has excellent rapid solubility even in cold water, does not deteriorate even in packaging of alkaline substances, etc., and also has strength as a packaging material. Material. Therefore, it has very excellent performance as a packaging material for agricultural chemicals and the like.

In the present invention, the term "quickly soluble in cold water" refers to the high-speed solubility of a film at a water temperature of 10 ° C. or lower. The film of the present invention is suitably used as a water transfer film or various unit packaging materials, which are applications of a conventionally used water-soluble film. It is also possible to use it as a packaging material that requires rapid dissolution in the above.

[0034]

The present invention will be described in more detail with reference to the following examples. In the text, if there is a part or%,
Unless otherwise specified, it is based on weight.

1. Production Example 1 of Component (A) Production Example 1 75 parts of vinyl acetate, 500 parts of methanol, 4.85 parts of itaconic acid, 1.10 parts of NaOH, and 0.3 part of azobisisobutyronitrile were charged into a separable flask, and 70 parts of
Polymerized at 9 ° C. for 9 hours. At this time, the polymerization rate was 81%. After removing unreacted vinyl acetate, 1 / theoretical amount
10 NaOH was added and saponified at 40 ° C. for 5 hours. The polymerization degree of the obtained carboxyl-modified PVA is 1,200,
The degree of saponification was 96.3 mol%. In addition, as analyzed by NMR, the carboxyl modification rate was 3.3 mol%.

Production Example 2 PVA (degree of polymerization: 50) was placed in a 4-liter horizontal blender.
0, saponification degree 88.2 mol%) 490 parts, 30% -Na
OH 200 parts, 50% -acrylamide aqueous solution 420
And 200 parts of isopropyl alcohol, and stirred at 60 ° C. for 8 hours. Next, 50 parts of 50% -NaOH was added, and the mixture was hydrolyzed at 70 ° C. for 1 hour. The obtained powder was purified with methanol and then dried to obtain a white powder. When this was analyzed by NMR, the carboxyl modification rate was 12.2 mol% and the amide modification rate was 8.9 mol%.

Production Example 3 PVA (degree of polymerization 2.5, 5) was placed in a 4-liter horizontal blender.
00, degree of saponification 98.8 mol%) 440 parts, 30% -N
200 parts of an aOH aqueous solution and 484 parts of a 50% -acrylamide aqueous solution were added, and the mixture was stirred at 60 ° C for 8 hours. Next, 100 parts of 50% -NaOH was added, and hydrolysis was performed at 90 ° C. for 1 hour. When the obtained powder was analyzed by NMR, the carboxyl modification ratio was 29.3 mol%.

Production Example 4 The same operation as in Production Example 3 was carried out except that 250 parts of acrylonitrile were used instead of 484 parts of a 50% aqueous solution of acrylamide. When the obtained powder was analyzed by NMR, the carboxyl modification rate was 37.6 mol%.

Production Example 5 PVA (polymerization degree 1,7) was placed in a 4-liter horizontal blender.
00, degree of saponification 98.5 mol%) 440 parts, 50% -N
280 parts of aOH aqueous solution and 50% -AMPS aqueous solution 8
28 parts were added and stirred at 80 ° C. for 7 hours. When the obtained powder was analyzed by NMR, the sulfone group modification rate was 14.
3 mol%.

Production Example 6 PVA (polymerization degree 5,0) was placed in a 4-liter horizontal blender.
00, saponification degree 98.2 mol%) 440 parts, 30% -N
70 parts of an aOH aqueous solution and 284 parts of a 50% -acrylamide aqueous solution were added, followed by stirring at 60 ° C. for 4 hours. Then 5
125 parts of 0% -NaOH was added, and the mixture was hydrolyzed at 70 ° C. for 1 hour.

Next, 460 parts of a 50% -AMPS sodium salt aqueous solution was added, and the mixture was stirred at 80 ° C. for 4 hours. When the obtained powder was analyzed by NMR, the carboxyl modification rate was 17.3 mol% and the sulfone group modification rate was 6.5 mol%.

2. Film Preparation Examples 1 to 6, Comparative Examples 1 and 2 Modified PVA of Production Examples 1 to 6 ((A)
Component), unmodified PVA for comparison, and fine powder (component (B)) were blended in the proportions shown in Table 1, and eight kinds of test films were prepared by the following methods.

[0043]

[Table 1] .

[Preparation of Film] First, the fine powder of the component (B) is suspended and dispersed in water, and then the modified PV of the component (A) is dispersed.
A and the sum of the weights of both components (A) and (B) (provided that
3% glycerin was added to the solid component and dissolved. The solution viscosity at this time was 15,000 to 25000 mPa.
Adjusted to s (BH type viscometer, 20 rpm, 25 ° C.). Next, these were cast on a PET film, left for 24 hours, and further dried at 100 ° C. for 1 hour to prepare a test film having a thickness of 40 μm.

3. Evaluation of Film A performance test was performed on the obtained film by the following method. The results are shown in Table 2.

[Dissolution rate in water]
It was cut into cm × 1 cm and marked with + with aqueous magic. Prepare 500 cc of water at 10 ° C. in a 1 liter beaker in advance, drop the film onto the still water surface,
The time until the mark disappeared completely was measured. When the film was rounded or adhered to the side surface of the beaker, the measurement was performed again. In addition, the result showed the average value of three times in "second". Further, the evaluation was performed at a water temperature of 5 ° C. in exactly the same manner as described above.

[Mechanical strength]
% RH for 72 hours under JIS K7127.
Tensile strength (TB: kg / cm ² ) and elongation (EB:%) were measured according to JIS K7128, and tear strength (TR: kg / cm) was measured according to JIS K7128.

[Alkali Resistance Test] The test film was 1c
cut into mx 1 cm, put on a Petri dish and put N on the film
The film was covered with Na ₂ CO ₃ on a ₂ CO ₃ and left in an oven at 40 ° C. for one month, and the dissolution rate in water was measured. Those that did not dissolve in 300 seconds were regarded as insoluble.

[Tactile sensation (feel)] After the film was allowed to stand for 5 hours under the conditions of 25 ° C. and RH 80%, the tactile sensation was judged by hand according to the following criteria.

：: good △: slightly sticky
×: Great stickiness [Film breakage] The film left for 48 hours under the conditions of 0 ° C. and RH 20% was bent, and the presence or absence of a film crack was evaluated.

[Comprehensive Evaluation] The results of the above performance test were comprehensively evaluated and evaluated on a scale of 1 to 5.

(Good) 5 → 4 → 3 → 2 → 1 (bad)

[Table 2] .

[0053]

The PVA film of the present invention comprises an anion-modified PVA having excellent cold water fast-solubility and alkali resistance, and a water-insoluble or poorly-soluble fine powder having an average particle diameter of 150 μm or less. It has excellent performance as a film.

That is, the water-soluble film of the present invention according to claims 1 to 3 1. dissolves quickly in cold water; 2. Deterioration is unlikely even when contacted with chemicals such as alkali. Stable to temperature and humidity with little change in physical properties. For example, it is possible to prevent film cracking and the like under low temperature and low humidity (0 ° C., 20%). 4. Excellent mechanical strength as a film or packaging material. It has features such as being non-sticky even when absorbing moisture under high humidity and maintaining a good tactile sensation.

Therefore, the water-soluble packaging material according to the fourth aspect comprising the water-soluble film of the present invention has the above-mentioned features, and for example, when used as an agricultural chemical packaging material, prevents the nozzle of the sprayer from being clogged. In addition to the above, it is possible to suppress quality deterioration due to chemicals or in an environment where temperature and humidity conditions are poor.

Claims (4)

[Claims] (1) The degree of modification by (A) anionic group is 2.
A water-soluble film comprising 0 to 40.0 mol% of modified polyvinyl alcohol and (B) a water-insoluble or poorly-soluble fine powder having an average particle diameter of 150 μm or less. 2. The aqueous solution according to claim 1, wherein the modified polyvinyl alcohol is a modified polyvinyl alcohol obtained by Michael addition of a vinyl compound to polyvinyl alcohol and then partially or completely hydrolyzing the polyvinyl compound. Film. 3. The modified polyvinyl alcohol according to claim 1, wherein the modified polyvinyl alcohol is a modified polyvinyl alcohol obtained by adding acrylonitrile or acrylamide to polyvinyl alcohol and then partially or completely hydrolyzing it. Water-soluble film. 4. A water-soluble packaging material comprising the water-soluble film according to claim 1.