JPH09272773A - Water-soluble film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-sol. film which dissolves very quickly in water, hardly undergoes degradation in water solubility with the lapse of time when used for wrapping chemicals such as an agricultural chemical or a detergent, hardly causing the migration of, the bleed-out to the film surface of, and the blocking due to a plasticizer, and is excellent in low-temp. impact resistance. SOLUTION: This film is formed from a compsn. prepd. by compounding 100 pts.wt. polyvinyl alcohol resin having structural units derived from a comonomer having a sulfo or carboxyl group with 3-100 pts.wt. compd. obtd. by the addition reaction of 1mol of a tri- to hexahydric alcohol with 1-4mol of an alkylene oxide.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a water-soluble solvent having very low plasticizer migration, little bleed-out of the plasticizer to the film surface, fast dissolution rate in water, and impact resistance at low temperature. Regarding film.

[0002]

2. Description of the Related Art In recent years, water-soluble films have been sealed and packed with a fixed amount of various chemicals such as pesticides and detergents, which are put into the water in their packaging form at the time of use, and dissolved or dispersed in water before use. The way to do it has been done. The advantages of this unit packaging are that it can be used without directly touching dangerous chemicals at the time of use, and it does not require weighing at the time of use because a certain amount is packaged. As a water-soluble film for unit packaging, a water-soluble film made of unmodified partially saponified polyvinyl alcohol is mainly used. The water-soluble film made of non-modified partially saponified polyvinyl alcohol has properties such that it is easily soluble in cold water and hot water, has excellent mechanical strength, and has good chemical resistance. However, there is a demand for excellent low-temperature impact resistance that dissolves at a faster rate, does not change water solubility in pesticides and other pharmaceutical packaging over time, and does not break during transportation or handling at low temperatures.

When chemicals such as agricultural chemicals and detergents are packaged in a water-soluble film and stored for a long period of time, the chemicals, activators, dispersants and carriers contained in these chemicals are gradually added to the polyvinyl alcohol of the film. However, there is a problem in that the water solubility decreases over time and becomes insoluble or hardly soluble in water during long-term storage. In addition, the conventional water-soluble film is mainly mixed with glycerin as a plasticizer in order to give impact resistance at low temperature, but glycerin migrates to the drug or carrier during long-term storage, and the plasticizer in the film Very small quantity. As a result, the film changes to a hard and brittle physical property at a low temperature, the impact strength at a low temperature is significantly reduced, and there is a problem that the film is broken during transportation or work. Due to these problems, the unit packaging of dangerous pesticides and detergents has a great advantage, but is not yet widely used.

As one of such measures, it has been attempted to utilize a polyvinyl alcohol film modified with a sulfonic acid group or a carboxyl group in order to suppress the decrease in water solubility. Films using polyvinyl alcohol containing these functional groups have a faster dissolution rate in water than films made of unmodified partially saponified polyvinyl alcohol, and even when various drugs are packaged. Little change in water solubility over time. However, when these functional groups are introduced into polyvinyl alcohol, the glass transition point of polyvinyl alcohol becomes high, and it tends to become hard and brittle at low temperature and low humidity. Therefore, measures such as lowering the saponification degree of polyvinyl alcohol and increasing the amount of plasticizer have been taken, but if the saponification degree is lowered, the strength decreases and the film becomes stiff, and further chemical resistance descend. Also, when a large amount of plasticizer such as glycerin is used, not only does the film bleed out or block on the film surface, but the plasticizer migrates to the drug during drug packaging, and the plasticizer in the film becomes extremely small and hard. Therefore, there is a problem that the impact strength at low temperature is greatly reduced. Various plasticizers have been investigated in order to eliminate the migration of the plasticizer. For example, polyethylene glycol, polypropylene glycol, polyglycerin, mannitol sorbitol, pentaerythritol, etc., which have less migration compared to glycerin, but have poor polyvinyl alcohol performance as a plasticizer and impart flexibility at low temperatures. And impact strength is not sufficiently improved. In addition, when a plasticizer that is solid at room temperature, such as sorbitol, migrates to the film surface, a white powder is deposited, which is a problem.

[0005]

DISCLOSURE OF THE INVENTION The present invention has solved the above-mentioned problems and is a film for packaging medicines such as agricultural chemicals and detergents, which has a high dissolution rate in water and is packaged for a long period of time. Even though it is water soluble, it retains initial water solubility, has very little plasticizer migration, has impact resistance at low temperatures, has excellent mechanical strength, and is flexible and tough. To provide a film.

[0006]

Means for Solving the Problems The present inventors have made diligent studies in view of the present situation, and as a result, added 100 parts by weight of a polyvinyl alcohol resin (A) containing a copolymer unit composed of a sulfonic acid group or a carboxyl group. A water-soluble film composed of a composition obtained by adding 3 to 100 parts by weight of a compound (B) obtained by addition reaction of 1 to 4 mol of alkylene oxide to 1 mol of polyhydric alcohol having 3 to 6 valences was found. The present invention has been completed.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The polyvinyl alcohol (hereinafter abbreviated as PVA) resin (A) used in the present invention is a saponified product of polyvinyl ester containing a copolymer unit having a sulfonic acid group or a carboxyl group. . As vinyl ester, vinyl acetate, vinyl propionate,
Vinyl formate, vinyl versatate, vinyl pivalate and the like can be mentioned. Among them, industrially produced,
Vinyl acetate, which is cost-effective, is usually used. As the copolymer unit composed of a sulfonic acid group or a carboxyl group, a monomer containing these functional groups and a vinyl ester are copolymerized in the presence of a radical initiator in a solvent such as a lump or an alcohol, and after that, Preferable examples include copolymerized units in the PVA-based resin produced by partially or highly saponifying with an alkali or acid catalyst.

The monomer containing a sulfonic acid group is
Any copolymer can be used as long as it can be copolymerized with a vinyl ester and the sulfonic acid group or its salt is present in the PVA-based resin after saponification. As a specific example, 2-acrylamide-2
-Methylpropanesulfonic acid or its alkali metal salt, 2-acrylamido-1-methylpropanesulfonic acid or its alkali metal salt, 2-methacrylamide-
Examples thereof include 2-methylpropanesulfonic acid or an alkali metal salt thereof, olefinsulfonic acid such as ethylenesulfonic acid, allylsulfonic acid, and methallylsulfonic acid, or a metal salt thereof. Among these, from the viewpoint of copolymerization reactivity with vinyl ester and stability during saponification,
2-Acrylamido-2-methylpropanesulfonic acid or its alkali metal salt is preferred.

The monomer containing a carboxyl group may be any monomer which can be copolymerized with a vinyl ester and in which the carboxylic acid or its salt is present in PVA after saponification. Specific examples thereof include maleic anhydride, mono- or di-alkyl maleic acid ester, itaconic acid or its alkyl ester, acrylic acid, allylcarboxylic acid, and (meth) acrylic acid ester derived from carboxylic acid or its salt after saponification. And the like. Among these, maleic anhydride, itaconic acid and derivatives thereof are preferable. The PVA-based resin of the present invention is a saponified product of polyvinyl ester containing one or more selected from these copolymer units, and may be used alone or in combination of several kinds. The content of these copolymerized units in the PVA-based resin is not particularly limited, but is 0.1 to 20 mol% and preferably 0.5 to 10 mol% in order to sufficiently exert the effects of the present invention. And more preferably 1 to
5 mol%. If it is less than 0.1 mol%, the stability of water solubility when the drug is packaged is poor and the dissolution rate in water is slow, and if it is more than 20 mol%, the strength of the film is greatly reduced and the film is hard and brittle. Become. The degree of polymerization of the PVA-based resin is not particularly limited, but in the case of a water-soluble film, the mechanical properties of the film are important, and strong strength and flexibility are required even in the case of a thin thickness of 10 to 100 μm. In view of the strength and toughness of the film, the viscosity average degree of polymerization (hereinafter abbreviated as the degree of polymerization) is 200 to 10,000, preferably 500 to 4,000. If the degree of polymerization is less than 200, the film strength will be weak, and if the degree of polymerization is more than 10,000, the solution viscosity will be high when the film is prepared, and there will be a problem in workability. The saponification degree of the PVA-based resin is usually 40 to 100 mol% in consideration of film strength, film stiffness and bag-making property. It is preferably 60 to 100 mol%, more preferably 70 to 99.5 mol%.

The compound (B) used in the present invention can be obtained by addition reaction of 1 to 4 mol of alkylene oxide with 1 mol of polyhydric alcohol alcohol having 3 to 6 valences. The compound (B) obtained by addition-reacting 1 to 4 mol of alkylene oxide with 1 mol of polyhydric alcohol having 3 to 6 valences is a liquid at room temperature and is an excellent phase for PVA-based resin (A). It has solubility and plasticizing properties, less migration to the outside of the film, and less bleed-out and blocking properties.

Examples of the trivalent to hexavalent polyhydric alcohol which is a raw material of the compound (B) include glycerin, trimethylolpropane, diglycerin, pentaerythritol, xylose, arabinose, ribulose and sorbitol. Preferred are glycerin, pentaerythritol, and sorbitol.

Examples of the alkylene oxide which is another raw material of the compound (B) include ethylene oxide and propylene oxide, and ethylene oxide is preferable. In some cases, ethylene oxide and propylene oxide may be mixed and addition-reacted. The number of added moles of alkylene oxide is preferably 2 to 3. If the average number of moles of alkylene oxide added is less than 1 mole, there is a problem in the migration of the plasticizer. If the average number of added moles exceeds 4 moles, PV
The compatibility with the A-based resin (A) decreases, and the plasticizing effect also decreases. The addition mole number referred to here is an average addition mole number, and the addition mole number may have a distribution. However, it is not preferable to add 50 mol% or more of the addition compound in an amount of 5 mol or more.

Compound (B) for PVA type resin (A)
Is 3 to 100 parts by weight, preferably 5 to 30 parts by weight, based on 100 parts by weight of the PVA-based resin (A). When the compounding amount of the compound (B) is less than 3 parts by weight, the flexibility is insufficient, and when it exceeds 100 parts by weight, the film strength is lowered, and problems such as blocking property and bag-making property occur.

As a method for forming a film of the composition comprising the PVA resin (A) and the compound (B) of the present invention, an aqueous solution thereof is cast or melted by heat and extruded from a T-die or an inflation molding machine. Any method such as is used. that time,
If necessary, ordinary additives such as colorants, fragrances, extenders, defoamers, release agents, UV absorbers, inorganic powders and the like may be appropriately mixed. Further, if necessary, a water-soluble polymer such as ordinary PVA, starch, carboxymethyl cellulose, methyl cellulose, hydroxymethyl cellulose or the like may be added within a range not losing the features of the present invention. Further, in the water-soluble film of the present invention, in some cases, in addition to the compound (B), a compound generally used as a plasticizer for the PVA-based resin (A) may be used in combination within a range not impairing the features of the present invention. it can. As these plasticizers, polyhydric alcohols such as glycerin, diglycerin and diethylene glycol, polyethers such as polyethylene glycol and polypropylene glycol, phenol derivatives such as bisphenol A and bisphenol S, amide compounds such as N-methylpyrrolidone, Examples include water.

[0015]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto. In the examples, unless otherwise specified,
"%" And "part" represent weight basis.

[Plasticizer Transferability Measuring Method] Using a heat sealer, a bag of 10 × 10 cm was prepared from the film, 15 g of diatomaceous earth was packaged and heat sealed. An aluminum / polyethylene laminate film bag was double-wrapped on the packed bag to prevent water and plasticizer from scattering to the outside, and the bag was allowed to stand in a constant temperature bath at 40 ° C. for a predetermined time. The amount of plasticizer in the film was measured before and after standing. The amount of plasticizer in the film was measured by drying the film sample in a vacuum dryer at 50 ° C for 5 hours to remove water, and then Soxhlet extraction with methanol. Was calculated. The "residual rate of plasticizer" after standing is indicated by "%", which is a value obtained by dividing the "amount of plasticizer after standing" by the "amount of plasticizer before standing".

[Method for measuring water-solubility of film] A film sample was cut into a square of 40 × 40 mm, scissored with a slide mount, and immersed in water stirred at 20 ° C. and 10 ° C. to completely remove the film. The time (seconds) until dissolution was measured.

[Measurement of low temperature impact strength] 20 films
After conditioned for 1 week at ℃, 40% RH, -5 ℃
After standing for 3 days, the impact strength at −5 ° C. was measured with a film impact tester.

Example 1 To a methanol solution of a copolymer obtained by copolymerizing vinyl acetate and sodium 2-acrylamido-2-methylpropanesulfonate in a methanol solvent, a methanol solution of sodium hydroxide was added. A saponification reaction was carried out by the method to obtain a sodium sulfonate-modified PVA having a degree of polymerization of 1750, a degree of saponification of 88 mol% and a content of a sodium sulfonate group-containing copolymer unit of 2 mol%. This modified PVA
An aqueous solution of a composition was prepared by adding 20 parts of a compound obtained by addition-reacting 2 parts of ethylene oxide to 1 part of sorbitol with 100 parts, cast on a hot roll at 70 ° C., and a film having a thickness of 40 μm. Got The plasticizer migration and low temperature impact strength of the produced film were measured. The results are shown in Table 1. The film of the present invention has a very small plasticizer migration property and is excellent in impact resistance at low temperatures. There was no bleed out of the plasticizer on the film surface, and the blocking property was also small. Further, when a film having a thickness of 40 μm of the present invention was immersed in water stirred at 20 ° C. and 10 ° C. respectively, and the time until the film was completely dissolved was measured, it was 18 seconds and 25 seconds, respectively, which was excellent. It had water solubility.

COMPARATIVE EXAMPLE 1 A film was prepared in the same manner as in Example 1 except that 20 parts of glycerin was used as a plasticizer in 100 parts of the modified PVA used in Example 1, and the plasticizer migration property and low temperature impact strength were obtained. Was measured. The results are shown in Table 1. The plasticizer migration is very large and the low temperature impact strength before standing is large, but the low temperature impact strength is greatly reduced by standing. Further, the plasticizer bleeded out to the film surface, and the blocking property was large.

Example 2 Vinyl acetate and maleic anhydride were copolymerized in a methanol solvent and a saponification reaction was carried out by a conventional method to obtain a polymerization degree of 1,200.
Sodium carboxylate base-modified PVA having a saponification degree of 96 mol% and a content of a maleic acid group-containing copolymer unit of 4 mol%
I got An aqueous solution of a composition was prepared by adding 100 parts of this modified PVA and 25 parts of a compound obtained by addition-reacting 3 mol of ethylene oxide with 1 mol of glycerin.
It was cast on a hot roll at 0 ° C. to obtain a film having a thickness of 40 μm. The plasticizer migration and low temperature impact resistance of the prepared film were measured. The results are shown in Table 1. Further, a bag of 10 cm × 10 cm was prepared from the film obtained above, and 20 g of alkaline tableware detergent having a pH of 10% of 1% aqueous solution was put therein and heat-sealed. Further, it was double-wrapped with a bag of aluminum / polyethylene laminate film, sealed, and left for 4 weeks in a constant temperature oven at 40 ° C. After standing for 4 weeks, the water solubility of the film was measured in the same manner as in Example 1. The complete dissolution time of the film before standing in water stirred at 20 ° C and 10 ° C was 21 each.
Seconds and 33 seconds, 20 of film after standing for 4 weeks
The complete dissolution times in water stirred at ℃ and 10 ℃ were 23 seconds and 35 seconds, respectively. The water solubility was good even after the drug was packaged and left standing.

Example 3 Vinyl acetate, sodium 2-acrylamido-1-methylpropanesulfonate and itaconic acid were terpolymerized and saponified by a conventional method to give a sulfonic acid group-containing copolymer unit. A modified PVA having an amount of 2 mol%, an itaconic acid group-containing copolymer unit content of 2 mol%, a degree of polymerization of 960, and a degree of saponification of 94 mol% was obtained. This modified PVA
An aqueous solution of a composition in which 15 parts of the compound (B) used in Example 1 was added to 100 parts was cast and cast on a hot roll at 70 ° C. to obtain a film having a thickness of 40 μm. The plasticizer migration and low temperature impact strength of the produced film were measured. The results are shown in Table 1.

Comparative Example 2 A film was prepared in the same manner as in Example 1 except that 20 parts of polyethylene glycol (# 400) was used as a plasticizer in 100 parts of the modified PVA used in Example 1, and the plasticizer migration property was improved. And the low temperature impact strength was measured. The results are shown in Table 1.
The plasticizer migration was small, but the impact resistance at low temperatures was poor.

[0024]

[Table 1]

[0025]

INDUSTRIAL APPLICABILITY The water-soluble film of the present invention has an extremely excellent rate of dissolution in water, shows little decrease in water solubility with the time of packaging chemicals such as agricultural chemicals and detergents, and is a plasticizer migration agent. The nature is small. Further, there is little bleeding out or blocking of the plasticizer on the film surface, and the impact resistance at low temperatures is excellent.

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Claims (1)

[Claims] 1. 100 parts by weight of a polyvinyl alcohol-based resin (A) containing a copolymer unit having a sulfonic acid group or a carboxyl group is added to 1 part of a polyhydric alcohol having 3 to 6 valences.
A water-soluble film comprising a composition comprising 3 to 100 parts by weight of a compound (B) obtained by addition reaction of 1 to 4 moles of alkylene oxide with respect to moles.