JPH11236419A - Modified polyvinyl alcohol, film using the same and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a modified polyvinyl alcohol capable of providing a water- soluble film having excellent low-temperature solubility and chemical resistance, by making the modified polyvinyl alcohol include a specific structural unit. SOLUTION: This modified polyvinyl alcohol (PVA for short) is a PVA having structural units of formula I (A is a 2-4C alkylene; (n) is an integer of 1-50), formula II and, if required, a formula III. Preferably the content of the structural unit of formula I is 0.01-3 mol.% in the modified PVA. Preferably the content of the structural unit of formula II is 97-99.99 mol.% in the modified PVA. The modified PVA can be obtained by saponifying the copolymer of a polyoxyalkylene vinyl ether of formula IV and vinyl acetate. Consequently a water-soluble modified PVA having excellent low-temperature solubility without heating to a high temperature of >=90 deg.C when an aqueous solution of a completely saponified PVA is prepared, capable of forming a flexible film without adding a plasticizer is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a water-soluble modified polyvinyl alcohol which is completely saponified polyvinyl alcohol, which is soluble in low-temperature water and forms a flexible film even in the absence of a plasticizer. It relates to a film having excellent low-temperature solubility and chemical resistance.

[0002]

2. Description of the Related Art When an aqueous solution of completely saponified polyvinyl alcohol (hereinafter abbreviated as PVA) is to be prepared,
The melting operation has to be performed at a high temperature, and therefore, there is no other way but to carry out an operation involving a danger of raising the melting temperature to 90 ° C. or higher and melting.

[0003] In recent years, water-soluble films have been hermetically packaged (unit wrapped) in a fixed amount of various chemicals such as agricultural chemicals and detergents, and put into water as they are in the form of packaging at the time of use to dissolve or disperse them in water. The method of using has been done. The advantage of this unit packaging is that it can be used without touching dangerous chemicals at the time of use, and that a fixed amount is packed so that weighing at the time of use is unnecessary. As the water-soluble film for unit packaging, a water-soluble film made of unmodified partially saponified PVA is mainly used.
A water-soluble film made of unmodified partially saponified PVA has advantages such as being easily soluble in cold water or hot water, excellent in mechanical strength, and good in chemical resistance.

However, 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, carriers and the like contained in these chemicals are gradually added to the PVA of the film. It has the drawback that it acts to reduce water solubility over time and becomes insoluble or poorly soluble in water during long-term storage. Also, conventional water-soluble films contain a large amount of glycerin mainly as a plasticizer in order to impart impact resistance at low temperatures. The amount of the agent becomes very small. As a result, the film changes to hard and brittle physical properties at a low temperature, and the properties at a low temperature are greatly reduced, so that there is a defect that the film is broken during transportation or operation.

[0005]

As one of measures against such a drawback, use of a PVA film modified with a sulfonic acid group or a carboxyl group has been proposed in order to suppress a decrease in water solubility (see, for example, Japanese Patent Application Laid-Open No. H11-157,837). Kaihei 9-27277
No. 3). Films using PVA containing these functional groups have a higher rate of dissolution in water than films made of unmodified partially saponified PVA, and even when various drugs are packaged, The property hardly changes over time.

However, when these functional groups are introduced into PVA, the glass transition point of PVA increases, and the PVA tends to become hard and brittle at low temperatures or low humidity. Measures such as increasing the dosage have been taken. However, when the saponification degree is reduced, there is a problem that the strength is reduced and the film becomes inflexible, and the chemical resistance is also reduced. Also, when a large amount of a plasticizer such as glycerin is used, the plasticizer not only bleeds out on the film surface or blocks,
There is a problem that the plasticizer migrates to the drug during the packaging of the drug, the amount of the plasticizer in the film becomes extremely small, the film becomes hard, and the properties at low temperatures are greatly reduced.

As another countermeasure against such a drawback,
It has been proposed to use a modified polyvinyl alcohol obtained by saponifying a copolymer of polyoxyalkylene allyl ether and vinyl acetate (Japanese Patent Publication No. 5-496).
No. 83 publication). However, this copolymer has a problem that it takes a long time to polymerize and produce each polymer, and the productivity is low.

[0008] The present invention is an improvement on the problem that when an aqueous solution of completely saponified PVA is to be obtained, it must be heated to 90 ° C or higher. Furthermore, even when used as a film for packaging pharmaceuticals such as agricultural chemicals and detergents, the dissolution rate in water is high, and even when the pharmaceuticals are packaged for a long period of time, the initial water solubility is maintained. Further, since the copolymer is plasticized, it has flexibility at low temperatures and has film properties excellent in mechanical strength. Further, the present invention provides a PVA or a film excellent in low-temperature solubility and chemical resistance. Further, the copolymer can be produced in a short time, and the productivity is high.

[0009]

That is, the present invention is a modified polyvinyl alcohol containing a structural unit represented by the following general formulas (1) and (2) and, if necessary, (3).

Embedded image The modified polyvinyl alcohol has a content of the structural unit represented by the general formula (1) in the range of 0.01 to 3 mol% in the modified polyvinyl alcohol, and is a film using the modified polyvinyl alcohol. . A modified polyvinyl alcohol production method characterized by saponifying a copolymer of polyoxyalkylene vinyl ether and vinyl acetate represented by the following general formula (4). General formula (4): CH ₂ ＣＨCHO (AO) _n CH ₃ (where A is an alkylene group having 2 to 4 carbon atoms, and n is 1
Is an integer of ５０50. )

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

That is, the present invention provides the following general formula (1):
A modified polyvinyl alcohol containing the structural unit represented by (2) and, if necessary, (3).

Embedded image

The content of the structural unit represented by the general formula (1) in the present invention is determined in the modified PVA, that is, in the general formulas (1) and (2).
And, if necessary, 0.01 to 3 mol% is preferable in the total mol of the structural units represented by (3). Simply completely saponified P
If the purpose is only to lower the melting temperature of VA, 0.01 to
If it is contained in an amount of 2 mol%, it can be dissolved at a temperature of 0 ° C. or less.

On the other hand, when used for molding a low-temperature soluble film, it is necessary to dissolve at a low temperature. In order to lower the dissolution temperature of completely saponified PVA, it is necessary to increase the amount of addition. Therefore, the content of the structural unit represented by the general formula (1) is preferably 1 to 3 mol% in the modified PVA.

The content of the structural unit represented by the general formula (2) of the present invention is preferably from 97 to 99.99 mol% in the modified PVA. For the purpose of simply lowering the dissolution temperature of fully saponified PVA, 98 to 99.99 mol% contains 0
It can be melted at a temperature of below ° C.

On the other hand, when used for molding a low-temperature soluble film, it is necessary to dissolve at a low temperature. In order to lower the melting temperature of the completely saponified PVA, it is necessary to increase the amount of the addition. Therefore, the content of the structural unit represented by the general formula (2) is preferably 97 to 99 mol% in the modified PVA.

The content of the structural unit represented by the general formula (3) of the present invention, that is, the so-called residual acetic acid group, is 0% in the modified PVA.
~ 1 mol% is preferred.

The average degree of polymerization of the modified PVA of the present invention is preferably 500 to 4000 from the viewpoint of mechanical properties,
3000 is preferred.

The modified PVA of the present invention can be obtained by saponifying a copolymer obtained by copolymerizing polyoxyalkylene vinyl ether and vinyl acetate.

The polyoxyalkylene vinyl ether is a polyoxyalkylene vinyl ether represented by the following general formula (4), and includes methoxy polyethylene vinyl ether and methoxy polypropylene vinyl ether. General formula (4): CH ₂ ＣＨCHO (AO) _n CH ₃ (where A is an alkylene group having 2 to 4 carbon atoms, and n is 1
Is an integer of ５０50. )

In the present invention, two or more kinds of polyoxyalkylene vinyl ethers having different types and different numbers of alkylene groups can be used in combination.

Examples of the method for copolymerizing polyoxyalkylene vinyl ether and vinyl acetate include known methods such as bulk polymerization, solution polymerization, suspension polymerization and emulsion polymerization. Among them, a bulk polymerization method or a solution polymerization method in which polymerization is performed without a solvent or in a solvent such as an alcohol is usually adopted. Examples of the alcohol used as a solvent during solution polymerization include lower alcohols such as methyl alcohol, ethyl alcohol and propyl alcohol.

The initiators used for the copolymerization are 2, 2
^, - azobisisobutyronitrile and ^2,2, - azobis (2, 4-dimethyl - valeronitrile) organic peroxide initiators of azo initiators and n- propyl peroxy carbonate and benzoyl peroxide such as And an initiator such as an agent. The polymerization temperature is not particularly limited, but is suitably in the range from room temperature to about the boiling point.

In the saponification of the copolymer of polyoxyalkylene vinyl ether and vinyl acetate, the copolymer is dissolved in an alcohol, and in some cases, a hydrous alcohol.
Examples of the alcohol used for the saponification reaction include lower alcohols such as methyl alcohol and ethyl alcohol, and methyl alcohol is preferable.

Examples of the catalyst used for the saponification reaction include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali catalysts such as sodium methylate, and acid catalysts such as mineral acids. The temperature of the saponification reaction is not particularly limited, but is preferably in the range of 20 to 60C. When a gel-like product precipitates with the progress of the saponification reaction, the product is pulverized and dried at that time to obtain the modified PVA polymer of the present invention.

In synthesizing the modified PVA of the present invention, other monomers copolymerizable with vinyl acetate can be used as long as the object of the present invention is not impaired. Examples of these monomers include olefins such as ethylene and propylene, polymerizable monocarboxylic acids such as acrylic acid, crotonic acid and isocrotonic acid, dicarboxylic acids such as maleic acid, fumaric acid and itaconic acid, and maleic anhydride. Polymerizable dicarboxylic anhydrides, polymerizable monocarboxylic acids and dicarboxylic acids esters and alkali metal salts thereof, polymerizable acid amides such as acrylamide and methacrylamide, methyl acrylate, ethyl acrylate and butyl acrylate and the like. Acrylates, methacrylates such as methyl methacrylate, ethyl methacrylate and butyl methacrylate, vinyl halides such as vinyl chloride and vinyl fluoride, vinylidene halides such as vinylidene chloride and vinylidene fluoride, and , Allyl glycidyl ether Monomers having a or glycidyl group such as glycidyl methacrylate and the like.

[0026]

According to the present invention, when an aqueous solution of fully saponified PVA is used, it has an excellent low-temperature solubility that an aqueous solution can be obtained even at a temperature of 90 ° C. or less. Furthermore, even when used as a film for packaging pharmaceuticals such as agricultural chemicals and detergents, the dissolution rate in water is high, and even when the pharmaceuticals are packaged for a long period of time, the initial water solubility can be maintained. Further, since the obtained modified PVA is plasticized, a water-soluble film having excellent mechanical properties at low temperatures can be obtained.

[0027]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples, but the present invention is not limited to only these Examples.

Example 1 1875 of vinyl acetate was placed in a 5 L polymerization tank equipped with a reflux condenser, a stirrer, a thermometer, a nitrogen inlet tube and a sampling port.
g, n = 10 99 g of methoxypolyethylene glycol vinyl ether and 625 g of methanol were charged. While the polymerization solution was stirred, the inside of the system was purged with nitrogen and then heated. When the temperature reached 60 ° C., 0.45 g of 2,2 ^, -azobisisobutyronitrile was added to initiate polymerization. From the start of the polymerization, the polymerization was carried out while analyzing the solid concentration in the system.
After a lapse of time, 500 g of methanol was added to the polymerization tank, and the system was further cooled to terminate the polymerization. The polymerization rate at the time of termination of the polymerization was 75%.

Methanol vapor was blown into the obtained copolymer paste, and when unreacted vinyl acetate became 0.1% by weight or less, a paste for saponification was obtained. Using 1150 g of saponified paste, the solid content was adjusted with methanol so that the solid content concentration was 30% by weight, and a methanol solution having a sodium hydroxide concentration of 5% was added while stirring at 40 ° C. (hydroxylation). Sodium is 0.02 to vinyl acetate
5 mol) and a saponification reaction for 60 minutes. After pulverizing the obtained gel, the liquid was separated by a centrifugal separator to obtain a modified PVA modified with methoxypolyethylene glycol vinyl ether. The modified PVA was dried at 110 ° C. for 1 hour to obtain a white modified PVA.

The composition analysis of the resulting modified PVA was carried out by ¹ H-N
Analyzed by MR. As a result, the content of methoxypolyethylene glycol vinyl ether was 0.4 mol%, the content of vinyl alcohol was 99.1 mol%, and the content of residual acetic acid groups was 0.5 mol%.

The physical properties of the obtained modified PVA were evaluated by the following test methods.
As a result of the solubility test, it was completely dissolved at 70 ° C.

(Measurement Method of Viscosity Average Polymerization Degree) The viscosity average polymerization degree (P) obtained by the following equation from the intrinsic viscosity [η] (g / dl) measured at 30 ° C. using an Ostwald viscometer and DMSO as a solvent. Represent. P = [η] ^1.525 × ^3.32 × 10 ⁴

(Measurement Method of Solubility Test) 10 g of modified PVA and 9 parts of water were added so that the concentration of modified PVA would be 10% by weight.
The 300 ml flask added to 0 g was immersed in a thermostatic water bath. While stirring the inside of the flask with a stirrer, the temperature of the thermostat was set to a predetermined temperature so that the modified PVA was dissolved. The presence or absence of undissolved matter in the flask was visually determined, and the temperature at which the substance was completely dissolved was taken as the dissolution temperature.

Example 2 In the same manner as in Example 1, methoxypolyethylene glycol vinyl ether (n = 10) and vinyl acetate were polymerized so as to obtain a modified PVA having a desired composition. Was demonomerized, saponified and dried to obtain the desired modified PVA. Modified P obtained
The composition of VA was 0.9 mol% of methoxypolyethylene glycol vinyl ether with n = 10,
A white powder-modified PVA having 8.4 mol% and residual acetic acid groups of 0.7 mol% having an average degree of polymerization of 1200 was obtained. As a result of the solubility test, it was completely dissolved at 50 ° C.

Example 3 The same operation as in Example 1 was carried out to obtain a composition comprising 1.3 mol% of methoxypolyethylene glycol vinyl ether (n = 10), 98.0 mol% of vinyl alcohol and 0.7 mol% of residual acetic acid groups. A modified white PVA powder having an average degree of polymerization of 1000 was obtained. As a result of the solubility test, it was completely dissolved at 30 ° C.

Example 4 The procedure of Example 1 was repeated, except that methoxypolyethylene glycol vinyl ether with n = 45 was used.
As a result, 0.1 mol% of methoxypolyethylene glycol vinyl ether of n = 45 and 99.2 of vinyl alcohol
Modified PVA as a white powder having a composition of mol% and a residual acetate group of 0.7 mol% and having an average degree of polymerization of 1500 was obtained. As a result of the solubility test, it was completely dissolved at 80 ° C.

Example 5 The procedure was as in Example 1, except that methoxypolyethylene glycol vinyl ether with n = 45 was used.
As a result, 0.3 mol% of methoxypolyethylene glycol vinyl ether of n = 45 and 99.2 of vinyl alcohol
Modified PVA as a white powder having a composition of mol% and residual acetic acid groups of 0.5 mol% and having an average degree of polymerization of 1700 was obtained. As a result of the solubility test, it was completely dissolved at 60 ° C.

Example 6 The procedure of Example 1 was repeated, except that methoxypolypropylenelenglycol vinyl ether with n = 15 was used. As a result, a white powder modified PVA having a composition of 0.3 mol% of methoxypolypropylene glycol vinyl ether (n = 15), 99.0 mol% of vinyl alcohol and 0.7 mol% of residual acetic acid groups and having an average degree of polymerization of 1600 was obtained. Was done. As a result of the solubility test, it was completely dissolved at 65 ° C.

Example 7 The procedure of Example 1 was repeated, except that methoxypolyethylene glycol vinyl ether of n = 10 was used.
As a result, it had a composition of 2.0 mol% of methoxypolyethylene glycol vinyl ether, 97.5 mol% of vinyl alcohol and 0.5 mol% of residual acetic acid groups, and a polymerization degree of 170.
Thus, a white powder of modified PVA was obtained. As a result of the solubility test, it was completely dissolved at 10 ° C.

Example 8 Using the modified PVA obtained in Example 7, a film was prepared by the following method, and the following various properties were measured. The following results were obtained. (1) Film solubility: Dissolved completely in 35 seconds and had excellent water solubility. (2) Low-temperature stability of the film: When measured at −5 ° C., no crack was generated in the film, no breakage occurred, and the low-temperature stability was good, and was ○. (3) Long-term storage stability of the film: 20 ° C., humidity 65%
Was left in a constant temperature / humidity bath for 2 months, and the dissolution time was measured. The dissolution time of the film after humidity control for 24 hours was almost the same, and the long-term stability was also good. (4) Chemical resistance of the film: Similarly, the dissolution time was measured based on the solubility test of the film. As a result, the film was dissolved in 36 seconds and the chemical resistance was good.

(Method for Producing Modified PVA Film) Modified P
60 parts by weight of water was mixed well with 40 parts by weight of VA, and the mixture was cast on a hot roll at 90 ° C. to prepare a film having a thickness of 40 μm.

(Method of Measuring Solubility of Modified PVA Film)
After conditioning the prepared film at 20 ° C for 24 hours,
After cutting to 40 mm, this was clamped and
The film was immersed in water stirred at ℃, and the time from immersion to complete dissolution of the film was measured.

(Method of Measuring Low Temperature Stability of Modified PVA Film) The prepared film was cut into a size of 30 mm × 100 mm, and allowed to stand in a low temperature constant temperature bath at −5 ° C. for 24 hours. The low temperature characteristics were determined based on the results. Judgment criteria: ○: No change, X: Cracked or broken

(Method of Measuring Long-Term Storage Stability) The prepared film was allowed to stand in a constant temperature bath at 40 ° C. for 4 weeks, and the dissolution time was measured by the same method as the method for measuring the solubility of the film.

(Method for Measuring Chemical Resistance of Modified PVA Film)
mm, calcium carbonate powder was put therein, and then the inlet was again sealed with a heat sealer to produce a sealed bag. After allowing to stand in a constant temperature bath at 40 ° C. for 4 weeks, one side was cut off with scissors and opened. The calcium carbonate in the inside was removed, and a solubility test was performed according to the solubility measurement method of the film.

Comparative Example 1 Completely saponified PVA K-17 manufactured by Denki Kagaku Kogyo KK
(Saponification degree of 99 mol% or more, polymerization degree of 1750) was evaluated in the same manner as in Example 8. (1) Solubility of film: 9 does not dissolve in water at 20 ° C.
It was not completely dissolved unless the dissolution temperature was raised to 0 ° C. or higher. (2) Low-temperature stability of film: Poor. (3) Long-term storage stability of the film: The film did not dissolve in water at 20 ° C, and did not completely dissolve unless the dissolution temperature was raised to 90 ° C or higher. (4) Chemical resistance of the film: did not dissolve in water.

Comparative Example 2 Partially saponified PVA B-17 manufactured by Denki Kagaku Kogyo KK
(2) The low-temperature stability of the film having a degree of saponification of 88 mol% and the degree of polymerization of 1750 and the chemical resistance of the film (4) were evaluated in the same manner as in Example 8. (2) Low-temperature stability of the film: The film was broken when the film was bent at a low temperature, and was evaluated as x. (4) Chemical resistance of the film: Undissolved matter remained at 20 ° C, and did not completely dissolve unless the temperature was 80 ° C or higher.

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI C08F 216: 14) C08L 29:04

Claims (4)

[Claims] 1. A modified polyvinyl alcohol containing a structural unit represented by the following general formulas (1) and (2) and, if necessary, (3). Embedded image 2. The modified polyvinyl alcohol according to claim 1, wherein the content of the structural unit represented by the general formula (1) is in the range of 0.01 to 3 mol% in the modified polyvinyl alcohol. 3. A film comprising the modified polyvinyl alcohol according to claim 1 or 2. 4. A method for producing a modified polyvinyl alcohol, comprising saponifying a copolymer of a polyoxyalkylene vinyl ether represented by the following general formula (4) and vinyl acetate. General formula (4): CH ₂ ＣＨCHO (AO) _n CH ₃ (where A is an alkylene group having 2 to 4 carbon atoms, and n is 1
Is an integer of ５０50. )