JP2006063242A - Film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide film having solubility to cold water, specifically, having film strength enough to be used as a packaging material, readily soluble to cold water and slight in film surface stickiness and mechanical strength drop due to moisture absorption. <P>SOLUTION: The film is 1-10 mol% in the copolymerization ratio of anionic group-containing vinyl units and contains a polyvinyl alcohol with a saponification degree of 80-89 mol% and a 4 mass% aqueous solution viscosity of 8-20 mP×s at 20°C. In the film, it is preferable that the anionic group be at least one functional group selected from carboxylic acid ester group, carboxylic acid group and carboxylic acid metal salt group. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a film of polyvinyl alcohol, and more particularly to a water-soluble film.

  As a water-soluble film, a film in which a specific amount of an amphoteric surfactant is contained in polyvinyl alcohol is known (see, for example, Patent Document 1).

As one of the usage methods of this film, various chemicals are sealed and packaged in a certain amount, put into water in the packaging form (hereinafter referred to as unit packaging), and the contents are dissolved or dispersed in water together with the packaging film. There is a method to use. This unit packaging has advantages such as that dangerous chemicals can be used without directly touching the human body, and that a certain amount of contents are packaged, so that weighing is unnecessary.
Japanese Patent Laid-Open No. 6-888002

  An object of the present invention is to provide a film that dissolves and decomposes rapidly even when the temperature of water is lower than 20 ° C., and can prevent stickiness of the film surface and decrease in mechanical strength due to moisture absorption.

  As a result of intensive studies, the present inventor has used a film containing polyvinyl alcohol in which the copolymerization rate of vinyl units containing an anionic group, the degree of saponification, and the viscosity of a 4% by mass aqueous solution at 20 ° C. are specified. The present invention has been completed by finding that this problem can be solved.

（但し、ｌ、ｍは０〜５の整数、Ａ、Ｂは水素又はアルキル基、Ｖ、Ｗは水素、アルカリ金属、アンモニウム基又はアルキル基を表す。）

（但し、ｎは０〜５の整数、Ｄ、Ｅ、Ｆは水素又はアルキル基、Ｘは水素、アルカリ金属、アンモニウム基又はアルキル基を表す。）

（但し、ｏ、ｐは０〜５の整数、Ｇ、Ｉは水素又はアルキル基、Ｙ、Ｚは水素、アルカリ金属、アンモニウム基又はアルキル基を表す。） That is, the present invention has a copolymerization rate of vinyl units containing an anionic group of 1 to 10 mol%, a saponification degree of 80 to 89 mol%, and a 4 mass% aqueous solution viscosity at 20 ° C. of 8 to 20 mPa · s. It is a film containing polyvinyl alcohol.
Further, in the present invention, the anionic group is preferably at least one functional group selected from the group consisting of carboxylic acid esters, carboxylic acids and carboxylic acid metal salts, and the vinyl unit containing an anionic group is It is preferable to polymerize or copolymerize at least one member selected from the group consisting of general formulas (Chemical Formula 4) to (Chemical Formula 6).

(However, l and m are integers of 0 to 5, A and B are hydrogen or an alkyl group, and V and W are hydrogen, an alkali metal, an ammonium group or an alkyl group.)

(However, n represents an integer of 0 to 5, D, E, and F represent hydrogen or an alkyl group, and X represents hydrogen, an alkali metal, an ammonium group, or an alkyl group.)

(However, o and p are integers of 0 to 5, G and I are hydrogen or an alkyl group, Y and Z are hydrogen, an alkali metal, an ammonium group or an alkyl group.)

  The film of the present invention has an effect of rapidly dissolving and decomposing even when the temperature of water is lower than 20 ° C. Further, even under an atmosphere of 20 ° C. and a relative humidity of 65%, the film surface can be prevented from stickiness and mechanical strength from being reduced due to moisture absorption.

  The present invention will be described in detail below. In the following description, “part” means “part by mass” unless otherwise specified.

  The vinyl unit containing an anionic group is obtained by polymerizing or copolymerizing a vinyl monomer containing at least one kind of anionic group. Examples of the vinyl monomer containing an anionic group include a carboxylic acid group-containing vinyl monomer and a sulfonic acid group-containing vinyl monomer. However, in terms of operability and safety, the carboxylic acid group-containing vinyl monomer is used. Those obtained by polymerizing or copolymerizing monomers are preferred.

  Examples of the carboxylic acid group-containing vinyl monomer include those described in the general formulas (Chemical Formula 4) to (Chemical Formula 6), for example, polymerizable monocarboxylic acids such as (meth) acrylic acid, crotonic acid, and isocrotonic acid, Examples thereof include polymerizable dicarboxylic acids such as esters, maleic acid, fumaric acid and itaconic acid, polymerizable dicarboxylic anhydrides such as maleic anhydride, and aliphatic vinyl esters.

  Among the carboxylic acid group-containing vinyl monomers, those having a general formula (Chemical Formula 4) and / or a general formula (Chemical Formula 6) in that the effect of improving the solubility in water at a temperature lower than 20 ° C. is high. Is preferred.

  Among these general formulas, the alkali metal is preferably selected from, for example, lithium, sodium, potassium and the like, and the alkyl group is preferably one having 1 to 4 carbon atoms. In addition, A and B in the general formula (Chemical Formula 4) are preferably hydrogen, and those where l = 0 and m = 1 are preferable. G and I in the general formula (Formula 6) are preferably hydrogen, and preferably o and p = 0.

  Examples of the sulfonic acid group-containing vinyl monomer include olefin sulfonic acids such as ethylene sulfonic acid and allyl sulfonic acid, 2-acrylamido-2-methylpropane sulfonic acid, 2-acrylamido-1-methylsulfonic acid, and 2-methacrylic acid. And amido-2-methylpropanesulfonic acid.

  The copolymerization rate of the vinyl monomer containing an anionic group in polyvinyl alcohol is 1 to 10 mol%, and more preferably 2 to 5 mol%. If the copolymerization rate of vinyl units containing an anionic group is less than 1 mol%, it may be difficult to dissolve in water at a temperature lower than 20 ° C. If it exceeds 10 mol%, the film absorbs moisture and becomes sticky. The mechanical strength of the film may not be obtained. In addition, the copolymerization rate of the vinyl unit containing an anionic group here means the copolymerization rate of the anionic group containing vinyl monomer when all the units of the obtained polyvinyl alcohol are 100 mol%. .

  The saponification degree of polyvinyl alcohol is 80 to 89 mol%, more preferably 83 to 86 mol%. If the degree of saponification is less than 80 mol%, the film may absorb moisture and become sticky, or the mechanical strength of the film may not be obtained. If it exceeds 89 mol%, it is difficult to dissolve in water at a temperature lower than 20 ° C. There is a risk. The saponification degree here is a value measured according to JIS K 6276 “3.5 degree of saponification”.

  The viscosity of a 4% by weight aqueous solution of polyvinyl alcohol at 20 ° C. is 8 to 20 mPa · s, and 9 to 15 mPa · s. s is more preferable. If the viscosity of a 4% by mass aqueous solution is less than 8 mPa · s, the mechanical strength of the film may not be obtained, and if it is greater than 20 mPa · s, it may be difficult to dissolve in water at a temperature lower than 20 ° C. Here, the 4 mass% aqueous solution viscosity in 20 degreeC is the value which measured the viscosity of polyvinyl alcohol aqueous solution at 20 degreeC and 30 rpm with BL type | mold rotational viscometer. In addition, 4 mass% aqueous solution viscosity can be adjusted with the quantity of the methanol added when superposing | polymerizing a polyvinyl alcohol and the polyvinyl alcohol.

The production method of polyvinyl alcohol is not particularly limited. For example, it is obtained by copolymerizing an aliphatic vinyl ester monomer and a vinyl monomer containing these anionic groups by a known polymerization method, and then saponifying. It is what
As the polymerization method, for example, solution polymerization using a solvent such as methanol, ethanol or isopropyl alcohol, emulsion polymerization, and suspension polymerization are also possible. In such solution polymerization, the vinyl acetate monomer and the vinyl monomer containing an anionic group may be charged by any means such as batch charging, split charging, and continuous addition. The polymerization reaction is performed using a known radical polymerization catalyst such as azobisisobutyronitrile, acetyl peroxide, benzoyl peroxide, or lauroyl peroxide. The reaction temperature is suitably selected from the range of about 50 ° C. to the boiling point of the reaction mixture.

  Examples of the aliphatic vinyl ester monomer include at least one of vinyl formate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl caprate, vinyl laurate, vinyl persate, vinyl palmitate, and vinyl stearate. The above can be used. Among these, vinyl acetate is preferable from a practical point of view.

  As a method of forming the film of the present invention, a method obtained by casting an aqueous solution of polyvinyl alcohol on a drum or a belt and drying water as a solvent, a melt extrusion film forming method, a blow molding method, or the like is used.

  Although the thickness of the film of this invention is not specifically limited, 5-200 micrometers is preferable. Furthermore, the film of the present invention may be embossed or printed on the surface, and glycerin or the like may be used as a plasticizer.

  Hereinafter, the present invention will be described in more detail with reference to examples.

Example 1
70 parts of vinyl acetate, 30 parts of methanol and 0.08% azobisisobutyronitrile with respect to vinyl acetate were charged into a polymerization vessel, heated after nitrogen substitution, and 2.4 parts of monomethyl maleate were continuously added. The polymerization was terminated at the boiling point, and the polymerization was stopped when the polymerization rate reached 80%. Subsequently, unpolymerized vinyl acetate was removed by a conventional method, and the resulting polymer was saponified with sodium hydroxide by a conventional method to obtain polyvinyl alcohol. Table 1 shows the copolymerization rate of vinyl units containing an anionic group, the degree of saponification, and the viscosity of a 4 mass% aqueous solution at 20 ° C in the obtained polyvinyl alcohol.

  The obtained 4% by mass aqueous solution of polyvinyl alcohol was cast on a polyethylene terephthalate plate having a smooth surface and dried under conditions of a temperature of 20 ° C. and a relative humidity of 60% to obtain a film having a thickness of 60 μm. The film was evaluated for mechanical strength, cold water solubility, and stickiness. The results are shown in Table 1.

(Test method)
The content of the vinyl unit containing an anionic group is calculated from the NMR measurement results, and the saponification degree is measured according to JIS K 6276 “3.5 saponification degree”.

  The viscosity of a 4% by mass aqueous solution was measured at a viscosity of 20 ° C. and 30 rpm with a BL type rotational viscometer. The mechanical strength was determined by allowing the obtained film to stand for 24 hours at 20 ° C. and a relative humidity of 65%. A tensile test was performed with a graph (manufactured by Shimadzu Corporation), and the breaking strength was measured.

  Cold water solubility was measured as follows. A 1 liter beaker containing 800 ml of distilled water was placed in a thermostat set at 20 ° C., and stirred using a stirrer so that the lower end of the vortex generated by stirring was positioned in the 600 ml line of the beaker. After the distilled water in the beaker reaches 20 ° C., the film is sandwiched between slide mounds with a window size of 35 mm × 24 mm, immersed in water, and the time from when the film is completely dissolved until the film is completely dissolved. Was measured.

  The stickiness was evaluated by touching the obtained film with a finger after leaving it at 20 ° C. and a relative humidity of 65% for 24 hours. △ was marked and X was markedly sticky.

(Examples 2 and 3, Comparative Examples 1-4)
An anionic group-containing polyvinyl alcohol having an anionic group-containing vinyl unit, a saponification degree, and a viscosity of 4% by mass aqueous solution shown in Table 1 was prepared and evaluated in the same manner as in Example 1. The results are shown in Table 1. In Table 1, the anionic group-containing vinyl monomer a is monomethyl maleate, the anionic group-containing vinyl monomer b is dimethyl maleate, the anionic group-containing vinyl monomer c is itaconic acid, an anionic group. The containing vinyl monomer d represents maleic acid.

The film of the present invention can be suitably used as a unit packaging material in which a certain amount of powder or granular chemicals such as detergents, insecticides / bactericides, bleaches, herbicides, and fertilizers are packaged.

Claims (3)

  Film containing polyvinyl alcohol having a copolymerization rate of vinyl units containing an anionic group of 1 to 10 mol%, a saponification degree of 80 to 89 mol%, and a 4 mass% aqueous solution viscosity at 20 ° C. of 8 to 20 mPa · s. .   The film according to claim 1, wherein the anionic group is at least one functional group selected from the group consisting of a carboxylic acid ester, a carboxylic acid, and a carboxylic acid metal salt. The film according to claim 1, wherein the vinyl unit containing an anionic group is obtained by polymerizing or copolymerizing at least one member selected from the group consisting of the general formulas (Chemical Formula 1) to (Chemical Formula 3).

(However, l and m are integers of 0 to 5, A and B are hydrogen or an alkyl group, and V and W are hydrogen, an alkali metal, an ammonium group or an alkyl group.)

(However, n represents an integer of 0 to 5, D, E, and F represent hydrogen or an alkyl group, and X represents hydrogen, an alkali metal, an ammonium group, or an alkyl group.)

(However, o and p are integers of 0 to 5, G and I are hydrogen or an alkyl group, Y and Z are hydrogen, an alkali metal, an ammonium group or an alkyl group.)