JPH0741585A - Film for envelope - Google Patents

Abstract

PURPOSE:To obtain a film for an envelop which has waterproofness and can be dispersed or dissolved in warm water by applying a waterproofing agent to the external surface of a film made of a polyvinyl alcohol resin having a specified degree of hydrolysis and a specified average degree of polymerization. CONSTITUTION:The film is prepared by applying a waterproofing agent to at least the external surface of a film made of a polyvinyl alcohol resin having a degree of hydrolysis of 50-99mol% and an average degree of polymerization of 100 or above. Examples of the polyvinyl alcohol resins which can be applied include a polyvinyl alcohol obtained by hydrolyzing a polymer of a vinyl ester or a vinyl ether and being easily dispersible or soluble in water at 5-70 deg.C-under an atmospheric pressure and a modified polyvinyl alcohol dispersible or soluble in warm water at 40-70 deg.C. As the waterproofing agent, a urethane resin is desirable. The coating thickness is usually 1-10mum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention improves the water resistance by coating a water resistant agent on one or both sides of a film made of a polyvinyl alcohol resin having a specific saponification degree, and water at 5 to 80 ° C. , Preferably 40-70
The present invention relates to an envelope film having a function of easily dispersing or dissolving in warm water of ℃ or water vapor, and particularly to an envelope window covering film.

[0002]

2. Description of the Related Art Conventionally, a water-insoluble film made of a polyethylene terephthalate resin or an olefin resin such as polypropylene or polystyrene has been used as an envelope film, particularly an envelope window covering film. However, when recycling envelope films made of these resins, since these films are insoluble in water, it cannot be recycled together with ordinary papers, especially in the case of envelope window covering films. A step of peeling this film from the envelope is required, which makes recycling very difficult.

[0003]

SUMMARY OF THE INVENTION The present invention is to solve the above-mentioned problems of the prior art, namely, at least the outer surface of a film made of a polyvinyl alcohol resin having a saponification degree of 50 to 99 mol% and an average degree of polymerization of 100 or more. The present invention provides a film for envelopes, which is characterized by being coated with a water-proofing agent, which has sufficient water resistance and under normal pressure,
It is a film that can be easily dispersed or dissolved in water of 5 to 70 ° C. (of course, it also dissolves in hot water having a higher temperature, and may be at a lower temperature under pressure).

[0004]

Means for Solving the Problems The inventors of the present invention have earnestly studied a film which has water resistance enough to be used as an envelope film and can be easily dispersed or dissolved in water at 5 to 70 ° C. under normal pressure. As a result, a film comprising a polyvinyl alcohol-based resin having a saponification degree of 50 to 99 mol% and an average degree of polymerization of 100 or more and a waterproofing agent applied to at least the outer surface of the film has sufficient water resistance to be used as an envelope film. Moreover, they have found that they can be easily dispersed or dissolved in water at 5 to 70 ° C. under normal pressure, and completed the present invention.

As the polyvinyl alcohol resin usable in the present invention, a polymer obtained by polymerizing a vinyl ester such as vinyl acetate or vinyl formate or a vinyl ether such as t-butyl vinyl ether or trimethylsilyl vinyl ether is hydrolyzed with an acid or an alkali. The obtained saponification degree is 50 to 99 mol%, preferably 60 to 99 mol%, the degree of polymerization is 100 or more, preferably 1000 to 2000, more preferably 1000 to 1700, and easily dispersed in water at 5 to 70 ° C. under normal pressure or It is a soluble polyvinyl alcohol.

When a polyvinyl alcohol resin having a saponification degree of less than 50 mol% or more than 99 mol% is used,
It is difficult to disperse or dissolve in hot water of 70 ° C or lower, which is not preferable. Polyvinyl alcohol having a degree of polymerization of less than 100 tends to be inferior in mechanical strength, and polyvinyl alcohol having a degree of polymerization of more than 2000 tends to be expensive.

Further, polyvinyl alcohol derivatives obtained by phosphorylating, sulfating or etherifying the above-mentioned polyvinyl alcohol, further vinyl acetate monomer and allyl alcohol or unsaturated carboxylic acids such as acrylic acid, crotonic acid, maleic acid and itaconic acid are used. Of the modified polyvinyl alcohols obtained by hydrolyzing the copolymerized copolymer, those which can be dispersed or dissolved in warm water at 40 to 70 ° C. can be similarly used.

In the envelope film of the present invention, if necessary, cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose, chitosan derivatives, starch, xanthan gum, polysaccharides such as carrageenan, polyacrylic acid or its derivatives, polyacrylamide, Poly-
N-vinylpyrrolidone, styrene-maleic anhydride copolymer, ethylene-maleic anhydride copolymer, water-soluble resin such as water-soluble polymer such as polyethylene oxide, polyhydric alcohol such as glycerin and ethylene glycol, or ethanol Plasticizers such as amines, nonionic or anionic surfactants, silica, zinc sulfate, cobalt sulfate, stannous acetate, lead formate and manganese bromide, etc., and anti-coloring agents, or the transparency (transparency) of the film is impaired. Pigments or dyes may be added to the extent that they do not exist, and the surface may be matte with a satin pattern. Further, the above water-soluble resin may be coated or formed into a film and laminated. In the case of the inner surface, the outer surface of the film or the laminated coating, the interface can be printed.

The polyvinyl resin film used in the present invention is a film produced by a known method such as a solution casting method, a melt casting method or a melt extrusion method. Water resistance of film,
Heat treatment or stretching may be added to improve the mechanical strength.

As the waterproofing agent used in the present invention, a polyvinyl chloride resin, a polyvinylidene chloride resin, a trifluorochloroethylene resin, a tetrafluoride resin having a low water absorption rate, as long as the resulting envelope does not impair the water solubility. Ethylene resin and silicone resin (including silane and silane coupling agent) are preferable, and urethane resin having a water supply rate of 0 to 0.5% is particularly preferable. The urethane resin is not particularly limited as long as it improves water resistance. The coating thickness is not particularly limited as long as the obtained envelope film does not impair the water solubility, but is usually 1 to 10 μm or less, preferably 2 to 8 μm.
Is. When it is less than 1 μm, pinholes and the like are generated and water resistance which is not enough to be used as an envelope film is often not obtained. When it exceeds 10 μm, dispersibility or dissolution in hot water at 70 ° C or less under normal pressure. It is not practical because the water resistance tends to deteriorate and the water resistant agent tends to remain in the form of a film. As a method for applying the urethane resin or the like to the polyvinyl alcohol-based resin film, a conventionally known method such as gravure, reverse or spray can be used, and if necessary, drying and heat treatment can be performed. The water-proofing agent may be applied to the outer surface of the envelope, but may be applied to both the inner and outer surfaces.

[0011]

[Function] The paper can be recycled together with ordinary papers. Especially, in the case of a window envelope, the step of peeling the window film from the window envelope at the time of recycling is unnecessary, and the window envelope can be easily recycled. Become.

[0012]

EXAMPLES Hereinafter, specific embodiments of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

(Example) Various polyvinyl alcohols shown in Table 1 were dissolved in water by heating, and this solution was applied to a sheet having a thickness of 100.
Apply to a polyethylene terephthalate resin of μm with a bar coater so that the thickness after drying becomes 35 μm.
After drying at 0 ° C. for 10 minutes, only the polyvinyl alcohol film obtained by peeling from the polyethylene terephthalate resin was heat-treated at 200 ° C. for 30 seconds.

A urethane resin [METNo. 17-1 manufactured by Dainippon Ink and Chemicals, Inc.] was added to the sample obtained by the above operation.
0] was applied to one side or both sides of the film with a bar coater and dried at 80 ° C. for 30 seconds with hot air. With respect to the polyvinyl alcohol-based resin film subjected to the water resistance treatment in this manner, a water solubility test and a water resistance test described later in (1) and (2) of the evaluation test are performed, and each film is evaluated based on the water resistance test. The results were shown in Table 1. No. 1 and No.
The film of No. 5 was dispersed in 50 ° C. hot water with stirring for 1 hour,
The films No. 2, No. 3 and No. 4 were dissolved after stirring for 1 hour in warm water at 50 ° C. Regarding the water resistance, no deformation was observed in all the films.

[0015]

[Table 1]

(Comparative Example 1) Polyvinyl alcohol shown in Table 2 was formed into a film by the same method as in Examples, and then urethane resin was applied to one side or both sides of the film with a bar coater and dried at 80 ° C for 30 seconds with hot air. . The results are shown in Table 2. The No. 1 and No. 4 films did not disperse or dissolve even after stirring in warm water at 50 ° C. for 5 hours, but no film deformation was observed in the water resistance test. No.
The film of 3 was dissolved in warm water at 50 ° C., but deformation of the film was observed in the water resistance test. The film of No. 2 had a small mechanical strength and could not be formed into a film.

[0017]

[Table 2]

Comparative Example 2 A polyethylene terephthalate resin film (15 μm) was subjected to a water solubility test and a water resistance test. As a result, in the water resistance test, no deformation of the film was observed and the film was good, but no dispersion or dissolution was observed in hot water at 50 ° C., which was poor.

(Evaluation Test Method) (1) Water Solubility Test The change was confirmed by immersing the film in warm water at 50 ° C. ◯: dissolved, Δ: dispersed, ×: insoluble. (2) Water resistance test Changes in the film after being left for 1 hour in a constant temperature and humidity chamber at 60 ° C and 80% were confirmed. ◯: No deformation, ×: There is deformation.

[0020]

EFFECT OF THE INVENTION The envelope film of the present invention is a conventional envelope film made of polyethylene terephthalate resin or olefin resin such as polypropylene and polystyrene, or window covering for envelopes, which is different from a physical film in that it is 5 Disperse or dissolve in water at 70 ° C. Therefore, when recycling envelopes, the envelopes using polyethylene terephthalate resin or olefin resin as window film for envelopes cannot be recycled together with ordinary paper because these films are insoluble in water or warm water. In particular, in the case of envelope window covering films, these films must be peeled off from the envelope once, but the envelope film of the present invention does not need to do this work, and can be recycled together with ordinary papers. be able to.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kiyofumi Tanaka 1-406, Yoshino-cho, Omiya-shi, Saitama 1 Shin-Etsu Polymer Co., Ltd. Tokyo factory (72) Inventor Yusuke Morita 1-406, Yoshino-cho, Omiya-shi, Saitama 1 Shin-Etsu Polymer Co., Ltd. Tokyo factory

Claims (1)

[Claims] 1. A saponification degree of 50 to 99 mol%, an average degree of polymerization of 10
An envelope film, which is obtained by coating a waterproofing agent on at least the outer surface of a film made of 0 or more polyvinyl alcohol resin.