JPH09324094A - Water-resistant polyvinyl alcohol composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a water-resistant polyvinyl alcohol compsn. which gives an aq. soln. having long pot life, is excellent in workability, and exhibits excellent heat resistance either when dried at low temps. or when thermally treated by compounding specified amts. of a specific PVA resin and a specific epoxy compd. SOLUTION: This compsn. comprises 100 pts.wt. PVA resin which is produced by, e.g. partly or wholly saponifying a copolymer of a vinyl ester monomer (e.g. vinyl acetate) and a vinyl monomer having at least one functional group selected from among amino, formamido, carbamate, and imido groups (e.g. N-vinylformamide) and contains 0.1-50mol%, pref. 2-20mol%, amino groups in the molecule and 0.1-100 pts.wt. compd. having at least two epoxy groups in the molecule (e.g. ethylene glycol diglycidyl ether).

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polyvinyl alcohol composition having excellent water resistance.

[0002]

2. Description of the Related Art Conventionally, polyvinyl alcohol has been widely used as a surface-treating paste for various films, binders, adhesives, paper and the like due to its excellent film-forming property and strength. However, since polyvinyl alcohol is water-soluble, it has a drawback that it has low water resistance as it is, and various methods have been studied for the purpose of improving water resistance. For example, a method is known in which a polyvinyl alcohol molecule is crosslinked with a metal salt, an aldehyde such as formaldehyde, or a dimethyl compound of urea or melamine to obtain a water resistant product. Also,
Japanese Unexamined Patent Publication No. 57-30751 discloses a water resistant method of crosslinking modified polyvinyl alcohol having an acetoacetyl group introduced into a polyvinyl alcohol molecule with an ammonium salt, and Japanese Unexamined Patent Publication No. 6-172727 discloses the same. A water resistant method is disclosed in which polyvinyl alcohol having an acetoacetyl group introduced is crosslinked with a hydrazine compound.

[0003]

Generally, the crosslinking reaction between a crosslinking agent and polyvinyl alcohol is carried out by preparing an aqueous solution of polyvinyl alcohol in advance and adding the crosslinking agent therein. In the reaction using the above-mentioned cross-linking agent, the cross-linking reaction of polyvinyl alcohol occurs rapidly, so that the viscosity of the aqueous solution rapidly increases due to the three-dimensionalization of the polyvinyl alcohol molecule and the generation of gel occurs. However, there was a problem that the workability was extremely poor due to the short time (pot life).

Further, when water resistance is made by using metal salts, there is a problem that thermal stability is poor and coloring during heating is remarkable. Further, when water-proofed by using a dimethylol compound of formaldehyde, urea or melamine, formaldehyde remains in the resin, and there is a problem that the application is limited from the viewpoint of safety. In the case of introducing an acetoacetyl group into a polyvinyl alcohol molecule to make it water resistant, there is a problem that the synthetic method is complicated and is an industrially disadvantageous method.

The object of the present invention is that it can be used for a long time even in an aqueous solution containing a cross-linking agent, it is excellent in workability, and it is excellent even if it is dried at a relatively low temperature or heat-treated. It is intended to provide a polyvinyl alcohol-based water resistant composition exhibiting water resistance.

[0006]

In order to achieve the above object, a polyvinyl alcohol-based water-resistant composition of the present invention comprises (A) a polyvinyl alcohol containing 0.1 to 50 mol% of amino groups in the molecule. 100 parts by weight of resin and (B)
Compound having two or more epoxy groups in the molecule 0.1-
It is characterized by comprising 100 parts by weight.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. The polyvinyl alcohol-based resin containing an amino group used in the present invention has an amino group in its side chain, and is selected from vinyl ester monomers and amino groups, formamide groups, carbamate groups, imide groups and the like. And a partially saponified product of a copolymer with a vinyl monomer having one or more kinds of functional groups. The formamide group, the carbamate group, and the imide group generate an amino group during saponification, but some of them may remain unreacted.

The vinyl ester monomer used to obtain the above copolymer includes vinyl formate, vinyl acetate,
Examples thereof include vinyl propionate, vinyl pivalate, vinyl versatate, and the like, among which vinyl acetate is industrially preferable.

Examples of the vinyl monomer having an amino group used for obtaining the above-mentioned copolymer include allylamine and the like, and as the vinyl monomer having a formamide group, a carbamate group, an imide group and the like. Examples thereof include vinyl compounds having a functional group that produces an amino group by hydrolysis with an acid or an alkali, such as N-vinylformamide, N-vinylcarbamate, N-vinylglycolimide, and N-vinylphthalimide. Among them, N-vinylformamide is industrially preferable because it has good copolymerizability with vinyl acetate and, when copolymerized, the saponification reaction with an acid or an alkali easily proceeds.

The above vinyl ester monomer and amino group,
As a method of copolymerizing with a vinyl monomer having one or more kinds of functional groups selected from formamide group, carbamate group, imide group and the like, conventionally known bulk polymerization, solution polymerization,
Various polymerization methods such as suspension polymerization and emulsion polymerization are possible,
Among them, solution polymerization using methanol as a solvent is industrially preferable.

As a method for saponifying the copolymer thus obtained, conventionally known alkali saponification or acid saponification can be applied. Among them, alkali hydroxide is used in a methanol solution. The method of alcohol decomposition is industrially preferable.

The content of amino groups in the polyvinyl alcohol resin containing amino groups is 0.1 to 50 mol%, preferably 0.2 to 20 mol%. When the content of the amino group is less than 0.1 mol%, the water resistance effect is small. Further, even if the content of the amino group exceeds 50 mol%, not only the water resistance effect becomes saturated, but also the hygroscopicity of the resin becomes high and the mechanical strength decreases. Also,
The degree of polymerization and the degree of saponification of the copolymer are not particularly limited, but the degree of polymerization is preferably 300 to 3,000, and the degree of saponification is preferably 60 mol% or more.

The polyvinyl alcohol resin containing an amino group in the molecule used in the present invention is a vinyl ester monomer, an amino group, a formamide group, a carbamate group, as long as the effect of the present invention is not impaired. Monomers copolymerizable with vinyl monomers having one or more kinds of functional groups selected from imide groups, that is, unsaturated monocarboxylic acids such as crotonic acid, acrylic acid and methacrylic acid and their esters, salts and anhydrides. Compounds, amides, nitriles, unsaturated sulfonic acids and salts thereof, α-olefins having 2 to 30 carbon atoms, alkyl vinyl ethers, vinyl pyrrolidone, and the like may be used for copolymerization. In addition, a polyvinyl alcohol resin obtained by copolymerization may be post-modified by a reaction such as acetalization, urethanization, etherification, grafting, or phosphoric acid esterification.

Next, 2 in the molecule used in the present invention.
Examples of the compound having at least one epoxy group include, for example,
Ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, neopentyl glyco-
Ludiglycidyl ether, glycerol-diglycidyl ether, glycerol triglycidyl ether, glycerol polyglycidyl ether, diglycerol polyglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-Hexanediol cyglycidyl ether, trimethylol propane polyglycidyl ether
Examples thereof include ter and sorbitol polyglycidyl ether. Particularly, ethylene glycol diglycidyl ether and the like are preferable since they have high reactivity with an amino group.
Further, a polymer having an epoxy group such as a polymer such as poly (glycidyl methacrylate) or a copolymer having glycidyl methacrylate as a monomer component, or an existing polymer is post-modified to obtain an epoxy group. It does not matter even if it is introduced.

The compound containing two or more epoxy groups in the molecule is used in an amount of 0.1 to 100 parts by weight based on 100 parts by weight of the amino group-containing polyvinyl alcohol resin, and 0.5 to 50 parts by weight is preferred. If the amount of the epoxy group-containing compound is less than 0.1 parts by weight, water resistance cannot be achieved, and if it exceeds 100 parts by weight, the water resistance effect becomes saturated, which is not economically advantageous. When the used epoxy group-containing compound is water-soluble, the unreacted compound may be eluted in water to lower the water resistance.

The water resistant composition of the present invention is usually used by dissolving it in water. At this time, a method of mixing a liquid epoxy group-containing compound or a solution thereof with a solution of an amino group-containing polyvinyl alcohol resin is usually used. Further, not limited to this method, a method of spraying, coating, dipping or the like with a compound having a liquid epoxy group or a solution thereof is applied to a molded product of a polyvinyl alcohol resin containing an amino group. The water resistant composition of the present invention exerts its effect by drying them. At this time, the water resistance effect is exhibited even at room temperature or by heat drying.

The water-resistant composition of the present invention includes the above-mentioned polyvinyl alcohol resin containing an amino group in the molecule, a compound having an epoxy group, and the water resistance and stability aimed at by the present invention are impaired. A solvent, various additives, another water-soluble resin, a polymer aqueous dispersion, or the like can be contained depending on the application as long as it is not present. Here, the additive is a plasticizer, various defoaming agents, various dispersants, nonionic or anionic surfactants, silane coupling agents, pH adjusting agents, and the like, and as the water-soluble resin, carboxymethyl cellulose , Cellulose derivatives such as hydroxyethyl cellulose, poly (meth) acrylic acid, polyhydroxy (meth) acrylate or copolymers thereof, (meth) acrylic polymers such as polyacrylamide, polyvinylpyrrolidone or the like. Copolymers and the like, and as the polymer dispersant, acrylic polymers and copolymers, ethylene-vinyl acetate copolymers, vinyl ester-based polymers and copolymers, styrene-butadiene copolymers and the like. An aqueous dispersion may be mentioned.

The reason why the water resistant composition of the present invention is excellent in water resistance is that the water-soluble polyvinyl alcohol is formed by the cross-linking reaction between the amino group contained in the polymer molecule and the epoxy group.
It is considered that the resin of this type becomes insoluble in water and is made water resistant. In addition, a mixed aqueous solution of a polyvinyl alcohol resin containing an amino group and a compound containing an epoxy group does not cause gelation or a rapid increase in viscosity. Although this has not been fully clarified, the crosslinking reaction does not easily occur in the aqueous solution because the amino group and the epoxy group are present at a relatively low concentration, and the crosslinking reaction gradually occurs as the water evaporates during the drying process. Thought to happen.

The water-resistant composition obtained by the present invention is useful as an adhesive (including an emulsion-dispersed system), a paper coating agent, a packaging film, and a binder, but is not limited thereto. Not a thing.

[0020]

EXAMPLES Next, the present invention will be specifically described with reference to examples. In addition, "%" and "part" in the examples represent weight basis unless otherwise specified.

Here, the water-insoluble content as an index of water resistance of the obtained water-resistant composition was 95 (dry weight W ₁ ) of the sample.
After dipping in hot water at ℃ for 1 hour and drying at 105 ℃, the weight W ₂ was measured and calculated by the following formula. Water insoluble matter rate (%) = (W ₂ / W ₁ ) × 100

The viscosity of the resulting aqueous solution of the water resistant composition was measured using a B type viscometer at 30 ° C. and 10 rpm. Furthermore, the criteria for evaluation of viscosity stability were set as follows. ◯: (viscosity 24 hours after addition of crosslinking agent) / (viscosity immediately after addition of crosslinking agent) <1.1 x: (viscosity after 24 hours addition of crosslinking agent) / (viscosity immediately after addition of crosslinking agent)> 1 In case of 1 or gelation

The criteria for comprehensive evaluation are defined as follows. ⊚: Viscosity stability is good, water insoluble content is 95% or more. ◯: Viscosity stability is good, water insoluble content is 90% or more and 95%.
Less than x: Poor viscosity stability or water insoluble content of 90%
Less than

Synthesis Example of Polyvinyl Alcohol-Based Resin Containing Amino Group in Molecule Synthesis Example 1 767 parts of vinyl acetate and N-vinylformamide are placed in a flask equipped with a stirrer, a thermometer, and a dropping funnel reflux condenser. After 26 parts and 207 parts of methanol were charged and the system was replaced with nitrogen, the internal temperature was raised to 60 ° C. To this system was added 0.06 part of 2,2-azobisisobutyrylonitrile to initiate polymerization. After 6 hours, m-dinitrobenzene was added as a polymerization inhibitor to terminate the polymerization. 50% methanol solution of vinyl acetate copolymer containing 5.2 mol% of N-vinylformamide copolymerization component while distilling off the remaining vinyl acetate while adding methanol vapor to the obtained reaction product. Got 50 parts of this solution, 5 parts of methanol, and 1 part of a 4% methanol solution of sodium hydroxide were thoroughly mixed with stirring, and a saponification reaction was carried out at 40 ° C.
Polyvinyl alcohol containing 5.2 mol% of amino groups (the degree of hydrolysis of formamide groups is about 100 mol%) in the molecule is obtained by pulverizing the obtained gel-like substance, washing it well with methanol and then drying it. A system resin was obtained. The degree of polymerization of this resin was 1740 and the degree of saponification was 99.3 mol%.

Synthetic Examples 2 to 4 Polyvinyl alcohol resins as shown in Table 1 were obtained in the same manner as in Synthetic Example 1 by changing the charged composition. The degree of modification in this case is expressed by the mol% of amino group content.

[0026]

[Table 1]

Example 1 Polyvinyl alcohol resin containing 5.2 mol% of amino groups obtained in Synthesis Example 1 (polymerization degree: 1740, saponification degree: 9)
9.3 mol%) 100 parts of a 10% aqueous solution containing 10 parts of ethylene glycol diglycidyl ether, cast on polyethylene terephthalate sheet, dried at 20 ° C., and a transparent film having a thickness of 100 μm. Was prepared, and the water-insoluble matter ratio when this film was immersed in hot water for 1 hour was measured, and it was a good value of 95%. Moreover, when the viscosity of the aqueous solution before the cast film was prepared was measured at 30 ° C., the viscosity immediately after the addition of the crosslinking agent was 1,560 mPa · s.
s, 1,540 mPa after standing at 30 ° C. for 24 hours
-It was s. The viscosity increase ratio after 24 hours was 0.99, and the viscosity stability was good.

Example 2 A film was prepared in the same manner as in Example 1 except that 1 part of glycerol diglycidyl ether was added instead of 10 parts of ethylene glycol diglycidyl ether, and its water-insoluble content was determined. When measured, it was a good value of 87%. Further, when the viscosity of the aqueous solution at 30 ° C. before making the cast film was measured, the viscosity immediately after the addition of the crosslinking agent was 1,
It was 550 mPa · s and was 1,520 mPa · s after standing at 30 ° C. for 24 hours. The viscosity increase factor after 24 hours was 0.98, and the viscosity stability was good.

Example 3 A film was prepared in the same manner as in Example 1 except that 20 parts of 1,6-hexanediol-diglycidyl ether was added instead of ethylene glycol-diglycidyl ether. When the insoluble content was measured, it was a good value of 93%. Moreover, when the viscosity of the aqueous solution before the cast film was measured at 30 ° C., the viscosity immediately after the addition of the crosslinking agent was 1,560 mPa · s, and it was 1,550 mPa · s after standing at 30 ° C. for 24 hours. . The viscosity increase ratio after 24 hours was 0.99, and the viscosity stability was good.

Example 4 Polyvinyl alcohol resin containing 0.5 mol% of the amino group obtained in Synthesis Example 2 (polymerization degree: 1760, saponification degree: 9)
9.1 mol%) to 10% aqueous solution containing 100 parts of ethylene glycol diglycidyl ether, 10 parts of this aqueous solution was cast onto a polyethylene terephthalate sheet, dried at 20 ° C., and transparent with a thickness of 100 μm. I made a new film. When the water insoluble content of this film when immersed in hot water for 1 hour was measured, it was a good value of 85%. Also, the temperature of the aqueous solution before making the cast film is 30 °
The viscosity immediately after the addition of the cross-linking agent was 1,620 mPa · s, and it was 1,630 mPa · s after standing at 30 ° C. for 24 hours. The viscosity increase ratio after 24 hours was 1.01, and the viscosity stability was good.

Example 5 Polyvinyl alcohol resin containing 18 mol% of amino groups obtained in Synthesis Example 3 (polymerization degree: 1030, saponification degree: 9)
9.4 mol%) to 10% aqueous solution containing 100 parts of ethylene glycol diglycidyl ether, and 10 parts of this aqueous solution was cast on a polyethylene terephthalate sheet and dried at 20 ° C. to obtain a transparent film having a thickness of 100 μm. I made a new film. When the water insoluble content of this film when immersed in hot water for 1 hour was measured, it was a good value of 97%. Also, the temperature of the aqueous solution before making the cast film is 30 ° C.
The viscosity immediately after addition of the cross-linking agent was 4
40 mPa · s, 45 after standing at 30 ° C. for 24 hours
It was 0 mPa · s. The viscosity increase factor after 24 hours is 1.0
It was twice, and the viscosity stability was good.

Example 6 Ethylene glycol diglycidyl ether was added in an amount of 6
A film was prepared in the same manner as in Example 1 except that the content was changed to 0 part, and the water-insoluble content was measured, and it was a good value of 90%. Moreover, when the viscosity of the aqueous solution before the cast film was measured at 30 ° C., the viscosity immediately after the addition of the crosslinking agent was 1,510 mPa · s, which was 24 at 30 ° C.
It was 1,520 mPa · s after being left for an hour. The viscosity increase ratio after 24 hours was 1.01, and the viscosity stability was good.

Comparative Example 1 10 parts of ethylene glycol diglycidyl ether was added to a 10% aqueous solution containing 100 parts of completely saponified polyvinyl alcohol (polymerization degree: 1740, saponification degree: 99.0 mol%), and this aqueous solution was added to a polyethylene terephthalate sheet. It was cast on the surface and dried at 20 ° C. to form a transparent film having a thickness of 100 μm. When the water insoluble content of this film when immersed in hot water for 1 hour was measured, it was a very bad value of 0%. The viscosity of the aqueous solution at 30 ° C. before the cast film was measured was 1,070 mPa · s immediately after the addition of the cross-linking agent, and 1,040 mPa · s after standing at 30 ° C. for 24 hours. . The viscosity increase ratio after 24 hours was 0.97 times.

Comparative Example 2 Polyvinyl alcohol resin containing 5.2 mol% of amino groups obtained in Synthesis Example 1 (polymerization degree 1740, saponification degree 9
0.01 part of ethylene glycol diglycidyl ether was added to a 10% aqueous solution containing 100 parts of 9.3 mol%), the aqueous solution was cast on a polyethylene terephthalate sheet, and dried at 20 ° C., A transparent film having a thickness of 100 μm was prepared. When the water insoluble content of this film when immersed in hot water for 1 hour was measured, it was a very poor value of 11%. The viscosity of the aqueous solution before the cast film was measured at 30 ° C. was 1,520 mPa · s immediately after the addition of the cross-linking agent, and 1,520 mPa · s after standing at 30 ° C. for 24 hours. . The thickening ratio after 24 hours was 1.00.

Comparative Example 3 Polyvinyl alcohol resin containing 5.2 mol% of amino groups obtained in Synthesis Example 1 (polymerization degree 1740, saponification degree 9
120 parts of ethylene glycol diglycidyl ether was added to a 10% aqueous solution containing 100 parts of 9.3 mol%), and this aqueous solution was cast on a polyethylene terephthalate sheet and dried at 20 ° C. to a thickness of 100 μm. I made a transparent film. When the water insoluble content of this film when immersed in hot water for 1 hour was measured, it was a bad value of 53%. In addition, the temperature of the aqueous solution before making the cast film is 30 ° C.
The viscosity immediately after the addition of the crosslinking agent was 1,470 mPa · s, and the viscosity was 1,520 mPa · s after standing at 30 ° C. for 24 hours. The viscosity increase ratio after 24 hours was 1.03 times.

Comparative Example 4 10 parts of adipic dihydrazide was added to a 10% aqueous solution containing 100 parts of polyvinyl alcohol resin (polymerization degree 500, saponification degree 98.5 mol%) containing 5.0 mol% of acetoacetyl groups. , Was cast on a polyethylene terephthalate sheet and dried at 20 ° C. to form a transparent film having a thickness of 100 μm, and when the film was immersed in hot water for 1 hour, the water insoluble content was measured to be 97%. Was a good value. However, when the viscosity of the aqueous solution before making the cast film was measured at 30 ° C., the viscosity immediately after the addition of the crosslinking agent was 420 mPa · s.
After left for a while, it had already gelled, and the viscosity after 24 hours could not be measured.

Comparative Example 5 Polyvinyl alcohol resin containing 60 mol% of amino groups obtained in Synthesis Example 4 (polymerization degree: 1730, saponification degree: 9)
8.6 mol%) was added to 10% aqueous solution containing 100 parts of ethylene glycol diglycidyl ether, and the aqueous solution was cast on a polyethylene terephthalate sheet and dried at 20 ° C. No cast film was obtained due to its high hygroscopicity. When the viscosity of the aqueous solution before the cast film was measured at 30 ° C., the viscosity immediately after the addition of the crosslinking agent was 1,670 mPa · s, and it was 1,700 mPa · s after standing at 30 ° C. for 24 hours. . The viscosity increase ratio after 24 hours was 1.02.

[0038]

[Table 2]

[0039]

As is apparent from the above description, according to the present invention, the usable time is long even in the state of the aqueous solution containing the crosslinking agent, the workability is excellent, and the drying is performed at a relatively low temperature. Even if it heat-processes, the polyvinyl-alcohol-type water resistant composition which shows the outstanding water resistance can be provided.

Claims (1)

[Claims] 1. 100 parts by weight of a polyvinyl alcohol resin containing (A) an amino group in an amount of 0.1 to 50 mol% and (B) a compound having two or more epoxy groups in an amount of 0.1 to 0.1. A polyvinyl alcohol-based water resistant composition comprising 100 parts by weight.