JP2006137845A - Modified polyvinyl alcohol composite resin and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a modified polyvinyl alcohol composite resin capable of forming coating film of high water resistance, especially moist heat resistance. <P>SOLUTION: The modified polyvinyl alcohol composite resin is obtained by dissolving a low-saponification degree polyvinyl alcohol in a hydrophobic solvent and carrying out a radical polymerization of a radical-polymerizable ethylenically unsaturated monomer in the presence of a polymerization initiator. This modified polyvinyl alcohol composite resin has such a structure that the polymeric portion formed from the radical-polymerizable ethylenically unsaturated monomer is grafted to the polyvinyl alcohol. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a resin that can be dissolved or dispersed in a non-hydrophilic solvent.

  One of constituent members of a liquid crystal display device is a polarizing film. Polyvinyl alcohol is frequently used for various applications including a polarizing film. Polyvinyl alcohol has characteristics such as transparency of the film itself and high orientation during stretching. However, since polyvinyl alcohol itself is a water-soluble polymer, it has a problem that the polyvinyl alcohol film is deformed and its optical properties are deteriorated because it easily absorbs water in a water resistance, particularly in a heat and moisture resistance test.

  As a method for solving these problems, polyimide is used as an alternative to polyvinyl alcohol. However, since polyimide itself is thermosetting, when the substrate is a film, it cannot be directly applied and heat-cured, which complicates the coating process. Also, the adhesion to the substrate has not reached a practical level.

On the other hand, it is also conceivable to improve water resistance with a coating film formed from a coating agent containing a composite resin obtained by grafting an acrylic monomer rich in hydrophobicity to polyvinyl alcohol. However, since polyvinyl alcohol is generally rich in hydrophilicity, it is necessary to carry out the grafting reaction in a hydrophilic solvent such as water. However, a hydrophobic acrylic monomer cannot be stably grafted in a hydrophilic solvent. Furthermore, even if the polymer portion formed from the hydrophobic acrylic monomer can be grafted onto polyvinyl alcohol, the solubility of the resulting composite resin in water or the like cannot be ensured and a stable resin solution cannot be obtained.
In addition, if a hydrophilic acrylic monomer is used, a stable composite resin solution can be obtained. However, since the entire composite resin is hydrophilic, improvement in water resistance and heat and moisture resistance of the coating film cannot be expected.

  An object of the present invention is to provide a modified polyvinyl alcohol composite resin suitable for a coating agent capable of forming a coating film having excellent water resistance, particularly moisture and heat resistance.

  As a result of intensive studies on the polyvinyl alcohol, the present inventors have found that the coating film of the modified polyvinyl alcohol composite resin having a structure in which an acrylic monomer component is grafted into the polyvinyl alcohol resin skeleton is excellent in water resistance, particularly moisture and heat resistance. And found the present invention.

That is, the present invention relates to a modified polyvinyl alcohol composite resin having a structure in which a polymer portion formed from a radically polymerizable ethylenically unsaturated monomer is grafted onto polyvinyl alcohol, and the polyvinyl alcohol has a saponification degree of 50% or less. It is preferable.
The polymer portion formed from radically polymerizable ethylenically unsaturated monomer is ethylene containing at least one functional group selected from the group consisting of hydrolyzable silyl group, carboxyl group, epoxy group and hydroxy group. It is preferably formed from a radically polymerizable ethylenically unsaturated monomer having a polymerizable unsaturated monomer as an essential component, and the ethylenically unsaturated monomer containing a functional group is ethylene capable of radical polymerization. The content is preferably 0.1 to 20% by weight in 100% by weight of the unsaturated monomer.
Moreover, it is preferable that the polyvinyl alcohol part and polymer part which comprise modified polyvinyl alcohol are 80-20: 20-80 (weight ratio).

Further, the present invention is a modification characterized by dissolving polyvinyl alcohol having a saponification degree of 50% or less in a non-hydrophilic solvent and polymerizing an ethylenically unsaturated monomer capable of radical polymerization in the presence of a polymerization initiator. The present invention relates to a method for producing a polyvinyl alcohol composite resin.
The solubility parameter of the non-hydrophilic solvent is preferably 10 or less, and the polymerization initiator is preferably a peroxide.

  Furthermore, the present invention relates to a coating agent containing the modified polyvinyl alcohol composite resin described in the above invention, wherein the coating agent is at least one selected from the group consisting of a hydrolyzable silyl group, a carboxyl group, an epoxy group and a hydroxy group. It is preferable to further include a crosslinking agent having a reactive functional group capable of reacting with the functional group, and further to include a crosslinking catalyst for promoting the crosslinking reaction between the modified polyvinyl alcohol composite resin and the crosslinking agent.

  Moreover, this invention relates to the coating material which provides the coating layer formed from the coating agent as described in the said invention on a plastic base material.

  Since the modified polyvinyl alcohol composite resin of the present invention can form a coating film having excellent water resistance, particularly moisture and heat resistance, a coating agent for a viewing angle correction film or a retardation film, which is a liquid crystal display-related material, etc. Is preferably used.

  The polyvinyl alcohol used in the present invention preferably has a relatively high hydrophobic property in consideration of the water resistance of the coating film to be formed. Specifically, a polyvinyl alcohol that can be dissolved in a non-hydrophilic solvent described later is preferable. . The polyvinyl alcohol that can be dissolved in the non-hydrophilic solvent preferably has a saponification degree of 50% or less, more preferably 20 to 50%. If the degree of saponification is too low, it is not preferable because it exhibits properties as polyvinyl acetate rather than polyvinyl alcohol. For example, Kuraray Poval LM-20 (degree of saponification: 38 to 42%, the same applies hereinafter), LM-25 (33 to 38%, manufactured by Kuraray Co., Ltd.), Gohsenol LL-02 (45 to 50%), L-5407 (30 to 38%), L-7514 (34 to 41%, manufactured by Nippon Synthetic Chemical Co., Ltd.) and the like can be mentioned, and these can be used alone or in combination of two or more.

The non-hydrophilic solvent capable of dissolving polyvinyl alcohol used in the present invention preferably has a solubility parameter of 10 or less, more preferably 5.0 to 10.0.
When the solubility parameter is too high, it is difficult to dissolve polyvinyl alcohol having a low saponification degree, and when the modified polyvinyl alcohol composite resin of the present invention is obtained, polyvinyl alcohol is precipitated, or the composite resin is stored during storage after obtaining the composite resin. This is because there is a high possibility of precipitation.
Examples of such non-hydrophilic solvents include methyl acetate (solubility parameter: 9.6, the same shall apply hereinafter), ester solvents such as ethyl acetate (9.1), acetone (10.0), methyl ethyl ketone (9. 3).

Next, the radically polymerizable ethylenically unsaturated monomer used for forming the graft portion of the modified polyvinyl alcohol composite resin will be described.
The radically polymerizable ethylenically unsaturated monomer is a compound having an ethylenically unsaturated double bond and in which polymerization is induced by a radical.
Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) ) Acrylate, n-hexyl (meth) acrylate, dodecyl (meth) acrylate, n-stearyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, tetrahydrofurfurin ( (Meth) acrylate, 2-ethoxyethyl (meth) acrylate, polypropylene glycol mono (meth) acrylate, (meth) acrylonitrile, (meth) acrylamide, 2-hydroxyethyl (meth) acrylamide, Iaseton (meth) acrylamide, styrene, alpha-methyl styrene, vinyl toluene, vinyl acetate, and the like. These are not limited at all, and can be used alone or in combination of two or more.

  From the viewpoint of improving the water resistance of the formed coating film, the monomer constituting the graft polymer portion is preferably rich in hydrophobicity, and the solubility of the radically polymerizable ethylenically unsaturated monomer in water at 20 ° C. The thing below 10 wt% is good. Specifically, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, t-butyl (meth) Acrylate, n-hexyl (meth) acrylate, dodecyl (meth) acrylate, n-stearyl (meth) acrylate, cyclohexyl (meth) acrylate, benzyl (meth) acrylate, 2-methoxyethyl (meth) acrylate, tetrahydrofurfurin (meta ) Acrylate, 2-ethoxyethyl (meth) acrylate, polypropylene glycol mono (meth) acrylate, (meth) acrylonitrile, styrene, α-methylstyrene, vinyltoluene, vinyl acetate and the like. These can be used alone or in combination of two or more.

In the present invention, it is preferable to use an ethylenically unsaturated monomer containing various functional groups when forming a polymer portion grafted on polyville alcohol (hereinafter also referred to as a graft polymer portion). By introducing various functional groups into the graft polymer portion and reacting with a crosslinking agent contained in the coating agent described later, it is possible to form a hard coating film having excellent adhesion to the substrate.
Examples of the crosslinkable functional group used in the present invention include a hydrolyzable silyl group, a carboxyl group, an epoxy group, and a hydroxy group. In particular, when a monomer having a hydrolyzable silyl group is used, it is hard. Can be obtained.

  Specific examples of the ethylenically unsaturated monomer having a hydrolyzable silyl group include (meth) acryloxy such as γ- (meth) acryloxypropyltrimethoxysilane and γ- (meth) acryloxypropylmethyldimethoxysilane. Alkylalkoxysilane, (meth) acryloxyalkylalkoxyalkylsilane, trimethoxyvinylsilane, dimethoxyethylsilane, triethoxyvinylsilane, triethoxyallylsilane, vinylmethyldimethoxysilane, vinylmethyldiethoxysilane, vinyltris (2-methoxyethoxy) silane, etc. Is mentioned.

Specific examples of the ethylenically unsaturated monomer having a carboxyl group include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and styrene sulfonic acid.
Specific examples of the ethylenically unsaturated monomer having an epoxy group include glycidyl methacrylate, glycidyl cinnamate, glycidyl allyl ether, glycidyl vinyl ether, vinylcyclohexane monoepoxide, 1,3-butadiene monoepoxide, and the like.
Specific examples of the ethylenically unsaturated monomer having a hydroxyl group include 2-hydroxyethyl (meth) acrylate, 1-hydroxypropyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 4-hydroxybutyl ( Examples include meth) acrylate, polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polytetramethylene glycol mono (meth) acrylate, and hydroxystyrene. These are not limited at all, and can be used alone or in combination of two or more.
The amount of the ethylenically unsaturated monomer having a functional group involved in crosslinking is in the range of 0.1 to 20% by weight in 100% by weight of the ethylenically unsaturated monomer capable of radical polymerization. Is preferred. This is because when it exceeds 20% by weight, a large amount of unreacted components not involved in crosslinking tend to remain when reacted with the crosslinking agent, and the water resistance of the coating film is extremely lowered.

  In the modified polyvinyl alcohol composite resin of the present invention, the polyvinyl alcohol part and the graft polymer part are preferably 80 to 20:20 to 80 (weight ratio). If there are many polyvinyl alcohol parts, it will become difficult to ensure the water resistance of a coating film, and conversely if it is few, optical characteristics and adhesiveness will tend to be poor.

The modified polyvinyl alcohol composite resin of the present invention can be obtained, for example, by the following production method.
That is, polyvinyl alcohol having a low saponification degree is previously dissolved in a non-hydrophilic solvent, and a radically polymerizable ethylenically unsaturated monomer capable of forming a graft portion in the polyvinyl alcohol solution and a polymerization initiator, Is added, and a radically polymerizable ethylenically unsaturated monomer is radically polymerized to obtain a modified polyvinyl alcohol composite resin having a structure in which a polymer portion formed from the unsaturated monomer is grafted to polyvinyl alcohol. be able to. The grafting reaction is preferably performed at 50 to 90 ° C.

  As the non-hydrophilic solvent used in obtaining the modified polyvinyl alcohol composite resin of the present invention, those having a solubility parameter of 10 or less are preferable, and those exemplified above as those capable of dissolving polyvinyl alcohol are exemplified similarly. Can do. Among these, non-hydrophilic solvents having a boiling point of 100 ° C. or less are preferable, and these can be used alone or in combination of two or more. When an ester solvent such as methyl acetate or ethyl acetate having a boiling point of 100 ° C. or less or a ketone solvent such as acetone or methyl ethyl ketone is used, the drying process at the time of forming the coating film can be performed in a short time.

As the polymerization initiator, azobisisobutyronitrile, benzoyl peroxide, t-butylperoxy 2-ethylhexanate, or the like can be used. In order to perform the graft reaction more efficiently, a peroxide type is used. It is preferable to use the polymerization initiator.
The polymerization initiator is preferably used in the range of 0.1 to 20.0 parts by weight with respect to 100 parts by weight of the ethylenically unsaturated monomer capable of radical polymerization. A method of adding a polymerization initiator while dropping is good.

  In the modified polyvinyl alcohol composite resin of the present invention thus obtained, when radically polymerizing an ethylenically unsaturated monomer capable of radical polymerization, the tertiary hydrogen of polyvinyl alcohol is simultaneously extracted, and the polymer portion is present at that site. It is considered to have a combined structure.

Next, the coating agent of the present invention will be described.
The coating agent of the present invention contains the modified polyvinyl alcohol composite resin. When the acrylic polymer part constituting the modified polyvinyl alcohol composite resin has a functional group such as a hydrolyzable silyl group, a carboxyl group, an epoxy group, or a hydroxy group as described above, the functional group capable of reacting with these functional groups It is preferable to contain a crosslinking agent having The water resistance of the coating film to be formed is improved by the reaction between the functional group of the acrylic polymer part constituting the modified polyvinyl alcohol composite resin and the functional group of the crosslinking agent.
Typical crosslinking agents include toluylene diisocyanate, naphthylene-1,5-diisocyanate, o-toluylene diisocyanate, diphenylmethane diisocyanate, trimethylhexamethylene diisocyanate, isophorone diisocyanate, 4,4′-diphenylmethane diisocyanate, hexamethylene diisocyanate, m -Diisocyanates such as xylene diisocyanate, p-xylene diisocyanate, lysine diisocyanate, hydrogenated 4,4'-diphenylmethane diisocyanate, hydrogenated tolylene diisocyanate, or both terminal isocyanate adducts of these with glycols or diamines, triphenyl Multivalent such as methane triisocyanate, polymethylene polyphenyl isocyanate, coronate L Isocyanate,

  Ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, phthalic acid Bisepoxy compound such as diglycidyl ester, manufactured by Yuka Shell Epoxy Co., Ltd., trade name Epicoat 801, 802, 807, 815, 827, 828, 834, 815X, 815XA1, 828EL, 828XA, 1001, 1002, 1003, 1055, 1004 , 1004AF, 1007, 1009, 1010, 1003F, 1004F, 1005F, 1100L, 834X90, 10 1B80,1001X70,1001X75,1001T75,5045B80,5046B80,5048B70,5049B70,5050T60,5050,5051,152,154,180S65,180H65,1031S, epoxy resins such as 1032H60,604,157S70,

  Dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, glutaric acid, hexanedioic acid, citric acid, maleic acid, methyl nadic acid, dodecenyl succinic acid, sebacic acid, pyromellitic acid, hexahydrophthalic acid, tetrahydrophthalic acid, and the like An acid anhydride of Grixo monkey.

When the graft polymer portion constituting the modified polyvinyl alcohol composite resin has a hydroxyl group or a carboxyl group, it is preferable to use a diisocyanate, a bisepoxy compound, an epoxy resin, or the like as a crosslinking agent.
Moreover, when the graft polymer part which comprises modified polyvinyl alcohol composite resin has an epoxy group, it is preferable to use dicarboxylic acid and its anhydride, diisocyanate, polyvalent isocyanate, etc. as a crosslinking agent.
Two or more kinds of these crosslinking agents may be used, and the total amount used is preferably 1 to 100 parts by weight, more preferably 5 to 50 parts by weight with respect to 100 parts by weight of the composite resin.

Further, the coating agent of the present invention has a functional group in order to promote a crosslinking reaction between functional groups in the modified polyvinyl alcohol composite resin, or a crosslinking reaction between the functional group in the modified polyvinyl alcohol composite resin and the crosslinking agent. Depending on the, various crosslinking catalysts can be used.
Typical crosslinking catalysts include aluminum triacetylacetonate, iron triacetylacetonate, manganese tetraacetylacetonate, nickel tetraacetylacetonate, chromium hexaacetylacetonate, titanium tetraacetylacetonate, cobalt tetraacetylacetonate, etc. Metal alkoxides such as aluminum ethoxide, aluminum propoxide, aluminum butoxide, titanium ethoxide, titanium propoxide, titanium butoxide,

  Sodium acetate, tin octylate, lead octylate, cobalt octylate, zinc octylate, calcium octylate, lead naphthenate, cobalt naphthenate, dibutyltin dioctate, dibutyltin dilaurate, dibutyltin malate dibutyltin di (2-ethyl) Metal salt compounds such as hexoate), formic acid, acetic acid, propionic acid, p-toluenesulfonic acid, trichloroacetic acid, phosphoric acid, monoalkyl phosphoric acid, dialkyl phosphoric acid, β-hydroxyethyl (meth) acrylate phosphate ester Acidic compounds such as monoalkyl phosphorous acid and dialkyl phosphorous acid,

  Acids such as p-toluenesulfonic acid, phthalic anhydride, benzoic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, formic acid, acetic acid, and their ammonium salts, lower amine salts, polyvalent metal salts, sodium hydroxide, lithium chloride , Diethylzinc, tetra (n-butoxy) titanium, and other organometallic compounds, dicyclohexylamine, triethylamine, N, N-dimethylbenzylamine, N, N, N ′, N′-tetramethyl-1,3-butanediamine And amines such as diethanolamine, triethanolamine, and cyclohexylethylamine.

When the modified polyvinyl alcohol composite resin has a hydrolyzable silyl group, it is preferable to use a metal complex compound, a metal alkoxide, a metal salt compound, an acidic compound, etc. among these crosslinking catalysts. In particular, the use of tin compounds such as dibutyltin diacetate, dibutyltin dioctate, dibutyltin dilaurate, and dibutyltin dimaleate and p-toluenesulfonic acid is preferred. When an ethylenically unsaturated monomer having a carboxyl group is used, it is preferable to use acids and their ammonium salts, lower amine salts, polyvalent metal salts and the like.
In addition, when the modified polyvinyl alcohol composite resin has an epoxy group, it is preferable to use an organometallic compound, an amine or the like as a crosslinking catalyst.
When the modified polyvinyl alcohol composite resin has a hydroxyl group, it is preferable to use an acidic compound, an acid and an ammonium salt thereof, a lower amine salt, a polyvalent metal salt, or the like as a crosslinking catalyst.
Two or more kinds of these crosslinking catalysts may be used, and the total amount used is 0.01 to 10 parts by weight, preferably 0.1 to 5 parts by weight, based on 100 parts by weight of the composite resin composition. .

Moreover, you may further mix | blend and use additives, such as a silane coupling agent, a leveling agent, and an antifoamer, in the coating agent of this invention as needed.
Specific examples of the silane coupling agent include tetrafunctional silanes such as tetramethoxysilane and tetraethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, γ-chloropropyltrimethoxysilane, and β- (3,4-epoxycyclohexyl). ) Ethyltrimethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltriethoxysilane, γ-isocyanatopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-morpholinopropyltrimethoxysilane, γ-morpholinopropyltriethoxy A trifunctional silane such as lanthanum, and a bifunctional silane in which a part of the trifunctional silane is substituted with an alkyl group, a phenyl group, a vinyl group, etc., such as dimethyldimethoxysilane, phenylmethyldimethoxysilane, vinylmethyldimethoxysilane, γ -Chloropropylmethyldimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane and the like.
Two or more types of silane coupling agents may be used, and the total amount used is preferably 0.1 to 100 parts by weight with respect to 100 parts by weight of the modified polyvinyl alcohol composite resin. More preferably, it is used within the range of parts.

The coating agent of the present invention can be used for coating various substrates. That is, a coating material can be obtained by applying the coating agent of the present invention to various substrates by various methods, and curing the coating film through drying and crosslinking.
Examples of the substrate include various materials and shapes, and a plastic sheet-like (film-like) substrate is preferable. Examples of the plastic sheet-like (film-like) substrate include polyethylene terephthalate, polycarbonate, polystyrene, polyamide, polyolefin, cellulose acylate and the like, and cellulose acylate-based triacetate cellulose substrate is particularly preferable.
Examples of the coating method include an extrusion coating method, a die coating method, a direct gravure coating method, and a reverse gravure coating method.

  The following examples illustrate the invention. In the examples, “part” represents “part by weight” and “%” represents “% by weight”.

Example 1
Polyvinyl alcohol LM-20 (degree of saponification: 39%) 50.0 parts by weight and methyl ethyl ketone 898.8 parts by weight were charged and dissolved in a 2000 ml reaction vessel equipped with a stirrer, a thermometer and a refluxer. Next, after the inside of the reaction vessel was saturated with nitrogen gas and the internal temperature was raised to 80 ° C., the acrylic monomer mixture shown in Table 1 and 1.25 parts by weight of benzoyl peroxide as a polymerization initiator were taken over 2 hours. The solution was then aged for 3 hours to obtain a modified polyvinyl alcohol composite resin solution having a solid content of about 10% by weight.

Examples 2-3
According to the composition shown in Table 1, an acrylic modified polyvinyl alcohol composite resin solution having a solid content of about 10% by weight was obtained in the same manner as in Example 1.

Production Example 1
Except that polyvinyl alcohol was not used, the acrylic monomer shown in the composition shown in Table 1 was polymerized in the same manner as in Example 1 to obtain an acrylic polymer solution having a solid content of about 10% by weight.

Production Example 2
50.0 parts by weight of polyvinyl alcohol LM-20 (degree of saponification: 39%) was dissolved in 900 parts by weight of methyl ethyl ketone to obtain a polyvinyl alcohol solution having a solid content of about 10% by weight.

Examples 4, 7, and 8
Each modified polyvinyl alcohol composite resin solution obtained in Examples 1 to 3 was directly used as a coating agent, applied on an untreated triacetate cellulose film with a bar coater, dried at 80 ° C. for 10 minutes, A coated product having a thickness of 0.5 μm was prepared. Further, various tests described below were performed on the obtained coated product. The results are shown in Table 2.

Example 5
To 50 parts of the modified polyvinyl alcohol composite resin solution obtained in Example 1 (5 parts of solid content), 0.5 part of hexyltrimethoxysilane was added as a crosslinking agent, and 5 parts of methyl ethyl ketone was further added, and the solid content was about 10%. Coating agent was obtained. Hereinafter, evaluation was made in the same manner as in Example 4, and the results are shown in Table 2.

Example 6
To 50 parts of the modified polyvinyl alcohol composite resin solution obtained in Example 1 (5 parts solids), 0.5 part of hexyltrimethoxysilane as a crosslinking agent and 0.05 part of dibutyltin laurate as a crosslinking catalyst were added, Further, 4.95 parts of methyl ethyl ketone was added to obtain a coating agent having a solid content of about 10%. Hereinafter, evaluation was made in the same manner as in Example 4, and the results are shown in Table 2.

Comparative Examples 1 and 2
The polyvinyl alcohol solution obtained in Production Example 1 and the acrylic polymer solution obtained in Production Example 2 were used as coating agents as they were. Hereinafter, evaluation was made in the same manner as in Example 4, and the results are shown in Table 2.

Comparative Example 3
The polyvinyl alcohol solution obtained in Production Example 1 and the acrylic polymer solution obtained in Production Example 2 were mixed at a ratio of 50/50. Hereinafter, evaluation was made in the same manner as in Example 4, and the results are shown in Table 2.

[Evaluation methods]
<Water resistance>: A drop of water was dropped on the surface of the coated product, allowed to stand for 1 minute, and the coated surface after wiping off the dropped water droplet was visually observed.
A: No change is seen at all.
○: Whitening occurs when water drops are attached, but no change is observed after the water drops are wiped off.
X: Swelling and peeling are seen on the water drop adhesion surface.
<Heat and heat resistance>: The coated material was stored in a thermostatic chamber at 60 ° C. × 90% for 1000 hours, and then the coated surface was visually observed.
○: No abnormality is observed.
X: Swelling and peeling are observed.
<Adhesiveness>: A cellophane tape is applied to the surface of the coating, and then pulled vertically to peel it off.
A: No peeling at all.
○: The coated material is in close contact with 98% or more of the cellophane tape adhesion area.
X: Peeling is observed in 2% or more of the cellophane tape adhesion area.
<Stability over time>: The coating agent was allowed to stand at room temperature for 1 week, and the subsequent state was visually observed.
○: No change ×: Change (with precipitates)

Claims (13)

A modified polyvinyl alcohol composite resin having a structure in which a polymer portion formed from an ethylenically unsaturated monomer capable of radical polymerization is grafted onto polyvinyl alcohol. The modified polyvinyl alcohol composite resin according to claim 1, wherein the polyvinyl alcohol has a saponification degree of 50% or less. The ethylenically unsaturated polymer part formed from radically polymerizable ethylenically unsaturated monomer contains at least one functional group selected from the group consisting of hydrolyzable silyl group, carboxyl group, epoxy group and hydroxy group. 3. The modified polyvinyl alcohol composite resin according to claim 1, wherein the modified polyvinyl alcohol composite resin is formed from a radically polymerizable ethylenically unsaturated monomer having a saturated monomer as an essential component. The modification according to claim 3, wherein the ethylenically unsaturated monomer containing a functional group is 0.1 to 20% by weight in 100% by weight of the ethylenically unsaturated monomer capable of radical polymerization. Polyvinyl alcohol composite resin. The modified polyvinyl alcohol composite resin according to any one of claims 1 to 4, wherein the polyvinyl alcohol and the polymer portion are 80 to 20:20 to 80 (weight ratio). A modified polyvinyl alcohol composite resin characterized by dissolving polyvinyl alcohol having a saponification degree of 50% or less in a non-hydrophilic solvent and polymerizing a radically polymerizable ethylenically unsaturated monomer in the presence of a polymerization initiator. Production method. The method for producing a modified polyvinyl alcohol composite resin according to claim 6, wherein the solubility parameter of the non-hydrophilic solvent is 10 or less. The method for producing a modified polyvinyl alcohol composite resin according to claim 6 or 7, wherein the polymerization initiator is a peroxide. A modified polyvinyl alcohol composite resin obtained by the production method according to claim 6. A coating agent comprising the modified polyvinyl alcohol composite resin according to claim 1. A reactive functional group capable of reacting with the modified polyvinyl alcohol composite resin according to claim 3 and at least one functional group selected from the group consisting of a hydrolyzable silyl group, a carboxyl group, an epoxy group, and a hydroxy group. The coating agent characterized by including the crosslinking agent which has. The coating agent according to claim 11, further comprising a crosslinking catalyst for promoting a crosslinking reaction between the modified polyvinyl alcohol composite resin and the crosslinking agent. A coated product comprising a coating layer formed from the coating agent according to claim 10 on a plastic substrate.