JP2007308588A - Aqueous adhesive for plastic substrate, laminate and polarizing plate using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an aqueous adhesive for a plastic substrate, which develops excellent bonding strength to a plastic substrate even when allowed to stand for a relatively long period of time. <P>SOLUTION: The aqueous adhesive for a plastic substrate comprises a hydrophobic polyisocyanate (A), a vinyl-based polymer (B) containing a nonionic group and an isocyanate group and an aqueous medium. The hydrophobic polyisocyanate (A) is dispersed into the aqueous medium by the vinyl-based polymer (B). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a water-based adhesive for plastic substrates that can be used for the production of plastic films such as optical films, food packaging films, and other industrial material films, and for bonding them.

  As an optical film used for a liquid crystal display (LCD) or the like, in general, a polarizer made of a polyvinyl alcohol film impregnated with a dichroic material such as iodine, triacetyl cellulose, a thermoplastic saturated norbornene resin, or the like. A laminate of transparent protective films made of is known.

  Conventionally, a water-based adhesive is preferably used for bonding the polarizer and the protective film. As such an adhesive, liquid crystal displays are used in various environments including outdoors. For example, even in a high temperature and high humidity environment, excellent adhesive strength to a plastic substrate can be obtained for a long time. There is a demand for materials that can be maintained across the board, and in particular, there is a demand from the industry for adhesives that are less likely to cause a decrease in adhesive strength even under the influence of water such as moisture, that is, excellent in water resistance.

  As an adhesive capable of exhibiting excellent water resistance and the like for the plastic substrate as described above, for example, it is composed of a water-dispersible isocyanate adhesive containing an isocyanate compound having a water-dispersible component in the molecule. An adhesive for polarizing plates is known (see, for example, Patent Document 1).

However, the isocyanate compound contained in the polarizing plate adhesive is increased in molecular weight by the reaction between the isocyanate group and water when left for a long time after blending the polarizing plate adhesive. In some cases, the adhesive strength should be reduced.
The phenomenon seen in the adhesive can be generally caused when an aqueous adhesive containing an isocyanate group-containing compound is left for about 5 to 6 hours after blending. Therefore, currently, when manufacturing various laminates such as polarizing plates using the adhesive, measures such as blending the adhesive immediately before applying the adhesive on the substrate are taken. Is the current situation.
However, if the blending time of the adhesive is restricted on the production of the laminate, the improvement of the production process is restricted, so that it is difficult to improve the production efficiency or defective rate of the laminate. There is. Therefore, from the industry, even when the adhesive compound liquid is left for a relatively long time, it does not affect the quality, and it can be used for plastic substrates that can express excellent adhesive strength to plastic substrates. There is a demand for the development of water-based adhesives.

JP 2003-107245 A

  The problem to be solved by the present invention is to provide a water-based adhesive for plastic substrates capable of expressing excellent adhesive strength to plastic substrates even when left for a relatively long period of time. is there.

  The problem to be solved by the present invention is to provide a laminate and a polarizing plate firmly bonded by the water base adhesive for plastic substrates.

  As a result of intensive studies to solve the above problems, the inventors of the present invention have a water base for plastic substrates in which a hydrophobic polyisocyanate is dispersed in an aqueous medium by using a vinyl polymer having a nonionic group and an isocyanate group. It has been found that the adhesive can solve the problems of the present invention.

That is, the present invention comprises a hydrophobic polyisocyanate (A), a vinyl polymer (B) having a nonionic group and an isocyanate group, and an aqueous medium, and the hydrophobic polyisocyanate (A) The present invention provides an aqueous adhesive for plastic substrates, characterized by being dispersed in an aqueous medium by the vinyl polymer (B).
The technical term “hydrophobic” is generally understood to mean that a substance has a property of weak interaction with water and weak affinity with water. The term “hydrophobic” means that a substance by itself has a property of not being substantially dispersed or dissolved in water.

  The water-based adhesive for plastic substrates of the present invention has a long pot life after water dispersion, and therefore has excellent coating workability even after being left for a relatively long period of time. Can produce excellent adhesive strength, and can form an adhesive layer with excellent transparency, durability, etc., for the production of optical films, food packaging films, and other industrial material films. It can be used.

The best mode for carrying out the invention will be described in detail below.
The aqueous adhesive for plastic substrates of the present invention comprises a hydrophobic polyisocyanate (A), a vinyl polymer (B) having a nonionic group and an isocyanate group, an aqueous medium, and other additives as required. The hydrophobic polyisocyanate (A) is dispersed in an aqueous medium by the vinyl polymer (B).

  The water-based adhesive for plastic substrates of the present invention is such that the vinyl polymer (B) acts as a dispersant for emulsifying and dispersing the hydrophobic polyisocyanate (A), whereby the hydrophobic polyisocyanate (A ) In the particles, and the particles in which the vinyl polymer (B) is localized on the particle surface are considered to be dispersed in the aqueous dispersion.

  First, the aqueous medium used in the present invention is water and an organic solvent miscible with water. Examples of organic solvents miscible with water include alcohols such as methanol, ethanol, n- and isopropanol; ketones such as acetone and methyl ethyl ketone; esters such as methyl acetate, ethyl acetate and ethylene glycol monomethyl ether acetate; ethylene Polyalkylene glycols such as glycol, diethylene glycol, and propylene glycol; alkyl ethers of polyalkylene glycol; amides such as N-methyl-2-pyrrolidone, and the like can be used. In the present invention, only water may be used, or a mixture of water and an organic solvent miscible with water may be used, or only an organic solvent miscible with water may be used. From the viewpoint of safety and environmental load, water alone or a mixture of water and an organic solvent miscible with water is preferred, and water alone is particularly preferred.

Next, the hydrophobic polyisocyanate (A) used in the present invention will be described.
The hydrophobic polyisocyanate (A) cannot be substantially dispersed or dissolved in water by itself. In the adhesive for plastic substrates of the present invention, the vinyl polymer having a self-water dispersibility ( B) is dispersed in water.

  Examples of the hydrophobic polyisocyanate (A) include 1,4-tetramethylene diisocyanate, ethyl (2,6-diisocyanate) hexanoate, 1,6-hexamethylene diisocyanate, 1,12-dodecamethylene diisocyanate, 2, Aliphatic diisocyanates such as 2,4- or 2,4,4-trimethylhexamethylene diisocyanate; 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanate-4-isocyanatomethyloctane, 2-isocyanate Aliphatic triisocyanates such as natoethyl (2,6-diisocyanato) hexanoate; 1,3- or 1,4-bis (isocyanatomethylcyclohexane), 1,3- or 1,4-diisocyanatocyclohexane, 3,5,5-trimethyl Cycloaliphatic diisocyanates such as 3-isocyanatomethyl) cyclohexyl isocyanate, dicyclohexylmethane-4,4′-diisocyanate, 2,5- or 2,6-diisocyanatomethylnorbornane; 2,5- or 2,6-di Alicyclic diisocyanates such as isocyanate methyl-2-isocyanate propyl norbornane; Aralkylene diisocyanates such as m-xylylene diisocyanate, α, α, α ′, α′-tetramethyl-m-xylylene diisocyanate; m -Or p-phenylene diisocyanate, tolylene-2,4- or 2,6-diisocyanate, diphenylmethane-4,4'-diisocyanate, naphthalene-1,5-diisocyanate, diphenyl-4,4'-diisocyanate, 4,4 ' -Diisosi Aromatic diisocyanates such as anat-3,3′-dimethyldiphenyl, 3-methyl-diphenylmethane-4,4′-diisocyanate, diphenylether-4,4′-diisocyanate; triphenylmethane triisocyanate, tris (isocyanatophenyl) ) Aromatic triisocyanates such as thiophosphate, etc. can be used.

  The hydrophobic polyisocyanate (A) has a polyisocyanate having a uretdione structure, a polyisocyanate having an isocyanurate structure, a polyisocyanate having a burette structure, a polyisocyanate having an oxadiazine trione structure, or an allophanate structure. Polyisocyanate and the like can be used.

Among the above-mentioned hydrophobic polyisocyanates (A), among them, the reaction of the isocyanate groups with water is suppressed, good work stability and the maintenance of adhesive strength are maintained, and the weather resistance of the adhesive layer is improved. In order to improve, it is preferable to use aliphatic diisocyanate or polyisocyanate, or alicyclic diisocyanate or polyisocyanate.
The hydrophobic polyisocyanate (A) includes an isocyanurate type polyisocyanate, a polyisocyanate having a burette structure, a polyisocyanate having a uretdione structure, a polyisocyanate having an allophanate structure, or a diisocyanate and a trivalent or higher polyol. It is preferable to use a polyisocyanate or the like obtained by reacting with the above in order to form an adhesive layer excellent in weather resistance and durability.

  In the present invention, in addition to the hydrophobic polyisocyanate (A), if necessary, hydrophilic polyisocyanate may be used in combination as long as the effects of the present invention are not impaired.

Next, the vinyl polymer (B) having a nonionic group and an isocyanate group used in the present invention will be described.
In the vinyl polymer (B), the hydrophobic polyisocyanate (A) can be dispersed in an aqueous medium. In addition, the vinyl polymer (B) can particularly suppress an increase in the molecular weight due to the reaction of the isocyanate group of the hydrophobic polyisocyanate (A) with water. In addition, since the vinyl polymer (B) has an isocyanate group, the reaction proceeds through the isocyanate group during the formation of the adhesive layer. Therefore, according to the aqueous adhesive for plastic substrates of the present invention containing the vinyl polymer (B), an adhesive layer excellent in weather resistance and durability can be formed.

  The vinyl polymer (B) is, for example, a nonionic group as a hydrophilic group among acrylic polymers, fluoroolefin polymers, vinyl ester polymers, aromatic vinyl polymers, polyolefin polymers, and the like. And those having an isocyanate group can be used. Among these, from the viewpoint of improving the compatibility with the hydrophobic polyisocyanate (A), it is preferable to use an acrylic polymer or a fluoroolefin polymer having a nonionic group and an isocyanate group.

  Examples of the nonionic group include polyoxyalkylene groups such as a polyoxyethylene group, a polyoxypropylene group, a polyoxybutylene group, a poly (oxyethylene-oxypropylene) group, and a polyoxyethylene-polyoxypropylene group. can do. Among these, it is preferable to use a polyoxyalkylene group having an oxyethylene unit in order to further improve the hydrophilicity.

  It is preferable that the nonionic group is blocked at the end from the viewpoint of suppressing an increase in viscosity accompanying the increase in molecular weight. For example, it is preferable that the hydroxyl group present at one end of the polyoxyalkylene group is blocked by forming an ether bond with an alkoxy group, a substituted alkoxy group or the like, or is blocked by forming an ester bond.

  The functional group that can be used for end-capping the nonionic group is preferably an alkoxy group, and particularly preferably a lower alkoxy group such as a methoxy group, an ethoxy group, or a butoxy group.

  The vinyl polymer (B) may have any amount of nonionic groups as long as the effects of the present invention are not impaired. Specifically, the abundance of the nonionic group is preferably 8 to 80% by mass of the total amount of the vinyl polymer (B), more preferably 12 to 65% by mass, and 15 to 55% by mass. It is particularly preferred that

  In addition, the number average molecular weight of the polyoxyalkylene group as a nonionic group stably expresses the properties such as the adhesive strength of the aqueous adhesive for plastic substrates of the present invention, and the curability of the adhesive. From the viewpoint of maintaining, it is preferably within the range of 130 to 10,000, more preferably within the range of 150 to 6,000, and particularly preferably within the range of 200 to 2,000.

  The weight average molecular weight of the vinyl polymer (B) is 5,000 to 200,000, more preferably 8,000 to 70,000. By using a vinyl polymer (B) having a weight average molecular weight in such a range, it is for a plastic substrate having a stable quality in terms of coating workability and adhesive strength even after being stored for a long period of time. An aqueous adhesive can be obtained.

  In addition, the vinyl polymer (B) has a hydrophobic group in addition to the nonionic group from the viewpoint of developing a better water dispersibility by adjusting the balance between hydrophilicity and hydrophobicity. What is doing is preferable.

As the hydrophobic group, for example, a group having 4 or more total carbon atoms is preferably used, a group having 4 to 22 is more preferable, and a group having 5 to 18 is particularly preferable.
Examples of the hydrophobic group having 4 or more total carbon atoms include n-butyl group, iso-butyl group, tert-butyl group, n-pentyl group, n-hexyl group, 2-ethylhexyl group, and n-octyl group. Alkyl groups such as n-dodecyl group or n-octadecyl group; cycloalkyl groups such as cyclobutyl group, cyclopentyl group, cyclohexyl group, cyclooctyl group, dicyclopentanyl group, bornyl group, isobornyl group; cyclopentylmethyl group, cyclohexyl An alkyl group substituted by a cycloalkyl group such as a methyl group, a 2-cyclopentylethyl group or a 2-cyclohexylethyl group; an aryl group or a substituted aryl group such as a phenyl group, a 4-methylphenyl group or a 1-naphthyl group; Examples include aralkyl groups such as 2-phenylethyl group. Among these alkyl groups, it is preferably a cycloalkyl group or cycloalkyl group is an alkyl group substituted.

  The hydrophobic group as described above is preferably present in the range of 1 to 45% by mass and more preferably in the range of 5 to 30% by mass with respect to the entire vinyl polymer (B). .

  The vinyl polymer (B) can be produced by various methods. For example, at least one selected from the group consisting of a hydrophobic polyisocyanate (b1), a hydroxyl group, a carboxyl group, an amino group, and an active methylene group. A method (1) of reacting a vinyl polymer (b2) having an active hydrogen-containing group and a nonionic group, and a vinyl monomer having an isocyanate group and a nonionic group-containing vinyl monomer. It can be produced by a method (2) for polymerization, a method (3) for reacting a nonionic group-containing compound with an isocyanate group-containing vinyl polymer, or the like. In particular, the method (1) is preferable because the production method is simple.

First, the method (1) will be described in detail.
The hydrophobic polyisocyanate (b1) and the vinyl polymer (b2) are, for example, a method (i) in which they are mixed and reacted under an atmosphere of an inert gas or the like, and a hydrophobic polyisocyanate (b1). By adding a vinyl polymer (b2) solution to the solution (ii), and by adding a hydrophobic polyisocyanate (b1) to the vinyl polymer (b2) solution (iii) Can do.
The reaction between the hydrophobic polyisocyanate (b1) and the vinyl polymer (b2) is preferably performed by the method (i) or (ii) from the viewpoint of suppressing the formation of a gelled product. The reaction is preferably allowed to proceed by heating and stirring at a temperature of about 50 to 130 ° C. for about 0.5 to 20 hours. In the reaction, various known and conventional catalysts capable of promoting the reaction between the isocyanate group of the hydrophobic polyisocyanate (b1) and the active hydrogen-containing group of the vinyl polymer (b2) are used. May be used.

  As the hydrophobic polyisocyanate (b1) that can be used in the production of the vinyl polymer (B), the same as those exemplified as the hydrophobic polyisocyanate (A) can be used.

  In addition, a vinyl heavy polymer having at least one active hydrogen-containing group and nonionic group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and an active methylene group, which can react with the hydrophobic polyisocyanate (b1) As the combination (b2), among the acrylic polymer, the fluoroolefin polymer, the vinyl ester polymer, the aromatic vinyl polymer, the polyolefin polymer, and the like, the nonionic group as the hydrophilic group is described above. Those having various active hydrogen-containing groups can be used. Among these, from the viewpoint of improving compatibility with the hydrophobic polyisocyanate (A), it is preferable to use an acrylic polymer or a fluoroolefin polymer.

  Examples of the active hydrogen-containing group possessed by the vinyl polymer (b2) include a hydroxyl group, an amino group, a carboxyl group, and an active methylene group, and particularly preferred are a hydroxyl group and a carboxyl group. The vinyl polymer (b2) may have only one kind of the active hydrogen-containing group or may have two or more kinds.

  The active hydrogen-containing group can be introduced into the vinyl polymer (b2) by various methods. For example, various monomers are copolymerized by a radical polymerization method in the presence of a polymerization initiator. When the vinyl polymer (b2) is produced by this, the vinyl polymer (b2) is prepared by copolymerizing a monomer having an active hydrogen-containing group together with various vinyl monomers described later. Can be introduced.

  Examples of the monomer having an active hydrogen-containing group include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate. 4-hydroxybutyl (meth) acrylate, methyl (2-hydroxymethyl) acrylate, ethyl (2-hydroxymethyl) acrylate, butyl (2-hydroxymethyl) acrylate, (4-hydroxymethylcyclohexyl) methyl (meth) acrylate, Contains hydroxyl groups such as glycerin mono (meth) acrylate, phthalic acid mono (2-hydroxypropyl) -mono [2- (meth) acryloyloxy] ethyl ester, 2-hydroxy-3-phenoxypropyl (meth) acrylate (Meth) acrylic acid esters; poly (oxyalkylene glycol) mono (meth) acrylates containing hydroxyl groups such as polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, polybutylene glycol mono (meth) acrylate; allyl Allyl compounds containing hydroxyl groups such as alcohol and 2-hydroxyethyl allyl ether; Vinyl ether compounds containing hydroxyl groups such as 2-hydroxyethyl vinyl ether, 4-hydroxybutyl vinyl ether and 6-hydroxyhexyl vinyl ether; N-methylol (meth) acrylamide Unsaturated carboxylic acid amide compounds having a hydroxyl group such as N-methylolcrotonic acid amide; hydroxyl-containing unsaturated fatty acids such as ricinoleic acid; ricinoleic acid alkyl Hydroxyl group-containing unsaturated fatty acid esters and the like; monomers wherein the various hydroxyl group-containing a monomer ε- caprolactone are added, may be used used or two or more kinds in combination.

  Typical examples of the monomer having a carboxyl group as an active hydrogen-containing group include (meth) acrylic acid, 2-carboxyethyl acrylate, crotonic acid, vinyl acetic acid, monovinyl adipate, monovinyl sebacate, and itacon. Monomethyl acid, monomethyl maleate, monomethyl fumarate, mono [2- (meth) acryloyloxyethyl] succinate, mono [2- (meth) acryloyloxyethyl] phthalate, mono [2- (meth) hexahydrophthalic acid Acryloyloxyethyl] and unsaturated monocarboxylic acids such as sorbic acid; unsaturated dicarboxylic acids such as itaconic acid, maleic acid and fumaric acid.

  Typical examples of the monomer having an amino group as the active hydrogen-containing group include 2- (N-methylamino) ethyl (meth) acrylate, 2- (N-ethylamino) ethyl (meth) acrylate, 2- (Nn-butylamino) ethyl (meth) acrylate, 2- (N-tert-butylamino) ethyl methacrylate, 2- (N-methylamino) ethyl crotonate, 2- (N-ethylamino) ethyl Examples include secondary amino group-containing vinyl monomers such as crotonate and 2- (N-butylamino) ethyl crotonate.

  Representative monomers having an active methylene group as the active hydrogen-containing group are, for example, vinyl acetoacetate, 2-acetoacetoxyethyl (meth) acrylate, 2-acetoacetoxypropyl (meth) acrylate, 3-aceto Examples include acetoxypropyl (meth) acrylate, 3-acetoacetoxybutyl (meth) acrylate, 4-acetoacetoxybutyl (meth) acrylate, allyl acetoacetate, and 2,3-di (acetoacetoxy) propyl methacrylate.

  The active hydrogen-containing group contained in the vinyl polymer (b2) is the vinyl heavy polymer from the viewpoint of suppressing the progress of the reaction between the isocyanate group contained in the aqueous adhesive for plastic substrates of the present invention and the aqueous medium. It is preferably in the range of 0.01 to 5 mol, more preferably in the range of 0.05 to 3 mol, and particularly preferably 0.1 to 2 mol per 1000 g of the union (b2).

  Moreover, as a nonionic group which the said vinyl polymer (b2) has, the thing similar to what was illustrated as a nonionic group which the said vinyl polymer (B) has can be used.

  The nonionic group can be introduced into the vinyl polymer (b2) by various methods. For example, various monomers are copolymerized by a radical polymerization method in the presence of a polymerization initiator. When the vinyl polymer (b2) is produced by the method, the vinyl polymer (b2) is prepared by a method of copolymerizing a nonionic group-containing vinyl monomer together with various vinyl monomers described later. Can be introduced inside.

  As the nonionic group-containing vinyl monomer, for example, (meth) acrylic acid ester, crotonic acid ester, itaconic acid ester, fumaric acid ester, vinyl ether and the like having a polyoxyalkylene group can be used. However, it is preferable to use a (meth) acrylic acid ester having a polyoxyalkylene group.

  Typical examples of the (meth) acrylic acid ester having a polyoxyalkylene group include monomethoxypolyethylene glycol, monomethoxylated polypropylene glycol, or a monopolyether diol having both oxyethylene units and oxypropylene units. Various monoalkoxylated polyether diols such as methoxy compounds and esters of (meth) acrylic acid can be used.

  The nonionic group of the vinyl polymer (b2) is a vinyl polymer (from the viewpoint of suppressing the progress of the reaction between the isocyanate group contained in the aqueous adhesive for plastic substrates of the present invention and an aqueous medium). It is preferable that it is 10-90 mass% with respect to the whole quantity of b2), It is more preferable that it is 15-70 mass%, It is especially preferable that it is 20-60 mass%.

  Moreover, as said vinyl polymer (b2), what was obtained by copolymerizing another monomer other than the above-mentioned various vinyl monomers as needed can be used.

  Examples of the other monomers include (meth) acrylic acid esters having an alkyl group having 3 or less carbon atoms such as methyl (meth) acrylate, ethyl (meth) acrylate, and n-propyl (meth) acrylate; Various ω-alkoxyalkyl (meth) acrylates such as 2-methoxyethyl (meth) acrylate or 4-methoxybutyl (meth) acrylate; carboxylic acids having 4 or less total carbon atoms such as vinyl acetate and vinyl propionate Vinyl esters; various crotonic acid esters having an alkyl group with 3 or less carbon atoms such as methyl crotonate or ethyl crotonate; 3 or less carbon atoms such as dimethyl malate, dimethyl fumarate, dimethyl itaconate Various unsaturated dibasic acid diesters having an alkyl group of A) Various cyano group-containing vinyl monomers such as acrylonitrile and crotononitrile; various fluoroolefins such as vinyl fluoride, vinylidene fluoride, tetrafluoroethylene, chlorotrifluoroethylene, and hexafluoropropylene Various chlorinated olefins such as vinyl chloride or vinylidene chloride; various α-olefins such as ethylene or propylene; various alkyls having 3 or less carbon atoms such as ethyl vinyl ether and n-propyl vinyl ether; Vinyl ethers; use of tertiary amide group-containing vinyl monomers such as N, N-dimethyl (meth) acrylamide, N- (meth) acryloylmorpholine, N- (meth) acryloylpyrrolidine or N-vinylpyrrolidone, etc. can do.

  Moreover, as said other monomer, the hydrophilic property which this vinyl type polymer (b2) has by introduce | transducing the hydrophobic group whose total carbon atom number is 4 or more into the said vinyl type polymer (b2). As appropriate, the balance between the group and the hydrophobic group can be adjusted so that excellent water dispersibility can be expressed, and the reaction between the isocyanate group contained in the water-based adhesive for plastic substrates and the aqueous medium can be promoted. For the purpose of further suppression, a monomer having a hydrophobic group having 4 or more total carbon atoms can be used.

  Typical vinyl monomers having a hydrophobic group having 4 or more total carbon atoms include n-butyl (meth) acrylate, iso-butyl (meth) acrylate, and tert-butyl (meth). (Meth) acrylic acid esters having an alkyl group having 4 to 22 carbon atoms in total, such as acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate; cyclopentyl (meth) acrylate, Various cycloalkyl (meth) acrylates such as cyclohexyl (meth) acrylate, bornyl (meth) acrylate, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate; cyclopentylmethyl (meth) acrylate, cyclohexylmethyl (meth) Acry , Cycloalkylalkyl (meth) acrylates such as 2-cyclohexylethyl (meth) acrylate; various aralkyl (meth) acrylates such as benzyl (meth) acrylate or 2-phenylethyl (meth) acrylate; styrene, p -Various aromatic vinyl monomers such as tert-butylstyrene, α-methylstyrene, vinyltoluene; carboxylic acids having 5 or more total carbon atoms such as vinyl pivalate, vinyl versatate or vinyl benzoate Various crotonic acid esters having an alkyl group having 4 to 22 carbon atoms such as crotonic acid-n-butyl and crotonic acid-2-ethylhexyl; di-n-butylmalate, di-n-butyl 4 carbon atoms such as fumarate and di-n-butyl itaconate Various unsaturated dibasic acid diesters having at least one alkyl group of ˜22; various alkyl vinyl ethers having an alkyl group of 4 to 22 carbon atoms such as n-butyl vinyl ether and n-hexyl vinyl ether; cyclopentyl Examples thereof include various cycloalkyl vinyl ethers such as vinyl ether, cyclohexyl vinyl ether, and 4-methylcyclohexyl vinyl ether.

  The hydrophobic group having 4 or more total carbon atoms gives excellent water dispersibility and further suppresses the progress of the reaction between the isocyanate group contained in the aqueous adhesive for plastic substrates and the aqueous medium. From 1 to 50% by mass, preferably from 5 to 30% by mass, based on the whole vinyl polymer (b2).

  Moreover, as said other monomer, what has a reactive functional group can be used. For example, vinyl monomers having hydroxyl groups blocked with triorganosilyl groups, vinyl monomers containing silyl ester groups, vinyl monomers containing hemiacetal ester groups or hemiketal ester groups, epoxy groups And vinyl monomers containing hydrolyzable silyl groups, and the like.

  Representative vinyl monomers having a hydroxyl group blocked with a triorganosilyl group include 2-trimethylsiloxyethyl (meth) acrylate, 2-trimethylsiloxypropyl (meth) acrylate, and 4-trimethylsiloxybutyl. (Meth) acrylate, 2-triethylsiloxyethyl (meth) acrylate, 2-tributylsiloxypropyl (meth) acrylate or 3-triphenylsiloxypropyl (meth) acrylate, 2-trimethylsiloxyethyl vinyl ether, 4-trimethylsiloxybutyl vinyl ether, etc. Is mentioned.

  Representative vinyl monomers containing the silyl ester group include trimethylsilyl (meth) acrylate, dimethyl-tert-butylsilyl (meth) acrylate, dimethylcyclohexylsilyl (meth) acrylate, trimethylsilylcrotonate, and adipic acid And monovinyl-monotrimethylsilyl ester.

  Representative vinyl monomers containing the hemiacetal ester group or hemiketal ester group include 1-methoxyethyl (meth) acrylate, 1-ethoxyethyl (meth) acrylate, 2-methoxy-2- Examples include (meth) acryloyloxypropane and 2- (meth) acryloyloxytetrahydrofuran.

  Typical examples of the vinyl monomer containing the epoxy group include glycidyl (meth) acrylate, methyl glycidyl (meth) acrylate, 3,4-epoxycyclohexyl (meth) acrylate, glycidyl vinyl ether, allyl glycidyl ether, and the like. Is mentioned.

  Representative vinyl monomers having a hydrolyzable silyl group include vinyltrimethoxysilane, vinyltriethoxysilane, vinylmethyldimethoxysilane, vinyltris (2-methoxyethoxy) silane, allyltrimethoxysilane, 2-trimethoxysilylethyl vinyl ether, 3-trimethoxysilylpropyl vinyl ether, 3- (methyldimethoxysilyl) propyl vinyl ether, 3- (meth) acryloyloxypropyltrimethoxysilane, 3- (meth) acryloyloxypropyltriethoxysilane, 3- (meth) acryloyloxypropylmethyldimethoxysilane, 3- (meth) acryloyloxypropyltri-n-propoxysilane, 3- (meth) acryloyloxypropyltriiso-propoxy Run, 3- (meth) acryloyloxy propyl methyl dichlorosilane, and the like.

  The vinyl polymer (b2) can be produced, for example, by copolymerizing the above-mentioned various monomers by a radical polymerization method in the presence of a polymerization initiator. It is convenient and preferable to carry out in a solvent.

  As the polymerization initiator, various known and commonly used compounds can be used. Typical examples include 2,2′-azobis (isobutyronitrile), 2,2′-azobis (2,4-dimethylbutyronitrile) or 2,2′-azobis (2-methylbutyronitrile). ) And the like; tert-butyl peroxypivalate, tert-butyl peroxybenzoate, tert-butyl peroxy-2-ethylhexanoate, di-tert-butyl peroxide, cumene hydroperoxide Or diisopropyl peroxycarbonate etc. are mentioned.

  In addition, as the organic solvent, those inert to isocyanate groups can be used. Typical examples include aliphatic or alicyclic hydrocarbons such as n-hexane, n-heptane, n-octane, cyclohexane and cyclopentane; aromatic hydrocarbons such as toluene, xylene and ethylbenzene. Various esters such as ethyl acetate, n-butyl acetate, n-amyl acetate and ethylene glycol monomethyl ether acetate; various ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl n-amyl ketone and cyclohexanone; diethylene glycol dimethyl ether and diethylene glycol Polyalkylene glycol dialkyl ethers such as diethyl ether and diethylene glycol dibutyl ether; Ethers such as 1,2-dimethoxyethane, tetrahydrofuran and dioxane; N-methylpyrrole Emissions, dimethylformamide, dimethylacetamide or ethylene carbonate, and the like, can be used in combination use of two or more of these alone.

  As the organic solvent, it is preferable to use one having a low water content from the viewpoint of maintaining the stability of the isocyanate group. Moreover, you may use what dehydrated the water mixed in the organic solvent by the azeotropic dehydration method etc. as needed.

  In producing the vinyl polymer (b2), the hydrophobic polyisocyanate (A) may be used in place of a part or all of the organic solvent. By using the hydrophobic polyisocyanate (A) instead of the organic solvent, the production of the vinyl polymer (b2) and the production of the vinyl polymer (B) can proceed in parallel. .

  The weight average molecular weight of the vinyl polymer (b2) is from the viewpoint of imparting excellent water dispersibility and further suppressing the progress of the reaction between the isocyanate group contained in the aqueous adhesive for plastic substrates and the aqueous medium. , Preferably in the range of 3,000-100,000, more preferably in the range of 5,000-40,000.

  The hydrophobic polyisocyanate (b1) and the vinyl polymer (b2) are an active hydrogen-containing group such as a hydroxyl group, a carboxyl group, an amino group, and an active methylene group contained in the vinyl polymer (b2). On the other hand, it is preferable to make it react by the molar ratio which the isocyanate group which the said hydrophobic polyisocyanate (b1) has becomes excess.

The molar ratio [isocyanate group of hydrophobic polyisocyanate (b1) / active hydrogen-containing group of vinyl polymer (b2)] is preferably in the range of about 1.5 to less than 3. When the reaction is carried out in the molar ratio range, an unreacted hydrophobic polyisocyanate (b1) may be mixed in addition to the vinyl polymer (B).
The aqueous adhesive for plastic substrates of the present invention is produced by mixing and dispersing the vinyl polymer (B) obtained by the above method and the hydrophobic polyisocyanate (A) in an aqueous medium. Can do.

  On the other hand, when the molar ratio is 3 or more and the hydrophobic polyisocyanate (b1) and the vinyl polymer (b2) are reacted, the vinyl polymer (B) and the unreacted hydrophobic polyisocyanate. A reaction product containing (b1) can be obtained. Since the unreacted hydrophobic polyisocyanate (b1) is substantially the same as the hydrophobic polyisocyanate (A), a reaction product obtained by reacting at a molar ratio in the above range is dispersed in an aqueous medium. By this, the water-based adhesive for plastic substrates of the present invention can be produced in one step.

  The molar ratio is in the range of 3 to 350 from the viewpoint of achieving both water dispersion stability and curability of the aqueous adhesive for plastic substrates of the present invention and simplifying the production process of the aqueous adhesive. The range of 5 to 300 is more preferable, the range of 10 to 250 is particularly preferable, and the range of 15 to 100 is most preferable.

  Next, the method (2), that is, a method for producing a vinyl polymer (B) by copolymerizing an isocyanate group-containing vinyl monomer and a nonionic group-containing vinyl monomer will be described. To do.

  Examples of the isocyanate group-containing vinyl monomer include 2-isocyanate propene, 2-isocyanate ethyl vinyl ether, 2-isocyanate ethyl methacrylate, m-isopropenyl-α, α-dimethylbenzyl isocyanate, and polyisocyanate. A reaction product with a vinyl monomer having a hydroxyl group can be used.

  Moreover, as a nonionic group containing vinyl-type monomer, the thing similar to what was illustrated as what can be used by the said method (1) can be used.

  In the method (2), in addition to the isocyanate group-containing vinyl monomer and the nonionic group-containing vinyl monomer, if necessary, a hydrophobic group having 4 or more total carbon atoms may be added. Other monomers such as a vinyl-based monomer can be used in combination. As other monomers such as vinyl monomers having a hydrophobic group having 4 or more total carbon atoms, the same monomers as exemplified in the method (1) can be used.

  Polymerization of the isocyanate group-containing vinyl monomer and the nonionic group-containing vinyl monomer, for example, using the same polymerization initiator and organic solvent exemplified in the method (1), It can be carried out by the same solution radical polymerization method as the method (1).

  The aqueous adhesive for plastic substrates of the present invention is obtained by mixing and dispersing the vinyl polymer (B) obtained by the method (2) and the hydrophobic polyisocyanate (A) in an aqueous medium. Can be manufactured.

Next, the method (3), that is, a method for producing a vinyl polymer (B) by reacting an isocyanate group-containing vinyl polymer with a nonionic group-containing compound will be described.
The said isocyanate group containing vinyl polymer can be manufactured by radically polymerizing the thing similar to the isocyanate group containing vinyl monomer illustrated by the method (2) by a well-known and usual method.

  As the nonionic group-containing compound, for example, polyoxyalkylene glycol having one end blocked with an alkoxy group or the like can be used.

  The isocyanate group-containing vinyl polymer and the nonionic group-containing compound are a functional group capable of reacting with the isocyanate group that the isocyanate group of the vinyl polymer has, It is preferable to make it react in the range of the molar ratio used as excess.

  The aqueous adhesive for plastic substrates of the present invention is obtained by mixing and dispersing the vinyl polymer (B) obtained by the method (3) and the hydrophobic polyisocyanate (A) in an aqueous medium. Can be manufactured.

  The aqueous adhesive for plastic substrates according to the present invention comprises the hydrophobic polyisocyanate (A) and the vinyl polymer (B) having a nonionic group and an isocyanate group in a mass ratio of (A) / (B). = 30/70 to 85/15, preferably 50/50 to 80/20, more preferably 60/40 to 80/20 Is most preferred. The water-based adhesive for plastic base materials in which the mass ratio of the hydrophobic polyisocyanate (A) and the vinyl polymer (B) is within the above-described range is excellent in water dispersion stability and is contained in the adhesive. The reaction of the isocyanate group with the aqueous medium can be sufficiently suppressed, and an adhesive layer having excellent hardness can be formed.

  Moreover, the water-based adhesive for plastic substrates of the present invention contains various water-dispersible or water-soluble resins as required in addition to the hydrophobic polyisocyanate (A) and the vinyl polymer (B). You may go out.

  Examples of the water-dispersible or water-soluble resins include vinyl acetate resins, styrene-butadiene resins, styrene-acrylonitrile resins, acrylic resins, fluoroolefin resins, silicon-modified vinyl polymers, and vinyl alcohols such as polyvinyl alcohol. Polyester resin, urethane resin, phenol resin, melamine resin, epoxy resin, alkyd resin, polyamide resin, polyether resin, synthetic resin other than vinyl polymer such as silicon resin; animal protein, starch, cellulose derivative, Natural polymers such as dextrin and gum arabic can be used. Among them, it is preferable to use a urethane resin that can improve adhesion to a plastic substrate.

  The urethane resin that can be used in the water-based adhesive for plastic substrates of the present invention is at least one selected from the group consisting of an anionic group, a nonionic group, and a cationic group when dispersed in water or dissolved in water. It is preferable to have a hydrophilic group, and it is most preferable to use a urethane resin (C) having an anionic group in order to form an adhesive layer excellent in water resistance, light resistance and adhesion.

  The urethane resin (C) having an anionic group has, for example, a carboxyl group, a sulfonic acid group or a salt thereof as an anionic group in the molecule.

  The content of the anionic group of the urethane resin (C) has a strong correlation with the particle diameter when the urethane resin (C) is made into an aqueous dispersion, and with respect to the urethane resin (C), The range is preferably 50 to 1000 mmol / kg. Within such a range, an adhesive layer having good water resistance can be formed, and an aqueous adhesive for plastic substrates having excellent water dispersion stability can be obtained.

  Such urethane resin (C) can be produced by reacting polyol and polyisocyanate as essential components. In that case, you may use a chain extender etc. as needed.

  As the polyol, for example, polyester polyol, polyether polyol, polycarbonate polyol, and other low molecular weight polyols can be used alone or in combination of two or more. Especially, it is preferable to mainly use the polyester polyol from the viewpoint of improving the adhesion to the plastic substrate and obtaining a high cohesive force of the resin.

  The polyester polyol can be produced, for example, by reacting a low molecular weight polyol with a polycarboxylic acid.

  Examples of the low molecular weight polyol include ethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, neo Pentyl glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, polyethylene glycol, 3-methyl-1,5-pentanediol, 2-butyl-2-ethyl-1,3-propanediol, etc. Aliphatic diols such as 1,4-cyclohexanediol, 1,4-cyclohexanedimethanol, hydrogenated bisphenol A and the like, and glycerin, trimethylolpropane, pentaerythrito as polyfunctional components Polyols such as Le or bisphenol A,, bisphenol S, may be used hydroquinone, bishydroxyethoxybenzene or the polyol having an aromatic cyclic structure such as those with an alkylene oxide adduct.

  Examples of the polycarboxylic acid include aliphatic dicarboxylic acids such as succinic acid, succinic anhydride, adipic acid, suberic acid, azelaic acid, sebacic acid and dimer acid, and alicyclic such as 1,4-cyclohexanedicarboxylic acid. Dicarboxylic acid, terephthalic acid, isophthalic acid, orthophthalic acid, 1,4-naphthalenedicarboxylic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, naphthalic acid, biphenyldicarboxylic acid, 1,2-bis (phenoxy) ) Aromatic dicarboxylic acids such as ethane-P, P′-dicarboxylic acid, their anhydrides or ester-forming derivatives, polycarboxylic acids such as trimellitic acid, pyromellitic acid, cyclohexanetricarboxylic acid and their anhydrides or Aromatic hydroxycarbo such as ester derivatives and p-hydroxybenzoic acid It may be used acids or their ester-forming derivatives. Moreover, as a polyester polyol, the polyester polyol which added cyclic lactones, such as (epsilon) -caprolactone and (gamma) -valerolactone, can also be used.

  In addition, as the polyether polyol, for example, a compound having at least two active hydrogen atoms described later is used as an initiator, and one or more compounds such as ethylene oxide, propylene oxide, butylene oxide, styrene oxide, and tetrahydrofuran are added. Those obtained by polymerization can be used.

  Examples of the compound having at least two active hydrogen atoms include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, and hexamethylene glycol. , Sucrose, glycerin, sorbitol; actinic acid, trimellitic acid, hemimellitic acid, phosphoric acid, ethylenediamine, propylenediamine, diethylenetriamine, triisopropanolamine, pyrogallol, dihydrobenzoic acid, hydroxyphthalic acid, 1,2,3-propanetri Thiols and the like can be used.

  As the polyether polyol, it is preferable to use polyethylene glycol, polypropylene glycol or polytetramethylene glycol. Moreover, as said polyol, you may use in the range which does not inhibit high molecular weight about the polyether monool by which some hydroxyl groups were blocked with monoalcohols, such as methanol and butanol.

  Examples of the polycarbonate polyol include 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, diethylene glycol, polyethylene glycol, polypropylene glycol, and polytetramethylene glycol ( And a reaction product of a diol such as PTMG) and a cyclic carbonate such as dimethyl carbonate represented by dimethyl carbonate or ethylene carbonate.

  Moreover, as polyisocyanate which can be used when manufacturing the said urethane resin (C), all can use well-known thing, For example, 1, 4- tetramethylene diisocyanate, 1, 6- hexamethylene diisocyanate, 1, 12-dodecamethylene diisocyanate, cyclohexane-1,3- or 1,4-diisocyanate, 1-isocyanato-3-isocyanatomethyl-3,5,5-trimethylcyclohexane, bis- (4-isocyanatocyclohexyl) methane, 2 -Or 4-isocyanatocyclohexyl-2'-isocyanatocyclohexylmethane, 1,3- or 1,4-bis- (isocyanatomethyl) -cyclohexane, bis- (4-isocyanato-3-methylcyclohexyl) methane, , 3- or 1,4- , Α, α'α'-tetramethylxylylene diisocyanate, 2,4- or 2,6-diisocyanatotoluene, 2,2'-, 2,4'- or 4,4'-diisocyanatodiphenylmethane, 1,5-naphthalene diisocyanate, p- or m-phenylene diisocyanate, xylylene diisocyanate, diphenyl-4,4′-diisocyanate, or the like can be used. As the polyisocyanate, it is preferable to use a diisocyanate having an aromatic cyclic structure in order to improve the mechanical strength of the obtained adhesive layer. Also, the durability and light resistance of the obtained adhesive layer are improved. From the viewpoint of improvement, it is preferable to use an aliphatic diisocyanate or a diisocyanate having an aliphatic cyclic structure.

  The chain extender can be generally used for the purpose of improving the agglomeration amount of the urethane resin, and representative examples thereof include 1,2-diaminoethane, 1,2- or 1,3- Diaminopropane, 1,2- or 1,3- or 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, piperazine, N, N′-bis- (2-aminoethyl) piperazine 1-amino-3-aminomethyl-3,5,5-trimethyl-cyclohexane (isophoronediamine), bis- (4-aminocyclohexyl) methane, bis- (4-amino-3-butylcyclohexyl) methane, 1, Diamines such as 2-, 1,3- or 1,4-diaminocyclohexane or 1,3-diaminopropane, diethylenetriamine, triethylenetetramine Hydrazine derivatives such as hydrazine or adipic acid dihydrazide, ethanolamine, N-methyldiethanolamine, propanolamine, N-methyldiisopropanolamine, N-ethyldiethyleneamine, N-ethyldiisopropanolamine, aminoethylethanol Alkanolamines such as amine and diethanolamine can also be used.

  Further, as the chain extender, low molecular weight polyols similar to those exemplified as those usable for the production of the polyester polyol can be used, and monoalcohols such as methanol, ethanol, butanol and the like can be used for the urethane. You may use in the range which does not inhibit high molecular weight formation of resin (C).

In addition, as the chain extender, a polyol and / or (poly) amine having a hydrophilic group can be used. For example, a polyol having an anionic group and / or (poly) amine can be used. it can.
As the polyol having an anionic group, for example, a polyol having a carboxyl group or a polyol having a sulfonic acid group can be used.

  Examples of the polyol having a carboxyl group include 2,2′-dimethylolpropionic acid, 2,2′-dimethylolbutanoic acid, 2,2′-dimethylolbutyric acid, 2,2′-dimethylolvaleric acid, and the like. be able to. Moreover, the carboxyl group-containing polyester polyol obtained by making these low molecular weight polyols and various polycarboxylic acids react as needed can also be used.

  Examples of the polyol containing a sulfonic acid group include dicarboxylic acids such as 5-sulfoisophthalic acid, sulfoterephthalic acid, 4-sulfophthalic acid, and 5 [4-sulfophenoxy] isophthalic acid, and their ester-forming derivatives, Na, Aromatic sulfonic acid groups obtained by reacting metal ions such as K and Li, sulfonates with ammonia, diethylamine, triethylamine and the like, various polyols, and if necessary, the polycarboxylic acid and / or cyclic lactone, or Polyester polyols containing these salts can be used.

  Examples of the (poly) amine having an anionic group include taurine, N- (2-aminoethyl) -2-aminoethanesulfonic acid (salt), and N- (2-aminoethyl) -2-aminopropionic acid. (Salt), 2- (β-amino-propionamide) -alkane sulfonate, and the like can be used, and among them, (poly) amine having a sulfonic acid group is excellent in stability in a wide pH range. Therefore, it is preferable.

  Moreover, when the anionic group which the said urethane resin (C) has is a carboxyl group or a sulfonic acid group, it imparts favorable water dispersibility to the urethane resin (C) by neutralizing part or all of them. can do.

  Examples of the neutralizing agent that can be used for the neutralization include organic amines such as ammonia, triethylamine, pyridine, and morpholine, alkanolamines such as monoethanolamine and dimethylethanolamine, and metal salts containing Na, K, Li, and the like. Can be used. The neutralization rate is preferably neutralizer / anionic group = 0.5 to 3.0 (molar ratio), more preferably neutralizer / anionic group = 0.9 to 2.0 (molar ratio). It is desirable to use in the range. Within such a range, stable water dispersibility can be imparted to the urethane resin (C) without impairing the water resistance of the adhesive layer.

Moreover, the said urethane resin (C) may have a nonionic group as needed other than the said anionic group.
The nonionic group can be introduced into the urethane resin (C) by, for example, reacting a polyol having a nonionic group with the polyol and polyisocyanate.
As the polyol having a nonionic group, for example, a polyol having at least 30% by mass or more of ethylene oxide repeating units can be used. As the polyol having a nonionic group, for example, polyalkylene glycol having a number average molecular weight of 300 to 10,000 can be used.
As nonionic group content, it is preferable to prepare so that it may become 10 mass% or less of the whole urethane resin (C). Within such a range, good water dispersion stability can be obtained without impairing water resistance.

  The urethane resin (C) is preferably used in an amount of 0 to 2000 parts by weight, and 30 to 200 parts by weight, based on 100 parts by weight of the hydrophobic polyisocyanate (A) and the vinyl polymer (B). More preferably. By using the urethane resin (C) in such a range, it is possible to obtain an aqueous adhesive for plastic substrates capable of forming an excellent adhesive layer having high durability such as transparency, heat resistance and water resistance. it can.

  The water-based adhesive for plastic substrates of the present invention further comprises inorganic fine particles (colloidal silica) for improving blocking resistance or slip resistance, if necessary, ethanol, isopropyl alcohol, etc. for improving wettability. Alcohols, anionic, nonionic hydrocarbon or fluorine surfactants, acetylene glycol leveling agent "Surfinol" (manufactured by Air Products), or BYK-348, 346, 345, 341 (BYK- A polyalkylene glycol-modified polysiloxane represented by Chemie GmbH may be included. Among these, in order to improve wettability, it is preferable to use an acetylene glycol leveling agent. Further, the water-based adhesive for plastic substrates according to the present invention is not only the above-mentioned, but also known and commonly used fillers, thickeners, antifoaming agents, ultraviolet absorbers, antioxidants, pigment dispersants and the like as necessary. The additive may be included. Moreover, the water-based adhesive for plastic substrates of the present invention may contain a publicly known organic solvent as long as it does not remain in the adhesive layer.

Next, the laminate of the present invention and the polarizing plate will be described.
The aqueous adhesive for plastic substrates of the present invention can be used for the production of laminates composed of various plastic substrates.

  The laminate has an adhesive layer formed by the aqueous adhesive for plastic substrates between two or more plastic substrates which may be the same or different, such as a polarizing plate or a food packaging. Can be used for

  The plastic substrate can be appropriately selected depending on the use of the resulting laminate, etc., and the plurality of plastic substrates to be bonded may be substrates made of the same material, , They may be substrates made of different materials.

  Examples of the plastic substrate include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, polystyrene, acrylonitrile / styrene copolymers ( AS resin) and other styrene polymers, polycarbonate polymers, polyethylene, polypropylene, polyolefins having a cycloolefin structure or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, nylon and aromatic polyamides, etc. Amide polymers, imide polymers, sulfone polymers, polyethersulfone polymers, polyetheretherketo Polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, polyoxymethylene polymers, epoxy polymers, or blends of the aforementioned polymers, acrylic resins and urethanes A film made of a resin, an acrylic urethane resin, an epoxy resin, a silicone resin, or the like can be used. Among them, a film or sheet made of a polyester polymer, an amide polymer, or a polyolefin polymer is preferably used. .

  Moreover, the polarizing plate of this invention has the adhesive bond layer formed with the said water-based adhesive for plastic base materials between the 2 or more plastic base materials which may be the same or different. As such a plastic substrate, what is generally called a transparent protective film and a polarizer is used.

  As the transparent protective film, it is preferable to use a plastic film made of a cellulose-based polymer such as triacetyl cellulose, a resin having a cycloolefin structure, a norbornene resin, or the like, from the viewpoint of improving polarization characteristics and durability.

  In addition, the polarizer is not particularly limited, and various types of polarizers can be used. For example, from a hydrophilic polymer such as polyvinyl alcohol, partially formalized polyvinyl alcohol, ethylene / vinyl acetate copolymer partially saponified product, etc. Using uniaxially drawn dichroic materials such as iodine and dichroic dyes on a plastic base material, polyene-based oriented films such as dehydrated polyvinyl alcohol and dehydrochlorinated polyvinyl chloride can do. Of these, it is preferable to use a polyvinyl alcohol film and a film on which a dichroic substance such as iodine is adsorbed.

  The thickness of the plastic substrate that can be used when producing the laminate and the polarizing plate of the present invention varies depending on the intended use, but is preferably in the range of about 10 μm to 3 mm.

  The surface of the plastic substrate is preferably subjected to a surface treatment such as corona discharge treatment, ultraviolet irradiation treatment or alkali treatment. It is preferable to use a plastic substrate having a surface condition of preferably 45 mN / m or more, more preferably 50 mN / m or more in terms of wetness index. In addition, the said wetting index means the critical surface tension by Zisman, and is a value measured with a standard wetting reagent based on JISK8768.

  As a method for producing a laminate, particularly a polarizing plate, by adhering the plastic substrate using the water-based adhesive for plastic substrate, a conventionally known method can be applied. We apply the wet lamination method in which bonding is performed without distilling off the solvent after coating on a plastic substrate, and the dry lamination method in which bonding is performed after the solvent is distilled off after the adhesive is applied to the substrate. It is preferable.

  As a method of applying the aqueous adhesive for plastic substrates of the present invention on the plastic substrate, after adjusting the aqueous adhesive to any resin concentration and viscosity as necessary, for example, gravure coating method, rod coating It can apply | coat on the said plastic substrate by conventionally well-known coating methods, such as a method, a spray coat method, an air knife coat method, a roll coat method. Under the present circumstances, it is preferable that the density | concentration of resin in this water-based adhesive is the range of 0.1-50 mass% from a viewpoint of maintaining favorable coating workability | operativity.

  The aqueous adhesive for plastic substrates of the present invention is preferably applied so that the dry film thickness is in the range of 0.01 to 100 μm, and more preferably in the range of 0.05 to 50 μm.

  Next, the present invention will be described in detail by examples and comparative examples.

Hydrophobic polyisocyanate (AI)
Hexamethylene diisocyanate-based isocyanurate-type polyisocyanate “Burnock DN-980S” (Dainippon Ink and Chemicals, Inc., isocyanate group content (hereinafter abbreviated as NCO group content)) 21% by mass in one molecule The average number of isocyanate groups present in the above (hereinafter abbreviated as the average number of NCO functional groups) is about 3.6;

[Preparation of an active hydrogen-containing group and a nonionic group-containing vinyl polymer (b-I)]
Into a four-necked flask equipped with a stirrer, thermometer, cooling tube, and nitrogen introduction tube was charged 429 parts by mass of diethylene glycol diethyl ether, heated to 110 ° C. under a nitrogen stream, and then methoxypolyethylene glycol methacrylate (oxygen per molecule). Contains an average of 9 ethylene units (hereinafter abbreviated as “MPEGMA-1”) 500 parts by mass, 300 parts by mass of methyl methacrylate, 50 parts by mass of 2-hydroxyethyl methacrylate (hereinafter abbreviated as 2-HEMA), cyclohexyl A mixed solution consisting of 150 parts by mass of methacrylate (hereinafter abbreviated as CHMA), 45 parts by mass of t-butylperoxy-2-ethylhexanoate, and 5 parts by mass of t-butylperoxybenzoate was added dropwise over 5 hours. . After the dropping, the mixture was reacted at 110 ° C. for 9 hours to obtain an acrylic polymer solution having a nonvolatile content of 70% by mass. Hereinafter, this is abbreviated as a vinyl polymer (b-I) solution having an active hydrogen-containing group.

[Preparation of Isocyanate Group and Nonionic Group-Containing Vinyl Polymer (B-I)]
429 parts by mass of diethylene glycol diethyl ether was charged into a four-necked flask equipped with a stirrer, a thermometer, a cooling pipe, and a nitrogen introduction pipe, heated to 110 ° C. under a nitrogen stream, and then subjected to 400 parts by mass of MPEGMA-1, A mixed liquid consisting of 100 parts by weight of isocyanate ethyl methacrylate, 500 parts by weight of methyl methacrylate, 45 parts by weight of t-butylperoxy-2-ethylhexanoate, and 5 parts by weight of t-butylperoxybenzoate was added dropwise over 5 hours. did. After the dropping, the mixture was reacted at 110 ° C. for 9 hours to obtain an acrylic polymer solution having a nonvolatile content of 70% by mass. Hereinafter, this is abbreviated as a vinyl polymer (BI) solution.

[Preparation of Urethane Resin (CI) Having Anionic Group]
While introducing nitrogen gas in a reaction vessel equipped with a thermometer, a nitrogen gas inlet tube, and a stirrer, 1480 parts by mass of dimethyl 5-sulfosodium isophthalate, 1240 parts by mass of 1,6-hexanediol, and dibutyltin oxide 0 .5 parts by mass, the temperature in the reaction vessel is maintained at 180 to 190 ° C. so that the tower top temperature is 60 to 70 ° C., and the ester exchange reaction is performed until the acid value becomes 1 or less, and then 210 ° C. Was reacted for 2 hours to obtain a polyester polyol having a hydroxyl value of 240 and an acid value of 0.3.
Next, the polyester polyol and 2280 parts by mass of ε-caprolactone were mixed and subjected to a ring-opening polymerization reaction at 180 ° C. for 3 hours to obtain a sulfonic acid group-containing polyester polyol having a hydroxyl value of 120 and an acid value of 0.3.
20 parts by mass of the sulfonic acid group-containing polyester polyol is mixed and dissolved in 50 parts by mass of methyl ethyl ketone, and then 29 parts by mass of isophorone diisocyanate is added and reacted at 80 ° C. for 3 hours, and then 50 parts by mass of methyl ethyl ketone is added up to 60 ° C. Cooled down.
Next, 3 parts by mass of neopentyl glycol and 100 parts by mass of polyester (hydroxyl value = 56) obtained by reacting 1,4-butylene glycol and adipic acid were added and reacted at 80 ° C. When the NCO group content of the reaction product is 1.01% by mass or less, the reaction product is cooled to 40 ° C., 280 parts by mass of water is added and sufficiently stirred and mixed, and then 23.4 parts by mass of 10% by mass aqueous piperazine solution (residual isocyanate group) The chain elongation reaction was carried out by adding 90 equivalent% as amine groups). Subsequently, the organic solvent was removed from the obtained emulsion to obtain a urethane resin (C-I) dispersion having a nonvolatile content of 40% by mass.

[Preparation of Urethane Resin (C-II) Having Anionic Group]
To isophorone, 3 parts by mass of neopentyl glycol and 100 parts by mass of polyester (hydroxyl value = 56) obtained by reacting 1,4-butylene glycol and adipic acid were mixed with 50 parts by mass of methyl ethyl ketone. 30 parts by mass of diisocyanate was added and reacted at 80 ° C. for 3 hours. Next, 50 parts by mass of methyl ethyl ketone was added and cooled to 60 ° C., and 6 parts by mass of 2,2′-dimethylolpropionic acid was added and reacted at 80 ° C. When the NCO group content of the reaction product is 1.13% by mass or less, the reaction product is cooled to 40 ° C. and neutralized with 4.5 parts by mass of triethylamine, and then 255 parts by mass of water is added. Further, the mixture was sufficiently stirred and mixed, and 23.7 parts by mass of a 10% by mass aqueous piperazine solution (90 equivalent% as an amine group with respect to the remaining isocyanate group) was added to carry out a chain extension reaction. Subsequently, the organic solvent was removed from the obtained emulsion to obtain a urethane resin (C-II) dispersion having a nonvolatile content of 40% by mass.

Example 1
After charging 200 parts by mass of a hydrophobic polyisocyanate (AI) and 100 parts by mass of a vinyl polymer (b-I) having an active hydrogen-containing group in a four-necked flask, the temperature was raised to 90 ° C. in a nitrogen stream. , By reacting with stirring at the same temperature for 6 hours, the reaction product (B-II) of the hydrophobic polyisocyanate (AI) and the vinyl polymer (b-I), and the hydrophobic polyisocyanate A polyisocyanate composition (P-1) containing an isocyanate (AI) having a nonvolatile content of 90% by mass and an NCO group content of 13% by mass was obtained.
Next, 800 parts by mass of water was added to 100 parts by mass of the obtained polyisocyanate composition (P-1), and the mixture was uniformly stirred and mixed using a stirrer to produce [hydrophobic polyisocyanate (AI). ) / Reactant (B-II)] was 200/70, and a water-based adhesive for plastic substrates (AD-1) having a nonvolatile content of 10% by mass was obtained.

Example 2
A four-necked flask was charged with 200 parts by weight of a hydrophobic polyisocyanate (AI) and 100 parts by weight of a vinyl polymer (BI), heated to 50 ° C. in a nitrogen stream, and then at the same temperature for 1 hour. By stirring and mixing under stirring, a polyisocyanate composition (P-2) having a nonvolatile content of 90% by mass and an NCO group content of 14.6% by mass was obtained.
Next, with respect to 100 parts by mass of the obtained polyisocyanate composition (P-2), 800 parts by mass of water was added, and the mixture was uniformly stirred and mixed using a stirrer, whereby a plastic group having a nonvolatile content of 10% by mass was obtained. It was set as the water-based adhesive for materials (AD-2).

Example 3
200 parts by mass of urethane resin (C-I) and 680 parts by mass of water are added to 10 parts by mass of the polyisocyanate composition (P-1) obtained in Example 1, and uniformly stirred and mixed using a stirrer. By doing this, the water-based adhesive for plastic substrates (AD-3) whose non volatile matter is 10 mass% was obtained.

Example 4
To 100 parts by mass of the polyisocyanate composition (P-1) obtained in Example 1, 100 parts by mass of urethane resin (C-I) and 1100 parts by mass of water are added, and the mixture is uniformly stirred and mixed using a stirrer. As a result, a water-based adhesive for plastic substrates (AD-4) having a nonvolatile content of 10% by mass was obtained.

Example 5
100 parts by mass of urethane resin (C-II) and 1100 parts by mass of water are added to 100 parts by mass of the polyisocyanate composition (P-1) obtained in Example 1, and the mixture is uniformly stirred and mixed using a stirrer. As a result, a water-based adhesive for plastic substrates (AD-5) having a nonvolatile content of 10% by mass was obtained.

Comparative Example 1
A four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen inlet tube 15 parts by weight of diethylene glycol diethyl ether, 36 parts by weight of methoxypolyethylene glycol (containing 12 average oxyethylene units per molecule), hydrophobic poly Methoxy with 100 parts by weight of isocyanate (AI) charged and heated to 90 ° C. over 30 minutes and then reacted at 90 ° C. for 6 hours, 90% by weight of nonvolatile content and 12% by weight of NCO group A polyisocyanate composition (P-3) modified with polyethylene glycol was obtained.
Next, with respect to 100 parts by mass of the obtained polyisocyanate composition (P-3), 800 parts by mass of water was added, and the mixture was uniformly stirred and mixed using a stirrer, whereby a plastic group having a nonvolatile content of 10% by mass was obtained. An aqueous adhesive for materials (AD-6) was obtained.

[Confirmation of pot life]
Isocyanate content determined by the back titration method to be described later, and calculated by the following formula, after the preparation or after the preparation, the content of isocyanate groups present in each water-based adhesive for plastic substrates stored for 5 hours in an environment of 25 ° C. The stability of isocyanate groups possessed by each water-based adhesive for plastic substrates was evaluated based on the group retention.

Isocyanate group residual ratio [% by mass] = (Isocyanate group content after standing for 5 hours / Isocyanate group content immediately after preparation) × 100
○: Retention rate 95% by mass or more Δ: Retention rate 90% by mass or more and less than 95% mass ×… Retention rate less than 90% by mass

[Back titration method]
The reverse of adding an excess of dibutylamine with respect to the isocyanate groups present in the water-based adhesive to each water-based adhesive for plastic substrates and then titrating the dibutylamine remaining in the water-based adhesive with hydrochloric acid. The content of isocyanate groups remaining in the water-based adhesive for plastic substrates was determined by a titration method.

[Adhesive strength]
Apply a water-based adhesive for plastic substrates, which has been stored for 5 hours in an environment of 25 ° C. immediately after preparation or after preparation, to a norbornene film (thickness: 100 μm) that has been pre-corona-treated using a bar coater (adhesion) After drying at 70 ° C. for 3 minutes, the adhesive-coated surface and the vinyl chloride film (thickness 2 mm) were pressed using a rubber roller to produce a laminate. Next, the peel strength of each laminate cured for 3 days in an environment of 40 ° C. was measured using a tensile tester (tensile speed = 100 mm / min T-type peel). The peel strength is preferably approximately 10 N / 25 mm or more, and is preferably at a level at which film breakage is caused.

Claims (12)

A hydrophobic polyisocyanate (A), a vinyl polymer (B) having a nonionic group and an isocyanate group, and an aqueous medium, wherein the hydrophobic polyisocyanate (A) is the vinyl polymer. A water-based adhesive for plastic substrates, which is dispersed in an aqueous medium according to (B). The aqueous adhesive for plastic substrates according to claim 1, wherein the vinyl polymer (B) has a urethane bond. The vinyl polymer (B) is a hydrophobic polyisocyanate (b1), at least one active hydrogen-containing group selected from the group consisting of a hydroxyl group, a carboxyl group, an amino group, and an active methylene group, and a nonionic group The water-based adhesive for plastic substrates according to claim 1 or 2, which is obtained by reacting a vinyl polymer (b2) having The water-based adhesive for plastic substrates according to any one of claims 1 to 3, further comprising a urethane resin (C) having an anionic group. The plastic group according to claim 4, wherein the urethane resin (C) is contained in an amount of 30 to 200 parts by mass with respect to a total of 100 parts by mass of the hydrophobic polyisocyanate (A) and the vinyl polymer (B). Water-based adhesive for materials. The aqueous adhesive for plastic substrates according to claim 4, wherein the anionic group of the urethane resin (C) is a sulfonic acid group. A laminate having an adhesive layer formed by the aqueous adhesive for plastic substrates according to any one of claims 1 to 6, between two or more plastic substrates which may be the same or different. body. The laminate according to claim 7, wherein the plastic substrate is a substrate made of a resin having a cycloolefin structure. The laminate according to claim 7, wherein the plastic substrate is a plastic film. Polarized light having an adhesive layer formed by the water-based adhesive for plastic substrates according to any one of claims 1 to 6, between two or more plastic substrates which may be the same or different Board. The polarizing plate according to claim 10, wherein the plastic substrate is a substrate made of a resin having a cycloolefin structure. The polarizing plate according to claim 10, wherein the plastic substrate is a plastic film.