JP2002061096A - Multilayered structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a multilayered structure which uses a coating liquid having a heat-reversible thickening property and whose layers have sufficient thicknesses in comparison with conventional multilayered structures. SOLUTION: This multilayered structure comprising a substrate and plural coating layers, characterized in that at least two layers of the coating layers are formed by the multicoating and multibaking treatments of a heat-reversible thickening agent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multilayer structure comprising a substrate and a plurality of coating layers, and more particularly, to a multilayer structure utilizing a coating liquid having a thermoreversible viscosity.

[0002]

2. Description of the Related Art Conventionally, in order to obtain a multilayer structure using a thermoreversible thickening coating solution, a first layer is coated with a thermoreversible thickening coating solution, dried, and then thermoreversible. It is manufactured by a method of applying and drying a coating liquid having no viscosity increase as a second layer.

[0003]

However, when a multilayer structure is obtained by the above-described manufacturing method, each coating layer penetrates each other, and a coating layer having a desired thickness cannot be obtained. Further, even if a thermoreversible thickening coating solution is used for only one layer of the multilayer structure, the permeation of the upper layer to the lower layer is not stopped, and a sufficiently thick coating layer is not formed on the second and subsequent layers. There was a problem.

[0004]

Means for Solving the Problems As a result of intensive studies, the present inventors have found that at least two of the coating layers are formed by applying a coating liquid (A) having a thermoreversible viscosity by multi-coating and multi-baking. As a result, it has been found that a multilayer structure in which each coating layer has a sufficient thickness and exhibits desired physical properties can be obtained, and the present invention has been achieved.

That is, the present invention relates to a multilayer structure comprising a base material and a plurality of coating layers, wherein at least two of the coating layers are multi-coated with a coating liquid (A) having thermoreversible viscosity. It is a multilayer structure characterized by being formed by multi-baking.

The multilayer structure according to the present invention comprises a substrate and a plurality of coating layers. The substrate is not particularly limited as long as it is a material covered by the coating layer. Base paper (high quality paper, medium paper, etc.), information paper base paper (thermal paper base paper, electrostatic recording paper base paper, thermal transfer paper base paper, inkjet paper base paper, discharge recording paper base paper, magnetic recording paper base paper, PPC paper base paper, etc.) Etc.), resin films [polyester, polyamide, polyethylene, polypropylene, cellophane etc.], wood [cedar, pine, cypress etc.],
Fibers [cotton, polyester, polyamide, rayon, etc.] and non-woven fabrics [polyester, polyamide, polyethylene, polypropylene, etc.] and the like.

[0007] The coating layer is usually at least two layers, preferably 2 to 12 layers, more preferably 2 to 2 layers.
It is composed of eight layers, and at least two layers, preferably two to six layers, of these layers are layers formed from the thermoreversible thickening coating solution (A). (A) is a multi-coated / multi-baked one. The multi-coat / multi-bake is a method of repeating the operation of applying and drying a kind of layer, and then applying and drying a second layer. In the present invention, the remaining coating liquid other than the coating liquid (A) for forming the multilayer structure is a coating liquid (B) having no thermoreversible thickening.

[0008] The coating liquid (A) in the present invention contains a thermoreversible thickener (a1), and may contain a resin binder (a2) and / or other additives as required.

As the thermoreversible thickener in the present invention, a thermoreversible thickener (a1) whose hydrophilicity and hydrophobicity reversibly change at a certain temperature (transition temperature) as a boundary is usually used. No. The above transition temperature is usually 40 to 95 ° C, preferably 60 to 80 ° C. When the transition temperature is lower than 40 ° C., the viscosity at room temperature of the coating liquid containing the thermoreversible thickener becomes too high, and when the transition temperature exceeds 95 ° C., the thermoreversible thickening is substantially increased. Not expressed in The transition temperature is determined by gradually heating a 1% by weight aqueous solution of a thermoreversible thickener and measuring the temperature at which the aqueous solution starts to become cloudy.

Specific examples of the thermoreversible thickener (a1) include (a) a (meth) acrylic acid ester of an adduct of 1 to 40 moles of an alkylene (C2-4) oxide of a cyclic amine as an essential monomer (B) (a) alkylene of acyclic amine having 5 or more carbon atoms (2 to 2 carbon atoms) such as a morpholinoethyl (meth) acrylate polymer described in JP-A-6-9848. 4) (co) polymers (diisopropylaminoethyl (meth) acrylate polymers and the like) containing (meth) acrylic acid ester of oxide 1-40 mol adduct as an essential monomer; (c) total carbon number of 3-6 (Co) polymers containing (meth) acrylamide of monoalkylamine or alkoxyalkylamine as an essential monomer [N-isopropyl (meth) acrylamide polymer, N-methoxypropyl (methyl (T) Acrylamide polymers and the like described in JP-A-1-142276]; (d) (meth) acrylamide of dialkylamine, dialkoxyalkylamine or cyclic amine having a total of 2 to 8 carbon atoms as an essential monomer (Co) polymer [N, N-diethyl (meth) acrylamide polymer, N- (meth) acryloylpyrrolidine polymer, etc.
No. 4]; (e) a (co) polymer having a vinyl monomer having a polyiminoethylene group (degree of polymerization of 2 to 50) as an essential monomer [tetraethyleneimine mono (meth) (F) Acrylamide polymers and the like described in JP-A-9-12781]; (f) a (meth) acrylamide having a cyclic amino group or an alkylamino group having 5 or more carbon atoms of an alkyl group as an essential monomer ( (Co) polymer [N-morpholinoethyl (meth) acrylamide polymer and the like]; (g) polyoxyalkylene having 2 to 4 carbon atoms in the alkylene group (degree of polymerization: 3 to 40) monool or diol mono (meth) Acrylate as an essential monomer (co)
Polymers [tetraethylene glycol monoethyl ether mono (meth) acrylate polymer, pentaethylene glycol monobutyl ether mono (meth) acrylate polymer, methoxytrioxypropylene tetraoxyethylene (meth) acrylate polymer, ethylene oxide 6 of tetrapropylene glycol Mono (meth) acrylate polymer of a molar adduct, etc.); (h) polyoxyalkylene having 2 to 4 carbon atoms in the alkylene group (degree of polymerization: 3 to 40) monool or diol monovinylphenyl ether as an essential monomer (Co) polymers (tetraethylene glycol monomethyl ether monovinyl phenyl ether polymer, pentaethylene glycol monoethyl ether monovinyl phenyl ether polymer, methoxypentaoxypropyl Tetraoxyethylene vinyl phenyl ether polymer, monovinyl phenyl ether polymer of 8 moles of ethylene oxide adduct of tetrapropylene glycol, etc.); alkylene oxide adduct of (li) alkyl naphthalene formalin condensate (JP-A-63-193901) And the like. (Nu) Polymers comprising a monomer having an epoxy group and an alkylamino group having 5 or more carbon atoms in a cyclic amino group or an alkyl group (eg, polymorpholinoethyl glycidyl ether such as JP-A-9-31340) JP-A-6-256617; (e) Cellulose-based thermoreversible thickeners (methylcellulose, hydroxymethylcellulose, etc.) ; (V) vinyl alkyl (carbon (Equations 1 to 6) Ether polymers (vinyl methyl ether polymer and the like) and (f) vinyl acetate / vinyl alcohol copolymer.

Of these, the thermoreversible thickeners (a1) are preferably (a) to (h) in terms of imparting a high temperature-sensitive viscosity, and are preferably vinyl vinyl selected from (a) to (d). Mers are particularly preferred. The weight average molecular weight of the (a1) by GPC is usually 1,000 to 5,000,000, preferably 2,000 to 500,000.

The thermoreversible thickener (a1) can be produced by a known radical polymerization method, and may be any method such as solution polymerization, bulk polymerization and emulsion polymerization. In addition, (a2) may be in any shape such as an aqueous solution, latex, or lump. The solid content in the case of an aqueous solution or latex is usually 5 to 5.
70% by weight, preferably 30-60% by weight, pH
Is usually 3 to 12, preferably 6 to 10.

The coating liquid (A) in the present invention contains a thermoreversible thickener (a1) and a resin binder (a2).
2) is a resin latex, a resin powder, or the like containing a resin component serving as a binder. Examples of the resin component include an acrylic resin, a styrene-acrylic resin, a styrene-butadiene resin, a butadiene-acrylic resin, and a butadiene. -Acrylonitrile resin, vinyl acetate resin, ethylene-vinyl acetate resin, ethylene-propylene resin, polybutadiene resin, polyvinyl alcohol resin, styrene-maleic resin, polyacrylic resin, modified polystyrene resin Examples include vinyl polymers such as resins.

The vinyl polymer constituting the resin binder (a2) is a (co) polymer of a radical polymerizable monomer. Examples of the radical polymerizable monomer include: (1) a nonionic monomer Group (cyclo) alkyl (C 1-22) (meta)
Acrylate [methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth)
Acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate, octadecyl (meth) acrylate, etc.]; aromatic ring-containing (meth) acrylate [benzyl (meth) acrylate, phenylethyl (meth) acrylate, etc.]; hydroxyl group-containing (meth) Acrylate [2
-Hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, diethylene glycol mono (meth) acrylate, glycerin mono (meth) acrylate, polyglycerin (polymerization degree 2 to 4) mono (meth) acrylate, etc.]; ) Acrylamide or its derivative [(meth) acrylamide, N, N
-Dibutyl (meth) acrylamide, cyclohexyl (meth) acrylamide, N-methyl (meth) acrylamide, N-methylol (meth) acrylamide, diacetone acrylamide, etc.]; cyano group-containing monomer [(meth) acrylonitrile, 2-cyanoethyl (Meth) acrylate, 2-cyanoethylacrylamide, etc.]; polyfunctional (meth) acrylate [(poly) ethylene glycol (number of oxyethylene units = 1 to 100) di (meth) acrylate, (poly) propylene glycol (oxypropylene unit) Number = 1-100) di (meta)
Acrylate, 2,2-bis (4-hydroxyethylphenyl) propane di (meth) acrylate, trimethylolpropane tri (meth) acrylate, etc.]; styrene monomers (styrene, α-methylstyrene, vinyltoluene, p-hydroxy Diene monomers (butadiene, isoprene, chloroprene, etc.); vinyl esters (vinyl acetate, vinyl propionate, vinyl butyrate, etc.); epoxy group-containing monomers [glycidyl (meth) acrylate, Monoolefins (ethylene, propylene, 1-butene, etc.); halogen-containing monomers (vinyl chloride, vinylidene chloride, etc.); heterocyclic-containing monomers (N-vinyl-2-pyrrolidone, N -Methylol maleimide, N-
Vinyl succinimide, etc.); unsaturated dibasic acid dialkyl esters [dialkyl maleate (C1-8), dialkyl itaconate (C1-8), etc.]; silyl group-containing monomer [3-tri (2) Anionic monomer Monocarboxylic acid monomer [(meth) acrylic acid, crotonic acid, monoalkyl maleate (C1-8) ester, itaconic acid] Monoalkyl (C1-8) ester, vinyl benzoic acid, etc.]; dicarboxylic acid monomer [(anhydride) maleic acid, fumaric acid, itaconic acid, etc.]; monosulfonic acid monomer [vinyl sulfonic acid, (Meth) allylsulfonic acid, styrenesulfonic acid, alkyl (1 to 1 carbon atoms)
10) allylsulfosuccinic acid and the like]; sulfate-based monomers [(meth) acryloylpolyoxyalkylene (polymerization degree 2 to 15) sulfate and the like]; and salts thereof [alkali metal salts such as sodium salt and potassium salt; Amine salts such as triethanolamine, tetraalkyl (C4
-18) Quaternary ammonium salts such as ammonium salts)]
(3) Cationic monomer Tertiary amino group-containing monomer [N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N-diethylaminoethyl ( (Meth) acrylate, N, N-diethylaminopropyl (meth) acrylate, N, N-dibutylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide And the like]; aromatic ring-containing cationic monomers [vinylaniline, p-aminostyrene, etc.]; heterocyclic-containing cationic monomers [N-vinylcarbazole, vinylimidazole, 2-vinylpyridine, etc.]; and salts thereof. (Inorganic acid salts such as hydrochloride and phosphate, and organic acid salts such as formate and acetate); and A combination of two or more thereof.

Preferred among these are aliphatic alkyl (C1 to C22) (meth) acrylates, styrene monomers and diene monomers, and diene monomers and alkyl (meth) acrylates. And / or a resin obtained by combination with a styrene monomer is particularly preferred. Further, these resin binders (a2) are usually in the form of latex, powder, or the like, and among them, latex is preferred.

When the resin binder (a2) is in the form of a latex, if the amount of the surfactant in the aqueous phase in the resin latex is 0.01 mmol / g (resin) or less, the temperature-sensitive thickening is reduced. 0.002 mmol is preferable because the temperature range from the start of thickening to gelation can be widened.
/ G or less is more preferable. The amount of the emulsifier in the aqueous phase is a molar concentration based on the weight of the resin component in the resin binder (a1). The amount of the surfactant in the aqueous phase was determined by diluting 50 g of the resin binder (a2) to a concentration of 10% by weight.
2.0 g of the supernatant obtained by centrifugation at 30,000 rpm for 30 minutes was taken and quantified by high performance liquid chromatography.

As a method for producing a resin latex in which the amount of an emulsifier in an aqueous phase is 0.01 mmol / g or less, for example,
Non-polymerizable emulsifiers having low solubility in water (for example, those having an HLB value of 3 to 9, for example, salts of amines or alkali metals of fatty acids having 22 or more carbon atoms, aliphatic or aromatic alcohols having 15 or more carbon atoms) Emulsion polymerization of a polymerizable monomer using ethylene oxide 1 to 6 mol adduct), a method of emulsion-polymerizing the monomer using an emulsifier having a radical polymerizable group, and a method of using a water-soluble polymer as a protective colloid. Emulsion polymerization method: After polymerizing a polymerizable monomer having an ion-forming group in an organic solvent by (co) polymerization to synthesize a polymer, the obtained polymer is neutralized with an acid or alkali, and then water is added to emulsify the polymer. And a method of removing the solvent.

Among these methods, the method of emulsion polymerization is preferable in that a latex containing a high molecular weight resin is obtained, and the method of emulsion polymerization of a polymerizable monomer using an emulsifier (E) having a radical polymerizable group. Is particularly preferred.

The emulsifier (E) having a radical polymerizable group includes, for example, a polymerizable emulsifier represented by the following general formula (1).

[0020]

Embedded image

Wherein Ar is an aromatic ring, R ¹ is a hydrogen atom or a methyl group, R ² and R ³ are monovalent hydrocarbon groups,
At least one of R ² and R ³ is a hydrocarbon group having an aromatic ring. m and n are 0 such that m + n is 1 to 8.
Or an integer of 1 to 4, R ⁴ and R ⁵ are a hydrogen atom or a methyl group, M is a cation, A is an alkylene group having 2 to 4 carbon atoms, and p and q are 0 or an integer of 1 to 40.

In the general formula (1), examples of the aromatic ring of Ar include a hydrocarbon aromatic ring and an aromatic ring containing a hetero atom. Examples of the hydrocarbon group include a benzene ring and a naphthalene ring, and examples of the aromatic ring containing a hetero atom include a thiophene ring and a pyrrole ring. R ² and R ³ are monovalent hydrocarbon groups, for example, an alkyl group,
They are an alkenyl group, an aralkyl group, an alkyl-substituted aralkyl group, a styryl group, a polystyryl group and a fused benzyl group, and at least one of R ² and R ³ is an aromatic ring-containing hydrocarbon. The alkyl group has 1 to 1 carbon atoms.
24 linear and branched hydrocarbons (methyl group, ethyl group,
Examples of n- and i-propyl groups, neopentyl groups, hexyl groups, octyl groups, etc., and alkenyl groups include straight-chain and branched hydrocarbons having 2 to 24 carbon atoms (allyl, propenyl, octenyl, nonenyl, decenyl). Groups, undecenel groups, dodecenel groups, etc.), aralkyl groups include benzyl group, 2-phenylethyl group, 3-phenylpropyl group, and the like, and polystyryl groups include groups obtained by condensing or adding 2 to 8 styrenes, Examples of the condensed benzyl group include groups obtained by condensing 2 to 8 benzyl chlorides. Of these, preferred are styryl groups,
They are a polystyryl group, a benzyl group and a condensed benzyl group, and the total of m and n is preferably 2 to 7. A has 2 to 2 carbon atoms
4 alkylene groups, which are an ethylene group, a propylene group, and a 1,2-butylene group. p and q are 0 or an integer of 1 to 40, preferably 5 to 40;
And the sum of q is preferably 15 to 40.

When at least one of R ² and R ³ is an aromatic ring-containing hydrocarbon, or when the sum of p and q is 5 or less, the emulsion stability during radical polymerization is excellent, and particles of the resin latex to be formed are obtained. Diameter can be optimized. When the sum of p and q is 40 or less, the hydrophilicity of the polymerizable emulsifier does not become too large, and also in this case, the emulsion stability of the monomer during radical polymerization is excellent, and the particle size of the resulting resin latex is optimized. it can.

Specific examples of the compound of the general formula (1) include
Bis (polyoxyalkylene polycyclic phenyl ether) sulfates of monomethacrylate may be mentioned, and bis (polyoxyalkylene polycyclic phenyl ether) includes polycyclic phenols (for example, styrenated phenol, benzylated phenol, etc.). In this case, the number of moles of styrene or benzyl added is 0.1 per phenol ring.
A carbonyl compound of 2 to 4 styrene or benzyl groups may be directly added to the phenol ring or a structure in which a plurality of styrene or benzyl groups are added to the styrene or benzyl group added to the phenol ring. For example, a product obtained by adding an alkylene oxide to a condensate of formaldehyde, acetaldehyde, acetone, or the like, or a product obtained by styrenating or benzylating a phenol of a bisphenol (for example, bisphenol A or bisphenol F) in the same manner as described above. Those to which an alkylene oxide has been added are exemplified. When the bis (polyoxyalkylene polycyclic phenyl ether) is a formaldehyde condensate, a trinuclear or higher condensate may be by-produced, and a monomethacrylate sulfate salt other than the general formula (1) may be used. Although produced, those containing these by-products can also be used as (E).

As a method for producing the compound of the general formula (1), polycyclic phenol is condensed with formaldehyde, alkylene oxide is added, and then (meth) ) After dehydration and esterification with acrylic acid, sulfated with a normal sulfating agent, and then neutralized if necessary.

As the polymerizable emulsifier (E), CH ₂ ＣC (R ¹ ) COO (CH ₂ ) _m SO ₃ M [wherein R ¹
Represents a hydrogen atom or a methyl group, m represents an integer of 1 to 24, and M represents an alkali metal ion, an ammonium ion or an aminium ion. CH ₂ ＣC (R ¹ )
COO (AO) pSO ₃ M or CH ₂ ＣC (R ¹ ) COO
(AO) pCH ₂ COOM wherein R ¹ is a hydrogen atom or a methyl group, AO is an oxyalkylene group having 2 to 4 carbon atoms, p
Represents an integer of 2 to 200, and M represents an alkali metal ion, ammonium ion or aminium ion. And the polymerizable emulsifiers described in JP-A-9-25454.

Of these, those of the general formula (1) are preferred in that they have good copolymerizability with various monomers, especially styrene.

The amount of the polymerizable emulsifier (E) to be used is generally 0.1 to 20% by weight, preferably 1 to 10% by weight, based on the resin content of the latex.

In producing the resin latex by the emulsion polymerization method, a known polymerization initiator is used. Examples of the polymerization initiator include organic polymerization initiators [peroxides (cumene hydroperoxide, diisopropylbenzene hydroperoxide, paramethane hydroperoxide,
Benzoyl peroxide, lauroyl peroxide, etc.), azo compounds (azobisisobutyronitrile, azobisisovaleronitrile, etc.), inorganic polymerization initiators, persulfates (sodium persulfate, ammonium persulfate,
Potassium persulfate, etc.), hydrogen peroxide, etc.].
The amount of the polymerization initiator to be used is generally 0.01 to 5% by weight, preferably 0.1 to 3% by weight, based on the total amount of the monomer mixture.

A known chain transfer agent can be used for adjusting the molecular weight of the resin, the gel content of the latex, and the like. Examples of the chain transfer agent include α-methylstyrene dimer (2,4-diphenyl-4-methyl-1-pentene, etc.), terpinolene, terpinene, dipentene, alkyl mercaptan having 8 to 18 carbon atoms, and 8 to 18 carbon atoms.
Alkylenedithiol, alkyl thioglycolate,
Dialkyl xanthogen disulfide, tetraalkyl thiuram disulfide, chloroform, carbon tetrachloride and the like can be mentioned. These can be used alone or in combination of two or more. The amount of the chain transfer agent is usually 0 to 15% by weight, preferably 0 to 15% by weight, based on the total amount of the monomer mixture.
5% by weight.

If necessary, a reducing agent [sodium pyrobisulfite, sodium sulfite, sodium hydrogen sulfate,
Ferrous sulfate, glucose, sodium formaldehyde sulfoxylate, L-ascorbic acid (salt)], chelating agent (glycine, alanine, sodium ethylenediaminetetraacetate, etc.), pH buffering agent (sodium tripolyphosphate, potassium tetrapolyphosphate, etc.) And the like may be used in combination. The amount of these additives is usually 0 to 5% by weight, preferably 0 to 3% by weight, based on the total amount of the monomer mixture.
It is.

In producing the resin latex by emulsion polymerization, the thermoreversible thickener (a
It may be carried out in the presence of 1), for example, with respect to monomer 0.1.
Before the start of emulsion polymerization, 001 to 20% by weight of (a1) is dissolved in water serving as a dispersion medium, and emulsion polymerization can be performed under the above conditions. In this case the product is a resin binder
Since (a2) and the thermoreversible thickener (a1) are included, it becomes a resin binder composition having thermoreversible thickening, as it is,
Or, if necessary, other additives described below can be added to use as the coating liquid of the present invention.

The weight average molecular weight of the resin binder (a2) of the present invention by GPC is usually 10,000 or more, preferably 100,000 to 1,000,000 or more.

The glass transition temperature (Tg) of the resin binder (a2) is usually -80 to 80 ° C, preferably -50 to
50 ° C. The Tg was measured by flowing a resin latex into a glass mold and drying under reduced pressure at 30 ° C. for 8 hours. A film having a thickness of about 0.3 mm was obtained by a differential scanning calorimeter (DS).
It is a value measured under the condition of 20 ° C./min under nitrogen using C). The gel content of the resin binder (a2) is
Usually, it is 5 to 95% by weight, preferably 30 to 80% by weight. The gel content is the content of the toluene-insoluble component in the dried resin, and the resin latex was poured into a glass mold having a thickness of 1 mm, dried under reduced pressure at 30 ° C. all day and night, and about 1 g of the obtained film was precisely weighed. Then, it is dissolved in 400 ml of toluene for 48 hours, filtered with a filter paper of known weight, dried under the above conditions, weighed precisely, and calculated by the following formula. Gel content (%) = [weight of toluene-insoluble matter on filter paper / weight of film before dissolving in toluene] × 100

When the resin binder is a latex, the average particle size (arithmetic average; by laser Doppler method)
Usually 50 to 500 nm, preferably 120 to 220 nm
It is.

When the resin binder is a latex or a solution, the solid content is usually 10 to 70% by weight, preferably 30 to 60% by weight, and the pH is usually 3 to 12%.
Preferably it is 6-10.

In the coating liquid (A) of the present invention,
When (A) contains (a2), the solid content weight ratio of (a1) to (a2) is usually (a1) :( a2) = (0.001 to 3)
0): (70 to 99.999), preferably (0.00
5 to 20): (80 to 99.995). When the amount of (a1) is 0.001 or more, the thermosensitive gelling property is easily exhibited, and when the amount is 30 or less, the viscosity of the coating solution (A) is not excessively high, which is preferable.

In the present invention, a known water-soluble polymer can be contained in the thermoreversible thickening coating solution (A), if necessary. Specific examples include polyvinyl alcohol and modified products thereof (partially saponified ethylene-vinyl acetate copolymer, partially acetalized polyvinyl alcohol, etc.), starch or modified products thereof (oxidized starch, phosphated starch, cationized product). Starch, etc.), cellulose derivatives (carboxymethylcellulose, etc.), poly (meth) acrylamides [(meth) acrylamide polymer, (meth) acrylamide-sodium (meth) acrylate copolymer, Mannich-modified polyacrylamide, etc.], Formalin condensation type resin (urea-formalin resin, melamine-formalin resin, etc.), polyethyleneimine, polyamide polyamine-epichlorohydrin, soda salt of styrene-maleic acid copolymer, (meth) acrylic acid alkyl ester- (meth) Soda salt of acrylic acid copolymer, casein, soybean protein, synthetic protein,
And mannangalactan derivatives. The content of the water-soluble polymer is usually 0 to 25 parts by weight, preferably 0.2 to 5 parts by weight, per 1 part by weight of the solid content of (a1) and (a2).

The coating liquid (A) for forming the multilayer structure of the present invention can contain known pigments, dyes, magnetic materials, resin beads, resin powders and the like according to the application of the multilayer structure. .

Examples of pigments include various clays, kaolin, calcium carbonate, satin white, titanium oxide, aluminum hydroxide, barium sulfate, zinc oxide, calcium sulfate, inorganic pigments such as talc, titanium white, white carbon, shirasu balloon, and plastics. Pigment (beads such as polystyrene, styrene / butadiene copolymer or styrene / acrylic copolymer), organic pigments such as epoxy beads, urethane beads, and polyethylene hollow beads.

The content of the pigment is usually 0 to 25 parts by weight, preferably 3 to 10 parts by weight, based on 1 part by weight of the total solid content of (a1) and (a2).

Examples of the dye include leuco dyes, fluoran dyes, diazo dyes, anthracene dyes, and the like. Further, if necessary, a phenol compound such as bisphenol or thiophenol may be used for coloring these dyes. A salicylic acid derivative or the like may be contained.

As magnetic materials, γ-Fe ₂ O ₃ , CrO
₂ and barium ferrite.

Further, if necessary, a pigment dispersant [sodium poly (meth) acrylate, sodium pyrophosphate, sodium hexametaphosphate, etc.] and an antifoaming agent (mineral oil-based antifoaming agent, silicon-based antifoaming agent, etc.) And other additives [lubricant, pH adjuster, preservative, waterproofing agent, printability improving agent, etc.]. The content of the additive is based on 1 part by weight of the total solid content of (a1) and (a2),
Usually 0 to 2.5 parts by weight, preferably 0.005 to 0.5
Parts by weight.

In the thermoreversible thickening coating solution (A), (a2) and / or other additives (such as the above-mentioned water-soluble polymer and pigment) may be used in the same manner as in the case of (a1) alone. Even in the case of containing, the thickening starts at a certain temperature by heating and then increases rapidly, and the thickening behavior is thermoreversible. The temperature at which this (A) thickens is a thermoreversible thickener.
Although defined by (a1), it is usually 50 to 90 ° C, preferably 60 to 70 ° C. The thickening behavior varies depending on the type of the pigment and / or the additive, but a sufficient effect is exhibited when the viscosity at least 1.2 times the viscosity at 25 ° C. occurs.

The thermoreversible thickening coating solution (A) comprises a thermoreversible thickener (a1) and, if necessary, a resin binder (a2) and / or
Alternatively, it can be obtained by mixing other additives with a usual mixer (paddle-type stirrer or the like) at a temperature lower than the temperature at which the hydrophilicity and hydrophobicity of (a1) change.

In the multilayer structure of the present invention, the coating liquid (B) having no thermo-reversible thickening, which is used if necessary, can contain a known resin binder if necessary.
For example, it may contain the resin binder (a2) described above. If necessary, the above-mentioned water-soluble polymer and / or other additives can be contained.

In the multi-coat / multi-bake of the present invention, first, one kind of thermo-reversible thickening coating solution (A1) is applied;
After drying, a second thermoreversible thickening coating solution (A2) is applied thereon, followed by drying. A method of repeating a plurality of times, or after, a coating having no thermoreversible thickening. A method in which the liquid (B) is applied and then dried, and a method in which: is performed after or after, and finally performed again. When a plurality of layers of the coating liquid (B) having no thermoreversible viscosity are continuously applied, multi-coat / multi-bake or multi-coat / one-bake may be used.
Further, at least the first layer is preferably a thermoreversible thickening coating liquid (A1) from the viewpoint of reducing the penetration into the substrate surface, and as a coating liquid applied thereon after drying. May be the same or different thermoreversible thickening coating liquid (A2) as (A1).

As the coating device, a conventionally known coating device such as a blade coater device, an air knife device, a spray device and the like can be used, and the first layer and the second and subsequent layers are coated by the same coating device. Or a combination of different devices.

For example, there is a method in which the first layer is coated with a blade coater or an air knife, and then the second and subsequent layers are coated with a spray. At this time, if the substrate is heated to a predetermined temperature (40 to 100 ° C.), a multilayer structure can be obtained more effectively.

The coating amount of the coating liquid per one coating layer in the present invention varies depending on the solid content of the coating liquid, but is usually 1 to 100 g / m ² , preferably 5 to 100 g / m ^2. 8
0 g / m ² . Further, the thickness of one type of coating layer is usually 0.1 to 100 μm.

The drying conditions of the coating layer are appropriately selected depending on the heat resistance of the substrate, the composition and the thickness of the coating layer, and the temperature of the coating layer surface is usually 40 to 120 ° C., preferably 60 to 120 ° C.
There is no particular limitation as long as the drying condition is 100 ° C, but the temperature of the hot air is usually 60 to 180 ° C. The drying device is not particularly limited, but a conventionally known circulating dryer or far-infrared dryer can be used.

Specific examples of the multilayer structure of the present invention include a multilayer structure using the above-mentioned base material such as paper, film, wood, fiber, non-woven fabric, metal and the like. In particular, water resistance,
It is suitable for a multilayer structure such as a recording medium or a printed matter which requires an overcoat layer for imparting abrasion resistance. For example, magnetic recording paper with an overcoating agent (such as acrylic resin latex) applied on the undercoat layer to prevent the magnetic material from falling off due to abrasion, and the strength of the coating layer is required more than ever. In the field of thermal recording paper, which is used, thermal recording paper overcoated with polymer materials such as PVA and acrylic resin, and in the field of coated paper, reduce costs while maintaining printability. Are required, and 2 having different pigment compositions
It is suitable for a coated paper having a plurality of coating layers.

As described above, the multilayer structure of the present invention is obtained by laminating materials exhibiting the functions corresponding to the respective applications without being mixed with each other, and can be widely used in various industrial fields.

[0055]

EXAMPLES The present invention will be further described with reference to the following examples, but the present invention is not limited to these examples. In the examples, parts are parts by weight and% is% by weight.

Production Example 1 (Thickener 1) 90 parts of morpholinoethyl methacrylate, 10 parts of methacrylic acid and 0.1 part of 2,2'-azobis (2,4-dimethylvaleronitrile) were put into an ampoule and frozen and degassed. Thereafter, the mixture was sealed and polymerized at 50 ° C. for 8 hours to obtain “thickener 1” (temperature at which hydrophilicity and hydrophobicity change = 65 ° C.).

Production Example 2 (Thickener 2) 100 parts of N-acryloylpyrrolidine and 2,2'-
1 part of azobis (2,4-dimethylvaleronitrile) can be put in an ampoule, frozen, degassed, sealed and polymerized at 50 ° C. for 8 hours to obtain “thickener 2” (temperature at which hydrophilicity and hydrophobicity change). = 56 ° C).

Production Example 3 (Binder 1) 102 parts of water, 45 parts of styrene, 9 parts of methyl methacrylate, 4 parts of methacrylic acid were placed in a pressurized reaction vessel equipped with a stirrer, a dropping cylinder, a nitrogen gas inlet tube and a thermometer. “Antox-60” as a polymerizable emulsifier ^{* 1)} 5 parts of [Nippon Emulsifier Co., Ltd.], 1 part of sodium persulfate and 0.2 part of lauryl mercaptan were charged, and the system was replaced with nitrogen gas under stirring and then replaced with nitrogen gas. 37 parts of butadiene was press-fitted from a dropping cylinder and reacted at 50 ° C. for 30 hours and further at 85 ° C. for 5 hours. Next, the unreacted monomer was stripped under reduced pressure, and the pH was adjusted to 9.5 with a 10% aqueous sodium hydroxide solution, whereby the solid content was 47.9%, the emulsifier amount in the aqueous phase was 0.0008 mmol / g (resin), Diameter 200n
m, an SBR resin latex (hereinafter, referred to as “binder 1”) having a weight average molecular weight of 2,000,000, a glass transition temperature of 9.8 ° C., and a gel content of 81%. * 1) Ammonium sulfate ammonium salt of bis (polyoxyethylene polycyclic phenyl ether) monomethacrylate [R ¹ is a methyl group, R ² and R ³ are polystyryl groups in general formula (1), and m + n is 2 to 6 ( The average is 4 to 5), A is an ethylene group, M is ammonium, and the sum of p and q is 23 to 25.
Mixture of

Production Example 4 (Binder 2) 102 parts of water, 45 parts of styrene, 20 parts of butyl methacrylate, 26 parts of methyl methacrylate were placed in a pressurized reaction vessel equipped with a stirrer, a dropping cylinder, a nitrogen gas inlet tube and a thermometer.
Parts, 4 parts of methacrylic acid, 0.05 parts of divinylbenzene,
As an emulsifier having a radical polymerizable group, 5 parts of sodium salt of methacryloyl polyoxypropylene (degree of polymerization = 10), 1 part of sodium persulfate and 0.2 part of lauryl mercaptan were charged, and the system was replaced with nitrogen gas under stirring. Thereafter, the reaction was carried out at 50 ° C. for 30 hours and further at 85 ° C. for 5 hours. Then, unreacted monomers are stripped under reduced pressure, and the pH is adjusted with a 10% by weight aqueous sodium hydroxide solution.
By adjusting to 9.5, the solid content was 47.9%, the emulsifier amount in the aqueous phase was 0.0080 mmol / g (resin), the particle diameter was 180 nm, the weight average molecular weight was 500,000, the glass transition temperature was 4.5 ° C., and the gel was A styrene-acrylic resin latex having a content of 37% (hereinafter referred to as "binder 2") was obtained.

Production Example 5 (Coating liquid) In a two-necked flask equipped with a stirrer and a thermometer, 100 parts of "Binder 1" and 0.1 part of "Thickener 1" were charged. The mixture was stirred and mixed at 250 rpm for 180 minutes. Further, add 1000 parts of kaolin, and add
The mixture was stirred and mixed for 0 minute to obtain a coating liquid (A1) having a solid content of 60%.

Production Examples 6 to 12 and Comparative Production Examples 1 to 4 Except that the thermoreversible thickener (a1), the resin binder (a2) and other additives shown in Table 1 were blended in the proportions shown in Table 1. In the same manner as in Production Example 5, coating solutions (A2) to (A8) and comparative coating solutions (X1) to (X4) were obtained.

[0062]

[Table 1]

Examples 1 to 6 and Comparative Examples 1 to 3 Commercially available PPC paper (basis weight: 64 g / m 2) was used as a substrate, and when two coating layers were used, the first layer was coated. 12 ±
No. to be 0.5 g / m2. After coating using a bar coater of Nos. 4 to 6, drying at a hot air temperature of 135 to 145 ° C. and a drying time of 30 seconds was performed once using a circulating drier. The second layer is coated using a spray coating machine at a coating amount of 10 ± 0.5 g / m 2.
Then, drying was performed once with a circulating dryer at a hot air temperature of 135 to 145 ° C. and a drying time of 30 seconds. When the coating layer has three layers, the third layer is further coated using a spray coating machine so as to have a coating amount of 10 ± 0.5 g / m 2, hot air temperature of 135 to 145 ° C., and drying time again. Drying for 30 seconds was performed once using a circulation dryer.

As an evaluation of the multilayer structure of each of the examples and comparative examples, cross-sectional observation was performed with an electron microscope (magnification = 1000 times, cross-sections at 10 locations were observed with a primary electron image), and the thickness of each layer (mixed). (Thickness of a layer without a layer) was measured, and the separability of the layer was evaluated. Transferability of pigment by cellotape (width 20 mm) (evaluation of pigment transfer to cellotape when cellotape (registered trademark) is adhered to the coated surface at a linear pressure of 10 kg / cm and peeled off at a speed of 50 cm / min)
Was measured and the surface protection effect was evaluated. Table 2 shows the results.

[0065]

[Table 2]

[0066]

As described above, in the multilayer structure, at least two layers are formed by multi-coating and multi-baking a coating solution (A) having a thermo-reversible viscosity, so that each coating layer is sufficiently separated. In addition, the thickness of the coating layer is not easily reduced, and a multilayer structure having good physical properties can be obtained. Therefore, since it has an excellent surface protection effect, it is extremely useful for recording media such as magnetic recording paper and thermal paper.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08F 20/34 C08F 20/34 20/56 20/56 C08J 7/04 C08J 7/04 Z D21H 19/82 D21H 19/82 F-term (reference) 4D075 AE03 DA04 DB18 DB31 DC27 DC28 EB10 EB24 4F006 AA02 AB24 AB32 BA02 BA05 CA01 CA02 4J011 KA04 KA06 4J100 AL08P AM17P AM19P AM21P BA03P BA04P BA08P BA31P JA79A37 AG037 AJ01 AJ03 AJ04 BE07 BE09 EA32 FA11 FA13 GA08 GA12 GA19

Claims (7)

[Claims] 1. A multilayer structure comprising a substrate and a plurality of coating layers, wherein at least two of the coating layers are multi-coated and multi-baked with a coating liquid (A) having a thermoreversible viscosity. A multilayer structure characterized by being formed of: 2. The coating liquid (A) contains a thermoreversible thickener (a1) whose hydrophilicity and hydrophobicity change reversibly at a certain temperature as a boundary, and a resin binder (a2). The multilayer structure according to claim 1. 3. The resin binder (a2) is in the form of a latex, and the amount of the surfactant in the aqueous phase in the latex is 0.03.
The multilayer structure according to claim 2, wherein the amount is 1 mmol / g (resin) or less. 4. The resin binder (a2) is a resin latex obtained by using a polymerizable emulsifier (E).
Or the multilayer structure according to 3. 5. The polymerizable emulsifier (E) has the following general formula (1)
The multilayer structure according to claim 4, wherein Embedded image [Wherein, Ar is an aromatic ring, R ¹ is a hydrogen atom or a methyl group, R ² and R ³ are monovalent hydrocarbon groups, and at least one of R ² and R ³ is a hydrocarbon having an aromatic ring. Group. m and n are an integer of 0 or 1 to 4 in which m + n is 1 to 8, R ⁴ and R ⁵ are a hydrogen atom or a methyl group, M is a cation, A is an alkylene group having 2 to 4 carbon atoms, p and q represents 0 or an integer of 1 to 40. ] 6. A thermoreversible thickener (a1) is a (co) polymer having a (meth) acrylate ester of an alkylene oxide adduct of a cyclic amine as an essential monomer, and a non-cyclic compound having 5 or more carbon atoms. (Co) polymer containing (meth) acrylic acid ester of amine alkylene oxide adduct as essential monomer, and (co) polymer containing (meth) acrylamide of monoalkylamine or alkoxyalkylamine as essential monomer ,
The multilayer according to any one of claims 2 to 5, which is at least one selected from the group consisting of (co) polymers having (meth) acrylamide of dialkylamine, dialkoxyalkylamine or cyclic amine as an essential monomer. Structure 7. The multilayer structure according to claim 1, wherein the substrate is paper or a resin film.