JP2002038123A - Heat-sensitive adhesive and heat-sensitive adhesive sheet - Google Patents

Abstract

PROBLEM TO BE SOLVED: To both obtain a heat-sensitive adhesive containing a compound which is nonadhesive at a normal temperature as a solid plasticizer but can develop adhesiveness by heating as is the case with a phthalic acid-based compound and a heat-sensitive adhesive sheet. SOLUTION: This heat-sensitive adhesive is characterized by comprising 2-hydroxy-4-benzyloxybenzophenone represented by general formula (1) and a thermoplastic resin.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a heat-sensitive adhesive which is non-tacky at room temperature but develops tackiness by heating, and after tackiness is developed, the tackiness is maintained for a while even if a heating source is removed. The present invention relates to a heat-sensitive adhesive sheet.

[0002]

2. Description of the Related Art Water-dispersible adhesives are often used in conventional heat-sensitive adhesives so that they do not have tackiness after application and drying. For example, "Glue manual"
As described in (12th edition, published by the Society of Polymer Publishing, 1980), a water-dispersed adhesive having a basic skeleton of a thermoplastic resin, a tackifier and a solid plasticizer is used as a composition. You. A thermoplastic resin is a base polymer that is a basic component of a heat-sensitive adhesive, and is a source of tackiness and adhesion. Solid plasticizers are basically solid at room temperature and therefore do not impart plasticity to the resin.The solid plasticizer melts when heated to swell or soften the resin, giving the adhesive a non-adhesive at room temperature. Responsible for expressing function. At this time, when the tackifier is present, the tackiness is more remarkably exhibited, and the practical characteristics are improved. That is, the tackifier is a component which is usually added to the base polymer for the purpose of imparting tackiness and improving adhesion without itself having adhesiveness ("Adhesion Handbook" (second edition), Published by the Japan Adhesive Tape Industry Association in 1995).

[0003] Heat-sensitive adhesives include paper such as high-quality paper, coated paper, art paper, vapor-deposited paper, synthetic paper, polyethylene, and the like.
Polyolefin resin such as polypropylene, applied on a plastic substrate such as a polyester resin represented by polyethylene terephthalate, to form a heat-sensitive adhesive sheet,
Such a heat-sensitive adhesive sheet is used as a label or the like on a metal, glass, or plastic surface. So-called poorly-adhesive plastic containers with low surface free energy, such as polyolefin resins such as polyethylene and polypropylene for food packaging applications and polyester resins typified by polyethylene phthalate for beverage bottles, cookware, and pharmaceutical bottle applications Is often used. Labels in these fields use conventional adhesives, pressure-sensitive adhesives, glue glues or heat-sensitive adhesives.

[0004]

Heretofore, phthalate compounds have been used as solid plasticizers. The present invention, like the phthalate compound, finds a compound that is non-tacky at room temperature as a solid plasticizer but can exhibit tackiness by heating, and a heat-sensitive adhesive containing the compound and a heat-sensitive adhesive It is intended to provide a functional adhesive sheet.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a heat-sensitive adhesive containing a thermoplastic resin and a solid plasticizer, wherein the solid plasticizer is 2-hydroxy-4-benzyloxy represented by the following general formula (1). Benzophenone was found to be a non-tacky compound at room temperature as a solid plasticizer, similar to a phthalic acid ester compound, but could develop tackiness by heating, and completed the present invention.

[0006]

Embedded image

That is, the first invention is a heat-sensitive adhesive containing a thermoplastic resin and a solid plasticizer, wherein the solid plasticizer is 2-hydroxy-4-benzyloxybenzophenone. Agent.

Further, a second invention is a heat-sensitive adhesive sheet obtained by applying the heat-sensitive adhesive to a substrate.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The heat-sensitive adhesive of the present invention which is non-tacky at room temperature contains 2-hydroxy-4-benzyloxybenzophenone. By heating, the heat-sensitive adhesive becomes tacky. Express. Further, the heat-sensitive adhesive of the present invention further improves practical properties by further containing a tackifier.

In the present invention, if necessary, a material known as a solid plasticizer may be used in addition to 2-hydroxy-4-benzyloxybenzophenone as a solid plasticizer. Solid plasticizers used in combination, for example, diphenyl phthalate, dihexyl phthalate, dicyclohexyl phthalate, dicyclohexyl terephthalate, dihydroabiethyl phthalate, dimethyl isophthalate, sucrose benzoate, ethylene glycol dibenzoate, trimethylol tribenzoate Ethane, glyceride tribenzoate, pentaerythritol tetrabenzoate, sucrose octaacetate, tricyclohexyl citrate, N-cyclohexyl-p-toluenesulfonamide, dibenzyl isophthalate, dibenzyl terephthalate, tribenzyl trimellitate, dicyclohexyl terephthalate 1,4-cyclohexanedimethanol ditoluate, 1,4-cyclohexanedimethanol di-p-tert-butylbenzoate, 1,4-bishydroxyethoxyben Njitorueto, 1,4
Cyclohexane dimethanol bisphenyl acetate,
Di-2-phenoxyethyl terephthalate, di-2-phenoxyethyl isophthalate, methyl m-hydroxybenzoate, ethyl m-hydroxybenzoate, phenyl m-hydroxybenzoate, methyl p-hydroxybenzoate,
Ethyl p-hydroxybenzoate, iso-propyl p-hydroxybenzoate, n-propyl p-hydroxybenzoate, n-butyl p-hydroxybenzoate, iso-butyl p-hydroxybenzoate, secondary p-hydroxybenzoate Butyl, n-butyl p-hydroxybenzoate, stearyl p-hydroxybenzoate, cyclohexyl p-hydroxybenzoate, benzyl p-hydroxybenzoate, allyl p-hydroxybenzoate, β-phenylethyl p-hydroxybenzoate, p-hydroxy 4-chlorobenzyl benzoate, 4-methylbenzyl p-hydroxybenzoate, methyl 2-hydroxy-3-naphthoate,
Ethyl 2-hydroxy-3-naphthoate, phenyl 2-hydroxy-3-naphthoate, phenyl 1-hydroxy-2-naphthoate, dimethyl 4-hydroxyphthalate, diethyl 4-hydroxyphthalate, di-hydroxyhydroxyphthalate n-propyl, diiso-propyl 4-hydroxyphthalate, dicyclohexyl 4-hydroxyphthalate, dimethyl 2-hydroxyisophthalate, diethyl 2-hydroxyisophthalate, diphenyl 2-hydroxyisophthalate, dimethyl 4-hydroxyisophthalate, 4- Phenolic hydroxyl group-containing aromatic carboxylic esters such as diethyl hydroxyisophthalate, diethyl 5-hydroxyisophthalate, and dimethyl hydroxyterephthalate, catechol dibenzoate, pentaerythritol tetrakis [3- (3,5 -Di-tert-butyl-4-hydroxyphenyl) propionate], thiodiethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-
Hydroxy-m-tolyl) propionate], hexamethylenebis [3- (3,5-di-tert-butyl-4)
-Hydroxyphenyl) propionate], 2- (2H-benzotriazol-2-yl) -p-cresol, 2- (2H-benzotriazol-2-yl) -4,6-bis ( 1-methyl-1-phenylethyl) phenol, 2-benzotriazol-2-yl-4,6-di-tert-butylphenol, 2- [5-chloro (2H) -benzotriazol-2-yl)]-4 -Methyl-6- (tert-butyl) phenol, 2,4-di-tert-butyl-6-
(5-chlorobenzotriazol-2-yl) phenol, 2- (2H-benzotriazol-2-yl)-
4,6-di-tert-pentylphenol, 2- (2
H-benzotriazol-2-yl) -4- (1,1,
Benzotriazole compounds such as (3,3-tetramethylbutyl) phenol, triphenylphosphine, 1,3
-Phenylenebis (dixylenylphosphate), diethyl [[3,5-bis (1,1-dimethylethyl) -4]
Phosphorus-based compounds such as -hydroxyphenyl] methyl] phosphonate. When another solid plasticizer is used in combination, pentaerythritol tetrabenzoate, tribenzyl trimellitate, benzyl p-hydroxybenzoate, hexamethylene Bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 2-
(2H-benzotriazol-2-yl) -4- (1,
1,3,3-tetramethylbutyl) phenol, diethyl [[3,5-bis (1,1-dimethylethyl) -4-
It is preferred to use [hydroxyphenyl] methyl] phosphonate.

The dispersed particle size of 2-hydroxy-4-benzyloxybenzophenone considerably affects the smoothness of the surface to which the heat-sensitive adhesive is applied. If the particle size is too large, the heat-sensitive adhesive is applied. Since the smoothness of the coated surface of the heat-sensitive adhesive sheet is deteriorated and the thermal activation time is prolonged, it is preferable to adjust the maximum particle diameter to 50 μm or less. On the other hand, if the particle size of 2-hydroxy-4-benzyloxybenzophenone is too small, the blocking resistance of the heat-sensitive adhesive sheet tends to deteriorate, so that the minimum particle size is 0.1 μm or more and the average particle size is 1 μm or more. It is preferably 2 to 5 μm from a practical viewpoint. The 2-hydroxy-4-benzyloxybenzophenone is mechanically pulverized in the presence of an aqueous resin having a protective colloid function, a surfactant, or a mixture of both, to give an aqueous dispersion of particles of the above size. 2-hydroxy-4-benzyloxybenzophenone is preferably provided to the heat-sensitive adhesive in the form of such an aqueous dispersion.

The thermoplastic resin used in the present invention includes acrylic, styrene-acrylic, styrene-butadiene, styrene-butadiene-acrylic, and the like.
Ethylene-vinyl acetate, ethylene-vinyl acetate-vinyl chloride, ethylene-vinyl chloride, ethylene-vinyl acetate-acryl, ethylene-vinyl acetate-acrylate, vinyl acetate, vinyl acetate-acryl,
Polymers such as ethylene-acrylic, butadiene-based, urethane-based, styrene-isoprene-based, isoprene-based, acrylonitrile-butadiene-based, and isobutylene-based polymers can be used, and one or more of them can be used in combination. Among these thermoplastic resins, in particular, acrylic, styrene-acrylic,
Styrene-butadiene, ethylene-vinyl acetate, ethylene-vinyl acetate-vinyl chloride, and ethylene-vinyl acetate-acrylic polymers are preferred. Further, the glass transition temperature of these thermoplastic resins is preferably 50 ° C. or lower. When the glass transition temperature is higher than 50 ° C., the tackiness when the heat-sensitive adhesive is activated by heat tends to be insufficient.

Among the thermoplastic resins used in the present invention, those obtained by radical polymerization can be obtained, for example, by a usual emulsion polymerization method. That is, in a dispersion system having water, a surfactant, each monomer, and a radical polymerization catalyst as the basic components, the monomers are polymerized, and a polymer as a thermoplastic resin can be obtained in an aqueous dispersion state.

As the tackifier for improving the adhesive performance of the heat-sensitive adhesive, conventionally known tackifiers can be used. However, those having a low softening temperature have poor blocking resistance, so that the softening temperature is 80 ° C. or higher. Are preferred. In the present invention, like the 2-hydroxy-4-benzyloxybenzophenone and the thermoplastic resin, it is more preferable that the tackifier is also incorporated into the heat-sensitive adhesive in the form of an aqueous dispersion. Examples of the tackifier include terpene resin, aliphatic petroleum resin, aromatic petroleum resin, cumarone-indene resin, phenol resin, terpene-phenol resin, rosin derivative (rosin, polymerized rosin, hydrogenated rosin and their glycerin, Esters with pentaerythritol, resin acid dimer, etc.), among which rosin derivatives are desirable, and rosin ester compounds are particularly desirable.

The tackifiers may be used alone or in combination of two or more. That is, as the combination of the heat-sensitive adhesive, terpene resin and aliphatic petroleum resin,
Aromatic petroleum resin and cumarone-indene resin, terpene-phenol resin and rosin derivative, terpene resin and rosin derivative, aliphatic petroleum resin and rosin derivative, aromatic petroleum resin and rosin derivative, cumarone-indene resin and rosin derivative It is also possible to use a mixture of two or more of a phenol resin and a rosin derivative, or three or more of a rosin derivative, an aliphatic petroleum resin and an aromatic petroleum resin.

The 2-hydroxy-4-benzyloxybenzophenone, thermoplastic resin, and tackifier used in the heat-sensitive adhesive of the present invention have a property of melting or softening when heated. ,
The state after melting or softening differs. That is, 2-hydroxy-4-benzyloxybenzophenone exhibits a distinct melting point, and after melting does not itself have tackiness. On the other hand, the thermoplastic resin itself has tackiness after softening. Further, the tackifier has a smaller molecular weight than a thermoplastic resin and does not itself have adhesiveness / tackiness after softening, but is a component that contributes to imparting tackiness and improving adhesiveness.

In addition, fillers and the like can be added to the heat-sensitive adhesive of the present invention in a range not to impair the object of the present invention. For example, inorganic substances such as titanium oxide, alumina, kaolin, and talc; Organic substances such as natural waxes, synthetic waxes, and natural fats and oils, and resin powders can be used. Further, if necessary, a dispersant, an antifoaming agent, a leveling agent, a lubricant, a thickener, a preservative, an ultraviolet absorber, an antioxidant, a pH adjuster, a surfactant and the like can be used.

The heat-sensitive adhesive sheet of the present invention can be obtained by applying the above-mentioned heat-sensitive adhesive in an aqueous dispersion state to a substrate, and removing the aqueous medium.

The heat-sensitive adhesive can be applied to the substrate using various coating apparatuses such as a gravure coater, an air doctor coater, a floating knife coater, a die coater, and a lip coater. For example, it may be provided so as to cover one entire surface of the base material, or may be provided so as to cover both ends or the periphery of one surface of the base material, and a stripe shape on one surface of the base material, They may be provided in a lattice or dot shape.

[0020]

The present invention will be specifically described below with reference to examples. However, the scope of the present invention is not limited at all by the following Examples. In the examples, “parts” means “parts by weight” and “%” means “% by weight”. [Examples 1 to 3 and Reference Example 1] A maleic acid resin solution was first added to a solid plasticizer such as 2-hydroxy-4-benzyloxybenzophenone in a pebble mill pot according to the formulation (non-volatile content) shown in Table 1. Add antifoam and water, 24
After pulverization for an hour, an emulsion of a tackifier and an emulsion of a thermoplastic resin were added, and mixed and stirred for 5 minutes to prepare a heat-sensitive adhesive. The obtained heat-sensitive adhesive was applied to one side of a double-side coated paper so that the coating amount at the time of drying was 15 g / m ^2, and dried at 40 ° C. for 4 minutes to obtain a heat-sensitive adhesive sheet. . The sheet was not tacky after drying. The adhesive strength of the heat-sensitive adhesive sheet was evaluated as shown below, and the results are shown in Table 1.

Adhesive strength: 150 ° C. for heat-sensitive adhesive sheet
After heating for 60 seconds to develop the adhesiveness, the film was immediately attached to a glass plate, and the adhesive strength was measured by 180-degree peeling, and evaluated according to the following criteria. ○ ・ ・ ・ ・ ・ ・ 5000mN / 25mm or more. ×: Less than 5000mN / 25mm.

[0022]

[Table 1]

* 1) Non-volatile content * 2) Glass transition temperature * 3) Softening temperature

From the results shown in Table 1, the heat-sensitive adhesive sheet coated with the heat-sensitive adhesive containing 2-hydroxy-4-benzyloxybenzophenone showed that the heat-sensitive adhesive sheet was prepared by using a phthalate compound as a solid plasticizer. It has been found that adhesiveness can be obtained by heat activation as in the case of the adhesive.

[0025]

According to the present invention, 2-hydroxy-4-benzyloxybenzophenone is used as a solid plasticizer in the same manner as a conventional heat-sensitive adhesive sheet coated with a heat-sensitive adhesive containing a solid plasticizer. As a result, a heat-sensitive adhesive sheet capable of satisfying practical characteristics in terms of adhesive strength has been obtained. The industrial significance of being able to pursue economical benefits by saving resources, such as labels, tapes, and packaging seals that do not require release paper, is extremely significant.

Continued on the front page F term (reference) 4J004 AA05 AA06 AA07 AA09 AA10 AB03 CA02 CA04 CA06 CC02 CE01 DB01 FA01 4J040 CA031 CA071 CA081 DA031 DA051 DA061 DA141 DB051 DB061 DC041 DE021 DE031 DF031 HB19 MA03 MA02 MA03 MA02 MA03 MA02

Claims (2)

[Claims] 1. A heat-sensitive adhesive containing a thermoplastic resin and a solid plasticizer, wherein the solid plasticizer is 2-hydroxy-4-benzyloxybenzophenone represented by the following general formula (1). Heat-sensitive adhesive. Embedded image 2. A heat-sensitive adhesive sheet obtained by applying the heat-sensitive adhesive according to claim 1 to a substrate.