JPH073239A - Delayed tack type tacky adhesive and tacky adhesive sheet - Google Patents

Abstract

PURPOSE:To obtain a delayed tack type tacky adhesive excellent in blocking resistance and tacky adhesive characteristics. CONSTITUTION:This delayed tack type tacky adhesive, which is not tacky at normal temperature but develops tacky adhesivity under heating or pressure, is obtained by compounding microcapsules containing a plasticizer, thermoplastics and a tackifier. Also, a tacky adhesive sheet is obtained by coating the tacky adhesive on a base. This tacky adhesive sheet has an improved blocking resistance compared with a tacky adhesive sheet coated with a conventional delayed type tacky adhesive and satisfies practical level in tacky adhesivity.

Description

Detailed Description of the Invention

[0001]

Industrial Applicability The present invention is non-adhesive at room temperature, but develops adhesiveness by heating or pressurizing, and after the adhesiveness develops, the heating or pressurizing source can be removed for a while.
The present invention relates to a heat-sensitive or pressure-sensitive delayed-tack type pressure-sensitive adhesive having persistent tackiness.

[0002]

2. Description of the Related Art A conventional delayed tack type adhesive is
"Handbook of Adhesion" (12th edition, 1980, published by Kobunshi Publishing Association)
As described in (1), the composition is based on a thermosensitive resin, a tackifier and a solid plasticizer as a basic skeleton. Thermoplastic resins are the source of tackiness and adhesiveness, and solid plasticizers do not impart plasticity to resins at room temperature, and they melt and swell or soften when heated, so non-sticky adhesives at room temperature. The agent acts to develop tackiness by heating. At this time, when the tackifier is present, the tackiness becomes more remarkable, and the practical properties are improved. However, even if the solid plasticizer is below the melting point, it softens and imparts plasticity to the resin depending on conditions such as the storage temperature, so that there is a problem in terms of blocking resistance.

A heat-sensitive adhesive comprising an ethylene-vinyl acetate copolymer, a tackifying resin, a crystalline plasticizer and a wax for the purpose of improving blocking resistance is disclosed in Japanese Patent Publication No. 62-21835. ing. However, blocking resistance is insufficient only with the wax added for the purpose of suppressing the tackiness at room temperature, and in such a melt-drying type heat-sensitive adhesive, the added organic compound does not melt. Therefore, the wax as disclosed in this patent cannot be expected to have improved blocking resistance.

Further, in order to improve the blocking resistance, a method is disclosed in JP-A-63-172784, in which the smoothness of the coated surface is set within a certain numerical range when the heat-sensitive adhesive is coated on the sheet. However, it is practically difficult to control the smoothness of the coated surface as described above. Further, a method of adding or mixing an organic compound is disclosed in
Although disclosed in JP-A-2-282050, simple addition of ordinary organic compounds is not sufficient.

That is, since the conventional delayed tack type pressure-sensitive adhesive has 1) poor blocking resistance and poor blocking resistance, the delayed tack type pressure-sensitive adhesive sheet prepared by applying the pressure-sensitive adhesive is wound and stored. In this case, there is a risk that the pressure-sensitive adhesive contact surface may become sticky. 2) When the improvement of 1) is performed, there is a defect that the adhesive force or the holding force is reduced.

[0006]

DISCLOSURE OF THE INVENTION As a result of intensive studies to overcome the above drawbacks, the present inventors have found that by encapsulating a plasticizer into microcapsules, it has excellent heat resistance or touch resistance with excellent blocking resistance and adhesive properties. The inventors have found that a pressure-sensitive delayed tack type pressure-sensitive adhesive can be obtained, and completed the present invention.

[0007]

That is, the present invention comprises microcapsules containing a plasticizer, a thermoplastic resin, and a tackifier, and is non-tacky at room temperature but develops tackiness by heating or pressing. Provided is a delayed tack type pressure-sensitive adhesive and a delayed tack type pressure-sensitive adhesive sheet obtained by coating the substrate with the delayed tack type pressure-sensitive adhesive.

The plasticizer is not limited to the solid plasticizer as in the conventional delayed tack type adhesive, and a liquid plasticizer or a mixture of the solid plasticizer and the liquid plasticizer may be used. Examples of the solid plasticizer include diphenyl phthalate, dihexyl phthalate, dicyclohexyl phthalate, dihydroabietyl phthalate, dimethyl isophthalate, sucrose benzoate, ethylene glycol dibenzoate, trimethylolethane tribenzoate, glyceride tribenzoate. , Pentaerythritol tetrabenzoate,
Examples include sucrose octaacetate, tricyclohexyl citrate, N-cyclohexyl-p-toluenesulfonamide and the like, with dicyclohexyl phthalate being preferred.

Examples of the liquid plasticizer include dimethyl phthalate, diethyl phthalate, dibutyl phthalate, diheptyl phthalate, di-2-ethylhexyl phthalate, di n-octyl phthalate, diisodecyl phthalate, butyl benzyl phthalate and diisononyl phthalate. , And dibutyl phthalate are preferred.
The above plasticizers may be used alone or may be mixed in a range that does not impair the plasticizing effect.

Examples of the method for microcapsulating the plasticizer include, for example, Japanese Patent Publication No. 38-19574 and Japanese Patent Publication No. 42-4.
Japanese Patent Publication No. 46, Japanese Patent Publication No. 42-771, Japanese Patent Publication No. 42-2882, Japanese Patent Publication No. 42-2283, Japanese Patent Publication No. 56-115371,
The interfacial polymerization method described in JP-A-60-60173, the Japanese Patent Publication No. 36-9168, US 3427250, the in situ polymerization method described in GB 1236498, etc., US 3787327, US 3551346 publication, liquid submerged coating method described in US 3574133 publication, etc., US 2800457 publication, US 2800458 publication, US 3577515 publication, GB 1117178 publication, etc., coacervation method, US 3523906 Publication, US 3
Interfacial precipitation method described in Japanese Patent No. 660304, US 3830750
The spray dry method described in Japanese Patent Publication can be used. Among these methods, since the thickness of the microcapsule wall can be made uniform and the strength of the microcapsule wall can be increased, polyurea can be used as the wall material and microencapsulated by the interfacial polymerization method. preferable.

The conditions for developing the tackiness of the delayed tack type pressure-sensitive adhesive of the present invention depend on the amount of the wall material of the microcapsule containing the plasticizer. When the amount of the wall material is increased, the blocking resistance is improved. , It becomes difficult for the adhesiveness to develop. Therefore, under normal conditions for developing tackiness, the amount of wall material is preferably 0.01 parts by weight or more and less than 0.5 parts by weight with respect to 100 parts by weight of the core substance. When the amount of the wall material is 0.5 parts by weight or more with respect to 100 parts by weight of the core substance, it becomes difficult for the adhesiveness to be exhibited by heating or pressurization, and sufficient adhesive force cannot be obtained. If it is less than 0.01 part by weight, the effect of microencapsulation cannot be obtained, and the blocking resistance of the pressure-sensitive adhesive sheet becomes poor.

The method of microencapsulating the solid plasticizer includes: 1) a method in which the solid plasticizer is heated above its melting point to carry out a reaction (a method in which the solid plasticizer is used as if it were a liquid plasticizer); 2) a solid plasticizer. There are three kinds of methods, that is, a method of dissolving or mixing the agent in an organic solvent to carry out the reaction, 3) a method of using as a solid, and the method of 1) is preferable. When the solid plasticizer and the liquid plasticizer are microencapsulated, the reaction may be carried out under the condition that the solid plasticizer and the liquid plasticizer are not mixed uniformly, that is, below the melting point of the solid plasticizer, and the microcapsulation is performed separately. You may mix after performing.

When microencapsulating the plasticizer,
For example, gelatin or its modified product, gum arabic, sodium alginate, polyvinyl alcohol, polyvinylpyrrolidone, methyl cellulose, carboxymethyl cellulose, maleic anhydride copolymer, pluronic type surfactant, sucrose fatty acid ester, sorbitan fatty acid ester, alkylbenzene sulfonate. , Alkylnaphthalene sulfonate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl ether,
1 or 2 such as alkyl trimethyl ammonium chloride
Mixtures of one or more can be used as appropriate dispersants.

The core material of the microcapsules may contain a foaming agent. The microcapsules are effective when the amount of the wall material of the capsules needs to be increased, for example, when blocking resistance is particularly required, because the foaming agent foams by heating and helps the capsules to collapse. As the foaming agent, organic and inorganic foaming agents that generate gas by thermal decomposition are used, but organic foaming agents are preferable. As the organic foaming agent, azodicarbonamide, azobisisobutyronitrile, dinitrosomethylenepentamine, 4,4-oxybisbenzenesulfonyl hydrazide,
A simple substance or a mixed system such as paratoluenesulfonyl hydrazide is used.

Examples of the thermoplastic resin include acrylic acid ester, styrene-acrylic acid ester, styrene-
Butadiene, ethylene-vinyl acetate, vinyl acetate, vinyl acetate-acrylic acid ester, ethylene-vinyl chloride,
Examples thereof include ethylene-acrylic acid ester, ethylene-acrylic acid, polybutadiene, urethane, and styrene-isoprene block polymer.

Further, as the tackifier for improving the tack performance of the tackifier, for example, terpene resin, aliphatic petroleum resin, aromatic petroleum resin, coumarone-indene resin, styrene resin, phenol resin, terpene-phenol. Examples thereof include resins and rosin derivatives (rosin, polymerized rosin, hydrogenated rosin and their esters with glycerin, pentaerythritol, etc., resin acid dimers, etc.).

The delayed tack type adhesive of the present invention comprises:
In addition to the encapsulated plasticizer, thermoplastic resin and tackifier, fillers and the like can be added within a range not hindering the object of the present invention, for example, titanium oxide, alumina, kaolin, inorganic substances such as talc, and the like, Organic substances such as paraffin, natural wax, synthetic wax and natural fats and oils can be used. Furthermore, if necessary, a dispersant, a defoaming agent, a thickener and the like can be used. The delayed tack type pressure-sensitive adhesive of the present invention can be applied to a substrate as an aqueous emulsion or an organic solvent solution to form a pressure-sensitive adhesive sheet.

[0018]

EXAMPLES The present invention will be specifically described below with reference to examples. However, the scope of the present invention is not limited to the following examples. In the examples, “part” represents “part by weight”. [Microcapsule Preparation Method 1] An oily liquid was prepared by dissolving 0.016 parts of polymethylene polyphenyl isocyanate and 0.008 parts of hexamethylene diisocyanate in 100 parts of heat-melted dicyclohexyl phthalate. On the other hand, prepare an aqueous solution in which 2 parts of polyvinyl alcohol and 2 parts of carboxymethyl cellulose are dissolved in 130 parts of water in advance, and the temperature is set to 80 ° C.
After heating, the above oily liquid was added and vigorously stirred to obtain a dispersion liquid having an average particle diameter of 5 μm. Then, 0.004 parts of diethylenetriamine was added to the dispersion, and the mixture was heated and stirred at 80 ° C. to carry out a polymerization reaction to prepare a microcapsule dispersion having a nonvolatile content of 44%.

[Microcapsule Preparation Method 2] A mixture of 95 parts of heat-melted dicyclohexyl phthalate and 5 parts of dibutyl phthalate was used in place of 100 parts of the heat-melted dicyclohexyl phthalate, and the same procedure as in Preparation Method 1 was repeated. A microcapsule dispersion having a content of 44% was prepared.

[Microcapsule Preparation Method 3] An oily liquid was prepared by dissolving 0.6 parts of polymethylene polyphenyl isocyanate and 0.3 part of hexamethylene diisocyanate in 100 parts of heat-melted dicyclohexyl phthalate. On the other hand, an aqueous solution prepared by previously dissolving 2 parts of polyvinyl alcohol and 2 parts of carboxymethyl cellulose in 130 parts of water was prepared, heated to 80 ° C., added with the oily solution described above, and vigorously stirred to obtain an average particle size of 5 μm. A dispersion was obtained. Then, 0.15 parts of diethylenetriamine was added to the dispersion liquid, and the mixture was heated and stirred at 80 ° C. to carry out a polymerization reaction to prepare a microcapsule dispersion liquid having a nonvolatile content of 44%.

[Examples 1-5 and Comparative Examples 1-2] Table 1
The composition shown in 1 was placed in a glass beaker and mixed with a homogenizer to prepare an adhesive. The obtained pressure-sensitive adhesive was directly applied onto one-sided art paper so that the applied amount was 20 g / m ^2, and dried at 40 ° C. for 2 minutes. In this state, tackiness could not be confirmed. Table 1 shows the results of evaluation of blocking properties of the coated products. Table 1 shows the results of evaluation of the adhesive strength after the adhesiveness of the coated product was developed. The coatings obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were heated at 150 ° C for 25 seconds, and the coatings obtained in Example 4 were heated at 130 ° C for 25 seconds and pressed. The pressure of 5 Kg / cm ² was applied, and the coating obtained in Example 5 was heated at 180 ° C. for 25 seconds and pressed at a pressure of 8 Kg / cm ² to develop tackiness.

The blocking property and the adhesive force were evaluated by the following methods. Blocking property: A load of 1000 g / cm ² was applied to the pressure-sensitive adhesive coated product, the product was stored at 55 ° C. for 1 hour, then peeled off, and judged according to the following criteria. ◎ ・ ・ ・ ・ ・ ・ No peeling resistance. ○ ・ ・ ・ ・ ・ ・ A slight noise is heard when peeling. × ・ ・ ・ ・ ・ ・ Pull fiber of paper when peeling. Adhesion: After the adhesiveness was developed, the adhesive coating was immediately attached to a stainless steel plate, and the adhesive strength was measured by peeling 180 degrees according to JIS K-6848, and the following criteria were used for judgment.
However, the glued part was 100 mm. ◎ ・ ・ ・ ・ ・ ・ 800g / 25mm or more. ○ ・ ・ ・ ・ ・ ・ 300g / 25mm or more, less than 800g / 25mm. × ・ ・ ・ ・ ・ ・ 300g / less than 25mm.

[0023]

[Table 1] * 1 Core material (dicyclohexyl phthalate) 100 parts, wall material 0.0024 parts * 2 Core material (dicyclohexyl phthalate + dibutyl phthalate) 100 parts, wall material 0.0024 parts * 3 Core material (dicyclohexyl phthalate) Amount of wall material is 0.9 parts for 100 parts * 4 Ethylene-vinyl acetate copolymer

[0024]

EFFECTS OF THE INVENTION According to the present invention, a pressure-sensitive adhesive sheet having improved blocking resistance and satisfactory adhesive strength as compared with a conventional pressure-sensitive adhesive sheet coated with a delayed tack type pressure-sensitive adhesive is obtained. Came to be. The industrial significance of being able to pursue resource-saving and economical benefits as labels, tapes, seals for packages, etc. that do not require release paper is extremely great.

Front page continuation (72) Inventor Akira Kikuchi 2-33 Kyobashi, Chuo-ku, Tokyo Toyo Inki Manufacturing Co., Ltd. (72) Eiichi Takama 2-3-13 Kyobashi, Chuo-ku, Tokyo Toyo Inn Ki Manufacturing Co., Ltd.

Claims (3)

[Claims] 1. A delayed tack type adhesive comprising microcapsules containing a plasticizer, a thermoplastic resin and a tackifier, which is non-adhesive at room temperature but develops adhesiveness by heating or pressurization. Agent. 2. The delayed tack type pressure-sensitive adhesive according to claim 1, wherein the microcapsules are composed of 0.01 parts by weight or more and less than 0.5 parts by weight of the wall material with respect to 100 parts by weight of the core substance containing the solid plasticizer. Agent. 3. A delayed tack type pressure-sensitive adhesive sheet obtained by applying the delayed tack type pressure-sensitive adhesive according to claim 1 or 2 to a substrate.