JP2914029B2 - Heat sensitive delayed tack adhesive - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive delayed tack type adhesive which is non-tacky at normal temperature but is activated by heating and has a long-lasting tackiness even after a heating source is removed.

[0002]

2. Description of the Related Art Thermosensitive delayed tack adhesives are:
"Adhesion Handbook" (12th edition, 1980, published by the Society of Polymer Publishing)
As described in the above, it basically contains a thermoplastic resin and a crystalline plasticizer and a tackifier which are solid at room temperature. Thermoplastic resin is the source of adhesive and adhesive strength, and crystalline plasticizer is a solid at room temperature and does not impart plasticity, but it melts when heated to swell or soften the resin. And the tackifier functions to improve the tackiness. The crystalline plasticizer in the heat-sensitive delayed tack adhesive slowly crystallizes after being melted by heating, so that the tackiness is maintained for a long time. However, the adhesive strength after the development of the adhesiveness was not sufficient. Therefore, as disclosed in JP-A-63-172784, the glass transition temperature (Tg) is from -20 ° C to -40 ° C.
Thermoplastic resins of about ° C have come to be used. A thermoplastic resin having a Tg of about −20 ° C. to −40 ° C. has excellent adhesive strength / adhesive strength because it has tackiness itself, but on the other hand, it has a soft holding power and blocking resistance. It was remarkably inferior and had a practical problem.

[0003] That is, the conventional heat-sensitive delayed tack-type pressure-sensitive adhesives include the following: 1) Blocking occurs, and pressure-sensitive adhesives prepared using a thermoplastic resin having a low Tg or a crystalline plasticizer having a low melting point include: When wound up after drying after being applied to a substrate or stored in a stacked state, blocking may occur due to pressure or high temperature. 2) It is difficult to improve the adhesive force and the holding force in a well-balanced manner, and the adhesive force and the holding force, which are important functions of the adhesive, are mutually contradictory properties. However, if the holding force is improved, the adhesive force is reduced. There is a problem.

[0004]

The present inventors have made intensive studies to solve these problems, and as a result, as a thermoplastic resin, an ethylene resin having a glass transition temperature of 0 ° C. or more was used.
It has been found that by using a vinyl acetate copolymer, a heat-sensitive delayed-tack type adhesive having excellent blocking resistance and adhesive properties can be obtained, and the present invention has been completed. The present invention makes it possible to use an ethylene-vinyl acetate copolymer, which was hard at room temperature and could not be used due to poor tackiness and adhesion, by making use of the plasticizing effect of a crystalline plasticizer, and to obtain a heat-sensitive layer. -To improve the holding power and blocking resistance of the tack adhesive. It is considered that the hardness of the resin contributes to the improvement of the blocking resistance.

[0005]

That is, the present invention comprises an ethylene-vinyl acetate copolymer having a glass transition temperature (Tg) of 0 ° C. or higher, a crystalline solid plasticizer and a tackifier. A heat-sensitive delayed tack adhesive is provided. The ethylene-vinyl acetate copolymer used in the present invention can be used in an aqueous emulsion or an organic solvent solution. These can be used alone or as a mixture of two or more kinds having different Tg.

[0006] Crystalline plasticizers that can be used to plasticize ethylene-vinyl acetate copolymers include:
Diphenyl phthalate, dihexyl phthalate, dicyclohexyl phthalate, dihydroabiethyl phthalate, dimethyl isophthalate, sucrose benzoate, ethylene glycol dibenzoate, trimethylol triethane benzoate, glyceride tribenzoate, tetrabenzoate Acid pentaerythritol,
Octaacetic acid sucrose, tricyclohexyl citrate, N-
Examples thereof include cyclohexyl-p-toluenesulfonamide, and dicyclohexyl phthalate having high versatility is preferable.

Further, as tackifying resins which can be used to improve the adhesive performance of the adhesive, terpene resins, aliphatic petroleum resins, aromatic petroleum resins, cumarone-indene resins, styrene resins, Phenol resins, terpene-phenol resins, rosin derivatives (rosin, polymerized rosin, hydrogenated rosin and their esters with glycerin, pentaerythritol, etc., resin acid dimer, etc.). However, in order to improve blocking resistance, a resin having a high softening point is preferable. These can be used as aqueous emulsions or organic solvent solutions. In addition, as an additive for preventing blocking, inorganic substances such as titanium oxide, alumina, colloidal silica, kaolin, and talc, and organic substances such as paraffin, natural wax, synthetic wax, natural oils and fats, and powdered styrene are further required. A dispersant, an antifoaming agent, a thickener and the like can be used according to the above.

[0008]

EXAMPLES The present invention will be described below in more detail with reference to examples, but these examples do not limit the present invention in any way. In the following examples and comparative examples, “parts” means parts by weight unless otherwise specified. Further, the adhesive strength, the holding power, and the blocking property in Examples and Comparative Examples are as follows:
Evaluation was made by the following method. Adhesive force: After heat-activating the coated product, immediately apply it to a stainless steel plate, leave it for 20 minutes, and adhere to JIS K-6848
The adhesive strength was measured by 180-degree peeling, and evaluated based on the following criteria. ○ ・ ・ ・ 1000g / 25mm or more × ・ ・ ・ 1000g / 25mm or less Retention force: After heat-activating the coated product, immediately apply it to a stainless steel plate, leave it for 20 minutes, and then conduct a creep test according to JIS K-6848. The evaluation was performed according to the following criteria. ○ ・ ・ ・ 2000sec or more △ ・ ・ ・ 1000sec or more, less than 2000sec × ・ ・ ・ less than 1000sec Blocking property: Applying a load of 500g / cm ² to the coating, leaving it at each temperature for 1 hour, and peeling it off. The judgment was made based on the standard. 5: No peeling resistance 4: Slight noise at the time of peeling 3: Continuous sound at the time of peeling 2: Pulling the fiber of the paper at the time of peeling 1: Paper is broken by blocking 0 ... Perfect adhesion (non-peelable)

Example 1 Dicyclohexyl phthalate 3
16 parts, maleic acid resin solution (solid content 30%) 53 parts, water 1
22 parts, 184 parts of ethylene-vinyl acetate copolymer emulsion (solid content: 50%) having a Tg of 0 ° C. and 158 parts of a rosin ester-based tackifier emulsion (solid content: 50%) are mixed to form a heat-sensitive delayed tack adhesive. Was prepared. [Example 2] 316 parts of diphenyl phthalate, 53 parts of maleic resin solution (solid content 30%), 122 parts of water, Tg 7 ° C ethylene-vinyl acetate copolymer emulsion (solid content 50%)
184 parts and 158 parts of a rosin ester-based tackifier emulsion (solid content: 50%) were mixed to prepare a heat-sensitive delayed tack type adhesive.

Comparative Example 1 Dicyclohexyl phthalate 3
16 parts, maleic acid resin solution (solid content 30%) 53 parts, water 1
22 parts, 184 parts of ethylene-vinyl acetate copolymer emulsion (solid content 50%) at Tg-20 ° C and 158 parts of rosin ester-based tackifier emulsion (solid content 50%) are mixed to form a heat-sensitive delayed tack type. An adhesive was prepared. 20 g / m ^{2 of} the adhesive emulsion prepared by the above method was applied to one-sided art paper.
Then, it was dried at 40 ° C. for 2 minutes. In this state, it was non-tacky. Adhesive strength,
Table 1 shows the results of evaluating the holding power and the blocking. The adhesion and the holding power were evaluated after heat-activating the coating at 120 ° C. for 25 seconds.

[0011]

[Table 1]

[0012]

As a result of the present invention, the adhesive strength is not inferior to the conventional heat-sensitive delayed tack type adhesive,
A pressure-sensitive adhesive having good blocking resistance was obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-85269 (JP, A) JP-A-63-89583 (JP, A) JP-A-63-172784 (JP, A) 91586 (JP, A) JP-A-6-100847 (JP, A) JP-A-6-100848 (JP, A) JP-A-6-57223 (JP, A) (58) Fields investigated (Int. ⁶ , DB name) C09J 123/00-123/36 C09J 131/00-131/04 C08L 23/00-23/36 C08L 31/00-31/04

Claims (1)

(57) [Claims] An ethylene having a glass transition temperature of 0 ° C. or higher.
A heat-sensitive delayed tack type adhesive comprising a vinyl acetate copolymer, a crystalline plasticizer and a tackifier.