JPH02252778A - Method for curing tacky agent - Google Patents

Abstract

PURPOSE:To improve the adhesive power of a tacky agent and cure the agent by applying the adhesive comprising a mixture of a carboxylated acrylic polymer with a specified amt. of a polyisocyanate to a release paper or substrate material and curing under a specified condition. CONSTITUTION:100 pts.wt. carboxylated acrylic polymer (e.g. a copolymer of butyl acrylate with acrylic acid) and 0.001-20 pts.wt. polyisocyanate (e.g. 4,4'-diphenylmethane diisocyanate) are mixed to give tacky agent, which is applied to a release paper or substrate material (e.g. polyethylene) and then cured in an atmosphere of a curing catalyst (e.g. diethylamine) at a temp. higher than the b.p. of the catalyst and lower than 200 deg.C.

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a method of curing an adhesive used for adhering automotive parts such as side protection moldings (hereinafter referred to as moldings). [Prior art] Conventionally, synthetic rubber-based adhesives, polyvinyl acetate-based adhesives, etc. have been used as adhesives generally used in various adhesive products, but they have poor moisture resistance, hot water resistance, heat resistance, etc. was insufficient. Furthermore, an adhesive made of an acrylic polymer having a carboxyl group and a polyisocyanate has been proposed as an adhesive used for mounting on automobile moldings and the like. This pressure-sensitive adhesive is heated to evaporate the solvent contained therein before being used. [Problems to be Solved by the Invention] However, in the pressure-sensitive adhesive made of an acrylic polymer containing a carboxyl group and a polyisocyanate, the reaction between the carboxyl group and the polyisocyanate does not proceed sufficiently when heated to the extent that the solvent is evaporated. Therefore, there was a problem that adhesive strength was low. In addition, in order to increase adhesive strength, for example, when curing a mixture of an acrylic polymer containing a carboxyl group and a tolylene diisocyanate adduct of trimethylolpropane or isocyanate 1m,
There were problems in that the curing temperature had to be raised and the curing time had to be lengthened. An object of the present invention is to provide a method for curing an adhesive that has high adhesive strength, low curing temperature, short curing time, and excellent workability.

[Means to solve the problem]

In order to achieve the above object, in the present invention, a pressure-sensitive adhesive consisting of a mixture of 100 parts by weight of an acrylic polymer having a carboxyl group and 0.001 to 20 parts by weight of polyisocyanate is applied to a release paper or a base material, and a curing catalyst is applied. A method of curing in a curing catalyst atmosphere at a temperature higher than the boiling point of and lower than 200° C. is adopted. [Detailed Description of Means] First, the adhesive will be explained. Acrylic polymers having carboxyl groups are usually obtained by copolymerizing acrylic esters and unsaturated carboxylic acids or their anhydrides by solution polymerization. As acrylic esters, butyl acrylate, isobutyl acrylate,
2-ethylhexyl acrylate and the like can be used. As the unsaturated carboxylic acid, acrylic acid, methacrylic acid, maleic acid, itaconic acid, etc. can be used, and as the anhydride of the unsaturated carboxylic acid, maleic anhydride, itaconic anhydride, etc. can be used. The proportion of this unsaturated carboxylic acid or its anhydride used in the acrylic polymer is 1-10! A range of i amount% is suitable. If it is less than 1% by weight, the adhesive strength of the adhesive tends to decrease;
If it exceeds 0% by weight, the adhesive will become hard and will not exhibit sufficient adhesive strength. As the polyisocyanate, 2,4-tolylene diisocyanate (TD I), 65/35 (2°4-
Ratio of tolylene diisocyanate and 2.6-)lylene diisocyanate, hereinafter the same) tolylene diisocyanate, 80/20 tolylene diisocyanate, 1.5-naphthalene diisocyanate (NDI), 4,4'-diphenylmethane diisocyanate) ( MDI), dianisidine diisocyanate, tridene diisocyanate, hexamethylene diisocyanate, xylene diisocyanate (MDI), metaxylene diisocyanate, 1.
6-hexamethylene diisocyanate (1°6HMDI
), hydrogenated 4,4'-diphenylmethane diisocyanate, hydrogenated xylene diisocyanate, hydrogenated 2.4-)lylene diisocyanate, hydrogenated 65/35) lylene diisocyanate, hydrogenated 80/20) lylene diisocyanate, isophorone diisocyanate (IPDI) etc. can be used. The proportion of this polyisocyanate used is in the range of 0.001 to 20 parts by weight based on 100 parts by weight of the acrylic polymer. If it is less than 0.001 part by weight, the adhesive strength tends to decrease, and if it exceeds 20 parts by weight, the adhesive becomes hard and brittle, and the adhesive strength tends to decrease. Next, polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), iE, etc. can be used as the base material for applying the adhesive, and the release paper is used to protect the adhesive. Those commonly used can be used. As the curing catalyst, amine compounds such as monoethylamine, diethylamine, triethylamine, propylamine, ethyl aminocrotonate, p-aminothiophenol, 2-aminothiophene, secondary amylamine, tertiary
7-mylamine, aldehyde ammonia, isoamylamine, isobutylamine, isopropylamine, thiamine, diisopropylamine, cyclohexylamine, dipropylamine, dimethylhydrazine, pyrazoline, pyridine, pyrrolidine, viroline, butylamine,
Secondary butylamine, tertiary butylamine, 2-methylpiperidine, 3-methylpiperidine, 4-methylpiperidine, N-methylpiperidine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, organometallic compounds such as tetramethyltin , tetramethyl lead, etc. 1 or 2
More than one species can be used. Next, a method of curing the adhesive will be explained. First, the above adhesive is applied to a release paper or base material to a thickness of about 80 to 150 μm. Next, the release paper or base material coated with this adhesive is cured at a temperature above the boiling point of the curing catalyst and below 200°C. Place in a catalytic atmosphere. The lower limit of this atmospheric temperature is determined by the boiling point of the curing catalyst, and the upper limit is determined by the type of release paper or base material used within a range that does not damage the release paper or base material. For example, when diethylamine is used as the curing catalyst and foamed polyethylene is used as the base material, the temperature is about 70°C. Moreover, the heating time is about 5 seconds at 200° C., and about 5 minutes at room temperature. In this way, the adhesive on the surface of the release paper or base material can be cured. [Function] By employing the above means, the carboxyl groups in the acrylic polymer and the isocyanate groups in the polyisocyanate in the adhesive react with each other in a curing catalyst atmosphere at a predetermined temperature, resulting in curing, and the cohesive force of the adhesive is reduced. In addition to preventing peeling at the adhesive layer, the strength of the interface between the adhesive layer and the base material increases due to the tackiness of the acrylic polymer and the increase in the molecular weight of the adhesive. It is estimated that the adhesive strength of

[Examples 1 to 7 and Comparative Examples 1 to 3] Hereinafter, a method for curing an adhesive embodying the present invention will be explained in comparison with a comparative example. In addition, each part represents a part by weight. First, using acrylic ester and unsaturated carboxylic acid in the ratio shown in Table 1 below, toluene/ethyl acetate =
An acrylic polymer having a solid content of 35% was synthesized by a solution polymerization method in a mixed solvent of 11 (weight ratio). Table-1 The abbreviations in Table-1 represent the following meanings. BuA Nibutyl acrylate AA Niacrylic acid 2-EHA: 2-Ethylhexyl acrylate AMA
: Maleic anhydride AIA : Itaconic anhydride (Example 1) 100 parts of the solid content of the acrylic polymer (■) and 4°4'-
An adhesive was prepared by mixing 1 part of diphenylmethane diisocyanate, and this was applied to a thickness of about 100 μm on 8 times expanded polyethylene as a base material. Next, the adhesive was cured by heating in diethylamine vapor at 70° C. for 30 seconds. Add another 25mm of 8x foamed polyethylene to this.
A test piece was prepared by applying a pressure of 5 kg for 1 minute to prepare a test piece with an adhesion area of 25 mm x 25 mm. Regarding this, the tensile shear strength was measured. The results are shown in Table 2 below. In addition, the tensile speed in measuring the tensile shear strength was 3゜l.
ll1/l1lin. (Example 2) 100 parts of the solid content of the acrylic polymer (2) and 4°41-
An adhesive was prepared by mixing 2 parts of diphenyl ether diisocyanate, and this was applied to the same substrate as in Example 1 to the same thickness. Then, the adhesive was cured by heating for 1 minute in isopropylamine vapor at 100°C. Thereafter, test pieces were prepared in the same manner as in Example 1. Regarding this, the tensile shear strength was measured. The results are shown in Table 2 below. (Example 3) An adhesive was prepared by mixing 100 parts of the solid content of the acrylic polymer 〇 and 5 parts of 1゜5-naphthalene diisocyanate, and this was applied to the same substrate as in Example 1 to the same thickness. . Next, the adhesive was cured by heating in butylamine vapor at 150"C for 1 minute. A test piece was prepared in the same manner as in Example 1. The tensile shear strength of this was measured. The results were It is shown in Table 2 below. (Example 4) An adhesive was prepared by mixing 100 parts of the solid content of the acrylic polymer 〇 and 1 part of xylene diisocyanate, and this was applied to the same base material as in Example 1 to the same thickness. 0 applied with
The adhesive was cured by heating for 1 minute in tertiary amine vapor at 150°C. Thereafter, test pieces were prepared in the same manner as in Example 1. Regarding this, the tensile shear strength was measured. The results are shown in Table 2 below. (Example 5) An adhesive was prepared by mixing 100 parts of the solid content of the acrylic polymer 〇 and 1 part of isophorone diisocyanate, and this was applied to the same substrate as in Example 1 to the same thickness. The adhesive was cured by heating for 1 minute in 2-methylpiperazine vapor at <0>C. Thereafter, test pieces were prepared in the same manner as in Example 1. Regarding this, the tensile shear strength was measured. The results are shown in Table 2 below. (Example 6) 100 parts of solid content of the acrylic polymer (1) and hydrogenation of 4.4 parts
' A pressure-sensitive adhesive was prepared by mixing 1 part of diphenylmethane diisocyanate, and this was applied to the same substrate as in Example 1 to the same thickness.Then, it was coated in tetramethyltin vapor at 200°C for 1 minute. The adhesive was cured by heating. Thereafter, test pieces were prepared in the same manner as in Example 1. Regarding this, the tensile shear strength was measured. The results are shown in Table 2 below. (Example 7) A test piece was prepared in the same manner as in Example 6, except that the blending ratio of hydrogenated 4.4' diphenylmethane diisocyanate was changed to 20 parts, and the tensile shear strength was measured. It was measured. The results are shown in Table 2 below. (Comparative Example 1) Hydrogenation with 100 parts of the solid content of the acrylic polymer (■): 4.4
A pressure-sensitive adhesive was prepared by mixing 1 part of diphenylmethane diisocyanate, and this was applied to the same substrate as in Example 1 to the same thickness. Then, a test piece was prepared in the same manner as in Example 1 except that it was not cured in a curing catalyst atmosphere. Regarding this, the tensile shear strength was measured. The results are also shown in Table 2 below. (Comparative Example 2) An adhesive was prepared by mixing 100 parts of the solid content of the acrylic polymer ① and 0.0001 part of 1°5-naphthalene diisocyanate, and this was applied to the same base material as in Example 1 to the same thickness. Coated. Then, the adhesive was cured by heating for 1 minute in isopropylamine vapor at 100°C. Thereafter, test pieces were prepared in the same manner as in Example 1. Regarding this, the tensile shear strength was measured. The results are also shown in Table 2 below. (Comparative Example 3) The same Comparative Example 2 except that the blending ratio of 1.5-naphthalene diisocyanate was 100 parts.
A test piece was prepared in the same manner as above, and the tensile shear strength was measured. The results are also shown in Table 2 below. Table 2 As seen from Table 2, Examples 1 to 7 of the present invention exhibit high tensile shear strengths of 7.5 to 7.9 kg/cn. On the other hand, when the mixture of acrylic polymer and polyisocyanate is used as is (Comparative Example 1), or when the amount of polyisocyanate mixed is too little or too much (Comparative Example 2.3), there is no adhesion or the tensile shear strength is 0. ．．
01~2.1kg/cI! It showed only a low value. The reason why the curing method of each example exhibits high tensile shear strength is that in each example, by heating the adhesive in a curing agent atmosphere at a predetermined temperature, the carboxyl group in the acrylic polymer and the isocyanate group in the polyisocyanate are combined. The cohesive force of the adhesive increases due to the reaction of the curing agent, and the adhesive strength between the two 8x expanded polyethylene is improved due to the adhesiveness of the acrylic polymer and the increase in the molecular weight of the adhesive. It is considered that Therefore, the method for curing adhesives of the present invention is suitable as a method for curing various adhesives used, for example, in resin products such as automobile moldings and interior parts, rubber products, and the like. [Effects of the Invention] According to the adhesive curing method of the present invention, the adhesive has a high adhesive strength, a low curing temperature (and a short curing time, and excellent workability).

Claims (1)

[Claims] 1. Apply an adhesive consisting of a mixture of 0.001 to 20 parts by weight of polyisocyanate to 100 parts by weight of an acrylic polymer having a carboxyl group on release paper or a base material, and heat the adhesive at a temperature above the boiling point of the curing catalyst and below 200°C. A method for curing an adhesive, characterized by curing in a curing catalyst atmosphere.