JPS6221396B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a pressure sensitive adhesive tape or sheet using a urethane pressure sensitive adhesive. Conventionally, adhesives made by solution polymerization or emulsion polymerization have been used as adhesives for pressure-sensitive adhesive tapes or sheets, but the former uses a large amount of organic solvent, which poses health and safety concerns and pollution. This method is problematic in that it requires extensive equipment for drying and recovering the solvent, and the latter requires a large amount of energy to evaporate the water. In order to eliminate the above-mentioned drawbacks, urethane pressure-sensitive adhesives have recently been studied. Urethane pressure-sensitive adhesives are manufactured by cross-linking polyols and polyisocyanates, and do not contain solvents such as organic solvents or water, so they do not have the above drawbacks and are suitable as adhesives for pressure-sensitive adhesive tapes or sheets. However, it had the disadvantage that the adhesive properties changed over time. In particular, when a phenol-based tackifier was added, the change over time was severe. In view of the above-mentioned drawbacks, the present invention provides a pressure-sensitive adhesive tape or sheet using a urethane-based pressure-sensitive adhesive whose adhesive properties do not change over time, particularly an adhesive in which a phenol-based tackifier is added to the urethane-based pressure-sensitive adhesive. The purpose of this work was to provide a method for producing pressure-sensitive adhesive tapes or sheets using The present invention relates to a method for producing a pressure-sensitive adhesive tape or sheet, characterized in that the pressure-sensitive adhesive tape or sheet is processed. The polyol used in the present invention is a compound having two or more hydroxyl groups, and preferably has an average molecular weight of 500 to 10,000, more preferably 1,000 to 10,000.
5,000 liquids or those that become liquid by heating at 50 to 100℃, such as polyoxyethylene glycol, polyoxypropylene glycol,
Polyether diols such as polyoxyethylene-polyoxypropylene glycol, polyoxytrimethylene glycol, polyoxytetramethylene glycol, polyoxybutylene glycol, and mixtures thereof, polyoxypropylene triol, polyoxyethylene-polyoxypropylene triol, etc. polyether triol,
Polyether polyols such as those obtained by co-condensing trimethylolpropane, glycerin, pentaerythritol, etc. into the molecule of the above polyether diols, or mixtures thereof, polypropylene glycol, dipolypropylene glycol, 1.4-
Condensates of low molecular weight glycols such as butanediol and 1,6-hexanediol with bifunctional organic acids such as phthalic acid and adipic acid, polyester polyols such as ring-opening polymers of ε-caprolactone,
Examples include liquid rubbers such as butadiene homopolymer, butadiene-styrene copolymer, and butadiene-acrylonitrile copolymer, which have a hydroxyl group at the end of the molecule. The polyisocyanate used in the present invention is a compound having two or more isocyanate groups, such as 2,4-toluene diisocyanate and 2,6-toluene diisocyanate or a mixture thereof, 1,5-naphthylene diisocyanate,
xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate,
Aliphatic, aromatic or cycloaliphatic diisocyanates such as 4,4'-dicyclohexylmethane diisocyanate and mixtures thereof, 4,4',4''-triphenylmethane triisocyanate, 1 mol of trimethylolpropane and 3 mol of toluene diisocyanate or tri- or tetra-isocyanate, which is an addition compound from 1 mole of pentaerythritol and 4 moles of toluene diisocyanate. In the present invention, the above polyol and polyisocyanate are mixed, and the resulting mixture is applied to a substrate. The ratio of the polyol to the polyisocyanate is preferably 0.7 to 1.50 in equivalent ratio (isocyanate group/hydroxyl group), more preferably 0.85 to 1.25.The base material may also be a base material for an adhesive tape or sheet. Any materials commonly used can be used, such as plastic films such as polyethylene, polypropylene, polyvinyl chloride, and polyester, stretched plastic films,
Examples include paper and cloth. Further, any coating method may be used, such as a knife coater, a roll coater, etc., to coat the base material to an appropriate thickness. In the above mixture, the hydroxyl group and isocyanate group of the polyol and polyisocyanate react to form a urethane bond, but a reaction catalyst may be added to promote the reaction. Examples of the reaction catalyst include dibutyltin laurate, tin octenoate, lead octenoate, triethylenediamine, triethylamine, and the like. In addition, the above mixture may contain a phenol resin, a terpene phenol resin, a coumaron-indene resin copolymerized with phenol, a tackifier such as rosin or rosin ester, a filler, an ultraviolet absorber, an antioxidant,
A softener or the like may be added. In the present invention, the mixture applied to the substrate is reacted, and after the reaction is completed, it is treated with water to produce a pressure-sensitive adhesive tape or sheet. The above reaction proceeds even at low temperatures, but it is accelerated at high temperatures, so in order to terminate the reaction,
Preferably, heating at ~140°C for 2-10 minutes. After the reaction is completed, the material is treated with water, which may be done by immersing it in water, bringing it into contact with water vapor, or keeping the atmosphere at high humidity. Note that high humidity preferably means relative humidity of 95% or more. In addition, the water treatment time may be determined as appropriate;
Preferably, this is carried out for 2 to 20 minutes. The manufacturing method of the present invention is as described above, and since the polyol and polyisocyanate are treated with water after the reaction is completed, the isocyanate groups and low molecular weight isocyanates that are easily released in the adhesive react with water, forming a strong urethane. Since bonds are formed, free isocyanate groups are not generated over time, and the adhesive properties do not change over time. Especially when a tackifier having a phenol group is added, the isocyanate group reacts with the phenol group,
This isocyanate group is easily released and causes deterioration over time, but through water treatment, this isocyanate group and water react to form a strong urethane bond, preventing the isocyanate group from being released over time. , a pressure-sensitive adhesive tape or sheet is produced that does not change over time. Next, the present invention will be explained by examples. Note that hereinafter, "parts" simply means "parts by weight." The physical properties were measured as follows. (1) SP adhesive strength - width 10mm on stainless steel plate
The sample was pasted and pressed with a 2 kg rubber roll 5 times, and after being left for 15 minutes, it was pressed at a speed of 300 mm/min.
The film was peeled off at 180° and the peel strength was measured. (2) Gel fraction Pressure sensitive adhesive in tetrahydrofuran at 40℃
It was expressed as a percentage of insoluble matter after soaking for 48 hours. Example 1, Comparative Examples 1 and 2 Polyoxypropylene glycol with an average molecular weight of 2000 (manufactured by Mitsui Nisso Urethane Co., Ltd., Diol-2000) 100
1 and 17.4 parts of tolylene diisocyanate (Takenate 80, manufactured by Takeda Pharmaceutical Co., Ltd.) to obtain a prepolymer (liquid A) having isocyanate at both ends. 100 parts of polyoxytetramethylene glycol (manufactured by Nippon Urethane Co., Ltd., PPG-500) with an average molecular weight of 2000, 50 parts of terpene phenol resin (softening point approximately 130°C, manufactured by Yasushi Oil Co., Ltd., YS Polystar 2130), 0.1 part of dibutyltin dilaurate, A mixed solution (Liquid B) was obtained by mixing 0.3 parts of an ultraviolet absorber (TINUVIN327, manufactured by Ciba Geigy) and 0.3 parts of an antioxidant (Irganox 1076, manufactured by Ciba Geigy). 94.4 parts of Part A, 150 parts of Part B and composition Diphenylmethane diisocyanate (average number of functional groups approximately 2.4, manufactured by Sumitomo Bayer Urethane, Sumidyur 44V20)
A mixture obtained by mixing two parts (isocyanate group / hydroxyl group equivalent ratio 1.0) was applied to a 25μ thick polyester film to a thickness of 50μ using a roll coater, and the reaction was completed by heating at 120℃ for 5 minutes. I got the tape. When the obtained tape was measured by infrared absorption spectrum, there was no absorption of isocyanate groups at all. Next, it was immersed in warm water at 80°C for 10 minutes to obtain a pressure-sensitive adhesive tape. The resulting tape was kept at a relative humidity of 60%, 60
The product was stored at a constant temperature of 0.degree. C., and the SP adhesive strength and gel fraction were measured immediately after production, 5 days later, and 20 days later, and the results are shown in Table 1. For comparison, a tape without water treatment was also measured in the same manner and the results are shown in Table 1. (Comparative Example 1) The above tape was aged at 80° C. for 12 hours and measured in the same manner, and the results are shown in Table 1. (Comparative Example 2) [Table]

Claims (1)

[Claims] 1. A method for producing a pressure-sensitive adhesive tape or sheet, which comprises applying a mixture of a polyol and a polyisocyanate to a base material, and treating the mixture with water after the reaction between the polyol and the polyisocyanate is completed.