Acrylic pressure sensitive adhesive acrylic monomer has excellent cohesibility

Acrylic monomers have excellent cohesiveness and can be polymerized by a variety of reaction systems, including solution polymerization, suspension polymerization, emulsion polymerization, and bulk polymerization technology.

For example, the following method has been proposed for the preparation of acrylic polymers. One method involves bulk polymerization by heating a mixture of acrylic monomers and mercaptans in the presence of oxygen at 20-200C (see Japan Patent Bulletin No.50(1975)-401). Another method involves polymerizing a mixture of acrylic monomers and mercaptans in nitrogen gas with essentially no initiator (see Japanese patent No258,251).

Another method involves using an extruded barrel device instead of a batch reactor for polymerization at high temperatures (near 150C) (see Japan Patent Bulletin No.2(1990)-55448). Another method involves irradiating the batch reactor with ultraviolet light through optical fibers and using ultraviolet pulse irradiation for polymerization (see Japan Patent Bulletin No.71995)-330815). Another method involves gradually changing the reaction temperature while irradiating the batch reactor with ultraviolet light. UV bulk polymerization is thus performed (see Japan Patent Bulletin No.11(1999)-49811).

However, when a conventional industrial batch reactor is used to react acrylic monomers in the presence of a thermal-decomposing polymerization initiator, the heat generation in the reactor is too strong for the reaction heat to be removed from the reaction system due to the high reactivity of the acrylic monomers. Therefore, it is not feasible to conduct bulk polymerization of acrylic monomers and control the reaction effectively in the presence of a thermal decomposition polymerization initiator in the reactor.

One disadvantage of using the barrel system is that the reaction requires setting the reaction temperature in the high-temperature region. As a result, the molecular weight distribution of the resulting polymer becomes wider and the molecular weight becomes more dispersed as the temperature control accuracy decreases.