Crosslinked solid type pressure-sensitive adhesive composition, pressure-sensitive adhesive sheet comprising the composition, and pressure-sensitive adhesive sheet for waterproofing/airproofing comprising the sheet

Abstract

A solid type pressure-sensitive adhesive composition capable of being applied without the necessity of using an organic solvent or water and a pressure-sensitive adhesive sheet, which are excellent in both adhesive force and holding power and, in particular, undergo no decrease in low-temperature adhesive force even when the adhesive layer thickness is small. The crosslinked solid type pressure-sensitive adhesive composition comprising (a) a rubbery polymer, (b) a tackifier, and (c) a crosslinking agent comprising at least one member selected from the group consisting of thiuram vulcanizing agents, quinoid vulcanizing agents, quinone dioxime vulcanizing agents, and maleimide vulcanizing agents.

Description

[0001] The present invention relates to a crosslinked solid type pressure-sensitive adhesive composition which does not substantially contain a solvent, and a pressure-sensitive adhesive sheet (including a tape, film and other form) obtained by applying the composition with heating to a substrate. The invention further relates to a pressure-sensitive adhesive sheet for waterproofing / airproofing comprising the pressure-sensitive adhesive sheet.DESCRIPTION OF THE RELATED ART[0002] Due to the enforcement of the Housing Quality Security Promotion Law, it is desired to completely eliminate the leaking of rain in houses, and various waterproof sheets are used. Recently, various airproof sheets also have been used with the demand for highly airtight, highly heat-insulated houses, which are highly effective in energy saving. Conventional pressure-sensitive adhesive sheets for use as such waterproof or airproof pressure-sensitive adhesive sheets employ a pressure-sensitive adhesive comprisin...

AI Technical Summary

Benefits of technology

[0011] Based on the idea described above, the present inventors selected a crosslinking agent capable of reacting with a rubber-based pressure-sensitive adhesive during kneading. They have found that when a rubber-based pressure-sensitive adhesive is kneaded together with this crosslinking agent with heating while monitoring the kneading torque and suitably regulating the kneading temperature and kneading time, then the crosslinking agent can be evenly dispersed in the material without causing the rubbery polymer to undergo a molecular weight decrease due to molecular chain cutting. As a result, the desired crosslinking can be realized and the cohesive force can be enhanced. The invention has thus been completed.

[0027] The solid type pressure-sensitive adhesive composition thus crosslinked has satisfactory moldability such that it readily softens upon heating. Consequently, when this pressure-sensitive adhesive composition is applied with heating to a substrate such as a fabric (e.g., cotton, rayon, artificial-fiber, or nonwoven fabric), a paper (e.g., Japanese paper or kraft paper), a plastic (e.g., cellophane, polyethylene, polyester, poly(vinyl chloride), cellulose acetate, polypropylene, poly(ethylene terephthalate), polystyrene, or polyacrylonitrile), a metal foil, or a plastic laminate of any of these by means of calender rolls, an extruder, or the like, then a pressure-sensitive adhesive sheet comprising the substrate and formed thereon a layer comprising the pressure-sensitive adhesive composition can be produced in the form of a sheet, tape, film, or the like. Since this process does not use any organic solvent causative of environmental pollution, or water which necessitates much energy for drying, there is no need of conducting a step for drying a coated substrate in a drying oven. This process is hence friendly to the global environment and can greatly contribute to energy saving.

[0029] The substrate may be subjected to conventional treatments in order to improve the adhesive force (anchoring force) of the pressure-sensitive adhesive layer. For example, that side of the substrate which is coated with the pressure-sensitive adhesive layer may be subjected to a surface treatment, such as a corona treatment or plasma treatment, or coated with a primer layer. That side of the substrate which is not coated with the pressure-sensitive adhesive layer may be suitably coated with a release agent represented by a silicone resin or a fluororesin in order to facilitate the unwinding of a roll of the sheet.

Problems solved by technology

Pressure-sensitive adhesive sheets in which the adhesive does not show cohesive failure upon peeling are undesirable because a space is formed between the adherend and the pressure-sensitive adhesive to pose the possibility that water might penetrate into the space to impair waterproofing.

On the other hand, the rubber-asphalt pressure-sensitive adhesive has a durability as short as about 10 years and shows poor adhesiveness at high temperatures and low temperatures.

The acrylic pressure-sensitive adhesive, which has been marketed recently, is less apt to show cohesive failure upon peeling from adherends and whether or not this pressure-sensitive adhesive retains a sufficient waterproofing function over many years has not been demonstrated.

Such solid type pressure-sensitive adhesive compositions are uncrosslinked compositions which have poor cohesive force especially at high temperatures and hence have often caused positional shifting.

In this case, the practical kneading temperature during the kneading is about 180.degree. C. at the most, and it is considerably difficult to heat the composition to, for example, 200.degree. C., which is necessary for the crosslinking reaction with sulfur generally used for the crosslinking of butyl rubbers.