Polylactic acid adhesive compositions and methods for their preparation and use

Abstract

New adhesives and methods for preparing them are disclosed that include polylactic acid irradiated with gamma radiation, such as by a Co60 source. Irradiation times are used that improve the characteristics of the adhesive materials. Generally, the dose of radiation is from about 5 kGy to about 200 kGy of gamma irradiation. The adhesives generally have melting temperatures in the range of at least about 140 to about 148° C. such that they can be conveniently used in conventional glue guns and other glue equipment. The disclosed adhesives can provide bond strengths in the range of about 1,600 psi or more to about 2,500 psi or more. The disclosed adhesives can include a crosslinking agents. They can be used to join a wide range of substrates including wood, metal, plastic, ceramic, glass or combinations of substrates. They can be conveniently prepared by heating a polylactic acid (polylactic acid) preparation and mixing the molten polylactic acid with one or more crosslinkers when present. The molten mixture can then be and the polylactic acid can be irradiated with the desired dose of gamma radiation. Irradiation can occur before during or after mixing with the crosslinking agent and before or after shaping into the desired shape or even after use to join substrates. The adhesives can be used to join substrates by any known method once heated to a molten state.

Dependencies are inferred from the claim text.