Polyisoprene articles and process for making the same

Abstract

The invention disclosed herein relates to an improved process for making elastomeric polyisoprene articles. In particular, the process of the invention is a system which produces synthetic polyisoprene articles exhibiting tensile strength properties similar to that of solvent-based processes using natural rubber latex. The process comprises an accelerator composition at the pre-cure stage comprising a dithiocarbamate, a thiazole and a guanidine compound. In a preferred embodiment, the accelerator composition comprises zinc diethyldithiocarbamate (ZDEC), zinc 2-mercaptobenzothiazole (ZMBT) and diphenyl guanidine (DPG), in conjunction with a stabilizer, such as sodium caseinate. The invention also includes an elastomeric polyisoprene product made by the process, such as a surgeon's glove.

Description

RELATED APPLICATION DATA[0001]This application is based on U.S. provisional patent application Ser. No. 60 / 275,087 filed on Mar. 12, 2001.FIELD OF THE INVENTION[0002]The invention relates to the field of elastomeric articles used in the medical field. In particular, the invention relates to improvements to the process of making elastomeric polyisoprene articles for medical applications.BACKGROUND OF THE INVENTION[0003]The manufacturing process for producing elastomeric articles from natural or synthetic rubber latex involves a curing step during which cross-linking or vulcanization through sulfur groups occurs between the polymer units. Conventional processes for making elastomeric articles from natural or synthetic latex typically involve preparing a latex dispersion or emulsion, dipping a former in the shape of the article to be manufactured into the latex and curing the latex while on the former. Desirable properties of certain elastomeric articles such as tensile strength are su...

AI Technical Summary

Benefits of technology

[0010]Another advantage of the invention is that conventional manufacturing equipment and most readily-available materials can be used in accordance with the invention to make the synthetic polyisoprene glove without the need for new or costly additional materials or equipment. Further, no complicated new process steps are required by the invention and the invention can be readily incorporated into existing glove making processes and systems.

[0011]Another aspect of the invention is that the compounded (or ready to use) polyisoprene latex composition formulated in accordance with the invention exhibits prolonged storage stability. For example, the pre-cure storage stability of the compounded polyisoprene latex composition (i.e., the time period prior to the use of the compounded polyisoprene latex composition in the dipping and curing stages) can extend up to about 8 days, in contrast to the typical current 3 to 5 day time period. By extending storage life of the latex, the amount of wasted latex can be significantly reduced and greater flexibility in scheduling manufacturing processes is permitted.

[0012]Yet another advantage is that the process of the invention allows for significantly reduced pre-cure process parameters (lower temperature and shorter time periods than conventionally used) and lower dipping temperatures in the manufacturing process. Accordingly, significant cost and resource advantages are provided over conventional manufacturing practices.

[0013]The invention provides for a process of making a synthetic elastomeric polyisoprene article comprising the steps of: a) preparing a compounded polyisoprene latex composition containing an accelerator composition containing a dithiocarbamate, a thiazole and a guanidine compound; b) dipping a former into said compounded polyisoprene latex composition; and c) curing said compounded polyisoprene composition on said former. Additionally, the initial pre-cure processing (i.e., prior to storage and article manufacture) can be performed at temperatures of less than 35° C. and in time periods as short as ranging from about 90 minutes (1.5 hours) to about 150 minutes (2.5 hours), preferably about 120 minutes (2.0 hours). The compounded polyisoprene latex composition can be stored for periods up to about 8 days at ambient temperatures (ranging from about 15° C. to about 20° C.). Lower temperatures can be used for the latex dipping step as well

[0014]The invention also provides for a synthetic elastomeric polyisoprene article made by a process comprising the steps of: a) preparing a compounded polyisoprene latex composition comprising an accelerator composition comprising a dithiocarbamate, a thiazole and a guanidine compound; b) pre-curing said compounded polyisoprene latex composition c) dipping a former into said compounded polyisoprene latex composition; and d) curing said compounded polyisoprene composition on said former. Elastomeric articles made by the process of the invention can exhibit tensile strengths of over 3000 psi (as measured in accordance with ASTM D412) even after as much as 7 days of latex storage prior to use in the article manufacturing process.

[0015]The invention further provides for a synthetic polyisoprene latex composition comprising:

Problems solved by technology

The use of natural rubber latex in the manufacture of certain articles such as medical gloves has been associated with disadvantageous properties, such as allergic reactions believed by some to be caused by natural proteins or allergens present within the natural rubber latex and the final product.

It is known that solvent-based systems are possible for polyisoprene, although such systems are poorly suited for the manufacture and molding of elastomeric articles for medical applications.

One difficulty in the field of gloves, for example, is the design of processes and materials which will produce a thin elastomeric article having desirable properties such as high tensile strength.

Another disadvantage of solvent-based systems is solvent toxicity.