Process for producing dip-formed rubber article

Abstract

A vulcanizable dip-forming rubber latex composition comprising an unsaturated nitrile-conjugated diene copolymer rubber latex, a sulfur-containing vulcanizer, and a vulcanization accelerator comprising at least one compound selected from (i) dithiocarbamic acid compounds of the formula: and (ii) zinc dithiocarbamate compounds of the formula: wherein R1 and R2 are hydrocarbon groups having at least 6 carbon atoms which may be the same or different, and an optional thiazole compound. A rubber article dip-formed from the rubber latex composition has no crack occurrence, good surface luster and good vulcanization properties, and does not contain a nitrosamine, and therefore, is suitable for medical use.

Description

[0001] This invention relates to a dip-forming, vulcanizable rubber latex composition comprising a sulfur-containing vulcanizer an a vulcanization accelerator, which is used for making a vulcanized unsaturated nitrile rubber article without production of a nitrosamine which is restricted by regulation, and further relates to a rubber article dip-formed therefrom.[0002] Certain N-nitrosamines (hereinafter abbreviated to "nitrosamines") are carcinogenic, and a problem arises in that it is possible that nitrosamines are produced in vulcanized rubber articles made from a solid polymer rubber or a polymer rubber latex.[0003] For example, as examples of the vulcanized rubber articles made from a polymer rubber latex, there can be mentioned those which are used in contact with the human body, such as a nipple, a balloon, gloves for operation, or medical examination or detection, a balloon sac, and other medical articles. It is possible that nitrosamines are detected in these vulcanized rub...

AI Technical Summary

Benefits of technology

[0010] To solve the problems encountered with the conventional vulcanization promoters, the present inventors have conducted researches into vulcanization accelerators and found that, when specified dithiocarbamic acid compounds are used as a vulcanization accelerator for an unsaturated nitrile rubber (NBR) latex, a vulcanized rubber article dip-formed therefrom has no crack occurrence, excellent surface luster and good vulcanization properties. Based on this finding, the present invention has been completed.

[0023] The unsaturated nitrile-conjugated diene copolymer rubber latex is prepared usually by an emulsion polymerization procedure. The temperature at which the emulsion polymerization is effected is not particularly limited, but is preferably not higher than about 40.degree. C. because the latex can be produced stably and a rubber article dip-formed therefrom has a high mechanical strength and a soft feeling.

[0037] The dithiocarbamic acid vulcanization accelerators used in the present invention do not produce a nitrosamine which is restricted by regulation. The dithiocarbamic acid vulcanization accelerators can exhibit a vulcanization accelerating activity and can impart vulvanization properties to rubber articles dip-formed therefrom, which are similar to those given by the conventional dithiocarbamic acid vulcanization accelerators which are considered in the art to be indispensable for making rubber articles by dip-forming and which produce nitrosamines restricted by regulation. The rubber articles dip-formed from the latex composition with the vulcanization accelerator used in the present invention do not give an offensive smell, are not colored or are colored only to a negligible extent, do not have cracks or have very few cracks, and have an excellent surface luster.

Problems solved by technology

Certain N-nitrosamines (hereinafter abbreviated to "nitrosamines") are carcinogenic, and a problem arises in that it is possible that nitrosamines are produced in vulcanized rubber articles made from a solid polymer rubber or a polymer rubber latex.

Especially a serious problem is caused in medical rubber articles which are used in direct contact with mucous membranes or organs.

At present, the restriction of nitrosamines contained in vulcanized rubber articles by regulation is an urgent problem in Japan and many other countries.

However, it is reported that when this vulcanization accelerator is used for a natural rubber latex, the resulting vulcanized rubbers generally have poor vulcanization properties as compared with vulcanized rubbers made with other conventional vulcanization accelerators (Polymer Digest, 1987, 12, p12-).

This vulcanization accelerator is however little or no practicality because it has a low storage stability and an offensive smell, and results in rubber vulcanizates with poor vulcanization properties.

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