CS220030B1 - A method for roughening the surface of dipped rubber articles - Google Patents

Abstract

The invention relates to a method for roughening the surface of dipped rubber products. The method according to the invention can be used to obtain products with a roughened surface according to a simple solvent-free process when dipping into smooth molds. When dipping into roughened molds, products roughened on both sides can be obtained. By roughening the surface of the products, an anti-slip treatment and a reduction in stickiness are achieved. The application mainly relates to rubber gloves, but this method can be used for various dipped rubber products. The essence of the method according to the invention lies in the precipitation of a roughening latex slurry on the basic slurry. The roughening mixture contains latex precipitated by the action of colloidal substances, which is in the form of fine grains suspended in an aqueous medium. This slurry achieves roughening of the surface of the finished products.

Description

The invention relates to a method of roughening the surface of rubber products, produced by dipping into latex mixtures and precipitation on molds. By roughening, the products acquire an anti-slip finish, reduce stickiness and improve appearance.

Currently, these roughened products, especially rubber gloves, are produced mainly by dipping into patterned molds or by methods using the swelling effect of some organic solvents on latex foams. Previously used methods were based on suspending solid particles in latex. The disadvantage of roughened molds is that they easily stain and clog fine pores and make it difficult to remove products from these molds. In methods using solvents, it is possible to dip into smooth molds and obtain, in addition to a roughened surface, coarser and more plastic patterns, but the disadvantage is the consumption of the solvent and the difficulty of removing it from the product in the further course of the production process due to its toxicity and possibly flammability.

The method of roughening the surface according to the invention enables the use of smooth molds with a simple and solvent-free technology. In the case of dipping on a rough mold, it is possible to obtain products roughened on both sides with minimal stickiness.

The essence of this method is that a thin layer of a second, roughening coating is deposited on the basic latex coating, which contains small grains or flakes of latex, previously precipitated by the effect of colloidal substances, acting here as internal coagulants with a delayed effect. This second coating adheres perfectly to the basic coating and, after drying, causes the surface to become rough.

The process according to the invention is explained below:

The slightly preheated mold is first soaked in a coagulant, which is most often an alcoholic solution of calcium salts, and after the coagulant has dried on the mold, it is dipped in some basic latex mixture according to common recipes for dipped rubber. After the desired thickness of the solution has precipitated and after a short pause during which part of the coagulant diffuses through the solution, it is dipped in a second latex mixture. This mixture is prepared by adding diluted latex, preferably of the chloroprene type with a high tendency to crystallize, to a very dilute solution of colloid, which gradually causes complete or partial flocculation of the latex. It is advantageous to use cellulose derivatives, which are used as thickeners of latex mixtures in lower concentrations, but cause precipitation after a certain concentration is exceeded, which leads in the case of diluted latexes to the formation of granules of partially coagulated latex, suspended in an aqueous medium, or possibly still in the presence of residues of uncoagulated latex. It is advantageous to work! with a mixture of latexes, for example chloroprene and natural, which makes the wet wet. By dipping into this roughening latex mixture, a thin layer of roughening wet wet precipitates due to the effect of diffused calcium salts, which, after drying, creates a rough surface of the product.

Composition of the mixtures used in the following embodiment:

Coagulant

Ethanol Calcium nitrate Sodium lauryl sulfate (wetting agent) 70 parts by weight 30 parts by weight 0.3 parts by weight Basic latex mixture Latex melcoammoniac 167 parts by weight content 60% by weight of natural rubber (100 parts dry matter J Ground sulfur 1.1 wt. 'drill Diethyldithiocarbamate zinc 1.1 parts by weight Methyl bis-naphthalenesulfonate sodium 0.2 parts by weight Distilled water 60 parts by weight

Roughening latex mixture

Part A:

Hydroxyethylcellulose

2%; solution 5 parts by weight

Distilled water 95 parts by weight

Part B:

Low ammonia latex 15 parts by weight, 60% by weight natural rubber content Chloroprene latex, with a high tendency to crystallize, 55% by weight rubber content 25 parts by weight

Distilled water 160 parts by weight

Note: The roughening mixture is preferably prepared by adding diluted latex (part BJ) to diluted cellulose solution (part A), thereby achieving approximately the same size of precipitated latex granules. Example of embodiment

Surface roughening in the production of rubber surgical gloves.

A smooth porcelain glove mold, preheated to a temperature of 50 to 60 °C, is soaked in the coagulant and, after it dries in the mold, it is precipitated in the basic latex mixture for 40 to 50 s. After a short pause, it is dipped into the stirred roughening latex mixture and precipitated for 30 to 40 s. Then other operations follow according to common rubber manufacturing procedures — drying, vulcanization, washing, etc. If washing is included before drying and vulcanization, a short pause is necessary between soaking and washing so that the latex from the second soaking completely coagulates.

Claims (1)

A method of roughening the surface of rubber articles made from latex mixtures by dipping and precipitation in molds, characterized in that the roughening is carried out by precipitation of the roughening latex feed within 20 to 60 seconds, positive on the latex feed, wherein the roughening composition comprises latex, preferably tendency to crystallize, at a concentration of 2 to 8 wt. % solids of rubber and colloidal component, preferably cellulose derivatives, at a concentration of 0.02 to 0.1 wt.