Latex-Reclaim-Casein Mixtures for Rubber-Cord Fabric Adhesion
Abstract A good bond, resistant to flexing, is afforded between rubber and rayon cord by the interposition of a mixed casein-rubber film. In a series of solutions in which the proportion of rubber solids was kept constant and the quantity of casein varied progressively, it was found that there was an optimum amount of casein for maximum adhesion. Taking into consideration also the handling of the solution and the stiffening of the cord, it would appear that for an adhesive with the usual total solids content of 15 to 20 per cent, the ratio of casein to rubber hydrocarbon should be approximately 1:6. When the rubber hydrocarbon is supplied by dispersed reclaim, the adhesion is a little higher than when latex is used. The most satisfactory solution from all points of view, however, contains approximately equal quantities of rubber hydrocarbon derived from the two sources. Wetting agents may be employed to improve the uniformity of application of the adhesive. The amount used must be very small, otherwise the adhesion is impaired. By dipping cord successively in casein and latex solutions and vice versa in the adhesive film, casein acts as a specific adhesive for rayon, whereas the rubber in the film gives the necessary affinity for the casing rubber which surrounds it. Treating a cord successively in a casein-rich mixture and then in a rubber-rich mixture appears to give a slightly better bond than the conventional treatment. The subsequent application of a rubber cement to a cord dipped in latex-reclaim-casein solution results in an improvement in the bond.