US1828736A - Degumming silk - Google Patents

Description

Patented Oct. 27, 1931 UITED STATES PATENT OFFICE NORMAN D. HARVEY, J'R OF PITTSBURGH, PENNSYLVANIA, ASSIGNOR TO CARBIDE & CARBON CHEMICALS CORPORATION, A CORPORATION OF NEW YORK DEGUMMING SILK No Drawing. Application filed February means of alkaline solutions, soap solutions or even boiling water.

The usual degumming process is to boil the silk, in skein form or after weaving, in a 7 water solution of a sodium or potassium soap. To remove the gum effectively the soap solution should have a pH of about 10.0. More strongly alkaline solutions damage the fibre rather rapidly, and even where the pH is below 10, prolonged boiling will injure the silk. It is customary to use high-grade olive oil soaps which are as nearly neutral as pos sible. A solution containing about 1% of soap is oftenused, the weight of soap being about of the weight of silk-to be degummed. During the degumming operation, the pH of the soap solution falls slowly to a value of about 8.5 to 9.0, at which it remainspracticallystationary. This change in the solution is explained by. the acidic properties of the gum dissolved. As its pH drops, the soap solution becomes less and less efiective as a degumming agent.

Ihave found that monoethanolamine, more or less completely saponified with oleic or other fatty acid, is an" excellent silk degumming agent. Monoethanolamine,

(OHQOHCHZNHQ),

is a high boiling, hygroscopic, slightly yellow liquid of faint ammoniacal'odor having an alkaline reaction and a pH of about 11.6. Silk degummed with this reagent is somewhat whiter and softer than silk degummed with the best olive oil soaps, and the material has other advantages as a degumming agent which will appear below.

I prefer to use a mixture of monoethanolamine and fatty; acid containing a stoichiometrical excess of the amine, for example, con" taining about equal weights of the amine and the fatty acid. The presence of the fatty acid lowers the pH of the mixture to about 10.0,

and this .value is found to remainalmost 3, 1930. Serial No. 425,727.

constant until a considerable proportion of sericin has been dissolved in the solution, owin to the fact that the original mixture contains considerably more base than is required for a neutral soap. In other words, monoethanolamine gives adegumming reagent whichretains its efliciency longer than the soaps used heretofore.

Comparing freshly made solutions, monoethanolamine soaps are somewhat more efficacious than -olive oil soap. A solution containing 0.4 gram of monoethanolamine and- 04 gram of oleic acid in 99.2 grams of water degums silk at as high a rate as a 1% s'plu tion of olive oil soap. The monoethanolamine oleate prepared with'an excess of base, as described herein, may be'rinsed from the silk somewhat more readily than alkali-metal soaps.

Less accurate control of the saponification' process is required when monoethanolamine is used as the base. The pH of this compound, I

being low as compared with caustic alkalies,

an excess of base is much less likely to raise the pH of the gumm'ing solution to a value sufiiciently high to injure the silk.

Instead of oleic acid, other soap-forming fatty acids may be used, the proportions of amine and fatty acid being adjusted to give a suitable pH. y

i I claim: v

1. Process of degumming silk which comprises dissolving the sericin in a solution containing a monoethanolamine soap, and an excess of the amine.

2. Process of degumming silk which comprises dissolving the sericin in a solution containing a monoethanolamine oleate, and an excess of monoethanolamine.

3. Process of degumming silk which comprises dissolving the sericin in a solution containing equal weights of monoethanolamine and oleic acid;

In testimony whereof, I aflix' my signature.

' NORMAN D. HARVEY, JR.