| 摘要 |
Articles are cut or stamped from unhardened rods, sheets or bars of animal or vegetable casein and then partially hardened by treatment with hardening liquid for a limited time, after which they are superficially dried, softened by the action of dry heat and pressed while in this state to their final form, the hardening being completed during the latter process. For example, the stamped articles are exposed to the action of formaldehyde as a hardening agent for about a week, then superficially dried by exposure to the air for about 24 hours, after which they are softened by dry heating to about 100 DEG C. As the amount of water present in the mixture affects the shrinkage in the final product, a constant water content is necessary to ensure uniformity of the finished article. In all cases, however, the casein should have a moisture content of about 10 per cent, and the amount of water in any added matter such as dyes should be taken into account. About 25 per cent of water is added before the mixture is worked up into the sheets, rods or bars. The composition and strength of the liquid in the hardening bath should also be constant to ensure a standard size of finished article. |
