Shell mold structures and processes and compositions for forming the same

Claim 1

AN INVESTMENT COMPOSITION FOR APPLICATION IN THE FORM OF A LAYER OF FILM TO A FROZEN MERCURY PATTERN BELOW THE FREEZING TEMPERATURE OF THE PATTERN MATERIAL AND PRODUCING A SHELL-LIKE MOLD AROUND SAID PATTERN, SAID COMPOSITION COMPRISING AS COMPOSITION INGREDIENTS A REFRACTORY MATERIAL OF SMALL PARTICLE SIZE CONTITUTING A PREDOMINANT AMOUNT OF THE NORMALLY SOLID COMPOSITION INGREDIENTS, AN ORGANIC RESINOUS BINDER FOR SAID REFRACTORY PARTICLES THAT IS ADHERENT TO THE FROZEN MERCURY PATTERN WHEN A FILM OR LAYER OF THE COMPOSITION IS APPLIED THERETO COMPRISING A MIXTURE OF POLYMERIZED VINYL ACETATE AND ETHYL CELLULOSE THAT HAS BEEN MATERIALLY ETHYLATED, WHICH MIXTURE CONSITUTES .25% TO 5% OF SAID SOLID INGREDIENTS AND IS PRESENT IN AN AMOUNT SUFFICIENT TO BIND THE REFRACTORY PARTICLES IN THE APPLIED LAYER OR FILM OF PATTERN AT SAID VERY LOW TEMPERATURES, DRYING SAID SHELL LAYER ON SAID FROZEN PATTERN AT SAID VERY LOW TEMPERATURES AND BELOW SAID BOILING POINT TO SOLIDIFY THE SHELL LAYER INTO A SELF SUPPORTING SHELL MOLD, LIQUEFYING THE FROZEN PATTERN AND REMOVING THE LIQUEFIED PATTERN MATERIAL FROM SAID SHELL MOLD AND THE REAFTER HEATING SAID SHELL MOLD TO SAID RAISED TEMPERATURE TO CAUSE SAID REFRACTORY PARTICLES AND SAID INORGANIC BINDER TO COMBINE INTO A HARD SHELL LAYER AND TO MODIFY AND DRIVE OFF SAID RESINOUS BINDER AND RENDER SAID SHELL MOLD POROUS SAID COMPOSITION TOGETHER OVER A TEMPERATURE RANGE FROM BELOW SAID FREEZING TEMPERATURE UP TO AT LEAST A TEMPERATURE 90*C. HIGHER THAN SAID FREEZING TEMPERATURE, AND SAID POLYMERIZED VINYL ACETATE AND ETHYL CELLULOSE EACH BEING PRESENT IN AN AMOUNT SUFFICIENT TO PROVIDE AT LEAST A SUBSTANTIAL PORTION OF THE BINDING ACTION OF SAID MIXTURE OVER SAID TEMPERATURE RANGE, AND A LIQUID CARRIER FOR SAID REFRACTORY PARTICLES AND SAID BINDER THAT IS IN THE LIQUID STATE AT TEMPERATURES BELOW SAID FREEZING TEMPERATURE AND HAS A BOILING POINT BELOW 0* C., SAID CARRIER BEING PRESENT IN AN AMOUNT SUFFICIENT TO HOLD DISPERSED SAID SOLID COMPOSITION INGREDIENTS AND PROVIDE A SLURRY OF SUFFICIENTLY LOW VISCOSITY AT BELOW SAID FREEZING TEMPERATURE TO ENABLE SAID COMPOSITION TO BE APPLIED TO THE FROZEN MERCURY PATTERN IN THE FORM OF A LAYER OR FILM FOR FORMING THEREOVER A SHELL MOLD.