Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
211 words
A process for injection compression molding ultra high molecular weight ployethylene having an intrinsic viscosity of at least 3 dl/g measured at 135° C. in decalin and a melt index of up to 0.01 g/10 min which comprises, (a) heating ultra high molecular weight polyethylene to 170°-240° C., (b) adjusting the volume of the mold cavity V 1 in a mold at a mold temperature of from 80° C. to 120° C. to be equal to the volume of the molded article V 0 , (c) injecting ultra high molecular weight polyethylene having volume V 0 into the molded cavity through a runner portion at a shear rate of at least 20,000 sec -1 , (d) instantaneously expanding the mold cavity to adjust its volume V 1 to satisfy the relation: 1.2 V.sub.0 ≦V.sub.1 at a time from T 1 , immediately before completion of injection and time T 2 while there is a pressure difference between the cavity and the runner portion, and the ultra high molecular weight polyethylene in the runner portion has not solidified, and (e) compressing the volume of the mold cavity V 1 to satisfy the relation: V.sub.1 =V.sub.0 while the ultra high molecular weight polyethlene in the mold cavity is still in a molten state.
Claim 2
Dependent Claim
211 words
A process for injection compression molding ultra high molecular weight ployethylene having an intrinsic viscosity of at least 3 dl/g measured at 135° C. in decalin and a melt index of up to 0.01 g/10 min which comprises, (a) heating ultra high molecular weight polyethylene to 170°-240° C., (b) adjusting the volume of the mold cavity V 1 in a mold at a mold temperature of from 80° C. to 120° C. to be equal to the volume of the molded article V 0 , (c) injecting ultra high molecular weight polyethylene having volume V 0 into the molded cavity through a runner portion at a shear rate of at least 20,000 sec -1 , (d) instantaneously expanding the mold cavity to adjust its volume V 1 to satisfy the relation: 1.2 V.sub.0 ≦V.sub.1 at a time from T 1 , immediately before completion of injection and time T 2 while there is a pressure difference between the cavity and the runner portion, and the ultra high molecular weight polyethylene in the runner portion has not solidified, and (e) compressing the volume of the mold cavity V 1 to satisfy the relation: V.sub.1 =V.sub.0 while the ultra high molecular weight polyethlene in the mold cavity is still in a molten state.
Claim 3
Dependent Claim
29 words
A process according to claim 1 in which the mold cavity is expanded to make the volume of the mold cavity V 1 satisfy the relation: 1.4 V.sub.0 ≦V.sub.1.
Claim 4
Dependent Claim
18 words
A process according to claim 1 in which the mold cavity is expanded immediately after completion of injection.
Claim 5
Dependent Claim
49 words
A process according to claim 1 in which the mold comprises a mold having a cavity and a movable core being fitted into the cavity, and retreat of the core results in expansion of the mold cavity while advance of the core results in compression of the mold cavity.
Claim 6
Dependent Claim
34 words
A process according to claim 1 in which the mold is heated to a temperature which is lower than the melting point of the ultra high molecular weight polyethylene by 10° C. or more.
Claim 7
Dependent Claim
17 words
A process according to claim 1 wherein the shear rate is at least 50,000 sec -1 .
Claim 8
Dependent Claim
13 words
A process according to claim 1 wherein the polyethylene temperature is 170°-200° C.