# US 5,352,732 A · Homogeneous, high modulus ultrahigh molecular weight polyethylene composites and processes for the preparation thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,352,732 A - Document ID: US5352732A - Status: Granted - Kind: A - Application number: 07/997,999 - Filed: 1992-12-29 - Granted: 1994-10-04 - Earliest claimed: 1990-08-07 - Assignees: E. I. Du Pont de Nemours and Company - Inventors: Edward G. Howard - Web page: https://patentgrep.com/patent/US5352732A ## CPC - C08F 10/02: Ethene - C08F: MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS ## Abstract A homogeneous composite is provided comprising (a) about 10 to 99.5% by weight of an ultrahigh molecular weight linear polyethylene having a molecular weight of at least about 400,000, a crystalline melting point of greater than 143.degree. C., the reduction of said melting point upon remelting being at least 3.degree. C., and a crystal morphology comprising a bimodal distribution of molecular chain fold spacings reflecting significant populations of both folded and very highly extended molecular chains, and (b) about 0.5 to 90% by weight of at least one filler compound having a neutral-to-acidic surface, said polyethylene being polymerized onto the surface of said filler, and said composite being substantially free of polymer-free filler and of filler-free polymer. Also provided are processes for the preparation of such composites. ## Claims ### Claim 1 A homogeneous composite comprising (a) about 10 to 99.5% by weight of an ultrahigh molecular weight linear polyethylene having a molecular weight of at least about 400,000, a crystalline melting point of greater than 143.degree. C., the reduction of said melting point upon remelting being at least 3.degree. C., and a crystal morphology comprising a bimodal distribution of molecular chain fold spacings reflecting significant populations of both folder and very highly extended molecular chains, and (b) about 0.5 to 90% by weight of at least one filler compound having a neutral-to-acidic surface, said polyethylene being polymerized onto the surface of said filler, and said composite being substantially free of polymer-free filler and of filler-free polymer. ### Claim 2 (depends on 1) The composite of claim 1 comprising at least 30% by weight of said filler. ### Claim 3 (depends on 2) The composite of claim 2 exhibiting an elastic or flexural modulus of about 300 to 1300 kpsi, a tensile modulus of about 350 to 1500 kpsi and a maximum tensile strength at break of at least 1 kpsi. ### Claim 4 (depends on 3) The composite of claim 3 wherein the tensile modulus is about 650 to 1500 kpsi. ### Claim 5 (depends on 4) The composite of claim 4 wherein the flexural modulus is about 700 to 1300 kpsi. ### Claim 6 (depends on 3) The composite of claim 3 wherein the reduction of said melting point upon remelting is at least 6.degree. C. ### Claim 7 (depends on 6) The composite of claim 6 wherein said filler compound is an inorganic compound selected from the group consisting of alumina hydrates, silicas, water-insoluble silicates, calcium carbonate, basic aluminum sodium carbonates, hydroxyapatite and calcium phosphates. ### Claim 8 (depends on 6) The composite of claim 6 wherein the neutral-to-acidic surface of said filler compound is prepared by coating a relatively basic surface with an acidic oxide. ### Claim 9 (depends on 8) The composite of claim 8 wherein the acidic oxide is phosphoric acid. ### Claim 10 (depends on 7) The composite of claim 7 wherein said filler compound is hydroxyapatite or calcium hydrogen phosphate. ### Claim 11 (depends on 3) The composite of claim 3 wherein the constituent polyethylene has a molecular weight of at least about 1,000,000. ### Claim 12 (depends on 1) An article comprising the composite of claim 1. ### Claim 13 (depends on 12) The article of claim 12 in the form of a film. ### Claim 14 (depends on 12) The article of claim 12 in the form of a cylindrical bar. ### Claim 15 (depends on 1) A prosthetic article comprising the composite of claim 1. ### Claim 16 (depends on 10) A prosthetic article comprising the composite of claim 10. ### Claim 17 (depends on 1) A process for preparing the composite of claim 1 comprising: (a) forming an article of a solid, homogeneous particulate composite comprising (i) about 10 to 99.5% by weight of ultrahigh molecular weight polyethylene having a molecular weight of at least about 400,000, and (ii) about 0.5 to 90% by weight of at least one finely-divided filler compound having a neutral-to-acidic surface and having interacted at the surface of said filler a catalytically active amount of transition metal compound, said polyethylene being polymerized onto the surface of said filler, said composite being substantially free of polymer-free filler and of filler-free polymer; (b) heating said article in an inert atmosphere to a temperature of at least 180.degree. C. sufficient to melt said polyethylene and, at this temperature, compressing said article at a pressure of at least 280 MPa for at least 2 minutes; (c) reducing the temperature to 175.degree. C. or lower while maintaining a pressure of at least 280 MPa, the rate of reduction of temperature being such that temperature gradients in the shaped article are substantially avoided; and, (d) rapidly cooling to a temperature below 100.degree. C. while maintaining a pressure of at least 280 MPa, then reducing the pressure in such a manner that remelting of the polyethylene constituent of the article is avoided. ### Claim 18 (depends on 17) The process of claim 17 wherein the polyethylene constituent of the composite in step (a) has a molecular weight of at least about 1,000,000. ### Claim 19 (depends on 17) The process of claim 17 wherein the finely divided filler compound in the step (a) composite has a weight-average equivalent spherical particle diameter of 0.1 to less than 50 microns. ### Claim 20 (depends on 19) The process of claim 19 wherein the transition metal compound interacted at the filler surface provides 0.000001-1.7 mg-atom of transition metal per gram of filler. ### Claim 21 (depends on 20) The process of claim 20 wherein the transition metal is selected from the group consisting of titanium, zirconium and chromium. ### Claim 22 (depends on 17) The process of claim 17 wherein the particulate composite of step (a) is a free-flowing powder having particle sizes in the range of 0.1 micron to 5 mm, and having a 10-second micronization homogeneity of at least 50% and a micronization homogeneity index of at least 20. ### Claim 23 (depends on 17) The process of claim 17 wherein the pressure in steps (b)-(d) is at least 300 MPa. ### Claim 24 (depends on 17) The process of claim 17 wherein the heating in step (b) is continued for at least 0.5 hour before pressure is applied. ### Claim 25 (depends on 17) The process of claim 17 wherein pressure is applied in steps (b)-(d) by means of a fluid. ### Claim 26 (depends on 25) The process of claim 25 wherein the fluid is water. ### Claim 27 (depends on 1) The composite of claim 1 comprising less than 10% by weight of said filler.