Abrasion-resistant mineral-filled thermosetting molding composition

Abstract

Mineral-filled thermosetting molding compositions having improved abrasion resistance. The addition of up to 10% polyethylene or other polyolefin greatly improves the abrasion resistance of conventional molding compositions containing 15% to 60% thermosetting resin, 40% to 85% mineral filler of which 50% may be fiberglass or other fibrous reinforcement. The addition is especially applicable with free radical initiated polymers, particularly polyester resins and epoxy-polybutadiene resins, with which it cross links. In some cases flexure strength is also slightly improved.

I claim: 
     
       1. A molding composition adapted to undergo thermosetting reaction under molding conditions to produce a thermoset molding having improved abrasion-resistance and low strength loss, comprising a basic composition of from 15 percent to 60 percent of a thermosetting resin consisting of a free radical initiated .Iadd.polyester or modified epoxy .Iaddend.polymer and a free-radical initiator therefor, and from 40 percent to 85 percent of mineral filler, and a component to improve the abrasion resistance of the basic composition, said component consisting of .[.a polyolefin.]. .Iadd.polyethylene or polypropylene resin which is solid at normal temperature, in a proportion of from about one-half of one percent up to about 3 percent of the total basic composition, said composition, when cured under heat and pressure, producing a molding which has little or no strength loss in comparison with moldings similarly prepared from the same composition without the abrasion-resistance improving component. 
     
     
       2. A molding composition as defined in claim 1 in which the abrasion-resistance component is .[.a.]. polyethylene 
     
     
       3. A molding composition .[.adapted to undergo thermosetting reaction under molding conditions to produce a thermoset molding having improved abrasion-resistance, comprising a basic composition of from 15 percent to 60 percent of a thermosetting resin consisting of a free radical initiated polymer and free radical initiator therefor, and from 40 percent to 85 percent of mineral filler, and a component to improve the abrasion resistance of the basic composition, said component consisting of a polyolefin resin which is solid at normal temperature, in a proportion of from about one-half of one percent up to about 10 percent of the total basic composition,.]. .Iadd.as defined in claim 1 .Iaddend.in which the abrasion-resistance component is .[.a.]. polypropylene resin. 
     
     
       4. A molding composition as defined in claim 1 .Iadd.adapted to undergo thermosetting reaction under molding conditions to produce a thermoset molding having improved abrasion-resistance, comprising a basic composition of from 15 percent to 60 percent of a thermosetting resin consisting of a free radical initiated polymer and a free-radical initiator therefor, and from 40 percent to 85 percent of mineral filler, and a component to improve the abrasion resistance of the basic composition, said component consisting of a polyolefin resin which is solid at normal temperature, in a proportion of from about one-half of one percent up to about 10 percent of the total basic composition, .Iaddend.in which the abrasion-resistance component is a polyethylene copolymer resin. 
     
     
       5. A molding composition as defined in claim 1 in which the filler contains mineral fiber reinforcement in an amount .Iadd.of .Iaddend.from 5% to 50% of the basic composition. 
     
     
       6. A molding composition as defined in claim .[.1.]. .Iadd.2 .Iaddend.in which the basic composition resin is a polyester resin. 
     
     
       7. A molding composition as defined in claim .[.1.]. .Iadd.2 .Iaddend.in which the basic composition resin is an epoxypolybutadiene resin. .[.8. A molding composition as defined in claim 1 in which the basic composition resin is selected from the group consisting of polyester and epoxy-polybutadiene resins..]. .[.9. A cured thermoset molding composed of a cured basic composition of from 15 percent to 60 percent of a thermosetting resin consisting of a free radical initiated polymer and a free radical initiator therefor, and from 40 percent to 85 percent of mineral filler, and from about one-half of one percent up to about 10 percent of a component interspersed in the basic composition to improve the abrasion resistance thereof, consisting of a polyolefin resin which is solid at normal temperature..]. .[.10. A molding as defined in claim 9 in which the basic composition resin is a polyester resin..]. .[.11. A molding as defined in claim 9 in which the basic composition resin is a polyester resin and the polyolefin resin is a polyethylene resin..]. .[.12. A molding as defined in claim 9 in which the polyolefin is at least partially cross linked with the free radical initiated polymer resin..]. 
     
     
        .Iadd.13.  A molding composition as in claim 2 in which the polyethylene is in the form of a fine powder, 100 mesh or finer. .Iadd.14. The method of improving the abrasion resistance of a fiber-reinforced thermoset molding having a basic composition of from 15 percent to 60 percent of a thermosetting resin consisting of a free radical initiated polyester or modified epoxy polymer and a free-radical initiator therefor, and from 40 percent to 85 percent of mineral filler which includes fiber reinforcement in an amount of at least 5 percent of the basic composition, which consists in including in the composition from which the molding is made, as an additive for improving the abrasion resistance of the molding, polyethylene or polypropylene resin which is solid at room temperature, in a proportion of from about one-half of one percent up to and including about 3 percent of the total basic composition. .Iaddend. .Iadd.15. The method of claim 14 in which the additive is polyethylene resin and the fiber reinforcement is glass fiber..Iaddend. .Iadd.16. The method of claim 14 in which the additive is polyethylene which is added in the form of a fine powder, 100 mesh or finer. .Iaddend.