Coupling agents for natural fiber-filled polyolefins

Abstract

The invention is a coupling agent, which is made from a polyolefin composition and is for wetting a cellulosic fiber. The coupling agent desirably includes a polyolefin resin having a melt flow index at 190° C. and 2.16 kg of about 0.5 to 100 (g/10 min). The polyolefin resin is combined with 1.6 to 4.0 weight percent maleic anhydride, and the composition has less than 1,500 ppm of free maleic anhydride. The coupling agent has a yellowness index of 20 to 70. A cellulosic composite can be made from the coupling agent by combining the coupling agent with cellulosic fiber and at least one thermoplastic polymer.

Description

Claims

1. A composition for wetting a natural fiber comprising: a polyolefin resin;1.6 to 4.0 percent maleic anhydride, said composition having less than 1,500 ppm of free maleic anhydride;wherein said composition has a melt flow index at 190° C. and 2.16 kg of about 0.1 to 500 (g/10 min); andwherein said composition has a yellowness index of 20 to 70.

2. The composition of claim 1 wherein: said maleic anhydride is 1.6 to 3.0 percent of said composition, said composition has less than 600 ppm of free maleic anhydride;wherein said composition has a melt flow index at 190° C. and 2.16 kg of about 0.5 to 100 (g/10 min); andwherein said composition has a yellowness index of 20 to 55.

3. The composition of claim 2 wherein: said maleic anhydride is 2.0 to 3.0 percent of said composition, said composition has less than 200 ppm of free maleic anhydride;wherein said composition has a melt flow index at 190° C. and 2.16 kg of about 2 to 50 (g/10 min); andwherein said composition has a yellowness index of 20 to 40.

4. The composition of claim 1 wherein said polyolefin is a polyethylene.

5. The composition of claim 4 wherein said polyethylene includes a member selected from the group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, copolymers with other alpha olefins, and combinations thereof.

6. The composition of claim 5 wherein said polyethylene is High-density polyethylene homo- and copolymers.

7. A cellulosic composite comprising: 10 to 90 percent cellulosic fiber;a first polyolefin resin having a melt flow index of 0.1 to 100 (g/10 min);0.1 to 10 weight percent of a coupling agent, said coupling agent comprises a second polyolefin resin having a melt flow index at 190° C. and 2.16 kg of about 0.1 to 500 (g/10 min);1.6 to 4.0 weight percent maleic anhydride, said coupling agent having less than 1,500 ppm of free maleic anhydride; andwherein said composition has a yellowness index of 20 to 70.

8. The cellulosic composite of claim 8 wherein said first polyolefin resin is a polyethylene being a member selected from the group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene copolymers with other alpha olefins, and combinations thereof.

9. The cellulosic composite of claim 8 wherein said maleic anhydride is grafted to polyethylene, said polyethylene is a member selected from the group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, copolymers with other alpha olefins, and combinations thereof.

10. The cellulosic composite of claim 10 wherein said first polyolefin resin has a melt flow index of 0.3 to 20, said cellulosic fiber is 20 to 80 percent of said composite, and said coupling agent is 0.5 to 3 percent of said composite.

11. The cellulosic composite of claim 11 wherein said first polyolefin resin is HDPE homo- and copolymers having a melt flow index of 0.3 to 5, said cellulosic fiber is 40 to 65 percent of said composite, and said coupling agent is 0.5 to 2 percent of said composite.

12. The composite material of claim 1 wherein the natural fiber is selected from the group consisting of wood fiber, wood flour, and combinations thereof.