Solid state process to modify the melt characteristics of polyethylene resins and products

• US 20070135584A1
• Filed: 12/12/2005
• Published: 06/14/2007
• Est. Priority Date: 12/12/2005
• Status: Active Grant

• Current Assignee: Equistar Chemicals LP (Lyondellbasell Industries NV)
• Original Assignee: Equistar Chemicals LP (Lyondellbasell Industries NV)
• Inventors: Mavridis, Harilaos, Scheie, Andrew
• Granted Patent: US 7,238,754 B1
• Time in Patent Office: Days
• US Class Current: 525/333.800
• CPC Class Codes: C08F 210/14 Monomers containing five or more carbon atoms
• CPC Class Codes: C08F 210/16 Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
• CPC Class Codes: C08F 2500/04 Broad molecular weight distribution, i.e. Mw/Mn > 6
• CPC Class Codes: C08F 2500/12 Melt flow index or melt flow ratio
• CPC Class Codes: C08F 2810/10 including a reactive processing step which leads, inter alia, to morphological and/or rheological modifications, e.g. visbreaking
• CPC Class Codes: C08F 8/00 Chemical modification by after-treatment graft polymers, block polymers, crosslinking with unsaturated monomers or with polymers C08F251/00 - C08F299/00; of conjugated diene rubbers C08C
• CPC Class Codes: C08K 5/14 Peroxides
• CPC Class Codes: C08L 23/0815 Copolymers of ethene with aliphatic 1-olefins

Abstract

A process for improving the melt characteristics of polyethylene resins is provided. The process involves contacting a polyethylene resin powder with a low level of free radical initiator at a temperature below the melting point of the resin.

Claims

1. A process for modifying the melt characteristics of polyethylene resins comprising contacting an ethylene copolymer resin powder with an effective amount of organic free radical initiator at a temperature above the initiation temperature of the organic free radical initiator and below the melting point of the ethylene copolymer resin to increase the melt elasticity of the modified resin at least 10 percent.

2. The process of claim 1 wherein the ethylene copolymer is a copolymer of ethylene and an α

-olefin comonomer selected from the group consisting of butene-1, hexene-1 and octene-1 having a density from 0.89 to 0.965 g/cm³ and the powder has an average particle size from 5 to 2000 microns.

3. The process of claim 2 wherein the amount of free radical initiator is from 0.5 to 450 ppm.

4. The process of claim 3 wherein the free radical initiator is selected from the group consisting of organic peroxides, organic hydroperoxides and azo compounds.

5. The process of claim 4 wherein the organic free radical initiator is an organic peroxide and is utilized in an amount from 1 to 350 ppm.

6. The process of claim 5 wherein the organic free radical initiator is an organic peroxide selected from the group consisting of dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and t-amyl peroxypivalate.

7. The process of claim 4 wherein the ethylene copolymer has a density from 0.910 to 0.955 g/cm³ and the powder has an average particle size from 75 to 1500 microns.

8. The process of claim 7 wherein the ethylene copolymer is an ethylene-butene-1 copolymer having a density from 0.915 to 0.945 g/cm³.

9. The process of claim 7 wherein the ethylene copolymer is an ethylene-hexene-1 copolymer having a density from 0.915 to 0.945 g/cm³.

10. A process for modifying the melt characteristics of a linear low density polyethylene resin comprising contacting a linear low density powder of a copolymer of ethylene and an α

-olefin selected from the group consisting of butene-1, hexene-1 and octene-1 having a density from 0.915 to 0.935 g/cm³ with 0.5 to 450 ppm free radical initiator selected from the group consisting of organic peroxides, organic hydroperoxides and azo compounds at a temperature above the initiation temperature of the free radical initiator and below the melting point of the linear low density copolymer resin to effect an increase in melt elasticity of at least 10 percent.

11. The process of claim 10 wherein the free radical initiator is an organic peroxide selected from the group consisting of dicumyl peroxide, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane and t-amyl peroxypivalate.

12. The process of claim 11 wherein the free radical initiator is utilized in an amount from 1 to 350 ppm and the temperature is from 50°

C. to 110°

C.

13. A film obtained using a modified linear low density polyethylene resin produced by the process of claim 10.

14. A process for modifying the melt characteristics of a polyethylene resin comprising contacting an ethylene copolymer resin powder under substantially non-oxidizing conditions with an effective amount of an organic free radical initiator at a temperature above the initiation temperature of the organic free radical initiator and below the melting point of the copolymer to increase the melt elasticity of the copolymer by at least 10 percent without substantially increasing the acid number, said copolymer being a copolymer of ethylene and an α

-olefin selected from the group consisting of butene-1, hexane-1 and octene-1 and having a density from 0.89 to 0.965 g/cm³ and said powder having an average particle size from 5 to 200 microns.