Cross-linked polyolefin separator and manufacturing method thereof

Patent metadata

Field	Value
Publication number	US-11674011-B2
Application number	US-201916766829-A
Country	US
Kind code	B2
Filing date	Aug 30, 2019
Priority date	Aug 31, 2018
Publication date	Jun 13, 2023
Grant date	Jun 13, 2023

Abstract

A method for manufacturing a crosslinked polyolefin separator and the crosslinked polyolefin separator obtained therefrom are provided. The method includes non-grafted polyolefin having a weight average molecular weight of 300,000 or more and silane-grafted polyolefin having a weight average molecular weight of 300,000 or more. The method minimizes gel formation, a side reaction occurring in an extruder during the manufacture of the separator, and provides the separator having a uniform surface.

First claim

What is claimed is:

1. A method for manufacturing a crosslinked polyolefin separator, comprising:
(S 1 ) mixing non-grafted polyolefin having a weight average molecular weight of 300,000 or more, silane-grafted polyolefin having a weight average molecular weight of 300,000 or more, a diluting agent, an initiator, an alkoxysilane compound containing a carbon-carbon double bonded group and a crosslinking catalyst to an extruder and then carrying out reactive extrusion at 200° C. or higher to obtain a silane-grafted polyolefin composition;
(S 2 ) molding and orienting the reactive extruded silane-grafted polyolefin composition in the form of a sheet;
(S 3 ) extracting the diluting agent from the oriented sheet to obtain a porous membrane;
(S 4 ) thermally fixing the porous membrane; and
(S 5 ) crosslinking the porous membrane in the presence of water,
wherein a content of the alkoxysilane compound containing the carbon-carbon double bonded group is 0.01-2 parts by weight based on 100 parts by weight of a total weight of the non-grafted polyolefin, silane-grafted polyolefin and the diluting agent.

2. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein a weight ratio of the non-grafted polyolefin to the silane-grafted polyolefin is 90:10-20:80.

3. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein the non-grafted polyolefin has a weight average molecular weight of 300,000-1,500,000.

4. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein the silane-grafted polyolefin has a weight average molecular weight of 300,000-1,000,000.

5. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein the reactive extrusion is carried out at a temperature of 200-250° C.

6. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein the alkoxysilane compound containing the carbon-carbon double bonded group includes vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, (3-methacryloxypropyl)trimethoxysilane, (3-methacryloxypropyl) triethoxysilane, vinylmethyl dimethoxysilane, vinyl-tris(2-methoxyethoxy)silane, vinylmethyldiethoxysilane or a mixture of at least two thereof.

7. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein a content of the alkoxysilane compound containing the carbon-carbon double bonded group is 0.05-1.2 parts by weight based on 100 parts by weight of the total weight of the non-grafted polyolefin, silane-grafted polyolefin and the diluting agent.

8. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein the non-grafted polyolefin has a weight average molecular weight of 300,000-1,000,000,
the silane-grafted polyolefin has a weight average molecular weight of 300,000-1,000,000,
a weight ratio of the non-grafted polyolefin to the silane-grafted polyolefin is 90:10-50:50,
the reactive extrusion is carried out at a temperature of 200-230° C., and
a content of the alkoxysilane compound containing the carbon-carbon double bonded group is 0.1-0.5 parts by weight based on 100 parts by weight of the total weight of the non-grafted polyolefin, silane-grafted polyolefin and the diluting agent.

9. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein the thermal fixing is carried out at a temperature of 100-230° C.

10. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , further comprising applying and drying slurry for forming a porous coating layer including inorganic particles, a binder polymer and a solvent, after (S 5 ).

11. The method for manufacturing the crosslinked polyolefin separator according to claim 1 , wherein a phosphorus compound containing a carbon-carbon double bonded group is further introduced to the extruder in (S 1 ).

12. The method for manufacturing the crosslinked polyolefin separator according to claim 11 , wherein (S 1 ) comprises mixing the non-grafted polyolefin having a weight average molecular weight of 300,000 or more, the silane-grafted polyolefin having a weight average molecular weight of 300,000 or more, the diluting agent, the initiator, alkoxy group-containing vinylsilane, the phosphorus compound containing the carbon-carbon double bonded group and a crosslinking catalyst to the extruder, and then carrying out reactive extrusion at 200° C. or higher to obtain the polyolefin composition having the silane compound and the phosphorus compound grafted to a backbone of polyolefin.

13. The method for manufacturing the crosslinked polyolefin separator according to claim 11 , wherein the phosphorus compound containing the carbon-carbon double bonded group includes diphenylvinylphosphine oxide, diphenylvinylphosphine, dimethyl vinyl phosphonate, diethyl vinyl phosphonate, diphenylvinyl phosphate, dimethylvinyl phosphate, diethylvinyl phosphate, ethenyl dihydrogen phosphate, isopropenyl dihydrogen phosphate, vinylphosphonic acid or a mixture of at least two thereof.

14. The method for manufacturing the crosslinked polyolefin separator according to claim 11 , wherein a total content of the alkoxysilane compound containing the carbon-carbon double bonded group and the phosphorus compound containing the carbon-carbon double bonded group is 0.01-2 parts by weight based on 100 parts by weight of the total weight of the non-grafted polyolefin, silane-grafted polyolefin and the diluting agent.

15. The method for manufacturing the crosslinked polyolefin separator according to claim 11 , wherein a weight ratio of the alkoxysilane compound containing the carbon-carbon double bonded group to the phosphorus compound containing the carbon-carbon double bonded group is 90:10-30:70.

16. The method for manufacturing the crosslinked polyolefin separator according to claim 11 , wherein the separator has a shutdown temperature of 135° C. or lower and a meltdown temperature of 185° C. or higher.

17. The method for manufacturing the crosslinked polyolefin separator according to claim 11 , wherein the separator has a temperature difference of 30° C. or higher between the shutdown temperature and meltdown temperature.

18. A crosslinked polyolefin separator obtained by the method as defined in claim 11 , wherein the separator comprises a silane compound and a phosphorus compound grafted to a backbone of polyolefin, and has a silane-derived crosslinking structure.

19. A crosslinked polyolefin separator obtained by the method as defined in claim 1 .

Assignees

• Lg Chemical Ltd

Inventors

• Lee Joo-Sung
• Bae Won-Sik
• Ryu Bi-Oh

Classifications

• C08L23/06

  Polyethylene · CPC title

• B29C48/08

  flexible, e.g. films · CPC title

• H01M10/0525

  Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries · CPC title

• C08J2323/00

  Characterised by the use of homopolymers or copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond; Derivatives of such polymers · CPC title

• C08L2312/08

  by silane · CPC title