Crosslinked Polyolefin Separator and Manufacturing Method Therefor

Patent metadata

Field	Value
Publication number	US-2020220139-A1
Application number	US-201916648562-A
Country	US
Kind code	A1
Filing date	Jul 26, 2019
Priority date	Jul 26, 2018
Publication date	Jul 9, 2020
Grant date	—

Abstract

A crosslinked polyolefin separator which has gels with a longer side length of 50 μm or more in a number ranging from 0 to 3 per 1 m 2 of the separator, and shows a standard deviation of absorbance ratio between the center of the separator and the side thereof ranging from 0.01 to 0.5 is provided. A method for manufacturing the crosslinked polyolefin separator is also provided. The method includes (S1) preparing a polyolefin porous membranes, and (S2) applying a coating solution containing an initiator and alkoxy group-containing vinylsilane onto at least one surface of the porous membrane. The coating solution can permeate even to the inside of exposed pores. Thus, it is possible to provide a crosslinked polyolefin separator in which silane crosslinking occurs uniformly even inside of the pores.

First claim

1 . A crosslinked polyolefin separator, comprising:
silane-crosslinked polyolefin, wherein the separator has gels with a longer side length of 50 μm or more in a number ranging from 0 to 3 per 1 m 2 of the separator, and the separator
shows a standard deviation of absorbance ratio between a center of the separator and a side thereof ranging from 0.01 to 0.5,
wherein the absorbance ratio is determined by I 1090 /I 2920 (×1000), I 1090 means an absorbance at 1090 cm −1 where a functional group of —Si—OCH 3 derived from crosslinking is detected, and I 2920 means an absorbance at 2920 cm −1 where a characteristic peak of polyolefin is expressed before crosslinking occurs.

2 . The crosslinked polyolefin separator according to claim 1 , wherein the standard deviation of absorbance ratio between the center of the separator and the side thereof is 0.25-0.40.

3 . The crosslinked polyolefin separator according to claim 1 , wherein the separator has a process capability index (Cp) of 1.3 or more, wherein the silane (S1) content in the separator is 700 ppm or more based on 100 parts by weight of the separator.

4 . The crosslinked polyolefin separator according to claim 1 , wherein the separator satisfies following [Formula 1] and [Formula 2] in a nail penetration test wherein a nail having a temperature of 250° C. or higher is dropped vertically:
b/a≤ 3.0  [Formula 1]

c /( b−a )≥0.75  [Formula 2]

wherein a represents a diameter of the nail used in the nail penetration test,
b represents a diameter of separator lost after nail penetration in the nail penetration test, and
c represents a length of a pore-blocked region after nail penetration.

5 . (canceled)

6 . A method for manufacturing a crosslinked polyolefin separator, comprising:
(S1) preparing a polyolefin porous membrane; (S2) applying a coating solution containing an initiator and alkoxy group-containing vinylsilane onto at least one surface of the porous membrane; (S3) drying and thermally fixing the porous membrane coated with the coating solution; and (S4) crosslinking the thermally fixed porous membrane in the presence of water.

7 . The method according to claim 6 , wherein (S1) comprises:
introducing and mixing polyolefin and a diluting agent to an extruder and carrying out extrusion to prepare a polyolefin composition; molding and orienting the extruded polyolefin composition in a form of a sheet; and extracting the diluting agent from the oriented sheet to obtain the porous membrane.

8 . The method according to claim 6 , wherein silane grafting occurs simultaneously in the porous membrane, in the thermal fixing (S3).

9 . The method according to claim 6 , wherein the alkoxy group-containing vinylsilane comprises trimethoxyvinylsilane, triethoxyvinylsilane, triacetoxyvinylsilane, or a mixture of two or more of them.

10 . The method according to claim 6 , wherein the thermal fixing is carried out at a temperature of 110-145° C.

11 . The method according to claim 6 , wherein the thermal fixing is carried out at a temperature of 110-145° C., and the alkoxy group-containing vinylsilane comprises two types of alkoxy group-containing vinylsilane having a-different boiling points.

12 . The method according to claim 6 , wherein the alkoxy group-containing vinylsilane is a mixture of trimethoxyvinylsilane with triethoxyvinylsilane, and the weight ratio of the trimethoxyvinylsilane to triethoxyvinylsilane is 90:10-30:70.

13 . The method according to claim 6 , wherein the thermal fixing is carried out at a temperature of 110-145° C., the alkoxy group-containing vinylsilane is a mixture of trimethoxyvinylsilane with triethoxyvinylsilane, and the weight ratio of the trimethoxyvinylsilane to triethoxyvinylsilane is 90:10-30:70.

14 . (canceled)

15 . The method according to claim 6 , wherein the coating solution further comprises a crosslinking catalyst.

16 . (canceled)

17 . The method according to claim 6 , further comprising:
removing the coating solution between (S2) and (S3).

18 . The method according to claim 17 , wherein the removing of the coating solution is carried out by removing the surplus coating solution by pressurizing the porous membrane coated with the coating solution.

19 . The method according to claim 18 , wherein the pressurization is controlled at a linear pressure of 0.1-100 kgf/cm.

20 . The method according to claim 17 , wherein the removing of the coating solution is carried out by passing the porous membrane through a gap between a first roller and a second roller facing each other to remove the surplus coating solution.

21 . The method according to claim 20 , wherein the gap between the first roller and the second roller is +10 m to −10 μm, and the gap, S, is defined by a formula of S=D−(R 1 +R 2 +T), wherein D represents a distance between the first roller center and the second roller center, R 1 represents a first roller radius, R 2 represents a second roller radius, and T represents a thickness of the polyolefin porous membrane.

22 . The method according to claim 17 , further comprising:
rubbing and absorbing the surplus coating solution between the removing of the coating solution and thermal fixing step (S3).

23 . The method according to claim 22 , wherein the rubbing is carried out by using a rubbing roller or rubbing cloth.

24 . (canceled)

Assignees

• Lg Chemical Ltd

Inventors

• Lee Joo-Sung
• Ryu Bi-Oh
• Bae Won-Sik
• Lee A-Young
• Song Heon-Sik

Classifications

• C08J7/16 Primary

  with polymerisable compounds · CPC title

• H01M50/417 Primary

  Polyolefins · CPC title

• H01M50/489

  Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties · CPC title

• H01M50/406

  Moulding; Embossing; Cutting · CPC title

• Y02T10/70

  Energy storage systems for electromobility, e.g. batteries · CPC title