Process for producing cellulose-nanofiber-filled microporous stretched polyolefin film, microporous cellulose-nanofiber composite film, and separator for non-aqueous secondary battery

Patent metadata

Field	Value
Publication number	US-10840491-B2
Application number	US-201414895856-A
Country	US
Kind code	B2
Filing date	Jun 4, 2014
Priority date	Jun 4, 2013
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

A method for producing a cellulose nanofiber-containing polyolefin microporous stretched film according to the invention includes: a first step of obtaining a cellulose powder dispersion mixture by uniformly dispersing a cellulose which has a powder particle shape and whose hydroxyl groups have been subjected to a lipophilizing treatment using a dibasic acid anhydride, in a plasticizer; a second step of melt-kneading the cellulose powder dispersion mixture and a polyolefin to obtain a polyolefin resin composition; a third step of extrusion-molding the polyolefin resin composition to obtain an extrudate; a fourth step of stretching the extrudate with a film stretcher to obtain a film; a fifth step of extracting out the plasticizer from the film; and a sixth step of thermally fixing the film from which the plasticizer has been extracted out for inhibiting contraction, while stretching the film at a temperature not higher than a melting point of the polyolefin, in which a twin-screw kneading extruder is used only once throughout the second and third steps.

First claim

The invention claimed is:

1. A method for producing a cellulose nanofiber-containing polyolefin microporous stretched film, the method comprising: a first step of obtaining a cellulose powder dispersion mixture by uniformly dispersing a cellulose which has a powder particle shape and whose hydroxyl groups have been subjected to a lipophilizing treatment using a dibasic acid anhydride, in a plasticizer; a second step of melt-kneading the cellulose powder dispersion mixture and a polyolefin to obtain a polyolefin resin composition; a third step of extrusion-molding the polyolefin resin composition to obtain an extrudate; a fourth step of stretching the extrudate with a film stretcher to obtain a film; a fifth step of extracting out the plasticizer from the film; and a sixth step of thermally fixing the film from which the plasticizer has been extracted out for inhibiting contraction, while stretching the film at a temperature not higher than a melting point of the polyolefin,
wherein a twin-screw kneading extruder is used only once throughout the second and third steps, and
wherein the lipophilizing treatment comprises performing a monoesterification treatment.

2. The method for producing a cellulose nanofiber-containing polyolefin microporous stretched film according to claim 1 , wherein the monoesterification is followed by performing a secondary propylene oxide addition treatment.

3. The method for producing a cellulose nanofiber-containing polyolefin microporous stretched film according to claim 1 , wherein one kind or a mixture of several kinds among: liquid paraffin, nonane, decane, decalin, paraxylene, undecane and dodecane which are linear or cyclic aliphatic hydrocarbons; mineral oil fractions whose boiling point corresponds to that of liquid paraffin, nonane, decane, decalin, paraxylene, undecane and dodecane; and dibutyl phthalate and dioctyl phthalate which are phthalates having a liquid form at room temperature, is used as the plasticizer.

4. The method for producing a cellulose nanofiber-containing polyolefin microporous stretched film according to claim 1 , wherein the cellulose powder is contained in an amount of from 0.01 to 30% by weight in the cellulose powder dispersion mixture.

5. A cellulose nanofiber microporous composite film comprising the cellulose nanofiber-containing polyolefin microporous stretched film produced by the production method according to claim 1 ,
wherein the cellulose nanofiber microporous composite film comprises cellulose nanofibers dispersed and compounded in polyolefin, and
wherein the cellulose nanofiber microporous composite film includes less aggregated cellulose than a comparative cellulose nanofiber microporous composite film which is prepared in the method according to claim 1 except for that the lipophilizing treatment is not performed.

6. The cellulose nanofiber microporous composite film according to claim 5 , wherein an amount of cellulose in the polyolefin microporous stretched film is from 0.01 to 30% by weight based on a total weight of the polyolefin microporous stretched film.

7. A separator for nonaqueous secondary batteries, comprising the cellulose nanofiber-containing polyolefin microporous stretched film produced by the production method according to claim 1 ,
wherein the separator comprises cellulose nanofibers dispersed and compounded in polyolefin.

Assignees

• Japan Steel Works Ltd

Inventors

• Nakamura Satoru
• Kushizaki Yoshiyuki
• ISHIGURO Ryou
• Yoshioka Mariko

Classifications

• B29D99/005 Primary

  Producing membranes · CPC title

• H01M50/417

  Polyolefins · CPC title

• H01M50/491

  Porosity · CPC title

• H01M50/429

  Natural polymers · CPC title

• H01M50/406

  Moulding; Embossing; Cutting · CPC title