# US 5,705,632 A · Process for the preparation of cellulose acetate film

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- Number: US 5,705,632 A
- Document ID: US5705632A
- Status: Granted
- Kind: A
- Application number: 08/582,355
- Filed: 1996-01-19
- Granted: 1998-01-06
- Earliest claimed: 1995-01-19
- Assignees: Fuji Photo Film Co., Ltd.; Daicel Chemical Industries, Ltd.
- Inventors: Kazuhiro Shimoda; Masahiko Murayama; Hidekazu Yamazaki; Tohru Shibata; Shu Shimamoto; Hiroyuki Takemoto; Naoto Habu
- Web page: https://patentgrep.com/patent/US5705632A

## CPC

- C08J 5/18: Manufacture of films or sheets
- C08J 2301/12: Cellulose acetate
- C08J: WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H (working, e.g. shaping, of plastics B29)

## Abstract

A process for the preparation of a cellulose acetate film comprises the steps of: cooling a mixture of cellulose acetate and an organic solvent to -100.degree. to -10.degree. C.; warming the cooled mixture to 0.degree. to 50.degree. C. to dissolve the cellulose acetate in the organic solvent; casting the obtained solution on a support; and evaporating the organic solvent to form the cellulose acetate film. The cellulose acetate has an average acetic acid content in the range of 58.0 to 62.5%. The organic solvent is acetone.

## Claims

### Claim 1

A process for the preparation of a cellulose acetate film which comprises the steps of:
cooling a mixture of cellulose acetate and an organic solvent to a temperature of -100.degree. to -10.degree. C., said cellulose acetate having an average acetic acid content in the range of 58.0 to 62.5%, said cellulose acetate being contained in the mixture in an amount of 10 to 40 wt %, and said organic solvent consisting essentially of acetone;
warming the cooled mixture to a temperature of 0.degree. to 50.degree. C. to dissolve the cellulose acetate in the organic solvent;
casting the obtained solution on a support; and
evaporating the organic solvent to form the cellulose acetate film.

### Claim 2 (depends on 1)

The process as claimed in claim 1, wherein the cellulose acetate has a viscosity average degree of polymerization in the range of 250 to 400.

### Claim 3 (depends on 1)

The process as claimed in claim 1, wherein the cellulose acetate contains a low molecular weight fraction of not more than 10 wt. %, said fraction being soluble in acetone at 25.degree. C.

### Claim 4 (depends on 1)

The process as claimed in claim 1, wherein the cellulose acetate has a viscosity average degree of polymerization represented by DP and a concentrated solution viscosity represented by .eta. which satisfy the formula (2):
2.814.times.ln(DP)-11.753.ltoreq.ln(.eta.).ltoreq.6.29.times.ln(DP)-31.469( 2)
wherein DP means the value of a viscosity average degree of polymerization, which is not less than 290; and .eta. is a period of time in terms of second taken for a ball to pass between the standard lines measured according to a falling ball method.

### Claim 5 (depends on 1)

The process as claimed in claim 1, wherein the cellulose acetate has a crystallization exotherm in terms of .DELTA.Hc in the range of 5 to 17 J/g.

### Claim 6 (depends on 1)

The process as claimed in claim 1, wherein the mixture of cellulose acetate and an organic solvent further contains a plasticizer in an amount of 0.1 to 20 weight parts based on 100 weight parts of the cellulose acetate.

### Claim 7 (depends on 1)

The process as claimed in claim 1, wherein the support on which the solution is cast has a surface temperature of not higher than 10.degree. C.

### Claim 8 (depends on 1)

The process as claimed in claim 1, wherein the cellulose acetate is contained in the mixture in an amount of 10 to 30 wt %.