# US 5,705,631 A · Laminar flow process of preparing cellulose diacetate fibers

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- Number: US 5,705,631 A
- Document ID: US5705631A
- Status: Granted
- Kind: A
- Application number: 08/572,910
- Filed: 1995-12-15
- Granted: 1998-01-06
- Earliest claimed: 1995-12-15
- Assignees: Eastman Chemical Company
- Inventors: Michael Orlando Malcolm
- Web page: https://patentgrep.com/patent/US5705631A

## CPC

- D01F 2/28: from organic cellulose esters or ethers, e.g. cellulose acetate
- D01D 5/06: Wet spinning methods {(D01D5/0046 takes precedence)}
- D01D 5/26: Formation of staple fibres (by flash-spinning D01D5/11)
- D01D 5/40: by applying a shearing force to a dispersion or solution of filament formable polymers, e.g. by stirring
- D01F: CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
- D01D: MECHANICAL METHODS OR APPARATUS IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS

## Abstract

A laminar flow process for preparing cellulose diacetate fibers is disclosed. In the process, a precipitation-acid stream and an acid-dope stream are contacted in a zone having substantially laminar flow. The acid-dope stream is annularly disposed within and flows in the same direction as the precipitation-acid stream. The precipitation-acid stream has a temperature of 100.degree. to 200.degree. F. and comprises 25 to 35 percent by weight acetic acid and 75 to 65 percent by weight water. The acid-dope stream has a temperature in the range of 100.degree. to 200.degree. F. and comprised of 5 to 22 weight percent of cellulose diacetate having an inherent viscosity of at least 1.0, and 95 to 78 percent by weight of a mixture comprising 65 to 90 weight percent acetic acid and 35 to 10 weight percent water. The precipitation-acid stream has a linear flow greater than or equal to the linear flow of the acid-dope stream. The weight ratio of the precipitation-acid stream to the acid-dope stream is at least 9:1. Contacting the two streams in this manner causes precipitation of cellulose diacetate fibers of predictable diameter as the two streams diffuse together.

## Claims

### Claim 1

A process for preparing cellulose diacetate fibers comprising contacting in a zone having a substantially laminar flow wherein the Reynold's number is less than 3000
(A) a precipitation-acid stream having a temperature of 100.degree. to 200.degree. F. and comprised of 25 to 35 percent by weight acetic acid and 75 to 65 percent by weight water, and
(B) an acid-dope stream annularly disposed within and flowing in the same direction as the precipitation-acid stream, the acid-dope stream having a temperature in the range of 100.degree. to 200.degree. F. and comprised of 5 to 22 weight percent of cellulose diacetate having an inherent viscosity of at least 1.0, and 95 to 78 percent by weight of a mixture comprising 65 to 90 weight percent acetic acid and 35 to 10 weight percent water,
wherein the precipitation-acid stream has a linear flow greater than or equal to the linear flow of the acid-dope stream and the weight ratio of the precipitation-acid stream to the acid-dope stream is at least 9:1.

### Claim 2 (depends on 1)

The process of claim 1 wherein the precipitation-acid stream comprises 30 percent by weight acetic acid and 70 percent by weight water.

### Claim 3 (depends on 1)

The process of claim 1 wherein the ratio of flow rate between the precipitation-acid stream and the acid-dope stream is greater than 10:1.

### Claim 4 (depends on 1)

The process of claim 1 wherein the contacting step comprises extruding the acid-dope stream into the precipitation-acid stream.