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US3846403A Expired / Lapsed US ⏱️ 0.0 years remaining

Production of cellulose esters from partially purified wood pulp by hemicellulose removal

Assignee: CELLULOSE CO Ltd
•
Filing: 1973-06-21
•
Granted: 1974-11-05
•
Expires: 1993-06-21
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Abstract

Abstract In the preparation of a solution of cellulose acetate by esterifying cellulose with acetic anhydride in acetic acid to form a solution of cellulose acetate in acetic acid, the improvement which comprises using as the cellulose source wood pulp which has been only partially purified but still contains at least about 5 percent by weight of hemicellulose. The hemicelluloses preferentially esterify so the reaction is interrupted after a few minutes and the solution containing the dissolved hemicellulose ester is separated from the undissolved, largely hemicellulose-free pulp. Additional acetylation medium is added and esterification resumed to completion. The hemicellulose acetate solution may optionally be blended in at this stage. The resulting cellulose acetate can be used in fiber extrusion without rapidly clogging filters and spinnerettes used in such operation so that there is a long time interval between shutdowns for filter and spinnerette replacement.

Inventors

  • 👤 K Gibney
  • 👤 R Evans

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-01 01:00
CPC Classifications
C; C08; C08B; C08B3/00; C08B3/06; C08B37/00; C08B37/0006; C08B37/0057

Claims Analysis

Total Claims: 8
Claim 1
Independent Claim 129 words
IN THE AMOUNT OF A SOLUTION OF A CELLULOSE LOWER ALKANOTE WHEREIN A CELLULOSE SOURCE IS SUBJECTED TO ESTERIFICATION WITH A LOWER ALKONIC ACID ANHYDRIDE IN A LOWER ALKANOIC ACID THEREBY TO FORM SAID CELLULOSE LOWER ALKANOTE DISSOLVED IN SAID ACID, THE IMPROVEMENT WHICH COMPRISES EMPLOYING AS SAID CELLULOSE SOURCE CELLULOSE HAVING A HEMICELLULOSE CONTENT IN EXCESS OF ABOUT 5 PERCENT BY WEIGHT, INTERRUPTING THE ESTERIFICATION WHEN THE HEMICELLULOSE CONTENT OF THE STILL UNDISSOLVED CELLULOSE SOURCE HAS FALLEN TO LESS THAN ABOUT ONE-HALF ITS INITIAL VALUE, FILTERING THE REACTION MASS TO REMOVE THEREFROM THE SOLUTION, ADDING FRESH ANHYDRIDE AND ACID TO THE FILTRATION RESIDUE, AND CONTINUING THE REACTION, WHEREBY THE RESULTING SOLUTION IS CHARACTERIZED BY A PERFORMANCE DURING SUBSEQUENT PROCESSING COMPARABLE TO THAT OF INITIALLY MORE PURE CELLULOSE SOURCES.
Claim 2
Dependent Claim 129 words
IN THE AMOUNT OF A SOLUTION OF A CELLULOSE LOWER ALKANOTE WHEREIN A CELLULOSE SOURCE IS SUBJECTED TO ESTERIFICATION WITH A LOWER ALKONIC ACID ANHYDRIDE IN A LOWER ALKANOIC ACID THEREBY TO FORM SAID CELLULOSE LOWER ALKANOTE DISSOLVED IN SAID ACID, THE IMPROVEMENT WHICH COMPRISES EMPLOYING AS SAID CELLULOSE SOURCE CELLULOSE HAVING A HEMICELLULOSE CONTENT IN EXCESS OF ABOUT 5 PERCENT BY WEIGHT, INTERRUPTING THE ESTERIFICATION WHEN THE HEMICELLULOSE CONTENT OF THE STILL UNDISSOLVED CELLULOSE SOURCE HAS FALLEN TO LESS THAN ABOUT ONE-HALF ITS INITIAL VALUE, FILTERING THE REACTION MASS TO REMOVE THEREFROM THE SOLUTION, ADDING FRESH ANHYDRIDE AND ACID TO THE FILTRATION RESIDUE, AND CONTINUING THE REACTION, WHEREBY THE RESULTING SOLUTION IS CHARACTERIZED BY A PERFORMANCE DURING SUBSEQUENT PROCESSING COMPARABLE TO THAT OF INITIALLY MORE PURE CELLULOSE SOURCES.
Claim 3
Dependent Claim 19 words
The process of claim 1 wherein said lower alkanoic acid is acetic acid and said anhydride is acetic anhydride.
Claim 4
Dependent Claim 27 words
The process of claim 1 wherein the esterification is interrupted when the hemicellulose content of the still undissolved cellulose is less than about 3 percent by weight.
Claim 5
Dependent Claim 29 words
The process of claim 1 including the further step of adding the filtrate of the interrupted eSterification to the solution which results when the final esterification is substantially complete.
Claim 6
Dependent Claim 24 words
The process of claim 1 wherein the cellulose source is wood pulp having a hemicellulose content in excess of about 8 percent by weight.
Claim 7
Dependent Claim 47 words
The process of claim 1, wherein the cellulose source is wood pulp, the lower alkanoic acid is acetic acid and the anhydride is acetic anhydride, and the esterification is interrupted when the hemicellulose content of the still undissolved cellulose is less than about 3 percent by weight.
Claim 8
Dependent Claim 29 words
The process of claim 6 including the further step of adding the filtrate of the interrupted esterification to the solution which results when the final esterification is substantially complete.

References Cited (Backward Citations)

US2028080A Cited
US2191525A Cited
US2772944A Cited
US3040027A Cited
US3037902A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1977-11-04 1978-05-06 1978-11-05 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1981-11-04 1982-05-06 1982-11-05 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 1985-11-04 1986-05-06 1986-11-05 $7700.00 Window Closed / Lapsed

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