US2816003A

US2816003A - Partial acetylation of cotton fibers

Info

Publication number: US2816003A
Application number: US517955A
Authority: US
Inventors: Esmond J Keating; Jr Albert S Cooper; Jr Edmund M Buras
Original assignee: Individual
Current assignee: Individual
Priority date: 1955-06-24
Filing date: 1955-06-24
Publication date: 1957-12-10
Anticipated expiration: 1974-12-10

Description

PARTIAL ACETYLATION F COTTON FIBERS Esmond J. Keating, Albert S. Cooper, Jr., and Edmund M. Buras, In, New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture Application June 24, 1955, Serial No. 517,955

2 Claims. (Cl. 8-121) (Granted under Title 35, U. S. Code (1952), sec. 266) A non-exclusive, irrevocable, royalty-free license in the invention herein described, for all governmental purposes, throughout the world, with the power to grant sublicenses for such purposes, is hereby granted to the Government of the United States of America.

This invention relates to the partial acetylation of cellulosic textile fibers, and provides an improved and more economical partial acetylation process.

Prior work resulted in the development of the practical process for the partial acetylation of vegetable textile fibers described in American Dyestufi Reporter, March 29, 1954, pages 203208. By means of that process, fibers such as cotton fibers are partially aceylated to a degree of substitution of from about 0.5 to 2, to improve their heat and rot resistance and the like properties. In conducting the process, the fibers are activated by soaking them in an activating liquid consisting essentially of acetic acid containing enough acetic anhydride to convert to acetic acid the regain moisture present in the fibers. The activated fibers are partially acetylated by reacting them with an acetylating liquid consisting essentially of an acetylating mixture of acetic anhydride and acetic acid containing a catalytic amount of perchloric acid. The portion of the acetylating liquid which is not retained in the porous portions of the fibers can be recovered, reconstituted and re-used in the activation of a subsequent portion of fibers. And, in a batchwise operation, the excess acetylating liquid, i. e., the portion of the liquid which drains off from the fibers, or which is removed by a conventional mechanical extraction using squeeze rolls, centrifuges and the like, can similarly be recovered and re-used a number of times.

However, as the partial acetylation process was heretofore conducted, in order to utilize the acetic acid and acetic anhydride that did not react in the partial acetylation reaction, it was necessary to fractionally distill spent acetylating liquids consisting of either the recovered acetylating liquids used in a batchwise operation that had been re-used for more than about 10 times, or the recovered acetylating liquids used in a continuous operation.

A primary object of the present invention is to provide an improved process for partially acetylating vegetable textile fibers by activating the fibers with acetic acid and partially acetylating the activated fibers by a per chloric acid-catalyzed reaction with an acetylating mixture of acetic anhydride and acetic acid; in which improved process, the unreacted acetic acid and acetic anhydride contained in spent acetylating liquids are utilized by chemically converting spent acetylating liquids to compositions suitable for reconstituting and replenishing the activating liquid.

We have now discovered several rather unobvious facts about the partial acetylation process. The fibers can be activated in an acetic acid-acetic anhydride activating liquid that contains up to about 0.05% by weight of perchloric acid. The fibers which are soaked in such a perchloric acid-containing activating liquid entrain and ice remove some of the perchloric acid. Such perchloric acid-containing activating liquids can be repeatedly replenished by the addition of mixtures of acetic acid and acetic anhydride containing up to about 0.015% perchloric acid, without causing an undesirable increase in the perchloric acid concentration of the activating liquid. And, a spent acetylating liquid can readily be converted to a mixture of acetic acid and acetic anhydride suitable for replenishing the activating liquid by mixing the spent acetylating liquid with potassium acetate and isolating the resulting precipitate of potassium perchlorate.

In general, in accordance with the present invention, the process of partially acetylating vegetable textile fibers to a degree of substitution of from about 0.5 to 2, by presoaking the fibers with an activating liquid consisting essentially of acetic acid containing enough acetic anhydride to convert to acetic acid the regain moisture present in the fibers and partially acetylating the activated fibers by reacting them with an acetylating liquid con sisting essentially of an acetylating mixture of acetic anhydride and acetic acid containing a catalytic amount of perchloric acid, is improved by: mixing an acetylating liquid, which was recovered from the partial acetylation of a preceding portion of fibers and which is unsuited for reconstitution and re-use as an acetylating liquid, with enough potassium acetate to neutralize from about to 100% of the amount of perchloric acid contained in the acetylating liquid; mechanically removing the resulting precipitate of potassium perchlorate; and using the remaining liquid, along with enough of at least one liquid of the group consisting of acetic acid and acetic anhydride to reduce the proportion of perchloric acid in the liquids used to not more than 0.015% by weight, to reconstitute and replenish the activating liquid.

The potassium acetate which is mixed with the spent acetylating liquid is preferably employed in the form of a solution of potassium acetate in acetic acid or water. The liquid that remains after the spent acetylating liquid has been freed of potassium perchlorate can either be mixed with enough acetic acid or acetic anhydride to produce a solution in which the proportion of perchloric acid is less than about 0.015% prior to using it to replenish the activating liquid, or can be mixed with the activating liquid before, during, or after such an amount of acetic acid or acetic anhydride is mixed with the activating liquid. Where these liquids are separately mixed, both the acetylating liquid from which most of the perchloric acid has been removed and the acetic acid or acetic anhydride should be mixed with the activating liquid before the activating liquid is used to activate fibers.

In the accompanying drawing, Fig. l and Fig. 2 are flow sheets illustrating a batchwise and continuous process, respectively, of partially acetylating cotton cloth and cotton yarn, respectively.

The following examples are illustrative of the details of at least one method of practicing the invention.

Example 1 A batch of purified cotton cloth amounting to 100 parts of cotton and 6 parts of regain moisture was sub jected to the batchwise process of partially acetylating vegetable textile fibers shown in Figure 1, using an acetylating liquid which had been used to acetylate previous batches of fibers. The partially acetylated cloth was freed of excess liquid by means of squeeze rolls.

The recovered liquid was a spent acetylating liquid consisting of 161 parts acetic acid, 13.2 parts acetic anhydride and 0.3 part perchloric acid. An amount of potassium acetate, 0.279 part, equivalent to about of the perchloric acid contained in the acetylating liquid, was dissolved in 2 parts of acetic acid and mixed with, the spent acetylating liquid.

The mixed liquids were allowed to stand overnight, to insure the settling of the resulting precipitated potassium perchlorate, and the supernatant liquid was mechanically isolated by decantation. The potassium perchlorate-free liquid consisted of about 7.6% acetic anhydride, 92.3 acetic acid and 0.01% perchloric acid.

The potassium perchlorate-free liquid was added to the activating liquid storage tank along with an additional 20.8 parts of acetic anhydride. The so-supplemented activating liquid was used as the activating liquid in the partial acetylatic-n of another 100 part batch of the same cloth by the same procedure. Its use resulted in a normal reaction that produced a normal partially acetylated cloth.

it will be noted on the flow sheet that the potassium perchlorate-free liquid contained the required amount of acetic acid, 160 parts, plus approximately /3 of the required amount of acetic anhydride, 13.2 parts, needed for replenishing the presoal; bath.

A comparison of the cost of this process of utilizing the unconverted reactants present in the excess reactant liquid, with the cost of the fractional distillation and purification steps heretofore practiced, indicated that the overall cost of the batch process for the partial acetyla tion of cotton fabric was materially reduced by use of this improved reclamation process.

Example 2 A lot of 8/5, purified cotton yarn amounting to 121.9 parts of cotton and 9.1 parts of regain moisture was subjected to the continuous process of partially acetylating vegetable textile fibers as shown in Figure 2. The partially acetylated yarn was freed of excess liquid by means of squeeze rolls.

The recovered liquid was a spent acetylating liquid amounting to 306.3 parts and consisting of 182.8 parts acetic acid, 121.9 parts acetic anhydride and 1.6 parts of perchloric acid. An amount of potassium acetate, 1.6 parts, equivalent to all but 0.007% of the perchloric acid concentration, was dissolved in 7.6 parts of water and mixed with the spent acetylating liquid.

The mixed liquids were allowed to stand overnight, to insure the settling of the resulting precipitated potassium perchlorate, and the supernatant liquid was mechanically isolated by decantation. The potassium perchlorate-free liquid consisted of about 26.1% acetic anhydride, 73.89% acetic acid and 007% perchloric acid.

The potassium perchlorate-free liquid was pumped to the activation feed tank and used as feed solution for the activation bath in the continuous partial acetylation of another 121.9 part lot of the same yarn by the same procedure. Its use resulted in a normal reaction that produced a normal partially acetylated yarn.

A comparison of the cost of this process with the cost of the fractional distillation and purification steps heretofore practiced, indicated that the overall cost of the continuous process for the partial acetylation of cotton yarn was materially reduced by use of this improved reclamation process.

We claim:

1. In a process of partially acetylating cellulosic textile fibers to a degree of substitution of from about 0.5 to 2 by, presoaking the fibers in an activating liquid consisting essentially of acetic acid containing an amount of acetic anhydride sutficient to convert to acetic acid the regain moisture present in the textiie material, then acetyiating the activated fibers by reacting them with an acetylating mixture of acetic anhydride and acetic acid containing a cataiytic ant-cunt of perchloric acid, the steps comprising mixing an acetylating liquid, which was recovered from the partial acctylaticn of a preceding portion of fibers and which is unsuited for reconstitution re-use as an acetylating liquid, with enough potassium acetate to nontralizze from about to of the perchloric acid contained in the acctylating liquid, mechanically removing the resulting precip e of potassium perchlorate mixing the remaining liquid with enough of at least one liquid of the group consisting of acetic acid and acetic anhydride to form a liquid composition in which the proportion of perchloric acid is not more than about 0.015% by weight, and mixing said liquid composition with said activating liquid to produce a reconstituted and replenished activat ing liquid containing up to about 0.05% by weight oi perchloric acid.

2. A process comprising mixing a spent acetylating liquid unsuited for reconstitution and reuse as an acetylating liquid for cellulosic textile fibers and consisting essentially of acetic acid, acetic anhydride, and an amount of perchloric acid exceeding about 0.05% by weight of said liquid with enough potassium acetate to neutralize from about 85% to 100% of the perchloric acid, removing the resulting precipitate of potassium perchlorate, mixing the resulting liquid with a sufiicient amount of at least one liquid of the group consisting of acetic acid and acetic anhydride to reduce the proportion of perchloric acid in the resulting mixture to a value not exceeding 0.0l5% by Weight, thereby producing a liquid composition suitable for reconstituting and replenishing the activating liquid used to activate cellulosic textile fibers prior to their partial acetylation to a degree of substitution of from about 0.5 to 2, and mixing said liquid composition with said activating liquid, to produce a reconstituted and replenished activating liquid containing up to about 0.05% by weight of: perchloric acid which is suitable for activating cellulosic textile fibers prior to their partial acetylation to a degree of substitution of from about 0.5 to 2.

Buras et al.: Practical Partial Acetylation of Cotton, American Dyestutf Reporter, March 29, 1954, pages 203 208 (page 206, last paragraph relied on).

Claims

1.IN A PROCESS OF PARTIALLY ACETYLATING CELULOSIC TEXTILE FIBERS TO A DEGREE OF SUBSTITUTION OF FROM ABOUT 0.5 TO 2 BY PRESOAKING THE FIBERS IN AN ACTIVATING LIQUID CONSISTING ESSENTIALLY OF ACETIC ACID CONTAINING AN AMOUNT OF ACETIC ANHYDRIDE SUFFCIENT TO CONVERT TO ACETIC ACID THE REGAIN MOISTURE PRESENT IN THE TEXTILE MATERIAL, THEN ACETYLATING THE ACTIVATED FIBERS BY REACTING THEM WITH AN ACETYLATING MIXTURE OF ACETIC ANHYDRIDE AND ACETIC ACID CONTAINING A CATALYTIC AMOUNT OF PERCHLORIC ACID,THE STEPS COMPRISING MIXING AN ACETYLATING LIQUID, WHICH WAS RECOVERED FROM THE PARTIAL ACETYLATION OF A PRECEDING PORTION OF FIBERS AND WHICH IS UNSUITED FOR RECONSTITION AND RE-USE AS AN ACETYLATING LIQUID,WITH ENOUGH POTASSIUM ACETATE TO NEUTRALIZED FROM ABOUT 85 T 100% OF THE PERCHLORIC ACID CONTAINED IN THE ACETYLATING LIQUID, MECHANICALLY REMOVING THE RESULTING PRECIPITATE OF POTASSIUM PERCHLORATE MIXING THE REMAINING LIQUID WITH ENOUGH OFAT LEAST ONE LIQUID OF THE GROUP CONSISTING OF ACETIC ACID AND ACETIC ANHYDRIDE TO TO FROM A LIQUID COMPOSITION IN WHICH THE PROPORTION OF PER CHLORIC ACID IS NOT MORE THAN ABOUT0.015% BY WEIGHT AND MIXING SAID LIQUID COMPOSITION WITH SAID ACTIVATING LIQUID TO PRODUCE A RECONSTITUTED AND REPLENISHED ACTIVATING LIQUID CONTAINING UP TO ABOUT 0.05% BY WEIGHT OF PERCHLORIC ACID.