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Publication numberUS3649341 A
Publication typeGrant
Publication dateMar 14, 1972
Filing dateNov 14, 1968
Priority dateNov 17, 1967
Also published asDE1808937A1
Publication numberUS 3649341 A, US 3649341A, US-A-3649341, US3649341 A, US3649341A
InventorsTammela Viljo, Turunen Olli
Original AssigneeNeste Oy
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method for manufacturing partially acylated regenerated cellulose foil or fiber
US 3649341 A
Abstract
Partly acetylated regenerated cellulose films or fibers are manufactured by first swelling them in a concentrated and water-free acetic acid solution of an alkali metal acetate at a temperature ranging between 50 DEG and 140 DEG C. Immediately thereafter and without drying the swelled films or fibers are esterified by an acetic acid anhydride solution containing alkali metal acetate at a temperature ranging between 100 DEG and 170 DEG C.
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Description  (OCR text may contain errors)

ited States atem Tammela et a1.

[ Mar. 14, 1972 [54] METHOD FOR MANUFACTURING PARTIALLY ACYLATED REGENERATED CELLULOSE FOIL OR FIBER Inventors: Viljo Tammela, Helsinki; Olli Turunen,

Porvoo; both of Finland Assignee: Neste 0y, Helsinki, Finland Filed: Nov. 14, 1968 Appl. No: 775,952

Foreign Application Priority Data Nov. 17. 1967 Finland ..3106/67 U.S.Cl ..1l7/1l8,8/121,1l7/60, 1 17/ 144 Int. (1. ..B44d 51/2, D06m 13/20 Field of Search ..8/120, 121; 117/60, 144.5, 117/ 144, l 18 References Cited UNITED STATES PATENTS 4/1936 McKee et a1. ..8/121 UX 2,772,944 12/1956 Allewelt ..8/121 2,780,511 2/1957 Takagi 1.8/1 2 1 3,215,490 11/1965 Fraizy et al. ..8/121 FOREIGN PATENTS OR APPLICATIONS 353,978 8/1931 Great Britain ....8/l2l 448,063 6/1936 Great Britain ....8/l2l 750,702 6/1956 Great Britain..... ....8/l21 930,208 7/1963 Great Britain ..8/121 Primary Examiner-William D. Martin Assistant Examiner-M. R. Lusignan Attorney-Richards & Geier 1 1 ABSTRACT Partly acetylated regenerated cellulose films 0r fibers are manufactured by first swelling them in a concentrated and water-free acetic acid solution of an alkali metal acetate at a temperature ranging between 50 and 140 Immediately thereafter and without drying the swelled films or fibers are esterified by an acetic acid anhydride solution containing alkali metal acetate at a temperature ranging between 100 and 1 70 C.

1 Claims, No Drawings METHOD FOR MANUFACTURING PARTIALLY ACYLATED REGENERATED CELLULOSE FOIL OR FIBER The present invention concerns a method for manufacturing partially acylated cellulose foil or fiber in which the foil or fiber which is to be esterified is at first swollen at elevated temperature and subsequently esterified, whereupon the product is washed and dried.

Since regenerated cellulose presents drawbacks as low wet strength and brown discoloration at high temperatures, methods have been developed in which the properties of regenerated cellulose foil or fiber are improved by means of partial acylation. By such methods the objectionable characteristics of regenerated cellulose foil or fiber can indeed be eliminated because partially acylated regenerated cellulose foil or fiber has good heat resistance and high wet strength. In the acylating methods of previous art initial treatment of the regenerated cellulose foil or fiber has been accomplished by first swelling the foil or fiber in aqueous solutions of salts, after which step it has been necessary to dry the swollen foil or fiber prior to esterification and only after this has the acylating process been performed with acid anhydrides. If acid esterification catalysts have been used as components in the acid anhydride solution, it has furthermore been necessary prior to esterification to remove by washing the salts absorbed by the foil and fibers during the swelling process. As a consequence of the circumstances mentioned, the acylating methods employed up to date have in fact been slow and complicated. In addition, partial depolymerization and discoloration of the cellulose may occur.

The object of the present invention is to afford a method for acylating regenerated cellulose foil or fiber which is superior to previous methods in speed and simplicity. The invention is accordingly mainly characterized in that swelling of the foil or fiber is accomplished in a substantially water-free aliphatic carboxylic acid solution containing salt of an alkali metal and an aliphatic carboxylic acid and that the product thus obtained is immediately esterified in a manner previously known in itself in a solution of the anhydride of a low-molecular carboxylic acid which contains salt of an alkali metal and an aliphatic carboxylic acid. Since it is not necessary in a method according to the invention to dry the swollen foil or fiber because the foil or fiber is swollen in a substantially water-free swelling solution, nor to wash it because esterification may be accomplished immediately after swelling without causing any damage to the foil or fiber, it follows that a method according to the invention surpasses any previous methods in the speed and simplicity with which it can be carried out.

it has been found that alkali metal salts of low-molecular aliphatic carboxylic acids, solved in aliphatic carboxylic acids, are most effective for use as cellulose-swelling agents in the method for manufacturing partially acylated regenerated cellulose concerned here. Alkali metal acetates solved in acetic acid have been found to be the most efficient ones among them.

The composition of the acid anhydride solutions used in the method may vary considerably. It is possible to use for acylating agent merely the anhydride of some low-molecular carboxylic acid or a mixture of these. With increasing molecular size of the anhydrides increasingly soft products are obtained, e.g., compared to the use of acetic acid anhydride alone.

For use as reaction accelerators in the esterifying solution the same salts are most effective as are used for bloating agents in the pretreatment.

It is possible to use as raw material e.g., unsoftened regenerated cellulose foil or fiber,

Pretreatment is accomplished by immersing the regenerated cellulose foil or fiber into a swelling bath at elevated temperature, e.g., at 50-l40 C.

The pretreated product thus obtained is immediately immersed, without intervening drying, into the esterifying solution at elevated temperature, e.g., at lO-l 70 C.

After completed esterification the acylated foil is washed with acetic acid and with water. Fiber may also be washed with water alone, whereby the luster characteristic of the fibers can be dulled.

The foils or fibers may be bleached upon completed washing if necessary,

If a more flexible product is desired, the partially acylated product may also be immersed into a solution containing a softener prior to drying.

Drying is accomplished by the usual method employed for regenerated cellulose.

By a method according to the invention partially acylated regenerated cellulose foil or fiber with good heat resistance and possessing wet strength is obtained.

The dry tensile strengths of the foils were determined according to the ASTM D 1708-59 method. The determination of wet tensile strength differed from the said method in that the test specimens were kept immersed in water at room temperature for 20 hours prior to the tensile test. The average dry and wet strengths of the original regenerated cellulose foils were 1,300 and 200 kp/cm. The determinations of heat resistance were carried out according to the ASTM D 1637-61 method, stating as the heat resistance of the foil the temperature at which the elongation of the specimen was 2 percent of its original length. The heat resistance of the regenerated cellulose foil, according to the ASTM D 1637-61 method, was 200 C.

The brown discoloration of the foils was studied by keeping the samples for 1 hour at 210 C. and, subsequently, determin ing their transparency with a spectrophotometer according to the ASTM D 1746-62 method. The transparencies were stated in percent at the wavelengths of 400 and 550 mu. Prior to the heat treatment, the transparencies of the original as well as the partially regenerated cellulose foil amounted to 84-85 percent at 400 mu and to 87-88 percent at 550 mu. The transparency of the original regenerated cellulose foil after heating for 1 hour at 200 C. was 67-70 percent at 550 my. and 40-42 percent at 400 mu.

The method according to the invention is illustrated by a few examples in the following.

EXAMPLE 1 Acetic anhydride Potassium acetate 98 parts by weight 2 parts by weight Acetylation was followed by washing for 30 seconds in acetic acid at room temperature, whereupon the foil was furthermore washed with water, and dried. The clear foil which was obtained had the following properties:

Thickness 37 ,4 Acetyl content 2471 Heat resistance 200 C.

Transparency after the discoloration test, at 400 my 74-75 percent, at 550 mp. 84-85 percent Wet tensile strength Dry tensile strength EXAMPLE 2 The test was performed as in Example 1, but the esterifying solution had a different composition, which was:

Acetic anhydride Potassium acetate Acetic acid 92 parts by weight 5 parts by weight 3 parts by weight The end product had the following properties:

Thickness 37 Acetyl content 23% Heat resistance 200 C.

Transparency after the discoloration test, at 400 mp. 73-74 percent, at 550 mp 84-85 percent Wet tensile strength Dry tensile strength EXAMPLE 3 The procedure applied in the test differed from that in Example only in respect of the esterifying solution, which was:

Acetic anhydride Potassium acetate Acetic acid 85 parts by weight 5 parts by weight l0 parts by weight The foil which was obtained had the following properties:

Thickness Acetyl content Heat resistance Transparency after the discoloration test, at 400 mp. 60-70 percent, at 550 mp 80-82 percent Wet tensile strength Dry tensile strength EXAMPLE 4 The test was performed as in Example 1, but a regenerated cellulose fiber bundle was used instead of regenerated cellulose foil. In addition, the acetylating solution had a composition differing from that mentioned above, and it was:

304 kp/cm. 956 ltplcm,

Acetic anhydride Potassium acetate Acetic acid EXAMPLES The test was performed in Example I, but the composition of the esterifying solution was different; it was:

Acetic anhydridc Potassium acetate 95 parts by weight 5 parts by weight After acetylation for 1 minute and after the subsequent washings, the foils had the following properties:

Thickness Acetyl content Hcitt tcststance Transparency after the discoloration test, at 400 mu 76-77 percent, at 550 mp. 83-86 percent Wet tensile strength Dry tensile strength EXAMPLE 6 The test was performed as in Example 1, but the composition of the esterifying solution was different from that mentioned above; it was:

Acetic anhydridc Butyric anhydride Potassium acetate Thickness 4.5;.

Acclyl content 28.4 Butyryl content 5.2% Heat resistance 200 C.

Transparency after the discoloration test, at 400 mp. 76 percent, at 550 mp 86 percent wet tensile strength Dry tensile strength The dry elongation was found to be 15 percent, whereas the dry elongation of merely acetylated foils is in the order of 10-12 percent; the addition of butyryl content thus exerts a plasticizing effect on the foils.

EXAMPLE 7 The test was performed as in Example l, but commercial regenerated cellulose foil (plasticizer content, about 10 percent) was used instead of isotropic foil. The esterifying solution had the following composition:

Acetic anhydride Potassium acetate After acetylation for 1 minute and subsequent washings. the foils had the following properties:

Thickness 28;; (Original. 30p.) Acetyl content 30% Heat resistance 2(l0"C. (Original, 200" C.)

Transparency after the discoloration test:

at 400 my. at 550 mp Wet tensile strength in the machine direction 435 kp/cm. (Original, 225 kp/cm?) Wet tensile strength across the machine direction 250 kp/cm. (Original. l40 kplcmf) Dry tensile strength in the machine direction Dry tensile strength across the machine direction tilS lip/cm. (Original, 500 lip/cm) Comparison of the acetyl contents of the foils obtained in Examples 2 and 3 reveals that the acetic acid present in the esterifying solution retards the reaction rate. This detriment can be avoided in a continuous process either by removing the acetic acid from the esterifying solution or by adding to it salt used to accelerate the reaction, whereby the acylating rate can be maintained virtually constant.

it is seen from the examples presented that in a method according to the invention the acetylating process takes less than 5 minutes, exclusive of potential bleaching, washing with water and drying.

The wet strength of the partially esterified (acetyl content, 30-35 percent) regenerated cellulose foil (400 kp/cm?) is markedly better than that of the merely regenerated cellulose foil (200 kp/cm?) and nearly equals that of cellulose acetate foils (450 kp/cm. The heat resistance of partially acetylated regenerated cellulose foil is 200 C. if the acetyl content is 33 percent. Such partially esterified cellulose foil is not soluble in a cellulose solvent such as Cadoxene solution nor in cellulose acetate solvents such as acetone, 2-methoxy ethanol acetic acid or chloroform.

We claim:

I. The method for manufacturing partly acetylated regenerated cellulose film or fibers, which comprises swelling the film or fibers in a substantially water-free acetic acid solution of an alkali metal acetate at a temperature of 50l40 C. and immediately thereafter esterifying them without drying by an acetic acid anhydride solution containing alkali metal acetate at a temperature of l-l70 C. and then washing and drying them.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US2036947 *Oct 6, 1930Apr 7, 1936Mckee Ralph HManufacture of cellulose acetate
US2772944 *Mar 27, 1953Dec 4, 1956American Viscose CorpProcess for the acetylation of regenerated cellulose fibers and product resulting therefrom
US2780511 *May 14, 1953Feb 5, 1957Toho Rayon KkMethiod of making cellulose acetate teixtile fibers by acetylization of relgenerated cellulose fibers
US3215490 *Sep 26, 1960Nov 2, 1965RhodiacetaProcess of acetylating a specific kind of regenerated cellulose and recovering ingredients from the used acetylating bath
GB353978A * Title not available
GB448063A * Title not available
GB750702A * Title not available
GB930208A * Title not available
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4592962 *May 11, 1984Jun 3, 1986Daiken Trade & Industry Co., Ltd.Impregnating with aqueous solution of an alkali metal acetate
US4804384 *Apr 8, 1987Feb 14, 1989The United States Of America As Represented By The Secretary Of AgricultureAcetylation of lignocellulosic materials
US5427852 *Jul 20, 1993Jun 27, 1995Rhone-Poulenc Rhodia AktiengesellschaftCellolose acetate filaments and/or cellulose acetate staple fiber; biodegradable; cigarettes
DE3417605A1 *May 11, 1984Nov 15, 1984Daiken Trade & IndustryVerfahren zur acetylierung von holzmaterial
Classifications
U.S. Classification427/308, 8/121, 427/399
International ClassificationD06M13/00, C08B3/00, C08B1/00, C08B1/02, D06M13/188, C08B3/06
Cooperative ClassificationC08B3/06, C08B1/02, D06M13/188
European ClassificationD06M13/188, C08B3/06, C08B1/02