US 3432252 A
Description (OCR text may contain errors)
United States Patent Office 3,432,252 METHOD FOR PRODUCING RESILIENT COTTON FABRICS THROUGH PARTIAL ESTERIFICATION John B. McKelvey, Ruth R. Benerito, and Ralph J. Berni, New Orleans, La., assignors to the United States of America as represented by the Secretary of Agriculture N Drawing. Filed Nov. 23, 1965, Ser. No. 509,419 US. Cl. 8-120 8 Claims Int. Cl. D06m 13/00, 1/00; C07d 51/18 A non-exclusive, irrevocable, royalty-free license in the invention herein described, for all Government 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 partial cellulose esters. More particularly, the invention relates to the production of monobasic saturated and unsaturated fatty acid esters of cellulose.
The primary object of the present invention is to provide an improved process for the partial esterification of hydroxyl group-containing cellulosic textile fibers using long-chain alkanoic acid halides without altering the desirable physical properties of the textile fibers and simultaneously imparting the important properties of resiliency (crease resistance) and increased elongation. Another object is to provide alkanoic and alkenoic esters of cellulose in fabric form by utilizing monobasic acid chlorides which cannot crosslink the cotton fiber and, consequently, will not alter some of the more desirable physical properties of these cellulosic materials. A further object of this invention is to produce partial cellulose esters having a degree of substitution (D.S.) of 0.05 to 0.2, having improved resiliency and still maintaining their resistance to abrasion.
Methods for the application of fatty acid chlorides to cellulosic material to obtain water repellent surfaces are known in the prior art. In most of these prior art processes, cotton cloth is first treated with sodium hydroxide and then introduced into carbon tetrachloride or other inert solvents containing an acid chloride. The product obtained is a fabric with a soft woolly texture, fatty feel and water repellent coating but either shows little or no change in, or loses some of its recovery properties. Other prior art processes include use of both DMF (dimethylformamide) and pyridine for producing esters of cellulose of DS 1, which are products having properties very different from untreated cotton fabric. Other prior art processes utilizing dimethylformamide and pyridine include treatment of fabric to obtain oil and water repellency using perfluoroalkanoyl chlorides. All of those prior art processes produced textile fabrics which failed in the commercially important property of retain ing their textile characteristics; of improved crease resistance or resiliency, abrasion resistance, and improved elongation.
We have now discovered an improved esterification process for the production of partial alkanoic and alkenoic esters .of cellulosic materials having degrees of substitution (D.S.) ranging from about 0.05 to 0.2 whereby the treated cellulosic material is not only rendered crease resistant in the conditioned (dry) and wet states but has the added advantage of improved elongation-atbreak. The novel esterification process of the present invention does not alter significantly the strength, color, appearance, hand, or fibrous form of the cellulosic material. This was unexpected.
In general, in accordance with the present invention, a hydroxyl group-containing cellulosic material is esterified by reacting with the halide of the esterifying agent of an alkanoic or alkenoic monobasic acid wherein the alkanoyl or alkenoyl radical contains from 8 to 22 car- 3,432,252 Patented Mar. 11, 1969 bon atoms. The esterification process of this invention is accomplished by a reaction between the hydroxyl groups of the cellulosic material and one or more of the alkanoyl or alkenoyl esterifying agents, in the presence of dimethylformamide solvent and a quantity of tertiary aromatic amine sufiicient to neutralize the generated acid reaction products to their respective amine salts. The process of the present invention is characterized by a critical sequence of addition of the reactants, and of washing the esterified cellulosic material, which sequences are described below.
Substantially any cellulosic material containing hydroxyl groups can suitably be employed in the present processes. Illustrative examples of such materials include cellulose derived from cotton, flax, ramie, wood, and the like; regenerated cellulose, such as viscose rayon and the like; partial ethers of cellulose such as partially acetylated cellulose, beta-propiolactone-reacted cellulose, and the like; and partial ethers of cellulose such as carboxymethyl cellulose and other partially etherified cellulosic materials. In general, the cellulosic textile materials in the form of free fibers, slivers, yarns, threads or fabrics, including the fibrous material and partial ethers or partial esters thereof which are produced by reactions in which the fibers retain their cellulosic textile properties, are preferred starting materials. The cellulosic textile fibers in the form of spun textiles, i.e., yarns, threads, or fabrics, are particularly suitable starting materials.
An alkanoyl or alkenoyl halide of substantially any alkanoic or alkenoic monobasic acid wherein the alkanoyl radical contains from about 8 to 22 carbon atoms can be employed as the esterifying agent in the present process. Acids whose esterifying agents can be employed include caprylic, nonanoic, capric, undecanoic, lauric, myristic, palmitic, stearic, oleic, linoleic, ricinoleic, petroselenic, erucic acids, and other like acids. Although alkanoyl or alkenoyl halides such as the chlorides, bromides and iodides may be prepared from the commercially available monobasic acids, we prefer to use the chlorides such as 12-hydroxystearoyl chloride. These chlorides may be prepared by the conventional method based on the use of thionyl chloride. After completion of the reaction the excess thionyl chloride is stripped off and the acid chlorides recovered by distillation at reduced pressures.
In this invention, the solvent plays an important role. It is a critical feature of our novel process that only aprotic solvents of high dielectric constant, such as dimethylformamide and dimethylsulfoxide, are capable of disrupting the active hydrogen bonded network in cellulose and result in the partial esterification of cellulose with long-chain fatty acid moieties at the desired sites. In order to attain conditioned (dry) and wet crease resistant (resilient) cellulosic materials, the sites of esterification must be at particular C hydroxyl sites of cellulose which were originally hydrogen bonded through water. Use of solvents with a low dielectric constant, or solvents not capable of disrupting the original hydrogen bonded network of cellulose, or protic solvents does not result in cellulosic materials possessing the properties described in this invention.
In reacting the cellulosic material with the esterifying agent of the alkanoic or alkenoic acid, substantially any apparatus usually employed such as a Pyrex cylinder in the esterification of cellulose may be used in carrying out our novel esterification process. The cellulosic material to be reacted is first thoroughly dried in an oven or appropriate drying apparatus before immersion into the reaction solution. The acid chloride and dimethylformamide (DMF) are mixed in the reaction vessel and are brought to the desired reaction temperature. It is usually preferred to employ from about 5 to 40 moles of dimethylformamide (or dimethyl sulfoxide) for each mole of anhydroglucose unit of cellulose to insure complete immersion and wetting of the fabric samples. The quantity of acid chloride added is not critical but it is preferred to use at least an equimolar ratio of acid chloride to anhydroglucose units. After the reaction mixture is brought to the desired temperature, which may range from about 25 to 105 C., preferably 60 to 105 C., an equimolar quantity of pyridine with respect to the acid chloride is entered into the reaction vessel. It is another critical feature of our invention that the pyridine is heated in a separate container to the reaction temperature prior to addition to the DMF-acid chloride solution. The amount of pyridine is not critical. However, since it is to be used as an acid scavenger, the amount used will depend upon the temperatures employed. At low temperatures, 25 C., less than equimolar quantities can be employed but at temperatures near 105 C. greater than equimolar quantities with respect to acid chloride employed are necessary to prevent physical damage to the cellulosic material. A preferred range of pyridine quantities would be from 0.16 to 4 moles of pyridine for every mole of acid chloride employed. After addition of the pyridine the dried fabric is entered into the reaction mixture, for. the required reaction time or period of dwell. The aforementioned sequence of addition of reactants is of utmost importance and must be followed in the esterification process of the present invention. It is unsatisfactory, for example, to dissolve the esterifying agent in DMF and pyridine and bring the reaction mixture to the desired temperature, because the pyridine-acid chloride complex formed will seriously affect the efficiency of the esterification of the cellulose. Most important, it will prevent the attainment of crease recovery.
The extent of reaction, and thus degree of substitution (i.e., the number of the three reactive hydroxyls per an hydroglucose unit which have been substituted, by replacing a hydrogen atom with an acyl radical, as indicated by the proportion of acyl groups per unit weight of the cellulosic material) can be varied widely.
The degree of substitution can be varied primarily by (a) varying the proportion of esterifying agent in contact with the cellulosic material during the esterification reaction and (b) varying time and temperature of the esterification reaction. In general it is preferable to conduct the esterification reaction at above the crystallization point of the solution used for the esterification and below the boiling point of the solution. Reaction temperatures from about room temperature 25 C. to about 105 C. are preferred. Under the preferred esterification conditions, resilient (crease resistant in conditioned (dry) and Wet states) cellulosic materials can be produced using reaction times as low as 5 minutes at 105 C. or in 8 hours at room temperature. As above, this resiliency can be realized at extremely low degrees of substitution of the cellulose. It is generally preferred to esterify the cellulose to a D5. between 0.05 and 0.20 to impart the aforementioned desirable properties.
Following completion of the esterification reaction, it is very important that the treated cellulosic material be washed free of reactant solution before washing the cellulosic material in water. In the preferred washing procedure, the treated material is separated from the reaction mixture and soaked three times in fresh pyridine in order to remove any pyridinium salts which may adhere to the fabric. Then the treated material is steeped three times in boiling methanol and finally quenched thoroughly in cold running water for at least 30 minutes. After washing, the fabrics are ironed dry or oven dried and then equilibrated at least 16 hours before weighing. If the material is first washed in hot water, the color-forming pyridinium salts will react with the cellulose and cause the final product to have not only a discolored appearance but also a foul odor.
The folowing examples are illustrative of certain details of the invention.
Methods of Testing Conditioned Crease Recovery using Monsanto Tester according to US. Federal Specification CCC-T-191b- Method 5212-U.S. Federal Supply Service.
Wet Crease Recovery-Lawrence ModificationLawrence, E. W. and Phillips, R. N., Am. Dyestuff Reptr. 45, 548-550 (1956).
Elongation-at-Break and Breaking Strength-A.S.T.M. Methods D3959.
Saponification ValuesEberstadt Titration as described by Genung, L. B. and Mallatt, R. C., Ind. Eng. Chem. Anal. Ed. 13, 369-374 (1941).
Example 1 (Preferred method of treatment) A 10 g. portion containing 0.06 mole of anhydroglucose units of x 80 cotton fabric (desized, scoured and bleached) was placed in an oven at C. for 45 minutes. Oleoyl chloride (0.06 mole) was dissolved in 2.1 moles ml.) of dimethylformamide and heated in a graduated cylinder at 105 C. for 45 minutes. Simultaneously, 0.25 mole pyridine was heated in a separate container at the same time. The pyridine was then added to DMF-acid chloride mixture and followed by the dried, rolled fabric which was immersed below the surface of the reaction mixture. The reaction proceeded for 30 minutes (a period of dwell) after which the fabric was removed from the reaction medium and soaked three times in pyridine and then steeped three times in boiling methanol. The fabric was then quenched for 45 minutes in cold running water before being ironed dry (at 150 C.). The resultant fabric consisted of alkenoyl (oleoyl) esters of cellulose having a D5. of 0.15 (as indicated by a weight gain of 27%) and a saponification value of 1.588 milliequivalents (meq.) of acyl groups per gram of sample.
The treated fabric had physical properties like those of the original fabric-that is, its tear strength, color, appearance, hand, and fibrous form were not physically altered by the treatment. It had a Monsanto Crease Recovery Angle (CRA) of 277 (warp-i-fill) when conditioned, and 240 (W+F) wet. (Control untreated cotton values are (W+F) conditioned and 150 (W+F) Wet.) The fabric had an elongation of 12.1% as compared to 7.9% for the untreated control. The fabric had excellent durability with respect to resiliency (crease recovery) since after ten home launderings it still possessed a Monsanto Wash Wear rating of 4.
Example 2 Another portion of the same cotton fabric used in Example 1 was treated according to the procedure of Example 1 except that reaction time was reduced to 5 minutes at 105 C. The resultant fabric had a D5. of .05 (weight gain8.7%) and a conditioned recovery angle of 225 (W+F) and a wet recovery angle of 187 (W+F).
Example 3 The following data are illustrated of the ranges of D.S., crease recoveries, and elongation that can be obtained.
Other portions of the same cotton fabric were treated according to the procedure in Example 1 except the reaction times were varied and products were obtained as lllustrated 1n the followmg table.
Crease Recovery Elongation Reaction Time D.S at break (minutes) Conditioned Wet (percent) Example 4 The following is illustrative of the other acyl chlorides which can be used to obtain improved crease recovery and elongation properties.
(e) adding the amine to the solvent solution of the acyl halide to form a reaction solution;
(f) immersing the dried cellulosic material into the reaction solution;
(g) maintaining a period of dwell at a temperature Other portions of the same cotton fabric were treated 5 f to f hrs. to 5 minutes; aflcorfilng to the p f P 1eXcl tthatTeac (h) removing tertiary aromatic amine salts from the tion tunes and the acid chlorlde used were varled, and the treated f b i b ki h f b i t l a t three results obtained are shown in the following table: times in fresh pyridine;
R ti T 11 E eac on e Acid Chloride time ecovery iii-k (min.) Cond. Wet (percent) Caprylic 180 00 0.10 200 212 9.5 Nonarioic 180 60 0. 13 213 202 9. 0 aprlc 180 60 0.09 223 206 9. 1 Undeceno 105 0. 17 239 220 13. 0 auric-.- 180 00 0.15 223 213 8.1 45 105 0.09 222 204 8.9 180 60 0.12 234 209 8.1 120 00 0.12 249 221 9.0 15 105 0.13 243 191 12.5 00 105 0.14 257 239 10.9 00 105 0.19 307 295 9.7 90 105 0.16 284 293 10.5 60 105 0.19 251 238 15.7 12-hydroxystearic. 60 105 0. 19 274 263 13. 3 Phenyl undecanoic 12 105 0.13 243 221 9.2 Acetylated Rieinoleic 60 105 0.08 270 247 10.5 oz-Bromostearic 50 105 0. 09 237 209 10. 0 Petroselenic... 50 60 0. 09 241 206 8. 2 Control (80x80) 195 150 7.9
Example 5 3 (i) removing the solution of reactants by steeping the The following example is illustrative of partial esterifi- 0 fabr1c three tlmes' 111 sh lllng methanol; cation carried out according to Example 1 0f USP. (I) th roughly Washing the treated fabric in cold runl,897,026 to illustrate that the products formed do not mng Water for 30 mmutes; possess improved conditioned and wet recovery. (k) f and equlhbratmg the treated Cenuloslc Sixteen parts by weight of the same cotton fabric used materlaliapd in Example 1 are first immersed in a 20 percent aqueous (l) determlnlng the degree of substltution of the dried caustic soda solution, thereupon pressed free of excess and equlhbrated f caustic solution, and are then introduced into carbon tetramethod as F F clam 1 Wperem the chloride in which there has previously been dissolved 28 aProtlc Solvent of dlelectrlc constant 18 ,Selected parts by weight of acid chloride mixture obtained by 40 frfml the 2 2 conslstmg of dlmethylformamlde and treatment of commercial stcarin (80% stearic acid-20% dl'methylsulfoxlde and ranges f about 5 to 40 moles palmitic acid with thionyl chloride and which, therefore, to one m anhydroglucose of cellulose consists principally of the chlorides of palmitic and stearic method as flescrlbed Glam 2 Y f the acids. The cotton fabric remains for one hour in the CC1 aprotlc solvent of hlgh dlelectnc constant dlmethyl' solution, which was expediently heated to 35-55 C. formamlde- The fabric that had been treated in this manner pos- A met11d as desqlbed 1n clalm Whetem the y sesses, with undiminished strength, a fatty feel, has a soft hallde 1S Pf P from a Selected from h woolly texture and is diflicult to moisten with water. How- P P alkanolc and alkenolc monobaslc ever, the conditioned and wet recovery obtained was 138 aclds and 1S Pf m at least one mole P mole anhy" and 166 (W-l-F) respectively. Control values are 195 drogluwse mm of cellulPsepr/+1? conditioned and 150 (W+F) wet 5. A method as described 1n claim 1 wherein the halide It will be observed that when the fabric is treated with is a chloride NaOH prior to reacting with the chlorides of palmitic 6 A method as described 1n 01am 1 wherein the and stearic acid, the treated fabric loses its elasticity and ternary aromatlc amlne 1S py 111 an its wet and dry crease recovery. Most important it loses ing from ab011tO-16 1110195 to P mole aftld ha11dethe physical properties of the original fabric, i.e., tear A methPd as descnbed m clalm 1 Wherem the strength, h l d appearance gree of substitution (D.S.) of the cellulose ranges from We claim: 0.05 to 0.2.
1. A method for increasing the resiliency and elonga- T Product P p y the PmceSs as descrlbed tion of cellulosic textile materials by partial esterifica- In clal'm tion without crosslinking the anhydroglucose molecules comprising the following steps in sequence: References Cited Y drymg h cellulosls f McKelvey et al.: Textile Research Journal vol. 34, pp.
(b) charglng to a reaction vessel an aprotlc solvent 11024104 1 4) of hlgh fhelectflc constant and an acyl hahde sald McKelvey et al.: Textile Research Journal, vol. 35, acyl halide being prepared from at least one i'nem- 365476 5 her of the group consisting of alkanoic and al-kenoic monobasic acids and contaln ng from about 8 to 22 NORMAN G. TORCHIN, Primary carbon atoms 1n the acyl chain, (c) bringing the solvent and the acyl halide to reac- CANNON Asslstam Exammertion temperature, (d) in a separate container bringing a tertiary aromatic amine to reaction temperature,
US. Cl. X.R.