US2864663A - Process for the production of vegetable protein fibers - Google Patents

Description

Dec. 16, 1958 T c. LIS 2, 63

PROCESS FOR THE PRODUCTION OF VEGETABLE PROTEIN FIBERS F iled Nov. 1, 1954 STRETCH POSTCURE DRY POSTCURE SOLUTION PRECURE FILTER SPIN 8:

COAGULATE IN VENTOL ZE'N M mmflm SOLUTION FILTER DEAREATE ATTORNEY PRUCESS FOR THE PRODUCTION OF VEGETABLE PROTEIN FIBERS Leon C. Lis, Narragansett, R. I., assignor to Virginia- Carolina Chemical orporation, Richmond, Va., a corporation of Virginia Appiication November 1, 1954, Serial No. 465,921

4 Claims. (Cl. 1854) This application is a continuation-in-part of my application Serial No. 228,116 filed May 24, 1951 and now abandoned.

This invention relates to the production of synthetic textile fiber fro-m corn proteins known as zein.

Objects of my invention are to provide a process which will produce fiber of high quality with respect to the properties generally considered in evaluating fiber such as uniformity, wet and dry tensile strengths and elongations, shrinkage, dyeing properties, retention of strength after dyeing, freedom from adhering fibers etc. and which presents no particular obstacle to its commercial operation such as high cost of materials, plant, labor etc.

A more particular object of my invention is to provide an improved process with respect to the cur-ing of the fiber by the action of formaldehyde.

The essence of the invention is believed to reside in the use of a high humidity atmosphere i. e. an atmosphere which is substantially saturated with water vapor in the curing treatment of the fiber.

The fiber may be formed by any known and suitable method, for instance, by extruding an alkaline solution of zein, which may contain formaldehyde as disclosed in U. S. Patent No. 2,478,248 e. g. a solution containing from about 16% to about 22% of zein and from 0.5 to of formaldehyde based on the weight of the zein in an aqueous solution of sodium hydroxide, said zein solution having a pH value of about 11 to 12.5, into a suitable coagulating bath, e. g. a bath containing from about 1% to about 3% of sulfuric acid, from about 2% to about 10% of formaldehyde, from about 1% to about 6% of ammonium sulfate and from about 0.1 to 0.5% of goulac, at a temperature of from about 80 F. to about 100 F. The coagulated fibers are collected together into the form of a tow as they are withdrawn from the coagulating bath and are precured by being permitted to remain wet with the adhering coagulating bath for a suitable length of time, c. g. from about /2 to about 3 hours. This may be done by passing the tow through a closed chamber the atmosphere of which is maintained at a high humidity and at a temperature of from about 80 F. to about 100 F. by the introduction of steam as required.

The tow of fibers then passes to the stretching operation. In the stretching operation the tow is passed back and forth between two conical or stepped rollers, progressing to larger and larger diameter whereby it is stretched the desired amount e. g. from 50% to 300% or more.

The two rollers dip into a body of liquid such as water maintained at from about 85 F. to about 140 F. so that as the tow passes back and forth over the rollers its temperature is raised to the desired stretching temperaturei The tow, as it leaves the stretching rollers is kept under tension and this tension is maintained while the tow is impregnated with postcure solution by passing back and forth around two cylindrical rollers dipping into the postcure solution. The postcure solution, at a temperature of from about 110 F. to about 140 F. preferably is a substantates Patent 2,864,663 Patented Dec. 16, 1958 squeezed to remove solution which otherwise would drain away thus leaving the tow wet with about its own dry weight of postcure solution. At this point the tension on the tow is relaxed and the relaxed tow is delivered to the postcure chamber. In the postcure chamber the tow is held at a temperature below 212 F. and preferably at about 1l0140 F. for a-corresponding period of time depending upon the degree of postcuring desired, i. e. the

type of fiber product to be produced. The period generally falls within the range from 30 minutes to 2 hours. This treatment may be carried out by plaiting the tow on a belt which moves slowly through a chamber in which the selected postcure temperature is maintained for example by the introduction of steam. The atmosphere in the postcure chamber is maintained at a relatively high humidity, e. g. at least relative humidity.

The process to this point is described in the accompanying flow-sheet.

The tow is then washed to varying degrees depending upon the qualities desired in the finished product and it may also be subjected to a baking treatment. In general the tow, following the postcure treatment, may be merely surface washed, i. e. washed for about 2 minutes with cold water to remove adhering postcure solution and then dried and baked or it may be subjected to ,a thorough washing treatment with warm water e. g. at about 80 F. for about 30 minutes to remove not only adhering'postcure solution but also to wash solution out of the fiber structure after which it is dried e. g. at about 150 F. for about 60 minutes and then baked or merely dried. The after treatment of the fiber, i. e. crimping, cutting into staple, the application of various finishing materials, etc. form no part of my present invention and therefore need not be considered.

The baking treatment is applied to the dried fiber tow and may be varied as to both time and temperature depending upon the specific properties desired but generally is carried out at a temperature of about 300 F. Depending upon the size of the tow it is necesary to adjust the baking time so that all portions of the fiber will be subjected to the selected baking temperature for at least about 15 minutes.

The fiber after baking and particularly if the washing after the postcure and before drying was limited to a mere surface washing preferably is given a final washing to remove any chemicals left in or on the fiber.

As has been indicated in the foregoing description the conditions employed in the several steps of the process.

are capable of considerable variation. For instance, the spin solution may vary as to both composition and temperature, the coagulating bath also may vary as to composition and temperature and the precure operation may be varied or even omitted, the object of these steps being primarily to deliver a coagulated fiber to the stretching and postcuring steps. Many specific methods'are known for accomplishing this result.

The feature of my process which contributes most to the control of the properties of the fiber product, to plant capacity and to the production of a tow with the fibers thereof well-alined is the so-called dry postcure step described above in which the tow carrying from about 70% to about of its weight of postcure solution is plaited onto a belt conveyor and transported through a chamber the atmosphere of which is maintained highly humid and at the desired temperature, for instance by the introduction of steam. It is possible, of course to vary the composition of the postcure solution and particularly the formaldehyde content thereof and it is possible also to vary the temperature in the postcure chamber but generally the desired variation in the qualities of the fiber may be obtained by simply varying the time that the tow is held in the postcure chamber.

The washing, drying andbaking steps which follow the postcure have beensufliciently described above.

Extensive research work has been done in connection with the production of protein fiber. Theories have been advanced to explain the purpose and effect of the different ingredients of the coagulating, precure and postcure solutions. My invention is not concerned with these matters butonly with the provision of a simple and efficient method or procedure for handling the fiber as it isbeing subjected to the known sequenceof coagulating, precuring, stretching, postcuring, washing, drying and baking steps; My invention'is more particularly concerned with thestretching, saturatingand postcuring steps and especially'with the so-called dry postcuring' stepin which the fiber-is cured by being held in or passed through a warm, or hot, humid atmosphere while at rest on a conveyor, where the curing is effected by the adhering and absorbed curing solution as distinguished from prior methods in which the postcuring generally has been effected by holding the tow for the required time in a postcuring bath maintained at the required temperature.

The invention is illustrated by the following specific examples.

EXAMPLE 1 An aqueous zein solution containing 20% by weight of zein and 2% by weight of sodium hydroxideand having a pH value of 12.5 was spun into an aqueous coagulating bath containing 1.5% by \veightof sulfuric acid, 4.4%

by weight of formaldehyde, 2.5% by weight of ammo-' bath solution through a closed chamber maintained at a temperature of 88 F. and at a relative humidity of 100%, each portion of the tow being subjected to the atmosphere in said chamber for 60 minutes. The tow was then passed back and forth between two stepped stretching rollers which dipped into a water bath maintained at 130 F. and thereby washed free of adhering coagulating bathsolution and stretched 295%. The tow was then passed, while being maintained under sufficient tension to maintain the stretch, back and forth between two rollers dipping into an aqueous postcure solution containing 3.5% by weight of formaldehyde, 5.0% by weight of sulfuric acid and sodium chloride to 100% saturation. The tow was then squeezed gently between rollers to remove excess postcure solution and leavean amount of said solution in the tow about equal to the dry weight of the tow. The tension on the tow was then relieved and the tow was passed through a chamber maintained at 120 F. at a relative humidity of 100%, each portion of the tow being subjected to the atmosphere in said chamber for 2 hours. The tow was then washed in water at 80 F. for 27 minutes and then dried at 150 F. for 60 minutes and then baked at 300 F. for 60 minutes.

The resulting fiber had the following properties:

Cond. elongation 43 percent.

4 EXAMPLE 2 Sample 1 Sample 2 2hrs. at120 F. 100% Soft and open.

2 hrs. at 81 F.

Slightly adhered filaments.

Difference of Curo Rel. Humidity of Cure Appearance of Sample- Mechanical Properties:

Denier of filament Wet tensile, gm./den Wet elongation, percent. 00nd. Tensile, gin/den Cond. Elongatiion, Percent: Shrinkage in Acid Dyeing, Percent. Dye Exhaust, Percent.. Properties after Acid Dyeing:

Wet Tensile, gmJden Wet Elongation, Percent- Cond. Tensile, gmJden.-- Cond. Elongation, Percent It is to be noted that the effect of this postcuring method i. e. subjecting the fiber to an atmosphere at 110- 140 F. at a relative humidity of at least for from 30 minutes to 2 hours, gives a greater effect on fiber produced as described in Example 1 than on fiber produced by theprocess of U. S. Patent No. 2,478,248 as described in Example 2 but the effect in both cases is significant and Well worthwhile.

I'claim:

1. In a process of curing synthetic zein fiber with formaldehyde the step which consists in stretching the fiber, impregnating the fiber in stretched condition with about an equal weight of an aqueous solution containing from about 3% to about 10% of sulfuric acid, from about-3% to about 10% of formaldehyde and at least 90% saturated with sodium chloride, relaxing the fiber and subjecting it to an atmosphere which is at least 90% saturated with water vapor at a temperature within the range from about F. to about 140 F. for a period of from about 30 minutes to about 2 hours.

2. Process as defined in claim 1 in which the aqueous solution contains about 3.5% of formaldehyde and 5% of sulfuric acid and in which the temperature is maintained at F. for 2 .hours.

3. Process for the production of synthetic textile fiber which comprises extruding an aqueous zein solution containing from about 0.5 to about 10% of formaldehyde into an aqueous bath containing from about 2 to about 10% of formaldehyde, and holding the resulting fiber in contact with said solution in an atmosphere which is saturated with water vapor at a temperature within the range from about 80 F. to about 100 F. for a period of from about /2 hour to about 3 hours, and thereafter treating the fiber as defined in claim 1.

4. In a process for the production of zein fiber involving the steps of spinning an alkaline zein solution into an acid coagulating bath, stretchingsthe fiber and curing the fiber by treatment with formaldehyde, the improvement which consists in impregnating a tow of the fiber in the stretched condition with an aqueous solution containing from about 3% to about 10% of formaldehyde, from about 3% toabout 10% of sulfuric acid and at least 90% saturated with sodium chloride, relaxing the fiber tow and subjecting. the relaxed to-w containing about an equal weight of said solution to an atmosphere which is main- References Cited in the file of this patent UNITED STATES PATENTS Swallen May 2, 1939 6 Wormell July 21, 1942 Atwood Feb. 29, 1944 Cline Oct. 15, 1946 Croston Aug. 9, 1949 Tetlow Aug. 28, 1951

Claims (1)

1. IN A PROCESS OF CURING SYNTHETIC ZEIN FIBER WITH FORMALDEHYDE THE STEP WHICH CONSISTS IN STRETCHING THE FIBER, IMPREGNATING THE FIBER IN STRETCHED CONDITION WITH ABOUT AN EQUAL WEIGHT OF AN AQUEOUS SOLUTION CONTAINING FROM ABOUT 3% TO ABOUT 10% OF SULFURIC ACID, FROM ABOUT 3% TO ABOUT 10% OF FORMALDEHYDE AND AT LEAST 90% SATURATED WITH SODIUM CHLORIDE, RELAXING THE FIBER AND SUBJECTING IT TO AN ATMOSPHERE WHICH IS AT LEAST 90% SATURATED WITH WATER VAPOR AT A TEMPERATURE WITHIN THE RANGE FROM ABOUT 110*F. TO ABOUT 140*F. FOR A PERIOD OF FROM ABOUT 30 MINUTES TO ABOUT 2 HOURS.

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