US3063787A - Process of wet spinning stereoregular polyvinyl alcohol - Google Patents

Description

Nov. 13, 1962 H. J. RYNKIEWICZ ETAL 3,063,787

PROCESS OF WET SPINNING STEREOREGULAR POLYVINYL ALCOHOL Filed June 17, 1960 WIND UP RPVA SOLVENT INVENTORS HENRY J. RYNKIEWICZ EUGENE W. K. SCHWARZ IRVING SKEIST WWMEOMW ATTORNEY S United States Patent 3,063,787 PROCESS OF WET SPINNING STEREOREGULAR POLYVINYL ALCOHOL Henry J. Rynkiewicz, Danbury, Conn., Eugene W. K. Schwarz, Brooklyn, N.Y., and Irving Skeist, Summit, N.J., assignors to Diamond Alkali Company, Cleveland, Ohio, a corporation of Delaware Filed June 17, 1960, Ser. No. 36,739 9 Claims. (CI. 1854) This invention relates to the production of films, fibers, threads, filaments and similar articles. More particularly, it relates to the production of such articles from polyvinyl alcohol.

It is known that polyvinyl alcohol, which is soluble in water, can be spun into fibers by wet or dry spinning methods from an aqueous solution of the resin. Such fibers, however, are characterized by their sensitivity, to water, particularly to hot water. If dipped in water at normal temperature, the fiber will shrink by more than 10% of its original length, and if the temperature of the water is around 70-90 C., the fiber will dissolve.

Polyvinyl alcohol (PVA) fibers have been made resistant to water by various methods including modification of the alcohol prior to spinning and by after-treatment of the fiber. It has been known to incorporate into the polyvinyl alcohol spinning solution a compound such as a dicarboxylic acid which is capable of forming a crosslinked structure under the influence of heat. It has also been known to acetalize the polyvinyl alcohol, then form a fiber and follow up with a heat treatment of the fiber.

Fibers, after being spun from a PVA solution, have been made resistant to water by various treatments such as stretching and heat-treating, stretching and reacting with a material such as an aldehyde, ketone or dibasic acid, exposure to formaldehyde vapors or elevated temperatures and treatment of the fiber surface with waxes, etc. Such treatments are expensive and often introduce undesirable physical characteristics and impurities in the treated fibers.

As with other types of synthetic fibers, a moderate amount of drawing or stretching orients the molecular structure and results in high tensile strength. This orientational drawing, however, is distinguished from the stretching which accompanies the aforementioned insolubilizing treatments.

3,063,787 Patented Nov. 13, 1962 This invention has as an object an oriented high-tensity polyvinyl alcohol fiber which, without the well-known insolubilizing treatments, is insoluble in boiling Water. A further object is a method of preparing such fibers from polyvinyl alcohol resins which are substantially insoluble in boiling Water. Other objects will be obvious from a careful study of the following description of this invention.

Conventional polyvinyl alcohol is obtained by saponification, hydrolysis or alcoholysis of polymerized vinyl esters, especially vinyl acetate. The molecular weight of the polyvinyl alcohol is dependent upon that of the ester, i.e., a high molecular weight polyvinyl alcohol is obtainable from an ester having a correspondingly high molecular weight. The conventional polyvinyl alcohol having a reduced viscosity of 1.0 is completely soluble in water at a temperature of about C. Accordingly, an aqueous solution of polyvinyl alcohol may be employed to produce fibers, films, etc. therefrom. v

The polyvinyl alcohol of this invention, hereafter referred to as Stereoregular polyvinyl alcohol or RPVA, is obtained by alcoholysis of polymerized vinyl halo esters, especially vinyl chloroacetates and vinyl fluoroacetates, as disclosed in US. patent application Ser. No. 689,768, filed October 14, 1957, and now Patent No. 2,901,341. The Stereoregular polyvinyl alcohol having a reduced viscosity of 1.1 will not dissolve in water at a temperature of 100 C. RPVA may be dissolved in water at a temperature of 1l5-120 C. The insolubility of Stereoregular polyvinyl alcohol in water at 100 C. has been attributed to the syndiotacticity of the alcohol as contrasted to an atactic structure possessed by conventional polyvinyl alcohol.

Since pressurized equipment is necessary to maintain a water temperature in the neighborhood of 120 C., it may be desirable to employ an organic solvent to form the spinning solution. Stereoregular polyvinyl alcohol is not only insoluble in boiling water but is also insoluble in most solvents or combinations thereof. In order to determine the effect of various solvents on RPVA, a film of the material was cast from a water dispersion of the resin. The dispersion was spread on a glass plate and the water evaporated therefrom to form a film. Small sections of this film were immersed in the solvents tested and the effect of numerous solvents is shown in Table I.

TABLE I Reagent After 5 hrs. at room After 24 hrs. at room Additional 5 hrs. at Additional 2 hrs. at

temp. temp. 5055 C. 95 0.

Water NNE.-- NE. NNE. NNE. Ethylene diamiue Dissolved Dissolved Dissolved Dissolved. Acetic acid, glacial NN N NE. NN V. sl. swollen. Acetic anhydride- NNE- NN NNE}- NNE. Ammonium thiochauate (sat. sol.)- Considerable swelling Considerable swelling... Considerable swelllng Considerable swelling. Formic acid (ea-%) do do Degradation. Lithium bromide (60% sol.) S1 swollen do Greatly swollen. Zinc chloride (60% sol.) N do Dissolved-pink. Ethylene chloride NNE at 50 C NNE at 50 C NNE. Propylene carbonate- NNE NNE NNE. Znitropropane- NNE NNE. NNE Butyr NNE NNE- Tetrahydroiurfuryl alcohol NNE NNE NNE. Chloromaleic anhydride. NNE NNE- NNE NNE. Triethylene diamine (sat. sol.) Apparently dissolved.-. Apparently dissolved--. Apparently dissolved. Morp holine. NNE NNE NN E V. sl. swollen. N-methyl NNE NNE Degradation v. v. sl.

swollen.

Piperdine- NNE. NNE. Swollen. Pyridine NNE- NNE- N NNE-darkened. Piperazine (sat. sol.) Appears to be dissolved- Appears to be dissolved- Appears to be dissolved. Triethanolamine NNE N N E- NN NN E. Diethaunlamine NNE... NNE NNE. Nitroethaue NNE NNE NNE Acetonitrile NNE. NNE. N-acetylmorpholine NNE NNE N NNE. 1,6-hexanedian1ine-72% Appears to be dissolved. Appears to be dissolved. Appears to be dissolved. Appears to be dissolved.

' See footnotes at end of table.

Reagent After 5 hrs. at room After 24 hrs. at room Additional 5 hrs. at Additional 2 hrs. at 7 temp. temp. 50-55 C. 90-95 C.

Resorcinol (sat. sol.) Swollen Considerable swelling-.- Considerable swelling. Greatly swollen. Caprolactarn (set. sol. N N E V. sl. swollen do Do. Dimethyl sulione (sat. sol.)-. Sl. swollen Swollen Do. Dime yl oxide Considerable swelling... Considerable swelling. IDo. Trioresyl phosphate. NNE N NE N N E. Chloroform NNE- NNE Sanoticizer 141 NN N NE. Diaeetiu NNE NNE. Formamide Sl. swollen- Sl. swollen. Triisooetyl phosph e NE--... NNE. Bis (2-ethylhexyl) hydrogen phosphate"... NNE.-. NNE. #:Hydroxypropionitrile NE Swollen. 2(2-am1noethylamine) ethanol NNE V. sl. swollen- Appears to be dissolved. 2-pyrrolidinone NE Greatly swollen. N-methylacetamide. S1. swollen. Propargyl alcohol--. V sl. sw ollen V. si. swollen. Shell curing agent T l. N E N N E. Diglyme NNE NN E. Tetramethyleno sulione NNE N N E. fl-Alanine (sat. sol.) V. s1. swollen Swollen. Glycine (sat. sol.) Swo1len--... o. Guanylurea phos hate (sat. sol.) do ..do Greatly swollen Greatly swollen. Methylannne sol.) Appears to be dissolved. Appears to be dissolved- Appears to be dissolved. Appears to be dissolved. Menthaue diamine NNE NNE NNE NNE. fl-Hydroxyethyl trimethyl ammonium- V. 51. swollen V. s1. swollen S1. swollen Swollen.

bicarbonate-4 Cyanamide (sat. sol.) Considerable swelling.-. Considerable swelling. Greatly swollen Dissolved. B-Propiolactone NNE NN E NNE Si. swollen. Urea (sat. sol.) Greatly swollen Greatly swollen Greatly swollen Disslolved (may contain go Onyx ETC-% 1 Considerable swelling-.. Considerable swelling- Considerable swelling. Considerable swelling. H01 (oone.). Dissolved Dissolved Dissolved i Swollend SOz/dimethyl fomamide, saturated.--- NE- NN E. sozftetrahydroiuran, saturated NNE. LiBr/dimethyl formarnide, saturated NNE. Greatly swollen Greatly swollen. LiBr/drmethyl sulfoxrde, saturated- NNE. Extremely swollen Extremely swollen. LlBr/tetrahydroiuran, saturated NNE- N 2 ZnClz/dimethyl iormarnide, saturated. N V. v. s1. swollen NNE. znchldlmelhyl ornde, saturated-.. Extremely swollen Partially dissolved. ZnCn/tetrahydroiuran, saturated.-. NN E Dimethyl iormamide/HaO, 4:1 ratio--. Extremely swollen. Dimethyl suli'oxide/HzO, 4:1 ratio S1 D0. B O/ethylene glycol, 4:1 ratio Greatly swollen. Triton X-lOOfH O, (cone. sol.)- Extremely swollen. Diacetone alcohol NNE Tetrahydropyran2-inethanol-. NNE. Ethyl oarbamate NNE. Ethylene glycol Swollen. Urea/tetrahydroiuran, saturated Urea/dimethyl iormamide, saturated Sl. swollen. Urea/ethylene glycol, saturated NNE. Swollen. Urealdimethyl sulfoxide, saturated Sl. swollen Extremely swollen. Urea/Z-pyrrolidone NNE Swollen. Cyanamideltetrahydroiuran, saturated- NNE.-. Cyanamide/dimethyl formamide, saturated. NNE V. v. 51. swollen. Cyanamide/ethylene glycol saturated NN E. Swollen. Cyanamide/dimethyl sulfoxide. saturated- Swollen- Considerable swelling- Considerable swelling. Triethylene diamine/tetrahydrofuran NN N N E Triethylene diamine/dimethyl formamide. NNE. S1. swollen. 'lriethylene diamine/ethylene glycol Swollen. Triethylene diamine/dimethyl sulioxide... Considerable swelling. Triethylene diamine/Q-pyrrolidone NN Extremely swollen. Caprolactamltetrahydroturan. 2 Csprolaetam/dirnethyl formamide. S1. swollen. Caprolaetamlethylene glycol D Piperazine (hydrate) ltetrahydrofuran Piperazine (hydrate)/dimethyl iormamide- NNE. Piperazine(hydrate)/ethylene glycol Swollen. Piperazine (hydrate)/dirnethyl suli'oxide. Dissolved. Guanylurea phosphate/tetrahydrofuran- 2 Guaniylurea phosphate/dimethyl iorma- S1. swollen.

m! e. Guanylurea phosphate/ethylene glycol- Swollen. Guanylurea phosphateldimethyl sulfoxide" Considerable swelling. Diehloroaeetio acid/glycerine NN V. s]. swollen. Dichloroacetic acidltetrahydroiuran. (z) .Diehloroecetie acid/dirnethyl iormamide S1. swollen. Diehloroaoetic aoid/dimethyl sulfoxide Considerable swelling. Extremely swollen. Extremely swollen. Formio acid/ethylene glycol- NNE N N E Considerable swelling. Triethylamine NNE NNE NNE NNE. Duponol WA/HzO Considerable swelling. Considerable swelling. Considerable swelling... Considerable swelling.

1 Alkyl (CrC dimethyl benzyl ammonium chloride-25% sol. Note-NNE =No noticeable efieot; v.=very; sl.=silghtly; conc.=concentrated; sat.=saturated; and sol.=solution.

From Table I it will be noted that ethylene diamine, saturated solution of triethylene diamine, saturated solution of piperazine, 72% solution of 1,6-hexanediamine, 30% solution of methylamine and concentrated hydrochlo'ricacid apparently dissolve the stereoregular poly- The aqueous solutions of triethylene diamine, piperazine, herranediamine and methylamine all are quite alkaline, having a pH in the neighborhood of about 12. Films of RPVA which were reciprocated from these solutions were found to be water-soluble and this led to the belief'that such materials cause a possible degradation of the alcohol, accounting for its solubility. Convinyl alcohol.

I Solvent boiled off.

up to four carbon atoms.

centrated HCl is very diflicult to handle and therefore is undesirable as a solvent. For preliminary Work, ethylene diamine was selected as the solvent in the preparation of the spinning solution.

Typically, a solution of stereoreguiar polyvinyl alcohol in ethylene diamine is extruded by means of a gear pump through a multihole spinnerette into a coagulating bath of methanol or other lower aliphatic alcohol containing From the coagulating bath the fiber or yarn is led to a positively-driven Godet and then through air to a positively-driven Wind-up bobbin. adjusting the speeds of the various drives, the fiber can 5 be stretched or drawn in controllable amounts either in the coagulating bath or in air between the Godet and wind-up or both. It has bec 1 found advantageous to pro vide a heat-setting operation following the drawing which comprises immersing the fiber or passing it through a hot mineral oil bath at a temperature of about 120 to 180 C. This heat-setting operation may be accompanied by a hot-stretch operation whereby the fiber, while hot, is stretched 4 to 8 times its original length. The combina tion of heat and stretch not only increases the insolubility of the fiber in hot water but also orients the fiber and increases its tensile strength.

Fibers produced from water-insoluble stercoregular polyvinyl alcohol having a reduced viscosity of 1.5, in accordance with this invention, have a tenacity of at least 7.5 grams per denier. Such fibers are important inindustrial uses such as cords for fires, fire hoses, industrial cords and belting, and in reinforcing fibers for many applications.

Reference has been made to the reduced viscosity (N of polyvinyl alcohol. This value is an indication of the molecular weight of the polymer and is equal to the specific viscosity (N divided by the concentration of polymer in the solution. The fiow timeof the polymer solution I and the flow time of the solvent t are usually measured by the capillary method. *From these values the specific viscosity is computed according to the formula t t o The reduced viscosity has a logarithmic relationship to the molecular weight of the polymer and, in general, the range is:

Since conventional polyvinyl alcihol is soluble in water, water generally is used as the solvent in determining the reduced viscosity. Reduced viscosity of RPVA cannot be determined in this manner, however, since it is insoluble in water. Accordingly, the reduced viscosity of the precursor, i.e., polyvinyl chloroacetates or polyvinyl fluoroacetates, is determined and, as is common practice in the polymer field, this value is assumed to be proportional to the reduced viscosity of the polyvinyl alcohol.

Denier of fibers is defined as the weight in grams of a 9,000-meter length of thread and is determined by measuring 9 meters of thread on a standard textile skeiner. The thread is removed from the skeiner and wound into a small loop about 1 inch in diameter. The loop of thread is agitated in isopropyl alcohol to remove any oil or other material which may be present on the thread surface and then air dried. The weight of the loop in milligrams, as determined on an analytical balance, equals the denier of the sample.

Apparatus for determining tensile strength and ultimate strength consists of a triple-beam laboratory scale. To one pan of the scale is attached a #25 chain which then loops over a sprocket and hand wheel near the level of the balance, such that turning the hand wheel adds more chain to the pan of the balance, thus gradually adding weight to that pan. The second pan of the balance has a drum-type fiber clamp attached below it. Directly below this clamp is a second clamp mounted with a rack and pinion which, through a hand Wheel, can raise or lower the clamp. In operating the apparatus, the chain and sliding weights on the balance are set at 0. The lower clamp is raised so that the clamps are inches apart. The thread sample is clamped in the upper clamp and then pulled through the lower clamp to a point where the balance pointer reads 0 to insure that the sample is caught between clamps. The chain hand wheel is turned at a rate so as to add about 1 gram per second to the 6 load. At the same time the other hand wheel is turned to lower the clamp, thus keeping the balance pointer at the center mark. When the thread sample breaks, rotation of both hand wheels is stopped. At this point the sample is checked to ascertain whether the break occurred at the nip of the clamps and, if such is the case, that reading is discarded. Using the sliding weights of the balance, the weight of the chain is balanced and the reading on the scale is the breaking point. The distance the lower clamp has moved from its original position determines the ultimate stretch. The arithmetic mean of 10 breaking strength determinations is divided by the denier of the thread to give the grams per denier. The average of 10 ultimate stretch values, calculated as a percentage of 5 inches, gives the ultimate stretch percent.

Tenacity in grams per denier is converted to pounds per square inch by the formula:

wherein S=strength in pounds A=cross sectional area of the fiber in square inches d=density of the fiber in grams per cubic centimeter g=strength or tenacity in grams per denier The density of RPVA has been determined as 1.30 gr./cc. Substituting this value in the above formula, the tenacity in pounds per square inch is equal to 16,000Xgrams per denier.

In order that those skilled in the art may more completely understand the present invention and the preferred methods by which the same may be carried into effect, the following specific examples are offered.

Example 1 A prototype laboratory spinning apparatus such as is shown schematically in the attached drawing is employed which comprises a reservoir for the spinning solution which feeds two positive displacement metering pumps which are so interconnected and are run by variable speed motor so as to permit the accurate metering of as little as 3 10 cc. per minute of the spinning solution. This apparatus is designed as a precision meter to extrude a uniform filament of spinning solution through the spinnerette orifice. A candle filter, using muslin as the filtering medium, is mounted in such a Way as to permit the spinnerette to be raised from and lowered into the coagulating bath without interfering with the flow of spinning solution. The main purpose of the filter is to minimize the incidence of clogging of the spinnerette orifice. The spinnerette is attached to the filter through a glass tube. The coagulating bath is contained in a stainless steel tray, 24 inches long, with an effective fiber immersion length of 18 inches. Single-stretching of the fiber is eifected by wrapping the fiber once around a step on a step cone, then to a rewind spool. The diameters of the steps are calculated to permit any elongation from 0 to 1000% in 50% increments. Sequential stretching is effected by two step cones mounted parallel and rotating at the same speed. The fiber is fed around the two smallest diameter steps, then around successive larger steps and is finally wound on a rewind spool. The diameters of the steps vary from Aa inch to 4 inches and As-inch increments, permitting up to 700% stretch by this method.

An ethylene diamine solution containing 24% steroregular polyvinyl alcohol having a reduced viscosity of about 0.4 is extruded through the spinnerette at a rate of 1.5 feet per minute into a coagulating bath of absolute methanol. At this extrusion rate the coagulation time is 60 seconds. The fiber is subjected to a total stretch or elongation of 450% and is then dried at C. for a period of 16 hours in order to remove all of the ethylene diamine. The fiber thus produced is insoluble in boiling water.

Example 2 A quantity of stereoregularpolyvinyl alcohol resin having a reduced viscosity of 1.5 is dissolved in ethylene diamine to provide a solution of about 10% solids. Using the apparatus of Example 1, this solution, at room temperature, is extruded through an eight-hole spinnerette at a rate of 1.5 feet per minute into a coagulating bath of absolute methanol. The RPVA fiber is stretched a total of eight times in two stages at ambient temperature, pressure and humidity. After drawing, the fiber is given a heat-setting treatment by immersion in a mineral oil bath at 130 to 160 C. for a period of 30 seconds. The fiber thus produced is an eight-filament yarn of which each filament is slightly less than one denier. This fiber is in soluble in boiling water.

Water resistance and dry tenacity of various fibers are presented in Table II:

A 10% solution of stereoregular polyvinyl alcohol in ethylene diamine is made by placing 140 grams of anhydrous ethylene diamine in a wide-mouth glass jar. To this is added a quantity of 15.5 grams of RPVA having a reduced viscosity of 1.5. The mixture is shaken vigorously to form a thin slurry and then is heated for 3 hours in a water bath at 5560 C. The solution is spun through a spinnerette containing 8 orifices, each of which is 0.003 inch in diameter, into an absolute methanol bath at a speed which permits approximately 45 seconds coagulation bath exposure. The strand is wet-stretched 1.5 times and wound on a supply spool. The supply spool is placed on a hot-stretch machine where the strand is passed through a bath of mineral oil maintained at a temperature of about 135-140" C. The exposure time of the strand in the bath is about 20 seconds. The amount of stretch applied to the strand is varied by changing the gear ratio of either the feed or take-01f capstan wheels so that the speed of the take-E wheel is 3 to 10 times that of the feed wheel. Table III gives the properties of the fibers thus produced.

TABLE III Ulti- Tensile strength Denier mate (grams) Grams Pounds Hot (8 filastretch per per sq. stretch ments) (perdenier in.

cent) Range Average Example 4 In order to determine the elfect of hot-stretch bath temperature, a 10% solution of RPVA in ethylene diamine is spun into fibers as in Example 3, except that the amount of hot-stretch is maintained at 8 times the original length and the bath temperature is varied. Results of this test are set forth in Table IV.

Example 5 In order to determine the eifect of size or denier per filament on physical properties, a 10% solution of RPVA in ethylene diamine is spun into filbers as in Example 3. Variation in denier is effected by changing the speed of the solution feed pump and the resultant drawdown at the spinnerette orifices. Results are set forth in Table V.

TABLE V Strength (grams) Thread Fila- Grams Pounds Ultimate denier ment per per elongation denier Range Averdenier sq. in. (percent) age Example 6 In order to determine the effect of varying both the hot-stretch bath temperature and monofilament size, a 10% solution of RPVA in ethylene diamine is spun into fibers as in Example 3, except that the solution is spun through a 16 orifice spinnerette. The amount of hotstretch is maintained at 8 times the original length.

TABLE VI Denier Hot stretch Tensile Grams Pounds temperastrength per per 16 filament Monofilature, 0. (grams) denier sq. in

ment

It is to be understood that although the invention has been described with specific reference to particular embodiments thereof, it is not to be so limited, since changes and alterations therein may be made which are within the full intended scope of this invention as defined by the appended claims.

What is claimed is:

1. The method of producing stereoregular polyvinyl alcohol fibers which are insoluble in water at 100 C. and have a tenacity of at least 6.8 grams per denier which comprises the steps of forming a solution of stereoregular polyvinyl alcohol in ethylene diamine containing about 3% to 24% by weight polyvinyl alcohol, extruding the solution through a spinnerette into a coagulating bath of lower aliphatic alcohol containing up to 4 carbon atoms, wet-stretching the fiber to about 1 to 3 times its original length and hot-stretching the fiber about 4 to 12 times its original length at a temperature of about 180 C.

2. The method of claim 1 wherein the solution contains about 10% polyvinyl alcohol.

3. The method of claim 1 wherein the polyvinyl alcohol has a reduced viscosity within the range of 0.4 to 1.5.

4. The method of claim 1 wherein the coagulating bath is absolute methanol.

5. The method of claim 1 wherein the polyvinyl a1- cohol has a reduced viscosity of at least 1.5.

6. The method of claim 1 wherein the fiber is Wetstretched about 1.5 times its original length and is hotstretched about 8 times its original length at a temperature in the neighborhood of 130-l60 C.

7. The method of claim 1 wherein the fiber is hotstretched in a bath of hot mineral oil.

8. The method of producing stereoregular polyvinyl alcohol fibers which are insoluble in water at 100 C. and have a tenacity of at least 6.8 grams per denier which comprises dissolving in ethylene diamine about 10% by Weight of stereoregular polyvinyl alcohol which is insoluble in boiling water and has a reduced viscosity of at least 1.2, extruding the solution through a spinnerette into a coagulating bath of lower aliphatic alcohol containing up to 4 carbon atoms, wet-stretching the fiber to about 1 to 3 times its original length and hot-stretching 10 the fiber about 4 to 12 times its original length at a temperature of about 120180 C.

9. The method of claim 8 wherein the stereoregular polyvinyl alcohol has a reduced viscosity of about 1.5 the fiber has a denier of 0.6 denier per filament, the hotstretch temperature is 171-175 C. and the tenacity of the fiber is 9.0 grams per denier.

References Cited in the file of this patent UNITED STATES PATENTS 2,447,140 Shelton et al Aug. 17, 1948 2,517,694 Merion et al. Aug. 8, 1950 2,610,359 Hatchard et al. Sept. 16, 1952 2,610,360 Cline et al. Sept. 16, 1952 2,642,333 Tomonari et al. June 16, 1953 2,715,763 Marley Aug. 23, 1955 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 3,063,787 November -l3- 1962 Henry J Rynkiewicz et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 2, lines 25 and 26 strike out and now Patent No, 2,901,341"; columns 1 and 2 TABLE I under the column heading "Reagent" line 5, for "'thiochanate" read -thiocya-nate same table, same column lneading line 18 for "Fiperd-ine" read Piperidine column 3 line 72 for "reciproEa-t-ed" read reprecipita'ted column 5 line 39 for al-cihol" read alcohol column 10, line 4 afterl'la5" insert a comma Signed and sealed this 24th day ofS-eptember 1963,

(SEAL) Attestz ERNEST w. SWIDER DAVID D Attesting Officer Commissioner of Patents

Claims (1)

1. ,1. THE METHOD OF PRODUCING STEREOREGULAR POLYVINYL ALCOHOL FIBERS WHICH ARE INSOLUBLE IN WATER AT 100*C. AND HAVE A TENACITY OF AT LEAST 6.8 GAMS DENIER WHICH COMPRISES THE STEPS OF FORMING A SOLUTION OF STEREOREGULAR POLYVINYL ALCOHOL IN ETHYLENE DIMINE CONTAINING ABOUT 3% TO 24% BY WEIGHT POLYVINYL ALCOHOL, EXTRUDING THE SOLUTION THROUGH A SPINNERETTE INTO A COAGULATING BATH OF LOWER ALIPHATIC ALCOHOL CONTAINING UP TO 4 CARBON ATOMS, WET-STRETCHING THE FIBER TO ABOUT 1 TO 3 TIMES ITS ORIGINAL LENGTH AND HOT-STREATCHING THE FIBER ABOUT 4 TO 12 TIMES ITS ORIGINAL LENGTH AT A TEMPERATURE OF ABOUT 120*-180*C.

Images