IL38170A - Acrylic fibers having improved hotwet properties - Google Patents

Description

ACRYLIO FIBERS HAV&NO IMPROVED HOT-WET PROPERTIES n na ga n%>¾ao on* iwt o»»*»np» T»a»o 0*DT11 o*nV 0.193 ACRYLIC FIBERS HAVING IMPROVED HOT-WET PROPERTIES ABSTRACT OF THE DISCLOSURE Grafted polymers having Improved hot-wet modulus properties are produced from a polymeric substrate comprising acrylonitrile and grafted polymer units of acrylic or metha-crylic acid ester of 1 - 5 carbon containing alcohols, i.e., methyl acrylate, isobutyl ethacrylate , propyl methacrylate , methyl methacrylate.

BACKGROUND OF THE INVENTION (1) Field of the Invention The invention relates to acrylonitrile containing polymers having improved physical properties, fore particularly, it relates to acrylic fibers exhibiting markedly improved tensile properties and good dyeing properties in the hot-wet state. The invention relates especially to a process and polymeric composition obtained from said process. (2) Description of the Prior Art It is known that polyacrylonitrile and copolymer of acrylonitrile and other mono-olefinic polymerizable monomers yield excellent fiber-fqrming polymers. The polyacrylonitrile and copolymers of more than 75 percent and preferably more than 85 percent acrylonitrile and up to 15 percent of other polymerizable monomers produce fibers with substantial tensile properties, desirable elongation, and excellent stability under a wide range of physical and chemical conditions.

- - In spite of the desirable physical properties manifested by acrylonltrile containing fibers there are a number of difficulties encountered during the processing of fabrics made therefrom, especially under hot-wet conditions. Various means have been employed in the art to improve the tensile properties of such fibers under hot-wet conditions. A number of means involve incorporating various chemical agents to modify the structural arrangement of the polymer itself; several methods have been employed which physically modify the fiber structure. These methods and combinations thereof have met with limited success . During processing of fabrics containing acrylonltrile where such fabrics are exposed to heat and water or steam, deformation owing in part to a low modulus of such acrylonltrile materials is frequently observed. Furthermore, wrinkling or overstretching when a woven or knitted fabric thereof is subjected to tension is often exhibited. Accordingly, there is a need for suitable means for improving, the hot-wet properties of fibers containing acrylonltrile without Impairment of other desirable properties afforded by such fibers.

SUMMARY OF THE INVENTION During the processing of fibers of those herein considered and especially during dyeing there are numerous problems encountered such as crease marks , loss of bulk and loss of stitch definition owing to the lower tensile properties of fibers of acrylonltrile polymers.

A principal object of this invention is to provide a dyeable fiber-forming acrylonltrile polymer having improved modulus under hot-wet conditions as comparied to an unmodified and conventional fiber.

C- 14-53-0027 Briefly, this invention describes a method of producing a polymer containing acrylonitrile having an enhanced and improved modulus when hot and wet by polymerizing acrylonitrile to form a polymer containing at least 80 percent by weight acrylonitrile and optionally other monomers which do not lower hot-wet modulus compared to the homopolymer fibers and thereafter grafting monomers of esters derived from acrylic or methacrylic acid and an aliphatic alcohol haveing from 1 to 5 carbon atoms.

In accordance with the present invention a fiber-forming composition is formed by grafting on a polymeric substrate comprising acrylonitrile a polymeric material being represented by the general formula: wherein R is hydrogen or methyl, R1 is R or ethyl, R_ is a lower alkyl radical of from 1 to 5 carbon atoms, and Λ^ ίώ an integer greater than 10.

It is well-known that quite different properties from ordinary copolymers are produced by grafting chains of one polymer onto a substrate of a second pclymer by means of chain reactions . The term chain reaction denotes a chain of similar occurrences which continue until either the reagent is consumed or reactive entity is diverted in a terminating reaction. The entity initiating the reaction may be a cation, anion, or a free radical, but most usually a free radical, and may be added in small amounts at the C- 14-53-0027 Preparation through conventional means in the production of graft copolymers generally follows three approaches, viz. . a chain-transfer type reaction, a redox reaction, or a radiative type reaction , on a polymer molecule having labile functional groups or a chemical modified polymer having active sites thereon.

It is known that monomeric methyl methacrylate can be grafted onto polypropylene to increase dyeability. The grafted monomer acts as a hydrophilic layer on the polypropylene substrate . Further., nylon may be surface grafted with monomeric methyl methacrylate via irradiation .

The class of grafting monomers to which the subject invention is addressed is the acrylate and methacrylate esters of 1 to 5 carbon alcohols by the formula: wherein R is hydrogen or methyl, R is hydrogen, methyl or ethyl, and R is a lower alkyl radical of from 1 to 5 carbon atoms.

Representative acrylate or methacrylate ester monomers include: butyl methacrylate, ethyl methacrylate, methyl methacrylate , methyl acrylate butyl acrylate , ethyl crotonate, ethyl acrylate . propyl acrylate . These esters may be used alone , or a mixture thereof.

A proportion of a polymerizable sulfonic acid salt may be used in conjunction with the above named esters . Representative sulfonates include: sodium vinyl sulfonate , sodium vinylbenzene sulfonate sodium sulfoethyl methacrylate , potassium isopropenylbenzene sulfonate, sodium sulfophenyl methallyl ether (SPME), sodium methallyl sulfonate, potassium sulfophehyl methacrylamide .

The substrate polymer may be polyacrylonitrile or a copolymer of acrylonitrile and small proportion of a monomer such as vinyl bromide, vinyl chloride, or vinylidene chloride which do not impair the hot-wet modulus of a fiber made therefrom as compared to a fiber from polyacrylonitrile.

The polymer may be made by any means known in the art, for example, suspension, emulsion, or solution polymeriza-tion in either batch or continuous procedure. Redox Initiators such as K S 0„/S0 or NaClO-VSO- or peroxide initiators such 2 2 8 2 3 2 as t-butyl peroxypivalate, benzoyl peroxide or azo initiators such as azobisisobutyronitrile may be employed. The level of initiator and molecular weight regulator (if any) is adjusted to give a suitable molecular weight (as measured by¾gp at 0.1 gm/dl in dimethylformamlde . The modulus of fibers along with other physical properties, such as melting point and tensile strength, generally increase with increasing molecular weight. However, many of these physical characteristics of linear high polymers do not continue to increase indefinitely with increasing molecular weight. Instead, these and other properties seemingly level off in value at some characteristic, high molecular weight, and any increase in the molecular weight above this limiting value causes no substantial or significant im-provement in such properties. It has been found that the most effective polymers for the preparation of fibers after C-14-53-0027 this invention are those of uniform physical and chemical properties and of relatively high molecular weight. It has been further found that polymers should have a weight average molecular weight of at least 65, 000 and preferably, with respect to this invention, between about 100, 000 and 250^000. The reaction medium may be water or an organic solvent for the polymer such ad dimethyl formamide or dimethylsulfoxide. Additionally, molecular weight regulators such as mercaptans and /or dispersing or emulsifying agents may be used.

Any temperature at which the production of radicals proceeds at a satisfactory rate may be employed. Temperatures of 35-70° C. , are preferred.

The substrate polymer must be substantially freed of monomeric acrylonitrile and other comonomers before the grafting reaction. This may be done by coagulation of emulsion polymers or precipitation of polymers prepared in solution, followed by filtration or centrifugation and washing.

The grafting reaction may take place in an aqueous medium wherein the substrate polymer and grafting monomers are suspended and the reaction initiated. The initiator is an acidic solution of a eerie salt such as eerie sulfate. The mechanism of the initiation is not fully understood but may involve abstraction of a hydrogen from the substrate leaving a grafting site as shown below.

C- 14- 53-0027 The grafting reaction of this invention will take place at room temperature although higher temperatures may be preferred for ease of control. When grafting is achieved, the suspended polymer is isolated by filtration or centrifugation, washing, and drying. Extraction with a suitable solvent for the homopolymer of the grafting monomer, for example benzene in the case of methyl acrylate, may be done to obtain the pure graft. Since the graft reaction is usually efficient, this step may be omitted.

The graft polymers may be converted into fibers by conventional methods , for example , wet spinning and dry spinning. They will have greatly improved affinity for basic dyes compared to the un-grafted fiber, yet retain the high hot- wet modulus.

The following examples are given to illustrate the invention and should not be construed as limiting it. In- the examples all parts and percents are given by weight unless otherwise indicated.

EXAMPLE 1 An acrylonitrile- vinyl bromide (ΛΝ— VBr) copolymer was prepared using the following ratios of reactants: water 400 parts, AN 91. 5 parts, VBr 8. 5 parts , KgSgOg 0. 65 parts , SOgias NaHSOg) 1. 5 parts, sodium lauryl sulfate 0. 5 part, Fe was added to give a slurry pH 3. Feeds were added over a 2 hour interval, the temperature being maintained at 50° C. After an additional one-half hour reaction, the polymer was isolated and washed well. The product, obtained in 95% yield had a tl (0. 1 g/dl in dimethylformamide (DMF) at 25° C. ) of 0. 15 and contained Bp 6. 4% VBr (by Br analysis) . ' < C- 14^53-0027 A 25% solids dope was prepared in dimethylacetamide (DMAc) . It was wet spun into (a) 57/43 DMAc/HgO at 38° C. , and (b) polyethylene . glycol (Carbowax 400, Union Carbide Corporation) at 95° C. Both fibers were stretched 6X in boiling water and dried at 135° C. They were annealed by 7 cycles steam at the desired pressure [ 35 psi for (a) , 5 psi for (b)] . Fiber properties are listed in Table I.

EXAMPLE 2 In a similar run using lower initiator quantities, viz . , 0. 35 part K2S2°8* 0 , 8 part S02 a Polvmer of ° - 25 containing 5. 4% VBr was prepared.

A 19% solids dope was prepared in DMF. Spinning was similar to that described in Example 1 except spin bath (a) was 60 /40 DMF/H^O at 35° C. Fiber properties are listed in Table I.

EXAMPLE 3 About 100 parts of the polymer of Example 1 was added to about 850 parts of water containing 3 parts sodium lauryl sulfate whereupon 20 parts of methyl acrylate (MA) was added and agitated under a nitrogen atmosphere for about 30 minutes. To this mixture was added 67 parts of 1. 0 N NaOH followed immediately by 40 parts 0. 1 N Ce (S04)2 in 2N H2S04. After about 18 hours at 30° C. , the slurry was filtered, washed and dried. The dried grafc polymer was thereafter extracted with hot benzene to remove any poly(methyl acrylate). Approximately 7% MA was found to be grafted on the AN/VBr substrate.

C- 11-53-0027 A 25% solids dope in DMF was spun according to the procedures of Example 2. Fiber properties are listed in Table I.

EXAMPLE 4 One hundred parts of the 0. 15 ""^p acrylonitrile and vinyl bromide (AN/VBr) copolymer was added to a solution of 3 parts sodium lauryl sulfate and 3 parts Na-sulfophenyl methallyl ether (SPME) in 850 parts water. Twenty parts methyl acrylate (MA) was then added and the mixture stirred in a N„ atmosphere for one-half hour. Then 67 parts 1. 0 N NaOH immediately followed by 40 parts 0. 1 N Ce(S04)2 in 2. 0 N HgS04 were added. After 20 hours at 30* C. , the slurry was filtered and washed. The dried graft polymer was extracted with hot benzene to remove any poly( methyl acrylate). The polymer contained approximately 8% MA and 0. 8% SPME. A 25% solids dope in DMF was spun according to the procedures of Example 2. Fiber properties are listed in Table I.

EXAMPLE 5 A polyacrylonitrile polymer was prepared using the following ratios of reactants: water 750 parts, AN 100 parts, K2S2°8 1 < 25 Parts* +2 S02 (as NaHSOg) 1. 25 parts, Fe 0. 25 ppm. H2so4 was added to maintain slurry pH at 3· Feeds were added over a two-hour interval, the temperature being maintained at 40° C. After an additional half hour reaction, the polymer was filtered and washed. The product, isolated in 89% yield has an of 0. 14.

A 25% solids dope in DMF was spun into Carbowax 400 at 95%C. , stretched 6X, dried at 135° C. , and annealed 7 cycles at 5 psi steam. Fiber C- 14-53-0027 EXAMPLE 6 One hundred parts of a polyacrylonitrile similar to that described in Example 5 was slurried into a solution of three parts sodium lauryl sulfate in 850 parts water. Twenty parts methyl acrylate was then added and the mixture stirred in atmosphere for one hour. Then 67 parts 1. 0 N NaOH immediately followed by 40 parts 0. 1 N Ce(S04>2 in 2. 0 N H2S04 were added. After stirring 18 hours at 30° C. , the polymer was filtered, washed and dried.

After benzene extraction, it was found to contain 8% MA. A 25% solids dope in DMF was spun by the procedure of Example 5. Fiber properties are given in Table I.

EXAMPLE 7 One hundred parts of the AN/VBr copolymer of Example 1 was slurried into a solution of 3 parts sodium lauryl sulfate in 1 , 000 parts water. Twenty parts methyl methacrylate (MMA) was added and the mixture stirred in a atmosphere for 1 hour. Then 40 parts 0. 1 N CefSO^ ), in 2. 0 N H SO was added and the mixture stirred at 30° C. , for 23 hours . to After filtration, washing, and drying, the graft polymer was extracted with hot benzene. Approximately 7% MMA was incorporated. A 26% solids dope was spun according to the procedure of Example 5. Fiber properties are given in Table I.

EXAMPLE 8 An AN-VBr-vinyl acetate (VA) ternary polymer was prepared by an aqueous suspension continuous overflow polymerization process . Feed compositions were 83. 3 parts AN, 8. 0 parts VBr, 8. 7 parts VA , 400 parts C-H-53-0027 H00, 0.67 part K_S_C» 1.70 part SO_, 1.75 part NaIICO_, and 0.25 +2 ppm Fe . Reactor contents were held at 50° C. , with an average dwell time of one hour. The polymer was shortstopped with 600 ppm ethylenediaminetetraacetlc acid (EDTA), filtered, washed and dried. The polymer was 0.16; it contained 5.1% VBr and 7.0% VA. A 25% solids dope in D Ac was spun according to the procedures of Example 1. Fiber properties are listed in: Table ί.

TABLE I Modulus in H2O* Fiber Example Polymer Composition 22° C 71° G 93° C BDA 1(a) 93 AN/7 VBr 0.14 -n 3 344..22 1 111..99 2 2..5 5 0.9 ¾sp Kb) 93 AN/7 VBr 0.14-* 5 500..00 1 155..22 4 4..0 0 0.6 xsp 2(a) 95 AN/5 VBr 0.25τ¾ρ j 6 611..33 2 255..88 7 7..3 3 CI 2(b) 95 AN/5 VBr , 0.25 in 8 844..00 2 222..00 7 7..4 4 <1 sp 3(a) 87 AN/ 5 VBr + 7 MA graft 5 522..33 1 155..44 4 4..6 6 3.7 3(b) 87 AN/6 VBr 4· 7 MA graft 5 533..33 1 188..22 4 4..6 6 1.9 4(a) 87 AN/6 VBr + 7 (MA+SPME) graft 4 477..66 1 199..11 5 5..0 0 10.5 4(b) 87 AN/6 VBr + 7 (MA+SPME) graft 5 533..11 2 255..33 5 5..6 6 4.2 PAN(3 dpf) 6 633..00 1 133..00 3 3..0 0 1.6 6 92 AN + 8 MA graft ( 3 dpf) 5 566..55 1 144..33 3 3..7 7 3.9 7 87 AN/6 VBr + 7 MMA graft 4 433..11 1 144..11 3 3..3 3 1.0 8(a) 88 AN/5 VBr/7 VA 0.16 4 477..88 7 7..11 0 0..7 7 8(b) 88 AN/5 VBr/7 VA 0.16 -n 3 399..55 3 3..33 0 0..8 855 4.2 SP * Initial modulus, grams per denier (single filament).

** Fiber basic dye acceptance (BDA) was measured using a procedure involvin "Sevron Blue 2G" dye (C.I. Basic Blue 22). The fiber was heated at 100p C for 2 hours with a buffered (pH 5.2) solution of the dye (20% based on fiber) The dye concentration in the liquor was determined spectrophotoinetrically, and from this the percentage of dye takeup by the fiber was calculated.

C-14-53-0027 Table I shows that the moduli in water at 71° C. , and 93° C. , for the AN/VBr copolymer fiber spun by either technique (Examples 1(a) and (b)) is better than those of the control fibers (Examples 8(a) and (b)), but the fiber basic dye acceptance (BDA) is much lower. An increase in molecular weight of the AN/VBr copolymer (Examples 2(a) and (b)) effects a further improvement in modulus. Grafting of MA on the AN/VBr copolymer (Examples 3(a) and (b)) improve the hot-wet moduli compared to Example 2 and significantly improves BDA. The mixed graft of MA and sodium sulfophenylmethallyl ether (SPME) (Examples 4(a) and (b)) results in a further improvement in moduli and BDA. These fibers are equal or superior in dyeability to the random terpolymer fibers (Examples 8(a) and (b)). Grafting of methyl methacrylate (Example 7) does not adversely affect hot-wet modulus; however, it is less effective than MA in improving BDA . Examples 6 and 7 show that polyacrylonitrile (PAN) itself may be improved in dyeability without impairment of hot- wet modulus by grafting of MA.

The modulus in water under various temperatures (viz . , 22° , 71° and 93° C. ) was determined in accordance with ASTM D2101-64T.

It would be understood to those skilled in the art that many apparently widely different embodiments of this invention can be made without departing from the spirit and the scope thereof. According, it is to be understood that this invention is not to be limited to the specific embodiments thereof except as defined in the appended claims .

Claims (7)

C-l'i-53-0027 That which is claimed is:

1. • 1. A fiber-forming composition having improved hot-wet modulus and basic dyeability characterized by a polymeric substrate comprising acrylonltrile, and a polymeric material grafted on said substrate and having the general formula: wherein R is hydrogen or methyl, R^is R or ethyl, R2 is a lower alkyl radical of from 1 to 5 carbon atoms , and is an integer greater than 10.

2. The composition of Claim 1 characterized in that the substrate has at least 85 percent by weight acrylonltrile and in the general formula R and R-, are hydrogen and R is selected from — CH. C2Hc and CH(CI )CH

3., The composition of claim 1 characterized in that the polymeric substrate is selected from polyacrylonitrile, and a polymer comprising acrylonltrile and a halogen-containing vinyl monomer, and the polymeric material also includes an in-terpolymer comprising: C-lM-53-0027 wherein R is hydrogen or methyl, is R or ethyl , M is hydrogen, mono or divalent salt-forming member fll is an integer greater than 10, and is an integer of one or greater.

4. The composition of claim 1 characterized in that the polymeric material is methyl acrylate.

5. A method of improving the hot-wet modulus of a dyeable fiber from an acrylonitrile containing polymer characterized by grafting onto said acrylonitrile containing polymer a graft polymer having the general formula: wherein R is hydrogen or methyl, ^ is R or ethyl, ^ is a lower alkyl radical of from 1 to 5 carbon atoms , and i rr is an integer greater than 10.

6. The method of claim 5 characterized in that the acrylonitrile containing polymer is polyacrylonitrile or a polymer comprising at least 85 percent by weight acrylonitrile and a halogen-containing monomer selected from vinyl bromide, C-14-53-0027 vinyl chloride and vinylidene chloride, and in the general formula R and R^ are hydrogen and R2 is a lower alkyl radical selected from the group consisting of — CH^, — an(* — H(CH3)CH3.

7. The method of claim 5 characterized in that the graft polymer also includes an interpolymer comprising: wherein R is hydrogen or methyl, R is R or ethyl, R2 is a lower alkyl radical of from 1 to 5 carbon atoms , < R is R or cyano, M is hydrogen, mono or divalent salt-forming member, n\ is an integer greater than 10, and is an integer of one or greater. COHEN ZEDEK & SPISBACH Regd. Patent Attorneys P.O. Box 33116, TEUAVIV, ISRAEL