US3642972A - Process of producing nonwoven fabrics using aziridine-modified polyurethane bonding agent - Google Patents

Abstract

NON-WOVEN FABRICS WHICH COMBINE GOOD TENSILE STRENGTH WITH POROSITY, AIR-PERMEABILITY, FLEXIBILITY, SOFTNESS, AND THE APPEARANCE AND HANDLE OF A WOVEN FABRIC. PRODUCTS OF THE INVENTION, ALTHOUGH MADE FROM WOOL, DO NOT SHRINK WHEN WASHED IN AQUEOUS SOAP OR DETERGENT FORMULATIONS. EXAMPLE: AN AZIRIDINE-MODIFIED POLYURETHANE IS DEPOSITED ON WOOL FIBERS WHICH ARE THEN ARRANGED IN THE FORM OF A THIN WEB AND CURED AT A TEMPERATURE OF ABOUR 100-170* C. UNDER A PRESSURE OF ABOUT 1000-5000 P.S.I.

Description

PROCESS OF PRODUCING NONWOVEN FABRICS USING AZIRIDINE-MODIFIED POLYURETHANE BONDING AGENT Howard L. Needles, Davis, and William L. Wasley, Berke- ":eley, Califz, assignorsto the United States of America as represented by-the Secretary-of Agriculture 3 No Drawing. FiledNov. 19, 1969, Ser. No. 882,407

. v I Int. Cl. D04h 1/00 U.S. Cl. 264-123 5 Claims ABSTRACT OF THE DISCLOSURE :Non-woven fabrics which combine good tensile strength with porosity, air-permeability, flexibility, softness, and the appearance and handle of a woven fabric. Products of the invention, although made from wool, do not shrink whenwashed in aqueous soap or detergent formulations. 'Example: An aziridine-modified polyurethane is deposited on wool fibers whichare then arranged in the form of a thin web and cured at a temperature of about 100170 C.-under a pressure of about 1000-5000 p.s.i.

[or knitting. More particularly, the invention concerns the provisionbf non-wovenfabrics which exhibit many of the characteristics of typical woven fabrics. Thus, the products of the invention combine good tensile strength with porosity, air-permeability, flexibility, softness, and

the appearance and handle of a woven fabric. Moreover, although. theproducts of the invention are made from wool, they 'do, not shrink when 'washed in aqueous soap or jde tergent formulations. Further objects and advantages of thelinvention will be evident from the following description wherein parts and percentages are by weight unless otherwise. specified.

Certainnon-woven fabrics are now available in commerce. These products consist of a skeleton of textile fibers bonded together by such resinous materials as polyvinyl esters,. polyacrylates, polystyrene, polyvinylidenes, and copolymers of these substances and the like. A common property of these known products is that they are stiff. Indeed, they are used as stiffening materials for 'lapels, collars, and similar garment parts. Another disadvantage of the known non-woven fabrics is that they cannot withstand the stresses encountered in laundering. When subjected to the, usual agitation in soap (or detergent) .and hot waterformulations they are ruptured or even disintegrated. For example, Nottebohm (U.S. Pat.

2,719,803.) explains that non-woven fabrics cannot be washed without damage, and to remedy thisproblem he finds it necessary to protect an inner layer of non-woven fabric by laminating it with outer layers of conventional woven fabrics.

A primary object of the invention is the provision of novel products which avoid the problems outlined above, that is, the provision of products which, among other advantages, are free from stiffness and which are stable to washing in aqueous media. I

In accordance with the invention, wool fibers are first Unit d S at Patented Eeb. 15, 1972 coated with an aziridine bonding agent (as hereinafter described). A preferred technique involves dissolving the aziridine in an inert, volatile solvent and applying the resulting solution to the wool fibers. Typical of the solvents which may be used are benzene, toluene, xylene, dioxane, diisopropyl ether, dibutyl ether, butyl acetate, chlorinated hydrocarbons such as chloroform, carbon tetrachloride, ethylene dichloride, trichloroethylene, 1,3-dichlorobenzene, fluorohydrocarbons such as benzotrifiuoride, 1,3-bis-(trifluoromethyl) benzene, etc., petroleum distillates such as petroleum naphthas, etc. Usually it is preferred to use the aziridines in the form of aqueous emulsions. These can be prepared by customary techniquesagitation of the aziridine with water and a conventional emulsifying agent such as an alkylphenoxypoly-(ethyleneoxy) ethanol, polyoxyethylene sorbitan monopalmitate, polyoxyethylene lauryl ether, polyoxyethylene lauryl ether, polyoxyethylene-polyoxypropylene stearate, sorbitan monopalmitate, sorbitan monolaurate, and the like. The concentration of the aziridine in the dispersionthis last term being herein employed in a generic sense to include solutions and emulsions-is not critical and may be varied depending on such circumstances as the solubility characteristics of aziridine, the amount of aziridine to be deposited on the fibers, the viscosity of the dispersion, etc. In general, a practical range of concentration would be from about 1% to about 25%. The dispersion may be distributed on the textile material by any of the usual methods, for example, by spraying, brushing, padding, dipping, etc. A preferred technique involves immersing the fibers in the dispersion and then passing them through squeeze rolls to remove the excess of liquid. Such techniques as blowing air through the treated textile may be employed to reduce the amount of liquid which exists in interstices between fibrous elements. In any case, the conditions of application are so adjusted that the textile material contains the proportion of aziridine desired. Generally, the amount of aziridine is about from 5 to 25%, based on the weight of the wool fibers but it is obvious that higher proportions may be used for special purposes.

After application of the aziridine, the treated fibers are dried to remove the solvent or dispersing vehicle. The drying may be at room temperature, or somewhat elevated temperatures, for example, up to about 60 C. The fibers are then arranged to form a thin sheet or web. The fibers may be arranged parallel, in a criss-cross pattern, or randomly. For best results the fibers are arranged in superposed layers with the fibers of each layer at an angle to the fibers of adjacent layers, thus to provide a multiplicity of points of contact between individual fibers.

The web or sheet of aziridine-treated fibers is then subjected to a temperature of about -l70 C. while under a pressure of about 1000-5000 p.s.i. applied, for

example, by heated platens or the like. By this heating aresult is, of course, advantageous as it yields a' product which is like a fabric (i.e, porous, resilient, etc.) and not impermeable and limp like a plastic foil or sheet. Anotherimportant result of the curing step is that the aziridine is chemically bonded to the wool fibers. Although the mechanism of this bonding has not been identified, it is believed to involve chemical combination of the aziridine with active radicals in the wool molecules, these active radicals including carboxyl, hydroxyl, amino, and thiol groups. This chemical combination of the aziridine with the wool fibers is of advantage as it adds to the durability of the products, particularly their ability to be washed without shrinking or other damage.

The non-woven fabrics prepared by the technique described above have many advantages properties. They are porous, air-permeable, soft, flexible, and resilient. Thus, unlike prior art products they exhibit most of the properties of the wool fibers themselves so that they are eminently suitable for preparing all kinds of garments. A particularly important advantage of our products is that they can be washed with the usual soap (or detergent) and hot water formulations without rupture, indeed without even shrinking. Moreover, the products display an excellent resistance to wrinkling and creasing.

The aziridines used in accordance with the invention are those described and claimed in the co-pending application of Allen G, Pittman and William L. Wasley, Ser. No. 675,038, filed Oct. 13, 1967, now Pat. 3,542,505. They may be aptly described as aziridine-modified polyurethanes, and have the structure A is the residue of a polyether polyol or polyester polyol having a valence of n,

R is a hydrocarbon radical containing at least two carbon atoms,

R is hydrogen, halogen, lower alkoxy, or a radical of the structure on R wherein:

CHR"

R" is hydrogen or a lower alkyl radical, n is an integer from 2 to 10, and x is an integer from 1 to 2.

-(In the formulas, 111 represents the number of tetramethylene repeating units. This may range, for example, about from 5 to 50.)

The reaction is carried out at about 10 to 40 C., and under essentially anhydrous conditions to avoid hydrolysis of the isocyanate groups. The alkylene imine is supplied in excess to ensure conversion of all isocyanate groups to aziridine groups. it is evident from the formulas above that modification in the aziridine rings can be effected by selection of the alkylene imine reactant. For example, if propylene imine is used instead of ethylene imine, the aziridine rings will be of the structure In other words, in this case R (in Formula I) is methyl.

Referring to Formula I, above, it is evident that selection of the polymer intermediatethe polyether or polyester polyurethane containing free isocyanate groups will determine the values of A, R, R, n, and x. The preparation of these intermediates is Well known in the art; they are widely used in the production of urethane foams for padding and insulation applications, and in the production of elastomers. Although the preparation of these intermediates forms no part of the present invention, this subject will be explained below to illustrate the wide range of intermediates which may be employed in producing the aziridine derivatives of the invention. Thus, for the purposes of the invention, the intermediate may be any polyether or polyester polyurethane which contains at least two free NCO groups per polymer molecule. Preferred are the polymer intermediates having a molecular weight of at least 500, more preferably those having a molecular weight of at least 1000. Also, it is generally preferred to use the polyether-based polymers, for example, the NCO-containing polyurethanes derived from polyalkylene ether glycols such as polyethylene ether glycols, polytrimethylene ether glycols, polytetramethyleue ether glycols, polypropyleneether glycols, and the like.

THE POLYMER INTERMEDIATES =Polyether (or polyester) polyurethanes containing free isocyanate groups useful as intermediates for the present invention may be prepared, as Well known in the art, by reacting a polyether (or polyester) polyol with a polyisocyanate, using an excess of the latter to ensure provision of free isocyanate groups in the product. A typical, but by no means limiting, example is illustrated:

Isoeyanate-terminatcd polyether polyurethane Isocyanate-terminated polyether polyurethane (In the above formulas, m represents the number of tetramethyleneether repeating units. This may range, for example, about from to 50.) v j Representative examples of polyisocyanates which may be employed for reaction with the polyether (or polyester) polyol' include: Y L

=toluene;2,4-diisocyanatetoluene-2,G-diisocyanate commercial mixtures o f toluene-2,4 and 2,6-diisocyanates ethylene diisocyanate ethylidene diiso'cyan-ate propylene-1,2-diisocyanate cyclohexylene-1,2-diisocyanate cyclohexylene-1,4-diisocyanate 3 m-phenylene diisocyanate -3,3-diphenyl}4;4' biphenylene dii socyanate 44'-biphenylene' diisocyanate 3,3 -'dichlor0-4,'4=biphenylene 'diisocyanate 1,6-hexamethylenediisocyanate 1',4 tetrarnethylene-diisocyanate' "1,10-deCamethylenediisocyanate 1,5-naphthalenediisocyanate cu'rherie-ZA-diisbcyanate l-rnethoxy-lfi-phenylenediisocyanate 4chloro-1,3-phenylenediisocyanate 4-bromo-1,3-phenylenediisocyanate 4- etho xy-l,3-phenylenediisocyanate 2,4 diisocyanatodiphenylether 5,6-dimethyl-1,3-phenylenediisocyanate 2,4'-dimethyl-1,3-phenylenediisocyanate 4,4'-diisocyanatodiphenylether benzidinediisocyanate 4y6-dimethyl-1,3ephenylenediisocyanate 9, IO-anthracenediisocyanate v I "4,4"-diisbyanatodibenzyl 3,3-dimethyl-4,4'-diisocyanatodiphenylmethane 2,6-dimethyL'4,4-diisocyanatodiphenyl 2,4-diisocyanatostilbene 3,3' dimethyl-4,4'-diisocyanatodiphenyl 3,3'-dimethoxy-4,4'-diisocyanatodiphenyl 1,4-anthracenediisocyanate 2,5-fluorenediisocy-anate r1,8-naphthalenediisocyanate 2,6-diisocyanatobenzfuran 2,4,6-toluenetriisocyanate, and

p,p',p"-triphenylmethane triisocyanate.

Itis evident that the selection of the polyisocyanate rewant will determine the values of R and R in Formula I. For example, where the reactant is a hydrocarbon diisocyanate, R will be a hydrocarbon radical and R will represent ahydrogenatom forming part of said hydro- .carbon radical. Where the reactant contains a substituent such as "chlorine or methoxy-as would be the case with, for example, '4-chloro-l,3-phenylene diisocyanate or L methoxy-1,3-phenylenediisocyanate-R will be the bydrocarbon residue of the reactant and R will be the substituentchlorine or methoxy in the given examples.

The polymer intermediates useful for the purposes of the invention may, in turn, be derived from any of a wide variety of polyether polyols and polyester polyols, and representative examples of these polyols are described below:

Among the polyether polyols which may be so used are those prepared by reaction of an alkylene oxide with an initiator containing active hydrogen groups, a typical example of the initiator being a polyhydric alcohol such as ethylene glycol. The reaction is usually carried out in the presence of either an acidic or basic catalyst. Examples of alkylene oxides which may be employed in the synthesis include ethylene oxide, propylene oxide, any of the isomeric butylene oxides, and mixtures of two or more different alkylene oxides such as mixtures of ethylene and propylene oxides. The resulting polymers contain a polyether backbone and are terminated by hydroxyl groups. The number of hydroxyl groups per polymer molecule is determined by the functionality of the active hydrogen initiator. For example, a difunctional alcohol such as ethylene glycol (as the active hydrogen initiator) leads to polyether chains in which there are two hydroxyl groups per polymer molecule. When polymerization of the oxide is carried out in the presence of glycerol, a trifunctional alcohol, the resulting polyether molecules contain an average of three hydroxyl groups per molecule. Even higher functionalitymore hydroxyl groupsis obtained when the oxide is polymerized in the presence of such polyols as pentaerythritol, sorbitol, dipentaerythritol, and the like. In addition to those listed above, other examples of polyhydric alcohols which may be reacted with alkylene oxides to produce useful polyether polyols include:

propylene glycol trimethylene glycol 1,2-butylene glycol 1,3-butanediol 1,4-butanediol 1,5-pentanediol 1,2-hexylene glycol 1,10-decanediol 1,2-cyclohexanediol 2-butene-1,4-dio1 3-cyclohexene-1,2-dimethanol 4-methyl-3-cyclohexene 1,1-dimethano1 3-methylene-1,5-pentanediol diethylene glycol (Z-hydroxyethoxy)-1-propanol 4- (Z-hydroxyethoxy -1-butanol 5-(Z-hydroxypropoxy)-1-pentanol 1-(Z-hydroxymethoxy)-2-hexanol l-(l-hydroxypropoxy)-2-octanol 3-allyloxy-1,5-pentanediol 7 2-allyloxymethyl-Z-methyl-1,3-propanediol [(4-pentyloxy) rnethyl]-1,3-propanediol 3-(o-propenylphenoxy)-1,2-propanediol thiodiglycol 2,2' [thiobis (ethyleneoxy) ]diethanol polyethyleneether glycol (molecular weight about 200) 2,2'-isopropylidenebis(p-phenyleneoxy)diethanol 1,2,6-hexanetriol 1,1,l-trimethylolpropane 3-(2-hydroxyethoxy)-1,2-propanediol 3- (Z-hydroxypropoxy 1 ,2-propanediol 2,4-dimethyl-2- (Z-hydroxyethoxy) methylpentanediol- 1,5 1, l,1-tris[ (Z-hydroxyethoxy methyl] ethane 1, l 1 -tris (Z-hydroxypropoxy methyl] propane triethanolamine triisopropanolamine resorcinol pyrogalol phloroglucinol hydroquinone 4,6-di-tertiarybutyl catechol catechol orcinol methylphloroglucinol hexylresorcinol 3-hydroxy-2-naphthol 2-hydroxy-l-naphthol 2,5-dihydroxy-1-naphthol bis-phenols such as 2,2-bis-(p-hydroxyphenyDpropan and bis-(p-hydroxyphenyl methane 1,1,2-tris- (hydroxyphenyl ethane 1,1,3-tris- (hydroxyphenyl) propane.

An especially useful category of polyether polyols are the polytetramethylene glycols. They are prepared by the ring-opening polymerization of tetrahydrofuran, and contain the repeating unit in the polymer backbone. Termination of the polymer chains is by hydroxyl groups.

The polyester polyols which may be employed as precursors for the aziridines of the invention, are most readily prepared by condensation polymerization of a polyol with a polybasic acid. The polyol and acid reactants are used in such proportion that essentially all of the acid groups are esterified and the resulting chain of ester units is terminated by hydroxyl groups. Representative examples of polybasic acids for producing these polymers are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassylic acid, thapsic acid, maleic acid, fumaric acid, glutaconic acid, a-hydromuconic acid, B-hydromuconic acid, a-butyl-ot-ethylglutaric acid, u,fi-diethylsuccinic acid, o-phthalic acid, isophthalic acid, terephthalic acid, hemimellitic acid, trimellitic acid, trimesic acid, mellophanic acid, prehnitic acid, pyromellitic acid, citric acid, benzenepentacarboxylic acid, 1,4-cyclohexanedicarboxylic acid, diglycollic acid, thiodiglycollic acid, dimerized oleic acid, dimerized linoleic acid, and the like. Representative examples of polyols for forming these polymers includes ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butylene glycol, 1,3-butylene glycol, 1,2-butylene glycol, butene-l,4-diol, 1,5-pentane diol, 1,4-pentane diol, 1,3-pentane diol, 1,6-hexane diol, hexene-1,6-diol, 1,7-

heptane diol, diethylene glycol, glycerine, trimethylol propane, 1,3,6-hexanetriol, triethanolamine, pentaerythritol, sorbitol, and any of the other polyols listed hereinabove in connection with the preparation of polyether polyols. 5 An interesting class of polyester polyols are those which include polyether units so that they may be considered as polyester polyols or as polyether polyols, depending on whether the ester or the ether groups are in majority. The compounds may be produced by the condensation polymerization of any of the above-mentioned polybasic carboxylic acids with a polyalkyleneether glycol-typically, a polyethyleneether glycol having a molecular weight of about 200 to 2000-using the glycol in the required proportion to assure termination by hydroxyl.

Esters of the hydroxyl-containing acid, ricinoleic acid, form another category of useful polyester polyols. Typically, one can use esters of ricinoleic acid with ethylene glycol, propylene glycol, glycerol, pentaerythritol, diglycerol, dipentaerythritol, polyalkyleneether glycols, and the like. Representative of this category of polyester polyols is castor oil which is composed mainly of the tri-glyceride of ricinoleic acid.

The invention is further demonstrated by the following illustrative examples.

EXAMPLE 1 The aziridine-modified polyurethane used in this instance was prepared as described in Ex. 4 below. It has the structure A 10% solution of the aziridine-modified polyurethane in toluene was prepared and used to treat wool sliver (a loose assembly of wool fibers). The wool sliver was passed through the solution and then excess liquid removed, using pad rolls to attain an 80-100% wet pick-up of solution. The treated sliver was dried at room temperature. The uptake of aziridine was 8%.

The dried sliver was cut into 15 cm. long segments (3 grams each) which were spread into 15 x 15 cm., singleply or 2-ply (crossed), webs between sheets of aluminum foil. The web in each foil was pressed at 2000 p.s.i. and 150 C. for 5 minutesin a hydraulic press. After removal from the press, the foil was removed to yield non-woven fabric samples which weighed approximately 13 mg./cm. The products were very resilent and could be laundered. Various tests were conducted on the samples, the results being tbulated below:

*ASTM test method D-89-49, l-incli wide strip.

EXAMPLE 2 The procedure described in Example 1 was repeated with the exception that the concentration of the aziridine solutions was increased to give uptakcs of the aziridine polymer of 14.4% and 28%. Tests were conducted on the resulting products, these including a shrinkproofing test 75 as follows:

Accelerotor shrinkage test This test for shrinkage was conducted in the following way: The samples were milled at 1700 r.p.m. for 2 minutes at 40-42 C. in an accelerotor with 0.5% sodium oleatej solution, using a liquor-to-wool ratio of 50 to 1. After this washing operation the samples were measured to determine their area and the shrinkage was calculated from the original area. The accelerotor is described in the American Dyestutf Reporter, vol. 45, p. 685, Sept. 10, 1956. The two-minute wash in this device is equal to about 15 home launderings. Conventional woven wool fabrics when treated in this manner exhibit an area shrinkage of 45 to 50%. The-results obtained are tabulated below:

The procedure described in Example 1 was repeated with these exceptions: The aziridine was that described in Example 6 below. It has the structure Direction The curing step was at 150 C., 2000 p.s.i. for 10 minutes. The products had an 11% uptake of the aziridine polymer. Tests on the products are tabulated below:

The following examples illustrate syntheses of the aziridines useful for the purposes of this invention.

EXAMPLE 4 Preparation of aziridine-modified polytetramethyleneether I polyurethane The starting material for this synthesis was a commercial liquid polyurethane having a molecular weight of seem 2000 and an isocyanate '(-NCO) content of 4.1%. It is believed to have the structure CH3 CHa 10 wherein A represents the residue of a polytetramethyleneether glycol containing about twenty-five -CH CH CH CH -O units.

Two hundred grams (0.1 mole) of the polyurethane were dissolved in 300 grams of toluene. While stirring the solution, 8 grams (0.2 mole) of ethylene imine were added dropwise. During the addition, the temperature of the solution was not allowed to exceed approximately 40 C. At the end of the addition, an infrared spectrum of the solution revealed no residual NCO groups. This indicated preparation of the desired aziridine derivative.

EXAMPLE 5 The starting material for this synthesis was a commercial liquid polyether polyurethane having a molecular weight of about 850 and an isocyanate (-NCO) content of about 9.5%. It is believed to have the structure.

wherein A represents the residue of a polytetramethyleneether glycol containing about seven -CH -CH CH --CH O units.

One hundred grams (0.12 mole) of the liquid polyurethane was dissolved in 300 ml. of dry benzene. While stirring, 13 ml. (0.26 mole) of ethylene imine was added at a rate slow enough that the reaction temperature did not rise above 40 C.

EXAMPLE 6 The starting material for the synthesis was a commercial liquid polyether polyurethane having a molecular weight of about 1300 and an isocyanate (-NCO) con- 14 45 tent of 6.5%. It is believed to have the structure EXAMPLE 7 A polypropyleneether glycol of molecular weight about 6000' was reacted with toluene diisocyanate in conventional manner to form an isocyanate-termined polyurethane. This, in turn, was reacted with propylene imine 12 to form an aziridine-modified polyurethane with terminal R" is hydrogen or a lower alkyl radical, groups of the structure n is an integer from 2 to 10, and

CH x is an integer from 1 to 2,

3 (b) arranging the treated wool fibers into the form CH2 5 of a thin web, and

(c) while constraining the fibers in the form of. a thin web, curing the web at a temperature of about 100- (IE-CH3 170 C. and a pressure of about 1000-5000 p.s.i.

l -CONH-P NHOON 2. The process of claim 1 wherein A is the residue of a Fifty grams of the aziridine-modified polymerhaving polyalkyleneether glycol and n is 2.

a molecular weight of 6300-6800 and containing 0.36 to 3, The process of laim 1 whe i 0.38 milli-equivalents of imine per gram of polymerwas dissolved in 50 grams of benzene and 2 grams of a commercial emulsifier, a polyoxyethylene-polyoxypropylene R5 monostearate, was added. While stirring the solution in a is the tolylene radical. blendor, water was gradually added to make 1000 gram 4. The process of claim 1 wherein the aziridine-modified of an emulsion. polyurethane has the structure (in, CH, CH; 0 0 0 I 0 CH,

It II II I /N NH NH-CO(CH CH CHg-CH -OM-C-NH NH-C-N CH1 Hz Having thus described the invention, what is claimed is: 5. The process of claim 1 wherein the aziridine-modified 1. A process for preparing a non-woven fabric which polyurethane has the structure comprises $H3 CHI Cs: 0 (I) 3 IO /CH: l Ni J-NH NH-ll-O(GH -CH CH2-CHg0)25-CNH NH-N\l OH: H]

(a) depositing on wool fibers an aZiridine-modified References Cited polyurethane Of the structure UNITED STATES PATENTS 0 3,542,505 11/1970 Pittman et a1. 8127.6

U AO -NH-RNH N i n ROBERT F. BURNETT, Primary Examiner wherein: R. O. LINKER, JR, Assistant Examiner A is the residue of a polyether polyol or polyester polyol having a valence of n, R is a hydrocarbon radical containing at least two 156 296, 331; 161-157, 170

carbon atoms, R is hydrogen, halogen, lower alkoxy, or a radical of the structure