US3102835A

US3102835A - Fibrous materials and method for making the same

Info

Publication number: US3102835A
Application number: US24317A
Authority: US
Inventors: Marion M White
Original assignee: Allen Industries Inc
Current assignee: Allen Industries Inc
Priority date: 1960-04-25
Filing date: 1960-04-25
Publication date: 1963-09-03
Anticipated expiration: 1980-09-03

Description

Sept. 3, 1963 M. M. WHITE 3,102,835

FIBRous MATERIALS AND METHOD FOR MAKING THE SAME Filed April 25. 1960 0f 128W ffy F461 dw/6%? Weis Kampfes.; 76 da/Ve,

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3,102,835' FIBROUS MATERIALS AND METHOD FDR MAKING THE SAME Marion M. White, Detroit, Mich., assigner to Allen Industries, lne., Detroit, Mich., a corporation of Delaware Filed Apr. 25, 196i?, Ser. No. 24,317 1i) Claims. (Cl. 156-29) The present invention relates to fibrous materials. More particularly this invention relates to fibrous materials of the type which are of open texture but in which the fibers are joined to each other at their points of contact, and to the method for making such materials having predetermined porosity, density and resiliency characteristics.

The use of natural and synthetic brous materials such as jute, sisal, cotton, hair, cellulose acetate and the like for cushioning, insulation and similar purposes has the disadvantage that such materials tend to pack during use and thus lose effectiveness. The present invention provides ya process which enables the use of low cost natural and synthetic fibers to form nonpacking materials having predetermined porosity and density and of particular utility as cushioning, insulation and packaging materials.

The present invention is based on the discovery of certain fiber saturants which confer the ldesired and improved properties on the fibers and a method of applying such saturants to those fibers which enables the arrangement of the fibers, in the saturant-coated condition, into the articles having the desired porosity, Weight and resiliency characteristics. The satunants of this invention possess the funique characteristic that they are capable of adhering to the fiber surfaces suiiiciently to enable the desired handling and arrangement of the fibers into the predetermined porosity form Without being stripped therefrom or losing their ability to be later converted into a more solid and stable form.

The saturant of this invention is a urethane pre-polymer which is capable of being converted in situ on the liber surfaces to `a polyurethane which unites the fibers into an integral body. The pre-polymer on the surface of the adjacent or contacting bers ycross-links and/ or chain extends under the impetus of catalytic action to form a single fiber-unifying polyurethane network which extends throughout the article. For a number of applications in which flexibility is a minor consideration or completely unimportant such as in insulation, sound deadener materials and the like, pre-polymers which form relatively rigid polyurethanes are satisfactory, although flexible, resilient polyurethanes are similarly useful and are inclu-ded in' this invention.

Urethane pre-polymers Which are suit-able for the purposes of this invention may be formed from a Wide variety of specic starting materials from the two classes generally designated polyisocyanates, difunctional or higher, and hydroxyl-rich compounds containing at least two hydroxyl gro-ups per molecule.

The hydroxyl-rich compounds broadly include the diols, triols, polyesters, lpolyethers, adducts of alkylene and arylene oxides with diols, triols, etc. The polyisocyanates broadly include the aromatic, aliphatic and cyclo-aliphatic diand tri-isocyanates and combinations of these types. The selected hydroxyl-rich compound and polyisocyanate for a specific application Will -obviously depend upon the characteristics which are desired in the final product, expense, ease of handling and the like, but those skilled in this art are now suiiiciently familiar with the effects of chain length, chain branching, hydroxyl availability, relative quantities of ingredients, reacting conditions and the like to be able to easily rates atet vce select suitable starting materials from the many which `are available and satisfactory. Typically suitable hydroxyl-rich compounds include such triols as glycerine, trimethylol propane, hexanetriol-1,2,6, etc.; diols, such as ethylene glycol, propylene glycol, butylene glycol-1,3, butylene glycol-2,3, 4diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, polyisocyanate modified alkylene glycols; polyoxyalkylene glycols and polyisocyanate-modiiied polyoxyalkylene glycols, polyether glycols such as polyethylene glycols, polypropylene glycols, etc., secondary glycols such :as 2,5-hexane diol, 2,6-heptane diol, etc., polymethylene glycols such as tetramethylene glycol, hexamethylene glycol, etc.

Polyesters are an excellent hydroxyl-rich starting material and a Wide variety of polyesters are suitable including polyisocyanate-moditied polyesteramides, etc. The polyesters may be branched and/ or line-ar and the useful polyesters tand/or polyesteramides may include those obtained by condensing any polybasic organic acid, such as .fadipic, sebacic, -amino-caproic, phthalic, isophthalic, terephthalic, oxalic, malonic, succinic, maleic, cyclohcx'ane, 1,2-dicarboxylic, cyclohexane-l,-4-dicarboxylic, polya'crylic, naphthalene-'l,Z-dicarboxylic, fumarie, itaconic, etc., with polyalcohols such as ethylene glycol, diethylene glycol, penta-glycol, propylene glycol, dipropylene glycol, polyethylene glycol, trimethanolethane, trimethylolpropane, mannitol, glycerol, sorbitol, triethanollamine, di-B-hydroxyethyl ether, etc., and/'or aminoalcohols such as ethanolamin'e, S-aminopropanol, 4-arninopropanol, 5-aminopentanol-1,6-aminohexanol, lO-aminodecanol, -amino-S-methylhexanol-l, p-hydroxymethylbenzylamine, etc.; and with mixtures of the above polyalcohols and amines such as ethylene diamine, hexamethylene diamine, S-methyl-hexamethylene diamine, decamethylene diamine and m-phenylenediamine, etc., and/ or amino alcohols, etc. ln the esterification, the acid per se may be used for condensation, or vvhere desirable, equivalent components, such as the acid halide or anhydride may be used.

Polyethers also represent an important class source for the hydroxyl-rich component and are particularly useful when flexibility or resilience is desired in the article. Useful polyethers may be derived fromwalkylene oxides or glycols or from Vheterocyclic ethers, such as di-oxolane, or the polyalkylene-ether-thioether glycols and the polya-lkylene-arylene-ethers, etc. The molecular Weight of the polyether glycol is preferably in the ran-ge of about 250 to :about 10,000 and polyether glycols having a molecular Weight in the range of about G-2,500 form preferred products of good resilience. Moreover, a Wide variety of adducts are useful, such as those resulting from the condensation of arylene `and alkyleue oxides and various triols and polyols, eg., trimethylol propane, pentaerythritol, sorbitol, mannitol, sugar, etc., `and mixtures of such addu'cts with minor `amounts of short chain polyols, eg., up to about 10% by Weight `of the adduct. Adducts of alkylen'e oxides and ethylene diamine and triethanolamine are also useful. Mixtures of such addncts and` polyethers in all proportions, may also be used sat.- isfactorily.

The polyisocyanates which may be employed in the reaction withthe hydroxyl-rich component include aromatic, aliphatic, cycloaliphatic fdiisocyanates and mixtures thereof and polyisocyanates in blocked or inactive form such as luis-phenyl canbamates of toluylene diisoscyanates, p,pdiphenyhnethane diisocyanate, p-phenylene diisocyanate and' 1,5 -naphthalene diisocyanate, etc. Of these types the tdiisozcyanates are preferred and While aliphatic and cycloaliphatic diisocyanates may be used, the most desirable type of polyisocyanate for the purposes of this invention is the arylene diisocyanates. Typically vlfrom the liber surfaces.

E suitable polyisocyanates include ethylene diisocyanate, ethylifdene diisocyanate, propylene-l,2diisocyanate, ibutylene-l,3diisocyanate, hexylene-1,6-diisocyanate, cyclohexylene-1,2-diisocyanate, m-phenylene diisocyanate, 2,4- toluylene diisocyanate, 1,6-toluylene diisocyanate, 3,3'di methyl 4,4' biphcnylene idiisocyanate, 3,3 dirnethoxy- 4,4dbiphenylene diisocyanate, 3,3dipheny1-4,4biphen ylene diisocyanate, 3,3'-dichioro-4,4biphenylene diisocyanate, 4,4biphenylene `diisocyanate, 4,4biphenylene diisocyanate, mixtures of 2,4- and 2,6-isomers Iott tol-uylene diisocyanates, tn'phenylmethane rtriisocyanate, 1,5- naphthalene idiisocyanate, and polyisocyanates in blocked form as above described.

As above stated, the pre-polymer is cross-linked and/ or chain extended in situ on the `fiber surfaces Iby contactingthe lcoated iibers with a cross-linking agent or accelerator and lit is not intended, for the purposes of this invention, that the pre-polymer form foam to fill the interstices `between and about the iibers. The use of Water is definitely contemplated however, and the typical Ifoam producing reaction may occur to some extent. The prepolymer selected, Where a foaming reaction is involved in the in situ polymerization, should be of insufficient viscosity, in the' thin surface ilm on the fiber surface, to entrap and'retain the gases liberated during such reaction, or at least should entrap only a minor portion of suchgases. A small amount of entrapped gas in the cross-linked and/ or chain extended polyurethane lfiber sur- Aface coating is not detrimental in many end uses for which the articles of this invention are Well adapted and in some instances such entrapped gas is advantageous.

'For most purposes, not more than about 25% or snch liberated igas should be retained and preferably less than about In any case, however, fthe portion of the 4coating or envelope for the fiber is continuously immedi ately adjacent to the iiber surface. The only additional requirements lwhich the pre-polymer must meet are that Vit be of sufficiently low viscosity or modifiable to sutciently low viscosity so that it can lbe applied to rthe fiber surfaces to fonm a substantially uniform coatingV thereon when any modifier is removed, and be insuliciently stiff or tacky to prevent the coated fibers from being carded, garnetted or otherwise arranged randomly into the desired bulk Idensity form Without iiaking `ofi? or being stripped Many of the pre-polymers Which are suitable :for fthe purposes or this :invention require the addition of a icarricr or solvent to enable a uni- [form application to the fibers, and the stiffness and tackiness is sometimes modified fby the addition `of a plasticizer to the pre-polymer solution, and pre-polymers capable oft this type of modification are to be understood to be included,

Solvents or carriers for the urethane pre-polymers inclnde any of those which are capable of :dissolving the pre-polymer without reacting and are compatible with the selected plasticizer, if any, but preferably are those which are non-flammable, eg., the chlorinated solvents. Typically suitable solvents include aliphatic hydrocarbons `such as petroleum Iether, mineral spirits, etc.; aromatic hydrocarbons such as benzene, xylene, 'toluylene, etc.; cyclichydro'caribons such as cyclohexane, tetrahydrofuran, etc.; aliphatic ketones such as acetone, methyl ethyl ketone,gunethyl isobutyl lketone, ctc.; aliphatic esters such as ethyl acetate, butyl acetate, amyl acetate, etc.; chlorinated hydrocarbons such as trichloroethylene, perchloroethylene, etc.; diol diethers such as ethylene glycol mono diethyl ether, diethylene glycol mono diethyl ether, etc.; and terpenes such as idipentene. The chlorinated hydrocanbons-arethe preferred solvents ttor the purposes of this invention.

Where the pre-polymer, per se, has a 'viscosity lower than about 2,000 cps. the presence of a plasticizer in the Saturant solution is unnecessary for the purpose of enabling the coated libers to be carded or garnetted, but asy the plasticizer normally lowers the pre-polymer viscosity, it may lbe added if desired. The plasticizer should be non-volatile at Iordinary room temperature and preferably is substantially non-volatile over a temperature range from room temperature to about 350 F., should not be reactive with the pre-polymer or solvent but compatible With the solvent and capable of rapidly reducing the prepolymer viscosity with the addition Vthereto of relatively small amounts, for example, 5%-40% by vweight of the pre-poiymer plus plasticizer. A number of materials having all of these properties have [been found to be satisfactory including the esters of phthalic, adipic, sebacic, azelaic, and stearic acids, with aliphaticrnonoatomic and diatornic alcohols having 2-10 carbon atoms such as dibutyl phthalate, dioctyl phthalate, diisodecyl phthalate, idi-Z-ethyl -hexyl adipate, idi-Z-ethyl hexyl azelate, butyl stearate and including polymeric esters of diols and dicarboxylic acids such as the reaction product ot 2-ethy1 1,3-hexanedriol and either adipic or azelaic acid. Tributyl and tricresyl phosphate have also been bound to be suitable. Another -fgroup of satisfactory plasticizers is the parafiin hydrocarbons having about l0 to 20 carbon atoms and a Viscosity or about 5 cps. to about 480 cps. and preferably about 40 Saylbolt vseconds to about 500 Saybolt seconds at F. Unusually good results have been obtained with a straight chain aliphatic petroleum oil having a lmixture of ycarbon chain lengths of from 8 to about 14 carbon atoans, and although substantially equivalent results are obtained lWith dibutyl and dioctyl phthalates, the paraiiin oils are preferred for economical and availability reasons.

The fibers which are suitable for the purposes of this invention are of various types including those oi animal, vegetable and synthetic origin, and generally speaking, the size of the fiber or fibers `is not critical. It is important that .the fibers be in the form of elongated filaments, have some inherent flexibility and be capable of passing through a card or garnetting apparatus Without disintegrating or substantial fiber breakage. Fibers possessing these requirements orf natural vegetable origin Which are suitable include cotton, hemp, jute, ramie, sisal, cellulose excelsior, abaca, etc. Typical natural animal origin fibers include Wool, silk, hair from cattle, horses and hogs; synthetic origin fibers include cellulose acetate, viscose rayon, nylon, vinyl chloride, protein base bers such as casein and soybean, chicken feathers, etc. Fibers which contain hydroxyl groups on or adjacent to their surface such as cotton land cellulosics or those which contain amino groups such as Wool :are preferred. The saturants contain radicals capable of intersreacting or cross-linking with hydroxyl or amino groups'and such libers are thought to enter into the final polymerization reactions of the saturant on the fiber surface to form the most preferred form of iber, in the fibrous articles of this invention.

The fiber diameter may vary yfrom that which is normal tEor fine technical fibers such las cotton, Wool, rayon, silk, cellulose' acetate, eg., 5-15 microns, up to that of coarse animal hairs, sisal, jute or excelsior, eg. l00-750 microns or even larger. 'It is also satisfactory to use mixtures of fibers, if desired. Unusually short fibers are less desirable than longer fibers. The fibers lare preferably at least 1/2 in length and the maximum length is restricted only by the requirement that they pass through the carding or garnetting apparatus being used. Fibers as long as Kabout 2 to 21/2" are, satisfactory and the best results have been obtained with ibers having lengths in the range of about 1X1 to about 1%". Especially good results have been obtained with kcotton libers, wool fibers, and mixtures of cotton and cellulose acetate, and cotton, Wool and cellulose iacetate. l

Generally stated, the process of this invention comprises the key steps of saturating the fibers with the saturant solution optionally containing `the pilasticizer, carding or garnetting the saturant-fiber mixture, forming fthe garnetted fibers into the desired shape and density article, and catalytically causing fthe saturant-coated fibers to cross-link and/or chain extend to thus form a unified, open fibrous article. be process employs the highly nonconventional step of carding or garnetting the fibers which are in a wet, or alternatively in a substantially solvent-free, saturant-coated condition. Attempts to garnett damp or wet fibers normally results yin clogging the garnett so badly that the operation cannot be continued. For this reason carding, and more particularly, garnetting heretofore has been performed on substantially dry fibers, and it was surprising to discover that the saturant-coated fibers could be carded or garnette'd to provide the random arrangement orf fibers and necessary bulk density thereof to enable the formation of the light-weight, porous iarticles of this invention. Moreover, yit was found ythat the step of garnetting the fibers having the urethane prepolymer on their surfaces served to wipe in, spread and distribute that pre-polymer more uniformly thereover, :and .to eliminate Iareas of variable saturant content in the fiber mass obtained from the step of saturating the fibers. During the carding or garnetting step the individual fibers are pulled and combed apart, forcefully rubbed against the `card or garnett teeth and each other many times so that each fiber becomes uniformly coated for its `full length, the wiping and numerous directional changes also serving to coat the fiber end surfaces. It is believed that this step is chiefly responsible for the high degree of unformity of the resulting products, their superior resistance to water and high humidity moisture and the uniformity of quality Ifrom piece to piece.

ln order to satisfactorily pass across the card `or garnett without packing or clogging, the viscosity of the saturant on the fibers should be relatively low, for example, between about 25 and 750 cps. tained by adding a sufiicient quantity of solvent or carrier to the selected prepolymer, to lower its viscosity to within this range, or a plasticizer may be added to the pre-polymer prior to the laddition `of the carrier. lt has been found .that the saturant coated fibers may be passed over fthe garnett with varying quantities of the carrier still present in the saturant, for example, from an amount as high as about 40% of the saturant to a saturant subi stantially free of the carrier. When the carrier is present in a substantial amount at the :time of carding or garnetting, the process is considered a wet process, and when substantially Iall of the carrier has been removed prior to orienting the fibers, the process is lconsidered a dry process. ln the dry process, a plasticizer is necessary to maintain the needed low viscosity in ythe saturant after the carrier is removed, and as above indicated about to about 40% in the weight of the pre-polymer and plasticizer of one of the above named plasticizers is satisfactory for this purpose. ln any particular saturant, the proportion o-f the carrier which is added is selected so as to form the desired quantity of urethane resin :on the fibers of the finished product, since the resin solids which remain Ion those fibers is a function of the concentration of the resin solids in the saturant applied toy the fibers. Fibrous materials having between about 5% to about 35%, by weight olf the total, of resin solids on fthe fiber surfaces are formed in accordance with this invention, and the saturant solutions to produce such materials may contain from about 5% to about 50% pre-polymer tor pre-polymer plus plasticizer solids, and from about 50% to about 95% of carrier. Preferably, the saturant solutions contain from about to about 35% of resin solids which may be pre-polymer solids or pre-polymer plus pl-asticizer solids.

The process is illustrated more completely in the drawings wherein:

FIGURE l is a diagrammatic flow sheet of the wet process; and

FIG. 2 is a diagrammatic flow sheet of the dry process.

Referring to the wet process, the illustrated process is Such low viscosity is at- 6 abbreviated to the extent that the saturant urethane prepolymer is preliminar-ily formulated with carrier and/ or plasticizer in accordance with the above generally discussed considerations. The first step in the process comprises the saturation of the fibers with the selected saturant urethane pre-polymer solution. Saturation is accomplished by immersing the fibers in the saturant solution and thereafter removing the excess saturant. This is conveniently done by positioning the fibers between a pair of screen aprons which advance the fibers to a series of compression rol-ls immersed in the saturant `solution and by the passage of the fibers between the compression rolls a `thorough `and uniform impregnation is effected. When the fibers wet with the saturant are removed from the saturating solution, the excess ysaturant is removed by centrifuging the mass or by passing it through another ser-ies of compression rolls. `By either method it is desirable to remove the saturant until the residuary quantity left lin the mass -is in the range of about 5% to about 50% and preferably about 20%-30% by weight of the total mass. As the proportion of residuary saturant which is left in the mass of fibers to be oriented,4 by carding or'garnetting, increases, the ease with which the fibers pass over the garnett decreases, and it is desirable to reduce the rate of feeding of the coated fibers across the garnett. On the other hand, it has been `found that the presence of a substantial quantity of the carrier in the fiber ma ss to be `garnetted enables the successful garnetting of fibers more inexpensively than by reducing the viscosity of the pre-polymer with plasticizer. i,

The fibers are then gar-netted and in the case of a saturant containing a high proportion of carrier, the degree of volatilization of that carrier during gametting is sufficiently high to justify the use of collecting means for the volatilized carrier to enable its reuse. 'I'he garnetted fibers which come from the garnett in the form of fluffy, thin webs `of oriented fibers are positioned on screen aprons and the webs are piled or laid over each other until a sufiicient weight of material is present to for-m ythe desired thickness of material of the desired density. The desired density is obtained by pressing the screen aprons together to compact the webs therebetween, and control of density and uniformity of product is achieved by compressing the screen aprons to a similar degree each time for any given density. The coated fibers can be polymerized into an open-textured network in which the bers are bonded to each other `at their points of contact at varying densities between about 0.5 and about 5 lbs/cu. ft. At the lower extreme the articles are self-sustaining and retain their shape and are excellent for use as insulation materials, sound deadening and the like, although they will not :support heavy sustained loads. As the density increases toward about 1.0 the articles become more` resilient and increasing densities increase the capability of supporting heavier loads. The compressed webs positioned between the screen aprons are preferably then heated to a temperature in the range of about F.-300 F., and contacted with. a catalyst which may be water vapor or water vapor including a catalyst to thereby cross-link and chain extend the prepoly-mer. The water vapor is normally introduced in the form of steam which should not be superheated but is preferably in a saturated condition.

Catalysts which are particularly suitable for this purpose are the steam distillable volatile tertiary amines such as isopropyl amine, triethanolamine, n-methy-lamine, n-ethyl amine, n-ethyl morpholine, etc. Such amines may be added directly to the steam or may be added to a boiling water bath and allowed to vaporize and rise through the pressed web of fibers. Cross-linking land/or chain extension of the urethane prepolyrner ordinarily occurs under these conditions in a relatively short time, 'for example, between about a half and five minutes, but conversion times as long as about one hour have `been experienced. The

'by the use of compression rolls. the temperature of the fibers to within the range of about employed in the -wet process.

time rwhich is required may be reduced by increasing the proportion of volatile amine which is present and fby in- -creasing the temperature toward the upper limit above suggested.

After reaction the excess catalyst removed by drying in air and prefer-ably 'by forcing hot air through the compressed webs, for example, -air at `a temperature of about 300 F. for 5-30 minutes. The material is concurrently dried and freed of excess catalysts 'by this procedure and is the product of this invention.

The dry process illustrated in detail in FIG. 2 differs primarily vfrom the Wet process in the third step which involves feeding the fibers into an oven to remove the carrier which remains in the saturant after the excess has ibeen removed in step No. 2 either by centrifuging or For this purpose raising 250-350 F. for 5 to 10 minutes is sufiicient to remove substantially all of the carrier which is present and under these conditions the fibers 'which Iare then -garnetted contain about 5% to about `40%` of saturant by weight of the total, and preferably about 25% to about 30% of the total. After garnetting the steps of compressing and cross-linking or curing the urethane pre-polymer in situ on the fiber surfaces are substantially the same as ere The removal of any excess catalyst which remains may be accomplished by merely leaving the .cured Vfibrous .article in open yair for ya few hours for force `air dried ras above indicated. As above indicated,` the saturantyfor use in the dry process nor- Vmally includes plasticizer and lfor this purpose a preferred Avjacent fibers are not bonded together and the web is easily shaped, molded or formed vto .any desired thickness and configuration. The webs are folded or laid one over the other :on the screen aprons until the weight lof fibers will produce the 'desired bulk density. 'Ilhe weight of the urethane pre-polymer on the fibers )does not change appreciably `during polymerization, and control of the bulk density lby Weighing 'the prepolymer coated fibers is completely satisfactory. Fibrous materials having bulk kdensities inthe range of about 0.5 to 5 pou-nds per cubic foot can be fabricated by using this procedure, however, materials having a bulk-density in the range of 0.8 to about 2.5 pounds per ycubic foot yare preferred.

The below given examples illustrate the typically useful saturant solutions, conditions for use in the method for 'this invention and the product which is obtained but it is to be understood that they are intended for illustration only and do not set forth the definitive limits of the proportions of materials and conditions of operations which have been given hereinabove.

Example l A urethane pre-polymer was prepared by placing 1.022 grams of toluylene di-isocyanate in a nitrogen atmosphere vflask and to this material 3,670 ygrams of polyoxypropylene was rapidly `added with stirring while the solution was heated rapidly to 120 C. and kept at that tempera-V ture for an hour and then cooled down to form the urethane pre-polymer. The polyoxypropylene employed was that available commercially under the designation v Niax PPG 2025, having a molecular weight of 2,000, a

hydroxyl number of 56, and a specific gravity of 1.005. The toluylene diisocyanate used was an 80e20 mixture of the 2,4- and 2,6-isomers. rThe urethane prepolymer, upon analysis, Was found to have an NCO content of 7.0% and a viscosity of 3,350 cps.

' substantially all of the trichloroethylene.

vand an analysis of this mixture showed it to contain 8.9%

NCO by weight. Twenty-six pounds of trichloroethylene was then added to this mixture to produce a saturant solution having a viscosity of 5 cps.

Two pounds of fibrous material containing 50% by weight of cotton linters and 50% by weight of cellulose acetate was then saturated in this saturant solution. The cotton linter fibers had `an average length of about j/2" with individual fibers varying from about 1/16 to `about 1%, While the cellulose acetate fibers were uniformly 1%6" in length. The fibers were saturated by immersing them in the saturant solution and, 4while immersed, they were passed between rubber compression rollers to thoroughly impregnate the fibers. Upon removal from the saturating solution, the fibers were centrifuged in a 12 radius centrifuge operating at 1200 r.p.m.` for 5 minutes. The centrifuged fibers were then positioned in an air atmosphere oven and heated for 10 minutes at 250 to remo-ve the trichloroethylene. The saturantcoated fibers, after drying, contained 20% by Weight of saturant and of bers. The saturant coated fibers were then fed slowly to a garnett at a uniform rate and the oriented fibers from the garnett were laid up on a screen apron having the size of 68"-25 by lapping the webs from the garnett until a total of 2.25 pounds was positioned thereon. A top screen apron was then positioned over the lofty fibrous Webs and pressed down until the bat had a thickness of 11/2. The screen aprons with the saturant coated fibers therebetween -were positioned in a vapor phase reactor at a temperature of 250 F. and contacted by the vapor resulting from boiling N-methyl morpholine in water beneath the fibrous pad. The time of contact between the fibers and the vapor azeotropic catalyst was about one minute and the screen aprons were removed from the vapor phase reactor and immediately positioned in an oven at 250 F. and maintained there for ten minutes. Upon removal from the oven, inspection of the pad showed Vthat it was a dry, self-sustaining rectangular pad of open texture in which the individual fibers were bonded to the contacting fibers at their points of contact. The pad had a density of 1.5 pounds per cubic foot and good resilience as determined by the standard falling ball test, that is a 1A diameter steel ball dropped from a height of 60 centimeters. The recovery was 54% which vcompared favorably with that which is characteristic of polyurethane foams.

Another quantity of the above described urethane prepolymer was formulated into a saturant solution containing 22.5% of urethane pre-polymer, 2.5% paraffin oil, of the type above specified, and 75% trichloroethylene. One pound of cotton fibers containing fiber lengths varying from about 1/16 to about Vs", were saturated by immersion in the saturant solution and passing lbetween squeeze rolls while immersed, and again after removal from the saturant. The saturated fibers were then dried at F. for 20' minutes to remove The saturantcoated fibers were fed to a garnett and the oriented fibers therefrom were collected on the above described screen apron by lapping the webs from the garnett until a total of 4.3 pounds was positioned thereon. The lofty fibrous webs Were then pressed down until the fibers had a thickness of 11/2" and the assembly was positioned in a vapor phase reactor at a temperature of 200 F. The pre-polymer was polymerized by passing the vapor from boiling water containing N-methyl morpholine upwardly through the fibrous mass for ten minutes at 200 `F. The assembly was then dried for 20 minutes at 200 F. in an air atmosphere furnace and upon removal of the screen aprons the bat was found to maintain its shape and to be of open porous texture.

A density determination showed the bat to have a density of 2.9 pounds per cubic foot. Portions of the bat were then subjected to a compression load deflection test in accordance with the recommended practice formulated by the SAE-ASTM technical committee on automotive rubber. The test is designed to measure the load which is necessary to produce a 25%, 50% and 75 compression over the entire top area of the urethane `foam specimen. Three specimens from the 68 X 25" x 11/2 bat having a size 2" X 2 x 11/2 and parallel top and bottom surfaces, were tested and the values reported for each degree of compression represent the mean value of the three samples. After first compressing the specimen, 75% of its original height twice,`

and allowing the specimen to rest for ten plus or minus minutes, the specimens were preloaded at 0.02 pound per square inch of the specimen area, the height then determined and a sutiicient load applied to the specimen to reduce its height by 25% of the height measured under 0.02 pound per sq. inch load. The load required, after one minute, -was recorded as the 25% compression load deflection. A similar procedure was employed for the 50% and 75% compression load deection determinations except the amount of the applied Iload was changed. The specimens had compression load deflec tion values as follows: 25%-0.30 pound per square inch; 50%-083 pound per square inch; 75 7a-4.85 pounds per square inch.

Resilience was tested by the standard falling ball test and `the pad was found to have a 47% recovery. These properties make the pad highly suitable for use in cushioning applications, as well as for sound deadening and insulation purposes.

Example Il The urethane pre-polymer ydescribed above in Example l but having an NCO content of 7.3%, was admixed with a lubricant and solvent to form la saturant solution containing 30.8% urethane pre-polymer, 7.7 paraiiin oil (Bakelite 1010), and 61.5% trichloroethylene.

Cotton, having iiber lengths similar to those stated in Example I, was saturated by immersion in the saturant solution, passing the cotton between compression rolls below the surface `of the solution, as well as compression rolls to remove the excess upon withdrawal. The sarnple was then slowly fed to a garnett, collected on screen aprons to form x 115" x 11/2 thick bats and then, while supported on the aprons, the bats were subjected to saturated steam in a vapor phase reactor at la temperature at `about 130 F. for 30 minutes. The screen apron assemblies were then positioned in an air circulating oven at 165 F. for one hour and an inspection `of the resulting hat showed that the urethane pre-polymer on the liber surface was incompletely polymerized and still partially had the characteristics of the urethane pre polymer.

The saturant solution was modified to one having a higher NCO content by the addition of toluylene di isocyanate. The modified saturant contained, in weight by percent, 30.5% urethane pre-polymer, 0.9% toluylene diisocyanate (80/20), 7.6% paraiiin oil (Bakelite 1010) and 61% trichloroethylene. This saturant was applied to cotton in the same manner as described above and, after 1i) minutes of vapor phase treatment in steam at 130 F. in the same reactor, the pad was detected to be alble to retain its shape. After minutes in the reactor, the pad was removed and positioned in a circulating -air oven at 165 F. for one hour. Upon withdrawal from the drying oven, the pad was found to have good shape retention, `a density of 1.1 pounds per cubic foot and to have an open texture porous structure.

i Example III A urethane pre-polymer was prepared in accordance with the procedures generally described above in Example `I by lcombining the adduct of propylene oxide and 1,2;6-hexanetriol having a molecular weight of 4400 and a hydroxyl number of 38 with toluylene diisocyanate in suoient quantity to produce a prepolymer having an NCO content of 10%. This reaction product was modiiied by combining `80% of the pre-polymer with 20% yot didecyl phthalate. A saturant solution was prepared by adding a carrier to form a saturant solution containing, in percent by weight, 7.14% ofthe modiiied urethane pre-1 polymer -and l92.86% of methyl ethyl ketone.

Thirty pounds of this saturant solution was positioned in a container and ten pounds of cotton was saturated in the saturant, compression rolled 'and thereafter dried in a `circulating air oven for twenty minutes at 180 F. After drying, it was determined that 1.7 pounds of resin solids were present on the ten pounds of cotton iibers. The drying step removed only a part of the methyl ethyl ketone and the wet saturantcoated cotton was slowly fed to the garnett with the resulting oriented fiber web being accumulated on screen aprons to form bats having a size 15" x 15" x 11/2. The bats were positioned in a vapor phase oven at 250 F. and polymerization was induced by vapors from boiling water containing sufcient N-rnethyl morpholine to form the azeotropic mixture and this contact was maintained for 10 minutes. p Thereafter the cotton 'bat was air dried at a 'temperature of 180 F. for ten minutes. Upon inspection, the bats were found to have good shape retention, Jgood resilience, `a density strength anda fair recovery from compression set.

Example I V A urethane prepolymer was prepared by interreacting a polyester and toluene diaisocyanate reaction under generally the same conditions as those set forth in Example I. The polyester employed was `a condensation product of cli-ethylene glycol and adipic acid, having a hydroxyl number of 60. .The (ii-ethylene glycol adipate was admixed in a ratio of one to one, by weight, with tri-methyloi propane .and this admixture was reacted with toluene diisocyanlate to form a prepolymer having an NCO content of 11.6% and a viscosity of 5,000. This prepolymer was admixed with carbon tetrachloride to form a saturant containing 16.7% urethane prepolyrner and 83.3% carbon tetrachloride. 45 pounds of this saturant solution was positioned in a container and 15 pounds of cotton, of the type described in Example l was saturated in the solution, the excess removed and the saturant coated cotton thereafter dried for 20 minutes in an oven at 180 F. The ipartially ldried saturant-coated iiber mass was garnetted and the garnetted tibers were positioned on screen aprons to produce bats having a size of 15" x 15" x 11/2. The screen apron assemblies were positioned in the vapor phase reactor land the urethane prepolyrner further polymerized by contact with a steam N-methyl morpholine azeotropic mixture, obtained by boiling water containing an excess of N-methyl morpholine below the pad, and this treatment was continued for ten minutes at F. Thereafter, the converted librous mass was dried in an oven for 30 minutes at 230 F. .After drying, an inspection of the bat showed that it retained its shape, had a density of 1.6 pounds per `cubic foot and had a 34% recovery in the standard drop `ball test. The resiliency of the product was suicient to make it suitable as packing material for parts requiring a resilient support dur-ing shipment.

Example V This example illustrates the effect of the proportion of resin solids in the saturant on the characteristics `of the resulting lbrous products.

The urethane prepolymer described above in Example HI was admixed with tri-chloroethylene lto produce a 1 l series of saturant solutions `containing varying resin solids concentrations as set forth in tabular form below.

Percent Percent Urethane Tri-Chloro- Sample Prepolymer ethylene Solids In separate one-gallon samples of each of the above saturant solutions 1/2 pound batches of cotton bers, of the type described in Example I wene saturated and the excess removed in pressure rolls. Thereafter, the saturated bers were garnetted without intervening drying. Each of the batches of saturant-coated cotton bers were successfully garnetted and the oriented bers from each sample were collected on screen aprons to :form a bat having a size of l5" x 15" x 11/2. The samples were positioned in a vapor phase reactor and the prepolymer further polymerized by contact with the azeotropes obtained by boiling water containing an excess of N-methyl morpholine and the contact was continued for 10 min` utes at 185 F. The bats were then dried at 185 F. in a circulating air oven for 20 minutes and thereafter subjected to the compression load deflection test described above in Example I. The results of these tests are set forth below in tabular form and :a typical polyurethane rubber, useful Afor cushioning and padding applications, is also shown for comparative purposes.

From these results it may be seen that saturant solutions containing as little as 1.6% urethane prepolymer solids, sample No. 7, form articles having resiliency characteristics which are suiciently close to the standard to make them suitable for use in a variety of cushioning applications. AIt may also be seen that as the proportion of prepolyrner solids increases, the density of the resulting article also increases, but not necessarily in straight line proportion, and the compression resistance is higher .for the denser articles. Resiliency as evidenced by the standard ball drop test shows a general decrease as the density decreases.

Example VI The modied urethane prepoly-mer described above in Example 3 was used to form a saturant solution containing 24% ofthe prepolymer, 16% di-octyl phthallate and 60% tri-chloroethylene.

A production size batch of treated bers were prepared by saturating approximately '200 lbs. of cotton bers, having the specifications described in Example I, in approximately 600 pounds of the saturant solution. The saturated cotton was Withdrawn and centrifuged for one minute in a one-foot radius centrifuge operating at 1200 rpm. The centrifuged bers 'were then dried in an air atmosphere oven at 150 F. for 30 minutes to remove substantially all of the tri-chloroethylene.

12 The lubricant containing prepolymer Vcoated bers were then garnetted and the oriented garnetted webs were collected on screen .frames having a size of 7 x 3' and suicient bers were collected to produce a bat having a thickness of 11/2 and a density of about 1.85 pounds per cubic foot. The screen frames with the gametted bers therebetween were subjected to the vapors of a boiling water-N-methyl monpholine solution at 200 F. `for ten minutes. The bats were then dried by position- 0 ing them in an air atmosphere oven at 185 F. for 30 minutes. Upon withdrawal, the bats were inspected and found to be open-textured, resilient materials having a density averaging 1.85 lbs. per cubic Ifoot. A number of samples taken Afrom various locations inthe 7 x 3 x 11/2" bat showed the density to be substantially the same throughout, the variation being only y0.05 pound per cubic foot.

Samples of the bats -were subjected to the above described compression load deflection test. The load required to compress a sample 25% of its original height was 0.25 pound per square inch. The loadrequired to compress a sample 50% of its original height was 0.76

, pound per square inch. The load required to compress a sample of its original height was 2.53 pounds per square inch. The bats were also tested .for resiliency by using the standard falling ball test and found to average a 52% recovery. The bats were found to be excellent for automobile seat padding, and also useful for insulation and sound deadening uses.

Example VII A urethane pre-polymer prepared in accordance with the procedures outlined in Example 3 was converted into a saturant solution by adding additional didecyl phthalate and trichloroethylene thereto to form a saturant solution containing 20% of the modified urethane pre-polymer, as described in Example 3, 5% didecyl phthalate and 75 tri-chloroethylene.

Sisal bers having a uniform length of 11/2 and an average diameter of about 0.01" were immersed in the saturant, passed through squeeze rolls within the solution, Iwithdrawn and positioned in a centrifuge. 'Ilhe centrifuge was a 12" radius centrifuge and was operated at 1200 rpm. for 11/2 minutes. The saturant coated sisal bers -were then positioned in an air circulating oven at F. for 15 minutes` and upon removal the mass contained about '80% ber and 20% saturant, by weight. The saturant coated bers were then garnetted and the oriented bers from the igarnett Were laid up on screen aprons to ,form bats having a size 15" x 15, and suiicient bers were positioned on the aprons to produce a bat having an approximate density of 1.8. After the top screen was positioned on the bats and the height of the bers reduced to 11/2", the screen aprons were positioned in a vapor phase reactor at a temperature in the range of F.-205 F. and at this temperature the urethane pre-polymer |was Lfurther polymerized by contact with the mixture of steam and n-methyl morpholine, actually the azeotrope produced by boiling water containing an excess of n-methyl morpholine in a vessel below the bers, and the contact between the bers and the polymerization catalyst was maintained for rive minutes. The screen aprons were then wit-hdrawn from the vapor phase reactor and positioned in a drying oven at 150- F. for I10 minutes. Upon withdrawal from the drying oven, an inspection of the bers showed that they were united at their points of contact, of open-texture and maintained the original shape of the space between the screen aprons. A determination showed that the density of the bats averaged 1.8. The bats were subjected to the standard fallingrball test and recoveries were obtained on different ones of the bats and at diierent locations thereon between about 60% recovery and about 75 recovery.

Specimens from lthe sisal pad were subjected to the t 13 standard constant deliection compression set test under the conditions established by the SAE-ASTM Technical Committee on Automotive Rubber. The test is conducted under the following conditions: 2 X 2" X 2" X 1 specimens were conditioned for 3 hours by positioning them in a controlled temperature and relative humidity atmosphere, the temperature being 73.4,`plus or minus 2 F., and the relative humidity being 50, plus or minus 2%. After conditioning, the specimens were withdrawn and their height measured and xthe specimens then positioned between two fiat plates arranged so lthat the plaftesare held parallel to each other by bolts or clamps and the space between the plates is adjustable tothe required defiection height by4 the use of spacers. rPhe 4'specimens were then defiected by 50%, plus or minus `height after wm'ting 35 minutes, plus or minus 5 minutes,

from the time of removal from the oven. Each reported value represents the mean of the values obtained from three specimens. The constant deflection compression set value is expressed as a percentage of the original height in accordance with the following formula:

ozio-z,

where C=compression set t=original thickness of specimen t1=thickness of specimen after removal from apparatus tsi=fthickness of spacer bar used The sisal samples subjected to this test were found to have a compresison set of :cumple VIII This example illustrates multiple saturation procedures to increase `the quantity of saturant on fiber surfaces wihere desired,

Baits, produced in accordance with the procedure of Example 3, in their completely polymerized and final form were re-saturated in the satunant of Example 3 by immersing the bats in the same saturant container and passing the bats between squeezerolls while immersed in the saturant solution. The excess saturant was` removed by passing the bats between squeeze rolls outside the saturant solution and the bats were then repositioned in the vapor phase reactor. The saturant on the fiber surfaces which was added by vthe second immersion step was further polymerized by a ten minute contact with the iazeotropic mixture of n-methyl morpholine and Water. Thereafter, the bats were dried in an air atmosphere drying oven at 180 F. for 10 minutes. An inspection of the bats after drying showed that the additional saturant was polymerized and the fibers were joined together at their points of contact by the extra saturaut as well as the original saturant. By weighing the samples, it was determined that between 50% and 75% of the original content of saturant was added by the saturating procedure. Samples of the re-saturated polymerized bats were subjected to the standard fahing ball tests and it was found that the resilience was improved by an amount between about 3% and about 8% of the original recovery values for the singly saturated bats.

What is claimed is:

1. A method for forming an open texture fibrous material which comprises the steps of (1) saturating fibers with a saturant comprising a urethane pre-polymer in a solvent to form a mass containing about %-50% 14 fibers and about 50%-85%, by weight of the total, of

`said saturant, (2) removing a pontion of said saturant `to form a mass of fibers containing about 501%-95% fibers and 5%-50%, by weight of the total, of said sa-turant containing less than 40% solvent, said saturant having a Viscosity in the range of about to about 750 cps., (3) passing said `mass of fibers from step 2 over a garnett to directionally orient said fibers and uniformly distribute said saturant over the surfaces thereof, and (4) polymerizing said urethane pre-polymer in situ on said fibers so as to bond said fibers to each other ait the points of contact.

2. A method in accordance with claim 1 wherein said fibers have lengths in the range `of about '1/2 inch to about 2 inches.

3. A method for forming an open-texture fibrous ma'- terial which comprises the steps of (1) saturating fibers with a saturant comprising a urethane prepolymer and about 5%-40% of a plasticizer, by Weight of Said prepolymer, and a solvent to form a mass containing about 15%-50% bers and about 50%-85% by weight of the total, of said saturant; (2) removing a portion of said saturant and thereafter removing substantially all of said solvent from the remaining said saturant to form a mass of fibers `containing about 60%-95% bers and 5%-40% by weight of the total of the residuary said saturant having a viscosity in the range of about 25 cps. to about 750 cps.; (3) pasing said mass of fibers from step 2 over a garnett to thereby uniformly distribute the residuary said saturant over the surfaces of said fibers and directionally arrange the same, and (4) polymeriziug said urethane prepolymer in situ on said fibers so as to bond said fibers to each other at the points of contact.

4. A method in accordance with claim 3 wherein said plasticizer is selected from the group consisting of the esters of phthalic, adipic, sebacic, azelaic and stearic acids with aliphatic, monatomic and diatomic alcohols having 2-10 carbon atoms and said carrier is a chlorinated hydrocarbon.

5. A method for forming an open-texture fibrous maferial which comprises the steps of (1) saturating fibers with a saturant comprising a urethane prepolymer and about 5%-40% of a plasticizer, by weight of said prepolymer, and a solvent to form a mass containing about 15 %-50% fibers and about 50%-85% by weight of the total, of said saturant, (2) removing a portion of said saturant ,and thereafter removing substantially al1 of said solvent from the remaining said saturant to form a mass of fibers containing about Gil-% fibers and 5%-40% by weight of the total, of the residuary said saturant having a viscosity in the range of about 25 cps. to about 750 cps., (3) passing said mass of fibers `from step No. 2 over a garnett to thereby uniformly distribute the residuary said saturant over the surfaces of said fibers and directionally arrange the same; (4) passing a polymerization-promoting agent through said garnetted fibers to thereby effect in situ polymerization of said urethane prepolymer and join lthe fibers to each other.

6. A method for making an openftexture fibrous material which comprises the steps of (l) saturating fibers with a saturant comprising a urethane prepolymer and about 5%-40% of a plasticizer, by weight of said prepolymer, and a solvent to form a mass containing about 15 i2-50% fibers and labout 50%-85% by weight of the total, of said saturant, (2) removing a portion of said saturant and thereafter removing substantially all of said solvent from the remaining said sarturant to form a mass of fibers containing about 60 %-95% fibers and 5%-40% by weight of the total, of the residuary said saturant having a viscosity in the range of about 25 cps. to about 750 cps.; (3) passing said mass of fibers from step 2 over polymerization-promoting agent through said garnetted residuary said saturant over the surfaces of said fibers and directionally arrange the same, (4) compressing said garnetted fibers into a mat having a density in the range of about 0.5- lbs. per cubic foot, and (5) passing a urethane prepolymer and join the iibers to each other.

7. A method in accordance with cla-im 6, wherein said polymerizationpromoting agent is steam.

-8. A method in accordance with claim 6, wherein said polymerization-promoting agent is steam containing a small amountof a volatile-tertiary amine.

V9. A method in accordance with claim 6 wherein said and n-mcthyl morpholine.

l10. A method for l'forming an open-texture ibrous materiaifhaving a bulk density in the range of about 0.5 to about 5 pounds per cubic -foo't which comprises the steps of (1) saturating iibers with asaturant comprising a urethane ,pre-polymer ein a solvent to form a mass containing about 15%-50% bers and about 50%-85%, by weight Aof the total, of said saturant, (2) removing a `portion of said saturant to form a mass of bers containing about 50%-95% fibers and 5%-50%, by Weight of the total, 'of said saturant, said saturant having a viscos- .polymerizationpromoting agent is a mixture of steam ity in the range of about to about 750 cps., (3) passing said mass of fibers from step 2 over a gamett to directionaliy orient and arrange said fibers and uniformly distribute said saturant over the Vsurfaces thereoff,

and collecting the webs of directionally orientedbers from said garnett and forming the same into an article having -a density in the range of 0.5 to about 5 pounds per cubic foot.

References Cite-1l in the le offthis patent UNITED STATES PATENTS 2,288,072 Collins June 30, 1942 y2,440,399 Hill Apr. 27, 1948 2,477,555 VRoberts et al. July 26, 1949 2,657,151 Gensel et all Oct. 27, `1953 2,723,935 Rodman NOV. 15, 195.5 2,734,841 Merriman Feb. 14, 1956 2,792,325 Downing et al. May 14, 1957 2,826,526 Meyrick etal. Mar. 11,1958

FOREIGN PATENTS i Great Brita-in Aug. 3, 1955

Claims

1. A METHOD FOR FORMING AN OPEN TEXTURE FIBROUS MATERIAL WHICH COMPRISES THE STEPS OF (1) SATURATING FIBERS WITH A SATURANT COMPRISING A URETHANE PRE-POLYMER IN A SOLVENT TO FORM A MASS CONTAINING ABOUT 15%-50% FIBERS AND ABOUT 50%-85%, BY WEIGHT OF THE TOTAL, OF SAID SATURANT, (2) REMOVING A PORTION OF SAID SATURANT TO FORM A MASS OF FIBERS CONTAINING ABOUT 50%-95% FIBERS AND 5%-50%, BY WEIGHT OF THE TOTAL, OF SAID SATURANT CONTAINING LESS THAN 40% SOLVENT, SAID SATURANT HAVING A VISCOSITY IN THE RANGE OF ABOUT 25 TO ABOUT 750 CPS., (3) PASSING SAID MASS OF FIBERS FROM STEP 2 OVER A GARNETT TO DIRECTIONALLY ORIENT SAID FIBERS AND UNIFORMLY DISTRIBUTE SAID SATURANT OVER THE SURFACES THEREOF, AND (4) POLYMERIZING SAID URETHANE PRE-POLYMER IN SITU ON SAID FIBERS SO AS TO BOND SAID FIBERS TO EACH OTHER AT THE POINTS OF CONTACT.