[1]0 3919;82677 Ullited States Pateiat Office 3,193,677 FOAMED POLYURET7-t'ANE GAS-GEP@ TZRAT-7rT@'@' C(I'@IPOSITIONS C-3iNT.,UNING INORGANAC ox@Dlz:,::Iz Richn@-d Ogdzn Tlio-@nas, Alexard-r'4a, ase@rnor 'IO 5 Atz'-qr.'@'le Research Fairfax, a corpo@f N3 DraY'Vliig. Filed July 27, 19@L2, Ser. No. 213,C,)Ao 14 149-19) 10 Ti-iis invenlion relates to ener.-etic seli.-combustible ,cellul@ar plastic compositions. The object of the inv@--iltion is to provide ce"@ltilar org-qnic polyrier compositions w'i-iich u-@ider,@c> selfsusta;ned co,-nbustion. 15 Anoth--r obj,'Cct is to p.@ovide solid cell-alar i@ioTioprop--'- lar.t copipositioiis ol. un;que i-itility because o@j'- tiieir specia' p'iysical and ballistic proll--rti--s. Other objecls and idvaita.-Ps will becom,- obv7ous from the following detailed descr-;,rtio@i. 20 Broadly speal;,'@n,-, m@ y ipvention comp.-Ises formin.- a compositio-@l containin@ an oxidizer coripoiicnt ir.@lo ,t so@id cellti,ar or foarr@ed stri-,c'Ltire, at le-,-,t oile comporient of which is a solid or-anic polv-rrier b-@Tider. L,l ter@ns of chemical coi-npositio-n, any sol".d, se',Ifsvstainin-, gas--.D-.ratirl- or monopropellant - comr3ositioil, containin@ an or.@anic .,3olyi-per binder known to the art can b-- employed for my purpose so loi- as it is formed physica'ly ir@to a cellular structure. Any of the s.-verall ;Cwell-known foar@ling t--chnin-ues applica:ble to th@- part. 30 ular pc)iymeric binder comT)one-@it of 4,he composition c,-,ii b.- used to produc@- the foamed combtistible structure. The or.-anic bin@',er can be any suitable cardonandhydro.-en-contai@i;n,@ 1)olymeric binder cr@i_pl@oye@d ii the pro!)el!aTit art. It car. -be an active or oxidant-type polyir.er, namely one conta,.nin,@ P-.olecu larly-con@bined oxidizin.@ element, stich as oxy.-en or fl,,iori-Tic, available for combi,-stion or oxidel-lon of ot@er mo lec,,ilarly-conibiied cor.,iponents of said polymer, such as nitrocellulo@e. It can also (and more go-ierally) be an ;nert or,--,In;c poly- 0 m,-r, @-iarnely one v,,hich does not contain combined oxy.-en or other ox:@d,'.Zin,@ eleiii--nt available for combustion and th,-refore reqtiires the addition of a s--parate or extern,al oxid;Zer compound for corftbustion. Exami.3ics of such rolvmers incii,-de t,ic vinyl polym-ers sucli as 45 poly-w'@nyl chloride, polyvinyl ac@-tate and tolystyrei-.e; c--',Iulos,- esters, such as celltilose acetate; cell@tilose ethers, slich as ethyl cellulose; polyuretha-pcs; polyepoxi.-s; hydrocarbon rolymers, such as polyethylene ar@d pol.3@propylene; laolymerized acrylic ind ir-ethae@-ylic acid esters 50 ar.d tmides; urea-al"ehyde aid oher@ol-aldehyde pol,,,merssynthetic rtibber pol,,,M.-rs, such as styren ---btitad'@-'.'IC COpo'ymers, buta,-Iien@--acrylonitril@e copoly.,iiers. neopreiie, a c-.polymer of 1, 3-batadiene and 2-vinyIDyridi@--le, a copolymer of 2-methoxy-3-ethylhexadiene ai.,d 3-vi-,i,71- iso- 55 qi-,;nol-;-Tle ard tle l-"ke. As is conventional bot'@i ip the orqanic nolymer ai7t and in the s@-!,'d propellant art, th.- or.@an,'@c polymer bir@d-or can be plasticized with a stiitable or.-anic liquid -IasLicizer to impart or to im!nrc)vc desired pfiysical ai-id ballist;c 60 propert@@'es. The plasticizer can be an ox' 'e-ant-t,,r.e lio@,iid containing active oxidiziii, a @roups such as nilro, niLr@l',c, nit@-ite and nitroso @-ouDs, e.g. nitro-lycer@ne, diethylene ,-iyeol dinitrate, penta--ryLhrit-ol trin,trate, 1,2,4-trinitrolc liquid plasticizci,-, 65 butane ar@d the 'iike, or -iiiert orgai3@, which fiinction as an aoditional flcl coin@ponent, as, for exar.qple, sebacat,2s, su,.ch as dib,-,tyl s.-bacate and dioetyl sebacat.-; phthalates, stich as dibu,N,71phLha-late aiid dioctyl Dlithalate; adipates, such as dioctyl adi,,jate; .-lycol esters of high--r fatty acids and the like. 70 The -as-generat-n- or r-ionor)ropellaiit compc)sit,'@o@l ca.'l b.- of :Cn-c dot,.bi.--base iyi,--, suc' i as -iitrocelltilos-- olasticPA'@-.en-teci Aug. 3,1965 2 ized with an oxid@ant-tN,,P,e organic liquid plasticizer as aforei.--scribed, such as nitro.-lycerir@e, or a mixttire of s@,ich a-@i oxidant-type plasticizer with an inert organic rlqtiid p'asticiz,-r, as aforedescribed, Til,.- gas-gencra'@ing or monopropellant composition can alsc) be of th-- conveitiorial composi,e type, namely of t'@ie typ,- which con@,qins, in addition to a fuel compourd, s,,ich as the organic @ol3tmer binders a'o-redescribed and/or 1 pl,,isticizer if present, a homogene@ously dispersed, solid, insc@itible, fi-.iely-,Iivided oxidizer. Any insoluble solid oxidizer colitainiii,@ an o---idizing component, such as Oxygcii, Pliorine, chlorine atid the like, r--adily availabl-. fcr combust;on, can be employed for my purpose. Such oxid@z@-rs are well lno@vn in the propellant art. They for example, inorgar@,c oxidizer salts, slich as the Na, K, and Li chlorates, perchloratos, and nitrat@,s; metal peroxides, si-ich as sodium, X a-,id Pb peroxid@-; hydr-azine nitroformate; or.aarilc oxidizers, such as pentacrytlir@itol totran 4 trate, hexaiiitroathane, @r@ianiiitol hexanitrate, and the lile. Th,- insoluble solid oxidizers ca,.i also @be incorporated into th-3 double-bas-. type prop-,I'lant comoositions pa:rticularly when si-i--h conipositions contain an inert f,iel con-iponent, such as an inert plast:@cizer or -a iinely-divid,-d, -inert, solid fuel, such as a ri-tal. or metal hydr'de, v@hich r,qtiires mo@:e oxidizer than can be provided by the active do@,ible-base co,-nponents. Other additives which can be employed in gas-.-eneratin,@ or iror@o,-ropallant comi)ositions s,,iitablz for rny ptirpos@- include finely-divided, soliid fuels, such as B, Si, and I pE,.-rt-ci-iiarly rr-etals such as Al, Mg, Be, Zr, Ti; and their aryhyclrides, which ai-e part:,Cularly desirable where hi.-h heats of coiiibustion ar.- desired. Ii some cases, it may bepreferable to inclti.de coolaits, suoh as monobasic ammoiiurii piios,,L)hate, barbituric. acid, ai-nn-io-.iium oxalate and the -'Like. Althoti.-h the cel@lular, oyidant compositiors can a@,-n,-ra,@'ly be f-orw-,alatec', to ha-,le exc@-ediri@ly Iii-h burning rates, partici-ilarly at elevated corribust;lon pressures, as is c,'Iarac,ceristic ol' iiionoi3rovellants, still higl-ler burnin.- rates can be achieved by incorporatin., bu.,-iiing rate catalysts. Svch catqlysls a@-e well-x'cnown in the art atid include, for examt)le, copper claron7i.'tte, ammoiium bichromate, ferric ferrocyanide, a@id the like. Co-qventioiial additiv,-s such as foam stabilizin.- agents and suri@ace-activ-- dispers@ing a.-ents can also b-- incorporaloci. into th,- cell-,ilor compositions. It will be Linderstood that the amolnt of insol,,able solid oxid-'@-7er required, if any, will be determined by the speC. ific se'if-sustainin.- gas-gener-atin,@ or monopro-ocllant conpositioi,. In the casa of doLble-bas-, type compositiois, it ea-.i be dispe.,i,@ed with eritirely because of the s-,If-oxida-.qt charactp-r of the poly-trer biider and, ge-@l.-rally, at least a portion of the liquid plasticizer. ,,In conapos@'@te comr-ositions, it mtist be ptesent in aniount sufficient to maintain active coil:bustion of th-@ i'Uel component or coir@pon@-nts. Beyond this the amount -will be deterniined by th.- p,,,rt-ciii,ar aplilication of the foamed compositioll-. The composillions can be processed in a variety of ways well known in the art. They can be made for example, by mixing the fully ctired polymer with liquid plasticizer t, d , .1r'idditives, such as insoluble oxidizer, finelydivid-.d insoluble solid fuel, and the like and then cured by heating to dissolve the plasticizer and polymer compoiients. A technique particularly suitable for this mode of processing is the plastisol method in which the polymer, sicii as n:trocellulose, pdlyvinyl cl-loricle, cellulose acetate, or ethyl cellulose, in the form of small, highde-,isity spherical particles, together with other additives as aforeire-titioned, is dispersed in the liquid plasticizer to prodlce a slurry which is then heated to solution te@nperature. In many cas@-s the gas-generating or rilonopropellant
[2]compositions are processed from a mixture of liquid monomers or liquid prepolymers i.ito which the requisite additives such as oxidizer, metal or metal hydride fuels and the like are dispersed. The mixture is then cured catalytically and/or by heat. Examples of compositions particularly suited to such processing are t'iie polyurethanes, the polyepoxies, the polymerized acrylic and methacrylic acid esters and amides, ureaaldehydes, phenol-aldehydes and the synthetic rlbbers. Any process for making foamed or cellular compositions known in the cellular polymer art can be emp"oyed for my purpose, it being necessary or,-ly to select a -proccdure best suited to the particular polymer composition, with further care being taken to avoid curin-. or foaming temperatures at or close to the auto-ignition temperature of the composition. The foaming a-,cnt can be an inert gas, such as nitrogen or C02 introduced under pressure into the composi+lion prior to curing and then permitted to expand by releasing the composition to ambient pressure. 'rbe foamin- agent can also be a compound dispersed in the propellant mix prior to curin.-, which is decomposed by the elevated cure or soltit:ion temderatitres to "orm gases, such as nitro.-en, carbon dioxide and the like. Examples of such blo-,ving agents include m,oc'-azobis(isobutyronitrile); 1,1'-azobis(formamide); N,N'- dinitrosopentamethylenetetramine; N, N'-dimethyl-N,N'- dinitrosoterephthalan@ ide; diazoaminobenz-@ne, p,p'-oxybis (benzenesulfonyl hydraz-kde) -1 benzenesulfonylhydrazide; and the like. Low boilin.- liquids such as water, ethanol, acetone, the liquid Freons, such as dichloromonofluoroethane, and the like, which volatilize at the curing temperature, can also be used as blowing agents. I In accordance with still other well-lnown processes, the blowing agent can be a gaseous product such as C02, @roduced as a by-product of the curing reaction. This is exemplified by the polyurethanes. If a small amount of water or carboxylic acid is provided in the reaction mixture, some of the availableisocyanate groups react with these components to produce C02. The density and cell structure of the foamed products caii be varied and controlled in generally known fashion, as by i-ise of different blowing agents, varying the reaction or cure teirperature, varying cornponent co-@ic;tptrations, the addition of foam stabihzing agents, and the like. Similarly, resilient, sernirigid, and rigid cellular structures can be obtained in known manner by proper selection of the polymeric binder and/or plasticizer, use of rigidifying cross4inking agents, and the like. I have found the foamed polyurethanes particularly suitable for my purpose. Such polymers are generally ,produced by reaction of a polyol witb an organic polyisocyanate. Suitable organic polyols include, for example, glycerol, trimethylol propane; butylene glycol; polyalkylene glycols, such as polyethylene glycol, polypropylene glycol, and polybuty'iene glycol; polyhydroxy polyesters, such as the reaction products of a polyhydroxy alcohol, e.g. glycerol, ethylene glycol, propylene glycol, polyethylene glycol, and trimethylol propane, with a polycarboxylic acid or anhydride, e.g. adipic acid, succinic acid, malonic acid, sebacic acid, diethyletberdicarboxylic acid, maleic anhydride, and phthalic anhydride; esters of hydroxy carboxy@@@ acids, such as castor ofl and glyceryl monoricinoleate; polyhydroxy amino alcohols, such as, N,N,N', N'tetrakis-(2-hydroxypropyl) ethylene dianiine (Quadrol), triethanol amine; and the like. Substantially any reactive organic polyisocyanate can be employed, including aliphatic diisocyanates, such as hexamethylene diisocyanate, and aromatic polyisocyanates, such as 2,4-tolylene diisocyanate mixtures of 2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate, m.phenylene diisocyanate, 3,3'-bitoly l.-pe-4,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, dianisidine diisocyanA "t,-, 1,5-ii--phl'qalare d3-@,.o-,yaiiate, tri-(p-i socyanylphenyl) inethane, the triisocyar-,lte adduct formed by reaction of 1 mol of hexanetriol and 3 mols of mtolylene diisocyanate, and the like. The particular polyisocyanate selected is - encrally d,-t,-r.-nined to a cons@@derable extent by its reaction rate in a given reaction system and the properties which it imparts to the final polymer product. In a highly reactive system, the use of a somewhat less reactive aliphatic diisocyanate, such as hexanethylene diisocyanate can beadvantageous to prevent excessive exotherm or to pr@-vent excessive hardening of the polymeric structure before good cell formation is obtained. In general, the aromatic diisocyanates are preferred because of their more rapid reaction rates, and, in particular, 2,4- or a mixture of 2,4- and 2,6-tolylene diisocyanate, because of its excellent performance, availability and low cost. T@ic rate of reaction of a relatively slowly reactive po'iyol, such as castor oil or, a polyester, with the poly20 @'sc)cya.-.,iate r-an be ircreased in accordance with convent-'@or@at prac@:@ce by means of a catalyst, such as an amine, 1,,ro,@--rably a ter'@iary amine, e.g. N-r@iethyl morpholine, trietrylene diar@i'inc, or tr:lethyl amine, or metal salts, e.g. iro-,i ac--tyl acetonate, lead @iaphthenate, cobalt r@aphthe25 iicite, zinc stearate, tributyl tin methacrylate, d-'@butyl tin d;butyl tin onide, sodium stearate, sodium ricinol--n@te, sodium sal:cylate, sodium citrate, or the like. I.Itliough, in ge@ierall s,,ich catalysis is a funct'on of basiciLy of the reaction mixture, with i@iorganic acids act@.ng 30 as iihibitors, Lewis acids, such as trimethyl boron, have c,,italytic activi"y. Where a highly reactive polyol, particularly a basic polyol, such as Quadrol or triethanol am;n,-, is inell,.ded in the reaction mixture, a catalyst can genera'ily be dispensed with. '@@ 5 Ary conventional foaming agent can be employed. '@'Vater, ivhic'i reacts wit'ii the polyisocyanate to form C02 is g,@ncrally )referred because of its low cost and ease of use. A carboxylic acid, pref-,rably of low molecular we-ight, such as acetic acid, propionic acid, lactic acid, or 40 6-hydrocy prop-Ionic acid, can also be used for its C02 forming reaction with the polyisocyanate. Other suitable foai@,.ng a.@en's include inert gases, such as nitrogen or C02 injected into the reaction mixture under pressure, low-boiling, nonsolvent, volatile compounds, such as the 4 @r, Freops, e.g. trichloromonofluoromethane, dich lorodifluororiethane, dichiorotetrafluoroethane, and the like, and compounds which are decomposed by the hea', produced by the exothermic polymerization reaction to form expandin.- - ases, such as azo bis-isobutyronitrile, diazo50 amirob-.-nzere, 1,1' azo-bis-('Lormamide), N,N'- dinitrosoperitamethylen-- totramine, N,N'-dimethyl-NN'-dinitroso terephthalam@'@de, benzene sulfonyl hydrazide, ammonium and sodium carbonate and bicarbonate, and the lik-e. Wli@-n water is employed as the foaming agent, it is 155 -,encrally desirable to follow the conventional practice of includin.@ an emtilsifier as a d-.spersing and stabilizing agent siiice water and most polyisocyanates are relatively immiscible and may, therefore, react too slowly. Th-emulsifier can be disp@-nsed with if other components, such 60 as a basic polyol, also possess surface-active c haracteristics. Any suitable surfaceactive agent can be employed, such as polyoxyethylated vegetable oils, polyglycol esters o-f fatty acids, polyglycol aryl and higher fatty alcohol ethers, alkyl aryl sulfonates, dialkyl siilfo-succi65 nates, petroleum sulfoilates, hi.-her fatty acid soaps and sulfated fatty acid soaps, etc. - Particula I rly effective for one-shot operation and because of their rigid properties are the polyurethane foams 70 described in Sl,ewart et al. application Ser. No. 813,334 of commoil assignee, ffled May 15, 1959. This application discloses foa@-ned polyurethanes comprising the reaction product of a polyhydroxy alcohol ester of ricinoleic acid containin.@ at least two ricinoleyl -roups and having 75 an equivalent weight in terms of its functional hydroxy
