Патент USA US3041326код для вставки
June 26, 1962> -w. R. GRIFFIN 3,041,316 ROOM TEMPERATURE VULCANIZATION OF' FLUORINATED HYDROCARBON ELASTOMERS Filed 0G13. 9, 1959 -lî ff /60 /20 / \0\" ` IN VEN TOR. @wem/4’. 6' » United States; dce 1 2 polymers having thermal stability at elevated tempera 3,041,316 tures. ROOM TEMPERATURE VULCANIZATION 0F FLUGRINATED HYDROCARBON ELASTO MERS A still further object of this invention is to provide a class of room temperature vulcanizable elastomeric halo gen-containing polymers having ñuid resistance. Warren R. Grijiin, Dayton, Ohio, assigner to the United States of America as represented by the United States Still another object of this invention is to provide a class of compositions useful as potting compounds for electronic equipment and as sealant materials in subsonic Aix- Force Filed Oct. 9, 1959, Ser. No. 845,579 13 Claims. (Cl. 260-79) (Granted under Title 35, U.S. Code (1952), sec. 266) 3,041,316 Patented June 26, 1962 aircraft. 10 The invention described herein may he manufactured and used by or for the United States Government for gov» ernmental purposes Without payment to me of any royalty thereon. This invention relates to the vulcanization of elastomers and more particularly relates to the room temperature vulcanization of fluorinated hydrocarbon elastomeric poly - The above and still other objects, advantages, and fea tures of this invention will become apparent upon con sideration of the following detailed description of speciñc embodiments thereof, especially when taken in conjunction with the accompanying drawing which is a graph illus trating the properties of a vulcanizate produced by this invention. lt has been found, in accordance with the invention, that the aforestated objects are accomplished by first pro~ mers suitable for use in high temperature resistant fuel viding chemically reactive sites at elevated temperatures tank and vehicle structure sealants for supersonic aircraft 20 on selected halogenated hydrocarbon polymers followed and missiles. In a more specific aspect this invention re by vulcanization at room temperature with a polyfunc lates to a method of vulcanizing selected fluorine-con tional compound. The halogenated hydrocarbon-«poly taining copolymers by ñrst providing chemically reactive mers found to be of special value in this invention are the sites on the copolymers at elevated temperatures followed halogenated alkyl-vinylidene fluoride copolymers which, by cross-linking through these sites at room temperatures. 25 as is well known, are not easily attacked at room tempera ' Various types of elastomeric materials have been em ture by cross-linking agents capable of complete reac ployed as fuel tank sealants. However, with the advent tion. Accordingly, it was found that by providing chem of high speed aircraft and missiles, it was necessary> that ically reactive sites or “handles” on the polymer chain at sealant materials be developed which would be ñuid re elevated temperatures, room temperature vulcanization sistant, resistant to elevated temperatures in the range of 30 could be eifected -by reacting the modiñed .polymer with 500°-600° F. and be capable of vulcanization at room temperatures. Room temperature vulcanization is a nec essary feature of the polymeric liquids used as sealants for polyfunctional cross-linking agents. The formation of the reactive sight is the ñrst step and is accomplished by using various amines. without this feature delicate electronic equipment, wing The amines which can be employed in this invention and cabin structures, and perhaps whole aircraft would 35 are primary amines such as ethylamine, propylamine and have to be subject to harmful exposure to conventionally the like; secondary amines such as diethylamine, diiso high vulcanization temperatures during manufacture. propylamine, di-n-butylamine, diisobutylamine, di-n-octyl While such exposures are not impossible, the need for high amine, diallylamine, and the like; and tertiary amines vulcanization temperatures has discouraged the use of many elastomeric polymers which would otherwise have 40 such as triethylamine, tripropylamine,. triamylamine, tet ramethylguanidine, and the like. The methyl homologs provided a suitable basis for sealant materials. of the primary secondary and tertiary amines undergo re Previously, subsonic aircraft employed sealant materials based on liquid polysuliide elastomers which were gener arrangement or decomposition and produce a cross-linked product during the site formation reaction.' Therefore, ally satisfactory. However, they were limited in thermal stability to 275° F. and under present `day operating con 45 the methyl homologs are not useful under the conditions Vdescribed herein. It is theorized that these agents pro ditions the need for sealant materials resistant at temper ature ranges of 500°-600° F. is urgent. vide reactive sites in the halogenated polymer such as The halogenated hydrocarbon elastomers, as is well commercially available Viton A (a copolymer of hexailuo known, possess the necessary thermal stability and ñuid ropropylenevinylidene fluoride). All of these amines resistance for high temperature sealant applications. 50 provide double bonds on the polymer chain and in the case However, prior to this invention the ñuorinated elasto of the unsaturated primary and secondary amines the mers required 300° and 400° F. temperatures with ap plied pressures for complete vulcanization. Accordingly, it is an object of this invention to circum vent the above-described limitations so as to produce a 55 sealant material which will operate effectively in high speed aircraft and missiles. Another object of this invention is to provide a proc ess for producing a class of vulcanizable elastomeric halo gen-containing polymers capable of being vulcanized at 60 room temperatures. A further object of this invention is to provide room temperature vulcanizable elastomeric halogen-containing double bonds of the amines are additional active sites, Examples of theorized reactive sites are illustrated as follows: ' ' 3,041,316 4 Hexamethylene dithiol CASE II.--PRIMARY UNSATURATED AMINES Presence of tIi-n-amylamine and moisture at 75° F. C Fs Additional sites for cross-linking ona-cn-cng-N-orn-oiho'm [-0 rt-crn-c-cri 25 CFíl x The vulcanizate produced -by the method of this inven tion and ,illustrated lby the. foregoing theoretical `reactions showedexcellent thermalfstability at 400° F. which sta Ci F a 30 bility. will be hereinafterï demonstrated in greater detail. -C Fà-CHrC- C 10i However, the products preparedusing; saturated and un-V saturated primary amines and tertiary amines appeared to The: following,equationillustrates. .the reactive site forl beinferior to the~ unsaturated andsaturated secondary mationzwith diallylamine: REACTION NO. 1.-REACTIVE SITE FORMATION amines during thermal stability tests. The pendant prod u uct ofthe primaryk amines are; activated at elevated tem FOR` CASE IV' peratures causing undesirable »hardening of the elastomer. The tertiary` amines de_not form pendant groups and are [ .-CF . 2-CH21-Cons F~C Fr _ x-l-CHFCH-ï-Oîïzl-NH-CHT-CH--CHQ Viton A Diallylamine Presence of lNIgO 300° F1 therefore freetocontinueïthe dehydrohalogenation reac tion. until decomposed or volatilized from the polymer. 40 mass. Thev following examples, inwhich parts given are by ~¿ weight, further illustrate the .principlesinvolved inthis. invention.l Example l> shows.- al representative .solvent basedlluorinated elastomeric polymer vulcanized inV ac 45 cordance Íwith this invention. However, it isv to he. clearlyv understood that true liquid polymers are equally operative Y withinY the scopeofthis invention. The purpose of the solvent _is to provide .aliquid'systenrfrom‘the .dry p__oly mers, which is preferable .forapplication _as fuel tank seal The reaction was conducted inthe presence of magne 50 ants. Thev subsequentexamples- are presented to further sium oxide at 300e F.' for 2 hoursäinthe conñned cavity illustrate this: inventionfso` that those skilled in the art of- a rubber mold. Although wide temperature ranges ~ may `hetter‘nnderstand theinvention and the» method by mayy be employed yin ‘ the „foregoing reaction, a tempera which the same mayv becarried into effect. tureranger otapproximately 25,09 to 310° F.V is »prefer-red. Lower temperatureranges. give a reaction `too’ Yslow Ito-be 55 EXAMPLE l A vulcanizate having the. following composition, was ofparticular value-while'the higher temperature ranges in ,excess «of 320° F. giveundesirable cross-linking. Y prepared. The composition-was‘separated into two parts, for storage stability, as-shown-in~the- followingiormu Following _the »formationof Athe reactive. sites, the modi ñediìluorinated` polymer was vulcanizedïby employing> polypfunctional cross-linking . agents active toward the 60 lation. Part A: modifiedpolymer and capable of reaction at room tem perature. Diallylamine ' _______________ __ _______ __ 30.00. 10.00 1.00V Methyl ethyl ketone ____________ __ _____ __ 141.00 l Part B: » Hexamethylene dithiol¿-______ ____________ _. end of the molecule. A possible explanation ofv the'roorn temperature vulcani’zation of ‘ the» modiñedîlñuorinated polymer is exemplified in the followingreactions: REACTION NO. 2.-CROSS-LINK FORMATION Partsby weight Medium thermal carbon .black ___________ _, Magnesiumoxide ____________________ ____ the present invention are dimercaptansV such` as hexa methylene dithiolj and glycol dimercapto-acetate; hetero cyclic amines such as pipera'zine; and alkanediamines such as'N,N’ dimethylr hexamethylene.` diamine, which are dir-secondary amines with a methyl group at each opposite Y Viton A 1____ ________________________ __ 100.00; Examples of`cross-linking agentsV suitable in . 1.50 Trienëarnylamine _____________________ __ 0.50 (1 Viton A is a hexañuoropropylenewinylidene-i‘luoride co-. havinga molecularweight of_about 60,000 and a 70 polymer. monomer ratio of 30% vinylid'ene Vfluoride and`,70%` hexa~ ñuoropropylene. It is disclosed and more fully.. described in a' pamphlet entitled -“Properties `of-v a-,blewy Fluoríne-Containing, Elastomer,” Contribution No. 111 Elastoniers Laboratory, FOR CASE IV Organic Chemicals Department, E. Í. du Pont de Neiuoursnnd. Polymer with `active‘sitesr Y _ +Hs-oHz-CHz-CHZ-Cngg-CHZ-CHZ-SH Company, lInc.) 75 ‘ ` The hexañuoropropylene-vinylidene iluorider. copolymer 5 13,041,316 6 is a Water clear, rubbery gum which easily forms a band on conventional rubber mixing equipment, hereinafter upon the concentrations of TAA and moisture. In the referred to as a mill. lyst; however, normally suñ‘icient moisture is contained by the rubber. The increase of either of the two catalysts The rubbery gum is banded on a mill with two parallel rolls adjusted to provide a rolling bank in the nip of the rolls. The rear roll rotates faster than the front, causing a shearing action which mixes the rubbery gum with the other ingredients. The remaining ingredients of Part A are weighed using the dry powdered carbon black to absorb the liquid diallylamine. The di allylamine is thereby in a less mobile state and incorpo rates into the rubber at a faster rate With less danger of loss. The carbon black-diallylamine mix is added to the revolving band and is immediately followed by the mag nesium oxide. The mixing action is continued until all near absence of moisture TAA does not function as a cata TAA or moisture, will result in an increase of rate of reaction. The extent of the cross-linking reaction is de pendent upon the number of active sites and how many of these are used in cross-linking. Desirable conditions would provide just enough HMDT to react with all of the reactive sites. The properties of the vulcanizate were determined dur ing the cross-linking period. A portion of catalyzed solu tion was ilowed out onto a clean steel plate. After it had reacted for 24 hours at room temperature (75° F.i5 °) the ingredients are uniformly blended. Uniformity is as it had suliicient strength to be stripped from the plate. sured by cutting the band from the mill roll, forming a A small part of this flowout was placed in methyl ethyl roll of the rubbery mass and end passing this roll through ketone. It swelled but did not dissolve, thus indicating the mill, which is set closer to provide approximately a that a substantial amount of cross-linking had occurred. 0.005 inch separation. During the above mixing, atmos The rate of vulcanization at room temperature was traced pheric conditions prevail except that the mix is cooled by 20 'by measuring tensile strength, percent elongation, hard circulating cold water through the hollow mill rolls. The ness and permanent set after break of the specimen. The blended rubbery mass, Part A, remains “warm to the test specimens were micro-dumbbells measuring 1/sf' x 5,/5" touch” from a balance between the cold water cooling in the constricted portion, with 1/2'" tabs. AThe tests except effect and the heat generated by the mixing action. The hardness were performed on a modified Twing-Albert blended rubbery mass is next heated to drive the diallyl 25 paper tensile tester, used because of its sensitivity to small amine-polymer reaction, under conditions which prevent changes in tensile strength. The test data obtained in the volatilization of the diallylamine. Two hours at 300° F. above referred to tests are presented in Table I. The are sufficient to drive this reaction, to completion. The tensile strength and percent elongation as a function of volatilization of the diallylamine is prevented by placing time for the room ltemperature vulcanizate of Example the blended rubbery mass in a standard A.S.T.M. cavity 1 (Viton A) is displayed graphically in the drawing. mold which has been liberally coated with a surfactant 30 mold release agent. The mold is then placed in a hydrau lic press at 300° F. under suiiicient pressure to keep it tightly closed. Usually, hydraulic pressures of about 500 pounds per square inch of mold area are sufficient. After a reaction time of two hours Athe pressure is released and 35 the blended rubbery mass is removed from the mold while Table I RATE OF CROSS-LINKING OF ROOM TEMPERATURE VULCANIZING VITONA Time After Catalyzing, hrs. are washed from the mass with cold water. Tensile . Elongation Break Set, Hardness, Strength, ‘ vpercent percent p.s.i. hot. The mold release agent and other foreign materials . Shore A . The water 73 235 is allowed to evaporate. The removal of foreign materials such as are usually encountered in a rubber factory are 810 ‘ 1,180 1, 470 1, 590 1, 600 not likely to interfere with or prevent subsequent reactions but their removal insures a product of more uniform quality. Part A is now refined, as before, by end passing 1,100 1,500 240 2_60 850 80- 20 45 55 790 730 700 500 70 50 40 20 55 57 58 62 on a tight cool mill in order to break up any agglomerates and to prepare the rubbery mass for rapid' attack by the solvent. Generally, ten passes are suñicient and result in a smooth material similar to the original mixture before the heat treatment. The refined material in the form of a thin crumpled sheet is weighed and placed in a container ture. Therefore, test specimens, exhibiting this state of esters and ketones, tetrahydrofuran and p-dioxane; how ever, methyl ethyl ketone is readily available and produces temperature vulcanized elastomers of Example I displayed a low viscosity solution with Part A. additional vulcanization occurring at this higher tempera The test results outlined in Table I indicated a good state of vulcanization after seven days at room tempera vulcanization were subjected to high ‘temperature tests. Micro-dumbbells,.similar to those. used in the tests 0ut-, with au equal weight of methyl ethyl ketone solvent. 50 lined in Table I were exposed to .TP-4 jet engine fuel in Other solvents may be used such as low molecular weight a pressure bomb at 400° F. for 70 hours. The room f excellent resistance to the hot fluid and also showed little As indicated in the above formulation, -Part B is a 55 ture. Similar test specimens were exposed to 500° F. air physical mixture of hexamethylene dithiol, hereinafter for 70 hours in a circulating air oven. ' i referred to as HMDT and tri-n-amylamine hereinafter The results of the foregoing high temperature tests are referred to as TAA. The HMDT was selected in prefer summarized in Table II. I ence to others because it is in a liquid state and has a low Table 1I vapor pressure. The TAA was chosen as the catalyst be-` 60 cause it is liquid at room temperature, strongly basic and AGING RESISTANCE OF ROOM TEMPERATURE VUL CANIZING VITON A found to have little eifect in the vulcanizate after high temperature exposure. The HMDT and TAA are water like in appearance and are completely miscible in the , Tensile Elonga- Hardness, Volume proportions used. The vulcanizate was prepared from a uniform disper sion of Parts A and B in which 1 part by weight of B was mixed into 141 parts by weight of A. In the presence Aging Conditions - tion, p.s.i. Percent Shore Change, . Percent 1, 500 700 57 70Fuel ___________________ -_ 1, B00 550 53 +7 leads to a vulcanized elastomer in approximately seven 70 days. The catalyzed solution may be ejected from a pres Oven .................. ._ 1, 450 320 65 ,-.173 sure gun used for applying sealants, worked into place by l vulcanized 108 hours at room temperature. of moisture a cross-linking reaction takes place which using spatulas and the like or ñowed out onto a flat sheet of metal or other surface to evaporate the solvent and vulcanize. The rate of the cross-linking reaction depends Original 1 ________________ __ Strength, ________ __ 70 Hours at 400° F., JP-4 Hours at 500° F., Air The above tests indicate that excellent physical proper ties are obtained by the room temperature vulcanization system disclosed herein and that a useful fluorinated elas 3,041,316 8 Part B: tomeric product is produced which fills an urgent need on Glycol dimercapto-acetate _________________ __ 1.5 high speed aircraft. Tri-n-amylamine ________________________ __ ' , While the invention and the advantages thereof have 5 been illustrated by reference to particular materials, it will be understood that other materials may be used in Parts by weight Triñuorochloroethylene - vinylidene fluoride copolymer _________________________ __ 100.00 Medium thermal4 carbon black __________ __ 30.00 Magnesium ., oxide _____ ___ _____________ __ 10.00 Diallyl'amine ________________________ __ 1.00 their places. Thus in place of the magnesium compound, which acts as a stabilizer, other lbasic oxides and carbonatos such as lead or Zinc be used. The medium thermal carbon black is a reinforcing ñller and may be replaced by other conventional reinforcing iìller materials such as other carbon blacks, clay or diatomaceous earth. The medium Methyl ethyl ketone ___________________ __ 141.00 Palt’B: Hexamethylene dithiol _________________ __ 1.50 Trien-.amylamine _____________________ __ 0.50 thermal carbon black is preferred for its general physical properties. The aforementioned examples indicate the The vulcanization of this example'and the subsequent examples, except Example 7, was conducted in accordance with the» procedure outlined in Example l. -In Example 7 need for abasic catalyst and the presence of moisture in order to give a greater degree of control over the room temperature reaction. The catalyst used most often is tri n-amylamine. The size of this molecule makes it less reac tive in dehydrohalogenation yet is basic enough to be an the> 2 hours at 300° F. treatment was done in 3 days at room temperature. The triiiuorochloroethylene-vinylidene fluoride copolymer of Example 2, above, is commercially 20 effective catalyst and suliiciently volatile to escape during available under the trade name Kel-F and comprises 30 to open air vulcanization. 50'fmolev percent of chlorotriiiuoroethylene, the remainder remove the mold release agent from the vulcanized poly mer, which is employed during the hydraulic press treat ment of the blended rubbery mass may be eliminated by being Vvinylidene ñuoride. EXAMPLE 3 Part'A: 100.00. Medium thermalV carbon black _____________ __ herein and in the appended claims is employed in a generic sense to designate synthetic rubbery polymers and copoly 30.00. Magnesium carbonate--- 20.00. 30 mers which are cross-linkable with polyfunctional com Diallylamine` hydrochlo ride __________ __-__-_ pounds capable of reacting therewith so as to effectuate 1.00. room temperature vulcanîzation whether or not admixed Ethyl acetate ________ _.. Dependent on desired vis with pigments, fillers, softeners, peptizers, antioxidants cosity. Part B: and other like materials. While specific embodiments of the invention have been described with particularity, it will be evident to those skilled in the art that the invention is not limited there to but that various modifications may be made without departing from the spirit of the invention as defined by Y Glycol dimercapto -vace tate ______________ __ >1.50. Tri-naamylamine _____ __ Q10-0.25. VDependent on desired rate '« ` of vulcanization. Acetone ____________ __ As needed tol make 40 a , ' homogeneous solution. EXAMPLE 4 Part A: y _ _ ___ ___ Y100.0() Medium thermal carbon black __________ __ 30.00 Magnesium carbonate _________________ __ Diamylamine _______________________ ___ 10.00 1.00 ethylene-vinylidene fluoride which comprises the steps of mixing said copolymer with a material capable of modify ing said copolymer by forming chemically reactive sites thereon, said material selected from the group consisting Methyl ethyl 'ketone ____ __ _____________ __ 141.00 Part B: N-,N' dimethylhexamethylene diamine___ of ethylamine, propylarnine, allylamine, diethylamine, di isopropylamine, di-n-butylamine, diamylamine, diisobutyl amine, di-n-octylamine, diallylarnine, triethyiamine, tri propylamine, triamylamine and tetramethylguanidine 1.50 EXAMPLE 5 Part‘A: Y' Y VitonA _____________________________ -_ 100.00 Medium thermal carbon black __________ __ Magnesium 4oxide ___________________ ____ Diallylamine heating the mixture to a temperature of from. about 250° 30.00 10.00 _____ __ ____ __ ___________ __. to 310° F. to provide said chemically reactive sites, cooling said mixture to room temperature, mixing the modified robbery copolymer with a cross-linking compound selected from the group consisting of hexameth 1.00 Methylethylïketone____`_ _____ ___ ______ __ 141.00 Part B: Piperazine ____________ __ __________ __ PartlA: ' . ~ ylene-dithiol, glycol dimercapto-acetate, piperazine and N, 1.00 60 EXAMPLE 6 . Viton A__'_____ ______________________ __ 100.00 Medium thermal" carbon black ______ __`___.. ‘ 30.00 Magnesium',` oxide. ____________________ __ 10.00 . Triamylamine: _________~_ _____________ __ 1.00 Methyl ethyl ketone__________________ ___ 141.00. Part‘B: Piperazine ______ ___ _________ __ ____ __ the scope of the appended claims. Having thus described my invention, what I claim and desire to protect by Letters Patent is: l. A process for the production of a vulcanized rubbery copolymer selected from the group consisting of hexa ñuoropropylene-vinylidene iiuoride and 'tritiuorochloro ' Parts by weightV Viton A The use of Water in order to the use of cellophane as a releasing material or the- use of a hot air autoclave. It is to be understood that the term “rubber” as used Parts by weight VitonA _____________ __ - .2 EXAMPLE 2` Part‘Az: 1.00 Nf ydimethyl hexamethylene diamine and an amine cata lyst to causeY a reaction therebetween, and then allowing said reaction to continue at room temperature, thereby producing a vulcanized rubbery copolymer. 2. A process in accordance with claim 1 wherein said polymer is hexatiuoropropylene-vinylideneV ñuoride. ' 3. VA process in accordance with claim l wherein said polymer is triñuorochloroethylene-vinylidene fluoride. 4. A process in accordance with claim 1 wherein saidv material'is ethylamine.` « EXAMPLE 'I Part A: L f Y ' Y Viton'A _____________________________ „100.00 Medium thermal carbon black'. _________ __ 30.00 ' VMagnesium’ oxide _______ __ _________ ___- Ethylamine. __ ________ „___-____ ______ __ Methyl ethyl ketone ______________ _______ 141.00 - 5. A. process in accordance with claim l wherein said material is diarnylamine. ' ~ 6. A process in accordance with claim l wherein said materialis triamylamine. 7. A processV in accordance'rwith claim 1 wherein said material Yis diallylamine. 3,041,316 10 8. A process in accordance with claim 1 wherein said period of time suiTìcient to produce a vulcanized copoly material is diethylamine. lmer. 9. A process in accordance with claim 1 wherein said compound is hexamethylene dithiol. References Cited in the tile of this patent UNITED STATES PATENTS 10. A process in accordance with claim 1 wherein said compound is glycol dimercapto-acetate. 11. A process in accordance with `claim 1 wherein said compound is piperazine. 12. A process in accordance with claim 1 wherein said compound is hexamethylene diamine. 13. A process for the production of a room tempera ture vulcanized hexañuoropropylene vinylidene fluoride copolymer which comprises the steps of mixing said co polymer with diallylamine in order to modify said copoly mer by forming chemically reacting sites thereon, heating 10 2,423,032 Le Beau ______________ __ I une 24, 1947 2,446,984 Rogers etal ___________ __ Aug. 10, 1948 2,662,874 2,793,200 Brown ______________ _.. Dec. 15, 1953 West ________________ __ May 21, 1957 Ayers et al. ___________ .__ Dec. 1, 1959 2,915,481 OTHER REFERENCES Moran et al.: “Safe Processing Curing System for Viton Fluoroelastomers,” Ind. and Eng. Chem., vol. 51, No. 7, said mixture to a temperature of about 300° F., cooling said mixture to room temperature, mixing the modified July 1959, pp. 831-832. copolymer with hexamethylene dithiol and a triamylamine October 1959, Elastomers Chemical Department (only Eubank et al.: “Viton in Mechanical Goods,” BL-360, Catalyst to cause a reaction therebetween, and then allow page 3 relied on), E. I. du Pont de Nemours and C0. ing said reaction to continue at room temperature for a 20 (Inc.), Wilmington 98, Del.