United States Patent (19) 11 4,255,536 Udipi 45 Mar. 10, 1981 54 AZODICARBOXYLATE-MODIFIED 56) References Cited COPOLYMERS r U.S. PATENT DOCUMENTS 75 Inventor: Kishore Udipi, Bartlesville, Okla. 4,29,531 2/1978 Rauer et al. ......................... 525/376 OTHER PUBLICATIONS 73 Assignee: Phillips Petroleum Company, Bartlesville, Okla. J. Org. Chem.; "Reaction of Ethyl Azodicarboxylate with Monoolefins,” vol. 29; 2226-2235 (1964). 21 Appl. No.: 32,978 Primary Examiner-William F. Hamrock 22 Fied: Apr. 24, 1979 57 ABSTRACT A copolymer of a conjugated diene/monovinylarene 51 Int. C. ................................................ CO8F 8/30 modified by reaction with a dihydrocarbyl azodicar 52 U.S.C. .................................... 525/314; 525/333; boxylate. 525/376 58 Field of Search ........................ 525/376, 333,314 35 Claims, No Drawings 4,255,536 1. 2 85:15. The copolymers can be prepared by methods AZODCARBOXYLATE-MODIFIED known in the art, such as by emulsion or solution poly COPOLYMERS merization. Presently preferred are the hydrocarby alkali metal-initiated solution polymerization methods FIELD OF THE INVENTION and resulting copolymers described, for example, in The invention pertains to azodicarboxylate-modified U.S. Pat. Nos. 2,975, 160, 3,078,254, 3,281,383, and copolymers. In another aspect, the invention pertains to 3,449,306, the disclosures of which are herein incorpo wet-skid resistant rubbers. In a still further aspect, the rated by reference. invention pertains to rubbery or resinous copolymers Conjugated diene monomers for the preparation of exhibiting oil-resistance (swell resistance). O the precursor copolymers ae those containing 4 to such as 12 carbon atoms per molecule. Exemplary conju BACKGROUND OF THE INVENTION gated monomers include such as 1,3-butadiene, iso The manufacture of such as tire tread compositions prene, 2,3-dimethyl-1,3-butadiene, piperylene, 3-butyl includes various natural and synthetic rubbery poly 1,3-octadiene, 2-phenyl-1,3-butadiene, and the like, and mers. Various blends or treatments have been proposed 15 mixtures thereof. Especially preferred is 1,3-butadiene to improve wet-skid resistance, particularly for pneu due to its availability and favorable cost. matic tires. Monovinylarene monomers suitable for the prepara Other applications of rubbery or resinous copolymers tion of the precursor copolymers contain 8 to such as 20 have dictated requirements for oil and fuel resistance, carbon atoms per molecule, and include those which when the polymers are utilized for seals requiring a further contain alkyl, cycloalkyl, and aryl substituents, composition resistant to oil or fuel to avoid swelling, or and combinations thereof such as alkylaryl, in which utilized for containers for hydrocarbon fluids which the total number of carbon atoms in the combined sub resist swelling and consequent weakening. stituents generally is not greater than 12. Exemplary Needed, however, are copolymers exhibiting im monovinylarene monomers include such as styrene, proved wet-skid resistance, or oil resistance. 25 alpha-methylstyrene, 3-methylstyrene, 4-n-propylsty rene, 4-cyclohexylstyrene, 4-dodecylstyrene, 2-ethyl-4- BRIEF SUMMARY OF THE INVENTION benzylstyrene, 4-p-tolystyrene, 4-(4-phenyl-n-butyl)sty This invention is directed toward novel dihydrocar rene, 1-vinylnaphthalene, 2-vinylnaphthalene, and the byl bicarbamate-modified copolymers of conjugated like, and mixtures. Styrene presently is preferred due to dienes and monovinylarenes. The novel modified co 30 its availability and effectiveness. polymers of my invention are formed from the addition Sovents for use in solution polymerization of such reaction of the dihydrocarbyl azodicarboxylate with a monomers include paraffinic, cycloparaffinic, and aro precursor copolymer to form a copolymer with pendant matic hydrocarbons, and mixtures thereof. Exemplary dihydrocarby bicarbamate groups. The novel bicarba solvents include n-pentane, n-hexane, n-heptane, 2,2,4- mate modified copolymers of my invention exhibit good 35 trimethylpentane, cyclohexane, benzene, toluene, Xy resistance toward swelling by hydrocarbon agents. Fur lene, and the like alone, or in admixture. Optionally, a thermore, cured rubbery compositions based on these mixture of a hydrocarbon solvent with a polar solvent novel bicarbamate modified copolymers exhibit im can be employed if it is desired to enhance the formation proved wet-skid resistance. of a particular polymer structure, i.e. high vinyl content DETALED DESCRIPTION OF THE or formation of random copolymer, or to improve the INVENTION efficiency of the polymerization process. Such a polar I have discovered that the reaction product of a dihy solvent of course should be such as does not adversely drocarbyl azodicarboxylate with a copolymer of at least interact with the initiator, monomers, coupling agents if one conjugated diene and at least one monovinylarene 45 employed, or other ingredients of the polymerization (characterized as having at least 5 mole percent residual recipe. Useful polar solvents include such as cyclic and olefinic unsaturation based on total moles of conjugated acyclic ethers, thioethers, tertiary amines, and other diene present in the copolymer) exhibits good resistance such polar solvents used for this purpose as known in toward oil and toward swelling by hydrocarbon agents. the art, frequently and typically tetrahydrofuran. Furthermore, the cured compositions which are rub 50 Initiators suitable for preparation of solution poly bery based on these copolymer-dihydrocarbyl azodicar merized precursor copolymers include any of the or boxylate addition products further exhibit good wet ganoalkali metal initiators known for anionic solution skid resistance. polymerization of the monomers described. These initi ators include the organolithium compounds of the gen PRECURSOR COPOLYMERS 55 eral formula R(Li), in which R is an aliphatic, cycloali The precursor copolymers suitable for reacting with phatic, aromatic, or combination hydrocarbyl radical. R the dihydrocarbyl azodicarboxylate to form the novel has a valence equal to the integer x and generally con modified copolymers of my invention are unsaturated tains 1 to 20 carbon atoms, although higher molecular random and block conjugated diene monovinylarene weight compounds can be utilized, and x is an integer of copolymers containing at least 5 mole percent residual SO 1 to 10, inclusive, preferably 1 to 4 due to availability. olefinic unsaturation. The block copolymers include n-Butyllithium is an example of an especially suitable those containing at least two pure homopolymer block polymerization initiator due to its ready availability and segments (one from each type of monomer) as well as activity. those containing one or more random or tapered block Other suitable organolithium initiation agents include segments, and other types of such copolymers. The 65 the alphalithio multisubstituted dialkylbenzenes and precursor copolymers generally will have a conjugated corresponding oligomers. Although these initiators diene:monovinylarene weight ratio of about 5:95 to normally consist of a mixture of various oligomers, the 95:5, and preferably will be rubbery of about 55:45 to mixture primarily is 1,3-bis(1-lithio-3-methylpentyl)ben 4,255,536 3 4. zene, and this initiator typically is referred to as DiLi-3. hydrogenation of unterminated copolymer in solution Additional information regarding such compounds is in in polymerization solvent. U.S. Pat. No. 3;668,283 to Morrison et al (1972) and U.S. Pat. No. 3,776,964 to Morrison et al. (1973). DIHYDROCARBYL AZODICARBOXYLATE The amount of organolithium initiator to be used can MODIFICATION vary widely, primarily depending on the desired molec The dihydrocarbyl azodicarboxylates suitable for use ular weight of the polymer, but generally is in the range in my invention can be represented by the general struc of about 0.1 to 100 millieduivalents of lithium per 100 tural formula: grams of total monomer, so long as the desired molecu lar weight for the precursor copolymer is achieved 10 O O either as the result of polymerization alone, or the result I of polymerization plus optional subsequent coupling. R'-O-C-N=N-C-O-R' The analogous sodium and potassium compounds also are suitable as initiators for preparation of the pre in which R" and R are alkyl, cycloalkyl, aryl, or combi cursor copolymers for use according to my invention. 15 nation radicals and can be the same or different. Typi Polymerization conditions generally known to one cally R' and R" each contain 1 to such as 12 carbon skilled in the art can be employed. The polymerization atoms. Presently preferred are the dialkyl azodicar temperatures can vary over a broad range, generally boxylates. Diethyl azodicarboxylate and di-t-butyl such as about -50° C. to 200 C. It is presently consid azodicarboxylate are examples of suitable available dial ered preferable to operate within a temperature range of 20 kyl azodicarboxylates for use in my invention. Other about 50' to 150° C. for convenience. Pressures em exemplary azodicarboxylates include such as similar ployed can be as convenient, usually sufficient to main azodicarboxylates wherein R and R' can be selected tain monomers/solvent substantially in a liquid phase. from various of such as methyl, dodecyl, cyclohexyl, Termination to remove active lithium, of course, is phenyl, and combinations. necessary, otherwise later treatment with azodicar 25 The reaction between the dihydrocarbyl azodicar