Thermoplastic elastomers of isobutylene and process of preparation

Abstract

Block copolymers compose a polyisobutylene rubbery soft segment of M n of about 5,000 to above 500,000 and glassy hard segments of M n of about 5,000 or higher and usually about 10,000 to 35,000 or more, are made by preparing a living polymer block of the polyisobutylene and then polymerizing on said living polyisobutylene block the glassy hard segments by adding thereto an electron donor having a donor number of 15 to 50 and then adding and polymerizing the monomers for the glassy hard segments. The monomers for the glassy hard segments are styrene and its derivatives and indene and its derivatives and mixtures thereof.

What is claimed is: 
     
       1. A living polymerization process for preparing linear or star-shaped block copolymers of isobutylene and another monomer comprising .[.polymerization isobutylene alone or with monomer at a temperature of about -10° C. to -90° C. in an anhydrous system of said isobutylene or another monomer, a mixed solvent, imitator and a metal halide selected from the metals of tin, titanium, aluminum, boron, said polymerization system being capable of producing an electron pair donor initiator having the formula.].: (.Iadd.a) forming a reaction mixture at a temperature of about -10° C. to -90° C. in an anhydrous system of isobutylene, a mixed solvent comprising a mixture of a non-halogenated hydrocarbon solvent and a halogenated solvent, and an initiator having the formula .Iaddend. ##STR3## in which R 1 , R 2  and R 3  are alkyl, aryl, or aralkyl groups and can be the same or different and .[.x.]. .Iadd.X .Iaddend.is .Iadd.selected from the group consisting of .Iaddend.a carboxyl, .Iadd.an .Iaddend.alkoxyl, .Iadd.an .Iaddend.hydroxyl .[.or.]. .Iadd.and a .Iaddend.halogen group, and i is a positive whole number.[., said mixed solvent being formed of at least one hydrocarbon or halohydrocarbon with or without an electron donor pair solvent having a donor number of about 15 to 50, when x is carboxyl or alkoxy; the mixed solvent being a mixture of hydrocarbon and halohydrocarbon with or without said electron donor pair solvent with said hydrocarbon or halohydrocarbon and when x is hydroxyl or halogen, the mixed solvent must contain an electron pair donor solvent of 15 to 50 donor number when said polymerization of another monomer occurs in the presence of the electron pair donor solvent, the mixed solvent and living polyisobutylene, said another monomer being selected from at least one of styrene, and its halo or alkyl styrenes, indene and alkylated indenes..]..Iadd.;   (b) adding a metal halide wherein the metal in the metal halide is selected from the group consisting of tin, titanium, aluminum, and boron to initiate the isobutylene polymerization forming a living polymer, except when X is the hydroxyl group or the halogen group and the initiator does not form an in-situ electron pair donor by an interaction with the metal halide, the reaction mixture is formed by combining the mixed solvent, initiator, isobutylene and an electron pair donor having a donor number, DN, from about 15 to about 50, and then adding the metal halide;   (c) adding the electron pair donor, except when X is the hydroxyl group or the halogen group, to form an electron pair donor with the metal halide, the electron pair donor having a donor number, DN, from about 15 to about 50, to obtain high blocking efficiency by preventing side reactions involving splitting of protons from the living polymer;   (d) adding at least one other monomer selected from the class consisting of styrene, derivatives of styrene, indene, derivatives of indene, and mixtures thereof, to the reaction mixture; and   (e) polymerizing the other monomer or mixture of other monomers to form a block copolymer in which the polyisobutylene polymer comprises the soft segment and the polymerized other monomer or mixture of other monomers form the glassy blocks of the block copolymer. .Iaddend.   
     
     
       2. The process according to claim 1 wherein said initiator forming in situ electron pair donor is selected from the group consisting of 2, methoxy-2-phenylpropane; 2-acetyl-2-phenylpropane;   1,4-di(2-methoxy-2-propyl)benzene;   1,4-di(2-acetyl-2-propyl)benzene;   1,3,5-tri(2-acetyl-2-propyl)benzene;   1,3,5-tri(2-methoxy-2-propyl)benzene;   3-tert.butyl-1,5-di(2-methoxy-2-propyl)benzene;   2-methoxy-2,4,4-trimethylpentane;   2-acetyl-2,4,4-trimethylpentane;   2,6-dimethoxy-2,4,4,6-tetramethylheptane and   2,6-diacetyl-2,4,4,6-tetramethylheptane; and wherein said initiator not forming in situ electron pair donors is selected from the group consisting of   2-chloro-2-phenylpropane;   1,4-di(2-chloro-2-propyl)benzene;   1,3,5-tri(2-chloro-2-propyl)benzene;   2-hydroxy-2-phenylpropane;   1,4-di(2-hydroxy-2-propyl)benzene;   1,3,5-tri(2-hydroxy-2-propyl)benzene;   2-chloro-2,4,4-trimethyl-pentane;   2,6-dichloro-2,4,4,6-tetramethylheptane;   2-hydroxy-2,4,4-trimethyl-pentane and   2,6-dihydroxy-2,4,4,6-tetramethylheptane.   
     
     
       3. The process according to claim 2 wherein said metal halide is titanium tetrachloride or boron trichloride. 
     
     
       4. The process according to claim 3 wherein said electron pair donor is selected from the class consisting of dimethyl sulfoxide, dimethyl acetamide and hexamethyl phosphoramide. 
     
     
       5. The process according to claim 4 wherein the ratio of said metal halide to said initiator on a molar basis, is from about 2 to 1 to about 50 to 1; the ratio of said electron pair donor to said initiator on a molar basis, is from about 1 to 10 to about 1 to 1; the ratio of said electron pair donor to said metal halide is at least 1 to 2; or the ratio of said electron pair donor plus said initiator forming in situ electron pair donors combined with said metal halide is at least 1 to 2; and the ratio of non-halogenated hydrocarbon solvent, on a volume basis, is from about 4 to 1 to about 1 to 1. 
     
     
       6. The process according to claim 5 wherein said hydrocarbon solvent is a cycloalkane, and said halogenated hydrocarbon solvent is a halogenated alkane. 
     
     
       7. The process according to claim 6 wherein said cycloalkane is cyclohexane or methylcyclohexane or mixtures thereof, and said halogenated alkane is selected from the group consisting of methyl chloride, methylene chloride, and mixtures thereof. 
     
     
       8. The polymerization process according to claim 1 said other monomer or mixture of other monomers is selected from the group consisting of styrene and its derivatives consisting of normal or branched alkyl or halogen substituents on the aromatic ring and indene and its derivatives consisting of normal or branched alkyl or halogen substituents on the aromatic ring. 
     
     
       9. The polymerization process according to claim 1 said other monomer or mixture of other monomers is selected from the group consisting of styrene, p-tert.-butylstyrene, p-methylstyrene, p-chlorostyrene, indene and mixtures thereof. 
     
     
       10. The polymerization process according to claim 1 wherein a proton scavenger is selected from the group consisting 2,6-di-tert.-butylpyridine, 4-methyl-2,6-di-tert.-butylpyridine, 1,8-bis(dimethylamino)-naphthalene and diisopropylethylamine and is added to the polymerization mixture in the beginning of the polymerization reaction. 
     
     
       11. The polymerization process according to claim 10 wherein said proton scavenger is 2,6-di-tert.-butylpyridine. 
     
     
       12. The process according to claim 11 wherein the concentration of said proton scavenger is at least equal to, or up to 1.5 times higher than the concentration of moisture in the polymerization system.