Acrylic rubber, crosslinkable acrylic rubber composition and moldings

Abstract

An acrylic rubber comprised of a copolymer comprising 0.1 to 20% by weight of (A) units of a butenedioic acid monoester monomer having an alicyclic structure and 50 to 99.9% by weight of (B) units of at least one kind of monomer selected from acrylic acid ester monomers and methacrylic acid ester monomers. A crosslinkable acrylic rubber composition comprising the acrylic rubber and a crosslinking agent, especially a polyamine crosslinking agent, has good process-stability and good shapability and gives a shaped article having high heat resistance and exhibiting reduced permanent set.

1 . An acrylic rubber comprised of a copolymer comprising 0.1 to 20% by weight of (A) units of a butenedioic acid monoester monomer having an alicyclic structure and 50 to 99.9% by weight of (B) units of at least one kind of monomer selected from acrylic acid ester monomers and methacrylic acid ester monomers.  
   
   
       2 . The acrylic rubber according to  claim 1  wherein said alicyclic structure has 3 to 20 carbon atoms and is at least one kind of alicyclic structure selected from a monocycloalkane structure, a monocycloalkene structure, a tetraline structure, a norbornane ring structure and a norbornene ring structure.  
   
   
       3 . The acrylic rubber according to  claim 1  wherein the copolymer comprises 0.1 to 20% by weight of (A) units of a butenedioic acid monoester monomer having an alcohol residue having 3 to 20 carbon atoms selected from monocycloalkyl groups, monocyloalkenyl groups, a naphthyl group, a norbornyl group and a norbornyl group, 50 to 99.9% by weight of (B) units of at least one kind of monomer selected from acrylic acid alkyl ester monomers, methacrylic acid alkyl ester monomers, acrylic acid alkoxyalkyl ester monomers, methacrylic acid alkoxyalkyl ester monomers, acrylic acid hydroxyalkyl ester monomers and methacrylic acid hydroxyalkyl ester monomers, and 0 to 49.9% by weight of units of a monomer copolymerizable with these monomers.  
   
   
       4 . The acrylic rubber according to  claim 1  wherein the units (A) of a butenedioic acid monoester monomer are units of a butenedioic acid monocycloalkyl ester monomer.  
   
   
       5 . The acrylic rubber according to  claim 1  wherein the content of the units (A) of a butenedioic acid monoester monomer is in the range of 0.5 to 10% by weight.  
   
   
       6 . The acrylic rubber according to  claim 1  which has a carboxyl group content in the range of 5×10 −4  to 4×10 −1  per 100 g of rubber.  
   
   
       7 . The acrylic rubber according to  claim 1  wherein the monomer units (B) comprises 30 to 100% by weight of units of a monomer selected from acrylic acid alkyl ester monomers and methacrylic acid alkyl ester monomers, and 0 to 70% by weight of a monomer selected from acrylic acid alkoxyalkyl ester monomers and methacrylic acid alkoxyalkyl ester monomers.  
   
   
       8 . The acrylic rubber according to  claim 1  wherein the content of the monomer units (B) is in the range of 60 to 95% by weight.  
   
   
       9 . The acrylic rubber according to  claim 1  which has a Mooney viscosity (ML 1+4 , 100° C.) in the range of 10 to 80.  
   
   
       10 . A crosslinkable acrylic rubber composition comprising the acrylic rubber as claimed in  claim 1 , and a crosslinking agent.  
   
   
       11 . The acrylic rubber composition according to  claim 10 , wherein the crosslinking agent is a polyamine crosslinking agent.  
   
   
       12 . The acrylic rubber composition according to  claim 10 , wherein the content of crosslinking agent is in the range of 0.05 to 20 parts by weight based on 100 parts by weight of the acrylic rubber.  
   
   
       13 . The acrylic rubber composition according to  claim 10 , which further comprises a compound having a base dissociation constant in the range of 10 −12  to 10 6  as measured in water at 25° C. as a crosslinking accelerator in an amount in the range of 0.1 to 20 parts by weight based on 100 parts by weight of the acrylic rubber.  
   
   
       14 . The acrylic rubber composition according to  claim 10 , which further comprises a monoamine compound in an amount in the range of 0.05 to 20 parts by weight based on 100 parts by weight of the acrylic rubber.  
   
   
       15 . The acrylic rubber composition according to  claim 10 , which is used for molding.  
   
   
       16 . The acrylic rubber composition according to  claim 10 , which is used for extrusion shaping.  
   
   
       17 . A shaped article obtainable by shaping and crosslinking the acrylic rubber composition as claimed in  claim 10 .  
   
   
       18 . The shaped article according to  claim 17 , which is a molded article.  
   
   
       19 . The shaped article according to  claim 18 , wherein the molded article is obtainable by compression molding, transfer molding or injection molding.  
   
   
       20 . The shaped article according to  claim 19 , wherein the molded article is a sealer.  
   
   
       21 . The shaped article according to  claim 17 , which is an extruded article.  
   
   
       22 . The shaped article according to  claim 21 ,wherein the extruded article is a hose member.