Dip-forming latex, dip-forming composition and dip-formed article

Abstract

A dip-forming latex obtained by copolymerization of (a) 50-89.5 weight parts of a conjugated diene monomer, (b) 10-40 weight parts of an ethylenically unsaturated nitrile monomer, (c) 0.5-10 weight parts of an ethylenically unsaturated acid monomer and (d) 0-20 weight parts of other copolymerizable ethylenically unsaturated monomer (the total of these monomers is 100 weight parts), wherein the copolymerization is initiated with a monomer mixture comprising at least 80 wt. % of (a), at least 50 wt. % of (b), 10-90 wt. % of (c) and least 80 wt. % of (d), and thereafter, the remainders of monomers are added to a polymerization system to continue copolymerization. This latex gives a dip-formed article exhibiting good softness of touch, high tensile strength and good retention of close fittingness.

1 . A dip-forming composition comprising a dip-forming latex obtained by copolymerization of 50 to 89.5 parts by weight of a conjugated diene monomer, 10 to 40 parts by weight of an ethylenically unsaturated nitrile monomer, 0.5 to 10 parts by weight of an ethylenically unsaturated acid monomer and 0 to 20 parts by weight of other copolymerizable ethylenically unsaturated monomer, provided that the total of these monomers is 100 parts by weight, wherein said copolymerization is initiated with a monomer mixture comprising at least 80% by weight of the amount of conjugated diene monomer used, at least 50% by weight of the amount of ethylenically unsaturated nitrile monomer used, 10 to 90% by weight of the amount of ethylenically unsaturated acid monomer used and at least 80% by weight of the amount of other copolymerizable ethylenically unsaturated monomer used, and thereafter, the remainders of monomers are added to a polymerization system to continue copolymerization. 
     
     
         2 . The dip-forming composition according to  claim 1 , which is obtained by copolymerization of 55 to 84 parts by weight of a conjugated diene monomer, 15 to 36 parts by weight of an ethylenically unsaturated nitrile monomer, 1 to 9 parts by weight of an ethylenically unsaturated acid monomer and 0 to 15 parts by weight of other copolymerizable ethylenically unsaturated monomer, provided that the total of these monomers is 100 parts by weight. 
     
     
         3 . The dip-forming composition according to  claim 1 , which is obtained by copolymerization of 65 to 81 parts by weight of a conjugated diene monomer, 18 to 27 parts by weight of an ethylenically unsaturated nitrile monomer, 1 to 8 parts by weight of an ethylenically unsaturated acid monomer and 0 to 10 parts by weight of other copolymerizable ethylenically unsaturated monomer, provided that the total of these monomers is 100 parts by weight. 
     
     
         4 . The dip-forming composition according to  claim 1 , wherein the copolymerization is initiated with a monomer mixture comprising at least 80% by weight of the amount of conjugated diene monomer used, at least 80% by weight of the amount of ethylenically unsaturated nitrile monomer used, 10 to 90% by weight of the amount of ethylenically unsaturated acid monomer used and at least 80% by weight of the amount of other copolymerizable ethylenically unsaturated monomer used, and thereafter, the remainders of monomers are added to a polymerization system to continue copolymerization. 
     
     
         5 . The dip-forming composition according to  claim 1 , wherein the copolymerization is initiated with a monomer mixture comprising at least 90% by weight of the amount of conjugated diene monomer used, at least 90% by weight of the amount of ethylenically unsaturated nitrile monomer used, 30 to 85% by weight of the amount of ethylenically unsaturated acid monomer used and at least 90% by weight of the amount of other copolymerizable ethylenically unsaturated monomer used, and thereafter, the remainders of monomers are added to a polymerization system to continue copolymerization. 
     
     
         6 . The dip-forming composition according to  claim 4 , wherein, after the copolymerization of the monomer mixture is initiated, the remainder of ethylenically unsaturated acid monomer is added while the polymerization conversion of the total monomers added is within a range of 5 to 90%, and the remainders of conjugated diene monomer, ethylenically unsaturated nitrile monomer and other copolymerizable ethylenically unsaturated monomer are added at any time before the termination of copolymerization. 
     
     
         7 . The dip-forming composition according to  claim 4 , wherein, after the copolymerization of the monomer mixture is initiated, the remainder of ethylenically unsaturated acid monomer is added while the polymerization conversion of the total monomers added is within a range of 20 to 80%, and the remainders of conjugated diene monomer, ethylenically unsaturated nitrile monomer and other copolymerizable ethylenically unsaturated monomer are added at any time before the termination of copolymerization. 
     
     
         8 . The dip-forming composition according to  claim 1 , wherein the copolymerization is initiated with a monomer mixture comprising at least 80% by weight of the amount of conjugated diene monomer used, 50 to 90% by weight of the amount of ethylenically unsaturated nitrile monomer used, 40 to 90% by weight of the amount of ethylenically unsaturated acid monomer used and at least 80% by weight of the amount of other copolymerizable ethylenically unsaturated monomer used, and thereafter, the remainders of ethylenically unsaturated nitrile monomer and ethylenically unsaturated acid monomer are added while the polymerization conversion of the total monomers added is within a range of 5 to 95%, and the remainders of conjugated diene monomer and other copolymerizable ethylenically unsaturated monomer are added at any time before the termination of copolymerization. 
     
     
         9 . The dip-forming composition according to  claim 8 , wherein the copolymerization is initiated with a monomer mixture comprising at least 90% by weight of the amount of conjugated diene monomer used, 55 to 85% by weight of the amount of ethylenically unsaturated nitrile monomer used, 50 to 85% by weight of the amount of ethylenically unsaturated acid monomer used and at least 90% by weight of the amount of other copolymerizable ethylenically unsaturated monomer used. 
     
     
         10 . The dip-forming composition according to  claim 8 , wherein, after the copolymerization of the monomer mixture is initiated, the remainders of ethylenically unsaturated nitrile monomer and ethylenically unsaturated acid monomer are added while the polymerization conversion of the total monomers added is within a range of 10 to 90%, and the remainders of conjugated diene monomer and other copolymerizable ethylenically unsaturated monomer are added at any time before the termination of copolymerization. 
     
     
         11 . The dip-forming composition according to  claims 8 , wherein, after the copolymerization of the monomer mixture is initiated, the remainder of ethylenically unsaturated nitrile monomer is added while the polymerization conversion of the ethylenically unsaturated nitrile monomer is within a range of 40 to 95%. 
     
     
         12 . The dip-forming composition according to  claim 8 , wherein, after the copolymerization of the monomer mixture is initiated, the remainder of ethylenically unsaturated acid monomer is added while the polymerization conversion of the total monomers added is within a range of 20 to 80%. 
     
     
         13 . The dip-forming composition according to  claim 8 , wherein, after the copolymerization of the monomer mixture is initiated, the remainder of ethylenically unsaturated nitrile monomer is added at two or more times. 
     
     
         14 . The dip-forming composition according to  claim 1 , wherein the conjugated diene monomer is at least one monomer selected from the group consisting of 1,3-butadiene and isoprene. 
     
     
         15 . The dip-forming composition according to  claim 1 , wherein the ethylenically unsaturated nitrile monomer is at least one monomer selected from the group consisting of acrylonitrile and methacrylonitrile. 
     
     
         16 . The dip-forming composition according to  claim 1 , wherein the ethylenically unsaturated acid monomer is at least one monomer selected from the group consisting of ethylenically unsaturated carboxylic acid monomers. 
     
     
         17 . The dip-forming composition according to  claim 1 , which further comprises a vulcanizer selected from the group consisting of sulfur and polyamines, and a vulcanization accelerator. 
     
     
         18 . A dip-formed article made by dip-forming the dip-forming composition as claimed in  claim 1 . 
     
     
         19 . The dip-formed article according to  claim 18 , which has a tensile stress at 300% elongation of not larger than 2.5 MPa, a tensile strength of at least 15 MPa, and a tensile stress retention of at least 70% as measured when 6 minutes elapses from the time of 100% elongation. 
     
     
         20 . The dip-formed article according to  claim 19 , which has a swelling degree in methyl ethyl ketone of not larger than 200%. 
     
     
         21 . The dip-formed article according to  claim 19 , which is a glove.