Foaming agent and manufacturing method forming agent therefor, rubber composition, cross-linked foam and manufacturing method therefor, and rubber molded article

Abstract

[Object] To provide an excellent foaming agent which does not have problems in handling and operation (example: risk of explosion or fire) and inhibition of cross-linking resulting from a foaming agent and problems, such as, mold pollution and environmental pollution, caused by a foaming agent residue, which has excellent uniform dispersibility in a subject of foaming, and which can be used as an alternative to the chemical decomposition type foaming agent. [Solution] A foaming agent formed from at least (A) a high molecular compound having a saturated water absorption of 10 to 1,000 g/g in ion-exchanged water (25° C.) and (B) water, wherein a storage modulus (G′) of the agent, determined on the basis of a viscoelasticity measurement at a temperature of 20° C., is 8.0×10 1 to 1.0×10 6 Pa at a frequency of 5 rad/s.

1 . A foaming agent formed from at least (A) a high molecular compound having a saturated water absorption of 10 to 1,000 g/g in ion-exchanged water (25° C.) and (B) water, wherein a storage modulus (G′) of the agent, determined on the basis of a viscoelasticity measurement at a temperature of 20° C., is 8.0×10 1  to 1.0×10 6  Pa at a frequency of 5 rad/s. 
     
     
         2 . The foaming agent according to  claim 1 , wherein the high molecular compound (A) has a saturated water absorption of 250 to 1,000 g/g in ion-exchanged water (25° C.). 
     
     
         3 . The foaming agent according to  claim 1 , which is a foaming agent for rubber foaming. 
     
     
         4 . The foaming agent according to  claim 1 , wherein the high molecular compound (A) is a carboxyl group-containing high molecular compound exhibiting a hydrogel-forming property. 
     
     
         5 . The foaming agent according to  claim 1 , wherein the water content is 99.85 to 70 percent by mass. 
     
     
         6 . A method for manufacturing the foaming agent according to  claim 1 , the method comprising the step of mixing (A) a high molecular compound having a saturated water absorption of 10 to 1,000 g/g in ion-exchanged water (25° C.) and (B) water. 
     
     
         7 . A forming agent for the foaming agent according to  claim 1 , comprising (A) a high molecular compound having a saturated water absorption of 10 to 1,000 g/g in ion-exchanged water (25° C.). 
     
     
         8 . A rubber composition comprising:
 100 parts by mass of (I) at least one type of rubber component selected from natural rubber and synthetic rubber; and   0.5 to 300 parts by mass of (II) the foaming agent according to  claim 1 .   
     
     
         9 . A rubber composition comprising 100 parts by mass of (I-1) an ethylene.α-olefin.nonconjugated polyene random copolymer and 0.5 to 300 parts by mass of (II) the foaming agent according to  claim 1 ,
 wherein 50 percent by mass or more of the copolymer (I-1) is a copolymer (X) containing structural units [A] derived from ethylene, structural units [B] derived from an α-olefin having the carbon number of 3 to 20, structural units [C-1] derived from a nonconjugated polyene, in which among carbon.carbon double bonds, only one carbon.carbon double bond polymerizable with a metallocene catalyst is present in one molecule, and structural units [C-2] derived from a nonconjugated polyene, in which among the carbon.carbon double bonds, two carbon.carbon double bonds polymerizable with a metallocene catalyst are present in one molecule, and satisfying the following requirements (1) to (3), 
 (1) the content of the structural units [B] is 10 to 50 percent by mole in 100 percent by mole of the total structural units of the copolymer (X), 
 (2) the total content of the structural units [C-1] and the structural units [C-2] is 1.0 to 6.0 percent by mole in 100 percent by mole of the total structural units of the copolymer (X), and 
 (3) the limiting viscosity [η] measured in a decalin solution at 135° C. is 2.0 to 4.0 d L/g. 
 
     
     
         10 . The rubber composition according to  claim 9 ,
 wherein in the copolymer (X),   at least part of the structural units [C-1] are structural units derived from 5-ethylidene-2-norbornene (ENB) and the content of structural units derived from ENB is 1 to 5 percent by mole in 100 percent by mole of the total structural units of the copolymer (X), and   at least part of the structural units [C-2] are structural units derived from 5-vinyl-2-norbornene (VNB) and the content of structural units derived from VNB is 0.01 to 0.45 percent by mole in 100 percent by mole of the total structural units of the copolymer (X).   
     
     
         11 . The rubber composition according to  claim 9 , which is a rubber composition for extrusion foam molding. 
     
     
         12 . A rubber composition comprising 100 parts by mass of (I-1) an ethylene.α-olefin.nonconjugated polyene random copolymer and 0.5 to 300 parts by mass of (11) the foaming agent according to  claim 1 ,
 wherein 50 percent by mass or more of the copolymer (I-1) is a copolymer (Y) containing structural units [A′] derived from ethylene, structural units [B′] derived from an α-olefin having the carbon number of 3 to 20, structural units [C-1′] derived from a nonconjugated polyene, in which among carbon.carbon double bonds, only one carbon.carbon double bond polymerizable with a metallocene catalyst is present in one molecule, and structural units [C-2′] derived from a nonconjugated polyene, in which among the carbon.carbon double bonds, two carbon.carbon double bonds polymerizable with a metallocene catalyst are present in one molecule, and satisfying the following requirements (4) to (6), 
 (4) the content of the structural units [B′] is 10 to 50 percent by mole in 100 percent by mole of the total structural units of the copolymer (Y), 
 (5) the total content of the structural units [C-1′] and the structural units [C-2′] is 1.0 to 6.0 percent by mole in 100 percent by mole of the total structural units of the copolymer (Y), and 
 (6) the limiting viscosity [η] measured in a decalin solution at 135° C. is 0.8 to 1.8 d L/g. 
 
     
     
         13 . The rubber composition according to  claim 12 ,
 wherein in the copolymer (Y),   at least part of the structural units [C-1′] are structural units derived from 5-ethylidene-2-norbornene (ENB) and the content of structural units derived from ENB is 1 to 5 percent by mole in 100 percent by mole of the total structural units of the copolymer (Y), and   at least part of the structural units [C-2′] are structural units derived from 5-vinyl-2-norbornene (VNB) and the content of structural units derived from VNB is 0.01 to 0.45 percent by mole in 100 percent by mole of the total structural units of the copolymer (Y).   
     
     
         14 . The rubber composition according to  claim 12 , which is a rubber composition for in-mold foam molding. 
     
     
         15 . A rubber composition comprising 100 parts by mass of (I-1) an ethylene.α-olefin.nonconjugated polyene random copolymer and 0.5 to 300 parts by mass of (11) the foaming agent according to  claim 1 ,
 wherein 10 to 50 percent by mass of the copolymer (I-1) is a copolymer (X) containing structural units [A] derived from ethylene, structural units [B] derived from an α-olefin having the carbon number of 3 to 20, structural units [C-1] derived from a nonconjugated polyene, in which among carbon.carbon double bonds, only one carbon.carbon double bond polymerizable with a metallocene catalyst is present in one molecule, and structural units [C-2] derived from a nonconjugated polyene, in which among the carbon.carbon double bonds, two carbon.carbon double bonds polymerizable with a metallocene catalyst are present in one molecule, and satisfying the following requirements (1) to (3), and 
 wherein 90 to 50 percent by mass of the copolymer (I-1) is a copolymer (Y) containing structural units [A′] derived from ethylene, structural units [B′] derived from an α-olefin having the carbon number of 3 to 20, structural units [C-1′] derived from a nonconjugated polyene, in which among carbon.carbon double bonds, only one carbon.carbon double bond polymerizable with a metallocene catalyst is present in one molecule, and structural units [C-2′] derived from a nonconjugated polyene, in which among the carbon.carbon double bonds, two carbon.carbon double bonds polymerizable with a metallocene catalyst are present in one molecule, and satisfying the following requirements (4) to (6), 
 (1) the content of the structural units [B] is 10 to 50 percent by mole in 100 percent by mole of the total structural units of the copolymer (X), 
 (2) the total content of the structural units [C-1] and the structural units [C-2] is 1.0 to 6.0 percent by mole in 100 percent by mole of the total structural units of the copolymer (X), 
 (3) the limiting viscosity [η] measured in a decalin solution at 135° C. is 2.0 to 4.0 dL/g, 
 (4) the content of the structural units [B′] is 10 to 50 percent by mole in 100 percent by mole of the total structural units of the copolymer (Y), 
 (5) the total content of the structural units [C-1′] and the structural units [C-2′] is 1.0 to 6.0 percent by mole in 100 percent by mole of the total structural units of the copolymer (Y), and 
 (6) the limiting viscosity [η] measured in a decalin solution at 135° C. is 0.8 to 1.8 d L/g. 
 
     
     
         16 . The rubber composition according to  claim 15 ,
 wherein in the copolymer (X),   at least part of the structural units [C-1] are structural units derived from 5-ethylidene-2-norbornene (ENB) and the content of structural units derived from ENB is 1 to 5 percent by mole in 100 percent by mole of the total structural units of the copolymer (X), and   at least part of the structural units [C-2] are structural units derived from 5-vinyl-2-norbornene (VNB) and the content of structural units derived from VNB is 0.01 to 0.45 percent by mole in 100 percent by mole of the total structural units of the copolymer (X), and   in the copolymer (Y),   at least part of the structural units [C-1′] are structural units derived from 5-ethylidene-2-norbornene (ENB) and the content of structural units derived from ENB is 1 to 5 percent by mole in 100 percent by mole of the total structural units of the copolymer (Y), and   at least part of the structural units [C-2′] are structural units derived from 5-vinyl-2-norbornene (VNB) and the content of structural units derived from VNB is 0.01 to 0.45 percent by mole in 100 percent by mole of the total structural units of the copolymer (Y).   
     
     
         17 . The rubber composition according to  claim 15 , which is a rubber composition for molding. 
     
     
         18 . The rubber composition according to  claim 8 , further comprising a cross-linking agent. 
     
     
         19 . A cross-linked foam produced by cross-linking foam molding the rubber composition according to  claim 8 . 
     
     
         20 . A rubber molded article comprising the cross-linked foam according to  claim 19 . 
     
     
         21 . An automobile weather strip sponge, an automobile cushioning material, or an automobile heat insulating material comprising the cross-linked foam according to  claim 19 . 
     
     
         22 . A method for manufacturing a cross-linked foam, comprising the steps of extruding the rubber composition according to  claim 12  by an extrusion molding method and heating the resulting extrusion molded material to induce cross-linking and foaming. 
     
     
         23 . A method for manufacturing a cross-linked foam, comprising a first foaming step to fill the rubber composition according to  claim 12  into a primary mold, perform heating under pressure and, subsequently, reduce the pressure to induce foaming and a second foaming step to put the primary foamed material obtained by the first foaming step into a secondary mold and perform heating at normal pressure to induce foaming. 
     
     
         24 . A method for manufacturing a cross-linked foam comprising the steps of injecting the rubber composition according to  claim 15  into a mold by a molding method and performing heating in the mold to induce cross-linking and foaming.