Injection-foamable styrenic monomer-diolefin copolymer, a method for the preparation thereof and use thereof

Abstract

A styrenic monomer-diolefin copolymer comprises polystyrenic monomer micro-blocks and polydiolefin micro-blocks, in which the content of styrenic monomer units is 10-80 wt %, the ratio of diolefin units of 1,2-structure is less than 30% in the total diolefin units, and the number-average molecular weight (Mn) of the copolymer is 25,000-500,000. The preparation methods and uses in foam products thereof are also disclosed.

1 . A styrenic monomer-diolefin copolymer comprising micro-blocks of polystyrenic monomer and micro-blocks of polydiolefin monomer. 
     
     
         2 . The styrenic monomer-diolefin copolymer of  claim 1 , consisting essentially of micro-blocks of polystyrenic monomer and micro-blocks of polydiolefin monomer. 
     
     
         3 . The styrenic monomer-diolefin copolymer of  claim 1 , wherein the content of styrenic monomer-derived units ranges from 10 to 80 wt %, 1,2-polymerized diolefin units comprises less than 30% of the total diolefin-derived units, and the copolymer has a number average molecular weight (Mn) ranging from 25,000 to 500,000. 
     
     
         4 . The styrenic monomer-diolefin copolymer of  claim 1 , which comprises:
 linear styrenic monomer-diolefin copolymer represented by the formula (I):
   PS X1 (PS X2 PB Y ) n PS X3   (I)
 
   wherein,   PS represents a polymeric segment of the styrenic monomer,   PB represents a polymeric segment of the diolefin monomer,   X1, X2, X3 and Y each represents the polymerization degree of the respective polymeric segment, and   X1 is an integer ranging from 0 to 150,   X2, in each appearance, is independently an integer ranging from 1 to 150,   Y, in each appearance, is independently an integer ranging from 1 to 500,   X3 is an integer ranging from 0 to 150, and   n is an integer ranging from 5 to 3000,   provided that at least 30 mol % of the styrenic monomer-derived units are within polystyrenic monomer segments having a polymerization degree of from 2 to 100, and at least 30 mol % of the diolefin monomer-derived units are within polydiolefin segments having a polymerization degree of from 2 to 400; or
 multi-armed star-shaped styrenic monomer-diolefin copolymer represented by the formula (II):
   (PS X1 (PSx 2 PB Y ) n ) m R  (II)
 
 
   wherein,   PS, PB, X1, X2, X3, Y and n are as defined for the formula (I) above,   R is a star-shaped coupling agent “nucleus”,   m is an integer of from 3 to 10,   provided that at least 30 mol % of the styrenic monomer-derived units are within polystyrenic monomer segments having a polymerization degree of from 2 to 100, and at least 30 mol % of the diolefin monomer-derived units are within polydiolefin segments having a polymerization degree of from 2 to 400; or
 a combination of the both. 
   
     
     
         5 . The styrenic monomer-diolefin copolymer of  claim 1 , which has a moving-window two-dimensional correlation infrared spectrum having two or three continuous thermal transition peaks in a temperature range of from about 70 to 150° C. in a wave number range of from about 2842 to 2848 cm-1. 
     
     
         6 . The styrenic monomer-diolefin copolymer of  claim 1 , wherein a plurality of PSX2PBY segments constitute a styrenic monomer-diolefin tapered block, of which composition varies gradually, and the (PSX2PBY)n segment consists of a plurality of such tapered blocks. 
     
     
         7 . A method for preparing the styrenic monomer-diolefin copolymer according to  claim 1 , comprising:
 1) adding an amount of a solvent and an activator to a polymerization reactor, and heating the contents to a temperature ranging from 50 to 110° C.;   2) adding 0 to 45 wt % of a styrenic monomer to the reactor;   3) adding a desired amount of an initiator to the reactor, and allowing the reaction to continue for 0 to 30 minutes;   4) after sufficiently mixing 10 to 100 wt % of the styrenic monomer with all of a diolefin monomer, adding the resulting mixture to the reactor over a period of time ranging from 5 to 180 minutes, either continuously, batch-wise, or pulsedly, with a reaction temperature inside the reactor being controlled during the addition so that the maximum reaction temperature differs from the initiating temperature by no more than 50° C.;   5) adding the remaining 0 to 45 wt % of the styrenic monomer to the reactor and allowing the reaction to continue for further 2 to 30 minutes; and   6) at the end of the reaction, terminating the reaction and recovering the produced copolymer; or   alternatively, comprising:   1) adding an amount of a solvent and an activator to a polymerization reactor, and heating the contents to a temperature ranging from 50 to 110° C.;   2) adding 0 to 45 wt % of a styrenic monomer to the reactor;   3) adding a desired amount of an initiator to the reactor, and allowing the reaction to continue for 0 to 30 minutes;   4) after sufficiently mixing 55 to 100 wt % of the styrenic monomer and 90 to 100 wt % of a diolefin monomer, adding the resulting mixture to the reactor over a period of time ranging from 5 to 180 minutes, either continuously, batch-wise, or pulsedly, with a reaction temperature inside the reactor being controlled during the addition so that the maximum reaction temperature differs from the initiating temperature by no more than 50° C.;   5) optionally, adding the remaining 0 to 10 wt % of the diolefin monomer to the reactor, and allowing the reaction to continue for 5 to 30 minutes;   6) adding a desired amount of a coupling agent to the reaction mixture, and allowing the reaction to continue for 5 to 60 minutes; and   7) at the end of the reaction, terminating the reaction, and recovering the produced copolymer.   
     
     
         8 . The method of  claim 7 , wherein the solvent is chosen from cyclohexane, n-hexane, hexanes, benzene, toluene, xylenes and combinations thereof. 
     
     
         9 . The method of  claim 7 , wherein the initiator is an alkyllithium. 
     
     
         10 . The method of  claim 7 , wherein the activator is tetrahydrofuran, and it is used in such an amount that its content in the polymerization solvent ranges from 50 to 1200 mg/kg. 
     
     
         11 . Use of the styrenic monomer-diolefin copolymer according to  claim 1  for the production of a foamed article. 
     
     
         12 . A method for producing a foamed article, comprising blending the styrenic monomer-diolefin copolymer according to  claim 1  with a processing aid, a crosslinking agent and a flowing agent, and optionally with processing scraps of said copolymer, an ethylene-vinyl acetate copolymer (EVA) and processing scraps of EVA, at a temperature below 110° C.; pelletizing the resultant blend at a temperature below 110° C.; and then injecting the resultant pellets via an injection molding machine into a mould and allowing it to foam therein, to form a foamed article. 
     
     
         13 . The method of  claim 12 , wherein a formulation is as follows: 100 parts by weight of said copolymer, 0 to 50 parts by weight of processing scraps of said copolymer, 0 to 60 parts by weight of the ethylene-vinyl acetate copolymer (EVA) and processing scraps thereof, 0.05 to 10 parts by weight of the flowing agent, 0.05 to 1 part by weight of the crosslinking agent, 0 to 100 parts by weight of a filler, and 0 to 5 parts by weight of a releasing agent. 
     
     
         14 . A foamed article obtained by the method of  claim 12 . 
     
     
         15 . The foamed article of  claim 14 , which may be used for manufacturing sand bench shoes, slippers, midsoles of tourist shoes and sports shoes, and outsole of leather shoes, or as vehicle interior decorative materials and heat insulators used in various situations.