| 摘要 |
Improved ABS plastics are disclosed which exhibit high impact resistance at lower rubber content than has heretofore been utilized while also exhibiting good flow properties, all by reason of containing an improved form of rubber toughener. The improved ABS toughener comprises a butadiene rubber in the form of large particles containing numerous small, hard particles of an insoluble vinyl aromatic reinforcing resin and having a graft overpolymerized coating of a styrene/acrylonitrile (SAN) copolymer resin. The size of the reinforcing resin particles is critical and should be between about 150 and about 800 A in average diameter, more preferably between about 200 and about 600 A, and most preferably between about 200 and about 400 A in average diameter. Also critical is the size and resin content of the rubbery substrate particles which should be not less than about 750 A, more preferably between about 1,000 and about 3,000 A, and most preferably between about 1,000 and 2000 A in average diameter at rubber-to-reinforcing resin weight ratios between about 20:1 and about 5:1, more preferably between about 15:1 and about 8:1, in order to yield both impact resistance and improved melt flow properties. The proportion of graft polymerized SAN on such large rubber substrate particles is not particularly critical and can range from as much as high 95 parts/wt. of total resin (SAN + reinforcing resin) on 5 parts/wt. of rubber (less reinforcing resin) to as low as 30 to 40 parts/wt. of SAN (less reinforcing resin) per 100 parts/wt. of rubber less reinforcing resin, more preferably between about 50 and about 500 parts/wt. of SAN for every 100 parts/wt. of rubber as reinforced rubber. On dilution of the SAN-coated toughener with rubber-free SAN, ABS plastic formulations are obtained which contain from about 5 to about 25%/wt. more preferably between about 10 and about 18%/wt. of rubber based on total polymer content and exhibit a unique combination of high impact strength and high melt flow.
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