Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-09-13
2004-04-27
Mullis, Jeffrey (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S067000, C525S071000
Reexamination Certificate
active
06727319
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to thermoplastic molding compositions and more particularly to compositions containing grafted rubber.
BACKGROUND OF THE INVENTION
Large quantities of ABS molding compositions have long been used for the production of moldings of all kinds. The range of properties of these thermoplastic resins here extend from relatively brittle to highly tough.
One specific area of application for ABS molding compositions is the production of moldings having elevated requirements for toughness on exposure to impact and the possibility of purposeful adjustment (gradations between gloss and matt) of surface gloss, for example in the automotive sector or for the production of casing components.
ABS products exhibiting elevated toughness and relatively high surface gloss may be produced using conventional emulsion ABS incorporating large quantities of rubber, but these are associated with disadvantages in other properties, for example modulus of elasticity, heat resistance and thermoplastic flow.
ABS products exhibiting relatively low surface gloss are obtainable, for example, by polymerization using the solution or bulk polymerization process; however, these processes do not give rise to products having elevated toughness at low temperatures.
While isolated improvements may indeed be achieved by blending conventional emulsion grades of ABS with solution or bulk grades of ABS (c.f. for example U.S. Pat. No. 4,430,478), elevated requirements for toughness and flow simultaneously combined with retention of the low surface gloss characteristic of bulk ABS are not fulfilled.
It is also known to blend ABS polymers produced by bulk polymerization with various graft rubber polymers having small and large particle size produced by emulsion polymerization (c.f. for example U.S. Pat. No. 4,430,478, U.S. Pat. No. 4,713,420, EP-A 190 884, EP-A 390 781, EP-A 436 381 and literature cited therein), but the resultant products do not exhibit improved low temperature toughness.
EP-A 845 497 describes a mixture of ABS polymer, obtained by bulk or suspension polymerization, and a specific graft rubber, obtained by emulsion polymerization using two rubber components. The toughness of the molding compositions produced therefrom is, however, often inadequate for the production of moldings exposed to severe stresses.
Apart from the stated mechanical disadvantages, all these described ABS polymers exhibit less than ideal colorability due to their excessive opacity and inadequate inherent color, as a result of which increased quantities of pigments are required to color the molding compositions, which consequently results in further impairment of toughness.
It has now been found that combining at least two special graft rubbers produced by emulsion polymerization with at least one graft polymer produced by solution, bulk or suspension polymerization gives rise to products having a combination of very good toughness, good processability, adjustable surface gloss, good inherent color and reduced opacity.
The present invention provides compositions containing
A) at least one graft rubber produced by free-radical emulsion polymerization of at least one vinyl monomer, preferably of styrene and acrylonitrile in a ratio by weight of 90:10 to 50:50, wherein styrene and/or acrylonitrile may be entirely or partially replaced by &agr;-methylstyrene, methyl methacrylate or N-phenylmaleimide, particularly preferably of styrene and acrylonitrile, in the presence of at least one rubber a) present in latex form and having a glass transition temperature of below 0° C., preferably a butadiene rubber, particularly preferably polybutadiene, present in latex form, using at least one peroxydisulfate compound as initiator,
B) at least one graft rubber produced by free-radical emulsion polymerization of at least one vinyl monomer, preferably of styrene and acrylonitrile in a ratio by weight of 90:10 to 50:50, wherein styrene and/or acrylonitrile may be entirely or partially replaced by &agr;-methylstyrene, methyl methacrylate or N-phenylmaleimide, particularly preferably of styrene and acrylonitrile, in the presence of at least one rubber b) present in latex form and having a glass transition temperature of below 0° C., preferably a butadiene rubber, particularly preferably polybutadiene, present in latex form, using at least one redox system as initiator, and
C) at least one graft polymer, which is obtainable by solution, bulk or suspension polymerization of styrene and acrylonitrile in a ratio by weight of 90:10 to 50:50, wherein styrene and/or acrylonitrile may be entirely or partially replaced by &agr;-methylstyrene, methyl methacrylate or N-phenylmaleimide, in the presence of a rubber, wherein the rubber contains 0 to 50 wt. % of another copolymerized vinyl monomer and wherein the weight ratio of graft monomers to rubber is 50:50 to 97:3, preferably 70:30 to 95:5.
Preferred compositions according to the invention contain 1 to 50 parts by weight, preferably 2.5 to 45 parts by weight and particularly preferably 5 to 40 parts by weight of the graft rubbers A) and B) produced by free-radical emulsion polymerization methods and 50 to 99 parts by weight, preferably 55 to 97.5 parts by weight and particularly preferably 60 to 95 parts by weight of graft polymer C).
The graft rubbers A) and B) produced by free-radical polymerization methods may here be present in any desired proportions, conventionally in the range from 5 to 95 parts by weight of A) and 95 to 5 parts by weight of B); preferred proportions are 20 to 90 parts by weight of A) and 10 to 80 parts by weight of B), particularly preferred proportions are 30 to 80 parts by weight of A) and 20 to 70 parts by weight of B), very particularly preferred proportions are 40 to 75 parts by weight of A) and 25 to 60 parts by weight of B) (in each case relative to 100 parts by weight of A+B).
The graft rubbers A) and B) preferably have rubber contents of greater than 50 wt. %, particularly preferably of greater than 55 wt. % and very particularly preferably of greater than 58 wt. %; graft polymer C) preferably has rubber contents of 3 to 50 wt. %, particularly preferably of 5 to 30 wt. % and very particularly preferably of 6 to 25 wt. %.
Molding compositions according to the invention may further contain as component D) at least one thermoplastic, rubber-free polymer obtained by polymerizing at least one resin-forming vinyl monomer, preferably styrene and acrylonitrile in a ratio by weight of 90:10 to 50:50, wherein styrene and/or acrylonitrile may be entirely or partially replaced by &agr;-methylstyrene, methyl methacrylate or N-phenylmaleimide.
In the event that a component D) polymer is additionally used, the quantity is up to 100 parts by weight, preferably up to 80 parts by weight and particularly preferably up to 60 parts by weight (in each case relative to 100 parts by weight of A+B+C).
The compositions according to the invention may moreover contain further rubber-free thermoplastic resins not synthesised from vinyl monomers, wherein these thermoplastic resins are optionally used in quantities of up to 1000 parts by weight, preferably of up to 700 parts by weight and particularly preferably of up to 500 parts by weight (in each case relative to 100 parts by weight of A+B+C+D).
Both the rubber a) present in latex form used in the production of graft rubber A) and the rubber b) present in latex form used in the production of graft rubber B) may be present in the form of latices exhibiting a monomodal, bimodal, trimodal or multimodal particle size distribution.
Preferred combinations of graft rubbers A) and B) are those in which at least one of the rubber latices a) and b) used in the production thereof exhibits a bimodal or trimodal particle size distribution.
Particularly preferred combinations of graft rubbers A) and B) are those in which the rubber latex a) used in the production thereof exhibits a monomodal particle size distribution and the rubber latex b) used exhibits a bimodal particle size distribution, or tho
Bayer Aktiengesellschaft
Gil Joseph C.
Mullis Jeffrey
Preis Aron
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