Highly impact-resistant ABS moulding materials

Details Highly impact-resistant ABS moulding materials Highly impact-resistant ABS moulding materials

2001-06-13

2002-06-18

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...

C525S066000, C525S067000, C525S068000, C525S069000, C525S071000

Reexamination Certificate

active

06407163

ABSTRACT:

For many years now ABS moulding compositions have been used in large quantities as thermoplastic resins for the production of moulded parts of all kinds. The property spectrum of these resins ranges from relatively brittle to very tough.
A specific field of application for ABS moulding compositions is the production of moulded parts with high demands in respect of toughness under the effect of impact, particularly also at low temperatures, and the possibility of selective adjustment (grades between glossy and matt) of the surface gloss (in the motor vehicle sector or to produce housing parts for example).
ABS products with high impact strengths and relatively high surface gloss may be produced by using traditional emulsion ABS and large quantities of rubber, but drawbacks in respect of other properties, e.g. E modulus, heat deflection temperature and thermoplastic flowability are associated with this.
ABS products with relatively low surface gloss are accessible, for example, by polymerization by the solution or bulk polymerization process; products with high low-temperature impact strength are not, however, obtained by this method.
Although certain specific improvements may be achieved by blending traditional emulsion ABS types with solution or bulk ABS types (cf. U.S. Pat. No. 4,430,478 for example), these materials do not meet the high demands in respect of impact strength and flowability while at the same time obtaining the low surface gloss characteristic of bulk ABS.
It is also known to blend ABS polymers produced by bulk polymerization with various graft rubber polymers of small and large particle size produced by emulsion polymerization (cf. U.S. Pat. Nos. 4,430,478, 4,713,420, EP-A 190 884, EP-A 390 781, EP-A 436 381 and literature cited therein for example) but the resulting products do not exhibit improved low-temperature impact strength. EP-A 845 497 describes a blend comprising ABS polymer, obtained by bulk or suspension polymerization and specific graft rubber, obtained by emulsion polymerization using two rubber components. The impact strength of the moulding compositions produced therefrom are, however, often inadequate for the production of moulded parts subject to extreme stress.
It has been found that products with extremely high impact strength values are obtained by combination of specific graft polymers produced by emulsion polymerization on the basis of a blend of three rubber latices with ABS polymers produced by solution, bulk or suspension polymerization.
The invention provides high impact ABS moulding compositions containing
I) a graft rubber polymer, which is obtainable by emulsion polymerization of styrene and acrylonitrile in the weight ratio 90:10 to 50:50, wherein styrene and/or acrylonitrile may be wholly or partially replaced by &agr;-methyl styrene, methyl methacrylate or N-phenyl maleinimide, in the presence of a mixture comprising a butadiene polymer latex (A) with an average particle diameter d
50
≦230 nm, preferably 150 to 220 nm, particularly preferably 170 to 215 nm and most particularly preferably 175 to 200 nm, and a gel content of 40 to 95 wt. %, preferably 50 to 90 wt. % and particularly preferably 60 to 85 wt. %, a butadiene polymer latex (B) with an average particle diameter d
50
of 250 to 330 nm, preferably 260 to 320 nm and particularly preferably 270 to 310 nm and a gel content of 35 to 75 wt. %, preferably 40 to 70 wt. % and particularly preferably 45 to 60 wt. %, and a butadiene polymer latex (C) with an average particle diameter d
50
≧350 nm, preferably 370 to 450 nm, particularly preferably 375 to 430 nm and most particularly preferably 380 to 425 nm and a gel content of 60 to 90 wt. %, preferably 65 to 85 wt. % and particularly preferably 70 to 80 wt. %, wherein the butadiene polymer latices each contain 0 to 50 wt. % of a further vinyl monomer in copolymerized manner and wherein the ratio by mass of graft monomers used to butadiene polymers used is 10:90 to 60:40, preferably 20:80 to 50:50 and particularly preferably 25:75 to 45:55,
II) at least one graft polymer, which is obtainable by solution, bulk or suspension polymerization of styrene and acrylonitrile in the weight ratio 90:10 to 50:50, wherein styrene and/or acrylonitrile may be wholly or partially replaced by &agr;-methyl styrene, methyl methacrylate or N-phenyl maleinimide, in the presence of a rubber, wherein the rubber contains 0 to 50 wt. % of a further vinyl monomer in copolymerized manner and wherein the ratio by mass of graft monomers used to rubber used is 50:50 to 97:3, preferably 70:30 to 95:5, and optionally
III) at least one rubber-free copolymer comprising styrene and acrylonitrile in the weight ratio 90:10 to 50:50, wherein styrene and/or acrylonitrile may be wholly or partially replaced by &agr;-methyl styrene, methyl methacrylate or N-phenyl maleinimide.
In general the moulding compositions according to the invention may 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 1,
50 to 99 parts by weight, preferably 55 to 97.5 parts by weight, and particularly preferably 60 to 95 parts by weight of II,
0 to 100 parts by weight, preferably 0 to 80 parts by weight, and particularly preferably 0 to 60 parts by weight of III.
Furthermore, the moulding compositions according to the invention may contain further rubber-free thermoplastic resins not composed of vinyl monomers, wherein these thermoplastic resins are used in quantities up to 500 parts by weight, preferably up to 400 parts by weight and particularly preferably up to 300 parts by weight (related to 100 parts by weight of I)+II)+III) in each case).
In the production of the graft rubber polymer (I) the butadiene polymer latices (A), (B) and (C) are preferably used in contents of 10 to 40 wt. %, preferably 20 to 37.5 wt. % and particularly preferably 22.5 to 35 wt. % of (A), 10 to 70 wt. %, preferably 20 to 65 wt. % and particularly preferably 30 to 60 wt. % of (B) and 5 to 50 wt. %, preferably 7.5 to 45 wt. % and particularly preferably 10 to 40 wt. % of (C) (related to the particular solids content of the latices in each case).
In the production of the graft rubber polymer (I), as a further preferred group the butadiene polymer latices (A), (B) and (C) are used in contents of 10 to 40 wt. %, preferably 20 to 35 wt. % of (A), 30 to 70 wt. %, preferably 35 to 65 wt. % of (B) and 5 to 45 wt. %, preferably 10 to 35 wt. % of (C) (related to the particular solids content of the latices in each case).
In particular the butadiene polymer latices (A), (B) and (C) are used in such quantities that the equations B≦A+C, B>A and B>C apply for the quantities of rubber.
The butadiene polymer latices (A), (B) and (C) may be produced by emulsion polymerization of butadiene. This polymerization process is known and described, for example, in Houben-Weyl, Methoden der Organischen Chemie, Makromolekulare Stoffe, Part 1, p. 674 (1961), Thieme Verlag publishers, Stuttgart. Up to 50 wt. %, preferably up to 30 wt. % (related to the entire quantity of monomer used for butadiene polymer production) of one or more monomers copolymerizable with butadiene may be used as comonomers.
Examples of such monomers are isoprene, chloroprene, acrylonitrile, styrene, &agr;-methyl styrene, C
1
-C
4
alkyl styrenes, C
1
-C
8
alkyl acrylates, C
1
-C
8
alkyl methacrylates, alkylene glycol diacrylates, alkylene glycol dimethacrylates, divinyl benzene; preferably butadiene is used alone. In the production of (A), (B) and (C) it is also possible initially to produce a fine-particle butadiene polymer by known methods and then agglomerate it in known manner to set the required particle diameter.
Relevant methods are described (cf. EP B 0 029 613; EP B 0 007 810; DD-PS 144 415; DE-AS 1 233 131; DE-AS 1 258 076; DE-OS 2 101 650; U.S. Pat. No. 1,379,391).
It is also possible to work according to the so-called seed polymerization method in which a fine-particle butadiene polymer is initially produced and then further polymerized to larger part

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