摘要:
A molding composition having good surface gloss, high elongation at break and good thermoplastic processability is disclosed. The composition contains (A) a graft polymer that is obtained by free-radical polymerization of resin-forming vinyl monomers in the presence of rubber in latex form, (B) a copolymer of styrene and acrylonitrile and an optional (C) a resin selected from the group consisting of polycarbonates, polyester-carbonates, polyesters and polyamides. The preparation of the graft polymer is characterized in that (i) before the start of the grafting polymerization reaction the rubber latex is brought to a pH of 9 to 11, (ii) the redox initiator components are employed in amounts of 0.1 to 2.5 wt. % (based on the monomers metered in) and (iii) during the entire grafting polymerization reaction the pH remains constant±0.5 and in the range of 11.0 to 8.8, and (iv) the temperature difference between the start and end of the reaction is at least 10° C.
摘要:
The invention relates to a process for the preparation of graft rubber polymers of the ABS type by emulsion polymerization according to the so-called fed batch process, in which latexes having markedly reduced residual monomer contents are obtained, and to compositions containing the mentioned graft rubber polymers. The polymers so obtained have no negative effects at all on other properties
摘要:
An elastic-thermoplastic graft polymer prepared by a multi-stage free radical polymerization is described. The elastic-thermoplastic graft polymer is prepared by polymerizing (i) one or more monomers containing vinyl groups, and (ii) at least one molecular weight regulating compound, in the presence of (iii) at least one rubber in latex form. The ratio of monomers (M) to the molecular weight regulating compound (MWR) is altered throughout the various stages of the polymerization method. The M:MWR ratio is: from 50:1 to 400:1 in the first stage; from 100:1 to 800:1 in the second stage; and from 200:1 to 2000:1 in the third stage of the polymerization. In at least one further reaction stage of the polymerization, the monomers, in the absence of the molecular weight regulating compound, are polymerized in the presence of the rubber. This further reaction stage occurs before the first stage and/or after the third stage of the polymerization. The multi-stage polymerization is conducted such that: M:MWR (first stage)≦M:MWR (second stage)
摘要:
A support housing (1) for valve and closure members, in particular for heart valve prostheses, has a base ring (2) which carries at least two symmetrically offset posts (4/5) substantially oriented in the direction of the ring axis and linked together by curved strips (3) for securing at least two flexible webs (6/7). In order to produce with such a support housing a valve or closure member, in particular a heart valve prosthesis, which operates reliably even with different closing pressure differentials, i.e. in particular even under varying physiological stress conditions, the stent (1) is only retained in sections and with limited flexibility. For that purpose the free ends (4) of the posts have a rigid form, and/or the bases of the posts have a flexibility limited by stops, and/or the strips (3) have a flexibility limited by stops.
摘要:
ABS type thermoplastic moulding compounds obtainable by A) producing a rubber latex with an average particle diameter d.sub.50 of 30 to 160 nm and a gel content of 75 to 100 wt. % B) emulsion polymerization of an amount of butadiene and optionally up to 50 wt. % (with reference to the total amount of monomer in stage B) of a comonomer in the presence of the rubber obtained in stage A, such that a rubber latex (B) with an average particle diameter d.sub.50 =220 to 330 nm and a gel content of 25 to 70 wt. % is produced, C) emulsion polymerization of 40 to 95 parts by wt. of a mixture of styrene and acrylonitrile, which optionally contains up to 50 wt. % (with reference to the total amount of monomers used in stage C) of one or more comonomers, in the presence of 5 to 60 parts by wt. (with reference to the solids) of the rubber obtained in stage B by introducing the monomer in such a way that 55 to 90 wt. % of the monomers are added within the first half of the total monomer introduction time, and D) mixing the polymer obtained in stage C, preferably after first converting it into a powder, with at least one thermoplastic vinyl resin.
摘要:
Thermoplastic moulding compositions of the ABS type of I) at least one graft copolymer which is obtainable by emulsion polymerization of styrene and acrylonitrile in the weight ratio 90:10 to 50:50, wherein styrene and/or acrylonitrile can be completely or partly replaced by .alpha.-methylstyrene, methyl methacrylate or N-phenylmaleimide, in the presence of at least two butadiene polymer latices of types (A) and (B), which each contain, copolymerized, 0 to 50 wt. % of a further vinyl monomer, and wherein the weight ratio of monomers used to butadiene polymers used is 25:75 to 70:30, and II) at least one copolymer of styrene and acrylonitrile in the weight ratio 90:10 to 50:50, wherein styrene and/or acrylonitrile can be completely or partly replaced by .alpha.-methylstyrene, methyl methacrylate or N-phenylmaleimide, characterized in that the butadiene polymer latex (A) has a particle diameter d.sub.50 .ltoreq.320 nm, a width of the particle size distribution (measured as d.sub.90 -d.sub.10 from the integral particle size distribution) of 30 to 100 nm, and a gel content.ltoreq.70 wt. % and the butadiene polymer latex (B) has a particle diameter d.sub.50 .gtoreq.370 nm, a width of the particle size distribution (measured as d.sub.90 -d.sub.10 from the integral particle size distribution) of 50 to 500 nm and a gel content.gtoreq.70 wt. %.
摘要:
A device is described for connecting two electric aerial cables. Each aerial cable has tube, containing optical fibers, which is cabled with electric conductors and strength member. Means are provided for the mechanical and electrically conductive joining of the electric conductors and strength members of the two cables. A sealed splice carrier for receiving the spliced connections of the optical fibers comprises two concentric tubes (7, 9) with a annular gap between them. The annular gap is sealed at both ends. The optical fibers are inserted into the annular gap through apertures in the end seals (8). The spliced connections and a length of optical fibers are stored in the annular gap. The splice carrier (5) surrounds the means (21, 3) for the mechanical and electrically conductive joining and is attached to the electrically conductive joining means (3) or to the aerial cables (1).
摘要:
Thermoplastic molding compounds of the ABS type of A) at least one graft polymer obtainable by emulsion polymerization of styrene and acrylonitrile in a ratio by weight of 90:10 to 50:50, the styrene and/or acrylonitrile being completely or partly replaceable by .alpha.-methyl styrene, methyl methacrylate or N-phenyl maleic imide, in the presence of at least two butadiene polymer latices of type (A) and (B), of which each contains 0 to 50% by weight of another vinyl monomer in copolymerized form, the ratio by weight of the monomers used to the butadiene polymers used being 25:75 to 70:30, and B) at least one copolymer of styrene and acrylonitrile in a ratio by weight of 90:10 to 50:50, the styrene and/or acrylonitrile being completely or partly replaceable by .alpha.-methyl styrene, methyl methacrylate or N-phenyl maleic imide, characterized in that the butadiene polymer latex (A) has a particle diameter d.sub.50 of .ltoreq.250 nm, a width of the particle size distribution (measured as d.sub.90 -d.sub.10 from the integral particle size distribution) of 500 to 1000 nm and a gel content of .ltoreq.70% by weight, the butadiene polymer latex (B) has a particle diameter d.sub.50 of .gtoreq.300 nm, a width of the particle size distribution (measured as d.sub.90 -d.sub.10 from the integral particle size distribution) of 50 to 500 nm and a gel content of .gtoreq.70% by weight and the graft polymerization is carried out by addition of the monomers to the mixture of butadiene polymer latices (A) and (B) in such a way that 55 to 90% by weight of the monomers are added in the first half of the monomer addition time.
摘要:
Thermoplastic molding compositions containinga. from 1 to 99 parts by weight of a thermoplastic copolymer offrom 40 to 70 parts by weight methyl methacrylate, from 20 to 50 parts by weight .alpha.-methyl styrene and from 5 to 15 parts by weight acrylonitrile,b. from 1 to 99 parts by weight of a statistical, thermoplastic copolymer offrom 70 to 95 parts by weight styrene and from 5 to 30 parts by weight maleic acid anhydride.