摘要:
A process for the production of thermoplastically processible moulding materials based on vinyl polymers of high chemical and molecular uniformity and having residual monomer contents of less than 0.1 mol % which comprises the steps of:(i) mass homogeneous phase polymerization of at least one vinyl monomer in a stirred continuously charged tank reactor to a conversion of from 25 to 60 mol %;(ii) directly concentrating the syrup consisting of residual monomers and vinyl polymer dissolved therein obtained from step (i) in a spiral tube evaporator at a temperature of from 60.degree. to 250.degree. C. and at a pressure of 100 m bar to 35 bar to obtain a solid content of vinyl polymer of from 40 to 90 mol %;(iii) directly charging the concentrate obtained from step (ii) to the inlet zone of a screw evaporator which consists of at least two sequential zones in order to effect further concentration, in which a first zone at a pressure of from 10 to 300 m bar and at a temperature of from 100.degree. to 250.degree. C. concentrates the vinyl polymer to a solid content of from 80 to 99 mol-%, and each subsequent zone at a pressure of 1 to 200 m bar and at a temperature of 150.degree. to 250.degree. C. concentrates the vinyl polymer to a solid content of at least 99.9 %; and(iv) recycling the residual monomers from step (ii) and the residual monomers from said first zone of the screw evaporator to the stirred and charged tank reactor without intermediate cleaning.
摘要:
The discharge apparatus comprises an at least four-shaft screw pump having engaging shafts (1,2,3,4) which rotate in opposite directions in pairs. The viscous product to be processed is caught up over a large area and removed by the screws. A double shaft screw pump is connected downstream of the actual collection zone as a pressure build-up zone. The two center screws (2, 3) of the collection zone merge equiaxially into the screw shafts (2a, 3a) of the pressure build-up zone. The collection zone and the pressure build-up zone are combined into one constructional unit. At least one screw shaft is driven. The resulting high viscosity product strands (7) are caught up by the screws in the collection zone and are moved on into the pressure build-up zone. The double shaft screw pump is used for the build up of a high operational pressure and thus provides the prerequisite for the subsequent connection of further procedural stages. The universal possibilities of use of this discharge apparatus are to be stressed in particular.
摘要:
The optical contact objects contain a wettable, optionally crosslinked copolymer comprising the components N-vinylcarboxamide, (meth)acrylates of a polysiloxane and, optionally, vinyl monomers.
摘要:
Contact lenses and implants for human medicine can be fabricated from a polymer blend comprising 98-80% by weight of component A and 2-20% by weight of component B wherein:component A is a cellulose ester of an aliphatic carboxylic acid with up to 40% by weight of total component A of an ethylene/vinyl acetate copolymer having 30-98% by weight, relative to ethylene/vinyl acetate, of incorporated vinyl acetate andcomponent B is a homopolymer or copolymer of water-soluble vinyl monomers and up to 10% by weight relative to the total polymer B of multifunctional crosslinker vinyl compounds.
摘要:
A thermoplastic moulding composition comprising:(1.) 80 to 20 parts by wt. of a thermoplastic polycarbonate based on a dihydroxy diaryl alkane,(2.) 20 to 80 parts by wt. of a graft polymer of2.2. a monomer mixture, polymerized onto2.1. a diene rubber with a glass transition temperature below -30.degree. C., of2.2.1. 95 to 50% by wt. of styrene, methyl methacrylate or a mixture thereof; and2.2.2. 50 to 5% by wt. of acrylonitrile, methacrylonitrile or a mixture thereof, the ratio by wt. of rubber (2.1) to monomer mixture (2.2.) being in the range of from 80:20 and 10:90, and the moulding composition containing from 5 to 35% by wt. of the rubber (2.1.), and(3.) 5 to 75 parts by wt. of a copolymer which is chemically uniform in structure and which comprises:(3.1.) 93 to 50 parts by wt. of styrene, methyl methacrylate or a mixture thereof;(3.2.) 40 to 5 parts by weight of acrylonitrile, methacrylonitrile or a mixture thereof; and(3.3.) 2 to 30 parts by wt. of maleic acid anhydride.
摘要:
Powdered coating agent for use in the sprayed powder process comprising a mixture ofA. free hydroxyl groups containing copolymers having been reacted with an acid anhydride;B. a cross-linker such as triglycidyl isocyanurate or bis- or tris-oxazolines and optionallyC. auxiliary agents such as pigments and levelling agents.The copolymer contains polymerized units of30 to 85% by weight of styrene or derivatives thereof or methylmethacrylate or mixtures thereof;5 to 60% by weight of acrylic or methacrylic esters excepted methylmethacrylate and10 to 30% by weight of hydroxyalkylester of acrylic or methacrylic acid, said copolymer having been reacted with an aliphatic or cycloaliphatic dicarboxylic acid anhydride;4 to 20 parts by weight of the cross-linker are employed for 96 to 80 parts by weight of the acidified copolymer.
摘要:
This invention relates to thermoplastic moulding compounds free from nitrile groups, containing a mixture of randomly structured copolymers containing methyl methacrylate, maleic acid anhydride and aromatic vinyl compounds, aromatic polycarbonate resins and an elastomer grafted with methyl methacrylate.
摘要:
This invention relates to thermoplastic moulding compounds which are free from nitrile groups, obtained from randomly structured aromatic vinyl copolymers containing N-phenyl- or methyl-maleimide, aromatic polycarbonate resins and an elastomer grafted with methyl methacrylate.
摘要:
The invention relates to new cross-linked copolymers of N-vinyl pyrrolidone, N-alkyl-N-vinyl carboxylic acid amides, methacrylates and optionally further copolymerizing monomers of a specific composition. the copolymers have a water absorption capacity of up to about 80% by weight, based on the hydrated state, and are suitable for the production of shaped articles which are in contact with living tissue in use. Examples include soft contact lenses and scleral lenses of high mechanical strength, in particular thin to very thin lenses for prolonged wear.
摘要:
Process for the preparation of thermoplastic copolymers of .alpha.-methylstyrene and acrylonitrile by continuous bulk copolymerization ofA. 30 to 50 mol % of .alpha.-methylstyrene andB. 70 to 50 mol % of acrylonitrileat temperatures from 60.degree. to 120.degree. C. with average residence times of 4 to 12 hours in the presence of initiators which supply free radicals, carried out in at least two continuously operated mixed tank reactors, characterized in that 100 molar parts of a monomer mixture ofA.sub.0. 34 to 52 mol % of .alpha.-methylstyrene andB.sub.0. 66 to 48 mol % of acrylonitrileare fed continuously into the first tank reactor per unit time, and, with back-mixing, are copolymerized up to a conversion of 5 to 30 molar parts to give a copolymer of the compositionA.sub.1. 49 to 53 mol % of .alpha.-methylstyrene andB.sub.1. 51 to 47 mol % of acrylonitrile,and the mixture consisting of 70 to 95 molar parts of the monomers A and B and 5 to 30 molar parts of the copolymer of the composition A.sub.1 -B.sub.1 is transferred continuously to the second tank reactor and is polymerized there up at a further conversion of 5 to 55 molar parts to a total conversion of 20 to 60 molar parts to give further copolymer of the compositionA.sub.1. 49 to 53 mol % of .alpha.-methylstyrene andB.sub.1. 51 to 47 mol % of acrylonitrile,0,5 to 11.5 molar parts of acrylonitrile being removed from the vapor condenser of the second tank reactor and recycled to the first tank reactor per unit time.