MX2008006059A - Process for preparing anhydride-containing vinylaromatic-vinyl cyanide copolymers - Google Patents

Abstract

The present invention relates to processes for preparing copolymers A) containing A1) one or more vinylaromatic monomers, A2) one or more vinyl cyanides and A3) one or more dicarboxylic anhydrides by bulk or solution polymerization, it being essential to the invention that the polymerization be performed in the presence of 0.01 to 0.5%by weight of water, based on the total weight of the polymerization mixture. The present invention further relates to the copolymers A), to thermoplastic moulding compositions comprising the copolymers A), to the use of the copolymers A) and of the thermoplastic moulding compositions, and to the mouldings, films, fibres and foams obtainable from the copolymers A) and the thermoplastic moulding compositions.

Description

PROCESS FOR THE PREPARATION OF AROMATIC VINYL-CYANIDE AROMATIC COPOLYMERS CONTAINING ANHYDRIDE VINYL The present invention relates to a process for the preparation of copolymers A) comprising Al) one or more aromatic vinyl monomers, A2) one or more cyanides of vinyl and A3) one or more dicarboxylic anhydrides, through mass polymerization or through solution polymerization. The present invention also relates to copolymers A), to thermoplastic molding compositions comprising copolymers A), to the use of copolymers A) and to thermoplastic molding compositions and also to molded products, sheets, fibers or foams which can be obtained from the copolymers A) and from the thermoplastic molding compositions. Vinyl aromatic vinyl cyanide copolymers comprising anhydride are known per se, an example being styrene-acrylonitrile-maleic anhydride copolymers, as well as processes for their preparation. By way of example, DT 25 40 517 A1 discloses polymers based on styrene, acrylonitrile, and maleic anhydride which are prepared through a specific continuous mass polymerization reaction in several stages of a process in the presence of polymerization initiators. The residual monomer contents of the polymers are reduced to contents below 0.5% by weight through the application of vacuum or through the introduction of inert gas. EP 0 001 625 A1 relates, inter alia, to specific terpolymers formed by styrene, acrylonitrile, and maleic anhydride. They were prepared through continuous bulk polymerization in the presence of an initiator that decomposes to provide free radicals. In subsequent steps of a process, the content of residual monomers is reduced to a level below 0.1% by weight through evaporation or through inert gas injection. EP 0 433 711 A2 describes specific processes for the preparation of terpolymers based on styrene, acrylonitrile and maleic anhydride, in which the reaction of the monomers is carried out in bulk without the admission of solvents or diluents. In a preferred embodiment, the polymerization reaction is thermally initiated without the addition of chemical initiators. Residual monomers can be removed in subsequent stages of a process. DE 100 58 302 A1 discloses stabilized styrene copolymers comprising aromatic vinyl monomers and one or more comonomers. The styrene copolymers are prepared in particular in bulk or in solution. The polymerization reaction can be initiated through the addition of chemical initiators or thermally.

Copolymers which can be prepared by known processes and consisting of vinyl aromatic monomers or vinyl cyanides, and dicarboxylic anhydrides are frequently still unsatisfactory in terms of their intrinsic color, melt stability, residual contents of low weight compounds molecular [for the purposes of this invention, the definition of low molecular weight compounds is compound whose average molar mass (weight average) Mw is less than or equal to 10,000 g / mol, as determined by gel permeation chromatography at 35 ° C using three polystyrene gel columns from Polymer Laboratories placed in series, with tetrahydrofuran as eluent (calibration with standard polystyrene), using the UV detector signal]. An object of the present invention was therefore to provide copolymers based on vinyl aromatic monomers, or vinyl cyanide, and on dicarboxylic anhydrides and having a lower intrinsic color, higher melt stability and / or lower residual contents of low molecular weight. Suitable preparation processes should also be provided for these copolymers with improved properties. Therefore, the processes defined at the beginning for the preparation of copolymers A) were found, and it is important for the invention here that the monomers are polymerized in the presence of 0.01% to 0.5% by weight of water, based on the total weight of the polymerization mixture. In addition, copolymers A) based on aromatic vinyl monomers, vinyl cyanide, and dicarboxylic anhydride, as well as thermoplastic molding compositions comprising these copolymers A), the use of these copolymers A) and these molding compositions were found. thermoplastics, and furthermore molded products, sheets, fibers, and foams comprising these copolymers A) and, respectively, these thermoplastic molding compositions. The processes, copolymers, thermoplastic molding compositions, uses and molded products, sheets, fibers or foams of the present invention are described below. In principle, any of the processes of bulk polymerization or solution polymerization known to the person skilled in the art and described in the prior art, for example, in DE 100 58 302 A1 and in the documents mentioned herein , it is suitable as a process of the invention for preparing the copolymers A) comprising Al), one or more aromatic vinyl monomers, A2) one or more vinyl cyanides, and A3) one or more dicarboxylic anhydrides, insofar as the monomers are polymerized in the presence of 0.01% to 0.5% by weight, preferably from 0.03% to 0.4% by weight, particularly preferably from 0.05% to 0.3% by weight, of water, based on the total weight of the mixture of polymerization. The component Al) used can comprise any of the vinyl aromatic monomers known to the person skilled in the art and described in the prior art, for example, in DE 100 58 302 Al; those preferably used are styrene, α-methylstyrene, p-methylstyrene, tert-butylstyrene, vinylnaphthalene, or a mixture thereof; the use of styrene is especially preferred. The component A2) used can comprise any of the vinyl cyanides known to the person skilled in the art and described in the prior art, for example, in DT 25 40 517 A; those preferably used are acrylonitrile, methacrylonitrile, or a mixture thereof; particular preference is given to the use of acrylonitrile. The component A3) used can comprise any of the dicarboxylic anhydrides known to a person skilled in the art and described in the prior art; preference is given to the use of maleic anhydride, methylmaleic anhydride, itaconic anhydride, or a mixture thereof; particular preference is given to the use of maleic anhydride. The component A4) used in the copolymers A) of the present invention may comprise monomers other than the components Al), A2), and A3), but copolymerizable therewith. Copolymers A) are particularly preferably styrene-acrylonitrile-maleic anhydride copolymers. Copolymers A) usually comprise from 50% to 94.7% by weight, preferably from 59% to 89% by weight, particularly preferably from 68% to 78.5% by weight, of component A); from 5% to 49.7% by weight, preferably from 10% to 40% by weight, particularly preferably from 20% to 30.5% by weight, of component A2); from 0.3% to 10% by weight, preferably from 1% to 85%, by weight, particularly preferably from 1.5% to 6% of component A3); and from 0% to 25% by weight, preferably from 0 to 15%, particularly preferably from 0% to 10% by weight, of component A4), wherein each of the percentages by weight is based on the total weight of components Al), A2), A3), and A), and its total is 100% by weight. The copolymers A) are prepared by bulk polymerization or solution polymerization, but preferably by solution polymerization in the presence of an organic solvent, such as, for example, cyclohexane, ethylbenzene, or dimethyl sulfoxide, preferably ethylbenzene. In principle, both in the solution polymerization reaction and in the bulk polymerization reaction, the polymerization reaction can be initiated by the addition of chemical polymerization initiators, for example, in accordance with that described in DE 100 58 302 Al; however, a purely thermal onset is preferred, that is, without the addition of any polymerization initiator. The process of preparation in batch or semi-batch can be used, but it is preferable to use a continuous process duct. In a particularly preferred embodiment of the processes of the present invention, the process conduit is continuous under constant state conditions; Constant state conditions mean that the concentration of all the reactants and the constitution of the copolymers A) formed remain substantially constant during the reaction time. (Information on the relationship between the monomeric constitution and the polymeric constitution, and also on the performance of the reaction in a state of equilibrium, can be found in particular in EP 0 001 625 A1 and DT 25 40 517 A1). Suitable process parameters, such as pressure, temperature, residence times, etc., suitable equipment to carry out the processes, and also suitable flow regimes for feeding the monomers and the solvents, if necessary. present, and initiators, if present, and other polymerization additives, if appropriate, are known to the person skilled in the art and described in the prior art. It is important for the invention that the monomers be polymerized in the presence of the specified amounts of water. Water can be added separately to the polymerization mixture, but can also be added to one of the monomer currents or - if present, solvent streams introduced. The water added to the polymerization mixture preferably takes the form of a mixture with component A2). The treatment of the polymerization mixture and the isolation of the copolymers A) can be carried out by methods known to the person skilled in the art and described in the prior art, for example, through the removal of low molecular weight by applying vacuum or exhaustion with inert gas. The copolymers A) prepared by the processes according to the present invention in the presence of the specified amounts of water in the polymerization mixture differ from the copolymers prepared without the presence of the specified amounts of water in the polymerization mixture but otherwise through comparable processes insofar as they have less intrinsic color, exhibit greater melt stability, and / or have residual contents less than low molecular weight compounds. The copolymers A) of the present invention can be processed with other thermoplastic polymers B), such as, for example, copolymers of styrene-acrylonitrile (SAN), polyamide (PA), poly (meth) acrylates (PMMA), or polycarbonate (PC), and with rubbers C), such as for example polybutadiene rubbers or acrylate rubbers, and with particulate or fibrous fillers, or with reinforcing materials D) particulate or fibrous, in particular glass fibers, and / or with additives E) conventional in plastics, for example, thermal stabilizers, UV stabilizers, lubricants, flame retardants, antistatic agents, colorants, color pigments, etc., to provide thermoplastic molding compositions. Preferred thermoplastic molding compositions comprise from 1% to 95% by weight of copolymers A), from 5% to 99% by weight of one or more thermoplastic polymers B) different from component A), from 0% to 50% of one or several rubbers C). from 0% to 40% by weight of one or more particulate or fibrous fillers or particulate or fibrous reinforcement materials D), and from 0% to 25% by weight of one or more conventional E) additives in plastic, wherein each of the percentages in pesos is based on the total weight of components A), B), C), and E) and its total is 100% by weight. The components B), C), D), and E), per se are known by the person skilled in the art and are described in the prior art, as well as processes for the preparation of thermoplastic molding compositions from of the individual components. The polymers A) of the present invention and the thermoplastic mole compositions comprising comprising the copolymers A) can be used to produce molded products, sheets, fibers, or foams, through processes known to the person skilled in the art. in the matter and described in the prior art as for example, injection molding, compression molding, calendering, or extrusion.The examples presented below are used to further explain the present invention. Examples: In each of the examples of According to the present invention and comparative examples presented below, copolymers were prepared and their properties determined Initial materials: Commercially available styrene (purum [pure]) from Fluka Riedel-de Haen (Sigma-Aldrich) was used as an Al-component Acrylonitrile commercially available (purum [pure]) from Fluka Riedel-de Haen (Sigma-Aldrich) was used as a Rapporteur A2-i Commercially available maleic anhydride (purum [pure]) from Fluka Riedel-de Haen (Sigma-Aldrich) was used as component A3-i. Commercially available ethylbenzene (purum [pure]) from Fluka Riedel-de Haen (Sigma-Aldrich) was used as a solvent for the polymerization reaction. All specified components Al-i, A2-i, A3-i, and solvent, were distilled immediately before use. The water content of the Al-i, A2-i, A3-i, and solvent distilled components was determined by Karl Fischer titration and in each case was less than 0.01% by weight with ase in the respective component or solvent. Preparation and properties of copolymers The respective parts by weight specified in Table 1 of components Al), A2), A3) and solvent and deionized water (no water was added in the comparative experiments) were introduced per unit of time in a stirred tank operated continuously in steady state (tank operated continuously), rinsed with nitrogen. In each case, the temperature of the polymerization mixture was 145 ° C, and in each case a purely thermal onset of the polymerization reaction was used. In each case, the polymerization mixture with a polymeric solids content of 50% by weight based on weight, based on the total weight of the polymerization mixture, was continuously withdrawn from the stirred tank, and in each case methods were used. identical in the two stages to remove monomers that did not react, solvents and other low molecular weight compounds. Each of the obtained copolymers was pelletized and dried. These pellets were used for the production of test samples to test certain properties in an injection molding machine at a melting temperature of 240 ° C and mold surface temperatures of 60 ° C. The following properties were determined: VN viscosity [ml / g]: Viscosity number VN was determined at 25 ° C in a 0.5% by weight solution of the respective copolymer in dimethylformamide to DIN 53726. YI yellowness index [without dimension]: The yellowness index (hue) yellow) YI was determined in accordance with ASTM D 1925 on molded injection plates (dimension: 60 mm x 60 mm x 2 mm; the melting temperature during injection molding was 240 ° C; the mold temperature during injection molding was 60 ° C). Change in melt viscosity as a measure of melt stability [%]: Melt viscosity? of the copolymers was determined using a high-pressure capillary rheometer (Rheograph 2003) from Gottfert at a cutoff frequency of 55 Hz at a melting temperature of 300 ° C after, respectively, 5 minutes (n5) and 30 minutes (n30 ). The melt stability measurement is calculated, in each case, by taking the numerical difference of the melt viscosities after 30 minutes and after 5 minutes as a ratio of the melt viscosity after 5 minutes and multiplying by 100%. |? 30 _? 5 | * 100% /? 5 > Content of low molecular weight compounds [% by weight] The weight content of compounds of average molar mass (weight average, in accordance with that determined by GPC) w is 10, 000 g / mole or less, based on the total weight of the copolymers, as determined by chromatography of gel permeation at 35 ° C using 3 polystyrene gel columns from Polymer Laboratories placed in series, with tetrahydrofuran as eluent (calibration with standard polystyrene), using the UV detector signal. The parts by weight of the introduced components, of the solvent, and of the deionized water, being the materials used to prepare the copolymers, are found in the Table 1 and also the properties of the copolymers. Table 1: Parts by weight of introduced components, solvent, and deionized water, and properties of copolymers * Examples indicated by "c" as comparative examples.

** In the comparative examples in which no water was introduced, the water content of the polymerization mixture was determined by Karl Fischer titration; was in each case less than 0.01% by weight, based on the total weight of the polymerization mixture. The examples provide evidence of the lower intrinsic color level, the higher melt stability and the lower residual content of low molecular weight compounds in the copolymers A) prepared according to the invention.

Claims (8)

1. CLAIMS 1. A process for the preparation of copolymers A) comprising: Al) one or more aromatic vinyl monomers, A2) one or more vinyl cyanides, and A3) one or more dicarboxylic anhydrides through bulk polymerization or through of solution polymerization, comprising carrying out the polymerization in the presence of 0.01% to 0.5% by weight of water, based on the total weight of the polymerization mixture.
2. 2. The process according to claim 1, wherein the polymerization is thermally initiated, without the addition of any polymerization initiator.
3. 3. The process according to claims 1 to 2, wherein the polymerization is a solution polymerization carried out in the presence of an organic solvent.
4. 4. The process according to claims 1 to 3, wherein the copolymers A) comprise from 50% to 94.7% by weight, of one or more aromatic vinyl monomers Al), from 5% to 49.7% by weight, of one or more vinyl cyanide A2), of 0.3 % to 10% by weight, of one or more dicarboxylic anhydrides A3), and from 0% to 25% by weight, of other copolymerizable monomers A4), wherein each of the percentages is based on the total weight of the Al components ), A2), A3), and A), and its total is 100% by weight.
5. 5. The process according to claims 1 to 4, wherein: component Al) is styrene, oi-methylstyrene, p-methylstyrene, tert-butylstyrene, vinylnaphthalene, or a mixture consisting of two or more of these monomers, component A2) is acrylonitrile, methacrylonitrile, or mixtures of these monomers, and component A3) is maleic anhydride, methylmaleic anhydride, itaconic anhydride, or a mixture formed by two or more of these monomers.
6. 6. The process according to claim 1 to 5, wherein the copolymer A) is a copolymer of styrene-acrylonitrile-maleic anhydride.
7. 7. A copolymer A), which can be prepared through a process according to any of claims 1 to 3. 8. A thermoplastic molding composition comprising: from 1% to 95% by weight of copolymers A), of according to claim 7, from 5% to 99% by weight of one or more thermoplastic polymers B) different from component A), from 0% to 50% of one or more rubber C). from 0% to 40% by weight of one or more particulate or fibrous fillers or particulate or fibrous reinforcement materials D), and from 0% to 25% by weight of one or more conventional E) additives in plastic, wherein each of the percentages in pesos is based on the total weight of components A), B), C), and E) and its total is 100% by weight. 9. The use of copolymer A) according to claim 7 or of the thermoplastic molding compositions according to claim 8 for the production of molded products, sheets, fibers or foams. 10. A molded article, a sheet, a fiber or a foam obtainable from the copolymers A) according to claim 7 or from the thermoplastic molding compositions according to claim
8. 8.