DE3430802A1 - Process for the preparation of maleimide-containing polymers - Google Patents

Abstract

The invention relates to a process for the preparation of thermoplastic moulding compositions comprising random vinylaromatic compound/maleimide copolymers, which are obtained by reacting random vinylaromatic compound/maleic anhydride copolymers with ammonia or a primary amine.

Description

Process for the preparation of maleimide-containing

Polymers The invention relates to a process for the production of thermoplastic molding compounds made from randomly structured vinyl aromatic / maleimide copolymers, the reaction of random vinyl aromatic / maleic anhydride copolymers with ammonia or a primary amine.

Thermoplastic molding compounds, consisting of a randomly structured Styrene / maleic anhydride copolymers are known (see DE-OS 22 26 726), as well thermoplastic molding compounds, consisting of randomly structured styrene / maleic anhydride / acrylonitrile terpolymers (see DE-OS 27 47 822).

Compared to the corresponding molding compounds, they show no Maleic anhydride contain improved heat resistance. Disadvantageous is, however, that at elevated temperatures, such as those in processing or compounding with other resins or

Impact modifiers are applied, decomposition reactions, foaming and crosslinking of the molding compositions can be observed. Processing difficulties result and moldings with an unsightly surface.

If, on the other hand, an N-substituted one is used instead of the maleic anhydride Maleinimia, these phenomena do not occur. Statistically structured styrene Maleimide copolymers are known (see DE-OS 15 95 639). You can through direct Copolymerization can be produced from the monomers. Although the direct copolymerization of the monomers usually providing the 1: 1 alternating copolymers are methods known for the production of non-equimolar copolymers (see DE-OS 27 24 360).

However, the disadvantage of this route is that the maleimides are expensive, because they are in two-stage reaction by reacting maleic anhydride with primary Amines are produced.

Therefore, it has been proposed on various occasions to use maleic anhydride To convert copolymers into imides by reaction with primary amines. So DE-AS 19 25 996 describes a two-stage process in which a maleic anhydride copolymer is first made to react in an autoclave with primary amines, the Acid half-amide stage isolated and then several hours at elevated temperature is annealed for imide formation.

Their production in the melt was also mentioned (US-PS 44 04 322).

DE-OS 23 43 408 describes a similar process in which copolymers containing dicarboxylic acids, anhydrides or half esters, several hours at increased Temperature can be reacted under pressure with aqueous amines.

DE-OS 31 48 965 describes a process by which a polymer mixture can be prepared by first polymerizing styrene with maleic anhydride in bulk is and then after the addition of an amine and acrylonitrile at the same time in Suspension polymerization a styrene / acrylonitrile copolymer produced and the Imidization of the previously formed styrene / maleic anhydride copolymer carried out will.

All of these processes have the disadvantage that they are discontinuous run with long residence times and thus uneconomical for a technical implementation are.

The task was therefore to find a process that would be economical Imidization of randomly structured vinyl aromatic / maleic anhydride copolymers allowed for short dwell times.

The invention therefore relates to a process in which continuously the vinyl aromatic / maleic anhydride copolymer with ammonia andioder one or several primary amines in a molar ratio of 2: 1 to 1: 2, based on the built-in Maleic anhydride, at temperatures between 1500C and 3000C and pressures between 1 bar and 300 bar with an average residence time from 1 minute to 30 minutes, if appropriate in the presence of catalysts, reacted is and immediately thereafter the water of reaction and the excess of ammonia or amine and other volatile compounds are removed.

A preferred imidized thermoplastic produced according to the invention The molding compound consists of: A) 20 to 95% by weight vinyl aromatic, B) 0 to 10% by weight maleic anhydride, C) 5 to 30% by weight maleimide or N-substituted maleimide, D) 0 to 50% by weight Comonomer from the group of aliphatic or cycloaliphatic esters of (meth) acrylic acid with 1 to 6 carbon atoms, particularly preferably acrylonitrile and methacrylonitrile, where A), B), C) and D) each add up to 100% by weight.

The starting copolymers can be randomly structured, thermoplastic Processable vinyl aromatic / maleic anhydride copolymers can be used. she Further comonomers which can be copolymerized with styrene or maleic anhydride can be used built-in included. As vinyl aromatics, styrene, 4-methylstyrene, p-methylstyrene, Ethylstyrene, p-tert-butylstyrene, o- or p-chlorostyrene, preferably styrene, are used will.

Acrylonitrile, methacrylonitrile, C1 to C8 alkyl, C5 10 cycloalkyl, C6 -C14 aryl esters of methacrylic acid or of acrylic acid like e.g. methyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, Benzyl methacrylate and phenyl methacrylate can be used.

The corresponding resins can by known methods in bulk, Solution or suspension can be prepared.

Batch processes require statistical production built-up copolymer due to the tendency of maleic anhydride to 1: 1 copolymerization costly top-up or feed approaches with styrene. The continuous bulk polymerization in a mixed tank reactor is preferred for these reasons.

The molar weights of usable starting resins can be in a wide range vary. Starting resins are preferred which have an intrinsic viscosity in dimethylformamide t 'D7MF from 0.3 to 1.5 dl / g measured at 250C.

The method according to the invention allows statistically structured Imidize vinyl aromatic / maleic anhydride copolymers with short residence times. It is advantageous that the process according to the invention is carried out continuously can be, whereby a more economical reaction is given. The products are evenly imidized.

Aliphatic and aromatic amines can be used as primary amines. In particular, there may be mentioned e.g.

Methyl, ethyl, n-propyl, isopropyl, n-butyl, t-butyl, hexyl, Cyclohexyl, aniline, p-toluidine, bromaniline, chloroaniline. Mixtures can also be used the amines are used.

By varying the molar ratio between the primary amine and the anhydride groups present in the starting resin, the degree of imidization influence. A deficit of amine makes molding compounds accessible that are still contain a residual content of anhydride groups, while with equimolar use of the Amine or, with an excess, complete conversion of the anhydride groups is possible is.

The molar ratio between the primary amine or

Ammonia and the copolymerized maleic anhydride should be 2: 1 up to 1: 2.

The reaction can be carried out at temperatures from 1500C to 3000C will.

The pressure can be varied within wide limits from 1 to 300 bar. In general, it is above the partial pressure of the amine at the reaction temperature, however, even below this, with good mixing in the reaction zone, a sufficient one can be used Sales can be achieved.

The mean residence time of the reaction mass in the reaction zone is 0.5 minutes to 30 minutes.

The reaction of the copolymer with primary amine or ammonia can be carried out in the presence of a catalyst. As catalysts, e.g. tertiary amines, such as trimethylamine, triethylamine, tripropylamine, tributylamine, N, N-dimethylaniline, N, N-diethylaniline or triethylenediamine can be used.

The amount of the catalyst is in the range from 0.01 to 10 mol%, based on the maleic anhydride used.

The process can be carried out in different reaction apparatuses will. A preferred embodiment is the reaction in a screw machine (R. Erdmenger, Maschinenmarkt 80 (1974) No. 1, 2-6 and No. 10.148-152). The starting resin can be fed to the screw machine in solid form, e.g. as granules or powder, supplied and melted in a first zone of the screw machine be, or the starting resin is the screw machine as a melt or supplied in dissolved form.

This can be done, for example, from a previous polymerization stage, wherein the starting resin still contains a residual content of monomers or solvents.

The amine or ammonia is under pressure in the melt of the starting resin dosed into the screw machine.

Resulting water as well as a possible excess of ammonia resp. Amine and other volatile compounds are removed immediately afterwards. This can e.g.

take place in a further stage of the screw machine or in another apparatus that is directly connected to the screw machine in which the Reaction occurs, is connected. This can be, for example, another screw machine or a thin layer.

In the case of the screw machine in which the reaction is carried out, it is preferably a multi-shaft type such as a twin screw machine with the same or opposite direction of rotation. You can also use a single-wave Use the screw machine, the housing side with shear bolts and corresponding Interruptions of the worm gear are provided to increase the mixing.

A preferred embodiment is the reaction in one static mixer.

This is a heatable tubular reaction vessel, that is provided with statically mixable internals.

The starting resin becomes continuous at one end of this mixer fed in molten or dissolved form and ammonia or the amine under pressure metered in and mixed. At the other end, the reaction mixture is removed from the mixer and fed to a directly connected evaporation apparatus. Here can For example, it is an evaporation screw machine or a thin-film machine.

In addition to a static mixer, dynamic mixers can also be used as Reaction vessel can be used.

A particularly advantageous embodiment is that you 1. a mixture of vinyl aromatic and maleic anhydride continuously mixed Tank reactor feeds, at temperatures between 700C and 1500C with a mean Dwell time from 10 min. To 120 min., If necessary with the aid of an in Radical decomposing initiator, up to a steady conversion of 30% by weight up to 60% by weight, based on the monomers fed in, polymerized, the partially withdrawn converted monomer / polymer mixture from the reactor in an amount that corresponds to the Entry corresponds to 2. this mixture through a heated heat exchanger in a heated vessel under reduced pressure is relaxed, with at least 90% by weight of the volatile components are separated off, 3. the remaining syrup second reactor feeds ammonia, a primary amine or a mixture of these compounds in a molar ratio of 1.2: 1 to 0.8: 1 based on the maleic anhydride used, feeds the mixture of these compounds through a second opening to the second reactor at temperatures between 1800C and 2500C. and pressures between 1 bar and 150 bar with an average residence time of 1 to 15 minutes in the plug stream with more intimate Cross-mixing leads through the second reactor and 4. Immediately then the remaining monomers and other volatile components under reduced Pressure removed.

The monomers separated in step 2 are condensed and directly returned to the polymerization kettle. A use of small amounts of one Solvents such as ethylbenzene or methyl ethyl ketone are possible. Through the Let the coupling of polymerization and imidization in one continuous process improved compared to a two-step, completely separate process Achieve product properties.

The isolation of the maleic anhydride-containing polymer according to the Polymerization and remelting prior to imidization are avoided.

The thermal stress and damage to the maleic anhydride Polymer is reduced.

A small part of the unreacted monomers from the polymerization stage The process also goes through the imidization stage. They improve the flowability the melt and allow a lower heating of the promoting organs and Pipelines.

In addition, the amine is mixed into the maleic anhydride-containing Polymers and mixing improved in the reaction part of the imidization stage.

This allows higher sales, all other things being equal of maleic anhydride.

The proportion of unreacted monomers caused by the imidization step is performed, but may not too high because this Monomers not or only after complex and expensive processing in the polymerization stage can be returned.

The molding compositions produced by this process have a reduced Residual amine content. This is especially beneficial for using this Molding compounds for blending with polycarbonate.

The imidized, thermoplastic produced according to the invention Compared to the non-imidized starting points, molding compounds show improved results thermal resistance to discoloration and crosslinking.

The imidized, thermoplastic produced according to the invention Molding compounds can be processed into "ABS molding compounds" with impact modifiers, for example will. Customary stabilizers, light stabilizers, anti-aging agents, Leveling and processing aids, fillers, mineral and organic Fiber and reinforcing fillers such as glass fiber, carbon fiber, metal wiskers, polyester, Polyamide, polyaramid fiber etc., pigments ect. be added. According to the invention produced molding compounds are particularly advantageous where there is a need for good weather resistance, high heat resistance, high toughness and ease of processing are important.

For example, they can be used to advantage in the production of pipelines, of high-quality seals, of dishes, of devices that can be sterilized with superheated steam, of washing machine parts, of battery boxes, of drying battery cases, of housings and other insulating parts in electrically operated machines, of electrical insulation foils, of saponification-stable container linings, chemically and thermally resistant filter cloths and many other things will. Preferred areas of application are the construction of vehicle parts, automotive, Motorcycles, aircraft and railroad construction, the production of intricately shaped injection molded parts, of which a high heat resistance is required, e.g. radiator grille, Mudguard inserts, interior panels, dashboards, grab handles, car roofs, Covers, housings of household appliances and office machines.

Examples 1-9 Unless otherwise specified, parts are parts by weight and percentages percentages by weight.

For the imidization of the randomly structured vinyl aromatic / maleic anhydride copolymers becomes a screw machine with two interlocking ones running in the same direction Waves used. The shafts have a diameter of 32 mm and a length of 1200 mm. The vinyl aromatic / maleic anhydride copolymer (Table 1) is the Screw machine continuously supplied as granules through a metering opening and melted in a subsequent zone of the screw machine.

The melting zone is created by a jump in the incline of the wave trains hydraulically sealed against the subsequent reaction zone. The reaction zone has a length of 600 mm. Immediately after the incline jump becomes the primary one Amine is pumped into the melt and mixed in.

The reaction mixture leaves the reaction zone via a further one Gradient jump and reaches a degassing zone in which volatile components pass through Application of vacuum can be removed. The melt leaves the screw machine a nozzle, is cooled and granulated.

The reaction conditions are summarized in Table 2.

Examples 10-14 The preparation of maleic anhydride-containing Polymers takes place in a jacketed vessel, which is equipped with an internal thermometer, stirrer, Inlet and outlet is provided. In the reactor of 8 l content 3 kg / h are one Monomer mixture dosed according to table 1. The monomer stream contains approx. 0.01 mol% azobisisobutyronitrile. At 1300C internal temperature, A solids content of approx. 45% is achieved with an average residence time of 40 min. The reactor 6.7 kg / h of the polymer syrup are removed and through a heat exchanger that is on 1900C is kept, fed to an expansion vessel. This is about 10 mbar Maintained pressure and heated to 2300C. The vapors are condensed and sent to the polymerization stage returned. The polymer melt, which is taken from this vessel at approx. 3 kg / h, contains a polymer according to Table 1 and small amounts of unreacted Monomer. The content of monomers (Table 4) can be determined by the amount on the expansion vessel applied pressure vary. The degassed polymer is made using a screw machine two co-rotating, interlocking shafts fed. The waves have a diameter of 32 mm and a length of 1200 mm. Immediately behind When the polymer is fed in, the primary amine is pumped into the melt and mixed in. The reaction zone has a length of 800 mm. The reaction mixture leaves the reaction zone over a pitch jump of the wave trains, which the reaction zone hydraulically shut off from the following degassing zone. The volatile components will be removed in the degassing zone by applying a vacuum at temperatures of approx. 240 "C. The melt of the imidized polymer leaves the screw machine through a Nozzle, is cooled and granulated.

The reaction conditions of the imidization reaction are shown in Table 4 summarized.

Table 3 contains the properties of the molding compositions produced. The heat resistance of the polymers is determined by the Vicat B temperatures, measured according to DIN 53 460, characterized. To assess the networking tendency of the molding compounds, the molding compounds are heated to 2600C and at this temperature held. After 5, 10, 15 and 20 minutes, the melt viscosity according to DIN 53 is then 735 measured. The half-life t in which the flowability of the melt is halved, is given in Table 3.

The optical assessment of the molding compositions was carried out on moldings which at 2600C after the melt has been heated to 260 ° C for 10 minutes beforehand became.

The surface of the molded body was discolored from surface defects examined.

Table 1 Composition of the monomer mixture and the polymers of of imidization monomer mixture (%) polymer composition (%) ST MSA ACN MMA ST MSA ACN MMA NPMI DMF A 94.2 5.8 --- --- 87.2 12.8 --- --- --- 0.6 B 78.9 5.1 16.0 --- 74.0 11.4 14.6 --- --- 0.6 C 42.4 4.6 --- 37.8 58.4 10.3 --- 31.3 --- 0.6 D 92.2 7.8 --- --- 82.6 17.4 --- --- --- 0.5 Comparison resins V1 80.9 2.4 --- --- 16.7 0.6 V2 69.0 1.8 13.6 --- 15.6 0.6 ST = styrene MSA = maleic anhydride ACN = acrylonitrile MMA = methyl methacrylate, NPMI = N-phenyl maleimide Table 2 imidization, Examples 1 - 9 Resin Amount Amine Amount Catalyst Amount T Reaction P Dwell P Conversion g / h g / h g / h C ° bar time min. evaporation% mbar 1 A 3,000 aniline 440 - - 240 5 4.8 1.2 80 2 A 3,000 aniline 440 Ttriethylamine 2.4 240 5 4.8 1.4 87 3 A 3,000 aniline 440 triethylenediamine 2.7 240 5 4.8 1.3 94 4 B 3,000 aniline 370 triethylenediamine 2.3 240 5 4.8 0.9 92 5 B 6,000 aniline 740 triethylenediamine 4.6 270 5 2.4 1.2 90 6 B 3,000 aniline 440 - - 240 5 4.8 1.4 81 7 C 3,000 aniline 350 triethylenediamine 2.2 210 5 4.8 1.5 83 8 D 3,000 aniline 600 TRiethylamine 3.3 240 5 4.8 1.5 85 9 A 3,000 aniline 330 triethylenediamine 2.7 240 5 4.8 1.3 72 Tabel 3 Properties of the Vicat B molding compounds produced according to the invention (° C) t1 / 2 (min) Discoloration of the surface 260 ° C / 10 '1 122 --- None smooth 2 126 --- "" 3 127 --- " "4 125 #" "5 124 #" "6 121 #" "7 120 ---" "8 134 ---" "9 123 ---" " 10 126 --- "" 11 125 # "" 12 121 --- "" 13 127 --- "" 14 124 # "" V1 120 --- light brownish small bubbles V2 119 31 brownish pores A 120 --- "bubbles B 123 15 rough brown streaks C 118 --- brown blisters D 132 --- brownish blisters Tabel 4 Resin Amount Residual Mo-Amine Amount Catalyst Amount T Reaction P Dwell P Conversion Residual amine g / h nomer g / h g / h bar time evaporation%% ° C min mbar 10 A 3,000 8 aniline 440 triethylenediamine 2.7 5 4.8 1.1 98 0.1 11 B 3,000 8 aniline 370 triethylenediamine 2.3 210 5 4.8 1.4 97 0.1 12 C 3,000 8 aniline 350 triethylenediamine 2.2 210 5 4.8 1.3 98 0.1 13 A 3,000 1 aniline 440 triethylenediamine 2.7 210 5 4.8 1.2 93 0.22 14 B 3,000 1 aniline 370 triethylenediamine 2.3 210 5 4.8 1.3 91 0.26 Tabel 3 shows that the imidized, thermoplastic molding compositions are exposed to thermal stress do not crosslink and that the shaped bodies do not have any surface defects due to bubbles or have discoloration in contrast to the starting resins A - D and the comparative resins V1 and V2, which were produced directly from monomers.

Claims (4)

Claims 1. Process for the production of thermoplastic Molding compounds made from randomly structured vinyl aromatic / maleimide copolymers Implementation of randomly structured vinyl aromatic / maleic anhydride copolymers with ammonia or primary amines, characterized in that one continuously the vinyl aromatic / maleic anhydride copolymer with ammonia and / or one or several primary amines in a molar ratio of 2: 1 to 1: 2, based on the built-in Maleic anhydride, at temperatures between 1500C and 3000C and pressures between 1 bar and 300 bar with an average residence time of 0.5 minutes to 30 minutes, optionally reacts in the presence of catalysts and immediately then the water of reaction and the excess of ammonia or Amine and other volatile compounds removed. 2. The method according to claim 1, characterized in that the imidization of the randomly constructed vinyl aromatic maleic anhydride copolymer in one Screw machine takes place, with the melted starting polymer in one zone Ammonia or a primary amine or mixtures of these compounds are metered in and are mixed in, the reaction is carried out in a further zone and the excess ammonia or amine and other volatile compounds are removed will. 3. The method according to claim 1, characterized in that the imidization of the randomly structured vinyl aromatic / maleic anhydride copolymer in one static mixer takes place, the melted starting polymer through a Pump is supplied, the ammonia or primary amine or Mixtures of these compounds in the molten starting polymer be dosed into the mixer, the reaction carried out, the reaction material from the Mixer is removed and the water of reaction and the excess of ammonia or Amine and other volatile compounds are removed immediately afterwards. 4. The method according to claim 1, characterized in that 1. a Mixture of vinyl aromatic and maleic anhydride continuously mixed Tank reactor feeds, at temperatures between 700C and 1500C with a mean Dwell time from 10 min. To 120 min., If necessary with the aid of an in Radical decomposing initiator, up to a steady conversion of 30% by weight up to 60% by weight, based on the monomers fed in, polymerized, the partially withdrawn converted monomer / polymer mixture from the reactor in an amount that corresponds to the Entry corresponds to, 2. this mixture through a heated heat exchanger relaxed in a heated, under reduced pressure vessel, with at least 90% by weight of the volatile components are separated off, 3. the remaining syrup second reactor feeds ammonia, a primary amine or a mixture of these compounds in a molar ratio of 1.2: 1 to 0.8: 1 based on the maleic anhydride used, feeds the mixture of these compounds through a second opening to the second reactor at temperatures between 1800C and 2500C and pressures between 1 bar and 150 bar with an average residence time of 1 minute to 15 minutes. in the plug stream with intimate cross-mixing through the second Reactor leads and 4. immediately afterwards the remaining monomers and others volatile components removed under reduced pressure.