POLYMER COMPOSITION

Abstract: The invention relates to a polymer composition containing a polymer A that contains vinyl-aromatic monomeric units and acrylonitrile monomeric units and a polymer B that contains vinyl-aromatic monomeric units, dicarboxylic acid anhydride monomeric units and/or imide monomeric units, and at least 1 wt. % spirodilactone monomeric units. The polymer composition has a higher glass transition temperature and an improved thermal stability.

Description: POLY ER COMPOSITION The invention relates to a polymer composition containing a polymer A that contains vinyl-aromatic monomeric units and acrylonitrile monomeric units and a polymer B that contains vinyl-aromatic monomeric units, dicarboxylic acid anhydride monomeric units and/or imide monomeric units. Such a polymer composition is known from DE-A- 3.332.326. The known polymer composition has good processability and great stiffness. Although the polymer composition has a relatively high glass transition temperature, said glass transition temperature is still insufficiently high for a large number of applications. The aim of the invention is to provide a polymer composition that does not have the aforementioned drawback. This is achieved because polymer B in the polymer composition according to the invention contains at least 1 wt.% spiroduactone monomeric units. The resultant higher glass transition temperature makes it possible to use the polymer composition according to the invention in articles that are exposed to higher temperatures. It is for example possible to use the polymer composition according to the invention in automotive parts that are mounted on or in the immediate vicinity of the motor, whereas this is not really possible with the known polymer composition. A further advantage of the polymer composition according to the invention is the greatly improved thermal stability relative to that of the known polymer composition. Because of this, the polymer composition can be processed into articles of a more complex design at even higher temperatures, and hence at a lower viscosity. In addition. the polymer composition can be used in articles that are exposed to elevated temperatures for long periods too. Polymer A generally contains 2-50 wt.% acrylonitrile monomeric units and 50-98 wt.% vinyl-aromatic monomeric units. Suitable vinyl-aromatic monomers are styrene, alpha-methylstyrene, para-methylstyrene or a mixture thereof. Preferably, use is made of styrene. In addition, polymer A may contain small amounts of one or more other monomeric units such as for example methylmethacrylate monomeric units. Preferably, polymer A has a weight average molecular weight of between 30,000 and 150,000 kg/kmol. Polymer B is known per se from O-90/06956. Polymer B can be prepared by preparing a polymer C that contains dicarboxylie-anhydride monomeric units and vinyl-aromatic monomeric units in a first step, using one of the known processes, and then converting polymer C into polymer B in a second step. Suitable vinyl-aromatic monomers are styrene, alpha-methylstyrene, para-methylstyrene and mixtures thereof. Preferably, use is made of styrene. Suitable dicarboxylic anhydrides are maleic anhydride, chloromaleic anhydride, citraconic anhydride, cyclohexylmaleic anhydride, benzylmaleic anhydride, phenylmaleic anhydride, aconitic anhydride, propylmaleic anhydride and mixtures hereof. Preferably, use is made of maleic anhydride (MA) . The conversion of polymer B into polymer C may be effected via heating to a temperature of preferably 200- 300°C. During the heating a conversion takes place in the chain of the polymer, in which dicarboxylic anhydride-vinyl aromatic monomer-dicarboxylic anhydride (Formula I) reacts to form spiroduactone (Formula II) according to the equation: - C - C - C - C - C - C - → I I I I I Form. I C - - c - c c - c - + co 2 τ / / 0 0 Form. II The polymer must be heated for a sufficient length of time to effect the desired conversion. However, this involves the risk that secondary thermal decomposition processes in the polymer may start to play an important part after some time, before the desired conversion is realized. This is one of the reasons why the heating is preferably done in the presence of a basic catalyst. By using the catalyst the desired conversion can be realized quicker and at a lower temperature. Examples of suitable catalysts are tertiary amines; preferably use is made of triethylamine (TEA) or 1,4- diazobicyclo[2,2,2]octane (DABCO) . The reaction can be carried out by heating the polymer per se, in which case the reaction takes place while the polymer is in a melted condition. It is also possible to carry out the reaction while the polymer is in solution. Suitable solvents are dimethylformamide, tetrahydrofuran, acetone and methylethyl ketone or other ketones. The glass transition temperature of the polymer composition increases with the spiroduactone monomeric units content of polymer B. Because of this, polymer B preferably contains at least 2 wt.% spiroduactone monomeric units. In another preferred embodiment polymer B contains at least 4 wt.% spiroduactone monomeric units. In yet another preferred embodiment polymer B contains at least 6 wt.% spiroduactone monomeric units. Preferably, polymer B has a weight average molecular weight of between 30,000 and 200,000 kg/kmol. If polymer B is prepared from polymer C, as described above, then this polymer B thus obtained after the conversion to the spiroduactone will still contain a certain amount of dicarboxylic-anhydride monomeric units, dependent on the distribution of the dicarboxylic-anhydride and vinyl- aromatic monomeric units across the chain of polymer C. It is also possible to only partly complete the conversion to the spiroduactone, which will result in an even greater amount of dicarboxylic-anhydride monomeric units in polymer B. In this way a polymer B is obtained that is more miscible with polymer A, as a result of which properties of the polymer composition according to the invention, for example the glass transition temperature, will be improved even more. Polymer B preferably contains 3-35 wt.% spiroduactone monomeric units and 5-45 wt.% dicarboxylic-anhydride monomeric units. An even better miscibility is obtained if the ratio of the amount of acrylonitrile monomeric units in polymer A and the amount of dicarboxylic-anhydride monomeric units in polymer B is between 0.3 and 2.2. Preferably, the ratio of the amount of acrylonitrile monomeric units in polymer A and the amount of dicarboxylic-anhydride monomeric units in polymer B is between 0.7 and 1.6. In this way a polymer composition according to the invention is obtained, in which polymer A and polymer B are completely molecularly miscible in any mixing ratio. This can be inferred from for example the fact that the polymer composition has a single, sharp glass transition temperature. If, besides polymer A and polymer B, the polymer composition contains no other additives such as fillers then the polymer composition is furthermore transparent. In another embodiment polymer B of the polymer composition according to the invention may contain imide monomeric units. As imide in polymer B use may be made of N-phenylmaleimide, malimide, citraconimide, itaconimide, aconimide, N-methyl- maleimide or mixtures thereof. Very good results are obtained if polymer B contains as monomeric units: 17-22 % (wt) maleic acid anhydride 4-7 % (wt) imide at least 2.5 % (wt), preferably at least 5 % (wt) of spirodilacton. In this way the composition shows optimal deflection temperature, mechanical properties and processability. A polymer composition according to the invention that has good impact resistance is obtained if the polymer composition contains a rubber as an impact modifier. To this end use is generally made of a rubber with a glass transition temperature of below -10°C. Examples of suitable rubbers are polybutadiene, EPDM, hydroxylated EPDM, polybutylacrylate and silicone rubber. Preferably, the rubber is grafted with a polymer that is miscible with the polymer composition. It is for example possible for the rubber to be grafted with polymer A or polymer B. Preferably, use is made of polybutadiene rubber grafted with styrene-acrylonitrile copolymer (SAN). The polymer composition according to the invention may contain the usual additives such as stabilisers, processing aids, fillers and fibres, for example glass fibres. A granulate may be produced consisting of the polymer composition according to the invention by mixing polymer A, polymer B, eventually a rubber and eventually the usual additives in a melt kneader and forcing the melt through a granulator. The granulate consisting of the polymer composition is very suitable for use in the production of for example automotive parts such as dashboards, valve caps, distributor caps, housings for electronic and electrical equipment, switches, connectors and the like. The invention is further elucidated with reference to the following examples without being limited thereto. Example I Different polymer B samples were prepared by extruding styrene-maleic anhydride copolymers (polymer C) with maleic-anhydride monomeric units (MA) contents of 28, 32 and 36 wt.% and a weight average molecular weight of 110,000 kg/kmol via a co-rotating W&P (R) twin-screw extruder of type ZSK 30, from Werner and Pfleiderer of Germany. The throughput was 6 kg/hour. The melting temperature was 250°C. TEA was continuously injected into the extruder and mixed with the melted polymer. By varying the amount of TEA thus supplied to the polymer, samples 1-15 of polymer B were obtained, which contained varying amounts of spirodilactone monomeric units. The MA content of the samples and the initial polymers C was determined using a Perkin Elmer (R) IR apparatus, type 1760 FT-IR. This was then used to calculate the spirodilactone monomeric units content of the samples with the aid of the equation given above in the specification of the present application, on the assumption that no side reactions took place. The glass transition temperature (T g ) was determined with the aid of a Perkin Elmer (R) DSC apparatus, type DSC 7. The samples weighed 10-15 mg. The heating rate was 10°C/minute. Table 1 shows the results. Table 1 sample MA in C TEA MA in B spirodilactone T c wt.% wt. -\ wt.% wt. ! ref. 28 28.0 161.5 167 171 174 173 175 170 170, 174 177 180 185 185 186 183 191 Mixtures were prepared of polymer B samples 1-15 and styrene-acrylonitrile copolymers (SAN) by mixing a granulate of a sample with granulate of a SAN copolymer in a 50/50 wt.% mixing ratio and then extruding them via the aforementioned twin-screw extruder. Table 2 shows the SAN copolymers used, the acrylonitrile monomeric units content (AN), the T g and the molecular weights. In the examples the mixtures of polymer A and polymer B are referred to as follows: SAN 20/2 is a mixture of 50 wt.% SAN 20 (Table 2) and 50 wt.% sample 2 (Table 1). Tables 3, 4 and 5 show the influence of the spirodilactone monomeric units content of the polymer on the. glass transition temperature of mixtures of SAN 26 and polymer B samples 1, 2, 5, 7, 10, 11, 12, 14, and 15. spirodilactone g wt.% °C 16.6 139 22.2 145 26.1 148 T g 136 137 142 144 The MA contents of the polymer B samples of the mixtures in Tables 3, 4 and 5 are comparable. Tables 3-5 show that the glass transition temperature of the mixtures to a great extent increases with the spirodilactone monomeric units content of polymer B. Example II The miscibility of polymer A and polymer B was determined by measuring the glass transition temperatures of the mixtures by means of DSC. Polymers A and B are completely miscible if the mixture has one glass transition temperature. Polymers A and B are partly miscible if the mixture has two glass transition temperatures, which are higher or lower than the glass transition temperatures of the polymers A and B used. Table 6 shows the results obtained with a series of mixtures of different SAN copolymers and sample 2; Table 7 shows the results obtained with a series of mixtures of different SAN copolymers and sample 10. Polymers A and B are partly miscible in mixtures SAN 13.8/2, SAN 29/2, SAN 33/2 and SAN 13.8/10 and completely miscible in the other mixtures. The miscibility of polymer B with SAN appears to increase with the MA content of polymer B (sample 2, 17.6 wt.% MA; sample 10, 21.7 wt.% MA). Example III Polymer B samples 1-15 were mixed with ABS, type Ronfalin (R) TZ 220 from DSM, as indicated in example I. The mixing ratio was in each case 60 wt.% ABS and 40 wt.% polymer B. The mixtures were processed into flat plates with a thickness of 3 mm and a length and width of 65 mm using an Arburg (R) Allround 220-90-350 injection-moulding machine. The melting temperature of the mixture in the injection-moulding machine was 310°C, the residence time of the mixture at this temperature was 5 minutes. The quality of the surface of the flat plates - the number of silver streaks per unit of surface area - was a measure of the thermal stability (TS) of the mixtures. The plates were compared with standard plates and were rated from 0 to 10 as follows: 0 = a large number of surface defects, poor thermal stability; 10 = no surface defects, very good thermal stability. Table 8 shows the results. Table 8 mixture MA in C MA in B spirodilactone TS wt.% wt.% wt.% ABS/ref. 28 28.0 0 0 The greater the degree of conversion to spirodilactone in polymer B, the greater the thermal stability of the mixture. Comparative experiment Mixtures were prepared of 50 wt.% SAN 26 and 50 wt.% styrene-maleic anhydride copolymers (SMA) as indicated in example I. Table 9 shows the MA monomeric units contents of the SMA copolymers and their weight average molecular weights. The T g of the samples was determined as indicated in example I. Table 9 shows the results. Table 9 The MA monomeric units contents of the successive SMA copolymers of Table 9 are comparable with the MA contents of the polymer B samples of Tables 4 and 5. Comparison of the mixtures of Table 9 with those of Tables 4 and 5 shows that the glass transition temperatures are substantially higher owing to the presence of spirodilactone monomeric units in polymer B.

Claims: C L I M S 1. Polymer composition containing a polymer that contains vinyl-aromatic monomeric units and acrylonitrile monomeric units and a polymer B that contains vinyl- aromatic monomeric units, dicarboxylic acid anhydride monomeric units and/or imide monomeric units, characterised in that polymer B contains at least 1 wt.% spirodilactone monomeric units. 2. Polymer composition according to claim 1, characterised in that polymer B contains at least 2 wt.% spirodilactone monomeric units. 3. Polymer composition according to claim 1, characterised in that polymer B contains at least 4 wt.% spirodilactone monomeric units. 4. Polymer composition according to any one of claims 1-3, characterised in that the ratio of the amount of acrylonitrile monomeric units in polymer A and the amount of dicarboxylic-anhydride monomeric units in polymer B is between 0.3 and 2.2. 5. Polymer composition according to any one of claims 1-4, characterised in that the ratio of the amount of acrylonitrile monomeric units in polymer A and the amount of dicarboxylic-anhydride monomeric units in polymer B is between 0.7 and 1.6. 6. Polymer composition according to any one claims 1-5, characterised in that, polymer B contains as monomeric units: 17-22 % (wt) maleic acid anhydride 4-7 % (wt) imide at least 2.5 % (wt) spirodilacton. 7. Polymer composition according to any one of claims 1-6, characterised in that the polymer composition contains a rubber as an impact modifier. 8. Polymer composition according to claim 7, characterised in that polybutadiene rubber grafted with styrene- acrylonitrile copolymer is used as rubber. 9. Polymer composition as described in the specification or the examples of this application. 10. Object entirely or substantially produced from the polymer composition according to any one of claims 1-9.

Inventors: FAIRLEY GARY ROBERT GERARD, MAAG LOUIS RICHARD, REID VALERIE MELVILLE CHRYSTIE, FAIRLEY, GARY, ROBERT, GERARD, MAAG, LOUIS, RICHARD, REID, VALERIE, MELVILLE, CHRYSTIE
Applicants: DSM NV, DSM N.V.
Application year: 1992
Main classification: C08L55
IPC codes: C08L25, C08L33, C08L35, C08L51, C08L55