NL1004855C2 - Polymer composition - Google Patents

Abstract

Polymer composition consisting of: (a) 5-95 wt.% copolymer of 90-99.8 wt.% methyl methacrylate and 10-0.2 wt.% ethylacrylate and/or methylacrylate; (b) 95-5 wt.% copolymer of 72-80 wt.% styrene and 20-28 wt.% maleic anhydride; and (c) 0-5 wt.% processing agents and/or stabilisers and/or colourants, and which composition has a haze of \~10%. Also claimed are moulded articles entirely or partly made from the above composition.

Description

- 1 - POLYMER COMPOSITION 5

The invention relates to a polymer composition consisting of a copolymer of styrene and maleic anhydride monomer units, a copolymer containing methyl methacrylate monomer units and optionally processing aids, stabilizers and / or dyes.

German patent application DE-A-2024940 discloses a polymer composition comprising: 1. 10-90 parts by weight of a copolymer of 70-90% by weight of styrene 10-30% by weight of maleic anhydride 2. 10-90 parts by weight of a copolymer of 60-100 wt% methyl metacrylate 20 30-0 wt% styrene 10-0 wt% of a 1-4 C-alkyl acrylate 3. 0-50 parts by weight of a copolymer of 60-90 wt% styrene 40-10 wt% acrylonitrile 25

It has further been described in the above-mentioned patent application that the polymer composition would be crystal clear, because the light refractive indices of the various components of the polymer composition 30 differ only slightly in value. If the light refractive indices of the individual components are important for the transparency of the mixture, this means that the components of the composition are not or insufficiently molecularly mixed. The transparency of the known polymer composition is therefore not very high and also other optical properties, such as for instance the haze, leave wishes to be desired. Furthermore, the polymer composition can only be used in a small range of temperatures and shear rates. , the so-called "processing window." If the known polymer-5 composition is processed outside the small "processing window", an even further separation of the components occurs and even a milky product is obtained with a very low or whole absent transparency.

The object of the invention is to provide a polymer composition with very good transparency.

Surprisingly, this object is achieved in that the polymer composition consists of the 15 components: a. 5-95% by weight of a copolymer of 90-99.8% by weight of methyl methacrylate 10-0.2% by weight of ethyl acrylate and / or methyl acrylate 20 b . 95-5 wt% of a copolymer of 72-80 wt% styrene 20-28 wt% maleic anhydride c. 0-5% by weight of one or more processing aids and / or stabilizers and / or dyes.

The components of the polymer composition surprisingly appear to be very miscible, while the components of the known polymer composition are immiscible or at least less miscible. The polymer composition according to the invention not only has a very high transparency, but surprisingly also has a very low haze.

A still further advantage is that the polymer composition according to the invention has a large processing window. For example, it is not only possible to extrude the polymer composition at high shear rates and high temperatures, but it is also possible to extrude the polymer composition at moderate temperature and low shear rates, while retaining the good optical properties.

The polymer composition also has a high heat-mold resistance.

A still further advantage is that the polymer composition according to the invention has a good resistance to chemicals, such as, for example, isopropyl alcohol.

10 In G.R. Brannock et al., Journal of Pol. Sci.,

Part B: Pol. Phys., Vol. 29, no. March 4, 1991, mixtures of acrylic polymers and copolymers of styrene and maleic anhydride (henceforth referred to as SMA copolymers) have been described. Although article 15 shows that polymethyl methacrylate with SMA copolymers is molecularly miscible, it also appears that polyacrylates, in particular polyacrylates, based on e.g. methyl acrylate and ethyl acrylate are immiscible with SMA. It is therefore all the more surprising that good results are achieved in the polymer composition according to the invention, in which a copolymer containing just methyl acrylate and / or ethyl acrylate monomer units is used. Furthermore, Brannock makes no statement about the composition of the SMA copolymer 25 and the optical properties of the mixture.

Although a polymer composition containing SMA and a copolymer of methyl methacrylate and ethyl acrylate is known from WO 86/1525, unlike the polymer composition according to the invention, one of the two components from WO 86/1525 is modified with a rubber.

The polymer composition according to the invention preferably consists of 90-50% by weight of component a., 10-50% by weight of component b. and 0-5 wt% component c.

Even more preferably, the polymer composition according to the invention consists of 85-70% by weight of component a., 15-30% by weight of component b. and 0-5; - - 3 5 5 - 4 - wt% component c.

Preferably component a. Of the polymer composition is a copolymer of 92-99.1 wt% methyl metacrylate and 8-0.3 wt% methyl acrylate and / or ethyl acrylate. As a result, the polymer composition according to the invention has an even better flow behavior. Even more preferably, component a. Is a copolymer of 98-99.6 wt.% Methyl methacrylate and 2-0.4 wt.% Methyl acrylate and / or ethyl acrylate.

Component a. Can be prepared, for example, by bulk or solution polymerization, according to the known methods. Component a can be a-tactical or syndiotactic depending on the preparation method. Preferably component a. Is a-tactical.

Component a., For example, has a weight average molecular weight of 30,000-300,000 kg / kmol. For injection molding applications, a component a. Is preferably used with a weight average molecular weight of 30,000-200,000 kg / kmol. For extrusion applications, a component a. With a weight average molecular weight of 100,000-300,000 kg / kmol is preferably used.

Preferably component b. of the polymer composition of the invention a copolymer of 79-73 wt% styrene and 21-27 wt% maleic anhydride. As a result, the polymer composition according to the invention has a larger processing window. Component b. can be prepared by introducing a mixture containing relatively much styrene and little maleic anhydride, optionally in conjunction with a solvent, under vigorous stirring and at a high temperature into a polymerization vessel, while at the same time removing the same amount by weight of the mixture from the polymerization vessel. Such a method is described, for example, in A.W. Hansen and R.L. Zimmerman, Industrial Engineering Chemistry 49, P. 1803 etc. (1957).

"·». " w V.

- 5 -

Preferably, the polymer composition according to the invention has a haze of at most 10%.

Surprisingly, a polymer composition with a haze of up to 5% 5 is obtained if during the polymerization of component b. is stirred very strongly. By stirring even more strongly, it is even possible that the haze of the polymer composition is at most 3%. A method in which component a. Can be prepared by vigorous stirring is known from EP-A-202,706. Still further improvements are achieved by rapidly mixing the styrene and maleic anhydride monomers fed to the reaction mixture with the reaction mixture and by mixing the monomers together before being fed to the reaction mixture. Rapid mixing of the monomers with the reaction mixture can be achieved, for example, by feeding the monomers close to the stirrer.

The haze is measured according to the ASTM D standard

20 1003.

Component b. for example, has a weight average molecular weight of 50,000-250,000 kg / kmol. Preferably, component b. a weight average molecular weight of 60,000 - 110,000 kg / kmol. As a result, the composition according to the invention has an optimal combination of good properties, such as, for example, chemical resistance, heat-mold resistance, optical properties and processability. As component 30 c. In principle, for example, the processing aids, stabilizers and dyes known for polymethyl methacrylate and styrene maleic anhydride copolymers can be used. Important here is the component c. and choosing an amount thereof such that the optical properties are not affected or are affected as little as possible.

- 6 -

The components a., B. and possibly c. can be mixed together, for example, at temperatures between 200 and 270 ° C in the melting phase, preferably using a continuous kneader, such as, for example, a twin screw kneader or a Buss (TM) co-kneader.

The composition according to the invention can very well be used for the production of molded parts, which place high demands on the optical properties. For example, the composition according to the invention can be used very well for injection molding of, for example, car rear lights, glazing of street lamps, garden lamps and other light fittings. It is also quite possible to extrude the composition according to the invention into plates, after which end products can be manufactured from the plates according to the methods known for that purpose. Examples of such end products are cover plates for billboards and skylights.

The invention is further elucidated by means of the examples, without being limited thereto.

Components used:

As component a., A copolymer of 98 wt.% Methyl methacrylate and 2 wt.% Ethyl acrylate, having a weight average molecular weight of 110,000 kg / kmol, designated PMMA-EA or a copolymer of 99 wt.% Methyl metacrylate, 1 wt. % methyl acrylate and a weight average molecular weight of 100,000 kg / kmol, denoted PMMA-MA. Components a. Are both non-tactical copolymers.

The following copolymers of styrene and maleic anhydride (SMA copolymers) were used: -SMA 32,110, copolymer of 32 wt% maleic anhydride and 68 wt% styrene, with a weight average molecular weight of 110,000 kg / kmol. -SMA 28,110 copolymer of 28 wt% 1004855-7 maleic anhydride and 72 wt% styrene, with a weight average molecular weight of 110,000 kg / kmol. -SMA 26,080 copolymer of 26 wt% maleic anhydride and 74 wt% styrene, with a weight average molecular weight of 80,000 kg / kmol. -SMA 22,110, copolymer of 22 wt% maleic anhydride and 78 wt% styrene, with a weight average molecular weight of 110,000 kg / kmol.

Examples I-VI and Comparative Experiment A

Different blends of PMMA 98.110 and the SMA copolymers were prepared using a twin screw kneader, type ZSK 30, supplied by Werner and Pfleiderer from Germany. The melting temperature was 260 ° C, the screw speed was 200 rpm and the yield was 5 kg / h.

The mixtures were injection molded into sheets of 80 * 80 * 3.2 mm using an injection molding machine with a closing force of 80 tons, supplied by Engel from Germany. The melting temperature was 245 ° C and the injection time was 2.5 sec.

Haze and transparency were measured on the plates according to ASTM 1003 and the yellowness index according to ASTM 1925.

Table 1 shows the composition of the mixtures and the results of the measurements.

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Table 1 shows that the composition according to the invention (Examples I-III) has a high transparency. The composition of the comparative experiment (A), on the other hand, has a very low haze and a very low transparency.

Examples VII-XII and comparative experiment B

The mixtures were prepared and tested as described above. However, the SMA copolymers were now prepared, while the agitator speed of the reactor had doubled from 20 to 40 rpm.

The results are shown in Tables 2 and 3.

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in i; - - 12 -

It can be seen from a comparison between Table 1 on the one hand and Table 2 and 3 on the other that by stronger stirring during the polymerization of the SMA copolymer, that of the compositions according to the invention further improve the optical properties, in particular the haze, while this is hardly the case for the composition of comparative experiments A and B.

1 Λ π / * · · -

Claims (7)

1. Polymer composition consisting of: 5 a. 5-95 wt.% Of a copolymer of 90-99.8 wt.% Methyl methacrylate 10-0.2 wt.% Ethyl acrylate and / or methyl acrylate b. 95-5 wt% of a copolymer of 72-80 wt% styrene 20-28 wt% maleic anhydride c. 0-5% by weight of processing aids and / or stabilizers and / or dyes. 2. Polymer composition according to claim 1, characterized in that the polymer composition consists of 90-50% by weight of component a., 10-50% by weight of component b. and 0-5 wt% component c. Polymer composition according to claim 1 or 2, characterized in that component a. Of the polymer composition is a copolymer of 92-99.7% by weight of methyl methacrylate and 8-0.3% by weight of methyl acrylate and / or ethyl acrylate. Polymer composition according to any one of claims 1-3, characterized in that component b. of the polymer composition is a copolymer of 79-73 wt% styrene and 21-27 wt% maleic anhydride. Polymer composition according to any one of claims 1-4, characterized in that the polymer composition according to the invention has a haze of at most 10%. Polymer composition according to any one of claims 1-4, characterized in that the polymer composition according to the invention has a haze of at most 5%. 1004855 - 14 - Molded parts made wholly or partly of the polymer composition according to any one of claims 1-6. 15