METHOD FOR PRODUCING A POLYCARBONATE MOULDING COMPOUND

Abstract

The present invention relates to a method for producing a thermoplastic moulding compound containing A) at least one aromatic polycarbonate and B) an additional polymer that is chemically different from polymer A and that contains at least one type of functional group selected from ester groups, epoxy groups, hydroxyl groups, carboxyl groups and carboxylic anhydride groups, comprising the steps of a) melting and thoroughly mixing the components A and B in the presence of a catalyst according to component Cat a temperature in the range of from 200° C. to 350° C. and b) solidifying the composition by cooling the composition, the component A having an average molecular weight M.sub.w of at least 3000 g/mol, characterised in that, in the method step a), at least one part of the component A is reacted with the component B to form a copolymer, and the catalyst C being a specific phosphonium salt. The invention also relates to a thermoplastic moulding compound produced by the method according to the invention, and to moulded bodies containing said moulding compound.

Claims

1. A process for producing a thermoplastic molding material containing A) at least one aromatic polycarbonate and B) a further polymer which is chemically distinct from polymer A and which contains at least one type of functional group selected from ester, epoxy, hydroxyl, carboxyl and carboxylic anhydride groups, the process comprising the steps of a) melting and commixing components A and B in the presence of a catalyst of component C at a temperature in the range from 200° C. to 350° C. and b) solidifying the composition by cooling the composition, wherein component A has an average molecular weight M.sub.w measured by gel permeation chromatography at room temperature in methylene chloride with a bisphenol A-based polycarbonate standard of at least 3000 g/mol, wherein in process step a) at least a portion of component A is reacted with component B to produce a copolymer and wherein catalyst C is a phosphonium salt according to formula (4) ##STR00006## wherein R.sub.1 and R.sub.2 each independently of one another represent C.sub.1-C.sub.10 alkyl, R.sub.3 and R.sub.4 each independently of one another represent C.sub.1-C.sub.10-alkyl or C.sub.6-C.sub.12-aryl, A.sup.n− represents an anion of a carboxylic acid and n represents 1, 2 or 3.

2. The process as claimed in claim 1, wherein component B is a polymer selected from the group consisting of vinyl (co)polymers containing structural units derived from an alkyl ester of acrylic acid, vinyl (co)polymers containing structural units derived from an alkyl ester of an alkyl-substituted derivative of acrylic acid, epoxy-containing vinyl (co)polymers, and epoxy-containing polyolefins.

3. The process as claimed in claim 1, wherein the mixture of the components A and B has a residual moisture content of 0.01% to 0.50% by weight based on the sum of A and B.

4. The process as claimed in claim 1, wherein that the component B is polymethyl methacrylate.

5. The process as claimed in claim 1, wherein component B is a polymer selected from the group consisting of epoxy-containing vinyl (co)polymers and epoxy-containing polyolefins.

6. The process as claimed in claim 1, wherein component A is an aromatic polycarbonate based on bisphenol A.

7. The process as claimed in claim 1, wherein polymer additives and/or further polymeric blend partners distinct from the components A and B are added as component D in step a).

8. The process as claimed in claim 7, wherein in step a) the composition comprises 0.5% to 99% by weight of the component A, 0.5% to 99% by weight of the components B, 0.01% to 0.5% by weight of the component C and 0.1% to 50% by weight of the component D.

9. The process as claimed in claim 1, wherein process step a) occurs in a continuous twin-screw extruder with a residence time of from 15 seconds to 1 minute.

10. The process as claimed in claim 1, wherein component B is an epoxy-containing vinyl (co)polymer or an epoxy-containing polyolefin and in process step a) at least 5 mol % of the epoxy groups in component B are converted.

11. The process as claimed in claim 1, wherein in catalyst C at least one of R.sub.1 and/or R.sub.2 represent an n-butyl group.

12. The process as claimed in claim 1, wherein in the catalyst C A.sup.n− represents an acetate ion or malonate ion.

13. The process as claimed in claim 1, wherein catalyst C is tetra-n-butylphosphonium acetate in the form of the acetic acid complex.

14. A thermoplastic molding material produced with a process according to claim 1.

15. A molded article containing a thermoplastic molding material as claimed in claim 14.

Description

DESCRIPTION OF THE FIGURES

[0242] FIG. 1

[0243] FTIR spectrum (E represents extinction and v represents wavenumber)

[0244] 1: Component A1

[0245] 2: Component B1

[0246] 3: acetone-insoluble proportion of molding material V1

[0247] 4: acetone-soluble proportion of molding material V1

[0248] 5: acetone-insoluble proportion of molding material 4

[0249] 6: acetone-soluble proportion of molding material 4

[0250] FIG. 2

[0251] FTIR spectrum (E represents extinction and v represents wavenumber)

[0252] 1: acetone-insoluble proportion of molding material 5

[0253] 2: acetone-insoluble proportion of molding material 4

[0254] FIG. 3

[0255] TEM image of a microtome section of a pellet of molding material V9

[0256] FIG. 4

[0257] TEM image of a microtome section of a pellet of molding material 10

[0258]

TABLE-US-00001 TABLE 1 PC/PMMA molding materials and their properties Example V1 V2 V3 4 5 V6 7 V8 Composition parts parts parts parts parts parts parts parts by wt. by wt. by wt. by wt. by wt. by wt. by wt. by wt. A1 50 50 50 50 50 50 50 50 B1 50 50 50 50 50 50 50 50 C1 0.05 C2 0.05 C3 0.05 0.05 C4 0.05 C5 0.05 C6 0.05 Water content A + B 0.105 0.105 0.105 0.105 0.060 0.105 0.105 0.105 [% by wt. based on A + B] Properties Elastic modulus [MPa] 2748 2875 2799 2838 2809 2741 2831 2779 Yellowness index 39.7 8.2 48.4 1.8 4.7 46.0 2.1 38.9 Haze 99.4 11.4 98.7 0.5 7.9 98.4 2.3 99.3

[0259] The data in table 1 show that the catalysts C3 and C5 according to the invention achieve lower yellowness indexes and higher transparencies (lower haze) than the catalysts C1 and C2 described in the prior art or the catalysts C4 and C6 which are structurally analogous to the catalysts according to the invention but are not catalysts according to the invention. Transparency is not achieved without a catalyst (comparative example V1). Higher elastic moduli are also achieved with the catalysts according to the invention than without a catalyst and a higher surface hardness and thus scratch resistance can therefore also be assumed.

[0260] The FTIR examinations in FIGS. 1 and 2 demonstrate that the reactive compounding of the molding materials 4 and 5 according to the invention results in formation of PC-PMMA copolymers by reaction of the component A1 with the component B1, wherein FIG. 2 further demonstrates that in the molding material 4, which was produced with the preferred higher water content in the mixture of components A1 and B1, a greater amount of these PC-PMMA copolymers was formed.

[0261] A comparison of the properties of the molding materials 4 and 5 of table 1 according to the invention shows that when using the catalysts according to the invention it is advantageous in terms of optimizing transparency, yellowness index and elastic modulus when the polymeric components A and B contain a minimum amount of moisture.

TABLE-US-00002 TABLE 2 PC/styrene-acrylonitrile-glycidyl methacrylate compositions Example V9 10 Composition parts by wt. parts by wt. A2 80 80 B2 20 20 C3 0.05 Water content A + B 0.044 0.044 [% by wt. based on A + B] Properties Epoxy content [% by wt.] 0.46 0.39 Epoxy conversion 2 17 (calculated) [%]

[0262] The data in table 2 show that in the presence of the catalyst according to the invention the process according to the invention can achieve a conversion of the epoxide of 15% in a twin-screw extruder with a residence time of about 60 seconds while in a process according to the prior art without such a catalyst such a conversion does not take place. A comparison of FIGS. 3 and 4 further shows that this conversion of the epoxide makes it possible to achieve a markedly finer phase dispersion of the styrene-acrylonitrile-glycidyl methacrylate terpolymer of component B in polycarbonate of component A.

TABLE-US-00003 TABLE 3 PMMA/PC molding materials and their properties Example V11 V12 V13 14 Composition parts parts parts parts by wt. by wt. by wt. by wt. A1 20 20 20 20 B1 80 80 80 80 C1 0.3 C2 0.3 C3 0.3 Water content 0.090 0.090 0.090 0.090 A + B [% by wt. based on A + B] Properties Elastic modulus 3087 3124 3084 3210 [MPa] Yellowness index 48.01 15.4 16.9 4.5 Haze 98.26 44.2 11.8 0.5

[0263] The examples in table 3 show that the PMMA/PC molding material 14 according to the invention which was produced with an catalyst according to the invention exhibits better transparency (lower haze), a lower intrinsic color (lower yellowness index) and a higher elastic modulus.