Process for producing acrylate rubber with reduced coagulate formation

Abstract

A process for producing a thermoplastic molding composition comprising: 10% to 40% by weight of a graft copolymer A comprising 50% to 70% by weight, based on A, of a graft base A1 formed from an elastomeric, crosslinked acrylic ester polymer and 30% to 50% by weight of a graft shell A2, 50% to 90% by weight of a hard matrix B formed from copolymers of styrene or -methylstyrene and acrylonitrile, 0% to 50% by weight of a further graft copolymer C, 0% to 15% by weight of additives D, wherein the reaction for preparation of the acrylic ester polymer A and/or the reaction for preparation of C is conducted in the presence of 0.01 to 4 times the molar amount of sodium carbonate, based on the sum total of the molar amount of initiator used in the preparation of the graft base and graft shell, leads to lower coagulate formation.

Claims

1. A process for the production of a thermoplastic molding composition comprising: from 10 to 40% by weight of at least one graft copolymer A comprising from 50 to 70% by weight, based on A, of a graft base A1 made of an elastomeric, crosslinked acrylate polymer, and from 30 to 50% by weight, based on A, of a graft shell A2 made of a vinylaromatic monomer and of a polar, copolymerizable, ethylenically unsaturated monomer, in a ratio by weight of from 80:20 to 65:35, from 50 to 90% by weight of a hard matrix B made of one or more copolymers of styrene, -methylstyrene, acrylonitrile, methyl methacrylate, and/or phenylmaleimide, from 0 to 50% by weight of another graft copolymer C which differs from the graft copolymer A and which has an average particle diameter in the range from 200 to 800 nm, comprising from 50 to 80% by weight, based on C, of an elastomeric crosslinked acrylate polymer C1 which differs from A1, from 2.5 to 25% by weight, based on C, of a first graft shell C2 made of a vinylaromatic monomer, and from 10 to 45% by weight, based on C, of a second graft shell C3 made of a mixture of a vinylaromatic monomer C31 and of a polar, copolymerizable, ethylenically unsaturated monomer C32, where the ratio by weight of C31 to C32 is from 90:10 to 60:40, and from 0 to 15% by weight of one or more additives D, where the entirety of A and B, and optionally C and D, gives 100% by weight, and where the reaction for the production of the graft copolymer A and the reaction for the production of the graft copolymer C is carried out in the presence of a molar quantity of sodium carbonate which is from 0.01 to 4 times the total molar quantity of initiator used in the production of the graft base and graft shell of graft copolymers A and C.

2. The process for the production of a thermoplastic molding composition as claimed in claim 1, where the graft base A1 is composed of from 55 to 65% by weight, based on A, of acrylate polymer particles with average size from 50 to 120 nm and the graft shell A2 is composed of from 35 to 45% by weight, based on A, of styrene and acrylonitrile.

3. The process for the production of a thermoplastic molding composition as claimed in claim 1, where the particle size distribution factor Q of the graft base A1 is from 0.01 to 0.5.

4. The process for the production of a thermoplastic molding composition as claimed in claim 1, where the quantity of coagulate formed in connection with the graft shell A2 is in the range from 0.01 to 0.5% by weight, based on the total weight of the graft copolymer A.

5. The process for the production of a thermoplastic molding composition as claimed in claim 1, where the quantity of sodium carbonate used in the production of the graft copolymers A and/or C is from 0.01 to 2.5 mol based on the sum of the molar quantities of initiator, used in the graft base and graft shell of graft copolymers A and/or C.

6. The process for the production of a thermoplastic molding composition as claimed in claim 1, where the molding composition comprises from 1 to 50% by weight of at least one graft copolymer C which differs from the graft copolymer A.

7. The process for the production of a thermoplastic molding composition as claimed in claim 1, where the molding composition comprises from 0.1 to 15% by weight of at least one additive D.

8. The process for the production of a thermoplastic molding composition as claimed in claim 1, where the molding composition comprises from 1 to 50% by weight of at least one graft copolymer C and the graft copolymer C has an average particle diameter in the range from 300 to 700 nm.

9. The process for the production of a thermoplastic molding composition as claimed in claim 1, where the sodium carbonate is first dissolved in a starting material for the production of the graft copolymer A and the graft copolymer C.

10. A process for the production of a thermoplastic molding composition comprising: from 50 to 90% by weight of a hard matrix B made of one or more copolymers of styrene, -methylstyrene, acrylonitrile, methyl methacrylate, and/or phenylmaleimide, from 10 to 50% by weight of a graft copolymer C with an average particle size in the range from 200 to 800 nm, comprising from 50 to 80% by weight, based on C, of an elastomeric crosslinked acrylate polymer C1, from 2.5 to 25% by weight, based on C, of a first graft shell C2 made of a vinylaromatic monomer, and from 10 to 45% by weight, based on C, of a second graft shell C3 made of a mixture of a vinylaromatic monomer C31 and of a polar, copolymerizable, ethylenically unsaturated monomer C32, where the ratio by weight of C31 to C32 is from 90:10 to 60:40, and from 0 to 15% by weight of one or more additives D, where the entirety of B and C, and optionally D, gives 100% by weight, and where the reaction for the production of the graft copolymer C is carried out in the presence of a molar quantity of sodium carbonate which is from 0.01 to 4 times the total molar quantity of initiator used in the production of the graft base and graft shell of graft copolymer C.

11. The process for the production of a thermoplastic molding composition as claimed in claim 10, where the quantity of coagulate formed in connection with the graft shell of component C is in the range from 0.01 to 0.5% by weight, based on the total weight of the graft copolymer C.

12. A molding, a film, or a coating comprising a thermoplastic molding composition produced by the process as claimed in claim 1.

13. The process as claimed in claim 1, wherein the initiator is PPS.

14. The process as claimed in claim 10, wherein the initiator is PPS.

15. The process for the production of a thermoplastic molding composition as claimed in claim 3, where the particle size distribution factor Q of the graft base A1 is from 0.1 to 0.4.

16. The process for the production of a thermoplastic molding composition as claimed in claim 5, where the quantity of sodium carbonate used in the production of the graft copolymers A and/or C is from 0.01 to 2.5 mol, based on the sum of the molar quantities PPS used in the graft base and graft shell.

17. The process for the production of a thermoplastic molding composition as claimed in claim 5, where the quantity of sodium carbonate used in the production of the graft copolymers A and/or C is from 0.1 to 2.5 mol, based on the sum of the molar quantities of initiator used in the graft base and graft shell of graft copolymers A and/or C.

18. The process for the production of a thermoplastic molding composition as claimed in claim 7, where the molding composition comprises from 0.1 to 5% by weight of at least one additive D.

19. The process for the production of a thermoplastic molding composition as claimed in claim 10, wherein the initiator is PPS.

20. The process for the production of a thermoplastic molding composition as claimed in claim 10, where the molding composition comprises from 0.1 to 5% by weight of one or more additives D.

21. The process for the production of a thermoplastic molding composition as claimed in claim 10, wherein the reaction for the production of the graft copolymer C is carried out in the presence of a molar quantity of sodium carbonate which is from 0.1 to 2.5 times the total molar quantity of initiator used in the production of the graft base and graft shell of graft copolymer C.

Description

EXAMPLES

(1) Re: Test Methods:

(2) Modulus of elasticity is determined in accordance with ISO 5272:1993.

(3) Average particle size, defined via the d50 value of the particle size distribution, is measured with the aid of HDC (Hydrodynamic Chromatography, W. Wohlleben, H. Schuch in Measurement of Particle Size Distribution of Polymer Latexes, 2010, eds.: L. Gugliotta, J. Vega, p. 130-153).

(4) Notched impact resistance (kJ/m.sup.2) is measured in accordance with DIN 53 453 (ISO 179 1eA).

(5) The MVR (220/10) is determined in accordance with ISO 1133.

(6) Re: General Production Process:

(7) The compositions are produced by mixing the respective components intimately in an extruder (ZSK 30 twin-screw extruder from Werner & Pfleiderer) at a temperature of 240 C.

(8) After the experiment, the coagulate of the graft polymer A is isolated by filtration, dried, and weighed. Deposits/encrustation on the plant components (e.g. vessel wall, agitator) was evaluated by each of 5 staff, working independently of the others.

(9) A) Production of Small-Particle Graft Copolymer (Particle Size 100 nm)

(10) The graft base A is produced by analogy with EP-A 0450485 (graft copolymer A; see p. 7, line 11). The appropriate salt here (in an appropriate quantity) is first dissolved in the starting material, and the polymerization is then carried out as described in EP 0450485. Experiment comp. 6 was carried out analogously for comparison.

(11) The acrylate graft polymer C and hard component B (SAN copolymer) are produced by analogy with EP 0450485. The experiments were carried out with 3.2 kg of graft rubber.

(12) a1) Production of Graft Base

(13) All data are in parts by weight. 16 parts by weight of butyl acrylate (BA) and 0.4 part by weight of dihydrodicyclopentadienyl acrylate (DCPA) are heated to 60 C., with stirring, in 150 parts by weight of water with addition of one part of the sodium salt of a C12-C18-paraffinsulfonic acid, 0.3 part by weight of potassium peroxodisulfate, and the corresponding stated quantities of sodium carbonate and, respectively, sodium bicarbonate (see table 1). 10 minutes after the polymerization reaction had begun, a mixture of 82 parts by weight of butyl acrylate and 1.6 parts by weight of DCPA was added within a period of 3 hours. The mixture was allowed to continue reaction for a further hour after monomer addition had ended.

(14) The solids content of the resultant rubber of the crosslinked butyl acrylate polymer was 40% by weight. Particle size distribution was narrow (quotient Q=0.20).

(15) a2) Production of Graft Copolymer

(16) 4200 g of the emulsion produced in accordance with specification (a1) were mixed with 2300 g of water and 5.4 g of potassium peroxodisulfate and heated to 65 C., with stirring. Once the reaction temperature had been reached, a mixture of 840 g of styrene and 280 g of acrylonitrile was metered into the mixture over the course of 3 hours. Once the addition had ended, the emulsion was kept at 65 C. for a further 2 hours. The graft polymer was precipitated from the emulsion by using calcium chloride solution at 95 C., washed with water, and dried in a stream of warm air. Table 1 lists the average particle sizes of the resultant graft copolymers.

(17) b) Production of Corresponding Molding Compositions

(18) The thermoplastic molding compositions were produced by incorporating the particulate graft polymers described above into a hard component, i.e. the SAN copolymer (75:25). Incorporation can be achieved by way of example in that the particulate graft polymer(s) is/are isolated (precipitated) from the emulsion by adding an electrolyte and then, optionally after drying, is/are mixed with the hard component (SAN) by extruding, kneading, or rolling the materials together.

(19) c) Production of Large-Particle Graft Copolymers C

(20) c1) Production of Graft Base

(21) The following are added to a starting material made of 2.5 parts by weight of the rubber produced as described in a1): 50 parts by weight of water and 0.1 part by weight of potassium peroxodisulfate over the course of 3 hours, and then firstly a mixture of 49 parts by weight of butyl acrylate and 1 part by weight of DCPA, and secondly a solution of 0.5 part by weight of the sodium carbonate and, respectively, sodium bicarbonate of a C.sub.12- to C.sub.18-paraffinsulfonic acid in 25 parts by weight of water. The temperature of the starting material here was 60 C. Once the feed had ended, polymerization was continued for two hours. The solids content of the resultant rubber was 40%. The average particle size (weight average) of the rubber was determined as 410 nm.

(22) c2) Production of Graft Copolymer

(23) 150 parts by weight of the rubber obtained in c1) were mixed with 15 parts by weight of styrene and 60 parts by weight of water, and heated for 3 hours to 65 C., with stirring, after addition of a further 0.03 part by weight of potassium peroxodisulfate and 0.05 part by weight of lauroyl peroxide. The resultant dispersion was polymerized for a further 4 hours with 25 parts by weight of a mixture of styrene and acrylonitrile in a ratio of 75:25, and precipitated by using calcium chloride solution at 95 C., and the product was isolated, washed with water, and dried in a stream of warm air. The degree of grafting was determined as 40%.

(24) d) Mixtures with SAN

(25) A possible effect on the abovementioned mechanical properties of the thermoplastic molding composition was investigated by using mixtures produced from the resultant graft copolymers (experiments 1, 3, and comp. 6) with a commercially available hard component, SAN copolymer made of styrene and acrylonitrile (75:25). The ratio by weight of SAN matrix to graft copolymer here is 70:30.

(26) TABLE-US-00001 TABLE 1 Comparison of particle size (after graft reaction), pH (at the end of the reaction), coagulate formation and encrustation under various conditions. Experiments 1 to 5 vary the quantity of Na.sub.2CO.sub.3, and experiment comp. 6 is buffered with NaHCO.sub.3 during the reaction (Rk). The theoretical weight of the entire mixture is 3.2 kg. The molar quantity of the salt used as buffer is stated, based on the PPS used as initiator (graft base and graft shell together). Particle size pH (at Ex- Salt used (after graft end of Coag- Encrustation peri- (molar reaction Rk reaction ulate (independent ment quantity) in nm) Rk) (g) evaluation) 1 Na.sub.2CO.sub.3: 0.1 75 5.4 3.3 very little 2 Na.sub.2CO.sub.3: 1.0 92 7.3 5 little 3 Na.sub.2CO.sub.3: 1.25 98 7.5 5 little 4 Na.sub.2CO.sub.3: 1.9 114 7.8 5 little 5 Na.sub.2CO.sub.3: 2.5 132 8.1 5 little comp. NaHCO.sub.3: 2.0 99 7.5 23 very 6 substantial

(27) As can be seen in table 1, coagulate formation, and also encrustation, in the reaction vessel is at a minimum when the quantity of Na.sub.2CO.sub.3 is 0.1 (molar quantity, based on total PPS); however, this does not change greatly for any quantity of Na.sub.2CO.sub.3 from 1.0 to 2.5.

(28) In contrast, experiment comp. 6 exhibits a high level of coagulate formation, and also substantial encrustation in the reaction vessel with use of NaHCO.sub.3.

(29) Achievement of a particle size of about 100 nm after the grafting reaction preferably requires only 1.25 mol of Na.sub.2CO.sub.3, based on PPS, instead of 2.0 mol of NaHCO.sub.3, based on PPS. A smaller quantity of buffer salt is therefore required for an identical size of the graft polymer particles.

(30) TABLE-US-00002 TABLE 2 Comparison of particle size (D.sub.50 after graft reaction), pH (at the end of the reaction), coagulate formation, and wall encrustation under various conditions. Experiments 7 to 13 vary the molar quantity of Na.sub.2CO.sub.3 (based on total PPS), and experiment comp. 14 reveals the results in a reaction buffered with NaHCO.sub.3. The theoretical weight of the entire mixture is 3.2 kg. Mol. quantity pH (at Dried of Na.sub.2CO.sub.3, the end coagulate based on of the HDC (weighed) Wall PPS.sub.total reaction) (D.sub.50) g encrustation 7 0.1 4.3 572 1.2 very little 8 0.5 7.1 571 1 very little 9 1 7.5 567 1.5 very little 10 1.25 7.6 592 2 very little 11 1.5 7.9 654 1.8 very little 12 2 8.2 817 2.1 very little 13 2.5 8.3 964 7.4 little Comparison using NaHCO.sub.3 instead of Na.sub.2CO.sub.3 comp. 14 2 7.7 666 16.8 substantial

(31) TABLE-US-00003 TABLE 3 Comparison of mechanical properties and processability of the graft copolymer products blended with SAN (75:25) from experiments 1 (small quantity of sodium carbonate), 3 (larger quantity of sodium carbonate), and comp. 6 (larger quantity of sodium hydrogencarbonate). Modulus of Notched impact Rubber from MVR elasticity resistance Ak experiment (220/10) (MPa) [kJ/m.sup.2], 23 C. 1 5.5 2521 3.48 3 5.4 2495 3.83 comp. 6 5.8 2529 3.19

(32) From table 3 it is apparent that there is no adverse effect on the mechanical properties of the moldings produced with SAN when the Na.sub.2CO.sub.3-buffered graft copolymers are used: MVR (melt flow rate) and modulus of elasticity are unchanged in comparison with the comparative experiment comp. 6 within the bounds of measurement tolerances, and notched impact resistance is improved.