METHOD FOR PRODUCING ACRYLATE RUBBER AT REDUCED EMULSIFIER CONCENTRATION

Abstract

Method for producing a thermoplastic moulding compound containing: up to 40 wt. % of a graft copolymer A, containing 50-70 wt. % graft base A1 from an acrylic ester polymer and 30-50 wt. % of a graft shell A2, and 0-90 wt. % of a hard matrix B, wherein the reaction for producing the graft copolymer A is carried out in the presence of 0.01 to 4 times the molar amount of sodium carbonate, relative to the molar amount of initiator, wherein the reaction for producing copolymer A is carried out in the presence of 0.1 to 1 wt. % of an emulsifier relative to the amount of the respective monomers used, and wherein during the polymerisation reaction, during the post-polymerisation and/or after the polymerisation reaction, water or an aqueous alkali solution are added to the reaction mixture for producing the graft copolymer A.

Claims

1-15. (canceled)

16. A process for producing a thermoplastic molding compound comprising: 10% to 40% by weight of at least one graft copolymer A comprising: 50% to 70% by weight, based on A, of a graft base A1 made of an elastomeric, crosslinked acrylate polymer, and 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 80:20 to 65:35, 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, 0% to 40% by weight of at least one further graft copolymer C which differs from the graft copolymer A and which has an average particle diameter (weight average) in the range from 200 to 800 nm, comprising: 50% to 80% by weight, based on C, of an elastomeric crosslinked acrylate polymer C1 which differs from A1, 2.5% to 25% by weight, based on C, of a first graft shell C2 made of a vinylaromatic monomer and of 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 in a weight ratio of C31 to C32 of 90:10 to 60:40; and 0% to 15% by weight of one or more additives D, wherein the sum total of A and B, and optionally C and D, is 100% by weight, and wherein the reaction for production of the graft copolymer A and the reaction for production of the graft copolymer C is conducted in the presence of 0.01 to 4 times the molar amount of sodium carbonate, based on the total molar amount of initiator, especially PPS, used in the production of the graft base and graft shell; and wherein the reaction for production of the graft copolymer A and the reaction for production of the graft copolymer C is conducted in the presence of 0.1% to 1% by weight of an emulsifier, especially an alkali metal alkylsulfonate, based on the amount of the monomers used in each case; and wherein water or an aqueous alkaline solution is added to the reaction mixture for production of the graft copolymer A and the graft copolymer C during the polymerization reaction, during the postpolymerization and/or after the polymerization reaction.

17. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein water or an aqueous alkaline solution is added after the addition of monomer has ended.

18. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein water or an aqueous alkaline solution is added in an amount of 1% to 50% by weight, based on the polymer latex L(A1) or L(C1) obtained from the emulsion polymerization reaction.

19. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein the aqueous alkaline solution is an aqueous solution of inorganic carbonates, hydrogencarbonates or hydroxides, and mixtures thereof.

20. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein the aqueous alkaline solution is an aqueous solution of Na.sub.2CO.sub.3, NaHCO.sub.3, NaOH and/or KOH having a concentration of 0.01% to 1% by weight.

21. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein the emulsifier used is a secondary alkylsulfonate.

22. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein the graft base A1 is composed of 55% to 65% by weight, based on A, of acrylate polymer particles having an average particle size of 50 to 120 nm and the graft shell A2 is composed of 35% to 45% by weight, based on A, of styrene and acrylonitrile.

23. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein the particle size distribution factor Q of the graft base A1 is 0.01 to 0.5, especially 0.1 to 0.4.

24. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein the average particle size of the particles of component A after the graft reaction is in the range from 70 to 150 nm.

25. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein the sodium carbonate is used in the production of the graft copolymers A and/or C in an amount of 0.01 to 2.5 mol, especially 0.1 to 2.5 mol, based on the sum total of the molar amounts of the amount of initiator, especially PPS, used in the graft base and graft shell.

26. The process for producing a thermoplastic molding compound as claimed in claim 16, wherein the molding compound comprises 1% to 40% by weight of at least one graft copolymer C which differs from the graft copolymer A.

27. A process for producing a thermoplastic molding compound comprising: 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, 10% to 50% by weight of at least one graft copolymer C with an average particle size (weight average) in the range from 200 to 800 nm, comprising: 50% to 80% by weight, based on C, of an elastomeric crosslinked acrylate polymer C1, 2.5% to 25% by weight, based on C, of a first graft shell C2 made of a vinylaromatic monomer and of 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 90:10 to 60:40; and 0% to 15% by weight, especially 0.1% to 5% by weight, of one or more additives D, wherein the sum total of B and C, and optionally D, is 100% by weight, and wherein the reaction for production of the graft copolymer C is conducted in the presence of 0.01 to 4 times the molar amount of sodium carbonate, based on the total molar amount of initiator, especially PPS, used in the production of the graft base and graft shell; and wherein the reaction for production of the graft copolymer C is conducted in the presence of 0.1%-1% by weight of an emulsifier, especially an alkali metal alkylsulfonate, based on the amount of the monomers used in each case; and wherein water or an aqueous alkaline solution is added to the reaction mixture for production of the graft copolymer C during the polymerization reaction, during the postpolymerization and/or after the polymerization reaction.

28. The process for producing a thermoplastic molding compound as claimed in claim 27, where the coagulate formation of the graft shell of component C is in a range from 0.01% to 0.5% by weight, based on the total weight of the graft copolymer C.

29. The use of the thermoplastic molding compound obtained as claimed in claim 16 for production of moldings, films, or coatings.

30. A molding, film, or coating made of a thermoplastic molding compound produced by a process as claimed in claim 16.

Description

EXAMPLE A) PRODUCTION OF THE SMALL-PARTICLE GRAFT COPOLYMER

[0128] The graft base A is produced by analogy with EP-A 0450485 (graft copolymer A; see page 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.

[0129] The acrylate graft copolymer C and hard component B (SAN copolymer) are produced by analogy with EP 0450485. The experiments were conducted with about 2 kg of graft rubber.

a1) Production of Graft Base A1

[0130] Proportions by weight are each reported relative to the total mass of the monomers (parts per hundred monomer, abbreviated hereinafter to pphm). This relates to the sum total, based on the mass, of the monomers for the base stage and the graft stage.

[0131] The initial charge at room temperature comprised 86.12 pphm of water (demin.), 0.61, 0.5 or 0.35 pphm of emulsifier (sodium alkylsulfonate) and 0.07 pphm of Na.sub.2CO.sub.3 or 0.23 pphm NaHCO.sub.3. The reaction vessel was evacuated and purged with nitrogen. Subsequently, the reaction mixture was heated to 59 C., and 0.18 pphm of PPS was added together with 5 pphm of water (demin.). Thereafter, 59.51 pphm of butyl acrylate and 1.21 pphm of DCPA were metered in over a period of 210 min. The reaction mixture was postpolymerized at 59 C. for 1 h. Table 1 summarizes the results of this polymerization.

a2) Production of Graft Copolymer A

[0132] An amount of 90.37 pphm of water (demin.) and 0.11 pphm of emulsifier (sodium alkylsulfonate) were added at 61 C. to the latex dispersion obtained in step a1). Subsequently, 5.22 pphm of water (demin.) and 0.16 pphm of PPS were added. Firstly, 6.3 pphm of styrene and 2.1 pphm of acrylonitrile were added over a period of 20 min, followed by a postpolymerization period of 20 min. Subsequently, 24 pphm of styrene and 8 pphm of acrylonitrile were added, followed by a postpolymerization period of one hour. Table 1 summarizes the results of this polymerization.

TABLE-US-00001 TABLE 1 Change in the latex particle size with reduced emulsifier concentration. Particle size of Particle size of the graft base the graft copolymer PPS Emulsifier from turbidity from turbidity NaHCO.sub.3 Na.sub.2CO.sub.3 initiator (graft base) photometry photometry Ex. (pphm) (pphm) (pphm) (PPhm) [nm] [nm] C1 0.23 0.18 0.61 77 89 1 0.07 0.18 0.61 62 72 2 0.07 0.18 0.5 66 77 3 0.07 0.18 0.35 75 87

[0133] It was found that the use of sodium carbonate (0.07 pphm) rather than sodium hydrogencarbonate (0.23 pphm in comparative example C1), the latter being the buffer substance customarily used, allows a distinct reduction in the amount of emulsifier, nevertheless obtaining latex particles having the desired diameter (of about 89 nm in the comparative example). While examples 1 and 2 led to particle sizes that were much smaller than that in comparative example C1, it was possible with a reduction in the amount of emulsifier used from 0.61 pphm to 0.35 pphm in example 3 to produce latex particles having a particle diameter corresponding roughly to that in comparative experiment C1.

[0134] Different amounts of water or aqueous alkaline solution were subsequently added to the polymer latices obtained, and the diluted emulsions were analyzed in the klaxon test. It was found that the reduction in the amount of emulsifier adversely affects the stability of the polymer latices L(A), and that there is more rapid coagulation.

[0135] However, this coagulation can be counteracted by the addition of alkaline solutions of Na.sub.2CO.sub.3 having a concentration of 1 mmol/L. It was found that, as a result of the addition of such a solution to a polymer latex in a ratio of 1:4 parts by weight of Na.sub.2CO.sub.3 solution:polymer latex L(A), the latex stability of the comparative latex with a greater amount of emulsifier can actually be exceeded. Similar results were achieved with NaHCO.sub.3 and KOH. The results are shown in table 2.

TABLE-US-00002 TABLE 2 Latex stability of small-particle graft copolymer latices Latex stability Example (klaxon test) latex Dilution (after the graft step) [sec.] C1 7 1 9 2 7 3 4 3 Water 15 Weight ratio of sample to water 1:4 3 Aqueous Na.sub.2CO.sub.3 solution (0.1% by weight) 19 Weight ratio of sample to solution 1:4 3 Aqueous KOH solution (0.1% by weight) 18 Weight ratio of sample to solution 1:4 3 Aqueous NaHCO.sub.3 solution (0.1% by weight) 11 Weight ratio of sample to solution 1:4

[0136] 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).

[0137] The graft copolymer is precipitated out of the emulsion by means of magnesium sulfate solution at about 60 C., washed with water, and dried in a stream of warm air. The amount of magnesium sulfate was reduced here compared to conventional processes.

b) Production of Corresponding Molding Compounds

[0138] The thermoplastic molding compositions were produced by incorporating the particulate graft copolymers 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 copolymer(s) is/are isolated (precipitated) out of the emulsion by adding an electrolyte and then, optionally after drying, mixed with the hard component (SAN) by extruding, kneading, or rolling the materials together.

c1) Production of Graft Base C1

[0139] To an initial charge of 0.3 pphm of the rubber produced as described in a1) were added 70.66 pphm and 0.18 pphm of potassium peroxodisulfate, followed by a mixture of 59.51 pphm of butyl acrylate and 1.21 pphm of DCPA over the course of 210 min. In parallel, a solution of emulsifier (sodium alkylsulfonate) in water was added. The amount of emulsifier added was varied over the addition time (210 min with 0.36 pphm of emulsifier in 16.6 pphm of water or 136 min with 0.23 pphm of emulsifier in 10.79 pphm of water). The temperature of the batch was 60 C. The end of the feeds was followed by a postpolymerization period of one hour.

c2) Production of Graft Copolymer C

[0140] To the latex dispersion obtained in step c1) were added 88.26 pphm of water and 0.11 pphm of emulsifier. Additional initiator (0.16 pphm of PPS in 5.61 pphm of water) was also added. Subsequently, 13.16 pphm of styrene were mixed in and the mixture was heated to 65 C. while stirring. The reaction mixture was kept at this temperature for 30 min. The dispersion obtained was polymerized together with 27.33 pphm of a mixture of styrene and acrylonitrile in a ratio of 75:25 for a further hour. The polymer latex L(C) obtained was then diluted with water or aqueous sodium carbonate solution, and the latex stability was examined.

[0141] The data obtained for the latices from the experiments and comparative experiments can be found in table 2.

TABLE-US-00003 TABLE 3 Latex stability of small-particle graft copolymer latices. Duration of Latex emulsifier stability Sam- addition (klaxon test) ple [min] Dilution (after the graft step) [sec] C1 34 1 210 20 2 136 6 2 136 Aqueous Na.sub.2CO.sub.3 solution 11 (0.1% by weight) Weight ratio of sample to solution 1:9 2 136 Aqueous Na.sub.2CO.sub.3 solution 23 (0.1% by weight) Weight ratio of sample to solution 1:4 2 136 Water 10 Weight ratio of sample to water 1:9 2 136 Water 19 Weight ratio of sample to water 1:4

[0142] C1 is a graft copolymer latex which has been stabilized after the polymerization reaction by the addition of an additional 0.04 pphm of emulsifier. By comparison, in examples 1 and 2, respectively, only 92% by weight and 67% by weight of the amount of emulsifier from example C1 have been used.

[0143] The results show that the reduction in the duration of addition of emulsifier results in a decrease in the stability of the polymer latex obtained. The inventive addition of water or aqueous sodium carbonate solution achieves a distinct improvement in the latex stability.

[0144] The graft copolymer was precipitated out of the emulsion by means of magnesium sulfate solution at 95 C., washed with water, and dried in a stream of warm air. The amount of magnesium sulfate was reduced here compared to conventional processes.

d) Production of Corresponding Molding Compounds

[0145] The thermoplastic molding compounds were produced by incorporating the particulate graft polymers described above into a hard component, for example the SAN copolymer (75:25). Incorporation can be achieved 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.

EXAMPLE PRODUCTION OF A FURTHER SMALL-PARTICLE GRAFT COPOLYMER

a1) Production of Graft Base A1

[0146] What are reported in each case are proportions by weight based on the total mass of the monomers (pphm). This relates to the sum total, based on the mass, of the monomers for the base stage and the graft stage. At room temperature, 86.12 pphm of water (demin.), 0.35 pphm of emulsifier (sodium alkylsulfonate) and 0.07 pphm of Na.sub.2CO.sub.3 were mixed. The reaction vessel was evacuated and purged with nitrogen. Subsequently, the reaction mixture was heated to 59 C., and 0.18 pphm of PPS was added together with 5 pphm of water (demin.). Thereafter, 59.51 pphm of butyl acrylate and 1.21 pphm of DCPA were metered in over a period of 210 min. The reaction mixture was postpolymerized at 59 C. for 1 h.

a2) Production of Graft Copolymer A

[0147] An amount of 90.37 pphm of water (demin.) and 0.11 pphm of emulsifier (sodium alkylsulfonate) were added at 61 C. to the latex dispersion obtained in step a1). Subsequently, 5.22 pphm of water (demin.) and 0.16 pphm of PPS were added. Firstly, 6.3 pphm of styrene and 2.1 pphm of acrylonitrile were added over a period of 20 min, followed by a postpolymerization period of 20 min. Subsequently, 24 pphm of styrene and 8 pphm of acrylonitrile were added, followed by a postpolymerization period of one hour. Thereafter, a suspension of 0.2 pphm of Lowinox TBM (hindered thiophenol, CAS No. 96-69-5) in 0.2 pphm of methanol is added.

COMPARATIVE EXAMPLES C1 AND C2

[0148] C1: in step a1) 0.23 pphm of NaHCO.sub.3 (in place of 0.07 pphm of Na.sub.2CO.sub.3), 0.61 pphm of emulsifier; in step a2) 0.04 pphm of emulsifier is also added with the Lowinox dispersion;

[0149] C2: in step a1) 0.23 pphm of NaHCO.sub.3 (in place of 0.07 pphm of Na.sub.2CO.sub.3), 0.61 pphm of emulsifier;

[0150] Table 4 shows particle sizes of base stage (a1) and graft stage (a2), and the latex stabilities determined by means of the klaxon test. The omission of the final addition of emulsifier in the last step of the graft stage (C1 vs. C2) does not show any particular effect.

TABLE-US-00004 TABLE 4 Emulsifier Latex stability (base stage) Particle size Particle size in klaxon test Sample [pphm] a1) [nm] a2) [nm] [s] C1 0.61 74 88 8 C2 0.61 74 87 8

[0151] The latex obtained after step a1) and a2) was diluted with dilute alkali (sodium carbonate) or water; the results are reported in table 5. A distinct increase in latex stability (klaxon test) is found, beyond the stability of comparative examples C1 and C2.

TABLE-US-00005 TABLE 5 Dilution Stability in Latex component Ratio of latex to klaxon test Sample [g] [g] dilution pH [s] Dilution with 0.1 wt % of Na2CO3 (0.009 mol/L) 1 49 1 49:1 8.6 5 2 48 2 24:1 8.9 5 3 45 5 9:1 9.7 6 4 40 10 4:1 10.2 18 Dilution with 0.1 wt % of NaHCO3 (0.012 mol/L) 1 49 1 49:1 8.0 7 2 48 2 24:1 8.2 6 3 45 5 9:1 8.2 8 4 40 10 4:1 8.4 16 Dilution with water 1 49 1 49:1 7.9 7 2 48 2 24:1 7.9 6 3 45 5 9:1 7.9 9 4 40 10 4:1 7.9 22

EXAMPLE

Production of Graft Base C1

[0152] To an initial charge of 0.3 pphm of the rubber produced as described in example C, a1) were added 70.66 pphm of water (demin.), 0.07 pphm of rubber latex No. 1, 2 (from table 5) or 0.15 pphm of No. 3, 4, 5 (from table 5) or 0.29 pphm of No. 6, 7 (from table 5), sodium carbonate and 0.18 pphm of potassium peroxodisulfate (dissolved in 5 pphm of demin. water), followed by a mixture of 59.51 pphm of butyl acrylate and 1.21 pphm of DCPA over the course of 210 minutes. In parallel, a solution of emulsifier (sodium alkylsulfonate) in water was added. The amount of emulsifier added was varied over the addition time (210 min with 0.36 pphm of emulsifier in 16.6 pphm of water, 168 min with 0.288 pphm of emulsifier in 13.28 pphm of water, 136 min with 0.23 pphm of emulsifier in 10.79 pphm of water). The temperature of the batch was 60 C. The end of the feeds was followed by a postpolymerization period of another hour.

c2) Production of Graft Copolymer C

[0153] To the latex dispersion obtained in step c1) were added 88.26 pphm of water and 0.11 pphm of emulsifier. Additional initiator (0.16 pphm of PPS in 5.61 pphm of water) was also added. Subsequently, 13.16 pphm of styrene were metered in over a period of 60 min, and the mixture was heated to 65 C. while stirring. The reaction mixture was kept at this temperature for 30 min. The dispersion obtained was polymerized together with 27.33 pphm of a mixture of styrene and acrylonitrile in a ratio of 75:25 for a further hour. Subsequently, a dispersion of 0.2 pphm of Lowinox TBM (CAS No. 96-69-5) and 0.2 pphm of methanol was added.

[0154] The results in table 6 show that latex stability decreases with the feed time.

TABLE-US-00006 TABLE 6 Rel. amount Emulsifier Particle Amount Stability Sam- of emulsifier feed time size (graft) of latex klaxon test ple [%] [min] [nm] [g] pH [sec] Na.sub.2CO.sub.3/PPS ratio 0.99 1 100 210 491 50 7.28 26 2 65 136 469 50 7.64 21 Na.sub.2CO.sub.3/PPS ratio 2.1 3 100 210 498 50 8.77 25 4 80 168 500 50 8.72 22 5 65 136 491 50 8.52 21 Na.sub.2CO.sub.3/PPS ratio 4.1 6 100 210 483 50 8.59 31 7 65 136 504 50 8.59 23

[0155] The latex stability of a latex (No. 5, table 6) which has been produced according to c1) and c2) with a reduced amount of emulsifier (65% based on the operational formulation) can be enhanced by dilution with sodium carbonate (No. 1, table 7), sodium hydrogencarbonate (No. 2, table 7) and water (No. 3, table 7).

[0156] In the case of dilution in a ratio of 4:1 (latex:dilution), the stability of the original latex is actually exceeded.

[0157] A similar picture is obtained with latex No. 7 (table 6); the results are reported in table 8. Here too, the latex stability can be increased by diluting with alkali or water.

TABLE-US-00007 TABLE 7 Dilution of latex No. 5 (table 6), Na2CO3/PPS ratio of 2.1 Amount Amount of Latex of latex diluent stability No. [g] [g] Dilution pH [sec] 1 40 10 Sodium carbonate 10.13 23 (0.1 wt %) 2 40 10 Sodium 8.67 24 hydrogen- carbonate (0.1 wt %) 3 40 10 Water 8.5 24

TABLE-US-00008 TABLE 8 Dilution of latex No. 7 (table 6), Na2CO3/PPS ratio of 4.1 Amount Amount of Latex of latex diluent stability Sample [g] [g] Dilution pH [sec] 1 40 10 Sodium carbonate 9.67 26 (0.1 wt %) 2 40 10 Sodium 8.63 26 hydrogen- carbonate (0.1 wt %) 3 40 10 Water 24