ABS MOLDING MATERIAL OBTAINED BY MASS OR SOLUTION POLYMERIZATION

Abstract

Acrylonitrile-Butadiene-Styrene molding compositions having improved organoleptic properties comprising a rubber modified vinylaromatic copolymer composition obtained by mass (bulk) or solution polymerization in a continuous process, and use of these molding compositions for various applications (e.g. automotive parts) are described.

Claims

1-16. (canceled)

17. A molding composition comprising: a) a rubber modified vinylaromatic copolymer composition A), composed of a matrix phase comprising a copolymer of monomers B1) and B2), and a dispersed phase comprising particles of graft rubber copolymer C′) composed of rubber polymer C) with grafts built up from monomers B1) and B2), obtained by mass or solution polymerization of monomers B1) and B2) B1: 50 to 85 wt.-%, based on B1), B2), and C), of at least one vinylaromatic monomer B1); B2: 10 to 40 wt.-%, based on B1), B2), and C), of at least one comonomer B2) different from B1); in a continuous process in the presence of C: 5 to 20 wt.-%, based on B1), B2), and C), of a rubber polymer C) made from: C1: 30 to 100 wt.-%, based on C1) and C2), of a conjugated diene C1); C2: 0 to 70 wt.-%, based on C1) and C2), of at least one comonomer C2); wherein the sum of components B1), B2), and C) is 100 wt.-%; b) 0 to 20 pbw, based on 100 pbw A), of at least one pigment D); and c) 0 to 10 pbw, based on 100 pbw of A), of at least one additive and/or processing aid E), different from component D); wherein the molding composition is characterized by; a mean weight particle size of graft rubber copolymer C′) of more than 0.5 μm; a melt volume rate MVR (220° C./10 kg) according to ISO 1133-1:2011 of more than 3 ml/10 min; a content of residual volatile organic compounds of not more than 500 ppm; and an amount of sulfur-containing chain transfer agent measured in a sulfur content of less than 500 ppm.

18. The molding composition according to claim 17, wherein the rubber modified vinylaromatic copolymer composition A) is obtained by mass or solution polymerization of B1: 59 to 70 wt.-%, based on B1), B2), and C), of the at least one vinylaromatic monomer B1); and B2: 19 to 30 wt.-%, based on B1), B2), and C), of the at least one comonomer B2) different from B1); in a continuous process in the presence of C: 11 to 18 wt.-%, based on B1), B2), and C), of the rubber polymer C).

19. The molding composition according to claim 17 comprising 0.01 to 10 pbw of the at least one additive and/or processing aid as component E).

20. The molding composition according to claim 17, wherein at least 1 wt.-% of the particles of the graft rubber copolymer C′) have a mean weight particle size in the range of 0.51 to 5 μm.

21. The molding composition according to claim 17, wherein the graft rubber copolymer C′) has a mean weight particle size in the range of 0.51 to 2 μm.

22. The molding composition according to claim 17, wherein the particles of the graft rubber copolymer C′) have a mono disperse particle size distribution.

23. The molding composition according to claim 17, wherein the monomers B1) and B2) are used in a B1):B2) weight-ratio of from 80:20 to 70:30.

24. The molding composition according to claim 17, wherein the mass or solution polymerization process is characterized by: i) dissolving the rubber polymer C) in monomers B1) and, optionally B2) and/or a solvent, by agitation of the slurry, thereafter addition of remaining comonomer B2) and optionally a solvent to the rubber polymer solution or slurry; ii) continuously feeding the solution or slurry obtained in step i) into a first agitated reactor and carrying out a first polymerization of monomers B1) and B2), by use of at least one radical initiator, and iii) optionally continuously feeding the content of the first agitated reactor into at least one further agitated reactor for a second polymerization to obtain a polymer melt; followed by iv) degassing the polymer melt obtained in step iii) by pre-heating the polymer melt followed by devolatilization in a devolatilizing apparatus.

25. The molding composition according to claim 24, wherein: in step ii) of the mass or solution polymerization process the first polymerization of monomers B1) and B2) in presence of rubber polymer C) is carried out at a temperature of 50° C. to 100° C.; and in step iii) the content of the first agitated reactor is continuously fed into at least one further agitated reactor for a second polymerization at temperatures of 100° C. to 150° C.; and wherein in steps ii) and optionally iii) a chain transfer agent in total amounts of 0.01 to 0.50 pbw, related to 100 pbw of the sum of B1), B2), and C) is added.

26. The molding composition according to claim 24, wherein: in step i) of the mass or solution polymerization process the rubber polymer C) is dissolved only in monomer B1), plus optionally a solvent.

27. The molding composition according to claim 24, wherein: in steps ii) and iii) of the mass or solution polymerization process at least one continuously stirred tank reactor (CSTR) is used having a stirring speed in the range of 5 to 200 rpm.

28. The molding composition according to claim 24, wherein in the mass or solution polymerization process two continuously stirred tank reactors (CSTR) in series are used, wherein one CSTR is used in step ii) and one further CSTR is used in step iii).

29. The molding composition according to claim 24, wherein in the mass or solution polymerization process three CSTRs in series are used, wherein one CSTR is used in step ii) and two further CSTRs are used in step iii).

30. The molding composition according to claim 24, wherein in step i) of the mass or solution polymerization process a solvent is used.

31. The molding composition according to claim 24, wherein in step iv) of the mass or solution polymerization process as the devolatilizing apparatus a partial evaporator or a falling strand devolatilizer is used.

32. A method of producing household and automotive applications comprising the molding composition according to claim 17.

33. The molding composition according to claim 17, wherein the at least one vinylaromatic monomer B1) is styrene or alpha methylstyrene and the at least one comonomer B2) is (meth)acrylonitrile or acrylonitrile.

34. The molding composition according to claim 17, wherein the conjugated diene C1) is 1,3-butadiene or isoprene and the at least one comonomer C2) is styrene.

35. The molding composition according to claim 20, wherein at least 50 wt.-% of the particles of the graft rubber copolymer C′) have a mean weight particle size in the range of 0.51 to 5 μm.

36. The molding composition according to claim 23, wherein the monomer B1) is styrene and the monomer B2) is acrylonitrile.

Description

EXAMPLES GENERAL DESCRIPTION OF THE EXPERIMENTS

[0081] The following experiments were performed in a 2-vessel-3-tower reactor cascade.

[0082] In a 250 l stainless steel vessel, rubber polymer crumbs plus stabilizer Irganox 1076 were dissolved in a mixture of styrene and ethyl benzene at 50° C., within a period of 14 to 16 hr. Via a filter with 100 μm mesh size, the obtained rubber polymer solution is pumped into a second vessel and acrylonitrile is added as co-monomer. The content of this second vessel is continuously fed into a 3-tower reactor cascade for the polymerization.

[0083] The reactor cascade consists of 3 tower reactors in series. Each of the tower reactors has a volume of 30 liter, a length/diameter (l/d) ratio of 1100/220 mm and contains on the inside horizontal, parallel layers of cooling pipes, with finger paddle agitators in between the pipes.

[0084] The first tower reactor—designated as PPT in Table 1b—acts as a reactor for the first polymerization, and is equipped with a dosing station, including static mixer, for adding mercaptane as molecular weight controller (MWC) as a 50% b.w. solution in ethyl benzene. The polymerization turnover was controlled via the amount of initiator and the temperature. The 2.sup.nd and 3.sup.rd tower reactors—designated as PT1 and PT2 in Table 1b—act as reactors for the 2.sup.nd polymerization.

[0085] Degassing was performed through a partial evaporator under nitrogen. Vacuum was generated via a liquid ring pump.

Variation of Rubber Polymer and Initiator

[0086] In Examples 1 to 6 (see Tables 1a and 1b below), the influence of increasing amounts of rubber component C on the behavior of polymerization process was investigated. The initiator was tert.-butyl perpivalate (=TBPPI). The rubber polymer C was a med-cis homo polybutadiene with medium solution viscosity (e.g. Buna HX 500, Diene® 35 AC10 from Lion Elastomers, Buna® CB 380 from Arlanxeo/solution viscosity 90 mPa*s). In order to obtain highly grafted polybutadiene-g-SAN rubber particles, the molecular weight of the matrix was controlled via the amount of TDDM (tert.-dodecycl mercaptane). The pre-polymerization tower reactor 1 was run at 80° C. and up to a conversion rate of 22%. Conversion was increased in tower reactors 2 and 3 to 75%.

[0087] In order to maintain the conversion in pre-polymerization tower 1, almost constant amounts of 2 (+/−0.2) mmol initiator per kg monomer (here: styrene and acrylonitrile) were required, which equals 45 to 15 mmol initiator per kg polybutadiene.

TABLE-US-00001 TABLE 1a Feed composition used for polymerization of polybutadiene rubber in styrene/acrylonitrile. Example No. 1 2 3 4 5 6 Polybutadiene (PBu) content [wt.-%] 5 8 10 13 16 18 Flow rate [l/h] 13.2 12.4 12.4 12.5 14.5 14.5 kg/h 11.2 11.0 11.0 11.1 12.9 12.9 Zulauf Styrene [pbw] 61.28 60.08 58.88 57.68 56.48 55.28 Acrylnitrile [pbw] 20.42 20.2 19.62 19.22 18.82 18.42 Ethyl benzene [pbw] 15.0 15.0 15.0 15.0 15.0 15.0 Irganox 1076 [pbw] 1.10 1.10 1.10 1.10 1.10 1.10 PBu [pbw] 3.2 4.80 6.40 8.0 9.60 11.20 MWC* relative to sum [%] 0.24 0.25 0.25 0.23 0.15 0.18 PPT/PT1 B1), B2), C) Initiator [TBPPI] [ml/h] 110 110 120 105 120 145 VPT (3% solution) [mmol/h] 16.4 16.4 17.9 15.7 17.9 21.7 rel. to sum [mmol/kg] 1.7 1.8 2.0 1.8 1.8 2.2 B1), B2), C) =[ppm] 300 320 360 320 320 400 rel. to PBu [mmol/kg] 44 31 25 18 16 15 Mole ratio Initiator/MWC 0.15 0.15 0.17 0.16 0.25 0.26 MWC* = Molecular weight controller (chain transfer agent): TDDM

TABLE-US-00002 TABLE 1b Process conditions used for polymerization of polybutadiene in styrene/acrylonitrile Example No. 1 2 3 4 5 6 PBu-content [wt.-%] 5 8 10 13 16 18 VPT temperature [° C.] 76-82 73-83 68-82 64-82 66-83 65-83 rpm* [1/min] 150 150 150 150 150 130 solid content [%] 19.7 22.1 23.5 22.0 22.5 26.1 PT1 temperature [° C.] 114-124 111-125 109-125 111-127 109-130 110-128 rpm [1/min] 100 100 100 100 100 80 solid content [%] 39.8 41.0 42.8 43.4 43.3 44.0 PT2 temperature [° C.] 124-135 124-137 124-137 124-140 126-140 125-144 rpm [1/min] 15 15 15 15 15 15 solid content [%] 60.6 61.3 63.0 61.4 60.0 62.5 degassing T.sub.top** [° C.] 260 265 265 240 250 280 T.sub.top*** [° C.] 313 313 312 312 310 310 T.sub.medium*** vacuum [mbar] ~10 ~10 ~10 ~10 ~10 ~10 conversion PPT [%] 20.0 21.5 21.7 18.1 17.0 20.1 PT1 [%] 24.6 23.6 24.6 27.8 27.6 24.3 PT2 [%] 25.5 25.3 24.7 23.4 23.1 25.8 rpm* = revolutions per minute T.sub.top** = temperature top part of degassing device T.sub.medium*** = temperature medium part of degassing device

[0088] Due to the specifically higher initiator concentration at lower polybutadiene content, (highly grafted) capsule particles are being formed at low polybutadiene content, while at higher polybutadiene content, the morphology turns into larger “salami type” particles.

[0089] The properties of the obtained molding composition (cp. Table 2) were determined by the following test methods:

[0090] Mean weight particle size analysis was done via OsO.sub.4 stained electron micrograph and a mathematical algorithm correcting for microtoming particles in random sections between the poles and the equator of a particle.

[0091] The content of sulfur-containing chain transfer agent, as well as the amount of residuals were determined via Headspace GC and a capillary column, with standard-substances to define retention time and with standard heating program from 80 to 300° C.

[0092] The organoleptic properties of the samples were tested as follows:

[0093] In a 100 ml Erlenmeyer Flask, a sample of 10 g was placed and 50 ml of freshly boiling water was added.

[0094] After 5 seconds the nose of a test panel person (in total 3 persons) was placed 10 cm above the Erlenmeyer flask and the smell was scored according to following scale: [0095] 0=absolutely no smell, completely neutral [0096] 1=a slight smell [0097] 2=a significant smell, still acceptable [0098] 3=a strong smell [0099] 4=very strong, disgusting smell

[0100] The target is to stay at or better than 2.

TABLE-US-00003 TABLE 2 Properties of the obtained ABS polymer compositions Example No. 1 Comp. 2 Comp. 3 Comp. 4 5 6 PBu content [wt.-%] 5 8 10 13 16 18 Grafted rubber C′ 0.30 0.30 0.40 0.80 0.60 1.3 mean weight particle size (μm) Visual appearance of injection molded 1 1 1 2-3 2 3 plaque (Tmolding = 250° C.) Glossiness (1 = high gloss in reflecting sunlight in 75° angle to the surface, 2 = slight haze, 3 = clearly less gloss, 4 = almost no light reflection, 5 = no light reflection Comp. = Comparative example

[0101] The data show that the molding compositions according to Ex. 4 to 6 have a significantly lower glossiness in comparison to the molding compositions of Comp. examples 1 to 3.

TABLE-US-00004 TABLE 3 Organoleptics tests of mass-ABS molding compositions Example 7 Comp. 8 9 total sulphur content 510 400 150 measured (ppm) mass-ABS Polybutadiene(wt. %) 16 13 11 composition - styrene (wt. %) 60 61 68 (wt.-% related to final Acrylonitrile (wt. %) 24 26 21 product) Organoleptics score 2-3 2 1 *based on 100 pbw of the sum of polybutadiene, styrene and acrylonitrile

[0102] The data show that the ABS molding compositions according to Examples 8 and 9 have improved organoleptic properties.