HIGH FATIGUE RESISTANCE ABS

Abstract

Thermoplastic molding compositionhaving an improved fatigue resistance, balanced mechanical properties and a high ductility for applications demanding high endurance under cyclic loading conditionscomprising 25 to 45 wt.-% ABS graft copolymer (A), consisting of 50.5 to 55 wt.-% of a graft sheath (AN content 30.5 to 34 wt.-%) (A2) and 45 to 49.5 wt.-% of a graft substrate (A1), and 55 to 75 wt.-% SAN copolymer (B) (AN content (30 to 33 wt.-%, melt flow rate 30 to 36 g/10 min (220 C./10 kg)).

Claims

1.-14. (canceled)

15. A thermoplastic molding composition comprising components A, B, and C: (A) 25 to 45 wt.-%, preferably 30 to 45 wt.-%, of a graft copolymer (A) consisting of: 50.5 to 55 wt.-% of a graft sheath (A2), and 45 to 49.5 wt of a graft substrate (A1), wherein (A1) is a mixture of agglomerated butadiene rubber latices (A1) and (A1) and wherein (A1) and (A2) sum up to 100 wt.-%, obtained by emulsion polymerization of styrene and acrylonitrile in a weight ratio of 69.5/30.5 to 66/34 to obtain a graft sheath (A2), wherein the styrene and/or acrylonitrile is optionally partially replaced by alpha-methylstyrene, methyl methacrylate, N-phenylmaleimide, or mixtures thereof, in the presence of at least one agglomerated butadiene rubber latex (A1) with a median weight particle diameter D.sub.50 from 150 to 350 nm, and at least one agglomerated butadiene rubber latex (A1) with a median weight particle diameter D.sub.50 of 425 to 650 nm, where the agglomerated rubber latices (A1) and (A1) are obtained by agglomeration of at least one starting butadiene rubber latex (S-A1) having a median weight particle diameter D.sub.50 of equal to or less than 120 nm with at least one acid anhydride; (B) 55 to 75 wt.-% of at least one copolymer (B) of styrene and acrylonitrile in a weight ratio of from 70/30 to 66/34, wherein the styrene and/or acrylonitrile is optionally partially replaced by alpha-methylstyrene, methyl methacrylate, N-phenylmaleimide, or mixtures thereof; wherein copolymer (B) has a melt flow rate of 30 to 36 g/10 min (220 C./10 kg); (C) 0 to 5 wt.-% of further additives and/or processing aids (C); where the components A, B, and, if present, C, sum up to 100 wt.-%.

16. The thermoplastic molding composition according to claim 15, comprising: 25 to 45 wt.-% component (A), 54.99 to 74.99 wt.-% component (B), and 0.01 to 5 wt.-% component (C).

17. The thermoplastic molding composition according to claim 15, comprising: 30 to 45 wt.-% component (A), 54.99 to 69.99 wt.-% component (B), and 0.01 to 5 wt.-% component (C).

18. The thermoplastic molding composition according to claim 15, wherein graft copolymer (A) consists of: 51 to 54 wt.-% of a graft sheath (A2), and 46 to 49 wt.-% of a graft substrate (A1).

19. The thermoplastic molding composition according to claim 15, wherein the graft sheath (A2) is obtained by emulsion polymerization of styrene and acrylonitrile in a weight ratio of 69/31 to 67/33.

20. The thermoplastic molding composition according to claim 15, wherein the agglomerated butadiene rubber latex (A1) has a median weight particle diameter D.sub.50 from 200 to 300 nm, and the at least one agglomerated butadiene rubber latex (A1) has a median weight particle diameter D.sub.50 of 450 to 600 nm.

21. The thermoplastic molding composition according to claim 15, wherein the weight ratio of the agglomerated butadiene rubber latices (A1) and (A1) is 50/50 to 90/10.

22. The thermoplastic molding composition according to claim 15, where in copolymer (B) the weight ratio of styrene and acrylonitrile is 69.5/30.5 to 67/33.

23. The thermoplastic molding composition according to claim 15, wherein copolymer (B) has a melt flow rate of 31 to 35 g/10 min (220 C./10 kg).

24. The thermoplastic molding composition according to claim 15, wherein the graft sheath (A2) and copolymer (B) consist of polymerized units of styrene and acrylonitrile.

25. A process for the preparation of the thermoplastic molding composition according to claim 15 by melt mixing the components (A), (B), and, if present (C), and optionally further polymers (TP) at temperatures in the range of from 160 C. to 400 C.

26. A shaped article produced by thermoforming, extruding, injection molding, calendaring, blow molding, compression molding, press sintering, deep drawing, or sintering of the thermoplastic molding composition according to claim 15.

27. A method of using the thermoplastic molding composition according to claim 15 for applications demanding high endurance under cyclic (static or dynamic) loading conditions.

28. A method of using the thermoplastic molding composition according to claim 15 for the production of spools, automotive components under load, or home appliances vibrating due to moving parts.

Description

EXAMPLES

Test Methods

[0086] Particle Size D.sub.w/D.sub.50

[0087] For measuring the weight average particle size D.sub.w (in particular the median weight particle diameter D.sub.50) with the disc centrifuge DC 24000 by CPS Instruments Inc. equipped with a low density disc, an aqueous sugar solution of 17.1 mL with a density gradient of 8 to 20% by wt. of saccharose in the centrifuge disc was used, in order to achieve a stable flotation behavior of the particles. A polybutadiene latex with a narrow distribution and a mean particle size of 405 nm was used for calibration. The measurements were carried out at a rotational speed of the disc of 24,000 r.p.m. by injecting 0.1 mL of a diluted rubber dispersion into an aqueous 24% by wt. saccharose solution. The calculation of the weight average particle size D.sub.w was performed by means of the formula

D.sub.w=sum(n.sub.i*d.sub.i.sup.4)/sum(n.sub.i*d.sub.i.sup.3)

n.sub.i: number of particles of diameter d.sub.i.

Melt Flow Index (MFI) or Melt Volume Flow Rate (MFR)

[0088] MFI/MFR test was performed on pellets (ISO 1133 standard) using a MFI-machine of CEAST, Italy.

Notched Izod Impact Strength (NIIS)

[0089] Izod impact tests were performed on notched specimens (ASTM D 256 standard) using an instrument of CEAST (part of Instron's product line), Italy.

Tensile Test

[0090] Tensile tests on ABS blends were carried out (ASTM D 638 standard) at 23 C. using a Universal testing Machine (UTM) of Lloyd Instruments, UK.

Flexural Test

[0091] Flexural tests were carried out on ABS blends (ASTM D 790 standard) using a UTM of Lloyd Instruments, UK.

Heat Deflection Temperature (HDT)

[0092] Heat deflection temperature test was performed on injection molded specimen (ASTM D 648 standard) using a CEAST, Italy instrument.

VICAT Softening Temperature (VST)

[0093] Vicat softening temperature test was performed on injection molded test specimen (ASTM D 1525-09 standard) using a CEAST, Italy machine. Test is carried out at a heating rate of 120 C./hr (Method B) at 50 N loads.

Rockwell Hardness

[0094] Hardness of the injection molded test specimen (ISO-2039/2-11) was tested using a Rockwell hardness tester.

Fatigue Drop Test

[0095] In this test a spool is dropped down from a height of 6.5 feet and the surface appearance of spool is checked. The test is passed if the spool sustains the drop impact test for minimum 50 cycles without any cracking.

Break Down Force (BDF)

[0096] In this test the molded component (spool) was fixed in between middle & upper jig fixture of a Universal Testing Machine of Fuel Instruments & Engineers Pvt. Ltd. (Fie group) and force was applied in vertically upward direction. Breakdown force was checked in measurement scale while the spool just breaks. The requirement of BDF for spool is 4000 kgf (40 kN).

Gasoline Effect Test

[0097] The molded component (spool) was dipped into gasoline for 3 hrs. This was followed by removal of the component and checking for surface softness (swelling) by scrapping with an sharp edge. If the component gets deformed or large lump of materials get chipped off during the test the product is not passed.

Washing Machine Lid Fatigue Test

[0098] The molded component, a lid of a washing machine, was fixed in the assembly 48 hours after molding. Then the lid was subjected to open/close test, 12000 cycles, cycle time: 4 sec off/4 sec on, and checked for cracking or any other kind of failure.

[0099] 3 identical samples of each molding composition (runs 1 to 3) were tested to get representative results.

[0100] Materials used:

Component (A)

Fine-Particle Butadiene Rubber Latex (S-A1)

[0101] The fine-particle butadiene rubber latex (S-A1) which is used for the agglomeration step was produced by emulsion polymerization using tert-dodecylmercaptan as chain transfer agent and potassium persulfate as initiator at temperatures from 60 to 80 C. The addition of potassium persulfate marked the beginning of the polymerization. Finally the fine-particle butadiene rubber latex (S-A1) was cooled below 50 C. and the non reacted monomers were removed partially under vacuum (200 to 500 mbar) at temperatures below 50 C. which defines the end of the polymerization. Then the latex solids (in % per weight) were determined by evaporation of a sample at 180 C. for 25 min. in a drying cabinet. The monomer conversion is calculated from the measured latex solids. The butadiene rubber latex (S-A1) is characterized by the following parameters, see table 1.

Latex S-A1-1

[0102] No seed latex is used. As emulsifier the potassium salt of a disproportionated rosin (amount of potassium dehydro-abietate: 52 wt.-%, potassium abietate: 0 wt.-%) and as salt tetrasodium pyrophosphate is used.

TABLE-US-00001 TABLE 1 Composition of the butadiene rubber latex S-A1 Latex S-A1-1 Monomer butadiene/styrene 90/10 Seed Latex (wt.-% based on monomers) ./. Emulsifier (wt.-% based on monomers) 2.80 Potassium Persulfate (wt.-% based on monomers) 0.10 Decomposed Potassium Persulfate (parts per 100 0.068 parts latex solids) Salt amount (wt.-% based on monomers) 0.559 Salt amount in percent relative to the weight of solids 0.598 of the rubber latex (=s) Monomer conversion (%) 89.3 D.sub.w (nm) 100 pH 10.6 Latex solids content (wt.-%) 42.6 K 0.91 K = W * (1-1.4 * s ) * D.sub.w W = decomposed potassium persulfate [parts per 100 parts rubber] s = salt amount in percent relative to the weight of solids of the rubber latex D.sub.w = weight average particle size (=median particle diameter D.sub.50) of the fine-particle butadiene rubber latex (S-A1)

Production of the Coarse-Particle, Agglomerated Butadiene Rubber Latices (A1)

[0103] The production of the coarse-particle, agglomerated butadiene rubber latices (A1) was performed with the specified amounts mentioned in Table 2. The fine-particle butadiene rubber latex (S-A1) was provided first at 25 C. and was adjusted if necessary with deionized water to a certain concentration and stirred. To this dispersion an amount of acetic anhydride based on 100 parts of the solids from the fine-particle butadiene rubber latex (S-A1) as fresh produced aqueous mixture with a concentration of 4.58 wt.-% was added and the total mixture was stirred for 60 seconds. After this the agglomeration was carried out for 30 minutes without stirring. Subsequently KOH was added as a 3 to 5 wt.-% aqueous solution to the agglomerated latex and mixed by stirring. After filtration through a 50 m filter the amount of coagulate as solid mass based on 100 parts solids of the fine-particle butadiene rubber latex (B) was determined. The solid content of the agglomerated butadiene rubber latex (A), the pH value and the median weight particle diameter D.sub.50 was determined.

TABLE-US-00002 TABLE 2 Production of the coarse-particle, agglomerated butadiene rubber latices (A1) latex A1 A1-1 A1-2 used latex S-A1 S-A1-1 S-A1-1 concentration latex S-A1 be- wt.-% 41 41 fore agglomeration amount acetic anhydride parts 0.88 1.22 amount KOH parts 1.46 2.07 concentration KOH solution wt.-% 50 50 solid content latex A1 wt.-% 30 30 coagulume wt.-% <0.1% <0.1% pH 8.7-9.5 8.7-9.5 D.sub.50 nm 250 550
Production of the Graft Copolymers (A) 59 wt.-parts of mixtures of the coarse-particle, agglomerated butadiene rubber latices A1-1 and A1-2 (ratio 80:20, calculated as solids of the rubber latices (A1)) were diluted with water to a solid content of 27.5 wt.-% and heated to 55 C. 51 wt.-parts of a mixture consisting of 67 wt.-parts styrene, 33 wt.-parts acrylonitrile and 0.4 wt.-parts tert-dodecylmercaptan were added in 3 hours 30 minutes. At the same time when the monomer feed started the polymerization was started by feeding 0.15 wt.-parts cumene hydroperoxide together with 0.57 wt.-parts of a potassium salt of disproportionated rosin (amount of potassium dehydroabietate: 52 wt.-%, potassium abietate: 0 wt.-%) as aqueous solution and separately an aqueous solution of 0.22 wt.-parts of glucose, 0.36 wt.-% of tetrasodium pyrophosphate and 0.005 wt.-% of iron-(II)-sulfate within 3 hours 30 minutes.

[0104] The temperature was increased from 55 to 75 C. within 3 hours 30 minutes after start feeding the monomers. The polymerization was carried out for further 2 hours at 75 C. and then the graft rubber latex (=graft copolymer A) was cooled to ambient temperature. The graft rubber latex was stabilized with ca. 0.6 wt.-parts of a phenolic antioxidant and precipitated with sulfuric acid, washed with water and the wet graft powder was dried at 70 C. (residual humidity less than 0.5 wt.-%).

[0105] The obtained product is graft copolymer (A-I).

[0106] ABS graft copolymer P-1 (D.sub.50 particle size (nm) of agglomerated rubber latices: 315/328 nm, graft sheath: 40.5 wt.-%, AN-content of graft sheath: 28 wt.-%, agglomerated with acetic anhydride) used in the comparative examples corresponds to graft rubber polymer 15 as disclosed in WO 2012/022710 A2 (p. 23 to 28) and was prepared accordingly.

Component (B)

[0107] (B-I): statistical copolymer from styrene and acrylonitrile with a ratio of polymerized styrene to acrylonitrile of 69:31 with a melt volume flow rate (MVR) at 220 C./10 kg of 33 mL/10 minutes and Mw 124000 g/mol (determined by means of Gel Permeation Chromatography in THF using polystyrene standards) produced by free radical solution polymerization.

[0108] (B-II): statistical copolymer from styrene and acrylonitrile with a ratio of polymerized styrene to acrylonitrile of 69:31 with a melt volume flow rate (MVR) at 220 C./10 kg of 27 mL/10 minutes, and Mw 132000 g/mol (determined by means of Gel Permeation Chromatography in THF using polystyrene standards) produced by free radical solution polymerization.

TABLE-US-00003 Component (C) C-1 ethylene bisstearamide C-2 polydimethylsiloxane with kinematic viscosity of 1000 cSt C-3 Distearyl pentaerythrol diphosphite C-4 magnesium stearate C-5 magnesium oxide C-6 Carbon black powder from Phillips Carbon Black Limited

Thermoplastic Compositions

[0109] Graft rubber polymers (A-I) or (P-1), SAN-copolymers (B-I) or (B-II), and the afore-mentioned components (C) were mixed (ratio see Table 3, batch size 5 kg) for 4 to 5 minutes in a high speed mixer to obtain a uniform premix and then said premix was melt blended in a twin-screw extruder at a speed of 80 rpm and at using an incremental temperature profile from 190 C. to 220 C. for the different barrel zones. The extruded strands were cooled in a water bath, air-dried and pelletized. Standard test specimens (ISO test bars) of the obtained blend were injection moulded. The temperature profile of the injection moulding machine barrel was 190 to 230 C.

[0110] The test results are presented in Tables 4 to 6.

TABLE-US-00004 TABLE 3 ABS Molding composition Cp. Cp. Ex. 1 Ex. 1 Ex. 2 Ex. 2 Components wt.-% P-1 34.23 22.75 A-1 39.12 25.00 B - 1 63.57 58.68 71.15 B - 2 72.04 Additives C-1 1.47 1.47 1.42 1.73 C-2 0.15 0.15 0.14 0.14 C-3 0.20 0.20 0.14 0.14 C-4 0.29 0.29 0.28 0.29 C-5 0.10 0.10 0.09 0.10 C-6 3.13 1.44

TABLE-US-00005 TABLE 4 Typical Cp. Cp. properties Standard Unit Ex. 1 Ex. 1 Ex. 2 Ex. 2 % Composition AN Test % 23.5 23.7 26.2 25.8 by FTIR BD method % 17.89 17.77 11.5 13 STY % 58.61 58.53 62.3 61.2 MFI, 220 C., 10 kg load ISO g/10 min 13 11.2 17.5 19 1133 NIIS, , 23 C., ASTM D kg .Math. cm/cm 39 37.1 24 16.5 256 NIIS, , 23 C., ASTM D kg .Math. cm/cm 50.5 55 36 28 256 Tensile strength at ASTM D kg/cm.sup.2 460 461.2 530 566 yield, 638 50 mm/min, Tensile Modulus, ASTM D kg/cm.sup.2 25300 24492 31000 30000 50 mm/min, 638 Elongation at Break, ASTM D % 19 33 19 22.9 50 mm/min, 638 Flexural Strength, ASTM D kg/cm.sup.2 750 759 900 944 5 mm/min, 790 Flexural Modulus, ASTM D kg/cm.sup.2 24500 24523 30300 31332 5 mm/min, 790 Density ISO g/cm.sup.3 1.045 1.044 1.046 1.045 1183 Rockwell hardness, ASTM D R-scale 106 105 111 113 23 C. 785 Vicat softening ASTM C. 100 100 102 103 temperature D1525, B-50 N HDT, annealed 80 C./ ASTM D C. 96 97 97 95 4 hrs 648, 1.80 mpa NIIS = Izod notched impact strength

TABLE-US-00006 TABLE 5 Fatigue test and special tests of the molding compositions Number of cycles Cp. Test standard Ex. 1 Ex 1 Drop test 50 58 37-40 Breakdown 40.0 40.2 37.5 force test [kN] chemical no surface passes fails resistance defect for in gasoline 3 hours standard = required properties

TABLE-US-00007 TABLE 6 Open/close fatigue test of washing machine lids number of cycles before failure of molding composition sample Run 1 Run 2 Run 3 Cp. Ex. 1 4300 4200 4300 Ex. 1 15000 10300 12000 Cp. Ex. 2 7000 7000 7000 Ex. 2 11000 12000 16000

[0111] The molding compositions according to the invention (see examples 1 and 2) exhibit an excellent fatigue resistance as shown by their elongation at break (Table 4), their drop test (cp. Tables 5 and 6) and open/close test of the washing machine lid.

[0112] Moreover, the presented data indicate that the molding compositions described have well-balanced properties, in respect to their key mechanical properties, chemical resistance, ductility and melt flow.