Thermoplastic moulding compositions for metal plated articles with improved resistance against repeated impact

Abstract

Thermoplastic moulding composition (F), comprising: A) from 5 to 80% by weight of a graft polymer (A) having bimodal particle size distribution and a moisture content of 0 to 27% by weight, made, based on (A), a.sub.1) from 40 to 90% by weight of an elastomeric particulate graft base (a.sub.1), obtained by emulsion polymerization of, based on (a.sub.1), a.sub.11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C.sub.1-8-alkyl acrylate, or of mixtures of these, a.sub.12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a.sub.13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; a.sub.2) from 10 to 60% by weight of a graft a2), made, based on a2), a.sub.21) from 64 to 76% by weight of at least one vinyl aromatic monomer, a.sub.22) from 24 to 36% by weight of acrylonitrile, a.sub.23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a.sub.24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; B) from 10 to 94% by weight of a thermoplastic polymer (B) having a viscosity number VN of from 50 to 120 ml/g, made, based on (B), b.sub.1) from 64 to 72% by weight of at least one vinyl aromatic monomer, b.sub.2) from 28 to 36% by weight of acrylonitrile, and b.sub.3) from 0 to 4% by weight of at least one other monoethylenically unsaturated monomer; whereby, the difference of the acrylonitrile content in component (B) and that in the graft shell a.sub.2) is minimal 2% by weight and maximal 6% by weight and optionally further components, have preferred optical appearance when coated with metal.

Claims

1. A thermoplastic moulding composition (F) comprising as components, A) from 10 to 70% by weight of a graft polymer (A) having a bimodal particle size distribution and a moisture content of 0 to 27% by weight, made, based on (A), a.sub.1) from 40 to 90% by weight of an elastomeric particulate graft base (a.sub.1), obtained by emulsion polymerization of, based on (a.sub.1), a.sub.11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C.sub.1-8-alkyl acrylate, or of mixtures of these, a.sub.12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a.sub.13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer, a.sub.2) from 10 to 60% by weight of a graft a.sub.2), made, based on a.sub.2), a.sub.21) from 64 to 76% by weight of at least one vinyl aromatic monomer, a.sub.22) from 24 to 36% by weight of acrylonitrile, a.sub.23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a.sub.24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; B) from 20 to 88% by weight of a thermoplastic polymer (B) having a viscosity number VN of from 50 to 120 ml/g, made, based on (B), b.sub.1) from 64 to 72% by weight of at least one vinyl aromatic monomer, b.sub.2) from 28 to 36% by weight of acrylonitrile, and b.sub.3) from 0 to 4% by weight of at least one other monoethylenically unsaturated monomer; whereby the difference of the acrylonitrile content in component (B) and that in the graft shell a.sub.2) is minimal 2% by weight and maximal 6% by weight, and C) from 1.2 to 3% by weight of a thermoplastic polymer (C) having a viscosity number VN of from 50 to 120 ml/g, made, based on (C), c.sub.1) from 64 to 76% by weight of at least one vinyl aromatic monomer, c.sub.2) from 17 to 35% by weight of acrylonitrile and c.sub.3) from 1 to 10% by weight of at least one other monoethylenically unsaturated monomer selected from dicarboxylic acids and their anhydrates, where the vinyl aromatic content of component (C) is larger than that of component (B); D) from 0 to 80% by weight of amorphous or (semi)-crystalline polymers; and E) from 0 to 50% by weight of additives E.

2. A thermoplastic moulding composition (F) according to claim 1, consisting of: A) from 10 to 70% by weight of a graft polymer (A) having a bimodal particle size distribution and a moisture content of 0 to 27% by weight, made, based on (A), a.sub.1) from 40 to 90% by weight of an elastomeric particulate graft base (a.sub.1), obtained by emulsion polymerization of, based on (a.sub.1), a.sub.11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C.sub.1-8-alkyl acrylate, or of mixtures of these, a.sub.12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a.sub.13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer, a.sub.2) from 10 to 60% by weight of a graft a.sub.2), made, based on a.sub.2), a.sub.21) from 64 to 76% by weight of at least one vinyl aromatic monomer, a.sub.22) from 24 to 36% by weight of acrylonitrile, a.sub.23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a.sub.24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; B) from 20 to 88% by weight of a thermoplastic polymer (B) having a viscosity number VN of from 50 to 120 ml/g, made, based on (B), b.sub.1) from 64 to 72% by weight of at least one vinyl aromatic monomer, b.sub.2) from 28 to 36% by weight of acrylonitrile, and b.sub.3) from 0 to 4% by weight of at least one other monoethylenically unsaturated monomer; whereby the difference of the acrylonitrile content in component (B) and that in the graft shell a.sub.2) is minimal 2% by weight and maximal 6% by weight, and C) from 1.2 to 3% by weight of a thermoplastic polymer (C) having a viscosity number VN of from 50 to 120 ml/g, made, based on (C), c.sub.1) from 64 to 76% by weight of at least one vinyl aromatic monomer, c.sub.2) from 17 to 35% by weight of acrylonitrile and c.sub.3) from 1 to 10% by weight of at least one other monoethylenically unsaturated monomer, where the vinyl aromatic content of component (C) is larger than that of component (B); D) from 0 to 80% by weight of amorphous or (semi)-crystalline polymers; and E) from 0 to 50% by weight of additives E.

3. A thermoplastic moulding composition (F) as claimed in claim 1, wherein the amount of component (C) is 2% by weight based on (F).

4. A thermoplastic moulding composition as claimed in claim 1, wherein the amount of the monoethylenically unsaturated monomer in component (C) is 2% by weight based on (C).

5. A thermoplastic moulding composition as claimed in claim 1, wherein the monoethylenically unsaturated monomer in component (C) is maleic anhydride.

6. A thermoplastic moulding composition as claimed in claim 1, wherein the conjugated diene (a.sub.11) is butadiene.

7. A thermoplastic moulding composition as claimed in claim 1, in which the vinylaromatic monomer (a.sub.21) and (b.sub.1) and (c.sub.1) is styrene or -methylstyrene or a mixture of styrene and -methylstyrene.

8. A thermoplastic moulding composition as claimed in claim 1, in which the graft (a.sub.2) consists essentially of, based on (a.sub.2), a.sub.21) from 70 to 76% by weight of styrene and/or -methylstyrene, a.sub.22) from 24 to 30% by weight of acrylonitrile, and the thermoplastic polymer (B) consists essentially of, based on (B), b.sub.1) from 64 to 72% by weight of styrene, b.sub.2) from 28 to 36% by weight of acrylonitrile.

9. A thermoplastic moulding composition as claimed in claim 1, in which the monoethylenically unsaturated monomer (a.sub.12) is styrene or n-butyl acrylate or a mixture of these.

10. A thermoplastic moulding composition as claimed in claim 1, in which the bimodal particle size distribution of the graft polymer (A) has two maxima, at particle sizes of from 25 to 200 nm and from 150 to 800 nm.

11. A process for producing a moulding composition (F) as claimed in claim 1, comprising the step of mixing: A) from 10 to 70% by weight of a graft polymer (A) having a bimodal particle size distribution, made, based on (A); a.sub.1) from 40 to 90% by weight of an elastomeric particulate graft base (a.sub.1), obtained by emulsion polymerization of, based on (a), a.sub.11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C.sub.1-8-alkyl acrylate, or of mixtures of these a.sub.12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a.sub.13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer, a.sub.2) from 10 to 60% by weight of a graft (a.sub.2), made, based on (a.sub.2), a.sub.21) from 64 to 76% by weight of at least one vinyl aromatic monomer, a.sub.22) from 24 to 36% by weight of acrylonitrile, a.sub.23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a.sub.24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; B) from 20 to 88% by weight of a thermoplastic polymer B) having a viscosity number VN of from 50 to 120 ml/g, made, based on (B), b.sub.1) from 64 to 72% by weight of at least one vinyl aromatic monomer, b.sub.2) from 28 to 36% by weight of acrylonitrile, and b.sub.3) from 0 to 4% by weight of at least one other monoethylenically unsaturated monomer; and, C) from 1.2 to 3% by weight of a thermoplastic polymer (C) having a viscosity number VN of from 50 to 120 ml/g, made, based on (C), c.sub.1) from 64 to 76% by weight of at least one vinyl aromatic monomer, c.sub.2) from 17 to 35% by weight of acrylonitrile, and c.sub.3) from 1 to 10% by weight of at least one other monoethylenically unsaturated monomer selected from dicarboxylic acids and their anhydrates, where the vinyl aromatic content of component (C) is larger than that of component (B); D) from 0 to 80% by weight of amorphous or (semi)-crystalline polymers; and E) from 0 to 50% by weight of additives E.

12. The process as claimed in claim 11, where in a first step, the components (A), (B), and (E) are mixed by co-extruding, kneading or roll-milling the components at temperatures of from 180 to 400 C., and in a second step, the granulate obtained in the first step (i) is then mixed with components (C), (D) and (E).

13. A moulding produced from a thermoplastic moulding composition as claimed in claim 1.

14. A method of use of a thermoplastic moulding composition (F), as claimed in claim 1 for producing metal plated mouldings.

15. A method of producing a metal plated moulding comprising the step of coating a moulding as claimed in claim 13 with a metal.

16. A process for producing a metal plated moulding, comprising the steps of I. mixing: A) from 10 to 70% by weight of a graft polymer (A) having a bimodal particle size distribution, made, based on (A), a.sub.1) from 40 to 90% by weight of an elastomeric particulate graft base (a.sub.1), obtained by emulsion polymerization of, based on (a.sub.1), a.sub.11) from 70 to 100% by weight of at least one conjugated diene, or of at least one C.sub.1-8-alkyl acrylate, or of mixtures of these, a.sub.12) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer and a.sub.13) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer, a.sub.2) from 10 to 60% by weight of a graft (a.sub.2), made, based on (a.sub.2), a.sub.21) from 65 to 95% by weight of at least one vinyl aromatic monomer, a.sub.22) from 5 to 35% by weight of acrylonitrile, a.sub.23) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer, and a.sub.24) from 0 to 10% by weight of at least one polyfunctional, cross linking monomer; B) from 20 to 88% by weight of a thermoplastic polymer (B) having a viscosity number VN of from 50 to 120 ml/g, made, based on (B), b.sub.1) from 74 to 78% by weight of at least one vinyl aromatic monomer, b.sub.2) from 22 to 26% by weight of acrylonitrile, and b.sub.3) from 0 to 30% by weight of at least one other monoethylenically unsaturated monomer; and C) from 1.2 to 3% by weight of a thermoplastic polymer (C) having a viscosity number VN of from 50 to 120 ml/g, made, based on (C), c.sub.1) from 64 to 76% by weight of at least one vinyl aromatic monomer, c.sub.2) from 17 to 35% by weight of acrylonitrile and c.sub.3) from 1 to 10% by weight of at least one other monoethylenically unsaturated monomer selected from dicarboxylic acids and their anhydrates, where the vinyl aromatic content of component (C) is larger than that of component (B); D) from 0 to 80% by weight of amorphous or (semi)-crystalline polymers; and E) from 0 to 50% by weight of additives E; II. processing the obtained thermoplastic moulding composition (F) into a moulding having the desired form, and III. coating the obtained moulding with a metal.

17. A metal coated moulding produced from a thermoplastic moulding composition (F) as claimed in claim 1.

Description

EXAMPLES

1. Preparation of the Graft Polymer (A)

(1) 1.1. Preparation of the Graft Base (a.sub.1)

(2) The preparation of the graft base (a.sub.1) was conducted on a production scale. The corresponding preparation can be scaled down by the following recipe:

(3) Emulsion polymerizations were carried out in a 150 liter reactor at a constant temperature of 67 C. 43120 g of the monomer mixture given in Table 1 were polymerized at 67 C. in the presence of 431 g t-dodecyl mercaptane (TDM), 311 g of the potassium salt of C.sub.12-C.sub.20 fatty acids, 82 g of potassium peroxidisulfate, 147 g of sodium hydrogen carbonate and 58400 g of water, to give a polybutadiene latex. First styrene, which corresponds to 10 w % of the total amount of monomer in the recipe, was added in 20 minutes. After the styrene addition, the first part of the butadiene, which corresponds to 10 w % of the total amount of monomer in the recipe, was added in 25 minutes. The remaining part of the butadiene, which corresponds to 80 w % of the total amount of monomer in the recipe, was added in 8.5 hours. The TDM being added in one portion at the start of the reaction. The conversion was 95% or greater. The resulting dispersion had a mean particle size (d.sub.50) of 110 nm. The gel content of the graft base (a.sub.1) was 80 and the swelling index was 10.

(4) To agglomerate the latex, 5265 g of the resultant latex, diluted to a TSC of 40%, is agglomerated (partial agglomeration) at 68 C. by adding 526.5 g of a dispersion (solids content 10% by weight) of 96% by weight of ethyl acrylate and 4% by weight of methacrylamide.

(5) 1.2. Preparation of the Graft (a.sub.2).

(6) The preparation of the graft (a.sub.2) was conducted on a production scale. The corresponding preparation can be scaled down by the following recipe:

(7) Component A1:

(8) Following agglomeration, 20 g emulsifier (potassiumstearate) and 3 g initiator (potassium peroxidisulfate) were added. Water was added in an amount to set the total solid content of the dispersion after completion of the polymerization to a theoretical value of 40%. 74.7 g of acrylonitrite, 298.8 g of styrene were then added. A mixture of 224.1 g of acrylonitrile, 896.4 g of styrene was then added over a period of 190 minutes, the temperature being raised to 83 C. after over half of the time. On completion of the addition of monomer, 3 g initiator (potassium persulfate) was again added and the polymerization was continued for 60 minutes.

(9) The resultant graft polymer dispersion, which had bimodal particle size distribution, had a mean particle size d.sub.50 of from 150 to 350 nm and a d.sub.90 of from 400 to 600 nm. The particle size distribution had a first maximum in the range from 50 to 150 nm and a second maximum in the range from 200 to 600 nm.

(10) To the dispersion there were added 0.2% by weight of a stabilizer, based, in each case, on the total solids content, and the mixture was cooled and coagulated at ca. 60 C. in an aqueous 0.5% MgSO.sub.4-solution followed by an aging step for 10 minutes at 100 C. Afterwards the slurry is cooled down, centrifuged and washed with water to obtain a graft polymer (a.sub.2).

(11) The resulting graft component A1 had a remaining moisture content of 27%.

(12) Component A2:

(13) The preparation of component A2 is identical to that for A1 except for the amounts of styrene and acrylonitrile. In the preparation of A2, 100.8 g acrylonitrile and 272.7 g styrene were added instead of 74.7 g and 298.8 g, respectively, after the dilution step. The subsequent monomer mixture added was a mixture of 302.5 g acrylonitrile and 818.0 g styrene instead of 224.1 g and 894.4 g, respectively.

(14) The resulting graft component A2 had a remaining moisture content of 24%.

2. Preparation of the Polymers (B), and (C)

(15) The thermoplastic polymers (B) and (C) were prepared by continuous solution polymerization, as described in Kunststoff-Handbuch, ed. R. Vieweg and G. Daumiller, Vol, V Polystyrol, Carl-Hanser-Verlag, Munich, 1969, p. 122-124. Table 3 gives the formulations and properties.

(16) TABLE-US-00001 TABLE 1 Components (B) and (C) Component B1 B2 C Styrene [weight-%] 74 67 74 Acrylonitrile [weight-%] 24 33 24 Maleic anhydride [weight-%] 2 Viscosity number VN [ml/g] 64 70 60

3. Preparation of the Blends

(17) The preparation of the blends was conducted on a production scale. The corresponding preparation and process can be scaled down by the following description:

(18) The graft rubber (A) containing residual water was metered into a Werner and Pfleiderer ZSK 30 extruder in which the front part of the two conveying screws were provided with retarding elements which build up pressure. A considerable part of the residual water was pressed out mechanically in this way and left the extruder in liquid form through water-removal orifices. The other components (B) and (E) were added to the extruder downstream behind the restricted flow zones, and intimately mixed with the dewatered component (A). The residual water still present was removed as steam via venting orifices in the rear part of the extruder. The extruder was operated at 250 C. and 250 rpm, with a throughput of 10 kg/h. The moulding composition was extruded and the molten polymer mixture was subjected to rapid cooling by being passed into a water bath at 25 C. The hardened moulding composition was granulated. This granulate was then compounded with component (C) and if present (D) and (E) on a normal ZSK 30 extruder at 250 C. and 250 rpm with a throughput of 10 kg/hour.

(19) The components used and their constituent amounts in dry weight % are in Table 2.

(20) TABLE-US-00002 TABLE 2 Example 1 (inv) 2 (inv) 3 (comp to 1) 4 (comp to 2) Component A1 30 30 Component A2 30 30 Component B1 70 68 Component B2 70 68 Component C 2 2 Component E 0.3 0.3 0.3 0.3 * mixture of 0.1% silicon oil, 0.1% Wingstay L and 0.1% distearyldithiopropionate.

(21) Sample Preparation:

(22) Plagues were produced by injection moulding at conditions typical for ABS thermoplastics. The mould temperature was 120 F. The dimensions of the plagues were 44 with a thickness of 3 mm.

(23) Metal Plating Process:

(24) The metal plating process is a standard metal plating technique analogue as described above.

(25) The specimens were treated according to the most widely spread metal plating procedure in industry. All parameters of the procedure were according to the instructions of the manufacturer of the chemicals involved. The etching times and etching bad temperatures were equal for all specimens and were within the ranges widely used in industry. These conditions were selected in such a way that surface structure of the etched plagues had a comparable quality. Scanning electron microscopy is the method of choice to verify this structure of the surface after etching. After etching and pretreatment, the subsequent standard procedures (including the rinsing between the steps), i.e. copperplating, nickelplating and chromium plating was conducted. By doing so, the thickness of the metal layer so obtained is typical for metal plated articles (copper layer between 13 and 20 m, Nickel layer between 21 and 26 m).

(26) Test:

(27) Gravelometer Test:

(28) In order to estimate the performance of the metal layer upon repeated impact, the metal plated plaques were subjected to a gravelometer. Details of such a gravelometer are described in the GM Worldwide Engineering Standard GMW 14700. All test specimens must be positioned at 90 degrees to the trajectory of the stones. Air is flow through the chamber. The gravel is fed to the air stream within an interval of 8+/2 seconds. For the purpose of the evaluation of the effectiveness of our invention, each plaque was subjected 10 times to this procedure. The procedure was carried out at room temperature conditions.

(29) For the purpose of evaluation the effectiveness of our invention, the plagues were visibly inspected for chips and defects. The total affected surface area was reported in mm.sup.2.

(30) Details of the Climate Shock:

(31) The samples were placed in a freezer at 40 C. for one hour and subsequently within 1 minute placed into an adjacent oven at 93 C. This procedure is derived from GMW14668.

(32) After the climate shock the samples were inspected for chips and defects. The total affected surface area was reported in mm.sup.2.

(33) The evaluation method of the resistance to repeated impact

(34) For our evaluation it was important to judge the overall performance (Grav2). That means a weight evaluation of the performance before the climate shock (Grav0) and after the climate shock (Grav1). The overall performance of the gravelometer test (Grav2) is defined as follows:
Grav2,i=(Grav0,i/Grav0,ref+Grav1,i/Grav1,ref)*()*100%

(35) Wherein i is the sample number and ref refers to the reference sample. The reference sample for the results in Table 3 is comparative example 1.

(36) The smaller the value for Grav2, the better the overall performance. Grav0 is the number of defects of the metal plated material after the gravelometer test. The lower the value for Grav0, the better its performance in this property. Grav1 is the number of defects of the metal plated material after the gravelometer test and subsequent thermoshock cycles. The lower the value for Grav1, the better its performance in this property.

(37) Results are shown in Table 3

(38) TABLE-US-00003 Comparative Example 1 (according to EP-A- Example 1 Example 2 1 940 950 (invention) (invention) (Gravelometer reference) Component A1 30 Component A 2 30 30 Component B1 70 Component B2 70 68 Component C 2 Component E* 0.3 0.3 0.3 Grav0 (mm.sup.2) 48 88 188 Grav1 (mm.sup.2) 5000 768 5013 Grav2 63% 54% 100%

(39) As can be concluded from the results in Table 3, the invention related samples 1 and 2 show an improved overall performance in the gravelometer test. Composition 1 according to the invention shows that the invention rubber results in a performance that is even better than the product described in EP-A 1 940 950. By including the compatibilizer the performance becomes even better.