Polyamide molding material, the use thereof, and molded parts produced therefrom

Abstract

A polyamide molding material is proposed, which comprises at least one partially crystalline, partially aromatic polyamide (A) and at least one amorphous polyamide (B). The polyamides (A) and (B) together make up 30-60 wt.-% of the polyamide molding material. Furthermore, the polyamide molding material comprises 40-70 wt.-% glass fibers (C) having flat cross section, 0-15 wt.-% of at least one nonhalogenated flame retardant (D), and 0-10 wt.-% further additives (E), the components (A) to (E) adding up to 100 wt.-% of the polyamide molding material. The at least one partially crystalline, partially aromatic polyamide (A) has a glass transition temperature of at least 105° C. The polyamide molding material according to the invention is preferably distinguished in an injection-molding burr formation test in that, at a melt temperature of 320° C. and a tool temperature of 90° C., and a dynamic pressure of 100 bar and a holding pressure of 400 bar, at the flow path end of a mold arm having a vent gap dimension of 30 μm, burrs having a length G of at most 30 μm result. Such a polyamide molding material results in molded parts having good surface quality and low warpage when injection molded and is suitable for the production of housings or housing parts of electrical and electronic devices.

Claims

1. A polyamide molding material comprising: at least one partially crystalline, partially aromatic polyamide (A) selected from a group consisting of PA 6T/6I /6, PA 6T/10T, PA 6T/10T/6I/10I and mixtures thereof; at least one amorphous polyamide (B); a weight ratio of the at least one partially crystalline, partially aromatic polyamide (A) to the at least one amorphous polyamide (B) being in the range of 30:70 to 70:30; the at least one polyamide (A) and the at least one polyamide (B) together making up 30 -60 wt.-% of the polyamide molding material; 40-70 wt.-% glass fibers (C) with flat cross section; 0-15 wt.-% of at least one nonhalogenated flame retardant (D); and 0-10 wt.-% further additives (E); the components (A) to (E) adding up to 100 wt.-% of the polyamide molding material; wherein the polyamide molding material, in an injection-molding burr formation test at a melt temperature of 320° C. and a tool temperature of 90° C., and a dynamic pressure of 100 bar and a holding pressure of 400 bar at the flow path end of a mold arm having a vent gap dimension of 30 μm, results in burrs having a length G of at most 30 μm, and the at least one partially crystalline, partially aromatic polyamide (A) has a glass transition temperature of at least 105° C.

2. The polyamide molding material according to claim 1, wherein the at least one partially crystalline, partially aromatic polyamide (A) is PA 6T/10T/6I/10I, which is synthesized from: 100 mol-% dicarboxylic acid component, composed of 72.0 -98.3 mol-% terephthalic acid and 28.0 -1.7 mol-% isophthalic acid 100 mol-% diamine component, composed of 60.0 -85.0 mol-% hexamethylene diamine and 15.0 -40.0 mol-% 1,10-decane diamine.

3. The polyamide molding material according to claim 1, wherein the at least one partially crystalline, partially aromatic polyamide (A) is PA, 6T/10T/6I/10I which is synthesized from: 100 mol-% dicarboxylic acid component, composed of 75.0 -95.0 mol-% terephthalic acid and 25.0 -5.0 mol-% isophthalic acid; 100 mol-% diamine component, composed of 60.0 -75.0 mol-% hexamethylene diamine and 25.0 -40.0 mol-% 1,10-decane diamine.

4. The polyamide molding material according to claim 1, wherein the at least one partially crystalline, partially aromatic polyamide (A) is PA 6T/10T/6I/10I, which is synthesized from: 100 mol-% dicarboxylic acid, composed of 80.0-90.0 mol-% terephthalic acid and 20.0-10.0 mol-% isophthalic acid; and 100 mol-% diamine component, composed of 62. 0-72.0 mol-% hexamethylene diamine and 28.0-38.0 mol-% 1 ,10-decane diamine.

5. The polymide molding material according to claim 1, wherein a relative viscosity of the at least one partially crystalline, partially aromatic polymide (A) is 1.45-2.0, measured using 0.5 g of the at least one partially crystalline, partially aromatic polyamide (A) in 100 ml m-cresol at 20°C.

6. The polyamide molding material according to claim 1, wherein the at least one amorphous polyamide (B) is selected from a group consisting of PA 6I/6T, PA 6I, PA MACMI/12, PA MACMI/MACMT/12, PA 6I/MACMI/12,PA 6I/6T/MACMI/MACMT, PA 6I/6T/MACMI/MACMT/12, PA MACMI/MACM12, PA MXDI, PA MXDI/6I, PA MXDI/MXDT/6I/6T, PA MXDI/12I, PA 6I/6T/6NDA, PA MACM12, PA MACM14, PA MACM18, PA NDT/INDT, PA MACMT/12, PA MACMI/MACMNDA, PA MACMT/MACMNDA, PA MACMI/MACM36, PA MACMT/MACM36, PA MACMT/MACM12, PA MACM6/11, PA 6I/6T/MACMI/MACMT/MACM12/612, PA 6I/6T/6NDA/MACMI/MACMT/MACMNDA, the laurin lactam being able to be entirely or partially replaced by caprolactam and/or the MACM being able to be replaced up to at most 20 mol-% by PACM.

7. The polyamide molding material according to claim 6, wherein the at least one amorphous polyamide (B) is a PA 6I/6T, in which the portion of the isophthalic acid in relation to the sum of isophthalic acid and terephthalic acid in the PA 6I/6T is 90 to 57 mol-%.

8. The polyamide molding material according to claim 1, wherein the weight ratio of the at least one partially crystalline, partially aromatic polyamide (A) to the at least one amorphous polyamide (B) is in the range of 40:60 to 65:35.

9. The polyamide molding material according to claim 1, wherein the molding material only comprises one polyamide (A) and one polyamide (B) each.

10. The polyainide molding material according to claim 1, wherein the at least one nonhalogenated flame retardant (D) is provided in a quantity of 0 to 13 wt-% in the polyamide molding material.

11. The polyamide molding material according to claim 10, wherein the at least one nonhalogenated flame retardant comprises a flame retardant (D) containing phosphorus.

12. The polyamide molding material according to claim 1, wherein a standard test body, which is produced from such a molding material and injection molded at a melt temperature of 320° C. and a tool temperature of 90° C. having plate-shaped dimensions of 60×60×2 mm, has a warpage, calculated as the difference between the transverse and longitudinal processing shrinkage according to ISO standard 294, of at most 0.22%.

13. A molded part produced by injection molding from a molding material according to claim 1, wherein the molded part has an amorphous or less crystallized surface region and a partially crystalline core region.

14. The polyamide molding material according to claim 5, wherein the relative viscosity of the at least one partially crystalline, partially aromatiepolyamide (A) is 1.5-1.9, measured using 0.5 g of the at least one partially crystalline, partially aromatic polyamide (A) in 100 ml m-cresol at 20° C.

15. The polyamide molding material according to claim 7, wherein the portion of the isophthalic acid in relation to the sum of isophthalic acid and terephthalic acid in the PA 6I/6T is 85 to 60 mol-%.

16. The polyamide molding material according to claim 7, wherein the portion of the isophthalic acid in relation to the sum of isophthalic acid and terephthalic acid in the PA 6I/6T is 75 to 60 mol-%.

17. The polyamide molding material according to claim 7, wherein the portion of the isophthalic acid in relation to the sum of isophthalic acid and terephthalic acid in the PA 6I/6T is 72 to 63 mol-%.

18. The polyamide molding material according to claim 8, wherein the weight ratio of the at least one partially crystalline, partially aromatic polyamide (A) to the at least one amorphous polyamide (B) is in the range of 40:60 to 60:40.

19. The polyamide molding material according to claim 8, wherein the weight ratio of the at least one partially crystalline, partially aromatic polyamide (A) to the at least one amorphous polyamide (B) is in the range of 45:55 to 56:44.

20. The potyamide molding material according to claim 8, wherein the weight ratio of the at least one partially crystalline, partially aromatic polyamide (A) to the at least one amorphous polyamide (B) is in the range of 45:55 to 49:51.

21. The polyamide molding material according to claim 10, wherein the at least one nonhalogenated flame retardant (D) is provided in a quantity of 9 to 13 wt.-% in the polyamide molding material.

22. The polyamide molding material according to claim 10, wherein the at least one nonhalogenated flame retardant (D) is provided in a quantity of 10 to 12 wt.-% in the polyamide molding material.

23. The polyamide molding material according to claim 6, wherein the MACM is able to be replaced up to at most 10 mol-% by PACM.

24. The polyamide molding material according to claim 11, wherein the flame retardant (D) containing phosphorus contains salts of phosphinic acid and/or diphosphinic acid and/or the polymers thereof.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows vent gap dimensions;

(2) FIG. 2 shows a vent width; and

(3) FIG. 3 shows a burr length of a test body.

DETAILED DESCRIPTION OF THE INVENTION

(4) The present invention will be explained in greater detail on the basis of the following examples, which merely illustrate the invention but are not to restrict it.

(5) The following materials were used in the examples and comparative examples, as listed in Table is (polyamides) and Table 1b (additives):

(6) TABLE-US-00001 TABLE 1a polyamides used components description trade name producer polyamide (A) partially crystalline copolyamide made of — EMS-CHEMIE AG, hexamethylene diamine (66.7 mol-%), terephthalic Switzerland acid (86.4 mol-%), isophthalic acid (13.6 mol-%), and 1,10-decane diamine (33.3 mol-%), in abbreviated notation PA 6T/10T/6I/10I RV 1.75, melting point 318° C., glass transition temperature 129° C. PA 6I/6T amorphous co-polyamide 6I/6T (66.7/33.3 mol- — EMS-CHEMIE AG, %) made of hexamethylene diamine, Switzerland isophthalic acid, and terephthalic acid RV 1.53, glass transition temperature 125° C. PA 6T/66 partially crystalline co-polyamide 6T/66 — EMS-CHEMIE AG, (52/48 mol-%) made of hexamethylene diamine, Switzerland terephthalic acid, and adipic acid RV 1.72, melting point 310° C., glass transition temperature 95° C. PA 66 polyamide 66 made of hexamethylene diamine Radipol A 45 Radici Chimica, and adipic acid Italy RV 1.75, melting point 260° C., glass transition temperature 70° C. RV = relative viscosity, measured on a solution of 0.5 g polyamide in 100 ml m-cresol at 20° C.

(7) TABLE-US-00002 TABLE 1b additives used components description trade name producer glass fibers, glass fibers, flat, 3 mm long, main cross- NITTOBO Nitto Boseki Co., flat sectional axis 28 μm, secondary cross- CSG3PA-820 Ltd., Japan sectional axis 7 μm, aspect ratio of the cross-sectional axes = 4 glass fibers, glass fibers, round 995 EC10-4.5 Saint-Gobain round 4.5 mm long, diameter 10 μm Vetrotex, France phosphinic acid aluminum diethyl phosphinate Exolit OP 1230 Clariant GmbH, salt Germany aluminum metahydroxide aluminum metahydroxide, ground Actilox 200 SM Nabaltec, Germany zinc borate hexaboron dizinc undecaoxide Firebrake 500 Borax Europe Ltd., United Kingdom PA 6T/6I oligomer copolyamide 6T/6I oligomer (70/30 mol-%) — EMS-CHEMIE AG, made of hexamethylene diamine, terephthalic Switzerland acid, and isophthalic acid RV 1.14 black masterbatch masterbatch based on polyamide 6 with 25 wt.- — EMS-CHEMIE AG, % carbon black Switzerland (carbon black Corax N115 from Evonik Germany) heat stabilizer N,N′-hexane-1,6-diylbis[3-(3,5-di-tert-butyl- Irganox 1098 BASF SE, 4-hydroxyphenyl)propionamide] Germany 2,6-NDA naphthalene-2,6-dicarboxylic acid 2,6-NDA Novolyte Technologies, Belgium lubricant montanic acids, CAS number 68476-03-9 Licowax S Clariant GmbH, Germany

PRODUCTION OF THE POLYAMIDE MOLDING MATERIALS FOR THE EXAMPLES AND COMPARATIVE EXAMPLES

(8) The dried polyamide granules were mixed with the additives. This mixture was homogenized for 30 min. under protective gas by means of a tumble mixer. This dry blend was metered via a scale into the intake of a dual-shaft extruder from Werner & Pfleiderer of the type ZSK 25. The glass fibers were conveyed via a side feeder six housing units in front of the nozzle into the polymer melt. The temperature of the first housing was set to 80° C., that of the remaining housings to 310° C. A speed of 200 RPM and a throughput of 15 kg/h was used and atmospheric degassing was performed. The strands were cooled in the water bath, cut, and the granules obtained were dried at 120° C. under vacuum (residual pressure 50 mbar) for 24 hours to a water content less than 0.1 wt.-%.

(9) If not otherwise noted in the description of the test methods, testing bodies were subsequently produced from the granules on an injection-molding machine from Arburg, model Allrounder 420 C 1000-250. A melt temperature of the polyamide molding material melt of 320° C. and a tool temperature of 90° C. were set. The testing bodies were stored for 48 hours at room temperature over silica gel before the measurement.

(10) The Measurements were Performed According To The Following Test Methods and Standards:

(11) Spiral Flow Test:

(12) The flow spirals were produced on an injection-molding machine from Arburg, model Allrounder 320-210-750 at a melt temperature of 320° C. and a tool temperature of 90° C. with an injection pressure of 1000 bar. The flow spirals had their sprue gate in the center and a cross section of 1.5×10 mm. The following distance marks were applied in the spirals: points at an interval of 1 mm strokes at full centimeters length specifications every 5 cm
Tensile Modulus of Elasticity: ISO 527 at a pulling speed of 1 mm/min ISO tension bar, standard: ISO/CD 3167, type A1, 170×20/10×4 mm, temperature 23° C.
Relative Viscosity (RV) ISO 307 0.5 g polyamide in 100 ml m-cresol temperature 20° C. calculation of the relative viscosity (RV) according to RV=t/t.sub.0 based on section 11 of the standard.
Melting Point (Tm) and Glass Transition Temperature (Tg) standard 11357 granules having a water content of less than 0.1 wt.-% Differential scanning calorimetry (DSC) was performed at a heating rate of 20 K/min. For the melting point, the temperature was specified at the peak maximum, for the glass transition temperature, the temperature was specified at the onset.
HDT (Heat Distortion Temperature, Dimensional Stability Under Heat) ISO 75 ISO test bar, standard: ISO/CD 3167, type B1, 80×10×4 mm HDT A load 1.80 MPa
Burr Formation Test: The tool used for the determination of the burr formation is a two-plate tool having a six-armed test body with central sprue gate. The length, width, and thickness of the arms are 90×10×1.5 mm. Vents are located at the beginning and at the end of each arm. The vents at the flow path end have different gap dimensions. The gap dimensions of the individual vents are 0, 4, 8, 12, 20, and 30 μm, as indicated in FIG. 1. The width of the vents is 2.95 mm (cf. FIG. 2). The burr length G (cf. FIG. 3) of the test body was evaluated at the flow path end of the arm having the vent gap dimension 30 μm. In Detail FIGS. 2 and 3, which show the end of the test body arm having 30 μm vent gap dimension, the components are not to scale, but rather shown schematically, so that the principle can be seen therefrom. In FIG. 3, the material burr protruding beyond the end of the test body arm, which has penetrated into the vent gap at the flow path end, is shown exaggeratedly large for illustration, and the burr length G is designated. These test bodies are manufactured on an injection-molding machine of the type Krauss Maffei 100-380CX. The parts are removed by hand, since otherwise damage to the burrs can occur. The injection speed is 100 mm/s, the screw speed 50 RPM, the dynamic pressure 100 bar, and the holding pressure 400 bar. 320° C. is used as the melt temperature and 90° C. is used as the tool temperature. The burr length G is determined based on images, which are recorded using a microscope of the type Leica/Wild M420 photomacroscope at a 40 to 50 fold magnification, by means of use of the focusing lens 2.0×, the burr being imaged in its entire width. The burr length G results from the distance between the base line (test body end) and the measuring line. The measuring line is laid so that the area of the indentations and bulges compensate for one another (cf. FIG. 3). The arithmetic mean value from the measurements on 5 different test bodies is specified.
Processing Shrinkage: ISO 294-4 plate, type D2, 60×60×2 mm (according to standard ISO 294-3) The plates are produced at a melt temperature of 320° C. and a tool temperature of 90° C. They are stored for 48 hours at room temperature over silica gel before the measurement. The processing shrinkage is determined longitudinally and transversely to the flow direction in relation to the mold cavity dimension. The arithmetic mean value from the measurements on 5 plates is specified.
Fire Test UL-94 of Underwriters Laboratories test bar 125×13×0.45 mm Each 5 test bodies are conditioned for at least 48 hours at 23° C. and 50% relative humidity (point 6.1 of UL-94). Each 5 test bodies are conditioned for 168 hours at 70° C. and subsequently cooled in an exsiccator for at least 4 hours at room temperature (point 6.2 of UL-94). The two sets of 5 test bodies each are subjected to the vertical fire test, which each of the sets must withstand. In the vertical fire test, the 5 test bodies of a set are each exposed to flame 2 times. The classification V0 is achieved if the self-extinguishing of each individual test body occurs after at most 10 seconds and the sum of the burning lengths of both flame exposures over all 5 test bodies is at most 50 seconds. The self-extinguishing and the smoldering after the second flame exposure must be ended after 30 seconds in each individual test body. No test body may burn down to the chucking clamp. Possibly occurring drips may not ignite the cotton wool.

(13) The four examples 1 to 4 according to the invention are represented in the following Table 2. Example 4 is a variant with flame retardant.

(14) TABLE-US-00003 TABLE 2 examples according to the invention examples unit 1 2 3 4 partially crystalline polyamide (A) wt.-% 24.85 25.95 21.95 23.5 PA amorphous PA PA 6I/6T wt.-% 20 21 25 13 filler glass fibers, flat wt.-% 50 50 50 50 flame retardant 1 phosphinic acid salt wt.-% — — — 9 flame retardant 2 aluminum metahydroxide wt.-% — — — 1.5 additives PA 6T/6I oligomer wt.-% 2.5 — — — black masterbatch wt.-% 1.6 1.6 1.6 1.6 heat stabilizer wt.-% 0.25 0.25 0.25 0.2 2,6-NDA wt.-% 0.4 0.8 0.8 1 lubricant wt.-% 0.4 0.4 0.4 0.2 glass transition temperature ° C. 126 127 125 124 tensile modulus of elasticity MPa 17600 17500 17000 18000 flow length mm 265 300 300 330 HDT A (1.80 MPa) ° C. 250 180 160 280 burr length G μm 17 20 19 23 (vent gap dimension 30 μm) visibility of the joint line* — 2 2 1 2 sink marks* — 1 1 1 2 surface quality* — 1 1 1 1 UL 94 at 0.45 mm — — — — V0 processing shrinkage longitudinal % 0.06 0.08 0.05 0.05 transverse % 0.23 0.26 0.20 0.20 warpage** % 0.17 0.18 0.15 0.15 *visual evaluation (scale 1-5): 1 = very good, 5 = very poor **warpage = difference of the processing shrinkage transversely and longitudinally

(15) The good to very good evaluation of the surface appearance (even in the flame retardant variant) and the extremely low warpage in these four examples according to the invention clearly verify the surprising effect of the polyamide molding compound according to the invention.

(16) This progress according to the invention is very clear upon the direct comparison to test bodies which were produced according to previously known polyamide molding materials, and which were compounded, injection molded, and tested in the same manner and on the same machines as the examples according to the invention, and are therefore directly comparable. Recipes from the cited documents of the prior art were also reproduced. Comparative examples numbers 5 to 11 are compiled in following Table 3.

(17) TABLE-US-00004 TABLE 3 comparative examples comparative examples unit 5 6 7 8 9 10 11 partially polyamide (A) wt.-% 25.95 — 47.35 36.5 — — — crystalline PA 6T/66 wt.-% — — — — 25.9 15.95 10.3 PA PA 66 wt.-% — 26.35 — — — — 17.4 amorphous PA 6I/6T wt.-% 21 21 — — 11.1 21.55 6.8 PA filler glass fibers, flat wt.-% — 50 50 50 50 50 50 glass fibers, round wt.-% 50 — — — — — — flame phosphinic acid salt wt.-% — — — 9 9 9 13 retardant 1 flame aluminum metahydroxide wt.-% — — — 1.5 1.5 1.5 1 retardant zinc borate wt.-% — — — — 0.6 0.1 0.3 2 additives black masterbatch wt.-% 1.6 1.6 1.6 1.6 1 1 1 heat stabilizer wt.-% 0.25 0.25 0.25 0.2 — — — 2,6-NDA wt.-% 0.8 0.4 0.4 1 0.7 0.7 0.5 lubricant wt.-% 0.4 0.4 0.4 0.2 0.2 0.2 — glass transition temperature ° C. 127 77 127 128 112 117 82 tensile modulus of elasticity MPa 17500 17000 18000 18300 18400 18000 17000 flow length mm 270 265 240 330 280 280 260 HDT A (1.80 MPa) ° C. 270 245 *** *** 250 200 250 burr length G μm 15 87 45 38 41 60 80 (vent gap dimension 30 μm) visibility of the joint line* — 2 2 3 3 4 2 3 sink marks* — 2 4 3 3 3 2 3 surface quality* — 4 2 4 4 3 2 2 UL 94 at 0.45 mm — — — — V0 V0 V0 V0 processing shrinkage longitudinal % 0.10 0.10 0.15 0.15 0.15 0.10 0.12 transverse % 0.60 0.45 0.50 0.50 0.45 0.35 0.47 warpage** % 0.50 0.35 0.35 0.35 0.30 0.25 0.35 *visual evaluation (scale 1-5): 1 = very good, 5 = very poor **warpage = difference of the processing shrinkage transversely and longitudinally ***HDT A higher than the maximum oil temperature of 280° C.

(18) The molding material of comparative example 5 having round glass fibers displays poor surface quality and significant warpage. Comparative example 6 having flat glass fibers and low glass transition temperature has good surface quality, but strong sink marks. The molding material of comparative example 6 additionally has extremely strong burr formation.

(19) The molding materials of comparative examples 9 and 10, which correspond to US 2010/0249292 A1, and the molding material of comparative example 11, which corresponds to WO 2011/126794 A2, also display strong burr formation. Finally, the molding materials of comparative examples 7 and 8, which correspond to EP 2 354 176 A1, have received a poor evaluation in all regards.

(20) EP 2 354 176 A1 discloses a partially crystalline, partially aromatic polyamide (A) as a polyamide component in a molding material, from which components may be produced, which can be soldered at 260° C. and higher temperatures, without forming bubbles during the soldering process.

(21) In consideration of the latter circumstance, it is all the more astounding and completely unexpected that using a polyamide (A) according to EP 2 354 176 A1, but as a component of a novel polyamide molding material according to the present invention, outstanding properties are achieved with respect to burr formation, warpage, and surface quality, which are significantly better both in relation to EP 2 354 176 A1 and also in relation to the closest prior art.

(22) It could therefore be shown on the basis of the examples that the polyamide molding materials according to the invention result in improved property combinations in relation to the polyamide molding materials previously known from the corresponding prior art with respect to burr formation, warpage, sink marks, and/or surface quality.