THERMOPLASTIC MOULDING COMPOSITION WITH GOOD DEMOULDING BEHAVIOUR

Abstract

The invention relates to a thermoplastic moulding composition comprising A) at least one thermoplastic polyurethane polymer obtainable by reacting at least the following constituent components: I) one or more aliphatic diisocyanates having a molecular weight of between 140 g/mol to 170 g/mol and II) one or more aliphatic diols having a molecular weight of between 62 g/mol to 120 g/mol, the constituent components used to produce the thermoplastic polyurethane polymer consisting of at least 95% by weight of one or more aliphatic diisocyanates I) and one or more aliphatic diols II), based on the total mass of the constituent components used, wherein the one or more aliphatic diisocyanates I) and the one or more aliphatic diols II) are present in a molar ratio in the range from 1:0:0.95 to 0.95:1.0, characterized in that the ratio (I) of the thermoplastic polyurethane polymer is in a range from 2.3 to 6, wherein (II) is the molar mass centrifugal agent and (III) is the molar mass average, in each case determined by gel permeation chromatography in hexafluoroisopropanol against polymethyl methacrylate as standard, also comprising B) at least one mould release agent. The invention also relates to the use of the moulding composition for producing mouldings and to the mouldings thereof.

Claims

1: A thermoplastic molding compound comprising A) at least one thermoplastic polyurethane polymer obtainable by the reaction of at least the following formation components: I) one or more aliphatic diisocyanates having a molecular weight of 140 g/mol to 170 g/mol and II) one or more aliphatic diols having a molecular weight of 62 g/mol to 120 g/mol, wherein the formation components used for production of the thermoplastic polyurethane polymer consist to an extent of at least 95% by weight of one or more aliphatic diisocyanates I) and one or more aliphatic diols II), based on the total mass of the formation components used, where the one or more aliphatic diisocyanates I) and the one or more aliphatic diols II) are used in a molar ratio in the range from 1.0:0.95 to 0.95:1.0, characterized in that the ratio M.sub.z/M.sub.w of the thermoplastic polyurethane polymer is within a range from 2.3 to 6, where M.sub.z is the centrifuge-average molar mass and M.sub.w the mass average molar mass, in each case determined by gel permeation chromatography in hexafluoroisopropanol against polymethylmethacrylate as standard, B) at least one demolding agent.

2: The molding compound as claimed in claim 1, characterized in that component B is at least one representative selected from the group consisting of long-chain carboxylic acids and soaps thereof, esters and amides of long-chain carboxylic acids, fatty acid alcohols, polar and nonpolar ethylene waxes, and ionomers, oxidized ethylene waxes and fatty acid alcohols derived therefrom.

3: The molding compound as claimed in claim 1, characterized in that component B is selected from the group consisting of esters, amides and soaps of long-chain carboxylic acids.

4: The molding compound as claimed in claim 1, characterized in that component B is present in a proportion of 0.01% to 1% by weight.

5: The molding compound as claimed in claim 1, characterized in that the M.sub.z of component A is within a range from 80 000 g/mol to 900 000 g/mol, determined by gel permeation chromatography in hexafluoroisopropanol against polymethylmethacrylate as standard.

6: The molding compound as claimed in claim 1, characterized in that component A consists to an extent of at least 96% by weight of one or more aliphatic diisocyanates I) and one or more aliphatic diols II), based on the total mass of the polyurethane polymer.

7: The molding compound as claimed in claim 1, characterized in that the one or more aliphatic diisocyanates I) are selected from the group consisting of 1,4-diisocyanatobutane, 1,5-diisocyanatopentane, 1,6-diisocyanatohexane, 2-methyl-1,5-diisocyanatopentane, and mixtures of at least two of these.

8: The molding compound as claimed in claim 1, characterized in that the one or more aliphatic diols II) are selected from the group consisting of ethane-1,2-diol, propane-1,2-diol, propane-1,3-diol, butane-1,2-diol, butane-1,3-diol, butane-1,4-diol, pentane-1,5-diol, hexane-1,6-diol, and mixtures of at least two of these.

9: The molding compound as claimed in claim 1, characterized in that component A has a urethane group content of 40% by weight to 60% by weight, based on the total weight of the thermoplastic polyurethane polymer.

10: The molding compound as claimed in claim 1, characterized in that component A is a semicrystalline thermoplastic polyurethane polymer.

11: The molding compound as claimed in claim 1, characterized in that component A has a glass transition point of <50° C., determined by differential scanning calorimetry to DIN EN 61006 (November 2004).

12: The molding compound as claimed in claim 1, characterized in that component A has a melting point of >150° C., determined by differential scanning calorimetry to DIN EN 61006 (November 2004).

13: The molding compound as claimed in claim 1, characterized in that the formation components used for production of component A consist to an extent of 95% by weight to 99.9% by weight of one or more aliphatic diisocyanates I) and one or more aliphatic diols II) and to an extent of 0.1% by weight to 5% by weight of one or more polyisocyanates III) and/or one or more NCO-reactive compounds IV), based on the total mass of the formation components used.

14: The use of a molding compound as claimed in claim 1 for production of moldings.

15: A molding comprising a molding compound as claimed in claim 13.

Description

[0131] The FIGURE elucidated hereinafter and the examples serve to further elucidate the invention, but these merely constitute illustrative examples of particular embodiments, and not a restriction of the scope of the invention. The individual FIGURES show:

[0132] FIG. 1: Preferred embodiment of a construction for performance of a two-stage continuous preparation of a thermoplastic polyurethane of the invention, by reaction sequence in loop reactor and extruder.

EXAMPLES

Production of Component A

[0133] All percentages are based on weight, unless stated otherwise.

[0134] The ambient temperature of 25° C. at the time of performing the experiments is referred to as RT (room temperature).

Raw Materials Used:

[0135] Hexamethylene 1,6-diisocyanate (HDI, purity≥99% by weight) was sourced from Covestro AG.
Butane-1,4-diol (BDO, purity≥99% by weight) was sourced from Ashland.
Hexafluoroisopropanol was sourced from flurochem in a purity of 99.9% by weight.
Potassium trifluoroacetate sourced from Aldrich, in a purity of 98% by weight.

Gel Permeation Chromatography:

[0136] The molar masses of the polymers were determined with the aid of gel permeation chromatography (GPC). For this purpose, the sample to be analysed was dissolved in a solution of 3 g of potassium trifluoroacetate in 400 cubic centimetres of hexafluoroisopropanol (sample concentration about 2 mg/cubic centimetre). The respective GPCs were measured with the following components at a flow rate of 1 cubic centimetre/minute: [0137] Pump: 515 HPLC pump (Waters GmbH) [0138] Detector: Smartline 2300 RI detector (Knauer Wissenschaftliche GerAte [0139] Columns: 1 pre-column, 1000 Å PSS PFG 7 μm, 300 Å PSS PFG 7 μm, 100 Å PSS PFG 7 μm in the sequence specified [0140] Degassing: PSS degasser (Polymer Standards Service GmbH) [0141] Injection volume: 100 microlitres [0142] Temperature: 23-25° C. [0143] Molar mass standard: Polymethylmethacrylate standard kit (PSS Polymer Standards Service GmbH) [0144] M.sub.z and M.sub.w were calculated as indicated above.

Differential Scanning Calorimetry (DSC)

[0145] Melting points and glass transition points were determined by means of DSC (differential scanning calorimetry) with a Mettler DSC 12E (Mettler Toledo GmbH, Giessen, Germany) in accordance with DIN EN 61006 (November 2004). Calibration was effected via the melt onset temperature of indium and lead. 10 mg of substance were weighed out in standard capsules. The measurement was effected by three heating runs from −50° C. to +200° C. at a heating rate of 20 K/min with subsequent cooling at a cooling rate of 20 K/min. Cooling was effected by means of liquid nitrogen. The purge gas used was nitrogen. The values reported are each based on the evaluation of the 2nd heating curve.

Production of Component A (FIG. 1):

[0146] From a 250 litre reservoir for hexamethylene 1,6-diisocyanate 1, with the aid of a toothed ring pump 2 (from HNP, MZR 7255), a hexamethylene 1,6-diisocyanate stream A was conveyed to a static mixer 7. The throughput of the hexamethylene 1,6-diisocyanate stream A was measured by means of a mass flow meter 3 (from Bronkhorst, Mini Cori-Flow MIX, max. flow rate 12 kg/h). From a 250 litre reservoir for butane-1,4-diol 4, with the aid of a toothed ring pump 5 (from HNP, MZR 7205), a butane-1,4-diol stream B was conveyed to the static mixer 7. The throughput of the butane-1,4-diol stream was measured by means of a mass flow meter 6 (from Bronkhorst, Mini Cori-Flow MIX, max. flow rate 8 kg/h). The temperature of the hexamethylene 1,6-diisocyanate was room temperature. The temperature of the butane-1,4-diol was 40° C. In the static mixer 7 (Sulzer SMX, diameter 6 mm, ratio of length to diameter L/D=10), the hexamethylene 1,6-diisocyanate stream A and the butane-1,4-diol stream B were mixed with one another. This is stream C.

[0147] The mixed and dispersed stream C is mixed in a circulation system with a circulating polymer stream D in a static mixer 8 (static mixer equivalent to Sulzer SMX, internal diameter 34 mm, L/D=20) to give a stream H. The temperature of stream D was 182° C.

[0148] The mixed and already partly reacted stream H was guided into a temperature-controllable static mixer 9. The reaction proceeded there for the most part, and the heat of reaction that arose was removed. The temperature-controllable static mixer 9 was of similar construction to a Sulzer SMR reactor with internal crossed tubes. It had an internal volume of 1.9 litres, and a heat exchange area of 0.44 square metre. It was heated/cooled with heat carrier oil. The heating medium temperature at the inlet was 180° C.

[0149] The product stream left the temperature-controllable static mixer 9 as a largely reacted stream E with a temperature of 183° C. At a branch 11, stream E was split into two substreams F and G. The pressure of substream F was increased at a gear pump 10. Substream F became the abovementioned substream D downstream of the pump.

[0150] The gear pump 10 (from Witte Chem 25, 6-3) had a volume per cycle of 25.6 cubic centimetres and a speed of 50 per minute.

[0151] The whole circulation system was filled completely, and the polymer was largely incompressible. Therefore, the mass flow rate of stream G was identical to that of stream C. Stream G consisted of oligomer.

[0152] The whole circulation system consisted of jacketed pipelines and apparatuses that were heated with thermal oil. The heating medium temperature was 182° C.

[0153] Beyond the pressure-retaining valve 12, stream G was run past a three-way valve 13. On startup and shutdown or in the event of faults, it was possible to run said stream G to a waste vessel 14, an open 60 litre metal vat with air extraction. In regular operation, stream G was guided to an extruder 18.

[0154] From the hexamethylene 1,6-diisocyanate reservoir 1, with the aid of a micro toothed ring pump 15 (MZR 6355 from HNP), a hexamethylene 1,6-diisocyanate stream J was withdrawn. The throughput of the hexamethylene 1,6-diisocyanate stream J was measured by means of a mass flow meter 16 (from Bronkhorst, Mini Cori-Flow MIX, maximum flow rate 2 kg/h). The temperature of the hexamethylene 1,6-diisocyanate stream J was likewise room temperature. This stream was likewise guided to the extruder 18.

[0155] The extruder 18 was a ZSK 26 MC from Coperion, which was operated at temperatures of 200° C. and a speed of 66 revolutions per minute. In this extruder, stream G, by means of a venting system 17 that was operated at a reduced pressure of about 1 mbar relative to ambient pressure, was freed of any inert gases entrained with streams of matter A and B and of possible volatile reaction products. Downstream of the addition of the oligomer stream G, the hexamethylene 1,6-diisocyanate stream J was added and the reaction to give the polymer was conducted. Before the end of the extruder, the resulting polymer stream was freed of volatile constituents via a degassing operation 19. The pressure in this degassing was 200 mbar below ambient pressure. The polymer stream K was expressed through two nozzles, cooled in a water bath 20 filled with deionized water (DI water), and chopped into pellets by means of a pelletizer 21.

[0156] Table 1 shows the streams of matter that were used for preparation of component A.

Description of the Extruder Configuration Used:

[0157] Where “elements” are mentioned in the description that follows, these may be one or more elements. It will be clear to the person skilled in the art that extruder elements, given the same outline, fulfil the same function, irrespective of subdivision.

[0158] An oligomer feed, followed by a reverse-conveying element of length 12 mm and slope 24 mm, followed by a devolatilization zone of length 84 mm with elements of slope 48 mm and 24 mm, with a housing opening length of 50 mm, followed by a reverse-conveying element of length 12 mm, followed by a feed zone with a conveying element, of length 24 mm with slope 48 mm for HDI, followed by a kneading zone of length 84 mm, a zone with conveying elements of slope 12 mm with length 240 mm, a zone with conveying elements of slope 16 mm with length 128 mm, a zone with a reverse-conveying element of slope 24 mm with length 12 mm, a zone for devolatilization with conveying elements of slope 48 mm with length 96 mm, on which the devolatilization screw was mounted at the side, and a zone with conveying elements of slope 16 mm with length 96 mm.

TABLE-US-00002 TABLE 1 Streams of matter in the production of component A A Stream A [kg/h] 4.590 Stream B [kg/h] 3.000 Stream J [kg/h] 0.980

Characterization of Component A Produced

[0159] The following characteristic values were found for the molar mass distribution of component A:

M.sub.z=307554 g/mol
M.sub.w=68990 g/mol, and so M.sub.z/M.sub.w=4.5

[0160] Component A has a glass transition temperature Tg of 34° C. and a melting temperature Tm of 183° C.

[0161] Component A has a urethane group content according to the calculation set out above of 48%.

Component B:

[0162] B1: pentaerythritol tetrastearate (PETS, Loxiol™ P 8.61, Emery Oleochemicals)
B2: calcium stearate (Ceasit™ SW, Baerlocher)
B3: zinc stearate (Zincum™ PS, Baerlocher)
B4: ethylenebisstearamide (Crodamid™ EBS, Croda)
B5: stearylerucamide (Crodamid™ 212, Croda)
B6: erucamide (Crodamid™ ER, Croda)
B7: montan wax, partly esterified and partly hydrolyzed with Ca(OH).sub.2 (Licowax OP, Clariant)
B8: montan wax ester (Licowax E, Clariant)
B9: micronized montan wax, partly esterified and partly hydrolyzed with Zn(OH).sub.2 (Ceridust™ 5551, Clariant)
B10: long-chain wax ester based on carnauba wax; this is an additive produced entirely from renewable raw materials

(Völpker Wax™ J 4418, Völpker)

[0163] B11: diglycerol fatty acid ester (POEM™ DL 100K, Riken Vitamine)

Production and Testing of the Molding Compounds of the Invention

[0164] The components were mixed in a Werner & Pfleiderer ZSK-25 twin-screw extruder at a melt temperature of 200° C. The moldings were produced at a melt temperature of 200° C. and a mold temperature of 60° C. on an Arburg 270 E injection molding machine.

[0165] The coefficients of friction were determined using a modified injection molding machine of the Arburg-370S-800-150 type. The method is described in EP 1 377 812 B1. Sticking friction is the friction number which is derived from the force needed to set bodies that are at rest relative to one another (ram/test specimen) in motion (threshold value). Sliding friction is derived correspondingly from the constant force needed to continue the movement uniformly.

[0166] The coefficient of friction is defined as follows: FR=μ×FN or, rearranged in μ,

μ=FR/FN (FN=normal force, FR=friction force, μ=coefficient of friction).

[0167] In the case of circular motion, the following relationship applies: FR=Md/rm

(Md=torque, rm=average radius of the friction area (ring area)) and Md/rm=μ×FN
and, rearranged in μ, μ=Md/(rm×FN).

[0168] In a coefficient-of-friction mold, a disk-shaped test specimen having an outside diameter of 92 mm and a thickness of 2.6 mm was produced. At the outer edge, this had a 5 mm-high and 3 mm-broad rim on which there were flat depressions, comparable to a toothed belt disk, by means of which the torque is transmitted from the mold to the test specimen.

[0169] It permits the direct determination of the coefficient of sticking friction and coefficient of sliding fiction on a disk-shaped test specimen immediately prior to the demolding. The applicable relationship here is that the friction force is proportional to the torque. When the mold is opened, a ram connected to a torque recorder presses against the molding (friction partner) with a defined normal force FN. On the other side of the molding, the test specimen is held and set in rotation. By means of the torque measured with the ram, the coefficient of sticking friction and the coefficient of sliding friction between ram and test specimen are ascertained. Since the friction is caused by the unevenness of the faces sliding against one another (sticking), the ram was designed with an average surface roughness Ra=0.05 μm.

[0170] The materials were melted in an injection molding machine and injected at a melt temperature of 220° C. into the closed coefficient-of-friction mold with a mold wall temperature of 60° C., and held under a hold pressure of 400 bar for 15 sec. After a residual cooling time of 17 sec., the mold was opened slightly, and the coefficients of sticking and sliding friction were determined.

[0171] Tables 2a and 2b summarize molding compounds and the coefficients of friction obtained as described here.

[0172] The data show that the molding compounds of the invention have distinctly reduced coefficients of sticking and sliding friction compared to the noninventive molding compound VI. Thus, demolding characteristics in the injection mold are also improved.

TABLE-US-00003 TABLE 2a Compositions of the molding compounds and their properties. V1 1 2 3 4 5 6 7 8 9 10 11 12 Component (pts. by wt.) A 100 99.8 99.5 99.8 99.5 99.8 99.5 99.8 99.5 99.8 99.5 99.8 99.5 B1 0.2 0.5 B2 0.2 0.5 B3 0.2 0.5 B4 0.2 0.5 B5 0.2 0.5 B6 0.2 0.5 Properties Coefficient of 0.96 0.61 0.56 0.4 0.34 0.34 0.26 0.32 0.29 0.44 0.41 0.6 0.36 sticking friction Coefficient of 1.49 1.04 0.59 0.72 0.75 0.3 0.24 0.5 0.45 0.68 0.56 0.71 0.50 sliding friction

TABLE-US-00004 TABLE 2b Compositions of the molding compounds and their properties. V1 13 13 15 16 17 18 19 20 21 22 Component (pts. by wt.) A 100 99.8 99.5 99.8 99.5 99.8 99.5 99.8 99.5 99.8 99.5 B7 0.2 0.5 B8 0.2 0.5 B9 0.2 0.5 B10 0.2 0.5 B11 0.2 0.5 Properties Coefficient of 0.96 0.34 0.3 0.28 0.24 0.27 0.26 0.28 0.28 0.35 0.31 sticking friction Coefficient of 1.49 0.72 0.63 0.54 0.50 0.54 0.46 0.68 0.56 0.57 0.49 sliding friction