STEAM-RESISTANT TRANSPARENT POLYAMIDES

Abstract

A transparent polyamide moulding with high resistance to steam, containing at least one copolyamide with polyamide units AB/AC/D, wherein: (A) is selected as a cycloaliphatic diamine from the group: MACM and PACM; (B) is selected as an aromatic dicarboxylic acid from the group: isophthalic acid (I), naphthalenedicarboxylic acid, and terephthalic acid (T); (C) is selected as an aliphatic dicarboxylic acid from the group: decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid; and (D) is selected as at least one lactam or α,ω-aminocarboxylic acid from the group: laurolactam, undecanolactam, 12-aminododecanoic acid, and 11-aminoundecanoic acid, wherein: the proportions of polyamide units AB are from 30 to 45 mol %, the proportions of polyamide units AC are from 30 to 40 mol %, and the proportions of polyamide units D are from 20 to 32 mol %, and wherein the sum total of polyamide units AB, AC and D is 100 mol %.

Claims

1-15. (canceled)

16. A polyamide moulding compound comprising at least one copolyamide formed at least from the polyamide units AB/AC/D, wherein: (A) is selected as at least one cycloaliphatic diamine from the group consisting of: bis(4-amino-3-methylcyclohexyl)methane (MACM) and bis(4-aminocyclohexyl)methane (PACM); (B) is selected as at least one aromatic dicarboxylic acid from the group consisting of: isophthalic acid (I), naphthalenedicarboxylic acid, and terephthalic acid (T); (C) is selected as at least one aliphatic dicarboxylic acid from the group consisting of: decanedioic acid, undecanedioic acid, dodecanedioic acid, tridecanedioic acid, tetradecanedioic acid, pentadecanedioic acid, hexadecanedioic acid; (D) is selected as at least one lactam or one α,ω-aminocarboxylic acid from the group consisting of: laurolactam (LC 12), undecanolactam (LC 11), 12-aminododecanoic acid, and 11-aminoundecanoic acid, wherein: the proportions of polyamide units AB are in the range from 30 to 45 mol %, the proportions of polyamide units AC are in the range from 30 to 40 mol %, and the proportions of polyamide units D are in the range from 20 to 32 mol %, and wherein the sum total of polyamide units AB, AC and D is 100 mol %.

17. The polyamide moulding compound according to claim 16, wherein the sum total of aliphatic polyamide units AC and D is in the range from 55-65 mol %, and the proportions of polyamide units AB are in the range from 35-45 mol %.

18. The polyamide moulding compound according to claim 16, wherein the sum total of aliphatic polyamide units AC and D is in the range from 58-64 mol %, and the proportions of polyamide units AB are in the range from 36-42 mol %.

19. The polyamide moulding compound according to claim 16, wherein the proportions of polyamide units AC are in the range from 31-38, and/or wherein the proportions of polyamide units D are in the range from 22-31.

20. The polyamide moulding compound according to claim 19, wherein the proportions of polyamide units AC are in the range from 32-35 mol %, and/or wherein the proportions of polyamide units D are in the range from 25-30 mol %.

21. The polyamide moulding compound according to claim 16, wherein (A) is selected as exclusively bis(4-amino-3-methylcyclohexyl)methane (MACM).

22. The polyamide moulding compound according to claim 16, wherein (B) is selected as a mixture of isophthalic acid (I) and terephthalic acid (T).

23. The polyamide moulding compound according to claim 22, wherein the ratio of isophthalic acid (I) to terephthalic acid (T) is in the range from 40:60 to 60:40.

24. The polyamide moulding compound according to claim 22, wherein the ratio of isophthalic acid (I) to terephthalic acid (T) is in the range from 45:55 to 55:45.

25. The polyamide moulding compound according to claim 16, wherein (C) is selected exclusively from dodecanedioic acid.

26. The polyamide moulding compound according to claim 16, wherein (D) is selected exclusively from laurolactam (LC 12).

27. The polyamide moulding compound according to claim 16, wherein the copolyamide is composed exclusively of the polyamide units AB/AC/D.

28. The polyamide moulding compound according to claim 16, wherein it is composed of: 85-100% by weight of copolyamide formed at least from the polyamide units AB/AC/D; and 0-15% by weight of additives.

29. The polyamide moulding compound according to claim 16, wherein it is composed of: 95.0-99.9% by weight, of copolyamide formed at least from the polyamide units AB/AC/D; and 0.1-5.0% by weight, of additives.

30. The polyamide moulding compound according to claim 16, wherein it is composed of: 85-100% by weight of copolyamide formed at least from the polyamide units AB/AC/D; snf 0-15% by weight of additives, selected from the group: polyamides different from the copolyamide AB/AC/D; UV stabilizers; heat stabilizers; free-radical scavengers; processing aids; inclusion inhibitors; lubricants; mould release aids, including metal stearates or metal montanates, including those in which the metal is selected from the group consisting of magnesium, calcium, barium; mineral oils or fatty acid amides; antifoams; plasticizers; functional additives for influencing the optical properties, including functional additives for influencing the refractive index; impact modifiers; fillers and/or admixtures; optical brighteners; dyes or mixtures thereof, wherein the fillers and/or admixtures can be nanoscale and/or are selected from the following group: glass fibres, glass beads, carbon fibres, carbon black, graphite, flame retardants, minerals including titanium dioxide, calcium carbonate or barium sulfate, or mixtures thereof.

31. The polyamide moulding compound according to claim 30, wherein the additives do not contain any particulate and/or fibrous fillers and/or admixtures.

32. A process for preparing a polyamide moulding compound according to claim 16, wherein the copolyamide formed at least from the polyamide units AB/AC/D is prepared in pressure vessels, with a pressure phase at 180° C. to 330° C., with a subsequent expansion at 260° C. to 350° C., with a subsequent degassing at 270° C. to 350° C., and discharge of the polyamide moulding compound in the form of strands, cooling, pelletizing and drying of the pelletized material, optionally compounding with additives as pelletized material and forming in an extruder at melt temperatures of 250° C. to 350° C. to form a strand, chopping using suitable pelletizers to give pellets.

33. A process for preparing a polyamide moulding compound according to claim 16, wherein the copolyamide formed at least from the polyamide units AB/AC/D is prepared in pressure vessels, with a pressure phase at 270° C. to 330° C., with a subsequent expansion at 260° C. to 320° C., with a subsequent degassing at 260° C. to 320° C., and discharge of the polyamide moulding compound in the form of strands, cooling, pelletizing and drying of the pelletized material, optionally compounding with additives as pelletized material and forming in an extruder at melt temperatures of 250° C. to 350° C. to form a strand, chopping using suitable pelletizers to give pellets.

34. A moulding made from a polyamide moulding compound or having at least one region made from a polyamide moulding compound according to claim 16.

35. A steam-resistant, transparent moulding according to claim 34.

36. The moulding according to claim 34, produced by means of injection moulding processes and/or injection-compression moulding processes at melt temperatures of 230° C. to 320° C., wherein the mould is adjusted to temperatures of 40° C. to 130° C. and wherein optionally the mould at temperatures of 40° C. to 130° C. after filling of the cavity applies compression to the hot moulding.

37. The moulding according to claim 36, wherein it has a resistance to more than 700, or to more than 1000, steam cycles.

38. The moulding according to claim 36, wherein it is a conduit or a container, including those for contact with water and/or steam.

39. The moulding according to claim 36, wherein it is a conduit or a container, for contact with water and/or steam in process technology, in food technology, or a container for the production and/or processing and/or heating of foods in the baby and/or infant food sector.

40. A method of using a moulding according to claim 34 as a food container or a part thereof, as a part of a kitchen appliance, or for the production and/or processing and/or heating of foods using steam.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Preferred embodiments of the invention are described below on the basis of the drawings, which serve merely for elucidation and are not to be interpreted as limiting. In the drawings:

[0056] FIG. 1 shows a moulding for determining the steam resistance;

[0057] FIG. 2 shows a device for determining the steam resistance.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0058] Preferred embodiments of the invention are described below on the basis of the exemplary embodiments, which serve merely for elucidation and are not to be interpreted as limiting. The transparent copolyamides according to the invention are prepared in a manner known per se in known stirrable pressure autoclaves having a reservoir vessel and a reaction vessel:

[0059] The reservoir vessel is initially charged with deionized water (25% by weight based on the mixture in Table 1) and the monomers and additives are added. This is followed by repeated inertization with nitrogen gas. The mixture is heated to 180 to 230° C. while stirring under the pressure which is established in order to obtain a homogeneous solution. This solution is pumped through a sieve into the reaction vessel, in which it is heated up to the desired reaction temperature of 260 to 350° C. at a pressure of not more than 30 bar. The mixture is kept at the reaction temperature in the pressure phase for 2 to 4 hours. In the subsequent expansion phase, the pressure is reduced to atmospheric pressure within 1 to 2 hours, in the course of which the temperature can fall slightly.

[0060] In the subsequent degassing phase, the mixture is kept at a temperature of 270 to 350° C. for 0.5 to 1 hour at atmospheric pressure. The polymer melt is discharged in the form of strands, cooled down in a water bath at 15 to 80° C. and pelletized. The pelletized material is dried at 80 to 120° C. for 12 hours under nitrogen or under reduced pressure to a water content of less than 0.1% by weight.

[0061] The following monomers are used to prepare the copolyamides described in the examples and comparative examples.

[0062] 3,3′-Dimethyl-4,4′-diaminodicyclohexylmethane (MACM): freezing range according to ASTM D1015-55: −7 to −0.6° C.; manufacturer: BASF AG, Germany.

[0063] Dodecanedioic acid (DDS): melting range: 128 to 132° C.; manufacturer: Invista Nederland B.V., the Netherlands.

[0064] Isophthalic acid (IPS): melting range: 345 to 348° C.; manufacturer: Flint Hills Resources, Switzerland.

[0065] Terephthalic acid (TPS): melting range: >400° C.; manufacturer: BP Amoco Chemical Company, USA.

[0066] Laurolactam (LL): melting range: 149 to 153° C.; manufacturer: EMS-CHEMIE AG, Switzerland

[0067] In addition, approximately 0.15% by weight of benzoic acid was used as chain regulator and approximately 0.01% by weight of Antifoam RD was used as antifoam (10% by weight emulsion, Dow Corning S.A., Belgium), the concentrations in each case being based on the mixture in Table 1.

[0068] The measurements were performed in accordance with the following standards and on the following test specimens.

[0069] Tensile Modulus of Elasticity:

[0070] ISO 527 (2012) with a pulling speed of 1 mm/min;

[0071] ISO tensile specimen, standard: ISO/CD 3167, A1 type, 170×20/10×4 mm; temperature 23° C.

[0072] Breaking strength and elongation at break:

[0073] ISO 527 (2012) with a pulling speed of 50 mm/min;

[0074] ISO tensile specimen, standard: ISO/CD 3167, A1 type, 170×20/10×4 mm; temperature 23° C.

[0075] Charpy Notched Impact Resistance:

[0076] ISO 179/*eA (*2=instrumented) (2011); ISO test specimen, standard: ISO/CD 3167, B1 type, 80×10×4 mm; temperature 23° C.

[0077] Glass Transition Temperature (Tg), Melting Point and Heat of Fusion:

[0078] ISO standard 11357-1, 11357-2, 11357-3 (2013); pelletized material; the differential scanning calorimetry (DSC) was carried out using a DSC 2920 instrument from TA Instruments with a heating rate of 20 K/min and a cooling rate of 5 K/min. The thermogram was analysed using the Universal Analysis 2000 program from TA Instruments. The sample was quenched in dry ice after the first heating run for the purpose of determining the glass transition temperature. The glass transition temperature (Tg) was determined on the second heating run. The midpoint of the glass transition range, which was reported as the glass transition temperature (Tg), was ascertained by the “half-height” method.

[0079] Transparency:

[0080] ASTM D 1003 (2013); 70 mm disc or 60×60 mm plate, 2 mm thickness, temperature 23° C.; Haze Gard plus measuring instrument from Byk Gardner using CIE illuminant C. The light transmittance value is reported as % of the amount of incident light.

[0081] Relative Viscosity:

[0082] ISO 307 (2007); 0.5 g in 100 ml of solvent in m-cresol; temperature 20° C.; calculation of the relative viscosity (RV) according to RV=t/t.sub.0 in accordance with Section 11 of the standard.

[0083] HDT A (1.8 M Pa) and HDT B (0.45 M Pa):

[0084] ISO 75; ISO impact specimen, 80×10×4.

[0085] Steam Resistance (Ability to Withstand Steam Cycles):

[0086] The mouldings 1, tubular pieces with a flange at one end (cf. FIG. 1), are produced by injection moulding from the materials described and have the dimensions given as follows: tube length L1=100 mm, internal diameter of tube D1=20 mm, wall thickness of tube and flange W=2 mm, flange diameter F1=100 mm, radius between tube and flange=5 mm. For the test, 4 mouldings are placed from above into the openings of the device for determining the steam resistance 2 (cf. FIG. 2), so that the tube 1-1 protrudes into the interior of the device and the flange 1-2 bears centrally on the outer side with respect to the opening 2-1 (diameter of the opening D2=50 mm). In order for the mouldings to keep this position during the test, guide elements are fitted to the upper side of the test apparatus. One steam introduction pipe 2-2 per moulding protrudes into the apparatus from below and is positioned vertically below the moulding in a central position at a distance of 5 cm. The supply of steam is controlled by valves. The device for determining the steam resistance 2 has the external dimensions 60×20×15 (L2×H×T) cm.

[0087] During the first part of the test, the steam treatment, the mouldings are exposed to a stream of steam with a temperature of 100° C. for 75 minutes. The stream of steam of a steam supply pipe in this case is 0.3 g/min. Condensed steam can flow away via an opening 2-3 in the lower part of the test apparatus, while the uncondensed fraction of the steam can escape through the openings in the mouldings.

[0088] After 75 minutes of steam treatment, the supply of steam is halted and the mouldings are allowed to cool down for a period of 75 minutes. The ambient temperature here is 23° C. and the relative air humidity is 60%.

[0089] After the cooling phase has ended, the new cycle begins again with the exposure of the mouldings to steam.

[0090] In the course of the test, the mouldings are assessed visually for the formation of hairline cracks. Hairline cracks form in particular on the tube close to the steam supply pipe and in the region of the transition to the flange. The table lists the respective number of test cycles at which hairline cracks were first observed on the moulding. If the mouldings do not exhibit any hairline cracks even after 1001 cycles, the test is terminated.

[0091] The test specimens are produced on an Allrounder 420 C 1000-250 model injection moulding machine from Arburg. Cylinder temperatures of between 230 and 320° C. are used here. The mold temperature is 80° C. Polished moulds are used for the plates for the transmittance measurement and the mouldings for the determination of the steam resistance.

[0092] Table 1 presented below compares the examples according to the invention (E1 and E2) with the comparative examples (CE1-CE4).

TABLE-US-00001 TABLE 1 Unit E1 E2 CE1 CE2 CE3 CE4 Reactants TPS g 6196 7200 13671 4652 8314 3520 IPS g 6196 7200 7595 11048 8314 8810 DDS g 16218 15500 0 18540 11034 14650 LL g 11924 10425 25634 0 11002 15350 MACM g 34972 36700 30913 41706 35288 32830 Structural units MACMT mol % 18.15 20.96 31.91 16 24.56 9.83 MACMI mol % 18.15 20.96 17.73 38 24.56 24.59 MACM12 mol % 34.28 32.54 0 46 23.51 29.5 12 mol % 29.41 25.55 50.37 0 27.36 36.08 MACMT + MACMI mol % 36.3 41.92 49.64 54 49.12 34.42 MACM12 + 12 mol % 63.69 58.09 50.37 46 50.88 65.58 Properties Tg ° C. 170 174 169 203 185 162 HDT B ° C. 153 157 150 189 175 139 HDT A ° C. 133 136 136 162 146 125 Modulus of MPa 1900 2000 2000 2130 2000 1930 elasticity Breaking strength MPa 74 76 79 78 80 76 Elongation at break % 120 115 90 91 72 115 Notched impact kJ/m.sup.2 12 12 11 12 11 10 resistance Transparency % 93.5 93.5 92.5 93.2 93.2 93.3 Steam cycles >1000 >1000 530 570 620 680 Relative viscosity 1.72 1.70 1.67 1.60 1.64x 1.74x

[0093] It can be seen from the examples and the comparative examples that the good combination of (thermo)mechanical properties (in particular good values for HDT, modulus of elasticity and elongation at break, and also notched impact resistance) and good ability to withstand steam cycles can only be achieved for the polyamide moulding compounds according to the invention. In particular, a comparison with CE1 shows that dodecanedioic acid (or corresponding long-chain diacids as claimed) is crucial as a structural unit, and a comparison with CE2 shows that laurolactam (or corresponding long-chain lactams as claimed) is crucial as a structural unit. Without these structural units, the properties of the invention cannot be achieved. In addition, a comparison with CE3 and with CE4 shows that the specific setting of the proportions is crucial. For instance (compare CE3), a moulding compound with too little dodecanedioic acid and too much aromatic dicarboxylic acids cannot ensure the ability to resist steam cycles. Furthermore, a comparison with CE4 shows that an excessively high proportion of aliphatic blocks likewise does not display sufficient ability to resist steam cycles.

[0094] The examples, in comparison with the comparative examples, therefore show that the individual polyamide units or structural units are critically responsible for ensuring the vital properties, and that the proportions are only permissible within the scope of the narrow ranges claimed in order to also effectively provide the vital properties.

TABLE-US-00002 LIST OF REFERENCE SYMBOLS 1 Moulding for determining the D1 Internal diameter of 1-1 steam resistance F1 Diameter of 1-2 1-1 Tube of 1 L1 Length of 1 1-2 Flange of 1 W Wall thickness of 1-1 2 Device for determining the D2 Diameter of 2.1 steam resistance H Height of 2 2-1 Opening in 2 for 1 L2 Length of 2 2-2 Steam introduction pipe 2-3 Drainage opening