THERMOPLASTIC COMPOSITION FOR MONOLAYER TUBE, AIR-CONDITIONING CIRCUIT AND METHOD FOR PREPARING THE COMPOSITION

Abstract

The invention relates to a thermoplastic composition for a monolayer tube (T1, T2), and particularly to an air-conditioning circuit for a motor vehicle comprising tubes transporting a refrigerating fluid.

The composition comprises in weight fractions: more than 20% and up to 40% of a PA 6.10 and/or a PA 6.12, from 45% to less than 60% of a polyphthalamide having a Tg higher than 120° C. and selected from PA 6.I/6.T, PA 9.T, PA 10.T, PA 10.T/X, and from 10% to 20% of a compatibilizing system comprising a reaction product between (a) a polymer of olefin comprising an unsaturated epoxide and (b) a polymer of olefin comprising an unsaturated carboxylic acid, with weight ratio (a):(b) greater than 1.

Claims

1. A thermoplastic composition capable of forming a monolayer tube for transporting a fluid, the monolayer tube being in particular adapted for transporting a refrigerant gas in an air-conditioning circuit of a motor vehicle, wherein the thermoplastic composition comprises in weight fractions: more than 20% and up to 40% of a PA 6.10 and/or a PA 6.12 as at least one aliphatic polyamide, from 45% to less than 60% of at least one polyphthalamide having a glass transition temperature higher than 120° C. and selected from the group consisting of PA 6.I/6.T, PA 9.T, PA 10.T, PA 10.T/X and mixtures thereof, where X represents at least one polyamide unit other than PA 10.T derived from an aliphatic diamine having from 6 to 9 carbon atoms and from an aromatic dicarboxylic acid comprising terephthalic or isophthalic acid, and from 10% to 20% of a compatibilizing system comprising a product of a reaction between (a) a polymer of at least one first olefin comprising an unsaturated epoxide and (b) a polymer of at least one second olefin comprising an unsaturated carboxylic acid, with a weight ratio (a):(b) greater than 1, said at least one second olefin being identical to or different from said at least one first olefin.

2. The thermoplastic composition as claimed in claim 1, wherein said at least one aliphatic polyamide is devoid of PA 6, being preferably further devoid of PA 4.6, PA 6.6, PA 10.10, PA 10.6, PA 11 and PA 12.

3. The thermoplastic composition as claimed in claim 1, wherein said at least one aliphatic polyamide comprises a PA 6.12 and preferably consists of said PA 6.12.

4. The thermoplastic composition as claimed in, claim 1, wherein said at least one polyphthalamide comprises a PA 6.I/6.T having said glass transition temperature higher than 122° C. and preferably consists of said PA 6.I/6.T.

5. The thermoplastic composition as claimed in claim 4, wherein said at least one aliphatic polyamide and said at least one polyphthalamide form separated phases in the thermoplastic composition.

6. The thermoplastic composition as claimed in claim 1, wherein said at least one polyphthalamide comprises at least one PA 10.T/X having said glass transition temperature higher than 122° C. and preferably consists of said at least one PA 10.T/X, wherein X represents a PA 6.T unit or a PA 6.3.T unit preferably with a molar ratio PA 10.T/X greater than 1.

7. The thermoplastic composition as claim 1, wherein in said compatibilizing system, said weight ratio (a):(b) is of from 1.5:1 to 3:1 and preferably of from 1.7:1 to 2.3:1.

8. The thermoplastic composition as claimed in claim 1, wherein in said compatibilizing system, (a) is a polymer of said at least one first olefin comprising an aliphatic or alicyclic glycidyl ester, and is preferably an olefin-glycidylmethacrylate copolymer.

9. The thermoplastic composition as claimed in claim 1, wherein in said compatibilizing system, (b) is a polymer of said at least second olefin comprising (meth)acrylic acid groups, and is preferably an olefin-acrylic acid copolymer.

10. The thermoplastic composition as claimed in claim 1, wherein the thermoplastic composition is devoid of a polymer comprising an unsaturated carboxylic anhydride, being in particular devoid of a copolymer of an olefin and an unsaturated carboxylic anhydride and of a polyolefin grafted with an unsaturated carboxylic anhydride, and preferably wherein the thermoplastic composition is devoid of an elastomer, being in particular devoid of a polyamide elastomer, of an olefinic elastomer such as an ethylene acrylate elastomer or an ethylene-alpha olefin copolymer, and of a styrenic rubber.

11. The thermoplastic composition as claimed in claim 1, wherein the thermoplastic composition is devoid of additional filler or fiber, and preferably consists of said at least one aliphatic polyamide, said at least one polyphthalamide and said compatibilizing system, and preferably wherein the thermoplastic composition comprises in weight fractions: from 25% to 35% of said at least one aliphatic polyamide, from 50% to 59% of said at least one polyphthalamide, and from 12% to 18% of said compatibilizing system.

12. The thermoplastic composition as claimed in claim 1, wherein the thermoplastic composition has: an initial Young modulus and an initial stress at rupture both measured according to ISO 527 standard after 168 hat 23° C., 50% HR and with a traction speed of 50 mm/min, and a final Young modulus and a final stress at rupture measured after thermal ageing according to ISO 527 standard after 168 hat 150° C. and with a traction speed of 50 mm/min, the variation in absolute value between said final Young modulus and said initial Young modulus and/or between said final stress at rupture and said initial stress at rupture being lower than 50%, and preferably wherein the thermoplastic composition has: an initial Charpy breaking energy measured according to ISO 179/1eA standard, and a final Charpy breaking energy measured according to ISO 179/1eA standard after thermal ageing after 168 h at 150° C., the variation in absolute value between said final Charpy breaking energy and said initial Charpy breaking energy being lower than 50%.

13. A monolayer tube for transporting a fluid, the monolayer tube being in particular adapted for transporting a refrigerant gas in an air-conditioning circuit of a motor vehicle, wherein the monolayer tube is made of the thermoplastic composition as claimed in claim 1, and preferably wherein the monolayer tube has: a water permeability, measured according to PSA standard D45 1729/--A during 288 hours at 70° C. and 95% RH, which is lower than 8.00 g/m.sup.2/72 h and preferably lower than or equal to 7.60 g/m.sup.2/72 h, and optionally a burst resistance measured in a conditioned enclosure according to ISO 1110 standard which is greater than 6.0 MPa at 23° C. and greater than 3.0 MPa at 125° C., and preferably which is greater than 7.0 MPa at 23° C. and greater than 3.3 MPa at 125° C., and/or a permeability to a refrigerant gas consisting of 2,3,3,3-tetrafluoropropene (R-1234yf), measured according to PSA standard D 451714, which is lower than 5.00 g/m.sup.2/72 h and preferably lower than 3.00 g/m.sup.2/72 h.

14. An air-conditioning circuit for a motor vehicle comprising a plurality of tubes adapted to transport a refrigerating fluid, the air conditioning circuit comprising a low-pressure loop which comprises low-pressure tubes and a high-pressure loop which comprises high-pressure tubes, wherein at least one of said tubes selected from the low-pressure tubes and the high-pressure tubes and combinations thereof comprises the monolayer tube as claimed in claim 13, and preferably wherein said low-pressure tubes each consist of a said monolayer tube and are connected to one another by thermoplastic connectors devoid of metal parts to form an entirely thermoplastic low-pressure line.

15. A method for preparing the thermoplastic composition as claimed in claim 1, wherein the method comprises kneading said at least one aliphatic polyamide, said at least one polyphthalamide and said compatibilizing system preferably in a twin-screw extruder, to perform a crosslinking chemical reaction for said at least one aliphatic polyamide and said at least one polyphthalamide, by said at least one polyolefin comprising an unsaturated epoxide.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0103] FIG. 1 is a diagrammatic perspective view of a typical air-conditioning circuit for a motor vehicle which may incorporate thermoplastic monolayer tubes according to the invention.

[0104] FIG. 2 is a perspective partial view of an example of a low-pressure tubing line of the invention usable in the air-conditioning circuit of FIG. 1, the low-pressure line incorporating thermoplastic monolayer tubes according to the invention.

[0105] FIG. 3 is a graph showing the respective evolutions over temperature T (° C.) of the storage modulus G′ (Pa), of the loss modulus G″ (Pa) and of tan delta measured for a composition C9 not according to the invention and for two compositions according to the invention 11 and 12, all in the form of separated phases.

[0106] FIG. 4 is a graph showing the respective evolutions over temperature T (° C.) of the storage modulus G′ (Pa), loss modulus G″ (Pa) and tan delta measured for a composition C7 not according to the invention and for a composition according to the invention I3, both in the form of mixed phases.

EMBODIMENTS OF THE INVENTION

[0107] The air-conditioning circuit 1 for a motor vehicle of FIG. 1 comprises a plurality of tubes adapted to transport a refrigerating fluid F, the air conditioning circuit 1 comprising a low-pressure loop 2 which comprises low-pressure tubes and a high-pressure loop 3 which comprises high-pressure tubes. in the example of FIG. 1, the low-pressure loop 2 is defined between an evaporator and blower assembly 4 and an inlet 5a of a compressor 5, and the high-pressure loop 3 is defined between an outlet 5b of the compressor 5 and an expansion valve 6 which it itself part of the low-pressure loop 2. In a usual manner, a condenser and fan assembly 7 and a drier 8 are provided in succession in the high-pressure loop 3 between the compressor outlet 5b and the expansion valve 6 (the refrigerating fluid being gaseous between the compression outlet 5b and condenser 7 and usually liquid between the condenser 7 and expansion valve 6).

[0108] According to an embodiment of the invention, at least one of the tubes of the air-conditioning circuit 1 in the low-pressure loop 2 and/or the high-pressure loop 3 and, preferably, at least the low-pressure loop 2 comprises a thermoplastic tubular structure 2a made of at least one thermoplastic composition according to the invention, such as the tubular structure 2a visible in the example of FIG. 2.

[0109] The thermoplastic tubular structure 2a may advantageously consist of a plurality of thermoplastic monolayer tubes T1, T2, etc. assembled to together in succession in the loop 2, 3 and are connected to one another by thermoplastic connectors C1, C2, etc. As a consequence, the thermoplastic tubular structure 2a may advantageously be used to form an entirely thermoplastic tubing line in the low-pressure loop 2 and/or high pressure loop 3, in contrast to the conventional tubing lines involving rubber and metal tube sections.

[0110] As demonstrated in the below examples, such a thermoplastic tubular structure 2a made of a thermoplastic composition of the invention may exhibit a remarkable trade-off of improved properties rendering it particularly suitable for forming such a thermoplastic tubing line in the low-pressure loop 2.

EXAMPLES

Tested Compositions

[0111] A number of thermoplastic control compositions C1-C12 and of thermoplastic compositions according to the invention I1-I3 were prepared by kneading, in a twin-screw extruder “Leistritz” of ZSE40MAXX type (L/D=44) for compositions C1-C9, C12 and I1-I3 and in a twin screw extruder “Leistritz” of ZSE18MAXX type (L/D=40) for compositions C10-C11, a polyamide mixture of a PA 6.12 (optionally combined to PA 6 for some control compositions) and of a PA 6.I/6.T or a PA 10.T/X in the presence of a compatibilizing system to crosslink this mixture. The compatibilizing system was introduced in each twin-screw together with this polyamide mixture.

[0112] The polyamides tested in these compositions were as recited below: [0113] PA 6.12: Grilamid® XE 4155 black 9992, from EMS-GRIVORY [0114] PA 6: Akulon® F136DH, from DSM [0115] PA 6.I/6.T: Grivory® G21 6506, from EMS-GRIVORY [0116] PA 10.T/X “M3000”: Vestamid® HT plus M3000, from EVONIK [0117] PA 10.T/X “HT3Z”: Grivory® HT3Z, from EMS-GRIVORY.

[0118] Chem. 1 represents the semi-structural chemical formula for PA 10.T/X «M3000», obtained by RMN 1H analysis with X=PA 6-3-T. Hence, PA 10.T/X “M3000” is a PA 10.T/PA 6.3.T. The RMN .sup.1H analysis disclosed a molar ratio block PA 10.T:block PA 6.3.T of 90:10 (±5% uncertainty). The number-average molecular weight Mn of this PA 10.T/PA 6.3.T was 13000 g/mol by GPC, which gave a number average polymerization degree (PDn) of 38.7 pour the blocks PA 10.T and of 4.5 pour the blocks PA 6.3.T.

##STR00001##

[0119] Chem. 2 represents the semi-structural chemical formula for PA 10.T/X «HT3Z», obtained by RMN .sup.1H analysis with X=PA 6.T. Hence, PA 10.T/X “M3000” is a PA 10.T/PA 6.T. The RMN .sup.1H analysis disclosed a molar ratio block PA 10.T: block PA 6.T of 90:10 (±5% uncertainty).

[0120] [Chem. 2]

##STR00002##

[0121] The compatibilizing system tested in these compositions consisted of the two following compounds (a) and (b) detailed below. [0122] (a) PE-GMA: Lotader® AX8840, from ARKEMA: a random copolymer of ethylene and glycidyl methacrylate, polymerized by high-pressure autoclave process, and [0123] (b) PE-AA: Primacor® 1410, from DOW: an ethylene-acrylic acid copolymer. In compositions of the invention, and the weight ratio (a):(b) was of 2:1.

[0124] Tables 1 and 2 below detail the formulations and process parameters of the tested compositions, respectively of control compositions C1-C8 in table 1 and of control compositions C9-C12 and compositions of the invention I1-I3 in table 2.

TABLE-US-00001 TABLE 1 C1 C2 C3 C4 C5 C6 C7 C8 Compositions (weight fractions) PA6 Akulon F136-DH 60 45 0 25 25 0 0 0 PA 6.12 GrilamidXE4155 25 25 25 0 30 25 42.5 40 PA 6.I/6.T Grivory G21 0 0 60 60 30 45 0 60 PA 10.T/X Vestamid HT 0 15 0 0 0 15 50 0 plus M3000 PA 10.T/X Grivory HT3Z 0 0 0 0 0 0 0 0 PE-GMA LotaderAX8840 10 10 10 10 10 10 5 0 PE-AA Primacor 1410 5 5 5 5 5 5 2.5 0 Twin screw extruder Screw speed (rpm) 280 260 260 260 260 260 260 260 Flow rate (kg/h) 60 60 75 75 75 75 80 75 Power (%) 68 61 67 65 72 61 65 64 Melt temperature (° C.) 253 243 262 267 263 264 289 272 Melt pressure (bar) 140 125 113 94 105 103 91 91

TABLE-US-00002 TABLE 2 C9 C10 C11 C12 I1 I2 I3 Compositions (weight fractions) PA 6 Akulon F136-DH 15 PA 6.12 GrilamidXE4155 25 42.5 50 15 40 30 30 PA 6.I/6.T Grivory G21 60 47.5 45 55 45 55 PA 10.T/X Vestamid HT 40 plus M3000 PA 10.T/X Grivory HT3Z 15 PE-GMA Lotader AX8840 10 6.7 3.3 10 10 10 10 PE-AA Primacor 1410 5 3.3 1.7 5 5 5 5 Twin screw extruder Screw speed (rpm) 260 500 500 400 260 400 400 Flow rate (kg/h) 75 6 6 100 75 100 100 Power (%) 64 70 70 65 68 66 81 Melt temperature (° C.) 275 280 280 262 276 260 295 Melt pressure (bar) 116 50 50 106 142 116 90

[0125] FIG. 3 shows the evolutions over temperature of the storage modulus G′, loss modulus G″ and tan delta for control composition C9 and compositions I1 and I2 of the invention which each comprise separated phases due to the crystalline PA 6.12 and the amorphous PA 6.I/6.T, illustrating the advantageous technical effect of using a PPA having a high Tg in compositions I1 and I2 (see the temperature of 120° C.) which comprise 45% and 55% of this PPA with only 40% and 30% pf PA 6.12, respectively. FIG. 3 shows that a high weight ratio of a high Tg PPA imparts a strong peak at the high temperature of 120° C. to a composition of the invention, while a low weight ratio of the high Tg PPA leads to a weak peak at this high temperature.

[0126] FIG. 4 also shows the comparative evolutions over temperature of the storage modulus G′, loss modulus G″ and tan delta for both thermoplastic composition C7 and I3, which each comprise a fully semi-crystalline mixture PA 6.12+PA 10.T/X in a form of mixed phases.

[0127] Tables 3 and 4 below both detail the following properties of the tested compositions.

[0128] Mechanical properties were measured at 23° C. with HR=50%, according to ISO 527 for the Young modulus and the stress at rupture (or the yield stress) in table 3, and according to ISO 178 for the flexion modulus in table 4.

[0129] Charpy breaking energy in table 3 was measured according to ISO 179/1eA. Thermal ageing in table 3 was carried out after 168 h at 150° C., and a traction speed of 50 mm/min. was used. Burst resistance in table 3 was measured according to ISO 1110 in a conditioned enclosure at 23° C. and 125° C.

[0130] Permeability to water of the monolayer tubes in table 3 was measured according to PSA standard D45 1729/--A during 288 hours at 70° C. and 95% RH. Permeability to R-1234yf of the monolayer tubes in table 3 was measured according to PSA standard D 451714.

[0131] Flexion properties recited in table 4 were measured in dry state at 23° C., and after conditioning according to ISO 1110 standard, with different thicknesses (3 mm and 5 mm) for the tested monolayer tubes and at different HR (%).

[0132] Further, chemical ageing of compositions I1-I3 due to oils was measured during 2000 hat 110° C., in the oils known under the names ND12, SPA2, HD100, VC200YF, VC100YF, NDB, PSR-1, PSD1, YR20, ND11, ZXL100PG and ZXL200PG. No significant variations were measured after contact with these oils for the above mechanical properties, particularly including the Young modulus and the stress at rupture.

[0133] Furthermore, the resistance of compositions I1-I3 to ZnCl.sub.2 was measured according to D 471011 standard by immersion in ZnCl.sub.2 of monolayer tubes made of compositions I1-I3 during 1 min. at 23° C. followed by dry heating during 3 h at 80° C. This test resulted in no change of aspect for these tubes made of compositions I1-I3.

[0134] Specifically according to D47 1011 standard, the samples were immersed so that the whole fir tree or snap-in interface/pipe was in contact with the liquid (ZnCl.sub.2/CaCl.sub.2=20%/80%). The samples were kept in the position without shaking for 1 minute +1-5 seconds. The samples were placed horizontally in the oven at 80° C. for 3 hours +1-5 minutes. 2 cycles were performed per day. At the end of each day, the samples that must be validated were left for a maximum of 20 hours at room temperature under a fume cupboard before starting a new cycle. The samples were immersed in the solution 4 cycles minimum to reach a rating of 5.

TABLE-US-00003 TABLE 3 Mechanical properties after Permeability Permeability thermal ageing (variations: %) Burst resistance (MPa) to water to R-1234yf Acceptable if variation < 50% 23° C. 125° C. (g/m.sup.2/72 h) (g/m.sup.2/72 h) Modules Stress Charpy Acceptable if > Acceptable if > Maximum Maximum variation variation variation 6 MPa 3.4 MPa value value C1 −0.3 3.8 −3.0 5.8 3.0 37.90 6.90 C2 4.2 −4.0 19.0 7.3 3.5 23.90 4.90 C3 29.7 32.7 −58.0 3.85 C4 Not Not Not 7.5 2.5 5.55 1.65 acceptable acceptable acceptable C5 32.5 −5.4 −40.0 6.0 2.5 11.60 3.30 C6 43.0 17.3 −62.0 6.0 2.5 3.80 8.40 C7 −4.0 13.8 −25.0 6.0 3.4 4.67 C8 20.0 28.0 −45.0 7.1 3.4 6.35 2.25 C9 11.0 26.0 −59.0 6.9 3.4 5.93 6.15 C10 30.0 9.0 −18.0 C11 40.0 12.0 −53.0 C12 73.0 14.0 −67.0 acceptable acceptable 8.14 acceptable I1 16.0 15.0 −15.0 7.35 3.4 10.45 3.05 I2 32.0 14.0 −27.0 9.1 acceptable 7.55 0.00 I3 12.0 −2.0 1.0 6 (flange 3.4 7.15 0.50 leak)

TABLE-US-00004 TABLE 4 Flexion modulus M (MPa) ΔM ΔM Dry Dry Conditioned Conditioned (%) (%) HR Dynamic stiffness 3 mm 5 mm 3 mm 5 mm at 3 mm at 5 mm (%) L-shaped test tube C1 348 528 140 217 −60 −59 2.05 C2 C3 C4 577 915 588 918 +2 0 2.0 C5 449 700 376 571 −16 −18 1.5 C6 465 732 489 772 +5 +6 1.2 C7 443 714 434 686 −2 −4 1.0 C8 551 871 515 804 −7 −8 2.2 C9 415 654 411 644 −1 −2 1.0 C10 C11 C12 457 725 457 711 0 −2 1.6 I1 370 572 346 534 −7 −7 1.9 ± I2 414 640 398 620 −4 −3 1.4 I3 411 647 365 567 −11 −12 1.1 ±

[0135] As a result from all the measured properties recited above, it may be noted the thermoplastic compositions I1, I2 and I3 of the invention exhibit advantageous properties, and that in particular the compositions I2 and I3 exhibit a satisfactory balance of properties including a very low permeation for water and also for a refrigerating gas, as well as very satisfactory mechanical properties even after thermal and chemical ageing, including an improved impact resistance, as witnessed by [0136] the water permeability of monolayer tubes made of compositions I1-I3 which is lower than 10.50 g/m.sup.2/72 h and advantageously lower than 7.60 g/m.sup.2/72 h (see compositions I2 and I3 in table 2), [0137] the R-1234yf permeability of monolayer tubes made of compositions I1-I3 which is lower than 3.10 g/m.sup.2/72 h and advantageously lower than 1.00 g/m.sup.2/72 h (see compositions I2 and I3 in table 2), [0138] a variation of mechanical properties after thermal ageing of less than 40% for compositions I1-I3 (and even less than 30%, see I1 and I3 in table 2), and [0139] an acceptable burst resistance of monolayer tubes made of compositions I1-I3.

[0140] These results of compositions of the invention compared to those of control compositions C1-C12 also specifically demonstrate the unexpected and advantageous selection in compositions I1-I3 of: [0141] more than 20% and up to 40% of PA 6.12 (in view of compositions C7 and C12), [0142] from 45% to less than 60% of the PPA according to the invention (i.e. PA 6.I/6.T and/or PA 10.T/X, for instance, in view of compositions C3 to C6 and C8 to C9 including either 30% or 60% of PPA(s)), and of [0143] from 10% to 20% for the compatibilizing system of the invention.

[0144] As a conclusion, these examples demonstrate that the compositions of the invention are very advantageously usable in entirely thermoplastic air-conditioning tubing lines incorporating thermoplastic monolayer tubes for example of in a low-pressure loop, in lieu of metal-rubber structures conventionally used therein.