MULTILAYER TUBULAR STRUCTURE INTENDED FOR TRANSPORTING AN AIR-CONDITIONING FLUID

Abstract

A multilayer tubular structure intended for transporting a heat-transfer fluid, the multilayer tubular structure including: a first layer including at least one long-chain polyamide having between 10 and 15 carbon atoms per nitrogen atom and including at least 50% aliphatic units relative to the sum of the units present in the long-chain polyamide; a second layer including at least one polyamide having between 4 and 9 carbon atoms per nitrogen atom, the polyamide including at least 50% aliphatic units relative to the sum of the units present in the polyamide; an optional layer, the first layer containing no continuous fibres, the second layer being in contact with the transported fluid when an optional layer is not present, and the layer or layers representing at least 50% of the total thickness of the tube.

Claims

1. A multilayer tubular structure (MLT) intended for transporting a heat-transfer fluid, said multilayer tubular structure comprising: at least one first layer comprising a first composition comprising predominantly at least one long-chain polyamide having 10 to 15 carbon atoms per nitrogen atom and comprising at least 50% of aliphatic units relative to the sum of the units present in said long-chain polyamide, at least one second layer situated underneath said first layer comprising a second composition comprising predominantly at least one polyamide having 4 to 9 carbon atoms per nitrogen atom, said polyamide comprising at least 50% aliphatic units relative to the sum of the units present in said polyamide, said second composition comprising up to 12% polyolefins, relative to the total weight of said second composition, and up to 2% by weight of at least one plasticizer relative to the total weight of said second composition, optionally, a third layer comprising a third composition as defined for composition, or comprising a third prime composition comprising predominantly a short-chain polyamide with 4 to 7 carbon atoms per nitrogen atom and at least 20%, by weight of at least one polyolefin relative to the total weight of said composition, or a fourth composition (4) comprising a polyamide comprising at least 50% semi-aromatic units, said first layer being devoid of continuous fibers. said second layer being in contact with said transported fluid when said optional layer is not present, and said second layer(s) representing at least 50% of the total thickness of the tube.

2. The multilayer tubular structure according to claim 1, wherein said third layer is present, said third layer being internal and in contact with said transported fluid.

3. The multilayer tubular structure according to claim 1, wherein said first layer is the outermost layer of said multilayer tubular structure.

4. The multilayer tubular structure according to claim 1, wherein said first composition comprises up to 40% of at least one polyolefin.

5. The multilayer tubular structure according to claim 1, wherein said first composition comprises at least 3% by weight of at least one polyolefin, relative to the total weight of said first composition.

6. The multilayer tubular structure according to claim 1, said first composition comprising up to 4% by weight of at least one plasticizer relative to the weight of said first composition.

7. The multilayer tubular structure according to claim 1, wherein the first layer is devoid of plasticizer.

8. The multilayer tubular structure according to claim 1, wherein said second layer is devoid of plasticizer.

9. The multilayer tubular structure according to claim 1, wherein said second layer and said first layer are devoid of plasticizer.

10. The multilayer tubular structure according to claim 1, wherein all the layers present in said structure are devoid of plasticizer.

11. The multilayer tubular structure according to claim 1, wherein said second composition comprises up to 6% by weight of polyolefin, relative to the total weight of said second composition.

12. The multilayer tubular structure according to claim 1, wherein said second composition is devoid of polyolefin.

13. The multilayer tubular structure according to claim 1, wherein said polyamide of said second composition comprises at least 60% of aliphatic units relative to the sum of the units present in said polyamide.

14. The multilayer tubular structure according to claim 1, wherein said polyamide of second composition comprises at least 60% aliphatic units relative to the sum of the units present in said polyamide and said long-chain polyamide of said first composition comprises at least 60% aliphatic units relative to the sum of the units present in said long-chain polyamide.

15. The multilayer tubular structure according to claim 1, wherein said polyamide of said first composition consists of aliphatic units.

16. The multilayer tubular structure according to claim 1, wherein said polyamide of said composition consists of aliphatic units.

17. The multilayer tubular structure according to claim 1, wherein said polyamide of said second composition consists of aliphatic units and said long-chain polyamide of said first composition consists of aliphatic units.

18. The multilayer tubular structure according to claim 1, wherein said second composition is devoid of polyamides other than aliphatic polyamide(s).

19. The multilayer tubular structure according to claim 1, wherein said second composition and said first composition are devoid of polyamides other than aliphatic polyamide(s).

20. The multilayer tubular structure according to claim 1, wherein said second layer represents at least 70% of the total thickness of the tube.

21. The multilayer tubular structure according to claim 1, wherein two second layers are present and separated by a layer consisting of ethylene vinyl alcohol (EVOH) copolymer.

22. The multilayer tubular structure according to claim 2, wherein said internal third layer is present, said third composition being identical to first composition.

23. The multilayer tubular structure according to claim 1, wherein the heat-transfer fluid is a refrigerant fluid selected from hydrocarbon, hydrofluorocarbon, ether, hydrofluoroether, CO.sub.2, NH.sub.3, SO.sub.2 and fluoroolefin compounds.

24. The multilayer tubular structure according claim 23, wherein the heat-transfer fluid is a refrigerant fluid selected from CO.sub.2, fluoropropenes, fluoropropanes and fluoroethanes, and mixtures thereof.

25. The multilayer tubular structure according to claim 23, wherein the heat-transfer fluid is a refrigerant fluid selected from 1,3,3,3-tetrafluoropropene (1234ze) and 2,3,3,3-tetrafluoropropene (1234yf), particularly the heat-transfer fluid is 2,3,3,3-tetrafluoropropene (1234yf).

26. The multilayer tubular structure according to claim 23, wherein the refrigerant fluid contains a lubricant.

27. The multilayer tubular structure according to claim 1, wherein said at least one polyamide of layer is selected from PA11, PA12, PA1010 and PA1012.

28. The multilayer tubular structure according to claim 1, wherein said at least one aliphatic polyamide of layer is selected from PA6, PA66, PA6/66, PA610, PA410, PA412 and PA612.

29. The multilayer tubular structure according to claim 1, wherein said at least one polyamide of layer, when it is present, is selected from PA11, PA12, PA11/10T, PA6, PA66, PA6/66, PA610, PA410, PA412 and PA612.

30. The use of a multilayer tubular structure as defined in claim 1, for transporting a heat-transfer fluid.

31. The use of a multilayer tubular structure as defined in claim 1, in order to satisfy an extractable test, said test particularly consisting of filling said multilayer tubular structure MLT with Forane and heating the assembly at 60° C. for 96 hours, then emptying it by filtering it into a beaker, then allowing the filtrate from the beaker to evaporate at ambient temperature and finally weighing this residue, the proportion of which must be less than or equal to approximately 6 g/m.sup.2 of internal tube surface and the proportion of residue on the filter after filtering being less than or equal to 1 g/m.sup.2.

Description

EXAMPLES

[0303] The invention will now be illustrated by the following examples without being in any way limited to these.

[0304] The following structures were prepared by extrusion:

[0305] The multi-layer tubes are manufactured by co-extrusion. An industrial McNeil multilayer extrusion line is used, equipped with 5 extruders, connected to a multilayer extrusion head with spiral mandrels.

[0306] The screws used are extrusion monoscrews having screw profiles adapted to polyamides. In addition to the 5 extruders and the multilayer extrusion head, the extrusion line comprises:

a die-punch assembly, located at the end of the coextrusion head; the internal diameter of the die and the external diameter of the punch are selected according to the structure to be produced and the materials of which it is composed, as well as the dimensions of the tube and the line speed;
a vacuum tank with an adjustable vacuum level. In this tank water circulates generally maintained at 20° C., in which a gauge is submerged making it possible to shape the tube to its final dimensions. The diameter of the gauge is adapted to the dimensions of the tube to be produced, typically from 8.5 to 10 mm for a tube with an external diameter of 8 mm and a thickness of 1 mm; a succession of cooling tanks in which water is maintained at around 20° C., allowing the tube to be cooled along the path from the head to the drawing bench;
a diameter meter;
a drawing bench.

[0307] The configuration with 5 extruders is used to produce tubes ranging from 2 layers to 5 layers. In the case of structures whose number of layers is less than 5, several extruders are then fed with the same material.

[0308] In the case of structures comprising 6 layers, an additional extruder is connected and a spiral mandrel is added to the existing head, in order to make the inner layer, in contact with the fluid.

[0309] Before the tests, in order to ensure the best properties for the tube and good extrusion quality, it is verified that the extruded materials have a residual moisture content before extrusion of less than 0.08%. Otherwise, an additional step of drying the material before the tests, generally in a vacuum dryer, is carried out overnight at 80° C.

[0310] The tubes, which satisfy the characteristics disclosed in the present patent application, were removed, after stabilization of the extrusion parameters, the dimensions of the tubes in question no longer changing over time. The diameter is controlled by a laser diameter meter installed at the end of the line.

[0311] Generally, the line speed is typically 20 m/min. It generally ranges from 5 to 100 m/min.

[0312] The screw speed of the extruders depends on the thickness of the layer and on the diameter of the screw as is known to those skilled in the art.

[0313] In general, the temperatures of the extruders and of the tools (head and connector) must be adjusted so as to be sufficiently higher than the melting temperature of the compositions in question, so that they remain in the molten state, thus preventing them from solidifying and jamming the machine.

[0314] The tubular structures were tested on different parameters shown in Table 1.

TABLE-US-00001 TABLE 1 Air- conditioning Burst at Water fluid ZnCl.sub.2 125° C.* perm.** barrier*** resistance**** Ex1 CPA11/CPA610/ 150/1350/150 μm B TB OK OK CPA11 Ex2 CPA11/CPA610/ 150/1350/150 μm B TB OK OK CPA6POF Ex3 CPA11/CPA610 150/1500 μm B TB OK OK Ex4 CPA11/CPA66/ 150/1350/150 μm TB AB OK OK CPA11 Ex5 CPA11/CPA66 150/1500 μm TB AB OK OK Ex6 CPA11/CPA610/ 150/750/750 μm TB B OK OK CPA66 Ex7 CPA11/CPA610/ 150/300/750/300/150 TB B OK OK CPA66/CPA610/ CPA11 Ex8 CPA11/CPA610/ 150/1350/150 μm B TB OK OK CPA1110TPOF Counter- Monolayer 1650 μm TB Mv OK NOK Ex1 CPA66 Counter- Monolayer 1650 μm TB Mv NOK NOK Ex2 CPA66plast Counter- CPA11/ 150/1350/150 μm Mv B OK OK Ex3 CPA610POF/ CPA11 Counter- CPA11/ 150/1350/150 μm Mv B NOK OK Ex4 CPA610plast/ CPA11 Counter- CPA11/CPA66/ 450/750/450 μm Mv TB OK OK Ex5 CPA11

[0315] Example 6 consists of, from left to right, one layer (1) and two layers (2).

[0316] Example 7 consists of, from left to right, one layer (1), three successive layers (2) (total thickness of layers (2)=1350 μm), and one layer (3).

[0317] The measurement methods and values corresponding to scoring are specified in Table 2

TABLE-US-00002 TABLE 2 Very good Good Limited Poor (VG) (G) (AB) (P) (*) Burst is the burst pressure in bars of a tube at 125° C. >93 93-83 82-80 <80 conditioned in 50% water for 15 days (according to DIN 53758). (**) Water permeability. Obtained from WVTR (Water vapor <16 16-22 23-33 >33 Transmission) measurement according to ASTM E 96/E 96M - 05 on 25 μm film thickness of each layer separately. Conditions 70° C., 100% relative humidity [g/m.sup.2 .Math. 72 h] OK NOK (***) Air-conditioning fluid barrier. Calculated from Film value. <3 >3 [cm.sup.3/m.sup.2 .Math. day .Math. atm] (****) ZnCl.sub.2 resistance. Failure time after introduction of ZnCl.sub.2 200 H <1 H solution on a tube section (width of section 5 mm ± 0.2 mm and tube 8 mm*1 mm) deformed to 30% (with stress retention). Analysis of the outer layer of structures. (***) The flow measurements were performed on films of the same composition as the layers of tubular structures with a permeation cell, by a Lyssy GPM500/GC coupling at a temperature of 23° C. and 0% relative humidity. The upper face of the cell is swept by the test gas, and the flow through the film in the lower part is measured by gas chromatography. Helium is used as a vector gas sweeping the lower part.

[0318] The permeation of tubular structures is calculated by the usual permeation law for a multilayer, namely:

[00001]$\frac{e}{P}=\frac{.Math.\mathrm{ei}}{P_i}$

e and P are the thickness and permeability of the multilayer structure
ei and Pi are the thicknesses and permeabilities of each of the structure's layers

Compositions

[0319] CPA11: denotes a composition based on polyamide 11 with Mn (molecular mass by number) 29,000, containing 20% of ethylene/ethyl acrylate/anhydride type impact modifier in a mass ratio of 68.5/30/1.5 (MFI 6 at 190° C. under 2.16 kg), and of 1.2% of organic stabilizers consisting of 0.8% of phenol (Lowinox 44B25 from Great Lakes), of 0.2% of phosphite (Irgafos 168 from Ciba), of 0.2% of anti-UV (Tinuvin 312 from Ciba). The melting temperature of this composition is 190° C.

[0320] CPA610: denotes a composition based on polyamide 610 with Mn (molecular mass by number) 30,000, containing 1.2% organic stabilizers consisting of 0.8% phenol (Lowinox 44B25 from Great Lakes), 0.2% phosphite (Irgafos 168 from Ciba), 0.2% anti-UV (Tinuvin 312 from Ciba). The melting temperature of this composition is 223° C.

[0321] CPA66: denotes a composition based on polyamide 66 with Mn (molecular mass by number) 32,000, containing 1.2% of organic stabilizers consisting of 0.8% of phenol (Lowinox 44B25 from Great Lakes), of 0.2% of phosphite (Irgafos 168 from Ciba), of 0.2% of anti-UV (Tinuvin 312 from Ciba). The melting temperature of this composition is 264° C.

[0322] CPA6POF: denotes a composition based on polyamide 6 with Mn (molecular mass by number) 18,000, containing 40% of POF and 1.2% organic stabilizers consisting of 0.8% phenol (Lowinox 44B25 from Great Lakes), 0.2% phosphite (Irgafos 168 from Ciba), 0.2% anti-UV (Tinuvin 312 from Ciba). The melting temperature of this composition is 220° C.

[0323] POF: is a composition based on 50% ethylene/ethyl acrylate/maleic anhydride type impact modifier in mass ratio 68.5/30/1.5 (MFI 6 at 190° C. under 2.16 kg), 25% ethylene/methyl acrylate/epoxide (GMA type) impact modifier, glycidyl methacrylate in mass ratio 67/25/8 with MFI 6 at 190° C. under 2.16 kg, and 25% ethylene/methyl acrylate/maleic anhydride type impact modifier, in mass ratio 76/18/6 with MFI 8 at 190° C. under 2.16 kg.

[0324] CPA1110TPOF: denotes a composition based on copolyamide 10.T/11 in mass proportion 68/32, with Mn (molecular mass by number) 20,000, containing 30% of POF and 1.2% organic stabilizers consisting of 0.8% phenol (Lowinox 44B25 from Great Lakes), 0.2% phosphite (Irgafos 168 from Ciba), 0.2% anti-UV (Tinuvin 312 from Ciba). The melting temperature of this composition is 255° C. POF is a composition based on 50% ethylene/ethyl acrylate/maleic anhydride type impact modifier in mass ratio 68.5/30/1.5 (MFI 6 at 190° C. under 2.16 kg), 25% ethylene/methyl acrylate/epoxide (GMA type) impact modifier, glycidyl methacrylate in mass ratio 67/25/8 with MFI 6 at 190° C. under 2.16 kg, and 25% ethylene/methyl acrylate/maleic anhydride type impact modifier, in mass ratio 76/18/6 with MFI 8 at 190° C. under 2.16 kg.

[0325] CPA610POF: denotes a composition based on polyamide 610 with Mn (molecular mass by number) 32,000, containing 20% of POF and 1.2% organic stabilizers consisting of 0.8% phenol (Lowinox 44B25 from Great Lakes), 0.2% phosphite (Irgafos 168 from Ciba), 0.2% anti-UV (Tinuvin 312 from Ciba). The melting temperature of this composition is 223° C.

[0326] CPA66plast: denotes a composition based on polyamide 66 with Mn (molecular mass by number) 30,000, containing 6% of BBSA (butyl benzene sulfonamide) plasticizer and 1.2% organic stabilizers consisting of 0.8% phenol (Lowinox 44B25 from Great Lakes), 0.2% phosphite (Irgafos 168 from Ciba), 0.2% anti-UV (Tinuvin 312 from Ciba). The melting temperature of this composition is 260° C.

[0327] CPA610plast: denotes a composition based on polyamide 66 with Mn (molecular mass by number) 32,000, containing 6% of BBSA (butyl benzene sulfonamide) plasticizer and 1.2% organic stabilizers consisting of 0.8% phenol (Lowinox 44B25 from Great Lakes), 0.2% phosphite (Irgafos 168 from Ciba), 0.2% anti-UV (Tinuvin 312 from Ciba). The melting temperature of this composition is 219° C.