STABILIZED POLYAMIDE

Abstract

An article may include a polyamide composition comprising at least one modified polyamide produced by polymerizing polyamide precursors in a polymerization reactor to form a polyamide and adding, before, during, or at the end of polymerization, a polyhydric alcohol comprising at least three hydroxyl groups to the precursors and/or polyamide in the polymerization reactor.

Claims

1-13. (canceled)

14. An article comprising a polyamide composition comprising at least one modified polyamide produced by polymerizing polyamide precursors in a polymerization reactor to form a polyamide and adding, before, during, or at the end of polymerization, a polyhydric alcohol comprising at least three hydroxyl groups to the precursors and/or polyamide in the polymerization reactor.

15. The article of claim 14, wherein the article is a radiator tank, a transfer pipe, a thermostatic tank, a degassing tank, a radiator, a turbo pipe, an air/air exchanger, an air inlet or outlet box of a turbo cooler, an air intake collector and the associated pipework, an article of the exhaust gas recycling circuit, a catalytic converter, a part of the engine-fan group, an intermediate cooler, a cylinder head cover, an oil sump, an oil filtration unit, a distribution sump, or oil-transporting assembly pipework.

16. (canceled)

17. A polyamide composition, comprising a modified polyamide that is produced by polymerizing polyamide precursors in a polymerization reactor to form a polyamide and adding, before, during, or at the end of polymerization, a polyhydric alcohol comprising at least three hydroxyl groups to the precursors and/or polyamide in the polymerization reactor.

18. The article of claim 14, wherein the hydroxyl groups of the polyhydric alcohol are borne by aliphatic carbons of the polyhydric alcohol.

19. The article of claim 14, wherein the amount of polyhydric alcohol added before, during, or at the end the polymerization, is from 0.05% to 20% by weight of polyhydric alcohol relative to the total weight of the polyamide and/or precursors thereof.

20. The article of claim 14, wherein a mole proportion of the added polyhydric alcohol that is covalently bonded to the polyamide is between 10% and 100%.

21. The article of claim 14, wherein the polyhydric alcohol is a compound of formula (I) represented by formula (I):
R(OH)n(I) in which: n is between 3 and 8, R is a substituted or unsubstituted aliphatic, cycloaliphatic or arylalkyl hydrocarbon-based radical, optionally comprising N, S, O and/or P heteroatoms.

22. The article of claim 14, wherein the polyhydric alcohol is chosen from the group comprising: glycerol, trimethylolpropane, 2,3-bis(2-hydroxyethyl)cyclohexan-1-ol, hexane-1,2,6-triol, 1,1,1-tris(hydroxymethyl)ethane, 3 -(2-hydroxyethoxy)propane-1,2-diol, 3 -(2-hydroxypropoxy)propane-1,2-diol, 2-(2-hydroxyethoxy)hexane-1,2-diol, 6-(2-hydroxypropoxy)hexane-1,2-diol, 1,1,1-tris [(2-hydroxyethoxy)methyl]ethane, 1,1,1-tris [(2-hydroxypropoxy)methyl]propane, 1,1,1-tris(4-hydroxyphenyl)ethane, 1,1,1-tris(hydroxyphenyl)propane, 1,1,3 -tris(dihydroxy-3 -methylphenyl)propane, 1,1,4-tris(dihydroxyphenyl)butane, 1,1,5-tris(hydroxyphenyl)-3-methylpentane, di(trimethylolpropane), trimethylolpropane ethoxylate, or trimethylolpropane propoxylate; pentaerythritol, dipentaerythritol, tripentaerythritol, cyclodextrin, D-mannose, glucose, galactose, sucrose, fructose, xylose, arabinose, D-mannitol, D-sorbitol, D- or L-arabitol, xylitol, iditol, talitol, allitol, altritol, gulitol, erythritol, threitol and D-gulonic-y-lactone, and in particular from glycerol, trimethylolpropane, 2,3 -bis(2-hydroxyethyl)cyclohexan-1-ol, hexane-1,2,6-triol, 1,1,1-tris(hydroxymethyl)ethane, 3 -(2-hydroxyethoxy)propane-1,2-diol, 3-(2-hydroxypropoxy)propane-1,2-diol, 2-(2-hydroxyethoxy)hexane-1,2-diol, 6-(2-hydroxypropoxy)hexane-1 ,2-diol, 1,1,1-tris [(2-hydroxyethoxy)methyl]ethane, 1,1,1-tris [(2-hydroxypropoxy)methyl]propane, di(trimethylolpropane), trimethylolpropane ethoxylate, or trimethylolpropane propoxylate; pentaerythritol, dipentaerythritol, tripentaerythritol, cyclodextrin, D-mannose, glucose, galactose, sucrose, fructose, xylose, arabinose, D-mannitol, D-sorbitol, D- or L-arabitol, xylitol, iditol, talitol, allitol, altritol, gulitol, erythritol, threitol and D-gulonic-y-lactone.

23. The article of claim 14, wherein the polyhydric alcohol contains one or more amine functions.

24. The article of claim 14, wherein the polyhydric alcohol is tris(hydroxymethyl)aminomethane and/or a salt thereof.

25. The article of claim 14, wherein the polyamide is a semicrystalline polyamide with an apparent melt viscosity of the polyamide of between 0.5 and 1200 Pa.s, measured according to standard ISO 11443 at a shear rate of 1000 s.sup.1 at a temperature equal to 20 C. above the melting point of the polyamide.

26. The article of claim 14, wherein the polyhydric alcohol is added to the polyamide precursors in the polymerization reactor before or during polymerization of the precursors to form the polyamide.

27. The article of claim 26, wherein as compared to a polyamide made by an analogous process wherein the polyhydric alcohol is added after polymerizing the polyamide precursors, the modified polyamide exhibits improved retention of tensile strength and of impact strength after ageing for 1000 hours at 170 C.

28. The article of claim 14, wherein the polyhydric alcohol is added to the polyamide in the polymerization reactor at the end of the polymerization.

29. The article of claim 28, wherein the polyhydric alcohol is added as a molten stream to the the polyamide in the polymerization reactor just before emptying the polymerization reactor.

30. The composition of claim 17, wherein the hydroxyl groups of the polyhydric alcohol are borne by aliphatic carbons of the polyhydric alcohol.

31. The composition of claim 17, wherein the amount of polyhydric alcohol added before, during, or at the end the polymerization, is from 0.05% to 20% by weight of polyhydric alcohol relative to the total weight of the polyamide and/or precursors thereof.

32. The composition of claim 17, wherein a mole proportion of the added polyhydric alcohol that is covalently bonded to the polyamide is between 10% and 100%.

33. The composition of claim 17, wherein the polyhydric alcohol is added to the polyamide precursors in the polymerization reactor before or during polymerization of the precursors to form the polyamide.

34. The composition of claim 17, wherein as compared to a polyamide made by an analogous process wherein the polyhydric alcohol is added after polymerizing the polyamide precursors, the modified polyamide exhibits improved retention of tensile strength and of impact strength after ageing for 1000 hours at 170 C.

Description

EXPERIMENTAL PART

Characterizations

[0128] Viscosity index as a solution in formic acid (IV in mL/g) according to standard ISO 307.

[0129] Acid end group (CEG) and amine end group (AEG) content: assayed by potentiometry, expressed in meq/kg.

[0130] Melting point (Mp) and associated enthalpy (Hf), and cooling crystallization temperature (T.sub.c): determined by Differential Scanning Calorimetry (DSC), using a Perkin Elmer Pyris 1 machine, at a rate of 10 C./min.

Comparative Example 1: Preparation of a PA 66

[0131] 150 g (0.572 mol) of N salt (1:1 salt of hexamethylenediamine and adipic acid), 136 g of deionized water and 2 g of an antifoam are placed in a polymerization reactor. The polyamide 66 is manufactured according to a standard process for polymerization of polyamide 66 type with 30 minutes of finishing at 272 C. The polymer obtained is cast in the form of rods, cooled, and formed into granules by cutting up the rods.

[0132] The polymer obtained has the following characteristics: CEG=85.7 meq/kg, AEG=43.7 meq/kg, and IV of 135 mL/g.

Example 1: Preparation of a PA 66 in the presence of DPE (content of target DPE structure of 2.5% by weight in the final polyamide)

[0133] 150 g (0.572 mol) of N salt (1:1 salt of hexamethylenediamine and adipic acid), 3.6 g of 90% dipentaerythritol (DPE) supplied by Acros, comprising a mixture of 90% dipentaerythritol and 10% monopentaerythritol (MPE), i.e. 0.0127 mol of DPE and 0.0026 mol of MPE, 136.3 g of demineralized water and 2 g of an antifoam are placed in a polymerization reactor. The polyamide 66 polymerized in the presence of DPE is manufactured according to a standard process for polymerization of polyamide 66 type with 30 minutes of finishing at 272 C. The polymer obtained is cast in the form of rods, cooled, and formed into granules by cutting up the rods.

[0134] The polymer obtained presents the following characteristics: CEG=52.8 meq/kg, AEG=88.1 meq/kg. In comparison with the PA 66 synthesized without DPE, it therefore contains more amine end functions than carboxylic acid end functions, indicating that a grafting reaction has taken place bonding the DPE and MPE to the polyamide chains. The viscosity index is IV=104.6 mL/g. The polymer is semicrystalline and has the following thermal characteristics: Tc=224.5 C., Mp=261.8 C. (values identical to those of a polyamide 66).

[0135] The PA 66 polymerized in the presence of DPE has EG=CEGAEG=35.3 meq./kg as opposed to EG=CEGAEG=42 meq./kg for a PA 66 polymerized without DPE, which indicates that the DPE (and MPE) has partially reacted via its hydroxyl functions with the acid functions of the adipic acid, to a proportion of 77.3 meq./kg. The amount of hydroxyl functions provided by the DPE is (60.0127+40.0026)1000/ ((150226.34/262.34+3.6)/1000)=651 meq/kg. The mole fraction of reacted hydroxyl functions of the DPE (and MPE) is equal to the ratio of the amount of reacted hydroxyl functions to the initial amount of hydroxyl functions in the DPE and MPE, i.e. 77.3/651=12%. If equal reactivity of the hydroxyl functions is considered, this means that on average 0.7 hydroxyl function per DPE has reacted and 0.5 hydroxyl function per MPE has reacted. On average, this means that 70 mol % of the DPE is bonded and that 50 mol % of the MPE is chemically bonded to the polyamide.

Comparative Example 2: Preparation of a PA 66

[0136] 80.0 kg (304.9 mol) of N salt, 72.8 kg of demineralized water and 5.5 g antifoam Silcolapse 5020 are added to a polymerization reactor. The polyamide is manufactured according to a standard process for polymerization of polyamide 66 type with 30 minutes of finishing at 275 C. The polymer obtained is cast in the form of rods, cooled, and formed into granules by cutting up the rods.

[0137] The polymer obtained has a viscosity index of 137.5 mL/g.

Example 2: Preparation of a PA 66 in the presence of DPE (content of target DPE structure of 2% by weight in the final polyamide)

[0138] 80.0 kg (304.9 mol) of N salt, 1.38 kg (5.43 mol) of dipentaerythritol, 72.8 kg of demineralized water and 5.5 g antifoam Silcolapse 5020 are placed in a polymerization reactor. The modified polyamide DPE is manufactured according to a standard process for polymerization of polyamide 66 type with 30 minutes of finishing at 275 C. The polymer obtained is cast in the form of rods, cooled, and formed into granules by cutting up the rods. The granules have a shiny surface aspect.

[0139] The polymer obtained presents the following characteristics: CEG=54 meq/kg, AEG=79 meq/kg, and IV of 106.5 mL/g.

Example 3: Preparation of a PA 66 in the presence of DPE (content of target DPE structure of 3% by weight in the final polyamide)

[0140] 80.0 kg (304.9 mol) of N salt, 2.07 kg (8.15 mol) of dipentaerythritol, 72.8 kg of demineralized water and 5.5 g antifoam Silcolapse 5020 are placed in a polymerization reactor. The modified polyamide DPE is manufactured according to a standard process for polymerization of polyamide 66 type with 30 minutes of finishing at 275 C. The polymer obtained is cast in the form of rods, cooled, and formed into granules by cutting up the rods. The granules have a shiny surface aspect.

[0141] The polymer obtained presents the following characteristics: CEG=44 meq/kg, AEG=96 meq/kg.

Examples 4 and 5: Preparation of the Formulations

[0142] Before extrusion, the polyamide granules of examples 2 and 3 and comparative example 2 are dried to a water content below 1500 ppm. Formulations are prepared by melt-blending various components and additives in a twin-screw co-rotating Werner & Pfleiderer ZSK 40 extruder operating at 40 kg/h and at a speed of 270 rpm. The temperature settings in the 8 zones are respectively: 250, 255, 260, 260, 265, 270, 275, 280 C. All the components in the formulation are added at the start of the extruder. The rod having exited the extruder is cooled in a water tank and cut into the form of granules using a granulator and the granules are packaged in a heat-sealed bag. Before being injection molded, the granules are dried so as to obtain a moisture content of less than 1500 ppm.

[0143] The formulations obtained are as follows:

Comparative example C3: polyamide of comparative example C2+CuI/KI from AJAY Europe+glass fiber (OCV 983 from Owens Corning Vetrotex)

Comparative example C4: polyamide of comparative example C2+Dipentaerythritol from Perstorp Di-penta, named DPE+glass fiber

Example 4: polyamide of example 2+glass fiber

Example 5: polyamide of example 3+glass fiber

[0144] The formulations prepared are injected, on a Demag 50T press at 280 C. with a mold temperature of 80 C., in the form of multifunction test pieces 4 mm thick, in order to characterize the tensile mechanical properties (tensile modulus, ultimate stress, ultimate strainmean obtained on 5 samples) according to the ISO 527/1A standard and the impact mechanical properties (unnotched Charpymean obtained on 10 samples) according to the ISO 179-1/1 cU standard at 23 C. before and after thermal aging in air.

[0145] The thermal aging ventilated in air is performed by placing the test pieces in a Heraeus TK62120 incubator regulated at 170 C. or 210 C. At various aging times, test pieces are removed from the incubator, cooled to room temperature and placed in heat-sealed bags in order to prevent them from taking up any moisture before evaluation of their mechanical properties.

[0146] The retention of ultimate tensile strength or of impact strength at a given aging time is then defined relative to these same properties before aging. The retention is thus defined as a percentage.

[0147] The formulations and properties are collated in table 1 below:

TABLE-US-00001 TABLE 1 C3 C4 4 5 PA 66 64.7 63.7 (Example C2) (%) PA 66/DPE 65.0 (Example C2) (%) PA 66/DPE 65.0 (Example 3) (%) Glass fiber 35.0 35.0 35.0 35.0 OCV 983 (%) DPE (%) 1.3 CuI/KI (%) 0.04/0.26 Before aging Ultimate tensile 210.2 212.3 213.4 210.8 strength (MPa) Unnotched Charpy impact strength 90 81 65 50 (kJ/m.sup.2) After aging for 500 h at 210 C. Ultimate tensile strength (MPa) 147.9 193.7 208.5 nm Unnotched Charpy impact strength 28 42 64 nm (kJ/m.sup.2) Retention of Ultimate 70 91 98 nm tensile strength (%) Unnotched Charpy impact strength 31 52 98 nm retention (%) After aging for 1000 h at 210 C. Ultimate tensile 101 121 145 nm strength (MPa) Unnotched Charpy impact strength 16 23 44 nm (kJ/m.sup.2) Ultimate tensile strength retention (%) 48 57 68 nm Unnotched Charpy impact strength 18 28 68 nm retention (%) After aging for 1000 h at 170 C. Ultimate tensile 191.7 nm nm 202.3 strength (MPa) Unnotched Charpy impact strength 41 nm nm 44 (kJ/m.sup.2) Ultimate tensile strength retention (%) 90 nm nm 96 Unnotched Charpy impact strength 45 nm nm 88 retention (%) %: the percentages are expressed on a weight basis nm = not measured

[0148] It is thus clearly observed that the presence of DPE makes it possible to improve the impact strength retention and the ultimate tensile strength after aging at 210 C. in a ventilated oven, relative to the CuI/KI mixture. This is the desired effect. On the other hand, it is observed, entirely surprisingly, that the introduction of DPE during the polymerization gives rise to greater retention of both the tensile mechanical properties and the impact mechanical properties than when it is introduced at the time of extrusion.

[0149] In addition, the resistance to aging is also improved at 170 C. by introducing the DPE during the polymerization, relative to the CuI/KI mixture.

Example 6: Preparation of Formulations for Industrial Yarns

[0150] Before extrusion, the polyamide granules of comparative example 2 are dried to a water content below 1500 ppm. The formulation is prepared by melt-blending the additive in a twin-screw co-rotating Werner & Pfleiderer ZSK 40 extruder operating at 40 kg/h and at a speed of 270 rpm. The temperature settings in the 8 zones are, respectively: 250, 255, 260, 260, 265, 270, 275, 280 C. All the components in the formulation are added at the start of the extruder. The rod having exited the extruder is cooled in a water tank and cut into the form of granules using a granulator and the granules are packaged in a heat-sealed bag.

[0151] The formulation obtained is as follows:

Comparative example C5: polyamide of comparative example C2+

[0152] Dipentaerythritol from Perstorp Di-penta, named DPE The granules have a matt surface aspect

Examples 2 and C5 arc postcondensed in solid form in a fixed bed under a stream of nitrogen at 190 C. to increase their viscosity index before extrusion.

[0153] The extrusion of the batches is performed at 1 kg/h on a single-screw extruder 18 mm in diameter, for which the temperature settings in the 5 zones are, respectively: 280, 290, 295, 295, 300 C. The extrusion pack is equipped with a woven 10 m metallic filter 48 mm in diameter and a die with 14 holes of 0.33*4D, whose nominal temperature is set at 293 C. for example 2 and 285 C. for comparative example C5. The extrusion is performed at 450 m/min on a Barmag SW4 winder with 1% Delion F5103 on yarn as size.

[0154] The examples and properties are collated in table 2 below:

TABLE-US-00002 TABLE 2 C5 6 PA 66 98 (Example C2) (%) PA 66/DPE 100 (Example 2) (%) DPE (%) 2 Postcondensation solid (PCS) Time at 190 C. (h) 5.5 8 IV (mL/g) 189 181 Granule aspect Pronounced Shiny exudation Extrusion Pressure increase of the 1.0 No extrusion packs (b/min) increase

[0155] Thus, after postcondensation, the granules of example C5 have a very matt surface aspect due to exudation amplified by the postcondensation. The exudate, analyzed by .sup.1H NMR, is DPE. After postcondensation, the granules of example 2 still have a shiny surface aspect. The use of the additive according to the present invention thus prevents the deleterious effects of exudation of said additive: especially the fouling of the equipment and the loss of additive.

[0156] In addition, the polymer of example C5 rapidly clogs the filter of the extrusion pack, to the point that the test must be stopped prematurely. On the other hand, the polymer of the present invention presents no difficulties on extrusion.

Example 7: Preparation of a PA 66 Functionalized with Tromethamine

[0157] 150 g (0.572 mol) of N salt (1:1 salt of hexamethylenediamine and adipic acid), 2.49 g (0.017 mol) of tromethamine (THAM) supplied by Sigma-Aldridge, 1.236 g (0.0085 mol) of adipic acid, 136.3 g of demineralized water and 2 g of an antifoam are placed in a polymerization reactor. The polyamide 66 polymerized in the presence of THAM is manufactured according to a standard process for polymerization of polyamide 66 type with 5 minutes of finishing at 272 C. The polymer obtained is cast in the form of rods, cooled, and formed into granules by cutting up the rods.

[0158] The polymer obtained presents the following characteristics: AEG=140.6 meq./kg, CEG=131.1 meq./kg. The polymer is semicrystalline and has the following thermal characteristics: Tc=215.5 C., Mp=259.7 C. (values identical to those of a polyamide 66).

PA 66 polymerized in the presence of THAM has EG=CEGAEG=9.5 meq./kg as opposed to EG=CEGAEG=42 meq./kg for a PA 66 polymerized without THAM, which indicates that the THAM has reacted chemically.

Example 8: Preparation of a PA 66 in the presence of dipentaerythritol or DPE (content of target DPE structure of 3% by weight in the final polyamide)

[0159] 150 g (0.572 mol) of N salt (1:1 salt of hexamethylenediamine and adipic acid), 4.0 g (0.016 mol) of dipentaerythritol, 1.1 g (0.008 mol, i.e. 117 meq./kg of polyamide) of adipic acid, 136.3 g of demineralized water and 2 g of an antifoam are placed in a polymerization reactor. The polyamide 66 polymerized in the presence of DPE is manufactured according to a standard process for polymerization of polyamide 66 type with 30 minutes of finishing at 272 C. The polymer obtained is cast in the form of rods, cooled, and formed into granules by cutting up the rods.

[0160] The polymer obtained presents the following characteristics: CEG=80.2 meq/kg, AEG=55.8 meq/kg. PA 66 polymerized in the presence of DPE has EG=CEGAEG=24.4 meq./kg. The PA 66 of comparative example 1, polymerized without DPE or compensation with adipic acid has EG=CEGAEG=42 meq./kg, which indicates that the polyhydric alcohol has partially reacted via its hydroxyl functions with the acid functions of the adipic acid, to a proportion of 117+4224.4=135 meq./kg. Similarly to the calculation of example 1, the mean mole fraction of reacted hydroxyl functions of the polyhydric alcohol is 135/721=19%. If equal reactivity of the hydroxyl functions is considered, this means that on average 1.1 hydroxyl functions per DPE have reacted and 0.7 hydroxyl function per MPE has reacted. On average, this means that all of the DPE is bonded and that 70 mol % of the MPE is chemically bonded to the polyamide.

Example 9: Preparation of a PA 66 in the presence of tripentaerythritol or TPE (content of target TPE structure of 3% by weight in the final polyamide)

[0161] 150 g (0.572 mol) of N salt (1:1 salt of hexamethylenediamine and adipic acid), 4.0 g (0.011 mol) of tripentaerythritol, 0.8 g (0.005 mol, i.e. 80 meq./kg of PA) of adipic acid, 136.3 g of demineralized water and 2 g of an antifoam are placed in a polymerization reactor. The polyamide 66 polymerized in the presence of tripentaerythritol (TPE, Aldrich) is manufactured according to a standard process for polymerization of polyamide 66 type with 30 minutes of finishing at 272 C. The polymer obtained is cast in the form of rods, cooled, and formed into granules by cutting up the rods.

[0162] The polymer obtained presents the following characteristics: CEG=76.1 meq/kg, AEG=60.4 meq/kg. PA 66 polymerized in the presence of TPE has EG=CEGAEG=15.7 meq./kg. The PA 66 of comparative example 1, polymerized without TPE or compensation with adipic acid has EG=CEGAEG=42 meq./kg, which indicates that the polyhydric alcohol has partially reacted via its hydroxyl functions with the acid functions of the adipic acid, to a proportion of 80+4215.7=107 meq./kg. Similarly to the calculation of example 1, the mean mole fraction of reacted hydroxyl functions of the polyhydric alcohol is 107/642=17%. If equal reactivity of the hydroxyl functions is considered, this means that on average 1.3 hydroxyl functions per TPE have reacted. On average, this means that all of the TPE is chemically bonded to the polyamide.