Polyamide, preparation process therefor and uses thereof

Abstract

The present disclosure relates to a novel polyamide synthesized from biobased monomers. The novel polyamide comprises the repeating unit of formula I, described herein, in which R represents a covalent bond or a divalent hydrocarbon-based group chosen from saturated or unsaturated aliphatics, saturated or unsaturated cycloaliphatics, aromatics, arylaliphatics and alkylaromatics. The present disclosure also relates to a process for preparing the said polyamide, to its uses, and to articles and compositions comprising the said polyamide.

Claims

1. A polyamide comprising the repeating unit of formula I below: ##STR00005## in which R represents a covalent bond or a divalent hydrocarbon-based group chosen from saturated or unsaturated aliphatics, saturated or unsaturated cycloaliphatics, aromatics, arylaliphatics and alkylaromatics.

2. The polyamide according to claim 1, in which R is chosen from linear or branched alkyl groups having from 1 to 36 carbon atoms.

3. The polyamide according to claim 2, in which R is a linear alkyl group having from 4 to 14 carbon atoms.

4. The polyamide according to claim 1, in which R is chosen from: (CH.sub.2).sub.4, (CH.sub.2).sub.5, (CH.sub.2).sub.6, (CH.sub.2)CH(CH.sub.3)(CH.sub.2).sub.3, (CH.sub.2).sub.10 and (CH.sub.2).sub.12.

5. The polyamide according to claim 1, in which R is a divalent aromatic hydrocarbon-based group comprising from 6 to 18 carbon atoms.

6. The polyamide according to claim 5, in which R is 1,4-benzene, 1,3-benzene or (CH.sub.2)-Ph-(CH.sub.2) in positions 1,3 and 1,4.

7. The polyamide according to claim 1, wherein said polyamide is a homopolyamide consisting entirely of the repeating unit of formula I.

8. The polyamide according to claim 1, wherein said polyamide is a copolymer comprising other repeating units different from the unit of formula I.

9. The polyamide according to claim 8, wherein the repeating units different from the unit of formula I comprise comonomers selected from dicarboxylic acids, diamines, amino acids and/or lactams.

10. The polyamide according to claim 8, wherein said polyamide is a copolymer chosen from the group consisting of: PA 6T/6TF, PA10T/10TF, PA6T/6TF/66, PA66/6TF, PA12T/12TF and PA610/6TF.

11. An article obtained from the polyamide according to claim 1, the said article being a molding or extrudate, yarn, fiber, filament, or film.

12. A composition comprising at least the polyamide according to claim 1, and optionally reinforcing fillers and/or various additives.

Description

EXAMPLES

(1) Melting temperature (Tm, and associated enthalpy Hm), crystallization temperature (Tc), and glass transition (Tg) are determined by Differential Scanning calorimetry (DSC) using a Perkin Elmer Pyris 1, with heating and cooling rate of 10 C./min.

(2) Thermal stability is evaluated by Thermo-Gravimetric Analysis (TGA) under nitrogen using a Perkin Elmer TGA7, by heating a 10 mg sample from 40 C. to 600 C. at a heating rate of 10 C./min. Degradation temperature corresponding to the weight loss of 1%, 3% and 10% are recorded and respectively named Tdec1%, Tdec3% and Tdec10%.

(3) 1H NMR analysis of polyamide is achieved using a Bruker AV500 in 1,1,1,3,3,3-Hexafluoro-2-propanol-d2 or D.sub.2SO.sub.4 if deuterated HFIP is not a good solvent.

(4) Amine end-groups (AEG) and carboxylic end-groups (CEG) concentrations (in mmol/kg) are determined by titration. We calculate the average molecular weight in number Mn.sub.EG from end-grous concentration by Mn.sub.EG=2000000/(AEG+CEG).

(5) Viscosity Index (VI, in mL/g) is measured in formic acid as a solvent according to ISO307.

Example 1: Preparation of a Polyamide from 2,5-Furandicarboxylic Acid (FDCA) and Hexamethylenediamine

(6) A salt of 2,5-furandicarboxylic acid (FDCA) and of hexamethylenediamine is prepared by adding 2 g of FDCA (0.0128 mol) to 4.59 g of aqueous 32.5% hexamethylenediamine solution (0.0128 mol). Exothermicity is produced during the salification, and the reaction medium is then maintained at 50 C. for 2 hours and becomes perfectly clear. The salt is recovered and then analysed by thermogravimetric analysis coupled to an infrared detector: this involves heating the salt at 10 C./min. A substantial evolution of CO.sub.2 and of furan is detected at and above 245 C., i.e. during the melting of the salt 6FDCA, which is a sign of degradation of the 2,5-furandicarboxylic acid units. It is therefore not possible to prepare polyamides of high molecular mass via this route.

Examples 2: Preparation of Polyamides from THFDCA and Diamines

(7) A salt of hexamethylenediamine and of 2,5-tetrahydrofurandicarboxylic acid (monomer noted THFDCA or TF) is prepared by mixing at room temperature the monomers in stoichiometric amount (2 g of TF (0.0125 mol) and 1.45 g of hexamethylenediamine) in ethanol. The reaction medium is heated at 70 C. for 2 hours. After cooling, the dry salt is recovered by filtration and drying. This is the salt named 6TF.

(8) A salt of 1,10-diaminodecane and of 2,5-tetrahydrofurandicarboxylic acid is prepared by mixing at room temperature the monomers in stoichiometric amount (2 g of TF (0.0125 mol) and 2.153 g of 1,10-diaminodecane) at 20% in water. The reaction medium is heated at 70 C. for 2 hours. After cooling, the dry salt is recovered by filtration and drying. This is the salt named 10TF.

(9) Each salt is heated above its melting point and the amidation reaction takes place. The polyamides obtained have satisfactory thermal characteristics.

Example 3: Synthesis of Homopolyamides by Diester Route

(10) Dimethyl 2,5-tetrahydrofuranoate cis/trans 90/10 (named dmTHFDCA cis/trans 90/10) is synthesized as follows. In a 3 L flask equipped with a reflux condenser and a thermometer furan-2,5-dicarboxylic acid (FDCA) (200 g, 1.28 mol), H.sub.2SO.sub.4 (98%, 90 ml) were dissolved in 1.4 L of methanol. The reaction mixture was stirred under reflux for 22 h. After cooling to R.T, the mixture was concentrated in vacuum and the residue was dissolved in 1.5 L of DCM. The obtained solution was washed by water (2400 ml), saturated NaHCO.sub.3 solution (2300 ml), and brine (2300 ml). The organic layer was dried and concentrated in vacuum to give 203 g of white solid (86% yield), and the solid was used for next step without further purification.

(11) In a 5 L Parr reactor the white solid obtained (250 g, 1.36 mol), Pd/C (10%, 25.0 g) were suspended in 2.5 L of methanol. The reaction mixture was stirred at 50 C. under an atmosphere of hydrogen at 20 bar, and monitored by LC/MS. When the reaction is completed the mixture was filtered through silica gel and the filtrate was concentrated in vacuo and distilled under reduced pressure to give 228 g of colorless oil (85 C./50 Pa, 89% yield).

(12) 2,5-tetrahydrofurandicarboxylic acid cis/trans 90/10 (named THFDCA) is synthesized as follows. In a 50 ml round-bottomed flask equipped with a reflux condenser the dmTHFDCA (1 g, 5.3 mmol) was dissolved in 1 ml of TFA and 5 ml of water. The mixture was heated at 100 C. and monitored by LC-MS. When the reaction is completed the mixture was concentrated under vacuum to give 0.78 g of white solid (92% yield). If necessary the product would be further purified by recrystallization.

(13) We synthesize polyamides starting from dimethyl 2,5-tetrahydrofuranoate cis/trans 90/10 (named dmTHFDCA cis/trans 90/10) and a stoichiometric amount of a diamine. Diamines evaluated are: hexamethylene diamine, 1,10-diaminodecane, 1,4-diaminobutane, meta-xylylene diamine, isophorone diamine, 1,3-bis(aminomethyl)cyclohexane and 4,4-Methylenebis(2-methylcyclohexylamine) mixture of isomers all supplied by Sigma-Aldrich.

(14) The same method is used to synthesize all the different polyamides. Here is described the method used for the synthesis of PA 10TF.

(15) In a glass reactor is introduced 16,002 g of dmTHFDCA cis/trans 90/10 prepared by ourselves according to the procedure described (purity 98%, 0.083 mol) and 14,666 g of 1,10-diaminodecane (purity 98%, 0.083 mol). Nitrogen blanket is then used and the monomers are stirred using a mechanical stirrer. The glass reactor is immersed in a heating bath regulated at 80 C. and then heated to final temperature (230 C.) with heating rate of 1.5 C./min. Methanol produced during the reaction between the diester and the diamine (beginning of the appearance of boiling in the reaction mixture when bath is at 90 C.) is removed by distillation. When the reactor is at final temperature, pressure in the glass reactor is decreased to about 60 mbar and maintained under vacuum during 30 minutes. Nitrogen is introduced to come back to atmospheric pressure, stirring is stopped and the glass reactor removed from heating bath to cool the reaction mixture. A yellowish transparent solid is recovered.

(16) 1H NMR analysis in deuterated HFIP confirms the reaction between THFDCA and 1,10-diaminodecane. Thermal properties analysis shows that the PA 10TF.sub.cis/trans90/10 is an amorphous solid with Tg=47 C. and has a very good thermal stability up to more than 280 C., giving a broad processing window between Tg and Tdec1%.

(17) A similar method is used for the synthesis of polyamides with dmTHFDCA cis/trans 90/10 and various diamines. Thermal properties of the homopolyamides are reported in Table 1.

(18) In any case, all homopolyamides are all yellowish transparent amorphous solids with Tg up to 162 C., depending on the rigidity of the diamine used. They can compete with other existing commercial amorphous polyamides.

(19) TABLE-US-00001 TABLE 1 Properties of homopolyamides synthesized using dmTHFDCA cis/trans 90/10. Tg Tdec1% Tdec3% Tdec10% Diamine C. C. C. C. PA 4TF 1,4-diamino butane 92 291 327 362 PA 6TF Hexamethylene diamine 65 283 342 381 PA 10TF 1,10 diamino decane 47 285 351 393 PA 1,3-BAMCTF 1,3-bis(aminomethyl) 133 296 336 377 cyclohexane mixture of isomers PA MXDTF Meta-xylylene diamine 117 306 335 355 PA ISOTF Isophorone diamine 143 N.D. N.D. N.D. PA MBMCTF 4,4-Methylenebis(2- 162 N.D. N.D. N.D. methylcyclohexylamine) mixture of isomers

Example 4: Synthesis of PA 66/6TF Copolyamides Using Salt Route

(20) We use a sample of THFDCA cis/trans 95/5 for the synthesis of PA 66/6TF 95/5, 90/10 and 80/20 mol/mol. Polymerization of theses copolyamides is achieved using a classical PA 66 synthesis process: we prepare an aqueous salt composed with diacids mixtures (adipic acid and THFDCA) and hexamethylene diamine at a concentration of 52 wt.-% in water and 70 C., we concentrate the aqueous salt up to 70 wt.-% under atmospheric pressure by removing water by heating, we then heat the reactor under 17.5 bar pressure (distillation of water under pressure), we depressurize to atmospheric pressure when the temperature of the reaction mixture reaches 250 C. and we finish the reaction at 272 C. during 30 min at atmospheric pressure. The copolyamides are extruded from the reactor under pressure, cooled in a cold water bath to get a strand and then pelletized.

(21) For PA 66/6TF 95/5 mol/mol, we started the reaction by mixing 142.62 g (0.544 mol) of Nylon 66 salt (stoichiometric salt of adipic acid and hexamethylene diamine), 11.78 g (0.0330 mol) of hexamethylene diamine at 32.5% in water, 4.57 g (0.029 mol) of THFDCA, 130 g of water and 2 g of an anti-foaming agent.

(22) For PA 66/6TF 90/10 mol/mol, we started the reaction by mixing 134.48 g (0.513 mol) of Nylon 66 salt (stoichiometric salt of adipic acid and hexamethylene diamine), 20.50 g (0.057 mol) of hexamethylene diamine at 32.5% in water, 9.12 g (0.057 mol) of THFDCA, 124 g of water and 2 g of an anti-foaming agent.

(23) For PA 66/6TF 80/20 mol/mol, we started the reaction by mixing 118.96 g (0.453 mol) of Nylon 66 salt (stoichiometric salt of adipic acid and hexamethylene diamine), 40.55 g (0.113 mol) of hexamethylene diamine at 32.5% in water, 18.13 g (0.113 mol) of THFDCA, 109 g of water and 2 g of an anti-foaming agent.

(24) Properties of these copolyamides are reported in Table 2.

(25) The more THFDCA is included in PA 66 chains, the lower the Tm, Hm and Tc. We generally use comonomers to decrease the crystallization kinetics to get molded part having a better surface aspect or for fiber spinning. As a comparison, a PA 66/6I 80/20 mol/mol (I=isophthalic acid) synthesized using the same method 80/20 mol/mol has the following thermal properties: Tm=240 C., Tc=193 C. and Tg=76 C. PA 66 copolyamides having THFDCA or isophthalic acid as comonomers in similar content exhibit similar crystallization kinetics but THFDCA doesn't increase Tg.

(26) We observed in our conditions that the cis/trans ratio of THFDCA changed from 95/5 to 82/18 mol/mol after the synthesis of PA 66/6TF 80/20 mol/mol.

(27) TABLE-US-00002 TABLE 2 Properties of copolyamides synthesized using THFDCA cis/trans 95/5. CEG AEG meq/ meq/ Mn.sub.-EG IV Tm Tc Tg* kg kg g/mol mL/g C. Hm C. C. PA 66 80 50 15390 129 262 65 220 67 PA 66/6TF 58.5 109 11940 105.9 255 63 211 69 95/5 mol/ mol PA 66/6TF 74.6 105 11140 97.7 250 56 206 68 90/10 mol/ mol PA 66/6TF 85 159.9 8170 74.1 237 45 188 66 80/20 mol/ mol *Determined at 40 C./min

(28) Pellets of copolyamides are then dried during 16 h at 90 C. under vacuum before being submitted to injection molding to get specimens (bars 90131.6 mm.sup.3) using a micro-extruder DSM MIDI 2000 with barrel temperature at 280 C. and mould temperature at 70 C.

(29) Water absorption (RH100, 23 C., saturation) of the copolyamides is analyzed by placing the specimens in water at room temperature and by following the weight of the specimens until no change in weight is observed. Water absorption is determined by calculating (mfmi)/mi, with mi=initial weight of the specimen before the test (dry), mf=final weight when the specimen is saturated with water.

(30) PA 66/6THF 100/0, 95/5, 90/10 and 80/20 mol/mol respectively absorb 8.5 wt.-%, 9.9 wt.-%, 11 wt.-%, 14 wt.-% of water. It is higher than water absorption obtain with isophthalic acid as a comonomer. These copolymers would be interesting to increase the moisture absorption of textile fiber to bring higher comfort.

Example 5: Synthesis of Polyphthalamide Copolyamide Using Salt Route

(31) We synthesized PA 6T/6TF 50/50 mol/mol and PA 10T/10TF 60/40 mol/mol using an aqueous salt route. We use a sample of THFDCA cis/trans 95/5 for these syntheses.

(32) Polymerization of theses copolyamides is achieved using a classical PA 66 synthesis process with a few modifications: we prepare an aqueous salt composed with diacids mixtures (terephthalic acid and THFDCA) and diamine at a concentration of 52 wt.-% in water and 70 C., we close the reactor and we heat the reactor under 17.5 bar pressure (distillation of water under pressure), we depressurize to atmospheric pressure when the temperature of the reaction mixture reach 260 C. and we finish the reaction at 290 C. during 10 min at atmospheric pressure. The copolyamides are extruded from the reactor, cooled in a cold water bath to get a strand and then pelletized.

(33) For PA 6T/6TF 50/50 mol/mol, we started the reaction by mixing 49.89 g (0.1767 mol) of Nylon 6T salt (stoichiometric salt of terephthalic acid and hexamethylene diamine), 66.61 g (0.1768 mol) of hexamethylene diamine at 30.85% in water, 28.34 g (0.177 mol) of THFDCA, 43.9 g of water and 2 g of an anti-foaming agent.

(34) For PA 10T/10TF 60/40 mol/mol, we started the reaction by mixing 28.61 g (0.172 mol) of terephthalic acid, 50.39 g (0.287 mol) of 1,10-diaminodecane (purity=98%), 18.39 g (0.115 mol) of THFDCA, 86.62 g of water and 2 g of an anti-foaming agent.

(35) TABLE-US-00003 TABLE 3 Properties of copolyamides synthesized using THFDCA cis/trans 95/5. Tm Tc Tg* C. Hm C. C. PA 6T/6TF 50/50 mol/mol 273 10 231 104 PA 10T/10TF 60/40 mol/mol 241/256 29 222 84 *Determined at 10 C./min

(36) THFDCA can be used in polyphthalamide to modulate the thermal properties of PA 6T and PA 10T.