NOVEL ROUTE FOR THE SYNTHESIS OF STATISTICAL, ALIPHATIC-AROMATIC COPOLYAMIDES, AND THE RESULTING STATISTICAL, ALIPHATIC-AROMATIC COPOLYAMIDES

Abstract

The present invention relates to a novel synthesis route that can be used to access novel statistical, aliphatic-aromatic copolyamides, by means of ring-opening polymerisation and chain-growth polycondensation, as well as to the resulting copolymers.

Claims

1. Method for preparing an aliphatic-aromatic copolyamide of formula (I): ##STR00014## where: p is an integer of between 5 and 11; n is the number average in number of aromatic units; And m is the number average in number of aliphatic units; Such that the ratio n/(n+m) is between 5 and 50%; / represents the statistical sequence of the aliphatic and aromatic units, said method comprising the reacting of: A lactam derivative of formula (II): ##STR00015## and/or one of the salts thereof, where p is defined as in formula (I); An alkyl 4-aminobenzoate of formula (III): ##STR00016## either in free form, in which case a strong base is added to the reaction mixture, or in the form of one of the salts thereof of formula (III): ##STR00017## where: R is a linear or branched C1-C6 alkyl group; and X.sup.+ is an alkali metal cation, or magnesium halide ion (MgHal.sup.+), or a phosphazenium ion (such as alkyl phosphazenium, in particular .sup.tBuP4H+); And: An activator.

2. The method according to claim 1, such that when the reaction is conducted from alkyl 4-aminobenzoate (III) in free form, the salt (III) is formed in situ via action of alkyl 4-aminobenzoate (III) with said strong acid.

3. The method according to claim 1, such that it is conducted from compounds (II) and (III) in the molten state, without solvent.

4. The method according to claim 2, such that at least 10% of salt (III) relative to the free form (III) is formed and engaged in the reaction.

5. The method according to claim 1, such that when the reaction is conducted from the salt of alkyl 4-aminobenzoate (III), the method additionally comprises the previous step of prior preparation of said salt from alkyl 4-aminobenzoate (III) and said strong base.

6. Statistical aliphatic-aromatic copolyamide of formula (I): ##STR00018## where: p is an integer of between 5 and 11; n is the number average in number of aromatic units; and m is the number average in number of aliphatic units; such that the ratio n/(n+m) is between 5 and 50%; / represents the statistical sequence of the aliphatic and aromatic units,

7. The aliphatic-aromatic copolyamide of formula (I) according to claim 6 meeting formula (I): ##STR00019## or meeting formula (I): ##STR00020## where m and n are defined as in claim 5.

8. The copolyamide according to claim 7, such that it has a glass transition temperature Tg of between 50 C. and 75 C.

9. The copolyamide according to claim 6, such that its number average molecular weight (Mn) is between 2 000 and 1 000 000 g/mol.

10. Thermoplastic composite comprising the copolyamide according to claim 6.

11. Automotive part comprising the composite according to claim 10.

Description

EXAMPLES

[0105] -caprolactam (CL) (BASF, 99%) was recrystallized from dry cyclohexane before use. The Bruggolen C20 activator (17 weight % isocyanate in CL, N, N-hexamethylenebis(2-oxo-1-azepanylcarboxamide) or hexamethylene-1-6-dicarbamoylcaprolactam in CL, Brggeman Chemical) was used as supplied. The ethyl 4-aminobenzoate (98% Aldrich) was dried by azeotropic distillation with toluene (99.9% Aldrich) and vacuum dried for 12 h. Tetrahydrofuran THF 99.9% Aldrich) was dried over sodium/benzophenone then distilled before use. The toluene was dried over CaH.sub.2, refluxed overnight, distilled and stored on polystyryllithium. Sodium bis(trimethylsilyl)amide (NaHMDS, 1.0 M in THF) was purchased from Sigma-Aldrich and used as supplied. NaHMDS can also be used in powder form (95% Aldrich) diluted in THF.

Example 1: Copolymerization from the Aromatic Monomer Salt (III) with Prior Synthesis of the Salt from the Aromatic Monomer in Free Form (III)

[0106] ##STR00012##

[0107] Synthesis of the Activated Monomer:

[0108] Ethyl 4-aminobenzoate (5.00 g; 29.55 mol) was dried with 3 dry toluene azeotropes (3*20 ml). A Schlenk tube, vacuum flame-dried and equipped with a magnetic stir bar, was charged under argon (or nitrogen) with 2.0 g (12.1 mmol) of ethyl 4-aminobenzoate subsequently solubilized in THF (10 ml). The solution was cooled to 0 C. before adding 12.5 ml of NaHMDS solution (1M) in THF. The mixture was left under agitation at 25 C. for 1 to 2 h. The mixture was used as such for copolymerization.

[0109] Polymerization Protocol:

[0110] A reactor containing a magnetic stir bar and purged under argon (or nitrogen) at 140 C. was charged with 1.00 g (6.06 mmol) of activated monomer in 4 ml of dry THF. The mixture was held at 140 C. under a stream of argon (or nitrogen) until complete evaporation of the solvent, after which E-caprolactam (CL 6.16 g, 54.55 mmol) was added under stream of argon. The mixture was left under agitation for 5-10 minutes until complete melting of E-caprolactam. The C20 activator (17% w/w of isocyanate in CL, N,Nhexamethylenebis(2-oxo-1-azepanylcarboxamide) or hexamethylene-1,6-dicarbamoylcaprolactam in CL, Brggemann Chemical) (415 mg; 0.180 mol) was then added under a stream of argon (or nitrogen) and the mixture held at 140 C. for 40 min.

[0111] The solid obtained was precipitated 3 times in THF (m=6.85 g, Yd.=90%). Targeted Mn=20 000 g.Math.mol.sup.1.

[0112] The same protocol was followed to prepare a copolymer having 25% aromatic content (by changing the molar ratios III and II).

[0113] The products obtained were analysed by NMR and exhibited the following aromatic contents:

TABLE-US-00001 Example % Aromatic (theoretical) % Aromatic (1H NMR) 1A 10 11 1B 25 16

Example 2: Properties of the Aromatic PA6s Obtained

[0114] The copolymers obtained in Example 1 were analysed by DSC. Measurements by differential scanning calorimetry (DSC) of the PA6 samples (about 10 mg) were taken with TA instrument DSC Q100 LN2, at a heating/cooling rate of 10 C./min for temperatures of between 20 C. and 250 C. under a stream of nitrogen (10 mL/min) using aluminium pans. The results were collected on and after the second pass which led to Tg values evaluated as from the inflection point of the heat capacity step change.

[0115] The results obtained are summarized in the table below:

TABLE-US-00002 Example Aromatic content Tg ( C.) Hf (J/g) Tf ( C.) 1A 11% 69 51.0 192.0 1B 16% 72 34.0 192.4

[0116] As comparative example, Example 1 was reproduced replacing ethyl 4-aminobenzoate by ethyl 4-butylaminobenzoate as aromatic monomer, applying the method described by Tunc Synthesis of functionalized polyamide 6 by anionic ring-opening polymerization, March 2016. The following results were obtained:

TABLE-US-00003 Example Aromatic content Tg ( C.) Hf (J/g) Tf ( C.) Comparative 25% 48 22.2 177

[0117] These results show that the use of ethyl 4-aminobenzoate allows an improvement in synthesis compared with ethyl 4-butylaminobenzoate in that higher Tg values are obtained with lower aromatic contents.

Example 3: Copolymerization from the Aromatic Monomer (Ill) with In Situ Synthesis of the Salt

[0118] ##STR00013##

[0119] Ethyl 4-aminobenzoate (5.00 g; 29.55 mmol) was dried with 3 dry toluene azeotropes (3*20 ml) then solubilized in dry THF (20 ml).

[0120] Deprotonation/Polymerization Protocol

[0121] A reactor containing a magnetic stir bar and purged under argon (or nitrogen) was charged with 1.00 g (6.05 mmol) of aromatic monomer in 4 ml of dry THF, NaHMDS (1M; 6.1 ml) then E-caprolactam (6.16 g; 54.45 mmol) under a stream of argon (or nitrogen). The mixture was rapidly brought to 140 C. under a stream of argon (or nitrogen). The C20 activator (415 mg; 0.180 mmol) was then added under a stream of argon (or nitrogen) and the mixture held at 140 C. for 40 min.

[0122] The solid obtained was precipitated 3 times in THF (m=6.85 g, Yd.=90%) for 10% aromatic content (theoretical).

[0123] The same protocol was followed to prepare a copolymer having 25% aromatic content (by changing the molar ratios III and II):

TABLE-US-00004 Aliphatic/aromatic composition Tg Copolymer (.sup.1H NMR) ( C.) Tm ( C.) Hm (J .Math. g.sup.1) 25% 75:25 75.0 175 42.0

Example 4: Copolymerization from the Mixture of Monomers (III and II) in the Molten State with In Situ Generation of the Salt

[0124] Ethyl 4-aminobenzoate (5.00 g; 29.55 mmol) was dried with 3 dry toluene azeotropes (3*20 ml) and used directly in powder form.

[0125] Deprotonation/Polymerization Protocol

[0126] A reactor previously heated to 140 C. containing a magnetic stir bar and purged under argon (or nitrogen) was charged with 1.00 g (6.05 mmol) of aromatic monomer followed by E-caprolactam (6.16 g, 54.45 mmol) under a stream of argon (or nitrogen). After complete melting of both reagents, NaHMDS (6.05 mmol) was added under a stream of argon (or nitrogen). The C20 activator (415 mg; 0.180 mmol) was next added under a stream of argon (or nitrogen) and the mixture held at 140 C. for 40 min.

[0127] The solid obtained was precipitated 3 times in THF (m=6.85 g, Yd.=90%) for 10% aromatic content (theoretical).

[0128] The same protocol was followed to prepare a copolymer having 5 to 20% aromatic content (by changing the molar ratios III and II).

TABLE-US-00005 Aliphatic/aromatic composition Tg Copolymer (.sup.1H NMR) ( C.) Tm ( C.) Hm (J .Math. g.sup.1) 5% 93:7 63.0 208 88.1 10% 83:17 79.0 191 78.6