Piperidine-containing semi-aromatic polyamide

TECHNICAL FIELD OF THE INVENTION

The present invention relates to non-crosslinked polyamides comprising structural units derived from piperidine and an aromatic dicarboxylic acid. The invention further relates to a method of preparing such polyamides, molded articles comprising such polyamides and thermoplastic composites comprising such polyamides.

BACKGROUND

Synthetic linear polyamides are generally prepared by condensation of substantially equimolecular amounts of a diamine and a dicarboxylic acid, or its amide-forming derivatives or by the self-condensation of relatively long chain amino acids or their amide- forming derivatives.

According to the composition of their main chain, polyamides can be classified as aliphatic polyamides, like PA6.6 being prepared from hexamethylenediamine and adipic acid, semi-aromatic polyamides, like PA6.T being prepared from hexamethylenediamine and terephthalic acid, and aromatic polyamides being prepared, for example, from phenylenediamine and terephthalic acid. The mechanical properties of polyamides depend on their molecular weight and the constitution of their monomers, i.e. the selection of the diamines and diacids. Despite the large number of known polyamides having a wide range of mechanical properties, there is still a need for further improvements, for example with respect to the glass transition temperature which should not be too high and the ultimate tensile strength (maximum stress) which for certain applications should be high. For example, the known polyamide PA6.I, which is prepared from hexamethylenediamine and isophthalic acid, has a desirable glass transition temperature of about l20°C but an undesirably low maximum stress. On the other hand, the present inventors found that replacing the hexamethylenediamine residue in PA6.I by a piperazine residue, as for example suggested in US 4,223,105, results in polymers having an undesirable high glass transition temperature of about 2l4°C.

It is therefore an object of the present invention to provide novel polyamides which overcome one or more of the drawbacks of the known polyamides, in particular with respect to their glass transition temperature and mechanical properties, such as their ultimate tensile strength. At the same time, the polyamides should have a low melt viscosity to facilitate molding. SUMMARY

An aspect of the present invention provides a polyamide which is non- crosslinked and which comprises structural units of formula (1):

A further aspect of the invention provides a method of preparing such polyamide, a molded article comprising such polyamide and a thermoplastic composition comprising such polyamide and fibers, such as glass or carbon fibers.

DETAILED DESCRIPTION

The present inventors found that by replacing the piperazine residues in the polyamides known in the prior art by piperidine residues not only the glass transition temperature of the obtained polymer can be significantly decreased but at the same time the ultimate tensile strength of the polymer can be significantly increased compared to the ultimate tensile strength of the known polyamide PA6.I.

The present invention therefore relates of a non-crosslinked polyamide comprising structural units of formula (1):

Here, and throughout the invention any bond crossing a ring structure means that the following atom is connected to any position of the ring by replacing a hydrogen atom. For example, in formula (1), the next (not shown) atom to which the pyridine ring is linked may be attached at 2-, 3- or 4-position relative to the nitrogen atom. The next (not shown) atom to which the phenyl ring is linked may be attached at ortho, meta or para position relative to the carboxy group.

In one embodiment, the polyamide according to the invention comprises structural units of formula (2):

wherein R ¹ is hydrogen, an organic monovalent residue, or an organic divalent residue which forms a ring together with R ² , and

R ² and R ³ are independently a bond or an organic divalent residue.

In the above structural unit of formula (2), R ¹ preferably is hydrogen or a linear, branched, cyclic and/or aromatic Ci_3o hydrocarbon residue. Optionally, this residue may form a ring together with R ² . If such ring is formed, any atom of the R ¹ hydrocarbon residue may be attached to any atom of R ² .

In the context of the present invention the term "hydrocarbon residue" is understood as a residue which mainly consists of carbon and hydrogen atoms. It is, however, also possible that the hydrocarbon residue contains heteroatoms, such as O, N, P, S, etc. In a preferred embodiment, the hydrocarbon residue consists of carbon and hydrogen atoms.

R ² and R ³ may independently be a bond or a linear, branched, cyclic and/or aromatic Ci_3o hydrocarbon residue, wherein the hydrocarbon residue is defined as above.

In a preferred embodiment, R ¹ in the structural unit of formula (2) is hydrogen or a linear, branched, cyclic and/or aromatic Ci_3o hydrocarbon residue which optionally forms a ring together with R ² , and R ² and R ³ are independently a bond or a linear, branched, cyclic and/or aromatic Ci_3o hydrocarbon residue.

In a further embodiment, R ¹ is hydrogen or a Ci_ ₆ alkyl residue, which optionally forms a ring together with R ² , R ² is a bond or a linear, branched and/or cyclic Ci_ 24 alkyl residue, preferably a bond or a linear Ci_ ₂₄ alkyl residue, more preferably a bond or a Ci_ ₆ alkyl residue, and R ³ is a bond, a Ci_ ₆ alkylaryl residue or an aryl residue preferably a bond or a phenyl residue. The polyamide according to the invention may comprise other structural units in addition to the above structural units. For example, the polyamide may comprise additional structural units being derived from caprolactame, hexamethylenediamine, phenylenediamine, adipic acid, etc. It is, however, preferred that such additional structural units are present in an amount of less than 50 %, preferably less than 30 % and even more preferably of less than 20 % of the total number of structural units in the polyamide. More preferably, the polyamide is a homopolymer which consists of structural units of formula (2). The polyamide according to the invention is obtainable by polymerization of a diamine of formula (3):

wherein R ¹ and R ² are defined as above, with an aromatic dicarboxylic acid, or ester of formula (4):

wherein R ³ is defined as above and X is hydroxy, Ci_ ₆ alkoxy or C2-20 aryloxy, preferably phenoxy.

In one embodiment, the diamine from which the polyamide according to the invention is obtainable has the formula (5):

wherein R ² is defined as above. Preferably, R ² is attached at 2- or 4-position of the piperidine ring. In another embodiment, the diamine, from which the polyamide according to the invention is obtainable has the formula (6):

wherein R ⁴ is a bond or a linear, branched and/or cyclic Ci_ ₂₄ alkyl residue, preferably a bond or a linear Ci_ ₂₄ alkyl residue.

In a preferred embodiment, the diamine from which the polyamide according to the invention is obtainable has the formula (7):

wherein n is an integer of 0 to 24, preferably 0 to 16, more preferably 2 to 16, even more preferably 3 to 10.

The aromatic dicarboxylic acid or ester from which the polyamide according to the invention can be obtained is not particularly limited and can be selected from known aromatic dicarboxylic acids and their derivatives. In a preferred embodiment, the dicarboxylic acid or ester has the above formula (4) wherein in a more preferred embodiment R ³ is a bond or aryl, even more preferably a bond or phenyl.

Examples of suitable diamines, from which the polyamide according to the invention can be obtained are 4,4'-bipiperidine, 4,4'-ethylenedipiperidine, 4,4'- trimethylenedipiperidine, 4-aminopiperidine, 4-(aminomethyl)piperidine, 2- (aminomethyl)piperidine, 3-(aminoethyl)piperidine, and 4- (aminobutyl)piperidine. Preferred diamines are 4,4'-trimethylenedipiperidine and 4-aminopiperidine.

Examples of suitable dicarboxylic acids from which the poylamide according to the invention can be obtained are isophthalic acid, terephthalic acid, diphenic acid, and biphenyl-4, 4’-dicarboxylic acid, among which isophthalic acid, terephthalic acid and diphenic acid are preferred.

The molecular weight of the polyamide according to the invention is not particularly limited and can be selected by the skilled person according to the requirements. It is, however, preferred that the number average molecular weight (Mn) of the polyamide is higher than 2,500 g/mol, preferably higher than 3,000 g/mol. On the other hand, in view of its moldability and mechanical properties the molecular weight of the polyamide should not exceed a certain limit. Therefore, the number average molecular weight (Mn) should be lower than 10,000 g/mol, preferably lower than 8,000 g/mol and even more preferably lower than 7,000 g/mol. The number average molecular weight (Mn) may range from 2,500 to 12,000 g/mol, notably from 2,500 to 10,000 g/mol, particularly from 3,000 to 10,000 g/mol. The number average molecular weight (Mn) of the polyamide may be calculated by end group analysis.

Th polyamide may also have a number average molecular weight (Mn) comprised from 6000 to 30000 g/mol, in particular from 10000 to 20000 g/mol, as notably determined by Size Exclusion Chromatography. The polyamide may have a weight-average molecular weight (Mw) comprised from 20000 to 150000 g/mol, in particular from 30000 to 100000 g/mol, as notably determined by Size Exclusion Chromatography. Preferably the Polydispersity Index, as a measure of the broadness of a molecular weight, defined by Mw/Mn ratio is comprised from 2 to 10, preferably from 2 to 8.

By determined by Size Exclusion Chromatography is meant a determination as follows: The Size Exclusion Chromatography for measuring relative molecular weights is performed in Hexafluoroisopropanol (HFIP) with 25 mM sodium trifluoroacetate (0.225 % w/w sodium trifluoro acetate in HFIP) as a solvent at 40°C, followed by refractometry RE Determination of the relative molecular weight and molecular weight distribution is realised by a conventional calibration with polymethylmethacrylate standards (PMMA).

One advantage of the polyamides according to the invention is their low glass transition temperature. Preferably, the glass transition temperature of the polyamide is below 2lO°C, more preferably below l80°C and even more preferably below l50°C.

The polyamide according to the invention may be prepared according to any method usual for the preparation of polyamides known to a person skilled in the art. For example, the polyamide can be prepared by a method which comprises the step of polymerizing a diamine of formula (3): wherein R ¹ and R ² are defined as above, with an aromatic dicarboxylic acid or ester of formula (4):

wherein R ³ is defined as above and X is hydroxy, Ci_ ₆ alkoxy or Ci_ ₂ o aryloxy, preferably phenoxy.

The present invention concerns then a method of preparing a non-crosslinked polyamide comprising structural units of formula (1):

which comprises the step of polymerizing at least a diamine of formula (3):

wherein R ¹ is hydrogen, an organic monovalent residue, or an organic divalent residue which forms a ring together with R ² , and R ² is a bond or an organic divalent residue;

with an aromatic dicarboxylic acid, or ester of formula (4): wherein R ³ is a bond or an organic divalent residue and X is hydroxy, Ci_ ₆ alkoxy or Ci_ ₂ o aryloxy.

The present invention also concerns a polyamide susceptible to be obtained by the method according to the invention.

Method of the present invention permits notably to produce a non-crosslinked polyamide comprising structural units of formula (2):

wherein R ¹ is hydrogen, an organic monovalent residue, or an organic divalent residue which forms a ring together with R ² , and

R ² and R ³ are independently a bond or an organic divalent residue.

Without otherwise specified, in the instant specification polyamide means homopolyamide or copolyamide.

The polyamide may be amorphous or semi-crystalline. By semi-crystalline is meant a polyamide having an amorphous phase and a crystalline phase, in particular the degree of crystallinity is in the range of 1 to 85%. What is meant by amorphous is a polyamide having no crystalline phase detected by thermal analysis, such as DSC (Differential Scanning Calorimetry) and with X-ray diffraction. Heat of fusion (DHί) may range from 2 to 170 J/g as measured according to ASTM D3418 using a heating and cooling rate of 20 °C/min.

By thermoplastic polyamide is meant a polyamide having a temperature above which the material is softening and melts without being degraded and which is hardening below such a temperature. The polyamide may comprise an amount of repeating units of formula (1), comprising at least one amide bond, from 2 to 100%, preferably from 10 to 100% relative to the total number of repeating units in the polyamide.

In the instant specification homopolyamide means a polyamide comprising an amount of one repeating unit of at least 95% relative to the total number of repeating units in the polyamide. On the other hand copolyamide means a polyamide comprising less than 95% of one repeating unit relative to the total number of repeating units in the polyamide.

Advantageously, the polyamide is thermoplastic. The polyamide may be amorphous; in this case it may have a Tg£280°C. The polyamide may also semi crystalline, and may have a Tm of less or equal to 370°C, notably less or equal to 350°C, particularly comprised from l50°C to 370°C.

In one embodiment, the diamine from which the polyamide according to the invention is obtainable has the formula (5):

wherein R ² is defined as above. Preferably, R ² is attached at 2- or 4-position of the piperidine ring.

In another embodiment, the diamine, from which the polyamide according to the invention is obtainable has the formula (6):

wherein R ⁴ is a bond or a linear, branched and/or cyclic Ci_ ₂₄ alkyl residue, preferably a bond or a linear Ci_ ₂₄ alkyl residue.

In a preferred embodiment, the diamine from which the polyamide according to the invention is obtainable has the formula (7): wherein n is an integer of 0 to 24, preferably 0 to 16, more preferably 2 to 16, even more preferably 3 to 10.

Examples of suitable diamines, from which the polyamide according to the invention can be obtained are 4,4'-bipiperidine, 4,4'-ethylenedipiperidine, 4,4'- trimethylenedipiperidine, 4-aminopiperidine, 4-(aminomethyl)piperidine, 2- (aminomethyl)piperidine, 3-(aminoethyl)piperidine, and 4-

(aminobutyl)piperidine. Preferred diamines are 4,4'-trimethylenedipiperidine and 4-aminopiperidine.

The amount of diamine of formula (3) may be comprised from 2 to 100 mol %, preferably from 10 to 100 mol % relative to the total amount of diamine monomers in the polyamide.

The amount of repetitive units of formula (1) may be comprised from 2 to 100 mol %, preferably from 10 to 100 mol % relative to the total amount of repetitive units in the polyamide.

The polyamide may also comprise at least one other diamine. This diamine may respond to the following formula H2N-R-NH2 wherein R is an aliphatic, an aromatic, an arylaliphatic or an alkylaromatic radical. In particular the diamine R radical, especially when free of heteroatom such as oxygen, comprises from 1 to 36 carbon atoms and more particularly from 4 to 14 carbon atoms.

By“arylaliphatic” is meant a radical comprising an aromatic cycle and which is linked to the main chain of the polymer by bonds on the aliphatic part, such as the radical meta-xylylene, for example deriving from meta-xylylene diamine. By“alkylaromatic” is meant a radical substituted by alkyl radical(s) and which is linked to the main chain of the polymer by bonds on the aromatic part.

The radical R of the diamine may be free of heteroatom, or may comprise a heteroaom, such as oxygen, nitrogen, phosphorus or sulphur, in particular oxygen or sulphur, and more particularly oxygen. When a heteroatom is present it may:

-interrupt the chain of the radical, for example as an ether function,

-be in a functional group interrupting the chain of the radical, such as carbonyl or sulfone function, and/or -be in a function grafted on the chain, such as a hydroxyl, sulfonic or sulfonate functions.

When the R radical is aliphatic it may be free of heteroatom. The aliphatic radical may be alicyclic or cycloaliphatic.

The diamines comprising an alicyclic aliphatic radical may comprise from 2 to 12 carbon atoms, they may be chosen from l,2-diaminoethane, 1,3- diaminopropane, 1, 3-diamino butane, 1 ,4-diaminobutane, l,5-diaminopentane, 1, 6-diamino hexane or hexamethylene diamine (HMD), 2-methyl pentamethylene diamine, 2-methyl hexamethylene diamine, 3 -methyl hexamethylene diamine, 2,5-dimethyl hexamethylene diamine, 2,2-dimethylpentamethylene diamine, 1,8- diaminooctane, methyl- 1, 8-diamino octane, in particular as the mixture of methyl- 1, 8-diamino octane and 1, 9-diamino nonane sold by Kuraray, 1,9- diamino nonane, 5-methylnonane diamine, l,lO-diamino decane or decamethylenediamine, 1,12-diamino dodecane, or dodecamethylene diamine, 2,2,4-trimethyl hexamethylene diamine and/or 2,4,4-trimethyl hexamethylene diamine, and/or 2,2,7,7-tetramethyl octamethylene diamine.

The aliphatic radical R may be a cycloaliphatic radical, in particular mono- or di- cyclic. Each cycle may comprise from 4 to 8 carbon atoms, more particularly the cycle comprise 4, 5 or 6 carbon atoms. The cycloaliphatic radical may be saturated or unsaturated, and may comprise one or two double bonds. The cycloaliphatic radical may comprise from 6 to 12 carbon atoms. Among the cycloaliphatic diamines may be cited 1 ,2-diaminocyclo hexane, 1,3- diaminocyclo hexane, 1 ,4-diaminocyclo hexane, in particular trans stereoisomer, the 4,4'-methylenebis(cyclohexyl amine), l,3-bis(aminomethyl)cyclo hexane, 1 ,4-bis(aminomethyl)cyclo hexane, diaminodicyclo hexyl-methane, isophoronediamine, C36 diamine dimer, and 2,5- bis(aminomethyl)tetrahydrofuran, being cis, trans or a mixture of the stereoisomers.

The aliphatic radical R may also comprise at least one heteroatom, in particular oxygen. Among this type of radical may be cited polyether diamines such as Jeffamine® and Elastamine®, from Huntsman, in particular having a molecular weight ranging from 100 to 5000 g/mol.

The diamine R radical may be aromatic, arylaliphatic or alkylaromatic, it may comprise from 6 to 24 carbon atoms, in particular from 6 to 18 carbon atoms and more particularly from 6 to 10 carbon atoms. It may be a mono- or di-cyclo compound, such as benzene or naphthalene. The aromatic, arylaliphatic or alkylaromatic diamine may be chosen from diaminodiphenylmethane and its isomers, sulfonyl dianiline and its isomers, 3,4'- oxydianiline also called 3,4'-diaminodiphenyl ether, l,3-bis-(4- aminophenoxy)benzene, l,3-bis-(3-aminophenoxy)benzene ; 4,4'-oxydianiline also called 4,4'-diaminodiphenyl ether, l,4-diaminobenzene, 1,3- diaminobenzene, l,2-diaminobenzene, 2,2'-bis(trifluoromethyl)benzidene, 4,4'- diaminobiphenyl; 4,4'-diaminodiphenyl sulphide, 9,9'-bis(4-amino)fluorene; 4,4'-diaminodiphenyl propane, 4,4'-diaminodiphenyl methane, benzidine, 3,3'- dichlorobenzidine, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 1, 5-diamino naphthalene, 4,4'-diaminodiphenyl diethylsilane, 4,4'-diamino diphenysilane, 4,4'-diaminodiphenyl ethyl phosphine oxide, 4,4'-diamino diphenyl N-methyl amine, 4,4'-diamino diphenyl N-phenyl amine, m-phenylene diamine, p-phenylene diamine, m-xylylenediamine, p-xylylendiamine, and 2,5- bis(aminomethyl)furan.

In particular the diamine is chosen from m-phenylene diamine, p-phenylene diamine, m-xylylenediamine, p-xylylenediamine, hexamethylenediamine, 2- methylpentamethylene-diamine, 1 , 10-diaminodecane, 1 , 12-diaminododecane, diaminodiphenylmethane and sulfonyldianiline.

The aromatic dicarboxylic acid or ester from which the polyamide according to the invention can be obtained is not particularly limited and can be selected from known aromatic dicarboxylic acids and their derivatives. In a preferred embodiment, the dicarboxylic acid or ester has the above formula (4) wherein in a more preferred embodiment R ³ is a bond or aryl, even more preferably a bond or phenyl.

The dicarboxylic acid may be an aromatic diacid [acid (AR)], in particular chosen from isophthalic acid, terephthalic acid, orthophthalic acid, naphthalene dicarboxylic acid, more particularly 2,6-napthalene dicarboxylic acid, 2,7- napthalene dicarboxylic acid, 1 ,4-napthalene dicarboxylic acid, 2,3-napthalene dicarboxylic acid, l,8-napthalene dicarboxylic acid, and 1 ,2-napthalene dicarboxylic acid, 2,5-pyridine dicarboxylic acid, 2,4-pyridine dicarboxylic acid, 3,5-pyridine dicarboxylic acid, 2,2-bis-(4-carboxyphenyl)propane, bis(4- carboxyphenyl)methane, 2,2-bis-(4-carboxyphenyl)hexafluoropropane, 2,2-bis- (4-carboxyphenyl)ketone, 4,4'-bis(4-carboxyphenyl)sulfone, 2,2-bis(3- carboxyphenyl)propane, bis(3-carboxyphenyl)methane, 2,2-bis-(3- carboxyphenyl)hexafluoropropane, 2,2-bis-(3-carboxyphenyl)ketone, bis(3- carboxyphenyl)methane and 4,4'-biphenyl dicarboxylic acid, 2- hydroxyterephthalic acid, 5-hydroxyisophthalic acid, 4-hydroxyisophthalic acid, 2,5-dihydroxyterephthalic acid, sodium 5-sulfoisophthalate, or AISNa, lithium 5- sulfoisophthalate, or AISLi, potassium 5-sulfoisophthalate, or AISK, and 2,5- furandicarboxylic acid.

Examples of suitable dicarboxylic acids from which the poylamide according to the invention can be obtained are isophthalic acid, terephthalic acid, diphenic acid, and biphenyl-4, 4'-dicarboxylic acid, among which isophthalic acid, terephthalic acid and diphenic acid are preferred.

The polyamide mays also comprise also at least one, in particular one or two, and more particularly one dicarboxylic acid.

The dicarboxylic acid may be an aliphatic diacid [acid (AL), herein after], in particular alicyclic, and more particularly chosen from oxalic acid (HOOC— COOH), malonic acid (HOOC— CH _2— COOH), succinic acid (HOOC— (CH ₂ ) _2— COOH), glutaric acid (HOOC— (CH ₂ ) _3— COOH), 2-methyl-glutaric acid (HOOC— CH(CH ₃ )— (CH ₂ ) _2— COOH), 2,2-dimethyl-glutaric acid

(HOOC— C(CH ₃ ) _2— (CH ₂ ) _2— COOH), adipic acid (HOOC— (CH ₂ ) _4— COOH), 2,4,4-trimethyl-adipicacid (HOOC— CH(CH ₃ )— CH _2— C(CH ₃ ) _2— CH _2—

COOH), pimelic acid (HOOC— (CH ₂ ) _5— COOH), suberic acid (HOOC— (CH ₂ ) _6— COOH), azelaic acid (HOOC— (CH ₂ ) _7— COOH), sebacic acid (HOOC— (CH ₂ ) _8— COOH), undecanedioic acid (HOOC— (CH ₂ ) _9— COOH), dodecanedioic acid (HOOC— (CH ₂ ) _I0— COOH), tridecanedioic acid (HOOC— (CH ₂ ) _H— COOH), tetradecanedioic acid (HOOC— (CH ₂ ) _I2— COOH), pentadecanedioic acid (HOOC— (CH ₂ ) _I3— COOH), hexadecanedioic acid (HOOC— (CH ₂ )i4— COOH), octadecanedioic acid (HOOC— (CH ₂ ) _I6— COOH) and C ₃₆ fatty acid dimer, in particular the one known as Pripol® by Croda.

The dicarboxylic acid may be a cycloaliphatic dicarboxylic acid comprising at least one carbocyclic ring having from 4 to 8 carbon atoms in the ring, like e.g. cyclohexane dicarboxylic acids, in particular such as 1, 2-cyclohexane carboxylic acid, 1, 3-cyclohexane dicarboxylic acid and 1, 4-cyclohexane dicarboxylic acid, 2,5-tetrahydrofurandicarboxylic acid, these acids may be cis, trans or mixtures thereof.

The dicarboxylic acid may be an aromatic diacid [acid (AR)] as previously described.

The polyamide may also comprise amino-acid repeating units. These repeating units may arise from lactams or amino-acids, in particular chosen from caprolactam, 6-amino hexanoic acid, lO-aminodecanoic acid, 11- aminoundecanoic acid, and l2-dodecanolactam.

The amount of repeating units arising from lactams or amino-acids may range from 0.1 to 50 mol %, in particular from 0.1 to 10 mol %, and more particularly from 0.1 to 5 mol % relative to the total amount of repeating units in the polyamide.

According to a preferred embodiment, the polyamide comprises recurring units derived from:

TMDP T (trimethylenedipepiridine, terephtalic acid)

TMDP I (trimethylenedipepiridine, isophthalic acid)

TMDP. DA (trimethylenedipepiridine, diphenic acid)

TMDP T/ 6T (trimethylenedipepiridine, terephtalic acid, hexamethylene diamine)

TMDP 1/ 61 (trimethylenedipepiridine, isophthalic acid, hexamethylene diamine) TMDP T / 9T (trimethylenedipepiridine, terephtalic acid, nonanediamine)

TMDP I / 91 (trimethylenedipepiridine, isophthalic acid, nonanediamine)

TMDP T / 10T (trimethylenedipepiridine, terephtalic acid, decanediamine) TMDP I / 101 (trimethylenedipepiridine, isophthalic acid, decanediamine) TMDP.T/TMDP.6 (trimethylenedipepiridine, terephtalic acid, adipic acid) TMDP.I/TMDP.6 (trimethylenedipepiridine, , isophthalic acid, adipic acid) TMDP.T/TMDP.10 (trimethylenedipepiridine, terephtalic acid, sebacic acid) TMDP.I/TMDP.10 (trimethylenedipepiridine, isophthalic acid, sebacic acid) According to another embodiment, the polyamide is a homopolyamide, in particular an aliphatic homopolyamide, obtained through polymerisation of one a diamine of formula (3), with a dicarboxylic acid of formula (4).

In addition, the polyamide may also comprise at least one, in particular one, mono-functional compound, such compounds may be chosen from monoamines, monoanhydrides, monoacids or a,b diacids such as they are able to from an intramolecular anhydride function, among chain limiters may be cited phthalic anhydride, l-aminopentane, 1 -amino hexane, 1 -amino heptane, l-aminooctane, 1- aminononane, l-aminodecane, l-aminoundecane, l-aminododecane, benzylamine, ortho-phthalic acid, or 1 ,2-benzenedicarboxylic acid, acetic acid, propionic acid, benzoic acid, stearic acid or their mixtures.

Amino End Groups (AEG) of the polyamide may be comprised from 5 to 550 meq/kg. Carboxylic End groups (CEG) of the polyamide may be comprised from 5 to 550 meq/kg. AEG and CEG may be measured by an acido-basic titration after solubilisation of the polyamide in a solvent. Sum of end groups (AEG + CEG) values may be comprised from 10 to 900 meq/kg, preferably from 150 to 600 meq/kg.

The number average molecular weight of the polyamide may notably be controlled by the following means:

-by using chain limiter(s), i.e. mono -functional compounds, in particular such as defined above,

-by a stoechiometric desequilibrium r=[poly carboxylic acid]/[diamine], wherein r may range from 0.8 to 1.2, preferentially from 0.9 to 1.1,,

-by adjusting the synthesis parameters, such as the reaction time, temperature, humidity, or pressure, or

-by a combination of this different means.

The polyamide of the invention may be obtained by molten polymerisation from mixtures of monomers or from their salts.

The polyamide may be obtained from polymerization medium which can, for example, be an aqueous solution comprising the monomers or a liquid comprising the monomers. Advantageously, the polymerization medium comprises water as solvent. This facilitates the stirring of the medium and thus its homogeneity. The polymerization medium can also comprise additives, such as chain- limiting agents. The polyamide is generally obtained by polycondensation between the various monomers, present in all or in part, in order to form polyamide chains, with formation of the elimination product, in particular water, a portion of which may be vaporized. The polyamide is generally obtained by heating, at high temperature and high pressure, for example an aqueous solution comprising the monomers or a liquid comprising the monomers, in order to evaporate the elimination product, in particular the water, present initially in the polymerization medium and/or formed during the poly condensation, while preventing any formation of solid phase in order to prevent the mixture from setting solid.

The poly condensation reaction may be carried out at a pressure from 20 mbar to 15 bar, notably from 100 mbar to 1 bar, for instance 200 to 500 mbar.

The polycondensation reaction may be carried out at a temperature from 100 to 380°C, in particular from 180 to 300°C, even more particularly from 250 to 300°C. The poly condensation may be continued in the molten phase at atmospheric or reduced pressure, so as to achieve the desired degree of progression. The poly condensation product is a molten polymer or prepolymer. It can comprise a vapour phase essentially composed of vapour of the elimination product, in particular of water, capable of having been formed and/or vaporized. This product can be subjected to stages of separation of vapour phase and of finishing in order achieving the desired degree of polycondensation. The separation of the vapour phase can, for example, be carried out in a device of cyclone type. Such devices are known.

The finishing consists in keeping the poly condensation product in the molten state, under a pressure in the vicinity of atmospheric pressure or under reduced pressure, for a time sufficient to achieve the desired degree of progression. Such an operation is known to a person skilled in the art.

The polycondensation product can also be subjected to a solid-phase postcondensation stage. This stage is known to a person skilled in the art and makes it possible to increase the degree of polycondensation to a desired value. The process may be similar in its conditions to the conventional process for the preparation of polyamide of the type of those obtained from dicarboxylic acids and diamines, in particular to the process for the manufacture of polyamide 6.6 from adipic acid and hexamethylenediamine. This process for the manufacture of polyamide 6.6 is known to a person skilled in the art. The process for the manufacture of polyamide of the type of those obtained from dicarboxylic acids and diamines generally uses, as starting material, a salt obtained by mixing a diacid with a diamine in a stoichiometric amount, generally in a solvent, such as water. Thus, in the manufacture of poly(hexamethylene adipamide), the adipic acid is mixed with hexamethylenediamine, generally in water, in order to obtain hexamethylenediammonium adipate, better known under the name of Nylon salt or“N Salt”.

Additives may be introduced during the process of the invention. Mention may be made, as examples of additives, of nucleating agents such as talc, matifying agents such as titanium dioxide or zinc sulphide, heat or light stabilizers, bioactive agents, antisoiling agents, antifoam, catalysts such as H ₃ P0 ₄ or H3PO3, etc. These additives are known to a person skilled in the art. This list is in no way exhaustive.

The process for preparing the polyamide may be continuous or may be done batchwise.

It is also known, in continuous processes for the preparation of polyamide, to inject an inert gas, such as nitrogen, into the finishing reactor. This method benefits from the same advantages as the vacuum finishing, namely a better productive output of the finishing stage, without exhibiting its disadvantages. Specifically, this method makes it possible to easily limit the risk of decomposition of hot polymer by eliminating the risk of entry of oxygen into the finishing reactor. The inert gas, which is generally dry, also makes it possible to remove the water produced during the polymerization reaction, which makes it possible to accelerate the latter.

The invention also concerns a composition comprising at least the polyamide of the invention.

The compositions may be obtained by mixing the different ingredients, fillers and/or additives. The processing temperature may be adjusted to the melting temperature of the polyamide having the higher melting temperature. The compounds may be introduced simultaneously or sequentially. In general an extruder is used in which the material is heated, then melted and subjected to a shearing strength to mix the different compounds. According to specific embodiments, it is possible to use a masterbatch, in a molten state or not, before preparing the final composition. For example it is possible to prepare a masterbatch by mixing the resin and other ingredients.

In particular the composition may be obtained by a hot mixing of the different ingredients, for example in a mono- or twin-screw extruder, at a temperature allowing to keep the polyamide in a molten state; or by a cold mixing, for example in a mechanical stirrer. The composition is preferentially obtained through mixture of the components in a molten state. Generally, the obtained mixture is extruded as rods which are chopped into pieces to give pellets. The compounds may be added at any time of the preparation of the plastic material, in particular by hot or cold mixing with the plastic matrix. The addition of the compounds and of the additives may be done by adding these compounds in the molten plastic matrix as pure compounds or as concentrated mixtures in a matrix such as a plastic matrix.

The invention also concerns a shaped article comprising a composition comprising or consisting of the polyamide of the invention. The shaped article may be a pellet, a powder, a granule, a rod, a bar, a complex structure obtained by injection molding or laser sintering, a tubing, a tank, a pipe, a hollow body, fibers, yams, films, sheets, or a substrate, in particular a metallic substrate, coated by the composition. The article may be shaped according to the means known for shaping thermoplastic polymers. The shaped article may be obtained through moulding, either injection moulding, blow moulding, water moulding, extrusion, extrusion moulding, pelletizing, and underwater pelletizing.

The polyamide according to the invention exhibits good mechanical performance and high melt fluidity as well as high thermal stability. Therefore, the polyamide is useful for the preparation of molded articles and thermoplastic composite applications, like a thermoplastic composite comprising the polyamide according to the invention and non-continuous and/or continuous fibers, such as glass or carbon fibers.

The molded articles which comprise the polyamide according to the invention can, for example, be an osmosis membrane or a medical implant.

The invention will now be explained in more detail with reference to the following examples, which are not intended as being limiting.

EXAMPLES

For the preparation of the polyamides, the following starting materials were used:

Isophthalic acid, 99%, from Sigma- Aldrich.

Piperazine, 99%, from Sigma- Aldrich.

4,4'-Trimcthylcncdi piperidine, 97%, from Sigma- Aldrich.

Hexamethylenediamine, from Solvay.

For determining the properties of the obtained polyamides the following methods were used:

^■ Thermogravimetric Analysis (TGA)

The TGA experiments were performed on raw samples in order to obtain a degradation temperature (T _d ) at 1% mass loss which constitutes an important parameter to be considered for the DSCs. Mass loss was measured for each sample by increasing the temperature from 30 °C to 600 °C, with 10 ° C/min under air flow (presence of oxygen).

^■ Differential Scanning Calorimetry (DSC)

The glass transition temperatures (Tg) were measured using a DSC of the company TA instruments.

The DSC analysis was carried out in 3 cycles as follows:

- Cycle 1 : -l0°C to 350°C, l0°C/min

- Cycle 2: 350°C to l0°C

- Cycle 3: l0°C to 350°C (Tg)

^■ Injections of test pieces for mechanical analyses In order to carry out the mechanical stress tests (tension), the polymers were dried, extruded and then injected under the conditions described in table 1. A micro compounder and a mini-press were used. Table 1. Experimental extrusion and micro compounder injection conditions

The soaking time in the extruder was 2 minutes.

The dumbbells had a thickness of 1.7 mm, a total length of 74 mm with a usable length of 26 mm, and a width of 4 mm (measured at the center of the test piece). ■ Tensile Properties

Bars were injected from the previously dried polymer granules to obtain test pieces for mechanical tests.

The tensile tests were carried out according to the ISO 527-2 standard corresponding to tensile tests on thermoplastic test pieces as follows:

- dumbbell tube type 5 A,

- zeroing of the force sensor,

- placing the test piece in the jaws,

- clamping the jaws,

- set a zero force (by moving the crossbar) to neutralize the forces (tension / compression) that occur during tightening,

- start the test,

- once the pretension is reached (O.lMPa), position the extensometer by contact (L0: 20mm),

- removal of the sample at 2% deformation; the deformations of the specimen are then determined with the traverse displacement (corrected by a factor k, determined before the removal of the extensometer),

- stop the test when the test piece breaks. Traverse speed during the determination of the module was lmm/min.

Module was between 0.05 and 0.25% deformation.

Test speed after the module was 50mm/min.

Carboxylic acid end-groups (CEG) concentration and amine end-groups (AEG) concentration were determined by potentio metric titration (unit : meq/kg).

Example 1: Production of a polyamide TMDP.I

The polyamide was prepared by polycondensation in the melt in a stirred pressure autoclave. 63.41 g (0.38 mol) of isophthalic acid and 82.39 g (0.39 mol) of 4,4'-Trimcthylcncdi piperidine were poured with 61.0 g of demineralized water, 0.012 g of phosphoric acid 85% and antifoam in a stainless steel clave. The clave atmosphere was purged with nitrogen, and the temperature was increased progressively to 220°C, with continuous stirring, letting pressure increase up to about 17.5 bar. The temperature was increased progressively up to 250°C, while maintaining the same level of pressure. The pressure was then progressively released while the temperature was increased to about 288°C. Vacuum was then applied to reach 500 mbar and kept for 30 min at the same temperature under continuous stirring. The vacuum was broken with nitrogen and the polymer was extruded in a strand. A glassy polymer was obtained which contained polyamide chains represented by the following formula:

wherein n denotes the mole fraction of the polyamide repeating unit. The polymer thus obtained had the following analytical data:

The amorphous had, at a relative humidity of zero (RH0), a glass transition temperature Tg = 119 ° C, measured in DSC according to the protocol described above; and a thermal degradation Td = 380 ° C, measured according to the protocol described above.

End-groups titrations were as follow: CEG = 177 meq/kg, AEG = 146 meq/kg, corresponding to an estimated Mn of 6193 g/mol, i.e. a DPn of 25. The mechanical properties of this TMDP.I were measured according to the conditions defined above after injection of specimen injected under the conditions described above. Under these conditions, the TMDP.I showed tensile behavior between fragile and ductile with an elastic modulus (E) of 3300MPa and with a maximum stress of l20MPa (see attached Figure 1).

The results are summarized in the following Table 2.

Table 2 Number average molecular weight (Mn) and weight-average molecular weight (Mw) have been also determined by Size Exclusion Chromatography and Polydispersity Index (PI=Mw/Mn) has been calculated. Size Exclusion Chromatography for measuring absolute molecular weights is performed in Hexafluoroisopropanol (HFIP) with 25 mM sodium trifluoroacetate (0.225 % w/w sodium trifluoroacetate in HFIP) as a solvent at 40°C, followed by refractometry RE The system was calibrated using the set of narrow poly disperse PMMA standard samples. Example 2: Production of a polyamide TMDP.T

Similarly to example 1, 63.43 g (0.38 mol) of terephthalic acid and 82.37 g (0.39 mol) of 4,4'-Trimcthylcncdi piperidine were poured with 62.0 g of demineralized water, 0.048 g of phosphoric acid 85% and antifoam in a stainless steel clave in a stainless steel clave, and allowed to polycondensate. The pressure was then progressively released while the temperature was increased to about 288°C, and kept under atmospheric pressure for 15 min at the same temperature under continuous stirring. The polymer was extruded in a strand. A glassy polymer was obtained which contained polyamide chains represented by the following formula:

wherein n denotes the mole fraction of the polyamide repeating unit. The polymer thus obtained had the following analytical data:

The amorphous had, at a relative humidity of zero (RHO), a glass transition temperature Tg = l37°C, measured in DSC according to the protocol described above.

End-groups titrations were as follow: CEG = 207 meq/kg, AEG = 223 meq/kg, corresponding to an estimated Mn of 4650 g/mol, i.e. a DPn of 27. Example 3: Production of a polyamide TMDP.DA

Similarly to example 1, 75.79 g (0.31 mol) of diphenic acid and 67,70 g (0.32 mol) of 4,4'-Trimcthylcncdi piperidine were poured with 62.0 g of demineralized water, 0.097 g of phosphoric acid 85% and antifoam in a stainless steel clave, and allowed to poly condensate. The pressure was then progressively released while the temperature was increased to about 288°C, and kept under vacuum for 45 min at the same temperature under continuous stirring. The polymer was extruded in a strand. A glassy polymer was obtained which contained polyamide chains represented by the following formula:

wherein n denotes the mole fraction of the polyamide repeating unit. The polymer thus obtained had the following analytical data:

The amorphous had, at a relative humidity of zero (RHO), a glass transition temperature Tg = l36°C, measured in DSC according to the protocol described aove. End-groups titrations were as follow: CEG = 30 meq/kg, AEG = 553 meq/kg, corresponding to an estimated Mn of 3429 g/mol, i.e. a DPn of 16.

Comparative Example 1: Production of a polyamide PIP.I

Similarly to example 1, 99.85 g (0.60 mol) of isophthalic acid and 52.92 g (0.61 mol) of piperazine were poured with 61.0 g of demineralized water, 0.016 g of phosphoric acid 85 % and antifoam in a stainless steel clave, and allowed to polycondensate. The pressure was then progressively released while the temperature was increased to about 288°C, and kept under atmospheric pressure for 15 min at the same temperature under continuous stirring. Due to a very high viscosity in the melt, the polymer was extruded with difficulty to collect only a small sample. A glassy polymer was obtained which contained polyamide chains represented by the following formula:

wherein n denotes the mole fraction of the polyamide repeating unit. The polymer thus obtained had the following analytical data:

The amorphous polyamide had a glass transition temperature of 2l4°C, and a thermal degradation onset of 443°C, and a char at 500°C of 34%.

End-groups titrations were as follow: CEG = 608 meq/kg, AEG = 298 meq/kg, corresponding to an estimated Mn of 2208 g/mol, i.e. a DPn of 20.

Comparative Example 2: Production of a polyamide 6.1

Similarly to example 1, 87.65 g (0.53 mol) of isophthalic acid, 62.86 g (0.54 mol) of hexamethylenediamine and l.42g (0.02mol) of acetic acid were poured with 63.0 g of demineralized water, 0.020 g of phosphorous acid 50% and antifoam in a stainless steel clave, and allowed to polycondensate. The pressure was then progressively released while the temperature was increased to about 275 °C. Vacuum was then applied to reach 500 mbar and kept for 30 min at the same temperature under continuous stirring. The vacuum was broken with nitrogen and the polymer was extruded in a strand. A glassy polymer was obtained which contained polyamide chains represented by the following formula:

wherein n denotes the mole fraction of the polyamide repeating unit. The polymer thus obtained had the following analytical data:

The amorphous had, at a relative humidity of zero (RHO), a glass transition temperature Tg = l20°C, measured in DSC according to the protocol described above; and a thermal degradation Td = 340 ° C, measured according to the protocol described above.

End-groups titrations were as follow: CEG = 100 meq/kg, AEG = 45 meq/kg, corresponding to an estimated Mn of 6116 g/mol, i.e. a DPn of 50. The mechanical properties of this 6.1 were measured according to the conditions defined above after injection of specimen injected under the conditions described above. Under these conditions, the 6.1 showed a fragile tensile behavior with an elastic modulus (E) of 3680MPa and with a maximum stress of 69MPa (see attached Figure 2).

The results are summarized in the following Table 3.

Table 3