MODIFIED POLYAMIDES HAVING ENHANCED FLOWABILITY/MECHANICAL PROPERTIES AND MOLDING COMPOSITIONS COMPRISED THEREOF

Abstract

The present invention relates to a polyamide and a process for the preparation thereof, and to compositions containing it. It relates more particularly to a polyamide obtained by polymerization of diacid and diamine monomers in the presence of multifunctional and monofunctional compounds capable of forming an amide function by reaction with either an aminated function or an acid function. This polyamide can in particular be used for the preparation of compositions intended, for example, to be moulded.

Claims

1. A polyamide capable of being obtained by polymerization in the presence of at least: (i) dicarboxylic acid and diamine monomers, or their salts, (ii) from 0.05 to 0.5 mol % of a polyfunctional compound comprising at least 3 functional groups X1, with respect to the sum of the number of moles of constituent monomers of the polyamide; (iii) from 0.2 to 2 mol % of a monofunctional compound comprising a functional group X2, with respect to the sum of the number of moles of constituent monomers of the polyamide; the functional groups X1 and X2 being carboxylic acid functional groups or amine functional groups capable of reacting with the dicarboxylic acid and diamine monomers (i) and of forming an amide bond; when the polyfunctional compound (ii) comprises functional groups X1 of carboxylic acid type, the monofunctional compound (iii) comprises a functional group X2 of carboxylic acid type; and when the polyfunctional compound (ii) comprises functional groups X1 of amine type, the monofunctional compound (iii) comprises a functional group X2 of amine type.

2. The polyamide as claimed in claim 1, wherein the constituent monomers of the polyamide of dicarboxylic acid type are aliphatic or aromatic and comprise from 4 to 12 carbon atoms.

3. The polyamide as claimed in claim 1, wherein the constituent monomers of the polyamide of diamine type are aliphatic or aromatic and comprise from 4 to 12 carbon atoms.

4. The polyamide as claimed in claim 1, wherein the constituent monomers of the polyamide are adipic acid and hexamethylenediamine, or their salts.

5. The polyamide as claimed in claim 1, wherein the polyfunctional compound (ii) is represented by the general formula (1):
R-[A-X1].sub.n(1) wherein: R is an aliphatic (linear or branched), cycloaliphatic or aromatic hydrocarbon radical comprising at least two carbon atoms and which can comprise one or more heteroatoms; A is a covalent bond or an aliphatic hydrocarbon radical which can comprise one or more heteroatoms, and which comprises from 1 to 20 carbon atoms; X1 is a carboxylic acid functional group or a primary or secondary amine functional group, or their salts; and n is an integer of between 3 and 10.

6. The polyamide as claimed in claim 1, wherein the polyfunctional compound (ii) is an aliphatic, cycloaliphatic or aromatic hydrocarbon compound comprising at least 4 carbon atoms which can comprise one or more heteroatoms.

7. The polyamide as claimed in claim 1, wherein the polyfunctional compound (ii) carrying carboxylic acid functional groups X1 is selected from the group consisting of: 2,2,6,6-tetra(-carboxyethyl)cyclohexanone, diaminopropane-N,N,N,N-tetraacetic acid, 3,5,3,5-biphenyltetracarboxylic acid, acids derived from phthalocyanin and naphthalocyanin, 1,3,5,7-naphthalenetetracarboxylic acid, 2,4,6-pyridinetricarboxylic acid, 3,5,3,5-bipyridyltetracarboxylic acid, 3,5,3,5-benzophenonetetracarboxylic acid, 1,3,6,8-acridinetetracarboxylic acid, trimesic acid, 1,2,4,5-benzenetetracarboxylic acid and 2,4,6-tri(aminocaproic acid)-1,3,5-triazine (TACT).

8. The polyamide as claimed in claim 1, wherein the polyfunctional compound (ii) carrying amine functional groups X2 is selected from the group consisting of: nitrilotrialkylamines, dialkylenetriamines, bishexamethylenetriamine, trialkylenetetramines and tetraalkylenepentamines, 4-aminoethyl-1,8-octanediamine, melamine, compounds originating from the reaction of trimethylolpropane or of glycerol with propylene oxide and amination of the end hydroxyl groups of general formula: ##STR00002## wherein: R.sub.1 represents a propane-1,1,1-triyl or propane-1,2,3-triyl radical and A represents a polyoxyethylene radical.

9. The polyamide as claimed in claim 1, wherein the monofunctional compound (iii) is an aliphatic, cycloaliphatic or aromatic hydrocarbon compound comprising at least 2 carbon atoms and which can comprise heteroatoms.

10. The polyamide as claimed in claim 1, wherein the monofunctional compound (iii) is selected from the group consisting of: n-hexadecylamine, n-octadecylamine and n-dodecylamine, acetic acid, lauric acid, benzylamine, benzoic acid, propionic acid and 4-amino-2,2,6,6-tetramethylpiperidine.

11. The polyamide as claimed in claim 1, wherein the functional groups X1 of the polyfunctional compound (ii) and the functional group X2 of the monofunctional compound (iii) are identical.

12. The polyamide as claimed in claim 1, comprising 0.2 to 0.5 mol % of polyfunctional compounds (ii), with respect to the sum of the number of moles of constituent monomers of the polyamide.

13. The polyamide as claimed in claim 1, comprising 0.5 to 1 mol % of monofunctional compounds (iii), with respect to the sum of the number of moles of constituent monomers of the polyamide.

14. The polyamide as claimed in claim 1, wherein a proportion of polyfunctional compounds (ii) and monofunctional compounds (iii) which obeys the following relationship:
(nCpoFX1)/nCmo of between 0.1 and 4, wherein: nCpo the number of moles of polyfunctional compounds (ii), nCmo the number of moles of monofunctional compounds (iii), and FX1 the number of functional groups X1 of the polyfunctional compound (ii).

15. The polyamide as claimed in claim 1, wherein the polymerization is carried out in the presence of an amino acid or a lactam.

16. The polyamide as claimed in claim 1, wherein the modified polyamide exhibits a viscosity in solution of between 80 and 120, according to standard ISO 307, with 0.5% of polymer in 90% of formic acid, at a temperature of 25 C.

17. A composition comprising at least the polyamide as claimed in claim 1.

18. The composition as claimed in claim 17, comprising the polyamide as the matrix.

19. The composition as claimed in claim 17, comprising a blend of a thermoplastic polymer and the polyamide.

20. The composition as claimed in claim 19, comprising a blend of a (co)polyamide and the polyamide.

21. The composition as claimed in claim 1, further comprising at least one reinforcing and/or bulking filler.

22. An article obtained by injection molding, injection/blow molding, extrusion, or extrusion/blow molding of the composition as claimed in claim 17.

Description

EXPERIMENTAL PART

Example 1

Manufacture of the Polyamides

[0075] The polymerization is carried out in a heated autoclave comprising stirring means.

[0076] 11.111 kg of N salt (equimolar amount of adipic acid and hexamethylenediamine), 81 g of 2,2,6,6-tetra(-carboxyethyl)cyclohexanone (0.25 mol %), 80 g of benzoic acid (0.78 mol %) and 40 g of antifoaming agent (Silcolapse) are added to the autoclave with 5 liters of distilled water at a temperature of 90 C.

[0077] The mixture, set stirring, is heated to a temperature of 280 C. under 7.5 atmospheres. It is maintained at this temperature and pressure for 2 hours.

[0078] The pressure is subsequently reduced and then the autoclave is swept with nitrogen for one and a half hours while maintaining the temperature at 280 C. The system is subsequently placed under vacuum, at a pressure of 0.5 atmosphere, for one hour.

[0079] The molten polymer is subsequently extruded in the form of rods, then rapidly cooled with water and cut up into granules.

[0080] Various polymers are synthesized in this way by varying the proportion of the polyfunctional and monofunctional compounds.

[0081] Example C1 corresponds to a linear polyamide 66 manufactured in the absence of polyfunctional and monofunctional compound.

Example 2

Polyamide Properties

[0082] The characteristics, rheological properties and mechanical properties of these polymers are collated in table 1 below. Test specimens produced by injection molding are manufactured in order to measure some of the properties.

TABLE-US-00001 TABLE 1 C1 1 2 3 4 Content of 0 0.25 0.3 0.25 0.4 polyfunctional compound (mol %) Content of 0 0.78 0.8 0.6 0.8 monofunctional compound (mol %) NH.sub.2 50 13 14 15 14 (meq/kg) COOH 70 190 205 180 222 (meq/kg) VI (1) 142 92 87 102 100 Melt flow index (2) 8 43.2 42.5 32 39 (g/10 min) Notched Izod impact 5.7 3.7 3.5 3.9 3.6 (kJ/m.sup.2) Unnotched Izod impact 72 60 63 78 (kJ/m.sup.2) Tensile strength 55 75 67 75 70 (N/mm.sup.2) Elongation 30 2.7 2.7 3.2 2.7 (%) Tensile modulus 3100 3410 3110 3080 3010 (N/mm.sup.2) (1) Viscosity index, measured from a 0.5% solution of polymer dissolved in 90% formic acid, according to standard ISO307 (2) Melt flow index (MFI), determined according to standard ASTM D1238, measured in g/10 min at 275 C. under a load of 325 g

[0083] The contents of acid and amine end groups are quantitatively determined by potentiometry, the Izod impacts are measured according to standard ISO 179/leU and ISO 179/leA and the tensile strength, the elongation and the tensile modulus are measured according to standard ISO 527 at a temperature of 23 C.

Example 3

Filler-Comprising Compositions

[0084] Compositions comprising, as polyamide matrix, the polyamides manufactured above, are charged with 50% by weight of glass fibers by melt blending in a twin-screw extruder of Werner-Pfleiderer ZSK 40 type with venting (L/D=36). The glass fibers are Vetrotex 99B. The extrusion parameters are as follows: extrusion temperature with an increasing profile 235-280 C.; rotational speed of the screw: 260 revolutions per minute; throughput of the composition: 40 kg/h; the motor torque and the motor output absorbed vary according to the polyamides.

[0085] The properties of the filler-comprising compositions are collated in table 2 below. Test specimens produced by injection molding are manufactured in order to measure some of the properties.

TABLE-US-00002 TABLE 2 C1 1 2 3 4 Melt flow index (3) 2.8 16.5 18 11 13 (g/10 min) Notched Izod 17.8 18.4 18.8 17 18 impact (kJ/m.sup.2) Unnotched Izod 92 86 90 81 82 impact (kJ/m.sup.2) Tensile force 224 244 251 233 247 (N/mm.sup.2) Elongation 2.7 2.3 2.5 2.2 2.3 (%) Tensile modulus 15 300 15 100 16 300 15 400 16 300 (N/mm.sup.2) Spiral test 33 45 48 40 45 (cm) Surface poor very very very very appearance good good good good Motor torque 50-55 30-35 30-35 30-35 30-35 (N/mm) Motor output 26 16 16 17 16 absorbed (A) (3) Melt flow index (MFI), determined according to standard ASTM D1238, measured in g/10 min at 275 C. under a load of 2160 g

[0086] The surface appearance is assessed visually; the spiral test makes it possible to quantify the flowability of the compositions by melting the granules and by injecting them into a spiral-shaped mold of semi-circular cross section with a thickness of 2 mm and a diameter of 4 cm, in a BM-Biraghi 85T press at a barrel temperature of 275 C., a mold temperature of 80 C. and an injection pressure of 80 bar (the result is expressed as length of mold correctly filled with the composition).

Example 4

Filler-Comprising Compositions Comprising a Blend of Linear Polyamide and of Polyamide According to the Invention

[0087] Compositions comprising the polyamide of example 4 (PA 4) and various proportions of polyamide 66 (PA C1) are manufactured by melt blending in a twin-screw extruder of Werner-Pfleiderer ZSK 40 type with venting (L/D=36), in the presence of 30% by weight of glass fibers. The extrusion parameters are as follows: extrusion temperature with an increasing profile 250-285 C.; rotational speed of the screw: 260 revolutions per minute; throughput of the composition: 40 kg/h; the motor torque and the motor output absorbed vary according to polyamides.

[0088] The properties of the filler-comprising compositions are collated in table 3 below. Test specimens produced by injection molding are manufactured in order to measure some of the properties.

TABLE-US-00003 TABLE 3 4 5 6 7 Polyamide 100% 80% PA 4 + 70% PA 4 + 50% PA 4 + composition PA 4 20% PA C1 30% PA C1 50% PA C1 Melt flow 10 11.5 10 8.1 index (3) (g/10 min) Notched 11 10 11 11 Charpy impact (kJ/m.sup.2) Unnotched 45 50 54 67 Charpy impact (kJ/m.sup.2) (3) Melt flow index (MFI), determined according to standard ASTM D1238, measured in g/10 min at 275 C. under a load of 2160 g

[0089] The Charpy impact is measured according to standard ISO 179/leA.

[0090] It is observed that the addition of linear polyamide 66 to the polyamide according to the invention makes it possible to enhance the mechanical properties of the resulting composition, without negatively affecting its melt flow index.

Example 5

Manufacture and Properties of Modified Polyamides

[0091] Modified polyamides according to the invention are manufactured as described in example 1 according to the proportions of the monomers of test 4 and with addition of 5 or 10% by weight of caprolactam (thus replacing 5 or 10% by weight of N salt).

[0092] The molten polymer is subsequently extruded in the form of rods, then rapidly cooled in water and cut up into granules.

[0093] The characteristics, rheological properties and mechanical properties of these polymers are collated in the table below.

TABLE-US-00004 TABLE 4 C1 4 8 9 Caprolactam 0 0 5 10 (% by weight) Melt flow 8 32 31 32 index (2) (g/10 min) Notched 4.5 3.4 4.2 4.6 Charpy impact (kJ/m.sup.2) (2) Melt flow index (MFI), determined according to standard ASTM D1238, measured in g/10 min at 275 C. under a load of 325 g