PROCESS FOR CHEMICALLY MODIFYING A POLYMERIC PART IN ORDER TO IMPART ANTISTATIC PROPERTIES THERETO OR TO IMPROVE THESE PROPERTIES

Abstract

A process for chemically modifying a polymeric part in order to impart antistatic properties thereto or to improve these properties, comprising the following steps: a step of reacting a polymeric part comprising at least one polymer comprising, as reactive groups, amine groups and/or hydroxyl groups, with a functional compound, also called first compound, comprising at least one isocyanate group and at least one heterocyclic type polymerisable group, the isocyanate groups covalently reacting with all or part of the amine groups and/or hydroxyl groups of the polymer(s), whereby this results in a polymeric part that is covalently bonded to residues of the functional compound; from the heterocyclic type polymerisable groups of the residues of the functional compound, a step of polymerising a second compound comprising at least one heterocyclic type polymerisable group in the presence of a metal complex, the reaction step and the polymerisation step being carried out in the presence of at least one supercritical fluid.

Claims

1.-14. (canceled)

15. A process for chemically modifying a polymeric part in order to impart antistatic properties thereto or to improve these properties, comprising the following steps: a step of reacting a polymeric part comprising at least one polymer comprising, as reactive groups, amine groups and/or hydroxyl groups, with a functional compound, also called first compound, comprising at least one isocyanate group and at least one heterocyclic type polymerisable group, the isocyanate groups covalently reacting with all or part of the amine groups and/or hydroxyl groups of the polymer(s), whereby this results in a polymeric part which is covalently bonded to residues of the functional compound; from the heterocyclic type polymerisable groups of the residues of the functional compound, a step of polymerising a second compound comprising at least one heterocyclic type polymerisable group in the presence of a metal complex, said reaction step and said polymerisation step being carried out in the presence of at least one supercritical fluid.

16. The process of claim 15, wherein the supercritical fluid is supercritical CO.sub.2.

17. The process of claim 15, wherein the polymeric part is a part comprising one or more polyamides.

18. The process according to claim 15, wherein the polymeric part is a polyamide-12 part.

19. The process according to claim 15, wherein the polymeric part is a polyamide-12 part, which has a density less than or equal to 960 kg/m.sup.3.

20. The process according to claim 19, wherein the density is less than or equal to 900 kg/m.sup.3.

21. The process according to claim 15, wherein the functional compound is a non-polymeric compound.

22. The process according to claim 15, wherein the functional compound comprises, as a heterocyclic type polymerisable group, a thiophene group.

23. The process according to claim 15, wherein the functional compound comprises an isocyanate group and a (3,4-ethylenedioxy)thiophene group.

24. The process according to claim 15, wherein the functional compound has the following formula: ##STR00007##

25. The process according to claim 15, wherein the reaction step comprises the following operations: an operation of placing, in a reactor, the polymeric part, the functional compound, optionally at least one cosolvent and optionally at least one catalyst; an operation of introducing CO.sub.2 into the reactor; an operation of pressurising and heating the reactor to a temperature higher than the critical temperature of the CO.sub.2 and to a pressure higher than the critical pressure of the CO.sub.2, this temperature and this pressure being maintained until the reaction is complete.

26. The process according to claim 15, wherein the polymerisation reaction step is carried out in the presence of at least one supercritical fluid, identical to that used in the reaction step with the functional compound.

27. The process according to claim 15, wherein the second compound comprises, as heterocyclic type polymerisation group(s), a thiophene group.

28. The process according to claim 15, wherein the second compound is a (3,4-ethylenedioxy) thiophene compound.

29. The process according to claim 15, wherein the metal complex is an iron (III) complex.

Description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Example 1

[0065] This example illustrates the implementation of a specific embodiment of the chemical modification process of the invention consisting of a chemical modification of a polyamide-12 part, so as to improve its electrical conductivity.

[0066] To do so, the conductive polymer PEDOT (or Poly(3,4-ethylenedioxythiophene)) was chosen. However, PEDOT is insoluble in supercritical CO2 and can only be implemented by direct polymerisation on the substrate through a redox reaction of the monomer (EDOT) with an iron complex. As EDOT (and PEDOT) cannot be directly bonded/grafted to the PA-12 matrix, specific grafting was thereby contemplated.

[0067] Therefore, three phases, which will be developed below in more detail, were implemented:

[0068] a) a phase of synthesising, in liquid phase, an intermediate compound (hereafter called isocyanate/EDOT intermediate compound) by reaction of hexamethyldiisocyanate with an EDOT-OH compound, this step can be illustrated by the following reaction scheme:

##STR00004##

[0069] b) a phase of grafting, under supercritical CO.sub.2, the intermediate compound with polyamide-12, this step can be illustrated by the following reaction scheme:

##STR00005##

[0070] n corresponding to the number of repetitions of the unit taken between brackets;

[0071] c) a phase of polymerising, under supercritical CO.sub.2, the 3,4-ethylenedioxythiophene (EDOT) monomer into PEDOT and doping with an iron Fe (III) based complex to obtain a conductive polymer, this step can be illustrated by the following reaction scheme:

##STR00006##

[0072] n corresponding to the number of repetitions of the units taken between brackets.)

[0073] 1° Synthesis of the Isocyanate/EDOT Intermediate Compound

[0074] The table below illustrates, in order, the steps leading to the synthesis of the isocyanate/EDOT intermediate compound.

TABLE-US-00001 Step 1 Introducing 260 mg of 1,4-diazabicyclo[2.2.2]octane (DABCO) (2.32 mmol), as catalyst, into a glass container Step 2 Flushing the container with argon Step 3 Adding 15 mL of diethyl ether Step 4 Stirring the mixture under argon bubbling until the DABCO is completely dissolved Step 5 Adding 500 mg of EDOT-OH (2.90 mmol) previously dissolved in 4 mL of diethyl ether Step 6 Adding 10 mL of anhydrous acetone Step 7 Adding 487 mg of hexamethyldiisocyanate (2.90 mmol) Step 8 Stirring the mixture under argon bubbling until the reagents are completely dissolved Step 9 Obtaining the isocyanate/EDOT intermediate compound

[0075] 2° Grafting the Intermediate Compound onto a Polyamide-12 Part and Polymerising into PEDOT and Doping

[0076] The initial polyamide-12 part is a disc of 60 mm diameter, 5 mm thick and having a mass of 7.8 g and a surface resistivity of 10.sup.11 ohm/square.

[0077] The above-mentioned part is subjected to the following successive steps: [0078] a step of impregnating/grafting the intermediate compound (called below “Step 1”); [0079] a step of impregnation with the EDOT monomer (called below “Step 2”); [0080] a step of impregnation with the iron (III) complex allowing both the polymerisation of the EDOT monomer and doping of the polymer thus formed to make it conductive (called below “Step 3”).

[0081] These three steps are carried out under supercritical CO.sub.2 in a batch reactor. More specifically, the reactor is a 600 mL stainless steel batch reactor equipped with an external heating system. CO.sub.2 is introduced into the reactor with a double piston pump the heads of which are cooled to a temperature below 5° C. in order to have CO.sub.2 in liquid phase at this stage before the reaction. It is provided with a 60 mL crystalliser at the bottom for accommodating the reagents, optional catalyst and optional cosolvent. The polyamide-12 part is suspended above the crystalliser to avoid any contact with it. The experiments start at room pressure. The reactor is then pressurised to a target pressure and heated to the desired temperature. The part is maintained under the treatment conditions for the required time until the reaction in question is complete. Heating of the reactor is then stopped inducing a slow depressurisation. The remaining pressure is discharged with the various valves located on the reactor lid.

[0082] More specifically, the operating conditions for the above steps are listed in the table below.

TABLE-US-00002 Step 1 Introducing the previously synthesised isocyanate/EDOT intermediate compound and reacting under supercritical CO.sub.2 (300 bar, 100° C.) for 4 hours Step 2 Introducing 2 g of EDOT into the reactor under supercritical CO.sub.2 (300 bar, 100° C.) for 4 hours Step 3 Introducing 2 g of iron (III) p-toluenesulphonate into the reactor under supercritical CO.sub.2 (300 bar, 100° C.) for 2 hours

[0083] The part obtained at the end of these steps has a mass gain of 2%, a good coating homogeneity and a surface resistivity of 108 ohm/square (that is an improvement by a factor of 1000).