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

Abstract

A process for chemically modifying a polymeric part in order to provide it with flame retardancy properties or to enhance the properties, the process comprising a step of reacting at least one polymeric part comprising at least one polymer of which the reactive groups comprise amine groups and/or hydroxyl groups with a flame retardant compound comprising at least one group that reacts, by nucleophilic substitution or nucleophilic addition, with some or all of the amine groups and/or hydroxyl groups of the polymer or polymers, the reaction being carried out with the compound in gaseous form.

Claims

1-14. (canceled)

15. A process for chemically modifying a polymeric part in order to impart flame retardant properties thereto or to improve these properties, said process comprising a step of reacting a polymeric part comprising at least one polymer comprising, as reactive groups, amine groups and/or hydroxyl groups, with a flame retardant compound comprising at least one group reacting, by nucleophilic substitution or nucleophilic addition, with some or all of the amine groups and/or hydroxyl groups of the polymer(s), the reaction being implemented with said compound in gaseous form.

16. The chemical modification process according to claim 15, wherein the polymeric part is a part comprising one or more polyamides.

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

18. The chemical modification process according to claim 15, wherein the group(s) of the flame retardant compound(s) reacting, by nucleophilic substitution or nucleophilic addition, with some or all of the amine groups and/or hydroxyl groups of the polymer(s), are selected from: nucleofuge groups, when the reaction step is a nucleophilic substitution reaction step; electrophilic groups, when the reaction step is a nucleophilic addition reaction step.

19. The chemical modification process according to claim 15, wherein the flame retardant compound(s) comprise at least one group comprising at least one phosphorus atom, at least one sulphur atom and/or at least one silicon atom.

20. The chemical modification process according to claim 15, wherein, when the reaction step is a nucleophilic substitution reaction step, the flame retardant compound(s) are selected from the following compounds: chloride compounds comprising an —SO.sub.2— group; chloride compounds comprising at least one —PO— group; and/or chloride compounds comprising at least one —PS— group.

21. The chemical modification process according to claim 20, wherein the chloride compounds comprising at least one —SO.sub.2— group further comprise a group comprising at least one heteroatom selected from N, O, Si or P.

22. The chemical modification process according to claim 20, wherein the chloride compounds comprising at least one —SO.sub.2— group are selected from trimethylsilyl chlorosulfonate or (2-trimethylsilyl)ethanesulfonyl chloride.

23. The chemical modification process according to claim 20, wherein the chloride compounds comprising at least one —PO— group further comprise a hydrocarbon, aliphatic or aromatic group and/or a group comprising at least one heteroatom selected from N, O, Si or P.

24. The chemical modification process according to claim 20, wherein the chloride compounds comprising at least one —PO— group are selected from: diphosphoryl chloride of formula Cl.sub.2P(O)OP(O)Cl.sub.2; N,N,N′,N′-tetramethylphosphorodiamidic chloride of formula [(CH.sub.3).sub.2N].sub.2P(O)Cl; phenyl dichlorophosphate of formula C.sub.6H.sub.5OP(O)Cl.sub.2; or 2-chloro-1,3,2-dioxaphospholane-2-oxide.

25. The chemical modification process according to claim 20, wherein the chloride compounds comprising at least one —PS— group further comprise a hydrocarbon, aliphatic or aromatic group and/or a group comprising at least one heteroatom selected from N, O, Si or P.

26. The chemical modification process according to claim 15, wherein, when the reaction step is a nucleophilic addition reaction step, the flame retardant compound(s) are selected from the following compounds: epoxy compounds comprising at least one pendant group comprising at least one heteroatom selected from N, O, Si or P; phosphorus anhydride compounds; and/or cyclic siloxane compounds.

27. The chemical modification process according to claim 15, wherein the reaction step is implemented exclusively in the presence of the polymeric part and the flame retardant compound(s).

28. The chemical modification process according to claim 15, wherein the reaction step includes the following operations: an operation of placing, in a first reactor, of the polymeric part, the reactor being heated to the temperature for implementing the process; an operation of pressurising the reactor to the pressure for implementing the process; an operation of vaporising the flame retardant compound(s) in a second reactor connected to the first reactor; an operation of injecting the flame retardant compound(s) in the gaseous state into the first reactor; an operation of maintaining the temperature and the pressure for implementing the process until the reaction is complete.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0066] FIG. 1 is a diagram illustrating a device for implementing the process of the invention.

DETAILED DISCLOSURE OF PREFERRED EMBODIMENTS

Example 1

[0067] This example illustrates the implementation of a specific mode of the chemical modification process of the invention consisting of a chemical modification of a polyamide-12 part, so as to improve the flame retardant properties thereof by a flame retardant compound: diphosphoryl chloride of formula (Cl.sub.2P(O)OP(O)Cl.sub.2).

[0068] This flame retardant compound was selected because it has vaporisation conditions in line with the properties of polyamide-12, in particular relative to its melting temperature. Indeed, the boiling temperature of diphosphoryl chloride is 214° C. at 1 bar, i.e. 140° C. for an absolute pressure of 130 mbar.

[0069] The reaction of polyamide-12 with the flame retardant compound mentioned above can be represented by the following reaction scheme:

[0070] the other chlorine atoms can also be involved in a nucleophilic substitution

##STR00001##

reaction with other —NH groups of the polyamide-12.

[0071] The process has been implemented in a device schematically illustrated in the appended FIG. 1.

[0072] The polyamide-12 sample to be treated (reference 1) is suspended in the deposition reactor 3, sealed and with magnetic stirring, previously heated to the treatment temperature then the latter is pressurised by vacuum drawing up to 40 mbar thanks to the vacuum pump 5 by opening the valve 7. Once the desired pressure has been obtained, the valve 7 is closed in order to maintain the deposition reactor 3 under vacuum and isolated.

[0073] In an adjacent reactor 9 which is connected to the deposition reactor 3, a known amount of flame retardant compound 11 is injected, at a temperature such that the latter is preheated or even in the gaseous state in order to facilitate its vaporisation.

[0074] When the temperature and pressure conditions allow maintaining the flame retardant compound in its vapour form, then the valve 13 between the deposition reactor 3 and the adjacent reactor 9 is opened. This is followed by the vaporisation of the compound in the conduit 15 inserted into deposition reactor 3 and thanks to the pressure difference between the two reactors 3 and 9.

[0075] The flame retardant compound is then inserted into the deposition reactor 3 via an injection nozzle 17 connected to the pipe 15. A plate 19 forming a physical barrier is located above the injection nozzle 17 to prevent any liquid projection of the flame retardant compound on the sample to be treated. The reaction (possibly its condensation) between the flame retardant compound and the sample to be treated thus takes place.

[0076] At the end of the duration of the process (from 1 to 30 minutes), purge cycles are performed in the reactor in order to recover the excess of the flame retardant compound which has not reacted. The pressure is released, then the treated sample is removed and placed in the oven (5 minutes to 1 hour), in order to completely eliminate the flame retardant compound which has not reacted.

[0077] More specifically, three tests were carried out with the operating conditions listed in the table below.

TABLE-US-00001 Test Temperature in the deposition reactor (in °C) Pressure in the deposition reactor (in mbar) Contact time (in min) Loading rate (in mg) Loading rate (in mass %) 1 140-145 40-45 6 10 0.1 2 140-145 40-45 15 200 2.5 3 140-145 40-45 30 360 4.5

[0078] For accuracy, the loading rate (in mg) corresponds to the amount of flame retardant compound deposited on the sample, while the loading rate loading rate (in mass %) corresponds to the mass ratio of the amount of flame retardant compound deposited on the total mass of the sample after treatment.

[0079] For these different tests, characterisation by spectroscopic analysis (XPS and ToF SIMS) of the treated samples has allowed highlighting and confirming the formation of covalent bonds between the polymer and the flame retardant compound. Indeed, there is a modification of the XPS spectrum of the element N obtained on the treated polyamide-12. The complementary ToF-SIMS analyses confirmed the formation of —NP(O)— groups.

[0080] Consequently, these characterisations confirm that this post-treatment does not constitute a simple surface deposition. This is truly a covalent chemical grafting of the flame retardant compound onto the PA-12. This feature then makes the deposition much more robust. Its adherence relative to PA-12 is then very strong.

[0081] For these different tests, flame tests were also carried out to determine whether the samples originating from these tests (having a length of 125 mm, a width of 13 mm and a thickness of 5 mm) belong to the fire classes V-0, V-1, V-2 according to a representative test of the UL94V standard. Under multiple ignition, both the residual combustion and afterglow time and the casting of ignited drops from the sample are evaluated for this purpose.

[0082] The results obtained correspond to a V-0, namely the results: [0083] a residual combustion time after ignition of less than 10 seconds; [0084] a residual combustion time after the second ignition of less than 10 seconds; [0085] no casting of ignited drops; [0086] no complete combustion of the samples.

[0087] Moreover, a comparative fire test was carried out with: [0088] a polyamide-12 part treated with diphosphoryl chloride in accordance with the protocol defined above (with a loading rate of 140 mg, i.e. 1.7 mg); [0089] an untreated polyamide-12 part.

[0090] On observation, it appears that, unlike the untreated part, the treated part reveals very low ignition times (or even zero) during the 2 ignitions. In addition, no glowing drop likely to ignite the cotton was observed with the treated part.

Example 2

[0091] This example illustrates the implementation of a specific mode of the chemical modification process of the invention consisting of a chemical modification of a polyamide-12 part, so as to improve the flame retardant properties thereof by a flame retardant compound: trimethylsilyl chlorosulfonate.

[0092] This flame retardant compound was selected because it has vaporisation conditions in line with the properties of polyamide-12, in particular relative to its melting temperature. Indeed, its vaporisation conditions are 80° C. at 50 mbar, 95° C. at 100 mbar or even 120° C. at 250 mbar.

[0093] The reaction of polyamide-12 with the flame retardant compound mentioned above can be represented by the following reaction scheme:

##STR00002##

[0094] Thus, the trimethylsilyl chlorosulfonate is grafted onto the surface of the PA-12 part by forming covalent bonds. This reaction is accompanied by the formation of HCI.

[0095] More specifically, seven tests were carried out according to a process similar to that set out in Example 1, with the specific operating conditions listed in the table below.

TABLE-US-00002 Test Post-treatment conditions Sample mass (g) Loading rate T(°C) P (mbar) Time (min) Before treatment After treatment mg m % 1 115-120 30-35 2 7.9296 7.974 44 0.5 % 2 8.0288 8.1157 87 1.1 % 3 8.0754 8.1651 90 1.1 % 4 7.9849 8.1067 122 1.5 % 5 5 7.9711 8.1102 139 1.7 % 6 10 7.6869 7.8422 155 1.9 % 7 7.963 8.1064 143 1.8 %

[0096] For accuracy, the loading rate (in mg) corresponds to the amount of flame retardant compound deposited on the sample, while the loading rate (in mass %) corresponds to the mass ratio of the amount of flame retardant compound deposited on the total mass of the sample after treatment.

[0097] The flame tests described in Example 1 and performed (test representative of the UL94V standard) on the polyamide-12 parts treated with trimethylsilyl chlorosulfonate revealed that the grade VO was obtained according to the UL94V standard.

[0098] Moreover, the test was carried out on a sample having a loading rate of 85 mg i.e. 1.1 m%. It then appears that even with a low loading rate, the ignition times are zero and no glowing drop is formed.