USE OF AT LEAST ONE PHENOLIC COMPOUND TO STABILISE ETHYLENE COPOLYMERISATION REACTIONS

Abstract

The present invention relates to the use of one or more phenolic compounds, as defined below, to stabilise ethylene copolymer reactions at high pressure.

The invention also relates to a method of preparing an ethylene copolymer at high pressure in the presence of one or more phenolic compounds, as defined below, and one or more initiators.

Claims

1-19 (canceled)

20. A phenolic compound of Formula (I): ##STR00004## Formula (I), wherein: R.sup.1 represents: a hydrogen atom; a linear C.sub.1-C.sub.8 alkyl radical; a linear C.sub.1-C.sub.8 hydroxyalkyl radical; a hydroxy group; R.sup.2, R.sup.3, R.sup.4 and R.sup.5, identical or different, represent: a hydrogen atom; a C.sub.1-C.sub.8 alkyl radical, linear or branched, optionally substituted by one or more hydroxy radicals; a C.sub.1-C.sub.8 alkoxy radical, linear or branched, optionally substituted by one or more hydroxy radicals; a hydroxy group, and it being understood that R.sup.4 and R.sup.5 can together form a five- or six-member cycle comprising an oxygen atom; said cycle being substituted by a C.sub.1-C.sub.17 alkyl radical, linear or branched, for use in stabilizing radical ethylene copolymerisation reactions at high pressure in the presence of one or more initiators.

21. The phenolic compound according to claim 20, wherein, in Formula (I): R.sup.1 represents: a hydrogen atom; a linear C.sub.1-C.sub.4 radical alkyl; R.sup.2, R.sup.3 and R.sup.4, identical or different, represent: a hydrogen atom; a C.sub.1-C.sub.5 radical alkyl, linear or branched; a hydroxy group; R.sup.5 represents: a hydrogen atom; a C.sub.1-C.sub.5 radical alkyl, linear or branched; a C.sub.1-C.sub.5 radical alkoxy, linear or branched; a hydroxy group; and it being understood that R.sup.4 and R.sup.5 can together form a six-member cycle comprising an oxygen atom; said cycle being substituted by a branched C.sub.1-C.sub.17 alkyl radical.

22. The phenolic compound according to claim 20, wherein, in Formula (I): R.sup.1, R.sup.2 and R.sup.3, identical or different, represent: a hydrogen atom; a methyl radical; and R.sup.4 and R.sup.5 together form a six-member cycle comprising an oxygen atom; said cycle being substituted by a branched C.sub.1-C.sub.17 alkyl radical.

23. The phenolic compound according to claim 22, wherein the phenolic compound(s) is or are chosen from Formula (I): ##STR00005## Formula (I), wherein R.sup.1, R.sup.2 and R.sup.3, identical or different, represent: a hydrogen atom; a methyl radical.

24. The phenolic compound according to claim 20, wherein, in Formula (I): R.sup.1, R.sup.2, R.sup.3 and R.sup.5 represent a hydrogen atom; and R.sup.4 represents a C.sub.1-C.sub.5 alkoxy radical.

25. The phenolic compound according to claim 20, wherein, in Formula (I): R.sup.1 and R.sup.3 represent a hydrogen atom; R.sup.2 and R.sup.5 represent a branched C.sub.1-C.sub.8 alkyl radical; and R.sup.4 represents a hydroxy group.

26. The phenolic compound according to claim 20, wherein the phenolic compound of Formula (I) is selected from the group consisting of 2,5-di-tert-butyl hydroquinone, 2,5-di(tert-amyl)hydroquinone, vitamin E and monomethyl ether hydroquinone.

27. The phenolic compound according to claim 26, wherein the phenolic compound of Formula (I) is vitamin E.

28. The phenolic compound according to claim 20, wherein the initiator(s) is or are selected from the group consisting of organic peroxides, oxygen azobisisobutyronitrile (AIBN) and mixtures thereof.

29. The phenolic compound according to claim 28, wherein the organic peroxides is or are selected from the group consisting of peroxy esters, dialkyl peroxides, hydroperoxides and peroxycetals.

30. A method of stabilizing radical copolymerization reactions comprising using the phenolic compound according to claim 20 with other comonomers selected from the group consisting of the esters of unsaturated carboxylic acid (or their salts), the carboxylic acid anhydrides, the vinyl esters, the alpha-olefins, the unsaturated carboxylic acids, the derivatives of (meth)acrylic acid, the vinyl ethers, the aromatic vinyl compounds, from carbon monoxide, and mixtures thereof.

31. The method according to claim 30, wherein the unsaturated carboxylic acids esters are selected from the group consisting of the C.sub.1-C.sub.24 (meth)alkyl acrylates and (meth)acrylates comprising an epoxy group.

32. The method according to claim 30, to limit the decomposition of ethylene during radical ethylene copolymerisation at high pressure.

33. A method for preparing ethylene copolymers comprising a radical ethylene copolymerisation step at high pressure in the presence of one or more initiators and one or more phenolic compounds according to claim 20.

34. The method of claim 33, wherein the radical copolymerisation step is performed in an autoclave reactor.

35. The method of claim 34, further comprising injecting the one or more initiators into a reaction mixture beginning at a temperature below 100 C.

36. The method of claim 35, wherein the method does not include a step in which the monomers are preheated prior to the introduction of said one or more initiators.

37. The method of claim 33, wherein pressure varies from 50 Mpa to 300 Mpa.

38. A polymer composition obtained by radical ethylene copolymerisation at high pressure in the presence of one or more initiators and of one or more phenolic compounds according to claim 20.

Description

EXAMPLES

[0162] The following examples were performed on a 110 ml continuous stirred autoclave micro-pilot.

[0163] This equipment operates continuously at pressures comprised from 500 to 2200 bar. The reactor wall temperature is set at 200 C. by means of heater rods placed in the walls of the reactor. Stirring is at 1540 rpm (revolutions per minute).

[0164] The temperature of the reaction medium in the reactor is measured by means of four thermocouples.

[0165] The reaction mixture is comprised of an ethylene mixture and acrylates which continuously flows into the reactor with residence time that can vary from 30 seconds to 120 seconds. The stabilising agent (phenolic compound) is introduced in mixture with acrylates.

[0166] The polymerisation initiator is continuously introduced into the reactor in amounts that enable a temperature of about 210 C. to be reached. When exiting the reactor, the polymer/monomer mixture is directly decompressed to three bars and the polymer is separated from the ethylene/acrylates mixture that did not react through a separation pot.

[0167] Operating Conditions: [0168] Reactor flow: 4 kg/hr, [0169] Peroxide used: Diluted Luperox 11 (tert-butyl peroxypivalate) in n-Heptane, [0170] Residence time in the reactor: approx. 50 seconds, [0171] Pressure: 1900 bar (190 Mpa), [0172] Monomers: mixture of acrylates (methyl acrylate and glycidyle methacrylate with mass weights of respectively 5% and 1.5% in feed), [0173] Stabilising agents: variable amounts that are introduced with acrylic monomers.

[0174] When the reaction has stabilised at the temperature of about 210 C. for approximately 5 to 10 min, the peroxide flow is then gradually increased every 4 minutes until decomposition is achieved (sometimes this limit is not reached), which enables the decomposition limits (or peroxide concentration sensitivity) to be determined.

[0175] The efficacy of the stabilising agent is determined by the amount of peroxides injected to achieve decomposition: the higher the amount of peroxide, the more effective the stabilising agent.

[0176] Trial #1: Testing with 230 ppm Moles of Stabilising Agent/Acrylate

[0177] In this trial, vitamin E was compared with butyl hydroxytoluene (BHT) with the same molar concentrations relative to acrylates. For each stabilising agent, a minimum of 3 trials was performed. The mean values for the trials are shown in the following table:

TABLE-US-00001 ppm mole stabilising Mean [C] Peroxide Stabilising agents agent relative to at decomposition (phenolic compounds) acrylates in ppm moles Without stabilising agent 60.4 BHT 230 108.8 Vitamin E 230 120.0

[0178] The results show that Vitamin E enables greater stabilisation of the ethylene copolymerisation reactions, as ethylene decomposition is achieved at much higher concentrations of organic peroxides than with butyl hydroxytoluene (BHT).

[0179] In these trials, the mean values are significantly different.

[0180] Test #2: Testing with 460 ppm Moles of Stabilising Agent/Acrylate

[0181] In this trial, vitamin E and monomethyl ether hydroquinone (MEHQ) were compared with butyl hydroxytoluene (BHT) with the same molar concentrations relative to acrylates. For each stabilising agent, a minimum of 3 trials was performed. The mean values for the trials are shown in the following table:

TABLE-US-00002 ppm mole stabilising Mean [C] Peroxide Stabilising agents agent relative to at decomposition (phenolic compounds) acrylates in ppm moles Without stabilising agent 60.4 BHT 460 92.9 MEHQ 460 97.3 Vitamin E 460 132.5

[0182] The results show that Vitamin E and monomethyl ether hydroquinone (MEHQ) enable greater stabilisation of the ethylene copolymerisation reactions than with butyl hydroxytoluene (BHT) as ethylene decomposition is achieved at much higher concentrations of organic peroxides.

[0183] Furthermore, the best results were obtained with Vitamin E.

[0184] In these trials, the mean values are significantly different.

[0185] Trials #3: Testing with 115 ppm Moles of Stabilising Agent/Acrylate

[0186] In this trial, vitamin E was compared with butyl hydroxytoluene (BHT) with the same molar concentrations relative to acrylates. For each stabilising agent, a minimum of 3 trials was performed. The mean values for the trials are shown in the following table:

TABLE-US-00003 ppm mole stabilising Mean [C] Peroxide Stabilising agents agent relative to at decomposition (phenolic compounds) acrylates in ppm moles Without stabilising agent 60.4 BHT 115 77.2 Vitamin E 115 102.8

[0187] The results show that Vitamin E enables greater stabilisation of the ethylene copolymerisation reactions than with butyl hydroxytoluene (BHT) as ethylene decomposition is achieved at much higher concentrations of organic peroxides.

[0188] In these trials, the mean values are significantly different.