Use of at least one phenolic compound to stabilise ethylene copolymerisation reactions

Abstract

A method of stabilizing radical ethylene copolymerization reactions for approximately 5 to 10 minutes, the method including using a phenolic compound with other comonomers and performing the radical ethylene copolymerization reactions at high pressure. Also, 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. A method of stabilizing radical ethylene copolymerization reactions for approximately 5 to 10 minutes, the method comprising using a phenolic compound with other comonomers, wherein the phenolic compound possesses a structure according to Formula (I): ##STR00004## 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; or 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; or 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; wherein the other comonomers comprise unsaturated carboxylic acid esters (or their salts), and optionally at least one other comonomer selected from the group consisting of carboxylic acid anhydrides, vinyl esters, alpha-olefins, unsaturated carboxylic acids, derivatives of (meth)acrylic acid, vinyl ethers, aromatic vinyl compounds, carbon monoxide, and mixtures thereof; wherein the unsaturated carboxylic acid esters include a C.sub.1-C.sub.24 (meth)alkyl acrylate and a (meth)acrylate possessing an epoxy group; wherein the method further comprises performing the radical ethylene copolymerization reactions at a high pressure in the presence of one or more initiators, wherein the method further includes a step of introducing a reaction mixture comprising ethylene and the comonomers into a reactor with a residence time of 30 to approximately 50 seconds and does not include a step in which the comonomers are preheated prior to the introduction of said one or more initiators, and wherein the method limits the decomposition of the ethylene during the radical ethylene copolymerization reactions at the high pressure.

2. The method of claim 1, wherein the radical copolymerization reactions are performed in an autoclave reactor.

3. The method of claim 2, further comprising injecting the one or more initiators into a reaction mixture at a temperature below 100° C.

4. The method of claim 1, wherein the radical copolymerization reactions are performed at a pressure from 50 MPa to 300 MPa.

5. A polymer composition obtained by radical ethylene copolymerization reactions according to claim 1.

6. The method of claim 1, wherein in Formula (I) of the phenolic compound: R.sup.1 represents: a hydrogen atom; or 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; or 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; or 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.

7. The method of claim 1, wherein in Formula (I) of the phenolic compound: R.sup.1, R.sup.2 and R.sup.3, identical or different, represent: a hydrogen atom; or 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.

8. The method of claim 1, wherein the phenolic compound is 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; or a methyl radical.

9. The method of claim 1, wherein in Formula (I) of the phenolic compound: 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.

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

11. The method of claim 1, 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.

12. The method of claim 1, wherein the phenolic compound of Formula (I) is vitamin E.

13. The method of claim 1, wherein the initiator(s) is or are selected from the group consisting of organic peroxides, oxygen azobisisobutyronitrile (AIBN) and mixtures thereof.

14. The method of claim 13, wherein the organic peroxides is or are selected from the group consisting of peroxy esters, dialkyl peroxides, hydroperoxides and peroxycetals.

15. The method according to claim 1, wherein the C.sub.1-C.sub.24 (meth)alkyl acrylate is selected from the group consisting of methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, ethyl-2-hexyl acrylate, cyclohexyl acrylate, n-octyl acrylate, methyl methacrylate, ethyl methacrylate and butyl methacrylate; and the (meth)acrylate possessing an epoxy group is selected from the group consisting of glycidyl methacrylate and glycidyl acrylate.

16. The method according to claim 15, wherein the C.sub.1-C.sub.24 (meth)alkyl acrylate is methyl acrylate, and the (meth)acrylate possessing an epoxy group is glycidyl methacrylate.

Description

EXAMPLES

(1) The following examples were performed on a 110 ml continuous stirred autoclave micro-pilot.

(2) 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).

(3) The temperature of the reaction medium in the reactor is measured by means of four thermocouples.

(4) 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.

(5) 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.

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

(7) 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.

(8) 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.

(9) Trial #1: Testing with 230 ppm Moles of Stabilising Agent/Acrylate

(10) 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:

(11) 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

(12) 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).

(13) In these trials, the mean values are significantly different.

(14) Test #2: Testing with 460 ppm Moles of Stabilising Agent/Acrylate

(15) 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:

(16) 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

(17) 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.

(18) Furthermore, the best results were obtained with Vitamin E.

(19) In these trials, the mean values are significantly different.

(20) Trials #3: Testing with 115 ppm Moles of Stabilising Agent/Acrylate

(21) 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:

(22) 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

(23) 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.

(24) In these trials, the mean values are significantly different.