GB2156368A

GB2156368A - Block copolymers and manufacture thereof

Info

Publication number: GB2156368A
Application number: GB08507762A
Authority: GB
Inventors: Francois Cansell; Michel Fontanille; Alain Siove
Original assignee: Chimique des Charbonnages SA
Current assignee: Orkem SA
Priority date: 1984-03-28
Filing date: 1985-03-26
Publication date: 1985-10-09
Also published as: ES8603522A1; GB2156368B; IT8547857A1; LU85818A1; IT1182724B; IE58344B1; GR850760B; FR2562079A1; NL8500919A; CH662574A5; DE3510624A1; ES541366A0; GB8507762D0; IT8547857A0; BE902035A; JPS6112712A; CA1281451C; FR2562079B1; IE850777L

Abstract

Block copolymers of formula (A)a(D)b(M)c, in which A is a vinyl aromatic block, D is a conjugated diene block, and M is a C3-13alpha-olefin block optionally including ethylene, a is 20-5000 and b is 1-10, are prepared by polymerising M in the presence of (i) a precursor polymer of formula (A)a(D)bLi and (ii) a titanium or vanadium halide. Certain block copolymers in which M is propylene are claimed per se.

Description

SPECIFICATION Block copolymers and manufacture thereof The present invention relates to block copolymers and to a process for their manufacture.

According to a first aspect of the present invention there is provided block copolymers comprising units derived from at least one conjugated diene D, units derived from at least one vinyl-aromatic compound A, and units derived from at least one a-ole- fin M, the structure of the block copolymer being representable by the formula (A)a(D)b(M)C, characterised in that: - a is greater than or equal to 20 and less than or equal to 5000, - b is greater than or equal to 1 and less than or equal to 10, - M is proplyene, - the degree c of copolymerisation of propyiene is such that the number-average molecular weight of the polypropylene block is from 10,000 to 200,000 and - the polypropylene block consists of a mixture of isotatic, heterotactic and syndiotactic triads.

The vinyl-aromatic compounds to be used in accordance with the invention are preferably compounds capable of undergoing anionic polymerisation such as, for example, styrene, amethylstyrene, vinylnaphthalene, vinyltoluene, 2vinyltoluene, 2-vinylpyridine, 4- vinylpyridine, methyl acrylate, ethyl acrylate, methyl methacrylate, ethyl methacrylate or mixtures of these substances. The conjugated dienes to be used are preferably 1,3-butadiene and substituted butadienes such as isoprene, piperylene, 2,3-dimethyl1,3-butadiene, 1-phenyl-1,3- butadiene or mixtures of these substances.

According to a preferred embodiment of the present invention, the polypropylene block of the block copolymer according to the invention consists of a mixture of isotactic, heterotactic and syndiotactic polymeric triads and this mixture may comprise from 30 to 60% of isotactic triads, from 20 to 35% of heterotactic triads and from 20 to 35% of syndiotactic triads.

According to a second aspect of the present invention there is provided a process for the manufacture of block copolymers by polymerising at least one monomer M chosen from among the aolefins having from 3 to 13 carbon atoms and mixtures of these a-olefins with ethylene, in at least one solvent and in the presence of a catalyst system comprising, firstly, a halide Mt of a transition metal chosen from among titanium and vanadium and, secondly, an organolithium polymer precursor of the formula (A)a(D)bLi, in which A is at least one vinyl-aromatic compound and D is at least one conjugated diene, the atomic ratio Li1Mt being from 1 to 3, characterised in that:: - the catalyst system essentially consists of the said organolithium polymer precursor and of a halide of the transition metal Mt, in which the metal is tetravalent, - a is greater than or equal to 20 and less than or equal to 5000, - b is greater than or equal to 1 and less than or equal to 10 and - the concentration of the said precursor in the reaction mixture is from 2.10-3 to 5,10-2 mole per litre.

The process according to the invention can be carried out at a temperature of from 0 to +100"C under a pressure of, approximately, from 0.8 bar to 1000 bars and in the presence of at least one hydrocarbon solvent.

Preferably, the hydrocarbon solvents to be used in the present process are aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene, aliphatic hydrocarbons such as hexane, heptane and the like, and cycloaliphatic hydrocarbons such as cyclopentane, cyclohexáne and methylcyclohexane. These solvents are inert and can be employed either alone or in the form of mixtures of two or more of them. The amount to be used of these hydrocarbon solvents may be generally from 1 to 20 parts by weight per part by weight of the total monomers. These solvents and the monomers should, before use, be completely freed from substances such as water, oxygen, carbon dioxide, certain sulphur compounds and acetylenes, which would destroy the initiators employed in the present process and the active ends of the growing polymer.According to another embodiment of the invention, it is also possible to obtain the block copolymer not only in solution but also in suspension in a solvent, by suitably choosing the sequence of addition of the solvents and of the monomers.

Among the transition metal halides present in the composition of the catalyst system according to the present invention, titanium tetrachloride, vanadium tetrachloride and mixtures of these are preferred.

The duration of the polymerisation reaction of the monomers M is advantageously fom 1 to 90 minutes depending on the chosen temperature and the chosen pressure.

Given the respective reactivities of ethylene and of the a-olefin in the presence of the catalyst system in question, it is preferable that the mixture subjected to polymerisation in the process according to the invention should comprise at least 20 mole% of a-olefin and at most 80 mole% of ethyl ene.

The examples which follow are given by way of illustration and are not intended to limit the present invention.

Example 1 An organolithium polymer precursor of the formula: (styrene),0O(butadiene)3Li is first of all prepared in accordance with the well- known methods described in particular by J.E.L. ROOVERS and S. BYWATER in Macromolecules 8, 3 (1975). This precursor is reacted, in toluene, with titanium tetrachloride, using a molar ratio Li/Ti of 2. The organolithium precursor thus formed is then introduced into a glass reactor kept under an inert gas atmosphere at the same time as an additional amount of toluene, so chosen that the precursor concentration in the mixture is 6.5 x 10-3 mole per litre.

Propylene is introduced into the reactor until the pressure reaches 850 millibars and the polymerisation is carried out at a constant temperature of 20"C for 60 minutes. At the end of the reaction there is obtained, in a yield of 280 grams per hour per atmosphere pressure and per gram-atom of titanium per litre, two-block copolymer of the formula: (styrene)10(butadiene)3(prnpylene), This coploymer is analysed: - first, by the gel permeation chromatography technique, in 1,2,4-trichlorobenzene at 140"C, using a WATERS GPC 200 apparatus, and - secondly, by the carbon 13 nuclear magnetic resonance spectrometry technique, using BRUCKER W.P. 60 D.S. and BRUCKER 250 apparatuses.

The number-average molecular weight of the polypropylene block, measured by the first-mentioned technique, is 30,500. Figure 1 shows the spectrum obtained by the second technique; this spectrum makes it possible to identify unambiguously the different blocks of the two-block copolymer and to establish that the polypropylene block contains 46% of isotactic triads, 27% of heterotactic triads and 27% of syndiotactic triads.

Example 2 Using the same catalyst system as in the preced ing example, in an amount of 3 x 103 mole of pre cursor per litre, a gas mixture consisting of 80 mole% of propylene and 20 mole% of ethylene is introduced into the reactor until a pressure of 850 millibars is reached. The copolymerisation of these monomers is carried out at a constant temperature of 20"C for 60 minutes. At the end of the reaction, a three-block copolymer is recovered in a yield of 655 grams per hour per atmosphere pressure and per gram-atom of titanium per litre, and is ana lysed in accordance with the same techniques as in Example 1. The gel permeation chromatography spectrum makes it possible to establish that the poly-(ethylene, copropylene) block has a number average molecular weight of 70,600 and that it comprises 50 mole% of units derived from ethylen and 50 mole% of units derived from propylene.

Figure 2 shows the carbon 13 nuclear magnetic resonance spectrum determined on the three-block copolymer obtained.

Claims

1. Block coploymers comprising units derived from at least one conjugated diene D, units derived from at least one vinyl-aromatic compound A, and units derived from at least one a-olefin M, the structure of the block copolymer being represented by the formula (A),(D)b(M),, wherein: a is greater than or equal to 20 and less than or equal to 5000.

b is greater than or equal to 1 and less than or equal to 10, M is propylene.

the degree c of copolymerisation of propylene is such that the average molecular weight of the polypropylene block is from 10,000 to 200,000 and the polypropylene block consists of a mixture of isotactic, heterotactic and syndiotactic triads.

2. Block copolymers according to Claim 1, wherein the mixture constituting the block (M) comprises from 30 to 60% of isotactic triads, from 20 to 35% of heterotactic triads and from 20 to 35% of syndiotactic triads.

3. Block copolymers according to Claim 1 or Claim 2 wherein the vinyl-aromatic compound is chosen from among styrene; a-methylstyrene, vinylnaphthalene, vinyltoluene and mixtures thereof.

4. Block copolymers according to any one of Claims 1 to 3 wherein the conjugated diene is chosen from among 1,3-butadiene, isoprene, piperylene, 2,3-dimethyl- 1,3-butadiene, 1-phenyl-1,3butadiene and mixtures thereof.

5. Process for the manufacture of block copolymers by polymerising at least one monomer M chosen from among the a-olefins having from 3 to 13 carbon atoms and mixtures of such a-oiefins with ethylene, in at least one solvent and in the presence of a catalyst system comprising (i) a halide of a transition metal M, chosen from among titanium and vanadium, and (ii) an organolithium polymer precursor of the formula (a)a(D)bLi, in which A is at least one vinyl-aromatic compound and D is at least one conjugated diene, the atomic ratio Li/Mt being from 1 to 3, wherein:: the transition metal Mt is tetravalent, a is greater than or equal to 20 and less than or equal to 5000, b is greater than or equal to 1 and less than or equal to 10, and the concentration of the said precursor in the reaction mixture is from 2 x 1O-3 to 5 x 10-2 mole per litre.

6. Process according to Claim 5, wherein the reaction pressure is from 0.8 bar to 1000 bars.

7. Process according to Claim 5 or Claim 6, wherein the reaction temperature is from 0 C to +100"C.

8. Process according to any one of Claims 5 to 7, wherein the solvent is chosen from among aliphatic, aromatic and cycloaliphatic hydrocarbons.

9. Process according to any one of Claims 5 to 8, wherein the solvent is used in an amount of from 1 to 20 parts by weight per part by weight of the total monomers

10. Process according to any one of Claims 5 to 9, wherein the monomer M is a mixture comprising at least 20 mole% of a-olefins and at most 80 mole % of ethylene.

11. Block copolymers substantially as hereinbefore described in Example 1 or Example 2.

12. Process for the manufacture of block copolymers substantially as hereinbefore described in Example 1 or Example 2.

13. Block copolymers whenever produced by the process of any one of Claims 5 to 10 and 12.