Polyolefin composition, production process and applications thereof

(54) COMPOSITION BASED ON DOLEFIN POLYMER, PROCESS FOR OBTAINING SAME AND USE THEREOF.

©) Composition based on olefin block copolymer, the polymer chains of which consist of at least one segment (A) derived from propylene and which may contain up to 100 monomer units derived from ethylene and / or from an α -C4-C8 olefin per 100 monomeric units derived from propylene and a segment (B) derived from ethylene and which may contain up to 100 monomeric units derived from C3-C8 ocolefin (s) per 100 monomeric units ethylene derivatives, at least one of the segments (A) or (B) having a weight average molecular weight of at least 200,000 daltons.

Process for obtaining and using it as a compatibilizing agent.

-1 Composition based on olefin polymer, process for obtaining and using it

The present invention relates to compositions based on olefin polymers and more particularly based on block copolymers, the polymer chains of which comprise at least one polypropylene segment and one polyethylene segment. The present invention also relates to a process for the preparation of these compositions as well as their use as an agent for compatibilizing polyolefins.

It is known that traditional Ziegler-Natta catalysts do not allow the synthesis of living polymers because the termination and chain transfer reactions are competitive with those of propagation. As a result, the so-called block copolymers obtained by successive polymerizations of different monomers using these catalysts are not real block copolymers in which the polymer chains consist of successive segments of different composition but consist essentially of mixing polymer chains of different compositions obtained during the successive polymerization stages.

However, under well-defined conditions, the soluble ZieglerNatta catalysts can give rise to living polymerization and therefore to real block copolymers. Thus, the document EP-0513216 describes block copolymers obtained, at low temperature, using ionic metallocene catalysts. However, the products obtained contain less than 70% by weight of said block copolymers and have relatively low molecular weights.

It is also known that catalysts based on a-di-immine nickel can give rise to living polymers and to real block copolymers. Thus, documents US-A-5891963 and J. Am. Chem. Soc. 1996, 118, p. 11664-11665 describe block copolymers whose polymer chains consist of polypropylene segments and polyhexene or polyoctene segments. However, these copolymers are obtained with relatively low yields and have a high cost linked to the nature of the comonomers used. In addition, the presence of monomer residues

- 2 heavy in the final polymer makes it difficult to separate the polymer from its preparation medium.

It therefore turns out to be advantageous to develop real block copolymers derived from propylene and ethylene which are economically profitable and which do not have the disadvantages of real block copolymers described in the prior art.

The present invention aims to satisfy such an objective.

To this end, the present invention relates to a copolymer-based composition containing olefin blocks, the polymer chains of which consist of at least one segment (A) derived from propylene and which may contain up to 100 monomer units derived from ethylene and / or d '' a C4-C8 α-olefin per 100 monomer units derived from propylene and a segment (B) derived from ethylene and which may contain up to 100 monomer units derived from C3-C8 aolefin (s) per 100 units derivative monomers ethylene, at least one of the segments (A) or (B) having a weight average molecular weight of at least 200,000 daltons.

The compositions according to the invention generally comprise at least 70% by weight of block copolymer and more particularly at least 75% by weight of block copolymers. Compositions containing at least 85% by weight of block copolymer are very suitable. The maximum content of block copolymer in the compositions according to the invention is not critical. It is noted however that this maximum content is most often less than 98% by weight, more particularly less than 95% by weight. Compositions consisting essentially of block copolymers also fall within the scope of the present invention. The term “compositions consisting essentially of block copolymers” is understood to mean compositions containing no other polymer constituent derived from a-olefin than the block copolymer (s) defined above.

In the context of the present invention, the term “block copolymer content of the compositions” is understood to mean the quantity of polymer insoluble in toluene at room temperature as measured below in relation to the examples illustrating the invention.

The fraction of the compositions according to the invention soluble in toluene most often consists of a mixture of polymer chains derived from propylene and of polymer chains derived from ethylene.

- 3 The block copolymer according to the invention can contain several segments (A) ct / or (B) of identical or different composition. Block copolymers of structure AB, ABA or BAB are particularly suitable. Among these, the block copolymers of structure AB and ABA give advantageous results. Block copolymers of structure AB are particularly preferred.

The relative proportions of segments (A) and (B) are not critical. However, block copolymers are preferred in which the molar ratio of the segment (s) (A) to the segment (s) (B) is from 0.1: 10 to 10: 0.1, more especially 1:10 to 10: 1. Block copolymers whose segments (A) and (B) are in 40:60 to 60:40 molar ratios give the best results.

It goes without saying that the polymer chains of block copolymers can contain other polymer segments such as, by way of nonlimiting examples, segments of polyolefins different from segments (A) and (B). More particularly, these segments can be polymer segments of α-olefins containing from 4 to 10 carbon atoms. As examples of such segments, mention may be made of polybutene, polyhexene or polyoctene segments. The content of these segments is most often less than 50% by weight relative to the weight of the block copolymer. Contents of less than 20% by weight and more particularly less than 10% by weight giving the best results.

One of the essential characteristics of the compositions according to the invention is the particularly high molecular weight of the block copolymers. It is in fact noted that the block copolymers are such that the average molecular mass of at least one of the segments (A) or (B) is at least 200,000 daltons, more particularly at least 220,000 daltons. Block copolymers with a weight average molecular weight of at least one segment is 250,000 daltons give the best results. Preferably the weight average molecular weight of the other segment is at least 100,000 daltons and more particularly at least 150,000 daltons. The preferred block copolymers are such that the weight average molecular weight of the segments (A) and (B) is at most 1,500,000, preferably at most 1,200,000 and more particularly at most 1,000. 000 daltons.

The molecular weight distribution of the block copolymers is also extremely narrow. Indeed, this distribution, characterized by the

- 4 ratio of the average molecular weight by weight to the average molecular weight by number, is most often less than 2.2 and more particularly less than 2.

Furthermore, when the compositions according to the invention are obtained using the catalytic system described below, it is most often noted that the polypropylene segments (A) may have a structure different from that of the polypropylene chains obtained with the systems traditional catalytics. This structure is characterized by a number of connections -CH3 coming from propylene lower than the number of groups -CH2- coming from propylene. In particular, when the segment (A) comprises only units derived from propylene, it is noted that the ratio of the number of connections -CH3 to the number of groups -CHg- present in the polymer chain is most often less than 1 and more particularly in the range of 400: 1000 to 800: 1000. Ratios greater than 800: 1000 and more particularly greater than or equal to approximately 950: 1000 which can be obtained when the polymerization is carried out at low temperature (less than 0 ° C.).

When the compositions according to the invention are obtained using the catalytic systems described below, it is most often noted that the polyethylene segment (B) has a relatively high number of connections. When segment (B) contains only monomeric units derived from ethylene, it is noted that this number of connections is most often from 10 to 150 per 1000 groupings -CKl ·? Polyethylene segments having less than 10 connections per 1000 -CH2- groups being obtained at low temperature (below 0 ° C).

Compositions which give good results are the compositions based on block copolymer having a diblock structure AB in which the segment (A) contains less than 50, more particularly less than 25 monomeric units derived from ethylene and / or from an α - C4-C8 olefin per 100 monomeric units derived from propylene. Particularly preferred compositions are such that the segment (B) contains less than 50, advantageously less than 25 monomeric units derived from C3-C8 a-olefin (s) per 100 monomeric units derived from ethylene. In addition, these block copolymers are most often such that the weight ratio of segment (A) to segment (B) is from 10: 100 to 100: 10, more particularly from 40:60 to 60:40. Particularly advantageous block copolymers being the

- 5 AB copolymers whose weight average molecular weight of segment (A) is from 200,000 to 600,000 daltons and the weight average molecular weight of segment (B) is preferably from 150,000 to 800,000 daltons.

These particular compositions advantageously contain at least 85% by weight of block copolymer.

The block copolymers according to the invention are most often characterized by a melting temperature of at least 80 ° C., advantageously at least 120 ° C. The melting temperature is also generally at most 160 ° C. Melting temperatures of at most 140 ° C giving good results.

The melting temperature of these block copolymers can be significantly different from the values ​​mentioned above when they contain one or more segments different from segments (A) and (B).

The melting point of the compositions according to the invention depends on their content of block copolymers and on the nature of the other components.

The compositions according to the invention exhibit a particularly advantageous compromise of properties. They also make it possible to effectively compatibilize mixtures of polymers and more particularly mixtures of polypropylene and polyethylene obtained by traditional Ziegler-Natta catalysis or with the intervention of metallocene catalysts.

The compositions according to the present invention can be used as they are. They can also contain various additives, such as, by way of nonlimiting examples, stabilizing agents, nucleating agents, antacids, antioxidants, organic or inorganic dyes, fillers, such as talc or fibers. of glass. The compositions according to the invention can also be used as a constituent (for example as a masterbatch) for subsequently producing other compositions.

The compositions according to the invention can be used by all the conventional processes for transforming thermoplastic materials such as for example by molding, extrusion, injection and on all the apparatus and devices used for this purpose.

The compositions according to the present invention are generally obtained by polymerization in at least two successive stages with the intervention of catalysts based on a di-imminic complex of metals from groups 8 to 10 of the periodic table corresponding to the general formula

<img file="FR2812645A1_D0001.tif" />

in which

M represents a metal from groups 8 to 10 of the periodic table,

R 'and R ”, identical or different, are each hydrogen, halogen, a hydrocarbon group containing from 1 to 35 carbon atoms, an alkoxy group, an amino group, a phosphorus-containing hydrocarbon group or a silicon-containing hydrocarbon group having from 1 to 20 carbon atoms,

- R¹ and R² are each independently of one another hydrocarbon groups such that the carbon atom bonded to nitrogen is also bonded to at least two other carbon atoms, and

R³ and R⁴ are each independently of the other hydrogen, a hydrocarbon group, substituted or not, the two groups R³ and R⁴can be linked together to form a cycle.

Among these compounds, the preferred catalysts are generally such that M is Ni, Fe, Co or Pd,

R 'and R ”are each a halogen or a hydrocarbon group of 1 to 10 carbon atoms,

Rl and R² are each independently of one another hydrocarbon groups containing from 3 to 30 carbon atoms such that the carbon atom bonded to nitrogen is hey with at least two other carbon atoms,

R³ and R⁴ are each independently of the other groups containing from 1 to 30 carbon atoms which can be linked together to form a ring.

The preferred catalysts are chosen from nickel compounds. Di- (2,6-iPr-Ph) diazobutane- (1,8 naphthenejNiBrq] and di- (2,6-iPrPh) diazobutane- (CH3) 2NiBr2 give particularly good results.

These catalysts are most often used in conjunction with activators preferably chosen from organoaluminum compounds such as, for example, aluminoxanes and ionizing agents. By aluminoxanes is meant the compounds corresponding to the formulas R2A10- (AlR0)_not -AIR2 and

- 7 XA1ROJû + 2 in which n is a number from 1 to 40 and R is an alkyl or aryl group containing from 1 to 12 carbon atoms or a hydrogen atom. Preferred compounds of this type are methyl-, ethyl- or isobutyl-aluminoxanes.

The term “ionizing agents” is intended to denote the compounds comprising a first part which has the properties of a Lewis acid and which is capable of ionizing the catalyst and a second part, which is inert with respect to the ionized catalyst and which is able to stabilize it. By way of example of such compounds, mention may be made of triphenylcarbenium tetrakis (pentafluorophenyl) borate, N, Ndimethylanilinium tetrakis (pentafluorophenyl) borate, tri- (n-butyl) amonium tetrakis (pentafluorophenyl) borate, tri (pentafluorophenyl) boron, triphenylboron, trimethylboron, tri (trimethylsilyl) borate and organoboroxins.

The preferred activators according to the present invention are aluminoxanes.

The amount of activator compound depends on the type of activator used. When the activator is an aluminoxane, the amount of activator is most often such that the atomic ratio between the aluminum of the aluminoxane and the metal of the catalyst is from 0.1 to 40,000. Preferably, this ratio is at least 1, more particularly at least 2. Most often, the activator is used in quantities such that the aluminum / metal atomic ratio is at most 10,000 and more particularly at most 5,000. When the activator is an ionizing agent, the catalyst is most often used in amounts such that the molar ratio of the catalyst and the activator is from 0.01 to 100. Preferably, this ratio is at least minus 0.5 and more particularly at most 25. Reports of about 1 to about 5 give particularly good results.

The compositions according to the invention are obtained in at least two successive polymerization stages during which the segments (A) and (B) are obtained. The order of the steps is not critical. However, it is preferred to polymerize a mixture based on propylene during the first step.

It goes without saying that polymer chains other than those of the block copolymer can be formed during these steps.

The polymerization stages can be carried out according to any known process, in solution or in suspension in a hydrocarbon diluent, in suspension in the, or one of the monomers maintained in the liquid state or in the gas phase. The polymerization temperature is most often from -70 ° C to + 80 ° C. The use of low temperatures

- 8 promoting living polymerization, it is preferable to carry out the polymerization at a temperature below 20 ° C., more particularly below 0 ° C.

Temperatures from -25 ° C to 0 ° C are suitable.

The pressure is preferably chosen between atmospheric pressure and 80 10 ^ Pa, more particularly between 5 and 40 10 ^ Pa. The duration of the various stages is not critical. It is generally chosen according to the desired molecular mass for the segments (A) and (B). The duration of each of the stages is most often between 1 minute and ten hours.

Duration greater than 5 minutes and more particularly greater than 10 minutes are suitable. Preferably the maximum duration of each of the stages does not exceed 5 hours, preferably not 2 hours.

It may also prove preferable to introduce into the polymerization medium one or more organoaluminum compounds making it possible to improve the activity of the catalyst and / or to capture the poisons of the polymerization reaction. These compounds can be aluminoxanes as described above or organoaluminum compounds corresponding to the formula R_m AlX3__m or R_m So²3__m in which R is a radical as defined above, X is a halogen atom, R² is a hydrocarbon radical containing from 1 to 20 carbon atoms and m is a number such that 0 &lt;m &lt;3.

Preferred organoaluminum compounds are trialkylaluminiums, alkylaluminium halides and aluminoxanes.

The following examples serve to illustrate the invention. The methods for measuring the quantities mentioned in the examples, the units expressing these quantities and the meaning of the symbols used in these examples are explained below.

The weight average molecular weight (Mw) is obtained by steric exclusion chromatography from a solution of polymer in trichlorobenzene at 0.5 g / 1, using a Waters Styragel HMW 6E polystyrene column sold by Waters. Co Ldt.

The distribution of molecular weights (Mw / Mn) is characterized by the ratio of the weight average molecular weight to the number average molecular weight obtained as described above.

CPB = content of block copolymer of the compositions according to the invention expressed in% by weight and determined from the weight of the fraction insoluble in toluene measured at room temperature (25 ° C) by adding 250 ml of toluene to 4g of composition under

- 9 magnetic stirring for a period of 24 hours. The suspension is then filtered on WHATMAN 113 paper which is then dried at room temperature (25 ° C) until a constant weight is obtained.

[A] = proportion of segment (A) in the block copolymer expressed in molar% and determined by Nuclear Magnetic Resonance 'H. The NMR spectrum is taken from a solution of the polymer at 120 ° C. in 1,1,2,2-tetrachloroethane from the bands corresponding to the -CH groups.₃ at about 0.25 ppm and bands -CHl ·? - at about 0.7 ppm [B] = proportion of segment (B) in the block copolymer obtained by difference from the value [A]

Tm = Melting temperature of the block copolymer measured by differential thermographic analysis (DSC) using an ELMER DSC SYSTEM device sold by the company Perkin Elmer

Examples 1 to 4

a) Preparation of the catalyst based on a diimminic complex

Synthesis of di- (2,6-iPr-Ph) diazobutane - (1,8 naphthene)

1.71 g (9.39 mmol) of acenaphthaquinone are introduced into a 100 ml beaker and 50 ml of methanol are added thereto, followed by 3.6 ml (19.2 mmol) of 2,6-diisopropyl aniline and 1 ml of formic acid.

The reaction is stirred for 12 hours and the precipitate is filtered and washed with methanol. Its purification by recrystallization from dichloromethane makes it possible to obtain diimine with a yield of 70% (3.5 g). Synthesis of di- (2,6-iPr-Ph) diazobutane - (1,8 naphthene) NiBr?

g (3.25 mmol) of (1,2-dimethoxyethane) NiBr₂ and 2 g (4 mmol) of the diimine are introduced into a 250 ml beaker.

100 ml of dichloromethane are added and the mixture is kept stirring for 24 hours. The solvent is then removed under vacuum and the residues are washed with diethyl ether. The final product (molecular weight 718.71) is isolated in the form of a yellow powder with a yield of 63% (1.9 g). The proton NMR spectrum shows the -CH groups₃ between 0.18 and 0.38 ppm and CH groups₃ between 0.6 and 0.8 ppm.

b) General polymerization conditions

In a 350 ml reactor, previously conditioned under nitrogen, 300 ml of toluene are added. The reactor is drawn under vacuum for 5 minutes then

- 10 connected to a 5 liter cylinder pressurized with propylene. The initial propylene pressure in the cylinder is such that the average pressure of the assembly is approximately 3 bars (example 1) or approximately 2 bars (examples 2 to 4), the reactor being maintained at -10 ° C.

After 30 minutes, a mixture of 5 ml of methylaluminoxane 10% (Witco Eurecene T 5010) and 5 ml of toluene is added and the polymerization is started by introduction of 12 mg (16.6 pmole) of di- (2,6-iPr -Ph) diazobutane (1.8 naphthenejNiBrg in solution in 15 ml of toluene. The temperature is maintained at -10 ° C throughout the duration of preparation of the first block. Then the reactor is disconnected from the cylinder and the propylene is degassed under empty for 5 minutes.

The reactor is then connected to another 5-liter cylinder pressurized to an ethylene pressure such that the average system pressure is around 2 bars at -10 ° C. The system is maintained under these conditions for the duration of the polymerization of the second block. The polymerization is stopped by degassing of the ethylene. The reactor is emptied into a beaker containing 100 ml of ethanol.

300 ml of toluene are introduced into the reactor and the latter is kept stirring for two hours at 100 ° C. under 5 bars of nitrogen before being emptied into the same beaker. A large excess of ethanol and 5 ml of concentrated HCl diluted in 50 ml of water are added to the 600 ml of toluene in order to precipitate the polymer and destroy the catalyst and the activator present. The precipitated polymer is filtered and dried to constant weight.

<td>Example</td><td> 1</td><td> 2</td><td> 3</td><td> 4</td>

<td>1st block</td><td></td><td></td><td></td><td></td>

<td>Duration (min)</td><td> 60</td><td> 90</td><td> 90</td><td> 90</td>

<td>2nd block</td><td></td><td></td><td></td><td></td>

<td>Duration</td><td> 15</td><td> 15</td><td> 15</td><td> 15</td>

<td>CPB (%)</td><td> 94</td><td> 90</td><td> 95</td><td> —</td>

<td>Mw (dalton)</td><td> 620000</td><td> 552000</td><td> 872000</td><td> 923000</td>

<td>Mw / Mn</td><td> 1.5</td><td> 1.9</td><td> 1.7</td><td> 2.0</td>

<td>Tm</td><td> 112</td><td> 119</td><td> 123</td><td> 131</td>

<td>[AT]</td><td></td><td> 37</td><td> 35</td><td> 37</td>

<td>[B]</td><td></td><td> 63</td><td> 65</td><td> 63</td>

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