Polyolefin composition, production process and applications thereof

Holder (s):

Agent (s): CABINET PEUSCET.

<img file="FR2812645B1_D0001.tif" />

-1 Composition based on olefin polymer, process for its production and use

The present invention relates to compositions based on olefin polymers and more particularly based on block copolymers whose polymer chains comprise at least one polypropylene segment and one polyethylene segment. The present invention also relates to a process for preparing 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 chain termination and transfer reactions are competitive with those of propagation. Therefore, the so-called block copolymers, obtained by successive polymerizations of different monomers with the intervention of these catalysts, are not true block copolymers in which the polymer chains consist of successive segments of different composition but are essentially made up of of mixing polymer chains of different compositions obtained during the successive polymerization steps.

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

It is also known that catalysts based on α-di-immine nickel can give rise to living polymers and to true 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 residues of monomers

- 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 true block copolymers derived from propylene and ethylene which are economically profitable and which do not exhibit the disadvantages of the true block copolymers described in the prior art.

The present invention aims to satisfy such an objective.

For this purpose, the present invention relates to a composition based on an 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 d '' one C4-C8 α-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 olefin (s) per 100 units monomeric derivatives of ethylene, at least one of 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 well suited. The maximum content of block copolymer in the compositions according to the invention is not critical. Note, 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 come 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 α-olefin than the block copolymer (s) defined above.

In the context of the present invention, the term “block copolymer content of the compositions” means the amount 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.

The block copolymer according to the invention may 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, 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 segment (s) (A) to segment (s) (B) is 0.1: 10 to 10: 0.1, plus particularly from 1:10 to 10: 1. Block copolymers in which the segments (A) and (B) are in molar ratios of 40:60 to 60:40 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 other than segments (A) and (B). More particularly, these segments can be segments of α-olefin polymer containing from 4 to 10 carbon atoms. As examples of such segments, mention may be made of segments of polybutene, polyhexene or polyoctene. The content of these segments is most often less than 50% by weight relative to the weight of the block copolymer. Contents 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 mass 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 of 250,000 daltons give the best results. Preferably the weight average molecular mass of the other segment is at least 100,000 daltons and more particularly at least 150,000 daltons. Preferred block copolymers are such that the weight average molecular mass of 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 block copolymers is also extremely narrow. Indeed, this distribution, characterized by the

- 4 ratio of the weight-average molecular mass to the number-average molecular mass 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 observed that the polypropylene segments (A) can have a structure different from that of the polypropylene chains obtained with the systems. traditional catalytic. This structure is characterized by a number of branches -CH₃ originating from propylene less than the number of -CH2- groups originating 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 the number of -CTb- groups present in the polymer chain is most often less than 1 and more particularly of the order 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 (below 0 ° C.).

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

Compositions giving good results are the compositions based on block copolymer having an AB diblock structure in which the segment (A) contains less than 50, more particularly less than 25 monomer units derived from ethylene and / or an α -C4-C8 olefin per 100 monomeric units derived from propylene. Particularly preferred compositions are such that segment (B) contains less than 50, preferably less than 25 monomer units derived from C3-C8 α-olefin (s) per 100 monomer units derived from ethylene. These block copolymers are also 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 mass of segment (A) is from 200,000 to 600,000 daltons and the weight average molecular mass 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 point of at least 80 ° C, advantageously of at least 120 ° C. The melting temperature is further generally at most 160 ° C. Melting temperatures of at most 140 ° C giving good results.

The melting point of these block copolymers can be appreciably 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 block copolymer content 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 efficiently compatibilize the mixtures of polymers and more particularly the mixtures of polypropylene and of polyethylene obtained by traditional Ziegler-Natta catalysis or by 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, stabilizers, 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) to subsequently produce other compositions.

The compositions according to the invention can be implemented by all the conventional processes for transforming thermoplastic materials such as, for example, by molding, extrusion, injection and on all the equipment and device 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

-63 ¹

R \ .N 'V

R '

R in which

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

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

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

- R³ and R⁴ are each independently of the other a hydrogen, a hydrocarbon group, substituted or not, the two groups R³ and R⁴that can be linked together to form a cycle.

Among these compounds, the preferred catalysts are generally such as

- 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 bonded to 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 naphthene) NiBr2] and di- (2,6-iPrPh) diazobutane- (CH3) 2NiBr2 give particularly good results.

These catalysts are most often used together with activators preferably chosen from organoaluminum compounds such as, for example, aluminoxanes and ionizing agents. The term “aluminoxanes” is understood to mean the compounds corresponding to the formulas R2A10- (AlR0)_not -AIR2 and

- 7 TAlROJh + 2 d^year 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 isobutylaluminoxanes.

By ionizing agents is meant 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) ammonium tetrakis (pentafluorophenyl) borate, tri (pentafluorophenyl) boron, triphenylboron, trimethylboron, tri (trimethylsilyl) borate and organoboroxins.

The preferred activators according to the present invention are the 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 0.1 to 40,000. Preferably, this ratio is at least 1, more particularly at least 2. Most often, the activator is used in amounts 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 of the activator is from 0.01 to 100. Preferably, this ratio is at least. at least 0.5 and more particularly at most 25. Ratios of about 1 to about 5 give particularly good results.

The compositions according to the invention are obtained in at least two successive polymerization steps during which 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 steps can be carried out according to any known process, in solution or in suspension in a hydrocarbon diluent, in suspension in or one of the monomers maintained in the liquid state or also in the gas phase. The polymerization temperature is most often -70 ° C to + 80 ° C. The use of low temperatures

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

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

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

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

It may also prove to be 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 A10R⁷3__rn in which R is a radical as defined above, X is a halogen atom, R⁷ 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 trialkylaluminums, alkylaluminum halides and aluminoxanes.

The following examples serve to illustrate the invention. The methods of 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 mass (Mw) is obtained by size exclusion chromatography from a solution of polymer in trichlorobenzene at 0.5 g / l, using a Waters Styragel HMW 6E polystyrene column marketed by Waters Co Ldt.

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

CPB = block copolymer content 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 4 g of composition under

- 9 magnetic stirring for a period of 24 hours. The suspension is then filtered through 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 mol% 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 -CH3 groups at about 0.25 ppm and the -CHl ·? Bands? - at around 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 marketed by the company Perkin Elmer

Examples 1 to 4

a) Preparation of the catalyst based on 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 kept under stirring for 12 hours and the precipitate is filtered off and washed with methanol. Its purification by recrystallization from dichloromethane makes it possible to obtain the 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 stirred for 24 hours. The solvent is then removed in vacuo and the residues are washed with diethyl ether. The final product (molecular mass 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 -CH3 groups between 0.18 and 0.38 ppm and the CH2 groups between 0.6 and 0.8 ppm.

b) General conditions of polymerization

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

- 10 connected to a 5 liter cylinder pressurized with propylene. The initial pressure of propylene 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 10% methylaluminoxane (Witco Eurecene T 5010) and 5 ml of toluene is added and the polymerization is started by introducing 12 mg (16.6 pmole) of di- (2,6-iPr -Ph) diazobutane (1.8 naphthenejNiBn in solution in 15 ml of toluene. The temperature is maintained at -10 ° C. throughout the duration of the 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 at an ethylene pressure such that the average pressure of the system is about 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 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 stirred 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 to 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>