CS262335B1 - Process for the production of polymers and copolymers of 1-alkenes - Google Patents

Abstract

The solution relates to the production of polymers and copolymers of 1-alkenes by polymerization at a pressure of 0.5 to 4.0 MPa and a temperature of 50 to 150 °C on catalysts formed by the gradual anchoring of at least one organic aluminum compound and optionally magnesium, at least one titanium or vanadium compound and optionally at least one organic magnesium compound onto an inert oxide of elements of group 3b or 4b of the periodic table. The molecular weight of the polymer can be regulated by the addition of hydrogen.

Description

The invention relates to a process for the production of polymers and copolymers of 1-alkenes using single-phase supported catalysts based on transition metals.

Polymers and copolymers of 1-alkenes are usually prepared using catalyst systems based on transition metals, which can be supported and are usually activated by reaction with a cocatalyst - an alkyl metal compound - directly in the polymerization device. These catalysts show high polymer productivity relative to the transition metal and easily copolymerize higher 1-alkenes. Depending on the type of transition metal selected and the ligands bound to the transition metal, the molecular weight distribution and polymerization activity can be influenced. The stereoregularity of the process in the polymerization of propene can also be influenced by the addition of electron donors to the catalytic system. The source of serious technological complications is the activation of the catalyst by organometallic compounds in the polymerization reactor. The concept of these catalysts is based on the preparation of a precursor of a suitable composition, which is not polymerization active. The interaction with the organometal results in a polymerization active system, which quickly loses activity without the presence of a monomer or the presence of a monomer is necessary for the formation of an active center. Therefore, this step is carried out in the polymerization reactor. This means that two components are introduced into the reactor - a catalytic precursor - usually in the form of a powder and an organometallic solution.

Free organometal initiates oligomerization of olefins, which cause undesirable deposits on the inner walls of the polymerization device. When interacting with atmospheric oxygen (e.g. leaks in the polymerization device), the organometal decomposes to aluminum oxide, which contributes to further formation of deposits. Deposits of oligomers with aluminum oxide can only be removed with great difficulty. The presence of free organometal also negatively affects the polymerization kinetics, since permanent contact of the organometal with active centers leads to undesirable changes in the catalyst, which results in loss of activity and ultimately an inappropriate distribution of polymer particle size - a high content of dust fractions and particles with a diameter below 0.1 mm. Another factor that significantly affects the properties of the polymer is the quality of anchoring the active component on the support. In most existing catalytic systems, perfect immobilization of the reaction products to the surface of the support is not ensured, which allows migration of individual components and thus further undesirable reactions leading to the disappearance of active centers. Transition metal-based catalytic systems with additional activation are described, for example, in patent documents US 4,302,566, US 3,787,384, US 4,148,754, US 4,063,009, US 4,173,547, GB 1,484,254,

GB 2,099,834, US 4,490,514 A.

In recent years, single-phase catalytic systems based on transition metals of groups 4a and 5a of the periodic table have been developed. When polymerizing 1-alkenes on single-phase catalysts based on titanium and vanadium, complications with catalyst dosing are eliminated, deposits do not form on the polymerization equipment, and the polymer obtained has the desired particle morphology. Single-phase catalytic systems based on titanium are described, for example, in patent documents BE 884 513, BE 866 420, JA 52 000 880.

This invention relates to a method for producing polymers and copolymers of 1-alkenes using catalysts described in Czech Patent Application No. 256,961 and Czech Patent Application No. 259,736.

The subject of the invention is a method for producing polymers and copolymers of 1-alkenes by polymerization of 1-alkenes with 2 to 10 carbon atoms on supported catalysts based on titanium, vanadium, magnesium and aluminum compounds, in which 1-alkenes containing up to 20% hydrogen by volume are brought into contact with a catalyst formed by successive anchoring of at least one organic aluminum compound and optionally magnesium, at least one titanium or vanadium compound and optionally at least one organic magnesium compound onto an inert oxide of elements of group 3b or 4b of the periodic table, at a pressure of 0.5 to 4.0 MPa, at a temperature of 50 to 150 °C.

For catalysts usable for the production of polymers and copolymers of 1-alkenes according to this invention, a suitable support is silica and/or alumina with a specific surface area of 50 to 500 m/g, a pore volume of 0.5 to 3 ml/g, having hydroxyl groups bound to the surface, the number of which can be varied by the dehydration temperature. This is carried out by blowing through the support layer with a stream of dry nitrogen or air. The procedure is that the temperature is first gradually and slowly increased to

200 °C so that water vapor can escape without disturbing the structure of the carrier or condensing in cooler parts of the device. Dehydration of the carrier is usually carried out at a selected temperature in the range of 200 to 850 °C for 4 hours. Cooling of the carrier is carried out with a stream of nitrogen, the water and oxygen content of which is lower than 1 ppm.

In a hydrocarbon solvent environment or in the gas phase, the carrier is then treated with an organometallic compound, e.g. trialkyls, dialkylhydrides, dialkylhalides, alkyldihalides or dialkylalkoxides of aluminum, or possibly dialkyls of magnesium, whereby the organometallic compound is firmly anchored. For uniform application, the carrier suspension or carrier layer must be stirred intensively; it is preferable to carry out the interaction in a fluidized bed.

The temperature during the interaction can vary within a wide range, depending on the vapor pressure of the organometallic compound, it is preferable to carry out the reaction at a temperature of 10 to 70 ° C, or at ambient temperature. In the next stage, at least one transition metal compound of group 4a or 5a, e.g. a halide, a halogen alkoxide, an oxyhalide, or a cyclopentadienyl derivative of titanium or vanadium, is applied to the support with the anchored organometallic compound. The reaction of the product formed by the interaction of the organometal with the hydroxyl groups of the support with the transition metal compound can be carried out preferably in a carbon environment or by direct contact of the vapor of the transition metal compound with the solid phase of the intermediate, preferably at room temperature.

By chemically binding the organometal to the free hydroxyl groups of the support, modification of its reducing capabilities and simultaneous immobilization on the surface is achieved. By fixing the organometal on the surface of the support, choosing the ratio of the organometal compound to the hydroxyl groups and the ratio of the transition metal compound to the organometal compound, the formation of optimal active structures on the surface of the support is achieved, which have the ability to polymerize 1-alkenes. Perfect anchoring of the components in the pores of the support and on its surface is a condition for high and long-term stable activity of the catalyst, good handling of the powder catalyst and its long-term storage.

According to Czechoslovak Patent Application No. 259 736, the properties of a single-phase catalyst can be further significantly improved by applying another layer - an organomagnesium compound - dialkylmagnesium. This layer has only slight reducing effects and serves primarily to protect the active centers in the pores of the carrier from penetrating impurities during the final phase of production, storage, transportation and dosing of the catalyst. The conditions and method of applying the organomagnesium compound are the same as for the previous components. The final phase of the preparation of a single-phase catalyst is the possible drying of the hydrocarbon solvent, if the preparation was carried out in it. This drying is not carried out if polymerization in the liquid phase follows.

The polymerization of 1-alkenes according to the invention on a single-phase catalyst can be carried out in a fluidized bed, in a mechanically stirred bed in the gas phase, in a liquid monomer, or in a solvent. The polymers are formed at a temperature of 50 to 150 °C; lower temperatures are preferred for the polymerization of higher 1-alkenes with a lower softening point, higher temperatures can be used for the full polymerization of ethylene in a fluidized bed (80 to 120 °C) and for the solution polymerization of 1-alkenes in a hydrocarbon solvent (110 to 150 °C). In gas phase polymerization, the temperature must be maintained 5 to 10 °C below the melting point of the polymer to prevent particle sticking. The polymerization pressure is usually 0.5 to 4.0 MPa, the optimum is 1.8 to 2.2 MPa, because at lower monomer pressures the catalyst productivity is lower (it is directly proportional to the monomer pressure), at pressures higher than 2.2 MPa the costs of purchasing and operating pressure vessels and of compressing working media increase. It is advantageous to carry out the polymerization continuously at constant pressure and temperature with continuous dosing of catalyst, monomer or their mixture and hydrogen and with continuous product withdrawal. The discontinuous process is not economically advantageous.

The molecular weight of polymers can be controlled by dosing hydrogen. Without hydrogen, ultra-high molecular weight polymers (UHMW) are formed; with increasing hydrogen content, the melt index of the polymer decreases sharply. At hydrogen contents of 10 to 20% by volume in the monomer mixture, highly fluid types of polymers (fiber types) are achieved.

AND

The catalyst dosage can be controlled by the instantaneous polymerization rate (temperature of the polymer layer or solution). The catalyst can be dosed continuously (e.g. with an adjustable stroke pump) or batchwise, when the frequency of individual doses can be changed. In gas phase polymerization, it is advantageous to dose a powdered catalyst (the content of volatile components in the polymer and impurities in the reactor does not increase), in liquid phase polymerization, a catalyst suspension in a hydrocarbon can be dosed (the step of drying the solvent during catalyst preparation is eliminated).

During polymerization, spherical polymer particles are formed, which are similar in shape to the initial catalyst particles and therefore to the carrier. The magnification factor is 20 to 50x, during polymerization, compact particles with a size of 0.5 to 5 mm are formed, depending on the polymerization time (in the case of a discontinuous process) or the residence time (in the case of a continuous process). The usual polymerization time or residence time is 1 to 8 hours, preferably 2 to 6 hours. With shorter polymerization times, the content of ash and catalytic residues in the polymer is higher, and the reactor productivity is high. On the contrary, with longer polymerization times, the quality of the polymer improves and the reactor productivity decreases. The polymer is stabilized with conventional stabilizers; due to the high activity of the catalyst and therefore the low content of catalytic residues, a small amount of stabilizers is sufficient. The catalyst is deactivated with air, steam or carbon monoxide after exiting the reactor; the catalytic residues do not need to be washed.

The advantage of the production method according to the invention is that an active catalytic system is used, which does not require further activation in the polymerization device. By fixing the components to the carrier, their migration and undesirable side reactions leading to the disappearance of active centers are prevented. The fixed active centers in the pores of the carrier allow polymerization at a high speed without the formation of undesirable molten polymer lumps.

This achieves:

- elimination of the initial phase of a sharp increase in the polymerization rate and its subsequent decrease,

- constant polymerization rate for 6 to 8 hours, that is, the residence time of the catalyst in continuous reactors,

- prevention of deposits on the inner walls of the polymerization device,

- high weight of the polymerization bed, ensuring high polymerization productivity,

- absence of dust content in the polymer and particles with a diameter below 0.1 mm,

- high bulk density of polymer powder (450 to 480 kg/m),

- possibilities to control the properties of the polymer by the type of catalytic system used and the polymerization conditions.

The invention will be illustrated by the following examples. The percentages in the examples are by weight unless otherwise stated.

Example 1 and 2 •

Into a cleaned reactor containing 50 ml of stripped n-heptane, 2 g of silica containing 0.5 mmol of hydroxyl groups per 1 g were added against a stream of pure nitrogen, a measured amount of butylethylmagnesium and organoaluminum composites I were added (see Table 1). After about 30 minutes of interaction at normal temperature, a given amount of transition metal compound II was measured and stirred for another 30 minutes. The last step of catalyst preparation was removal of the solvent by a stream of nitrogen or by evacuation.

Example 3

In a 1000 ml flask equipped with a mechanical stirrer and a pure nitrogen inlet, containing 500 g of silica activated for 4 hours in a nitrogen stream at 600 °C, containing 0.75 mmol of hydroxyl groups per 1 g, vapors of organoaluminum compound X were introduced to the bottom so that the outgoing gases passed through a well-stirred layer of silica. After evaporation of all the liquid organometal into nitrogen and after interaction with silica, the titanium compound, II, and finally the magnesium compound III were bubbled through with nitrogen. Acceleration of the evaporation of these compounds was achieved by heating the bubbler to a temperature of 50 to 100 °C.

Examples 4 to 6

Into a cleaned reaction vessel containing 50 ml of stripped n-heptane, 2 g of silica containing 0.75 mmol of hydroxyl groups per 1 g were poured against a stream of pure nitrogen, a measured amount of organoaluminum compound or their mixture I was added (see Table 1) and after about 30 minutes of interaction at laboratory temperature with stirring, titanium compound II was dosed. The final stage of catalyst preparation was the dosing of organomagnesium compound III in the form of a solution in a hydrocarbon and removal of the solvent by evacuation after a short interaction time. For the ratios, see Tab. 1.

The catalysts prepared according to Examples 1 to 6 can be obtained in the form of dry powders, or loose powders, containing solvent residues up to a maximum value of about 50%. Above this limit, a slurry or sticky powder is obtained, which cannot be successfully pneumatically transported and dosed into the polymerization reactor. In the case of polymerization in the liquid phase (see Example 9), a suspension of the catalyst in a hydrocarbon solvent can be used directly, without having to dry it.

During the preparation, storage, transport and dosing of catalysts, it is necessary to exclude the access of catalytic poisons of the electron donor type, such as oxygen, water, dienes, carbon monoxide, etc., all operations must be carried out in an inert atmosphere, e.g. under a stream of pure nitrogen or argon.

Note to table no. 1:

1. Abbreviations: Et = ethyl, Bu = n-butyl

2. Davison 952 silica with a specific surface area of 250 to 300 m 2 /g and a pore volume of 1.6 ml/g and a maximum pore radius of 11 nm, dried at a temperature of 800 °C (examples and 2) and 600 °C (examples 3, 4 and 6), and alumina with a specific surface area of 150 m ² /g, a pore volume of 1.0 ml/g and a maximum pore radius of 40 nm, dried at a temperature of 800 °C (example 5) were used as the carrier.

Table No. 1

Example Content of OH groups in mmol OH/g carrier Organometallic I mol I/mol OH Compound II I/II, Imol/IImol Organometallic III III/II, mol/mol 1 0.5 MgEtBu - 0.18 AlEt ₃ - 0.15 TiCl ₄ - 0.15 - 2 0.5 MgEtBu - 0.4, AlEt ₂ OEt - 0.2 In Cl ₄ - 0.2 3 0.75 AlEtj - 0.8 TiCl ₄ - 5 MgEtBu - 1 4 0.75 AlEtCl ₂ - 0.95 TiCl ₄ - 7.5 MgEtBu - 4 5 0.75 AlEtCl ₂ - 2.0 AlEt ₂ Cl - 1.0 Ti(OEt) ₄ - 1.5 MgBu ₂ - 10 6 1.5 AlEtCl ₂ - 1.0 TiOCl ₂ - 50 MgBu ₃ “ 1

Polymerizations were carried out according to the following examples:

Example 7

The powder catalyst is dosed into the lower part of the continuous pilot reactor by a dosing device using nitrogen overpressure. The polymerization takes place in a fluidized bed consisting of a mixture of powdered polymer and catalyst, kept in suspension by the flow of the monomer mixture. The flow rate of the mixture is 3 to 6 times higher than the minimum speed required for fluidization. A steady state is maintained, defined by a pressure of 1.8 to 2.0 MPa, a temperature in the range of 70 to 110 °C and molar ratios of the inserts (monomers and hydrogen) according to Table 2. A polymer is formed, which is discontinuously discharged from the reactor depending on the rate of formation. The productivity of the reactor depends on the residence time (usually 2 to 6 hours), on the cooling efficiency of the recycling monomer mixture (given by the design parameters, the maximum productivity is 25 kt/h) and on the activity and concentration of the catalyst (directly proportional).

Example 8

A laboratory reactor with a volume of 1.5 dm, which allows the preparation of 300 g of polymer, was purged overnight (16 hours) with a flow rate of 500 ml/min of ultrapure nitrogen, then at the temperature of the future polymerization it was alternately pressurized 5 times with nitrogen to a pressure of 2 MPa and evacuated, finally pressurized 2 times with ethylene to 2 MPa and evacuated. The reactor temperature was maintained at the desired polymerization temperature by means of temperature control of the reactor jacket. The reactor was filled with a mixture of monomers with hydrogen at the desired pressure and concentration of components according to Table 2. The polymerization began by breaking a glass tray containing 50 to 150 mg of catalyst. The fluid layer was kept in suspension by mechanical stirring, the polymerization rate was measured from the consumption of the supplied monomer mixture. After a certain time (usually 4 hours), the reactor was depressurized, opened and the polymer isolated.

Example 9

In a laboratory reactor with a volume of 1.5 dm^, the solvent (n-hexane, n-heptane, 1-hexene or 1-decene) was stripped off with a stream of ultrapure nitrogen so that more than 15% of the solvent was evaporated. Then the pressure in the reactor was adjusted by dosing the monomer mixture at the polymerization temperature - see Table 2. The polymerization began by crushing a glass ampoule with the catalyst (powder or in suspension in a hydrocarbon) and proceeded at constant temperature, pressure and composition of the monomer mixture for four hours. After opening the reactor, the polymer was isolated by evaporation of the solvent and drying in a vacuum oven.

After deactivation of the catalyst (e.g. with air, carbon monoxide or water vapor), the polymers must be stabilized against ultraviolet radiation and oxidation at higher temperatures with conventional stabilizers. For example, a mixture of a sterically hindered phenolic antioxidant and tris-(nonylphenyl)phosphite in a weight ratio of 1:0.5 to 1.5 in an amount of 0.01 to 0.03% by weight per polymer can be used. Due to the high activity of the catalysts, the amount of stabilizers required is low. The polymer consists of large particles (usually 0.5 mm and larger), so it does not need to be granulated before processing.

Notes to Table 2:

C ₂ , C j , C ^ , C g , C _Q denote ethylene, propylene, 1-butene, 1-hexene and 1-decene respectively

IT ₂ j - flow index at 190 °C and a load of 2.3 kg

MFR - ratio of flow indices at loads of 23 kg and 2.3 kg

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Claims (1)

SUBJECT OF THE INVENTION Process for preparing polymers and copolymers of 1-alkenes by polymerizing 1-alkenes of 2 to 10 carbon atoms on supported catalysts based on titanium, vanadium, magnesium and aluminum compounds, characterized in that the 1-alkenes containing up to 20% by volume of hydrogen are pressurized at 0, 5 to 4.0 MPa and a temperature of 50 to 150 ° C contact with the catalyst formed by the gradual anchoring of at least one organic aluminum and optionally magnesium compound, at least one titanium or vanadium compound and optionally at least one organic magnesium compound to the inert oxide of elements 3b; 4b of the periodic group. Severografla, n. P “MOST