CS262452B1 - 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 successive anchoring of at least one organic aluminum compound, at least one titanium and/or vanadium compound and at least one organic aluminum compound and optionally a paraffinic hydrocarbon onto an inert oxide of elements of group 3b or 4b of the periodic table. The molecular weight of the polymer can be controlled by the addition of hydrogen and the catalyst can be passivated by the addition of a paraffinic hydrocarbon with a melting point of 25 °C to 150 °C.

Description

The invention relates to a process for producing polymers and copolymers of 1-alkenes using single-phase supported catalysts based on titanium, vanadium and aluminum compounds.

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 catalyst system. The source of serious technological complications is the activation of the catalyst by organometallic compounds 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. The free organometallic initiates the oligomerization of olefins, which cause undesirable deposits on the inner walls of the polymerization device. When interacting with atmospheric oxygen and moisture (e.g., when the polymerization equipment is leaking, during shutdown), the organometal decomposes to aluminum oxide, which contributes to further formation of deposits. The presence of free organometal also negatively affects the polymerization kinetics, since the permanent contact of the organometal with the active centers leads to undesirable changes in the catalyst, which results in a loss of activity and ultimately an unfavorable distribution of the polymer particle size, i.e. a high content of dust particles and particles with a diameter below 0.1 mm. Catalytic systems based on transition metals 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 4,490,514A.

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

BE 884 513, BE 866 420, JA 52 000 880 and in Czech. AO No. 256 961, Czechoslovak AO No. 262 451 and in the Czech Republic

AO 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 and aluminum compounds, in which 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, at least one titanium and/or vanadium compound and at least one organoaluminum 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.

Furthermore, the invention relates to a method for producing polymers and copolymers of 1-alkenes according to the invention, in which the catalysts are treated with 0.5 to 100% by weight of a paraffinic hydrocarbon with a melting point of 25 to 150°C before polymerization.

For the catalyst usable for the production of polymers and copolymers of 1-alkenes according to the present invention 2, 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 3.0 ml/g, which is dehydrated at temperatures of 200 to 950 °C with a stream of air and/or nitrogen in a fluidized bed for at least 4 hours. The silica thus treated contains, depending on the dehydration temperature, 0.3 to 3.0 mmol of OH groups per 1 g.

In a hydrocarbon solvent environment or in the gas phase, the support is treated with an organoaluminum component, for example trialkylaluminum, dialkylhaloaluminum, dialkylalkoxyaluminum, alkyldihaloaluminum, or a mixture thereof. Reaction products are formed that are firmly fixed on the surface of the support. The molar ratio of the sum of organometals I to the -OH groups of the support is in the range of 0.1 to 10, preferably 0.5 to 1.0. In order to uniformly apply the organometal I, it is necessary to stir the support suspension or the support layer intensively. The temperature during the interaction can vary within a wide range depending on the vapor pressure of the organometallic compound at the boiling point of the hydrocarbon used; it is preferable to carry out the reaction at 10 to 70 °C, or at ambient temperature.

In the next phase, at least one titanium and/or vanadium compound, e.g. a halide, haloalkoxide, alkoxide, oxyhalide of vanadium and/or titanium II, is applied to the support with the anchored organoaluminum component. This reaction can be advantageously carried out in a hydrocarbon medium or by direct contact of the titanium and/or vanadium compound vapors with the solid phase of the intermediate, preferably at laboratory temperature. The titanium and/or vanadium compounds are firmly anchored on the support and react with the fixed reaction products from the previous reaction. The molar ratio of the sum of organoaluminum compounds I to the sum of compounds II is maintained within the limits of 1 to 100, preferably 5 to 20.

By chemically binding organometal I to free -OH groups of the support, modification of its reducing capabilities and simultaneous immobilization on the support surface is achieved. By choosing the ratio of organometal compound (I) to hydroxyl groups and the ratio of titanium and/or vanadium (II) compounds to organoaluminum compound, the formation of active structures on the support surface, which have the ability to polymerize 1-alkenes, is achieved.

According to AO No. 259 736, the properties of the single-phase catalyst can be further significantly improved by using another organometal - organomagnesium compound. According to the present invention, a similar effect is achieved by creating another layer using an organoaluminum compound III, e.g. trialkylaluminum, dialkylhaloaluminum, alkyldihaloaluminum, dialkylalkoxyaluminum, etc. The molar ratio III/II is maintained in the range of 0.5 to 20, preferably 1 to 8. The formation of the polymerization-active form of titanium and/or vanadium compounds is thus divided into two steps, which allow for significantly more sensitive tuning of the reduction or alkylation of the transition metal compound. The conditions and method of applying the organoaluminum compounds are the same as for the previous components. The final stage of catalyst preparation is the optional drying of the solvent with a stream of inert gas or by evacuation.

The properties of the catalyst are further improved by applying a paraffinic hydrocarbon to the surface of the catalyst particles, similarly to the Czechoslovak Patent Application No. 262 451. The melting point of the paraffinic hydrocarbon lies between the polymerization temperature and the maximum normal temperature of the environment in which the catalyst is manufactured, stored and transported. Paraffin with a melting point of 50 to 70 °C, atactic polypropylene or other saturated hydrocarbons with a suitable melting point can be used. The presence of multiple bonds and heteroatoms in the chains of paraffinic hydrocarbons is undesirable, as they reduce the activity of the catalyst. Low-molecular impurities of the electron donor type have the same negative effect. The paraffinic hydrocarbon can be applied to the finished catalyst, suspended in a hydrocarbon solvent, or simultaneously with the last component of the catalyst, i.e. with the organoaluminum compound III. The paraffinic hydrocarbon is applied so that its content is 0.5 to 50% by weight of the catalyst, preferably 1 to 10% by weight. The principle of action of the paraffinic hydrocarbon is to coat the catalyst particles and prevent the diffusion of impurities to the active polymerization centers during the isolation, storage, transport and dosing of the catalyst. The creation of a diffusion barrier on the catalyst surface further stabilizes the catalytic system in the absence of monomer. The reactivity of the catalyst components is significantly reduced and a large part of the active centers are formed only after the paraffinic hydrocarbon has melted in the reactors.

The polymerization of l-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 polymerization is carried out 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 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). During polymerization in the gas phase, the temperature must be maintained 5 to 10 °C below the melting point of the polymer to avoid agglomeration of the particles. 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) and 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 flow index of the polymer decreases sharply. At hydrogen contents of 10 > to 20 S by volume in the monomer mixture, highly fluid types of polymers (fiber types) are achieved.

The catalyst dosage can be controlled by the instantaneous polymerization rate (given by the temperature of the polymer layer or solution). The catalyst can be dosed continuously (e.g. by a pump with adjustable stroke) 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 does not increase), in liquid phase polymerization, a suspension of the catalyst 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 thus 1 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 h, preferably 2 to 6 h. With shorter polymerization times, the ash content of the catalyst residues in the polymer is higher, and the reactor productivity is high. Conversely, with longer polymerization times, the polymer quality 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 catalyst residues, a small amount of stabilizers is sufficient. The catalyst is deactivated with air, steam and/or carbon monoxide after exiting the reactor. The catalyst residues do not need to be washed.

The advantage of the method for producing polymers and copolymers of 1-alkenes according to the present 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 high-speed polymerization without the formation of undesirable molten polymer lumps.

This is achieved

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

- constant polymerization rates for 6 to 8 h, that is, the residence time of the catalyst in continuous reactors;

- preventing the formation of deposits on the inner walls of the polymerization device;

- high polymer bed weight, ensuring high polymerization productivity;

- absence of dust content in the polymer;

- high bulk density of polymer powder (480 to 520 kg/m ³ );

- 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:

Example 1 to 8

In a cleaned reactor containing 50 ml of nitrogen-stripped heptane, 2 g of silica (support) were poured in a countercurrent of pure nitrogen and the appropriate amount of organometal (I) was added according to Table 1. After 5 min of stirring, the vanadium and/or titanium compound II according to Table 1 was added, stirring was continued for another 5 min and then the organometallic compound III according to Table 1 was added. The last step in the catalyst preparation was the removal of solvents (by nitrogen flow or evacuation).

The catalysts prepared according to Examples 1 to 8 can be obtained in the form of dry powders containing solvents up to a maximum value of about 50% by weight. Above this limit, a sticky powder or slurry is obtained, which cannot be successfully pneumatically transported and dosed into a polymerization reactor. In the case of polymerization in the liquid phase, a suspension of the catalyst in a hydrocarbon can be used directly.

During the preparation, storage, transport and dosing of the catalyst, 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 and manipulations with the catalyst must be carried out in an inert atmosphere, e.g. in a stream of pure nitrogen or argon.

Table 1

Example Content of -OH group Organometallic I Compound Ti,V Organometallic III pin of carrier mmol/g of carrier II mmol/g of carrier mmol/g of carrier mmol/g

1 0.55 AlEt ₃ (0.30) TiCl ₄ (0.1) Al(OEt)Et- (0.15) .2 0.55 _AlEt2Cl (5.5) TiCl ₄ (0.01) AlEt ₃ (0.9) VC1 ₄ (0.05) AliBu ₃ (0, 3) 3 0.75 AlEt ₃ (0.25) Ti(OEt) ₄ (0.1) Al(0Bu)Bu ₂ (0.2) _AlEt2Cl (0.25) AlEt ₂ Cl (0 ,D 4 0.75 AlEtj (0.25) AlEt ₂ Cl (0.25) TiBuClj (0.1) AliBUj (0, 15) 5 0.75 AlEt ₂ Cl (0.08) VOC1 ₃ (0.1) AlEt ₃ (0.2) VC1 ₄ (0.05) 6 0.80 AlEt ₃ (0.3) AlEt ₂ Cl (0.3) TiCl ₄ (0.1) Al(OEt)Et ₂ (0.2) 7 2.80 Al(OEt)ET ₂ (2, 7) Ti(OEt) ₄ (2.7) AliBu ₃ (1, 3) 8 2.80 AlHex ₃ (1.03) TiCljEt (1.03) AliBUj (2, 1) Notes 1. Abbreviations i : Et = ethyl O.E.T. = ethoxide Bu = n-butyl BOTH = n-butoxide Hex = hexyl iBu = isobutyl 2. It was used as a carrier Silica DAVISON 952 with a specific surface area of 250 up to 300 m^/g, about volume

pore volume of 1.6 ml/g with a maximum pore radius of 11 nm, activated at a temperature of 800 °C (examples 1 and 2),

600 °C (Examples 3 to 5) and 200 °C (Examples 7 and 8) and alumina with a specific surface area of 150 m^/g, a pore volume of 1.0 ml/g, a maximum pore radius of 40 nm, dried at a temperature of 800 °C (Example 6).

Polymerizations were carried out according to the following examples (molar ratios of the monomer mixture composition and polymer properties - see Table 2):

Example 9

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 and a temperature in the range of 70 to 110 °C. 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 h), on the cooling efficiency of the recycling monomer mixture (given by the design parameters) and on the activity and concentration of the catalyst (max. productivity 20 kg/h).

Example 10

A laboratory reactor with a volume of 1.5 dm, allowing the preparation of 300 g of polymer, was purged with a flow rate of 500 ml/min of ultrapure nitrogen for 16 h, then pressurized 10 times with nitrogen to 0.6 MPa at the polymerization temperature and finally rinsed 2 times with ethylene. The reactor temperature was maintained at the desired polymerization temperature by means of temperature control through the reactor jacket. A mixture of monomers (or hydrogen) was charged into the reactor. The polymerization was initiated by breaking a glass flask with 50 to 150 mg of catalyst. The fluid layer was kept in suspension by mechanical stirring using a double-flow spiral, the polymerization rate was measured from the consumption of the replenished monomer mixture. After approximately 4 h, the reactor was depressurized, opened and the polymer was further processed (stabilization, etc.).

Example 11

In a laboratory reactor with a volume of 1.5 dm ³ , the solvent (n-hexane, n-heptane, 1-hexene or 1-decene) was stripped with a stream of ultrapure nitrogen so that more than 15% by weight of the solvent was evaporated. Then, the pressure in the reactor was adjusted by dosing the monomer mixture at the polymerization temperature, which was initiated by breaking the glass ampoule with the catalyst and proceeded for 4 h. After opening the reactor, the polymer was isolated by evaporation of the solvent and drying in a drying oven.

After deactivation of the catalyst (e.g. by air), the polymers must be stabilized against UV radiation and oxidation at higher temperatures with conventional stabilizers. For example, a mixture of a sterically hindered phenolic antioxidant and tri(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 catalyst, the amount of stabilizer required is low. The polymer consists mainly of large particles (mostly 0.5 mm and larger) and therefore it does not need to be granulated before processing.

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Claims (2)

object of the invention A process for the preparation of polymers and copolymers of 1-alkene by 2 to 10 carbon atoms of 1-alkene on supported catalysts based on titanium, vanadium and aluminum compounds, characterized in that the 1-alkenes containing up to 20% by volume of hydrogen at a pressure of 0.5 up to 4.0 MPa and at a temperature of 50 to 150 ° C contact the catalyst transportable by successively anchoring at least one organic aluminum compound, at least one titanium compound and / or vanadium and at least one organic aluminum compound to the inert oxide of Group 3b or 4b elements of elements. 2. A process for the preparation of polymers and copolymers of 1-alkenes by polymerizing 1-alkenes of 2 to 10 carbon atoms on supported catalysts according to claim 1, characterized in that the catalysts are treated with 0.5 to 100% by weight paraffinic hydrocarbon of melting point 25 to 100. 150 [deg.] C.