JPS6360043B2 - - Google Patents

Description

[Detailed description of the invention]

[] Background of the Invention The present invention relates to a method for homopolymerizing and copolymerizing ethylene at a high temperature of 125° C. or higher and a high pressure of 200 kg/cm ² or higher using an extremely highly active Ziegler type catalyst. There are two methods for polymerizing ethylene that are used on a large scale industrially. The first method is to process ethylene at high temperature and pressure.
For example, polymerization is carried out at a temperature of 125° C. or higher and 500 kg/cm ² or higher, typically 140-300° C. and 1000-3000 kg/cm ² or higher. Polymerization is carried out in the presence of a polymerization initiator consisting of a compound capable of generating free radicals, typically peroxide or oxygen or a combination thereof. This method is generally referred to as the "high pressure method" and is characterized by the production of branched polyethylene. The second method is to process ethylene at relatively low temperatures and pressures, e.g. below 250°C and below 200 kg/ ^cm2 .
Usually, polymerization is carried out under conditions of 50 to 90°C and 30 kg/cm ² or less. A typical catalyst used in this method is an organometallic complex compound also called a "Ziegler type catalyst." The term "Ziegler-type catalyst" is used for a catalyst consisting of a combination of a compound of a transition metal of subgroups a to a of the periodic table and an organometallic compound of a metal of group -a of the periodic table. The widely used Ziegler-type catalysts are based on a combination of a titanium compound, such as titanium tetrachloride or titanium trichloride, and an aluminum compound, such as triethylaluminum or diethylaluminum chloride. Products made using the Ziegler process, or low pressure process, are linear polyethylene with virtually no branching, and have a melting point of over 130℃, compared to the typical high pressure process polyethylene, which has a melting point in the range of 105 to 120℃. have. Furthermore, the specific gravity of low-pressure polyethylene is generally higher than that of high-pressure polyethylene, typically less than 0.935 for high-pressure polyethylene, whereas the specific gravity of low-pressure polyethylene is typically greater than 0.95, usually about 0.96. . By the way, a third method has been proposed, although it has not been generalized as a large-scale industrial manufacturing method for polyethylene. For example, British Patent No. 823828 discloses that olefins, ^particularly ethylene, are reacted with Ziegler-type catalysts (i.e. organometallic compounds a, a or A method has been proposed in which olefin is polymerized by adding 25 to 500 ppm by weight of a complex compound catalyst with a compound other than the oxide of a group metal. Since then, many improved techniques have been proposed for this ethylene polymerization method using ionic polymerization catalysts such as Ziegler catalysts under high temperature and high pressure conditions, but none of them have been fully satisfactory in terms of catalytic activity. It was difficult to say anything. The fact that the catalyst activity is not sufficiently high means that there is a large amount of catalyst residue in the produced olefin polymer, and if the catalyst decomposition and purification steps are omitted, the product polymer will be colored and odor prone to thermal and oxidative deterioration. A strong product. In particular, the ionic polymerization method under high pressure and high temperature often uses polyethylene production equipment using high-pressure radical polymerization, but if catalytic decomposition and purification steps are required, large-scale equipment modifications are required. Improving catalyst activity is an important point in commercializing this technology from the viewpoint of a significant increase in polymer production costs. Furthermore, in the ionic polymerization method under high pressure and high temperature, it is necessary to supply the catalyst to the reactor with a high-pressure pump. It is necessary to have good dispersibility. Furthermore, in general, when ethylene and α-olefin are copolymerized, the catalyst activity decreases, so in the case of copolymerization, an even more highly active catalyst is required. [] SUMMARY OF THE INVENTION The present invention aims to provide a solution to the above-mentioned problems, and attempts to achieve this aim by using a transition metal catalyst made in a specific manner. Therefore, the method for polymerizing ethylene according to the invention comprises the following components A and B at a pressure of at least 200 Kg/cm ² and a temperature of at least 125°C.
It is characterized by bringing ethylene or ethylene and at least one other α-olefin into contact with a catalyst consisting of a combination of ethylene and at least one other α-olefin. Component A Organoaluminum compound or alkylsiloxalane derivative. Component B: A solid product obtained by contacting a titanium compound in which titanium has a tetravalent valence with magnesium dihalide (the dihalogenated magnesium has a surface area of at least 5 m ² /g). Effects According to the invention, the homopolymerization of ethylene and the copolymerization of ethylene with at least one other α-olefin using this particular Ziegler-type melt at a pressure of at least 200 Kg/cm ² and a temperature of at least 125° C. When this is carried out, both the amount of polymer produced per transition metal and the amount of polymer produced per carrier are high. As a result, the polymer is less susceptible to heat and oxygen degradation, and has almost no coloration or odor. The effects of the present invention are obtained when the above-mentioned component B, magnesium dihalide, has a surface area of at least 5 m ² /g. surface area is 5
If it is less than m ² /g, there is almost no activity. The reason for this is not necessarily clear, but as the surface area of the magnesium dihalide of component B increases, the diffraction intensity at the lattice distance of the magnesium dihalide measured in the X-ray diffraction spectrum decreases or the lattice distance expands. This is presumed to be because magnesium dihalide becomes more active. [] Detailed Description of the Invention 1 Catalyst Used The catalyst used in the present invention consists of a combination of component A and component B. This catalyst belongs to the category of "Ziegler-type catalysts" and component A can also be considered a co-catalyst for component B in the transition metal component. 1 Component A (1) Organoaluminum compound Specific examples of organoaluminum compounds include the general formula R ¹ _3-p AlX ¹ _p (where R ¹ is a hydrocarbon having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms). residue or hydrogen, X ¹ is a halogen or an alkoxy group having 1 to 20 carbon atoms, preferably 1 to 6 carbon atoms, and p is a number of 0p2, preferably 0p1.5) There is something. Specifically, (a) trialkylaluminum such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trioctylaluminum, tridecylaluminum, (b) dialkylaluminum monohalide such as diethylaluminum monochloride and diisobutylaluminum monochloride, (c) Alkyl aluminum sesquihalides such as ethyl aluminum sesquichloride, (d) dialkyl aluminum hydrides such as diethyl aluminum hydride and diisobutyl aluminum hydride, (e)
Examples include alkyl aluminum alkoxides such as diethylaluminum ethoxide, diethylaluminum butoxide, and diethylaluminium phenoxide. Among these, in the polymerization under high temperature and high pressure according to the present invention, halogen-containing organic aluminum gives better results in terms of polymerization activity than trialkylaluminum. Preference is given to mixtures with halides or alkylaluminum sesquihalides, with particular preference being given to using dialkylaluminum halides. (2) Alkylsiloxalane derivatives Alkylsiloxalane derivatives can also be used as further cocatalysts. The alkylsiloxalane derivative is represented by the following general formula. Here, R ² and R ³ are each a hydrogen atom or a saturated hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, and R ⁴ , R ⁵ , and R ⁶ are each a saturated hydrocarbon group having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms. ~6, is a saturated hydrocarbon group,
R ⁶ is a halogen atom or (R ⁷ , R ⁸ , R ⁹ above each have 1 to 1 carbon atom
10, preferably 1 to 6 saturated hydrocarbon groups. ) can also be a group. Moreover, this alkylsiloxalane can also take the form of a polymer when polysiloxane is used as a starting material for synthesizing this alkylsiloxalane. The Si/Al atomic ratio of these alkylsiloxalane is preferably 1 to 3. Specifically, trimethyldimethylsiloxalane, trimethyldiethylsiloxalane, trimethyldipropylsiloxalane,
Examples include trimethyldibutylsiloxalane, trimethyldioctylsiloxalane, dimethylethyldiethylsiloxalane, and the like. These alkylsiloxalane derivatives are generally synthesized in advance by reacting trialkylaluminium and polysiloxanes, but they can also be prepared on the spot by mixing the two in a polymerization reactor. It may be something you did. (3) Amount of component A used There is no particular restriction on the amount of these organoaluminum compounds or alkylsiloxalane derivatives used, but the Al/Ti atomic ratio is 0.5 to 1000 with respect to the solid catalyst component of the present invention shown below. , especially 1-200,
is preferred. 2 Component B Component B is a solid product obtained by contacting a titanium compound in which titanium has a tetravalent valence and magnesium dihalide. Provided that the magnesium halide compound has a surface area of at least 5 m ² /g before or after contact with the titanium compound. (1) Titanium Compound Examples of titanium compounds in which titanium has a tetravalent valence include titanium halides, specifically titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, and the like. Among these, titanium tetrachloride is particularly preferred. (2) Magnesium compound Magnesium dihalides to be brought into contact with such a titanium compound include MgF ₂ ,
Examples include MgCl ₂ , MgBr ₂ , MgI ₂ , etc. Among these, _MgCl2 is preferred. In the present invention, it is necessary that the dihalogenated magnesium be "activated". That is, the magnesium dihalide must have a surface area of 5 m ² /g or more before and/or after contact with the titanium compound. One specific example of an "activated" magnesium dihalide is one in which the surface area of the magnesium dihalide prior to contact with the titanium compound is
m ² /g or more, and is obtained, for example, by pulverizing magnesium dihalide or precipitating it by evaporating the solvent from a solution of dissolved magnesium in an organic solvent such as alcohol or ether. Another specific example of activated magnesium dihalide is one in which the surface area of the magnesium dihalide is increased to 5 m ² /g or more by pulverization during or after contact with a titanium compound. (The dihalogenated magnesium may have a surface area of 5 m ² /g or more before contact with the titanium compound).
When the surface area of magnesium dihalide is pulverized after contact with a titanium compound, the surface area of magnesium dihalide can be measured on a product after the supported titanium compound has been sufficiently washed away. The surface area of B) can be used instead. (3) Contact method Catalyst component B of the present invention can be produced by the method shown below. One preferred method is to mix and grind the titanium compound and magnesium dihalide to a surface area of at least 5 m ² /g. Preferably, the surface area is greater than or equal to 10 m ² /g, most preferably between 15 and 200 m ² /g. In order to achieve such a state, the pulverization method, pulverization conditions, pulverization time, etc. may be appropriately selected and pulverized. As the crushing device, a ball mill, a vibration mill, a rod mill, an impact mill, and various other devices can be used. In these pulverizers, the pulverization time required to obtain the desired catalyst varies depending on the combination of various conditions such as ball filling rate, pulverized sample filling rate, ball diameter, rotation speed or vibration frequency, and pulverization temperature. However, to give an example, the internal volume
0.46 liters, ball diameter 16mm, ball volume/
When pulverizing is performed under the conditions of pot volume = 0.2 and rotation speed of 90 rpm, one hour is required. If necessary, grinding can be carried out either wet or dry. Another method for producing component B is to produce the magnesium dihalide itself under the above-mentioned grinding conditions to a surface area of at least 5 m ² /g, and then to contact it with the titanium compound by stirring in the presence of an inert diluent. be. After the contact, further wet or dry pulverization may be performed. The amount of the titanium compound used in the production of the supported catalyst can be any value as long as the effects of the present invention are observed, but it is generally 1 to 50% by weight based on the magnesium dihalide. In particular, a range of 3 to 40% by weight is preferred. The temperature at which the titanium compound and the magnesium dihalide are brought into contact is preferably -20 to 200°C, more preferably 0 to 150°C. 3. Preparation of Catalyst Component A and component B described above may be combined within or outside the polymerization zone. Since solid component A or component A and component B are injected into the high-pressure polymerization zone using a high-pressure pump, these must be in the form of liquid or fine particles or a slurry thereof, and therefore the particle size is approximately 10 μm. Below, preferably 1 to 5μ
It is desirable that the 2 Polymerization of Ethylene 1 Polymerization Apparatus The polymerization method of the present invention can be carried out as a batch operation, but it is more preferable to carry out the polymerization in a continuous manner. As the polymerization apparatus, an apparatus commonly used in high-pressure radical polymerization of ethylene can be used. Specifically, there is a continuous stirring tank reactor or a continuous tubular reactor. The polymerization can be carried out as a single zone process using these single reactors, but it is also possible to use many reactors in series, possibly connected with condensers, or
Alternatively, a single reactor can be used, the interior of which is effectively divided into several zones for a multi-zone process. In a multi-zone process, monomers are added to each reactor or reaction zone in such a way that the reaction conditions in each zone are different to control the properties of the polymer obtained in each reactor or reaction zone. It is common to adjust the composition, catalyst concentration, molecular weight regulator concentration, etc. When multiple reactors are connected in series, in addition to the combination of two or more tank reactors or two or more tubular reactors, one or more tank reactors and one or more pipe reactors are used. Combinations with type reactors can also be used. The polymer produced in one or more reactors can be separated from unreacted monomers and treated as in conventional high-pressure processes without removing the catalyst residues. can. Removal of catalyst residue is
In the conventional method using Cheekler catalyst at low pressure,
This is a very expensive and time consuming process. The unreacted monomer mixture is mixed with an additional amount of the same monomer, repressurized and recycled to the reactor. The additional amount of monomer added as described above is of a composition that returns the composition of the mixture to that of the original feed, and generally this additional amount of monomer is added to the polymer separated from the polymerization vessel. It has a composition roughly equivalent to that of the coalescence. The catalyst is, for example, injected as a finely divided dispersion in a suitable inert liquid directly into the reactor using a high-pressure pump. Suitable inert liquids include:
Examples include white spirits, hydrocarbon oils, pentane, hexane, cyclohexane, heptane, toluene, higher branched chain saturated aliphatic hydrocarbons, and mixtures of these liquids. The dispersion is preferably kept under a nitrogen blanket to avoid contact with water and air before introducing it into the reactor. Ethylene and other monomers must also be substantially free of water and oxygen. As mentioned above, the resulting polymer can be processed without removing the catalyst. This is because the catalyst used in the present invention has a very high activity, and therefore a high conversion rate of monomer to polymer can be achieved using an extremely small proportion of catalyst. 2. Monomers and comonomers and resulting polymers The polymerization carried out using the catalyst system of the present invention is the homopolymerization of ethylene or ethylene with the general formula R-
At least one other α represented by CH=CH ₂
- copolymerization with olefin. In the case of homopolymerization of ethylene, the produced polymer has a specific gravity of 0.95~
Typically high density polyethylene in the 0.97 range. General formula R-CH=CH ₂ (where R has 1 to 12 carbon atoms
is a hydrocarbon residue. ) Specific examples of comonomers represented by: propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1 4-methylpentene-
1, decene-1, etc. These α-olefins can be copolymerized in the resulting copolymer up to 30% by weight, preferably from 3 to 20% by weight.
Copolymerization of ethylene with these alpha-olefins provides polymers with a wide range of specific gravities.
The specific gravity of the resulting polymer is controlled by the type of comonomer, the feed composition of the comonomer, and the like. Specifically, a polymer having a desired density within the range of about 0.890 to 0.955, preferably about 0.89 to 0.94 can be obtained. The method of the present invention is particularly suitable for producing the above-mentioned copolymers, and can provide medium to low density ethylene copolymers in high yields. These copolymers not only have a density different from that of conventional low-pressure processed high-density polyethylene, but also have different properties from conventional high-pressure processed low-density polyethylene, namely, they have substantially no long chain branching and molecular weight. It has a narrow distribution (Q value) of 3 to 5, and is a polymer excellent in mechanical strength, especially tensile strength, and environmental destructive stress. 3 Polymerization conditions (1) Polymerization pressure The polymerization pressure employed in the present invention is at least 200 Kg/ ^cm2 , preferably 500 to 4000 Kg/cm2.
cm ² , more preferably within the range of 500 to 3000 Kg/cm ² . (2) Polymerization temperature The polymerization temperature is at least 125°C, preferably within the range of 150 to 350°C, and more preferably within the range of 200 to 320°C. Although not essential, under the combination of polymerization pressure and temperature employed, the polymerization reaction mixture may form a single fluid phase or may be separated into two phases. (3) Reactor feed gas composition The reactor feed gas composition employed in the present invention is 5 to 100% by weight of ethylene, 0 to 95% by weight of at least one α-olefinic comonomer, and a molecular weight regulator. Usually, the hydrogen content is in the range of 0 to 20 mol%. (4) Residence Time The average residence time in the reactor is related to the duration of activity of the dissolving medium under the reaction conditions employed. The half-life of the catalyst used is influenced by temperature among other reaction conditions, and as the lifetime of the catalyst increases, it is preferable to increase the residence time of the monomers in the reactor. The average residence time employed in the present invention is in the range of 2 to 600 seconds, preferably 10 seconds to
It is within the range of 150 seconds, more preferably 10 seconds to 120 seconds. (5) Others From the viewpoint of polymerization temperature and pressure, the polymerization method according to the present invention belongs to the category of high-pressure polymerization of ethylene. Therefore, the polymerization method according to the present invention is carried out substantially without using a liquid dispersion medium, except for a small amount of liquid medium introduced as a dispersion medium for the catalyst or for other purposes. Therefore, in the method of the present invention, it is only necessary to separate unreacted monomers from the polymer after polymerization, and separation of the liquid medium from the polymer and purification of the liquid medium are not necessary. According to the method of the present invention, the amount of catalyst residue in the produced polymer is extremely small, so there is no need to decompose or purify the catalyst, and the produced polymer is separated from unreacted monomers in a separator. After that, it becomes a product. This product may be used as is, or may be subjected to various post-treatment steps such as those already used for products obtained by high-pressure radical polymerization. 3 Examples Example 1 Production of catalyst component A stainless steel pot with an internal volume of 460 ml and an inner diameter of 90 mmφ was filled with 43 stainless steel balls of 16 mmφ, and anhydrous powder having a surface area of Im ² /g was filled with 1.0 g of _TiC14 . 20 g of MgCl ₂ was sealed under N ₂ atmosphere and ground in a rotating ball mill for 8 hours. The rotation speed was 90r.pm. The Ti content of the ground product is 1.2% by weight;
The surface area was 61 m ² /g. Also carried
After thorough washing and removal of TiCl ₄ , the surface area of the product was 62 m ² /g. Preparation of catalyst dispersion: Add 300 ml of thoroughly degassed n-hexane to a 1 liter flask that has been thoroughly purged with nitrogen. Then, 15.0 g of the aforementioned solid component (a) and diethylaluminium chloride were added to preactivate the mixture to make the Al/Ti atomic ratio 16. Next, sufficiently degassed and purified hexene-1 was added, and hexene/
After adjusting the molar ratio of Ti to 20, the mixture was stirred for 2 hours to obtain a fine catalyst suspension. This catalyst suspension was placed in a catalyst preparation tank equipped with a stirrer and purged with nitrogen, and then sufficiently degassed and purified n-hexane was added to the tank until the volume reached 25 liters to make the concentration of solid components 0.6 g/liter. This is the catalyst a-
I got it. High-pressure polymerization of ethylene Ethylene was polymerized under the reaction conditions shown in Table 1 in a stirred autoclave-type continuous reactor with an internal volume of 1.5 liters. As the catalyst, the above a-i was used. Hydrogen was added as a chain transfer agent to control the molecular weight of the resulting polymer. The ethylene and hydrogen used were thoroughly degassed and purified. As a result of polymerization, 3,300g per 1g of solid catalyst component
of polymer (PE) was obtained. In other words, the yield to catalyst (g PE/g solid catalyst component) = 3,300,
Yield per 1g of Ti (g・PE/g・Ti)=275,
It was 000. Examples 2 to 4 and Comparative Example 1 Catalyst components b to e and catalyst dispersions b to e were prepared in exactly the same manner as in Example 1 except that the pulverization time was changed as shown below.
A was manufactured.

[Table] Using the obtained catalyst dispersions b-i to e-i,
Table 1 shows the results of high-pressure polymerization of ethylene in the same manner as in Example 1. Looking at this table, it can be seen that there is no activity at all when the surface area is less than 5 m ² /g. Examples 5 to 6 Catalyst components f to g and catalyst dispersion f-i to g-i was produced.

[Table] Using the obtained catalyst dispersions f-i to g-i,
Table 1 shows the results of high-pressure polymerization of ethylene in the same manner as in Example 1. Example 7 Manufacture of catalyst component 20 g of anhydrous _MgC12 having a surface area of 1 m ² /g was pulverized under exactly the same pulverizing conditions as in Example-2.
The surface area was 86 m ² /g. 200 milliliters of thoroughly degassed and purified n-heptane was introduced into a 1-liter flask that had been sufficiently purged with nitrogen, and then 20 g of the pulverized MgCl ₂ described above was added.
3.3g of _TiC14 was introduced and stirred at 30°C for 3 hours. After stirring, the solvent was evaporated to give a solid product. The Ti content of the obtained solid product is 0.8% by weight
It was hot. Preparation of Catalyst Dispersion The above-mentioned solid product h was treated in the same manner as in Example-1 to produce a catalyst dispersion h-i. High-pressure polymerization of ethylene High-pressure polymerization of ethylene was carried out in exactly the same manner as in Example 1, except that catalyst dispersion h-i was used. 3000g per 1g of solid catalyst component as shown in Table 1
of polymer was obtained. That is, the yield to catalyst (g·PE/g·solid catalyst component) was 3,000, and the yield per 1 g of Ti (g·PE/gTi) was 375,000. Comparative Example 2 Manufacture of Catalyst Component The same procedure as that of Example 2 was carried out except that _MgC12 having a surface area of 3 m ² /g was used in the manufacture of the catalyst component of Example 7.
Solid product i was obtained in exactly the same manner as in Example 7. The Ti content of the obtained solid product was 0.08% by weight. Preparation of catalyst dispersion In the same manner as in Example-1, the above-mentioned solid product i
was treated to produce a catalyst dispersion i-i. High-pressure polymerization of ethylene High-pressure polymerization of ethylene was carried out in exactly the same manner as in Example-A except that catalyst dispersion i-i was used.
Almost no polymer was obtained, and the catalyst had no activity. Examples 8 to 10 Using the catalyst component f obtained in the same manner as in Example-5, the diethylaluminium chloride (cocatalyst) used in the preparation of the catalyst dispersion in Example-1 was changed to the compounds shown below. Alternatively, the catalyst dispersion f-
I got ro-f-ni.

[Table] High-pressure polymerization of ethylene was carried out in exactly the same manner as in Example 1 using the catalyst dispersions f-RO to F-NI obtained above. The results are shown in Table-1. Examples 11-21 Ethylene homopolymerization and copolymerization with other α-olefins were carried out using the same equipment as in Example-1. Table 2 shows the catalyst dispersion used, the reaction conditions employed, and the polymerization results.

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【table】 [Brief explanation of drawings]

FIG. 1 is a flowchart to help understand the technical contents of the present invention regarding Ziegler catalysts.

Claims (1)

[Claims] 1. At a pressure of at least 200 kg/cm ² and a temperature of at least 125° C., ethylene or ethylene and at least one α-olefin is added to a catalyst consisting of a combination of components A and B as described below. A method for polymerizing ethylene, which is characterized by contacting. Component A Organoaluminium compound or alkylsiloxalane derivative. Component B: A solid product obtained by contacting a titanium compound in which the valence of titanium is tetravalent with magnesium dihalide (provided that the magnesium dihalide has a surface area of at least 5 m2 before or after contact with the titanium compound). ² /g).