JPS6239165B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing propylene-ethylene block copolymers. More specifically, the present invention relates to an improved method for producing a heteroblock copolymer in which two types of ethylene-propylene random copolymers having different compositions are block-polymerized on the polypropylene main chain. Using a so-called Ziegler-Natsuta catalyst consisting of titanium trichloride and an organoaluminum compound, propylene is polymerized in the first stage in the presence of a diluent such as an inert liquid hydrocarbon, and then in the second stage or second stage. A method is already known in which ethylene and propylene are randomly copolymerized in the third stage to obtain a heteroblock copolymer through so-called two-stage or three-stage polymerization. However, the titanium trichloride conventionally used in these methods is, for example, one obtained by reducing titanium tetrachloride with an organoaluminum compound, one obtained by reducing titanium tetrachloride with metallic aluminum,
Alternatively, there are products obtained by heat-treating and pulverizing these, especially those called TiCl ₃ -AA, which not only have low polymerization activity but also have a large amount of amorphous polymer as a by-product. It has the following drawback. Since the polymerization activity is low, it is actually impossible to significantly increase the amount of polymer produced per unit amount of catalyst. Therefore, after the polymerization is completed, the polymer slurry is treated with alcohol, etc., and the catalyst residue can be used as a diluent. Catalyst residues must be removed from the polymer by solubilization and separation of the polymer and diluent.
In addition, it is desirable to remove the by-product amorphous polymer from the product polymer because it impairs the rigidity, which is one of the advantages of polypropylene. It increases by copolymerization, and this not only reduces the yield of the polymer product, but also
This causes adhesion of the rubbery polymer to the vessel wall, agglomeration between polymer particles, and blockage of piping, etc., making stable continuous operation impossible. That is, when carrying out propylene-ethylene block copolymerization using the above conventional titanium trichloride, for example TiCl ₃ -AA, which has low polymerization activity and produces a large amount of amorphous polymer as a by-product, catalyst residue and amorphous polymer are produced. At the polymerization stage due to the need to remove the polymer,
Alternatively, it has been essential to use a diluent in the post-treatment stage after polymerization. In addition, a process for separating and recovering the alcohol, etc. and amorphous polymer used for catalyst removal from the diluent is required, which further increases the cost of producing the polymer. On the other hand, the physical properties of block copolymers are characterized by the fact that they greatly improve the impact strength and low-temperature brittleness, which are disadvantages of propylene homopolymers, without significantly impairing their high rigidity, which is an advantage of propylene homopolymers. For this purpose, the polymerization is divided into two stages. In the first stage, propylene homopolymerization is carried out, and then in the second stage, propylene-polymerization is carried out in the presence of the propylene polymer produced in the first stage.
A method of random ethylene copolymerization is known, but as shown in Japanese Patent Publication No. 47-31119, the impact strength improves as the propylene/ethylene ratio in the second stage increases, but at the same time, the impact strength of the amorphous polymer increases. According to the same issue, the recovery rate of the product block copolymer from the polymerization diluent (heptane) was 80%.
Only ~90%. As a method of reducing the amount of amorphous polymer, the polymerization is divided into three stages, the first stage is propylene homopolymerization, and the second stage contains a small amount of ethylene in the presence of the propylene polymer produced in the first stage. A method has been proposed in which propylene is polymerized and then propylene-ethylene random copolymerization is carried out in the third step in the presence of the propylene-ethylene copolymer produced in the second step. For example,
In No. 20621, the propylene/propylene + ethylene ratio in the second stage gas phase was 86 to 96 mol%.
In No. 26190, the same ratio is 91 to 99.8 mol%, JP-A-49-
In No. 45308, the same ratio is 99 mol% or more, and the propylene/propylene+ethylene ratio in the second stage exceeds 85 mol% in all cases. Nevertheless, among the above,
For example, according to Japanese Patent Publication No. 44-20621, the recovery rate of the product block copolymer from the diluent after polymerization is 90%.
However, it is only a slight improvement over the method of conducting polymerization in two stages. Furthermore, in JP-A-50-142652, JP-A-52-8094, and JP-A-52-98045, H ₂ is not used as a molecular weight modifier during propylene-ethylene copolymerization in the second stage. A method for producing a propylene-ethylene block copolymer is described, but according to studies by the present inventors, when hydrogen is not used, the surface condition of the melt extrudate is poor and the polymer has poor flow during melting. All I could get was that. The present inventors have conducted intensive studies to develop a method that can carry out the above-mentioned three-step block copolymerization in liquefied propylene and in the gas phase in the absence of liquid hydrocarbons. By using a specific highly active catalyst, the amount of amorphous polymer produced as described above can be reduced, the catalyst removal process can be simplified or omitted, and the powder properties of the obtained polymer can also be improved. In addition, the propylene/propylene+ethylene ratio and propylene partial pressure in the gas phase at each stage are determined, and the melt flow index of the polymer produced using hydrogen as a molecular weight modifier at each stage is determined to be a specific value. It has been found that by doing so, a polymer of excellent quality, ie, high rigidity, high impact strength, and low embrittlement temperature, as well as excellent surface condition (rough skin) of the melt extrudate, can be obtained, and the present invention has been achieved. The gist of the present invention is to use a catalyst system in which the aluminum content is 0.15 or less in terms of the atomic ratio of aluminum to titanium, and the catalyst system is mainly composed of a solid titanium trichloride-based catalyst complex containing a complexing agent and an organoaluminium compound. , a method for producing a propylene-ethylene block copolymer by dividing the polymerization into three stages, wherein (a) in the first stage, propylene is polymerized in the presence of liquefied propylene and hydrogen, and 70% of the total polymer production amount is % to 90% by weight and whose melt flow index is 1 to 60; Propylene and ethylene are copolymerized in the presence of hydrogen under a propylene partial pressure of 0.5 Kg/cm ² or more with a ratio of +ethylene of 95 mol % or less to produce 3 wt % to 20 mol % of the total polymer production. % by weight and whose melt flow index is 0.1 or less; Copolymerizing ethylene and propylene in the presence of hydrogen with a ratio of +ethylene lower than that in the second stage, and the melt flow index is 5% to 20% by weight of the total polymer production. The present invention relates to a method for producing a propylene-ethylene block copolymer, which is characterized in that it produces an ethylene-propylene copolymer having a block copolymer of 1 or less. To further explain the present invention in detail, the solid titanium trichloride-based catalyst complex used as a catalyst in the present invention has an aluminum content in the atomic ratio of aluminum to titanium of 0.15 or less, preferably 0.1.
More preferably, it is 0.02 or less and contains a complexing agent. The content of the chaining agent is 0.001 or more, preferably 0.01 or more in molar ratio of the complexing agent to titanium trichloride in the solid titanium trichloride-based catalyst complex. Specifically, titanium _trichloride , ^the formula AlR ³ _p atom, p
is a number of 0≦p≦2) containing a complexing agent in a molar ratio of 0.001 or more to aluminum halide and titanium trichloride, for example,
_{TiCl 3 ・} ⁽ _AlR ³ _p 2, C is a complexing agent, x is a number of 0.15 or less, and y is a number of 0.001 or more.) Of course, TiCl ₃ components, AlR ³ In addition _{to the p} It may contain a solid, an olefin polymerized powder such as polyethylene, polypropylene, etc. Examples of the complexing agent C include ethers, thioethers, ketones, carboxylic acid esters, amines, carboxylic acid amides, and polysiloxanes, among which ethers and thioethers are particularly preferred. As an ether or thioether,
General formula R ⁴ -O-R ⁵ or R ⁴ -S-R ⁵ (wherein R ⁴ ,
R ⁵ represents a hydrocarbon group having 15 or less carbon atoms. ), specifically those described below. As AlR ³ _p X _3-p , AlCl ₃ , AlR ³ Cl ₂
etc. Furthermore, the solid titanium trichloride-based catalyst complex used in the method of the present invention has an X-ray diffraction pattern at a position corresponding to the strongest peak position of α-type titanium trichloride (2θ=
Particularly preferred is one having a halo of maximum strength at an angle of around 32.9°. Further, it is preferable that the solid titanium trichloride-based catalyst complex is not subjected to thermal history at a temperature exceeding 150° C. during production. Furthermore, the solid titanium trichloride-based catalyst complex used in the method of the present invention has a pore radius of 20 Å or more as measured by a mercury porosimeter method.
Amorphous polymers are characterized by an extremely fine pore volume with a cumulative pore volume of 0.02 cm ³ /g or more between 500 Å, especially 0.03 cm ³ /g to ^{0.15 cm 3} /g. This is particularly preferred since it is not necessary to remove coalescence. However, such a solid titanium trichloride-based catalyst complex can be prepared from a liquid containing titanium trichloride liquefied in the presence of (a) ether or thioether at 150°C;
Precipitate at the following temperature (b) Easily produce solid titanium trichloride obtained by reducing titanium tetrachloride with an organoaluminum compound or metal aluminum by a method such as treatment with a complexing agent and treatment with a halogen compound. I can do it. Method (a) has already been used in Japanese Patent Application No. 49-88476 and Patent Application No. 49-88476.
88477, 49-120100, 50-1154, 50-
16722, 50-19552, 52-140922, 52-
147590, etc., but to be more specific, there are two methods for obtaining a liquid material containing liquefied titanium trichloride. (A) A method in which titanium tetrachloride is used as a starting material and reduced with an organoaluminum compound in the presence of an ether or thioether and, if necessary, a suitable hydrocarbon solvent. (B) Using solid titanium trichloride as a starting material, if necessary in the presence of a suitable hydrocarbon solvent,
Method of treatment with ether or thioether. Examples of the ether or thioether used include those represented by the general formula shown above, where R ⁴ and R ⁵ are ethyl, n-
Propyl, n-butyl, n-amyl, n-hexyl, n-heptyl, n-octyl, n-decyl,
Examples include alkyl groups such as n-dodecyl, preferably linear alkyl groups; alkenyl groups such as butenyl and octenyl, preferably linear alkenyl groups; aryl groups such as tolyl, xylyl, and ethyl phenyl; and aralkyl groups such as benzyl. . Preferred are dialkyl ethers, dialkenyl ethers, alkyl alkenyl ethers, dialkyl thioethers, and the like. In addition, as a hydrocarbon solvent, n-pentane,
n-hexane, n-heptane, n-octane, n
- Saturated aliphatic hydrocarbons such as dodecane and liquid paraffin; alicyclic hydrocarbons such as cyclohexane and methylcyclohexane; aromatic hydrocarbons such as benzene, toluene, and xylene, etc., and are selected appropriately depending on the type of ether. be done. for example,
In the general formula shown above as an ether or thioether
When at least one of R ⁴ and R ⁵ is an alkyl group or alkenyl group having 3 to 5 carbon atoms,
Preferably, aromatic hydrocarbons are selected, followed by ring hydrocarbons, and when R ⁴ and R ⁵ are an alkyl group or alkenyl group having 6 or more carbon atoms, saturated aliphatic hydrocarbons are preferably selected. be done. Next ^, as an organoaluminum compound in method (A), for example, the general formula _AlR ⁶ _q (X represents a halogen atom) is used, and the amount used is shown in the molar ratio of titanium in titanium tetrachloride to hydrocarbon group (R ⁶ in the general formula) in the organoaluminum compound. , 1:
The ratio is in the range of 0.1 to 1:50, preferably 1:0.3 to 1:10. The amount of ether or thioether used is the molar ratio of ether:titanium tetrachloride, 1:
It is in the range of 0.05 to 1:5, preferably 1:0.25 to 1:2.5. The method of conducting the reduction reaction is arbitrary, and usually 0
The three components are brought into contact in any order to form a liquid at a temperature of ~50°C. In addition, if a small amount of iodine, titanium tetraiodide, or titanium tetrabromide is added to titanium tetrachloride, for example, at a molar ratio of about 0.005 to 0.3 to titanium tetrachloride, solid titanium trichloride will be precipitated. Catalyst complexes are particularly preferred because they provide polymers with high activity and high stereoregularity. As solid titanium trichloride in method (B), titanium trichloride produced by reducing titanium tetrachloride with hydrogen gas, aluminum, etc. can also be used, but titanium trichloride produced by reducing titanium tetrachloride with an organoaluminum compound can also be used. Particularly preferred is titanium trichloride. The amount of ether or thioether used is a molar ratio of titanium trichloride:ether or thioether of 1:1 or more, preferably 1:1 to 5. Ether or thioether treatment is usually carried out at 0 to 100°C, preferably at 20 to 50°C.
It is carried out at a temperature of around ℃. In method (a), a fine particulate solid titanium trichloride-based catalyst complex is precipitated at a temperature of 150°C or less from a liquid material containing titanium trichloride liquefied by either method (A) or (B) above. However, there are no particular restrictions on the method, and the liquid can be heated as is or after adding a hydrocarbon diluent as necessary, at a temperature of 150℃ or less,
The temperature is usually raised to 20 to 150°C, preferably 40 to 120°C, and particularly preferably 60 to 100°C to precipitate. Note that when the total number of moles of titanium and aluminum in the titanium trichloride liquid is smaller than the number of moles of ether or thioether, a liberating agent may be added to promote precipitation. The liberating agent has the function of reacting with the complex of titanium trichloride and ether or thioether constituting the liquid material to precipitate free solid titanium trichloride,
Lewis acids that are more acidic than titanium trichloride, e.g.
Titanium tetrachloride, boron trifluoride, boron trichloride,
Examples include vanadium tetrachloride, aluminum trichloride, alkyl aluminum dihalide, alkyl aluminum sesquihalide, dialkyl aluminum halide, and the like. Among these, titanium tetrachloride,
Aluminum halides, such as aluminum trihalides and alkyl aluminum dihalides, are preferred. The amount of the liberating agent used is preferably 5 times the mole or less of titanium in the liquid material. Next, the method (b) is JP-A-47-34478, JP-A-48
-64170, Japanese Patent Application No. 49-17120, Japanese Patent Application No. 49-29622, etc., but specifically, titanium tetrachloride is first reduced with an organoaluminum compound or metallic aluminum. As the organoaluminum compound, those having the general formulas listed in (A) of (A) can be similarly used. The reduction reaction may be performed by a known method. For example, when reducing with an organoaluminum compound, add the organoaluminum compound to titanium tetrachloride in a diluent in an amount of 1 mole or more, preferably 1 to 10 times the amount of titanium tetrachloride, at about -50 to 30°C. The reaction may be completed by adding at a certain temperature and raising the temperature to -10 to 100°C. When reducing with metallic aluminum, 0.1 to 1 gram atom of metallic aluminum is added per mole of titanium tetrachloride in a diluent such as xylene or in the presence of a small amount of AlCl ₃ to titanium tetrachloride in the absence of a diluent. Add, 80-300℃ preferably 100℃
Just heat it to ~200℃. In the method (b), the solid titanium trichloride obtained as described above is treated with a complexing agent and a halogen compound. As the complexing agent, those exemplified above as complexing agent C can be similarly mentioned.
Examples of the halogen compound include titanium tetrachloride and carbon tetrachloride. The complexing agent treatment and the halogen compound treatment may be performed at the same time, or the complexing agent treatment and the halogen compound treatment may be performed first. The complexing agent treatment is usually carried out by adding a complexing agent to solid titanium trichloride in a diluent in an amount of 0.2 to 3 moles relative to TiCl ₃ at a temperature of -20 to 80°C. After the complexing agent treatment, it is preferable to separate and wash the obtained solid. Halogen compound treatment is usually carried out in a diluent at a temperature of -10 to 50°C. The amount of halogen compound used is usually 0.1 per TiCl ₃
~10 times by mole, preferably 1 to 5 times by mole. After the halogen compound treatment, it is preferable to separate and wash the obtained solid. The solid titanium trichloride-based catalyst complex used in the method of the present invention is preferably one produced by the method (a) or (b) above. Method (a) is preferred, especially method (b) via method (A), but in addition to methods (a) and (b), as described in JP-A-123796-1987,
To solid titanium trichloride obtained by reducing titanium tetrachloride with an organoaluminum compound, add an ether compound at a molar ratio of 0.5 to 5 to the titanium trichloride, heat to 50 to 120°C, and then separate the solid. Those produced by this method can also be used. In the method of the present invention, the solid titanium trichloride-based catalyst complex as described above is used as a catalyst. Pure titanium trichloride (TiCl ₃ ) obtained by hydrogen reduction of titanium tetrachloride, titanium trichloride-aluminum trichloride eutectic (TiCl ₃ 1/3 AlCl ₃ ) obtained by aluminum reduction of titanium tetrachloride, and these trichlorides. Mechanically ground titanium and the like are not suitable as catalysts in the process of the invention. On the other hand, as a cocatalyst organoaluminum compound, the general formula
It is preferable to use a compound represented by AlR ¹ _o Cl _3-o (wherein R ¹ represents a hydrocarbon group having 1 to 20 carbon atoms, and n represents a number from 1.95 to 2.10). Among these, diethylaluminum monochloride in which R ¹ is an ethyl group and n is 2 can be sufficiently used, but those in which R ¹ is a normal propyl group or a normal hexyl group are particularly preferred.
When R ¹ is normal propyl group or normal hexyl group, it is important that n is 1.95≦n≦2.10, and if it is within this range, polymerization can be carried out in combination with the solid titanium trichloride catalyst complex described above. High results can be obtained in both polymerization activity and stereoregularity of the polymer. Furthermore, when using n > 2.10, the decrease in stereoregularity is greater than the improvement in polymerization activity, while when using n < 1.95, on the other hand, the polymerization activity decreases more than the improvement in stereoregularity. is significant, giving unfavorable results in either case.
The organoaluminum compound that is the cocatalyst may have both a normal propyl group and a normal hexyl group as R ¹ in the above general formula. Therefore, the method for producing such an organoaluminum compound which is a cocatalyst may be a known method, for example, by reacting tri-n-propyl aluminum or tri-n-hexyl aluminum with aluminum trichloride; Normal propylaluminum, trinormalhexylaluminum or aluminum trichloride and (b) general formula
Produced by reacting with a compound represented by AlR ² _n Cl _3-n (wherein R ² represents a normal propyl group or a normal hexyl group, and m represents a number of 0<m<3). Ru. Furthermore, there is a method that combines these two methods, that is, first, tri-n-propyl aluminum or tri-n-hexyl aluminum is reacted with aluminum trichloride to produce, for example, AlR ² _n Cl _3-n where m is about 0.9 to 2.1. can be produced by adding and reacting a small amount of tri-n-propyl aluminum, tri-n-hexyl aluminum or aluminum trichloride to this to give the desired n. The reaction temperature during these reactions is room temperature or
150°C, usually 50°C to 100°C, and a reaction time of several minutes to several hours, usually 1 to 2 hours, is sufficient. Although the reaction does not require the use of a solvent, it is possible to use solvents such as aliphatic hydrocarbons such as n-hexane and n-heptane, aromatic hydrocarbons such as toluene and xylene, and alicyclic hydrocarbons such as cyclohexane and methylcyclohexane. You can go in their presence. In addition, when trialkylaluminum having an alkyl group different from R ² in AlR ² _n Cl _3-n is used as a reactant added in the second stage reaction, normal hexyl group and normal propyl group are A compound having both is obtained. After the reaction is completed, it may be used as a cocatalyst as it is, but it is preferable to use it after purification by distillation under reduced pressure or the like. Furthermore, in the method of the present invention, in addition to the above catalyst and cocatalyst, an electron donating compound may be used as the third catalyst component to improve the stereoregularity of the produced polymer without reducing the polymerization activity. Such electron-donating compounds include one electron-donating atom or group.
Compounds containing more than one compound, such as ethers, polyethers, alkylene oxides, furans, amines, trialkylphosphines, triarylphosphines, pyridines, quinolines, phosphoric esters,
Examples include phosphoric acid amide, phosphine oxide, trialkyl phosphite, triarylphosphite, ketone, carboxylic acid ester, and carboxylic acid amide. Among these, preferred are carboxylic acid esters such as ethyl benzoate, methyl benzoate, and phenyl acetate; glycine esters such as dimethylglycine ethyl ester and dimethylglycine phenyl ester; and triphenyl phosphite and trinonyl phenyl phosphite. Examples include triarylphosphite and the like. The ratio of each catalyst component used is usually selected from the range of 1:1 to 100, preferably 1:2 to 40, based on the molar ratio of titanium trichloride to organoaluminum compound in the solid titanium trichloride catalyst complex. When the aforementioned third catalyst component is used, the molar ratio of titanium trichloride to the third catalyst component is selected to be 1:0.01 to 10, preferably 1:0.05 to 2. Furthermore, aromatic hydrocarbons such as benzene, toluene, and xylene may also be used as the third catalyst component. Note that the solid titanium trichloride-based catalyst complex used as a catalyst may be used as it is for polymerization, but
It is preferable to pre-treat with a small amount of olefin such as propylene or ethylene in the presence of an organoaluminum compound before use. This pretreatment is effective in improving the physical properties of the polymer slurry, such as bulk density. Pretreatment is performed at a temperature lower than the polymerization temperature, generally from 20℃
At 60°C, titanium trichloride in the polymer/solid titanium trichloride catalyst complex produced by pretreatment = 0.1~
The ratio is 50/1 (weight ratio), usually 1 to 20/1. In the method of the present invention, the polymerization is carried out in three stages in the method for producing propylene-ethylene copolymer using a catalyst system mainly composed of a solid titanium trichloride-based catalyst complex and an organoaluminum compound as described above. However, in the first step, propylene is homopolymerized in the presence of liquefied propylene. Here, in order to supply the solid titanium trichloride catalyst complex and organoaluminum compound into the polymerization tank, aliphatic hydrocarbons such as hexane and heptane, alicyclic hydrocarbons such as cyclohexane, and aromatic hydrocarbons such as benzene and toluene are used. It is preferred to use inert liquid hydrocarbons as diluents, and it is therefore within the scope of the invention for trace amounts of these inert liquid hydrocarbons to coexist with the liquefied propylene. The polymerization temperature and time are selected so that the amount of propylene homopolymer is 70 to 90% by weight of the total polymer production. Polymerization temperature is usually 40~100℃, preferably 55~
Selected from a range of 80℃. The polymerization pressure is the sum of the vapor pressure of liquefied propylene determined by the polymerization temperature, the pressure of hydrogen used as a molecular weight regulator, and the vapor pressure of a small amount of the inert liquid hydrocarbon used as a diluent for the catalyst component, but usually 30 ~40Kg/ ^cm2 .
The melt flow index of the propylene homopolymer obtained in the first step (230℃, load
Extrusion amount g/10 min at 2.16Kg, ASTM D1238−
By 70. In the following, it will be abbreviated as MFI. )but,
The polymerization temperature and amount of molecular weight regulator are selected so that the molecular weight is 1 to 60. Examples of the molecular weight modifier include hydrogen, dialkylzinc, etc., but hydrogen is preferred.
Typically, the hydrogen concentration in the gas phase is about 1-20 mole percent. Next, in the second stage, in the presence of the propylene homopolymer produced in the first stage and in the substantial absence of a liquid hydrocarbon such as liquefied propylene,
Perform ethylene random copolymerization. That is, the second
In this step, polymerization is carried out using a gas phase polymerization method in which the catalyst is brought into direct contact with ethylene and propylene gases. The propylene/propylene+ethylene ratio is selected from a range of 95 mol% or less. And the propylene partial pressure must be 0.5Kg/cm ² or more. If the propylene/propylene+ethylene ratio exceeds 95 mol%, the improvement in impact strength will be insufficient, which is not preferred. In particular, this ratio is preferably 95 to 60 mol%. If the propylene partial pressure is less than 0.5 Kg/cm ² , the copolymer production rate per unit amount of catalyst will be low and it will be economically disadvantageous, which is not preferred. Especially 1-50
Kg/cm ² is preferred. And the amount of propylene-ethylene random copolymer is 3 to 20% of the total polymer production amount.
The polymerization temperature and time are chosen so that the weight percent. If this amount is less than 3% by weight, the effect of improving impact strength etc. will be small, and if it exceeds 20% by weight, the bulk density and free flow properties will deteriorate, the rigidity and transparency will be greatly reduced, and the shrinkage rate of the molded product will also be large, so it is preferable. do not have. It is preferable that the amount produced in the second stage is the smallest among the stages 1 to 3. Polymerization temperature is usually 40~100℃,
Preferably, the temperature is selected from the range of 60 to 90°C. Polymerization pressure is usually 10 to 50 kg/cm ² . Then, the polymerization temperature and the amount of hydrogen, which is a molecular weight regulator, are selected so that the MFI of the propylene-ethylene random copolymer is 0.1 or less. If MFI exceeds 0.1, the improvement in impact strength will be insufficient. The hydrogen concentration in the gas phase is usually about 0.01 to 30 mol%. As mentioned above, if hydrogen is not present, the molded product will have rough skin, which is not preferable. In the third stage, random copolymerization of ethylene and propylene is carried out in the presence of the propylene-ethylene copolymer produced in the second stage and in the substantial absence of a liquid hydrocarbon such as liquefied propylene. That is, the polymerization is carried out by a gas phase polymerization method in which the catalyst is brought into direct contact with ethylene or propylene gas. The propylene/propylene+ethylene ratio is chosen to be lower than that of the second stage. If this ratio is higher than that in the second stage, low temperature brittleness will not be improved and problems will likely occur in formability, which is not preferred. Usually this ratio is preferably 10
Selected from the range of ~50 mol%. The polymerization temperature, polymerization pressure, and polymerization time are selected so that the amount of propylene-ethylene random copolymer is 5 to 20% by weight of the total amount of polymer produced. If this amount is less than 5%, the improvement in low temperature brittleness will be insufficient. 20% by weight
Exceeding this is not preferable because the transparency of the molded product will be greatly reduced. The polymerization temperature is usually selected from the range of 40 to 100°C, preferably 60 to 90°C. The polymerization pressure is usually 1 to 50 kg/cm ² . MFI of propylene-ethylene random copolymer is 1 or less, preferably 0.1
The polymerization temperature and the amount of hydrogen, which is a molecular weight regulator, are selected as follows. The hydrogen concentration in the gas phase is usually about 1 to 150 mol%. If MFI exceeds 1, the effect of improving impact strength will not be sufficient and this is not preferred. Polymerization is carried out continuously or batchwise. In the continuous system, a separate polymerization vessel is used for each stage, the transfer of the polymer between the polymerization vessels being conveniently carried out by means of pressure differences. Therefore, it is preferable to determine the polymerization pressure so that the pressure in the polymerization tank satisfies the following relationship: first stage≧second stage≧third stage. It is also possible to increase the pressure in the initial stage by adding an inert gas such as nitrogen or argon. The propylene-ethylene block copolymer obtained by the method of the present invention has high crystallinity and the amount of amorphous polymer produced is small, so there is no need to remove the amorphous polymer. Moreover, it has excellent impact strength, rigidity, and low-temperature brittleness even without removing the amorphous polymer. In addition, in the method of the present invention, the amount of propylene-ethylene block copolymer produced is 16,000 g or more, and even 20,000 g per 1 g of titanium trichloride.
It is so high that it exceeds g. Therefore, the titanium trichloride residue remaining in the polymer is 19 ppm titanium.
Below that, it becomes even less than 15 ppm, and there is no longer any need to remove titanium. At the end of the third stage of polymerization, the propylene-ethylene block copolymer powder is in a powder state with excellent free-flowing properties. Since it is not necessary to remove the amorphous polymer and the Ti in the catalyst residue, there is no need to use inert liquid hydrocarbons, alcohols, etc. That is, after the polymerization is completed, the powder state is directly pelletized, or in order to remove the chlorine in the catalyst residue,
As seen in No. 25888, it can be pelletized after a simple process of bringing the polymer powder into gas-solid contact with a small amount of gaseous alkylene oxide at 80 to 120°C for several minutes, or it can be made into powder grade without being pelletized. It becomes possible to make the final product as is. In order to operate the method of the present invention stably and continuously for a long period of time,
The powder properties of the catalyst-containing olefin polymer powder in the polymerization system were measured at a temperature of 30 to 130°C, with a bulk density of 0.35 g/cm ³
The above is preferably 0.40 g/cm ³ or above, and the angle of repose is 30.
~50°, preferably 30-45°, and a sliding angle of 25-50°
The angle is preferably 25 to 43°, and the average particle diameter is preferably 100 μm or more, preferably 200 μm or more.
In order to obtain such a powdery polymer powder, the above-mentioned (a) or (b) must be used as the solid titanium trichloride catalyst complex.
It is sufficient to use the product manufactured by the method (a), especially the method (a). Here, the angle of repose and the angle of slip are the angles at which the above powder remains stable, as measured on a polished stainless steel plate, as described in Zoku Shin Chemical Engineering Course, published by Nikkan Kogyo Shimbun, Vol. 18, pages 5-8. and the angle at which it begins to slide. EXAMPLES The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof. The meanings of the abbreviations and various measurement methods in the examples are as follows. Catalyst efficiency CE (g/g) is the amount of copolymer produced in grams per gram of titanium trichloride. Isotactic Index II (%) is the residual amount (% by weight) after extraction with boiling n-heptane for 6 hours in a modified Soxhlet extractor.
Since the amorphous polymer is soluble in boiling n-heptane, II (%) indicates the yield of the crystalline polymer. The bulk density ρ _B (g/cc) was based on JIS-6721. The ethylene content [E] _IR (%) in the copolymer was determined from the peak height ratio of 4396 cm ^-1 and 4325 cm ^-1 in the infrared absorption spectrum of a 0.2 mm thick press sheet. Melt flow index MFI (g/10min)
According to ASTM D1238−70, 230℃, load 2.16Kg
It shows the amount of polymer extruded when . The density ρ (g/cc) was determined at 20°C by the density gradient tube method in accordance with ASTM-D1505. The first descending strength YS (Kg/cm ² ) is ASTM D638−
It was determined by a tensile test of a dumbbell piece punched from a press sheet with a thickness of 1.0 mm in accordance with 72. Unless otherwise specified, values are measured at 20°C. Izotsu impact strength (Kg・cm/cm) is ASTM
Measurements were made using D256 on a notched strip cut out from a 5.0 mm thick press sheet. Unless otherwise specified, values are at 20°C. The elongation at break of the weld portion (%) was determined by making a 3 mm thick two-point gate dumbbell piece using a 1 oz injection molding machine and conducting a tensile strength test. This is a measure of the strength of the weld portion. The embrittlement temperature Tb (°C) was determined according to ASTM D746 for a test piece punched from a 2.0 mm thick flat plate made using a 1 oz injection molding machine. The tensile impact strength was measured according to ASTM D1822. In the Examples and Comparative Examples below, the MFI in the second stage and the third stage were determined by separately conducting polymerization only in the second stage or the third stage, respectively. Catalyst production example 1 (Production of solid titanium trichloride-based catalyst complex) (A) Production of homogeneous titanium trichloride solution Into a 500 ml four-necked flask that was thoroughly purged with dry argon, 120 ml of n-heptane and 100 mmol of titanium tetrachloride were charged. , and further added 90 mmol of di-n-octyl ether. A solution of 33 mmol of diethylaluminum monochloride dissolved in 50 ml of n-heptane was gradually added dropwise to the mixture while stirring and maintaining the temperature at 25°C. A homogeneous solution of titanium trichloride in n-heptane with a greenish brown color was obtained. It was done. (B) Formation of precipitate of titanium trichloride and production of catalyst When the homogeneous solution of titanium trichloride obtained in step (A) above was heated to 95°C, a precipitate of purple titanium trichloride was formed during the heating process. Admitted. After stirring at 95°C for 30 minutes, the precipitate was separated and washed twice with 100 ml of n-heptane and then three times with 100 ml of toluene to obtain a finely granular purple solid titanium trichloride catalyst complex. Elemental analysis showed that the catalyst complex had a composition of the formula TiCl ₃ (AlCl _{3 ) 0.003 [} (n-C _{8 H 17} ) ₂ O] _0.10 . In addition, when we measured the X-ray diffraction spectrum of this catalyst complex using CuKα radiation, we found that 2Θ
It had a halo of maximum intensity at =32.9°. In addition, the cumulative pore volume measured using a mercury porosimeter (60,000 psig) has a pore radius of 20 ~
It was 0.04 cm ³ /g within 500 Å. Catalyst production example 2 (Production of solid titanium trichloride catalyst complex) (A) Production of reduced solid In a four-necked 500 ml flask purged with argon,
Add 45 ml of n-hexane and 100 mmol of titanium tetrachloride, cool to 0°C, and add 70 ml of n-hexane with stirring.
ml and ethylaluminum sesquichloride 200
A solution consisting of mmol was added dropwise over 30 minutes. After completion of the dropwise addition, stirring was continued for another 2 hours at 0°C for ripening. Then, it was washed 5 times with 100 ml of n-hexane, and 21 g of a reddish-purple solid substance was removed.
I got it. (B) Complexing agent treatment 150 ml of n-hexane and 21 ml of diisoamyl ether were added to the reddish-purple solid substance obtained in (A) above, and the reaction was carried out at 30°C for 1 hour with stirring. The mixture was then washed five times with 100 ml of n-hexane and dried under reduced pressure to obtain 21 g of a brown substance. (C) Titanium tetrachloride treatment 400 m
mol of titanium tetrachloride was added. After reacting at 35°C for 1.5 hours, washing with 100 ml of n-hexane 8 times produced a purple solid titanium trichloride catalyst complex.
I got g. Elemental analysis revealed that it had a composition of the formula TiCl ₃ .(AlCl _{3 ) 0.01 .} [(i-C _{5 H 11} ) ₂ O] _0.11 . In addition, when we measured the X-ray diffraction spectrum using CuKα radiation, we found that 2Θ
It had a halo of maximum intensity at =32.9°. In addition, the cumulative pore volume measured using a mercury porosimeter was 0.16 when the pore radius was between 20 and 500 Å.
cm ³ /g. Catalyst production example 3 (Production of solid titanium trichloride-based catalyst complex) (A) Production of homogeneous titanium trichloride solution 150 ml of purified toluene and 90% titanium tetrachloride were placed in a 500 ml four-necked flask purged with dry argon.
mmol and further di-n-butyl ether
85 mmol was added. Titanium tetrachloride and di-n-butyl ether reacted with some heat and were uniformly dissolved in toluene to obtain an orange-yellow homogeneous solution. While stirring the solution and keeping it at 25°C, add 45ml of diethylaluminum monochloride.
When a solution of mol of titanium trichloride dissolved in 20 ml of toluene was gradually added, a dark orange homogeneous solution of titanium trichloride was obtained. (B) Formation of precipitate of titanium trichloride and production of catalyst When the homogeneous solution of titanium trichloride obtained in step (A) above was heated to 95°C, a precipitate of purple titanium trichloride was formed during the heating process. Admitted. After stirring at 95℃ for 30 minutes, separate the precipitate and add toluene.
The mixture was washed once with 100 ml and then five times with 100 ml of n-heptane to obtain a finely divided purple titanium trichloride catalyst complex. Elemental analysis showed that the catalyst complex had a composition of the formula TiCl ₃ (AlCl _{3 ) 0.004 [} (n- _{C 4} H ₉ ) ₂ O] _0.06 . Furthermore, when we measured the X-ray diffraction spectrum of this catalyst complex using CuKα radiation, we found that 2Θ=
It had a halo of maximum intensity at 32.9°. Example 1 An induction stirring autoclave with a capacity of 2 and having a built-in anchor-type stirring blade was used. After thoroughly drying, vacuuming and purging with nitrogen gas, di-n-propyl aluminum monochloride 2.0 was placed in an autoclave purged with propylene gas.
mmol was charged. Charge 1.2Kg/ ^cm2 of hydrogen gas,
Then, after charging 700 g of liquefied propylene, the temperature of the autoclave was raised. Autoclave internal temperature is 70
When the temperature reached 18 °C, the solid titanium trichloride-based catalyst complex obtained in Catalyst Preparation Example 1, TiCl ₃ as 18
5 ml of toluene slurry containing 1.0 mg of toluene was injected under pressure with nitrogen gas. At this time, the first stage polymerization reaction was started, and the polymerization reaction was continued at 70° C. for 3.0 hours with stirring. The total pressure was 32.4 kg/cm ² gauge pressure. After 3.0 hours, purge the liquefied propylene and hydrogen gas and reduce the autoclave internal pressure to gauge pressure 0 Kg/cm ²
Then, a siphon was attached under nitrogen gas, several grams of powdered polypropylene homopolymer was collected under nitrogen gas pressure, and the Ti content was measured using fluorescent X-rays.
The yield and MFI of polymer in each step were determined. Then, after quickly adjusting the internal temperature of the autoclave to 70°C, propylene gas was charged at 14.1 kg/cm ² ethylene gas was charged at 2.9 kg/cm ² hydrogen gas was charged at 0.5 kg/cm ² . This time is the start of the second stage polymerization reaction, and the temperature is 70°C.
The polymerization reaction was continued under stirring for 1.0 hour. During this time, ethylene gas was continuously charged so that the ethylene partial pressure was 2.9 Kg/cm ² , and propylene gas was continuously charged so that the propylene partial pressure was 14.1 Kg/cm ² . The total pressure was 17.5 kg/cm ² gauge pressure. The propylene/propylene + ethylene ratio in the gas phase is the average
83mol%, average H ₂ /propylene + ethylene ratio
It was 3 mol%. After 1.0 hours, the propylene gas, ethylene gas, and hydrogen gas were purged, and the internal pressure of the autoclave was set to 0 kg/cm ² gauge pressure, and a siphon was attached under nitrogen gas. The Ti content was measured using pre-fluorescent X-rays to determine the polymer yield in the second stage. Then, quickly adjust the internal temperature of the autoclave to 70℃, then charge 4.5 kg/ ^cm2 of hydrogen gas, and 2.5 kg/ ^cm2 of propylene gas.
10.0Kg/ ^cm2 was charged. At this time, the third stage polymerization reaction was started, and the polymerization reaction was continued at 70° C. for 1.0 hour with stirring. During this time, ethylene gas was continuously charged so that the ethylene partial pressure was 10.0 Kg/cm ² , and propylene gas was continuously charged so that the propylene partial pressure was 2.5 Kg/cm ² . The total pressure was 17.0 Kg/cm ² gauge pressure. Propylene/propylene+ in gas phase
The ethylene ratio was 27 mol% on average, and the _H2 /propylene+ethylene ratio was 29 mol% on average. After 1.0 hour, the propylene gas, ethylene gas, and hydrogen gas were purged, and 385 g of a free-flowing white powdery propylene-ethylene block copolymer with no agglomerates was taken out from the autoclave. Table 1 shows the polymerization conditions and various measurement results. The bulk density ρ _B of the copolymer powder was 0.46 g/cc, and II was 93.5%, but these values were based on the ρ of the propylene homopolymer extracted at the end of the first stage.
_B = 0.46 g/cc, which was almost unchanged compared to II = 96.8%. Also, the average particle size of the copolymer powder is
330μ, the angle of repose was 36°, and the angle of slip was 35°.
On the other hand, in terms of physical properties, even without removing the amorphous polymer, both the first yield strength and the Izot impact strength were high, and the embrittlement temperature was sufficiently low. Catalyst efficiency CE is
21400 and the amount of Ti remaining in the copolymer is 15ppm
It was low enough that there was no need to remove it. The tensile impact strength was 913Kgcm/ ^cm2 . Examples 2 to 4 Polymerization was carried out in the same manner as in Example 1 except that the polymerization conditions were changed as shown in Table 1 to obtain a propylene-ethylene block copolymer with excellent free flow properties. Various measurement results are shown in Table 1. In Example 4, titanium trichloride obtained in Catalyst Production Example 3 was used. Comparative Example 1 Table 1 shows the polymerization results and various measurement results obtained when the third stage polymerization was not performed in Example 1. Without the third stage of polymerization, the embrittlement temperature and impact strength were insufficient.

[Table] Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that the polymerization conditions were changed as shown in Table 2 to obtain a propylene-ethylene block copolymer. Various measurement results are shown in Table 2. Gas phase in the second stage
When the H ₂ concentration was 0, so-called "rough skin" appeared on the surface of the melt extrudate, impairing its aesthetic appearance. Comparative Example 3 In Example 1, 150 mg of commercially available titanium trichloride TiCl ₃ 1/3 AlCl ₃ was used instead of the solid titanium trichloride catalyst complex obtained in Catalyst Production Example 1, and 2.0 mmol of di-n-propyl aluminum monochloride was used instead. to
Polymerization was carried out in the same manner except that 5.0 mmol was used. The results of various measurements are shown in Table 2, and it was found that the copolymer powder had poor free flow properties and had many aggregates. The average particle size could not be measured due to stickiness, and the angle of repose was 71° and the angle of slip was 68°. Furthermore, in terms of physical properties, the first yield strength is low, and therefore, in order to obtain a copolymer with high rigidity, it is necessary to remove the amorphous polymer. Comparative Example 4 In Example 1, 310 mg of commercially available titanium trichloride TiCl ₃ 1/3 AlCl ₃ was used instead of the solid titanium trichloride catalyst complex obtained in Catalyst Production Example 1, and diethyl was used instead of di-n-propyl aluminum monochloride. Polymerization was carried out using the same apparatus and operation except that 10 mmol of aluminum monochloride and 750 ml of n-heptane were used instead of the liquid propylene solvent and the polymerization conditions shown in Table 2 were followed. Further, after the first and second stages were completed, the polymer was extracted as a slurry under nitrogen pressure. After completion of the entire polymerization operation, the solvent and volatile components were directly dried under reduced pressure, and the resulting polymer was a copolymer powder with strong stickiness and poor free-flowing properties. Therefore, the average particle size and bulk density could not be measured. The results of various physical property measurements are shown in Table 2, and in order to obtain a copolymer with good physical properties similar to the results of Comparative Example 3, it is necessary to remove the amorphous polymer.

【table】

[Table] Examples 5 to 8 In Example 1, as the solid titanium trichloride-based catalyst complex, the complex obtained in Catalyst Production Example 2, TiCl ₃
Polymerization was carried out in the same manner, except that 5 ml of hexane slurry containing 20 mg of chloride was used and the polymerization conditions were changed as shown in Table 3. Table 3 shows various measurement results.
It was shown to. The angle of repose of the polymer powder of Example 5 is 39
The slip angle was 38°, and the average particle size was 320μ.

【table】

【table】

Claims (1)

[Scope of Claims] 1. A catalyst system which has an aluminum content in an atomic ratio of aluminum to titanium of 0.15 or less and is mainly composed of a solid titanium trichloride-based catalyst complex containing a complexing agent and an organoaluminum compound. use,
A method for producing a propylene-ethylene block copolymer by dividing polymerization into three stages, the method comprising: (a) polymerizing propylene in the presence of liquefied propylene and hydrogen in the first stage to produce 70% by weight of the total polymer production; to 90% by weight and whose melt flow index is 1 to 60; (b) in a second step propylene/propylene+ in the gas phase in the substantial absence of liquid hydrocarbons; Propylene and ethylene are copolymerized in the presence of hydrogen under a propylene partial pressure of 0.5 Kg/cm2 or ^more with an ethylene ratio of 95 mol% or less to produce 3 to 20% by weight of the total polymer production. % and whose melt flow index is 0.1 or less, (c) in the third step, in the substantial absence of liquid hydrocarbons, propylene/propylene + Ethylene and propylene are copolymerized in the presence of hydrogen, with the ratio of ethylene being lower than that in the second stage, and the melt flow index is 5% to 20% by weight of the total polymer production. 1. A method for producing a propylene-ethylene block copolymer, which comprises producing an ethylene-propylene copolymer having a molecular weight of 1 or less. 2. The method for producing a block copolymer according to claim 1, wherein the ratio of propylene/propylene+ethylene in the gas phase in the second stage is 60 mol% to 95 mol%. 3. The method for producing a block copolymer according to claim 1 or 2, wherein the ratio of propylene/propylene+ethylene in the gas phase in the third step is 10 mol% to 50 mol%. 4 The solid titanium trichloride-based catalyst complex has the formula AlR ³ _p X _3-p (wherein R ³ is a hydrocarbon having 1 to 20 carbon atoms group, X is a halogen atom, p
is a number of 0≦p≦2), and contains a complexing agent in a molar ratio of 0.001 or more to aluminum halide and titanium trichloride. Process for producing the block copolymer described. 5 Pore radius of 20 Å to 500 Å measured by mercury porosimeter method as a solid titanium trichloride catalyst complex
A method for producing a block copolymer according to any one of claims 1 to 4, which uses a block copolymer having a cumulative pore volume of 0.02 cm ² /g or more. 6. Claims 1 to 6, wherein the solid titanium trichloride-based catalyst complex is precipitated at a temperature of 150°C or less from a liquid containing titanium trichloride liquefied in the presence of an ether or thioether. A method for producing a block copolymer according to any one of Item 5. 7. A patent claim in which the solid titanium trichloride-based catalyst complex is obtained by treating solid titanium trichloride obtained by reducing titanium tetrachloride with an organoaluminum compound or metal aluminum by treating it with a complexing agent and a halogen compound. A method for producing a block copolymer according to any one of items 1 to 5.