JPH0312086B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a propylene-ethylene copolymer with excellent low-temperature impact resistance, rigidity, and transparency in high yield. Specifically, the present invention relates to an improved method for producing a propylene-ethylene copolymer having excellent physical properties by combining a specific catalyst and a specific polymerization method. Many methods have already been proposed for producing propylene-ethylene copolymers with excellent low-temperature impact resistance, rigidity, and transparency suitable for blow grade or sheet grade for food containers. 11230, and a method disclosed in Japanese Patent Publication No. 44-4992. The former method is characterized by carrying out copolymerization with a propylene-ethylene mixture after propylene homopolymerization (polymerization rate of 20 to 90% by weight) in the first stage, but low-temperature impact resistance and transparency are insufficient. On the other hand, according to the method proposed in JP-A-53-35788, propylene is polymerized in the range of 5 to 20% by weight of the total polymerization amount in the first stage, and then in the second stage, the ethylene content is 1 to 20% by weight. By carrying out copolymerization with a 20% by weight propylene-ethylene mixture, a propylene-ethylene copolymer with an excellent balance of various physical properties such as low-temperature impact resistance, rigidity, and transparency can be obtained with a good product yield. On the other hand, with recent improvements in catalysts, especially those in which titanium halide is supported on a support mainly composed of magnesium halide, it has become possible to obtain products with extremely high yields per titanium and extremely high stereoregularity. It's coming. If these highly active and highly stereoregular catalysts are used and the above polymerization method is applied, propylene-ethylene with an excellent balance of physical properties can be produced extremely efficiently without the need to remove catalyst residue or atactic polypropylene. It is assumed that a copolymer is obtained. However, simply applying a highly active catalyst supported on the above-mentioned carrier has many problems. Among them, polymerization of propylene alone at 65°C
If the amount is less than that, not only the activity will be low, but also the stereoregularity will be low, resulting in a large decrease in the rigidity of the resulting copolymer. Therefore, a step is required to remove catalyst residue and atactic polypropylene,
There is almost no advantage of applying a highly active catalyst, and on the contrary, the yield of the product relative to the amount of propylene used is greatly reduced, which is rather disadvantageous as a whole. As a result of various studies, the present inventors surprisingly found that (a) a transition metal catalyst component containing magnesium dihalide, an electron donating compound, and titanium tetrahalide, and (b) AlR _o X _3-o (In the formula, R is a hydrocarbon residue having 1 to 12 carbon atoms, X is a halogen atom, and 1≦n≦3) and (c) ester, ether, orthoester, alkoxy silicon, amine, amide, phosphoric acid ester It has been discovered that when polymerization is carried out at a temperature of 65°C or higher using a catalyst system consisting of at least one organic compound selected from If polymerization is carried out at a relatively high temperature of 65°C or higher using a bulk polymerization method using propylene itself as a solvent, the bulk specific gravity will not decrease and propylene with good powder properties will be produced.
The present invention was completed by discovering that an ethylene copolymer can be obtained. The purpose of the present invention is to achieve propylene-ethylene copolymerizability with an excellent balance of various physical properties such as low-temperature impact resistance, stiffness, and transparency in an extremely high yield per catalyst and which has no adverse effect on the physical properties of the resulting polymer. The object of the present invention is to provide a method for producing a low molecular weight, low crystalline polymer which has little value on its own without substantially producing side effects. The highly active and highly stereoregular catalyst, which is the first element of the present invention, comprises (a) a transition metal catalyst component containing magnesium dihalide, an electron-donating compound, and titanium tetrahalide; and (b) AlR _o X _{3- o} (in the formula, R is a hydrocarbon residue having 1 to 12 carbon atoms, X is a halogen atom, and 1≦n≦3) and (c) ester, ether, orthoester, alkoxy silicon, amine, amide, phosphoric acid A catalyst consisting of at least one organic compound selected from esters, and (a) a transition metal catalyst component containing magnesium dihalide, an electron donating compound, and titanium tetrahalide, which can be obtained by various methods, such as Some of the inventors of the present invention have already
Catalysts such as those proposed in JP-A-103494, JP-A-54-116079, JP-A-55-102606, etc. can be used. Specifically, anhydrous magnesium chloride and various organic compounds such as esters, orthoesters,
A method of obtaining a solid catalyst by co-pulverizing alkoxy silicon, halogenated hydrocarbon, aromatic hydrocarbon, ether, alcohol, etc. with titanium tetrahalide, or a method of obtaining a solid catalyst by co-pulverizing with alkoxy silicon, halogenated hydrocarbon, aromatic hydrocarbon, ether, alcohol, etc. By reacting magnesium compounds with various halogenating agents, it is possible to create compounds that are insoluble in inert solvents.
One example is a method in which a solid support containing Mg and Cl is synthesized and further treated with an electronic compound or titanium halide. (b) The organoaluminum compound has the general formula AlRmX3-m (in the formula:
R is a hydrocarbon residue having 1 to 12 carbon atoms, X is a halogen atom, and an organic aluminum compound represented by 1≦m≦3 is preferably used. Examples of organic compounds used as component (c) include esters, ethers, orthoesters, alkoxy silicones, amines, amides, phosphate esters, and more specifically ethyl benzoate, methyl toluate, orthobenzoic acid. Methyl, tetraethoxysilane, phenyltriethoxysilane, dibutyl ether, triethylamine, diethylaniline, triethyl phosphate and the like are preferably used. The ratio of the three components mentioned above constituting the catalyst used in the method of the present invention can be changed arbitrarily under the conditions that the yield per solid catalyst is 4000 g/g or more and a highly stereoregular polymer is obtained. Although the appropriate range differs depending on the compound used, in general, (a)
For 1 mole of Ti, (b) organic aluminum is 1 to 1 mole
The organic compound used as component (c) is preferably used in an amount of 1 to 250 mol. The second element of the present invention is to divide the polymerization into two stages, and in the first stage, propylene is polymerized using the above catalyst system at a temperature of 65°C or higher in an amount corresponding to 5 to 20% by weight of the total polymerization amount. In the second stage, ethylene/
Polymerization with a reaction ratio of propylene in the range of 1/99 to 20/80% by weight is carried out in the range of 80 to 95% by weight of the total polymerization amount, and the first and second stage polymerization is carried out in bulk polymerization using propylene itself as a solvent. It's about doing what's legal. The first stage polymerization is carried out in the second stage by polymerizing a highly crystalline homopolymer of propylene by polymerizing with the above catalyst system at a temperature of 65°C to 85°C, preferably 65°C to 80°C. The properties of the slurry during propylene-ethylene copolymerization are maintained well, and reductions in high rigidity, hardness, softening point, etc., which are excellent properties unique to polypropylene, can be kept to a minimum. By carrying out the first stage polymerization using a bulk polymerization method, even if the above catalyst is polymerized under conditions that give a highly active and highly stereoregular polymer, that is, at a relatively high temperature of 65° to 85°C, bulk polymerization is possible. There is almost no decrease in specific gravity, especially under conditions of 65° to 80°C, and virtually no decrease in bulk specific gravity is observed. On the other hand, in the solvent method using a relatively high-boiling hydrocarbon compound as a medium, the bulk specific gravity decreases at temperatures of 65°C or higher, and particularly decreases significantly at 70°C or higher. If the first stage polymerization is carried out at a temperature lower than 65°C, the stereoregularity will be greatly reduced, and the properties of the slurry during the copolymerization reaction will be significantly deteriorated, and the excellent properties unique to polypropylene will be lost if it is carried out as it is. The reduction in certain high rigidity, hardness, softening point, etc. becomes large, and when the by-produced atactic polypropylene is removed by counter-current cleaning etc., a large amount of by-product atactic polypropylene which has almost no commercial value by itself is generated. raw and undesirable. On the other hand, the first stage polymerization was carried out at 85
If carried out at temperatures above ℃, there is a disadvantage that the bulk specific gravity decreases significantly and the productivity of the copolymer decreases, while at the same time the rate of catalyst deactivation increases and as a result, the yield of polymer per catalyst decreases. There is also. The propylene homopolymer in the first stage must be produced in an amount of 5 to 20% by weight of the total polymerization amount, and if this proportion is less than 5% by weight, the properties of the slurry during copolymerization in the second stage will change. It is defective, cannot withstand industrial production sufficiently, and cannot be said to have sufficient rigidity. Further, when this portion is 20% by weight or more, the rigidity is relatively good, but the transparency and impact resistance are poor, and it cannot be said to be suitable for the purpose of the present invention. In the present invention, the polymerization temperature in the propylene-ethylene copolymerization part in the second stage is 50° to 85°C.
However, it is preferable to carry out the polymerization at a temperature that is the same as the first stage polymerization temperature or about 5 to 15°C lower. The reaction ratio of ethylene/propylene in the propylene-ethylene copolymerization part in the second stage is 1/99 ~
The weight ratio is 20/80, preferably 2/98 to 15/85. If the weight ratio is less than 1/99, the effect of improving transparency and impact strength will be small, and if the weight ratio is more than 20/80, the impact strength will be improved. However, the rigidity is significantly reduced, and furthermore, the properties of the slurry during polymerization are significantly deteriorated. The pressure during the polymerization is automatically determined by setting conditions such that propylene is present in liquid form at a predetermined temperature and a desired ethylene/propylene reaction ratio is achieved in the second stage. The polymerization and copolymerization of the present invention are carried out in the presence of hydrogen to control the molecular weight and to prevent the formation of high molecular weight polymers that adversely affect transparency and cause blemishes. The propylene-ethylene copolymer obtained by the method of the present invention has good transparency, relatively high rigidity, and high impact resistance, so it is suitable not only for blow grades and sheet grades for food packaging, but also for films and injection molded products. It is very useful industrially, has good slurry properties during polymerization, and has a high yield of copolymer per catalyst, so it substantially removes catalyst residue and by-product atactic polypropylene. It is possible to obtain propylene-ethylene copolymer without any oxidation, making it a very advantageous method for industrial production. The present invention will be explained in more detail with reference to Examples below. In the Examples and Comparative Examples, bending rigidity ASTM D747-63 Shape (notched) impact strength
ASTM D256-56 Dupont impact strength Based on JIS K6718, MI was measured at 230°C, load was 2.16Kg, bending rigidity was measured at 20°C, and Shalpy and Dupont were measured at 0°C. Intrinsic viscosity number (hereinafter abbreviated as η) is 135℃
Measured using tetralin solution. Isometric index (hereinafter abbreviated as II)
was calculated as (boiling n-heptane extraction residue/total polymer). Example 1 (i) Preparation of solid catalyst component A vibratory mill equipped with four grinding pots each having an internal volume of 4 and containing 9 kg of steel balls each having a diameter of 12 mm was prepared. Add 300 g of magnesium chloride, 60 ml of tetraethoxysilane, α, α,
45 ml of α-trichlorotoluene was added and pulverized for 40 hours. Add 3 kg of the above pulverized material and 20 titanium tetrachloride to an autoclave with an internal volume of 50 °C, stir at 80 °C for 2 hours, remove the supernatant liquid by decantation, then add 35 kg of n-heptane and stir at 80 °C for 15 °C.
After stirring for a minute, the washing operation of removing the supernatant liquid by decantation was repeated seven times, and then 20 ml of n-heptane was added to form a solid catalyst slurry.
A portion of the solid catalyst slurry was sampled and n-
When the heptane was evaporated and analyzed, the solid catalyst contained 1.4% by weight of Ti. (ii) Production of propylene-ethylene copolymer 25 kg of propylene is charged into a jacketed 100 autoclave which has been thoroughly dried, purged with nitrogen, and further purged with propylene. On the other hand 1
500 ml of n-heptane, 4.8 ml of diethylaluminum chloride, 2.8 ml of p-methyl toluate, and 1 g of the above solid catalyst were placed in a flask, and after stirring at room temperature for 2 minutes, 1 ml of triethyl aluminum was added and the mixture was pressurized into the autoclave No. 100. . Next, 15N of hydrogen was injected under pressure. Pour hot water into the jacket to raise the internal temperature to 75℃.
While keeping the temperature at °C, hydrogen was charged so that the hydrogen concentration was 4.0 vol%, while a solution of 3 ml of triethylaluminum in 57 ml of n-heptane was charged into the autoclave at a rate of 0.5 ml/min while propylene was added to the autoclave. The homopolymerization of was continued for 12 minutes. After that, 150g of ethylene was charged, and ethylene and propylene were copolymerized for 108 minutes while charging ethylene at a rate of 5.6g/min. After that, 50ml of isopropanol was pressurized to stop the polymerization, and unreacted ethylene and propylene were copolymerized. was purged. After this, take out the propylene-ethylene copolymer 60
After drying at 150mmHg for 10 hours at °C and weighing.
It weighed 12.6Kg. The intrinsic viscosity of this powder is
2.21dl/g, bulk specific gravity is 0.40g/ml, II is
The ethylene unit content was 82.5%, and the ethylene unit content measured by infrared absorption spectroscopy was 5.0%.
This powder-like polymer was granulated with known additives, and then molded using an injection molding machine to form a 2 mm sheet.
When the Dupont impact strength was measured, each
It was 3.9Kg・cm/cm ² and 8.5Kg・cm/1/2″φ.
On the other hand, the light transmittance and bending rigidity (20℃) of a 1 mm press sheet formed from pellets are
It was 87.0, 6700Kg/ ^cm2 . Example 2 A polymerization reaction was carried out in the same manner as in Example 1, except that propylene alone was polymerized for 22 minutes, and ethylene was copolymerized at 70° C. for 110 minutes at the amount shown in the table. The results are shown in the table. Example 3 Polymerization time of propylene alone was 12 minutes, and copolymerization of ethylene/propylene was carried out under the charging conditions shown in the table.
The polymerization reaction was carried out in the same manner as in Example 1, except that the polymerization reaction was carried out for 100 minutes. The results are shown in the table. Comparative Example 1 The polymerization temperature was changed to 50°C in the first stage, the amount of triethylaluminum charged was changed to 0.2ml/min,
Total polymerization time was 4 hours (polymerization using propylene alone)
(24 minutes, copolymerization for 216 minutes), and other conditions were as shown in the table. The bending rigidity was greatly reduced due to a large decrease in II, and the powder formed into lumps during drying, making it extremely difficult to loosen them. Comparative Example 2 Polymerization was carried out in the same manner as in Example 1 except that the first stage polymerization time was 2 minutes and the second stage polymerization time was 118 minutes. The results are shown in the table. Significant decrease in bulk specific gravity and bending rigidity. Comparative Example 3 Polymerization was carried out in the same manner as in Example 1 except that the first stage polymerization time was 40 minutes and the second stage polymerization time was 80 minutes. The results are shown in the table. Transparency has deteriorated significantly. Comparative Example 4 Activated titanium catalyst (same catalyst as used in Example 6 in JP-A-53-35788) Using 5 g of TiCl ₃ composition and 20 ml of diethyl aluminum chloride, an additional charge of triethyl aluminum was added. Example 1 after polymerization was carried out under the conditions shown in Table 1 without
I performed the same operation. In addition to forming lumps during drying, the bulk density was very poor and the powder was colored yellow.

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*Colored.

Claims (1)

[Claims] 1. In a method for producing a propylene-ethylene copolymer by bulk polymerization using propylene itself as a solvent using a stereoregular catalyst, (a) the stereoregular catalyst undergoes (a) dihalogenation. A transition metal catalyst component containing magnesium, an electron-donating compound, and titanium tetrahalide, and (b) AlR _o X _3-o (wherein R is a hydrocarbon residue having 1 to 12 carbon atoms, n≦3) and (c) at least one compound selected from esters, ethers, orthoesters, alkoxy silicones, amines, amides, and phosphoric acid esters, and a polymer per transition metal catalyst component. The profit margin
4000g/g transition metal catalyst component or more, (b) In the first stage, only propylene is polymerized in the range of 5 to 20% by weight of the total polymerization amount at a temperature of 65°C to 85°C, and (c) In the subsequent step A propylene-ethylene copolymer characterized in that in two steps, polymerization is carried out at an ethylene/propylene reaction ratio in the range of 1/99 to 20/80 weight ratio in the range of 80 to 95% of the total polymerization amount. manufacturing method.