JPH0580496B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method for producing a propylene block copolymer. Specifically, the present invention relates to a method for producing a propylene block copolymer by a bulk polymerization method using propylene itself as a liquid medium. BACKGROUND OF THE INVENTION It is well known to copolymerize polypropylene with other α-olefins, especially ethylene, in order to improve its impact resistance, especially at low temperatures, and also to simplify the process or transfer it to liquid media. A bulk polymerization method in which propylene itself is used as a liquid medium is also well known for the purpose of reducing soluble polymers. However, the problem with producing block copolymers using the bulk polymerization method is that in order to reduce the propylene/ethylene reaction ratio, it is necessary to increase the amount of ethylene used and raise the overall pressure. There is a problem in that it is difficult to reduce the reaction ratio of propylene/ethylene in the latter stage and carry out continuous polymerization, and to solve this problem,
30534, JP 57-145114, JP 57-145115,
Known examples include JP-A-57-149319 and JP-A-57-149320. Problems to be Solved by the Invention However, although the method of combining continuous polymerization and batch polymerization described above allows reactions with a relatively small propylene/ethylene reaction ratio to be carried out to some degree, it is necessary to increase the ethylene partial pressure. There were problems such as the need to recover a large amount of ethylene. Means for Solving the Problems The inventor of the present invention has completed the present invention after intensive studies on methods for solving the above problems. That is, the present invention uses propylene itself as a liquid medium to first polymerize substantially only propylene, and then copolymerizes propylene/ethylene so that the reaction ratio is 80/20 to 5/95 by weight. This is a method for producing a propylene block copolymer, characterized in that copolymerization is carried out at a reaction ratio of ethylene of 80/20 to 5/95 in the presence of organomagnesium. In the present invention, the catalyst used for propylene polymerization is not particularly limited, and any known catalyst system that provides polypropylene with high stereoregularity can be used. For example, solid catalysts include titanium trichloride obtained by reducing titanium tetrachloride with metal aluminum, hydrogen, or organic aluminum, or those obtained by modifying them with electron-donating compounds, as well as carriers such as magnesium halides, or titanium trichloride obtained by reducing titanium tetrachloride with metal aluminum, hydrogen, or organoaluminum, or supports such as magnesium halides, or titanium trichloride obtained by reducing titanium tetrachloride with metal aluminum, hydrogen, or organic aluminum; Examples include those treated with chemical compounds and modified with titanium halides. The above-mentioned solid catalyst is used in the polymerization of propylene in combination with an organoaluminum compound and, if necessary, an electron-donating compound. As the organoaluminum compound, trialkylaluminum, dialkylaluminum halide, alkylaluminum sesquihalide, and alkylaluminum dihalide can be used. Examples of the alkyl residue include methyl group, ethyl group, propyl group, butyl group, and hexyl group. Examples include chlorine, bromine, and iodine. As a preferable catalyst system, solid catalysts include carriers such as magnesium halide, or those treated with electron-donating compounds and modified with titanium halide. Specifically, magnesium chloride and an organic compound are co-pulverized. The treated product is treated with titanium tetrachloride, or the reaction product of magnesium chloride and alcohol is dissolved in a hydrocarbon solvent and then treated with a precipitant such as titanium tetrachloride to make it insoluble in the hydrocarbon solvent, and if necessary, an ester is produced. Examples include those obtained by a method such as modification treatment with an electron-donating compound such as ether, and then treatment with titanium tetrachloride. Preferably, the organoaluminium used in combination includes trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, dimethylaluminum chloride, diethylaluminum chloride, dipropylaluminum chloride, dibutylaluminum chloride, etc., and stereoregularity improvers are used as necessary. As such, esters, ethers, orthoesters, and alkoxy silicones are used in combination. Here, the usage ratio of organoaluminum and stereoregularity improver to the solid catalyst is usually 0.5 to 100, respectively.
It is between 0.01 and 30. In the present invention, propylene itself is used as the polymerization medium, but if necessary, other inert media such as hexane, heptane, benzene, toluene, etc. may be used in combination up to 20 wt%. In the present invention, the initial polymerization of substantially only propylene is carried out using only the above catalyst system. The amount of polymerization under these conditions is preferably 50 to 95% of the total polymerization amount, and if it is less than 50% by weight, the inherent rigidity of polypropylene will be lost, and if it is more than 95% by weight, the impact resistance will not be improved sufficiently. Not. Here, substantially propylene alone refers to whitening resistance,
It also contains copolymerization with other α-olefins such as ethylene, butene-1, hexene-1, and 2-methylpentene-1 in an amount of up to 6% by weight for the purpose of improving transparency, gloss, etc. The above reaction is preferably carried out at 50 to 90°C, and the reaction pressure is determined by the inert solvent used, hydrogen for adjusting the molecular weight, etc. In the present invention, copolymerization is then carried out such that the reaction ratio of propylene/ethylene is 80/20 to 5/95 by weight. What is important here is the presence of organomagnesium during this reaction. Specific examples of organic magnesium include ethylbutylmagnesium, diisobutylmagnesium, dihexylmagnesium, diphenylmagnesium, ethylallylmagnesium, mixtures thereof, and complex compounds with organic aluminum. The amount of organic magnesium used is not particularly limited, but it is generally used at a weight ratio of 0.5 to 100 with respect to the solid catalyst, and the above-mentioned organic aluminum can also be used in combination. The propylene/ethylene copolymerization reaction is generally carried out at 30 to 60°C, and the pressure is determined depending on the desired concentration of ethylene and hydrogen in the gas phase. In the present invention, the reaction ratio of propylene/ethylene is preferably 80/20 to 5/95, and if it is greater than 80/20, the effect of improving impact resistance is insufficient.
Further, when the ratio is smaller than 5/95, the effect of improving impact resistance is not sufficient. The reaction ratio of propylene/ethylene is 80/20 to 5/
The proportion of the copolymerized portion with 95 is preferably 50 to 5% by weight based on the total weight; if it is more than 50% by weight, the rigidity will be poor, and if it is less than 5% by weight, the impact resistance will be poor. Effects By carrying out the method of the present invention, a propylene block copolymer can be efficiently produced and is extremely valuable industrially. In other words, it is possible to produce a propylene-ethylene copolymer with a small reaction ratio of propylene/ethylene even at a relatively low ethylene partial pressure, and it is possible to produce the desired propylene with a lower ethylene partial pressure, or in other words, using less ethylene. It is possible to obtain a copolymerized portion with a reaction ratio of /ethylene, which is extremely valuable industrially. Examples The present invention will be further explained with reference to Examples below. Reference example 1 Adjustment of solid catalyst component Prepare a vibratory mill equipped with four grinding pots with an internal volume of 4 each containing 9 kg of steel balls with a diameter of 12 mm. 300 g of magnesium chloride in a nitrogen atmosphere in each pot.
60 ml of tetraethoxysilane and 45 ml of α,α,α,-trichlorotoluene were added and pulverized for 40 hours. Put 300g of the above co-pulverized material into flask 5,
Add 1.5 titanium tetrachloride and 1.5 toluene and bring to 100°C.
The mixture was stirred for 30 minutes. Next, remove the supernatant liquid, add 1.5% of titanium tetrachloride and 1.5% of toluene, stir at 100°C for 30 minutes, remove the supernatant liquid, and wash the solid content using n-heptane from step 4. was repeated 10 times. When a portion of the obtained solid catalyst slurry was sampled and titanium was analyzed, it was found to be 1.9 wt%. Polymerization reaction 20 mg of the above solid catalyst was added to an autoclave with an internal volume of 5 under a nitrogen atmosphere.
0.128 ml, methyl P-toluate 0.06 ml, and triethylaluminum 0.03 ml were added, then 1.8 kg of propylene was charged, and 3.3 N of hydrogen was added to carry out a polymerization reaction at 75°C for 2 hours. Then, unreacted propylene was purged and the polymer was was taken out, dried and weighed, and then the intrinsic viscosity in a tetralin solution at 135°C and the proportion of the extraction residue extracted for 6 hours with boiling n-heptane (hereinafter abbreviated as η and II, respectively) were measured.
The results are shown in the table. Reference Example 2 Polymerization similar to the polymerization reaction of Reference Example 1 was carried out. However, after 2 hours of polymerization, the temperature of the autoclave should be changed to 40℃.
The temperature was lowered to 40°C, and stirring was continued for 1 hour at 40°C, and then unreacted propylene was purged. The results are shown in the table. Reference Example 3 The same procedure as Reference Example 2 was carried out. However, after the temperature was lowered to 40°C, ethylene was charged so that the partial pressure of ethylene was 10 kg/cm ² -G. The results are shown in the table. From the results of Reference Examples 2 and 3, it can be seen that the polymerization reaction did not proceed regardless of the presence or absence of ethylene in the reaction at 40° C. after 2 hours from the start of polymerization. Examples and Comparative Examples In Reference Example 2, the temperature was lowered to 40°C, and then ethylene was charged so that the partial pressure of ethylene was as shown in the table. An organometallic compound was added and a polymerization reaction was carried out under the conditions shown in the table. The reaction ratio at the copolymerization part of the obtained copolymer was determined by the column fractionation method (Chubu Chemical Association Branch Federation Autumn Conference 13th Lecture Proceedings 3A20), and the total weight of the ethylene and propylene copolymer W ₁
From the ethylene content W ₂ of the part, (W ₁ − W ₂ )/W ₂
It was calculated as The block copolymer was granulated with the addition of a known stabilizer, and an injection sheet having a thickness of 1 mm was prepared, and the following physical properties were measured. Melt flow index ASTM D1238
(230℃) Bending rigidity ASTM D747-63 (20℃) Izot (notched) impact strength ASTM
D256-56 (20℃, -10℃) Dupont impact strength JISK6718 (20℃, -10℃) The results are shown in the table. The table shows that by adding organomagnesium, polymerization progresses at a relatively high ethylene reaction ratio even at low ethylene partial pressures, and when the same reaction ratio and the same copolymerization part are used, the polymerization is more rigid than that obtained by polymerization with organoaluminium alone. It can be seen that there is a good balance between impact resistance and impact resistance. 【table】

Claims (1)

[Claims] 1 Propylene block copolymer is produced by first polymerizing substantially only propylene using propylene itself as a liquid medium, and then copolymerizing so that the reaction ratio of propylene/ethylene is 80/20 to 5/95 by weight. 1. A method for producing a propylene block copolymer, which comprises carrying out copolymerization at a propylene/ethylene reaction ratio of 80/20 to 5/95 by weight in the presence of organomagnesium.