JPS6336325B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a propylene-ethylene block copolymer having excellent physical properties such as impact resistance and rigidity, and more specifically, using a highly active and highly stereoregular catalyst, the copolymer is produced in an amount of 60 to 95% by weight of the total polymerization amount. is continuously polymerized using a bulk polymerization method, and furthermore, 40~
This invention relates to a method for effectively producing a propylene-ethylene block copolymer having excellent physical properties by batchwise polymerizing 5% by weight. Since the invention of stereoregular catalysts by Ziegler and Natsuta et al., crystalline polyolefin has become a general-purpose resin with excellent properties such as excellent rigidity and heat resistance, and its molded products are lightweight. is increasing. However, crystalline polypropylene has the disadvantage of being brittle at low temperatures, so it is difficult to use in applications that require impact resistance at low temperatures. Much research and development has already been carried out on methods to improve this drawback, and various improvement methods have been proposed. Among them, a method of block copolymerizing propylene and other olefins, especially ethylene, is an industrially useful method, for example, as disclosed in Japanese Patent Publication No. 38-14834 and Japanese Patent Publication No. 39-1989.
It was proposed in 1836, Special Publication No. 39-15535, etc.
However, block copolymers produced by these methods have disadvantages such as lower rigidity and transparency of molded products than crystalline polypropylene, and whitening of deformed parts when deformed by impact or bending. In order to solve these problems, a method of conducting block copolymerization in three stages was proposed, for example, in Japanese Patent Publication No. 44-20621 and Japanese Patent Publication No. 47-24593, and the physical properties of the resulting block copolymers were very excellent. . However, these methods use catalysts with relatively low activity and inert solvents such as n-heptane, so it is necessary to remove the catalyst residue and recover the inert solvent, and therefore the post-processing steps are extremely necessary. The process is complicated, and a considerable amount of inert solvent-soluble polymer is produced, which significantly increases manufacturing costs. On the other hand, methods for obtaining block copolymers by bulk polymerization or gas phase polymerization that do not substantially use inert solvents include, for example, Japanese Patent Publication No. 42-17488 and Japanese Patent Application Laid-open No. 49-1989.
120986, JP-A-52-3684, etc. Since these methods do not substantially use an inert solvent, the solvent recovery step is omitted and the polymer drying step is also greatly simplified, but since the catalyst has low activity, it is necessary to remove the catalyst residue. In addition, bulk polymerization and gas phase polymerization have a negative effect on the physical properties of the resulting polymer, and it is difficult to remove low molecular weight and low crystallinity polymers that are of little value by themselves. The physical properties deteriorate and the polymer becomes difficult to handle due to its stickiness. On the other hand, in order to increase the productivity of the propylene-ethylene block copolymer per unit time and per unit volume of the polymerization tank, a method of continuously producing the propylene block copolymer is desired. However, although this method is good for batchwise use, there are many problems in applying it to continuous methods.
In particular, in the production of block copolymers, several polymerization stages with different ethylene/propylene reaction ratios are often provided in order to provide appropriate physical properties.
Therefore, it is necessary to prepare a number of polymerization vessels equal to the number of stages. Also, when several polymerization tanks are lined up and polymerization is performed in each polymerization tank in succession, in a polymerization tank equipped with a complete mixing tank, the residence time of the catalyst is different in each polymerization tank, and therefore the polymerization per catalyst has a distribution. Therefore, the continuous polymerization method is inferior to the batch polymerization method in terms of the physical properties of the polymer, both in terms of rigidity and impact resistance. Furthermore, in bulk polymerization using propylene itself as a solvent, when increasing the ethylene/propylene reaction ratio in a later stage, the pressure in the later polymerization tank generally increases, so the slurry must be pumped from the low pressure side to the high pressure side. Not only does this equipment become expensive, but also the polymer melts due to the increased heat generated by pressure feeding, which tends to cause line blockage problems. The purpose of the present invention is to eliminate production difficulties such as adhesion of the polymer to equipment or agglomeration of the polymer during polymerization or drying of the produced polymer, and to eliminate catalyst residues and low molecular weight, low crystallinity polymers. The object of the present invention is to provide a method for producing a propylene-ethylene block copolymer having high impact resistance and high rigidity without substantially removing the propylene. Another object of the present invention is to produce a propylene-ethylene block copolymer having excellent physical properties such as impact resistance and high rigidity, without substantially deteriorating the physical properties as compared with at least complete batch polymerization. It is an object of the present invention to provide a method for manufacturing while increasing productivity per unit volume of a polymerization tank and per unit time. The present invention provides a method for producing a propylene-ethylene block copolymer through multi-stage polymerization in which two or more polymerization tanks are connected in series using a stereoregular catalyst. In at least one of the first polymerization tanks connected to the polymerization tank, propylene alone or propylene itself in the absence of substantially an inert solvent at 65 to 85°C with an ethylene/propylene reaction ratio of 6/94 or less by weight is used. Bulk polymerization using the solvent as a solvent is carried out continuously, and the proportion of the above continuous polymerization amount is 60 to 95% by weight of the total polymerization amount, (ii) In the final tank of the polymerization tanks connected in series, the polymerization amount in that tank is Bulk polymerization in propylene itself as a solvent in the substantial absence of an inert solvent at a temperature of 30 to 65°C with an ethylene/propylene reaction ratio in the range of 15/85 to 95/5 by weight to at least 80% by weight of Alternatively, the present invention relates to a method for producing a propylene-ethylene block copolymer, which is characterized in that gas phase polymerization is carried out batchwise in the absence of a substantially liquid polymerization medium. One component of the highly active and highly stereoregular catalyst used in the present invention is a solid catalyst containing at least Mg, Ti, and Cl, and the solid catalyst can be obtained by various methods.
For example, some of the inventors of the present invention have already
Catalysts such as those proposed in JP-A No. 103494, JP-A-54-116079, and JP-A-55-102606 can be used. Specifically, anhydrous magnesium halide (for example, magnesium chloride) and various organic compounds, such as aromatic orthocarboxylic acid esters, alkoxy silicon and halogenated hydrocarbons, orthocarboxylic acid esters and halogenated hydrocarbons, and carboxylic acid esters. A solid catalyst can be obtained by co-pulverizing a complex with AlCl ₃ and alcohol and heat-treating it with titanium halide. Alternatively, inert solvent-insoluble Mg and
It can also be obtained by synthesizing a solid support containing Cl and further treating it with an electron-donating compound, titanium halide. Next, the organoaluminum compound that is one component of the catalyst has the general formula AlRmX ₃ -m (wherein: R is a hydrocarbon residue having 1 to 12 carbon atoms, X is a halogen atom,
and 1≦m≦3) is preferably used. For example, triethylaluminum, tri-n-butylaluminum,
Triinbutylaluminum, tri-n-hexylaluminum, diethylaluminum monochloride, and the like may be used alone or in combination of two or more. Also, at least one Co-o and/or C-
As a compound having 2-20 carbon atoms and having an N bond,
Esters, ethers, orthoesters, alkoxysilicon, amines, amides, phosphate esters, etc. are used, and more specifically, ethyl benzoate, methyl toluate, methyl orthobenzoate, tetraethoxysilane, phenyltriethoxysilane, Dibutyl ether, triethylamine, diethylaniline, triethyl phosphate and the like are preferably used. The ratio of the three components constituting the catalyst used in the present invention is arbitrary, and the appropriate range varies depending on the compound used, but generally the organic aluminum is in the range of 1 to 500 mol per 1 mol of Ti in the solid catalyst. and the compound containing C-O bond or C-N bond is 1
-250 moles. The catalytic activity expressed as the number of grams of polymer produced per gram of solid catalyst is 4000 or more. If it is less than 4000, a large amount of catalyst residue will be present which will adversely affect the physical properties of the resulting copolymer, which is not preferable. In the method of the present invention, in at least one of the first polymerization tanks of two or more polymerization tanks connected in series, the reaction of propylene alone or ethylene/propylene is inert at 65 to 85°C in a weight ratio of 6/94 or less. Bulk polymerization using propylene itself as a solvent, in which substantially no solvent is present, is carried out continuously up to 60 to 95% by weight of the total polymerization amount. By carrying out bulk polymerization under such conditions, a non-tacky polymer powder with a high bulk specific gravity can be obtained. When the reaction ratio of bulk polymerized ethylene/propylene exceeds 6/94 weight ratio, the bulk specific gravity of the powder obtained is small;
Furthermore, since the powder has high stickiness, it may aggregate during drying, or the amount of propylene-soluble polymer may increase, causing clogging of piping during the drying process, and furthermore, it becomes extremely difficult to remove the heat of polymerization. Furthermore, if the above-mentioned bulk polymerization is carried out at a temperature below 65° C., stereoregularity decreases, resulting in a decrease in the rigidity of the resulting polymer, and propylene-soluble polymer increases, resulting in agglomeration during drying. Moreover, it is not preferable because the activity of the catalyst decreases. On the other hand, when the polymerization temperature exceeds 85° C., the bulk specific gravity of the resulting polymer decreases significantly, so that the productivity per unit volume decreases and the catalyst activity decreases quickly. Propylene alone or the reaction ratio of ethylene/propylene in a range of 6/94 weight ratio or less is 60 to 95% by weight of the total polymerization, which means that the resulting block copolymer has a good balance of impact resistance and rigidity. If it is less than 60%, the rigidity will be significantly reduced, and if it exceeds 95%, the impact resistance will be significantly reduced. It is of course possible to carry out part of the step of polymerizing propylene alone or with an ethylene/propylene reaction ratio of 6/94 or less by weight, but in order to increase productivity by continuous polymerization, continuous polymerization is necessary. It is preferable to perform as many steps as possible. It is of course possible to carry out the continuous polymerization step in one tank, but in order to make the amount of polymerization per catalyst as uniform as possible, it is preferable to connect two or more polymerization tanks in series and perform polymerization in multiple tanks. Then, following a continuous bulk polymerization step, in the final vessel of the series of polymerization vessels, the reaction ratio of ethylene/propylene is 15/85 to 95/5 by weight, up to at least 80% by weight of the polymerization amount in that vessel. Ratio range from 30 to 65
The polymerization is carried out either by bulk polymerization in propylene itself as a solvent in the substantial absence of an inert solvent at a temperature of 45 to 55 °C, or batchwise by gas phase polymerization in the absence of a substantially liquid polymerization medium. It will be done.
Ethylene/propylene reaction ratio is 15/85 to 95/5
The step of polymerizing within a range of weight ratios is an essential step in order to obtain a propylene-ethylene block copolymer with excellent impact resistance. In order to maintain a well-balanced physical property of the block copolymer, such as impact resistance, rigidity, transparency, and the prevention of whitening of deformed parts when deformed by impact or folding, ethylene/
It is preferred that the polymerization is carried out in several stages in which the reaction ratio of propylene is in the range of 15/85 to 95/5 by weight. For example, it is possible to adopt two stages of polymerization, one in the range of 15/85 to 60/40 weight ratio and the other in the range of 50/50 to 95/5, or to use several polymerization stages to produce polymers with different molecular weights. Polymerization can be carried out in several stages while simultaneously adjusting the molecular weight by changing the reaction ratio of ethylene/propylene. The reaction ratio of ethylene/propylene is 15/85~95/
Adoption of batch polymerization within the range of 5 weight ratios enables multi-stage polymerization to be performed in one polymerization tank in order to improve the balance of physical properties as described above. In order to carry out all multi-stage polymerization in a continuous manner, it is necessary to prepare a number of polymerization tanks equal to the number of stages, which is not economical. In addition, when the ethylene-rich reaction or the reaction that produces polymers with greatly different molecular weights are all carried out in a continuous manner, such as when the ethylene/propylene reaction ratio is 70/30 or more by weight, the resulting copolymer is molded, although the reason is not clear. In this case, the surface becomes rough, which not only significantly reduces the commercial value but also deteriorates the impact resistance. Ethylene/propylene reaction ratio 15/85 to 95/5
Polymerization in a range of weight ratios Because a large amount of polymer is eluted in propylene carried out at temperatures exceeding 65°C, low molecular weight polymers with little commercial value are used in purification processes that involve conventional filtration or countercurrent washing with propylene, etc. , a large amount of low-crystalline polymer is produced as a by-product, increasing the cost of the product. In addition, if a product is obtained by directly removing excess unreacted monomer by evaporation, the polymer dissolved in propylene precipitates and adheres to the surface of the powder, increasing the stickiness of the powder and causing agglomeration. Furthermore, since the bulk specific gravity of the polymer is greatly reduced, the production amount per unit volume is significantly reduced. On the other hand, in order to carry out polymerization at temperatures below 30°C, it is difficult to remove the polymerization heat using ordinary cooling water.
Special cooling equipment is required, and furthermore, polymerization activity is significantly reduced. By using the method of the present invention, polymers with excellent impact resistance and rigidity can be obtained with high productivity without any manufacturing difficulties, and are of great industrial significance. The present invention will be explained in more detail with reference to Examples below. In the examples, MI is based on melt flow index ASTM D1238 (hereinafter abbreviated as MI), bending rigidity ASTM D747-63 Izot (with notch) ASTM D256-56 DuPont JIS K6718, and MI under the conditions of 230℃ and 2.16Kg load. The bending stiffness was measured at 20°C, and the Izod and Dupont impact strengths were measured at 20°C and -10°C, respectively. The isotactic 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 with a diameter of 12 mm is prepared. 300 mg of magnesium chloride in a nitrogen atmosphere in each pot
g, 60ml of tetraethoxysilane and α, α,
45 ml of α,-trichlorotoluene was added and the mixture was ground for 40 hours. Add 3 kg of the above pulverized material and 20% titanium tetrachloride to an autoclave with an internal volume of 50%, stir at 80°C for 2 hours, remove the supernatant liquid by decantation, then add 35% n-heptane and 80%
After stirring for 15 minutes at
- Added 20% heptane to make a solid catalyst slurry. When a portion of the solid catalyst slurry was sampled, n-heptane was evaporated, and analyzed, it was found that the solid catalyst contained 1.4% by weight of Ti. (ii) Polymerization Polymerization is carried out using the polymerization apparatus shown in FIG. In an autoclave with an internal volume of 50 ml that has been thoroughly dried and purged with nitrogen, add 30 ml of n-heptane, 50 g of the above solid catalyst, and 240 ml of diethylaluminum chloride.
ml, and 140 ml of methyl p-toluate were added thereto and stirred at 25°C. This mixture is used as a catalyst slurry mixture. 60 kg of propylene was charged into an autoclave A with an internal volume of 300 which had been thoroughly dried, purged with nitrogen, and further purged with propylene gas, and 1 kg of propylene was charged as a solid catalyst.
The above catalyst slurry mixture was fed continuously from separate feed ports at a rate of 4 ml/h, triethylaluminum at a rate of 4 ml/h, and liquid propylene at a rate of 30 kg/h, and the polypropylene slurry was continuously fed at a rate of 30 kg/h from the bottom of the autoclave. Polymerization was started at 75°C while being withdrawn from the system. At this time, the hydrogen concentration in the gas phase was charged to 6.5 vol%. After 6 hours had passed from the start of polymerization and the polymerization was stable, a small amount of slurry was extracted from the system.
After measuring the physical properties of the powder, the slurry that is continuously extracted from the bottom is thoroughly dried, replaced with nitrogen, and then replaced with propylene gas.
200 autoclave B. At this time,
The slurry was extracted at 180 kg/h for 5 minutes. After the slurry was transferred to autoclave B of 200, the slurry was not discharged from autoclave A until the time of transfer, and the amounts of propylene, catalyst slurry mixture, and triethylaluminum charged to autoclave A were kept constant. Therefore, the amount of propylene slurry in autoclave A is 47.5
It will vary between Kg and 60Kg. The continuous polymerization tank is operated with an average residence time (amount of slurry in the polymerization tank/amount of slurry charged or discharged per hour) of 2 hours, but when starting batch polymerization, it is necessary to transfer to the batch polymerization tank in a short time. Because the slurry is discharged all at once, the amount of slurry in the continuous polymerization tank is reduced (charging is 30Kg/h, discharge is 180Kg/h),
Until the end of discharging slurry to the batch polymerization tank
The amount of slurry is 47.5Kg. During polymerization in the batch polymerization tank, there is no slurry discharge in the continuous polymerization tank, so the amount of slurry increases from 47.5Kg to 60Kg in 25 minutes until the slurry is discharged.
Discharge to the next batch polymerization tank is repeated in the same manner as above. On the other hand, in autoclave B, 5 kg of liquid propylene was injected while purging the gas phase to bring the internal temperature to 50°C and at the same time raise the hydrogen concentration to 0.3 vol%. Furthermore, ethylene and hydrogen were charged to reduce the hydrogen concentration in the gas phase to 0.60vol% and the ethylene concentration to 35.0%.
Polymerization was carried out at 50° C. for 7.5 minutes as mol%. Furthermore, ethylene was added all at once to increase the hydrogen concentration to 0.55vol%.
After polymerization for 1.5 minutes at an ethylene concentration of 40.0 mol%, the mixture was dried in advance, purged with nitrogen, then replaced with propylene, and then pressure-transferred at once to an autoclave C with an internal volume of 200 containing 10 kg of liquid propylene and 50 ml of isopropanol to deactivate the catalyst. The inside of autoclave B was washed with liquid propylene, which was discharged into autoclave C, and then left until the next slurry was received at a gauge of about 3 kg/cm ² . On the other hand, the slurry in the autoclave C was fed under pressure to a flash tank D, and then passed through a hopper E and taken out as a powder.
After autoclave C is discharged, liquid propylene is
Add 10 kg and 50 ml of isopropanol and wait until the next reception. Copolymerization is carried out batchwise by repeating the above operations. The operation in autoclave B took approximately 25 minutes from receiving the slurry to completing preparations for the next reception. The slurry was received every 30 minutes, and the operation in autoclave B was repeated 50 times for 25 hours of polymerization, yielding about 250 kg of propylene ethylene block copolymer as a product. During the 25 hours of operation, operation was possible without any problems such as pipe blockage. The amount of polymerization per solid catalyst was determined from the Ti content in the product, and it was found to be 11,800 g/g solid catalyst. The obtained block copolymer was heated to 60℃ and 100mm
It was further dried with Hg for 10 hours, granulated with conventional additives, and its physical properties were measured. The results are shown in Table 2. FIG. 2 shows the relationship between the ethylene/propylene reaction ratio (weight ratio) and the ethylene partial pressure (atmospheric pressure). 50
The results of a model experiment conducted using the catalyst of Example 1 at ℃ are shown. From this graph, the ethylene/propylene reaction ratio corresponding to the ethylene concentration at each stage of the batch polymerization in Table 1 can be estimated. Example 2 Using the catalyst obtained in Example 1 (i), polymerization was carried out in the same manner as in Example 1, except that the hydrogen concentration and ethylene concentration were changed as shown in Table 1. Polymerization was possible without any abnormalities during 25 hours of polymerization. Example 5 TiCl ₃ , 1/3 AlCl ₃ pulverized product [manufactured by Toho Titanium Co., Ltd.
AA type catalyst (TAC)] 2g/h, diethylaluminium chloride 8ml/h, propylene 15Kg/h
The polymerization was carried out in the same manner as in Example 1 except that the batch polymerization cycle was 60 mm and the polymerization time of each stage was as shown in Table 1. After performing batch polymerization three times, no powder came out from hopper F, so after washing flash tank E and hopper F with n-heptane and discharging the polymer as a slurry, polymerization was continued. After conducting the polymerization twice, no powder was produced again, so the polymerization was stopped. During this time, the polymer taken out as a powder was treated in the same manner as in Example 1, and its physical properties were measured.
Furthermore, the polymerization activity per solid catalyst was estimated from the Ti content in the powder. Note that the granulated pellets were colored yellow. Example 6 Polymerization was carried out in the same manner as in Example 1, except that the polymerization temperature in autoclave A was 50°C, the amount of propylene charged was 17 kg/h, and the hydrogen concentration, ethylene concentration, etc. were as shown in Table 1. After performing the batch polymerization five times, no powder came out from the hopper F, so the polymerization was stopped. The powder obtained during this period was treated in the same manner as in Example 1, its physical properties were measured, and the polymerization activity per solid catalyst was estimated from the Ti content in the powder. Example 7 Polymerization was carried out in autoclave B at 70°C in the same manner as in Example 1, with hydrogen concentration, ethylene concentration, etc. shown in Table 1. After performing the batch polymerization four times, no powder came out from Potsupar F, so the polymerization was stopped. The obtained powder was treated in the same manner as in Example 1, and its physical properties were measured. Example 3 A polymerization apparatus is used in which an autoclave G having an internal volume of 300 is further disposed between autoclave A and autoclave B. Autoclave G is charged with 1.5 ml/h of triethylaluminum and 60 kg of propylene at the start of polymerization in autoclave A, and then continuously charged with polypropylene slurry from autoclave A at 30 kg/h, and at the same time triethyl aluminum is charged at 3.0 ml/h. Polymerization was carried out in the same manner as in Example 1, except that the procedure for discharging the polymer from autoclave G to autoclave B in the same manner as in Example 1 was performed. Continuous polymerization for 25 hours could be carried out without any abnormality, and the physical properties of the product were good. Note that the slurry was discharged from autoclave A to G using a normal slurry pump. Example 4 30 autoclaves H were connected in front of autoclave A, and 5 kg of propylene was added to autoclave H.
The catalyst slurry mixture used in Example 1 was charged as a solid catalyst at a rate of 1 g/h, triethylaluminum at a rate of 0.8 ml/h, and liquid propylene at a rate of 29.2 g/h.
The slurry is continuously charged from separate feed ports at a rate of 29.2 kg/h from autoclave H to autoclave A charged with 60 kg of propylene.
0.8 kg/h, ethylene 160 g/h, and triethylaluminum 4 ml/h were fed, and continuous polymerization was carried out under the conditions shown in Table 1. Furthermore, the slurry was fed from autoclave A to autoclave B in the same manner as in Example 1, and the slurry was fed as shown in Table 1. Batch polymerization was carried out under the conditions shown. Polymerization was possible without any abnormality during the 20 hours of polymerization. Although the rigidity and impact resistance were slightly decreased, the transparency was extremely excellent. Example 1 when measuring the light transmittance of a 1 mm thick press sheet
82 compared to less than 70% for the copolymer.
It was %.

【table】

[Table] Amount of slurry in the polymerization tank **)

Claims (1)

[Claims] 1 Propylene is produced through multi-stage polymerization by connecting two or more polymerization tanks in series using a stereoregular catalyst.
In the method for producing an ethylene block copolymer, (i) propylene is used alone or the reaction ratio of ethylene/propylene is 6/94 or less by weight in at least the first tank of two or more polymerization tanks connected in series; Continuously carry out bulk polymerization using propylene itself as a solvent in the absence of substantially an inert solvent at 65 to 85 °C in the range of 65 to 85 ° C, and the proportion of the continuous polymerization amount is 60 to 95% by weight of the total polymerization amount, (ii) In the final loading of said series-connected polymerization vessels, at least 80% by weight of the amount of polymerization in said vessels, with an ethylene/propylene reaction ratio ranging from 15/85 to 95/5 by weight, from 30 to 65°C. A propylene-ethylene block copolymer characterized in that bulk polymerization using propylene itself as a solvent in the absence of an inert solvent or batch polymerization in a gas phase in the absence of a substantially liquid polymerization medium is carried out at a temperature of Polymer manufacturing method.