JPS6138925B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a propylene-ethylene block copolymer having a good balance between physical properties such as impact resistance and rigidity. 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 low temperatures, and therefore is difficult to use in applications requiring 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, one of the industrially advantageous methods is the method of block copolymerizing propylene and other olefins, especially ethylene, as described in Japanese Patent Publication No. 1983-
14834, Special Publication No. 39-1836, 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 folding. . To solve these problems, a method of carrying out block copolymerization in three stages was proposed in Japanese Patent Publication No. 44-20621, Japanese Patent Publication No. 49-24593, etc., and the physical properties of the resulting block copolymers were extremely excellent. . On the other hand, in order to increase the productivity of the propylene-ethylene block copolymer per unit time and unit volume of the polymerization tank, and to obtain a large quantity of products with as uniform physical properties as possible, a continuous production method is desired. However, even if this method provides a propylene-ethylene block copolymer with an excellent balance of physical properties in a batchwise manner, there are many problems in applying it to a continuous method. In order to obtain a block copolymer with appropriate physical properties in a continuous process, polymerization stages with different ethylene/propylene reaction ratios are often provided, and therefore it is necessary to prepare polymerization tanks according to the number of stages. . Furthermore, when multiple polymerization tanks are connected in series and polymerization is performed continuously, the residence time of the catalyst differs depending on each polymerization tank in a polymerization tank equipped with a complete mixing tank, and therefore the amount of polymerization per catalyst varies. Because of the distribution, the physical properties of the produced polymer differ greatly between the continuous method and the batch method, and the former generally shows a particularly low impact resistance compared to the batch method. One way to solve these problems is to use a method for producing an ethylene-propylene block copolymer in which the polymerization of propylene alone or propylene-rich ethylene/propylene accounts for most of the total polymerization amount. One possible method is to carry out the ethylene/propylene polymerization step continuously, and then carry out several polymerization steps batchwise while changing the ethylene/propylene reaction ratio. By adopting this method, a relatively small number of A block copolymer with well-balanced physical properties can be obtained using a polymerization tank. However, during the transfer of the slurry from the continuous polymerization stage to the batch polymerization stage, from the batch polymerization stage to the deactivation stage, and while adjusting the hydrogen concentration, etc., unplanned and uncontrollable polymerization occurs, and the resulting polymer The balance of physical properties deteriorates. Transfer of the slurry from the continuous polymerization stage to the batch polymerization stage, and further transfer of the slurry from the batch polymerization stage to the catalyst deactivation process.
Unplanned and uncontrollable polymerization can be significantly reduced by using methods such as using a large capacity pump or pressure difference to perform the process in a short time, and by adjusting the hydrogen concentration and increasing the purge volume. be able to. However, rapid discharge of slurry from a continuous polymerization tank will cause a sudden change in the level of the polymerization tank in which continuous polymerization is being carried out, making it difficult to control the temperature of continuous polymerization and the molecular weight of the produced polymer. Further, when the slurry is transferred using a pump, a pump with a large capacity is required, which increases the equipment cost. Although the impact is small when the slurry is transferred from the batch polymerization stage to the catalyst deactivation process in a short time, it not only increases the equipment cost as described above, but also requires the temperature control of the deactivation tank and the slurry It becomes difficult to remove the product. The purpose of the present invention is to produce a propylene-ethylene block copolymer having excellent physical properties such as impact resistance and high rigidity without difficulty in controlling the polymerization process, and to obtain better properties than in the case of batch polymerization. without substantially reducing the physical properties of the polymer
The object of the present invention is to provide a method for increasing productivity per unit time per unit volume of a polymerization tank. The present invention involves continuous polymerization in which the reaction ratio of ethylene/propylene is 6/94% by weight or less during multi-stage polymerization in which two or more polymerization tanks are connected using a stereoregular catalyst. The ratio is
In a method for producing a propylene-ethylene block copolymer by batchwise polymerization of 15/85 to 95/5% by weight, at the same time as or before transferring the slurry to a polymerization tank for batch polymerization. By adding a catalyst activity reducing agent to the slurry, the catalyst activity is reduced to 1/4 or less of the catalytic activity when the reducing agent is not added, and then, after the slurry is transferred to a polymerization tank for batch polymerization, an organoaluminum compound is added. By doing so, batch polymerization is carried out under conditions where the activity is increased to 1.1 times or more of the activity before adding the organoaluminum compound, and then, at the same time as the polymerization in the batch polymerization tank is completed, by adding a catalyst activity reducing agent. , relates to a method for producing a propylene-ethylene block copolymer, characterized in that the activity is reduced to 1/2 or less of the activity before adding the reducing agent. The stereoregular catalyst used in the present invention is not particularly limited as long as it is a catalyst generally used for propylene stereoregular catalysts, but (a) at least Mg,
A solid catalyst containing three types of elements, Ti and C,
(b) A catalyst consisting of an organoaluminum compound is preferred. A solid catalyst containing at least three elements, Mg, Ti, and C, can be produced by various methods. For example, some of the inventors have already reported that
116079, JP-A-55-102606, etc. Specifically, magnesium halides (for example, anhydrous MgC ₂ ) and various organic compounds, such as aromatic orthocarboxylic esters, alkoxy silicon and halogenated hydrocarbons, orthocarboxylic esters and halogenated hydrocarbons,
A solid catalyst can be obtained by heat-treating a complex of a carboxylic acid ester and AC ₃ and an alcohol together with a titanium halide. Alternatively, a solid support containing Mg and C, which is insoluble in an inert solvent, is synthesized by reacting an organoaluminum compound soluble in an inert solvent with various halogenating agents, and further an electron-donating compound,
It can also be obtained by treatment with titanium halides. The organoaluminum compound (b), which is a component of the catalyst, has the general formula ARmX _3-n (wherein: R is a hydrocarbon residue having 1 to 12 carbon atoms, Compounds are preferably used.For example, triethylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, diethylaluminium monochloride, etc. are used alone or in combination of two or more.C-O or By using a compound having at least one C-N bond in combination, the stereoregularity of the obtained polymer can be enhanced and the physical properties can be well balanced.As a compound having at least one C-O or C-N bond, ester, ether,
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 proportion of each component constituting the catalyst used in the present invention is arbitrary, and the appropriate range varies depending on the compound used, but in general, Ti1 in the solid catalyst
Organoaluminum compounds are 0.1 to 500 per mole
and the compound having at least one C--O or C--N bond ranges from 0 to 250 moles. In the method of the present invention, 80% or more of the polymerization with an ethylene/propylene reaction ratio of 6/94% by weight or less is carried out continuously using one or more polymerization tanks connected together, and the ethylene/propylene reaction ratio is 15% by weight or less. /85～
An ethylene/propylene block copolymer is produced by carrying out 90% or more of the 95/5 weight % polymerization batchwise. Of course, polymerization in which the reaction ratio of ethylene/propylene is 6/94% by weight or less also includes polymerization of propylene alone. Polymerization at the reaction ratio can be carried out in the presence of an inert solvent, or by bulk polymerization using propylene itself as a solvent in the absence of substantially an inert solvent, or by gas phase polymerization in the substantial absence of a liquid polymerization solvent. can. Polymerization at an ethylene/propylene reaction ratio of 6/94% by weight or less is necessary to maintain a good balance between impact resistance and rigidity of the ethylene/propylene block copolymer, and especially polymerization at this reaction ratio reduces the total polymerization amount. It is desirable that the amount is 60 to 95% by weight in order to increase the rigidity of the ethylene/propylene block copolymer. The polymerization temperature at the above reaction ratio varies depending on the catalyst system, but is generally 40 to
90°C, especially 60-80°C is preferred. Further, in order to increase productivity, it is preferable to carry out the polymerization step at the above reaction ratio as continuously as possible. Next, the reaction ratio of ethylene/propylene is 15/85 ~
The 95/5% by weight polymerization step is an essential step in order to obtain a propylene-ethylene block copolymer with excellent impact resistance, and the polymerization is carried out in the presence of an inert solvent or when the inert solvent is substantially Bulk polymerization using propylene itself, which is not present in the solvent, as a solvent, or gas phase polymerization, in which a liquid polymerization solvent is not substantially present, can also be carried out. The above polymerization temperature varies depending on the ethylene/propylene reaction ratio, etc., but is generally 30 to 70°C, particularly preferably 40 to 60°C. In the method of the present invention, a catalyst activity reducing agent is added to the slurry at the same time or before the slurry is transferred to a polymerization tank for batch polymerization, so that the catalyst activity is reduced to 1/4 or less of the case where the reducing agent is not added. By adding an organoaluminum compound after the transfer of the slurry to the polymerization where the slurry is lowered and then subjected to batch polymerization, batch polymerization is carried out under conditions where the activity is increased by 1.1 times or more than the activity before adding the organoaluminum compound, Then, at the same time as the polymerization in the batch polymerization tank is completed, a catalyst activity reducing agent is added to reduce the activity to 1/2 or less of the activity before adding the catalyst activity reducing agent. During the transfer of the slurry from the continuous polymerization process to the batch polymerization process, from the batch polymerization process to the deactivation process, and during the adjustment of the hydrogen concentration in the gas phase, unplanned and uncontrollable polymerization occurs, resulting in problems with the resulting polymer. The balance of physical properties deteriorates significantly. Therefore, in order to reduce the unplanned and uncontrollable polymerization amount as much as possible, an activity reducing agent is added when or before transferring the slurry to the batch polymerization tank to reduce the catalyst activity in the polymerization tank to 1/4 of the original activity. Hereinafter, it is preferably reduced to 1/4 to 1/10. If it is larger than 1/4, the effect of uncontrollably reducing the amount of polymerization will be small, while if it is smaller than 1/10, the amount of organoaluminum compound added to restore the activity will increase. After the slurry is transferred to the batch polymerization vessel, an organoaluminum compound is added to restore appropriate catalytic activity determined by the batch polymerization time and amount of polymerization. The proportion of the organoaluminum compound to be used depends on the type and amount of the activity reducing agent, but it is an amount that increases the activity by at least 1.1 times, preferably from 1.1 to 10 times, the activity before adding the organoaluminum compound. In other words, the activity, which was reduced to 1/4 to 1/10, is improved due to batch polymerization (in a controlled state), and an improvement in activity is observed.
It is sufficient if the amount of polymerization is improved in a controlled state,
If there is an improvement in activity, it will have a certain effect, but if the lower limit is reduced to 1/10, unless there is an improvement of at least 1.1 times that 1/10,
This is because the effectiveness of improving activity is insufficient. On the other hand, since polymerization is carried out under controlled conditions, the greater the activity improvement, the better; however, it is difficult to remove heat in the actual process to increase the activity to more than the pre-decreased activity (=1). This is not desirable as there are problems such as Therefore, when the activity is reduced to 1/10 of the lower limit of the activity reduction, the maximum activity improvement is 1/10 x 10 = 1, so the upper limit is 10 times. Next, after the batch polymerization is completed, an activity reducing agent is added to the polymerization tank to reduce the activity to 1/2 or less of the activity before adding the reducing agent. The lower the activity after polymerization, the better, but there is also the problem of the amount of reducing agent added, and if it is at least 1/2 or less, it will have the effect of reducing the activity. The amount of reducing agent added is the amount necessary to reduce the activity to 1/2 or less, and the amount of reducing agent remaining after discharging the slurry after copolymerization and performing simple washing is enough to transfer the slurry to the batch tank. The amount may be sufficient as long as it does not lower the activity more than the desired level upon receipt. Such activity reducing agents can be used as long as they reduce the catalytic activity, and include various organic compounds and AC
₃ , inorganic compounds such as SiC ₄ are used,
Preferably, those that reduce the activity without significantly reducing the stereoregularity of the resulting polymer are preferred. In particular, the activity reducing agent added when transferring the slurry to a polymerization tank for batch polymerization can reduce the activity without reducing the stereoregularity, and the activity can be restored by adding a small amount of organoaluminum compound. It is preferable to use a compound such that For example, compounds having at least one C--O or C--N bond are shown which are used as preferred components of the above-mentioned catalysts. Specific examples of compounds are as described above. Further, as the organoaluminum compound used to restore the activity, the organoaluminum compound used as a component of the catalyst described above can be used. By using the method of the present invention, a propylene-ethylene block copolymer having an excellent balance of impact resistance and rigidity can be efficiently produced under controlled conditions, which is of great industrial significance. The present invention will be explained in more detail with reference to Examples below. In the examples and comparative examples, melt flow index (hereinafter abbreviated as MI)
ASTM D1238 Bending stiffness ASTM D747-63 Izot (notched) ASTM D256-56 Dupont Based on JIS K6718, MI is at 230℃ and load 2.16Kg, bending stiffness is at 20℃, and Izot and DuPont Impact strength was measured under conditions of 20°C and -10°C, respectively. The limiting viscosity number (hereinafter abbreviated as η) is
Measured at 135°C using a tetralin solution. The isotactic index (hereinafter abbreviated as II) is boiling n-heptane extraction residual polymer/total polymer (%)
It was calculated as Example 1 (i) Adjustment 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. 300 mg of magnesium chloride in a nitrogen atmosphere in each pot
g, 60 ml of tetraethoxysilane, and 45 ml of α,α,α-trichlorotoluene were added and the mixture was pulverized for 40 hours.
3 kg of the above pulverized material was placed in an autoclave with an internal volume of 50 kg.
After adding titanium tetrachloride 20 and stirring at 80°C for 2 hours, the supernatant was removed by decantation, and then n
After adding 35% of -heptane and stirring at 80°C for 15 minutes, the washing operation of removing the supernatant liquid by decantation was repeated 7 times, and then 20% of n-heptane was added to form a solid solvent slurry. When a portion of the solid solvent slurry was sampled, n-heptane was evaporated, and analyzed, it was found that the solid solvent 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 inner volume of 50 ml that was sufficiently dried and purged with nitrogen, 30 ml of n-heptane and the above solid catalyst were added.
50g, diethyl aluminum, chloride 240
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. Autoclave A with an internal volume of 300, fully dried, purged with nitrogen, and further purged with propylene gas.
and B are connected in series, and autoclaves C1 and C2 with an internal volume of 200 are connected next to autoclave B in parallel. Autoclave D with an internal volume of 300
are connected in series to autoclave C1.
Charge 60 kg of propylene to autoclaves A and B. 1 g/h of the above catalyst slurry mixture as a solid catalyst, and 1.5 ml/h of triethylaluminum, another organoaluminum compound catalyst component.
Further, liquid propylene is charged into autoclave A at a rate of 30 kg/h. Triethylaluminum was added to autoclave B at a rate of 3.0 ml/h, and polypropylene slurry was added from autoclave A at a rate of 3.0 ml/h.
While continuously charging the polypropylene slurry at 30 kg/h from autoclave B, charging hydrogen so as to maintain the gas phase hydrogen concentration in autoclave A and B at the amount shown in Table 1. 75
Polymerization was carried out at
In order to confirm whether a powder having the following properties was obtained, a small amount of slurry was taken out from autoclave B and the physical properties of the powder were measured. The results are shown in Table 2 under the section of continuous polymerization final powder physical properties. Next, the slurry being continuously drawn out from the lower part of autoclave B and methyl P-toluate were simultaneously charged into autoclave C1 at a rate of 1.4 ml/30 min, and after being received in slurry C1 for 30 minutes, the slurry from autoclave B was The transfer destination of methyl P-toluate was changed to autoclave C2.
In C1, 5 kg of liquid propylene was injected under pressure while simultaneously receiving the slurry and purging the gas phase.
The internal temperature was set to 50°C and the hydrogen concentration was set to 0.3 vol% at the same time. The activity during this period was reduced to about 1/5 by charging P-toluic acid. Furthermore, ethylene and hydrogen were charged to bring the hydrogen concentration in the gas phase to 0.55 vol%, and the ethylene concentration to 35.0 mol%.Furthermore, 3.0 ml of triethylaluminum was injected at once to increase the activity to approximately 2.5 vol%.
Polymerization was carried out at 50°C for 9 minutes while maintaining the above hydrogen and ethylene concentrations, and then ethylene was added to increase the hydrogen concentration to 0.50 vol% and the ethylene concentration to 40.0 mol%.
Polymerization took place for 2.0 minutes. Next, after charging 2 ml of p-methyl toluate, add liquid propylene in advance.
10 kg and 50 ml of isopropanol were pumped into autoclave D for 7 minutes. Autoclave C1
The inside was washed with liquid propylene, and the washed propylene was also sent to autoclave D. Autoclave C1 was ready to receive the next slurry at approximately 3 Kg/cm ² -gauge. Meanwhile, while charging isopropanol at 1 ml/h to autoclave D, the slurry was transferred from the bottom to flash tank E.
Furthermore, it was taken out as a powder after passing through Potsupur F. The autoclave D was discharged continuously at a rate of about 40 kg/h, and when the slurry was then received from the autoclave C2, about 10 kg of slurry remained in the autoclave D. Autoclave C2 received the slurry from autoclave B and methyl P-toluate for 30 minutes, and then
The copolymerization operation was carried out in the same manner as in 1. Continuous polymerization was carried out for 25 hours by operating autoclaves C1 and C2 25 times each for a total of 50 times to obtain about 250 kg of propylene-ethylene block copolymer as a product. During the above operations, operation was possible without any abnormality. in the product
The amount of polymerization per solid catalyst was determined from the Ti content. The obtained block copolymer was dried at 60° C. and 100 mmHg for 10 hours, granulated with commonly used additives, and its physical properties were measured. The results are shown in Table 2. Reference example In Figures 2 and 3, the catalyst synthesized in Example 1 (i) is used, the blending ratio of solid catalyst, diethylaluminium chloride, and triethylaluminum is kept constant, and only the amount ratio of methyl P-toluate is changed. The relationship between the activity and the usage amount of P-methyl toluate when The relationship between the amount of aluminum used is shown. From this, it is possible to estimate the amounts of methyl P-toluate and triethylaluminum to be added to obtain the desired activity. Example 2 Methyl P-toluate 0.6 added when receiving slurry into autoclaves C1 and C2
ml/30min to tetraethoxysilane 2.0ml/30min
The same procedure as in Example 1 was carried out, except that the activity was reduced to about 1/5 by changing to Table 2 shows the results of the polymerization. Example 3 Methyl P-toluate added when receiving slurry into autoclaves C1 and C2 1.4
ml/30min was changed to ethyl orthoacetate 0.9ml/30min to reduce the activity to about 1/4 and autoclave C.
The amount of triethylaluminum added at the start of batch polymerization with 1 and C2 was changed to 2.5 ml to increase the activity to about 2.0 ml.
Table 2 shows the results of polymerization carried out in the same manner as in Example 1 under the conditions shown in Table 1 except that the amount was doubled. Comparative Example 1 Batch Polymerization was carried out in the same manner as in Example 1 under the conditions shown in Table 1 without adding any additives or organoaluminum compounds to the polymerization tank. Table 2 shows the results.
Shown below. Impact resistance is very poor. Comparative Example 2 Polymerization was carried out in the same manner as in Comparative Example 1, except that the polymerization time of each stage of the batch polymerization was changed. The results are shown in Table 2. Although the impact resistance was considerably improved by increasing the ethylene content, the rigidity was insufficient.

【table】

【table】 [Brief explanation of the drawing]

FIG. 1 shows an example of a polymerization apparatus for carrying out the method of the present invention. FIGS. 2 and 3 are graphs showing the relationship between the catalyst activity and the amount of methyl P-toluate used, and the relationship between the catalyst activity and the amount of triethylaluminum used, respectively. Note that the units are expressed as relative values. A, B: Autoclave for continuous polymerization, C1, C
2: Autoclave for batch polymerization, D: Autoclave for deactivating catalyst, E: Flash tank, F: Hopper.

Claims (1)

[Claims] 1. Two or more polymerization tanks are continuously operated using a solid catalyst obtained by supporting titanium halide on a carrier containing magnesium halide and a stereoregular catalyst consisting of an organoaluminum compound. During stepwise polymerization, polymerization with an ethylene/propylene reaction ratio of 6/94% by weight or less is carried out continuously, and polymerization with an ethylene/propylene reaction ratio of 15/85 to 95/5% by weight is carried out batchwise. In the method for producing a propylene-ethylene block copolymer, a catalyst activity reducing agent is added to the slurry at the same time as or before the slurry is transferred to a polymerization tank for batch polymerization, thereby reducing the catalyst activity without adding the reducing agent. After reducing the activity to 1/4 or less, and then adding an organoaluminum compound after transferring the slurry to a polymerization tank for batch polymerization, the activity is increased to 1.1 times or more of the activity before adding the organoaluminium. The ethylene/propylene block is characterized in that batch polymerization is carried out under the same conditions, and then, at the same time as the batch polymerization is completed, a catalyst activity reducing agent is added to reduce the activity to 1/2 or less of the activity before adding the catalyst activity reducing agent. Method for producing polymers. 2. The method according to item 1, wherein the activity reducing agent added to the batch polymerization tank at the time of slurry transfer and at the end of polymerization is a compound having at least one C-O or C-N bond.