JPH0621133B2 - Continuous production method of high melt viscoelastic polypropylene - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a continuous process for producing high melt viscoelastic polypropylene. More specifically, the present invention is a method for producing polypropylene having a broad molecular weight distribution, which is suitable for post-processing sheets and blow molding, by polymerizing propylene in multiple stages using two or more polymerization vessels connected in series. Regarding

[Conventional technology]

The general-purpose polypropylene has the following problems in the application field of the post-processing sheet. That is, a sheet processed using the polypropylene is post-processed (or 2
The following problems with the heat-formed letters for (subsequent processing): rapid sagging of the sheet, narrow range of processing conditions, poor molding efficiency, large sag of wide sheets, The thickness was likely to be uneven and wrinkles were likely to occur.

General-purpose polypropylene also has the following problems in the field of application for blow molding. That is, since the parison of the molding letter is drooping largely, the wall thickness of the molded product becomes uneven, and therefore the blow molding method can be applied only to the production of small molded products.

If high molecular weight polypropylene is used to prevent the above-mentioned drooping, poor flowability, large load and energy loss at the time of molding, risk of causing mechanical troubles, and rough surface of the molded product causing loss of commercial value. And so on.

In order to improve the above-mentioned sheet moldability and blow moldability when a general-purpose polypropylene is used, the following techniques a to c have been proposed.

That is, a. In JP-B-47-80614 and JP-A-50-8848, low density polyethylene is mixed with polypropylene.
However, a molded article using such a mixture is liable to cause rough skin, and in order to prevent this, strong kneading is required at the time of melting the mixture, which is restricted in terms of selection of a kneading machine and power consumption. In addition, there is a problem that the rigidity of the molded product decreases.

Then b. JP-A-57-185336, JP-A-187337, JP-A-58-7
439 et al. Propose a method of kneading polypropylenes having different molecular weights using a granulator or the like. However, when the mixture obtained in this way is used, roughening of the molded product is more likely to occur than in the case where the above-mentioned low-density polyethylene is mixed, and the kneading method and the selection condition of the molecular weight difference between the mixtures are restricted. To be done.

In addition, c. In order to solve the problems caused by the mixing method such as the above a and b, various methods for expanding the molecular weight distribution of polypropylene by a multi-stage polymerization method of propylene have been proposed. For example, JP-A-57-185304 and JP-A-1900
In the examples of JP-A-58-7406, JP-A-7409, JP-A-59-172507, etc., the molecular weight difference is imparted to polypropylene by performing the above-mentioned multistage polymerization operation in a batch polymerization method. The batch polymerization method has a problem that the productivity per volume of the polymerization vessel is low because there is essentially an empty time during which the polymerization reaction is not performed, such as charging of raw materials and withdrawal of products.

However, the invention of group c mentioned above also refers to the continuous method. In order to produce polypropylene containing a difference in molecular weight by the continuous method, it can be divided into two according to the order of production. First, when a high molecular weight-low molecular weight combination sequence is used for production, it can be performed by simply adding hydrogen in the latter-stage polymerization vessel, and the operation is smooth, but there are problems described below. Secondly, in the case of producing a low molecular weight-high molecular weight combination sequence, it is necessary to remove excess hydrogen by an operation such as depressurization degassing for the reaction mixture after the production of the low molecular weight polypropylene in the preceding stage. It is stated that it is inferior in smoothness of operation to the case of 1.

The present inventor has found that the following problems 1 and 2 exist as a result of a study on the method for producing the high molecular weight / low molecular weight combination sequence described above in the invention of group c. That is, the melt flow rate of the high molecular weight portion of the obtained polypropylene (hereinafter referred to as MFR)
When it is low, it becomes difficult to measure the MFR of the high molecular weight part, and it becomes difficult to adjust the MFR by adjusting the operating conditions (Note: it is possible to measure the viscosity [η] of such polypropylene, It takes time to measure [η] and is not suitable as a means of operation management). Furthermore, for polypropylene produced in the order of high molecular weight-low molecular weight, the MFR value of the powder before granulation and the MFR value of the pellet after granulation are extremely large (Note.
It was found that there is a problem in controlling the molecular weight difference and the MFR (granulated product) as a product for the polypropylene.

As a result of various studies to solve the above-mentioned technical problems, the inventors of the present invention firstly connected two abnormal polymerization reactors in series and supplied the catalyst and hydrogen only to the first tank to carry out propylene polymerization. As the polymerization reaction mixture in the tank was sequentially transferred to the subsequent polymerization reactor, the catalyst concentration and hydrogen concentration in the reactor in the subsequent polymerization reactor decreased, so that a higher molecular weight polymer was produced. Based on this knowledge, we have proposed the invention of Japanese Patent Application No. 60-264593 based on the knowledge that polypropylene having a wide molecular weight distribution can be obtained as the final product polypropylene. However, the above-mentioned method has a problem that the operation management is complicated because three or more polymerization vessels are required and the reaction amount ratio and the polymerization conditions in each polymerization vessel are limited.

[Problems to be solved by the invention]

As a result of continuing the study to solve the above-mentioned problems, the present inventor connected two or more polymerizers in series and supplied a catalyst and hydrogen only to the first tank to polymerize propylene, and then successively polymerized the latter stage. Since the hydrogen concentration in the reactor decreases, it is possible to generate higher molecular weight polymers, but by extracting 1 part of the gas in the gas phase, there is no need to install equipment such as a degassing tank in the middle. Furthermore, they have found that the molecular weight of each polymerization unit can be arbitrarily adjusted at a practical level, and completed the present invention.

As is clear from the above description, the object of the present invention is a continuous process for producing a high-melting viscoelastic polypropylene having a wide molecular weight distribution and good moldability, in particular, excellent runnability and easy improvement of quality control. It is to provide an extra salary. Another object is to provide a high melt viscoelastic polypropylene produced by the above method and having excellent moldability.

[Means for Solving Problems] The present invention has the following main configuration (1) and the practical solar configuration (2) to (4).

(1) In the method of continuously producing polypropylene by polymerizing propylene by slurry method or bulk polymerization method using a Ziegler-Natta type catalyst, using two or more polymerization reactors connected in series, The whole amount is supplied to the first polymerization reactor, the catalyst is continuously moved to the second and subsequent polymerization reactors together with the reaction mixture, hydrogen is used as a molecular weight regulator, and the entire amount of the hydrogen used is transferred to the first polymerization reactor. The hydrogen is supplied to the reactors together with the reaction mixture in succession to the second and subsequent polymerization reactors to sequentially form polypropylene polymerized in each polymerization reactor on the catalyst, and then the final polymerization reactors. Therefore, the reaction slurry is continuously discharged, and degassing is performed from the gas phase part of the polymerization vessel in any one or more of the second and subsequent polymerization vessels, and the amount of the degassing is the volume of the polymerization vessel being V ₁ age When 0.5V ₁ / hr~10 in MTP terms
Continuous production method of high melt viscoelastic polypropylene characterized by setting V ₁ / hr.

(2) In two or more polymerization vessels connected in series, the ratio of MFR value of the polymer produced in each of the first polymerization vessel and the last polymerization vessel is adjusted to be within the range of the following formula [1]. The continuous production method according to item (1) above.

However, MFR ₁ ; MFR of the polymer produced in the first polymerization reactor MFR ₅ ; MFR of the polymer produced in the last polymerization reactor (3) Any one of the second and subsequent polymerization reactors is removed from the gas phase part of one or more polymerization reactors. The production method as described in the above item (1), wherein the discharged gas is circulated to the first polymerization vessel together with the gas recovered from the degassing tank.

(4) A small amount of ethylene and / or α-olefin together with propylene is supplied to one or more polymerization reactors.
The production method according to item (1).

The structure and effect of the present invention will be described in detail below.

The catalyst used in the present invention is not particularly limited as long as it is a so-called Ziegler-Natta type catalyst relating to a combination of a transition metal compound and an organic compound of Group I to III metals of the periodic table, hydride or the like. However, it is preferable to use a catalyst that basically combines a titanium compound and an organoaluminum compound. As the titanium compound, titanium trichloride or a titanium trichloride composition obtained by reducing titanium tetrachloride with hydrogen or metallic aluminum is further crushed by a ball mill, a vibration mill or the like, or activated.
Furthermore, the above-mentioned activated material is treated with an electron-donating compound, or titanium tetrachloride is reduced with an organoaluminum compound, and further various treatments (for example, titanium trichloride composition in which crystal transition is caused by heating in TiCl ₄ ). , A highly activated titanium trichloride composition treated with an electron-donating compound and / or an electron-accepting compound) and a tetrachloride on a carrier such as magnesium chloride. A catalyst generally used for stereoregular polymerization of propylene such as a so-called supported catalyst obtained by supporting titanium can be used.

As the organoaluminum compounds mentioned above preferably used in the present _{invention, AlR n R 'n' X} 3 - compound represented by (n + n ') it is particularly preferred. In the formula, X represents halogen such as fluorine, chlorine, bromine and iodine, and n and n ′ are 0 <n + n ′.
Represents any positive number of 3. Specific examples thereof include trialkylaluminums and dialkylaluminums, and two or more kinds of these may be mixed and used.

The above-mentioned catalyst may be used in combination with an electron donor known as a so-called third component.

Polymerization methods include, in addition to raw material propylene and a catalyst, slurry polymerization using an inert solvent such as propane, hexane, heptane, octane, benzene or toluene, or a hydrocarbon solvent, or bulk polymerization using propylene itself as a solvent (dispersion medium). Can be used.

As the polymerization vessel used in the method of the present invention, preferably two or more tank type reactors are connected in series, and as a method for transferring the reaction mixture, a part of the liquid phase (slurry) portion in the polymerization vessel at the preceding stage is used. Are continuously transferred to the next-stage polymerization vessel. The two or more polymerizers must be connected in series.

In the method of the present invention, the catalyst is supplied in its entire amount only to the first tank. The catalyst (solid), together with the above-mentioned reaction mixture, successively forms polypropylene on each solid of the same catalyst through the second and subsequent polymerization reactors in the respective polymerization reactors, and a reaction including such catalyst solids. The mixture is continuously withdrawn from the polymerizer in the final tank. If a catalyst is added to any of the polymerization vessels in the second and subsequent tanks to carry out polymerization, a polymer having a significantly different MFR from that in the first tank is formed on the additional catalyst particles. However, it is not preferable because it is not uniformly mixed even after granulation after the product is obtained, and the appearance of the processed product such as fisheye (FE) is deteriorated.

In the method of the present invention, the hydrogen used as the molecular weight regulator is supplied to the first tank only in its total amount as in the above-mentioned catalyst. The supply position of hydrogen in the polymerization vessel may be a liquid phase part or a gas phase part. However, when supplying hydrogen to the liquid phase portion, it is necessary to take care so that the supply material is not trapped as bubbles in the withdrawn (transferred) slurry to the second tank. This is because, in the method of the present invention, hydrogen supplied to the second and subsequent tanks is generally supplied from the tank immediately before each in a state of being dissolved in the reaction mixture (slurry). Therefore, when hydrogen trapped as bubbles is sent to the next tank, the difference in molecular weight between the polypropylene produced in the tank and the polypropylene produced in the next tank is
This is not preferable because it becomes smaller than expected and the molecular weight distribution of the final product polypropylene cannot be sufficiently wide.

Further, in the method of the present invention, the polymerization vessels are connected in series to each other.
Use more than one. Different from the above-mentioned catalyst and hydrogen supply method, propylene or propylene as a raw material and a small amount of ethylene or α-olefin or solvent can be supplied to the polymerization reactors at respective stages in required amounts. A small amount of ethylene or α-olefin used in combination with propylene is 30% by weight or less, preferably 10% by weight or less, particularly 5% by weight or less in weight ratio with respect to propylene. Alternatively, it can be supplied as a mixture with propylene. The α-olefin is not limited to butene-1,2-methylbutene-1,4-methylpunter-1
And so on. In the polymerizer second and subsequent layers, the amount of gas withdrawn from the polymerization vessel vapor phase if the volume of the polymerization vessel was V _1, NTP i.e. 0 ° C., to 0.5V without ₁ per hour 0 kg / cm ² G in terms 10V _It is preferably carried out in the range of ₁ . If the amount of gas extracted is less than 0.5 V _1, the effect of increasing the molecular weight of the produced polymer is small,
If it is more than 10V _{1, the} difference in molecular weight from the polymer produced in the immediately preceding polymerization vessel becomes too large, the fluidity of the resin at the time of production becomes non-uniform, and molding defects, surface roughness, etc. may occur, which is preferable. Absent. or, Is less than 2, the broadening of the molecular weight distribution, which is the basic object of the present invention, is insufficient.

As described above, the polymerization reaction mixture is sequentially transferred from the first polymerization vessel to the final polymerization vessel. The polymerization reaction mixture or slurry withdrawn from the final polymerization vessel is transferred to a pressure reduction tank for pressure reduction. Since the gas generated in the pressure drop tank contains a large amount of propylene, it is usually compressed and circulated to the polymerization vessel for reuse. Further, the gas extracted from the gas phase portion of the second and subsequent polymerization reactors can be recycled together with the gas generated in the depressurization tank to be recycled without loss of raw materials.

The polymerization temperature of the method of the present invention is not limited, but is usually 20 to 1
It is easy to carry out at 00 ° C, preferably 40 to 80 ° C. The temperature of each polymerization vessel may be the same or different.

The polymerization pressure in the method of the present invention is not limited, but normally atmospheric pressure to 50 kg / cm ² G is used. The polymerization pressures of the respective polymerization reactors connected in series according to the method of the present invention may be the same or different from each other.

In the method of the present invention, the average residence time of the reaction mixture in each polymerization vessel connected in series is not limited, but is usually 30
~ 10 hours.

Besides, the transfer of the slurry between the polymerization vessels connected in series is
There are no special restrictions as it is possible to recreate conventional pumping, differential pressure transportation and other methods.

The MFR of the polypropylene according to the present invention obtained as described above is usually 0.01 to 100, but particularly for sheet molding and blow molding, the MFR value is 0.05 to 10, preferably 0.10 to 5.0. What is used.

The main effects of the method of the present invention are summarized as follows.

First, since the polypropylene according to the method of the present invention has a good molecular weight distribution, it has good flowability in extrusion molding, and has effects such as an increase in the amount of extrusion by an extruder and saving of power consumption. Further, since it has characteristics such as excellent fluidity at the time of injection molding, it is possible to exert excellent effects in terms of quality and processing efficiency in applications in various molding fields.

Secondly, the method of the present invention is very easy to control the polymerization process or adjust the polymerization conditions as each step polymerization method.

That is, the catalyst is supplied only to the first tank of the polymerization tanks connected in series of two or more units, and the gas is continuously extracted from the gas phase portion of the polymerization tanks of the second and subsequent tanks to obtain a special intermediate degassing tank. Also, the polypropylene having a wide molecular weight distribution, which is the object of the present invention, can be obtained without installing a slurry transfer pump, a gas recovery device, and the like accompanying it.

The present invention will be described in more detail with reference to the examples, but the present invention is not limited thereto.

The following methods were used for measuring the physical property values according to the examples of the present invention.

1) Melt flow rate (MFR): ASTM D 1238 2) Calculation of MFR of polymer produced in each polymerization vessel: MFR ₁ ; 1st stage (MFR (* 1) MFR ₂ ; 2nd 〃 MFR _{1 + 2} ; Total MFR (* 1) W ₁ produced in the 1st and 2nd stages; Polymerization ratio of the 1st stage (* 2) W ₂ ; 2nd 〃 (* 2) W ₁ + W ₂ = 1.0 * 1; Measure at each stage by sampling.

* 2: The titanium content (fluorescent X-ray analysis) in the polymer was measured by sampling at each stage, and the polymerization rate was calculated.

The calculation of MFR ₂ was obtained by the following relational expression.

3) Physical properties measurement method for sheet molded products: Young's modulus; ASTMD 882 (kgf / mm ² ) Heating behavior; Chisso method To evaluate the sheet heating vacuum forming accuracy as a model, the keto is fixed to a 40 cm × 40 cm frame. The following physical properties were measured by placing in a thermostatic chamber at 200 ° C. That is, a) Vertical amount of sheet (m
m), b) Maximum return amount (Note. {1/150 × (150-maximum recovery drooping amount (mm) x 100}), and c) holding time from maximum recovery to restarting drooping (seconds) Is.

4) Method of calculating the amount of gas discharged: The amount of gas discharged from the polymerization vessel was measured by a flow meter and
The value converted into the state of 0 ° C. is shown by Nl. Calculated as an ideal gas.

P ₀ = 1 kg / cm ² T ₀ = 0 ° C. = 273 ° K V ₀ = 1 atm, amount of discharged gas at 0 ° C. (/ hr) P ₁ = pressure of discharged gas at flow meter T ₁ = Temperature of discharged gas with flow meter V ₁ = amount of discharged gas (measured value with flow meter) (/ hr) Example 1 (1) Preparation of catalyst n-hexane 6, diethyl aluminum monochloride (D
EAC) 5.6 mol and diisoamyl ether 12.0 mol were mixed at 25 ° C. for 5 minutes and reacted at the same temperature for 5 minutes to obtain a reaction solution (I).
(Diisoamyl ether / DEAC molar ratio 2.4) was obtained. 40 mol of titanium tetrachloride was placed in a reactor purged with nitrogen and heated to 35 ° C. The entire amount of the above reaction product liquid (I) was added dropwise to this in 180 minutes, then kept at the same temperature for 30 minutes and then raised to 75 ° C. The mixture was heated and reacted for 1 hour, cooled to room temperature, the supernatant was removed, and n-hexane 30 was added and decantation was repeated 4 times to obtain 1.9 kg of a solid product (II).

1.6 kg of diisoamyl ether and titanium tetrachloride were suspended at 20 ° C with the total amount of this (II) suspended in 30 n-hexane.
3.5 kg was added at room temperature for about 5 minutes and reacted at 65 ° C. for 1 hour. After the reaction was completed, the reaction mixture was cooled to room temperature (20 ° C), the supernatant was removed by decantation, 30 n-hexane was added, the mixture was stirred for 15 minutes, and allowed to stand to remove the supernatant, which was repeated 5 times. After that, it was dried under reduced pressure to obtain a solid product (III).

(2) Preparation of catalyst n-hexane 40, diethyl aluminum chloride 580 g, the above solid product 360 g, methyl paratoluate 3.8 g were charged into a tank having an internal volume of 50, and then 180 g of propylene gas while maintaining stirring at 30 ° C. / H was supplied for 2 hours for pretreatment.

(3) Polymerization method Polymerization was carried out using the polymerization apparatus shown in FIG.

N-Hexane 28 / H / catalyst slurry 120m / h to polymerization vessel (1)
l / H was continuously fed. The temperature of the polymerization vessel (1)-(2) is 70
Propylene was supplied to each polymerization vessel so that the temperature and the pressure were 6 kg / cm ² G and 8 kg / cm ² G, respectively.

Further, the gas was continuously discharged from the polymerization vessel (2) at 530 Nl / H.
The liquid level in each polymerization vessel was withdrawn by a control valve so that the liquid level was 80%. The gas from the degassing tank was compressed by a compressor and circulated to the polymerization vessel (1). The polymer produced was obtained at 5 kg / H.

The analytical values are as shown in Table 1.

(4) Granulation method and sheet molding 15 kg of the white polymer powder obtained above was mixed with BHT (2.6-di-t-Buty
LP-cresol) 15g, Irganox zgzg (Tetrakis 〔Methyle
ne (3.5-di-t-butyL-4-Hydrocinnamate)) methane) 7.5
g and Calcium stearate 30 g were added, and the mixture was granulated using a 40 mmφ granulator. Then, the granulated product is extruded with a 50 mmφ extruder.
A sheet having a width of 60 cm and a thickness of 0.4 mm was produced by processing at 225 ° C., and the physical properties of the sheet were evaluated by the above methods. The results are
Shown in 2.

Comparative Example 1 The procedure of Example 1 was repeated except that the gas phase gas was not discharged from the polymerization machine (2). The heating behavior of the sheet was inferior.

Comparative Example 2 The same procedure as in Example 1 was carried out with the same hydrogen concentration in the vapor phase of the polymerization reactor by supplying hydrogen to various polymerization reactors. In this case, the heating behavior of the sheet was significantly inferior.

Examples 2 to 4, Comparative Examples 3 and 4 In Example 1, the gas phase hydrogen concentration and the amount of exhaust gas were changed as shown in the table.

Example 5 In Example 1, the polymerization temperature and the gas phase hydrogen concentration were changed as shown in the table. Further, 60 g / H of ethylene gas was continuously supplied to each of the polymerization vessels (1) and (2). The content in the obtained polymer was 2.5%.

Example 6 In Example 1, methyl paratoluate was fed to the polymerization vessel (1) in an amount of 1 g per 1 g of the solid product in the catalyst slurry. Also, the supply amount of the catalyst slurry was changed to 240 ml / H. As shown in the table, the catalyst system showed a significant increase in Young's modulus and an improvement in heating behavior.

[Brief description of drawings]

FIG. 1 is a flow sheet of a polymerization apparatus used in the examples of the present invention. In the figure, 1: first polymerizer (200), 2: second polymerizer 200) 3: degassing tank (100), 4: pump 5: heat exchanger, 6: compressor

Claims (4)

[Claims] 1. A method for continuously producing polypropylene by polymerizing propylene by a slurry method or a bulk polymerization method using a Ziegler-Natta catalyst, using two or more polymerization vessels connected in series. The total amount of the catalyst is fed to the first polymerization reactor, and the catalyst is continuously moved to the second and subsequent polymerization reactors together with the reaction mixture, hydrogen is used as a molecular weight regulator, and the total amount of the hydrogen used is adjusted to the first polymerization reactor. It is supplied to one polymerization reactor, and the hydrogen is continuously transferred to the second and subsequent polymerization reactors together with the reaction mixture, and polypropylene produced by polymerization in each polymerization reactor is sequentially formed on the catalyst, followed by the final polymerization. The reaction slurry is continuously discharged from the reactor, and degassing is performed from the gas phase part of the polymerizer in any one or more of the second and subsequent polymerizers. ₁ 0.5V ₁ / hr~10V ₁ / h in the NTP in terms of when you
Continuous production method of high melt viscoelastic polypropylene characterized by r 2. In two or more polymerizers connected in series, the ratio of MFR value of the polymer produced in each of the first polymerizer and the final polymerizer is within the range of the following formula [1]. The continuous manufacturing method according to claim (1), which is adjusted as described above. However, MFR ₁ : MFR of the polymer produced in the first polymerization reactor MFR _t : MFR of the polymer produced in the last polymerization reactor 3. The gas extracted from the gas phase of at least one of the second and subsequent polymerization vessels is circulated to the first polymerization vessel together with the gas recovered from the degassing tank. The manufacturing method as described in the range (1). 4. The process according to claim 1, wherein a small amount of ethylene and / or α-olefin is supplied together with propylene to one or more polymerization vessels.