KR890004064B1 - The making method of prophilen individual and uselessly union - Google Patents

Abstract

Propylene homopolymers or copolymers are prepd. by bulk polymn. of propylene alone or a copolymerizable α-olefin in the presence of catalysts based on transition metal compds. and organo metallic compds. and H2 as a mol. wt. modifier. Reaction is carried out at const. temp. in a reaction tank with a reflux condenser. The temp. is kept const. by balancing the heat generated with the heat lost by condensing monomers in the reflux condenser. The amt. of H2 present is calculated by formula and determines the mol. wt. of the polymer obtained.

Description

Process for preparing propylene homopolymer or copolymer

1 is an example of a device suitable for practicing the method of the present invention.

2 is a schematic diagram showing the relationship between the volume of hydrogen consumed in a polymerization example at a constant temperature and the ultimate viscosity number of the resulting polymer measured with its tetratin solution.

3 is a schematic diagram showing the relationship between the passage of time in the implementation, the hydrogen concentration in the reactor and the ultimate viscosity number of the product polymer.

* Explanation of symbols for main parts of the drawings

1: reactor 2: reflux cooler

3: jacket 4-3: flow rate control valve

4-1, 4-2, 4-4, 4-5: detector 5, 7, 10-1: introduction tube

6, 9, 10-2: discharge pipe 8: data processor

18 blower

The present invention relates to a single polymerization method or copolymerization method of propylene. In particular, the present invention provides a mixture of propylene alone or a mixture of propylene with other α-olefins copolymerizable with propylene while using propylene or a mixture thereof as a liquid medium in the presence of hydrogen as a molecular weight regulator in a reactor equipped with a reflux condenser. A method for controlling the molecular weight of a propylene homopolymer or copolymer obtained by bulk polymerization.

In the case of polymerizing propylene in the presence of a Ziegler-Natta Catalyst, it is well known that the molecular weight of the resulting polypropylene can be controlled by controlling the volume of hydrogen added during the polymerization reaction. For example, J. Ploymer SCT., (2, 109 (1974)), because there is a constant correlation between the concentration of gas phase means and the molecular weight of polypropylene produced (eg, J. Ploymer SCT, Part AI , Vol. 8,2717 (1970)), polypropylenes are generally produced by controlling the hydrogen concentration in the gas phase uniformly, so that the molecular weight of the resulting polypropylene has a constant value.

In the case of producing a polypropylene by a bulk polymerization method in a large-sized reactor, it is difficult to remove the heat of polymerization if it is simply to remove heat through the wall of the reactor or only by a heat exchanger installed inside the reactor. Therefore, it is also well known to use a reflux cooler that uses the latent heat of the liquid medium. However, in the case of carrying out the bulk polymerization reaction of polypropylene in the reaction tank with the reflux condenser described above, the concentration of gaseous hydrogen is remarkably changed depending on the load of the reflux condenser. Therefore, the introduction or discharge of hydrogen into and out of the reactor should be repeated frequently to keep the hydrogen concentration in the gas phase constant, ie to control the molecular weight of the resulting polymer. This means that a large amount of hydrogen is discharged, and there is a problem that the aforementioned method is uneconomical because a large amount of propylene is discharged along with the discharge of hydrogen.

The present inventors conducted extensive research in order to solve the above-mentioned problem. As a result, the present inventors have found a method of controlling the molecular weight of polypropylene without loss of hydrogen and / or propylene with excellent controllability.

Accordingly, it is an object of the present invention to provide a method for producing a propylene homopolymer or copolymer capable of controlling the molecular weight without loss of raw materials.

According to the present invention, a monomer or a monomer is used in the reaction tank to which a reflux condenser is attached, in the presence of hydrogen as a molecular weight regulator, using propylene or a mixture thereof as a liquid medium and cooling at least part of the heat of polymerization in the reflux condenser while removing at least a part of the heat of polymerization. Provided is a method for producing a propylene homopolymer or copolymer by bulk polymerizing propylene alone or a mixture of propylene with another α-olepan copolymerizable with propylene at a constant temperature. The method comprises the steps of calculating the amount of polymerized monomer or monomer mixture per unit time based on the calorific value calculated by the sum of the calories artificially removed from the same reaction unit per unit time and naturally dissipated heat, and a 135 ° C. tetralin solution. The relationship between the ultimate viscosity number (η) of a propylene homopolymer or copolymer and the volume of hydrogen consumed per unit amount of each propylene homopolymer or copolymer (X)

1n η = 1 n X + A

A process for determining the required volume of hydrogen per unit amount of a homopolymer or copolymer having a predetermined molecular weight using the formula (A: constant), and the amount of monomer or monomer mixture calculated above with the hydrogen volume determined above A process of controlling the volume of hydrogen charged into the reactor according to the hydrogen consumption volume change in the reactor calculated by subtracting the volume of hydrogen introduced into the reactor from the sum of the hydrogen volume discharged with the slurry from the slurry. Is done.

Said "other alpha-olefin which can be copolymerized with propylene" is at least one of ethylene, butene-1, hexene-1, and the like, hereinafter referred to as "copolymerizable alpha-olefin". When the propylene copolymer is produced by the method of the present invention, there is no particular limitation on the amount of α-olefin copolymerizable as long as the polypropylene does not remain in the slurry state. Generally, however, there is no particular limitation on the amount of copolymerizable α-olefins other than propylene in each of the resulting polymers. However, in general, the upper limit of the proportion of copolymerizable α-olefins other than propylene in each of the resulting polymers is approximately 40% by weight.

In order to facilitate the description of the present invention, in addition to the examples, "propylene" used in the description of the present specification should include not only propylene alone but also a mixture of propylene and other α-olefins capable of polymerizing with propylene. Thus, as used herein in the description of the specification, in addition to the examples, "polypropylene" refers to copolymers of mixtures as well as propylene homopolymers.

For the following reasons, the method of the present invention turns out to be of great importance in the case of polymerizing propylene in the presence of hydrogen as a molecular weight regulator in a reaction tank equipped with a reflux condenser.

In a reactor without reflux condenser, the gaseous phase and the liquid phase remain gas-liquid parallel, and furthermore the gas phase is in a fairly stable state. Therefore, when the gas in the gaseous phase is taken out and the hydrogen concentration is measured, the hydrogen concentration in the gaseous phase can be accurately measured. The hydrogen concentration measured in this way is compared with a predetermined hydrogen concentration by a conventional comparison means, and the hydrogen supply valve of the reactor is continuously introduced based on the comparison result to continuously introduce hydrogen deficiency into the reaction tank so that the concentration of gaseous hydrogen is approximately constant. The molecular weight of the resultant polypropylene can be controlled by maintaining it.

However, the gas phase and the liquid phase do not always maintain the gas-liquid equilibrium when the polymerization reaction is carried out using a reactor equipped with a reflux condenser. As described above, the hydrogen concentration in the gas phase changes with the load of the reflux cooler as time passes. As a result, it is difficult to control the molecular weight of the resulting polypropylene if the above simple automatic control method is applied.

Examples of the polymerization catalyst useful in the method of the present invention include a catalyst system composed of a conventional transition metal catalyst and an organometallic compound. If necessary, more than one type of stereoregulator may be used in combination. Examples of the polymerization catalyst are not particularly limited, but examples of transition metal catalysts include titanium trichloride obtained by reducing titanium tetrachloride with a reducing agent such as aluminum, free aluminum, or organic magnesium, or titanium trichloride with an oxygen-containing organic compound, titanium tetrachloride, or the like. Pulverized after the activation treatment, or supported by a support such as magnesium chloride or titanium trichloride or titanium tetrachloride. Examples of the organometallic compound include organoaluminum such as trialkylaluminum, dialkylaluminum halides, alkylaluminum sesquihalides, and alkylaluminum dihalides, and organomagnesiums such as dialkylmagnesium.

The following describes an embodiment of the present invention based on the accompanying drawings.

FIG. 1 shows an example of a device suitable for carrying out the method of the present invention, in which a reactor (1) with a stirrer is provided, a reflux cooler (2) in the form of a cell-tube type heat exchanger, and a jacket (3) of the reactor (1). And an introduction tube 5 for introducing the slurry into the reaction tank 1.

In the case where the reactor 1 is used for a single reactor polymerization or as the first reactor in a multiple reactor polymerization connected in series, the introduction tube 5 is used for introduction of the catalyst slurry. In the case where the reactor 1 is the second or subsequent reactor of the plural reactor, the introduction tube 5 is used to introduce the reaction slurry from the entire reactor. In addition, a discharge tube 6 for removing slurry from the reaction tank 1, a charging tube 7 for introducing propylene and a catalyst, a sampling tube 9 for collecting gas from the gas phase of the reaction tank 1, and a reflux cooler In FIG. 2, there is shown a blower 18 which is configured to recycle an uncooled gas body, which is not cooled but mainly comprises hydrogen gas, to the reaction tank 1.

Also, a detector 4-1 for detecting the flow rate and temperature of the gas at the inlet of the reflux condenser 2, and another detector for detecting the flow rate and temperature of the condensate recycled to the reactor 1 for recovery from the reflux condenser 2 (4-2), another detector (4-4) for detecting the flow rate and temperature of the cooling gas (or heating water) of the hydrogen gas flow rate control valve (4-3) introduced into the reaction tank (1), the jacket (3) ), Another detector 4-5 for detecting the flow rate and temperature of the cooling water (or heating water) introduced into the jacket 3, an introduction tube 10-1 for introducing the cooling water into the reflux cooler 2, and the cooling water. The discharge pipe 10-2 for discharging is shown.

The following process is an example for calculating the amount of monomer or monomer mixture polymerized per unit time in the reactor 1. The data signals (a), (b), (c), and (d) output from the detectors (4-1), (4-2), (4-4), and (4-5), respectively, are the data processor (8). The amount of heat generated per unit time in the reactor 1 at the time of outputting the data signal is calculated by correcting the amount of heat removed per unit time from the reactor 1 based on the overall structure of the polymerization system and its operating conditions. It is calculated from the data signals (a), (b), (c) and (d) according to the calculated amount of dissipation heat.

Since the relationship between the polymerization amount of the monomer or the monomer mixture and the heat of reaction can be seen from the composition of the monomer or the monomer mixture polymerized by the prior art, the above-described calorific value is the monomer polymerized per unit time in the reactor 1 in the data processor 8. Or the amount of monomer mixture. In other words, the relationship between the molecular weight of the polypropylene of a predetermined composition and the volume of hydrogen required for the production of propyl pen can be seen in FIG.

That is, the following formula

1n η = 1 n X + A

In the formula, η: intrinsic viscosity number of polypropylene measured in the form of a 135 ° C tetraffin solution: X: volume of hydrogen consumed per unit weight of polypropylene: A: constant. Therefore, by storing the above relational expression in advance in the data processor 8, and then inputting a predetermined polypropylene molecular weight into the data processor 8, the volume of hydrogen required per unit weight of charged propylene can be determined.

In the above-described method, the volume of hydrogen required in the reactor 1 is calculated as a product of the volume of hydrogen required per unit weight of charged polypropylene and the amount of polymerized monomer or monomer mixture precomputed in the data processor 8.

When the present invention is applied to a reaction system in which a plurality of reactors are connected in series to perform a continuous polymerization and the molecular weight of the resulting polymer is continuously increased as it goes from one reactor to the next, hydrogen is introduced through the inlet tube 5. Since hydrogen is introduced and dissolved in both slurries discharged through the discharge pipe 6, hydrogen is introduced and discharged respectively with the two slurries.

Therefore, it is necessary to input the information of the hydrogen volume into the data processor 8 and perform correction based on this information. That is, the operation is performed in the data processor 8, and the volume of hydrogen introduced into the slurry into the reactor is discharged along with the slurry from the reactor 1 and the product of the required volume of hydrogen per unit of polypropylene and the polymerized monomer. Subtract from the sum with the volume of hydrogen.

The operation result is output as the signal e from the data collimator 8.

Accordingly, the volume of hydrogen introduced into the reactor 1 can be controlled. That is, since the reaction can be carried out while maintaining the hydrogen concentration in the gas phase of the reactor 1 approximately constant, the conditions under which the opening degree of the hydrogen gas flow rate control valve 4-3 is adjusted in accordance with the change in the value of the signal e. Under the conditions, polypropylene having a uniform molecular weight can be produced.

For calorimetry and calculation of the polymerization reaction, the heat removed from the reflux cooler 2 is based on the data signals (a) and (b) output from the detectors 4-1 and 4-2 of the above embodiment. Calculate Further, the data signals obtained after measuring the temperature and the flow rate of the cooling medium of the reflux condenser 2 in the inlet pipe 10-1 and the discharge pipe 10-2 are replaced with the signals (a) and (b) described above. The amount of heat removed by the reflux condenser 2 can be calculated by inputting into the processor 8.

On the other hand, when a single reactor polymerization is carried out in the reaction tank 1 described above or when a plurality of reactors of the same type as the reactor 1 are connected in series to perform polymerization, each reactor is already a liquid medium at the start of the reaction. It is filled with a large amount of propylene as a reaction raw material. Therefore, even if hydrogen is charged in the present invention, that is, the volume corresponding to the amount of polymerization propylene calculated on the basis of the measured and calculated heat of polymerization reaction, a polymer having a predetermined molecular weight cannot be obtained. Considering the volume of hydrogen dissolved in the liquid propylene filled in each reactor at the start of the reaction and the volume of the gaseous phase of the liquid medium, the volume of hydrogen corresponding to the liquid propylphene at the start of the reaction should be charged once to perform the polymerization reaction. . The molecular weight of the produced polypropylene is measured and compared with a predetermined value. Based on the comparison, a small amount of hydrogen or propylene is added to the reactor. The microcalibration described above is repeated until the molecular weight of the resulting polypropylene reaches a predetermined value. The polypropylene of constant molecular weight can then be produced by further proceeding the reaction according to the process of the invention.

In the practice of the present invention, a reaction tank with a reflux condenser is used. There is no particular limitation on the heat removal capacity of the reflux condenser.

The invention is particularly effective when the steady state, ie the temperature of the reactor during the practice of the invention, is controlled by removing heat through a reflux condenser.

The present invention provides a high molecular weight of polypropylene with a high efficiency as well as excellent controllability by carrying out the bulk polymerization of propylene according to the method of the present invention in the presence of hydrogen as a molecular weight regulator by using a reactor equipped with a reflux condenser. Very useful in enemy terms.

EXAMPLE

Continuous bulk polymerization of liquid propylene was carried out at 70 ° C. in the presence of a catalyst composed of titanium trichloride and diethylaluminum chloride while using liquid propylene as a medium in a reactor having a structure shown in FIG.

At the start of the reaction, first, 3000 kg of propene and 35 Nm 3 of hydrogen were charged to the reactor. Hot water was flowed through the jacket to heat the medium to 70 ° C. The polymerization reaction was started while charging the catalyst and propylene at a constant charging rate (titanium trichloride: 1.0 kg / hr, diethylaluminum chloride: 16 kg / hr, propylene: 10000 kg / hr). During the reaction, the reaction slurry was taken out of the reactor and the molecular weight of the produced polypropylene was measured. The molecular weight thus measured was compared with a predetermined value. Based on this comparison result, it adjusted so that the molecular weight of the polypropylene produced | generated by repeating the micro correction which supplies a small amount of hydrogen to a reaction tank several times may become a predetermined value. It took approximately 30 minutes to reach the predetermined value.

According to the method of the present invention, continuous bulk polymerization of propylene was carried out. In other words, propylene, titanium trichloride and diethylaluminum chloride were charged into the reactor at constant speeds, that is, 6000 kg / hr, 0.8 kg / hr and 8 kg / hr, respectively. At the same time, the slurry was discharged from the reactor at a rate of about 6000 kg / hr to keep the slurry in the reactor constant. During this polymerization reaction, data signals (a), (b), (c), and (d) were detected per unit time from detectors (4-1), (4-2), (4-4) and (4-5). The amount of polymerized monomer was input to a data processor that corrects the amount of heat dissipated and performs various conversions. In addition, an intrinsic viscosity number 1.73 corresponding to a predetermined molecular weight of polypropylene as a final product as a value measured in the form of a 135 ° C. tetralin solution was input to the data processor. This intrinsic viscosity number was converted into the volume of hydrogen consumed per unit weight of polypropylene having a predetermined molecular weight according to the above formula. Subsequently, the volume of hydrogen and the product of the polymerization monomer amount determined above were calculated. The volume of hydrogen discharged with the slurry from the reactor was corrected. As a result, the volume of hydrogen consumed in the reactor is output as the data signal e from the data processor. The reaction was continued while controlling the volume of hydrogen charged into the reactor according to the change of the data signal e.

3 shows polypropylene in the slurry discharged through the discharge pipe 9 shown in FIG. 1 and other changes in the time of the hydrogen concentration (vol%) of the gaseous phase taken out through the sampling pipe 9 shown in FIG. It is a schematic diagram showing the change over time of the limit viscosity number of.

As can be seen in FIG. 3, the hydrogen concentration in the gas phase changed but the limit viscosity number did not change. That is, the molecular weight was kept constant.

On the other hand, about 65% of the total heat removed through the jacket and the reflux cooler was at steady state, i.e. when the process of the invention was carried out at an average of 860M Cal / hr.

Claims (2)

In a reaction tank equipped with a reflux cooler, propylene or a mixture thereof is used as a liquid medium in the presence of hydrogen as a molecular weight regulator, and the vapor of the medium in the reflux cooler is cooled to remove at least part of the heat of polymerization. A process for producing a propylene homopolymer or copolymer by bulk polymerizing a mixture of propylene with another α-olefin copolymerizable with the propylene at a constant temperature, wherein the amount of the polymerized monomer or monomer mixture per unit time is the same unit. Calculation based on the calorific value calculated by the sum of the calories artificially removed from the reaction vessel and the naturally dissipated calories per hour, and the ultimate viscosity number (η) of the propylene homopolymer or copolymer measured in 135 ° C tetralin solution. And propylene homopolymers or balls Polymer units relationship between volume (X) of hydrogen consumed respectively per weight 1n η = 1 n X + A (Wherein A is a constant) to determine the volume of hydrogen required per unit weight of a homopolymer or copolymer having a predetermined molecular weight, and the hydrogen volume determined above and the amount of monomer or monomer mixture calculated above. A volume obtained by subtracting the volume of hydrogen introduced with the slurry into the reactor from the sum of the product and the volume of hydrogen discharged with the slurry from the reactor is determined according to the change in the hydrogen consumption volume in the reactor. A process for producing a propylene homopolymer or copolymer, characterized by comprising a step of controlling. The method of claim 1, wherein the propylene uses a single monomer.

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