JPS5811448B2 - Manufacturing method of block copolymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a novel method for continuously producing propylene-ethylene block copolymers.

The propylene-ethylene block copolymer produced by the present invention has excellent impact resistance despite the continuous production method, and even when processed into a film, it has excellent physical properties with very few fish eyes.

In the present invention, the polymerization rate of the catalyst refers to the polymerization rate of titanium trichloride (hereinafter also abbreviated as TlCl3) and diethylaluminum monochloride (hereinafter also abbreviated as AIEt2CI).
TiC13 with a molar ratio of EtzCI/TiCls of 10
- It is the amount of polypropylene produced per 131 g of TiC obtained by polymerizing propylene at a temperature of 65° C. for 1 hour using propylene itself as a solvent in the presence of a binary catalyst of -AIEt2C1.

In addition, the total polymerization activity of the catalyst is AIEt2C1/TiCl
2 of TiC13-AIEt2C1 with a molar ratio of 10 of 3
It refers to the yield of polypropylene obtained by polymerizing propylene at a temperature of 65° C. for 4 hours using propylene itself as a solvent in the presence of a base catalyst based on 31 g of TiCl.

Conventionally, various methods for polymerizing propylene have been proposed.

However, polypropylene does not have sufficient impact resistance, especially at low temperatures.

For this reason, methods for producing propylene-ethylene block copolymers have attracted attention and have been adopted industrially.

The block copolymer is usually produced by a first step of first polymerizing propylene or propylene and another olefin in the presence of a catalyst, and a first step of copolymerizing ethylene and propylene in the presence of a polymer containing the catalyst obtained in the first step. It is obtained by a polymerization method consisting of a second step of polymerization.

The above polymerization methods include a batch method in which copolymerization in the second step is carried out after completing the polymerization in the first step, and a continuous method in which the polymerization product in the first step is supplied to the second step and carried out continuously. It can be roughly divided into two methods.

When block copolymerization is carried out in this batch manner, it is possible to obtain a product with physical properties such as impact resistance and rigidity, but it not only increases the product cost due to operational deficiencies and increased equipment costs. It is rarely used industrially because it is unsuitable for mass production.

On the other hand, the continuous method, which is the complete opposite of the batch method, is industrially superior technology and is widely adopted, but it has inferior impact resistance compared to products obtained by the batch method, and when processed into a film, it may cause fish eyes. There are defects such as the occurrence of oxidation, which limits its uses and causes dissatisfaction with its physical properties.

Therefore, establishing a technology for manufacturing products equivalent to batch-type products using a continuous method is a major challenge in the field of this application.

For this purpose, for example, JP-A No. 49-96836, JP-A No. 4
Although many methods such as No. 9-53990 have been proposed, they are not industrially satisfactory.

That is, the former (obtained by the method of JP-A No. 49-96836, when formed into a film, the fish eyes are somewhat reduced, but the impact resistance is also reduced at the same time;
If the method of No. 9-53990) is to be adopted, the physical properties are improved compared to the former method, but not only does it require a large amount of equipment cost, but it also requires extremely complicated operation.

The inventors of the present invention have been making earnest efforts for many years to develop a technology that not only gives block copolymers obtained by continuous polymerization methods substantially the same physical properties as those obtained by batch polymerization methods, but also is industrially satisfactory.

First, we investigated the cause of the deterioration of the physical properties of block copolymers obtained by continuous polymerization, and found that the amount of polymer produced in the first step of the continuous method was small, and the amount of polymer produced in the second step was small. It has been confirmed that if the proportion of high molecular weight polymers mainly produced in the second step exceeds a certain level, fins may develop in the film and adversely affect physical properties such as impact strength.

Based on this confirmation, we repeated various statistical experiments, and as a result, we established and proposed a method for producing a block copolymer with fewer fish eyes and excellent physical properties such as impact strength.

That is, the present invention involves the polymerization of propylene or propylene and other olefins in the presence of a catalyst comprising titanium trichloride and an organoaluminium compound, the catalyst having a polymerization rate of at least 2500.9 polymers/g-TIC/hour. The first step and the second step of copolymerizing ethylene and propylene in the presence of the catalyst-polymer obtained in the first step are carried out continuously to obtain a block copolymer. Polymerization is carried out at 10 to 70% of the total polymerization activity of the catalyst, and the catalyst-polymer composition obtained in the first step is continuously supplied to the second step, and the gas phase region in the polymerization tank of the second step is This is a method for producing a block copolymer in which copolymerization is performed under conditions other than when the hydrogen concentration in the hydrogen concentration is 50 mol% or more.

The greatest feature of the present invention is that in the first step of polymerizing propylene or propylene and other olefins in the presence of a catalyst, the degree of polymerization of monomers is kept within a specific range,
The point is that the catalyst activity in the second step is used in a sufficiently high state.

That is, the degree of polymerization of the monomer in the first step in the present invention is 10 to 70%, preferably 15 to 60% of the total polymerization activity of the catalyst.
It is necessary to keep it at a minimum.

When attempting to obtain a block copolymer industrially, it is advantageous both economically and in terms of production efficiency to use all the polymerization activity of the catalyst.

Therefore, conventional industrial practice is to polymerize propylene or propylene and other olefins in a first step to consume most of the total polymerization activity of the catalyst, and in a second step, only the required amount of ethylene is polymerized. The catalyst-polymer composition obtained in the first step was supplied with all remaining polymerization activities.

That is, 90% or more of the total polymerization activity of the catalyst used is generally consumed in the first step.

When a propylene-ethylene block copolymer is continuously obtained by the conventional method, the yield of block copolymer bodies per unit catalyst is certainly excellent, which is industrially advantageous.

However, according to the confirmation of the present inventors, if the total polymerization activity of the catalyst in the first step is to be fully exhibited, that is, if the degree of polymerization of the monomers is to be increased, the physical properties of the block copolymer obtained are The physical properties tend to decrease in proportion to the degree of polymerization.

Although the mechanism by which this phenomenon occurs is not clear, Nagisa et al. speculate as follows.

That is, when the catalyst-polymer composition obtained in the first step is continuously fed to the second step, the residence time of the catalysts in the first step cannot all be made the same, and even catalysts with short residence times cannot be made the same. Even if the proportion is small, it is supplied to the second process.

The catalyst with a short residence time in the first step, that is, the catalyst with high polymerization activity, is intensively polymerized in the second step, producing a high molecular weight polymer, which is then incorporated into the block copolymer. It is thought that this may cause poor dispersibility, and may even lead to the appearance of fish eyes or deterioration of physical properties.

In the present invention, as described above, the degree of polymerization of the monomer in the first step is reduced, that is, 10 to 7 of the total polymerization activity of the catalyst.
Although this may seem industrially disadvantageous since it is carried out at 0%, the resulting propylene-ethylene copolymer has extremely excellent physical properties, so it can be fully compensated for in terms of product value.

Moreover, the block copolymer obtained by the present invention has significantly reduced fish eyes when formed into a film compared to conventional ones, and the impact resistance of the block copolymer is also more sufficient than expected.

These effects are contrary to the effects of the conventional method described above, in that even if a catalyst with a short residence time is supplied to the second step in the first step, most of the catalyst supplied to the second step is still insufficient. Because of its catalytic activity, the catalyst that stays for a short time in the first step will not intensively produce high molecular weight products in the second step, and polymerization will be carried out in a relatively average manner for all catalysts. considered to be a thing.

Therefore, the formation of high molecular weight substances with poor dispersibility is suppressed in the block copolymer obtained in the second step, making it possible to obtain a block copolymer having the above-mentioned excellent properties.As described above, the present invention The polymerization of propylene or propylene with other olefins in the first step is preferably carried out at 10 to 70% of the total polymerization activity of the catalyst, preferably 1
A range of 5 to 60% is suitable.

Even if it is within the above range, Tt is as much as economically possible due to the equipment.
It is preferable to keep the amount of monomer polymerized relative to the C13 unit weight low.

However, if the total polymerization activity of the catalyst in the first step is lower than the above lower limit, the catalyst residue in the resulting propylene-ethylene copolymer may not be sufficiently removed, resulting in poor whiteness and weather resistance of the product. , which is not preferable because it impairs heat resistance and the like.

Further, if the temperature is higher than the above upper limit, the effects of the present invention cannot be fully exhibited, which is not preferable.

The means for implementing the first step in the present invention is not particularly limited as long as it polymerizes propylene or propylene and other olefins at 10 to 70% of the total polymerization activity of the catalyst. Generally, the first step can be adopted. The polymerization temperature in one step is set to a low temperature, e.g. 30~
Methods such as a method of carrying out the reaction at 80° C., preferably 40 to 70° C., a method of shortening the residence time of the catalyst in the first step, or a combination of these methods are preferably employed.

Further, in order to further exhibit the effects of the present invention, it is preferable to pre-treat the catalyst to be supplied to the first step.

As the pretreatment, it is preferable to adopt a means of preliminarily polymerizing a small amount of olefin to a catalyst containing titanium trichloride and an organoaluminum compound.

For example, titanium trichloride and an organoaluminum compound, if necessary, an electron donor, are mixed in an inert solvent such as heptanehexane, petroleum ether, etc., propylene, ethylene,
It is sufficient to supply an olefin such as butene-1 or a mixture thereof for polymerization.

This pretreatment is generally called prepolymerization, but
As the prepolymerization conditions, known conditions can be used as they are.

For example, it is generally carried out at a temperature range of 30 to 70°C, preferably 40 to 60°C.

Further, the degree of polymerization in the prepolymerization is preferably as high as possible per unit weight of TlCl3 of the catalyst used, but from the viewpoint of equipment or economy, a degree of about 1 to 100 g/g TiCl3 is most commonly employed.

Of course, it is possible to add a molecular weight regulator such as water to the polymerization system in the prepolymerization, if necessary.

It is generally preferred industrially to carry out the prepolymerization in a batch manner.

With catalysts prepolymerized in a batch manner, even if a small amount of prepolymerization is performed, a nearly constant amount of polymer is formed on the catalyst on average, and when the prepolymerized catalyst is fed to the first step, the induction period is Polymerization starts immediately.

Therefore, even if a catalyst with a short residence time in the first step is supplied to the second step, it will reduce the heterogeneity of the polymer in the second step compared to a catalyst that does not undergo prepolymerization pretreatment. reduce

The catalyst used in the present invention is not particularly limited, and any catalyst that can polymerize propylene or propylene and other olefins can be used as necessary.

Generally, industrially, it is preferable to employ a binary catalyst of titanium trichloride and an organoaluminum compound, or a ternary catalyst in which a third component is added as an electron donor to the binary catalyst.

Various methods of manufacturing titanium trichloride have been proposed, but they can be used without any particular limitations in the present invention.

The effect of the present invention is best exhibited by highly active titanium trichloride having a catalyst polymerization rate of at least 2,500 g/g/g of TiCl/1 hour.

The method for producing highly active titanium trichloride is described, for example, in JP-A-47-3.
No. 4478, No. 50-126590, No. 50-114
No. 394, No. 50-93888, No. 50-12309
No. 1, No. 50-74594, No. 50-74595,
No. 50-104191, No. 50-98489, No. 5
No. 1-92885, No. 51-136625, No. 52-
It is preferable to employ those described in No. 30888, No. 52-35283, and the like.

Furthermore, organoaluminum compounds that are generally used in the polymerization of propylene in combination with titanium trichloride can be used without particular limitation.

Examples include trialkyl aluminum, dialkyl aluminum monochloride, alkylaluminum senukichloride, alkyl aluminum dichloride, etc.
Particularly suitable are dialkyl aluminum monohalides such as diethylaluminium monochloride.

Furthermore, as the electron donor used as the third component of the catalyst, any known electron donor may be used without particular limitation.

For example, nitrogen-containing compounds, phosphorus-containing compounds, ether compounds, etc. as shown in JP-A-50-123182 can be suitably employed.

The polymerization in the first step of the present invention is carried out in the presence of the above-mentioned catalyst or a pretreated catalyst in an inert solvent such as heptane, hexane, petroleum ether, etc., or in the presence of propylene or propylene and other olefins themselves as a solvent. It may be carried out under the conditions described above.

Further, in the first step, a molecular weight regulator such as hydrogen may be used as necessary.

The polymer obtained in the first step of the present invention may be taken out in the form of a slurry containing a catalyst and continuously fed to the second step as it is or after removing unreacted monomers, for example by flashing.

Of course, the removal of the catalyst-polymer composition in the first step is
It is preferable to operate so that the liquid level in the polymerization tank does not fluctuate, and the removed catalyst-polymer composition is preferably fed to the second step so as to keep the slurry concentration constant.

For example, if the first step is a polymerization operation using propylene or propylene and another olefin as a substantial solvent, it is generally advisable to remove unreacted monomers by flashing them in a flash tank, for example. The polymer containing the catalyst can also be supplied to the second step as a slurry having an appropriate constant concentration by adding the necessary amount of the above-mentioned inert solvent.

The addition or mixing ratio of each catalyst component used in the first step of the present invention is not particularly limited, and a suitable ratio may be determined in advance from known ratios.

In general, the molar ratio of organoaluminum compound to titanium trichloride, that is, organoaluminum compound/titanium trichloride (
The molar ratio) is preferably in the range of 1 to 30, preferably 3 to 20.

In particular, when the highly active titanium trichloride is used as titanium trichloride, the molar ratio of organoaluminum compound/titanium trichloride is preferably in the range of 5 to 20.

Further, when an electron donor, that is, a third component is used as a catalyst component, since there is a difference depending on the type of the third component, it is preferable to determine the preferable usage amount in advance according to the type of the third component.

Generally, the electron donor/titanium trichloride (molar ratio) is 0.
A range of 0001 to 1 is preferably used.

The second step of the present invention is a step of copolymerizing propylene and ethylene in the presence of the catalyst-containing polymer obtained in the first step.

As is already known, the copolymerization can be carried out using the monomer itself as a solvent, but in many cases it is generally advantageous to carry out the copolymerization in an inert solvent as described above in terms of copolymerization control.

Furthermore, it is generally preferable to supply hydrogen as a molecular weight regulator to the second step.

In this case, hydrogen is preferably supplied so that the concentration in the gas phase region is 20 mol% or less, preferably 1 to 10 mol%.

The mixing ratio of propylene and ethylene to be supplied to the second step of the present invention depends on the physical properties required of the resulting block copolymer, the copolymerization conditions in the second step, and the polymerization conditions in the first step. etc., and cannot be limited to one part, but
Generally, the ethylene/propylene molar ratio is 1/9 to 8/2
Preferably, the range of 2/8 to 515 is most widely adopted.

Moreover, the content of ethylene contained in the block copolymer obtained in the second step is generally widely used in the range of 2 to 20% (by weight).

The copolymerization conditions in the second step of the present invention are not particularly limited and may be selected from known operating conditions, but generally
The temperature is preferably 70°C, preferably 40 to 60°C, and the reaction is generally carried out for 30 minutes to 3 hours.

It is also possible to improve the polymerization activity by adding a small amount of an organoaluminum compound in the second step.

In this case, it is preferably used in an amount of 0.1 to 4.0 times mole relative to titanium trichloride.

The block copolymer obtained in the second step of the present invention is usually continuously taken out as a slurry so as to keep the liquid level in the polymerization tank constant.

the slurry is continuously transferred to a flash tank;
The block copolymer of the present invention can be obtained by purging and separating unreacted monomers.

Further, if necessary, alcohol can be added to deactivate the catalyst and a deashing operation can be performed to separate the alcohol and then drying to produce a product.

Any known method may be used to prepare a block copolymer product from the slurry taken out from the second step.

The olefin used in the present invention may be a lower unsaturated hydrocarbon such as propylene, ethylene or butene.

These olefins may be used in combination with propylene, if necessary.

Furthermore, the apparatuses, reactors, etc. used to carry out the present invention are not particularly limited and may be used, and the type, system, attached equipment, etc. may be determined as necessary.

Furthermore, the second step of the present invention may be carried out in two parts,
Operations such as repeatedly performing the first step and the second step of the present invention as one unit can also be adopted as necessary.

A typical manufacturing process of the present invention will be specifically described below with reference to the accompanying drawings.

FIG. 1 of the accompanying drawings shows a typical manufacturing process of the present invention, in which the first step uses propylene itself as a solvent, and the second step uses propylene itself as an inert solvent.

A catalyst containing titanium trichloride and an organoaluminium compound or a prepolymerized polymer catalyst is supplied to autoclave A from line 1.

The autoclave A is supplied with the necessary propylene or propylene and other olefins from line 2.

Further, hydrogen can also be supplied from line 3 if necessary.

In autoclave A, that is, the first step of the present invention, the propylene or propylene and other olefins are polymerized in the required amount, and the polymerization in autoclave A is carried out in a range of 10 to 70% of the total polymerization activity of the catalyst.

When a mixture of propylene and other olefins is used as a monomer, it is preferable to use propylene in an amount exceeding 50% by volume.The catalyst-polymer obtained in the first step, that is, autoclave A, is passed through line 4 as a slurry. Flash tank B
guided by.

In Franch tank B, unreacted propylene or other olefins are removed in a canine by flanching and purged through line 5.

Ganu purged from line 5 can be used as raw material 5 or purified.

The polymer-catalyst obtained in flash tank B is in line 6.
For example, the slurry is introduced into a slurry tank C using a rotary feeder, and is made into a slurry by an inert solvent supplied from line 1.

The slurry prepared in slurry tank C is led through line 8 to autoclave D, that is, to the second step.

In the autoclave D, propylene and ethylene are supplied through lines 9 and 10, respectively, to obtain a block copolymer.

Generally, it is preferable to supply hydrogen from line 11 to adjust the molecular weight.

The block copolymer obtained in autoclave D is led to flash tank E through line 12 to remove unreacted raw materials.

Unreacted raw materials can be recycled to the raw material supply line 9 or 10 of the autoclave D, either as they are or after being separated and purified.

The block copolymer obtained in the flash tank E may be dried after separating the inert solvent using a centrifuge or the like, if necessary.

EXAMPLES In order to explain the present invention more specifically, Examples and Comparative Examples will be described below, but the present invention is not limited to these Examples.

The abbreviations and methods for measuring physical properties used in the examples are as follows.

AIE12C1: Diethylaluminum monochloride PP: Polypropylene (1) The C2H4 content in the polymer was determined by infrared absorption Nuvector analysis.

(2) The number of fish eyes was measured as follows.

Using the obtained block copolymer as a raw material, a blown film is formed by a water cooling method using a 65 gmφ extruder.

The number of fish eyes in the formed film 1007 was calculated visually.

(3) Flexural modulus is 0 measured by ASTM D-790 (4) Izod and Charpy
rpy) The impact values were each measured according to ASTM D-256.

(5) The embrittlement temperature was measured according to ASTM D-746.

(6) The amount of polymerization was expressed as the amount of polymer obtained per unit weight (y) of T iCl s in the first step.

Examples 1 to 7, Comparative Example 1 After treating brown titanium trichloride obtained by reducing titanium tetrachloride with diethylaluminum monochloride in an inert solvent at room temperature with about an equimolar amount of diisoamyl ether,
The brown titanium trichloride was chemically treated with a 65° C. hexane solution containing 1.5 times the molar amount of titanium tetrachloride to obtain titanium trichloride.

The polymerization rate of this titanium trichloride is 3.300. @・Polymer/g・TiCl3/1 hour, and the total polymerization activity was 11.
The weight was 200 g/9 T t CI s.

Using this catalyst, polymerization was carried out according to the process shown in FIG. 1 of the attached drawings.

That is, using a polymerization apparatus in which 3001 autoclaves A, flash tank B, slurry tank C, autoclave D, flash tank E, and washing tank F are arranged in series, the second step is a so-called solvent-free method in which propylene itself is used as a solvent, and the second step is Propylene-ethylene copolymerization was carried out continuously by a so-called solvent method using hebutane as a solvent.

First, titanium trichloride,
Diethylaluminum monochlorite, liquid propylene, and hydrogen gas were continuously fed.

The amount of liquid propylene supplied and the amount of produced propylene homopolymer withdrawn were set so that the average residence time of the catalyst was 4 hours.

Furthermore, hydrogen gas is supplied to achieve a predetermined M, 1. It was controlled so that the value was obtained.

In this way, the slurry of propylene homopolymer produced is continuously transferred to flash tank B so as not to fluctuate the liquid level as much as possible, and after purging unreacted monomers there, the slurry of the propylene homopolymer is transferred to a rotary feeder. Continuously transferred to tank C.

Along with the supply of the polymer, 40% heptane was added to this tank.
The mixture was fed at a rate of 1/hour to form a uniform slurry while stirring.

Subsequently, the polymer slurry was continuously transferred to autoclave D set at 50° C., and ethylene gas, propylene gas, and hydrogen gas were continuously supplied.

The amount of polymer slurry supplied to and withdrawn from autoclave D was set so that the average residence time of the polymer slurry was 2 hours, and the supply of ethylene gas and propylene gas was determined by the molar ratio of ethylene/propylene in the gas phase region. The supply of hydrogen gas was controlled by gas chromatography so that the amount was reduced to 1/3, and the hydrogen gas was supplied at a predetermined amount in the gas phase region.

The block copolymer slurry produced in this way is
It was continuously transferred to a flash tank E, and after purging unreacted monomers, it was transferred to a washing tank F.

Subsequently, the catalyst was treated by adding a predetermined amount of alcohol, and then the solid and liquid were separated using a centrifuge.

The solid thus obtained was dried for 6 hours to obtain a white granular polymer.

The polymerization conditions of each example are shown in Table 1, and the physical property values are shown in Table 2.

In Example 7, ethylene gas was supplied together with liquid propylene in the first step, and the polymer produced in the first step was a random copolymer.

The content of ethylene was 0.7 wt%. Example 8 Heptane 51 was injected into a 101 autoclave equipped with a stirrer, and 50 g of titanium trichloride used in Example 1 and 5 times the mole of diethylaluminium monochloride based on titanium trichloride were added, and the temperature was raised to 50°C. When this amount was reached, the supply of propylene gas was started.

Polymerization was carried out for 1 hour while maintaining the temperature at 50°C, and then unreacted propylene gas was purged to stop the reaction.

The amount of polymerization was 15 g per g of titanium trichloride.

This nullary was continuously supplied to the polymerization tank of the first step, and then Example 3 was carried out under the same conditions to obtain a white granular polymer.

The polymerization conditions are shown in Table 3, and the physical property values are shown in Table 4.

Example 9 The procedure was as in Example 8, except that the prepolymerization time was 2 hours.

The amount of polymerization was 26.9 per g of titanium trichloride.

The polymerization conditions are shown in Table 3, and the physical property values are shown in Table 4.

Example 10 Brown titanium trichloride obtained by reducing titanium tetrachloride with diethylaluminum monochloride in an inert solvent was treated with about an equimolar amount of diisoamyl ether at room temperature, and then
6 of equimolar titanium tetrachloride to the brown titanium trichloride
It was chemically treated with a hexane solution at 5°C to obtain titanium trichloride.

The polymerization rate of this titanium trichloride is 2,90 (1 polymer/j
i-TtC13/h, and the total polymerization activity was 9.900
．． 9 polymer/El-TiC"13.

Using this catalyst, a block copolymer was produced under the same conditions as in Example 2 to obtain a white granular polymer.

The polymerization conditions are shown in Table 5, and the physical property values are shown in Table 6.

Example 11 Brown titanium trichloride obtained by reducing titanium tetrachloride with diethylaluminium monochloride in an inert solvent was treated with about an equimolar amount of diisoamyl ether at room temperature, and then
The titanium trichloride was chemically treated with a 70° C. hexane solution containing 1.7 times the molar amount of titanium tetrachloride relative to the titanium trichloride.

The polymerization rate of this titanium trichloride is 3,600. ! i'polymer/9TiC13/hour, the total polymerization activity was 12.5
00II polymer/gTiCls.

Using this catalyst, a block copolymer was produced under the same conditions as in Example 2 to obtain a white granular polymer.

The polymerization conditions are shown in Table 5, and the physical property values are shown in Table 6.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing typical steps of the present invention. A: autoclave, B: flash tank, C: slurry tank, D: autoclave, E: flash tank, 1; catalyst supply line 12: propylene supply line,
3; Molecular weight regulator supply line, 4; Polymer slurry supply line, 5; Unreacted monomer purge line, 6; Polymer supply line, 1; Inert solvent supply line, 8; Polymer slurry supply line, 9; Olefin feed line, 10;
Olefin supply line, 11; Molecular weight regulator supply line, 12; Block copolymer supply line, 13; Unreacted monomer purge line, 14; Block copolymer slurry take-out line.

Claims (1)

[Claims] 1. Contains titanium trichloride and an organoaluminum compound, and has a catalyst polymerization rate of at least 2500 g.polymer/g.Ti.
a first step of polymerizing propylene or propylene and other olefins in the presence of a catalyst of Cl3/1 hour; and a second step of copolymerizing ethylene and propylene in the presence of the resulting catalyst-polymer. 2 steps are carried out continuously,
The polymerization in the first step is carried out at 10 to 70% of the total polymerization activity of the catalyst, and the catalyst-polymer composition obtained in the first step is continuously supplied to the second step, and the catalyst-polymer composition obtained in the first step is continuously fed into the polymerization tank of the second step. A method for producing a block copolymer, characterized in that copolymerization is carried out under conditions other than when the hydrogen concentration in the gas phase region is 50 mol% or more. 2. The method according to claim 1, wherein the catalyst supplied to the first step is propylene or propylene and other olefins prepolymerized to 1 to 100 g/g of titanium trichloride. 3. The method according to claim 1, wherein the copolymerization in the second step is carried out in the presence of hydrogen such that the hydrogen concentration in the gas phase region of the polymerization tank is 20 mol% or less. 4. The method according to claim 1, wherein the organoaluminum compound is diethylaluminum monochloride.