JPS5812891B2 - Method for producing propylene polymer using pre-polymerization activated catalyst - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing propylene-based polymers using pre-polymerization activated catalysts, and more particularly, the present invention highly suppresses the formation of amorphous polypropylene, and when using catalyst activity. This invention relates to a method for producing a propylene polymer using a catalyst for producing crystalline polypropylene that is activated before polymerization and has increased stability.

It is possible to polymerize propylene to obtain crystalline polypropylene using a combination catalyst of an organic compound of a metal of Groups ① to ① of the periodic table and a transition metal compound of groups ① to ① in the presence or absence of an inert solvent. well known.

When producing crystalline polypropylene industrially according to this method, it is extremely important to reduce the production ratio of amorphous propylene polymer (hereinafter referred to as amorphous polymer) from the viewpoint of economy and solid waste. Several % per propylene
Even the reduction in this amount cannot be ignored, and it is also important from the viewpoint of resource and energy conservation.

Many attempts have been made in the past to suppress the formation of amorphous polymers.

In the past, catalysts were improved by adding a third component such as an amine or an ether to a combination catalyst of a transition metal compound and an organometallic compound.

However, although the method of adding a third component can reduce the production of amorphous polymers, the degree of this is not significant and the propylene polymerization activity also tends to decrease.

Subsequently, improvements were made by chemically treating catalyst components for the same purpose.

For example, a method of chemically treating titanium trichloride having a composition of approximately TiCl3.1/3 AICl3 with a complexing agent (Japanese Patent Publication Nos. 42-3024, 43-12810, 4.7-26385, (See JP-A-48-34281) or a method of modifying titanium trichloride by applying a complex compound of a complexing agent and TiCl4 (JP-A-48-34281).
29694) Furthermore, a method for producing a high-performance titanium trichloride composition using a method different from the conventional method for producing titanium trichloride (
JP-A-47-34478) was developed.

These modified titanium trichloride compositions and organoaluminium compound catalysts have significantly improved polymerization activity and amorphous polymer production rate compared to conventional catalysts in the polymerization of propylene. This is an improved version.

However, although such modified titanium trichloride compositions have improved in performance, the catalysts prepared from them exhibit such improved performance due to significant changes in performance over time during storage in a slurry state and during use. There is a tendency for the stability to be poor, and when a propylene polymerization plant using this catalyst is operated, the production rate of amorphous polymers unexpectedly increases due to deterioration of the catalyst, that is, a decrease in performance due to the instability of the catalyst. often experienced.

In particular, it is known that when operating a propylene polymerization plant using a continuous polymerization method, the production rate of amorphous polymer tends to be higher than when a batch polymerization method is used.

This disadvantage is particularly noticeable in the copolymerization of propylene, for example in the copolymerization of small amounts of ethylene with propylene.

This not only increases the unit consumption of propylene and ethylene monomers (the number of kilograms of monomer required per ton of crystalline polymer product), but also makes it impossible to transport the polymer slurry and separate it by P in the plant. This causes problems such as clogging of the material, and heat loss due to polymer film adhesion to the vessel wall, resulting in a decrease in equipment efficiency.

The object of the present invention is, firstly, to provide a method of using a propylene polymerization catalyst with excellent performance that has been subjected to a novel pre-polymerization activation treatment so that the catalyst has stable performance during the polymerization. In addition, the second objective is to provide a method for extremely reducing the ratio of amorphous polymers produced, and a second purpose is to substantially remove amorphous polymers from polypropylene when producing crystalline polypropylene. The third objective is to provide a polymerization method that does not require removal, and the third objective is to provide crystalline polypropylene that is easy to process after polymerization and has good practical physical properties.

Other purposes will be made clear by the description below.

As a result of various experiments and studies for this purpose, the inventors of the present invention found that a special treatment with improved performance compared to conventional grinding-activated titanium trichloride (e.g. TiC13.+AICI3AA) was found. The polymerization catalyst obtained by reacting a catalyst system consisting of a modified titanium trichloride composition and an organoaluminum compound with propylene under appropriate conditions has a high rate of formation of stereoregular polymers in propylene polymerization, especially in continuous polymerization. The present invention was achieved by grasping and confirming the fact that the production ratio of amorphous polymers can be significantly reduced without reducing the performance, and the reproducibility of the performance is extremely good.

That is, the present invention provides: (1) TiCl3.1/3 AICI3 or AICl
A δ-type titanium trichloride composition obtained by reacting β-type titanium trichloride containing 3 with a complexing agent or a complex compound of a complexing agent and titanium tetrachloride to make it pulverizable and the general formula RnAIC1
A catalyst dispersion obtained by mixing an alkyl aluminum chloride represented by 3-n (R; alkyl, n = 1 to 2) in an inert solvent is maintained at 10°C to 50°C, and a small amount of propylene is added to the liquid. is slowly absorbed, and the absorbed amount is determined to be 0.0% of the weight of the δ-type titanium trichloride composition in the catalyst dispersion.
A method for producing a propylene polymer using an activated catalyst before polymerization, which comprises using a catalyst activated by increasing the amount by 5 to 5 times by weight.

(2) In the method described in (1) above, the complexing agent is a dialkyl ether represented by the general formula R-0-R', a polyethylene glycol dialkyl represented by the general formula R-0-(CH2CH20)n-R' Ether, general 2R-
A method selected from dialkylthioethers represented by S-R', alicyclic organic ethers represented by the general formula (CH2)n-00, and organic acid esters represented by the general formula RCOOR'.

(3) In the method described in (1) above, the pulverization activation includes:
A product obtained by reacting β-type titanium trichloride containing TiCl3・1/3 AIC13 or AICl3 with a complexing agent or a complex compound of a complexing agent and titanium tetrachloride is heated at 0°C to 200°C in a ball mill, vibration mill, or tube mill. A method characterized by doing.

(4) In the method described in (1) above, a method in which propylene is absorbed into the catalyst dispersion in the substantial absence of hydrogen.

(5) The polymerization method according to (1) above, characterized in that propylene is supplied in a fixed amount or within a fixed pressure range to a fixed amount of catalyst in a polymerization vessel.

(6) The method described in (1) above, characterized in that a certain amount of catalyst or propylene is continuously supplied into the polymerization vessel, and the reaction mixture containing the produced polymer is continuously taken out.

(7) A method for producing a propylene polymer according to the method described in (1), (5), or (6) above, characterized in that the resulting polymer is decatalytically treated and then the solvent is removed.

To describe the present invention in detail by way of example, (A) a modified titanium trichloride composition, for example titanium trichloride having approximately TiCl3.-A-AIC3, and a certain complexing agent or the complexing agent; and Ti
A catalyst dispersion is prepared by adding a titanium trichloride composition, which has been chemically treated by adding a complex compound with Cl4, and (B) an alkylaluminum chloride, such as diethylaluminum chloride, to an inert hydrocarbon solvent. The catalyst dispersion system is maintained at a temperature range of 10°C to 50°C, and a small amount of propylene is gradually fed in the substantial absence of hydrogen for a reaction treatment (propylene itself or propylene reacts with the catalyst). In this method, a polymerization catalyst liquid is activated before polymerization, and propylene is then polymerized using a conventional method using the thus activated catalyst.

During this activation, the feed rate of propylene was adjusted to 0.02 to 1 part by weight per hour per 1 part by weight of the titanium trichloride composition, and the total absorbed amount was 0.5 parts by weight per 1 part by weight of the titanium trichloride composition.
Although it is desirable to adjust the amount to ~5 parts by weight, there are other methods of supplying propylene that achieve substantially the same effect, such as a method of supplying an inert solvent in which propylene is dissolved at an appropriate rate, or a method of circulating the catalyst liquid. Alternatively, the propylene may be allowed to pass through a propylene zone (for example, an absorption tower), and the substantial supply rate and reaction amount may be kept within the above ranges.

The titanium trichloride composition for pre-polymerization activation treatment used in the present invention is obtained by reducing titanium tetrachloride with metallic aluminum or by mixing and pulverizing TiCl3 and AICI3, and has a composition of approximately TiC3 + AICl3. A complexing agent or a complex compound of the complexing agent with titanium tetrachloride, which will be described later, is added to titanium chloride before, during, or after pulverization of the composition to cause a reaction.

More preferably, the composition is activated by grinding (
A) a modified titanium trichloride composition chemically treated with a complexing agent such as an organic ether, an organic ketone, and an organic carboxy derivative; or (B) a reaction product of the complexing agent and titanium tetrachloride. selected from modified titanium trichloride compositions that have been chemically treated with

Alternatively, highly active titanium trichloride obtained by reducing titanium tetrachloride with organic aluminum is treated with a complexing agent such as an organic ether before, during or after crushing, and then reacted with titanium tetrachloride. selected from titanium trichloride compositions.

The complexing agent used to obtain the above-mentioned titanium trichloride to be treated is a dialkyl ether represented by the general formula R-O-R' (CH2CH20).

polyethylene glycol dialkyl ether represented by -R', dialkylthioether represented by the general formula R-S-R', alicyclic organic ether represented by the general formula ThH2ffi, organic acid ester represented by the general formula RCOOR', etc. To be elected.

Further, the reaction ratio of titanium tetrachloride and the complexing agent and the addition ratio of the obtained product to the titanium trichloride composition are arbitrarily set within a range that does not impede the effects of the present invention.

The alkylaluminum chloride used in the prepolymerization activation of the catalyst used in the present invention has the general formula RnAICl3-n
Among the compounds represented by (n-1 to 2), ethylaluminum chloride and di-isobutylaluminum chloride are preferred.

Further, as a third component of the combination catalyst of titanium trichloride composition and dialkyl aluminum chloride used for pre-polymerization activation of the catalyst used in the present invention, electrons such as polyether, organic amine, organic phosphorus compound, thioether, etc. A suitable amount of a donor substance such as diethylene glycol dimethyl ether, triethylamine, tri-N-N' dimethyl-phosphoramide, etc. may be added.

As the inert solvent for pre-polymerization activation of the catalyst used in the present invention, non-polymerizable liquid hydrocarbons such as normal pentane, normal hexane, normal hebutane and the like are particularly used.

Both solvents are used after being purified by dehydration, desulfurization, etc. to remove polymerization inhibitors.

In the pre-polymerization activation treatment of the catalyst used in the present invention, if the temperature at which propylene is absorbed into the catalyst liquid is lower than 10°C, the feed rate of propylene must be slowed down, and the time required for the treatment is too long. Not practical.

Even at temperatures lower than 10°C, it is possible to increase the propylene supply rate by applying pressure, for example, but in this case, the molecular weight of the initial polymer formed by the reaction of propylene becomes too high, and this is the result of normal polymerization. It is undesirable because it mixes with the polypropylene product and causes the product to lack uniformity, and when the product is processed into a film or the like, fish eyes are generated and the physical properties of the processed product are impaired.

In addition, at absorption temperatures exceeding 50°C, it is necessary to increase the feed rate in order to achieve uniform absorption, and slow treatment is not possible, but the treated catalyst particles tend to aggregate, which makes continuous polymerization difficult. This is not preferred because the transport pump used to transport the treated catalyst slurry to the polymerization vessel is likely to become clogged.

More decisively, when propylene is absorbed and treated at such high temperatures, the main objective of the present invention, which does not lose its effect of reducing the production rate of amorphous polymers, is completely unachieved.

Next, the propylene used in the pre-polymerization activation treatment of the catalyst liquid used in the method of the present invention may be of a purity level (purity) that is used in normal industrial polymerization.
The following treatment has no effect at all.

That is, for example, when the catalyst liquid is treated with a mixture in which 10 vol% hydrogen is present relative to propylene, the proportion of amorphous polymer produced during propylene polymerization using a propylene polymerization catalyst resulting from the propylene treatment will be the same as that without treatment. As in the case of , there is no decline at all.

As a result of a detailed study of this fact, we found that the hydrogen concentration in the propylene used for this treatment is 1 vol.% or less, preferably 0.5 vol.% or less.
It is necessary to maintain the concentration at 1 vol % or less, and it is more preferably carried out in the absence of hydrogen.

If the propylene supply rate in the pre-polymerization activation treatment of the catalyst used in the present invention is less than 0.02 parts by weight per hour per 1 part by weight of the titanium trichloride composition, the time required for the treatment will be too long to be practical.

In addition, if the amount exceeds 1 part by weight per hour, the molecular weight of the initial polymer produced by the reaction of propylene with the combined catalyst becomes too large, which impedes the uniformity of the quality of the final polypropylene product, and makes it difficult to process the product into films, etc. This is not preferable because fisheye may occur or be likely to occur.

Furthermore, if regular propylene polymerization is carried out using a catalyst obtained by treating propylene with a feed rate in a range other than the above range, that is, 0.02 to 10 parts by weight/hour, the production ratio of amorphous polymer will not decrease. Otherwise, the catalyst particles tend to aggregate during the polymerization, which is not preferable.

The presence of other inert gases than hydrogen, such as nitrogen, argon, propane, etc., does not interfere with the implementation of the prepolymerization activation method of the catalyst used in the present invention.

In the pre-polymerization activation treatment of the catalyst used in the present invention, the amount of propylene absorbed into the combined catalyst is preferably 0.5 to 5.0 parts by weight per 1 part by weight of the titanium trichloride composition.

If it is less than 0.5, the effect of reducing the production ratio of amorphous polymer in the polymerization of the present invention is small, and if it is more than 5.0, the slurry concentration of the catalyst liquid treated with propylene will increase too much, and as a result, it cannot be used in the present invention. During transportation to the polymerization reactor, troubles such as clogging of piping occur frequently, which is not desirable.

The concentration of the titanium trichloride composition when added to the inert solvent is suitably 0.5 to 10% by weight (preferably 5% by weight or less).

If this concentration is too low, such as 0.5% by weight, the solvent will be used in an unnecessarily large amount, and the effect of the prepolymerization activation treatment of the catalyst used in the present invention will decrease, which is not preferable. If it is too high, fluidity may become poor or insufficient when the propylene-treated catalyst liquid is transported to the polymerization vessel, which is not preferable.

In order to activate the catalyst liquid for batchwise or continuous polymerization of propylene as described above before polymerization, it is desirable to use a dedicated absorption tank or reaction tank.

In this case, an ordinary agitator is sufficient as the stirring means.

In addition, this reaction tank does not require a pressure-resistant one;
A material having a pressure resistance of about g/cm2G is sufficient.

Although it is possible to use the catalyst slurry storage tank itself, it becomes difficult to adjust the concentration of catalyst components and other components, maintain a constant amount of activated catalyst, etc.

As mentioned above, in order to significantly reduce the production ratio of amorphous polymer in the production of polypropylene of the present invention,
It is clear that the type of catalyst used and the propylene treatment conditions must match.

Next, a general method for activating a catalyst before polymerization used in the present invention will be exemplified.

A predetermined amount of an inert hydrocarbon, such as n-hexane, is charged into a catalyst preparation tank equipped with a stirrer, and while stirring, a predetermined amount of diethylaluminum chloride is charged, and then a predetermined amount of a titanium trichloride composition is added thereto.

Next, while keeping the temperature of the catalyst liquid at 10 to 50°C and stirring, add propylene to the catalyst liquid in the catalyst preparation tank at an absorption amount of 0.02 to 1.0 kg per 1 kg of titanium trichloride composition. 0kg/hr
．． The amount of absorption is 0.5 to 5.5% per 1 kg of titanium trichloride composition. When the 0 kg range is reached, the propylene injection is stopped.

The catalyst solution thus prepared is fed into a polymerization tank batchwise or continuously depending on the polymerization method.

In the polymerization tank, propylene, hydrogen, and an inert solvent are fed under predetermined conditions to continuously produce polypropylene in the form of a slurry.

The polymer slurry continuously extracted from the polymerization tank undergoes various known steps to obtain purified polypropylene (however, extraction and separation of soluble polymers can be omitted).

According to the method of the present invention, when homopolymerization of propylene is carried out in a conventional batch-type or continuous polymerization apparatus using a pre-polymerization activated catalyst liquid, (1) the stability of the catalyst in the catalyst storage tank is improved ( In other words, (2) the rate of amorphous polymer production is significantly increased without reducing the polymerization rate of propylene, and (2) the rate of production of amorphous polymer is significantly reduced without decreasing the polymerization rate of propylene. It is possible to obtain values of less than 1% for propylene.

Furthermore, (3) since the molecular weight and viscosity of the amorphous polymer produced are low, the thermal efficiency and equipment efficiency of the propylene polymerization apparatus can be improved.

Further, the practical physical properties of the crystalline polypropylene obtained by the method of the present invention are almost the same as those of the conventional ones even when the soluble polymer is not extracted and separated, and there is no problem in terms of use.

When using the pre-polymerization activated polymerization catalyst used in the method of the present invention which brings about such remarkable effects, as mentioned above, the amorphous polymerization process that is essential in conventional batch-type or continuous polymerization methods is required. It is possible to obtain all the produced polymers as crystalline polypropylene products without carrying out separation and removal operations, and in fact, it is possible to obtain all the polymers produced using the activated catalyst of the present invention in practical use. The physical properties were no different from those of commercially available polypropylene.

Therefore, by using the pre-polymerization activated catalyst used in the present invention, it is possible to perform a manufacturing process that does not require the separation step of an amorphous polymer in a batch-type or continuous production equipment for polypropylene, and from the perspective of improving equipment efficiency. It is also possible to significantly reduce the manufacturing cost of polypropylene.

These effects can be obtained by applying the prepolymerization activated catalyst used in the present invention to polymerization in liquid propylene in the absence of an inert medium and gas phase polymerization.

The present invention will be explained below based on various examples, comparative examples, and reference examples.

Examples 1 to 6, Reference Examples 1 and 3 500 liters of normal hexane that had been purified in advance was charged into a catalyst preparation tank with an internal volume of IM3, and then an appropriate amount of hexane solution of a predetermined amount of diethylaluminum chloride was added to each tank while stirring. Add an appropriate amount of titanium trichloride or titanium trichloride composition shown in the table to bring the total volume to 700 liters.

The catalyst liquid is maintained at a predetermined temperature, and propylene is continuously fed at a predetermined rate for 6 hours to activate the catalyst of the present invention.

During this time, the temperature of the catalyst liquid increases by 5 to 10°C due to the reaction.

On the other hand, normal hexane and liquid propylene were added in advance to a reactor with an internal volume of 2M3 at 600 l/hr and 400 l/hr, respectively. Continuously feed the reactor at a speed of 100 mL and automatically open and close the extraction pipe to keep the liquid level in the reactor constant.

Under this condition, the activated catalyst solution of the present invention, which has been treated in the preparation tank, is pumped at a rate of 3 l/hr. feed into the reactor continuously at a rate of .

The polymerization reaction was controlled to 70° C. and 10 kg/cm, and a predetermined amount of hydrogen was fed to produce polypropylene, which was continuously carried out for 20 hours.

During this time, the slurry continuously extracted from the reactor was subjected to the steps of separating unreacted propylene, removing catalyst, removing the amorphous polymer, and removing the solvent according to a known method to obtain crystalline polypropylene powder.

Comparative Examples 1 to 4, Reference Examples 2 and 4 Same as Example 1 except that titanium trichloride or titanium trichloride composition shown in Table 1 was used and the operation of absorbing propylene in the catalyst preparation tank was removed. Propylene was polymerized under the following conditions.

Explanation A of Table 1: Milling activated TiCl3・1/3 AICl35
g of hexane at 60°C for 2 hours. l2 and 1 m.
11 of (n-Bu)2O and reacted B: TiC3・+AICl3 activated by grinding was immersed in Et
20 and TiC14 treated with a reaction product C: Titanium trichloride composition obtained by the same method as described in JP-A-47-34478 D: Commercially available titanium trichloride AA (Toho Titanium Products) E: Commercially available titanium trichloride AA was heated under reduced pressure (1.00 mmHg).
) was heat-treated at 150° C. for 1 hour Judging from the results of the examples and the corresponding comparative examples, the effect of propylene treatment of the catalyst liquid on the amorphous polymer production rate is very significant.

This tendency is also seen in the results of the reference examples, but as seen from the relative ratio of the production rate of amorphous polymers, it is especially true for the polymerization examples using the catalyst system activated by the method of the present invention. Remarkable.

In addition, from the physical properties of the amorphous polymers produced, the molecular weight and softening point of the amorphous polymers produced in Examples 1 to 6 according to the method of the present invention are significantly lower than in other examples. I can see that you are doing it.

Example 7 Titanium trichloride composition B was prepared using the same equipment as Example ①.
1 kg of Et2AICI and 6 kg of Et2AICI as catalyst raw materials, and 1.5 kg of propylene at a temperature of 22 to 30°C. 5 kg/hr. The total absorption amount is 8. The activated catalyst solution of the present invention was obtained by processing the catalyst until it weighed 25 kg.

As a result of carrying out the same polymerization operation as in Example 1 using this catalyst liquid, 820 parts by weight of stereoregular polypropylene was obtained per unit weight of the catalyst.

This polymer has a melt flow rate of 6.4 and a bulk density of 0.
．． 48, IR-ζ0.918.

The production rate of amorphous polymer produced in this polymerization is 0.7
It was 2%.

Comparative Examples 5 and 6 An experiment was conducted under the same conditions as in Example 7, except that instead of the pre-polymerization activation treatment of the catalyst liquid used in the present invention, the catalyst liquid was treated with propylene in the presence of hydrogen.

That is, when hydrogen was treated with propylene in an amount of 10% by volume based on the propylene used, and the resulting catalyst was subjected to polymerization, 790 parts by weight of stereoregular polymer was obtained per unit weight of the catalyst.

This polymer has a melt flow rate of 5.8 and a bulk density of 0.
40, IR-ζ 0.920.

In addition, the amorphous polymer produced in this polymerization is 2.58%
(Comparative Example 5).

On the other hand, when polymerization was carried out using a catalyst treated with propylene in the presence of 0.1% by volume of hydrogen, 1.52% of an amorphous polymer was produced (Comparative Example 6).

As seen from Example 7 and Comparative Examples 5 and 6, it is clear that when hydrogen is present in the propylene treatment operation, the effect of suppressing amorphous polymers is lost or diminished.

Comparative Example 7 An experiment was conducted in the same manner as in Example 7, except that the catalyst liquid was treated with propylene at a temperature of 70 to 75°C.

As a result, 3.06% of amorphous polymer was obtained.

From the results of Example 7 and Comparative Example 7, it is clear that the production rate of amorphous polymer increases when temperature conditions higher than the range of the present invention are applied in the operation of treating the catalyst liquid with propylene.

Comparative Example 8 The same operation as in Example 7 was carried out except that in the propylene treatment of the catalyst liquid, the propylene supply rate was set to 20 kg/hour per 1 kg of titanium trichloride composition B.

As a result, 4.0% of amorphous polymer was produced.

The results of Example 7 and Comparative Example 8 show that when a propylene feed rate higher than the range of the present invention is applied in the propylene treatment operation, the production rate of amorphous polymer increases.

Examples 9 and 10 Using the catalysts prepared in Examples 3 and 7, continuous copolymerization of propylene and a small amount of ethylene was carried out.

The results are shown in Table 2 together with Comparative Example 9.

Comparative Example 9 Using the catalyst prepared in Comparative Example 2, a copolymerization experiment was conducted in the same manner as in Example 9.

From this result, it is preferable that the polymerization catalyst used for copolymerization be one that has been treated with propylene according to the method of the present invention, and the production rate of amorphous polymers is extremely low compared to an untreated catalyst.

Example 11 The polymerization catalyst prepared in Example 1 was stored in a catalyst tank, kept under stirring for 3 days, and then continuously fed into a polymerization vessel to perform the same experiment as in Example 1.

The results are shown in Table 3.

Comparative Example 10 An experiment was carried out in the same manner as in Comparative Example 2, except that the polymerization catalyst liquid was stored under stirring for 3 days.

The results are shown in Table 3.

As is clear from the table, the catalyst prepared by the method according to the present invention exhibited excellent stability when stored in a slurry state.

This fact indicates that the intended performance of the present invention can be maintained during the normal storage period used in plant operations.

Usage Examples 1, 2 2.6 to the polypropylene powder obtained in Example 7
Add 0.1% ditertiary butylphenol at 23°C.
The pellets extruded in Example 7 and the polymerization slurry obtained in Example 7 were separated by extraction to deactivate the catalyst, and then dried as they were without separating and removing the amorphous polymer. 0.1% of Charybutylphenol was added to pelletize.

A test piece was made from the obtained beresoto and its practical properties were evaluated (Table 4).

According to the same table, it is clear that there is no difference in practical physical properties between the two polymers.

Claims (1)

[Claims] 1 δ-type titanium trichloride composition obtained by reacting β-type titanium trichloride containing TiCl31/3AICI3 or AICI3 with a complexing agent or a complex compound of a complexing agent and titanium tetrachloride and pulverization activation and general formula RnAICI3,
A catalyst dispersion obtained by mixing (R; alkyl, n-1 to 2) alkylaluminum chloride in an inert solvent is maintained at 10°C to 50°C, and the liquid is heated to zero in the substantial absence of hydrogen. A small amount of propylene is slowly absorbed at a rate of .02 to 1.0 times the weight of the δ-type titanium trichloride composition/hour, and the absorbed amount is determined by the weight of the δ-type titanium trichloride composition in the catalyst dispersion. 1. A propylene-based polymer using a pre-polymerization activated catalyst, characterized in that a catalyst activated by 0.5 to 5 times the weight of the propylene polymer is used.