JPS6125728B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a stabilized polyolefin, and more particularly, to an improvement in the method for producing a stabilized polyolefin by inactivating the residual catalyst in the polyolefin with an epoxide. It is.

Polyolefins are made by combining olefins such as ethylene and propylene with halogen compounds of transition metals such as titanium, vanadium, and zirconium.
It is obtained by polymerization using a catalyst prepared from an organometallic compound such as an alkyl aluminum or an alkyl aluminum halide.

This type of polymerization catalyst, especially its transition metal halogen compound, is insoluble in inert hydrocarbons as diluents in the polymerization reaction and in the liquefied monomers present in excess, and most of them are contained in the resulting polymer after the polymerization reaction. remains. These residual catalysts cause undesirable coloring during thermoplasticization of polyolefins.
Since it reduces the thermal stability of the molded product, it must be removed from the polymer as much as possible.

As a method for removing the residual catalyst from the produced polyolefin, there are known methods such as treating the produced polymer with alcohol to solubilize the remaining catalyst, followed by extraction with water or washing with liquefied hydrocarbon. However, in this alcohol treatment method, the hydrogen halide generated by the reaction between the remaining catalyst and alcohol corrodes the equipment, and not only does the equipment require expensive corrosion-resistant materials, but also dissolves the decomposition products of the catalyst. Complex equipment and processes are required to recover and purify alcohol, hydrocarbons, etc. from the cleaning fluid used. Therefore, the development of a method that can easily remove or deactivate the residual catalyst in the produced polyolefin is of extremely important industrial significance.

In recent years, various highly active catalysts have been proposed with the aim of simplifying the catalyst removal process by reducing the amount of catalyst used. Polyolefins polymerized in the presence of this type of highly active catalyst contain a relatively small amount of residual catalyst, but a small amount of catalyst with metal-halogen bonds still remains, and the polymer Generates active halogen during thermoplasticization,
Corrodes equipment. In addition, polyolefins containing a small amount of residual catalyst of this type have extremely poor thermal stability when only ordinary stabilizers are added, and undesirable coloring occurs during thermoplasticization. Such coloring is caused by reaction products between low-valent transition metal halogen compounds and phenolic antioxidants, etc.
It is also known that this coloration can be prevented if the catalyst remaining in the polymer is treated with a compound that has special chelating ability. In short, even if polyolefin is polymerized using a highly active catalyst and has a small amount of residual catalyst, it will lack commercial value if it is not deactivated. In order to improve stability, it is essential to remove active halogens and inactivate transition metal compounds.

The present inventors further discovered that the polyolefin obtained using a highly active catalyst was subjected to extremely simple treatment, that is, the polyolefin slurry was treated with an epoxide, and a part of the liquid phase was separated from the resulting polyolefin slurry. Polyolefin liquid content 40~120
It has been found that the passivation process can be achieved by obtaining a weight percent crude polyolefin and then subjecting the crude polyolefin to an evaporation process. However, according to this method, the liquid content of polyolefin is 40~
Since 120% by weight of crude polyolefin is evaporated, a considerable amount of thermal energy is required. Therefore, if the liquid content of crude polyolefin can be lowered,
The thermal energy required for evaporation is reduced, and the evaporator and the vapor recovery device can be downsized, thereby further simplifying the inactivation process. Additionally, if the amount of liquid contained in the crude polyolefin is small, the amount of volatile halogen-containing compounds contained in the liquid will also be reduced, reducing corrosion problems in the evaporation equipment, and reducing the amount of volatile halogen-containing compounds contained in the liquid. The amount of transition metal compound may also be reduced, improving the color of the product polyolefin and reducing the amount of stabilizer required.

However, as a result of intensive study on the above points, the present inventors found that if the polyolefin has specific granular properties, it is possible to reduce the liquid content of the crude polyolefin to less than 40% by weight in the above treatment. We have completed the present invention by discovering that it is possible to further simplify the deactivation treatment process, reduce corrosion of the evaporator, improve the color of the polyolefin product, and reduce the amount of stabilizer.

That is, the gist of the present invention is to polymerize α-olefin in the presence of a catalyst containing a transition metal halide compound and an organoaluminum compound, so that the bulk density is 0.4 g/cc or more and the porosity is 0.2 cc/g or less. The first step is to obtain a polyolefin, the second step is to make a slurry of the polyolefin, the third step is to add epoxide to the polyolefin slurry obtained in the second step to deactivate the remaining catalyst in the polyolefin. Part of the liquid phase is separated from the polyolefin slurry obtained in the 3rd step to determine the liquid content of the polyolefin.
Fourth step to separate less than 40% by weight of crude polyolefin
and a fifth step of evaporating the crude polyolefin.

To further explain the method of the present invention in detail, the polyolefins used in the present invention include ethylene, propylene, butene-1, 4-methylpentene-1,
Examples include polymers or random or block copolymers of α-olefins such as 3-methylbutene or mixtures of these α-olefins.

Further, in the present invention, the catalyst used for the polymerization of these α-olefins is mainly composed of a transition metal halide compound and an organoaluminum compound. As the first component of the catalyst, a variety of transition metal halogen compounds can be used, but titanium trichloride or titanium trichloride combined with other metal halogen compounds is particularly preferred. It is a eutectic or a mixed crystal. Further, these halogen compounds may be a pulverized product, a mixture of two or more types, a mixture with other organic compounds, or a complex compound, and there is no problem even if they are supported on a suitable carrier.

Although various organoaluminum compounds can be used as the second component of the catalyst, aluminum alkyls and aluminum alkyl halides are particularly preferred. In addition to these two components, the catalyst also contains N,
A third component such as various compounds containing O, P, or Si, or an unsaturated hydrocarbon may be added.
Particularly preferred catalysts for application of the present invention are so-called high-activity catalysts, with a catalyst efficiency (number of grams of polymer produced per gram of catalyst) of 5,000 or more, preferably 8,000 or more.
That's all.

The α-olefin polymerization reaction of the present invention, that is, the first step of the present invention, can be carried out by various methods. For example, polymerization can be carried out in the presence of the above-mentioned catalysts and diluents. As such a diluent, a hydrocarbon such as propane, butane, pentane, hexane, heptane, etc., kept in a liquid state, or an excess of monomer kept in a liquid state at the polymerization reaction pressure is used. Preferred diluents are relatively low boiling hydrocarbons, such as hydrocarbons with boiling points below 40°C, more preferably hydrocarbons such as propane, butane, with boiling points below 10°C, or monomers. Therefore, from the viewpoint of process simplification, it is most advantageous to use a liquefied monomer as a diluent. Note that a so-called gas phase polymerization method in which polymerization is performed using a gaseous monomer without using a diluent can also be used.

In the first step of the polymerization reaction of the present invention, a polyolefin having a bulk density of 0.4 g/cc or more and a porosity of 0.2 cc/g or less is obtained. Here, bulk density is a value measured according to JIS 6721, and porosity is the total volume of pores contained within polymer particles that can contain gas or liquid, expressed per unit weight of polymer particles. Anal.Chem.27 1963
(1955) or Catalyst Engineering Course, 4, 67, etc. If the bulk density is less than 0.4 g/cc or the porosity exceeds 0.2 g/cc, the settling volume concentration of the slurry in the second step described below will be small, and the content of the crude polyolefin obtained in the fourth step will be lower. This is not preferable because the liquid ratio also increases. Bulk density is 0.4g/cc or more and porosity is 0.2
If the polyolefin powder is less than g/cc, when it is made into a slurry in the second step described below, the sedimentation volume concentration of the slurry will be large, that is, 50% by weight or more, and the fourth step
The liquid content of polyolefin obtained in the process decreases.

Therefore, an advantageous polymerization method for obtaining a solid polyolefin having such bulk density and porosity uses titanium trichloride, which does not contain an inert metal halide such as aluminum chloride, as a transition metal halide component. , isotactic
High catalytic efficiency (5000 or more, preferably 8000 or more) under conditions that yield a polyolefin with an index (proportion of solid insoluble matter when the polymer is extracted with boiling n-heptane for 6 hours, weight %) of 95% or more. An example of this method is polymerization. The highly active titanium trichloride used here, which does not contain an inert metal halide such as aluminum chloride, is obtained by reducing titanium tetrachloride with an organoaluminum compound in the presence of ether to form a liquid, and then liberating it. A method for obtaining fine particulate solid titanium trichloride using a chemical agent, reducing titanium tetrachloride with an organoaluminum compound,
It can be easily obtained by treating the obtained reduced solid with ether and then using titanium tetrachloride or carbon tetrachloride.

Furthermore, in order to obtain such a polyolefin with high bulk density and low porosity, when precipitating fine particulate titanium trichloride from the liquid titanium trichloride,
In addition to using improved catalysts such as the presence of iodine, the presence of seed crystals to be precipitated in two stages, or the presence of a carrier, it is also possible to use improved catalysts such as the presence of a third component such as a carboxylic acid ester during polymerization, or to perform prepolymerization. It is preferable to use a polymerization method. In the case of slurry polymerization, it is preferable to use aliphatic hydrocarbons such as pentane, hexane, heptane, etc., and gas phase polymerization is more preferable. The polymerization temperature is selected from a range of 70°C or less, the cocatalyst organoaluminum compound/titanium trichloride molar ratio is 2 to 50, and the titanium trichloride concentration in the polymerization reaction system is 0.1% by weight or less based on the solvent. . Alternatively, the batch method may be used, but
It is advantageous to carry out continuous polymerization. Bulk density 0.4g/
To explain in more detail using an example how to obtain a polyolefin having a porosity of cc or more and a porosity of 0.2 cc/g or less, as is clear from Example 1, titanium tetrachloride and ether are added to an organic solvent to obtain a homogeneous polyolefin. By making a solution and adding an organoaluminum compound to this, a blackish brown homogeneous solution of titanium trichloride is obtained.
By heating this solution, a purple solid titanium trichloride catalyst is obtained. Together with the thus obtained catalyst, triphenyl phosphite was added as a tertiary catalyst using diethylaluminium chloride as a co-catalyst.
As a component, when polymerizing propylene with high catalytic efficiency, the bulk density (ρ _B ) is 0.45 g/cc and the porosity (V _G )
Polypropylene with a content of 0.15 cc/g is obtained.

In the second step of the present invention, the polyolefin obtained in the first step is made into a slurry. The slurry concentration is preferably 5 to 55% by weight, particularly 10 to 40% by weight. The reason for using a polyolefin slurry is to improve the contact efficiency between the polymer and the epoxide to be added. That is,
After polymerization, the residual catalyst contained in the polymer is protected by the polymer, and direct contact with the epoxide is not easy. Provides effective stabilization.

To form a slurry in the second step and adjust the slurry concentration, an appropriate diluent can be added to the polyolefin obtained in the first step. Similar diluents can be used. The diluent may be added directly to the reaction product of the first step, or may be added to the reaction product of the first step by purge treatment,
Alternatively, it may be added after flashing treatment is performed to remove some or all of the unreacted monomers and/or the diluent used in the polymerization reaction. Further, the first step and the second step of the present invention can be performed simultaneously. That is, it is possible to carry out the polymerization reaction of the present invention by adding a sufficient amount of diluent, and to carry out the polymerization reaction so that the produced olefin remains as it is, and a polyolefin slurry having a slurry concentration of 5 to 55% by weight is obtained. Yes, such embodiments are particularly preferred.

Therefore, one of the characteristics of the polyolefin slurry obtained in the second step of the present invention is that the sedimentation volume concentration is 50% by weight or more. Here, the sedimentation volume concentration is measured by the following method, and the following formula
Defined in (1).

That is, the polyolefin inslurry is placed in a measuring cylinder, thoroughly mixed, and then allowed to settle naturally. Polymer particles begin to deposit, forming an interface between the deposited layer and the supernatant layer, and grow upwards. When the sedimentation is completed and the height of the interface between the sediment layer and the supernatant liquid layer does not change over time, only the supernatant liquid layer is removed by decanting.
For the deposited layer, the percentage of the weight of the polymer relative to the sum of the weights of the liquid and the polymer is defined as the sedimentation volume concentration.

Sedimentation volume concentration = Polymer weight of deposited layer / (polymer + liquid) weight of deposited layer (1) If the sedimentation volume concentration is less than 50% by weight, the liquid content of the crude polyolefin obtained in the fourth step below will be I don't like it because it gets bigger. In order to make the sedimentation volume concentration 50% by weight or more, the first
In addition to increasing the bulk density and decreasing the porosity of the polyolefin solid obtained in the process, it is sufficient to use as light a solvent as possible as a diluent.

In the third step of the present invention, epoxide is added to the polyolefin slurry obtained in the second step to inactivate the remaining catalyst in the polyolefin. The addition of epoxide in this third step can be carried out simultaneously with the second step. For example, when adding a diluent in the second step,
The epoxide can be mixed with the diluent or added simultaneously without mixing, so that the addition of the epoxide in the second and third steps of the present invention can be carried out substantially simultaneously.

The epoxide used in the third step of the present invention is preferably an epoxide having 2 to 8 carbon atoms, such as ethylene oxide, propylene oxide, 1,2-epoxybutane, 2,3-epoxybutane, 1,2-epoxypentane, 2・3
-Epoxypentane, 1,2-epoxypentene, 1,2-epoxyhexane, 1,2-epoxyhexene, cyclohexene oxide, styrene oxide and epichlorohydrin.
Particularly preferred epoxides are those with low boiling points such as ethylene oxide and propylene oxide. The amount of epoxide used is usually 15 times or less by mole relative to the amount of catalyst components in the slurry (total amount of transition metal halide compound and organoaluminum compound), and the preferred amount is 10 times or less by 1 mole. The range is up to twice that.

The epoxide may be added to the polyolefin inslurry as it is, or may be mixed with a suitable diluent. The diluent for adding the epoxide is preferably the same type as the diluent constituting the polyolefin inslurry, but a different type of diluent can also be used.

The temperature of the inactivation treatment by adding epoxide is above room temperature, preferably above 70°C and below the melting temperature of the polymer, particularly preferably between 80°C and below.
It is in the range of 100℃. At temperatures below room temperature, the reaction between the remaining catalyst in the polymer and the epoxide does not proceed sufficiently, making it difficult to remove the halogen and deactivate the catalyst. Further, at temperatures above the melting temperature of the polymer, the polymer melts and sufficient contact with the epoxide does not take place, making it similarly difficult to expect removal of halogen and deactivation of the catalyst. The inactivation treatment time is usually several minutes to 180 minutes, preferably 10 to 180 minutes.
It is 60 minutes.

In the fourth step of the present invention, a portion of the liquid phase is separated from the polyolefin slurry obtained in the third step after the catalyst deactivation treatment.

As the separation means, decantation, filtration, natural sedimentation, or centrifugal sedimentation can be used.

The liquid phase separated in the fourth step is mainly composed of a diluent and/or unreacted monomer as a liquid component constituting the polyolefin inslurry. Contains volatile halides, unreacted epoxides, and small amounts of atactic polyolefins. When the separated liquid phase is distilled, the diluent, volatile halide, and unreacted epoxide can be recovered or obtained as the top components, and the atactic polyolefin solution can be recovered as the bottom liquid. The recovered diluent can be recycled and used repeatedly as a diluent for the polymerization reaction in the first step and/or for the polyolefin slurry in the second step. The mixture of volatile halogen-containing compounds and unreacted epoxides is enriched in volatile halogen-containing compounds and epoxides, for example by further distillation, and the epoxides are recycled for catalyst deactivation in the third step. Can be reused.

Therefore, in the fourth step of the present invention, crude polyolefin having a liquid content of less than 40% by weight relative to polyolefin can be obtained by the mechanical liquid phase separation means as described above. The liquid content in the crude polyolefin is
If it is 40% by weight or more, the amount of liquid to be evaporated in the next fifth step increases, which is not preferable.

In the fifth step of the present invention, the crude polyolefin having a liquid content of less than 40% by weight obtained in the fourth step is evaporated. This evaporation treatment is a treatment for evaporating liquid components contained in the crude polyolefin, and is performed without washing the crude polyolefin with a liquid hydrocarbon or the like. The crude polyolefin contains volatile halogen-containing compounds generated in the third step and the remainder of unreacted epoxide (remaining unaccompanied by the separated liquid phase), but after the evaporation treatment in the fifth step During this process, these are vaporized and removed from the polyolefin simultaneously with the evaporation of the liquid components.

Therefore, the gas phase generated in the evaporation treatment in the fifth step consists of diluent and/or monomer, unreacted epoxide, volatile halogen-containing compounds, etc., but the volatile halogen-containing compounds are relatively small. Since it has a high boiling point, it can be easily liquefied and separated by condensation by cooling, for example. The unreacted epoxide, diluent and/or monomer from which volatile halogen-containing compounds have been removed in this way can be recycled and used as the epoxide and diluent in the third and second steps. Therefore, in the case of the present invention, contamination of monomers, diluents, etc. by catalyst decomposition products is relatively less of a problem.

Therefore, in the fifth step of the present invention, since the amount of liquid in the crude polyolefin to be evaporated is small, the evaporator and the vapor recovery device may be small-sized, and the energy required for evaporation may also be small. . In addition, the volatile halogen-containing compound produced in the third step is corrosive under the high temperature and high concentration conditions in the evaporator and recovery device of the fifth step, but in the fifth step of the present invention, the volatile halogen-containing compound in the crude polyolefin is corrosive. The lower amount of liquid reduces the amount of volatile halogen-containing compounds involved, reducing the corrosion problem described above. Therefore, inexpensive materials can be used for the evaporator and recovery device.

In short, the method for producing a stabilized polyolefin of the present invention is a method characterized by including the five steps from the first step to the fifth step described above. As described above, in some cases, two of these steps can be performed substantially simultaneously. Moreover, the method of the present invention can also include other steps in addition to these five steps. For example, a purge or flash treatment step for removing some or all of the monomer and/or diluent may be inserted between the first step and the second step, and a purge or flash treatment step may be inserted between the first step and the second step, and a In the epoxide treatment, it is also possible to add alcohol together with the epoxide so that part of the catalyst is partially decomposed by the alcohol.

The method of the present invention has been described above, and as described above, the method of the present invention involves adding epoxide to the polyolefin inslurry to inactivate it, then removing a portion of the liquid phase, and evaporating the remaining liquid. This is an industrially advantageous method for inactivating the residual catalyst in the polyolefin solid after the polymerization reaction through a simple process that (1) allows the evaporation treatment device and the vapor recovery device to be made smaller; (2) the evaporation treatment device (3) The color of the product polyolefin can be improved; and (4) the stabilizer used to maintain the color and thermal stability of the product polyolefin can be used. It is possible to achieve merits such as being able to reduce the required amount.

Next, the present invention will be explained with reference to examples.

In the following examples, the bulk density of the polymer (abbreviated as ρ _B ), isotactic index (abbreviated as II), and settling volume concentration of the polymer slurry (abbreviated as wc) were measured using the following methods: Using the method described above, the porosity (V
Abbreviated as _G. ) was measured using the following method (Anal.Chem., 27 , 1963).

Accurately weigh approximately 2 g of dry polymer powder into a weighing bottle. 13. Place the weighing bottle containing the polymer powder above the inner pan of a vacuum dessicator containing a 1% by volume solution of cetane in carbon tetrachloride. After evacuating the desiccator and thoroughly replacing the air with carbon tetrachloride vapor, the desiccator was left standing at 25°C for 10 hours. After the pressure was restored, the weight increase per unit weight of the polymer powder was converted to the liquid volume of carbon tetrachloride, which was defined as the porosity.

Example 1 (a) Production of a homogeneous titanium trichloride solution In a 300 ml four-necked flask that had been thoroughly purged with dry argon, 75 ml of n-heptane and 5.0 ml of titanium tetrachloride were charged, followed by 13.3 ml of di-n-octyl ether. Added. Next, 0.19 g of iodine was added to make a homogeneous solution, and the solution was further stirred.
While maintaining the temperature at 30℃, add 1.9ml of diethylaluminum monochloride to it and leave it for about 1 hour.
When the temperature was maintained at .degree. C., a homogeneous solution of titanium trichloride in n-heptane was obtained which was blackish brown with a slight green tinge.

When the homogeneous solution of titanium trichloride obtained above was heated to 90°C, a purple titanium trichloride precipitate was observed to form during the temperature rise. 1 at 90℃
After continuing to stir for an hour, the precipitate was separated and washed five times with 100 ml of n-hexane to obtain a purple solid titanium trichloride catalyst.

(b) Polymerization of propylene Using an induction-stirred autoclave with a capacity of 2, under a sufficiently dry argon atmosphere, 35 mg of titanium trichloride prepared in (a), 155 mg of diethylaluminium chloride, 3 mg of triphenyl phosphite, and 750 ml of n-heptane. Prepare
Fill with hydrogen gas up to 0.6Kg/cm ² at gauge pressure.
Raise the temperature to 60℃ and pump propylene at 12Kg/gauge pressure.
cm ² was introduced, and after polymerization was carried out for 4 hours, unreacted propylene gas was purged to obtain a polymer slurry. The polymer concentration of this slurry was adjusted to 35% by weight. The wc of this slurry was 57% by weight.

In addition, Ti and Cl are 40 ppm and 40 ppm, respectively, in the polypropylene separated from this slurry.
It contained 162ppm. No iodine was detected. Also, its polypropylene II is 97.3%
It was hot. In addition, this II boils the polymer.
- It is the ratio (% by weight) of solid insoluble matter when extracted with heptane for 6 hours. Also, the ρ of this powder
_B was 0.45 g/cc and V _G was 0.15 cc/g.

(c) Post-treatment of polypropylene 4.2 mg of propylene oxide is added to 100 g of the polypropylene slurry with a polymer concentration of 35% by weight obtained in (b) and treated at 83°C for 1 hour. The treated slurry is centrifuged to obtain crude polypropylene having a liquid content of 23% by weight relative to the polymer. This crude polypropylene was dried with hot air at a temperature of 60°C for 2 hours.

(d) Physical properties of product polypropylene The polypropylene obtained in (c) had II of 98.1%, Ti and Cl contents of 9 ppm and <5 ppm, respectively, and was a white powder.

In addition, this polypropylene was added with tetrakis-[methylene-], a commercially available antioxidant for polypropylene.
(3,5-di-t-butyl-4-hydroxycinnamate) (trade name manufactured by Ciba Geigy)
Irganox 1010) and dilauryl thiodipropionate, the former for 100 g of polypropylene.
Add and blend the latter at a ratio of 0.07g and 0.25g,
Press molded at 210℃ to obtain a colorless and transparent test piece (thickness/mm), and this test piece was subjected to a polymer long-term thermal stability test (hereinafter referred to as "LTHS test") in an electric furnace at 150℃. Where I went,
Results were obtained in 30 days.

Example 2 (c) Post-treatment of polypropylene 4.2 mg of propylene oxide was added to 100 g of the polypropylene slurry obtained in Example 1 (b) (polymer concentration 35% by weight), and the mixture was treated at 83° C. for 1 hour.

The slurry after treatment was filtered to obtain a filter cake having a liquid content of 30% by weight relative to the polymer.

This cake was dried with hot air at 60°C for 2 hours.

(d) Physical properties of the product polypropylene The polypropylene powder obtained in (c) above
The Ti and Cl contents were 11 ppm and 5 ppm, respectively, and the powder was white.

Irganox 1010 and dilaurylthiopropionate were blended into this polypropylene in the same proportions as in Example 1(d), and an LTHS test was conducted under the same conditions. Results were obtained on the 29th.

Comparative Example 1 (b) Polymerization of propylene 36 mg of titanium trichloride, 155 mg of diethylaluminum chloride, and 750 ml of n-heptane prepared in Example 1(a) were used in an induction-stirred autoclave with a capacity of 2 under a sufficiently dry argon atmosphere. and hydrogen gas at a gauge pressure of 0.6
Enclose up to Kg/cm ² . The temperature was raised to 75° C., propylene was introduced at a gauge pressure of 12 kg/cm ² , polymerization was carried out for 4 hours, and unreacted propylene gas was purged to obtain a polymer slurry. The polymer concentration of this slurry was 35% by weight.

In addition, Ti and Cl are 42 ppm and 42 ppm, respectively, in the polypropylene separated from this slurry.
It contained 170ppm. Moreover, the II of the polypropylene was 94%.

Incidentally, II is the proportion (% by weight) of solid insoluble matter when the polymer is extracted with boiling n-heptane for 6 hours. ρ _B is 0.36g/cc, V _G is 0.25
cc/g powder, and the wc of the slurry was 48%.

(c) Post-treatment of polypropylene 4.2 mg of propylene oxide is added to 100 g of the polypropylene slurry with a polymer concentration of 35% by weight obtained in (b) and treated at 83°C for 1 hour. The treated slurry is passed through to obtain crude polypropylene having a liquid content of 45% by weight relative to the polymer. This crude polypropylene was dried with hot air at a temperature of 60°C for 2 hours.

(d) Physical properties of product polypropylene The polypropylene obtained in (c) has 97% II, and the Ti and Cl contents are 16 ppm and 16 ppm, respectively.
The concentration was 9 ppm, and the color was a white powder.

Also, Irganox 1010 is added to this polypropylene.
and dilauryl thiodipropionate, 0.1g of the former and 0.1g of the latter per 100g of polypropylene.
It was added and blended at a ratio of 0.3g, press-molded at 210°C, and when the LTHS test was conducted on this test piece, a result of 28 days was obtained.

Claims (1)

[Claims] 1. An α-olefin is polymerized in the presence of a catalyst containing a transition metal halogen compound and an organoaluminum compound to have a bulk density of 0.4 g/cc or more and a porosity.
A first step to obtain a polyolefin with a concentration of 0.2 cc/g or less, a second step in which the above polyolefin is made into a slurry, and an epoxide is added to the polyolefin slurry obtained in the second step to inactivate the remaining catalyst in the polyolefin. The third step is to separate a part of the liquid phase from the polyolefin slurry obtained in the third step to determine the liquid content of the polyolefin.
Fourth step to separate less than 40% by weight of crude polyolefin
A method for producing a stabilized polyolefin, comprising the steps of: and a fifth step of evaporating the crude polyolefin. 2. The method according to claim 1, wherein the polyolefin inslurry obtained in the second step has a sedimentation volume concentration of 50% by weight or more.