JP2002327008A - Heat treatment method of propylene-based polymer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method in which the volatile components such as non- reacted monomers, various solvents added to a polymerization system and catalyst and various low-molecular weight compounds produced as byproducts in the polymerization are sufficiently removed using a heat transfer type dryer without developing the fouling in powder and to a wall of the dryer. SOLUTION: The heat treatment method of a propylene-based polymer is characterized in that the heat treatment is performed while maintaining an inner wall surface of the drier in a temperature range from 80 deg.C to a temperature lower by 2 deg.C than a melting point of the polymer having the a degree of dispersion of elution (σ) of <=9 which is polymerized using a metallocen catalyst when the polymer is subjected to the heat treatment with the dryer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for heat-treating a propylene homopolymer or copolymer obtained by using a metallocene catalyst, and more particularly, to a method for preventing a heat transfer dryer from falling. The present invention relates to a method for heat-treating a propylene-based polymer, wherein the heat-treatment is performed efficiently and stably.

[0002]

2. Description of the Related Art One of the main uses of a propylene-based polymer is its use as a packaging material because of its ease of heat sealing, excellent safety for contents, and excellent hygiene.

However, volatile components derived from the polymerization operation such as unreacted monomers, various solvents added to the polymerization system or the catalyst, and various low-molecular-weight compounds produced during the polymerization remain in the propylene-based polymer immediately after the polymerization. are doing.

[0004] These residual volatile components cause not only the generation of smoke and an unpleasant odor during the processing, but also the odor of the packaging material after the processing, and thus it is necessary to remove as much as possible. Examples of the method of removal include extraction with a solvent, degassing during granulation, a method of subjecting the pellets after granulation to hot air heat treatment using a hopper dryer, and a method of immersing the pellets in hot water. However, most commonly, heat treatment is performed by a heat transfer dryer in a powder state.

However, a propylene polymer obtained by polymerization in the presence of a conventional Ziegler-Natta type catalyst, particularly a polymer having a relatively low melting point, which is used for applications requiring heat sealability, is required. On the other hand, if the temperature load required for removing the residual volatile components is applied, the so-called sticky components (low crystalline components) melt and the powders aggregate,
There is a disadvantage that the particles themselves adhere to the wall surface of the dryer. Therefore, there has been a problem that the heat treatment temperature cannot be sufficiently increased, and as a result, residual components cannot be sufficiently removed.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to use a heat transfer dryer without adding powder to unreacted monomers, a polymerization system or a catalyst without causing fouling between powders or the walls of the dryer. It is an object of the present invention to provide a method for sufficiently removing volatile components such as various solvents produced and various low molecular weight compounds by-produced during polymerization.

[0007]

As a result of various studies, the present inventors have found that a propylene-based polymer obtained by polymerization in the presence of a metallocene catalyst has a melting point and / or
It has been found that the operable upper limit of the inner wall surface temperature of the heat transfer dryer increases according to the composition distribution. Further, as a result, they have found that a propylene polymer having a very small amount of residual volatile components can be obtained, and have completed the present invention.

The heat treatment at such a high temperature is a technique which cannot be achieved with a propylene-based polymer produced with a Ziegler-Natta catalyst in which the composition distribution of the polymer is very wide and low crystalline components are always present.

That is, according to the present invention, a propylene-based polymer which is polymerized using a metallocene catalyst and has an elution dispersity (σ) of 9 or less in a temperature-rise elution fractionation (TREF) is obtained by using a heat transfer dryer. A heat treatment method for a propylene polymer, wherein the heat treatment is performed while maintaining the temperature of the inner wall surface of the dryer at 80 ° C. to 2 ° C. lower than the melting point of the propylene polymer. Is what you do.

The present invention also provides a method for heat treating a propylene polymer, wherein the temperature of the inner wall surface of the dryer is 5 ° C. or lower than the melting point of the propylene polymer. The above-mentioned heat treatment method for a propylene-based polymer having an average elution temperature (T50) of 70 ° C. or more and an elution dispersity (σ) of 9 or less in elution fractionation (TREF), and the inner wall temperature of the dryer is calculated by the following formula. An object of the present invention is to provide a method for heat-treating the above-mentioned propylene-based polymer, wherein the heat-treatment is carried out while maintaining the required upper limit temperature Tw or lower.

Tw = Tm-ΔT ΔT = 1.1 ^0.122 σ (where Tm is the melting point of the propylene-based polymer and σ is the dissolution degree) Further, the propylene-based copolymer has a melting point of 140 to 11.
An object of the present invention is to provide a method for heat-treating the above propylene-based polymer which is a propylene-ethylene random copolymer at 0 ° C.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The propylene polymer used in the present invention is obtained using a metallocene catalyst.

As the metallocene catalyst for obtaining the propylene polymer used in the present invention, known catalysts can be used. For example, the components [A] and [B] described below and [C] used as necessary Can be mentioned.

Component [A] Metallocene complex: transition metal compound of Group 4 to 6 of the periodic table having at least one conjugated five-membered ring ligand Component [B] Promoter: Compound [B] and metallocene complex [A] A compound capable of activating the metallocene complex [A] by reacting component [C] an organoaluminum compound.

As the metallocene catalyst, it is preferable to use a supported metallocene catalyst among the above-mentioned olefin polymerization catalysts. Specific examples of the metallocene-supporting carrier include inorganic substances such as silica and alumina and organic substances such as a polypropylene-based polymer. And the component [C] in contact with an organoaluminum compound. Further, it may or may not be subjected to the preliminary polymerization treatment.

Particularly preferred examples of the supported metallocene catalyst include those in which the carrier is an ion-exchangeable layered silicate which also functions as a promoter. Specifically, it is obtained by combining component [A], component [B] described below, and component [C] added as needed.

Component [A] metallocene complex: transition metal compound of Groups 4 to 6 of the periodic table having at least one conjugated five-membered ring ligand Component [B] Promoter: ion-exchange layered silicate Component [C ] Organoaluminum compounds.

As the above component [A], specifically,
The compound represented by the following general formula [1] can be used.

[0019] _{Q (C 5 H 4-a} R 1 a) (C 5 H 4-b R 2 b) MXY [1] In the above general formula [1], Q is two conjugated five-membered ring ligand Represents a bonding group that crosslinks M is the fourth to sixth periodic table
Represents a group transition metal, among which titanium, zirconium and hafnium are preferred.

X and Y are each independently hydrogen,
Halogen group, C1-20 hydrocarbon group, C1
It represents an oxygen-containing hydrocarbon group having 20 carbon atoms, a nitrogen-containing hydrocarbon group having 1 to 20 carbon atoms, a phosphorus-containing hydrocarbon group having 1 to 20 carbon atoms, or a silicon-containing hydrocarbon group having 1 to 20 carbon atoms.

R ¹ and R ² each independently represent a hydrocarbon group having 1 to 20 carbon atoms, a halogen group, a hydrocarbon group containing 1 to 20 carbon atoms, an alkoxy group, an aryloxy group, a silicon-containing hydrocarbon group. Group, a phosphorus-containing hydrocarbon group, a nitrogen-containing hydrocarbon group or a boron-containing hydrocarbon group. Further, two adjacent R ¹ or two R ² may be bonded to each other to form a C _{4 to} C ₁₀ ring. a and b
Is an integer satisfying 0 ≦ a ≦ 4 and 0 ≦ b ≦ 4.

The linking group Q bridging between the two conjugated five-membered ring ligands is, for example, an alkylene group, an alkylidene group,
Examples thereof include a silylene group and a germylene group. These may be those in which a hydrogen atom is substituted by an alkyl group, halogen, or the like.

Specific examples of the metallocene complex include the following compounds. (1) methylene bis (cyclopentadienyl) zirconium dichloride (2) methylene (cyclopentadienyl) (3,4-dimethylcyclopentadienyl) zirconium dichloride (3) isopropylidene (cyclopentadienyl)
(3,4-dimethylcyclopentadienyl) zirconium dichloride (4) ethylene (cyclopentadienyl) (3,5-dimethylpentadienyl) zirconium dichloride (5) methylenebis (indenyl) zirconium dichloride (6) ethylenebis ( 2-methylindenyl) zirconium dichloride (7) ethylene 1,2-bis (4-phenylindenyl) zirconium dichloride (8) ethylene (cyclopentadienyl) (fluorenyl) zirconium dichloride (9) dimethylsilylene (cyclopentadiene) (Enyl) (tetramethylcyclopentadienyl) zirconium dichloride (10) dimethylsilylenebis (indenyl) zirconium dichloride (11) dimethylsilylenebis (4,5,6,7-tetrahydroindenyl Zirconium dichloride (12) dimethylsilylene (cyclopentadienyl)
(Fluorenyl) zirconium dichloride (13) Dimethylsilylene (cyclopentadienyl)
(Octahydrofluorenyl) zirconium dichloride (14) methylphenylsilylenebis [1- (2-methyl-4,5-benzo (indenyl)] zirconium dichloride (15) dimethylsilylenebis [1- (2-methyl-
4,5-benzoindenyl)] zirconium dichloride (16) dimethylsilylenebis [1- (2-methyl-4)
H-azulenyl)] zirconium dichloride (17) dimethylsilylenebis [1- (2-methyl-4)
-(4-chlorophenyl) -4H-azulenyl)] zirconium dichloride (18) dimethylsilylenebis [1- (2-ethyl-4
-(4-chlorophenyl) -4H-azulenyl)] zirconium dichloride (19) dimethylsilylenebis [1- (2-ethyl-4
-Naphthyl-4H-azulenyl)] zirconium dichloride (20) diphenylsilylenebis [1- (2-methyl-
4- (4-chlorophenyl) -4H-azulenyl)] zirconium dichloride (21) dimethylsilylenebis [1- (2-methyl-4
-(Phenylindenyl))] zirconium dichloride (22) dimethylsilylenebis [1- (2-ethyl-4)
-(Phenylindenyl))] zirconium dichloride (23) dimethylsilylenebis [1- (2-ethyl-4)
-Naphthyl-4H-azulenyl)] zirconium dichloride (24) dimethylgermylene bis (indenyl) zirconium dichloride (25) dimethylgermylene (cyclopentadienyl)
(Fluorenyl) zirconium dichloride In addition, the same compounds as described above can also be used for other Group 4, 5, and 6 transition metal compounds such as titanium compounds and hafnium compounds. These compounds may be used in combination for the catalyst component and catalyst of the present invention.

The component [B] ion-exchangeable phyllosilicate is
Not only natural products but also artificial products may be used. A clay compound can be used as the ion-exchange layered silicate. Specific examples of the clay compound include, for example, the following described in “Clay Mineralogy” by Haruo Shiramizu, Asakura Shoten (1995) Layered silicates are mentioned. (1) 1: 1 is a main constituent layer, kaolin group such as dickite, nacrite, kaolinite, anoxite, metahaloisite, halloysite, etc .; serpentine group such as chrysotile, risaldite, antigorite, etc. (2) 2: One layer is a main constituent layer, such as montmorillonite, zauconite, beidellite, nontronite, saponite, hectorite, smectite group such as stevensite, vermiculite group such as vermiculite,
Mica, such as mica, illite, sericite, chlorite, attapulgite, sepiolite, palygorskite, bentonite, pyrophyllite, talc, and chlorite.

The silicate used in the present invention includes the above (1)
The layered silicate which formed the mixed layer of (2) may be used.
In the present invention, the silicate as the main component is preferably a silicate having a 2: 1 type structure, more preferably a smectite group, and particularly preferably montmorillonite.

The silicate used in the present invention can be used as it is without any particular treatment, but its state can be adjusted by a chemical treatment, which is preferable.
Here, the chemical treatment can be any of a surface treatment for removing impurities adhering to the surface and a treatment that affects the structure of the clay.

Specific examples include acid treatment, alkali treatment, salt treatment and the like. The acid treatment increases the surface area by removing impurities on the surface and eluting cations such as Al, Fe, and Mg in the crystal structure. The alkali treatment destroys the crystal structure of the silicate, causing a change in the structure. In the salt treatment and the organic substance treatment, an ion complex, a molecular complex, an organic derivative, and the like are formed, and the surface area and the interlayer distance can be changed. By utilizing the ion exchange property and replacing the exchangeable ions between the layers with another large bulky ion, it is also possible to obtain a layered material in which the layers are expanded.

The acid used in the acid treatment is preferably selected from hydrochloric acid, sulfuric acid, nitric acid, oxalic acid, phosphoric acid and acetic acid. The salt and the acid used for the treatment may be two or more. When the salt treatment and the acid treatment are combined, there are a method of performing the salt treatment and then performing the acid treatment, a method of performing the acid treatment and then performing the salt treatment, and a method of simultaneously performing the salt treatment and the acid treatment.

The conditions for the treatment with salts and acids are not particularly limited.
A substance constituting at least one compound selected from the group consisting of ion-exchanged phyllosilicates under the conditions of 80% by weight, a treatment temperature of room temperature to a boiling point and a treatment time of 5 minutes to 24 hours. By controlling the dissolution of silicate, it is possible to produce a silicate suitable for the present invention.

The salts and acids are generally used in an aqueous solution. As the treatment conditions, it is preferable to perform the acid treatment or the treatment in the presence of an acid and a salt at least once,
The reaction is carried out at an acid concentration of 1 mol / L or more and 12 mol / L or less, preferably 2 mol / L or more and 8 mol / L or less. As described above, it is possible to obtain a desired silicate by controlling the treatment temperature and the treatment time under a condition where the acid concentration is relatively high, which is a preferable method. For example, when sulfuric acid is used, preferably 18% by weight or more,
The concentration becomes 58% by weight or less.

In the present invention, the above-described acid treatment or the coexistence treatment of an acid and a salt is preferably performed. However, the shape may be controlled by pulverization or granulation before, during, or after the treatment. Further, a chemical treatment such as an alkali treatment or an organic substance treatment may be used in combination.

These silicates usually contain adsorbed water and interlayer water. In the present invention, it is preferable to use the water after removing these adsorbed water and interlayer water.

Here, the adsorbed water is water adsorbed on the surface of the silicate compound particles or the crystal fracture surface, and the interlayer water is water existing between the crystal layers. In the present invention, these adsorbed water and / or interlayer water can be removed by heat treatment before use.

The method of heat dehydration treatment of silicate adsorbed water and interlayer water is not particularly limited, and methods such as heat dehydration, heat dehydration under gas flow, heat dehydration under reduced pressure, and azeotropic dehydration with an organic solvent are used. Can be Although the temperature at the time of heating cannot be specified unconditionally depending on the type of silicate, it is 100 ° C. or higher, preferably 150 ° C. or higher so that interlayer water does not remain. Although it depends on the heating time, for example, 800 ° C. or more) is not preferable.

In the case of heat dehydration under a gas flow, an inert gas is usually used, but heat treatment with air is also possible. The heating time is selected depending on the relationship with the heat treatment temperature of the silicate compound particles, but is generally at least 1 minute, preferably at least 1 hour. At that time, when the water content of the silicate after the removal was 0% by weight when the water content when dehydrated for 2 hours under the condition of a temperature of 200 ° C. and a pressure of 1 mmHg,
It is preferably at most 3% by weight, preferably at most 1% by weight.

As described above, in the present invention, a particularly preferred silicate is an ion-exchangeable layered silicate having a water content of 1% by weight or less obtained by salt treatment and / or acid treatment. .

Component [C] is an organoaluminum compound. Organic aluminum compounds used as component [C] in the present invention, the compound represented by formula ^{_{(AlR 4 p X 3-p}} ) q is suitable.

In the present invention, it goes without saying that the compounds represented by this formula can be used alone, in combination of two or more kinds. This use is possible not only at the time of catalyst preparation but also at the time of prepolymerization or polymerization. In this formula, R ⁴ represents a hydrocarbon group having 1 to 20 carbon atoms, and X represents a halogen, hydrogen, an alkoxy group, or an amino group. p is an integer of 1 to 3, and q is an integer of 1 to 2. R ⁴ is preferably an alkyl group, X is chlorine when it is a halogen, an alkoxy group having 1 to 8 carbon atoms when it is an alkoxy group, and 1 to 8 carbon atoms when it is an amino group. Is preferred. Among these, a trialkylaluminum and a dialkylaluminum hydride having p = 3 and q = 1 are preferable. More preferably, R ⁴ is a trialkyl aluminum having 1 to 8 carbon atoms.

The metallocene catalyst used in the present invention is desirably subjected to a prepolymerization treatment before the main polymerization is performed.
Examples of the monomer to be subjected to the prepolymerization include ethylene, propylene, 1-butene, α-olefins such as 1-hexene, diene compounds such as 1,3-butadiene, styrene,
A vinyl compound such as divinylbenzene can be used.

The propylene polymer has an elution dispersity (σ)
Is used, but is not limited to propylene homopolymer as long as the conditions are satisfied, and is a copolymer with ethylene and / or an α-olefin having 4 or more carbon atoms. You may.

A propylene polymer having an elution dispersity (σ) of 9 or less can be easily obtained by polymerizing in the presence of a metallocene catalyst. There is no particular limitation on the type of polymerization, and for example, slurry polymerization in an inert solvent, bulk polymerization using liquefied propylene as a solvent, gas phase polymerization, and the like can be used.

The heat transfer dryer used in the present invention is of the type described in, for example, Handbook of Powder Engineering (2nd edition, p. 358, edited by The Society of Powder Engineering, published by Nikkan Kogyo Shimbun). ,
It may be a batch type or a continuous type, and may be any type such as a stirring type, a vibration type, and a screw conveyor type.

The lower limit of the inner wall surface temperature of the heat transfer dryer is 80.
℃ or more, the upper limit is 2 ℃ from the melting point of the propylene polymer
Lower temperature, preferably 5 ° C lower temperature, more preferably 7 ° C
It should be operated at a low temperature. Here, the melting point of the polymer refers to a peak temperature measured by DSC. When there are a plurality of peaks, it refers to the temperature of the peak with the lowest temperature.

If the temperature of the inner wall surface is lower than 80 ° C., the heat treatment will be insufficient, and the removal of volatile components may be insufficient. If the temperature of the inner wall surface is high, adverse effects such as the possibility that the propylene-based polymer itself may start to dissolve, and at least aggregation of the powders and fouling on the inner wall surface of the dryer appear. The temperature of the inner wall surface of the dryer may have a temperature distribution in the upper and lower portions of the dryer and near the entrance and exit, but the inner wall surface temperature in the present invention refers to the highest temperature among them.

Generally, the temperature of the inner wall surface at the point where the heat medium enters the dryer jacket becomes highest. As a method of monitoring the temperature of the inner wall surface, various known methods can be adopted, but typically, a thermometer is installed on the wall surface. In an industrial-scale plant, since the heat loss can be almost ignored, it may be simply represented by the temperature of the heating medium of the dryer jacket.

The propylene polymer obtained by using the metallocene catalyst has an elution dispersity (σ) of 9 or less in a temperature rise elution fractionation (TREF) and an average elution temperature (T50) of an elution curve of 70 ° C. or more. It is desirable that

As shown in the following formula (1), the elution dispersity (σ) is determined as follows: the temperature (T15.9) at which the cumulative weight of the eluted polymer becomes 15.9%, and the eluted polymer at 84. It shows the temperature difference of the temperature (T84.1) when it becomes 1%.

Σ = (T84.1) − (T15.9) (1) The elution dispersity (σ) is significant in expressing the size of the molecular weight distribution and particularly the size of the composition distribution. When σ exceeds the above range, the molecular weight distribution and composition distribution increase, and when the inner wall temperature of the dryer is raised to near the melting point of the propylene-based polymer, polymer aggregation and inner wall Adhesion to the surface occurs, which is not preferable for stable operation of the plant.

The above average elution temperature (T50) indicates the temperature at which the cumulative weight of the eluted polymer becomes 50% in the temperature-rise elution fractionation (TREF). Since this parameter is significant in expressing the melting point and molecular weight of the propylene-based polymer, it is an important factor in determining the heat treatment temperature. If T50 is less than the lower limit of the above range, the melting point is too low or the molecular weight is too low, so that stable operation becomes difficult in the operation of the polymer heat treatment.

Measurement of the peak of the elution curve by temperature rising elution fractionation (TREF) is carried out by heating once to completely dissolve the polymer, then cooling, forming a thin polymer phase on the surface of the inert carrier, and then measuring the temperature. The temperature is raised continuously or stepwise to recover the eluted components, and the concentration is continuously detected. The composition distribution of the polymer can be measured from a graph (elution curve) drawn by the elution amount and the elution temperature. For details of the measurement of temperature rise elution fractionation (TREF), see Journal of Applied.
Polymer Science Vol. 26, No. 4217
~ 4231 (1981).

<Calculation of upper limit temperature Tw of dryer inner wall temperature>
As described above, one of the features of the present invention is that the upper limit of the heat treatment temperature is estimated from the composition distribution of the polymer, so that heat treatment with high efficiency can be performed.

That is, the upper limit temperature Tw of the inner wall temperature of the dryer.
Can be determined by the following formula.

Tw = Tm-ΔT ΔT = 1.1 ^0.122 σ (where Tm indicates the melting point of the propylene-based copolymer and σ indicates the dissolution degree) The significance of this equation is that the wider the composition distribution, the higher the polymer The difference Δ between the dryer inner wall temperature Tw and the polymer melting point Tm during the heat treatment
This indicates that T (ΔT = Tm−Tw) needs to be increased. It is empirically recognized that the rate of increase of ΔT increases exponentially.

It is particularly preferable that ΔT = 1.1
^The relationship is expressed by ^0.124 σ. Therefore, the range of the operable temperature T of the dryer is a range represented by T ≧ 80, T ≦ Tm−ΔT (ΔT = ^1.11.122 σ) 5 ≦ σ ≦ 9.

[0055]

The following examples further illustrate the present invention, but the present invention is not limited by these examples without departing from the gist thereof.

(Method of measuring residual solvent amount) Polymer 5.0
g was placed in a platinum boat, heated in a pyrolysis furnace at 210 ° C. for 60 seconds, and then introduced into a gas chromatograph directly connecting the gas in the decomposition furnace for 10 seconds to write a chart.
Repeated times, the residual solvent amount was calculated from the total of each peak area using a calibration curve prepared in advance.

(Method of measuring polymer bulk density) ASTM
It measured according to D1895-69.

(MFR (Melt Flow Rat)
e)) Melt flow rate of JIS-K-6758 polypropylene test method (condition: 230 ° C, load: 2.16K)
gf).

(Measurement method of Tm by DSC) A sample (about 5 mg) was taken using a DSC measurement device manufactured by Seiko Co., Ltd.
After melting at 00 ° C. for 5 minutes, the temperature is lowered to 40 ° C. at a rate of 10 ° C./min for crystallization, and then the temperature is raised to 200 ° C. at a rate of 10 ° C./min. Was evaluated.

(Measurement method of temperature rise elution fractionation (TREF)) The peak of the elution curve by temperature rise elution fractionation (TREF) is measured by completely dissolving the polymer once at a high temperature, then cooling, and then cooling the surface of the inert carrier. By elevating the temperature continuously or stepwise to collect the eluted components, continuously detecting their concentrations, and measuring their elution volume and elution temperature. It was measured. The measurement of the elution curve was performed under the following measurement conditions. Solvent: o-dichlorobenzene Measurement concentration: 4 mg / ml Injection amount: 0.5 ml Column: 4.6 mmφ × 150 mm Cooling rate: 100 ° C. × 120 minutes <Example-1> (Preparation of catalyst) Under active gas, deoxygenation,
This was performed using a solvent and a monomer that had been dehydrated. The previously chemically treated montmorillonite is reduced to 200 ° C. under reduced pressure.
For 2 hours. Further, 200 g of the dried montmorillonite obtained above was introduced into a glass reactor having an inner volume of 3 L and equipped with a stirring blade, and normal heptane and a heptane solution of triethylaluminum (10 mmo) were introduced.
l) was added and stirred at room temperature. After 1 hour, washing with normal heptane (residual liquid ratio less than 1%),
It was adjusted to 0 mL.

Next, (r) -dimethylsilylenebis [2-methyl-4- (4-chlorophenyl) -4
[H-azulenyl] zirconium dichloride 3 mmol of a toluene slurry 870 mL and triisobutylaluminum (30 mmol) of a heptane solution 42.6 mL were reacted at room temperature for 1 hour, added to the montmorillonite slurry, and stirred for 1 hour.

Subsequently, the internal volume 1 sufficiently replaced with nitrogen
Normal heptane 2.1 in a 0 L stirred autoclave
L was introduced and maintained at 40 ° C. The montmorillonite / complex slurry prepared above was introduced therein. Temperature 40
When the temperature became stable at ℃, propylene was fed at a rate of 100 g / hour, and the temperature was maintained. After 4 hours, the supply of propylene was stopped and maintained for another 2 hours. About 3 L of the supernatant was removed from the recovered prepolymerized catalyst slurry, and a solution of triisobutylaluminum (30 mmol) in heptane was added.
After adding 70 mL and stirring for 10 minutes, heat treatment was performed at 40 ° C. under reduced pressure. By this operation, a prepolymerized catalyst containing 1.43 g of polypropylene per 1 g of the catalyst was obtained.

(Production of Propylene-Ethylene Copolymer)
As shown in FIG. 1, a bulk polymerization tank system comprising a liquid phase polymerization tank 1 having an internal volume of 400 L with a stirrer, a slurry circulation pump 2 and a circulation line 3, a double-pipe heat exchanger 4
And a degassing system 6 comprising a fluidized flash tank 5 and a process incorporating a screw feeder type dryer 12 having an inner diameter of 115 mm, a length of 2.0 m, a paddle blade of diameter 110 mm and a jacket on the outside. -Continuous production of ethylene copolymer was carried out.

Reference numeral 7 denotes a heat exchanger, 8 denotes a blower, 9 denotes a low-pressure degassing tank, 10 denotes a cyclone for separating a monomer and a polymer, and 11 denotes a circulating gas blower.

The prepolymerized catalyst produced above was added to liquid paraffin (White Rex 335, manufactured by Tonen Co.) at a concentration of 20.
% By weight, and as a catalyst component, 1.65 g / hr.
Introduced in. 123 kg of liquid propylene in this reactor
/ Hr, ethylene 1.85 kg / hr, hydrogen 0.3
7 g / hr, 28.4 g of triisobutylaluminum
/ Hr, and the polymerization was carried out while maintaining the internal temperature at 70 ° C. The temperature of the heating medium entering the dryer 12 is set to 125 ° C., the direction and the number of revolutions of the paddle blades are adjusted so that the residence time is 1 hour, and the dry nitrogen at room temperature is supplied in the direction of powder flow. Heat treatment was performed by flowing at a flow rate of 12 m ³ / hr in the flow direction. As a result, a powdery propylene / ethylene random copolymer was obtained at 22.3 kg / hr.

Examination of the resulting powder and the inside of the dryer revealed no agglomeration of the powders or adhesion to the dryer wall. Powder MFR = 7.4, Tm = 13
5.5 ° C., bulk density = 0.50 g / cc, residual solvent amount 35
ppm, average elution temperature (T50) by TREF is 8
At 5.3 ° C., the elution dispersion degree (σ) was 6.7.

Example 2 Powder heat treatment was performed in the same manner as in Example 1 except that the temperature of the heating medium in the screw feeder type dryer was changed to 130 ° C. As in Example 1, no agglomeration of the powders or adhesion to the dryer wall was observed at all. Powder bulk density = 0.50
g / cc and the residual solvent amount was 31 ppm.

Example 3 A powder heat treatment was performed in the same manner as in Example 1 except that the temperature of the heating medium of the screw feeder type dryer was set to 133 ° C. There was no agglomeration between the powders and slight adhesion to the dryer wall, but there was no problem to the distribution of the powder. The bulk density of the powder was 0.50 g / cc, and the residual solvent amount was 28 ppm.

Example 4 In Example 1, the amount of the prepolymerized catalyst was 1.42 g / hr, the amount of ethylene was 1.89 kg / hr, and the amount of hydrogen was 0.52 g / h as a catalyst component.
The polymerization was carried out in the same manner as in Example 1 except that r and triisobutylaluminum were changed to 34.3 g / hr, and 24.0 kg.
/ Hr, a powdery propylene / ethylene random copolymer was obtained.

When the obtained powder was subjected to a heat treatment under the same conditions as in Example 2, no aggregation of the powders and no adhesion to the dryer wall were observed at all, as in Example 1. Powder MFR = 46.3, Tm = 133.4
° C, bulk density = 0.49 g / cc, residual solvent amount 33pp
m, average elution temperature (T50) by TREF is 83.1.
° C and the dissolution degree (σ) were 6.4.

<Example-5> In Example 1, the amount of the prepolymerized catalyst was 1.18 g / hr, ethylene was 3.43 kg / hr, and hydrogen was 0.35 g / hr as a catalyst component.
Polymerization was carried out in the same manner as in Example 1 except that r and triisobutylaluminum were 29.0 g / hr and the polymerization temperature was 60 ° C., to obtain a powdery propylene / ethylene random copolymer at 15.9 kg / hr. Was. The obtained powder was heated to a heating medium temperature of 12 of a screw feeder type dryer.
Except that the temperature was set to 0 ° C., the powder was heat-treated in the same manner as in Example 1. As in Example 1, no agglomeration of the powders or adhesion to the dryer wall was observed. MFR of powder = 38.7, Tm = 124.9 ° C., bulk density =
0.47 g / cc, the residual solvent amount was 42 ppm, the average elution temperature (T50) by TREF was 75.4 ° C., and the elution dispersity (σ) was 7.6.

<Comparative Example 1> (1) Production of Ziegler-Natta-based solid catalyst component 10 equipped with a stirring blade, a thermometer, a jacket, and a cooling coil
In a 0 L reactor, 30 mol of Mg (OEt) ₂ was charged, and then Ti (OBu) ₄ was charged with Mg (OEt) charged.
t) Ti (OBu) ₄ / M for magnesium in ₂
It was charged so that g = 0.60 (mr). Further, 19.2 kg of toluene was charged, and the temperature was raised while stirring. After reacting at 139 ° C. for 3 hours, the temperature was lowered to 130 ° C., and the toluene solution of MeSi (OPh) ₃ was added to the magnesium in Mg (OEt) ₂ previously charged with M
eSi (OPh) _{3 /} Mg was added so as to be 0.67 (mr). The amount of toluene used here was
It was 7.8 kg. After completion of the addition, the reaction was carried out at 130 ° C. for 2 hours, and then the temperature was lowered to room temperature, and Si (OEt) ₄ was added. The amount of Si (OEt) ₄ added depends on the amount of M
g (OEt) ₂ with respect to magnesium, Si (OE
t) ₄ /Mg=0.056 (mr)

Next, toluene was added to the obtained reaction mixture so that the magnesium concentration was 0.58 (mol / L · TOL). Further, diethyl phthalate (DEP) was added to magnesium in Mg (OEt) ₂ previously charged with DEP / Mg = 0.10 (m.
r. ). The resulting mixture was cooled to −10 ° C. with continued stirring, and TiCl ₄ was added dropwise over 2 hours to obtain a homogeneous solution. Note that TiCl
₄ was set so that TiCl ₄ /Mg=4.0 (mr) with respect to magnesium in Mg (OEt) ₂ previously charged. After completion of the addition of TiCl _{4, the} mixture was stirred at 0.
The temperature was raised to 15 ° C. at 5 ° C./min, and kept at the same temperature for 1 hour. Next, the temperature was raised again to 50 ° C. at a rate of 0.5 ° C./min and maintained at the same temperature for 1 hour. Further, the temperature was raised to 118 ° C. at 1 ° C./min, and the treatment was performed at the same temperature for 1 hour. After completion of the treatment, the stirring was stopped, the supernatant was removed, and the mixture was washed with toluene so that the residual liquid ratio was 1/73, to obtain a slurry.

Next, toluene and TiCl ₄ were added to the obtained slurry at room temperature. Note that TiCl ₄
Shows that TiCl ₄ / Mg (OEt) ₂ = 5.0 (m.m.) with respect to magnesium in Mg (OEt) ₂ previously charged.
r. ). Toluene is TiCl
_{4 The} concentration was adjusted to 2.0 (mol / L · TOL). The temperature of the slurry was increased while stirring, and
The reaction was carried out at a temperature of 1 hour. After completion of the reaction, stop stirring,
After removing the supernatant, the remaining liquid ratio was 1/15 with toluene.
It was washed so as to be 0, and a slurry of a solid component was obtained.

Further, among the solid components obtained above, 4
00 g was transferred to another reactor having a stirring blade, a thermometer, and a cooling jacket, and diluted with normal hexane to a solid component concentration of 5.0 (g / l). While stirring the resulting slurry at 15 ° C., trimethylvinylsilane, TEA and TBMDES were added. Here, TBMDES indicates t-butylmethyldiethoxysilane, and t-butyl indicates a tertiary butyl group. In addition, TEA, trimethylvinylsilane,
The amount of TBMDES added was 3.1 (mmol), 0.2 (g), and 1 g of the solid component in the solid component, respectively.
(Ml) and 0.2 (ml). After completion of the addition, the mixture was kept at 15 ° C. for 1 hour with continued stirring, further heated to 30 ° C., and stirred at the same temperature for 2 hours. Next, the temperature was again lowered to 15 ° C., and while maintaining the same temperature, 1.2 kg of propylene gas was fed to the gas phase of the reactor at a constant speed over 72 minutes to perform prepolymerization. After the feed was completed, the stirring was stopped to remove the supernatant, and then washing was performed with normal hexane to obtain a slurry of the prepolymerized catalyst component. In addition, the residual liquid ratio was set to 1/12. The obtained prepolymerized catalyst component was 2.8 g per 1 g of the solid component.
Of the propylene polymer.

(Polymerization) The polymerization was carried out using the same reactor system used in Example 1. The prepolymerized catalyst component obtained above was dispersed at a concentration of 2% by weight in liquid paraffin (manufactured by Tonen Corp .: White Rex 335), and 0.17 g / hr was introduced as a catalyst component. The reactor was charged with liquid propylene at 120 kg / hr and ethylene at 2.0 kg / hr.
hr and hydrogen were continuously supplied at 211 g / hr and triethylaluminum at 16.3 g / hr, and polymerization was carried out while maintaining the internal temperature at 70 ° C. The dryer was set so that the temperature of the heating medium was 125 ° C., and the heat treatment was performed by adjusting the direction and the number of revolutions of the paddle blade so that the residence time was 1 hour. As a result, a powdery propylene / ethylene random copolymer was obtained at 34.6 kg / hr. Examination of the resulting powder and the inside of the dryer revealed that the powders were strongly agglomerated and adhered to the dryer wall. Powder M
FR = 29.1, Tm = 141.1 ° C., bulk density = 0.3
9g / cc, residual solvent amount 35ppm, average elution temperature (T50) by TREF is 92.7 ° C, elution dispersity (σ)
Was 24.9.

Comparative Example 2 A powder heat treatment was performed in the same manner as in Comparative Example 1, except that the heating medium temperature of the screw feeder type dryer was 120 ° C. Examination of the resulting powder and the inside of the dryer revealed a small amount of aggregation between the powders and adhesion to the dryer wall. The bulk density of the powder was 0.43 g / cc, and the residual solvent amount was 38 ppm.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a polymerization process used in Examples.

[Explanation of symbols]

 1, polymerization tank 2, slurry circulation pump 3, circulation line 4, double tube heat exchanger 5, fluidized flash tank 6, degassing system 9, low pressure degassing tank 10, cyclone 12, dryer

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Takao Tayano 1 Toho-cho, Yokkaichi-shi, Mie Japan F-term in the Process Development Center of Polychem Corporation (reference) 4J100 AA02Q AA03P CA01 CA04 DA24 DA36 FA10 GB02 GB18 GC00 GC29 GC37

Claims (5)

[Claims] 1. Polymerization using a metallocene catalyst, wherein the dispersity (.sigma.) In the temperature-rise elution fractionation (TREF) is 9
When the following propylene-based polymer is heat-treated using a heat transfer dryer, the inner wall surface temperature of the dryer is 80
A heat treatment method for a propylene-based polymer, wherein the heat treatment is performed while maintaining a temperature range of from 0 ° C to 2 ° C lower than the melting point of the propylene-based polymer. 2. The heat treatment method for a propylene polymer according to claim 1, wherein the heat treatment is performed at a temperature lower than the melting point of the propylene polymer by 5 ° C. or less. 3. The propylene polymer has an average elution temperature (T50) of 70 ° C. in temperature rising elution fractionation (TREF).
The elution dispersion degree (σ) is 9 or less.
Or the heat treatment method for a propylene-based polymer according to 2. 4. The method for heat treating a propylene-based polymer according to any one of claims 1 to 3, wherein the heat treatment is performed in a state where the inner wall temperature of the dryer is maintained at or below an upper limit temperature Tw determined by the following equation. Tw = Tm−ΔT ΔT = 1.1 ^0.122 σ (where Tm indicates the melting point of the propylene-based polymer and σ indicates the dissolution degree). 5. A propylene copolymer having a melting point of 140 to 1
The method for heat-treating a propylene-based polymer according to any one of claims 1 to 4, which is a propylene-ethylene random copolymer at 10C.