JPH0670107B2 - Method for producing propylene-block copolymer - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention provides a propylene block copolymer having high rigidity, high impact strength and good fluidity, while having high activity and reduced by-product of low crystalline component. The present invention relates to a polymerization method.

2. Description of the Related Art Crystalline polypropylene has a problem that rigidity is excellent in heat resistance, but impact resistance, particularly resistance to attack at low temperature, is weak.

As a method for improving this point, a method in which propylene and ethylene or other olefins are stepwise polymerized to form a block copolymer is already known (Japanese Patent Application Laid-Open No. 43-43187).
-11230, JP-B-44-16668, JP-B-44-20621, JP-B-49-24593, JP-B-49-30264, JP-A-48-25781,
JP-A-50-115296, JP-A-53-35789, JP-A-54-1100
No. 72, etc.).

However, when propylene and ethylene are polymerized in a two-stage or multi-stage polymerization, impact resistance is improved, but the product contains a copolymerized portion. However, there is an industrial problem that a large amount is produced as a by-product. Therefore, many attempts have been made to reduce by-produced low crystalline components.

On the other hand, a titanium trichloride type catalyst is well known as an olefin stereoregular catalyst, but since it has a low activity and a large content in the produced polyolefin, a step for removing it (detouching step) is required. is there.

As a method of greatly improving the activity before the detouching step is unnecessary, it is known that there is an effect of introducing a magnesium compound into the solid catalyst component (Japanese Patent Publication No. 39-12105).
Japanese Patent Publication No. 47-41676 and Japanese Patent Publication No. 47-46269).
However, when olefins are polymerized by these methods, the activity is high, but the amount of low crystalline components by-produced is large, and the practical value is low.

Then, in order to suppress the by-production of low crystalline components, a method using an electron donor as a solid catalyst component or a third polymerization component has been proposed (JP-A-47-9842, JP-A-50-126590). , JP-A-51-57789). A method for producing a propylene block copolymer using these catalyst systems has also been proposed (JP-A-52-98045 and JP-A-53).
-No. 88049 publications). However, these methods are still unsatisfactory in practical use because the amount of low crystalline components produced as by-products is still large.

Therefore, in order to improve this, as a polymerization third component
It has been proposed to use an organic silicon compound having a Si—O—C or Si—O—N bond (Japanese Patent Laid-Open No. 58-83016).

However, this method has the following problems because the molecular weight of the ethylene / propylene rubber portion or the polyethylene portion is smaller than that of the conventional titanium trichloride type catalyst.

(1) The produced rubber is easily extracted from the polymer and becomes a by-product low crystalline component. Especially when the rubber portion is large, the produced polymer is sticky and causes aggregation and sticking of the polymer, which may cause operational troubles. Become.

(2) The effect of improving low temperature impact resistance is small.

(3) In order to maintain the MFR of the entire polymer, the molecular weight of the crystalline polypropylene part must be necessarily increased, which deteriorates the spiral flow, that is, the fluidity of the polymer in the mold.

SUMMARY OF THE INVENTION The present invention aims to provide a solution to the above problems,
It is an attempt to achieve this object by carrying out a specific block polymerization using a catalyst having a characteristic composition.

Therefore, in the method for producing a propylene-block copolymer according to the present invention, the following polymerization steps (A) and (B) are carried out in the presence of a catalyst comprising a combination of the following catalyst components (A) to (C). , Is a feature.

Catalyst component (A) A solid composition containing magnesium, titanium and halogen as essential components.

(B) Organoaluminum compound.

(C) A sterically hindered amine compound.

Polymerization step A step of producing a block copolymer comprising the following steps (A) and (B) and having a total ethylene content of 3 to 50% by weight.

(A) Propylene or a propylene / ethylene mixture is polymerized in a single-stage or multi-stage manner, and a propylene homopolymer or a propylene / ethylene copolymer having an ethylene content of 7% by weight or less is equivalent to 60 to 95% by weight of the total polymerization amount. Forming process.

(B) a step of polymerizing a propylene / ethylene mixture in a single-stage or multi-stage to obtain a propylene / ethylene copolymer having an ethylene content of 75 to 95% by weight (however, the polymerization step (B))
Polymerization of ZrCl ₄ , Ti (OC ₄ H ₉ ) ₂ Cl ₂ or (and) AlCl
Except when carrying out in the presence of _3. )

Effects By producing a propylene copolymer by the method according to the present invention, by-products of a highly active and low crystalline component are suppressed, and a propylene / ethylene copolymerized portion and / or
It is possible to produce a propylene / ethylene block copolymer having an increased molecular weight in the polyethylene portion and having high rigidity and high impact strength.

Further, according to the method of the present invention, the polymer powder does not become sticky even if there are many copolymerized portions, and therefore there is no operational trouble due to aggregation or sticking of the polymer powder.

Furthermore, according to the present invention, since the molecular weight of the crystalline polypropylene portion can be reduced, the resulting copolymer has improved spiral flow, that is, fluidity in the mold.

DETAILED DESCRIPTION OF THE INVENTION Catalyst Component The catalyst used in the present invention comprises a combination of components (A) to (C).

Solid Composition (A) The solid composition (A) is a highly active solid catalyst component containing magnesium, titanium and halogen as essential components. This solid catalyst may contain other elements or an inorganic or organic compound, especially an electron donor compound, in addition to the above essential components. Inclusion of an electron donor compound is particularly preferred. Further, it may be diluted with an inorganic or organic diluent.

Such a catalyst component can be manufactured by the following method.

(1) A method in which an activated magnesium halide, a titanium compound and optionally an electron donor are simultaneously or stepwise co-ground or brought into contact with each other in a liquid state. A halogenating agent may be contacted in any process (JP-A-53-45688, JP-A-55-90510, etc.).

(2) A titanium compound and, if necessary, an electron donor are added to a precipitate obtained by reacting a magnesium compound in a uniform state with a halogenating agent, a reducing agent, or the like in the presence or absence of an electron donor. Method by contacting (JP-A-54-40293, JP-A-56-811, JP-A-58-1)
83708, JP-A-58-183709, etc.).

(3) A method in which an organomagnesium compound such as a Grignard reagent is allowed to act with a halogenating agent, a reducing agent, etc., and then an electron donor and a titanium compound are brought into contact therewith (JP-A-52-14672, JP-A-52-14672). Sho 53-100986, etc.)

Among these methods, the method (2) is preferable.

Magnesium oxide, magnesium hydroxide, hydroxymagnesium halide, magnesium dihalide, alkoxymagnesium halide, allyloxymagnesium halide, dialkoxymagnesium, dialoxymagnesium are used as the magnesium compound for preparing the solid composition (A). , Magnesium carboxylate, alkyl magnesium halide, dialkyl magnesium, and the like.

Examples of the titanium compound used for preparing the solid composition (A) include titanium tetrahalide, alkoxy titanium halide, allyloxy titanium halide, alkoxy titanium, and allyloxy titanium. Of these, titanium tetrachloride is particularly preferable. A molecular compound obtained by reacting these titanium compounds with an electron donor compound may be used.

The halogen atom which is an essential constituent element of the solid composition (A) is fluorine, chlorine, bromine and iodine or a mixture thereof, and chlorine is particularly preferable.

The electron donor compound optionally used in the solid composition (A) includes oxygen-containing compounds such as organic and inorganic acid esters, acid amides, acid halides, acid anhydrides, alkoxysilanes, ketones and ethers. Is mentioned. As the acid, an organic acid, particularly an aliphatic monobasic C _{1 to} C ₁₀ ~
Dibasic acids and aromatic monobasic-dibasic carboxylic acids of about C ₇ -C ₁₅ are suitable, C ₁ -C ₁₀ as ester as one functional derivative of its carboxyl group Esters with a degree of monohydric or dihydric alcohol are typical. The alcohol in this case may be an ether group-containing alcohol. Particularly preferred in the present invention are organic acid esters such as cellosolve acetate, butyl o-propionyl benzoate and diheptyl phthalate, and particularly preferred are acid halides such as phthaloyl chloride.

The amount ratio of the constituents of the solid composition (A) is Ti / Mg.
Molar ratio is in the range of 1 × 10 ^-2 to 1, the halogen / Mg molar ratio, electron donor / Mg molar ratio in the case of using the located electron donor in the range of 0.5 to 4, 1 × 10 ^- It is preferably in the range of ² to 1.

Organoaluminum Compound (B) As the organoaluminum compound (B) referred to in the present invention,
General formula ▲ R ¹ _a ▼ ▲ R ² _b ▼ ▲ R ³ _c ▼ AlXd (OR ⁴ ) e (where
R ¹ , R ² , R ³ and R ⁴ may be the same or different and have from 1 to 1 carbon atoms.
About 20 hydrocarbon residues or hydrogen, and X is a halogen atom. When a + b + c + d + e = 3, 0 ≦ a ≦ 3, 0 ≦ b ≦
3, 0 ≦ c ≦ 3, 0 ≦ d ≦ 3, 0 ≦ e ≦ 3) are suitable.

Specific examples of such compounds include (a) triethylaluminum, triisobutylaluminum, trihexylaluminum, diethylisobutylaluminum, and other trialkylaluminums, (b) diethylaluminum monochloride, diylbutylaluminum monochloride, ethylaluminum. Sesquichloride,
Alkyl aluminum halides such as ethyl aluminum dichloride, (ha) Diethyl aluminum halides, alkyl aluminum hydrides such as diisobutyl aluminum hydride, (d) Diethyl aluminum ethoxide, diethyl aluminum butoxide, alkyls such as diethyl aluminum phenoxide Examples thereof include aluminum alkoxide and allyloxide. These may be used alone or in combination of two or more.

The amount of the organoaluminum compound (B) used is preferably within the range of 0.1 to 1000 in weight ratio with respect to the solid composition (A).

Sterically hindered amine (C) The sterically hindered amine used in the production of the propylene-block copolymer of the present invention is an aromatic or aliphatic primary amine or secondary amine having a bulky atomic group near the nitrogen atom. And tertiary amines. Of these, aliphatic secondary amines are preferable, and amines having the structure shown below are used.

In the formula, R ¹ , R ² , R ³ and R ⁴ are a hydrocarbon residue having 1 to 10 carbon atoms or halogen.

Specifically, the one represented by the following formula is suitable.

In the formula, R ⁵ is a hydrocarbon residue, preferably a substituted or unsubstituted alkylene group. When it is a substituted alkylene group, the substituent includes, for example, a hydrocarbon group such as an alkyl group, an acyloxy group and an alkoxy group. R ⁶ , R ⁷ , R ⁸ ,
R ⁹ is hydrogen or a hydrocarbon group which may have a substituent, and at least one of R ⁶ and R ⁷ is a hydrocarbon group. R ⁶ and R ⁷ or R ⁸ and R ⁹ may combine with each other to form a ring. Preferred compounds are R ⁶ , R ⁷ ,
All of R ⁸ and R ⁹ are hydrocarbon groups. Also,
When one of the combinations of R ⁶ and R ⁷ and R ⁸ and R ⁹ is hydrogen, the other is preferably a secondary or tertiary hydrocarbon group.

Specific examples include 2,6-substituted piperidines, 2,5-substituted pyrrolidines, 2,6-substituted tetrahydropyrans, and 2,5-substituted tetrahydrofuran. In this case, the substituents are methyl group, ethyl group, isopropyl group, tert-
A butyl group is typical.

Among these, 2,2,6,6-tetramethylpiperidine, 2,
Compounds having a skeleton such as 6-diisopropylpiperidine, 2,2,5,5-tetramethylpyrrolidine and 2,5-diisopropylpyrrolidine are preferable, and 2,2,6,6-tetramethylpiperidine is particularly preferable.

Catalyst composition The ratio of components (A) to (C) is as follows.

The molar ratio of the organoaluminum compound (B) to the halogenated titanium in the solid catalyst (A) is usually in the range of 10 to 1000. The molar ratio of the sterically hindered amine (C) to the organoaluminum compound (B) is usually 0.01 to 1.0, preferably 0.02 to 0.5.

Polymerization of Propylene The polymerization step of the present invention carried out in the presence of the catalyst comprises at least two steps, step (step A) and step (step B).
It is industrially advantageous to carry out the step (step A) and the step (step B) in this order.

Step (step A) In step (step A), propylene homopolymer or a propylene / ethylene mixture is fed to a polymerization system having the catalysts (A), (B) and (C) to give a propylene homopolymer or an ethylene content of 7% by weight. Hereinafter, it is a step of forming propylene / ethylene copolymer in an amount of preferably 0.5% by weight or less in one step or in multiple steps so as to be an amount corresponding to 60 to 95% by weight of the total polymerization amount.

When the ethylene content in the propylene / ethylene copolymer is further increased in the step (step A), the bulk density of the final copolymer is lowered, and the amount of the low crystalline polymer by-produced is significantly increased. Further, even when the polymerization ratio is less than the above range, the same phenomenon as in the case where the ethylene content in the propylene / ethylene copolymer is large still occurs. On the other hand, when the polymerization ratio exceeds the above range, the amount of the by-product of the low crystalline polymer tends to decrease, but the impact strength, which is the object of block copolymerization, decreases, which is not preferable. The effect of improving the spiral flow is more remarkable as the polymerization ratio in the step (step A) is smaller.

The polymerization temperature in the step (step A) is 30 to 90 ° C, preferably 50 to 80
℃, about. The polymerization pressure is about 1 to 30 kg / cm ² .

In the step (step A), it is preferable to use a molecular weight modifier so that the final polymer has an appropriate fluidity. Hydrogen is preferably used as the molecular weight modifier.

Process (Otsu) In the process (Otsu), following the process (O), the propylene / ethylene mixture is further introduced to give an ethylene content of 75-
This is a step of obtaining 95% by weight of a propylene / ethylene copolymer in a single stage or multiple stages. In this step, the total amount of polymer is 5
It is desirable to form an amount corresponding to ~ 40% by weight.

When the polymerization ratio in the step (B) and the composition of the propylene / ethylene mixture are less than the above range, the impact resistance (particularly low temperature impact resistance) is poor and the effect of improving spiral flow is small. On the other hand, when the amount exceeds the above range, there is a problem in operation that the amount of by-product of the low crystalline polymer is greatly increased and the viscosity of the polymerization solvent is remarkably increased.

In the step (B), a small amount of another comonomer may coexist. Examples of such comonomers include α-olefins such as 1-butene, 1-pentene and 1-hexene.

The polymerization temperature in the process (B) is 30 to 90 ° C, preferably 50 to 80
℃, about. The polymerization pressure is about 1 to 30 kg / cm ² .

When transferring from step (step A) to step (step B), it is preferable to purge propylene gas or propylene / ethylene mixed gas derived from step (step A) and hydrogen gas and move to step (step B).

In the step (B), the molecular weight modifier may or may not be used depending on the purpose. That is, when it is desired to increase the impact resistance of the final polymer, it is preferable to carry out this step in the substantial absence of the molecular weight modifier.

Polymerization Method The method for producing the copolymer according to the present invention can be carried out by any of a batch method, a continuous method and a semi-batch method. At this time, a method of carrying out the polymerization in an inert hydrocarbon solvent such as heptane, a method of using the used monomer itself as a medium, and a method of carrying out the polymerization in a gaseous monomer without using the medium. , And a method combining these can be adopted.

Further, prior to subjecting the solid catalyst to polymerization, it is possible to carry out prepolymerization under milder conditions than planned polymerization conditions (see JP-A-55-71712 and JP-A-56-57814).

Modification Although the polymerization according to the present invention is carried out as described above, as long as the gist of the present invention is not unduly impaired,
Various modifications are possible.

One such modification is to add a polymerization step other than those specified in both steps, before, in the middle or after the steps (A) and (B). The polymer to be produced in that case is up to 20% by weight of the final total polymer.

The steps (A) and (B) do not have to maintain the same polymerization conditions throughout the entire process, and the polymerization conditions can be changed according to the progress of each step.

Experimental Example Example-1 1) Synthesis of solid catalyst component 2 liters of sufficiently dehydrated and deoxygenated n-heptane was introduced into a 10 liter flask that had been sufficiently purged with nitrogen, and then
2 mol of MgCl ₂ and 4 mol of Ti (OC ₄ H ₉ ) ₄ were introduced and reacted at 95 ° C. for 2 hours. After the reaction was completed, the temperature was lowered to 40 ° C., 300 ml of methylhydropolysiloxane was introduced, and the reaction was carried out for 3 hours. After completion of the reaction, the produced solid component was washed with n-heptane.

1 liter of n-heptane was introduced into a 5 liter flask that had been sufficiently replaced with nitrogen, and the above solid component was converted to Mg atom and converted to 0.
9 mol was introduced. Then, 1.5 mol of SiCl ₄ was introduced at 30 ° C. for 30 minutes and reacted at 70 ° C. for 1 hour. Further, 0.12 mol of phenyltoluethoxysilane was added and the reaction was carried out at 70 ° C. for 1 hour. After completion of the reaction, it was washed with n-heptane.

Then, 0.09 mol of phthaloyl chloride was introduced at 30 ° C. for 30 minutes and reacted at 50 ° C. for 1 hour. After completion of the reaction, it was washed with n-heptane.

Finally, 250 ml of TiCl ₄ was added and reacted at 100 ° C. for 2 hours. After completion of the reaction, it was washed with n-heptane to obtain a solid composition (A).

The Ti loading of the solid composition thus obtained is 2.
It was 4% by weight.

2) Polymerization After thoroughly replacing the stirring autoclave with an internal volume of 200 liters with propylene, 63 liters of sufficiently dehydrated and deoxygenated n-heptane was introduced, and triethylaluminum (B) was added.
6.5 g, 3.2 g of the solid composition (A) and 2.0 g of 2,2,6,6-tetramethylpiperidine (C) were introduced at 55 ° C. under a propylene atmosphere.

In the first stage polymerization, after heating the autoclave to 75 ℃, 9kg of propylene while controlling the hydrogen concentration to 2.5%.
Started by introducing / at the speed of time.

After 220 minutes, the introduction of propylene was stopped and the polymerization was further carried out at 75 ° C.
It continued for 90 minutes. The gas phase propylene was purged to 0.2 kg / cm ² G.

The second-stage polymerization was carried out for 110 minutes by cooling the autoclave to 60 ° C., introducing propylene at 0.50 kg / hour and ethylene at 3.03 kg / hour.

The slurry thus obtained is dried over,
36.1 kg of polymer was obtained. Polymer bulk density is 0.503g / c
It was c.

The by-product low crystal polymer was 380 g. The details of the results are shown in Table 1.

The weight ratio between step (1) and step (2) and the weight ratio between propylene and ethylene in step (2) are values calculated on a polymerization basis.

Comparative Example-1 Polymerization was carried out in the same manner as in Example 1 except that the same amount of diphenyldimethoxysilane was added instead of 2,2,6,6-tetramethylpiperidine in the first stage polymerization.

The details of the results are shown in Table 1.

Comparative Example-2 The same polymerization as in Example 1 was conducted except that the same amount of N, N, N, N-tetramethylenediamine was added in place of 2,2,6,6-tetramethylpiperidine in the first stage polymerization. I did. Since the activity in the first stage was low and the pressure increase due to the constant rate introduction of propylene was remarkable, the polymerization had to be terminated in 2 hours.

Comparative Example-3 In Example-1, except that the propylene feed time was 250 minutes in the first-stage polymerization, the propylene and ethyl feed rates were 1 kg / hr and the feeding time was 40 minutes in the second-stage polymerization, respectively. Similar experiments were conducted.

The details of the results are shown in Table 1.

Example-2 In Example-1, the supply time of propylene in the step (step A) was set to 20.
The same operation was performed except that the time was set to 0 minutes and the supply time of propylene and ethylene in the step (Exhibit B) was set to 160 minutes.

The details of the results are shown in Table 1.

Comparative Example-4 The same operation was carried out except that the same amount of diphenyldimethoxysila was added in place of 2,2,6,6-tetramethylpiperidine in Example-2.

The details of the results are shown in Table 1.

Evaluation of physical properties (a) MFR (melt flow rate) MFR was measured according to ASTM-1238. MFR-2 of the process (B) is calculated by the following formula from MFR-1 of the process (A) and MFR-A of the product.

alog (MFR-1) + (1-a) log (MFR-2) = log (MFR-A) a: Polymerization ratio in all polymers in step (1) (b) Ethylene content The ethylene content in the product is , By infrared absorption spectrum.

(C) APP by-product ratio This is an index showing the by-product ratio of the amorphous polymer, and is based on the following calculation formula.

(D) Physical property measurement The following additives were added to the powdery polymer obtained in each Example and Comparative Example, and the mixture was pelletized by an extruder under the same conditions, and a sheet having a thickness of 4 mm was prepared by an injection molding machine. Then, the physical properties were evaluated.

Additives 2,6-di-tert-butylphenol 0.10% by weight RA1010 (Ciba Geigy) 0.05% by weight Calcium stearate 0.10% by weight PTBBA-Al (Shell Chemical) 0.10% by weight Physical property measurements The following methods are used to measure various physical properties. According to

(A) Flexural modulus: ASTM-D790 (b) Izod impact strength (0 ° C): ASTM-D256 (with notch) (c) Spiral flow measurement method Cross sections using various SJ type (inline screw type) injection molding machines Was measured under the following conditions using a 2 mm × 8 mm mold.

Molding temperature: 240 ℃ Injection pressure: 800kg / cm ² Injection time: 6 seconds Mold temperature: 40 ℃ Injection rate: 50g / second

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideo Sakurai, No. 1 Toho-cho, Yokkaichi-shi, Mie Inside the Resin Research Laboratory, Mitsubishi Petrochemical Co., Ltd. (56) References: Japanese Patent Publication 4-10889 (JP, B2)

Claims (1)

[Claims] 1. The following polymerization steps (A) and (B) in the presence of a catalyst comprising a combination of the following catalyst components (A) to (C):
A method for producing a propylene-block copolymer, which comprises carrying out Catalyst component (A) A solid composition containing magnesium, titanium and halogen as essential components. (B) Organoaluminum compound. (C) A sterically hindered amine compound. Polymerization step A step of producing a block copolymer comprising the following steps (A) and (B) and having a total ethylene content of 3 to 50% by weight. (A) Propylene or a propylene / ethylene mixture is polymerized in a single-stage or multi-stage manner, and a propylene homopolymer or a propylene / ethylene copolymer having an ethylene content of 7% by weight or less is equivalent to 60 to 95% by weight of the total polymerization amount. Forming process. (B) A step of polymerizing a propylene / ethylene mixture in a single-stage or multi-stage to obtain a propylene / ethylene copolymer having an ethylene content of 75 to 95% by weight (however, the polymerization step (B))
Polymerization of ZrCl ₄ , Ti (OC ₄ H ₉ ) ₂ Cl ₂ or (and) AlCl
Except when carrying out in the presence of _3. )