JPH0725849B2 - Method for producing propylene-ethylene copolymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing a propylene-ethylene copolymer, and more specifically, an injection having excellent transparency, aging resistance, and balance between rigidity and impact resistance. The present invention relates to a method for producing a propylene-ethylene copolymer having good moldability.

[Prior art]

Propylene-ethylene copolymers containing a small amount of ethylene are widely used in the fields of films, injection molded products and the like.

In the field of injection molding processing such as food containers and medical equipment,
Good balance of transparency, rigidity and impact resistance.
Particularly in the field of medical devices, irradiation with radiation such as γ-rays or heat treatment may be performed for the purpose of sterilization, and sufficient aging resistance against such treatment is required.

Regarding the above problems, as a means for improving the balance between rigidity and impact resistance, (1) a method of mechanically blending an ethylene homopolymer or an ethylene-propylene rubber with a propylene homopolymer (JP-A-41 -7345).

(2) A method in which propylene and ethylene are polymerized stepwise to obtain a copolymer (JP-B-44-4992, JP-A-58-10415, and JP-A-58-10415).
7-67611, 58-162621) and the like are known.

With respect to the method (1), although impact resistance is slightly improved, it is difficult to obtain a composition having a good balance between rigidity and impact resistance, and various steps are required for mechanical blending. It is hard to say that it is an industrially effective means.

Regarding the method (2), a method of producing a propylene-ethylene copolymer by two-step polymerization or three-step polymerization has been conventionally proposed.

On the other hand, as a method of preventing aging by irradiation of radiation or heat treatment, a method of adding a hindantamine compound, a phenol compound or the like to a propylene homopolymer or a propylene-ethylene copolymer, for example, JP-A No. 58-42638 and 58-49737 are disclosed. or,
A method of adding a sorbitol derivative, a phosphite compound, a polyamine compound and an organic peroxide, for example, Japanese Patent Laid-Open No.
No. 60-212442 and the like.

[Problems to be solved by the invention]

In the conventional method, for example, two-step polymerization, Japanese Patent Publication No.
As disclosed in Japanese Patent No.
A propylene-ethylene copolymer produced by a method of producing propylene homopolymer in an amount of less than or equal to wt% and then performing propylene-ethylene copolymerization has a relatively slow crystallization rate, and is molded from a mold during injection molding. The releasing property of the product was poor and the rigidity was insufficient.

On the other hand, in the three-step polymerization, for example, Japanese Patent Publication No. 58-1041
5, the propylene-ethylene copolymer produced by the copolymerization method as disclosed in JP-A-57-67611, JP-A-58-162621, etc. has a good balance of rigidity and impact resistance,
Since the copolymer having a high ethylene content is produced in the third step, there is a problem that the transparency is deteriorated.

In addition, particularly when used in applications where it is necessary to sterilize by radiation, polypropylene produced by a conventional method even if the above-mentioned additives are added, the transparency and impact strength after irradiation of radiation are improved. There is a problem that the decrease is remarkable or the effect of suppressing the decrease in impact strength is low.

[Means for solving problems]

The inventors of the present invention have solved the above problems, and have earnestly studied a method for producing a propylene-ethylene copolymer having excellent transparency, aging resistance, rigidity and impact resistance, and good injection moldability. As a result of overlapping, the present invention has been reached.

That is, in the method for producing a propylene-ethylene copolymer of the present invention, in the method for producing a propylene-ethylene copolymer using a stereoregular catalyst, the polymerization is divided into three steps, and (a) in the first step Then, propylene homopolymer is polymerized so as to be 5 to 20% by weight of the total polymer, and then (b) in the second stage, the propylene-ethylene copolymer having an ethylene content of 0.5 to 1.5% by weight is completely added. Copolymerized so as to be 5 to 20% by weight of the polymer, and further, (c) in the third stage, the ethylene content was 1.5 to 10.0.
It is characterized in that propylene-ethylene copolymer, which is wt%, is copolymerized so as to be 90 to 60 wt% of the total polymer, and the ethylene content of the total polymer is in the range of 1.0 to 8.0 wt%. It is what

The stereoregular catalyst used in the present invention is not particularly limited as long as it is a catalyst which gives a highly stereoregular propylene-based polymer, and various known catalysts can be used, but generally, transition metal catalysts and organometallic catalysts can be used. A catalyst composed of a compound is used, specifically, a transition metal compound such as a titanium compound, a chromium compound and a vanadium compound, particularly a halogen compound of titanium is preferably used, and titanium trichloride is optionally used together with an electron donating compound. Obtained by pulverizing, or by treating titanium trichloride obtained by reducing titanium tetrachloride with organoaluminum by an electron donating compound as necessary, or by supporting a transition metal compound on a carrier such as magnesium chloride. A catalyst or the like is used.

Examples of the organometallic compound include organoaluminum, organomagnesium, organozinc, and the like, for example, trialkylaluminum, dialkylaluminum halide, organoaluminum such as alkylaluminum dihalide,
Organic magnesium such as dibutyl magnesium and dihexyl magnesium is preferably used.

The polymerization method according to the present invention is either a solvent polymerization method using a saturated hydrocarbon as a solvent, a bulk polymerization method using liquefied propylene as a solvent, or a gas phase polymerization method in which polymerization is performed in a gas of propylene or a mixture of propylene and ethylene. Alternatively, the polymerization may be carried out in the presence of a chain transfer agent such as hydrogen in order to control the molecular weight.

The polymerization conditions according to the present invention include a polymerization pressure of atmospheric pressure to 80 kg.
A / cm ² gauge and a polymerization temperature in the range of room temperature to 100 ° C are preferably used.

The propylene homopolymer in the first stage according to the polymerization method of the present invention must be produced in a proportion of 5 to 20% by weight based on the total polymer. When the amount of polymerization produced in the first stage is less than 5% by weight, the crystallization rate of the obtained propylene-ethylene copolymer is slow, and the crystallization by cooling with a mold during injection molding is insufficient. In addition, the releasability deteriorates, the molded product is scratched or clouded, and the commercial value of the molded product is significantly impaired. On the other hand, if the amount of polymerization produced exceeds 20% by weight, there is a problem that the impact strength decreases. The molecular weight of the propylene homopolymer is 0.5 to 4.0 dl / g as the intrinsic viscosity in tetralin at 135 ° C.

The amount of propylene-ethylene copolymer having an ethylene content of 0.5 to 1.5% by weight in the second stage is 5 to 5% of all polymers.
20% by weight. If the polymerization ratio of the copolymer is less than 5% by weight, deterioration of aging resistance and transparency after irradiation of radiation or heat treatment is caused, and problems such as reduction of impact strength and clouding occur. On the other hand, when the production amount exceeds 20% by weight, deterioration of aging resistance and transparency after the above treatment is not observed,
This causes a reduction in the balance between rigidity and impact resistance.

The amount of propylene-ethylene copolymer having an ethylene content of 1.5 to 10.0% by weight in the third stage was 90% of the total polymer.
~ 60% by weight. The ethylene content in the copolymer is 1.
If it is less than 5% by weight, impact resistance is lowered and transparency is adversely affected. On the other hand, when the ethylene content exceeds 10.0% by weight, the rigidity is remarkably reduced.

The ethylene content of the propylene-ethylene copolymer in the present invention is in the range of 1.0 to 8.0% by weight, preferably 2.
It is 0 to 6.0% by weight. The intrinsic viscosity of the propylene-ethylene copolymer in tetralin at 135 ° C is 0.5 to 4.0 dl /
g, preferably 1.0 to 3.0 dl / g.

〔Example〕

 Hereinafter, the present invention will be specifically described with reference to examples.

In Examples and Comparative Examples, the physical properties were as follows: tris (2,4-di-t-butylphenyl) phosphite 0.10 relative to 100 parts by weight of propylene-ethylene copolymer.
Parts by weight 1,3,2,4-di (ethylbenzylidene) sorbitol 0.25
Parts by weight calcium stearate 0.10 parts by weight dimethyl succinate-1- (2-hydroxyethyl) -4-hydroxy-2,2,6,6-tetramethylpiperidine polycondensate (molecular weight 3000 or more) 0.04 parts by weight 2,5- After adding and mixing 0.06 parts by weight of dimethyl-2,5-bis (t-butylperoxy) hexane, granulating at 240 ° C, the injection molding temperature was measured using J-100S type injection molding machine of Japan Steel Works. 240 ° C
Then, a test piece for measuring physical properties having a thickness of 2 mm was prepared.

The physical property measurement items are as follows.

Haze: ASTM-D1003 Bending elastic modulus: ASTM-D790 DuPont impact strength: JIS-K6718 Crystallization rate (t _1/2 ): Crystallization measuring device by depolarization intensity method with scattered light compensation mechanism (Kotaki Manufacturing ( MK-701 Co., Ltd.
Mold), the semi-crystallization time was measured under the conditions of sample thickness 0.2 mm, melting temperature 210 ° C., melting time 4 minutes, initial light source voltage 3.2 V, and crystallization temperature 136 ° C.

For DuPont impact strength, test the physical properties with cobalt-60
After irradiating the source with γ-rays of 2.5 Mrad, 2 at the temperature of 80 ℃
After leaving for a week, the intensity before and after irradiation was measured.

Example-1 A commercially available titanium trichloride catalyst (TAC-S-21 manufactured by Toho Titanium Co., Ltd.) obtained through a step of contacting a titanium trichloride / aluminum chloride co-crystal with an electron donor per 500 g
30 g of the catalyst washed three times with 3 l of toluene, 90 ml of diethylaluminum chloride and 40 l of toluene were used to replace the catalyst slurry of 100 l of a well-dried jacketed autoclave with nitrogen and further with propylene, and then 25 kg of propylene and Titanium trichloride catalyst was continuously fed at 2 g / H while charging 3 L of toluene. At that time, hot water was passed through the jacket, hydrogen was charged so that the internal temperature was maintained at 72 ° C, and the gas phase hydrogen concentration was 2.5%, and propylene was charged at 15 kg / H and polymerization was carried out at an average residence time of 12 minutes. (First stage polymerization).

Next, the first-stage polymerization slurry was continuously transferred at 15 kg / H to the same 100 liter autoclave as in the first stage, and the autoclave internal temperature was 67 ° C, vapor phase hydrogen concentration was 2.0%, ethylene vapor phase concentration was 0.3%. While hydrogen and ethylene were charged so that the temperature was maintained at 15 kg / H and propylene was charged at 15 kg / H, polymerization was carried out at an average residence time of 17 minutes (second stage polymerization).

Furthermore, the second-stage polymerization slurry was continuously transferred at 15 kg / H to a 300 l autoclave with a jacket, and the internal temperature of the autoclave was 64 ° C, the gas phase hydrogen concentration was 2.0%, and the ethylene gas phase concentration was 1.6%.
% So that the average residence time was 90 minutes while charging with 50 kg / H of propylene (third stage polymerization).

After the completion of the third stage polymerization, 50 ml of n-butyl alcohol was added and the mixture was stirred at 63 ° C. for an average residence time of 30 minutes. The obtained slurry has an inner diameter of 10 cm in the thin part, an inner diameter of the thick part in the upper part is 30 cm, the length of the thin part is 10 m, and the length of the thick part in the upper part is 2 m. / H, propylene was introduced at a rate of 55 kg / H from the lower part, 77 kg / H was taken from the washing liquid in countercurrent contact with the slurry from the upper part, and 28 kg / H was taken from the lower part. The taken-out slurry was discharged into a cyclone kept at atmospheric pressure through a double tube heated through a steam of 1 kg / cm ² gauge having an inner diameter of 1 inch and a length of 40 m. Polymer is produced at 16 kg / H,
The polymer taken out from the cyclone was dried at 70 ° C. and 50 mmHg in a vacuum dryer for 8 hours.

Polymer was recovered at 0.3 kg / H from the washing liquid from the upper part of the one-way washing tower. Therefore, the yield of the product polymer based on the total polymer was about 98%. A test piece was prepared from the obtained polymer by granulation and injection molding under the above-mentioned conditions, and the physical properties of the test piece were measured. The results are shown in Table-1.

Example-2 An example except that the average residence time in the first stage was 20 minutes, the gas phase concentration of ethylene in the third stage was 3.0%, and the polymerization was carried out at an average residence time of 55 minutes in Example-2. A polymer was obtained in the same manner as in -1. The results are shown in Table-1.

Example-3 In Example-1, the vapor phase concentration of ethylene in the second step was
0.5%, autoclave temperature 69 ° C, average residence time 8
Minutes, the vapor phase concentration of ethylene in the third stage is 1.3%,
A polymer was obtained in the same manner as in Example-1 except that the temperature inside the autoclave was 67 ° C and the average residence time was 90 minutes. The results are shown in Table-1.

Comparative Example-1 The catalyst slurry prepared in Example-1 was continuously supplied as titanium trichloride at 2 g / H into a jacketed 100 l autoclave charged with propylene and toluene in the same manner as in Example-1. At that time, hot water was passed through the jacket, hydrogen was charged so that the internal temperature was maintained at 72 ° C and the gas phase hydrogen concentration was 2.5%, and the polymerization was carried out at an average residence time of 4 minutes while charging propylene at 10 kg / H. (First stage polymerization).

Then, the first-stage polymerization slurry was continuously transferred at 10 kg / H to a 300 l autoclave with a jacket, and the internal temperature of the autoclave was 67 ° C, the gas phase hydrogen concentration was 2.0%, and the ethylene gas phase concentration was 2.0%.
Polymerization was carried out at an average residence time of 85 minutes while charging hydrogen and ethylene so as to be maintained at 1.3% and charging with propylene 55 kg / H (second stage polymerization).

After completion of the second stage polymerization, 50 ml of n-butyl alcohol was added and the slurry obtained at 63 ° C. with an average residence time of 30 minutes while stirring was washed in a countercurrent washing tower in the same manner as in Example-1. The polymer was obtained at 16 kg / H. The polymer obtained is 70
It was dried at 50 ° C. and 50 mmHg for 8 hours using a vacuum dryer.

Polymer was recovered at 0.7 kg / H from the washing liquid from the upper part of the one-way washing tower. Therefore, the yield of the product polymer based on the total polymer was about 97%. Further, a test piece was prepared from the obtained polymer in the same manner as in Example-1, and the physical properties were measured. The results are shown in Table-1.

Comparative Example-2 In Comparative Example-1, the average residence time in the first stage was 40 minutes, propylene was charged at 15 kg / H, the gas phase concentration of ethylene in the second stage was 1.6%, and propylene was 50 kg / H. A polymer was obtained in the same manner as in Comparative Example-1 except that the polymerization was carried out with the average residence time of 60 minutes while charging. The results are shown in Table-1.

Comparative Example-3 In Example-1, the average residence time in the first stage was 25 minutes, the vapor phase concentration of ethylene in the second stage was 0.5%, the average residence time was 3 minutes, and the vapor phase of ethylene in the third stage was set. Concentration 1.
A polymer was obtained in the same manner as in Example-1 except that the polymerization was performed at an average residence time of 95 minutes at 6%. The results are shown in Table-1.

Comparative Example-3 In Example-1, the gas phase concentration of ethylene in the third stage was
A polymer was obtained in the same manner as in Example-1 except that the polymerization was carried out at an autoclave internal temperature of 55% at an average residence time of 60 minutes at 5.0%. The results are shown in Table-1.

〔The invention's effect〕

By carrying out the present invention, it becomes possible to efficiently produce a propylene-ethylene copolymer having excellent transparency, aging resistance, and a balance of rigidity and impact resistance, which is industrially valuable.

Front page continuation (56) Reference JP-A-53-35789 (JP, A) JP-B 1-13488 (JP, B2) JP-B 62-39165 (JP, B2) JP-B 60-36203 (JP) , B2) Japanese Patent Publication Sho 62-50484 (JP, B2)

Claims (1)

[Claims] 1. A method for producing a propylene-ethylene copolymer using a stereoregular catalyst, wherein the polymerization is divided into three steps, and (a) in the first step, the propylene homopolymer is added to the total of 5 parts of the total polymer. To 20% by weight, and then in the second step (b), a propylene-ethylene copolymer having an ethylene content of 0.5 to 1.5% by weight is added to 5 to 20% by weight of the total polymer. And (c) in the third stage, the ethylene content is 1.5 to 10.0.
It is characterized in that propylene-ethylene copolymer, which is wt%, is copolymerized so as to be 90 to 60 wt% of the total polymer, and the ethylene content of the total polymer is in the range of 1.0 to 8.0 wt%. And a method for producing a propylene-ethylene copolymer.