JPH11100421A - Polypropylene block copolymer - Google Patents

Abstract

(57) [Problem] To provide a polypropylene block copolymer having good transparency, improved impact properties at low temperatures, and reduced bleed during high-temperature heat treatment. A part (CXIS part) containing at least 5% by weight of a xylene-soluble part (CXS part) at 20 ° C. and excluding a CXS part.
The melting temperature (Tm) in DSC of 130 ° C. ≦ Tm ≦ 15
A polypropylene block copolymer having a temperature of 5 ° C. and a thickness of 150 μm obtained by forming the copolymer by extrusion.
A polypropylene-based block copolymer in which the difference in transparency (haze) between before and after the treatment at 110 ° C. for 1 hour is 8% or less.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a polypropylene block copolymer. More specifically, the present invention relates to a polypropylene block copolymer having excellent transparency, impact resistance at a low temperature, and excellent bleed control during heat treatment.

[0002]

2. Description of the Related Art Polypropylene is widely used in the fields of films, sheets, containers and the like because of its excellent heat resistance and rigidity. In recent years, in the field of food packaging,
A material having flexibility, transparency, impact resistance, and heat resistance has been demanded. However, although propylene homopolymer has excellent heat resistance, flexibility, transparency, and impact resistance at low temperatures are inferior.Although propylene and α-olefin random copolymers have excellent transparency, Impact resistance was insufficient and the use was limited. As a method for imparting impact resistance, some attempts have been made mainly to improve the impact resistance by using a polypropylene-based block copolymer. As a block copolymer of propylene (hereinafter referred to as P) and ethylene propylene (hereinafter referred to as EP), JP-A-6-93061 discloses the use of a Ziegler-Natta type catalyst, which is substantially inert. A P-EP block copolymer has been proposed in which a propylene-based polymer portion is polymerized in the first step in the absence of a solvent, and then the EP copolymer is polymerized in the gas phase in the second step. ing. Polymerization in the gaseous phase provided good impact resistance at low temperatures but low transparency and was inadequate as compared with polymers produced by the conventional solvent method.

A block copolymer comprising an EP copolymer part and an EP copolymer part having a different composition is also known. JP 56
JP-A-84712 discloses that the melt flow index is 0.01 to 0.3 g / 10 minutes, and that the A part (EP copolymer part obtained in the first step) has an ethylene content of less than 20% by weight;
Part B (EP copolymer part obtained in the second step) discloses a polypropylene-based block copolymer having characteristics such as an ethylene content of 20% or more. Specifically, a polymer polymerized by a solvent method is disclosed. Although disclosed, it was unsatisfactory in terms of transparency. In Comparative Example, a structure in which the ethylene concentration in Part B was lowered to improve transparency was described, but the impact strength was low and was unsatisfactory. Japanese Patent Application Laid-Open No. Hei 8-283349 proposes a composition in which a random copolymer of ethylene, propylene and α-olefin having different comonomer contents is blended with a random copolymer of ethylene, propylene and α-olefin. In the case of the blend, uniform compatibility like the block copolymer produced by polymerization was not exhibited, and the transparency was insufficient. The present inventors have studied to solve the drawbacks of the conventional block copolymer and to develop a polypropylene block copolymer having good transparency and improved low-temperature impact resistance. No. 141358, the specific composition of E
A method for producing a composition having transparency, impact resistance and the like by polymerizing a P-EP block copolymer substantially in the absence of an inert solvent has been proposed. However, the specific EP-EP obtained by polymerization in the substantial absence of a solvent
The use of the block copolymer was insufficient for applications such as medical packaging bags that require extremely low changes in transparency during high-temperature heat treatment. The change in transparency is mainly attributable to the change in haze due to bleed-out of low molecular weight components due to heat treatment, and a resin composition that suppresses bleeding at high temperatures has been desired. Here, the block copolymer is obtained by sequentially performing the polymerization in the first step and the polymerization in the second step, and is not a true block copolymer but a kind of a blend system.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polypropylene block copolymer having good transparency, improved impact properties at low temperatures, and reduced bleed during high-temperature heat treatment. It is.

[0005]

Means for Solving the Problems The present inventors have conducted studies to solve the drawbacks of the conventional block copolymers.
The present inventors have found that the above problems can be solved by a specific block copolymer obtained by polymerization in the substantial absence of an inert solvent, and have reached the present invention. That is, the present invention is as follows. (1) DS of a portion (CXIS portion) containing 5% by weight or more of a xylene-soluble portion (CXS portion) at 20 ° C. and excluding the CXS portion
A polypropylene-based block copolymer having a melting temperature (Tm) in C of 130 ° C. ≦ Tm ≦ 155 ° C., and a film having a thickness of 150 μm formed by extrusion of the copolymer at 110 ° C. for 1 hour A polypropylene block copolymer having a difference in transparency (haze) before and after treatment of 8% or less. (2) In the first step, the ethylene content is 3% by weight or less and the butene content is 3 to 25 in the substantially absence of an inert solvent.
A propylene-butene or ethylene-propylene-butene copolymer [hereinafter referred to as (ethylene) -propylene-butene copolymer] part (A component) in an amount of 40 to 85% by weight of the total polymerization amount, Then, in the second step, the ethylene content is 17% by weight or less and the butene content is 3% in the gas phase.
A block copolymer obtained by polymerizing 15 to 60% by weight of the total weight of the (ethylene) -propylene-butene copolymer portion (component B) to 35% by weight, and the intrinsic viscosity of the component B ([ η] B) is 1.5 to 5 dl / g, and the ratio ([η] B / [η] A) between the intrinsic viscosity of component B ([η] B) and the intrinsic viscosity of component A ([η] A). Is 0.5 ≦ [η] B /
[Η] The polypropylene-based block copolymer according to the above (1), wherein A ≦ 1.8. (3) When the ethylene content of the component B is CBE weight%, the butene content is CBB weight%, the ethylene content of the component A is CAE weight%, and the butene content C is AB weight%, the formula 3 ≦ CBE The polypropylene-based block copolymer according to the above (2), which satisfies -CAE≤15 and CAB-5≤CBB≤CAB + 10. (4) The polypropylene block copolymer as described in (1), (2) or (3) above, wherein the content of the component having a molecular weight of 26,000 or less in the xylene-soluble portion at 20 ° C. is 6% by weight or less. .

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION The polypropylene block copolymer of the present invention has a xylene-soluble part (CXS part) of 5 ° C at 20 ° C.
Wt.% Or more, excluding the CXS part (CXIS
Part) has a melting temperature (Tm) of 130 ° C. ≦ Tm ≦
It is necessary that the difference in transparency (haze) between a block copolymer having a temperature of 155 ° C. and a 150 μm film formed by extrusion processing at 110 ° C. for 1 hour is not more than 8%. If the content of the CXS portion is less than 5% by weight, the rigidity is high and the impact properties are insufficient, which is not preferable. In order to exhibit heat resistance, the melting temperature (Tm) of the CXIS section by DSC is 13
0 ° C. ≦ Tm is required, and Tm ≦ 155 ° C. is required in order to suppress rigidity and develop transparency. Extrusion of 150 μm film formed by extrusion in order to suppress bleeding of low molecular weight components during heating and to prevent poor transparency due to structural change.
It is necessary that the structure has a transparency (haze) difference of 8% or less before and after the treatment at 0 ° C. for 1 hour.

[0007] In a method for producing a polypropylene-based block copolymer exhibiting the desired properties of the present invention, a Ziegler-Natta type catalyst is used in a first step in the absence of an inert solvent in the presence of ethylene. Content of 3% by weight or less,
(Ethylene) -propylene-butene copolymer portion (A component) having a butene content of 3 to 25% by weight
(E) -propylene-butene copolymer portion (component B) having an ethylene content of 17% by weight or less and a butene content of 3-35% by weight in the gas phase in the second step. Is polymerized at 15 to 60% by weight of the total weight. The proportion of the copolymer part (component A) polymerized in the first step and the copolymer part (component B) polymerized in the second step is 40 to 85% by weight for the component A and 15 to 60% for the component B.
% By weight. If the B component is 15% by weight or less, the impact resistance at low temperatures is insufficient, and if it is 60% by weight or more, the heat resistance deteriorates. In particular, when used for film applications, the proportion of the B component is more preferably 17 to 35% by weight from the viewpoint of moldability. The ethylene content of the (ethylene) -propylene-butene copolymer portion (component A) polymerized in the first step is preferably 3% by weight or less, and the butene content is preferably 3 to 25% by weight. 3 ethylene content
When the content is more than 10% by weight, the effect of suppressing bleeding in high-temperature heat treatment is inferior. When the butene content is less than 3% by weight, transparency is not exhibited, and when it exceeds 25% by weight, heat resistance is reduced. In particular, a butene content of 6 to 20% by weight is more preferable from the viewpoint of transparency and heat resistance.

The ethylene content of the (ethylene) -propylene-butene copolymer portion (component B) polymerized in the second step is preferably 17% by weight or less, and the butene content is preferably 3 to 35% by weight. If the ethylene content exceeds 17% by weight, the effect of suppressing bleeding in high-temperature heat treatment cannot be expected. Particularly, the ethylene content is preferably 8% by weight or less from the viewpoint of transparency. When the butene content is less than 3% by weight, the transparency is reduced, and when it exceeds 35% by weight, bleeding is promoted. The intrinsic viscosity ([η] B) of the component B of the polypropylene-based block copolymer of the present invention is 2.0 to 5.0 dl / g,
The ratio ([η] B / [η] A) between the intrinsic viscosity ([η] B) of the component B and the intrinsic viscosity ([η] A) of the component A is 0.5 ≦.
[Η] B / [η] A ≦ 1.8 is preferable from the viewpoint of transparency. When [η] B is less than 2.0 dl / g, bleeding increases due to an increase in low molecular weight components, and when it exceeds 5.0 dl / g, the fluidity of the ethylene-propylene block copolymer decreases, Workability decreases. In particular, the intrinsic viscosity ([η] B) of the component B of the ethylene-propylene copolymer is more preferably 2.5 to 4.0 dl / g from the viewpoint of the balance between the suppression of low molecular weight components and the processability. If the [η] B / [η] A ratio exceeds 1.8 or falls below 0.5, the compatibility between the component A and the component B decreases, and the transparency decreases. In particular, the ratio of [η] B / [η] A is more preferably 0.8 ≦ [η] B / [η] A ratio ≦ 1.5 from the viewpoint of transparency.

In order to exhibit transparency, the polypropylene block copolymer of the present invention has an ethylene content of the B component of CBE weight% from the viewpoint of compatibility between the A component and the B component.
When the butene content is CBB weight% and the ethylene content of the A component is CAE weight% and the butene content CAB weight%, 3 ≦ CBE-CAE ≦ 15 and CAB-5 ≦ CB
It is preferable to satisfy B ≦ CAB + 10. In the polypropylene block copolymer of the present invention, the content of the component having a molecular weight of 26,000 or less in the 20 ° C. xylene-soluble component in the total polymer after melt-kneading is 6% by weight or less. Is preferred in terms of suppressing In particular, when used as a food packaging material, 20 ° C in the total polymer
More preferably, the content of the xylene-soluble component having a molecular weight of 26,000 or less is 3.5% by weight or less.

The polypropylene block copolymer of the present invention can be prepared by a batch polymerization method in which a component A is polymerized in the same polymerization tank using a Ziegler-Natta type catalyst, and then a component B is polymerized. It can be produced by a continuous polymerization method for continuously polymerizing the component A and the component B using a polymerization tank comprising at least two tanks. Specifically, for example,
(A) In the coexistence of an organosilicon compound having a Si—O bond, a compound represented by the general formula Ti (OR ¹ ) _n X _4-n (R ¹ has ¹ to 2 carbon atoms)
0 represents a hydrocarbon group, X represents a halogen electron, and n represents a number 0 <n ≦ 4. The trivalent titanium compound obtained by treating a solid product obtained by reducing the titanium compound and / or ether compound represented by the formula (1) with an organomagnesium compound with a mixture of an ester compound, an ether compound and titanium tetrachloride. (B) an organoaluminum compound; (c) a catalyst system comprising a silicon compound having a Si—OR ² bond (R ² is a hydrocarbon group having 1 to 20 carbon atoms); A Ziegler-Natta type catalyst containing titanium, magnesium and halogen as essential components can be used. Furthermore, (a) the general formula Ti (OR
¹ ) A titanium compound represented by _n X _4-n (R ¹ is a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen electron, and n is a number satisfying 0 <n ≦ 4); ² mY _3-m (R ²
Is a hydrocarbon group having 1 to 20 carbon atoms, Y is a halogen electron,
m represents a number of 1 ≦ m ≦ 3. ), A solid product containing a hydrocarbyloxy group insoluble in a hydrocarbon solvent obtained by reduction with an organoaluminum compound represented by the formula (1), is subjected to a prepolymerization treatment with ethylene, and then an ether compound and titanium tetrachloride in the hydrocarbon solvent. 80 to 10 in the presence of
A hydrocarbyloxy group-containing solid catalyst component obtained by treating in a slurry state at a temperature of 0 ° C. and a Ziegler-Natta type catalyst such as a catalyst system comprising (b) an organoaluminum compound can be used. In the polymerization, (b)
The molar ratio of Al atoms in the component / Ti atom in the component (a) is 1 to 2000, preferably 5 to 1500,
(B) the molar ratio of Al atoms in the component is 0.02 to 500;
The polymerization temperature is preferably 0.05 to 50, the polymerization temperature is 20 to 150C, preferably 50 to 95C, and the polymerization pressure is atmospheric pressure to 40Kg / cm2G, preferably ^{2 to} 40K.
g / cm < ² > G, propylene and butene-1 (and optionally ethylene) and hydrogen for controlling the molecular weight were supplied in the first step in the substantial absence of an inert solvent to produce propylene-butene. After the polymerization of the 1- (ethylene) copolymer portion (component A), propylene, butene-1 (and optionally ethylene) and hydrogen are supplied in the gas phase in the second step, and propylene-butene- It can be produced by polymerizing a 1- (ethylene) copolymer portion (component B).

The polypropylene-based block copolymer of the present invention changes its fluidity typified by a melt flow rate by a known method in the presence or absence of a diazo compound and an organic peroxide during melt-kneading. It is possible to do. As the radical generator, those having a half-life at 130 ° C. of about 2.0 to 10.0 hours are preferable. As such a radical generator, 2,5-dimethyl-
2,5-di (tert-butylperoxy) hexane,
2,5-dimethyl-2,5-di (tert-butylperoxy) hexine-3, dicumyl peroxide, di-tert-butyl peroxide, and tert-butylcumyl peroxide are exemplified. Of these, particularly preferred are 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane, 2,5-dimethyl2,
5-di (tert-butylperoxy) hexin-3. Also, if necessary, antioxidants, ultraviolet absorbers,
It can contain an antistatic agent, an antifogging agent, a nucleating agent and the like. Although the polypropylene block copolymer of the present invention can be used alone, it can also be used as a mixture with a different resin composition as long as the object of the present invention is not hindered. The polypropylene block copolymer of the present invention is suitable as a material for films, sheets, molded containers and the like. When a film or sheet is obtained, it can be formed as a single layer or at least one layer of a multilayer structure with a different resin by a generally used inflation method, T-die method, calendering method or the like. It is also possible to use a multi-layer by a method, a heat laminating method, a dry laminating method or the like. Further, the obtained film and sheet can be uniaxially or biaxially stretched and used by, for example, a roll stretching method, a tenter stretching method, a tubular stretching method, etc., and are usually employed industrially. Surface treatment such as corona discharge treatment, flame treatment, plasma treatment, and ozone treatment can also be performed. As a molded article, a bottle obtained by a direct blow molding method, a biaxial stretch blow molding method or the like, a container obtained by vacuum forming, pressure forming, or the like, or a molded article obtained by injection molding or the like can be used. The molded article can be used alone or as at least one layer of a multilayer structure with different resins. Particularly suitable for specific layers of retort food packaging film from the viewpoint of flexibility, transparency, heat resistance, and impact resistance at low temperatures, and for medical liquids from the viewpoint of transparency, heat resistance, and bleed control during heat treatment. Suitable as a back material.

[0012]

The present invention will be specifically described below with reference to examples.
The scope of the present invention is not limited only to the examples.
In addition, the measurement of each item of the physical property in this invention was implemented by the following method. (1) Content of component A and component B (% by weight) The content of component A (PA) and the content of component B (PB) were determined from the material balance during polymerization of component A and component B. (2) Intrinsic Viscosity ([η]) Measurement was performed in tetralin at 135 ° C. using an Ubbelohde viscometer. Intrinsic viscosity of component A and component B ([η] A,
[Η] B) Intrinsic viscosity [η] A measured after completion of polymerization of component A in the first step, intrinsic viscosity [η] AB measured after completion of polymerization in second step, and content of component A (PA) The intrinsic viscosity [η] B of the B component was determined from the following formula from the content (PB) of the B component. [Η] A × PA / 100 + [η] B × PB / 100 =
[Η] AB (3) Ethylene and butene content Polymer Handbook (1995, published by Kinokuniya Bookstore)
13C- by the method described on page 616 of
The measurement was performed by the NMR method. Ethylene concentration of components A and B (EA, EB) Ethylene concentration measured after polymerization of component A in the first step and ethylene concentration EA measured after polymerization of second step
From the content of the B and A components (PA) and the content of the B component (PB), the ethylene concentration EB of the B component was determined by the following equation. EA × PA / 100 + EB × PB / 100 = EAB Butene was determined in the same manner. (4) Melt flow rate (MFR) Measured according to JIS K7210 under the condition -14. (5) 20 ° C. xylene-soluble part (CXS) After completely dissolving 5 g of polypropylene in 500 ml of boiling xylene, the temperature is lowered to 20 ° C. and left for 4 hours or more.
Thereafter, this was separated into a precipitate and a solution by filtration, the filtrate was dried and dried at 70 ° C. under reduced pressure. (6) Impact resistance At -10 ° C, the impact strength of the film was measured using a film impact tester manufactured by Toyo Seiki using a hemispherical impact head having a diameter of 15 mm. (7) Transparency (haze) Measured according to JIS K7105. (8) Bleed A film having a thickness of 0.15 mm obtained under extrusion film forming conditions at a resin temperature of 250 ° C and a chill roll temperature of 30 ° C was left in an oven at 110 ° C for 1 hour, and the difference in transparency before and after the treatment was used as an index of bleed. did. Transparency (haze) is JIS K710
5 was measured. (9) Low molecular weight component P. The CXS component was measured by C (gel permeation chromatography) under the following conditions. The calibration curve was created using standard polystyrene. Model 150CV type (manufactured by Millipore Waters) Column Shodex M / S 80 Measurement temperature 145 ° C Solvent Orthodichlorobenzene Sample concentration 5mg / 8ml Using this molecular weight distribution, the content of components having a molecular weight of 26,000 or less was measured, and the following standards were used. Was evaluated. ○ Content of less than 2.6% by weight △ Content of 2.6% by weight or more and 6.0% by weight or less × Content of more than 6.0% by weight (10) Melting point (Tm) Differential scanning calorimeter (PerkinElmer) DSC). 220 ° C in a nitrogen atmosphere
, And the temperature is lowered to 40 ° C. at a rate of 5 ° C./min. Thereafter, the temperature was raised at a rate of 5 ° C./min, and the peak temperature of the maximum peak of the obtained melting curve was defined as the melting point (Tm).

Example 1 [Synthesis of solid catalyst] After replacing a 200 LSUS reaction vessel equipped with a stirrer with nitrogen, 80 L of hexane, 6.55 mol of tetrabutoxytitanium, and diisobutyl phthalate 2.8 were obtained.
And 98.9 mol of tetraethoxysilane were added to obtain a uniform solution. Next, a diisobutyl ether solution 51 of butylmagnesium chloride having a concentration of 2.1 mol / L was prepared.
L was gradually added dropwise over 5 hours while maintaining the temperature in the reaction vessel at 5 ° C. After completion of the dropwise addition, the mixture was further stirred at room temperature for 1 hour, then subjected to solid-liquid separation at room temperature, and washed three times with 70 L of toluene. Next, toluene was added so that the slurry concentration became 0.2 kg / L, 47.6 mol of diisobutyl phthalate was added, and the reaction was carried out at 95 ° C. for 30 minutes. After the reaction, the mixture was separated into solid and liquid, and washed twice with toluene. Next, 3.13 mol of diisobutyl phthalate, 8.9 mol of butyl ether and 274 mol of titanium tetrachloride were added, and the mixture was reacted at 105 ° C. for 3 hours. After the completion of the reaction, the mixture was subjected to solid-liquid separation at the same temperature, and then washed twice with 90 L of toluene at the same temperature. Next, the slurry concentration was adjusted to 0.4 kg /
After adjusting to L, 8.9 mol of butyl ether and 137 mol of titanium tetrachloride were added, and the mixture was reacted at 105 ° C. for 1 hour. After the completion of the reaction, solid-liquid separation was performed at the same temperature, and the solid was washed three times with 90 L of toluene at the same temperature.
After washing three times with 0 L, the solid catalyst component was dried under reduced pressure.
4 kg was obtained. The solid catalyst component contains 1.8% by weight of titanium atom, 20.1% by weight of magnesium atom, 8.4% by weight of phthalic ester, 0.3% by weight of ethoxy group and 0.2% by weight of butoxy group, and has no fine powder. It had good particle properties. [Production of polymer] <Pre-activation of solid catalyst component>
1.5 L of n-hexane, triethyl aluminum 3 sufficiently dehydrated and degassed in an autoclave with a stirrer
7.5 mmol, 37.5 mmol of t-butyl-n-propyldimethoxysilane and 15 g of the above solid catalyst component were added, and propylene 1 was added while keeping the temperature in the tank at 30 ° C. or lower.
After pre-activation was performed by continuously supplying 5 g over about 30 minutes, the obtained solid catalyst slurry was subjected to an internal volume of 150 L.
Was transferred to a SUS autoclave equipped with a stirrer, and 100 L of liquid butane was added and stored. <Polymerization> Two SUS fluidized bed reactors having an internal volume of 1 m ^{3 with} a stirrer were connected to each other. Rear part (B
Component) propylene, butene-1 and ethylene are continuously copolymerized. (1) Production of component A in the first tank In a fluidized bed reactor with an internal volume of 1 m ^{3 and} a stirrer, under conditions of a polymer hold-up amount of 60 kG, a polymerization temperature of 75 ° C. and a polymerization pressure of 1.8 MPa, 70 mmol of triethylaluminum. / H, 14 mmol / h of t-butyl-n-propyldimethoxysilane and 0.32 g / h of the preactivated solid catalyst component are continuously supplied, and the hydrogen concentration in the gas phase is 0.3 vol%, Butene-1 concentration 15vo
Propylene, butene-1 and hydrogen were supplied so as to maintain 1%, and propylene and butene-1 were continuously copolymerized to obtain a polymer of 11.5 kg / h. The obtained polymer was continuously transferred to the second tank without deactivation. Also, as a result of sampling and analyzing a part of the polymer,
The butene-1 content was 14 wt%, and the intrinsic viscosity ([η]) at 135 ° C. of tetralin was 3.6 dl / g. (2) Production of component B in the second tank In a fluidized-bed reactor with an internal volume of 1 m ^{3 and} a stirrer, it is transferred from the first tank under the conditions of a polymer hold-up amount of 90 kg, a polymerization temperature of 75 ° C, and a polymerization pressure of 1.2 MPa. Gaseous hydrogen concentration of 0.3 vo
While supplying propylene, butene-1 and ethylene so as to maintain 1%, gas-phase butene-1 concentration of 18 vol% and gas-phase ethylene concentration of 8 vol%, the copolymerization of propylene, butene-1 and ethylene is continuously carried out. Perform 17.2
A polymer of Kg / h was obtained. The ethylene content of the obtained polymer is 2.3 wt%, the butene-1 content is 14 wt%,
The intrinsic viscosity ([η]) of tetralin at 135 ° C. is 3.8 dl
/ G. The polymerization ratio of the first tank and the second tank is 6
The ethylene content of the component B obtained from the analysis values of the component A and the final polymer was 7 wt%, butene-1
The content was 14 wt%, and the intrinsic viscosity ([η]) at 135 ° C. of tetralin was 4.6 dl / g. (3) Adjustment of MFR of block copolymer 0.032 parts by weight of 2,5-dimethyl 2,5-di (tert-butylperoxy) hexane was added to 100 parts by weight of the obtained copolymer. After mixing with a Henschel mixer, the mass discharged at 220 ° C. with a 40φ granulator was 10 kg / hr.
And extruded simultaneously with the melt-kneading to adjust the MFR to 3.4 g / 10 minutes.

The polypropylene-based block copolymers shown in Tables 1 and 2 were produced. Table 3 shows the evaluation results.
The resulting block copolymer film had good transparency and impact resistance, and had little change in transparency due to bleed after high-temperature heat treatment.

Example 2 The same procedure as in Example 1 was repeated except that the concentrations of ethylene, butene-1 and hydrogen were changed to obtain block copolymers shown in Tables 1 and 2. Then, the block copolymer was subjected to the same thermal decomposition as in Example 1, and the MFR was adjusted as shown in Table 2. Table 3 shows the evaluation results.

Comparative Example 1 Tables 1 and 2 were prepared in the same manner as in Example 1 except that the concentrations of ethylene and hydrogen were changed and butene-1 was not used.
Was obtained. Then, the block copolymer was subjected to the same thermal decomposition as in Example-1.
The MFR was adjusted as shown. Table 3 shows the evaluation results. Bleeding was observed after high temperature heat treatment.

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

[Table 3]

[0020]

EFFECT OF THE INVENTION The polypropylene block copolymer of the present invention has good transparency, has improved low-temperature impact properties, and has little bleed during high-temperature heat treatment.

Claims (4)

[Claims] 1. A part containing at least 5% by weight of a xylene-soluble part (CXS part) at 20 ° C. and excluding the CXS part (CXIS part)
The melting temperature (Tm) in DSC of 130 ° C. ≦ Tm ≦ 15
A polypropylene-based block copolymer in which the difference in transparency (haze) before and after 1 hour of treatment at 110 ° C. for a 150 μm thick film formed by extrusion of the copolymer at 5 ° C. is 8% or less. 2. In the first step, an ethylene content of 3% by weight or less and a butene content of 3% by weight in the substantially absence of an inert solvent.
The propylene-butene or ethylene-propylene-butene copolymer portion (component A) is polymerized in an amount of 40 to 85% by weight based on the total polymerization amount. % Or less, butene content is 3 to 3
5% by weight of a propylene-butene or ethylene-propylene-butene copolymer part (component B)
60% by weight, the intrinsic viscosity of component B ([η] B) is 1.5 to 5 dl / g, the intrinsic viscosity of component B ([η] B) and the intrinsic viscosity of component A ([η] A) Ratio ([η] B /
The polypropylene block copolymer according to claim 1, wherein [η] A) satisfies 0.5 ≦ [η] B / [η] A ≦ 1.8. 3. An ethylene content of the component B is defined as CBE weight%,
When the butene content is CBB weight%, the ethylene content of the component A is CAE weight%, and the butene content is CAB weight%, the formulas 3 ≦ CBE-CAE ≦ 15 and CAB-5 ≦ CBB ≦ CAB + 10 must be satisfied. The polypropylene-based block copolymer according to claim 2, wherein: 4. The molecular weight of the xylene-soluble portion at 20 ° C. is 26,000.
4. The polypropylene-based block copolymer according to claim 1, wherein the content of the following components is 6% by weight or less.