JPH01103442A - Polypropylene composite laminated molded body - Google Patents

Abstract

PURPOSE:To obtain a composite laminated molded body superior in low- temperature heat-sealing properties by a method wherein the title polypropylene is made into a repeating unit resulting from propylene of a specific ratio, a respeating unit resulting from ethylene, a repeating unit resulting from alpha-olefin and a mol ratio of a specific range. CONSTITUTION:A composite laminated molded body is obtained by laminating a base material layer comprised of crystalline polypropylene and a layer comprised of a propylene random copolymer. A propylene.alpha-olefin random copolymer besides a single polymer is used for the crystalline polypropylene constituting the base material layer. In a composition A of the propylene random copolymer, a propylene ingredient (a), ethylene ingredient (b) and alpha-olefin ingredient (c) fall respectively within ranges of 96-86mol%, 0.5-6mol% and 2.5-13mol%. A mol ratio (C)/ [(b)+(c)] falls within a range of 0.3-0.9 in relation to the ethylene ingredients (b) and olefin ingredient (c). Consequently, a polypropylene composite laminated molded body whose heat-sealing properties and heat-sealing strength under a low temperature are excellent and a heat-sealable temperature sphere is improved can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application 1] The present invention relates to a polypropylene composite laminate molded product with improved heat sealability. More specifically, the present invention relates to a polypropylene composite laminate molded product having improved heat-sealability, heat-sealability, transparency, anti-blocking property, solvent elution property, and heat-seal strength at low temperatures.

[Prior art] Crystalline polypropylene film has excellent mechanical properties such as tensile strength, rigidity, surface hardness, and impact strength, optical properties such as gloss and transparency, and food hygiene properties such as nontoxicity and odorlessness. Because of this, it is widely used in the field of packaging, especially food packaging.

However, a single layer polypropylene film has the disadvantage that the temperature at which it can be heat-sealed is high and the appropriate temperature range is narrow.

In order to improve the heat sealability of this polypropylene film, several methods have already been proposed in which a low melting point resin is laminated on one or both sides of a crystalline polypropylene film.

For example, JP-A-55-65552 discloses a propylene random copolymer consisting of an ethylene hata propylene random copolymer containing propylene as a main component and a propylene/α-olefin random copolymer containing propylene as a main component. A method of laminating a composition to a crystalline polypropylene film is disclosed. Also, JP-A-55-916
65, a propylene random copolymer composition consisting of an ethylene/propylene random copolymer containing propylene as a main component and a 1-butene/ethylene random copolymer containing 1-butene as a main component is described as crystalline polypropylene. A method of laminating the film is disclosed. Furthermore, JP-A-54-106585 discloses ethylene-propylene random copolymers containing propylene as the main component, 1-butene/ethylenically unsaturated monomer copolymers containing 1-butene as the main component, and A method of laminating a propylene random copolymer composition comprising a molecular weight thermoplastic resin to a crystalline polypropylene film is disclosed.

Furthermore, the above-mentioned Japanese Patent Application Publication No. 55-91665 (Japanese Patent Application No. 53-1)
65137) and the above-mentioned JP-A-54-106535 (
U.S. Pat. 1-butene, whose main component is
A propylene random copolymer composition is disclosed that can include an embodiment in which a propylene random copolymer composition, which can include a composition consisting of a propylene copolymer, is laminated onto a crystalline polypropylene film. However, no specific example of the above-mentioned aspect is shown, and the above-mentioned Japanese Patent Application Laid-Open No.
As specified in No.-106585, in this embodiment, only an example in which a low molecular weight thermoplastic resin is further used in combination is shown.

Although the heat-sealability of the propylene film in the laminates obtained by these methods is improved, the heat-sealable temperature is still quite high, and the applicable temperature range is narrow, so it is still far from being sufficient. It was also difficult to say that the heat seal strength was sufficient. In addition, in order to develop antistatic performance in these polyp-a-pyrene composite laminates, a method of subjecting them to low-temperature heat treatment for several days is usually adopted, but in that case, the heat-sealing temperature increases considerably. There were drawbacks such as. In this way, in the field of packaging applications using polypropylene films, polypropylene composite laminates have been developed that lower the heat-sealable temperature, expand the range of heat-sealable applications, have excellent heat-sealing strength, and have a small increase in heat-sealable temperature due to heat treatment. The body is in high demand.

[Problem to be solved by the invention J The inventors have
Research was conducted with the aim of developing a polypropylene composite laminate molded product that has crystalline polypropylene as a base layer and has excellent low-temperature heat-sealability and heat-seal strength. As a result, a polypropylene composite laminate formed by laminating a layer made of a propylene-based random copolymer mainly composed of propylene on at least one side of a base material layer made of crystalline polypropylene can be heated at a relatively low temperature. It has been discovered that heat sealing is possible, that the heat sealing temperature range is wide, that the heat sealing strength is excellent, and that the degree of increase in the heat sealable temperature due to heat treatment is small.

Therefore, the object of the present invention is to have excellent low-temperature heat sealability,
It is an object of the present invention to provide a heat-sealable polypropylene composite laminate molded product having excellent heat-sealing strength and having a small increase in heat-sealable temperature due to heat treatment.

The above objects and many other objects and advantages of the present invention will become more apparent from the following description.

[Means and effects for solving the problems] According to the present invention, in a polypropylene composite laminate molded article in which a layer made of a propylene random copolymer is laminated on at least one side of a base material layer made of crystalline polypropylene, , the propylene-based random copolymer has repeating units derived from propylene (propylene component), repeating units derived from ethylene (ethylene component), and repeating units derived from butene-1, an α-olefin component having 4 to 20 carbon atoms. A propylene-based random copolymer consisting of the following items (A) 96 to 86 mol% of repeating units derived from propylene (,) and 0.5 to 6 repeating units (b) derived from ethylene. mol% and the repeating unit (e) derived from the α-olefin is 2.5 and e) is 0.
．． (B) Intrinsic viscosity [η1, measured in decalin at 135°C, is in the range 0.5 to 6 dfl/g, (C) Measured by differential scanning calorimeter. (D) Xl! (E) The butene-containing fiBt (mol%) in the components soluble in n-decane at 25°C is 0.582≦B, ≦5, O
A polypropylene composite laminate molding, characterized in that it is a propylene-based random copolymer that satisfies the following formula: H2 is in the range of 1, B2 represents the butene content (mol%) in the propylene-based random copolymer. The body is provided.

The polypropylene composite laminate molded product of the present invention is a composite laminate molded product in which scraps made of a propylene-based random copolymer are laminated on one or both sides of a base material layer made of crystalline polypropylene, and its shape can be any shape. Examples thereof include laminated films, laminated sheets, laminated packaging bags, laminated containers, and other molded bodies of various shapes that impart heat sealability.

The base material layer made of crystalline polypropylene constituting the polypropylene composite laminate molded product of the present invention may be in an unstretched state, -axially stretched state, or biaxially stretched state,
Similarly, the layer made of the propylene random copolymer may be in an unstretched state, a -axially stretched state, or a biaxially stretched state.

Therefore, the base material layer made of crystalline polypropylene and the layer made of the propylene-based random copolymer of the polypropylene composite laminate molded product may be constructed from any of the above-mentioned combinations.

The thickness of the base material layer made of crystalline polypropylene constituting the polypropylene composite laminate molded product is arbitrary and not particularly limited, but the thickness of the heat seal layer made of a propylene random copolymer is generally 0.1 to 1. 50μ, preferably in the range of 0.5 to 30μ. When the polypropylene composite laminate molded product is a composite laminate film or a composite laminate sheet, the thickness of the crystalline polypropylene base material is in the range of 5 to 200μ, preferably 10 to 70μ, and the propylene random composite The thickness of the heat sealing layer of polymer is usually in the range of 0.1 to 50 microns, preferably 0.5 to 30 microns.

Examples of the method for manufacturing the polypropylene composite laminate molded product of the present invention include the following method.

(1) A method in which a base material made of crystalline polypropylene and the propylene random copolymer are laminated by coextrusion, and if necessary, longitudinal stretching and V/or transverse stretching are performed separately or simultaneously. .

(2) The propylene random copolymer is extruded and laminated in a molten state on the surface of a crystalline polypropylene base that has been unstretched, -axially stretched or biaxially stretched, and the base material is
If it is in a stretched state, it is further subjected to one-pongee stretching or two-wheel stretching as necessary.

In addition, when the base material is in a uniaxially stretched state, the method involves similarly extruding and laminating, and then further stretching in the same direction or in a cross direction as the base material, if necessary.

(3) A method of laminating a film of the propylene random copolymer on the surface of a substrate made of crystalline polypropylene using an adhesive.

The crystalline polypropylene constituting the base material layer of the polypropylene composite laminate molded product of the present invention includes, in addition to a crystalline propylene homopolymer, a crystalline propylene/α-olefin random copolymer mainly composed of propylene, For example, propylene/ethylene random copolymers with an ethylene content of 0.1 to 5 mol%, propylene/ethylene with an ethylene content of 0.1 to 4 mol%, and a 1-butene content of 0.1 to 5 mol%. Examples include a 1-butene random copolymer and a propylene/1-butene random copolymer with a 1-butene content of 0.1 to 5 mol%. The intrinsic viscosity of the crystalline polypropylene measured in decalin at 135°C [η1 is usually 1.5 to 4
dl/g, preferably in the range of 1.7 to 3.5 dI/g, and the crystallinity measured by X-ray diffraction is usually 50 to 70%, preferably 55 to 70%.
% range.

The propylene random copolymer constituting the polypropylene composite laminate of the present invention is a copolymer containing propylene as a main component, and includes at least a propylene component (,).
, the ethylene component (b) and the number of carbon atoms is 4 to 20
It is a copolymer consisting of the α-olefin component (c).

The composition (A) of the propylene random copolymer has a propylene component (, ) of 96 to 86 mol%, preferably 95 to 87 mol%, more preferably 95 to 8 mol%.
8 mol%, ethylene component (b) 0.5 to 6 mol%
, preferably 1.0 to 5.0 mol%, more preferably 1.5 to 4.0 mol%, and an α-olefin component (C) having 4 to 20 carbon atoms, 2.5 to 13
It ranges from 3 to 11 mol%, more preferably from 4 to 10 mol%.

Regarding the ethylene component (b) and the α-olefin component (c), the molar ratio c/(b+c) is from 0.3 to 0.9, preferably from 0.4 to 0.8, more preferably from 0.5 to 0.5. It is in the range of 8.

The α-olefin having 4 to 20 carbon atoms constituting the propylene random copolymer includes 1-butene, 1-
Pentene, 1-hexene, 4-methyl-1-pentene,
3-methyl-1-pentene, 1-heptene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1
- Octadecene and other carbon atoms having 10 or less carbon atoms are preferable, and those having 4 to 6 carbon atoms are more preferable, particularly 1-
Butene is preferred. These α-olefins may be used alone (or in a mixture of two or more types).

The intrinsic viscosity ['7] (B) of the propylene random copolymer measured in decalin at 135°C is 0.5 to 6.
dl/g, preferably in the range from 1 to 5 di/.

The melting point [TM] (C) of the propylene random copolymer measured by a differential scanning calorimeter, Model DSC-II manufactured by Parking Elmer, is in the range of 115°C to 133°C, preferably 120°C to 130°C. . here,
The DSC melting point is determined by heating a press sheet with a thickness of 0.11 after 20 hours of molding at a temperature increase rate of 10°C/section from θ to 200°.
It was measured at C*, and the maximum endothermic peak was designated as T-.

The crystallinity (D) of the propylene random copolymer measured by X-ray diffraction is in the range of 30 to 60%, preferably 35 to 55%.

The crystallinity is 1.5111 m thick after 20 hours after molding.
It was determined by X-ray diffraction measurement of the press sheet.

Butene content fi [B+mot%] (E
) satisfies the following general formula.

0.5B2≦B1≦5. OB2 preferably 0, 682≦B1≦3. OB2 More preferably 0.782≦BI≦1,782 Particularly preferably 0.7 B2≦B1≦1.5B2 In the E formula, B2 is the butene content (no
1%) 1 The propylene random copolymer is (A) as described above.
A more preferable copolymer satisfies the binding factor expressed by the characteristic value of E) or E), and also satisfies the following (F').

n- of the propylene random copolymer at 25°C
The amount soluble in decane [w+w%] (T'') is determined by the general formula % in relation to the melting point Tm of the copolymer, preferably by the general formula 0.04 (165-Ta+)≦-1 ≦0.13 (185
-To) It particularly preferably satisfies the general formula % (where Tm is the numerical value of the melting point of the copolymer, excluding dimensions).

In the present invention, the amount of copolymer into n-decane solvent at 25°C is collected by the following method.

That is, in a flask with 12 stirring blades, 5 g of copolymer sample and 0.3 g of 2,6-di-tert-butyl-4-
Add 7 ethyl methyl, 500 x 2 n-decane, and add 1
Dissolve on a 40°C oil bath. After dissolution, the mixture is allowed to cool naturally at room temperature for about 3 hours, and then cooled on a 25°C water bath for 12 hours. The n-decane solution containing the precipitated copolymer and dissolved polymer was separated by filtration using a G-4 glass filter, and the solution was separated by filtration.
Dry at 150℃ at 0m5+Hg until constant weight, 25
Collect the polymer that is soluble in n-decane at <0>C. The weight was measured, and the amount of the copolymer soluble in the n-decane solvent at 25°C was calculated and determined as a percentage of the weight of the sample copolymer.

The propylene random copolymer constituting the polypropylene composite laminate of the present invention contains, for example, (A) magnesium, titanium, halogen, and an electron donor as essential components, and has an average particle size of about 5 to about A highly active and highly stereoregular titanium catalyst component having a geometric standard deviation value of particle size distribution of less than 2.1 at 300μ, (B) an organometallic compound catalyst component of a metal from Group 1 to Group 3 of the periodic table, and (C ) a catalyst formed from an electron donor catalyst component, and the titanium catalyst component (
20 to 100,100 moles per gram of said catalyst component (A) in the presence of a catalyst containing from 0.5 to 30 moles of electron donor (C) per gram atom of titanium of A).
In the presence of an α-olefin prepolymerization catalyst obtained by prepolymerizing α-olefins having 2 to 20 carbon atoms in the O range, at least propylene, ethylene, and α-olefins having 4 to 20 carbon atoms are but'
At least the organometallic compound catalyst component (B
) and an electron donor catalyst component (C) in coexistence, and copolymerization can be carried out.

For catalyst components, copolymerization conditions, and other manufacturing conditions, please refer to
The propylene random copolymer can be produced according to this method, as it is described in the patent application specification of Japanese Patent Application No. 61-239338 "Method for Producing Propylene Random Copolymer" filed by the present applicant. . At the time of manufacturing, according to the method for measuring and determining characteristics (A) to (E), which has already been described in detail, characteristics (A) to (E) are satisfied, and more preferably characteristic (F) is determined.
This can be easily carried out by selecting and setting the catalyst and polymerization conditions experimentally in advance so as to satisfy the following conditions.

In addition to the above polymer components, the propylene random copolymer may contain heat stabilizers, weather stabilizers, nucleating agents, lubricants, slip agents, antistatic agents, antiblocking agents, antifogging agents, pigments, dyes, etc. It may be blended, but the blending ratio is appropriate within a range that does not impair the low-temperature heat-sealability and heat-seal strength of the polypropylene composite laminate molded product.

Effect 1 of the invention The polypropylene composite laminate molded product of the present invention, which is formed by laminating a layer made of the propylene random copolymer on one or both sides of a base material made of crystalline polypropylene, can be heat-sealed at low temperatures. It has excellent heat-sealability and heat-sealing strength, has an improved heat-sealable temperature range, and has excellent scratch resistance and blocking resistance. Therefore, the polypropylene composite laminate molded product can be used for food packaging, food packaging, etc. by utilizing such characteristics.
Suitable for wrapping daily necessities such as clothing and miscellaneous goods.

[Example J] Next, the present invention will be specifically explained with reference to Examples. In addition, in the examples, each evaluation item was evaluated according to the following method.

(1) Cloudiness Measured by ASTM D1003 method.

(2) Heat seal strength Evaluation was made according to JIS Z1707.

The surfaces of the polypropylene composite film on which the low-crystalline propylene copolymer compositions are laminated are placed on top of each other, and the temperature is set at 100 to 150°C at 5°C intervals at 2 kg/as.
After heat-sealing with a 5-1 seal bar for 1 second at a pressure of The lowest heat-sealing temperature at which breakage occurred outside was taken as the complete heat-sealing starting temperature, and the peel strength at that temperature was taken as the heat-sealing strength.

(3) Blocking resistance Evaluated according to ASTM D1893. Cut the polypropylene composite film into a piece with a diameter of 15cm and a length of 20cm, overlap the surfaces on which the low-crystalline propylene copolymer composition is laminated, and sandwich the film between two glass plates.
A load of 1 kg was placed on it and it was left in an air oven at 50°C. After 10 days, the sample was taken out and its peel strength was measured using a universal testing machine, and the peel strength per IC- was taken as the blocking value. In addition, the extent to which the low molecular weight components were embossed on the surface of the low-crystalline propylene copolymer composition layer of the same film (presence or absence of whitening) was visually evaluated.

(4) Slip property A film made according to ASTM D1894 was
The sample was left in an open air environment at 0° C. for one day, and the static friction coefficient and dynamic friction coefficient of the surface of the low-crystalline propylene copolymer composition layer were measured.

Example 1 [Preparation of highly active, highly stereoregular solid titanium catalyst component J] 714 g of anhydrous magnesium chloride, 3.72 g of decane, and 3.51 g of 2-ethylhexyl alcohol were mixed at 130°C with 2
After a heating reaction was carried out for a period of time to form a homogeneous solution, anhydrous 7-talic acid was added to this solution, and stirring and mixing was further carried out at 130° C. for 1 hour to uniformly dissolve the anhydrous 7-talic acid in the solution. After cooling the homogeneous solution thus obtained to room temperature, -2
The entire amount was dropped into titanium tetrachloride 202 maintained at 0° C. over 1 hour. After charging, the temperature of this liquid mixture was raised to 110°C over 4 hours, and when it reached 110°C, diisobutyl 7 clay) 0. Add i and keep stirring at the same temperature for 2 hours.

After the completion of the 2-hour reaction, collect the solid part by hot filtration, resuspend this solid part in 281 TiCl<, and then heat the reaction again at 110°C for 2 hours.6 After the completion of the reaction. The solid portion was collected again by hot filtration and thoroughly washed with decane and hexane at 110° C. until no titanium compound was detected in the washing liquid.

The titanium catalyst component synthesized by the above production method was dried using a dryer. The composition of the titanium catalyst component thus obtained was 2.3% by weight of titanium, 58.0% by weight of chlorine,
The content was 18.0% by weight of magnesium and 14.0% by weight of diisobutyl 7 clay.

The titanium catalyst component was a granular catalyst with an average particle size of 18 μm and a geometric standard deviation (δg) of particle size distribution of 1.2.

[Prepolymerization 1 100 mmol of triethylaluminum and 20 mmol of diphenyldimethoxysilane were mixed in 101 mmol of hexane. A titanium catalyst (dry product) synthesized by the above synthesis method was added to the mixed solution (10 mmol in terms of titanium atoms), and reslurry was carried out for 2 hours. Next, feed propylene at 38rf so that the amount is 50g per 1g of titanium catalyst component.
Prepolymerized.

The polymerization temperature was controlled at 0-8°C. After the prepolymerization was completed, it was washed 6 times with hexane, and then washed once so that the concentration of the titanium catalyst component was 2 mmol/l as Ti atoms.
Diluted with hexane and stored in a container with a stirrer.

[Polymerization] A polymerization reaction was carried out using a fluidized bed polymerization reactor having a diameter of 340 mm and a reaction volume of 402 mm. The catalyst was supplied to the fluidized bed polymerization reactor through a catalyst supply nozzle at a rate of 0.6 mmol T.
It is continuously sprayed and supplied as a mixture consisting of a ratio of i/Hr and a ratio of N2y 100 NI/Hr and propane (liquid) 2.572/H, and a mixed olefin consisting of ethylene, propylene, and 1-butene as a raw material olefin. A continuous gas phase polymerization reaction was carried out while continuously supplying H2tt and H2tt as a molecular weight control agent. Among the raw material olefins, 1-butene was vaporized using a vaporizer. The raw material gas composition at the time of supply is as follows,
The propylene supply rate was 516 ONl/H.

C, /Cff (mol) 0.0977C2/
C3('t) 0.0233H2/C3("
> 0.0016N2103 (” )
0.0388 During the gas phase polymerization reaction, the temperature is 90℃, the pressure is 8゜0 kg/am2G, and the superficial velocity of W gas is 40℃.
cm/s, and the amount of prepolymerized catalyst supplied was controlled so that the amount of ethylene, propylene, and 1-butene random copolymer produced was 5 kg/H.

Triethylaluminum was prepared in advance with hexane to a concentration of 200 mmol/12, and was continuously supplied at a rate of 15 to 20 mmol/H. Diphenyldimethoxysilane, which had been prepared in advance at a concentration of 200 mmol/l with hexane, was also continuously fed at a rate of 15-20 mmol/hr. Other polymerization conditions and basic physical properties of the polymer obtained by the above polymerization are shown in Table 1.

[1ft of composite film! ] The low crystalline propylene copolymer composition obtained by the above production method was supplied to a two-layer film die at a resin temperature of 240°C.

Meanwhile, in another extruder, isotactic index 96
%, the crystalline polypropylene that will become the base material layer with a melt index of 1°5 is melted, and the above 271% is melted at a resin temperature of 240°C.
The low-crystalline propylene copolymer composition and the crystalline polypropylene for the base material layer are co-extruded by supplying it to a film gooey, and the base material layer (4) made of the crystalline polypropylene is coextruded.
A composite film was obtained, which was formed from a layer (10μ) of the low-crystalline propylene copolymer composition. Table 3 shows the performance evaluation results of this polypropylene composite film.

Examples 2 to 4 Prepolymerization was carried out in the same manner as in Example 1 using a titanium catalyst component prepared in the same manner as in Example 1. Random copolymerization was then carried out by gas phase polymerization under the conditions shown in Table 1. Table 1 shows the basic physical properties of the resulting copolymer.

In addition, only in Example 4, the prepolymerization conditions were changed such that the amount of propylene supplied was 96 g per 1 g of the titanium catalyst component and the darkness during prepolymerization was 5 hours.

Composite films were prepared in the same manner as in Example 1 in Examples 2 and 14, and in Example 3 only in the following manner.

After melting the crystalline polypropylene base material used in Example 1 with an extruder, it was extruded through a T-guy at a resin temperature of 270°C.
The mixture was cooled and solidified, and then passed through heating rolls to be stretched in the longitudinal direction at a stretching ratio of 5 times, to form a single sheet of crystalline polypropylene. On one side of this single stretched sheet of crystalline polypropylene, the low crystalline propylene copolymer composition listed in Table 1, which was melt-kneaded using another extruder, was melted and heated to a resin temperature of 250 using another T-die.
The base material layer ( 22μ) and the low-crystalline propylene copolymer composition are laminated, and the crystalline polypropylene base layer is biaxially stretched, and the low-crystalline propylene copolymer composition A polypropylene composite film was obtained in which the layer consisting of the following was uniaxially stretched. The performance evaluation results of the obtained polypropylene composite film are shown in Table 3.

Comparative Example 1 Polymerization was carried out in the same manner as in Example 1, except that the polymerization amount of child fi1 was changed to 3 g per 1 g of catalyst and the copolymerization conditions were changed to those shown in Table 2. A film was prepared and evaluated.

The results are shown in Tables 2 and 3.

Claims (1)

[Claims] (1) In a polypropylene composite multilayer molded article in which a layer made of a propylene-based random copolymer is laminated on at least one side of a base material layer made of crystalline polypropylene, the propylene-based random copolymer is at least derived from propylene. Repeating unit (a) Repeating unit derived from ethylene (b) and α- having 4 to 20 carbon atoms
A propylene-based random copolymer consisting of a repeating unit (c) derived from an olefin, wherein the following item (A) has a repeating unit (a) derived from propylene of 96
86 mol% of repeating units derived from ethylene (
b) is 0.5 to 6 mol% and repeating unit (c) derived from the α-olefin is 2.5 to 13 mol%
and the molar ratio c/(b+c) is in the range of 0.3 to 0.9; (B) 135 in decalin;
Intrinsic viscosity [η] measured at °C is 0.5 to 6 dl/g
(C) The melting point [Tm] measured by differential scanning calorimeter is in the range of 115 to 133°C, (D) The degree of crystallinity measured by X-ray diffraction method is (E) Butene content B_1 (mol%) in the components soluble in n-decane at 25°C is 0.5B_2≦B_1≦5.
．． 0B_2 [wherein B_2 represents the butene content (mol%) in the propylene random copolymer] body.