JPH11179866A - Film for packaging retort food - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film for packaging a retort food having an excellent transparency, impact resistance and food hydienic qualities. SOLUTION: The film for packaging a retort food comprises at least (a) a layer, and (b) a layer. The (a) layer is made of a crystalline propylene random copolymer having a repeating unit derived from a propylene and a repeating unit derived from an ethylene and/or a repeating unit derived from a 4- C α- olefin or a resin composition containing the copolymer. And, the (b) layer is made of a propylene block copolymer having 5 wt.% or more of 20 deg.C xylene soluble part (CXS part) and 130 to 155 deg.C of a highest melting peak temperatureTM of a part (CXIS part) except the CXS part or a resin composition containing the propylene block polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a retort food packaging film having excellent transparency, low-temperature impact strength, and excellent food hygiene.

[0002]

2. Description of the Related Art Polypropylene films are widely used in packaging fields such as food packaging and fiber packaging because of their excellent appearance, mechanical properties and packaging suitability.

[0003] Propylene homopolymers and crystalline propylene-α-olefin random copolymers are excellent in transparency and food hygiene, but have poor low-temperature impact resistance.
Although the propylene block copolymer has a certain degree of low-temperature impact resistance, it is inferior in transparency, and each has its limitations.

[0004] For these reasons, propylene block copolymers are used, although they are inferior in transparency, especially in applications requiring impact resistance, while crystallinity is used in applications requiring transparency in addition to impact resistance. A material having impact resistance obtained by blending a low-crystalline ethylene-α-olefin copolymer with a propylene-α-olefin random copolymer is generally used. However, in order to impart sufficient impact resistance, blending many low-crystalline ethylene-α-olefin copolymers with a crystalline propylene-α-olefin random copolymer results in deterioration of food hygiene, If the blend amount of the low crystalline ethylene-α-olefin copolymer is small, there is a problem that sufficient impact resistance cannot be obtained.

[0005] A retort food packaging film excellent in transparency, impact resistance and food hygiene has not been obtained by the conventionally known methods.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a retort food packaging film having excellent transparency, impact resistance and food hygiene.

[0007]

Means for Solving the Problems The inventors of the present invention have made intensive studies on such problems, and as a result, have found that a multilayer film comprising at least two layers, a layer comprising a specific crystalline propylene random copolymer and a The inventors have found that the object of the present invention can be achieved by laminating layers composed of a propylene-based block copolymer, and have completed the present invention.

That is, the present invention is a retort food packaging film comprising at least the following layers (a) and (b). (A) layer: a repeating unit derived from propylene,
A layer comprising a crystalline propylene random copolymer comprising a repeating unit derived from ethylene and / or a repeating unit derived from an α-olefin having 4 or more carbon atoms or a resin composition containing the copolymer (b) ) Layer: a portion containing at least 5% by weight of a xylene-soluble portion (CXS portion) at 20 ° C. and excluding the CXS portion (CXIS)
Part) has a maximum melting peak temperature (Tm) of 130 to 155 ° C.
The present invention will be described in detail below with reference to a layer composed of a propylene-based block copolymer or a resin composition containing the propylene-based block copolymer.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The retort food packaging film of the present invention is a film comprising at least the following layers (a) and (b). The (a) layer is composed of a repeating unit derived from propylene (hereinafter, referred to as a “propylene unit”) and a repeating unit derived from ethylene (hereinafter, referred to as “propylene unit”) from the viewpoints of transparency, food hygiene, and low-temperature sealability.
A crystalline propylene random copolymer (I) comprising an ethylene unit) and / or a repeating unit derived from an α-olefin having 4 or more carbon atoms (hereinafter referred to as an “α-olefin unit”) or This is a layer made of a resin composition containing the copolymer. As the α-olefin, butene-1, hexene-1, octene-
Α-olefins having 4 to 10 carbon atoms, such as 1, decene-1 and the like. The content of the ethylene unit and / or the α-olefin unit having 4 or more carbon atoms is usually 0.5 to 30% by weight. The crystalline propylene-ethylene and / or α-olefin random copolymer (I) having 4 or more carbon atoms is not particularly limited, but has a melting point of 130 to 155 ° C.
Are preferred.

[0010] The crystalline propylene-ethylene and / or α-olefin random copolymer (I) having 4 or more carbon atoms used in the present invention can be produced by a known method. For example, a Ziegler-Natta type catalyst, cyclopentane Catalyst system consisting of a transition metal compound of group IVB having a dienyl ring and an alkylaluminoxane, or reacting with a transition metal compound of group IVB having a cyclopentadienyl ring to form an ionic complex It can be produced by a batch polymerization method, a continuous polymerization method of continuous polymerization, or the like, using a catalyst system comprising a compound to be reacted and an organoaluminum compound.

The layer (b) contains at least 5% by weight, preferably 7 to 30% by weight, of a xylene-soluble portion (CXS portion) at 20 ° C. from the viewpoint of transparency and impact resistance, and excludes the CXS portion. Melting peak temperature (T
m) is a layer composed of a propylene-based block copolymer (II) having a temperature of 130 to 155 ° C or a resin composition containing the copolymer (II). Maximum melting peak temperature (Tm)
Is measured with a differential scanning calorimeter (DSC). The CX
When the content of the S portion is less than 5% by weight, the impact resistance is poor.
When the maximum melting peak temperature (Tm) of the CXIS part is lower than 130 ° C., heat resistance and food hygiene are inferior.
When it exceeds 5 ° C., transparency is poor.

The propylene-based block copolymer (II) used in the present invention comprises at least a repeating unit derived from propylene (hereinafter referred to as "propylene unit") and a repeating unit derived from ethylene (hereinafter referred to as "ethylene unit"). ") And / or a repeating unit derived from butene-1 (hereinafter, referred to as" butene-1 unit "), and at least a propylene unit and an ethylene unit and / or Butene
A propylene-based block copolymer obtained by continuously producing a copolymer component (component B) different from the above-mentioned component A, which is composed of 1 unit, and is a 20 ° C. xylene-soluble part (C
XS part) is 5% by weight or more, preferably 7 to 30% by weight, and the maximum melting peak temperature (Tm) of the part excluding the CXS part (CXIS part) is 130 to 155 ° C. Coalescence is preferred.

The propylene-based block copolymer is different from the propylene-ethylene and / or butene-1 copolymer component (A component) in the first step and the A component in the second step. A copolymer obtained by successively polymerizing a propylene-ethylene and / or butene-1 copolymer component (component B), wherein a copolymer terminal and another copolymer terminal are connected by a bond. It is not a typical block copolymer but a kind of a blend-type copolymer. The propylene-based block copolymer is also called an impact-resistant propylene copolymer.

CX of the above propylene block copolymer
If the S portion is less than 5.0% by weight, the impact resistance is poor, which is not preferable. Also, the maximum melting peak temperature (Tm) of the CXIS part of the propylene-based block copolymer is 130.
When the temperature is lower than ℃, the heat resistance is insufficient. On the other hand, when the temperature is higher than 155 ° C., transparency is inferior.

The propylene block copolymer (II)
Means that the content of ethylene units in the first step is 1.5 to 6.0.
% Of the propylene-ethylene copolymer portion (A component) is produced in an amount of 40 to 85% by weight of the total polymerization amount (the sum of the A component and the following B component). 17% by weight of propylene-ethylene copolymer part
(B component) is from 15 to the total polymerization amount (total of A component and B component).
A block copolymer obtained by producing 60% by weight, and the intrinsic viscosity ([η] B) of the component B is 2 to 5 dl / g;
Intrinsic viscosity of component B ([η] B) and intrinsic viscosity of component A ([η] A)
A propylene-based block copolymer having a ratio ([η] B / [η] A) of 0.5 to 1.8 is preferable.

The content of ethylene units in the propylene-ethylene copolymer portion (component A) produced in the first step is as follows:
2.5 to 4.5 from the viewpoint of the balance between flexibility and heat resistance
% Is more preferred.

The ethylene unit content of the propylene-ethylene copolymer part (component B) produced in the second step is as follows:
From the viewpoint of the balance between impact resistance and transparency at low temperatures,
12% by weight is more preferred.

The proportion of the propylene-ethylene copolymer part (component A) produced in the first step and the propylene-ethylene copolymer part (component B) produced in the second step is such that the amount of the component A is less than the total polymerization amount. Preferably 40 to 85% by weight, more preferably 55 to 83% by weight, B component is preferably 60 to 15% by weight, more preferably 45 to 17% by weight of the total polymerization amount.
It is.

The intrinsic viscosity ([η] B) of the B component of the propylene block copolymer is 2 to 5 dl / g, the intrinsic viscosity of the B component ([η] B) and the intrinsic viscosity of the A component ([η]). A)
Is preferably 0.5 to 1.8 ([η] B / [η] A) from the viewpoint of transparency. In particular, propylene
The intrinsic viscosity ([η] B) of the component B of the ethylene copolymer is as follows:
1. From the viewpoint of the balance between suppression of low molecular weight components and processability.
It is more preferably from 5 to 4.0 dl / g. [Η] B / [η]
The A ratio is more preferably 0.8 to 1.5 from the viewpoint of transparency.

From the viewpoint of transparency and impact resistance at low temperatures, the propylene-based block copolymer has a difference between the content of ethylene units of component B (EB) and the content of ethylene units of component A (EA). (EB-EA) is more preferably in the range of 3 to 15% by weight, and from the viewpoint of balance between transparency and impact resistance at low temperature, (EB-EA) is particularly preferably 5 to 10% by weight.

Further, from the viewpoint of suppressing bleeding whitening at a high temperature, the propylene-based block copolymer has an ethylene unit content of 3% by weight or less in the first step, butene-1
Propylene-ethylene-butene-1 copolymer portion (component A) having a unit content of 3 to 25% by weight is produced in an amount of 40 to 85% by weight based on the total polymerization amount (the sum of the component A and the following component B). In the second step, the content of ethylene units is 17% by weight or less,
A propylene-ethylene-butene-1 copolymer portion (B component) having a butene-1 unit content of 3 to 35% by weight is formed in an amount of 15 to 60% by weight based on the total polymerization amount (the sum of the components A and B). The intrinsic viscosity ([η] B) of component B is 1.5 to 5.0 dl / g, the intrinsic viscosity of component B ([η] B) and the intrinsic viscosity of component A Ratio with viscosity ([η] A)
([η] B / [η] A) is preferably a propylene-based block copolymer having a ratio of 0.5 to 1.8.

Ratio of propylene-ethylene-butene-1 copolymer part (component A) produced in the first step and propylene-ethylene-butene-1 copolymer part (component B) produced in the second step Is preferably 4% of the total polymerization amount of the A component.
0-85% by weight, more preferably 55-83% by weight, B
The component is preferably 60 to 15% by weight, more preferably 45 to 17% by weight of the total polymerization amount.

The intrinsic viscosity of component B ([η] B) of the propylene block copolymer is 1.5 to 5 dl / g, the intrinsic viscosity of component B ([η] B) and the intrinsic viscosity of component A ([[η] B). η]
The ratio ([η] B / [η] A) to A) is preferably from 0.5 to 1.8 from the viewpoint of transparency. In particular, the intrinsic viscosity ([η] B) of the B component of the propylene-ethylene-butene-1 copolymer is 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. More preferred.
[Η] B / [η] A ratio is 0.8 to 0.8 from the viewpoint of transparency.
1.5 is more preferred.

The ethylene unit content is measured by the ¹³ C-NMR method according to the method described on page 616 of a Handbook of Polymer Analysis (1995, published by Kinokuniya Bookstore). The ethylene unit content (EA) of the component A is analyzed by sampling the copolymer after the completion of the polymerization in the first step. The ethylene content (EB) of the component B is obtained by sampling the block copolymer after the completion of the polymerization in the second step and analyzing the ethylene content (EAB) of the block copolymer.
Further, it is determined from the following formula from the ratio of the A component (PA) and the ratio of the B component (PB). EA × PA / 100 + EB × PB / 100 = EAB EB = (EAB−EA × PA / 100) × 100 / PB

The propylene block copolymer (II)
Is a propylene-ethylene-butene-1 block copolymer, the ratio of the component A (PA) and the ratio of the component B (PB) are measured with a differential scanning calorimeter for the component A and all the polymers, respectively. From the melting peak calorific value. The ethylene unit content (EA) of the component A and the butene-1 unit content (BA) of the component A are analyzed by sampling the copolymer after the completion of the polymerization in the first step. The ethylene unit content (EB) of the B component and the butene-1 unit content (BB) of the B component are as follows:
After the completion of the polymerization in the second step, the block copolymer was sampled, and the ethylene unit content (EAB) and butene-
The content of one unit (BAB) was determined by analysis, and the ratio of component A (PA) and the ratio of component B (PB), the content of ethylene unit of component A (EA) and the butene-1 unit of component A It is determined from the content (BA) by the following equation. EB = (EAB−EA × PA / 100) × 100 / PB BB = (BAB−BA × PA / 100) × 100 / PB

The intrinsic viscosity is measured in tetralin at 135 ° C. using an Ubbelohde viscometer. The intrinsic viscosity ([η] A) of the component A is analyzed by sampling the copolymer after completion of the polymerization in the first step. Intrinsic viscosity of component B ([η] B)
Is to sample the block copolymer after completion of the polymerization in the second step, analyze the intrinsic viscosity ([η] AB) of the block copolymer, and further determine the ratio of the component A (PA) and the ratio of the component B (PB). From the following equation. [η] A × PA / 100 + [η] B × PB / 100 = [η] A
B [η] B = ([η] AB− [η] A × PA / 100) × 100
/ PB

The propylene block copolymer (II) used in the present invention is obtained by polymerizing the component A in the same polymerization tank in the presence of, for example, a Ziegler-Natta type catalyst, and subsequently polymerizing the component B. The production can be performed by a batch polymerization method or a continuous polymerization method in which the A component and the B component are continuously polymerized using a polymerization tank having at least two tanks.

Specifically, for example, (a) in the coexistence of an organosilicon compound having a Si—O bond, a compound of 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 atom, 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); or (a) A titanium compound represented by the general formula Ti (OR ¹ ) _n X _4-n (R ¹ is a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen atom, and n is a number satisfying 0 <n ≦ 4). An organoaluminum compound represented by the general formula: AlR ² _m Y _3-m (R ² represents a hydrocarbon group having 1 to 20 carbon atoms, Y represents a halogen atom, and m represents a number of 1 ≦ m ≦ 3) Obtained by reducing A solid product containing a hydrocarbyloxy group insoluble in a hydrocarbon solvent is prepolymerized with ethylene, and then a slurry is formed at a temperature of 80 to 100 ° C in a hydrocarbon solvent in the presence of an ether compound and titanium tetrachloride. In the presence of a Ziegler-Natta type catalyst comprising at least titanium, magnesium and halogen as essential components, such as a hydrocarbyloxy group-containing solid catalyst component obtained by treating in a state, (b) a catalyst system comprising an organoaluminum compound, The molar ratio of Al atoms in the component (b) / Ti atoms in the component (a) is from 1 to 2000, preferably from 5 to 1500,
The molar ratio of Al atoms in component (c) / component (b) is set to 0.0
The polymerization temperature is 20 to 150 ° C, preferably 50 to 95 ° C.
° C., the polymerization pressure is atmospheric pressure ~40kg / cm ² G, preferably under conditions of 2~40kg / cm ² G, and supplies the hydrogen to propylene and ethylene and the molecular weight regulator in the first step propylene - ethylene copolymer After the production of the polymer portion (component A), propylene, ethylene and hydrogen are supplied in the second step to produce the propylene-ethylene copolymer portion (component B).

The crystalline propylene-ethylene and / or α-olefin random copolymer (C) having 4 or more carbon atoms (I) and the propylene-based block copolymer (II) used in the present invention can be prepared in the presence of an organic peroxide. It is possible to change the flowability typified by the melt flow rate in the absence of any known method, for example. The crystalline propylene random copolymer (I) and the propylene-based block copolymer (II) have a melt flow rate of 1.0 to 10 g / 1.
Those having a range of 0 minutes are preferred from the viewpoint of high-speed processability at the time of film formation, and a range of 1 to 5 g / 10 minutes is more preferred.

The retort food packaging film of the present invention comprises:
The method is not particularly limited as long as a polypropylene film is produced by a melt extrusion method such as a T-die film forming method or a tubular film forming method, which is usually used in industry. The T-die film forming method in which the film is carried out is preferred. The retort food packaging film of the present invention can be stretched and used by a tenter film forming method or the like as long as its purpose is not impaired.

The retort food packaging film of the present invention comprises:
Other films, for example, a polypropylene biaxially stretched film, an unstretched and stretched nylon film, a stretched polyethyl terephthalate film or an aluminum foil, and at least one layer of a composite film produced by a method such as a dry lamination method or an extrusion lamination method. Are also preferably used, especially after forming into a composite film.
It can be used for heat-resistant applications such as heat treatment in the range of 125C to 125C.

[0032] The retort food packaging film of the present invention comprises 2
In the case of a layer, from the viewpoint of transparency and food hygiene, it is preferable to use the layer (b) by bonding it to a stretched nylon film or the like. The thickness of the retort food packaging film of the present invention is usually 10 to 500 μm, preferably 30 to 150 μm, and the thickness ratio of each layer (a) layer / (b) layer is usually 1/9 to
9/1, and preferably 1/9 to 7 / from the viewpoint of impact resistance.
3. In the case of three layers, the thickness ratio of each layer (a) layer / (b)
Layer / other layers are usually 1/50/1 to 50/1/5
0, preferably 1/50/1 to 10/1/10.

The retort food packaging film of the present invention comprises:
Antioxidants, if necessary, as long as the purpose is not impaired,
An ultraviolet absorber, an antistatic agent, an antiblocking agent, a lubricant, an antifogging agent and the like can be included.

[0034]

Hereinafter, the present invention will be described based on examples.
The present invention is not limited to these examples.

Next, methods for measuring physical properties in Examples and Comparative Examples will be described. (1) Ratio of Component A and Component B (% by Weight) The ratio of component A (PA) and the ratio of component B (PB) were determined from the material balance during polymerization of component A and component B. (2) Intrinsic viscosity ([η]) The measurement was carried out in tetralin at 135 ° C. using an Ubbelohde viscometer. Intrinsic viscosity of component A and component B ([η] A, [η] B) Intrinsic viscosity [η] measured after completion of polymerization of component A in the first step.
A and intrinsic viscosity [η] A measured after the completion of the polymerization in the second step.
B and the proportion of the A component (PA), the proportion of the B component (P
From B), the intrinsic viscosity [η] B of the component B was determined by the following equation. [η] B = ([η] AB− [η] A × PA / 100) × 100
/ PB (3) Ethylene unit content According to the method described on page 616 of Polymer Analysis Handbook (1995, published by Kinokuniya Bookstore), ¹³ C-NM was obtained.
The measurement was performed by the R method. Content of ethylene unit of component A and component B (EA, EB) The content of ethylene unit (EA) measured after the polymerization of component A in the first step and the ethylene unit measured after the polymerization of the second step are completed. From the content (EAB), the ratio of the component A (PA), and the ratio of the component B (PB), the content (EB) of the ethylene unit of the component B was determined by the following equation. EB = (EAB-EA × PA / 100) × 100 / PB (4) 20 ° C. xylene-soluble part (CXS) After completely dissolving a 5 g sample in 500 ml of boiling xylene, the temperature was lowered to 20 ° C. and 4 hours or more. I left it. Thereafter, this was separated into a precipitate (CXIS part) and a solution by filtration, the filtrate was dried and dried at 70 ° C. under reduced pressure, and the weight of the obtained solid was measured. (5) Maximum melting peak temperature (Tm) of CXIS part Using a differential scanning calorimeter (DSC manufactured by PerkinElmer), 10 mg of the CXIS part obtained in (7) above was melted at 220 ° C for 5 minutes in a nitrogen atmosphere. After that, the temperature was lowered to 40 ° C. at a rate of 5 ° C./min. Thereafter, the temperature was increased at 5 ° C./min, and the peak temperature of the maximum peak of the obtained melting endothermic curve was defined as the maximum melting peak temperature (Tm) of the CXIS part.
The melting point of indium (In) measured at a heating rate of 5 ° C./min using this measuring instrument was 156.6 ° C. (6) Melt flow rate (MFR) The melt flow rate was measured according to JIS K7210 under the condition -14. (7) Transparency (haze) Measured according to JIS K7105. (8) Impact strength At −10 ° C., using a film impact tester manufactured by Toyo Seiki, using a hemispherical impact head having a diameter of 15 mm,
The impact strength of the film was measured. (9) Extraction amount of n-hexane According to the method described in FDA 177.1520 (d) (3) (ii), a film having a thickness of 60 μm was subjected to n-hexane extraction at 50 ° C.
The amount of hexane extracted was measured.

The following samples were used as the samples used in the examples and comparative examples. (1) Crystalline propylene-ethylene and / or α-olefin random copolymer having 4 or more carbon atoms (I) PPI: Propylene-ethylene random copolymer (Noblene trade name WF577P manufactured by Sumitomo Chemical) (2) Propylene block Copolymer (II) PPII-: Propylene block copolymer composition [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, phthalate Diisobutyl acid 2.8
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 20 ° C. for 1 hour, then subjected to solid-liquid separation at 20 ° C., and washed three times with 70 L of toluene. Then, the slurry concentration was 0.2 kg /
After adding toluene so as to obtain L, 47.6 mol of diisobutyl phthalate was added, and the mixture was reacted 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 set 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 were 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 acid ester, 0.3% by weight of ethoxy group and 0.2% by weight of butoxy group. And good particle properties.

[Preparation of polymer] <Pre-activation of solid catalyst component>
Dehydrated and degassed 1.5 L n-hexane, triethylaluminum sufficiently in an autoclave equipped with a stirrer.
5 mmol, 37.5 mmol of t-butyl-n-propyldimethoxysilane and 15 g of the above solid catalyst component were added, and propylene 15
g was continuously supplied over about 30 minutes to perform pre-activation, and then the obtained solid catalyst slurry was transferred to a SUS autoclave with an internal volume of 150 L with a stirrer, and 100 L of liquid butane was added and stored. .

<Polymerization> Two fluidized bed reactors made of SUS and having an internal volume of 1 m ³ and equipped with a stirrer are connected in two tanks. In the second tank, copolymerization of propylene and ethylene in the latter part (component (B)) was continuously carried out. The analysis result of the obtained propylene-based block copolymer powder was [η] A
= 3.0 dl / g, [η] B = 3.9 dl / g, content of ethylene unit in component A is 3.6% by weight, content of ethylene unit in component B is 14% by weight, ratio of component A The content of the component B was 49% by weight, and the content of the CXS part was 27% by weight. The maximum melting peak temperature of the CXIS part of the propylene-based block copolymer was 138 ° C. <Composition> The above propylene-based block copolymer powder 10
0 parts by weight, calcium stearate 0.05
Parts by weight, Irganox 1010 0.2 parts by weight, Irgafos 168 0.03 parts by weight, a melt flow rate modifier was added, and the mixture was melt-extruded with a granulator and melt flow rate (MFR) = 2.5 g / 10 min. And the propylene-based block copolymer composition (PPII-
) Got.

PPII-: Propylene block copolymer composition A SUS fluidized bed reactor with an internal volume of 1 m ^{3 and} a stirrer
In the first tank, the copolymerization of propylene and ethylene in the first part (component A) and the copolymerization of propylene and ethylene in the second part (component B) in the second tank in the presence of the solid catalyst. Performed continuously. The analysis result of the obtained propylene-based block copolymer powder shows that [η] A = 3.5 dl / g,
[η] B = 3.8 dl / g, content of ethylene unit in component A 4.0% by weight, content of ethylene unit in component B 1
3% by weight, 55% by weight of component A, 45% of component B
The content of the CXS part was 22% by weight. Also,
The maximum melting peak temperature of the CXIS part of the propylene-based block copolymer was 135 ° C. <Composition> The above propylene-based block copolymer powder 10
0 parts by weight, calcium stearate 0.05
Parts by weight, 0.2 parts by weight of Irganox 1010, 0.03 parts by weight of Irgafos 168, a melt flow rate modifier, and melt-extrusion with a granulator to give a melt flow rate (MFR) of 3.7 g / 10 min. And the propylene-based block copolymer composition (PPII-
) Got.

(3) Low crystalline ethylene-α-olefin copolymer PO-1 (trade name, manufactured by Mitsui Petrochemical Co., Ltd.)

Example 1 PPII- was melt-kneaded using a 40 mmφ extruder, while a composition obtained by pellet blending 95% by weight of PPI and 5% by weight of POI was mixed with a 40 mmφ extruder and 50 mm
Melt and knead using φ extruder, feed block type T
It is introduced into a die (die width 600 mm, lip opening 0.8 mm) and melt-extruded at a die temperature of 240 ° C. so as to have a PPII- / PPI (layer thickness ratio of 1/2).
Cool with a cooling roll through which cooling water of 0 ° C.
An unstretched film of 0 μm was obtained. Table 1 shows the physical properties of the obtained film.

Comparative Example 1 PPII- was extruded from two 40 mmφ extruders and 50 mmφ
The mixture was melt-kneaded using an extruder, introduced into a feed block type T-die (die width: 600 mm, lip opening: 0.8 mm), melt-extruded at a die temperature of 240 ° C., and passed through cooling water of 30 ° C. Cool with a cooling roll, thickness 60μm
Was obtained as a single-layer unstretched film. Table 1 shows the physical properties of the obtained film.

Comparative Example 2 A composition obtained by pellet blending of 85% by weight of PPI and 15% by weight of POI was mixed with two 40 mmφ extruders and 50% by weight.
Melt kneading using a mmφ extruder, feed block type T die (die width 600 mm, lip opening 0.8 mm)
And extruded at 240 ° C.
Cool with a cooling roll through which cooling water of 0 ° C.
A single-layer unstretched film having a thickness of 0 μm was obtained. Table 1 shows the physical properties of the obtained film.

Example 2 PPII- and PPI were melt-kneaded with a 50 mmφ extruder and a 40 mmφ extruder, respectively, and a feed block type T die (die width 600 mm, lip opening 0.8 mm)
PPI / PPII- / P at a die temperature of 280 ° C
It is melt-extruded so as to have a PI (layer thickness ratio of 1/10/1), and cooled by a cooling roll through which cooling water of 30 ° C. is passed to obtain an unstretched film having a thickness of 30 μm and 60 μm. Was. Haze of the obtained 30 μm film,
Table 2 shows the impact and the amount of n-hexane extracted from the 60 μm film.

Comparative Example 3 PPII- was melted and kneaded with a 50 mmφ extruder and a 40 mmφ extruder, introduced into a feed block type T-die (die width 600 mm, lip opening 0.8 mm) and melted at a die temperature of 250 ° C. It was extruded and cooled with a cooling roll through which cooling water of 30 ° C. was passed.
A single-layer unstretched film of μm was obtained. 30 μm obtained
Table 2 shows the haze and impact of the film and the amount of n-hexane extracted from the 60 μm film.

Comparative Example 4 90% by weight of PPI and 10% by weight of POI were pellet-blended, melt-kneaded with a 50 mmφ extruder and a 40 mmφ extruder, and fed block type T-die (die width 600 mm, lip opening 0.1 mm). 8 mm), melt-extruded at a die temperature of 250 ° C., and cooled by a cooling roll through which cooling water of 30 ° C. was passed.
A single-layer unstretched film of μm was obtained. 30 μm obtained
Table 2 shows the haze and impact of the film and the amount of n-hexane extracted from the 60 μm film.

[0047]

[Table 1]

[0048]

[Table 2]

Claims (4)

[Claims] A retort food packaging film comprising at least the following layers (a) and (b): (A) layer: a repeating unit derived from propylene,
A layer comprising a crystalline propylene random copolymer comprising a repeating unit derived from ethylene and / or a repeating unit derived from an α-olefin having 4 or more carbon atoms, or a resin composition containing the copolymer (b) ) Layer: a portion containing at least 5% by weight of a xylene-soluble portion (CXS portion) at 20 ° C. and excluding the CXS portion (CXIS)
Part) has a maximum melting peak temperature (Tm) of 130 to 155 ° C.
Consisting of a propylene-based block copolymer or a resin composition containing the copolymer 2. A propylene-based block copolymer comprising at least a repeating unit derived from propylene and a repeating unit derived from ethylene and / or butene-1.
And a repeating unit derived from propylene and at least a repeating unit derived from propylene and a repeating unit derived from ethylene and / or a repeating unit derived from butene-1. , A copolymer component different from the component A (component B)
Is a propylene-based block copolymer obtained by continuously producing a CXS-soluble part (CXS part) at 20 ° C. in an amount of 5% by weight or more and excluding the CXS part (CX
IS part) has a maximum melting peak temperature (Tm) of 130 to 15
The retort food packaging film according to claim 1, which is a propylene-based block copolymer at 5 ° C. 3. A propylene-based block copolymer comprising a propylene-ethylene copolymer portion (A component) having a content of a repeating unit derived from ethylene in the first step of 1.5 to 6.0% by weight. Total polymerization amount (total of component A and component B below)
In the second step, and the content of the repeating unit derived from ethylene is 7 to 17% by weight.
Is a block copolymer obtained by producing 15 to 60% by weight of the total polymerization amount (the sum of the components A and B) of the propylene-ethylene copolymer portion (component B), and the intrinsic viscosity of the component B ([η] B) 2-5 dl / g, intrinsic viscosity of B component
([η] B) and the intrinsic viscosity ([η] A) of component A ([η] B /
The retort food packaging film according to claim 1, wherein [η] A) is a propylene-based block copolymer having a ratio of 0.5 to 1.8. 4. A propylene-based block copolymer having a content of repeating units derived from ethylene in the first step of 3
Propylene-ethylene-butene-1 copolymer portion (component A) having a content of a repeating unit derived from butene-1 of 3 to 25% by weight of the total polymerization amount (component A and component B below) In the second step, the content of repeating units derived from ethylene is 17% by weight or less, and the content of repeating units derived from butene-1 is 3 to 35% by weight. Propylene-ethylene-
A block copolymer obtained by forming the butene-1 copolymer portion (B component) in an amount of 15 to 60% by weight based on the total polymerization amount (the sum of the A component and the B component), and the intrinsic viscosity of the B component ( [η]
B) is 1.5 to 5.0 dl / g, and the intrinsic viscosity of component B ([η]
Ratio ([η] B / [η]) between B) and the intrinsic viscosity ([η] A) of component A
The retort food packaging film according to claim 1, wherein A) is a propylene-based block copolymer of 0.5 to 1.8.