JPH10211683A - Packing stretch film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a packing stretch film extremely excellent in heat resistance, flexibility, mechanical strength, transparency, cutting properties, and deformation recovery. SOLUTION: A packing stretch film is obtained by laminating a layer composed of a polyethylene resin (b) on at least the single surface of a layer containing a propylene type block copolymer (a) obtained by forming a propylene-ethylene copolymer part (A-component) containing 1.5-6.0wt.% of a repeating unit originating from ethylene in an amt. of 40-85% by wt. of the total polymerization amt. (the sum total of components A, B) in a first process and forming a propylene-ethylene copolymer part (B-component) containing 7-17wt.% of a repeating unit originating from ethylene in an amt. of 15-60% by with the total polymerization amt. (the sum total to components A, B) and characterized by that the intrinsic viscosity ([η] B) of the B-component is 2-5dl/g and a ratio ([η] B/[η] A) of the intrinsic viscosity ([η] B) of the B-component and the intrinsic viscosity ([η] A) is 0.5-1.8 as one component.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a stretch film for packaging. More specifically, in a stretch film for packaging, in which food is placed directly or on a plastic tray or the like and stretch-wrapped with a film, good heat resistance, flexibility, mechanical strength, transparency, cutability and deformation recovery properties are obtained. The present invention relates to a stretch film for packaging.

[0002]

2. Description of the Related Art Conventionally, vinyl chloride resin is mainly used as a stretch film for packaging in which foods such as fruits and vegetables, fresh fish, fresh meat, and prepared foods are placed directly or on a plastic tray or the like and stretch-wrapped with a film. ing. In recent years, from the viewpoint of safety and health, development of polyethylene resins such as low-density polyethylene and ethylene-vinyl acetate copolymer has been actively conducted instead of conventional vinyl chloride resins.

However, when low-density polyethylene or the like is used alone, the desired uniformity of film elongation, film rigidity and the like cannot be satisfied at the same time.
In addition, the ethylene-vinyl acetate copolymer film can solve the above-described problems of the low-density polyethylene film if the content and the molecular weight of the repeating unit derived from vinyl acetate are appropriately selected. However, there is a problem that the paper is torn and torn when the food is sharp or when packaging food having a sharp part.

For this reason, for example, Japanese Patent Publication No. 2-12187
As shown in Japanese Patent Publication No. 2-18983 and Japanese Patent Publication No. 2-18983, an ethylene-α-olefin copolymer is laminated with an ethylene-vinyl acetate copolymer so as to simultaneously satisfy the required performance. Stretch films have been proposed. However, although the film is excellent in mechanical strength, it is inferior in flexibility and deformation recovery, and furthermore, due to lack of heat resistance, there is a problem that a hole is formed in the film when heat-sealing the film at the bottom of the tray.

For this reason, for example, Japanese Patent Application Laid-Open No.
No. 4 proposes a film in which an ethylene resin is laminated on a layer made of a mixture of a crystalline olefin resin and an olefin elastomer. Also, Japanese Patent Application Laid-Open No. 6-9 / 1994
No. 27 proposes a film in which an ethylene-based resin is laminated on a layer made of a resin composition containing an amorphous polyolefin and a crystalline polypropylene. However, although the film has excellent deformation recovery properties, the repulsion of the film is too strong, so when packaging a plastic tray containing food with an automatic packaging machine, the film breaks due to the repulsion at the time of film cutting, and the packaging machine stops. There was a problem.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a stretch film for packaging, particularly for food and the like, which is extremely excellent in heat resistance, flexibility, mechanical strength, transparency, cutability and deformation recovery. To provide.

[0007]

Means for Solving the Problems The present inventors have intensively studied a stretch film for packaging which is extremely excellent in heat resistance, flexibility, mechanical strength, transparency, cutting properties and deformation recovery properties as well as conventional performance. As a result, they have found that a stretch film for packaging formed by laminating a polyethylene resin layer on at least one side of a layer containing a specific propylene-based block copolymer as one component achieves the object of the present invention,
The present invention has been completed.

That is, in the present invention, in the first step, the propylene-ethylene copolymer portion (component A) having a content of a repeating unit derived from ethylene of 1.5 to 6.0% by weight is converted into a total polymerization amount (A Of the propylene-ethylene copolymer part (component B) having a content of the repeating unit derived from ethylene of 7 to 17% by weight in the second step. A block copolymer obtained by forming 15 to 60% by weight of the total polymerization amount (the sum of the component A and the component B), and the intrinsic viscosity of the component B ([η] B)
Is 2 to 5 dl / g, the intrinsic viscosity of component B ([η] B) and A
Ratio of component to intrinsic viscosity ([η] A) ([η] B / [η])
A) is characterized in that a layer comprising a polyethylene resin (b) is laminated on at least one surface of a layer containing a propylene-based block copolymer (a) having 0.5 to 1.8 as one component. It is a stretch film for packaging. Hereinafter, the present invention will be described in detail.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The propylene-based block copolymer (a) used in the present invention has a content of a repeating unit derived from ethylene (hereinafter referred to as "ethylene unit") of 1.5 to 1.5 in a first step. A propylene-ethylene copolymer portion (component A) of 6.0% by weight is produced in an amount of 40 to 85% by weight of the total polymerization amount (the sum of the component A and the following component B). Is 7 to 17% by weight of propylene
A block copolymer obtained by forming an ethylene copolymer portion (component B) in an amount of 15 to 60% by weight based on the total polymerization amount (total of component A and component B), and the intrinsic viscosity of component B ([η B) is 2 to 5 dl / g, and the ratio ([η] B / [η] A) of the intrinsic viscosity of component B ([η] B) to the intrinsic viscosity of component A ([η] A) is 0. It is a propylene-based block copolymer of 5 to 1.8.

The propylene-based block copolymer according to the present invention includes a propylene-ethylene copolymer portion in the first step and a propylene-ethylene copolymer having a different ethylene unit content in the second step. Is a copolymer obtained by sequentially polymerizing a part of a copolymer, not a typical block copolymer in which one end of a copolymer and another end of a copolymer are connected by a bond. Means coalescence.

The content of ethylene units in the propylene-ethylene copolymer portion (component A) polymerized in the first step is as follows:
If the amount is less than 1.5% by weight, the flexibility is lowered, and if it is more than 6.0% by weight, the heat resistance is undesirably reduced. In particular, the content of the ethylene unit is 2.5 to 4.5% by weight.
Is preferred from the viewpoint of the balance between flexibility and heat resistance.

The content of ethylene units in the propylene-ethylene copolymer portion (component B) polymerized in the second step is as follows:
If the amount is less than 7% by weight, the impact resistance at low temperatures is reduced, and
If it exceeds 7% by weight, transparency is undesirably reduced. In particular, a content of 8 to 12% by weight of the ethylene unit is preferable from the viewpoint of a balance between impact resistance and transparency at low temperatures.

The content of the ethylene unit is determined by the Polymer Analysis Handbook (1995, published by Kinokuniya Publishing Co., Ltd.).
According to the method described on page 616, ¹³ C-NM
It is measured by the R method. Content of ethylene unit of component A (E
In A), the copolymer is sampled and analyzed after the completion of the polymerization in the first step. Content of ethylene unit of component B (E
B) samples the block copolymer after the completion of the polymerization in the second step and determines the ethylene content (E
AB) is analyzed, and the ratio of the A component (PA) and the ratio of the B component (PB) are determined by the following equation. EA × PA / 100 + EB × PB / 100 = EAB EB = (EAB−EA × PA / 100) × 100 / PB

The ratio of the propylene-ethylene copolymer part (component A) polymerized in the first step and the propylene-ethylene copolymer part (component B) polymerized in the second step is A
The component is 40 to 85% by weight, preferably 55 to 83% by weight, and the B component is 15 to 60% by weight, preferably 17 to 45%.
% By weight.

If the content of the component B is less than 15% by weight, the impact resistance at low temperatures is insufficient, and if it exceeds 60% by weight, the heat resistance is undesirably deteriorated. In particular, the ratio of the component B is 17-4.
Preferably it is 5% by weight.

In order to obtain a propylene-ethylene block copolymer in which the component B is particularly 17 to 45% by weight, it is possible to prepare a block copolymer in which the component B is 17 to 45% by weight in the polymerization stage. For example, it is also possible to prepare a block copolymer having a B component ratio of 27 to 60% by weight by polymerization and adjust the ratio of the B component by additionally adding only the A component at the time of melt-kneading.

The intrinsic viscosity ([η] B) of the component B of the propylene block copolymer used in the present invention is 2 to 5 dl /.
g, the ratio ([η] B / [η] A) of the intrinsic viscosity ([η] B) of the B component and the intrinsic viscosity ([η] A) of the A component is 0.5 to
1.8 is necessary from the viewpoint of transparency.
If [η] B is less than 2 dl / g, the low molecular weight component increases, which is not preferable. If it exceeds 5 dl / g, the fluidity of the propylene-ethylene block copolymer decreases, and the processability decreases, which is not preferable. . In particular, the intrinsic viscosity ([η] B) of the B component of the propylene-ethylene copolymer is 2.
It is more preferably from 5 to 4.0 dl / g from the viewpoint of balance between suppression of low molecular weight components and processability.

The ratio of [η] B / [η] A exceeds 1.8,
Or, when it is less than 0.5, the compatibility between the component A and the component B decreases, and the transparency decreases, which is not preferable. Especially,
The ratio of [η] B / [η] A is preferably 0.8 to 1.5 from the viewpoint of transparency.

The intrinsic viscosity is measured at 135 ° C. in tetralin using an Ubbelohde viscometer. The intrinsic viscosity ([η] A) of the component A is analyzed by sampling the copolymer after the completion of the polymerization of the component A in the first step. The intrinsic viscosity ([η] B) of the component B is determined by sampling the block copolymer after the completion of the polymerization in the second step, analyzing the intrinsic viscosity ([η] AB) of the block copolymer, and further calculating the ratio of the component A. (P
A) and B components are calculated from the following equation from the ratio (PB). [Η] A × PA / 100 + [η] B × PB / 100 =
[Η] AB [η] B = ([η] AB-[η] A x PA / 100) x
100 / PB

The weight-average molecular weight of the xylene-soluble component at 20 ° C. in the propylene block copolymer used in the present invention is 260.
The content of the component of not more than 00 is not more than 6% by weight.
-It is preferable in terms of suppressing the amount of extraction with hexane or the like.
In particular, when used as a food packaging material, the weight-average molecular weight of 2600 °
More preferably, the content of the component of 0 or less is 3.5% by weight or less.

The propylene block copolymer used in the present invention has a content of ethylene unit of component B (EB) and a content of ethylene unit of component A (EA) from the viewpoint of transparency and impact resistance at low temperature. (EB-EA) is preferably in the range of 3 to 15% by weight, and (EB-EA) is 5 to 10 from the viewpoint of balance between transparency and impact resistance at low temperatures.
% By weight is particularly preferred.

The propylene-based block copolymer used in the present invention may be prepared, for example, in the presence of a Ziegler-Natta type catalyst.
After polymerizing component A in the same polymerization tank,
It can be produced by a batch polymerization method for polymerizing the components, or a continuous polymerization method for continuously polymerizing the A component and the B component using a polymerization tank having at least two tanks.

Specifically, for example, in the presence of (a) an organosilicon compound having a Si—O bond, a compound of the general formula Ti (OR
¹ ) a titanium compound represented by _n X _4-n (wherein R ¹ is a hydrocarbon group having 1 to 20 carbon atoms, X is a halogen atom, n is a number satisfying 0 <n ≦ 4) and / or Or a solid catalyst component containing a trivalent titanium compound obtained by treating a solid product obtained by reducing an ether compound with an organomagnesium compound with an ester compound and a mixture of an ether compound and titanium tetrachloride; ) an organoaluminum compound (c) Si-oR ² bond (wherein, R ² is a catalyst system consisting of a silicon compound having a.) a hydrocarbon group having 1 to 20 carbon atoms, or (a) the general formula Ti ( OR ¹ ) _n
X _4-n (wherein, R ¹ is a hydrocarbon group having 1 to 20 carbon atoms;
Represents a halogen atom, and n represents a number 0 <n ≦ 4. ) Is represented by the general formula AlR ² _m Y _3-m (wherein R ² is a hydrocarbon group having 1 to 20 carbon atoms, Y is a halogen atom, and m is a number of 1 ≦ m ≦ 3). The solid product containing a hydrocarbyloxy group insoluble in a hydrocarbon solvent obtained by reduction with an organoaluminum compound represented by the formula 80 in the presence of titanium chloride
A hydrocarbyloxy group-containing solid catalyst component obtained by treating the slurry in a slurry state at a temperature of -100 ° C, (b) a catalyst system comprising an organoaluminum compound, etc. Ziegler-Natta containing at least titanium, magnesium and halogen as essential components Al in the component (b) using a type catalyst
The molar ratio of atom / Ti atom in component (a) is 1 to 200.
0, preferably 5 to 1500, and the molar ratio of Al atoms in the component (c) / component (b) is 0.02 to 500, preferably 0.05 to 50, and the polymerization temperature is 20 to 1
50 ° C., preferably 50 to 95 ° C., and the polymerization pressure is from atmospheric pressure to
40 kg / cm ² G, preferably ^{2 to} 40 kg / cm ² G
In the first step, propylene and ethylene are supplied in the first step and hydrogen is supplied for controlling the molecular weight to polymerize the propylene-ethylene copolymer part (component A). Subsequently, in the second step, propylene, ethylene and hydrogen are supplied. To polymerize the propylene-ethylene copolymer part (component B).

The propylene block copolymer used in the present invention can change the fluidity represented by, for example, a melt flow rate by a known method in the presence or absence of an organic peroxide. . The propylene-based block copolymer may further contain an antioxidant, an ultraviolet absorber, an antistatic agent, an antifogging agent, a nucleating agent, and the like, if necessary.

In the present invention, a layer containing the propylene-based block copolymer (a) as one component may be blended with another resin within a range not to hinder the present invention.

The propylene-based block copolymer (a) is
As the layer containing as a component, a layer composed of a resin composition (d) containing 80 to 20% by weight of a propylene-based block copolymer (a) and 20 to 80% by weight of an amorphous polyolefin (c) is preferable. .

The layer containing the propylene-based block copolymer (a) as one component includes 80 to 20% by weight of the propylene-based block copolymer (a) and 20 to 80% by weight of the amorphous polyolefin (c). More preferably, the layer is composed of a resin composition (f) containing 60 to 95% by weight of a resin composition containing (d) and 40 to 5% by weight of a petroleum resin or a hydrogenated product thereof (e).

The amorphous polyolefin (c) referred to in the present invention
The term "insoluble in boiling n-heptane" means that the content of insolubles in Soxhlet extracted by boiling n-heptane is 70% by weight or less, preferably 60% by weight or less. Boiling n-
If the heptane-insoluble content is more than 70% by weight, the ratio of the amorphous portion becomes small, and the resulting film cannot be provided with the desired flexibility and deformation recovery properties. In the present invention, the amorphous polyolefin may be used alone or in combination of two or more.

The amorphous polyolefin (c) used in the present invention includes, for example, polypropylene, polybutene-1, propylene-ethylene copolymer, butene-1-ethylene copolymer, propylene-butene-1 copolymer, propylene- Amorphous polyolefins such as butene-1-ethylene terpolymer, propylene-hexene-1-ethylene terpolymer, and butene-1-hexene-1-ethylene terpolymer are exemplified.

Among these, the content of the repeating unit derived from propylene (hereinafter referred to as “propylene unit”) and / or the repeating unit derived from butene-1 (hereinafter referred to as “butene-1 unit”) is reduced. Amorphous polyolefins that are at least 50% by weight are preferred. Assuming that the content of propylene units in the amorphous polyolefin is (PA)% by weight, the content of propylene units and butene-1 unit in the amorphous polyolefin is preferably such that (PA) is 0%.
When it is ~ 65% by weight (50 + 0.230 × PA)% by weight
As described above, when (PA) exceeds 65% by weight, (PA)% by weight or more, more preferably, when (PA) is 0 to 80% by weight, (50 + 0.375 × PA)% by weight or more, (PA)
Is more than 80% by weight (PA) or more.
As the amorphous polyolefin, for example, Ube Tack UT2385 or UT2780 manufactured by Ube Lexen Co., Ltd. can be used.

The petroleum resin or a hydrogenated product thereof used in the present invention and (e) is a thermoplastic resin polymerized to solidify the cracked oil fraction produced by pyrolysis of petroleum, a C ₅ fraction Aliphatic as a raw material, aromatic as a C ₉ fraction as a raw material, and a copolymer thereof, dicyclopentadiene,
Further, a hydrogenation system obtained by hydrogenating them may be mentioned. Specifically, for example, commercially available products such as Heylets and Petrozine manufactured by Mitsui Petrochemical Industries, Ltd., and Alcon manufactured by Arakawa Chemical Industries, Ltd. can be used.

Among these petroleum resins or hydrogenated products thereof, hydrogenated systems are excellent in color tone and odor.

The method for preparing the resin composition (d) used in the present invention is not particularly limited, and known methods, for example, kneaders such as kneaders, Banbury mixers, rolls, and single or twin screw extruders. Etc., and can be performed by heat-melting and kneading. Further, various resin pellets may be dry-blended.

The method for preparing the resin composition (f) used in the present invention is not particularly limited, and known methods, for example, kneaders such as kneaders, Banbury mixers, rolls, and single-screw or twin-screw extruders. And heat-melting and kneading. Further, various resin pellets may be dry-blended.

The resin composition (d) used in the present invention may optionally contain various additives and fillers such as antioxidants, antifogging agents, antistatic agents, nucleating agents and flame retardants. It is possible to include. Furthermore, other resins may be blended and used within a range not to hinder the present invention.

Further, the resin composition (f) used in the present invention may optionally contain various additives and fillers such as antioxidants, antifogging agents, antistatic agents, nucleating agents, flame retardants and the like. It is possible to include. Furthermore, other resins may be blended and used within a range not to hinder the present invention.

The resin composition (d) used in the present invention preferably contains 80 to 20% by weight of a propylene block copolymer (a) and 20 to 80% by weight of an amorphous polyolefin (c). In particular, 70 to 30% by weight of the propylene-based block copolymer (a) and the amorphous polyolefin (c)
The resin composition (d) containing 30 to 70% by weight is more preferable from the viewpoint of the balance between flexibility, deformation recovery and heat resistance.

The resin composition (f) used in the present invention
More preferably, the resin composition contains 60 to 95% by weight of the resin composition (d) and 40 to 5% by weight of a petroleum resin or a hydrogenated product thereof (e). In particular, the resin composition (d) 70
~ 90% by weight and petroleum resin or its hydrogenated product (e) 3
The resin composition (f) containing 0 to 10% by weight is more preferable from the viewpoint of the balance between the cuttability and the impact strength.

The polyethylene resin (b) used in the present invention
Examples thereof include low-density polyethylene, medium-density polyethylene, high-density polyethylene, ethylene-propylene copolymer, ethylene-butene-1 copolymer, and ethylene-4-
Methylpentene-1 copolymer, ethylene-hexene-1
Copolymers of ethylene and α-olefins having 3 to 10 carbon atoms, such as copolymers, ethylene-octene-1 copolymers and ethylene-decene-1 copolymers, and furthermore ethylene and conjugated dienes or non-conjugated Ethylene copolymers comprising unsaturated compounds such as dienes or copolymerization components such as acrylic acid, methacrylic acid and vinyl acetate are also included. Further, these polymers may be those modified with an acid, for example, polymers modified by grafting with an α, β-unsaturated carboxylic acid, an alicyclic carboxylic acid, or a derivative thereof.

The polyethylene resin (b) is a low-density polyethylene, ethylene-butene-1 copolymer, ethylene-
Ethylene such as 4-methylpentene-1 copolymer, ethylene-hexene-1 copolymer, ethylene-octene-1 copolymer, ethylene-decene-1 copolymer and the like and having 3 to 1 carbon atoms
And at least one polyethylene resin selected from a copolymer with α-olefin of No. 0, an ethylene-vinyl acetate copolymer, an ethylene-acrylate copolymer and an ethylene-methacrylate copolymer.

The polyethylene resin (b) is composed of ethylene having the following properties (b1) and (b2) and ethylene
A copolymer with an α-olefin of 10 to 10 or a repeating unit derived from ethylene (hereinafter, referred to as “ethylene unit”) having a content of 70 to 95% by weight, and a repeating unit derived from vinyl acetate (hereinafter, referred to as “ethylene unit”). An ethylene-vinyl acetate copolymer having a content of 30 to 5% by weight (referred to as "vinyl acetate unit") is particularly preferred. (B1) a density of 0.870 to 0.915 g / cm ³ (b2) a maximum melting peak temperature measured by a differential scanning calorimeter (DSC) of 60 ° C. or more and less than 100 ° C., and the heat of fusion of the melting peak is all 0.8 or more for calorific value

Here, the ethylene-α-olefin copolymer can be obtained, for example, by the method described in JP-A-2-77410. That is, in a hydrocarbon solvent, (a) VO (OR) _n X as a transition metal component
_3-n (where R is a hydrocarbon group, X is a halogen, 0 <n <
3) a vanadium compound represented by the formula: and (b) an organic metal component represented by R ' _m AlX _3-n (where R' is a hydrocarbon group, X is a halogen, and 1 <m <3). (C) As the third component, the following general formula R ″ (CO) OR ″ ′ (where R ″ has 1 to 20 carbon atoms,
Partially or completely halogen-substituted organic groups,
R ″ ′ is a hydrocarbon group having 1 to 20 carbon atoms), and ethylene and an α-olefin having 3 to 10 carbon atoms are copolymerized using a catalyst system formed from an ester compound represented by M (abbreviated as M). Al / V (molar ratio) is 2.5 or more and M /
Under a catalyst condition in which V (molar ratio) is 1.5 or more, the molar ratio of ethylene to α-olefin is 35/65 to 60/40.
At a polymerization temperature of 40 ° C. to 80 ° C., the copolymerization is carried out in the coexistence state of a hydrocarbon solvent-insoluble polymer (slurry part) and a hydrocarbon solvent-soluble polymer (solution part) to obtain the ethylene-α-olefin copolymer. Can be Further, it can be obtained by similarly polymerizing a vanadium compound obtained by reacting vanadium trichloride with an alcohol described in JP-A-60-226514 as the transition metal component (a).

The method for producing the ethylene-vinyl acetate copolymer is not particularly limited, and may be a known method, for example, a method of copolymerizing ethylene, vinyl acetate and a radical initiator.

The polyethylene resin may contain various additives as required, for example, an antioxidant, an antifogging agent, an antistatic agent, a lubricant, a nucleating agent and the like.

The present invention is a stretch film for packaging obtained by laminating a layer made of the above polyethylene resin on at least one surface of a layer containing the propylene-based block copolymer as one component. The production of the film is, for example, a method of forming a film by a usual method such as an inflation method, a T-die method, and then heat laminating the film. It is possible to form a film with a T-die film forming machine.

In the present invention, if the packaging stretch film requires shrinkage, it is preferred that the film be stretched at least uniaxially after the film is formed. Stretching can be uniaxial or biaxial. In the case of uniaxial stretching, for example, a commonly used roll stretching method is preferable. In the case of biaxial stretching, for example, a sequential stretching method in which uniaxial stretching is performed and then biaxial stretching may be performed, or a simultaneous biaxial stretching method such as tubular stretching may be used.

[0047]

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

The methods for measuring physical properties in the examples and comparative examples are as follows. (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]) Measurement was performed in tetralin at 135 ° C. using an Ubbelohde viscometer. Intrinsic viscosities of components A and B ([η] A, [η] B) Intrinsic viscosities [η] A measured after completion of polymerization of component A in the first step, and intrinsic viscosities measured after completion of polymerization in the second step [Η] AB, ratio of component A (PA), ratio of component B (PB), intrinsic viscosity of component B [η] B
Was decided. [Η] B = ([η] AB− [η] A × PA / 100) ×
100 / PB (3) Ethylene Unit Content The measurement was carried out by ¹³ C-NMR according to the method described on pages 615 to 616 of a Polymer Analysis Handbook (1995, published by Kinokuniya Bookstore). Content of ethylene units of components A and B (EA, EB) Content of ethylene units (EA) measured after completion of polymerization of component A in the first step
And the content of the ethylene unit of the component B (EAB), the ratio of the component A (PA), and the ratio of the component B (PB) measured after the completion of the polymerization in the second step. EB). EB = (EAB-EA × PA / 100) × 100 / PB (4) Contents of propylene unit and butene-1 unit Described in pages 615 to 619 of a handbook for polymer analysis (1995, published by Kinokuniya Bookstore). The measurement was performed by the ¹³ C-NMR method according to the method described above.

(5) Melt flow rate (MFR) The propylene block copolymer is JIS K7210.
According to the method of condition -14. Moreover, the polyethylene resin followed the method prescribed | regulated to JISK6760. (5) Density of ethylene-α-olefin copolymer (d) According to the method specified in JIS K6760. 100
The temperature was measured after annealing for 1 hour in water at ℃. (6) Maximum melting peak temperature (Tm) Using a differential scanning calorimeter (DSC manufactured by PerkinElmer), 10 mg of a sample was previously melted at 220 ° C for 5 minutes in a nitrogen atmosphere, and then at a rate of 5 ° C / min. The temperature was lowered to 40 ° C. Thereafter, the temperature was raised 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). The melting point of indium (In) measured at a heating rate of 5 ° C./min using this measuring instrument was 15
6.6 ° C. In addition, the ethylene-α-olefin copolymer had a thickness of about 0.1 produced by hot pressing.
Approximately 10 mg of a specimen cut out from a 5 mm sheet is DS
Place in a sample pan for C measurement, preheat at 150 ° C for 5 minutes, cool down to 40 ° C at 1 ° C / min, hold for 5 minutes, then heat up to 150 ° C at a rate of 10 ° C / min to obtain a thermogram Was. The ratio of the amount of heat of fusion of the above-mentioned melting peak to the total amount of heat is a value obtained by dividing the area of the endothermic curve having the above-mentioned melting peak by the total endothermic area. (7) Content of vinyl acetate unit The measurement was performed according to JIS K6730.

(8) Heat-resistant temperature According to Tokyo Metropolitan Ordinance No. 1072 “Quality indication of wrap film”, a 2.5 cm long strip of a 3 cm wide and 14 cm long strip film sample is sandwiched between jigs and placed under the sample sample. 10
g weight was lowered. In this state, the maximum ambient temperature at which the film did not break even after 1 hour was indicated in increments of 10 ° C. The higher the temperature, the better the heat resistance. (9) Young's modulus According to the method specified in ASTM D882. The smaller this value is, the higher the flexibility is. MD / TD was measured. However, the shape of the test piece: a strip of 20 mm × 120 mm, the distance between the chucks: 50 mm, the tensile speed: 5 mm / min, (10) Tensile strength at break and elongation at break The method specified in JIS K6781 was used. MD /
The TD was measured. (11) Transparency (Haze) According to the method specified in ASTM D1003. A smaller value indicates better transparency. (12) Cutability Folding after film cutting when packaging a polystyrene foam tray using a commercially available push-up type tray automatic packaging machine (AW2600AT-III.PE manufactured by Teraoka Seiko Co., Ltd.) was determined as follows. ：: No break in the film, very good. Δ: The film was slightly folded, but good. X: The film is folded. (13) Deformation recovery property A circular sample film 1 having a diameter of 44.45 mm is fixed to a film fixing jig 2, and the center of the film has a tip with a radius of 6.3.
The 5 mm hemispherical pin 3 was pushed into the predetermined depth 5 at a speed of 100 mm / min using the load cell 4 and immediately pulled up at the same speed, and it was measured whether or not the push mark completely disappeared within 30 seconds. . The maximum indentation depth 5 at which the imprint disappeared completely was defined as the degree of deformation recovery. FIG. 1 is a plan view of an apparatus for measuring the degree of deformation recovery.

Example 1 [Synthesis of solid catalyst] After replacing a 200 LSUS reactor equipped with a stirrer with nitrogen, 80 L of hexane, 6.55 mol of tetrabutoxytitanium, and 2.8 of diisobutyl phthalate 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 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.

[Production 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 SUS fluidized bed reactors having an internal volume of 1 m ^{3 with} a stirrer were connected, and the first tank (A)
The copolymerization of propylene and ethylene of the component (Component) and the copolymerization of propylene and ethylene of the latter part (Component B) are continuously carried out in the second tank. (1) First tank (component A) In a fluidized bed reactor with a stirrer having an internal volume of 1 m ³ , a polymerization temperature of 70 ° C., a polymerization pressure of 18 kg / cm ² G, a hydrogen concentration of 0.2 vol% in a gas phase, While supplying propylene, ethylene and hydrogen so as to maintain an ethylene concentration of 2.4 vol% in the gas phase, 75 mmol / h of triethylaluminum / 7.5 mmol / h of t-butyl-n-propyldimethoxysilane /
h and 0.29 g / h of the pre-activated solid catalyst component are continuously supplied, and the polymer hold amount of the fluidized bed is 45 kg.
To copolymerize propylene and ethylene at 9.6 kg / h
Was obtained. The obtained polymer was continuously transferred to the second tank without deactivation. As a result of sampling and analyzing a part of the polymer, the ethylene content was 3.7% by weight, and the intrinsic viscosity ([η] A) at 135 ° C. of tetralin was 2.80 dl / g.

(2) Second tank (component B) In a fluidized bed reactor with an internal volume of 1 m ^{3 and} a stirrer, the polymerization temperature was 80 ° C., the polymerization pressure was 12 kg / cm ² G, and the hydrogen concentration in the gas phase was 0. 2 vol%, gas phase ethylene concentration 9.0 vo
while supplying propylene, ethylene and hydrogen so as to maintain 1%, the polymer hold amount of the fluidized bed was set to 80 k.
g, by continuously continuing the copolymerization of ethylene and propylene with the catalyst-containing polymer transferred from the first tank, a white polymer of 18.1 kg / h with good fluidity was obtained. The ethylene content of the polymer obtained is 8.
8% by weight, intrinsic viscosity at 135 ° C of tetralin ([η])
Was 2.89 dl / g. From the above results, the polymerization ratio of the first tank and the second tank was 53/47, the ethylene content of the component B obtained from the analysis values of the component A and the final polymer was 14.6% by weight, The intrinsic viscosity ([η] B) at 135 ° C. was 3.0 dl / g. The obtained polymer was thermally decomposed in the presence of peroxide, and the MFR was adjusted to be 2.6 g / 10 minutes to obtain a propylene-based block copolymer. Therefore, [η] B / [η] A
Was 1.1. Weight-average molecular weight of the xylene-soluble portion of the obtained propylene block copolymer at 20 ° C. of 260
The content of the components of 00 or less was 1.4% by weight.

[Production of Film] The obtained propylene-based block copolymer was used as an intermediate layer, and ethylene-butene-
1 copolymer (Esprene SPO manufactured by Sumitomo Chemical Co., Ltd.)
N0372, MFR = 2 g / 10 min, d = 0.89 g /
cm ³ , maximum melting peak temperature (Tm) 83 ° C., ratio of the maximum heat of fusion to the total heat of fusion = 1.0) in the surface layer. Die temperature 200
By processing at 3.0 ° C. and a blow ratio of 3.0, the thickness configuration is 5 μm / 5 μm / 5 μ in the order of surface layer / intermediate layer / surface layer.
m, a packaging stretch film having a total thickness of 15 μm was produced. Table 1 shows various characteristic values of the obtained film.

Example 2 In Example 1, instead of the ethylene-butene-1 copolymer, a low-density polyethylene (Sumikacene F200-0 manufactured by Sumitomo Chemical Co., Ltd., MFR = 2 g / 10 min, d = 0.
923 g / cm ³ ) is supplied to a three-layer T-die film processing machine manufactured by Mitsubishi Heavy Industries, Ltd. and processed at a die temperature of 240 ° C. and a chill roll temperature of 30 ° C. to obtain a thickness. A stretch film for packaging having a structure of 6 μm / 6 μm / 6 μm in the order of surface layer / intermediate layer / surface layer and a total thickness of 18 μm was produced. Table 1 shows the evaluation results of the obtained films.

Example 3 In Example 1, an ethylene-vinyl acetate copolymer (Evatate H2081, manufactured by Sumitomo Chemical Co., Ltd., MFR = 2 g / 10) was used in place of the ethylene-butene-1 copolymer.
, Content of ethylene units = 85% by weight, content of vinyl acetate units = 15% by weight) in the same manner as in Example 1 except that the thickness configuration was surface layer / intermediate layer / surface layer. In this order, a 5 μm / 5 μm / 5 μm, and a total thickness of 15 μm of a stretch film for packaging was produced. Table 1 shows the evaluation results of the obtained films.

Example 4 In Example 1, an ethylene-vinyl acetate copolymer (Evatate H2081, manufactured by Sumitomo Chemical Co., Ltd., MFR = 2 g / 10) was used in place of the ethylene-butene-1 copolymer.
Propylene obtained by melt-kneading with a Banbury mixer instead of a propylene-based block copolymer instead of a propylene-based block copolymer. Block copolymer 50
% By weight, and as an amorphous polyolefin, propylene-butene-1 copolymer (Ube Tack U manufactured by Ube Lexen Co., Ltd.)
T2780, content of propylene unit = 65% by weight, content of butene-1 unit = 35% by weight) Except for using 50% by weight of the resin composition for the intermediate layer, the thickness configuration was the same as in Example 1. Is 5 μm / in the order of surface layer / intermediate layer / surface layer.
A 5 μm / 5 μm stretch film for packaging having a total thickness of 15 μm was produced. Table 1 shows the evaluation results of the obtained films.
Shown in

Example 5 In Example 1, an ethylene-vinyl acetate copolymer (Evatate H2081, manufactured by Sumitomo Chemical Co., Ltd., MFR = 2 g / 10) was used in place of the ethylene-butene-1 copolymer.
, A content of ethylene = 85% by weight, a content of vinyl acetate units = 15% by weight) as a surface layer, and instead of the propylene-based block copolymer, 50% by weight of a propylene-based block copolymer; As the polyolefin, 50% by weight of a propylene-butene-1 copolymer (Ube Tack UT2780 manufactured by Ube Lexen Co., Ltd., content of propylene unit = 65% by weight, content of butene-1 unit = 35% by weight)
A resin composition prepared by melt-kneading 20% by weight of a petroleum resin (Alcon P125 manufactured by Arakawa Chemical Industry Co., Ltd.) with a resin composition of 80% by weight in a single screw extruder was used for the intermediate layer. In the same manner as in Example 1, a packaging stretch film having a thickness of 5 μm / 5 μm / 5 μm in the order of surface layer / intermediate layer / surface layer and a total thickness of 15 μm was produced.
Table 2 shows the evaluation results of the obtained films.

Comparative Example 1 In Example 1, a propylene-ethylene random copolymer (Noblen RH120B manufactured by Sumitomo Chemical Co., Ltd., MFR = 2.
6 g / 10 min, propylene unit content 97.5% by weight, ethylene unit content = 2.5% by weight) in the same manner as in Example 1 except that the thickness configuration was the surface layer / intermediate layer. / 5 μm / 5 μm / 5 μm in order of surface layer, total thickness 15
A μm-stretch film for packaging was produced. Table 2 shows the evaluation results of the obtained films. This film was inferior in flexibility and deformation recovery as compared with the film of Example 1.

Comparative Example 2 In Example 1, an ethylene-hexene-1 copolymer (Sumikacene α FZ201-0 manufactured by Sumitomo Chemical Co., Ltd., MFR = 2 g) was used in place of the propylene block copolymer.
/ 10 min, density = 0.912 g / cm ³ ) as an intermediate layer, and instead of the ethylene-butene-1 copolymer, an ethylene-vinyl acetate copolymer (Evatate H2081, manufactured by Sumitomo Chemical Co., Ltd., MFR = 2 g / 10 min, ethylene unit content = 85% by weight, vinyl acetate unit content = 15w
t%) in the surface layer is supplied to a three-layer inflation film processing machine manufactured by Placo Co., Ltd., and processed at a die temperature of 170 ° C. and a blow ratio of 3.0.
5 μm / 5 μ in thickness order of surface layer / intermediate layer / surface layer
An m / 5 μm, 15 μm total thickness stretch film for packaging was produced. Table 2 shows the evaluation results of the obtained films. This film was inferior to the film of Example 1 in heat resistance and cutability.

[0062]

[Table 1]

[0063]

[Table 2]

[0064]

As described in detail above, according to the present invention,
A packaging stretch film having extremely excellent heat resistance, flexibility, mechanical strength, transparency, cutability and deformation recovery can be provided. Further, the present invention can provide a stretch film for packaging excellent in safety and health.

[Brief description of the drawings]

FIG. 1 is a plan view of an apparatus for measuring a degree of deformation recovery of a film.

[Explanation of symbols]

1 ... Circular sample film, 2 ... Film fixing jig, 3 ... Pin 4 ... Load cell, 5 ... Pushing depth

 ────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Ikuo Yamamoto 5-1, Anesaki Beach, Ichihara-shi, Chiba Sumitomo Chemical Co., Ltd.

Claims (7)

[Claims] In the first step, the propylene-ethylene copolymer portion (component A) having a content of repeating units derived from ethylene of 1.5 to 6.0% by weight is fully polymerized (component A and component B below). Of the repeating units derived from ethylene in the second step.
17% by weight of the propylene-ethylene copolymer portion (B component) is 15 to 60% of the total polymerization amount (the sum of the A component and the B component).
% By weight, and the intrinsic viscosity ([η] B) of the component B is 2 to 5 dl / g.
The ratio ([η] B / [η] A) of the intrinsic viscosity ([η] B) of the component and the intrinsic viscosity ([η] A) of the component A is 0.5 to
A stretch film for packaging, comprising a layer containing a polyethylene resin (b) laminated on at least one surface of a layer containing the propylene-based block copolymer (a) as a component of 1.8. 2. The propylene-based block copolymer (a) is
The layer containing as a component comprises 80 to 20% by weight of a propylene-based block copolymer (a) and an amorphous polyolefin (c).
The stretch film for packaging according to claim 1, which is a layer composed of the resin composition (d) containing 20 to 80% by weight. 3. A propylene-based block copolymer (a) containing 1
The layer containing as a component comprises 80 to 20% by weight of a propylene-based block copolymer (a) and an amorphous polyolefin (c).
Resin composition (d) containing 20 to 80% by weight of 60 to 9
5% by weight, and a petroleum resin or its hydrogenated product (e) 4
The packaging stretch film according to claim 1, which is a layer composed of the resin composition (f) containing 0 to 5% by weight. 4. The polyethylene resin (b) is a low-density polyethylene, a copolymer of ethylene and an α-olefin having 3 to 10 carbon atoms, an ethylene-vinyl acetate copolymer, and an ethylene-acrylate copolymer. The stretch film for packaging according to claim 1, wherein the stretch film is at least one polyethylene resin selected from the group consisting of ethylene glycol and ethylene-methacrylate copolymer. 5. The method according to claim 1, wherein the polyethylene resin (b) is
1) and ethylene having the properties of (b2) and carbon number 3-1
The stretch film for packaging according to claim 1, which is a copolymer with an α-olefin of 0. (B1) a density of 0.870 to 0.915 g / cm ³ (b2) a maximum melting peak temperature measured by a differential scanning calorimeter (DSC) of 60 ° C. or more and less than 100 ° C., and the heat of fusion of the melting peak is all 0.8 or more for calorific value 6. Ethylene-vinyl acetate wherein the polyethylene resin (b) has a content of repeating units derived from ethylene of 70 to 95% by weight and a content of repeating units derived from vinyl acetate of 30 to 5% by weight. The stretch film for packaging according to claim 1, which is a copolymer. 7. A propylene-based block copolymer (a) comprising:
The stretch film for packaging according to claim 1, which is a copolymer obtained by polymerizing in the presence of a Ziegler-Natta type catalyst.