JP3497767B2 - Polyolefin stretch packaging film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretch film suitable for use in food packaging, and particularly to a stretch packaging film made of a chlorine-free material.

[0002]

2. Description of the Related Art Conventionally, a polyvinyl chloride-based film has been mainly used as a stretch packaging film for so-called pre-packing, in which fruits and vegetables, meat, prepared foods, etc. are placed on a lightweight tray and overlapped with the film. . These have good packaging efficiency, good packaging finish, and other properties. In addition, they have excellent elastic recovery to return to their original shape when the film after packing is pressed with fingers, etc., and also have good bottom sealing properties. This is because it has the quality superiority recognized by both sellers and consumers that the product value does not decrease, such as film peeling is less likely to occur during transportation display.

[0003]

However, in recent years, problems such as hydrogen chloride gas generated during incineration and elution of a plasticizer contained in a large amount have been regarded as problems with polyvinyl chloride films. Therefore, various materials replacing the polyvinyl chloride film have been studied, and in particular, various stretch packaging films having a structure using a polyolefin resin have been proposed. For example, ethylene-vinyl acetate copolymer (EV
A), a stretch packaging film having a constitution of EVA / polybutene-1 / EVA, EVA / straight chain ethylene-α-olefin copolymer / EVA, etc. have been proposed. In recent years, ethylene-vinyl acetate copolymer is used for the front and back layers, and various polypropylene-based resins for the intermediate layer for reasons such as good surface characteristics and transparency as a film for stretch packaging, moderate heat resistance, flexibility in material design, and economic efficiency. Stretch films of two-kind three-layered structure mainly composed of are being actively studied.

However, the stretch films mainly composed of various polypropylene resins that have been proposed at present have major packaging suitability (automatic machine, hand packaging) such as packaging workability, packaging finish, elastic recovery, and bottom sealability. And the comprehensive evaluation in the market including economic efficiency is still unsatisfactory.
Previously, the present inventors proposed in JP-A-9-154479 a stretch film for food packaging containing a relatively low crystalline propylene polymer and petroleum resins and having specific viscoelastic properties. ing.

The film composed of a propylene polymer and petroleum resins described in the above publication has relatively good characteristics such as wrapping workability, wrapping finish, elastic recovery, and bottom sealability, but has a desired viscosity. In order to have elastic properties, a relatively large amount (30% by weight) of petroleum resins must be contained, so the strength of the film changes over time, and the petroleum resins bleed onto the surface, causing In that case, there is a problem that the films block each other.

[0006]

As a result of extensive studies, the present invention uses a specific soft polypropylene-based resin as a main component, and controls viscoelastic properties to improve packaging workability,
We succeeded in obtaining a non-polyvinyl chloride stretch film that has excellent properties such as packaging finish, elastic recovery, bottom sealability, and stability over time and economic efficiency. It is a soft polypropylene resin with controlled stereoregularity in which a crystalline block and an amorphous block portion are mixed in the chain, and mainly resin that satisfies the following conditions (1) to (3) Ingredient layer
Surface layer made of polyolefin resin is laminated on both sides of
Which has a storage elastic modulus (E ′) measured at a frequency of 10 Hz and a temperature of 20 ° C. by a dynamic viscoelasticity measurement of 5.0 × 10 ⁸ to 5.0 × 10 ⁹ dyn /
cm ² and loss tangent (tan δ) are in the range of 0.2 to 0.8. A polyolefin stretch wrapping film (hereinafter, may be abbreviated as a stretch film or simply a film). (1) The glass transition temperature measured when the temperature is raised at a heating rate of 10 ° C / min using a differential scanning calorimeter is -15 ° C or higher. (2) Crystallization is performed at a heating rate of 10 ° C / min using a differential scanning calorimeter. After melting, the temperature of crystallization measured when the temperature was raised to 200 ° C., held at 200 ° C. for 5 minutes, and then cooled to room temperature at a cooling rate of 10 ° C./min, was 10 to 60 J / g (3) Melt flow rate ( MFR) (JISK721
0, 230 ° C, 2.16 kg load) 0.4-40 g /
10 minutes

Further, as a soft polypropylene resin having controlled stereoregularity in which crystalline blocks and amorphous block parts are mixed in the above molecular chain, 95 mol% of propylene-based monomer units are used. The above content, the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rr
A resin having rr) in the range of 30 to 70% can be preferably used.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention is described in detail below.
BEST MODE FOR CARRYING OUT THE INVENTION The stretch film of the present invention is a soft polypropylene resin having controlled stereoregularity, in which crystalline blocks and amorphous block portions are mixed in the molecular chain, and the following (1) to (3) A layer whose main component is a resin that satisfies the conditions
Surface layer made of polyolefin resin is laminated on both sides of
The film has a three-layer structure and has specific viscoelastic properties as the entire film. (1) The glass transition temperature measured when the temperature is raised at a heating rate of 10 ° C / min using a differential scanning calorimeter is -15 ° C or higher. (2) Crystallization is performed at a heating rate of 10 ° C / min using a differential scanning calorimeter. After melting, the temperature of crystallization measured when the temperature was raised to 200 ° C., held at 200 ° C. for 5 minutes, and then cooled to room temperature at a cooling rate of 10 ° C./min, was 10 to 60 J / g (3) Melt flow rate ( MFR) (JISK721
0, 230 ° C, 2.16 kg load) 0.4-40 g /
10 minutes

Here, the soft polypropylene resin (hereinafter sometimes referred to as the component (A)) in which a crystalline block and an amorphous block portion are mixed in the molecular chain generally has rubber elasticity. It has the characteristics that it is flexible, hard to break, and has good transparency. Also, the crystalline block part of the isotactic structure and syndiotactic structure showing rigidity and the amorphous block of atactic structure showing elastomeric property. It is suitable for achieving the object of the present invention by balancing the ratio with the block portion. here,
The mixture of a crystalline block and an amorphous block portion in the molecular chain means that the crystalline block and the amorphous block portion exist randomly and / or in a block manner. Although the chain length of each block portion may be arbitrary, in the present invention, it is preferable that the distribution is random in terms of transparency and appearance. In addition, in the layer containing the component (A), the main component in the present invention is (A) in the compound resin constituting the layer.
The highest content (% by weight) of ingredients, preferably 5
It means that the content is more than 0% by weight.

Polypropylene-based resins generally have high crystallinity and high strength. Among polyolefin-based resins, they have relatively high melting points and good heat resistance, but due to their high crystallinity, they require a great deal of force during extension, and It exhibits only non-uniform elongation and these properties remain in the mixture. Therefore, in the present invention, it is preferable to use a polypropylene resin having relatively low crystallinity in order to obtain a film having good elongation. Conventionally, the above polypropylene-based resin contains ethylene or α-olefin having about 4 to 12 carbon atoms in a form of copolymerization of about 10 mol% or more with propylene in order to impart low temperature characteristics and flexibility at room temperature. The above-mentioned products are often used, and some of them are also used for films, but these alone are not suitable for the present invention because of viscoelasticity. That is, since a large amount of α-olefin is contained in propylene in this type of resin, its glass transition temperature is the glass transition temperature of polypropylene (about -10 ° C).
This is because the loss tangent (tan δ) described later is extremely small at less than 0.1 at room temperature.

The component (A) applied to the present invention is capable of satisfying the viscoelastic properties described later, and mainly by controlling the stereoregularity, the crystallinity is lowered and the glass transition temperature is polypropylene. Original glass transition temperature (-1
The tan δ at normal temperature is increased by not significantly lowering the temperature than about 0 ° C.). Specifically, as the condition (1), a heating rate of 10 ° C./using a differential scanning calorimeter
The glass transition temperature measured when the temperature is raised in minutes is -15 ° C.
As mentioned above, what is -10 degreeC or more is used suitably. When the glass transition temperature is less than -15 ° C, the peak temperature of loss tangent (tan δ) shifts to the low temperature side, and the value at room temperature, which is the object of the present invention, becomes extremely small, which is not preferable.

As condition (2), a differential scanning calorimeter was used to melt the crystal at a heating rate of 10 ° C./min, the temperature was raised to 200 ° C., the temperature was held at 200 ° C. for 5 minutes, and then the cooling rate was 10 ° C./min.
The amount of heat of crystallization measured when the temperature is lowered to room temperature in 10 minutes is 10
What is in the range of -60 J / g, preferably 20-50 J / g is used. When the amount of heat of crystallization is less than 10 J / g, the crystallinity is too low and the film-forming property is extremely poor. At room temperature, the film is too soft or lacks strength, which is a problem in practical use. Further, if the heat of crystallization exceeds 60 J / g, a large force is required at the time of stretching the film, and only non-uniform elongation is exhibited.
Not suitable for stretch film. Further, as the condition (3), the melt flow rate (MFR) at 230 ° C. under a load of 2.16 kg is 0.4 to 40 g / 10 minutes, preferably 0.5.
-30 g / 10 minutes, more preferably 1.0-20 g / 1
Use the one in the range of 0 minutes. If the melt flow rate is less than 0.4 g / 10 min, the viscosity of the polymer itself is too high and extrusion molding becomes difficult, which is not suitable. If it exceeds 40 g / 10 min, the viscosity of the polymer itself is too low and the film-forming stability becomes poor. There is a problem in practical use because the film disappears or the strength of the film itself is insufficient.

As such a soft polypropylene resin, in the Soxhlet extraction with boiling n-heptane, its insoluble content is 60% by weight or less, preferably 2 to
50% by weight, in the Soxhlet extraction with cold xylene, the insoluble content is 95% by weight or less, preferably 50% by weight.
To 90% by weight, and the propylene-based monomer unit in the copolymer composition is at least 90 mol% or more, preferably 95% by weight.
Mol% or more and the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rrrr) is 30 to 70
Those controlled in the range of% are preferably used. Here, as the component other than propylene, ethylene or α-olefin having 4 to 12 carbon atoms or 4-methylpentene-
1, cyclic olefin, styrene and the like can be mentioned, but ethylene is most preferably used. If the content of insoluble matter due to boiling n-heptane exceeds 60% by weight or the content of insoluble matter due to cold xylene exceeds 95% by weight, the crystallinity is high and the flexibility is lowered, which is an object of the present invention. It is not preferable because the loss tangent (tan δ) at room temperature does not easily fall within the desired range.

Further, the propylene-based monomer unit is 9
When it is less than 0 mol%, the heat resistance is lowered, the controllability of crystallinity due to stereoregularity is narrowed, and when the α-olefin is copolymerized, the glass transition temperature is (-10) The loss tangent (tan δ) at room temperature becomes extremely small, and it is not preferable from the economical viewpoint.
Regarding the stereoregularity, the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rrrr) is in the range of 30 to 70%, and the mesopentad fraction (mmmm) is preferably 2 as one index showing the proportion of the crystalline block portion.
5 to 60%, especially 25 to 50%, and the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rrr
It is preferable that r) is controlled in the range of 40 to 65%. Here, if the above (mmmm + rrrr) is less than 30%, the crystallinity is too low and the film-forming property is extremely poor. Further, at room temperature, the film is too soft or has insufficient strength, which poses a practical problem. Further, the raw material itself tends to be blocked, which is not preferable in terms of handleability. On the other hand, (mmmm
When + rrrr) exceeds 70%, the loss tangent (tan δ) at room temperature, which is the object of the present invention, is difficult to fall within the desired range, which is not preferable. In addition, it requires a large amount of force when the film is stretched, and since it shows only non-uniform elongation, it is difficult to use as a stretch film.

The values of the mesopentad fraction (mmmm) and racemopentad fraction (rrrr) used in the present invention are calculated based on the measurement results of ¹³ C-NMR (nuclear magnetic resonance) spectrum. That is, the ¹³ C-NMR spectrum was measured and determined from the signal intensity ratio of each split peak (mmmm to mrrm) appearing in the 22.5 ppm to 19.5 ppm region due to the difference in chemical shift due to the stereoregularity of the methyl group. The mmmm (mesopentad fraction) is a stereo structure in which all of the five methyl groups that are side chains are located in the same direction with respect to the main chain formed by carbon-carbon bonds composed of any five continuous propylene units. It means a structure or a ratio thereof, and rrrr (racemopentad fraction) means that the main chain formed by any continuous five propylene units is composed of carbon-carbon bonds, and five side chain methyl groups are alternated. Means a three-dimensional structure located in the opposite direction or a ratio thereof. The attribution of the signal in the methyl group region is as described in A. Zambelli et al
(Macromolecules 8 , 687, (197
5))

As the component (A), two or more kinds may be mixed and used as long as they meet the purpose of the present invention. In addition, as a method for producing such a soft polypropylene-based resin, an inexpensive propylene monomer is used as a main component, various metallocene-based catalysts (single-site catalysts), solid titanium-based catalysts, etc. are used, and good moldability is obtained. Efficient soft polypropylene resin with controlled stereoregularity,
A method of polymerizing at low cost has been proposed, and the resin to be used is not particularly limited as long as it satisfies the gist of the present invention. Specific products include Hunts.
An example is the product name “REXflex” of man Polymer Corporation.

[0017] The present invention films, frequency 10Hz by dynamic viscoelasticity measurement, storage modulus measured at a temperature 20 ℃ (E ') is ^{5.0 × 10 8 ~5.0 × 10 9} dyn / c
It is necessary to use those having m ² and loss tangent (tan δ) in the range of 0.2 to 0.8. Here, tan δ (loss tangent) is the ratio of the loss elastic modulus (E ″) to the storage elastic modulus (E ′), that is, the loss tangent (tan δ = E ″ / E).
'), Which means that in the temperature range where this value is high, the loss elastic modulus (E ″) of the material, that is, the viscoelasticity has a large contribution rate to the viscoelasticity. By evaluating the temperature range shown, it can be used as a large standard for judging the stress relaxation behavior of the film in the hand wrapping using a stretch film and various wrapping processes by an automatic machine.

The storage elastic modulus (E ') is 5.0 × 10.
⁸dyn / cm²If it is less than, soft and against deformation
The stress is too small, resulting in poor workability and
Suitable for stretch film without rum tension
Yes. On the other hand, E'is 5.0 × 10 ⁹dyn / cm²Beyond
Then, it becomes a hard and difficult-to-stretch film, and the tray deforms.
It is easy to get crushed. The preferred range of E'is 8.0 × 1
0⁸~ 3.0 x 10⁹dyn / cm²Is. Also, t
When an δ is less than 0.2, the film elongation
The film is placed on the bottom of the tray due to the instantaneous recovery behavior.
The film will recover in a short time before folding.
The film does not stretch well and wrinkles easily occur. Well
The heat-sealed state of the bottom of the
Since sufficient fusion due to heat is difficult to make, transport after packaging.
It is easy for the bottom seal to peel off during or after display.
Become. If tan δ exceeds 0.8, the packaging finish is good.
Good, but shows plastic deformation and external force of the pack
Too tight for stacking during shipping or display
The film on the top of the tray is easily sagged due to stickiness, etc.
It is easy to lose value. Also, in the case of automatic packaging, it stretches vertically.
Since it is easy, problems such as defective chucks are likely to occur. tan
A particularly suitable range of δ is 0.30 to 0.60.

Further, since the stretch film is sometimes used at low temperature, it is desirable that the stretch film has excellent low-temperature characteristics (especially elongation). For that purpose, storage measured at a frequency of 10 Hz and a temperature of 0 ° C. by dynamic viscoelasticity measurement. Elastic modulus (E
') Is preferably in the range of 1.5 × 10 ¹⁰ dyn / cm ² or less. The soft polypropylene resin mainly controlled in stereoregularity that conforms to the present invention has a higher glass transition temperature than other low crystallinity polypropylene resins, and therefore has the above characteristics in order to ensure flexibility such as low temperature elongation. It is preferable to consider to satisfy. For that purpose, the mesopentad fraction (mmmm) and the racemopentad fraction (rrr)
The ratio of the crystalline block portion such as r), the kind and the ratio of the component copolymerized with propylene, or the kind of other resin mixed with it may be adjusted. In order to bring the viscoelastic properties of the film of the present invention into the above range, it is necessary to select an appropriate component as the component (A), but it is possible to make E ′ and tan δ compatible with only the component (A). Since it may be difficult in some cases, it is practical to adjust the characteristics by laminating layers of other materials or mixing other materials.

In the case of lamination, a polyolefin resin is used as the other resin layer, and by laminating these, the viscoelastic properties of the film are adjusted, and the tensile properties of the film are improved, so that appropriate strength is obtained. And the elongation at low temperature is improved. Here, as the laminated material, particularly a polyolefin resin,
It is suitable from the viewpoint of imparting surface characteristics and economy, and is low-density polyethylene, ultra-low-density polyethylene (copolymer of ethylene and α-olefin), ethylene-vinyl acetate copolymer (EVA), ethylene-alkyl acrylate. It is recommended to use a copolymer, an ethylene-alkyl methacrylate copolymer, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, an ionomer resin, a propylene-based elastomer material or the like.

In practice, for example, the above EVA can be preferably used, and as the EVA, the vinyl acetate content is 5 to 25% by weight, preferably 10 to 20% by weight, and the melt flow rate (MFR) is 0. .2 to 5 g / 10 minutes (J
ISK7210, 190 ° C., 2.16 kg load) is preferable. When the vinyl acetate content is less than 5% by weight, the obtained film is hard, the flexibility and elastic recovery are lowered, and the surface tackiness is not easily exhibited. On the other hand, when it exceeds 25% by weight, the surface tackiness is too strong and the unwinding property and the appearance are likely to be deteriorated. When the MFR is less than 0.2 g / 10 min, the extrusion processability is deteriorated, while when it is more than 5 g / 10 min, the film-forming stability is deteriorated and thickness unevenness, deterioration of mechanical strength and variation are likely to occur. Therefore, it is not preferable.

When other materials are mixed,
It is preferable to mix (B) a petroleum resin, a terpene resin, a coumarone-indene resin, a rosin resin, or a hydrogenated derivative thereof. Since the component (B) has a high glass transition temperature, the glass transition temperature of the mixture can be increased. This is effective in satisfying both the storage elastic modulus (E '), which exhibits suitable extensibility as a stretch film at room temperature, and the loss tangent (tan δ), which exhibits appropriate stress relaxation properties.

Among the components (B), the petroleum resins include alicyclic petroleum resins derived from cyclopentadiene or a dimer thereof and aromatic petroleum resins derived from the C ₉ component. The terpene resin is β-pinene. Examples of the terpene resin and terpene-phenol resin described in (1), and examples of the rosin-based resin include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin, pentaerythritol, and the like. The above component (B) is the above (A)
It is known that when it is mixed with components and the like, it exhibits a relatively good compatibility, but it is preferable to use a hydrogenated derivative from the viewpoint of color tone, thermal stability and compatibility. As the component (B), those having various glass transition temperatures mainly depending on the molecular weight are obtained, but those having a glass transition temperature of 50 to 100 ° C., preferably 70 to 90 ° C. are applicable to the present invention. is there. When the glass transition temperature is lower than 50 ° C., it is necessary to add a large amount in order to obtain desired viscoelastic properties when mixed with the above-mentioned component (A), and blocking of a material or film by bleeding on the surface. Easy to invite. In addition, the mechanical strength of the film as a whole is insufficient and the film tends to be broken, which may cause a problem in practical use. On the other hand, when the glass transition temperature exceeds 100 ° C., the compatibility with the component (A) deteriorates, and bleeding may occur over time on the film surface, leading to blocking and deterioration of transparency.

From the above reason, it is preferable that the content of the component (B) is as small as possible within the range where the above-mentioned viscoelastic properties can be achieved. In this respect, the soft polypropylene resin having controlled stereoregularity applied to the present invention has a glass transition temperature of about −10 ° C. or higher, and therefore α-olefins and the like are conventionally added to propylene which has been commonly used. Even when the content of the component (B) is as small as about 20% by weight or less as compared with the low-crystallinity polypropylene resin contained in a large amount, it works effectively for adjusting to desired viscoelastic properties. In the film of the present invention, in addition to the above-mentioned component (B), the following polyolefin-based resins which are usually used in ordinary polyolefin-based compositions within a range not exceeding the gist of the present invention and not deteriorating the appearance of the film. Or a styrene elastomer can be blended.

For example, in a polypropylene resin, a homopolymer of propylene or a copolymer with another monomer copolymerizable with propylene (propylene-ethylene copolymer, propylene-ethylene-α-olefin copolymer). Etc.) and the like, in the polyethylene resin, ethylene-vinyl acetate copolymer (vinyl acetate content is 5 to 40% by weight), low density polyethylene, and ethylene-α-olefin copolymer of α-olefin having 4 to 8 carbon atoms. Polymer, ethylene-acrylic acid copolymer (acrylic acid content is 5 to 20% by weight),
A metal salt (Zn, Na, K, Li) of an ethylene-methyl methacrylate copolymer, a copolymer of an α-olefin such as ethylene and propylene and a monomer selected from acrylic acid, methacrylic acid, maleic acid and the like. , Mg, etc., and styrene-based elastomers include styrene-butadiene block copolymers or hydrogenated derivatives thereof, hydrogenated derivatives of styrene-butadiene random copolymers, hydrogenated derivatives of styrene-isoprene block copolymers, and the like. To be

One or more of these may be used in an amount of less than 50% by weight, preferably 1 to 4 for the purpose of improving the suitability for packaging such as the cuttability and low-temperature characteristics of the film and improving the economy.
0 wt% can be blended. The thickness of the film of the present invention is generally in the range used for ordinary stretch packaging, that is, about 8 to 30 μm, typically 10
˜20 μm. Further, in the case of a laminated film, the thickness of the layer containing the component (A) as a main component has a ratio to the total thickness of 0.3 to 0.9, preferably 0.4 to 0.8, Specifically, it is preferably 5 to 20 μm from the viewpoint of various properties and economical efficiency as a stretch film.

The film of the present invention can be obtained by melt-extruding a material from an extruder and forming it into a film by inflation molding or T-die molding. When forming a laminated film, it is advantageous to coextrude with a multilayer die. Practically, it is preferable to melt-extrude the material resin from an annular die and perform inflation molding, and the blow-up ratio (bubble diameter / die diameter) at that time is preferably 4 or more, and particularly preferably in the range of 5 to 7. . The cooling method at that time may be either a method of cooling from the outer surface of the tube or a method of cooling from both the outer surface and the inner surface of the tube.
Further, the film obtained here is heated to a temperature not higher than the crystallization temperature of the resin and is drawn 1.2 to 5 times in the machine direction of the film by utilizing the speed difference between the nip rolls, or 1. It may be biaxially stretched 2 to 5 times.

In the film of the present invention, the following various additives are added to the surface layer and / or the component (A) in order to impart antifogging properties, antistatic properties, slip properties, self-adhesive properties and the like. It can be appropriately added to the layer containing the main component. For example, an aliphatic alcohol fatty acid ester which is a compound of an aliphatic alcohol having 1 to 12 carbon atoms, preferably 1 to 6 and a fatty acid having 10 to 22 carbon atoms, preferably 12 to 18, specifically, , Monoglycerin oleate, polyglycerin oleate, glycerin triricinoleate, glycerin acetyl ricinoleate, polyglycerin stearate, polyglycerin laurate, methyl acetyl ricinoleate, ethyl acetyl ricinoleate, butyl acetyl ricinoleate, propylene glycol oleate, propylene glycol Laurate, pentaerythritol oleate, polyethylene glycol oleate, polypropylene glycol oleate, sorbitan oleate, sorbitan laurate, polyethylene glycol sorbitan oleate, poly Chi glycol sorbitan laurate, as well as polyalkylene ether polyols include polyethylene glycol, polypropylene glycol or the like, at least one compound selected from paraffinic oils and the like, a resin component 1 constituting each layer
0.1 to 12 parts by weight, preferably 1 to 100 parts by weight
It is preferable to mix it up to 8 parts by weight.

[0029]

EXAMPLES The present invention will be described in more detail with reference to examples below, but the present invention is not limited thereto. Various measured values and evaluations of the films shown in this specification were carried out as follows. Where the film is taken from the extruder (flow direction)
Is called the vertical direction, and the orthogonal direction is called the horizontal direction.

(1) E ', tanδ Viscoelasticity spectrometer VES- manufactured by Iwamoto Manufacturing Co., Ltd.
Vibration frequency 1 in the lateral direction of the film using F3
It measured from -50 degreeC to 150 degreeC at 0 Hz and a heating rate of 1 degreeC / min, and the value at the temperature of 20 degreeC and 0 degreeC was displayed from the obtained data.

(2) Stretch wrapping suitability An automatic wrapping machine (ISHIDA / WminMK-I manufactured by Ishida Koki Co., Ltd.) is used by using a stretch film having a width of 350 mm.
I) Expanded polystyrene tray (length 200 mm,
(Width 130 mm, height 30 mm) was packaged, and the items shown in Table 3 were evaluated. In addition, using the same film and tray, hand wrapping machine (Dia Wrapper A manufactured by Mitsubishi Plastics Co., Ltd.)
-105) and the packaging test was conducted.

(3) Stability of film formation The stability of bubbles when forming a film was evaluated by an inflation manufacturing facility. ◎… Very stable ○… Stable △… Slightly unstable ×… No film formation

(4) Glass transition temperature (Tg), melting temperature (Tm) Using a DSC-7 manufactured by Perkin Elmer, a sample of 10 m
According to JIS-K7121, g was determined from a thermogram when the temperature was raised at a heating rate of 10 ° C./min.

(5) Crystallization temperature (Tc), heat of crystallization Using DSC-7 manufactured by Perkin Elmer, a sample of 10 m
According to JIS-K7121 and JIS-K7122, g was melted at a heating rate of 10 ° C./minute, the temperature was raised to 200 ° C., the temperature was maintained at 200 ° C. for 5 minutes, and then the cooling rate was 10 ° C./minute.
It was calculated from the thermogram when the temperature was lowered to room temperature in minutes.

(6) Melt flow rate (MFR) The melt flow rate (MFR) was measured according to JIS-K7210 under the conditions of a test temperature of 230 ° C. and a test load of 2.16 kgf.

(7) Mesopentad fraction (mmmm),
Racemopentad Fraction (rrrr) JNM-GSX-270 ( ¹³ C-nuclear magnetic resonance frequency 67.8 MHz) manufactured by JEOL Ltd. was used and measured under the following conditions. Measurement mode: ¹ H-complete decoupling pulse width: 8.6 microseconds Pulse repetition time: 30 seconds Number of integrations: 7200 times Solvent: Orthodichlorobenzene / deuterated benzene mixed solvent (80/20% by volume) Sample concentration: 100 mg / 1 ml solvent measurement temperature: 130 ° C. Here, each pentad fraction was determined by measuring the split peak in the methyl group region of the ¹³ C-nuclear magnetic resonance spectrum. Further, the attribution of signals in the methyl group region is as described in A.
Zambelli et al (Macromolec
ules 8 , 687, (1975)).

(8) Aging of the obtained film roll at a temperature of 50 ° C. and a relative humidity of 60
% In the temperature-controlled room for 10 days, and the surface condition and rewindability after that were evaluated. ⊚: No bleeding of additives on the surface and no blocking between films. B: Almost no bleeding of the additive on the surface, but there is some blocking between the films. B: There is a little bleeding of the additive on the surface, and peeling is slightly heavy due to blocking between the films. X: Many bleeding of additives on the surface, blocking between films is terrible and practically unusable.

Example 1 Soft polypropylene resin (I) with controlled stereoregularity (propylene content: 100)
Mol%, mmmm = 35.3%, rrrr = 15.4
%, MFR = 16 g / 10 minutes, Tm = 155 ° C., Hun
tsman Polymer Corporation
Manufactured by REXflex W101) as an intermediate layer having a thickness of 11 μm, EVA (vinyl acetate content 15% by weight, 190 ° C., MFR at 2.16 kg load) on both sides thereof =
2.0 g / 10 min) 100 parts by weight of melt-kneaded composition of 3.0 parts by weight of diglycerin monooleate as an antifogging agent so that each layer has a thickness of 2 μm.
Coextrusion inflation molding at 0 ° C, blow-up ratio 5.5, total thickness 15μm (2μm / 11μm / 2μ
A film of m) was obtained.

The characteristics of the film made of the soft polypropylene resin (I) alone were measured as follows. Storage elastic modulus at 0 ° C. (E ′) 5.4 × 10 ⁹ dyn / cm ² Storage elastic modulus at 20 ° C. (E ′) 4.8 × 10 ⁸ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 34 glass transition temperature (Tg) -6 ° C heat of crystallization 25 J / g crystallization temperature (Tc) 99 ° C

Example 2 In Example 1, as a raw material for the intermediate layer, 80% by weight of the soft polypropylene resin (I) was used, and hydrogen of cyclopentadiene petroleum resin having a softening point of 125 ° C. (glass transition temperature 81 ° C.) was used. A film having a total thickness of 15 μm (2 μm / 11 μm / 2 μm) was obtained in the same manner as in Example 1 except that a mixed composition containing 20% by weight of the added derivative was used.

The characteristics of the film made of only the mixture of the soft polypropylene resin (I) and hydrogenated petroleum resin were as follows. Storage elastic modulus (E ′) at 0 ° C. 1.9 × 10 ¹⁰ dyn / cm ² Storage elastic modulus (E ′) at 20 ° C. 1.4 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 59 glass transition temperature (Tg) 2 ° C

(Example 3) In Example 2, instead of the soft polypropylene resin (I), the soft polypropylene resin (II) (propylene content: 100 mol%, mmm
m = 44.5%, rrrr = 12.3%, MFR = 6 g
/ 10 minutes, Tm = 158 ° C., Huntsman Pol
yer Corporation, "REXfle
x W110 ″) was used to obtain a film having a total thickness of 15 μm (2 μm / 11 μm / 2 μm) in the same manner as in Example 1.

The soft polypropylene resin (I
I) The characteristics of the film made of the simple substance measured were as follows. Storage elastic modulus at 0 ° C. (E ′) 1.1 × 10 ¹⁰ dyn / cm ² Storage elastic modulus at 20 ° C. (E ′) 1.5 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 25 glass transition temperature (Tg) -7 ° C heat of crystallization 35J / g crystallization temperature (Tc) 102 ° C

The soft polypropylene resin (I
The measured properties of a film consisting only of a mixture of I) and a hydrogenated petroleum resin were as follows: Storage elastic modulus (E ′) at 0 ° C. 1.8 × 10 ¹⁰ dyn / cm ² Storage elastic modulus (E ′) at 20 ° C. 2.6 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 49 Glass transition temperature (Tg) 5 ° C

Example 4 In Example 1, as a raw material for the intermediate layer, the stereoregular controlled soft polypropylene resin (III) (propylene content: 97 mol%, ethylene content: 3 mol%, mmmm = 37.4%, rrr
r = 11.4%, MFR = 19 g / 10 min, Tm = 14
9 ℃, Huntsman Polymer Corpo
"REXflex W201" manufactured by ration) 85
15% by weight of the hydrogenated petroleum resin used in Example 2
A film having a total thickness of 15 μm (2 μm / 11 μm / 2 μm) was obtained in the same manner as in Example 1 except that the mixed composition of wt% was used.

The soft polypropylene resin (II
I) The characteristics of the film made of the simple substance measured were as follows. Storage elastic modulus at 0 ° C. (E ′) 2.9 × 10 ⁹ dyn / cm ² Storage elastic modulus at 20 ° C. (E ′) 4.3 × 10 ⁸ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 26 glass transition temperature (Tg) -10 ° C heat of crystallization 21 J / g crystallization temperature (Tc) 95 ° C

The soft polypropylene resin (I
The measured properties of a film consisting of a mixture of II) and a hydrogenated petroleum resin were as follows. Storage elastic modulus (E ′) at 0 ° C. 9.2 × 10 ⁹ dyn / cm ² Storage elastic modulus (E ′) at 20 ° C. 6.2 × 10 ⁸ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 52 glass transition temperature (Tg) -2 ° C

(Example 5) Example 1 was repeated except that the lamination thickness ratio of the intermediate layer to the front and back layers was changed as follows.
15μm (4μm / 7μm / 4μ)
A film of m) was obtained.

Comparative Example 1 In Example 1, a low crystalline propylene-ethylene-propylene copolymer elastomer (propylene content: 88 mol%, MFR, was used as the raw material for the intermediate layer, instead of the soft polypropylene resin (I). =
1.5 g / 10 minutes, Tm = 156 ° C., manufactured by Tokuyama Corp., P. E. R. T310J) (hereinafter referred to as "PER") except that the total thickness is 15μ in the same manner as in Example 1.
A film of m (2 μm / 11 μm / 2 μm) was obtained.

The characteristics of the film made of the above PER alone were measured as follows. Storage elastic modulus at 0 ° C. (E ′) 3.6 × 10 ⁹ dyn / cm ² Storage elastic modulus at 20 ° C. (E ′) 2.1 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 07 glass transition temperature (Tg) -25 ° C heat of crystallization 31 J / g crystallization temperature (Tc) 101 ° C

(Comparative Example 2) In Example 1, a soft polypropylene resin (IV) (propylene content: propylene content:
100 mol%, mmmm = 63.0%, rrrr = 8.
0%, MFR = 2 g / 10 minutes, Tm = 158 ° C., Hun
tsman Polymer Corporation
Manufactured by REXflex W105) was used, and the total thickness was 15 μm (2 μm / 11 μm) in the same manner as in Example 1.
/ 2 μm) film was obtained.

The soft polypropylene resin (I
V) The characteristics of the film made of a single substance were as follows. Storage elastic modulus at 0 ° C. (E ′) 1.6 × 10 ¹⁰ dyn / cm ² Storage elastic modulus at 20 ° C. (E ′) 3.7 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 14 glass transition temperature (Tg) -6 ° C heat of crystallization 54J / g crystallization temperature (Tc) 108 ° C

(Comparative Example 3) P used in Comparative Example 1 in place of the soft polypropylene resin (I) in Example 2
The total thickness is 15 μm in the same manner as in Example 2 except that ER is used
A film of m (2 μm / 11 μm / 2 μm) was obtained.

The characteristics of the film made of only the mixture of PER and hydrogenated petroleum resin were as follows. Storage elastic modulus at 0 ° C. (E ′) 4.8 × 10 ⁹ dyn / cm ² Storage elastic modulus at 20 ° C. (E ′) 1.2 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 23 Glass transition temperature (Tg) -16 ° C

Comparative Example 4 In Example 1, 70% by weight of PER used in Comparative Example 1 was used as a raw material for the intermediate layer.
A total thickness of 1 was obtained in the same manner as in Example 1 except that the hydrogenated petroleum resin used in Example 2 was mixed with 30% by weight.
A film of 5 μm (2 μm / 11 μm / 2 μm) was obtained.

The characteristics of the film made of only the mixture of PER and hydrogenated petroleum resin were as follows. Storage elastic modulus at 0 ° C. (E ′) 9.0 × 10 ⁹ dyn / cm ² Storage elastic modulus at 20 ° C. (E ′) 2.0 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 35 glass transition temperature (Tg) -7 ° C

Comparative Example 5 A total thickness of 15 μm (2 μm / 11 μm /) was obtained in the same manner as in Example 2 except that the soft polypropylene resin (I) was replaced with the soft polypropylene resin (IV). 2 μm) film was obtained.

Soft polypropylene resin (IV)
The measured properties of the film consisting only of the mixture of the hydrogenated petroleum resin were as follows. Storage elastic modulus at 0 ° C. (E ′) 2.2 × 10 ¹⁰ dyn / cm ² Storage elastic modulus at 20 ° C. (E ′) 6.5 × 10 ⁹ dyn / cm ² Loss tangent at 20 ° C. (tan δ) 0. 26 Glass transition temperature (Tg) 6 ° C

Comparative Example 6 A commercially available polyvinyl chloride stretch film (thickness: 15 μm) was evaluated.
Regarding the above Examples 1 to 5 and Comparative Examples 1 to 6, Table 1 shows measured values of viscoelastic properties of each laminated film (Comparative Example 6 is a single layer), and Table 2 shows evaluation of stretch packaging suitability and the like. .

[0060]

[Table 1]

[Table 2]

[Table 3]

From Tables 1 to 3, the films of Examples 1 to 5 in which the resin specified in the present invention is used and the viscoelastic properties are within the range specified in the present invention are all comprehensive in various properties as a stretch film. It turns out that it is excellent. On the other hand, it can be seen that the films of Comparative Examples 1 to 5, which have different resins or whose viscoelastic properties are out of the range defined by the present invention, are inferior in overall properties as a stretch film.

[0062]

EFFECT OF THE INVENTION According to the stretch film of the present invention, when used in an automatic wrapping machine or the like, the film can be cut / conveyed or lapped without any problems, the bottom sealing property is good, and the film tension is good. It is possible to obtain a package, and has a feature that has never been seen as a chlorine-free stretch film. Further, it is excellent in stability over time and economical efficiency.

Claims (6)

(57) [Claims] 1. A soft polypropylene resin having controlled stereoregularity in which a crystalline block and an amorphous block portion are mixed in a molecular chain, and the conditions (1) to (3) below are satisfied. On both sides of the layer whose main component is a resin that satisfies
Three-layer structure in which surface layers made of reffin resin are laminated
A film having a frequency of 10 by dynamic viscoelasticity measurement.
The storage elastic modulus (E ') measured at 5 Hz and a temperature of 20 ° C is 5.
A polyolefin stretch wrapping film having a range of 0 × 10 ^{8 to} 5.0 × 10 ⁹ dyn / cm ² and a loss tangent (tan δ) of 0.2 to 0.8. (1) The glass transition temperature measured when the temperature is raised at a heating rate of 10 ° C / min using a differential scanning calorimeter is -15 ° C or higher. (2) Crystallization is performed at a heating rate of 10 ° C / min using a differential scanning calorimeter. After melting, the temperature of crystallization measured when the temperature was raised to 200 ° C., held at 200 ° C. for 5 minutes, and then cooled to room temperature at a cooling rate of 10 ° C./min, was 10 to 60 J / g (3) Melt flow rate ( MFR) (JISK721
0, 230 ° C, 2.16 kg load) 0.4-40 g /
10 minutes 2. A soft polypropylene resin having a controlled stereoregularity, in which a crystalline block and an amorphous block portion are mixed in the molecular chain, in which 95 mol% or more of propylene-based monomer units are contained. The polyolefin stretch-wrapping film according to claim 1, wherein the sum of the mesopentad fraction and racemopentad fraction (mmmm + rrrr), which is contained and is determined from ¹³ C-NMR spectrum, is in the range of 30 to 70%. 3. A mesopentad fraction (mmmm) obtained from ¹³ C-NMR spectrum of a soft polypropylene resin having a controlled stereoregularity in which a crystalline block and an amorphous block portion are mixed in a molecular chain. ) Is 25-50
%, And the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rrrr) is in the range of 40 to 65%. 3. The polyolefin stretch wrapping film according to claim 1 or 2, wherein 4. A storage elastic modulus (E ′) measured by dynamic viscoelasticity measurement at a frequency of 10 Hz and a temperature of 0 ° C. is 1.5 × 10 ^10.
The polyolefin-based stretch wrapping film according to any one of claims 1 to 3, which has a dyn / cm ² or less range. 5. The following component (B) is mixed in a layer mainly composed of a stereoregularly controlled soft polypropylene resin in which a crystalline block and an amorphous block portion are mixed in the molecular chain. The polyolefin-based stretch wrapping film according to any one of claims 1 to 4. (B) Petroleum resin, terpene resin, coumarone-indene resin, rosin resin, or hydrogenated derivatives thereof 6. A layer comprising a soft polypropylene resin having a controlled stereoregularity, in which a crystalline block and an amorphous block portion are mixed in a molecular chain, as a main component, and having a glass transition temperature of 50 to 50. The polyolefin stretch wrapping film according to claim 5, wherein the component (B) at 100 ° C is mixed in a range of 20% by weight or less.