JP2000044695A - Polyolefin-based film for stretch packaging - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide nonchlorine-type stretch film having good workability and finish in packaging and also excellent in storage stability and economic efficiency. SOLUTION: This polyolefin-based film for stretch packaging has at least one layer where the stereoregularity of a soft polypropylene-based resin having crystalline blocks and amorphous ones in its molecular chain in a coexisting state is controlled and the resin is included as a principal ingredient. And the film has 5.0×108 dyn/cm2-5.0×109 dyn/cm2 storage elasticity (E') and (0.2-0.8) loss tangent (tan δ) respectively according to dynamic viscoelastic measurement at a frequency of 10 Hz and 20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Conventionally, as a stretch packaging film for so-called prepackaging, in which fruits and vegetables, meat, side dishes, etc. are placed on a lightweight tray and overlapped with a film, a polyvinyl chloride-based film has been mainly used. . These have good packaging efficiency such as good packaging efficiency, good packaging finish, and excellent elastic recovery that returns to the original state even after applying deformation such as pressing the packed film with a finger, and good bottom sealability. This is because the merchandise and the consumer have the superiority of the quality that the value of the merchandise does not decrease such that the film is not easily peeled off during the transportation display.

[0003]

However, in recent years, problems such as hydrogen chloride gas generated during incineration of a polyvinyl chloride film and elution of a large amount of a plasticizer contained therein have been regarded as problems. For this reason, various alternatives to the polyvinyl chloride-based film have been studied, and in particular, various stretch packaging films using a polyolefin-based resin have been proposed. For example, ethylene-vinyl acetate copolymer (EV
A), stretch packaging films having a structure of EVA / polybutene-1 / EVA, EVA / linear ethylene-α-olefin copolymer / EVA, etc. have been proposed. In recent years, ethylene-vinyl acetate copolymer has been used for the front and back layers, and various polypropylene resins have been used for the intermediate layer because of good surface characteristics and transparency, moderate heat resistance, freedom of material design, economy, etc. as a film for stretch packaging. Studies are being actively conducted on a stretch film having a two-component three-layer structure mainly composed of.

[0004] However, the currently proposed stretch films containing various polypropylene-based resins as main components are mainly suitable for packaging such as packaging workability, packaging finish, elastic recovery force, bottom sealability (automatic machine, hand packaging). Comprehensive evaluations in the market, including economics, are still unsatisfactory.
The present inventors have previously proposed in Japanese Patent Application Laid-Open No. 9-154479 a food packaging stretch film containing a relatively low-crystalline propylene polymer and petroleum resins and having specific viscoelastic properties. ing.

The film comprising a propylene polymer and a petroleum resin described in the above publication has relatively good properties such as packaging workability, packaging finish, elastic recovery force 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 that the strength of the film changes over time, or the petroleum resins bleed to the surface, and the In such a case, there were problems such as blocking between the films.

[0006]

As a result of intensive studies, the present invention uses a specific soft polypropylene-based resin as a main component and controls viscoelastic characteristics to improve packaging workability.
In addition to properties such as packaging finish, elastic recovery, and bottom sealing properties, we have succeeded in obtaining a non-PVC-based stretch film with excellent film stability over time and economic efficiency. A soft polypropylene resin having a controlled stereoregularity in which a crystalline block and an amorphous block portion are mixed in a chain, and a resin satisfying the following conditions (1) to (3) is mainly used. Having at least one layer as a component, and having a frequency of 1
The storage elastic modulus (E ′) measured at 0 Hz and a temperature of 20 ° C. is from 5.0 × 10 ⁸ dyn / cm ^{2 to} 5.0 × 10 ⁹ dyn.
/ Cm ² and a loss tangent (tan δ) in the range of 0.2 to 0.8 in a polyolefin-based stretch packaging film (hereinafter sometimes abbreviated as a stretch film or simply a film). . (1) The glass transition temperature measured at a heating rate of 10 ° C./min using a differential scanning calorimeter is −15 ° C. or more. (2) Crystals at a heating rate of 10 ° C./min using a differential scanning calorimeter. After melting, the temperature was raised to 200 ° C., kept at 200 ° C. for 5 minutes, and the heat of crystallization measured when the temperature was lowered 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) is 0.4 to 40 g /
10 minutes

Further, as a soft propylene resin having a controlled stereoregularity in which a crystalline block and an amorphous block portion are mixed in the molecular chain, a monomer unit based on propylene is 95 mol%. And the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rr
Resins having rr) in the range of 30 to 70% can be suitably used.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The stretch film of the present invention is a soft polypropylene-based resin having a controlled stereoregularity in which a crystalline block and an amorphous block portion are mixed in a molecular chain, and comprises the following (1) to (3) It has at least one layer containing a resin that satisfies the conditions as a main component, and has specific viscoelastic properties as a whole film. (1) The glass transition temperature measured at a heating rate of 10 ° C./min using a differential scanning calorimeter is −15 ° C. or more. (2) Crystals at a heating rate of 10 ° C./min using a differential scanning calorimeter. After melting, the temperature was raised to 200 ° C., kept at 200 ° C. for 5 minutes, and the heat of crystallization measured when the temperature was lowered 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) is 0.4 to 40 g /
10 minutes

[0009] Here, a soft polypropylene resin in which a crystalline block and an amorphous block portion are mixed in a molecular chain (hereinafter sometimes referred to as component (A)) generally has rubber elasticity. It has the characteristics of being flexible and resistant to tearing, and having good transparency.It also has crystalline blocks of isotactic structure and syndiotactic structure showing rigidity, and amorphous structure of atactic structure showing elastomeric properties. It is suitable to achieve the object of the present invention by balancing the ratio with the block portion. here,
A mixture of a crystalline block and an amorphous block in a molecular chain means that the crystalline block and the amorphous block are present randomly and / or in blocks. Although the chain length of each block portion may be arbitrary, it is preferable in the present invention that the distribution is random in terms of transparency, appearance, and the like. Further, the main component in the present invention refers to a layer containing the component (A) in a compounded resin constituting the layer.
The content (% by weight) of the component is the highest, preferably 5%.
It means that it is contained in excess of 0% by weight.

[0010] Polypropylene resins are generally high in crystallinity and high in strength, and have relatively high melting points and good heat resistance among polyolefin resins. It shows only non-uniform elongation and these properties remain in the mixture. Therefore, in the present invention, in order to obtain a film having good elongation, it is preferable to use a polypropylene resin having relatively low crystallinity. Conventionally, as the above-mentioned polypropylene resin, propylene contains ethylene or an α-olefin having about 4 to 12 carbon atoms in an amount of about 10 mol% or more in order to impart low-temperature properties and flexibility at room temperature. Those that have been used are often used and are also partially used for films, but these alone are not suitable for the present invention in terms of viscoelasticity. That is, since this kind of resin contains a large amount of α-olefin in propylene, its glass transition temperature is the original glass transition temperature of polypropylene (around -10 ° C.).
This is because the loss tangent (tan δ) to be described later is extremely small, less than 0.1, at room temperature.

The component (A) applied to the present invention is capable of satisfying the viscoelastic properties described below, and mainly controls stereoregularity to lower the crystallinity and increase the glass transition temperature of polypropylene. Original glass transition temperature (-1
(About 0 ° C.), thereby increasing tan δ at normal temperature. Specifically, a heating rate of 10 ° C. /
-15 ° C glass transition temperature measured when heated in minutes
As described above, a material having a temperature of −10 ° C. or more is preferably used. If the glass transition temperature is lower than −15 ° C., the peak temperature of the loss tangent (tan δ) shifts to a lower temperature, and the value at room temperature, which is the object of the present invention, is not preferable.

As condition (2), the crystal is melted at a heating rate of 10 ° C./min using a differential scanning calorimeter, heated to 200 ° C., kept at 200 ° C. for 5 minutes, and cooled at a cooling rate of 10 ° C./min.
The heat of crystallization measured when the temperature is lowered to room temperature in 10 minutes is 10
６０60 J / g, preferably 20 to 50 J / g. If the heat of crystallization is less than 10 J / g, the crystallinity is too low, resulting in extremely poor film-forming properties. At room temperature, the film is too soft or has insufficient strength, which poses a practical problem. On the other hand, when the heat of crystallization exceeds 60 J / g, a large force is required at the time of film extension, and only non-uniform elongation is exhibited.
Not suitable for stretch film. Further, as a condition (3), the melt flow rate (MFR) at 230 ° C. and a load of 2.16 kg is 0.4 to 40 g / 10 min, preferably 0.5 to 40 g / 10 min.
-30 g / 10 min, more preferably 1.0-20 g / 1
Use 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 to make extrusion molding difficult, and if it exceeds 40 g / 10 min, the viscosity of the polymer itself is too low and the film forming stability is poor. Or the strength of the film itself is insufficient, causing a practical problem.

In the case of such a soft polypropylene resin, its insoluble content is 60% by weight or less, preferably 2 to 50% by Soxhlet extraction with boiling n-heptane.
50% by weight, in Soxhlet extraction with cold xylene, the insoluble content is 95% by weight or less, preferably 50% by weight.
Propylene-based monomer unit in the copolymer composition is at least 90 mol%, preferably 95 mol% or more.
Mol% or more, and the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rrrr) is 30 to 70.
% Is preferably used. Here, as components other than propylene, ethylene or an α-olefin having about 4 to 12 carbon atoms or 4-methylpentene-
1, cyclic olefin, styrene and the like, and ethylene is most preferably used. Here, if the insoluble content due to boiling n-heptane exceeds 60% by weight or the insoluble content due to cold xylene exceeds 95% by weight, the crystallinity is high, and the flexibility is reduced, which is the object of the present invention. The loss tangent (tan δ) at room temperature is difficult to fall within a desired range, which is not preferable.

Further, the monomer unit based on propylene is 9
If the amount is less than 0 mol%, the heat resistance is reduced, the control range of crystallinity by stereoregularity is narrowed, and when α-olefin is copolymerized, the glass transition temperature becomes lower than that of polypropylene (−10). (Approximately 0.degree. C.), the loss tangent (tan.delta.) At room temperature becomes extremely small, and is not preferable from the viewpoint of economy.
Regarding stereoregularity, the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rrrr) is in the range of 30 to 70%, and preferably the mesopentad fraction (mmmm) is 2 as one index indicating the proportion of the crystalline block portion.
5 to 60%, particularly 25 to 50%, and the sum of the fractions of mesopentad and racemopentad (mmmm + rrr
It is preferable that r) be 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, and at room temperature, the film is too soft or has insufficient strength, causing a practical problem. Further, the raw material itself is easily blocked, which is not preferable in terms of handling properties. On the other hand, (mmmm
If (+ rrrr) exceeds 70%, the loss tangent (tan δ) at room temperature, which is the object of the present invention, becomes difficult to fall within a desired range, which is not preferable. Further, a large force is required at the time of film extension, and furthermore, only non-uniform elongation is exhibited.

The values of the mesopentad fraction (mmmm) and the 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, a ¹³ C-NMR spectrum was measured and determined from a signal intensity ratio of each splitting peak (mmmm to mrrm) appearing in a 22.5 ppm to 19.5 ppm region due to a difference in chemical shift due to stereoregularity of a methyl group. The mmmm (mesopentad fraction) refers to a three-dimensional structure in which all five methyl groups that are side chains are located in the same direction with respect to a main chain formed by carbon-carbon bonds composed of any five consecutive propylene units. Rrrr (racemopentad fraction) refers to the structure or the ratio thereof, and rrrr (racemopentad fraction) means that five methyl groups as side chains alternate with a main chain formed by carbon-carbon bonds composed of any five consecutive propylene units. Means the three-dimensional structure located in the opposite direction or the ratio thereof. The assignment of the signal in the methyl group region is described in A. Zambelli et al
(Macromolecules 8 , 687, (197
5))

The component (A) can be used as a mixture of two or more kinds as long as it meets the object of the present invention. As a method for producing such a soft polypropylene-based resin, an inexpensive propylene monomer is used as a main component, and various metallocene-based catalysts (single-site catalysts) and solid titanium-based catalysts are used. Efficient soft polypropylene resin with controlled stereoregularity
In addition, 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.
An example is the trade name “REXflex” of man Polymer Corporation.

The film of the present invention has a storage elastic modulus (E ') of 5.0 × 10 ⁸ dyn / cm ^{2 to} 5.0 × 1 measured at a frequency of 10 Hz and a temperature of 20 ° C. by dynamic viscoelasticity measurement.
⁰⁹ dyn / cm ² , loss tangent (tan δ) is 0.2 to
It is necessary to use one in the range of 0.8. Here, tan δ (loss tangent) is a ratio of loss elastic modulus (E ″) to storage elastic modulus (E ′), that is, loss tangent (ta).
nδ = E ″ / E ′), and in a temperature range where this value is high, it means that the loss elastic modulus (E ″) of the material, that is, the contribution rate of the viscosity among the viscoelastic properties is large. This t
By evaluating the value of an δ and the temperature region showing a high value, it becomes a large standard for judging the stress relaxation behavior and the like of the film in various packaging processes by hand packaging using a stretch film or an automatic machine.

The storage elastic modulus (E ') is 5.0 × 10
⁸dyn / cm^TwoIf it is less than
Since the stress is too small, workability is poor, and
Suitable for stretch film with no stretch
No. On the other hand, E ′ is 5.0 × 10 ⁹dyn / cm^TwoBeyond
Will result in a hard, stretchy film that will deform the tray
It is easy to break. The preferred range of E 'is 8.0 × 1
0⁸~ 3.0 × 10⁹dyn / cm^TwoIt is. Also, t
When anδ is less than 0.2, the elongation of the film
The film rests on the bottom of the tray due to the instantaneous recovery behavior.
The film will be restored in a short time before folding.
In addition, the film is not stretched well and wrinkles are likely to occur. Ma
The heat-sealed state of the bottom
Since it is difficult for sufficient fusion by heat to occur, after packaging, transport
It is easy to cause the bottom seal to peel off gradually during middle or display
Become. If tan δ exceeds 0.8, the packaging finish is good
Good, but shows plastic deformation and external force of the packaged product
Is too weak and is being transported or displayed
The film on the top of the tray is easy to sag due to
Value tends to decrease. In the case of automatic packaging,
Therefore, problems such as chuck failure are likely to occur. tan
A particularly preferred range of δ is 0.30 to 0.60.

Further, since the stretch film is sometimes used at a low temperature, it is desirable that the stretch film has excellent low-temperature characteristics (especially, elongation). For this purpose, the storage film measured at a frequency of 10 Hz and a temperature of 0 ° C. by dynamic viscoelasticity measurement. It is preferable that the elastic modulus (E ') is in the range of 1.5 × 10 ¹⁰ dyn / cm ² or less. Soft polypropylene resin mainly controlled stereoregularity conforming to the present invention has a higher glass transition temperature than other low crystalline polypropylene resins, so the above properties are required to ensure flexibility such as low temperature elongation. It is preferable to take care to satisfy. For this purpose, the mesopentad fraction (mmmm) and the racemopentad fraction (r
The ratio of the crystalline block portion such as (rrr), the type and ratio of the component to be copolymerized with propylene, or the type of other resin mixed therewith may be adjusted. In order to make the viscoelastic properties of the film of the present invention within the above range, the above (A)
Although it is necessary to select an appropriate component, it is sometimes difficult to make E ′ and tan δ compatible with the component (A) alone. Therefore, it is difficult to laminate layers of other materials or to use other materials. It is practical to adjust the characteristics by mixing them.

In the case of lamination, a non-chlorine-based material layer such as a polyolefin-based resin or a flexible styrene-butadiene-based elastomer can be used as the other resin layer. Along with the adjustment, the tensile properties of the film are improved to provide moderate strength and elongation, and improved low temperature elongation. Here, as the laminated material, a polyolefin resin is particularly preferable from the viewpoint of imparting surface characteristics and economy,
Low-density polyethylene, ultra-low-density polyethylene (copolymer of ethylene and α-olefin), ethylene-vinyl acetate copolymer (EVA), ethylene-alkyl acrylate copolymer, ethylene-alkyl methacrylate copolymer, ethylene- Use of an acrylic acid copolymer, an ethylene-methacrylic acid copolymer, an ionomer resin, a propylene-based elastomer material, or the like is recommended.

In practical use, for example, the above-mentioned EVA can be suitably used. The EVA has a vinyl acetate content of 5 to 25% by weight, preferably 10 to 20% by weight, and a melt flow rate (MFR) of 0%. 0.2 to 5 g / 10 min (J
(ISK7210, 190 ° C., 2.16 kg load) is preferable. Here, when the vinyl acetate content is less than 5% by weight, the obtained film is hard, the flexibility and the elastic recovery are reduced, and the surface tackiness is hardly developed. On the other hand, if it exceeds 25% by weight, the surface tackiness is too strong, and the unwinding property and appearance are liable to deteriorate. If the MFR is less than 0.2 g / 10 min, the extrudability decreases, while if it exceeds 5 g / 10 min, the film-forming stability decreases, and unevenness in thickness, a decrease in mechanical strength, and variations tend to occur. Therefore, it is not preferable.

When other materials are mixed,
(B) It is preferable to mix a petroleum resin, a terpene resin, a cumarone-indene resin, a rosin-based 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 for achieving both a storage elastic modulus (E ′) exhibiting suitable extensibility at room temperature as a stretch film and a loss tangent (tan δ) exhibiting appropriate stress relaxation properties.

[0023] Here, as the (B) petroleum resin of the component, there are aromatic petroleum resins from alicyclic petroleum resins and C ₉ components from cyclopentadiene or its dimer, the terpene resin β- pinene Examples of the rosin resin include rosin resins such as gum rosin and wood rosin, and esterified rosin resins modified with glycerin, pentaerythritol and the like. The component (B) is the component (A)
It is known that when mixed with components, etc., it shows 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 can be obtained, but those having a glass transition temperature of 50 to 100 ° C., preferably 70 to 90 ° C. are suitable for the present invention. is there. If the glass transition temperature is lower than 50 ° C., it is necessary to incorporate a large amount of the viscoelastic property when mixed with the above-mentioned component (A) in order to obtain desired viscoelastic properties. Easy to invite. Further, the mechanical strength of the film as a whole is insufficient, and the film is easily broken, which may cause a practical problem. On the other hand, when the glass transition temperature exceeds 100 ° C., the compatibility with the component (A) deteriorates, and bleeds to the film surface over time, which may cause blocking or a decrease in transparency.

For the above reasons, it is preferable that the content of the component (B) is as small as possible within a range in which the above-mentioned viscoelastic properties can be achieved. In this regard, the soft propylene resin controlled in stereoregularity applied to the present invention has a glass transition temperature of about −10 ° C. or more. Compared to a low-crystalline polypropylene resin contained in a large amount, even a small amount of the component (B) of about 20% by weight or less effectively acts to adjust the desired viscoelastic properties. In the film of the present invention, other than the component (B) described above, the following polyolefin-based resins usually used in a polyolefin-based composition as long as they do not exceed the gist of the present invention and do not deteriorate the appearance of the film. Or a styrene elastomer.

For example, in the case of a polypropylene resin, a propylene homopolymer or a copolymer with another monomer copolymerizable with propylene (propylene-ethylene copolymer, propylene-ethylene-α-olefin copolymer) And the like, for example, ethylene-vinyl acetate copolymer (vinyl acetate content is 5 to 40% by weight), low-density polyethylene, ethylene-α-olefin having 4 to 8 carbon atoms of α-olefin. Polymer, ethylene-acrylic acid copolymer (acrylic acid content is 5 to 20% by weight),
Metal salts (Zn, Na, K, Li) of ethylene-methyl methacrylate copolymers, copolymers of α-olefins such as ethylene and propylene with monomers selected from acrylic acid, methacrylic acid, maleic acid, etc. Styrene-based elastomers such as 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. Can 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 packaging suitability such as film cut properties and low-temperature properties and improving economic efficiency.
0% by weight can be blended. The thickness of the film of the present invention is generally in a range used for ordinary stretch packaging, that is, about 8 to 30 μm, typically 10 to 30 μm.
２０20 μm. When a laminated film is used, the ratio of the thickness of the layer containing the component (A) to the total thickness is 0.3 to 0.9, preferably 0.4 to 0.8, Specifically, the thickness is preferably 5 to 20 μm from the viewpoint of various characteristics and economy 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. In the case of forming a laminated film, it is advantageous to co-extrude with a multilayer die. Practically, it is preferable to melt-extrude the material resin from the annular die to 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. . As a cooling method at that time, either a method of cooling from the outer surface of the tube or a method of cooling from both the outer and inner surfaces of the tube may be used.
Further, the film obtained here is heated to a temperature not higher than the crystallization temperature of the resin, and stretched 1.2 to 5 times in the machine direction of the film by utilizing the speed difference between the nip rolls, or 1. Biaxial stretching may be performed 2 to 5 times.

In order to impart properties such as antifogging property, antistatic property, slipping property and self-adhesiveness to the film of the present invention, the following various additives are added to the surface layer and / or the component (A). 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 carbon atoms, specifically , Monoglycerin oleate, polyglycerin oleate, glycerin triricinoleate, glycerin acetyl resinolate, polyglycerin stearate, polyglycerin laurate, methyl acetyl resinolate, ethyl acetyl resinolate, butyl acetyl resinolate, 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 the 8 parts by weight.

[0029]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited thereto. In addition, various measured values and evaluations of the film displayed in this specification were performed as follows. Here, the direction of taking out the film from the extruder (flow direction)
Is called the vertical direction, and the orthogonal direction is called the horizontal direction.

(1) E ', tan δ Viscoelastic spectrometer VES- manufactured by Iwamoto Seisakusho Co., Ltd.
Using F3, vibration frequency 1
The temperature was measured from -50 ° C to 150 ° C at a rate of 1 ° C / min at 0 Hz, and values at temperatures of 20 ° C and 0 ° C were indicated from the obtained data.

(2) Suitability for stretch packaging Using a stretch film having a width of 350 mm, an automatic packaging machine (ISHIDA / WminMK-I manufactured by Ishida Koki Co., Ltd.)
I) foamed polystyrene tray (length 200mm,
130 mm in width and 30 mm in height) were packaged, and the items shown in Table 3 were evaluated. Using the same film and tray, a hand wrapping machine (Diawrapper A manufactured by Mitsubishi Plastics, Inc.)
-105) to conduct a packaging test.

(3) Stability of Film Formation The stability of bubbles when a film was formed by an inflation production facility was evaluated. ◎: Extremely stable ○: Stable △: Slightly unstable ×: Film formation not possible

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

(5) Crystallization temperature (Tc), heat of crystallization Using a Perkin Elmer DSC-7, a 10 m sample was prepared.
g was melted according to JIS-K7121 and JIS-K7122 at a heating rate of 10 ° C./minute, then heated to 200 ° C., kept at 200 ° C. for 5 minutes, and then cooled at a rate of 10 ° C./minute.
It was determined from the thermogram when the temperature was lowered to room temperature in minutes.

(6) Melt flow rate (MFR) Measured at a test temperature of 230 ° C. and a test load of 2.16 kgf according to JIS-K7210.

(7) Mesopentad fraction (mmmm),
Racemopentad fraction (rrrr) Measured under the following conditions using JNM-GSX-270 ( ^13C- nuclear magnetic resonance frequency 67.8 MHz) manufactured by JEOL Ltd. Measurement mode: ¹ H-complete decoupling Pulse width: 8.6 microseconds Pulse repetition time: 30 seconds Total number of times: 7,200 times Solvent: mixed solvent of orthodichlorobenzene / deuterated benzene (80/20% by volume) Sample concentration: 100 mg / 1 ml solvent Measurement temperature: 130 ° C. Here, each pentad fraction was determined by measuring a splitting peak in a methyl group region of ¹³ C-nuclear magnetic resonance spectrum. The assignment of the signal in the methyl group region is described in A.I.
Zambelli et al (Macromolec)
ules 8 , 687, (1975)).

(8) Time-dependent change The obtained film roll was heated at a temperature of 50 ° C. and a relative humidity of 60.
% For 10 days, and then evaluated the surface condition and the rewinding property. ◎: There is no bleeding of the additive on the surface and no blocking between films. …: There is almost no bleeding of the additive on the surface, but there is a little blocking between the films. Δ: There is little bleeding of the additive on the surface, and peeling is slightly heavy due to blocking between films. ×: There is much bleeding of the additive on the surface, and the blocking between the films is so severe that it cannot be used practically.

(Example 1) Soft polypropylene resin (I) having a controlled stereoregularity (propylene content: 100)
Mol%, mmmm = 35.3%, rrrr = 15.4
%, MFR = 16 g / 10 min, Tm = 155 ° C., Hun
tsman Polymer Corporation
And “EXFVA (REXflex W101”) as an intermediate layer having a thickness of 11 μm and an EVA (vinyl acetate content of 15% by weight, 190 ° C., 2.16 kg load) on both surfaces.
2.0 g / 10 minutes) A three-layer annular die temperature of 100 parts by weight was melt-kneaded with 3.0 parts by weight of diglycerin monooleate as an antifogging agent so that each layer had a thickness of 2 μm.
Co-extrusion blown molding at 0 ° C. and a blow-up ratio of 5.5 gave a total thickness of 15 μm (2 μm / 11 μm / 2 μm).
m) was obtained.

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

Example 2 In Example 1, 80% by weight of a soft polypropylene resin (I) as a raw material for an intermediate layer was mixed with hydrogen of a cyclopentadiene petroleum resin having a softening point of 125 ° C. (glass transition temperature 81 ° C.). 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 properties of the film composed of only the mixture of the soft polypropylene resin (I) and the hydrogenated petroleum resin were as follows. Storage modulus at 0 ° C. (E ′) 1.9 × 10 ¹⁰ dyn / cm ² Storage modulus at 20 ° C. (E ′) 1.4 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 0. 59 Glass transition temperature (Tg) 2 ℃

Example 3 In Example 2, a soft polypropylene-based resin (II) (propylene content: 100 mol%, mmm) was used in place of the soft polypropylene-based resin (I).
m = 44.5%, rrrr = 12.3%, MFR = 6 g
/ 10 min, Tm = 158 ° C., Huntsman Pol
ymer Corporation's “REXfle
xW110 ”), except that 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.

The soft polypropylene resin (I)
I) The properties of a film composed of a single substance were as follows. Storage modulus at 0 ° C. (E ′) 1.1 × 10 ¹⁰ dyn / cm ² Storage modulus at 20 ° C. (E ′) 1.5 × 10 ⁹ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 0. 25 Glass transition temperature (Tg) -7 ° C Heat of crystallization 35 J / g Crystallization temperature (Tc) 102 ° C

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

Example 4 In Example 1, as a raw material for the intermediate layer, a soft polypropylene resin (III) having a controlled stereoregularity (propylene content: 97 mol%, ethylene content: 3 mol%, mmmm = 37.4%, rrr
r = 11.4%, MFR = 19 g / 10 min, Tm = 14
9 ° C, Huntsman Polymer Corpo
ratio, "REXflex W201") 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 weight% of the mixed composition was used.

The soft polypropylene resin (II)
I) The properties of a film composed of a single substance were as follows. Storage modulus at 0 ° C. (E ′) 2.9 × 10 ⁹ dyn / cm ² Storage modulus at 20 ° C. (E ′) 4.3 × 10 ⁸ dyn / cm ² Loss tangent (tan δ) at 20 ° C. 0. 26 Glass transition temperature (Tg) -10 ° C Heat of crystallization 21 J / g Crystallization temperature (Tc) 95 ° C

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

Example 5 Example 1 was the same as Example 4 except that the laminated thickness ratio between the intermediate layer and the front and back layers was changed as follows.
15 μm (4 μm / 7 μm / 4 μ)
m) was obtained.

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

The properties of the film consisting of the PER alone were 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. 0. 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-based resin (IV) (propylene content:
100 mol%, mmmm = 63.0%, rrrr = 8.
0%, MFR = 2 g / 10 min, Tm = 158 ° C., Hun
tsman Polymer Corporation
Ex., “REXflex W105”), except that a total thickness of 15 μm (2 μm / 11 μm
/ 2 μm).

The soft polypropylene resin (I)
V) The properties of the film composed 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. 0. 14 Glass transition temperature (Tg) -6 ° C Heat of crystallization 54 J / g Crystallizing temperature (Tc) 108 ° C

(Comparative Example 3) The P used in Comparative Example 1 in Example 2 in place of the soft polypropylene resin (I)
Except that ER was used, the total thickness was 15 μ
m (2 μm / 11 μm / 2 μm).

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

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

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

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

The soft polypropylene resin (IV)
The properties of a film composed of only a mixture of styrene and a 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 (tan δ) at 20 ° C. 0. 26 Glass transition temperature (Tg) 6 ° C

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

[0060]

[Table 1]

[Table 2]

[Table 3]

As shown in Tables 1 to 3, the films of Examples 1 to 5 using the resin specified in the present invention and having the viscoelastic properties in 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 is understood that the films of Comparative Examples 1 to 5 in which the resins are different or whose viscoelastic properties are out of the range specified in the present invention are inferior in overall properties as a stretch film.

[0062]

According to the stretch film of the present invention, when used in an automatic wrapping machine, the film can be cut / transported and wrapped without any problem, the bottom sealing property is good, and the film tension is good. A package can be obtained, and it has a feature not found in the past as a chlorine-free stretch film. Furthermore, it has excellent stability over time and economic efficiency.

Claims (7)

[Claims] 1. A soft polypropylene-based resin having a controlled stereoregularity in which a crystalline block and an amorphous block portion are mixed in a molecular chain, comprising the following (1) to (3):
At least one layer mainly composed of a resin satisfying the following conditions, and a frequency of 10 Hz and a temperature of 2
Storage elastic modulus (E ') measured at 0 ° C. is 5.0 × 10 ⁸ d
A polyolefin-based stretch packaging film, characterized in that the film has a yn / cm ^{2 to} 5.0 × 10 ⁹ dyn / cm ² and a loss tangent (tan δ) in the range of 0.2 to 0.8. (1) The glass transition temperature measured at a heating rate of 10 ° C./min using a differential scanning calorimeter is −15 ° C. or more. (2) Crystals at a heating rate of 10 ° C./min using a differential scanning calorimeter. After melting, the temperature was raised to 200 ° C., kept at 200 ° C. for 5 minutes, and the heat of crystallization measured when the temperature was lowered 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) is 0.4 to 40 g /
10 minutes 2. A soft propylene-based resin having a controlled stereoregularity in which a crystalline block and an amorphous block portion are mixed in a molecular chain, wherein a monomer unit based on propylene is 95 mol% or more. The polyolefin-based stretch packaging film according to claim 1, wherein the sum (mmmm + rrrr) of the mesopentad fraction and the racemopentad fraction determined from the ¹³ C-NMR spectrum is in the range of 30 to 70%. 3. A mesopentad fraction (mmmm) determined from a 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 25-5
The polyolefin stretch packaging film according to any one of claims 1 to 2, wherein 0% and the sum of the mesopentad fraction and the racemopentad fraction (mmmm + rrrr) is in the range of 40 to 65%. 4. A dynamic viscoelasticity measurement at a frequency of 10 Hz,
The storage elastic modulus (E ') measured at a temperature of 0 ° C. is 1.5 × 10
4. The polyolefin-based stretch packaging film according to claim 1, which is in a range of ¹⁰ dyn / cm ² or less. 5. A layer mainly composed 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.
The polyolefin stretch packaging film according to any one of claims 1 to 4, wherein the components are mixed. (B) petroleum resin, terpene resin, cumarone-indene resin, rosin resin, or hydrogenated derivative thereof 6. A layer mainly composed of a soft polypropylene resin whose tacticity is controlled, in which a crystalline block and an amorphous block portion are mixed in a molecular chain, has a glass transition temperature of 50 to 50. 20% by weight of component (B) at 100 ° C.
The polyolefin stretch packaging film according to claim 5, wherein the film is mixed in the following range. 7. A vinyl acetate content on both sides of a layer mainly composed of a soft polypropylene resin whose stereoregularity is controlled, in which a crystalline block and an amorphous block portion are mixed in a molecular chain. Is 5 to 25% by weight and a melt flow rate (JIS K7210, 190 ° C., 2.16 kg load)
7. A polyolefin stretch packaging film according to claim 1, wherein said film comprises a layer in which a layer mainly composed of an ethylene-vinyl acetate copolymer of 0.2 to 5 g / 10 minutes is laminated.