JP2001129945A - Polyolefinic resin multilayered stretched film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyolefinic resin multilayered stretched film excellent in cutting properties and the suppressing properties of the generation of torn refuse while keeping flexibility and also excellent in heat shrinkability, heat sealability and optical characteristics. SOLUTION: A multilayered stretched film contains a polypropylene type resin with an MFR of 15-120 g/10 min and a boiling n-heptane extraction quantity of 20-90 weight % and is characterized by that a degree of crystallization based on the polypropylene type resin in the heat-resistant layer present in an inner layer is 3-20% and a degree of crystallization based on the polypropylene type resin in the whole of the film is 1-10%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stretched film of a polyolefin resin suitably used for various packaging applications such as stretch or stretch shrink packaging, and more particularly to stretch or stretch shrink packaging by an automatic packaging machine such as a stick-up type or a linear type. The present invention relates to a stretched polyolefin-based resin film suitable for:

[0002]

2. Description of the Related Art The characteristics required for stretch or stretch shrink wrapping films include suitability for hand wrapping and automatic machine wrapping (hereinafter simply referred to as machine wrapping), film gloss, anti-fog properties, and indentation recovery properties. And other display effects. Among the important film properties related to the suitability for packaging, the stretch properties, ie, appropriate breaking elongation and moderate elongation stress, and the heat sealing properties, ie, the seal initiation temperature at which practical fusion occurs between the films (seal lower limit temperature), indicate the film properties. The temperature range of heat sealing up to the temperature at which melt holes occur is wide,
The sealing is uniformly and sufficiently performed, and the sealing portion on the lower surface of the tray is smooth without being raised. Also,
In the case of mechanical packaging, the cutability for cutting the film to an appropriate length using a blade and the transportability of the film by a feed belt are also mentioned. In the case of stretch shrink wrapping, an appropriate heat shrinkage for removing slack in the film is also included.

[0003] As a soft stretched polypropylene film,
For example, JP-A-8-12772 and JP-A-8-323
No. 856 discloses a stretched polypropylene-based film having low crystallinity, that is, a low isotacticity index. It says that a film having excellent heat resistance, flexibility and transparency can be obtained. However, these prior arts do not sufficiently satisfy the requirements as a stretch or stretch shrink film as described below.

[0004] When the above-mentioned prior art is applied as it is, flexibility is certainly exhibited, but in particular, the film having a thickness of about 15 µm or less does not satisfy the tear propagation strength. Furthermore, no suggestion has been made regarding the heat shrinkability, and the film is heat shrunk by easy removal of wrinkles on the side of the tray during heat sealing in stretch packaging, smoothing of the sealing portion, and stretch shrink wrapping, and the upper surface of the tray. There is no device for removing wrinkles.

[0005] Further, there is no suggestion that a multi-layer structure is taken, and the heat resistance described here is merely due to the high temperature at which a melt hole is formed,
The temperature range of the heat sealing property of the stretch film from the lower limit of the heat sealing temperature to the temperature at which the film has a melt hole is insufficient. In addition, compared to the case where the polypropylene resin layer is not in the inner layer, especially more flexibility
When other resins are mixed to impart tear propagation strength, the deterioration of optical properties becomes severe.

[0006] Here, an example of the packaging process of the push-up type packaging machine will be described. (A) The film is fed in a longitudinal direction (hereinafter referred to as MD) from a film roll by sandwiching both ends of the film between film guide belts. (B) Thereafter, when the film length has reached a certain length, a perforation is made in a direction perpendicular to the feeding direction of the film (hereinafter referred to as TD) so that the cutting blade pushes up on the film, and the film is pulled to the MD. Thereby, the perforations are propagated to the TD and cut.

(C) Further, the film is conveyed by the belt to the pushed-up portion of the packaged object. (D) The film is folded into the lower part of the tray while removing the wrinkles on the upper surface of the tray by making the film stretched while the packaged object (tray) pushes up on the film. (E) Finally, the tray is placed on the hot plate. By pressing the bottom surface, heat sealing is performed and the packaging process is completed.

(F) When further shrink wrapping,
The film is heat shrunk by passing the package through a hot air tunnel to remove film wrinkles from the package. What is important here is that when the tear propagation strength of the film is low, the MD of the film is notched when the film is perforated in the step (a). At that time, when the film is stretched in the step (d), the notch of the MD becomes a starting point, the notch propagates, the film is torn off, and film debris is generated, and the debris remains on the belt.

On the other hand, when the tear propagation strength of the film is too strong, no perforation is formed in the step (a),
Even if it enters, the film may be transported without being able to cut completely without tear propagation to the TD. The type of the packaging machine, the shape of the packaged material and the packaging conditions are greatly affected, but in general, the tear propagation strength of the film, which achieves both suppression of the chipping of the film and cutability, is 10 to 200 g in both the vertical and horizontal directions. Preferably it is 20 to 150 g, most preferably 30 to 100 g. The tear propagation strength is 1
If it is less than 5 g and less than 10 g in the horizontal direction, the amount of torn chips increases, while if the tear propagation strength exceeds 200 g, the cuttability tends to be poor, and all of these are levels that hinder packaging. On the other hand, if the heat shrinkage ratio is small, the heat shrinkage of the heat seal portion and its peripheral portion is insufficient due to the heat at the time of the heat seal in the step (e), and the lower portion of the tray feels swelled.
Further, in the step (f), the slack of the film can be sufficiently removed, and wrinkles remain.

[0010]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a film which is excellent in stretch wrapping and stretch / shrink wrapping, especially stretch wrapping by a wrapping machine. While maintaining or further improving a certain flexibility, it is excellent in improving the cut property of the film and the tear resistance during film stretching, that is, excellent in suppressing the generation of chipping of the film, and also in the heat shrinkage property, heat sealing property, optical properties It is to provide an excellent film.

[0011]

That is, the polypropylene resin is a propylene homopolymer or propylene-α.
An olefin (2 or 4 to 12 carbon atoms) random copolymer including an inner layer made of a polypropylene resin satisfying the following formulas (1) and (2), wherein at least one of the inner layers has the following formula (3) A multi-layer stretched polyolefin resin film which satisfies the following heat-resistant layer and further satisfies the following formula (4). 0.5 g / 10 min ≦ MFR ≦ 20 g / 10 min (1) Extraction amount of boiling n-heptane = 20 to 90% by weight (2) 3% ≦ Xch ≦ 20% (3) (However, Xch is a suggestive scan described later) Of the crystallinity measured by the calorimetric method (DSC), the crystallinity based on the polypropylene resin in the layer containing the largest amount of the polypropylene resin. 1% ≦ Xc ≦ 10% (4) (where Xc Is the crystallinity based on the polypropylene-based resin out of the crystallinity of the whole film measured by the differential scanning calorimetry (DSC) described later.) Hereinafter, the present invention will be described in detail.

In general, in a stretched film, an appropriate orientation is formed in the film by a stretching process, and as a result, an appropriate elongation load and tear propagation strength are imparted to the film. In the present invention, focusing on the isotacticity and the crystallinity of the polypropylene resin which is a high melting point resin (heat resistant resin) with respect to this orientation, and as a result of eagerly examining the relationship with the stretching, it has been found that the tearing of the film at the time of packaging is reduced. It has been found that both suppression and cutting properties are compatible, and that there is a range in which the heat shrinkage, the heat sealing property and the optical properties are excellent. Particularly, a layer containing the largest amount of the polypropylene resin in a certain range or more among the layers containing the polypropylene resin (referred to as a heat-resistant layer or an H layer).
Greatly affects physical properties.

First, the advantages of the present invention as compared with the prior art will be described below using examples and comparative examples. In the film of the present invention (Example 1, Experiment No. 1), the heat-resistant layer was a blend of TPO5 (TPO E2700 manufactured by Idemitsu Petrochemical Co., Ltd.) and polybutene-1 (PB), and the skin layer and the intermediate layer were polyethylene-based. Although it was made of resin,
The tear propagation strength, which is an index for controlling the generation of torn chips and cutting properties, is 20/15 g in the longitudinal direction / lateral direction,
Even if 100 packs were packaged, the amount of waste generated was less than 1 g, which was within the allowable range, and the cut surface was also beautiful. Further, there is no film wrinkle after packaging, the heat sealing property is good, and the appearance such as glossiness is excellent. When the physical properties of this film are shown in the longitudinal and transverse directions, the heat shrinkage at 100 ° C. is 45/30%, 1
The heat shrinkage at 20 ° C. is 65/55%, and the elongation at break is 5
It was 50/600%.

On the other hand, the conventional film (Experiment No. 2 of Comparative Example 1) is a single-layer film of TPO5. When the tear propagation strength is shown in the longitudinal direction / lateral direction, 5
/ 3 g, and when the same packaging operation was performed, 5 g of waste was generated. The machine stopped 5 times during packaging. In addition, 18 packages to be repackaged due to film breakage occurred. In addition, heat sealability and glossiness were significantly poor. When the physical properties of this film are shown in the machine direction / lateral direction, the heat shrinkage at 100 ° C. is 40 /
The heat shrinkage at 30% and 120 ° C. was 60/55%, and the elongation at break was 180/280%.

A conventional film (Experiment N of Comparative Example 1)
o. 3) is a single layer film of TPO5 obtained by direct inflation. The tear propagation strength is as large as 40/100 g in the longitudinal / transverse direction, but the number of chips is 1
g. In addition, the cut surface was not clean, and there was some difficulty in the cutability. Moreover, the film wrinkles after packaging remained considerably, and the film tension was insufficient. Regarding the glossiness, Experiment No. It was worse than two. When the physical properties of this film are shown in the vertical and horizontal directions, it is 10
The heat shrinkage at 0 ° C. was 20/3%, the heat shrinkage at 120 ° C. was 25/5%, and the elongation at break was 370/480%.

From the above, it can be seen that the film of the present invention is superior as a stretch or stretch shrink wrapping film as compared with a conventional film using a single layer of a polypropylene resin alone. Hereinafter, the film of the present invention is made of a polypropylene-based resin MFR (JIS
According to K7210, the temperature is 230 ° C and the load is 2.
(16 kg condition) is required to be 0.5 to 15 g / 10 minutes.

Experiment No. 1 as an example of the film of the present invention. No. 22 uses a polypropylene resin having an MFR of 12 g / 10 min. Experiment No. 2 using a polypropylene resin having an MFR of 1.5 g / 10 min, which is another film example of the present invention. Although the film-forming stability was inferior to that of No. 21, it was within an allowable range. In addition, the cutting property was slightly deteriorated, but was within an allowable range. On the other hand, in Experiment No. which is a comparative example. 23 was a polypropylene-based resin having an MFR of 30 g / 10 min. However, film formation by direct inflation was not possible.

From the above, the MFR of the heat-resistant resin is 0.5
It turns out that it is necessary to be 〜15 g / 10 min. That is, when the MFR is less than 0.5 g / 10 minutes, the obtained stretched film is too oriented, and as a result, the film has a low tear propagation strength and a film with low elongation at break and poor stretchability. There is a tendency. When the MFR is larger than 20 g / 10 minutes, it is difficult to form a film by direct inflation. In addition, the gloss is deteriorated, and in particular, since the polypropylene resin is dispersed in the MD of the film in a streak shape, the TD gloss of the film tends to be deteriorated.

The MFR is generally 0.8 to 15 g / 10
Min, preferably 1.2 to 10, most preferably 2.3 to
8.5 g / 10 min. Next, the fact that the present invention is superior to the prior art in suppressing the generation of torn chips in a film at the time of packaging is performed by mechanically packaging a film of the present invention and a conventional film by a top-up packaging machine. The differences will be described in detail. The film of the present invention has a crystallinity of 3% ≦ Xch ≦ 20 when the crystallinity based on the polypropylene-based resin in the layer containing the largest amount of the polypropylene-based resin is Xch among the crystallinity measured by the DSC method. % Of the heat-resistant layer will be described with reference to Examples and Comparative Examples.

Xch of the film of the present invention is 7.7%
(Corresponding to Example 1, Experiment No. 1), the tear propagation strength was 20/15 g, whereas Xch = 3.
In the example of 8% (corresponding to Experiment No. 8 of Example 2), the tear propagation strength was 35/28 g. When packaging was performed with the film of the present invention (Experiment No. 8 of Example 2), the amount of generated debris was 0.0 g even when 100 packages were packaged. The film formation stability was on the lower limit of the acceptable level.

Further, in the comparative film (corresponding to Experiment No. 10 of Comparative Example 2) in which Xch = 2.8%, the orientation tension of the resin was insufficient, and it was difficult to obtain a stretched film.
On the other hand, the film of the present invention with Xch = 18.8% (corresponding to Experiment No. 5 of Example 2) had a tear propagation strength of 15 /
It was 10 g. When the film of the present invention (Experiment No. 4 of Example 2) was wrapped, the amount of generated debris was 1.8 g even in 100-pack packaging, and the generation of debris was slightly anxious. Was at a possible level, and the cut surface was also beautiful.

Further, the comparative film with Xch = 30.6% (corresponding to Experiment No. 9 of Comparative Example 2) had a tear propagation strength of 8/7 g. Occurred. In addition, the machine stopped four times during packaging, which was in a range where continuous use was impossible. In addition, the number of items to be repackaged due to film breakage is 1
Five occurred.

From the above, it can be seen that the crystallinity Xch derived from the heat-resistant resin in the heat-resistant layer needs to be 3 to 20%. That is, when Xch is smaller than 3%, the orientation tension of the resin is hardly applied, and it becomes difficult to take up or stretch the raw material. Also, the cutting properties of the machine tend to be poor. If Xch is greater than 20%, the resulting stretched film is too oriented, resulting in a film with low tear propagation strength. Furthermore, there is a tendency that a film having a small elongation at break is inferior in stretchability.

Xch is generally 4 to 18%, preferably 5 to 16%, and most preferably 7 to 10%.
Next, when the crystallinity based on the above-mentioned heat-resistant resin is defined as Xc among the crystallinity of the entire film of the present invention, it is necessary to satisfy 1% ≦ Xc ≦ 10% at the same time. A description will be given using examples and comparative examples. Examples of the film of the present invention in which Xc was set to 2.3% (Example 1,
Experiment No. 1) (corresponding to Experiment No. 11 of Example 3), whereas the tear propagation strength was 20/15 g, whereas the film example of the present invention (corresponding to Experiment No. 11 of Example 3) with Xc = 1.7% had a tear propagation strength of 35. / 30 g.

The film of the present invention (Experiment N of Example 3)
o. In the case where the packaging was performed in 11), the amount of generated debris was 0.0 g even after packaging 100 packs. The film-forming stability was at an acceptable lower limit. Furthermore, the comparative film (corresponding to Experiment No. 13 of Comparative Example 3) with Xc = 0.9% had insufficient orientation tension of the resin, and it was difficult to obtain a stretched film. On the other hand, the film of the present invention in which Xc = 9.0% (corresponding to Experiment No. 12 in Example 3) had a tear propagation strength of 15/10 g.

The film of the present invention (Experiment N of Example 3)
o. When packaging is performed in step 12), the amount of generated debris is 1.8 g even if 100 packs are packaged. there were. Further, the comparative film with Xc = 10.5% (corresponding to Experiment No. 14 of Comparative Example 3) had a tear propagation strength of 6/5 g, and the same packaging operation produced 3 g of debris. In addition, the machine stopped during packaging four times, which was in a range where continuous use was impossible, and fifteen to-be-packaged products that had to be repacked due to film breakage occurred.

From the above, it can be understood that the crystallinity Xc derived from the heat-resistant resin in the heat-resistant layer needs to be 1 to 10%. That is, when Xc is smaller than 1%, the orientation tension of the resin is hardly applied, and it becomes difficult to take up or stretch the raw material. Also, the cutting properties of the machine tend to be poor. When Xc is larger than 10%, the obtained stretched film is too oriented, and as a result, the film has a low tear propagation strength and a film with low elongation at break and poor stretchability. Xc is generally 1-6%, preferably 1.3-4.5%, most preferably 2.0-4.0%.

Next, the film of the present invention needs to have a boiling n-heptane extraction amount, which has a correlation with the isotacticity of the polypropylene resin, of 20 to 90% by weight, using Examples and Comparative Examples. explain. Xch = 12.
2%, Xc = 3.2%, and the amount of boiling n-heptane extracted =
An example of the film of the present invention using TPO1 of 62 wt% and fmmmm = 40 mol% (Experiment No. 19 of Example 4)
) Had a tear propagation strength of 20/15 g.

Further, the above-mentioned Xch = 18.8%, Xc =
The film of the present invention using the above-mentioned TPO1 (Experiment No. 5 of Example 2) also had a tear propagation strength of 15/1.
Although it is 0 g, when packaging with these films, the amount of generated debris is 1-2 g even when packed in 100 packs, and the generation of debris is slightly anxious, but it is a level that can be used continuously, The cut surface was also beautiful. In contrast, Xch
= 11.6%, Xc = 4.6%, and a control film (corresponding to Experiment No. 20 of Comparative Example 4) using PP with boiling n-heptane extraction amount = 9 wt% and fmmmm = 91 mol% The tear propagation strength was 9/8 g, and the same packaging operation produced 3 g of debris. In addition, the machine stopped four times during packaging, which was in a range where continuous use was impossible. Further, 15 packages to be repacked due to the tearing of the film occurred. In addition, streaks that seemed to be poor dispersion of PP were observed in the film, and the appearance was problematic.

From the above, it can be understood that it is necessary that the boiling n-heptane extraction amount of the polypropylene resin is 20 to 90% by weight. That is, when the amount of boiling heptane extracted is less than 20% by weight, the obtained stretched film is too oriented, and as a result, the film has a low tear propagation strength. Furthermore, there is a tendency that a film having a small elongation at break is inferior in stretchability. Further, when blended with another resin, the compatibility is deteriorated, streaks are formed in the film, and the appearance of the film such as gloss is deteriorated.
On the other hand, when the amount of boiling n-heptane extracted is larger than 90% by weight, the orientation tension of the resin is hardly applied, and it becomes difficult to take up and stretch the raw material. Further, the cutting property of the machine is also deteriorated.

The boiling n-heptane extraction amount is generally 30 to 90% by weight, preferably 55 to 90% by weight, and most preferably 60 to 90% by weight. From the above, it can be seen that the film of the present invention is superior to the conventional film in suppressing the generation of torn chips in the film at the time of packaging, and is also compatible with the cut property. In addition, when the film of the present invention is used as a stretch film, it is not always necessary to positively exhibit the heat shrinkage action of the film. However, since the film of the present invention is obtained by stretching, the melting point of the heat-resistant resin-
By heating the film to “10 ° C.”, a film having a heat shrinkage of 5% or more in at least one direction can be obtained. In addition, when used as a stretch / shrink film, the longitudinal direction of the film at 120 ° C
It is general that the horizontal direction is 20% or more. In addition, such a film becomes smooth without the swelling of the bottom seal portion even during stretch packaging.

The polypropylene resin used in the present invention is specifically propylene homopolymer, propylene / ethylene / random copolymer, propylene / ethylene / α-olefin (4-12 carbon atoms) / random copolymer And a propylene / α-olefin (having 4 to 12 carbon atoms) / random copolymer. As described above, the propylene homopolymer (hereinafter, referred to as HPP) and the propylene / ethylene random copolymer (hereinafter, referred to as RPP) used in the present invention are those isotactic polypropylene components (hereinafter, referred to as iPP). The isotacticity of the polypropylene resin is specified in a specific range, and an index of the amount of the iPP component is the boiling n-heptane extraction amount of the polypropylene resin. Generally, the boiling n-heptane extraction component has a component (mainly an amorphous component) other than the isotactic PP component as a main component, and tends not to be strongly oriented as in the case of the isotactic PP component when stretched. It is easy to adjust the orientation to achieve the purpose. The boiling n-heptane extract component also contains a low molecular weight isotactic component, which is also different from the high molecular weight isotactic component and is similar to the high molecular weight isotactic PP component when stretched. It tends not to be strongly oriented.

Preferred examples of the polypropylene-based resin include a transparent type of Idemitsu TPO manufactured by Idemitsu Petrochemical Co., Ltd., which is referred to as "reactor TPO" and has a boiling n-heptane extraction amount of 20 to 90% by weight. Those belonging to the HPP such as WL100s of FPO manufactured by the company, and those belonging to the RPP such as WL200s of the FPO manufactured by the company. These are different from the propylene / ethylene block copolymer (hereinafter referred to as BPP) -based reactor TPO in which EPC and iPP have a clear sea-island structure.
The P-based reactor TPO has excellent compatibility when blended with another resin, and as a result, is excellent in optical properties, tear propagation strength and the like.

The amount of boiling n-heptane extracted is "new edition".
Polymer Handbook ", p613-614, Kinokuniya Shoten Co., Ltd. (1995) In other words, using a Soxhlet extractor, about 3 mg of a powder or film sample was put into a cylindrical filter paper, and about 100 ml. Extraction for 8 hours using n-heptane of
The ratio of the amount of extraction was determined. Among the polypropylene resins having the above-mentioned boiling n-heptane extraction amount in a specific range, a more preferred polypropylene resin is HPP having an isotactic pentad fraction (fmmmm) of 10 to 75 mol%.
The base is an RPP-based polypropylene resin. Examples of such a resin include a solid catalyst containing magnesium, tetravalent titanium, halogen and an aromatic dicarboxylic acid diester as essential components, an organic aluminum compound, and an aromatic compound containing an alkoxy group, which are described in JP-B-7-103173. A propylene polymer obtained by one-stage polymerization using a compound as a catalyst, or a magnesium halide-supported substrate co-milled without adding an electron donor at a specific ratio indicated in Japanese Patent No. 2912483, aluminum trihalide, Propylene homopolymers obtained by one-stage polymerization using a catalyst system comprising a titanium tetrahalide and a trialkylaluminum as a promoter are mentioned. The product produced by these reactors is distinctly different from, for example, a blend of HPP or RPP with polypropylene wax or low-crystalline or amorphous polypropylene, and the dispersibility of both is much higher than this. This is preferable in that the optical properties are excellent, the amorphous component has a high molecular weight and an appropriate alignment tension, the film-forming property is much more excellent, and the flexibility of the resin composition is greatly expanded. It is also advantageous for obtaining an appropriate tear propagation strength.

A specific example is Idemitsu TP manufactured by Idemitsu Petrochemical Co., Ltd.
O transparent or Huntsman FPO (WL100 series, WL200 series), these are crystal lamellae (mainly isotactic components) in the sea of amorphous components (mainly atactic PP components) in a transmission electron microscope. Are observed as finely dispersed and floating. Further, among these resins, fmmmm is generally 20 to 75 mol%, and more preferably fmmmm is 25 to 75 mol%.
55 mol%, and the most preferred fmmmm is 30 to 4
5 mol%. Further, among these, from the viewpoint of heat resistance, H
PP is preferred.

The isotactic pentad fraction was determined by A.I.
Macromolecul by Zambelli et al.
es, 6, 925 (1973), a nuclear magnetic resonance spectrum ( ¹³ C-N
It is an isotactic fraction in pentad units in a polypropylene molecular chain measured using MR). In other words, the isotactic pentad fraction is a fraction of propylene monomer units in which five propylene monomer units are consecutively meso-bonded. However, regarding the assignment of peaks, Macromolecules, 8, 687 (1
975) based on the revised version of the above-mentioned document.
Specifically, the isotactic pentad unit is measured based on the intensity fraction of all absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum. In the RPP, the methyl carbon peak of the propylene unit adjacent to the ethylene unit in this methyl carbon region overlaps the other methyl carbon peaks. RPP having an ethylene unit content of about 3 mol% or less has a small effect on the isotactic pentad fraction.
As in P, the isotactic pentad fraction of RPP is calculated.

The heat-resistant resin is generally a polypropylene resin having a melting point of 140 ° C. or more, preferably 150 ° C., and most preferably 154 ° C. or more from the viewpoint of heat sealing properties. On the other hand, in the present invention, in order to make Xch 3 to 20%, polypropylene resin is blended with 10 to 90% by weight, and polyethylene resin and / or polybutene-1 resin is blended with 90 to 10% by weight. It is common. The content of the polypropylene resin in the heat-resistant layer is generally 10 to 90% by weight, preferably 15 to 65% by weight, and most preferably 20 to 50% by weight.

At this time, as the resin to be blended with the polypropylene-based resin, a resin that is unlikely to cause crystal orientation during stretching is used. Among them, a polybutene-1 resin (hereinafter referred to as PB) is a preferred example from the viewpoint that the compatibility with the polypropylene resin is good, the crystallization rate is low, and the transparency of the resulting film is not reduced. No. As PB, polybutene-1 homopolymer, butene-
1. ethylene copolymer, butene-1 propylene copolymer, butene-1 alpha olefin (5-12 carbon atoms) copolymer. Among them, butene-1.
An ethylene copolymer or a butene-1 propylene copolymer, and more preferably an ethylene content of 2-1.
It is a 0 mol% butene-1 · ethylene copolymer or a butene-1 · propylene copolymer having a propylene content of 10 to 30 mol%. An example of this preferred resin is Tuffmer BL manufactured by Mitsui Chemicals, Inc. The preferred MI of PB is 19 (according to JIS K7210).
At 0 ° C. and a load of 2.16 kg) is 1.5 g / 10
Minutes or more, and particularly preferably 3 to 6 g / 10 minutes.

In order to improve the indentation recovery of the film, an ethylene-α-olefin copolymer having a density of 0.902 g / cm ³ or less may be blended with the heat-resistant resin.
Preferably, the density is 0.880 g / cm ³ or less, more preferably, the density is 0.865 to 0.875 g / cm ³ . Further, a block copolymer composed of an amorphous polyolefin block and a crystalline polyolefin block may be blended in order to improve the indentation recovery of the film. As an example, DYNARO manufactured by Nippon Synthetic Rubber Co., Ltd.
N. CEBC and the like.

Further, mineral oil, polyolefin wax and the like may be added as long as the object of the present invention is not impaired. The film of the present invention has a multilayer structure, and it is necessary to form a layer (H layer) containing a heat-resistant resin as an inner layer from the viewpoint of heat sealing properties and optical properties. A skin layer (S layer), an intermediate layer (I layer), and the like can be laminated on the H layer. Here, a resin suitable for forming the S layer of the film of the present invention will be described.

The S layer can impart film properties such as sealing properties, gloss, anti-fog properties, and slip properties to the film. For the S layer, an ethylene copolymer having a melting point of 100 ° C. or less is preferably used. Specifically, for example, ethylene
α-olefin (C 3-12) copolymer or a copolymer of ethylene and a monomer selected from vinyl ester monomer, aliphatic unsaturated monocarboxylic acid, and monocarboxylic acid / alkyl ester derivative Examples include an ethylene / vinyl acetate copolymer, an ethylene / alkyl acrylate copolymer, an ethylene / alkyl methacrylate copolymer, and an ethylene / acrylic acid copolymer. More preferably, an ethylene / vinyl acetate copolymer (hereinafter referred to as EVA) or a metallocene-based catalyst or a vanadium catalyst having a vinyl acetate content of 10 to 20% by weight in view of compatibility with the anti-fogging agent and stretchability of the film. 0.86 polymerized density
It is selected from an ethylene / α-olefin copolymer of 5 to 0.910 g / cm ³ .

From the orientation balance of the resin due to the melt tension at the time of melt extrusion, the M
I is generally 0.5 to 20 g / 10 min, preferably MI is 1 to 12 g / 10 min, more preferably 1.
5 to 8 g / 10 min. In order to impart antifogging property, a surfactant can be added to each layer as an antifogging agent. Generally, a nonionic surfactant or HLB is used.
Is added in an amount of 0.5 to 5% by weight based on the S layer. Specifically, a resin obtained by adding 1 to 3% by weight of a monoglycerin fatty acid ester and / or diglycerin fatty acid ester and / or 0.5 to 1.5% by weight of a polyoxyethylene fatty acid ester to the resin of the S layer is used. .

In the S layer, additives such as plasticizers such as mineral oil and polyolefin wax, ultraviolet absorbers, silver-based antibacterial agents, freshness preserving agents such as hinokitiol and wasabi extract and chitosan, and lubricants such as fatty acid amides are used. Can be added. Further, in the present invention, an intermediate layer (hereinafter, referred to as I layer) can be provided. 0.865 density in the middle layer
An ethylene / α-olefin copolymer of up to 0.910 g / cm ³ is preferably used for improving the tear propagation strength and puncture resistance of the film. Preferably, it is polymerized with a single site catalyst such as a metallocene catalyst and has a molecular weight distribution (weight average molecular weight / number average molecular weight) of 3 or less. In this case, the melting point of the copolymer is preferably 40 ° C. or higher, more preferably 50 ° C. or higher, lower than the melting point of the heat-resistant resin. By increasing the difference in melting point from the heat-resistant resin, the stability of heat sealing properties and film forming properties tends to increase.

Incidentally, the MI of the I layer is generally 0.5 to 15 g / 10 min. An antifogging agent may be added to the I layer in the same manner as the S layer. Generally, a 0.5 to 5% by weight of a nonionic surfactant is added to the I layer. Specific examples include those obtained by adding 1 to 3% by weight of a monoglycerin fatty acid ester and / or a diglycerin fatty acid ester to the resin of the I layer. Further, additives such as a plasticizer such as mineral oil and polyolefin wax, an ultraviolet absorber, a freshness preserving agent such as hinokitiol and wasabi extract and chitosan may be added to the I layer.

As a combination of each of the above layers, S / S
H / S, S / H / I / S for 4 layers, S / I / H for 5 layers
/ I / S, S / H / I / H / S, and S / I / H /
I / H / I / S, S / H / I / H / I / H / S, and the like. The total thickness of the film is generally about 5 μm to 30 μm from the viewpoint of handleability, stretchability, tear propagation strength and piercing strength of the film, and preferably about 8 μm.
１５15 μm.

The thickness ratio of the S layer, the H layer, and the I layer is generally
Layers are 5-45% per layer, H layers are 10-9 per layer
0%, and the I layer is 0 to 80% per layer. Further, the absolute thickness of the S layer is preferably 1 μm or more from the viewpoint of antifogging property and optical characteristics. Further, in order to exhibit sufficient sealing strength even in high-speed packaging, it is preferable that the thickness of the S layer is 3 μm or less and the thickness of the H layer is 2 μm or more.

A recycled resin such as a film trim loss can be added to the H layer or the I layer. When the recycled resin is added to the H layer or the I layer, the gloss is slightly deteriorated, but it is found that the purpose of the present invention is satisfied. However, when the recycled resin is added to the I layer, the tear propagation strength is lower than when the recycled resin is added to the H layer, and accordingly, a little more debris is generated. Also, the gloss tends to be worse when added to the I layer than when the H layer is added. The cause of poor gloss is due to fine roughness of the film surface. Polyethylene resin generally has poor compatibility with heat-resistant polypropylene resin, and accordingly, fine irregularities are generated at the interface between the H layer and the I layer. It is considered that the unevenness is reflected on the innermost layer. From that viewpoint, it is better to add the recycled resin to the innermost layer.

In order to achieve both slipperiness and anti-fog properties on the film surface, a surfactant is applied to the entire surface of the film, or a predetermined width is applied from the entire surface of the film or the edge of the film (product) to the film holding belt of the packaging machine. Silicone oil or an emulsion thereof may be applied only to the part that comes into contact (0.3 to 50 mg / m ³ per side). The physical properties of the film obtained by adopting the constitution of the present invention are as follows. That is, when expressed in the longitudinal direction / lateral direction of the film, the tear propagation strength is 15/10 g or more, the generation of debris is excellent, and the elongation at break is 200 / g from the viewpoint of stretchability.
300% or more, and the gloss is 130 /
120% or more, from the viewpoint of removing film wrinkles during stretch shrink wrapping, the heat shrinkage at 120 ° C is 20 /
Preferred physical properties are obtained when the content is 20% or more. More preferably, the tear propagation strength is 20/15 g or more, and the breaking elongation is 30.
0/400% or more, gross is 140/130% or more, 1
The heat shrinkage at 20 ° C. is 30/30% or more, most preferably the tear propagation strength is 25/20 g or more, the breaking elongation is 400/400% or more, and the gloss is 145/140%.
As described above, the heat shrinkage at 120 ° C. is 45/45% or more.

Next, a method for producing the film of the present invention will be described. The method for producing the stretched film of the present invention may be any method such as coextrusion T-die to tenter stretching, direct inflation (hereinafter, referred to as DI method), double bubble inflation (hereinafter, referred to as DB method),
Among them, the preferred production method is the DB method. Here DB
A preferred example of the method will be described in more detail, but is not limited thereto.

The resin composition is melted, extruded by a circular die, quenched and solidified by a refrigerant, turned into a tubular raw material, folded by a roll, and taken up. At this time, a surfactant in the tube for the purpose of improving properties such as antifogging property and slip property,
It may be filled with silicone oil or the like. If necessary, the raw material may be irradiated with an energy beam such as an electron beam to perform a crosslinking treatment. Next, air is injected into the raw material to form a tube, and the stretching start temperature of the raw material is controlled between the two pairs of differential nip rolls within the temperature range from the glass transition point to the melting point of the polypropylene resin. The film is tubular-stretched up to 36 times, the film is cooled, folded by two pairs of converging rolls, taken up by a nip roll, and heat-treated using a roll heat setting device or a hot air oven if necessary. The film is obtained by winding in a cooled state. Further, a corona discharge treatment or the like may be performed after the heat treatment. First, the resin composition of each layer is melted by a separate extruder, and combined and laminated by a multilayer circular die to extrude a multilayer film.

Next, preferred temperature conditions in the DB method in the present invention will be described. In addition, all the temperatures shown below are the surface temperatures of the film. First, when the melt-extruded raw material is first quenched and solidified, it is necessary to cool the film to a temperature lower than the crystallization peak temperature of the polypropylene resin and the main resin other than the polypropylene resin, usually 5 to 75 ° C. It is preferable for suppressing crystallization of the crystalline resin. Experiment No. In No. 1, the laminate was quenched and solidified to 30 ° C., which is 73 ° C. or lower, which is the crystallization peak temperature of the ethylene / vinyl acetate copolymer (EVA1) or the ethylene / octene-1 copolymer (VL1).

Next, before stretching, the raw material is reheated to a temperature not lower than the crystallization temperature of the polypropylene resin or the melting temperature of the main resin other than the polypropylene resin, preferably not higher than "the melting point of the polypropylene resin-20 ° C". . Usually, the heating temperature is about 90 to 140 ° C., and this temperature corresponds to the stretching start temperature, that is, the temperature of the bubble neck.
Experiment No. In No. 1, heating to 125 ° C. and 3.8 in the longitudinal direction
Stretched 3.3 times in the transverse direction.

Here, the stretching ratio for giving proper orientation is usually 2 to 36 times in area ratio. Further, when the stretching ratio is less than 2 times, the orientation unevenness or the orientation unevenness different in the degree of orientation depending on the portion of the film, or the thickness unevenness of the film tends to increase, and when the stretching ratio is larger than 36 times, excessive orientation or The thickness of the raw sheet increases, making it difficult to control the temperature, and also tends to increase unevenness in orientation and thickness of the film. Next, after stretching, the film is cooled to at least the crystallization temperature of the main resin other than the polypropylene-based resin, that is, usually 75 ° C. or less, preferably 50 ° C. or less, and more preferably 30 ° C. or less, and the stretching is terminated and taken off. Experiment No. In No. 1, the sheet was cooled to 40 ° C. at the end point of stretching and then folded and taken out.

When the heat treatment is performed thereafter, the heat treatment temperature is preferably in the range of “room temperature + 10 ° C.” to the crystallization temperature of the main resin of the S layer. At a temperature of "room temperature + 10 ° C" or less, orientation relaxation and dimensional stability, which are the objectives of the heat treatment, cannot be performed, and if the temperature is not lower than the crystallization temperature of the main resin of the S layer, the film may be fused. When the relaxation heat treatment is performed in a hot air oven or the like, the heat treatment temperature is set to about 45 to 75 ° C., and the relaxation rate is -10 to 30% in the vertical and horizontal directions, respectively.
In general,

Finally, the temperature at which the film is wound is lower than the crystallization temperature of the main resin of the S layer, that is, usually 45 ° C. or lower, preferably 35 ° C. or lower, more preferably 3 ° C. or lower.
0 ° C. or less. Here, the temperature of 45 ° C. is used to prevent the films from blocking each other at the time of winding and extending in the vertical direction. Experiment No. 25 for 1
C. and cooled. When such a temperature setting, particularly the reheating temperature and the stretching temperature of the raw material are set as described above,
In addition to easily achieving the desired physical properties of the present invention, there is an advantage that a film can be stably formed, and the obtained film can be obtained with less unevenness in the horizontal and vertical directions.

Here, the “result of film forming property” in the evaluation method described later was in good agreement with the orientation of the film. That is, in order to stabilize stretched bubbles during stretch film formation, Xc
h must be 3.0% and Xc must be 1% or more. Generally, Xch is 4.0% or more, preferably Xch is 5.0%.
% Or more, and Xc is 1.3% or more. Most preferably X
ch is 7% or more and Xc is 2.0% or more. Also, D
In the case of the method I, since the melt tension needs to be at least a certain level, the MFR must be at most 15 g / 10 min, more preferably at most 8 g / 10 min.

When the DB method is compared with the DI method, there are several points that the DB method is superior to the DI method in the present invention. First, in the DB method, the melt-extruded tubular raw material is quenched and solidified and stretched in a low-temperature atmosphere, compared to the DI method in which the bubble is formed while the resin is melted from the die. There is an advantage that a resin having a lower melt tension can be used than in the DI method in which bubbles are formed.

Further, since the film is oriented as compared with the DI method, it is possible to stably produce a film having less thickness unevenness than the DI method, and the DI method is difficult.
An ultrathin film of 0 μm or less can be stably obtained. Looking further at the film obtained by the DI method, it is generally difficult to obtain a transparent film of the polypropylene resin having a melting point of 150 ° C. or more by the air-cooled DI method, and it is difficult to obtain a wide lateral magnification by the water-cooled DI method. It is in. In the case where the isotactic pentad fraction (fmmmm) of HPP or RPP is 10 to 75 mol%, a relatively transparent film can be obtained by the air-cooled DI method. Experiment No. of Comparative Example 5
As is clear from the fact that 23 could not be formed, if the MFR of the polypropylene resin is not less than 15 g / 10 minutes, the melt tension of the film becomes insufficient and the DI method becomes difficult.

According to the DI method, a relatively high tear propagation strength can be obtained, but the TD tends to be stronger than the MD of the film. In particular, and in particular, inferior cutability is often found. In addition, it is difficult to adjust the orientation by the DI method, and it is difficult to apply an appropriate orientation as compared with the DB method. Therefore, the heat shrinkage ratio during heating is small, and the film tends to be unsuitable as a stretch shrink packaging film. Even when such a package item is subjected to thermal shrinkage by passing the package item through a heating tunnel or the like, since the shrinkage is incomplete, the film wrinkles of the package item tend to be incompletely removed.

As described above, the DB method allows a wider choice of resins than the DI method, and changes the degree of orientation of the film by changing the crystallinity, molecular weight, stretching temperature, and cooling conditions of the resin.
As a result, it is preferable in that the physical properties of the film can be easily adjusted. The measuring method and the evaluation method used in the present invention are as follows. First, a method for measuring physical properties of a film will be described.

(1) Xch Here, Xch is a propylene-based heat-resistant layer calculated from the heat of fusion of the heat-resistant layer of the film derived from the propylene-based resin (hereinafter referred to as ΔHh). Crystallinity derived from resin. The measurement of the heat of fusion was performed according to JIS-K7121 using Perkin Elmer DSC-7 as a differential scanning calorimeter (DSC).
Specifically, the measurement sample was set on a DSC device of about 10 mg and held at -10 ° C for 1 minute. Then, the temperature was raised to 185 ° C at a rate of 10 ° C / minute, held for 1 minute, and the temperature was lowered at 10 ° C. /
The temperature is lowered to −10 ° C. in 1 minute, maintained for 1 minute, and the amount of heat of fusion is determined again from the melting profile at the second temperature increase when the temperature is increased to 185 ° C. at a rate of 10 ° C./minute again.

The heat of fusion obtained from the melting profile of the propylene-based resin alone is ΔHp (J / g), and the weight fraction of the propylene-based resin in the heat-resistant layer is represented by wh (wt.
%) ΔHh = ΔHp · wh / 100 where the theoretical crystal fusion heat of the propylene-based resin is H (J /
Xc was determined from the following equation as g). Xch (%) = 100 · ΔHh / H For theoretical crystal melting heat of resin, see “Chemical Handbook Application
Revised 2nd Edition ", p836-841, Maruzen Co., Ltd. (197
Referenced to 3). The theoretical heat of fusion of the polypropylene resin was 219.9 J / g, and in the case of each random copolymer, the calculation was performed using the theoretical heat of fusion of the resin having the largest monomer unit in the copolymer. The melting point was defined as the melting peak temperature that appeared at the highest temperature in the melting profile during the second heating.

(2) Xc Xc as used herein means a crystal derived from the polypropylene resin in the whole film, which is calculated from the heat of fusion derived from the polypropylene resin in the heat of fusion of the whole film (hereinafter referred to as ΔH). Degree of chemical conversion. In the same manner as in Xch, when the weight fraction of the polypropylene-based resin in the whole film is w (wt%), Xc was determined from the following equation in the same manner as in Xch, where ΔH = ΔHp · w / 100. Xc (%) = 100 · ΔH / H

(3) Tear Propagation Strength In accordance with JIS-K-7128, using a light load tear strength tester manufactured by Toyo Seiki Co., Ltd., the film was measured in each of the longitudinal direction and the lateral direction of the film. g). Note that the tear strength is usually measured in a measurement range such that the scale is in the range of 20 to 60. In the present invention, the measurement range is set to 100 g in a region where the tear propagation strength is 80 g or less in order to keep the tearing speed together. did. 80-180g
In the region, the measurement range was 200 g. In the table, the tear propagation strength was simply referred to as tear strength, and represented by (longitudinal tear propagation strength) / (lateral tear propagation strength). Next, evaluation items at the time of film formation will be described.

(4) Heat Shrinkage A multilayer film sample of 100 mm square was cut out, and
The film was placed in a hot-air circulating thermostat set at a temperature of ° C. for 30 minutes while freely shrinking, and then taken out, and the shrinkage ratio in the longitudinal and transverse directions of the film was determined. Hot air temperature is 10
Two levels of 0 ° C and 120 ° C were set.

(5) Elongation at break A sample film was cut into a length of 100 mm and a width of 10 mm in each of the machine direction (MD) and the transverse direction (TD), and was subjected to a tensile tester set at 50 mm between chucks at 23 ° C.
Pulling at a speed of 200 mm / min under the condition of 50% RH,
The amount of deformation at break was divided by the original length and expressed as a percentage.

(6) Stretching Start Temperature When there is a temperature gradient in the stretching zone, the raw surface temperature at the stretching start point is defined as the stretching start temperature. In the examples of the present invention, the film surface temperature at the neck portion of the bubble in the stretching zone (the stretching start point in the transverse direction) was measured with an infrared radiation non-contact thermometer, and this was taken as the stretching start temperature (° C.). . The emissivity was 0.90.

(7) Film-forming properties-Evaluation method Evaluation is made such that bubbles can be easily formed without generating blisters or the like when bubbles are formed by injecting air, and the formed bubbles are stable without shaking the neck. Was visually evaluated.・ Evaluation criteria Evaluation scale Symbol Remarks The bubble is very stable. ◎ Particularly preferable because stable film formation is possible. ○ The level bubble at which normal production takes place is unstable. △ Level at which marginal film formation is possible It is difficult to form bubbles. × Next, a method for measuring the suitability for packaging will be described.

(8) Torn Resistance-Evaluation Method 200 g using a 400 mm wide film using a Wmini-zero 1 manufactured by Ishida as a packaging machine.
Chuo Kagaku's foam tray with clay (SK-20)
F: When 100 pieces of 195 × 155 × 37 (mm) were packaged, the torn film pieces were collected and weighed (g, 2 significant figures). The packing conditions were adjusted by using a polyolefin film to adjust the tension: front 3, rear 1, left and right 7, and length 5. In the table, "dust" is indicated.・ Evaluation criteria Evaluation scale Symbol Remarks Weight = 0.0 ◎ Particularly preferred 0.0 <Weight ≦ 1.0 ○ Practically no problem level 1.0 <Weight ≦ 2.0 △ Level 2.0 that can be used continuously <weight x no value as a product

(9) Cutability Evaluation method 300 mm with an A-18X automatic packaging machine manufactured by Fujiki Kai Co., Ltd.
330mm, 350mm, 380mm, 400mm, 4
A film having a film width of 30 mm, 450 mm, 480 mm, and 500 mm is fed out, and the maximum width W that can be cut by setting the distance (blade length) from the holder of the cutting blade to the tip of the cutting blade with two standard cutting blades to 14 mm.
(Mm) was measured.・ Evaluation criteria Evaluation scale Symbol Remarks 450 ≦ W ◎ Excellent cutability 350 ≦ W <450 ○ or higher Pass level 300 ≦ W <350 △ Minimum acceptable level W <300 × No commercial value

(10) Wrinkles Evaluation method A packaging test was performed using a straight type packaging machine STC-IIB (with a hot-air type simple shrink tunnel) manufactured by Omori Machinery Co., Ltd. A foam tray (C20F (common name: Sanma tray): 330 × 98 × 12 (mm)) manufactured by Chuo Kagaku Co. on which 200 g of clay is placed using a film having a film width of 330 mm is packaged under the conditions of 50 packs / min. The top and side surfaces were observed for wrinkles. The hot air temperature was 120 ° C.・ Evaluation criteria Evaluation scale Symbol Remarks No wrinkles ◎ Excellent heat sealability There are very small wrinkles of about 2 to 3mm ○ Above pass level There are wrinkles of about 1 to 2cm △ Practical minimum allowable level In the state where the film is slack No tension × No commercial value

(11) Heat sealing property ・ Evaluation method 30 g, 150 g and 300 g of PP tray
g of clay and wrapped it in film. In this case, at the bottom of the tray, the film was wrapped so as to have one portion, two overlapping portions, three overlapping portions, and five overlapping portions. After the bottom of the tray was brought into contact with a hot plate set at a temperature of 60 ° C. to 10 ° C. for 1 second and 2 seconds, the state of the heat seal was observed. A test piece that was completely sealed even in a portion where five sheets were overlapped and that did not make a hole in one piece was judged as acceptable. Combining the above measurement conditions resulted in 42 conditions, of which the ratio of passed conditions was taken as the pass rate (%).・ Evaluation criteria Evaluation scale Symbol Remarks Pass rate ≧ 70% ◎ Excellent heat sealability 70%> Pass rate ≧ 55% ○ Above pass level 55% ＞ Pass rate ≧ 40% △ Practical minimum allowable level 40% ＞ Pass rate × No commercial value Next, a method for measuring practical suitability after packaging will be described.

(12) Glossiness ・ Evaluation method A 60-degree specular gloss (GL) was measured in accordance with JIS-K7105.
OSS,%) was measured. When the gloss of the film was anisotropic, the lowest value of GLOSS was evaluated.・ Evaluation criteria Evaluation scale Symbol Remarks 140 ≦ GLOSS ◎ Excellent gloss 130 ≦ GLOSS <140 ○ Normally used level 120 ≦ GLOSS <130 △ Level at which film gloss is anxious GLOSS <120 × Not suitable for practical use

[0074]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. First, the resins used in this example and comparative examples are shown below. Table 1 summarizes the propylene resins used as the heat-resistant resin. PB: butene-1 · ethylene copolymer [MI = 4.0
g / 10 minutes, melting point 98 ° C (Tuffmer BL3 manufactured by Mitsui Chemicals, Inc.)
450)] EVA1: Ethylene-vinyl acetate copolymer [vinyl acetate content = 15% by weight, MI = 6 g / 10 minutes, melting point 92]
C, crystallization temperature 73 ° C.] and diglycerin laurate (Rikemar L71D manufactured by Riken Vitamin Co.) and monoglycerin oleate (Rikemar O manufactured by Riken Vitamin Co.) as antifogging agents.
L100) at a composition ratio of 1: 2 to 2% by weight.
Added.

VL1: Ethylene octene-1 copolymer [octene-1 content: 12% by weight, density 0.902 g
/ Cm ³ , MI = 3.3 g / 10 min, melting point = 99 ° C. (PL1850 manufactured by Dow Chemical Co.)] and diglycerin laurate (Likemar L71 manufactured by Riken Vitamin Co.) as an antifogging agent.
1.6% by weight of a mixture of D) and monoglycerin oleate (Rikemar OL100 manufactured by Riken Vitamin Co.) at a composition ratio of 1: 2. VL2: ethylene-octene-1 copolymer [octene-1 content: 24% by weight, density 0.87 g / cm ³ , MI
= 1.0 g / 10 min, melting point = 61 ° C., crystallization temperature 42 ° C.
(EG8100 manufactured by Dow Chemical Company)] Diglycerin laurate (Rikemar L7 manufactured by Riken Vitamin Co., Ltd.) as an anti-fog agent
1D) and monoglycerin oleate (Rikemar OL100 manufactured by Riken Vitamin Co., Ltd.) mixed at a composition ratio of 1: 2, and 1.6% by weight was added.

[0076]

Embodiment 1 EVA as S layer (first and fifth layers)
1 as an H layer (third layer) of 25% by weight of TPO5 and P
B was blended at 75% by weight, VL1 was used as an I layer (second and fourth layers), and S / I / H / I / S
(Thickness ratio = 10% / 25% / 30% / 25% / 10%)
Circular multilayer die (lip diameter: 200)
mm, lip opening 1 mm) and extruded into a tube shape (extrusion rate 15 kg / hour). The extruded laminate was cooled with 20 ° C. cold water (film surface temperature: 30 ° C.) and folded to obtain a 140 μm thick raw material. At this time, 35
An 8% aqueous solution of sodium oleate at 0 ° C. was applied to the inner surface of the tubular laminate by filling. Sodium oleate is also transferred to uncoated surfaces in roll form. At this time, the coating amount of sodium oleate was 0.005% by weight based on the total weight of the film. Next, the folded web is sent to a stretching machine, air is injected into the web, the web surface temperature at the stretching start point is heated to 125 ° C., and the web is stretched in the longitudinal direction (TUR). 3.8 times, horizontal direction (B
UR) is stretched by a factor of 3.3 and folded by a roll type deflator while cooling with air at 20 ° C., and the speed ratio of the deflator to the main pinch roll is 0.9.
No. 9 take-up roll. The film surface temperature at the end point of stretching was 40 ° C, and the film surface temperature when wound up by a take-up roll was 25 ° C. The film thickness is 11μ
m.

The physical properties of the obtained film were measured and evaluated according to the measuring methods and evaluation methods described in the text.
Table 3 shows the results. The resulting film was packaged in 100 packs, and the amount of generated debris was within an allowable range of less than 1 g, and the cut surface was also beautiful. Further, there is no film wrinkle after packaging, the heat sealing property is good, and the appearance such as glossiness is excellent. When the physical properties of this film are shown in the machine direction / lateral direction, the heat shrinkage at 100 ° C. is 45/30.
%, The heat shrinkage at 120 ° C. was 65/55%, and the elongation at break was 550/600%.

[0078]

Comparative Example 1 Next, Experiment No. 2 for all extruders
Diglycerin laurate (Likemar L71D manufactured by Riken Vitamin Co.) and monoglycerin oleate (Likemar OL100 manufactured by Riken Vitamin Co.) were used as antifogging agents in PO5:
Experiment No. 2 except that only a mixture of 2% by weight and a mixture at a composition ratio of 2 were added. As in the case of 1, the thickness is 11 μm
Was evaluated by obtaining a single-layer film having only the H layer.

Further, in Experiment No. As No. 3, a mixture of TPO5 mixed with diglycerin laurate (Rikemar L71D manufactured by Riken Vitamin Co.) and monoglycerin oleate (Rikemar OL100 manufactured by Riken Vitamin Co.) as anti-fogging agent in all extruders at a composition ratio of 1: 2 was used. Experiment No. 1 was added only by weight% addition. Using the same die as in Example 1, with the same extrusion rate, inject air while pulling it upwards and inject air at 30 ° C from the air ring installed outside the bubble.
15m / min taking-off speed while blowing air, BUR
= 3.3, direct inflation molding was performed, and a single-layer film having only an H layer having a thickness of 11 μm was obtained and evaluated.

Comparative Example 1 Experiment No. 2 and Experiment N
o. Table 3 shows the evaluation results of the film No. 3. Experiment No.
The tear propagation strength of the film No. 2 was 5/3 g in the longitudinal direction / horizontal direction. When the operation of packing 100 packs using this film was performed, 5 g of debris was generated. The machine stopped 5 times during packaging. In addition, the number of items to be repackaged due to film breakage is 1
Eight occurred. In addition, heat sealability and glossiness were significantly poor. When the physical properties of this film are shown in the machine direction / lateral direction, the heat shrinkage at 100 ° C. is 40/30%, 120
The heat shrinkage at 60 ° C. is 60/55% and the elongation at break is 180.
/ 280%.

Further, in Experiment No. Film No. 3 had a large tear propagation strength of 40/100 g in the longitudinal / transverse directions, but generated less than 1 g of debris. In addition, the cut surface was not clean, and there was some difficulty in the cutability. Moreover, the film wrinkles after packaging remained considerably, and the film tension was insufficient. Regarding the glossiness, Experiment No. It was worse than two. The physical properties of this film can be expressed as 1
The heat shrinkage at 00 ° C. is 20/3%, the heat shrinkage at 120 ° C. is 25/5%, and the elongation at break is 370/480%.
Met.

[0082]

Example 2, Comparative Example 2 4 to Experiment No. 4 8
(Examples above) and Experiment Nos. 9, Experiment No. Experiment No. 10 (Comparative Example) Experiment No. 1 was conducted except that the resin composition of the H layer of No. 1 was changed as shown in Table 4. The same experiment as 1 was repeated. In the above Experiment No. 4 to Experiment No. 4 Table 5 shows the evaluation results of the 10 films. Experiment No. 2 of Example 2 8
In the case of packaging with the film of No. 1, the amount of generated debris was 0.0 g even after packaging 100 packs. The film-forming stability was at an acceptable lower limit.

Experiment No. of Comparative Example 2 Film No. 10 lacked resin orientation tension, and it was difficult to obtain a stretched film. Experiment No. 2 of Example 2 In the case of packaging with the film of No. 5, the amount of waste generated is 1.
The weight was 8 g, and the generation of debris was slightly anxious, but was at a level that could be used continuously, and the cut surface was also beautiful. Comparative Example 2
Experiment No. The film No. 9 produced 3 g of debris when the packaging operation of 100 packs was performed. In addition, the machine stopped four times during packaging, which was in a range where continuous use was impossible. Further, 15 packages to be repacked due to the tearing of the film occurred.

[0084]

Example 3, Comparative Example 3 11, Experiment No. 1
2 (Examples) and Experiment Nos. 13, Experiment No. 14
(Comparative Examples), as Experiment Nos. Experiment No. 1 except that the layer constitution of Example 1 and the resin constitution of the H layer were changed as shown in Table 6. 1
The same experiment was repeated. In the above Experiment No. 11 to Experiment No. Table 7 shows the evaluation results of the 14 films. Experiment 3 of Example 3 When wrapping was performed with the film No. 11, the amount of generated debris was 0.0 g even after packing 100 packs. The film-forming stability was at an acceptable lower limit.

Experiment No. 3 of Comparative Example 3 In the case of the film No. 13, the orientation tension of the resin was insufficient, and it was difficult to obtain a stretched film. On the other hand, in Experiment No. 3 of Example 3, In No. 12, the tear propagation strength was 15/10 g. Experiment 3 of Example 3 12
When the film is wrapped in a film, the amount of waste generated is 1.8 g even after packaging 100 packs. there were. Experiment No. of Comparative Example 3 When the same packaging operation was performed for the film No. 14, 3 g of debris was generated. In addition, the machine stopped during packaging four times, which was in a range where continuous use was impossible, and fifteen to-be-packaged products that had to be repacked due to film breakage occurred.

[0086]

Example 4, Comparative Example 4 15-Experiment No. 1
9 (the above examples) and Experiment Nos. Experiment No. 20 (Comparative Example) Experiment No. 1 was conducted except that the layer constitution and the resin constitution of Table 1 were changed as shown in Table 8. The same experiment as 1 was repeated. However, Experiment No. As for Experiment No. 18, experiment No. 18 was performed except that air at 15 ° C. was blown from an air ring installed outside the bubble. Performed similarly to 3. In the above Experiment No. 15-Experiment No. Table 11 shows the evaluation results of the No. 20 films.

Experiment No. of Comparative Example 4 When a packaging operation of 100 packs was performed using 20 films, 3 g of debris was generated. Also, the machine stops during packaging four times,
It was in a range where continuous use was impossible. Further, 15 packages to be repacked due to the tearing of the film occurred. In addition, streaks that seemed to be poor dispersion of PP were observed in the film, and the appearance was problematic.

Further, in Experiment No. 4 of Example 4, 15-Experiment N
o. The film of No. 18 uses recycled resin for every layer.
Wt.% H layer, and Numeral 19 is assumed to be added to the I layer. Experiment No. The fact that the tear propagation strength was reduced in 19 suggests that the ethylene-octene-1 copolymer used for layer I had an effect on improving the tear propagation strength.
Note that the experiment No. When the physical properties of the film No. 15 are shown in the longitudinal direction / horizontal direction, the heat shrinkage at 100 ° C. is 50/40%,
The heat shrinkage at 120 ° C. was 65/60%, and the elongation at break was 650/680%.

[0089]

Example 5, Comparative Example 5 21, Experiment No. 2
2 (Examples) and Experiment Nos. Experiment No. 23 (Comparative Example) The resin composition of the H layer of Sample No. 1 was changed as shown in Table 10, and the manufacturing method was changed to that of Experiment No. 1. Other than experiment No. 18 were performed. The same experiment as 18 was repeated. In the above Experiment No.
21 to Experiment No. Table 11 shows the evaluation results of the 23 films.

Experiment No. 22 is MFR = 12 g / 10
MFR =
Experiment No. 1.5 of a polypropylene-based resin of 1.5 g / 10 min.
The film-forming stability was inferior to that of No. 21 but was within an acceptable range. In addition, the cut property was slightly deteriorated. On the other hand, Experiment No. 23 was a polypropylene-based resin having an MFR of 30 g / 10 min. However, film formation by direct inflation was not possible.

[0091]

Embodiment 6 Experiment No. 24, Experiment No. As 27,
Experiment No. Experiment No. 1 was conducted except that the resin composition of Sample No. 1 was changed as shown in Table 12. The same experiment as 1 was repeated. Experiment N
o. 25, Experiment No. Experiment No. 26 The resin composition of the H layer of No. 1 was changed as shown in Table 12, and the manufacturing method was changed to experiment N
o. Other than Experiment No. 18, Experiment No. The same experiment as 1 was repeated.

In the above Experiment No. 24 to Experiment No. Table 13 shows the evaluation results of the No. 27 films. Experiment No. Reference numeral 24 denotes an I layer using an ultra-low density ethylene elastomer. Experiment No. In Experiment No. 25, the resin to be blended with the polypropylene resin in the H layer was formed from a polybutene-1 resin by a low-density ethylene resin to form a film by the DI method.
Numeral 26 is an ultralow density ethylene elastomer. Experiment No. 27 is Experiment No. 27. 26 was formed by the DB method.

Experiment No. 24 is Experiment No. 24. Although the tear propagation strength is slightly inferior to that of No. 7, almost the same performance can be expressed.
Due to the elastomer component of the I-layer, the indentation recovery was slightly improved. Experiment No. In No. 25, the glossiness was deteriorated because the polybutene-1 resin was changed to a low-density ethylene resin. Experiment N using ultra-low density ethylene elastomer
o. Experiment No. 26 is Experiment No. 26. The gloss was slightly improved from 25. This is considered to be due to the fact that the ultra-low density ethylene-based resin has a lower degree of crystallization than the low-density ethylene-based resin and a lower crystallization rate. When this was formed into a film by the DB method, the glossiness was further improved. This seems to be due to the quenching effect during stretching.

[0094]

[Table 1]

[0095]

[Table 2]

[0096]

[Table 3]

[0097]

[Table 4]

[0098]

[Table 5]

[0099]

[Table 6]

[0100]

[Table 7]

[0101]

[Table 8]

[0102]

[Table 9]

[0103]

[Table 10]

[0104]

[Table 11]

[0105]

[Table 12]

[0106]

[Table 13]

[0107]

According to the present invention having the above-described structure,
While maintaining or further improving the flexibility characteristic of conventional films, the film has improved cutability and tear resistance during film stretching, that is, it is excellent in suppressing the generation of chips from the film, and has excellent heat shrinkage and heat sealing properties. A film excellent in stretchability and optical properties can be obtained.

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Claims (5)

[Claims] 1. A polypropylene resin, wherein the polypropylene resin is a propylene homopolymer or a propylene / α-olefin (2 or 4 to 12 carbon atoms) random copolymer and satisfies the following formulas (1) and (2): A heat-resistant layer that satisfies the following formula (3), and further includes a polyolefin resin multilayer stretched film that satisfies the following formula (4). 0.5 g / 10 min ≦ MFR ≦ 20 g / 10 min (1) Extraction amount of boiling n-heptane = 20 to 90% by weight (2) 3% ≦ Xch ≦ 20% (3) (However, Xch is a suggestive scan described later) Of the crystallinity measured by the calorimetric method (DSC), the crystallinity based on the polypropylene resin in the layer containing the largest amount of the polypropylene resin. 1% ≦ Xc ≦ 10% (4) (where Xc Is the crystallinity based on the polypropylene-based resin among the crystallinity of the entire film measured by the suggestive scanning calorimetry (DSC) described later.) 2. The heat-resistant layer is made of a polypropylene resin.
The polyolefin resin multilayer stretched film according to claim 1, comprising 0 to 90% by weight and 90 to 10% by weight of the polyethylene resin and / or the polybutene-1 resin. 3. The ¹³ C-NM of the polypropylene resin
The polyolefin resin multilayer stretched film according to claim 1 or 2, wherein the isotactic pentad fraction (fmmmm) determined by R is 10 to 75 mol%. 4. 120 ° C. in the longitudinal and transverse directions of the film
The multi-layer stretched polyolefin-based resin film according to any one of claims 1 to 3, wherein the heat shrinkage in the above is 20% or more. 5. The film has an elongation at break of 200% in the machine direction.
The multilayer stretched film of polyolefin resin according to any one of claims 1 to 4, wherein the elongation at break and in the transverse direction are 300% or more.