JP3462129B2 - Polyolefin resin multilayer stretched film - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyolefin resin stretched film which is suitably used for various packaging applications such as stretch or stretch shrink packaging, and particularly stretch or stretch shrink packaging by an automatic packaging machine such as a protruding type or a straight type. The present invention relates to a polyolefin resin stretched film suitable for.

[0002]

2. Description of the Related Art Required properties for a stretch or stretch shrink wrapping film include wrapping suitability in hand wrapping and automatic machine wrapping (hereinafter simply referred to as machine wrapping), film gloss, anti-fog property, and indentation recovery property. And the display effect. Among them, the important physical properties of the film regarding packaging suitability include stretchability, that is, appropriate elongation at break and appropriate elongation stress, and heat sealing property, that is, the sealing start temperature at which practical fusion between films occurs (lower limit temperature of sealing) to the film. Wide heat seal temperature range up to the temperature where melt holes occur
It can be mentioned that it is uniformly and sufficiently sealed, and that the sealing portion on the lower surface of the tray is smooth without rising. Also,
In mechanical packaging, the cutability for cutting the film to an appropriate length with a blade and the transportability of the film by a feed belt are also included. Further, in the stretch shrink wrapping, an appropriate heat shrinkage rate for removing the slack of the film is also mentioned.

As a soft stretched polypropylene film,
For example, JP-A-8-12772 and JP-A-8-323.
Japanese Patent No. 856 discloses a polypropylene-based stretched film having low crystallinity, that is, a low isotacticity index. It is said that a film excellent in heat resistance, flexibility and transparency can be obtained. However, these conventional techniques cannot be said to sufficiently satisfy the requirements as a stretch or stretch shrink film as described below.

When the above-mentioned conventional technique is applied as it is, flexibility is certainly exhibited, but the tear propagation strength is not satisfied particularly in a film having a thickness of about 15 μm or less. Furthermore, no suggestion has been made regarding heat shrinkability.Easy removal of wrinkles on the side of the tray during heat sealing in stretch packaging, smoothing of the seal area, and shrink shrink wrapping of the film heat shrink the top surface of the tray. No ingenuity is found in removing wrinkles.

Further, there is no suggestion of taking a multi-layered structure, and the heat resistance described here is only about the high temperature at which a melt hole occurs,
In the heat-sealing property of the stretch film, the width of the temperature range from the lower limit of the heat-sealing temperature to the temperature at which the film has melt holes is insufficient. In addition, compared to when there is no polypropylene resin layer in the inner layer
Deterioration of the optical properties becomes serious when another resin is mixed for imparting the tear propagation strength.

Here, an example of the packaging process of the push-up packaging machine will be described. (A) Both ends of the film are sandwiched between film guide belts, and the film is fed out from the film roll in the longitudinal direction (hereinafter, referred to as MD). (A) After that, when the film length reaches a certain length, a perforation is made in the direction perpendicular to the feeding direction of the film (hereinafter referred to as TD) by making the cutting blade push up the film, and the film is pulled to MD. As a result, the perforations are propagated to the TD and cut.

(C) Further, the belt conveys the film to the portion for pushing up the object to be packaged. (D) The film to be packed (tray) is pushed up against the film to stretch the film to remove wrinkles on the top surface of the tray, and the film is folded under the tray. (E) Finally, the tray is placed on the hot plate. By pressing the bottom surface of the, heat sealing is performed and the packaging process is completed.

(F) In the case of 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 weak, a notch is formed in the MD of the film 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 serves as a starting point, the notch propagates, the film is torn and film scraps are generated, and the scrap remains on the belt.

On the other hand, if the tear propagation strength of the film is too strong, no perforation may occur in the step (a),
Even if it enters, the film may be conveyed without being completely propagated in the TD without being completely cut. Although it depends greatly on the type of packaging machine, the shape of the object to be packaged and the packaging conditions, the tear propagation strength of the film that achieves both control of the film tears and cutability is 10 to 200 g in both the longitudinal and transverse directions. It is preferably 20 to 150 g, and most preferably 30 to 100 g. Tear propagation strength is 1
If it is less than 0 g, the amount of scraps increases, while if the tear propagation strength exceeds 200 g, the cut property tends to be poor, and both are at a level that hinders packaging. If the heat shrinkage rate is small, the heat shrinkage of the heat seal portion and its peripheral portion is insufficient due to the heat at the time of heat sealing in the step (e), and the tray feels as if the lower part swells. Further, in the step (f), the slack of the film cannot be sufficiently removed, and wrinkles remain.

[0010]

DISCLOSURE OF THE INVENTION The present invention is to provide a film which is excellent in stretch wrapping and stretch shrink wrapping, particularly stretch wrapping property by a wrapping machine. More specifically, it is characterized by the characteristics of conventional films. With a certain level of flexibility maintained or further improved, the film cuttability and tear resistance during film stretching are improved, that is, excellent control of the generation of chipping scraps, and also in heat shrinkability, heat sealability, and optical properties. To provide an excellent film.

[0011]

[Means for Solving the Problems] That is, the inner layer is composed of a propylene homopolymer or a propylene / α-olefin (having 2 or 4 to 12 carbon atoms) random copolymer, and has the following formulas (1) and (2): Satisfying, containing a polypropylene resin, the inner layer contains 10 to 90% by weight of the polypropylene resin, and an ethylene content of 2 to 10 mo.
1% butene-1 ethylene copolymer 90 to 10% by weight
Consists of the highest amount of polypropylene resin,
Satisfies the following formula (3), viewed contains a heat-resistant layer, the multilayer film
As the tear propagation strength is 10 to 200 g, the following (4)
A polyolefin resin multilayer stretched film, which satisfies the formula . 0.5 g / 10 min ≤ MFR ≤ 20 g / 10 min (1) Boiling n-heptane extraction amount = 20 to 90% by weight (2) 3% ≤ Xch ≤ 20% (3) (However, Xch is a differential scan described later. Among the crystallinities measured by the calorimetric method (DSC), the crystallinity based on the polypropylene resin in the heat resistant layer is 1% ≦ Xc ≦ 10% (4) (where Xc is Among the crystallinity of the whole film measured by the differential scanning calorimetry (DSC) described later , the
Crystallinity based on all polypropylene resins included . ) Hereinafter, the present invention will be described in detail.

Generally, in a stretched film, a suitable orientation is formed in the film by a process of stretching, 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 crystallinity of the polypropylene resin which is a high melting point resin (heat resistant resin) with respect to this orientation, as a result of diligent examination of the relationship with the stretching, the result is It has been found that there is a range in which both suppression and cutability are compatible with each other, and further, the heat shrinkage rate, the heat sealability and the optical characteristics are excellent. Particularly, a layer containing the most polypropylene-based resin in a predetermined range or more among the layers containing the polypropylene-based resin (referred to as a heat-resistant layer or an H layer).
Has a great influence on the 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 is made of resin,
The tear propagation strength, which is an index for suppressing the generation of chips and cutting properties, is 20/15 g in the vertical / horizontal direction,
Even if it was packed in 100 packs, 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 are no wrinkles of the film after packaging, the heat sealability is good, and the appearance such as glossiness is excellent. When the physical properties of this film are shown in the longitudinal / transverse directions, the heat shrinkage ratio at 100 ° C. is 45/30%, 1
Heat shrinkage at 20 ° C is 65/55%, elongation at break is 5
It was 50/600%.

On the other hand, the conventional film (Experiment No. 2 of Comparative Example 1) is the single monolayer film of TPO5. The tear propagation strength is 5 in vertical / horizontal directions.
It was / 3 g, and when the same packaging operation was performed, 5 g of waste was generated. The machine also stopped 5 times during packaging. In addition, there were 18 items to be packaged that had to be repacked due to film breakage. In addition, the heat-sealing property and glossiness were significantly poor. When the physical properties of this film are shown in the lengthwise direction / widthwise direction, the heat shrinkage ratio at 100 ° C.
The heat shrinkage at 30% and 120 ° C was 60/55%, and the elongation at break was 180/280%.

Furthermore, a conventional film (Experiment N of Comparative Example 1)
o. 3) is a single monolayer film of TPO5 obtained by direct inflation. The tear propagation strength is as large as 40 / 100g in the vertical / horizontal direction, but the amount of scrap is 1
The occurrence was less than g. In addition, the cut surface was not beautiful, and there was some difficulty in cutting. In addition, film wrinkles remained considerably after packaging, and the film tension was insufficient. Regarding the glossiness, Experiment No. It was worse than two. The physical properties of this film are 10 in terms of the lengthwise and widthwise directions.
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 packaging film as compared with the film using a conventional polypropylene resin single layer as a single layer. Below, the film of the present invention is a polypropylene-based resin MFR (JIS
According to K7210, the temperature is 230 ° C and the load is 2.
It will be explained that the condition (16 Kg) is required to be 0.5 to 15 g / 10 minutes.

Experimental No. 1 given as an example of the film of the present invention. No. 22 is a polypropylene resin with MFR = 12 g / 10 min. Another film example of the present invention, an experiment No. using a polypropylene resin having MFR = 1.5 g / 10 min. The film-forming stability was inferior to that of No. 21, but it was within the allowable range. The cuttability also deteriorated slightly, but it was within the allowable range. On the other hand, Experiment No. which is a comparative example. No. 23 was a polypropylene resin having MFR = 30 g / 10 min, but film formation by direct inflation was impossible.

From the above, the MFR of the heat resistant resin is 0.5.
It can be seen that ~ 15 g / 10 min is required. That is, when the MFR is less than 0.5 g / 10 min, the obtained stretched film is overly oriented, and as a result, the film has a low tear propagation strength and a small elongation at break, which is inferior in stretchability. There is a tendency. When the MFR is larger than 20 g / 10 minutes, it becomes difficult to form a film by direct inflation. In addition, the gloss deteriorates, and in particular, since the polypropylene resin disperses linearly in the MD of the film, the TD gloss of the film tends to deteriorate.

MFR is generally 0.8 to 15 g / 10.
Min, preferably 1.2-10, most preferably 2.3-
It is 8.5 g / 10 minutes. Next, the present invention is superior to the prior art in suppressing the generation of scraps of the film at the time of packaging, when the film of the present invention and the conventional film are mechanically packaged by a rush type packaging machine. The difference will be described in detail. The film of the present invention has a crystallinity of 3% ≦ Xch ≦ 20, where Xch is the crystallinity based on the polypropylene resin in the layer containing the most polypropylene resin, out of the crystallinities measured by the DSC method. The necessity of containing a heat-resistant layer of 10% will be described using Examples and Comparative Examples.

7.7% of Xch in the film of the present invention
(Corresponding to Example 1 and Experiment No. 1) had a tear propagation strength of 20/15 g, whereas Xch = 3.
In the case of 8% (corresponding to Experiment No. 8 of Example 2), the tear propagation strength was 35/28 g. When the film of the present invention (Experiment No. 8 of Example 2) was packaged, the amount of generated scraps was 0.0 g even after 100 packs were packaged. The film-forming stability was at an allowable lower limit.

Further, the comparative control film having Xch = 2.8% (corresponding to experiment No. 10 of Comparative Example 2) lacked the orientation tension of the resin, 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 packaged, the amount of scraps generated was 1.8 g even after 100 packs were packed, and the generation of scraps was a little worrisome, but continued use The cut surface was clean and the cut surface was beautiful.

Further, the comparative control film having Xch = 30.6% (corresponding to the experiment No. 9 of Comparative Example 2) had a tear propagation strength of 8/7 g, and when the same packaging operation was performed, 3 g of scraps were produced. Occurred. In addition, the machine stopped four times during packaging, which was a range where continuous use was impossible. Furthermore, there is no need for repacking due to film breakage.
Five occurred.

From the above, it is understood 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 less than 3%, the orientation tension of the resin is hardly applied, and it becomes difficult to take or draw the original fabric. In addition, the cuttability of the machine tends to deteriorate. When Xch is larger than 20%, the obtained stretched film is over-oriented, and as a result, the film has low tear propagation strength. Further, the film tends to have a small elongation at break and poor stretchability.

Xch is generally 4 to 18%, preferably 5 to 16%, and most preferably 7 to 10%.
Next, the crystallinity of the entire film of the film of the present invention
Among them, when the crystallinity based on the resistance heat the resin is defined as Xc,
The fact that 1% ≦ Xc ≦ 10% needs to be satisfied at the same time will be described using examples and comparative examples. Among the film examples of the present invention, those having Xc of 2.3% (Example 1, Experiment N)
o. (Corresponding to Experiment No. 11 of Example 3), the tear propagation strength was 35/35. It was / 30g.

This film of the present invention (Experiment N of Example 3)
o. In the case of packaging in 11), the amount of waste generated was 0.0 g even after 100 packages were packaged. The film-forming stability was at an allowable lower limit. Further, the comparative control film with Xc = 0.9% (corresponding to Experiment No. 13 of Comparative Example 3) lacked the 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 of Example 3) had a tear propagation strength of 15/10 g.

This film of the present invention (Experiment N of Example 3)
o. In the case of packaging in 12), the amount of scraps generated was 1.8 g even if 100 packs were packed, and although the generation of scraps is a little worrisome, it is at a level where continuous use is possible and the cut surface is also clean. there were. Further, the comparative control film with Xc = 10.5% (corresponding to Experiment No. 14 of Comparative Example 3) had a tear propagation strength of 6/5 g, and when the same packaging operation was performed, 3 g of scrap was generated. Further, the machine stopped 4 times during the packaging, which was in the range where continuous use was impossible, and 15 items to be packaged which had to be repacked due to film breakage occurred.

The above description or we X c is found to be required to be 1-10%. That is, when Xc is less than 1%, the alignment tension of the resin is almost not applied,
It becomes difficult to pick up or stretch the raw fabric. In addition, the cuttability of the machine tends to deteriorate. When Xc is more than 10%, the obtained stretched film is excessively oriented, and as a result, the film has a low tear propagation strength and a low elongation at break, which is inferior in stretchability. X
c is generally 1 to 6%, preferably 1.3 to 4.5%,
Most preferably, it is 2.0 to 4.0%.

Next, the film of the present invention is required to have a boiling n-heptane extraction amount of 20 to 90% by weight, which correlates with the isotacticity of the polypropylene resin, by using Examples and Comparative Examples. explain. Xch = 12.
2%, Xc = 3.2%, boiling n-heptane extraction amount =
An example of the film of the present invention using TPO1 of 62 wt% and fmmmm = 40 mol% (Experiment No. 19 of Example 4)
Corresponding to 1) had a tear propagation strength of 20/15 g.

Further, the above-mentioned Xch = 18.8%, Xc =
5.6%, the film of the present invention using TPO1 (Experiment No. 5 of Example 2) also has a tear propagation strength of 15/1.
Although the amount is 0 g, when packaging is performed with these films, the amount of waste generated is 1 to 2 g even if 100 packs are packed, and the generation of waste is a little worrisome, but it is a level at which continuous use is possible, The cut surface was also beautiful. In contrast, Xch
= 11.6%, Xc = 4.6%, boiling n-heptane extraction amount = 9 wt%, fmmmm = 91 mol% of the comparative control film using PP (corresponding to Experiment No. 20 of Comparative Example 4). The tear propagation strength was 9/8 g, and when the same packaging operation was performed, 3 g of waste was generated. In addition, the machine stopped four times during packaging, which was a range where continuous use was impossible. Further, 15 items to be packaged which required repacking due to film breakage were generated. In addition, streaks that seemed to be poor PP dispersion were found in the film, and there was a problem in appearance.

From the above, it can be seen 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 boiling heptane extraction amount 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. Further, the film tends to have a small elongation at break and poor stretchability. Also, when blended with other resins, the compatibility becomes poor, streaks occur in the film, and the appearance of the film deteriorates, such as deterioration of gloss.
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 almost not applied, and it becomes difficult to take or draw the raw fabric. In addition, the cuttability of the machine also deteriorates.

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 scraps in the film during packaging, and is also compatible with the cut property. When the film of the present invention is used as a stretch film, it is not always necessary to positively express the heat shrinkage effect of the film, but 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 ratio of 5% or more in at least one direction can be obtained. Furthermore, when using it as a stretch / shrink film, the longitudinal direction of the film at 120 ° C
It is generally 20% or more in the lateral direction. Further, such a film becomes smooth without stretch of the bottom seal portion even during stretch packaging.

The polypropylene resin used in the present invention is specifically a propylene homopolymer, a propylene / ethylene / random copolymer, a propylene / ethylene / α-olefin (having 4 to 12 carbon atoms) / random copolymer. , Propylene / α-olefin (having 4 to 12 carbon atoms) / random copolymer. 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) as described above. The isotacticity of (Note) is within a specific range, and the boiling n-heptane extraction amount of the polypropylene resin is mentioned as an index of the iPP component amount. 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 like the isotactic PP component when stretched. It is easy to adjust the orientation to achieve the purpose. Further, 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, like the high molecular weight isotactic PP component when stretched. It tends not to be strongly oriented.

A preferred specific example of the polypropylene resin is a transparent type of Idemitsu TPO manufactured by Idemitsu Petrochemical Co., Ltd. or Huntsman, which has a boiling n-heptane extraction amount of iPP called "reactor TPO" of 20 to 90% by weight. Those belonging to HPP such as WL100 series of FPO manufactured by the same company and those belonging to RPP such as WL200 series of FPO manufactured by the same company are mentioned. These are different from the propylene / ethylene block copolymer (hereinafter referred to as BPP) type reactor TPO which has a clear sea-island structure of EPC and iPP, and is different from HPP or RP in comparison with this BPP type TPO.
The P-type reactor TPO has excellent compatibility when blended with other resins, and as a result, has excellent optical properties and tear propagation strength.

The boiling n-heptane extraction amount is "new edition".
Polymer Analysis Handbook ", p613-614, Kinokuniya Shoten Co., Ltd. (1995). Soxhlet extractor was used to put about 3 mg of powdery or film sample into a cylindrical filter paper, and about 100 ml. Extraction for 8 hours using n-heptane of
The ratio of the extracted amount was calculated. Among the polypropylene-based resins in which the boiling n-heptane extraction amount is in a specific range, a more preferable polypropylene-based resin is an HPP having an isotactic pentad fraction (fmmmm) of 10 to 75 mol%.
The system sieve is an RPP polypropylene resin. As such a resin, for example, a solid catalyst containing magnesium, tetravalent titanium, halogen, and an aromatic dicarboxylic acid diester disclosed in Japanese Patent Publication No. 7-103173, an organic aluminum compound, an alkoxy group-containing aromatic compound A propylene polymer obtained by one-step polymerization using a compound as a catalyst, or a magnesium halide-supporting base material co-milled without adding an electron donor at a specific ratio shown in Japanese Patent No. 2912483, aluminum trihalide, A propylene homopolymer obtained by one-step polymerization using a catalyst system composed of titanium tetrahalide and trialkylaluminum as a co-catalyst is mentioned. What is 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 characteristics are excellent, the amorphous component has a high molecular weight and an appropriate orientation tension, and the film-forming property becomes much excellent, and the degree of freedom in resin constitution is greatly expanded. Further, it is also advantageous for obtaining an appropriate tear propagation strength.

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

The isotactic pentad fraction is A.
Macromolecule by Zambelli et al.
es, 6, 925 (1973), the nuclear magnetic resonance spectrum ( ¹³ C-N
MR) is the isotactic fraction in pentad units in the polypropylene molecular chain. In other words, the isotactic pentad fraction is the fraction of propylene monomer units in which five propylene monomer units are continuously meso-bonded. However, regarding the attribution of the peak, Macromolecules, 8, 687 (1
975).
Specifically, the isotactic pentad unit is measured by the intensity fraction of all absorption peaks in the methyl carbon region of the ¹³ C-NMR spectrum. In RPP, the methyl carbon peak of the propylene unit adjacent to the ethylene unit overlaps with the other methyl carbon peaks in this methyl carbon region. For RPP having an ethylene unit content within about 3 mol%, the effect on the isotactic pentad fraction is small, so HP including its peak is also included.
Similar to 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 higher, preferably 150 ° C. or higher, and most preferably 154 ° C. or higher from the viewpoint of heat sealability. On the other hand, in the present invention, in order to set Xch to 3 to 20%, 10 to 90% by weight of polypropylene resin and 90 to 10% by weight of polyethylene resin and / or polybutene-1 resin are blended. 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 resin, a resin in which crystal orientation does not easily occur during stretching is used. Among them, polybutene-1 resin (hereinafter referred to as PB) is a preferable example from the viewpoint of good compatibility with polypropylene resin, slow crystallization rate, and not decreasing the transparency of the resulting film. Can be mentioned. As PB, polybutene-1 homopolymer, butene-
Examples thereof include a 1-ethylene copolymer, a butene-1 / propylene copolymer, and a butene-1 / α-olefin (having 5 to 12 carbon atoms) copolymer. Among them, butene-1
It is an ethylene copolymer or a butene-1 · propylene copolymer, and more preferably has an ethylene content of 2 to 1.
It is a 0 mol% butene-1-ethylene copolymer or a propylene content of 10-30 mol% butene-1-propylene copolymer. An example of this preferable resin is Tuffmer BL manufactured by Mitsui Chemicals, Inc. The preferred MI of PB (in accordance with JIS K7210, the temperature is 19
At 0 ° C. and a load of 2.16 Kg) is 1.5 g / 10
Min. Or more, particularly preferably 3 to 6 g / 10 min.

In order to improve the indentation recovery property 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.
The density is preferably 0.880 g / cm ³ or less, more preferably 0.865 to 0.875 g / cm ³ . In addition, a block copolymer composed of an amorphous polyolefin block and a crystalline polyolefin block may be blended in order to improve the push-in recovery property of the film. As an example, DYNARO manufactured by Japan Synthetic Rubber Co., Ltd.
N.CEBC etc. are mentioned.

Further, mineral oil, polyolefin wax or the like may be added within a range not impairing the object of the present invention. The film of the present invention has a multi-layered structure, and it is necessary to use a layer containing a heat-resistant resin (H layer) 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, the resin suitable for constituting the S layer of the film of the present invention will be described.

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

From the orientation balance of the resin due to the melt tension at the time of melt extrusion, M of the above ethylene-based copolymer is determined.
I is generally 0.5 to 20 g / 10 minutes, preferably MI is 1 to 12 g / 10 minutes, and more preferably 1.
It is 5 to 8 g / 10 minutes. Further, 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.
Of 12 or more is added to the S layer in an amount of 0.5 to 5% by weight. Specific examples include resins in which the S layer is added with 1 to 3 wt% of monoglycerin fatty acid ester and / or diglycerin fatty acid ester and / or 0.5 to 1.5 wt% of polyoxyethylene fatty acid ester. .

In the S layer, additives such as plasticizers such as mineral oil and polyolefin wax, ultraviolet absorbers, silver-based antibacterial agents, freshness-retaining agents such as hinokitiol and wasabi extract and chitosan, and lubricants such as fatty acid amides. 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. It is preferably 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 more lower than the melting point of the heat resistant resin, and most preferably 50 ° C. or more lower. By widening the melting point difference from the heat-resistant resin, the stability of heat sealing property and film forming property tends to increase.

The MI of the I layer is generally 0.5 to 15 g / 10 minutes. An antifogging agent may be added to the I layer similarly to the S layer, and generally, 0.5 to 5% by weight of the nonionic surfactant antifogging agent is added to the I layer. Specific examples thereof include monoglycerin fatty acid ester and / or diglycerin fatty acid ester added to the resin of the layer I in an amount of 1 to 3% by weight. Further, additives such as a plasticizer such as mineral oil and polyolefin wax, an ultraviolet absorber, a hinokitiol or a horseradish extract, and a freshness-keeping agent such as chitosan may be added to the I layer.

As a combination of the above layers, S / in three layers
H / S, S / H / I / S in 4th layer, S / I / H in 5th layer
/ I / S, S / H / I / H / S, S / I / H / in 7 layers
I / H / I / S, S / H / I / H / I / H / S and the like can be mentioned. The total thickness of the film is generally about 5 μm to 30 μm, and preferably 8 from the viewpoints of handleability of the film, stretchability, tear propagation strength, puncture strength and the like.
Is about 15 μm.

The thickness ratio of the S layer, H layer, and I layer is generally S
5 to 45% for each layer, 10 to 9 for H layer
0%, I layer is 0 to 80% per layer. The absolute thickness of the S layer is preferably 1 μm or more in view 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.

Recycled resin such as film trim loss can be added to the H layer and I layer. When the recycled resin is added to the H layer and the I layer, the gloss is slightly deteriorated, but it can be seen 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 that when the recycled resin is added to the H layer, and accordingly, a little amount of waste is generated. Further, the glossiness tends to be worse when added to the I layer than when added to the H layer. The cause of the poor gloss is due to minute roughness on the film surface. Polyethylene-based resins generally have poor compatibility with polypropylene-based resins, which are heat-resistant resins, and as a result, minute irregularities occur at the layer interface of the H layer or I layer, and even if the S-layer has a masking effect, the surface is It is considered that the unevenness is reflected in the above, and from that viewpoint, it is better to add the recycled resin to the innermost layer.

In order to achieve both slipperiness and anti-fog property on the film surface, a surfactant is applied to the entire surface of the film, or a predetermined width from the entire surface of the film or the end of the film (product) (for a film holding belt of a packaging machine). Silicone oil or its emulsion may be applied only to the contacting portion) (0.3 to 50 mg / m ³ per side). The physical properties of the film obtained by the constitution of the present invention are as follows. That is, when expressed in the machine direction / transverse direction of the film, the tear propagation strength is 15/10 g or more, which is excellent in suppressing the generation of scraps and has a breaking elongation of 200 / in view of stretchability.
300% or more, and in terms of appearance, the gloss is 130 /
120% or more, the heat shrinkage ratio at 120 ° C is 20 / from the viewpoint of removing film wrinkles during stretch shrink wrapping.
A preferable physical property 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 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 elongation at break is 400/400% or more, and the gloss is 145/140%.
As described above, the heat shrinkage ratio 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), and the like.
Among them, the preferred manufacturing method is the DB method. DB here
A preferred example of the method will be described in more detail, but is not limited thereto.

The resin composition is melted, extruded with a circular die, rapidly cooled and solidified with a refrigerant to form a tube-shaped original fabric, which is folded by a roll and taken up. At this time, a surfactant is added in the tube for the purpose of improving properties such as antifogging property and slipperiness.
Silicone oil or the like may be filled. If necessary, the raw material may be irradiated with an energy ray such as an electron beam to be crosslinked. Next, air is injected into the original fabric to form a tube, and the stretching start temperature of the original fabric is adjusted between the glass transition point and the melting point of the polypropylene-based resin between two pairs of differential nip rolls, and then the area magnification is 2 ~ 36 times tubular stretch, cool the film, fold it with two pairs of converging rolls, take it with a nip roll, heat it with a roll heat set device or hot air oven if necessary, and finally draw the film. A film is obtained by winding in a cooled state. Further, corona discharge treatment or the like may be performed after the heat treatment. First, the resin compositions of the respective layers are melted by separate extruders, combined and laminated with a multilayer circular die, and a multilayer film is extruded.

Next, preferred temperature conditions in the DB method in the present invention will be described. The temperatures shown below are all surface temperatures of the film. First, when the melt-extruded raw material is rapidly cooled and solidified, it is possible to cool it to a temperature not higher than the crystallization peak temperature of the polypropylene resin and the main resin other than the polypropylene resin, usually 5 to 75 ° C. And it is preferable for suppressing crystallization of the crystalline resin. Experiment No. In No. 1, the laminate was rapidly solidified by cooling to 30 ° C., which is 73 ° C. or lower which is the crystallization peak temperature of the ethylene / vinyl acetate copolymer (EVA1) and the ethylene / octene-1 copolymer (VL1).

Next, before stretching, the raw fabric 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 "melting point of polypropylene resin-20 ° C." or lower. . 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 neck portion of the bubble.
Experiment No. In No. 1, it was heated to 125 ℃, 3.8 in the vertical direction.
And stretched 3.3 times in the transverse direction.

Here, the stretching magnification for giving proper orientation is usually 2 to 36 times in area magnification. Further, if the stretching ratio is less than 2 times, the orientation tends to be insufficient, the orientation unevenness in which the degree of orientation varies depending on the site of the film, or the thickness unevenness of the film tends to increase. Since the raw sheet becomes thicker, it becomes difficult to control the temperature, and the unevenness in the orientation and the unevenness in the thickness of the film also tend to increase. Next, after stretching, the film is cooled to at least the crystallization temperature of the main resin other than the polypropylene resin, that is, usually 75 ° C. or lower, preferably 50 ° C. or lower, more preferably 30 ° C. or lower, and the stretching is terminated and the film is taken out. Experiment No. In No. 1, it was cooled to 40 ° C. at the end point of stretching and then folded and taken out.

When heat treatment is carried out thereafter, it is preferable that the heat treatment temperature is 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 lower, orientation relaxation and dimensional stability, which are the objectives of heat treatment, cannot be imparted, and the film may be fused unless the temperature is lower than the crystallization temperature of the main resin of the S layer. When performing the relaxation heat treatment 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 longitudinal direction and the transverse direction, respectively.
Is generally used.

Finally, the temperature at which the film is wound is below the crystallization temperature of the main resin of the S layer, that is, usually below 45 ° C, preferably below 35 ° C, more preferably 3 ° C.
It is 0 ° C or lower. Here, 45 ° C. is to prevent the films from blocking each other or stretching in the longitudinal direction during winding. Experiment No. 25 in 1
It was cooled to ℃ and wound up. When such a temperature setting, especially the reheating temperature and the stretching temperature of the original fabric are set as described above,
There are advantages that the desired physical properties of the present invention can be easily achieved, stable film formation can be performed, and the obtained film has less uneven thickness 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 the stretching bubble during stretching 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.
% 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 Method I, since the melt tension needs to be above a certain level, it is necessary that the MFR is 15 g / 10 minutes or less, more preferably 8 g / 10 minutes or less.

When the DB method and the DI method are compared, there are some points in the present invention in which the DB method is superior to the DI method. First of all, in the DB method, compared with the DI method in which bubbles are formed in a state where the resin is still melted from the die, in the DB method, the melt-extruded tubular raw material is rapidly cooled and solidified and stretched in a low temperature atmosphere. It is possible to use a resin having a smaller melt tension than the DI method in which bubbles are formed by using the method, which is advantageous.

Since the film is more oriented than the DI method, it is possible to stably produce a film with less thickness unevenness than the DI method, and it is difficult to use the DI method.
An ultrathin film having a thickness of 0 μm or less can be stably obtained. Furthermore, looking at the film obtained by the DI method, it is generally difficult to obtain a transparent film with a polypropylene resin having a melting point of 150 ° C. or higher by the air-cooled DI method, and the water-cooled DI method tends to have a large lateral magnification. It is in. The HPP or RPP having an isotactic pentad fraction (fmmmm) of 10 to 75 mol% described above can be used to obtain a relatively transparent film even by the air-cooled DI method. Experiment No. of Comparative Example 5
As is clear from the fact that No. 23 could not be formed into a film, if the MFR of the polypropylene resin is not less than 15 g / 10 min, the melt tension of the film will be insufficient and the DI method will be difficult.

According to the DI method, a film having a relatively high tear propagation strength can be obtained, but TD tends to be stronger than MD of the film, and a proper tear propagation strength region in which the generation of scraps and the cutting property are compatible with each other. Is often narrowed, and in particular, it is often found that the cutting property is poor. In addition, since the DI method has difficulty in controlling the orientation and tends to have less suitable orientation than the DB method, the heat shrinkage rate at the time of heating tends to be small, and the stretch shrink packaging film tends to be unsuitable. Such a product tends to be incomplete in removing film wrinkles from the packaged item because the shrinkage is incomplete even when the packaged item is thermally shrunk by passing through a heating tunnel or the like.

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

(1) Xch The term “Xch” as used herein means a propylene-based heat-resistant layer calculated from the amount of heat of fusion derived from the propylene-based resin in the heat of fusion of the heat-resistant layer of the film (hereinafter referred to as ΔHh). It is the crystallinity derived from the resin. The heat of fusion was measured according to JIS-K7121 using DSC-7 manufactured by Perkin Elmer Co. as a differential scanning calorimeter (DSC).
Specifically, the measurement sample was set in a DSC apparatus of about 10 mg and held at -10 ° C for 1 minute, then the temperature rising rate was raised to 185 ° C at 10 ° C / minute, held for 1 minute, and the temperature lowering rate was 10 ° C. /
The amount of heat of fusion is determined from the melting profile at the second temperature rise when the temperature is decreased to −10 ° C. in minutes, held for 1 minute, and again increased to 185 ° C. at a temperature increase rate of 10 ° C./minute.

The heat of fusion obtained from the melting profile of the propylene resin alone is ΔHp (J / g), and the weight fraction of the propylene resin in the heat resistant layer is wh (wt
%), ΔHh = ΔHp · wh / 100 where the heat of fusion of the theoretical crystal of the propylene-based resin is H (J /
Xc was calculated from the following equation as g). Xch (%) = 100 ・ ΔHh / H For the theoretical heat of crystal fusion of resin, refer to “Chemical Handbook Application”
Revised 2nd edition ", p836-841, Maruzen Co., Ltd. (197
Reference was made to 3). The theoretical heat of fusion of polypropylene resin was 219.9 J / g, and in the case of each random copolymer, the theoretical heat of fusion of the resin of the most monomer unit in the copolymer was used for calculation. The melting point was defined as the melting peak temperature that appears at the highest temperature in the melting profile during the second temperature increase.

(2) Xc Xc as used herein is a crystal derived from a polypropylene resin in the entire film, which is calculated from the heat of fusion derived from the polypropylene resin in the heat of fusion of the entire film (hereinafter referred to as ΔH). It is the degree of aging. Similarly to Xch, assuming that the weight fraction of the polypropylene resin in the entire film is w (wt%), ΔH = ΔHp · w / 100 Xch was obtained from the following equation in the same manner as Xch. Xc (%) = 100 ・ ΔH / H

(3) Tear Propagation Strength According to JIS-K-7128, a light load tear strength tester manufactured by Toyo Seiki Co., Ltd. was used to measure in each of the machine direction and the transverse direction of the film. g). Note that the tear strength is usually measured in a measuring range in which the scale is in the range of 20 to 60, but in the present invention, the measuring range is 100 g in the region where the tear propagation strength is 80 g or less in order to combine the tearing speeds. did. Also 80-180g
In the region of, the measurement range was 200 g. In the table, the tear propagation strength is simply referred to as the tear strength, and is represented by (tear propagation strength in the longitudinal direction) / (tear propagation strength in the lateral direction). Next, the evaluation items during film formation will be described.

(4) A multilayer film sample having a heat shrinkage of 100 mm square was cut out and cut into 20 pieces.
The film was placed in a hot-air circulating constant temperature bath set at a temperature in steps of ° C for 30 minutes in a freely shrinkable state, and then taken out to determine the shrinkage rates in the machine direction and the transverse direction of the film, respectively. Hot air temperature is 10
There were two levels of 0 ° C and 120 ° C.

(5) Elongation at Break The 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 the tensile tester was 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 fabric surface temperature at the stretching start point is set as the stretching start temperature. In the examples of the present invention, the film surface temperature of the neck portion of the bubble (stretching start point in the transverse direction) in the stretching zone 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 Formability / Evaluation Method In the evaluation, the bubble can be easily formed without causing blister when the bubble is formed by injecting air, and the formed bubble is stable without shaking. Whether or not it was visually evaluated.・ Evaluation criteria Evaluation scale Symbol Note Bubbles are very stable. ◎ Stable film formation is possible, which is especially preferable. The neck sways slightly. ○ The level bubble in which normal production takes place is unstable. Δ Level at which the film can be barely formed. Bubble formation is difficult. × Next, a method for measuring packaging suitability will be described.

(8) Tear resistance / evaluation method Wini-zero1 manufactured by Ishida Co., Ltd. was used as a packaging machine and a film having a film width of 400 mm was used to weigh 200 g.
Foam tray (SK-20 made by Chuo Kagaku Co.)
F: When 100 pieces of 195 × 155 × 37 (mm) were packaged, the torn film pieces were collected, and the weight (g, effective digit 2 digits) was measured. The packing conditions were using a polyolefin film to adjust the tension: front 3, rear 1, left and right 7, and the length was 5. In the table, "trash" is displayed. -Evaluation criteria Evaluation scale Symbol Remark Weight = 0.0 ◎ Particularly preferred 0.0 <Weight ≤ 1.0 ○ Level with practically no problem 1.0 <Weight ≤ 2.0 △ Sustainable level 2.0 <Weight x No value as a product

(9) Cuttability / Evaluation Method 300 mm with A-18X automatic packaging machine manufactured by Fujikikai Co., Ltd.
330mm, 350mm, 380mm, 400mm, 4
30mm, 450mm, 480mm, 500mm film width is respectively fed, the distance from the holder of the cutting blade to the tip of the cutting blade (blade length) is 14mm with two standard cutting blades, and the maximum width W that can be cut
(Mm) was measured.・ Evaluation criteria Evaluation scale Symbol Remark 450 ≦ W ◎ Excellent in cutability 350 ≦ W <450 ○ Above Pass level 300 ≦ W <350 △ Minimum allowable level W <300 × No commercial value

(10) Wrinkle / Evaluation Method A packaging test was carried out using a straight-line type packaging machine STC-IIB (with hot air type simple shrink tunnel) manufactured by Omori Machinery Co., Ltd. A foam tray made by Chuo Kagaku Co. (C20F (commonly known as San Matray): 330 x 98 x 12 (mm)) on which 200 g of clay was placed using a film having a film width of 330 mm was packed under the condition of 50 packs / minute, and the tray was packed. The presence or absence of wrinkles on the upper and side surfaces was observed. The hot air temperature was 120 ° C.・ Evaluation criteria Evaluation scale Symbol Remarks No wrinkles ◎ Excellent heat-sealing property There are small wrinkles of about 2 to 3 mm ○ Pass level above wrinkles of about 1 to 2 cm △ Practical minimum allowable level In a loose film state No tension × No commercial value

(11) Heat Sealing Property / Evaluation Method PP trays 30 g, 150 g and 300, respectively.
g of clay was placed and wrapped with a film. In this case, the bottom of the tray was wrapped so that the film had one part, a double overlapping part, a three overlapping part, and a five overlapping part. After bringing the bottom portion of the tray into contact with a hot plate which had been set at a temperature of 60 ° C. to 10 ° C. step for 1 second and 2 seconds, the state of heat sealing was observed. Even if the portion where 5 sheets were overlapped was completely sealed, and even if the portion where 1 sheet was not perforated, it was regarded as acceptable. 42 conditions were obtained by combining the above-mentioned measurement conditions, and the ratio of the passed conditions was defined 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% △ Minimum practically acceptable level 40%> Pass rate × No commercial value Next, the method for measuring the practical suitability after packaging will be described.

(12) Glossiness / Evaluation Method According to JIS-K7105, 60 degree specular gloss (GL
OSS,%) was measured. The minimum value of GLOSS was evaluated when the gloss of the film was anisotropic.・ Evaluation criteria Evaluation scale Symbol Remark 140 ≦ GLOSS ◎ Excellent gloss 130 ≦ GLOSS <140 ○ Normally used level 120 ≦ GLOSS <130 △ Gloss of film is noticeable GLOSS <120 × Not practically suitable

[0074]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be specifically described below with reference to Examples and Comparative Examples. First, the resins used in this example and comparative examples are shown below. The propylene-based resins used as the heat-resistant resin are summarized in Table 1. PB: butene-1 ethylene copolymer [MI = 4.0
g / 10 minutes, melting point 98 ° C. (Mitsui Chemicals Tuffmer BL3
450)] EVA1: ethylene / vinyl acetate copolymer [vinyl acetate content = 15% by weight, MI = 6 g / 10 min, melting point 92
℃, crystallization temperature 73 ℃] as anti-fog agents diglycerin laurate (Rikenmal L71D manufactured by Riken Vitamin) and monoglycerin oleate (Rikemar O manufactured by Riken Vitamin)
L100) mixed at a composition ratio of 1: 2 is 2% by weight.
What was 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 as an antifogging agent (Rikemar L71 manufactured by Riken Vitamin Co., Ltd.
D) and monoglycerin oleate (Rikemar OL100 manufactured by Riken Vitamin Co.) were mixed at a composition ratio of 1: 2, and 1.6% by weight was added. VL2: ethylene-octene-1 copolymer [octene-1 content: 24% by weight, density 0.87 g / cm ³ , MI
= 1.0 g / 10 minutes, melting point = 61 ° C., crystallization temperature 42 ° C.
(EG8100 manufactured by Dow Chemical Co.)] Diglycerin laurate (Rikemar L7 manufactured by Riken Vitamin Co. as an antifogging agent
1D) and monoglycerin oleate (Rikemar OL100 manufactured by Riken Vitamin Co.) were mixed at a composition ratio of 1: 2, and 1.6% by weight was added.

[0076]

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

Each physical property of the obtained film was measured and evaluated by the measuring method or evaluation method described in the text,
The results are shown in Table 3. The obtained film was packaged in 100 packs, but 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 are no wrinkles of the film after packaging, the heat sealability is good, and the appearance such as glossiness is excellent. When the physical properties of this film are shown in the longitudinal direction / horizontal direction, the heat shrinkage ratio at 100 ° C. is 45/30.
%, The heat shrinkage ratio at 120 ° C. was 65/55%, and the elongation at break was 550/600%.

[0078]

[Comparative Example 1] Next, Experiment No. T for all extruders as 2
Diglycerin laurate (Rikenmar L71D manufactured by Riken Vitamin Co.) and monoglycerin oleate (Rikemar OL100 manufactured by Riken Vitamin Co.) were used as an antifogging agent in PO5 1:
Experiment No. 2 except that only a mixture containing 2% by weight of the mixture having the composition ratio of 2 was added. 11 μm in the same manner as 1
A single-layer film having only the H layer was obtained and evaluated.

Experiment No. As 3 for all extruders, TPO5 mixed with diglycerin laurate (Rikemar L71D manufactured by Riken Vitamin Co.) and monoglycerin oleate (Rikemar OL100 manufactured by Riken Vitamin Co.) at a composition ratio of 1: 2 was used as 2 Experiment No. Using the same die as in 1 above, with the same extrusion rate, pulling this in the upward direction and injecting air, 30 ° C from the air ring installed outside the bubble
BUR with a take-up speed of 15 m / min while blowing air
= 3.3, direct inflation molding was performed to obtain a monolayer film having an H layer having a thickness of 11 μm and evaluated.

Comparative Example 1 Experiment No. 2 and experiment N
o. The evaluation results of the film No. 3 are shown in Table 3. Experiment No.
The tear propagation strength of the film of No. 2 was 5/3 g in the longitudinal direction / transverse direction, and when the operation of packaging 100 packs using this film was performed, 5 g of waste was generated. The machine also stopped 5 times during packaging. Furthermore, there is no need for repacking due to film breakage.
Eight occurred. In addition, the heat-sealing property and glossiness were significantly poor. When the physical properties of this film are shown in the longitudinal / transverse directions, the heat shrinkage ratio at 100 ° C. is 40/30%, 120
Heat shrinkage at 60 ° C is 60/55%, elongation at break is 180
/ 280%.

Experiment No. The film of No. 3 had a large tear propagation strength of 40/100 g in the machine direction / transverse direction, but generated less than 1 g of scraps. In addition, the cut surface was not beautiful, and there was some difficulty in cutting. In addition, film wrinkles remained considerably after packaging, and the film tension was insufficient. Regarding the glossiness, Experiment No. It was worse than two. The physical properties of this film are 1 in the vertical and horizontal directions.
Thermal shrinkage at 00 ° C is 20/3%, thermal shrinkage at 120 ° C is 25/5%, elongation at break is 370/480%.
Met.

[0082]

Example 2, Comparative Example 2 Experiment No. 4-Experiment No. 8
(The above examples) and Experiment No. 9, Experiment No. Experiment No. 10 (above Comparative Example). Experiment No. 1 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. The above experiment No. 4-Experiment No. Table 5 shows the evaluation results of 10 films. Experiment No. 2 of the second embodiment. 8
In the case of packaging with the film of No. 1, the amount of waste generated was 0.0 g even after packaging with 100 packs. The film-forming stability was at an allowable lower limit.

Experiment No. 2 of Comparative Example 2 The film of No. 10 lacked the orientation tension of the resin, and it was difficult to obtain a stretched film. Experiment No. 2 of the second embodiment. In the case of packaging with the film of No. 5, the amount of generated waste is 1.
Although the amount was 8 g, the generation of scraps was a little worrisome, but the level was such that continuous use was possible, and the cut surface was also beautiful. Comparative example 2
Experiment No. The film of No. 9 produced 3 g of waste when 100 packs were packed. In addition, the machine stopped four times during packaging, which was a range where continuous use was impossible. Further, 15 items to be packaged which required repacking due to film breakage were generated.

[0084]

Example 3, Comparative Example 3 Experiment No. 11, Experiment No. 1
2 (above examples) and Experiment No. 13, Experiment No. 14
As the above comparative example, the experiment No. Experiment No. 1 except that the layer structure of No. 1 and the resin structure of the H layer were changed as shown in Table 6. 1
The same experiment was repeated. The above experiment No. 11-Experiment No. Table 7 shows the evaluation results of 14 films. Experiment No. 3 of Example 3. When the film of No. 11 was used for packaging, the amount of waste generated was 0.0 g even after packaging of 100 packs. The film-forming stability was at an allowable lower limit.

Experiment No. 3 of Comparative Example 3 In the film of No. 13, the orientation tension of the resin was insufficient, and it was difficult to obtain a stretched film. On the other hand, the experiment No. No. 12 had a tear propagation strength of 15/10 g. Experiment No. 3 of Example 3. 12
When the film is wrapped with the film, the amount of waste generated is 1.8 g even if it is wrapped in 100 packs, and although the generation of waste is a little worrisome, it is a level that can be continuously used, and the cut surface is also clean. there were. Experiment No. 3 of Comparative Example 3 When the film of 14 was subjected to the same packaging operation, 3 g of waste was generated. Further, the machine stopped 4 times during the packaging, which was in the range where continuous use was impossible, and 15 items to be packaged which had to be repacked due to film breakage occurred.

[0086]

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

Experiment No. 4 of Comparative Example 4 When 100 packs were packed using 20 films, 3 g of waste was generated. In addition, the machine stopped 4 times during packaging,
It was in a range where continuous use was impossible. Further, 15 items to be packaged which required repacking due to film breakage were generated. In addition, streaks that seemed to be poor PP dispersion were found in the film, and there was a problem in appearance.

In addition, in Experiment No. 4 of the fourth embodiment. 15-Experiment N
o. 18 films are made of recycled resin 20 for all layers
Wt% added to the H layer, and in Experiment No. 19 is assumed to be added to the I layer. Experiment No. The fact that the tear propagation strength is reduced in 19 suggests that the ethylene-octene-1 copolymer used for the I layer has an influence on the improvement of the tear propagation strength.
In addition, the experiment No. 15 shows the physical properties of the film in the longitudinal / transverse directions, the heat shrinkage ratio at 100 ° C. is 50/40%,
The heat shrinkage ratio at 120 ° C. was 65/60%, and the elongation at break was 650/680%.

[0089]

Example 5, Comparative Example 5 Experiment No. 21, Experiment No. Two
2 (above examples) and Experiment No. No. 23 (above Comparative Example), Experiment No. The resin composition of the H layer of No. 1 was changed as shown in Table 10, and the manufacturing method was changed to Experiment No. Experiment No. 18 is the same as that of Experiment No. 18. The same experiment as 18 was repeated. The above experiment No.
21-Experiment No. Table 11 shows the evaluation results of the film No. 23.

Experiment No. 22 is MFR = 12 g / 10
Although it is made of polypropylene resin for MFR,
Experiment No. 1 of polypropylene type resin of 1.5 g / 10 min.
The film-forming stability was inferior to that of No. 21 but was within the allowable range. Also, the cutting property was slightly deteriorated. On the other hand, the comparative experiment No. No. 23 was a polypropylene resin having MFR = 30 g / 10 min, but film formation by direct inflation was impossible.

[0091]

Example 6 Experiment No. 24, Experiment No. As 27
Experiment No. Experiment No. 1 except that the resin composition of No. 1 was changed as shown in Table 12. The same experiment as 1 was repeated. Also, 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. No. 18 other than Experiment No. The same experiment as 1 was repeated.

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

Experiment No. No. 24 is the experiment No. 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 layer I, the indentation recovery property was slightly superior. Experiment No. In No. 25, since the polybutene-1 resin was changed to a low density ethylene resin, the glossiness was deteriorated. Experiment N using ultra low density ethylene elastomer
o. Experiment No. 26 is The glossiness was slightly improved over 25. It is considered that this is because the ultra low density ethylene resin has a smaller crystallinity than the low density ethylene resin and the crystallization speed is slow. The glossiness of the film formed by the DB method was further improved. This seems to be due to the effect of quenching 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]

The present invention has the above-mentioned structure,
While maintaining or further improving the flexibility, which is the characteristic of conventional films, it is excellent in improving the cuttability of the film and tear resistance during film stretching, that is, it is excellent in suppressing the generation of scraps of the film, heat shrinkability, and heat sealing. It is possible to obtain stretch wrap and stretch / shrink wrapping film with excellent properties and optical characteristics.

Claims (4)

(57) [Claims] 1. A polypropylene resin in which the inner layer is made of a propylene homopolymer or a propylene / .alpha.-olefin (having 2 or 4 to 12 carbon atoms) random copolymer and satisfies the following formulas (1) and (2). containing, during inner layer, wherein the polypropylene-based resin 10 to 90 wt%, and ethylene content is from 2 to 10 mol% of butene-1-ethylene copolymer 90-10 wt% of polypropylene
Contains the largest amount of resin, satisfies the following formula (3),
Look containing a heat-resistant layer, a multilayer film, tear propagation strength 1
A polyolefin-based resin multilayer stretched film, which has a weight ratio of 0 to 200 g and satisfies the following formula (4) . 0.5 g / 10 min ≤ MFR ≤ 20 g / 10 min (1) Boiling n-heptane extraction amount = 20 to 90% by weight (2) 3% ≤ Xch ≤ 20% (3) (However, Xch is a differential scan described later. Among the crystallinities measured by the calorimetric method (DSC), the crystallinity based on the polypropylene resin in the heat resistant layer is 1% ≦ Xc ≦ 10% (4) (where Xc is Among the crystallinity of the whole film measured by the differential scanning calorimetry (DSC) described later , the
Crystallinity based on all polypropylene resins included . ) 2. A ¹³ C-NM of the polypropylene resin.
The polyolefin resin multilayer stretched film according to claim 1, wherein the isotactic pentad fraction (fmmmm) determined by R is 10 to 75 mol%. 3. The film according to claim 1, wherein the film has a heat shrinkage ratio of 20% or more at 120 ° C. in the machine direction and the transverse direction.
The polyolefin resin multilayer stretched film according to any one of 1. 4. The breaking elongation of the film in the machine direction is 200% or more and the breaking elongation in the transverse direction is 300% or more.
~ The polyolefin resin multilayer stretched film according to any one of claims 3 to 4.