JP6270385B2 - Curl-free multilayer film - Google Patents

Description

  The present invention relates to a multilayer film that does not curl to the extent that it becomes a practical impediment.

  When producing a multilayer film by the coextrusion water cooling inflation method, a highly hygroscopic resin layer made of layers of different resins, for example, a saponified product of nylon or ethylene-vinyl acetate copolymer (abbreviated as “EVOH”), and a polyolefin When a low hygroscopic resin layer such as the above is laminated, the obtained multilayer inflation film (hereinafter sometimes abbreviated as “multilayer inflation film”) is often curved (hereinafter abbreviated as “curl”). ).

Such curling becomes a hindrance in the process of processing the multilayer film into a bag or actually filling the object to be encapsulated.
In order to solve such problems, the present applicant has proposed a curl-free multilayer film having a specific layer structure as Patent Document 1 (Patent No. 3227301).

Japanese Patent No. 3227301

In recent years, the emergence of multilayer films that are less curled and easy to use has been desired.
Patent Document 1 does not necessarily have a clear connection between the manufacturing conditions and the curl, and the appearance of a more curl-free multilayer film has been desired.

Under such circumstances, the present inventors have intensively studied to solve the above problems, and as a result, have thought that the curling property is due to the difference in crystallinity in the cooling step.
However, the relationship between the degree of crystallinity and the curlability is largely dependent on the cooling conditions, and is difficult to define. Therefore, the present inventors have found that curling of a film can be suppressed if a specific parameter (a peak shape derived from carbonyl stretching vibration is a shape index due to asymmetry) is satisfied, and the present invention is completed. It came to.

The configuration of the present invention is as follows.
[1] An endothelium layer (F), a core layer (B), and an outer skin layer (E) are composed of at least three layers laminated in this order,
Highly hygroscopic nylon in which the core layer (B) is at least one selected from 6-nylon, 66-nylon, a mixture of 6-nylon and 66-nylon, and a cocondensate of 6-nylon and 66-nylon Consists of
The outer skin layer (E) is made of 610-nylon,
Endothelial layer (F) consists of a single polyolefin resin or two or more polyolefin resins,
The shape index defined in the following equation (1), which represents the peak shape of the Raman spectrum of the outer skin layer (E), is 1.35 or more,

（但し、カルボニル伸縮振動に由来するピークの前後で接線を引いてベースラインとし、当該ベースラインに対して上記のピークの頂点から垂線を下ろし、ピークが強度１／２に相当する高さで水平線を引き、垂線より高波数側のピーク幅をＬａ、低波数側のピーク幅をＬｂとする。）
かつ、共押出水冷インフレーション法によって製造されたものであることを特徴とする無カール性多層フィルム。

(However, a tangent line is drawn before and after the peak derived from the carbonyl stretching vibration to make a base line, and a perpendicular line is drawn from the peak apex to the base line, and the peak is a horizontal line at a height corresponding to an intensity of 1/2. And the peak width on the high wavenumber side from the perpendicular is La and the peak width on the low wavenumber side is Lb.)
And a curl-free multi-layer film produced by a coextrusion water-cooled inflation method.

[2] The polyolefin resin of the endothelial layer is
A polyethylene resin having a density of 0.88 to 0.97 g / cc, MI (190 ° C .; 2.16 kgf) of 0.1 to 30 g / 10 min and a melting point (Tm) of 90 to 138 ° C. A mixture of two or more, or
[1] non-curling multilayer film which is a polypropylene resin having a MFR (230 ° C .; 2.16 kgf) of 0.5 to 45 g / 10 min and a melting point (Tm) of 125 to 165 ° C. or a mixture of two or more of these resins. .

  According to the present invention, by setting the shape index determined from the peak shape derived from the carbonyl stretching vibration to a specific range by Raman analysis, a multilayer film that can reduce curl and has an excellent appearance can be obtained. The multilayer film obtained by co-extrusion water-cooled inflation molding with the above layer structure is rich in a high-class feeling having high gloss and high transparency, which are the advantages of nylon, despite being non-curl.

It is a sketch which shows a curvature radius typically. (ap) is a plan view showing the position, direction and length of the cut for generating the curl on the sample film, (bp) is a plan view of the state after the cut is made on the sample film, and (br) is (bp) ) Is a sketch of the state of FIG.

Hereinafter, the present invention will be described, but the present invention should not be construed as being limited thereto.
Curled Multilayer Film The curled multilayer film according to the present invention is formed by laminating an endothelial layer (F), a core layer (B), and an outer skin layer (E) in this order.

・ Core layer (B)
The core layer (B) is made of highly hygroscopic nylon.
Highly hygroscopic nylon for the core layer (B) is 6-nylon, 66-nylon (6,6-nylon), a mixture of 6-nylon and 66-nylon or co-condensation of 6-nylon and 66-nylon Highly hygroscopic nylon such as body.
Here, “highly hygroscopic” means that the water absorption rate (according to ASTM D570) is 1% or more, preferably 1.4% or more.

・ Skin layer (E)
The outer skin layer is composed of 610-nylon. Commercially available 610-nylon can be used without particular limitation.

・ Endothelial layer (F)
The polyolefin resin for the endothelial layer (F) is a resinous material obtained by polymerizing (including copolymerization) one or more 1-olefins having about 2 to 10 carbon atoms. Polyethylene, which is the most frequently used polyolefin resin, includes not only ethylene homopolymers but also copolymers of ethylene and 1-olefins of propylene or more (3 or more carbon atoms). In general, in a polyethylene resin, the amount of comonomer contained is about 15 mol% or less.

  Polyethylene resins are also divided into high density, medium density and low density resins. Among these, the low-density polyethylene resin has a preferable property as a film that is excellent in heat sealability in addition to being most transparent and flexible. For the purposes of the present invention, low density polyethylene resin is most preferred. Of course, a high density polyethylene resin may be employed for special applications. In particular, it is more suitable than low density polyethylene resin for applications that are required to withstand high temperatures, high tension, and the like.

  As the polyethylene resin suitable for the present invention, MI (190 ° C .; 2.16 kgf) is usually 0.1 to 30 g / 10 min, preferably 1 to 5 g / min, and density is usually 0.91 to 0.965 g / cc, preferably 0. 0.92 to 0.95 g / cc and a melting point (Tm) of usually 90 to 138 ° C, preferably 100 to 130 ° C.

  Polypropylene resin can also be used. The polypropylene resin used for the endothelial layer in the present invention is MFR (230 ° C .; 2.16 kgf) usually 0.5 to 45 g / 10 min, preferably 2 to 12 g / 10 min and melting point (Tm) usually 125 to 165 ° C., preferably 130. ~ 150 ° C. A wide variety of copolymers are also commercially available for polypropylene resins, and examples include propylene-ethylene copolymers and propylene-1-butene copolymers. An appropriate one can be selected from these according to the application.

Adhesive resin In the multilayer film of the present invention, if necessary, an appropriate amount of an adhesive modified polyolefin resin is blended in the polyolefin resin for the purpose of improving the adhesiveness of each layer or made of an adhesive polyolefin resin. A form in which an adhesive layer is interposed may be employed. Examples of the adhesive resin include maleic anhydride-modified polyolefin.
If necessary, a barrier layer made of EVOH, MXD-6, or the like can be disposed.

Shape Index The multilayer film of the present invention has a shape index defined by the following formula (1), which represents the peak shape of the Raman spectrum of the outer skin layer (E), of 1.34 or more, preferably 1.35 or more. By setting it as such a range, the curl in 23 degreeC and 50% RH can be reduced.

（但し、カルボニル伸縮振動に由来するピークの前後で接線を引いてベースラインとし、当該ベースラインに対して上記のピークの頂点から垂線を下ろし、ピークが強度１／２に相当する高さで水平線を引き、垂線より高波数側のピーク幅をＬａ、低波数側のピーク幅をＬｂとする。）

(However, a tangent line is drawn before and after the peak derived from the carbonyl stretching vibration to make a base line, and a perpendicular line is drawn from the peak apex to the base line, and the peak is a horizontal line at a height corresponding to an intensity of 1/2. And the peak width on the high wavenumber side from the perpendicular is La and the peak width on the low wavenumber side is Lb.)

The peak derived from the carbonyl stretching vibration of the amide bond is approximately 1650 cm ⁻¹ .
Such a shape index reflects the crystallinity, but the crystallinity itself is greatly affected by the co-extrusion water-cooled inflation conditions, and the cooling conditions vary depending on the type, thickness, number of layers, etc. of the resin. Therefore, it is difficult to directly define the relationship with the curl property. On the other hand, according to the shape index, a curl-free multilayer film can be obtained because the shape index is not affected by the resin type and manufacturing conditions.

  The measurement of the Raman spectrum for obtaining the shape index (La / Lb) is performed under the conditions shown in the examples.

<Measurement device>
Measuring instrument: “NRS-3100” manufactured by JASCO
Detector: DV401-FI CCD detector manufactured by Andor Inc. Excitation light source: Semiconductor-excited solid-state laser (Nd-YAG laser (λ = 1.064 μm) second harmonic oscillation (takes out light with a wavelength of 1/2))
Excitation wavelength: 532.05nm

<Measurement conditions>
Laser power: 11.5mW
Beam diameter (reference value for each magnification):
1 μm (× 100)
Integration time: 180 sec (1 sec x 180 times)

-Definition of curl-freeness The term "curl-free" in this specification is not necessarily a complete curl-free state, that is, not only a state in which the radius of curvature of the test piece curl is infinite. The case where the curl stays at a level that does not become a hindrance in practice is also included in the “curl-free” of the present invention. Specifically, it is a comprehensive expression in the case where a value of at least 1.5 cm or more can be maintained for the radius of curvature (r) in the curl measurement method under the conditions of a temperature of 25 ° C. and a relative humidity (RH) of 50%. Above this value, there is no curl at a level that is substantially satisfactory.

  Fig. 1 shows the measurement of the radius of curvature. FIG. 1 (br) is a view of the curled state as viewed from the direction (lateral direction) perpendicular to the long axis of the bag, and clearly shows that the two triangles 31 and 33 facing each other are curled. Can be seen. An arrow r from the center of the arc formed by both triangles to the arc represents the radius of curvature of the arc. When r is large, the degree of curling of the bag is low (slow), and when it is small, the degree of curling is high (violent).

In the present invention, the presence or absence of curl at the bag mouth portion is greatly influenced by the direction parallel to the take-up direction (MD, that is, 31 and 33 in FIG. 1). For this reason, evaluation is performed using the measured radius of curvature in the MDs 31 and 33 in FIG.
When the curl is large, there are problems such as a significant hindrance during processing into a bag or in a process of filling an object to be encapsulated.

Production method The curl-free multilayer film of the present invention is produced by a coextrusion water-cooled inflation molding method. Such a molding method is a method of coextrusion inflation molding the material constituting each of the above layers from, for example, a concentric annular die. At this time, a method of rapidly cooling the multilayer inflation tube through the cooling water tank is called co-extrusion water cooling inflation. Here, the cooling water includes those in which various additives are blended depending on the use of the product.

  In the method for producing a curl-free multi-layer film of the present invention, each material is laminated in the order of the endothelium layer (F), the core layer (B), and the outer skin layer (E), and coextrusion is performed from a concentric annular die. Is molded. For applications that require strong interlayer adhesion to the highly hygroscopic nylon layer forming the core layer (B), an appropriate amount of an adhesive modified polyolefin resin is blended in the polyolefin resin, or an adhesive polyolefin It is also possible to adopt a form in which a resin adhesive layer is interposed.

  Specifically, usually, a water tank having a size ring inside is disposed below the annular die, and an equipment in which an inner plate and a winding roll are sequentially disposed below the water tank is used. After each layer material is co-extruded from the annular die and cooled through the size ring, the laminated film cylindrical body is fed to the take-up roll through the inner plate and folded to form a multilayer tube. To do.

Layer configuration of the curl-free multilayer film The thickness of each layer of the curl-free multilayer film (including the sheet) of the present invention is as follows:
Outer layer thickness: usually 0.5 to 20 μm, preferably 1 to 15 μm
Core layer thickness: usually 5 to 50 μm, preferably 10 to 40 μm
Endothelial layer thickness: usually 15 to 130 μm, preferably 30 to 70 μm
Total layer thickness (outer skin layer thickness + core layer thickness + endothelial layer thickness): usually 50 to 150 μm, preferably 60 to 90 μm.

  There is no restriction | limiting in particular in the number of the layers which comprise the multilayer film of this invention. In addition, the “skin layer (E)” which is an essential layer, the “skin layer (B)” and the core layer (B) which are located on the inner side and firmly adhere to the skin layer (E) and are protected from curling. There are no particular restrictions on the configuration or order of the other layers except for the point constituted by the inner endothelial layer (F) and the properties and order of each layer. Each constituent layer may be a mixture of two or more of the same type of resin, or may be formed of two or more layers.

  Such a multilayer film is suitably used for industrial products such as electronic parts and food packaging such as ham and sausage. In particular, since the end portion does not curl, there is no trouble in filling and packaging. Moreover, transparency is also high and the visibility of the contents is excellent.

[Example]
EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited to these examples.
The curvature radius of the curl is a measurement result in the measurement method and measurement conditions described in the above specification.

Also, legends for resin abbreviations are as follows:
6-NY: 6-nylon [relative viscosity 3.6; degree of polymerization 250; molecular weight 28000; water absorption (ASTM D570) 1.3 to 3.5% (24 h)];
610-NY: 610-nylon [relative viscosity 2.7; degree of polymerization 160; molecular weight 18 × 10 ³ ; water absorption (ASTM D570) 0.3 to 1.5% (24 h)];
L-LDPE: linear low density polyethylene [MI (190 ° C; 2.16 kgf) 1.0 g / 10 min];

<Layer configuration, coextrusion inflation molding and quenching operations and conditions>
Endothelial layer (F): LDPE, core layer (B): 6-nylon, outer skin layer (E): 610-nylon Extrusion equipment: co-extrusion water-cooled inflation device Extrusion temperature: 210 ° C (L-LDPE), 250 ℃ (6-NY), 250 ℃ (610-NY),
-Swelling ratio: about 1;
Cooling water temperature (° C): 25, 35 (Examples), 45 (Comparative examples):
・ Cooling water volume (L / min): 15, 25 (Example), 28, 35 (Comparative example)
-Passing linear velocity in cooling water bath (m / min): 20 to 150 (same as above).

<Measurement and evaluation of curls>
As shown in FIG. 1, a square (5 cm on a side) having two sides of an original fabric take-up direction and a direction perpendicular thereto is drawn on a sample multilayer film, and cuts (× mark shape) are formed on both diagonal lines. Further, the radius of curvature (r) appearing at the curved portions of the four petal-like pieces is measured and obtained as an arithmetic average value thereof.
The measurement is performed under conditions of a temperature of 23 ° C. and a relative humidity of 50%. Here, the smaller the numerical value of the “curl radius of curvature r (cm)”, the stronger the curl.

<Measurement of shape index>
・ Measuring device measuring instrument: “NRS-3100” manufactured by JASCO
Detector: DV401-FI CCD detector manufactured by Andor Inc. Excitation light source: Semiconductor-excited solid-state laser (Nd-YAG laser (λ = 1.064 μm) second harmonic oscillation (takes out light with a wavelength of 1/2))
Excitation wavelength: 532.05nm
・ Measurement condition Laser output: 11.5mW
Beam diameter (reference value for each magnification):
1 μm (× 100)
Integration time: 180 sec (1 sec x 180 times)
Test piece: 100mm square

[Examples 1 to 4]
The outer layer (E), the core layer (B), and the inner layer (F) are selected from the combinations shown in Table 1 and the molding shown in Table 1 by selecting a combination of various types of resins, layer thicknesses and layer configurations exemplified in Table 1. A multilayer film was prepared and evaluated under each condition.

[Comparative Examples 1-3]
A laminated film was prepared in the same manner as in Example 1 except that the cooling water temperature and the cooling water amount in the embodiment of Example 1 were changed as shown in Table 1.

上記表より、形状指数を所定の範囲とすることで、カールの曲率半径の大きい（すなわちより無カール性）の積層フィルムが得られることが判明した。

From the above table, it was found that a laminated film having a large curl radius of curvature (ie, more curl-free) can be obtained by setting the shape index within a predetermined range.

31 Parts separated by cuts provided in the sample film (upper side in the figure)
32 Parts separated by cuts provided in the sample film (left side of the figure)
33 Parts separated by cuts provided in the sample film (bottom side of the figure)
34 Parts separated by cuts in the sample film (right side of the figure)

Claims (2)

Endothelial layer (F), core layer (B) and outer skin layer (E) are laminated in this order, and are composed of at least three layers.
Highly hygroscopic nylon in which the core layer (B) is at least one selected from 6-nylon, 66-nylon, a mixture of 6-nylon and 66-nylon, and a cocondensate of 6-nylon and 66-nylon Consisting of a simple,
The outer skin layer (E) is made of 610-nylon,
Endothelial layer (F) consists of a single polyolefin resin or two or more polyolefin resins,
The shape index defined in the following equation (1), which represents the peak shape of the Raman spectrum of the outer skin layer (E), is 1.35 or more and 1.41 or less ,

(However, a tangent line is drawn before and after the peak derived from the carbonyl stretching vibration to make a base line, and a perpendicular line is drawn from the peak apex to the base line, and the peak is a horizontal line at a height corresponding to an intensity of 1/2. And the peak width on the high wavenumber side from the perpendicular is La and the peak width on the low wavenumber side is Lb.)
And a curl-free multi-layer film produced by a coextrusion water-cooled inflation method. The polyolefin resin of the endothelium layer
A polyethylene resin having a density of 0.88 to 0.97 g / cc, MI (190 ° C .; 2.16 kgf) of 0.1 to 30 g / 10 min and a melting point (Tm) of 90 to 138 ° C. A mixture of two or more, or
2. A polypropylene resin having a MFR (230 ° C .; 2.16 kgf) of 0.5 to 45 g / 10 min and a melting point (Tm) of 125 to 165 ° C., or a mixture of two or more of these resins. The curl-free multilayer film as described.

Images