JP3227301B2 - Non-curl multilayer film and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coextrusion wherein the outer layer (E) comprises at least a low hygroscopic polymer material of the same family as the core layer (B), and the core layer (B) comprises at least a high hygroscopic polymer material. The present invention relates to a multilayer film which is produced by a water-cooled inflation method and does not cause curl so as to be a practical obstacle, and a method for producing the same.
Specifically, in the present invention, the core layer (B) is made of a high hygroscopic polymer material (usually a resin), and the outer layer (E) is a low hygroscopic (moisture proof) polymer material similar to the core layer (B). In particular, the present invention relates to a curl-free multilayer film obtained by a coextrusion water-cooled inflation method and a method for producing the same.

[0002]

2. Description of the Related Art When a multilayer film is produced by a co-extrusion water-cooled inflation method, layers made of different kinds of resins are used.
For example, when a highly hygroscopic resin layer made of a saponified product of nylon or ethylene-vinyl acetate copolymer (abbreviated as "EVOH") and a low-hygroscopic resin layer such as polyolefin are laminated, the obtained multilayer blown film (hereinafter, referred to as " However, there is a problem that the multilayered inflation film is sometimes curved (hereinafter, sometimes referred to as "curl").

For example, a multi-layer tubular film (sometimes abbreviated as “film A”) composed of at least two layers of an inner layer (F) of polyethylene and an outer layer (E) of 6-nylon is commonly used. When manufactured by the extrusion water-cooled inflation method, curl is generated in a curved shape outside the tubular film (see FIG. 1). This phenomenon is particularly noticeable at the open end (mouth) of the tubular body.

[0004]

The problem to be solved will be described below by comparing the conventional multilayer film with the curl-free multilayer film of the present invention with reference to the drawings.

FIG. 1 is a front view and a schematic cross-sectional view of a bag made from a conventional two-layer film (inner LDPE // outer 6-NY). FIG. 1A is a front view of a bag made of a conventional two-layer film, and 1 in FIG. 1 shows a bag body. 1 shows a state in which the vicinity of the bottom edge is sealed, and the top edge, that is, the mouth L is curled outward due to the difference in hygroscopicity. L1 is a rim located on the front side of the bag, and L2 is a rim located on the opposite side of the bag, which curls and opens the mouth. FIG. 1B is a schematic cross-sectional view of the conventional multilayer film cut along the line AA. In FIG. 1, the edge L1 and the edge L2 curl to opposite sides. State clearly.

FIG. 2 (a) is a schematic cross-sectional view of a laminated film forming the conventional bag 1, which is highly hygroscopic nylon (6-NY).
It comprises a layer (B1) and a low-density polyethylene (LDPE) layer (E1). When the B1 surface comes into contact with cooling water, it absorbs moisture and curls. In the following description, the description of the adhesive layer that is provided between the nylon layer and the polyolefin layer and exhibits strong adhesiveness to both layers is basically omitted.

FIG. 2 (b) shows an example of the multilayer film of the present invention in which the outer layer (E21) which is in contact with the aqueous coolant is formed of low moisture absorbing nylon (610-NY), and which is not in contact with the aqueous coolant. Core layer
(B21) shows a laminate 21 in which the endothelial layer (F21) is formed of a low-density polyolefin (LDPE) layer inside of the highly hygroscopic nylon (6-NY). When the outer skin layer (E21) and the core layer (B21) constituting the laminate 21 are both nylon homologs, or when the outer skin layer (E21) is a low hygroscopic nylon but the core layer (B21) is EVOH. , The two layers are fused together so that they cannot be separated.

FIG. 2C shows a second example of the multilayer film of the present invention.
In an embodiment, the outer skin layer (E22) is made of another kind of low moisture absorbing nylon (612).
-NY), the core layer (B22) is another kind of highly hygroscopic nylon (66-NY)
Here, an example of the laminate 22 in which the endothelial layer (F22) is formed of low-density polyethylene (LDPE) is shown. Also in the laminate 22, the outer skin layer (E22) and the core layer (B22) are fused to each other so that they cannot be separated from each other.

FIG. 2 (d) shows a third example of the multilayer film of the present invention.
As an embodiment, the outer skin layer (E23) is made of another kind of low hygroscopic nylon (MXD
6), the core layer (B23) is made of another kind of highly hygroscopic nylon (6-NY) and E
An example of the laminate 23 in which the endothelial layer (F23) is formed of a low-density polyethylene (LDPE) in a mixture with VOH is shown. Also in the laminate 23, the outer skin layer (E23) and the core layer (B23) are fused so that they cannot be separated from each other.

FIG. 3 shows a procedure for quantitatively grasping the curl state of the multilayer film in four directions perpendicular to each other. (Ap) of FIG. 3 is 5 cm on one side at the center of the sample multilayer film.
, Define a range 3 surrounded by squares, and cut two diagonal lines thereof with a knife to form four right-angled isosceles triangles 3 congruent with each other.
1, 32, 33 and 34 are formed.

When the multilayer film is curled, each triangle is curled by the above diagonal cutting. That is, since the four vertexes that are in contact with each other at the intersection of the two diagonal lines are located at the free ends, they tend to warp up from the film surface and separate.

FIG. 3 (bp) is a schematic plan view showing a state in which the triangles 31 to 34 are warped from the surface of the film. The degree of curl of the four triangles in FIG. In particular, when the bag is stretched in any one direction, it naturally does not match. Even when the bag is biaxially stretched, if the stretching ratio in each direction is significantly different, the difference differs according to each direction. Can be recognized.

FIG. 3 (br) is a view of the curled state as viewed from a direction (lateral direction) perpendicular to the long axis of the bag.
The state in which the triangles 31 and 33 are curled can be clearly seen. The arrow r from the center of the arc formed by both triangles to the arc indicates the radius of curvature of the arc. This r
Is large, the degree of curl of the bag is low (slow),
Conversely, a small value indicates that the degree of curl is high (severe).

[0014] In the above phenomenon, if the generated curl is larger than a certain degree, it becomes a significant hindrance in the bag making process using the obtained co-extruded water-cooled inflation tube or the process of filling the bag with the envelope. However, there still remain major problems in practical aspects.

The size of the curl (in other words, the smallness of r)
Although it varies depending on environmental conditions such as humidity and temperature, the practical experience is that the curl radius of curvature measured by the method described below under the conditions of a temperature of 25 ° C. and a relative humidity (RH) of 60% is 1.5 cm or more. The present inventors have confirmed that if there is, there is no particular problem due to curling in a process of processing a multilayer inflation film and filling a bag obtained from the film.

At present, if the film A is manufactured by the co-extrusion water-cooled inflation method without taking any particular curl suppressing measures, a curl (small radius of curvature) that is so strong as to cause a practical problem is generated. Therefore, in order to provide the strongly curled film A to the automatic bag making process or the automatic filling process, a post-treatment for removing the curl is required.

On the other hand, a method of manufacturing a multilayer film, which goes one step further and removes the source of curl generation, is well known. The principle is that the layer structure of the multilayer film is symmetrically arranged. For example, in a multilayer film composed of a nylon layer (NY) and a polyethylene layer (PE), a skin layer (E) and an endothelial layer (F)
A polyethylene layer (PE) and a core layer (B) interposed between the two layers as a nylon layer (NY) to form a multilayer film [PE //
NY // PE (sometimes abbreviated as "film B")], a multilayer film can be obtained in which curling is almost completely eliminated. The limitation of this method is that in a multilayer film composed of a nylon layer and a polyethylene layer, the layer structure that can be employed is limited to a symmetric arrangement.

Unfortunately, while the multilayer film having a nylon layer as the core layer (B), such as the film B, has excellent advantages such as excellent pinhole resistance and the like, it has disadvantages and a lack of glossiness and sealing. With insufficient gender. If,
A multilayer film having a nylon layer, which is a high melting point resin, as an outer skin layer (E) should be able to fully exhibit excellent glossiness and the like and provide a film having excellent sealing properties.
However, it is extremely difficult to directly produce a non-curl multilayer film by a co-extrusion water-cooled inflation method while using a high moisture-absorbing nylon layer as a skin layer (E) even though it is a high melting point resin.

[0019]

The present inventor has succeeded in removing the cause of curl generation on the basis of a completely different principle from the conventional method. That is, the present invention provides an endothelial layer comprising a hydrophobic resin.
(F) Highly hygroscopic nylon lined with low moisture absorption nylon on a core layer (B) formed from a mixture of plain or high hygroscopic nylon and a small amount of EVOH polymer or PVOH polymer The present invention relates to a non-curl multilayer water-cooled inflation film having excellent curling and excellent glossiness by laminating an outer layer (E) formed from a non-curl film and an easy and reliable production method thereof.

The present invention comprises the following multilayer water-cooled inflation films and a method for producing them: [Basic layer structure of multilayer film] The core layer (B) is made of the following highly hygroscopic nylon plain or highly hygroscopic nylon. EVOH polymer and PVOH as main components
The outer layer (E) is composed of a low-hygroscopic nylon plain or a low-hygroscopic nylon as shown below, and a highly hygroscopic nylon as shown below is used as the outer layer (E). A curl-free multilayer film produced by a co-extrusion water-cooled inflation method, wherein the material added in a small amount and the endothelial layer (F) are composed of at least three layers composed of a polyolefin resin alone or two or more polyolefin resins. The highly hygroscopic nylon is at least one selected from 6-nylon, 66-nylon, a mixture of 6-nylon and 66-nylon, and a co-condensate of 6-nylon and 66-nylon; -Nylon, 612-nylon,
Non-curl multilayer film which is at least one selected from 11-nylon and 12-nylon.

[Improved Layer Structure 1 of Multilayer Film] Core Layer (B)
Having a hygroscopic nylon content of 60 to 100% by weight and an ethylene unit content of 24 to 50% by mole;
The curl-free multilayer film described in "Basic Layer Structure of Multilayer Film", comprising 0 to 40% by weight of at least one selected from polymers and combining them so that the sum of both is 100% by weight.

[Improved structure 2 of multilayer film] Outer skin layer (E)
Is composed of at least 60 to 100% by weight of at least one kind of low hygroscopic nylon and at least 40 to 0% by weight of at least one kind of high hygroscopic nylon (combined so that the sum of both becomes 100% by weight). The curl-free multilayer film described in "Basic layer configuration" and "Improved layer configuration 1 of multilayer film".

[Improved Structure 3 of Multilayer Film] The highly hygroscopic nylon is 6-nylon, 66-nylon, a mixture of 6-nylon and 66-nylon or a co-condensate of 6-nylon and 66-nylon, Low hygroscopic nylon 610-nylon, 612-
1 selected from nylon, 11-nylon, 12-nylon and meta-xylylenediamine-dicarboxylic acid co-condensation polymer
Non-curl multilayer film described in "Basic layer structure of multilayer film" and "Improved layer structure 1 of multilayer film" and "Improved structure 2 of multilayer film" which are at least one kind.

[Improved Structure 4 of Multilayer Film] The polyolefin resin of the endothelial layer has a density of 0.88 to 0.97 g /
cc, MI (190 ° C; 2.16 kgf) 0.1 to 30 g / 10 min and melting point
(Tm) Polyethylene resin of 90-138 ° C, modified polyester
Tile resin or a mixture of two or more of these resins
Yes or MFR (230 ° C; 2.16kgf) 0.5-45g / 10min
And a polypropylene resin having a melting point (Tm) of 125 to 165 ° C.
Non-curl multilayer film described in “Basic structure of multilayer film” and “Improved layer structure 1 of multilayer film” to “Improved layer structure 3 of multilayer film” , which is a simple substance or a mixture of two or more of these resins. .

[Basic Production Method of Multilayer Film] The core layer (B) is composed mainly of the following highly hygroscopic nylon or a highly hygroscopic nylon, and an EVOH polymer and PV
A mixture to which a small amount of one or more selected from OH polymers is added is used as the outer layer (E). The mixture added in a small amount is characterized by co-extrusion water-cooled inflation molding of a mixture of a polyolefin resin alone or a polyolefin resin as a main component and a small amount of the highly hygroscopic nylon described below as the inner layer (F). Non-curl multilayer film production method, wherein the highly hygroscopic nylon is 6-nylon, 66-nylon, 6-nylon
Mixture of nylon and 66-nylon and 6-nylon and 66-
Non-curl , one or more selected from co-condensates with nylon, and the low hygroscopic nylon is one or more selected from 610-nylon, 612-nylon, 11-nylon and 12-nylon
Method for producing functional multilayer film .

[Improved Production Method 1 of Multilayer Film] As the core layer (B), a highly hygroscopic nylon of 60 to 100% by weight and an ethylene unit content of 24 to 50% by mole of an EVOH polymer and PVO
A mixture of at least one selected from H polymers of 0 to 40% by weight (combined so that the sum of both is 100% by weight) is used as the outer layer (E) as a single layer of low hygroscopic nylon or low hygroscopicity. A mixture consisting of 100 to 60% by weight of water-soluble nylon and 0 to 40% by weight of highly hygroscopic nylon (combined so that the sum of both becomes 100% by weight) is used as an endothelial layer (F) as a polyolefin resin plain or polyolefin. A method for producing a multilayer film as described in "Basic method for producing a multilayer film", wherein a mixture comprising a resin as a main component and a small amount of highly hygroscopic nylon added thereto is co-extruded and water-cooled inflation-molded.

[0027]

[Layer Structure and Layer Thickness of Multilayer Film] The layer structure and the overall thickness of the most common three-layer film among the multilayer films of the present invention are shown below as the core layer (B) and the outer layer.
(E) is shown in Table 1 separately.

[0029]

[Table 1]

<Preferred Embodiments of the Invention> (1) Highly hygroscopic nylon for the core layer (B) alone or a mixture containing the same as the main component The highly hygroscopic nylon in the present invention is 6-nylon or 66-nylon.
Highly hygroscopic nylon such as nylon (6,6-nylon), a mixture of 6-nylon and 66-nylon, or a co-condensate of 6-nylon and 66-nylon. Another example of the material forming the core layer (B) is a mixture of the highly hygroscopic nylon and at least one selected from ethylene-vinyl alcohol polymer and polyvinyl alcohol, and the mixture ratio of both (sum of both). Is 100% by weight) and the highly hygroscopic nylon is 60 to 100% by weight, preferably 70 to 90% by weight, and the EVOH polymer (and / or PVOH) is 40 to 0%.
%, Preferably not more than 30% by weight.

Here, "highly hygroscopic" means the water absorption (ASTM).
D570) is 1% or more, preferably 1.4% or more. These are described in detail below. (1-1) Highly hygroscopic nylon, EVOH polymer and PV
Specific examples of OH: ◆ Used for the bag-like material for laminated packaging of the present invention, such as 6-nylon, 66-nylon, a mixture of 6-nylon and 66-nylon, or a co-condensate of 6-nylon and 66-nylon The EVOH polymer obtained has an ethylene unit content of usually 24 to 50 mol%, preferably 29 to 44 mol%, and its MI (190 ° C .;
gf) Usually 0.5 to 15 g / 10 min, preferably 1 to 7 g / 10 min
belongs to. ◆ Polyvinyl alcohol (PVOH) is obtained by highly hydrolyzing a homopolymer of vinyl acetate due to similar restrictions on chemical reactions. However, since many of them are water-soluble, they are rarely used as a single resin. ◆ A mixture comprising two or more of the above-mentioned highly hygroscopic resins. (2) Low moisture-absorbing nylon for outer layer (E) The low moisture-absorbing nylon in the present invention conceptually does not belong to the above-mentioned "high moisture-absorbing nylon". But,
Actually, it is not familiar to be strictly distinguished from "highly moisture-absorbing nylon" on the basis of the water absorption, but it is only a relative classification.
This is because the value of the water absorption can vary considerably depending on the measuring method and its conditions. As a tentative standard for water absorption,
The above-mentioned nylon having a water absorption of 1.0% or less, preferably 0.8% or less and a mixture of two or more thereof can be referred to as "low moisture-absorbing nylon" in the present invention. Nevertheless, in practice, it is only possible to make a distinction based on the specific examples described below.

Incidentally, a small amount of highly hygroscopic nylon can be blended with the low hygroscopic nylon. In the present invention, "small amount" means that the curl property of the multilayer film obtained by the blending does not exceed the expected upper limit, and the blending amount is a high moisture absorbing nylon / low moisture absorbing ratio in a weight ratio. Nylon is 40/60 or less, preferably 30/7
Set to 0 or less (select each such that the sum of the numerical value of the numerator and the numerical value of the denominator becomes 100).

Specific examples of low hygroscopic nylon plain: ◆ 610-nylon (6,10-nylon), 612-nylon (6.1
2-nylon), 11-nylon or 12-nylon and a meta-xylylenediamine-dicarboxylic acid co-condensation polymer [may be abbreviated as "MXDC" in the present invention]. In addition,
"MXD6" indicates that the dicarboxylic acid is adipic acid (C = 6)]. ◆ A mixture of 610-nylon and meta-xylylenediamine-dicarboxylic acid co-condensation polymer, a mixture of 612-nylon and meta-xylylene diamine-dicarboxylic acid co-condensation polymer, or 610-nylon, 612-nylon and meta-xylylene A mixture with an amine-dicarboxylic acid co-condensation polymer. (3) Polyolefin resin for endothelial layer (F) Polyolefin resin is a resinous material obtained by polymerizing (including copolymerizing) one or more of 1-olefins having about 2 to 10 carbon atoms. .

Polyethylene, which is the most frequently used polyolefin resin, includes not only a homopolymer of ethylene but also a copolymer of ethylene and a 1-olefin having at least propylene (having 3 or more carbon atoms). Generally, in polyethylene resin,
The amount of comonomer contained is not more than about 15 mol%.

Polyethylene resins are also classified into high density, medium density and low density resins. Among these, the low-density polyethylene resin has the most preferable properties as a film that is most excellent in transparency and flexibility and also excellent in heat sealability. Low density polyethylene resins are most preferred for the purposes of the present invention. Of course, high density polyethylene resins may be employed for special applications. In particular, it is more suitable than a low-density polyethylene resin for an application that needs to withstand high temperature and high tension.

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 / c.
c, preferably 0.92 to 0.95 g / cc and a melting point (Tm) of usually 90 to 138C, preferably 100 to 130C.

Polypropylene resins are widely used for molds because of their higher melting point, higher transparency, higher rigidity and higher tensile strength than polyethylene, but are not used as widely as polyethylene for film applications. . The polypropylene resin used for the endothelial layer in the bag of the present invention is MF
R (230 ° C .; 2.16 kgf) usually 0.5 to 45 g / 10 min, preferably 2 to 12 g / 10 min, melting point (Tm) usually 125 to 160
° C, preferably 130 to 150 ° C. A wide variety of copolymers are also commercially available as the polypropylene resin, and examples thereof include a propylene-ethylene copolymer and a propylene-1-butene copolymer. Appropriate ones can be selected from these depending on the application.

<Production of Non-Curl Multilayer Film> In the co-extrusion water-cooled inflation molding for producing the non-curl multilayer film of the present invention, a multilayer tube is formed by co-extrusion from a concentric annular die with the following layer constitution. Mold: ◆ Core layer (B): Highly hygroscopic nylon, for example, 6-nylon, 66
-Nylon, a mixture of 6-nylon and 66-nylon, a co-condensate of 6-nylon and 66-nylon or a mixture of the highly hygroscopic nylon and a specific range of EVOH polymer (and / or PVOH), etc. ◆ Skin layer (E): low moisture-absorbing nylon such as 610-nylon, 612-nylon, 11-nylon, 12-nylon, meta-xylylenediamine-adipic acid co-condensate and meta-xylylenediamine-dicarboxylic acid Condensation polymer, mixture of 610-nylon and meta-xylylenediamine-dicarboxylic acid co-condensation polymer, mixture of 612-nylon and meta-xylylene diamine-dicarboxylic acid co-condensation polymer, and 610-nylon, 612-nylon and meta-xylylene diamine A mixture of a dicarboxylic acid co-condensation polymer or a mixture of the low-hygroscopic nylon with a small amount of a high-hygroscopic nylon, etc. ◆ Endothelial layer (F): A low-hygroscopic resin, for example, a polyolefin resin, especially a low-density polyethylene resin, is disposed. For applications in which a strong interlayer adhesion is required for 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 the adhesive polyolefin is used. A mode in which a resin adhesive layer is interposed can also be adopted.

At the time of molding, the multilayer inflation tube is rapidly cooled by passing it through an aqueous cooling medium such as water. The quenching treatment with the liquid refrigerant is useful for improving the dimensional accuracy and transparency of the multilayer film. The temperature of the liquid cooling medium is usually 10 to 60 ° C.
The passing linear velocity in the cooling medium is usually set at 5 to 80 m / min.

<Layer Structure of Non-Curl Multilayer Film of the Present Invention> The layer structure frequently used in the co-extruded water-cooled blown film of the present invention is, for example, as follows: ◆ The outer layer (E) has low hygroscopicity. , 10-nylon, 6,12-nylon, 11-nylon, 12-nylon, co-condensation polymer of meta-xylylenediamine and dicarboxylic acid such as adipic acid, 61
A mixture of 0-nylon and a meta-xylylenediamine-dicarboxylic acid co-condensation polymer, a mixture of 612-nylon and a meta-xylylene diamine-dicarboxylic acid co-condensation polymer, and 61
0-nylon and 612-nylon and meta-xylylenediamine-
At least one selected from a mixture with a dicarboxylic acid co-condensation polymer or a mixture of these low hygroscopic nylons with a small amount of a high hygroscopic nylon; ◆ the core layer (B) is made of a highly hygroscopic nylon such as 6 -Nylon, 66-
Nylon, a mixture of 6-nylon and 66-nylon or a co-condensate of 6-nylon and 66-nylon or an EVOH resin or PV which is highly hygroscopic with the highly hygroscopic nylon
A mixture with an OH resin or the like, for example, a mixture of 6-nylon and EVOH [6-NY / EVOH = 60/40 to 100/0 (wt / wt)]
The adhesiveness between the outer layer (E) and the core layer (B) is extremely strong and cannot be practically peeled off. ◆ The endothelial layer (F) is made of a polyolefin resin or the like, which is a low hygroscopic resin, and exists in a state where it is sufficiently strongly laminated further inside the core layer (B). For that purpose, the core layer (B) and the endothelial layer (F)
And an adhesive substance for promoting adhesion between the two layers. As another measure for improving the adhesiveness, it is important to blend maleic anhydride-modified polyolefin or the like as an affinity-imparting additive in at least one of the two layers.

<Thickness of Each Layer> The thickness of each layer of the non-curl multilayer film (including the sheet) of the present invention is as follows: Skin thickness: usually 3 to 20 μm, preferably 5 to 15 μm core Layer thickness: usually 10 to 50 μm, preferably 15 to 30 μm Endothelial layer thickness: usually 30 to 80 μm, preferably 40 to 70
μm Overall layer thickness (skin layer thickness + core layer thickness + endothelial layer thickness): usually 50 to
110 μm, preferably 60 to 90 μm.

The co-extrusion water-cooled inflation molding method essential in the molding method of the present invention is a method of co-extrusion inflation molding of each of the above-mentioned layers from, for example, a concentric annular die. At this time, a method of rapidly cooling the multilayer inflation tube through an aqueous cooling medium bath is called co-extrusion water-cooled inflation. Here, the aqueous cooling medium is usually water (including hot water), but also includes a mixture of various additives depending on the use of the product.

The number of layers constituting the multilayer film of the present invention is not particularly limited. In addition, the "skin layer (E)" which is an essential layer, the "core layer (B)" and the core layer which are located inside and are firmly adhered to the skin layer (E) and protected from curling.
There are no particular restrictions on the configuration or order of the other layers, except for the point composed of the hydrophobic endothelial layer (F) located inside (B) and the properties and order of each layer. Examples thereof are shown in Table 1. However, it is needless to say that one or more of the constituent layers may be a mixture of two or more resins of the same type.

<Definition of curllessness> In the present invention, the term "curllessness" naturally does not necessarily refer to a completely curlless state, that is, a state in which the radius of curvature in the curl of a test piece is infinite. . The case where the generated curl remains to the extent that it does not hinder practical use is also included in the “curllessness” of the present invention. More specifically, this is a comprehensive expression in a case where a value of at least 1.5 cm or more can be maintained in the radius of curvature (r) in the curl measurement method described above.

Of course, the state of the curl varies depending on the temperature and humidity of the outside air. That is, since the curl state of the same multilayer film also varies depending on the environment, it is difficult in principle to express and maintain the literally “curl-free” state.

[0046]

EXAMPLES Examples of various preferred embodiments of the present invention are shown below as examples, and aspects of the prior art are shown in Table 1 as comparative examples. What is described in the column of the radius of curvature of the curl in the table is the measurement result under the measuring method and the measuring conditions described in the specification text. The measurement results are shown in Table 2 below.

The melting point (Tm) of the resin in the present invention is
The temperature at which a peak is located in an endothermic curve of a sample observed using a differential scanning calorimeter (abbreviated as “DSC”). When two or more peaks are observed, the temperature at which the peak with the largest area is located is defined as the melting point.

Legends for resin abbreviations are as follows: 6-NY: 6-nylon [relative viscosity: 3.6; degree of polymerization: 250; molecular weight: 28,000; water absorption (ASTM D570): 1.3 to 3.5. %(twenty four
h)]; 66-NY: 6,6-nylon [relative viscosity 2.95; degree of polymerization 18]
0; molecular weight 20 × 10 <SUP> 3 </ SUP>; water absorption (ASTM D570)
1.2-2.5% (24h)]; 11-NY: 11-nylon [relative viscosity 1.48; degree of polymerization 18]
0; molecular weight 20 × 10 <SUP> 3 </ SUP>; water absorption (ASTM D570)
1.1-1.5% (24h)]; 12-NY: 12-nylon [relative viscosity 1.56; degree of polymerization 20]
0; molecular weight 23 × 10 <SUP> 3 </ SUP>; water absorption (ASTM D570)
0.25-0.75% (24h)]; 610-NY: 610-nylon [relative viscosity 2.7; degree of polymerization 16]
0; molecular weight 18 × 10 <SUP> 3 </ SUP>; water absorption (ASTM D570)
0.3-1.5% (24h)]; 612-NY: 612-nylon [relative viscosity 2.7; degree of polymerization 16]
0; molecular weight 18 × 10 <SUP> 3 </ SUP>; water absorption (ASTM D570)
MXDC: meta-xylylenediamine-dicarboxylic acid co-condensation polymer, a co-condensation polymer in which the dicarboxylic acid unit is adipic acid (MXD6) [MXV6] [relative viscosity 2. 7; molecular weight 2500
LDPE: low-density polyethylene [MI (190 ° C .; 2.16 kgf) 1.
HDPE: high density polyethylene [MI (190 ° C; 2.16 kgf) 1.
PP: polypropylene [MFR (230 ° C; 2.16 kgf) 10.5 g / 1]
0 min]. EVOH polymer: ethylene-vinyl alcohol copolymer [ethylene unit content: 32 mol%] <Layer composition, each operation of co-extrusion inflation molding and quenching and conditions thereof>-Endothelial layer (F): low density polyethylene, high density Polyethylene or polypropylene; Core layer (B): 6-nylon, 66-nylon or a mixture of 6-nylon and 66-nylon or EVOH resin or PVOH resin or a mixture of 6-nylon and EVOH,
A mixture of 66-nylon and EVOH or a mixture of 6-nylon, 66-nylon and EVOH; ・ Skin layer (E): 610-nylon, 612-nylon, 11-nylon, 12-nylon, meta-xylylenediamine- Adipic acid co-condensation polymer, mixture of 610-nylon and meta-xylylenediamine-dicarboxylic acid co-condensation polymer, mixture of 612-nylon and meta-xylylene diamine-dicarboxylic acid co-condensation polymer, 610-nylon, 612-nylon and meta Mixture with xylylenediamine-dicarboxylic acid co-condensation polymer; ・ Extrusion equipment: screw extruder with three-layer die ・ High moisture-absorbing resin used: <BR> ・ Nylon: 6-nylon, 66-nylon EVOH polymer: Extrusion temperature: 160 ° C (LDPE), 190 ° C (HDPE), 210
° C (PP), ・ Extrusion temperature: 250 ° C (6-NY), 290 ° C (66-NY), 25
0 ° C (610-NY), 215 ° C (EVOH polymer), 260 ° C (MXD
6); ・ Expansion ratio: about 1.5; ・ Cooling water temperature (° C.): 10 to 60 (outside 610-NY // core 6-NY)
// In the case of LDPE); ・ Linear velocity passing through the cooling water bath (m / sec): 5 to 80 (as above).

<Measurement and evaluation of curl> As shown in FIG.
Draw a square (5 cm 2 on a side) as a side on the sample multilayer film and make a radius of curvature (r) appearing at the curved portions of the four petal-like pieces formed by making cuts (x marks) on both diagonal lines.
Are measured and determined as their arithmetic mean. Table 2 shows the results.

It can be seen from Table 2 that the smaller the measured radius of curvature (r), the stronger the curl, and the larger the radius of curvature, the less the curl. In a multilayer film using a low moisture-absorbing nylon as the outer layer (E), the curl changes depending on environmental conditions such as humidity and temperature. However, from practical experience, if the radius of curvature measured by the above method at a temperature of 25 ° C. and a relative humidity of 60% is 1.5 cm or more, the multilayer film is made into a bag and the resulting bag is automatically filled. There is no particular problem due to curling in any of the steps.

[0051]

Examples 1 to 9 The types of various resins exemplified in Table 1,
An outer skin layer (E), a core layer (B), and an endothelial layer (F) were formed by selecting a combination of the layer thickness and the layer configuration with the molding equipment and molding conditions described above, and were laminated. Breakdowns of various non-curl laminated films (sheets) are listed in the column of "Structure of raw material" in Table 2, and their properties are "curl radius of curvature r (cm)" and "gloss (gloss)". It is shown in the column of “Product evaluation” in Table 2. here,
It should be noted that the smaller the value of "curl radius of curvature r (cm)", the more severe the curl.

[0052]

Comparative Example 1 Aspect of Example 1 ("No. 1" in Table 1)
A laminated film was prepared in the same manner as in Example 1 except that the skin layer resin in Example 1 was changed from 610-NY having low hygroscopicity to 6-NY having high hygroscopicity. The details of the laminated film (sheet) are listed in the column of "Structure of raw material" in Table 2, and the properties of "curl radius of curvature r (cm)" and "glossiness (gloss)" in Table 2 are shown in Table 2. Product evaluation ". It can be seen that the laminated film in this comparative example is much more severely curled than each laminated film in the example.

[0053]

[Table 2]

[0054]

【The invention's effect】

(1) According to the co-extrusion water-cooled inflation molding method of the present invention, the outer layer (E) has a low hygroscopic nylon such as 610-nylon, 612-nylon or meta-xylylenediamine-adipic acid co-condensed polymer or the like. Non-curl laminate, which is a laminate of three or more layers in which highly hygroscopic nylon such as 6-nylon or 66-nylon or EVOH resin or PVOH resin is used for the layer (B) and polyethylene is used for the endothelial layer (F). Multilayer films can be manufactured. (2) Multi-layer film obtained by performing co-extrusion water-cooled inflation molding with the above layer configuration is rich in luxury with high gloss and high transparency, which is the advantage of nylon, despite being non-curl. Become.

[Brief description of the drawings]

FIG. 1A is a front view of a bag made of a conventional curable multilayer film, and FIG. 1B is a schematic longitudinal sectional view of the bag taken along the line AA.

2 (a) is a schematic cross-sectional view of a conventional single-layer film made of a highly hygroscopic resin, and FIG. 2 (b) is a first embodiment of a three-layer film of the present invention. FIG. 2 is a schematic sectional view of FIG.
(c) is a schematic cross-sectional view of a laminate as a second embodiment of the three-layer film of the present invention, and FIG. 2 (d) is a schematic cross-sectional view of a laminate as a third embodiment of the three-layer film of the present invention. It is.

FIG. 3 (ap) is a plan view showing the position, direction and length of a cut for generating curl in a sample film,
FIG. 3 (bp) is a plan view of the state that occurs after the cut is formed in the sample film, and FIG. 3 (br) is a plan view of the state of (bp) of FIG. 3 viewed from the lateral direction.

[Description of Signs] 1 Bag itself made of conventional film 2 Non-curl three-layer film of the present invention (inclusive) 3 Entire cut-out portion for curl generation 11 Conventional multi-layer film 21 Non-curl of the present invention One embodiment of the three-layer film 22 Another embodiment of the non-curl three-layer film of the present invention 31 A portion divided by a cut provided on the sample film (upper side in the figure) 32 A portion divided by a cut provided on the sample film (Left side of the figure) 33 Part cut by a cut provided on the sample film (lower part of the figure) 34 Part separated by a cut provided on the sample film (right side of the figure) r Curled part of the sample film Curvature radius B1 Core layer constituting conventional multilayer film B2 Core layer constituting curlless multilayer film of the present invention (inclusive) E1 Conventional layer The outer layer constituting the multilayer film E2 The outer layer constituting the non-curl multilayer film of the present invention (inclusive) F2 The inner layer constituting the non-curl multilayer film of the present invention (inclusive) L1 The curl generated at the mouth of the bag Portion (front side of the drawing) L2 Curled portion generated at the mouth of the bag (opposite side of the drawing) B21 First embodiment of core layer constituting non-curling multilayer film of the present invention B22 Non-curling multilayer film of the present invention B23 Third embodiment of the core layer constituting the curl-free multilayer film of the present invention E21 First embodiment of the outer skin layer constituting the curl-free multilayer film of the present invention E22 None of the present invention E23 Second embodiment of outer skin layer constituting curlless multilayer film of the present invention E23 First embodiment of endothelial layer constituting curlless multilayer film of the present invention A third aspect of the endothelial layer of the non-curling multilayer film of the second aspect F23 invention endothelial layer constituting the non-curling multilayer film of 22 the invention

Continuation of the front page (56) References JP-A-7-205380 (JP, A) JP-A 7-1544 (JP, A) JP-A-5-57855 (JP, A) JP-A-62-234930 (JP) JP-A-5-329999 (JP, A) JP-A-5-77352 (JP, A) JP-A-2-22052 (JP, A) JP-A-4-216933 (JP, A) 1-225550 (JP, A) Fully open 1984-192332 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) B32B 1/00-35/00

Claims (7)

(57) [Claims] 1. A core layer (B) comprising a mixture of a highly hygroscopic nylon alone or a highly hygroscopic nylon described below and a small amount of one or more selected from EVOH polymers and PVOH polymers. The outer skin layer (E) is composed of a low-hygroscopic nylon alone or a low-hygroscopic nylon as shown below, and a small amount of the high-hygroscopic nylon as described below is added thereto, and the endothelial layer (F) is a polyolefin resin. A non-curl multilayer film comprising at least three layers consisting of plain or two or more polyolefin resins and produced by a co-extrusion water-cooled inflation method, wherein the highly hygroscopic nylon is 6-nylon, 66-nylon, 6 One or more selected from a mixture of -nylon and 66-nylon and a co-condensate of 6-nylon and 66-nylon, wherein the low-hygroscopic nylon is 610-nylon, 612-nylon, 11-nylon and 1
Non-curl multilayer which is one or more selected from 2-nylon
Film . 2. The core layer (B) is made of highly hygroscopic nylon 60-10.
EV with 0% by weight and ethylene unit content of 24 to 50 mol%
At least one selected from OH polymers and PVOH polymers;
The curl-free multilayer film according to claim 1, wherein the non-curl multilayer film is composed of -40% by weight and (combined so that the sum of both is 100% by weight). 3. An outer skin layer (E) comprising 60% to 100% by weight of at least one kind of low hygroscopic nylon and at least one kind of high hygroscopic nylon.
The curl-free multilayer film according to claim 1 or 2, which is composed of -40% by weight (combined so that the sum of both is 100% by weight). 4. The polyolefin resin of the endothelial layer has a density of 0.5.
88 to 0.97 g / cc, MI (190 ° C; 2.16 kgf) 0.1 to 30 g
Polyethylene resin having a melting point (Tm) of 90 to 138 ° C., a modified polyethylene resin alone or a mixture of two or more of these resins, or an MFR (230 ° C .; 2.16 kgf) of 0.5
The curl-free multilayer film according to any one of claims 1 to 3, which is a single polypropylene resin having a melting point (Tm) of 125 to 165C and a mixture of two or more of these resins. 5. The core layer (B) is composed mainly of the following highly hygroscopic nylon alone or highly hygroscopic nylon, and is made of EVOH.
A mixture containing a small amount of one or more selected from a polymer and a PVOH polymer is used as an outer layer (E), mainly composed of a low-hygroscopic nylon alone or a low-hygroscopic nylon as described below, and a high-hygroscopic type as described below. Water-cooled inflation molding of a mixture to which a small amount of water-soluble nylon is added, and a mixture of a polyolefin resin alone or a polyolefin resin as a main component and a small amount of the highly hygroscopic nylon described below added thereto as an endothelial layer (F). A method for producing a curl-free multilayer film, characterized by comprising 6-nylon, 66-nylon, 6-nylon as a highly hygroscopic nylon.
Mixture of nylon and 66-nylon and 6-nylon and 66-
One or more selected from co-condensation polymer of nylon, 610- nylon as a low hygroscopicity nylon, 612- nylon, free to use at least one member selected from 11-nylon and 12-nylon
A method for producing a curable multilayer film . 6. A highly hygroscopic nylon 60 or more as a core layer (B).
A mixture comprising 100% by weight and at least one selected from the group consisting of an EVOH polymer and a PVOH polymer having an ethylene unit content of 24 to 50% by mole (0 to 40% by weight).
% Of low-hygroscopic nylon alone or a mixture of 60 to 100% by weight of low-hygroscopic nylon and 40 to 0% by weight of high-hygroscopic nylon as the outer layer (E). The method for producing a curl-free multilayer film according to claim 5, wherein the polyolefin resin alone or a mixture of polyolefin resins is co-extruded and water-cooled inflation molding as the endothelial layer (F). 7. The polyolefin resin of the endothelial layer has a density of 0.5.
88 to 0.97 g / cc, MI (190 ° C; 2.16 kgf) 0.1 to 30 g
/ 10 min and a melting point (Tm) of 90 to 138 ° C., a polyethylene resin, a modified polyethylene resin alone or a mixture of two or more thereof, or an MFR (230 ° C .; 2.16 kgf) of 0.5 to 45.
The method for producing a curl-free multilayer film according to claim 5 or 6, wherein the resin is at least one selected from a polypropylene resin having a g / 10 min and a melting point (Tm) of 125 to 165 ° C, a modified polypropylene resin, and a mixture of both resins. .