JPH0325351B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Field of Application] The present invention relates to a multilayer laminated film. More specifically, the laminated film has a laminated structure in which two sheets of a laminated film including a film having uniaxial orientation and at least two or more layers including a layer having uniaxial orientation are bonded together by an adhesive layer, and the laminated film The present invention relates to a multilayer laminated film in which the orientation direction of one of the orientation layers is laminated such that the orientation direction of one of the orientation layers intersects the orientation direction of the other orientation layer. [Prior Art] By laminating two uniaxially oriented single-layer sheets so that the orientation direction of one of the sheets intersects the orientation direction of the other sheet, the tensile strength in the longitudinal and lateral directions can be increased.
The fact that a film with excellent tear strength and balance can be obtained is disclosed in Japanese Patent Publication No. 5319 of 1972 and Japanese Patent Publication No. 42 of 1973.
14191, and Japanese Patent Publication No. 47-38621. However, since the outer layer of such an oriented laminated film is uniaxially oriented, it is difficult to heat seal it. Therefore, when making bags from the film, methods such as hot-melt adhesive and sewing must be used, which has the drawback of complicating the process. [Problems to be Solved by the Invention] That is, an object of the present invention is to provide a multilayer laminated film that has excellent tensile strength and tear strength, is well balanced in length and width, and has heat sealability. [Means for Solving the Problems] The present invention comprises: () a layer made of synthetic resin A selected from polypropylene or high-density polyethylene and having uniaxial orientation; and () a layer also made of synthetic resin A and having uniaxial orientation. () are laminated so that their orientations intersect with each other via an adhesive layer made of a thermoplastic resin having a lower melting point and heat adhesive properties than the synthetic resin A, and the synthetic resin A
A substantially non-oriented layer made of a synthetic resin B having a melting point lower than that of the synthetic resin A is laminated by co-extrusion on the side not facing the layer and/or the adhesive layer. It is a multilayer laminated film. [Operation] The multilayer laminated film of the present invention has a multilayer structure as illustrated in FIGS. 1 and 3. 2 and 4 are explanatory diagrams illustrating the positional relationship of each layer of the multilayer laminated film of FIGS. 1 and 3, respectively. The multilayer laminated film of the present invention will be explained with reference to FIGS. 1 and 2. The layer is made of a synthetic resin A selected from polypropylene or high-density polyethylene, and is uniaxially oriented. It is made of the same synthetic resin A and is also uniaxially oriented. It is preferable that the degree of orientation of the resin in the layer and the layer is the same. is an adhesive layer made of a thermoplastic resin with a lower melting point than synthetic resin A and heat-adhesive properties, such as low-density polyethylene, ethylene/vinyl acetate copolymer, or ethylene/acrylic acid ester copolymer, or synthetic rubber, such as ,ethylene·
It is formed from propylene rubber, ethylene-propylene-diene rubber, styrene-butidiene rubber, polybutadiene, chloroprene rubber, chlorinated polyethylene, polyisobutylene, etc., and mixtures thereof. In the present invention, by using a thermoadhesive resin with a lower melting point than the synthetic resin of the layers as the adhesive layer, the uniaxial orientation of the layers is relaxed or eliminated when the layers are laminated. It is possible to obtain a multilayer laminated film with excellent strength. In the multilayer laminated film of the present invention, the above-described synthetic resin A layer having uniaxial orientation and the synthetic resin A layer having uniaxial orientation are positioned adjacent to each other with an adhesive layer interposed therebetween. However, Figure 2
As shown in the figure, the layers are provided so that their orientation directions intersect. By arranging the layers in such a positional relationship, a film with excellent tensile strength and tear strength and well-balanced length and width can be obtained. It is preferable that the layers are oriented obliquely to the longitudinal direction of the film because manufacturing is easy. In the multilayer laminated film of the present invention, as illustrated in FIGS. 1 to 4, the synthetic resin B having a melting point lower than the melting point of the synthetic resin A is provided on the side not facing the synthetic resin A layer and/or the adhesive layer. A layer consisting of is formed. 1 and 2 are examples in which synthetic resin B layers and ' are provided on the outer surfaces of synthetic resin A layer, and FIGS. 3 and 4 are examples in which synthetic resin B layers are provided only on the outer surface of synthetic resin A layer. This is an example. The synthetic resin B is a different type of resin from the synthetic resin A, and is selected from a resin that has a lower melting point than the synthetic resin A and has good heat sealability. The synthetic resin layer B,' is a substantially non-oriented layer. The layers may be provided on both outer surfaces of the layers, as shown in FIG. 1, or may be provided only on the outer surface of the layers or one of the layers, as shown in FIG. Such an unoriented layer,
The synthetic resin B forming the compound ' usually has a melting point lower than that of the synthetic resin A described above, preferably a melting point lower by 20°C or more, and such characteristics can impart heat-sealing properties to the film of the present invention. . The and 'layers may be made of the same type of synthetic resin or may be made of different types of synthetic resin. In the present invention, the synthetic resin ' is not limited to a single layer, but may be composed of two or three or more layers. Examples of the structure of the multilayer laminated film of the present invention include ethylene/vinyl acetate copolymer/uniaxially oriented high density polyethylene/low density polyethylene/uniaxially oriented high density polyethylene, ethylene/α-olefin copolymer/uniaxially oriented high density Polyethylene/low density polyethylene/uniaxially oriented high density polyethylene,
Four-layer structure of ethylene/vinyl acetate copolymer/uniaxially oriented polypropylene/propylene-α-olefin random copolymer/uniaxially oriented polypropylene,
Ethylene/vinyl acetate copolymer/uniaxially oriented high density polyethylene/low density polyethylene/uniaxially oriented high density polyethylene/ethylene/vinyl acetate copolymer, ethylene/α-olefin copolymer/uniaxially oriented polypropylene/propylene/α-olefin Examples include random copolymer/uniaxially oriented polypropylene/ethylene/vinyl acetate copolymer. As a method for producing the multilayer laminated film of the present invention as described above, from an industrial production standpoint, it is preferable to rely on the production method described below. In the manufacturing method of the present invention, FIG. 5, FIG. 6 or FIG.
A device such as the one illustrated in is used. An example of an apparatus suitable for producing the multilayer laminated film of the present invention will be explained with reference to FIG. 5, where 1 is a first extruder and 2 is a second extruder. 19 and 20 are adapters. 3 is a fixed multi-layer annular die;
1 and 22 are annular slits. First extruder 1
The resin melted in the second extruder 2 is extruded from the inner annular slit 21 of the multilayer annular die 3, and the resin melted in the second extruder 2 is extruded from the outer annular slit 22 of the multilayer annular die 3. A flow path is formed. 4 is an outer layer tubular film, 5 is an inner layer tubular film, and 6 is a multilayer tubular film. Reference numeral 7a denotes a first mandrel fixedly provided on the upper part of the annular die 3 on a concentric axis. 9a is a second mandrel provided on a concentric shaft downstream of the first mandrel, and this second mandrel is provided so as to be rotated about the central axis by a motor 15. Annular suction slits 8 and 10 are provided on the surfaces of the first mandrel 7a and the second mandrel 9a, each communicating with a suitable external pressure reduction device (not shown). Coolant and/or heat medium circulation paths are appropriately formed inside the first mandrel 7a and the second mandrel 9a to adjust the temperature of the mandrels. Reference numeral 11 denotes a rotary table, which rotates the second mandrel on the same axis as the second mandrel 9a by means of a driving motor 18.
It is provided so that it can rotate in synchronization with the mandrel 9a. Reference numeral 12 denotes a tension roll, which is installed on the rotary table and serves to stretch the two-layer tubular film 6 and send it to a winding roll or the like for the next process. Reference numeral 17 denotes an air hole for expanding the tubular film extruded from the annular die, and is connected to an appropriate air introduction pipe (not shown). An air ring 14 blows a refrigerant, usually air, from the outer surface of the multilayer tubular film 6 through an annular slit (not shown) to cool the film. Reference numeral 16 denotes a slack prevention plate, which is provided so as to freely rotate independently of the first mandrel 7a and the second mandrel 9a. FIG. 6 shows an example in which an outer cylinder 9b is used in place of the second mandrel 9a in the manufacturing apparatus shown in FIG. The outer cylinder 9b is located on the downstream side of the same central axis of the first mandrel 7a, and is provided so as to be rotated about the central axis by a motor 15 in synchronization with the rotary table 11. Note that in this method, synchronously rotating means rotating in the same direction and at the same rotation speed. An annular suction slit 1 is provided on the inner surface of the outer cylinder 9b.
0, and the slit communicates with a suitable external pressure reducing device (not shown). FIG. 7 shows extruders 1 and 2 in the manufacturing apparatus shown in FIG.
This is an example of an apparatus in which the first mandrel 7a rotates in synchronization with the rotation of the extruder, while the second mandrel 9a and the tension roll 12 are fixed or rotate in reverse. Since the tension roll 12 is fixed, there is no need to provide a turntable. Although the two extruders are rotated in the apparatus of FIG. 7, similar results can be obtained even if the extruders 1 and 2 are fixed and the multilayer annular die 3 is rotated (not shown). As described above, an apparatus that can be used in such a manufacturing method includes two or more extruders, an adapter, a multilayer annular die, a first contact tube guide, a second contact tube guide, a tension roll, and The multilayer annular die and the first contact tube guide are synchronized, the second contact guide and the tension roll are synchronized, and there is no relative rotation between the first contact tube guide and the second contact tube guide. Various embodiments are possible as long as a difference can be formed. An example of the method for manufacturing the multilayer laminated film of the present invention will be explained based on the drawings. First, the synthetic resin A is heated and melted in the first extruder 1, and is supplied to the multilayer annular die 3 via the adapter 19, and then the internal annular slit is 21 as the inner annular film 5. On the other hand, the synthetic resin B is similarly melted in the second extruder 2, supplied to the multilayer annular die 3 through the adapter 20, and extruded as the outer annular film 4 through the outer annular slit 22. Techniques and equipment for extruding multilayer tubular film 6 by melting and coextruding two or more synthetic resins have already been described.
Modern Plastics, 46, 128 (Jan 1969), Tokko Sho
No. 41-13628. Although FIGS. 5, 6, and 7 illustrate an example in which two extruders are used to extrude a two-layer laminated film, three or more extruders are used to extrude a two-layer laminated film. A technique for extruding a film or a technique for extruding a laminated film consisting of three or more layers using two extruders are both examples of the method for producing a multilayer laminated film of the present invention. In addition, in FIGS. 5 to 7, the multilayer annular die 3
The inner annular slit 21 and the outer annular slit 2
2, but instead of such a die, in the die, the annular flow path of synthetic resin A and the annular flow path of synthetic resin B flow together and are extruded from one annular slit. It's okay to get used to it. Next, the extruded multilayer tubular film 6 is expanded by the expansion pressure air blown out from the air hole 17, and then cooled and solidified while contacting the first contact tube guide, and then moved downstream. If the multi-layer tubular film 6 is insufficiently cooled due to high-speed molding, etc., an air ring 14 may be provided to blow a cooling medium, particularly air, onto the outer surface of the multi-layer tubular film 6. Note that the contact tube guide in this method refers to a means for sliding the tubular film 6 in contact with each other to cool or heat the film, as shown in FIG.
and inside mandrel 7a in FIG.
and 9a correspond to the inside mandrel 7a and the outer cylinder 9b in FIG. These contact tube guides are provided with annular suction slits 8, 10 in which the suction force applied by the vacuum source brings the film 6 into close contact with the circumferential surface of the contact tube guides. This suction force can be changed by changing the degree of vacuum, but the frictional force between the contact tube guide circumferential surface and the film 6 is applied to the film 6 in an oblique orientation, which will be described later, while the film 6
It is important to adjust the degree of vacuum so that it can move to the receiving side. The multilayer tubular film 6 that has passed through the first contact tube guide comes into contact with the outer periphery of the annular deflection prevention plate 16 . It is preferable to provide the deflection prevention plate 16 in order to obtain a uniform film, and it is in close contact with the inner surface of the film 6 and freely rotates as the film rotates. The multilayer tubular film 6 that has moved further downstream is
Closely contacts the circumferential surface of the second contact tube guide. In such a manufacturing method, any or all layers of the multilayer tubular film 6 are given an oblique orientation by the relative rotation that occurs between the first contact tube guide and the second contact tube guide. Therefore, the number of rotations of this relative rotation is closely related to the direction of orientation imparted to any or all layers of the multilayer tubular film 6. In the application intended by the present inventor, the direction of orientation of the film is preferably 30 to 60 degrees with respect to the longitudinal direction of the film 6. In this manufacturing method, the structure of the first contact tube guide and the second contact tube guide and the temperature of the multilayer tubular film 6 between the first contact tube guide and the second contact tube guide are important. By selecting these conditions, it is possible to produce laminated films with different degrees of orientation. First, as shown in Fig. 5, the first
When a second inside mandrel 9a is used as a second contact tube guide (referred to as method a), the first mandrel and the second
The temperature of the innermost layer of the multilayer tubular film 6 in contact with the mandrel of the synthetic resin A forming the layer is
temperature range, usually between the melting point and the second order transition point, preferably between (melting point -3°C) and (melting point -30°C)
℃). By being in this orientation temperature range, the innermost layer of the multilayer tubular film 6 is obliquely oriented due to the relative rotation that occurs between the two mandrels. On the other hand, the temperature of the other layer of the multilayer tubular film is the same as the temperature of the synthetic resin B forming the layer.
The temperature must be higher than at least the orientation temperature range of the synthetic resin B, which is usually higher than the melting point of the synthetic resin B. If the temperature is lower than this temperature, the obliquely oriented film that is the object of the present invention cannot be obtained. From the above temperature relationship, in method a, it is easier to select a resin having a higher melting point than the resins forming the other layers as the synthetic resin A forming the innermost layer. Next, as shown in FIG. 6, when the inside mandrel 7a is used as the first contact tube guide and the outer tube 9b is used as the second contact tube guide (referred to as method b), the synthetic resin A forming the innermost layer is oriented. Must be within temperature range. Next, although not shown, in contrast to method b, the case where an outer cylinder is used as the first contact tube guide and an inside mandrel as the second contact tube guide (referred to as method c) is similar to method b. I can say that. Furthermore, although not shown, a first outer cylinder is used as a first contact tube guide, and a second outer cylinder is used as a second contact tube guide.
When using the outer cylinder (referred to as d method), it corresponds to the same conditions as in method a, where the innermost layer is changed to the outermost layer, synthetic resin A is read as synthetic resin B, and synthetic resin B is read as synthetic resin A. A multilayer tubular film having two types of orientation is obtained. The multilayer tubular film 6, which has been obliquely oriented by the above methods a to d, is coated with an adhesive supplied from the slit of the second mandrel 9a on its inner surface as necessary. Then, the second mandrel 9a is expanded while being appropriately expanded so as not to cause sagging or wrinkles.
A pair of tension rolls 12 provided on a rotary table 11 that rotates in synchronization with the drawings are drawn into a flat shape, and at the same time, they are pasted together with an adhesive and sent to a winding section (not shown). In addition, in the methods a to d, when the adhesive is not applied to the inner surface of the multilayer tubular film 6, the multilayer tubular film 6 is folded by the tension roll 12 and then cut by a slitter (not shown). The two flat composite films P are then laminated together by another lamination method, such as an extrusion lamination method or a dry lamination method, to produce the desired multilayer laminated film. In this lamination method,
One of the two composite films to be laminated is the composite film P manufactured by the method described above, and the other film Q is considered to be one of the following three cases. It will be done. (1) A film with a laminated structure symmetrical to the composite film P. (2) A film in which the obliquely oriented layer is symmetrical to that of the composite film P, but the non-oriented layer is different. (3) Single layer film of obliquely oriented synthetic resin A. Among these, the composite films Q of (1) and (2) can be manufactured by the method for manufacturing multilayer tubular films described above. on the other hand
The method (3) for producing a single-layer obliquely oriented film is already known and can be produced by using only one extruder in the production apparatus used in the production method of the present invention. No. 48-100464, Special Publication Showa 53
It can be manufactured using an apparatus such as No.-18072. According to the dry lamination method or the extrusion lamination method, various composite films Q can be selected in this way, but in any case, the orientation layer of the film P and the orientation layer of the film Q are symmetrical, and the orientation layer of the film P is symmetrical. It is important to bond so that the orientation direction and the orientation direction of the film Q intersect. [Effects of the Invention] As described above, in the multilayer laminated film of the present invention, layers having uniaxial orientation are laminated via an adhesive layer made of a thermoadhesive resin with a lower melting point than the layers. In order to achieve strong lamination without relaxing or losing the uniaxial orientation of the layers, a synthetic resin with excellent strength and a high melting point was selected as the resin for the inner layer, and as the resin for the outer layer,
By selecting a resin with low melting point and heat-sealing properties, it is possible to obtain an oriented laminated film that has excellent tensile strength and tear strength, is well-balanced in length and width, and has heat-sealability. Bag making of oriented laminated films, which previously relied on adhesives or sewing using sewing machines, can be carried out extremely easily by heat sealing. Example 1 Synthetic resin A is high-density polyethylene (product name:
A layer with uniaxial orientation (Hi-zex5300S) and the same layer are extruded at 280℃ using low-density polyethylene (product name: Mirason 16) at 280℃, and the orientation of the layers intersects. It was pasted like this. Although this extrusion lamination is performed at a relatively high temperature as mentioned above, it is cooled by a cooling roll at the same time as the lamination, so the orientation of the layers does not relax or disappear, resulting in a laminated layer with excellent physical properties. You get a body. The physical properties are shown in Table 1.

[Table] In the table, the tensile strength of layer indicates the strength in the orientation direction. The above laminated film is made of low density polyethylene (product name: Mirason 16) as synthetic resin B on the outside of the layer.
was formed, and it was possible to heat seal with a good appearance without relaxing the orientation of the layers and with almost no shrinkage. Reference Example The same procedure as in Example 1 was carried out except that the layers were laminated using a commonly used isocyanate adhesive. The physical properties are shown in Table 2.

[Table] Similar to Example 1, the heat sealing of the bonded film was excellent. Comparative Example 1 The same procedure as in Example 1 was carried out except that the layers were heat-sealed at 220°C. The layers were shrunk by heat, and the appearance was wrinkled, making it unusable. The physical properties are shown in Table 3.

[Table] Comparative Example 2 The same procedure as Comparative Example 1 was carried out except that the layers were heat-sealed at 160°C. The resulting laminate film also had poor appearance and poor physical properties due to shrinkage. The physical properties are shown in Table 4.

[Table] Comparative Example 3 The same procedure as Comparative Example 1 was carried out except that the heat sealing temperature was 130°C. As a result, the layer merely blocked and was easily peeled off, making it unusable for practical use.

[Brief explanation of drawings]

1 and 3 are cross-sectional views showing an example of the multilayer laminated film of the present invention, and FIGS. 2 and 4 are explanatory views showing the positional relationship of each layer of the multilayer laminated film of FIGS. 1 and 3, respectively. FIG. 5, FIG. 6, and FIG. 7 are explanatory diagrams showing an example of an apparatus used in the method for manufacturing a multilayer laminated film of the present invention. 1, 2...Extruder, 3...Multilayer annular die, 4...
... Outer layer tubular film, 5... Inner layer tubular film,
6...Multilayer tubular film, 7a...First mandrel, 9a...Second mandrel, 9b...Outer cylinder, 8, 10...Annular suction slit, 11...Rotating table, 12...Tension roll , 13...Rotary joint, 14...Air ring, 16...Sag prevention plate, 17...Air hole, 18...Motor, 19, 20...Adapter.

Claims (1)

[Scope of Claims] 1 () A layer made of synthetic resin A selected from polypropylene or high-density polyethylene and having uniaxial orientation, () A layer also made of synthetic resin A and having uniaxial orientation, () Synthesis The synthetic resin A is laminated so that the orientation thereof crosses through an adhesive layer made of a thermoplastic resin having a lower melting point and heat adhesive properties than the resin A, and the synthetic resin A
A substantially non-oriented layer made of a synthetic resin B having a melting point lower than that of the synthetic resin A is laminated by coextrusion on the side not facing the layer and/or the adhesive layer. Multilayer laminated film.