JPS5949915B2 - Method for manufacturing laminates - Google Patents

Description

[Detailed Description of the Invention] The present invention uses a cloth made by weaving drawn synthetic resin yarn as one base material, and uses kraft paper, other papers, aluminum foil, etc. as the other base material. The present invention relates to a method for producing a laminate in which the following materials are bonded together by extrusion coating of a synthetic resin.

In recent years, in the field of heavy-duty packaging bags, so-called laminate packaging bags have been put on the market in which the drawbacks of single packaging materials are improved by using composite materials.

One of these is a laminate material that is made by weaving drawn threads of polyolefin synthetic resin such as polyethylene or polypropylene into cloth, which is bonded to kraft paper by extrusion coating molding of polyolefin synthetic resin such as polyethylene or polypropylene. There is a bag of ivy.

This type of bag is used as a packaging bag for plastics, raw salt, pulverized salt, powder for building materials, etc., but the cloth woven from drawn threads of polyolefin synthetic resin is bonded together by extrusion coating. As a result, the strength of the laminate bag decreases, and as a result, the strength of the laminate bag does not reach the originally expected level. That is, in the usual production of such laminates, practically sufficient adhesion to kraft paper cannot be obtained unless the molten web temperature of the polyolefin synthetic resin to be extrusion coated is about 300° C. or higher.

On the other hand, when a cloth woven from drawn yarns of polyolefin synthetic resin is extrusion coated at a molten resin web temperature of 300°C or higher, the drawn yarns are partially melted due to excessive heat and the stretching is relaxed, resulting in lower strength. It will drop. Conversely, if the molten polyolefin web temperature is lowered to, for example, 270°C in order to protect the strength of the woven fabric of polyolefin drawn yarn, this will result in insufficient adhesion between the coated polyolefin and the kraft paper. As a result, the strength of the laminate becomes weaker. In other words, in conventional lamination methods, regardless of the processing temperature selected, the strength of the manufactured laminate does not reach the value obtained by combining the strengths inherent in the base materials. , large and small reductions in strength have occurred. The present inventor conducted extensive research on this problem and arrived at the present invention. That is,
The present inventor has proposed that when manufacturing a laminate by laminating a woven fabric of drawn polyolefin yarn to kraft paper, other papers, aluminum foil, etc. using a molten web of polyolefin, the molten resin web and the substrates on both sides are bonded together. Focusing on the fact that each material adheres to the other material by a different mechanism, we adjusted the temperature on both sides of the molten resin web to be optimal for each material, and as a result, we were able to create a laminate with extremely high strength. It became possible to manufacture it.

The details are described below. Adhesion between the molten web of polyolefin and the woven fabric of drawn polyolefin yarn occurs when the molten resin web melts the surface of the woven fabric of drawn yarn.

The melt adhesion of the surface of the drawn yarn by this molten resin web varies depending on various conditions such as the thickness of the web, the air gap, the preheating condition of the drawn yarn woven fabric, and the lamination processing speed, but especially the influence of the temperature of the molten resin web. is the largest, and in terms of only adhesion, it is preferable that the temperature of the molten resin web be as high as possible within the range that allows lamination. By the way, the strength of polyolefin drawn yarn woven fabric is determined by the resin used, the thickness of the drawn yarn, the degree of stretching, the weaving density of the woven fabric (the number of yarns per unit length D), etc. When a molten web of polyolefin is bonded to a woven fabric of drawn polyolefin yarn, the surface of the woven fabric of the drawn yarn is melted by the heat from the molten resin web, which means that the stretching of the drawn yarn occurs at the same time that adhesion occurs. This means that it is partially relaxed, causing a decrease in strength. Therefore, from the viewpoint of preventing the strength of the drawn yarn woven fabric from decreasing,
It is preferable that the temperature of the molten resin web be as low as possible while laminating is possible. As described above, in thermal bonding of a woven polyolefin web and a woven fabric made of drawn polyolefin yarn, the temperature of the molten resin web has a contradictory relationship with the adhesive strength and the strength of the drawn yarn woven fabric.

As a result of various experiments conducted by the present inventor regarding this point, we found that when the coating thickness of molten polyolefin is 20 μm or more and the laminating speed is 40 m/min or more, the molten resin web temperature is 220°C or more, more preferably 240°C or more. It has been found that adhesion with the drawn yarn woven fabric is possible if the molten resin web temperature is 290° C. or lower, more preferably 280° C. or lower, and the strength of the drawn yarn woven fabric decreases very little. That is, when extrusion coating a woven fabric of drawn polyolefin yarn with molten polyolefin, the temperature of the molten resin web should be in the range of 220 to 290°C, more preferably in the range of 240 to 280°C, from the viewpoint of adhesion between the two and prevention of decrease in strength of the woven fabric. I found out that you can set it to . On the other hand, the adhesion between the molten polyolefin web and paper is due to chemical adhesion between the polar groups generated by oxidation of the polyolefin and the paper, and physical adhesion caused by the molten polyolefin penetrating into the gaps between the paper fibers. It depends on both adhesion.

In this case, the higher the temperature of the melted polyolefin, the more the oxidation of the resin progresses and the formation of polar groups, and the lower the viscosity of the melt, making it easier for the resin to seep into the gaps between the paper fibers, making it easier to bond. Improves sex. Bonding a molten polyolefin web to paper by extrusion coating typically requires a web temperature of 300 to 330°C. Further, when the base material is aluminum foil, the molten polyolefin must be oxidized to generate polar groups, and sufficient adhesion cannot be obtained unless the wafer temperature of the molten polyolefin is 300 to 330°C. In this way, when a woven fabric made of drawn polyolefin yarn is laminated with various types of paper, aluminum foil, etc. using a molten polyolefin web, the optimum temperature of the molten resin web for the woven fabric made of drawn polyolefin yarn is 220 to 290.
℃, more preferably 240 to 280°C, while the optimum molten resin web temperature for various substrates such as paper and aluminum foil is 300 to 330°C. FIG. 1 shows a conventionally known bonding method using extrusion coating.

In conventional laminating methods, lamination is performed by setting the molten resin web temperature at an intermediate temperature between the above two temperature ranges, for example 280 to 300°C, but this molten resin web temperature is optimal for each individual base material. Since the temperature is not high enough, the known method cannot obtain the strength that should be obtained by combining the strengths originally possessed by the base materials on both sides, resulting in a decrease in strength. In order to overcome this drawback of the known method, the present inventors have proposed using a coextrusion die to vary the temperature of the two sides of the molten polyolefin depending on the substrates in contact with each other, that is, the polyolefin drawn yarn woven fabric of the molten resin web. It was discovered that by lowering the temperature of the surface in contact with the material and setting the temperature of the surface in contact with various types of paper, aluminum foil, etc. to a high temperature, the strength of the bonded laminate can be greatly increased.

The woven fabric of the drawn yarn used in the present invention is preferably made of polyolefin synthetic resin such as polyethylene or polypropylene, and there are no particular specifications regarding the thickness, degree of stretching, weaving density, etc. of the drawn yarn. The other base material used in the present invention is bleached kraft, unbleached kraft, Kurupakku, bag-making paper and other papers, aluminum foil and laminates thereof, woven fabrics of natural or synthetic fibers, stretched nylon film, stretched polyester. It does not matter if it is a plastic film such as film. Extrusion coating resins used in the present invention include polyolefin-based synthetic resins such as polyethylene and polypropylene, ethylene-propylene copolymers, and copolymers of ethylene or propylene with butene-1, benzene-1 and other α-olefins, Also included are copolymers of ethylene and acrylic acid or methacrylic acid, copolymers of ethylene and acrylic ester or methacrylic ester, and blends of two or more of these.

The kraft paper, other papers, or aluminum foil used in the present invention may be subjected to extrusion coating as is, but it is more preferable to undergo preheating treatment using a heat roll or infrared heater, flame treatment, corona discharge treatment, etc. to improve adhesion. It is better to treat it.

In the present invention, a coextrusion coating device is used to create a temperature difference between the surface of the molten resin web in contact with the drawn yarn woven fabric and the other surface in contact with a base material such as paper or aluminum foil.

There are three types of coextrusion coating equipment: black box method, multi-manifold die method, and two-slot die method, depending on the method of merging multiple resins used.
Either type of device may be used in the present invention. Among these, a 2-slot die is most suitable because it has two separate flow paths for the resin from the inlet to the outlet of the die and can therefore create a large temperature difference between the resins. The present invention will be explained below with reference to the drawings. FIG. 1 shows a conventionally known bonding method using extrusion coating, in which the polyolefin resin A melt-kneaded inside the extruder passes through the joint part 2 and is heated by heaters 5 and 5'. The resin is guided into the die 1, expanded in the width direction of the die by the manifold 3, and then extruded out of the die through the J die lips 4 and 4'0 to become a molten resin web a.

This molten resin web a is a woven fabric Y of polyolefin drawn yarn.
and a base material X such as paper or other paper or aluminum foil, and is pressed against a cooling roll 7 by a nip roll 6 to bond the base materials X and Y together. At this time, the temperature of the molten resin web a directly under the die is such that, as described above, the strength decreases due to adhesion with the drawn yarn woven fabric Y and thermal deterioration of the woven fabric Y, and furthermore, the adhesion with paper or aluminum foil x. Taking everything into consideration, the temperature is usually set at 280 to 300°C.
With conventionally known methods, it is impossible to change the temperature of the surface of the molten resin web a in contact with the base material x and the surface in contact with the base material Y. Since the above-mentioned molten resin web temperature is not the optimum temperature for each of the base materials x and Y, in the known method, the strength that should be obtained by the combination of the strengths originally possessed by the base materials x and Y is is not obtained, resulting in a decrease in strength. Second
3 and 4 show an example of the method for manufacturing a laminate according to the present invention.

Figure 2 shows the bonding method using the black box method.
FIG. 3 shows a bonding method using a multi-manifold die method, and FIG. 4 shows a bonding method using a two-slot die method. In FIG. 2, resin A that has been melt-kneaded at a temperature of 300° C. or higher in the first extruder is led to a black box 8 via a joint section 10.

Also, in the second extruder, resin A. ). Resin B, which has been melted and kneaded at a low temperature, is similarly led to the black box 8 via the joint section 9. Resin A and B are black box 8
The two layers merge at the internal confluence point 11 to form two layers), enter the extrusion die 12 in that state, and are expanded in the die width direction by the manifold 13, then die lips 14 and 14'.
f) Extruded as a two-layer web through the gap and out of the die. This molten resin web is composed of layer a made of high-temperature resin A and layer b made of low-temperature resin B. Layer a is in contact with base material X such as paper or aluminum foil, and layer b is made of polyolefin. The drawn yarn is dropped between the base materials X and Y so as to contact the woven fabric Y, and is pressed onto the cooling roll 7 by the nip roll 6, thereby bonding the base materials x and Y together. At this time, the resin temperature directly under the die of the a layer of the molten resin web in contact with the base material X such as various papers or aluminum foils is determined by the presence or absence of pre-treatment of the base material X, its degree, the air gap, the take-up speed, etc. Depending on the molding conditions, 300 to 3
The temperature is set to 30°C. Further, the resin temperature of layer B of the molten resin web in contact with the woven fabric Y of the polyolefin drawn yarn is set to 220 to 290°C, more preferably 240 to 280°C. In order to create a temperature difference between layer a and layer b of the molten resin web,
In addition to setting a temperature difference in advance between the resins A and B entering the black box 8, it is also possible to set a difference in temperature on both sides of the extrusion die 12, which are heated by the heaters 15 and 15'. It is valid. Note that resins A and B may be the same resin or different resins. In Fig. 3, 16 indicates the multi-manifold die body;
17 and 18 are the joint parts of the die, and 19 and 2 are the joint parts of the die, respectively.
0 is the manifold, 21 is the confluence of the two resins, 22, 224 is the die lip, and 23, 234 is the confluence point of the two resins.
Each shows a heater.

In the multi-manifold die method as well, the bonding process is carried out in the same manner as in the case of the above-mentioned box box method. A multi-manifold die is different from a black box die in that the two resins join together after the resins are spread in the width direction of the die, and that the distance from the merge point to the die exit is shorter than that of a black box die. Both of these points are advantageous in creating a temperature difference between the a layer and the b layer of the molten resin web.
FIG. 4 shows a 2-slot die system.

In FIG. 4, resin A melted and kneaded at a temperature of 300°C or higher in the first extruder is led to the two-slot die 24 through the joint part 26, expanded in the die width direction by the manifold 28, and then It passes between the plate 29 and the die jaw 30 and is extruded out of the die to become a molten resin web a. On the other hand, resin B, which was melt-kneaded at a lower temperature than resin A in the second extruder, is similarly led to the two-slot die 24 via the joint part 25, and after being expanded in the die width direction by the manifold 2T, it is inserted into the partition plate. 29 and the die jaw 30' (7), and is extruded out of the die to become a molten resin web b. At this time, the temperature of the molten resin web a is 300 to 330°C directly below the die, and the temperature of the molten resin web b is 220 to 290°C, preferably 240 to 280°C, directly below the die. The temperatures of the resins A and B and the temperatures on both sides of the two-slot die 24 heated by the heaters 31 and 31 are set. These molten resin webs a and b are arranged in such a way that the high temperature a contacts the base material X such as paper or aluminum foil, and the low temperature b contacts the woven fabric Y of polyolefin drawn yarn. :． The base materials X and Y are bonded together by being dropped into the middle of Y and pressed onto the cooling roll 7 by the nip roll 6. The laminate thus obtained according to the present invention has much better mechanical strength than the laminate manufactured by the known laminating method shown in FIG. As described above, according to the present invention, by laminating a woven fabric of drawn polyolefin yarn and a base material such as paper or aluminum foil with a molten web of polyolefin synthetic resin, the adhesive strength between each layer is sufficiently strong. It has become possible to produce a laminate with extremely superior strength compared to conventional laminates with the same structure, without any decrease in the strength of the reeds or drawn yarn woven fabric.
Example Low density polyethylene [Milason 11 manufactured by Mitsui Polychemicals (Ml 6.5, density 0.917) was produced using the first extruder.
], and low density polyethylene [Milason 68 manufactured by Mitsui Polychemicals (Ml23, density 0.916
)] are melt-kneaded and introduced into a 2-slot type coextrusion die, and extruded through the coextrusion die.
The temperature of the resin directly under the die is set so that the temperature of the resin extruded from the first extruder side is 310℃, that of the resin extruded from the second extruder side is 270℃, and the temperature of the resin extruded from the first extruder side is 270℃. The molten web of the resin extruded from the second extruder was placed in contact with the 45t/Cfl kraft paper, and the molten web of the resin extruded from the second extruder was coated with high-density polyethylene flat yarn cloth (weaving density, 12 x 12 yarns/cross). Co-extrusion was carried out so that the paper/polyethylene/
A laminate of cross yarn composition was obtained.

The physical properties of the obtained laminate are shown in the table below.

The strength was stronger than that of Comparative Examples 1, 2, and 3 described below, and the adhesion between each layer was also sufficient. Comparative Example 1 Low-density polyethylene (Mirason 11) was melt-kneaded in an extruder, and a single-layer molten resin web was extruded from a normal extrusion die under conditions such that the resin temperature directly below the die was 270°C. A laminate was obtained by extrusion coating so as to bond the two base materials described in Examples with a resin web.

At this time, the coating thickness of the low density polyethylene was 20 μm, and the acceleration was 100 m/min. The physical properties of the obtained laminate are shown in the table. Comparative Example 2 Low density polyethylene in Comparative Example 1 (Mirason 11)
The lamination process was carried out in the same manner as in Comparative Example 1 except that the resin temperature immediately below the die was 310°C.

Table 1 shows the physical properties of the obtained laminate. Comparative example
3 Low density polyethylene in Comparative Example 1 (Mirason 11)
Lamination was carried out in the same manner as in Comparative Example 1, except that the resin temperature immediately below the die was 290°C.

The physical properties of the obtained laminate are shown in the table.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating a method for manufacturing a laminate using a conventionally known processing method, and FIGS. 2, 3, and 4 are diagrams explaining a method for manufacturing a laminate according to the present invention. 6...Nippro roll, 7...Cooling roll, 8...(...Packbox, 9,17,2
5...Low temperature side joint part, 10, 18, 26
...High temperature side joint part, 11, 21...
...Confluence point, 12...Die, 13, 19, 20
, 27, 28... Manifold, 14, 14,
22, 22, 30, 30... Dailip, 15
, 15, 23, 23, -31, 31...Heater, 16...Multi-manifold die, 24.
...2-slot die, 29...partition plate, A...high temperature resin, B...low temperature resin,
a...High temperature molten resin web, b...Low temperature molten resin web, X...Base material such as paper or aluminum foil, Y...Polyolefin stretching Woven yarn fabric.

Claims (1)

[Scope of Claims] 1 One base material is a cloth made by weaving drawn synthetic resin threads, paper, aluminum foil, etc. is used as the other base material, and both base materials are extruded and coated with synthetic resin. In a method for producing a laminate that is bonded together by a coextrusion die, the temperature of the side of the molten web of synthetic resin that is extrusion coated using a coextrusion die, which is in contact with the cloth woven from the drawn synthetic resin threads, is lowered to the other base material side. A method for manufacturing a laminate, characterized by making the temperature lower than the temperature of the surfaces in contact with each other. 2. A patent claim characterized in that the cloth serving as one of the base materials is a cloth woven from drawn threads of polyolefin-based synthetic resin, and the molten web of synthetic resin to be extrusion coated is a molten web of polyolefin-based synthetic resin. A method for producing a laminate according to item 1. 3 The temperature of the surface of the molten web of synthetic resin to be extrusion coated that contacts the cloth woven from the drawn synthetic resin threads is 24
0°C to 280°C, and the temperature of the surface in contact with the other substrate such as paper or aluminum foil is 300°C to 330°C.
A method for producing a laminate according to claim 1 or 2, characterized in that: