JPH0628952B2 - Laminating method of plastic film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a method for laminating a plastic film. Plastic film usually has a thickness of 0.1 m
What is less than or equal to m, and more than that is called a plastic sheet, but here we will use it as a concept that includes both.

(b) Conventional technology In the case of forming a composite by laminating plastic films, a plastic film may be adhered to the surface of a substrate by a so-called coating, or by a laminate, A, B2.
In some cases, different types of base materials may be attached via an adhesive layer.
Further, in recent years, the film molding technology by the extrusion molding method has advanced, and two kinds of thermoplastic synthetic resins A and B are simultaneously extruded,
A method in which resins are fusion-bonded and laminated until they come out of the mold has come to be used. As the base material, plastic film, paper, metal foil, woven fabric, etc. are used. As the adhesive layer, in addition to various adhesives originally used as adhesives, plastic film as seen in the melt extrusion laminating method. In some cases, it itself functions as an adhesive. In any case, each is a means that has been used to combine the functions possessed by each layer to provide a higher-performance film material. Will be called.

Further, in the present specification, the term “laminate” is used as a concept including not only a base material such as a sheet or a film but also sandwiching thin sheets of various shapes between a plurality of sheets or films in a sandwich shape. The thin material is not limited to plastic, and includes woven and knitted fabrics, pressed flowers, butterfly specimens, trees and bamboo leaves, all of which have a small thickness. Further, it may be a powder or a granular material which cannot be generally called a thin material.
After all, any material can be used as long as it can be sandwiched between plastic films or sheets in a continuous or discontinuous layered form.

The need for laminates has become more demanding for the functions of various industrial material fields, and in many cases the performance of a single plastic material cannot be satisfied, and this is increasing more and more in recent years.

The most commonly used field of laminated products is the individual packaging of food and medical products, and recently, magnetic cards are often used. In addition, it is difficult to stand out for things such as various building materials, automobile interior materials, stationery, miscellaneous goods, and various home appliances that are attached to other things, but if you include these things, laminated products Can be said to be used for more and more diverse applications.

Currently, the following methods are available for manufacturing such a laminated product.

Extrusion laminating method (including co-extrusion) This method is the most commonly used method among laminating methods. There are various base materials such as cellophane, various plastic films, metal foils, and textiles. However, most of the laminate materials are polyethylene, and other materials such as ethylene-vinyl acetate copolymer, polypropylene and Surlyn A are used according to the purpose. Further, a method is provided in which two or more coating heads are provided for laminating multiple layers at one time, or two or more layers of molten resin film are simultaneously extruded from the same mold by coextrusion and laminated on a substrate. When laminating on a plastic film or a metal foil, it is usual to coat the base material with a primer before laminating the molten resin in order to enhance the adhesive strength.

In this method, since there are many kinds of base materials and it is possible to laminate multiple layers at once as described above, the method can be used for multiple purposes. For example, a film used for preserved foods is not enough for a single layer to secure the appealing effect of contents, storage performance, heat resistance that can withstand heat sterilization, and heat sealability during automatic packaging. In many cases, a multilayer film having at least two layers is used. In such cases, the extrusion lamination method is most often used.

Dry Lamination Method This method is also a method in which two types of base materials, A and B, are bonded together using an adhesive. Most adhesives are reactive. In recent years, a room temperature curing type that does not use a solvent has been increasingly used. As a method, an adhesive is applied to any one of the base materials A and B, and when a solvent is used, the solvent is volatilized to form an appropriate uncured adhesive surface, and then the other one is used. The base materials of are adhered and adhered. In the case of a so-called non-solvent type adhesive that does not use a solvent, the drying step can be omitted. It is usual that after bonding, both of them are aged and cured for a whole day and night. With this method, it is possible to laminate various kinds of plastics with each other or laminate plastics with metal foil. There are vinyl-based, cellulose-based, and epoxy-based adhesives, which are selected according to the type and purpose of the base material. This method is the second most popular method after extrusion lamination, and is often used for laminating substrates that cannot be formed by extrusion lamination.

Hot-melt laminating method In this method, heat-melted low-molecular-weight polyethylene (copolymer with vinyl acetate), waxes, etc. are stuck to a plastic film, aluminum foil, paper, etc. and cooled. A so-called coating film in which a hot melt material is applied to a substrate is also manufactured by this process.

As the adhesive, a mixture of paraffin wax and microcrystal wax has been used for a long time, but recently, a low molecular weight ethylene vinyl acetate copolymer, an ethylene acrylate ester copolymer, etc. have been used.

According to this method, a composite film having an appropriate moisture-proof effect can be produced at a relatively low cost, and thus it is used for packaging confectioneries, snack foods and the like.

Wet Laminating Method This method is a method in which an adhesive is applied to a plastic film or a metal foil, and a base material such as paper, which easily absorbs water, is immediately attached and the water is volatilized for adhesion.
As the adhesive, water-soluble starch, polyvinyl alcohol, emulsion of polyvinyl acetate, polyvinyl chloride, or the like is used depending on the purpose. As a typical example,
There is a composite material of aluminum foil and high-quality paper used for the interior material of cigarettes.

(c) Problems to be Solved by the Invention The above conventional methods have the following drawbacks.

The extrusion laminating method is a method which has a wide range of selection of the base material as described above and is very widespread. However, a base material weak against heat cannot be used. In addition, the laminate material is naturally assumed to be thermoplastic and capable of extrusion molding, and even if co-extrusion technology is used together, for example, a condition that two kinds of resins A and B can be adhered should be provided. is necessary. Also, even if a multi-layer laminate can be molded at the same time by providing extrusion equipment for melting each resin, the installation area will be large and the equipment will be very large scale, so the amount of money required for the equipment is also high. It has the drawback that

Further, when the extruder is stopped, unusable resin remains, resulting in waste of material.

Even in the dry laminating method of (1), when a solvent-type adhesive is used, a solvent drying facility is required and the base material is exposed to high temperature. Therefore, in this case as well, it is necessary to avoid the use of a heat-sensitive substrate. In addition, aging is required until the adhesion is complete, which takes time. For that reason, there is a drawback that it is extremely difficult to form multiple layers at the same time.

The hot-melt laminating method (1) has a drawback that it is unsuitable for obtaining a laminated product requiring heat resistance because the laminating material itself has a low melting point and is therefore weak against heat.

The wet laminating method is a method used within the limit that at least one of the base materials is made of paper or cloth that absorbs water, and this limitation itself can be a drawback.

As a whole, the base materials used in the laminated products produced by the conventional method have been exposed to the surface layer with the exception of the conventional method, and have played a leading role. The exception is the molten extruded resin, which is directly in contact with the surface of a metal roll (casting) as seen in film or sheet molding by extrusion coating or coextrusion method (including the case of being used for extrusion coating). This is the case of forming the surface layer. Even in this case, the surface properties obtained by the extrusion molding method cannot be improved, and the smoothness,
In terms of film uniformity and appearance of foreign matter such as fish eyes,
It has a drawback that it cannot form a film-like surface state by the solution casting method.

This means that in recent years, the surface smoothness of plastic films has
For products that strictly require the uniformity of the film, the range of use of the composite film is significantly narrowed and the price of the composite film is soared.

In addition, this is also a common problem. Depending on the nature of the base material, it is easy for deformation such as curling to occur due to various causes such as the influence of the amount of water contained, shrinkage due to heat during lamination, and in various ways. There were some inconveniences when using it. However, if it is generally thin and used for coloring, it does not matter if it is in an acceptable condition in the process of packaging, but it is relatively thick and curling or warping occurs during use. Therefore, in the case where a serious inconvenience occurs, it cannot be said that it is extremely difficult to prevent curling or the like from any of the conventional methods for a product that strictly requires its uniformity.

(d) Means for Solving Problems In view of the current situation as described above, the present inventor has completed the method of the present invention as a result of earnest research, and is characterized in that it is cured by the presence of air. The photosensitive composition to be interfered is spread on a metal surface, irradiated with light from the side opposite to the metal surface to partially cure, and the uncured portion of the first film is bonded to another adhesive film, and then light is irradiated again. It is in the point of being irradiated and completely cured.

The photosensitive plastic material refers to a composition that is cured by irradiation with light, and is not particularly limited and can be applied to all photosensitive compositions. However, although it is necessary that the curing is inhibited by the presence of air (oxygen), there is no problem because it is normally inhibited except for exceptional cases. The viscosity of the composition is not particularly limited as long as it can be spread.

As described above, the method of the present invention conversely utilizes the curing inhibition due to air, which is a serious drawback of the photosensitive composition, and the idea is novel. That is, in the prior art, since the curing is hindered by air, in order to solve it, it is better to use an atmosphere of an inert gas such as nitrogen or to cover with a film, and it is better not to have the property of inhibition. As such, nothing needed inhibitory properties.

The photosensitive composition may be not only a monomer but also an oligomer, a prepolymer or the like as long as it is cured by irradiation with light, and a monomer having an acryloyl group or an allyl group as a functional group is common. .

For example, HEMA (2-hydroxyethyl methacrylate), N-methyl acrylamide, etc. are available.

Further, the composition need not be a single composition, but may be a mixture of various photosensitive compositions.

Moreover, you may mix a high molecular polymer with this photosensitive composition. As an example of the polymer to be mixed, a polyamide-based polymer may be mentioned. Among them, N-methoxy-6-nylon was found to have transparency even in the cured film, and was found to have a sheet forming ability.

The metal surface refers to a metal surface having a smooth surface, and may have any shape such as a plate shape, a belt shape, and a roll shape.

The sandwiching roll means a cylindrical drum having a metal surface. In this way, the photosensitive composition is spread on the metal surface and hardened, so that the finish is very smooth. That is, the metal surface serves as a replica during surface molding. In other words, it is necessary to finish the metal surface to be smooth so as to meet the required smoothness.

Spreading refers to placing the composition on a roll by casting, which is usually discharged from a narrow slit-shaped inlet.

The side opposite to the metal surface is a direction in which the spread composition is irradiated with light, and means not from the metal side but from the composition side spread on the metal surface. Of course, it is not necessary to irradiate at a right angle.

The light here is basically ultraviolet light, but any light that can be used for curing visible light or the like may be used.

The reason why such a method is possible is that when the photosensitive composition is irradiated with light, the surface of the surface which is in contact with air undergoes curing inhibition by oxygen, so that the curing is very slow and the metal surface side is reflected. This is because it is considered that the resin will cure quickly due to the influence of light. Further, it is considered that air dissolves and permeates from the surface of the composition before curing and is inhibited thereby, but this dissolution and permeation does not reach the metal side.

The result of the inventor's experiment is shown in FIG. In FIG. 1, the horizontal axis represents time (seconds) and the vertical axis represents the spread thickness of the composition. In this case, the spread thickness is 3000μ. Therefore, the point where the thickness is 0 is the side in contact with air,
The point of is the side in contact with the metal roll. Curve (11) is the gelling curve and curve (12) is the curing curve. In this example, the point about 400μ from the surface is the fastest (about 30 seconds)
Gelled and cured. Next, gelation proceeded in the vertical direction of the layer, and after about 60 seconds had elapsed, gelation and curing started from the metal surface, and in about 120 seconds, the surface layer was completely cured leaving about 20 μ of the surface layer. In the figure, (13) shows a solution state, (14) shows a gel state, and (15) shows a solid state.

As described above, when exposed to air, a certain thickness from the surface is not cured (or curing is extremely slow), and thus the method of the present invention is possible.

Further, since the curing is completed before the adhesion except for a small part of the surface to be adhered to the adhesive film, the shrinkage rate due to the curing is very small after the adhesion, and it is possible to laminate the photosensitive composition as a practical problem. It can be said that it has become.

The spreading roll is a roll for spreading the photosensitive composition, and refers to a roll other than the two sandwiching rolls that form a proximity point for bonding. This is also a metal roll in terms of structure and material and may be the same as the sandwiching roll.

In this way, by separating the spreading roll and the bonding roll from each other, it is possible to absorb the shrinkage caused by the first curing by ultraviolet irradiation. That is, by changing the rotation speed or the diameter of both rolls, the feed speed is different and the cause of tension due to contraction can be eliminated.

When the spreading roll is used, the partially cured product sags due to gravity between the spreading roll and the sandwiching roll, resulting in uneven spreading and bending. To prevent this, it is also beneficial to hang a metal belt between them. Further, the same applies even if a separate roll is provided in the middle without the belt being stretched between the spreading roll and the sandwiching roll.

Further, since it is unavoidable that reaction heat is generated in the case of ultraviolet curing, warping or curling may occur in the composite due to contraction or extension due to this heat. In order to prevent this, the metal roll may be provided with a temperature adjusting function and cooled or heated to prevent it. These things are performed by an electric heater, cooling water piping, cooling air blowing, or the like.

Furthermore, the metal roll itself does not have such a function,
A heating device and a cooling device can be separately provided.

By adjusting the temperature in this manner, the difference in shrinkage rate due to the temperature difference between the partially cured product of the photosensitive composition and the adhesive film is absorbed. Of course, if the contraction rate is different,
It is also possible to adjust the temperature so that a temperature difference is intentionally provided.

(e) Example FIG. 2 is a schematic sectional view showing an example of the method of the present invention.
Two sandwiching rolls (2) are arranged close to each other, and a hopper (3) and a first private line irradiation device (4) are provided on one roll.
When the photosensitive composition (5) is spread from the hopper (3) onto the sandwich roll, the rolls rotate and the adjacent points of both rolls are approached.
Guided by (6). Until the approach point (6) is reached, ultraviolet rays are irradiated by the first ultraviolet ray irradiation device (4) to cure the portion of the composition excluding the atmospheric side surface. Then, it is pressure-bonded to the adhesive film (7) at the proximity point (6). The pressure-bonded laminated film (8) is irradiated with ultraviolet rays by the second ultraviolet irradiation device (9) arranged below to completely cure the photosensitive composition. This completes the laminate. In this example, a transparent polyester film is used as the adhesive film (7), but it may be non-transparent or partially transparent. However, in this case, the second ultraviolet irradiation device (9) does not need to irradiate from the adhesive film (7) side.

The example shown in FIG. 3 is the same as the apparatus except that the hopper (3) of the photosensitive composition is provided on the spreading roll (10).

The manufacturing method is the same as in the case of FIG. 2, but since the partially cured product of the photosensitive composition is introduced from the spreading roll (10) to the sandwiching roll (2) at a certain distance and time, it is cured. The shrinkage due to the reaction is absorbed, and only a slight amount of curing at the time of adhesion remains. In this example, the spreading roll (10) is the nip roll (2)
It is provided above, but below it,
A direction changing roll may be provided at the intermediate position. In this example, the spreading roll (10) may be provided with a cooling device (not shown) to absorb reaction heat. Similarly, a cooling device may be provided in the sandwich roll (2) in order to absorb reaction heat at the time of bonding. By doing so, it is possible even if the adhesive film or the thin object is weak to heat. This is because, unlike the hot-melt bonding method as described above, heat is not necessary for bonding, and the reaction heat is generated as a result and is not an essential requirement.

The example shown in FIG. 4 is similar to that of FIG. 3, but another roll is provided between the spreading roll (10) and the sandwiching roll (2), and the roll and the spreading roll (10) are provided. Are connected by a metal belt (11). In this case, since the irradiation of ultraviolet rays can be performed on the metal belt, the irradiation time can be long and the partially cured product does not sag due to gravity. Furthermore, since the edges of the sandwiching roll (2) and the spreading roll (10) are cut, it is possible to absorb the shrinkage due to curing.

The example shown in FIG. 5 is similar to that of FIG. 2 except that the hopper (3) of the photosensitive composition is provided on the spreading roll (10) as an apparatus.

The manufacturing method is the same as in the case of FIG. 2, but two partially cured products of the photosensitive composition are introduced into the proximity point (6), and the adhesive film (7) is sandwiched between them. It Then, after pressure bonding, it is completely cured by the second ultraviolet irradiation device (9). In this case, there is no problem whether the adhesive film (7) is transparent or non-transparent. In the case of this example, unlike the example shown in FIG. 2, a composite film having extremely high smoothness on both sides can be formed. It is needless to say that the use of the photosensitive composition on both sides can be carried out also in the examples of FIGS. 3 and 4.

The example shown in FIG. 6 is a case where the thin objects to be held are discontinuous. In this example, bamboo leaves are used as the thin material. It is one of the great features of the present invention that even such discontinuous materials that are weak to heat can be easily laminated.

In the example shown in FIG. 7, a direction changing roll (12) is provided between the spreading roll (10) and the sandwiching roll (2). further,
All of the rolls shown are individually designed to be variable in their feed rate and the two nip rolls (2) are also individually temperature-adjustable.

In this example, the ultraviolet irradiation time on the spreading roll (10) can be long, the initial curing and the adhesion are temporally far apart from each other, and the feeding speed can be freely changed. The influence of shrinkage caused by the primary curing on the bonded portion is reduced. In addition to the fact that the temperature can be adjusted separately by the sandwiching rolls (2), warpage and curling can be remarkably reduced.

(f) Effects of the Invention The invention described above has the following advantages.

The composite film can be easily manufactured.

The surface of the composite film can be made extremely smooth, and the smoothness can be increased to an accuracy that cannot be achieved by the conventional laminated sheet or laminated film.

Since most of the curing reaction is completed before the bonding, it is possible to laminate using a photosensitive composition which cannot be laminated due to a large shrinkage ratio (5 to 30%).

Since even those having low heat resistance can be laminated, there are many types of films that can be laminated.

When reacting or adhering while controlling the temperature, a highly accurate laminated product with very little curling or warping can be obtained.

Unlike the conventional laminating method, the material can be easily changed, and the material and time can be changed with little waste. In the past, the material remaining in the device was wasted, and there was a waste of time and heat such as cooling the device and then raising the temperature again.

Since discontinuous materials can be easily laminated, a composite sheet or film with an unprecedented aesthetic appearance can be obtained.

The device itself is simple, and there is no need to create a special atmosphere in the entire room or vaporize the solvent at all, and it can be made inexpensive and safe.

As described above, this is a very useful invention.

[Brief description of drawings]

FIG. 1 is a graph showing the cured state of the composition, FIG. 2 is a schematic view showing an example of the method of the present invention, FIG. 3, FIG. 4, FIG.
6 and 7 are schematic views showing another example. 2 ... Nip roll 3 ... Hopper 4 ... First UV irradiation device 5 ... Photosensitive composition 6 ... Proximity point 7 ... Adhesive film 8 ... Laminated film 9 ... Second UV irradiation device 10 ... Spread roll 11 …… Metal belt 12 …… Direction roll

Claims (10)

[Claims] 1. A photosensitive composition which is cured by the presence of air is spread on a metal surface and irradiated with light from the side opposite to the metal surface to partially cure the partially cured first film. A method for laminating a plastic film, which comprises irradiating light again and completely curing it after laminating the part to another adhesive film. 2. At least two nipping rolls made of metal are arranged, a photosensitive composition which is hardened by the presence of air is spread on one roll, and the photosensitive composition is applied to the photosensitive composition from the side opposite to the nipping roll. The first film, which is irradiated with light and cured on the side in contact with the sandwiching roll, is guided to the other sandwiching roll, and is bonded to another adhesive film by the other sandwiching roll. A method for laminating a plastic film as described above. 3. A nipping roll is disposed in proximity to each other, a spreading roll made of metal is placed at a distance from the rolling roll, and a photosensitive composition which is subjected to curing inhibition by the presence of air is spread on the spreading roll. The method for laminating a plastic film according to claim 1, wherein the plastic film is spread, guided to the sandwiching roll, and laminated with an adhesive film at a point close to the sandwiching roll. 4. The plastic according to claim 3, wherein a metal belt is stretched between the sandwiching roll and the spreading roll, or a metal belt is stretched over a roll separately provided between the sandwiching roll and the spreading roll. Film laminating method. 5. At least one of the various rolls is temperature-adjustable. Claims 2, 3, or 4
A method for laminating a plastic film according to the item. 6. A temperature control device is separately provided in addition to the roll to perform the operation.
A method for laminating a plastic film according to the item. 7. The adhesive film is also obtained by spreading a photosensitive composition, which is subjected to curing inhibition by the presence of air, on a metal surface and irradiating light from the side opposite to the metal surface to partially cure the composition. A method for laminating a plastic film according to item 2 or 3. 8. The method for laminating a plastic film according to claim 7, wherein another thin material is sandwiched between the first film and the adhesive film. 9. The method for laminating a plastic film according to claim 8, wherein the thin material is a plastic film. 10. The method for laminating a plastic film according to claim 2 or 3, wherein the adhesive film is a plastic film which has already been polymerized.