JP4817048B2 - Method for manufacturing paper articles - Google Patents

Description

  The present invention relates to a paper article such as a paper container, and more particularly to a method for manufacturing a paper article in which an exposed end portion of a formed paper is waterproofed.

  In recent years, paper containers such as paper cans have been developed and put into practical use from the viewpoint of environmental protection as substitutes for metal cans and plastic containers containing liquids such as soft drinks.

  As shown in FIG. 1, a conventional metal can substitute paper container has a container body made of a paper laminate material, which is closed by a body 1 having both ends open and a bottom material 2, and the other opening is a lid. What is obstructed by the material 3 is known. The lid 3 is provided with a drinking mouth 4, and the drinking mouth 4 is previously closed by an easy peel sealing material 5. In general, in the conventional metal can substitute paper container, an aluminum foil is used as a barrier material, and the easy peel sealing material 5 for closing the drinking mouth 4 previously formed in the lid 3 is, for example, An aluminum sheet laminated with a synthetic resin is used.

  FIG. 2 illustrates a typical cross-sectional structure of the paper container as shown in FIG. 1, and as shown in this example, the paper container closes the body 1 and the opening of the body 1. A container body composed of a bottom material 2 and a lid 3 forms a container structure as shown in the figure, and the lid 3 has an easy peel property by an inner film 5a and a pull tab 5b closed from the outside as an opening structure for discharging contents. A sealing material is formed.

  Further, as shown in FIG. 2, a sealing portion 10 made of a resin composition or the like is formed over the entire circumference at the folded end portion of the trunk portion to which the lid member 3 and the trunk portion 1 are engaged and fixed. Processing has been applied. Such a sealing portion 10 can also be formed at the bottom of the container as shown in the figure.

  Normally, the outermost layer in contact with the external environment of the paper container and the innermost layer in contact with the contents are covered with a coating layer such as a polyethylene resin layer, which is excellent in waterproofing effect. Since the cross section of the paper material is exposed at the end portion of the material, water is absorbed from the end portion, which causes a decrease in strength of the container and generation of mold.

  In the manufacture of a conventional paper container, the sealing portion 10 is formed by hot melt coating using a hot melt engaging adhesive. However, in the conventional hot melt coating method, bubbles are generated from the end of the paper after coating, and therefore the end cannot be completely sealed, and moisture can enter from the non-sealed portion. There is a problem in that the air bubbles are solidified while remaining in the sealing portion, and thus the quality of the container is lowered. According to the knowledge of the present inventor, it is presumed that the bubble generation problem as described above is caused by a high temperature condition in hot melt coating.

  The present invention has been made in view of the above-described problems of the prior art, and provides a manufacturing method including a sealing process in which bubbles are prevented from being generated when waterproofing is applied to an end of a paper article. It is intended.

  In order to solve the above-mentioned problems, the paper product manufacturing method according to the present invention is characterized in that the paper product is subjected to waterproof treatment with a hot melt adhesive on the end of the paper product whose surface is coated with a resin. This method includes a step of performing a hot air treatment in which the end portion is heated with high-temperature air and then sealing the end portion with a hot-melt adhesive.

  In a preferred embodiment of the method for producing a paper article according to the present invention, the temperature of the air by the hot air treatment is desirably 60 to 600 ° C, preferably 200 to 500 ° C, more preferably 250 to 450 ° C. .

  In a preferred embodiment of the method of the present invention, the hot melt adhesive comprises at least one selected from the group consisting of an EVA resin composition, a polyolefin resin composition, and a rubber composition. The coating temperature of the hot-melt adhesive in the sealing process is desirably 80 to 300 ° C, preferably 100 to 200 ° C, and more preferably 100 to 130 ° C.

  The porosity of the hot melt adhesive layer sealed by the above method can be 50% or less, preferably 30% or less, more preferably several% or less.

  Furthermore, the present invention includes a paper container manufactured by the above method.

  The method for producing a paper article according to the present invention is such that when the edge of a paper article whose surface is coated with a resin is waterproofed with a hot-melt adhesive, the edge of the paper article is subjected to high-temperature air. And a step of sealing the end with a hot-melt adhesive after the hot air treatment is performed.

  The method of the present invention will be described with reference to the paper container illustrated in FIG. 2 described above. As shown in this example, the paper container includes a barrel portion 1 and a bottom material 2 for closing the opening portion of the barrel portion 1 and The container body formed of the lid material 3 forms a container structure as shown in the figure, and an easy peel sealing material is formed on the lid material 3 by an inner film 5a and a pull tab 5b closed from the outside as an opening structure for discharging contents. Has been. And the sealing part 10 is formed with the hot-melt-type adhesive agent in the folding | circulating end part of the trunk | drum by which the cover material 3 and the trunk | drum 1 are engagedly fixed, and the waterproof process is performed by this. . Such a sealing portion 10 can also be formed at the bottom of the container as shown in the figure.

  According to the knowledge of the present inventor, when the sealing part 10 is formed over the entire circumference with the hot melt adhesive as described above, when the temperature condition of the hot melt coating exceeds a specific temperature, the end part of the paper material It has been found that the generation of bubbles from the cross section is significantly increased. In the present invention, in order to prevent such abnormal bubble generation, a hot air treatment is performed in which the end of a paper product to be sealed in advance is heated with high-temperature air prior to hot melt coating. However, by adopting a process of sealing the end with a hot melt adhesive, the temperature of the hot melt coating is a high temperature condition at which bubbles are generated in the conventional method. Has also found that the generation of bubbles can be effectively prevented. Moreover, by adopting such a process, the adhesive strength of the sealing layer can be made sufficiently good at the same time.

  The reason why the bubble generation can be prevented by the pretreatment process using hot air as described above is not necessarily clear, and the present invention is not limited to any theory, but can be estimated as follows. it can. For example, if hot-melt coating is performed without hot air treatment in advance, components such as gas and water vapor contained in the fiber of the paper material near the end face are released from the end face into the atmosphere by expansion and vaporization due to the heat of the hit melt. I will try. At this time, when hot melt coating is performed over the entire circumference of the end face in a relatively short time, the expanded or vaporized gas component loses the escape field and remains as bubbles in the hot melt adhesive layer being solidified. . Therefore, the air in the paper material is forcibly expanded by heating the paper material in the vicinity of the hot melt coating in advance by hot air treatment, and the components that can be further vaporized are thereby forcibly vaporized. The generation of gas from the inside of the paper material due to the heat of the melt coating can be prevented in advance, and as a result, the generation and residual of gas in the hot melt adhesive layer can be effectively prevented. Conceivable.

  In such hot air treatment, the temperature of the air sprayed onto the sealing portion is preferably about 60 to 600 ° C, more preferably 200 to 500 ° C, and particularly preferably 250 to 450 ° C. When the temperature of the jet air is 60 ° C. or less, the effect of suppressing the generation of bubbles is poor. On the other hand, when the air temperature exceeds 600 ° C., the heat load on the paper material becomes excessive, which causes problems such as deformation of the material.

  After the hot air treatment, hot melt coating is subsequently performed according to a conventional method. For this hot melt coating, a conventionally used hot melt coating apparatus can be used.

  In a preferred embodiment of the method of the present invention, as the hot melt adhesive, at least one selected from the group consisting of an EVA resin composition, a polyolefin resin composition, and a rubber composition is preferably used. obtain. In addition, when the resin used for coating the paper material constituting the paper container is, for example, a polyethylene resin, the melting point of the resin is 90 to 140 ° C. Therefore, in this case, the application temperature of the hot melt adhesive in the sealing treatment is preferably 80 to 300 ° C, preferably 100 to 200 ° C, more preferably 100 to 130 ° C.

  In the present invention, by adopting the method as described above, the porosity (bubble content) of the hot-melt adhesive layer subjected to the sealing treatment is 50% or less, preferably 30% or less, more preferably It becomes possible to make it the range of several% or less (substantially including 0%).

  Further, the present invention includes a paper container manufactured by the above method, but the scope of the present invention is not limited to the paper container, and can be widely applied to various paper articles that require waterproofing. .

Examples of the present invention will be shown below, but the present invention is not limited to the following embodiments.

  The end of the paper container as shown in FIG. 2 was hot melt coated using an EVA hot melt adhesive. The coating layer of this paper container is a polyethylene resin.

  As temperature conditions of the hot air treatment, it was performed in a range of 200 ° C to 500 ° C. In addition, as a result of examining the generation of bubbles in the sealing layer and the adhesion to the container surface under the temperature condition at the time of hot melt coating of 120 ° C., the bubble generation rate is reduced for those subjected to the hot air treatment. Good effects were obtained in both prevention of pinhole generation on the container surface and improvement in adhesion. In particular, in the hot air temperature range of 250 to 450 ° C., a result in which bubble generation was not substantially observed was obtained.

  On the other hand, in the case where the hot air treatment was not performed in the above example, generation of bubbles exceeding 50% was observed, and generation of pinholes on the container surface was also observed. Furthermore, the adhesiveness of the hot melt coating agent was also inferior to that in the above examples.

  As is clear from the results of the above experimental examples, the sealing layer formed by the method according to the present invention is excellent in both the effect of suppressing the generation of bubbles (pinholes) and the adhesiveness.

EFFECT OF THE INVENTION When waterproofing the edge of a paper article according to the present invention, both the suppression of bubbles at the sealing portion and the effect of improving adhesiveness are harmonized and excellent.

The perspective view which shows one specific example of a structure of a paper container. Sectional drawing of the paper container which concerns on one Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 trunk | drum 2 bottom material 3 lid material 4 drinking mouth 5 easy peel sealing material 10 sealing layer

Claims (6)

When the end of a paper article whose surface is coated with a resin is waterproofed with a hot melt adhesive,
In the sealing process, the process includes a step of performing hot air treatment in which an end portion of the paper product is heated with high-temperature air at 200 to 500 ° C., and then sealing the end portion with a hot-melt adhesive . A method for producing a paper article, wherein the coating temperature of the hot melt adhesive is in the range of 100 to 130 ° C. The method according to claim 1, wherein the temperature of the air by the hot air treatment is in a range of 250 to 450 ° C.   The method according to claim 1, wherein the hot melt adhesive is made of at least one selected from the group consisting of an EVA resin composition, a polyolefin resin composition, and a rubber composition. The porosity of the sealing process, hot-melt adhesive layer is at 50% or less, The method of claim 1. The method according to claim 1, wherein a porosity of the sealed hot-melt adhesive layer is 30% or less. The method for producing a paper article according to claim 1, wherein the paper article is a paper container.

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