JP2532037B2 - Laminated product and laminating method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a bonded product such as a cardboard box and a bonding method. More specifically, the present invention relates to a laminated article having an adhesive layer having a multi-layer structure and a laminating method in which two coating solutions are separately applied and adhered to different adhesive surfaces.

(Prior Art) In recent years, materials such as various packaging materials have been molded and then assembled using various adhesives. In particular, cardboard boxes are used in various industries among packaging materials, and their use amount is remarkably increasing as an alternative to wooden boxes.

In this cardboard box, liner paper, corrugated paper, etc., which are base papers, are processed and formed as paperboard, and then part of the corners are overlapped and pasted with a metal stapler, or pasted with an adhesive as described above. Have been combined.

Bonding with a metal stapler has problems such as poor airtightness and rust, and when dissolving cardboard paper with water to produce recycled pulp, use a metal stapler that is an insoluble foreign substance. Need to be removed.

For this reason, a bonding method using an adhesive is being changed, and various kinds of adhesives are used. For example, starch paste is used in a wide range of fields as an adhesive that is inexpensive and soluble in water and has an adhesive strength that is not much different from the strength of cardboard paper.

However, the cardboard box to which this adhesive method using starch paste is applied is weak against moisture and humidity, and the adhesive dissolves due to water applied from the outside or water droplets caused by condensation of moisture in the air on the refrigerated items. The adhesive may peel off.

Vinyl acetate adhesives have come to be used as adhesives for solving this problem.

(Problems to be Solved by the Invention) The initial adhesiveness is a problem when this vinyl acetate-based adhesive is used for adhering paper materials such as cardboard paper. The reason why this initial adhesiveness becomes a problem is that when bonding packaging materials such as cardboard boxes, the gluing speed is as high as 2 to 6 m / sec, and the bonding speed is necessarily the same. Becomes By the way, the water content of both starch paste and vinyl acetate adhesive is a dispersion medium, and it is necessary to pass through a long-distance heating zone in order to evaporate the water content contained in a packaging material such as a cardboard box after the gluing. If the initial adhesiveness is poor, the final adhesive strength cannot be obtained.

This is because when the cardboard box is bonded, it is necessary to bend and bond the area around the glue margin, but the cardboard base paper generally has a thickness of about 3 to 10 mm, and
Since it is formed by stacking a plurality of sheets, the force to return to the original state may act on the adhesive portion due to the springback (folding repulsion) of the bent portion, and the adhesive portion may be peeled off.

In view of such a situation, the present inventors have completed the present invention as a result of intensive studies.

(Structure of the invention) That is, the present invention, "the applied adhesive layer, coating amount 0.
Laminated product having a first layer of 5 to 50 g / m ² of boric acid or borate (hereinafter sometimes simply referred to as a boron compound) and a second layer of a vinyl acetate resin containing polyvinyl alcohol "A laminated structure in which the applied adhesive layer has a vinyl acetate-based resin layer containing polyvinyl alcohol and a layer made of boric acid or borate having a coating amount of 0.5 to 50 g / m ² on both sides of the resin layer.""," One of the surfaces to be adhered has a coating amount of 0.5-50 g / m after drying at least boric acid or borate in advance.
² is applied, then the other adhered surface is coated with a vinyl acetate-based resin containing polyvinyl alcohol, and both adhered surfaces are adhered together ", and" both acid or boric acid is applied to both adhered surfaces ". After applying the acid salt with a coating amount of 0.5 to 50 g / m ² after drying, a vinyl acetate resin containing polyvinyl alcohol is applied to either one of the coating surfaces, and both surfaces to be bonded are bonded together. Regarding

The bonded product of the present invention is not limited to a cardboard box, and includes paper cosmetic boxes, various case boxes, paper bags or cloth and wooden bonded products.

Generally, a vinyl acetate-based adhesive containing polyvinyl alcohol, when used as an adhesive for woodworking and paper, is applied as a white emulsion having a solid content of 30 to 60% to an object to be adhered, and a dispersion medium is used. The film formed by the evaporation of some water becomes the adhesive layer, which is, so to speak, a uniform single-layer adhesive layer.

Further, it has been known that the boron compound used in the present invention is used as an initial adhesiveness improver for a vinyl acetate adhesive containing such polyvinyl alcohol.

However, the conventional method of using a boron compound is to use it by mixing it in an emulsion before adhesion, and the adhesive layer in the adherend formed by this is, of course, It is presumed that the reaction product of the boron compound and polyvinyl alcohol and the vinyl acetate resin are mixed to form a single layer.

In the case described above taking the case of bonding a cardboard box as an example, it seems that there is no problem if a boron compound is mixed into the vinyl acetate adhesive from the beginning and this is used. However, when a boron compound is mixed in a vinyl acetate-based adhesive containing polyvinyl alcohol, the hydroxyl group portion of polyvinyl alcohol in the adhesive is considered to develop because metal crosslinks occur intramolecularly and intermolecularly. The phenomenon of “spotting” occurs.

When this "spattering" phenomenon occurs, the adhesive is scattered and contaminated from the adhesive transfer roll rotating at high speed as described above.

The feature of the present invention found there is that, when the boron compound and the adhesive containing polyvinyl alcohol are separately applied to the adherends and then laminated, the polyvinyl alcohol is cross-linked by the boron compound as described above. Then, the initial adhesive strength is increased.

An adhesive layer of a bonded product obtained by separately applying and adhering two kinds of materials to an adherend in this way is schematically shown in FIGS. 1 and 2.

FIG. 1 is a cross-sectional view of a bonded portion of a bonded article having two adhesive layers, where reference numeral 1-1 is one piece of the bonded article, and reference numeral 2-2 is boric acid or borate. Layer, reference numeral 3-3 is a vinyl acetate adhesive layer containing polyvinyl alcohol, reference numeral 4-4 is the other piece of the bonded product, and the adhesive layer is a layer 2-2 made of boric acid or borate. And a vinyl acetate adhesive layer containing polyvinyl alcohol.

FIG. 2 is a cross-sectional view of a bonded part of a bonded product having three adhesive layers. Reference numeral 5-5 is one piece of the bonded product, and 6-6 is boric acid or borate. Layer, 7-7 is a vinyl acetate adhesive layer containing polyvinyl alcohol, 8
-8 is a layer made of boric acid or borate, 9-9 is the other piece of the laminated product, and the adhesive layer is a vinyl acetate adhesive layer 7-7 containing polyvinyl alcohol and this adhesive. Layer 7-7 comprises layers 6-6,8-8 of boric acid or borate adjacent to both sides of layer 7-7.

As shown in FIG. 1, in the case of manufacturing a bonded product having two adhesive layers, one piece 1-1 of the bonded product is coated with boric acid or borate, and the other piece 4- 4 is coated with a vinyl acetate adhesive containing polyvinyl alcohol, which is then laminated.

As shown in FIG. 2, when a bonded product having three adhesive layers is manufactured, both pieces 5-5 and 9-9 of the bonded product are manufactured.
Boric acid or borate is applied to the
Alternatively, a vinyl acetate adhesive containing polyvinyl alcohol is applied to 9-9, and the adhesive is attached.

What can be considered here is that it is meaningless if one side of the adhesive layer is only a vinyl acetate adhesive containing polyvinyl alcohol and only a bonded product as shown in FIG. Is.

As shown in FIG. 1, although the vinyl acetate adhesive containing polyvinyl alcohol only adheres to one surface not coated with boric acid or borate, initial adhesiveness is exhibited. Is due to the following reasons.

That is, usually, for example, a method is used in which an adhesive is applied to one piece of cardboard base paper or the like and the other piece is attached without applying anything. When applying this adhesive, it is a short time after the adhesive is transferred from the adhesive transfer roll to one piece of the cardboard base paper, but before it is attached to the other piece of the cardboard base paper which is not coated, There is a time (open time) for the adhesive to penetrate into the cardboard base paper.

On the other hand, the other cardboard base paper to which the adhesive has not been transferred does not have such an open time, and the bonding is performed instantly. It was found that the delicate difference between the two greatly affects the adhesive strength. Compensating for this subtle difference is the role of the separately applied boric acid or borate.

Therefore, it is not always necessary to apply boric acid or borate to both of the laminated base papers as shown in FIG.

In the case where there is almost no open time as described above due to the structure of the manufacturing machine, it is preferable to apply boric acid or borate to both pieces.

The step of applying boric acid or borate may be performed immediately before the adhesive application step in the production of a bonded product such as a cardboard box, or may be applied in the production of the base paper.

The boric acid or borate to be applied is usually prepared as an aqueous solution, and its concentration is preferably 1 to 5%, preferably 1 to 2%. If it exceeds 5%, the solubility will be poor at room temperature, and when a high-concentration aqueous solution is applied, the amount of boric acid or borate formed near the surface will increase, and the adhesive strength will decrease.

Therefore, the amount of boric acid or borate applied is 0.5 to 5
It should be about 0g / m ² .

In the present invention, boric acid H ₃ BO ₃ , borax Na ₂ B ₄ O ₇ · 10H ₂ O, and various other borate salts are used as the boron compound.

When this aqueous solution of the boron compound is applied, the initial adhesion is more improved when the applied surface is dried.

Further, the boron compound may be applied only to the "glue margin" portion of the pasting, or may be mixed at the time of paper making so as to be contained in the entire paper.

(Effects of the Invention) The bonded product and the bonding method of the present invention have the following advantages.

Even at a high sizing speed of 2 to 6 m / sec, it is possible to prevent the stringing and the sticking phenomenon of the adhesive. In addition, even in the case of cardboard paper or the like having a large bending repulsion force, particularly in the bonding using a vinyl acetate adhesive containing polyvinyl alcohol, the initial adhesiveness is improved, and as a result, the adhesive strength is significantly improved.

(Examples) The effects of the present invention will be described below with reference to Examples and Comparative Examples.

Example A K-liner paper having a basis weight of 220 g / m ² that is a cardboard base paper was cut into 2.5 cm × 20 cm strips to prepare test pieces, and an adhesive was applied using a bar coater # 30. The aqueous solution of was applied using a brush.

The adhesion surface was clamped by pressing a rubber roll back and forth once.

As the adhesive, polyvinyl acetate, polyvinyl alcohol, diztyl phthalate (plasticizer) as the main component, 55% solids for cardboard paper adhesive (manufactured by Daicel Chemical Industries Ltd., Sebian A-350) With a coating amount of about 50 g / m
^The test was conducted in a room of 20 ° C. and 65% RH.

Boric acid is used as the boron compound, and the concentration of the aqueous solution is 1
%, 2.5% and 5% boric acid aqueous solutions were used to change the coating amount.

The coating amount of the boron compound on the K liner paper is shown in Table 1.

After applying the boric acid solution, the test piece is
It was left to dry for a period of time.

As the test pieces, a boric acid aqueous solution was applied to only one piece of the bonded test piece, and one piece was applied to both pieces.

In Table 1, "paper break seconds" means the number of seconds that an adhesive was applied to a test piece, the test pieces were pasted together, and then left for a peeling operation. For example, 10 seconds means that the test piece left for 10 seconds broke during the peeling work, and the smaller the number of seconds, the better the initial adhesiveness.

According to the data shown in Table-1, the paper with 30-40 g / m ^{2 of} boric acid has about half the paper break seconds and the initial adhesiveness is doubled as compared with the non-coated one. There was found. It was also found that when the amount of boric acid applied was too large, the initial adhesiveness was poorer than in the case of no application. Furthermore, it was found that boric acid applied to both pieces or only to one piece did not change the initial adhesiveness.

[Brief description of drawings]

FIG. 1 shows an example of the bonded product of the present invention, in which the adhesive layer is 2
FIG. 2 is a cross-sectional view of a laminated product having layers, and FIG. 2 shows another example of the laminated product of the present invention, which is a cross-sectional view of a bonded product having three adhesive layers.

Claims (8)

(57) [Claims] 1. The applied adhesive layer has a coating amount of 0.5 to 50 g / m 2.
A first layer consisting of ² boric acid or borate, combined product adhered, characterized in that it comprises a second layer comprising a vinyl acetate resin comprising a polyvinyl alcohol. 2. The applied adhesive layer has a vinyl acetate resin layer containing polyvinyl alcohol and a layer made of boric acid or borate having a coating amount of 0.5 to 50 g / m ² on both sides of the resin layer. A laminated product characterized by the following. 3. The laminated product according to claim (1) or (2), wherein the borate is Na ₂ B ₄ O ₇ · 10H ₂ O. 4. The bonded product according to claim 1, which is a cardboard. 5. The bonded product according to claim 1 or 2, wherein the bonded product is a cosmetic box. 6. A vinyl acetate resin containing at least boric acid or borate applied to one surface to be adhered in advance at a coating amount of 0.5 to 50 g / m ² after drying, and polyvinyl alcohol containing polyvinyl alcohol on the other surface to be adhered. Is applied, and both surfaces to be adhered are adhered to each other. 7. A vinyl acetate-based adhesive containing both surfaces to be adhered with boric acid or borate at a coating amount of 0.5 to 50 g / m ² after drying, and then polyvinyl alcohol containing polyvinyl alcohol on either one of the coating surfaces. A laminating method characterized by applying a resin and laminating both surfaces to be adhered. 8. The laminating method according to claim 6 or ₇ , wherein the borate is Na ₂ B ₄ O ₇ · 10H ₂ O.