JPS6264877A - Bubble-containing adhesive - Google Patents

Abstract

PURPOSE:To obtain an economically advantageous bubble-contg. adhesive which is less susceptible to penetration into the inside of a porous material and has a long open time and an excellent bonding strength, by specifying a bubble diameter and incorporating a foam stabilizer. CONSTITUTION:0.1-10wt% foam stabilizer (e.g., sodium dialkyl sulfosuccinate) is added to a water-soluble resin (e.g., PVA) or water-dispersible resin (e.g., vinyl acetate resin). The mixture is dissolved or dispersed in water to obtain a water-base adhesive. The adhesive is rapidly stirred to obtain a bubble-contg. water-base adhesive which contains bubbles in an amt. of 0.2-20 times by vol. based on the vol. of the water-base adhesive free from bubbles and contains 50vol% or more bubbles having a diameter equal to or less than the thickness of a film formed by application of the adhesive.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a water-based adhesive containing fine air bubbles. More specifically, the present invention relates to a binder-containing adhesive that is effective in realizing an economical bonding process for the first time in bonding porous adherends.

(Prior Art) Conventionally, when bonding porous adherends such as paper, wood, concrete, mortar, etc., water-based adhesives that are water-dilutable and have water-soluble or water-dispersible resins as their main component have been preferred. It is used. The reason for this is that water-based adhesives generally have the following characteristics: they are less fire-hazardous, contain less toxic organic solvents, do not contaminate the environment in which adhesive work is performed, and are easy to handle as they can be washed with water. It is from.

However, in the case of a porous adherend, an excessive amount of adhesive is absorbed into the interior of the adherend from the surface thereof, and it is difficult to leave the adhesive on the surface to be adhered. For this reason, it is necessary to apply a large amount of adhesive, resulting in an economic disadvantage.

As a means of preventing excessive penetration of these adhesives, increasing the viscosity of the adhesive has been carried out. However, this method has serious drawbacks, such as the increased viscosity, which makes it difficult to apply the adhesive, and the time required to complete the adhesive. Therefore, as the bonding process is becoming faster, it cannot help but be economically disadvantageous.

Adhesion systems other than water-based adhesives, such as hot-melt adhesive systems, have been considered, but they have drawbacks such as high equipment costs and poor adhesive heat resistance.

Furthermore, it has been proposed to reduce the adhesive coating film by incorporating a predetermined volume of air bubbles into the water-based adhesive (Japanese Patent Laid-Open No. 57-1989-1).
148870). However, with this technology alone,
Although it is possible to reduce the amount of adhesive applied, it does not solve the problem when the adhesive contains air bubbles.

The problem with containing air bubbles is that it changes the workability of the adhesive, and there are also areas where there is almost no adhesive on the adhesive surface, or where there is insufficient adhesive cover. This causes problems in the bonding process. Therefore, antifoaming agents, i.e., agents that quickly break foams that contain air bubbles and prevent air bubbles from being contained in adhesives, have traditionally been considered essential components of adhesives. , is actually used.

Furthermore, adhesives are required not only to have inherent adhesive properties but also to have workability that allows normal operation to be continued during long-term continuous or intermittent bonding operations. However, depending on the adhesive containing the above-mentioned technology, bubble breakage or the like may occur, which changes the state of the bubbles and thus the workability, making it difficult to continue normal operation for a long period of time.

(Means for solving the problem) The present inventors focused on the effect of air bubbles in water-based adhesives, and as a result of intensive study, determined the size of the air bubbles and used a bubble stabilizer. The inventors have discovered that the above-mentioned problems can be solved by doing so, and have arrived at the present invention.

That is, the present invention requires that the bubble component containing bubbles and having a diameter equal to or less than the film thickness at the time of adhesive application (wetting) accounts for 50% by volume or more of the entire bubbles, and also contains a bubble stabilizer. The present invention provides a water-based adhesive containing a curing agent having the following characteristics.

The adhesive of the present invention contains air bubbles, of which the adhesive coating (
The proportion of bubbles with a diameter less than the film thickness when wet (wet) must be at least 50% by volume, preferably at least 80% by volume. In other words, the effects of the present invention can be specifically achieved by controlling the size of the bubbles so that the diameter is essentially smaller than the coating thickness of the adhesive in a wet state.

It is more preferable that the diameter of all the bubbles is equal to or less than the thickness of the coating film. However, as long as the amount of bubbles having a diameter less than the coating thickness is greater than or equal to the above value, the effects of the present invention can be exerted even if a portion contains bubbles having a diameter greater than the coating thickness. In this case, it is possible to uniformly coat the porous surface of the adherend. However, if the amount of bubbles with a diameter equal to or less than the adhesive coating thickness is less than the above value, the adhesive may not have been applied during drying, or even if it has been applied, only a small amount has been applied. , there are many parts with poor adhesion, and the effect of the invention is not achieved.

The adhesive of the present invention contains a bubble stabilizer as an essential component.

Here, the bubble stabilizer is a kind of surfactant generally called a foaming agent or blowing agent, which stabilizes the bubbles when gas and liquid are mixed in contact, and is used to stabilize fine bubbles. It is used to mix evenly. Specific examples of these include Perex 0TP (Kao Soap Co., Ltd. product).
dialkyl sulfosuccinic acid sodium salt), emal 10
Powder (iE, &li Sum(a) product, lauryl sulfate soda salt), Perex TFA (Kao Soap Co., Ltd.)
Examples include surfactants described on pages 5 to 12 of published patent publication No. 55-500761).

If a bubble stabilizer is not added, it may be difficult to control the diameter of the bubbles in the adhesive within the range of the present invention, or even if the diameter of the bubbles can be temporarily controlled, the diameter of the bubbles of the present invention may be difficult to control during the bonding process. It deviates from the range and causes a change in the bubble content in the adhesive, deteriorating the bonding workability. As a result, it becomes difficult to continue normal bonding work for a long period of time, and it cannot be used in actual bonding work processes.

The type and content of these bubble stabilizers should be determined depending on the bar of the bubbles to be controlled and their diameter, and is not particularly limited, but is usually 0.1% of the non-volatile content in the adhesive. Heavy duty % to 10 heavy duty company 96 is used.

It is also possible to use a mixture of many types of bubble stabilizers.

Generally, the amount of air bubbles contained in the adhesive is suitably 0.2 to 20 times the capacity of the water-based adhesive that does not contain air bubbles. If the volume of the bubbles is less than 0.2 times the volume, a sufficient bubble effect cannot be obtained, and if it exceeds 20 times the volume, the adhesive strength may be extremely reduced, and water evaporation in the water-based adhesive may cause porosity. Penetration of water into the adherend is slowed down, and the time it takes to develop adhesive strength becomes extremely long.

However, the amount of bubbles is determined by the ease with which bubbles break during the bonding process.
It should be varied depending on the adhesive strength required and the type of adherend. That is, it is preferable to mix a large amount of air bubbles into adherends with relatively low surface strength, such as paper-like materials, nonwoven fabrics, and woven fabrics. - Concrete with strong blade surface strength,
For mortar and the like, it is preferable to keep the amount of bubbles relatively small. Furthermore, the bubble content should be changed depending on the ease with which bubbles break during the process of forming the adhesive into a film.

In the present invention, the water-based adhesive is an adhesive that contains a water-soluble resin or a water-dispersible resin as a main component and is dilutable with water. Examples of water-soluble resins include starch, water-soluble polysaccharides such as cellulose derivatives, water-soluble proteins such as glue and gelatin, and synthetic water-soluble polymers such as polyvinyl alcohol and sodium polyacrylate. be. Examples of the water-dispersible resin include emulsion polymers such as vinyl acetate resin, vinyl acetate-acrylic acid ester copolymer, and vinyl acetate-ethylene copolymer, and water-dispersible resins emulsified with surfactants.

Typical water-based adhesives are listed in the New Paper Processing Handbook (published by Shigyo Times).

Various known techniques can be used to incorporate air bubbles into the water-based adhesive. For example, it is possible to mix air into the adhesive by rapidly stirring it, or it is possible to forcibly mix the adhesive with compressed air and release it into the atmosphere to create fine air bubbles in the adhesive. A method of mixing can also be used.

Also, if you want particularly fine air bubbles or a foam-containing adhesive that does not contain large-diameter air bubbles, pass the foam-containing adhesive through a mesh of a fixed size so that the coarse bubbles are absorbed into the adhesive. It is also possible to prevent them from mixing.

By the various methods described above, it becomes possible to easily control the content and size of bubbles in the adhesive, and the effects of the present invention can be exhibited.

Of course, the present invention is not limited by the method of containing air bubbles, the method of regulating the size of air bubbles, or the method of regulating the size of air bubbles.

(Operation and Effect) The water-based adhesive containing specific air bubbles of the present invention not only penetrates into the interior less than porous surfaces and can be bonded with a small amount of adhesive, but surprisingly, After applying the adhesive to one adherend, it takes a long time to attach the other adherend, which is generally referred to as open time, making it an extremely easy-to-use adhesive. .

Furthermore, in conventional foam-containing adhesives, when the volume of air bubbles was increased to more than 100 times the volume of the adhesive without air bubbles, the adhesive strength deteriorated considerably.
As mentioned above, when the adhesive of the present invention is reduced in volume by about 200 times, the adhesive strength does not deteriorate significantly, and this becomes economically advantageous. In addition, with conventional adhesives, if the amount of bubbles was less than twice the volume, the effect due to the inclusion of bubbles was insufficient, but in the case of the adhesive of the present invention, the effect was insufficient.
．． Even at double the volume, the effect due to the inclusion of bubbles can be seen (lO).

Hereinafter, the effects of the present invention will be specifically explained using Examples. The present invention is not limited in any way by the first embodiment.

Example 1 100 parts by weight of ethylene-vinyl acetate copolymer emulginone (trade name: Sumikaflex 400, manufactured by Sumitomo Chemical Co., Ltd.), which is a water-dispersible resin, was added with Neoperex F-25 (Kao Soap (Kao Soap)) as a bubble stabilizer. A water-based adhesive was prepared by adding 1.0 overlapping portions of 1.0 overlapping portions of 1.0 overlapping portions of 1.0 overlapping portions of 1.0 overlapping portions of 1.0 overlapping portions of 1.0 overlapping portions of A. Apply this water-based adhesive to 100Orp.
Stirring was performed for 5 minutes using a stirrer with a rotational speed of m, to prepare a binder-containing adhesive. The stability of the bubbles is relatively good at 10
There was no decrease in the number of bubbles even after the solution was allowed to stand for a minute. Immediately after stirring, the adhesive containing the adhesive was observed under a microscope, and it was found that the average diameter of the bubbles was 80 microns. 50 again
When the volume of these bubbles was calculated by counting the number of bubbles larger than μ, it was found that they accounted for 10% (capacity) of the total volume of the bubbles. Similarly, the container with bubbles larger than 20μ occupied 80% capacity. In addition, as a result of measuring the specific gravity of the water-based adhesive before foam was mixed in and the water-based adhesive after foam was mixed, the volume of the foam in the adhesive containing foam was 1 times the volume based on the volume of the water-based adhesive before foam was mixed in. It turned out to be.

Using these adhesives, the film thickness in the wet state can be increased to 20%.
Coat with an applicator on Rasha paper (basis weight 160 g/m") so that the thickness is μ, 50 μ, 80 μ, 150 μ, 800 μ. ) were stacked together, and after 15 BeC, the two sheets of paper were separated and their adhesion was observed. In addition, the adhesive before containing bubbles was applied at various film thicknesses and bonded in the same manner as the foam-containing adhesive.
Its adhesion was observed.

The results are shown in Table 1. The adhesive of the present invention causes material destruction of the paper, but water-based adhesives related to existing technology, that is, emulginon adhesives, are greatly affected by open time and application amount, and can perform bonding work. It has been shown that the range is narrow and it is economically disadvantageous.

Interosseous "Hbdo-ti4fl'/'/ (t)ノ Reference Example 1 An adhesive was prepared using the water-based adhesive used in Example 1 with the same equipment as in Example 1, stirring for 1 minute, and containing 1 times the volume of foam. A drug was created.

As a result of observing the state of bubbles in the same manner as in Example 1,
The volume percentage of bubbles with a size of 60μ or more exceeded 60%. These were applied with a wet adhesive film thickness of 55μ as in Example 1, and
After an open time of 5 seconds and 80 seconds, it was found that although the adhesive was bonded, there were many streaks in the adhesive and that it was not applied uniformly. The amount of adhesive was extremely small at the bottom of the streaks, and this area clearly showed poor adhesion.

Example 2 The water-based adhesive used in Example 1 was passed through a mixer (trade name: Minimix, manufactured by Warner Matisse) that can mix compressed air and liquid in careful proportions to form adhesives with various loading contents. After measuring the diameter of the bubbles and the content capacity of various bubbles in the same manner as in Example 1,
Using the same adherend, we adhered both wave adherends after a certain oven time, and measured the minimum adhesion time (generally referred to as set time) at which material breakdown of the adherend occurs. .

The results are shown in Table 2.

Example 8 In the same manner as in Example 1, the ethylene-acetic acid-vinyl emulsion in Example 1 was replaced with an acetic acid-bi-malate copolymer emulgene (trade name: Movinyl DM-IH1, a product of Hoechst Synthesis Co., Ltd.). A water-based adhesive was created. This water-based adhesive was passed through the mini-filtering solution used in Example 2 to prepare adhesive-containing adhesives with 5 times, 10 times, 15 times, and 80 times the capacity of the water-based adhesive. Using these binder-containing adhesives, we made rasha paper (basis weight 150g/*) and polyester nonwoven fabric (basis weight 50g/*).
/g") and the conditions shown in Table 8.

The results are shown in Table 8.

Table 8 The oven time was kept constant at 25 seconds.

* Material breakage indicates the area (area percentage) where material breakage occurs when the adherend is peeled off after the adhesive has completely dried.

Example 4 Partially saponified polyvinyl alcohol (trade name: Kuraray Bobal 217, manufactured by Kuraray Co., Ltd.) was used as a water-soluble resin for 14 hours.
% aqueous solution, 0.5 part of Perex OTP (product of Kao Soap Co., Ltd.) was added to 100 parts of this aqueous solution, and the mixture was stirred with a cooking hand mixer to adjust the amount of foam mixed in to 2 times the volume. When the diameter of the bubbles was measured in the same manner as in Example 1, the average diameter of the bubbles was 4()μ, the capacity of bubbles of 60μ or less was 45%, and the volume of bubbles of 80μ or less was 80%. After various even times had elapsed using the same adherends and methods as in Example 1, the adherends were stacked together and 50 seconds later, the two sheets of paper were peeled off and their adhesion was observed. For comparison, an adhesive before foam was mixed was used, and the adhesive was applied to the same dry weight as the adhesive containing the foam, and the adhesive was bonded.

If no bubbles are mixed in, the adhesion is defective, and when the cross section of the adhesion is observed under a high-magnification microscope, it is clear that the adhesive has penetrated deeply into the adherend paper and only a small amount of adhesive remains on the adhesion surface. Adhesion failure was due to insufficient adhesive. On the other hand, in the case of foam-containing adhesives, a large amount of adhesive remains on the bonding surface, and bonding is possible even when a small amount is applied, and it has been found that it has a large economical effect. The results in this case are shown in Table 4.

Table 4 The display of the adhesion state is the same as in Table 1.

Claims (1)

[Claims] A foam-containing aqueous adhesive characterized in that the foam component with a diameter equal to or less than the film thickness at the time of adhesive application (wetting) accounts for 50% by volume or more of the entire foam, and contains a foam stabilizer. agent.