JP2002020717A - Water-swelling adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water-swelling adhesive capable of being furnished with stable adhesive strength by moisture in the atmosphere, and further capable of being swollen by alkaline water after adhesion so as to be decreased in the adhesive strength. SOLUTION: This water-swelling adhesive comprises a moisture-curing prepolymer made from polyethylene glycol, polypropylene glycol and tolylene diisocyanate, and having isocyanate groups at its terminals, wherein the prepolymer contains the isocyanate group in an amount of 2.5-4.0%, has a continuous structure formed by addition polymerization of the polyethylene glycol, the polypropylene glycol and the tolylene diisocyanate, and preferably has no tolylene diisocyanate which exists freely. The composition can be cured to be adhesive at room temperature by the moisture in the atmosphere, and further swollen by the free alkaline water in concrete after adhesion so as to be furnished with releasability, because the prepolymer is made to contain the isocyanate in the amount of 2.5-4.0%. Thus the composition can be easily released while keeping the adhesive strength, when the composition is used for adhering natural stones or the like to a frame for decorative panel.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-swellable adhesive, which has a moisture-curable adhesive and has an initial adhesive property, and at the same time, has a water-swellable property and can be peeled off with a reduced adhesive strength. It is suitable for use when, for example, natural stones or tiles are adhered to a decorative formwork or the like, and the decorative formwork is peeled off and transferred after placing concrete.

[0002]

2. Description of the Related Art In recent years, not only in concrete structures such as buildings, but also in retaining walls and retaining lands, the concrete surface is decorated in order to improve the aesthetic appearance and harmonize with the surroundings without leaving the concrete in an exposed state. In many cases, designs such as natural stone patterns are applied.

[0003] As one of the methods for applying such a natural stone pattern or the like, a synthetic resin decorative form is attached to a concrete casting form, and a natural stone previously ground together with an inverted pattern is glued on the surface of the form. In some cases, natural stones are transferred along with the pattern to the concrete to be cast, and then the decorative formwork is removed.

[0004] When natural stones, artificial stones, tiles, and the like are bonded to such a decorative mold, a urethane-based adhesive is often used as an adhesive, and all of them are polypropylene glycol / polypropylene triol / triol. This is based on the adhesiveness after moisture curing with range isocyanate.

[0005]

However, in such a urethane-based adhesive, when concrete is poured in a state where natural stones or the like are adhered to the surface of the decorative formwork, the concrete is degraded by alkali moisture and the tackiness is reduced. And the adhesive remains on the surface of natural stone, etc., and part of the decorative form remains on the surface of natural stone, so it cannot be peeled off in a stable state. There is a problem that can not be done well.

Further, in the case of the moisture-curable urethane-based adhesive, there is a problem that the curing by moisture is easily affected by the atmosphere, and a constant adhesive strength cannot always be obtained.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to obtain a stable adhesive strength due to the moisture in the atmosphere, and further, swells with alkali moisture after bonding to lower the adhesive strength. It is an object of the present invention to provide a water-swellable adhesive which can be made to adhere.

[0008]

The present inventors have studied the moisture-curable urethane-based adhesives used in the past, and found that after securing the initial adhesive strength due to moisture, the increase in adhesive strength due to moisture is suppressed. The adhesive strength may be unstable due to the excessive content of polypropylene glycol or polypropylene triol in the conventional moisture-curable urethane-based adhesive. Was found to increase.

Therefore, the present inventors have conducted intensive studies on moisture-curable prepolymers comprising polyethylene glycol, polypropylene glycol, and tolylene diisocyanate and having an isocyanate group at the terminal, and found that the mixing ratio when polyethylene glycol and polypropylene glycol are used in combination. Eliminating the presence of free tolylene diisocyanate by determining the content of isocyanate groups in the prepolymer in the absence of free tolylene diisocyanate further ensures initial adhesion strength and swelling due to moisture This makes it possible to achieve both releasability based on the fact that the cohesive force of the adhesive layer can be maintained at an appropriate level, thus completing the present invention.

In order to solve the problems of the prior art, a water-swellable adhesive according to claim 1 of the present invention is a moisture-curable adhesive comprising polyethylene glycol, polypropylene glycol and tolylene diisocyanate, and having an isocyanate group at a terminal. A prepolymer, wherein the isocyanate group content is in the range of 2.5 to 4.0% and polyethylene glycol, polypropylene glycol, and tolylene diisocyanate have a continuous structure by an addition reaction. Things.

The water-swellable adhesive is a moisture-curable prepolymer comprising polyethylene glycol, polypropylene glycol, and tolylene diisocyanate and having an isocyanate group at a terminal, wherein the content of the isocyanate group is 2.5. ~ 4.0% and polyethylene glycol, polypropylene glycol,
When the tolylene diisocyanate has a continuous structure by the addition reaction, no free tolylene diisocyanate is present, and the content of the isocyanate group in the prepolymer is in the range of 2.5 to 4.0%, the room temperature is lowered. It can be cured and adhered by moisture in the atmosphere underneath, and after adhesion, it can be swelled by alkali moisture etc. in concrete to give releasability, used for adhesion of natural stone etc. to decorative formwork Thereby, it is possible to easily peel off while securing the adhesive strength.

The water-swellable adhesive according to a second aspect of the present invention is characterized in that, in addition to the constitution according to the first aspect, the blend of the polyethylene glycol and the polypropylene glycol is adjusted so that the released tolylene diisocyanate does not exist. The polypropylene glycol is added in an amount of 0.75 to 4.0 with respect to the weight ratio of the polyethylene glycol of 1.
It is characterized by having.

According to this water-swellable adhesive, the blend of the polyethylene glycol and the polypropylene glycol is adjusted so that the polypropylene glycol is mixed with the polyethylene glycol at a weight ratio of 1 within a range where the free tolylene diisocyanate does not exist. 0.75-4.
0, free tolylene diisocyanate does not exist, and the isocyanate group content in the prepolymer can be in the range of 2.5 to 4.0%, and stable adhesive strength and peeling performance can be obtained. Can be granted.

Further, the water-swellable adhesive according to claim 3 of the present invention, in addition to the constitution according to claim 1 or 2, has a molecular weight in the range of 300 to 1000 for the polyethylene glycol and a molecular weight in the polypropylene glycol for the polypropylene glycol. 50
It is characterized by being in the range of 0 to 1200.

According to this water-swellable adhesive, the molecular weight of the polyethylene glycol ranges from 300 to 1,000, and the molecular weight of the polypropylene glycol ranges from 500 to 1,000.
When the molecular weight of polyethylene glycol is in this range, water solubility can be imparted, and when the molecular weight of polypropylene glycol is in this range, peeling can be performed without increasing the adhesiveness. I have to.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the water-swellable adhesive of the present invention will be described below in detail. This water-swellable adhesive is a moisture-curable prepolymer comprising polyethylene glycol, polypropylene glycol, and tolylene diisocyanate and having an isocyanate group at a terminal, wherein the content of the isocyanate group is 2.5 to 4.0.
%, And a structure in which polyethylene glycol, polypropylene glycol, and tolylene diisocyanate are continuous by an addition reaction.

That is, the water-swellable adhesive must have the following components in order to achieve both stable initial adhesiveness and peelability.

It comprises polyethylene glycol, polypropylene glycol, tolylene diisocyanate,
A moisture-curable prepolymer having an isocyanate group at a terminal, wherein the content of the isocyanate group is 2.5 to
Be within the range of 4.0%. All isocyanate groups originate from tolylene diisocyanate. Each reaction component has a morphology of tolylene diisocyanate / polyethylene glycol / tolylene diisocyanate / polypropylene glycol / tolylene diisocyanate / polyethylene glycol / tolylene diisocyanate. Does not contain free tolylene diisocyanate. Further, preferably, the molecular weight of polyethylene glycol is 300 to 1,000, and the molecular weight of polypropylene glycol is 500 to 1200.

In this water-swellable adhesive, free tolylene diisocyanate must not be present in order to obtain stable adhesive strength and release performance. This not only causes foaming due to moisture, but also makes it impossible to obtain stable adhesive performance.

Further, even when free tolylene diisocyanate is not present, if the content of the isocyanate group in the prepolymer exceeds 4.0%, the adhesive strength due to the isocyanate group becomes too strong, and the When used for a mold, the decorative mold cannot be peeled off after hardening of the concrete.

The phenomenon that the adhesive strength is increased by the isocyanate group is remarkably observed when the content of the isocyanate group is a certain value or more even when the prepolymer of polyethylene glycol and tolylene diisocyanate is remarkably water-soluble. Therefore, in this water-swellable adhesive, the releasability can be obtained while ensuring the adhesive strength by preventing the content of the isocyanate group in the prepolymer from exceeding 4.0%. .

On the other hand, if the content of the isocyanate group in the prepolymer is small, it is impossible to obtain a stable adhesive strength.
The content is set to 5% or more so that a necessary initial adhesive strength is secured.

In addition, the peeling property, which is one of the functions required as an adhesive used for a decorative formwork, is that after the concrete is cast, the adhesive which has been cured by the moisture contained in the concrete dissolves. If it does, peelability can be easily obtained, but since the decorative form is used outdoors, it may be exposed to rain before peeling, and too much emphasis is placed on the water solubility after curing. If the adhesive strength is reduced by rain, it cannot be used as an adhesive.

For this reason, a water-soluble polymer such as starch or polyvinyl alcohol cannot be used as the water-swellable adhesive, and a synthetic resin foam such as styrene foam is used as a cosmetic mold. Therefore, it is necessary to contain no organic solvent.

Therefore, as a water-swellable adhesive satisfying such requirements, the glycol component is composed of polyethylene glycol and polypropylene glycol, and the molecular weight of polyethylene glycol, which is an important component for imparting water solubility, is small. Required, and the range is 300-1000. If the molecular weight of polyethylene glycol is smaller than 300, the water solubility increases and dissolution due to rain cannot be ignored. If the molecular weight exceeds 1000, the water solubility decreases and the fluidity at room temperature decreases. As a result, the applicability as an adhesive deteriorates.

On the other hand, if the molecular weight of the polypropylene glycol is too large, even if the adhesive molecules swell due to water absorption in the polyethylene glycol portion, the adhesiveness of the polypropylene glycol is too strong to be able to be peeled off. The range is 500 to 1200.
If the molecular weight of the polypropylene glycol is less than 500, it will not be possible to obtain the necessary tackiness.

Further, tolylene diisocyanate constituting the prepolymer of the water-swellable adhesive includes 2,2.
A mixture of 4 tolylene diisocyanate and 2,6 tolylene diisocyanate is used, e.g.
Tolylene diisocyanate is used in a mixing ratio ranging from 20 to 35% by weight.

Therefore, in order to impart stable adhesive strength and releasability as such a water-swellable adhesive, it is important to satisfy not only the above-mentioned constitutional requirements but also the mixing ratio of polyethylene glycol and polypropylene glycol as the components. And the ratio of polypropylene glycol to polyethylene glycol 1 by weight is in the range of 1 to 3.0,
In addition, the content of the isocyanate group is adjusted to be in the range of 2.5 to 4.0.

In the water-swellable adhesive, a catalyst is used in combination to cause a moisture curing reaction. For example, triethylenediamine, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, diazabicycloundecene Using N, ethyl morpholine, N-methylformoline, triethylamine, dibutyltin dilaurate, tin octylate, zinc octylate, tetraethylhexamethylenediamine, pentamethyldiethylenetriamine, tin acetylacetonate, zinc acetylacetonate, etc. as a catalyst Can be.

The use amount of these catalysts is preferably about 0.001 to 0.5 parts by weight per adhesive.

Further, humidification or heating may be performed to promote moisture curing. In addition, in this water-swellable adhesive, in consideration of outdoor handling, swelling due to slight rain, to suppress a decrease in adhesive strength due to dissolution, a water repellent may be added as an additive, For example, liquid paraffin, a low molecular weight urethane-based substance having a perfluoroalkyl group, silicon oil, or the like can be used.

Further, polyethylene powder, polypropylene powder and the like can be used in combination as an adhesion inhibitor.

As described above, according to the water-swellable adhesive of the present invention, the initial adhesiveness can be secured, and the adhesive strength is reduced by swelling due to the alkali moisture of the concrete.
Peelability can be obtained.

Therefore, the crushed stone is bonded to the decorative form,
It is suitable as an adhesive when it is necessary to peel off the decorative formwork after transferring to concrete.

Further, it is obtained by bonding crushed stones or the like to a non-woven fabric or the like, temporarily fixing the crushed stones to a decorative form having an uneven pattern formed thereon, pouring lightweight concrete thereon, curing, and then peeling the non-woven fabric. The surface is decorated with uneven patterns and crushed stones, and this is used as an integral form with the concrete that is cast as it is as a formwork. In the case of a remaining formwork for makeup, as an adhesive between the nonwoven fabric and the crushed stone, the adhesive strength is secured. , And a suitable adhesive.

[0036]

EXAMPLES Hereinafter, examples of the water-swellable adhesive of the present invention will be described, but the present invention is not limited to these examples.

Examples 1, 2, 3, 4 Polyethylene glycol (PEG) having a molecular weight of 40
Three types of 0,700,1000 are prepared, and the molecular weight is 700,100 as polypropylene glycol (PPG).
0 is prepared.

These were mixed with tolylene diisocyanate (TDI80) and synthesized, and a prepolymer having an isocyanate group content (NCO%) of 2.5 to 4.0% was used.

PEG, PPG, TDI of Examples 1-4
(% By weight) and NCO% are as shown in Table 1.

In order to evaluate the performance of the water-swellable adhesive thus obtained, the following adhesion and peeling tests were performed.

As a decorative mold, a foamed styrene having a size of 300.times.600.times.100 mm (Achilles Matrices) was prepared, and about 30 g of the adhesive of each embodiment was applied per sheet. The average particle size of cherry granite is 3
mm crushed stones were evenly placed, left overnight to cure the adhesive, and then inverted to remove excess crushed stones.

The crushed stone is bonded and has a compression strength of 21.
0 kg / cm2, slump 10 cm of fresh concrete was poured.

After natural curing for 5 days, the decorative form was peeled from the concrete, and the peelability at that time was evaluated. As a result, as shown in Table 1, in any of Examples 1 to 4, the decorative formwork could be easily peeled off, and crushed stone of cherry granite was embedded in the concrete surface, and washed concrete It was finished beautifully.

[0044]

[Table 1]

Comparative Examples 1 to 7 The blending (weight%) and NCO% of PEG, PPG and TDI of each comparative example are as shown in Table 2.

In Comparative Examples 1, 2, and 3, polyethylene glycol (PEG) and tolylene diisocyanate (TDI8) were used.
0), and in Comparative Examples 1 and 2, the NCO% is out of the range of the present invention.
5.0 and 11.2), and Comparative Example 3 is a modification of the blending amount of polyethylene glycol (PEG) and tolylene diisocyanate (TDI80).

Comparative Example 4 was prepared using polypropylene glycol (P
PG) and tolylene diisocyanate (TDI80) to synthesize a polymer.

In Comparative Examples 5, 6, and 7, polyethylene glycol (PEG), polypropylene glycol (PPG) and tolylene diisocyanate (TDI8)
Comparative Example 5 has a NCO% outside the range of the present invention (8.0), and Comparative Example 6 has a compounding ratio of PPG to PEG of 400: 20.
Comparative Example 7 had a molecular weight of 15 as PPG.
00 is used.

These Comparative Examples 1 to 7 were also evaluated by performing the same adhesiveness and peeling tests as in the examples, and the results are shown in Table 2. Comparative Examples 1, 2, 4, 5, and 6 all had strong adhesive strength, and the decorative formwork was broken.

In Comparative Example 3, the viscosity of the adhesive itself was high, so that it could not be applied to the surface of the decorative mold.

Further, in Comparative Example 7, the cosmetic mold could be peeled off, but the adhesive remained on the surface of the cherry granite.
The solubility of the concrete due to alkali moisture was insufficient.

[0052]

[Table 2]

Next, polyethylene glycol (PEG)
Example and Comparative Example of Compounding Ratio of Polypropylene Glycol (PPG) and Polyethylene Glycol (PPG)
400), while the blending amounts of polypropylene glycol (PPG1000) were 2400 and 800, and Examples 5 and 6 were used, while the blending amount was 400 wt% in Comparative Example 8. (See Table 3 for formulation).

The obtained adhesive was subjected to the same adhesive and peeling tests as in the above Examples and Comparative Examples, and the results are shown in Table 3.

In each of Examples 5 and 6, the decorative formwork could be easily peeled off, and crushed cherry granite was embedded in the concrete surface, and the concrete was finished as clean as washed concrete. In Comparative Example 8, the adhesive form was strong and the decorative mold was broken.

[0056]

[Table 3]

[0057]

According to the water-swellable adhesive according to the first aspect of the present invention, as specifically described above with reference to one embodiment, it comprises polyethylene glycol, polypropylene glycol and tolylene diisocyanate. A moisture-curable prepolymer having isocyanate groups, wherein the content of the isocyanate groups is 2.5 to 4.0.
%, And a structure in which polyethylene glycol, polypropylene glycol, and tolylene diisocyanate are continuous by an addition reaction. Therefore, free tolylene diisocyanate does not exist, and the isocyanate group content in the prepolymer is 2. It is in the range of 5 to 4.0%, and can be cured and adhered by moisture in the air at room temperature, and after adhesion, it can be swelled by alkali moisture or the like in concrete to give releasability.

Thus, by using the stone for bonding natural stones or the like to the decorative form, it is possible to easily peel off after transferring to concrete while securing the bonding strength.

Further, according to the water-swellable adhesive according to the second aspect of the present invention, the blend of the polyethylene glycol and the polypropylene glycol can be adjusted so that the weight of the polyethylene glycol is within a range where the free tolylene diisocyanate is not present. Since the ratio of the polypropylene glycol was set to 0.75 to 4.0 with respect to the ratio 1,
There is no free tolylene diisocyanate, and the content of isocyanate groups in the prepolymer is 2.5 to
It can be in the range of 4.0%, and stable adhesive strength and peeling performance can be imparted.

Further, according to the water-swellable adhesive according to the third aspect of the present invention, the molecular weight of the polyethylene glycol is in the range of 300 to 1,000, and the molecular weight of the polypropylene glycol is in the range of 500 to 1200. Therefore, by setting the molecular weight of polyethylene glycol within this range, water solubility can be imparted, and by setting the molecular weight of polypropylene glycol within this range, peeling can be performed without increasing tackiness.

Claims (3)

[Claims] 1. A moisture-curable prepolymer comprising polyethylene glycol, polypropylene glycol and tolylene diisocyanate and having an isocyanate group at a terminal, wherein the content of the isocyanate group is 2.5 to 2.5.
In the range of 4.0% and polyethylene glycol,
A water-swellable adhesive characterized in that polypropylene glycol and tolylene diisocyanate have a continuous structure by an addition reaction. 2. The mixing ratio of the polyethylene glycol and the polypropylene glycol is set to 0.75 to 4.0 with respect to a weight ratio of the polyethylene glycol of 1 within a range in which the free tolylene diisocyanate is not present. The water-swellable adhesive according to claim 1, wherein 3. The water-swellable adhesive according to claim 1, wherein the polyethylene glycol has a molecular weight of 300 to 1,000, and the polypropylene glycol has a molecular weight of 500 to 1200.