JPS5844714B2 - Doshitsu Antei Kahou - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing soil using an improved urea-based soil stabilizer. This invention relates to a method of stabilizing soft ground into solid ground using formaldehyde resin liquid.

Traditionally, as a method of stabilizing soil quality, it has been known to inject various chemical solutions into the soil and harden them.In recent years, in particular, chemical solutions and hardening agents mainly composed of urea-formaldehyde initial condensates have been used as injection agents. So-called urea-based soil stabilizers are attracting attention because of their low price and the high strength of the stabilized soil after treatment.

The urea-formaldehyde initial condensate is usually easily obtained as an aqueous solution or dispersion by reacting urea and formaldehyde in an aqueous medium. is left behind.

However, if such a chemical solution is simply injected into the soil together with a hardening agent and hardened, it is not easy to prepare and inject the chemical solution because formaldehyde is a harmful stimulant, and the stabilized soil after treatment is A large amount of formaldehyde remains in the soil, causing various problems when excavating the soil.

Therefore, in order to overcome the various obstacles caused by this residual formaldehyde, a conventional method has been used in which a resin liquid that has removed the formaldehyde odor by reacting urea with an aqueous solution of a urea-formaldehyde initial condensate is injected into the soil together with a hardening agent and hardened. (Japanese Patent Publication No. 45-24951), or by adding an ammonium salt and an alkaline substance to a mixture of an aqueous solution of a urea-formaldehyde initial condensate and urea, causing a reaction to eliminate the formaldehyde odor, and injecting the resin liquid into the soil together with a hardening agent. method of curing (Special Publication No. 48-9336
(No. Publication), etc. have been proposed.

However, in either method, the storage stability of the resin liquid from which the formaldehyde odor has been removed (hereinafter simply referred to as odorless resin liquid) is poor, and it is necessary to carry out deodorization treatment at the construction site. This is accompanied by some complications.

In addition, the present inventors have proposed a soil stabilization method using a urea-formaldehyde resin liquid that is odorless and has good storage stability in Japanese Patent Application No. 487,406.
We proposed a method in which an ammonium salt is added to an aqueous formaldehyde condensate solution to make it odorless, and a resin solution containing various metal salts and urea is injected into the soil together with a curing agent to harden the solution.

The storage stability of the deodorized resin liquid used in this method is better than that in the above-mentioned methods, but if the amount of urea present in the deodorized resin liquid in this method is small, The storage stability of urea is very good, but when it is injected into the soil with a hardening agent and hardened, the soil strength is still not sufficient, and when the amount of urea is increased, the soil Although it is possible to increase the strength, the storage stability of the test solution cannot be said to be sufficiently good. For example, during high temperatures in the summer, it is necessary to transport the test solution to the construction site and treat the soil within a relatively short period of time after production. Must be.

In other words, in this method, it is not possible to increase the stabilized soil strength sufficiently by using an odorless resin solution that has sufficiently good storage stability and can be stored for a sufficiently long time even at high temperatures in summer.

Therefore, the present inventors corrected the above-mentioned drawbacks of this method, and
In order to improve the strength of the stabilized soil even when soil is treated using an odor-free resin liquid with sufficiently good storage stability, we have conducted various studies to improve the strength of the stabilized soil by adding it to the raw material initial condensate aqueous solution. Metal salts should be limited to monovalent or divalent neutral metal salts with a water solubility ratio.

In addition to ammonium salts, ammonia or a mixture of ammonia and ammonium salts are advantageously used to deodorize the aqueous solution; A small amount of urea or other similar compounds is added in advance to the soil, and when treating the soil, an appropriate amount of urea is added to further increase the strength of the soil, and the mixture is hardened in the soil with a hardening agent. The present invention was developed based on the knowledge that this can be achieved.

That is, the present invention proposes that ``a urea-formaldehyde initial condensate aqueous solution is added with a monovalent or divalent neutral metal salt at a water solubility ratio and reacted with ammonia or/and an ammonium salt to eliminate the formaldehyde odor. , thiourea and ethylene urea in an amount of 1 to 10% based on the solid resin content.
A urea-formaldehyde resin liquid containing % by weight of
This is a soil stabilization method characterized by mixing urea and a hardening agent with the soil during soil treatment, or by infiltrating the soil and hardening it.

The present invention will be explained below.

The urea-formaldehyde initial condensate aqueous solution used in the present invention is prepared by a known method, and a solid resin content of about 40 to 70% by weight is preferably used.

In addition, the urea-formaldehyde initial condensate in the present invention refers not only to the initial condensate of urea and formaldehyde, but also to thiourea, ethylene urea, guanylurea,
It also includes those modified as appropriate using one or more of guanylurea phosphate, melamine, phenol, methanol, ethylene glycol, carboxymethylcellulose, ethylce/L/lose, acrylamide, polyvinyl alcohol, etc.

The most common method for producing an aqueous solution of urea-formaldehyde initial condensate is 2 to 3 moles of formaldehyde per mole of urea (usually 36 to 40% formalin or paraform is used as the formaldehyde source).

) was adjusted to pH 4-6 using one or more of sodium hydroxide, aqueous ammonia, triethanolamine, etc., and the pH was adjusted to about 4 at 80-100°C
Allow to react for ~10 hours.

After the reaction, the reaction product is neutralized to improve its storage stability, and neutralizing agents include sodium hydroxide, potassium hydroxide, sodium acetate, sodium formate, sodium phosphate, and triethanolamine. 1 or 2 such as
More than one species is used.

In the present invention, an aqueous monovalent or divalent neutral metal salt is added to the aqueous solution of the urea-formaldehyde initial condensate produced as described above, and ammonia, ammonium salt, etc. are added to the aqueous solution to make it odorless. Caro and react.

At this time, the metal salts used have various desirable roles, such as extending the odor-free period of the odorless resin liquid, improving storage stability, and increasing the strength of the stabilized soil, as will be explained in detail later. It fulfills the following.

There are many types of metal salts that can be used, but typical examples include calcium chloride, calcium nitrate, sodium chloride, potassium chloride, manganese chloride, magnesium chloride, barium chloride, and magnesium sulfate. In addition, other appropriate metal salts that dissolve in water and make the liquid near neutral can be used.

If a metal salt that makes the aqueous solution acidic or alkaline is used, condensation of the initial condensate will progress and the storage stability of the resin liquid will deteriorate, which is not preferable.

In addition, near neutrality in the present invention usually means pH 6.5 to
This refers to the area of 8.5.

In the present invention, effects when calcium chloride, for example, is used as the metal salt will be explained below.

FIG. 1 is a graph showing the increase in free formaldehyde during storage of a urea-formaldehyde resin liquid that has been made odorless by treatment with ammonia, ammonium salt, etc., which will be described later. In the figure, 1 indicates that no calcium chloride is added. In case, 2,3::! Calcium chloride (
This is the case where 10 and 20% by weight of CaCl2 and 2H20) are added, respectively, based on the solid resin content.

As is clear from the figure, the odorless resin liquid to which calcium chloride has been added in advance has a small increase in free formaldehyde during storage, and this tendency becomes more pronounced as the amount of calcium chloride increases.

Normally, the free formaldehyde concentration in the resin liquid is 0.6%.
The liquid is sufficiently odorless as long as the resin liquid remains odorless, and the figure shows that calcium chloride has the effect of making the resin liquid remain odorless for a longer period of time.

Figure 2 shows the relationship between the pot life (time until the resin liquid gels) of an odorless resin liquid at 20°C and the concentration of C ac 12.2F■20 added to the resin liquid. From this, it can be seen that calcium chloride has the effect of prolonging the gelation time of the resin liquid.

That is, calcium chloride improves the storage stability of the odorless resin liquid.

Although the mechanism of action of calcium chloride that brings about such favorable effects is still unclear, it is likely that similar effects can be obtained when other monovalent or divalent water-soluble neutral metal salts are used. This is thought to be due to the action of metal ions.

The amount of the metal salt added is preferably as large as possible within the range of solubility, as described above, but it can be changed as appropriate depending on the type of metal salt used.

Usually, the amount used is 1% based on the solid resin content in the resin liquid.
It is suitably selected within the range of ~200% by weight, particularly 10~100% by weight, and dissolved in the resin liquid.

Some of the metal salts used in the above-mentioned Japanese Patent Application No. 48-7406 are insoluble in water, but the above effects cannot be obtained with such metal salts.

Other effects of the metal salts used in the present invention include increasing the strength of stabilized soil.

This is an excellent effect similar to the above-mentioned effect, and if metal salts are not used, a large amount of urea is required to increase soil strength, but by using metal salts, this urea Quantity can be saved.

Furthermore, since the metal salts used in the present invention are generally cheaper than urea, it is economically advantageous to replace a portion of urea with the metal salts.

In the present invention, the urea-formaldehyde resin liquid to which the water-soluble monovalent or divalent neutral metal salt is added,
Ammonia, ammonium salt, etc. are added and reacted to make it odorless.

These react with free formaldehyde remaining in the resin solution to produce odorless hexamethylenetetramine, so that the resin solution after treatment no longer has formaldehyde odor.

The amount used should be at least equivalent to the free formaldehyde, but if too much is used, the methylol groups in the resin will be consumed and the storage stability of the resin liquid will be affected. becomes worse.

This is not desirable as it may weaken the hardened soil strength.

Examples of ammonium salts used in the present invention include ammonium chloride, ammonium nitrate, ammonium sulfate, ammonium carbonate, ammonium formate, and ammonium fluoride. Any suitable ammonium salt can be used.

When an ammonium salt is used, the resin liquid usually becomes acidic due to the acid generated from its anion, but
The curing reaction of the well-known urea-formaldehyde initial condensate rapidly progresses under acidic conditions.

Therefore, when an ammonium salt is used for deodorizing treatment, an alkali agent is usually used in combination to maintain the resin liquid during the treatment at a stable neutrality level even if the initial condensate is present.

At this time, the alkaline agents used include sodium hydroxide, potassium hydroxide, barium hydroxide, water glass, etc. The use of water glass is particularly advantageous because it can strengthen the stabilized soil strength. It is.

However, when ammonium carbonate, ammonium bicarbonate, or the like is used, the resin liquid remains approximately neutral, so there is no need to use an alkaline agent in combination, and the operation becomes simpler.

Ammonia may be blown into the resin liquid in a gaseous state, or may be made into an aqueous solution of an appropriate concentration and added to the resin liquid.

When ammonia is used, it is advantageous because there is no need to use an alkaline agent in combination, as in the case of ammonium carbonate, but in this case, if a small amount of ammonium salt or acidic substance is used in combination, It can save time.

Acidic substances used include hydrochloric acid, nitric acid, sulfuric acid, acetic acid,
Examples include inorganic and organic acids such as oxalic acid, and salts that dissolve in water and make the liquid acidic, such as aluminum chloride and iron chloride.

The concentration during deodorizing treatment with ammonia, ammonium salt, etc. is usually 0 to 100°C, particularly preferably 0 to 40°C.

In the present invention, urea, thiourea, ethylene urea, etc. is added in an amount of 1 to 10% by weight based on the solid resin content, in order to maintain the odorless and stable state of the resin liquid over a long period of time.

FIG. 3 is a graph showing the increase in free formaldehyde during storage when, for example, urea is added to the resin liquid, and 1 in the figure is a control, and when urea is not added ( Cac 12 ・2H20 is added at a ratio of 20% by weight based on the solid resin content) 2 and 3 are cases where 5 and 10% by weight of urea are added to the system 1, respectively, based on the solid resin content. .

As is clear from the figure, the resin liquid to which urea has been added exhibits significantly less free formaldehyde during storage.

That is, urea significantly suppresses the generation of formaldehyde from odorless resin liquid, and in the present invention, the cooperative action of metal salt and urea significantly suppresses the generation of formaldehyde odor during storage of odorless resin liquid. It is something to do.

In this case, if the amount of urea added is too small, the formaldehyde odor of the resin liquid will become strong in a relatively short period of time, and if it is too large, the formaldehyde odor will not occur, but the storage stability of the resin liquid will deteriorate.

That is, FIG. 4 shows 20% of the resin liquid to which urea has been added.
The relationship between pot life and urea concentration at °C is shown. As is clear from the figure, as the urea concentration increases, the storage stability ratio of the resin liquid deteriorates.

Therefore, the amount of urea to be added is determined depending on how long the stability of the odorless resin liquid is to be maintained.As stated above, the purpose of the present invention is to maintain the stability of the odorless resin liquid for a long period of time even at high temperatures in the summer. The purpose of the present invention is to provide a deodorized resin liquid that can be used as an odorless resin liquid.

For this purpose, the amount of urea added to the resin liquid varies depending on the structure and type of the resin, but it is usually 1 to 10% by weight, especially 5 to 10% by weight based on the solid resin content. It is appropriate to set it as a range.

The storage stability of the resin liquid to which such an amount of urea has been added is sufficiently good, and it remains odorless for more than two weeks at, for example, 40°C.

When thiourea, ethylene urea, etc. are used in place of urea, the same or better effects than urea can be obtained, so these can also be used as appropriate in the present invention.

Soil stabilization is achieved by mixing the odorless urea-formaldehyde resin liquid produced by the above method with soil together with urea and a curing agent, or by permeating it into the soil and curing it.

At this time, the urea used is useful for increasing the stabilized soil strength after treatment, and the urea also captures formaldehyde released when the resin solution hardens in the soil. , significantly reduces formaldehyde odor in stabilized soil.

The amount of urea to be used can be changed as appropriate depending on the strength of the target soil, but is usually selected within the range of 30 to 60% by weight based on the solid resin content in the resin solution.

In addition, the types of curing agents used include sulfuric acid, hydrochloric acid,
Examples include phosphoric acid, acidic sodium sulfate, etc., and these are usually 1 to 100% by weight based on the solid resin content in the resin liquid.
It is appropriate to use it within the range of .

For soil stabilization, a chemical solution in which each of the above-mentioned components is dissolved in water is used.

Chemical solutions are usually two-component, that is, it is appropriate to prepare the curing agent and other components separately, and this combination is (brominated urea-formaldehyde resin liquid → combination of + (urea) and curing agent). is preferred.

The two liquids are simultaneously mixed with soil or allowed to permeate into the soil, thereby causing a hardening reaction in the soil and solidifying the soil particles.

Next, the method of the present invention will be specifically explained using examples.

In each example, all parts or percentages refer to weight.

Examples 1 to 13 Production of aqueous solution of raw material urea-formaldehyde initial condensate A mixture of 500 parts of 37% formalin and 100 parts of urea was adjusted to pH 5.0 using an aqueous solution of l-IJ hydroxide.
After adjusting the pH to 9 and reacting at 83°C for 10 hours, an aqueous sodium hydroxide solution was again added to the cooled reaction product to adjust the pH.
was adjusted to 8.2.

As a result, an aqueous initial condensate solution with a solid resin content of 45.5% and an apparent viscosity of 25 centipoise (20° C.) was obtained.

The concentration of free formaldehyde contained in the aqueous solution is 4.
At 1%, the formaldehyde stimulant was extremely strong.

[■] Production of the debrominated urea-formaldehyde resin liquid of the present invention A water-soluble neutral metal salt, ammonia, ammonium salt, etc. were charged in the ratio shown in Table 1 to 240 parts of the initial condensate aqueous solution pot of CI). The reaction was carried out at 30°C.

When using ammonia, add aqueous ammonia as it is, or use an appropriate amount of ammonium salt, acidic substance, etc. to react near neutrality. When using ammonium salt, use an aqueous sodium hydroxide solution together. Similarly, the reaction was carried out near neutrality.

After the reaction, the products were diluted with water to a total of 300 parts each.

The reaction results are shown in Table 1.

Next, urea, thiourea, ethylene urea, etc. were added to each reaction product as an odor-free retaining agent in the proportions shown in Table 1.

Table 1 shows the results of testing the amount of free formaldehyde contained and the storage stability of the odorless urea-formaldehyde resin liquid of the present invention thus obtained.

For comparison, the results obtained when urea was not added to the reaction products of Examples 5 and 6 and when a large amount of urea was added beyond the value limited by the present invention were used as control examples.
Also listed in the table.

As is clear from the table, when urea is not added, there is a large increase in free formaldehyde during storage, and when urea is added in a large amount exceeding the limit value of the present invention, storage stability is poor and it can be stored for a long time in summer. It is found to be unsuitable for storage.

(9) Stabilization of soil quality (48 parts of urea was added to the odorless urea-formaldehyde resin solution of each ID example, and then diluted with water to make a total amount of 625 parts, while 60 parts of 98% sulfuric acid was added to The total amount was diluted with 625 parts.

Next, a chemical solution obtained by uniformly mixing the two was injected into a Toyoura standard crusher, hardened, and left for 7 days.

After standing, the compressive strength of the hardened sand was measured and the results are shown in Table 2.

Table 2 also shows the results of measuring the amount of free formaldehyde in the water squeezed out from the hardened homogel after hardening the chemical solution without forcing it into the crusher. It is easily understood that there is a corresponding amount of formaldehyde contained in the sand.

For comparison, the results of a test similar to the above without adding urea to the odor-free resin liquid of Example 1 are also listed in Table 2 as Control Example 3.

[Brief explanation of the drawing]

Figures 1 and 3 are graphs showing the increase in free formaldehyde during storage of an odor-free urea-formaldehyde resin liquid, and Figure 2 is a graph showing the concentration of CaCl2.2H2O in the pot life of the resin liquid. FIG. 4 is a graph showing the relationship between the pot life of the resin liquid and the dark purple urea in the liquid.

Claims (1)

[Claims] 1. A urea-formaldehyde resin liquid produced as described below is mixed with soil together with urea and a hardening agent, or
Or a soil stabilization method characterized by infiltrating the soil and hardening it. (a) adding a water-soluble monovalent or divalent neutral metal salt to the urea-formaldehyde initial condensate aqueous solution;
(b) After eliminating formaldehyde odor by reacting with ammonia or/and ammonium salt, ←→urea,
A urea-formaldehyde resin liquid containing 1 to 10% by weight of at least one compound selected from the group consisting of thiourea and ethylene urea based on the solid resin content.