JP2001252630A - Cleaning method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cleaning method which is low in environmental load, is high in the safety of the cleaning liquid itself to the human body, is capable of executing safe and hygienic cleaning and does not give rise to the pollution and eutrophication of waste water after cleaning. SOLUTION: The dirt of the object to be cleaned is swollen and dissociated in a stable state by using an alkaline buffer, by which the dirt components mainly composed of the oil-component in the liquid are suspension separated. The cleaning method which does not always require a surfactant and pays consideration to the environment is thus obtained. Further, a cleaning effect to the object is improved by adding a material having an effect of preventing the readhesion of the materials separated by the cleaning from the object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a cleaning method,
In particular, the present invention relates to a cleaning method capable of obtaining a sufficient detergency even in a state where a surfactant is not contained in a cleaning solution and causing less environmental pollution by wastewater after cleaning.

[0002]

2. Description of the Related Art In the food manufacturing industry, washing is repeatedly performed at various places in a manufacturing process. Conventionally, synthetic detergents using various surfactants have been used for such washing. Further, a similar cleaning method is performed in general households.

[0003] In the electronics industry as well, it is necessary to carry out a step of cleaning a printed board or a glass substrate having organic oil stains or inorganic stains such as metal powders and minerals adhered to the surface.
Conventionally, such cleaning has been performed using a CFC-based solvent, an acetone-alcohol-based organic solvent, or a surfactant.

[0004] However, in the above-mentioned cleaning method using a surfactant, a large amount of the surfactant remains in the cleaning wastewater, causing a problem of eutrophication of rivers and the ocean, that is, a cause of water pollution. . Further, a cleaning method using a chlorofluorocarbon-based or organic solvent-based organic solvent has caused problems such as adverse effects on the human environment, such as the global environment and environmental hormones caused by these organic solvents.

[0005]

DISCLOSURE OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and has a small environmental load, a high safety of the cleaning solution itself to a human body, and a safe and hygienic cleaning. It is another object of the present invention to provide a cleaning method that does not cause pollution of wastewater after cleaning and eutrophication.

[0006]

SUMMARY OF THE INVENTION In view of the above, the present invention has been made. Specifically, an alkaline buffer solution is used to swell and dissociate stains on an object to be washed, and an oil component is contained in the solution. The main purpose is to float dirt components. The term “buffer solution” as used herein is a generic term for a solution that has an action of alleviating the influence of an external factor that changes the temperature or the pH, and has a stable pH even when the solution is diluted or concentrated. In particular, in the case of an alkaline buffer, since the reaction with the contaminant is active, it is possible to positively remove the dirt attached to the object to be cleaned placed in the cleaning tank, and as a feature of the buffer, Even if the alkalinity is affected by a change in pH due to dissolution of the dirt component in the liquid as the washing proceeds, the influence of the change can be reduced and washing is performed under stable conditions.

[0007] Various types of alkaline buffers can be exemplified. With respect to these alkaline buffers, NBS (National Bureau of Standards) is used.
According to those described in. Alternatively, buffer solutions of various pHs can be obtained by using the compounding ratio described in Maruzen Kagaku Binran Handbook, Basic Edition, page II355.

Among them, a buffer solution containing a salt of a weak acid (particularly an alkali metal salt such as sodium or potassium) as a main component is preferably used in view of environmental friendliness, a large washing effect, and cost. . Further, examples of the weak acid include carbonic acid, boric acid, and phosphoric acid. However, phosphoric acid and its salts are greatly involved in the above-mentioned eutrophication, and are not preferred from this aspect.

[0009] The safety aspect, cleaning action,
Specific buffers more preferable in terms of environment, cost and the like include sodium hydrogen carbonate, sodium carbonate, potassium carbonate, sodium tetraborate, potassium tetraborate alone or a complex salt thereof. In addition, an organic buffer such as sodium acetate may be optionally added in a small amount, for example, 30% by weight or less, as an auxiliary for the inorganic buffer.

[0010] The concentration of these alkaline buffers is not specified separately, but in general, the higher the concentration, the greater the buffering effect. If the concentration exceeds a certain concentration, problems such as precipitation of the buffer occur. For this reason, it is preferable to carry out the treatment at a relatively high concentration of about 10% by weight. The washing temperature is cold water (15 ° C).
There is no particular problem as long as the temperature is not lower than normal temperature and not below.

In some cases, a synergistic washing effect can be obtained by adding a small amount of a surfactant (particularly, a nonionic surfactant) to the alkaline buffer of the present invention.

Further, by adding a substance having an effect of preventing a substance released by washing from the object to be washed from re-adhering (anti-adhesion agent), the effect of washing the object to be washed is further improved. . These anti-redeposition agents generally include carboxymethyl cellulose (CMC),
Cellulose derivatives such as methylcellulose (MC) and hydroxyethylcellulose, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, saponin and the like are used. The ratio of adding these surfactants and anti-redeposition agent may be 30% by weight or less of the buffer.

[0013]

Embodiments of the present invention and comparative examples will be described below with reference to the drawings.

FIG. 1 shows a cleaning test device prototyped on the basis of a linac type test device specified by JIS as an example of a test device for comparing cleaning power.

A beaker 1 is filled with an appropriate amount of a washing liquid 2 so that a contaminated portion 5 adhered to an object 4 to be washed fixed by a sample fixture 3 is immersed. The object 4 to be cleaned is washed with the cleaning liquid 2 by the stirrer 6.
Is fixed by the sample fixture 3 so that it does not drop even when it is stirred. Further, it is fixed so that the positional relationship with the beaker 1 does not change due to the stirring.

The stirring by the stirrer 6 is performed according to JIS K 336.
The cleaning rate is evaluated based on the amount of the contaminants retained on the object 4 to be cleaned 4 for 10 minutes.

FIG. 2 is a conceptual diagram of an apparatus for producing alkaline ionized water used in Comparative Examples 1 and 3.

A water tank 7 is filled with a solution 8 containing an electrolyte, and an electrolytic voltage is applied between an anode 9 and a cathode 10 via a cation permeable membrane 11. The water thus obtained on the cathode 10 side is called alkaline ionized water, taken out from the outlet 12 and used in Comparative Examples 1 and 3. Generally, tap water contains an electrolyte sufficient for electrolysis. Therefore, when tap water is used, the operation of dissolving the electrolyte is not performed.

<Example 1> Contamination to be adhered to an object to be cleaned is prepared as follows.

The water used was calcium chloride dihydrate.
Weigh 0 mg and 27.2 mg of magnesium chloride hexahydrate and dissolve in water to make 1000 ml. Prepare 1100 ml of this working water. As a substitute for beef tallow (Japanese Pharmacopoeia) and soybean oil (Japanese Pharmacopoeia), 20 g of fat mixed with 10 g each of salad oil, 10 g of commercially available margarine, and monoolein (a lipophilic product based on cosmetic raw materials) 0.25 g of glycerin oleate and oil red (Sudan III Color Index 26)
It is prepared by dissolving 0.1 g simultaneously in 60 ml of chloroform (added to color the stain so that the adhesion and desorption of the stain can be visually checked).

The slide glass immersed in the dirty bath is JIS
Use a standard type specified in R 3703, wash and dry in a clean state, and measure the weight up to 1 mg. This value is defined as the initial weight (ag) of the slide glass.

After the weight is measured, the slide glass is immersed in a fouling solution, and the fouling is allowed to adhere. This value is defined as the weight (bg) after the adhesion and drying of the stain.

JIS K33, which is a method for evaluating the detergency of the synthetic detergent for kitchen, on the object to be cleaned thus prepared.
A cleaning test was performed based on No. 62. After the washing, the glass pieces are air-dried at room temperature for 1 hour and then weighed. This value is defined as the weight (cg) after the washing and drying. Detergency is JIS
Unlike the detergency evaluation defined in K 3362, the determination was made using the equation (1) based on the change in weight obtained using these values.

On the other hand, the alkaline buffer is prepared by the following method.

For example, sodium hydrogen carbonate and sodium hydroxide, which are generally sold as baking soda, are mixed. To give a concrete example, 17.8 ml of a 0.1 mol / l sodium hydroxide solution was added to 50 ml of a 0.05 mol / l sodium hydrogen carbonate solution, diluted with water and diluted with 100 ml.
ml. For convenience, 0.05 mol (0.48 g) of sodium bicarbonate and 0.037 mol (0.15 g) of sodium hydroxide are dissolved and mixed in 1000 ml of water, and the pH is adjusted to 10.5.
To obtain an alkaline buffer solution.

Using this, it was put into a lnut-type cleaning test tank shown in FIG. 1 and an object to be cleaned was installed to perform a cleaning power test. The cleaning rate was calculated for each test piece, and a value that can be compared with other test pieces was calculated.

Cleaning rate (%) = (bc) / (ba) × 100 Formula (1) The cleaning rate was simultaneously set in a cleaning tank and subjected to a cleaning test.
Evaluate the average degree of washing of the sample. Table 1 shows the results.

[0028]

[Table 1]

Example 2 On the other hand, an alkaline buffer having a pH of 10.6 can be adjusted by the following method. For example,
Generally, sodium tetraborate (borax) and sodium hydroxide are mixed. To show a concrete example, 0.025m
ol / l solution (50 ml), 0.1 mol / l sodium hydroxide solution (23.3 ml) was added and diluted with water to 100 m
l.

The alkaline buffer water prepared at this ratio is
A washing test was carried out in the same manner as in Example 1, except for the method of preparing an object to be washed, except that the buffer was used in place of the buffer used in Example 1. Table 1 shows the results.

Example 3 On the other hand, a weak alkaline buffer having a pH of 8.0 can be adjusted by the following method.

For example, generally, potassium hydrogen phosphate KH
₂ Mix PO ₃ and sodium hydroxide. More specifically, 46.1 ml of a 0.1 mol / l sodium hydroxide solution is added to 50 ml of a 0.1 mol / l sodium bicarbonate solution, and diluted with water to 100 ml.

The alkaline buffer thus obtained is
A washing test was carried out in the same manner as in Example 1, except for the method of preparing an object to be washed, except that the buffer was used in place of the buffer used in Example 1. Table 1 shows the results.

<Comparative Example 1> The case of washing with alkaline ionized water produced by electrolysis using a commercially available ionized water generator shown in FIG. 2 will be described in detail.

An alkaline ionized water generator CI-2000 manufactured by Corona was used as the alkaline ionized water generator. It is connected to a tap of tap water (pH 6.8), and performs ion separation applying electrolysis in the internal tank of the generator. The energization time was 1 minute, and the pH of the generated alkaline water was 9.5.
A washing test was carried out in the same manner as in Example 1, except for the method of preparing the object to be washed, except that the alkaline ionized water thus obtained was used instead of the buffer used in Example 1. Table 1 shows the results.

<Comparative Example 2> A washing test was carried out in the same manner as in Example 1, except that ion-exchanged water was used instead of the buffer solution. Table 1 shows the results.

From the above results, the cleaning method of Example 1 was
Compared with the cleaning rates of Comparative Example 1 and Comparative Example 2, it was found that the cleaning rate was superior in removing contaminants.

Example 4 10 g of sodium 4-borate
(Powder for a commercially available pH standard solution) was dissolved in 500 ml of ion-exchanged water to prepare a cleaning solution for a cleaning test. At this time, the pH of the cleaning solution was 9.22 (20 ° C.). The washing test was carried out in the same manner as in Example 1 except that the buffer used in Example 1 was used in place of the buffer used in Example 1, except for the method of preparing the object to be washed. Table 1 shows the results.

According to the cleaning method of Example 2 as in Example 1, it was found that the cleaning rate of Comparative Example 1 and Comparative Example 2 was excellent in removing contaminants.

Further, without using a commercially available buffer tablet,
In the case of self-manufacturing from a buffer tablet, the medicine described in Example 1 can be sufficiently mixed at a predetermined mixing ratio in a mortar or mortar, and a necessary amount thereof is fractionated and used.

<Example 5> The case where the anti-redeposition agent was added to the alkaline buffer used in Example 1 will be described in detail.

The same procedures as in Example 1 were carried out, except for the method of preparing the object to be cleaned, except that 10 mg of carboxymethylcellulose (CMC) was weighed and added to 500 ml of the alkaline buffer used in Example 1 to prepare a cleaning solution. A cleaning test was performed. Table 2 shows the results.

<Comparative Example 3> Except for the preparation method of the object to be cleaned, except that 10 mg of carboxymethylcellulose (CMC) was weighed and added to 500 ml of the alkaline ionized water used in Comparative Example 1 to prepare a cleaning solution. A cleaning test was performed in the same manner as in Example 1. Table 2 shows the results.

<Comparative Example 4> Except for weighing 10 mg of carboxymethylcellulose (CMC) and adding it to 500 ml of the ion-exchanged water used in Comparative Example 2 to prepare a washing liquid, the method of preparing an object to be washed was the same. A cleaning test was performed in the same manner as in Example 1. Table 2 shows the results.

Although the cleaning rate is improved by adding the anti-redeposition agent, the cleaning method of Example 5 is applied to Comparative Example 3
And it was found that the cleaning rate of Comparative Example 4 was excellent in removing contaminants.

[0046]

[Table 2]

[0047]

Since the electrolytic cell is unnecessary, troublesome installation work such as electric work is not required. Even in ordinary households, a buffer solution can be easily formed by mixing, and by using this, more efficient washing can be performed.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a cleaning test test jig used for a cleaning test of the present invention.

FIG. 2 is a conceptual diagram of an apparatus for generating alkaline ionized water used in a comparative example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Beaker 2 Cleaning liquid 3 Sample fixture 4 Object to be cleaned 5 Contaminated part 6 Stirring blade 6 'Stirring motor 7 Water tank 8 Solution containing electrolyte 9 Anode 10 Cathode 11 Cation permeable membrane 12 Discharge port

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C11D 7/26 C11D 7/26 (72) Inventor Kazuhiro Enomoto 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka (72) Inventor Noritake Sumida 22-22 Nagaikecho, Abeno-ku, Osaka City, Osaka Prefecture F-term (reference) 3B201 BB92 BB96 CC21 4H003 BA12 DA15 DA17 EA16 EA18 EA21 ED02 FA01 FA03 FA06

Claims (5)

[Claims] 1. A cleaning method, comprising washing an object to be washed with an alkaline buffer. 2. The method according to claim 1, wherein the alkaline buffer contains a salt of a weak acid containing an alkali metal. 3. The cleaning method according to claim 2, wherein the weak acid comprises one of carbonic acid, phosphoric acid, and boric acid. 4. The salt according to claim 2, wherein the salt of the weak acid is sodium carbonate, potassium carbonate, sodium hydrogencarbonate, potassium hydrogencarbonate, sodium tetraborate alone or a complex thereof. Cleaning method. 5. The cleaning method according to claim 1, wherein an anti-redeposition agent is added to the alkaline buffer in advance.