JPH0760209A - Washing method - Google Patents

Abstract

PURPOSE:To improve the breaking of foam and the drainage of water at the time of rinsing and to enhance washing efficiency by lowering the surface tension of rinsing water by using degassed water as rinsing water in aqueous washing. CONSTITUTION:When aqueous washing is applied to a metal or plastic part, degassed water is used as rinsing water in order not only to improve the breaking of the foam of the detergent bonded to an article to be washed but also to conserve the amt. of rinsing water. Since the surface tension of degassed water is becomes lower than that of normal water, the breaking of foam and the drainage of water of the article to be washed is improved and, especially, when the article to be washed is rinsed in a plurality of rinsing tanks, the amt. of the rinsing water carried in a next tank can be reduced and washing can be efficiently performed. The degassed water is prepared by a membrane type vacuum degassing method or a vacuum degassing method. The concn. of dissolved oxygen of this degassed water is pref. set to 10-100ppb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cleaning method for saving the amount of rinse water in water cleaning of parts and the like.

[0002]

2. Description of the Related Art Conventionally, chlorofluorocarbon has been used for cleaning metal parts, plastic parts and the like. However, due to restrictions on the use of chlorofluorocarbon, water-based cleaning using water has come to be performed.
In the case of water-based cleaning, after cleaning with a detergent, rinsing with water is performed to remove the detergent. When rinsing is performed in the rinsing tank and there are a plurality of rinsing tanks, a water-saving method is implemented in which water is supplied to the subsequent rinsing tank and overflows from the latter stage to the preceding stage to supply each stage.

[0003]

However, when the article to be cleaned has a complicated shape, bubbles and water are poorly drained, and the amount of detergent collected increases, so that the required number of rinse steps increases, It was necessary to increase the amount of rinse water.

[0004]

DISCLOSURE OF THE INVENTION The inventors of the present invention have diligently studied a method for reducing the amount of rinse water by improving the defoaming of the detergent adhering to the article to be cleaned during the water-based cleaning. Arrived That is, the present invention resides in a cleaning method characterized by using degassed water as rinse water in an aqueous cleaning.

According to the present invention, by using degassed water as the rinse water, the surface tension becomes lower than that of ordinary water, so that the degreasing of the article to be cleaned is improved, and the dewatering is improved. In this case, since the rinse water brought into the next tank is reduced and the cleaning is efficiently performed, the number of rinse tanks can be reduced and the amount of rinse water can be saved.

The article to be cleaned according to the present invention includes glass plates for liquid crystal display boards, electronic parts such as printed wiring boards, bearings,
Examples thereof include magnetic heads, hard disks (recording materials), metal parts (including intermediate products and final products) such as OPC drums, and various plastic parts (including intermediate products and final products).

The rinsing water of the present invention is water used for removing the detergent after cleaning it with a detergent for removing oil content, cutting dust and the like of the article to be cleaned. Degassed water used as rinse water in the present invention (hereinafter referred to as degassed water) has a dissolved oxygen concentration of 5 wt ppm or less, preferably 3 wt ppm or less, and more preferably 1
Water is less than ppm by weight. Although the dissolved oxygen concentration may be limited in terms of economy, there is no inconvenience in itself because it is low.

Particularly, when it is necessary to prevent the product to be cleaned from being oxidized, the dissolved oxygen concentration of degassed water is preferably 100 weight ppb or less or 10 weight ppb or less. Incidentally, the saturated oxygen concentration of water in air at 25 ° C. and 1 atm is 8.1 ppm by weight (according to the Chemical Handbook). Dissolved gases other than oxygen, such as nitrogen, have a saturated dissolved amount of 8 in air.
It is preferable that the gas is degassed to 0% or less, but it is difficult to measure, and it is empirically clear that when oxygen is removed, other dissolved gas is also removed. Is determined by the dissolved oxygen concentration.

The dissolved oxygen concentration can be measured by the Ostwald method (Experimental Chemistry Lecture 1 Basic Operation [I], page 241, 1975, Maruzen) or the mass spectrum method.
It can be measured by a simple oxygen concentration meter such as a galvanic battery type or polarographic type or a colorimetric analysis method.

The degassing method is arbitrary, and methods such as membrane vacuum degassing, vacuum degassing, heating degassing, and bubbling of gas other than oxygen can be adopted, but the equipment is small and the dissolved oxygen concentration is Membrane-type vacuum degassing is preferred because it can be lowered
Vacuum degassing is preferred next. Membrane-type vacuum degassing is a method in which water is passed through one side of a membrane that is permeable to gas but not water, and the other side is depressurized.Vacuum degassing depressurizes the inside of a packed tower or shower tower. Is the way. These methods are preferable because they are effective in removing not only dissolved oxygen but also dissolved nitrogen and dissolved carbon dioxide gas.

The membrane-type vacuum degassing method is preferable in that the apparatus is small in size, easy to handle, and capable of high-level degassing. Since the membrane is a hollow fiber membrane, The deoxidizer can be made compact, and the hollow fiber membrane having an inner diameter of 250 μm or less can be made more compact. Further, since the heterogeneous membrane has a high gas permeation rate and there is no risk of water leakage, it is suitable as a deoxidizing membrane,
Poly-4-methylpentene-1 is hydrophobic and has a high gas permeation rate and strength, and is suitable as a membrane material.

As the decompression device, various vacuum pumps, aspirators, ejectors and the like can be used, but water-sealed vacuum pumps, diaphragm-type vacuum pumps, dry-type vacuum pumps and water-flow aspirators are used for inhaling a large amount of water vapor. It is preferable because it withstands.

When deaerated water is left to stand, air is redissolved and the dissolution rate is increased by stirring. Therefore, when degassed water cannot be stored after being cut off from the air, it is preferable to use it immediately after production of degassed water, and when handling degassed water, avoid entrapment and agitation of air as much as possible. preferable.

The rinsing method is not particularly limited as long as it can wash the detergent, and any method such as a shower method, stirring in a rinsing tank or ultrasonic method can be adopted. When rinsing is performed by immersing the article to be cleaned in a water tank, it can be performed by supplying deaerated water to the water tank. When there are a plurality of rinse tanks, it is preferable to use degassed water for all the tanks, and it is also preferable to supply degassed water to the latter stage and to supply the degassed water to the respective stages by overflowing from the latter stage to the preceding stage.

[0015]

EXAMPLES The present invention will be described in more detail with reference to the following examples. [Example 1] <Preparation of degassed water> A module having a membrane area of 1 m ² using a poly (4-methylpentene 1) hollow fiber heterogeneous membrane was prepared by the method disclosed in JP-A-63-258605, and the hollow portion was prepared. Ion-exchanged water was caused to flow inside the yarn, and the outside of the hollow fiber membrane was depressurized to 100 torr by a diaphragm type vacuum pump to prepare deaerated water having a dissolved oxygen concentration of 1.5 ppm by weight. <Rinse test> A rinse model test was performed. 1 kg of ball bearings with a diameter of about 3 mm was placed in a stainless steel basket, ultrasonically washed with a detergent (2 wt% concentration) mainly containing sodium dodecylbenzenesulfonate, and then dissolved oxygen concentration of 0.45 wt ppm Rinsing was performed by applying ultrasonic waves in a first rinse tank and a second rinse tank each having a volume of 1 liter filled with degassed water.

After rinsing 10 items to be cleaned without changing the water in each rinsing tank, the sodium dodecylbenzenesulfonate concentration was measured by a liquid chromatograph. The first rinsing tank had 293 ppm by weight,
The 2nd rinse tank was 20.8 weight ppm. [Comparative Example 1] The same rinse test as in Example 1 was performed, except that the rinse tank was filled with non-degassed ion-exchanged water (dissolved oxygen concentration: 8.2 weight ppm). After rinsing 10 items to be cleaned, the sodium dodecylbenzenesulfonate concentration was 293 ppm by weight in the first rinse tank and 28.1 ppm by weight in the second rinse tank.

In both Example 1 and Comparative Example 1, the concentration of the detergent in the first tank was about the same and the method of removing the detergent was the same, but the use of degassed water improved foam breakage and water drainage. The amount of detergent brought into the tank has decreased.

[0018]

[Effect] By using degassed water as the rinse water, the effect of lowering the surface tension of the rinse water improves the bubbles and water loss during the rinse, and the amount of rinse water can be saved because cleaning is performed efficiently. . Especially when rinsing is performed in a plurality of rinse tanks, the amount of detergent brought into the next tank is reduced, and the amount of rinse water can be saved. In addition, in the case of metal products, oxidation is prevented.

Claims (4)

[Claims] 1. A cleaning method, wherein deaerated water is used as rinse water in water-based cleaning. 2. The dissolved oxygen concentration of the rinse water is 5 weight pp.
The cleaning method according to claim 1, wherein the cleaning method is m or less. 3. The cleaning method according to claim 1, wherein the rinse water is degassed by a membrane vacuum degassing method or a vacuum degassing method. 4. The cleaning method according to claim 1, wherein the rinsing is performed by immersing the article to be cleaned in a water tank.