JPH08337799A - Purification of rinsing water - Google Patents

Abstract

PURPOSE: To easily and inexpensively purify a used rinsing water to reusable quality by dripping it as fine droplets onto the surface (or injecting closely to the surface) of water kept at a temperature higher than the cloud point of the rinsing water to effect mutual contact between the rinsing water and the water followed by separating off the oily components resin afloat. CONSTITUTION: A rinsing water containing a detergent essentially containing a polyoxyethylene alkyl ether <=13 in HLB number [e.g. a mixture of a compound of the formula R1 COOR2 (R1 is a 11-17C hydrocarbon residue; R2 is a 1-13C hydrocarbon residue) with a compound of the formula R3 O(CH2 CH2 O)n H (R3 is an 8-12C hydrocarbon residue; (n) is 3-8) having an HLB number of <=13] is continuously or intermittently dripping as fine droplets onto the surface (or injecting closely to the surface) of water kept at a temperature >=10 deg.C higher than the cloud point of the rinsing water to effect mutual contact between the rinsing water and the water followed by separating the oily components such as the detergent risen afloat from the rinsing water.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is for cleaning precision parts such as printed circuit boards used in the electronic and electrical fields, or metal, glass and plastic parts having hard surfaces such as various parts used in the mechanical field. The present invention provides a method for purifying used rinse water generated at the time.

[0002]

2. Description of the Related Art Parts used in the fields of electronics and electricity and machinery are manufactured using CFCs such as CFC 113 or trichloroethane in order to remove the solder flux and metal working oil adhering to their surfaces during the manufacturing process. Washed with different halogenated hydrocarbons. However, these are prohibited from use as ozone-depleting substances or due to their toxicity to the human body at the end of December 1995. Various cleaning agents have been developed as alternatives to these cleaning agents, and are partially in the stage of practical application. These are roughly classified into water-based or semi-water-based detergents containing an activator as a main ingredient and solvent-based detergents such as hydrocarbons and lower alcohols. When this internal water-based or semi-aqueous cleaning agent is used, it is necessary to rinse the cleaning liquid adhering to the surface of the object to be cleaned with water, which causes a large amount of waste water containing the cleaning agent. Usually, this waste water is either discarded as industrial waste, or is heated and evaporated to be concentrated and then discarded, or burned, or if the water and the cleaning agent are relatively easy to separate, pass the oil and water separation device to separate the water portion after the oil and water separation device. The method of reuse as rinse water is adopted. However, both cases are very costly.
That is, in the case of disposal, a great deal of cost is required for disposal, and for processing, a large amount of equipment cost is required for processing. It also requires a lot of space. Further, even if the water portion is reused as rinse water in oil-water separation, the degree of oil-water separation is insufficient, the organic matter content in water is high, and it is often unsuitable as rinse water.

[0003]

Therefore, in the present invention, the biggest problem of the water-based or semi-water-based cleaning system is to reduce the purification reuse of the rinse water containing the cleaning agent, which occurs when rinsing with water after cleaning. It provides a cost-effective way.

[0004]

As a result of intensive studies to solve the above problems, the present inventors have used a cleaning agent having a specific composition as a cleaning agent for cleaning, and separating it from a specific oil-water separation. The problem was solved by the combination with the method, and the present invention was achieved.
That is, rinse water containing a cleaning agent containing a polyoxyethylene alkyl ether having an HLB of 13 or less as an essential component is continuously added to the surface of water kept at a temperature of 10 ° C. or higher from the cloud point of the rinse water or water near the surface. This is a method for purifying rinse water, which is characterized in that the two liquids are brought into contact with each other by making them into fine liquid droplets and injecting them to separate the oil such as the floating detergent. In this purification method, it is essential that HLB contains a polyoxyethylene alkyl ether having an HLB of 13 or less as a detergent contained in the rinse water, but the following detergents are particularly excellent. That is, a fatty acid ester represented by the general formula (1) R ₁ COOR ₂ (1) (wherein R ₁ is a hydrocarbon residue having 11 to 17 carbon atoms, and R ₂ is a hydrocarbon residue having 1 to 13 carbon atoms). And R ₃ (CH ₂ CH ₂ O) nH (2) (wherein R ₃ is a hydrocarbon residue having 8 to 12 carbon atoms, and n is 3 to
A blend with a polyoxyalkyl ether having an HLB of 13 or less represented by 8).

No special expensive oil-water separator is required to practice the present invention. That is, there is an inlet into which the water kept at a temperature 10 ° C or more higher than the cloud point of the rinse water can be introduced to continuously and intermittently introduce the used rinse water, and an outlet from which the water layer after oil separation can be continuously or intermittently taken out. Any vertically long container provided can be used, and it can be manufactured at extremely low cost. In addition, the size of the container does not need to be large. Because the oil and the water layer are separated at the moment when the rinse water is brought into contact with the water in the container, and the dripping or pouring place of the rinse water is near the water surface, and it does not take time to float the separated oil. Is.

In the present invention, the temperature of the water in the container for oil-water separation may be higher than the cloud point of the rinse water,
In order for the oil layer and the water layer to be clearly separated, the temperature must be at least 10 ° C. or higher. On the other hand, if the temperature becomes too high, convection of water in the container occurs and the amount of oil in the water layer increases, which is not preferable. When operating under normal pressure, 90 ° C or higher is not preferable.

An essential requirement of the present invention is that the rinse water to be treated contains a polyoxyethylene alkyl ether component having an HLB of 13 or less. This component is derived from the cleaning liquid used in the cleaning process. Specific examples of polyoxyethylene alkyl ethers include polyoxyethylene octyl ether, polyoxyethylene decyl ether, polyoxyethylene dodecyl ether, polyoxyethylene lauryl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene. Among oleyl ethers and the like, the number of moles of ethylene oxide added is adjusted in the range of HLB 13 or less.

Polyoxyethylene alkyl ether is 1
It is produced by adding ethylene oxide to a polyhydric alcohol. In this case, ethylene oxide partly replaced with propylene oxide or butylene oxide is also included.

These ethers can be used alone or in combination of several kinds. Other ethylene oxide adducts such as fatty acids and alkylphenols with ethylene oxide added may be added in a very small amount, but if the amount is increased, oil-water separation of used rinse water is deteriorated, which is preferable. Absent.

H of polyoxyethylene alkyl ether
LB is important in terms of reuse of used rinse water by separating oil and water. If the HLB exceeds 13, a high temperature is required for the oil / water separation operation of the used rinse, and the convection of water in the oil / water separator becomes harsh, which is not preferable. In addition, the content of organic matter in the water after oil-water separation becomes high, which is not preferable for reuse as rinse water.

If the fatty acid ester is contained in the rinse to be treated at the same time as the polyoxyethylene alkyl ether having an HLB of 13 or less, regeneration of the rinse water by oil-water separation becomes easier. This component is also derived from the detergent used in the washing step.

Specific examples of the fatty acid ester in the present invention include methyl laurate, ethyl laurate, butyl laurate, 2-ethylhexyl laurate, tridecyl laurate, tridecyl myristate, palmitic acid 2
-Mixed fatty acid esters such as ethylhexyl, methyl oleate, ethyl oleate, butyl oleate, 2-ethylhexyl oleate, and butyl coconut oil fatty acid may be used in the same manner, or some esters may be blended. Absent.

[0013]

EXAMPLES Examples will be described below, but the present invention is not limited thereto.

[0014]

Example 1 90 parts of a cleaning agent composed of 55 parts of butyl oleate and 45 parts of polyoxyethylene lauryl ether (HLB 12.1) and 2 parts of impurities composed of 10 parts of flux.
% Of used rinse water (40 ° C) containing 1.1% of 20m
A beaker having a bottom area of 120 cm ² and a height of 25 cm is dripped at a rate of 1 / min from the water surface to a particle size of the liquid of about 1 to 2 mm. Into the beaker, 1.5 liters of the same used rinse water was preheated to 70 ° C and placed. During the dropping, the liquid temperature is maintained at 70 ° C. After the dropping is completed, 1.2 l of the aqueous layer is drawn from the bottom of the beaker. A part of this liquid is sampled to obtain the evaporation residue amount. Remaining liquid 1.1
2% of the impurities consisting of 90 parts of the cleaning agent and 10 parts of the flux described above are added to 1 l, and oil and water are separated and the water layer is collected by the same operation as described above. The above operation is repeated eight more times. 10 in total
The amount of evaporation residue of the water layer collected by one operation is 0.3 ± 0.1
%, Both of which are at levels that can be used as the quality of rinse water.

[0015]

Example 2 40 parts of 2-ethylhexyl palmylate,
Polyoxyethylene lauryl ether (LB12.1)
Oil-water separation was performed in the same manner as in Example 1 except that used rinse water (40 ° C.) containing 2% of impurities of 10 parts of flux in 90 parts of 60 parts of detergent. The amount of evaporation residue of the water layer after oil-water separation is 0.2 ± 0.1%
The water quality of the rinse layer was sufficient.

[0016]

Example 3 90% of a cleaning agent composed of 45 parts of butyl oleate and 55 parts of polyoxyethylene lauryl ether (HLB10.8) and 2% of an impurity composed of 10 parts of machine oil.
Oil-water separation was performed in the same manner as in Example 1 except that used rinse water (40 ° C.) contained therein was used to separate oil-water at 60 ° C. The amount of evaporation residue in the water layer after oil-water separation is 0.1 ±
It was in the range of 0.1%, and both were sufficient as water quality for the rinse layer.

[0017]

[Comparative Example] 90 parts of a cleaning agent composed of 60 parts of isopropyl palmitate and 40 parts of polyoxyethylene laurate (HLB14.3) and 2 parts of an impurity composed of 10 parts of flux.
Oil water separation was carried out in the same manner as in Example 1 except that the used rinse water (40 ° C.) contained was used. The interface between the oil layers after the oil-water separation was unclear, the degree of cloudiness of the water layer was severe, and the water content in the oil layer was high. The evaporation residue amount of the water layer after oil-water separation was in the range of 1.1 ± 0.2%, and the effect of oil-water separation was poor.

[0018]

As described above, according to the present invention, the treatment of used rinse water, which has been the biggest bottleneck of the conventional water-based or semi-water-based cleaning system, can be purified to a reusable level as rinse water by an extremely simple operation. enable.

Claims (2)

[Claims] 1. Rinsing water containing a cleaning agent containing a polyoxyethylene alkyl ether having an HLB of 13 or less as an essential component is kept at a temperature of 10 ° C. or more above the cloud point of the rinsing water, or near the surface of the water. A method for purifying rinse water, which comprises continuously or intermittently forming fine droplets into water to drop or inject them into contact with the two liquids to separate the oil such as the floating cleaning agent. 2. The cleaning agent contained in the rinse water is represented by the general formula (1) R ₁ COOR ₂ (1) (wherein R ₁ is a hydrocarbon residue having 11 to 17 carbon atoms, and R ₂ is 1 to 13 carbon atoms). A hydrocarbon residue) and a general formula (2) R ₃ O (CH ₂ CH ₂ O) _n H (2) (wherein R ₃ is a hydrocarbon residue having 8 to 12 carbon atoms, The method for purifying rinse water according to claim 1, wherein n is a mixture with a polyoxyalkyl ether having an HLB represented by 3 to 8 carbon atoms and having an HLB of 13 or less.