JPH0426057B2 - - Google Patents

Description

Detailed Description of the Invention The present invention relates to a dispersant for magnetic powder liquid used in wet magnetic flaw detection, which maintains dispersion and defoaming effects for a long time even at high temperatures of about 40° to 50°C. An object of the present invention is to provide a dispersant for magnetic powder liquid that has the ability to be maintained over a long period of time and has excellent long-term storage stability.

In general, magnetic flaw detection is well known as a typical non-destructive testing method for magnetic materials. In this method, when a defect such as a crack or a pinhole exists on the surface of a magnetic material (for example, a square piece of steel) or in a relatively shallow part below the surface, when a current is passed through the magnetic material, the magnetic resistance of the defective part is reduced. Because the area is larger than other healthy parts, magnetic flux drifts in that area and leaks into the air. This phenomenon is utilized, and iron powder, stainless steel powder, etc. magnetically conductive powder (generally called "magnetic powder").
Magnetic powder coated with fluorescent material is
It is called "fluorescent magnetic powder." ) is scattered on the surface of the inspected object, and the magnetic particles are collected in the area of the above leakage magnetic flux, and the defective part of the object to be inspected is detected by the pattern of the magnetic particles. A method of dispersing it directly into the air and spraying it on the surface of the object to be inspected (generally known as the "dry magnetic flaw detection method")
It is called. ) and magnetic particles are dispersed in water using a surfactant at a concentration of usually 1 to 3 g/1 liter of water to form a magnetic powder dispersion (generally called ``magnetic particle liquid''). A method of spraying on the surface of the inspection object (generally called "wet magnetic flaw detection")
There is. The latter wet magnetic flaw detection method is particularly widely used in the steel industry, and is used to detect flaws in steel materials such as square billets and round billets.

The present invention relates to a "dispersant for magnetic powder liquid" used in the preparation of magnetic powder liquid in the above-mentioned wet magnetic flaw detection method.
This is related to.

As mentioned above, the magnetic particle concentration of the magnetic powder liquid is usually 1 to 1.
It is said to be 3g/1l of water, but this means that if it is less than 1g/1l of water, the amount of magnetic particles that collect on defects on the surface of the object to be inspected will be small and practical flaw detection accuracy will not be obtained. This is because if the amount of water exceeds 1 liter, magnetic particles will adhere to areas other than the defective area, causing a "background" phenomenon and reducing flaw detection accuracy.

As is well known, when spraying magnetic powder liquid with a magnetic particle concentration of 1 to 3 g/1 liter of water, it is required that the magnetic particles are sufficiently dispersed and that the magnetic particle liquid uniformly wets the surface of the object to be inspected. .

Furthermore, the dispersed magnetic powder liquid is collected and reused, and in this industry, normally, a magnetic powder liquid stirring device as shown in Fig. 1 is used, the magnetic powder liquid is poured into a tank 1, and a pump 2 is used from the tank 1. transport the magnetic powder liquid to a predetermined spraying location and spray it on the inspection object A, collect the sprayed magnetic powder liquid into tank 1, and transport the collected magnetic powder liquid from tank 1 again to the predetermined spraying location using pump 2. The method is to repeat the cycle of transporting and dispersing. This aspect is described in detail in, for example, Japanese Utility Model Publication No. 47-41518. That is, the magnetic powder liquid is usually used in a stirred state, and the magnetic powder liquid during use is in a state where it is very easy to foam. If there is a lot of foaming,
It is easy to understand that bubbles may form on the surface of the object to be inspected, impeding flaw detection, or may overflow from the tank 1. Therefore, in addition to the above, it is required that the magnetic powder liquid during use does not cause any bubbling phenomenon.

In the industry, dispersants for magnetic powder liquids are used in preparing magnetic powder liquids in order to meet the above requirements.

The typical formulation of dispersants for magnetic powder liquids currently on the market is "1 to 3% by weight silicone antifoaming agent (hereinafter referred to as
All percentages by weight are simply abbreviated as %. ), surfactant 2
~6%, the balance being water, and if necessary, 3~5% of a rust preventive agent is added to this (in addition, in formulations that contain a rust preventive agent, add an amount commensurate with the amount of the mixer). The amount after subtracting the water becomes the "remaining water.")

To explain in more detail, first, the silicone antifoaming agent in the formulation is a polyethylene glycol type dimethylpolysiloxane oil with an HLB value of 10 to 11, which is considered to be the best antifoaming agent to be added to dispersants for magnetic powder liquids. Oil-in-water (O/
W) A silicone antifoaming agent in the form of an emulsion, the blending ratio of which is 10-30% dimethylpolysiloxane oil, 5-10% surfactant, and the balance water, and this ratio is an oil-in-water that is stable during use. It is said to be the optimum ratio for maintaining the mold emulsion.
In addition, as a commercially available product, "Silicone antifoaming agent KM68-
1F), "KM-70" and "KM-72F" (all product names: manufactured by Shin-Etsu Chemical Co., Ltd.) are well known.

The silicone antifoaming agent mentioned above is, of course, blended to meet the above requirements.

Next, the surfactant in the formulation has an HLB value of 10 to
13 polyethylene glycol type nonionic surfactant. It is said that in order to keep the oil-in-water emulsion of the silicone antifoaming agent stable during use, it is necessary to use a surfactant with properties similar to those of the surfactant used in the silicone antifoaming agent. Selected based on viewpoint. in particular,
For example, polyoxyethylene nonyl phenyl ether, polyoxyethylene lauryl ether, polyoxyethylene dovanol ether, etc. are used.

The above surfactant is blended to meet the above requirements. As mentioned above, the silicone antifoaming agent also contains a surfactant, but it is completely impossible to sufficiently disperse the magnetic particles with just the amount of surfactant contained in the silicone antifoaming agent. As mentioned above, 2 to 6% of surfactant is blended as the amount of surfactant necessary to sufficiently disperse the magnetic powder and satisfy wettability during spraying. ~
The specified amount of 6% does not include the amount of surfactant pre-blended in the silicone antifoaming agent. ) Next, the rust preventive agent added as necessary is sodium nitrite, triethanolamine, etc., and is added when it is necessary to prevent rusting of the object to be inspected.

The commercially available dispersant for magnetic powder liquid used in the wet magnetic flaw detection method, which has the above formulation, has a dispersant concentration of 1 to 3%/1 liter of water, and a magnetic powder concentration of 1 to 3 g/l. When the magnetic powder liquid is prepared to make 1 liter of water, the magnetic powder liquid will have the following properties at room temperature (20° to 30°C)
It meets the above requirements and ensures that sufficient flaw detection accuracy is obtained for practical use, and also guarantees that the defoaming effect is maintained for 10 to 20 hours after the start of use of the magnetic powder liquid. It is something.

In addition, there is a dispersant for magnetic powder liquids that maintains the antifoaming effect for a longer period of time, as disclosed in Japanese Patent Application Laid-Open No. 155354/1982. 0.1 to 0.5 dimethylpolysiloxane-polyoxyalkylene copolymer (however, the number of moles of ethylene group is 5 moles or less)
% blending (In addition, in a formulation containing the copolymer, the amount of water commensurate with the blended amount becomes the "remaining water"), and is a liquid material for this magnetic powder liquid. When a magnetic powder liquid is prepared in exactly the same manner as above using a dispersant, the magnetic powder liquid has the following properties at room temperature:
This is to ensure that the antifoaming effect is maintained for 40 to 50 hours after the start of use of the magnetic powder liquid while satisfying the above requirements.

Note that the dimethylpolysiloxane-polyoxyalkylene copolymer is a known substance, and for example, one of the following formula is well known: In addition, as a commercially available product, “Silicone Surfactant
SP-2990'', ``SP-2972'', and ``SP-3637'' (all product names and manufactured by Shin-Etsu Chemical Co., Ltd.).

Further, the amount added must be in the range of 0.1 to 0.5%; if it is less than 0.1%, there will be no effect and the foaming phenomenon of the magnetic powder liquid will be promoted. Addition of 0.1% or more can significantly extend the antifoaming effect maintenance time, and the greater the addition amount, the greater the effect, but if it is 0.5% or more,
Since it has a negative effect on the dispersibility of the magnetic powder and the wettability of the liquid, it is said that the addition must be limited to a maximum of 0.5%.

In addition, the use concentration of the above-mentioned commercially available dispersant for magnetic powder liquid and a dispersant for magnetic powder liquid obtained by adding dimethylpolysiloxane-polyoxyalkylene copolymer (hereinafter referred to as known dispersant) is 1 to 1. 3
%/1 liter of water is because in order to meet the above requirements, a concentration of at least 1%/1 liter of water is required, and even if the concentration is 3%/1 liter of water,
This is because no significant improvement in the dispersion and wetting effects was observed. Further, the defoaming effect maintenance time hardly changes even if the concentration of the known dispersant added to the magnetic powder liquid is 3%/1 liter of water or more.

The known dispersants described above have the following drawbacks.

That is, when the liquid temperature of the magnetic powder liquid prepared using a known dispersant is room temperature (20° to 30°C), it exhibits high performance that satisfies the above requirements without any problems, but when the liquid temperature is about When the temperature exceeds 40°C, the dispersion effect and antifoaming effect are suddenly lost, which leads to an extremely low flaw detection accuracy and a severe bubbling phenomenon.

Of course, a situation in which the temperature of the magnetic powder liquid exceeds 40°C during wet magnetic flaw detection usually rarely occurs.

However, when wet magnetic flaw detection is applied to a square billet that has undergone heat treatment such as rolling or annealing to room temperature in the summer, the temperature of the magnetic powder liquid is 40°C. It is not rare for the dispersant to exceed the above range, and in such cases, the known dispersants exhibit the above-mentioned drawbacks.

As far as the present inventor is aware, there is no dispersant for magnetic powder liquids in Japan or other countries that can maintain the dispersion effect and antifoaming effect when the liquid temperature of the magnetic powder liquid exceeds approximately 40°C. be.

Therefore, in this industry, the liquid temperature of magnetic powder liquid is approximately
There has been a strong desire for a dispersant for magnetic powder liquids that does not lose its dispersing and antifoaming effects even when the temperature exceeds 40°C.

The present inventor has discovered that a known dispersant has a liquid temperature of about 40°C.
As a result of thorough investigation into the factors that cause the rapid loss of dispersion and antifoaming effects when temperatures exceed I learned that the reason for this is the cloud point of ). To be more specific, as mentioned above, the known dispersant contains 1 to 3% of the silicone antifoaming agent, and the silicone antifoaming agent contains dimethylpolysiloxane oil as an oil-in-water emulsion. Contains a polyethylene glycol type nonionic surfactant with an HLB value of 10-11. As is well known, the optimal HLB value for making dimethylpolysiloxane oil into an oil-in-water emulsion is 10.5, and when producing the silicone antifoaming agent mentioned above, polyethylene glycol type non-containing material with an HLB value of 10.5 is used. Use a single ionic surfactant, or use multiple polyethylene glycol-type nonionic surfactants with an HLB value of 10 to 11 and an HLB value of 10.5.
They are used in combination so that the latter is generally used, and it is said that a more stable oil-in-water emulsion can be obtained by using the latter.

By the way, the cloud point of a polyethylene glycol type nonionic surfactant with an HLB value of 11 or less is about 40°C or less.

As is well known, polyethylene glycol type nonionic surfactants have the property of being hydrophobic and soluble in water at temperatures below the cloud point, but not soluble in water at temperatures above the cloud point.

In other words, known dispersants always contain a polyethylene glycol type nonionic surfactant with an HLB value of 10 to 11, and their cloud point is 40°C or lower, so magnetic powder liquids using known dispersants cannot be used. When the liquid temperature exceeds 40°C, the surfactant separates from water and dimethylpolysiloxane oil. The separated surfactants adhere to each other to form hydrophobic oil droplets, to which the magnetic particles adhere, and the dimethylpolysiloxane oil separated from the surfactant naturally separates from water as well, forming hydrophobic oil droplets. Oil droplets are formed, to which the magnetic particles also adhere, and thus the magnetic particles are no longer uniformly dispersed. At the same time, the dimethylpolysiloxane oil separates from the water, resulting in a foaming phenomenon.

As mentioned above, when the liquid temperature of the magnetic powder liquid exceeds approximately 40°C, the dispersion effect and antifoaming effect of known dispersants are lost. contained in the drug
This is due to the fact that the cloud point of a polyethylene glycol type nonionic surfactant with an HLB value of 10 to 11 is about 40°C or lower.

Therefore, as a solution, it is natural to think that the surfactant contained in the above-mentioned silicone antifoaming agent should have a high clouding point, for example, one with a clouding point of about 50°C or higher. It will be done. However, in order to maintain dimethylpolysiloxane oil as a stable oil-in-water emulsion during use, it is necessary to use a polyethylene glycol type nonionic surfactant with an HLB value of 11 or less and a cloud point of 40°C or less. , cloud point approximately 50℃ (in this case
If a polyethylene glycol-type nonionic surfactant with an HLB value of 12 to 15) is used, the silicone antifoaming agent will convert dimethylpolysiloxane into a stable oil-in-water oil during use, even if the liquid temperature is below 40°C. This results in something that cannot be maintained as a mold emulsion.

In addition, if we focus only on the dispersion effect of magnetic powder, we can compare polyethylene glycol type nonionic surfactants with an HLB value of 10 to 13, which are blended in 2 to 6% in known dispersants, to a cloud point of approximately 50 with an HLB value of 12 to 15. ℃ or higher, but in this case, even if a dispersion effect is obtained, an antifoaming effect cannot be obtained, and even if the temperature of the magnetic powder liquid is below 40℃, severe foaming occurs. That's what happens. (This is because when blending a polyethylene glycol type nonionic surfactant with an HLB value of 12 to 15 and a cloud point of approximately 50°C or higher, the properties will be significantly different from those of the surfactant contained in the silicone antifoaming agent. This is because the oil-in-water emulsion of the silicone antifoaming agent is destroyed during use and the dimethylpolysiloxane oil separates from the water.Also, the higher the cloud point, the more hydrophilic groups the surfactant has. The present inventors have developed a solution that can be achieved without changing the surfactants contained in known dispersants. Research has been carried out to find out, and when using a known dispersant with a specific amount of Setsuken added, it has been found that even when the temperature of the magnetic powder liquid exceeds 40°C, it has the same dispersing effect and antifoaming effect as when the liquid temperature is room temperature. We have found the remarkable fact that it can be maintained for a long time and does not have any adverse effects on the above-mentioned conditions.

The amount of Setsuken added is important, at least 1
% or more, the temperature of the magnetic powder liquid will be about 40℃.
It is not possible to maintain the dispersion effect and the antifoaming effect when the amount exceeds the above range. Furthermore, if the content is 40% or more, the viscosity of the dispersant itself becomes extremely high, making it difficult to handle.

That is, when blending 1 to 40% of Setsuken into a formulation of a known dispersant (in a formulation containing Setsuken, the "remaining water" is obtained by subtracting an amount of water commensurate with the blended amount). Even if the temperature of the liquid exceeds 40°C, up to about 50°C, it must be maintained for 10 to 20 hours after the start of use of the magnetic powder liquid (if the dimethylpolysiloxane-polyoxyalkylene copolymer 40-50 for formulations containing 0.1-0.5%
The defoaming effect can be maintained over a period of time.

Based on the above-mentioned knowledge, the present inventor has completed a dispersant for magnetic powder liquid that can be used at high temperatures, and has filed a patent application (Japanese Patent Application No. 143837/1983 (Japanese Patent Application Laid-Open No. 35252/1983)).

By the way, when 1 to 40% of Setsuken is blended with a known dispersant, the above requirements can be met at high temperatures (approximately 40° to 50°C).
There is a problem with its shelf life.

That is, when a liquid product is obtained by blending 1 to 40% of Setsuken with a known dispersant, the viscosity increases due to a gelation phenomenon after about 2 months from the time of blending, and the viscosity increases by about 3%.
After several months, it turns into a pudding-like gel and is no longer a liquid.

When preparing a magnetic powder liquid using a dispersant for magnetic powder liquid, the usual method is to first thoroughly mix a predetermined amount of a dispersant for magnetic powder liquid with a predetermined amount of magnetic powder;
Next, this mixture is poured into a predetermined amount of water, stirred, and the concentration of the dispersant for magnetic powder liquid is 1 to 3%/1 liter of water.
In addition, the magnetic powder liquid has a magnetic powder concentration of 1 to 3 g/1 liter of water. The reason why such an embodiment is adopted is that in order to fully exhibit the properties of the dispersant for magnetic powder liquid, it is preferable to attach the dispersant to each grain of magnetic powder.

Therefore, the dispersant for magnetic powder liquid must be in a liquid state at the time of use, and if it is in a pudding-like state at the time of use, when preparing the magnetic powder liquid according to the above embodiment, the dispersant for magnetic powder liquid must be in a liquid state. This causes problems in mixing, and it becomes extremely difficult to attach the dispersant to each grain of magnetic powder.

However, it is possible to make a liquid by adding an appropriate amount of water to a pudding-like dispersant for magnetic powder liquid and stirring well. However, in this case, extremely complicated weighing work is required to obtain the desired concentrations of the dispersant and magnetic powder in the magnetic powder liquid, and it is not necessary to require field workers to perform such complicated weighing work. The current situation is that it is almost impossible.

The present inventor has conducted repeated research with the aim of providing a dispersant for magnetic powder liquid that can be used at high temperatures and remains liquid for at least one year after production and does not form a pudding-like product.

When 1 to 40% of Setsuken is blended with a known dispersant and a specific amount of alcohol is added, it is possible to completely prevent the formation of a pudding-like substance for at least one year after production. It has been found that there is no adverse effect on the above-mentioned ~ under high temperature conditions.

To be more specific, the present inventors first investigated the factors that cause the liquid material to change over time into a pudding-like material when 1 to 40% of the liquid material is blended with a known dispersant. I learned that the cause of this phenomenon was the gradual introduction of silicone antifoaming agent and water into the micelle lattices of Setsuken. Considering that this phenomenon is unavoidable as long as alcohol is used, we investigated a number of additives with the aim of suppressing this phenomenon. Although it is impossible to completely avoid the occurrence of , completed the present invention.

That is, the present invention provides silicone antifoaming agents 1 to 1 which are made of dimethylpolysiloxane oil as an oil-in-water emulsion using a polyethylene glycol type nonionic surfactant with an HLB value of 10 to 11 and a cloud point of 40°C or less.
3%, 2-6% polyethylene glycol type nonionic surfactant with an HLB value of 10-13 and a cloud point of 50°C or less,
A dispersant for magnetic powder liquid used in wet magnetic flaw detection, consisting of 1 to 40% Setsuken, 0.5 to 25% alcohol, and the balance water, and a polyethylene glycol type nonionic surfactant with an HLB value of 10 to 11 and a cloud point of 40°C or less. 1 to 3% silicone antifoaming agent using dimethylpolysiloxane oil as an oil-in-water emulsion;
2-6% polyethylene glycol type nonionic surfactant with HLB value 10-13 and cloud point 50℃ or less, dimethylpolysiloxane-polyoxyalkylene copolymer (however, the number of moles of ethylene group is 5 moles or less) 0.1
~0.5%, Setsuken 1~40%, Alcohol 0.5~25
%, the balance being water. This is a dispersant for magnetic powder liquid used in wet magnetic flaw detection (hereinafter referred to as an improved dispersant).

The most characteristic feature of the present invention is that when adding Setsuken to the above-mentioned formulation of a known dispersant, 0.5 to 25% of alcohol is further added (in addition, in formulations containing alcohol, the amount The amount of water that is subtracted is the "remaining water.") This is the point.

The amount of alcohol added is important, at least
It will not be effective unless it is added at 0.5% or more.
In addition, a blend of 25% or more must be avoided as there is a risk that the oil-in-water emulsion of the silicone antifoaming agent in the formulation will be destroyed and a portion of the dimethylpolysiloxane oil will separate from the water. Therefore, the amount of alcohol added is selected within the range of 0.5 to 25%.

As the alcohol, monohydric alcohols such as methanol, ethanol, n-propyl alcohol, and isopropyl alcohol, and polyhydric alcohols such as ethylene glycol, propylene glycol, and hexylene glycol are used.

In addition, the ingredients used in the present invention include sodium laurate (C ₁₁ H ₂₃ COONa), sodium myristate (C ₁₃ H ₂₇ COONa), sodium palmitate (C ₁₅ H ₃₁ COONa), and sodium stearate (C ₁₇ H ₃₅ COONa), sodium oleate (C ₁₇ H ₃₃ COONa), sodium soap such as beef tallow fatty acid sodium (NS soap: product name: Kao Soap Co., Ltd.), potassium laurate (C ₁₁ H ₂₃ COOK), myristic acid Potassium (C ₁₃ H ₂₇ COOK), potassium palmitate (C ₁₅ H ₃₁ COOK), potassium stearate (C ₁₇ H ₃₅ COOK), potassium oleate (C ₁₇ H ₃₃ COOK), potassium tallow fatty acid (FR−
Potassium preparations such as 14: trade name: manufactured by Kao Soap Co., Ltd.) and castor oil potassium (FR-25: trade name: manufactured by Kao Soap Co., Ltd.) are used.

The formulation of the improved dispersant according to the present invention is exactly the same as that of the above-mentioned known dispersant, except that alcohol and soap are added.

Further, as in the case of known dispersants, a rust preventive agent such as sodium nitrite or triethanolamine may be added in a range of 3 to 5%, if necessary.

The method for producing the improved dispersant is extremely easy, and the desired product can be obtained by mixing and stirring predetermined amounts of each compound. When mixing and stirring, it is desirable to heat the mixture to approximately 50° to 70°C in order to dissolve it in a short period of time. It is desirable to mix and stir under heating, then cool to room temperature, and then mix and stir the silicone antifoaming agent.

The improved dispersant obtained as described above is a liquid, and it is guaranteed that it will remain liquid for at least one year after production and will not become a pudding-like substance.

The method for using the improved dispersant is exactly the same as that for known dispersants, and the improved dispersant is used at concentrations of 1 to 3.
%/1 liter of water, add 1 to 100% of magnetic powder to the water.
Prepare a magnetic powder solution by adding so that the concentration is 3g/1L of water. This magnetic powder liquid has a temperature of about 50°C not only when the liquid temperature is between 20° and 30°C, but also when the liquid temperature exceeds 40°C.
It can be guaranteed that the above requirements are met and that sufficient flaw detection accuracy is obtained for practical use.
Even when the liquid temperature exceeds 40℃, it takes about 10 to 20 hours after the start of use to reach about 50℃ (40 to 50 hours for formulations containing 0.1 to 0.5% dimethylpolysiloxane-polyoxyalkylene copolymer). It is ensured that the defoaming effect is maintained over a period of time. It should be noted that there is almost no possibility that the temperature of the magnetic powder liquid will exceed approximately 50℃, and if it exceeds 50℃, the wet magnetic flaw detection method itself may become impossible due to burns on the inspector. It becomes possible.

Unfortunately, it has not been possible to theoretically elucidate the effect of adding alcohol in the present invention, but the effect is remarkable as seen in the Examples below.

Regarding the effect of adding Setsuken in the present invention, Setsuken does not have a cloud point and remains dissolved even when the liquid temperature exceeds 40°C. The aforementioned HLB value that occurs when the temperature exceeds 40℃
10 to 11 suppresses the separation of the polyethylene glycol type nonionic surfactant with a cloud point of 40℃ or less, water, and dimethylpolysiloxane oil, and at the same time, the foaming of the dissolved settsuken itself is suppressed by silicone quenching. It is presumed that this is suppressed by the presence of foaming agents.

Next, the structure and effects of the present invention will be explained using Examples and Comparative Examples.

Example 1 <Formulation> Silicone antifoaming agent KM-68-1F (product name: Shin-Etsu Chemical Co., Ltd.) 3% polyoxyethylene nonyl phenyl ether (3 mole adduct) HLB6.1, cloud point 10°C or less 1% Polyoxyethylene lauryl ether (6.5 mol adduct) HLB11.6 cloud point 38℃ 4% Sodium myristate 10% Sodium nitrite 5% n-propyl alcohol 2% Water 75% First, mix ~ and 60℃ The mixture was thoroughly stirred at a temperature of 100.degree. C., then cooled to room temperature (24.degree. C.), and then added and stirred to obtain a translucent improved dispersant.

The viscosity of the improved dispersant thus obtained immediately after production, 2 months later, and 1 year later was measured using a B-type viscometer (manufactured by Tokyo Keiki Seisakusho Co., Ltd.). 165cp (24℃), 167cp (24℃) and
It showed 175 cp (24℃), and it was confirmed that it remained liquid even one year after it was manufactured.

For comparison, excluding the above prescription, 77%
The viscosity immediately after production, after 2 months, and after 3 months was measured in the same manner as above for the comparative formulation obtained by the same procedure as above. (at 24°C), and after 2 months it showed 430 cp (at 24°C), and after 3 months it had become a pudding-like substance, and as it was not liquid, it was impossible to measure the viscosity.

<Preparation of magnetic powder liquid> 600 c.c. of the improved dispersant obtained here, which has been manufactured for about 1 year, and 120 g of fluorescent magnetic powder are thoroughly mixed, and this mixture is mixed with 60 g of water. A magnetic powder solution having an improved dispersant concentration of 1%/water and a magnetic powder concentration of 2 g/1 was prepared by charging it into tank 1 (volume 100) shown in FIG.

<Implementation of wet magnetic flaw detection method> Pump 2 in Figure 1 was activated to circulate the magnetic particle liquid as indicated by the arrow in the figure, and while the magnetic particle liquid was maintained at approximately 40°C, a defect with a depth of 0.88 mm was detected. A square billet of medium 65 low carbon steel is used as the object to be inspected, and the axial energization method DC
Apply current at -1000A, spread the magnetic powder liquid, and visually judge the flaw detection accuracy at each point 5 minutes, 8 hours, and 12 hours after the start of circulation of the magnetic particle liquid under black light irradiation. . As a result, defects were clearly observable at all times, and at approximately 40°C.
It was determined that the magnetic particles in the magnetic powder liquid were sufficiently dispersed not only after 5 minutes, but also after 12 hours, even at a liquid temperature of .

Furthermore, even 12 hours after the start of circulation of the magnetic powder liquid, there were no bubbles overflowing from the top of tank 1, and it was determined that sufficient antifoaming effect was maintained at a liquid temperature of approximately 40°C. Ta.

Example 2 <Formulation> Silicone antifoaming agent KM-72F (Product name: Shin-Etsu Chemical Co., Ltd.
Co., Ltd.) 1% Polyoxyethylene nonyl phenyl ether (5 mole adduct) HLB10.0 cloud point 10℃ or less 1.8% Polyoxyethylene dopanol ether (4.5
Molar adduct) HLB10.7 Cloud point 50℃ 4.2% Sodium tallow fatty acid (NS soap: product name: manufactured by Kao Soap Co., Ltd.) 1% Sodium nitrite 5% Ethanol 23% Water 64% Conducted according to the above formulation A translucent improved dispersant was obtained by the same procedure as in Example 1.

The viscosity of the improved dispersant thus obtained immediately after production, 2 months later, and 1 year later were measured in the same manner as in Example 1, and found to be 140 cp (24°C) and 140 cp (24°C), respectively.
It showed 143cp (24℃) and 154cp (24℃), and it was confirmed that it remained liquid even one year after production.

For comparison, excluding the above prescription, 87%
The viscosity immediately after production, after 2 months, and after 3 months was measured in the same manner as above for the comparative formulation obtained by the same procedure as above. (24°C), 2 months later it showed 388 cp (24°C), and after 3 months it had become a pudding-like substance, and because it was not liquid, it was impossible to measure the viscosity with a B-type viscometer.

Using the improved dispersant that has been manufactured for about one year, <preparation of magnetic powder liquid> was carried out in exactly the same manner as in Example 1, and the liquid temperature of the magnetic powder liquid was adjusted using the same method as in Example 1. <Wet magnetic flaw detection method> was carried out in the same manner as in Example 1 except that the temperature was maintained at 42°C.

As a result, as in Example 1, defects can be clearly observed at any time point, and the magnetic particles in the magnetic powder liquid are still sufficiently dispersed even after 12 hours, even at a liquid temperature of approximately 42°C. I was able to determine that.

Furthermore, even 12 hours after the start of circulation of the magnetic powder liquid, there were no bubbles overflowing from the top of tank 1, and it was determined that sufficient antifoaming effect was maintained at a liquid temperature of approximately 42°C. .

Example 3 <Formulation> Silicone antifoaming agent KM-70 (Product name: Shin-Etsu Chemical
Co., Ltd.) 2% Polyoxyethylene noniphenyl ether (8.5 mol adduct) HLB12.6 Cloud point 44℃ 2% Castor oil potassium (FR-25: Product name: Kao Soap Co., Ltd.) 32% Submersible Sodium nitrate 3% Dimethylpolysiloxane-polyoxyalkylene copolymer (however, number of moles of ethylene group is 3): Silicone surfactant SP-2972 (product name:
(manufactured by Shin-Etsu Chemical Co., Ltd.) 0.2% Hexylene glycol 10% Water 50.8% A translucent improved dispersant was obtained using the above formulation and the same operations as in Example 1.

The viscosity of the improved dispersant thus obtained immediately after production, 2 months later, and 1 year later were measured in the same manner as in Example 1, and found to be 230 cp (24°C) and 230 cp (24°C), respectively.
It showed 234 cp (at 24°C) and 251 cp (at 24°C), confirming that it remained liquid even one year after production.

For comparison, excluding the above prescriptions, 60.8
The viscosity immediately after production, 2 months later, and 3 months later were measured in the same manner as above for the comparative formulation obtained by the same procedure as above. It showed 260cp (24°C), 600cp (24°C) after 2 months, and turned into a pudding-like substance after 3 months, and because it was not liquid, it was impossible to measure the viscosity with a B-type viscometer.

Using the improved dispersant that has been manufactured for about one year, <preparation of magnetic powder liquid> was carried out in exactly the same manner as in Example 1, and the liquid temperature of the magnetic powder liquid was adjusted using the same method as in Example 1. <Wet magnetic flaw detection method> was carried out in the same manner as in Example 1 except that the temperature was maintained at 42°C.

As a result, as in Example 1, defects can be clearly observed at any time point, and the magnetic particles in the magnetic powder liquid are still sufficiently dispersed even after 50 hours, even at a liquid temperature of about 42°C. I was able to determine that.

Furthermore, even 50 hours after the start of circulation of the magnetic powder liquid, there were no bubbles overflowing from the top of tank 1, and it was determined that sufficient antifoaming effect was maintained at a liquid temperature of approximately 42°C. Ta.

The silicone antifoaming agents used in Examples 1 to 3 all have HLB values of 10 to 11, which are considered optimal as antifoaming agents for use in dispersants for magnetic powder liquids, and cloud points of 40°C.
A commercially available silicone antifoaming agent made of dimethylpolysiloxane oil as an oil-in-water emulsion using the following polyethylene glycol type nonionic surfactant, dimethylpolysiloxane oil 10
~30% surfactant, 5~10% surfactant, and the balance water.

[Brief explanation of drawings]

FIG. 1 is a partial longitudinal cross-sectional explanatory view showing a magnetic powder liquid stirring device commonly used in wet magnetic flaw detection. In the figure, 1 is a tank, 2 is a pump, and A is an object to be inspected. Note that the arrows in the figure indicate the circulation system path of the magnetic powder liquid.

Claims (1)

[Claims] 1. 1 to 3% by weight silicone antifoaming agent made of dimethylpolysiloxane oil as an oil-in-water emulsion using a polyethylene glycol type nonionic surfactant with an HLB value of 10 to 11 and a cloud point of 40°C or less. ,
2-6% by weight of polyethylene glycol type nonionic surfactant with an HLB value of 10-13 and a cloud point of 50°C or less, 1-40% by weight of soap, 0.5-25% by weight of alcohol,
A dispersant for magnetic powder liquid used in wet magnetic flaw detection with the remainder being water. 2 1 to 3% by weight silicone antifoaming agent made of dimethylpolysiloxane oil as an oil-in-water emulsion using a polyethylene glycol type nonionic surfactant with an HLB value of 10 to 11 and a cloud point of 40°C or less;
2 to 6% by weight of polyethylene glycol type nonionic surfactant with HLB value of 10 to 13 and cloud point of 50°C or less, dimethylpolysiloxane-polyoxyalkylene copolymer (however, the number of moles of ethylene group is 5 moles or less)
A dispersant for magnetic powder liquid used in wet magnetic flaw detection, consisting of 0.1 to 0.5% by weight, 1 to 40% by weight of soap, 0.5 to 25% by weight of alcohol, and the balance water.