JPH0832961B2 - Acid cleaner - Google Patents

Description

TECHNICAL FIELD The present invention relates to an acid cleaner, particularly a paste-like acid cleaner for cleaning and removing stainless steel scale.

[Prior Art] There is known a method of chemically removing a scale generated at a welded portion of stainless steel using an acid cleaner.
Applying an adhesive paste-like acid cleaner to the part of the stainless steel where you want to remove the scale, reacting it for a certain period of time, and then washing with water is a method in which the target you want to remove the scale from is large or there is local scale. It has a feature that it can be easily applied even in the case.

Conventional paste-like acid cleaners contain hydrofluoric acid and nitric acid as acid components, and starch, CMC, PVA, and
An organic polymer such as an acrylic polymer and an inorganic powder such as diatomaceous earth, clay, bentonite, or magnesium sulfate were mixed to form a paste. Also,
It has also been known to add a surfactant in order to improve the dispersibility of the inorganic powder.

[Problems to be Solved by the Invention] However, since the above-mentioned acid detergent contains hydrofluoric acid and nitric acid and has very strong acidity, even if an acrylic polymer having relatively high acid resistance is used. However, there is a problem that they are decomposed during storage and the liquid is separated from the detergent or colored in yellow. The cleaning agent from which the liquid is separated needs to be mixed again at the time of use, and if the mixing is insufficient, there is a problem that liquid sags and the treated surface becomes non-uniform.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and is an acid detergent comprising hydrofluoric acid, nitric acid, a polysaccharide, and an inorganic powder, which is an organopolysiloxane. The present invention provides an acid detergent comprising:

In the present invention, it is necessary that the acid detergent contains an organopolysiloxane. Among these, organopolysiloxane is more preferable. As the organopolysiloxane, silicone oils such as dimethyl silicone oil and alkyl-modified silicone oil are preferable, and silicone polyether copolymers and the like can also be used. These can be used in the form of emulsion, solvent type, oil compound and the like. The amount of the organopolysiloxane used is preferably 0.01 to 5% by weight based on the total amount of the acid detergent. A more preferable range is 0.5 to 3% by weight.

The acid detergent of the present invention is required to contain a polysaccharide. Polysaccharides having acid resistance are preferable, and natural species such as xanthan gum, locust bean gum, tamarindone, gum arabic, guar gum, tragacanth gum, pectin, and furceleran are preferable because they have high acid resistance and little change with time. Of these, xanthan gum, locust bean gum and tamarindone are particularly preferable.
The amount of the polysaccharide used is preferably about 0.01 to 7% with respect to the total amount of the acid detergent.

In the present invention, the acid cleaning component is a mixed acid of hydrofluoric acid and nitric acid. The content of HF is based on the total amount of the pasty detergent.
About 10 to 20% by weight and about 15 to 20% by weight of HNO ₃ are preferable. In addition to hydrofluoric acid and nitric acid, ammonium acid fluoride,
It is also possible to use a mixture of phosphoric acid, hydrochloric acid, sulfuric acid and the like.

In the present invention, the inorganic powder can be used without particular limitation as long as it does not decompose or deteriorate with an acid detergent. Preferred examples of the inorganic powder include magnesium sulfate, sodium sulfate, aluminum sulfate, magnesium nitrate, sodium nitrate and aluminum nitrate. The amount used is preferably about 30 to 40% by weight based on the total amount of the detergent.

The cleaning agent of the present invention is a paste obtained by uniformly mixing the above components. The viscosity is preferably 500 to 50,000 cps. If the viscosity is less than 500 cps, liquid dripping may occur, which is not preferable. When the viscosity is higher than 50,000 cps, it is difficult to obtain a uniform and thin coating film, a large amount of cleaning agent may be required, and unevenness may occur, which is not preferable.

The acid cleaner of the present invention can be effectively used particularly for removing scale generated on stainless steel.

As a method of removing the scale of stainless steel using the cleaning agent of the present invention, for example, the following method is preferable. First, a cleaning agent is applied to the portion where the scale is to be removed with a brush or the like. Then, after leaving it as it is for about 0.5 to 24 hours, the whole cleaning agent is washed with water. Post-treatment can be carried out if necessary.

Example 1 Example 1 34 kg of magnesium sulfate, 0.14 kg of xanthan gum, 0.8 kg of 30% aqueous dimethylpolysiloxane emulsion and 31.06 of water.
kg was added and the mixture was sufficiently stirred to form a slurry. to this,
A mixed acid solution obtained by previously mixing 18 kg of nitric acid (62.5%) and 16 kg of hydrofluoric acid (55%) was added and mixed and stirred. After stirring for 1 hour, a white paste-like acid cleaner having a viscosity of about 1500 cps was obtained.

This cleaning agent was applied to a welded scale portion of SUS 304 and SUS 316 with a nylon brush, left for 3 hours, and then washed with water. In both cases, the scale was completely removed, and a homogeneous, shiny, and specular metal surface was obtained.

When this cleaning agent was placed in an airtight container and left standing for 6 months, the same cleaning test as above was conducted again, and there was no change in the cleaning property. Further, the cleaning agent was not discolored.

Example 2 Magnesium sulfate 34 kg, tamarindone 0.2 kg, silicone oil (dimethyl polysiloxane) 1 kg and water 30.8 kg
Was added and stirred sufficiently. To this, 18.9 kg of nitric acid (62.5%) was added, and further 15.1 kg of hydrofluoric acid (55%) was added and mixed by stirring, and 1 hour later, a white paste-like acid cleaner having a viscosity of about 1500 cps was obtained.

When the cleaning property and the stability were evaluated in the same manner as in Example 1, the same good and stable performance as in Example 1 was obtained.

[Effect] The acid cleaning agent of the present invention has high stability and is homogeneous and has no liquid separation even after long-term storage, and can be uniformly and thinly applied onto the material to be cleaned. Therefore, the scale such as stainless steel can be removed evenly.

Claims (3)

[Claims] 1. An acid cleaner comprising hydrofluoric acid, nitric acid, a polysaccharide, and an inorganic powder, which contains an organopolysiloxane. 2. The acid detergent according to claim 1, wherein the polysaccharide is one or more selected from the group consisting of xanthan gum, locust bean gum, tamarindone, gum arabic, guar gum, tragacanth gum, pectin and furceleran. 3. An inorganic powder selected from the group consisting of magnesium sulfate, sodium sulfate, aluminum sulfate, magnesium nitrate, sodium nitrate and aluminum nitrate.
The acid cleaning agent according to claim 1 or 2, which is one or more kinds.