JPS5940492B2 - Method and device for controlling air bubble content in aqueous slurry - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the amount of air bubbles contained in an aqueous slurry, particularly an aqueous slurry containing air bubbles, when the slurry is prepared.

Preparation of an aqueous slurry containing air bubbles is often employed as one of the product manufacturing processes in food, cosmetics, synthetic leather, building materials, and various other industrial fields.

There are two methods for preparing a foam-containing aqueous slurry: a foaming method using a foaming agent and a foaming method (foaming method) using a foaming agent such as a surfactant. It is technically quite difficult to prepare a slurry containing a desired amount of air bubbles with high accuracy, and it has relied more on experience and intuition than in the past.

This tendency was particularly strong in the latter method. That is,
The amount of air bubbles contained in the slurry is determined by the quantitative balance between the air bubbles that are generated or introduced and the air bubbles that disappear.The balance is determined by the temperature, viscosity, pH, impact applied to the slurry, and shear during stirring. This is because a large number of factors, such as external mechanical forces such as force, are intricately related and can constantly cause variations in the bubble content. Variations in the air bubble content in the slurry greatly reduce product yield, especially in continuous production systems. Furthermore, Setsukou,
It is also a significant disadvantage when producing products such as cement or thermosetting resins which have a short pot life and require rapid introduction or generation of air bubbles and kneading. Therefore,
An object of the present invention is to provide a control method for quickly detecting the amount of air bubbles in an air-containing slurry and thereby adjusting the air bubble content to a desired level, thereby reducing the variation in air bubble content of an air-filled product. The purpose is to manufacture.

As a result of extensive research in accordance with the above-mentioned objective, the present inventors have found that the air bubble content in an aqueous slurry is inversely proportional to the electrical conductivity or proportional to the electrical resistance value of the slurry. The present invention was completed based on the discovery that the content of air bubbles in an aqueous slurry can be determined by measuring the value of electrical resistance.

Next, the principle of the present invention will be explained.

Generally, the conductivity in an aqueous medium is determined by the mobility of ions eluted therein, and in particular, hydroxide ions and hydrogen ions make a larger contribution to the conductivity than other ion species.

This is because both ions use the special two-structure 2 of water to transfer charges, and unlike other ion species, ions do not directly transfer charges. Since pure water contains only trace amounts of hydrogen ions and hydroxide ions, its electrical conductivity is also extremely low. However, industrially used water usually contains a wide variety of ionic species, including acids and alkalis, and typically exhibits fairly high conductivity. Therefore, in an aqueous slurry, by controlling the conductivity of the slurry to a constant value,
It is considered that the above-mentioned variation factors such as viscosity and stirring speed can be ignored to some extent. This will be explained using cement slurry as an example. The true specific gravity of the cured cement is approximately 2.3. On the other hand, the specific gravity of a slurry with a water/cement weight ratio of 1:2 is around 1.8, so if we were to introduce air bubbles into this slurry to prepare air bubble-containing slurries with various specific gravity of 5. The required amount of bubbles is as follows. As is clear from this table, even if there is a relatively small difference in slurry specific gravity, there is a very large difference in the amount of bubbles to be introduced. The present inventors focused on the remarkable change in the amount of bubbles due to changes in the specific gravity of the slurry containing bubbles, the insulating properties of the bubbles themselves, and the special conductivity type of water described above. After knowing the content, we decided to apply this knowledge to control the amount of bubbles. That is, the bubble content control method according to the present invention is a bubble content control method for preparing an aqueous slurry containing a desired amount of bubbles, and includes at least one pair of bubbles in the bubble-containing aqueous slurry. The content of air bubbles in the slurry is detected by dipping a counter electrode and measuring the electrical conductivity or electrical resistance of the slurry existing between the electrodes. The intention is to adjust the amount of bubbles contained in the slurry so as to maintain the value of electrical conductivity or electrical resistance corresponding to the content.

In order to adjust the amount of air bubbles contained in the aqueous slurry so as to maintain a value of conductivity or electrical resistance corresponding to a desired air bubble content, depending on the method of preparing the aerated slurry, for example, adding a foaming agent to the aqueous slurry may be necessary. This can be done by adjusting the stirring speed of the aqueous slurry contained, or by adjusting the amount of the foamed liquid foamed by the foaming agent mixed with the aqueous slurry that does not yet contain the foaming agent. I can do it.

In that case, automatic control can be performed by feeding back information on the detected air bubble content in the air bubble-containing slurry to the mechanism controlling the stirring speed or the air bubble-containing liquid feeding mechanism. FIG. 1 is an explanatory diagram showing an example of an apparatus used in the method of the present invention described above.

The control device includes an air bubble content detection device 1 in the slurry, an air bubble amount adjustment device 2 for increasing or decreasing the amount of air bubbles in the slurry, and information from the detection device 1 is fed back to the air bubble amount adjustment device 2 to control the air bubble content in the slurry. device 3 for controlling the operation of 2;
It is composed of: The bubble amount detection device 1 includes a pair of opposing electrodes (for example, platinum plates) 1a and a conductivity meter or electrical resistance meter 1b electrically connected to the electrodes.
In the figure, the counter electrode 1a is arranged in a conduit for taking out the bubble-containing slurry. Further, a plurality of pairs of counter electrodes 1a may be arranged. The bubble amount adjusting device 2 includes a stirring blade 2a provided in the mixer and a motor 2b for rotationally driving the stirring blade 2a.
and a transmission 2c for the motor 2b. Furthermore, the control device 3 includes a means for presetting a value of conductivity or electrical resistance corresponding to a desired bubble content, and a means for setting in advance a value of electrical conductivity or electrical resistance that corresponds to a desired bubble content, and a means for setting in advance a value of electrical conductivity or electrical resistance that is actually measured. A means is included for applying an electric signal to the bubble amount adjusting device 2 to adjust the rotational speed of the stirring blade 2a so as to maintain the rotational speed of the stirring blade 2a. The aqueous solution in which the foaming agent is dissolved is fed from the storage tank 4 to the foam liquid preparation tank 6 via the metering pump 5.

The preparation tank 6 has a stirring blade 8 connected to a drive motor 7.
is provided, where a bubble-containing liquid is created. The aerated liquid is then sent to an aerated slurry preparation mixer 9. On the other hand, cement and other powders, which are the solid content of the slurry, are supplied to the preparation mixer 9 from a metering feeder 10, and mixed with the bubble liquid by a stirring blade 2a. The bubble-containing slurry thus prepared is taken out from the slurry outlet conduit 11. In this case, the air bubble content in the slurry flowing through the pipe line 11 is detected by the detection device 1 in the form of the electrical conductivity or electrical resistance of the slurry, and the rotational speed force of the stirring blade 2a changes depending on the content. adjusted accordingly. Therefore, the slurry taken out from the preparation mixer 9 can always contain a desired amount of air bubbles. In the above description, an example has been described in which information from the bubble detection device is fed to the rotation of the stirring blade of the bubble-containing slurry, but in addition to this, the feed back destination may be a bubble-containing liquid feed rate adjustment valve.

Next, examples will be shown in order to clarify the effects of the present invention.

In addition, as a reference example, it is also shown that there is a certain relationship between the bubble content, that is, the specific gravity of the bubble-containing slurry, and the electrical conductivity of the slurry, and this result is the basis of the invention according to the present invention.

In this example, an example in which a bubble-containing slurry of a rapidly hardening cement composition was prepared using the apparatus shown in FIG. 1 will be described.

Foaming liquid composition Water: 100 parts by weight Slurry water Foaming liquid/rapidly setting cement composition = 55 (weight ratio) The prepared aerated cement concrete slurry was poured into five molds continuously at regular intervals. Aerated concrete was produced by pouring into the concrete.

After curing, the concrete was removed from the mold and the specific gravity of each cellular concrete was measured. As a result, the average specific gravity was 0.873 and the mean square error was 0.014. For comparison, the same type of aerated concrete manufactured by the conventional method, that is, the method by skilled workers, has an average specific gravity of 0.832 and a mean square error of 0.078.
It was hot.

From these results, according to the present invention, the air bubble content in the slurry can be maintained at a constant predetermined value, and therefore, the variation in the air bubble content of manufactured products can be significantly reduced. I can do it. Reference Example Among the methods for preparing a bubble-containing slurry of a rapidly hardening cement composition shown in the example, a bubble-containing slurry with a different bubble content, that is, a specific gravity, was prepared with the same composition and formulation except for varying the amount of sodium dodecylbenzenesulfonate added. A pair of platinum electrode plates measuring 20mm x 20mm were placed opposite each other at a distance of 30ml, and the conductivity was measured.

As a result, a certain relationship as shown in FIG. 2 was obtained, and it was found that the specific gravity of the slurry, that is, the bubble content, can be determined by measuring the electrical conductivity (or electrical resistance) of the slurry.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of an apparatus used in the method of the present invention, and FIG. 2 is a graph showing the relationship between specific gravity and electrical conductivity of a bubble-containing slurry. Explanation of symbols, 1...Bubble content detection device, 1a
...Counter electrode, 1b...Conductivity meter or electrical resistance meter, 2...Bubble amount adjustment device, 3...
... Control device, 4 ... Foaming agent-containing aqueous solution storage tank, 6 ... Foaming liquid adjustment tank, 8 ...
... Stirring blade, 9... Bubbles-containing slurry adjustment mixer, 10... Metering feeder for cement, etc.,
11...Bubble-containing slurry extraction pipe.

Claims (1)

[Scope of Claims] 1. A method for controlling air bubble content for preparing an aqueous slurry containing a desired amount of air bubbles, the method comprising: immersing at least one pair of opposing electrodes in an aqueous slurry containing air bubbles; Detecting the bubble content in the slurry by measuring the conductivity or electrical resistance of the slurry existing between the electrodes,
The air bubbles contained in the slurry can be reduced by adjusting the stirring speed of the slurry so that the electrical conductivity or electrical resistance value maintains the electrical conductivity or electrical resistance value corresponding to the desired air bubble content. A method for controlling air bubble content in an aqueous slurry, comprising adjusting the amount. 2. A method of controlling air bubble content for preparing an aqueous slurry containing a desired amount of air bubbles, the method comprising: immersing at least a pair of opposing electrodes in an aqueous slurry containing air bubbles; detecting the air bubble content in the slurry by measuring the conductivity or electrical resistance of the slurry;
By adjusting the amount of the bubble-containing liquid mixed with the slurry so that the conductivity or electrical resistance value maintains the value of the electrical conductivity or electrical resistance corresponding to the desired bubble content, A method for controlling the content of air bubbles in an aqueous slurry, the method comprising adjusting the amount of air bubbles contained in an aqueous slurry.