JP2979103B2 - Thermal analyzer - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a thermoanalytical device, and more particularly to an improvement in a device used for thermogravimetry, differential thermogravimetry, and the like, which measures a change in weight of a sample due to temperature.

[Prior art] Conventionally, in a thermoanalytical apparatus, thermogravimetry (TG), which measures the weight change of a substance while heating or cooling the substance, or placing a sample and a reference substance in a furnace and heating them, Differential thermal analysis (DTA) for measuring the temperature difference between the two, and differential thermogravimetric analysis (TG-DTA) combining the two. In recent years, with this type of apparatus, measurement has been performed under various conditions, such as finer weight measurement, measurement under high pressure, and low pressure, and measurement has been diversified.

FIG. 4 shows a conventional differential thermogravimetric analysis type (TG-DT
The apparatus of A) is shown. In the figure, a protective tube 2 is provided in an electric furnace 1, and a sample holder 3 on which a sample is placed is provided in the protective tube 2. On the sample holder 3, for example, both a reference material and a sample to be inspected are placed at predetermined positions so that comparison with the reference material can be performed. Further, various atmospheric gases can flow into the protective tube 2 from the gas supply port 4a via the sleeve 4b, and can be measured under an arbitrary atmosphere.

The sample holder 3 is connected to one end of the balance 6 in the main body device 5, and when the weight of the sample changes, the balance 6
It is configured to move up and down with the point as a fulcrum, and a magnetic force driving means 7 including a magnet, a feedback (control) coil and the like is provided in order to return the movement of the balance 6 thus moved to the original position. I have. The sample holder 3 is provided with a thermocouple (not shown) at a place where the sample is placed.
The thermocouple can detect a change in the temperature of the sample itself.

The magnetic driving means 7 and the thermocouple are connected to a measuring circuit 8. The measuring circuit 8 converts the electric power required to drive the magnetic driving means 7 into a weight, and converts the weight of the sample into a weight. The change is measured, while the temperature of the sample is measured by detecting the electromotive force generated by the thermocouple.

In general, the measurement is usually performed under normal pressure. However, in the above example, the pressure setting means 10 such as a rotary pump is connected to the apparatus main body 5 via the valve 9, and the sample is subjected to low pressure. Alternatively, it can be measured under high pressure.

According to the above configuration, the gas supply port is provided in the protective tube 2.
The gas is supplied from 4a to form a predetermined atmosphere, and the sample on the sample holder 3 is heated by the electric furnace 1, so that the weight of the sample changes and the temperature of the sample itself changes.

Then, the change in the weight is measured by the output of the magnetic force driving means 7 for returning the moved balance 6. In this case, since the weight of the reference material does not change, the change in the weight of only the sample can be measured. Further, since a change in temperature appears as an electromotive force of the thermocouple, a change in temperature of the sample itself is detected in comparison with a reference substance by measuring the amount of current from the thermocouple.

By the way, in the conventional thermal analysis measurement, as the above-mentioned atmospheric gas, various gases such as an inert gas or an active gas other than air are used, and the sample reacts by heating to generate a separation gas. In some cases, exhaust of these gases is a problem. Some of these exhaust gases can be discharged into the air as they are, but it is preferable to collect them as much as possible.

Therefore, the present applicant has proposed a method of dissolving the exhaust gas in a solution as a simple method of recovering the exhaust gas. According to this proposal, as shown in FIG. The liquid tank 12 from the gas outlet 2a through the exhaust tube 11
Exhaust gas is introduced inside. According to this, the exhaust gas can be dissolved in the solution 13 such as water, and the gas used for the measurement or the separated gas can be recovered in a dissolved state.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional thermal analyzer, when introducing a gas into the solution, the pressure in the protective tube 2 which is a measurement chamber and the pressure in the device main body 5 are changed. There is a problem that the measurement becomes unstable.

That is, as shown, the exhaust tube 11 is
Since it is arranged at the bottom of 12, the pressure of the solution (for example, water) for the height h in the figure is applied to the tip of the tube 11,
The gas bubbles 100 emitted from the distal end of the tube 11 are discharged into the solution against the above-mentioned liquid pressure. Therefore, bubbles
The pressure for discharging 100 is given from the inside of the protection tube 2, but at the moment when the gas bubbles are discharged into the solution, the pressure in the protection tube 2 decreases and the pressure in the protection tube 2 fluctuates. I do. This pressure change causes a variation in the measured value of the balance 6 to reduce the measurement accuracy, and particularly, a minute weight change, for example, several μm.
When a change in g is measured, a large measurement error will result.

The present invention has been made in view of the above problems, and an object of the present invention is to make it possible to effectively collect exhaust gas and to stably prevent the exhaust gas from being affected by a pressure change in a measurement chamber generated at that time. Another object of the present invention is to provide a thermal analyzer capable of performing highly accurate measurement.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a thermal analyzer for applying heat to a sample placed in an electric furnace and measuring a change in the weight of the sample. A gas storage chamber partitioned by a porous material is provided, and an exhaust tube for the gas in the electric furnace is provided in the gas storage chamber, and gas exhausted from the electric furnace is discharged from a wall of the gas storage chamber. A gas recovery unit for recovering the sample in an aqueous state by guiding it into the solution in the liquid tank, a holder for mounting a reference substance for reference, and a holder for mounting the sample are arranged on a balance beam, and the weight change of the sample is determined by a differential method. And a differential balance unit for detecting.

In the above description, the water-soluble state includes not only a state of being dissolved in water but also a state of being dissolved in another solution.

[Operation] According to the above configuration, when the atmosphere gas or the separation gas is introduced into the solution in the gas recovery unit, a pressure change occurs in the measurement chamber when the gas is bubbled and sent into the solution. This pressure change affects not only the sample but also the reference material.

However, since the differential balance measures only the weight difference between the reference material and the sample, the apparent weight change given to both the sample and the reference material due to the pressure change is offset and appears in the measured value. Is prevented.

Further, when the gas is led to the storage chamber partitioned by the porous material, the gas is gradually released from the wall of the porous material into the solution, so that the pressure change caused by the generation of bubbles can be reduced, and The measured value will be stable.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a thermal analyzer according to an embodiment, and the embodiment performs differential thermogravimetric analysis (TG-DTA).

In the figure, a protective tube 2 is provided in an electric furnace 1, an exhaust tube 11 is attached to a gas outlet 2 a at an upper portion of the protective tube 2, and the exhaust tube 11 is disposed inside. A liquid tank 12 in which a solution 13 is stored is provided, and these members 11 to 13 constitute a gas recovery unit.
Therefore, the atmosphere gas or the separation gas exhausted from the protective tube 2 in the electric furnace 1 is dissolved in the solution in the liquid tank 12, and at this time, the bubbles 100 are introduced into the solution. Each time, a pressure change occurs in the protection tube 2 or the like.

On the other hand, a holder 17a for mounting the sample 15 and a holder 17b for mounting a reference substance for reference are provided in the protective tube 2, and the sub-beams 18a and 18b are attached to the holders 17a and 17b, respectively. The auxiliary beams 18a and 18b are rotatably connected to the main beam 20 at auxiliary fulcrums B set on the support members 19a and 19b. The main beam 20 balances the center fulcrum A. It is supported by the torsion band 21 to keep it. In addition, the sub beams 18a and 18b
Are mutually pulled by a pull wire 22 at the lower part thereof,
This prevents the sample holder 17 and the sub beam 18 from swinging, stabilizes the balance, and keeps the position of the sample 15 in the electric furnace 1 constant.

And the torsion band supporting the main beam 20
A control coil 23 is attached near 21 to the main beam 20 and connected to the main beam 20. A magnet 24 is attached to the apparatus main body in the vicinity of the control coil 23. Therefore, the main beam above
When the motor 20 is tilted, the main beam 20 can be returned to the original horizontal state by supplying a current to the control coil 23.

The main beam 20 has a shutter piece 25 facing downward.
On the other hand, a light emitting unit 26a and a light receiving unit 26b composed of a photoelectric element are provided on the apparatus main body side, and when the main beam 20 is not inclined, the shutter piece 25 blocks light emission of the light emitting unit 26a. Thus, the inclination of the main beam 20 can be detected by receiving light from the light receiving unit 26b.

In the embodiment, the temperature of the sample itself is also detected, and in the holders 17a and 17b, thermocouples 27a and 27b are provided on the mounting surfaces of the sample 15 and the reference material 16, and the thermocouples 27a and 27b are used. sample
The temperature of the reference substance 15 and the reference substance 16 can be converted into a current value and measured.

Further, in order to control the entire apparatus, a weight measuring circuit 28a,
A control circuit 28 incorporating a temperature measurement circuit 28b is provided.The weight measurement circuit 28a controls the control coil 23 and is connected to a light emitting unit 26a and a light receiving unit 26b.The temperature measurement circuit 28b is connected to the thermocouple. Input 27 output current.
The control circuit 28 controls the electric furnace 1 and controls the output of the measured values obtained by the measuring circuits 28a and 28b to a data processing unit (computer) 29.

The embodiment has the above configuration, and its operation will be described below.

For example, when a predetermined atmosphere is set around the measurement sample, carbon monoxide (CO), ammonia (NH ₃ ) or the like flows from the gas supply port 2b, and the atmosphere gas is exhausted from the gas discharge port 2a. The liquid is introduced into the liquid tank 12 through the tube 11. Therefore, the gas is dissolved by the bubbles 100 coming out of the end of the exhaust tube 11 into the solution. At this time, every time the bubbles 100 leave the exhaust tube 11, the pressure in the protective tube 2 and the auxiliary beam The pressure inside the apparatus main body where the main beam 18 and the main beam 20 are arranged slightly changes.

On the other hand, the electric furnace 1 shown in FIG.
The temperature of the reference material 16 is raised and lowered according to a predetermined program. For example, if the weight of the sample 15 is changed by heating to about 1000 ° C. (may not change), the reference material 16 does not change by heating. Will cause a weight difference. This weight difference is transmitted from the sub beam 18 to the main beam 20 via the sub fulcrum B, and when the sample 15 becomes lighter, the left side of the main beam 20 falls with the central fulcrum A as a fulcrum. At this time, since the shutter piece 24 moves, the light receiving unit 26
The weight measurement circuit indicates that the weight change has occurred due to the light detection of
Determined by 28a.

Then, the weight measuring circuit 28a detects the tilted main beam 2
Since a current is supplied to the control coil 22 so that 0 is returned to the horizontal state, a change value of the weight is measured by detecting the supplied current value.

In the above measurement, a pressure change occurs during gas recovery, and this pressure change affects the measured value of the weight change of the sample. This effect is exerted not only on the sample but also on the reference substance. ing. Therefore, the influence of the pressure change is cancelled, and only the difference between the reference substance and the sample, that is, only the change in weight of the sample is measured.

FIG. 2 shows the measured values of the baseline performed by the apparatus of the embodiment and the conventional apparatus, and the measurement was performed by a 50 μg full-scale apparatus. The curve 200 shown in FIG. 7A is measured by a conventional apparatus, and has a baseline waving up and down with a width of about 10 μg. On the other hand, in the present embodiment, the curve 201 in FIG.
3 μg with little waving as shown in FIG.
, And a stable baseline can be obtained.

In the embodiment, a current proportional to the temperature of the sample 15 and the reference substance 16 is supplied from the thermocouples 27a and 27b,
The temperature is specified by the temperature measurement circuit 28b. Therefore, in the embodiment, the temperature change of the sample itself can be measured in addition to the weight change of the sample due to heating, and the weight measurement (TG-DTA), the differential thermal analysis (DTA), and the like for the temperature change of the sample can be performed. it can. Then, these measured values are output from the control circuit 28 to the data processing unit 29 and stored and held therein, and the CRT shown in FIG.
The image is displayed on the display 30 and can be printed out to a recording device (not shown) if necessary.

Next, a modification of the gas recovery unit in the present invention will be described with reference to FIG.

In FIG. 3, a gas storage chamber 31 partitioned by a partition plate 12a of a porous material is provided from the middle to the bottom of the liquid tank 12, and the partition plate 12a is made of a material for unsintering. It can be made of a material with a small mesh. Then, the exhaust tube 11 is fixed to the wall of the liquid tank 12 by the fixture 32 and its tip is introduced into the storage chamber 31. In this case, the tip of the exhaust tube 11 projects from the solution surface 300 of the storage chamber 12a. To prevent hydraulic pressure from being applied to the tube tip.

According to this, gas bubbles come out from the small holes (pores) in the partition plate 12a of the storage chamber 31, and the gas is dissolved in the solution, and the pressure change in this case is extremely small. Therefore, there is an advantage that the pressure change applied to the measurement chamber can be significantly reduced.

In the above-described embodiment, the description of the discharge of the atmospheric gas introduced by the gas flow type has been described. However, the present invention is not limited to the gas flow type, and the separation gas generated by the thermal reaction, for example, chlorine (Cl ₂ ), iodine (I ₂ ) It can be applied to the case of collecting the information.

In the above-described embodiment, the method in which the differential balance unit attaches both holders 17a and 17b to both ends of one main beam 20 has been described. However, the present invention is not limited to this. Holder 17a for mounting and holder 1 for mounting reference material
Differential balances in which 7b is separately arranged on the two main beams or other types of differential balances can be used.

[Effects of the Invention] As described above, according to the present invention, a gas storage chamber partitioned by a porous material is provided in a liquid tank, and gas exhausted from the electric furnace is discharged from the wall of the gas storage chamber. Since the liquid is guided into the solution in the liquid tank and is recovered in an aqueous state, transmission of a pressure change due to the generation of bubbles into the measurement chamber can be suppressed. In addition, the balance section arranges a holder for placing a reference material for reference on the balance beam and a holder for placing the sample, and detects a change in weight of the sample by a differential method, so it is assumed that there is a pressure change during gas recovery. However, there is an advantage that the influence can be eliminated and stable and accurate measurement can be performed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main configuration of a thermal analyzer according to an embodiment of the present invention, and FIG. 2 is a diagram showing a result of an experiment [FIG. FIG. 3 is a diagram showing another modification of the gas recovery unit in the embodiment, and FIG. 4 is a diagram showing a schematic configuration of a conventional thermal analyzer. DESCRIPTION OF SYMBOLS 1 ... Electric furnace, 2 ... Protective tube, 3 ... Sample holder, 5 ... Main body, 6 ... Balance, 7 ... Magnetic driving means, 11 ... Exhaust tube, 12 ... Liquid tank, 12a ... … Partition plate, 13… solution, 15 …… sample, 16 …… reference material, 17a, 17b …… holder, 18a, 18b …… sub beam, 20 …… main beam, 21 …… torsion band, 22 …… Pull wire, 23 ... Control coil, 24 ... Magnet, 25 ... Shutter piece, 26a ... Light emitting unit, 26b ... Light receiving unit, 28 ... Control circuit, 28a ... Weight measuring circuit, 28b ... Temperature measurement Circuit, 31 ... Reservoir.

Claims (1)

(57) [Claims] In a thermal analyzer for applying heat to a sample placed in an electric furnace and measuring a change in weight of the sample, a gas storage chamber partitioned by a porous material is provided in a liquid tank. A gas recovery tube is provided in the gas storage chamber, and gas exhausted from the electric furnace is introduced into the solution in the liquid tank by guiding the gas exhausted from the electric furnace from the wall of the gas storage chamber. And a differential balance unit for arranging a holder for mounting a reference material for reference and a holder for mounting the sample on a balance beam, and detecting a change in weight of the sample by a differential method. Analysis equipment.