JP3195816B2 - Method and apparatus for measuring sample vapor pressure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to the vapor pressure of the sample vapor pressure of about 10 ^-4 Torr to several tens Torr for determining the relationship between the vapor pressure versus temperature of the sample based on the differential thermogravimetric measurement under a vacuum atmosphere,
The present invention relates to a method and an apparatus for measuring a temperature in a range of -150 ° C to 1500 ° C.

[0002]

2. Description of the Related Art Conventional methods for measuring vapor pressure include: (1) a method for directly measuring the vapor pressure at a constant temperature;
There are a method of measuring the flow rate of the sample vapor in the gas stream, and (3) a method of measuring the rate of weight loss due to evaporation of the sample. Each of these methods is a so-called constant temperature measurement method in which measurement is performed at a constant temperature.

[0003]

In the above-mentioned constant temperature measurement method, the constant temperature measurement method can perform precise measurement, but has a problem that the time required for the measurement is long and not simple. By the way, there is a constant-rate temperature rise measurement method as compared with the constant temperature measurement method. The constant-rate temperature rise measurement method is simpler than the constant temperature measurement method, but has a problem that the measurement accuracy is not high. Accordingly, it is an object of the present invention to provide a method and an apparatus for measuring the vapor pressure of a sample, which can solve the problems of the prior art and can simply and accurately measure the sample.

[0004]

According to the first aspect of the present invention, a sample temperature is directly measured in a vacuum chamber maintained at a constant pressure, and the measured temperature is measured. As a detection end, there is provided a method for measuring the vapor pressure of a sample, wherein the sample is heated at a constant heating rate, and the weight loss caused by evaporation of the sample at that time is measured together with the sample temperature. Further, according to the second aspect of the present invention, the sample temperature is directly measured in a vacuum chamber maintained at a constant pressure, and the measured temperature is used as a detection end to raise the temperature of the sample at a constant heating rate. There is provided a method for measuring the vapor pressure of a sample, characterized in that the amount of weight loss per unit time due to evaporation of the sample caused at the time is measured together with the temperature of the sample. Further, according to the third aspect of the present invention, the sample temperature is directly measured in a vacuum chamber maintained at a constant pressure, and the measured temperature is used as a detection end to raise the temperature of the sample at a constant rate. The amount of weight loss due to evaporation of the sample and the amount of weight loss per unit time are measured together with the sample temperature, and a change in the vapor pressure of the sample temperature with respect to the absolute temperature is obtained based on the measured data. A method for measuring the vapor pressure of a sample is provided. Still further, as a device for performing each of the above methods, in the fourth invention of the present invention, a sample container housed in a vacuum tank maintained at a predetermined degree of vacuum, and provided in contact with the sample container, A thermocouple that measures the temperature of the sample placed in the sample container, a support that supports the thermocouple and the sample container, and a weight measuring device that is connected to the support in a vacuum chamber and measures the weight of the sample, An infrared heating furnace placed outside the vacuum chamber, a temperature control device for controlling the operation of the infrared heating furnace to raise the temperature of the sample container at a constant speed, a device for trapping the evaporated sample, a thermocouple and a weight A device for recording the rate of change of weight versus temperature based on the output from the measuring device.

[0005]

In each method of the present invention, the sample starts to evaporate at a certain temperature or higher as the temperature rises, resulting in a weight loss.
By keeping the temperature rise rate of the sample constant and continuously measuring the rate of decrease in sample weight at each temperature, the rate of evaporation of the sample versus temperature can be obtained. Further, in the apparatus of the present invention, a part of the sample heated and evaporated by the heating furnace is sucked by the vacuum evacuation device, and most of the sample is condensed and adhered to the surface of the low-temperature tube wall and the surface of the parts of the weight measuring device. However, the coagulated sample is trapped by the trapping mechanism of the evaporated sample, and the influence on the weight measurement can be prevented.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows the principle of the apparatus of the present invention. Reference numeral 1 denotes a quartz glass protective tube that forms a part of a vacuum chamber.
A sample container 2 in which a sample to be measured is placed is arranged, and a thermocouple 3 for measuring the temperature of the sample in the sample container 2 is provided below the bottom of the sample container 2 in contact therewith. It is housed in an insulating alumina tube 4, one end of which supports the sample container 2, and the other end communicates with the lower end of the quartz glass protective tube 1 and extends into another portion 5 of the vacuum chamber. It is attached to one end of the rod of the balance mechanism 6 housed in the balance.

As shown, a weight measuring circuit 7 for continuously measuring a change in weight of the sample and a time differentiator 8 for continuously measuring a time differential value of the weight of the sample are connected to the balance mechanism 6. The outputs of the measuring circuit 7 and the time differentiator 8 are X
The XY recorder 9 is connected to a Y recorder 9 and records the relationship between the weight change rate and the temperature.

A part of the vacuum chamber, that is, the quartz glass protective tube 1 and the other part 5 of the vacuum chamber are connected to a vacuum pump 10 forming an evacuation device.
In the lower part of the inside, an annular water-cooled trap having a funnel cross section surrounding an insulating alumina tube 4 forming a support of the sample container 1 is provided.
The water-cooled trap 11 allows the sample vapor evaporated from the sample in the sample container 2 by heating to enter the other portion 5 of the vacuum tank communicating with the lower end of the quartz glass protective tube 1, and the balance mechanism 6. It has the function of preventing it from condensing and adhering to each part. That is, a part of the evaporated sample is sucked into the vacuum pump 10, but most of the sample is condensed and attached to the surface of the low-temperature tube wall in the middle and the surface of the component of the balance mechanism 6 at the bottom. This cohesion and adhesion becomes a noise source for weight measurement and also causes a failure of the balance mechanism 6. Therefore, the water-cooled trap 11 is configured to trap the coagulated and adhered sample.

Further, an infrared heating furnace 12 using an infrared lamp for heating a sample in a sample container 2 housed therein is provided on the outer periphery of the quartz glass protective tube 1. The operation of the infrared heating furnace 12 is controlled by a program temperature control device 13, that is, the program temperature control device 13 receives an output from the thermocouple 3 and controls the operation of the infrared heating furnace 12 according to the measurement temperature of the sample by the thermocouple 3. Program and control the temperature so that the temperature rise rate of the sample becomes constant.

Next, the method of the present invention will be described with reference to the operation of the illustrated apparatus. The inside of the quartz glass protective tube 1 and the other portion 5 of the vacuum chamber are evacuated by a vacuum pump 10 and maintained at a predetermined degree of vacuum (for example, 0.3 Torr).
The thermocouple 3 measures the temperature of the sample, and its output is input to a temperature control device 13, which programs the operation of the infrared heating furnace 12 according to the measured temperature of the sample from the thermocouple 3. For example, the temperature of the sample is controlled to be raised at a rate of 6 ° C./min (0.1 ° C./sec). When the sample is heated in this way, the sample starts to evaporate at a certain temperature or higher as the temperature rises, and a weight loss occurs. In this case, by keeping the temperature rising rate of the sample constant and continuously measuring the decreasing rate of the sample weight at each temperature, the evaporation rate of the sample can be obtained. The weight change Δw (mg) of the sample is calculated by the balance mechanism 6
And the weighing circuit 7 automatically and continuously measures and measures the sample temperature T on the XY recorder 9 on the horizontal axis.
(° C.), the weight change curve (referred to as A curve) is recorded with the sample weight change Δw on the vertical axis, and the recorded curve is shown in FIG. At the same time, the output of the weight measuring circuit 7 is input to the time differentiator 8 for continuously measuring the time differential value of the weight of the sample.
The time derivative d (△ w) / dt (mg / sec) of Δw is continuously obtained. On the XY recorder (11), the horizontal axis represents the sample temperature, and the vertical axis represents the weight change time derivative d ( Δw) / dt, and a weight differential curve (referred to as a B curve) was recorded.
Shown in When the gram molecular weight of the evaporated molecules of the sample is M, the surface area of the sample container 2 is A (cm ² ), and the value of the vertical axis of the weight differential curve (B curve) is divided by MA, the vertical axis value is expressed in units. The molecular evaporation rate per hour is m (mol / (sec · cm ² )),
This curve is called a molecular evaporation rate curve and is shown in FIG.

The following equation, proposed by Langmuir, holds between the evaporation rate of the sample and the vapor pressure. m = ap · [M / 2πRT] ^1/2 (1) where m, a, p, M, R, and T are the evaporation rate, the coagulation coefficient, the vapor pressure, the molecular weight of the vapor, the gas constant, Absolute temperature of the evaporation surface. According to the Langmuir equation, if the vapor can be evaporated without disturbing free space, a
Is approximately equal to 1. Therefore, equation (1) is expressed as follows. m = 5.85 × 10 ⁻² · p · [M / T] ^1/2 (2) When the equation (2) is rewritten for the vapor pressure p, p = 17.1 · m · [T / M] ^1/2 (3) The value of m on the vertical axis in FIG. 4 can be converted to the vapor pressure p by equation (3). Also, when the temperature and T on the horizontal axis in FIG. 4 are graduated by the reciprocal 1 / T of the absolute temperature, and the vertical axis is the natural logarithm of the vapor pressure p, as shown in FIG. 5, ln (p) 〜1 / T A diagram representing the relationship is obtained. Further, the vertical axis may be ln (p) as in FIG. 5, and the temperature T may be graduated on the horizontal axis. In that case, a curve as shown in FIG. 6 is obtained.

The vapor pressure versus temperature curve thus obtained can be applied, for example, to provide basic data for synthesizing a polymer by a vapor deposition polymerization method. One example will be described with reference to FIGS. FIG. 7 is a principle diagram in the case where a monomer A and a monomer B are vapor-deposited and polymerized in a bell jar 20. Inside the bell jar 20, a container 21 for the monomer A and a container 22 for the monomer B are arranged side by side, and these containers have heaters 23 and 24 for heating the monomer, respectively, and a thermocouple 25 for measuring and controlling the temperature of the monomer. , 26 are provided. A substrate 27 is disposed at an upper position inside the bell jar 20. The inside of the bell jar 20 is maintained at a certain degree of vacuum by a vacuum exhaust device (not shown). In this state, the monomer A and the monomer B are supplied to the heater 23, respectively.
24 When adjusted to the optimum temperature, monomers A and B evaporate,
On the upper substrate 27, a high molecular substance AB is formed. The most important point in this technology is
20 are the degree of vacuum, the holding temperature of monomer A, and the holding temperature of monomer B. If these are not appropriate, monomer A
And the vapor pressure of the monomer B become unequal. As a result, it becomes impossible to synthesize the monomer A and the monomer B in equal amounts.

Therefore, the vapor pressure versus temperature curve of the monomers A and B is obtained by using the present invention as shown in FIG. 8 so that, for example, the pressure corresponding to the degree of vacuum in the tank of 0.3 Torr in FIG. The respective temperatures TA and TB of the monomers A and B are obtained. Next, the pressure in the bell jar 20 of FIG. 7 is set to 0.3 Torr, and the holding temperature of the monomer A is controlled to TA and the holding temperature of the monomer B is controlled to TB.
A polymer film of AB is synthesized on the substrate 27. FIG. 9 shows a curve of the reciprocal of the vapor pressure / absolute temperature of two monomers used for the vapor deposition polymerization of polyimide known as a heat-resistant polymer, and a polyimide film is vapor-deposited and polymerized according to this data.

[0014]

As described above, according to the method of the present invention, the sample temperature is directly measured in a vacuum chamber maintained at a constant pressure, and the sample is heated at a constant rate based on the measured temperature. Since the temperature is increased and the weight loss due to evaporation of the sample and / or the weight loss per unit time is measured together with the sample temperature, the temperature versus vapor pressure curve of the sample can be easily calculated. For example, data on vapor pressures for many organic compounds which are equal to none at present can be easily obtained. In addition, by using the apparatus of the present invention, the relationship between the vapor pressure and the temperature of a substance, particularly an organic compound, can be obtained accurately and in a short time without the influence of coagulation and adhesion due to the evaporation of the sample. Data can be provided for operations.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of a vapor pressure measuring device according to the present invention.

FIG. 2 is a weight change curve showing a relationship between weight loss and temperature of a sample measured according to the present invention.

FIG. 3 is a weight differential curve showing the relationship between the weight change differential amount of a sample measured according to the present invention and temperature.

FIG. 4 is a molecular evaporation curve showing the relationship between the molecular evaporation rate and temperature of a sample obtained according to the present invention.

FIG. 5 is a curve showing the relationship between the logarithm of the vapor pressure of a sample obtained according to the present invention and the reciprocal of the absolute temperature.

FIG. 6 is a curve showing the relationship between the logarithm of the vapor pressure of a sample obtained according to the present invention and the absolute temperature.

FIG. 7 is a schematic diagram of an apparatus showing an example in which the present invention is applied to a vapor deposition polymerization method of a monomer.

8 is a curve showing vapor pressure / temperature characteristics of two types of monomers obtained by carrying out the present invention in vapor deposition polymerization of the monomers shown in FIG.

FIG. 9 is a curve showing vapor pressure / temperature characteristics of oxydianiline and pyromellitic anhydride, monomers for polyimide synthesis.

[Explanation of symbols]

 1: Vacuum tank 2: Sample container 3: Thermocouple 4: Support body 5: Vacuum tank 6: Balance mechanism 7: Weight measurement circuit 8: Time differentiator 9: XY recorder 10: Vacuum exhaust device 11: Water-cooled trap 12: Infrared heating furnace 13: Programmed temperature controller

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-51-43187 (JP, A) JP-A-4-140640 (JP, A) JP-A-59-54944 (JP, A) (58) Investigation Field (Int.Cl. ⁷ , DB name) G01N 5/04 G01N 7/00 JICST file (JOIS)

Claims (4)

(57) [Claims] The temperature of a sample is directly measured in a vacuum chamber maintained at a constant pressure, and the measured temperature is used as a detection end to raise the temperature of the sample at a constant rate of heating. A method for measuring the vapor pressure of a sample, comprising measuring the amount of decrease together with the temperature of the sample. 2. A unit for measuring a sample temperature directly in a vacuum chamber maintained at a constant pressure, heating the sample at a constant heating rate using the measured temperature as a detection end, and evaporating the sample at that time. A method for measuring the vapor pressure of a sample, comprising measuring the amount of weight loss per hour together with the temperature of the sample. 3. A sample temperature is directly measured in a vacuum chamber maintained at a constant pressure, and the measured temperature is used as a detection end to raise the temperature of the sample at a constant heating rate. A method for measuring the vapor pressure of a sample, comprising measuring the amount of decrease and the amount of weight loss per unit time together with the sample temperature, and obtaining a change in the vapor pressure of the sample temperature with respect to the absolute temperature based on the measured data. 4. A sample container housed in a vacuum chamber maintained at a predetermined degree of vacuum, and a thermocouple provided in contact with the sample container and measuring the temperature of the sample placed in the sample container. ,
A support for supporting the thermocouple and the sample container, a weight measuring device connected to the support in the vacuum chamber to measure the weight of the sample, an infrared heating furnace disposed outside the vacuum chamber, and operation of the infrared heating furnace A temperature control device for controlling the temperature of the sample container at a constant speed by controlling the temperature, and a device for trapping the evaporated sample,
A device for recording the rate of change of weight versus temperature based on the output from the thermocouple and the weight measuring device.