JP2910871B2 - Measuring device for molecular weight of polymer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for measuring the molecular weight of a polymer.

[0002]

2. Description of the Related Art Generally, when measuring the molecular weight of a polymer, a viscosity average molecular weight (Mη) is used. This viscosity average molecular weight is measured by measuring the viscosity of a solution obtained by diluting the polymer using a commercially available Ubelohde capillary viscometer,
From the results, the molecular weight is calculated by using a certain calculation formula according to the type of the polymer.

[0003] In order to carry out a molecular weight measurement utilizing such a viscosity measurement, a pretreatment of the sample, for example, dilution and purification of the sample is required, and as a result, the measurement requires 1-2 hours. The temperature control at the time of measurement is, for example, 30 ±
Strict control of about 0.25 ° C. is required, and furthermore, there is a problem that a measurement result having a large error occurs unless the measurement method is mastered. Therefore, in a polymerization step or the like, it is necessary to sample a sample from a reactor and pre-treat the sample, measure the viscosity, and determine whether or not the result has reached a predetermined molecular weight. When the molecular weight has not reached the predetermined value, it is necessary to advance the polymerization reaction again.

As described above, when the conventional molecular weight measuring method based on viscosity measurement is used, time-consuming manual analysis is required, and errors occur due to differences in a measurer and proficiency.
As a result, the reaction time varies.

[0005]

Therefore, it is necessary to provide an apparatus for measuring the molecular weight of a polymer in a short time without error in order to carry out an efficient polymerization operation.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to apply heat to a polymer by a heating element, and to detect a temperature difference between at least two portions of the polymer which are differently thermally affected by the heating by the heating element. It is found that the problem is solved by a polymer molecular weight measuring apparatus characterized by measuring and calculating the molecular weight of the polymer corresponding to the temperature difference from the relationship between the temperature difference and the molecular weight of the polymer determined in advance. Was issued.

[0007] The present invention is based on the concept described below. In general, the dissipation of heat applied to a substance is greatly influenced by the flow properties of the substance, especially the viscosity. That is, a substance having a high viscosity has a low heat transfer rate, and a substance having a low viscosity has a high heat transfer rate. Therefore, the viscosity of the polymer can be measured by measuring the heat transfer characteristics of the polymer, and the molecular weight of the polymer is determined from the viscosity measured using the previously determined viscosity-molecular weight relationship as in the past. Can be estimated.

Conventionally, it has been known to estimate the viscosity of a substance other than a polymer from the heat transfer characteristics thereof. For example, reference can be made to JP-A-60-152943. However, due to the heat transfer properties of the material,
There is no example in which the concept of measuring the viscosity of the substance is applied to a system containing a polymer, and at present it is not known to estimate the molecular weight of the polymer from the obtained viscosity.

In practice, the heat transfer characteristics are conveniently measured as the temperature difference formed by the balance between the amount of heat applied and the dissipation of heat from the system. Also, viscosity is only a parameter that theoretically intervenes between the heat transfer characteristics (or temperature difference) and the molecular weight of the polymer, and in fact, it is necessary to directly determine the relationship between the temperature difference and the molecular weight. Can be.

The apparatus of the present invention is a simple apparatus, but has an excellent effect that the molecular weight can be measured with the same accuracy as the measurement by the viscosity method, and the temperature control at the time of the measurement is required by the viscosity method. Control accuracy (± 0.25
(° C.) is not required and ± 2 to 3 ° C. is sufficient, and can be sufficiently used for measuring the molecular weight of a polymer requiring high accuracy.

Polymers that can be measured by the present invention include olefins (eg, polyethylene), vinyls (eg, polyvinyl chloride), dienes (eg, polybutadiene), ring-opening polymerizations (eg, polypropylene glycol), polycondensation / polycondensation. additional system (e.g. oligoester acrylate), a petroleum resin (e.g., C ₅ petroleum resin), fluorine-containing (e.g. fluoroolefin telomers), a polymer such as silicone-based (e.g., cyclic dimethylpolysiloxanes), and polysulfide particularly Although not limited, it can be preferably applied to polymerization of a ring-opening polymerization system such as a synthetic organic polymer, particularly a polyoxyalkylene. It is suitable for measuring the viscosity of a low-molecular-weight (oligomer) having a molecular weight of about 2 × 10 ⁴ .

Regarding a polymer having too high a viscosity, even if the molecular weight of the measured portion is accurate, it may not be said that the molecular weight representing the polymer is measured from the viewpoint of homogeneity of the entire system. . Therefore, the viscosity of the polymer measured by applying the apparatus of the present invention is 1000 poise.
The following is preferred.

In the present invention, the heating element is not particularly limited as long as it is a suitable element capable of uniformly applying heat to the polymer. For example, a commonly used stainless steel sheath heater or the like is used. Can be exemplified. In a particularly preferred embodiment, a sensor exemplified in JP-A-62-56849 is used as a heating element. Further, to apply heat to the polymer by the heating element means to apply a certain amount of heat to the polymer for a certain period of time using the heating element, that is, to uniformly apply the heat to the polymer. Or continuous heating.

In the present invention, the temperature detecting element is not particularly limited as long as it is a suitable element for measuring the temperature of the polymer, and examples thereof include a temperature measuring resistor. Measuring the temperature of at least two polymers subject to different thermal effects is the same as measuring the heat transfer characteristic as a temperature difference, but the thermal effects are the same and the polymer temperatures are equal. Then, the heat transfer characteristics cannot be measured as the temperature difference. In addition, at least two locations mean that at least one data is measured as a temperature difference. Therefore, for example, it is also possible to measure the temperatures at three or more locations to determine the respective temperature differences, and to use the average value, for example. The term "thermally affected" means a state where the temperature of the polymer at the measurement point is affected by the heating when the polymer is heated by the heating element. Therefore, when the heating amount is small, the polymer is not affected by the heating at a position far from the heating element, so that an accurate molecular weight cannot be obtained even if the temperature of the polymer at such a location is measured.

Considering that some error may occur in the temperature measurement, it is preferable to measure the temperature at two points close to the heating element and separated by an appropriate distance. Especially 1
Preferably, the location measures the temperature of the polymer immediately adjacent to the heating element. Thus, in the most preferred embodiment, the heating element and one
Use an element that integrates two temperature sensing elements.
Such an element is, for example, a thermometer having a structure capable of measuring the temperature of the heated resistor itself by applying a minute current to the resistor built in the stainless steel tube to generate heat. It is sufficient to select at least two locations for measuring the temperature difference so that the temperatures at the two locations are different, but it is preferable to select the temperature difference to be large. These two
The distance between the points depends on the polymer to be measured, and further depends on whether the fluid to be measured is stationary or flowing, but is generally about 20 to 30 mm in a stationary system, and about 20 to 30 mm in a flowing system. About 10 to 20 mm, for example, about 10 mm is sufficient.

In the apparatus of the present invention, no special operation is required except for measuring the temperature difference, and the molecular weight can be immediately estimated by an appropriate method from the relationship between the previously determined temperature difference and the molecular weight of the polymer. it can.

Therefore, since the temperature can be measured in real time, the present invention can be applied not only when the polymer is in a static state in terms of molecular weight and fluidity but also in a dynamic state. Can be applied. For example, the present invention can be applied even when the system is agitated, in a stationary state, in a state in which the molecular weight does not change, or in a state in which the molecular weight is changing.

In principle, in the apparatus of the present invention, it is necessary to previously determine the relationship between the viscosity and the molecular weight of the polymer as in the conventional method. The relationship between the molecular weight and the viscosity is determined in advance using the temperature of the reaction system as a parameter, whereby the actually measured value can be corrected. As explained earlier, in practice, the relationship between the temperature difference and the molecular weight can be determined directly, so it is necessary to determine in advance how the relationship between the two will be affected by the temperature of the reaction system. is necessary. Therefore, it is necessary to determine in advance the relationship between the temperature difference and the molecular weight at a temperature around the actual temperature of the molecular weight increasing system to be measured.

In this case, strictly speaking, there are two types of system temperatures because the measurement temperatures are different at two points.
Since the temperature difference between the points is not large enough to affect the viscosity beyond the measurement error, the temperature of the system is, for example, 2
The averaging temperature of the temperatures of the locations may be used, or any one of the temperatures may be used.

The apparatus of the present invention can be applied in any case where it is necessary to estimate the molecular weight of the polymer. Particularly useful is the following operation in the polymerization process. It is necessary to judge by. In particular, when molecular weight data is required in real time, the molecular weight can be estimated online, so that the next operation can be performed without a time lag, leading to an improvement in productivity.

Specifically, the relationship between the temperature difference between sensors at a predetermined system temperature and the molecular weight is determined in advance as a calibration curve, and only the temperature difference is measured in the actual molecular weight increase reaction to determine the molecular weight. calculate. In some cases,
To check the calibration curve, at one point of the molecular weight increase reaction, sample the reaction system and measure the molecular weight by the conventional method to confirm that the state of the system is the same as when the calibration curve was obtained. May be appropriate. For example,
Checked points may not always be on the calibration curve due to differences in raw material lots and differences in the amount of impurities contained in the raw materials. Even in this case, a calibration curve obtained in advance may be used depending on the desired design molecular weight standard. If more precise control of the molecular weight is required, if the reaction system is of the same type of molecular weight increasing reaction, the calibration curve obtained in advance is translated in the direction of the temperature difference so that the checked point comes on. It has been confirmed that even if the molecular weight is estimated from the measured temperature difference using a new calibration curve, a practically satisfactory result can be obtained.

In particular, when a polymer having a low degree of polymerization with a known molecular weight is further increased in molecular weight, or when the molecular weight is measured at least once during polymerization by a viscometer or the like, the shape of the calibration curve is changed. If the calibration curve is moved and corrected as described above while maintaining the same, extremely accurate molecular weight measurement can be performed.

Further, in a particularly preferred embodiment of the present invention, the apparatus of the present invention is provided with a relation between the molecular weight of the polymer measured in advance and the temperature difference, and immediately calculates the molecular weight from the actually measured temperature difference. It has a data processing device capable of.

Further, according to the present invention, heat is applied to the polymer by a heating element, and the temperature difference between at least two places of the polymer which is differently affected by the heating by the heating element is measured by a temperature detecting element to obtain the temperature difference in advance. The present invention also provides a method for measuring the molecular weight of a polymer, which comprises calculating the molecular weight of the polymer corresponding to the temperature difference from the relationship between the temperature difference and the molecular weight of the polymer.

Next, the present invention will be specifically described based on examples. Example 1 A description will be given based on the stirring reaction tank (with a jacket) shown in FIG. Terminal O of PPG (polypropylene glycol)
20 kg of an alcoholate compound in which 90% or more of the H groups were alkoxylated was charged into the stirring reaction tank 3 via the raw material receiving tank 1 and the raw material measuring tank 2. After the charging is completed, the gas phase
After the replacement at ₂ , the temperature was simultaneously raised to a predetermined temperature (130 ° C.) by the temperature control unit 6. After the completion of the temperature rise, the kinematic viscosity monitoring system (manufactured by JEOL Ltd.) 7 was started, and the measurement of the temperature difference between the heated part and the non-heated part (two temperature differences in the reaction system) was started.

One sensor of this monitoring system has a resistor 400 built in a stainless steel tube.
This is a thermometer having a structure capable of generating a current by flowing a current of mA and measuring the temperature of the heated resistor itself. The other sensor used was a normal temperature measuring resistor separated by a distance of 10 mm.

Thereafter, a polyhalide, which is a molecular weight increasing reagent, is dropped from the raw material measuring tank 2 little by little, and the temperature difference is sequentially measured by the kinematic viscosity monitoring system 7, and at the same time, the molecular weight (Mη) by the Ubbelohde method at that time is measured. It was measured. The relationship between the measured temperature difference and Mη was plotted as shown in FIG. 2 to obtain a calibration curve.

When the same reaction as the above molecular weight increasing reaction is repeated, the molecular weight calculated from the temperature difference measured based on the obtained calibration curve is compared with the molecular weight Mη measured by the Ubbelohde method. Both were found to be consistent within an error range of about ± 1% or less.

Thus, it can be seen that the molecular weight of the polymer can be accurately measured from the temperature difference with the same precision as the measurement by the Ubbelohde method. The reaction for increasing the molecular weight of the alcoholate compound (starting molecular weight M ₀ = 2400) was carried out by continuously dropping the molecular weight increasing reagent while monitoring the molecular weight using the calibration curve obtained as described above.
When the molecular weight is sequentially calculated from the temperature difference by the calibration curve,
About 1 hour later, since the desired molecular weight (8100) was reached, the addition of the molecular weight increasing reagent was stopped. When the finally obtained polymer was measured by the Ubbelohde method, the molecular weight was 81.
It was 50.

Comparative Example 1 The same molecular weight increasing reaction as in the above example (starting molecular weight = 2
400, design molecular weight = 8100) based on the molecular weight measurement by the Ubbelohde method. In the case of the molecular weight increasing reaction using only the conventional viscosity method, the molecular weight increasing reagent cannot be continuously dropped because the molecular weight is not known in real time. It is not desirable for the molecular weight to be much larger than the design molecular weight, so it is necessary to add the reagent slightly less than the estimated amount corresponding to the design molecular weight (Mη = 8100). Thereafter, a polymer having a desired molecular weight cannot be accurately obtained unless a shortage of a molecular weight increasing reagent is further added to cause a reaction.

First, according to the conventional viscosity method, a slightly smaller molecular weight increasing reagent than the estimated amount corresponding to the design molecular weight (Mη = 8100) was added at once. As a result of sampling at the first hour after addition and measuring the molecular weight, Mη = 78.
00. (This measurement took about 1.5 hours.) Since this value is 300 less than the designed molecular weight of 8100,
Again, the estimated amount corresponding to the molecular weight increase of 300 was added all at once for the molecular weight increasing reagent. After the re-addition, sampling was performed 30 minutes later, and the molecular weight was measured. As a result, Mη = 8150, and the reaction was completed. (The measurement time was about 1.5 hours.)

As described above, according to the conventional viscosity method, after measuring the molecular weight, it is necessary to determine whether or not to continue the reaction by re-adding the molecular weight increasing reagent based on the measured value. It took a very long time to obtain a polymer. (The total travel time was 4.5 hours.)

Example 2 Example 1 using an alcoholate compound in which 90% or more of the terminal OH groups of PPG having different production conditions were alkoxylated.
The reaction for increasing the molecular weight was carried out under the same conditions as described above. As in Example 1, the relationship between the temperature difference and the molecular weight according to the Ubbelohde method was measured.

The measurement results are shown in FIG. 3 together with the results of Example 1.
(The results of Example 1 are indicated by 、 and the results of Example 2 are indicated by △.) The relationship between the temperature difference and the molecular weight indicates the relationship between the temperature difference obtained in Example 1 and the calibration curve. A slight shift occurred without being on the calibration curve. However, even in this case, it was found that when the calibration curve obtained in Example 1 was translated in the direction of the temperature difference, a calibration curve that best represented the result obtained in Example 2 was obtained. .

Therefore, if the types of polymers are the same, it is not necessary to create a new calibration curve. If the relationship between the temperature difference and the molecular weight is determined in advance as a calibration curve for a specific polymer, the molecular weight can be reduced. If the relationship between the temperature difference and the molecular weight of the conventional method is measured at one point in the increase reaction, simply moving the calibration curve in the direction of the temperature difference so as to pass through the measurement point will cause the increase in the molecular weight increase reaction system. A calibration curve can be obtained.

[0036]

According to the apparatus of the present invention, the molecular weight of the polymer in the molecular weight increasing reaction can be measured in real time, so that the judgment in the polymerization operation is much easier than in the case where the conventional method is applied. And increase productivity.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a reaction apparatus when a molecular weight increasing reaction is performed using the apparatus of the present invention.

FIG. 2 is a graph showing the results of Example 1.

FIG. 3 is a graph showing the results of Example 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Raw material receiving tank, 2 ... Raw material measuring tank, 3 ... Stirring reaction tank, 4 ...
Stirring blades, 5: discharge valve, 6: temperature control unit, 7: kinematic viscosity monitoring system.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yoshihiro Ikeda 2-63 Kounama-cho, Takasago-machi, Takasago-shi, Hyogo Prefecture (72) Inventor Toru Nakagawa 1-12-35, Nishihata, Takasago-shi, Hyogo (72) Inventor Ito Kensuke 238-6, Harita-cho, Kodaira-shi, Tokyo (72) Inventor Yukihiro Saeki 201-2, Fujikin, Tsurugashima-cho, Iruma-gun, Saitama Prefecture (72) Inventor Saburo Ishii 2-19-12 Kamihei, Fussa-shi, Tokyo (72) Invention Person Kenji Aoyama 3-13-4 Hyakunincho, Shinjuku-ku, Tokyo (56) References JP-A-3-172734 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01N 25 / 00-25/72 G01N 11/00 JICST file (JOIS)

Claims (2)

(57) [Claims] 1. An apparatus for measuring the molecular weight of a polymer, comprising: an element for heating the polymer; and a temperature sensing element for measuring a temperature difference between at least two places affected differently by the heating of the heating element. 2. The apparatus for measuring the molecular weight of a polymer according to claim 1, wherein the heating element also functions as one of the temperature detecting elements.