JP3154683B2 - Viscosity measurement method with spring-type rotational viscometer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to is used when measuring the viscosity of the viscous fluid, such as paint by a spring-type rotary viscometer, <br/> shall relates to a viscosity measuring method according to the spring-type rotary viscometer It is.

[0002]

2. Description of the Related Art A spring-type rotational viscometer is widely used for measuring viscosity. As shown in FIG. 1, a pointer shaft 4 having a rotor 3 is connected to a drive shaft 2 rotated by a motor 1 via a spring 5 as shown in FIG. A scale 6 is fixed to the drive shaft 2, and a rotation angle θ of the pointer shaft 4 with respect to the drive shaft 2 by a pointer 7 extending from an upper end of the pointer shaft 4.
(The pointer angle θ) can be read. For this reason, if the rotor 3 is brought into contact with the fluid to be measured and the drive shaft 2 is rotated by the motor 1, the pointer angle θ changes according to the shear stress τ, and the shear stress τ obtained from the pointer angle θ From the shear rate obtained from the rotation speed n, η = shear stress τ /
The viscosity η can be measured by the equation of the shear rate.

It is known that the viscosity varies greatly depending on the value of the shear rate. In particular, the state of sagging and leveling of the paint and the like largely depends on the viscosity in a low shear rate region of 0.1 / s or less. For this reason,
A method for measuring the viscosity in such a low shear rate region is required, but the conventional spring-type rotational viscometer as shown in FIG. 1 cannot rotate the motor 1 at such a low speed. , Measurement in the low shear rate range was not possible.

In order to measure the viscosity in such a low shear rate range, a spring relaxation type viscometer as shown in FIG. 2 has been developed. This viscometer of the spring relaxation type includes an elevating mechanism 8 that can lock the rotor 3 as shown on the left side of FIG. 2. In this state, only the drive shaft 2 can be rotated by the motor 1 by the target angle θ. It has become. Therefore, when the lock of the rotor 3 is released, the rotor 3 returns slowly by the force of the spring 9, and the viscosity in a low shear rate region of 0.1 / s or less can be measured. However, this spring-relaxed viscometer has a problem in that it is expensive due to the complicated mechanism for locking and the like. As described above, the calculation of the viscosity requires the shear stress τ and the shear rate. As shown in FIG. 6, the shear rate dθ / dt measured by the spring relaxation type viscometer has a different shear stress τ. May show a certain value in spite of
In some cases, the viscosity η cannot be uniquely determined.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems and accurately measures the viscosity in a low shear rate range of 0.1 / s or less without requiring an expensive spring relaxation type viscometer. has been made to provide a viscosity measuring how the spring-type rotational viscometer capable of.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a method of measuring viscosity using a spring-type rotary viscometer according to the present invention is to provide a pointer shaft having a rotor on a drive shaft rotated by a motor. Contact spring loaded rotary viscometer connected via
Then, after the drive shaft reaches a steady rotation state, the rotation of the drive shaft is stopped, and the viscosity is calculated from the pointer angle θ when the pointer angle θ returns to 0 and its time change dθ / dt. It is assumed that. Note that the finger of the spring-type rotational viscometer
From the data of the needle angle θ and the number of rotations n of the rotor,
Search for data where the rotation speed n is 0.
Relaxation analysis can be performed. In this case, the time change
Using the data after the absolute value of dθ / dt becomes maximum,
Spring relaxation analysis can be performed.

[0007] Viscosity measurement by the spring-type rotational viscometer of the present invention
According to the method , the viscosity in a low shear rate region can be measured using an inexpensive spring-type rotational viscometer. The finger
After performing smoothing processing on the graph showing the relationship between the needle angle θ and time t, the shear stress τ and the time variation d [theta] / d
By obtaining a curve showing the relationship with t, the viscosity η can be obtained more accurately. In this case, smoothing processing for all t is difficult, and simple smoothing processing can be performed by performing two-dimensional or three-dimensional approximation on a part.

[0008]

Embodiments of the present invention will be described below. In the present invention, a pointer shaft 4 having a rotor 3 on a drive shaft 2 rotated by a motor 1 as shown in FIG.
Using a spring-type rotational viscometer connected via a. The rotor 3 of the spring-type rotary viscometer is brought into contact with a viscous fluid to be measured, and the drive shaft 2 is rotated at a low speed of, for example, about 0.1 / s. The rotation speed n may be the minimum rotation speed at which the spring-type rotational viscometer operates stably.

FIG. 3 is a graph in which the vertical axis represents the rotation angle θ of the pointer shaft 4 with respect to the drive shaft 2 (the pointer angle θ) and the rotation speed n, and the horizontal axis represents time t. As shown in this graph, when the drive shaft 2 is rotated at a low speed of about 0.1 / s, the pointer angle θ increases from 0 and stabilizes at a constant value. This is because the rotor 3 in contact with the viscous fluid receives resistance due to the shear stress τ in accordance with the viscosity of the viscous fluid. As described above, the pointer angle θ is equivalent to the shear stress τ.

The viscosity measurement by the conventional spring relaxation type viscometer is performed after mechanically fixing the pointer angle θ, but in the present invention, the rotor 3 is constantly rotated so that the rotation speed n becomes non-zero and the pointer is rotated. After the angle θ is stabilized, the rotation of the drive shaft 2 is stopped. Then, the pointer shaft 4 provided with the rotor 3 becomes a spring 5
The pointer angle θ gradually returns to zero as shown in FIG. Pointer angle θ and time t at this time
From the graph showing the relationship between the shear stress τ and the shear rate dθ
By obtaining / dt, a graph as shown in FIG. 4 can be obtained. From the gradient, the viscosity η can be calculated by the equation of η = shear stress τ / shear rate. In addition, since the shear rate dθ / dt finally becomes 0, the viscosity η may be calculated by selecting a low shear rate range of 0.1 / s or less.

In the graph showing the relationship between the rotation angle θ and the time t shown in FIG. 3, if there is a linear portion having a constant gradient due to the resolution of the measuring instrument, the shear stress τ is different at that portion. Nevertheless, dθ / dt becomes a constant value, and the viscosity η cannot be uniquely determined as described above. For this reason, in the present invention, it is preferable to perform a smoothing process on the data before and after the straight line portion on the graph of FIG. 3 and then obtain a curve showing the relationship between the shear stress τ and dθ / dt.

In order to carry out the above viscosity measuring method ,
It can be used incorporating a data analysis algorithm spring type rotary viscometer. As described above, this data analysis algorithm searches for data in which the rotation speed n of the rotor 3 is 0 from the data of the pointer angle θ of the spring-type rotational viscometer and the rotation speed n of the rotor, and performs a spring relaxation analysis on the data. This will be described in more detail below with reference to FIG.

As shown in FIG. 5, according to the data analysis algorithm used in the present invention , the rotor 3 of the spring-type rotary viscometer is shifted from the non-zero rotation state to the zero rotation state. ,
The data of the pointer angle θ and the number of rotations n of the rotor during that time are stored. This measurement may be repeated several times. Next, data having a rotation speed n of 0 is searched from the stored data, and only that data is stored in the array. The data of the pointer angle θ may be subjected to an averaging process with data of neighboring needles. If the data sampling intervals are not equal, the measurement elapsed time is also stored.

Next, a time change dθ / dt of the pointer angle θ is obtained from the array storage data. In some cases, the averaging process may be performed on the preceding and following data. Then, the shear angle τ is determined by multiplying the pointer angle θ by the mechanical constant, the shear rate is determined by multiplying dθ / dt by the mechanical constant, and the viscosity η is determined by the equation of η = shear stress τ / shear rate. The “spring relaxation analysis” in claims 1 and 2 means that the pointer angle θ is obtained from the array storage data.
And dθ / dt to calculate the viscosity η. However, in practice, even if the rotation speed n of the rotor 3 is set to 0, the behavior often does not conform to the theory of spring relaxation for a few seconds. Therefore, as shown in FIG. 5, the maximum value of the absolute value of the dθ / dt data is obtained. It is preferable to perform the spring relaxation analysis by selecting the data after that.

In FIG. 5, all the data during the transition from the non-zero rotation state to the zero rotation state is stored,
Although the rotation data is searched, only the 0 rotation data may be selected and stored directly in the array. Further, a predetermined flag may be added to the data of 0 rotation to be subjected to the spring relaxation processing, and the data may be stored, and only the data with the flag may be searched to perform the spring relaxation analysis. This method is effective for specifying data for performing the spring relaxation analysis when there are a plurality of zero rotation measurements.

In performing the above-described spring relaxation analysis, the following algorithm is added when performing smoothing processing. The value twice as large as the shear rate dγ / dt (1) for which the shear stress is to be determined is dγ / dt (max), and half the value is dγ / dt (min).
In the array data, the value of dθ / dt is from dγ / dt (min)
Using data up to dγ / dt (max), a least-squares approximation curve is obtained with a quadratic polynomial y = ax2 + bx + c, where θ is y and dθ / dt is x. X of this approximation curve is dγ / dt
Substitute (1) and find θ (1). dγ / dt (1) and θ (1)
Is multiplied by a mechanical constant to obtain a shear rate and a shear stress.

By performing the above-described smoothing process, it is possible to solve the drawback of the conventional product in which the measured value of the different shear stress is obtained in spite of the same shear speed without using the effective number of digits of the measuring device in the low shear speed range. . Note that dγ
The values of / dt (max) and dγ / dt (min) do not necessarily have to be twice or half, and may be different values depending on the processing. However, if the data range selected is too large, the approximation error will increase. Also, in the conventional spring-type rotational viscometer, if there is a step of 0 rotation at the end of the measurement program,
Some models do not perform that step. In this case,
It is necessary to add a dummy zero rotation measurement step at the end so that the zero rotation measurement step is executed.

[0018]

The effects of the present invention are listed below. According to the present invention, utilizing the return of the pointer shaft due to the spring force when the spring-type rotational viscometer is stopped from the steady rotation state, the viscosity measurement in the low shear rate region similar to the spring relaxation type viscometer can be performed. it can. Therefore, an expensive spring relaxation type viscometer is not required. In a conventional spring relaxation type viscometer, the initial shear rate is 0 since the measurement is started from a stopped state. On the other hand, in the present invention, the initial shear rate is a non-zero value of, for example, 0.1 / s, which is suitable for evaluating sagging and leveling of paints and the like. This is because a constant shear rate is applied to the paint during coating and the structure is destroyed, whereas the conventional measurement is performed with the initial shear rate set to 0 when the structure is recovered. Because it deviates from the actual situation. To measure the viscosity at a relatively high shear rate such as 0.1 / s using a spring relaxation type viscometer, trial and error was required to determine the initial set amount of θ, and automatic measurement was not possible However, automatic measurement is possible in the present invention. When the relationship between the measured value and the printing failure was actually obtained for 30 types of printing pastes, the correlation coefficient (R2 value) with the yield stress obtained by ordinary steady flow measurement was obtained.
Was 0.61, whereas the correlation coefficient including the yield stress obtained by the measurement method of the present invention was 0.69, and the correlation with the printing failure could be more accurately determined.

[Brief description of the drawings]

FIG. 1 is a perspective view of a spring-type rotational viscometer.

FIG. 2 is a perspective view of a spring relaxation type viscometer.

FIG. 3 is a graph showing a relationship between a rotation angle θ and time t in the present invention.

FIG. 4 is a graph showing a relationship between a shear stress τ and a shear rate dθ / dt.

FIG. 5 is a block diagram showing an algorithm used in the present invention.

FIG. 6: Shear stress τ and shear rate determined by a conventional method
6 is a graph showing a relationship with dθ / dt.

[Description of Signs] 1 Motor 1, 2 Drive shaft, 3 Rotor, 4 Pointer shaft,
5 spring, 6 dial, 7 pointer, 8 lifting mechanism, 9
Spring

Claims (4)

(57) [Claims] 1. A spring-type rotary viscometer in which a pointer shaft provided with a rotor is connected to a drive shaft rotated by a motor via a spring.
In the above, after the drive shaft reaches a steady rotation state, the rotation of the drive shaft is stopped, and the viscosity is calculated from the pointer angle θ when the pointer angle θ returns to 0 and its time change dθ / dt. A viscosity measurement method using a spring-type rotational viscometer. 2. A rotational speed n of the rotor from the data of the rotational speed n of the guidance angles θ and rotor spring rotary viscometer locate the data of 0, performing the spring relaxation analysis on the data according
Item 4. A viscosity measurement method using a spring-type rotational viscometer according to Item 1. 3. A process according to claim 2 in which the absolute value of the time change d [theta] / dt makes the spring relaxation analysis using the data after that the maximum
A viscosity measurement method using the above-described spring-type rotational viscometer. 4. A curve showing the relationship between the shear stress τ and the time change dθ / dt after performing a smoothing process on a graph showing the relationship between the pointer angle θ and time t. 1
A viscosity measurement method using the above-described spring-type rotational viscometer.