Viscosity measurement piping, viscometer, and method for measuring viscosity

Abstract

The present invention provides viscosity measurement piping with which it is possible to accurately measure viscosity within a broad range of shear speeds and which can be designed within a range such that the dimensions of the piping are not too large or too small. This viscosity measurement piping is configured such that a plurality of items of unit piping are disposed in a continuous manner and satisfies the following matters, where one side is designated as first unit piping (width W1 and height H1), and the other side is designated as second unit piping (width W2 and height H2).　When the first unit piping is capillary-type piping and the second unit piping is slit-type piping: H2 / H1 is greater than 1, and W2 / W1 is greater than 1. When the first unit piping is slit-type piping and the second unit piping is capillary-type piping: H2 / H1 is greater than 1, and W2 / W1 is less than 1. When both the first unit piping and the second unit piping are slit-type piping: H2 / H1 is greater than 1, and W2 / W1 is greater than 1. When both the first unit piping and the second unit piping are capillary-type piping: H2 / H1 is greater than 1, and W2 / W1 is greater than 1.

Description

Viscosity measurement pipe, viscometer, and viscosity measurement method

[0001] The present invention relates to a viscosity measurement pipe, a viscometer, and a viscosity measurement method.

[0002] Newton's law of viscosity is known, which states that a proportional relationship exists between the shear stress and shear rate of a fluid, with the viscosity coefficient (viscosity) serving as the proportionality constant. Based on this law, the viscosity of a fluid can be measured by measuring the shear stress and shear rate of the fluid flowing through a pipe. However, for non-Newtonian fluids, whose shear stress changes with shear rate, the viscosity of the fluid cannot be determined from measurements at only one shear rate; viscosity measurements must be performed at multiple different shear rates.

[0003] Viscometers for measuring the viscosity include capillary die rheometers (CDRs), which have a circular cross-sectional shape of the pipe, and slit die rheometers (SDRs), which have a rectangular cross-sectional shape of the pipe (e.g., JIS K 7199 (1999)). Both of these measure the viscosity of a fluid by calculating the shear stress from the pressure loss of the fluid flowing through the pipe and the shear rate from the flow rate of the fluid and the size of the pipe.

[0004] Viscometers that simultaneously measure viscosity at multiple different shear rates are known. For example, Patent Document 1 describes a viscosity measurement device that uses multiple differential pressure measurement pipes with different pipe diameters connected in series in descending order of diameter, with the largest pipe positioned upstream and a fluid to be measured flowing through the differential pressure measurement pipes. Patent Document 1 calculates pressure loss in each of the multiple differential pressure measurement pipes. Furthermore, the shear rate (shear rate) in each differential pressure measurement pipe is calculated from the flow rate measured by a flow meter installed separately from the differential pressure measurement pipes and the size of each differential pressure measurement pipe. The viscosity of the fluid to be measured in each differential pressure measurement pipe is then calculated from the calculated pressure loss and shear rate. Note that all of the differential pressure measurement pipes used in Patent Document 1 are capillary-type pipes. Patent Document 1 describes that by arranging the differential pressure measurement pipes so that the pipe with the largest diameter is positioned upstream and performing viscosity measurements in ascending order of shear rate, the viscosity in each differential pressure measurement pipe can be accurately measured.

[0005] Furthermore, Patent Document 2 describes a rheometer plate having multiple pressure sensors that can be used in a viscometer that combines multiple slit-type pipes. Patent Document 2 states that by using this rheometer plate as the upper part of the viscometer body and combining it with an upper part of the body that is shaped so that slits of different sizes are formed at positions corresponding to each pressure sensor, a viscometer having multiple slits of different sizes can be created. Patent Document 2 also states that each flow path (slit) is configured so that the ratio of width W to gap (height) is greater than 10.

[0006] Furthermore, Patent Document 3 describes an apparatus for obtaining rheological property values ​​of a non-Newtonian fluid, which includes three or more parallel pipes arranged in parallel to a main pipe. In Patent Document 3, these three or more parallel pipes are capillary-type pipes with different radii or flow rates. Each of these three or more parallel pipes has a pressure sensor (elastic body or strain gauge) disposed within the flow path to measure pressure loss within the flow path. Rheological property values, such as the viscosity coefficient of the non-Newtonian fluid, are calculated using these three or more parallel pipes, and a relational expression that more closely approximates the relationship between shear stress and shear rate is obtained from these calculated rheological property values.

[0007] Japanese Patent Laid-Open No. 6-74887 Japanese Patent Laid-Open No. 2008-286802 Japanese Patent Laid-Open No. 2020-118491

[0008] As described in Patent Documents 1 to 3, there is known a viscometer in which three or more pipes of different sizes are arranged side by side to measure viscosity at a plurality of different shear rates at once.

[0009] When recycling waste plastics, multiple types of waste plastics of unknown origin are often melted and mixed. The viscosity of these waste plastics varies greatly depending on the type of resin. Even if only waste plastics of the same resin are selected, the viscosity can vary greatly due to significant differences in molecular weight, etc. Therefore, the viscosity of the fluid resulting from melting and mixing waste plastics is often unpredictable and constantly changes during the melting and mixing process.

[0010] In order to accurately measure the viscosity of such unpredictable fluids, it is necessary to measure the viscosity over a wide range of shear rates. According to the findings of the present inventors, viscosity measurement of such fluids requires simultaneous measurement of the viscosity at a certain shear rate and at a shear rate 100 times higher than that.

[0011] However, according to the findings of the present inventors, it is extremely difficult in practice to use a viscometer such as those described in Patent Documents 1 to 3 to simultaneously measure viscosity over a wide shear rate range in which there is a difference of at least about 100 times between the minimum and maximum shear rates.

[0012] For example, when the viscosity is measured using the viscometer described in Patent Document 1, the pressure loss in the narrowest pipe diameter is too large, making it impossible to accurately measure the pressure loss in the widest pipe diameter. Furthermore, when the viscosity is measured using the viscometer described in Patent Document 2, the width-to-height ratio of each flow path must be greater than 10, resulting in a design where the largest flow path is greater than 1 m in width. Arranging a small flow path and a large flow path in series creates a large amount of unnecessary dead volume in the viscometer, significantly restricting the device design. Furthermore, when the viscosity is measured using the viscometer described in Patent Document 3, the radius of all the pipes must be extremely small when measuring at low flow rates, making it very difficult to install a pressure gauge in the pipes.

[0013] In view of the above problems, an object of the present invention is to provide a viscosity measurement pipe that can accurately measure viscosity over a wide shear rate range and that enables the dimensions of the pipe to be designed within a range that is neither too large nor too small, a viscometer that has the viscosity measurement pipe, and a viscosity measurement method that uses the viscosity measurement pipe.

[0014] A fluid viscosity measurement pipe according to one aspect of the present invention for solving the above problems is a viscosity measurement pipe as set forth in the following [1] to

[15] . [1] A fluid viscosity measurement pipe, comprising a plurality of unit pipes arranged in succession, each of which includes a capillary-type unit pipe and a slit-type unit pipe, each capable of measuring the pressure of the fluid flowing through it, wherein the length of a flow path in the width direction of the slit-type unit pipe is defined as the width of each unit pipe included in the viscosity measurement pipe, the length of a flow path in the thickness direction of the slit-type unit pipe is defined as the height of each unit pipe included in the viscosity measurement pipe, and a direction perpendicular to both the width direction and the thickness direction is defined as the length direction, and for consecutive unit pipes among the plurality of unit pipes, the unit pipe arranged on one side in the length direction is defined as a first unit pipe, and the unit pipe arranged on the other side in the length direction is defined as a second unit pipe, and the width of the first unit pipe is defined as W １ , height H １ The width of the second unit pipe is W ２ , height H ２ A viscosity measurement pipe in which the following relationship is always satisfied: (A) When the first unit pipe is a capillary type unit pipe and the second unit pipe is a slit type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is greater than 1. (B) When the first unit pipe is a slit-type unit pipe and the second unit pipe is a capillary-type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is smaller than 1. (C) When the first unit pipe is a slit type unit pipe and the second unit pipe is a slit type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is greater than 1. (D) When the first unit pipe is a capillary type unit pipe and the second unit pipe is a capillary type unit pipe, H ２ / H １ is greater than 1, and W ２ / W１ is greater than 1. [2] The viscosity measurement pipe according to [1], wherein the plurality of unit pipes include three or more of the unit pipes. [3] The viscosity measurement pipe according to [1] or [2], wherein the plurality of unit pipes are arranged in the order of a capillary-type unit pipe, a slit-type unit pipe, and a slit-type unit pipe along the length direction. [4] The viscosity measurement pipe according to [1] or [2], wherein the plurality of unit pipes are arranged in the order of a slit-type unit pipe, a capillary-type unit pipe, and a capillary-type unit pipe along the length direction. [5] The viscosity measurement pipe according to [1] or [2], wherein the plurality of unit pipes are arranged in the order of a slit-type unit pipe, a slit-type unit pipe, and a capillary-type unit pipe along the length direction. [6] A viscosity measurement pipe according to [1] or [2], wherein the first unit pipe is a capillary-type unit pipe and the second unit pipe is a slit-type unit pipe, and wherein in the combination of the first unit pipe and the second unit pipe, H ２ / H １ is 1.1 or more, and W ２ / W １ The viscosity measurement pipe according to any one of [1], [2], [4] and [5], wherein the length of the flow path in the longitudinal direction is the length of each unit pipe included in the viscosity measurement pipe, and the length of the first unit pipe is LL １ , the length of the second unit pipe is LL ２ When this is done, LL ２ / LL １ [8] A viscosity measurement pipe according to [6], wherein the first unit pipe is a slit-type unit pipe and the second unit pipe is a capillary-type unit pipe, and the combination of the first unit pipe and the second unit pipe is a slit-type unit pipe, and wherein H ２ / H １ is 1.5 or more, and W ２ / W １ [9] The viscosity measurement pipe according to any one of [1], [2], [4] and [5], wherein the length of the flow path in the longitudinal direction is the length of each unit pipe included in the viscosity measurement pipe, and the length of the first unit pipe is LL１ , the length of the second unit pipe is LL ２ When this is done, LL ２ / LL １

[10] A viscosity measurement pipe according to [8], wherein the first unit pipe is a slit-type unit pipe and the second unit pipe is a slit-type unit pipe, and the combination of the first unit pipe and the second unit pipe is a slit-type unit pipe, and in the combination of the first unit pipe and the second unit pipe, H ２ / H １ is 1.5 or more, and W ２ / W １

[11] The length of the flow path in the longitudinal direction is the length of each unit pipe included in the viscosity measurement pipe, and the length of the first unit pipe is LL １ , the length of the second unit pipe is LL ２ When this is done, LL ２ / LL １

[12] A viscosity measurement pipe according to

[10] , wherein the first unit pipe is a capillary type unit pipe and the second unit pipe is a capillary type unit pipe, and the combination of the first unit pipe and the second unit pipe is a capillary type unit pipe, and in the combination of the first unit pipe and the second unit pipe, H ２ / H １ is 1.5 or more, and W ２ / W １

[13] The length of the flow path in the longitudinal direction is the length of each unit pipe included in the viscosity measurement pipe, and the length of the first unit pipe is LL １ , the length of the second unit pipe is LL ２ When this is done, LL ２ / LL １

[14] The viscosity measurement pipe according to any one of [1] to

[13] , wherein a tapered connecting pipe whose width and height gradually increase along the length direction is disposed between two of the unit pipes arranged in series.

[0015] Another aspect of the present invention for solving the above problems is a viscometer described in the following

[15] .

[15] A viscometer having a viscosity measurement pipe described in any one of [1] to

[14] .

[0016] Another aspect of the present invention for solving the above problems is a viscosity measurement method described in the following

[16] to

[20] .

[16] A method for measuring the viscosity of a fluid flowing through a viscosity measurement pipe described in any of [1] to

[14] , comprising determining a shear rate and a shear stress of the fluid for each of the capillary-type unit pipe and the slit-type unit pipe, and determining a shear viscosity η of the fluid as a value obtained by dividing the shear rate by the shear stress in the capillary-type unit pipe and the slit-type unit pipe.

[17] The viscosity measurement method described in

[16] , wherein the plurality of unit pipes include three or more unit pipes, and determining the shear viscosity η of the fluid in each of the three or more unit pipes.

[18] The viscosity measurement method described in

[16] or

[17] , wherein the shear viscosity η of the fluid is determined as a value obtained by dividing the corrected shear rate by the shear stress.

[19] The viscosity measurement method according to any one of

[16] to

[18] , wherein the volumetric flow rate is set by a gear pump.

[20] The viscosity measurement method according to any one of

[16] to

[20] , wherein the fluid is a polymer melt.

[0017] According to the present invention, there are provided a viscosity measurement pipe that can accurately measure viscosity over a wide shear rate range and that enables the dimensions of the pipe to be designed within a range that is neither too large nor too small, a viscometer that has the viscosity measurement pipe, and a viscosity measurement method that uses the viscosity measurement pipe.

[0018] FIG. 1 is a schematic diagram showing the configuration of a viscosity measurement pipe according to a first embodiment of the present invention. FIG. 2 is a schematic diagram showing the surfaces of the first and second plates of the viscosity measurement pipe shown in FIG. 1 that face each other. FIG. 3 is a schematic diagram showing the state of a flow path formed by combining the first and second plates. FIG. 4 is a block diagram showing an exemplary configuration of a viscometer having a viscosity measurement pipe. FIG. 5 is a schematic diagram showing the configuration of a viscosity measurement pipe 2. FIG. 6 is a schematic diagram showing the surfaces of the first and second plates of the viscosity measurement pipe 2 that face each other. FIG. 7 is a graph showing the results of Example 1, Comparative Example 1, and a simulation. FIG. 8 is a graph showing the results of Example 2, Comparative Example 2, and a simulation. FIG. 9A is a plot of the results of Example 1 on a curve showing the shear rate dependence of the shear viscosity of a steady flow according to the Cox-Merz law. FIG. 9B is a plot of the results of Comparative Example 1 on the same curve. Figure 10A shows the results of plotting the results of forward flow in the viscosity measurement pipe 2 on a curve showing the shear rate dependency of the shear viscosity of a steady flow according to the Cox-Merz law. Figure 10B shows the results of plotting the results of backward flow in the viscosity measurement pipe 2 on the same curve.

[0019] The present invention will be described below with reference to several embodiments.

[0020] [Viscosity Measurement Pipe] FIG. 1 is a schematic diagram showing the configuration of a viscosity measurement pipe 100 according to a first embodiment of the present invention.

[0021] The viscosity measurement pipe 100 is formed by combining a first plate 210 and a second plate 220. FIG. 2 is a schematic diagram showing the facing surfaces of the first plate 210 and the second plate 220. As shown in FIG. 2, grooves having the shapes of the unit pipes and connecting pipes are formed on the facing surfaces of the first plate 210 and the second plate 220. By combining the first plate 210 and the second plate 220 so that the surfaces on which these grooves are formed are in contact with each other, the viscosity measurement pipe 100 is formed, which has a plurality of unit pipes and a plurality of connecting pipes, each of which has a different size or shape. The viscosity measurement pipe 100 may have screw holes 230 into which screws are inserted to secure the combined first plate 210 and second plate 220.

[0022] The configuration of the viscosity measurement pipe 100 is not limited to a configuration in which a plurality of unit pipes are formed on the same substrate (plate) as shown in Fig. 2, but each unit pipe may be formed on a different substrate, making them separable. By making the unit pipes separable, any of the unit pipes constituting the viscosity measurement pipe can be replaced with any other unit pipe.

[0023] 3 is a schematic diagram showing the state of a flow path formed by combining a first plate 210 and a second plate 220. The viscosity measurement pipe 100 has a plurality of unit pipes, each of which can measure the pressure of the fluid flowing therethrough, and these unit pipes include capillary-type unit pipes and slit-type unit pipes.

[0024] A slit-type unit pipe is a unit pipe whose flow path has a rectangular cross-sectional shape, and a capillary-type unit pipe is a unit pipe whose flow path has a circular cross-sectional shape. In this specification, the length of a flow path in the width direction of a slit-type unit pipe is referred to as the width W of each unit pipe included in the viscosity measurement pipe 100, and the length of a flow path in the height direction of a slit-type unit pipe is referred to as the height H of each unit pipe included in the viscosity measurement pipe 100. The direction perpendicular to both the width direction and the thickness direction is referred to as the length direction, and the length of a flow path in the length direction is referred to as the length LL of each unit pipe included in the viscosity measurement pipe 100. For ease of understanding, the length of a flow path in the width direction of a capillary-type unit pipe is referred to as the width W of the unit pipe, and the length of a flow path in the height direction of a slit-type unit pipe is referred to as the height H of the unit pipe. In a capillary-type unit pipe, both the width and height of the unit pipe are equal to the diameter of the flow path having a circular cross-section, and when the radius of the unit pipe is R, W = H = 2R.

[0025] In addition, a slit-type unit pipe having a rectangular cross section is used to measure the shear stress due to the upper and lower walls in the height direction, but if the ratio of width to height is too small, the influence of the shear stress due to the left and right walls in the width direction will occur. In order to eliminate the influence of the shear stress due to the left and right walls, the length of the flow path in the width direction of the rectangular cross section (flow path width) is preferably 8 to 20 times, and more preferably 9 to 12 times, the length of the flow path in the height direction (flow path height).

[0026] 3, the viscosity measurement pipe 100 has, in this order along its length, a first capillary-type unit pipe 110, a second slit-type unit pipe 130, and a third slit-type unit pipe 150. A first connection pipe 120 is disposed between the first unit pipe 110 and the second unit pipe 130, connecting these unit pipes. A second connection pipe 140 is disposed between the second unit pipe 130 and the third unit pipe 150, connecting these unit pipes. A third connection pipe 160 is disposed on the other side of the third unit pipe 150, connecting the third unit pipe 150 to an external flow path. While the number of unit pipes is not limited, it is preferable to have three or more unit pipes, all of which are capable of measuring pressure, in order to adequately grasp the viscosity at each shear rate of a non-Newtonian fluid whose viscosity is shear rate dependent. The upper limit of the number of unit pipes is not particularly limited, but is preferably 5 or less, and more preferably 3. In addition, as shown in Figures 1 to 3, in this embodiment, the fluid is circulated from one side to the other side (from the first unit pipe 110 side to the third unit pipe 150 side), but this is not limited thereto, and the fluid may be circulated from the other side to one side (from the third unit pipe 150 side to the first unit pipe 110 side).

[0027] The first unit pipe 110, the second unit pipe 130, and the third unit pipe 150 are all capable of measuring the fluid pressure on the upstream and downstream sides of the unit pipes using pressure gauges. The pressure difference (pressure loss) between the upstream and downstream sides can be calculated from the measurements of these pressure gauges, and the shear stress in each unit pipe can be determined. In this embodiment, the second unit pipe 130 has two pressure gauges, 132 and 134, and the third unit pipe 150 has two pressure gauges, 152 and 154.

[0028] In this embodiment, the multiple unit pipes are arranged so that their sizes change along the longitudinal direction from one side to the other. By combining unit pipes of different sizes, the velocity (shear rate) of the fluid flowing through each unit pipe can be changed, allowing viscosity measurements at different shear rates to be performed at once. Furthermore, by combining slit-type unit pipes with capillary-type unit pipes, the size of the unit pipes at positions where they tend to become large can be kept within an appropriate range.

[0029] Specifically, for consecutive unit pipes among the plurality of unit pipes, the unit pipe arranged on one side in the length direction is defined as a first unit pipe, the unit pipe arranged on the other side in the length direction is defined as a second unit pipe, and the width of the first unit pipe is defined as W １ , height H １ The width of the second unit pipe is W ２ , height H ２ When the first unit pipe is a capillary type unit pipe and the second unit pipe is a slit type unit pipe, the following relationship is satisfied between all the first unit pipes and the second unit pipes. (A) When the first unit pipe is a capillary type unit pipe and the second unit pipe is a slit type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is greater than 1. (B) When the first unit pipe is a slit-type unit pipe and the second unit pipe is a capillary-type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is smaller than 1. (C) When the first unit pipe is a slit type unit pipe and the second unit pipe is a slit type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is greater than 1. (D) When the first unit pipe is a capillary type unit pipe and the second unit pipe is a capillary type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is greater than 1

[0030] Here, by increasing the width and height of the second unit pipe, it becomes possible to perform viscosity measurements over a wider viscosity range at once using the viscosity measurement pipe 100. On the other hand, by not making the width and height of the second unit pipe too large, it is possible to keep the size of the unit pipe on the other side within an appropriate range.

[0031] From the above viewpoint, (A) when the first unit pipe is a capillary type unit pipe and the second unit pipe is a slit type unit pipe, H ２ / H １ is preferably 1.1 or more, more preferably 1.2 or more, and even more preferably 1.3 or more. ２ / H １ is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. Similarly, when (A) the first unit pipe is a capillary type unit pipe and the second unit pipe is a slit type unit pipe, W ２ / W １ is preferably 10 or more, more preferably 11 or more, and even more preferably 12 or more. ２ / W １ is preferably 30 or less, more preferably 25 or less, and even more preferably 20 or more.

[0032] Similarly, (B) when the first unit pipe is a slit type unit pipe and the second unit pipe is a capillary type unit pipe, H ２ / H １ is preferably 1.5 or more, more preferably 1.7 or more, and even more preferably 2.0 or more. ２ / H １ is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. On the other hand, (B) when the first unit pipe is a slit-type unit pipe and the second unit pipe is a capillary-type unit pipe, from the viewpoint of keeping the size of the second unit pipe within an appropriate range, W ２ / W１ may be 0.9 or less, or may be 0.8 or less. In addition, from the viewpoint of making the size of the second unit pipe appropriate and facilitating the measurement of viscosity, W ２ / W １ may be 0.1 or more, may be 0.2 or more, or may be 0.3 or more.

[0033] As shown in (A), (C), and (D), in this embodiment, the size of the unit pipe increases from one side to the other. This improves the accuracy of the viscosity measurement value and enables viscosity measurement over a wide shear rate range. However, (B) when the first unit pipe is a slit-type unit pipe and the second unit pipe is a capillary-type unit pipe, the height of the second unit pipe is greater than that of the first unit pipe, but the width of the second unit pipe is smaller than that of the first unit pipe. Under the conditions that the flow rates of the first and second unit pipes are the same and the width W of the slit-type first unit pipe is greater than the height H, the width of the second unit pipe is necessarily smaller than that of the first unit pipe in order to bring the shear rate calculated in Equations (1) and (2) described below into the predetermined range required for viscosity measurement.

[0034] In addition, (C) when the first unit pipe is a slit type unit pipe and the second unit pipe is a slit type unit pipe, H ２ / H １ is preferably 1.5 or more, more preferably 1.7 or more, and even more preferably 2.0 or more. ２ / H １ is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. Similarly, (C) when the first unit pipe is a slit type unit pipe and the second unit pipe is a slit type unit pipe, W ２ / W １ is preferably 1.5 or more, more preferably 1.7 or more, and even more preferably 2.0 or more. ２ / W １is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less.

[0035] Furthermore, (D) when the first unit pipe is a capillary type unit pipe and the second unit pipe is a capillary type unit pipe, H ２ / H １ is preferably 1.5 or more, more preferably 1.7 or more, and even more preferably 2.0 or more. ２ / H １ is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. Similarly, (D) when the first unit pipe is a capillary type unit pipe and the second unit pipe is a capillary type unit pipe, W ２ / W １ is preferably 1.5 or more, more preferably 1.7 or more, and even more preferably 2.0 or more. ２ / W １ is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less.

[0036] In addition, in any combination of (A) to (D), the length of the first unit pipe is LL １ The length of the second unit pipe is LL ２ When the above is true, LL is set between at least one pair of the first unit pipe and the second unit pipe, preferably between all pairs of the first unit pipe and the second unit pipe. ２ / LL １ is preferably 1.5 or more, more preferably 1.7 or more, and even more preferably 2.0 or more. This allows a sufficient pressure difference to be generated in the fluid when it flows through each unit pipe, and the measurement accuracy of the pressure difference can be further improved. In addition, LL is set between at least one pair of first unit pipe and second unit pipe, and preferably between all first unit pipes and second unit pipes. ２ / LL １is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. This allows the pressure loss in each unit pipe to be kept within an appropriate range, and allows the fluid to flow through the viscosity measurement pipe with an appropriate amount of power. In addition, the amount of heat generated by the pressure loss can be reduced.

[0037] In this embodiment, the first unit pipe 110, the second unit pipe 130, and the third unit pipe 150 are respectively of a capillary type, a slit type, and a slit type. By combining unit pipes of different types in this way, it is possible to keep the dimensions of each unit pipe within an appropriate range even when performing viscosity measurements over a wide shear rate range in which the difference between the minimum and maximum shear rates is at least about 100 times.

[0038] The combination of the types of each unit pipe is not limited to the above order. According to the findings of the inventors, when the flow rate of the fluid flowing through the viscosity measurement pipe is relatively low (for example, 100 kg / h or less (in the example described later (the density of the fluid at 230°C is 0.76 g / cc)), the viscosity of the fluid is 3.7 x 10 －３ m ３ / s or less), by using the order of capillary type, slit type, and slit type, the overall size of the viscosity measurement pipe 100 can be adjusted to a moderate range that is neither too large nor too small. If all unit pipes are slit type, it would be necessary to combine unit pipes with very large widths, which would increase the overall weight of the viscosity measurement pipe and likely result in the generation of large, unnecessary dead volumes within the viscosity measurement pipe. Furthermore, if all unit pipes are capillary type, the size of all unit pipes would be too small, making it difficult to install a pressure gauge. In response to these issues, by arranging capillary type unit pipes, which are easier to reduce in size, at the end on the side where the size is smallest, the size of the slit type unit pipes arranged at the opposite end can be kept within a moderate range. Furthermore, by arranging slit type unit pipes at the position of unit pipes where the size is large, it becomes easier to install a pressure gauge and it is possible to prevent an increase in the thickness of the viscosity measurement pipe. In this case, any other unit pipes may be arranged outside the above three unit pipes in the longitudinal direction.

[0039] According to the findings of the present inventors, when the flow rate of the fluid flowing through the viscosity measurement pipe is relatively high (for example, 100 kg / h or more (in the example described later (the density of the fluid at 230°C is 0.76 g / cc)), the viscosity is 3.7 × 10 －３ m ３ / s or more), the overall size of the viscosity measurement pipe 100 can be adjusted to a moderate range by arranging the pipes in the order of slit type, capillary type, and capillary type, or slit type, slit type, and capillary type. If all unit pipes are slit type, it would be necessary to arrange unit pipes with very large widths at the end, which would increase the overall weight of the viscosity measurement pipe and likely result in the generation of large, unnecessary dead volumes within the viscosity measurement pipe. In contrast, by arranging capillary type unit pipes, which are easier to reduce in size, at the other end (the most downstream side in this embodiment), the size of the viscosity measurement pipe can be kept within a moderate range. Furthermore, if a slit type unit pipe is arranged at the position where the size is largest, the width W of the slit type unit pipe becomes very large. For unit pipes on the slit side with a large width W, it is difficult to precisely process the height H to a constant value throughout the entire width W direction, making it difficult to fabricate unit pipes with high dimensional accuracy for accurate viscosity measurement. Furthermore, if the width W of a slit-type unit pipe is large, the height is likely to change due to the pressure of the resin flowing inside the unit pipe. Therefore, it is preferable to place a capillary-type unit pipe at the most downstream side. Furthermore, if a slit-type unit pipe is placed at the most downstream side, fluid may stagnate on the wall surface of the slit-type unit pipe, causing a delay in the flow of the resin, which in turn may slow down the viscosity measurement. In contrast, by placing a capillary-type unit pipe at the most downstream side, fluid is less likely to stagnate on the wall surface of the pipe, making it less likely that a delay will occur in the viscosity measurement.

[0040] In this embodiment, the shape of the flow path inside the unit pipe is constant along the length direction in all of the first unit pipe 110, the second unit pipe 130, and the third unit pipe 150. However, this is not limited to this, and as long as the shape of the flow path between the pressure gauges is constant, the shapes before and after the pressure gauges may be changed.

[0041] In this embodiment, the second unit pipe 130 has two pressure gauges, a pressure gauge 132 and a pressure gauge 134 , and the third unit pipe 150 has two pressure gauges, a pressure gauge 152 and a pressure gauge 154 .

[0042] Each pressure gauge is preferably placed at a position where the flow of fluid in the unit pipe is stable, and more preferably at a predetermined distance from the end (inlet and outlet) of the unit pipe. On the other hand, from the viewpoint of providing a sufficient distance between the two points for measuring the pressure difference, it is preferable to place the pressure gauge at a position where the distance from the end of the unit pipe is not too large. From the viewpoint of balancing these factors, each pressure gauge is preferably positioned at a location where the distance between the adjacent ends of the unit flow path (for pressure gauges positioned upstream (pressure gauges 132 and 152 when fluid is circulating from the first unit pipe 110 to the third unit pipe 150 as in this embodiment), the inlet of the second unit pipe 130 and the third unit pipe 150, respectively; for pressure gauges positioned downstream (pressure gauges 134 and 154 in this embodiment), the outlet of the second unit pipe 130 and the third unit pipe 150, respectively) is 3% or more and 35% or less, more preferably at a location where the distance is 5% or more and 30% or less, and even more preferably at a location where the distance is 6% or more and 25% or less, of the length LL of the flow path of the unit pipe.

[0043] Specifically, the second unit pipe 130 and the third unit pipe 150 have a longitudinal distance L between a position on one side where the pressure of the fluid is measured and the one-side end of the flow path of each unit pipe. Ｕ The distance in the length direction between the other end of the flow path of the unit pipe and the other end of the fluid pressure measurement position on the other side is defined as L. Ｄ The flow path length of the unit pipe is L Ｗ When this is the case, the ratio of the distance between the position where the fluid pressure is measured and the end of the unit pipe to the flow path length of the unit pipe is L Ｕ / L ｗ and L Ｄ / L ｗ However, it is preferable that each of them is 3% or more and 35% or less.

[0044] In this embodiment, since the first unit pipe 110, which is a capillary type, is small in size, it may be difficult to place a pressure gauge inside. In such a case, portions with a wide flow path width W may be provided before and after the capillary type unit pipe, and pressure gauges may be placed in those portions, and the pressure difference of the fluid flowing through the first unit pipe 110 may be calculated from the measurements of these pressure gauges. In this embodiment, a pressure gauge 112 is placed before the fluid flows into the viscosity measurement pipe 100, and the pressure difference between the measurement value obtained by this pressure gauge and the measurement value obtained by the pressure gauge 132 placed in the second unit pipe is used as the pressure difference of the fluid flowing through the first unit pipe 110. However, even in this case, when measuring shear stress, which will be described later, the shear stress σ is calculated based on the length of the first unit pipe 110 and the difference (pressure difference) in the measurements between the pressure gauge 112 and the pressure gauge 132. In such a case, a preferable L Ｕ / L ｗ and L Ｄ / L ｗ The range is not necessarily limited to the above range.

[0045] In this way, when the size of a capillary-type unit pipe is small and it is difficult to place a pressure gauge, it is preferable to place a slit-type unit pipe adjacent to the capillary-type unit pipe so that the pressure of the unit pipe at the inlet or outlet side of the capillary-type can be measured upstream or downstream of it.

[0046] In this embodiment, a first connecting pipe 120 for continuously changing the flow path shape between the first unit pipe 110 and the second unit pipe 130 is disposed between these unit pipes. The first connecting pipe 120 is a pipe having a tapered flow path shape in which the flow path size increases smoothly and gradually from the first unit pipe 110 side toward the second unit pipe 130 side.

[0047] Similarly, a second connecting pipe 140 for continuously changing the flow path shape between the second unit pipe 130 and the third unit pipe 150 is disposed between these unit pipes. The second connecting pipe 140 is a pipe having a tapered flow path shape in which the flow path size increases smoothly and gradually from the second unit pipe 130 side toward the third unit pipe 150 side.

[0048] Furthermore, a third connection pipe 160 for connecting the third unit pipe 150 to an external flow path is disposed on the other side of the third unit pipe 150. The flow path shape of the third connection pipe 160 is not particularly limited, but it is preferably a shape that does not cause an influence on the measurement results due to a sudden increase in pressure, and is preferably a shape that continuously and smoothly changes toward the shape of the external flow path.

[0049] By using the tapered piping for both the first connecting pipe 120 and the second connecting pipe 140, it is possible to prevent the formation of a step between the unit pipes where the flow path shape changes suddenly, thereby suppressing fluid retention at the step. This reduces fluid loss (dead volume) due to the retention. Furthermore, it is possible to cause the fluid flowing into each unit pipe to form a stable flow from the beginning, and by positioning the pressure gauge closer to the inlet of each unit pipe, it is possible to shorten the length of the unit pipe and enable measurements to be taken in a shorter time. Furthermore, when the fluid is a polymer, for example, heat generation due to the retention can cause thermal decomposition of the polymer, reducing measurement accuracy. However, suppressing the retention can also prevent a decrease in measurement accuracy due to heat generation.

[0050] The tapered shape may be a simple tapered shape in which the cross-sectional shape of the channel end sides is made up of only straight lines, a coat hanger shape in which the channel size gradually increases on one side and remains almost constant on the other side, or a fishtail shape in which the rate at which the channel size expands changes from one side to the other, and the shape is not particularly limited.

[0051] The angle formed by the channel end in the cross section of the tapered type with respect to the longitudinal direction is preferably 30° to 60°, more preferably 40° to 50°. In the case of a coat hanger type or a fishtail type, the angle can be the angle formed by an imaginary line connecting the channel end at the inlet and the channel end at the outlet of the connecting pipe with respect to the longitudinal direction.

[0052] It is not necessary to provide connecting pipes between the respective unit pipes. However, from the viewpoint of fully obtaining the above-mentioned effect, it is preferable to provide connecting pipes between all the unit pipes, and it is more preferable to provide tapered connecting pipes between all the unit pipes.

[0053] Although not shown, the viscosity measurement pipe 100 may have a heater for adjusting the temperature of the fluid, a temperature detector (such as a thermocouple) for measuring the temperature of the fluid, and a control unit for controlling heating by the heater. Furthermore, the viscosity measurement pipe 100 may have a heat insulating material on its outer surface to prevent heat radiation to the outside, and may have a support unit for supporting the viscosity measurement pipe 100.

[0054] The material of the viscosity measurement pipe 100 is not particularly limited as long as it is not easily deformed by the pressure and temperature of the flowing fluid. Examples of materials for the viscosity measurement pipe 100 include known steel materials and alloys such as mechanical structural carbon steel (S-C material), structural alloy steel (manganese steel (SMn), manganese chromium steel (SMnC), chromium molybdenum steel (SCM), nickel chromium steel (SNC), nickel chromium molybdenum steel (SNCM), aluminum chromium molybdenum steel (SACM), SKD4, SKD5, SKD6, SKD61, SKD62, SKT2, SKT3, SKT4, SKT5, SKT6, SUS304, SUS309S, SUS316, SUS317, SUS321, SUS347, SUS405, SUS430, SUS410, Hastelloy X, Inconel 600, and Inconel 718.

[0055] Furthermore, the overall size of the viscosity measurement pipe 100 is not particularly limited as long as it is not easily deformed by the pressure and temperature of the fluid flowing through it. For example, the width of the viscosity measurement pipe 100 at the same position can be 1.2 to 3 times the width W of each pipe.

[0056] [Viscometer] The viscosity measurement pipe 100 can be used in an in-line viscometer. The device configuration of a viscometer having the viscosity measurement pipe 100 and a method for measuring viscosity using the viscometer will be described below.

[0057] 4 is a block diagram showing an exemplary configuration of a viscometer 400 having a viscosity measurement pipe 100. The viscometer 400 has a gear pump 410 that adjusts the flow rate of the fluid flowing through the viscosity measurement pipe 100, and a CPU 420 that calculates the viscosity.

[0058] The gear pump 410 causes a fluid to flow at a predetermined flow rate through the viscosity measurement pipe 100. In this embodiment, the gear pump 410 causes a fluid to flow through the viscosity measurement pipe 100, which integrally includes the first unit pipe 110, the second unit pipe 130, and the third unit pipe 150. Therefore, the flow rate in each unit pipe is the same. Although each unit pipe may be provided separately and the fluid may flow independently, and the flow rate measured for each unit pipe, externally adjusting the flow rate using the gear pump 410 eliminates the need to install a flow measurement device in each unit pipe, enabling more accurate viscosity measurement. Furthermore, externally adjusting the flow rate using the gear pump 410 ensures that the flow rates in each unit pipe are the same, making subsequent calculations easier. The gear pump 410 may be of any type, as long as it can externally adjust the flow rate.

[0059] The fluid caused to flow by the gear pump 410 is introduced into the viscosity measurement pipe 100, and flows through the first unit pipe 110, the first connecting pipe 120, the second unit pipe 130, the second connecting pipe 140, and the third unit pipe 150 in this order. Then, the fluid is discharged from the third connecting pipe 160 into the viscosity measurement pipe 100. At this time, the pressure of the fluid at each measurement position is measured by the pressure gauge described above.

[0060] The CPU 420 is a known information processing device, and includes the functional units of a shear rate calculation unit 422, a shear stress calculation unit 424, a correction unit 426, and a viscosity calculation unit 428. These functional units can be installed in the CPU as software that performs the following processes.

[0061] The shear rate calculation unit 422 calculates the shear rate of the fluid flowing through each unit pipe based on the flow rate of the fluid obtained from the gear pump 410 and information on the known size of each unit pipe.

[0062] Specifically, for a capillary-type unit pipe (in this embodiment, the first unit pipe 110), the shear rate calculation unit 422 calculates the shear rate of the fluid in the unit pipe using equation (1) based on the width W and height H of the unit pipe (both the width W and the height H are the diameters of the unit pipe) and the volumetric flow rate Q obtained from the gear pump 410.

[0063]

[0064] In addition, indicates the shear rate.

[0065] Furthermore, for slit-type unit pipes (in this embodiment, the second unit pipe 130 and the third unit pipe 150), the shear rate of the fluid in the unit pipe is calculated using equation (2) based on the width W and height H of the unit pipe and the volumetric flow rate Q obtained from the gear pump 410.

[0066]

[0067] As described above, for a slit-type unit pipe, there is a relationship between W and H such that W is preferably 8 to 20 times, and more preferably 8 to 12 times, H.

[0068] The shear stress calculation unit 424 calculates the pressure loss ΔP of the fluid as it flows through each unit pipe, and based on this pressure loss ΔP and information on the known size of each unit pipe, calculates the shear rate of the fluid as it flows through each unit pipe.

[0069] Specifically, when a fluid is caused to flow in a direction from the first unit pipe 110 to the third unit pipe 150 as in this embodiment, the shear stress calculation unit 424 calculates the difference between the pressure measurement value by the pressure gauge 112 arranged before the fluid flows into the viscosity measurement pipe 100 and the pressure measurement value by the pressure gauge 132 arranged upstream of the second unit pipe 130, and sets this as the pressure loss ΔP when the fluid flows through the first unit pipe 110. In addition, the shear stress calculation unit 424 calculates the difference between the pressure measurement value by the pressure gauge 132 arranged upstream of the second unit pipe 130 and the pressure measurement value by the pressure gauge 134 arranged downstream of the second unit pipe 130, and sets this as the pressure loss ΔP when the fluid flows through the second unit pipe 130. In addition, the difference between the pressure measurement value by the pressure gauge 152 located upstream of the third unit pipe 150 and the pressure measurement value by the pressure gauge 154 located downstream of the third unit pipe 150 is calculated to obtain the pressure loss ΔP when flowing through the third unit pipe 150.

[0070] Then, for each of the capillary-type unit pipes and the slit-type unit pipes, the shear stress σ of the fluid in each unit pipe is calculated using equation (3) based on the height H of the unit pipe (for a capillary-type unit pipe, the height H is the diameter of the unit pipe), the longitudinal distance L between the pressure measurement points (in this embodiment, for the first unit pipe 110, the length LL of the first unit pipe 110 is taken as the distance L. For the second unit pipe 130, it is the distance between the pressure gauges 132 and 134, and for the third unit pipe 150, it is the distance between the pressure gauges 152 and 154), and the pressure loss ΔP in each of the unit pipes.

[0071]

[0072] In addition, the viscosity calculation unit 428 may calculate the viscosity η of the fluid (at each shear rate) in each unit pipe using equation (4) based on the shear rate obtained by the shear rate calculation unit 422 and the shear stress σ obtained by the shear stress calculation unit 424.

[0073]

[0074] The viscosity obtained at this time is the apparent viscosity of the fluid, without any correction as described below.

[0075] The apparent viscosity is obtained by calculating the shear rate using a formula that assumes that the fluid is a Newtonian fluid. Since most actual fluids are non-Newtonian, the apparent viscosity may not accurately represent the viscosity of the fluid. Therefore, in this embodiment, the shear rate obtained by the shear rate calculation unit 422 is corrected by the correction unit 426 to determine the true viscosity of the non-Newtonian fluid.

[0076] Specifically, the correction unit 426 defines adjacent unit pipes as unit pipe A and unit pipe B, and calculates the shear rate measured in unit pipe A as The shear stress measured in unit pipe A is σ Ａ The shear rate measured in unit pipe B is The shear stress measured in unit pipe B is σ Ｂ The non-Newtonian exponent n, which represents the shear rate dependency of the shear viscosity of the fluid, is calculated using equation (5).

[0077]

[0078] In non-Newtonian fluids, the relationship between shear rate and shear stress is not linear, so the non-Newtonian exponent n in equation (5) is not a constant value and is shear rate dependent.

[0079] In this embodiment, with regard to the non-Newtonian index n, which is the slope of equation (5), the non-Newtonian index n for the first unit pipe 110 can be obtained from the first unit pipe 110 and the second unit pipe 130, and the non-Newtonian index n for the third unit pipe 150 can be obtained from the set of the second unit pipe 130 and the third unit pipe 150. The non-Newtonian index n for the second unit pipe 130 is calculated from the moving average of these two n's. In order to calculate this non-Newtonian index n and calculate the true density with high accuracy, it is preferable that the number of unit pipes is three or more. When the number of unit pipes is four or more, the non-Newtonian index n for each unit pipe can be calculated using the same procedure.

[0080] Then, for a capillary type unit pipe, the correction unit 426 obtains the true shear velocity of the fluid using equation (6).

[0081]

[0082] For a slit-type unit pipe, the true shear rate of the fluid is calculated using equation (7).

[0083]

[0084] The above correction for determining the true shear rate is known as the Rabinowich correction.

[0085] Then, the viscosity calculation unit 428 calculates the true viscosity η of the fluid (at each shear rate) in each unit pipe using equation (8) based on the true shear rate obtained by the correction unit 426 and the shear stress obtained by the shear stress calculation unit 424.

[0086]

[0087] Then, by curve fitting, a viscosity curve representing the true viscosity of the fluid at each shear rate can be obtained, thereby obtaining the viscosity at each shear rate of a non-Newtonian fluid whose viscosity is shear rate dependent.

[0088] In this case, from the viewpoint of obtaining true viscosity over a wide range of shear rates, it is desirable to be able to measure true viscosity over a wide range of shear rates, with a difference of at least 100 times between the minimum and maximum shear rates.

[0089] From the viewpoint of measuring viscosity over a wide shear rate range, when measuring viscosity using three unit pipes, the shear rate in the unit pipe with the slowest shear rate (the third unit pipe 150 in this embodiment) is defined as rate A, the shear rate in the unit pipe with the most intermediate shear rate (the second unit pipe 130 in this embodiment) is defined as rate B, and the shear rate in the unit pipe with the fastest shear rate (the first unit pipe 110 in this embodiment) is defined as rate C. It is preferable that rate B be approximately 9 to 50 times rate A, and it is preferable that rate C be approximately 90 to 1500 times rate A.

[0090] The above-described viscosity measurement pipe enables viscosity measurement over such a wide range of shear rates.

[0091] The viscosity measurement using the above viscometer can be applied to the measurement of the viscosity of polymer melts, organic substances such as oils that are fluid at room temperature, and various other dispersions. Among these, the present invention is suitable for measuring the viscosity of polymer melts, the viscosity of which is highly difficult to predict, particularly when melt-mixing various types of waste plastics.

[0092] The polymer may be any thermoplastic resin, such as polyolefin resin, polycarbonate resin, thermoplastic polyester resin, ABS resin, polyacetal resin, polyamide resin, polyphenylene oxide resin, polyimide resin, polyurethane resin, polylactic acid resin, furan resin, silicone resin, etc. However, the type of polymer is not limited to these.

[0093] The definitions and manufacturing methods of these thermoplastic resins are well known and are described in publications such as "Practical Plastics Encyclopedia" (edited by the Practical Plastics Encyclopedia Editorial Committee, published by Sangyo Chosakai Co., Ltd.).

[0094] The polyolefin resin is not particularly limited, and conventionally known polyolefin resins can be used. Examples of the polyolefin resin include polyethylene resins such as low-density polyethylene, linear low-density polyethylene, and high-density polyethylene, polypropylene resin, polyethylene terephthalate resin, vinyl chloride resin (chlorinated polyolefin), ethylene-vinyl acetate copolymer, and ethylene-methacrylic acid acrylate copolymer. Among these, low-density polyethylene, linear low-density polyethylene, high-density polyethylene, and polypropylene resin are preferably used. The polyethylene resin and polypropylene resin may be various modified products.

[0095] The polyethylene resin may be an ethylene homopolymer or an ethylene copolymer. The ethylene copolymer is preferably a copolymer of ethylene and one or more α-olefins. The α-olefin is preferably an α-olefin having 3 or more carbon atoms, more preferably an α-olefin having 3 to 8 carbon atoms. Examples of α-olefins having 3 or more carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, and 4-methyl-1-pentene.

[0096] Examples of the polypropylene resin include propylene homopolymers and propylene copolymers. The propylene copolymer is preferably a copolymer of propylene and one or more α-olefins. The α-olefin is preferably an α-olefin having 2 or more carbon atoms (excluding 3 carbon atoms), more preferably an α-olefin having 2 to 8 carbon atoms (excluding 3 carbon atoms). Examples of α-olefins having 2 or more carbon atoms include ethylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 4-methyl-1-pentene, etc.

[0097] The polycarbonate resin is typically a resin obtained by reacting an aromatic diol (e.g., bisphenol A) with phosgene. Examples of commercially available polycarbonate resins include NOVAREX ("NOVAREX" is a registered trademark of Mitsubishi Chemical Corporation), Panlite ("Panlite" is a registered trademark of Teijin Chemicals Limited), and Lexan ("Lexan" is a registered trademark of GE Plastics Japan Co., Ltd.). Naturally, these commercially available products are also suitable for use in the present invention.

[0098] The thermoplastic polyester resin is typically a resin obtained by polycondensation of a dicarboxylic acid and a diol. Examples of the thermoplastic polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene 2,6-naphthalenedicarboxylate, and polycyclohexane terephthalate.

[0099] The ABS resin is typically an impact-resistant resin obtained by graft polymerizing polybutadiene with acrylonitrile and styrene. In the present invention, the polybutadiene component may be 5 to 40% by weight, and the weight ratio of the styrene component to the acrylonitrile component (styrene / acrylonitrile) may be 70 / 30 to 80 / 20.

[0100] The polyacetal resin is typically a resin obtained by ring-opening polymerization of formalin or trioxane, optionally together with ethylene oxide, in the presence of a cationic catalyst, and has a polyoxymethylene chain as the main skeleton. In the present invention, copolymer-type resins are preferred.

[0101] The polyamide resin is typically a resin obtained by polycondensation of a diamine and a dicarboxylic acid, or by ring-opening polymerization of caprolactam, etc. In the present invention, a polycondensation reaction product of an aliphatic diamine and an aliphatic or aromatic dicarboxylic acid is preferred.

[0102] The polyphenylene oxide resin is typically obtained by oxidative coupling of 2,6-dimethylphenol in the presence of a copper catalyst. Modified polyphenylene oxide resins obtained by further modifying this polyphenylene oxide resin can also be used in the present invention.

[0103] [Other embodiments] It should be noted that each of the above-described embodiments represents an example of the present invention, and the present invention is not limited to the above-described embodiments. Needless to say, various other embodiments are possible within the scope of the concept of the present invention.

[0104] The present invention will be described in more detail below with reference to examples and comparative examples, but the scope of the present invention should not be construed as being limited by these examples and comparative examples.

[0105] [First Experiment] A viscosity measurement pipe was prepared by combining three unit pipes of different sizes. Using this viscosity measurement pipe, a comparison was made between a case where a fluid was passed through a unit pipe of a smaller size in order to a unit pipe of a larger size in order (the present invention) and a case where a fluid was passed through a unit pipe of a larger size in order to a unit pipe of a smaller size in order (see Patent Document 1), to investigate the difference in accuracy of the viscosity measurements obtained.

[0106] 1. Viscosity measurement pipe The viscosity measurement pipe 1 shown in Figures 1 to 3 and viscosity measurement pipes 2 with different types of unit pipes at each position were prepared. Figure 5 is a schematic diagram showing the configuration of the viscosity measurement pipe 2, and Figure 6 is a schematic diagram showing the surfaces of the first plate 210 and the second plate 220 that constitute the viscosity measurement pipe 2, facing each other. When molten resin was flowed through these viscosity measurement pipes, the shear stress values ​​in each unit pipe were actually measured.

[0107] The viscosity measurement pipe 1 is configured such that a capillary type unit pipe (first unit pipe), a slit type unit pipe (second unit pipe), and a slit type unit pipe (third unit pipe) are arranged along the length direction of the fluid, and the size of each unit pipe is as shown in Table 1. The width W of the first capillary type unit pipe is １ and height H １are the diameters of the flow path of the first unit pipe. The overall shape of the viscosity measurement pipe 1 was a box shape with a total length of 300 mm, a total width of 100 mm, and a total height of 70 mm, and was formed by combining two upper and lower plates. Each of the upper and lower plates had a groove formed on its surface so that when combined, a pipe of the following shape and size was formed. A pressure gauge P0 was placed in the flow path before the inlet of the viscosity measurement pipe, pressure gauges P1 and P2 were placed in the second unit pipe, and pressure gauges P3 and P4 were placed in the third unit pipe.

[0108]

[0109] The viscosity measurement pipe 2 is configured such that a slit-type unit pipe (first unit pipe), a capillary-type unit pipe (second unit pipe), and a capillary-type unit pipe (third unit pipe) are arranged along the length direction of the fluid, and the size of each unit pipe is as shown in Table 2. The width W of the second capillary-type unit pipe is ２ and height H ２ are the diameters of the flow paths of the second unit pipes. ３ and height H ３ are the diameters of the flow paths of the third unit pipe. The overall shape of the viscosity measurement pipe 2 is a box-like shape made up of two upper and lower plates, each 350 mm long, 180 mm wide, and 160 mm high, connected to a 350 mm long circular pipe with an outer diameter of 70 mm. Each of the upper and lower plates of the box-like portion has a groove formed on its surface so that when combined, the first and second unit pipes form pipes with the following shapes and sizes. The third unit pipe is composed of a circular pipe portion connected to the box-like portion with a flange. Pressure gauges P0 and P1 were placed on the inlet and outlet sides of the slit of the first unit pipe, respectively, pressure gauges P2 and P3 on the second unit pipe, and pressure gauges P4 and P5 on the third unit pipe. Using six pressure gauges in this way is ideal, but since the pressure difference between P3 and P4 is not large, it is also possible to omit either P3 or P4, leave five pressure gauges, determine the correction coefficient α to match the actual measurement, and treat it as P3 = αP4.

[0110]

[0111] 2. Comparison with Simulation Results 2-1. Experimental Conditions A polypropylene homopolymer having a melt flow rate of 9.0 measured in accordance with JIS K 7210 under conditions of 230°C and a load of 2160 g was passed through the viscosity measurement pipe 1 from the first unit pipe side to the third unit pipe side at 230°C. The polypropylene homopolymer was extruded by connecting a Zenith gear pump (PEP-II-0.6cc) to a Technovel Co., Ltd. twin-screw extruder (KZW15TW-45MG-NH), setting the cylinder to 6 zones at 180°C, 200°C, 230°C, 230°C, 230°C, and 230°C, with a screw rotation speed of 100 rpm and gear pump flow rates of 30 rpm (0.2398 cc / s) and 60 rpm (0.4797 cc / s), respectively, so that the molten polypropylene homopolymer was flowing. The pressure of this polypropylene homopolymer was measured using the viscosity measurement pipe connected to the gear pump.

[0112] Example 1 The polypropylene homopolymer was flowed from the first unit pipe to the third unit pipe of the viscosity measurement pipe 1, and the pressure values ​​at pressure gauges P0 to P4 were measured. At this time, a Dynisco NP462-1 / 2-15-45 pressure gauge with a full scale of 20 MPa was used for P0, and a Dynisco NP462-1 / 2-3.5MPa-15-45 pressure gauge with a full scale of 3.5 MPa was used for P1 to P4. The pressure measurements were performed when the gear pump flow rate was set to 30 rpm (0.2398 cc / s) and 60 rpm (0.4797 cc / s).

[0113] Comparative Example 1 The polypropylene homopolymer was flowed from the third unit pipe of the viscosity measurement pipe 1 to the first unit pipe, and the pressure values ​​were measured using pressure gauges P1 to P4 and at P5 set at the front end of the third unit pipe. A Dynisco NP462-1 / 2-15-45 pressure gauge with a full scale of 20 MPa was used for P5, and a Dynisco NP462-1 / 2-10MPa-15-45 pressure gauge with a full scale of 10 MPa was used for P1 to P4. Pressure measurements were performed when the gear pump flow rate was set to 30 rpm (0.2398 cc / s) and 60 rpm (0.4797 cc / s). The reason why the pressure gauges used at P1 to P4 were changed between Example 1 and Comparative Example 1 is that in the Comparative Example, the pressure at P1 to P4 greatly exceeded 3.5 MPa, exceeding the range of the full scale of the pressure gauge. In Example 1, pressure gauges with smaller full scales were used at P1 to P4 in order to measure the pressure more accurately.

[0114] (Simulation) The type of resin, extrusion conditions, and temperature conditions were set to the same as those used in the actual measurements, and the pressure inside the viscosity measurement pipes 1 and 2 was simulated using scFLOW (MSC Software / Hexagon Group).

[0115] 2-2. Results FIG. 7 shows the results of Example 1, Comparative Example 1, and the simulation.

[0116] 7 plots the measured values ​​of pressure gauges P0 to P4 in Example 1 when the gear pump flow rate was set to 0.2398 cc / s and 0.4797 cc / s, and also shows the simulation results under the same conditions. The simulation results when the gear pump flow rate was set to 0.2398 cc / s are shown by a solid line, and the results when the gear pump flow rate was set to 0.4797 cc / s are shown by a dashed line.

[0117] 7 plots the measured values ​​of pressure gauges P1 to P5 in Comparative Example 1 when the gear pump flow rate was set to 0.2398 cc / s and 0.4797 cc / s, and also shows the simulation results under the same conditions. The simulation results when the gear pump flow rate was set to 0.2398 cc / s are shown by a solid line, and the results when the gear pump flow rate was set to 0.4797 cc / s are shown by a dashed line.

[0118] 7, the measurement results of Example 1 were almost identical to the simulation results, but the measurement results of Comparative Example 1 deviated significantly from the simulation results. This is thought to be because in Comparative Example 1, the magnitude of the signal from the third unit pipe, which was larger in size, was close to the level of white noise originating from the power source, making it impossible to measure the signal correctly.

[0119] Furthermore, both the measurement results and simulation results for Comparative Example 1 showed high pressure values ​​at each measurement point. This is thought to be because the pressure loss at the pressure gauge P0, which measured the pressure first, was so large that the measurement results at the other measurement points were obscured by the result at P0. As is clear from Figure 7, in Comparative Example 1, the pressure difference at each measurement point was small, making it difficult to measure the pressure difference accurately.

[0120] FIG. 8 shows the results of a simulation of the viscosity measurement pipe 2.

[0121] In FIG. 8, the solid line shows the simulation results of the measured values ​​of the pressure gauges P0 to P5 when the polypropylene homopolymer was flowed in the viscosity measurement pipe 2 in the forward flow (corresponding to the example) and the backward flow (corresponding to the comparative example) with the gear pump flow rate set to 18.366 cc / s (equivalent to a discharge rate of 50 kg / h).

[0122] As in Figure 7, in the case of forward flow, a small full-scale pressure gauge with small compound error can be used on the piping on the low shear rate side, so it is expected that the influence of white noise will be small. However, in the case of reverse flow, a large full-scale pressure gauge must be used on the piping on the low shear rate side, so there are concerns about the influence of noise, and it is expected that the measurement accuracy will be poor.

[0123] 3. Variation in Experimental Results 3-1. Experimental Conditions Under the same conditions as in Example 1 and Comparative Example 1 in "2. Comparison with Simulation Results," the molten polypropylene homopolymer was circulated through the viscosity measurement pipe, and the viscosity was measured at each point.

[0124] The viscosity measurement was carried out continuously for 15 minutes, with sampling every second. The coefficient of variation (standard deviation / average value) of the difference ΔP in the measured values ​​between pressure gauges P1 and P2 in Example 1 and between pressure gauges P4 and P3 in Comparative Example 1, both of which were at approximately the same distance from the inlet, was calculated for a gear pump flow rate of 0.2398 cc / s and 0.4797 cc / s.

[0125] 3-2. Results Table 3 shows the rate of change in ΔP when the flow rate of the gear pump was set to 0.2398 cc / s and 0.4797 cc / s in Example 1 and Comparative Example 1, respectively.

[0126]

[0127] As shown in Table 2, the fluctuation rate was small and the dispersion of the measurement results was small in Example 1, but the fluctuation rate was large and the dispersion of the measurement results was large in Comparative Example 1. This is thought to be because noise was more likely to occur in the third unit pipe, which was larger in size in Comparative Example 1.

[0128] 4. Shear Rate Dependence of Shear Viscosity 4-1. Experimental Conditions The polypropylene homopolymer was sandwiched between two parallel plates, and one of the parallel plates was rotated while the temperature was changed in 20°C increments from 170°C to 250°C. Using a TA Instruments rheometer (DHR-3), the frequency dispersion of the linear viscoelastic function was measured over a frequency range of ω = 0.1 to 500 rad / s. From the results obtained, a master curve was obtained using the time-temperature conversion law with 230°C as the reference temperature. Assuming that the Cox-Merz empirical law holds, the master curve showing the frequency dependence of the complex viscosity was considered to be the shear rate dependence of the shear viscosity of a steady flow.

[0129] The true viscosity was obtained by applying Rabinovich correction to the measured values ​​obtained in Example 1 and Comparative Example 1. The true viscosity obtained by applying Rabinovich correction was plotted on the curve showing the shear rate dependency of the shear viscosity of the steady flow.

[0130] 9A shows the results of Example 1 plotted on the curve. FIG. 9B shows the results of Comparative Example 1 plotted on the curve. In FIG. 9A, black circles indicate the true viscosity when the gear pump flow rate was 0.2398 cc / s, and dotted circles indicate the true viscosity when the gear pump flow rate was 0.4797 cc / s. In FIG. 9B, crosses indicate the true viscosity when the gear pump flow rate was 0.2398 cc / s, and squares indicate the true viscosity when the gear pump flow rate was 0.4797 cc / s.

[0131] Figure 10A shows the results of a simulation of forward flow through the viscosity measurement pipe 2 plotted on the above curve. Figure 10B shows the results of a simulation of reverse flow through the viscosity measurement pipe 2 plotted on the above curve. The error bars show the viscosity calculated from the pressure difference between each pipe at +5% and -5%, assuming a pressure range of 0-10 MPa and a composite error of ±5%.

[0132] 9A and 9B, the viscosity obtained in Example 1 matched the above curve, but the viscosity obtained in Comparative Example 1 deviated significantly from the above curve. In addition, the backflow in the viscosity measurement pipe 2 was significantly affected by variations due to compound errors.

[0133] 4-2. Results The results shown in Figures 7, 8, Table 2, Figures 9A and 9B, and Figures 10A and 10B show that flowing a fluid from a smaller-sized unit pipe to a larger-sized unit pipe in sequence significantly improves the accuracy of the viscosity measurements obtained, compared to flowing a fluid from a larger-sized unit pipe to a smaller-sized unit pipe in sequence. Furthermore, the results shown in Figures 9A and 9B, and Figures 10A and 10B show that flowing a fluid through unit pipes of increasing size from one to the other (excluding condition (B)) that satisfy the above-mentioned (A) to (D) enables viscosity measurements over a wide shear rate range (e.g., 1 kg / h, 10 kg / h, 100 kg / h, and 500 kg / h).

[0134] [Second Experiment] For a viscosity measurement pipe consisting of a combination of three unit pipes of different sizes, the size of each unit pipe was investigated to obtain three different shear rates. The size of each unit pipe was adjusted so that the difference between the minimum and maximum shear rates was at least 100 times. Based on the results of the first experiment, the three unit pipes were arranged so that the fluid flowed from the smallest unit pipe to the largest unit pipe.

[0135] 1. Conditions It was assumed that the polypropylene homopolymer used in the first experiment was melted and distributed at 230° C. The density of the polypropylene homopolymer at 230° C., measured under the following conditions and by the following method, was 0.76 g / cc.

[0136] (Density measurement conditions) Measuring device: PVT-100 manufactured by SWO Polymertechnil GmbH Measuring method: isobaric cooling test Measuring temperature: 30 to 260°C Cooling rate: 5°C / min Pressure level: 20, 40, 60, 80, 120 MPa Sample drying: none

[0137] (Method of measuring density) Approximately 0.75 g of a sample was placed in the measuring cylinder of the device, heated to 260°C, set at a pressure of 20 MPa, and measured for density while cooling to 30°C at a cooling rate of 5°C / min. Using this procedure, similar measurements were performed at 40 MPa, 60 MPa, 80 MPa, and 120 MPa, and the specific volume at 230°C was obtained by extrapolating the specific volume at each pressure to a pressure of 0.1 MPa. The density is the reciprocal of the specific volume, and was calculated to be 0.76 g / cc.

[0138] (Method of determining the size of the unit pipe) The size of the unit pipe was calculated so that it could accommodate all flow rates of 1 kg / h, 10 kg / h, 50 kg / h, and 500 kg / h, and so that the shear rates along the direction from the first unit pipe to the third unit pipe were 100 / sec, 10 / sec, and 1 / sec. In addition, the size of each unit pipe (and the combination of unit pipes in Example 2) was determined so that the overall volume of the viscosity measurement pipe would be as small as possible.

[0139] 2. Results (Comparative Example 2) Table 4 shows the calculation results when all three unit pipes were slit-shaped, with a constant height H and an increasing width W (see Figures 14 and 15 of Patent Document 2).

[0140]

[0141] As shown in Table 4, in the arrangement of Comparative Example 2, the width of the unit pipe becomes very large, and the difference in width between the minimum and maximum unit pipes becomes very large (bold underlined part in Table 4). As a result, it is presumed that problems such as an increase in the overall weight of the viscosity measurement pipe and the occurrence of a large amount of unnecessary dead volume that does not serve as a flow path in the viscosity measurement pipe will occur.

[0142] Comparative Example 3 Table 5 shows the calculation results when all three unit pipes were slit-shaped, with a constant width W and an increasing height H (see FIGS. 12 and 13 of Patent Document 2).

[0143]

[0144] As shown in Table 5, the arrangement of Comparative Example 3 results in an overall increase in the width of the unit pipes (bold underlined parts in Table 5). As a result, problems arise, such as an increase in the overall weight of the viscosity measurement pipes and the occurrence of a large amount of unnecessary dead volume in the viscosity measurement pipes that does not serve as a flow path.

[0145] (Comparative Example 4) The calculation results for the case where all three unit pipes were slit-shaped and had shapes in which the width W and height H both increased are shown in Table 6. Note that the size of the slit-shaped unit pipes was determined so that the width W was 10 times the height H.

[0146]

[0147] As shown in Table 6, even with the arrangement of Comparative Example 4, the width of the unit pipes is still large overall (bold underlined part in Table 6). As a result, problems such as an increase in the overall weight of the viscosity measurement pipes and the generation of a large amount of unnecessary dead volume that does not serve as a flow path within the viscosity measurement pipes occur. Also, as shown in Table 6, with the arrangement of Comparative Example 4, the height H of the first unit pipe at a flow rate of 1 kg / h is very small, at 1.3 mm. With such a small slit-type unit pipe, it is difficult to make the angle of the height direction relative to the width direction perpendicular during manufacturing, and there is a possibility that the pressure of the flowing resin will cause a gap at the mating surfaces of the upper and lower plates.

[0148] Comparative Example 5 Table 7 shows the calculation results when all three unit pipes were capillary type and had shapes in which the diameters (width W and height H) all increased (see FIG. 6 of Patent Document 3).

[0149]

[0150] As shown in Table 7, in the arrangement of Comparative Example 5, when the flow rate is reduced, both the width W and height H of the pipe become extremely small (bold underlined parts in Table 7). With such small sizes, it is very difficult to install a pressure gauge inside the pipe, making viscosity measurement impractical.

[0151] (Example 2) The calculation results for three unit pipes, each of which is a combination of a capillary type and a slit type, with the width W and height H (diameter for the capillary type) increasing, are shown in Table 8. The size of the slit type unit pipe was determined so that the width W was 10 times the height H.

[0152]

[0153] As shown in Table 8, by combining capillary and slit type unit pipes for the three unit pipes, the overall size of the viscosity measurement pipe can be kept within a reasonable range. When the flow rate is 1 kg / h, the diameter of the capillary type pipe, which is the first unit pipe, is 1.54 mm. In this case, the pressure loss in the first unit pipe can be found from the pressure difference between the pressure gauge P0 arranged in the first unit pipe and the pressure gauge P1 arranged in the second unit pipe, and the shear stress can be calculated based on this pressure loss, as described above.

[0154] Furthermore, as shown in Table 8, when the flow rate is reduced, by arranging a capillary-type unit pipe, a slit-type unit pipe, and another slit-type unit pipe in that order along the direction from the first unit pipe to the third unit pipe, the overall shape can be made smaller, and by making the first unit pipe, which is smaller in size, a capillary-type pipe, the problem of it being difficult to arrange a pressure gauge in the first unit pipe can be solved by using the second unit pipe, which is a slit type and in which it is easy to arrange a pressure gauge.

[0155] Furthermore, as shown in Table 8, when the flow rate is increased, the overall size of the viscosity measurement pipe can be reduced by arranging a capillary-type unit pipe at the most downstream side, that is, by arranging a slit-type unit pipe, a slit-type unit pipe, and a capillary-type unit pipe, or by arranging a slit-type unit pipe, a capillary-type unit pipe, and a capillary-type unit pipe.

[0156] 3. Results The results shown in Tables 4 to 8 show that by combining slit-type unit pipes and capillary-type unit pipes, the overall size of the viscosity measurement pipe can be set within an appropriate range.

[0157] This application claims priority from Japanese Patent Application No. 2022-075959, filed May 2, 2022. The entire disclosures of the specification, claims, and drawings of that application as originally filed are incorporated herein by reference.

[0158] The kneading apparatus of the present invention can measure the viscosity of non-Newtonian fluids, whose viscosity exhibits shear rate dependency, over a wide range of shear rates at once. The present invention is useful for measuring the viscosity of various fluids.

[0159] REFERENCE SIGNS LIST 100 Viscosity measurement pipe 110 First unit pipe 120 First connecting pipe 130 Second unit pipe 140 Second connecting pipe 150 Third unit pipe 160 Third connecting pipe 112, 132, 134, 152, 154 Pressure gauge 210 First plate 220 Second plate 230 Screw hole 400 Viscometer 410 Gear pump 420 CPU 422 Shear rate calculation section 424 Shear stress calculation section 426 Correction section 428 Viscosity calculation section

Claims

1. A pipe for measuring the viscosity of a fluid, a plurality of unit pipes each having a flow path through which the fluid can flow; Each of the plurality of unit pipes is capable of measuring a pressure of the fluid flowing through the flow path of the respective unit pipes, The plurality of unit pipes include a capillary type unit pipe and a slit type unit pipe, the plurality of unit pipes are arranged such that the fluid sequentially flows through the flow paths of the plurality of unit pipes, The length of the flow path in the width direction of the flow path of the slit-type unit pipe is defined as the width of each unit pipe included in the viscosity measurement pipe, the length of the flow path in the thickness direction of the flow path of the slit-type unit pipe is defined as the height of each unit pipe included in the viscosity measurement pipe, and the direction perpendicular to both the width direction and the thickness direction is defined as the length direction, Regarding two adjacent unit pipes among the plurality of unit pipes, the unit pipe arranged on one side in the longitudinal direction is defined as a first unit pipe, and the unit pipe arranged on the other side in the longitudinal direction is defined as a second unit pipe, The width of the first unit pipe is W １ , height H １ year, The width of the second unit pipe is W ２ , height H ２ When The following relations are always satisfied: Piping for viscosity measurement. (A) When the first unit pipe is a capillary type unit pipe and the second unit pipe is a slit type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is greater than 1 (B) When the first unit pipe is a slit type unit pipe and the second unit pipe is a capillary type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is less than 1 (C) When the first unit pipe is a slit type unit pipe and the second unit pipe is a slit type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is greater than 1 (D) When the first unit pipe is a capillary type unit pipe and the second unit pipe is a capillary type unit pipe, H ２ / H １ is greater than 1, and W ２ / W １ is greater than 1

2. The viscosity measuring pipe according to claim 1 , wherein the plurality of unit pipes includes three or more unit pipes.

3. 2. The viscosity measurement pipe according to claim 1, wherein the plurality of unit pipes are arranged in the following order along the length direction: a capillary type unit pipe, a slit type unit pipe, and a slit type unit pipe.

4. 2. The viscosity measurement pipe according to claim 1, wherein the plurality of unit pipes are arranged in the following order along the length direction: a slit type unit pipe, a capillary type unit pipe, and a capillary type unit pipe.

5. 2. The viscosity measurement pipe according to claim 1, wherein the plurality of unit pipes are arranged in the following order along the length direction: a slit type unit pipe, a slit type unit pipe, and a capillary type unit pipe.

6. The first unit pipe is a capillary type unit pipe, and the second unit pipe is a slit type unit pipe. In the combination of the first unit pipe and the second unit pipe, ２ / H １ is 1.1 or more, and W ２ / W １ 2. The viscosity measuring pipe according to claim 1, wherein the viscosity is 10 or more.

7. The length of the flow path in the longitudinal direction is defined as the length of each unit pipe included in the viscosity measurement pipe, The length of the first unit pipe is LL １ The length of the second unit pipe is LL ２ When LL ２ / LL １ 7. The viscosity measuring pipe according to claim 6, wherein the viscosity is 1.5 or more.

8. The first unit pipe is a slit type unit pipe, and the second unit pipe is a capillary type unit pipe. In the combination of the first unit pipe and the second unit pipe, ２ / H １ is 1.5 or more, and W ２ / W １ 2. The viscosity measuring pipe according to claim 1, wherein is smaller than 1.

9. The length of the flow path in the longitudinal direction is defined as the length of each unit pipe included in the viscosity measurement pipe, The length of the first unit pipe is LL １ The length of the second unit pipe is LL ２ When LL ２ / LL １ The viscosity measuring pipe according to claim 8, wherein the viscosity is 1.5 or more.

10. The first unit pipe is a slit type unit pipe, and the second unit pipe is a slit type unit pipe. In the combination of the first unit pipe and the second unit pipe, ２ / H １ is 1.5 or more, and W ２ / W １ 2. The viscosity measuring pipe according to claim 1, wherein the viscosity is 1.5 or more.

11. The length of the flow path in the longitudinal direction is defined as the length of each unit pipe included in the viscosity measurement pipe, The length of the first unit pipe is LL １ The length of the second unit pipe is LL ２ When LL ２ / LL １ The viscosity measuring pipe according to claim 10, wherein the viscosity is 1.5 or more.

12. The first unit pipe is a capillary type unit pipe, and the second unit pipe is a capillary type unit pipe. In the combination of the first unit pipe and the second unit pipe, ２ / H １ is 1.5 or more, and W ２ / W １ 2. The viscosity measuring pipe according to claim 1, wherein the viscosity is 1.5 or more.

13. The length of the flow path in the longitudinal direction is defined as the length of each unit pipe included in the viscosity measurement pipe, The length of the first unit pipe is LL １ The length of the second unit pipe is LL ２ When LL ２ / LL １ The viscosity measuring pipe according to claim 12, wherein the viscosity is 1.5 or more.

14. 2. The viscosity measuring pipe according to claim 1, further comprising a tapered connecting pipe between two of said unit pipes arranged in series, the connecting pipe having a width and height gradually increasing along the length direction.

15. A viscometer comprising the viscosity measuring pipe according to any one of claims 1 to 14.

16. A method for measuring the viscosity of a fluid flowing through a viscosity measurement pipe according to any one of claims 1 to 14, comprising the steps of: determining a shear rate and a shear stress of the fluid for each of the capillary type unit pipe and the slit type unit pipe; In the capillary type unit pipe and the slit type unit pipe, a shear viscosity η of the fluid is calculated from the shear rate and the shear stress. How to measure viscosity.

17. The plurality of unit pipes includes three or more of the unit pipes, The viscosity measuring method according to claim 16, further comprising determining a shear viscosity η of the fluid in each of the three or more unit pipes.

18. 17. The method of claim 16, further comprising the step of: determining a shear viscosity η of the fluid as a value obtained by dividing the corrected shear rate by the shear stress.

19. 17. The method of claim 16, further comprising setting a volumetric flow rate of the fluid by a gear pump, and using the volumetric flow rate to determine the shear rate.

20. The method for measuring viscosity according to claim 16, wherein the fluid is a polymer melt.