JP2020094159A - Viscous fluid and viscous fluid-filled damper - Google Patents

Abstract

To provide a viscous fluid having excellent vibration damping characteristics and a viscous fluid-filled damper.SOLUTION: A viscous fluid comprising a viscous base liquid having dispersed therein powders comprising primary particles and aggregated particles thereof, which is characterized in that the powders have an aggregation parameter P in the range of 1.4 to 1.7, the parameter being defined by equation (1): P=D2/D1...(1) (wherein D1 represents an average diameter of the primary particles and D2 represents a median diameter of the powders).SELECTED DRAWING: None

Description

The present invention relates to a viscous fluid that attenuates transmitted vibration in an anti-vibration technology used for audio equipment including in-vehicle equipment, consumer equipment, video equipment, information equipment, various precision equipment, household appliances such as refrigerators, and the like. The present invention relates to a viscous fluid-sealed damper that is filled with a viscous fluid and damps vibrations transmitted between a support and a supported body.

In an electronic device including a drive mechanism such as a motor or an actuator, the drive mechanism may serve as a vibration source and adversely affect the normal operation of the electronic device itself. In addition, vibration or shock may occur in the environment in which the electronic device is used and be transmitted to the electronic device, which may adversely affect the normal operation of the electronic device. In order to damp internal vibrations generated from the inside of such electronic devices and external vibrations generated in the usage environment of the electronic devices, electronic devices equipped with a viscous fluid-filled damper are known. The viscous fluid-sealed damper is mounted on an electronic device, for example, a disk reproducing device for reproducing a disk-shaped recording medium, an unmanned multi-wing flying body called a drone, or the like. Further, a conventional viscous fluid-sealed damper is described in, for example, Japanese Patent Laid-Open No. 2013-249335 (Patent Document 1).

JP, 2013-249335, A

A conventional viscous fluid-sealed damper has a structure in which a viscous fluid is sealed inside a closed container having a flexible portion made of an elastically deformable rubber-like elastic body. In general, the viscous fluid sealed in the viscous fluid-sealed damper forms a viscous viscous fluid by dispersing powder (filler) such as silica powder in a viscous base liquid such as silicone. However, generally, a powder made of an inorganic material or an organic material contains primary particles and agglomerated particles formed by aggregating the primary particles. Therefore, when the powder is simply dispersed in the viscous base liquid, not only primary particles of the powder but also agglomerated particles are scattered in the viscous base liquid.

On the other hand, with the increase in precision of the electronic devices described above, a viscous fluid having higher vibration damping characteristics and a viscous fluid-sealed damper enclosing the viscous fluid are desired.

Therefore, the present invention has been made in response to the above-mentioned demands, focusing on agglomerated particles derived from powder in a viscous base liquid, and viscous particles having higher vibration damping characteristics than conventional viscous fluids. Provided is a fluid and a viscous fluid-enclosed damper for enclosing the fluid.

In order to achieve the above object, the present invention has the following features.

That is, the viscous fluid of the present invention is a viscous fluid in which a powder containing primary particles and agglomerated particles thereof is dispersed in a viscous base liquid, the average particle diameter of the primary particles is D1, and the median diameter of the powder ( When D50v) is D2, the aggregation parameter P defined by the following equation (1) is 1.4 to 1.7.
Aggregation parameter P=D2/D1 (1)

Since the viscous fluid of the present invention has the coagulation parameter defined by the above formula (1) within the above range, the vibration damping characteristic is improved as compared with the conventional viscous fluid. Here, when a part of the primary particles having an average particle diameter of D1 are aggregated, the aggregated aggregate behaves as one particle itself. Therefore, the presence of the agglomerated particles makes the median diameter larger than the average particle diameter D1 of the primary particles. The aggregation parameter is a parameter whose numerical value changes depending on the amount of aggregation, and in the present invention, the aggregation parameter is specified to be 1.4 to 1.7. The viscous fluid of the present invention has a coagulation parameter in the above range, and thus the resonance magnification Q becomes low even when the resonance frequency f ₀ is the same as that of the conventional viscous fluid. Since the viscous fluid of the present invention has a low resonance magnification Q, it is excellent not only in the vibration isolation of the high frequency component but also in the vibration isolation of the low frequency component as compared with the conventional viscous fluid. Here, for example, when the resonance magnification Q is large, and when the stroke of the shaft of a viscous fluid-sealed damper (hereinafter, also referred to as “damper”) described later is insufficient, a problem such as bottom bumping may occur. Even if the vibrations have the same acceleration, the amplitude becomes larger as the frequency becomes lower, so that the space in the damper needs to be made larger in the height direction due to the vibrations. On the other hand, since many electronic devices are required to be downsized, it is difficult to increase the space inside the damper in the height direction. Also from the viewpoint of miniaturization of the electronic device as described above, the viscous fluid of the present invention can be isolated from vibration by a damper that is smaller than the conventional one, even if it contains a low frequency component.

Further, in the powder of the viscous fluid of the present invention, in the volume-based particle size distribution, the relationship between the appearance frequency F3 of particles having a particle size three times as large as D1 and the appearance frequency F1 at D1 is as follows (2). Meet
F3/F1<0.40 (2)

The viscous fluid of the present invention can have a particularly low resonance magnification Q as compared with the conventional viscous fluid by satisfying the relationship of the expression (2). As a result, the viscous fluid of the present invention has improved vibration damping properties not only for high frequency components but also for low frequency components.

With respect to the powder in the viscous fluid of the present invention, in the volume-based particle size distribution, the relationship between the appearance frequency F3 of particles having a particle size three times as large as D1 and the appearance frequency F1 at D1 satisfies the following (3). ..
F3/F1<0.15 (3)

When the viscous fluid of the present invention satisfies the relationship of the expression (3), the resonance magnification Q can be made particularly lower than that of the conventional viscous fluid. As a result, the viscous fluid of the present invention is further improved in vibration damping properties of not only high frequency components but also low frequency components.

In the viscous fluid of the present invention, the median diameter D2 of the powder in the viscous fluid is 10 to 200 μm. In the viscous fluid of the present invention, when the median diameter D2 is within the above range, dispersion in the viscous base liquid is facilitated, a dispersion parameter in a desired range is obtained, and a stable dispersion system is obtained. Further, the obtained viscous fluid can have a desired viscosity.

The powder in the viscous fluid of the present invention is a high molecular weight polyolefin. The viscous fluid of the present invention has high dispersibility because the high molecular polyolefin as powder has a high affinity with the viscous base liquid in which the powder is dispersed, and as a result, a dispersion parameter in a desired range can be obtained. It is possible to obtain a stable viscous fluid.

The viscous fluid-sealed damper of the present invention is a damper in which any one of the above viscous fluids is sealed in a flexible molded body. As described above, since the viscous fluid-sealed damper of the present invention contains a viscous fluid having higher vibration damping characteristics than the conventional damper, even if the damper is downsized as compared to the conventional damper, only the high-frequency component is contained. It is also excellent in low frequency component anti-vibration.

The viscous fluid of the present invention can exhibit higher vibration damping characteristics than the conventional viscous fluid. Further, the viscous fluid-sealed damper of the present invention is superior to the conventional damper even in miniaturization of the damper, and is excellent in the vibration damping property of not only the high frequency component but also the low frequency component.

It is an SEM image of a viscous fluid in the present invention. It is a SEM image of a viscous fluid with aggregated particles scattered. It is a SEM image explaining an example of how to calculate the arithmetic mean particle diameter of the primary particle in powder. It is a sectional view of a viscous fluid sealing damper which is an example of an embodiment of the present invention. 5A and 5B are schematic views of a reproduction mechanism for performing a vibration test of the viscous fluid-sealed damper shown in FIG. 4, in which FIG. 5A is a sectional view taken along the line VA-VA in FIG. 5B and FIG. 5B is a side view of the reproduction mechanism. .

(Viscous fluid)
The present invention will be described in detail based on the embodiments. In the photocurable composition of the present invention, the viscous fluid is a viscous fluid in which a powder containing primary particles and agglomerated particles thereof is dispersed in a viscous base liquid, and the average particle diameter of the primary particles is D1. When the median diameter (D50v) of the body is D2, the aggregation parameter P defined by the following formula (1) is 1.4 to 1.7.
Aggregation parameter P=D2/D1 (1)

Since the viscous fluid of the present invention has the coagulation parameter defined by the above formula (1) within the above range, the vibration damping characteristic is improved as compared with the conventional viscous fluid. In particular, the viscous fluid of the present invention has a low resonance magnification Q even when the resonance frequency f ₀ is the same as that of the conventional viscous fluid. Since the viscous fluid of the present invention has a low resonance magnification Q, it is excellent not only in the vibration isolation of the high frequency component but also in the vibration isolation of the low frequency component as compared with the conventional viscous fluid. Here, for example, when the resonance magnification Q is large, and when the stroke of the shaft of a viscous fluid-sealed damper (hereinafter, also referred to as “damper”) described later is insufficient, a problem such as bottom bumping may occur. Even if the vibrations have the same acceleration, the amplitude becomes larger as the frequency becomes lower, so that the space in the damper needs to be made larger in the height direction due to the vibrations. On the other hand, since many electronic devices are required to be downsized, it is difficult to increase the space inside the damper in the height direction. Also from the viewpoint of miniaturization of the electronic device as described above, the viscous fluid of the present invention can be isolated from vibration by a damper that is smaller than the conventional one, even if it contains a low frequency component.

The viscosity of the viscous fluid sealed in the viscous fluid sealing damper described below is preferably 10 to 5000 Pa·s. By adjusting the viscosity of the viscous fluid within the above viscosity range based on the weight of the vibration-damping target, the frequency and amplitude of the vibration to be damped, etc., a viscous fluid-sealed damper having excellent vibration damping characteristics can be obtained. I can.

Next, the constitution of the viscous fluid of the present invention will be described in detail.

<Viscous base liquid>
The viscous fluid of the present invention viscously flows in a closed container such as a viscous fluid-sealed damper described later to absorb vibration energy, and thus has an appropriate viscosity, stability over time in the closed container, and heat resistance. Is required. Therefore, a viscous fluid in which a viscous base liquid and a powder that does not dissolve in the viscous base liquid are mixed is used.

More specifically, as the "viscous base liquid" in the viscous fluid of the present invention, dimethyl silicone oil, methylphenyl silicone oil, silicone-based oil including fluorine-modified silicone oil, poly-α-olefin-based oil, paraffin-based oil, Various mineral oils, vegetable oils, synthetic oils such as polyethylene glycol-based oils can be used, and silicone-based oils, which have little change in viscosity with temperature and are excellent in heat resistance, are preferably used.

The viscosity of the viscous base liquid is preferably 1 to 100 Pa·s. If the viscosity is lower than 1 Pa·s, the powder may easily settle and the vibration damping characteristics may not be stable, and if the viscosity is higher than 100 Pa·s, the viscosity of the viscous fluid tends to be high. However, the powder filling amount may be too small.

<Powder>
The "powder" in the viscous fluid of the present invention includes primary particles and aggregated particles thereof. Here, the "particles" refer to individual powders constituting the powder. The term "primary particle" means a unit in which powder cannot be loosened any more by a blade mixer. In the present specification, the “average particle size of primary particles” is obtained by observing with a scanning electron microscope (SEM), measuring the particle size of any 100 particles, and calculating the arithmetic mean thereof. Desired. The sample used for the scanning electron microscope and the measurement conditions of the scanning electron microscope will be described in detail in the section of Examples. The "median diameter of powder (D50v)" refers to the particle diameter at which the cumulative appearance frequency is 50% in the volume-based particle size distribution.

An example of the form of powder in the viscous fluid of the present invention is shown in FIG. In the powder shown in FIG. 1, the primary particles have almost the same particle size, and some agglomerated particles are also seen, but the degree of agglomeration is not large. The powder shown in FIG. 1 falls within the range of the aggregation parameter P shown in the above formula (1). On the other hand, FIG. 2 shows an example of another form of powder. Large agglomerated particles are present in the portion surrounded by the dotted line in FIG. As shown in FIG. 2, when a large number of the large aggregated particles are scattered in the powder, the aggregated parameter P is out of the range shown in the above-mentioned formula (1). As described above, the particle size of the primary particles is observed with a scanning electron microscope (SEM) as shown in FIG. 3, and the particle size of any 100 particles in total is measured while changing the field of view. Then, the arithmetic mean is calculated.

The powder used in the present invention may be crushed in advance so as to satisfy the condition of the formula (1) and further satisfy the conditions of the following formulas (2) and (3). .. Examples of the method for crushing the powder include a method using a known crusher such as a blade mixer, a hammer mill, a twin-screw crusher, a pin mill crusher, and a rotary blade crusher.

In the powder used in the present invention, preferably, in the volume-based particle size distribution, the relationship between the appearance frequency F3 of particles having a particle size three times the D1 and the appearance frequency F1 in the D1 is as follows (2). Meet
F3/F1<0.40 (2)

The viscous fluid of the present invention can have a particularly low resonance magnification Q as compared with the conventional viscous fluid by satisfying the relationship of the expression (2). As a result, the viscous fluid of the present invention has improved vibration damping properties not only for high frequency components but also for low frequency components.

Further, in the powder used in the present invention, more preferably, in the volume-based particle size distribution, the relationship between the appearance frequency F3 of particles having a particle size three times the D1 and the appearance frequency F1 in the D1 is as follows. (3) is satisfied.
F3/F1<0.15 (3)

When the viscous fluid of the present invention satisfies the relationship of the expression (3), the resonance magnification Q can be made particularly lower than that of the conventional viscous fluid. As a result, the viscous fluid of the present invention is further improved in vibration damping properties of not only high frequency components but also low frequency components.

The median diameter D2 of the powder in the viscous fluid of the present invention is preferably 10 to 200 μm, more preferably 10 μm to 160 μm. If the median diameter D2 of the powder is smaller than 10 μm, it is difficult to disperse it in the viscous base liquid, and it is difficult to stabilize the quality of the viscous fluid. When the median diameter D2 of the powder is larger than 200 μm, it is difficult to impart a predetermined viscosity and the vibration damping effect tends to be insufficient. In particular, when the median diameter D2 of the powder is 10 μm to 160 μm, the dispersibility of the powder in the viscous base liquid becomes good and the dispersion parameter in a desired range can be obtained, so that the viscous fluid has a predetermined viscosity. Is easy to obtain, and changes over time are unlikely to occur.

The powder used in the viscous fluid of the present invention is preferably heat-resistant resin particles. The heat resistant resin particles may be thermoplastic resin particles and thermosetting resins. As an index of the heat resistance of the heat resistant resin particles, the melting point may be 130° C. or higher. If the temperature is lower than 130° C., the heat-resistant resin particles may be melted by the heat generated by stirring the viscous fluid. This melting point is measured according to ASTM D2117-82 (1998) e1.

As the heat resistant resin particles, high molecular weight polyolefin is more preferable. High-molecular-weight polyolefin is preferable because, as other particles to be described later, when silica or calcium carbonate powder is added and mixed, the viscosity of the viscous fluid can be easily adjusted while maintaining high stability. Because you can. Specific examples of the high molecular weight polyolefin include high molecular weight polyethylene and polypropylene. Among them, as the high molecular weight polyolefin, high molecular weight polyethylene is more preferable because it has high chemical resistance, is stable to a viscous base liquid, and is easily available.

Here, the “high molecular weight” in the “high molecular weight polyolefin” preferably has a weight average molecular weight of 5.0×10 ^{5 to} 6.0×10 ⁶ , and 1.0×10 ^{6 to} 3.5×10. ⁶ is more preferable. This is because when the weight average molecular weight of the high molecular weight polyolefin is less than 5.0×10 ⁵ , the melt flow index value becomes large and the heat resistance becomes poor. Further, when the weight average molecular weight of the high molecular weight polyolefin is larger than 6.0×10 ⁶ , the impact strength becomes weak and it becomes difficult to stabilize the quality of the heat resistant resin particles. As a result, the quality of the viscous fluid tends to be unstable. The reason is that if the weight average molecular weight of the high molecular weight polyolefin is in the range of 1.0×10 ^{6 to} 3.5×10 ⁶ , it is preferable to secure heat resistance within the actual environment temperature of use. Here, in the present specification, the weight average molecular weight of the high-molecular-weight polyolefin is measured using a GPC method (Gel Permeation Chromatography) and based on a calibration curve (calibration curve) measured by standard polystyrene. did.

The viscous fluid of the present invention has high dispersibility because the high molecular polyolefin as powder has a high affinity with the viscous base liquid in which the powder is dispersed, and as a result, a dispersion parameter in a desired range can be obtained. It is possible to obtain a stable viscous fluid.

The particles of the powder used in the viscous fluid of the present invention are preferably particles having a small aspect ratio, and flat particles or rods are less preferred. This is because the granular form is more stable in the viscous base liquid and is less likely to change with time. Further, solid particles having as few holes as possible and not porous are preferable. This is because in the porous body, the amount of the viscous base liquid adsorbed in the solid particles increases and the amount of adsorption tends to change with time, so that stable properties are difficult to obtain.

<Mixing ratio of viscous base liquid and powder>
From the viewpoint of desired viscosity and vibration damping characteristics, the mixing ratio of the viscous base liquid and the powder is about 30:70 to 70:30 by weight, preferably 40:60 to 65:35, and 45:55. -60:40 is more preferable.

<Other additives>
As other additives, the predetermined heat-resistant resin particles, in the range that does not deteriorate the desired dispersion performance, and for the purpose of improving the dispersion performance and adjusting the viscosity as compared with the case of the heat-resistant resin particles alone. Other particles can be added. Other particles include, for example, silicone resin powder, calcium carbonate powder, polymethylsilsesquioxane powder, wet silica particles, dry silica particles, glass beads, glass balloons, crystalline potassium silicate zonolite, and bases. Inorganic fine powders such as acidic magnesium sulfate and kaolin of aluminum silicate, and those obtained by subjecting these particles to a surface treatment, etc., can be used alone or in combination, and can be mixed as necessary. Among the other particles described above, it is preferable to add silica or calcium carbonate powder that functions as an anti-sagging agent (viscosity modifier) for the predetermined heat resistant resin particles.

From the viewpoint of adjusting the viscosity of the viscous fluid, the ratio of the other particles to the predetermined heat-resistant resin particles is 0 to 20 parts by mass when the heat-resistant resin particles are 100 parts by mass.

Further, as other additives, additives such as a dispersant, a flame retardant, a plasticizer, an antioxidant, a colorant, and an anti-settling agent may be added.

[Damper with viscous fluid]
FIG. 4 is a sectional view of an example of the viscous fluid-sealed damper of the present invention. The viscous fluid-sealed damper 11 shown in FIG. 4 has a cylindrical peripheral wall portion 13 made of hard resin, a flexible film portion 14 made of a rubber-like elastic body fixed to one end thereof, and a stirring member for inserting and holding the shaft 7. A container body is formed with the tubular portion 15, and the container body is fixed to a lid body 16 made of hard resin to form a closed container 18. Further, the above-mentioned viscous fluid 12 having a vibration damping characteristic is enclosed inside the closed container 18.

The rubber-like elastic body serving as the flexible film portion 14 and the stirring cylinder portion 15 is made of synthetic rubber or thermoplastic elastomer (TPE). For example, a synthetic rubber such as silicone rubber, urethane rubber, butyl rubber, chloroprene rubber, nitrile rubber, or ethylene propylene rubber, or a thermoplastic elastomer such as styrene TPE, olefin TPE, urethane TPE, or polyester TPE can be used. ..

Hard resin or metal can be used as a material for the peripheral wall portion 13 and the lid body 16, but it is preferable to use a hard resin from the viewpoint of ease of molding and weight reduction, and in particular, it can be integrally molded with the rubber-like elastic body. Preferred are thermoplastic resins. Considering the required performance such as dimensional accuracy, heat resistance, mechanical strength, durability and reliability of the target member, and weight reduction and workability, polyethylene resin, polypropylene resin, polyvinyl chloride resin, polystyrene resin, acrylonitrile -Styrene-acrylate resin, acrylonitrile-butadiene-styrene resin, polyamide resin, polyacetal resin, polycarbonate resin, polyethylene terephthalate resin, polybutylene terephthalate resin, polyphenylene oxide resin, polyphenylene sulfide resin, polyurethane resin, polyphenylene ether resin, modified polyphenylene ether resin , Thermoplastic resins such as silicone resins, polyketone resins, and liquid crystal polymers, and these resins can be used alone or as a composite material. Further, it is possible to improve the dimensional accuracy and the heat resistance by adding a powdery or fibrous metal, a filler such as a glass or a filler to these thermoplastic resins.

The viscous fluid-sealed damper 11 made of these materials can be formed by a molding method such as two-color molding of a hard resin material and a soft elastomer. For example, after the stirring cylinder portion 15 and the flexible film portion 14 made of the predetermined rubber-like elastic body and the peripheral wall portion 13 made of hard resin are integrally formed by two-color molding or insert molding to form a container body, The fluid 12 is filled and the viscous fluid 12 is sealed by fixing the container body and the lid 16 to each other. It is preferable that the container body and the lid 16 are fixed to each other by ultrasonic welding because both the peripheral wall portion 13 and the lid 16 are made of hard resin.

Next, the present invention will be described in more detail based on examples (comparative examples).

<Preparation of sample>
A sample was prepared as shown below. First, as the viscous fluid-sealed damper 11, the viscous fluid-sealed damper 11 shown in FIG. 4 in which the closed container 18 had a diameter of 15 mm and a height of 10 mm was manufactured. A polypropylene resin is used for the peripheral wall portion 13 and the lid body 16, and a styrene-ethylene/butylene-styrene block copolymer (hereinafter abbreviated as "SEBS") is used for the flexible film portion 14 and the stirring cylinder portion 15. I was there. Further, as the viscous fluid 12 sealed in the closed container 18, a viscous fluid obtained by mixing a viscous base liquid and powder shown below was used. Then, the viscous fluid-sealed dampers 11 in which only the viscous fluid to be sealed are different were designated as Sample 1 to Sample 7.

Powder pretreatment:
Ultra high molecular weight polyethylene particles (average molecular weight: 2.0×10 ⁶ , average particle diameter D50: 42 μm, MFR: less than 0.01 g/10 minutes, intrinsic viscosity η: 14 dl/g) 100 g were treated using a blade mixer. By changing the time from 1 minute to 60 minutes (provisional condition), each pretreated powder to be used for Samples 1 to 5 having different aggregate contents was obtained. Samples 6 and 7 are untreated powders.

Sample 1 was a viscous base liquid in which 100 parts by mass of dimethyl silicone oil having a viscosity at 25° C. of about 20 Pa·s and a specific gravity of 0.974 was used as powder, and ultra-high molecular weight polyethylene particles were crushed in advance, 70 parts by mass of the pretreated powder shown in Table 1 was mixed, and further 8 parts by mass of silica (hydrophobic surface-treated silica, secondary particle size: 8.6 μm) was added as an anti-sagging agent and mixed sufficiently. The viscous fluid obtained in this way was used as the viscous fluid 12.

Samples 2 and 3 were prepared by crushing ultra-high molecular weight polyethylene particles in advance instead of the powders used in Sample 1 and using the pretreated powders shown in Table 1 as the powders. The viscous fluid obtained by mixing in the same manner as in Sample 1 was used as the viscous fluid 12.

In Samples 4 and 5, instead of the powder used for Sample 1, the ultra-high molecular weight polyethylene particles were crushed in advance and the pretreated powders shown in Table 1 were used. The viscous fluid obtained by mixing in the same manner as in Sample 1 was used as the viscous fluid 12 except that the amount of powder mixed in the viscous base liquid was changed.

Sample 6 was the same as Sample 1 except that ultra-high molecular weight polyethylene particles themselves were used as the powder instead of the powder used in Sample 1, and the amount of powder to be blended in the viscous base liquid was changed. The viscous fluid obtained by mixing was used as the viscous fluid 12.

Sample 7 was a powder obtained in the same manner as in Sample 1, except that ultra-high molecular weight polyethylene particles themselves were used instead of the powder used in Sample 1 to obtain a viscous fluid.

The viscosity of the viscous fluid used in Samples 1 to 6 was 1500 Pa·s. On the other hand, the viscosity of the viscous fluid used for the sample 7 was 8400 Pa·s, which was outside the viscosity in the desired range used for the damper. Therefore, the vibration damping characteristic of the sample 7 was not measured. Here, the rotational viscosity was measured at a rotational speed of 1.0 rpm and a measurement temperature of 25° C. using a rotational viscometer (Spindle No. 14) manufactured by Brookfield.

<Various measuring methods, tests and evaluations>

Pretreatment for separation of powder in viscous fluid:
A predetermined amount (1.5 g) of the viscous fluid used for Samples 1 to 6 is placed in a beaker. Then, add 50 ml of 100 cs dimethyl silicone to a beaker and stir until uniform. Put 50 ml in a funnel with filter paper and filter the powder. At this time, as the filter paper, “Qualitative filter paper No. 2” manufactured by Advantech (corresponding to two types defined in JIS P 3801: 1995 [filter paper (for chemical analysis)]) is used. Then, 50 ml of dimethyl silicone in the beaker 100 cs is poured again, and the residue in the beaker is poured into the funnel to wash the powder on the filter paper. This operation is repeated to wash the powder on the filter paper. Then, the filter paper was allowed to stand at room temperature (28° C. on average) for one week, and the dimethyl silicone was dried to obtain a sample for measurement of each particle size described later. The filtrate that passed through the filter paper during the filtration was transparent. In addition, it is extremely unlikely that the particle size of the powder present in the viscous fluid changes due to the pretreatment for separation.

Measuring method of average particle size of primary particles in powder:
A small amount of powder pre-separated from the viscous fluid as described above was attached to a carbon tape, and then excess powder was blown off with an air duster to prepare a product. Then, a platinum film was formed on the surface of the prepared sample using a sputtering device. These were observed with a scanning electron microscope (SU3500, manufactured by Hitachi High-Technologies Corporation) at a magnification of 400 times. As shown in FIG. 3, the powder after separation pretreatment from the viscous fluid used in Sample 1 had a particle size of 100 arbitrary (randomly selected) primary particles based on the obtained SEM image. Was measured and the arithmetic mean was calculated. At this time, the diameter of the spherical particles shall be measured, and in the case of particles having an aspect ratio such as an elliptical shape or an amorphous shape, the average value by measuring the length in the direction perpendicular to the long axis and the long axis. Was defined as the particle size. Moreover, when 100 primary particles were not present in one visual field of the scanning electron microscope, the particle size was measured in a plurality of visual fields. For Samples 2 to 6, as in the case of Sample 1, the measurement was performed on the powder after the pre-separation treatment as described above.

Measuring method of median diameter (D50v) of powder:
The median diameter (also referred to as “D50v”) disclosed in the present specification was measured using Beckman Coulter MULTISIZER 3 (manufactured by Beckman Coulter). Representative sampling may be performed as follows. A small amount of powder sample (about 1 g) that was pretreated by separation from viscous fluid as described above was placed in an aqueous electrolyte solution (4% aqueous sodium chloride solution) to obtain a concentration of about 10%, then this sample was Subject to Beckman Coulter Multisizer 3. The measurement conditions were an aperture of 200 μm, a bottle of 300, and a particle size range of 4 μm to 120 μm for 60 seconds to obtain a median diameter (D50v) and a volume-based particle size distribution.

Vibration damping characteristic test:
First, the device used for the test will be described. For the samples of each example, the vibration damping characteristics were evaluated using the mass model shown in FIG. The mass model was set as a secondary side member to be vibration-isolated in the vibration path, specifically, set as the reproducing mechanism 1 such as a CD player and tested. The reproducing mechanism 1 includes a vibrating table 2, three viscous fluid-sealed dampers 11 and three supporting walls 3 arranged on the vibrating table 2, a coil spring 4 suspended on each supporting wall 3, and three coils. The supported plate 5 supported by the spring 4 and the weight 6 arranged at the center of the upper surface of the supported plate 5 are provided. Three shafts 7 are arranged on the back surface of the supported plate 5, and are inserted in the corresponding viscous fluid-sealed dampers 11, respectively. Then, the vibration was vertically vibrated at a constant acceleration of 9.8 m/s ² and a frequency of 7 Hz to 200 Hz, and the vibration damping ratio τ ₁₀₀ (dB) between the vibration table 2 and the supported plate 5 was measured. Further, the resonance magnification Q (dB) is calculated by measuring the acceleration a2 of the supported plate 5 with respect to the acceleration a1 of the vibration table 2 at the resonance frequency f ₀ (Hz) and converting it by the relational expression of 20 Log (a2/a1). I asked.

Good vibration damping characteristics mean that the resonance magnification Q is low especially when f ₀ is substantially the same. Further, the fact that the resonance magnification Q is small means that a problem is unlikely to occur even if the low frequency component is included. Although it is preferable that the vibration damping rate τ ₁₀₀ is small, in this embodiment, if the vibration damping rate τ ₁₀₀ is -10 dB or less, it is determined that the vibration damping characteristic is sufficient.

<Analysis of test results>

From the results shown in Table 1, it was found that Samples 1 and 3 had particularly good vibration damping characteristics, Samples 2 and 4 had good vibration damping characteristics and could be used, and Samples 5 and 6 had poor vibration damping characteristics. From these results, in samples 1 and 3, the aggregation parameter P defined by the above formula (1) is 1.4 to 1.7, and F3/F1<0.15 defined by the above (3) is satisfied. Since it satisfies the condition, the vibration damping characteristic is particularly good.

1 Reproduction Mechanism 2 Vibration Table 3 Support Wall 4 Coil Spring 5 Supported Plate 6 Weight 7 Shaft 11 Viscous Fluid Encapsulation Damper 12 Viscous Fluid 13 Peripheral Wall Part 14 Flexible Membrane 15 Stirring Cylinder 16 Lid 16a Hole 18 Closed Container

Claims (6)

A viscous fluid in which a powder containing primary particles and its agglomerated particles is dispersed in a viscous base liquid,
When the average particle diameter of the primary particles is D1 and the median diameter of the powder is D2,
A viscous fluid having a coagulation parameter P defined by the following equation (1) of 1.4 to 1.7.
Aggregation parameter P=D2/D1 (1) The particle size distribution of the powder, the relationship between the appearance frequency F1 of the particles having a particle size three times the D1 and the appearance frequency F1 of the D1 satisfies the following (2). Viscous fluid.
F3/F1<0.40 (2) The particle size distribution of the powder, the relationship between the appearance frequency F1 of the particles having a particle size three times the D1 and the appearance frequency F1 of the D1 satisfies the following (3). Viscous fluid.
F3/F1<0.15 (3) The viscous fluid according to any one of claims 1 to 3, wherein a median diameter D2 of the powder is 10 to 200 µm. The viscous fluid according to claim 1, wherein the powder is a high molecular weight polyolefin. A viscous fluid-sealed damper in which the viscous fluid according to any one of claims 1 to 5 is sealed in a flexible molded body.