KR101926742B1 - Magnetrorheological fluid composition comprising nanoclay - Google Patents

Abstract

Disclosed herein is a magnetorheological fluid composition comprising a nanoclay having an average particle size on the order of nanometers and a method of making the composition. The magnetorheological fluid composition according to one aspect of the present invention can uniformly control the distribution of magnetic particles in the composition, minimize precipitation, and minimize curing after precipitation. In addition, the magnetorheological fluid composition of the present invention has a small viscosity change according to temperature, and particularly has improved stability at a cryogenic temperature and a high temperature, and is capable of maintaining the performance of a magnetorheological fluid even in an extreme temperature environment. Therefore, the composition can be widely used in various friction dampers, automobile suspension devices, and the like.

Description

MAGNETORHEOLOGICAL FLUID COMPOSITION COMPRISING NANOCLAY [0002]

Disclosed herein is a magnetorheological fluid composition comprising a nanoclay.

A magnetorheological fluid means a material whose viscosity changes reversibly depending on the intensity of a magnetic field added from the outside. The magnetorheological fluid has a large variation range of flow characteristics such as a viscosity characteristic of a fluid as the magnetic field is applied, has excellent durability, is relatively less sensitive to contaminants, has a very high response speed to a magnetic field, and is reversible, Vibration control devices such as automobile clutches, engine mounts, dampers, and high-rise building seismic devices.

In order to effectively utilize the magnetorheological fluid, the magnetic particles in the magnetorheological fluid must be uniformly distributed in the dispersion medium, the viscosity of the fluid must be sufficiently low so that the fluid can quickly return to the original state before and after the magnetic field application, It is necessary to exhibit a constant flow characteristic at all times.

However, magnetorheological fluids are difficult to obtain good dispersibility due to precipitation due to the density of magnetic particles in magnetorheological fluids. In order to overcome these limitations, there has been an effort to reduce the size of the magnetic particles. However, when the dispersing agent is used as a mineral oil (mineral oil), the dispersing ability can be improved. On the other hand, There is a limit in that the vibration absorbing effect of the oil is not obtained, the pour point is too high, the evaporation amount is large, and the stability at low temperature or high temperature is low. In particular, fumed silica having a nanoscale particle size may be used as a dispersing agent, but in this case, coagulation phenomenon or curing phenomenon occurs during long-term storage, which has a limitation in that redispersibility is very low.

Therefore, it is inevitable to improve the dispersibility of the magnetorheological fluid, and at the same time, to prepare a composition capable of maintaining good properties such as fluidity, evaporation amount and stability at low temperature / high temperature of the magnetorheological fluid.

KR 2008-0079472 A

In one aspect, an object of the present invention is to provide a magnetorheological fluid with improved viscosity variation with temperature change.

In another aspect, an object of the present invention is to provide a magnetorheological fluid which is economical and has excellent viscosity, pour point and flash point, evaporation characteristic and specific gravity characteristic.

In order to achieve the above object, the present invention provides a magnetic particle comprising: a magnetic particle; A dispersion medium; And a dispersant, wherein the dispersant comprises a clay mineral having an average particle size of 0.01 to 100 nm, and the dispersion medium comprises an ester and a polyalphaolefin.

In order to achieve the above object, the present invention also provides a magnetic particle comprising: a magnetic particle; A dispersion medium; And a dispersing agent to prepare a first mixture; And dispersing the first mixture by stirring at 145 to 155 DEG C at 40 to 50 rpm to prepare a magnetorheological fluid composition.

One aspect of the present invention is a magnetorheological fluid composition capable of uniformly controlling the distribution of magnetic particles in the composition, minimizing precipitation, and minimizing hardening after precipitation. In addition, the magnetorheological fluid composition of the present invention has a small viscosity change according to temperature, and particularly has improved stability at a cryogenic temperature and a high temperature, and is capable of maintaining the performance of a magnetorheological fluid even in an extreme temperature environment.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view showing a pour point according to the kind of a dispersion medium. FIG.
2A and 2B show evaporation amounts (22 hours and 94 hours, respectively) in accordance with the dispersion medium.
FIG. 3 is a graph showing changes in viscosity of a magnetorheological fluid (FIG. 3A) and a viscosity of a dispersion medium of 54sCt according to the content of iron powder when a dispersion medium having a viscosity of 32sCt was used. (Fig. 3B).
FIG. 4 is a graph showing a change in specific gravity of magnetorheological fluid according to the content of iron powder when a dispersion medium having a viscosity of 32 s Ct is used.
FIG. 5A is a view showing a magnetorheological fluid immediately after preparation, and FIG. 5B is a diagram showing the deposition of a magnetorheological fluid after 2 weeks from the production. The samples in Figures 5A and 5B indicate the results when using mineral oil, polyalphaolefin oil (PAO), PAO + ester and ester, from left to right.
6 is a view showing a test report verifying the performance of the magnetorheological fluid composition of the present invention.

Hereinafter, the present invention will be described in detail.

In one aspect, the present invention relates to magnetic particles; A dispersion medium; And a dispersant, wherein the dispersant comprises a clay mineral having an average particle size of 10 to 300 nm, the dispersion medium comprising a synthetic oil, wherein the synthetic oil comprises an ester oil and a poly alpha olefin oil / RTI > is a magnetorheological fluid composition.

In the present specification, the average particle diameter may mean an arbitrary measured average value of the diameters of the particles, excluding the longest axis and the shortest axis.

In the above aspect, the clay mineral of the dispersant may have an average particle size of 10 to 300 nm. When the diameter of the clay mineral is on the order of nanometers as in the case of the diameter of 10 nm, the precipitation of the magnetic particles can be greatly improved and the hardening after precipitation can be improved as compared with the case of the average particle diameter on the micrometer level, . When the average particle size of the clay minerals is in the above range, the precipitation phenomenon and the dispersing ability improvement effect can be obtained.

In one embodiment, the clay mineral may comprise bentonite.

In addition, the dispersing agent may include clay minerals, and in one embodiment may include clay minerals having an average particle size of 0.01 to 100 nm. When the dispersant is a clay mineral having an average particle diameter of the order of nanometers, as compared with a material generally used as a dispersant such as nano silica, graphite, molybdenum dioxide, carbon nano tube, or polytetrafluoroethylene, And the curing phenomenon after precipitation can be remarkably improved.

Further, in the above aspect, the ester oil and the polyalphaolefin oil may be contained in the magnetorheological fluid composition at a weight ratio of 1: 2.5 to 3.5. In the case of containing only polyalphaolefin as the dispersion medium, the pour point is low but the evaporation rate is low, so there is a limit to use as a dispersion medium of the magnetorheological fluid. In the case of including only ester, the evaporation rate is low but the pour point is high , There is a limit in ensuring stability at low temperatures. On the other hand, the esters and polyalphaolefins may be contained in a weight ratio of 1: 2.5 to 3.5, preferably 1: 2.8 to 3.2, more preferably 1: 2.9 to 3.1. When the ester oil and the polyalphaolefin oil are contained in the above weight ratio, the viscosity of the dispersion medium can be adjusted to the following range.

In the above aspect, the viscosity of the dispersion medium may be 25 to 35 mm ² / sec, preferably 30 to 35 mm ² / sec, and more preferably 31 to 33 mm ² / sec. When the viscosity of the dispersion medium exceeds 35 mm ² / sec, the content of the magnetic particles required for maintaining the proper viscosity of the magnetorheological fluid is lowered, and there is a limit that the vibration absorbing force or the shock absorbing ability of the magnetorheological fluid is lowered. When the viscosity of the dispersion medium is less than 25 mm ² / sec, there is a limit in that the viscosity of the magnetorheological fluid becomes low.

The magnetic particles and the dispersing medium fine dispersing agent may be contained in an amount of 75 to 85 wt%: 12 to 22 wt%: 0.5 to 2 wt% based on the total weight of the magnetorheological fluid composition, 85% by weight: 12 to 22% by weight: 0.5 to 1.5% by weight. When the magnetic particles are contained in an amount of more than 85% by weight based on the total weight of the composition, the viscosity and specific gravity of the magnetorheological fluid composition become excessively high, so that the dispersibility and flow characteristics are lowered. , There is a limitation in that the vibration absorbing ability of the magnetorheological fluid is lowered.

In one embodiment, the average particle size of the magnetic particles may be between 4 and 6 mu m. When the average particle diameter of the magnetic particles is less than 4 탆, the magnetic particles are too small to have a low vibration absorbing ability. When the average particle diameter exceeds 7 탆, the deposition speed of the magnetic particles becomes high and the dispersing ability is low.

In this aspect, the magnetic particles may be selected from the group consisting of iron or iron-containing materials, nickel, cobalt, and alloys of at least one of the foregoing.

In this aspect, the magnetorheological fluid composition may comprise one or more of the following properties at 22-26 ° C and 30-50% humidity environment:

i) a specific gravity measured according to KS A 0601 of 2.5 to 3.5; ii) a flash point of 220 ° C or higher, as measured in accordance with KS M 2010; iii) 0.3 to 0.5% by weight, based on the total weight of the composition, the amount of evaporation measured after 22 hours at 99 DEG C according to KS M 2037; iv) the pour point measured according to KS M 2016 is not more than -30 ℃; And v) a viscosity measured according to KS A 0531 of 20 to 30 mPa · s.

In one embodiment, the magnetorheological fluid composition comprises: i) a specific gravity measured according to KS A 0601 of 3.3; ii) The flash point measured according to KS M 2010 is 221 ℃; iii) 0.34 wt% of evaporation measured after 22 hours at 99 DEG C according to KS M 2037, based on the total weight of the composition; iv) the pour point measured according to KS M 2016 is -35 ° C; And v) the viscosity measured according to KS A 0531 may be 26 mPa · s. These properties are equivalent to those of LORD's magnetorheological fluid, which is known to have excellent physical properties in the composition of the magnetorheological fluid, at a low cost, and have a specific gravity, an evaporation amount and a viscosity property which are equivalent to each other, and the flash point and the pour point are greatly improved by 10% or more.

Further, in the above-mentioned aspect, the composition may further include an additive, and the additive may include at least one of an antioxidant, a corrosion inhibitor and an abrasion inhibitor. The antioxidant may be p, p'- The corrosion inhibitor may be an N-alkylated benzotriazole, and the abrasion inhibitor may be zinc phosphate dithiophosphate (Zn-DTP) ).

The additive may be included in an amount of 0.5 to 5% by weight, based on the total weight of the composition. In one embodiment, the antioxidant may be included in an amount of 0.8 to 1.2% by weight, the corrosion inhibitor may be included in an amount of 0.3 to 0.7% by weight, and the abrasion inhibitor may be included in an amount of 0.3 to 0.7% by weight. The antioxidant can improve the lifetime shortening of the magnetorheological fluid and the damper by the shrinkage of the dispersion medium, and the corrosion inhibitor can prevent the corrosion of the iron powder in the mechanical and magnetorheological fluids used, It is possible to prevent the dispersant from being abraded between the iron powder due to the friction caused by the fluid flow.

In one aspect, the present invention relates to magnetic particles; A dispersion medium; And a dispersing agent to prepare a first mixture; And dispersing the first mixture by stirring at 145 to 155 DEG C at 40 to 50 rpm to prepare a magnetorheological fluid composition.

The mixing temperature may preferably be 148 to 152 캜, and the stirring speed may be 43 to 47 rpm. The mixing temperature and stirring speed are optimized for the dissolution of the first mixture.

In one embodiment, the method may further comprise the step of adding an additive to the first mixture after the dispersing step to produce a second mixture, and the step of preparing the second mixture comprises adding the additive to the first Lt; RTI ID = 0.0 > 60-70 C < / RTI > prior to addition to the mixture.

Hereinafter, the constitution and effects of the present invention will be described in more detail with reference to examples and test examples. However, these examples and test examples are provided for illustrative purposes only in order to facilitate understanding of the present invention, and the scope and scope of the present invention are not limited by the following examples.

The test specifications used in this embodiment are as shown in Table 1 below.

Performance indicator Test Specification importance KSE 0601 flash point KS M 2010 Evaporation amount KS M 2037 Viscosity KSE 0531 Pour point KS M 2016

[Example 1] Dispersion medium selection

PAO (PAO 6, INEOS), Minenal oil (Yubase 6, SK) and Ester oil (HATCOL 2938, HATCO) were selected as suitable candidates for the dispersion medium of MR fluid. Then, to find out the dispersion medium optimized for the magnetorheological fluid, the pour point and the evaporation amount (22 hours and 94 hours) of the fluid mixed with 13 to 15% of each oil and 82 to 84% of iron powder having an average particle diameter of 4 to 6 μm Evaporation amount after elapse of time). As a result, PAO has excellent flowability at low temperature but has a limitation due to high evaporation amount. In case of Minenal oil, properties of both pour point and evaporation amount are poor, and Ester oil has excellent high temperature characteristics, However, it was expensive and had a low pour point (Table 2). Therefore, PAO and Ester oil were mixed with each other to satisfy economical efficiency and to improve the pour point. When the ratio of PAO to Ester was 3: 1, the pour point was as low as -35 ℃ and the evaporation amount was low, indicating that it was the most optimal dispersion medium for the magnetorheological fluid.

oil oil content
(wt%) Iron powder content (wt%) Test result Pour point Evaporation amount 22 hours 22 hours 46 hours 70 hours 94 hours mineral oil 13 84 -15 ℃
0.75 1.02 1.32 0.65 PAO 13 84 -40 ° C 0.71 0.97 1.24 1.50 PAO + Ester 14 83 -35 ° C 0.33 0.45 0.51 0.62 Ester 15 82 -20 ° C 0.24 0.17 0.25 0.31

[Example 2] Development of optimum content of iron powder

The impact absorption force (damper force) was measured in the following manner. The iron powder having an average particle diameter of 4 to 6 占 퐉 was used. As a result, when the iron powder content was less than 82%, the viscosity and specific gravity of the MR fluid were lowered. Especially, the viscosity was lowered to about 22P, and the lowered viscosity caused the damper value to fail to attenuate the main vibration of the MR fluid. In addition, when the iron powder content was above 85%, the damper value was satisfactory but the viscosity and specific gravity of the MR fluid were increased. Especially, the viscosity was increased to 35P or more and the fluidity was greatly decreased. As a result, it was found that the optimum iron powder content was 82 ~ 84%, which is the most optimal value of viscosity and specific gravity against impact absorption force (Table 3).

Iron powder content (% by weight) and result 82 82 or more and less than 85 85 Viscosity 22P 26P 35P importance 3.2 3.3 3.5

[Example 3] Development of optimum particle diameter of iron powder

The average grain size of the iron powder used as magnetic particles was adjusted, and the optimum particle size was developed by measuring the impact absorption capacity and the deposition rate. As a result, when the particle size was less than 3 탆, the deposition rate was the slowest at the same rate, but the damper force was greatly lowered due to the fine particles and the price was high. On the other hand, when the average particle diameter was 7 ~ 10 ㎛, the particle size was large and the deposition rate was accelerated (immersed within 5 days), and a high damper value exceeding the vibration attenuation level was required. As a result, the specific gravity and the viscosity were lowered. On the other hand, when the iron powder had a particle size of 4 to 6 μm, it was found that the particle diameter of 4 to 6 μm was the most preferable because the precipitation speed was 7 days or more while having an appropriate damper value.

Iron powder content (wt%) Particle size (탆) result 82 to 85 wt% 1-3 Deposition rate (deposit completion date): 9 days 4 to 6 Deposition rate (deposit completion date): 7 days 7 to 10 Deposition rate (deposit completion date): 5 days

[Example 4] Development of optimum viscosity of dispersion medium

Since the viscosity of the magnetorheological fluid is highly related to the viscosity of the dispersion medium, the viscosity of the dispersion medium is controlled so that the viscosity of the magnetorheological fluid is 20 to 30P. As a result, when the viscosity of the dispersion medium is 54 mm ² / sec, it is necessary to contain a small amount of iron powder (less than 81%) in order to control the viscosity of the magnetorheological fluid to 20 to 30 P, There was a limit in which sufficient damper force required could not be obtained. On the other hand, when the viscosity of the dispersion medium is less than 32 mm ² / sec, iron powder must be added in a high content in order to prepare a magnetorheological fluid having an appropriate viscosity. In this case, iron powder is easily deposited and can not act as a dispersant .

As a result, it was found that the viscosity of the optimized dispersion medium was 32 mm ² / sec (see Tables 5 to 7).

Viscosity change of magnetorheological fluid with viscosity of dispersion medium and content of iron powder mineral oil PAO Ester PAO + Ester (3: 1) 32 mm ² / sec 64 mm ² / sec 32 mm ² / sec 64 mm ² / sec 32 mm ² / sec 64 mm ² / sec 32 mm ² / sec 64 mm ² / sec Iron powder 85% 35 40 36 39 36 41 35 40 Iron powder 83% 26 33 26 32 27 35 26 34 Iron powder 81% 18 26 18 26 20 28 20 28

The specific gravity change of magnetorheological fluid according to iron powder content when the viscosity of dispersion medium is 32 mm ² / sec mineral oil PAO Ester PAO + Ester (3: 1) Iron powder 85% 3.52 3.54 3.77 3.56 Iron powder 83% 3.31 3.30 3.57 3.32 Iron powder 81% 3.20 3.19 3.35 3.22

Change of damper force according to iron powder content when the viscosity of dispersion medium is 32mm ² / sec mineral oil PAO Ester PAO + Ester (3: 1) Iron powder 85% - - - - Iron powder 83% - O O O Iron powder 81% - X X X

(O: with damper force, X: without damper force)

[Example 5] Development of optimum dispersant

(Average particle diameter: 10 to 300 nm), and the iron powder content (82 to 84 wt%) of the optimal dispersion medium of the present invention (mixture of PAO and ester in a ratio of 3: 1, viscosity of 32 mm ² / sec) Clay, silica, graphite, MoS ₂ , CNT and polytetrafluoroetylene (PTFE) were added in the same amount, and the dispersibility according to the kind of each dispersant was confirmed. As a result, when the nanometer sized clay of the present invention was used, it was confirmed that the dispersibility and the precipitation improving effect were much better than those of the other types of dispersants. Particularly, the dispersibility and the improvement of the precipitation were better than those of the nanosilica and carbon nanotubes having an average particle diameter of the dispersant of nanometer level (Table 8).

division
(weight%) One 2 3 4 5 6 7 8 Base oil
14wt% PAO: Ester (3: 1)
Viscosity 32 mm ² / sec (at 40 ° C) Iron
Powder
83 wt%) 4 to 6 μm Filler
(1.0%) - Nano
Clay Clay Nano
Silica Graphite MoS2 CNT PTFE Additive
(1 wt%) Antioxidant + corrosion inhibitor texture
and Sedimentation X ◎ △ ○ △ △ △ △ Hardening X ◎ ◎ × × × × ×

(?: Very excellent,?: Excellent,?: Fair, X: not effective)

[Example 5] Development of optimum concentration of dispersant

The concentration of dispersant that can optimize the physical properties of magnetorheological fluid was investigated. As a result, when the content of the nano-clay was less than 0.5 wt%, iron powder could not be suspended, and when it exceeded 1.5 wt%, there was a limit to lower the damper force of the magnetorheological fluid due to inter- 9).

Content of nano clay (wt%) result 1.5 Lower damper force 1.0 Deposition delayed as damper force is maintained 0.5 Failure to float iron horse

Claims (14)

Magnetic particles; A dispersion medium; And a dispersant,
The dispersant includes clay minerals having an average particle diameter of 10 to 300 nm,
Wherein the dispersion medium comprises a synthetic oil, the viscosity of the dispersion medium is 25 to 35 mm < ² > / sec,
The synthetic oil comprises an ester oil and a polyalphaolefin oil,
The ester oil and the polyalphaolefin oil are contained in a weight ratio of 1: 2.5 to 3.5. delete The method according to claim 1,
Wherein said clay mineral comprises bentonite. delete The method according to claim 1,
The magnetic particles, the dispersion medium, and the dispersant may be dispersed in the magnetic fluid composition,
75 to 85 wt%: 12 to 22 wt%: 0.5 to 2 wt%. delete The method according to claim 1,
Wherein the average particle diameter of the magnetic particles is 4 to 6 占 퐉. The method according to claim 1,
Wherein the magnetic particles are selected from the group comprising iron or an iron-containing material, nickel, cobalt and alloys of at least one of the foregoing. The method according to claim 1,
Wherein said magnetorheological fluid composition comprises at least one of the following properties in a 22-26 < 0 > C and 30-50% humidity environment:
i) a specific gravity measured according to KS A 0601 of 2.5 to 3.5;
ii) a flash point of 220 ° C or higher, as measured in accordance with KS M 2010;
iii) 0.3 to 0.5% by weight, based on the total weight of the composition, the amount of evaporation measured after 22 hours at 99 DEG C according to KS M 2037;
iv) the pour point measured according to KS M 2016 is not more than -30 ℃; And
v) The viscosity measured according to KS A 0531 is 20 to 30 mPa · s. The method according to claim 1,
Wherein the magnetorheological fluid composition comprises:
Further comprising an additive,
Wherein the additive comprises at least one of an antioxidant, a corrosion inhibitor and an abrasion inhibitor. 11. The method of claim 10,
Wherein the additive is included in an amount of 0.5 to 5% by weight based on the total weight of the composition. A process for the preparation of the magnetorheological fluid composition of any one of claims 1, 3, 5, and 7 to 11,
The method comprises:
Magnetic particles; A dispersion medium; And a dispersing agent to prepare a first mixture; And
And dispersing the first mixture by stirring at 145 to 155 DEG C at 40 to 50 rpm. 13. The method of claim 12,
After the dispersing step
Further comprising adding an additive to the first mixture to produce a second mixture. 14. The method of claim 13,
Wherein the step of preparing the second mixture comprises:
Lt; RTI ID = 0.0 > 60-70 C < / RTI > prior to adding the additive to the first mixture.

Images