JP2010024420A - Dilatant composition, process for producing the same, oscillation inhibitor and oscillation inhibitor for antisqueal shim - Google Patents

Abstract

A dilatancy vibration-proof composition (dilatant composition) having both anti-squealing effect and brake feeling and improved coatability (productivity) is provided.
SOLUTION: It is composed of inorganic particles and a silicone medium held between the inorganic particles, and the silicone medium is a linear or cyclic silicone oil in which a methyl group and / or a phenyl group is bonded to a silicon atom. A dilatant composition characterized.
[Selection] Figure 1

Description

  The present invention relates to a dilatant composition in which an apparent viscosity increases due to an increase in applied shear rate and gels at rest, and a method for producing the same. The present invention also relates to an anti-vibration agent excellent in vibration damping and an anti-squeal shim anti-vibration agent excellent in brake noise.

  A dilatant fluid is a fluid having dilatancy that increases the apparent viscosity by increasing the applied shear rate. This fluid is composed of microparticles and a liquid held between these microparticles, and shows low fluidity and high fluidity under a low shear rate, but has a high apparent viscosity under a large shear rate. And exhibits low fluidity.

  Such a phenomenon is caused by a change in the relative arrangement of the fine particles in the fluid due to the difference in the applied shear rate. Under a large shear rate, the free space existing between the fine particles increases. Therefore, it is considered that the fine particles are attracted to each other by a kind of negative pressure action when the surrounding liquid is sucked into this free space, the resistance increases, and the fluid exhibits high viscosity and decreases fluidity. .

  The dilatant fluid is disposed between two objects that move relatively close to each other, and transmits a high torque between the two objects when the shear rate is high and low torque when the shear rate is low. Is used as a working fluid in, for example, a clutch or a vibration isolator. Currently, "Dilatal (trademark)", a product manufactured by BASF Germany, is known as a dilatant fluid. The dilatant fluid is formed by dispersing fine particles of an acrylate ester / styrene copolymer in water.

  By the way, various methods are being studied for preventing the skill noise of the disc brake of an automobile. As one of them, rubber with vibration damping is bonded to the surface of anti-squeal shims (hereinafter referred to as shims) used to reduce vibration transmission from the source, and viscoelastic properties are used for the shims to enhance the effect. Apply grease. As anti-vibration compositions, greases using a high-viscosity base oil, highly elastic substances such as grease added with copper powder, and dilatancy fluids have been proposed for clutches and anti-vibration devices.

  The problem with conventional anti-skill shim greases is that grease with the addition of viscoelastic properties and high damping properties (including metals) of a high-viscosity base oil that has a high anti-squealing effect is superior in anti-squealing performance, but applied. Sometimes stringing occurs due to viscosity, and productivity deteriorates. Also, since the elastic force is large, it is more advantageous to apply a thick coating for the effect of preventing squealing, but the brake feeling such as fluffy feeling (sponge feeling) may deteriorate due to the elasticity of grease. In addition, when mineral oil is used as a base, the base oil evaporates due to heat from the brake pads, which may reduce the viscoelastic effect.

  As a problem of the conventional dilatancy fluid, a normal dilatancy fluid, which is said to have a high anti-vibration effect, becomes liquid when it has a low shear rate and does not adhere, so it flows out unless it is sealed. It cannot be applied to shims because there is no adhesive force to prevent outflow.

  Skill noise of the disc brake is a vibration phenomenon between the brake pad and the rotor. As a method for preventing the noise, there are a countermeasure of the generation source or a method of cutting off the generated vibration path, and the latter problem will be described below. Shim grease is used for the purpose of absorbing vibration by internal loss, that is, damping effect, and reducing vibration transmission. The damping effect is higher with the high viscosity base oil. In addition, for the purpose of enhancing the damping effect, a soft metal such as copper powder or lead powder may be blended, or a solid lubricant such as graphite or boron nitride (BN) may be used. For example, it is known that commercially available PBC grease (KS Paul Product Co.) is enriched with bentonite based on mineral oil, and copper and lead-based materials are used as additives. In the following Patent Document 1, it is proposed to add BN to grease based on high-viscosity silicone oil.

  When mineral oil with high evaporability is used in brake parts, light components in the base oil evaporate, and eventually the grease itself hardens, resulting in a loss of viscosity and a short duration of damping characteristics.

  In addition, the use of a high viscosity silicone oil is advantageous in terms of sustainability because there is almost no evaporation, but the tackiness increases as the molecular weight of the base oil increases, and therefore the grease causes stringing. When a certain amount of grease is applied from a grease nozzle at a production facility, the surrounding parts may be soiled, or the specified amount may not be applied. There is a short problem.

  Furthermore, when the viscosity is high, the oil film becomes thick, and when the brake is stepped on by the elastic body, the brake piston and the pad are floated by the oil film, which may cause a deterioration of the brake feeling such as a sponge feeling.

  Since the conventional dilatant fluid is assumed to be used in a closed container, it is liquid in a steady state. If this is applied to a shim that is sandwiched in a gap that is not hermetically sealed, it may flow out because of poor adhesion. If it begins to flow, it will adhere to the brake pads and rotor and the worst brakes may not work.

Japanese Patent No. 3765558

  The present invention provides a dilatant composition capable of preventing leakage due to heat from the brake, reducing brake squeeze noise and brake feeling, and improving productivity by improving stringiness during coating and A manufacturing method thereof is provided. That is, the present invention provides a dilatancy vibration-proof composition (dilatant composition) that achieves both the anti-squealing effect and the brake feeling and has improved coatability (productivity).

  The present inventors have found that the above problems can be solved by a combination of specific inorganic particles and a specific medium, and have reached the present invention.

  That is, first, the present invention is an invention of a dilatant composition, comprising inorganic particles and a silicone medium held between the inorganic particles, wherein the silicone medium has a methyl group and / or a phenyl group on a silicon atom. It is characterized by being a linear or cyclic silicone oil bonded with.

  In the present invention, the average particle size of the inorganic particles is preferably 0.1 μm to 15 μm.

  In the dilatant composition of the present invention, inorganic particles having an average particle size of 0.1 μm to 15 μm are used, and the inorganic particles may be pulverized or spherical. Usually, it is said that the higher the sphericity, the more dilatancy is exhibited, and it can be said that it is a new finding that the pulverized inorganic particles can be used in the present invention.

  Although it does not restrict | limit especially as an inorganic particle used for the dilatant composition of this invention, A metal oxide and / or a metal nitride are preferable.

The silicone medium used in the dilatant composition of the present invention preferably has a kinematic viscosity at 25 ° C. of 30 to 100 mm ² / s.

  It is preferable to further add graphite powder to the dilatant composition of the present invention.

  In order for the dilatant composition of the present invention to exhibit effective dilatancy, the silicone medium is preferably 18 to 25 parts by mass with respect to 100 parts by mass of the inorganic particles.

  In the dilatant composition of the present invention, it is also effective to make the inorganic particles a mixture of particles having an average particle diameter of 10 μm or more and particles having an average particle diameter of 1 μm or less.

  It is also effective to add a silicone resin powder to the dilatant composition of the present invention.

  Second, the present invention is an invention of a method for producing the dilatant composition, wherein the inorganic particles are mixed and dispersed in a hydrofluoroether having a boiling point of 100 ° C. or less, and then the silicone medium is mixed to form a slurry. And heated at 100 ° C. or higher.

  Thirdly, the present invention is an anti-vibration agent comprising the above-described dilatant composition. The dilatant composition of the present invention is used for various applications by taking advantage of its dilatancy. Among these, it is suitable for use as an anti-vibration agent, and further suitable for an anti-squeal shim anti-vibration agent comprising the above-described dilatant composition.

  The dilatant composition of the present invention is a dilatant vibration-proof composition that achieves both a squeal prevention effect and a brake feeling, and has improved coatability (productivity).

  This is a dilatancy fluid that is in the form of a low-viscosity grease at the time of low shear when applied to the brake anti-skill shim, and that becomes very viscous and partially solidifies at the time of high shear when the brake vibration is generated. Brake caliper pad, uniform application between shim and piston can suppress noise transmission by suppressing brake vibration transmission.

  The inorganic particles as a component constituting the dilatant fluid may be not only spherical but also an irregularly pulverized metal oxide. Silica is most suitable as a component that is stable and chemically and thermally stable when sandwiched between the shim, the pad, and the piston, and may be a hard component such as alumina or zirconia. As for the particle size, the average particle size is preferably 1 to 10 μm, and if it is too fine, the dilatancy characteristic is difficult to appear. In addition, if the particle size is too large, the particles are difficult to move and the dilatancy characteristic does not appear, and the wear of shims or the like may be accelerated.

The silicone medium is a heat-stable liquid transmitted from the brake to 150 ° C. or higher. Silicone oil is most suitable for those having good compatibility with inorganic particles. Fluorine oil such as perfluoropolyether, poly α-olefin oil, polyalkylene glycol oil or the like may be added. Among silicone oils, cyclic or linear dimethyl silicone oil or methylphenyl silicone oil having better heat resistance is preferable. The viscosity of the medium is preferably 30 to 100 mm ² / s at 25 ° C. If the viscosity is too low, the evaporating property is increased and the sustainability of the dilatancy is lost. If the viscosity is too high, the amount of particles cannot be increased, and the dilatancy characteristic will not be exhibited due to a decrease in the viscosity ratio.

  It has been found that the ratio of the inorganic particles and the silicone medium is a substance that exhibits dilatancy characteristics only in a limited range. If the particle ratio is large, it does not become grease-like, and if it is small, it becomes slurry-like and does not exhibit dilatancy characteristics.

Examples of the present invention will be described below.
[Example 1]
100 parts by mass of crushed silica FS-3DC (average particle size 3.0 μm, particle size distribution 1 to 10 μm) as inorganic particles, and 22 parts by mass of dimethylsiloxane (KF96-30CS manufactured by Shin-Etsu Chemical) as silicone media Were mixed and stirred to obtain a dilatant composition.

[Example 2]
The silicone medium was changed to KF96-100CS with respect to 100 parts by mass of the pulverized silica of Example 1, and 22 parts by mass was mixed and stirred to obtain a dilatant composition.

[Example 3-7]
As shown in Table 1, each main component was changed to obtain a dilatant composition in the same manner as in Example 1.

[Comparative Example 1]
100 parts by mass of crushed silica (FS-3DC) manufactured by Denki Kagaku Kogyo Co., Ltd. and 25 parts by mass of dimethylsiloxane (KF96-30CS) were mixed and stirred, but became a slurry substance and did not become a dilatant composition.

[Comparative Example 2]
100 parts by mass of pulverized silica (FS-3DC) manufactured by Denki Kagaku Kogyo Co., Ltd. and 18 parts by mass of dimethylsiloxane (KF98-30CS) were mixed and stirred. .

[Comparative Example 3]
An anti-squeaming grease for shims using a base oil as a high viscosity silicone oil and silica as a thickener was prepared.

[Comparative Example 4]
A composition was prepared in the same manner as in Example 1 except that the base oil was mineral oil.

[Characteristic evaluation]
About the above-mentioned Example 1-7 and Comparative Example 1-4, change in apparent viscosity when changing the shear rate (number of rotations) at 25 ° C., brake squeal prevention property, high temperature evaporation prevention property (150 ° C. × 24 h) ), And the results of the stringiness test are shown in Table 1 below.

  Moreover, about Example 1, 2 and Comparative Examples 1-3, the change of an apparent viscosity when changing a shear rate (rotation speed) at 25 degreeC is shown in FIG.

  In FIG. 1, Examples 1 and 2 show typical dilatancy characteristics in which the viscosity suddenly increases from a certain number of rotations as the number of rotations increases, whereas in Comparative Examples 1 and 3, the number of rotations increases. However, no increase in viscosity is observed. In Comparative Example 2, measurement was impossible.

  In Table 1, the anti-squeaking property is not recognized in Comparative Example 1. Comparative Example 3 has stringiness and is difficult to apply in a line.

[Example 8]
A composition was prepared in the same manner as in Example 1, except that dimethyl silicone oil (KF-96-30CS, kinematic viscosity: 30 mm ² / s @ 25 ° C.) was used as the medium, and the blending ratio with various inorganic particles was changed. . Table 2 below shows the compounding ratio and physical properties. In the table, S: slurry, G: grease, D: dilatancy, x: unmixable, and Δ: hard compound. In the table, CS represents centistokes, and 1 mm ² / s = 1 cSt. KF-96 is a trade name of Shin-Etsu Chemical's dimethyl silicone oil, and “30CS” is a grade of a silicone oil manufacturer and represents a viscosity. “30CS” is a kinematic viscosity of 30 mm ² / s at 25 ° C.

[Example 9]
A composition was prepared in the same manner as in Example 3 using dimethyl silicone oil (KF-96-100CS, kinematic viscosity: 100 mm ² / s @ 25 ° C.) as a medium and changing the blending ratio with various inorganic particles. . Table 3 below shows the compounding ratio and physical properties. In the table, S: slurry, G: grease, D: dilatancy, x: unmixable, and Δ: hard compound. KF-96 is a trade name of Shin-Etsu Chemical's dimethyl silicone oil, “100CS” is a grade of silicone oil manufacturer, and represents viscosity, and “100CS” is 100 mm ² / s dynamics at 25 ° C. Viscosity.

[Example 10]
A composition was prepared in the same manner as in Example 3 by using methylphenyl silicone oil (KF-54, kinematic viscosity: 400 mm ² / s @ 25 ° C.) as a medium and changing the blending ratio with various inorganic particles. Table 4 below shows the compounding ratio and physical properties. In the table, S: slurry, G: grease, D: dilatancy, x: unmixable, and Δ: hard compound. KF-54 is a trade name of methyl phenyl silicone oil manufactured by Shin-Etsu Chemical Co., Ltd., and a viscosity of 400 mm ² / s is commercialized.

[Example 11]
Inorganic particles tend to exhibit dilatancy characteristics because pulverized powder inhibits fluidity at high shear at the corners of the particles. However, the initial shape cannot be maintained due to the change of the particles over time, and the dilatancy may change. In that case, spherical particles having shape stability of the particles can also be used as the particles. It is particularly preferable to use spherical silica. The actual car squealing effect has a wider range of squeal prevention with pulverized powder, but there is no problem in practical use.

  100 parts by mass of spherical silica (FB-3SDC: average particle size 3.0 μm, particle size distribution 1 to 10 μm) manufactured by Denki Kagaku Kogyo as inorganic particles, and 20 parts by mass of dimethylsiloxane (KF96-30CS manufactured by Shin-Etsu Chemical) as a silicone medium The dilatant composition was obtained by mixing and stirring. In the case of a true sphere, if the amount of the silicone medium is larger than that of the pulverized powder, it becomes a slurry and does not exhibit dilatancy characteristics.

  In the same manner as in Examples 1 and 2, the dilatancy characteristic by the rotational viscometer, the actual vehicle squealing test, and the string pullability test were passed, and the high temperature evaporation characteristic test was 0.36%. In addition, as a result of continuing the actual vehicle squeal test, the time for the squeal prevention range to be narrowed was extended.

[Example 12]
It was found that, by adding graphite acting as a solid lubricant to Examples 1 and 2, lubrication characteristics can be imparted and internal damping characteristics can be enhanced, and the effect of preventing brake squeal can be broadened.

  A commercially available artificial graphite fine powder or a natural graphite having an average particle diameter of 3 μm, for example, UF-G5 manufactured by Showa Denko, 3 parts by mass added to 100 parts by mass of the composition of Example 1 As a result of conducting a squeal stop test, the squeal prevention range has been expanded.

[Example 13]
When the compositions of Examples 1 and 2 are produced, the amount of inorganic particles is large, so that the silicone medium cannot be sufficiently dispersed and mixing and stirring take time. The mixing usually took 24 hours, but it could be shortened by the following method.

  30 parts by mass of hydrofluoroether, for example, Novec (HFE7100: boiling point 61 ° C.) manufactured by Sumitomo 3M Co., was mixed with 100 parts by mass of pulverized silica FS-3DC of inorganic particles to obtain a slurry-like substance. After mixing and stirring 22 parts by mass of dimethylsiloxane (KF96-30CS) as a silicone medium with respect to 100 parts by mass of pulverized silica, heat treatment at about 100 ° C. was performed to evaporate the hydrofluoroether to obtain a dilatant composition. . By this method, the manufacturing time can be shortened by about 10 hours.

[Example 14]
Optimal blending of inorganic particles with 10 μm larger particles and 1 μm fine particles than aggregates of the same particle size can lower the porosity and increase the particle density, thus increasing the contact resistance of the particles, resulting in more dilatancy. Increased properties. In the case of a true sphere, if the powder has the same particle size, the porosity will be 26%, so mixing a suitable amount of fine particles of a size that will fit in the gap will reduce the porosity, increasing the resistance during flow and increasing the dilatancy. Increases properties. The optimum ratio is 10 μm particles: 1 μm particles = 80: 20.

[Example 15]
As a method of increasing the internal damping force while ensuring the dilatancy characteristics, the rigidity of the particles can be lowered by mixing all or a certain amount of silicone resin in addition to the inorganic particles. If the rigidity is lowered, the amount of internal loss when vibration is applied increases, and brake noise can be reduced.

[Example 16]
When the density of the inorganic particles and the silicone medium are brought close to each other, it becomes difficult to separate the mixture. In particular, when the brake heat is applied, the silicone medium has a lower density, so that the loss can be prevented. For this purpose, inorganic particles that are hollowed in order to approach the density are used.

  The dilatant composition of the present invention is used for various applications by taking advantage of its dilatancy. Among them, it is suitable for use as an anti-vibration agent, and further suitable for an anti-scheme shim anti-scheme comprising the above-described dilatant composition.

The change in apparent viscosity when the shear rate (number of rotations) is changed is shown.

Claims (12)

  A dilatant comprising an inorganic particle and a silicone medium held between the inorganic particles, wherein the silicone medium is a linear or cyclic silicone oil in which a methyl group and / or a phenyl group are bonded to a silicon atom. Composition.   The average particle diameter of the inorganic particles is 0.1 μm to 15 μm, and the silicone medium is a linear or cyclic silicone oil in which a methyl group and / or a phenyl group are bonded to a silicon atom. A dilatant composition according to claim 1.   The dilatant composition according to claim 1, wherein the inorganic particles are pulverized and / or spherical.   The dilatant composition according to any one of claims 1 to 3, wherein the inorganic particles are a metal oxide and / or a metal nitride. The dilatant composition according to claim 1, wherein the silicone medium has a kinematic viscosity at 25 ° C. of 30 to 100 mm ² / s.   The dilatant composition according to any one of claims 1 to 5, further comprising graphite powder.   The dilatant composition according to any one of claims 1 to 6, wherein the silicone medium is 18 to 25 parts by mass with respect to 100 parts by mass of the inorganic particles.   The dilatant composition according to any one of claims 1 to 7, wherein the inorganic particles are a mixture of particles having an average particle diameter of 10 µm or more and particles having an average particle diameter of 1 µm or less.   Furthermore, the silicone resin powder was added, The dilatant composition in any one of the Claims 1 thru | or 8 characterized by the above-mentioned.   10. The method for producing a dilatant composition according to claim 1, wherein the inorganic particles are mixed and dispersed in a hydrofluoroether having a boiling point of 100 ° C. or less, and then the silicone medium is mixed to form a slurry. And a method for producing a dilatant composition, characterized by heating at 100 ° C. or higher.   An anti-vibration agent comprising the dilatant composition according to any one of claims 1 to 9.   An anti-squeal shim vibration preventing agent comprising the dilatant composition according to any one of claims 1 to 9.

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