JP2019094922A - Seal member - Google Patents

Abstract

To provide a seal member that has corrosion prevention function and can effectively prevent a member to be sealed from corroding.SOLUTION: A seal member include a rubber base material and a coating which is disposed on the rubber base material and includes a hardened silicone rubber having type A durometer hardness of less than 50 and saturated fatty acid. The coating includes 30 mass% or more and less than 70 mass% of the hardened silicone rubber and 30 mass% or more and 60 mass% or less of lauric acid.SELECTED DRAWING: None

Description

  The present invention relates to a seal member.

  In vehicles and general-purpose machines such as automobiles, a sealing member is used to seal a housing in an engine, a device that accommodates an electronic component, and the like. For example, the sealing member is elastically deformed by being sandwiched in a compressed state between a pair of members constituting the housing, and the housing is sealed by sealing the pair of members.

  Automobiles sometimes travel in the beach area or in areas where snow melting agents are sprayed. At this time, if salt water or a snow melting agent adheres to parts of the automobile and there is a gap between the sealing member and the sealing member, salt water or a snow melting agent component intrudes into the gap to clamp the sealing member. Corrosion (gap corrosion) may occur in the pressing member. If this corroded portion penetrates the seal line of the seal member and penetrates into the interior of the housing, it leads to corrosion of the material constituting the housing.

  In recent years, in the automobile field, weight reduction has been actively promoted to improve fuel consumption, and the use of aluminum, which is lighter than iron-based members, is expanding. In general, aluminum is superior in corrosion resistance to iron, but the above-mentioned crevice corrosion tends to easily occur.

  Heretofore, methods of performing various treatments on the surface of aluminum have been studied in order to prevent corrosion of aluminum. As surface treatment methods of metal materials such as aluminum, mainly, three methods of alumite (anodization) treatment, plating treatment, and corrosion prevention coating are used.

Patent documents 1 and 2 disclose alumite treatment, patent document 3 discloses plating treatment, and patent documents 4 to 9 disclose corrosion preventing coatings.
More specifically, Patent Document 1 discloses an alumite member in which an anodized film and cobalt and / or chromium are present on the surface of an aluminum base or an aluminum alloy base.
Patent Document 2 discloses a fuel pump in which an alumite layer is formed on the entire surface of a pump body.
Patent Document 3 discloses a highly corrosion resistant Ni-based composite plating film in which a Cu-based plating film is formed on the surface of a metal component and a Ni-based plating film is formed thereon.
Patent Document 4 discloses a composition for coating a metal surface substantially containing hexavalent chromium, which contains water, an ion source such as aluminum, a chromium (III) cation source and the like.
U.S. Pat. No. 5,958,015 discloses a device coated with a coating comprising a cured binder and hydrophilic flakes whose surface comprises a metal oxide.
Patent Document 6 discloses a steel plate on which a coating film to which an ultraviolet curable resin composition has been applied is formed.
Patent Document 7 is composed of a nitride-based material composed of CrN, TiN, AlN, BN, BCN, and AlBN, and a diamond-like carbon (DLC) containing hydrogen, and TiC on the surface of a substrate composed of a magnetic substance in contact with seawater. Disclosed is a corrosion-resistant magnetic material having a coating layer composed of at least one material selected from carbon-based materials.
Patent Document 8 discloses an aluminum alloy material for a heat exchanger, in which a fluorine resin paint film having an isocyanate group or a siloxane group is directly provided on the surface.
U.S. Pat. No. 5,958,015 discloses a corrosion resistant composition comprising a polyamideimide (PAI) heat resistant polymer binder, a liquid solvent, and inorganic filler particles.

JP, 2015-232155, A JP, 2008-261282, A Patent No. 5365928 Japanese Patent Application Publication No. 2016-513755 Japanese Patent Publication No. 2015-509140 gazette Patent No. 5483296 JP, 2010-177326, A Patent No. 5189823 gazette Patent No. 5319282

  In the conventional corrosion prevention method, corrosion is prevented by performing surface treatment etc. to a member to be sealed. However, there are cases where the corrosion prevention effect of the member to be sealed can not be sufficiently achieved by the method of directly treating the member to be sealed. In particular, in the case of an aluminum housing used under an environment in which aluminum susceptible to crevice corrosion as a material of a member to be sealed is brought into contact with salt water, the corrosion prevention effect may be significantly reduced.

  As a result of examining the above problems, the inventors of the present invention have effectively applied the corrosion prevention function to the seal member in contact with the member to be sealed, instead of performing the surface treatment on the member to be sealed itself. It has been found that the corrosion of the member to be sealed can be prevented.

  That is, an object of the present invention is to provide a seal member having a corrosion prevention function and capable of effectively preventing corrosion of a member to be sealed.

The essential features of the present invention are as follows.
[1] rubber base,
A coating comprising a cured silicone rubber having a Type A durometer hardness of less than 50 and a saturated fatty acid on said rubber substrate;
Have
The content of the cured silicone rubber in the coating is 30% by mass or more and less than 70% by mass,
The seal member, wherein the content of saturated fatty acid in the coating is 30% by mass or more and 60% by mass or less.
[2] The seal member according to [1], wherein the cured silicone rubber is a one-pack condensation cured silicone rubber.
[3] The seal member according to [1] or [2], which is a seal member for an aluminum housing.

  It is possible to provide a seal member which has a corrosion prevention function and can effectively prevent corrosion of a member to be sealed.

  The seal member of one embodiment has a rubber substrate, and a coating comprising a cured silicone rubber having a hardness of less than 50 type A durometer hardness and a saturated fatty acid on the rubber substrate. The content of the cured silicone rubber in the coating is 30% by mass or more and less than 70% by mass. Moreover, the content of the saturated fatty acid in the coating is 30% by mass or more and 60% by mass or less. In addition, Type A durometer hardness represents the hardness measured by the measuring method prescribed | regulated to JISK6253-3: 2012.

  As described above, in the seal member according to one embodiment, the hardness of the cured silicone rubber contained in the coating is as low as less than 50 in type A durometer hardness. Therefore, for example, when the seal member is pressed, the coating is easily deformed, and the adhesion between the seal member and the surface to be sealed of the member to be sealed (the surface where the seal member and the member to be sealed contact) is enhanced. Thus, it can have high sealing performance.

  Generally, after a material for coating containing silicone rubber is applied on a rubber substrate, it has tackiness in the state before drying, so that impurities such as dust may be attached to the surface. However, since the seal member of one embodiment contains saturated fatty acid in the coating, it is possible to prevent impurities from adhering to the coating before drying.

  Saturated fatty acid in the coating of the sealing member of one embodiment can prevent corrosion of the pinching member by permeating out of the coating into the pinching member during use as the seal member. More specifically, since the coating is in direct contact with the member to be sealed, saturated fatty acid can be efficiently supplied to the surface to be sealed of the member to be sealed by the saturated fatty acid leaking out of the coating. . The sealed surface to which the saturated fatty acid that has leaked out exhibits excellent water repellency, and a corrosive component such as salt water infiltrates and stays in the gap between the member to be sealed and the seal member due to capillary action or the like. It can be effectively prevented. Thus, the surface to be sealed of the member to be sealed can be effectively prevented from corrosion, and the sealing function of the seal member can be maintained. In addition, even when saturated fatty acid adhering to the sealed surface is dissolved and separated when the sealed member is used in an environment where it is in contact with salt water etc. for a long time, saturated fatty acid is gradually removed from the coating of the sealing member. Thus, the water repellency on the surface to be sealed is not impaired, and the corrosion prevention effect can be maintained for a long time.

  In particular, conventionally, when the aluminum housing is used in an environment in contact with a corrosive component such as salt water, the cathode polarization is increased in the oxygen deficient gap portion, and the potential sufficient for maintaining the passive film is the anode. The passive film was not sufficiently formed because it was not maintained in part. As a result, the corrosion prevention function of the passive film is less likely to be exhibited, and the gap corrosion of the aluminum housing is promoted. On the other hand, when the seal member of one embodiment is used as a seal member for an aluminum housing which is a member to be sealed, saturated fatty acid is gradually supplied from the coating of the seal member, and therefore the aluminum housing is configured. It is possible to effectively prevent the entry of corrosive components such as salt water into the gap between the pair of pressing members and the sealing member. As a result, corrosion of the aluminum housing can be effectively prevented and the sealing function can be maintained.

  Further, the shape of the seal member is not particularly limited, and may be any shape, for example, a sheet-like seal member such as a square, a rectangle, or a disk, an annular seal member such as an O ring or a square ring. .

  Below, the structure of the sealing member of one Embodiment, and its manufacturing method are demonstrated.

(Rubber base)
The material of the rubber substrate is not particularly limited as long as the effect of the present invention is not impaired, but a water-resistant elastomer is preferable, for example, a cured ethylene / propylene / diene terpolymer rubber (EPDM), nitrile rubber (NBR) And at least one material selected from the group consisting of hydrogenated nitrile rubber (HNBR). In addition, such materials may contain various additives as needed.

  In addition, the rubber substrate preferably has excellent water resistance. From such a point of view, the material of the rubber substrate is more preferably at least one selected from cured EPDM, NBR and HNBR, and it is further preferable to include at least one of EPDM and HNBR.

  The hardness of the rubber substrate type A durometer is preferably 40 or more and 90 or less, more preferably 50 or more and 80 or less, and still more preferably 60 or more and 70 or less. When the hardness of the type A durometer of the rubber substrate is in these ranges, the adhesion and sealability of the seal member to the member to be sealed can be further improved.

(coating)
The coating comprises a cured silicone rubber having a Type A durometer hardness of less than 50 and a saturated fatty acid. The content of the cured silicone rubber in the coating is 30% by mass or more and less than 70% by mass, and the content of the saturated fatty acid is 30% by mass or more and 60% by mass or less.

  The structure of the cured silicone rubber is not particularly limited as long as it is a crosslinked product having a siloxane bond. As the cured silicone rubber, one-component type or two-component type can be mentioned, and even if it is either one-component type or two-component type, condensation reaction type, addition reaction type, UV reaction type cured silicone Rubber can be mentioned. A one-component condensation reaction type cured silicone rubber is preferred because the curing reaction of the silicone rubber is fast and the number of steps can be shortened. Hardened silicone rubber type A durometer hardness is less than 50, preferably 9 or more and 46 or less. When the hardness of the type A durometer of the cured silicone rubber is in these ranges, the seal member can be easily deformed according to the shape of the member to be sealed, and can have more excellent adhesion. Further, the content of the cured silicone rubber in the coating is 30% by mass or more and less than 70% by mass, and preferably 30% by mass or more and 60% by mass or less. By the content of the cured silicone rubber in the coating being within these ranges, the sealability of the seal member can be made better.

  Saturated fatty acid is present inside the coating in a contained state that can exude to the surface of the coating, so that when the seal member comes in contact with the surface to be sealed of the member to be sealed, it adheres to the surface to be sealed, It plays a role in imparting aqueous. The content of saturated fatty acid in the coating is 30% by mass or more and 60% by mass or less. When the content of the saturated fatty acid in the coating is within these ranges, the saturated fatty acid can be stably supplied from the coating to the entire surface to be sealed, and excellent water repellency can be imparted to the surface to be sealed.

  Here, the inside of the coating refers to all parts of the coating, including the surface. Moreover, a containing state means the state to which the saturated fatty acid is uniformly mixed with the inside of coating.

  The state in which saturated fatty acid can leach out to the surface of the coating is not particularly limited, but when used as a sealing member, it is preferable that saturated fatty acid gradually oozes out on the surface of the sealing member due to clamping pressure, In a normal state (room temperature, normal pressure), saturated fatty acid may be gradually exuded to the surface of the seal member, or may be exuded under high temperature conditions.

  The saturated fatty acid is not particularly limited as long as it contains only a carbon-carbon single bond and does not contain a carbon-carbon double bond and a carbon-carbon triple bond, and examples thereof include lauric acid, myristic acid, palmitic acid and stearin. An acid, an arachidic acid, etc. can be used suitably. The saturated fatty acid may be used alone or in combination of two or more. As a saturated fatty acid, lauric acid is preferably used because it has an excellent water repellent function.

  The saturated fatty acid is preferably one that can increase the contact angle of water when it is attached to the surface to be sealed (for example, an aluminum surface) as compared to the surface to be sealed before adhesion. The larger the contact angle of water, the better the water repellency of the surface to be sealed.

  When the sealing member is used as a sealing member for an aluminum housing, the thickness of the coating is preferably larger than the maximum height roughness Rz of the sealed surface of the aluminum housing, for example, Rz = 6 μm of the sealed surface When the thickness of the coating is more than 6 μm is preferred. Due to the coating having these thicknesses, the seal member can have better sealability.

  The coating can contain other additives besides the cured silicone rubber particles. Such additives include thickeners, flow aids, antifoams, fillers, leveling agents, adhesion promoters and the like.

(Aluminum housing)
The sealing member according to one embodiment is elastically deformed by being sandwiched in a compressed state between a pair of members constituting the aluminum housing, and sealing between the pair of members is achieved. Thus, the aluminum housing can be sealed by the sealing member. When the conventional aluminum housing is used in an environment in contact with a corrosive component such as salt water, the passivation film is not sufficiently formed, and the gap corrosion of the aluminum housing is promoted. On the other hand, when the seal member of one embodiment is used as a seal member for an aluminum housing, since saturated fatty acid is gradually supplied from the coating of the seal member, a pair of pinching members constituting the aluminum housing In addition, it is possible to effectively prevent the entry of corrosive components such as salt water into the gap between the seal member and the seal member. As a result, corrosion of the aluminum housing can be effectively prevented and the sealing function can be maintained.

  As a material of the aluminum housing, aluminum or an aluminum base alloy can be used. The aluminum base alloy is an alloy in which the main component (the component having the largest content in the component) is aluminum, and as an alloy component other than aluminum, copper (Cu), silicon (Si), zinc (Zn), iron (Fe), magnesium (Mg) etc. are mentioned.

  In the aluminum housing, at least one of the members for pressing the seal member may be the above-described aluminum or aluminum-based alloy, and the other pressing member may be a metal member other than the aluminum-based member or a resin member. Further, the shape, size, and the like of the member for pressing the seal member are not particularly limited, and can be appropriately selected according to the use site and purpose of the seal member.

  The type of aluminum housing is not particularly limited, but is preferably used in an environment in contact with salt water. Examples of the aluminum housing include an aluminum housing for a vehicle, such as a converter, an electric power steering / control computer, a continuously variable transmission, an electric water pump, a stroke sensor, an aluminum housing such as a brake, a thermo housing, etc. Can.

(Method of manufacturing sealing member)
The manufacturing method of the seal member of one embodiment is described below. First, prepare a rubber substrate. The rubber substrate may be one obtained by obtaining a rubber substrate having a desired shape and made of already cured rubber, or may be obtained by curing and molding a rubber material.

  Next, a coating comprising a cured silicone rubber and a saturated fatty acid is formed on the rubber substrate. Although the method of forming the coating is not particularly limited, a liquid material containing silicone rubber, saturated fatty acid and optionally additives is applied onto a rubber substrate, and then the liquid material is dried by heat treatment for a predetermined time to dry the liquid material. And curing methods. In addition, after a liquid material containing silicone rubber and optionally additives is applied onto a rubber substrate, a saturated fatty acid is added, and the liquid material is further dried by heat treatment for a predetermined time to cure the liquid material. May be used. In any of the above methods, the content of the cured silicone rubber in the coating after formation is 30% by mass to less than 70% by mass, and the content of the saturated fatty acid is 30% by mass to 60% by mass. Adjust the blending amount of these materials.

  The application method of the liquid material is not particularly limited, and methods such as wire bar coater, film applicator, spray, air knife coating, die coating, ink jet printing and the like can be mentioned. Spray coating is preferred because a coating having a uniform film thickness can be obtained.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, but includes all aspects included in the concept and claims of the present invention, and various modifications are possible within the scope of the present invention Can be modified.

  Next, in order to further clarify the effects of the present invention, examples and comparative examples will be described, but the present invention is not limited to these examples.

Example 1
As a rubber substrate, an O-ring made of hardened ethylene-propylene-diene terpolymer rubber (EPDM) having a hardness of 70 type A durometer and a test piece of 20 mm × 50 mm × 2 mm in size were prepared. Next, after degreasing the surface of the O-ring and the test piece with methyl ethyl ketone, a primer (DY39-067, manufactured by Toray Dow Corning Co., Ltd.) was applied by spray. After this, the O-ring and the primer applied to the surface of the test piece were dried at room temperature for 30 minutes. Next, 5 parts by mass of silicone rubber (3145 manufactured by Toray Dow Corning Co., Ltd.) was dissolved in 95 parts by mass of toluene, and then 2.2 parts by mass of lauric acid was dissolved. The amount of lauric acid added corresponds to 31% by weight in the cured coating.

  The above toluene solution containing silicone rubber and lauric acid was applied onto both sides of the O-ring and one side of the test piece by spraying. After this, the toluene solution applied to the surface of the O-ring and the test piece is dried at 150 ° C. for 30 minutes to cure the silicone rubber, thereby curing the cured silicone rubber and the saturated fatty acid on the surface of the O-ring and the test piece Finally, a seal member comprising a rubber substrate and a coating was obtained. The cured silicone rubber had a Type A durometer hardness of 46.

  The obtained seal member is sandwiched between a pair of aluminum substrates (ADC 12) so that the compression ratio is 17%, and the seal member sandwiched by the aluminum substrates is 50% at a salt concentration of 5% by mass. Immersed for 720 hours in brine at ° C. Thereafter, the seal member held by the aluminum base was taken out of the salt water, and the O-ring held between the aluminum base was further removed. Next, the presence or absence of rust on the surface of the aluminum base in contact with the seal member was visually confirmed. The case where rust was confirmed visually was evaluated as "x", and the case where rust was not confirmed was evaluated as "(circle)." This evaluation result was made into "the salt-water immersion test result."

  Prepare a pair of transparent resin plates with rough surfaces and sandwich the seal member so that the compression ratio is 17% between the pair of transparent resin plates, and then use a microscope to make contact between the seal member and the transparent resin plate I confirmed the condition. And, when there is a gap between the seal member (O ring) and the transparent resin plate, and a passage passing through between the outer peripheral side and the inner peripheral side of the O ring is recognized, "x", the seal member (O ring) The case where no gap was observed between the transparent resin plates was evaluated as “o”. This evaluation result was taken as the "sealability result".

  After spray coating a toluene solution on the O-ring, apply a 52 μm thick polyimide (PI) sheet to the test piece before drying, and visually check whether the coating material has been transferred from the test piece to the PI sheet confirmed. The PI sheet adheres to the test piece, the case where the coating is transferred is "x", the PI sheet does not adhere to the test piece, but the case where the transfer of the coating is confirmed is "Δ", the PI sheet is a test piece The case where adhesion was not observed and transfer of the coating was not confirmed was "○". This evaluation result was made into "the tackiness result at the time of application | coating."

  In addition, a chrome-plated steel ball of 10 mm in diameter is slid under a load of 0.49 N at a speed of 50 mm / min on the above-mentioned test piece provided with a coating, and at that time using a surface property measuring instrument (TYPE 140 R) manufactured by HEIDON. The coefficient of kinetic friction was measured. Under the present circumstances, the dynamic friction coefficient was computed from the average load except the peak value of static friction force.

(Example 2)
The sealing member was prepared in the same manner as in Example 1 except that the amount of lauric acid added to the toluene solution was changed to 5 parts by mass and the content of lauric acid in the coating after curing was changed to 50% by mass. Made. Evaluation similar to Example 1 was performed about the obtained sealing member.

(Example 3)
The seal is the same as in Example 1 except that in Example 1, the amount of lauric acid added to the toluene solution is changed to 7.5 parts by mass, and the content of lauric acid in the coating after curing is changed to 60% by mass. A member was produced. Evaluation similar to Example 1 was performed about the obtained sealing member.

(Comparative example 1)
A seal member was produced in the same manner as in Example 1 except that lauric acid was not added to the toluene solution in Example 1. Evaluation similar to Example 1 was performed about the obtained sealing member.

(Comparative example 2)
A seal is performed in the same manner as in Example 1 except that the amount of lauric acid added to the toluene solution is changed to 1.25 parts by mass and the content of lauric acid in the coating after curing is changed to 20% by mass. A member was produced. Evaluation similar to Example 1 was performed about the obtained sealing member.

(Comparative example 3)
The sealing member was prepared in the same manner as in Example 1 except that the amount of lauric acid added to the toluene solution was changed to 12 parts by mass and the content of lauric acid in the coating after curing was changed to 71% by mass. Made. Evaluation similar to Example 1 was performed about the obtained sealing member.

(Comparative example 4)
A seal member was produced in the same manner as in Example 1 except that the toluene solution in Example 1 was changed so as not to contain the cured silicone rubber. Evaluation similar to Example 1 was performed about the obtained sealing member.

  The “saltwater immersion test results”, the “sealing result”, the “coating tackiness result”, and the dynamic friction coefficient in Examples 1 to 3 and Comparative Examples 1 to 4 are shown in Tables 1 and 2 below.

  From the results of Table 1, in Examples 1 to 3, the coating contains a cured silicone rubber having a hardness of less than 50 type A, and a coating containing saturated fatty acid, and the content of the cured silicone rubber in the coating is 30% by mass Since it is less than 70% by mass and the content of lauric acid is 30% by mass or more and 60% by mass or less, the result of the saltwater immersion test, the sealability result, and the application tackiness result were both “o”.

  On the other hand, according to the results of Table 2, in Comparative Example 1, although the coating of the seal member contained no saturated fatty acid, the salt water immersion test result and the sealability result were "o", but the tackiness result at the time of application was "x" became.

  In Comparative Example 2, since the content of lauric acid in the coating of the seal member was as low as 20% by mass, the result of the saltwater immersion test and the sealability result were “o”, but the tackiness result at the time of application was “Δ” became.

  In Comparative Examples 3 and 4, since the content of lauric acid in the coating of the seal member is as high as 71% by mass and 100% by mass respectively, the tackiness result at the time of application was “o”, but the salt water immersion test result and seal Sex results were "x".

Claims (3)

Rubber base material,
A coating comprising a cured silicone rubber having a Type A durometer hardness of less than 50 and a saturated fatty acid on said rubber substrate;
Have
The content of the cured silicone rubber in the coating is 30% by mass or more and less than 70% by mass,
The seal member, wherein the content of saturated fatty acid in the coating is 30% by mass or more and 60% by mass or less.   The seal member according to claim 1, wherein the cured silicone rubber is a one-pack condensation cured silicone rubber.   The seal member according to claim 1, which is a seal member for an aluminum housing.