JP2014005886A - Transmission oil seal for automobile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transmission oil seal for an automobile superior in a sliding characteristic over the whole area from a low-speed running to high-speed running.SOLUTION: The transmission oil seal for the automobile includes an elastic member having a seal lip portion provided with at least a main lip portion. The elastic member is composed of a composition including acrylic rubber (A) and fluorine resin (B), and has a projecting portion on, at least, a surface of the main lip portion, the projecting portion is composed of the fluorine resin (B) included in the composition, and the fluorine resin (B) is a copolymer including a tetrafluoroethylene unit (a) and a hexafluoropropylene unit (b).

Description

The present invention relates to an automobile transmission oil seal.

2. Description of the Related Art In transmissions for automobiles and the like, transmission oil seals for automobiles that prevent fluid such as oil from leaking to the outside from the power shaft protruding from the transmission housing and the end of the output shaft are used.
Various transmission oil seals have been proposed. For example, in Patent Document 1, an oil seal used for a transmission is made of an elastic body such as nitrile rubber, acrylic rubber, silicone rubber, or fluoro rubber, and includes a seal lip. A seal member is disclosed.

In recent years, with the demand for higher performance and fuel efficiency of engines, the sliding characteristics of automobile transmission oil seals have improved, especially the sliding characteristics over the entire range from low speed to high speed. It has been demanded.

For example, Patent Document 2 proposes a method of forming a fluororesin coating film on a rubber surface for the purpose of reducing sliding resistance of a seal lip portion of an oil seal.

By the way, Patent Document 3 discloses a seal lip provided with at least a main lip portion as an automotive transmission oil seal that uses fluororubber as an elastic member and has excellent sliding characteristics over the entire range from low speed running to high speed running. A transmission oil seal for automobiles having an elastic member having a portion, wherein the elastic member is made of a composition containing fluororubber and fluororesin, and has a convex portion at least on the surface of the main lip portion, The convex portion is substantially made of a fluororesin contained in the composition, and the fluororesin is a copolymer including a polymer unit based on ethylene and a polymer unit based on tetrafluoroethylene, and the fluororubber is An automotive transmitter characterized by being a polymer containing polymerized units based on vinylidene fluoride Deployment oil seal is disclosed.

JP 2005-61454 A JP 2006-292160 A International Publication No. 2011-1111631 Pamphlet

An object of the present invention is to provide a transmission oil seal for automobiles that is excellent in sliding characteristics over the entire region from low speed traveling to high speed traveling.

The present invention is an automobile transmission oil seal provided with an elastic member having a seal lip portion provided with at least a main lip portion, wherein the elastic member contains an acrylic rubber (A) and a fluororesin (B). And has at least a convex portion on the surface of the main lip portion, and the convex portion is substantially made of a fluororesin (B) contained in the composition, and the fluororesin (B) An automobile transmission oil seal characterized by being a copolymer containing a fluoroethylene unit (a) and a hexafluoropropylene unit (b).

The fluororesin (B) preferably has a melting point of 200 ° C. or lower.

The acrylic rubber (A) is a polymer comprising polymerized units based on at least one acrylate selected from the group consisting of ethyl acrylate, butyl acrylate, butoxyethyl acrylate, and methoxyethyl acrylate. It is preferable.

In the automobile transmission oil seal of the present invention, the area ratio of the region having the convex portion to the surface of the seal lip portion is 0.04 or more, and the volume ratio of the fluororesin (B) to the seal lip portion is 0.03 to 0.00. 45, and it is preferable that the area ratio of the region having the convex portion is 1.1 times or more the volume ratio of the fluororesin (B).

The convex portion preferably has a height of 0.1 to 30.0 μm.

The convex part preferably has a bottom cross-sectional area of 0.1 to 2000 μm ² .

It is preferable that the number of convex portions is 500 to 60000 pieces / mm ² .

The transmission oil seal for automobiles of the present invention includes an elastic member having a seal lip portion provided with a main lip portion, the elastic member is made of a specific composition, and at least the surface of the main lip portion is Since it has the convex part which consists of a fluororesin substantially contained in this specific composition, it will be excellent in a sliding characteristic over the whole area at the time of low speed driving | running | working at high speed.

It is sectional drawing which shows the usage aspect of the transmission oil seal for motor vehicles of this invention typically, and is an enlarged view of A area | region shown in FIG. It is sectional drawing which shows typically the transmission using the transmission oil seal for motor vehicles of this invention. It is a perspective view of the transmission oil seal for motor vehicles shown in FIG. (A) is a perspective view showing the shape of the convex portion of the sealing lip has schematically protrusions 31 in a plane containing the (b) is a straight line perpendicular B ₁ and the line B ₂ on the surface of (a) FIG. 6C is a cross-sectional view taken along a plane including a straight line C ₁ and a straight line C ₂ parallel to the surface of FIG. It is a schematic diagram of the oil seal torque tester used in the Example.

The transmission oil seal for automobiles of the present invention is an automobile transmission oil seal provided with an elastic member having a seal lip portion provided with at least a main lip portion, and the elastic member includes acrylic rubber (A) and a fluororesin. (B) and at least the surface of the main lip part has a convex part, and the convex part consists essentially of the fluororesin (B) contained in the composition, and the fluororesin (B) is a transmission oil seal for automobiles, which is a copolymer containing a tetrafluoroethylene unit (a) and a hexafluoropropylene unit (b).
Hereinafter, embodiments of a transmission oil seal for automobiles of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing how the transmission oil seal for automobiles of the present invention is used, and is an enlarged view of a region A shown in FIG. 2 is a cross-sectional view schematically showing a transmission using the automobile transmission oil seal of the present invention, and FIG. 3 is a perspective view of the automobile transmission oil seal shown in FIG. In addition, the transmission oil seal for automobiles in FIG. 1 is a drawing of a cross section taken along line AA in FIG.

As shown in FIGS. 1 to 3, the transmission oil seal 11 for an automobile of the present invention has an annular structure having a substantially (reverse) U-shaped radial cross section, and includes a fluororesin (B) and an acrylic rubber ( An elastic member 12 made of a composition containing A), an annular metal ring 16 and a ring spring 17 are provided.
The elastic member 12 has a seal lip portion provided with a main lip portion 13 having a radial cross-sectional wedge shape that contacts the axle 21 on the inner peripheral side, and a fitting portion 14 that closely contacts the housing 20 on the outer peripheral side. The metal ring 16 is built in the elastic member 12, and thereby plays a role of reinforcing the transmission oil seal 11 for automobiles. The ring spring 17 is disposed on the outer peripheral surface side of the main lip portion 13, and the main lip portion 13 comes into contact with the axle 21 by the urging force of the ring spring 17.

The automotive transmission oil seal 11 is arranged so that the ring spring 17 is exposed to the inside of the transmission 10, the main lip portion 13 slidably contacts the axle 21 of the transmission 10, and the fitting portion 14 is in close contact with the housing 20. And press fit into the gap between the axle 21 and the housing 20. In FIG. 2, 22 is a main shaft (input shaft) connected to the crankshaft, and 23 is a counter shaft (output shaft) arranged in parallel with the main shaft.

The transmission oil seal 11 for automobiles is slidably disposed not only on the axle 21 but also on the main shaft 22 and the counter shaft 23 as shown in FIG.

Here, the transmission oil seal 11 for automobiles has a convex portion on the surface of the seal lip portion 30 having the main lip portion 13 while the elastic member 12 is made of a composition containing a fluororesin (B) and an acrylic rubber (A). 31 (see FIG. 4). That is, the automobile transmission oil seal 11 has a convex portion 31 at a contact portion with the axle 21.

And since the transmission oil seal 11 for motor vehicles has the said convex part 31, a friction coefficient between shafts (an axle, a main shaft, a countershaft) is small, and it is excellent in a sliding characteristic.
Hereinafter, in the present specification, the term “shaft” simply includes an axle, a main shaft, and a counter shaft.
The effect of being excellent in the sliding characteristics can be exerted over the entire range from the low rotational speed to the high rotational speed regardless of the rotational speed of the shaft. I will explain this in more detail.
The material of the main lip portion 13 of the automobile transmission oil seal 11 is a composition containing a fluororesin (B) and an acrylic rubber (A). Therefore, it is excellent in sliding characteristics as compared with other conventionally known transmission oil seal materials for automobiles, such as nitrile rubber, acrylic rubber, acrylic rubber not containing fluororesin (B), and the like.
In addition, the automobile transmission oil seal 11 has a convex portion made of the above composition.
When the automobile transmission oil seal slides with respect to the shaft, it is known that oil is interposed (an oil film is formed) between the automobile transmission oil seal and the shaft. And it is thought that this oil functions as a lubricant between both. In other words, the transmission oil seal for automobiles can be slid with a low frictional resistance due to the presence of oil.
On the other hand, since it is a major premise that the transmission oil seal for automobiles functions as a seal material, the seal lip portion is in contact with the shaft without any gap. Therefore, in order for oil to intervene between the transmission oil seal for automobiles and the shaft from this state, the seal lip portion is deformed, and oil can enter between the seal lip portion and the shaft following this deformation. Necessary. Here, since the deformation of the seal lip portion follows the rotation of the shaft, the seal lip portion is also easily deformed when the shaft is rotating at a high rotation speed, and oil easily enters between the two. . On the other hand, when the rotational speed of the shaft is low, the seal lip portion is less likely to be deformed than when the rotational speed is high, and as a result, oil is interposed between the shaft and the seal lip portion. It becomes difficult.
Therefore, when the rotational speed of the shaft is low, the sliding characteristics tend to be inferior compared to the case of high rotational speed. Especially in the transmission oil seal for automobiles, the rotational speed of the shaft is particularly low. In some cases, improvement of sliding characteristics is desired.
On the other hand, the transmission oil seal for automobiles of the present invention has a convex portion on the surface of the seal lip portion as described above, and this essentially prevents oil from leaking out of the transmission. Microscopically, it has a very small gap between the seal lip portion and the shaft, and has a structure that easily deforms following the rotation of the shaft.
Therefore, in the transmission oil seal for automobiles of the present invention, oil is likely to intervene between the transmission oil seal for automobiles and the shaft, and the oil is slid over the entire range from the low rotation speed to the high rotation speed regardless of the rotation speed of the shaft. Excellent dynamic characteristics.

The said convex part consists of a fluororesin (B) substantially contained in the said composition. Since the fluororesin (B) has a much lower coefficient of friction than the acrylic rubber (A), the frictional resistance when contacting the shaft is much lower than that of the acrylic rubber (A). Such a convex part can be formed by depositing the fluororesin (B) contained in the composition on the surface, for example, by a method described later.
Therefore, the convex part and the elastic member 12 having the convex part are integrally formed, and an effect that it is difficult to drop off or to be lost when the shaft rotates is obtained.
Here, the fact that the convex portion is substantially made of the fluororesin (B) contained in the composition is to obtain the peak ratio derived from the acrylic rubber (A) and the fluororesin (B) by IR analysis or ESCA analysis. It can be shown that the convex portion is substantially made of the fluororesin (B). Specifically, in the region having the convex portion, the ratio of the characteristic absorption peak derived from the acrylic rubber (A) to the characteristic absorption peak derived from the fluororesin (B) (component-derived peak ratio = (acrylic) by IR analysis. Rubber (A) -derived peak intensity) / (fluorine resin (B) -derived peak intensity)) is measured at each of the convex part and outside the convex part, and the component-derived peak ratio outside the convex part is the convex part. It means that it is 2 times or more, preferably 3 times or more, relative to the component-derived peak ratio.

The shape of the protrusion will be described in more detail with reference to the drawings.
4 (a) is a perspective view showing the shape of the convex portion of the sealing lip has schematically, (b) is convex in a plane including the straight line B ₁ and the line B ₂ perpendicular to the surface of (a) is a cross-sectional view of the part 31 is a cross-sectional view taken along (c) is a plane including a surface parallel to the straight line C ₁ and the line C ₂ of the (a). 4A to 4C schematically depict a minute region on the surface of the seal lip portion. As shown in FIGS. 4A to 4C, for example, a substantially conical (cone-shaped) convex portion 31 is formed on the surface of the seal lip portion.

Here, the height of the convex portion 31 refers to the height of the portion protruding from the surface of the seal lip portion (see H in FIG. 4B). Further, the bottom cross-sectional area of the protrusions 31, the protrusions 31, protrusions 31 (FIG observed in cut surface with (a plane including the straight line C ₁ and the line C ₂₎ seal lip portion parallel to the surface plane 4 (c)) refers to the area value in the cross section.

It is preferable that the area ratio of the area | region which has a convex part is 0.03 (3%) or more with respect to the surface area of a seal lip part. A more preferable area ratio is 0.15 (15%) or more, and further preferably 0.30 (30%) or more. The area ratio of the region having the convex portion on the surface of the seal lip portion refers to the ratio of the area occupied by the convex portion in the cut surface for evaluating the bottom cross-sectional area of the convex portion.

In the seal lip part, the volume ratio of the fluororesin (B) is preferably 0.03 to 0.45 (3-45% by volume) with respect to the seal lip part. The lower limit of the volume ratio is more preferably 0.05 (5% by volume), and still more preferably 0.10 (10% by volume). The upper limit of the volume ratio is more preferably 0.40 (40% by volume), and still more preferably 0.35 (35% by volume).
The fluororesin (B) has excellent heat resistance. Therefore, since it is not decomposed by the molding cross-linking step and heat treatment step described later, the volume ratio is the volume ratio of the fluororesin (B) in the non-cross-linked acrylic rubber composition used to form the elastic member. It can be assumed that they are the same.

In the seal lip portion, the area ratio of the region having the convex portion is preferably 1.1 times or more, more preferably 1.2 times or more the volume ratio of the fluororesin (B). The ratio of the area | region which has a convex part in a seal lip part surface in a seal lip part is higher than the volume ratio of the fluororesin (B) of a seal lip part, and the fluororesin (B) in the uncrosslinked acrylic rubber composition mentioned later It becomes higher than the volume ratio.
Due to this feature, the seal lip has improved wear resistance, low friction and non-adhesiveness, which are disadvantages of acrylic rubber, even when the mixing ratio of fluororesin (B) is small. There is no damage and the compression set is small. In addition, the area ratio of the region having the above-described convex portion is determined according to the present invention as long as the seal lip portion is achieved in a portion where low friction, wear resistance, or non-adhesiveness is required depending on the application to be used. The effect of is fully demonstrated.

The convex part preferably has a height of 0.1 to 30.0 μm. When the height of the convex portion is within this range, low friction, wear resistance and non-adhesiveness are excellent. A more preferable height is 0.3 to 20.0 μm, and further preferably 0.5 to 15.0 μm.

The convex part preferably has a bottom cross-sectional area of 0.1 to 2000 μm ² . When the bottom cross-sectional area of the convex portion is within this range, wear resistance, low friction and non-adhesiveness are excellent. A more preferable bottom cross-sectional area is 0.3 to 1500 μm ² , and a still more preferable bottom cross-sectional area is 0.5 to 1000 μm ² .

The seal lip part preferably has a standard deviation of the height of the convex part of 0.300 or less. When in this range, wear resistance, low friction and non-adhesiveness are more excellent.

The number of convex portions of the seal lip portion is preferably 500 to 60000 pieces / mm ² . When in this range, wear resistance, low friction and non-adhesiveness are more excellent.

The area ratio, the height of the convex portion, the sectional area of the bottom portion of the convex portion, the number of convex portions, etc., for example, manufactured by Keyence Corporation, using a color 3D laser microscope (VK-9700) as analysis software WinRooF Ver. It can be calculated using 6.4.0. The area ratio of the region having the convex part is obtained as the ratio of the total cross-sectional area to the total cross-sectional area value obtained by calculating the bottom cross-sectional area of the convex part. The number of convex portions is obtained by converting the number of convex portions in the measurement region into a number per 1 mm ² .

In the seal lip portion, the convex portion may be formed on a part of the surface of the seal lip portion, and the surface of the seal lip portion may have a region where the convex portion is not formed. For example, the convex portion need not be formed in a portion where low friction and non-adhesiveness are not required.
Hereafter, each component which comprises the engine oil seal for motor vehicles of this invention is explained in full detail.

(A) Acrylic rubber The acrylic rubber (A) is a polymer composed of polymerized units based on an acrylate ester. The acrylic rubber (A) may be a homopolymer composed of polymer units based on one kind of acrylate ester, or may be a copolymer composed of polymer units based on two or more kinds of acrylate esters. The copolymer which consists of a polymer unit based on the seed | species or 2 or more types of acrylic ester, and a polymer unit based on the monomer copolymerizable with an acrylic ester may be sufficient.
Acrylic rubber (A) can adjust normal physical property, cold resistance, oil resistance, etc. by selecting the kind of acrylic ester and the quantity of a polymerization unit.

The acrylic acid ester is preferably an acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms or an acrylic acid alkoxyalkyl ester having an alkoxyalkyl group having 1 to 12 carbon atoms.
Examples of the acrylic acid alkyl ester include methyl acrylate, ethyl acrylate, n-butyl acrylate, n-propyl acrylate, isobutyl acrylate, n-pentyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-methylpentyl acrylate, and n-octyl. Examples include acrylate, 2-ethylhexyl acrylate, n-decyl acrylate, n-dodecyl acrylate, and n-octadecyl acrylate.
Examples of the alkoxyalkyl acrylate include 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, 2- (n-propoxy) ethyl acrylate, 2- (n-butoxy) ethyl acrylate, 3-methoxypropyl acrylate, 3-ethoxypropyl Examples thereof include acrylate, 2- (n-propoxy) propyl acrylate, 2- (n-butoxy) propyl acrylate and the like.

The cold resistance and oil resistance of the transmission oil seal for automobiles of the present invention can be adjusted by adjusting the amount of polymerized units based on these acrylate esters.
For example, increasing the copolymerization ratio of n-butyl acrylate can improve cold resistance. Moreover, oil resistance can be improved by increasing the copolymerization ratio of ethyl acrylate.

The acrylic rubber (A) is also preferably a copolymer comprising polymerized units based on an acrylate ester and polymerized units based on a monomer copolymerizable with the acrylate ester.

The monomer copolymerizable with the acrylate ester is at least one monomer selected from the group consisting of methacrylate ester, vinyl acetate, cross-linking site-containing monomer (excluding vinyl acetate), and ethylene. The body is preferred.

Examples of methacrylic acid esters include methacrylic acid alkyl esters and methacrylic acid alkoxyalkyl esters. The methacrylic acid ester is preferably, for example, a methacrylic acid alkyl ester having an alkyl group having 2 to 14 carbon atoms or a methacrylic acid alkyl ester having an alkoxyalkyl group having 2 to 14 carbon atoms.

Vinyl acetate is used to maintain mechanical properties such as elongation of the elastic member by cross-linking the molecules when the acrylic rubber composition for forming the elastic member is thermally aged. By adjusting the blending amount of vinyl acetate, the intermolecular crosslinking of the elastic member can be adjusted.
An elastic member may have its main chain cut by the influence of heat, ultraviolet rays, or the like, and mechanical properties such as tensile strength and elongation at break may be reduced. Therefore, when vinyl acetate having a carboxyl group that easily undergoes a crosslinking reaction is copolymerized with the main chain of the acrylic rubber (A), when the main chain of the acrylic rubber is broken, a polymer unit based on vinyl acetate is obtained. The inside carboxyl group becomes a cross-linking site (cross-linking site), and the broken molecules can be cross-linked again.

The polymer unit based on vinyl acetate is preferably 15% by mass or less based on the total polymer units constituting the acrylic rubber (A). When the content of the polymerized units based on vinyl acetate is within this range, it is possible to suppress the deterioration of the mechanical properties while maintaining the heat aging resistance of the elastic member.

The crosslinking site-containing monomer is copolymerized with acrylic rubber as necessary, and is for adjusting the hardness and elongation characteristics of the resulting acrylic rubber by promoting intermolecular crosslinking.

The crosslinking site-containing monomer is preferably a monomer having at least one selected from the group consisting of an active chlorine group, an epoxy group, a carboxyl group, and a hydroxyl group (excluding the hydroxyl group contained in the carboxyl group).

Although the crosslinking site-containing monomer is not particularly limited, for example, a monomer having an active chlorine group such as 2-chloroethyl vinyl ether, 2-chloroethyl acrylate, vinyl benzyl chloride, vinyl chloroacetate, and allyl chloroacetate. Monomers containing carboxyl groups such as acrylic acid, methacrylic acid, crotonic acid, 2-pentenoic acid, maleic acid, fumaric acid, itaconic acid, maleic acid monoalkyl ester, fumaric acid monoalkyl ester and cinnamic acid; glycidyl Examples include monomers containing an epoxy group such as acrylate, glycidyl methacrylate, allyl glycidyl ether, and methallyl glycidyl ether.

The polymer unit based on the crosslinking site-containing monomer is preferably 10% by mass or less, more preferably 5% by mass or less, based on all polymer units constituting the acrylic rubber (A). When the polymerization unit based on the crosslinking site-containing monomer is used in this range, it can be efficiently crosslinked, without losing rubber elasticity, and the elastic member has excellent strength. When the polymerized unit based on the crosslinking site-containing monomer exceeds 10% by mass, the obtained crosslinked product may be cured and lose rubber elasticity.

The acrylic rubber (A) can be copolymerized with other monomers copolymerizable with these monomers as long as the object of the present invention is not impaired. Other monomers that can be copolymerized are not particularly limited. For example, alkyl vinyl ketones such as methyl vinyl ketone; vinyl ethers or allyl ethers such as vinyl ethyl ether and allyl methyl ether; styrene, α-methyl styrene Vinyl aromatic compounds such as chlorostyrene, vinyl toluene and vinyl naphthalene; vinyl nitriles such as acrylonitrile and methacrylonitrile; acrylamide, propylene, butadiene, isoprene, pentadiene, vinyl chloride, vinylidene chloride, vinyl fluoride, vinylidene fluoride, Examples thereof include ethylenically unsaturated compounds such as ethylene and vinyl propionate.

When the acrylic rubber (A) has a polymerized unit based on ethylene, the polymerized unit based on ethylene is preferably 50% by mass or less based on all polymerized units constituting the acrylic rubber (A). By copolymerizing ethylene, an acrylic rubber with significantly improved strength can be obtained.

The acrylic rubber (A) can be obtained by copolymerizing the above monomers by a known method such as emulsion polymerization, suspension polymerization, solution polymerization, bulk polymerization and the like.

The acrylic rubber (A) has 40 to 95% by mass of polymerized units based on acrylic acid esters based on all polymerized units, and consists of an active chlorine group and a hydroxyl group (excluding the hydroxyl group contained in the carboxyl group). The polymerization unit based on a monomer having at least one group selected from the group is preferably 1 to 20% by mass. More preferably, the polymerized unit based on an acrylate ester is 50 to 90% by mass, and is at least one group selected from the group consisting of an active chlorine group and a hydroxyl group (excluding the hydroxyl group contained in the carboxyl group). The polymerized units based on the monomer having a content of 2 to 10% by mass.

The acrylic rubber (A) is obtained by, for example, a latex obtained by the following polymerization method, coagulating the polymer by a normal salting out operation, washing with water, and drying the polymer obtained by a crosslinking method described later. It can be obtained by crosslinking. As a salting-out agent, salt etc. can be used.

In a 2 liter beaker, 5.0 g of an anionic emulsifier, dioctylsulfosuccinate sodium salt is dissolved in 1250 g of deionized water, and 300 g of the monomer mixture constituting the acrylic rubber is added thereto and emulsified using a small mixer. Next, the monomer emulsion is introduced into a polymerization vessel with a 2-liter reflux condenser, and the temperature is raised to 70 ° C. under a nitrogen stream. To this, 10 g of a 10% aqueous solution of ammonium persulfate is added to initiate polymerization. After the start of polymerization, the temperature in the polymerization vessel is increased from the initial 70 ° C. to 80 ° C., and maintained in the range of 80 to 82 ° C. for 2 hours to complete the polymerization reaction.

(B) Fluororesin The fluororesin (B) is a copolymer (hereinafter also referred to as “FEP”) containing a tetrafluoroethylene unit (a) and a hexafluoropropylene unit (b). By using the fluororesin (B), it is possible to form a convex portion substantially made of the fluororesin (B) on the surface of the seal lip, and as a result, over the entire range from low speed to high speed. An automobile transmission oil seal having excellent sliding characteristics can be obtained.

FEP is based on a copolymer consisting only of TFE units (a) and HFP units (b), or TFE units (a), HFP units (b), and monomers copolymerizable with TFE and HFP. It is a copolymer comprising polymerized units. FEP is also advantageous in that the heat resistance of an automobile transmission oil seal is excellent.

When FEP is a copolymer composed of TFE units (a), HFP units (b), and polymerized units based on monomers copolymerizable with TFE and HFP, the copolymer can be copolymerized with TFE and HFP. As a polymer, the following formula:
CF ₂ = CF-ORf ⁶
(Wherein Rf ⁶ represents a C 1-5 perfluoroalkyl group) perfluoro (alkyl vinyl ether) [PAVE] represented by the following formula:
CX ⁵ X ⁶ = CX ⁷ (CF ₂ ) _n X ⁸
(Wherein X ⁵ , X ⁶ and X ⁷ are the same or different and represent a hydrogen atom or a fluorine atom, X ⁸ represents a hydrogen atom, a fluorine atom or a chlorine atom, and n represents an integer of 2 to 10) And a vinyl monomer represented by the following formula:
_{CF 2 = CF-OCH 2 -Rf} 7
(Wherein Rf ⁷ represents a perfluoroalkyl group having 1 to 5 carbon atoms), and the like. The monomer copolymerizable with TFE and HFP is preferably a perfluoromonomer, more preferably PAVE, because the friction resistance and non-stickiness of the automotive transmission oil seal are more excellent. preferable.
The fluororesin (B) is preferably at least one copolymer selected from the group consisting of a TFE / HFP copolymer and a TFE / HFP / PAVE copolymer, for example.

The PAVE is selected from the group consisting of perfluoro (methyl vinyl ether) [PMVE], perfluoro (ethyl vinyl ether) [PEVE], perfluoro (propyl vinyl ether) [PPVE], and perfluoro (butyl vinyl ether). It is preferably at least one, and more preferably at least one selected from the group consisting of PMVE, PEVE and PPVE.

The fluororesin (B) is preferably a perfluorofluororesin from the viewpoints of low friction and non-adhesiveness.

Although melting | fusing point of a fluororesin (B) is suitably determined by the kind of acrylic rubber (A), it is preferable that it is 200 degrees C or less, and it is more preferable that it is 190 degrees C or less. If the melting point is too high, the fluororesin does not melt at the time of cross-linking molding, and there is a possibility that a molded product having a desired shape cannot be obtained. Moreover, when forming the convex part which is mentioned later on the surface of a seal lip part, there exists a possibility that the seal lip part which has a sufficient number of convex parts may not be obtained. Moreover, although a minimum is not specifically limited, For example, it may be 150 degreeC. Further, the melting point of the fluororesin (B) may be equal to or higher than the crosslinking temperature of the acrylic rubber (A).
Furthermore, when the melting point of the fluororesin (B) is in the above range, the low compression set of the elastic member can be improved. Therefore, an automobile transmission oil seal having excellent sealing properties can be obtained.
The melting point of the fluororesin is measured using a differential scanning calorimeter at a rate of temperature increase of 10 ° C./min in accordance with ASTM D-4591. Once the endothermic end point temperature of the melting point peak reaches 30 ° C., the temperature decreases. The temperature is lowered to 50 ° C. at a rate of −10 ° C./min, the temperature is raised again to the endothermic end temperature + 30 ° C. at a temperature rising rate of 10 ° C./min, and the peak temperature of the obtained endothermic curve is taken as the melting point.

The fluororesin (B) preferably has a melt flow rate [MFR] at 280 ° C. of 0.3 to 200 g / 10 minutes, more preferably 1 to 100 g / 10 minutes. If the MFR is too small, the wear resistance may be inferior, and if the MFR is too large, molding may be difficult.
The MFR is a value obtained by measuring at a temperature of 280 ° C. and a load of 5 kg in accordance with ASTM D3307-01.

The fluororesin (B) preferably has a storage elastic modulus (E ′) at 70 ° C. by dynamic viscoelasticity measurement of 10 to 160 MPa from the viewpoint of reducing the compression set of the seal lip portion.
The storage elastic modulus is a value measured at 70 ° C. by dynamic viscoelasticity measurement. More specifically, a sample having a length of 30 mm, a width of 5 mm, and a thickness of 0.5 mm is pulled using a dynamic viscoelastic device DVA220 manufactured by IT-Measurement Control Co., Ltd. It is a value measured under conditions of a speed of 2 ° C./min and a frequency of 1 Hz. A preferable storage elastic modulus (E ′) at 70 ° C. is 10 to 160 MPa, a more preferable storage elastic modulus (E ′) is 20 to 140 MPa, and a further preferable storage elastic modulus (E ′) is 30 to 100 MPa.

From the viewpoint of further reducing the compression set of the seal lip, the fluororesin (B) is at least one selected from the group consisting of the following fluororesins (B1) and (B2) having a specific composition. Is preferred.
The fluororesins (B1) and (B2) are copolymers composed of tetrafluoroethylene units and hexafluoropropylene units having a specific composition. By using the fluororesin (B1) or (B2) having a specific composition, the low compression set of the elastic member can be improved without impairing the low friction and non-adhesiveness of the seal lip surface. .

The fluororesin (B1) is a polymer composed only of tetrafluoroethylene (TFE) units (a) and hexafluoropropylene (HFP) units (b), and the TFE units (a) / HFP units (b) It is a copolymer having a ratio of 80.0 to 87.3 / 12.7 to 20.0. When the fluororesin (B1) having the composition in the specific range is used, low friction and non-tackiness can be imparted to the seal lip portion without deteriorating the compression set of the elastic member.

The fluororesin (B1) has a molar ratio of 82.0 to 87.0 / from the viewpoint of not deteriorating the compression set of the elastic member and improving the mechanical properties. It is preferably 13.0 to 18.0, more preferably 83.0 to 86.5 / 13.5 to 17.0, and 83.0 to 86.0 / 14.0 to 17.0. More preferably. If (a) / (b) is too large, the compression set of the elastic member may be impaired. If (a) / (b) is too small, the mechanical properties tend to decrease.

The fluororesin (B2) is a copolymer comprising a TFE unit (a), an HFP unit (b), and a polymerized unit (c) based on a monomer copolymerizable with TFE and HFP, (a) / (B) is 80.0-90.0 / 10.0-20.0 in molar ratio, and (c) / {(a) + (b)} is 0.1-10 in molar ratio. 0.0 / 90.0-99.9 (where {(a) + (b)} means the total of TFE units (a) and HFP units (b)). . (A) / (b) is 80.0 to 90.0 / 10.0 to 20.0 in molar ratio, and (c) / {(a) + (b)} is 0.0 in molar ratio. By being 1-10.0 / 90.0-99.9, low friction property and non-adhesiveness can be imparted to the seal lip portion without deteriorating the compression set of the elastic member.

The fluororesin (B2) has a molar ratio of (8) to 88.0 / 12.0 in terms of (a) / (b) from the viewpoint of further reducing the compression set and improving the mechanical properties. It is preferably ˜18.0.

As for a fluororesin (B2), it is preferable that (c) / {(a) + (b)} is 0.3-8.0 / 92.0-99.7 in molar ratio.

The monomers copolymerizable with TFE and HFP are the same as described above.

In the fluororesin (B2), the polymerized unit (c) based on the monomer copolymerizable with TFE and HFP is preferably a PAVE unit. The fluororesin (B2) is more preferably a copolymer composed only of TFE units, HFP units, and PAVE units.

The composition containing the acrylic rubber (A) and the fluororesin (B) is a usual additive blended in the acrylic rubber as necessary, for example, a filler, a processing aid, a plasticizer, a colorant, a stabilizer. , Adhesive aids, mold release agents, conductivity-imparting agents, thermal conductivity-imparting agents, surface non-adhesives, flexibility-imparting agents, heat resistance improvers, flame retardants, etc. These additives may be used as long as the effects of the present invention are not impaired.

Next, the manufacturing method of the transmission oil seal for automobiles of the present invention will be described. The transmission oil seal for automobiles having the convex portion on the surface of the seal lip portion can be manufactured by a manufacturing method described later.

The transmission oil seal for automobiles of the present invention comprises (I) co-coagulated uncrosslinked acrylic rubber (A1) and fluororesin (B) to obtain a co-coagulated composition; (II) molding and crosslinking an uncrosslinked acrylic rubber composition to obtain a crosslinked molded product, and (III) heating the crosslinked molded product to a temperature equal to or higher than the melting point of the fluororesin (B). An elastic member having a predetermined shape can be manufactured by a method including a heat treatment step, and a metal ring can be incorporated or a ring spring can be provided as necessary. In addition, uncrosslinked acrylic rubber (A1) is acrylic rubber (A) before bridge | crosslinking.

Hereinafter, each step will be described.

(I) Process This process is a process of obtaining a non-crosslinked acrylic rubber composition after co-coagulating the uncrosslinked acrylic rubber (A1) and the fluororesin (B) to obtain a co-coagulated composition.

Examples of the co-coagulation method include: (i) a method of coagulating after mixing an aqueous dispersion of uncrosslinked acrylic rubber (A1) and an aqueous dispersion of fluororesin (B); Method of coagulating after adding powder of crosslinked acrylic rubber (A1) to fluororesin (B), (iii) Adding powder of fluororesin (B) to aqueous dispersion of uncrosslinked acrylic rubber (A1) The method of coagulating later is mentioned.

As the co-coagulation method, the above method (i) is particularly preferable in that each resin is easily dispersed uniformly.

The coagulation in the coagulation methods (i) to (iii) can be performed using a flocculant, for example. Such a flocculant is not particularly limited, and examples thereof include aluminum salts such as aluminum sulfate and alum, calcium salts such as calcium sulfate, magnesium salts such as magnesium sulfate, sodium chloride and potassium chloride. Known aggregating agents such as valent cation salts can be mentioned. When coagulating with a flocculant, the pH may be adjusted by adding an acid or an alkali in order to promote aggregation.

Since a crosslinking agent is required depending on the crosslinking system of the acrylic rubber, the step (I) is after co-coagulating the uncrosslinked acrylic rubber (A1) and the fluororesin (B) to obtain a co-coagulated composition. The step of obtaining an acrylic rubber composition by mixing the co-coagulated composition and the crosslinking agent is also preferred.
The cross-linking agent may be appropriately selected depending on the type of acrylic rubber and the like, and a cross-linking agent generally used for cross-linking of the acrylic rubber composition can be used. A crosslinking agent may not be used depending on the type of acrylic rubber.

The co-coagulation composition and the crosslinking agent can be mixed by a conventionally known method. For example, the coaggregating composition and the cross-linking agent may be mixed using an open roll at a time and temperature sufficient to be mixed.
Moreover, you may mix not only a crosslinking agent but an acid acceptor, a crosslinking accelerator, a subsidiary material, etc.

Although the addition amount of a crosslinking agent is not specifically limited, 0.1-10 mass parts is preferable with respect to 100 mass parts of uncrosslinked acrylic rubber compositions. When the addition amount is in the above range, sufficient crosslinking treatment can be performed. If the amount of the crosslinking agent is less than 0.1 parts by mass, the uncrosslinked acrylic rubber composition becomes insufficiently crosslinked, and mechanical properties such as tensile strength and elongation at break of the resulting crosslinked product may be deteriorated. Moreover, when it exceeds 10 mass parts, there exists a possibility that the crosslinked material obtained may be hardened and may lose elasticity.

The crosslinking agent is preferably at least one selected from the group consisting of polyamine compounds, imidazole compounds, and peroxides. When the uncrosslinked acrylic rubber (A1) includes a polymer unit based on a crosslinking site-containing monomer, an appropriate crosslinking agent may be selected according to the crosslinking site-containing monomer.

For example, when the crosslinking site-containing monomer is a monomer having a carboxyl group, a polyamine compound is preferred as the crosslinking agent, and a guanidine compound is preferably used as the crosslinking accelerator.

Examples of the polyamine compound include 4,4′-bis (4-aminophenoxy) biphenyl, 4,4′-diaminodiphenyl sulfide, 1,3-bis (4-aminophenoxy) -2,2-dimethylpropane, 1,3. -Bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) pentane, 2,2-bis [4- (4-aminophenoxy) Phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] sulfone, 4,4′-diaminodiphenylsulfone, bis (4-3-aminophenoxy) phenyl sulfone, 2,2-bis [ 4- (4-Aminophenoxy) phenyl] hexafluoropropane, 3,4'-diaminodiphenyl ether, 4,4'-diamy Aromatic polyamine compounds such as diphenyl ether, 4,4′-diaminobenzanilide, bis [4- (4-aminophenoxy) phenyl] sulfone, hexamethylene diamine, hexamethylene diamine carbamate, N, N′-dicinenamilidene-1,6 -Aliphatic polyamine compounds such as hexanediamine, diethylenetriamine, triethylenetetramine, and tetraethylenepentamine.

Examples of the guanidine-based compound include guanidine, tetramethylguanidine, dibutylguanidine, diphenylguanidine, di-o-tolylguanidine and the like.

When the crosslinking site-containing monomer is a monomer having an epoxy group, the crosslinking agent is preferably an imidazole compound. Examples of imidazole compounds include 1-methylimidazole, 1,2-dimethylimidazole, 1-methyl-2-ethylimidazole, 1-benzyl-2-methylimidazole, 1-benzyl-2-ethylimidazole, 1-benzyl-2- Ethyl-5-methylimidazole, 1-benzyl-2-phenylimidazole, 1-benzyl-2-phenylimidazole trimellitic acid salt, 1-aminoethylimidazole, 1-aminoethyl-2-methylimidazole, 1-aminoethyl 2-ethylimidazole, 1-cyanoethyl-2-methylimidazole, 1-cyanoethyl-2-phenylimidazole, 1-cyanoethyl-2-ethyl-4-methylimidazole, 1-cyanoethyl-2-undecylimidazole, 1 -Cyanoethyl-2-me Ruimidazole trimellitate, 1-cyanoethyl-2-phenylimidazole trimellitate, 1-cyanoethyl-2-ethyl-4-methylimidazole trimellitate, 1-cyanoethyl-2-undecyl-imidazole trimellitate, 2,4 -Diamino-6- [2'-methylimidazolyl- (1) '] ethyl-s-triazine isocyanuric acid adduct, 1-cyanoethyl-2-phenyl-4,5-di- (cyanoethoxymethyl) imidazole, N- (2-methylimidazolyl-1-ethyl) urea, N, N′-bis- (2-methylimidazolyl-1-ethyl) urea, 1- (cyanoethylaminoethyl) -2-methylimidazole, N, N ′ -[2-Methylimidazolyl- (1) -ethyl] -aziboyldiamide, N, N '-[2- Tylimidazolyl- (1) -ethyl] -dodecandioyldiamide, N, N ′-[2-methylimidazolyl- (1) -ethyl] -eicosanedioyldiamide, 2,4-diamino-6- [2′- Methylimidazolyl- (1) ′)-ethyl-s-triazine, 2,4-diamino-6- [2′-undecylimidazolyl- (1) ′]-ethyl-s-triazine, 1-dodecyl-2-methyl Examples include -3-benzylimidazolium chloride and 1,3-dibenzyl-2-methylimidazolium chloride.

When the crosslinking site-containing monomer is a monomer having an epoxy group, as a crosslinking accelerator, a curing agent for epoxy resin, for example, pyrolysis ammonium salt, organic acid, acid anhydride, amines, sulfur and sulfur compounds, etc. Can be used.

When the crosslinking site-containing monomer is not used, the crosslinking agent is preferably a peroxide. Examples of the peroxide include 3-chlorobenzoyl peroxide, t-butyl cumyl peroxide, dicumyl peroxide, cumene hydroperoxide, benzoyl peroxide, 2,4-dichloro-benzoyl peroxide, t-butyl peroxide, t-butyl hydro Peroxide, 1,1-di- (t-butylperoxy) -3,3,5-trimethylcyclohexane, n-butyl-4,4-di- (t-butylperoxy) -valerate, dicumyl peroxide, di-t -Butylperoxy-isopropylbenzene, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne, 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, 2,2-bis (T-butylperoxy) -4-diisopropylbenzene, 1,3-bi (T-butylperoxy) -4-diisopropylbenzene and the like.

The amount of peroxide added is, for example, preferably 5 to 10 parts by mass, more preferably 6 to 10 parts by mass with respect to 100 parts by mass of the uncrosslinked acrylic rubber composition.
If the amount of peroxide added is less than 5 parts by mass, crosslinking is insufficient, and mechanical properties such as tensile strength and elongation at break of the resulting elastic member may be reduced. Moreover, when it exceeds 10 mass parts, the obtained elastic member will harden | cure and there exists a possibility that elasticity may be impaired.

Depending on the type of the uncrosslinked acrylic rubber (A1), crosslinking may be performed by blending an acid acceptor and a crosslinking accelerator without using a crosslinking agent.

As the acid acceptor, for example, a metal oxide, a metal hydroxide, or the like can be used. Examples of the metal oxide include magnesium oxide, zinc oxide, calcium oxide and the like. Examples of the metal hydroxide include magnesium hydroxide, zinc hydroxide, calcium hydroxide, and aluminum hydroxide.

As the crosslinking accelerator, a quaternary ammonium salt or a quaternary phosphonium salt can also be used. Examples of the quaternary ammonium salt include tetraethylammonium chloride, tetraethylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium bromide, n-dodecyltrimethylammonium chloride, n-dodecyltrimethylammonium bromide, octadecyltrimethylammonium bromide, cetyldimethylammonium. Examples include chloride, 1,6-diaza-bicyclo (5.4.0) undecene-7-cetylpyridium sulfate, trimethylbenzylammonium benzoate, and the like. Examples of the quaternary ammonium salt include triphenylbenzylphosphonium chloride, triphenylbenzylphosphonium bromide, tricyclohexylbenzylphosphonium chloride, tricyclohexylbenzylphosphonium bromide and the like.

The hydroxyl group that the crosslinking site-containing monomer may have is preferably a phenolic hydroxyl group, and the crosslinking site-containing monomer having a phenolic hydroxyl group includes α-methyl-o-hydroxystyrene, o-cabycol, p, m-hydroxy. Examples include vinyl benzoate, vinyl salicylate, eugenol, isoeugenol, p-isopropenylphenol, o, m, p-allylphenol, 2,2- (o, m, p-hydroxyphenyl-4-vinylacetyl) propane, and the like. It is done.

Examples of the crosslinking site-containing monomer having an active chlorine group include o, m, p-hydroxystyrene, 2-chloroethyl vinyl ether, vinyl monochloroacetate, chloromethyl styrene, and allyl chloride.

The uncrosslinked acrylic rubber composition obtained in the step (I) has a volume ratio (uncrosslinked acrylic rubber (A1)) / (fluororesin (B)) between the uncrosslinked acrylic rubber (A1) and the fluororesin (B). 97/3 to 55/45. The uncrosslinked acrylic rubber composition slides over the entire range from low speed to high speed when the volume ratio (uncrosslinked acrylic rubber (A1)) / (fluororesin (B)) is in the above range. An automobile transmission oil seal having excellent characteristics can be provided.
If the amount of the fluororesin (B) is too small, the sliding characteristics of the automotive transmission oil seal may not be sufficient, and if the amount of the fluororesin (B) is too large, the flexibility of the automotive transmission oil seal may not be sufficient. There is. The volume ratio of uncrosslinked acrylic rubber (A1) to fluororesin (B) (uncrosslinked acrylic rubber (A1)) / (fluorine) because the sliding characteristics and flexibility of the resulting automobile transmission oil seal are well balanced. The resin (B)) is preferably 95/5 to 60/40, more preferably 90/10 to 65/35.

The uncrosslinked acrylic rubber composition contains the uncrosslinked acrylic rubber (A1) and the fluororesin (B), and if necessary, a crosslinking agent, a crosslinking accelerator, an acid acceptor, etc., and further for improving compatibility. , It may contain at least one polyfunctional compound. The polyfunctional compound is a compound having two or more functional groups having the same or different structures in one molecule.

The uncrosslinked acrylic rubber composition may contain at least one polyfunctional compound for improving compatibility between the fluororesin (B) and the uncrosslinked acrylic rubber (A1). The polyfunctional compound is a compound having two or more functional groups having the same or different structures in one molecule.

The functional groups possessed by the polyfunctional compound include carbonyl groups, carboxyl groups, haloformyl groups, amide groups, olefin groups, amino groups, isocyanate groups, hydroxy groups, epoxy groups, etc., which are generally known to have reactivity. Any group can be used. The compound having these functional groups not only has high affinity with the uncrosslinked acrylic rubber (A1), but also reacts with functional groups known to have the reactivity possessed by the fluororesin (B). It is expected that the solubility will be improved.

The uncrosslinked acrylic rubber composition may further contain a secondary material added to a normal rubber compound.

Secondary materials include anti-aging agents (eg, diphenylamine derivatives, phenylenediamine derivatives), processing aids (eg, stearic acid), fillers (eg, carbon black, kaolin clay, talc, diatomaceous earth, etc.), plastics Various additives such as agents, colorants, stabilizers, adhesion aids, mold release agents, conductivity imparting agents, thermal conductivity imparting agents, surface non-adhesives, flexibility imparting agents, heat resistance improvers, flame retardants, etc. Is mentioned. These auxiliary materials may be used within a range not impairing the effects of the present invention.

The uncrosslinked acrylic rubber composition includes, for example, the uncrosslinked acrylic rubber (A1) and the fluororesin (B), and a crosslinking agent, a crosslinking accelerator, an acid acceptor, an auxiliary material and the like used as necessary. It can be obtained by kneading with a general open mill roll, an internal mixer or the like used in the rubber industry. By such a method, an acrylic rubber composition is obtained as pellets or the like. When using a co-coagulated composition obtained by co-coagulation of uncrosslinked acrylic rubber (A1) and fluororesin (B), co-coagulated uncrosslinked acrylic rubber (A1) and fluororesin (B) After the co-coagulated composition is obtained, the co-coagulated composition may be kneaded with the acid acceptor, the crosslinking accelerator, the auxiliary material, and the like.

(II) Molding / Crosslinking Step This step is a step for producing a crosslinked molded product having substantially the same shape as the elastic member to be produced by molding and crosslinking the uncrosslinked acrylic rubber composition obtained in the step (I). The order of molding and crosslinking is not limited, and may be crosslinked after molding, may be molded after crosslinking, or may be molded and crosslinked simultaneously.

Examples of the molding method include, but are not limited to, a pressure molding method using a mold or the like, an injection molding method, and the like.

As the crosslinking method, a steam crosslinking method, a pressure molding method, a normal method in which a crosslinking reaction is started by heating, a radiation crosslinking method, or the like can be adopted.

The molding and crosslinking methods and conditions may be within the range of known methods and conditions for the molding and crosslinking employed. Further, the molding and the crosslinking may be performed in any order, or may be performed in parallel at the same time.

The temperature at which crosslinking is performed is not less than the crosslinking temperature of the acrylic rubber (A) and is preferably less than the melting point of the fluororesin (B). If the crosslinking is performed at a melting point or higher of the fluororesin (B), the fluororesin (B) is melted at the time of cross-linking molding, and a seal lip portion having a sufficient number of convex portions may not be obtained. More preferably, the crosslinking temperature is less than 5 ° C. lower than the melting point of the fluororesin (B) and not less than the crosslinking temperature of the acrylic rubber (A). The crosslinking time is, for example, 1 minute to 24 hours, and may be appropriately determined depending on the type of the crosslinking agent used.

Further, when manufacturing an automobile transmission oil seal provided with a metal ring as an automobile transmission oil seal, in this step (II), for example, a metal ring is previously placed in a mold and integrated molding is performed. Just do it.

In the crosslinking of uncrosslinked rubber, a post-treatment process called secondary crosslinking may be performed after the first crosslinking treatment (referred to as primary crosslinking), which will be described in the next heat treatment step (III). As described above, the conventional secondary crosslinking step is different from the molding crosslinking step (II) and the heat treatment step (III) of the present invention.

(III) Heat treatment step In this heat treatment step (III), the obtained crosslinked molded product is heated to a temperature not lower than the melting point of the fluororesin (B). Through the heat treatment step (III), convex portions (mainly made of fluororesin (B)) can be formed on the surface of the elastic member to be manufactured.

The heat treatment step (III) is a treatment step performed to increase the ratio of the fluororesin (B) on the surface of the cross-linked molded product, and in accordance with this purpose, the melting point of the fluororesin (B) and the acrylic rubber (A) and A temperature lower than the thermal decomposition temperature of the fluororesin (B) is employed as the heating temperature.

When the heating temperature is lower than the melting point of the fluororesin (B), the convex portions of the fluororesin (B) are not sufficiently formed on the surface of the crosslinked molded product. In order to avoid thermal decomposition of the acrylic rubber (A) and the fluororesin (B), the temperature must be lower than the thermal decomposition temperature of the acrylic rubber (A) or the fluororesin (B), whichever is lower. A preferable heating temperature is a temperature that is 5 ° C. or more higher than the melting point of the fluororesin (B) from the viewpoint of easily reducing friction in a short time.

In the heat treatment step (III), the heating temperature is closely related to the heating time. When the heating temperature is relatively close to the lower limit, the heating is performed for a relatively long time, and when the heating temperature is relatively close to the upper limit, the heating is relatively short. It is preferable to employ time.

In the elastic member manufactured through the steps (I) to (III), a convex portion is formed on the entire surface. However, in the automobile transmission oil seal of the present invention, at least the surface of the seal lip portion. As long as a convex portion is formed on the surface of the sealing lip portion, the convex portion may not be provided on a portion other than the surface of the seal lip portion. And when manufacturing the elastic member of such an aspect, what is necessary is just to remove the convex part of an unnecessary part by grinding | polishing etc. after performing the process of said (III), for example.

By the way, in the conventional secondary crosslinking, the crosslinking agent remaining at the end of the primary crosslinking is completely decomposed to complete the rubber crosslinking, thereby improving the mechanical characteristics and compression set characteristics of the crosslinked molded product. This is a process performed for this purpose.

Therefore, the conventional secondary crosslinking conditions that do not assume the coexistence of the fluororesin (B) are present in the secondary crosslinking even if the crosslinking conditions accidentally overlap with the heating conditions of the heat treatment step in the present invention. Is not used as a factor for setting the crosslinking conditions, but only the heating conditions within the range of the purpose of complete crosslinking of the uncrosslinked rubber (complete decomposition of the crosslinking agent) are adopted, and the fluororesin (B) is blended. In such a case, conditions for heat softening or melting the fluororesin (B) in a crosslinked rubber (not an uncrosslinked rubber) cannot be derived.

In addition, in the shaping | molding bridge | crosslinking process (II) in this invention, you may perform secondary bridge | crosslinking in order to complete bridge | crosslinking of uncrosslinked acrylic rubber (A1) (in order to decompose | disassemble a crosslinking agent completely).

Further, in the heat treatment step (III), the remaining crosslinking agent may be decomposed and the crosslinking of the uncrosslinked acrylic rubber (A1) may be completed, but the crosslinking of the uncrosslinked acrylic rubber (A1) in the heat treatment step (III) may be completed. Is only a secondary effect.

In addition, after performing the said heat processing process (III), you may perform the process of arrange | positioning a ring spring as needed.

The transmission oil seal for automobiles obtained by the manufacturing method including the step (I), the molding / crosslinking step (II), and the heat treatment step (III) is convex on the surface of the elastic member due to the surface migration phenomenon of the fluororesin (B). It is presumed that the ratio of the fluororesin (B) is increased in the surface region (including the inside of the convex portion) while the portion is formed.

In addition, the transmission oil seal for automobiles of the present invention is uncrosslinked by powder-mixing powders obtained by coagulating each of the uncrosslinked acrylic rubber (A1) and the fluororesin (B) instead of the step (I). It can be obtained by a production method including a step of obtaining an acrylic rubber composition, or a step of obtaining a non-crosslinked acrylic rubber composition by melt-kneading uncrosslinked acrylic rubber (A1) and fluororesin (B). Since the fluororesin (B) is uniformly dispersed in the uncrosslinked acrylic rubber composition, and an automobile transmission oil seal having better low friction and non-adhesiveness can be obtained, the process (I) is included. It is preferably obtained by a production method.

Moreover, from the point that the transition to the surface layer of the fluororesin (B) occurs smoothly, the heat treatment at the melting point of the fluororesin (B) is particularly excellent in the heat treatment step.

The state in which the ratio of the fluororesin (B) in the surface region of the automobile transmission oil seal is increased can be verified by chemically analyzing the surface of the elastic member by ESCA or IR.

By the way, in the case where the surface of the acrylic rubber is modified by application or adhesion of the fluororesin (B), the characteristic convexity of the transmission oil seal for automobiles of the present invention is not observed on the surface. A transmission oil seal for automobiles provided with a convex portion on which the fluororesin (B) in a simple composition is deposited is a novel transmission oil seal for automobiles that has not been used conventionally.

According to the above manufacturing method, there is provided a transmission oil seal for automobiles provided with an elastic member having a seal lip portion, which is significantly improved in characteristics of the fluororesin (B), for example, low friction and non-adhesiveness than those not subjected to heat treatment. Can be obtained. In addition, the characteristics of acrylic rubber (A) can be exhibited outside the surface area of the elastic member, and as a whole, the transmission oil for automobiles is well balanced in any of low compression set, low friction, and non-adhesiveness. A seal is obtained. Furthermore, the resulting transmission oil seal for automobiles is modified by applying or bonding the fluororesin (B) to the surface of the acrylic rubber (A) without dropping or peeling the fluororesin (B) -rich area on the surface. Compared to the case, the durability is excellent.

Next, the present invention will be described with reference to examples, but the present invention is not limited to such examples.

Various characteristics in this specification were measured by the following methods.

(1) Monomer composition of fluororesin: Using a nuclear magnetic resonance apparatus AC300 (manufactured by Bruker-Biospin), the measurement temperature was (polymer melting point + 50) ° C. and ¹⁹ F-NMR measurement was performed.

(2) Fluorine resin melting point differential scanning calorimeter RDC220 (manufactured by Seiko Instruments Co., Ltd.) was used to measure heat at a heating rate of 10 ° C./min in accordance with ASTM D-4591 and once the end of the melting point peak endotherm When the temperature reaches + 30 ° C., the temperature is decreased to 50 ° C. at a temperature decrease rate of −10 ° C./min, and the temperature is increased again to the endothermic temperature + 30 ° C. at a temperature increase rate of 10 ° C./min. Asked.

(3) Melt flow rate of fluororesin [MFR]
MFR is based on ASTM D3307-01, using a melt indexer (manufactured by Toyo Seiki Co., Ltd.), the mass of polymer flowing out per 10 minutes from a nozzle with an inner diameter of 2 mm and a length of 8 mm under a load of 280 ° C. and 5 kg ( g / 10 min) was defined as MFR.

(4) Storage elastic modulus (E ') of fluororesin
The storage elastic modulus is a value measured at 70 ° C. by dynamic viscoelasticity measurement. A sample having a length of 30 mm, a width of 5 mm, and a thickness of 0.25 mm is pulled by a dynamic viscoelastic device DVA220 manufactured by IT-Measurement Control Co., Ltd. The measurement was performed under the conditions of a grip width of 20 mm, a measurement temperature of 25 ° C. to 200 ° C., a temperature increase rate of 2 ° C./min, and a frequency of 1 Hz.

(5) Crosslinking (vulcanization) characteristics The minimum torque (ML), maximum torque (MH), induction time (T10) and optimum vulcanization time (T90) are measured with a curast meter type II (manufactured by JSR Corporation). did.

(6) 100% modulus (M100)
It measured according to JIS K6251.

(7) Tensile strength at break (Tb)
It measured according to JIS K6251.

(8) Tensile elongation at break (Eb)
It measured according to JIS K6251.

(9) Hardness (Shore A)
It was measured with a durometer type A according to JIS K6253 (peak value).

(10) Area ratio of regions having convex portions, height of convex portions, bottom sectional area of convex portions, area ratio of regions having number of convex portions, height of convex portions, bottom sectional area of convex portions The number of convex portions is, for example, a color 3D laser microscope (VK-9700) manufactured by Keyence Co., Ltd., and analysis software such as WinRooF Ver. Calculated using 6.4.0. The area ratio of the region having the convex part is obtained as the ratio of the total cross-sectional area to the total cross-sectional area value obtained by calculating the bottom cross-sectional area of the convex part. The number of convex portions is obtained by converting the number of convex portions in the measurement region into a number per 1 mm ² .

(11) Measurement of rotational torque of transmission oil seal The rotational torque of the transmission oil seal was measured by the following method.
In the oil seal torque tester 50 shown in FIG. 5, a shaft 54 is rotatably disposed in a housing 59 via a bearing 53. An oil chamber 52 is provided on the distal end side (right side in FIG. 5) of the shaft 54, and an oil seal holding member 57 is attached. The measurement transmission oil seal 51 is slidably fixed to the oil seal holding member 57 in the gap between the oil chamber 52 and the oil seal holding member 57. A load cell 56 is connected to the oil chamber 52. In FIG. 5, 55 is an oil seal.
When the measurement transmission oil seal 51 is attached, the temperature (oil temperature) of the oil chamber 52 is set to a predetermined temperature, and the shaft 54 is rotated at a predetermined rotation by a motor (not shown). The seal holding member 57 rotates integrally with the shaft 54 and slides with respect to the measurement transmission oil seal 51. At this time, the load of the measurement transmission oil seal 51 is measured by the load cell 56, and the rotation radius is measured. To convert to torque. Here, the measurement conditions were that the oil temperature (test temperature) was normal temperature, and the rotation speed of the shaft 54 was 2000 rpm or 5000 rpm.

(12) Coefficient of dynamic friction Measurement was performed with a friction player FPR2000 manufactured by Reska Co., with a load of 20 g (Pin is φ5 mm material SUJ2), a rotation mode, a rotation speed of 120 rpm, and a rotation radius of 10 mm. The friction coefficient at the time was read, and the value was taken as the dynamic friction coefficient.

Acrylic rubber (A1)
XF-5140 (Toepe Co., Ltd.) emulsion concentration 31.1 wt%
Acrylic rubber (A2)
XF-5140 (Toupe Co., Ltd.) base polymer

Synthesis Example 1 Fluororesin (B1)
In a stainless steel autoclave having an internal volume of 3 L equipped with a stirrer, 1767 g of deionized water and CH ₂ ═CFCF ₂ —O— (CF (CF ₃ ) CF ₂ O) —CF (CF ₃ ) —COONH as a fluorine-containing allyl ether compound ₄ 50% aqueous solution of 0.283 g (amount corresponding to 80ppm of deionized water), the fluorine-containing anionic surfactants as _{F (CF} 2) 5 COONH ₄ 50% aqueous solution of 3.53 g (deionized water In an amount equivalent to 1000 ppm). After the inside of the autoclave was evacuated and purged with nitrogen, hexafluoropropylene [HFP] was introduced to 3.4 MPa and the temperature was raised to 95 ° C. Subsequently, HFP and TFE were introduced until the pressure reached 4.0 MPa. Subsequently, 16 g of a 3.0% by mass ammonium persulfate aqueous solution was injected as a polymerization initiator to initiate polymerization. Since a pressure drop starts after 5 minutes have passed since the polymerization initiator was injected, a mixed gas of TFE / HFP = 70/30 (molar ratio) was supplied so that the polymerization tank pressure was maintained at 4.0 MPa. Continued. Further, in order to maintain the polymerization rate, a 3.0 mass% ammonium persulfate aqueous solution was constantly injected from the start of the polymerization, and a total of 35 g was added until the end of the polymerization. Stirring was stopped 4 hours after the start of the polymerization, the monomer gas was released, and the reaction was stopped. Then, it cooled to room temperature and obtained the white TFE / HFP copolymer [FEP] dispersion (emulsion) 1990g. When a part of the obtained emulsion was dried and the solid content concentration was measured, it was 20.0% by mass.

300 g of the obtained dispersion was diluted twice, and aluminum sulfate was added for coagulation, and the slurry was filtered off. 1 L of ion exchange water was added to the recovered slurry for redispersion, and then filtered again and washed. This washing process was repeated three more times. Subsequent drying at 110 ° C. yielded 58 g of polymer.

The obtained polymer had the following composition and physical properties.
TFE / HFP = 83.2 / 16.8 (molar ratio)
Melting point: 179 ° C
MFR: 8.5 g / 10 min (280 ° C., 5 kg)
Storage elastic modulus (E ′) at 70 ° C .: 58 MPa
Thermal decomposition start temperature (1% mass loss temperature): 375 ° C.

Synthesis Example 2 Fluororesin (B2)
In a stainless steel autoclave having an internal volume of 3 L equipped with a stirrer, 1767 g of deionized water and CH ₂ ═CFCF ₂ —O— (CF (CF ₃ ) CF ₂ O) —CF (CF ₃ ) —COONH as a fluorine-containing allyl ether compound ₄ 50% aqueous solution of 0.283 g (amount corresponding to 80ppm of deionized water), the fluorine-containing anionic surfactants as _{F (CF} 2) 5 COONH ₄ 50% aqueous solution of 3.53 g (deionized water In an amount equivalent to 1000 ppm). After the inside of the autoclave was evacuated and purged with nitrogen, hexafluoropropylene [HFP] was introduced to 3.4 MPa, 17 g of perfluoro (propyl vinyl ether) [PPVE] was injected, and the temperature was raised to 95 ° C. Subsequently, HFP and TFE were introduced until the pressure reached 4.0 MPa. Subsequently, 16 g of a 3.0% by mass ammonium persulfate aqueous solution was injected as a polymerization initiator to initiate polymerization. Since a pressure drop starts after 5 minutes have passed since the polymerization initiator was injected, a mixed gas of TFE / HFP = 70/30 (molar ratio) was supplied so that the polymerization tank pressure was maintained at 4.0 MPa. Continued. Further, in order to maintain the polymerization rate, a 3.0 mass% ammonium persulfate aqueous solution was constantly injected from the start of the polymerization, and a total of 35 g was added until the end of the polymerization. Stirring was stopped 4 hours after the start of the polymerization, the monomer gas was released, and the reaction was stopped. Then, it cooled to room temperature and obtained 2000 g of white TFE / HFP / PPVE copolymer [FEP] dispersion (emulsion).
When a part of the obtained emulsion was dried and the solid content concentration was measured, it was 20.3% by mass.

300 g of the obtained dispersion was diluted twice, and aluminum sulfate was added for coagulation, and the slurry was filtered off. 1 L of ion exchange water was added to the recovered slurry for redispersion, and then filtered again and washed. This washing process was repeated three more times.
Subsequent drying at 110 ° C. yielded 56 g of polymer.

The obtained polymer had the following composition and physical properties.
TFE / HFP / PPVE = 84.2 / 14.8 / 1.0 (molar ratio)
Melting point: 178 ° C
MFR: 9.2 g / 10 min (280 ° C., 5 kg)
Storage elastic modulus (E ′) at 70 ° C .: 63 MPa
Thermal decomposition start temperature (1% mass loss temperature): 372 ° C.

(filler)
Stearic acid paraffin wax now guard # 445 (Uniroy)
Seast V (manufactured by Tokai Carbon Co., Ltd.)

(Crosslinking agent)
CHEMINOX AC-6 (Unimatec Co., Ltd.)

(Crosslinking accelerator)
Noxeller DT (Ouchi Shinsei Chemical Industry Co., Ltd.)

Example 1
In a mixer having a capacity of 1 L, FEP aqueous dispersion (B1) and acrylic rubber dispersion (A1) were mixed in a solution prepared by mixing 500 cc of water and 4 g of magnesium chloride in advance, and the solid content was 75/25 (acrylic rubber / 400 cc of a solution previously mixed so as to be a fluororesin (FEP)) was added, mixed for 3 minutes with a mixer, and co-coagulated.
After co-coagulation, the solid content was taken out and dried in a drying oven at 80 ° C. for 48 hours, and then the predetermined compound shown in Table 1 was mixed with an open roll to obtain an uncrosslinked acrylic rubber composition.
After that, a metal ring is arranged in the mold of the transmission oil seal for automobiles, an uncrosslinked acrylic rubber composition is introduced, pressurized to 8 MPa, vulcanized at 180 ° C. for 5 minutes, and then a crosslinked molded product (applicable) (Shaft diameter 80 mm, outer diameter 98 mm, width 8 mm).
Thereafter, the obtained cross-linked molded article was placed in a heating furnace maintained at 230 ° C. for 24 hours and subjected to a heat treatment to obtain an automobile transmission oil seal having a structure as shown in FIG. Using the obtained automobile transmission oil seal, the number of convex portions, the bottom cross-sectional area, the height, and the area ratio of the regions having the convex portions were measured. In addition, the rotational torque of the automobile transmission oil seal was measured. The results are shown in Table 1.

Example 2
Except for using (B2) instead of the FEP dispersion (B1) in Example 1, an automobile transmission oil seal was obtained in the same manner as in Example 1, and various measurements were performed.

Comparative Example 1
A predetermined composition shown in Table 1 was mixed with acrylic rubber (A2) with an open roll to obtain a crosslinkable composition. Thereafter, an automobile transmission oil seal was obtained in the same manner as in Example 1, and various measurements were performed.

DESCRIPTION OF SYMBOLS 10 Transmission 11 Automotive transmission oil seal 12 Elastic member 13 Main lip part 14 Fitting part 16 Metal ring 17 Ring spring 20 Housing 21 Axle 22 Main shaft (input shaft)
23 Countershaft (output shaft)
30 Seal lip portion 31 Convex portion 50 Oil seal torque tester 51 Transmission oil seal for measurement 52 Oil chamber 53 Bearing 54 Shaft 55 Oil seal 56 Load cell 57 Oil seal holding member 59 Housing

Claims (7)

An automobile transmission oil seal provided with an elastic member having a seal lip portion provided with at least a main lip portion,
The elastic member is made of a composition containing acrylic rubber (A) and a fluororesin (B), and has a convex portion on at least the surface of the main lip portion, and the convex portion is substantially in the composition. Made of contained fluororesin (B),
The transmission oil seal for automobiles, wherein the fluororesin (B) is a copolymer containing a tetrafluoroethylene unit (a) and a hexafluoropropylene unit (b). The automotive transmission oil seal according to claim 1, wherein the fluororesin (B) has a melting point of 200 ° C. or lower. The acrylic rubber (A) is a polymer comprising polymerized units based on at least one acrylate selected from the group consisting of ethyl acrylate, butyl acrylate, butoxyethyl acrylate, and methoxyethyl acrylate. The transmission oil seal for automobiles according to claim 1 or 2. The area ratio of the region having the convex portion with respect to the seal lip portion surface is 0.04 or more,
The volume ratio of the fluororesin (B) to the seal lip is 0.03 to 0.45,
The transmission oil seal for automobiles according to claim 1, 2, or 3, wherein the area ratio of the region having the convex portion is 1.1 times or more the volume ratio of the fluororesin (B). The automotive transmission oil seal according to claim 1, 2, 3, or 4, wherein the convex portion has a height of 0.1 to 30.0 µm. Projections, motor vehicle transmission oil seal according to claim 1, 2, 3, 4 or 5, wherein the bottom cross-sectional area is 0.1~2000μm ^2. Automotive transmission oil seals number claim 2, 3, 4, 5 or 6, wherein the 500 to 60,000 pieces / mm ² of the convex portion.

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