JP2009281524A - Gasket material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively provide a gasket material for enhancing strength, while highly maintaining flexibility. <P>SOLUTION: This gasket material is composed of a joint sheet 1 formed by pressure-laminating and vulcanizing a raw material mixed with rubber, reinforced fiber and a filler by a calender roll. The gasket material is characterized in that the basic composition of the raw material is composed of 16-28 wt.% NBR as rubber, 4-8 wt.% aramid fiber as the reinforced fiber, 10-20 wt.% needle-like dolomite as the reinforced fiber, 8-20 wt.% silica particle as the filler and residual part of an inorganic filler as the filler. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a material for a gasket used in an engine or a transmission mounted on a vehicle or the like, and in particular, a raw material obtained by kneading rubber, a reinforcing fiber, and a filler is pressure-laminated and vulcanized with a calender roll. The present invention relates to a gasket material made of a molded joint sheet.

  The gasket insertion part between the housing of the transmission combined with the engine and the cover fixed with bolts has a large temperature change due to repeated operation and stop of the engine. In this case, repeated relative displacement (fretting) occurs between the joint surfaces of the housing and the cover and the gasket due to repeated temperature changes. Moreover, since the rigidity of the structure has been reduced due to the weight reduction, fretting occurs due to an external force applied to the cover or the like.

  For this reason, as described in Patent Document 1, the base material layer is combined with a surface layer and a back layer having different fixing strengths to greatly improve the seal durability as a three-layer structure, or as described in Patent Document 2, The base material layer is combined with a surface layer and a back layer having different friction coefficients to provide a three-layer structure, thereby greatly improving the seal durability.

Further, the strength is improved by increasing the amount of the reinforcing fiber mixed with the rubber material or the filler or increasing the fiber length of the reinforcing fiber. However, aramid fibers are particularly expensive, and the amount of aramid fibers needs to be reduced in order to reduce costs.
Japanese Patent Application Laid-Open No. 2004-036808 JP 2002-105437 A Japanese Patent Application No. 2004-035806

  However, since aramid fiber is a reinforcing material for changing the asbestos fiber which is now prohibited from use and improving the tensile strength and the like of the rubber, it is difficult to reduce the compounding amount.

  In addition, the conventional sheet has a three-layer structure, and this three-layer structure inevitably increases raw material costs, complicates the material blending, kneading process and sheet forming process. The complexity of this process is high. This leads to cost reduction.

  In order to solve such problems, the sheet described in Patent Document 3 has a two-layer structure, and kneaded aramid fiber, barium sulfate, etc. into a rubber material to increase strength while increasing flexibility of the joint sheet. However, it is necessary to set a blending amount of 20 wt% or more for expensive aramid fibers, which hinders cost reduction.

  The present invention has been made in order to advantageously solve the above-mentioned problems, and the gasket material of the present invention is obtained by pressure laminating and vulcanizing a raw material in which rubber, reinforcing fiber and filler are mixed with a calender roll. In the gasket material composed of the formed joint sheet, the basic composition of the raw materials is NBR as rubber: 16 to 28 wt%, aramid fiber as reinforcing fiber: 4 to 8 wt%, and acicular dolomite as reinforcing fiber : 10 to 20 wt%, silica particles as a filler: 8 to 20 wt%, and an inorganic filler as a filler: the balance.

That is, the gasket material of the present invention aims to reduce the cost while maintaining the performance of the joint sheet.
Usually, when the blending amount of aramid fibers is decreased, a decrease in tensile strength, a decrease in sealing performance due to a decrease in flexibility, and a decrease in heat resistance occur.
In this regard, in the gasket material of the present invention, the aramid fiber as the reinforcing fiber has a blending amount of 4 to 8 wt%, and the aramid fiber has a specific surface area of 6 to 12 m ² / g, which is an index of the degree of fibrillation, For example, it is preferable to improve the degree of fibrillation using an aromatic polyamide fiber (pulp type).
Further, in the gasket material of the present invention, the silica particles as the filler have a blending amount of 8 to 20 wt%, and the silica particles preferably have a primary particle diameter of, for example, 32 to 48 nm.

Furthermore, glass fiber is usually used as the reinforcing fiber, but when this glass fiber is used, the surface of the sheet becomes rough, so that a three-layer structure or the like is often used to cover this.
On the other hand, in the gasket material of the present invention, acicular dolomite as another reinforcing fiber is used at a blending amount of 10 to 20 wt%, and the acicular dolomite has, for example, an average particle diameter of 4 to 12 μm and a fine needle. It is preferable to proceed with shaping. According to this acicular dolomite, since it can finish smoothly, without making the sheet surface rough, a two-layer structure can be made possible, maintaining sealing performance.

  For example, clay particles (hydrous aluminum silicate), barium sulfate, calcium carbonate, diatomaceous earth, magnesium oxide and the like can be blended with the remaining inorganic filler as the filler.

  According to the gasket material of the present invention, since the reinforcing fibers are entangled during mixing, the tensile strength of the joint sheet is improved. Further, the heat resistance can be improved by improving the compression recovery property and the stress relaxation property.

  Further, according to the gasket material of the present invention, since the composition blending amount of the reinforcing fiber and the fiber length of the reinforcing fiber are not increased, the gasket surface can be smoothed and the sealing performance can be sufficiently enhanced. The strength of the joint sheet is not improved by the method of increasing the roll pressure or the temperature of the hot roll when the joint sheet is formed, so that the hardness of the joint sheet can be kept low, and the sealing performance can be sufficiently enhanced. It is possible to improve the sealing performance.

  Furthermore, according to the gasket material of the present invention, the strength of the reinforcing fiber is increased by increasing the composition amount of the reinforcing fiber, the strength of the reinforcing fiber is increased by increasing the morphological effect, and the rubber and the reinforcing fiber. Since the blending ratio of the filler is changed between the intermediate layer and the surface layer so that the surface layer is more flexible than the intermediate layer, it is manufactured by soaring raw material costs and complicated raw material compounding processes. The problem of increasing costs can be avoided.

  Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 is a cross-sectional view showing an embodiment of the gasket material of the present invention. Reference numeral 1 in the drawing denotes a joint sheet as a gasket material of the embodiment, and the joint sheet 1 is a so-called intermediate material. It has a two-layer structure of a main layer 1a made of and a surface layer 1b made of so-called dish material.

  The joint sheet 1 according to this embodiment includes NBR as rubber, fibrillated (fine fiber) aramid fibers as reinforcing fibers, acicular dolomite as reinforcing fibers, and silica particles as fillers. Also, the raw material mixed with an inorganic filler such as clay as a filler is supplied onto a hot roll of a calender roll having a pair of rolls of a hot roll and a cold roll, and kneaded with these rolls. It is formed by being laminated on a hot roll by pressurizing while being further vulcanized and cured by the heat of the hot roll and then peeled off from the hot roll. And in that case, as shown in FIG. 1, two layers, the main layer 1a and the surface layer 1b, are formed by varying the composition of the reinforcing fiber and the filler.

  By the way, in the joint sheet 1 of this embodiment, the basic composition of the above raw materials is NBR: 16 to 28 wt%, aramid fiber: 4 to 8 wt%, acicular dolomite: 10 to 20 wt%, and silica particles: 8 ˜20 wt%, and inorganic filler: balance.

Here, for the aramid fiber, for example, an aromatic polyamide fiber (pulp type) having a specific surface area that is an index of fibrillation degree of 6 m ² / g or more and 12 m ² / g or less is used. This is because if the specific surface area of the aramid fiber is less than 6 m ² / g, the tensile strength and buckling fatigue surface pressure of the joint sheet and hence the gasket formed therefrom cannot be sufficiently increased. If the specific surface area exceeds 12 m ² / g, the aramid in the raw material This is because it is difficult to disperse the fibers.

  Further, as the silica particles, those having a primary particle diameter of 32 nm or more and 48 nm or less are used. This is because if the silica particles having a primary particle diameter of less than 32 nm and more than 48 nm are used, the axial force reduction rate of the joint sheet and thus the gasket formed therefrom is increased.

  As the acicular dolomite, those having an average particle diameter of 4 μm or more and 12 μm or less are used. This is because if the average particle diameter of the acicular dolomite is less than 4 μm, the joint sheet and thus the tensile strength and buckling fatigue pressure of the gasket formed therefrom cannot be sufficiently increased, and if it exceeds 12 μm, the surface of the joint sheet becomes rough. .

  According to the joint sheet 1 of this embodiment, the reinforcing fibers composed of 4 to 8 wt% aramid fibers and 10 to 20 wt% acicular dolomite are entangled during mixing, and the flexibility of the joint sheet is kept high. However, since the strength is increased, the sealing performance can be ensured even if fretting occurs in a structure such as a housing or a cover.

  Moreover, since the strength is not improved by increasing the composition amount of the reinforcing fiber or increasing the fiber length of the reinforcing fiber, the raw material cost of the gasket can be kept low, and the gasket surface can be smoothed and the sealing performance is sufficient. Since the strength of the joint sheet is not improved by increasing the roll pressure or the temperature of the hot roll when the joint sheet is laminated, the joint sheet hardness can be kept low, and the gasket against repeated compressive stress can be maintained. As a result, it is possible to prevent the deterioration of the sealing performance due to the buckling fatigue of the gasket.

  In addition, increase the composition amount of the reinforcing fiber to improve the strength, increase the fiber length of the reinforcing fiber to improve the strength by increasing the morphological effect, and the mixing ratio of rubber, reinforcing fiber and filler to the intermediate layer Since the surface layer is not made to be more flexible than the intermediate layer, the problem is that the cost of raw materials increases and the manufacturing cost increases due to the complexity of the raw material blending process. It can be avoided.

  Therefore, according to a gasket such as a vehicle seat gasket formed by cutting the joint seat 1 of this embodiment into a predetermined contour shape, the rigidity of the structure such as a transmission is low, and the structure, for example, the housing When a high bolt fastening force is applied to the gasket insertion portion between the cover and the cover, excellent sealing durability can be exhibited even if a large force is applied to the structure. That is, when the rigidity of the structure is low, the surface pressure generated in the gasket insertion portion is high immediately below and in the vicinity of the fastening bolt, but is low between the spans of the fastening bolt. For this reason, the gasket to be inserted into the gasket insertion portion is required to have high buckling resistance and good flexibility sealing properties. However, according to the gasket using the joint sheet 1 of this embodiment, these high values are required. It is possible to provide buckling resistance and sealability with good flexibility.

  The above-described characteristics of the gasket such as a vehicle seat gasket formed by using the joint sheet 1 of this embodiment, conversely, the pitch of the fastening bolt or the like when designing the portion of the structure to be sealed with the gasket. The degree of freedom such as the size and the cover thickness can be increased, and the weight of the structure can be reduced.

A joint sheet was prepared by changing the blending ratio of aramid fiber, acicular dolomite, silica, rubber, and inorganic filler as shown in Tables 1 to 8 and Examples 1 to 12 of the present invention. The performance was confirmed by the tensile strength, the axial force decrease rate, and the limit seal pressure test.
(Tensile test)
A tensile test was performed under the conditions defined in JIS K 6251.
(Axial force decrease rate test)
The joint sheet was clamped and clamped to a limit seal pressure test jig with a bolt axial force of 500 kgf, then set in an electric furnace, and the axial force decrease rate after elapse of 150 ° C. × 32 hours was measured with a strain gauge.
(Limit seal pressure test)
Bolt span 100mm, M6 x 4 square jigs with a square frame-shaped joint sheet along its outline with a bolt torque of 11.8Nm, heated at 150 ° C for 32 hours, after cooling, frame-shaped joints The inside of the seat was pressurized with oil and examined for leaks.

  Table 1 shows the results of performing a tensile test, an axial force reduction test, and a limit seal pressure measurement test under the above-described conditions for these joint sheets. From these results, Examples 1 to 16 are general examples. As a result, it was confirmed that the gasket material had good characteristics with a tensile strength of 16 MPa or more, a limit sealing performance of 0.7 MPa or more, and an axial force reduction rate of 12% or less. On the other hand, Comparative Examples 1-8 did not satisfy any one or more of the tensile strength of 16 MPa or more, the limit sealing performance of 0.7 MPa or more, and the axial force decrease rate of 12% or less.

As is clear from Table 1, the basic composition of the joint sheet is
NBR: 16-28 wt%, more preferably 16-24 wt%,
Aramid fiber: 4-8 wt%, more preferably 4-6 wt%,
Acicular dolomite: 10-20 wt%,
Silica particles: 8-20 wt%, more preferably 10-15 wt%,
It is preferable that it consists of an inorganic filler: remainder.

FIG. 2 shows the results of a tensile test conducted in the same manner as described above, with the specific surface area serving as an index of the degree of fibrillation of the aramid fibers changed for the joint sheet 1 of the above embodiment. As is apparent from this figure, in the joint sheet 1 of the above embodiment, the fibrillation degree of the aramid fibers is 6 m ² / g or more and the tensile strength of the joint sheet 1 is 16 MPa or more. On the other hand, when it is less than 6 m ² / g, the tensile strength of the joint sheet 1 rapidly decreases. Therefore, it was found that the specific surface area of the aramid fiber is desirably 6 m ² / g or more, and 6 to ¹² m ² / g is effective.

  Moreover, FIG. 3 shows the result of changing the silica particle diameter for the joint sheet 1 of the above embodiment and performing the axial force reduction rate test in the same manner as described above. As is apparent from this figure, in the joint sheet 1 of the above embodiment, the reduction in axial force of the joint sheet 1 is reduced to 12% or less when the silica particle diameter is 32 to 50 nm. Moreover, if it becomes less than 32 nm, the axial-force fall rate of the joint sheet 1 will rise rapidly. Therefore, it was found that the silica particle diameter is desirably 32 nm or more, and that 32 to 50 nm is effective.

  Furthermore, FIG. 4 shows the result of changing the needle-like dolomite particle diameter of the joint sheet 1 of the above embodiment and performing a tensile test in the same manner as described above. As is apparent from this figure, in the joint sheet 1 of the above embodiment, the particle diameter of the acicular dolomite is 4.0 μm or more, and the tensile strength of the joint sheet 1 is 16 MPa or more. Therefore, it was found that the particle size of acicular dolomite is preferably 4.0 μm or more, and 4 to 12 μm is effective.

  As mentioned above, although demonstrated based on the example of illustration, this invention is not limited to the above-mentioned example, It can change suitably in the description range of a claim.

  Thus, according to the gasket material of the present invention, the reinforcing fibers composed of 4 to 8 wt% aramid fibers and 10 to 20 wt% acicular dolomite are entangled during mixing, while maintaining the flexibility of the joint sheet high. Since the strength is increased, the sealing performance can be ensured even if fretting occurs in a structure such as a housing or a cover.

  Moreover, since the strength is not improved by increasing the composition amount of the reinforcing fiber or increasing the fiber length of the reinforcing fiber, the raw material cost of the gasket can be kept low, and the gasket surface can be smoothed and the sealing performance is sufficient. Since the strength of the joint sheet is not improved by increasing the roll pressure or the temperature of the hot roll when the joint sheet is laminated, the joint sheet hardness can be kept low, and the gasket against repeated compressive stress can be maintained. As a result, it is possible to prevent the deterioration of the sealing performance due to the buckling fatigue of the gasket.

  In addition, increase the composition amount of the reinforcing fiber to improve the strength, increase the fiber length of the reinforcing fiber to improve the strength by increasing the morphological effect, and the mixing ratio of rubber, reinforcing fiber and filler to the intermediate layer Since the surface layer is not made to be more flexible than the intermediate layer, the problem is that the cost of raw materials increases and the manufacturing cost increases due to the complexity of the raw material blending process. It can be avoided.

It is sectional drawing which shows one Embodiment of the gasket raw material of this invention. It is explanatory drawing which shows the result of having calculated | required the tensile strength by changing the fibril degree of an aramid fiber about the joint sheet | seat as a gasket raw material of the said embodiment. It is explanatory drawing which shows the result of having obtained the axial-force fall rate by changing the silica particle diameter about the joint sheet | seat as a gasket raw material of the said embodiment. It is explanatory drawing which shows the result of having calculated | required the tensile strength by changing the acicular dolomite particle diameter about the joint sheet | seat as a gasket raw material of the said embodiment.

Explanation of symbols

1 Joint sheet (gasket material)
1a Main layer 1b Surface layer

Claims (6)

In the gasket material consisting of a joint sheet formed by pressure laminating and vulcanizing the raw material mixed with rubber, reinforcing fiber and filler with a calender roll,
The basic composition of the raw material is
NBR as rubber: 16 to 28 wt%,
Aramid fiber as reinforcing fiber: 4 to 8 wt%;
Acicular dolomite as a reinforcing fiber: 10 to 20 wt%,
Silica particles as a filler: 8 to 20 wt%,
Inorganic filler as filler: the remainder,
A gasket material characterized by comprising: The gasket material according to claim 1, wherein the aramid fiber has a fibril degree of 6 to 12 m ² / g in specific surface area (BET).   The gasket material according to claim 1, wherein the silica particles have a primary particle diameter of 32 to 48 nm.   The gasket material according to claim 1, wherein the acicular dolomite has an average particle diameter of 4 to 12 µm.   A vehicle seat gasket using the gasket material according to any one of claims 1 to 4.   The said sheet | seat gasket has a two-layer structure of a surface layer and the main layer which consists of the said gasket raw material, The gasket raw material in any one of Claim 1 to 4 characterized by the above-mentioned. Vehicle seat gasket.

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