JPH11199780A - Flexible joint boot made of thermoplastic elastomer resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a boot which prevents a strange noise due to rubbing the tops of bellows from being made by compounding a high-molecular thermoplastic elastomer resin with a low-melting fatty acid amide having a specified m.p. and a high-melting fatty acid amide having a specified m.p., each in a specified amt. SOLUTION: This compsn. contains 100 pts.wt. thermoplastic elastomer resin, 0.2-1.5 pts.wt. low-melting fatty acid amide having an m.p. of 20-60 deg.C, and 0.03-0.15 pt.wt. high-melting fatty acid amide having an m.p. of 60 deg.C or higher, pref. 80-150 deg.C. Fatty acid amides are represented by formulas I, II, and III (R1 and R2 are each a 6C or higher hydrocarbon group; and R3 is a 2C or higher hydrocarbon group). A compd. of formula II is suitable for the low-melting fatty acid amide; and that of formula III, suitable for the high-melting fatty acid amide. A thermoplastic polyester elastomer resin is suitable for the thermoplastic elastomer resin. Thus, a strange rubbing noise is prevented and satisfactory sealing properties and reliability are achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint boot made of a thermoplastic elastomer resin (TPE) such as a thermoplastic polyester elastomer (TPEE).
More specifically, the present invention relates to a bellows-like joint boot used for a constant velocity joint of an automobile or the like.

[0002]

2. Description of the Related Art In order to hold grease sealed in joints of drive shafts of automobiles and industrial machines,
Alternatively, a tubular elastic film called a joint boot is mounted to prevent dust and the like.

[0003] Such joint boots are, for example,
As shown in FIG. 4, the joint boot has a cylindrical bellows structure having a difference in diameter at both ends, and a universal joint case 3 and a shaft 2 are attached to a large-diameter end cylindrical portion 5 and a small-diameter end cylindrical portion 6 of the joint boot. It is inserted and fixed by a clamping clamp 4, respectively. In the universal joint case 3, the shaft 2 and another shaft are connected by a universal joint capable of transmitting a rotational driving force. On the inner circumference of the large-diameter end cylindrical portion 5 and the small-diameter end cylindrical portion 6, a sealing ridge 91 having a mountain-shaped cross section is formed, and the sealing ridge 91 is tightened and held down by the clamp 4. Thus, leakage of the enclosed grease is prevented.

Conventionally, such joint boots have been manufactured by injection molding a rubber material such as a chloroprene rubber material. However, in automotive applications, the warranty period of parts has been prolonged in recent years, and such general-purpose synthetic rubber materials have not been able to sufficiently satisfy the requirements for ozone resistance and abrasion resistance.

Therefore, thermoplastic elastomer resins such as thermoplastic polyester elastomer resins have been used as materials capable of satisfying these requirements.

[0006] The thermoplastic elastomer resin is generally
The polymer chain has a high-melting crystalline hard segment and a low-melting soft segment connected to each other, and exhibits performance as an elastomer due to the fact that the hard segments are aggregated and physically crosslinked. Things. The term thermoplastic elastomer resin is used in a broad sense, including one in which a chemical cross-link is partially formed, and is also used broadly in the present specification.

[0007] Polyester-based thermoplastic elastomer resins generally include a hard segment composed of a high-melting crystalline aromatic polyester unit, a low-melting polyether unit such as polytetramethylene glycol, or a low-melting polyester such as polycaprolactone. An ester bond is formed with a soft segment composed of units. A thermoplastic polyester elastomer resin is particularly suitable as an elastomer resin for joint boots because of its wide usable temperature range, excellent bending fatigue resistance, and excellent strength.

However, when such a thermoplastic elastomer resin is mounted on a joint such as a constant velocity joint of an automobile which repeats a relatively wide-angle deformation deformation (typically, 20 degrees or more in the case of a constant velocity joint), the rotation of the thermoplastic elastomer resin is reduced. At the time of driving, the bellows peaks or the bellows peaks rub against the shoulders of the large-diameter end portions, causing unpleasant noise. Such abnormal noise due to rubbing is particularly remarkable when moisture adheres to the outer surface of the bellows. In the case of a joint boot mounted on a car, the abnormal noise caused by the rubbing causes discomfort to the people in the car and impairs the riding comfort, thereby reducing the competitiveness of the car as a product.

For the purpose of suppressing abnormal noise due to rubbing of bellows, Japanese Patent Application Laid-Open No. Hei 9-177797 proposes that a fatty acid amide of a higher fatty acid such as diethylene bisstearic acid (melting point 140 ° C.) be used as a lubricant. Have been. By adding, for example, 0.08 to 0.2 parts by weight of a fatty acid amide of a higher fatty acid to 100 parts by weight of the polyester-based elastomer resin, abnormal noise due to rubbing can be suppressed. Further, in order to maintain the effect of the fatty acid amide of the higher fatty acid as a lubricant, a fatty acid amide having a melting point higher than 120 ° C., which is the upper limit of the use temperature of the joint boot, is desirable.

[0010]

However, when a required amount of such fatty acid amide of higher fatty acid is added,
This has been a problem because the adhesion at the seal portion is reduced. If the adhesion at the seal portion is not sufficiently enhanced, the sealability may be impaired and grease may leak. Therefore, for example, the width of the small-diameter cylindrical part (axial dimension)
It is necessary to take measures such as increasing the diameter of the joint or providing a ridge on the outer surface of the universal joint case connected to the large-diameter cylindrical portion. However, all of these have an adverse effect such as an increase in the manufacturing cost of the joint portion.
In addition, sufficient sealing properties were not always obtained.

In addition, the method using fatty acid amides of higher fatty acids has a remarkably insufficient effect of suppressing abnormal noise due to rubbing in a normal temperature to low temperature range. In the case of joint boots mounted on automobiles, the operating environment temperature can be as high as −30 ° C. to 100 ° C., but in the conventional technology, generation of abnormal noise due to rubbing in such a wide temperature range is caused. Could not be sufficiently suppressed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and can suppress the generation of abnormal noise due to the rubbing of bellows mountain parts over a wide temperature range. An object of the present invention is to provide a resin boot capable of securing sufficient reliability of a seal portion without increasing the size.

[0013]

In the flexible joint boot made of a thermoplastic elastomer resin according to the first aspect, a large-diameter-end short cylindrical portion for connecting to a universal joint storage case fixed to one shaft of the universal joint. When,
In a flexible joint boot made of a thermoplastic elastomer resin consisting of a small-diameter end short cylindrical portion for connecting to the other shaft of the universal joint and a bellows whose diameter is sequentially reduced from the large-diameter end to the small-diameter end, For 100 parts by weight of the thermoplastic elastomer resin polymer component,
A low-melting fatty acid amide having a melting point of
It is characterized by containing 0.03 to 0.15 parts by weight of a high melting point fatty acid amide having a melting point of 60 ° C. or more.

According to the above configuration, it is possible to avoid abnormal noise due to rubbing of the bellows ridges over a wide temperature range, and to achieve sufficient reliability of the seal portion without increasing parts cost and process load for tightening the seal portion. Can be secured.

In the flexible joint boot made of a thermoplastic elastomer resin according to the second aspect, the high melting point fatty acid amide has a melting point of 80 to 150 ° C. in the flexible joint boot made of the thermoplastic elastomer resin according to the first aspect. It is characterized by.

According to the above configuration, generation of abnormal noise due to rubbing can be suppressed even in a high temperature region of 50 ° C. or more.

In the flexible joint boot made of thermoplastic elastomer resin according to claim 3, the high melting point fatty acid amide and the low melting point fatty acid amide are represented by the following formula (I). ) To (III).

R ₁ -CONH ₂ (I) (monoamide) R ₁ -CONH-R ₂ (II) (N-substituted amide) R ₁ -CONH-R ₃ -NHCO-R ₁ (III) (bisamide) , R ₁ and R ₂ are any of an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group, and have 6 or more carbon atoms.

R ₃ is any of an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group, and has 2 or more carbon atoms.

According to a fourth aspect of the present invention, there is provided a flexible joint boot made of a thermoplastic elastomer resin according to the third aspect, wherein the low melting point fatty acid amide is represented by the following formula (II). Wherein the high melting point fatty acid amide is a bisamide represented by the following formula (III).

R ₁ -CONH-R ₂ (II) (N-substituted amide) R ₁ -CONH-R ₃ -NHCO-R ₁ (III) (bisamide) wherein R ₁ and R ₂ are alicyclic Any of a hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group having 6 or more carbon atoms.

R ₃ is any of an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group, and has 2 or more carbon atoms.

According to a fifth aspect of the present invention, there is provided a flexible joint boot made of a thermoplastic elastomer resin according to the fourth aspect, wherein the thermoplastic elastomer resin is a thermoplastic polyester elastomer resin. It is characterized by.

[0024]

DETAILED DESCRIPTION OF THE INVENTION Thermoplastic elastomer resin (TP)
As E), any of polyester, polyurethane, polyolefin and the like can be used as long as it has grease resistance, flex fatigue resistance and flexibility, but polyester (TPEE) is preferred. It is.

The thermoplastic polyester elastomer resin (TPEE) is a block copolymer composed of a high melting point polyester segment and a low melting point polymer segment having a molecular weight of 400 to 6000. Is formed of a component having a melting point of 150 ° C. or higher when formed, and a melting point or softening point of 80 ° C. or lower when measured only at the low-melting polymer segment constituent part. The melting point of the entire thermoplastic polyester elastomer resin is 80 ° C. or higher.

The high-melting-point polyester segments constituting the thermoplastic polyester elastomer resin include terephthalic acid, isophthalic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, bisbenzoate Acids, bis (p-carboxyphenyl) methane, aromatic dicarboxylic acid residues such as 4,4-sulfonyldibenzoic acid, ethylene glycol, propylene glycol, butylene glycol, tetramethylene glycol, pentamethylene glycol,
First, polyesters composed of diol residues such as 2,2-dimethyltrimethylene glycol, hexamethylene glycol, decamethylene glycol, p-xylene glycol, and cyclohexanedimethanol are mentioned.
Here, the polyester constituting the high melting point polyester segment may be a copolyester using two or more kinds of dicarboxylic acids or two or more kinds of diols among the above-listed.

Particularly preferred as the high melting point polyester segment is polybutylene terephthalate.

As the high melting point polyester segment,
Also, p- (β-hydroxyethoxy) benzoic acid, p-
Examples thereof include a polyester derived from a hydroxy acid such as hydroxybenzoic acid or a residue thereof, and a polylactone such as polypivalolactone, or 1,4-bis (4,4-dicarboxyphenoxy).
A polyether ester comprising a residue of an aromatic ether dicarboxylic acid such as ethane and the above-mentioned diol residue can be mentioned.

As the high melting point polyester segment,
Polyesters other than those described above may be any as long as they belong to the aforementioned copolyesters combining dicarboxylic acids, hydroxy acids, diols and the like, and have a melting point of 150 ° C. or higher.

On the other hand, as the low melting point polymer segment,
A polyester-based block copolymer having a molecular weight of 400 to 6000 and showing a substantially amorphous state is used. The melting point or softening point when measured only at this segment component is 80 ° C. or less. The weight fraction of the low melting polymer segment in the thermoplastic polyester elastomer resin is 3 to 90%.

Typical low-melting-point copolymer segments include polyether glycols such as polyoxyethylene glycol, polyoxypropylene glycol, and polyoxytetramethylene glycol, and copolymers thereof.
As well as mixtures thereof.

As the low melting point copolymer segment,
An aliphatic or alicyclic dicarboxylic acid having 2 to 12 carbon atoms,
Examples of the polyester include an aliphatic or alicyclic glycol having 2 to 10 carbon atoms. For example, aliphatic polyesters such as polyethylene adipate, polytetramethylene adipate, polyethylene sebacate, polyneopentyl sebacate, polytetramethylene dodecane, polytetramethylene azelate, and polyhexamethylene azelate. An aliphatic polyester obtained by using two kinds of dicarboxylic acids or two kinds of glycols may be used.

The low-melting-point copolymer segment further includes an aliphatic polyester made of a polylactone such as poly-ε-caprolactone.

The low melting point copolymer segment may be a polyetherester copolymer obtained by combining the above aliphatic polyester and the above aliphatic ether.

The thermoplastic polyester elastomer resin can be produced by a usual polymerization method. Suitable production methods include the following (1) to (3).

(1) An aromatic dicarboxylic acid or a dimethyl ester thereof, a low molecular diol forming the high melting point polyester segment together with the aromatic dicarboxylic acid, and a diol forming the low melting point polymer segment are mixed in the presence of a catalyst in the presence of a catalyst. A method in which an esterification reaction or a transesterification reaction is performed by heating to 150 to 260 ° C., and then polycondensation is performed by removing excess low-molecular diol under vacuum.

(2) A prepolymer constituting a high-melting-point polyester segment and a prepolymer constituting a low-melting-point polymer segment are prepared in advance, and a chain extender which reacts with these terminals is added and mixed. After the reaction, a method of completing the polymerization reaction by removing volatile components under high vacuum.

(3) A method in which a high-melting polyester having a high degree of polymerization and a lactone are mixed by heating to carry out a transesterification reaction while ring-opening polymerizing the lactone.

As such a thermoplastic polyester elastomer resin, Pelprene manufactured by Toyobo Co., Ltd.
Hytrel manufactured by DuPont, and the like.

A low melting point fatty acid amide having a melting point of 20 to 60 ° C. and a high melting point fatty acid amide having a melting point exceeding 60 ° C. are added to the thermoplastic elastomer resin as a lubricant.

As described above, the combined use of the low-melting fatty acid amide and the high-melting fatty acid amide effectively suppresses noise caused by rubbing in a wide temperature range from a low temperature to a high temperature, for example, -23 ° C. to 50 ° C. be able to. In addition, since the low-melting fatty acid amide bleeds on the surface of the joint boot to form a coating, bleeding of the high-melting fatty acid amide that causes slippage of the seal portion is suppressed. Therefore, the sliding of the seal portion can be effectively suppressed for a long period of time.

The low melting point fatty acid amide alone is not sufficiently effective in suppressing abnormal noise caused by the rubbing of the bellows of the joint boot in the normal temperature to high temperature region. Further, the use of the high-melting fatty acid amide alone does not have a sufficient effect of suppressing abnormal noise due to rubbing at a normal temperature to a low temperature, and also deteriorates the sealability of the seal portion.

On the other hand, the melting point of the low melting point fatty acid amide is 20 ° C.
If it is less than 20 ° C., the effect of suppressing abnormal noise due to rubbing in the region of 20 to 60 ° C. is not sufficient, which is not preferable.

The high melting point fatty acid amide preferably has a melting point of 80 to 150 ° C. If the melting point of the high-melting fatty acid amide is less than 80 ° C., the effect of suppressing abnormal noise due to rubbing in a temperature range of about 50 ° C. or more is not necessarily sufficient.

As the low-melting fatty acid amide and the high-melting fatty acid amide, any of those having a melting point in the above range can be used. For example, they are represented by any of the following formulas (I) to (III). Are preferred.

R ₁ -CONH ₂ (I) (monoamide) R ₁ -CONH-R ₂ (II) (N-substituted amide) R ₁ -CONH-R ₃ -NHCO-R ₁ (III) (bisamide) , R ₁ and R ₂ are any of an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group, and have 6 or more carbon atoms. R ₁ and R ₂ preferably have 11 to 25 carbon atoms.

R ₃ is any one of an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group and an unsaturated hydrocarbon group, and has 2 or more carbon atoms. . R
₃ preferably has 2 to 16 carbon atoms.

As the low melting point fatty acid amide having a melting point of 20 to 60 ° C., an N-substituted amide represented by the following formula (II) (a compound in which a primary amine and a fatty acid are condensed) is preferable.
Further, as the high melting point fatty acid amide having a melting point of 60 ° C. or more, a bisamide represented by the following formula (III) is preferable.

R ₁ -CONH-R ₂ (II) (N-substituted amide) R ₁ -CONH-R ₃ -NHCO-R ₁ (III) (bisamide) where R ₁ and R ₂ are alicyclic Any of a hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group having 6 or more carbon atoms. R ₁ and R ₂ preferably have 11 to 25 carbon atoms.

R ₃ is any of an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group, and has 2 or more carbon atoms.

As the N-substituted amide represented by the formula (II) as the low melting point fatty acid amide, for example, N-oleyl oleic acid amide is preferable.

Formula (III) as a high melting fatty acid amide
Preferred examples of the bisamide represented by are ethylene bisoleic acid amide.

The amount of the low-melting fatty acid amide is preferably 0.2 to 1.5 parts by weight (ie, 0.2 to 1.5 phr) based on 100 parts by weight of the base resin. When the amount of the low-melting fatty acid amide is less than 0.2 phr,
The effect of suppressing abnormal noise due to rubbing is not sufficient, and if the amount is more than 1.5 phr, the durability is undesirably reduced. A more preferred compounding amount is 0.3 to
1.5 phr.

On the other hand, the amount of the fatty acid amide having a high melting point is
It is preferably from 0.03 to 0.15 phr, more preferably from 0.05 to 0.1 phr. When the amount of the high-melting fatty acid amide is less than 0.03 phr, the effect of suppressing abnormal noise due to rubbing is not sufficient, and when the amount exceeds 0.15 phr, the slip of the seal is generated and It is not preferable because durability is lowered.

Hereinafter, specific examples of the present invention will be described.

<Mixing> The base resin of the joint boot is Perprene P46D, a thermoplastic polyester elastomer manufactured by Toyobo Co., Ltd.

As the fatty acid amide having a melting point of 20 to 60 ° C., N-substituted amide, N-oleyl oleic amide (A) was used. Melting point was 45 ° C. here,
The melting point was measured by using a METTLER-type melting point measuring apparatus at a heating rate of 2 ° C./min and observing a 0.5 g powder sample in a liquid state with a magnifying glass.

As the fatty acid amide having a melting point of 80 to 150 ° C., ethylene bisoleic acid amide (B), one of unsaturated fatty acid bisamides, was used. The melting point was measured at 118 ° C. by the same method as above.

With respect to 100 parts by weight of the base resin, 0.2 to 1.5 parts by weight of N-oleyl oleic amide (A) and 0.03 to 1.5 parts by weight of ethylene bis oleic amide (B) are used.
After adding 0.15 parts by weight, the mixture was kneaded at a temperature of 230 ° C., extruded into strands, and then used as chips to prepare test pieces by injection molding.

<Bleed of lubricant in sheet molding>
The amount of the lubricant (fatty acid amide) of the sheet molded product was measured after leaving it in a thermostat at 23 ° C. and 50 ° C. for a predetermined number of days and then taken out and bleed. The bleed amount was calculated from the weight loss when the lubricant bleeding on the surface was wiped off with a cloth soaked in alcohol.

[0061]

[Table 1] In Comparative Examples 1 to 3 in which only a high-melting fatty acid amide was blended, in both cases of leaving at 23 ° C and leaving at 50 ° C,
The amount of bleed increased uniformly with the passage of days. On the other hand, in Examples in which the fatty acid amide having a low melting point was used in combination, there was little change in the bleed amount.

<Preparation of Joint Boot Product> A joint boot product was prepared from the resin composition having the above composition by a press blow method.

FIG. 1 shows the shape of the bellows of the created joint boot. In FIG. 1, the right half is an axial sectional view, and the left half is a side view. Here, the diameter of the large-diameter end cylindrical portion 5 of the joint boot is about 100 mm.

This joint boot has a shape
It has the following features (1) to (8).

(1) The diameters of the peaks and valleys of the bellows gradually decrease from the large-diameter end to the small-diameter end.

(2) The first valley starts from the edge of the large-diameter end cylindrical portion 5 connected to the joint case.

(3) In the cross section in the boot axial direction, the distance in the boot axial direction between the midpoint C1 of the large-diameter end cylindrical portion and the midpoint C2 of the small-diameter end cylindrical portion is L, and the large-diameter end cylindrical portion is L0 is the distance in the boot axis direction from the midpoint of the first mountain to the ridgeline of the first mountain, L1 is the distance in the boot axis direction from the ridgeline of the fifth mountain to the midpoint of the small-diameter end cylindrical portion, and L1 is the distance from the ridgeline of the first mountain. The distance in the boot axial direction to the ridgeline of five mountains is L2
L0 is 5 to 15% of L, and L1 is 12 to 12 of L
22% and L2 is 67 to 77% of L.

(4) In each valley, the dimension (valley surface depth) in the boot radial direction (radial direction of the joint boot) on the large-diameter end side slope is determined by the joint boot at the mountain ridge line on the small-diameter end side. It is 28 to 40% of the outer diameter.

(5) The outer diameter of the large-diameter end cylindrical portion is about 100 m
When m, the radius of curvature at the ridge is about 2 mm.

(6) The thickness near the ridgeline of the bellows is 60 to 100% of the thickness near the valley bottom.

(7) The slopes constituting the bellows, which are not directly connected to the large-diameter end cylindrical portion and the small-diameter end cylindrical portion, that is, those other than both ends of the bellows, have a joint boot in the cross-sectional shape in the boot axial direction. Are convex toward the outside and have a radius of curvature of 0. 0 of the outer diameter of the large-diameter end cylindrical portion.
3 to 2 times (referred to as convex R shape).

(8) In the valley between the two ridge lines of the bellows, the distance in the joint boot axial direction from the large diameter end ridge line to the valley bottom is the distance in the joint boot axial direction between these two ridge lines. 30 to 40% (referred to as a saw blade shape).

If the shape of the bellows of the joint boot is as described above, a simulation is performed on the stress applied to each part when the joint boot is deformed (Japanese Patent Application No. 9-2).
29528), on the inside of the bend, the peaks of the bellows stack relatively neatly, and the pressure between the bellows and the shaft can be reduced. Therefore, it is possible to reduce the torque acting in the direction in which the large diameter end side seal portion is peeled off from the inside of the boot.

Further, even at the outside of the bend, the bellows peak does not protrude toward the small diameter end, and the folding of the peak adjacent to the small diameter end can be reduced. for that reason,
The torque acting in the direction in which the small-diameter end seal portion is peeled off from the inside of the boot can be reduced.

FIG. 2 shows the shape of the seal portion of the joint boot thus produced.

The sealing portion has a substantially semicircular sealing ridge 91 in a sectional view cut in the boot axial direction.
On this back surface, a groove 92 is formed in a shape like a slightly flattened square. In the cross-sectional view, the left-right symmetric axis of the seal portion outer surface groove 92 coincides with the left-right symmetric axis of the sealing ridge 91. The height of the projection of the sealing ridge 91 and the depth b of the groove 92 are substantially the same as the thickness of the joint boot at a portion adjacent to the sealing ridge 91. Also, the sealing ridges 91 extend from the bottom of the groove 92.
The minimum distance to the outer surface is about the same as the film thickness.

The seal portion can be made as shown in FIG. In the seal part of the joint boot shown in FIG.
In the sectional view cut in the boot axial direction, the sealing ridge 91 has a trapezoidal shape with rounded corners.
A substantially semicircular groove 92 having a substantially inverted wedge-shaped ridge 93 at the center is formed. The height of the protrusion of the sealing ridge 91 is about twice the film thickness of the joint boot at a portion adjacent to the sealing ridge 91, and the depth b of the groove 92 is:
It is about 1.5 times the film thickness. The height of the protrusion of the ridge 93 in the groove is substantially equal to the depth of the groove 92. Also, the groove 92
The distance from the bottom surface to the outer surface of the sealing ridge 91 is the shortest and is about the same as the film thickness.

By forming the shape of the seal portion as shown in FIG. 2 or FIG. 3, the strength of the tightening clamp and the
The adhesion at the seal portion and the reliability of the seal can be improved without increasing the load of the tightening operation.

<Joint Boot Product Test> The joint boot product prepared as described above was assembled to a constant velocity joint, and evaluation was made on the suppression of abnormal noise due to rubbing, the sealing property, and the durability.

The test method is as follows.

(1) Suppression of abnormal noise due to rubbing: -20 ° C.
After leaving for 2 weeks and 6 weeks in each atmosphere of 23 ° C. and 50 ° C., drive is performed by assembling to a constant velocity joint,
When no generation of abnormal noise due to rubbing was observed, it was judged as ○, and when observed, it was judged as ×. At this time, the ambient temperature was 30 ° C. and the joint angle of the constant velocity joint was 39.
The rotation speed was set to 150 rpm. In addition, water was sprayed on the surface of the joint boot in advance.

(2) Sealability: A joint case or a joint in a seal portion of a joint boot (a portion at a large-diameter end or a small-diameter end, which is tightened by a tightening clamp) after being assembled into a constant velocity joint and continuously driven for a predetermined period. Deviation from a predetermined position due to sliding with the outer surface of the shaft,
Alternatively, the grease was observed for leakage. When either was observed, it was judged as x, and when neither was observed, it was judged as o. Specifically, the joint boot product is assembled to a constant velocity joint, and continuous driving is performed for 2 weeks, 6 weeks, and 8 weeks under the conditions of an ambient temperature of 30 ° C., a joint angle of 47 °, and a driving rotation speed of 100 rpm. After each predetermined period, the state after driving was observed.

(3) Durability: The ambient temperature was set at 100 ° C., the joint angle was set at 43 degrees, the rotation speed was set at 500 rpm, and the time until a through crack was generated in the joint boot body was measured. When the target value of 15.5 hours was reached, it was judged as ○, and when it was not reached, it was judged as ×.

The results of the tests on the joint boot products are summarized in Table 2.

[0085]

[Table 2] As shown in Table 2, the amount of the low-melting fatty acid amide (A) was 0.2 to 1.5 phr, and the amount of the high-melting fatty acid amide (B) was 0.03 to 0.15 phr. At certain times, good results were obtained (Examples 1 to 4). Especially,
The amount of the low-melting fatty acid amide (A) is 0.3 to 1.5.
phr, and when the blending amount of the fatty acid amide (B) having a high melting point is 0.06 to 0.15 phr, very good results are obtained in all items of suppression of abnormal noise, sealing property and durability. (Examples 1 to 3).

When the amount of the low-melting fatty acid amide (A) exceeds 1.5 phr (Comparative Example 2), the sealability after 6 weeks or more has been insufficient, and the durability of the product has been poor. Was inadequate. When the fatty acid amide (A) having a low melting point was not blended (Comparative Example 1), the suppression of abnormal noise due to rubbing after standing at room temperature or lower was extremely insufficient, and the seal after 6 weeks or more had passed. Sex was inadequate.

When the amount of the high-melting fatty acid amide (B) exceeds 0.15 phr (Comparative Example 3), the sealability after 6 weeks or more has been insufficient.
The durability of the product was insufficient. When the fatty acid amide (B) having a high melting point was not blended (Comparative Example 5), the suppression of the rubbing noise after standing at room temperature or higher was insufficient.

[0088]

In the bellows-like joint boot corresponding to a relatively wide-angle bending deformation, it is possible to suppress the generation of abnormal noise due to the rubbing of the bellows peak, and it is possible to sufficiently reduce the cost without increasing the product cost. Sealability and its reliability can be ensured.

[Brief description of the drawings]

FIG. 1 is a half sectional half side view showing the dimensions and shape of a joint boot used for performance evaluation.

FIG. 2 is a longitudinal sectional view of a seal portion in a joint boot used for performance evaluation.

FIG. 3 is a longitudinal sectional view showing another possible shape of the seal portion.

FIG. 4 is a cutaway side view for conceptually explaining a joint boot.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Joint boot 2 Shaft 3 Joint case 4 Tightening band 5 Large-diameter end cylindrical part 6 Small-diameter end cylindrical part 7 Bellows ridge line 8 Bellows valley line 9 Seal part 91 Seal ridge 92 Groove on the back of seal ridge 93 ridges

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masayuki Toriumi 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka Toyo Tire & Rubber Co., Ltd. (72) Inventor Atsuyuki Uda 1-17-18 Edobori, Nishi-ku, Osaka-shi, Osaka No. Toyo Tire & Rubber Co., Ltd.

Claims (5)

[Claims] 1. A large-diameter end short cylindrical portion for connecting to a universal joint storage case fixed to one shaft of a universal joint, and a small-diameter end short cylindrical portion for connecting to the other shaft of the universal joint. In a flexible joint boot made of a thermoplastic elastomer resin consisting of bellows whose diameter is gradually reduced from a large diameter end to a small diameter end, the melting point is 20 to 100 parts by weight of the thermoplastic elastomer resin polymer component. A thermoplastic elastomer comprising 0.2 to 1.5 parts by weight of a low-melting fatty acid amide having a melting point of 60 ° C and 0.03 to 0.15 parts by weight of a high-melting fatty acid amide having a melting point of 60 ° C or more. Flexible joint boot made of resin. 2. The flexible joint boot made of a thermoplastic elastomer resin according to claim 1, wherein the high melting point fatty acid amide has a melting point of 80 to 150 ° C. 3. The flexible joint boot made of a thermoplastic elastomer resin according to claim 2, wherein the high melting point fatty acid amide and the low melting point fatty acid amide are represented by the following formulas (I) to (II).
A flexible joint boot made of a thermoplastic elastomer resin, which is represented by any one of the following (I). R ₁ -CONH ₂ (I) (monoamide) R ₁ -CONH-R ₂ (II) (N-substituted amide) R ₁ -CONH-R ₃ -NHCO-R ₁ (III) (bisamide) where R ₁ And R ₂ are any of an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group, each having 6 or more carbon atoms. R
₃ is an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group,
It has two or more carbon atoms. 4. The flexible joint boot made of a thermoplastic elastomer resin according to claim 3, wherein the low melting point fatty acid amide is an N-substituted amide represented by the following formula (II), and the high melting point fatty acid amide is A flexible joint boot made of a thermoplastic elastomer resin, which is a bisamide represented by the formula (III). R ₁ -CONH-R ₂ (II) (N-substituted amide) R ₁ -CONH-R ₃ -NHCO-R ₁ (III) (bisamide) where R ₁ and R ₂ are alicyclic hydrocarbon groups , An aromatic hydrocarbon group, an aliphatic hydrocarbon group, or an unsaturated hydrocarbon group having 6 or more carbon atoms. R
₃ is an alicyclic hydrocarbon group, an aromatic hydrocarbon group, an aliphatic hydrocarbon group, and an unsaturated hydrocarbon group,
It has two or more carbon atoms. 5. A flexible joint boot made of a thermoplastic elastomer resin according to claim 4, wherein said thermoplastic elastomer resin is a thermoplastic polyester elastomer resin.