JPH11153226A - Resin flexible boots - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To obtain a resin flexible boot excellent in bending fatigue resistance, appearance, and production stability. A resin flexible boot having a shape in which a large diameter portion and a small diameter portion are connected by a bellows portion,
The resin forming the flexible boot is a thermoplastic polyester elastomer obtained by blending 0.01 to 10 parts by weight of a bifunctional or more epoxy compound (B) with 100 parts by weight of the polyester block copolymer (A). A flexible boot made of resin, characterized in that:

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible boot mounted on a universal joint for dust prevention and for holding grease for lubricating the universal joint, and more particularly to a flexible boot molded from a thermoplastic polyester elastomer.

[0002]

2. Description of the Related Art Hitherto, chloroprene rubber has been mainly used for flexible boots for dustproof and grease holding of a universal joint such as a constant velocity joint of an automobile. However, when it is used as a flexible boot for a constant velocity joint of an automobile, chloroprene rubber is insufficient in durability against repeated bending stress, and there is a problem that cracks occur due to long-term use, leading to breakage. . Moreover, since it is inferior in cold resistance, it may be hardened at the time of use in an extremely cold region and may be damaged. In addition, chloroprene rubber flexible boots with low mechanical strength can be damaged by stepping stones during running, or abnormally expanded during high-speed rotation such as high-speed running of automobiles, resulting in deformation or damage due to interference with other parts. Problems arise.

In order to solve such problems, bending fatigue resistance,
As a material having excellent cold resistance and mechanical strength, a flexible boot formed of a thermoplastic polyester elastomer has been proposed. For example, Japanese Patent Application Laid-Open No. 9-1947
No. 04 discloses an automobile constant velocity joint boot molded article obtained by blow molding a resin composition obtained by blending an organic polyisocyanate compound and a silicone compound with a polyester elastomer. Further, resin compositions in which a polyepoxy compound is blended with a polyester elastomer are disclosed in JP-A-48-100495 and JP-A-63-30927.

[0004]

SUMMARY OF THE INVENTION The aforementioned Japanese Patent Application Laid-Open No. 9-19 / 1997
The constant velocity joint boot molded article disclosed in Japanese Patent No. 4704 is certainly excellent in abrasion resistance, mechanical properties, and flexibility. However, since an organic polyisocyanate compound is used as a thickener, the surface of the boot molded article can be improved. And it is easy to fall into a state where the gelled resin is present in a fish-eye state inside. Such boot molded articles not only have poor appearance,
Concentration of stress on the fish-eye-like gel portion lowers bending fatigue resistance, which is indispensable for boot performance. Further, since the polyester elastomer resin composition containing the organic polyisocyanate compound contains a polymer produced by the reaction of the organic polyisocyanate compounds during the melt residence, when the boot is molded, it is volatilized and the gold is evaporated. It is easy to cause mold contamination attached to the mold. In this case, the mold often needs to be cleaned, resulting in a boot having low productivity. When the volatile matter is transferred to a boot molded product, the boot has a poor appearance. further,
Since the melt viscosity of the polyester elastomer resin composition containing the organic polyisocyanate compound is liable to change during the stagnation of the melt, a boot molded product having an unstable weight and thickness is easily obtained. Such boot molded articles have the disadvantage of causing breakage from thin portions.

Therefore, the present inventors have found that there is no transfer of fish eyes and mold contaminants, and that the weight and thickness are stable,
As a result of examining resin flexible boots with excellent appearance, bending fatigue resistance, and productivity, it was found that the above targets were achieved in flexible boots molded using a specific thermoplastic polyester elastomer. The invention has been reached.

[0006]

That is, the present invention relates to a resin-made flexible boot having a shape in which a large-diameter portion and a small-diameter portion are connected by a bellows portion, wherein the resin forming the flexible boot is a polyester block copolymer. (A) A thermoplastic boot made of a thermoplastic polyester elastomer obtained by mixing 0.01 to 10 parts by weight of a bifunctional or more epoxy compound (B) with respect to 100 parts by weight.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[0008] The thermoplastic polyester elastomer (A) used in the resin-made flexible boot of the present invention is a polyester block copolymer (A) comprising a high melting crystalline polyester polymer segment (a) and a low melting polymer segment (b). A) is mainly used.

The high melting point crystalline polyester polymer segment (a) of the polyester block copolymer (A) constituting the thermoplastic polyester elastomer used in the resin-made flexible boot of the present invention is formed of an aromatic dicarboxylic acid or an ester thereof. A polyester formed from an acidic derivative and an aliphatic diol, preferably with terephthalic acid and / or dimethyl terephthalate and 1,4-
Polybutylene terephthalate derived from butanediol, and in addition, a dicarboxylic acid component such as isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid, or an ester-forming derivative thereof, and a molecular weight of 300 or less. Diols such as ethylene glycol,
Trimethylene glycol, pentamethylene glycol,
Hexamethylene glycol, neopentyl glycol,
Aliphatic diols such as decamethylene glycol, 1,4
Alicyclic diols such as cyclohexanedimethanol, tricyclodecanedimethylol, bis (p-hydroxy) diphenyl, bis (p-hydroxyphenyl) propane, 4,4′-dihydroxy-p-terphenyl,
Polyesters derived from aromatic diols such as 4,4'-dihydroxy-p-quarterphenyl and the like, or copolymer polyesters using two or more of these dicarboxylic acid components and diol components in combination may be used.
Further, an aliphatic dicarboxylic acid such as adipic acid or sebacic acid may be copolymerized. Furthermore, it is also possible to copolymerize a trifunctional or higher polyfunctional carboxylic acid component, a polyfunctional oxyacid component, a polyfunctional hydroxy component and the like in a range of 5 mol% or less.

The low-melting-point polymer segment (b) of the polyester block copolymer (A) constituting the thermoplastic polyester elastomer used in the resin flexible boot of the present invention is an aliphatic polyether and / or an aliphatic polyester. is there. Examples of the aliphatic polyether include poly (ethylene oxide) glycol, poly (propylene oxide) glycol, poly (tetramethylene oxide) glycol, and poly (hexamethylene oxide).
Glycol, a copolymer of ethylene oxide and propylene oxide, an ethylene oxide addition polymer of poly (propylene oxide) glycol, and a copolymer of ethylene oxide and tetrahydrofuran. In addition, examples of the aliphatic polyester include polycaprolactone, polyenantholactone, polycaprylolactone, polybutylene adipate, and polyethylene adipate. Among these aliphatic polyethers and / or aliphatic polyesters, poly (tetramethylene oxide) glycol, ethylene oxide adduct of poly (propylene oxide) glycol, polycaprolactone, Butylene adipate and polyethylene adipate are preferred. Further, the number average molecular weight of these low melting polymer segments is 300 to 300 in the copolymerized state.
It is preferably about 6000. The copolymerization amount of the low-melting polymer segment (b) in the polyester block copolymer (A) is preferably 10 to 80% by weight, more preferably 15 to 75% by weight.

The compound constituting the thermoplastic polyester elastomer used in the resin-made flexible boot of the present invention is a bifunctional or more functional epoxy compound (B) in addition to the polyester block copolymer (A). Examples of such an epoxy compound include bisphenol A type epoxy resin produced by a condensation reaction of bisphenol A and epichlorohydrin, ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, neopentyl glycol diglycidyl ether,
1,6-hexanediol diglycidyl ether, diglycidyl ether compounds of glycols such as dibromoneopentyl glycol diglycidyl ether, polyethylene glycol diglycidyl ether, polypropylene glycol diglycidyl ether, glycerol polyglycidyl ether, trimethylolpropane polyglycidyl ether, Polyglycidyl ether compounds of polyols such as diglycerol polyglycidyl ether, polyglycerol polyglycidyl ether, sorbitol polyglycidyl ether, diglycidyl phthalate, diglycidyl isophthalate, diglycidyl terephthalate, diglycidyl hexahydrophthalate , Naphthalenedicarboxylic acid diglycidyl ester, bibenzo Diglycidyl ester, methyl terephthalic acid diglycidyl ester, tetrahydrophthalic acid diglycidyl ester, cyclohexanedicarboxylic acid diglycidyl ester, adipic acid diglycidyl ester, succinic acid diglycidyl ester, sebacic acid diglycidyl ester, dodecane dicarboxylic acid diglycidyl ester, Examples include diglycidyl ester compounds of dicarboxylic acids such as octadecane dicarboxylic acid diglycidyl ester and dimer acid diglycidyl ester, and polyglycidyl ester compounds of polycarboxylic acids such as trimellitic acid triglycidyl ester and pyromellitic acid tetraglycidyl ester. Among these, a bifunctional epoxy compound having two glycidyl groups in the compound is preferable. Further, glycidyl ester compounds are preferred.

The compounding amount of the bifunctional or higher epoxy compound (B) is 0.01 to 10 parts by weight, preferably 0.05 to 8 parts by weight, based on 100 parts by weight of the polyester block copolymer (A). Parts, more preferably 0.1
-5 parts by weight. If the compounding amount is less than 0.01 part by weight, a sufficiently high melt viscosity for molding a flexible boot cannot be obtained, and if the compounding amount exceeds 10 parts by weight, gelation occurs due to molten stagnation during molding and molding cannot be performed.

The method for producing the thermoplastic polyester elastomer used in the resin-made flexible boot of the present invention is not particularly limited, and examples thereof include a polyester block copolymer and a bifunctional or higher functional epoxy compound. A method in which additives are mixed in advance and supplied to a screw-type extruder and melt-kneaded, or a method in which each raw material is separately supplied to a screw-type extruder and melt-kneaded, may be used.

The method for producing the resinous flexible boot of the present invention is not particularly limited, and examples thereof include blow molding methods such as extrusion blow, injection blow, and press blow, and injection molding methods.

The resin-made flexible boot of the present invention does not transfer fish eyes and mold contaminants, has a stable weight and thickness, and is excellent in appearance, bending fatigue resistance and productivity.

[0016]

EXAMPLES The effects of the present invention will be described below with reference to examples. All percentages and parts in the examples are on a weight basis unless otherwise specified.

Example 1 Polybutylene terephthalate was used as a hard segment,
Polyester block copolymer having a soft segment of polytetramethylene oxide glycol having a molecular weight of 1400 (weight ratio of hard segment / soft segment = 4)
5/55) For 100 parts, "Irganox" 10
10 parts (Ciba Geigy's hindered phenolic antioxidant), 0.5 part of hexahydrophthalic acid diglycidyl ester, and 1 part of carbon black were blended and mixed in a Henschel mixer. / D
= 30, the set temperature of the cylinder and the die is 240 ° C, and the screw rotation speed is 130 rpm
m and melt-kneaded. The polymer was discharged from the die in water in a strand form, cut, and pelletized to obtain a thermoplastic polyester elastomer (A-1).

After drying the obtained thermoplastic polyester elastomer (A-1) with hot air at 80 ° C. for 5 hours, AST
Measurement temperature 220 ° C, load 21 according to MD1238
While measuring the melt flow rate at 60 g, a test piece was prepared by injection molding and evaluated as follows.

Surface hardness: based on JIS K7215,
Measured on durometer D scale.

Tensile properties: in accordance with JIS K7113,
Measured for No. 2 test piece.

A test piece having a thickness of 2 mm and a width of 20 mm was prepared by press molding, and the bending fatigue resistance was evaluated. The evaluation was performed under the following conditions, and the crack length after one million bending cycles was measured. In this test, the smaller the occurrence of cracks, the better the durability. Table 1 shows the results.

Test conditions: Test machine: Dematcher flex fatigue test machine Test temperature: 100 ° C. Distance between chucks: 25 mm ← → 5.6 mm Flex cycle: 300 times / min

[Table 1] Next, the thermoplastic polyester elastomer (A-1) dried with hot air at 80 ° C. for 5 hours was pressed at a cylinder temperature of 230 ° C., a nozzle temperature of 230 ° C., and a mold using a press blow molding machine (SBE50 / 140 manufactured by Osberger). Temperature 3
Under a molding condition of 0 ° C., a large-diameter portion and a small-diameter portion are formed into a flexible boot for a constant velocity joint having a weight of 60 g and having a shape in which five ridges and five valleys are connected by a bellows having a thickness of 0.5 mm and having five valleys. did. The molding is performed continuously for 8 hours.
Five boots were sampled every hour, the appearance was examined, and the boot weight was measured. Also, when the boot is placed with the small caliber part up, the mountain which is the third mountain from the top,
The thickness of the cross section of the boot, which was cut vertically, was measured for the valley following it, and the difference in thickness between the peak and the valley was determined. Table 1 shows the results
Shown in As is clear from Table 1, in this example, the bending fatigue resistance of the boot material was excellent, and no fish eyes were observed in any of the boots sampled at the time of molding. Further, there was no appearance defect due to transfer of the mold contaminants. The boot weight is all within the range of 60 ± 0.5g, and the difference between the thickness of the peak and the valley is 0.1m.
m or less.

Comparative Example 1 A polyester block copolymer having the hard segment of polybutylene terephthalate used in the examples and the soft segment of polytetramethylene oxide glycol (hard segment / soft segment weight ratio = 45)
/ 55) For 100 parts, "Ilganox" 101
0 (a hindered phenolic antioxidant manufactured by Ciba-Geigy) 0.5 part, diphenylmethane diisocyanate 0.1 part.
5 parts and 1 part of carbon black were blended and mixed in a Henschel mixer, and then supplied to a twin screw extruder having an inner diameter of 40 mm and L / D = 30. The set temperature of the cylinder and the die was 240 ° C., and the screw rotation speed was 130 rpm. Was melt-kneaded. The polymer was discharged from the dice into a strand in water, cut and pelletized to obtain a thermoplastic polyester elastomer (B-1).

The obtained thermoplastic polyester elastomer (B-1) was evaluated in the same manner as in the examples. Table 2 shows the results. As is clear from Table 2, in this comparative example using the organic isocyanate compound, the bending fatigue resistance of the boot material was not sufficient. In addition, the proportion of fish boots observed in the boots sampled at the time of molding was high, and the appearance defect due to the transfer of mold contaminants also progressed with time. Furthermore, the boot weight was not stable, and the weight range was 60 ± 1.5 g. The thickness of the boot is not stable, and the difference in thickness between the peak and the valley is 0.21 m at the maximum.
m.

[0025]

[Table 2] Comparative Example 2 Polyester block copolymer having polybutylene terephthalate used as a hard segment and polytetramethylene oxide glycol as a soft segment used in Examples (hard segment / soft segment weight ratio = 45)
/ 55) For 100 parts, "Ilganox" 101
0 (Ciba Geigy's hindered phenolic antioxidant) 0.5 part and only 1 part of carbon black are blended,
After mixing in Henschel mixer, inner diameter 40mm,
It is fed to a twin screw extruder with L / D = 30, the set temperature of the cylinder and the die is 240 ° C., and the screw rotation speed is 13
The mixture was melt-kneaded at 0 rpm. The polymer was discharged from the dice into a strand in water, cut and pelletized to obtain a thermoplastic polyester elastomer (B-2). The obtained thermoplastic polyester elastomer (B-2) was evaluated in the same manner as in the examples, but the thermoplastic polyester elastomer (B-2) was too low in melt viscosity to be blow molded. Was.

Comparative Example 3 Polybutylene terephthalate was used as a hard segment,
Polyester block copolymer having a soft segment of polytetramethylene oxide glycol having a molecular weight of 1400 (weight ratio of hard segment / soft segment = 4)
5/55) For 100 parts, "Irganox" 10
10 (Ciba Geigy's hindered phenolic antioxidant), 0.5 part of hexahydrophthalic acid diglycidyl ester and 1 part of carbon black were blended and mixed in a Henschel mixer. =
The mixture was fed to a 30-screw extruder, and melt-kneaded at a cylinder and die set temperature of 240 ° C. and a screw rotation speed of 130 rpm. The polymer was discharged from the dice into a strand in water, cut and pelletized to obtain a thermoplastic polyester elastomer (B-3). An attempt was made to evaluate the obtained thermoplastic polyester elastomer (B-3) in the same manner as in the example, but the thermoplastic polyester elastomer (B-3) was gelled and could not be blow-molded. Was.

Example 2 Polybutylene terephthalate was used as a hard segment,
100 parts of a polyester block copolymer having polycaprolactone as a soft segment (weight ratio of hard segment / soft segment = 45/55) to “Irganox” 1010 (a hindered phenolic antioxidant manufactured by Ciba Geigy) 0.5 Part, diglycidyl terephthalate 0.3 part and carbon black 1 part were blended and mixed in a Henschel mixer.
m, L / D = 30 to a twin screw extruder, cylinder and die set temperature 240 ° C., screw rotation speed 1
The mixture was melt-kneaded at 30 rpm. The polymer was discharged from the die into water in a strand form, cut, and pelletized to obtain a thermoplastic polyester elastomer (A-2). The obtained thermoplastic polyester elastomer (A-
2) was evaluated in the same manner as in Example 1. Table 3 shows the results. As is evident from Table 3, also in this example, the material for boots was excellent in bending fatigue resistance, and no fisheye was observed in any of the boots sampled at the time of molding. Further, there was no appearance defect due to transfer of the mold contaminants. Boot weights were all in the range of 60 ± 0.5 g. Furthermore, the difference in thickness between the peak and the valley is
All were 0.1 mm or less.

[0028]

[Table 3]

[0029]

According to the present invention, the flexible boot using a thermoplastic polyester elastomer obtained by blending a polyester block copolymer with a bifunctional or more epoxy compound has no appearance defect due to transfer of fish eyes and mold contaminants. Excellent flex fatigue resistance and production stability.

Continued on the front page (72) Inventor Yoko Furuta 19804, Kita-ku, Hoshiboshizaki-cho, Minato-ku, Nagoya-shi, Aichi 19 Toray Dupont Co., Ltd.

Claims (7)

[Claims] 1. A resin flexible boot having a shape in which a large diameter portion and a small diameter portion are connected by a bellows portion, wherein the resin forming the flexible boot is based on 100 parts by weight of the polyester block copolymer (A). A flexible boot made of resin, which is a thermoplastic polyester elastomer obtained by mixing 0.01 to 10 parts by weight of a bifunctional or more epoxy compound (B). 2. An epoxy compound (B) having two or more functional groups,
The resin-made flexible boot according to claim 1, which is a bifunctional epoxy compound. 3. An epoxy compound (B) having two or more functional groups,
The resin-made flexible boot according to claim 1, which is a glycidyl ester compound. 4. Polyester block copolymer (A)
Has a high melting point crystalline polymer segment (a) mainly composed of crystalline aromatic polyester units and a low melting point polymer segment (b) mainly composed of aliphatic polyether units and / or aliphatic polyester units. The resin-made flexible boot according to any one of claims 1 to 3, which is a united product. 5. The resin-made flexible boot according to claim 1, wherein the high-melting crystalline polymer segment (a) of the polyester block copolymer (A) is composed of polybutylene terephthalate units. 6. The low melting point polymer segment (b) of the polyester block copolymer (A) has a poly (tetramethylene oxide) glycol unit, an ethylene oxide addition polymer unit of poly (propylene oxide) glycol, a polycaprolactone unit, and a poly (propylene glycol) unit. Butylene adipate units,
The resin-made flexible boot according to any one of claims 1 to 5, wherein the flexible boot is made of any one selected from polyethylene adipate units. 7. The copolymerization amount of the low melting point polymer segment (b) in the polyester block copolymer (A) is 10
The resin-made flexible boot according to any one of claims 1 to 6, wherein the content of the flexible boot is from 80 to 80% by weight.