JP2003227568A - Resin made flexible boot and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a resin made flexible boot improves sustaining effect of suppression of abnormal noise occurrence and secures sealing property and durability. <P>SOLUTION: The resin made flexible boot is formed using thermoplastic elastomer resin as a base resin material, and a large diameter opening is connected to a small diameter opening through a bellows. Mineral oil or vegetable oil is added to the thermoplastic elastomer resin. The thermoplastic elastomer resin is preferably thermoplastic polyester elastomer, and the mineral oil is preferably process oil with an aromatic component content of 13% or less. The resin made flexible boot is used as a flexible boot for covering constant velocity joint of an automobile. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bellows-shaped resin flexible boot used for a constant velocity joint of an automobile and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art This type of flexible resin boot is
A large-diameter opening fitted to the housing of a constant velocity joint of an automobile and a small-diameter opening fitted to the axle are connected by a tapered bellows, which is enclosed in the constant velocity joint. It prevents grease from leaking and prevents dust from entering.

Chloroprene rubber has generally been mainly used as a molding material for such flexible boots. However, flexible boots made of chloroprene rubber are abnormally inflated and deformed due to centrifugal force during rotation, especially during high-speed rotation, and that state continues for a long time.
When expansion and contraction are repeated, there is a problem that the product is liable to be damaged in a short time due to mechanical deterioration, resulting in a short product life.

Therefore, recently, a thermoplastic elastomer resin such as a highly elastic thermoplastic polyester elastomer has come to be used as a molding material having excellent heat resistance, bending resistance and strength. However, the flexible boot made of such a highly elastic thermoplastic elastomer resin also has a drawback. That is, when a flexible boot made of a highly elastic thermoplastic elastomer resin is attached to a constant velocity joint of an automobile and rotated in a state of bending displacement at a wide angle, the ridges of the bellows rub against each other, and this rubbing action causes a difference. A sound is generated, and the material is worn away due to this abnormal noise. In particular, when moisture adheres to the outer surface of the flexible boot, such abnormal noise is likely to occur remarkably.

As a measure for suppressing such abnormal noise generation, it has been proposed to add silicone oil or fatty acid amide to the thermoplastic polyester elastomer as an abnormal noise suppression agent. Among them, the technique of blending a fatty acid amide is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-177971.

However, the above-mentioned JP-A-9-1779 in which a fatty acid amide is blended with a thermoplastic polyester elastomer.
The resin flexible boot described in Japanese Patent No. 71 can suppress the generation of abnormal noise in the initial stage when it is attached to a constant velocity joint of an automobile and continuously rotated in a state of being bent and displaced at a wide angle. It was found that the duration of sound suppression was short, and abnormal noise started to occur after a certain time while the vehicle was running. To improve the continuous effect of suppressing the generation of abnormal noise,
It is possible to increase the amount of fatty acid amide compounded,
When the amount of the fatty acid amide compounded is increased, the fatty acid amide is precipitated in the form of powder on the surface of the flexible boot, the amount of the precipitated fatty acid amide is large, and it is easily scraped off, and the effect of suppressing abnormal noise is not prolonged. Furthermore, since the amount of the precipitation increases, the large-diameter opening portion or the small-diameter opening portion of the flexible boot lowers the friction coefficient between the housing portion or the axle portion of the constant velocity joint and becomes slippery. We have found that there is a positional shift that causes grease leakage, and that grease leakage actually occurs, resulting in poor sealing performance.

[0007]

SUMMARY OF THE INVENTION The object of the present invention is to solve the above problems, and the continuous effect of suppressing the generation of abnormal noise is improved while maintaining the initial effect of suppressing abnormal noise generation. In order to provide a flexible boot made of resin, the sealing property and durability are ensured.

[0008]

A flexible boot made of resin according to claim 1 of the present invention is formed by using a thermoplastic elastomer resin as a base resin material, and has a large diameter mouth portion and a small diameter mouth portion. A flexible boot made of resin connected by bellows is characterized in that mineral oil is added to the thermoplastic elastomer resin.

According to the resin flexible boot having the above-mentioned structure, no abnormal noise is initially generated even when the resin flexible boot is mounted on a constant velocity joint of an automobile and continuously rotated while being bent and displaced at a wide angle. The duration of suppressing the generation of abnormal noise can be lengthened. In addition, sealing performance and durability can be secured. The reason for this is that in the case of mineral oil, the liquid deposits (bleed) that deposit on the surface of the flexible boot are adhered in the form of an oil film, and unlike solid powder-like deposits such as fatty acid amides, it is easy to use from the surface of the flexible boot. It is thought that this is because it does not rub off.

As the thermoplastic elastomer resin, it is preferable to use a thermoplastic polyester elastomer having a hard segment composed of an aromatic dicarboxylic acid and a low molecular weight glycol and a soft segment having a molecular weight of 400 to 4000 as its constituent components.

Mineral oil, which is excellent in heat resistance, flex resistance and strength,
By combining with an oil such as a vegetable oil, it is possible to obtain a flexible boot having a particularly excellent effect of preventing the generation of abnormal noise at the initial stage and a long-lasting effect of suppressing the generation of abnormal noise while ensuring the sealing property and durability.

It is preferable that the thermoplastic elastomer resin is a thermoplastic polyester elastomer having a hard segment composed of an aromatic dicarboxylic acid and a low molecular weight glycol and a soft segment having a molecular weight of 400 to 4000 as constituent components.

In the thermoplastic polyester elastomer constituting the flexible boot, the aromatic dicarboxylic acid constituting the hard segment is at least one selected from terephthalic acid and naphthalenedicarboxylic acid, and the low molecular weight glycol is ethylene. It is preferably at least one selected from glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and dimer glycol. The aromatic dicarboxylic acid is terephthalic acid and the low molecular weight glycol is 1,4.
Particularly preferred is butanediol.

In the thermoplastic polyester elastomer constituting the flexible boot, the soft segment is polyoxytetramethylene glyco-
It is preferable that the soft segment is polyoxytetramethylene glycol, and it is particularly preferable that the soft segment is polyoxytetramethylene glycol.

When polyoxytetramethylene glycol is used as the soft segment, the copolymerization amount of polyoxytetramethylene glycol in the thermoplastic polyester elastomer is preferably 35 to 55% by weight, and polyoxytetramethylene glycol is preferably used. It is more preferable that the copolymerization amount of is 40 to 50% by weight.

In the resin flexible boot of the present invention, the mineral oil is at least one process oil selected from paraffin oil and naphthene oil having an aromatic content of 13% or less. preferable.

The process oil is a thermoplastic polyester elastomer (hereinafter sometimes abbreviated as TPEE).
Since it has a moderate compatibility with, it does not cause physical property deterioration such as strength reduction of TPEE due to swelling, moderately bleeds on the surface of the flexible boot and adheres in a thin film form, and an initial noise generation prevention effect, It exerts a long-lasting effect of suppressing the generation of abnormal noise. When the content of the aromatic component in the process oil exceeds 13%, the swelling degree of TPEE increases,
Not preferable.

The mineral oil has an aromatic content of 1 to
More preferably, it is at least one process oil selected from paraffin oils and naphthene oils of 10% or less. When the content of the aromatic component is less than 1%, the effect of increasing the duration of suppressing abnormal noise is TP.
It may not be sufficient depending on the composition of EE.

The process oil is preferably blended in an amount of 5 parts by weight or less with respect to 100 parts by weight of the thermoplastic elastomer resin. When it is mixed in an amount exceeding 5 parts by weight, the duration for suppressing the generation of abnormal noise can be lengthened, but depending on the composition of the TPEE used, cracks may occur in the troughs of the bellows at an early stage. In some cases, sufficient durability may not be obtained.

More preferably, the process oil is blended in an amount of 3 parts by weight or less based on 100 parts by weight of TPEE. Since the time until crack initiation can be extended as compared with the case of adding 5 parts by weight or less of mineral oil, the durability performance can be further improved.

Another resin-made flexible boot of the present invention is a resin-made flexible boot formed by using a thermoplastic elastomer resin as a base resin material and connecting a large diameter mouth portion and a small diameter mouth portion with a bellows portion. The feature is that vegetable oil is added to the thermoplastic elastomer resin.

Even in the resin flexible boot having the above-mentioned structure, even when it is mounted on a constant velocity joint of an automobile and continuously rotated in a bending displacement at a wide angle, the abnormal noise is not generated in the initial stage. The duration of sound generation suppression can be extended. In addition, sealing performance and durability can be secured. It is considered that this is because the vegetable oil is a liquid oil like the mineral oil and has the same action as that of the mineral oil.

In the above resin flexible boot, it is preferable that vegetable oil is blended in an amount of 5 parts by weight or less with respect to 100 parts by weight of the thermoplastic elastomer resin.

When more than 5 parts by weight of vegetable oil is added to 100 parts by weight of the thermoplastic elastomer resin, the duration of suppressing the generation of abnormal noise can be prolonged, but cracks penetrate through the valleys of the bellows at an early stage. The required and sufficient durability cannot be obtained.

The vegetable oil is a thermoplastic elastomer resin 10.
It is more preferable that the amount is 3 parts by weight or less with respect to 0 parts by weight. As compared with the case where the amount of vegetable oil is 5 parts by weight or less, the time until crack initiation can be increased and the durability performance is further enhanced.

In the resin flexible boot formed by blending TPEE with mineral oil, the degree of swelling of the polyester elastomer with the mineral oil is preferably 8 vol% or less.

If the degree of swelling is more than 8 vol%, swelling may cause cracks to be formed in the valleys of the bellows in a penetrating manner, and necessary and sufficient durability may not be obtained.

In the resin flexible boot formed by blending TPEE with mineral oil, the degree of swelling of the polyester elastomer with the mineral oil is preferably 6 wt% or less.

If the degree of swelling exceeds 6 wt%, cracks may occur in the valleys of the bellows in a penetrating manner due to swelling, and necessary and sufficient durability may not be obtained.

The degree of swelling is measured by immersing a thermoplastic polyester elastomer (a commercially available resin alone which is not blended with mineral oil, vegetable oil or the like and used as a boot molding material) in mineral oil for 48 hours.

In the method of manufacturing a resin flexible boot of the present invention, a resin flexible boot in which a large diameter mouth portion and a small diameter mouth portion are connected by a bellows portion is manufactured by using a thermoplastic polyester elastomer as a base resin material. On the occasion of
A pellet of the thermoplastic polyester elastomer is heated in a state where a liquid additive containing a mineral oil or a vegetable oil is added and mixed and stirred, and the obtained mixture is kneaded and extruded using an extruder to form a molding material, The resin-made flexible boot is molded using this molding material.

According to this manufacturing method, since the thermoplastic polyester elastomer pellets are heated, a liquid additive containing mineral oil or vegetable oil is added to the pellets and mixed and stirred, so that the surface of the pellets is softened. It becomes easily compatible with mineral oil or vegetable oil, and the liquid additive uniformly adheres to the surface of the pellet. Therefore, a mixture of pellets of a thermoplastic polyester elastomer and a liquid additive is kneaded and extruded using an extruder, and a molding material in which a mineral oil or a vegetable oil is uniformly dispersed in the thermoplastic polyester elastomer. The flexible boot molded with this molding material can prolong the duration of suppressing abnormal noise.

In the above-mentioned manufacturing method, the solid additive is added to the mixture of the pellets and the liquid additive containing the mineral oil or vegetable oil, and the mixture is stirred. The resulting mixture is kneaded and extruded. A molding material may be made.

The pellets and the solid additive may be heated and mixed and stirred, and then the liquid additive may be mixed and stirred, and the pellets may be mixed with the liquid additive in a heated state. You may mix and stir. Further, the pellets, the liquid additive, and the solid additive may be heated and then mixed and stirred to obtain the mixture.

In the above-described method for producing a flexible boot made of resin, the heating temperature is set to 60 ° C. or higher, more preferably 70 to 100 ° C. At temperatures lower than 60 ° C, the viscosity of mineral oil and vegetable oil is high and may not be dispersed uniformly. At temperatures higher than 100 ° C, the pellets of the thermoplastic polyester elastomer are stirred by a mixer as a heating method, and the friction of the pellets is agitated. When heating using heat,
This is because heating takes a long time, which is not efficient.

[0036]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view (longitudinal side view) of a flexible resin boot 1 according to an embodiment of the present invention. This resin flexible boot 1 has a large diameter mouth portion 2 at one end.
Has a small-diameter opening 3 at the other end, and the large-diameter opening 2 and the small-diameter opening 3 are connected by a tapered bellows 4 for injection molding, press blow molding, or injection blow molding. It is integrally molded by a known molding method such as direct blow molding.

The resin-made flexible boot 1 molded in this way is, for example, as shown in FIG. 2, an inboard joint (universal joint) 7 for interlockingly connecting a drive shaft 6 to a rear axle 5 of the automobile so as to allow bending displacement. The outer case 8 and the outer case 10 of the outboard joint 9 are fitted with the large-diameter openings 2 respectively and fixed by a tightening clamp 12, and the rear axle 5 is fitted with the small-diameter openings 3 respectively. The joints 7 and 9 are covered by tightening and fixing them with a tightening clamp 12, and the grease-filled space 1 is provided inside each bellows portion 4.
1 and 11 are formed.

As a molding material for the resin flexible boot 1 having the above-mentioned structure, a thermoplastic elastomer resin is used as a base resin material, and mineral oil or vegetable oil is mixed with the base resin material. The mixing ratio is 5 parts by weight or less, more preferably 3 parts by weight or less, and particularly preferably 0.5 to 3 parts by weight, with respect to 100 parts by weight of the thermoplastic elastomer resin. If the mineral oil or the vegetable oil is added in an amount of more than 5 parts by weight, cracks may occur in the troughs of the bellows portion 4 early in a penetrating state, resulting in poor durability.

As the thermoplastic elastomer resin (TPE), polyester (TPEE), polyolefin (TPO), polyamide (TPAE), as long as it has grease resistance, bending fatigue resistance and flexibility, Any of urethane type (TPU) and the like can be used, but polyester type (TPEE) is preferable.

As described above, TPEE comprises a hard segment composed of an aromatic dicarboxylic acid and a low molecular weight glycol and a soft segment having a molecular weight of 400 to 4000 as its constituent components. The polyester segment constituting the hard segment has a melting point of 180 ° C. or higher when the high segment alone is a high polymer, while the soft segment has a softening point or melting point of 80 ° C. or lower.

Specific examples of the aromatic dicarboxylic acid constituting the hard segment include terephthalic acid, diphenylcarboxylic acid, 5-sodium sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid and 1,5-
Examples thereof include naphthalenedicarboxylic acid such as naphthalenedicarboxylic acid and 1,4-naphthalenedicarboxylic acid, and it is particularly preferable to use at least one selected from terephthalic acid and naphthalenedicarboxylic acid. The combined use of these aromatic dicarboxylic acids with aliphatic or alicyclic dicarboxylic acids is a preferable mode because the degree of freedom in adjusting the characteristics of TPEE is increased. Examples of such aliphatic to alicyclic dicarboxylic acids include cyclohexanedicarboxylic acid, tetrahydrophthalic anhydride, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, dimer acid, hydrogenated dimer acid and the like. It is illustrated.

When the aromatic dicarboxylic acid and the aliphatic or alicyclic dicarboxylic acid are used in combination, the aromatic dicarboxylic acid content is preferably 70 mol% or more, more preferably 75 mol% or more, based on the total acid content. is there.

The low molecular weight glycol constituting the hard segment is, specifically, ethylene glycol,
1,3-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, dimethylolheptane, dimethylolpentane, tricyclode Examples include candimethanol, bisphenol A ethylene oxide adduct, bisphenol F ethylene oxide adduct, bisphenol S ethylene oxide adduct, 1,4-cyclohexanedimethanol, dimer glycol and the like. Among these, at least one selected from ethylene glycol, 1,4-butanediol, 1,4-cyclohexanedimethanol, and dimer glycol is particularly preferable.

In the hard segment, the aromatic dicarboxylic acid is terephthalic acid and the low molecular weight glycol is 1,4-
Butanediol is particularly preferred.

As the soft segment in the thermoplastic polyester elastomer used in the present invention,
Specifically, polyoxytetramethylene glycol (P
TMG), polyoxypropylene glycol (PP
G) and aliphatic polyester diols are exemplified. The polyoxypropylene glycol preferably has an ethylene oxide unit at the terminal. Examples of the aliphatic polyester diol include aliphatic dicarboxylic acids such as adipic acid, azelaic acid, sebacic acid, dodecanoic acid, dimer acid and hydrogenated dimer acid, ethylene glycol, 1,3
-Propylene glycol, 1,4-butanediol,
Condensation polymers of glycols such as 1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, neopentyl glycol, dimethylolheptane and dimethylolpentane, ring-opening polymers of ε-caprolactone, PTMG Examples thereof include copolymers in which ε-caprolactone is ring-opened and added. The soft segment is preferably polyoxytetramethylene glycol, polyoxypropylene glycol, or poly ε-caprolactone diol, and particularly preferably the soft segment is polyoxytetramethylene glycol.

Examples of thermoplastic polyester elastomers using the above-mentioned constituents include Perprene (trade name, manufactured by Toyobo Co., Ltd.), Hytrel (trade name, manufactured by Toray Dubon Co., Ltd.), ARNITEL (manufactured by DSM), etc. Is commercially available and recommended for use. In particular, a polymer of terephthalic acid and 1,4-butanediol is used as the hard segment, and PTMG is used as the soft segment.
As a thermoplastic polyester elastomer having a TMG copolymerization amount of 40 to 50% by weight, Perprene P46D is used.
Is exemplified as a suitable commercial product.

Mineral oils added to thermoplastic elastomer resins include paraffinic process oils, naphthenic process oils, and aromatic process oils. These are commercially available for rubber softeners, lubricants, and the like.
Process oils are usually paraffin, naphthene,
It contains aromatic components and is classified as paraffin-based process oil, naphthene-based process oil, and aroma-based process oil according to its composition ratio. Among these process oils, the process oil preferably used in the resin flexible pouch of the present invention is a paraffinic or naphthenic process oil having an aromatic content of 13% or less as described above, More preferably, it is a paraffinic or naphthenic process oil having an aromatic content of 1 to 10%, and even more preferably a paraffinic process oil having an aromatic content of 1 to 10%. Particularly preferred paraffinic process oil in combination with TPEE has a paraffin component content of 60 to 78% and a naphthene component content of 20 to 35.
%, An aromatic component content of 1 to 10%, and a paraffinic process oil such as BJ oil (trade name, Kyodo Yushi Co., Ltd.).
Are commercially available and their use is recommended.

The contents of paraffin component, naphthene component and aromatic component in the process oil are measured by the ring analysis method (n-
d-M method) ("Lubrication Handbook" Japan Society of Lubrication 19
1982, 6th edition).

Suitable vegetable oils are rapeseed oil, linseed oil, soybean oil, castor oil and the like.

By adding such a mineral oil or vegetable oil, preferably a process oil having an aromatic content of 13% or less, to the thermoplastic polyester elastomer, the compatibility of the two is very well balanced, and the oil content is a thermoplastic elastomer resin. Since it is deposited little by little on the surface, it is possible to exert the effect of preventing abnormal noise for a long period of time. In addition, since the mineral oil or vegetable oil does not adversely affect the physical properties of the thermoplastic elastomer resin, the standard for durability can be sufficiently satisfied.

When a process oil is used as the mineral oil, its average molecular weight, that is, the number average molecular weight, the weight average molecular weight, and the Z average molecular weight, can be measured by gel permeation chromatography (GPC) method using GMH _XL- GMH as a column. _XL- G2000H _XL (manufactured by Tosoh Corporation) was used, and chloroform was used as a solvent (flow rate 0.7 ml / min) at 40 ° C. with SYSTEM-21 (manufactured by Showa Denko KK), and a single refractive index (RI) was used. Dispersed polystyrene is used as a standard substance in terms of polystyrene.

The number average molecular weight of the process oil is 200-
It is 2000, more preferably 500 to 1000. In the flexible boot 1 made of a thermoplastic elastomer resin to which a process oil having a number average molecular weight of more than 2000 is added, an abnormal noise (initial abnormal noise) is immediately generated. In the flexible boot 1 made of a thermoplastic elastomer resin to which a process oil having a number average molecular weight of less than 200 is added,
Initial noise does not occur, but the duration of suppression of noise generation is short. Therefore, the number average molecular weight of the process oil is preferably within the above range.

The weight average molecular weight of the process oil is 200.
˜2000, more preferably 500 to 1400. In the flexible boot 1 made of a thermoplastic elastomer resin to which a process oil having a weight average molecular weight of more than 2000 is added, an initial abnormal noise is generated. In the flexible boot 1 made of the thermoplastic elastomer resin to which the process oil having the weight average molecular weight of less than 200 is added, the initial noise is not generated, but the duration of suppressing the noise generation is short. Therefore, the weight average molecular weight of the process oil is preferably in the above range.

The Z-average molecular weight of the process oil is 200-
It is more preferably 3000 to 500 to 2000. Initial noise is generated in the flexible boot 1 made of the thermoplastic elastomer resin to which the process oil having a Z-average molecular weight of more than 3000 is added. Z average molecular weight is 20
In the flexible boot 1 made of the thermoplastic elastomer resin to which the process oil of less than 0 is added, the initial abnormal noise does not occur, but the duration of suppressing the abnormal noise generation is short. Therefore, the Z-average molecular weight of the process oil is preferably in the above range.

The kinematic viscosity of the process oil is 100-100.
0 mm ² / sec, more preferably 100 to 500 mm
² / sec. In addition, this kinematic viscosity measurement is measured and calculated using a B-type viscometer at a temperature of 25 ° C. (in accordance with JIS K7117).

The kinematic viscosity of the process oil is 1000 mm ^2.
If it exceeds / sec, the process oil is less likely to deposit on the surface of the flexible boot and the effect of suppressing abnormal noise is less effective. If it is less than 1000 mm ² / sec, the process oil is deposited on the surface of the flexible boot early, which is different. It is preferable that the kinematic viscosity of the process oil is within the above range because the durability of suppressing sound generation is reduced.

When kneading a liquid additive such as mineral oil or vegetable oil, a liquid antioxidant and the like into a thermoplastic elastomer resin, a method of uniformly dispersing the liquid additive in the resin becomes a problem. Solid additives such as antioxidants and pigments are added to the base resin of the thermoplastic elastomer, but in this case, after the solid additives are added and stirred, a liquid additive such as mineral oil or vegetable oil is added. Then, the solid additive and the liquid additive may form a lump and may not be uniformly dispersed in the thermoplastic elastomer resin.

Further, the viscosity of the liquid additive such as mineral oil or vegetable oil becomes high in a low temperature atmosphere such as in winter, so that the solid additive and the liquid additive are likely to form a lump. Even if the mixture in such a state is kneaded and extruded using a twin-screw extruder, a resin in which the solid additive and the liquid additive are uniformly dispersed may not be obtained.

Therefore, it was found that when mineral oil or vegetable oil is added to the pellets of the thermoplastic polyester elastomer in a heated state and mixed and stirred, the mineral oil or vegetable oil is uniformly attached to the surface of the resin pellets. It was Furthermore, when a solid additive such as other antioxidant or pigment is added to the mixture in this state and stirred, the solid additive or mineral oil or vegetable oil, the liquid additive such as the liquid antioxidant becomes a resin. It was found that they adhere uniformly to the surface of the pellets.

Further, after pellets of the thermoplastic polyester elastomer and liquid additives such as mineral oil or vegetable oil and liquid antioxidant are heated and mixed and stirred, other solid additives are added thereto. You may mix and stir. Further, the pellet of the thermoplastic polyester elastomer and the solid additive may be heated and mixed and stirred, and then the liquid additive may be mixed and stirred. Furthermore, the pellets of the thermoplastic polyester elastomer, the liquid additive containing mineral oil or vegetable oil, and the other solid additive may be heated and mixed and stirred.

When the mixture of the pellets of the thermoplastic polyester elastomer thus mixed and stirred and the liquid additive and the solid additive is kneaded and extruded by using a twin-screw extruder, In addition, a boot molding material in which a liquid additive and a solid additive are uniformly dispersed can be obtained, which can contribute to obtaining a flexible boot having an excellent sustaining effect of suppressing abnormal noise.

In the above manufacturing method, the liquid additive may be only mineral oil or vegetable oil, or may contain additives such as liquid antioxidant.

The temperature for heating the above-mentioned resin pellets or the like is 60 ° C. or higher, more preferably 70 to 100 ° C.
At temperatures below 60 ° C, the viscosity of mineral oil and vegetable oil is high,
May not be evenly dispersed. When the temperature is higher than 100 ° C., as a heating method, a method of stirring the pellets of the base resin of the thermoplastic polyester elastomer with a mixer or the like as described later and heating by using frictional heat of the pellets is used. It takes a long time to warm up, which reduces production efficiency.

As a method for heating the pellets of the thermoplastic polyester elastomer, the pellets are stirred by a mixer or the like, and the frictional heat of the pellets is used to heat the pellets, or a general hot air dryer is used. There is a method of heating.

A mixer, a tumbler or the like may be generally used for the above stirring method. As an extruder for kneading and extruding the above mixture, a general single-screw extruder can be used, but further, a boot molding material in which a liquid additive and a solid additive are uniformly dispersed in a resin is used. It is preferable to use a twin-screw extruder in that it can be obtained.

In the resin flexible boot of the present invention, a thermoplastic elastomer resin, preferably TPEE is used.
It is a preferred embodiment that various additives are added to improve properties, processability, and the like, and examples of such additives include antioxidants, light stabilizers, antistatic agents, and molecular regulators such as peroxides. ,
Examples include metal deactivators, organic or inorganic nucleating agents, fillers, extenders, reinforcing agents, colorants and the like.

As the antioxidant, known liquid or solid antioxidants such as hindered phenol type, sulfur type and phosphorus type can be used, and as the light stabilizer, hindered amine type, triazole type and benzophenone types. system,
Known light stabilizers such as benzoate type, nickel type and salicyl type can be used.

As the filler, extender, reinforcing agent, and colorant, known ones can be used without limitation, and specifically, carbon blacks, silica, calcium silicate,
Examples thereof include silicic acid compounds such as kaolin, talc, clay, diatomaceous earth and wollastonite, metal carbonates such as calcium carbonate and barium carbonate, and organic or inorganic pigments.

[0070]

EXAMPLES (Examples 1 to 5) A polymer of terephthalic acid and 1,4-butanediol was used as a hard segment as a base material, and PTMG was used as a soft segment, and a copolymerization amount of PTMG was 40 to 50% by weight. % Of thermoplastic polyester elastomer Perprene P4
6D (manufactured by Toyobo Co., Ltd.) was used to prepare a boot molding material by using BJ oil (manufactured by Kyodo Yushi Co., Ltd.), which is a paraffin-based process oil, as a mineral oil to be added to 6D, and the obtained boot molding The material was used to mold a flexible resin boot with an injection molding machine. The blending amount of the mineral oil was 0.5 to 5.0 parts by weight as shown in Table 1 with respect to 100 parts by weight of the thermoplastic polyester elastomer.

Analysis of the BJ oil by ring analysis (ndM method) revealed that the content of paraffinic components was 68%, the content of naphthenic components was 25%, and the content of aromatic components was 8%. . The molecular weight measured by the GPC method varies depending on the lot, but the number average molecular weight is 660 to 700, the weight average molecular weight is 810 to 850, and the Z average molecular weight is 100.
It was 0-1100 and the kinematic viscosity was 260-400.

(Comparative Examples 1 to 6) The thermoplastic polyester elastomers used in Examples 1 to 5 were used as a base material, and in Comparative Example 1, mineral oil was not added, and an injection molding machine was used as in Examples 1 to 5. The flexible boot made of resin was molded into. In Comparative Example 2, the thermoplastic elastomer resin 10
7 parts by weight of the mineral oil used in Examples 1 to 5 was added to 0 parts by weight, and a resin flexible boot was molded in the same manner. In Comparative Examples 3 to 6, low melting point fatty acid amide A was added to 100 parts by weight of the thermoformable elastomer resin.
(Oleyl oleic acid amide) and high melting point fatty acid amide B
(Ethylenebisstearic acid amide) was added in an amount shown in Table 1 to form a resin flexible boot in the same manner.

The resin flexible boot products of Examples 1 to 5 and Comparative Examples 1 to 6 molded as described above were assembled in a constant velocity joint, and the performance of suppressing abnormal noise, the sealing property and the durability were evaluated. . The results are shown in Table 1.
Each test method was carried out as follows.

(1) Suppression of Abnormal Noise Generation Assembled in a constant velocity joint and rotated at a low speed to confirm whether or not the initial abnormal noise is generated. If no abnormal noise is generated, "○" is given.
When it was observed, it was judged as "x". Also,
The time until abnormal noise was generated during continuous rotation was confirmed, and when abnormal noise was generated within the time shorter than 25 minutes, which is the target value for abnormal noise suppression duration, it was judged as “x” and lasted longer than that. In this case, it was judged as "○". The measurement conditions are normal temperature atmosphere (R
At T), set the maximum angle of the constant velocity joint (angle α in Fig. 1) to 4
The rotation speed was 9 ° and the rotation speed was 150 rpm. Also, the surface of the flexible boot was kept in a state where water was always attached.

(2) Sealability The outer case is assembled in a constant velocity joint and continuously rotated for a predetermined period of time, and at the seal portion tightened by the tightening clamp 12 in the large diameter mouth portion 2 or the small diameter mouth portion 3 of the flexible boot. It was observed whether or not there was a deviation from a predetermined position due to slippage with the outer peripheral surface of the rear axle 5 or 8, 10 or grease leakage. When any of them was observed, it was judged as "x", and when neither was observed, it was judged as "○". Specifically, the flexible boot product was assembled in a constant velocity joint and the ambient temperature was 30
℃, the maximum angle of the constant velocity joint is 47 °, and the rotation speed is 1
Continuous rotation was performed for 6 weeks under the condition of 00 rpm, and the state immediately after that was observed.

(3) Durability In a high temperature atmosphere of 100 ° C., the maximum angle of the equal joint is 43.
The rotation speed was set to 500 rpm, and the time taken for a crack to penetrate through the valley of the bellows of the flexible boot was measured. Further, when it occurred in a time shorter than the target value of 30 hours, it was judged as "x", and when it occurred after a time longer than that, it was judged as "○".

As shown in Table 1, Examples 1 to 5 in which 0.5 to 5 parts by weight of paraffinic mineral oil was blended
In the case of No. 2, extremely good results were obtained in all of the performance of suppressing the generation of abnormal noise, the sealing property and the durability performance.

In Comparative Example 1 in which no mineral oil was added, abnormal noise was recognized from the beginning. In Comparative Example 2 in which the addition amount is 7 parts by weight even when the mineral oil made of paraffinic oil is added, the noise suppression performance and the sealing property are good, but the valley portion of the bellows portion cracks relatively quickly. Occurred and the durability was not satisfactory.

Fatty acid amide (A / B) was used as a lubricant, and its blending amount was 0.7 / 0.06 parts by weight, or 1.5 / 0.
In the case of Comparative Examples 3 and 4 in which the amount was 15 parts by weight, the sealing property and durability were good, and no abnormal noise was initially generated, but the duration of suppressing abnormal noise was short and abnormal noise was generated. The suppression effect was not sufficient. Further, in the case of Comparative Example 5 in which the blending amount of the fatty acid amide (A / B) was 1.8 / 0.15 parts by weight, no abnormal noise was initially generated, but the duration of suppression of abnormal noise generation was It was short and inferior in sealability and durability. Also, the content of fatty acid amide (A / B) is 1.5 / 0.2.
In the case of Comparative Example 6 which is a part by weight, no abnormal noise was initially generated, and the abnormal noise suppressing effect was long and the noise suppressing effect was good, but the sealing property and durability were poor. Was there.

[0080]

[Table 1]

(Examples 6 to 10) The thermoplastic polyester elastomers used in Examples 1 to 5 were used as the base material, and the mineral oil added thereto was as shown in Table 2.
The number average molecular weight of each is 200 (Example 6), 500
Paraffinic process oils of (Example 7), 750 (Example 8), 1000 (Example 9), and 2000 (Example 10) were used to mold a flexible resin boot in the same manner as in Example 1. . In each of Examples 6 to 10, the amount of the paraffin-based process oil blended was 1 with respect to 100 parts by weight of the thermoplastic polyester elastomer.
It was 5 parts by weight.

(Comparative Examples 7 to 9) As shown in Table 2, each number average molecular weight was 100 (Comparative Example 7), 2250.
(Comparative Example 8) Examples 6 to 10 described above except that the paraffinic process oil of 2500 (Comparative Example 9) was used.
A flexible boot made of resin was molded in the same manner as in.

Examples 6 to 10 prepared as described above
The resin flexible boot products of Comparative Examples 7 to 9 were assembled in a constant velocity joint, and the performance of suppressing abnormal noise was evaluated. The test method was assembling to a constant velocity joint, rotating at low speed, and measuring the presence or absence of initial noise generation and the time until abnormal noise generation during continuous rotation (the target value for the duration of noise suppression is 25 minutes). . At this time, the room temperature atmosphere (RT),
The maximum angle (α angle in FIG. 1) of the constant velocity joint was 49 ° and the rotation speed was 150 rpm. Also, the surface of the flexible boot was kept in a state where water was always attached. The results are shown in Table 2.

As a result, Comparative Example 7 having a small number average molecular weight
No abnormal noise was initially generated, but the duration of suppressing abnormal noise was relatively short at 10 minutes, and the effect of suppressing abnormal noise was insufficient. In Comparative Examples 8 and 9 in which the number average molecular weight was extremely large, paraffin-based process oil did not easily deposit (bleed) on the surface of the flexible boot product, and abnormal noise was observed from the beginning. On the other hand, Examples 6 and 1
In 0, the duration of suppression of abnormal noise generation was 25 minutes, and the target was achieved. In Examples 7, 8 and 9, good results were obtained in which the duration of suppressing abnormal noise generation was 60 minutes or longer.

[0085]

[Table 2]

(Examples 11 to 15) The thermoplastic polyester elastomers used in Examples 1 to 5 were used as base materials, and mineral oils added to the thermoplastic polyester elastomers were weight-averaged as shown in Table 3. The molecular weight is 200 (Example 1
1), 500 (Example 12), 950 (Example 13),
Using the paraffinic process oils of 1400 (Example 14) and 2000 (Example 15), a resin flexible boot was molded by an injection molding machine. Each Example 11-
In Paragraph 15, the blending amount of the paraffinic process oil was 1.5 parts by weight with respect to 100 parts by weight of the thermoplastic polyester elastomer.

(Comparative Examples 10 to 12) As shown in Table 3,
Its weight average molecular weight is 100 (Comparative Example 10), 2
Resin flexible boots were molded in the same manner as in Examples 11 to 15 except that the paraffinic process oils of 250 (Comparative Example 11) and 2500 (Comparative Example 12) were used.

Examples 11 to 1 prepared as described above
5 and the resin-made flexible boot products of Comparative Examples 10 to 12 were assembled in a constant velocity joint, and the performance of suppressing abnormal noise generation was evaluated. The test method is as described in Examples 6 to 10,
It carried out by the method similar to the case of Comparative Examples 7-9. The results are shown in Table 3.
Shown in.

As a result, in Comparative Example 10 having a small weight-average molecular weight, no abnormal noise was initially generated, but the duration of suppressing abnormal noise was 10 minutes, which was relatively short, and the effect of suppressing abnormal noise was sufficient. There wasn't. In Comparative Examples 11 and 12 having an extremely large weight average molecular weight, generation of abnormal noise was recognized from the initial stage. On the other hand, in Examples 11 and 15, the abnormal sound generation suppression duration was 25 minutes, and the target was achieved. Example 1
In Nos. 2, 13 and 14, good results were obtained in which the duration of suppressing abnormal noise generation was 60 minutes or more.

[0090]

[Table 3]

(Examples 16 to 20) The thermoplastic polyester elastomers used in Examples 1 to 5 were used as the base material, and the mineral oil added to the thermoplastic polyester elastomers had the Z-means thereof as shown in Table 4. A molecular weight of 200 (Example 16),
500 (Example 17), 1300 (Example 18), 20
A flexible boot made of resin was molded in the same manner as in Example 1 using the paraffinic process oil of 00 (Example 19) and 3000 (Example 20). Example 1
In 6 to 20, the blending amount of the paraffinic process oil was 1.5 parts by weight with respect to 100 parts by weight of the thermoplastic polyester elastomer.

Comparative Examples 13 to 15 As shown in Table 4,
Each Z average molecular weight is 100 (Comparative Example 13), 35
Flexible resin boots were molded in the same manner as in Examples 16 to 20 except that the paraffinic process oils of 00 (Comparative Example 14) and 4000 (Comparative Example 15) were used.

Examples 16 to 2 prepared as described above
The resin flexible boot products of No. 0 and Comparative Examples 13 to 15 were assembled in a constant velocity joint, and the performance of suppressing abnormal noise was evaluated. The test method is as described in Examples 6 to 10,
It carried out by the method similar to the case of Comparative Examples 7-9. The results are shown in Table 4.
Shown in.

As a result, Comparative Example 1 having a small Z-average molecular weight
In No. 3, no abnormal noise was initially generated, but the duration of suppressing abnormal noise was relatively short at 10 minutes and the effect of suppressing abnormal noise was insufficient. In Comparative Examples 14 and 15 having an extremely large Z-average molecular weight, generation of abnormal noise was recognized from the initial stage. On the other hand, in Examples 16 and 20, the abnormal sound generation suppression duration was 25 minutes, and the target was achieved. Examples 17, 1
In Nos. 8 and 19, good results were obtained in which the duration of suppressing abnormal noise generation was 60 minutes or longer.

[0095]

[Table 4]

(Examples 21 and 22) As the material of the flexible boot made of resin, as in Example 1, Perprene P was used.
46D was used. The temperature of the pellets of this thermoplastic polyester elastomer was 60 ° C (Example 21), 80 ° C.
(Example 22) was heated, 1.5 parts by weight of paraffin-based process oil (BJ oil, manufactured by Kyodo Yushi Co., Ltd.) was added, stirred with a mixer, and then oxidized as another solid additive. 1.0 part by weight of an inhibitor (trade name: Nocrac 810-NA, manufactured by Ouchi Shinko Co., Ltd.) and 1.0 part by weight of a pigment (carbon black, seast GSO, average particle size 43 nm) are added and stirred, and this mixture is added. Was kneaded and extruded using a twin-screw extruder (two-screw extruder TEM100 manufactured by Toshiba Corp.) to prepare a molding material. Flexible boots were molded using this boot molding material. Here, the pellet heating is
This was performed by stirring the pellets at 100 rpm using Supermixer SMC-300N manufactured by Kawata Co., Ltd. The extrusion was carried out at a screw rotation speed of 100 rpm and a temperature setting of 240 ° C.

(Comparative Example 16) A molding material was prepared in the same manner using the same thermoplastic polyester elastomer pellets and additives as those in Examples 21 and 22, and a flexible boot was molded using the material. However, Comparative Example 16
Then, the paraffin oil was added at room temperature (23 ° C.) without heating the pellet.

Examples 21 and 2 prepared as described above
For the flexible boots of No. 2 and Comparative Example 16, the ability to suppress the generation of abnormal noise was evaluated by the same test method as in Examples 6 to 10 and Comparative Examples 7 to 9 described above. The results are shown in Table 5.

As shown in Table 5, in Example 21 (pellet temperature 60 ° C.) and Example 22 (pellet temperature 80 ° C.), the duration of suppressing the generation of abnormal noise was 25 minutes or longer, and the target was achieved. In Comparative Example 16, the dispersibility of the liquid additive and the solid additive in the resin was relatively poor, and the effect of suppressing abnormal noise generation was as short as 15 minutes.

[0100]

[Table 5]

(Example 23) Example 1 as a base material
To the thermoplastic polyester elastomer used in Examples 1 to 5, and the paraffin oil used in Examples 1 to 5 as the mineral oil to be added thereto, 1.5 parts by weight of the oil is added to 100 parts by weight of the resin. Then, the resin-made flexible boot was molded by an injection molding machine.

(Comparative Example 17) Example 2 as a base material
Using the same thermoplastic polyester elastomer as in No. 3, 0.3 parts by weight of oleyl oleic acid amide and 0.08 parts by weight of ethylenebisstearic acid amide were added to 100 parts by weight of resin instead of adding paraffinic oil. Then, a resin flexible boot was molded in the same manner.

With respect to the flexible boots of Example 23 and Comparative Example 17 molded as described above, the deposition characteristics of oil or fatty acid amide which is a noise suppressing material were examined.
Specifically, the molded flexible boots are left at room temperature, (a) simply left, (b) wiped off every 14 days,
(C) The amount of oil or fatty acid amide deposited on the boot surface was measured in each case of wiping every 7 days. The deposition amount was measured by wiping the inner and outer surfaces of the boot with a soft cloth (waste) and measuring the weight change. Boots 1
It was expressed by the weight (mg) per piece (55 g).

In the case of the above (a) simple leaving, 1
The amount of precipitation was measured after 3, 4, 7, 14, 28, 42 and 56 days. In (b) every 14 days,
The deposit amount deposited on the surface of the boot was wiped off every 14 days from the molding, and the deposit amount after a predetermined number of days of standing was measured. In the wiping every 7 days of (c), the amount of deposition after a predetermined number of days of standing was measured while wiping the deposits deposited on the boot surface every 7 days after molding.

The results are shown in FIG.
Compared with Comparative Example 16, the amount of the abnormal sound generation suppressing material deposited was large,
Further, in the wiping test, the amount of deposition after wiping decreased, but the amount of deposition was larger than that of the comparative example, and it was immediately recovered to the minimum level (13 mg) or higher at which abnormal noise can be suppressed. On the other hand, in Comparative Example 16, the amount of precipitation after wiping was small and the lowest level (7 mg / 1
(Boots) It didn't recover much.

[Measurement of Degree of Swelling] Perprene P46D, which is a raw material containing no process oil and is used as a molding material for resin flexible boots, was immersed in various process oils and the degree of swelling was measured. The measurement was performed according to JIS K6258 (vulcanized rubber immersion test). The measurement conditions are as follows. In Table 6, Cp, Cn, and Ca are ring analysis methods (nd-d-, respectively).
The paraffin component content rate, the naphthene component content rate, and the aromatic (aromatic) component content rate measured by the M method) are shown. Test piece: 20 mm × 50 mm × 2.0 mm Test temperature: 100 ° C. Immersion time: 48 hours The measurement results were obtained by the volume change rate (vol%) and the weight change rate (wt%). The measurement results are shown in Table 6. From these results, the paraffin component content is 60 to 78%, the naphthene component content is 20 to 35%, and the aromatic component content is 1.
When 10% of paraffinic process oil is added to TPEE, it bleeds while being properly held, and it is possible to suppress the initial abnormal noise generation of the resin flexible boot and improve the continuous effect of suppressing the abnormal noise generation. It can be seen that the sealing property and the durability can be improved.

[0107]

[Table 6]

[0108]

According to the present invention, even when the resin flexible boot is mounted on a constant velocity joint of an automobile and continuously rotated while being bent and displaced at a wide angle, it is possible to suppress the generation of abnormal noise in the initial stage of the resin flexible boot. The advantage is that the continuous effect of suppressing the generation of abnormal noise can be improved, and the sealability and durability can be improved.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional side view illustrating the shape of a flexible boot made of resin.

FIG. 2 is a cross-sectional view showing a usage situation of a flexible boot made of resin.

FIG. 3 is a graph showing precipitation characteristics of an abnormal sound generation inhibitor in resin flexible boots manufactured in Example 23 and Comparative Example 17, where (a) is simply left and (b) is 14;
Day-by-day wiping, (c) shows each test result of wiping every 7 days.

[Explanation of sign]

1 ... Resin flexible boots 2 ... Large mouth 3 ... Small diameter mouth 4 ... Bellows

   ─────────────────────────────────────────────────── ─── Continued front page    (31) Priority claim number Japanese Patent Application 2000-138903 (P2000-138903) (32) Priority date May 11, 2000 (May 11, 2000) (33) Priority claiming country Japan (JP) (72) Inventor Masayuki Toriumi             1-17-18 Edobori, Nishi-ku, Osaka City, Osaka Prefecture             Toyo Tire & Rubber Co., Ltd. (72) Inventor Hiroshi Ohno             1-17-18 Edobori, Nishi-ku, Osaka City, Osaka Prefecture             Toyo Tire & Rubber Co., Ltd. (72) Inventor Hitoshi Ueno             2-1 1-1 Katata, Otsu City, Shiga Prefecture Toyobo             Koki Co., Ltd. F term (reference) 3J043 AA03 CA09 CB13 CB24 FB04                 3J045 AA04 AA06 BA03 DA10 EA03

Claims (26)

[Claims] 1. A flexible boot made of resin, which is formed by using a thermoplastic elastomer resin as a base resin material and in which a large-diameter mouth portion and a small-diameter mouth portion are connected by a bellows portion,
A flexible boot made of resin, wherein mineral oil is added to the thermoplastic elastomer resin. 2. The resin according to claim 1, wherein the thermoplastic elastomer resin is a thermoplastic polyester elastomer having a hard segment composed of an aromatic dicarboxylic acid and a low molecular weight glycol and a soft segment having a molecular weight of 400 to 4000 as constituent components. Made flexible boots. 3. The aromatic dicarboxylic acid constituting the hard segment is at least one selected from terephthalic acid and naphthalene dicarboxylic acid, and the low molecular weight glycol is ethylene glycol, 1,4-butanediol, 1, The resin-made flexible boot according to claim 2, which is at least one selected from 4-cyclohexanedimethanol and dimer glycol. 4. The resin flexible boot according to claim 2, wherein the aromatic dicarboxylic acid constituting the hard segment is terephthalic acid, and the low molecular weight glycol is 1,4-butanediol. 5. The soft segment is polyoxytetramethylene glycol, polyoxypropylene glycol, or an aliphatic polyester diol.
Flexible boots made of resin according to. 6. The resin flexible boot according to claim 2, wherein the soft segment is polyoxytetramethylene glycol. 7. The resin flexible boot according to claim 6, wherein the copolymerization amount of polyoxytetramethylene glycol in the thermoplastic polyester elastomer is 35 to 55% by weight. 8. The resin flexible boot according to claim 6, wherein the copolymerization amount of polyoxytetramethylene glycol in the thermoplastic polyester elastomer is 40 to 50% by weight. 9. The mineral oil has an aromatic content of 1 or less.
The resin flexible boot according to any one of claims 1 to 8, which is at least one process oil selected from paraffinic oil and naphthenic oil of 3% or less. 10. The mineral oil is at least one process oil selected from paraffin oils and naphthene oils having an aromatic content of 1 to 10% or less. Flexible boots made of resin according to. 11. The resin flexible boot according to claim 9, wherein 5 parts by weight or less of process oil is mixed with 100 parts by weight of the thermoplastic elastomer resin. 12. A process oil having a number average molecular weight of 20.
It is 0-2000, The claim 9 or 10 characterized by the above-mentioned.
Flexible boots made of resin according to. 13. A process oil having a weight average molecular weight of 1
It is 00-2000, The claim 9 or 1 characterized by the above-mentioned.
Flexible boots made of resin according to item 0. 14. The process oil has a Z-average molecular weight of 20.
It is 0-3000, It is characterized by the above-mentioned.
Flexible boots made of resin according to. 15. The process oil has a kinematic viscosity of 100 to 1000 mm ² / sec (2
The resin flexible boot according to claim 9 or 10, wherein the temperature is 5 ° C). 16. A resin flexible boot formed by using a thermoplastic elastomer resin as a base resin material, and connecting a large-diameter mouth portion and a small-diameter mouth portion with a bellows portion, wherein vegetable oil is added to the thermoplastic elastomer resin. Resin flexible boots characterized by being added. 17. The resin-made flexible boot according to claim 16, wherein 5 parts by weight or less of vegetable oil is mixed with 100 parts by weight of the thermoplastic elastomer resin. 18. The resin flexible boot according to claim 9, wherein the degree of swelling of the polyester elastomer with the mineral oil is 8 vol% or less. 19. The resin flexible boot according to claim 9, wherein the degree of swelling of the polyester elastomer with the mineral oil is 6 wt% or less. 20. When manufacturing a resin flexible boot in which a large-diameter mouth portion and a small-diameter mouth portion are connected by a bellows portion using a thermoplastic polyester elastomer as a base resin material, pellets of the thermoplastic polyester elastomer are added. A liquid additive containing mineral oil or vegetable oil is added to this in a warm state, mixed and stirred, and the obtained mixture is kneaded and extruded using an extruder to prepare a molding material. A method of manufacturing a flexible boot made of resin, which comprises molding a flexible boot made of resin. 21. The molding material is produced by adding a solid additive to a mixture of the pellets and the liquid additive, mixing and stirring the mixture, and kneading and extruding the mixture. 20. The method for manufacturing a resin-made flexible boot described in 20. 22. The resin-made flexible boot according to claim 20, wherein the pellet and the solid additive are heated and mixed and stirred, and then the liquid additive is mixed and stirred. Method. 23. The method according to claim 20, wherein the liquid additive is mixed and stirred with the pellet while being heated.
23. The method for producing a flexible resin boot according to any one of 22. 24. The pellet, the liquid additive,
The method for producing a resin-made flexible boot according to claim 20, wherein the solid additive is heated and then mixed and stirred to obtain the mixture. 25. The method for producing a resin-made flexible boot according to claim 20, wherein the heating temperature is 60 ° C. or higher. 26. The method for producing a resin flexible boot according to claim 20, wherein the heating temperature is 70 to 100 ° C.