JP2003147058A - Polyester elastomer - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyester elastomer which is used for fields in which flexibility and resistance to flex fatigue are required, particularly cover boots for industrial mechanical apparatuses, e.g. cover boots for rack-and-pinion steering gears, cover boots for constant velocity joint driving apparatuses, cover boots for suspension systems or cover boots for automatic welding apparatuses and the other kinds of cover boots, e.g. cover boots for agricultural mechanical apparatuses. SOLUTION: This thermoplastic polyester elastomer comprises a polyester block copolymer obtained by reacting a high melting point polymer segment consisting of an acid component mainly composed of an aromatic dicarboxylic acid and a glycol component mainly composed of an aliphatic and/or alicyclic dihydroxy compound with a low melting point polymer segment having 1,800 to 2,200 molecular weight.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field requiring flexibility and bending fatigue resistance, and more particularly to a cover boot using a thermoplastic elastomer composition, a cover boot for a rack and pinion boot type steering device, and a constant velocity joint. The present invention relates to a polyester elastomer used for cover boots of various devices such as cover boots of drive devices, cover boots of suspension suspension devices, cover boots of automatic welding devices, and other industrial machinery devices, and cover boots of other agricultural machinery devices.

[0002]

2. Description of the Related Art Conventionally, rubber such as chloroprene has been known as a general material for cover boots having a bellows shape. Rubber is a material suitable for a cover boot because it is inexpensive, has appropriate flexibility, and has excellent creep characteristics. On the other hand, it has a drawback that the manufacturing process is complicated because a vulcanization process is required. Recently, polyester elastomers have begun to be used as a material for cover boots. Since the polyester elastomer is a thermoplastic resin, it has features such as a simplified manufacturing process, excellent bending fatigue resistance, and excellent heat resistance. The durability life of the cover boot is longer than that of the rubber boot. However, with polyester elastomers commonly used in cover boot applications, when reducing the size of the boot,
Since the hardness of the material is high, the stress generated in the valley portion in a bent state of the boot becomes high, and the bending fatigue property becomes short. In addition, there is a problem that heat resistance and crepe resistance are deteriorated by simply softening.

[0003]

The object of the present invention is to provide flexibility suitable for a small boot requiring a flexible material, particularly a small CVJ boot having a weight of the front axle of 50 g or less, further 40 g or less. Another object of the present invention is to provide a polyester elastomer having excellent bending fatigue resistance, heat resistance, water resistance, heat aging resistance, oil resistance, and chemical resistance.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that an aromatic dicarboxylic acid as a main acid component and an aliphatic and / or alicyclic dihydroxy compound. It was found that a polyester type block copolymer obtained by reacting a high melting point polymer segment consisting of a main glycol component with a low melting point polymer segment having a molecular weight of 1800 to 2200 solves the above problems, and the present invention Reached

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below. The polyester elastomer in the present invention,
It is a copolymer composed of a high-melting point polyester segment having an aromatic ring and a low-melting point polymer segment having a molecular weight of 1800 to 2200, and the melting point when the high polymer is formed only by the high-melting point polyester segment constituent components is 180 ° C. or higher, A polyester elastomer having a melting point or softening point of 80 ° C. or less when measured only with the low melting point polymer segment constituents.

The polyester elastomer will be described in more detail. As a high melting point polyester segment constituent having an aromatic ring, terephthalic acid, isophthalic acid, diphenyldicarboxylic acid, 5-sodium sulfoisophthalic acid, 2,6-naphthalenedicarboxylic acid, 1, Aromatic dicarboxylic acids such as 5-naphthalenedicarboxylic acid and 1,4-naphthalenedicarboxylic acid or esters thereof and carbon number 1
-25 glycols and their ester-forming derivatives can be used. The aromatic dicarboxylic acid is preferably 70 mol% or more of all the acid components. Carbon number 1
The glycol of ~ 25 is, for example, ethylene glycol,
Diethylene glycol, propylene glycol, 1,3
-Butanediol, 1,4-butanediol, 1,5-
Pentanediol, 1,6-hexanediol, 1,9
-Nonanediol, neopentyl glycol, dimethylolheptane, dimethylolpentane, tricyclodecane dimethanol, ethylene oxide derivatives of bisphenol X (X is A, S, F) and ester-forming derivatives thereof. Preferred examples include ethylene glycol, 1,4-butanediol and ester-forming derivatives thereof. As the acid component of the high melting point polyester segment constituent component, terephthalic acid is preferably 70 mol% or more of the total acid component.

As other acid components, examples of aromatic dicarboxylic acids include terephthalic acid, diphenyldicarboxylic acid, isophthalic acid and 5-sodiumsulfoisophthalic acid. Examples of the alicyclic dicarboxylic acid include cyclohexanedicarboxylic acid and tetrahydrophthalic anhydride, and as the aliphatic dicarboxylic acid, succinic acid, glutaric acid, adipic acid, azelaic acid, sebacic acid, dodecanoic acid, dimer acid, water. Examples thereof include added dimer acid. These amounts are 30 mol% or less, preferably 25 mol% or less of the total acid components. The lower limit of the melting point is not particularly limited, but is generally preferably 150 ° C or higher, and particularly preferably 180 ° C or higher.

The number average molecular weight of the low melting point polymer segment used in the present invention is 1800 to 2200. When the number average molecular weight is less than 1800, crystallinity is poor and fatigue resistance is poor. When the number average molecular weight is larger than 2200, the composition becomes hard at low temperature and the fatigue property deteriorates. Examples of the low melting point polymer segment having a molecular weight of 1800 to 2200 include polyalkylene ether glycols such as poly (ethylene oxide) glycol, poly (propylene oxide) glycol, poly (tetramethylene oxide) glycol and mixtures thereof, and polyethers thereof. Copolymerized polyether glycols having a glycol composition may be mentioned. Poly (tetramethylene oxide) glycol is preferable from the viewpoint of high melting point and moldability, and the total polyester weight is 45%.
It is preferably ˜65%. Particularly, from the viewpoint of durability and flexibility, the range of 50 to 60% is preferable.

Any known method can be applied to the production of the polyester elastomer of the present invention. For example, a melt polymerization method, a solution polymerization method, a solid phase polymerization method, or the like can be appropriately used. In the case of melt polymerization, a transesterification method or a direct polymerization method may be used. It is, of course, desirable to carry out solid-state polymerization after melt polymerization in order to improve the viscosity of the resin, in order to improve moldability and durable life of the molded body.

Antimony catalysts, germanium catalysts, and titanium catalysts are preferable as the catalysts used in the reaction of the polyester elastomer. Particularly preferred are titanium catalysts, specifically, tetraalkyl titanates such as tetrabutyl titanate and tetramethyl titanate, and metal oxalate salts such as potassium potassium oxalate. The other catalyst is not particularly limited as long as it is a known catalyst, and examples thereof include tin compounds such as dibutyltin oxide and dibutyltin dilaurylate, and lead compounds such as lead acetate.

Further, the obtained polyester elastomer includes known antioxidants such as hindered phenol type, sulfur type and phosphorus type, hindered amine type, triazole type,
Benzophenone-based, benzoate-based, nickel-based, salicyl-based light stabilizers, antistatic agents, lubricants, molecular regulators such as peroxides, metal deactivators, organic and inorganic nucleating agents, neutralizing agents, control agents. Acidic agents, antibacterial agents, optical brighteners, glass fibers, carbon fibers, silica fibers, inorganic fiber materials such as alumina fibers, carbon black, silica, quartz powder,
Glass beads, glass powder, calcium silicate, kaolin, talc, clay, diatomaceous earth, silicates such as wollastonite, metal oxides such as iron oxide, titanium oxide, zinc oxide, alumina, calcium carbonate, barium carbonate Such as metal carbonates, powdered fillers such as other various metal powders, mica, glass flakes, plate-like fillers such as various metal powders, flame retardants, flame retardant aids, organic / inorganic pigments, etc. More than one kind can be added.

Further, in order to improve the viscosity, after the polymerization of the polyester, the chain may be extended with a compound having two or more functional groups capable of reacting at the end of the polymer chain. Specific examples include 4,4′-diphenylmethane diisocyanate, naphthalene diisocyanate, isophorone diisocyanate, hexamethylene diisocyanate, bisphenol A-diglycidyl ether, bisphenol F-diglycidyl ether, bisphenol S-diglycidyl ether, isocyanuric acid triglycidyl ether, Examples include cresol novolac glycidyl ether, phenol novolac glycidyl ether, pyromellitic dianhydride, phthalic anhydride, polycarbodiimide, and bisoxazoline compounds. As a particularly preferred example,
Examples thereof include bisphenol A-diglycidyl ether, bisphenol F-diglycidyl ether, bisphenol S-diglycidyl ether and isocyanuric acid triglycidyl ether compound.

Further, it is possible to add silicone oil, an amide type lubricant, a liquid olefin type polymer, a polyether compound and the like which are used for improving the friction and wear characteristics.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described below with reference to Examples. In addition, each measurement item in these Examples followed the following method.

(Example 1) 472.8 g of dimethylene terephthalate (DMT), 151.4 g of 1,4-butanediol (BD), 233.9 g of polytetramethylene glycol (PTMG) having a molecular weight of 2000, and Irganox-1330 ( Ciba Co., Ltd.) 1.60 g and tetrabutyl titanate (TBT) 0.8 g were charged into a 4 L autoclave, and the temperature was raised to 220 ° C. to perform a transesterification reaction. Then, the inside of the can was gradually decompressed and further heated, and the initial condensation reaction was performed at 250 ° C. and 1 torr or less. Further, the polymerization reaction was carried out for 2 hours at 250 ° C. and 1 torr or less, and the polymer was taken out in pellet form.
Predetermined tests were conducted on the obtained polymer. 100 parts by weight of the obtained polyester block copolymer chip, the pigment, the stabilizer and the thickener shown in Table 1 were placed in a drum tumbler and stirred at room temperature for 10 minutes. 40 mm mixture
φ Extruded at 230 ° C. in the same direction twin-screw extruder, cooled with water, and cut into chips. The chips thus obtained were dried under reduced pressure at 100 ° C. to obtain chips of the polyester elastomer composition of the present invention.

Example 2 A chip of a polyester elastomer composition was prepared in the same process as in Example 1 except that PTMG having a number average molecular weight of 1850 was used in polymerizing the polyester copolymer described in Example 1. Got

Example 3 A polyester elastomer composition chip was produced in the same process as in Example 1 except that PTMG having a number average molecular weight of 2200 was used in polymerizing the polyester type copolymer described in Example 1. Got

Comparative Example 1 A chip of a polyester elastomer composition was prepared in the same process as in Example 1 except that PTMG having a number average molecular weight of 1000 was used in polymerizing the polyester copolymer described in Example 1. Got

(Comparative Example 2) A chip of a polyester elastomer composition was prepared in the same process as in Example 1 except that PTMG having a number average molecular weight of 1500 was used in polymerizing the polyester type copolymer described in Example 1. Got

Comparative Example 3 Chips of the polyester elastomer composition were prepared in the same process as in Example 1 except that PTMG having a number average molecular weight of 2,500 was used in polymerizing the polyester copolymer described in Example 1. Got

[0021]

[Table 1]

The above Examples 1, 2, 3 and Comparative Examples 1, 2,
The polyester elastomer composition obtained in No. 3 was evaluated for the following items.

[Surface hardness] In accordance with the test method described in JIS K7215, the hardness was measured with a D scale of a durometer.

[Tensile breaking strength / elongation] Using an injection molding machine (Yamashiro Seiki model-SAV), the chip is 100 mm × 100 mm × 2 mm
After molding into a flat plate of No. 3, a dumbbell-shaped No. 3 test piece was punched out from the flat plate. Tensilon UTM-III manufactured by Toyo Seiki Co., Ltd. was used to extend the obtained test piece at a speed of 500 mm / min, and the load (kg) when the test piece broke was the initial cross-sectional area (m ² ).
The value obtained by dividing the above was taken as the tensile breaking strength (Mpa), and the ratio of the sample elongation until the test piece was broken to the original sample length was taken as the tensile breaking elongation (%).

[Melt Viscosity] The melt flow rate (MFR) at 230 ° C. was measured according to the test method described in JIS K6760.

[Friction Coefficient and Amount of Wear] Based on the thrust type wear test method described in JIS K7218, the polyester elastomer compositions were rubbed together to measure the friction coefficient and the amount of wear.

[Bending fatigue] injection molding machine (Yamashiro Seiki Co., Ltd.
del-SAV) using the sample piece (100mm x
20mm x 3.6mm, 1.2mm deep in the center, with R = 2.4mm groove)
After molding, the sample piece was fixed to the vibrating metal fitting at both ends with the groove portion being the center and the interval of 70 mm. The movement (Fig. 2) of shortening the interval between the vibrating metal fittings to 28 mm and further expanding the interval to 70 mm was performed at a frequency of 300 cycles / minute. The measurement was performed under the conditions of a relative humidity of 50% and a temperature of 100 ° C. The number of cycles until the sample breaks is shown.

(Low temperature property) Using the dumbbell-shaped No. 3 test piece used in the tensile test, and using Tensilon UTM-III manufactured by Toyo Seiki Co., Ltd., the above test piece was extended at a speed of 50 mm / min to obtain 10 The% elongation stress was measured at room temperature and −40 ° C., and the degree of change was judged at −40 ° C./normal temperature. Those with large changes were judged to have poor bass characteristics. (Boot low temperature performance evaluation) Using the chip created above,
A compact boot having a 5-mount shape and a weight of 38 g was prepared by a press blow molding machine (SBE50 / 140 manufactured by Osberger Co., Ltd.). The boots were mounted on a rotation tester with a joint removed from a small car, and a rotation test was performed under normal temperature and -40 ° C atmosphere with a shaft angle of 40 degrees and a rotation speed of 100 rpm.

Table 2 shows the results of predetermined tests conducted on Examples 1, 2 and 3 and Comparative Examples 1, 2 and 3.

[0030]

[Table 2]

[0031]

As described above, by polymerizing the polyester type block copolymer by using the number average molecular weight of 1800 to 2200 as the low melting point segment, the polyester is flexible and has excellent bending fatigue property, moldability and low temperature characteristics. An elastomer composition can be provided.

[Brief description of drawings]

FIG. 1 is a shape diagram of a sample used for a bending fatigue test.

FIG. 2 is a schematic diagram showing a method for testing flex fatigue.

[Explanation of symbols]

1 test sample 10 grooves 20 vibration metal fittings 21 Sample fixing screw

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 3J045 AA04 AA06 AA09 AA14 BA03                       CB00 EA03 EA04 EA10                 4J029 AA03 AB01 AC03 AD01 AE01                       BA02 BA03 BA05 BA07 BA08                       BA09 BA10 BD05 BF09 BF25                       BF26 CA02 CA04 CA05 CA06                       CB05 CB06 CB10 CD03 CH02                       CH07 DB02 GA12 GA22 GA23                       HA01 HB01 JE18 KB02

Claims (3)

[Claims] 1. A low melting point polymer segment having a molecular weight of 1800 to 2200 is reacted with a high melting point polymer segment comprising an aromatic dicarboxylic acid as a main acid component and an aliphatic and / or alicyclic dihydroxy compound as a main glycol component. A thermoplastic polyester elastomer comprising a polyester block copolymer obtained as described above. 2. A thermoplastic polyester elastomer, wherein the low melting point polymer segment comprises poly (oxytetramethylene) glycol. 3. A thermoplastic polyester elastomer, wherein the poly (oxytetramethylene) glycol component is 45 to 65% of the total polyester weight.