JPH0770432A - Polyamide resin composition for bicycle wheel and bicycle wheel obtained by molding the same - Google Patents

Abstract

PURPOSE:To obtain a polyamide resin composition excellent in both of flexural modulus and impact resistance, having low specific gravity and being lightweight and having good appearance of moldings. CONSTITUTION:This polyamide resin composition for bicycle wheels consists of 100 pts.wt. of a polyamide resin, 20-40 pts.wt. of a polyolefin-based elastomer and 60-100 pts.wt. of glass fiber having 6-15mum average fiber diameter.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyamide resin composition for bicycle wheels, which is excellent in rigidity, toughness and heat resistance, and a bicycle wheel.

[0002]

2. Description of the Related Art Polyamide resins are widely used as outdoor products for automobiles because of their excellent heat resistance, moldability, rigidity and toughness, but recently, they have been used for bicycles and unicycle wheels. With respect to the above, attention has been paid to the use of a metal as a resin in order to improve weight reduction, rust prevention and fashionability. Among the resins, a polyamide resin excellent in rigidity and toughness is attracting attention.

Among polyamide resins, nylon 610,
High-grade polyamides represented by nylon 612, nylon 11, and nylon 12 have good toughness, low water absorption, and dimensional stability, but lack sufficient rigidity as a metal substitute material. On the other hand, Nylon 6 and Nylon 66 have high heat resistance, high rigidity, and are inexpensive, so they have a considerable track record of being used as automotive exterior parts, but they are difficult to develop as bicycle wheels because of their large water absorption.

Therefore, nylon 6 or nylon 66
Attempts have also been made to blend lower polyamides such as ## STR3 ## and higher polyamides such as nylon 11 and nylon 12 to compensate for the drawbacks of both. (JP-A-57-212252
JP-A-57-80448, JP-A-57-
There is also an example in which glass fibers having a small diameter (φ3 μm to φ8 μm) are kneaded and reinforced to improve rigidity such as bending elastic modulus. (See Japanese Patent Application Laid-Open No. 60-38459) In polybutylene terephthalate, there are some examples in which a polyolefin elastomer and glass fiber are kneaded and reinforced to improve toughness such as impact resistance. (JP-A-4-
(See Japanese Patent No. 173861)

[0005]

Synthetic resin is lighter than metal, and in the case of thermoplastic resin, injection molding is possible so that it can be integrally molded, and productivity is improved, and coloring with pigments, dyes, etc. is possible. Since it has the advantages of being fashionable, it is attracting attention as a material for bicycle wheels, but bicycle wheels exert considerable force when driving on rough roads or when braking. The material and structure must be rigid and tough enough to withstand.

The method of mixing glass fibers having a small diameter (φ3 μm to φ8 μm) surely improves the flexural modulus significantly, but on the other hand, the specific gravity becomes high, which is contrary to the purpose of reducing the weight of the bicycle wheel. Therefore, the blending amount of glass fiber is limited.
Further, the method of blending polybutylene terephthalate with an elastomer and glass fiber cannot be said to be excellent in both physical properties such as flexural modulus and impact resistance. Therefore, it has been a problem to provide a resin composition or a molded product having both such high rigidity and high toughness, which are contradictory physical properties, and having a low specific gravity.

[0007]

In order to solve the above problems, the present invention takes the following means. That is, the polyamide resin composition for a bicycle wheel of the present invention comprises 100 parts by weight of a polyamide resin, 20 to 40 parts by weight of a polyolefin-based elastomer, and 60 to 100 parts by weight of glass fibers having an average fiber diameter of 6 to 15 μm. The bicycle wheel according to the present invention is a resin composition obtained by injection molding the above polyamide resin composition for bicycle wheel into a predetermined shape.

The polyamide resin used in the present invention includes nylon 6, nylon 66, nylon 46, nylon 11, nylon 12, nylon 610, nylon 61.
2, nylon 6/66 and the like. The "polyolefin elastomer" used in the present invention is preferably a copolymer of ethylene and an α-olefin such as butene-1, propylene and pentene-1, and specifically ethylene-
A propylene copolymer and an ethylene-propylene-diene copolymer are preferable.

The addition amount of the polyolefin elastomer of the present invention is 20 to 4 with respect to 100 parts by weight of the polyamide resin.
If it is less than 20 parts by weight, the impact resistance is not sufficient, and if it exceeds 40 parts by weight, the rigidity and mechanical strength are deteriorated, and the appearance is deteriorated. I can't get the wheel. As the glass fiber in the present invention, any glass fiber having an average fiber diameter of 6 to 15 μm can be used, but maleic anhydride and //
Alternatively, glass fibers treated with a surface treatment agent containing the residue are preferable. The surface treating agent containing a maleic anhydride residue means a surface treating agent containing a diammonium salt of maleic acid, a dimetal salt or the like.

The amount of the surface treatment agent adhering to the glass fibers is 0.1 to 2 per 100 parts by weight of the glass fibers.
It is 0 part by weight, preferably 0.3 to 1.2 parts by weight. The addition amount of the glass fiber of the present invention is polyamide resin 10
It is 60 to 100 parts by weight with respect to 0 parts by weight. If it is less than 60 parts by weight, rigidity, mechanical strength and dimensional stability decrease, and
If it exceeds 100 parts by weight, the specific gravity becomes heavy, the appearance becomes poor, and it is not possible to obtain a molded product or a bicycle wheel having excellent characteristics.

The method of treating the glass fiber with the surface treating agent is not particularly limited, and a method of treating the surface of the glass fiber during production (spinning) or a method of blending the glass fiber and the surface treating agent is used. It is also possible to surface-treat the glass fiber with a silane coupling agent before the treatment with the above-mentioned surface treatment agent, and in that case, the silane coupling agent is preferably an aminosilane coupling agent.

The "polyamide containing an aromatic ring in the molecular constitution unit" preferably used in the present invention is a wholly aromatic polyamide obtained only from an aromatic compound or an equimolar salt of an aliphatic diamine and an aromatic dicarboxylic acid. It is a polyamide in which an aromatic ring is contained in the main chain constituting a molecule, such as a copolymerized polyamide of polymerized semi-aromatic polyamide or aliphatic polyamide and wholly aromatic polyamide or semi-aromatic polyamide.

The aliphatic diamine used here has preferably 4 to 8 carbon atoms, and more preferably 6 carbon atoms. As the aliphatic polyamide, nylon 4, nylon 6, nylon 46 and nylon 66 are preferable, and nylon 6,
Nylon 66 is preferred. As the wholly aromatic polyamide used, there are p-phenylene terephthalamide, p-phenylene isophthalamide and the like.

As the semi-aromatic polyamide, polyhexamethylene terephthalamide (abbreviated as nylon 6T. T is terephthalic acid, the same applies hereinafter) and nylon 6I.
(I stands for isophthalic acid), nylon 4T, nylon 4
I, nylon 6 / 6T, nylon 6 / 6T / I, nylon 66 / 6T and the like. The method for mixing the polyamide, the polyolefin-based elastomer, and the glass fiber is not particularly limited, and a commonly known method can be adopted. That is, any method such as a method of uniformly mixing polyamide, a polyolefin-based elastomer, and glass fibers with a high-speed stirrer, followed by melt-kneading with an extruder having sufficient kneading ability, a method of dry blend injection or extrusion molding can be adopted. .

The bicycle wheel of the present invention is molded by injection molding. The molded article of the present invention is suitable for use as a wheel material for bicycles and unicycles because of its high impact resistance, high rigidity and low specific gravity. The “bicycle” in the present invention is a general term including ordinary non-powered bicycles (two-wheeled vehicles), unicycles, three-wheeled vehicles, and the like. Further, the resin composition of the present invention, other moldability, other components unless impairing the physical properties, for example, pigments, dyes, heat-resistant agents, antioxidants, weather-resistant materials, lubricants,
A crystal nucleating agent or the like can be added and introduced.

[0016]

EXAMPLES The present invention will be described in more detail with reference to the following examples, but the present invention is not limited thereto without departing from the gist thereof. The physical properties of the molded articles and corresponding test pieces described in Examples and Comparative Examples were measured and evaluated by the methods described below.

(1) Relative viscosity: JIS K6810 (2) Tensile property: ASTM D638 (3) Bending property: ASTM D790 (4) Izod Impact strength: ASTM D256 Example 1 Nylon 6, 100 weight of relative viscosity 2.70 MFR in the section
30 parts by weight of 0.4 ethylene-propylene copolymer and an average fiber diameter of 12.8 μm surface-treated with maleic anhydride
m chopped strand glass fiber (length 3mm) 70
Add 45 parts by weight, and mix evenly with a stirrer.
It was melt-kneaded and pelletized by a twin-screw extruder having a diameter of mm.

The pellets obtained here were vacuum dried at 80 ° C., and then an ASTM dumbbell piece and a 20-inch bicycle resin wheel were molded by an injection molding machine under the conditions of a cylinder temperature of 270 ° C. and a mold temperature of 80 ° C. . Table 1 shows the measurement results of the physical properties of the obtained dumbbell pieces during absolute drying, the atmospheric water absorption equilibrium rate, and the bending elastic modulus at the atmospheric water absorption equilibrium. This composition has a good balance between impact value and flexural modulus, and has a low specific gravity,
Suitable for bicycle wheel material. The obtained bicycle resin wheel had a good appearance and was sufficiently practical. Example 2 100 parts by weight, 23 parts by weight and 100 parts by weight of 6 nylon, ethylene-propylene copolymer and chopped strand glass fiber used in Example 1 were mixed, respectively, and extruded, dried and molded in the same manner as in Example 1. ,evaluated. The physical property measurement results are shown in Table 1.

As in Example 1, high impact, high rigidity, low specific gravity,
It had a good appearance and was suitable for bicycle wheel materials. Example 3 Nylon 66 / 6T having a relative viscosity of 2.55 (66 / 6T =
65/35% by weight) 100 parts by weight of the copolymer of Example 1
23 parts by weight of ethylene-propylene copolymer and chopped strand glass fiber used in
Parts by weight, stirring and mixing in the same manner as in Example 1, extruding,
It was dried, molded and evaluated. The physical property measurement results are shown in Table 1.

It was suitable for a bicycle wheel material because of its high impact, high rigidity, low specific gravity, good appearance, low atmospheric equilibrium water absorption rate, and high flexural elastic modulus at the time of water absorption. Comparative Example 1 Nylon 6 having a relative viscosity of 2.70, 100 parts by weight of chopped strand glass fiber having an average fiber diameter of 12.8 μm
120 parts (length 3 mm) was added, a dumbbell piece was molded in the same manner as in Example 1, and the physical properties were measured. The results are shown in Table 1.

This composition had poor impact resistance, large specific gravity, and the appearance of the molded product was poor. Comparative Example 2 To 100 parts by weight of the nylon 66 / 6T copolymer used in Example 3, 82 parts by weight of the glass fiber used in Comparative Example 1 was added,
The same test as in Comparative Example 1 was performed. The results are shown in Table 1.

This composition lacked impact resistance. Comparative Example 3 Nylon 6 used in Comparative Example 1 was added to 100 parts by weight of Example 1
The same test as in Comparative Example 1 was conducted by adding 15 parts by weight of the ethylene-propylene copolymer used in Example 1 and 35 parts by weight of the glass fiber used in Comparative Example 1. The results are shown in Table 1. This composition had poor impact resistance and high water absorption, and was unsuitable as a bicycle wheel material.

[0023]

[0024]

INDUSTRIAL APPLICABILITY The composition of the present invention has excellent impact resistance and rigidity, is lightweight, and is most suitable as a bicycle wheel material. Moreover, the bicycle wheel has a good appearance and is excellent in productivity.

Claims (4)

[Claims] 1. A polyamide resin composition for a bicycle wheel, which comprises 100 parts by weight of a polyamide resin, 20 to 40 parts by weight of a polyolefin-based elastomer, and 60 to 100 parts by weight of glass fibers having an average fiber diameter of 6 to 15 μm. 2. The glass fiber is treated with a surface treatment agent containing maleic anhydride and / or its residue, and the amount of the treatment agent attached is 0.1 to 2.0 with respect to 100 parts by weight of the gasra fiber.
The polyamide resin composition for a bicycle wheel according to claim 1, wherein the polyamide resin composition is parts by weight. 3. The polyamide resin composition for a bicycle wheel according to claim 1, wherein the polyamide resin contains an aromatic ring as a molecular constitutional unit. 4. A bicycle wheel formed by injection molding the polyamide resin composition according to claim 1.