JP3103149B2 - High specific gravity polyamide resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high specific gravity polyamide resin containing a polyamide resin as a main component and metal powder dispersed uniformly.

[0002]

2. Description of the Related Art In recent years, reinforcing materials or fillers have been compounded using a synthetic resin as a matrix material, such as an electromagnetic wave shielding material in which metal fibers are mixed in a synthetic resin or a plastic magnet material in which ferrite or the like is mixed in a synthetic resin. The use of materials is increasing. Such a material is molded by an injection molding method or an extrusion molding method which is generally performed at present, and is used for various uses.

[0003] One of such application fields is a flywheel or an inertia gear which requires a material having a high specific gravity. All of these provide smooth rotation by utilizing the inertial force of the object. Therefore, a material formed of a material having a large specific gravity capable of maintaining a large inertia force can obtain a large inertia force even if it is small, and is therefore advantageous for use in a small space.

[0004] For that purpose, it is necessary to increase the content of metal powder in the resin. However, when the content of the metal powder is increased, the mechanical properties of the formed product are reduced, and the flow of the melt-kneaded product is deteriorated, so that the molding becomes impossible.

[0005] These materials also need to be balanced. In the case of unbalanced material, the inertial force becomes non-uniform, and the shaft of the flywheel and the inertia gear oscillates and the rotation becomes uneven. Therefore, it is necessary that the metal powder to be blended is uniformly dispersed in the resin.

Conventionally, in order to solve these problems, a method of blending a lubricant or a plasticizer to lower the melt viscosity, or a method of improving the wettability with a resin by treating a metal powder with a silane coupling agent or the like. Accordingly, a method of reducing the melt viscosity has been performed.

In particular, the latter is generally used because it has a large effect without significantly changing the mechanical strength. However, when a polyamide resin is used as the binder, there have been problems such as that the heating temperature is too high, the heating time is long, and the melt viscosity increases as the regeneration is repeated.

As a result of intensive studies on the polyamide resin used as a binder, the present inventors have solved the above-mentioned problems by using a specific terminal-modified polyamide resin whose terminal is modified with a monocarboxylic hydrocarbon compound. They have found that they can do this and have completed the present invention.

[0009]

That is, according to the present invention, the terminal is modified with a monocarboxylic hydrocarbon compound having a terminal carboxyl group concentration of 90 mg equivalent / kg or less and a terminal amino group concentration of 40 mg equivalent / kg or less. A high specific gravity polyamide resin comprising a polyamide resin and a metal powder.

The polyamide resin used in the present invention is one or two selected from nylon 6, nylon 11, nylon 12, nylon 46, nylon 66, nylon 610, nylon 612, nylon 1212, and copolymers thereof. The above is obtained by modifying the terminal with a monocarboxyl hydrocarbon compound.

The terminal carboxyl group concentration is 90 mg
Equivalent / kg or less, preferably 7
5 mg equivalent / kg or less. When the terminal carboxyl group concentration is higher than 90 mg equivalent / kg, the properties as a binder are reduced and the strength of the molded product is not satisfied. Further, the terminal amino group concentration needs to be 40 mg equivalent / kg or less, and preferably 20 mg equivalent / kg or less.
When the terminal amino group concentration is higher than 40 mg equivalent / kg,
Crosslinking occurs during heating, resulting in thickening. The lower limit of the terminal amino group concentration is not particularly limited, and those having no terminal amino group can be used.

The monocarboxylic hydrocarbon compound used for the terminal modification of the polyamide resin of the present invention has a boiling point of 180 ° C. or higher, preferably 200 ° C. or higher, and a thermal decomposition temperature of 200 ° C. or higher, preferably 250 ° C. or higher. A heat-resistant, relatively high-molecular-weight monocarboxyl hydrocarbon compound is preferred. For example, pentanoic acid, hexanoic acid (caproic acid), heptanoic acid, octanoic acid, decanoic acid, dodecanoic acid (lauric acid), octadecanoic acid (stearic acid), benzoic acid and the like can be mentioned. The terminal modification of the polyamide resin is performed by a usual method of adding these monocarboxyl hydrocarbon compounds during polymerization of the polyamide resin.

The terminal-modified polyamide resin of the present invention can be mixed with a lubricant, a plasticizer or the like to lower the melt viscosity, and it is also possible to add a stabilizer and other additives.

The metal powder used in the present invention includes Fe,
Mg, Zn, Sn, Pb, Cu, Mn, Cr, Ni, C
Powders of metals such as o and Nb and alloys thereof, and powders of oxides, borides and silicates of these metals can be cited, but iron powder is preferably used in terms of price. Ferromagnetic powder such as strontium ferrite and barium ferrite, and soft ferrite powder can also be used.

[0015] The metal powder used in the present invention may be obtained by any method, and the shape of the metal powder may be any. However, a metal powder that is too square may deteriorate the fluidity of the material. In addition, the apparatus for obtaining the resin composition or the molded article is worn, which is not preferable because it may cause foreign matters to enter the molded article.

The particle size of the metal powder is 0.1 to 300 μm.
m, but preferably 0.1 to 5
Those having a particle size of 0 μm are preferred. When the particle size is smaller than 0.1 μm, it is inconvenient to handle, and when the particle size is larger than 300 μm, molding is inhibited, which is not preferable.

In order to improve the wettability between the terminal-modified polyamide resin used in the present invention and the metal powder and reduce the melt viscosity, the metal powder may be treated in advance with a coupling agent or a surface modifier. Examples of the coupling agent and surface modifier used include various surface modifiers such as silane-based, titanate-based, aluminum-based, phosphite and other organic phosphorus compound-based, chromium / methacrylate-based, and amino acid-based agents. However, in order to improve the compatibility with the polyamide resin, it is preferable to use one having an amino group. For example, γ-aminopropyltriethoxysilane, N-β-
(Aminoethyl) -γ-aminopropyldimethoxymethylsilane, γ-benzylaminopropyltrimethoxysilane and the like.

The preferred amount of the coupling agent varies depending on the particle size, surface area, surface activity and the like of the metal powder, but is usually 0.2 to 2% by weight based on the metal powder. If the content is less than 0.2% by weight, the surface treatment is not sufficiently performed.
If the content is more than 2% by weight, aggregation of the metal powder occurs, and a uniformly dispersed molded product cannot be obtained.

The content of the metal powder in the high specific gravity polyamide resin of the present invention is 97 to 50% by weight, preferably 95 to 65% by weight based on the total amount. If it is 97% by weight or more, sufficient formability and mechanical strength cannot be obtained, and if it is 50% by weight or less, a sufficient specific gravity cannot be obtained.

[0020]

The high specific gravity polyamide resin of the present invention has the following effects.

(1) The frictional resistance between the metal powders and between the metal powders and the polyamide resin is reduced, and the metal powders are uniformly dispersed to obtain a well-balanced molded product.

(2) When the kneaded product is molded by using an injection molding machine, the moldability is high even if a large amount of metal powder is contained because the kneaded melt of the metal powder and the polyamide resin has high fluidity. Good.

(3) The coefficient of friction between the molding machine wall surface and the kneaded material is reduced, the wear of the molding machine is reduced, and the life of the molding machine is prolonged. In addition, foreign matter such as abrasion is not mixed into the molded product, and the quality of the molded product is improved.

(4) In the case of a resin permanent magnet using a ferromagnetic powder as a metal powder, even if a large amount of ferromagnetic powder is contained, a magnet having good orientation and excellent magnetic properties can be obtained. (5) Since the melt viscosity does not increase even after long-time heating and kneading, the resin can be recycled.

Having these characteristics, the high specific gravity polyamide resin of the present invention is suitably used for various applications such as flywheels, inertia gears, and resin magnets.

[0026]

Next, the present invention will be described with reference to examples and comparative examples.

Examples 1 to 3 The polyamide resin was modified at the end by adding lauric acid during the polymerization of Nylon 12 from Daicel Huls.
Different types of terminal-modified polyamide resins were used. 0.5
% M-cresol solution has a relative viscosity of 1.58 to 1.
62. Table 1 shows the terminal carboxyl group concentration and terminal amino group concentration of these terminal-modified polyamide resins. The terminal carboxyl group concentration was measured by dissolving the polyamide resin in benzyl alcohol and performing neutralization titration by potentiometric titration using 0.01 N-KOH. The terminal amino group concentration was measured by dissolving the polyamide resin in a mixed solvent of phenol / methanol (volume ratio: 10/1) and performing neutralization titration by potentiometric titration using 0.01 N-HCl.

Strontium ferrite manufactured by Toda Kogyo was used as the metal powder. 100 parts by weight of the ferrite was previously subjected to a surface treatment with 1 part by weight of β- (aminoethyl) -γ-aminopropyltrimethoxysilane.

A test was conducted on a lab plast mill (Model 75C100 manufactured by Toyo Seiki Seisaku-sho) in which 270 g of a composition comprising 88 parts by weight of the surface-treated ferrite and 12 parts by weight of a terminal-modified polyamide resin was heated to 300 ° C. in advance. It was put into a chamber, kneaded at a rotation speed of 50 rpm under heating at 300 ° C. using a roller type (R-100 type) blade, and the torque value of the melt was measured over time. Table 1 shows the measurement results. The higher the torque value, the higher the viscosity of the melt,
Indicates poor liquidity.

Comparative Example 1 A test was conducted in the same manner as in the Examples, using a polyamide resin having a high terminal carboxyl group concentration, which was modified by adding dodecane diacid during polymerization of Nylon 12 manufactured by Daicel Huls Co., Ltd. Table 1 shows the results.

Comparative Example 2 A test was conducted in the same manner as in the Example using a polyamide resin having a high terminal amino group concentration, modified by adding hexamethylene diamine during polymerization of Nylon 12 manufactured by Daicel Huls Co., Ltd. Table 1 shows the results.

COMPARATIVE EXAMPLE 3 A test similar to the example was conducted using a polyamide resin having a high terminal amino group concentration, which was modified by adding laurylamine during polymerization of Nylon 12 manufactured by Daicel Huls Co., Ltd. Table 1 shows the results.

[0033]

[Table 1]

Claims (2)

(57) [Claims] 1. A terminal carboxyl group concentration of 90 mg equivalent / kg or less and a terminal amino group concentration of 40 mg equivalent / kg.
A high specific gravity resin composition comprising a polyamide resin whose terminals are modified with a monocarboxyl hydrocarbon compound and a metal powder, each having a weight of not more than kg. 2. A terminal amino group concentration of 20 mg equivalent / kg.
The high specific gravity resin composition according to claim 1, which is: