JPH07103307B2 - High specific gravity polyamide resin - Google Patents

Description

TECHNICAL FIELD The present invention relates to a high specific gravity polyamide resin containing a polyamide resin as a main component and a metal powder uniformly dispersed therein.

(Prior Art and Problems) In recent years, the use of a material containing a polyamide resin as a matrix material and a reinforcing agent or a filler is increasing. These materials are used for their respective purposes by revealing their shapes by using the injection molding method or the extrusion molding method which are generally used at present.

One of these application fields is a flywheel or inertia gear that requires high specific gravity materials. All of these apply a smooth rotation by utilizing the inertial force of the object. Therefore, a material formed of a material having a large specific gravity capable of keeping a large inertial force can obtain a large inertial force even if it is small, and thus is advantageous for use in a small space. For that purpose, it is necessary to increase the content of the metal powder. However, when the content of the metal powder is increased, the mechanical properties of the molded product are deteriorated and the flow of the melt-kneaded product is deteriorated, so that the molding becomes impossible. Further, the amount of wear of the injection molding machine and the like increases, which not only shortens the life of the molding machine, but also has a drawback that impurities are mixed in the molded product and the quality is deteriorated.

It is also necessary that these materials be balanced. If the balance is not balanced, the inertial force will be non-uniform, causing shaft runout and uneven rotation. That is, it is necessary that the metal powder to be blended is uniformly dispersed. In order to solve these drawbacks, there is a method of reducing the melt viscosity by mixing a lubricant or a plasticizer.

On the other hand, there is a method of treating the surface of a ferromagnetic powder with a silane coupling agent or the like to improve the wettability with a resin and thereby reduce the melt viscosity. The latter is generally used because it does not significantly change the mechanical strength and is highly effective. However, when a polyamide resin is used as the binder, there are problems that the heating temperature is too high, the time is long, or the melt viscosity becomes high during repeated regeneration.

As a result of earnest research on a polyamide resin used as a binder, the present inventor has found that the above problems can be solved by using a resin having a low terminal carboxyl group concentration, and has completed the present invention.

(Means for Solving Problems) That is, the present invention has a terminal carboxyl group concentration of 70 mg equivalent.
A high specific gravity polyamide resin composition obtained by mixing 95 to 65% by weight with respect to the total amount of metal powder surface-treated with a silane coupling agent, in a polyamide resin of not more than / kg.

The polyamide resin used in the present invention is nylon 6,1
One, two or more selected from 1, 12, 6, 6, 6, 10, 6, 12, and copolymers thereof.

The terminal carboxyl group concentration of these polyamide resins is 70 mg.
Equivalent / kg or less is required, preferably 50 mg
Equivalent / kg or less. Crosslinking occurs when heated above 70 mg equivalent / kg. There is no limitation on the lower limit of the terminal carboxyl group concentration, and those having no terminal carboxyl group can be used.

A method well known to those skilled in the art in which a polyamide resin having a low terminal carboxyl group concentration is added with m-xylenediamine, p-xylylenediamine, hexamethylenediamine, dodecamethylenediaminestearylamine having an amino group in the molecule during polymerization. Can be manufactured by.

A polyamide resin may be mixed with a lubricant, a plasticizer, or the like to reduce the melt viscosity, and an optional fourth component such as a stabilizer may be used.

As the metal powder according to the present invention, powders of Fe, Zn, Sn, Pb, Cu and alloys thereof, oxides, silicates and the like are used, but iron powder is preferable from the viewpoint of cost. Further, it can be applied to a so-called plastic magnet by using strontium or barium ferrite magnetic powder or samarium or neodymium rare earth magnetic powder.

The metal powder used in the present invention may be a metal powder obtained by any method. The metal powder may have any shape, but a shape closer to a sphere than a square metal powder is preferable. The angular metal powder not only deteriorates the fluidity of the material, but also easily abrades the resin composition or an apparatus for obtaining a molded product, and therefore foreign matter may be mixed into the molded product.

The particle size of the metal powder can be 0.1-300μ, but
Desirably, those having a particle size of 0.1 to 50 μ are preferable. If the particle size is smaller than 0.1 μ, handling is inconvenient, and if it is larger than 300 μ, molding may be hindered.

As the silane coupling agent of the present invention, one having an amino group is generally used in order to improve the compatibility with the polyamide resin. For example, methyltrialkoxysilane,
γ-aminopropyltrialkoxysilane, β- (aminoethyl) -γ-aminopropyltrialkoxysilane, γ-benzylaminopropyltrialkoxysilane, vinyltrichlorosilane, allyldichlorosilane,
Vinyltrialkoxysilane, vinyltris- (β-methoxyethoxy) -silane, vinyltriacetoxysilane and the like.

The preferred addition amount of the silane coupling agent varies depending on the particle diameter, surface area, surface activity, etc. of the metal powder, but is usually 0.2 to 2% by weight based on the metal powder. 0.2% by weight
In the following, the surface treatment is not sufficiently performed, and in the case of 2% by weight or more, the metal powder agglomerates and a uniformly dispersed molded product cannot be obtained.

Further, the content of the metal powder is 97 to 50% by weight based on the total amount,
It is preferably 95 to 65% by weight.

(Effects of the Invention) The high specific gravity polyamide resin of the present invention has the following effects.

(1) Friction resistance between the metal powders and between the metal powders and the resin is reduced, and the metal powders are uniformly dispersed to obtain a balanced molded product.

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

(3) The coefficient of friction between the wall surface of the molding machine and the kneaded material becomes small,
Very little wear on the molding machine and longer life of the molding machine. Furthermore, foreign matters such as wear are rarely mixed in the molded product, and the quality of the molded product is improved.

(4) In the resin permanent magnet using the ferromagnetic powder as the metal powder, even if a large amount of the ferromagnetic powder is contained, the orientation is good and the magnetic property is excellent.

Further, the molded product obtained by the present invention showed excellent heat resistance without changing the shape and the like even when left at a high temperature of 150 ° C. or higher for a long time.

From the above, the high specific gravity polyamide resin of the present invention is suitably used for flywheels, inertia gears, resin magnets and the like.

(Examples) Next, examples and comparative examples of the present invention will be described.

Examples 1 to 3 Nylon 12 manufactured by Daicel-Huls was selected as the polyamide resin, and iron powder was selected as the metal powder. As the iron powder, atomized iron powder manufactured by Kobe Steel, Ltd. was used, which was previously surface-treated with 1 part by weight of β- (aminoethyl) -γ-aminopropyltrimethoxysilane per 100 parts by weight of the iron powder. I prepared it and used it.

The molecular weight of nylon 12 was calculated by the relative viscosity method to be 13,0
The one of 00 to 15,000 was used. Terminal carboxyl group (-CO
The concentration of (OH) was measured by dissolving a polyamide resin in benzyl alcohol and titrating with 0.1N-KOH using a 1% phenolphthalene-methanol solution as an indicator.

A composition comprising 88% by weight of surface-treated iron powder and 12% by weight of nylon 12, having a low terminal carboxyl group concentration shown in Table 1, was melted and kneaded using a pressure kneader, and then 3 to The pellets were obtained by crushing to a size of 5 mm. The fluidity (MI value) of this pellet was measured.

After melting and kneading the pellets again with a pressure kneader, 3
The pellets were obtained by crushing to a size of ~ 5 mm. After performing this series of operations three times, the MI value of the obtained pellet was measured. The results are shown in the table.

Example 4 Nylon manufactured by Daicel-Huls as a polyamide resin
Tests were carried out according to Examples 1 to 3 except that 0.3 parts by weight of calcium stearate was kneaded with 100 parts by weight of 12. The results are shown in the table.

Example 5 Nylon manufactured by Daicel-Huls as a polyamide resin
The test was conducted according to Examples 1 to 3 except that 10 parts by weight of N-butylsulfonamide was kneaded with 100 parts by weight of 12. The results are shown in the table.

Comparative Example 1 The procedure of Example 1 was followed except that iron powder that had not been surface-treated was used. The results are shown in the table.

Comparative Examples 2, 3 Nylon 12 having a high terminal carboxyl concentration was used and the same as in the examples. The results are shown in the table.

Claims (1)

[Claims] 1. A high specific gravity obtained by blending a polyamide resin having a terminal carboxyl group concentration of 70 mg equivalent / kg or less with a metal powder surface-treated with a silane coupling agent in an amount of 95 to 65% by weight based on the total amount. Polyamide resin composition.