JPH0733905A - Composition for balancing weight of instrument pointer - Google Patents

Abstract

PURPOSE:To provide the title composition which can easily be produced, has a high weight accuracy necessary for a balancing weight and has excellent surface smoothness. CONSTITUTION:The composition is one containing 86-96wt. % heavy metal powder having a mean particle diameter of 1-30mum and 4-14wt.% thermoplastic resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is applicable to, for example, automobiles and automobiles.
The present invention relates to a composition used for a balance weight of a pointer of an instrument attached to a vehicle instrument under a vibrating environment such as Toby, and further to a composition for a balance weight that is easy to mold and has high weight accuracy.

[0002]

2. Description of the Related Art Conventionally, it has been a general practice to cast an alloy mainly of heavy metals such as tungsten and molybdenum to form a simple disk-shaped block, and then machine the required shape from the block by lathing. It was target.

[0003]

However, when a heavy metal is cast into a disk-shaped block and the required shape is obtained from the block,
And in the conventional method of cutting to the required weight, the cutting amount is large,
There is much waste of material. In addition, there is a problem that the cutting process is burdened, the cost is high, and the quality is not stable. The present invention is to solve such problems, a balance weight of the pointer of the vehicle instrument, in the high filling of heavy metals, excellent surface smoothness, and a composition with high weight accuracy and good moldability, The purpose is to provide.

A composition using a combination of heavy metal powder and a thermoplastic resin as a weight for an automatic timepiece (Japanese Patent Laid-Open No. 60-244).
No. 888) is also known, but the proportion of heavy metals is high, and therefore the weight accuracy is poor, and it cannot be put to practical use as a balance weight for instrument pointers.

[0005]

The present invention has an average particle size of 1 μm.
The present invention relates to a balance weight composition for measuring instruments, comprising 86 to 96% by weight of a heavy metal powder of m to 30 μm and 4 to 14% by weight of a thermoplastic resin.
The basic composition of the balance weight composition of the pointer of the vehicle instrument of the present invention is a heavy metal powder having an average particle size of 1 μm to 30 μm, and if it exceeds 30 μm, the unevenness of the surface of the molded product is 10 μm.
The above is not preferable. Further, if the particles are less than 1 μm, the fluidity is deteriorated and molding processability is difficult.

The thermoplastic resin used is a polyolefin resin, a polyamide resin, a polycarbonate resin, or a PBT resin, and has a viscosity of 1000 when melted.
It is preferably 0 cps or less. 10,000 cps
If it is above, it cannot be sufficiently impregnated at the time of kneading with the heavy metal powder, and the impregnation residue and bubbles are likely to occur. The heavy metals preferably have a specific gravity of 19 or more. By using a heavy metal having a specific gravity of 19 or more, the specific gravity of 5 to 10 required as a balance weight can be maintained even when used in combination with a thermoplastic resin.

Heavy metal powders include tungsten, gold,
Alternatively, platinum is preferred. Further, tungsten is desirable because it is easy to make the particle diameter uniform as a powder and is economically superior. For example, the mixing ratio of tungsten powder and resin is 86% by weight to 96% by weight of tungsten powder and 4% by weight of resin.
If it is ˜14 wt% and less than 86 wt% of the tungsten powder, the specific gravity of the composition becomes 5 or less, and the volume of the balance weight becomes large, which is not suitable for practical use. Further, when the content of the tungsten powder is 96% by weight or more, the moldability is poor and the strength is lowered.

In addition, the thermoplastic resin used may be an additive for preventing thermal deterioration of the resin, such as a high molecular weight phenolic compound, more specifically tetrakis [methylene {3-
(3,5 ditert butyl-4-hydroxyphenyl)
p-lopanote}] A silane-based or titanium-based coupling agent or the like may be added, if necessary, for the purpose of improving the wettability between methane and tungsten powder and the resin.

[0009]

The present invention will be described in more detail based on the following examples. Example 1 90% by weight of tungsten powder having an average particle diameter of 6.0 μm, 9% by weight of polypropylene resin, and 1% of an antioxidant and the like.
After adding and mixing by weight, the mixture was kneaded and granulated by a twin-screw extruder, and the pellets were molded into a balance weight by an injection molding machine. It was 0.01 or less, and the weight accuracy was sufficiently satisfactory for practical use. It was excellent in surface smoothness and had no problem in appearance, and when used as a balance weight for instrument pointers for vehicles, it was sufficiently durable to use.

Example 2 90% by weight of tungsten powder having an average particle size of 6.0 μm, 4% by weight of tungsten powder having an average particle size of 1.0 μm, 5.5% by weight of polyamide resin and 0.5% by weight of other additives were mixed. After that, kneading and granulation was performed with a twin-screw extruder, and a balance weight was formed by injection molding from the pellets. The average specific gravity of the molded product was 9.34. The standard deviation of variation in specific gravity was 0.02, which was a good balance weight in terms of quality.

[0011]

The composition for balance weight of the present invention is
It is easy to manufacture, has a high weight accuracy required as a balance weight, and has a smooth surface. That is, a balance weight with high weight accuracy can be obtained by ordinary injection molding without using the conventional method of cutting.

Claims (2)

[Claims] 1. A balance weight composition for measuring instruments, comprising 86 to 96% by weight of a heavy metal powder having an average particle size of 1 to 30 μm and 4 to 14% by weight of a thermoplastic resin. 2. A balance weight composition for measuring instruments, wherein the heavy metal powder is at least one powder selected from tungsten, gold and platinum.