JPH0781094B2 - Metallic pigment for kneading synthetic resin - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generally relates to a metallic pigment for kneading a synthetic resin, and particularly when a synthetic resin containing metal powder particles is subjected to injection molding, it does not occur on the surface of the molded product. The present invention relates to a metallic pigment that can prevent weld lines or flow marks.

Weld line is a phenomenon that occurs more or less when injection molding synthetic resin, and this is the position in the mold where the molten resin branches along the flow path of the mold and merges again to completely fuse. It is a linear defect that occurs.

Further, the flow mark is a defect that the trace of the flow of the molten resin in the mold cavity becomes a vague pattern and remains in the molded product.

In particular, the synthetic resin containing the metal powder particles has a higher thermal conductivity than the non-containing synthetic resin and causes the temperature drop of the molten resin flowing in the mold. It is thought that the occurrence of () will be remarkable, but it has not been clarified in detail,
At present, no means has been found to completely prevent the occurrence of weld lines.

As metal powder particles for kneading, commercially available ones such as atomized powder are used as they are without any special measures. For a coating having excellent surface glossiness, especially when a metallic feeling is required. The metallic pigment of may be used.

Metallic pigments, such as aluminum pigments, are used for building materials, for the purpose of giving an article an excellent metallic feeling and surface gloss feeling.
It is blended in paints and printing inks for coating light electrical equipment, machinery, ships, vehicles, automobiles, etc., but in particular, instead of the conventional method of coating metallic paints on synthetic resins,
A method of manufacturing an article having a metallic feel by directly kneading a metallic pigment into a synthetic resin and then molding the resin is attracting attention as an energy-saving and low-cost method. However, metallic pigments that have been conventionally used for paints or inks generally have a small average particle size and are scaly. Therefore, when kneading this into synthetic resin or rubber with high consistency, a resin extruder is used. As a result of the shearing action, the metal particles have cracks on the surface thereof or are further pulverized, so that only a molded product exhibiting a turbid gray or black feeling can be obtained. Therefore, in order to obtain a particularly metallic feeling, fine particles having an average particle size of about 10 μm are used.
We are not satisfied.

The present inventor, through the microscopic observation of the distribution state and orientation state of the metal powder particles in the molded product using the conventional scale-like metal powder particles, the metal powder particles in the weld line has a slightly smaller distribution density and the molded product. It was found that they were oriented so that they were just protruding in the direction perpendicular to the surface.

Furthermore, the present inventor further advanced the study on the shape and particle size distribution of the metal powder particles in order to provide a resin composition in which the occurrence of weld lines is small, and as a result, it is a granular or thick plate-like powder and has a relatively small particle size. It was found that a molded product having an excellent appearance with almost no generation of weld lines can be obtained by using a metallic pigment composed of metal powder particles of large size, and the present invention was accomplished.

In the present invention, the average shape ratio (thickness / particle size) is a value obtained by dividing the average thickness by the average median diameter, and the average thickness is
Aluminum Paint and Powder, by JD Edwards and RI
Wray, 3rd Ed., Reinhold Publishing Corp., New York
(1955) based on the method described in pp16-22, the sample powder is first treated with stearic acid to be leafing, then floated on the water surface without a gap to form a single layer, and the water surface diffusion area (WCA ) Is calculated from the formula: WCA (cm ² / g) = measured area (cm ² ) / mass of sample (g), and then the average thickness is calculated by the formula: average thickness (μm) = 4000 (cm ² · μm / g) / It is calculated from the water surface diffusion area (cm ² / g). Also, the average median diameter is measured by MI
It was performed using a CROTRAC particle size measuring device.

The metallic pigment for kneading the synthetic resin of the present invention has an average shape ratio (thickness / particle size) of 1/25 to 1/2, a 500 mesh Tyler standard sieve passage rate of 30% or less, and a 200 mesh Tyler standard. It consists of flaky metal powder particles that have a particle size distribution with a sieve passage rate of 90% or more and have an excellent surface gloss.

The metallic pigment of the present invention is best blended in a synthetic resin with 100% metal content, but it may be blended as a composition containing a small amount of volatile components as follows.

Metal powder particles 85-95% Fatty acid lubricant 0.1-3% Volatile hydrocarbon 14.9-2% As fatty acid lubricant, stearic acid, palmitic acid,
Oleic acid, linoleic acid, linoleic acid, etc. can be used. As the volatile hydrocarbon, both an aliphatic hydrocarbon and an aromatic hydrocarbon can be used.

The metal powder particles constituting the metallic pigment of the present invention have an average shape ratio (thickness / particle diameter) of 1/25 to 1/2, preferably 1/15 to 1/2. In the present invention, the average shape ratio 1/100 to 1/50 is thicker than the conventional metallic pigment consisting of metal powder particles, that is, since metal powder particles having a non-scaled shape are used, particles The directionality of itself is small. By using such particles having a small directional property, in the present invention, the conventional scale-like metal powder particles have a problem of a weld line that occurs because the orientation of the particles is not aligned along the flow direction of the synthetic resin during molding. Therefore, in the present invention, it is possible to obtain a molded product having almost no weld lines even if a molding method such as injection molding in which the flow of resin does not easily become constant is used.

Metal powder particles constituting the metallic pigment of the present invention, 500
The Tyler standard sieve passage rate of the mesh is 30% or less, preferably
20% or less and 9 mesh Tyler standard sieve passage rate of 9
It is a relatively large particle having a particle size distribution of 0% or more, preferably 95% or more.

Particles under the size of 500 mesh Tyler standard sieve
Since non-scaly fine particles of less than m have poor surface gloss and metallic feel, a molded product having the desired appearance cannot be obtained even if compounded with a synthetic resin, and the viscosity of the molten resin is greatly increased. As a result, it becomes more difficult for multiple resin streams to join together in the mold cavity and to completely fuse them, as a result, the metal powder particles are oriented in a direction perpendicular to the surface of the molded product, creating a weld line. It is not preferable because it causes the On the other hand, particles on a 200-mesh Tyler standard sieve, that is, large particles having a particle size of more than 74 μm, are also unsuitable because the individual particles are not noticeable and the desired color tone cannot be obtained.

Conventional paint pigments, printing ink pigments, synthetic resin kneading pigments have an average shape ratio of about 1/50 or less, and consist of metal powder particles with a 500 mesh Tyler standard sieve passage rate of 50% or more. Therefore, the metallic pigment composed of the metal powder particles having the shape and the particle size distribution specified in the present invention is a novel pigment that has never existed before.

The metal powder particles constituting the metallic pigment of the present invention have an average particle size of 30 to 60 μm, preferably 35 to 50 μm.

In the present invention, since the metal powder particles having a relatively large particle diameter as compared with the conventional ones are used, there is a drawback in using the conventional scaly fine metal powder particles as described above. When the metallic pigment is kneaded into the synthetic resin to be molded, there is almost no fear that it will be finely powdered due to the shearing action of the resin extruder to lose the metallic feeling.

The metal powder having the above shape can be produced by a conventionally known method, for example, a wet ball mill method, an attritor method, a vibration mill method or the like.

The synthetic resin in which the metallic pigment of the present invention is mixed and kneaded is not particularly limited, but is selected from a wide range of synthetic resins such as polyolefin resins such as polyethylene and polypropylene, vinyl chloride resins, polystyrene resins, acrylic resins, polycarbonate resins and the like. .

The amount of the metallic pigment of the present invention mixed with the synthetic resin is
It can be variously changed according to the required or desired color tone,
Generally, it is mixed in a proportion of 0.3 to 10 parts by weight as a metal component.

Other additives such as pigments, dyes, stabilizers, dispersants, weathering agents, antistatic agents, etc. may be added to the metal-containing synthetic resin.

The synthetic resin containing the metallic pigment of the present invention is then
It can be molded by a usual molding method such as injection molding, calender molding, blow molding, etc., but when the injection molding method is used, the effect of the metallic pigment for synthetic resin of the present invention is most remarkably observed.

The metallic pigments of the present invention are
Although an aluminum pigment is illustrated as an example, the metal powder is not limited to the aluminum pigment, and the metal powder may be another metal, for example, a metal powder pigment such as stainless steel, nickel, or bronze, or aluminum and another metal (nickel, copper,
It may be an alloy powder such as an alloy with silicon).

As described above, by using the metallic pigment composed of the metal powder particles having the specified shape and particle size distribution of the present invention, a molded product having an excellent appearance with almost no generation of weld lines can be obtained. However, in the present invention, it has been described above that the metal powder particles may take the form of a pigment composition containing a small amount of volatile matter, but as described above, since the composition contains a small amount of volatile hydrocarbons, a two-layer structure is provided. There is no fear of separation, and since it is volatile, it does not affect the finish of the molded product. In addition, since the metallic pigment of the present invention has a low hiding power, it is possible to obtain a molded product having an excellent color tone by further enhancing the addition effect when other colorants are added.

Hereinafter, the present invention will be described with reference to examples.

Example 1 Five types having an average shape ratio (thickness / particle diameter) of about 1/8 and having the following 500 mesh Tyler standard sieve passage rate, 200 mesh Tyler standard sieve passage rate, average thickness and average median diameter 3 parts by weight of aluminum pigment (all 90% metal content, balance mineral spirits) to 100 parts by weight of ABS resin in terms of metal content, and 3 hole on / off switch box molding using injection molding machine I got a thing.

For the obtained molded product, the result of evaluating the presence or absence of weld lines and the appearance (metallic feeling) is first.
Shown in the table.

From Table 1, it can be seen that only when samples No. 2 and No. 3 (particularly No. 3), that is, the aluminum pigment having the shape and particle size distribution specified in the present invention are used, the generation of weld lines is hardly generated, which is excellent. It is clear that moldings with a different appearance are obtained.

Example 2 Five aluminum pigments having the following average shape ratios (thickness / particle size) and having a 500 mesh Tyler standard sieve passage rate of 11% and a 200 mesh Tyler standard sieve passage rate of 98% ( 95% metal content, balance mineral spirits)
Was mixed with 100 parts by weight of polyethylene resin in an amount of 3 parts by weight in terms of metal, and an injection molding machine was used to obtain a molded product similar to that of Example 1.

Table 2 shows the results of evaluation of the obtained molded product in the same manner as in Example 1.

Table 2 shows that samples No. 6, No. 7 and No. 8, that is, excellent appearance with almost no generation of weld lines only when the aluminum pigment having the shape and particle size distribution specified in the present invention is used. It is clear that moldings having are obtained.

Claims (5)

[Claims] 1. An average shape ratio (thickness / particle diameter) of 1/25 to 1/2
For kneading synthetic resin consisting of flaky metal powder particles with a surface mesh of 500 mesh with a Tyler standard sieve passage rate of 30% or less and a 200 mesh Tyler standard sieve passage rate of 90% or more. Metallic pigment. 2. The pigment according to claim 1, which has an average shape ratio of 1/15 to 1/2. 3. A Tyler standard sieve passing rate of 500 mesh is 20.
%. The pigment according to claim 1, which is at most%. 4. A 200 mesh Tyler standard sieve passage rate is 95.
The pigment according to claim 1, which is at least%. 5. The pigment according to any one of claims 1 to 4, wherein the metal powder is aluminum powder.