JPS58196270A - Preparation of electrically conductive paint - Google Patents

Abstract

PURPOSE:To prepare an electrically conductive paint having good applicability, film properties, mechanical strength, etc. and highly uniform electrical conductance, and useful for the coating of a molded plastic article, at a low cost, by dispersing metal powder in a solution of a synthetic resin binder, and kneading and dispersing metallic fibers in the above dispersion. CONSTITUTION:The objective paint having a specific resistance of <=10<2>OMEGA-cm can be prepared by (1) adding (A) 10-35vol% of metallic powder having particle diameter of <=80mu (e.g. carbon black or graphite powder) to (B) a solution of a synthetic resin binder, and dispersing the secondary particle to primary particles uniformly with a dispersing apparatus such as ball mill, atomizer, roll mill, etc., and (2) adding (C) 2-15vol% of metallic fibers having diameter of <=100mu and length of >=1mm., and kneading and dispersing in the above dispersion with a dispersing apparatus such as kneader, dissolver, etc. EFFECT:Also excellent in shielding electromagnetic wave and electromagnetic field, and reflecting electrical radiation.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a stable highly conductive paint containing conductive powder and metal fiber as a conductive filler. The present invention relates to a method of manufacturing a conductive paint used for electromagnetic shielding, electromagnetic shielding, radio wave reflection, etc. by applying it by coating, spray coating, or the like.

Plastic materials have the characteristics of electrical insulation, light weight,
It is used in a wide range of fields due to its properties such as workability, but
Depending on the application, problems due to electrostatic interference or electromagnetic waves may occur, and the demand for imparting conductivity to plastics has rapidly increased, and conductive compositions made by combining various types of plastics with conductive fillers have been developed.

Conventionally, the most common type of conductive paint has been a synthetic resin binder with graphite or carbon black as conductive fillers, and a stable conductive paint can be obtained with a relatively low additive amount. The specific resistance is 102Ω-
Sono was the limit.

In order to obtain even higher conductivity, highly conductive metal powders such as silver, copper, and nickel are used, but since the conductive mechanism is due to contact between particles, if the concentration is low, metal powders such as silver, copper, and nickel are used. The particles do not come into sufficient contact with each other and become isolated in the polymer matrix, making it impossible to obtain high conductivity.In order to obtain satisfactory high conductivity, it is necessary to add a large amount of metal particles, approximately 30% by volume or more. there were. However, when metal powder is added in too large a quantity, it causes deterioration in film forming properties as a paint, adhesion to substrates, and mechanical strength of the film, so it is necessary to use a small amount if possible to achieve its function.

In addition, when using metal fibers such as copper, stainless steel, aluminum, etc. as conductive fillers, the longer the fiber length, the easier it is to obtain contact between the fillers when dispersed in the resin than in powder form, and the capacity ratio of about 5 to 15 High conductivity can be obtained with a relatively low addition amount. Furthermore, there are conductive compositions in which the carbon powder and carbon fibers as a fibrous conductive substance are mixed in a polymer matrix, but these fibrous conductive compositions can be used as conductive paints. In this case, the longer the fiber length, the more difficult it is to achieve uniform dispersion.The resulting conductivity is unstable, and there are concerns about reproducibility and uniformity.Furthermore, metal fibers in particular may be shaped due to stress such as impact and shearing during kneading. was damaged and it was difficult to obtain effective conductivity. Furthermore, from an economic point of view, metal powder is expensive, but metal fiber is even more expensive, and if the amount added is large, it is economically disadvantageous.

The present invention was developed in order to solve the above-mentioned drawbacks, and in other words, as a first step, metal powder having a particle size of 80μ or less is added to a synthetic resin binder solution, and then a ball mill, attritor, After uniformly loosening and dispersing the secondary particles into primary particles using a dispersion device with excellent shearing force and mixing power such as a roll mill, as a second step, metal fibers with a diameter of 100μ or less and a length of 11II or more are added. By cross-dispersing the metal fibers using a dispersion device with low mechanical stress, such as a kneader or desilver, without destroying the shape of the metal fibers, the metal powder with a volume ratio of 10 to 35 and the metal powder with a volume ratio of 2 to 15 in the solid content are mixed. This is a method for producing a conductive paint containing fibers and having a specific resistance value of 102Ω-I or less.

Moreover, by adding 5 to 20 volumes of conductive powder such as carbon blank or graphite to the metal powder as the conductive powder, further improvement in conductivity was obtained and was effective.

Figure 1 shows the state of the conductive paint obtained by the present invention, and is a conductive paint film made by dispersing conductive powder (2) and metal fibers (3) in a synthetic resin binder film. In the first step, for example, ethylene-vinyl acetate copolymer, acrylic resin, alkyd resin, urethane resin, unsaturated polynisder resin, phenolic resin, amino resin, vinyl chloride resin, salt In a synthetic resin binder solution in which vinyl acetate resin, cellulose resin, butyral resin, etc. are dissolved in a solvent, copper, nickel, iron, aluminum, stainless steel, zinc, s and Metal powder made of these alloys is made into conductive powder, one or more of these are added to the solid content in an amount of 10 to 35% by volume, and in order to impart coating suitability, a solvent and a dispersion aid, In addition, antioxidants are added and the agglomeration of particles is loosened using a dispersion device such as a ball mill, attritor, or roll mill that has relatively excellent dispersion ability and shearing force, and the conductive powder is pulverized and the oxide film is destroyed. and disperse it uniformly to form a conductive paint.

□The smaller the particle size of the metal powder, the more difficult it will be to make into a paint, but the cost will be higher, and if it is over 100 μm, it will be difficult to obtain uniform conductivity due to the decrease in specific surface area, so it is preferable that the waveton is 80 μm or less. Appropriate.

Next, as a second step, aluminum or copper with a diameter of 100μ or less and a length of 1% or more is added to the conductive paint obtained in the first step.
One or more metal fibers (3) made of metals such as stainless steel, nickel, iron, and alloys thereof are added to the solid content in an amount of 2 to 15% by volume, and relatively shearing force, impact force, etc. Using a dispersion device such as a kneader or desilver with low mechanical stress, adjust the crosstalk conditions, etc. 5.
The metal fibers are dispersed without destroying their shape as much as possible, and a conductive paint with a specific resistance value of 102Ω-true or less is made.

Incidentally, the longer the fiber length of the metal fiber, the easier it is to obtain high conductivity with less addition, but it becomes difficult to disperse, and if it is too short, its properties will not be fully exhibited, so it is preferably 19% or more and 10% or less.

Further, the fiber diameter is preferably 100 μm or less; if it is larger than this, sedimentation and separation become severe and the rigidity becomes strong, making it unsuitable for use as a paint.

The amount of metal fiber added needs to be as small as possible from an economic point of view, but a sufficient addition effect cannot be obtained if the content is less than 2 to 15% of the total solid content.
Capacity: 1. % was appropriate.

In addition, as a conductive powder in the first step, the combined use of carbon blatter, graphite, etc. with low specific gravity is effective in stabilizing the paint and obtaining stable conductivity, and the amount added is about 5 to 20% by volume. is appropriate, and the solid content is 20
Addition of more than 5% by volume deteriorates paint suitability and limits conductivity, and addition of less than 5% by volume results in no effect.

In other words, in order to prevent mechanical strength deterioration due to high addition of conductive powder (2), the present invention combines metal fiber (3), which can obtain high conductivity with a relatively low addition, without destroying its properties. This reduces the amount of conductive powder (2) added, compensates for the shortcomings of the double-groove conductive filler, and allows each of the strengths to function effectively, resulting in less deterioration of coating suitability, coating film characteristics, mechanical strength, etc.
This is a method for producing a highly conductive paint that is economical and has good conductivity uniformity.

Next, examples and comparative examples of the present invention will be described using figures.

Comparative Examples 1 to 6 Polyester resin solution (Pylon” 200C Toyobo KK
I 20% solids, solution toluene/methyl ethyl)7
= 1/1), nickel powder (44 μ [elliptical metal KK)] was added to the solid ratio shown in Table 1, kneaded for 8 hours using an attritor, and the resulting conductive paint was mixed using a knife coater. After coating on release paper and drying for 5 minutes at an oven temperature of 80C, 20017. A coating film was formed and the conductivity was measured after peeling.

Table 1 (Volume %) Comparative Examples 7 to 13 Solid ratio of copper fiber (50μ diameter, length 39 [Kobe Cast Iron KK)] to polyester resin solution (same product as Comparative Examples 1 to 6) shown in Table 2 The conductive paint was added so that

Table 2 (Volume %) Comparative Examples 14 to 18 Polyester resin solution (same product as Comparative Examples 1 to 6)
Kel powder (same product as Comparative Examples 1 to 6) and copper fiber (same product as Comparative Examples 7 to 15) were added to the solid ratio shown in Table 6, and kneaded in an attritor for 8 hours. The conductive paints obtained were evaluated in the same manner as in Comparative Examples 1-6.

Table 3 (Volume %) Examples 1 to 5 As the first step, nickel powder (same product as Comparative Examples 1 to 6) was added to a polyester resin solution (same product as Comparative Examples 1 to 6) Table 4
Add to achieve the solid ratio shown in 8.
As a second step, the conductive paint obtained by kneading for a period of time is
Copper fibers (similar to Comparative Examples 7 to 13) were added to achieve the solid ratio shown in 4, and the conductive paint obtained by dispersing for 4 hours in a dissilver was evaluated in the same manner as Comparative Examples 1 to 6. .

Table 4 (Volume %) The curve fat in Figure 2 is a diagram of the above Comparative Examples 1 to 6.
, which shows the case where nickel powder is dispersed alone in the resin, and similarly, the curve (bl shows the case where copper fibers are individually dispersed in the resin).

The curve tc+ shows the case where nickel powder and copper fibers are added to the resin and kneaded at the same time, that is, the conventional method. curve(
At shows an example of the present invention, and shows the performance of a conductive paint obtained by dispersing resin and nickel powder in the first step and dispersing copper fibers in the second step.

As can be seen from the curve fa), when nickel powder is used alone, approximately 20% by volume or more is required to obtain a conductivity below 102 Ω. It is obtained at approximately 7 capacity factors or more.

However, in these cases, as mentioned above, in the case of conductive powder, the performance of the coating film deteriorates significantly and the suitability of the coating is poor, and in the case of fibers, uniform dispersion is difficult and the stability of conductivity and reproducibility are poor. It was inferior in terms of gender.

In addition, when the conductive powder and conductive fibers were dispersed in one step as shown in song 1(c), the shape of the copper fibers was destroyed due to the mechanical stress required for uniform dispersion, and the effect of the copper fiber composite almost disappeared. has been done. Curve (dlO) In the example according to the present invention, conductivity of 102Q-rn is obtained even when the nickel powder is 10 volumes and the copper fiber is about 6 volumes.

Example 6 Among the following compositions, in the first step, acrylic resin solution, copper powder and carbon black were kneaded in an attriter for 2 hours,
As a second step, aluminum fibers were added to the obtained conductive paint and dispersed in a dissilver for 4 hours, and the obtained conductive paint was evaluated in the same manner as Comparative Examples 1 to 6.
A good highly conductive paint was obtained, which had high conductivity with a specific resistance value of 10 −3 Ω and exhibited improved liquid stability and uniform conductivity, which is thought to be due to the effect of adding carbon black.

Conductive paint composition [Kobe Cast Iron KK] 5 tt As described above, the present invention provides two methods for combining conductive powder based on metal powder and conductive fibers made of metal fibers.
Separated by process, conductive powder is thoroughly cross-dispersed, and metal fibers are dispersed in the next process so that the fiber shape is not damaged as much as possible, and the manufacturing method is used to make paint, which fully maintains the characteristics of both conductive materials. This makes it possible to reduce the amount of each used when compared to using them alone.In particular, it is possible to reduce the suitability of paint due to the addition of a high amount of conductive powder, deterioration of the physical properties of the paint film, and further reduce the conductivity when using metal fiber alone. A good conductive paint with improved non-uniformity was obtained.

[Brief explanation of the drawing]

The drawings show examples of the present invention, FIG. 1 is an explanatory diagram showing the structure of the coating film of the conductive paint, and FIG. 2 shows the metal powder and metal fiber content and conductivity (specific resistance) of the examples and comparative examples. This is a graph showing the relationship between (1) Synthetic resin binder (2) Conductive powder (3) Metal fiber Patent applicant Toppan Printing Co., Ltd. Representative Kazuo Suzuki Shuya Cb) →

Claims (2)

[Claims] (1) As the first step, 80%
Add metal powder with a particle size of μ or less, and uniformly loosen it from secondary particles to primary particles using a dispersion device with excellent shearing force and mixing power, such as a ball mill, attritor, or roll mill.
After dispersion, in the second step, metal fibers with a diameter of 100μ or less and a length of 111II+ or more are added and cross-dispersed using a dispersion device with low mechanical stress such as a kneader or desilver so as not to destroy the shape of the metal fibers. A method for producing a conductive coating material having a specific resistance value of 102 Ω or less and containing 10 to 35% by volume of metal powder and 2 to 15% by volume of metal fibers in the solid content. (2) Carbon black or graphite powder is added to the synthetic resin binder solution in the first step so that the solid content is 5 to 20% by volume.
The manufacturing method according to item 11.