JPS59147059A - Coating composition - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] When using various electronic devices, electromagnetic interference (EMI)
) and radio frequency interference (RFI). Many electronic devices, such as electronic memories, are extremely sensitive to EMI or RFI contamination, and these interfering effects can unprogram the memory, destroy the circuitry, and thus potentially ruin the device. . Historically, this has not been a problem at the industrial level. This is because the metal housing acts as a shield and sensitive electronic equipment has not been widely used. When Blesstic materials are used in place of metal in manufacturing housings for electronic devices, the resulting structure is one that allows electromagnetic waves to flow into the device substantially unhindered.

Federal Communications Commission
ati. one Commission) has established regulations limiting the amount of electromagnetic radiation emitted by electronic devices (FO(! Doclcet Nu 207'8
0). This regulation classifies combiner equipment into two broad categories: commercial (Class A) and domestic (Class B) equipment. Limits are set for electromagnetic waves of less than or equal to a specified radio field strength at a specified distance over a specified frequency range (7). However, these are very expensive.

Other industry standards for this type of product are ■DF.

German national standard 0 8 7 1/6.7 8, proposed sAE
AIR 1499, and U.S. Department of Health uDsL2o
It is 1-o 0 4.

A number of solvent-based coatings are used for this reason and these contain conductive additives such as nickel, copper and silver. MrPlastink-1 is used to refer to commonly used polymeric materials such as polyphenylene needles, polycargenates, polyacrylates, polysulfones, polystyrenes, flame-retardant polystyrenes, epoxy resins, etc. for electronic device housings.

The inventor glued onto a plastic substrate and made a sensitive electronic
We have found a method for producing a coating composition containing electrically conductive flakes that ultimately forms a coating capable of shielding 15 items from electromagnetic radiation.

Accordingly, a primary object of the present invention is to provide a coating composition that is capable of shielding electromagnetic waves and that adheres to a plastic substrate ICtP.

The detailed description of the invention provides a method of making a novel external electromagnetic wave attenuating composition. The method includes the steps of: (a) forming a curable film-forming coating composition; and then (b) dispersing an effective amount of a conductive additive into the curable film-forming composition under low shear conditions. and forming an electromagnetic shielding composition. It becomes more.

Although the properties of the hard material and the forming composition are not critical to the present invention, the conductive flakes can be sufficiently dispersed and the conductive flakes can be sufficiently dispersed. It is necessary to select a material that provides an adhesive bond. A system that dissolves in water is suitable. In this regard, it is preferred to add a suitable amount of a suitable wetting agent, preferably an anionic surfactant, to the composition as an additive.

Suitable curable film-forming coating compositions include aqueous dispersions of acrylic and urethane resins. These aqueous compositions contain surfactants to form the conductive film. It is best to thoroughly wet the acrylic resin in the curable film-forming composition, Example 1. Styrene-acrylic copolymer (
Neocryl A-621, Po1. yvjn7-L Chl'lmj. Ca
l O O. -4 <, Id and other commercially available acrylic resins, such as Rh Op'lle .Qg '1
4 or Stacryl 200 (St+-tn
ley Ohomjcals.

Co. (manufactured by). Urethane Jugetsuji 1r. 1: %
]! ;ncyclopedia of Polymer
Science and Technology, Vo
l. II, PP. 5 5 5 ~5 5 8
aqueous aliphatic urethanes that can be prepared according to the method described in . Briefly, these materials are produced by reacting diisocyanates with polyols and water. Suitable diisocyanates have the formula 0ON-R-
Neo, where R represents an organic group. appropriate R
The group is (CH2)n, where n is an integer from 1 to B. Specific examples of diisocyanates include hexamethylene diisocyanate, methylcyclohexene diisocyanate, lysine zoisozoanate, his(2-isocyanatoethyl) fumarate and bis(2-isocyanatoethyl) carbonate.

A suitable aliphatic urethane is NeorθzR-960 (Po1.
Chemica], Indu+u;rj ee
(commercially available from ).

When using an anionic surfactant, the present invention does not need to be limited to a specific anionic surfactant, and various substances such as sodium lauryl sulfonate, sodium alkyl sulfonate, and alkylaryl sulfonate may be used.
, 2.2-') naphthyl-methane-6, b'-> sulfonate, etc. can be used. Other anionic surfactants include “McOutcheon' θDeterge
Detergents and Emulsifiers (Detergents and Emulsifiers) Ji 979 edition.

To impart resistance to polar solvents such as methanol, additives can be added to the urethane-based composition, the additives being derivatives of ethyleneimine,
A trifunctional aziridine compound having the following formula: This is 0o
Product name: XAMA
- Available for 7K.

Conductive additives include nickel, copper, iron, silver, chromium, tin, aluminum, zinc or carbon materials, which are
When 0 to 60% by volume of the additive is dispersed in the curable film-forming coating composition, it has a physical form that maintains the formation of a conductive layer. A preferred additive is nickel in flake form. The term [Conductivity-1] shall mean a film surface resistivity of about 75 ohms/hole or less as measured by the test method described below. The preferred range of conductivity is 50~
0.005 ohm/mouth, and particularly preferably a conductivity of 0.1 to 0.07 ohm/mouth. Electrical conductivity can be correlated to the surface properties required to shield electromagnetic waves, and is a useful test for determining how well a composition is suitable for attenuating electromagnetic waves.

The compositions of the present invention preferably contain about 40 to 80 parts by weight of a 20 to 40 weight percent dispersion of the curable film-forming composition and about 20 to 60 parts by weight of a conductive additive. . If desired, a trifunctional aziridine compound can be added in an amount of 0.5 to 5 parts by weight, and if a surfactant is introduced, the composition may be an aqueous dispersion of 20 to 50% solids of surfactant.
It can contain 20 parts by weight.

The manner in which the compositions of the invention are manufactured and the physical form of the conductive additives are of great importance for the manufacture of coatings capable of adequately attenuating electromagnetic waves. The use of high shear mixing equipment should be avoided when dispersing the conductive additive into the curable film-forming composition. The use of high shear mixing equipment tends to break up the conductive additive and reduce its particle size, thus reducing the degree of overlapping and tangential contact of the additive particles, resulting in loss of conductivity. The use of a low shear mixing process can avoid the destruction of conductive particles, and the appropriate type of low shear mixing process can be selected based on the shear dust that results in a coating with the appropriate degree of conductivity and electromagnetic attenuation. can.

Curing conditions for the compositions of the present invention depend on the nature of the curable film-forming composition. Suitable compositions, aqueous compositions, can be air dried under ambient conditions. If desired, heat, for example on the order of 72 to 150 degrees below, can be used to accelerate curing of the film-forming composition.

The term "ohm/mouth" is a unitless term in which two silver dimes (61 mθ) are placed on the test surface equal to the diameter of the silver coin.
．． Based on tests that measure the resistance between these silver coins placed a long distance apart. Measure the resistance using a S i,mp pt30 n meter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Example 1 Anionic surfactants derived from ammonium salts of polycarboxylic acids (Tamol, 165, Rohm
A styrene-acrylic copolymer having an acid value of 30 and 1,623 parts by weight of an aqueous dispersion with a solid content of 21% and an acid value of 30. -(Neocry) A-621, Po
lyvinylChem]Ca]Co, fl)
6o? A composition was prepared from TIGL Crab Aqueous Dispersion 2455. Add all of the styrene-acrylic copolymer dispersion and water and stir until experimental Hockmθ
yer stirrer with 5 inch holed blade 200
This was done by rotating with Orpm. The anio' surfactant was added slowly (1 minute) to avoid shocking the styrene-acrylic copolymer and separating it from the aqueous dispersion. Mixing continued for approximately 60 minutes thereafter. The composition is removed from the Hockmeyer stirrer and a surface motion is created using a Hockmeyer laboratory impeller, thereby reducing the
■ Placed under constant stirring. Next, nickel flakes (N+-n
C-11, US New Chassis-H7
manufactured by amθ, flake type deafness ratio 55:1, density ilo 1/
'Fly,. 'V uniform flake thickness 12 microns) 51.6
Add 1 part by weight and blend for 15-20 minutes with low shear stirring 1
-7 is used as a film-forming base. By preparing the composition in this way, it is possible to minimize the risk of breakage with the nickel flake form.
4b! ＋恍(-1) These were tested for adhesion, surface resistivity, and electric and magnetic wave attenuation. The results are shown in Table 1.

Example 2 Solid content of the same anionic surfactant as Example 1: 20% by weight
166 parts by weight of an aqueous dispersion of aliphatic polyurethane (Ne
oRez960, Po]yviny'l Chem
icalCorp) 38% by weight aqueous dispersion 8!1
A composition was prepared from 4 parts by weight of nickel and 83 parts by weight of the same nickel 7 lake 5 nickel as in Example 1. This composition was prepared using the same procedure as in Example 1. The cured films exhibited excellent adhesion on both foamed and unfoamed polycarbonate compositions and on foamed and unfoamed polyphenylene oxide-rubber modified high impact styrene compositions. The resistivity was less than 1 ohm/mouth.

Example 6 The composition of Example 2 was partially changed. In other words, 5-fold % triple t4'? Valid aziridine compound %I (XAMA-7゜0o
(manufactured by Ohemjcal Oompa, NY) to obtain a composition with excellent resistance to polar solvents such as methanol. A film obtained by curing this composition exhibited a resistivity of less than 1 ohm/mouth.

Example 4 This example compares the method of the present invention with a high shear mixing method. Composition 1 of Example 1 was mixed with artificial graphite (Ae Bury Graphite, New Chassis, USA) in various chambers.
(manufactured by Mjco 1θ) and mixed with '/r. The resistivity of the cured film was measured. The results are shown in Table 2.

Table 2 35) 1000 62 40 120 18 60 35 51
1 g 1 : Using Cowles at about 200 Orpm 2 : Procedure of Example 1 This data demonstrates that the mixing process of the present invention has a healthy effect on the resistivity of the cured film.

Obviously, other modifications and variations of the present invention are possible in accordance with the above teachings. It is therefore to be understood that various modifications may be made to the specific embodiments of the invention described above and are encompassed within the scope of the invention.

Claims (1)

Claims: 1. (a) forming a curable film-forming coating composition in a curable film-forming coating composition, and then (b) incorporating an effective amount of a conductive additive into said film-forming composition under low shear conditions. A method for producing an electromagnetic wave attenuating composition comprising the step of dispersing to form an electromagnetic wave shielding composition. 2. The method according to claim 1, wherein the curable film-forming composition is an aqueous dispersion of the film-forming composition. 3. The method according to claim 2, wherein the conductive additive is flaky nickel. 4. The method according to claim 5, wherein the curable film-forming composition is an acrylic resin. 5. The method according to claim 3, wherein the curable film-forming composition is an aliphatic urethane resin. 0. The method according to claim 4 or 5, wherein the curable film forming agent comprises an anionic surfactant. 7. Aqueous compositions for use in forming electromagnetic barriers on plastic surfaces, characterized in that conductive additives are dispersed in a curable film-forming coating composition under low shear conditions. 8. The composition according to claim 7, wherein the coating composition contains an acrylic resin and flaky nickel. ? 8. The composition of claim 7, wherein the coating composition contains an aliphatic urethane resin and flaky nickel. 10. The composition according to claim 8, wherein the composition contains an anionic surfactant. 11. The composition according to claim 9, wherein the composition contains an anionic surfactant. 12. A cured composition of an aqueous composition used to form an electromagnetic wave barrier on a plastic surface, characterized in that a conductive additive is dispersed in a curable film-forming coating composition under low shear conditions. Coated plastic-substrate.