JPS62199663A - Electrically conductive coating material composition - Google Patents

Abstract

PURPOSE:The titled composition, obtained by blending a dispersion of carbon black, etc., in an organic solvent with a solution of a high polymer material in an organic solvent and deaerating the resultant blend in a vacuum and having a small change in volume resistivity, variation range thereof and small change in resistance with increasing temperature and improved adhesive property to substrates. CONSTITUTION:A composition, obtained by blending (A) a dispersion of carbon black, e.g. electrically conductive acetylene black, etc., and/or graphite having 100-5,000cP viscosity in an organic solvent, preferably in 5-15wt% concentra tion with (B) a solution of a high polymer material, e.g. fluororubber, etc., having 1,000-5,000cP viscosity in an organic solvent, preferably in 10-30wt% concentration and deaerating the resultant blend in a vacuum and having high adhesive property to substrates, e.g. cloth, etc., and high mechanical strength of electrically conductive rubber when formed into heating elements.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to conductive coating compositions.

(Prior art) Conductive paint, which is made by uniformly dispersing conductive carbon black or carbon black and graphite in a solvent together with a solvent-based polymer material, has excellent electrical properties and is therefore used as a material for various electrical parts. ! It is widely used in various fields as a building material.

Usually, this conductive paint is prepared by uniformly kneading carbon black or graphite powder and a polymeric material with an organic solvent. However, it is quite difficult to uniformly and stably disperse carbon black or graphite in the polymer solution that is the paint base because each component has different specific gravity, particle size, and fluidity. is difficult to obtain with good reproducibility. In addition, if the dispersion is non-uniform, there is also the problem that even if a large amount of carbon black or the like is mixed in, the volume resistivity cannot be reduced accordingly.

Conventionally, the method of uniformly dispersing carbon black or carbon black and graphite in a polymer solution is to mix a conductive material and a polymer material sufficiently in advance using two rolls, a mixer, etc., and mix it with an organic solvent to create a paint. Alternatively, a method of kneading a conductive material and a polymeric material with an organic solvent in a ball mill or the like to form a paint is used.

However, in the former method, the particle size of the carbon black and the polymeric material are significantly different, so a homogeneous coating film cannot be obtained, the volume resistivity is high, and the reproducibility is poor. In order to solve these problems, if the conductive carbon is strongly mixed by mechanical means, the stractures of the conductive carbon will be cut, and although uniform dispersion can be achieved, the volume resistivity will not be reduced.

On the other hand, in the latter method, the viscosity increases during kneading, making it difficult to obtain a uniform mixture. Therefore, the viscosity is lowered by lowering the concentration of the solution or by reducing the amount of conductive material mixed in, so paints with high volume resistivity are used. I can only get it.

The present inventors have conducted extensive research in order to obtain a solvent-based conductive paint in which a large amount of carbon black or a conductive material (hereinafter referred to as conductive material) consisting of carbon black and graphite is uniformly dispersed in a polymeric material. As a result of repeated efforts, he discovered that the goal could be achieved by mixing a dispersion liquid in which a conductive material was uniformly dispersed in an organic solvent using a ball mill, etc., and a polymeric material dissolved in an organic solvent. No. 58-132058). however,
This electrically conductive paint has the disadvantage that its volume resistivity value is still large and its fluctuation range is large, and furthermore, the resistance change due to external temperature is also large.

(Problems to be Solved by the Invention) The purpose of the present invention is to solve the above-mentioned conventional drawbacks and to provide improved electrical conductivity that has a small volume resistivity value, a small variation range thereof, and a small change in resistance due to temperature rise. An object of the present invention is to provide a coating composition.

(Means for Solving the Problems) The present invention provides the following methods: after mixing (a) an organic solvent dispersion of carbon black and V/or graphite; and (b) an organic solvent solution of a polymeric material soluble in the organic solvent. , relates to a conductive coating composition obtained by vacuum degassing treatment.

Conductive carbon black has a large specific surface area and high oil absorption, so when kneaded with a polymer solution, the viscosity increases and it is impossible to obtain a uniform dispersion. However, according to the present invention, conductive carbon black Low viscosity (typically IOO~5000c) is achieved by kneading in an organic solvent at a concentration of 5~15%
A homogeneous dispersion of low viscosity (typically too~5 cp) is obtained, preferably about 100 to 2000 cp.
00Qcp1 (preferably about 1,000 to 3,000 cp) is easily stirred and mixed with a polymer solution, and a conductive paint in which the conductive material is uniformly dispersed can be obtained. When stirring is continued, the viscosity gradually increases, and the viscosity is higher than that of either dispersion (a) or solution (b) (usually 5,000 to 100,000 cp, preferably about 6,000 cp).
~20,000cp) A coating composition is produced.

According to the present invention, by mixing the conductive material in a very high proportion, it is possible to easily obtain a uniform mixture by adding, for example, 10 to 200 parts by weight of the conductive material to 100 parts by weight of the polymeric material. can.

Carbon black, which is a conductive material, has a DBP oil absorption of 100-400ml/100g and an average particle size of 10-70μ.
The product of the product is preferably used.

As the graphite, crystalline natural or artificial graphite having a particle size of several microns to several hundred microns is used. The conductive material is
It is preferably added in an amount of 10 to 60% by weight based on the total weight of the composition.

Preferred examples of the polymeric material include fluororubber, urethane rubber, and vinylidene fluoride/tetrafluoroethylene copolymer, with fluororubber being particularly preferred.

The fluororubber used in the present invention is a highly fluorinated elastic copolymer, and the most preferred fluororubber is usually 40 to 85 mol% of vinylidene fluoride and at least one species copolymerizable therewith. and other fluorine-containing ethylenically unsaturated monomers.

Also, as fluororubber, polymers often contain iodine, for example, 0.001 to 10% by weight at the end of the polymer chain.
, preferably 0.01 to 5 wt. Fluororubber whose main composition is an elastic copolymer consisting of
can also be used effectively. Examples of other fluorine-containing ethylenically unsaturated monomers that can be copolymerized with vinylidene fluoride to produce elastic copolymers include hexafluoropropylene, penta7fluoropropylene, tri7fluoroethylene, tripleochloroethylene, and Trouble fluoroethylene, vinyl fluoride, perfluoro(
methyl vinyl ether), perfluoro (ethyl vinyl ether), perfluoro (propyl vinyl ether)
etc. are exemplified as representative examples. Particularly preferred fluororubbers are vinylidene fluoride/hexafluorobrobylene dielastic copolymers and vinylidene fluoride/tetrofluoroethylene/hexafluoropropylene ternary elastomeric copolymers.

Examples of organic solvents include methanol, ethanol, propane/
Alcohols such as alcohol, ethylene gelcol, calpitol, and cellosolve, and ketones such as methyl ethyl ketone and methyl isobutyl ketone are used. In addition to these, other solvents such as isophorone, toluene,
Xylene or the like can be used.

In addition to the above-mentioned components, the composition of the present invention may optionally contain a surfactant, a vulcanization Q1 acid acceptor, a filler, and the like.

A surfactant is mainly used when kneading a conductive material in a solvent, and promotes uniform dispersion. Similar effects can also be obtained by using fatty acid esters.

Any surfactant M can be used as the surfactant. Specific examples of surfactants include nonionic surfactants such as sorbitan 7-year-old ate and alkyl alkylolamide, anionic surfactants such as lauryl alcohol sulfate sodium salt, and cationic surfactants such as Examples include ethylenedodecylamine.

The surfactant is used in an amount of 1 to 30 parts by weight, preferably 4 to 15 parts by weight, based on 100 parts by weight of the conductive material.

As the vulcanizing agent, an aminosilane compound or an amino compound or a mixture thereof is used.

Examples of aminosilane compounds include γ-7mi-7brobyltriethoxysilane (hereinafter referred to as A-1100), N-β
-ami7ethyl-γ-ami/propyltrimethoxysilane, N-(trimethoxysilylpropyl)ethylenediamine, N-β-7minoethyl-γ-ami/propylmethyldimethoxysilane, γ-ureidopropyltriethoxysilane, no-β- Examples include 7minoethyl-γ-7minoprobyltrimethoxysilane.

As the amino compound, an amine compound having at least one terminal amide group directly connected to an aliphatic hydrocarbon group is preferable, and representative examples thereof include ethylamine, propylamine, butylamine, pencylamine, allylamine, n- Monoamines such as 7-milamine and ethanolamine, ethylenediamine, trimethylenediamine, tetramethylenediamine, hexamethylenediamine, hexamethylenediamine carbamate, N, N'-
Dicinnamylidene-1,6-hexanezamine, 4.4
'-bis(aminocyclohexyl)methanecarbame 1
．． 3.9-bis(3-aminopropyl)-2,4,8,
10-tetraoxaspiro(5,5) lunch.

Examples include diamines such as V-11 (hereinafter referred to as V-11), polyamines such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine, among which amine compounds having two or more terminal amino groups are used. More preferred.

The amount of the aminosilane compound and/or amine compound added is usually 1 to 30 parts by weight, preferably 1 to 20 parts by weight per 100 parts by weight of fluororubber.

As the acid acceptor, those commonly used in the vulcanization of fluororubber can be similarly used, such as one or more divalent metal oxides or hydroxides. In the military, 〒
Examples include oxides or hydroxides of nesium, calcium, zinc, lead, and the like. *As the filler, silica, clay, diatomaceous earth, talc, etc. are used.

The composition of the present invention can be obtained by stirring and mixing the above-mentioned components by known means and then subjecting the mixture to vacuum deaeration treatment. The vacuum degassing treatment is preferably performed while cooling and stirring. The degree of deaeration treatment is appropriately determined in consideration of the vapor pressure of the organic solvent, but is usually about 500 mm Hg or less, preferably in the range of about 100 to 400 mm Hg.

The thus obtained coating composition of the present invention is applied to or impregnated onto a substrate by a conventional coating method (painting, dipping, spraying, etc.) at room temperature to 400°C, preferably 10°C.
By drying and curing at a temperature of 0 to 400°C, the desired conductive coating film can be obtained.

(Effects of the Invention) The characteristic values of the conductive rubber obtained from the composition of the present invention are improved as described below.

(a) Volume resistivity value (ρV value) decreases.

(b) The fluctuation range of the ρV value is reduced.

(c) The rate of change in resistance during heating is small.

Furthermore, when the paint is applied to a base material such as thread or cloth to form a heating element, there are the following advantages.

(d) Adhesion between the paint and the base material is improved.

(e) The mechanical strength of the conductive rubber is improved.

(Example) Next, examples and comparative examples will be given and explained.

Example 1 17 g of carbon black (trade name, Ketjen Black EC) and graphite (trade name DCB) as conductive materials
Using 68 g, 498 g of methyl ethyl ketone and 5 g of a surfactant (trade name: UNISTAR M476) were added thereto, and mixed in a ball mill for 16 hours to prepare a dispersion having a viscosity of 2000 cp.

Separately, vinylidene fluoride/hexafluoropropylene/tetrafluoroethylene copolymer comb (Dai-El G501ANJ, manufactured by Daikin Industries, Ltd.) 85 was dissolved in 255 g of methyl ethyl ketone to prepare a solution with a viscosity of 5000 cp.

The obtained dispersion and solution were stirred and mixed at high speed using a stirrer equipped with a flat blade turbine. The resulting paint (viscosity 30
000 cp) was transferred to a stainless steel beaker, placed in a transparent desiccator, and the internal pressure was reduced to 10 mmHg using a vacuum pump. The air bubbles contained within the paint generated large bubbles on the paint surface, and the bubbles disappeared after about 30 minutes. At this point, the vacuum degassing treatment was stopped to obtain the intended coating composition.

The resulting paint was applied to a polyester film with a wet film thickness of 10 mils (257μ111) using a doctor blade, air-dried indoors for 16 hours, and then dried in a constant temperature bath at 160°C for 30 minutes to obtain a conductive film. .

When the volume resistivity value of this film was measured 10 times, the average value was 0.0166Ω·cIIl.

Comparative Example 1 A conductive coating composition was obtained in the same manner as in Example 1 except that the vacuum degassing treatment was omitted.

A conductive film was obtained using the obtained paint in the same manner as in Example 1, and its volume resistivity was measured 10 times, and the average value was 0,0205 Ω·cm.

(that's all)

Claims (9)

[Claims] (1) A conductive material obtained by vacuum degassing after mixing (a) an organic solvent dispersion of carbon black and/or graphite, and (b) an organic solvent solution of a polymeric material soluble in the organic solvent. paint composition. (2) The composition according to claim 1, wherein the concentration of carbon black and/or graphite in the dispersion (a) is 5 to 15% by weight, and the viscosity of the dispersion is 100 to 5000 cp. (3) The composition according to claim 1, wherein the carbon black is an electrically conductive acetylene black, furnace black, channel black or thermal black. (4) The polymer material concentration of solution (b) is 10 to 30% by weight
The composition according to claim 1, wherein the solution has a viscosity of 1000 to 5000 cp. (5) The composition according to claim 1, wherein the polymeric material is fluorine rubber, urethane rubber, or vinylidene fluoride/tetrafluoroethylene copolymer. (6) The composition according to claim 1, wherein the viscosity of the composition before vacuum degassing treatment is higher than 5000 cp and lower than 100000 cp. (7) The composition according to claim 1, which contains 10 to 150 parts by weight of carbon black and/or graphite per 100 parts by weight of the polymeric material. (8) The composition according to claim 1, wherein the film obtained from the composition before vacuum degassing has a volume resistivity of 0.01 to 1.0 Ω·cm. (9) The composition according to claim 1, wherein the solid content in the composition is 10 to 40% by weight.