JP2929360B2 - Fluororubber-based screen coating liquid - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluorine rubber-based screen coating liquid suitable for thick film coating for forming a metal gasket, which prevents drying of a screen and enables continuous operation.

[0002]

2. Description of the Related Art Heretofore, as a coating solution for screen printing containing a fluororubber in a solution state, one using methyl ethyl ketone or methyl isobutyl ketone as a solvent for dissolving the fluororubber has been known. Such a coating liquid is used for forming a metal gasket such as a cylinder head gasket by providing a fluororubber coating layer on one or both surfaces of a metal core material such as a single plate or a laminated plate.

[0003] However, the ketone-based solvent is excellent in solubility of fluororubber, but has a high vapor pressure at room temperature or the like and is liable to volatilize, and the coating liquid using the same is dried during coating by a screen printing method. This causes the screen to be clogged, making continuous operation impossible.

[0004] In view of the above, when the volatility is reduced by using a high boiling point solvent, there is a problem that the solubility of the fluororubber becomes weak and the viscosity of the obtained coating liquid becomes high.
Coating liquids with high viscosity have the problem of clogging of the screen due to slight volatilization, in addition to the problem of poor coatability.Thick film coating must be performed due to a decrease in concentration if the amount of solvent is increased to prevent clogging. There are problems that make it difficult.

[0005]

SUMMARY OF THE INVENTION According to the present invention, even when a high-concentration solution is used in order to achieve thick film coating, it is possible to make continuous operation possible by hardly clogging the screen during the coating operation by the screen printing method. Development of fluororubber-based screen coating liquids

[0006]

SUMMARY OF THE INVENTION The present invention is a coating solution for screen printing containing a fluororubber in a solution state, wherein the solvent dissolving the fluororubber has a boiling point of not less than isoamyl acetate and not more than isobornyl acetate. The present invention provides a fluororubber-based screen coating solution comprising an ester having a content of 60 to 100% by weight.

[0007]

Illustrative Embodiment The fluororubber-based screen coating solution can also be prepared as a fluororubber solution containing various additives. The additives include fillers, acid acceptors, processing aids, anti-aging agents, pigments, coloring agents, coupling agents, anti-scorch agents, various rubbers other than fluororubber, water-absorbing and oil-absorbing resins. Are used.

[0008]

By using the above-mentioned ester solvent for dissolving the fluororubber, it is possible to obtain a fluororubber solution having a lower viscosity than a ketone solvent having an approximate boiling point, and to prepare a high-concentration solution for the purpose of thick film coating. In addition, it is possible to obtain a fluororubber-based screen coating liquid which is hardly dried, does not clog the screen during the coating operation by the screen printing method, and enables continuous operation. In addition, a thick film coat can be efficiently formed using the above-mentioned high concentration solution, and a metal gasket or the like having excellent sealing performance can be easily mass-produced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The fluororubber-based screen coating solution of the present invention is a coating solution for screen printing containing a fluororubber in a solution state. The solvent for dissolving the fluororubber is isoamyl acetate or more and isobornyl acetate or less. Of an ester having a boiling point of 60 to 100% by weight.

As the solvent comprising the ester, ie, an ester solvent, various solvents having a boiling point of not less than isoamyl acetate and not more than isobornyl acetate can be used. Specific examples thereof include isoamyl acetate, n-amyl acetate, cyclohexyl acetate, isoamyl propionate, isoamyl butyrate, butyl butyrate, isobornyl acetate, and the like.

For dissolving the fluororubber, one or more ester solvents can be used. If necessary, a solvent other than the ester-based solvent, for example, a ketone-based solvent such as methyl ethyl ketone or methyl isobutyl ketone can be used in combination.

When a solvent other than an ester solvent is used in combination, a solvent composition containing at least 60% by weight of the ester solvent is used. If the content of the ester-based solvent is less than 60% by weight, it may be difficult to prepare a high-concentration solution that is difficult to dry due to a reduction in the viscosity of the fluororubber solution. Easy to become liquid. The content of the ester solvent is preferably 65% by weight or more, more preferably 70% by weight or more, and particularly preferably 75% by weight or more from the viewpoint of lowering the viscosity of the fluororubber solution.

The screen coating solution of the present invention contains a fluororubber in a solution state. The type of the fluororubber is not particularly limited, and an appropriate fluororubber is used according to the purpose of use of the coating solution. be able to. Further, the screen coating liquid may have a composition in which an appropriate additive is blended depending on the purpose of use.

Incidentally, any fluororubber can be used when preparing a coating solution for forming a metal gasket. Especially, Mooney viscosity is ML _{1 + 10} , 121
A fluororubber having a temperature of 30 ° C. or less is preferably used. The fluororubber is used in a composition that can be vulcanized by using a vulcanizing agent, a vulcanizing aid, and a vulcanization accelerator in combination, if necessary.

Additives that may be added to the coating solution for forming a metal gasket include, for example, carbon, talc, clay, barium sulfate, silica, mica,
Fillers such as vermiculite, alumina and calcium carbonate, acid acceptors such as calcium hydroxide, processing aids, antioxidants, pigments, coloring agents, coupling agents, scorch inhibitors and the like. The amount of such an additive is a usual amount.

Additives which may be blended with (hydrogenated) acrylonitrile / butadiene rubber, acrylic rubber, epichlorohydrin rubber, natural rubber, styrene / butadiene rubber, silicone rubber, and other various rubbers other than fluorine rubber. Is given as an example. The amount of the additive is equal to or less than that of the fluororubber.

Further, a water-absorbing or oil-absorbing resin is also an example of an additive that may be blended in the coating solution.
Such a resin is blended in an amount of 10 to 100 parts by weight per 100 parts by weight of a fluororubber for the purpose of swelling by water absorption or oil absorption and improving the sealing performance against water, oil and the like by volume expansion.

The water-absorbing resin is insoluble in water,
Various materials that absorb water and swell can be used. Examples include carboxyl, sulfone, phosphate,
Contains an ionizable group such as a quaternary ammonium base, an amino group, an imino group, a pyridium base or a salt thereof, and / or a nonionic hydrophilic group such as a hydroxyl group, an ether group, a linear or cyclic amide group, or a nitrile group. And natural or synthetic hydrophilic and water-insoluble polymer substances.

Specific examples of the high molecular substance include acrylic acid or a salt thereof, a copolymer thereof with divinylbenzene, an alkali hydrolyzate of a copolymer of acrylonitrile, vinyl chloride and an ethylene monomer, and acrylonitrile and chloride. Alkaline hydrolyzate of copolymer of vinylidene and ethylene monomer, crosslinked formaldehyde of acrylamide copolymer, acid condensate of polyacrylic acid and polyvinyl alcohol, crosslinked epichlorohydrin of polyvinyl alcohol, acrylonitrile polymer Examples include a crosslinked formaldehyde of an alkali hydrolyzate and a phosphoric acid condensate of polyvinyl alcohol.

Further, a copolymer of 2-hydroxyethyl methacrylate and ethylene glycol dimethacrylate, a copolymer of 2-methyl-5-vinylpyridine and N, N'-methylenebisacrylamide, N, N'-dimethyl Copolymers of aminoethyl methacrylate and N, N'-methylenebisacrylamide, copolymers of N-vinyl-2-pyrrolidone and ethylene glycol dimethacrylate, radiation crosslinked polyoxyethylene, starch under acidity Heated condensates, saponified starch / acrylonitrile graft copolymers, saponified copolymers of vinyl esters and ester-based unsaturated carboxylic acids or their derivatives (dried products), isobutylene / maleic acid copolymers, etc. Can be

As the oil-absorbing resin, a resin that absorbs oil and swells is used. Examples thereof include a polynorbornene rubber-based oil-absorbing resin and a self-swelling acrylic polymer. Commercially available products include, for example, Oleosorb (trade name, manufactured by Nippon Shokubai Chemical Industry Co., Ltd.). Above all, granular water slurry type (Oreosorb SL
-200), especially emulsion type (oleosorb)
EM-631) and the like are preferably used.

The preparation of the screen coating solution can be performed, for example, by a method of mixing the respective components or a mixture thereof via a solvent. The solid content concentration in the screen coating solution is arbitrary, but may be 1 when a thick film is applied as in the case of forming a metal gasket.
5 to 70% by weight, preferably 20 to 60% by weight, especially 25 to 5%
It can be a high concentration solution of 0% by weight.

The metal gasket is formed by, for example, coating a coating liquid on one or both sides of a metal core material by a screen printing method and drying or vulcanizing the coating layer under heating. be able to. The thickness of the coating layer to be formed may be appropriately determined according to the purpose of use, but is usually 500 μm or less, particularly 5 to 200 μm, from the viewpoint of reducing the thickness of the gasket.
In particular, it is 10 to 100 μm.

Examples of the metal core include steel, iron, and the like.
Flatness with a thickness of 50 μm to 1 mm made of iron-based metal such as galvanized iron and tin-plated iron, copper-based metal such as copper and brass, aluminum-based metal such as aluminum and its alloys, and other high-strength metals such as stainless steel A simple veneer, a laminated plate, a material partially folded by press working, a bead working, and the like are generally used. At the time of coating, a suitable adhesive such as an acrylonitrile rubber / phenol resin solution or a silane coupling agent may be applied to the metal core material in advance to improve the adhesion.

Example 1 Fluorine rubber (Mooney viscosity: 30 (ML _{1 + 10} , 121
C), containing a vulcanizing agent) 100 parts (parts by weight, solid content, the same applies hereinafter), magnesium oxide (vulcanizing aid) 3 parts, calcium hydroxide 6 parts, MT carbon 10 parts, and a water absorbing resin (aqualic) 20 parts of CAML-20 (manufactured by Nippon Shokubai Chemical Industry Co., Ltd., same hereafter) were mixed with isoamyl acetate to prepare a coating solution composed of a mixed solution having a solid content concentration of 25% by weight, and the coating solution was formed into a 200 μm thick stainless steel core material. Coated by screen printing, dried and vulcanized to a thickness of 20μ
A metal gasket having m coating layers on both sides was obtained.

Example 2 A metal gasket was obtained in the same manner as in Example 1 except that isobornyl acetate was used instead of isoamyl acetate.

Comparative Example 1 A metal gasket was obtained in the same manner as in Example 1 except that methyl ethyl ketone was used instead of isoamyl acetate.

Comparative Example 2 50 parts of isoamyl acetate and 50 parts of methyl ethyl ketone
A metal gasket was obtained in the same manner as in Example 1 except that the mixed solvent in parts was used.

Comparative Example 3 A metal gasket was obtained in the same manner as in Example 1 except that methyl isobutyl ketone was used instead of isoamyl acetate.

Evaluation Test Continuous Workability When metal gaskets were continuously produced in Examples and Comparative Examples, the coating area until the screen was clogged by drying of the coating liquid and the formation of the metal gaskets became difficult was examined. .

Viscosity The viscosities of the coating solutions obtained in Examples and Comparative Examples were examined.

The results are shown in Table 1.

[Table 1]

[0033]

According to the present invention, it is possible to prepare a low-viscosity fluororubber solution even in the case of a high-concentration solution, and it is difficult to dry the solution. It is possible to obtain a fluororubber-based screen coating solution that enables operation. In addition, a thick film coat can be efficiently formed using the above-mentioned high concentration solution, and a metal gasket or the like having excellent sealing performance can be easily mass-produced.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-48-15931 (JP, A) JP-A-6-271807 (JP, A) JP-A-58-59275 (JP, A) (58) Investigation Field (Int.Cl. ⁶ , DB name) C09D 127/12 B05D 7/24 301 B05D 7/24 302

Claims (3)

(57) [Claims] 1. A coating solution for screen printing containing a fluororubber in a solution state, wherein the solvent dissolving the fluororubber is an ester having a boiling point of not less than isoamyl acetate and not more than isobornyl acetate.
A fluororubber-based screen coating solution comprising 100% by weight. 2. The fluororubber screen according to claim 1, wherein the ester solvent is isoamyl acetate, n-amyl acetate, cyclohexyl acetate, isoamyl propionate, isoamyl butyrate, butyl butyrate or isobornyl acetate. Coating liquid. 3. The fluororubber-based screen coating liquid according to claim 1, which is a high-concentration liquid for coating a thick film for forming a metal gasket.