JP2017170399A - Heat-proof coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a heat-proof coating method in which anticorrosion property is excellent and cracking or the like does not occur after high temperature heating.SOLUTION: A heat-proof coating method including: a process (1) in which an inorganic zinc-rich paint containing a hydrolysis condensate of alkyl silicate and zinc powders is coated on a base material surface, and an inorganic zinc-rich coating film is formed under the condition of drying at room temperature; and a process (2) in which a heat-resistant paint containing a polysiloxane resin, an aluminum flake and an inorganic needle-like pigment having an aspect ratio of 3.5 or more is coated on the inorganic zinc-rich coating film obtained in the process (1), and a heat-resistant coating film is formed under the condition of drying at room temperature. A content of the inorganic needle-like pigment in the heat-resistant paint falls within 20 to 150 parts by mass based on polysiloxane resin of 100 parts by mass.SELECTED DRAWING: None

Description

  The present invention relates to a heat-resistant coating method using a heat-resistant paint applicable to a large steel structure such as an oil plant.

  For painting large steel structures and pipes such as oil and gas plants, the substrate may reach a high temperature range, so the curing conditions after painting are room temperature drying conditions, and heating is not required. The cured coating film is coated with a so-called heat resistant paint that requires heat resistance of 200 ° C. or higher.

  In general, since a coating film using an organic resin such as an acrylic resin or an epoxy resin as a binder component does not have sufficient heat resistance at high temperatures, heat resistant coatings using a polysiloxane resin as a binder component have been proposed. However, polysiloxane resins have poor drying properties at normal temperatures, and cracks and peeling may occur in the coating performance after high-temperature heating.

  Regarding such problems, for example, Patent Document 1 discloses a heat-resistant polysiloxane coating composition containing alkoxysilane, colloidal silica, and a layered pigment. According to such a heat-resistant coating composition, a coating film having excellent adhesion and hardness can be obtained in a wide temperature range, and a coating film free from cracks and peeling can be obtained up to a temperature of around 500 ° C.

  Patent Document 2 describes a heat-resistant coating containing polysiloxane, alkyl titanate, talc, and aluminum pieces. In a severe corrosive environment, after applying an inorganic zinc rich paint as an anticorrosion base, the heat-resistant coating is described. There has been proposed a painting method for painting a conductive coating.

  Such a heat-resistant coating has a low viscosity suitable for painting, and a cured coating film obtained by this coating can form a coating film excellent in corrosiveness in a wide temperature range of −30 ° C. to 400 ° C. However, when a heat-resistant coating is applied on the inorganic zinc rich paint, a large crack may occur in the coating film due to the upper heat-resistant coating.

  In particular, if the heat-resistant coating is thick or the curing condition is poor and the inorganic zinc rich paint is not sufficiently cured, the heat-resistant coating becomes remarkably cracked and needs to be improved.

JP-A-6-9928 JP-T 2009-522388

  An object of the present invention is to propose a heat-resistant coating method that is excellent in anticorrosion properties and does not generate cracks after high-temperature heating.

  As a result of intensive studies on the above-mentioned problems, the present inventors have included a specific amount of a specific inorganic acicular pigment as a top coating to be provided on an inorganic zinc rich coating with an inorganic zinc rich paint, so that the heat resistant coating has a high temperature. The present inventors have found that it is difficult to crack even after heating and on an inorganic zinc rich coating film, and have reached the present invention.

That is, the present invention
Step (1) of coating an inorganic zinc rich paint containing alkylsilicate hydrolyzed condensate and zinc powder on the surface of the substrate, and forming an inorganic zinc rich coating film under conditions of room temperature drying
On the inorganic zinc-rich coating film obtained in step (1), a heat-resistant paint containing polysiloxane resin, aluminum flakes and inorganic needle pigment having an aspect ratio of 3.5 or more is applied, and heat-resistant coating is performed under conditions of room temperature drying. Step (2) of forming a film
The heat-resistant coating method is characterized in that the content of the inorganic needle pigment in the heat-resistant coating is in the range of 20 to 150 parts by mass based on 100 parts by mass of the polysiloxane resin.

  Both the inorganic zinc-rich paint and the heat-resistant paint used in the heat-resistant coating method of the present invention have a good drying property and a very good curability at room temperature.

  In addition, the composite coating made of inorganic zinc-rich paint and heat-resistant paint obtained by this coating method is excellent in both anti-corrosion and heat-resistance, so it protects objects to be coated in harsh environments that are exposed to high temperatures. Suitable for doing. In addition, since the heat-resistant coating film used in the method of the present invention has an appropriate internal stress, it is resistant to cracking even when subjected to high-temperature heating after film formation or severe conditions such as on an inorganic zinc rich paint film. Is excellent.

  This invention consists of an inorganic zinc rich coating-film formation process (1) and a heat-resistant coating-film formation process (2).

  First, the inorganic zinc rich coating film forming step (1) will be described.

<Inorganic zinc rich coating film formation process (1)>
The inorganic zinc-rich paint for forming an inorganic zinc-rich coating film that can be an undercoat film by the method of the present invention is a paint containing an alkyl silicate hydrolysis condensate and a large amount of zinc powder.

  Examples of the alkyl silicate used as the raw material for producing the alkyl silicate hydrolysis condensate include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, tetrabutoxysilane, and tetraisobutoxysilane; Alkyltrialkoxysilanes such as methoxysilane, methyltriethoxysilane, methyltripropoxysilane, ethyltrimethoxysilane, and ethyltriethoxysilane; dialkyldisilanes such as dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, and diethyldiethoxysilane An alkoxysilane etc. are mentioned. In the alkyl silicate hydrolysis condensate, these alkyl silicates can be used alone or in combination of two or more.

  In the present invention, the theoretical hydrolysis rate of the hydrolyzed condensate of alkyl silicate is in the range of 55 to 105%, preferably 70 to 105%. Suitable from

  In this specification, the theoretical hydrolysis rate of the alkyl silicate hydrolysis condensate is a value indicating the ratio of addition of water to the alkyl silicate, and the case where water having twice the number of moles of the alkyl silicate compound is added. , The value converted as 100%. For example, the hydrolysis rate of ethyl silicate being 300% indicates that water having an amount 6 times the number of moles of ethyl silicate is added.

  The zinc powder contained in the inorganic zinc rich paint is not particularly limited, and for example, those composed of substantially spherical particles having an average particle diameter of 1 to 15 μm can be used.

  The average particle diameter of the zinc powder is an average particle diameter on a volume basis, and when the accumulation is determined with the total volume of zinc powder as 100% based on the particle size distribution in the dispersion of zinc powder, the cumulative volume is 50 % Means the particle size of the point. The average particle size can be measured with a particle size distribution measuring apparatus using a laser diffraction / scattering method.

  The amount of zinc powder contained in the inorganic zinc rich paint in the method of the present invention is 100 to 2000 parts by mass, preferably 300 to 1500 parts by mass, based on 100 parts by mass of the alkylsilicate hydrolysis condensate. Desirable from the viewpoint of sex.

  It is suitable that the inorganic zinc rich paint contains an extender pigment. This is because the composite coating film obtained by the method of the present invention is excellent in crack resistance.

  As the extender pigment, conventionally known pigments can be used without particular limitation, and specific examples thereof include silica powder, mica, barium sulfate, calcium carbonate, talc, kaolin, clay, and the like, either alone or Two or more types can be used in combination.

  As the extender pigment, mica is preferably used from the viewpoint of crack resistance of the inorganic zinc rich coating film and the composite coating film obtained by drying at room temperature.

  The extender pigment should contain 20 to 200 parts by weight, preferably 50 to 150 parts by weight, based on 100 parts by weight of the alkylsilicate hydrolyzed condensate. It is desirable in terms of cracking properties.

  If necessary, the inorganic zinc-rich paint further contains, as necessary, conventional paint additives such as resins other than alkyl silicates, curing catalysts, organic solvents, anti-settling agents, sagging inhibitors, and adhesion-imparting agents. be able to.

<Heat resistant paint>
In the method of the present invention, the heat-resistant paint that can be a top coat film of the composite paint film is a paint containing a polysiloxane resin, aluminum flakes, and inorganic needle pigments.

  Examples of the polysiloxane resin include a polysiloxane having a branched structure in which a siloxane bond (—Si—O—Si—) is a main chain and a side chain has a substituent such as an alkyl group, an aryl group, a hydroxyl group, or an alkoxy group. Can be mentioned.

  The polysiloxane resin preferably has at least one functional group of a hydroxyl group and an alkoxy group. It is preferable that at least one of the hydroxyl group or the alkoxy group is directly bonded to the silicon atom.

  In addition to the hydroxyl group or alkoxy group, the polysiloxane resin preferably has an alkyl group or a phenyl group directly bonded to a silicon atom.

  The molecular weight of the polysiloxane resin is not particularly limited. For example, the weight average molecular weight may be in the range of 200 to 100,000, preferably 1400 to 80,000.

  In this specification, the polysiloxane has a number average molecular weight of GPC (gel permeation chromatography) manufactured by Tosoh Corporation under the conditions of dissolving a sample in tetrahydrofuran, using tetrahydrofuran as a developing solvent and a flow rate of 0.6 ml / min, and a column temperature of 40 ° C. The measurement was made using “HLC-8220”. A calibration curve was prepared by standard polystyrene conversion.

  Typical commercially available products of such polysiloxane resins include “3037 INTERMEDIATE”, “3074 INTERMEDIATE”, “Z-6018”, “217 FLAKE”, “220 FLAKE”, “233 FLAKE”, “249 FLAKE”, “ "QP8-5314", "SR2402", "AY 42-163" (all manufactured by Toray Dow Corning Co., Ltd.); "TSR160", "TSR165", "TSR3168" (all manufactured by Momentive Performance Materials) "KR-211", "KR-216", "KR-213", "KR-9218" (all manufactured by Shin-Etsu Chemical Co., Ltd.); "SILRES SY 231", "SILRES SY 550", "SILRES KX" , “SILRES SY 30 "," SILRES SY 409 "," SILRES IC368 "," SILRES MSE100 "(all by Asahi Kasei Wacker Silicone Co., Ltd.) are exemplified, and these may be used alone or in combination.

  The heat-resistant paint used in the method of the present invention contains aluminum flakes. Such aluminum flakes are not particularly limited, and those commonly used for paints can be used, and the average particle diameter thereof is in the range of 5 to 33 μm, preferably 9 to 30 μm. It is suitable from the point of the anticorrosion property of the composite coating film formed by (1).

In this specification, the average particle diameter of aluminum flakes can be determined by calculating the volume average from the particle size distribution measured by the laser diffraction method.
The aluminum flake is a polysiloxane resin solid content from the viewpoints of heat resistance and corrosion resistance of the composite coating film formed by the method of the present invention, as well as interlayer adhesion between the zinc coating film and the heat-resistant coating film after high-temperature heating. It is suitable that the mass is in the range of 20 to 200 parts by mass, preferably 50 to 155 parts by mass based on 100 parts by mass.

  The heat-resistant paint contains an inorganic needle pigment. In the present specification, the inorganic needle pigment is not particularly limited in its material, production method and production area. Specific examples of the inorganic needle pigment include, for example, glass flakes, silicon carbide, silicon nitride, wollastonite, sepiolite, chrysotile, amosite, tremolite, zeolite, calcium metasilicate, zonolite, potassium titanate, rock wool, aluminum silicate, Examples include carbon fiber, glass fiber, aramid fiber, aluminum borate, acicular calcium carbonate, acicular basic magnesium sulfate, acicular zinc oxide, aragonite type light calcium carbonate, spindle type light calcium carbonate, satin white, etc. Can be used alone or in combination of two or more.

  Among these, wollastonite, glass flakes, and glass fibers are suitable from the viewpoint of crack resistance after high-temperature heating.

  In the method of the present invention, the inorganic needle pigment contained in the heat-resistant paint is characterized by using an aspect ratio of 3.5 or more, and the aspect ratio is preferably in the range of 4 to 20. .

  The aspect ratio is a value of the major axis diameter / minor axis diameter of the inorganic needle pigment, and the minor axis diameter and the major axis diameter referred to here are each 100 primary particles existing in a certain area by observation with an electron microscope. The short axis diameter and the long axis diameter were measured and averaged.

  If the aspect ratio of the inorganic needle pigment is less than 3.5, the crack resistance after high-temperature heating of the composite coating obtained by the method of the present invention becomes insufficient, which is not preferable.

  In the present invention, the amount of the inorganic acicular pigment contained in the heat-resistant paint is characterized by being in the range of 20 to 150 parts by mass based on 100 parts by mass of the polysiloxane resin, preferably 25. It is preferable that it exists in the range of -105 weight part.

  If the content of the inorganic needle pigment in the heat-resistant coating is less than 20 parts by mass, the crack resistance after high-temperature heating of the composite coating is insufficient, and if it exceeds 150 parts by mass, the corrosion resistance of the composite coating is insufficient, which is preferable. Absent.

  The heat-resistant paint may contain paint additives such as a curing catalyst, a color pigment, an extender pigment, a dehydrating agent, a thickener, a dispersant, and an organic solvent.

  Among the above, examples of the curing catalyst include organic tin compounds such as diacetyltin diacetate, dibutyltin dilaurate, dibutyltin diacetate, dioctyltin dilaurate, diacetyltin dioctoate, tin octylate, dibutyltin diacetate, and dibutyltin dioctoate; Organo aluminum compounds such as aluminum trimethoxide, aluminum tris (acetylacetonate), aluminum tri-n-butoxide, aluminum tris (acetoacetate ethyl), aluminum diisopropoxy (acetoacetate ethyl), aluminum acetylacetonate; titanium tetra (Monoethyl ethoxide), titanium tetra (monoethyl ethoxide), titanium tetra (monobutyl ethoxide), titanium tetrakis (acetyl) Acetonate), organic titanium compounds such as tetranormal butyl titanate; zirconium tetra (monomethyl ethoxide), zirconium tetra (monoethyl ethoxide), zirconium tetra (monobutyl ethoxide), zirconium normal propylate, zirconium normal butyrate, zirconium Organic zirconium compounds such as tetrakis (acetylacetonate); organic zinc compounds such as zinc naphthenate; organic cobalt compounds such as cobalt octylate and cobalt naphthenate; trimethylamine, triethylamine, 2- (dimethylamino) ethyl methacrylate, 1,4 -Diazabicyclo [2.2.2] octane, 1,8-diazabicyclo [5.4.0] -7-undecene, 1,5-diazabicyclo [4.3.0] -5-nonene Aliphatic amines such as 1-methylpiperidine and 1-methylpyrrolidine, amine catalysts such as pyridine, 4-dimethylaminopyridine, 4- (1-piperidyl) pyridine, N-methylimidazole and N, N-dimethylaniline; carboxylic acid Lead, tin, zinc, and iron complexes of trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, triphenyl borate, tri (4-chlorophenyl) borate, trihexafluoroisopropyl borate, etc. Examples thereof include boric acid compounds such as boric acid esters, and these can be used alone or in combination of two or more. Among these, organic titanate compounds are preferable from the viewpoints of room temperature drying property and coating film hardness of the heat-resistant coating film.

  The content of the curing catalyst is 0.5 to 20 parts by mass, preferably 1 to 10 parts by mass based on 100 parts by mass of the polysiloxane resin solid content. It is suitable from the viewpoint of room temperature drying property and coating film hardness.

  The heat-resistant paint used in the above-described method of the present invention can have an internal stress of a heat-resistant coating film after heating at 200 ° C. of 13 MPa or less, preferably 12 MPa or less.

  In the present specification, the internal stress of the heat-resistant coating film after heating at 200 ° C. can be determined as follows in accordance with the outline of paint physical property engineering (by Kozo Sato), page 128.

  The sample is applied to one side of a phosphor bronze plate of length x width x thickness (0.1 x 20 x 120) mm using air spray so that the dry film thickness is about 15 to 25 μm. After being placed on a knife edge arranged at an interval of about 1 cm, it was dried in a 23 ° C. and 51% relative humidity environment for 7 days and then heated in a 200 ° C. oven for 8 hours.

  Thereafter, the sample is allowed to cool naturally for 16 hours without opening the oven door, and a sample piece for measuring internal stress is prepared. Since the sample piece that has undergone the drying, heating, and cooling processes bends in an arc shape due to contraction of the coating film, the curvature radius p can be obtained by the following equation if the deflection δ at the center of the plate is read and measured with a microscope.

p = (L ² / 8δ) + (δ / 2) ≈L ² / 8δ

  L is the distance between the knife edges, and the internal stress P is calculated by substituting the p value obtained by the above equation into the following equation.

P (MPa) = E ₂ bh ₂ ³ / 12bh ₁ × F (m, n) / pH

Here, b: width of the coating film piece, h ₁ : thickness of the coating film, h ₂ : thickness of the phosphor bronze plate, E ₁ : Young's modulus of the coating film, E ₂ : Young's modulus of the phosphor bronze plate.

Note that m = E ₁ / E ₂ , n = h ₁ / h ₂ , H = h ₁ + h ₂ , and F (m, n) is expressed as follows.

F (m, n) = ((1-mn ² ) (1-m) + (mn (n + 2) +1) ³ + m (mn ² + 2n + 1) ³ ) / (1 + mn) ³

  The substrate surface to which the method of the present invention is applied is not particularly limited. For example, steel materials such as non-treated steel materials, blast-treated steel materials, acid-treated steel materials, galvanized steel materials, and stainless steel materials; aluminum (alloy) materials, copper ( Non-ferrous metal materials such as (alloy) materials; concrete; various structures made of plastics, etc., particularly oil and gas plants, power plants, ships and other places where heat resistance is required. These steel materials and non-ferrous metal materials may have weld lines.

  In the method of the present invention, when rust is generated in the coating site, a ground treatment such as blast treatment, power tool treatment, hand cleansing with a wire brush or the like can be appropriately performed. When there is a deteriorated old paint film, it is preferable to remove the old paint film by the same base treatment. In addition, when there is an old coating film that has not deteriorated, it is preferable to perform a roughening treatment instead of the base treatment.

  As a method for applying the inorganic zinc rich paint or the heat-resistant paint, a general coating method such as brush coating, roller coating, or spray coating can be used. The coating may be performed once or a plurality of times.

  In the method of the present invention, the dry film thickness of the inorganic zinc-rich coating film is 20 to 200 μm, preferably 25 to 120 μm, and the dry film thickness of the heat resistant coating film is in the range of 15 to 160 μm, preferably 20 to 150. Is preferable from the viewpoint of corrosion resistance of the composite coating film and crack resistance after high-temperature heating.

  In this specification, a dry film thickness can be calculated | required by calculating a coating amount solid content and dividing | segmenting by a coating area.

  After the application of the inorganic zinc rich paint, it is usually preferable to apply a heat resistant paint after drying and curing at room temperature for about 16 hours to 7 days.

  A top coating material may be further applied on the composite coating film thus obtained. The top coating is not particularly limited, and a coating known per se can be used. For example, alkyd resin, acrylic resin, chlorinated rubber, epoxy resin, silicon alkyd resin, urethane resin, Silicon acrylic resin-based or fluororesin-based paints can be used.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to only these examples. In the following examples, “part” and “%” mean “part by mass” and “% by mass”, respectively.

<Creation of test coating plate>
Examples 1-15 and Comparative Examples 1-4
As a base material, a steel sheet obtained by treating a black-skinned steel sheet (SS400) to a surface roughness Sa2.5 by sandblasting is prepared. And cured for 48 hours in an environment with a relative humidity of 51% at 23 ° C. to obtain inorganic zinc rich coating films (A-1) to (A-7). Next, on each inorganic zinc-rich coating film, a heat-resistant paint was applied by air spray so as to have the composition and film thickness shown in Table 3, and cured for 7 days in an environment of 23% relative humidity 51%. (B-1) to (B-13) were obtained, and a test coating plate of a composite coating film with an inorganic zinc rich paint-heat resistant paint was prepared.

(Note) Modified silicate resin 1: ethyl silicate hydrolysis condensate, hydrolysis rate 80%,
(Note) Modified silicate resin 2: ethyl silicate hydrolysis condensate, hydrolysis rate 100%,
(Note) Modified silicate resin 3: ethyl silicate hydrolysis condensate, hydrolysis rate 60%,
(Note) Zinc powder: average particle size, 6μm,
(Note) Silicone resin: Methylsilicone resin, weight average molecular weight, 2000,
(Note) Aluminum flakes: average particle size 15 μm,
(Note) Talc: aspect ratio 3,
(Note) Glass flakes: aspect ratio 5,
(Note) Glass fiber: aspect ratio of 10,
(*) Internal stress after heating at 200 ° C .: Measured according to the method described in the specification.

(*) Corrosion resistance Each test coating plate was scratched using a single blade specified in JIS 5600 5-4 until it reached the substrate, and a neutral salt spray test specified in ISO 9227 was conducted for 7 days. The general part was visually evaluated according to the following criteria.
A: Rust and blisters are not generated in the general part and cut part.
○: Rust and blisters are not generated in the general part, and rust and blisters are slightly generated in the cut part.
Δ: Slight bulge is generated in both the general part and the cut part.
X: Rust and blisters are remarkably generated in the general part and the cut part.
(*) Heat resistance Each test coated plate was scratched until it reached the substrate using a single blade specified in JIS 5600 5-4, then heated in an electric furnace at 400 ° C for 5 hours, cut part, end part The general part is visually evaluated according to the following criteria.
A: No occurrence of blistering or cracking in the general part, cut part and end part.
○: There is no blistering or cracking in the general part, but a slight swelling is generated at the cut part or end part.
Δ: Slight swelling or cracking occurs in the general part, cut part, and end part.
X: Swelling and cracking are remarkably generated in the general part, the cut part, and the end part, and peeling is also generated between the inorganic zinc and the heat-resistant coating film or in the inorganic zinc coating film.

Claims (7)

A step (1) of applying an inorganic zinc rich paint containing a hydrolyzed condensate of alkyl silicate and zinc powder on the surface of the substrate, and forming an inorganic zinc rich coating film under conditions of room temperature drying;
On the inorganic zinc-rich coating film obtained in step (1), a heat-resistant paint containing polysiloxane resin, aluminum flakes and inorganic needle pigment having an aspect ratio of 3.5 or more is applied, and heat-resistant coating is performed under conditions of room temperature drying. A step (2) of forming a film;
And the inorganic needle pigment content in the heat resistant paint is in the range of 20 to 150 parts by mass based on 100 parts by mass of the polysiloxane resin. The heat-resistant coating method according to claim 1, wherein the hydrolysis rate of the alkyl silicate hydrolysis condensate is 55% or more. The heat-resistant coating method according to claim 1 or 2, wherein the amount of zinc powder contained in the inorganic zinc-rich coating film is in the range of 100 to 2000 parts by mass based on 100 parts by mass of the alkylsilicate hydrolysis condensate. The heat-resistant coating method according to any one of claims 1 to 3, wherein the inorganic needle pigment is at least one selected from wollastonite, glass flakes, and glass fibers. The heat-resistant coating method according to any one of claims 1 to 4, wherein the heat-resistant paint further contains an organic titanate compound. The heat-resistant coating method according to any one of claims 1 to 5, wherein the internal stress of the heat-resistant coating film after heating at 200 ° C is 13 MPa or less. The dry coating film thickness of an inorganic zinc rich coating film is 20-200 micrometers, and the dry film thickness of a heat resistant coating film exists in the range of 15-160 micrometers, The heat-resistant coating method of any one of Claim 1 thru | or 6.