JP2007126905A - Kitchen sink superior in flaw resistance, staining resistance and hot water resistance - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a stainless steel kitchen sink for maintaining a beautiful surface over a long period by improving flaw resistance, staining resistance and hot water resistance. <P>SOLUTION: This kitchen sink is formed by arranging a clear coating film of an organic/inorganic composite type via a fluororesin coating film on a surface of a stainless steel plate drawn in a sink shape. In this case, the clear coating film includes resin powder having lubricity and inorganic powder of presenting a delustering appearance, and the fluororesin coating film is mainly composed of a thermoplastic acrylic resin, a polyvinylidene fluoride resin and an epoxy resin. Fluororesin powder, polyethylene-fluororesin composite powder, polyacrylonitrile resin powder and silicone resin powder exist as the resin powder. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a stainless steel kitchen sink that has been subjected to a surface treatment for improving rust resistance, contamination resistance, and hot water resistance.

  Stainless steel kitchen sinks take advantage of stainless steel's inherent toughness, elasticity, and other characteristics, and offer the advantage of not causing cracks even if you drop dishes such as teacups carelessly. However, the disadvantage is that the surface hardness is low and the surface is easily soiled with wrinkles. The stainless steel kitchen sink has one of the advantages of the beautiful appearance unique to stainless steel, but wrinkles and dirt can significantly deteriorate the appearance. For this reason, various methods have been proposed in the past in order to improve the scratch resistance and stain resistance.

For example, in order to make wrinkles inconspicuous, a plurality of irregularities are formed on the surface of a stainless steel plate by embossing (Patent Documents 1 and 2), and a rust preventive film having an inorganic oxide thickness of 100 nm or less is formed to prevent contamination. (Patent Document 3), improving film resistance and antifouling properties with a metal oxide film having a thickness of 0.1 to 50 μm (Patent Document 4), etc.
JP 2001-246433 A JP 2004-137796 A JP 2001-173056 A JP 2004-76071 A

  In a kitchen sink with embossed irregularities, the wrinkles that are cut off from the bottom of the pottery will not be noticeable, but the protrusions will still stick. When scrubbing the surface of a stainless steel plate with a scrubber during cleaning, a fine wrinkle is also attached to the recess where the scissors tip reaches. That is, wrinkles become inconspicuous due to the provision of irregularities, but improvement in wrinkle resistance cannot be expected.

  When the metal oxide film is formed with a thin film of 100 nm or less, the initial antifouling property is improved, but there is a problem in durability. The thickening of the metal oxide film makes it difficult to wrinkle, imparts hydrophilicity and improves antifouling resistance. However, it is practically only possible to obtain a film thickness of 5 μm or less. Moreover, since the metal oxide film is hard but brittle, it cannot maintain scratch resistance over a long period of time. In a kitchen sink that is frequently exposed to warm water, there is a concern about film peeling due to poor adhesion, and the initial function cannot be maintained by film peeling.

  The present invention has been devised to solve such problems. By providing an organic / inorganic composite clear coating film on the surface of a stainless steel plate via a fluororesin coating film, it is possible to prevent scratching and contamination. The objective is to provide a stainless steel kitchen sink with excellent heat resistance and water resistance.

  The kitchen sink of the present invention has a stainless steel plate drawn into a sink shape as a base material, and an organic / inorganic composite clear coating film containing a resin powder having lubricity and / or an inorganic powder exhibiting a matte appearance is coated with a fluororesin. It is provided on the surface of the substrate through a film. As the base material, a stainless steel BA material is usually used, but the surface can be finished by pickling, polishing, or the like.

The fluororesin coating and the clear coating may be formed either before or after the drawing process. However, considering the introduction of defects accompanying the processing, it is preferable to pre-process and paint the stainless steel plate processed into a sink shape.
The fluororesin coating film is formed from a coating material of thermoplastic acrylic resin: 20 to 50% by mass, polyvinylidene fluoride resin: 45 to 75% by mass, and epoxy resin: 5 to 35% by mass. An organic / inorganic composite clear coating is laminated on the fluororesin coating.
Prior to the formation of the fluororesin coating film, an oxide layer having an OH group may be provided on the surface of the stainless steel plate. The oxide layer is mainly composed of one or more selected from SiO ₂ , TiO ₂ , ZrO ₂ , and Al ₂ O ₃ , and is preferably formed with a film thickness of 0.01 to 1.0 μm.

  The organic / inorganic composite clear coating film is a coating film having a thickness of 1 to 30 μm in which resin powder having lubricity and / or inorganic powder exhibiting a matte appearance is fixed with a binder. The binder is an organoalkoxysilane partially hydrolyzed condensate containing alkoxysilane: 20 to 70% by mass, polymer or copolymer of unsaturated ethylenic monomer: 20 to 70% by mass, colloidal silica: 10 to 60% by mass. % Composition is adjusted.

  Lubricating resin powder includes fluororesin powder, polyethylene-fluororesin composite powder (powder in which fluororesin particles are bonded to the surface of polyethylene resin particles), polyacrylonitrile resin powder, and silicone resin powder. It is preferable to use 1 to 20% by mass of a resin powder having a particle size of 1 to 30 μm. Silica particles are generally used as the inorganic powder exhibiting a matte appearance, and when the visibility of dust, blisters, etc. is reduced by matting, a coating film exhibiting a calm appearance can be obtained.

  When coating a sink base material for imparting scratch resistance, it is common to form a hard inorganic film. However, even if the surface is hardened with an inorganic film, the scratch resistance is not necessarily improved. This is because the inorganic film is hard but fragile, and when the loaded abrasive paper is pressed against the surface of the film and moved in the in-plane direction, the film is locally destroyed and easily wrinkled with high visibility. Can also understand.

  Although it is conceivable to mix resin powder having lubricity as a measure to prevent wrinkles resulting from film breakage, the upper limit of the film thickness of the inorganic film needs to be about 10 μm in order to produce a clear feeling, which is necessary for the expression of lubricity. An amount of resin powder cannot be secured. Therefore, as a result of various investigations and examinations on the relationship between the clear coating film and the anti-scratch property, a clear coating film having a pencil hardness of 5H or more was obtained by using an organic / inorganic composite type, and the anti-scratch property was greatly improved I found it to improve.

  The organic / inorganic composite type clear coating film has a large amount of silica and contains some organic components of acrylic silicone. Therefore, flexibility is imparted by acrylic silicone while maintaining sufficient hardness as an inorganic coating film. Therefore, even if the abrasive paper pressed against the surface of the coating film is moved in the in-plane direction, the coating film which is a cause of wrinkles is hardly broken. In addition, the lubricating action of the acrylic silicone component exposed on the coating film surface can be expected. From this, it is considered that the scratch resistance is improved.

When a resin powder having lubricity is blended with an organic / inorganic composite type clear coating film, the lubricating action of the resin powder is superimposed and the wrinkle resistance is further improved. Even if resin powder such as PTFE (polytetrafluoroethylene), PE (polyethylene) -PTFE, and PAN (polyacrylonitrile) is added alone as a resin powder having lubricity, the scratch resistance is improved. Further, the scratch resistance is improved.
The organic / inorganic composite type clear coating is non-tacky due to the acrylic silicone component present on the surface of the coating, and even if dirt such as salad oil adheres, the binding force with the coating surface is weak, so running water Easily removed by washing. As a result, the antifouling property is excellent and a beautiful appearance is maintained for a long time.

Hot water resistance is improved by the undercoat fluororesin coating.
An organic resin undercoating film is usually provided to improve adhesion, but a coating film based on an epoxy resin, a polyester resin, an acrylic resin, or the like cannot provide satisfactory warm water resistance. The clear coating film of the top coat is porous because it is formed by dehydration condensation of silica, and although it exhibits water repellency due to acrylic silicone, it cannot completely prevent the penetration of warm water. Even if a coating film such as an epoxy resin, a polyester resin, or an acrylic resin is provided under the clear coating film, the water resistance of the coating film itself is insufficient, so that it is considered that the warm water resistance is also poor.

  On the other hand, the fluororesin coating film is considered to be excellent in hot water resistance since the coating film itself has good water resistance. Further, although there is a concern about the poor adhesion of the fluorine-based resin to the surface of the stainless steel plate, the adhesion can be improved by blending the epoxy resin. By providing an oxide layer having an OH group between the stainless steel plate and the fluororesin coating film, the adhesion of the coating film is further improved, but the oxide layer also contributes to the improvement of hot water resistance.

[Substrate material]
The sink base material is not limited by the steel type as long as it is a material that can be deep-drawn into a predetermined shape, but specifically, an austenitic or ferritic stainless steel plate is used. The stainless steel plate is processed into a sink shape, and then subjected to pretreatment such as alkali degreasing, pickling, and phosphate treatment as necessary.
In some cases, an aqueous dispersion containing an oxide precursor such as a hydroxide of Si, Ti, Zr, or Al, a hydrolyzate of alkoxide, or a hydrated oxide is applied and baked at 300 ° C. or lower. Thus, an oxide layer is formed.

〔undercoat〕
A primer base material subjected to pretreatment such as degreasing is coated with an undercoat paint of thermoplastic acrylic resin: 20 to 50% by mass, polyvinylidene fluoride resin: 45 to 75% by mass, epoxy resin: 5 to 35% by mass, and baked. By doing so, a fluororesin coating film is formed. When the mass ratio of the thermoplastic acrylic resin / polyvinylidene fluoride resin is less than 20/75, the coating film adhesion is lowered, and when it exceeds 50/45, the hot water resistance tends to be insufficient. Moreover, when the epoxy resin is less than 5% by mass, the coating film adhesion in a warm water environment is inferior, and conversely when it exceeds 30% by mass, yellowing easily occurs under light irradiation conditions.

The fluororesin coating film is preferably formed with a film thickness of 0.5 to 15 μm. When the film thickness is less than 0.5 μm, the adhesion of the coating film in a warm water environment is insufficient, and when the film thickness exceeds 15 μm, the wear resistance after the formation of the top coating film is lowered.
The fluororesin coating film is formed by spraying a fluororesin paint having a predetermined composition on the surface of a stainless steel plate and heating to 210 to 260 ° C. for 1 minute or more. If the heating temperature does not reach 210 ° C, the compatibility of the resin becomes insufficient, and if the heating temperature exceeds 260 ° C, yellowing proceeds remarkably. Cooling after baking is optional, but forced cooling suppresses crystallization and imparts flexibility to the resin coating.

[Clear coating]
After forming the fluororesin coating film, an organic / inorganic composite clear coating film is formed by applying and baking a paint containing a resin powder having lubricity and / or an inorganic powder exhibiting a matte appearance. The binder of the organic / inorganic composite clear coating is a solid or unsaturated ethylenic monomer polymer or copolymer consisting of silica, organoalkoxysilane, organoalkoxysilane partial hydrolysis condensate such as water, alcohol, etc. It is prepared by dispersing and mixing in a solvent.

  Silica includes colloidal silica, which is used in a state where high molecular weight silicic acid is dispersed in a solvent such as water or alcohol. The colloidal silica is preferably dispersed in a solvent such as water or alcohol at an average particle size of 150 nm or less (further 30 nm or less) and a blending amount of 10 to 60% by mass.

The organoalkoxysilane partial hydrolysis condensate contained in the organic / inorganic composite binder is an organohydroxysilane represented by the general formula: R ¹ Si (OH) ₃ or a partial condensate thereof. The general formula: R ¹ Si ( It is prepared by hydrolyzing an organoalkoxysilane represented by OR ² ) ₃ in an acidic colloidal silica dispersion. In the formula, R ¹ is an alkyl group having 1 to 3 carbon atoms, vinyl group, 3,4-epoxycyclohexylethyl group, γ-glycidoxypropyl group, γ-mercaptopropyl group or γ-chloropropyl group, R ² is It is a C1-C4 alkyl group, a C1-C4 alkoxyethyl group, or an aryl group.

Considering the coating film hardness, methylhydroxysilane is preferable, but a small amount of other organoalkoxysilane can be mixed. It is preferable that 80% by mass or more of the organoalkoxysilane is methylhydroxysilane.
The addition amount of the organoalkoxysilane partial hydrolysis condensate is selected in the range of 20 to 70% by mass with respect to the total solid content of the binder composition. If the organoalkoxysilane partial hydrolysis-condensation product is less than 20% by mass, the adhesion of the coating film is lowered, and conversely if it exceeds 70% by mass, the scratch resistance is lowered.

  Unsaturated ethylenic monomers that are organic sources of organic / inorganic composite binders include methyl acrylate, ethyl acrylate, 2-ethylhexyl (meth) acrylate, t-butyl (meth) acrylate, 2-hydroxymethyl (meth) acrylate , 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, glycidyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, diethylaminoethyl ( Examples thereof include acrylic esters and methacrylic esters such as (meth) acrylate, methoxydiethylene glycol (meth) acrylate, methoxytetraethylene glycol (meth) acrylate, and allyl (meth) acrylate. A small amount of another monomer such as styrene may be added to the unsaturated ethylenic monomer.

  The addition amount of the polymer or copolymer of the unsaturated ethylenic monomer is selected in the range of 20 to 70% by mass with respect to the total solid content of the organic / inorganic composite binder. If the addition amount is less than 20% by mass, the maximum film thickness that can be formed is only a few μm, and cracks cannot be prevented from occurring in the coating film due to heat shrinkage or the like. On the other hand, when the addition amount exceeds 70% by mass, the coating film hardness is lowered and sufficient scratch resistance cannot be obtained.

  As a solvent for the organic / inorganic composite binder, a mixed solvent such as a lower aliphatic alcohol and a glycol derivative is used, and a small amount of water derived from aqueous colloidal silica or the like may be contained. For lower aliphatic alcohols, methanol, ethanol, propanol, isopropanol. There are n-butanol and t-butanol. Examples of the glycol derivative include ethylene glycol, propylene glycol, butylene glycol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and acetic acid ethylene glycol monoethyl ether.

The organic / inorganic composite binder is preferably adjusted in the range of pH 3 to 6.5 (more preferably pH 3 to 5) in order to maintain the storage stability. In addition to aqueous ammonia, organic amines such as triethanolamine and dimethylamino ether can be used for pH adjustment.
The resin powder to be included in the organic / inorganic composite clear coating is not limited by the type of resin as long as it has lubricity, but fluororesin powder, polyethylene-fluororesin composite powder, polyacrylonitrile resin powder, silicone resin powder, etc. Suitable resin powder. The resin powder can be added singly, but the rust resistance is further improved by mixing plural kinds of resin powders.

  The resin powder is preferably a powder having an average particle size of 1 to 30 μm. A fine powder having a particle size of less than 1 μm tends to aggregate and is difficult to disperse in an organic / inorganic composite binder. On the contrary, the resin powder having a particle size exceeding 30 μm is distributed as large protrusions on the surface of the coating film and easily falls off during wear. The addition amount of the resin powder is selected in the range of 1 to 20% by mass based on the entire coating film. If the addition amount is less than 1% by mass, the effect of the resin powder effective for improving the lubricity is insufficient, and conversely if it exceeds 20% by mass, the clearness of the coating film is impaired.

  In order to reduce the visibility of dust and blisters by matting the surface of the clear coating film and to give a calm appearance, an inorganic powder exhibiting a matte appearance may be dispersed in the organic / inorganic composite clear coating film. As the inorganic powder, silica particles having an average particle diameter of 1 to 10 μm are generally used. Fine powders having an average particle size of less than 1 μm have poor dispersibility with respect to the paint, and conversely, if the particle size exceeds 10 μm, the properties of the resin powder effective for developing lubricity may be impaired. This kind of inorganic powder is added at a ratio of 20% by mass or less based on the entire coating film.

  A clear paint film having a dry film thickness of 1 to 30 μm is formed by applying a paint obtained by blending a resin powder and an inorganic powder into an organic / inorganic composite binder to a sink base material and baking at 150 to 300 ° C. Uniform coating is difficult with a thin film of less than 1 μm, and coating film hardness, and consequently, anti-scratch resistance, is deteriorated with a thick film of more than 30 μm. If the baking temperature does not reach 150 ° C, the polycondensation of the organic / inorganic composite coating will not progress sufficiently and will tend to cause poor adhesion, but if it exceeds 300 ° C, the coating will crack and the coating will adhere in a hot water environment. There is a risk that the performance will be reduced.

  The stainless steel kitchen sink painted in this way has excellent rust resistance, contamination resistance, and warm water resistance, and maintains a beautiful appearance even in environments exposed to running water such as cold water and hot water over a long period of time. To do. In addition, it has a whitish matte tone and a high-class appearance, so when installed as a system kitchen, it blends well with surrounding furniture and creates an impressive kitchen environment.

[Preparation of undercoat]
The following two types of fluororesin paints for undercoating were prepared.

[Preparation of top coat]
Acidic aqueous colloidal silica dispersion: 21.2 g (average particle size: 10 to 20 nm, solid content: 20% by mass) and methanolic colloidal silica dispersion: 38.8 g (average particle size: 10 to 20 nm, solid content: 30% by mass), 13.9 g of methylmethoxysilane was added, and the mixture was stirred at room temperature for 5 hours to complete the hydrolysis. Isopropanol was added to the obtained product to obtain a dispersion A of colloidal silica and organoalkoxysilane having a solid content of 20% by mass.

  On the other hand, a mixture of methyl methacrylate: 20 g, γ-methacryloxypropyltrimethoxysilane: 10 g was diluted with a mixed solvent of isopropanol: 20 g, ethylene glycol monobutyl ether: 50 g, and polymerized at 80 ° C. for 6 hours to obtain unsaturated ethylene. Resin solution B having a solid content of 30% by mass was obtained as a polymer or copolymer of a functional monomer.

  Dispersion A: 83 g and resin solution B: 22 g were mixed to prepare an organic / inorganic composite binder having a pH of 4.5. By adding PE-PTFE with an average particle size of 3 μm, PAN with an average particle size of 10 μm, silicone resin with an average particle size of 5 μm, and silica particles with an average particle size of 3.5 μm to this organic / inorganic composite binder,・ Inorganic composite type clear paint was prepared.

  For the coating original plate, a SUS304 stainless steel plate having a thickness of 0.7 mm subjected to various finishes was drawn into a sink shape. After the molded sink base was alkali degreased, a fluororesin coating was applied, and a fluororesin coating film was formed by baking at 230 ° C. for 10 minutes. Next, a clear paint was sprayed, and a clear coating film having a film thickness of 5 μm was formed by baking at 200 ° C. for 20 minutes.

A test piece was cut out from the bottom of a painted stainless steel kitchen sink and subjected to a flaw test, a contamination test, and a hot water test.
[Test with wrinkles]
A metal rod with a diameter of 30 mm with the same roughness and hardness as the bottom of the earthenware pan is set at a right angle to the coating surface with a load of 1 kg, and the stroke is 50 mm at 100 reciprocations per minute. The coating was rubbed with a metal rod. After 1000 round trips, the coating surface is observed. The coating film with the entire surface markedly marked x, the coating film with 1-5 ridges reaching the substrate is △, the coating does not reach the substrate, but the marking is visible The scratch resistance was evaluated with ◯ as the coating film to be evaluated, and ◎ as the coating film with no wrinkles reaching the substrate and without noticeable wrinkling.

[Contamination test]
Salad oil: 1 ml was dropped on the coated steel sheet, and tap water was allowed to flow for 1 minute, and then the appearance was observed. Contamination resistance was evaluated by assuming that the coating film in which the salad oil remained clearly was X, the coating film in which the salad oil remained slightly was △, and the coating film in which no residual was detected was ◯.

[Hot water test]
The coated steel plate was continuously immersed in 85 ° C. hot water for 168 hours, then dried, and the adhesion of the coating film in a hot water environment was examined by a tape peeling test. The hot water resistance was evaluated with a coating film with peeling of 10% by area or more being evaluated as “x”, a coating film peeled off in a dotted manner as “Δ”, and a coating film without peeling at all as “◯”.

  As shown in the survey results in Table 1, by laminating an organic / inorganic composite clear coating on a fluororesin-based primer coating, it has excellent characteristics such as scratch resistance, stain resistance, and warm water resistance. Is granted. On the other hand, with a stainless steel plate primed with epoxy-modified polyester, acrylic, and epoxy resin, sufficient coating film adhesion is not obtained in a warm water environment. Excellent scratch resistance is imparted by the organic / inorganic composite clear coating film, but the blend resistance is further improved by blending resin powder having lubricity.

  Plate thickness: A SUS430 stainless steel plate with a thickness of 0.7 mm was used as the coating original plate, and a clear coating film was formed under the same conditions as No. 5 in Example 1 to provide scratch resistance, stain resistance, and hot water resistance. investigated. Also in this case, by laminating the organic / inorganic composite clear coating on the fluororesin coating, excellent properties in all of the anti-fouling property, stain resistance and hot water resistance were obtained.

  As described above, the kitchen sink of the present invention is provided with an organic / inorganic composite clear coating film on the surface of the stainless steel plate through a fluororesin coating film. Excellent as a product that maintains a beautiful surface for a long time. Moreover, it has a whitish and matte appearance, so that the cold metallic feeling unique to stainless steel is suppressed, creating a high-quality kitchen atmosphere that is easy to harmonize with surrounding furniture. The property improvement brought about by the combination of fluororesin coating and organic / inorganic composite clear coating is not limited to kitchen sinks, but baths, bathroom walls, kitchen panels, kitchen tops, range hoods, etc. that require hot water resistance. It can also be applied to.

Claims (5)

  An organic / inorganic composite clear coating containing a resin powder with lubricity and / or an inorganic powder exhibiting a matte appearance is formed on the surface of the substrate via a fluororesin coating. A kitchen sink characterized by being provided in.   The kitchen sink according to claim 1, wherein the fluororesin coating film has a composition of thermoplastic acrylic resin: 20 to 50 mass%, polyvinylidene fluoride resin: 45 to 75 mass%, and epoxy resin: 5 to 35 mass%.   Organic alkoxysilane partially hydrolyzed condensate containing alkoxysilane: 20 to 70 mass%, polymer or copolymer of unsaturated ethylenic monomer: 20 to 70 mass% Colloidal silica: The kitchen sink of Claim 1 which has a composition of 10-60 mass%.   The kitchen sink according to claim 1, wherein the resin powder having lubricity is one or more selected from fluororesin powder, polyethylene-fluororesin composite powder, polyacrylonitrile resin powder, and silicone resin powder.   The kitchen sink according to claim 1, wherein the fluororesin coating film is provided on the surface of the base material through an oxide layer having an OH group.