Patent Application
20240181494
The present invention relates to an aqueous composition for metallic surface treatment and more specifically for surface treatment on stainless steel, galvanized steel and its alloys. The present invention also relates to a process of treating a metallic surface with the invented aqueous composition.
Compositions for metallic surfaces treatment are used onto surfaces of metals before painting or coating to form films and therefore the obtained metallic surfaces are enabled good performances in repaintability, resistance to darkening, corrosion, alkali, boiling water and solvents etc. The homogeneity of the formed films is significant to bring good properties to metallic surfaces.
In one example of industrial practice, treating metallic surfaces is carried out by rollers and comprises following steps: (1) contacting stainless steel pick-up roller in rotating with a composition for metallic surface treatment to adhere the composition to surfaces of the pick-up roller; (2) transferring the composition from surfaces of the pick-up roller to that of a polyurethane coating roller in synchronous rotation; and (3) transferring the composition from surfaces of the polyurethane coating roller to that of a quickly-moving metal sheet to finish the surface treatment. The metal sheet could be replaced by a sheet having metallic surfaces.
The temperature on surfaces of the stainless steel pick-up roller and the polyurethane coating roller will reach 50° C. or even higher in summer. Such a high temperature will lead to residues of the compositions on rollers, which leads to inhomogeneity of the films formed on the metallic surfaces after being treated. Furthermore, the composition residues increase roughness of the rollers and as a consequence, the rollers have to be replaced more frequently.
Some compositions have been developed to obtain homogeneous films after metallic surface treatment. For example, CN100554389C provided a polyurethane resin composition comprising (a) a polyurethane resin having polyester backbone part and polyether backbone part, a tensile strength at break of not less than 3.92 kN/cm2 and a tensile elongation at break of not more than 50%, measured according to JISK 7113, and a glass transition temperature (Tg) of from 80° C. to 150° C. measured according to JISK 7121; (b) fine polyolefin resin particles having a melting point of from 70° C. to 160° C. and a particle diameter of from 0.5 μm to 5 μm; and (c) a colloidal silica having a particle diameter of from 5 nm to 50 nm. However, it is not applicable for scenario of using rollers.
Therefore, it is still required to provide a composition for metallic surface treatment that could be used for rollers and meanwhile could form homogeneous film and further bring excellent performances in repaintability, resistance to high temperature, darkening, corrosion, alkali, boiling-water and solvents etc.
In one aspect, the present invention provides an aqueous composition for metallic surface treatment, which is particularly suitable for roller application. The aqueous composition comprises components of:
Preferably, the aqueous composition of the present invention further comprises component (E): from 3% to 10% by weight of a hydroxyl-donating compound, based on the total weight of the composition.
In another aspect, the present invention relates to a process of treating metallic surfaces with the invented aqueous composition comprising the step of
In another aspect, the present invention provides a metal having surfaces treated by the invented aqueous composition.
In a further aspect, the present invention relates to an article having a metal and its surface is treated by the invented aqueous composition.
The aqueous composition of the present invention has a decreased adhesion to stainless steel roller and polyurethane roller, which dramatically extends the lifetime of the rollers.
Furthermore, the film formed from the invented aqueous composition is homogeneous and shows excellent performances in repaintability, resistance to high temperature, darkening, corrosion, alkali, boiling water and solvents etc.
The present invention now will be described more fully hereinafter, in which some, but not all embodiments of the inventions are shown. Indeed, this invention can be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.
In the present disclosure, expressions “a”, “an”, “the”, when used to define a term, include both the plural and singular forms of the term.
The terms “comprise”, “comprising”, etc. are used interchangeably with “contain”, “containing”, etc. and are to be interpreted in a non-limiting, open manner. That is, e.g., further components or elements may be present. The expressions “consists of” or “consists essentially of” or cognates, if used, may be embraced within “comprises” or cognates.
The term “article” means an article made of a metal or an article having a metallic surface.
The term “metallic surface” means a surface of a metal or a surface made of a metal.
The term “film-forming” means the formation of a film from a material having a high polymer content, such as a polymer dispersion, in which process primarily polymer particles turn into a uniform film, preferably at room temperature (5-40° C.) or slightly elevated temperature.
The term “minimum film-forming temperature (MFT)” means the lowest temperature at which resin particles in an emulsion will form a continuous film that is measured according to GB/T 9267-1988.
The term “(meth)acrylate” means any acrylate and/or methacrylate monomer.
The term “acrylic resin” means any acrylic polymer and/or methacrylic polymer and the derivatives thereof.
The term “hydroxyl-donating compound” means a compound that is capable of providing hydroxyl groups.
All percentages and ratios regarding the composition are mentioned by weight unless otherwise indicated.
The aqueous composition of the present invention uses acrylic resin as a film-forming component. Acrylic resins capable of forming a film and applicable in a surface-treatment composition may be used in the present invention.
Suitable acrylic resins used as component (A) may be prepared from emulsion polymerization of monomers in the presence of a polymerization initiating agent. Typical initiating agents are known in the art and can be selected by persons skilled in the art.
There is no limitation on the emulsion polymerizations to prepare acrylic resins. Persons skilled in the art can select appropriate conditions and procedures for the emulsion polymerizations.
Monomers for preparing acrylic resin are known in the art, for example, methyl acrylate, methyl methacrylate, acrylic acid, methacrylic acid, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, butyl acrylate, butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, amyl acrylate, amyl methacrylate, hexyl acrylate, hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, 3,3,5-trimethylhexyl acrylate, 3,3,5-trimethylhexyl methacrylate, stearyl acrylate, stearyl methacrylate, lauryl acrylate or lauryl methacrylate, cycloalkyl acrylates and/or cycloalkyl methacrylates, such as cyclohexyl (meth)acrylate, (meth)acrylate esters of alkyl-substituted cyclohexanol, and (meth)acrylate esters of alkanol-substituted cyclohexane, such as 2-tert-butyl and 4-tert-butyl cyclohexyl (meth)acrylate, 4-cyclohexyl-1-butyl (meth)acrylate, and 3,3,5,5,-tetramethyl cyclohexyl (meth)acrylate; isobornyl (meth)acrylate; isomenthyl (meth)acrylate; cyclopentyl (meth)acrylate, (meth)acrylate esters of alkyl-substituted cyclopentanols, and (meth)acrylate esters of alkanol substituted cyclopentanes; adamantanyl (meth)acrylates; cyclododecyl (meth)acrylate; cycloundecanemethyl (meth)acrylate; dicyclohexylmethyl (meth)acrylate; cyclododecanemethyl (meth)acrylate; menthyl (meth)acrylate; and the combinations thereof. In some embodiments, comonomers, for example styrenic monomers such as styrene and olefinically unsaturated silicon-containing monomers such as vinyltriacetoxysilane may also be added for copolymerization to prepare acrylic resins.
Preferably, the acrylic resin as component (A) in the aqueous composition has an average particle diameter in a range of from 50 μm to 200 μm, preferably from 50 μm to 100 μm measured by dynamic light scattering according to ISO13321:2004.
The acrylic resin as component (A) is added into the aqueous composition in form of aqueous emulsion. The amount of the acrylic resin as component (A) in the aqueous composition is calculated based on the weight of the acrylic resin in the emulsion. The suitable solid content of the aqueous acrylic resin emulsion may be in a range of from 20% to 60% by weight, preferably in a range of from 30% to 55% by weight, such as from 30% to 50% by weight or from 40 to 50% by weight based on the weight of the emulsion, measured according to GB/T20623-2006.
In one embodiment, the aqueous acrylic resin emulsion may be GS-354 commercially available from Changzhou Guangshu Chemical Technology, Jiangsu of China.
In some embodiments, the minimum film-forming temperature at 1 atm of the aqueous acrylic resin emulsion is in a range of from 20° C. to 50° C., such as from 25° C. to 40° C., preferably from 30° C. to 35° C.
As the film-forming component, the acrylic resin as component (A) is present in the aqueous composition in an amount of from 10% to 35% by weight, preferably from 15% to 26% by weight based on the total weight of the aqueous composition.
Suitable acrylic resins used as component (A) do not contain hydroxyl group in the molecule.
The aqueous composition of the present invention comprises a film-forming aid as component (B).
Film-forming aid acts as a specific solvent which swells and softens the surface of the polymer particles and thus make it possible to change their geometries through melting the organic particles. Preferably, after evaporation of the water, the film-forming aids are almost evaporated and do not remain in the film permanently.
Film-forming aids are known in the art. For the purpose of the present invention, the film-forming aid as component (B) has a boiling point of no more than 300° C. under 1 atm, in particular in a range of from 100° C. to 250° C., such as from 150° C. to 250° C.
For example, the film-forming aid may be selected from a group consisting of ethylene glycol butyl ether, diethylene glycol butyl ether, ethylene glycol phenyl ether, propylene glycol butyl ether, dipropylene glycol butyl ether, tripropylene glycol butyl ether, propylene glycol phenyl ether, dipropylene glycol propyl ether and the combination thereof.
In some embodiments, component (B) is a film-forming aid having a static surface tension of from 20 mN/m to 50 mN/m, such as from 25 mN/m to 40 mN/m measured by DuNouy ring tensiometer.
The amount of component (B) in the aqueous composition is in a range of from 0.1% to 4%, preferably from 1% to 4% by weight based on the weight of the composition.
A lubricant is added in the aqueous composition as component (C). At least one wax selected from a group consisting of paraffins, polyethylenes and polypropylenes may be used as lubricant. For example, at least one oxidized wax and/or at least one microcrystalline wax may be used in the present invention. In some embodiments, component (C) is at least one selected from a group consisting of paraffin, polyethylene wax, polypropylene wax, polytetrafluoroethylene wax, oxidized polyethylene wax or/and oxidized polypropylene wax.
For the purpose of the present invention, the average particle diameter of the lubricant particles is in a range of from 100 nm to 600 nm, preferably from 100 nm to 400 nm, such as from 100 nm to 200 nm, measured by dynamic light scattering according to ISO13321:2004.
Preferably, the lubricant used in the present invention has a melting point of from 100° C. to 160° C., such as from 100° C. to 150° C., measured according to ISO 11357-1-2016.
The amount of component (C) in the aqueous composition is in a range of from 1% to 8% by weight, preferably from 2% to 6% by weight, based on the total weight of the composition.
The aqueous composition of the present invention comprises a water-soluble chromium compound as component (D). The water-soluble chromium compounds commonly used in the treatment on metallic surfaces are applicable to the aqueous composition of the present invention. For example, the water-soluble chromium compound may be selected from a group consisting of chromium fluoride, chromium nitrate, chromium sulfate, chromic anhydride, ammonium chromate, and ammonium dichromate. In one embodiment of the present invention, the water-soluble chromium compound is ammonium chromate.
Component (D) is present in the aqueous composition of the present invention in an amount of from 0.1% to 1% by weight, based on the weight of the composition. The weight of Component (D) is calculated from that of chromium element. In one embodiment of the invention, the amount of component (D) is in a range of from 0.2% to 0.8% by weight, based on the weight of the aqueous composition.
In some embodiments, the amount of component (D) in the aqueous composition is in a range of from 1 g/L to 10 g/L, such as 2 g/L to 8 g/L.
Preferably, the aqueous composition of the present invention could further comprise a hydroxyl-donating compound as component (E). The hydroxyl-donating compound can be selected by persons skilled in the art provided that it will not bring negative effects to the functions of other components of the composition. For example, the hydroxyl-donating compound may be selected from hydroxyl-functional resins, such as hydroxyl-functional polyesters, hydroxyl-functional poly(meth)acrylates, and hydroxyl-functional polyurethanes etc.
The hydroxyl value of component (E) is in a range of from 3 mg KOH/g to 100 mg KOH/g, preferably from 20 mg KOH/g to 80 mg KOH/g, such as from 50 mg KOH/g to 70 mg KOH/g, measured according to DIN-53240.
When present, the amount of component (E) is in a range of from 3% to 10%, preferably from 3% to 8% by weight, based on the total weight of the aqueous composition.
The aqueous composition of the present invention may further comprise additives as component (F) in proper amounts, such as defoaming agents, pigments and so on.
In some embodiments, the aqueous composition of the present invention further comprises pigments. Persons skilled in the art could select appropriate pigments according to specific applications.
When present, the amount of component (F) in the aqueous composition may be in a range of from 1% to 10%, such as from 3% to 7 by weight, based on the total weight of the aqueous composition.
The aqueous composition of the present invention may be applied by a process known in the art. For example, the aqueous composition of the present invention may be applied by roller coating, flow coating, blade coating, spattering, spraying, brushing or dipping, also dipping at elevated temperature of the aqueous composition, and by subsequent squeegeeing, for example with a roller.
The aqueous composition of the present invention is particularly suitable for being applied by a process wherein the use of a roller is involved, especially stainless steel roller and/or polyurethane roller.
The aqueous composition of the present invention is suitable for treating metals and especially suitable for treating stainless steel, galvanized steel and the alloys thereof.
Furthermore, articles having metallic surfaces, in particular metallic surfaces of stainless steel, galvanized steel and the alloys thereof, can be treated with the aqueous composition of the present invention. These articles can be wire, strip, sheet, cladding, screening, car body, a part of vehicle, trailer, caravan or flying body, a covering, housing, lamp, light, traffic light element, an item of furniture or furniture element, an element of domestic appliance, frame, profile, a formed part with complex geometry, a crash barrier element, radiator element or fencing element, a bumper, a part consisting of or having at least one pipe or/and profile, a window, door or bicycle frame, a wire winding and wire mesh.
Below embodiments further illustrate how this invention could be carried out.
An aqueous composition for metallic surface treatment comprising components of:
The aqueous composition of embodiment 1, wherein component (A) is in a form of aqueous emulsion having a minimum film-forming temperature at 1 atm in a range of from 20° C. to 50° C., preferably in a range of from 25° C. to 40° C. and more preferably in a range of from 30° C. to 35° C. according to GB/T 9267-1988.
The aqueous composition of any one of embodiments 1 to 2, wherein component (B) has a static surface tension of from 20 mN/m to 50 mN/m, preferably from 25 mN/m to 40 mN/m measured by DuNouy ring tensiometer.
The aqueous composition of any one of embodiments 1 to 3, wherein component (C) has a melting point of from 100° C. to 160° C. measured according to ISO 11357-1-2016.
The aqueous composition of any one of embodiments 1 to 4, wherein it further comprises component (E):
The aqueous composition of embodiment 5, wherein said hydroxyl-donating compound is at least one selected from hydroxyl-functional resins, preferably at least one selected from a group consisting of hydroxyl-functional polyesters, hydroxyl-functional poly(meth)acrylates and hydroxyl-functional polyurethanes.
The aqueous composition of any one of embodiments 1 to 6, wherein it further comprises component (F):
A process of metallic surface treatment comprising steps of
A metal having surface treated with the aqueous composition of any one of embodiments 1 to 7.
The metal of embodiment 9, preferably selected from stainless steel, galvanized steel and its alloys.
An article having a metal of any one of embodiments 8 to 9.
The present invention will be better understood in view of the following non-limiting examples.
In examples, a hot-dip Al—Zn-galvanized steel sheet (55% Al-1.6% Si—Zn), double-side galvanized, having a galvanizing amount of 100 g/m2 is used as the metal substrate.
All components list in Table A in the amounts of Tables 1 and 4 are added into deionized water under stirring to form aqueous compositions.
Treatment on Metallic Surfaces with Aqueous Compositions
The metallic surfaces are treated with an aqueous composition in a process comprising steps of:
Properties of an aqueous composition such as volatilization speed and adhesion to polyurethane roller and stainless-steel roller, and the properties of a treated metallic surface such as corrosion resistance, darkening resistance, alkali resistance, solvent resistance, heat resistance, boiling water resistance, and repaintability are tested. The test results are summarized in Tables 2, 3 and 5.
Below marks in each and every property test are interpreted as follows:
Corrosion resistance is evaluated by neural salt spraying test (NSST) method according to GB/T 10125-2012 for 500 hours.
Results are rated as follows:
Darkening resistance is evaluated as follows:
Results are rated as follows:
Alkali resistance is evaluated as follows:
measuring the parameters L, a and b of the treated metallic surface of a metal substrate by ColorFlex Spectrocolorimeter; and
placing the metal substrate in a 0.1 wt % aqueous NaOH solution at room temperature (5-40° C.) for 1 hour; then taking out the metal substrate, washing it by water and drying; and then measuring again the parameters L, a and b of the treated metallic surface to determine color difference ΔE value.
Results are rated as follows:
Solvent resistance is evaluated as follows:
Results are rated as follows:
Heat resistance is evaluated as follows:
Results are rated as follows:
Boiling-water resistance is evaluated as follows:
Results are rated as follows:
Repaintability is evaluated as follows:
Results are rated as follows:
Volatilization speed is measured by the instrument Sartourius MA150 using auto model at 100° C. with the procedure as follows:
evaporated weight=0.3 g*normalized evaporated weight (%); and
volatilization speed=evaporated weight/(area*time),
Results are rated as follows:
Adhesion to polyurethane roller and stainless-steel roller are evaluated using a new and clean stainless-steel pick-up roller (with microporous treatment Cr-plated surface, Ra: 4˜5 μm; Hardness: HRc 40˜50) and a new and clean polyurethane coating roller (with polyurethane surface, Ra: 0.6˜1.0 μm; Hardness: HRc 50˜60), by a process comprising steps of:
Results are rated as follows:
A series of aqueous compositions are prepared according to the formulations provided in table 1, wherein compositions 1 to 7 and 9-10 are aqueous compositions of the present invention while compositions 8 and 11-13 are comparative compositions. For each composition, the amounts are provided in % by weight and the balance is water.
2%
2%
2%
1%
The test results of the aqueous compositions and formed films are summarized in tables 2 and 3.
A series of aqueous compositions are prepared according to the formulations provided in table 4, wherein compositions 1, 2, 4, and 5 are aqueous compositions of the present invention while compositions 3 and 6 to 14 are comparative compositions. For each composition, the amounts are provided in % by weight and the balance is water. 5
The test results of the aqueous compositions and formed films are summarized in table 5.
| Number | Date | Country | Kind |
|---|---|---|---|
| PCT/CN21/92748 | May 2021 | WO | international |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP22/61910 | 5/4/2022 | WO |
