Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D7/00—Features of coating compositions, not provided for in group C09D5/00; Processes for incorporating ingredients in coating compositions
  • C09D7/40—Additives
  • C09D7/60—Additives non-macromolecular
  • C09D7/61—Additives non-macromolecular inorganic
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K3/00—Use of inorganic substances as compounding ingredients
  • C08K3/34—Silicon-containing compounds
  • C08K3/36—Silica

Definitions

• Coating compositions comprising micro silica
• the present invention is concerned with coating formulations. These may be aqueous or solvent based and may be UV-cured. In particular, the invention is applicable to water-based primers, solvent-based top coats, water-borne clear coats and UV-cured coatings. Background art
• Coating formulations in the form of dispersions which are dried and cured to form a final coating are extensively used in many fields.
• a significant factor which is relevant to the coating formulations is the amount of solvent that has to be recovered and either re-cycled or disposed of. Since this is a costly aspect of the coating operation and represent serious HSE issues, it is desirable that the solvent duty is minimised, and this represents a further aspect of the invention.
• the solvent is mainly used for lowering the viscosity of the formulation any non-volatile compound that decreases the viscosity will allow the formulation to save time and avoid strict regulation constrains.
• the surface properties of the coating like abrasion resistance and scratch resistance are important factors for coatings. It is therefore an object of the present invention to modify a coating formulation in such a way that the solvent proportion is reduced while maintaining a suitable viscosity and to improve wear resistance of the coatings.
• individual formulation systems have respective issues such as adhesion, gloss, waviness, distinction of image (DOI), hardness, and matting. It is important that these properties do not deteriorate significantly and it would be desirable is they could be maintained or even improved.
• fillers in coating formulations.
• Known fillers include talc, TiO 2 , natural silicates, fumed silica and precipitated silica.
• Fumed silica is produced by burning silane gas and has a very small particle size and a very high surface area of 100 to 200 m /g.
• Precipitated silica is produced by precipitating silica particles from aqueous solutions.
• talc is a common filler used for primers and for topcoats. It has a lamellar structure and can be used to adjust rheology. Since it has some hydroxyl groups on the surface it improves adhesion. Due to its low hardness it leads to advantages in sanding and flexibility. Silicates, such as SILLITHIN Z86 may be used as a filler in water-based coatings to improve abrasion resistance.
• Fumed Silica may be incorporated for rheology and levelling control. Precipitated silica may be employed for cost reduction. Both these forms of silica may be used as a matting agent, to decrease gloss. Both fumed silica and precipitated silica do exhibit a high water and oil absorption and will thus increase the solvent demand for coatings in order to have a suitable viscosity. In addition, fumed silica has other disadvantages like strong hazing. Finally fumed silica is, due to its very low particle size, a very fluffy material resulting in handling problems and also negative health issues.
• a coating formulation in the form of a solid/liquid dispersion comprising a liquid solvent, a resin and up to 25 wt% microsilica, based on the total weight of the formulation.
• the resin may be curable or not curable.
• microsilica used in the specification and claims of this application refers to particulate, amorphous SiO 2 obtained from a process in which silica (quartz) is reduced to SiO-gas and the reduction product is oxidised in the vapour phase to form amorphous silica.
• Microsilica may contain at least 70% by weight silica (SiO 2 ), and preferably >97% and has a specific density of 2.1-
• the primary particles are substantially spherical and may have an average size of about 0.15 ⁇ .
• Microsilica particles further have a solid surface and do not absorb water. Microsilica is preferably obtained as a co-product in the production of silicon alloys in electric reduction furnaces.
• the formulation includes from 1 to 15 wt% microsilica.
• the solvent may be water.
• the resin may be a polyester and preferably the formulation comprises from 2 to 15% microsilica.
• the resin comprises up to 37wt% of the formulation, more preferably, 25 to 37 wt% and the formulation optionally from 10 to 22 wt% of an additional filler.
• the formulation additionally comprises additives selected from pigment and eventually a curing agent or polymerisation initiator.
• a preferred formulation for water based solvent comprises, by weight, 37% polyester resin, 35% water, 10% TiO 2 , 2% additives and 15.5% microsilica.
• Another preferred formulation comprises, by weight, 36% polyester resin, 34% water, 10% TiO 2 , 2% additive, 12% silicate filler and 5% microsilica.
• the water-borne resin may alternatively be a polyurethane resin.
• the formulation then comprises 2 to 5 wt% microsilica, and preferably comprises up to 32 wt% resin and optionally up to 13 wt% of an additional filler Preferably the formulation comprises 5 to 30 wt% resin.
• Such a formulation may provide a clear coating.
• a preferred formulation comprises; by weight 32% polyurethane resin, 53% water, 2% microsilica and 13% other additives. Another preferred formulation comprises by weight; 32% polyurethane resin, 53% water, 5% microsilica and 10% other additives. Formulations with contents of microsilica and other additives between these two formulations are also contemplated.
• the solvent may be non-aqueous.
• the formulation may then be a (nonaqueous) solvent-based top coat and the resin may compromise a polyurethane (PU) resin.
• the solvent may be a hydrocarbon resin, xylene, ethylacetate or another such solvent.
• the formulation preferably comprises from 1 to 2.5 wt% microsilica.
• One preferred formulation includes as a filler, 1.9 wt% talc and 1.0 wt% microsilica.
• the talc may be replaced entirely and the formulation may include 2.5 wt% microsilica.
• Formulations with contents of talc and microsilica between these two formulations are also contemplated.
• a preferred formulation comprises up to 55 wt% resin, up to 19 wt% solvent, up to 9 wt% pigment and up to 12 wt% TiO 2 as a filler.
• the microsilica can be incorporated in a solvent or in water to form a concentrated paste, by using specific additives and mixing operations.
• the formulation may comprise an aery late resin, much as an epoxy aery late oligomer.
• the solution monomer (solvent) may be tripropylene glycol diacrylate (TPGDA).
• TPGDA tripropylene glycol diacrylate
• the formulation may then contain from 2 to 10 wt% microsilica.
• the formulation additionally includes one or more photo-initiators for the resin and the solvent and optionally one or more adhesion promoters.
• One preferred formulation comprises up to 64 wt% resin, up to 30 wt% solvent and 2 wt% microsilica.
• a second preferred formulation comprises up to 60 wt% resin, up to 30.4 wt% solvent and 5 wt% microsilica.
• a third preferred formulation comprises up to 54 wt% resin, up to 31.2 wt% solvent and 10 wt% microsilica. Formulations with contents of resin, solvent and microsilica between the first and third of these formulations are also contemplated.
• the reduction of the viscosity is due to the shape and size of the microsilica. Its spherical, non-porous morphology promotes a so-called "ball bearing" effect. Hence, when it is formulated with an uneven, angular filler of greater size, the flow of the liquid formulation is facilitated. It should be noted that the "ball bearing effect" is great enough to overcome the higher specific surface area of the microsilica (20g/m , compared to 14 g/m for the filler), which should act as a countereffect in the viscosity reduction. By replacing 5% of a conventional filler (e.g. silicate), it may therefore be possible to decrease the water content and thereby achieve a higher solid content. It is assumed that a higher solid content is an advantage because it will allow a dilution of the binder at constant viscosity, and/or lower the energy consumption when evaporating the water.
• a conventional filler e.g. silicate
• the coatings may show a drastic improvement in surface properties.
• the overall surface properties e.g. dullness and waviness can be lowered, and the gloss was increased.
• typical inconveniences such as "orange peel” can be overcome without costly efforts of re-formulation.
• the enhancement of surface properties can be explained by the better flow during paint application, due to the above-mentioned positive effect of the spherical shape of the microsilica particle. Additionally, the small size of the microsilica allows the particles to fill the filler's interparticle voids, allowing more water to be available. Similar benefits can be observed when replacing the conventional filler (e.g. talc) with microsilica in a solvent borne formulation. As previously mentioned, the spherical shape of the particles allows a "ball bearing effect" to take place, hence allowing a formulation of higher solid content, and/or enhancing the flow. The greater oil demand for microsilica as compared to talc (60 and 40g linseed oil/lOOg resp.) is compensated by the benefits imparted by the shape of the particles. Hence, coatings with lower VOC can be achieved.
• talc 60 and 40g linseed oil/lOOg resp.
• the invention also extends to a method of forming a coating on a substrate by applying a formulation as described to the substrate, drying the formulation to drive off the solvent, and curing the resin.
• the curing may be effected by any convenient mechanism, such as heating and/or applying a source of UV radiation.
• the invention also extends to a coating formed in this way and to the coated substrate.
• composition of a prior art coating formulation used in this Example is set out in Table 1. All percentages are by weight.
• the formulation is an aqueous polyester dispersion.
• This example examines the effect of partially or wholly replacing the conventional filler (SILLITHIN Z 86) in the formulation shown in Table 1 with microsilica. Details of the fillers are set out in Table 2.
• the conventional filler, SILLITHIN Z 86 is a quartz/kaolinite silicate.
• the SIDISHIELD C25 filler is microsilica from Elkem AS having a specific surface area of about 25 m 2 /g and the SIDISHIELD C30 filler is microsilica having a specific surface area at about 30 m 2 /g. Table 2
• the TiO 2 also acts as a filler material.
• the formulation was formed into an aqueous dispersion using a pearl-mill.
• Table 3 shows the effect of partially and wholly replacing the conventional filler by microsilica.
• the formulations were applied to a pre-treated steel substrate by means of a compressed air spray gun, operating at a pressure of 2.5 bar, at 22 ° C and 60% relative humidity.
• the primer coatings were dried and cured by ventilating for
• composition of a prior art two-component coating formulation is set out in Table 4. All percentages are by weight.
• the formulation is a solvent-borne polyurethane.
• the formulations were prepared as follows: The component A was prepared by mixing the two resin binders before adding the Bentone paste with stirring. It was then mixed for 5 minutes. The two additives were then added with stirring and mixed for 5 minutes. The pigments, TiO 2 , extender and filler were added to the formulation and mixed for 10 minutes. The formulation was further processed through a pearl mill to a finenesss of ⁇ 10 ⁇ . The remaining solvent was then added under stirring, and mixed for 10 minutes.
• the component B was prepared by stirring the solvent slowly and adding the curing agent before a ten minute mixing. It was then put in a container and stored under nitrogen. The replacement of the filler with SIDISHEILD was made on a volume basis in order to compare the viscosity.
• Table 6 shows the effect of partially and wholly replacing the talc by microsilica.
• the scratch resistance test was carried out on an Erichsen equipment. The weight at which the first damage to the paint film was observed was recorded. Adhesion was evaluated though the cross-cut test.
• the formulations were applied to a pre-treated steel substrate by means of a compressed air gun with a pressure of 2.5 bars, at 23°C and 65% relative air humidity. The drying lasted 7 days at ambient temperature.
• composition of a prior art (reference) coating formation is set out in Table 7. All percentages are by weight.
• the formulation is an aqueous polyurethane dispersion.
• This example examines the effect of adding microsilica to an aqueous polyurethane dispersion which is used to provide a clear coat on parquet flooring.
• the dispersion was formed using a pearl-mill and the formulation was applied to a parquet tile to a thickness of 150 ⁇ in two layers using a doctor blade. The coatings were then allowed to dry for three weeks at ambient temperature.
• the effect on gloss of using microsilica as a matting agent in place of the Acematt TS 100 in formulation 1 1 is shown in Table 8.
• SIDISHIELD C25 acts as a matting agent with no "polishing" effect. Polishing is a decrease of matting when low shear frictions are applied. Typical matting agents, e.g. wax, are subject to the polishing effect.
• microsilica is added as a paste or dispersion whose components are set out in Table 9.
• TPGDA is tripropylene glycol diacrylate
• Disperbyk 2009 is an acrylic copolymer dispersing agent.
• the three components are formed into a dispersion using a pearl-mill.
• Table 10 shows a conventional UV coating formulation and similar formulations with various proportions and microsilica (SIDISHIELD C25) added.
• the formulations were formed into dispersions and applied to an aluminium substrate and UV-cured. All coatings were applied with a doctor blade in 3 strokes with a thickness of 25 ⁇ . The distance between substrate and UV- lamp was 8cm and the curing time in the UV-tunnel was 30 seconds. A mercury vapour lamp was used with an approximate power of 150m/cm 2 . The resulting coatings were tested for abrasion resistance using a Taber Abrasion Wheel CS-10 with a 500g load. The results after 3000 rotations are set out in Table 1 1. All percentages are by weight. Table 1 1
• microsilica in the coating significantly improves abrasion resistance, even when the content is as low as 2% by weight.

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• Chemical & Material Sciences (AREA)
• Inorganic Chemistry (AREA)
• Life Sciences & Earth Sciences (AREA)
• Engineering & Computer Science (AREA)
• Materials Engineering (AREA)
• Wood Science & Technology (AREA)
• Organic Chemistry (AREA)
• Paints Or Removers (AREA)

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• 2009
  • 2009-09-03 NO NO20092956A patent/NO20092956A1/no not_active Application Discontinuation
• 2010
  • 2010-08-25 EP EP10814002A patent/EP2473571A4/de not_active Withdrawn
  • 2010-08-25 WO PCT/NO2010/000314 patent/WO2011028125A1/en not_active Ceased

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