FR2765885A1 - Use of opacifying agent in protective varnish compositions - Google Patents

Abstract

Use of 0.1-5 wt.% of an opacifying agent that diffuses all visible light in a varnish composition, to cover the surface of wood with a protective layer without affecting the colour of the material onto which it is applied, is new. Also claimed are: (i) a protective varnish composition for wooden surfaces comprising a film-forming binder, a carrier for the binder and 0.1-5 wt.% of an opacifying agent that diffuses all visible light, such that the dried varnish gives a colourless layer that does not affect the colour of the material onto which it is applied; and (ii) a protective varnish composition for wooden surfaces in the form of an aqueous emulsion.

Description

 The invention relates to varnishes, in particular varnishes for protecting wooden surfaces.

 It is known to protect wood surfaces both inside and outside buildings by applying a layer of varnish for producing a protective film on the surface of the wood, said film optionally comprising components intended for protect the wood from ultraviolet rays, insects and / or fungi.

 There are currently in the general public two large families of varnishes that differ in the nature of the vehicle used. The first family includes oil paints whose vehicle is a volatile organic solvent, especially an aliphatic hydrocarbon, the typical representatives being oleoglycerophthalic varnishes. The second family comprises the water-based water-based varnishes which consist of aqueous emulsions of polymer resins, especially acrylic resins.

 The varnishes, whether based on an aqueous or organic vehicle all produce a modification of the color of the wood on which they are applied, this effect of "reheating the wood" due to the significant wetting action of the resin is translating into a yellowing that increases with time.

 In some cases, this yellowing may be a desired effect.

In other cases, however, the change in the color of the wood is undesirable, since the consumer wishes that the protective treatment modifies as little as possible the hue and initial appearance of the wood, especially in the case of light woods.

 The problem of yellowing of the wood stain, when applying a varnish, arises regardless of the nature of the varnish employed, but is more pronounced for the oleoglycerophthalic-type varnishes.

 The present invention proposes to remedy this drawback by providing a varnish composition which, applied to a wooden surface, does not appreciably modify the original hue of the wood, especially in the case of light wood, and does not cause yellowing effect even after a prolonged period following its application.

 The subject of the invention is a protective lacquer composition for a wooden surface, characterized in that it comprises at least one film-forming binder, a vehicle for said binder and, at least one opacifying agent totally diffusing visible light, present in a amount ranging from 0.1 to 5% by weight, relative to the total weight of said composition, so that said composition provides after drying a substantially colorless film not substantially modifying the shade of the substrate to which it is applied.

 By opacifying agent diffusing in all the visible light is meant a component diffracting the visible light rays so as to restore all the incident light.

 The opacifying component is a white pigment.

 The white pigment may be a mineral white pigment.

All white mineral pigments may be suitable. There may be mentioned titanium oxide-based pigments, in particular titanium oxide, TiO2
BaSO4, lithopone or zinc oxide.

 The white pigment may also be an opaque organic polymer for introducing air into a film in small volumes distinct from each other, after application and drying of said composition.

 Polymers of this type are well known to those skilled in the art and are usually used in white paints as partial or total replacement of white pigments for economic reasons.

 They consist of multi-cellular vesicular particles. They are generally in the form of emulsion polymer, hard, non-film-forming, the cavity contains encapsulated water.

 When the opaque polymer beads dry in the paint film, the water evaporates irreversibly and is replaced by air.

Once the film is dry, the water can no longer penetrate the cavity of the opaque polymer.

 During drying, the polymer shell retains its shape and thus ensures the stability of the volume of air introduced.

 The chemical nature of the polymer is indifferent. All polymers capable of forming vesicular particles whose cavity contains water, are suitable.

 A resin of this type is a resin marketed under the trade name Opaque, by Rohm and Haas.

 In particular, resins in the form of aqueous emulsions of hollow polystyrene beads may be mentioned.

 The resin beads advantageously have a homogeneous particle size distribution, the minimum and maximum particle sizes being 0.1 to 10 μm, preferably 0.4 to 10 μm, respectively.

 The varnish composition according to the invention may comprise one or the other of the inorganic or organic pigments described above or a mixture of the two.

 Advantageously, a composition comprising only a pigment in the form of hollow beads as described above is used.

 The content of opacifying agent is more generally between 0.1 and 2% by weight, preferably about 1% by weight, when the opacifying agent is a mineral oxide, in particular titanium oxide and between 0.5 and 5% by weight. % by weight, especially 1 and 3% by weight, preferably about 1.5% by weight, when the opacifying agent is an aqueous emulsion of organic resin beads, preferably an aqueous emulsion of opaque polymer beads.

 The opacifying agents according to the invention are traditionally used in white paints for their opacifying effect. To obtain the desired white color, however, they are used in substantially higher levels than those of the invention.

 It was therefore unexpected that by adding in a varnish composition which by definition must be transparent, a small amount of an opacifying agent, or obtain a varnish which not only remains transparent when applied to a wooden surface, but also plus allows to obtain a shade substantially identical to the original color of the wood.

 The amount of opacifying agent that is introduced into the varnish composition according to the invention is a function of the clarity of the wood shade on which it is intended to be applied. The opacifying agent content will therefore be included in the lower limit of the range mentioned for very light woods of pine, fir and spruce type and in the upper limit for darker oak or chestnut woods.

 Advantageously, the varnish composition according to the invention also comprises a compound absorbing ultraviolet rays. For this purpose, mention may be made of benzophenone or benzotriazole. The amount of ultraviolet absorbing agent added to the composition is generally from 0.2 to 5% by weight based on the dry weight of the lacquer composition.

When this is intended to be applied to a wooden surface inside a building, the quantity shall be located in the lower part of the range mentioned above and shall be preferably approximately 1%, by dry weight, whereas when the lacquer composition is intended to be applied to a wooden surface at
The outside therefore subjected to climatic constraints and in particular to a more intense ultraviolet radiation, it will be advantageous to use a quantity of ultraviolet ray absorber located in the upper zone of the range mentioned above.

 The composition according to the invention may be in the form of both an oil solution and an aqueous emulsion.

In a first embodiment of the invention, the composition of the varnish is in the form of an oil varnish and comprises in percentage by weight relative to the total weight:
- 24 to 55% of binder, especially a glycerophthalic resin (or alkyd);
- 39 to 75% of an organic vehicle;
0.1 to 5% of an opacifying component as defined above
0 to 10% of additives for varnishes, especially agents absorbing ultraviolet rays, siccatives, antioxidants, defoamers, fungicides, insecticides, thickeners and / or gelling agents.

 The glycerophthalic resin (or alkyd) can be replaced by any suitable resin of the type used as a binder in conventional organic vehicle paints, for example a modified alkyd urethane type alkyd resin.

 Organic vehicle is any type of organic vehicle usually used. Terpene hydrocarbons, for example turpentine, aliphatic hydrocarbons, for example "white-spirit", cyclohexane, chlorinated hydrocarbons, alcohols, for example methanol, isopropanol and alcohol, may be mentioned. benzyl, glycols, for example monoethylene glycol, diethylene glycol, ketones, for example cyclohexanone, methyl isobutyl ketone, esters, for example ethyl acetate and butyl acetate, these vehicles being used alone or as a mixture .

 The choice of vehicle depends essentially on the nature of the binder. Thus, for glycerophthalic coatings, aliphatic hydrocarbons are advantageously used.

In a second embodiment of the invention, the varnish is a water-based varnish, the binder consisting of any type of resin used in aqueous varnishes in the form of aqueous emulsions. Mention may be made of homopolymers, in particular polyacrylate, for example methyl polyacrylate, polymethacrylate, for example polymethyl methacrylate,
Polyacrylic acid, polyacrylonitrile, polyurethane resins, polyvinyl resins, polyester resins, polyamide resins, polystyrene resins, such as polyvinyl chloride, polyvinyl acetate, polyvinyl acetals, polystyrene, polyacrylates and polymethacrylates and copolymers, especially vinyl acetate / vinyl chloride, vinylidene chloride / acrylonitrile, styrene / butadiene and their derivatives and styrene / acrylic.

 When the varnish is a water-based varnish, the composition furthermore advantageously comprises from 0.1 to 5% of organic solvent acting as a coalescing agent.

 An organic solvent, for example a propylene glycol ether, will be used.

A preferred water-based varnish composition according to the invention comprises as a percentage by weight relative to the total weight
-40à65% of unliant;
0.1 to 5% of the opacifying agent described above
- 0 to 15% of various additives
0 to 5% of a coalescing agent;
- 20 to 40% demineralised water.

 When the opacifying agent comprises a mineral pigment, especially titanium oxide, an emulsifier for said mineral pigment is added to the varnish composition. Such emulsifiers are known to those skilled in the art and are, for example, sodium or ammonium polyacrylate.

 The additives used in the compositions of the invention include drying agents, anti-oxidants or anti-skin agents, anti-foam agents, fungicides, insecticides, bactericides, thickeners and / or gelling agents.

 The siccatives are those commonly used including organic acids of cobalt, zinc, zirconium, cesium and aluminum, alone or mixed. Mention may in particular be made of cobalt naphthenate alone or as a mixture with zirconium naphthenate and / or zinc naphthenate.

 As anti-skin agents, mention may be made of phenols, in particular alkylphenols, for example methoxyphenol and oximes, especially butyriloxime, methyl-ethyl-ketoxime and cyclohexanoneoxime, with oximes being preferred.

 The anti-foaming agents are advantageously silicones or mineral oils.

 As a fungicide, mention may be made of copper 8-quinolinate, azoles, especially a triazole, preferably azaconazole, propiconazole or tebuconazole, carbamates, in particular IPBC (3iodopropynylbutylcarbamate), and phenylsulfamides, in particular tolylfluanid and dichlofluanid.

 As thickener, polyurethanes or acrylics are advantageously used, alone or as a mixture.

 As a bactericidal preservative in the pot, isothiazolinone derivatives are advantageously used.

 As a gelling agent, a bentone is generally used.

 The compositions according to the invention are prepared by mixing the ingredients by any type of appropriate liquid-liquid mixing technique.

A preferred varnish composition according to the invention comprises in percentage by weight relative to the total weight of the composition:
50 to 60% of a binder composed of an aqueous emulsion of a polyacrylate or polymethacrylate;
1 to 2% of a polystyrene resin in the form of hollow beads whose particle size is between 0.1 and 10 μm, preferably 0.4 μm and 10 μm;
0.1 to 3% of matting agent;
0.1 to 2% of anti-ultraviolet agent;
0.1 to 2% of antifoam agent;
0.1 to 0.3% of bactericidal agent;
0.1 to 3% of a thickener;
- 0.5 to 2% of a drying retarder;
2-8% of a gelling agent;
0.5 to 5% of a film-forming agent;
- 20 to 40% demineralised water.

 The subject of the invention is also a process for coating a wood surface with a protective lacquer which does not substantially modify the color of the wood, characterized in that 0.1 to 5% of lacquer is added to the lacquer composition. weight relative to the total weight of said composition of an opacifying component diffusing all the visible light.

 The varnish composition according to the invention can be applied to any wood. It is particularly advantageous when it is to be applied on light wood for which it is desired to preserve as much as possible the original shade of the raw wood.

 The following woods can be mentioned: fir, pine, beech, spruce, birch, poplar, ash, hornbeam, oak, chestnut.

 It is intended to cover both the wooden surfaces inside the buildings, including the paneling and floors that are outside.

 For interior wooden surfaces, a water-based varnish composition is advantageously used, whereas for exterior surfaces it is desirable to use an oil-based varnish composition.

 The invention also more generally relates to the use in a protective coating for wood surface of an opacifying agent, diffusing in all the visible light, present in an amount ranging from 0.1 to 5% by weight, by relative to the total weight of said composition, so that said composition provides after drying a substantially colorless film not substantially modifying the hue of the substrate on which it is applied.

 The following is an example of a varnish composition according to the invention and the results obtained with this composition compared to those obtained with commercial varnishes.

EXAMPLE
A water varnish is prepared by mixing the following ingredients. The quantities are indicated in percentage by weight relative to the total weight:

<tb> Name <SEP> commercial <SEP> of <SEP> constituents <SEP> Percentage
<tb>#<SEP><SEP> Ropaque <SEP> OP <SEP> 62 <SE> LO <SEP> (Rohm <SEP> and <SEP> 1,5
<tb><SEP> Haas (1) <SEP>
<tb>#<SEP><SEP> Mowilith <SEP> LDM <SEP> 7965 <SEP> 53.4
<tb><SEP> Hoechst <SEP>(2><SEP>
<tb><SEP> Monopropylene Glycol <SEP> 1.5
<tb><SEP>#<SEP> Texanol <SEP><SEP> (Eastman <SEP> Kodak) (4) <SEP> 1,2
<tb><SEP> Water <SEP> demineralized <SEP> 31.8
<tb><SEP>#<SEP><SEP> Coatex <SEP> BR100 <SEP> SEPC <SEP> (SEPC) (5) <SEP> 0.4
<tb><SEP>#<SEP><SEP> Freeze <SEP> Bentone <SEP> EW <SEP> to <SEP> 3 <SEP>% <SEP> (6) <SEP> 6
<tb><SEP>#<SEP><SEP> CROSFIELD <SEP> HP <SEP> 240 (7) <SEP> 2
<tb><SEP> Ammonia <SEP> 22eB <SEP> 0.1
<tb><SEP>#<SEP><SEP> COATEX <SEP> THIXOL <SEP> 53L (8) <SEP> 0.5
<tb><SEP>#TEGO<SEP><SEP> 805 (9) <SEP> 0.6
<tb><SEP>#<SEP><SEP> Tinuvin <SEP> 1130 <SEP> nail <SEP> I
<tb> XMERGAL <SEP> K9N <SEP> (HOECHST) <SEP> (11) <SEP> 0.1
<tb> (1) opaque polymer: emulsion of hollow beads of opaque polymer.

(2) acrylic binder emulsion: copolymer dispersion of acrylic esters.

(3) drying retarding solvent: 1,2 propane diol.

(4) 2,2,4-trimethyl-1,3-monoisobutyrate coalescing solvent
pentanediol.

(5) polyurethane thickeners: water-soluble polyurethane in a mixture
water / 2-butoxy ethanol.

(6) bentone type thickener: modified smectite-based clay.

(7) matting silica: precipitated silica coated with paraffin wax.

(8) acrylic thickener: acrylic copolymer in aqueous dispersion.

(9) antifoam: organic modified polysiloxane emulsion.

(10) ultraviolet absorber: class of hydroxy phenyl benzotriazole.

 (11) bactericidal agent: emulsion based on isothiazolinone derivatives.

 This composition was applied to a spruce board and allowed to dry. The color difference AF obtained with respect to the uncoated board was measured.

 We also measured the color differences obtained with the same board covered with an oil varnish (Commercial V33 Clear Varnish) and a water varnish (Commercial V33 High Varnish Clear Varnish).

 The color difference was measured either in the CIELAB space or in the C.M.C. space.

Indeed, each point of color can be identified either by its rectangular coordinates L *, a *, b * or by its cylindrical coordinates
L *, C *, H * where:
L * represents clarity,
a * represents the chromatic component Green-Red,
b * represents the yellow-blue color component
and
L * represents clarity,
C * represents chroma (saturation),
H * represents the hue angle.

In the CIELAB space, the formula for measuring the color difference is as follows:

where dE is the total color difference
AL *, the difference of clarity
Sa *, the color gap in the Red-Green
Ab *, the color difference in Yellow-Blue
In the CMC space, some coordinates undergo an AL * AC * mathematical modification, in particular AL * becomes SL 'AC * becomes SC # H *
AH * becomes SH and the color difference formula becomes

 (the coordinates a and b remain unchanged).

 It may be noted that the cylindrical coordinates also undergo mathematical modifications in the C.M.C.

 The deviations on L *, C *, H * being respectively AL *, AC * and AH * in the space CIELAB, they become #L, #C and #H in the space C.M.C.

SL SC SH
But these differences (except #L) do not intervene in the calculation
SL of the total AE color difference.

The results are reported respectively in Tables I to
III below:
TABLE I
Color differences measured on a spruce board covered with the composition of Example 1 with respect to an uncoated wood board

<tb><SEP> Number <SEP> of <SEP> AE <SEP> AL * iSL <SEP> ta * <SEP> Ab * <SEP> AC * / SC <SEP> AH * / SH
<tb><SEP> measures
<tb><SEP> 1 <SEP> 1.89 <SEP> -1.38 <SEP> 1.08 <SEP> 0.74 <SEP> 0.60 <SEP> -1.14
<tb><SEP> 1 <SEP> 2 <SEP> 1.90 <SEP> -1.31 <SEP> 1.23 <SEP> 1.03 <SEP> 0.88 <SEP> -1.05
<tb><SEP> 3 <SEP> 1.64 <SEP> -1.36 <SEP> 0.74 <SEP> 0.85 <SEP> 0.58 <SEP> -0.73
<tb><SEP> 1 <SEP> 1.71 <SEP> -1.24 <SEP> 0.94 <SEP> 0.98 <SEP> 0.74 <SEP> -0.93
<tb><SEP> 2 <SEP> 2 <SEP> 1.75 <SEP> -1.17 <SEP> 1.13 <SEP> 1.23 <SEP> 0.98 <SEP> -0.85
<tb><SEP> 3 <SEP> 1.54 <SEP> -1.21 <SEP><SEP> 0.64 <SEP> 1.12 <SEP> 0.74 <SEP> -0.59
<tb><SEP> 1 <SEP> 1.68 <SEP> -1.21 <SEP> 0.92 <SEP> 0.99 <SEP> 0.75 <SEP> -0.91
<tb><SEP> 3 <SEP> 2 <SEP> 1.72 <SEP> -1.14 <SEP> 1.12 <SEP> 1.24 <SEP> 0.98 <SEP> -0.83
<tb><SEP> 3 <SEP> 3 <SEP><SEP> 1.51 <SEP> -1.18 <SEP> 0.63 <SEP> 1.14 <SEP> 0.75 <SEP> -0 57
<tb><SEP> 1 <SEP> 1.89 <SEP> -1.30 <SEP> 1.04 <SEP> 1.25 <SEP> 0.93 <SEP><SEP> -1.01 <SEP >
<tb><SEP> 4 <SEP> 2 <SEP> 1.94 <SEP> -1.23 <SEP> 1.30 <SEP> 1.53 <SEP> 1.19 <SEP> -0.92
<tb><SEP> 3 <SEP> 1.70 <SEP> -1.28 <SEP> 0.71 <SEP> 1.43 <SEP> 0.94 <SEP> -0.63
<tb><SEP> 1 <SEP> 2.90 <SEP> -2.11 <SEP> 1.62 <SEP> 1.52 <SEP> 1.18 <SEP> -1.61
<tb><SEP> 5 <SEP> 2 <SEP> 2.93 <SEP> -2.00 <SEP> 1.90 <SEP> 1.96 <SEP> 1.58 <SEP> -1.44
<tb> ~ <SEP> 3 <SEP> 2.58 <SEP> -2.07 <SEP> 1.11 <SEP> 1.74 <SEP> 1.16 <SEP> -1.02
<Tb>
TABLE II
Color differences measured on a board of spruce covered with the V33 glycerophthalic varnish composition compared to a raw wood board

<tb> Number <SEP> of <SEP> AE <SEP> AL * / SL <SEP> Aa * <SEP> Ab * <SEP> AC * / SC <SEP> AH * / S <SEP> H <SEP>
<tb> measures
<tb><SEP> 1 <SEP> 6.35 <SEP> -1.91 <SEP> 1.81 <SEP> 9.17 <SEP> 6.03 <SEP> -0.52
<tb> 1 <SEP> 2 <SEP> 6.46 <SEP> -1.66 <SEP> 3.23 <SEP> 9.60 <SEP> 6.25 <SEP> -0.15
<tb><SEP> 3 <SEP> 6.65 <SEP> -1.76 <SEP> 1.22 <SEP> 10.40 <SEP> 6.40 <SEP> -0.28
<tb><SEP> 1 <SEP> 6.35 <SEP> -1.79 <SEP> 1.60 <SEP> 9.29 <SEP> 6.09 <SEP> -0.32
<tb> 2 <SEP> 2 <SEP> 6.44 <SEP> -1.55 <SEP> 3.07 <SEP> 9.66 <SEP> 6.25 <SEP> -0.33
<tb><SEP> 3 <SEP> 6.69 <SEP> -1.64 <SEP> 1.08 <SEP> 10.54 <SEP> 6.48 <SEP> -0.14
<tb><SEP> 1 <SEP> 6.32 <SEP> -1.72 <SEP> 1.51 <SEP> 9.29 <SEP> 6.08 <SEP> -0.23
<tb> 3 <SEP> 2 <SEP> 6.40 <SEP> -1.48 <SEP> 2.99 <SEP> 9.64 <SEP> 6.22 <SEP> -0.41
<tb><SEP> 3 <SEP> 6.67 <SEP> -1.58 <SEP> 1.02 <SEP> 10.54 <SEP> 6.48 <SEP> -0.09
<tb><SEP> 1 <SEP> 6.31 <SEP> -1.83 <SEP> 1.70 <SEP> 9.17 <SEP> 6.02 <SEP> -0.43
<tb> 4 <SEP> 2 <SEP> 6.41 <SEP> -1.59 <SEP> 3.15 <SEP> 9.56 <SEP> 6.20 <SEP> -0.22
<tb><SEP> 3 <SEP> 6.62 <SEP> -1.69 <SEP><SEP> 1.15 <SEP> 10.40 <SEP> 6.40 <SEP> -0.22
<tb><SEP> 1 <SEP> 6.51 <SEP> -1.83 <SEP> 1.65 <SEP> 9.53 <SEP> 6.24 <SEP> -0.33
<tb> 5 <SEP> 2 <SEP> 6.60 <SEP> -1.58 <SEP> 3.16 <SEP> 9.90 <SEP> 6.40 <SEP> -0.33
<tb><SEP> 3 <SEP> 6.86 <SEP> -1.68 <SEP> 1.11 <SEP> 10.81 <SEP> 6.65 <SEP> -0.15
<Tb>
TABLE III
Color differences measured on a board of spruce covered with the composition of Varnish Clear High Decoration V33 compared to a plank of raw wood

<tb> Number <SEP> of <SEP> AE <SEP> AL * / SL <SEP> Sa * <SEP> Ab * <SEP> AC * iSC <SEP> SH * / SH <SEP>
<tb> measures
<tb><SEP> 1 <SEP> 4.80 <SEP> -1.35 <SEP> 0.52 <SEP> 6.88 <SEP> 4.60 <SEP> 0.37
<tb> 1 <SEP> 2 <SEP> 4.82 <SEP> -1.19 <SEP> 1.72 <SEP> 7.05 <SEP> 4.61 <SEP> 0.75
<tb><SEP> 3 <SEP> 5.08 <SEP> -1.25 <SEP> 0.28 <SEP> 7.77 <SEP> 4.91 <SEP> 0.33
<tb><SEP> 1 <SEP> 4.91 <SEP> -1.35 <SEP> 0.47 <SEP> 7.04 <SEP> 4.70 <SEP> 0.43
<tb> 2 <SEP> 2 <SEP> 4.92 <SEP> -1.19 <SEP> 1.70 <SEP> 7.21 <SEP> 4.70 <SEP> 0.83
<tb><SEP> 3 <SEP> 5.19 <SEP> -1.25 <SEP> 0.24 <SEP> 7.96 <SEP> 5.03 <SEP> 0.38
<tb><SEP> 1 <SEP> 5.13 <SEP> -1.55 <SEP> 0.86 <SEP> 7.28 <SEP> 4.89 <SEP> 0.07
<tb> 3 <SEP> 2 <SEP> 5.19 <SEP> -1.37 <SEP> 2.11 <SEP> 7.54 <SEP> 4.98 <SEP> 0.52
<tb><SEP> 3 <SEP> 5.40 <SEP> -1.44 <SEP> 0.51 <SEP> 8.22 <SEP> 5.21 <SEP> 0.15
<tb><SEP> 1 <SEP> 6.02 <SEP> -1.56 <SEP> 1.34 <SEP> 8.61 <SEP> 5.81 <SEP> -0.23
<tb> 4 <SEP> 2 <SEP> 6.15 <SEP> -1.34 <SEP> 2.71 <SEP> 9.00 <SEP> 5.98 <SEP> -0.40
<tb><SEP> 3 <SEP> 6.34 <SEP> -1.42 <SEP> 0.85 <SEP> 9.74 <SEP> 6.17 <SEP> -0.05
<tb><SEP> 1 <SEP> 5.58 <SEP> -1.40 <SEP> 1.06 <SEP> 8.03 <SEP> 5.40 <SEP> -0.03
<tb> 5 <SEP> 2 <SEP> 5.67 <SEP> -1.20 <SEP> 2.36 <SEP> 8.34 <SEP> 5.52 <SEP> -0.53
<tb><SEP> 3 <SEP> 5.89 <SEP> -1.27 <SEP> 0.66 <SEP> 9.07 <SEP> 5.75 <SEP> -0.07
<Tb>
Large aperture / spectrum Incl.

1) Du5 / 1 0 deg (daylight illuminant) 2) A / 10 deg (incandescent type artificial light) 3) CWF / 10 deg (fluorescent artificial light)
It is clearly seen that the color difference is markedly less pronounced for wood coated with a varnish according to the invention compared to varnishes of known type, the color difference being in particular markedly reduced in yellow-blue.

Claims (14)

 1. Protective varnish composition for wooden surfaces, comprising at least one film-forming binder and a vehicle for said binder, characterized in that it further comprises at least one opacifying agent which diffuses in all the visible light, present in an amount of from 0.1 to 5% by weight, based on the total weight of said composition, so that said composition provides after drying a substantially colorless film not substantially modifying the hue of the substrate on which it is applied.  2. protective lacquer composition for wood surfaces according to claim 1, characterized in that the opacifying agent is a white mineral pigment.  3. Protective varnish composition for wooden surfaces according to claim 1 or 2, characterized in that it comprises from 0.1% to 2%, preferably about 1% by weight of inorganic pigment, especially titanium oxide. , zinc oxide or lithopone, alone or in admixture.  4. Protective varnish composition for wooden surfaces according to claim 1, characterized in that the opacifying agent is an opaque organic polymer for introducing air into the varnish film after application and drying of said varnish composition .  5. protective lacquer composition for wooden surfaces according to claim 4, characterized in that it comprises from 0.5 to 5% by weight, especially from 1 to 3% by weight, preferably about 1.5% by weight a polymer in the form of vesicles whose cavity contains encapsulated water.  6. Protective varnish composition for wooden surfaces according to claim 1, characterized in that it contains a white mineral pigment and an opaque organic polymer for introducing air into the varnish film after application and drying of said varnish composition.  7. protective lacquer composition for wooden surfaces according to one of the preceding claims, characterized in that it further contains an ultraviolet ray absorber.  8. Protective varnish composition for wooden surfaces according to one of the preceding claims, characterized in that it is in the form of a solution in an oil.  9. Protective varnish composition for wooden surfaces, characterized in that it is in the form of an aqueous emulsion.  10. Protective varnish composition for wooden surfaces according to claim 1, characterized in that it comprises in percentage by weight relative to the total weight of the composition:  25 to 55% of binder, in particular a glycerophthalic resin;  - 39 to 75% of an organic vehicle;  0.1 to 5% of an opacifying component as defined in claim 2 or claim 3;  0 to 5% of additives for varnishes, especially agents absorbing ultraviolet rays, siccatives, antioxidants, defoamers, fungicides, insecticides, thickeners and / or gelling agents.  11. protective lacquer composition for wooden surfaces according to claim 1, characterized in that it comprises in percentage by weight relative to the total weight of the composition:  40 to 65% of binder in the form of an aqueous emulsion of a polymer resin;  0.1 to 5% of an opacifying component as defined in claim 2 or claim 3;  0 to 5% of a coalescing agent;  0 to 15% of additives for varnishes, in particular ultraviolet absorbers, siccatives, antioxidants, anti-foam agents, fungicides, insecticides, thickeners and / or gelling agents;  - 20 to 40% demineralised water.  12. Protective varnish composition for wooden surfaces according to claim 11, characterized in that it comprises in percentage by weight relative to the total weight of the composition:  50 to 60% of a binder composed of an aqueous emulsion of a polyacrylate or polymethacrylate;  1 to 2% of a polystyrene resin in the form of hollow beads whose particle size is between 0.1 to 10 μm, preferably 0.4 μm and 10 μm;  0.1 to 3% of matting agent;  0.1 to 2% of anti-ultraviolet agent;  0.1 to 2% of antifoam agent;  0.1 to 0.3% of bactericidal agent;  0.1 to 3% of a thickener;  - 0.5 to 2% of a drying retarder;  2-8% of a gelling agent;  0.5 to 5% of a film-forming agent;  - 20 to 40% demineralised water.  13. A method for coating a wooden surface with a protective varnish which does not substantially modify the color of the wood, characterized in that 0.1 to 5% by weight relative to the total weight is added to the varnish composition. of said composition of an opacifying component diffusing all the visible light.  14. Use in a protective coating for a wooden surface of an opacifying agent diffusing all the visible light, present in an amount ranging from 0.1 to 5%, relative to the total weight of said composition, so that said After drying, the composition provides a substantially colorless film that does not substantially change the color of the substrate to which it is applied.