(19)
(11)EP 2 563 866 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
05.08.2015 Bulletin 2015/32

(21)Application number: 11715568.9

(22)Date of filing:  22.04.2011
(51)International Patent Classification (IPC): 
C09D 7/00(2006.01)
C09D 7/12(2006.01)
(86)International application number:
PCT/EP2011/056491
(87)International publication number:
WO 2011/134907 (03.11.2011 Gazette  2011/44)

(54)

IMPROVED LOW TITANIUM DIOXIDE COATINGS

VERBESSERTE BESCHICHTUNGEN MIT GERINGEM TITANDIOXIDANTEIL

REVÊTEMENTS AMÉLIORÉS À FAIBLE TENEUR EN DIOXYDE DE TITANE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 27.04.2010 US 328383 P
27.04.2010 EP 10161203

(43)Date of publication of application:
06.03.2013 Bulletin 2013/10

(73)Proprietor: Akzo Nobel Coatings International B.V.
6824 BM Arnhem (NL)

(72)Inventors:
  • WHEELER, Stephen, Arthur
    Slough Berkshire SL1 2HP (GB)
  • BARCOCK, Richard
    Aylesbury Buckinghamshire HP22 5YR (GB)
  • PEARCE, Colin
    Aylesbury Buckinghamshire HP18 9DW (GB)
  • JEFFERSON, Gary
    Reading Berkshire RG30 2SR (GB)
  • WOODS, Anthony, David
    Slough Berkshire SL1 6NG (GB)
  • EMMETT, Simon, Nicholas
    Egham Surrey TW20 0NS (GB)
  • PEREZ-AMOROS, Javier
    Reading Berkshire RG1 3LJ (GB)

(74)Representative: Akzo Nobel IP Department 
Velperweg 76
6824 BM Arnhem
6824 BM Arnhem (NL)


(56)References cited: : 
EP-A2- 0 113 435
US-A- 5 201 948
US-A- 4 277 385
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description


    [0001] This invention relates to reduced energy content pigmented coating compositions, especially pigmented paints of low to medium sheen, also known as matt or soft sheen paints. In particular it relates to paints of pigment volume content from 78 to 85% and having sheen of less than 30% when measured at 85°.

    [0002] Light coloured pigmented paints usually contain high levels of titanium dioxide, TiO2. This is because such pastel shades are predominantly white with a small amount of non-white colour added. Titanium dioxide is the best source of whiteness due to its high refractive index relative to typical binders used in paints. Unfortunately, TiO2 requires large amounts of energy to extract it from the ground and then purify. In fact, in known high pigment volume content (PVC) paints of pastel/light colour, for example matt whites and matt light shades as hereinbelow described, the high TiO2 content (typically 10 to 20vol%) used to achieve the desired colour and opacity is the main contributor to the total energy content of the paint.

    [0003] By energy content, we mean the energy required to extract, refine and manufacture the ingredients comprising the paint; and the energy required to manufacture the paint itself.

    [0004] Since most energy is generated by burning fossil fuel, high energy content usually results in high carbon dioxide emissions - hence the use of the alternative measure 'embedded CO2' to indicate the energy content.

    [0005] The adverse effect of such emissions on the global environment, especially climate change, is generally accepted by most serious commentators. Thus there is a need to reduce the energy consumed in producing such paints.

    [0006] One approach to this is to reduce the TiO2 content of the paint. However, this simply reduces the opacity of the dried coating and, whilst each coat of dried paint may well have reduced energy content, additional coats will be required in order to achieve opacity. Consequently, any benefit is lost or at least, significantly diminished. Other approaches replace some or all of the TiO2 with extender pigments such as chalk. Whilst such extenders require less energy than TiO2 to extract and refine, the lower refractive index of such extenders is very close to the binders used in paint. As such, they do not scatter light as well as TiO2 and in order to compensate for the reduced amount of TiO2 more extender must be added to the paint to achieve the correct colour and opacity. However, this raises the PVC further, eventually to the extent that air is trapped in the dried paint film. Whilst this increases the opacity, it also usually results in poorer wet scrub resistance.

    [0007] One possible way out of this dilemma is to use calcined clay as this has good opacity and is less detrimental to the scrub resistance. However, manufacture of calcined clay requires clay to be heated to 1000°C thereby consuming large amounts of energy. Clearly, this does not result in significant energy savings and is thus not a preferred option.

    [0008] United States Patent US 4,277,385 discloses paint compositions having PVC between 75 and 85% and further teaches that to avoid cracking in high PVC paint films, the formulation should be free of non-opacifying inorganic pigments (another name for extenders) essentially replacing them with non-film forming solid polymer particles. However, no attempt is made to minimise the TiO2 content in these formulations and, thus the problem of high energy content and high CO2 emissions are not addressed. European Patent application EP 0113435 describes an aqueous paint having reduced TiO2 content at PVC from 20 to 80%. It teaches to use mixtures comprising pigmented vesiculated polymer beads and larger opaque polymer particles having microvoids- but no pigments, to replace TiO2 whilst maintaining burnish/scrub resistance. However, as pointed out in that application, pigmented vesiculated polymer beads themselves contain TiO2 and thus add considerably to the TiO2 content. This does little, if anything, to reduce the total energy content of the paint. Pigmented vesiculated polymer beads are polymer particles containing both and TiO2 microvoids.

    [0009] Thus, there is a need for improved paint compositions having reduced TiO2 content and thus low energy content whilst also having good opacity and good wet scrub resistance.

    [0010] Accordingly, there is provided an aqueous pigmented coating composition having a PVC of from 78 to 85% comprising, based on the total volume solids of the dry coating unless otherwise stated,
    1. a) opacifying pigment particles comprising
      1. i) from 3 to 10% titanium dioxide
      2. ii) from 0 to 20% of hollow polymeric particles
    2. b) non-opacifying extender particles comprising
      1. i) calcium magnesium carbonate and/or
      2. ii) calcium carbonate and/or
      3. iii) nepheline syenite and/or
      4. iv) kaolin
      wherein i)+ii)+iii)+iv) = 40 to 80% and iv) is 0 to 20%
    3. c) polymer binder particles of calculated Fox Tg of from 5 to 25°C having an acid value of from 15 to 65mg KOH/g of polymer and wherein the polymer particles are derived from acrylic monomers and optionally further comprising styrene and/or its derivatives
    4. d) dispersant having a weight average molecular weight of at least 3500 Daltons and selected on the basis that the demand for dispersant of a mixture of the opacifying pigment particles, other than the hollow polymeric particles, of a), and the extender particles of b) is greater than 0.35wt%, calculated on the weight of the titanium dioxide and extender particles, as determined by the method hereinbelow described
    5. e) fugitive coalescing solvent
    wherein the composition is free of non-fugitive coalescing solvent

    [0011] Preferably the pigment volume content is from 79 to 85, more preferably from 80 to 85, even more preferably from 80 to 84 and most preferably from 81 to 83%. Any difference between the actual PVC and the sum of a) and b) is made up with other non-opacifying extender pigments as defined hereinbelow.

    [0012] Preferably, the opacifying pigment particles are white.

    [0013] More preferably, the opacifying pigment particles consist of TiO2 and hollow polymer particles. Even more preferably, the opacifying pigment particles consist of TiO2 only. TiO2 produced by the well known chloride process is preferred in this invention as it requires less energy to manufacture and thus introduces less embedded CO2 to the coating.

    [0014] The titanium dioxide is preferably in the rutile form as anatase is a less efficient scatterer and thus more is required to achieve the same degree of opacity.

    [0015] Preferably the TiO2 comprises 3 to 9, more preferably from 3 to 8, even more preferably from 5 to 8, yet more preferably from 6 to 8, still more preferably from 5 to 7 and most preferably from 6 to 7vol% of the composition.

    [0016] Hollow polymeric, preferably spherical, particles may also be used to provide white opacity. Suitable such particles contain a void of from 30 to 50% by vol of the particle. Such particles are available as aqueous dispersions under the tradename Ropaque™. However, the composition preferably contains less than 10% by volume of such polymeric hollow sphere white pigments because they contribute significantly to the energy content of the paint. Additionally, they tend to provide unwanted gloss to the dried paint film following drying. More preferably, the composition is free of such hollow polymeric particles.

    [0017] Similarly, calcined clay, a white pigment may be used as a partial replacement for TiO2. However, since the production of calcined clay is itself energy intensive, care must be taken to limit the amount of calcined clay used in the formulation. To take maximum advantage of the energy savings to be made it is preferred that the coating composition is free of calcined clay. Nevertheless, preferably, up to 30vol% of calcined clay may be used, more preferably from 5 to 20vol% and most preferably from 10 to 15vol%. Pigmented vesiculated polymer beads are also preferably avoided.

    [0018] Of course, coloured opacifying pigments of different hue may also be added to the compositions of the present invention, in addition to the other opacifying pigment particles, to produce pastel/light colours as discussed in greater detail hereinbelow.

    [0019] By non-opacifying extender particles is meant inorganic particles that have a refractive index the same as or similar to that of the polymer binder. Since the opacifying strength of a particulate material is a consequence of the difference in refractive index of the material and the medium in which it is dispersed and its particle size, such extenders are regarded essentially as non-opacifiers, see page 35 to 37, Paint and Surface Coatings - theory and practice edited by R.Lambourne and published by John Wiley and Sons. That is not to say that they do not contribute to opacity at all but rather that any contribution is small in comparison to TiO2.

    [0020] Extenders are usually not pure white and can provide some grey or yellow hue to the coating.

    [0021] Suitable examples of non-opacifying extender particles include calcium magnesium carbonate, calcium carbonate, nepheline syenite, kaolin, talc, silica, diatomaceous silica, mica and calcium sulphate. Preferably, the non-opacifying extender particles are selected from the group consisting of calcium magnesium carbonate, calcium carbonate, nephelene syenite and kaolin. Preferably, the non-opacifying extender particles are selected from the list consisting of calcium magnesium carbonate, calcium carbonate, nephelene syenite and kaolin. Even more preferably they are selected from the group consisting of calcium magnesium carbonate, calcium carbonate and kaolin.

    [0022] The mineral known as dolomite is a convenient and cost effective source of calcium magnesium carbonate, CaMg(CO3)2. Dolomite is a preferred source of calcium magnesium carbonate for use in the present invention. It is available in powder form of differing mean particle sizes.

    [0023] Suitable forms of calcium carbonate include calcite including precipitated calcite. Socal P3 is an example of suitable precipitated calcium carbonate, in the form of calcite. A suitable ground calcium carbonate is Omyacoat 850 OG.

    [0024] Nepheline syenite can be used to partly or wholly replace the calcium carbonate

    [0025] Kaolin, Al2Si2O5(OH)4, is a type of clay. Adding kaolin above 20vol% to the composition (based on the dry coating) results in poor wet scrub resistance. Furthermore, at such high levels of kaolin, the coating viscosity is too high to allow easy application using conventional application techniques-such as rollers or brushes-and allow the paint to flow to produce an acceptably smooth finish. Advantageously, the amount of kaolin should be from 0.5 to 20, more preferably from 5 to 15 and most preferably from 6 to 12vol%.

    [0026] Preferably, the non-opacifying extender particles comprise from 50 to 75, more preferably from 50 to 70 and most preferably from 55 to 67vol% of the dry coating.

    [0027] Advantageously, from 20 to 50% of the total volume solids of the dry coating should comprise extender particles having mean particle size d50 of ≤2 microns. This ensures that the TiO2 particles are sufficiently spaced apart so that scattering is efficient and therefore opacity optimised.

    [0028] The particle sizes of the extenders are quoted as d50 diameters. This means that 50% of the particles by volume are below this diameter.

    [0029] The binder comprises an aqueous dispersion of polymer binder particles, often referred to as latex. More preferably, such dispersions are made using emulsion polymerisation methods.

    [0030] For simplicity, the word 'polymer' in this specification is used to cover homopolymers and copolymers comprising two or more monomer variants.

    [0031] The polymer comprising the binder particles is preferably a styrene-acrylic copolymer or a pure acrylic.

    [0032] By pure acrylic is meant that the polymer is derived only from monomers selected from the esters of acrylic acid and methacrylic acid and the acids themselves.

    [0033] By styrene-acrylic is meant that some styrene and/or its copolymerisable derivatives are copolymerised in the polymer. Suitable such styrene derivatives include α-methyl styrene and vinyl toluene.

    [0034] More preferred are styrene-acrylic polymer particles as these require the least amount of energy to produce them compared to the pure acrylics and most preferably, the polymer binder in the present invention is derived from styrene, butyl acrylate and a copolymerisable acid. Most preferably, the copolymerisable acid is acrylic acid and/or methacrylic acid.

    [0035] Preferably the binder level of the coating is from 5 to 20%, more preferably 5 to 15 and most preferably from 8 to 15% calculated on volume solids.

    [0036] Suitable acrylic monomers include alkyl esters of acrylic or methacrylic acid such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, ethyl acrylate, butyl acrylate, hexyl acrylate, n-octyl acrylate, lauryl methacrylate, 2-ethylhexyl methacrylate, nonyl acrylate,decyl acrylate, benzyl methacrylate, isobutyl methacrylate, isobornyl methacrylate the hydroxyalkyl esters of the same acids such as 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and 2-hydroxypropyl methacrylate.

    [0037] The acid value of the polymer is preferably from 15 to 60, more preferably from 15 to 55, even more preferably from 15 to 45 and most preferably from 16 to 30mg KOH/g non-vol polymer. Below an acid value of 15mg KOH/g polymer produces dried paint of poorer wet scrub resistance, whilst above 65 mg KOH/g polymer tends to degrade the wet scrub resistance of the dried paint.

    [0038] The acid value is varied by copolymerising acid functional monomers into the polymer comprising the particles. Suitable such monomers include acrylic acid, methacrylic acid and maleic acid or its anhydride. Preferably, the acid used is acrylic acid.

    [0039] Polymers of mean particle size no more than 0.3 µm are preferred as they are better at binding together the particulate components of the composition.

    [0040] Preferably the number average mean particle size of the polymer particles is from 0.05 to 0.30 µm, more preferably from 0.07 to 0.15 µm and most preferably from 0.08 to 0.14 µm. The number refers to the diameter of the particles. The smaller particle size is preferred as it results in improved scrub resistance, which is particularly important at the high PVC of the present invention.

    [0041] The glass transition temperature, Tg, of the polymer binder can be adjusted by the choice of monomers and the relative amounts of each comprising the polymer. Preferably, it is from 6 to 21°C, more preferably from 6 to 19°C, even more preferably from 6 to 16°C, ..

    [0042] For the avoidance of doubt, any reference to Tg in this specification is to calculated Fox Tg unless otherwise stated.

    [0043] When higher Tg polymers are used, more coalescing and/or plasticizing solvents are required to enable a coherent coating film to form at normal room temperature of approximately 20 to 25°C. Lower Tg polymers are preferred as these can film form effectively with reduced levels of solvents thereby keeping both the volatile organic content of the paint and the energy content of the paint to a minimum.

    [0044] Pigment dispersants generally comprise a hydrophilic portion and a hydrophobic portion and, depending on the nature of the dispersing medium and the pigment surface, one portion will have a greater affinity for the pigment surface and the other portion for the dispersing medium. In this way a stable dispersion of pigment dispersed in the medium can be produced.

    [0045] In the present invention, the dispersant is required to disperse and stabilise the non-polymeric opacifying pigments (including any colour pigments) and non-opacifying extender particles. The weight average molecular weight of the dispersant must be at least 3500 Daltons and the dispersant demand according to the test method described hereinbelow must be greater than 0.35wt% of non-vol dispersant calculated on the weight of the inorganic opacifying pigments and non-opacifying extender particles. Dispersants which do not satisfy these two requirements produce dried films which are unacceptable for wet scrub resistance.

    [0046] Preferably, the weight average molecular weight of the dispersant is at least 4000, more preferably 5000 and most preferably 6000 Daltons. The upper limit of the weight average molecular weight is preferably 50000 Daltons, more preferably 40000, even more preferably 30000, still more preferably 20000 and most preferably 15000 Daltons. The most preferred average molecular weight of the dispersant is from 3500 to 20000 Daltons.

    [0047] The dispersant demand is the minimum amount of dispersant which, when added to a dispersion of non-polymeric opacifying pigment particles (including any colour pigments), and extenders, produces a minimum viscosity. By minimum viscosity is meant that further addition of dispersant, usually as a solution, does not produce any further drop in viscosity.

    [0048] A suitable method to estimate the dispersant demand includes the following steps;i) gradually add dispersant to an aqueous dispersion of the non-polymeric opacifying pigment (including any colour pigments) and extender particles and monitor the viscosity of the resulting mixture to determine the minimum viscosity and ii) identify the minimum amount of dispersant added to reach the minimum viscosity as the dispersant demand.

    [0049] An even more preferred method is described in the test procedures. Suitable dispersants for use in the present invention include Orotan™ 681, Orotan™ 731 and Orotan 2002. Each of these has molecular weight greater than 3500 Daltons and the dispersant demand is in accordance with the test. Dispex HDN is another dispersant suitable for use in the present invention and is described by the manufacturer as 'a hydrophobic sodium salt of an acrylic copolymer'.

    [0050] The method for estimating the dispersant demand is described hereinbelow.

    [0051] Pastel colours are usually produced by adding small amounts of various colour pigments, in the form of a concentrated dispersion (also known as colorants or tinters), to a white paint.

    [0052] In order to achieve the desired scrub resistance it is important that the coalescing solvent is fugitive, meaning that it must leave the paint film. Depending on the solvent and the polymer composition of the binder, this may happen very quickly or may take some days. For guidance, we have found that a coating such as example 1 of the invention (2wt% Texanol on liquid paint) contains only 0.06wt% of Texanol in the film after 24 hrs of drying under drying ambient conditions and only 0.01wt% after a further six days

    [0053] Preferably, the fugitive coalescing solvent is able to reduce the calculated Fox Tg of the polymer to from -10 to -80°C, more preferably to from -10 to -60°C, even more preferably to from -10 to -40°C and most preferably to from -10 to -20°C. The reduction is preferably achieved using up to 4wt%, even more preferably up to 3wt%, yet more preferably up to 2wt%, still more preferably up to 1% and most preferably up to 0.5wt% calculated on the liquid formulation.

    [0054] The extent to which a coalescing solvent reduces the calculated Fox Tg of a particular polymer may be calculated according to equation 1:

    where Tgp and Tgs is the glass transition temperature of the polymer and the solvent respectively

    Tg is the glass transition temperature of the plasticised system

    Vp and Vs are the volume fractions of the polymer and the solvent respectively

    α is a factor accounting for small changes in plasticising efficiency and is assumed to be 1 for the purposes of this invention.



    [0055] Suitable fugitive coalescing solvents include Lusolvan™ FBH (di-isobutyl ester of a mixture of dicarboxylic acids), Lusolvan™ PP (di-isobutyl ester of a mixture of dicarboxylic acids), Loxanol™ EFC 300 (linearic ester), Buty Carbitol™, Butyl Cellosolve, Dowanol™ EPh (ethylene glycol phenyl ether), Dowanol™ PPh (propylene glycol phenyl ether), Dowanol TPnB (tripropylene glycol n-butyl ether), ™Dowanol DPnB, DBE_9™ (a mixture of refined dimethyl gluterate and dimethyl succinate), Eastman DB™ solvent, Eastman EB™ (ethylene glycol monbutyl ether), Texanol™ (2,2,4-trimethyl-1,3-pentanediol monoisobutyrate), Dapro™ FX 511, Velate™ 262, Arcosolve™ DPNB, Arcosolve™ TPnB and benzyl alcohol.

    [0056] A list of solvents and their glass transition temperatures can be found in the article 'An Applied Approach to Film Formation' by JW Taylor and TD Klots, presented at the 29th Annual Waterborne, High Solids and Powder Coatings Symposium.

    [0057] Some representative glass transition temperatures of solvents are listed below:
    Pamolyn™ 300 -80°C
    Texanol™ -84°C
    Arcosolv™ PtB -88°C
    Carbitol ™Acetate -95°C
    Butyl carbitol™ acetate -100°C
    Thickeners are used in coating compositions to control the viscosity and rheology profile of the compositions. Suitable rheology modifiers for use in the present invention include carboxymethyl cellulose types such as Blanose™ 731; hydroxyethyl cellulose such as Natrosol™ 250 and Tylose™ H grades; hydrophobically modified hydroxyethyl cellulose such as Natrosol™ plus and Tylose™ HX grades; ethyl and ethylmethyl hydroxyethyl cellulose such as Beromocoll™ EHM grades; non-ionic synthetic associative thickener (NSAT's) such as Acrysol™ RM825, Acrysol™ SCT 275, Acrysol™ RM2020, Aquaflow™ NHS300, Coapur™ 830W, Rheolate™ 450, Bermodol™ PUR grades; hydrophobically modified alkali swellable emulsion (HASE) thickeners such as Acrysol™ TT935, Acrysol™ DR73, Ciba Rheovis™; Alkali swellable synthetic thickeners (ASST).

    [0058] The NSAT, HASE, ASST and HEUR type thickeners are preferred over the cellulosic types.

    [0059] The benefits of the invention are advantageously achieved in coloured coating compositions normally requiring high levels of TiO2. Such colours are the greys and lightly coloured coatings, often referred to as pastel or light colours, and of course, the whites.

    [0060] These, and all colours, can be defined using the well known Y, C*, h* system. In the system, any colour can be represented by
    1. i. its hue, depicted by h*
    2. ii. its chroma, C*,
    3. iii. its light reflectance value, Y


    [0061] These terms are defined scientifically by the Commission Internationale de l'Eclairage (CIE) [see 'International Lighting Vocabulary', 4th Edition, published IEC/CIE 017.4-1987. ISBN 978 3 900734 077].

    [0062] For the avoidance of any doubt, any reference to coating colour in this specification is to the colour of the coating when dry, unless otherwise stated.

    [0063] Hue is a measure of how close the colour is to red, yellow, green and blue. It is depicted by hue angle ranging from 0 to 360° where the angle defines the position of the hue in colour space, where red, yellow, green and blue are at angles of 0, 90, 180 and 270° respectively. Angles between these 'cardinal points' indicate intermediate colours eg a hue angle of 45° is a reddish yellow (orange) colour.

    [0064] Chroma is a measure of colour intensity, ie the extent to which it is either a pastel/ light colour or a strong colour or something in between. Chroma can take values from 0 to 100 with the higher numbers indicating stronger colours. Colours having a chroma value of 0 are 'neutral' greys lying on an axis from black to white.

    [0065] The light reflectance value is a measure of the perceived lightness of the colour, ranging from 0 to 100, with 0 representing black and 100 white.

    [0066] Figure 1 shows a simplified representation of the Y, C*, h* system. It shows a slice of colour space at about the mid point of the light reflectance value, Y, range. The Y axis runs from 0 to 100. Red, yellow, green and blue are shown in their appropriate positions on the hue, circle. The C* axis runs from zero at the origin to 100 at the perimeter. At each value of Y, further slices of hue are associated representing lighter and darker colours. At both the dark and the light end of the Y scale, the colours are less intense, and thus chroma is inevitably low. For this reason, colour space is often depicted as a sphere, although in truth it is more an irregular cylinder in shape.

    [0067] Using the CIE notation, the grey or light coloured compositions which benefit most from the present invention, can be identified as those colours, including whites, satisfying the following criteria;



    where m and Ccritical take the values in Table 1 below.
    Table 1
    Hue angle h*MCcritical
    0 0.098 39.063
    10 0.063 42.739
    20 0.231 40.130
    30 0.399 37.522
    40 0.498 37.444
    50 0.579 38.000
    60 0.655 39.500
    70 0.732 41.000
    80 0.793 45.286
    90 0.854 49.571
    100 0.803 47.136
    110 0.740 43.955
    120 0.663 41.727
    130 0.580 39.909
    140 0.498 38.565
    150 0.416 37.696
    160 0.346 37.381
    170 0.318 39.586
    180 0.283 40.850
    190 0.190 39.350
    200 0.101 38.000
    210 0.060 38.000
    220 0.021 38.333
    230 -0.007 40.000
    240 -0.041 40.314
    250 -0.083 38.600
    260 -0.125 36.886
    270 -0.167 35.171
    280 -0.152 34.640
    290 -0.131 34.240
    300 -0.079 34.000
    310 0.016 34.000
    320 0.112 34.000
    330 0.207 34.000
    340 0.235 34.471
    350 0.161 35.647
    360 0.098 39.063


    [0068] Above the Ccritical value the colour intensity is too high to be perceived as a pastel colour.

    [0069] The values of m and Ccritical at intermediate hue angles can be calculated by linear interpolation.

    [0070] The table enables the calculation of C* and Y for any given hue and thus the whites, grey or pastel/light shades are explicitly identified.

    [0071] Coatings having chroma, C* less than about 5 and a Y value more than 95 are perceived by the human eye as white.

    [0072] The values of C*, Y and h* of any colour may be calculated from the spectral reflectance curve of the colour, measured using a spectrophotometer in accordance with the manufacturers instructions. A suitable spectrophotometer is the Datacolor Spectraflash SF 600.

    [0073] Preferably, the dried coating compositions of the invention satisfy equations 1 and 2. More preferably, the dried coating compositions have a chroma less than 5 and a Y value greater than 85.

    [0074] Preferably, the gloss value of the dried coating is less than 30%,when measured at 85°, more preferably less than 20%, even more preferably less than 10%, yet more preferably less than 5% and most preferably from 2 to 8%.

    [0075] The coating composition may also contain other ingredients that are standard for coatings such as waxes, rheological modifiers, surfactants, anti-foams, tackifiers, plasticisers, crosslinking agents, flow aids, biocides and clays.

    [0076] In another aspect of the invention there is provided a method of coating an article or structure having a surface with a composition according to the present invention including the steps of applying at least one liquid layer of the coating by brush, roller, pad or spray and allowing or causing the layer to dry and/or harden.

    [0077] In a further aspect of the invention there is provided an article or structure having a surface coated with a composition according to the present invention.

    [0078] The following ingredients were used in preparing the examples.
    Tioxide™ TR92 is a Rutile form of TiO2 (density of 4.05g/cm3) available from Huntsman Tioxide Europe Ltd, Hartlepool, Cleveland, United Kingdom.
    Microdol™ H200 and H600 are both dolomites (density of 2.85g/cm3) and are available from Omya. Omya House, Derby, United Kingdom
    Socal™ P3 is precipitated calcium carbonate (density of 2.70g/cm3) and is available from Solvay, Rheinberg, Germany.
    China Clay Supreme-kaolin (density 2.60g/cm3) is available from Imerys.
    Ropaque™ Ultra E is a 30% non-vol dispersion of hollow polymeric spherical particles (density of 0.591g/cm3) and is available from Rohm and Haas, Philadelphia, USA.
    Steabright™ is a talc (density of 2.78g/cm3) available from Rio Tinto PLC, London, United Kingdom
    Texanol™ is an ester alcohol coalescent available from Eastman Chemical Company, Tennessee, USA.
    TegMer™ 804 is a tetra ethylene glycol ester available from Hallstar, 120 South Riverside Plaza, Suite 1620, Chicago, Illinois 60606, USA.
    Orotan™ 731 A is a pigment dispersing agent (25wt% non-vol; density of non-vol is 1 g/cm3) available from Rohm & Haas Philadelphia, USA.
    Disponil™ A1580 is a surfactant (80wt% non-vol; density of non-vol is 1.00 g/cm3) and is available from Cognis Deutschland GmbH & Co. KG. PO Box 130164, Germany.
    Dispex N40 is a dispersant available from Ciba.
    Dispelair™ CF 823 is a defoamer (60wt% non-vol; density of non-vol is 1.00g/cm-3) and is available from Blackburn Chemicals Ltd, Whitebirk Industrial Estate, Blackburn, United Kingdom.
    Blanose™ 7M 31C SCS 9554 (density 1.59g/cm3) is available from Hercules GmbH, Dusseldorf, Germany.
    Acticide CHR 0107 a biocide is available from Thor at Wincham Avenue, Wincham, Northwich, Cheshire, England.
    Aquaflow™ NHS 300 (23wt% non-vol; density of non-vol is 1.00g/cm3) is a thickener/rheology modifier and is available from Hercules GmbH, Dusseldorf, Germany.
    China Clay Supreme (density is 2.60g/cm3) is available from Imerys.
    Latex 1 is a styrene/butyl acrylate/methacrylic acid copolymer of Tg 10°C and Acid value 23.5mg KOH/g polymer and 50wt% solids content. Latex 2 is a styrene/butyl acrylate/methacrylic acid copolymer of Tg -10°C and Acid Value 23.5mg KOH/g polymer and 50wt% solids content.
    Latex 3 is a styrene/butyl acrylate/methacrylic acid copolymer of Tg 10°C and Acid Value 11mg KOH/g polymer and 50wt% solids content.

    [0079] The following test methods were used:

    Molecular Weight of Dispersant



    [0080] Aqueous GPC was used set up was used to measure molecular weight.

    [0081] The equipment and conditions used were;

    Columns: 2 x 30cm TSK GMPWXL GPC columns from Tosoh

    Eluent: 0.3M Sodium Nitrate, 0.01M Sodium Phosphate with pH adjusted to 7.5 using 0.1M NaOH

    Flow rate: 1.0 ml/min

    Detector; Waters 410 differential refractive index detector.

    Software; Waters Millennium 32 v3.05.01



    [0082] The instrument was calibrated with Dextran standards covering the range 342 - 401000 g/mol.

    [0083] Samples were prepared by diluting 0.1 g in 10 mls of eluent and filtering through a 0.45 micron PVDF membrane.
    Injection Volume was 100µl

    Opacity (Contrast Ratio)



    [0084] Opacity was measured in accordance with BS 3900-D4.

    [0085] At least 90% is considered acceptable.

    [0086] The measured opacity is not linear in its relationship to how the eye perceives opacity. Thus, small differences in measured opacity are seen by the eye as much larger differences.

    Gloss



    [0087] Gloss was measured in accordance with BS EN ISO 2813, BS 3900-D5.

    Wet Scrub Resistance



    [0088] Scrub resistance of the dried film was measured in accordance with BS EN ISO 11998 using 200 cycles with the modification that the loss was recorded as mg/cm2. A loss of less than 6mg/cm2 removal is acceptable.

    High Shear Viscosity



    [0089] The high shear viscosity is measured at 25°C using an ICI Cone and Plate viscometer (available from Research Equipment London Ltd, London, TW2 5NX) operating at 10,000s-1.

    Rotothinner viscosity (Paint)



    [0090] The medium shear viscosity is measured at 25°C using a Rotothinner viscometer (available from Sheen Instruments Ltd, Kingston-upon-Thames, Surrey, UK) fitted with a standard disc rotor rotating at about 562rpm which is equivalent to a shear rate of ca 250 s-1.

    Particle Size of Extenders



    [0091] Particle size of the extenders was measured using a Mastersizer in accordance with ISO 13323 part 1&2.

    Method for determining dispersant demand



    [0092] The basis of the test is to gradually add dispersant to an aqueous dispersion of the inorganic opacifying pigment and non-opacifying extender particles whilst measuring viscosity until a minimum viscosity is reached. The amount of dispersant added to achieve this viscosity expressed as wt% non-vol dispersant calculated on the weight of the particles is the dispersant demand. The amounts of the ingredients used are taken from the weight% formulation.

    [0093] The following method was used to determine the dispersant demand:
    1. 1. To a 500 cm3 lacquered metal can arranged to be stirred with a high speed stirrer (HSD) fitted with a 40 to 50 mm blade add approximately 150g of water. The exact amount of water will depend on the formulation.
    2. 2. Add about 50 to 65wt% of the expected final amount of candidate dispersant- this may require a first titration to make an initial estimate of the dispersant demand in order to make a more accurate second determination.
    3. 3. Whilst stirring at about 200 rpm, add all of the ingredients other than opacifying pigments, non-opacifying extender particles, thickener, biocide and the binder, to the mixture in step 2. Stir for a further 2 minutes.
    4. 4. Add the non-opacifying extender particles and the non-polymeric opacifying pigment other than any coloured opacifying pigment. Increase the stirring during the addition to about 2500rpm or as required to maintain a vortex in the can. The solids of the mixture at this stage should be about 70wt%.
    5. 5. Measure the viscosity using a Rotothinner viscometer fitted with a ball rotor rotating at 562rpm. For convenience, the viscosity at this stage should be approximately 6.0 to 7.0 Pa.s. Some trial and error may be necessary to achieve this. If it is so high that it cannot be stirred, additional dispersant and/or water may be added. For some extender combinations the viscosity might be too high or low, in which case, start from step 1, this time using either more or less water as required.
    6. 6. Add more dispersant to the mixture and mix in using the HSD.
    7. 7. Repeat steps 5 and 6 until the viscosity change, on further addition of dispersant, is small compared to earlier additions.
    8. 8. The dispersant demand is estimated by plotting a graph of viscosity vs added dispersant expressed as wt% dispersant calculated on the sum of the weight of the opacifying pigment particles.and the weight of the non-opacifying extender particles. The minimum amount of non-vol. dispersant to achieve the minimum viscosity is taken as the dispersant demand.


    [0094] The candidate dispersant should be used at as high a non-vol content as possible to avoid viscosity drops as a result of simple dilution.

    [0095] The Rotothinner viscometer (Ref. 455N/15) is available from Sheen Instruments, 2, Gatton Park Business Centre, Wells Place, Redhill, Surrey, RH1 3LG

    [0096] By way of example, the dispersant demand (for Orotan 731) of example 1 was determined as follows:
    1. 1. To a 500 cm3 lacquered metal can arranged to be stirred with a high speed disperser (HSD) fitted with a 40 to 50 mm blade add 128g of water.
    2. 2. To this was added 5.3g of Orotan 731 as supplied at 25% active.
    3. 3. Then Texanol (17.7g), Disponil A1580 (4.42g) and Dispelair CF823 (1.15g) was added to the mixture in step 2 and stirred for 2minutes at 200rpm.
    4. 4. Whilst stirring slowly a pre-mixed blend of Microdol H600 (75.2g), Socal P3 (110.57g), China Clay Supreme (48.65g), Steabright (75.2g), Microdol H200 (75.2g) and Tioxide TR92 (57.5g) was added. The stirrer speed was increased during the addition to 2500rpm and maintained for 5 minutes.
    5. 5. The Rotothinner viscosity was measured as 6.5 Pa.s
    6. 6. Then an extra 0.87g of Orotan 731 (at 25% active) was added and the mixture was dispersed at 2500rpm for another 2 minutes and the Rotothinner viscosity was measured as 5.4 Pa.s.
    7. 7. This was repeated until the viscosity of 2.2 Pa.s was reached. As can be seen from the plot in Figure 1, dispersant was added past this minimum viscosity point in order to estimate the dispersant demand.


    [0097] For Orotan 731, a total of 8.76g of dispersant was added to reach the minimum viscosity. The dispersant demand was 0.50wt%.
     wt%wt/g
    Water 21.25 128.00
    Texanol 2.94 17.70
    Orotan 731 1.45 8.76
    Disponil A1580 0.73 4.42
    Dispelair CF823 0.19 1.15
    Microdol H600 12.48 75.20
    Socal P3 18.37 110.57
    China Clay Supreme 8.08 48.65
    Steabright 12.48 75.20
    Microdol H200 12.48 75.20
    Tioxide TR92 9.55 57.50


    [0098] Note that, other than the water, the ingredients are in the correct ratio relative to each other. The reduced water content allows the viscosity minimum to be detected.

    [0099] Figure 1 shows a plot of viscosity against added non vol. dispersant for various dispersants.

    Line A represents the plot for Dispex N40 (Dispersant demand 0.12wt%)

    Line B represents the plot for potassium tripolyphosphate

    Line C represents the plot for Orotan 731 (Dispersant demand 0.50wt%)

    Line D represents the plot for Strodex PK-80A

    Line E represents the plot for Orotan 681 (Dispersant demand 1.50wt%)

    Line F represents the plot for Nuosperse FA-196 Of these, only Orotan 681 and Orotan 731 are suitable for use in the present invention as these are the only two of molecular weight greater than Mw.3500 Daltons and of dispersant demand greater than 0.35wt%.


    Examples



    [0100] The invention will now be illustrated by the following examples.

    [0101] Numbered examples are of the invention and comparative examples are referenced with letters. In all cases the wt% formulation refers to the liquid paint and the vol% to the dried coating.

    [0102] The following method was used to make the paints in each case.

    Millbase stage



    [0103] Using a 5 litre metal dispersion vessel, load the Water (1), Texanol, Orotan or Dispex, Disponil, Acticide and half the amount of Dispelair. Place vessel under High Speed Disperser fitted with a saw tooth blade. Stir at slow speed so that no splashing is observed. Add Microdol H200 and H600, Socal P3, China Clay Supreme, Steabright and Tioxide TR92, run for 2 minutes at slow speed then add Blanose thickener. Over 5minutes slowly increase the speed as the paint thickens. Unit should be running at approximately 2500 r.p.m. (depending on volume), but without splashing. Stir for a further 30minutes. Stop unit half way through to ensure no pigment has stuck to sides/base of vessel by hand stirring. Turn unit back on to high speed, after 30 minutes reduce to slow speed. Check the state of dispersion of the millbase for bits by brushing out on a card. If acceptable amount of bits, add Water (2) and run for a further 2minutes and then switch off the stirrer.

    [0104] The total amount of water showed in the example formulation was in the ratio of: water (1) : water (2) : water (3) =45.5 : 30.3 : 24.2

    Paint stage



    [0105] Load Latex 1 into a suitably sized vessel and place under a stirrer fitted with a paddle blade.

    [0106] Load Ropaque, the rest of the Dispelair, the Millbase prepared above, Water (3) and Aquaflow. Adjust the stirrer speed as the volume in the vessel increases, being careful to avoid splashing.

    [0107] Stir for a further 15 minutes at low speed (approx 500 r.p.m)

    Examples 1 and A



    [0108] Examples 1 and A are essentially identical other than for the difference in PVC Comparative example A, at PVC 86, fails the wet scrub test.
    Example1A
     wt% (wet coating)vol% (dry coating)wt (% of wet coating)vol% (dry coating)
    Aquaflow NHS 300 1.50 1.01 1.50 1.06
    Acticide CHR 0107 0.24 0.07 0.24 0.08
    Disponil A1580 0.50 1.60 0.5 1.68
    Dispelair CF823 0.23 0.60 0.23 0.63
    Orotan731 A 1.00 0.65 1.00 0.69
    Blanose 7M 31C 0.50 1.32 0.50 1.39
    Texanol 2.00 0 2.00 0
    Water (Mains) 33.53 0 36.06 0
    Tioxide TR92 6.50 6.77 6.50 7.12
    Socal P3 12.50 19.43 12.50 20.44
    Steabright 8.50 12.83 8.50 13.50
    China Clay Supreme 5.50 8.88 5.50 9.34
    Microdol H600 8.50 12.97 8.50 13.64
    Microdol H200 8.50 12.74 8.50 13.40
    Ropaque (Tm) Ultra E 4.00 8.49 4.00 8.93
    Latex 1 6.50 12.63 3.97 8.11
    Total 100.00 100.00 100.00 100.00
             
    Wet scrubs weight loss (mg/cm2)   5.8   16.5
    Density (kg/L)   1.49   1.49
    PVC (%)   82.12   86.37
    vol% solids   35.55   33.77
    Sum non-opacifying particles (% of dry vol)   66.86   70.31


    [0109] The Tg of the polymer binder in the presence of the coalescing solvent is calculated using equation 1 as previously discussed



    [0110] The Tg of Texanol is -84°C

    [0111] The volume fractions are calculated based on the polymer and the solvent alone.

    [0112] So for example 1 the total weight% of polymer is 3.25 (being 50% of 6.5) and the solvent is 2.00. The specific gravity of the polymer and the solvent is 1.08 and 0.95 respectively and the volume fraction is therefore 0.15 and 0.85 respectively. So the Tg of the polymer in the presence of the Texanol is -9.5°C.

    Examples 2 and B



    [0113] These are essentially identical other than the level of China Clay Supreme (kaolin). Comparative example B, at a kaolin level of 28.52vol% fails the wet scrubs test.

    Example



    [0114] 
    Example2B
    wt% (wet coating)vol% (dry coating)wt (% of wet coating)vol% (dry coating)
    Aquaflow NHS 300 1.50 1.02 0.50 0.36
    Acticide CHR 0107 0.24 0.07 0.25 0.08
    Disponil A1580 0.50 1.62 0.50 1.70
    Dispelair CF823 0.25 0.66 0.25 0.69
    Orotan731 A 1.00 0.66 1.50 1.04
    Blanose 7M 31C 0.70 1.87 0.50 1.40
    Texanol 2.00 0 1.00 0
    Water (Mains) 33.65 0 38.13 0
    Tioxide TR92 7.50 7.91 5.97 6.61
    Socal P3 12.61 19.84 5.76 9.51
    Steabright 8.44 12.89 11.37 - 18.24
    China Clay Supreme 5.53 9.03 16.63 28.52
    Microdol H600   0 0 0
    Microdol H200 16.88 25.61 10.5 16.72
    Ropaque (Tm) Ultra E 4.00 8.60 2.08 4.69
    Latex 1 5.20 10.22 5.06 10.45
    Total 100.00 100.00 100.00 100.00
             
    Wet scrubs weight loss (mg/cm2)   5.2   17.94
    Contrast Ratio   93.3   94.18
    Density (kg/L)   1.5   1.5
    PVC (%)   83.9   84.3
    vol% solids   35.6   33.4
    Sum non-opacifying particles (% of dry vol)   67.4   73.0

    Examples 3 and C



    [0115] Examples 3 and C are identical except that the Tg of the latex in the two examples is different. Comparative example C, using a latex of Tg -10°C, fails the wet scrubs test.
    Example3C
    wt% (wet coating)vol% (dry coating)wt (% of wet coating)vol% (dry coating)
    Aquaflow NHS 300 1.50 1.01 1.50 1.01
    Acticide CHR 0107 0.24 0.07 0.24 0.07
    Disponil A1580 0.50 1.60 0.50 1.60
    Dispelair CF823 0.23 0.60 0.23 0.60
    Orotan731 A 1.00 0.65 1.00 0.65
    Blanose 7M 31C 0.50 1.32 0.50 1.32
    Texanol 2.00 0 2.00 0
    Water 33.53 0 33.53 0
    Tioxide TR92 6.50 6.77 6.50 6.77
    Socal P3 12.50 19.43 12.50 19.43
    Steabright 8.50 12.83 8.50 12.83
    China Clay Supreme 5.50 8.88 5.50 8.88
    Microdol H600 8.50 12.97 8.50 12.97
    Microdol H200 8.50 12.74 8.50 12.74
    Ropaque (Tm) Ultra E 4.00 8.49 4.00 8.49
    Latex 1 6.50 12.63 0 0
    Latex 2 0 0 6.5 12.63
    Total 100.00 100.00 100.00 100.00
     
    Wet scrubs weight loss (mg/cm2)   4.9   7.4
    Density (kg/L)   1.49   1.49
    PVC (%)   82.12   82.12
    vol% solids   35.55   35.55
    Sum non-opacifying particles (% of dry vol)   66.86   66.86

    Examples 4 and D


    Effect of latex acid value.



    [0116] Comparative example D, using latex 3 of AV 11mg KOH/g polymer, fails the wet scrubs test.
    Example4D
     wt% (wet coating)vol% (dry coating)wt (% of wet coating)vol% (dry coating)
    Aquaflow NHS 300 1.50 1.01 1.50 1.01
    Acticide CHR 0107 0.24 0.07 0.24 0.07
    Disponil A1580 0.50 1.60 0.50 1.60
    Dispelair CF823 0.23 0.60 0.23 0.60
    Orotan731 A 1.00 0.65 1.00 0.65
    Blanose 7M 31C 0.50 1.32 0.50 1.32
    Texanol 2.00 0 2.00 0
    Water 33.53 0 33.53 0
    Tioxide TR92 6.50 6.77 6.50 6.77
    Socal P3 12.5 19.43 12.5 19.43
    Steabright 8.50 12.83 8.50 12.83
    China Clay Supreme 5.50 8.88 5.50 8.88
    Microdol H600 8.50 12.97 8.50 12.97
    Microdol H200 8.50 12.74 8.50 12.74
    Ropaque (Tm) Ultra E 4.00 8.49 4.00 8.49
    Latex 1 6.50 12.63    
    Latex 3     6.50 12.63
    Total 100.00 100.00 100.00 100.00
    Wet scrubs weight loss (mg/cm2)   3.6   8.0
    Density (kg/L)   1.49   1.49
    PVC(%)   82.12   82.12
    vol% solids   35.55   35.55
    Sum non-opacifying particles (% of dry vol)   66.86   66.86

    Example 5 and E



    [0117] Effect of using a dispersant producing a dispersant demand of <0.45wt%.
    Example5E
     wt% (wet coating)Vol% (dry coating)wt (% of wet coating)vol% (dry coating)
    Aquaflow NHS 300 0.50 0.34 0.50 0.34
    Acticide CHR 0107 0.24 0.07 0.24 0.07
    Disponil A1580 0.50 1.61 0.50 1.62
    Dispelair CF823 0.25 0.65 0.25 0.66
    Orotan731 A 1.00 0.66    
    Dispex N40     0.20 0.23
    Blanose 7M 31C 0.50 1.33 0.50 1.33
    Texanol 2.00 0 2.00 0
    Water (Mains) 34.51 0 35.31 0
    Tioxide TR92 6.50 6.81 6.50 6.84
    Socal P3 12.50 19.55 12.50 19.64
    Steabright 8.50 12.91 8.50 12.97
    China Clay Supreme 5.50 8.93 5.50 8.97
    Microdol H600 8.50 13.05 8.50 13.11
    Microdol H200 8.50 12.82 8.50 12.88
    Ropaque (Tm) Ultra E 4.00 8.55 4.00 8.58
    Latex 1 6.50 12.71 6.50 12.76
    Total 100.00 100.00 100.00 100.00
             
    Wet scrubs weight loss (mg/cm2)   4.6   9.0
    Contrast Ratio   93.19   93.3
    Density (kg/L)   1.49   1.49
    PVC (%)   82.63   82.99
    vol% solids   35.31   35.12
    Sum non-opacifying particles (% of dry vol)   67.27   67.56


    [0118] Dispersant demand for Comparative example E is <0.45wt%.

    Examples 6 and F


    Effect of non-fugitive coalescing solvent.



    [0119] 
    Example6F
    wt% (wet coating)Vol% (dry coating)wt (% of wet coating)vol% (dry coating)
    Aquaflow NHS 300 1.50 1.01 1.50 0.97
    Acticide CHR 0107 0.24 0.07 0.24 0.07
    Disponil A1580 0.50 1.60 0.50 1.53
    Dispelair CF823 0.25 0.65 0.25 0.62
    Orotan731 A 1.00 0.65 1.00 0.63
    Blanose 7M 31C 0.50 1.32 0.50 1.27
    Texanol 1.00 0 0 0
    Tegmer 804     1.00 4.10
    Water 34.51 0 34.51 0
    Tioxide TR92 6.50 6.77 6.50 6.49
    Socal P3 12.50 19.42 12.50 18.62
    Steabright 8.50 12.83 8.50 12.30
    China Clay Supreme 5.50 8.87 5.50 8.51
    Microdol H600 8.50 12.97 8.50 12.43
    Microdol H200 8.50 12.73 8.50 12.21
    Ropaque (Tm) Ultra E 4.00 8.49 4.00 8.14
    Latex 1 6.50 12.62 6.50 12.11
    Total 100.00 100.00 100.00 100.00
             
    Wet scrubs weight loss (mg/cm2)   4.3   18.0
    Density (kg/L)   1.49   1.49
    PVC (%)   82.08   78.71
    vol% solids   35.60   37.14
    Sum non-opacifying particles (% of dry vol)   66.82   64.08

    Example 7



    [0120] A coating free of hollow polymeric particles
     wt (% of wet coating)vol% (dry coating)
    Aquaflow NHS 300 1.48 1.10
    Acticide CHR 0107 0.24 0.08
    Disponil A1580 0.50 1.77
    Dispelair CF823 0.23 0.66
    Orotan731 A 1.00 0.72
    Blanose 7M 31C 0.49 1.43
    Texanol 2.00 0
    Water (Mains) 38.43 0
    Tioxide TR92 6.54 7.54
    Socal P3 12.32 21.21
    China Clay Supreme 5.55 9.93
    Microdol H200 16.43 27.27
    Omyacoat 850 OG 8.22 14.14
    Ropaque (Tm) Ultra E 0 0
    935-1052 std 6.57 14.14
    Total 100.00 100.00
         
    Wet scrubs weight loss (mg/cm2)   4.0
    Contrast Ratio   93.05
    Density (kg/L)   1.48
    PVC (%)   80.10
    vol% solids   31.77
    Sum non-opacifying particles (% of dry vol)   72.53

    Standards (i) and (ii)



    [0121] Standards (i) and (ii) show that at PVC<78% any dispersant may be used without compromising the wet scrubs. Dispex N40, used in standard (ii), does not satisfy the dispersant demand criterion of <0.35wt%, but the coating passes the wet scrubs test.
    Standard(i)(ii)
     wt% (wet coating)vol% (dry coating)wt (% of wet coating)vol% (dry coating)
    Aquaflow NHS 300 1.50 0.97 1.50 0.97
    Acticide CHR 0107 0.24 0.07 0.24 0.07
    Disponil A1580 0.50 1.54 0.50 1.54
    Dispelair CF823 0.25 0.62 0.25 0.63
    Orotan 731 A 1.00 0.63    
    Dispex N40     0.25 0.28
    Blanose 7M 31C 0.70 1.78 0.70 1.78
    Texanol 2.00 0 2.00 0
    Water 31.41 0 32.16 0
    Tioxide TR92 8.00 8.01 8.00 8.03
    Socal P3 11.5 17.18 11.5 17.24
    Steabright 8.00 11.60 8.00 11.65
    China Clay Supreme 5.00 7.76 5.00 7.78
    Microdol H200 15.6 22.47 15.6 22.55
    Ropaque (Tm) Ultra E 4.00 8.16 4.00 8.19
    Latex 1 10.3 19.23 10.3 19.30
    Total 100.00 100.00 100.00 100.00
    Wet scrubs weight loss (mg/cm2)   1.7   1.7
    Contrast Ratio   91.14   91.63
    Density (kg/L)   1.47   1.47
    PVC (%)   75.17   75.44
    vol% solids   36.57   36.40
    Sum non-opacifying particles (% of dry vol)   59.00   59.21



    Claims

    1. An aqueous coating composition having a PVC of from 78 to 85% comprising, based on the total volume solids of the dry coating unless otherwise stated,

    a) opacifying pigment particles comprising

    i) from 3 to 10% titanium dioxide

    ii) from 0 to 20% of hollow polymeric particles

    b) non-opacifying extender particles comprising

    i) calcium magnesium carbonate and/or

    ii) calcium carbonate and/or

    iii) nepheline syenite and/or

    iv) kaolin

    wherein i)+ii)+iii)+iv) = 40 to 80% and iv) is 0 to 20%

    c) polymer binder particles of calculated Fox Tg of from 5 to 25°C having an acid value of from 15 to 65mg KOH/g of polymer and wherein the polymer particles are derived from acrylic monomers and optionally further comprising styrene and/or its derivatives

    d) dispersant having a weight average molecular weight of at least 3500 Daltons and selected on the basis that the dispersant demand of a mixture of the opacifying pigment particles, other than the hollow polymeric particles, of a), and the extender particles of b) is greater than 0.35wt%, calculated on the weight of the titanium dioxide and extender particles

    e) fugitive coalescing solvent

    wherein the composition is free of non-fugitive coalescing solvent.
     
    2. A coating composition according to claim 1 wherein any difference between the actual PVC and the sum of a) and b) is made up with other non-opacifying extender particles.
     
    3. A coating composition according to claim 1 or claim 2 wherein the opacifying pigments are white.
     
    4. A coating composition according to claim 3 wherein the white opacifying pigments are selected from titanium dioxide and hollow polymeric particles.
     
    5. A coating composition according to any one of the previous claims wherein the polymeric hollow spheres comprise less than 10% by vol.
     
    6. A coating composition according to any one of the previous claims wherein the extender particles are selected from the group consisting of calcium magnesium carbonate, calcium carbonate, nephelene syenite and kaolin.
     
    7. A coating composition according to claim 6 wherein from 20 to 50% of the total volume solids of the dry coating comprises extender particles of d50 ≤2 microns.
     
    8. A coating composition according to any one of the previous claims wherein the polymer binder has a calculated Fox Tg of from 6 to 21°C.
     
    9. A coating composition according to any one of the previous claims wherein the polymer binder is derived from styrene, butyl acrylate and acrylic acid.
     
    10. A coating composition according to any one of the previous claims wherein the binder comprises from 5 to 20% of the dried coating.
     
    11. A coating composition according to any one of the preceding claims wherein the acid value of the polymer binder is from 15 to 60mg KOH/g of polymer.
     
    12. A coating composition according to anyone of the preceding claims wherein the acid component comprises acrylic acid and/or methacrylic acid and/or maleic acid and/or its anhydride.
     
    13. A coating composition according to any one of the preceding claims wherein the dispersant demand is estimated by the following method or its equivalent; i) gradually adding dispersant to an aqueous dispersion of the non-polymeric opacifying pigment and extender particles and monitoring the viscosity of the resulting mixture to determine the minimum viscosity ii) identifying the amount of dispersant added to reach the minimum viscosity as the dispersant demand.
     
    14. A coating composition according to any one of the preceding claims containing up to 4wt% of coalescing solvent based on the liquid formulation.
     
    15. A coating composition according to anyone of the preceding claims wherein the coalescing solvent reduces the calculated Fox Tg of the polymer binder to from -10 to -80°C.
     
    16. A coating composition according to any one of the preceding claims and further containing colour pigments.
     
    17. A coating composition according to any one of the previous claims and having a colour when dry satisfying the criteria of
    C * < Ccritical and
    Y > mC* + 35
    when calculated using m and Ccritical according to the table below
    Hue angle h*mCcritical
    0 0.098 39.063
    10 0.063 42.739
    20 0.231 40.130
    30 0.399 37.522
    40 0.498 37.444
    50 0.579 38.000
    60 0.655 39.500
    70 0.732 41.000
    80 0.793 45.286
    90 0.854 49.571
    100 0.803 47.136
    110 0.740 43.955
    120 0.663 41.727
    130 0.580 39.909
    140 0.498 38.565
    150 0.416 37.696
    160 0.346 37.381
    170 0.318 39.586
    180 0.283 40.850
    190 0.190 39.350
    200 0.101 38.000
    210 0.060 38.000
    220 0.021 38.333
    230 -0.007 40.000
    240 -0.041 40.314
    250 -0.083 38.600
    260 -0.125 36.886
    270 -0.167 35.171
    280 -0.152 34.640
    290 -0.131 34.240
    300 -0.079 34.000
    310 0.016 34.000
    320 0.112 34.000
    330 0.207 34.000
    340 0.235 34.471
    350 0.161 35.647
    360 0.098 39.063

     
    18. A coating composition according to claim 17 having a C* value of less than 5 and a Y value greater that 85.
     
    19. A coating composition according to any one of the preceding claims and having a sheen of less than 15% when measured at 85°.
     
    20. A method of coating an article or structure having a surface with a composition as defined in any one of the preceding claims including the steps of applying at least one liquid layer of the coating by brush, roller, pad or spray; allowing or causing the layer to dry and/or harden.
     
    21. An article or structure having a surface coated with a composition as defined in any one of claims 1 to 19.
     


    Ansprüche

    1. Wässrige Beschichtungszusammensetzung mit einer Pigmentvolumenkonzentration (PVK) von 78 bis 85%, umfassend, bezogen auf das Gesamtvolumen der Feststoffe der trockenen Beschichtung, wenn nichts Anderes angegeben ist:

    a) deckende Pigmentteilchen, umfassend:

    i) 3 bis 10% Titandioxid;

    ii) 0 bis 20% hohle polymere Teilchen;

    b) nichtdeckende Verschnittmittelteilchen, umfassend:

    i) Calciummagnesiumcarbonat und/oder

    ii) Calciumcarbonat und/oder

    iii) Nephelinsyenit und/oder

    iv) Kaolin;

    wobei i) + ii) + iii) + iv) = 40 bis 80% ist und iv) = 0 bis 20% ist;

    c) Polymerbindemittelteilchen mit einer berechneten Fox-Tg von 5 bis 25 °C mit einem Säurewert von 15 bis 65 mg KOH/g Polymer, wobei die Polymerteilchen von Acrylmonomeren abgeleitet sind und gegebenenfalls weiterhin Styrol und/oder seine Derivate umfassen;

    d) Dispergiermittel mit einem Gewichtsmittel des Molekulargewichts von wenigstens 3500 Dalton, das so ausgewählt ist, dass der Dispergiermittelbedarf eines Gemischs der deckenden Pigmentteilchen von a) außer den hohlen polymeren Teilchen und den Verschnittmittelteilchen b) größer als 0,35 Gew.-% ist, bezogen auf das Gewicht des Titandioxids und der Verschnittmittelteilchen;

    e) ein flüchtiges koaleszierendes Lösungsmittel, wobei die Zusammensetzung frei von nicht-flüchtiges koaleszierendes Lösungsmittel ist.


     
    2. Beschichtungszusammensetzung gemäß Anspruch 1, wobei ein Unterschied zwischen der tatsächlichen PVK und der Summe von a) und b) mit anderen nichtdeckenden Verschnittmittelteilchen erzeugt wird.
     
    3. Beschichtungszusammensetzung gemäß Anspruch 1 oder Anspruch 2, wobei die deckenden Pigmente weiß sind.
     
    4. Beschichtungszusammensetzung gemäß Anspruch 3, wobei die weißen deckenden Pigmente aus Titandioxid und hohlen polymeren Teilchen ausgewählt sind.
     
    5. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei die polymeren Hohlkugeln weniger als 10 Vol.-% ausmachen.
     
    6. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei die Verschnittmittelteilchen aus der Gruppe ausgewählt sind, die aus Calciummagnesiumcarbonat, Calciumcarbonat, Nephelinsyenit und Kaolin besteht.
     
    7. Beschichtungszusammensetzung gemäß Anspruch 6, wobei 20 bis 50% des Gesamtfeststoffvolumens der trockenen Beschichtung Verschnittmittelteilchen mit einem d50 von ≤ 2 µm umfassen.
     
    8. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei das Polymerbindemittel eine berechnete Fox-Tg von 6 bis 21 °C hat.
     
    9. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei das Polymerbindemittel von Styrol, Butylacrylat und Acrylsäure abgeleitet ist.
     
    10. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei das Bindemittel 5 bis 20% der getrockneten Beschichtung umfasst.
     
    11. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei derie Säurewertzahl des Polymerbindemittels 15 bis 60 mg KOH/g Polymer beträgt.
     
    12. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei die Säurekomponente Acrylsäure und/oder Methacrylsäure und/oder Maleinsäure und/oder deren Anhydrid umfasst.
     
    13. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei der Dispergiermittelbedarf nach dem folgenden oder einem äquivalenten Verfahren abgeschätzt wird: i) allmähliches Hinzufügen von Dispergiermittel zu einer wässrigen Dispersion der nichtpolymeren deckenden Pigment- und Verschnittmittelteilchen und Überwachen der Viskosität des resultierenden Gemischs zur Bestimmung der minimalen Viskosität; ii) Identifizieren der Menge an Dispergiermittel, die zum Erreichen der minimalen Viskosität hinzugefügt wurde, als Dispergiermittelbedarf.
     
    14. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, die bis zu 4 Gew.-% koaleszierendes Lösungsmittel enthält, bezogen auf die flüssige Zubereitung.
     
    15. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, wobei das koaleszierende Lösungsmittel die berechnete Fox-Tg des Polymerbindemittels auf -10 bis -80 °C reduziert.
     
    16. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, die weiterhin Farbpigmente enthält.
     
    17. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, die im trockenen Zustand eine Farbe hat, die die folgenden Kriterien erfüllt:

    C* < Ckritisch und

    Y > mC* + 35;

    wenn unter Verwendung von m und Ckritisch gemäß der folgenden Tabelle gerechnet wird:
    Bunttonwinkel h*mCkritisch
    0 0,098 39,063
    10 0,063 42,739
    20 0,231 40,130
    30 0,399 37,522
    40 0,498 37,444
    50 0,579 38,000
    60 0,655 39,500
    70 0,732 41,000
    80 0,793 45,286
    90 0,854 49,571
    100 0,803 47,136
    110 0,740 43,955
    120 0,663 41,727
    130 0,580 39,909
    140 0,498 38,565
    150 0,416 37,696
    160 0,346 37,381
    170 0,318 39,586
    180 0,283 40,850
    190 0,190 39,350
    200 0,101 38,000
    210 0,060 38,000
    220 0,021 38,333
    230 -0,007 40,000
    240 -0,041 40,314
    250 -0,083 38,600
    260 -0,125 36,886
    270 -0,167 35,171
    280 -0,152 34,640
    290 -0,131 34,240
    300 -0,079 34,000
    310 0,016 34,000
    320 0,112 34,000
    330 0,207 34,000
    340 0,235 34,471
    350 0,161 35,647
    360 0,098 39,063

     
    18. Beschichtungszusammensetzung gemäß Anspruch 16, die einen C*-Wert von weniger als 5 und einen Y-Wert von mehr als 85 aufweist.
     
    19. Beschichtungszusammensetzung gemäß einem der vorstehenden Ansprüche, die einen bei 85° gemessenen Glanz von weniger als 15% aufweist.
     
    20. Verfahren zur Beschichtung eines Artikels oder einer Struktur, der oder die eine Oberfläche aufweist, mit einer Zusammensetzung gemäß einem der vorstehenden Ansprüche, umfassend die Schritte des Auftragens wenigstens einer flüssigen Schicht der Beschichtung mit einem Pinsel, einer Rolle, einem Kissen oder Sprühnebel und des Trocknenlassens oder Trocknens und/oder Härtenlassens oder Härtens der Schicht.
     
    21. Artikel oder Struktur, der oder die eine Oberfläche aufweist, die mit einer Zusammensetzung gemäß einem der Ansprüche 1 bis 19 beschichtet ist.
     


    Revendications

    1. Composition de revêtement aqueuse ayant une CPV de 78 à 85 % comprenant, sur la base du volume total des solides du revêtement sec et sauf indication contraire,

    a) des particules de pigment opacifiant comprenant

    i) de 3 à 10 % de dioxyde de titane,

    ii) de 0 à 20 % de particules de polymère creuses,

    b) des particules de charge non opacifiantes comprenant

    i) du carbonate de calcium-magnésium et/ou

    ii) du carbonate de calcium et/ou

    iii) de la syénite néphélinique et/ou

    iv) du kaolin,

    où i) + ii) + iii) + iv) = 40 à 80 % et iv) représente de 0 à 20 %,

    c) des particules de liant polymère ayant une Tg Fox calculée de 5 à 25°C et ayant un indice d'acide de 15 à 65 mg KOH/g de polymère, les particules de polymère dérivant de monomères acryliques et comprenant en outre éventuellement du styrène et/ou ses dérivés,

    d) un dispersant ayant une masse moléculaire moyenne en masse d'au moins 3500 Daltons choisi sur la base de la demande en dispersant d'un mélange des particules de pigment opacifiant, autres que les particules de polymère creuses, de a), et des particules de charge de b), qui est supérieure à 0,35 % en poids, calculée par rapport au poids du dioxyde de titane et des particules de charge,

    e) un solvant de coalescence fugitif,

    où la composition ne contient pas de solvant de coalescence non-fugitif.
     
    2. Composition de revêtement selon la revendication 1, dans laquelle toute différence entre la CPV réelle et la somme de a) et b) est compensée avec d'autres particules de charge non opacifiantes.
     
    3. Composition de revêtement selon la revendication 1 ou selon la revendication 2, dans laquelle les pigments opacifiants sont blancs.
     
    4. Composition de revêtement selon la revendication 3, dans laquelle les pigments opacifiants blancs sont choisis parmi le dioxyde de titane et les particules de polymère creuses.
     
    5. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle les sphères creuses polymères représentent moins de 10 % en volume.
     
    6. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle les particules de charge sont choisies dans le groupe constitué par le carbonate de calcium-magnésium, le carbonate de calcium, la syénite néphélinique, et le kaolin.
     
    7. Composition de revêtement selon la revendication 6, dans laquelle de 20 à 50 % en volume du total des solides du revêtement sec comprennent des particules de charge ayant une valeur d50 ≤ 2 micromètres.
     
    8. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle le liant polymère a une Tg Fox calculée de 6 à 21°C.
     
    9. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle le liant polymère dérive de styrène, d'acrylate de butyle et d'acide acrylique.
     
    10. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle le liant représente de 5 à 20 % du revêtement séché.
     
    11. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle l'indice d'acide du liant polymère est de 15 à 60 mg KOH/g de polymère.
     
    12. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle le composant acide comprend de l'acide acrylique et/ou de l'acide méthacrylique et/ou de l'acide maléique et/ou son anhydride.
     
    13. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle la demande en dispersant est estimée par le procédé suivant ou son équivalent : i) addition progressive de dispersant à une dispersion aqueuse du pigment opacifiant non polymère et des particules de charge, et surveillance de la viscosité du mélange résultant pour déterminer la viscosité minimale ; ii) identification de la quantité de dispersant ajoutée pour atteindre la viscosité minimale, représentant la demande en dispersant.
     
    14. Composition de revêtement selon l'une quelconque des revendications précédentes, contenant jusqu'à 4 % en poids, sur la base de la formulation liquide, de solvant de coalescence.
     
    15. Composition de revêtement selon l'une quelconque des revendications précédentes, dans laquelle le solvant de coalescence réduit la Tg Fox calculée du liant polymère de -10 à -80°C.
     
    16. Composition de revêtement selon l'une quelconque des revendications précédentes, contenant en outre des pigments colorés.
     
    17. Composition de revêtement selon l'une quelconque des revendications précédentes, ayant une couleur à l'état sec satisfaisant aux critères suivants :

    C* < Ccritique et

    Y > mC* + 35

    lors d'un calcul utilisant m et Ccritique conformément au tableau ci-dessous :
    Angle de nuance h*mCcritique
    0 0,098 39,063
    10 0,063 42,739
    20 0,231 40,130
    30 0,399 37,522
    40 0,498 37,444
    50 0,579 38,000
    60 0,655 39,500
    70 0,732 41,000
    80 0,793 45,286
    90 0,854 49,571
    100 0,803 47,136
    110 0,740 43,955
    120 0,663 41,727
    130 0,580 39,909
    140 0,498 38,565
    150 0,416 37,696
    160 0,346 37,381
    170 0,318 39,586
    180 0,283 40,850
    190 0,190 39,350
    200 0,101 38,000
    210 0,060 38,000
    220 0,021 38,333
    230 -0,007 40,000
    240 -0,041 40,314
    250 -0,083 38,600
    260 -0,125 36,886
    270 -0,167 35,171
    280 -0,152 34,640
    290 -0,131 34,240
    300 -0,079 34,000
    310 0,016 34,000
    320 0,112 34,000
    330 0,207 34,000
    340 0,235 34,471
    350 0,161 35,647
    360 0,098 39,063

     
    18. Composition de revêtement selon la revendication 16, ayant une valeur C* inférieure à 5 et une valeur Y supérieure à 85.
     
    19. Composition de revêtement selon l'une quelconque des revendications précédentes, ayant un lustre inférieur à 15 % quand il est mesuré à 85°.
     
    20. Procédé pour revêtir un article ou une structure ayant une surface avec une composition telle que définie dans l'une quelconque des revendications précédentes, comprenant les étapes consistant à appliquer au moins une couche liquide du revêtement à la brosse, au rouleau, au tampon ou par pulvérisation ; laisser ou forcer la couche à sécher et/ou durcir.
     
    21. Article ou structure ayant une surface revêtue d'une composition telle que définie dans l'une quelconque des revendications 1 à 19.
     




    Drawing











    Cited references

    REFERENCES CITED IN THE DESCRIPTION



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    Patent documents cited in the description




    Non-patent literature cited in the description