NEW PRODUCT

The present invention relates to a new form of protective coating that can be applied to substrates such as pigments. It also relates to a new method of treating pigments, including in particular pigments to which the new protective coating of the invention has been applied, so as to provide them with improved properties. In particular, the invention enables the production of stabilized fine pigments (e.g. aluminium pigments) with a superior combination of optical properties (e.g. gloss and/or lightness) and chemical resistance.

Background to the Invention

Protective coatings are known in the art. For instance, metallic effect pigments such as those based on aluminium, bronze, iron oxide or steel can react with water, acids or bases in coating or ink formulations, and so the addition of a protective coating to such pigments may therefore be used to improve their chemical resistance. One drawback associated with applying such protective coatings to pigments, though, is that it may generally be expected to impact negatively on their optical properties. So there is often a trade-off between the potentially competing aims of optimising the chemical resistance and also maintaining good optical properties with pigments. For instance, among known commercially available coated aluminium (Al) pigments, those sold by Eckart under the“PCU” trade name have been described as being the best Al pigment product in the market in terms of chemical resistance. However, this useful attribute comes at the expense of the optical properties of the pigment. This is illustrated, for instance, in Figure 2, which is an image of two polymer powder coating samples. One of them features PCU1000 pigment, and the other features pigment particles having the same particle size (namely 15 pm) but sold by Schlenk under the trade name POWDAL 8500 and having a different protective coating.

As explained in more detail below, the POWDAL 8500 product can be seen to have better optical properties, but inferior chemical resistivity.

Other coated pigments that have been discussed in the art include those described in CN106317969, CN106700662, WO9638506 and US20110195244 and include coatings prepared using poly addition reactions.

Summary of the Invention

The present invention is based on the finding that a particular method of coating a pigment leads to a product with a surprisingly advantageous combination of both chemical resistivity and optical properties. Thus, the present invention provides a method of coating a substrate, the method comprising (a) a step of subjecting an inorganic network former and an organofunctional network former to a condensation-type reaction, and subsequently (b) one or more further steps in which an inorganic network former and an

organofunctional network former are subjected to a condensation-type reaction.

The present invention also provides a method of preparing a coated substrate, the method comprising one or more steps in which an inorganic network former and an

organofunctional network former are subjected to a condensation-type reaction in the presence of a product, wherein said product is obtainable by subjecting an inorganic network former and an organofunctional network former to a condensation-type reaction in the presence of the substrate. This aspect of the invention focuses on just step (b) of the method of the invention as defined above. The preferred aspects of the invention as outlined herein apply correspondingly to this embodiment.

In this regard, coated substrates prepared by the above process have been found to enable a combination of high chemical resistivity and good optical properties that is believed to be unobtainable using previous coating methods. Also, the coating which results from the above process is believed to be more effective at reducing the likelihood of ignition during subsequent processing and handling as compared to coatings applied using previous coating methods. Also, the coating which results from the above process is believed to be more effective at improving gassing stability as compared to coatings applied using previous coating methods. However, the precise structural differences that result from using a method including the two steps (a) and (b) may not always be immediately susceptible to simple and immediate characterisation, and so the new products are most appropriately defined by reference to the particular combination of properties that they exhibit. Thus, the present invention also provides a coated substrate obtainable by the method of the invention as defined above. Also, the present invention provides a coated metal pigment or coated metal oxide pigment which (i) has a chemical resistivity score of no more than 12 in the“ Test method for measuring chemical resistivity of coated pigments” set out further below, and (ii) has a gloss variance value (X) of <5.0, wherein:

X = Y / (13 - the chemical resistivity score of the coated pigment),

Y is the percentage change in gloss resulting from the addition of the coating to the pigment, calculated as (100 * (Y1 - Y2) / Yl),

Y1 is the gloss of the uncoated pigment, and

Y2 is the gloss of the coated pigment,

wherein gloss is measured by preparing a sample containing the coated or uncoated pigment according to steps (a) to (g) of the“ Test method for measuring chemical resistivity of coated pigments” set out further below, and then using a glossmeter to measure the gloss at 60°.

Further, the present invention provides a coated metal pigment or coated metal oxide pigment which (i) has a chemical resistivity of less than 12 in the“ Test method for measuring chemical resistivity of coated pigments” set out further below, and (ii) a lightness variance LA or LB value of >90, wherein:

- LA is calculated as (100 * (1 + (Q2 - Ql) / Ql)),

Q1 is the lightness at 15 ° of the uncoated pigment, and

Q2 is the lightness at 15 ° of the coated pigment;

- LB is calculated as (100 * (1 + (Q4 - Q3) / Q3)),

Q3 is the lightness at -15 ° of the uncoated pigment, and

Q4 is the lightness at -15 ° of the coated pigment;

wherein lightness at 15 ° and -15 ° is measured by preparing a sample containing the coated or uncoated pigment according to steps (a) to (g) of the“ Test method for measuring chemical resistivity of coated pigments’’ set out further below, and then using a

spectrophotometer.

Further, the present invention provides a coated metal pigment or coated metal oxide pigment which has a value of at least 40 mJ m2/g for MIE* surface area (preferably at least 55 mJ m2/g), wherein MIE is the minimum ignition energy and the surface area is the surface area as measured by the BET method.

Further, the present invention provides a coated metal pigment or coated metal oxide pigment which (i) has a gassing stability score of >700 seconds (preferably >1000 seconds) in the“ Test method for measuring gassing stability of coated pigments” set out further below, and (ii) has a gloss variance value (X) of <5.0, wherein:

X = Y / (13 - the chemical resistivity score of the coated pigment),

Y is the percentage change in gloss resulting from the addition of the coating to the pigment, calculated as (100 * (Y1 - Y2) / Yl),

Y1 is the gloss of the uncoated pigment, and

Y2 is the gloss of the coated pigment,

wherein gloss is measured by preparing a sample containing the coated or uncoated pigment according to steps (a) to (g) of the“ Test method for measuring chemical resistivity of coated pigments” set out further below, and then using a glossmeter to measure the gloss at 60°.

Further, the present invention provides a coated metal pigment or coated metal oxide pigment which (i) has a gassing stability of at least 700 seconds (preferably >1000 seconds) in the“ Test method for measuring gassing stability of coated pigments” set out further below, and (ii) a lightness variance LA or LB value of >90, wherein:

- LA is calculated as (100 * (1 + (Q2 - Ql) / Ql)),

Q1 is the lightness at 15 ° of the uncoated pigment, and

Q2 is the lightness at 15 ° of the coated pigment;

- LB is calculated as (100 * (1 + (Q4 - Q3) / Q3)),

Q3 is the lightness at -15 ° of the uncoated pigment, and

Q4 is the lightness at -15 ° of the coated pigment;

wherein lightness at 15 ° and -15 ° is measured by preparing a sample containing the coated or uncoated pigment according to steps (a) to (g) of the“ Test method for measuring chemical resistivity of coated pigments’’ set out further below, and then using a

spectrophotometer.

PVD pigments tend to be particularly susceptible to chemical corrosion and it has been found that protective coatings applied to other pigment types may not work effectively on PVD pigments. However, the coating of the present invention is believed to provide PVD pigments with higher levels of chemical resistivity than has previously been possible.

Thus, the present invention also provides a coated PVD metal pigment or coated PVD metal oxide pigment which has a chemical resistivity score of no more than 12 in the“ Test method for measuring chemical resistivity of coated pigments’’ set out herein.

The present invention also provides a coated PVD metal pigment or coated PVD metal oxide pigment which has a gassing stability score of >700 seconds (preferably >1000 seconds) in the“ Test method for measuring gassing stability of coated pigments” set out herein.

The present invention also provides a coated PVD metal pigment or coated PVD metal oxide pigment which has a gassing stability score after 21 days of <5 ml in the“extended gassing test method” set out herein.

The present invention also provides a method comprising applying one or more surface modifiers to a coated substrate of the invention as defined above, wherein the substrate is a pigment.

The present invention also provides a method comprising:

either (i) coating a substrate by a method as defined above, or (ii) preparing a coated substrate by a method as defined above,

and subsequently

applying one or more surface modifiers to the coated substrate,

wherein the substrate is a pigment.

The present invention also provides a method of treating a pigment, the method comprising simultaneously, separately or sequentially applying one or more surface modifiers to the pigment, wherein said one or more surface modifiers include:

(a) both (i) an organophosphorous compound, and (ii) a compatibilizer as defined further below (wherein a major part of the compatibilizer does not become covalently bonded to the pigment);

(b) both (i) a fatty acid, and (ii) a compatibilizer as defined further below (wherein a major part of the compatibilizer does not become covalently bonded to the pigment); or

(c) both (i) an organofunctional network former, and (ii) an organophosphorous compound. Thus, by way of example, the present invention provides a method of treating a pigment, the method comprising simultaneously, separately or sequentially applying one or more surface modifiers to the pigment, wherein said one or more surface modifiers include an

organophosphorous compound and a compatibilizer as defined further below, and wherein a major part of the compatibilizer does not become covalently bonded to the pigment.

The present invention also provides a pigment having on its surface (a) an

organophosphorous compound and a compatibilizer as defined further below, wherein a major part of the compatibilizer is not covalently bonded to the pigment; (b) a fatty acid and a compatibilizer as defined further below, wherein a major part of the compatibilizer is not covalently bonded to the pigment; or (c) an organofunctional network former and an organophosphorous compound. (Thus, by way of example, the present invention provides a pigment having on its surface an organophosphorous compound and a compatibilizer as defined further below, wherein a major part of the compatibilizer is not covalently bonded to the pigment.)

The present invention also provides a product comprising a coated substrate of the invention as defined herein, which product is a varnish, automobile finish, paint, printing ink, powder coating material, architectural paint, plastic, security printing ink, ceramic, glass or cosmetic agent.

The present invention also provides a method of coating an article, which method comprises electrostatically applying a powder coating material to an article, and, optionally, curing the applied coating material, wherein the powder coating material comprising a coated substrate of the invention as defined herein.

The present invention also provides a coated article comprising a coated substrate of the invention as defined herein.

Description of Figures

Figure 1 shows images of two test samples, each prepared from a polymer powder plus a coated pigment of the invention and having been subjected to chemical resistivity testing.

Figure 2 shows, for comparative purposes, images of two corresponding samples, each prepared from a different commercially available pigment.

Each of Figures 3 to 5 shows images of two samples after chemical resistivity testing. In any given Figure the two samples differ only in terms of the pigment used to prepare them (with one being of the invention and the other a commercially available product). The formulation for each pair of samples (in each Figure) was different in terms of composition and/or how it was made. In other words, the invention was compared against the commercially available product in a range of different powder coating environments.

Figure 6 shows images of drawdown samples made using a liquid coating, after chemical testing. The left hand sample was made with a coated pigment of the invention, and the right hand one with a commercially available pigment product.

Figure 7 shows a suitable gassing rig for use in the test procedure discussed below in connection with Examples 4 ID and 4 IE.

Detailed description

The substrate

The substrate for use in the invention is not particularly limited. It may be a large-scale material such as a panel or girder, or may be a small-scale material such as a particulate product - e.g. flakes or platelets.

Preferably, the substrate is a flake or platelet product (e.g. a pigment) having a dso value of at least 1 pm, more preferably at least 2 pm, at least 3 pm, at least 4 pm, or at least 5 pm. The dso value is preferably no more than 2000 pm, such as no more than 1500 pm, no more than 1000 pm, no more than 500 pm, no more than 200 pm, no more than 150 pm, no more than 100 pm, no more than 80 pm, no more than 60 pm, no more than 50 pm, no more than 40 pm, no more than 35 pm, no more than 30 pm, or no more than 25 pm. Typical ranges of dso values are 2 to 2000 pm, preferably 3 to 1000 pm, more preferably 4 to 500 pm, even more preferably 5 to 100 pm, even further preferably 5 to 50 pm, and more preferably still 5 to 25 pm. The dso value is preferably measured by a laser diffraction method.

Preferably, the substrate is a flake or platelet product (e.g. a pigment) having an average aspect ratio of at least 5, more preferably at least 10, at least 25, at least 50, at least 75, at least 100, at least 110, at least 120, at least 130, at least 140, at least 150, at least 160, at least 170, at least 180, at least 190, or at least 200. The average aspect ratio is preferably no more than 2000, such as no more than 1500, no more than 1000, or no more than 750. Suitable ranges of average aspect ratios are 5 to 2000, preferably 50 to 2000, more preferably 100 to 2000, even more preferably 120 to 2000, even further preferably 150 to 2000 and more preferably still 200 to 2000. The average aspect ratio may be measured by taking the average (mean) aspect ratio of 30 (preferably 50, more preferably 100) individual flakes or platelets in the flake or platelet products as measured by microscopy, such as by scanning electron microscopy (SEM), transmission electron microscopy (TEM) or atomic force microscopy (AFM), wherein the aspect ratio for a given flake or platelet is defined as the longest diameter of the flake or platelet divided by the thickness.

Preferably, the aspect ratios of the individual flake or platelet products are measured by scanning electron microscopy, e.g. using a Hitachi TM 4000PLUS apparatus.

Preferably, the substrate has an aspect ratio of at least 100 (such as at least 120) and a d o value of no more than 50 pm, no more than 40 pm, no more than 35 pm, no more than 30 pm, or no more than 25 pm.

Preferably, the substrate has a surface area as measured by the BET method of >1 m2/g, such as >2 m2/g or >3 m2/g. In some embodiments it may be higher still, such as >4 m2/g or >5 m2/g.

Preferably, the substrate has d o value of no more than 35 pm (such as no more than 30 pm or no more than 25 pm) and an aspect ratio of at least 120, such as at least 150, or at least 200

The substrate may comprise (or be substantially composed of) an inorganic material such as mica or glass, and/or it may comprise (or be substantially composed of) metal, either elemental or alloy. The substrate may comprise (or be substantially composed of) an inorganic material or metal having a coating of one or more metal oxide layers.

Preferably, the substrate is a metal or metal oxide. More preferably, the substrate is a metal flake or metal platelet, wherein the metal is preferably aluminium, bronze, copper or

zinc, and most preferably is aluminium. Examples of a suitable aluminium pigments are SPARKLE SILVER Elite 010, SPARKLE SILVER Elite 012, SPARKLE SILVER Elite Oi l LM and SPARKLE SILVER Elite 015 LM, available from Silberline Manufacturing Co., US.

In a preferred embodiment the substrate is a metal pigment, more preferably an aluminium, bronze, copper or zinc pigment, most preferably an aluminium pigment. When the substrate is a metal (e.g. Al) pigment, the proportion of metal (e.g. Al) is preferably >90%, such as >95%, >98%, >99%, >99.5% or >99.9% by weight of the total weight of the uncoated metal (e.g. Al) pigment.

The substrates (e.g. metal flake pigments or metal platelet pigments) for use in the invention may be produced by known means. For instance, metal flake pigments or metal platelet pigments may be produced by a milling process, such as ball-milling. In another embodiment, metal flake pigments or metal platelet pigments may be produced by a vacuum metallisation process, such as by physical vapour deposition (PVD). In a further embodiment, metal flake pigments or metal platelet pigments may be produced by forming a metal oxide layer on the products of the above milling or vacuum metallisation processes.

The inorganic network former

For the avoidance of doubt, while the claims and specification refer generally to the presence of“an” inorganic network former, it is of course possible for more than one different type of inorganic network former to be present in a given step of the method of the invention. Thus, references herein to“an inorganic network former” are intended to refer to situations where either one inorganic network former is present alone, or two or more inorganic network formers are present together.

The inorganic network former is preferably a compound of formula (I)

MX„

(I)

wherein

M is Si, Al, Ti, Zr, B, Fe, Mg, Mn, Sb, Cr, Zn and/or Ce,

each X is independently an optionally hydrolysable and/or condensable group selected from halogen, -OH, or -OR, and/or one, two or three pairs of X moieties together represent a divalent chelating ligand, wherein each R group is a Ci-io alkyl group in which the carbon chain is optionally interrupted by one or more heteroatoms selected from N, O and S, and

n is an integer from 2 to 6 and corresponds to the oxidation state of M.

Naturally not all possible values of n (from 2 to 6) will always be possible for all options for M. Persons of skilled in the art will be aware of which options for n are possible for a given option for M, taking into account the possible oxidation states of that option for M. For instance, if M is Sb (V), n may preferably be 5; if M is Si, Ti or Zr, n may preferably be 4; if M is Al, Ce, Fe(III), SB (III) or B, n may preferably be 3; and if M is Zn, Fe(II) or Mg, n may preferably be 2.

In a preferred embodiment, the inorganic network former is a compound of formula (I) wherein M is Si, Al, Ti, Zr or Fe; each X is Ci-6 alkoxy; and n is 2, 3 or 4. In a further preferred embodiment, M is Si; X is methoxy or ethoxy; and n is 4. Typically, the inorganic network former is tetraethoxysilane (TEOS).

The organofunctional network former

For the avoidance of doubt, while the claims and specification generally refer to the presence of“an” organofunctional network former, it is of course possible for more than one different type of organofunctional network former to be present in a given step of the method of the invention. Thus, references herein to“an organofunctional network former” are intended to refer to situations where either one organofunctional network former is present alone, or two or more organofunctional network formers are present together.

The organofunctional network former is preferably a compound of formula (II)

R\ R2, R SiX(4 - -j - k) (II)

wherein

each of i, j and k is independently 0 or 1, provided that at least one of i, j and k is 1, each of R1, R2 and R3 is independently an organic group, provided that at least one of R1, R2 and R3 is a reactive organic group, and

each X is independently an optionally hydrolyzable and/or condensable group selected from halogen, -OH, -OR7, or -Y, and/or one pair of X moieties together represent a divalent chelating ligand, wherein

o each R7 is independently an organic group, preferably a Ci-io alkyl group in which the carbon chain is optionally interrupted by one or more heteroatoms selected from N, O and S, and

o each Y is independently -(0-R4-0-Si(R5)m(X’)2-m-)nR6, wherein

■ each R4 is independently a divalent organic group,

■ each R5 is independently an organic group,

■ each m is independently 0, 1 or 2

■ each X’ is independently an optionally hydrolyzable and/or condensable group selected from halogen, -OH, or -OR7, and/or one or more pairs of geminal X’ moieties together represent a divalent chelating ligand, wherein each R7 is independently an organic group,

n is 1 to 10, and

■ R6 is an organic group.

The reactive organic groups of the above compounds of formula (II) are preferably hydrocarbyl groups having one or more substituents selected from epoxy, amino, hydroxyl, thiol, acrylate, methacrylate, vinyl, allyl, alkenyl, alkynyl, carboxyl, carboxylic anhydride, isocyanate, cyanate, ureido and carbamate.

Preferably, the organofunctional network former is a compound selected from

aminoalkyltrialkoxysilane, N-(alkyl)-aminoalkyltrialkoxysilane, N-aminoalkyl-aminoalkyl(alkyl)dialkoxysilane, N-aminoalkyl-aminoalkyltrialkoxysilane,

epoxyalkyltrialkoxysilane, mercaptoalkyltrialkoxysilane, alkacryloxyalkyltrialkoxysilane (e.g. methacryloxyalkyltrialkoxysilane) and ureidoalkyltrialkoxysilane. Preferably the alkyl moieties are each independently selected from Ci-io alkyl, more preferably Ci-6 alkyl, such as Ci-4 alkyl. Preferably the alkoxy moieties are Ci-io alkoxy, more preferably Ci-6 alkoxy, such as Ci-4 alkoxy (typically they are ethoxy or methoxy, most commonly ethoxy).

For instance, suitable organofunctional network formers include the following:

3-aminopropyltrimethoxysilane, 3 -aminopropyltriethoxysilane,

N-(n-butyl)-3-amino-propyltrimethoxysilane, N-(n-butyl)-3-amino-propyltriethoxysilane, N-2-aminoethyl-3-aminopropyl(methyl)dimethoxysilane,

N-2-aminoethyl-3-aminopropyl(methyl)diethoxysilane,

N-2-aminoethyl-3-aminopropyltrimethoxysilane,

N-2-aminoethyl-3-aminopropyltriethoxysilane, 3-glycidyloxypropyltriethoxysilane, 3-glycidyloxypropyltrimethoxysilane, 3 -mercaptopropyltrimethoxy silane,

3-mercaptopropyltriethoxysilane, 3-methacryloxypropyltrimethoxysilane,

3-methacryloxypropyltriethoxysilane, 3-ureidopropyltrimethoxysilane, and

3 -urei dopropyltri ethoxy sil ane .

Suitable agents in this regard are commercially available. For instance, agents having epoxy groups are available from Evonik Resource Efficiency GmbH, Germany under the Dynasylan® trade name, such as Dynasylan® GLYEO and Dynasylan® GLYMO; and agents having amino groups are also available from Evonik Resource Efficiency GmbH, Germany under the Dynasylan® trade name, such as Dynasylan® AMEO (3-aminopropyltriethoxysilane) Dynasylan® AMMO (3-aminopropyltrimethoxysilane), Dynasylan® DAMO (N-2-aminoethyl-3-aminopropyltrimethoxysilane) and Dynasylan® TRIAMO (Triamino-functional propyltrimethoxy-silane).

The method

As was mentioned above, the present invention provides a method of coating a substrate, the method comprising:

(a) a step of subjecting an inorganic network former and an organofunctional network former to a condensation-type reaction,

and subsequently:

(b) one or more (e.g. one or two) further steps in which an inorganic network former and an organofunctional network former are subjected to a condensation-type reaction.

Applying a hybrid coating in this manner, i.e. employing two or more separate steps in which an inorganic network former and an organofunctional network former are subjected to a condensation-type reaction, has been found to yield a coated substrate having surprisingly superior properties as compared to (e.g.) a corresponding coated substrate prepared by subjecting an equivalent overall amount of inorganic network former and organofunctional network former to a condensation-type reaction in a single step (the properties are of particular benefit when the substrate is a metal pigment, such as an aluminium pigment). It is believed that one reason for this may relate to the fact that introducing the reagents in two steps could facilitate the formation of chemical bonds between organofunctional moieties present on the substrate following step (a) and the organofunctional moieties of the organofunctional network former used in step (b). For instance if the organofunctional network former in step (a) features epoxy moieties, then the condensation-type reaction of step (a) may be expected to yield a substrate having terminal hydroxyl groups. If the organofunctional network former in step (b) features epoxy moieties, then those moieties may react with the terminal hydroxyl groups present following step (a). Thus, in a preferred aspect, the organofunctional network former in step (b) includes an organofunctional moiety capable of reacting with (and which does react with) an organofunctional moiety present on the substrate surface following step (a) (and derived from the organofunctional network former used in step (a)), to form a chemical bond, such as a covalent bond. Having said that, it is also believed that this possible explanation (relating to the potential facilitation of chemical bond formation between organofunctional moieties) is just one of a number of reasons why the method of the present invention provides superior coatings, and accordingly, it may not be essential for the organofunctional network former in step (b) to be capable of reacting with one or more organofunctional moieties present on the substrate surface following step (a), to form a chemical bond, in order to enjoy some of the advantages of the invention; it is preferred, though.

For instance, preferred embodiments include ones where

- the organofunctional network former in step (a) comprises one or more epoxy, amino, mercapto, and/or ureido moieties, and

the organofunctional network former in step (b) comprises one or more epoxy or alkacryl (e.g. methacryl) moieties; or

the organofunctional network former in step (a) comprises one or more alkacryl (e.g. methacryl) moieties, and

the organofunctional network former in step (b) comprises one or more amino, mercapto, and/or ureido moieties (preferably one or more amino moieties).

Further preferred embodiments include ones where the organofunctional network former in step (a) includes one or more epoxy or amino moieties; and the organofunctional network former in step (b) includes one or more epoxy or alkacryl (e.g. methacryl) moieties (preferably one or more epoxy moieties).

In one preferred embodiment of the method of the invention:

the inorganic network former in each of steps (a) and (b) is a tetraalkoxysilane, the organofunctional network former in step (a) is an epoxysilane or an aminosilane, and

- the organofunctional network former in step (b) is an epoxysilane.

It will be appreciated from the definition of the method of the invention as set out above, and in particular the fact that it is a method of coating the substrate, that step (a) is to be carried out in the presence of the substrate (to be coated), and similarly that step (b) is to be carried out in the presence of the substrate which has already been coated during step (a). Thus the present method (of the invention) of coating a substrate comprises (a) a step of coating the substrate by subjecting an inorganic network former and an organofunctional network former to a condensation-type reaction in the presence of the substrate, and subsequently (b) one or more further steps in which the substrate is further coated by subjecting an inorganic network former and an organofunctional network former to a condensation-type reaction in the presence of the substrate that was coated in step (a).

As indicated above, the method of the present invention may include more than two of the condensation-type reactions, e.g. three of more such reactions. For instance, in one embodiment the method of the present invention comprises

(a) a step of subjecting an inorganic network former and an organofunctional network former to a condensation-type reaction,

and subsequently:

(b) a first further step of subjecting an inorganic network former and an

organofunctional network former to a condensation-type reaction, and then subsequently a second (and optionally more) further steps in which an inorganic network former and an organofunctional network former are subjected to a condensation-type reaction.

Carrying out three or more such condensation-type reaction steps may afford the coated pigment further enhanced properties. In this regard, though, as indicated above, it is not merely a case of carrying out an extra reaction to make a thicker (and thus more protective) overall layer. Rather, the advantages of the method of the invention arise over

corresponding products wherein the same amount of overall coating is applied in less steps, such as in a single step.

It is preferred that the condensation-type reaction in step (a) proceeds to a substantial degree of completeness (e.g. >30% completeness, >40% completeness, >50%

completeness, >60% completeness, >70% completeness, >80% completeness, or >90% completeness) prior to the subsequent condensation-type reaction in step (b). In the case that step (b) comprises more than one step in which an inorganic network former and an organofunctional network former are subjected to a condensation-type reaction, it is further preferred that each condensation-type reaction proceed to a substantial degree of completeness (i.e. >30% completeness, >40% completeness, >50% completeness, >60% completeness, >70% completeness, >80% completeness, or >90% completeness) prior to any subsequent condensation-type reaction.

Preferably, the condensation-type reaction in step (a) proceeds for >5 minutes, such as >10 minutes, >15 minutes, >20 minutes, >30 minutes, >45 minutes, >60 minutes, >75 minutes, >90 minutes, or >120 minutes prior to step (b). In the case that step (b) comprises more than one step in which an inorganic network former and an organofunctional network former are subjected to a condensation-type reaction, it is further preferred that each condensation-type reaction proceed to a substantial degree of completeness (e.g.

proceeding for >5 minutes, such as >10 minutes, >15 minutes, >20 minutes, >30 minutes, >45 minutes, >60 minutes, >75 minutes, >90 minutes, or >120 minutes) prior to any subsequent condensation-type reaction. In both steps there is not particular upper limit for the length of the reaction, though generally it is unnecessary to continue the reaction any longer than, say, 10 hours as no extra benefit would be expected (typically the reaction may be stopped after <5 hours, such as <4 hours or <3 hours).

In a preferred embodiment, the condensation-type reaction(s) in step (a) and/or (b)

(preferably all such reactions) in the method of the present invention is (are) carried out in the presence of a catalyst. The catalyst may be an acid or a base. Preferably, the catalyst is a Bronsted-basic or Lewis-basic catalyst, preferably a nitrogen-based Bronsted-basic or nitrogen-based Lewis-basic catalyst. Suitable nitrogen-based Bronsted-basic or nitrogen-based Lewis-basic catalysts may be ammonia, amines (including polyamines),

aminoalcohols or nitrogen-containing aromatic or heteroaromatic compounds. Particularly preferred nitrogen-based Bronsted-basic or nitrogen-based Lewis-basic catalysts include ethylenediamine (EDA), monoethanol amine (MEA) and N-methylimidazole (NMI). Such agents may be used directly or in admixture with a solvent.

In a preferred embodiment, the condensation-type reaction(s) in step (a) and/or (b) (preferably all such reactions) in the method of the present invention is (are) carried out in a solvent. Preferably, the solvent is a protic solvent, more preferably an alcohol such as a Ci-6 alkanol or a Ci-6 alkoxy-Ci-6 alkanol. Suitable solvents include isopropanol (IP A) and 1 -methoxy-2-propanol .

In a preferred embodiment, the condensation-type reach on(s) in step (a) and/or (b)

(preferably all such reactions) in the method of the present invention is (are) carried out at elevated temperature. The appropriate temperature will depend on the specific reagents present, an in particular any solvent that may be employed. Preferred temperatures are ones of >50 °C, such as >60 °C, >70 °C, or >80 °C. The temperature is preferably <200 °C, such as <170 °C, <150 °C, or <130 °C.

In step (a) and/or (b) (preferably both) in the method of the present invention, the molar ratio of inorganic network former to organofunctional network former may be defined as X: l. Preferably X is >0.5, such as >1, >2, >3, >4, >5, >6, >7, or >8. Preferably X is <200, such as <160, <140, <120, <110, or <100. A typical range is 1 to 120, or 5 to 120.

The absolute amounts of inorganic network former and organofunctional network former to be employed will depend on the available surface area of the substrate which is to be coated. For pigment substrates, surface area will naturally depend on particle size. These agents may be used in an amount to provide a coated substrate wherein the coating has a thickness of Y. Preferably Y is >2 nm, such as >3 nm, >4 nm, >5 nm, >6 nm, >7 nm, or >8 nm. Preferably Y is <300 nm, such as <250, <200, <150, <120, <100, <90, <90, <80,

<70, <60, or <50 nm. A typical range is 5-70 nm.

The coatings obtainable by the method of the present invention may have relatively high silicon contents. In a preferred aspect, the silicon content of the coating may be >12%, such as >13 %, >14 %, or >15 % as measurable by EDS.
CLAIMS

1. A method of coating a substrate, the method comprising:

(a) a step of subjecting an inorganic network former and an organofunctional

network former to a condensation-type reaction,

and subsequently:

(b) one or more further steps in which an inorganic network former and an

organofunctional network former are subjected to a condensation-type reaction.

2. A method according to claim 1, wherein part (b) comprises one or two further steps in which an inorganic network former and an organofunctional network former are subjected to a condensation-type reaction.

3. A method according to claim 1 or 2, wherein the substrate is a metal or metal oxide.

4. A method according to any one of claims 1 to 3, wherein the substrate is a metal pigment.

5. A method according to any one of claims 1 to 4, wherein the substrate comprises, or is, an aluminium, bronze, copper or zinc pigment.

6. A method according to claim 5, wherein the substrate is an aluminium pigment and the proportion of aluminium is >99% by weight based on the total weight of the uncoated aluminium pigment.

7. A method according to any one of claims 1 to 6, wherein the inorganic network former is a compound of formula (I):

MX„ (I)

wherein

- M is Si, Al, Ti, Zr, B, Fe, Mg, Mn, Sb, Cr, Zn and/or Ce,

each X is independently an optionally hydrolysable and/or condensable group selected from halogen, -OH, or -OR, and/or one, two or three pairs of X

moieties together represent a divalent chelating ligand, wherein each R group is a Ci-io alkyl group in which the carbon chain is optionally interrupted by one or more heteroatoms selected from N, O and S, and

n is an integer from 2 to 6 and corresponds to the oxidation state of M.

8. A method according to claim 7, wherein

- M is Si, Al, Ti, Zr or Fe,

each X is C 1-6 alkoxy, and

n is 2, 3 or 4.

9. A method according to claim 7, wherein

- M is Si,

X is methoxy or ethoxy, and

n is 4.

10. A method according to any one of claims 1 to 9, wherein the organofunctional network former is a compound of formula (II):

wherein

each of i, j and k is independently 0 or 1, provided that at least one of i, j and k is 1,

each of R1, R2 and R3 is independently an organic group, provided that at least one of R1, R2 and R3 is a reactive organic group, and

each X is independently an optionally hydrolyzable and/or condensable group selected from halogen, -OH, -OR7, or -Y, and/or one pair of X moieties together represent a divalent chelating ligand, wherein

o each R7 is independently an organic group, and

o each Y is independently -(0-R4-0-Si(R5)m(X’)2-m-)nR6, wherein

■ each R4 is independently a divalent organic group,

■ each R5 is independently an organic group,

■ each m is independently 0, 1 or 2

■ each X’ is independently an optionally hydrolyzable and/or condensable group selected from halogen, -OH, or -OR7, and/or one or more pairs of

geminal X’ moieties together represent a divalent chelating ligand, wherein each R7 is independently an organic group,

■ n is 1 to 10, and

■ R6 is an organic group.

11. A method according to claim 10, wherein each reactive organic group is,

independently, a hydrocarbyl group having one or more substituents selected from epoxy, amino, hydroxyl, thiol, acrylate, methacrylate, vinyl, allyl, alkenyl, alkynyl, carboxyl, carboxylic anhydride, isocyanate, cyanate, ureido and carbamate.

12. A method according to claim 10, wherein the organofunctional network former is selected from:

3 -aminopropyltrimethoxy silane,

3 -ami nopropyl tri ethoxy si lane,

N-(n-butyl)-3-amino-propyltrimethoxysilane,

N-(n-butyl)-3-amino-propyltriethoxysilane,

N-2-aminoethyl-3-aminopropyl(methyl)dimethoxysilane,

N-2-aminoethyl-3-aminopropyl(methyl)diethoxysilane,

N-2-aminoethyl-3-aminopropyltrimethoxysilane,

N-2-aminoethyl-3-aminopropyltriethoxysilane,

3 -gly ci dyl oxypropyltri ethoxy sil ane,

3-glycidyloxypropyltrimethoxysilane,

3-mercaptopropyltrimethoxysilane,

3-mercaptopropyltriethoxysilane,

3-methacryloxypropyltrimethoxysilane,

3-methacryloxypropyltriethoxysilane,

3-ureidopropyltrimethoxysilane, and

3 -urei dopropyltri ethoxy sil ane .

13. A method according to any one of claims 1 to 12, wherein:

- the inorganic network former in each of step (a) and (b) is, independently, a tetraalkoxysilane,

- the organofunctional network former in step (a) is an epoxysilane or an

aminosilane, and

- the organofunctional network former in step (b) is an epoxysilane.

A method of preparing a coated substrate, the method comprising one or more steps in which an inorganic network former and an organofunctional network former are subjected to a condensation-type reaction in the presence of a product, wherein said product is obtainable by subjecting an inorganic network former and an

organofunctional network former to a condensation-type reaction in the presence of the substrate.

A coated substrate obtainable by a method as defined in any one of claims 1 to 14.

A coated metal pigment or coated metal oxide pigment which (i) has a chemical resistivity score of no more than 12 in the“ Test method for measuring chemical resistivity of coated pigments” set out in the description, and (ii) has a gloss variance value (X) of <5.0, wherein

X = Y / (13 - the chemical resistivity score of the coated pigment),

Y is the percentage change in gloss resulting from the addition of the coating to the pigment, calculated as (100 * (Y1 - Y2) / Yl),

Y1 is the gloss of the uncoated pigment, and

Y2 is the gloss of the coated pigment,

wherein gloss is measured by preparing a sample containing the coated or uncoated pigment according to steps (a) to (g) of the“ Test method for measuring chemical resistivity of coated pigments’’ set out in the description, and then using a glossmeter to measure the gloss at 60°.

A coated metal pigment or coated metal oxide pigment which (i) has a chemical resistivity of less than 12 in the“ Test method for measuring chemical resistivity of coated pigments” set out in the description, and (ii) a lightness variance LA or LB value of >90, wherein:

- LA is calculated as (100 * (1 + (Q2 - Ql) / Ql)),

Q1 is the lightness at 15 ° of the uncoated pigment, and

Q2 is the lightness at 15 ° of the coated pigment;

- LB is calculated as (100 * (1 + (Q4 - Q3) / Q3)),

Q3 is the lightness at -15 ° of the uncoated pigment, and

Q4 is the lightness at -15 ° of the coated pigment;

wherein lightness at 15 ° and -15 ° is measured by preparing a sample containing the coated or uncoated pigment according to steps (a) to (g) of the“ Test method for measuring chemical resistivity of coated pigments” set out in the description, and then using a spectrophotometer.

A coated metal pigment or coated metal oxide pigment which has a value of at least 40 mJ m2/g (preferably at least 55 mJ m2/g) for MIE* surface area, wherein MIE is the minimum ignition energy and the surface area is the surface area as measured by the BET method.

A coated metal pigment or coated metal oxide pigment which (i) has a gassing stability score of >700 seconds (preferably >1000 seconds) in the“ Test method for measuring gassing stability of coated pigments” set out in the description, and (ii) has a gloss variance value (X) of < 5.0, wherein:

X = Y / (13 - the chemical resistivity score of the coated pigment),

Y is the percentage change in gloss resulting from the addition of the coating to the pigment, calculated as (100 * (Y1 - Y2) / Yl),

Y1 is the gloss of the uncoated pigment, and

Y2 is the gloss of the coated pigment,

wherein gloss is measured by preparing a sample containing the coated or uncoated pigment according to steps (a) to (g) of the“ Test method for measuring chemical resistivity of coated pigments” set out in the description, and then using a glossmeter to measure the gloss at 60°.

A coated metal pigment or coated metal oxide pigment which (i) has a gassing stability of >700 seconds (preferably >1000 seconds) in the“ Test method for measuring gassing stability of coated pigments” set out in the description, and (ii) a lightness variance LA or LB value of >90, wherein:

- LA is calculated as (100 * (1 + (Q2 - Ql) / Ql)),

Q1 is the lightness at 15 ° of the uncoated pigment, and

Q2 is the lightness at 15 ° of the coated pigment;

- LB is calculated as (100 * (1 + (Q4 - Q3) / Q3)),

Q3 is the lightness at -15 ° of the uncoated pigment, and

Q4 is the lightness at -15 ° of the coated pigment;

wherein lightness at 15 ° and -15 ° is measured by preparing a sample containing the coated or uncoated pigment according to steps (a) to (g) of the“ Test method for measuring chemical resistivity of coated pigments” set out in the description, and then using a spectrophotometer.

21. A coated PVD metal pigment or coated PVD metal oxide pigment which has a chemical resistivity score of no more than 12 in the“ Test method for measuring chemical resistivity of coated pigments” set out in the description.

22. A coated PVD metal pigment or coated PVD metal oxide pigment which has a gassing stability score of >700 seconds (preferably >1000 seconds) in the“ Test method for measuring gassing stability of coated pigments’’ set out in the description.

23. A coated PVD metal pigment or coated PVD metal oxide pigment which has a gassing stability score after 21 days of <5 ml in the“extended gassing test method” set out in the description.

24. A coated substrate as defined in any one of claims 15 to 23 (and preferably as defined in any one of claims 15 to 18 and 21), wherein the substrate is a pigment having (i) a dso value of <30 pm and (ii) an average aspect ratio of at least 100.

25. A method comprising applying one or more surface modifiers to a coated substrate as defined in any one of claims 15 to 24 (and preferably as defined in any one of claims 15 to 18, 21 and 24), wherein the substrate is a pigment.

26. A method comprising:

• either (i) coating a substrate by a method as defined in any one of claims 1 to 13, or (ii) preparing a coated substrate by a method as defined in claim 14, and subsequently

• applying one or more surface modifiers to the coated substrate,

wherein the substrate is a pigment.

27. A method according to claim 25 or 26, wherein said one or more surface modifiers include

(a) both (i) an organophosphorous compound, and (ii) a compatibilizer having a molecular weight of 5,000 or less, and wherein the organophosphorous compound and compatibilizer are applied simultaneously, separately or sequentially;

(b) both (i) a fatty acid, and (ii) a compatibilizer having a molecular weight of 5,000 or less, and wherein the fatty acid and compatibilizer are applied

simultaneously, separately or sequentially; or

(c) both (i) an organofunctional network former, and (ii) an organophosphorous compound and wherein the organofunctional network former and

organophosphorous compound are applied simultaneously, separately or sequentially.

28. A method according to claim 25 or 26, wherein said one or more surface modifiers include both (i) an organophosphorous compound, and (ii) a compatibilizer having a molecular weight of 5,000 or less, and wherein the organophosphorous compound and compatibilizer are applied simultaneously, separately or sequentially.

29. A method according to claim 28, wherein the organophosphorus compound is a compound of formula (III):

I-X-P(0)(OR1)(OR2) (III)

wherein

- R1 and R2 are each independently H, optionally substituted hydrocarbyl,

optionally substituted amine, polyether, an ammonium ion, an alkali metal, or an alkaline earth metal;

X is divalent and is (a) a straight or branched hydrocarbon chain, said hydrocarbon chain being optionally interrupted by one or more heteroatoms selected from O, S and N, (b) an optionally substituted carbocyclic ring, wherein said ring is selected from cycloalkyl, cycloalkenyl, aryl and a fused carbocyclic group, or (c) an optionally substituted heterocyclic ring including one or more heteroatoms selected from O, S and N; and

I is H or an initiator moiety for polymerization.

30. A method according to claim 29, wherein

- R1 and R2 are H;

X is C4-14 alkyl ene; and

- I is H.

31. A method according to any one of claims 28 to 30, wherein the compatibilizer is a melamine resin, an isocyanate resin, a polyurethane resin or an acrylic resin.

32. A method according to claim 28, wherein the compatibilizer is a C1-4 alcohol- etherified melamine-formaldehyde resin or an isophorone diisocyanate trimer resin.

33. A method according to claim 27, wherein said one or more surface modifiers

include both (i) a fatty acid, and (ii) a compatibilizer having a molecular weight of 5,000 or less, wherein the fatty acid and compatibilizer are applied simultaneously, separately or sequentially, the fatty acid is a compound of formula R-C(0)OH wherein R is an alkyl or alkenyl group having 3 to 29 carbons, and the

compatibilizer is as defined in claim 31 or 32.

34. A method according to claim 27, wherein said one or more surface modifiers

include both (i) an organofunctional network former, and (ii) an

organophosphorous compound, wherein the organofunctional network former and organophosphorous compound are applied simultaneously, separately or sequentially, the organofunctional network former is an aminoalkyltrialkoxysilane, and the organophosphorous compound is as defined in claim 29 or 30.

35. A method of treating a pigment, the method comprising simultaneously, separately or sequentially applying one or more surface modifiers to the pigment, wherein said one or more surface modifiers (a) include an organophosphorous compound and a compatibilizer as defined in any one of claims 28 to 32, and wherein a major part of the compatibilizer does not become covalently bonded to the pigment; (b) include a fatty acid (preferably a fatty acid as defined as in claim 33) and a compatibilizer as defined in any one of claims 27 to 32, and wherein a major part of the

compatibilizer does not become covalently bonded to the pigment; or (c) include an organofunctional network former (preferably an organofunctional network former

as defined in claim 34) and an organophosphorous compound as defined in any one of claims 27 to 30.

36. A method of treating a pigment, the method comprising simultaneously, separately or sequentially applying one or more surface modifiers to the pigment, wherein said one or more surface modifiers (a) include an organophosphorous compound and a compatibilizer as defined in any one of claims 28 to 32, and wherein a major part of the compatibilizer does not become covalently bonded to the pigment.

37. A method according to claim 36, which comprises a step of applying the

organophosphorous compound to the pigment, and subsequently a step in which the compatibilizer is applied to the pigment.

38. A method according to claim 35, 36 or 37 (preferably a method according to claim 36 or 37), wherein the pigment is a coated pigment as defined in claim 25.

39. A pigment having on its surface (a) an organophosphorous compound and a

compatibilizer having a molecular weight of 5,000 or less, wherein a major part of the compatibilizer is not covalently bonded to the pigment; (b) a fatty acid and a compatibilizer having a molecular weight of 5,000 or less, wherein a major part of the compatibilizer is not covalently bonded to the pigment; or (c) an

organofunctional network former and an organophosphorous compound.

40. A pigment having on its surface an organophosphorous compound and a

compatibilizer as defined in any one of claims 28 to 32, wherein a major part of the compatibilizer is not covalently bonded to the pigment.

41. A pigment according to claim 40, wherein the pigment having on its surface an organophosphorous compound and a compatibilizer, is a coated pigment as defined in claim 25.

42. A product comprising a coated substrate according to claim 15, a coated pigment according to any one of claims 16 to 24 (preferably a coated pigment according to any one of claims 16 to 18, 21 and 24), or a pigment according to claim 39, 40 or 41 (preferably according to claim 40 or 41), which product is a varnish, automobile finish, paint, printing ink, powder coating material, architectural paint, plastic, security printing ink, ceramic, glass or cosmetic agent.

43. A powder coating material according to claim 42, which further comprises a

polymer.

44. An aqueous coating composition (preferably a paint) comprising a coated pigment according to any one of claims 16 to 24 or a pigment according to claim 40 or 41.

45. An aqueous coating composition according to claim 44, wherein the pigment (a) has on its surface an organofunctional network former and an organophosphorus compound, and/or (b) is obtained or obtainable by a method comprising

simultaneously, separately or sequentially applying one or more surface modifiers to the pigment, wherein said one or more surface modifiers include an

organofunctional network former and an organophosphorus compound

46. An aqueous coating composition according to claim 45, wherein the pigment is obtainable by method of coating a pigment substrate and then applying one or more surface modifiers to the (thus obtained) coated pigment substrate, wherein

- the method of coating the pigment substrate comprises (a) a step of subjecting an inorganic network former and an organofunctional network former to a

condensation-type reaction, and subsequently (b) one or more further steps in which an inorganic network former and an organofunctional network former are subjected to a condensation-type reaction; and

- in the step of applying one or more surface modifiers to the (thus obtained) coated pigment substrate, said one or more surface modifiers include both (i) an organofunctional network former, and (ii) an organophosphorus compound.

47. A method of coating an article, which method comprises electrostatically applying a powder coating material as defined in claim 42 or 43 to an article, and, optionally, curing the applied coating material.

48. A method according to claim 47, wherein the article is an automobile.

49. A coated article comprising a coated substrate according to claim 15, a coated pigment according to any one of claims 16 to 24 (and preferably a coated pigment according to any one of claims 16 to 18, 21 and 24), or a pigment according to claim 39, 40 or 41 (preferably according to claim 40 or 41).