EP3959249A1

EP3959249A1 - Polymer dispersion for coating wood for blocking migratable compounds

Info

Publication number: EP3959249A1
Application number: EP20719476.2A
Authority: EP
Inventors: Clément BAZIN; Patricia Beurdeley; Frédéric Lefevre; Fatoumata Camara; Chantal ROIDOT
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2019-04-25
Filing date: 2020-04-23
Publication date: 2022-03-02
Also published as: BR112021020190A2; MX2021012791A; WO2020216850A1; US20220154033A1; CN113748146A; CA3136868A1; FR3095444A1; FR3095444B1

Abstract

The invention relates to an aqueous polymer dispersion, with said polymer comprising in its structure incorporated monomer units, from a monomer composition comprising: a) at least one (meth)acrylic monomer which is a C1-C18 (meth)acrylic ester, with no ionic group; b) at least one ethylenically unsaturated monomer having at least one carboxylic acid group; c) at least one ethylenically unsaturated monomer having a tertiary amine, and with said polymer additionally having blocked silane grafted groups in the form of -Si(OR1)₃ or -Si-R2(OR1)₂ or -Si-(R2)₂(OR1), preferably -Si(OR1)₃ or -Si-R2(OR1)₂ with R1, R2 being the same or different C1 to C4 alkyl, and with said blocked silane graft groups being incorporated by at least one of the following two paths or the combination thereof; d) presence with the monomers a), b) and c) of at least one ethylenically unsaturated comonomer d) having, in addition to said ethylenic unsaturation, at least one blocked silane group as defined above and/or e) presence with the monomers a), b) and c) of, or after-treatment of the aqueous dispersion by, at least one silane compound e) having at least one blocked silane group as defined above and at least one functional group selected from: epoxy, amino, thio, hydroxy, isocyanate, preferably epoxy, the latter group being capable of reacting, at least in part, with the carboxylic groups of said monomer b). The invention also relates to a coating composition comprising said dispersion of the invention and the use thereof for aqueous protective coating compositions for wood.

Description

POLYMER DISPERSION FOR WOOD COATING FOR BLOCKING MIGRABLE COMPOUNDS

The invention relates to an aqueous polymer dispersion specific by its composition and its use in a coating composition for wood. In particular, said coating has specific application performance on wood to prevent (block) the migration of tannins and other compounds present in wood and in particular in wood knots; which can migrate to the surface and form spots. In addition, said coating resulting from the dispersion of the present invention exhibits very good resistance to blistering.

The present invention relates more particularly to the problem of stains formed on the surface of a coating on wood due to the migration of tannins from the wood and other colored compounds of wood such as lignin and its derivatives on the surface of said coating. This problem is even more accentuated for wooden surfaces to be coated, the wood of which has visible knots on the surface or in the heart. Indeed, wood knots are an important source of tannins and other colored compounds such as lignin and derivatives that can migrate to the surface of the coating, especially if said knots are already visible on the surface of the wood. Mainly present in soft and resinous woods (cedar, spruce, pine, fir, spruce ...), knots can ooze, or even sink, for years. The exuding resin creates a yellowish color that even passes through a coat of paint forming spots and blisters. The knots sweat resin until they are completely dry.

In this context, the surface migration of the coating, of tannins and other wood compounds that can migrate, such as lignin and derivatives, ultimately causes colored stains and blisters over time. This relates in particular to aqueous coatings such as paint, whether it is a primary and / or finishing, or a varnish or a stain. In fact, when applying an aqueous coating, more or less brown lifts appear on the wood and can spoil the aesthetic effect. These stains are uplifts of tannins and other colored compounds such as lignin and its derivatives or also terpene derivatives that can migrate to the surface of the coating and are extremely resistant: despite several coats of paints, the stains may reappear. Tannins are polyphenols and are present in beech wood, oak, chestnut, cherry, walnut for the best known non-resinous and all exotic woods among softwoods, mainly pine, fir, cedar, spruce.

Said migration can take place after application of the coating and over time by a phenomenon of diffusion-migration of tannin molecules and / or other compounds such as lignin and its derivatives. These stains can affect the performance of the coating on wood both on the aesthetic aspect of the coating (poor appearance) and on the aspect of durability. of said coating by the formation of blistering bubbles of the coating by the effect of accumulation of tannins and other compounds mentioned above, with poor adhesion of the coating to the points of accumulation where, among other things, stains are formed.

In general, this type of problem is encountered for coatings on wood having a high concentration of knots. More particularly, the wood concerned is wood of: pine, fir, beech, oak, cedar, spruce, poplar, chestnut, cherry, walnut, exotic woods.

Aqueous phase coatings, for wood application to block tannins and other wood compounds which can migrate to the surface, are already known especially as primers based on cationic polymers or based on anionic emulsions.

These solutions known from the state of the art, however, exhibit insufficient performance to improve and some drawbacks, including:

Coatings based on cationic polymers allow good blocking but most often they are used as a primer (limitation) because they turn yellow over time. On the other hand, in aqueous paint formulation, the presence of specific additives is essential, which restricts the choice, unlike coatings based on anionic emulsion, especially because of the necessary compatibility of said additives with these polymers which is a serious limitation for industrial manufacture.

Regarding coatings based on anionic emulsions, they have limited performance in terms of blocking because they are anionic, because they do not or little retain the migratable compounds, their surfactants not being favorable to this blocking.

No aqueous coating composition known from the state of the art describes compositions based on an aqueous dispersion as defined according to the present invention having at least the performance of solutions already known from the state of the art cited but without their cited disadvantages.

The solution of the present invention is characterized in particular by an aqueous dispersion combining in its composition the presence of a carboxylic acid monomer with a monomer bearing a tertiary amine group, the polymer of the dispersion having blocked silane groups, this combination allowing the targeted performance of blocking tannins and other compounds mentioned and improved resistance to blistering. More particularly, the dispersion of the invention applies to a single-component aqueous coating system insofar as said dispersion is self-crosslinkable without the need for addition of crosslinking agent. The invention first relates to an aqueous dispersion of polymer having a specific monomer composition with the polymer having carboxylic acid, tertiary amine and graft silane groups.

The second object of the invention relates to a coating composition comprising said dispersion.

Another object of the invention relates to the use of said aqueous dispersion as a binder in a coating composition.

Another object of the invention relates to a coating resulting from the use of an aqueous polymer dispersion or of a coating composition according to the invention.

Finally, the invention also covers a coated substrate, in particular, of wood having visible knots on the surface or knots in the heart of the wood.

The first subject of the invention therefore relates to an aqueous polymer dispersion, in which said polymer comprises in its structure incorporated monomer units, from a composition of monomers comprising: a) at least one (meth) acrylic monomer which is a (meth) acrylic ester of C1 -C18 alkyl, or of C6-C18 cycloalkyl, without any ionic group, b) at least one ethylenically unsaturated monomer bearing at least one carboxylic acid group c) at least one monomer ethylenically unsaturated carrying a tertiary amine and with said polymer carrying in addition silane graft groups blocked in the form -Si (OR1) ₃ or -Si-R2 (OR1) or -Si- (R2) ₂ (OR1), preferably -Si (OR1) ₃ or -Si-R2 (OR1) ₂ with R1, R2, being an identical or different C1 to C4 alkyl, and with said blocked silane groups being incorporated by at least one of the following two routes or their combination: d) presence with the monomers a), b) and c) of at least one co monomer d) ethylenically unsaturated, carrying in addition to said ethylenic unsaturation, at least one blocked silane group as defined above and / or e) presence with the monomers a), b) and c) of, or post- treatment of the aqueous dispersion with at least one silane compound e) carrying at least one blocked silane group as defined above and at least functional group selected from: epoxy, amino, thio, hydroxy, isocyanate, preferably epoxy , this last group being capable of reacting, at least in part, with the carboxylic groups of said monomer b)

and preferably by e).

The dry extract or level of solids of the dispersion according to the invention can vary from 35 to 60% and more particularly from 40 to 55% by weight according to the ISO 3251: 2019 method.

The volume average size of the particles of said polymer dispersion can vary from 50 to 500 nm, preferably from 50 to 400 nm according to the ISO 22412: 2017 method. The average size of the particles can in particular be measured by light diffraction.

The dispersion according to the invention can be prepared by a standard emulsion polymerization process containing the monomers a), b) and c) and depending on the case d), in the presence of an emulsion polymerization initiator which can be selected. from: ammonium persulfate, sodium persulfate, potassium persulfate, tert-butyl hydroperoxide, hydrogen peroxide or the combination of an oxidant with a reducing agent such that the oxidants can be selected from the tert- butyl hydroperoxide and ammonium persulfate (the compounds mentioned above) and the reducing agents can be selected from sodium formaldehyde sulfoxylate, sodium hydrosulfite, sodium metabisulfite, ascorbic acid, sodium thiosulfate, sodium salt. sodium from 2-hydroxy -2- sulfinato acetic acid (Bruggolite ^® FF6) preferably: ammonium persulfate, sodium persulfate, potassium persulfate or the red / ox tert-butyl hydroperoxide / sodium salt system 2-hydroxy -2-sulfinato acetic acid or sodium tert-butyl hydroperoxide / formaldehyde sulfoxylate.

The emulsion of monomers a), b) and c) and optionally d) and / or e) is prepared with a surfactant system comprising at least one ionic surfactant and at least one nonionic surfactant. Among the suitable ionic surfactants, mention may be made of: sulfates, sulfonates, phosphates or phosphonates, phosphinates of C8-C14 fatty alcohols optionally alkoxylated with ethoxy and / or propoxy, ethoxy being preferred with a number of ethoxy of 1 to 30, preferably 2 to 10.

As suitable nonionic surfactants, mention may be made of: alkoxylated C12-C16 fatty alcohols with ethoxy and / or propoxy, the ethoxy being preferred with the number of ethoxys from 3 to 50, preferably from 5 to 40.

The emulsion polymerization can take place at a temperature ranging from 55 ° C to 95 ° C, preferably from 65 ° C to 85 ° C.

Said compound e) can be an oligomeric compound, preferably having a molecular mass of at least 300 and less than 1500 and preferably of 300 to 1000 and / or a non-oligomeric compound of molecular mass <300. It can be present with the monomers a), b), c) and d) or it is post-added in the polymer dispersion at the end of the polymerization and in a separate step of polymerization.

For the purposes of the present invention, the term “ethylenically unsaturated” means a compound having at least one C = C double bond. means a compound comprising a polymerizable carbon-carbon double bond. A polymerizable carbon-carbon double bond is a carbon-carbon double bond that can react with another carbon-carbon double bond in a polymerization reaction. A polymerizable carbon-carbon double bond is generally included in an acrylate group (-0-C (= 0) -CH = CH ₂ also called acryloxy), methacrylate (-0-C (= 0) -C (CH ₃ ) = CH ₂ also called methacryloxy), acrylamide (-NH-C (= 0) -CH = CH ₂ also called acrylamido), methacrylamide (-NH-C (= 0) -C (CH ₃ ) = CH ₂ also called methacrylamido) , alkenyl (-CH = CH-), vinyl (- CH = CH ₂ ), vinyl ether (-0-CH = CH ₂ ) or allyl (-CH ₂ -CH = CH ₂ ). Carbon-to-carbon double bonds in a phenyl ring are not considered polymerizable carbon-to-carbon double bonds.

For the purposes of the present invention, the term “(meth) acrylic monomer” means a monomer having at least one group chosen from acrylate, methacrylate, acrylamide, methacrylamide and their mixtures.

For the purposes of the present invention, the term “vinyl monomer” means a monomer having at least one group chosen from alkenyl, vinyl, vinyl ether, and mixtures thereof.

For the purposes of the present invention, the term “allyl monomer” means a monomer having at least one allyl group.

Monomer b) is an ethylenically unsaturated monomer carrying at least one carboxylic acid group.

The term "carboxylic acid group" means a -COOH group and its derivatives. Carboxylic acid derivatives are groups which can generate one or two -COOH groups by hydrolysis, in particular anhydrides (-C (= 0) -0-C (= 0) -). The anhydrides can be linear or cyclic.

As suitable monomer b), there may be mentioned a monomer selected from (meth) acrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, tetrahydrophthalic acid, itaconic anhydride, fumaric anhydride, maleic anhydride, crotonic anhydride, tetrahydrophthalic anhydride, hemi-esters of dicarboxylic acid with a hydroxyalkyl (meth) acrylate in which said alkyl, linear or branched, comprises from 2 to 4 carbon atoms, and may optionally be alkoxylated, in particular by a alkoxy group comprising from 2 to 4 carbon atoms, the hemi-esters of dicarboxylic acid with a monohydroxylated oligomer of polyether-mono (meth) acrylate or of polyester-mono (meth) acrylate, preferably the oligomers polyether diols or polyester diols serving base on these (meth) acrylated oligomers bearing a carboxylic acid function having a number-average molecular mass Mn (calculated by measuring the terminal functions) of less than 1000 and preferably less than 500.

Preferably, monomer b) is (meth) acrylic acid or itaconic acid.

According to a particular embodiment, the monomer composition comprises 0.5 to 10%, preferably from 1 to 5%, of monomer b).

Monomer c) is an ethylenically unsaturated monomer carrying a tertiary amine. Monomer c) can in particular be a (meth) acrylic monomer bearing a tertiary amine or a vinyl monomer bearing a tertiary amine, preferably a (meth) acrylic monomer bearing a tertiary amine. Said monomer c) can be selected from: 2-dimethylaminoethyl (meth) acrylate, 2-diethylaminoethyl (meth) acrylate, N- (3- (N, N-dimethylamino) propyl) (meth) acrylamide, (meth) acrylate 3-dimethylaminopropyl, 3-diethylaminopropyl (meth) acrylate, 4- (N, N-dimethylamino) styrene, 4- (N, N- diethylamino) styrene, 4-vinylpyridine, 2-dimethylaminoethyl vinyl ether, 2-diethylaminoethyl vinyl ether, 3-dimethylaminopropyl vinyl ether, 3-diethylaminopropyl vinyl ether, 4-dimethylaminobutyl vinyl ether and 6-dimethylaminohexyl vinyl ether, preferably 2-dimethylaminoethyl (meth) acrylate and 2-diethylaminoethyl (meth) acrylate.

According to a particular embodiment, the composition of monomers comprises 0.5 to 20%, preferably from 1 to 15%, of monomer c).

Monomer a) is a (meth) acrylic monomer without any ionic group, in particular without a carboxylic acid group.

Monomer a) is C1-C18 alkyl (meth) acrylate or C6-C18 cycloalkyl (meth) acrylate. The monomer a) can in particular correspond to the formula

R ¹ -0-C (= 0) -CR ² = CH ₂

with

R ^{1 is} C1-C18 alkyl or C6-C18 cycloalkyl; and

R ² is H or methyl.

The term “alkyl” means a monovalent saturated acyclic hydrocarbon radical of formula -C _n H _{2n + i} . Alkyl can be linear or branched. A "C1-C18 alkyl" means an alkyl comprising 1 to 18 carbon atoms. Examples of alkyl groups are methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, pentyl, hexyl, 2-ethylhexyl, n-octyl, isooctyl, nonyl, decyl, dodecyl, stearyl.

The term "cycloalkyl" means a monovalent hydrocarbon radical having one or more non-aromatic rings. Cycloalkyl can be saturated or unsaturated. A "C6-C18 cycloalkyl" means a cycloalkyl comprising 6 to 18 carbon atoms. Examples of cycloalkyl groups are cyclohexyl, dimethylcyclohexyl, trimethylcyclohexyl, tert-butyl-cyclohexyl, isobornyl, norbornyl, dicyclopentadienyl.

As monomer a) suitable for said dispersion, there may be mentioned a C1 -C18 alkyl (meth) acrylate chosen from methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, (meth) acrylate ) butyl acrylate, in particular of n-butyl, 2-ethylhexyl (meth) acrylate, isooctyl or n-octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, (meth) acrylate ) lauryl acrylate and stearyl (meth) acrylate, or a C6-C18 cycloalkyl (meth) acrylate chosen from: cyclohexyl (meth) acrylate with cyclohexyl substituted or not by a C1 -C4 or C1 -C2 alkyl, isobornyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, preferably cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and norbornyl (meth) acrylate.

According to a particular embodiment, the composition of monomers comprises 50 to 98%, preferably from 70 to 90% of monomer a).

The aqueous dispersion according to the invention may comprise by weight relative to the total weight of the monomers a) + b) + c):

from 50 to 98%, preferably from 70 to 90% of said monomer a)

from 0.5 to 10%, preferably from 1 to 5% of said monomer b)

from 0.5 to 20%, preferably from 1 to 15% of said monomer c),

with the sum of% a) + b) + c) being equal to 100.

The aqueous dispersion according to the invention can be obtained from a composition of monomers comprising:

from 50 to 98%, preferably from 70 to 90% of monomer a),

from 0.5 to 10%, preferably from 1 to 5% of monomer b), and

from 0.5 to 20%, preferably from 1 to 15% of monomer c),

the% being% by weight relative to the weight of the monomer composition.

According to a particular embodiment, the composition of monomers comprises less than 25%, less than 20%, less than 15%, less than 10%, less than 5%, or less than 1%, by weight vinyl aromatic monomers, in particular vinyl toluene and / or styrene, relative to the weight of the monomer composition.

According to a particular option of the invention, in said aqueous dispersion, said monomer a) is a mixture of a monomer a1) at least one (meth) acrylate of C1 -C2 alkyl and of a monomer a2) at least a C4-C18, preferably C4-C12, alkyl (meth) acrylate, more particularly with a weight ratio of a1 / (a1 + a2) ranging from 25 to 75%, preferably from 35 to 65%.

More particularly, said mixture a) comprises as monomer a1) methyl or ethyl (meth) acrylate and as monomer a2) butyl or 2-ethylhexyl or lauryl (meth) acrylate.

The polymer of the aqueous dispersion according to the invention preferably has a Tg determined by DSC with a heating rate of 10 ° C / min in two passes ranging from -20 to 60C and preferably from -10 to 50 ° C.

Said aqueous dispersion of the invention has in particular a minimum film formation temperature TMF according to standard method ISO 21 15: 1996, which ranges from 0 to 60 ° C and preferably from 0 to 40 ° C.

The acid number of the polymer of said dispersion can vary from 5 to 100, preferably from 5 to 50 mg KOH / g calculated by the material balance (% acid monomer relative to the total weight of monomers).

The tertiary amine number of said polymer can vary from 5 to 100, preferably from 10 to 70 mg KOH / g by calculation from the material balance as for the acid number.

More particularly, said silane groups grafted with the polymer of said dispersion are incorporated into said polymer by the presence with said monomers a), b) and c) of at least one silane monomer d) selected from: (meth) acrylic, vinyl monomers or allylic bearing at least one blocked silane group as defined above, preferably from (meth) acrylic or vinyl monomers.

As (meth) acrylic monomers bearing at least one blocked silane group as defined above, there may be mentioned: (meth) acryloxymethyl trimethoxysilane, 3- (meth) acryloxypropyl triisopropoxysilane, 3- (meth) acryloxypropyl trimethoxysilane, 3- (meth) acryloxypropyl triethoxysilane, 3- (meth) acryloxypropyl tributoxysilane (with butoxy = n-butoxy or iso-butoxy), 3- (meth) acryloxypropyl methyldimethoxysilane, 3- (meth) acryloxypropyl dimethylmethoxysilane, 3- (methoxhyildi-propyl) 3- (meth) acrylamidopropyl trimethoxysilane. For the purposes of the present invention, the term “(meth) acryloxy” means acryloxy or methacryloxy. The term "(meth) acrylamido" means acrylamido or methacrylamido.

As vinyl monomers bearing at least one silane group blocked as defined above, there may be mentioned: vinyl triisopropoxysilane, vinyl trimethoxysilane, vinyl triethoxysilane.

As allyl monomers carrying at least one blocked silane group as defined above, there may be mentioned: allyl trimethoxysilane, allyl triethoxysilane

Said grafted silane groups can be incorporated into said polymer by the presence with said monomers a), b) and c) of at least one silane compound e), in the presence of said monomers a), b) and c) or in post- treatment of said dispersion with said silane compound e) selected from: epoxy-silanes, amino-silanes, thiosilanes, hydroxy-silanes and isocyanato-silanes, the silane groups being blocked and as defined above, preferably from epoxy- silanes.

An epoxy-silane is a compound having at least one epoxy group (also called glycidyl) and at least one blocked silane group. As examples of epoxy-silane compounds e) suitable for the dispersion according to the invention, there may be mentioned: 2- (3,4-epoxycyclohexyl) ethyl trimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyl triethoxysilane, 3- glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl methyldiethoxysilane, 3-glycidoxypropyl methyldimethoxysilane, 3-glycidoxypropyl éthyldiméthoxysilane, 3-glycidoxypropyl éthyldiéthoxysilane, preferably 3-glycidoxypropyl trimethoxysilane, 3-glycidoxypropyl triethoxysilane, 3-glycidoxypropyl methyldiethoxysilane 3- glycidoxypropyl methyldimethoxysilane, 3-glycidoxypropyl ethyldimethoxysilane, 3-glycidoxypropyl ethyldiethoxysilane.

The epoxy-silane compound may or may not be oligomeric with an epoxy functionality ranging from 1 to 10 and a blocked silane functionality as defined above ranging from 1 to 10.

An amino silane is a compound having at least one primary or secondary amine group and at least one blocked silane group. As an example of amino silanes, mention may be made of 3-aminopropyl trimethoxysilane, 3-aminopropyl triethoxysilane, 3- (2-aminoethylamino) propyl trimethoxysilane, 3- (2-aminoethylamino) propyl triethoxysilane.

A thiosilane is a compound having at least one thiol group (also called mercapto) and at least one blocked silane group. Examples of thiosilane include 3-mercaptopropyl trimethoxysilane, 3-mercaptopropyl triethoxysilane. An isocyanato-silane is a compound having at least one isocyanate group and at least one blocked silane group.

According to another particular option of the invention, said grafted silane groups are incorporated into said polymer by combining said routes d) and e).

Said grafted silane groups may be present with a content by weight of said monomer d) and / or of said compound e) ranging from 0.01 to 5% and preferably from 0.05 to 2.5%, or 0.1 to 2 %, or 0.5 to 1.5%, based on the dry weight of said polymer. In the case of the presence of monomer d) and of compound e), said level by weight relates to the sum of monomer d) and of compound e).

The composition of monomers used to obtain the polymer of the dispersion according to the invention can optionally comprise, in addition to the components mentioned, at least one other component f) which is an additional monomer and can be a vinyl aromatic monomer or vinyl ester of the. vinyl alcohol with acetic or versatic acid or a C1 - C6 diester of maleic or fumaric acid, preferably vinyl aromatic monomer. As vinyl aromatic monomer, mention may be made of styrene and vinyl toluenes (o-, m- and p-). Such a monomer f) if present can represent from 5 to 50%, preferably from 10 to 30% by weight of component a) as defined above.

The second object of the invention relates to a coating composition, which comprises at least one polymer dispersion as defined above according to the invention.

More particularly, in said coating composition, said dispersion represents from 10 to 60% and preferably from 15 to 50% by dry weight of solids relative to the total weight of solids of said coating composition.

More preferably, said coating composition of the invention is an aqueous composition of paint, varnish or stain for the protection of wood, preferably for wood comprising knots in the heart and on the surface which are visible. More particularly, it is a primer and / or topcoat which is resistant to blistering and migration of tannins and other compounds which may migrate to the surface from wood knots.

Said other compounds which can migrate can be lignin and its derivatives present in wood and in particular in said wood knots.

Even more particularly, said coating composition is a coating composition which can be crosslinked with or without the addition of a crosslinking agent and in particular self-crosslinkable. In the case without the addition of a crosslinking agent, the coating composition of the invention has the advantage of being a single-component crosslinkable aqueous system, compared to known two-component aqueous systems.

In fact, the coating composition of the invention can crosslink on its own without the addition of a crosslinking agent by condensation reaction between two blocked silane groups (after hydrolysis) carried by different polymer chains during film formation (coalescence of the polymer particles ) and drying the formed coating film.

The coating composition may additionally include, in the case of a paint, at least one pigment, organic or inorganic. The pigment concentration by volume (CPV) of the aqueous paint composition according to the invention can vary from 15 to 70%, preferably from 20 to 45%.

The coating composition can have a solids content (dry extract) which can vary from 5 to 70%, preferably from 10 to 65%.

Other additives may be present in the aqueous coating composition such as: biocides, fungicides, thickener, wetting agent, antifoaming agent, coalescing agent, rheology agent, mineral fillers.

Another subject of the invention relates to the use of the aqueous dispersion of the invention as a binder in aqueous coating compositions and in particular in aqueous paint compositions, more particularly in primer and / or finishing paints, varnishes. or stains, preferably for wood protection. Said use relates more particularly to the protection of wood having visible knots on the surface or knots in the heart of the wood. In said use, said coatings are preferably paints, in particular primer and / or topcoat paints to improve resistance to blistering and migration of tannins and compounds that can migrate to the surface from knots in the wood, for example compared to a paint using a polymer dispersion without a combination of the monomer c) and the blocked silane groups incorporated into said polymer by said route d) and / or by said route e) as defined according to the invention above.

Another object of the invention relates to the coating which results from the use of an aqueous polymer dispersion or of a coating composition as defined above, according to the invention. Preferably, it is a paint coating, in particular a primary and / or finishing paint or a varnish or stain coating.

The last subject of the invention relates to a substrate coated with at least one coating layer as defined above according to the invention. More particularly, said substrate is made of wood and in particular comprises visible knots or knots in the heart of the wood on the surface. Said substrate wood is preferably chosen from wood, in particular from: pine, fir, beech, oak, cedar, spruce, poplar, chestnut, cherry, walnut and exotic woods. Examples of suitable exotic woods include: teak, merbau, mohagany, movingui.

The following examples are presented below by way of illustration of the invention and its performance and do not limit its coverage which is defined by the claims.

EXAMPLES

I) Raw materials used for synthesis and application

[Table 1]

II) Examples of preparation of the dispersions according to the invention and comparison

The procedure described below describes the synthesis of the dispersion according to Example 1. It remains the same for the other dispersions of the other examples described in this patent (except for the modifications indicated in the compositions). Example 1 (according to the invention)

Equipment used

A 3 L reactor (internal capacity) in glass, equipped with a double jacket, equipped with efficient stirring (vortex), a triple-flow condenser, control and regulation of the material temperature . The reactor has the number of inlet fittings necessary for the separate introduction of different components, as well as a dedicated inlet for inerting the assembly with nitrogen. The tightness is checked before each synthesis. The installation is equipped with a system to control the feed rates of the components.

Preparation of the initial charge at the bottom of the tank

52 g of Rhodafac ^® RS610 are dissolved in 791 g of demineralized water. The temperature of the starter is brought to 65-68 ° C.

Preparation of preemulsion 1

20 g of Rhodafac ^® RS610 are dispersed in 85 g of demineralized water with good stirring. Are added in turn and with good agitation:

250 g of MAM

100 g of ABU

130 g of AE2H

20 g AA

The preemulsion thus formed is white and stable and it will be kept under gentle agitation. Preparation of preemulsion 2

20 g of Rhodafac ^® RS610 and 7.5 g of disponil ^® A3065 are dispersed in 180 g of demineralized water with good stirring. Are added in turn and with good agitation:

240 g of MAM

190 g of AE2H

70 g MADAME

The preemulsion thus formed is white and stable and it will be kept under gentle agitation.

Preparation of catalyst solutions

4.3 g of TBHP (70%) are dissolved in 19 g of water.

3 g of SFS are dissolved in 73.4 g of water. 1) Seeding

The starter with the initial charge, being temperature stable at 65-68 ° C, 7% of the preemulsion 1, are introduced for inoculation. Once the temperature has stabilized, 14.8% of the TBHP solution and 14.8% of the SFS solution are added. The maximum exothermy marks the end of this stage.

2) Polymerization 1

Once the maximum exotherm is reached, we continue with the launch of the separate introductions over 120 min at a temperature maintained between 65 ° C and 69 ° C of:

93% of preemulsion 1

22.5% of the TBHP solution

22.5% of the SFS solution

3) Neutralization

The pH of the reaction medium is brought to a pH of 7.5 - 8 by adding ammonia.

4) Red-ox treatment 1

15.1% of the TBHP solution and 15.1% of the SFS solution are added over 60 minutes at 65 ° C-69 ° C.

5) Polymerization 2

Launch of separate introductions in 120 min at a temperature maintained between 65 ° C and 69 ° C of:

100% of pre-emulsion 2 30% of the TBHP solution 30% of the SFS solution

6) Red-ox treatment 2

17.6% of the TBHP solution and 17.6% of the SFS solution are added over 60 minutes at 65 ° C-69 ° C. 7) Final additions

After cooling the reaction medium to 30-35 ° C, the latex is post-added with a biocide. After 30 minutes of stirring, 7.9 g of Silquest ^® A-187 were added over 15 minutes and then the reaction medium is stirred for 40 minutes. The dry extract of the latex is then adjusted with water to a dry extract of 43%, then the product is filtered through a 100 micron cloth.

The final particle size is around 100 nm and the measured TMF is close to 15 ° C.

Example 2 (comparative outside the invention)

The dispersion of Comparative Example 2 is obtained in the same way as that of Example 1, however, in this example Silquest ^® A-187 is not added.

The physicochemical characteristics of the dispersions prepared (Examples 1 and 2) are presented in Table 2 below with composition and characteristics T5MF, Tg, ES).

[Table 2]

Physico-chemical characterization of dispersions a) Dry extract (ES)

The dry extract of aqueous dispersions is measured according to ISO 3251: 2019.

b) pH

The pH of aqueous dispersions is measured according to ISO 976: 2013.

c) Particle size

The particle size is measured by light diffraction according to ISO 22412: 2017, using a Delsa max pro apparatus from Beckman Coulter. d) Minimum film forming temperature (TMF) measured

The TMF of aqueous dispersions is measured according to the ISO 21 15: 1996 standard. e) Glass transition temperature (Tg)

The Tg is measured by DSC (Differential Scanning Calorimetry) with a ramp of 10 ° C per minute after drying the samples for 2 hours at 105 ° C.

III) Evaluation of coatings

Formulations tested, compositions and preparation

The emulsion is 33% of the formula (calculated based on the dry-dry resin of the paint which has a solids content of 58.6% by weight). The paint has a pigment concentration by volume of 40% (without additives). The composition of the formulation is shown in Table 3 below.

The emulsion has a dry extract of 43%.

Primary paint formulation

ITable 3]

Procedure for testing the blocking of knots in the wood of a blocking primer

The wood knot blocking test consists of applying, with a brush, to a wooden specimen having visible knots on its surface a layer with a wet yield of 150 g / m ² of primer of the composition described above (table 3) then two coats of satin acrylic finish paint with a wet yield of 150 g / m ² , exhibiting no stain blocking performance, as described above for the present invention. The wood chosen in this example is pine (Pinus Pinaster) with visible knot and a moisture content of about 10% by weight.

The drying time between each of the three coats is 16 hours in a controlled atmosphere at 23 ° C and 50% relative humidity. After the application of the last coat, the test piece is conditioned for 7 days under a controlled atmosphere at 23 ° C and 50% relative humidity.

Then, the test tube is prepared to undergo accelerated aging of 72 hours by exposure in a QUV aging chamber.

The accelerated aging cycle is as follows: 4 hours of exposure to a UVA cycle at 60 ° C then 4 hours of exposure to a condensation cycle under 50 ° C.

After 72 hours of accelerated aging, the specimen is removed and then dried with a dry cloth. The test piece is conditioned for 24 hours in a controlled atmosphere at 23 ° C and 50% relative humidity.

The result is expressed by measuring the DE ^* , before and after accelerated aging, of the painted surface above the node. DE ^* is measured using a Konica Minolta Spectro CM2600D, D65 / 10 °. A visual appreciation of the coloring of the test piece and of the blistering is given.

Application results

See table 4 below

[Table 4]

Claims

1. Aqueous polymer dispersion, characterized in that said polymer comprises in its structure incorporated monomer units, from a composition of monomers comprising: a) at least one (meth) acrylic monomer which is a (meth) acrylic ester of C1-C18 alkyl or C6-C18 cycloalkyl, without any ionic group, b) at least one ethylenically unsaturated monomer bearing at least one carboxylic acid group c) at least one ethylenically unsaturated monomer bearing a tertiary amine and in that said polymer also carries grafted silane groups blocked in the form -Si (OR1) ₃ or -Si-R2 (OR1) or -Si- (R2) ₂ (OR1), preferably -Si (OR1) ₃ or -Si-R2 (OR1) ₂ , with R1, R2 being a C1 to C4 alkyl identical or different, and in that said blocked silane groups are incorporated by at least one of the following two routes or a combination thereof: d) presence with the monomers a), b) and c) of at least one comonomer d) ethylenically in saturated, carrying in addition to said ethylenic unsaturation, of at least one blocked silane group as defined above and / or e) presence with the monomers a), b) and c) of, or post-treatment of the aqueous dispersion by at least one silane compound e) bearing at least one blocked silane group as defined above and at least functional group selected from: epoxy, amino, thio, hydroxy, isocyanate, preferably epoxy, the latter group being capable of reacting, at least in part with the carboxylic groups of said monomer b), and preferably by route e).

2. Aqueous polymer dispersion according to claim 1, characterized in that said monomer b) is selected from (meth) acrylic acid, itaconic acid, fumaric acid, maleic acid, crotonic acid, preferably (meth) acrylic acid and itaconic acid.

3. Aqueous polymer dispersion according to claim 1 or 2, characterized in that said monomer c) is selected from: 2-dimethylaminoethyl (meth) acrylate, 2-diethylaminoethyl (meth) acrylate, N- (3- (N , N-dimethylamino) propyl) (meth) acrylamide, 3-dimethylaminopropyl (meth) acrylate, 3-diethylaminopropyl (meth) acrylate, 4- (N, N- dimethylamino) styrene, 4- (N, N-diethylamino) styrene, 4-vinylpyridine, 2-dimethylaminoethyl vinyl ether, 2-diethylaminoethyl vinyl ether, 3-dimethylaminopropyl vinyl ether, 3- diethylaminopropyl vinyl ether, 4-dimethylaminobutyl vinyl ether and 6 -dimethylaminohexyl vinyl ether, preferably 2-dimethylaminoethyl (meth) acrylate and 2-diethylaminoethyl (meth) acrylate.

4. Aqueous dispersion according to one of claims 1 to 3, characterized in that said monomer a) is a C1 -C18 alkyl (meth) acrylate selected from (meth) methyl acrylate, (meth) acrylate. ethyl, propyl (meth) acrylate, butyl (meth) acrylate, in particular n-butyl, 2-ethylhexyl (meth) acrylate, isooctyl or n-octyl (meth) acrylate, (meth) acrylate nonyl, decyl (meth) acrylate, lauryl (meth) acrylate and stearyl (meth) acrylate or a C6-C18 cycloalkyl (meth) acrylate chosen from: cyclohexyl (meth) acrylate with cyclohexyl substituted or not by an alkyl C1 -C4 or C1 -C2, isobornyl (meth) acrylate, norbornyl (meth) acrylate, dicyclopentadienyl (meth) acrylate, preferably cyclohexyl (meth) acrylate, isobornyl (meth) acrylate and norbornyl (meth) acrylate.

5. Aqueous dispersion according to one of claims 1 to 4, characterized in that the monomer composition comprises:

from 50 to 98%, preferably from 70 to 90% of said monomer a)

from 0.5 to 10%, preferably from 1 to 5% of said monomer b)

from 0.5 to 20%, preferably from 1 to 15% of said monomer c)

the% being% by weight relative to the weight of the monomer composition.

6. Aqueous dispersion according to one of claims 1 to 5, characterized in that said monomer a) is a mixture of a monomer a1) at least one (meth) acrylate of C1 - C2 and a2) at least a C4-C18, preferably C4-C12, alkyl (meth) acrylate, more particularly with a weight ratio of a1 / (a1 + a2) ranging from 25 to 75%, preferably from 35 to 65%.

7. Dispersion according to claim 6, characterized in that said mixture a) comprises as monomer a1), methyl or ethyl (meth) acrylate and as monomer a2), butyl or 2- (meth) acrylate. ethylhexyl or lauryl.

8. Aqueous dispersion according to one of claims 1 to 7, characterized in that said polymer has a Tg determined by DSC with a heating rate of 10 ° C / min in two passages ranging from -20 to 60 ° C and preferably -10 to 50 ° C.

9. Aqueous dispersion according to one of claims 1 to 8, characterized in that it has a minimum film formation temperature (TMF) according to standard method ISO 21 15: 1996, which ranges from 0 to 60 ° C and preferably 0 to 40 ° C.

10. Dispersion according to one of claims 1 to 9, characterized in that said grafted silane groups are incorporated into said polymer by the presence with said monomers a), b) and c) of at least one silane monomer d) selected. from: (meth) acrylic, vinyl or allylic monomers bearing at least one blocked silane group as defined in claim 1, preferably from (meth) acrylic or vinyl monomers.

1 1. Dispersion according to one of claims 1 to 9, characterized in that said grafted silane groups are incorporated into said polymer by the presence with said monomers a), b) and c) of at least one silane compound e) in the presence of said monomers a), b) and c) or in post-treatment of said dispersion with said silane compound e) selected from: epoxy-silanes, amino-silanes, thiosilanes, hydroxy-silanes, said silane groups being defined as in claim 1, preferably from epoxy-silanes.

12. Dispersion according to one of claims 1 to 9, characterized in that said grafted silane groups are incorporated into said polymer by combining said routes d) and e).

13. Dispersion according to one of claims 1 to 12, characterized in that said grafted silane groups are present with a content by weight of said monomer d) and / or of said compound e) ranging from 0.01 to 5% and preferably from 0.05 to 2.5%, or 0.1 to 2%, or 0.5 to 1, 5%, relative to the dry weight of said polymer.

14. Coating composition characterized in that it comprises at least one polymer dispersion as defined according to one of claims 1 to 13.

15. Coating composition according to claim 14, characterized in that said dispersion represents from 10 to 60% and preferably from 15 to 50% by dry weight of solids relative to the total weight of solids of said coating composition.

16. Coating composition according to claim 14 or 15, characterized in that it is an aqueous composition of paint, varnish or stain for the protection of wood, preferably for wood comprising knots in the heart and on the surface which are apparent. .

17. Coating composition according to one of claims 14 to 16, characterized in that it is a primer and / or finish paint resistant to blistering and migration of tannins and other compounds which can migrate to the surface from the wood knots.

18. Coating composition according to one of claims 14 to 17, characterized in that it is crosslinkable with or without the addition of a crosslinking agent and in particular self-crosslinkable.

19. Use of an aqueous dispersion as defined according to one of claims 1 to 13 as a binder in aqueous coating compositions and in particular in aqueous paint compositions, in particular primer and / or finishing paints, varnishes. or stains, preferably for wood protection.

20. Use according to claim 19, characterized in that it relates to the protection of wood having visible knots on the surface or knots in the heart.

21. Use according to claim 19 or 20, characterized in that said coatings are paints, in particular primer and / or finishing paints to improve the resistance to blistering and to migration of tannins and compounds which can migrate to the surface. , derived from the knots of wood relative to a paint using a polymer dispersion without a combination of the monomer c) and the silane groups incorporated into said polymer by said route d) and / or by said route e) as defined according to claim 1.

22. Coating characterized in that it results from the use of an aqueous polymer dispersion as defined according to one of claims 1 to 13 or from a coating composition as defined according to one of claims 14 to 1 8.

23. Coating according to claim 22, characterized in that it is a paint coating, in particular primary and / or finishing paint or a varnish or stain coating.

24. Substrate coated with at least one coating layer as defined in claim 22 or 23.

25. Substrate according to claim 24, characterized in that said substrate is made of wood and in particular comprises on the surface visible knots or knots in the heart of the wood.

26. Substrate according to claim 25, characterized in that said wood is chosen from: pine, fir, beech, oak, cedar, spruce, poplar, chestnut, cherry, walnut or exotic wood.