WO2000071631A1 - Protective insulating coating formulated as a hydrodispersible polycondensate - Google Patents

Abstract

The invention relates to a protective insulating coating which can be used against migration of tannin and instantaneous corrosion. The inventive coating can be obtained by applying a dispersion onto a surface which is to be treated.Said dispersion contains a hydrodispersible polycondensate, such as a polyamide, having a highly hydrophilic group, and an acrylic, vinyl or styrene polymer.

Description

 INSULATING AND PROTECTIVE COATING FORMULATED WITH A HYDRODISPERSIBLE POLYCONDENSATE.

The invention relates to the field of surface treatment of various materials, in particular to the surface treatment of wood and steel and more particularly to the insulating and protective coating, preventing the migration of water-soluble compounds present on the surface and within of material to the surface of the coating.

In general, the compositions used for the surface treatment of materials such as metals, paper, glass, wood, building materials can be aqueous or based on organic solvents.

The use of aqueous formulations, despite their practical and ecological advantages, comes up against the problem of migration of water-soluble coloring substances present on the surface and in the material to be coated. On contact with an aqueous formulation, these water-soluble substances dissolve and rise to the surface. Thus, for example, certain species of wood, such as tropical species, are rich in water-soluble coloring substances, called tannins. When these untreated woods are coated with an aqueous system (such as a latex paint) the tannins are extracted from the substrate and migrate to the surface, which they color unaesthetically. The coloring manifests itself through successive layers, unless an insulating layer blocks the ascent of the coloring substance. The same migration problem arises for the renovation of walls contaminated by a yellowish deposit left by cigarette smoke, by the soot which migrates through the wall of the chimney, by the stains of humidity consecutive to a water leak. or a leak in the building.

Likewise, when an aqueous system is applied to untreated steel, rust spots appear almost instantly on the surface. The phenomenon is called instant corrosion. These coloring substances are generally not soluble in the organic solvents of glycerophthalic paints; so applying a traditional non-aqueous system solves the problem. With a water system, on the other hand, all the constituents (binder, pigmentation, additives and solvents) must be selected with a view to optimizing the insulating power of the coating. These choices are often made at the expense of other useful properties, such as ease of application, open time, appearance, gloss, adhesion, so that the final result is only moderately satisfactory. by only partially ensuring the objective of blocking the recovery of water-soluble substances.

Some of these coloring substances, water-soluble at basic pH, have an anionic character. One strategy for immobilizing them is to make them insoluble by precipitating them with insoluble cationic resins. US 3,494,878, filed in 1,970, describes the tannin blocking effect and instant corrosion obtained by the combination of a film-forming latex and an insoluble cationic or anionic resin. Patent application WO 94/29393 similarly exploits the blocking properties of a non-film-forming cationic resin used in combination with a compatible film-forming aqueous dispersion for formulating an aqueous correction fluid. EP 322 1 88 (921007) invokes the same principle to improve water resistance by fixing anionic surfactants on an aqueous dispersion of a non-film-forming and insoluble polymer, functionalized with a weak base. An improvement in the blocking of tannins is mentioned as an additional benefit of the combination. It is remarkable that the weakly basic resin loses its blocking efficiency when it is film-forming. In US Patent 3,494,878, it is already observed that certain species of tannins escape the blocking power of the cationic resin, that an anionic resin would be more effective in fixing. A combination of cationic and anionic functionality provides a wider blocking effectiveness field. According to EP 8371 10, the resin cationic ion exchanger (typically a divinylbenzene-styrene copolymer carrying a quaternary ammonium), combined, as in US 3,494,878, with the emulsion polymer, is activated by a water-soluble anionic polymer. US 5, 141, 784 describes a treatment of a wood rich in tannins which consists in the application of enough carboxylic acid salt and / or a water-soluble polymer functionalized by quaternizable amino groups and of molecular weight of 50 to 300,000. US 5,051,283 describes an aqueous coating which comprises an alkaline salt of a mono- or dicarboxylic acid and a water-soluble polymer carrying quaternizable amino groups and of molecular weight 50 to 300,000.

US 4,075,394 describes the treatment of a wood rich in tannins with a polyaziridine.

Numerous documents describe the functionalization of dispersions of addition polymers based on vinyl or ethylenically unsaturated monomers by amino monomers, optionally quaternized, for the coating. EP 290777 and US 4,760.1 10 claim that amphoteric latexes are obtained by a 2-step process. US 3,404.1 14 already used in 1 968 a sequenced process for introducing an aminoacrylate into a functionalized latex. MATBAE is introduced in the 2nd step after neutralization to obtain a stable latex. The latex described in EP 587333 (94031 6) comprises an insoluble and functionalized tertiary amine polymer grafted onto an acid functionalized water-soluble polymer. The latex is stable and is formulated in semi-transparent stain, water resistant and having a good open time. The blocking of water-soluble substances is however not claimed.

The presence of amino functional groups does not ipso facto confer efficacy on blocking tannins and various spots: The formulation plays a decisive role: the formulation pH, the choice of neutralizing agent, the presence of zinc, zirconium or zinc salts contribute to the formation of effective complexes: According to EP 407085 (1 991), anteriorized by US 375 653 (07/05/89), it is possible to obtain a tannin blocking efficiency equivalent to that of a glycerophthalic primary in solvent phase by formulating a latex cationic functionalized at acidic to neutral pH with an aminosilane dispersant.

EP 622427 (941 102) and US 5,527.61 9 (960618) describe a combination of an acid functionalized polymer with an aminosilane, which confers excellent blocking properties of tannins and various stains. EP 1 92077 describes the formulation of a primer based on a dispersion comprising a zinc-amine complex of water-soluble polymer. The primer in question effectively blocks the tannins in the wood. US 5,681,880 claims an improvement on the previous patent by suggesting replacing the zinc complexes with water-soluble zirconium complexes.

The Applicant has just discovered that the problems mentioned above can be solved more simply by treatment of the substrate with an aqueous dispersion based on a water-dispersible polycondensate and / or a polymer based on vinyl or ethylenic monomers radical polymerized.

It is also possible to formulate a coating with a dispersion according to the invention which has good insulating power and good application properties and this without the use of active pigments and specific additives. The object of the invention is the use of the aqueous dispersion as described above for the surface treatment of various supports such as wood, textile, leather, paper, metal, glass and building materials.

The dispersion according to the invention constitutes both an active binder and a universal binder. Indeed ; it confers by itself a good insulating and protective power without calling on particular active constituents, although an addition of these makes it possible to reinforce these effects (binder active). At the same time, the composition lends itself to conventional formulation methods and makes it possible to obtain low levels of volatile organic compounds. This generates a significant ecological advantage. The treatment according to the invention has good properties in application: good gloss potential, good stretch, low tackiness. It will thus meet the specifications both in primer on wood and metal and in finishing. Furthermore, the dispersion according to the invention can be modified and formulated at will according to the requirements of the intended application. The treatment of the invention is obtained from an aqueous dispersion containing at least one radical polyaddition polymer and a water-dispersible polycondensate.

The water-dispersible polycondensate is typically a polyester, a polyester-amide, a polyetherester amide or a polyamide, the water-dispersible nature of which is linked to the incorporation of sulphate or sulphonate groups. Precise compositions of polyesters and polyesteramides, as well as their manufacturing process, are contained in US 5, 277, 978 WO 95/0541 3, WO 95/01 382 and EP 532961. Furthermore, water-dispersible polyamides are described precisely in WO 98/500450, WO 98/03567.

The polycondensate can also contain a grafting site such as a double bond reactive by radical polymerization.

The dispersion of the invention can be obtained in various ways. According to one form, the water-dispersible polycondensate taken in the form of a powder or an aqueous dispersion is mixed with an aqueous dispersion containing the acrylic, vinyl and / or styrene polymer.

According to another form, the acrylic, vinyl and / or styrene polymer is obtained by radical polymerization in aqueous emulsion of at least one acrylic, vinyl and / or styrene monomer in the presence of at least one water-dispersible polycondensate which then plays the role of protective colloid and makes it possible to reduce, or even completely eliminate during synthesis, the micromolecular surfactants harmful to the application.

To carry out the dispersion according to this latter form, the procedure is as follows: Firstly, the water-dispersible unsaturated polycondensate is prepared by polycondensation and functionalization using a chain limiter according to the procedure described later, then a preferably an aqueous dispersion of 0.1 to 40% by weight of the polyamide and is introduced into the bottom of the reactor vessel. The temperature of the medium is brought to the usual temperatures for emulsion polymerizations (conventionally from 50 ° C to 80 ° C). The monomer (s) (A) or the mixture (s) of acrylic, vinyl and / or styrenic monomers is then poured at constant speed onto the dispersion according to the semi-continuous processes or sequences known from the skilled in the art. An aqueous solution of water-soluble initiator of the type of those conventionally used as an emulsion is poured in parallel into the reactor so as to initiate the radical polymerization of the monomer (s). Optionally, a first pouring of hydrophilic monomers can be carried out before adding, in a second step, the mixture (s) of more hydrophobic monomers to promote a reverse core-shell mechanism and obtaining small particles. . A weakly concentrated solution of macromolecular surfactant can also be poured.

The monomer A is chosen from the group containing: 1. Relatively hydrophilic monomers such as C1 -C3 alkyl or hydroxyalkyl amides and esters of (meth) acrylic acids and other unsaturated acids, acrylic, methacrylic and itaconic acids, vinyl alcohol esters, acrylonitrile, methacrylonitrile, crotonaldehyde, (meth) acrylates carrying hydrophilic groups such as segments based on polyoxyethylene. 2. Hydrophobic monomers such as: The alkyl (meth) acrylates, C3-C1 2 / ^'are styrenic, vinyl, dienes, (meth) acrylates containing a substituted nitrogen atom such as methacrylate, t-butyl aminoethyl methacrylate diethyl aminoethyl. The preferred monomer A is chosen from: acrylic acid methacrylic acid

(meth) acrylate substituted by hydroxyalkyls (HEMA, etc.)

(meth) acrylates substituted by Cn, n <3 alkyl styrene butyl acrylate ethyl hexyl acrylate

(meth) octyl acrylate.

Preferably, the polycondensates used to produce the dispersion of the invention are water-dispersible polyamides having at least one unsaturation, designated below by PAHDI. They are obtained by polycondensation and functionalization using a chain limiter carrying an unsaturated group which can be polymerized by the radical route.

In general, polycondensation is carried out between a diacid and a diamine. The water dispersibility is obtained thanks to a monomer, in general a diacid containing the unit resulting from a salt of an alkali metal of 2 or 1-sulfoisophthalic acid, the salt being able to be a salt of sodium, potassium , lithium or amine corresponding to the following formula:

X ≈ Na, K, Li As diacids there may be mentioned: isophthalic, adipic, azelaic, sebacic, dodecandioic, butane-dioic acids, 1,4-cyclohexyl dicarboxylic, terephthalic (fatty acids less than 12% by weight), fatty acids dimerized (these dimerized fatty acids preferably have a dimer content of at least 98%; preferably they are hydrogenated; they are marketed under the brand "PRIPOL" by the company "UNICHEMA", the most interesting grades are PRIPOL 1 008, PRIPOL 1 009 and

PRIPOL 1 01 3 or under the Empol brand by the company HENKEL).

As diamines, mention may be made of hexamethylenediamine, tetramethylenediamine, octamethylenediamine, decamethylenediamine, dodecamethylenediamine, 1, 5-diamino-hexane, 2,2,4-trimethyl-1, 6-diamino-hexane, piperazine , 3,3'-dimethyl-4,4'diaminodicyclohexylmethane, 4,4'-diamino-dicyclohexyl-methane, 2,2 '- (4,4'- diaminodicyclohexyl) -propane, isophoronediamine, 1 , 4-diamino-cyclohexane, meth-xylylene-diamine. It is also possible to use polyol diamines sold under the name "Jeffamine" by the company Huntsman Corp. The preferred grades are the Jeffamine D400 and the Jeffamine D2000. These polyether chains in particular increase the hydrophilicity of the resins. Their weight rate can reach up to 60%. Diacids and diamines can be replaced by amino acids or lactams such as caprolactam, enanthalactam, laurolactam, their open forms and 1 1 -amino-undecanoic acid. As chain limiter, the following can be used: The unsaturated compounds, bearing the abovementioned groups, which may belong to different classes of organic compounds. They may in particular be of the RR ² C = CR ³ X (1) type where the groups or atoms R, R ² , R ³ , similar or different, are: H, halogen, alkyl, aryl, in particular phenyl, and carboxyl, norbornyl, thienyl, pyrrolyl or furanyl, while the active group X can be: - (CH ₂ ) _n COOH with n = 0 to 1 7; -CH ₂ NH (CH ₂ ) n COOH; -

(OCH ₂ CH2) _k OH with k = 20

-COO-glycidyl;

YC ₆ H ₄ - (CH ₂ ) _n , - COOR with n '= 0 or 1, Y being -COO, -CONH,

R being H, alkyl or aryl; -CH ₂ OH; - (CH ₂ ) _m NH ₂ with m = 0 to 1 8 or - (OCH ₂ CH ₂ ) OH.

Thus, particularly favorable examples of the compounds according to formula (1) are: acids or esters of unsaturated acids, acrylic, methacrylic, cinnamic, crotonic, citraconic, itaconic, vinylacetic, undecylenic, maleic, fumaric, 5'-norbornene- 2 acrylic, 3'-furanyl-2 acrylic, 3'-pyrrolyl-2 acrylic, N-allyl aminobezoic, N-acryloyl or N-methacryloyl p-aminophenylacetic, N-allyl amino-1 1 -undecanoic, and the like.

Another type of unsaturated compound, suitable for the process according to the invention, may be possible without being limited: acids and N-maleimido esters: hexanoic, p.benzoic, dodecanoic, etc. Mention may also be made of anhydrides and imides derived from anhydrides such as tetrahydrophthalic, p. Benzoic N-maleimido, p- (endo-cis-bicyclo (2,2, 1) -5 heptene-2,3 dicarboxylic).

When preparing the dispersions of the invention, it is necessary that the number of PAHDI particles in the reactor is large enough so that the monomer can be added and polymerized at high speeds. Depending on the composition and characteristics of the copolyamide used, there is an optimal window in which these conditions are obtained (for a minimum concentration value of 0.1%). We have also observed that the interactions between the monomers and the polyamide vary according to the polarity of the monomers used. So it is necessary optimize the synthesis process (temperature, nature of initiators) according to the nature of the polyamide and of the vinyl or acrylic monomers overpolymerized.

Compared with conventional dispersions obtained by polymerization and which generally contain from 1 to 3 parts of low-mass surfactants which can diffuse out of paint films, the dispersions obtained by this invention from 0.1 to 10% by weight of polyamide , have the advantage of having small sizes, preferably less than 120 nm and of containing only very small quantities of macromolecular surfactants and a majority proportion of surfactant of high mass, which has the effect of minimizing the species likely to migrate into movies. In addition, the grafting of the polyamide to the acrylic, vinyl and / or styrene copolymer described in the present invention completely eliminates the migration of this macromolecular surfactant out of the film. This property limits the deterioration of the films over time, in particular eliminating the phenomena of exudation, sensitivity to water and loss of adhesion to the substrates.

The behavior of the dispersion with respect to the usually used mineral fillers can be improved by the presence at the periphery of the latex particles of a polyamide carrying an ionic and / or polar group. Grafting when it exists can stabilize the interactions between mineral fillers and latex particles during the formation of the paint film, thus ensuring better cohesion and better resistance to abrasion, in particular to wet abrasion. The dispersion of the invention, whatever its method of production, consists of:

- 0.1% to 100% by weight of the total weight of the polycondensate polymer particles, and preferably from 0.1% to 40%, and

- 99.9% to 0% by weight of the total weight of the particles of polymers of acrylic, vinyl and / or styrenic polymers, with a preference ranging from 60% to 99.9%. The particle size is between 20 nm and 1 μm, preferably less than 120 nm.

The coating is formulated or not with pigments and fillers, and will therefore be opaque or (semi) -transparent. The additives or active pigments, generally introduced to obtain the blocking of the coloring substances, can also be used in the coating according to the invention in order to reinforce the insulating and protective effect. The coatings obtained after formulation can be film-forming or non-film-forming.

The coating according to the invention is obtained by applying to the support to be treated and drying a composition according to the invention.

The composition can be formulated or not.

Drying can be carried out at room temperature or hot, at atmospheric pressure or at reduced pressure.

Depending on the monomer composition of the dispersion and its formulation, the coating is suitable for coating inorganic (masonry, walls to be renovated, ...), organic (wood, paper, leather, ...) and metallic substrates.

The coating is characterized by the power to block the rise of water-soluble species, in particular those, such as nicotine, wood tannins or metal salts, which cause an iestetic coloring of the film surface.

Applied on metal, the coating according to the invention makes it possible to obtain protection against instantaneous corrosion to that accessible by a formulation based on a conventional latex. Examples

Example 1: Preparation of a water-dispersible unsaturated polyamide (PAHDI) monounsaturated with cinnamic acid.

We operate in a reactor of 4 liters capacity, with three pipes: gas inlet, communication with a distillation system comprising a condenser connected to a distillate receiver, as well as an anchor stirrer. In this reactor, we introduce: 339.0g of lactam 6 or 3.0 mole, 1 96.5g of AH salt (adipic acid and hexamethylenediamine salt) or 0.75 mole, 1 87.34g of hexamethylenediamine or 1.61 5 mole, 1 68.5g of isophthalic acid or 1 .01 5 mole, 1 61 .0 of mono sodium salt of isophthalic sulfo acid is 0.6 mole, and 22.5g of cinnamic acid or 0.1 52 mole which corresponds to one unit of cinnamic acid per PAHDI chain and 50g of water.

The reactor is purged with nitrogen, then heated with all valves closed to 200 ° C material in 1 hour, the pressure is then 6.0 bar. Then, with stirring, the temperature rose in 1 hour to 240 ° C, the pressure is then 15 bars. The reaction is allowed to take place at 240 ° C. material for 4 hours, the pressure reaches at the end of the 4 hour plateau 18 bar and stabilizes, which means firstly that all the monomers react and secondly that the equilibrium of amide formation is achieved. At this point, the expansion begins, which lasts 90 minutes, the material temperature at the end of the expansion is 270 ° C. A stream of nitrogen of 301 / h is passed for 1 5 minutes and the PAHD is removed from the reactor. , collected in a cooled tray to ensure rapid solification.

The product obtained is slightly yellow, brittle, odorless. The number-average molecular mass measured by viscosimetry is 6650 g / mole. The Tg is 89 ° C (measured by DSC: 10K / min). PAHD is easily dispersible in water up to 40% by weight. The particle size of the dispersion is 62 nanometers.

Example 2: Preparation of dispersions according to the invention. Example 2.1 using the PAHDI of Example 1. In a 20 I double-jacket reactor equipped with a condenser and purged with nitrogen, 300 g of a polyamide dispersion, described in Example 1 of the invention, containing 5.0% of dry extract, are added.

The reactor is purged with nitrogen and the temperature is brought to 75 ° C. at 150 rpm. When the temperature is reached and stabilized, 200 g of the mixture of monomers consisting of 92.0 g of methyl methacrylate,

1 04.0g of butyl acrylate and 4.0g of acrylic acid and a solution of 0.8g of TBHP initiator (Terbutylhydroperoxide) in 25 ml of water and a solution of 0.28g of FORMOPON activator (sodium salt of formaldehyde sulfoxylate) in 25 ml of water are drained off in 300 min. After 90 min of polymerization, a solution of 1.23 g SDS in 25 ml of water is poured in 21 0 min.

After the end of the addition, the reaction medium is maintained at 75 ° C. for 60 min, then cooled to room temperature and filtered through a 100 micrometer filter. The dry extract and the particle size were then determined (Table 1). Example 3

Formulation

The low CPV paint, the formulation of which is given below, is produced according to the invention with an acrylic dispersion on PAHD seed: It is shiny and has good tension. The present formulation does not contain active substances generally introduced to block the recovery of water-soluble coloring substances. Nevertheless, applied on merbau, the coloring of the film is minimal after drying. There is almost no instant corrosion either when the paint is applied to degreased steel. In comparison, the coloring by the tannins of the merbau and the instantaneous corrosion are pronounced when the paint is formulated with a standard latex polymerized according to a conventional technology. In addition, the functionalized latexes for blocking water-soluble materials do not lend themselves well to the formulation of a glossy and taut paint.

Claims

1. Use of an aqueous dispersion based on polymer particles containing, - 0.1% to 100% by weight of the total weight, of the water-dispersible polyamide particles, and, - 99.9% to 0% by weight of the total weight, of acrylic, vinyl and / or styrenic polymer particles, for the treatment of surfaces of materials such as paper, textile, wood, leather, metal, glass, building materials . 2. Use according to 1, characterized in that said dispersion preferably contains, - 0.1% to 40% by weight of the total weight, of the particles of water-dispersible polyamide and, - 60% to 99.9% by weight of the total weight, of acrylic, vinyl and / or styrenic polymer particles 3. Use according to one of the preceding claims, characterized in that the aqueous dispersion is obtained by mixing the polyamide dispersion and optionally a dispersion of the vinyl, acrylic and / or styrene polymer. 4. Use according to one of the preceding claims, characterized in that the aqueous dispersion is obtained by the polymerization in the presence of water-dispersible polyamide of at least one vinyl, acrylic and / or styrene monomer. 5. Use according to one of the preceding claims, characterized in that the dispersion is formulated with a pigment, and / or fillers, and / or a thickener, and / or other adjuvants to form a film-forming or non-film-forming coating. ; the dispersion can in particular be formulated with “active” pigments and / or adjuvants. 6. Use according to one of the preceding claims for preventing the migration of coloring substances from a substrate to be coated; especially as a tannin inhibitor in the treatment of wood. 7 Use according to one of the preceding claims as an inhibitor of instant corrosion in the treatment of steel.