EP3529318A1

EP3529318A1 - Self-adhesive composition for coating metal surfaces

Info

Publication number: EP3529318A1
Application number: EP17797703.0A
Authority: EP
Inventors: Ornella ZOVI; Jean-Charles Durand; Jean-Yves Loze; Emilie-A DELATTRE
Original assignee: Arkema France SA
Current assignee: Arkema France SA
Priority date: 2016-10-24
Filing date: 2017-10-24
Publication date: 2019-08-28
Also published as: US11667797B2; FR3057875A1; US20190264037A1; JP2019535852A; CN109863211A; WO2018078275A1; FR3057875B1

Abstract

The present invention relates to a self-adhesive powder composition comprising: at least one polyamide, and at least one ethylene-vinyl alcohol copolymer, and at least one hydrophobic agent, and optionally at least one filler.

Description

SELF-ADHERENT COMPOSITION FOR COATING METAL SURFACES

Field of the invention

The invention relates to a self-adhering polyamide-based powder composition for coating metal surfaces.

Technical background

Metal surface coating is widely used in industry and has a wide variety of applications, including automotive, fluid transfer, electrical and electronic industries.

The adhesion of a coating to these supports is of paramount importance for their mechanical behavior and for their protection against corrosion.

Polyamides are commonly used for coating metal surfaces. In order to ensure a durable adhesion of the polyamide coating to the metal support, the latter is previously coated with an underlayer, called adhesion primer. However, this requires additional installations, an increase in the duration of coating operations and an increase in production costs.

Alternatives for the coating of metal surfaces with polyamide-based compositions that do not require an adhesion primer have therefore been sought.

The patent application US 2012/0070670 thus describes the coating of metal parts with a composition comprising a copolyamide, an isocyanate, an epoxide and a functionalized polyolefin.

However, it is desirable in some cases, especially for water pipes, to avoid the presence of isocyanate compounds or epoxides, especially bisphenol A.

In this context, the international application WO 2008/029070 describes a self-adhering polyamide-based powder composition for coating metal surfaces, which does not require a primer. In this case, the adhesion is obtained thanks to a coating having a dry and / or wet modulus greater than or equal to 2200 MPa [NF EN ISO 527 standard], this module being itself affected by the presence of a high amount of charges in the composition. However, this high level of charge makes the coating brittle when dry. It is therefore an object of the present application to provide a polyamide-based composition for the coating of metal surfaces devoid of these defects. Summary of the invention

The present invention results from the unexpected demonstration by the inventors that the addition of a hydrophobic agent, combined with an adhesion promoter of the ethylene-vinyl alcohol copolymer type, with a polyamide-based pulverulent composition, not having an epoxy and having a low charge ratio, allowed to obtain a metal surface coating having excellent adhesion and flexibility before and after immersion in water at 50 ° C for several weeks without modification the appearance of the coating.

Thus, the present invention relates to a self-adhering powder composition comprising:

at least one polyamide, and

at least one ethylene-vinyl alcohol copolymer, and

at least one hydrophobic agent, and

possibly at least one load.

Advantageously, the self-adhering powdery composition comprises:

55 to 99% of at least one polyamide, and

0.5 to 23% of at least one ethylene-vinyl alcohol copolymer, and

- 0.5 to 22% of at least one hydrophobic agent,

by weight, on the total weight of the composition.

In a preferred embodiment, the composition according to the invention comprises: at least one homopolyamide and / or one copolyamide, and

at least one ethylene-vinyl alcohol copolymer, and

at least one hydrophobic agent, and

possibly at least one load.

In another preferred embodiment, the composition according to the invention comprises:

at least one homopolyamide and optionally at least one copolyamide, and at least one ethylene-vinyl alcohol copolymer, and

at least one hydrophobic agent, and possibly at least one load.

Preferably, the composition according to the invention comprises:

at least one homopolyamide, and

at least one copolyamide, and

at least one ethylene-vinyl alcohol copolymer, and

at least one hydrophobic agent, and

possibly at least one load.

The composition according to the invention advantageously comprises:

55 to 98.5%, preferably 65 to 84%, of at least one homopolyamide and / or copolyamide with a melting point greater than 150 ° C., and

0.5 to 15%, preferably 2 to 10%, of at least one ethylene-vinyl alcohol copolymer, and

0.5 to 15%, preferably 2 to 10%, of at least one hydrophobic agent, and

- 0.5 to 15%, preferably 2 to 15%, of at least one copolyamide with a melting point in the range of 80 to 150 ° C,

by weight, on the total weight of the composition.

We differentiate here the two types of copolyamides:

those used as an additive in the range of 0.5 to 15% and a melting point in the range of 80 to 150 ° C; of

those used, where appropriate, as the base polyamide (PA) of the composition, said composition according to the invention containing from 55 to 98.5% of PA homopolyamide and / or copolyamide, and said copolyamide present, if appropriate, in this PA of base having a melting point above 150 ° C. In the present description, the melting temperature or melting point (Tf) of the copolyamide is measured according to ISO Standard 1,1357-3 Plastics - Differential scanning calorimetry (DSC) Part 3.

Advantageously, the composition comprises less than 20% by weight of filler, preferably comprises from 0.01 to 12% by weight, preferably from 3 to 8% by weight, of filler relative to the total weight of the composition, in which the composition charge is preferably calcium carbonate.

In another preferred embodiment, the composition according to the invention does not comprise an epoxy compound.

The present invention also relates to the use of a composition as defined above for coating a metal surface. In a preferred embodiment of the use according to the invention, the metal surface has not previously been coated with a layer of adhesion primer.

The present invention also relates to a method of coating a metal surface, comprising a step of contacting a metal surface with a composition as defined above.

In a preferred embodiment, the coating method according to the invention comprises the following steps:

- heating the metal surface to a temperature sufficient for the composition to melt on contact,

- Soaking the metal surface in a fluidized bed comprising the composition.

In another preferred embodiment, the coating method according to the invention comprises the following steps:

- load the composition electrically,

- Spray the composition on the metal surface, the metal surface being connected to a zero potential,

heating the metal surface covered with powder to a temperature sufficient to obtain the melting of the composition.

In yet another preferred embodiment, the coating method according to the invention comprises the following steps:

- Spray the composition on the metal surface.

In a particularly preferred embodiment, the coating method according to the invention does not include a step of coating the metal surface with a layer of adhesion primer prior to its contact with the composition.

The present invention also relates to a material comprising a metal surface, the metal surface being coated with a coating obtained by melting a composition as defined above.

The present invention also relates to a method of manufacturing a composition as defined above, comprising the following steps:

- Mixing the constituents of the composition in the molten state,

grinding the mixture after solidification to obtain a powder of particles. Detailed description of the invention

As a preliminary, as understood here, the term "comprising" means "including", "containing" or "encompassing", that is to say that when an object "includes" one or more elements, d other elements than those mentioned can also be included in the object. On the other hand, the expression "consisting of" means "consisting of", that is, when an object "consists of" one or more elements, the object can not include other elements than those mentioned.

Polyamide

As used herein, the term "polyamide" (PA) refers to any condensation product of lactam (s), amino acid (s) or diacid (s) and diamine (s) and, as a general rule, any polymer formed by units interconnected by amide functions. Polyamides are well known to those skilled in the art. The polyamide according to the invention may be a homopolyamide and / or a copolyamide (coPA). In the case where the polyamide comprises at least two different monomers, it forms a copolyamide. The term "monomer" in the present description of polyamides should be understood as "repetitive unit". Indeed, the case where a repeating unit of the PA consists of the combination of a diacid with a diamine is particular. It is considered that it is the combination of a diamine and a diacid, that is to say the diamine pair. diacid (in equimolar quantity), which corresponds to the monomer. This is because, individually, the diacid or diamine is only one structural unit, which is not sufficient on its own to polymerize.

Advantageously, said polyamide powder comprises at least one monomer chosen from aminocarboxylic acids, preferably alpha, omega-aminocarboxylic acids, comprising from 4 to 18 carbon atoms, diamine pairs. diacid comprising from 4 to 36 carbon atoms, lactams comprising from 3 to 18 carbon atoms, and mixtures thereof.

According to a preferred embodiment of the invention, said polyamide-based particles comprise at least one polyamide and / or at least one copolyamide and / or their mixtures. By copolyamide (abbreviated as COPA) is meant the products of polymerization of at least two different monomers chosen from:

amino-acid or aminocarboxylic acid monomers, and preferably alpha, omega-aminocarboxylic acids;

- Lactam type monomers having from 3 to 18 carbon atoms on the main ring and may be substituted;

monomers of the "diamine" type. diacid "derived from the reaction between an aliphatic diamine having 4 and 36 carbon atoms, preferably 4 to 18 carbon atoms and a dicarboxylic acid having 4 and 36 carbon atoms, preferably 4 to 18 carbon atoms ; and

their mixtures with monomers with a different carbon number in the case of mixtures between an amino acid type monomer and a lactam type monomer.

Amino acid type monomers:

By way of examples of alpha, omega-amino acids, mention may be made of those having from 4 to 18 carbon atoms, such as aminocaproic acid, 7-aminoheptanoic acid, 1-aminoundecanoic acid, N-heptyl-11-aminoundecanoic acid and 12-Aminododecanoic.

Monomers of the lactam type:

Examples of lactams include those having from 3 to 18 carbon atoms on the main ring and may be substituted. Examples that may be mentioned include β, β-dimethylpropriolactam, α, α-dimethylpropriolactam, amylolactam, caprolactam also known as lactam 6, capryllactam also known as lactam 8, oenantholactam and lauryllactam, also known as lactam 12.

Monomers of the diamine type. diacid ":

As examples of dicarboxylic acid, there may be mentioned acids having 4 and 36 carbon atoms. Mention may be made, for example, of adipic acid, sebacic acid, azelaic acid, suberic acid, isophthalic acid, butanedioic acid, 1,4-cyclohexyldicarboxylic acid, terephthalic acid, sodium or lithium salt of sulphoisophthalic acid, dimerized fatty acids (these dimerized fatty acids have a dimer content of at least 98% and are preferably hydrogenated) HOOC- (CH2) 10-COOH dodecanedioic acid, and tetradecanedioic acid.

More particularly, dimerized fatty acids or dimerized fatty acids are understood to mean the product of the fatty acid dimerization reaction (generally containing 18 carbon atoms, often a mixture of oleic and / or linoleic acid). It is preferably a mixture comprising from 0 to 15% of Cl 8 monoacids, from 60 to 99% of C36 diacids, and from 0.2 to 35% of C 54 or more triacids or polyacids.

As an example of diamine, there may be mentioned aliphatic diamines having from 4 to 36 atoms, preferably from 4 to 18 atoms, which may be aryl and / or saturated cyclic. By way of examples, mention may be made of hexamethylenediamine, piperazine (abbreviated "Pip"), aminoethylenepiperazine, tetramethylenediamine, octamethylenediamine, decamethylene diamine, dodecamethylenediamine, 1,5 diaminohexane, , 2,4-trimethyl-1,6-diamino-hexane, diamine polyols, isophorone diamine (IPD), methyl pentamethylenediamine (MPMD), bis (aminocyclohexyl) methane (BACM), bis (3-methyl) 4-aminocyclohexyl) methane (BMACM), methaxylyenediamine, and bis-p-aminocyclohexylmethane.

As an example of diamines. diacids, more particularly those resulting from the condensation of 1,6-hexamethylenediamine with a dicarboxylic acid having from 6 to 36 carbon atoms and those resulting from the condensation of 1,10-decamethylenediamine with a diacid having 6 at 36 carbon atoms.

As examples of monomers of the type "diamine. diacid "include, in particular, the monomers: 6.6, 6.10, 6.1 1, 6.12, 6.14, 6.18. Mention may be made of the monomers resulting from the condensation of decanediamine with a C6 to C36 diacid, especially the monomers: 10.10, 10.12, 10.14, 10.18.

Preferably, the polyamide powders of the invention comprise at least one polyamide chosen from polyamides and copolyamides comprising at least one of the following monomers: 4.6, 4.T, 5.6, 5.9, 5.10, 5.12, 5.13, 5.14, 5.1. , 5.18, 5.36, 6, 6.6, 6.9, 6.10, 6.12, 6.13, 6.14, 6.16, 6.18, 6.36, 6, 9, 10.6, 10.9, 10.10, 10.12, 10.13, 10.14, 10.16, 10.18, 10.36, 1, 12, 12.6, 12.9, 12.10, 12.12, 12.13, 12.14, 12.16, 12.18, 12.36, 12.T, and mixtures thereof; in particular, chosen from PA 1 1, PA 12, PA 10.10, PA 6, PA 6.10, PA 10.12, PA 6.14 and / or PA 6.6 / 6, PA 6/12, PA 1 1 / 10.10 , and their mixtures. Preferably, the polyamide type PA XY or PA diamine. diacid according to the invention is selected from the group resulting from the condensation between, on the one hand (for X) hexamethylenediamine and / or decanediamine and / or dodecanediamine and, on the other hand (for Y) hexamethylenediacid and / or sebacic acid and / or dodecanedioic acid.

Preferably, the composition according to the invention comprises at least one homopolyamide selected from the group consisting of PA 10.10, PA1 1 and PA12.

PA10, PA1 1 and PA12 are well known to those skilled in the art.

The PA10.10 according to the invention results in particular from the condensation of decanediamine with sebacic acid, a natural fatty acid obtained from castor oil. As an example of PA 10.10 according to the invention available commercially, it is possible to mention the Hiprolon® brand products from Arkema, such as Hiprolon® 200.

The PA 1 1 according to the invention is a polyundecanamide resulting in particular from the condensation of 11-aminoundecanoic acid, an amino acid derived from castor oil. As an example of PA 1 1 according to the invention, it is possible to cite the Rilsan® brand products from Arkema such as Rilsan® PA 1 1 BMNO and Rilsan® PA 1 1 BMFO.

PA 12 according to the invention is a polylauramide resulting in particular from the condensation of lactam 12 or lauryllactam. As an example of PA 12 according to the invention, it is possible to mention the Rilsamid® and Rilsan® range products from Arkema.

By way of examples of copolyamides formed from the various types of monomers described above, mention may be made of the copolyamides resulting from the condensation of at least two alpha, omega-aminocarboxylic acids or two lactams or a lactam and an alpha, omega-aminocarboxylic acid. Mention may also be made of the copolyamides resulting from the condensation of at least one alpha, omega-aminocarboxylic acid (or a lactam), at least one diamine and at least one dicarboxylic acid. Mention may also be made of the copolyamides resulting from the condensation of an aliphatic diamine with an aliphatic dicarboxylic acid e † of at least one other monomer chosen from aliphatic diamines different from the preceding one and aliphatic diacids different from the preceding one.

As examples of copolyamides, mention may be made of copolymers of caprolactam and lauryllactam (PA 6/12), copolymers of caprolactam, hexamethylenediamine and adipic acid (PA 6 / 6.6), copolymers of caprolactam , lauryllactam, hexamethylenediamine and adipic acid (PA 6/12 / 6.6), copolymers of caprolactam, hexamethylenediamine and azelaic acid, 1-aminoundecanoic acid, and lauryllactam, ( PA 6 / 6.9 / 1 1/12), copolymers of caprolactam, adipic acid and hexamethylenediamine, 1 1 -aminoundecanoic acid, lauryllactam (PA 6 / 6.6 / 1 1/12), copolymers hexamethylene diamine, azelaic acid, and lauryllactam (PA 6.9 / 12), copolymers of caprolactam and 11-aminoundecanoic acid (PA 6/1 1), copolymers of lauryllactam and capryllactam (PA 12 / 8), copolymers of capryllactam and caprolactam (PA 8/6), copolymers of lauryllactam and capryllactam (PA 12 / 8), copolymers of lauryl lactam and 11-aminoundecanoic acid (PA 12/1 1).

One or more of the following copolyamides are advantageously used in the composition or process of the present invention:

PA 6 / 6.6 / 12, whose mass ratios in corresponding monomers can be (in percentage): 40/20/40, 35/20/45, 45/35/20, 30/30/40, 22/18/60 40/25/35;

PA 6 / 6.6 / 1 1/12, whose mass ratios in corresponding monomers can be for example (in percentage): 30/15/10/45, 30/20/20/30, or 15/25/25/35 ;

- PA 6/12 mass ratio 70/30;

PA 6.9 / 12 of 30/70 mass ratio;

PA Pip.9 / Pip.l 2/1 1 mass ratio 15/70/15;

PA 6 / IPD.6 / 12 of mass ratio 20/15/65;

PA IPD.9 / 12 of 20/80 mass ratio;

- PA6 / MPMD.12 / 12 of mass ratio 27/33/33;

PA 6 / 6.12 / 12 of 30/30/40 mass ratio;

PA 6 / Pip.l 2/12 of 30/20/50 mass ratio;

PA 6 / 6.12 / 1 1 /PEG.l 2 of mass ratio 25/21 / 25/30;

PA 6.10 / 1 1 /PEG.l 0 mass ratio 14/14/42/30; PA 6 / 6.6 / 6.1 0 / 6.1 mass ratio 40/10/40/10;

PA 6.10 / Pip.1 0 / Pip.12 of mass ratio 20/40/40;

PA 6/1 1 /] 2 of mass ratio 10/36/54;

PA Pip.l 2/1 2 of mass ratio 35/65;

- PA IPD.l 0/1 2 of mass ratio 80/20;

PA Pip.l 0/1 2 of mass ratio 72/28;

PA 6/1 1 of mass ratio 50/50;

AP Pip.l 0/1 1 /Pip.9 of mass ratio 65/30/5;

PA 6 / 6.6 / 6.1 0 of mass ratio 35/30/35

Examples of copolyamides that may be mentioned include those marketed under the name Platamid® and Platamid® Rnew by ARKEMA, Vestamelt® by Evonik, and Griltex® by EMS.

Preferably, the polyamide used in the present invention comprises at least one copolyamide chosen from: PA 6 / 6.6 / 12, PA 6 / 6.6 / 1 1/1 2, PA 6/1 2, PA 6.9 / 12, PA Pip. 9 / Pip.I 2/1 1, PA 6 / IPD.6 / 1 2, PA IPD.9 / 1 2, PA6 / MPMD.1 2/12, PA 6 / 6.12 / 1 2, PA 6 / Pip. 1 2/12, PA 6 / 6.6 / 6.10 / 6.1, PA 6.10 / Pip.1.0 / Pip.1.2, PA 6/1 1/12, PA Pip. 1 2/12, PA IPD.l 0/1 2, PA Pip.l 0/1 2, PA 6/1 1, PA Pip. 1 0/1 1 /Pip.9, PA 6 / 6.6 / 6.1 0, and in particular those whose mass ratios are defined above, and mixtures of these copolyamides.

The melting point of the preferred COPA additives of the composition according to the invention is generally in the range of 80 to 150 ° C, preferably 100 to 130 ° C.

Composition

The term "self-adhesive pulverulent composition" according to the invention refers to a composition in the form of powder particles which can adhere to a surface without the addition of additional compounds.

As used herein, the ethylene-vinyl alcohol copolymer (EVOH) results from the condensation of polyethylene and polyvinyl alcohol. The ethylene-vinyl alcohol copolymer according to the invention is used in particular as an adhesion promoter. As an example of an ethylene-vinyl alcohol copolymer according to the invention, it is possible to mention the Evasin products from Arkema, such as Evasin 3251 F and Evasin 4405F. The hydrophobic agent according to the invention, possibly of all types known to those skilled in the art. Preferably the hydrophobic agent is a wax, especially selected from the group consisting of polyethylene waxes and / or polypropylene and / or ethylene bis stearamide. By way of example of hydrophobing agent according to the invention, mention may be made of those of the Ceridust (Clariant) brand or those of the Crayvallac (Arkema) brand.

In a preferred embodiment, the composition according to the invention comprises at least one filler.

The filler according to the invention may be of any type suitable for the preparation of compositions based on polyamides. However, it is preferred that the filler be selected from the group consisting of talc, calcium carbonates, manganese carbonates, potassium silicates, aluminum silicates, dolomite, magnesium carbonates, quartz, nitride. boron, kaolin, wollastonite, titanium dioxide, glass beads, mica, carbon black, mixtures of quartz, mica and chlorite, feldspar and dispersed nanometric fillers such as carbon nanotubes and silica. In a particularly preferred manner, the filler according to the invention is calcium carbonate.

Furthermore, it is also preferred that the composition according to the invention comprises less than 30% by weight, more preferably less than 20% by weight, and even more preferably less than 10% by weight, of charge, the charge preferably consisting of calcium carbonate.

Preferably, the composition according to the invention further comprises at least one additional agent selected from the group consisting of a pigment, a dye, an anti-crater and / or spreading agent, a reducing agent, an antioxidant, a UV stabilizer, a fluidizing agent and a corrosion inhibitor.

The pigment according to the invention may be of any type known to those skilled in the art. Preferably, the pigment according to the invention is selected from the group consisting of titanium dioxide, carbon black, cobalt oxide, nickel titanate, molybdenum disulfide, aluminum flake, oxide iron, zinc oxide, organic pigments, such as phthalocyanine and anthraquinone derivatives, and zinc phosphate.

The dye according to the invention may be of any type known to those skilled in the art. Preferably, the dye according to the invention is selected from the group consisting of azo dyes, anthraquinone dyes, dyes derived from indigo, triarylmethane dyes, chlorine dyes and polymethine dyes.

The anti-crater and / or spreading agent may be of any type known to those skilled in the art. Preferably, the anti-cratering and / or spreading agent according to the invention is selected from the group consisting of polyacrylate derivatives.

The UV stabilizer according to the invention, perhaps of any type known to those skilled in the art. Preferably, the UV stabilizer according to the invention is selected from the group consisting of resorcinol derivatives, benzotriazoles, phenyltriazine and salicylates.

The antioxidants according to the invention may be of any type known to those skilled in the art. Preferably, the antioxidants according to the invention are selected from the group consisting of copper iodide combined with potassium iodide, phenol derivatives and hindered amines.

The fluidizing agent according to the invention may be of any type known to those skilled in the art. Preferably, the fluidizing agent is selected from the group consisting of aluminas and silicas.

The corrosion inhibitors according to the invention may be of any type known to those skilled in the art. Preferably, the corrosion inhibitors according to the invention are selected from the group consisting of phosphosilicates and borosilicates.

The powder particles of the composition may have a spherical, spheroidal or nonspherical shape.

Preferably, the particle size of the pulverulent composition according to the invention is between 5 μιτι and 1 mm, more preferably between 10 and 800 μιτι and even more preferably between 80 and 200 μιτι. As used herein, the term "particle size" refers to the average diameter or D50 of the powder particles of the composition. In the context of this description, the term "diameter" is used to describe the diameter of the circumscribed circle of the particles. The D50 is the value of the particle size that divides the analyzed particle population into exactly two. In other words, 50% of the particles are smaller than the D50. The D50 is measured according to ISO 9276 - Parts 1 to 6: "Representation of data obtained by particle size analysis". In the present description, a laser granulometer (for example of the Malvern type) is used to obtain the particle size distribution of the powder and to deduce the D50. Further, throughout this specification, the term "between" refers to a range including the cited boundaries.

Method of making the composition

The composition is preferably carried out by mixing the constituents in the molten state, in particular in a kneader, and then grinding the mixture after its solidification. It is then possible to select the powder particles of the composition thus formed having a desired particle size.

Preferably, the powder particles having a particle size of between 5 μιτι and 1 mm, more preferably between 10 and 800 μιτι and even more preferably between 80 and 200 μιτι, are selected.

Preferably, the temperature of the mixing step is between 150 and 300 ° C, more preferably between 180 and 270 ° C.

The grinding according to the invention can be carried out by any means. Preferably, grinding according to the invention is selected from the group consisting of hammer milling, knife milling, disk milling, air jet milling and cryogenic milling.

Coating

The composition according to the invention is preferably used for coating metal surfaces.

The composition according to the invention can be applied to or contacted with a metal surface according to many coating techniques well known to those skilled in the art. Preferably, the coating according to the invention is made by a method selected from the group consisting of fluidized bed dipping, electrostatic spraying and hot dusting.

Fluidized bed dipping coating is well known to those skilled in the art. Preferably, the metal surface to be coated is preheated to a temperature permitting the melting of the composition according to the invention. The metal surface is then immersed in a fluidized bed comprising a composition according to the invention. The composition according to the invention melts in contact with the object and forms a coating thereon. The coated object is then cooled in ambient air. Preferably, the granulometry of the composition during a dip coating in a fluidized bed is between 10 and Ι ΟΟΟμιτι, and preferably between 80 and 200μηη.

Preferably the fluidized air for the fluidization of the composition is cold, clean and free of oil.

Preferably, the heating temperature of the metal surface is between 200 and 500 ° C, and preferably between 300 and 400 ° C.

Preferably, the soaking time of the metal surface in the fluidized bed is between 1 and 10 seconds, more preferably between 3 and 5 seconds.

Preferably, the thickness of the coating obtained by dipping in a fluidized bed is between 150 and 1000 μιτι, and preferably between 200 and 700 μιτι. It will be apparent to those skilled in the art that a thicker coating can be obtained by increasing the soaking time or by performing several successive soaks in the fluidized bed.

Electrostatic spray coating is well known to those skilled in the art. The electrostatic spraying coating consists in depositing powder particles of the composition according to the invention electrostatically charged onto a metal surface, especially at room temperature. The composition according to the invention can be electrostatically charged during its passage through the nozzle of a projection equipment. The composition thus charged can then be projected on the object comprising the metal surface to be coated which is connected to a zero potential. The coated object can then be placed in an oven at a temperature to melt the composition.

The material for the projection of the composition according to the invention can be of any type. Preferably, the nozzle is brought to a high potential of between ten and a hundred kilovolts, of negative or positive polarity. Preferably, the material allowing projection of the composition according to the invention is an electrostatic gun which charges the composition according to the invention by Corona effect and / or by triboelectrification.

Preferably, the particle size of the composition during an electrostatic spraying coating is between 5 and 100 μιτι and, preferably, between 5 and 65 μιη. Preferably, the powder flow rate in the blasting material is between 10 and 200 g / min, and more preferably between 50 and 120 g / min.

Preferably, the electrostatic application temperature of the powder is between 15 and 25 ° C.

Preferably, the residence time of the metal part in the oven is between 3 and 15 minutes.

Preferably, the melting temperature of the composition is from 200 to 250 ° C, more preferably from 210 to 220 ° C.

The thickness of the coating obtained is preferably between 50 and 200 μιτι, and more preferably between 80 and 150 μιτι.

As is well known, the hot powdering generally comprises a step of spraying the composition according to the invention on a metal surface previously heated to a temperature permitting the melting of the composition. The part can then be cooled to room temperature.

The thickness of the coating obtained by hot powdering is preferably between 200 and 1000 μιτι, and preferably between 200 and 700 μιτι.

The sprayed composition during hot powdering can be electrostatically charged or not.

The metal surface to be coated according to the invention can be of any type. Preferably, the metal surface according to the invention is selected from the group consisting of ordinary or galvanized steel parts, aluminum parts or aluminum alloy. The metal surface of ordinary steel, aluminum or aluminum alloy could undergo one or more surface treatments well known to those skilled in the art and selected from the group consisting of a coarse degreasing, an alkaline degreasing , brushing, shot blasting or sandblasting, fine degreasing, hot rinsing, phosphating degreasing, iron / zinc / tri-cation phosphating, chromating, cold rinse and a chromic rinse.

Preferably, the metal surface to be coated according to the invention is selected from the group consisting of degreased steel, smooth or blasted, phosphated defatted steel, iron or zinc phosphated steel, Sendzimir galvanized steel, electro-galvanized steel, bath-galvanized steel, cataphoresis-treated steel, chromated steel, anodized steel, corundum sanded steel, defatted aluminum, smooth or blasted aluminum, aluminum chromate, cast iron and any other metal alloy. As will become apparent to those skilled in the art, the material comprising a metal surface according to the invention is preferably intended for any market for which a metal part is coated.

Thus, the material comprising a metal surface according to the invention is preferably intended:

transfer of fluids, especially in the form of piping, accessories, pumps, or valves;

automotive, particularly in the form of a spline shaft, sliding door rail or springs;

- wire products, especially in the form of a dishwasher basket or spring.

Examples

1. Materials and methods 1 .1. compositions

Table 1 below presents the different compositions tested (the data are expressed in parts):

Constituents:

PA 1: polyamide 1 1 (PAU) Rilsan® (BMNO) (Arkema);

PA 2: polyamide 1 1 (PA) Rilsan® (BMNO) (Arkema);

CoPA: PA 80/20 molar ratio IPD.10 / 12, copolyamide Platamid® (Arkema);

EVOH 1: ethylene-vinyl alcohol copolymer comprising 32 mol% of ethylene (Evasin 3251 F) (Arkema);

EVOH 2: ethylene-vinyl alcohol copolymer comprising 44 mol% of ethylene (Evasin 4405F) (Arkema);

Biofunctional hindered phenolic antioxidant Palmarole AOOH 98 (Adeka Palmarole);

Anti-scratch additive based on polyacrylate: Byk-360-P (Byk);

Charge: CaCO3 (Atomite, Imerys);

Hydrophobic agent: micronized wax of modified amide polypropylene (Ceridust wax 6721 from Clariant);

E1 and E2 are examples according to the invention.

Cl, C2 and C3 are comparative examples. C3 represents a composition according to the international patent application WO2008 / 029070. 1 .2. Preparation of compositions

The constituents are mixed in an extruder at a temperature between 180 ° C and 300 ° C. The mixing time is adapted so that the mixture is homogeneous. The mixture is milled in a cryogenically cooled apparatus to obtain the desired particle size for application by a fluidized bed coating method having a mean diameter (D50) of about 100 μιτι. The powder particles obtained are selected by sieving.

1 .3. Coating of a metallic surface with the compositions

The compositions are used in a fluidized bed dipping coating process. Prior to the application of the composition, 100x100x3 mm steel plates are degreased and shot blasted. The steel plates are then heated for 10 minutes at 330 ° C and then quenched in the fluidized bed for 4 seconds. The coated plates are then cooled in ambient air.

1 .4. Evaluation of the coating

The metal substrate coating plays a role in protecting the metal against external aggressions. This protection is effective only if the adhesion to the metal is retained even when the coating is in prolonged contact with the water, which is why an adhesion test after immersion in water has been carried out.

The abrasion resistance, impact and cathodic separation tests are conventional mechanical tests used in various international standards to characterize in particular the resistance to aging of coatings.

1 .4.1. Immersion test in water.

Adhesion of the coating is evaluated after immersion in water at different temperatures.

1 .4.2. Adhesion test.

The adhesion test consists of a peel test of a sectioned strip in the coating and an evaluation of the peel strength. The test is performed at a temperature of 23 ° C ± 2 ° C and a relative humidity of 50% ± 10%. Using a sharp tool, cut the coating (to the metal) along two straight lines 10mm apart and of sufficient length to define a strip of at least 30mm length.

Introduce a blade (carpenter's chisel type) under the end of the strip by grasping the end cut and try to tear the latter from the metal support.

A score of 0 to 4 is given as follows:

0- No adhesion: the separation of the coating is done as soon as the cutting tool passes

1 - Regular connection: the coating separates easily but opposing only a weak resistance to tearing force.

2- Like the rating 1 but we note the presence of some points of strong hook and regularly distributed

3- The coating separates irregularly: a perfect bond is observed on about 50% of the surface

4- Good adhesion: no detachment, the blade allows the lifting of the end of the tongue but it breaks without additional detachment, or the blade only detaches the fragments it cuts.

1 .4.3. Abrasion test

A Taber abrasion test according to ISO 9352 (10000 cycles, Cs-17 under 1 kg) was carried out to evaluate the wear resistance of the coating. The test consists in measuring the mass of coating abraded after 1000 cycles of rotation of the wheels Cs-17, with a weight of 1 kg.

1 .4.4. Shock test

An impact resistance test according to the ASTM G14 standard has been carried out: it consists in evaluating the mechanical resistance of the coating following the fall of a metal ball (diameter and weight defined by the standard) of a certain height and evaluate the integrity of the coating after the ball has dropped by means of a low-voltage electrical detector (as described in ASTM G62 under the name "Low Voltage Holiday Detector." The result is expressed in Joules. 1 .4.5. Cathodic detachment test (Australian standard).

The test is performed according to AS / NZS 4352, using test cell A or B at 23 ° C for 28 days. The test makes it possible to determine the ability of the coating applied to metallic substrates to resist cathodic detachment when the surface coating is likely to have discontinuities.

2. Results

2.1. Water Immersion Test: Evaluation of Adhesion of Coatings

Table 2 below shows the adhesion results:

It is observed that the compositions according to the invention (E1 and E2) have performances similar to those of the state of the art (C3) with significantly lower loading amounts. The comparison with Cl and C2 establishes that the presence of the hydrophobic agent makes it possible to explain these performances. The comparison of E2 with E1 shows that the presence of copolyamide, with a melting point in the range of 80 to 150 ° C according to the invention, makes it possible to improve the performance of the compositions according to the invention under the conditions of more drastic (immersion for 4 days in water at 70 ° C).

2.2. Abrasion test

An average of 13.3 mg is obtained for El. The coating therefore has excellent abrasion resistance comparable to that of polyamide-based coatings 1 1. It allows in particular to comply with various international standards defining the properties of coatings for metals in contact with water, including drinking.

2.3. Shock test

We obtain 2.1 J (at 400 μιτι) for El. The coating therefore has excellent impact resistance, similar to that of polyamide-based coatings 1 1. It allows in particular to comply with various international standards defining the properties of coatings for metals in contact with water, including drinking. 2.4. Cathodic detachment test (Australian standard)

For this test, metal plates of dimensions 200x100x6 mm previously blasted were used.

They were heated (i) at 300 ° C. to obtain a coating of 380 μιτι of thickness and (ii) at 330 ° C. to obtain a coating 400-450 μιτι thick.

For E we get 8.2 J in condition (i) and 4.0 J for condition (ii).

These results indicate that the coating, even when damaged to metal, limits the spread of corrosion. These results make it possible to meet the requirements of various international standards defining the properties of coatings for metals in contact with water, especially drinking water.

Claims

claims

A self-adhering powder composition comprising:

55 to 99% of at least one polyamide, and

0.5 to 23% of at least one ethylene-vinyl alcohol copolymer, and

0.5 to 22% of at least one hydrophobic agent,

by weight, on the total weight of the composition.

2. Composition according to claim 1, comprising:

55 to 98.5% of at least one homopolyamide and / or copolyamide, said copolyamide having a melting point greater than 150 ° C., and

0.5 to 15% of at least one ethylene-vinyl alcohol copolymer, and

0.5 to 15% of at least one hydrophobic agent, and

0.5 to 15% of at least one copolyamide having a melting point in the range of 80 to 150 ° C,

by weight, on the total weight of the composition.

3. The composition of claim 1 or 2, comprising a homopolyamide selected from the group consisting of PA10.10, PA1 1 and PA12.

4. Composition according to any one of claims 1 to 3, comprising:

65 to 84%, of at least one homopolyamide and / or copolyamide with a melting point greater than 150 ° C., and

2 to 10%, of at least one ethylene-vinyl alcohol copolymer, and

2 to 10%, of at least one hydrophobic agent, and

2 to 15% of at least one copolyamide having a melting point in the range of 80 to 150 ° C,

by weight, on the total weight of the composition. A composition according to any one of the preceding claims, wherein the composition comprises less than 20% by weight of filler, preferably comprises from 0.01 to 12% by weight, preferably from 3 to 8% by weight, of charge on the total weight of the composition, wherein the filler is preferably calcium carbonate.

6. Composition according to any one of the preceding claims, wherein the hydrophobic agent is a wax, especially selected from the group consisting of polyethylene waxes and / or polypropylene and / or ethylene bis stearamide.

7. Composition according to any one of the preceding claims, not comprising an epoxy compound.

The composition of any of the preceding claims, further comprising at least one additional agent selected from the group consisting of a pigment, a dye, an anti-crater and / or spreading agent, an antioxidant. , a UV stabilizer, a fluidizing agent, a corrosion inhibitor, and mixtures thereof.

9. Use of a composition as defined in one of claims 1 to 8 for coating a metal surface.

10. Use according to claim 9, wherein the metal surface has not previously been coated with a primer layer of adhesion.

1. A method of coating a metal surface, comprising a step of contacting a metal surface with a composition as defined in one of claims 1 to 8 and a step of melting the composition.

12. The coating method according to claim 11 comprising the following steps:

- Soaking the metal surface in a fluidized bed comprising the composition.

13. The coating method according to claim 11 comprising the following steps:

- load the composition electrically, - Spray the composition on the metal surface, the metal surface being connected to a zero potential,

14. The coating method according to claim 11, comprising the following steps

heating the metal surface to a temperature sufficient for the composition to melt at its contact,

- Spray the composition on the metal surface.

15. A coating method according to any one of claims 1 1 to 1 4, comprising no step of coating the metal surface with a primer layer prior to contacting the composition.

16. Material comprising a metal surface, the metal surface being coated with a coating obtained by melting a composition as defined in any one of claims 1 to 8.

17. Material according to claim 1 6, intended for:

- The transfer of fluids, especially in the form of piping, accessory, pump or valve;

the automobile, particularly in the form of a splined shaft, a sliding door rail or a spring;

- wire products, especially in the form of a dishwasher basket or spring.

18. A method of manufacturing a composition as defined in one of claims 1 to 8, comprising the following steps:

- Mixing the constituents of the composition in the molten state,

grinding the mixture after solidification to obtain a powder of particles.

19. The manufacturing method according to claim 18, wherein the powder particles having a particle size of between 5 μιτι and 1 mm are selected.