Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
  • C09D167/00—Coating compositions based on polyesters obtained by reactions forming a carboxylic ester link in the main chain; Coating compositions based on derivatives of such polymers
  • C09D167/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/60—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from the reaction of a mixture of hydroxy carboxylic acids, polycarboxylic acids and polyhydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
  • C08G63/00—Macromolecular compounds obtained by reactions forming a carboxylic ester link in the main chain of the macromolecule
  • C08G63/02—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds
  • C08G63/12—Polyesters derived from hydroxycarboxylic acids or from polycarboxylic acids and polyhydroxy compounds derived from polycarboxylic acids and polyhydroxy compounds
  • C08G63/16—Dicarboxylic acids and dihydroxy compounds
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L67/00—Compositions of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Compositions of derivatives of such polymers
  • C08L67/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10S525/00—Synthetic resins or natural rubbers -- part of the class 520 series
  • Y10S525/934—Powdered coating composition
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31511—Of epoxy ether
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31511—Of epoxy ether
  • Y10T428/31529—Next to metal
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31678—Of metal
  • Y10T428/31681—Next to polyester, polyamide or polyimide [e.g., alkyd, glue, or nylon, etc.]
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
  • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
  • Y10T428/00—Stock material or miscellaneous articles
  • Y10T428/31504—Composite [nonstructural laminate]
  • Y10T428/31786—Of polyester [e.g., alkyd, etc.]
  • Y10T428/31794—Of cross-linked polyester

Definitions

• Polyester containing tertiary carboxyl groups, its preparation process and thermosetting powder compositions containing it Polyester containing tertiary carboxyl groups, its preparation process and thermosetting powder compositions containing it.
• the present invention relates to new polyesters containing tertiary carboxyl groups, to their process of preparation as well as to thermosetting powder compositions containing as binder said polyesters and a crosslinking agent capable of reacting with their carboxyl groups.
• the invention also relates to the use of these compositions for the preparation of powder paints and varnishes making it possible to produce coatings, as well as to the coatings thus obtained.
• Thermosetting powder compositions are well known in the art and are widely used as paints and varnishes for coating a wide variety of objects.
• the advantages of these powders are numerous; on the one hand the problems linked to the use of solvents is completely eliminated, on the other hand the powders are used at 100%, since only the powder in direct contact with the substrate is retained by the latter, the excess powder being, in principle, fully recoverable and reusable. This is why these powder compositions are preferred over coating compositions which are in the form of solutions in an organic solvent.
• thermosetting powder compositions have already found a wide outlet in the coating of household appliances, accessories for the automotive industry, etc. They generally contain thermosetting organic compounds constituting the paint binder, fillers, pigments, catalysts and various additives to adapt their behavior to their use.
• thermoplastic powder compositions include polymers which do not have chemical reaction groups. When this type of powder is heated on a substrate, the particles melt, coalesce and spread over the substrate to form a smooth and regular coating.
• thermosetting powder compositions contain a chemical reaction group, for example a carboxyl, or hydroxyl or even epoxy group.
• a crosslinking agent is added which comprises chemical groups which will react with those of the polymers when the powder is cooked on the substrate. This results in harder coatings, more resistant to chemical agents, which adhere better to metal surfaces and do not soften when exposed to high temperatures.
• the crosslinking of thermosetting powders creates a series of new problems compared to thermoplastic powders. First of all, cross-linking can cause a lack of surface regularity, which gives it an orange peel appearance. This is due to the fact that the powder, when baking, already crosslinks before the powder particles have had time to spread out to make a even coating.
• thermosetting powder compositions Another consequence of this premature crosslinking is that air bubbles can remain trapped in the coating, which alters its surface appearance, its adhesion to the substrate and its protective effect.
• Another problem encountered with thermosetting powder compositions is to provide coatings which lack flexibility. In the case where a coating is deposited on metal sheets intended to manufacture articles where they will have to be folded from various angles, it is essential that the coating does not crack at the location of the fold. In addition, it is essential that the powder is stable in storage. In other words, it must remain in a finely pulverulent state for a sufficiently long time, and not re-agglomerate, which implies that the polymer used as a powder binder has a sufficiently high glass transition temperature.
• thermosetting powder composition when intended to make coatings on articles used in architectural constructions, it is very important that these coatings resist weathering.
• amorphous polyesters carrying carboxyl groups, containing a majority of isophthalic acid as acid component, in mixture with triglycidyl isocyanurate (TGIC) as crosslinking agent.
• TGIC triglycidyl isocyanurate
• This does give coatings good resistance to photodegradation and hydrolysis of ester groups, but the coatings thus obtained do not exhibit good impact resistance.
• TGIC tends to be used less than before because of health and safety concerns.
• TGIC is relatively toxic, its lethal dose LD50 being 0.4 g / kg orally in rats, and it is mutagenic according to the Ames mutagenicity test; it would also cause allergic reactions resulting in eczema and asthma.
• this speed being high, the coating does not have sufficient time to spread well during its melting, which causes surface defects such as the formation of an orange peel.
• this esterification is accompanied by a release of water, which does not have time to escape from the coating when it hardens, which also results in surface defects.
• thermosetting powder compositions which essentially contain a polyester carrying groups carboxyl and a beta-hydroxyalkylamide, which is applied to a substrate and which is then crosslinked at a temperature of 160 to 200 ° C.
• benzoin which are added as a degassing agent, water and air bubbles remain trapped in the cured coating after it has melted and crosslinked, especially if the coating is relatively thick.
• the flow of the powder during its melting is not optimal.
• thermosetting powder compositions containing an amorphous polyester containing carboxyl groups, a semi-crystalline polyester containing carboxyl groups and a crosslinking agent are described.
• the semi-crystalline polyester is used relative to all of the polyesters, and the crosslinking agent can be a beta-hydroxyalkylamide.
• the presence of semi-crystalline polyester in these compositions improves the mechanical properties of the coatings they provide.
• the presence of these semi-crystalline polyesters also increases the rate of hardening of these compositions, which could be an unfavorable factor for the good flow and degassing of these during their melting, leading to surface defects of the coatings. .
• thermosetting powder compositions also containing a polyester carrying carboxyl groups and a beta-hydroxyalkylamide are also described.
• the polyesters of this patent application have a functionality in carboxyl groups of less than 2, obtained by the addition of monofunctional acids or alcohols during the synthesis of polyester. Thanks to this reduced functionality, the polyester is less reactive, which gives better flow to the powder when it melts, and allows bubbles of air and carbonated water to escape from the coating before it hardens.
• the polyester has chain ends which do not carry a reaction group, these ends do not participate in the formation of the three-dimensional network during the crosslinking of the powder, which reduces the resistance to solvents and the flexibility of the coatings thus obtained.
• thermosetting powder composition that brings together all the qualities that we would like to find, such as good storage stability, good flow during fusion to ensure a smooth, taut and shiny appearance, free of orange peel and bubbles, good flexibility and good surface hardness, as well as good resistance to solvents, weathering and hydrolysis.
• thermosetting powder compositions which combine the qualities mentioned above, more particularly in the case where these compositions contain a beta-hydroxyalkylamide as crosslinking agent.
• the present invention relates to a polyester carrying tertiary carboxyl groups which makes it possible to solve most of these problems. Finding a good one compromise between the reactivity of the tertiary carboxyl groups of the polyester which contains them, its functionality and its acid number (factor which is correlated with the molecular weight and which therefore regulates its viscosity, essential element of good flow in the state according to the present invention, to produce coatings whose surface has a very good appearance, smooth and taut, without orange peel or bubbles retained in the coating. In addition, these coatings have very good flexibility and very good resistance to weathering and hydrolysis.
• the invention also provides a particular process for the preparation of these polyesters in several stages, the tertiary carboxyl groups being predominantly located at the end of the polyester chains.
• thermosetting powder compositions containing this polyester and a crosslinking agent as well as the use of these compositions for the preparation of powder paints and varnishes, which provide coatings combining the majority of the favorable properties mentioned above. -above.
• One of the objects of the present invention is therefore a polyester carrying tertiary carboxyl groups, characterized in that it consists of:
• the aliphatic or cycloaliphatic polyol (a) is chosen from neopentylglycol, 2,2-butylethyl-1,3-propanediol, neopentylglycol hydroxypivalate, 1,4-cyclohexanedimethanol, trimethylolpropane, ditrimethylolpropane, pentaerythritol, .
• the aliphatic, cycloaliphatic or aromatic polycarboxylic acid (b) is chosen from isophthalic acid, terephthalic acid, phthalic acid or anhydride, 1,2-cyclohexanedicarboxylic acid, acid 1, 3- cyclohexanedicarboxylic acid 1, 4-cyclohexanedicarboxylic, etc.
• isophthalic acid, terephthalic acid, phthalic acid or anhydride 1,2-cyclohexanedicarboxylic acid, acid 1, 3- cyclohexanedicarboxylic acid 1, 4-cyclohexanedicarboxylic, etc.
• 85 to 100% by weight of an aromatic dicarboxylic acid, terephthalic acid and / or isophthalic acid in particular is used, relative to the total weight of the polycarboxylic acids. 5
• the aliphatic, cycloaliphatic or aromatic compound (c) comprising, on the one hand, a tertiary carboxyl group, and, on the other hand, a primary or secondary carboxyl or hydroxyl group, can be represented by the following general formula I
• R and R ⁇ signify, independently of one another, an alkyl group having from 1 to 12 carbon atoms, a cycloalkyl group or an aryl group,
• Y represents a carboxyl or hydroxyl group
• R 3 represents a hydrogen atom or has the same meaning as R ⁇ or R ⁇ , preferably, R 3 represents a hydrogen atom
• the compound (c) is a hydroxy acid containing a primary or secondary hydroxyl group, preferably primary, and a tertiary carboxyl group, which may be chosen from hydroxypivahque acid (or 3-hydroxy-2,2-dmethylpropanoic acid), 3-hydroxy acid 2,2-d ⁇ phenylpropano ⁇ que, 3 hydroxy-2-methyl-2-phenylpropano ⁇ que acid, 2- (hydroxymethyl) -2-methylbutano ⁇ que acid, 2-ethyl-2- (hydroxymethyl) butano ⁇ que acid, acid 2- (hydroxymethyl) -2-phenylbutano ⁇ que, 2- (hydroxymethyl) -3-methyl-2-phenylbutano ⁇ que acid, 2- (hydroxymethyl) -2- methylpentanoic acid, 2-ethyl-2 acid (hydroxymethyl ) pentanoic
• the compound (c) is a diacid containing a tertiary carboxyl group and a primary or secondary, preferably primary, carboxyl group which can be chosen from 2,2-dmethylsucc ⁇ n ⁇ que acid, 2-ethyl-2-methylsucc ⁇ mque acid, 2,2-demethylsucc ⁇ mque acid, 2 methyl-2- propylsuccinic acid, 2- ⁇ sopropyl-2-methylsucc ⁇ mque acid, 2-ethyl-2- acid propylsucc ⁇ n ⁇ que, 2,2-d ⁇ propylsucc ⁇ n ⁇ que acid, 2-hexyl-2-methylsucc ⁇ n ⁇ que acid, 2-heptyl-2- methylsuccimque acid, 2,2-b ⁇ s (2-methylpropyl) acid, l 2,2-b ⁇ s ( ⁇ sobutyl) succinic acid, 2-decyl-2-methylsuccm ⁇ que acid, 2-decyl-2-propylsuccm ⁇ que
• the polyester carrying tertiary carboxyl groups according to the invention has an acid number of 15 to 50 mg of KOH / g, preferably 25 to 35 mg of KOH / g, and a hydroxyl number of 0 to 10 mg of KOH / g. Its number average molecular weight ranges from 1,800 to 10,500, preferably from 2,900 to 5,000. The functionality of this polyester ranges from 1.6 to 2.8, preferably from 1.85 to 2.25.
• ICI viscosity measured by the cone / plate method at 200 ° C varies from 10 mPa.s to 10,000 mPa.s, and its glass transition temperature is between 45 and 85 ° C, when measured by scanning calorimetry differential (DSC), with a temperature rise of 20 ° C / min.
• DSC scanning calorimetry differential
• Another subject of the present invention is a process for the preparation of a polyester carrying tertiary carboxyl groups, characterized in that it is carried out in several stages, the first stages consisting in the preparation of a prepolyester by condensation between (a) an aliphatic or cycloaliphatic polyol, and (b) an aliphatic, cycloaliphatic or aromatic polycarboxylic acid, the last step consisting in condensing this prepolyester with (c) an aliphatic, cycloaliphatic or aromatic compound comprising, on the one hand, a tertiary carboxyl group, and, on the other hand, either a primary or secondary carboxyl group, or a primary or secondary hydroxyl group.
• a prepolyester carrying hydroxyl groups is first prepared by condensation between the compounds (a) and (b), using a stoichiometric excess of the polyol (a) relative to the polycarboxylic acid (b) , (ii) the prepolyester obtained in (1) (i) is then condensed with a polycarboxylic acid (b), however excluding terephthalic acid, to form a prepolyester carrying carboxyl groups, and (iii) finally the prepolyester is condensed obtained in (1) (ii) with a compound (c) comprising, on the one hand, a tertiary carboxyl group, and, on the other hand, a primary or secondary hydroxyl group; or
• a prepolyester carrying carboxyl groups is first prepared by condensation between the compounds (a) and (b), using a stoichiometric excess of the polycarboxylic acid (b) relative to the polyol (a) , however excluding terephthalic acid, (ii) the prepolyester obtained in (3) (i) is then condensed with a compound (c) comprising, on the one hand, a tertiary carboxyl group, and, on the other hand, a primary or secondary hydroxyl group.
• the compounds (a), (b) and (c) used for the preparation of the polyester carrying tertiary carboxyl groups are the same as those described above with regard to the polyester according to the invention.
• the molar quantities in which they are present are also the same.
• the values of acid and hydroxyl index, molecular weight, functionality, viscosity and glass transition temperature which characterize the polyesters obtained by this synthesis process are also those of the polyester carrying tertiary carboxyl groups according to the invention .
• This particular mode of synthesis in which the compound (c) is used in the last stage of synthesis, guarantees the obtaining of a polyester in which the tertiary carboxyl groups are for the majority at the end of the polyester chains, without having practically reacted.
• the primary and / or secondary and / or aromatic hydroxyl and carboxyl groups of the compounds (a) and (b) on the other hand have practically completely reacted with one another.
• Patent application EP 634434 describes a linear polyester containing tertiary aliphatic carboxyl groups as a constituent of a thermosetting powder composition. This polyester is synthesized in one step and contains:
• hydroxyl are secondary.
• the single-stage synthesis method described in this patent application is only possible, with the compounds used, with secondary diols, which react very difficult with tertiary carboxyls, but can react with secondary carboxyls , like those of hexahydrophthalic acid used in the examples and preferred compound according to this patent application.
• polyesters prepared in the examples of this patent application have two major drawbacks compared to those of the present invention. Indeed, the vast majority of the monomers used for their preparation are aliphatic and cycloaliphatic compounds, and it is known that this type of monomer provides polyesters whose weathering resistance is not good. Furthermore, the acid number of these polyesters ranges from 67.3 to 87.0 mg KOH / g, very high values which increase the reactivity of these polyesters to the point of completely counterbalancing the beneficial effect of the least reactivity of the tertiary carboxyl groups which they contain, which prevents a slowing down of the crosslinking reaction, which is precisely at the origin of the favorable results obtained according to the present invention.
• the preparation of the polyester carrying tertiary carboxyl groups according to the invention can be carried out by mass polycondensation, in 2 or 3 stages, using a conventional polyesterification reactor, equipped with an agitator, a distillation column connected to a water condenser, a nitrogen inlet and a thermometer connected to a thermoregulator.
• the polycarboxylic acids (b) are placed in the reactor with a stoichiometric excess of the polyols (a), with stirring, at the temperature of 120 to 150 ° C, under nitrogen and in the presence of an esterification catalyst.
• the temperature is increased to 200-250 ° C, while the water begins to distill at 190 ° C.
• the prepolyester carrying hydroxyl groups is cooled and a polycarboxylic acid (b), other than terephthalic acid (too sparingly soluble according to this process) is added to it.
• a polycarboxylic acid (b), other than terephthalic acid (too sparingly soluble according to this process) is added to it.
• the carboxylation and any chain extension of the prepolyester are carried out, at the temperature of 200-250 ° C., first at atmospheric pressure, then under vacuum until the desired prepolyester is obtained, by following its acid number, its hydroxyl number and its viscosity.
• the compound (c) carrying a tertiary carboxyl group and a primary or secondary hydroxyl group is added, between 180 and 200 ° C., with stirring.
• the reaction is continued at 225-250 ° C, under vacuum, until the desired acid and hydroxyl numbers and viscosity are obtained.
• the usual additives can be added to the polyester carrying tertiary carboxyl groups thus obtained, before discharging it from the reactor.
• a prepolyester carrying hydroxyl groups is first prepared in the same manner as in the first stage of the process (1). then 9
• the compound (c) comprising a tertiary carboxyl group and a primary or secondary carboxyl group.
• the reaction is continued at the temperature of 180 to 220 ° C, under vacuum, until the desired acid and hydroxyl numbers and viscosity are obtained.
• An alternative to this second step consists in using the anhydride of the same compound (c), at a temperature of 160 to 200 ° C., with stirring, until the desired acid and hydroxyl numbers and viscosity are obtained. .
• the usual additives can be added to the polyester carrying tertiary carboxyl groups thus obtained, before discharging it from the reactor.
• a prepolyester carrying carboxyl groups is first prepared by adding a stoichiometric excess of one or more polycarboxylic acids (b), other than terephthalic acid (because too poorly soluble according to this process), to polyols (a) at a temperature of 120 to 150 ° C, under nitrogen and with stirring, in the presence of an esterification catalyst.
• the temperature is increased to 200-250 ° C, while the water begins to distill at 190 ° C.
• the condensation is continued under vacuum until the prepolyester carrying the desired carboxyl groups is obtained, by following its acid number, its hydroxyl number and its viscosity.
• the compound (c) carrying a tertiary carboxyl group and a primary or secondary hydroxyl group is added, between 180 ° and 200 ° C, with stirring.
• the reaction is continued at 225-250 ° C under vacuum, until the desired acid and hydroxyl numbers and viscosity are obtained.
• the usual additives can be added to the polyester carrying tertiary carboxyl groups thus obtained, before discharging it from the reactor.
• tin derivatives are used, for example, such as dibutyltin dilaurate, dibutyltin oxide, n-butyltin trioctoate, or titanium derivatives, such as tetrabutoxytitanate. add 0 to 1% of phenolic derivatives, such as Irganox 1010, alone or with various stabilizers of the phosphite type, such as tributylphosphite.
• the present invention also relates to thermosetting powder compositions containing the polyester carrying tertiary carboxyl groups according to the invention and a crosslinking agent carrying functional groups capable of reacting with the carboxyl groups of the polyester.
• the invention also relates to the preparation of varnishes and powder paints, as well as to the varnishes and powder paints obtained using these compositions.
• thermosetting powder composition in accordance with the invention by spraying with an electrostatic spray gun or triboelectric or by deposition in a fluidized bed followed by baking of the coating thus obtained at a temperature of 160 to 225 ° C. for a period of approximately 5 to 30 minutes.
• the crosslinking agent used for the preparation of the thermosetting powder compositions in accordance with the invention is chosen from compounds containing functional groups capable of reacting with the carboxyl groups of the polyester carrying tertiary carboxyl groups.
• these compounds the following are used as crosslinking agents: - polyepoxide compounds which are solid at ordinary temperature and which contain at least two epoxy groups per molecule, such as for example triglycidyl isocyanurate (such as that marketed under the name of Araldite PT 810 by the company CIBA-GEIGY), although this is not preferred because of its toxicity, or the epoxidized resin Araldite PT 910 (of the same company), which contains a 75/25 mixture of diglycidyl terephthalate and of triglycidyl trimellitate, or else the reaction product of 2,2-bis- (4-hydroxyphenyl) propane and epichlorohydrin such as GT 7004 from the company CIBA-GEIGY or Epikote 1055 from the company SHELL.
• acrylic copolymers containing glycidyl groups obtained from glycidyl methacrylate and / or glycidyl acrylate and a (meth) acrylic monomer and optionally an ethylenically monounsaturated monomer different from glycidyl (meth) acrylate and (meth) acrylic monomer.
• An example of this type of acrylic copolymer is GMA252 sold by the company ESTRON CHEMICAL Inc. - beta-hydroxyalkylamides which contain at least one, preferably two bis (beta-hydroxyalkyl) amide groups, for example those mentioned in the applications for WO 91/14745, EP 322,834, EP 473,380 and in US patents 4,7271 1 1, US
• beta-hydroxyalkylamides which are the preferred crosslinkers according to the present invention, correspond to the following general formula II: in which A represents a mono- or polyvalent organic group derived from the groups
• 2-n saturated or unsaturated alkyls having from 1 to 60 carbon atoms, or an aryl group, or a trialkene-amino group having from 1 to 4 carbon atoms, or a carboxy-alkenyl group or also an alkoxy-carbonyl group alkenyl;
• R * represents a hydrogen atom or an alkyl group having from 1 to 5 carbon atoms, or alternatively a hydroxyalkyl group having from 1 to 5 carbon atoms
• R ⁇ and R 3 are similar or different and independently represent a hydrogen atom or a linear or branched alkyl group having from 1 to 5 carbon atoms, one of the groups R ⁇ and one of the groups R 3 can also forming a cycloalkyl group with the carbon atom adjacent to it; m and n are between 1.6 and 2.0; preferably, A represents an alkyl group having from 1 to 10 carbon atoms; 1 1
• R 1 represents a hydrogen atom or a hydroxyalkyl group having from 1 to 5 carbon atoms
• R 1 and R 3 represent a hydrogen atom or a methyl or ethyl group
• the preferred beta-hydroxyalkylamides correspond to the following general formula III
• n varies from 0.2 to 1 and R 3 may be a hydrogen atom (product sold under the name Primid XL 552 by the company EMS) or a methyl group (product sold under the name P ⁇ mid QM 1260 by the company EMS)
• thermosetting powder compositions in accordance with the invention may also contain, in addition to the polyester carrying tertiary carboxyl groups and the crosslinking agent, a semi-crystalline polyester carrying carboxyl groups, in a minor amount relative to all the polyesters, by example from 0 to 40% by weight
• a semi-crystalline polyester carrying carboxyl groups in a minor amount relative to all the polyesters, by example from 0 to 40% by weight
• Such semi-crystalline polyesters are well known in the state of the art, for example by patent application WO 91 / 14,745
• Their acid number is between 10 and 70 mg of KOH / g, preferably between 15 and 40 mg of KOH / g and their number-average molecular weight ranges from
• thermosetting compositions in accordance with the invention may in certain cases further contribute to improving the surface appearance, the flexibility and the weather resistance of the coatings.
• crosslinking agent described above is used at a rate of 0.25 to 1.4, preferably 0.5 to 1.05 equivalent of epoxy or beta-hydroxyalkyl groups, per equivalent of carboxyl groups existing in the polyester carrying tertiary carboxyl groups and the semi-crystalline polyester carrying carboxyl groups which may be present
• thermosetting powder compositions in accordance with the invention may, for example, contain from 97 to 60 parts by weight of the polyester carrying tertiary carboxyl groups and from the semi-crystalline polyester, and from 3 to 40 parts by weight of crosslinking agent, relative to the total weight of polyesters and 1 crosslinking agent 12
• thermosetting powder compositions according to the invention can also contain various auxiliary substances conventionally used in the manufacture of powder paints and varnishes.
• the auxiliary substances optionally added to the thermosetting compositions in accordance with the invention are inter alia ultraviolet ray absorbing compounds such as Tinuvin 900 (from CIBA-GEIGY Corp.), light stabilizers based on sterically hindered amines (by example Tinuvin 144 from CIBA-GEIGY Corp.).
• a variety of pigments and mineral fillers can also be added to the thermosetting compositions according to the invention.
• pigments and fillers examples include metal oxides such as titanium dioxide, iron oxide, zinc oxide, etc., metal hydroxides, metal powders, sulfides, sulfates, carbonates, silicates such as for example aluminum silicate, carbon black, talc, kaolins, barytes, iron blues, lead blues, organic reds, organic browns, etc.
• Fluid regulating agents such as Resiflow PV5 (from WORLEE) or Modaflow (from MONSANTO) or Acronal 4F (from BASF), plasticizers such as dicyclohexyl phthalate, triphenyl phosphate, will also be mentioned as auxiliary substances.
• auxiliary grinding agents, drying oils and degassing agents such as benzoin.
• thermosetting powder compositions For the preparation of the thermosetting powder compositions, the components of the composition are dry mixed, for example in a drum mixer. This mixture is then homogenized at a temperature in the range of 80 to 150 ° C in an extruder, for example a Buss-Ko-Kneder single screw extruder or a twin screw extruder of the Prism or A.P.V. type. Then, the extrudate is allowed to cool, it is ground, optionally cryogenically using liquid nitrogen, and it is sieved to obtain a powder whose particle size is between 10 and 150 micrometers.
• an extruder for example a Buss-Ko-Kneder single screw extruder or a twin screw extruder of the Prism or A.P.V. type.
• the extrudate is allowed to cool, it is ground, optionally cryogenically using liquid nitrogen, and it is sieved to obtain a powder whose particle size is between 10 and 150 micrometers.
• the powder paints and varnishes thus obtained are perfectly suitable for application to the article to be coated by traditional techniques, that is to say by the well-known technique of deposition in a fluidized bed or by application with an electrostatic or triboelectric spray gun. .
• additives known to add charge are added in triboelectric systems.
• the coatings deposited are cured by baking in an oven at a temperature of 160 to 225 ° C. for a period of approximately 5 to 30 minutes in order to obtain complete crosslinking of the coating.
• % retention gloss 60 "after 200 hours of exposure x 100 gloss 60 ° at the start of the experiment the acid number and the hydroxyl number were determined by titration according to standards DIN 53402 and DIN 53240 and expressed in mg of KOH per gram of polyester; - the glass transition temperature (Tg) and the melting point (Tm) were determined by differential scanning calorimetry (DSC) at a scanning speed of 20 ° C per minute; the number average molecular weight (Mi) of the polyesters was determined by gel permeation chromatography (GPC), using monodispersed polystyrene as standard; - the melt viscosity of the polyesters, expressed in mPa.s, was measured with the ICI cone / plate viscometer according to standard ASTM D 4287-88; it is also called "ICI viscosity" and was measured at the temperatures indicated in the examples; the resistance to acid hydrolysis of the coatings is indicated by the values rs Delta-b * according to the L * a * b * color measurement
• a test cycle consists in placing the panels for 8 hours, at 45 ° C., in an atmosphere containing 2 liters of sulfur dioxide, followed by degassing at room temperature for 16 hours
• the Delta-b * value is measured by means of a spectrophotometer having a measurement geometry of 0/45 °, with a light source of type D65
• the value b * indicates a variation of blue / yellow color
• the compositions of green color of the formulations C containing the yellow pigment Sicomm LS 1522 turn blue by exposure to the acid conditions, because of the destruction of the pigment LS 1522, if the coatings no longer protect the pigment well due to lack of resistance to acid hydrolysis conditions
• At least the Delta-b * value is high, at most the resistance to acid hydrolysis conditions is high e, it is considered that a coating is sufficiently resistant to acid hydrolysis if its Delta b *
• Third stage To the prepolymer obtained in the second stage, 69.38 parts of hydroxypivahque acid and 1.0 part of n-butyltin trioctoate are added at 180 ° C. The mixture is then gradually heated to 230 ° C. After about half an hour at this temperature, the reaction mixture is placed under a pressure of 50 mm of Hg while it has become transparent. After three hours at this temperature and under this pressure, the polyester has the following characteristics:
• the polyester containing tertiary carboxyl groups thus obtained is cooled to 180 ° C. and discharged from the flask.
• Examples 2 to 5 Synthesis of polyesters containing tertiary carboxyl groups in three stages.
• NPG neopentylglycol TMP trimethylolpropane HPN neopentylglycol hydroxypivalate BEPD 2,2-butylethyl- 1,3-propanediol TPA terephthalic acid
• iPA isophthalic acid
• Example 2 Example 3 Example 4 Example 5 First step
• Example 6 Synthesis of a polyester containing tertiary carboxyl groups in two stages.
• First stage In a 4-necked flask provided with an agitator, a distillation column connected to a cold water condenser, a nitrogen inlet and a thermometer connected to a thermoregulator, place 431, 37 parts of neopentylglycol. The contents of the flask are heated to a temperature of 140 ° C., under nitrogen and with stirring, and 639.54 are added thereto. 17
• Second stage To the prepolymer obtained in the first stage, 75, 14 parts of 2,2-dimethylsuccinic anhydride are added at 180 ° C. After 2 hours at this temperature, and when the reaction mixture is transparent, the polyester obtained has the following characteristics: IA: 33.5 mg of KOH / g
• the polyester containing tertiary carboxyl groups thus obtained is cooled to 180 ° C. and discharged from the flask.
• Example 7 Synthesis of a semi-crystalline polyester containing primary carboxyl groups in two stages.
• adipic acid 3 parts are added at 200 ° C., 101, and the whole is heated to 235 ° C. After 2 hours at this temperature, 1.0 part of tributyl phosphite is added and the contents of the flask are placed under a pressure of 50 mm of Hg.
• the polyester obtained has the following characteristics: 18
• the semi-crystalline polyester carrying primary carboxyl groups thus obtained is cooled to 160 ° C and discharged.
• Example 8 Synthesis of a semi-crystalline polyester carrying primary carboxyl groups in a single stage.
• 500.0 parts of 1,4-cyclohexanediol, 655, 1 parts of adipic acid and 2.5 parts of n-butyltin trioctoate are placed.
• the mixture is then heated to 140 ° C, under nitrogen and with stirring, and the esterification water begins to distill at 190 ° C. Heating is continued gradually until the temperature of 200 ° C.
• 1.0 part of tributyl phosphite and 1.0 part of n-butyltin trioctoate are added and the contents of the flask are placed under a pressure of 50 mm Hg. After 5 hours at this temperature and under this pressure, the polyester obtained has the following characteristics: IA: 23.5 mg of KOH / g
• the semi-crystalline polyester carrying primary carboxyl groups thus obtained is cooled to 160 ° C and discharged.
• Comparative Example 9 relates to the synthesis in two stages, following the procedure of the first two stages of Example 1, of a linear polyester carrying aromatic carboxyl groups, fully condensed. This polyester is well known in the state of the art.
• Comparative Example 10 a polyester very similar to that of Comparative Example 9 was synthesized, prepared in the same way with complete condensation, but by introducing into it a small amount of monomers known for their plasticizing effect.
• This linear polyester carrying aromatic carboxyl groups improves the flow in the molten state of the powder which contains it, thanks to the presence of plasticizing monomers. 19
• Comparative Example 11 a polyester very similar to that of Comparative Example 9 was prepared, prepared in the same way as the latter, however stopping the synthesis before the condensation was complete.
• This linear polyester carrying aromatic carboxyl groups due to its incomplete condensation, has a lower number average molecular weight than the polyester of Comparative Example 9, which improves its melt flow, as well as a lower functionality. , which decreases the reactivity of the powder which contains it.
• Comparative Example 12 relates to a polyester containing the same monomers as the polyester of Example 1 according to the invention, but it was prepared as in Example 1 in three steps, however reversing the order of steps 2 and 3.
• the hydroxypivahque acid is incorporated into the polyester in the second synthesis stage, by reaction between the primary hydroxyl groups of the prepolyester carrying hydroxyl groups obtained in the first stage and the tertiary carboxyl group.
• hydroxypivahque acid which leads to a prepolyester carrying hydroxyl groups derived from hydroxypivalic acid.
• the third synthesis step leads to carboxylation with isophthalic acid, which provides an unplasticized linear polyester, completely condensed, carrying aromatic carboxyl groups similar to the polyester of Comparative Example 9.
• Comparative Example 13 we attempted to prepare a polyester having the same monomer composition as the polyester of Example 1 according to the invention, however proceeding in a single step, as in patent application EP 634,434. This synthesis was not possible, the polycondensation stopping at a very early stage to provide a reaction mixture of milky appearance where the terephthalic acid precipitates in large quantities.
• Table 2 shows the amounts of monomers used in the synthesis of the polyesters of Comparative Examples 9 to 12, as well as the stages of synthesis and the characteristics of the prepolyesters and final polyesters obtained. In this table 2, the abbreviations used are the same as in table 1. In addition, the following have been designated: EG: ethylene glycol AdA: adipic acid.
• Example 9 Example 10 Example 11 Example 12 First step
• Example 14 Preparation of thermosetting powder compositions and characteristics of the coatings which they make it possible to obtain.
• Titanium dioxide (1) 300.0 parts
• Fluidity control agent (2) 10.0 parts
• Fluidity control agent (2) 10.0 parts Benzo ⁇ ne 3.5 parts
• Titanium dioxide (1) 40.0 parts
• Fluidity control agent (2) 10.0 parts
• the binder of these formulations always contains the crosslinking agent, as well as either the polyester carrying tertiary carboxyl groups according to the invention as the only polyester (compositions 15 to 23 and 27), or such a polyester mixed with a semi polyester -crystalline 22
• compositions 24 to 26 a polyester carrying aromatic carboxyl groups (compositions 28 to 33), as indicated in table 3.
• compositions are prepared by dry mixing and homogenization of the various constituents in a PRISM 16 mm L / D 15/1 twin screw extruder, at an extrusion temperature of 85 ° C.
• the homogenized mixture is then cooled and ground in a RETSCH ZM100 grinder, with a screen diameter of 0.5 mm.
• the powder thus obtained is sieved so as to obtain a particle size of 10 to 100 micrometers.
• compositions 24 to 26 containing two polyesters, these are mixed together in a round flask in the molten state, prior to the operations described above.
• compositions formulated as described above, are applied with the GEMA-Volstatic PCG1 electrostatic spray gun, at a voltage of 60 kV, on cold-rolled steel panels, untreated, in a film thickness of 50 to 70 micrometers. .
• the coated plasters are then baked in a ventilated oven with air, at a temperature of 200 ° C, for a period of 15 minutes.
• the hardened coatings thus obtained are subjected to conventional tests. The results obtained are reported in Table 3.
• the 1st column gives the number of the composition prepared in Example 14, the 2nd column, the type of formulation, A, B or C, the 3rd column, the number of the example of preparation of the carrier polyester of tertiary carboxyl groups used, with the quantity used (compositions 15 to 27) and of the comparison polyester carrying aromatic carboxyl groups (compositions 28 to 33), the 4th column, the number of the example of preparation of the semi polyester -crystalline carrying carboxyl groups, with the amount used (which represents 10% by weight of the semi-crystalline polyester, relative to the total weight of the polyesters; compositions 24 to 26), the 5th column, the nature and the quantity of crosslinking agent used, with the following abbreviations:
• XL Primid XL 552 from the company EMS, a beta-hydroxyalkylamide of formula III in which R represents a hydrogen atom
• QM Primid QM 1260 from the company EMS, a beta-hydroxyalkylamide of formula III in which R3 represents a methyl group
• GMA GMA252 from ESTRON CHEMICAL Inc., an acrylic glycidyl copolymer. the 6th and 7th columns, the value of impact resistance, in kg. cm, reverse shock and direct shock respectively, 23
• composition Type of Polyester to Polyester Resistance Agent with Appearance ⁇ b * Gloss 60 ° carboxyl formulation semi-crosslinking impact> tertiary crystalline
• compositions marked "" are tested for comparison 03
• compositions 15 to 27 have a very high quality surface, smooth and well stretched, without orange peel (compositions 15 to 27). These coatings also have very good flexibility (compositions 15, 18 and 27 for example), at least equal, if not greater than that of coatings of the state of the art (compositions 28, 30, 32 and 33 for example), as shows the impact resistance.
• the hydrolysis resistance of these coatings is also very good, as shown by the compositions according to the invention 20 to 22 and 25.
• compositions 24 to 26 With the compositions also containing a semi-crystalline polyester (compositions 24 to 26), an appearance is obtained. improved surface in some cases; Unlike the compositions of patent application WO 91 / 14,745, the addition of a semi-crystalline polyester in the compositions according to the invention practically does not increase the speed of crosslinking.
• the coatings obtained with the comparative compositions all have one or the other defects.
• the surface appearance of all of these is never as good as with the compositions of the invention.
• composition 29 it is found that if one seeks to obtain a good surface appearance by using an incompletely condensed polyester, to facilitate its flow during melting (composition 29), the flexibility deteriorates. If, for the same purpose, a composition containing a polyester prepared by means of plasticizing monomers (composition 32) is used, good flexibility is found, but the resistance to hydrolysis becomes very poor.
• polyesters carrying tertiary carboxyl groups according to the invention in thermosetting powder compositions, coatings are obtained which have an excellent appearance, excellent flexibility and very good resistance to water. hydrolysis, ie a set of properties which it is not possible to find combined from the compositions containing polyesters carrying carboxyl groups of the state of the art.
• Example 15 Weather resistance of paint coatings.
• the weather resistance of paint coatings obtained with composition 23 according to the invention is compared with that of coatings obtained with composition not in accordance with invention 33.
• the pigmented powders formulated according to type B, as described in Example 14, are applied with an electrostatic gun to aluminum panels chromated under the same conditions as in Example 14.
• the coatings were subjected to an accelerated aging test in order to estimate the weather resistance (Q-UV test), as described at the beginning of the examples.
• the coating obtained according to the invention with a composition containing a polyester carrying tertiary carboxyl groups has excellent weather resistance, comparable to that of a coating obtained with a composition known in the art. the state of the art.

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