WO2015000724A1

WO2015000724A1 - Polycarboxylic acid polyepoxy ester and curable epoxy resin compositions based thereon

Info

Publication number: WO2015000724A1
Application number: PCT/EP2014/063083
Authority: WO
Inventors: Hans-Josef Thomas; Norma Lidia NEGRETE HERRERA; Stefan Dahmen; Ivan GARCIA ROMERO
Original assignee: Basf Se
Priority date: 2013-07-03
Filing date: 2014-06-23
Publication date: 2015-01-08

Abstract

Cured epoxy resins are widely used on account of their excellent mechanical and chemical properties. Normally, epoxy resins based on bisphenol A or bisphenol F diglycidyl ethers are used, but because of the endocrine effect of bisphenol A these are regarded as critical for many applications. The present invention relates to polycarboxylic acid polyepoxy esters that can be produced from at least one aromatic dicarboxylic acid and at least one polyglycidyl ether having more than two glycidyl groups, and curable epoxy resin compositions based thereon, as an alternative to bisphenol A and bisphenol F diglycidyl ethers and epoxy resin compositions based thereon.

Description

Polycarboxylic acid polyepoxyesters and curable epoxy resin compositions based thereon

description

The present invention relates to certain Polycarbonsäurepolyepoxyester and their use for the production of adhesives, composites, moldings or coatings. The present invention further relates to curable epoxy resin compositions comprising certain polycarboxylic acid polyepoxy esters as the resin component and a curing agent component, and to methods for curing these curable epoxy resin compositions and cured epoxy resins obtainable by curing these curable epoxy resin compositions.

As epoxy resins are usually called oligomeric compounds having on average more than one epoxide group per molecule, which are converted by reaction with suitable curing agents or by polymerization of the epoxy groups in thermosets or cured epoxy resins. Cured epoxy resins, because of their excellent mechanical and chemical properties, such as high impact strength, high abrasion resistance, good heat and chemical resistance, in particular a high resistance to alkalis, acids, oils and organic solvents, high weather resistance, excellent adhesion to many materials and high electrical insulation capacity , widespread. They serve as a matrix for composites and are often the main component in electro-laminates, structural adhesives, casting resins, coatings and powder coatings.

Most commercial (uncured) epoxy resins are prepared by coupling epichlorohydrin to compounds having at least two reactive hydrogen atoms, such as polyphenols, mono- and diamines, aminophenols, heterocyclic imides and amides, aliphatic diols or polyols, or dimer fatty acids , Epoxy resins derived from epichlorohydrin are referred to as glycidyl based resins. As a rule, bisphenol A or bisphenol F diglycidyl ethers or the corresponding oligomers are used as epoxy resins.

Especially on coatings of containers for the storage of food and drinks high demands are made. Thus, the coating should withstand strongly acidic or salt-containing foods (eg tomatoes) or drinks, so that no corrosion of the metal occurs, which in turn could lead to contamination of the contents. On the other hand, the coating must not affect the taste or appearance of the food. Since coated containers are often further formed during the manufacture of the containers, the coating must be flexible. Many fillings, eg food, are first sterilized in the can; Therefore, the coating must survive heating to 121 ° C for at least 2 hours undamaged and without migration of ingredients into the product. The required property profile of flexibility, good adhesion and high resistance of the cured polymeric coatings is usually achieved by combining aromatic structural units with secondary hydroxyl groups and different network densities of the thermosets. enough. These structural elements characterize the commonly used cured epoxy resins based on bisphenol A and F.

Epoxy resins are e.g. described in US 4722981, US 2002/0128428, EP 501575,

WO 99/55759, US 5852163, WO 98/51728, US 4302574, CA 1091690, US 3864316,

US 4474935, US 5171820, WO 00/01779 and WO 2008/045882.

The use of epoxide resins based on bisphenol A or bisphenol F diglycidyl ether is identified in more and more areas as problematic because the corresponding diols are considered to be of concern because of their endocrine activity. To solve this problem, various proposals have been made:

US 2012/01 16048 discloses a bisphenol-A (BPA) and bisphenol-F (BPF) -free polymer which, in addition to ester linkages, also comprises hydroxy ether bridges, using diepoxides which are based on open-chain aliphatic diols such as neopentyl glycol (NPG), simple cyclic aliphatic diols such as 1,4-cyclohexanedimethanol or aromatic diols such as resorcinol. Experience has shown, however, that the described aliphatic and cycloaliphatic diols give very soft and low temperature and chemical resistant coatings. WO 2012/089657 discloses a BPA-free preparation of a film-forming resin and an adhesion promoter. As the resin, an epoxidized resin is prepared, for example, from the diglycidyl ethers of NPG, ethylene glycol, propylene or dipropylene glycol, 1,4-butanediol or 1,6-hexanediol. Here are the same limitations of the coating properties as expected in the previous example.

WO 2010/100122 proposes a coating system obtainable by reacting an epoxidized vegetable oil with hydroxy-functional compounds, e.g. Propylene glycol, propane-1,3-diol, ethylene glycol, NPG, trimethylolpropane, diethylene glycol, and the like. US 2004/0147638 describes a 2-layer (core / shell) system in which the core of a BPA or BPF-based epoxy resin, the top layer of e.g. is formed from an acrylate resin. Critical here is whether the top coat can really completely prevent the migration of BPA or bisphenol A diglycidyl ether (BADGE) into the product. WO 2012/162299 describes a system consisting of a polyether polyol with a

OH functionality of 3-8 OH groups per molecule and a reaction product of phosphorus-containing acid with polyepoxides and / or polyester-polyols, which is cured with phenolic or amino resins. Again, attention is drawn to the absence of bisphenol-A as a feature.

CN 102952253 A describes certain epoxy resins made from 2,5-furandicarboxylic acid and certain mono-epoxy-functional epihalohydrins, for example epichlorohydrin. US 6353082 describes a way of producing highly branched polyesters by reaction of polyfunctional acid chlorides with polyfunctional epoxides. The resulting polymers are chloride-containing and can contain both epoxy and acid chloride functionalities as reactive end groups. The direct conversion of acid groups with epoxy groups to chloride-free polyesters is not mentioned therein.

Organically bound chlorine in the polymer structure always carries the risk in coating applications that it can lead to splitting off of HCl during degeneration, which has a very corrosive effect. In food contact applications, the toxicology of organic chlorine compounds is another very critical topic, where migration of chlorine-containing fission products can lead to problems. Therefore, there is an interest in chlorine-free compounds and chlorine-free synthesis routes or on polymers with the lowest possible proportion of organically bound chlorine. The object of the present invention was to provide a structure that can replace the bisphenol A-based epoxy resin in the application as a resin component of curable epoxy resins, especially for applications for internal coating of food packaging, the synthesis route and end product should be as free of chlorine as possible. The invention provides polycarboxylic acid polyepoxy esters which can be prepared by reacting (A) with at least one aromatic dicarboxylic acid

(B) at least one polyglycidyl ether which has an average glycidyl functionality of greater than two, preferably of at least 2.3. The reaction of the acid groups of the dicarboxylic acid with the epoxy groups of the polyglycidyl ether is catalyzed in particular by a suitable catalyst, for example a phosphorus catalyst, in particular a phosphine catalyst such as triphenylphosphine or one of the catalysts mentioned below. In the reaction, in each case an aromatic carboxylic acid group H02C-Ar ~ reacts with in each case one epoxy group of a glycidyl group

to form a hydroxy ester moiety ~0-CH2-CHOH-CH2-O-CO-Ar ~.

Aromatic dicarboxylic acids are compounds in which two carboxylic acid groups are bonded directly to one or two aromatic rings.

Unless stated otherwise, alkyl groups in the context of the invention preferably have 1 to 20 C atoms. They can be linear, branched or cyclic. Preferably, they have no substituents with heteroatoms. Aryl groups within the meaning of the invention preferably have 6 to 20 carbon atoms. Preferably, they have no substituents with heteroatoms. Heteroatoms are all atoms except C and H atoms. Preferably, the aromatic dicarboxylic acid (A) is selected from those of the general formula

H0 ₂ C-Ar-C02 [-R 0 ₂ C-Ar-C02] nH

where n is a number from 0 to 10,

Ar is a divalent aromatic ring or a divalent aromatic ring system, preferably phenylene or furanylene and

Ra is a linear alkylene group, a branched alkylene group, a cyclic alkylene group or a divalent aromatic group, preferably each having up to 100 carbon atoms.

Suitable aromatic dicarboxylic acids are e.g. Di-, tri- or tetracarboxylic acids of benzene (in particular phthalic acid or terephthalic acid), poly (alkylene terephthalate) having two terminal acid groups and preferably 1 to 4 carbon atoms in the alkylene group, di-, tri- or tetracarboxylic acids of furan, especially 2.5 -Furandicarbonsäure.

Preferably, the aromatic dicarboxylic acid (A) is selected from 2,5-furandicarboxylic acid and those of the formula

where n is a number from 0 to 10 and A is an alkylene group having 1 to 4 C atoms, preferably ethylene. Particularly preferred is terephthalic acid.

Suitable polyglycidyl ethers (B) are e.g. Glycidyl ethers of non-alkoxylated polyfunctional alcohols having 3 to 10 OH groups and alkoxylated, polyfunctional alcohols having 3 to 10 OH groups, i. wherein the underlying alcohols each have 3 to 10 OH groups and wherein in each case more than two of the OH groups, preferably on average at least 2.3, at least 2.5 or at least three of the OH groups are functionalized with glycidyl ether groups ,

Particular preference is given to glycidyl ethers of alkoxylated, in particular propoxylated, polyfunctional alcohols. Alkoxylated alcohols are alcohols in which at least one of the alcoholic OH groups is alkoxylated, ie is derivatized with a group - (AO) _n -, where A is an alkylene group having preferably 1 to 4 C atoms and n is a number of at least 1, preferably at least 2 and preferably up to 10. A is particularly preferably a propylene group, ie the polyglycidyl ether (B) is a glycidyl ether of a propoxylated polyalcohol.

Polyglycidyl ethers (B) are, for example, those of the general formula

wherein n is a number of at least 3, preferably 3 to 10 and R is derived from an n-valent, non-alkoxylated or alkoxylated, preferably propoxylated polyfunctional alcohol having 3 to 10 OH groups, of which more than two, preferably on average at least 2.3, at least 2.5 or at least three of the OH groups are functionalized with glycidyl ether groups. For the structure of R, preference is given to using a reaction product of pentaerythritol with propylene oxide (preferably at least 1 mol, for example from 2 to 10 mol per mol of pentaerythritol).

The polyfunctional alcohol on which the polyglycidyl ethers (B) are based is preferably selected from glycerol, trimethylolpropane, pentaerythritol, sorbitol, isosorbide and the addition products of the abovementioned compounds with ethylene oxide and / or preferably with propylene oxide. A preferred polyglycidyl ether (B) is a glycidyl ether of propoxylated pentaerythritol with more than two, e.g. an average of at least 2.3, at least 2.5 or at least three glycidyl ether groups, e.g. a reaction product of pentaerythritol with 4 to 8 mol, preferably 5 to 6 mol of propylene oxide and 2 to 4 mol, preferably 2.5 to 3.7 mol of epichlorohydrin.

Polycarboxylic acid polyepoxyesters according to the invention are e.g. those of the general formula

(Gly-) _m R-O [-CH ₂ -CHOH-CH ₂ -O-CO-Ar-CO-O-CH ₂ -CHOH-CH ₂ -O-R (-Gly) _m -i] n-Gly where m is a number from 2 to 9, preferably 2 to 4,

n is a number from 1 to 100, preferably 1 to 10,

-Gly is a glycidyl radical having the formula

-R- is an (m + 1) -valent alkoxylated or non-alkoxylated radical of a polyfunctional alcohol having 3 to 10, preferably 3 to 5, OH groups,

wherein the corresponding branched via lateral glycidyl oligomers and polymers are also possible.

The following reaction scheme according to the invention is a synthesis example for the reaction of terephthalic acid with a triglycidyl ether:

Where n is a number from 0 to 100 and R is the radical of an at least trifunctional alcohol, whereby the corresponding branched over the lateral glycidyl oligomers and polymers are possible.

Another synthesis example is the reaction product of furandicarboxylic acid with a triglycidyl ether:

Where also here as in the previous example, the corresponding oligomers and polymers are possible.

The present invention further relates to a process for the preparation of polycarboxylic polyepoxy esters wherein at least one (described above) aromatic dicarboxylic acid with at least one (described in more detail above) polyglycidyl ether having more than two or at least three glycidyl groups is reacted and the reaction by a suitable catalyst is catalyzed.

Suitable catalysts are, for example, phosphines, amines, quaternary ammonium and phosphonium salts, for example tetraethylammonium chloride, tetraethylammonium bromide, tetraethylammonium iodide, tetraethylammonium hydroxide, tetra (n-butyl) ammonium chloride, tetra (n-butyl) ammonium bromide (TBAB), tetra ( n-butyl) ammonium iodide, tetra (n-butyl) ammonium hydroxide, tetra (n-octyl) ammonium chloride, tetra (n-octyl) ammonium bromide, tetra (n-octyl) ammonium iodide, tetra (n-octyl) ammonium hydroxide, methyltris (n- octyl) ammonium chloride, tetrabutylphosphonium bromide (TBPB), bis (tetraphenylphosphoranylidene) ammonium chloride, ethyltri-p-tolylphosphonium acetate and its acetic acid complex, ethyltriphenylphosphonium acetate and its acetic acid complex, N-methylmorpholine, 2-phenylimidazole, or combinations thereof and the like. Preferred catalysts are phosphines and onium catalysts. Preferred onium catalysts are phosphonium or ammonium salt catalysts, in particular tetrabutylammonium bromide, tetrabutylphosphonium bromide (TBPB), ethyltriphenylphosphonium iodide, tetraphenylphosphonium bromide and tetrakis (n-butyl) ammonium bromide and the corresponding chlorides, iodides, bromides, acetates, formats, phosphates, borates, Trifluoroacetates, oxalates and bicarbonates. Particularly preferred is a phosphorus catalyst, preferably a phosphine or phosphonium catalyst such as triphenylphosphine or an equivalent catalyst such as ethyl-triphenylphosphonium iodide.

The equivalent ratios of the reactants (acid groups and epoxy groups) are preferably chosen as follows: Preferably, at least 0.1 equivalent of carboxylic acid is reacted with 1 equivalent of epoxy groups. The equivalence ratio is particularly preferably at least 0.3: 1.0. The catalyst used is an amount of from 0.05 to 0.5% (based on the mixture of starting materials).

The reaction is usually carried out in a temperature range of 100 ° C to 200 ° C, preferably 120 ° C to 160 ° C. The reaction can also be carried out in a suitable solvent. The choice of solvent depends on the solubility of the educts and the boiling range required for the reaction.

According to the invention, epoxifunctional compounds (preferably oligomers) are obtained which, in addition to a rigid core (aromatic ring of the dicarboxylic acid), contain soft structural elements and, in addition, permit high crosslinking densities when used as a curable epoxy resin, which are necessary for good chemical resistance.

The compounds of the invention are well suited as coatings, ie for coating, laminating or painting a variety of substrates such as metal, wood, glass, plastics, textiles, etc. The treated surfaces can walls, windows, bridges, piles, beams, floors, roofs, metal containers such Cans, barrels, containers, tubes or parts thereof.

The invention therefore also provides a curable epoxy resin composition comprising at least one resin component and at least one hardener component, wherein the resin component is a polycarboxylic acid polyesters according to the invention.

Preferably, the curable epoxy resin composition according to the invention comprises less than 40 wt .-%, preferably less than 10 wt .-%, more preferably less than 5 wt .-%, in particular less than 1 wt .-% of bisphenol A or bisphenol F based compounds based on the entire resin component. Preferably, the curable epoxy resin composition of the invention is free of bisphenol A or bisphenol F based compounds. Bisphenol A or bisphenol F based compounds in the context of the present invention are Bisphenol A and bisphenol F themselves, their diglycidyl ethers, and oligomers or polymers based thereon.

In a preferred embodiment of the curable epoxy resin composition according to the invention, the polycarboxylic acid polyepoxy esters according to the invention overall make up a proportion of at least 40% by weight, preferably at least 60% by weight, in particular at least 80% by weight, based on the total resin component.

In a preferred embodiment of the curable epoxy resin composition according to the invention, the total resin component makes up at least 10% by weight, in particular at least 25% by weight, based on the total curable epoxy resin composition.

For the purposes of the present invention, all epoxy compounds are attributable to the resin component. Epoxide compounds in the context of the present invention are compounds having at least one epoxide group, that is to say corresponding reactive diluents, for example. Preferably, the epoxy compounds of the resin component have on statistical average more than 2, or at least 2.5, at least 3 or at least 4 epoxide groups per molecule.

Hardeners in the context of the invention are compounds which are suitable for effecting crosslinking of the polycarboxylic acid polyepoxy esters according to the invention. By reaction with hardeners, polyepoxide compounds can be converted into non-fusible, three-dimensionally "crosslinked", duroplastic materials. When curing epoxy resins, a distinction is made between two types of curing. In the first case, the curing agent has at least two functional groups which can react with the oxirane and / or hydroxyl groups of the polyepoxide compounds to form covalent bonds (polyaddition reaction). Curing then results in the formation of a polymeric network of covalently linked units derived from the polyepoxide compounds and units derived from the hardener molecules, the degree of crosslinking being controllable via the relative amounts of the functional groups in the hardener and in the polyepoxide compound.

In the second case, a compound is used which causes the homopolymerization of Polyepoxidverbindungen each other. Such compounds are often referred to as initiator or catalyst and are often used in conjunction with hardeners to accelerate crosslinking. Homopolymerization-inducing catalysts are Lewis bases (anionic homopolymerization, anionic curing catalysts) or Lewis acids (cationic homopolymerization, cationic curing catalysts). They cause the formation of ether bridges between the epoxide compounds. It is believed that the catalyst reacts with a first epoxide group to form a reactive hydroxy group, which in turn reacts with another epoxide group to form an ether bridge, resulting in a new reactive hydroxy group. Due to this reaction mechanism, the sub-stoichiometric use of such catalysts is sufficient for curing. Imidazole is an example of a catalyst that induces anionic homopolymerization of epoxide compounds. Boron trifluoride is an example of a catalyst containing a cationic homopolymerization triggers. Mixtures of various polyaddition reaction incoming hardeners and mixtures of homopolymerization-inducing hardeners, as well as mixtures of polyaddition reaction incoming and homopolymerization-inducing hardeners can be used for the curing of polyepoxide compounds.

Suitable functional groups which can undergo a polyaddition reaction with the oxirane groups of polyepoxide compounds (epoxy resins) are, for example, amino groups, hydroxy groups, thioalcohols or derivatives thereof, isocyanates and carboxyl groups or derivatives thereof, such as anhydrides and dicyandiamide. Accordingly, as curing agents for epoxy resins, aliphatic, cycloaliphatic and aromatic polyamines, carboxylic anhydrides, carboxylic acids, polyamidoamines, aminoplasts, e.g. Formaldehyde condensation products of melamine, urea, benzoguanamine or phenoplasts, such as e.g. Novolak, used. Also acrylate-based oligomeric or polymeric curing agents having hydroxy or glycidyl functions in the side chain as well as epoxy vinylester resins are used. The skilled worker knows for which applications a fast or slow-acting hardener is used. For example, for storage-stable one-component formulations, he will use a hardener which acts very slowly (or only at a higher temperature). Optionally, one will use a hardener which is released as an active form only under conditions of use, for example ketimines or aldimines. Known hardeners have a linear or at most weakly crosslinked structure. They are described, for example, in Ullmann's Encyclopedia of Industrial Chemistry, 5th Edition on CD-ROM, 1997, Wiley-VCH, Chapter "Epoxy Resins", which is hereby incorporated by reference in its entirety.

Suitable hardeners for the curable epoxy resin composition according to the invention are, for example, polyphenols, polycarboxylic acids, polymercaptans, polyamines, primary monoamines, sulfonamides, aminophenols, aminocarboxylic acids, carboxylic anhydrides, phenolic hydroxy-containing carboxylic acids, sulfanilamides, and mixtures thereof. In the context of this invention, the respective poly compounds (for example polyamine) are also to be understood as the corresponding di compounds (for example diamine). Preferred hardeners for the curable epoxy resin composition according to the invention are polycarboxylic acids, polyols and phenolic resins.

In a particular embodiment, the curable epoxy resin composition according to the invention comprises at least one polycarboxylic acid as curing agent. Polycarboxylic acid hardeners suitable for the polyaddition reaction are compounds which have at least two carboxylic acid groups. By linking the acid groups of the polycarboxylic acid with the epoxide groups of the polyepoxide compound, polymers are formed whose units derive from the hardeners and the polyepoxide compounds. Carboxylic acid hardeners are therefore generally used in a stoichiometric ratio to the epoxide compounds. If the carboxylic acid hardener has, for example, three functional groups, ie can couple with up to three epoxide groups, crosslinked structures can be formed. Instead of the free polycarboxylic acids, the corresponding polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof can also be used. The polycarboxylic acids may be aliphatic, cycloaliphatic, araliphatic, aromatic or heterocyclic and optionally, for. B. by halogen atoms, substituted and / or unsaturated. Suitable examples are aromatic polycarboxylic acids, in particular aromatic dicarboxylic acids. Also suitable are linear, branched or cyclic aliphatic polycarboxylic acids, for example having 2 to 20, preferably 3 to 10 or 4 to 8 carbon atoms. Examples of these are: suberic acid, azelaic acid, phthalic acid, isophthalic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acids. Linear aliphatic dicarboxylic acids are, for example, those of the general formula HOOC- (CH 2) _y -COOH, where y is a number from 1 to 20, preferably an even number from 2 to 20, for. Succinic acid, adipic acid, sebacic acid and dodecanedicarboxylic acid.

Preferred polycarboxylic acid hardeners are dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, adipic acid and longer-chain homologues such as sebacic acid. Also suitable are dimer fatty acids (e.g., Empol 1022, Emery), as well as more highly functionalized polycarboxylic acids such as citric acid, trimellitic acid, and the like. Also suitable are carboxylic anhydrides such as phthalic anhydride, Tetrahydrophthalsäureanhyhdrid, trimellitic anhydride and others. Particularly suitable are reaction products of polycarboxylic acids with higher functional alcohols, e.g. Glycerol, trimethylolpropane or pentaerythritol (polycarboxylic acid polyester).

In the case of the curable epoxy resin composition according to the invention, polyepoxide compound and hardener are preferably used in an approximately stoichiometric ratio, based on the epoxy or curing agent functionality. Particularly suitable ratios of epoxide groups to hardener functionality are, for example, 1: 0.6 to 0.6: 1.

In a particular embodiment, the curable epoxy resin composition of the present invention includes a phenolic resin as a curing agent. Phenol resins suitable for the polyaddition reaction have at least two hydroxyl groups. By linking the hydroxyl groups of the phenolic resin with the epoxide groups of the polyepoxide compound, polymers are formed whose units are derived from the phenolic resins and the polyepoxide compounds. Phenolic resins can typically be used in both stoichiometric and substoichiometric proportions to the epoxy compounds. When substoichiometric amounts of the phenolic resin are used, the use of suitable catalysts promotes the reaction of the secondary hydroxyl groups of the already formed epoxy resin with epoxide groups. Examples of suitable phenolic resins are novolaks, phenolic resoles, generally condensation products of aldehydes (preferably formaldehyde and acetaldehyde) with phenols. Preferred phenols are phenol, cresol, xylenols, p-phenylphenol, p-tert.-butyl-phenol, p-tert.amyl-phenol, cyclopentylphenol, p-nonyl- and p-octylphenol.

The curable epoxy resin composition of the invention may also comprise an accelerator for curing. Examples of suitable curing accelerators are imidazole or imidazole derivatives or urea derivatives (urones), such as, for example, 1,1-dimethyl-3-phenyl urea (Fenuron). The use of tertiary amines such as triethanolamine, benzyldimethylamine, 2,4,6-tris (dimethylaminomethyl) phenol and tetramethylguanidine as curing accelerator is described (US 4,948,700). As is known, for example, the curing of epoxy resins with DICY can be accelerated by the addition of fenuron.

The prepolymers used for the preparation of cured epoxy resins often have a high viscosity, which makes the application difficult. In addition, the high viscosity of the resins often limits the use of fillers, which is desirable for modifying the mechanical properties of the cured resin composition. In addition, in many cases, the use of fillers allows to reduce the cost of the products made from the resins, such as moldings or coatings. Therefore, diluents are often added to the uncured epoxy resin which reduce the viscosity of the resin to the value desired for use. The curable epoxy resin composition of the present invention may therefore also include a diluent. Diluents for the purposes of this invention are conventional diluents or reactive diluents. The addition of diluent to a curable epoxy resin composition usually lowers its viscosity. In the case of diluents, a distinction is made between conventional diluents and reactive diluents. Conventional diluents are typically organic solvents or mixtures thereof, for example ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone (MIBK), diethyl ketone or cyclohexanone, esters of aliphatic carboxylic acids such as ethyl acetate, propyl acetate, methoxypropyl acetate or butyl acetate, glycols such as ethylene glycol, diethylene glycol, triethylene glycol or propylene glycol, etc ., Glykolderivate such as ethoxyethanol, ethoxyethanol acetate, ethylene or propylene glycol mono- or dimethyl ether, aromatic hydrocarbons such as toluene or xylenes, aliphatic hydrocarbons such as heptane, and alkanols such as methanol, ethanol, n- or isopropanol or butanols. During the curing of the epoxy resin, they evaporate from the resin composition. This can lead to an undesired volume reduction of the resin (shrinkage) or to pore formation, and thus adversely affect mechanical properties of the cured material, such as, for example, the breaking strength as well as the surface properties. The disadvantages of the conventional solvents can be at least partially circumvented by the use of reactive diluents.

Reactive diluents are low molecular weight substances which, in contrast to conventional solvents, have functional groups, generally oxirane groups, which can react with the hydroxy groups of the resin and / or the functional groups of the hardener to form covalent bonds. Reactive diluents also lower the viscosity of the epoxy resin. Reactive diluents for the purposes of the present invention are aliphatic or cycloaliphatic compounds. They do not evaporate during curing, but are covalently bonded into the forming resin matrix during curing. Suitable reactive diluents are, for example, mono- or polyfunctional oxiranes. Examples of monofunctional reactive diluents are glycidyl ethers of aliphatic and cycloaliphatic monohydroxy compounds having generally 2 to 20 C atoms, such as. B. Ethylhexyl xylglycidylether and glycidyl esters of aliphatic or cycloaliphatic monocarboxylic acids with usually 2 to 20 carbon atoms. Examples of polyfunctional reactive diluents are, in particular, glycidyl ethers of polyfunctional alcohols with generally 2 to 20 C atoms, which on average typically have 1, 5 to 4 glycidyl groups, such as 1,4-butanediol diglycidyl ether,

1,6-hexanediol diglycidyl ether, diethylene glycol diglycidyl ether or the glycidyl ethers of trimethylolpropane or pentaerythritol. A variety of pigments or fillers can be added to the curable epoxy resin compositions of this invention. Suitable are e.g. Metal oxides such as titanium dioxide, zinc oxide and iron oxide or hydroxides, sulfates, carbonates, silicates of these or other metals, for example calcium carbonate, aluminum oxide, aluminum silicates. Further suitable fillers are, for example, silicon dioxide, pyrogenic or precipitated silica and also carbon black, talc, barite or other nontoxic pigments. Mixtures of fillers and pigments can also be used. The proportion by weight of the fillers and pigments in the coating, their particle size, particle hardness and their aspect ratio will be selected by a person skilled in the art according to the application requirements.

The curable epoxy resin composition according to the invention may contain further additives as required, for example defoamers, dispersants, wetting agents, emulsifiers, thickeners, biocides, co-solvents, bases, corrosion inhibitors, flame retardants, release agents and / or waxes. The curable epoxy resin composition of the present invention may also contain reinforcing fibers such as glass fibers or carbon fibers. These can be present for example as short fiber pieces of a few mm to cm in length, and as continuous fibers, wound or tissue.

The present invention further relates to a process for producing a cured epoxy resin comprising curing the curable epoxy resin composition of the invention described above. The curing can be carried out at atmospheric pressure and at temperatures up to 250 ° C, in particular at temperatures of 20 ° C to less than 235 ° C, preferably at temperatures of 40 to 220 ° C or from 50 to less than 220 ° C, in particular in a temperature range of 100 ° C to 200 ° C. The curing time is preferably 0.1 to 60 minutes, or 0.5 to 20 minutes. more preferably 1 to 10 min.

The curing of the curable epoxy resin composition to moldings is usually carried out in a tool until dimensional stability is achieved and the workpiece can be removed from the tool. The subsequent process for reducing residual stresses of the workpiece and / or completing the crosslinking of the cured epoxy resin is called tempering. In principle, it is also possible to carry out the annealing process before removing the workpiece from the tool, for example to complete the cross-linking. The annealing process usually takes place at temperatures at the boundary of the molding It is customary to use at temperatures of 120 ° C. to 220 ° C., preferably at temperatures of 150 ° C. tempered to 220 ° C. Usually, the hardened workpiece is exposed to the tempering conditions for a period of 30 to 240 minutes Depending on the dimensions of the workpiece, longer annealing times may also be appropriate.

When the curable epoxy resin composition is cured to give coatings, the curable epoxy resin composition is first applied to the substrate to be coated, and then the curable epoxy resin composition is cured on the substrate. The curable epoxy resin composition can be applied before or after the desired article is formed by dipping, spraying, rolling, brushing, knife coating or the like in liquid formulations or by applying a powder coating. The application can be carried out on individual pieces (for example can parts) or on basically endless substrates, for example steel rolls in coil coating. The final shape of the articles may be before or after application of the epoxy resins.

Suitable substrates, especially for metal containers, are usually made of steel, tinplate (tinned steel) or aluminum (e.g., for beverage cans), which may also be made in 2 or 3 parts by methods known to those skilled in the art. A detailed description of the common types of metal packaging and their manufacture, metals and alloys used and coating methods is given in P.K.T. Oldring and U. Nehring: Packaging Materials, 7th Metal Packaging for Foodstuffs, ILSI Report, 2007, to which reference is hereby made. The present invention further relates to the cured epoxy resins obtainable or obtained by curing the curable epoxy resin composition according to the invention, in particular in the form of coatings on metallic substrates.

The present invention further relates to the use of the polycarboxylic acid polyepoxy esters according to the invention or of the curable epoxy resin composition according to the invention for the production of adhesives, composites, moldings and coatings, in particular of coatings preferably of containers, in particular of metal containers such as metal cans, preferably for food packaging ie for the storage or storage of food. The invention will now be explained in more detail by the following nonlimiting examples.

Examples of starting materials:

terephthalic acid

Glycidyl ether: reaction product of pentaerythritol with 5.5 moles of propylene oxide and

3.3 moles of epichlorohydrin

triphenylphosphine

Phenodur® PR 516 / 60B: crosslinker; Phenolic resin, (Cytec)

Polycarboxylic acid polyester crosslinker, reaction product of 4 mol of citric acid and

1 mol of trimethylolpropane

Cycat® XK 406N: phosphoric acid based catalyst, (Cytec)

MPA methoxypropyl acetate; solvent

Beckopox® EP 307 50% in MPA, bisphenol A based epoxy resin

Example 1: Preparation of polycarboxylic acid polyepoxyester

In a 11 four-necked flask equipped with stirrer, thermometer and reflux condenser, 200 g of glycidyl ether and 25 g of terephthalic acid and 0.5 g of triphenylphosphine were weighed. The reaction mixture was heated with stirring to 160 ° C, which was initially cloudy (undissolved terephthalic acid). After 1 h, the reaction mixture became clear and a sample was taken to determine the epoxide content. An EEW (epoxy equivalent weight) of 391 was determined. After a further hour at 160 ° C, an EEW of 397 and an acid number of 0.02 mg KOH / g was determined. There was obtained a yellow, viscous liquid having a viscosity of 6700 mPa s (Brookfield, DV II, 40 ° C, 10 rpm, spindle 31). In the IR spectrum, an ester band was observed at 1720 cm ^-1 , the acid band of terephthalic acid at 1670 cm ^-1 had disappeared.

Example 2: Epoxy Coating Composition

The epoxy resin prepared according to Example 1 was used in a standard formulation for can

Coating coatings in comparison with a bisphenol A-based epoxy resin (Beckopox® EP 307, 50% solution in methoxypropyl acetate, Fa. Cytec) tested (see Table 1).

The paint tests were carried out on tinplate. The coating formulations were applied by means of a doctor blade machine equipped with a 20 μm helical doctor blade (winding speed 25 mm / s). The coatings thus prepared were under the hood for 30 min. at room temperature (about 20 ° C) predried (evaporation of the solvent). The burn-in time was 12 minutes at 200 ° C. The film thickness after drying gives 7.3 μηη. investigations:

1) Testing the pendulum hardness

Pendulum damping test according to DIN EN ISO 1522 of 2000

Result indication as pendulum duration in seconds, the higher the value, the higher the pendulum hardness

Solvent resistance (MEK double rubs)

Solvent Rub test according to ASTM D4752

Rubbing a cured film with a cheesecloth soaked in methyl ethyl ketone until the film has defects.

Results in number of reciprocating rubs (double rubs) until the occurrence of defects. 3) Cross-cut test (liability)

The adhesion of the coatings to the substrate was carried out by means of a cross-cut test in accordance with DIN EN ISO 2409.

For all coatings the highest grade GT 0 was achieved.

The characteristic value GT 0 means: "The cutting edges are completely smooth. No part of the paint has flaked off. "

4) Flexibility (bending test)

The coated sheets are rapidly bent by up to 180 °, with the coated surface lying on the outside of the bend. With good flexibility of the coating no damage or delamination in the buckling area are observed.

A brittle coating tears at the bending edge, here the degree of bending is specified, in which the coating is just not damaged.

The formulations and test results are summarized in the table below.

Table 1: Epoxy resin compositions and test results

Comparison A B C

Amounts [g] Amounts [g] Amounts [g] Amounts [g]

Beckopox® EP 307 25,6 - - -

Epoxy resin Example 1 - 9,15 7,35 10

Phenodur® PR 516 / 60B 9,15 15,25 18,35 -

Polycarboxylic acid polyesters - - - 2.1

Cycat® XK 406N 0.55 0.55 0.55 0.3

MPA 14,7 25,05 23,75 21

Total 50 50 50 33.4

Amount of catalyst [%] 0.04 0.04 0.04 0.07

Solids content 36.7 36.7 36.8 36.3 Comparison ABC

Amounts [g] Amounts [g] Amounts [g] Amounts [g]

Solvent [%] 63.3 63.3 63.2 63.7

Paint tests:

Appearance Gold lacquer Gold lacquer Gold lacquer Clear lacquer

Pendulum hardness [s] 232 216 222 217

MEK double rubs approx. 90 approx. 90 approx. 100 approx. 100

Flexibility Bending test 180 ° 180 ° 180 ° 180 °

Cross cut test GT O GT O GT O GT O

It was found that with the prepared according to Example 1, bisphenol A-free glycidyl ester formulated and cured coatings have the same properties as the comparison coating based on the bisphenol-A epoxy resin.

Example 3

In a laboratory reactor equipped with stirrer, thermometer and reflux condenser, 1600 g of glycidyl ether and 199.6 g of terephthalic acid and 4.0 g of triphenylphosphine were weighed. The reaction mixture was heated with stirring to 130 ° C, which was initially cloudy (undissolved terephthalic acid). After 3 h, the reaction mixture became clear and a sample was taken to determine the epoxide content. An EEW (epoxy equivalent weight) of 376 was determined. After two more hours at 130 ° C an EEW of 397 and an acid number of 0.02 mg KOH / g was determined. A yellow, viscous liquid with a viscosity of 40,400 mPas was obtained (Anton Paar, MC302, 22 ° C.). In the IR spectrum, an ester band was observed at 1720 cm ^-1 , the acid band of terephthalic acid at 1670 cm ^-1 had disappeared.

Example 4

In an 11 four-necked flask equipped with stirrer, thermometer and reflux condenser, 400 g of glycidyl ether and 49.9 g of terephthalic acid and 1, 0 g dimethylethanolamine were weighed. The reaction mixture was heated with stirring to 130 ° C, which was initially cloudy (undissolved terephthalic acid). After 1 h, the reaction mixture became clearer, the color changed to reddish brown, and a sample was taken to determine the epoxide content. An EEW (epoxy equivalent weight) of 403.5 and an acid number of 1.4 mg KOH / g were determined. After a further hour at 130 ° C., an acid number of 0.35 mg KOH / g was determined. After a further hour at 130 ° C, the acid number was 0.09. An orange-yellow, viscous liquid was obtained. In the IR spectrum, an ester band was observed at 1720 cm ^-1 , the acid band of terephthalic acid at 1670 cm ^-1 had disappeared. Examples 5-8

The following further syntheses were carried out according to the same scheme as described above:

Table 2: Epoxy resins

In accordance with Example 2 (paint formulation), the following formulations were also tested:

Table 3: Epoxy resin compositions D to G:

D E F G

Amounts [g] Amounts [g] Amounts [g] Amounts [g]

Epoxy resin Example 5 7.4 - - -

Epoxy resin Example 6 - 7,4 - -

Epoxy resin example 7 - - 7,4 -

Epoxy resin Example 8 - - - 7.4

Phenodur® PR 516 / 60B 18,35 18,35 18,35 18,35

Cycat® XK 406N 0.55 0.55 0.55 0.3

MPA 23.9 23.9 23.9 23.9

Total 50.15 50.15 50.15 50.15

Amount of catalyst [%] 0.09 0.09 0.09 0.09

Solids content 36.7 36.7 36.7 36.7

Solvent [%] 63.3 63.3 63.3 63.7 Table 4: Test results of the epoxy resin compositions D to G

Paint tests: D E F G

Appearance Gold Lacquer Gold Lacquer Gold Lacquer Gold Lacquer

Pendulum hardness [s] 214 209 217 242

MEK double rubs> 100> 100> 100> 100

Flexibility Bending test 180 ° 180 ° 180 ° 180 °

Cross cut test GT O GT O GT O GT O

Claims

claims

Polycarbonsaurepolyepoxyester, prepared by reaction of

(A) at least one aromatic dicarboxylic acid with

(B) at least one polyglycidyl ether which has an average glycidyl functionality of greater than two, preferably of at least 2.3.

Polycarboxylic acid polyepoxyester according to claim 1, characterized in that the polyglycidyl ether (B) is a glycidyl ether of a propoxylated polyhydric alcohol.

Polycarboxylic acid polyepoxyester according to one of the preceding claims, characterized in that the aromatic dicarboxylic acid (A) is selected from those of the general formula

H0 ₂ C-Ar-C02 [-R 0 ₂ C-Ar-C02] nH

where n is a number from 0 to 10,

Ra is a linear alkylene group, a branched alkylene group, a cyclic alkylene group or a divalent aromatic group each having up to 100 carbon atoms.

4. polycarboxylic acid polyepoxyester according to any one of the preceding claims, characterized in that the aromatic dicarboxylic acid (A) is selected from 2,5-furandedicarboxylic acid and those of the formula

where n is a number from 0 to 10 and A is an alkylene group having 1 to 4 C atoms, preferably ethylene.

5. Polycarbonsäurepolyepoxyester according to any one of the preceding claims, characterized in that the polyglycidyl ether (B) is selected from glycidyl ethers of non-alkoxylated, polyfunctional alcohols having 3 to 10 OH groups and alkoxylated th, preferably propoxylated polyfunctional alcohols having 3 to 10 OH Groups, wherein in each case more than two of the OH groups are functionalized with glycidyl ether groups.

6. Polycarbonsäurepolyepoxyester according to any one of the preceding claims, characterized in that the polyglycidyl ether (B) is selected from those of the general formula

wherein n is a number from 3 to 10 and R is derived from an n-valent, non-alkoxylated or alkoxylated, preferably propoxylated polyfunctional alcohol having 3 to 10 OH groups, of which more than two of the OH groups are functionalized with glycidyl ether groups.

Polycarboxylic acid polyepoxyester according to one of the two preceding claims,

characterized in that the polyfunctional alcohol is selected from glycerol,

Trimethylolpropane, pentaerythritol, sorbitol, isosorbide and the addition products of the aforementioned compounds with ethylene oxide and / or preferably propylene oxide.

Polycarboxylic acid polyepoxyester according to one of the preceding claims, characterized in that the polyglycidyl ether (B) is a glycidyl ether of propoxylated pentaerythritol with on average more than two glycidyl ether groups.

Polycarboxylic acid polyepoxyester according to one of the preceding claims, characterized in that it has the general formula

(Gly) _m R-O [-CH ₂ -CHOH-CH ₂ -O-CO-Ar-CO-O-CH ₂ -CHOH-CH ₂ -O-R (-Gly) _m -i] n-Gly, where m is a number from 2 to 9,

n is a number from 1 to 100,

-Gly is a glycidyl radical having the formula

-R- is an (m + 1) valent alkoxylated or non-alkoxylated radical of a polyfunctional alcohol having 3 to 10 OH groups,

including the corresponding oligomers and polymers branched via pendant glycidyl groups.

Polycarbonsäurepolyepoxyester according to claim 1, characterized in that the reaction is catalyzed by a phosphorus catalyst, preferably by triphenylphosphine.

1 1. A curable epoxy resin composition containing at least one resin component and at least one hardener component, said resin component containing at least one polycarboxylic acid polyepoxyester according to any one of the preceding claims. A curable epoxy resin composition according to the preceding claim, wherein the at least one curing agent component is selected from the group consisting of polycarboxylic acids and phenolic resins.

A curable epoxy resin composition according to any one of claims 11 to 12, wherein the polycarboxylic acid polyepoxy ester accounts for at least 40% by weight of the total resin component.

14. The curable epoxy resin composition according to any one of claims 11 to 13, wherein the curable epoxy resin composition has a content of less than 40% by weight of bisphenol A or bisphenol F based compounds based on the entire resin component.

15. A process for the preparation of a cured epoxy resin, comprising curing the curable epoxy resin composition according to any one of claims 1 1 to 14.

16. A cured epoxy resin obtainable by curing the curable epoxy resin composition according to any one of claims 1 1 to 14.

17. Use of the Polycarbonsäurepolyepoxyester according to any one of claims 1 to 10 or a curable epoxy resin composition according to any one of claims 1 1 to 14 for the production of adhesives, composites, moldings or coatings.

18. Use according to the preceding claim for coating metal cans, in particular for food packaging.

19. A process for preparing polycarboxylic acid polyepoxy esters wherein at least one aromatic dicarboxylic acid is reacted with at least one polyglycidyl ether having more than two glycidyl groups in the presence of a catalyst, preferably a phosphorus catalyst.