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EP-4543959-B1 - SOLUTION OF POLYPHENOLS IN AMINE

EP4543959B1EP 4543959 B1EP4543959 B1EP 4543959B1EP-4543959-B1

Inventors

  • Kasemi, Edis
  • BURCKHARDT, URS
  • STADELMANN, URSULA
  • KRAMER, ANDREAS

Dates

Publication Date
20260513
Application Date
20230619

Claims (15)

  1. Solution comprising 5% to 65% by weight of room temperature solid polyphenols and 35% to 95% by weight of amines of the formula (I) R-NH-A-NH 2 (I) where A is a linear or branched alkylene radical having 2 to 10 carbon atoms and R is a monovalent hydrocarbon radical optionally containing an oxygen atom and having 1 to 12 carbon atoms, where the amine of the formula (I) has a total of 8 to 15 carbon atoms and the two nitrogen atoms are separated from one another by at least two carbon atoms.
  2. Solution according to Claim 1, characterized in that the room temperature solid polyphenol is selected from the group consisting of gallic acid, diphenolic acid, resveratrol, catechin and polymers containing phenol groups, especially phenolic resins.
  3. Solution according to either of Claims 1 and 2, characterized in that the room temperature solid polyphenol is a phenolic resin of the formula (II) where n has an average value of 1 to 45, preferably 1 to 25, especially 1 to 8, and R 1 is independently H or an aliphatic hydrocarbon radical having 1 to 15 carbon atoms, preferably H, methyl or a linear aliphatic C 15 hydrocarbon radical having zero, one, two or three double bonds.
  4. Solution according to any of Claims 1 to 3, characterized in that A is selected from 1,2-ethylene, 1,2-propylene, 1,3-propylene, 1,4-butylene, 1,3-butylene, 2-methyl-1,2-propylene, 1,3-pentylene, 1,5-pentylene, 2,2-dimethyl-1,3-propylene, 1,6-hexylene, 2-methyl-1,5-pentylene, 1,7-heptylene, 1,8-octylene, 2,5-dimethyl-1,6-hexylene, 1,9-nonylene and 1,10-decylene, especially 1,2-ethylene.
  5. Solution according to any of Claims 1 to 4, characterized in that R contains at least one aromatic or aliphatic ring and is especially selected from benzyl, furfuryl, 2-phenylethyl, cyclohexylmethyl and tetrahydrofurfuryl.
  6. Solution according to any of Claims 1 to 5, characterized in that it includes - 5% to 65% by weight, preferably 10% to 50% by weight, especially 20% to 45% by weight, of room temperature solid polyphenols, - 35% to 95% by weight, especially 50% to 90% by weight, of amines of the formula (I), and - 0% to 30% by weight of further amines that do not conform to the formula (I) and/or thinners and/or further accelerators.
  7. Solution according to Claim 6, characterized in that it additionally includes - at least one amine of the formula (Ia) and/or one amine of the formula (Ib) R-NH-A-NH-R (Ia) NH 2 -A-NH 2 (Ib) where A and R are each the same radical as in the corresponding amine of the formula (I), - and/or amine-functional adducts of the amine of the formula (I) with at least one mono- or polyepoxide.
  8. Solution according to any of Claims 1 to 7, characterized in that the viscosity at 20°C measured by cone-plate viscometer is in the range from 0.01 to 100 Pa·s, more preferably 0.02 to 50 Pa·s, more preferably 0.03 to 20 Pa·s, especially 0.05 to 10 Pa·s.
  9. Use of the solution according to any of Claims 1 to 8 for production of a curing agent for epoxy resins, wherein the curing agent contains at least one further amine having at least three amine hydrogens.
  10. Use according to Claim 9, characterized in that the further amine having at least three amine hydrogens is selected from the group consisting of amines of the formula (I), 1,5-diamino-2-methylpentane, 2-butyl-2-ethylpentane-1,5-diamine, 2,2(4),4-trimethylhexane-1,6-diamine, 1,2-diaminocyclohexane, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, bis(4-aminocyclohexyl)methane, isophoronediamine, 2(4)-methyl-1,3-diaminocyclohexane, 2,5(2,6)-bis(aminomethyl)bicyclo[2.2.1]heptane, 1,3-bis(aminomethyl)benzene, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, dipropylenetriamine, N-(2-aminoethyl)propane-1,3-diamine, N,N'-bis(3-aminopropyl)ethylenediamine, bis(hexamethylene)triamine, polyoxypropylenediamines having an average molecular weight M n in the range from 200 to 500 g/mol, polyoxypropylenetriamines having an average molecular weight M n in the range from 300 to 500 g/mol, 3-(3-(dimethylamino)propylamino)propylamine, 2,5-bis(aminomethyl)furan, 2,5-bis(aminomethyl)tetrahydrofuran, bis(5-aminomethylfuran-2-yl)methane, bis(5-aminomethyltetrahydrofuran-2-yl)methane, 2,2-bis(5-aminomethylfuran-2-yl)propane, 2,2-bis(5-aminomethyltetrahydrofuran-2-yl)propane, amine-functional adducts of the amines mentioned with mono- or polyepoxides, phenalkamines and mixtures of two or more of the amines mentioned.
  11. Use according to either of Claims 9 and 10, characterized in that the curing agent contains 2% to 30% by weight, preferably 5% to 25% by weight, of room temperature solid polyphenols based on the sum total of all liquid or dissolved constituents present in the curing agent.
  12. Use according to any of Claims 9 to 11, characterized in that the curing agent, based on the sum total of all liquid or dissolved constituents present in the curing agent, has an amine hydrogen equivalent weight of 50 to 140 g/eq, preferably 55 to 120 g/eq, more preferably 60 to 100 g/eq, especially 65 to 90 g/eq.
  13. Use according to any of Claims 9 to 12, characterized in that the curing agent, based on the sum total of all liquid or dissolved constituents present in the curing agent, has a viscosity at 20°C measured by cone-plate viscometer in the range from 10 to 5,000 mPa·s, preferably 10 to 1,000 mPa·s, more preferably 10 to 500 mPa·s, especially 10 to 250 mPa·s.
  14. Epoxy resin composition comprising a resin component containing at least one epoxy resin and either - a curing agent component comprising the curing agent as described in any of Claims 9 to 13 or - a curing agent component comprising at least one amine having at least three amine hydrogens and, as a separate, third component, the solution according to any of Claims 1 to 8.
  15. Cured epoxy resin composition obtained from the epoxy resin composition according to Claim 14 after mixing the components.

Description

Technical field The invention relates to solutions of polyphenols in amines, their use for the production of hardeners for epoxy resins and room temperature-curing epoxy resin compositions therefrom. State of the art Room-temperature curing epoxy resin-based polymer compositions are widely used in the construction industry. They consist of liquid resin and hardener components, which are mixed before application and cure at ambient temperatures to form a high-strength and durable material. However, under cool ambient conditions, such as temperatures between 15 and 0 °C, these systems often cure slowly and fail to achieve the desired final hardness even after subsequent heating. Furthermore, they are prone to surface defects such as clouding, staining, roughness, or stickiness, also known as "blushing," which occurs particularly in high humidity. These disadvantages are highly undesirable, especially in coating applications where high surface quality and hardness are crucial, and often lead to costly rework. The use of common accelerators such as 2,4,6-tris(dimethylaminomethyl)phenol usually only partially or not at all resolves the problem. Phenol compounds are also well-known as accelerators, especially for rapid curing at low temperatures. However, common liquid phenolic compounds such as phenol itself, tert-butylphenol, or nonylphenol are highly toxic substances and have therefore been largely unusable in epoxy resin products for some time. Cardanol, a phenol substituted with a C15 hydrocarbon chain and obtained from cashew nut shells, is also known. However, the accelerating effect of cardanol is weak, it is poorly compatible with epoxy resins in higher quantities, and it has an undesirable lowering effect on the glass transition temperature of the cured products. Polyphenols, especially so-called phenolic resins, particularly those resulting from the polymerization of phenol, are also known as accelerators. with formaldehyde. However, polyphenols are typically solid at room temperature, sparingly soluble, and usually highly viscous when dissolved in common amine hardeners. Dilution with solvents such as xylene is therefore disadvantageous, as it results in undesirably high emissions. US 6,649,729 describes the use of phenolic resins in epoxy resin products with common amine hardeners such as isophorone diamine (IPDA) or diethylenetriamine to accelerate curing and reduce blushing. US 2010/0210758 describes the use of high amounts of phenolic resin in epoxy resin coatings with amine hardeners such as 1,3-bis(aminomethyl)benzene (MXDA) or trimethylhexanediamine (TMD) to accelerate curing and increase chemical resistance. Alkylated amines such as N-benzyl-1,2-ethanediamine are known as hardeners for epoxy resins, for example from WO 2020/070082 They also enable epoxy resin coatings with beautiful surfaces at cold temperatures, although their final hardness after curing in the cold tends to be lower than after curing at room temperature. EP3489272A1 reveals solutions containing polyphenols and polyamines. Description of the invention The object of the present invention is to provide a room-temperature liquid accelerator for the curing of epoxy resins, which exhibits high accelerator activity, low viscosity, and is readily miscible and compatible with epoxy resins, and which ensures trouble-free and complete curing even under cold ambient conditions. Surprisingly, this object is achieved with a solution comprising 5 to 65 wt% of room-temperature solid polyphenols and 35 to 95 wt% of amines of formula (I), as described in claim 1. The amine of formula (I) is able to dissolve surprisingly high amounts of polyphenols at a manageable viscosity. The solution according to the invention is particularly advantageous for the production of a hardener for epoxy resins. With the solution according to the invention, hardeners with a readily adjustable polyphenol content can be easily produced, which are particularly low-viscosity and excellently miscible and compatible with epoxy resins. The key advantage is that these hardeners enable epoxy resin products with particularly trouble-free cold curing and exceptionally high final hardness. In particular, they allow for epoxy resin coatings with surprisingly high hardness after 7 days of cold curing (8°C/80% relative humidity) followed by 14 days of curing in standard climate conditions, which is very close to the hardness achieved after 14 days of curing in standard climate conditions. Preferably, the hardness, measured as the "king's hardness," reaches at least 70%, more preferably at least 80%, and most preferably at least 90% of the value after curing in standard climate conditions. This cold curing is achieved with a surprisingly small amount of the solution according to the invention, resulting in excellent processability of such coatings even without or with very little thinner, and thus making them particularly low-emission. The amines commonly used as hardeners for