Composition of Bronsted acid and monoamine

Abstract

The invention relates to compositions of a) at least one metal, ammonium or phosphonium salt of a strong Bronsted acid and b) at least one aliphatic primary monoamine, to processes for their preparation and to their use.

Description

Technical Field

[0001] The present invention relates to compositions comprising strong Bronsted acids, to processes for their preparation and to their use. Since the compositions according to the invention are particularly well suited as catalyst compositions, in particular for the curing of epoxy resins, the present invention also relates to catalyst preparations comprising strong Bronsted acids. Background Art

[0002] Epoxy resins, in particular those prepared from bisphenol A and epichlorohydrin, are known raw materials for the preparation of high-quality casting resins, coating materials, composite materials and adhesives. Aromatic epoxy resins cured with polyamines have good chemical and solvent resistance and good bond strength on many substrates.

[0003] In order to accelerate the curing of epoxy-amine coating systems, catalysts can be used (US Pat. No. 3,492,269 A, US Pat. No. 5,470,896 A, GB 1,105,772 A).

[0004] EP 0 083 813 A1, EP 2 957 584 A1, US Pat. No. 5,441,000 A, US Pat. No. 5,629,380 A, WO 96 / 09352 A1 disclose the catalytic curing of epoxy resins using various amines.

[0005] US Pat. No. 8,980,979 B2 discloses the curing of epoxy resins with cyclic diamines, in particular selected from piperazine or homopiperazines, optionally in the presence of catalysts.

[0006] EP 0 969 030 A1 discloses an epoxy / amine coating system whose amine component is an aliphatic amine. The composition may contain a catalyst.

[0007] US 4,775,734 A discloses the use of aminoethylpiperazine to cure epoxy resins in the presence of tetrafluoroborate or hexafluorophosphate of different amines of catalytic amount. In addition, in comparative example (Example 2), an experiment of curing epoxy resins with aminoethylpiperazine in the presence of lithium tetrafluoroborate is disclosed. However, no reaction occurs under the ratio of the epoxy group: NH group used. Another embodiment (Example 14) discloses the reaction of ammonium hexafluorophosphate and diethylamine.

[0008] US 5,134,239 A discloses an adduct consisting of a heterocyclic nitrogen-containing compound and a salt. As an example not according to the invention, Example 58 discloses the synthesis of a butylamine-tetrabutylphosphonium fluoroborate complex in a methanol solution.

[0009] WO 2017 / 074810 A1 discloses compositions comprising epoxy resins, polyetheramines and further amine curing agents, wherein these may especially be aliphatic amines, and optionally metal triflate catalysts.

[0010] Applications EP 3 569 629 A1, EP 3 569 630 A1, EP 3 569 631 A1 and EP 3 569 632 A1 disclose compositions comprising at least one epoxy resin, at least one cyclic amine having at least two amino groups and at least one salt of a Brönsted acid.

[0011] It is desirable to accelerate the curing of epoxy formulations with catalysts in order to be able to save energy and reaction time. It has been found that salts of strong Bronsted acids (i.e. those with a pKa value of less than or equal to 2), in particular salts of very strong Bronsted acids (i.e. those with a pKa value of less than or equal to -9.01), are particularly suitable. However, they have the disadvantage that they are solid and it is difficult to homogenize them in liquid epoxy formulations. Dissolution or dispersion in a solvent beforehand is also disadvantageous - in the case of dispersing or dissolving the catalyst in an inert solvent, the VOC (volatile organic content) ratio of the epoxy composition is thereby increased. In contrast, reactive solvents lead to precipitation, discoloration and reduced reactivity. Summary of the invention

[0012] It was therefore an object of the present invention to provide compositions containing salts of strong Brønsted acids which are very suitable as catalysts for epoxy preparations and which do not have the abovementioned disadvantages.

[0013] Surprisingly, it has been found that salts of strong or very strong Bronsted acids, in particular salts of trifluoromethanesulfonic acid (trifluoromethanesulfonic acid), dissolve well in primary aliphatic monoamines. Here, surprisingly, it has been found that primary aliphatic monoamines dissolve the mentioned salts much better than secondary aliphatic monoamines or other monoamines.

[0014] The present invention therefore provides a composition of a) at least one metal, ammonium or phosphonium salt of a strong Brønsted acid and b) at least one primary aliphatic monoamine.

[0015] Preferably, the composition has 10-95% by weight of component a) and 5-90% by weight of component b), based on the initial weight of components a) and b). Further preferably, the composition has 30-70% by weight of component a) and 70-30% by weight of component b), based on the initial weight of components a) and b), and further preferably has 40-60% by weight of component a) and 60-40% by weight of component b), based on the initial weight of components a) and b).

[0016] The composition according to the invention comprises at least one metal salt, ammonium salt or phosphonium salt of a strong Bronsted acid. The corresponding salts are good catalysts. Such strong acids are understood to mean acids whose pKa value (or the pKa value of the first protonation stage in the case of polyprotic acids) is less than or equal to 2. Preferably, the pKa of the corresponding acid is less than or equal to -2.

[0017] pKa is defined as the negative decimal logarithm of the equilibrium constant Ka and is considered a measure of the strength of an acid. The smaller the pKa value, the stronger the acid. As F. G. Bordwell states in "Equilibrium Acidities in Dimethylsulfoxide Solution", Acc. Chem. Res. 1988, 21 The pKa values ​​were determined as disclosed in , 456-463.

[0018] Preferred salts are the corresponding salts of the strong acids summarized in the first column of Table 1 below:

[0019] Table 1:

[0020] acid pKa value References, if not published in Bordwell oxalic acid 1.5 Bayer Walter, Lehrbuch der organischen Chemie, 21st edition, Hirzelverlag 1988, page 324 p-Toluenesulfonic acid 0.7 Römpp Lexikon Chemie, 10th edition, Georg Thieme Verlag, Stuttgart, New York, Verlag 1999, pp. 4580-1. Trifluoroacetic acid 0.2 Bayer Walter, Lehrbuch der organischen Chemie, 21st edition, Hirzelverlag 1988, page 272 Tetrafluoroboric acid -0.4 , pp. 1-4, Conference; General Review; Online Computer File, 2001 Nitric acid -1.4 Hollemann Wiberg, Lehrbuch der anorganischen Chemie, ed. 91.-100, Walter derGruyter Verlag, Berlin, New York, 1985, p. 603. sulfuric acid -3 Römpp, Lexikon Chemie, 9th edition, Georg Thieme Verlag, Stuttgart, New York 1991, p. 3459. hydrochloric acid -8 Hydrobromic acid -9 Perchloric acid -10 Hollemann Wiberg, Lehrbuch der anorganischen Chemie, ed. 91.-100, Walter derGruyter Verlag, Berlin, New York, 1985, p. 428 Trifluoromethanesulfonic acid -14 Hydrogen iodide -9.5 Journal of Physical Chemistry AVolume 120, Issue 20, pages 3663-3669. Hexafluorophosphoric acid -10 http: / / www.periodensystem-online.de / index.#timg#= wertdesc&prop=pKs-Werte&show=list&id=acid Hexafluoroantimonic acid -17 http: / / www.periodensystem-online.de / index.#timg#= wertdesc&prop=pKs-Werte&show=list&id=acid

[0021] Preferably, the salt is a salt of a very strong acid, wherein a very strong acid is understood here to mean an acid whose pKa value (or the pKa value of the first protonation stage in the case of a polyprotic acid) is less than or equal to -9.01. Preferably, the pKa value of the very strong acid is from -9.5 to -25, particularly preferably from -9.9 to -21.

[0022] Very particularly preferably, component a) is a salt of a Brønsted acid selected from the group consisting of perchloric acid, trifluoromethanesulfonic acid, hydrogen iodide, hexafluorophosphoric acid and hexafluoroantimonic acid.

[0023] Still further preferred, the salt is a triflate, ie a salt of trifluoromethanesulfonic acid.

[0024] The strong Bronsted acid salts are metal salts, ammonium salts or phosphonium salts. Metal salts are understood here to mean salts containing metal ions (i.e. having at least one ion derived from at least one metal, preferably having ions derived from at least one metal atom, particularly preferably having exactly one ion derived from at least one metal atom), as well as metal-containing ions (i.e. also having non-metallic parts). Thus, the counterions of the acids mentioned are selected from metal ions, metal-containing ions, phosphonium ions and ammonium ions.

[0025] Preferred metal ions are alkaline earth metal cations, in particular beryllium, magnesium, calcium, strontium and barium, and also lithium, aluminum, bismuth, zinc and europium.

[0026] The metal-containing ion is an ion containing at least one metal but not a pure metal ion. Preferably, it is a metal compound ion, such as a tetraphenylantimony ion.

[0027] The ammonium ion can be unsubstituted (= NH4 + ), alkylated and / or arylated. The phosphonium ion may be unsubstituted (= PH4 + ), alkylated and / or arylated. The preferred ammonium ion is NH4 + The preferred phosphonium ion is PH4 + Very particular preference is given to ammonium ions.

[0028] Preferred salts of strong acids are calcium trifluoromethanesulfonate, europium trifluoromethanesulfonate, barium trifluoromethanesulfonate, aluminum trifluoromethanesulfonate, bismuth trifluoromethanesulfonate, lithium trifluoromethanesulfonate, lithium perchlorate, barium perchlorate, lithium hexafluorophosphate and zinc perchlorate. Very particular preference is given to calcium trifluoromethanesulfonate, europium trifluoromethanesulfonate, lithium hexafluorophosphate and lithium perchlorate.

[0029] Best results were achieved with calcium triflate.

[0030] The composition furthermore comprises at least one aliphatic primary monoamine. Here, an aliphatic primary monoamine is understood to mean a primary monoamine (i.e. an amine having only one primary amino group) which has only aliphatic, i.e. straight-chain or branched, alkyl, cycloalkyl and / or (cyclo)alkyl groups. Here, a (cyclo)alkyl group is understood to mean a group which has both a cyclic and a straight-chain or branched alkyl part. Preferred aliphatic groups have in each case 3 to 30, particularly preferably 3 to 10, very particularly preferably 3-6 carbon atoms. The monoamine may be substituted by hydroxyl groups on one of its alkyl, cycloalkyl and / or (cyclo)alkyl groups. However, no other substituents are present. Furthermore, preferably, all aliphatic groups of the monoamine are unsubstituted.

[0031] Preference is given to using monoamines having a boiling point (measured at 1013.25 hPa) of from 30 to 300° C., preferably from 30 to 200° C.

[0032] Very particularly preferably, the monoamine is selected from the group consisting of n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, n-pentylamine, n-hexylamine and ethanolamine.

[0033] Still further preferably, the monoamine is n-butylamine.

[0034] The best results were obtained when component a) was calcium trifluoromethanesulfonate and component b) was n-butylamine.

[0035] The invention further provides a process for preparing the composition according to the invention, wherein a) at least one metal salt, ammonium salt or phosphonium salt of a strong Brønsted acid and b) at least one aliphatic monoamine are mixed with one another, optionally in the presence of further components.

[0036] Furthermore, the present invention also provides for the use of the composition according to the invention as a catalyst composition. The composition according to the invention is particularly suitable as a catalyst composition for curing epoxy resins, very preferably for curing epoxy resins with amines. DETAILED DESCRIPTION

[0037] Example

[0038] Example 1)

[0039] In order to confirm the special reactivity of the claimed catalyst, the model tests were compared with each other. For this purpose, 0.025 Mol (3.75 g) of 1,2-epoxy-3-phenoxypropane was added to a mixture consisting of 22.7 g toluene (solvent) and 2.08 g tetradecane (internal standard) in each case. 0.025 Mol (2.13 g) of piperidine was added thereto, and 0.06 g of calcium trifluoromethanesulfonate was dissolved in an equal amount of amine or alcohol as a comparison. GC was performed immediately after mixing and the content of 1,2-epoxy-3-phenoxypropane was compared with the content of tetradecane. After 4 hours at room temperature (RT), the residual content of 1,2-epoxy-3-phenoxypropane (EP) was determined by GC detection (calibrated by internal standard tetradecane). The following results were obtained:

[0040] Comparison of catalysts

[0041] Amine or alcohol Residual %EP in 0-sample Residual %EP after 4 hours at room temperature 1 No amines or alcohols 97 0 2 Abutamine 78 3 3 Hexylamine 75 4 4 Octylamine 76 4 5 3-Methylpropylamine 83 4 6 2-Ethylhexylamine 78 5 7 2-Ethylpropylamine 85 6 8 n-Aminopentylamine 77 2 9 Ethanolamine 78 8 Comparative Example 1 Ethanol 89 32 Comparative Example 2 Ethylene glycol 89 32 Comparative Example 3 Propylene glycol 86 46 Comparative Example 4 Butanediol 96 31 Comparative Example 5 Ethylenediamine 90 33

[0042] The claimed monoamines are suitable as solvents for calcium trifluoromethanesulfonate and do not lead to a significant reduction in reactivity (residual EP content after 4 hours, max. 10%). In contrast, pure alcohols, diols or diamines lead to a significant reduction in reactivity.

Claims

1. A catalyst composition for curing epoxy resins comprising a) at least one metal, ammonium or phosphonium salt of a strong Brønsted acid, and b) at least one aliphatic primary monoamine, wherein all aliphatic groups of the monoamine are unsubstituted, The Brønsted acid is trifluoromethanesulfonic acid, and the monoamine b) has only aliphatic groups having 3 to 10 carbon atoms.

2. The catalyst composition according to claim 1, It is characterized in that The composition has 10 to 95% by weight of component a) and 5 to 90% by weight of component b), based on the weight of components a) and b).

3. The catalyst composition according to claim 1 or 2, It is characterized in that The monoamines b) have exclusively aliphatic groups having 3 to 6 carbon atoms.

4. The catalyst composition according to claim 1 or 2, It is characterized in that The monoamines b) have a boiling point in the range from 30 to 300° C., measured at 1013.25 hPa.

5. The catalyst composition according to claim 1 or 2, It is characterized in that The amine b) is selected from the group consisting of n-propylamine, isopropylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, n-pentylamine and n-hexylamine.

6. The catalyst composition according to claim 1 or 2, It is characterized in that The salt of a strong Bronsted acid a) is calcium trifluoromethanesulfonate and the monoamine b) is n-butylamine.

7. A process for preparing a catalyst composition according to any one of claims 1 to 6, wherein: A) at least one metal salt, ammonium salt or phosphonium salt of a strong Brønsted acid and b) at least one primary aliphatic monoamine are mixed with one another.

8. Use of the catalyst composition according to any one of claims 1 to 6 as a catalyst composition for curing epoxy resins.

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