Search

EP-4737500-A1 - RAPID CURE EPOXY RESIN HARDENERS

EP4737500A1EP 4737500 A1EP4737500 A1EP 4737500A1EP-4737500-A1

Abstract

The invention relates to a class of epoxy resin curatives which act as rapid curing epoxy resin hardeners. In particular, the invention is directed to a class of epoxy resin curatives comprising a benzoic acid moiety and at least one Mannich base group, as well as a curative composition comprising the epoxy resin curative, processes for preparing the epoxy resin curative, and uses thereof. In one aspect, the epoxy resin curative has the formula (1) below:

Inventors

  • JONES, PAUL

Assignees

  • Jones, Paul

Dates

Publication Date
20260506
Application Date
20251030

Claims (15)

  1. An epoxy resin curative of formula (1): wherein: ring A is a monocyclic or polycyclic ring comprising at least one aromatic or heteroaromatic group; x is 0, 1, 2, 3, or 4; y is 0, 1, 2, 3, 4, 5, or 6; z is 1, 2, 3, or 4; each R is independently selected from: -C 1 to C 20 alkyl, -C 1 to C 20 haloalkyl, -C 3 to C 20 cycloalkyl, -C 4 to C 20 heterocycloalkyl, -C 5 to C 20 cycloalkenyl, -C 5 to C 20 heterocycloalkenyl, an optionally substituted 6 to 10 membered aromatic group, an optionally substituted 5 to 10 membered heteroaromatic group, an optionally substituted -(CHR 3 )-(6 to 10 membered aromatic group), an optionally substituted -(CHR 3 )-(5 to 10 membered heteroaromatic group), -C 2 to C 20 alkenyl, -C 2 to C 20 alkynyl, -C 1 to C 20 alkyloxy, -C 1 to C 20 alkylamino, -OH, -OR 2 , -NH 2 , -NHR 2 , -NR 2 2 , -C(O)OH, -C(O)OR 2 , - C(O)NH 2 , -C(O)NHR 2 , -C(O)NR 2 2 , -O(CO)H, -O(CO)R 2 , -NH(CO)H, -NH(CO)R 2 , - NR 2 (CO)H, -NR 2 (CO)R 2 , -SH, -SR 2 , -SO 2 H, -SO 2 R 2 , -SO 3 R 2 , -SO 3 H, -SiR 2 3 , -NO 2 , -CN, - F, -Cl, -Br, and -I; each R 1 is independently selected from: -C 1 to C 20 alkyl, -C 1 to C 20 haloalkyl, -C 3 to C 20 cycloalkyl, -C 4 to C 20 heterocycloalkyl, -C 5 to C 20 cycloalkenyl, -C 5 to C 20 heterocycloalkenyl, an optionally substituted 6 to 10 membered aromatic group, an optionally substituted 5 to 10 membered heteroaromatic group, an optionally substituted -(CHR 3 )-(6 to 10 membered aromatic group), an optionally substituted -(CHR 3 )-(5 to 10 membered heteroaromatic group), -C 2 to C 20 alkenyl, -C 2 to C 20 alkynyl, -C 1 to C 20 alkyloxy, -C 1 to C 20 alkylamino, -OH, -OR 2 , -NH 2 , -NHR 2 , -NR 2 2 , -C(O)OH, -C(O)OR 2 , - C(O)NH 2 , -C(O)NHR 2 , -C(O)NR 2 2 , -O(CO)H, -O(CO)R 2 , -NH(CO)H, -NH(CO)R 2 , - NR 2 (CO)H, -NR 2 (CO)R 2 , -SH, -SR 2 , -SO 2 H, -SO 2 R 2 , -SO 3 R 2 , -SO 3 H, -SiR 2 3 , -NO 2 , -CN, - F, -Cl, -Br, -I, =O, =NH, =NR 2 , =NH 2 (+) , =NHR 2(+) , and =NR 2 2 (+) ; each R 2 is independently selected from: -C 1 to C 20 alkyl, -C 1 to C 20 haloalkyl, -C 3 to C 20 cycloalkyl, -C 4 to C 20 heterocycloalkyl, -C 5 to C 20 cycloalkenyl, -C 5 to C 20 heterocycloalkenyl, an optionally substituted 6 to 10 membered aromatic group, an optionally substituted 5 to 10 membered heteroaromatic group, -C 2 to C 20 alkenyl, -C 2 to C 20 alkynyl, -C 1 to C 20 alkoxy, and -C 1 to C 20 alkylamino; each R 3 group is independently selected from: -H, -C 1 to C 10 alkyl, -C 1 to C 10 haloalkyl, -C 3 to C 12 cycloalkyl, -C 2 to C 10 alkenyl, -C 2 to C 10 alkynyl, a 6 to 10 membered aromatic group, and a 5 to 10 membered heteroaromatic group; wherein each R 3 is optionally substituted with one or more groups selected from -C 1 to C 10 alkyl, -C 1 to C 10 haloalkyl, -C 1 to C 10 alkoxy, -OH, and =O; each R 4 is independently selected from hydrogen or a C 1 to C 100 hydrocarbyl group; each R 5 is independently selected from hydrogen or a C 1 to C 100 hydrocarbyl group; wherein each R 4 and R 5 may be taken together with the nitrogen atom to which they are attached to form a cyclic C 3 to C 100 hydrocarbyl group; or a salt thereof.
  2. The epoxy resin curative of Claim 1, wherein the epoxy resin curative has the formula (1a), or (1c):
  3. The epoxy resin curative of Claim 1 or Claim 2, wherein ring A is a structure selected from: wherein represents the point of attachment to the remainder of the molecule; wherein V is selected from: -N=, -CR 6 =, and -SiR 6 =; wherein W is selected from: -O-, - NR 6 -, -S-, -S(O)-, -S(O 2 )-, -CR 6 2 -, and -SiR 6 2 -; and wherein each R 6 is independently selected from hydrogen, or -C 1 to C 6 alkyl; preferably wherein W is -O-; and/or wherein ring A is a structure selected from: wherein each R 1a is independently selected from: -OH, -OR 2 , -NH 2 , -NHR 2 , and -NR 2 2 ; and wherein R 1b is selected from =O, =NH, =NR 2 , =NH 2 (+) , =NHR 2(+) , and =NR 2 2 (+) ; preferably wherein each group is present at a position ortho to an R 1a or R 1b ; and wherein represents the point of attachment to the remainder of the molecule.
  4. The epoxy resin curative of any one of the preceding claims, wherein ring A is further substituted with one or two substituents of structure (B): wherein represents the point of attachment to the remainder of the molecule; wherein R 1 , R 2 , R 3 , R 4 , and R 5 are as defined in any preceding claim; wherein n is 0, 1, 2, or 3; preferably wherein each substituent of structure (B) is of the formula (B1) or (B2): more preferably wherein each substituent of structure (B) is of the formula (B1i), (B2i), (B1ii), or (B2ii):
  5. The epoxy resin curative of claim 4, when dependent on claim 3, wherein the one or two substituents of structure (B) are present at positions ortho to an R 1a or R 1b .
  6. The epoxy resin curative of any one of the preceding claims, wherein each R is independently selected from: -C 1 to C 20 alkyl, -C 1 to C 20 haloalkyl, -C 2 to C 20 alkenyl, an optionally substituted 6 to 10 membered aromatic group, an optionally substituted 5 to 10 membered heteroaromatic group, an optionally substituted -(CHR 3 )-(6 to 10 membered aromatic group), an optionally substituted -(CHR 3 )-(5 to 10 membered heteroaromatic group), -C 1 to C 20 alkyloxy, -C 1 to C 20 alkylamino, -OH, -OR 2 , -NH 2 , - NHR 2 , -NR 2 2 , -C(O)OH, -C(O)OR 2 , -C(O)NH 2 , -C(O)NHR 2 , -C(O)NR 2 2 , -SO 2 H, -SO 2 R 2 , - SO 3 R 2 , -SO 3 H, -NO 2 , -CN, -F, -Cl, -Br, and -I; and wherein each R 2 is independently selected from: -C 1 to C 20 alkyl, -C 1 to C 20 haloalkyl, -C 2 to C 20 alkenyl, -C 1 to C 20 alkoxy, and -C 1 to C 20 alkylamino; preferably wherein each R is independently selected from: -C 1 to C 20 alkyl, -C 2 to C 20 alkenyl, -OH, -OR 2 , -NH 2 , -NHR 2 , -NR 2 2 , -C(O)OH, -C(O)OR 2 , -C(O)NH 2 , - C(O)NHR 2 , -C(O)NR 2 2 , -F, -Cl, -Br, and -I; and wherein each R 2 is independently selected from: -C 1 to C 20 alkyl.
  7. The epoxy resin curative of any one of the preceding claims, wherein each R 1 is independently selected from: -C 1 to C 20 alkyl, -C 1 to C 20 haloalkyl, -C 2 to C 20 alkenyl, an optionally substituted 6 to 10 membered aromatic group, an optionally substituted 5 to 10 membered heteroaromatic group, an optionally substituted -(CHR 3 )-(6 to 10 membered aromatic group), an optionally substituted -(CHR 3 )-(5 to 10 membered heteroaromatic group), -C 1 to C 20 alkyloxy, -C 1 to C 20 alkylamino, -OH, -OR 2 , -NH 2 , - NHR 2 , -NR 2 2 , -C(O)OH, -C(O)OR 2 , -C(O)NH 2 , -C(O)NHR 2 , -C(O)NR 2 2 , -SO 2 H, -SO 2 R 2 , - SO 3 R 2 , -SO 3 H, -NO 2 , -CN, -F, -Cl, -Br, -I, =O, =NH, =NR 2 , =NH 2 (+) , =NHR 2(+) , and =NR 2 2 (+) ; and wherein each R 2 is independently selected from: -C 1 to C 20 alkyl, -C 1 to C 20 haloalkyl, -C 2 to C 20 alkenyl, -C 1 to C 20 alkoxy, and -C 1 to C 20 alkylamino; preferably wherein each R 1 is independently selected from: -C 1 to C 20 alkyl, -C 2 to C 20 alkenyl, -OH, -OR 2 , -NH 2 , -NHR 2 , -NR 2 2 , -C(O)OH, -C(O)OR 2 , -C(O)NH 2 , - C(O)NHR 2 , -C(O)NR 2 2 , -F, -Cl, -Br, -I, =O, =NH, =NR 2 , =NH 2 (+) , =NHR 2(+) , and =NR 2 2 (+) ; and wherein each R 2 is independently selected from: -C 1 to C 20 alkyl.
  8. The epoxy resin curative of any one of the preceding claims wherein each R 3 group is independently selected from: -H, -C 1 to C 10 alkyl, a 6 to 10 membered aromatic group, and a 5 to 10 membered heteroaromatic group; preferably -H or furanyl; and/or wherein each R 4 and/or each R 5 are independently selected from: -H, -C 1 to C 20 alkyl, -C 1 to C 20 haloalkyl, -C 3 to C 20 cycloalkyl, -C 2 to C 20 alkenyl, -C 2 to C 20 alkynyl, -C 1 to C 20 alkyloxy, -C 1 to C 20 alkylamino, -C 6 to C 20 aryl, and C 2 to C 20 heteroaryl; preferably: -H, -C 1 to C 20 alkyl, -C 3 to C 20 cycloalkyl, -C 2 to C 20 alkenyl, and -C 1 to C 20 alkylamino.
  9. A process of preparing an epoxy resin curative of formula (1) as defined in any one of claims 1 to 8, the method comprising performing a Mannich reaction using: i) a precursor of formula (2); ii) one or more aldehyde having the structure HR 3 C=O; and iii) one or more amine having the structure HNR 4 R 5 ; wherein R, R 1 , R 2 , R 3 , R 4 , R 5 , A, x and y are as defined in any one of claims 1 to 8.
  10. The process of Claim 9, wherein the Mannich reaction further comprises: iv) an optionally substituted 6 to 10 membered aromatic compound or an optionally substituted 5 to 10 membered heteroaromatic compound, preferably a phenolic compound, more preferably phenol.
  11. The process of Claim 9 or Claim 10, wherein the precursor of formula (2), the one or more amine having the structure HNR 4 R 5 , and optionally a substituted phenolic compound, are mixed prior to addition of the one or more aldehyde having the structure HR 3 C=O; and/or wherein the aldehyde is formaldehyde, and is optionally introduced to the reaction in the form of a paraformaldehyde.
  12. An epoxy resin curative composition comprising an epoxy resin curative as defined in any one of Claims 1 to 8.
  13. A method for preparing a cured epoxy resin, said method comprising: a) contacting an epoxy resin with an epoxy resin curative as defined in any one of Claims 1 to 8 or a composition according to Claim 12; and b) forming a cured epoxy resin, preferably wherein the epoxy resin is selected from glycidyl amines, epoxidized novolacs and bisphenols (A or F) or halogenated analogues thereof.
  14. A cured epoxy resin prepared, or preparable, by the method of Claim 13.
  15. Use of an epoxy resin curative as defined in any one of Claims 1 to 8 or of a composition according to Claim 12, for causing crosslinking in an epoxy resin.

Description

The invention relates to a class of epoxy resin curatives which act as rapid curing epoxy resin hardeners. In particular the invention is directed to a class of epoxy resin curatives comprising a benzoic acid moiety and at least one Mannich base group, as well as a curative composition comprising the epoxy resin curative, processes for preparing the epoxy resin curative, and uses thereof. BACKGROUND OF THE INVENTION There is an array of crosslinking agents available for epoxy functional materials, but amines and products derived from amines offer the greatest versatility for curing epoxy resins. Collectively these materials offer the means of formulating systems that can provide the potential for curing in thin films and/or mass at a broad spectrum of temperatures. Polyamides and phenolic derived Mannich base curing agents have been used extensively but due to the inability of the polyamides to low temperature cure, and the regulatory and toxicity issues associated with free phenol, the scope of use and availability of these materials has substantially reduced. Many commercial curing agent formulations are based on amines such as aliphatic, cyclo-aliphatic aryl-aliphatic and to a lesser extent aromatic amines or combinations thereof. These amines are generally modified in order to enhance the processing and/or performance aspects, to improve the active hydrogen equivalent weight and combining ratio with epoxy resins or to reduce the toxicity of the amine. Mannich bases are examples of modified amines which offer enhanced properties, especially with regard to improved compatibility with epoxy resins, optimisation of cure speed and degree of cure, as well as resistance to carbamation. Commercially available Mannich bases include phenolic derived compounds that are the reaction product of an aldehyde (generally formaldehyde), a phenolic compound, or a substituted derivative thereof, and an amine. An example structure of a phenolic Mannich base is shown below: EP0779311 describes a Mannich base prepared by the Mannich reaction using (i) butyraldehyde, (ii) a phenolic compound, and (iii) a primary or a secondary polyamine. The use of butyraldehyde, rather than formaldehyde or paraformaldehyde, is reported to lower viscosity in the Mannich base products, which can be advantageous when used in epoxy curative applications. However, the molecular weight, polydispersity and residual free phenol monomer levels have led to the reduction in availability and a decline in popularity of this class of materials. The conventional Mannich base with residual free phenol carries both acute toxicity labelling and a chronic health hazard warnings. The removal of several of the Hazard statements associated with free monomeric phenol and substituted phenols, is now mandated by some organisations, e.g. REACH (Registration, Evaluation, Authorisation and restriction of Chemicals). There remains a need for alternative Mannich bases that offer high process performance, broad compatibility with epoxy resins, and avoid the toxicity and environmental issues associated with known amine-derived epoxy resin curatives. Various specialist epoxy resin hardeners and accompanying cured epoxy resin systems have been designed to mitigate chemical toxicity, such as those described in WO2022112776 and WO2021152281, as well as to mitigate environmental damage such as those described in WO2023233151. Conventional phenolic Mannich bases useful as epoxy resin curatives are limited in terms of their cure time and their peak exotherm. Epoxy resin hardeners which have longer cure times can be disadvantageous, for example in industrial processes. Long cure times will slow down production of any articles involving a cured epoxy resin. Additionally, long cure times increase the risk of contamination or defects during the curing process as the extended time increases the potential for exposure to environmental factors such as dust, moisture, or temperature fluctuations, which can compromise the quality of the final product. High peak exotherms in epoxy resin curatives can also be disadvantageous. Excessive heat generated during curing can cause thermal stress, leading to cracking or warping of the resin, which can compromise the quality of the final product. It can also increase the risk of premature curing, particularly in thicker sections, resulting in uneven or incomplete curing. Additionally, highly exothermic reactions can create safety hazards such as thermal runaway, especially on an industrial scale. The present invention relates to a hitherto unknown class of epoxy resin curatives comprising a benzoic acid moiety and at least one Mannich base group. Without being bound to a particular theory, it is believed that the benzoic acid moiety comprised within the epoxy resin curative structure provides improved performance in terms of decreased cure time and decreased peak exotherm in the systems to which it is applied. SUMMARY OF THE INVENTION In a first aspe