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CN-121991321-A - N-hydroxyethyl piperidine (NHEP) as new curing agent for epoxy systems

CN121991321ACN 121991321 ACN121991321 ACN 121991321ACN-121991321-A

Abstract

The invention relates to an amine-based curing agent comprising at least 1% by weight of at least one tertiary amine, and optionally primary and/or secondary amines. The tertiary amine is preferably an N-substituted piperidine tertiary amine, and more preferably N-hydroxyethyl piperidine (NHEP). The invention also relates to epoxy resin compositions formed using such amine-based curing agents and to methods of preparing the epoxy resin compositions. These tertiary amines enhance the desired properties of the epoxy resin composition without the negative impact on mechanical properties in the cured product that is typically seen with tertiary amine-based curing agents.

Inventors

  • P.G. PATEL
  • G.S. Lai
  • D.M. Lakemal

Assignees

  • 赢创运营有限公司

Dates

Publication Date
20260508
Application Date
20170807
Priority Date
20161221

Claims (20)

  1. 1. A method of preparing a cured epoxy resin composition, the method comprising: (a) Combining an epoxy resin component with an amine-based curative component to form an initial epoxy resin composition, the amine-based curative component comprising at least a first amine component represented by the structure: , Wherein A is CH 2 , O or NR ', R' is H or an alkyl group of 1 to 10 carbon atoms, R is an alkyl group having 1 to 10 carbon atoms and optionally one or more heteroatoms, and the first amine component comprises at least 1% by weight of the amine-based curing agent, and (B) Allowing a chemical reaction between the at least one amine component and the epoxy resin component to occur to form a cured epoxy resin composition.
  2. 2. The method of claim 1, wherein the first amine component comprises at least one N-substituted piperidine tertiary amine.
  3. 3. The method of claim 2, wherein the first amine component comprises N-hydroxyethyl piperidine.
  4. 4. The method of claim 1, wherein the amine-based curative component further comprises a second amine component having at least one amine compound selected from the group consisting of primary and secondary amines.
  5. 5. The method of claim 1, the method further comprising: (c) Performing steps (a) and (b) at a first ambient temperature, and (D) Maintaining a maximum internal temperature of the initial epoxy resin composition during steps (a) and (b) that is no more than 50 ℃ above the first ambient temperature.
  6. 6. The method of claim 5, wherein step (a) further comprises combining an epoxy resin component with an amine-based curative component to form an initial epoxy resin composition having a first viscosity of at least 50 cps, and step (b) further comprises forming a cured epoxy resin composition having a T g of at least 70 ℃.
  7. 7. The method of claim 1, the method further comprising: (c) Applying the initial epoxy resin composition to a reinforcing fiber substrate after step (a) is performed.
  8. 8. A composition comprising the reaction product of an epoxy resin component and a curing agent component, Wherein the curative component comprises: a first amine component represented by the structure: Wherein A is CH 2 , O or NR ', R' is H or an alkyl group of 1 to 10 carbon atoms, and R is an alkyl group having 1 to 10 carbon atoms and optionally one or more heteroatoms, and Wherein the first amine component comprises at least 1% by weight of the curing agent.
  9. 9. The composition of claim 8, wherein the first amine component comprises an N-substituted piperidine tertiary amine.
  10. 10. The composition of claim 8 wherein R is CH 2 CH 2 OH.
  11. 11. The composition of claim 8, wherein the first amine component comprises N-hydroxyethyl piperidine.
  12. 12. The composition of claim 8, wherein the curative component further comprises a second amine component having at least one amine compound selected from the group consisting of primary and secondary amines.
  13. 13. The composition of claim 12, further comprising a stoichiometric ratio of the second amine component to the epoxy resin component, wherein the stoichiometric ratio is less than 1.
  14. 14. The composition of claim 8, wherein the epoxy resin component comprises from about 30% to about 99% by weight of the composition.
  15. 15. The composition of claim 8, wherein the epoxy resin component comprises a glycidyl ether of a polyhydric phenol.
  16. 16. The composition of claim 8 wherein the epoxy resin composition comprises at least one glycidyl ether selected from the group consisting of resorcinol, hydroquinone, bis- (4-hydroxy-3, 5-difluorophenyl) -methane, 1-bis- (4-hydroxyphenyl) -ethane, 2-bis- (4-hydroxy-3-methylphenyl) -propane, 2-bis- (4-hydroxy-3, 5-dichlorophenyl) propane, 2-bis- (4-hydroxyphenyl) -propane, bis- (4-hydroxyphenyl) -methane, novolac resins, and combinations thereof.
  17. 17. The composition of claim 8 wherein the epoxy resin component comprises at least one dihydric phenol of the structure: Wherein m is 0to 25, and R is a divalent hydrocarbon group.
  18. 18. The composition of claim 8 wherein the epoxy resin component comprises at least one member selected from the group consisting of bis (3, 4-epoxycyclohexylmethyl) oxalate, bis (3, 4-epoxycyclohexylmethyl) adipate, bis (3, 4-epoxy-6-methylcyclohexylmethyl) adipate, vinylcyclohexene diepoxide; alkylene diepoxides, bis (3, 4-epoxycyclohexylmethyl) pimelate, dicyclopentadiene diepoxide, 3-epoxycyclohexylmethyl 3, 4-epoxycyclohexane carboxylate, for example 3, 4-epoxycyclohexylmethyl 3, 4-epoxycyclohexane carboxylate, 3, 4-epoxy-1-methylcyclohexane carboxylate, 3-epoxy-1-methylcyclohexyl-methyl 3, 4-epoxycyclohexane carboxylate, 6-methyl-3, 4-epoxycyclohexylmethyl 3, 4-epoxy-3-methylcyclohexane carboxylate, 3, 4-epoxy-2-methylcyclohexyl-methyl 3, 4-epoxycyclohexane carboxylate, and combinations thereof.
  19. 19. The composition of claim 8, wherein R comprises one or more heteroatoms, and the one or more heteroatoms each comprise O, N or S.
  20. 20. The composition of claim 12, wherein the second amine comprises at least one member selected from the group consisting of poly (propylene glycol) bis (2-aminopropyl ether), aminopropyl cyclohexane, diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), hexamethylenediamine (HMDA), N- (2-aminoethyl) -1, 3-propanediamine (N 3 -amine), N '-1, 2-ethanediylbis-1, 3-propanediamine (N 4 -amine) or dipropylenetriamine, arylaliphatic polyamines such as m-xylene diamine (mXDA) or p-xylene diamine, cycloaliphatic polyamines such as 1, 3-diaminocyclohexane (1, 3-BAC), isophorone diamine (IPDA) or 4,4' -methylenedicyclohexylamine (PACM), 4 '-methylenebis (2-methylcyclocyclohexane), aromatic polyamines such as m-phenylenediamine, diaminodiphenyl sulfone (DDM) or diaminodiphenyl sulfone (N, N' -1, 3-ethanediyl-bis-1, 3-propanediamine) or p-xylylenediamine (3, 3-diaminocyclohexane) wherein the 5-oxo-5-2-biphenylene-oxa-amine (1, 3-oxo-N-butylene-1, 3-oxa) is a copolymer of the amino groups of which is 1, 3-bis (N-2-propyleneamine) or 5-oxo-N-oxa-bis (1, 5-methyl amine, such as 4, 7-dioxadecane-1, 10-diamine, 1-propylamine, 3'- (oxybis (2, 1-ethanediyloxy)) bis (diaminopropylated diethylene glycol ANCAMINE 1922A), poly (oxy (methyl-1, 2-ethanediyl)), α - (2-aminomethylethyl) ω - (2-aminomethylethoxy), triethylene glycol diamine and oligomers, poly (oxy (methyl-1, 2-ethanediyl)), α, α' - (oxybis-2, 1-ethanediyl) bis (ω - (aminomethylethoxy)), bis (3-aminopropyl) polytetrahydrofuran 350, bis (3-aminopropyl) polytetrahydrofuran 750, poly (oxy (methyl-1, 2-ethanediyl)), a-hydrogen-w- (2-aminomethylethoxy) ether and 2-ethyl-2- (hydroxymethyl) -1, 3-propanediol (3:1), and diaminopropyl dipropylene glycol.

Description

N-hydroxyethyl piperidine (NHEP) as new curing agent for epoxy systems The divisional application is based on China patent application with the application number 201780084173.8, the application date 2017, 8 and 7, and the name of N-hydroxyethyl piperidine (NHEP) which is a new curing agent for epoxy systems. Background Amines are commonly used as epoxy curatives for thermally cured structural composites and adhesive applications. The class of amines used as curing agents is critical to achieving the final properties of the cured product. To achieve complete curing, each of the amine groups (primary, secondary or tertiary) is cured at a specific temperature. The curing temperature determines the end use temperature, which is indicated by its T g. Generally, epoxy resins are cured primarily with primary and secondary amines. Tertiary amines are typically used in combination with primary and secondary amines as co-curing agents or catalysts. Tertiary amines are known to cause homopolymerization of the epoxy during curing, which results in lower mechanical properties due to embrittlement. Tertiary amines, such as Benzyl Dimethylamine (BDMA), 2,4, 6-tris- (dimethylaminomethyl) phenol (Ancamine K-54) and mono-dimethylaminomethyl phenol (a1110°), are unsuitable for use as primary curing agents for curing epoxy because they cause homopolymerization, which results in lower mechanical properties due to embrittlement and high exotherm during curing. Epoxy resin systems are used to produce a variety of structural components, including composites and adhesives. Examples of articles being evaluated for manufacture from epoxy resin systems include composite tubes, pressure vessels, automotive parts, and windmill blades. Manufacturing such components involves many requirements for efficient manufacturing, especially when complex manufacturing processes are used. Such processes include, but are not limited to, resin infusion (infusion), resin transfer molding, filament winding, and bulk casting. One requirement in this field is for reduced exothermic release during curing of the epoxy resin system of the article (composite) in the thicker parts of the article, since in such parts the exothermic release during curing cannot be easily conducted away from the article. If excessive temperatures are reached during the curing process, thermal degradation of the cured resin in "hot spots" may occur, resulting in loss of mechanical properties in the manufactured part. In addition, during curing, the composite part may undergo thermal shrinkage. The thermal shrinkage of the cured epoxy resin results in stress build-up in the composite during cooling down from the highest temperature reached during or after gelation. The stress sometimes causes interlayer cracking in the article, resulting in a loss of mechanical properties. The higher the temperature reached during curing after the gel point, the greater the amount of stress that will build up in the article during cooling. Standard epoxy systems used to make structural parts are cured with stoichiometric amounts of aliphatic amines (typically primary amines). The systems generally have a high cure exotherm temperature wherein the center of a 100 gram mass of resin/curing agent mixture (contained within a3 inch diameter cylinder) often reaches a peak temperature of 250 ℃ or higher when cured in a 70 ℃ oven. Alternatively, epoxy systems cured with anhydride-based curing agents can often have lower exothermic release of curing than those cured with primary amines. However, anhydride cured systems typically require higher mold temperatures than systems cured with primary aliphatic amines to achieve acceptable levels of cure and cured performance. Other requirements in the art include the absence of highly volatile components in the system used for elevated temperature curing. Emissions of volatile compounds during processing cause undesirable environmental, health and safety concerns. Systems for composite processing require an initial mix viscosity that is sufficiently low (and a rate of viscosity increase at the impregnation temperature that is sufficiently low) so that the reinforcing fiber preform can be completely wetted with resin before the resin system becomes too viscous to satisfactorily flow through the fibers and fabrics of the substrate. As composite part sizes increase, the requirements for low initial viscosity and long pot life become more stringent. In view of the foregoing, there is a need in the art for improved curing agents for preparing epoxy resin systems having a combination of reduced exothermic release and desirable cured mechanical properties when compared to prior art resin compositions. Such curing agents must be free of undesirable features such as volatile emissions. Disclosure of Invention Summary of The Invention It has been found that N-substituted piperidine tertiary amines, preferably N-hydroxyethyl piperidine (NHEP), can be used as the primary curi