A recyclable epoxy resin system for electrical insulation

Abstract

A recyclable epoxy resin system for electrical insulation is provided The recyclable epoxy resin system comprises a resin component, at least recyclable curing agent and at least one filler. Said recyclable epoxy resin has a dielectric strength (t=2 mm) of more than 22 kV / mm as measured by IEC 60243 and a dry arc resistance of more than 400 seconds as measured by ASTM D 495.

Description

[0001] A RECYCLABLE EPOXY RESIN SYSTEM FOR ELECTRICAL INSULATION

[0002] FIELD OF THE INVENTION

[0003] The present disclosure relates to an epoxy resin system for electrical insulation. In particular, the present disclosure relates to a recyclable epoxy resin system for electrical insulation, having high dielectric strength and dry arc resistance.

[0004] DESCRIPTION OF THE BACKGROUND ART

[0005] The generation of electricity and its efficient transmission and distribution is essential part of the ecosystem. Electrical and electronic components are an integral part of almost all devices / machines that are being manufactured, be it, simple devices such as children’s toys, or complex devices such as smartphones and computers, or large machines such as ships or airplanes. For proper functioning of these components, it is important that they are protected. Epoxy resins, with their exceptional electrical insulating properties, thermal stability, adhesion, and resistance to environmental factors, play a critical role in safeguarding the electrical and electronic components.

[0006] Traditionally, epoxy-anhydride systems are preferred as polymeric insulating materials for industrial applications in the field of electrical casting, potting, and encapsulation to manufacture components such as insulators, bushings, transformers, switch gear components, power generators etc. The epoxy-anhydride systems are thermoset materials that cannot be recycled and hence generate electrical and electronics (e-waste) at the end of life. It is estimated that only a fraction of the waste generated is formally recycled and the remaining waste is either ending up in landfills or is being informally recycled. The waste in landfill contaminates soil and groundwater, putting food supply systems and water sources at risk. Epoxy resin compositions for electrical insulation require a combination of excellent thermo-mechanical properties, electrical insulation, voltage resistance, heat resistance, mechanical strength, and crack resistance. However, achieving a balance of all these properties simultaneously is challenging,

[0007] SUMMARY

[0008] The disclosure provides a recyclable epoxy resin system for electrical insulation comprising at least one resin component; at least one recyclable curing agent and at least one filler. The recyclable curing agent is selected from a group consisting of a compound of Formula (I):

[0009] Formula I wherein: if m is 2, then n is 2; if m is 1, then n is 3; or if m is 0, then n is 4; each R1is independently hydrogen, alkyl, cycloalkyl, heterocycle, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkoxyalkyl, or alkynyl; each A is independently alkyl, alkylene, alkenene, alkylene-hetero-alkylene, alkylene-heterocyclo-alkylene, carbonyl, thiocarbonyl, alkylene-oxy-alkylene, 1,4-alkyl substituted piperazine, aryl, or heteroaryl; each R2is independently — NHR.3, — SH, or heterocycloalkyl, wherein each R3is independently hydrogen, alkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, heterocycle, alkenyl, aryl, or heteroaryl; or, every two — O-A-R2 groups, together with the carbon atom to which they are attached to, can independently form an dioxanyl ring with no less than 4 ring members and one or more of the ring carbon atom(s), other than the carbon atom to which the two — O-A-R2 groups are attached, are independently substituted with one or more independent amino group or aminoalkyl wherein each amino is independently a primary or secondary amino group; and a compound of Formula (II):

[0010] (R5)t— Si — (- o — W— NH2)q

[0011] Formula (II) wherein: q is 4, 3, 2, or 1; t is 0, 1, 2, or 3; the sum of q and t is 4; each occurrence of W is independently alkylene, cycloalkylene, heterocyclylene, alkenylene, alkynylene, cycloalkenylene, arylene, or heteroarylene; and each occurrence of R5is independently hydrogen, alkyl, aminoalkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl, heteroaryl or — ORC, wherein Rcis alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl or heteroaryl. The recyclable epoxy resin system , has a dielectric strength (t=2 mm) of more than 22 kV / mm as measured by IEC 60243 and a dry arc resistance of more than 400 seconds as measured by ASTM D 495.

[0012] BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1, provides the comparison of change in flexural strength on thermal aging @180°C of the recyclable epoxy resin systems and non-recyclable epoxy resin system for electrical insulation in accordance with an embodiment of the disclosure and conventional system.

[0014] Figure 2, provides the comparison of change in flexural strength on thermal aging @180°C of the recyclable epoxy resin systems for electrical insulation in accordance with an embodiment of the disclosure.

[0015] Figure 3, provides the comparison of change in flexural strength on thermal aging @180°C of the recyclable epoxy resin systems for electrical insulation in accordance with embodiments of the disclosure. Figure 4, provides the comparison of change in flexural strength on thermal aging @180°C of the recyclable epoxy resin systems for electrical insulation in accordance with embodiments of the disclosure.

[0016] Figure 5, depicts the recycling and recovery process of a component (flat panel) prepared from recyclable epoxy resin system for electrical insulation in accordance with an embodiment of the disclosure.

[0017] DETAILED DESCRIPTION

[0018] For the purpose of promoting an understanding of the principles of the disclosure, reference will now be made to embodiments and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended, such alterations and further modifications in the disclosed composition and method, and such further applications of the principles of the disclosure therein being contemplated as would normally occur to one skilled in the art to which the disclosure relates.

[0019] The present disclosure relates to an epoxy resin system for electrical insulation having high. In the broadest sense the present disclosure provides a recyclable epoxy resin system for electrical insulation that comprises:

[0020] (a) at least one resin component;

[0021] (b) at least one recyclable curing agent; and

[0022] (c) at least one filler, having high dielectric strength and dry arc resistance. The recyclable epoxy resin system has a dielectric strength (t=2 mm) of more than 22 kV / mm as measured by IEC 60243 and a dry arc resistance of more than 400 seconds as measured by ASTM D 495.

[0023] In some embodiments, the recyclable epoxy resin system, has a critical stress intensity factor (K1C) of at least 1.3 MPa m1 / 2and critical strain energy release rate (G1C) of at least 550 J / m2as measured by ISO13586 method. Epoxy resin component:

[0024] In accordance with an aspect, the recyclable epoxy resin system for electrical insulation comprises of an epoxy resin component. In some embodiments, the epoxy resin component comprises at least one epoxy resin selected from a group consisting of Bisphenol A epoxy resin, Bisphenol F epoxy resin, multifunctional epoxy resin, and a combination thereof. Other known epoxy resins may also be added to the epoxy resin component.

[0025] In some embodiments, the epoxy resin component is a high purity epoxy resin. In accordance with an embodiment, the high purity epoxy resin has by-products and impurities less than 5000 ppm. Said by-products and impurities may include compounds such as hydrolysable chlorine, alpha glycol, moisture and volatile organics, the concentration of the individual impurity being not more than 1000 ppm.

[0026] Curing agent

[0027] In accordance with an aspect, the recyclable curing agent is selected from a group consisting of a compound of Formula (I) and a compound of Formula (II).

[0028] The compound of Formula (I) is represented by:

[0029] Formula (I) wherein if m is 2, then n is 2; if m is 1, then n is 3; if m is 0, then n is 4; the sum of m and n is 4; each Ri is independently hydrogen, alkyl, cylcoalkyl, heterocycle, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkoxyalkyl, or alkynyl; each A is independently alkyl, alkylene, alkenene, alkylene-hetero-alkylene, alkylene-heterocyclo-alkylene, carbonyl, thiocarbonyl, alkylene-oxy-alkylene, 1,4- alkyl substituted piperazine, aryl, or heteroaryl; each R2 is independently — NHR3, — SH, or heterocycloalkyl, wherein each R3is independently hydrogen, alkyl, aminoalkyl, alkylaminoalkyl, cylcoalkyl, heterocycle, alkenyl, aryl, or heteroaryl; or, every two — 0-A-R2 groups, together with the carbon atom to which they are attached to, can independently form an dioxanyl ring with no less than 4 ring members and one or more of the ring carbon atom(s), other than the carbon atom to which the two — 0-A-R2 groups are attached, are independently substituted with one or more independent amino group or aminoalkyl wherein each amino is independently a primary or secondary amino group.

[0030] In some embodiments, in the compound of Formula (I) m is 2, n is 2; each R1is hydrogen or alkyl; A is independently alkyl or aryl; each R2is independently — NHR3, or — SH; and each R3 is independently hydrogen or alkyl.

[0031] In some embodiments, the compound of Formula (I) is a compound of formula (III) represented by:

[0032] (Formula III) wherein R is independently hydrogen, methyl or ethyl. In an embodiment, the compound of Formula (I) is:

[0033] RC (I)

[0034] In such embodiments, where the curing agent is a compound of Formula (I), the recyclable epoxy resin system exhibits less than 55% drop in flexural strength after thermal aging @180°C for 3,000 hours when

[0035] The compound of Formula (II) is represented by:

[0036] Formula (II) wherein: q is 4, 3, 2, or 1; t is 0, 1, 2, or 3; the sum of q and t is 4; each W is independently alkylene, cycloalkylene, heterocyclylene, alkenylene, alkynylene, cycloalkenylene, arylene, or heteroarylene; and each R5is independently hydrogen, alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl, heteroaryl or — ORC, wherein Rcis alkyl cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl, or heteroaryl.

[0037] In some embodiments, in the compound of Formula (II) q is 3 or 4; t is 1 or 0; W is independently alkylene, cycloalkylene, or arylene; and R5is independently hydrogen, alkyl, or aminoalkyl. In some embodiments, the compound of Formula (II) is a compound of Formula (IV) represented by:

[0038] Formula (IV) wherein each R is independently hydrogen, methyl or ethyl.

[0039] In some embodiments, the compound of Formula (II) is:

[0040] Formula (IV)

[0041] In an embodiment, the compound of Formula (I) and the compound of Formula (II) is used as the recyclable curing agent for curing thermosetting polymers such as epoxies. The compound of Formula (I) and the compound of Formula (II) enable the degradation of the cured thermosetting polymers due to the presence of cleavable linkage. The cleavage linkage is acid labile and undergo a bond cleavage reaction at an elevated temperature or in an acidic solution resulting in dissolution of the thermosetting polymers. The cleavage linkage includes either an acetal linkage a ketal linkage, an orthoester linkage, or an orthocarbonate linkage. Fillers

[0042] The recyclable epoxy resin system for electrical insulation comprises fillers. In some embodiments, the fillers are selected from the group consisting of silica, quartz, wollastonite, alumina trihydrate and combination thereof.

[0043] Additives

[0044] The recyclable epoxy resin system for electrical insulation further comprises additives. In some embodiments, the additives include but are not limited to tougheners, anti-oxidants, UV and hindered amine light stabilizers, pigments, air release agents, defoamers, and wetting agents. These additives improve processability or specific performance properties of recyclable epoxy resin system for electrical insulation.

[0045] Other components

[0046] In some embodiments, recyclable epoxy resin system for electrical insulation further comprises of diluents selected from a group consisting of mono-di-tri functional aliphatic, aromatic reactive diluents and non-reactive diluents. The diluents may be added to the epoxy resin component, the recyclable curing agent or as a separate component. In some embodiments, the diluents may form a part of the epoxy resin component. In one embodiment, the epoxy resin component comprises of high purity epoxy resin and reactive diluents.

[0047] Examples of the diluents include but are not limited to 1,4 butane diol diglycidyl ether, C12-C14 alkyl glycidyl ether, 1,6-hexanediol diglycidyl ether, cresyl glycidyl ether, trimethylolpropane triglycidyl ether and a combination thereof. In accordance with another embodiment the diluents may comprise of a high purity epoxidized reactive diluent. The high purity epoxidized reactive diluent possesses impurities less than 5000 ppm. Examples of the high purity epoxidized reactive diluents include but are not limited to a high purity 1-4 butane diol diglycidyl ether, a high purity 1-6 hexanediol diglycidyl ether, a high purity cresyl glycidyl ether, a high purity trimethylolpropane triglycidyl ether and a combination thereof.

[0048] In some embodiments, the ratio of epoxy resin component to recyclable curing agent in the recyclable epoxy resin system for electrical insulation is in a range of 100:20 to 100:55 by weight. In some embodiments, the amount of additives added to the recyclable epoxy resin system for electrical insulation is in a range of 0.005 to 2.0 wt. % of the epoxy resin component. In some embodiments, the amount of fillers added to the recyclable epoxy resin system for electrical insulation is in a range of 50% to 70 wt. % of the epoxy resin component. In some embodiments, the other components are added to the recyclable epoxy resin system for electrical insulation in a range of 0.005 to 5 wt.% of the epoxy resin component.

[0049] The invention will now be described with respect to the following examples which do not limit the disclosed composition / method in any way and only exemplify the claimed composition / method. It will be apparent to those skilled in the art that various modifications and variations can be made to the composition / method / process of the present disclosure without departing from the scope of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the method / process disclosed herein. It is intended that the specification and examples be considered as exemplary only.

[0050] EXAMPLES

[0051] Example 1: Preparation of the recyclable epoxy resin system for electrical insulation in accordance with an exemplary embodiment.

[0052] Recyclable epoxy resin systems for electrical insulation 1 to 4 were prepared using the components provided in the Table 1 below. The epoxy resin and curing agent components of recyclable epoxy resin systems when mixed in stoichiometric ratios (as provided in Table 1) along-with the fillers constitutes as casting systems that are further characterized for process, mechanical and electrical insulation properties. Table 2 provides the details of the components. Table 3 provides the process, mechanical, electrical insulation properties of the recyclable epoxy resin systems.

[0053] Table 1: Examples of Recyclable Epoxy Resin Systems

[0054] Table 2: Details of the components

[0055] Table 3: Process, Mechanical, Electrical Insulation Properties of the

[0056] Recyclable Epoxy Resin Systems

[0057] The suitability of the recyclable epoxy resin system for electrical casting and insulation application was confirmed by conducting accelerated thermal aging test at 180°C and determining the change in flexural strength with time at different time 5 duration. Comparison was made with standard or conventional non-recyclable thermal class H system (comparative example) based on epoxy-anhydride chemistry. Table 4 provides a comparison of change in flexural strength on thermal aging of the recyclable epoxy resin systems. Figure 1, provides the comparison of change in flexural strength on thermal aging @180°C of the recyclable epoxy resin 0 systems and non-recyclable epoxy resin system (comparative example) for electrical insulation. Table 4: Comparison of change in flexural strength on thermal aging of the recyclable epoxy resin systems

[0058] Example 2: Preparation of the recyclable epoxy resin system for electrical insulation in accordance with an exemplary embodiment.

[0059] Recyclable epoxy resin systems 5, 6 and 7 was prepared using the components provided in the Table 5 below and compared with recyclable epoxy resin system 1 of example 1. The details of the components are provided in Table 6 below. Table 5: Examples of Recyclable Epoxy Resin Systems

[0060] Table 6: Details of the components The epoxy resin component and curing agent component of recyclable epoxy resin systems are mixed in stoichiometric ratios as provided in Table 5. The prepared epoxy resin systems are further characterized for process, mechanical and electrical insulation properties. Table 7 provides the process, mechanical, electrical insulation properties of the recyclable epoxy resin systems. Table 7: Process, Mechanical, Electrical Insulation Properties of Recyclable Epoxy Resin Systems Accelerated thermal aging test at 180°C was carried out to determine the change in flexural strength with time at different time duration. Comparison between recyclable system 5 (without additive and recyclable epoxy resin systems 1, 6 and 7 with additives was done. Table 8 provides the thermal aging of the recyclable epoxy resin systems. Figure 2, provides the comparison of change in flexural strength on thermal aging @180°C.

[0061] Table 8: Comparison of Change in Flexural Strength on Thermal Aging of the Recyclable Epoxy Resin Systems

[0062] Example 3: Preparation of the recyclable epoxy resin system for electrical insulation in accordance with an exemplary embodiment. Recyclable epoxy resin systems 8, 9, and 11 were prepared using the components provided in the Table 9 below and compared with recyclable epoxy resin system 1 of example 1. The details of the components are provided in Table 10 below.

[0063] Table 9: Examples of Recyclable Epoxy Resin Systems Table 10: Details of the components

[0064] The epoxy resin component and curing agent component of recyclable epoxy resin systems are mixed in stoichiometric ratios as provided in Table 9. The prepared 5 epoxy resin systems are further characterized for process, mechanical and electrical insulation properties. Table 11 provides the process, mechanical, electrical insulation properties of the recyclable epoxy resin systems.

[0065] Table 11: Process, Mechanical, Electrical Insulation Properties of Recyclable

[0066] 10 Epoxy Resin Systems

[0067] Accelerated thermal aging test at 180°C was carried out to determine the change in flexural strength with time at different time duration. Table 12 provides the thermal aging of the recyclable epoxy resin systems. Figure 3, provides the comparison of

[0068] 5 change in flexural strength on thermal aging @180°C.

[0069] Table 12: Comparison of Change in Flexural Strength on Thermal

[0070] Aging of the Recyclable Epoxy Resin Systems

[0071] Example 4: Preparation of the recyclable epoxy resin system for electrical insulation in accordance with an exemplary embodiment. Recyclable epoxy resin systems 12, 13 and 14 were prepared using the components provided in the Table 12 below and compared with recyclable epoxy resin system 1 of example 1. The details of the components are provided in Table 13 below.

[0072] Table 13: Examples of Recyclable Epoxy Resin Systems

[0073] Table 14: Details of the components The epoxy resin component and curing agent component of recyclable epoxy resin systems are mixed in stoichiometric ratios as provided in Table 13. The prepared epoxy resin systems are further characterized for process, mechanical and electrical insulation properties. Table 15 provides the process, mechanical, electrical insulation properties of the recyclable epoxy resin systems. Table 15: Process, Mechanical, Electrical Insulation Properties of Recyclable Epoxy Resin Systems

[0074] Accelerated thermal aging test at 180°C was carried out to determine the change in flexural strength with time at different time duration. Table 16 provides the thermal aging of the recyclable epoxy resin systems. Figure 4, provides the comparison of

[0075] 5 change in flexural strength on thermal aging @180°C.

[0076] Table 16: Comparison of Change in Flexural Strength on Thermal

[0077] Aging of the Recyclable Epoxy Resin Systems

[0078] Specific Embodiments:

[0079] Specific embodiments are disclosed hereinafter. A recyclable epoxy resin system for electrical insulation comprising:

[0080] (a) a resin component;

[0081] (b) at least one recyclable curing agent wherein the recyclable curing agent is selected from a group consisting of a compound of Formula (I):

[0082] Formula I wherein: if m is 2, then n is 2; if m is 1, then n is 3; or if m is 0, then n is 4; each R1 is independently hydrogen, alkyl, cycloalkyl, heterocycle, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkoxyalkyl, or alkynyl; each A is independently alkyl, alkylene, alkenene, alkylene-hetero-alkylene, alkylene-heterocyclo-alkylene, carbonyl, thiocarbonyl, alkylene-oxy-alkylene, 1,4-alkyl substituted piperazine, aryl, or heteroaryl; each R2 is independently — NHR3, — SH, or heterocycloalkyl, wherein each R3 is independently hydrogen, alkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, heterocycle, alkenyl, aryl, or heteroaryl; or, every two — 0-A-R2 groups, together with the carbon atom to which they are attached to, can independently form an dioxanyl ring with no less than 4 ring members and one or more of the ring carbon atom(s), other than the carbon atom to which the two — O-A-R2 groups are attached, are independently substituted with one or more independent amino group or aminoalkyl wherein each amino is independently a primary or secondary amino group; and a compound of Formula (II):

[0083] Formula (II) wherein: q is 4, 3, 2, or 1; t is 0, 1, 2, or 3; the sum of q and t is 4; each occurrence of W is independently alkylene, cycloalkylene, heterocyclylene, alkenylene, alkynylene, cycloalkenylene, arylene, or heteroarylene; and each occurrence of R5is independently hydrogen, alkyl, aminoalkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl, heteroaryl or — ORC, wherein Rcis alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl or heteroaryl; and

[0084] (c) at least one filler wherein the recyclable epoxy resin system, has a dielectric strength (t=2 mm) of more than 22 kV / mm as measured by IEC 60243 and a dry arc resistance of more than 400 seconds as measured by ASTM D 495.

[0085] Such recyclable epoxy resin system(s), wherein the recyclable epoxy resin system, has a critical stress intensity factor (K1C) of at least 1.3 MPa m1 / 2and critical strain energy release rate (G1C) of at least 550 J / m2as measured by ISO13586 method.

[0086] Such recyclable epoxy resin system(s), wherein the compound of Formula (I) m is 2, n is 2; each R1is independently hydrogen or alkyl; each A is independently alkyl, or aryl; each R2is independently — NHR3, or — SH; and each R3is independently hydrogen or alkyl.

[0087] Such recyclable epoxy resin system(s), wherein the compound of Formula (II) q is 3 or 4; t is 1 or 0; W is independently alkylene, cycloalkylene, or arylene; and each occurrence of R5 is independently hydrogen, alkyl, or aminoalkyl.

[0088] Such recyclable epoxy resin system(s), wherein the compound of Formula (I) is a compound of Formula (III) represented by:

[0089] Formula (III) wherein each R is independently hydrogen, methyl or ethyl. Such recyclable epoxy resin system(s), wherein the compound of Formula (II) is a compound of Formula (IV) represented by:

[0090] Formula (IV) wherein each R is independently hydrogen, methyl or ethyl.

[0091] Such recyclable epoxy resin system(s), wherein the compound of Formula (II) is a compound of Formula (V)

[0092] Formula (V)

[0093] Such recyclable epoxy resin system(s), wherein the epoxy resin component comprises at least one epoxy resin selected from a group consisting of Bisphenol A epoxy resin, and Bisphenol F epoxy resin, and a combination thereof

[0094] Such recyclable epoxy resin system(s), wherein the epoxy resin component comprises high purity epoxy resin with by-products and impurities less than 5000 ppm; and a reactive diluent. Such recyclable epoxy resin system(s), wherein the epoxy resin is a multifunctional epoxy resin.

[0095] Such recyclable epoxy resin system(s), wherein the filler is selected from a group consisting of silica, quartz, wollastonite, alumina trihydrate and combination thereof.

[0096] Such recyclable epoxy resin system(s), wherein the ratio of epoxy resin component to recyclable curing agent is in a range of 100:20 to 100:55 by weight.

[0097] Such recyclable epoxy resin system(s), wherein the fillers are in a range of 50% to 70 wt. % of the epoxy resin component.

[0098] Such recyclable epoxy resin system(s), wherein the recyclable epoxy resin system further includes an additive selected from a group comprising of tougheners, antioxidants, UV and hindered amine light stabilizers, pigments, air release agents, defoamers, and wetting agents.

[0099] Such recyclable epoxy resin system(s), the additives added are in a range of 0.005 to 2.0 wt. % of the epoxy resin component.

[0100] Such recyclable epoxy resin system(s), wherein the recyclable epoxy resin system exhibits less than 55% drop in flexural strength after thermal aging @180°C for 3,000 hours when the curing agent is a compound of Formula (I).

[0101] Industrial applicability

[0102] The recyclable epoxy resin system as disclosed is intended for manufacturing of electrical and electronics insulation components by casting, potting and encapsulation processes. The electrical components prepared from said epoxy resin systems exhibit exceptional mechanical, thermal and electrical insulation properties. Importantly, the electrical components such as transformers, bushings, insulators etc., that are prepared from said recyclable epoxy resin system can be recycled to recover the metal and non-metallic parts, fillers and epoxy matrix as a thermoplastic. The recovered materials can be re-used and re-purposed thereby addressing the global concern on management of e-waste at the end-of-life and driving circularity.

[0103] Moreover, the recyclable systems exhibit superior thermal oxidative stability, retaining flexural strength even after thermal aging. Notably, recyclable systems specifically based on ketal amines demonstrate lower thermal oxidative degradation compared to anhydride systems, resulting in better durability. Additionally, these systems showcase exceptional electrical insulation properties, with higher arc resistance and dielectric strength compared to anhydride systems, making them ideal for applications requiring reliable performance and stability. Moreover, the recyclable epoxy resin system for electrical insulation provides REACH compliant alternative that overcomes the challenges posed by SVHC listing of anhydrides by ECHA.

Claims

We Claim:

1. A recyclable epoxy resin system for electrical insulation comprising:(a) a resin component;(b) at least one recyclable curing agent wherein the recyclable curing agent is selected from a group consisting of a compound of Formula (I):Formula I wherein: if m is 2, then n is 2; if m is 1, then n is 3; or if m is 0, then n is 4; each R1is independently hydrogen, alkyl, cycloalkyl, heterocycle, heterocycloalkyl, alkenyl, cycloalkenyl, aryl, heteroaryl, alkoxyalkyl, or alkynyl; each A is independently alkyl, alkylene, alkenene, alkylene-hetero- alkylene, alkylene-heterocyclo-alkylene, carbonyl, thiocarbonyl, alkylene-oxy-alkylene, 1,4-alkyl substituted piperazine, aryl, or heteroaryl; each R2is independently — NHR3, — SH, or heterocycloalkyl, wherein each R3is independently hydrogen, alkyl, aminoalkyl, alkylaminoalkyl, cycloalkyl, heterocycle, alkenyl, aryl, or heteroaryl; or, every two — O- A-R2 groups, together with the carbon atom to which they are attached to, can independently form an dioxanyl ring with no less than 4 ring members and one or more of the ring carbon atom(s), other than the carbon atom to which the two — O-A-R2 groups are attached, are independently substituted with one or more independent amino group or aminoalkyl wherein each amino is independently a primary or secondary amino group; anda compound of Formula (II):<R5)t — Si — (- O — W — NH2)qFormula (II) wherein: q is 4, 3, 2, or 1; t is 0, 1, 2, or 3; the sum of q and t is 4; each occurrence of W is independently alkylene, cycloalkylene, heterocyclylene, alkenylene, alkynylene, cycloalkenylene, arylene, or heteroarylene; and each occurrence of R5 is independently hydrogen, alkyl, aminoalkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl, heteroaryl or — ORc, wherein Rc is alkyl, cycloalkyl, heterocyclyl, alkenyl, alkynyl, cycloalkenyl, aryl or heteroaryl; and(c) at least one filler wherein the recyclable epoxy resin system, has a dielectric strength (t=2 mm) of more than 22 kV / mm as measured by IEC 60243 and a dry arc resistance of more than 400 seconds as measured by ASTM D 495.

2. The recyclable epoxy resin system as claimed in claim 1, wherein the recyclable epoxy resin system, has a critical stress intensity factor (K1C) of at least 1.3 MPa m1 / 2and critical strain energy release rate (G1C) of at least 550 J / m2as measured by ISO13586 method.

3. The recyclable epoxy resin system as claimed in claim 1, wherein the compound of Formula (I) m is 2, n is 2; each R1is independently hydrogen or alkyl; each A is independently alkyl, or aryl; each R2is independently — NHR3, or — SH; and each R3is independently hydrogen or alkyl.

4. The recyclable epoxy resin system as claimed in claim 1, wherein the compound of Formula (II) q is 3 or 4; t is 1 or 0; W is independently alkylene, cycloalkylene, or arylene; and each occurrence of R5 is independently hydrogen, alkyl, or aminoalkyl.

5. The recyclable epoxy resin system as claimed in claim 1, wherein the compound of Formula (I) is a compound of Formula (III) represented by:Formula (III) wherein each R is independently hydrogen, methyl or ethyl.

6. The recyclable epoxy resin system as claimed in claim 1, wherein the compound of Formula (II) is a compound of Formula (IV) represented by:Formula (IV) wherein each R is independently hydrogen, methyl or ethyl.

7. The recyclable epoxy resin system as claimed in claim 1, wherein the compound of Formula (II) is a compound of Formula (V)Formula (V)8. The recyclable epoxy resin system as claimed in claim 1, wherein the epoxy resin component comprises at least one epoxy resin selected from a group consisting of Bisphenol A epoxy resin, and Bisphenol F epoxy resin, and a combination thereof9. The recyclable epoxy resin system as claimed in claim 1, wherein the epoxy resin component comprises high purity epoxy resin with by-products and impurities less than 5000 ppm; and a reactive diluent.

10. The recyclable epoxy resin system as claimed in claim 1, wherein the epoxy resin is a multifunctional epoxy resin.

11. The recyclable epoxy resin system as claimed in claim 1, wherein the filler is selected from a group consisting of silica, quartz, wollastonite, alumina trihydrate and combination thereof.

12. The recyclable epoxy resin system as claimed in claim 1, wherein the ratio of epoxy resin component to recyclable curing agent is in a range of 100:20 to 100:55 by weight.

13. The recyclable epoxy resin system as claimed in claim 1, wherein the fillers are in a range of 50% to 70 wt. % of the epoxy resin component.

14. The recyclable epoxy resin system as claimed in claim 1, wherein the recyclable epoxy resin system further includes an additive selected from a group comprising of tougheners, anti-oxidants, UV and hindered amine light stabilizers, pigments, air release agents, defoamers, and wetting agents.

15. The recyclable epoxy resin system as claimed in claim 14, the additives added are in a range of 0.005 to 2.0 wt. % of the epoxy resin component.

6. The recyclable epoxy resin system as claimed in claim 1, wherein the recyclable epoxy resin system exhibits less than 55% drop in flexural strength after thermal aging @180°C for 3,000 hours when the curing agent is a compound of Formula (I).

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