FIELD OF INVENTION

The present disclosure relates to an epoxy-based material. Specifically, the present disclosure relates to an epoxy-based phase change material. More specifically, the present disclosure relates to an epoxy resin modified with an organic compound having two or more terminal hydroxyl groups. Further, the present disclosure relates to a process for making the epoxy-based phase change material. The present disclosure also relates to an epoxy-based phase change composition comprising an epoxy-based phase change material, a solvent and a filler.

BACKGROUND AND PRIOR ART

A phase change material (PCM) is a substance which releases or absorbs sufficient energy at phase transition to provide useful heat/cooling. When substances change phase, thermal energy is absorbed and released (known as latent heat). Many materials have the ability to absorb a large quantity of heat energy during the phase transition. At different temperatures, different materials melt and solidify, and they may absorb varying amounts of heat energy. PCMs can be used to control the temperature in a wide range of applications since they melt and solidify at precise, specified temperatures. Amongst various applications, PCM is also utilized widely in automobile applications. PCMs are being researched in relation to potting applications.

Thermal energy can be stored in a material as sensible heat, latent heat and thermochemical energy etc., and may be a combination of more than one. Latent heat storage is considered the most convenient and efficient method for this purpose. PCMs have the further advantages of high heat-storage ability, thermal stability and easily controlled phase-change processes. A large number of organic, inorganic, polymeric, and eutectic PCMs have been designed owing to increasing interest in these materials, combined with understanding of their potential.

Patent literature US 7,488,773 B2 discloses silicone rubber materials containing finely divided phase change materials such as crystalline alkyl hydrocarbons or salt hydrates. The phase change material provides a thermo-regulating system which enhances the thermal performance of silicone rubber materials substantially. Patent literature US005755987A describes a phase change material comprising a dibasic ester. Patent literature WO2021035649A1 discloses a resin type phase change energy storage material comprising resin, phase change powder and curing agent.

Patent literature CN107541027B discloses a phase-change energy storage material prepared from polymer matrix material, phase change material, porous filler and heat conducting filler. The phase change material used is paraffin wax. It is to be noted that paraffin wax as a phase change material has low temperature stability or lower operation temperature.

Patent literature CA2720844A1 discloses a curable epoxy-based composition comprising an epoxy resin, a hardener, and an endothermic transition additive (PCM). The endothermic transition additive (PCM) discloses are such as an organic polymer, including thermoplastic materials or inorganic materials including sodium thiosulfate pentahydrate, sodium acetate trihydrate, sodium sulfate decahydrate, barium hydroxide hydrate, nickel nitrate tetrahydrate, zinc nitrate hexahydrate, blends thereof, alloys thereof, and eutectic mixtures thereof.

However, it is still desired to obtain a phase change material which allows improvement in performance of electronic components, safety and has ability to reduce and even eliminate the potential for thermal runaway or propagation in electronic devices. It is still desired to obtain a phase change material which is suitable for a broad range of applications. The present disclosure addresses above by providing an epoxy -based phase change material, composition and a method of preparing the same.

Accordingly, the present disclosure provides an epoxy-based phase change material and a method of preparing the same. The present disclosure also relates to an epoxy-based phase change composition comprising an epoxy-based phase change material. The present disclosure also provides products based on epoxy-based phase change material which demonstrates phase change temperature of -40-55 °C.

SUMMARY OF THE INVENTION

The present disclosure relates to a solid to semisolid (and reverse) epoxy-based phase change material comprising a reaction product of an epoxy resin, an organic compound having two or more terminal hydroxyl groups, and a coupling agent, wherein the epoxy-based phase change material is represented by the following formula (1): wherein ‘A’ represents the backbone of the epoxy resin, ‘B’ represents backbone of an organic compound, and ‘n’ represents an integer having value 1 to 12. An epoxy equivalent weight (EEW) of the epoxy-based phase change material is the range of 300 - 400.

The epoxy-based phase change material improves performance of electronic components, safety and has ability to reduce and even eliminate the potential for thermal runaway or propagation in electronic devices. Further, the present disclosure relates to a process for making the epoxy-based phase change material.

The present disclosure also relates to an epoxy-based phase change composition comprising an epoxy-based phase change material. The epoxy-based phase change composition is prepared by mixing an epoxy-based phase change material, a solvent and a filler.

DETAILED DESCRIPTION

While the invention is susceptible to various modifications and alternative forms, specific aspect thereof has been shown by way of example and will be described in detail below. It should be understood, however that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention.

The Applicants would like to mention that the examples are mentioned to show only those specific details that are pertinent to understanding the aspects of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

The terms “comprises”, “comprising”, or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a composition or process that comprises a list of components does not include only those components but may include other components not expressly listed or inherent to such process. In other words, one or more elements in a composition, system or process proceeded by “comprises... a” does not, without more constraints, preclude the existence of other elements or additional elements in the system or process. Accordingly, one aspect of the present disclosure relates to an epoxy-based phase change material comprising a reaction product of:

An epoxy resin;

An organic compound having two or more terminal hydroxyl groups;

A coupling agent; wherein the epoxy -based phase change material is represented by the following formula (1): wherein ‘A’ represents the backbone of the epoxy resin, wherein ‘B’ represents backbone of an organic compound having two or more terminal hydroxyl groups, and wherein ‘n’ represents an integer having value 1 to 12, and wherein the organic compound is an aromatic organic compound having two or more terminal hydroxyl groups or a combination of an aromatic and non-aromatic organic compound having two or more terminal hydroxyl groups.

In one of the embodiments, the ratio of epoxy resin to organic compound is in the range of 7:1 - 10:1.5, preferably in the range of 7.5: 1.1 - 8.5 :1.2.

In one of the embodiments, the epoxy equivalent weight (EEW) of the epoxy based phase change material is the range of 300 - 400.

In yet another aspect of the present disclosure the EEW is measured by a titration method involving following steps:

(i) Weighing sample 0.3 to 0.4 gm in conical flask.

(ii) Adding in step 1, 10 ml of 1,4 dioxane and 10 ml chlorobenzene in conical flask and stir until the sample is dissolved completely.

(iii) Adding in step 2, 10 ml of TEAB solution and stir.

(iv) Adding in step 3, 2-3 drops of crystal violet indicator and stir well.

(v) Titrate the achieved solution against 0.1 N std perchloric acid solution. (vi) End point: appearance of crystal violet to green color.

EEW calculation formula = wt of sample xlOOO/Burette reading xNormality of HCIO4 g/eq

In one of the embodiments, the phase change temperature is between 40 to 55 °C.

In yet another aspect of the present disclosure, the phase change temperature is measured by following methods.

The PCM material is placed in a petri dish and is gradually heated inside an oven at a temperature in the range of 25° C to 60° C and recording the temperature wherein the phase transition occurs.

The PCM temperature can also be measured by putting PCM material in the flask equipped with thermometer and then gradually heating it and then recording the temperature wherein the phase transition occurs.

The epoxy oligomers or polymers suitable for the compositions of the present disclosure include those derived from Bisphenol-A, hydrogenated Bisphenol-A, Bisphenol-F, Bisphenol-S, novolac epoxies, phenol novolac epoxies, cresol novolac epoxies, N-glycidyl epoxies, glyoxal epoxies dicyclopentadiene phenolic epoxies, silicone-modified epoxies, and epsilon- caprolactone modified epoxies. Combinations of different halogenated epoxy oligomers can also be used.

In one of the preferable embodiments, the backbone of the epoxy resin ‘A’ is selected from bisphenol-A based epoxy resins such as Bisphenol A diglycidyl ether (DGEBA or BADGE), or bisphenol-F based epoxy resin (BPF).

The bisphenol-A based epoxy resins and bisphenol-F based epoxy resin are commercially available such as EPIKOTE 828/EPOTEC YD 128 and EPIKOTE 862.

In one of the embodiments, backbone of the epoxy resin ‘A’ is preferably selected from but not limited to halogenated bisphenols-A based resins or bisphenol-F based resins, or mixtures thereof.

In one of the preferable embodiments, the aromatic organic compound having two or more terminal hydroxyl groups is selected from hydroquinone, resorcinol, catechol, or mixtures thereof. In another one of the preferable embodiments, the non-aromatic organic compound having two or more terminal hydroxyl groups is selected from 1,6-hexanediol, 1,4-butanediol or mixtures thereof.

In yet another embodiment of the present disclosure the coupling agent can be used as known in the art and is not limited, but preferably selected from triphenyl phosphonium acetate, or triphenylphosphine or mixtures thereof.

In yet another embodiment of the present disclosure the amount of epoxy resin is selected from 50 - 99 wt%, preferably selected in the range of 70-90 wt%.

In yet another embodiment of the present disclosure the amount of organic compound having two or more terminal hydroxyl groups is selected from 1 -50 wt%, preferably selected in the range of 10 -30 wt %.

In yet another embodiment of the present disclosure the amount of coupling agent is selected from 0.005- 3 wt%, preferably 0.01-0.1 wt%.

Another aspect of the present disclosure relates to a method of preparing an epoxy-based phase change material comprising the following steps: a. adding an epoxy resin, an organic compound having two or more terminal hydroxyl groups and a coupling agent in a vessel followed by stirring, b. increasing the temperature from room temperature to a minimum of 70 °C, preferably between 70 °C to 140 °C and maintaining the temperature for 2 to 5 hours to provide an epoxy-based phase change material. wherein the epoxy -based phase change material is represented by the following formula (1): wherein ‘A’ represents the backbone of the epoxy resin, wherein ‘B’ represents backbone of an organic compound having two or more terminal hydroxyl groups, and wherein ‘n’ represents an integer having value 1 to 12, and wherein the organic compound is an aromatic organic compound having two or more terminal hydroxyl groups or a combination of an aromatic and non-aromatic organic compound having two or more terminal hydroxyl groups.

Yet another aspect of the present disclosure relates to an epoxy -based phase change composition comprising an epoxy-based phase change material, a solvent and a filler.

In one embodiment of the present disclosure, the epoxy-based phase change composition is prepared by mixing an epoxy-based phase change material, a solvent and a filler.

In another embodiment of the present disclosure, the amount of the epoxy-based phase change material is in the range of 20 - 70 wt%.

In yet another embodiment of the present disclosure, the filler is selected from but not limited to aluminum trihydrate (ATH), alumina, boron nitride, aluminum nitride, zinc oxide, or combinations thereof.

In yet another embodiment of the present disclosure, the amount of filler is selected from 10 - 90 wt%, preferably selected in the range of 30 - 70 wt%.

In one of the embodiments of the present disclosure, the solvent is selected from but not limited to propylene carbonate, 1,6- hexanediol glycidyl ether, phenyl glycidyl ether or mixtures thereof.

In yet another embodiment of the present disclosure, the amount of solvent is selected from 5 - 20 wt%.

In another embodiment of the present disclosure, the latent heat capacity of the thermally conductive phase change material at 40°C is in the range of 17580 to 18500 KJ/kg by DSC analysis.

In yet another embodiment of the present disclosure, the epoxy-based phase change material is used in insulated gate bipolar transistor (IGBT) gel applications, in energy storage devices and in electric vehicle potting applications.

Another aspect of the present disclosure relates to products based on epoxy-based phase change material which demonstrates phase change temperature of -40-55 °C along with improved thermal conductivity (TC) of -15-25 %. Further salient features of the epoxy-based phase change material and the method of preparing the same providing the disclosed enhancements are discussed in the examples provided below.

EXAMPLES

Preparation of epoxy-based phase change material (PCM):

PCM 1: Standard epoxy resin DGEBA (89.58 parts by wt%), resorcinol (10.39 parts by wt%) and ethyl triphenyl phosphonium acetate (0.03 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature was increased from room temp to 70°C for 30 min, then 80°C for 30 min., 100°C for another 30 min, 120°C for 1 hr and then 130-140°C for 90 min. The reaction mixture was cooled and the product having a dark brown solid was obtained.

The PCM had epoxy equivalent weight (EEW) of 330 -350.

PCM 2: Standard epoxy resin DGEBA (89.58 parts by wt%), Catechol (10.39 parts by wt%) and ethyl triphenyl phosphonium acetate (0.03 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature was increased from room temp to 70°C for 30 min, then 80°C for 30 min., 100°C for another 30 min, 120°C for Ihr and then 130-140°C for 90 min. The reaction mixture was cooled and the product having a dark brown solid was obtained.

The PCM had epoxy equivalent weight (EEW) of 320 -350.

PCM based on bisphenol F epoxy resin

PCM 3: Bisphenol F Epoxy resin (89.58 parts by wt%), hydroquinone (10.39 parts by wt%) and ethyl triphenyl phosphonium acetate (0.03 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature was increased from room temp to 70°C for 30 min, then 80°C for 30 min., 100°C for another 30 min, 120°C for Ihr and then 130-140°C for 90 min. The reaction mixture was cooled and the product having a dark brown solid was obtained.

The PCM had epoxy equivalent weight (EEW) of 300 -350.

PCM 4: Bisphenol F Epoxy resin (89.58 parts by wt%), Resorcinol (10.39 parts by wt%) and ethyl triphenyl phosphonium acetate (0.03 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature increased from room temp to 70°C for 30 min, then 80°C for 30 min., 100°C for another 30 min, 120°C for Ihr and then 130-140°C for 90 min. The reaction mixture was cooled and the product having a dark brown solid was obtained. The PCM had epoxy equivalent weight (EEW) of 310 -350.

PCM 5: Bisphenol F Epoxy resin (89.58 parts by wt%), Catechol (10.39 parts by wt%) and ethyl triphenyl phosphonium acetate (0.03 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature was increased from room temp to 70°C for 30 min, then 80°C for 30-40 min., 100°C for another 30 min, 120°C for Ihr and then 130-140°C for 2hr. The reaction mixture was cooled and the product having a dark brown solid was obtained.

The PCM had epoxy equivalent weight (EEW) of 320 -350.

PCM based on bisphenol- A-liquid epoxy resin (DGEBA)

PCM 6: Standard epoxy resin DGEBA (87.29 parts by wt%), hydroquinone (11.19 parts by wt%), 1,6-Hexanediol (1.46 parts by wt%), and ethyl triphenyl phosphonium acetate (0.06 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature was increased from room temp to 220°C and maintained for 4hr. The reaction mixture was cooled and the product having a dark brown solid was obtained.

The PCM had epoxy equivalent weight (EEW) of 360 -380.

PCM 7: Standard epoxy resin DGEBA (87.29 parts by wt%), Resorcinol (11.20 parts by wt%), 1,6-Hexanediol (1.46 parts by wt%), and ethyl triphenyl phosphonium acetate (0.03 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature was increased from room temp to 220°C and maintained for 4hr. The reaction mixture was cooled and the product having a dark brown solid was obtained.

The PCM had epoxy equivalent weight (EEW) of 370 -390.

PCM 8: Standard epoxy resin DGEBA (YD 128) (87.30 parts by wt%), Catechol (11.19 parts by wt%), 1,6-Hexanediol (1.46 parts by wt%), and ethyl triphenyl phosphonium acetate (0.03 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature was increased from room temp to 220°C and maintained for 4hr and finally 250°C for Ihr. The reaction mixture was cooled and the product having a dark brown solid was obtained.

The PCM had epoxy equivalent weight (EEW) of 355 -380.

Control 1 (Comparative example) Control 1: Standard epoxy resin DGEBA (85.14 parts by wt%), 1,6-Hexanediol (14.81 parts by wt%), and ethyl triphenyl phosphonium acetate (0.05 parts by wt%) were charged in a clean, dry kettle and stirred. The reaction temperature was increased from room temp to 220°C and maintained for 4hr. Cool the reaction mixture. The reaction mixture was cooled and the product having a dark brown solid was obtained.

The Control 1 had an epoxy equivalent weight (EEW) of 360 -375.

The above examples are reproduced in Table 1 below:

Preparation of an epoxy-based phase change composition: The epoxy-based phase change composition is prepared by mixing an epoxy-based phase change material (PCM) with a filler and a solvent in a vessel. The amount of the epoxy-based phase change material is in the range of 20 - 70 wt% with respect to the amount of filler being in the range of 30 - 80 wt%. The fillers used in examples of present disclosure are Aluminum oxide/ Alumina and Boron nitride. The solvent used in examples of present disclosure is propylene carbonate.

The examples (Example 1-9 and comparative example 1) prepared by above mentioned method were analysed for PCM temperature. The results are denoted in Table 2 below: Table 1: Epoxy -based phase change materials (PCM)

Table 2: Examples according to present disclosure

From Table 2, it is evident that the epoxy -based phase change composition comprising an epoxy-based phase change material (PCM) according to the present disclosure results in phase change temperature of -40-55 °C.

As has been described above, according to the epoxy-based phase change material (PCM) of the present disclosure, it is possible to improve performance of electronic components, ensure safety and to reduce and even eliminate the potential for thermal runaway or propagation in electronic devices.

The advantages of the disclosed invention are thus attained in an economical, practical, and facile manner. While preferred embodiments and examples have been shown and described, it is to be understood that various further modifications and additional configurations will be apparent to those skilled in the art. It is intended that the specific embodiments herein disclosed are illustrative of the preferred and best modes for practicing the invention and should not be interpreted as limitations on the scope of the invention.