WO2023286081A1

WO2023286081A1 - Epoxy modified resin

Info

Publication number: WO2023286081A1
Application number: PCT/IN2022/050632
Authority: WO
Inventors: Amol Murlidharrao KENDHALE; Shashikant Sangmeshwar Paymalle
Original assignee: Elantas Beck India Limited
Priority date: 2021-07-13
Filing date: 2022-07-12
Publication date: 2023-01-19
Also published as: WO2023286081A9

Abstract

The present disclosure relates a modified epoxy resin and a process for making the modified epoxy resin. The modified epoxy resin includes an aromatic group having at least one free hydroxy group. The modified epoxy resin demonstrates low temperature or room temperature fast curing along with better acid resistance. Further, the cured product demonstrates improved a thermal conductivity (TC) ~20-30% along with high glass transition temperature (Tg) and hardness.

Description

“EPOXY MODIFIED RESIN”

FIELD OF INVENTION

The present disclosure relates to an epoxy resin. Specifically, the present disclosure relates to a self-accelerated modified epoxy resin. More specifically, the present disclosure relates to an epoxy resin modified with an aromatic group having at least one free hydroxy group. Further, the present disclosure relates to a process for making the self-accelerated modified epoxy resin.

BACKGROUND AND PRIOR ART

Epoxy resin compositions which impart enhanced thermal properties are desirable in the application areas such as electrical, electronic, coating, adhesives, molded components and composites. However, such resin compositions are typically expensive to formulate and may suffer from inferior performance capabilities.

An epoxy resin composition to be used in above mentioned application areas consists mainly of epoxy resin and a hardener, with other additives being added as required. Epoxy resin materials are used as main component of an epoxy resin composition and include general- purpose glycidyl ether of bisphenol A, general-purpose glycidyl ether of bisphenol F, novolac glycidyl ether etc. Known hardeners generally used with epoxy resin include aliphatic polyamines, aromatic polyamines, acid anhydrides, and Lewis acid complexes. Further, to achieve efficient curing or gelling the said epoxy resin compositions preferably contain an accelerator which is added as an additive and preferably selected from the group of strong acid ester, onium salt, Lewis acid, amine complex, and polyphenol etc.

Several current technologies use free phenolic compounds as an accelerator. The accelerators are added as additives in the epoxy resin composition and include alcohols, phenols, Mannich base derivatives, tertiary amine bases, or strong acids, sulfur-containing compounds. These accelerator additives are undesirable due to toxicity, corrosiveness, compatibility with the rest of the formulation, or deleterious effects on the final physical properties.

Further, these accelerators have disadvantages such as high amount of accelerator is needed to allow a good cure response at room temperature (RT), highest exotherm can lead to polymer degradation, coloring, undesired side effect of blushing, blooming or hazing, leaching, small molecules that do not react into the polymer network, thus causing significant lowering of hardness and glass transition temperature (Tg), water absorption, low chemical resistance, etc. These additive compounds are also regulated by governmental authorities due to their potential use as chemical weapons precursors and regulatory compliance.

In addition, accelerators such as phenolic accelerators are often solids and contribute undesired color or ultraviolet light sensitivity to the final formulation. Further, widely used liquid accelerators, such as nonyl phenol, mono-nonyl phenol (MNP), dinonyl phenol etc., sometimes also act as plasticizers and thus leads to undesirable impact on Hardness, leach out, lowering chemical resistance and the glass transition temperature (Tg) of resin systems.

For instance, the document JP2005255813A discloses epoxy resin composition comprising curing accelerator such as phenols or phenol salts that are added as an additive in the composition in a specified amount. These curing accelerators are used singly or in combination of two or more, and the amount used is 0.1 to 7% by mass with respect to the total epoxy resin of the composition. However, the amount has to be precisely adjusted since it greatly affects the curability and storage stability of the composition. Thus, the type of curing accelerator and amount used thereof has to be adjusted so as not to impair the characteristics of the epoxy resin composition.

Another document EP2639252A1 attempts to solve the drawbacks by providing oligomeric condensation products of (hydroxymethyl) phenol as alternative accelerators for epoxy resins or curing agents for epoxy resins.

The present disclosure addresses one or more problems as discussed above and other problems associated with the art by providing a self-accelerated modified epoxy resin and a method of preparing the same. The self-accelerated modified epoxy resin minimizes disadvantages and help epoxy system to cure at lower temperature and that could be formulated in a fast-reacting system at such low temperature.

Accordingly, the present disclosure provides a self-accelerated (modified) epoxy resin and a method of preparing the same. The present disclosure also provides cured products based on self-accelerated epoxy resin which demonstrate a high glass transition temperature (T_g), good acid resistance and an improved thermal conductivity (TC) -20-30%. SUMMARY OF THE INVENTION

A self-accelerated modified epoxy resin is obtained by reacting an epoxy resin, an aromatic group having at least one free hydroxy group and a coupling agent wherein, the aromatic group having at least one free hydroxy group is covalently incorporated within the epoxy resin and wherein one of the hydroxy groups of the aromatic group having at least one free hydroxy group which is free to act as an accelerator. Thus, the self- accelerated modified epoxy resin of the present disclosure overcomes the disadvantages of commercially available accelerators as it acts as a self-accelerated epoxy resin wherein the accelerator is an oligomeric or polymeric in nature and not required to be added as an additive.

The modified epoxy resin achieves faster cure at low temperature irrespective of types of hardeners used for cure. It minimizes the disadvantages of commercial accelerator additives as mentioned above as it itself acts as an accelerator and be the part of cure backbone. Apart from this, the cured product also demonstrates a higher thermal conductivity in comparison to an unmodified Bisphenol A diglycidyl ether (DGEBA) composition. Additionally, the cured product demonstrates better acid resistance and high glass transition temperature (Tg). Thus, overcoming the problems associated with slow cure of epoxy resin and hardener and other disadvantages of accelerators when used as an additive. Further, the present disclosure relates to a process for making the self-accelerated epoxy resin.

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 spirit and 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 a self-accelerated/modified epoxy resin obtained by reacting: an epoxy resin, an aromatic group having at least one free hydroxy group, and a coupling agent, wherein the aromatic group having at least one free hydroxy group is covalently attached to the epoxy resin as represented by the following formula (1):

(1) wherein ‘A’ represents the backbone of the epoxy resin, wherein ‘B’ represents an epoxy group, wherein ‘C’ represents an aromatic group having at least one free hydroxy group, and wherein ‘n’ represents an integer having value 1 to 10.

In one of the embodiments, the backbone of the modified epoxy resin ‘A’ is based on an epoxy oligomer or an epoxy polymer.

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 modified epoxy resin ‘A’ is selected from bisphenol-A based epoxy resins such as Bisphenol A diglycidyl ether (DGEBA or BADGE), bisphenol-F based epoxy resin (BPF) or cycloaliphatic epoxides containing one or more aliphatic rings in the molecule on which the oxirane ring is contained.

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

In one of the embodiments, the cycloaliphatic epoxides contain one or more aliphatic rings having 10 to 15 carbon atoms. In yet another embodiment, the cycloaliphatic epoxide is preferably selected from but not limited to 3,4-Epoxycyclohexylmethyl-3’,4’- epoxycyclohexane carboxylate (Syna-Epoxy 21).

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

In one of the preferable embodiments, an aromatic group having at least one free hydroxy group is preferably selected form hydroquinone, resorcinol, catechol or Bisphenol A or mixtures thereof.

In one of the preferable embodiments, the self-accelerated/modified epoxy resin is based on the bisphenol-A epoxy resin and hydroquinone, resorcinol or catechol having the following structure according to the present disclosure:

In yet another embodiment, the bisphenol-A epoxy resin is based on the hydroquinone modified epoxy resin having the following structure according to the present disclosure:

In yet another embodiment, the bisphenol-F epoxy resin is based on the hydroquinone modified epoxy resin having the following structure according to the present disclosure:

In yet another embodiment, the cycloaliphatic epoxides resin is based on the hydroquinone modified epoxy resin having the following structure according to the present disclosure:

In another preferable embodiment, the self-accelerated/modified epoxy resin is based on the bisphenol-A epoxy resin and diols having the following structure according to the present disclosure:

R = -CH₂-, -O-, -NR¹-, or R = Direct bond/biphenyl wherein R¹ = H, SO₂, alkyl or aryl

In one of the embodiments of the present disclosure the epoxy resin represented by the formula (1) has a molecular weight preferably in the range 200 - 3000.

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 triphenyl phosphine.

In yet another embodiment of the present disclosure the amount of epoxy resin is selected from 50 - 99wt%, preferably selected in the range of 80 to 90. In yet another embodiment of the present disclosure the amount of aromatic group having at least one free hydroxy group is selected from 1 -50 wt%, preferably selected in the range of 5 to 20 wt%.

In yet another embodiment of the present disclosure the amount of coupling agent is selected from 0.1 - 10 wt%, preferably selected in the range of 0.05 to 0.2 wt%.

In yet another embodiment of the present disclosure the the viscosity of the epoxy resin composition is in the range of 8000 mPas to 70,000mPas, preferably in the range of 8000 to 45000 mPas.

In one of the embodiments of the present disclosure the modified epoxy resin composition further includes a hardener. The hardener is preferably selected from selected from amines, polyether amines, polyamides or anhydrides or mixtures thereof.

In one of the embodiments, the hardener and the modified epoxy resin are mixed in the ratio 5 to 100, preferably in the ratio 8 to 100.

Another aspect of the present disclosure relates to a method of preparing a modified epoxy resin comprising the following steps: i. adding an epoxy resin, an aromatic group having at least one free hydroxy group and a coupling agent in a vessel followed by stirring, ii. increasing the room temperature to a minimum of 80 °C, preferably between 80 °C to 100 °C and maintaining the temperature for 2 to 5 hours to produce a self-accelerated (modified) epoxy resin.

In one of the embodiments, the method may further include a step of adding a hardener to the self-accelerated modified epoxy resin.

In one of the embodiments, the hardener is preferably selected from selected from amines, polyether amines, polyamides or anhydrides or mixtures thereof.

In one of the embodiments, the epoxy resin utilized in the method of preparing epoxy resin has preferably a molecular weight in the range 200 to 3000.

In yet another embodiment, the epoxy resin utilized in the method of preparing epoxy resin is preferably selected from bisphenol-A based resins (DGEBA), bisphenol-F based resin (BPF) or cycloaliphatic epoxides containing one or more aliphatic rings in the molecule on which the oxirane ring is contained.

In one of the embodiments, the coupling agent utilized in the method of preparing epoxy resin is preferably selected from but not limited to triphenyl phosphonium acetate, and triphenyl phosphine.

In one of the embodiments, the hardener is preferably selected from but not limited to amines, polyether amines, polyamides and anhydrides.

The amines used for the present disclosure may be an aliphatic or aromatic amines preferably selected from but not limited to TETA, DETA, TEPA, AEP (Aminoehylpiperazine). The polyether amines used for the present disclosure may be selected from but not limited to Jeffamine D230, Jeffamine D400, Jeffamine D2000.

The polyamides used for the present disclosure may be selected from but not limited to CYNAMID 140, Dromide® 9315. The anhydrides used for the present disclosure may be selected from but not limited to MTHPA, DDSA, MHHPA.

In yet another embodiment, the hardener is preferably selected from but not limited to triethylenetetramine (TETA), methyltetrahydrophthalic anhydride (MTHPA) or commercially available curing amine composition (ETHACURE^® 100), polyetheramine (JEFFAMINE^® D- 230).

Another aspect of the present disclosure relates to a cured products based on modified epoxy resin composition which demonstrate a high glass transition temperature (T_g) and an improved thermal conductivity (TC) -20-30%.

In one of the embodiments, the modified epoxy resin composition can be preferably used as a tool that can be used across epoxy formulations to expediate cure speed and achieve desired performance. The cured material is good for surface cure and molded components.

In one of the embodiments, the modified epoxy resin composition is useful for casting and potting applications. In one of the embodiments, the modified epoxy resin composition is useful in paints for quick drying or in coatings, etc.

One of the aspects of the present disclosure relates to a paint or coating comprising the modified epoxy resin composition as disclosed herein.

One of the aspects of the present disclosure relates to a molded article comprising the modified epoxy resin composition as disclosed herein.

In one of the embodiments, the modified epoxy resin composition is self-accelerating and provides fast cure, low temperature and room temperature cure, better acid resistance, high Tg & hardness.

Additional features and advantages of the modified epoxy resin composition is that it minimizes disadvantages of commercially available accelerator additives, as it itself acts as an accelerator and be the part of cure backbone. Further, it is compatible with the regulatory legal compliance as it is a polymeric accelerator composition.

Further salient features of the modified epoxy resin composition and the method of preparing the same providing the disclosed enhancements are discussed in the examples provided below.

EXAMPLES

Preparation of modified epoxy resin:

Composition based on bisphenol-A-based liquid epoxy resin (DGEBA BLR)

Composition 1: Charge standard epoxy resin DGEBA (90 parts by wt%), hydroquinone (10 parts by wt%) and ethyl triphenyl phosphonium acetate (0.1 parts by wt%) in a clean, dry kettle and start stirring. Increase reaction temperature from room temp to 80°C for 1 hr and then maintain at 100°C for 3-4 hr. Cool the reaction mixture. This results in the modified epoxy resin composition having a dark brown liquid.

The modified epoxy resin composition has epoxy equivalent weight (EEW) of 210 -240 & viscosity of 31,000-36000 mPas.

Composition 2: Charge standard epoxy resin DGEBA (90 parts by wt%), Resorcinol (10 parts by wt%) and ethyl triphenyl phosphonium acetate (0.1 parts by wt%) in a clean, dry kettle and start stirring. Increase reaction temperature from room temp to 80°C for 1 hr and then maintain at 100°C for 3-4 hr. Cool the reaction mixture. This results in the modified epoxy resin composition having a dark brown liquid.

The modified epoxy resin composition has epoxy equivalent weight (EEW) of 190 -225 & viscosity of 32000-35000 mPas.

Composition 3: Charge standard epoxy resin DGEBA (90 parts by wt%), Catechol (10 parts by wt%) and ethyl triphenyl phosphonium acetate (0.1 parts by wt%) in a clean, dry kettle and start stirring. Increase reaction temperature from room temp to 80°C for 1 hr and then maintain at 100°C for 3-4 hr. Cool the reaction mixture. This results in the modified epoxy resin composition having a dark brown liquid.

The modified epoxy resin composition has epoxy equivalent weight (EEW) of 200 -240 & viscosity of 30,000-33000 mPas.

Composition 4: Charge standard epoxy resin DGEBA (90 parts by wt%), Bisphenol A (10 parts by wt%) and ethyl triphenyl phosphonium acetate (0.1 parts by wt%) in a clean, dry kettle and start stirring. Increase reaction temperature from room temp to 80°C for 1 hr and then maintain at 100°C for 4-5 hr. Cool the reaction mixture. This results in the modified epoxy resin composition having a dark brown liquid.

The modified epoxy resin composition has epoxy equivalent weight (EEW) of 250-300 & viscosity of 35,000-45000 mPas.

Composition based on Bisphenol F epoxy resin

Composition 5: Charge Bisphenol F Epoxy resin (90 parts by wt%), hydroquinone (10 parts by wt%) and ethyl triphenyl phosphonium acetate (0.1 parts by wt%) in a clean, dry kettle and start stirring. Increase reaction temperature from room temp to 80°C for 1 hr and then maintain at 100°C for 3-4 hr. Cool the reaction mixture. This results in the modified epoxy resin composition having a dark brown liquid.

The modified epoxy resin composition has epoxy equivalent weight (EEW) of 200 -225 & viscosity of 8,000 mPas to 10,000mPas.

Composition 6: Charge Bisphenol F Epoxy resin (95 parts by wt%), hydroquinone (5 parts by wt%) and ethyl triphenyl phosphonium acetate (0.13 parts by wt%) in a clean, dry kettle and start stirring. Increase reaction temperature from room temp to 80°C for 1 hr and then maintain at 100°C for 3-4 hr. Cool the reaction mixture. This results in the modified epoxy resin composition having a dark brown liquid.

The modified epoxy resin composition has epoxy equivalent weight (EEW) of 200 & viscosity of 18,000 mPas.

Composition 7: Charge Bisphenol F Epoxy resin (85.5 parts by wt%), hydroquinone (14.5 parts by wt%) and ethyl triphenyl phosphonium acetate (0.13 parts by wt%) in a clean, dry kettle and start stirring. Increase reaction temperature from room temp to 80°C for 1 hr and then maintain at 100°C for 3-4 hr. Cool the reaction mixture. This results in the modified epoxy resin composition having a dark brown liquid.

The modified epoxy resin composition has epoxy equivalent weight (EEW) of 240 -250 & viscosity of 35,500 mPas.

Composition based on 1,4-butanediol-epoxy resin (Comparative example)

Composition 8: Charge standard epoxy resin DEGBA (90 parts by wt%), 1,4-butandiol (10 parts by wt%) and ethyl triphenyl phosphonium acetate (0.1 parts by wt%) in a clean, dry kettle and start stirring. Increase reaction temperature from room temp to 80°C to 100°C and maintain 100 °C for 2-5 hr. This results in the modified epoxy resin composition having a dark brown liquid.

The modified epoxy resin composition has epoxy equivalent weight (EEW) of 220 - 235 & viscosity 15,000 mPas to 20,000mPas.

Gelling Effect of self-accelerated modified epoxy resin

The modified epoxy resin composition prepared according to the method of the present disclosure as discussed above have been mentioned in Table 1 below. The modified epoxy resin compositions were utilized for studying the gelling behaviour of the composition in Examples 1 to 12 (Table 2) by mixing with a hardener at room temperature. The hardener was preferably selected from polyether amine, polyamide, amine, anhydride and aromatic hardeners. The gelling time for the self-accelerated modified) epoxy compositions has been recorded in the Table 2. Further, comparative epoxy compositions using the non-modified or differently modified epoxy resins have been prepared by mixing with a hardener and the gelling time has been recorded in the Table 3. Table 1: Epoxy resin compositions

Table 2: Examples according to present disclosure

Table 3: Comparative Examples

From Table 2 and 3 it is evident that the self-accelerated modified epoxy according to the present disclosure when mixed with a hardener result in an improved gelling i.e., fast cure at room temperature. As denoted in Table 2, the epoxy equivalent weight (EEW) is of the the self-accelerated modified epoxy from 165 to 300 and the viscosity is from 8000 to 45000 mPas. The gel time has improved for inventive examples having the self-accelerated modified epoxy as can be seen from Table 3.

Further, higher enhanced thermal conductivity (TC) of the cured product ~ 20-30% in comparison to the compositions based on conventional epoxy resin compositions is observed. Further, the self-accelerated modified epoxy demonstrates a high Tg & hardness for the cured product along with high thermal conductivity. In contrast the comparative examples (Table 3) based on traditional or commercially available epoxy resins demonstrate extremely poor or no curing and result in a much-reduced thermal conductivity and low Tg.

As has been described above, according to the self-accelerated modified epoxy of the present disclosure, it is possible to immediately cure at low temperatures, and it is also possible to effectively prevent defects from occurring in cured products. Further, the cured products achieved from the self-accelerated modified epoxy demonstrate a higher thermal conductivity, better acid resistance and high Tg over conventional epoxy resin compositions. Thus, overcoming the problems associated with slow cure of epoxy resin and hardener and other disadvantages of accelerators when used as an additive.

The advantages of the disclosed invention are thus attained in an economical, practical and facile manner. While preferred embodiments and example 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.

Claims

The Claims:

1. A self-accelerated modified epoxy resin obtained by reacting: an epoxy resin, an aromatic group having at least one free hydroxy group, and a coupling agent, wherein the aromatic group having at least one free hydroxy group is covalently attached to the epoxy resin as represented by the following formula (1):

(1) wherein ‘A’ represents the backbone of the epoxy resin, wherein ‘B’ represents an epoxy group of the epoxy resin, wherein ‘C’ represents an aromatic group having at least one free hydroxy group, and wherein ‘n’ represents an integer having value 1 to 10, wherein the epoxy group (B) is represented by

or, wherein the epoxy equivalent weight (EEW) is from 165 to 300, and wherein the viscosity is from 8000 to 45000 mPas.

2. The self-accelerated modified epoxy resin as claimed in claim 1, wherein the backbone ‘A’ of the modified epoxy resin is an epoxy oligomer or an epoxy polymer.

3. The self-accelerated modified epoxy resin as claimed in claim 1, wherein the backbone ‘A’ of the modified epoxy resin is selected from bisphenol-A based epoxy resins, bisphenol-F based epoxy resin or cycloaliphatic epoxides, or mixtures thereof.

4. The self-accelerated modified epoxy resin as claimed in claim 1, wherein the epoxy resin has a molecular weight in the range 200 to 3000.

5. The self-accelerated modified epoxy resin as claimed in claim 1, wherein the aromatic group having at least one free hydroxy group is selected from hydroquinone, resorcinol, catechol or Bisphenol A or mixtures thereof.

6. The self-accelerated modified epoxy resin as claimed in claim 1, wherein the coupling agent is selected from ethyl triphenyl phosphonium acetate or triphenylphosphine.

7. The self-accelerated modified epoxy resin as claimed in claim 1, wherein the amount of epoxy resin is in the range of from 50 - 99wt%, the amount of aromatic group having at least one free hydroxy group is in the range of 1 -50 wt% and the amount of coupling agent is in the range of from 0.05 - 10 wt%.

8. The self-accelerated modified epoxy resin as claimed in claim 1, further comprising a hardener, preferably selected from selected from amines, polyether amines, polyamides or anhydrides or mixtures thereof.

9. A method of preparing self-accelerated modified epoxy resin as claimed in claims 1 to 8, comprising the following steps: a. adding an epoxy resin, an aromatic group having at least one free hydroxy group and a coupling agent in a vessel followed by stirring, b. increasing the temperature from room temperature to a minimum of 80 °C, preferably between 80°C to 100°C and maintaining the temperature for 2 to 5 hours to provide a self-accelerated modified epoxy resin.

10. The method as claimed in claim 9, further including a step of adding a hardener to the self-accelerated modified epoxy resin.

11. The method as claimed in claim 9, wherein the hardener and the modified epoxy resin composition are mixed in the ratio 5 to 100.

12. The method as claimed in claim 9, wherein the amount of epoxy resin is in the range 50 - 99wt%, the amount of an aromatic group having at least one free hydroxy group is in the range 1 -50 wt% and the amount of coupling agent is in the range 0.05 - 10 wt%.

13. A cured product comprising the modified epoxy resin as claimed in claims 1 to 8 and a hardener.

14. A paint or coating comprising the modified epoxy resin as claimed in claims 1 to 8.

15. A molded article comprising the modified epoxy resin as claimed in claims 1 to 8.