A light-curable resin formulation

Abstract

The present invention relates to a light curable resin formulation comprises: a.) one or more cross linked methacrylate monomer present in amount of 5% to 90%w / w; b.) relative aliphatic initiator present in an amount of 10% to 30%; c) light initiator present in an amount of 0.1% to 10% w / t; d) thixotropic agents present in an amount of 0.5%to 25% wt. The formulation provides improved light-curing properties, suitable for orthopaedic cast formulation. The combination of these components enhances the resin's performance, including its viscosity, cure rate, and mechanical properties when exposed to light. This invention further offers a balance between high reactivity, easy processing, and excellent final material properties.

Description

[0001] Title- A LIGHT-CURABLE RESIN FORMULATION

[0002] FIELD OF INVENTION:

[0003] The present invention relates to a light curable resin formulation comprises: a.) one or more cross linked methacrylate monomer present in amount of 5% to 90%w / w; b.) relative aliphatic initiator present in an amount of 10% to 30%; c) light initiator present in an amount of 0.1% to 10% w / t; d) thixotropic agents present in an amount of 0.5%to 25% wt. More particularly, the present invention relates to the process for the preparation of a light-curable resin formulation.

[0004] BACKGROUND OF INVENTION:

[0005] Composite resin materials are widely used in medicinal fields such as dentine. With continuous development in Materials Science, composite materials have significantly improved their physical, mechanical, and biocompatibility properties. Despite these advances, composite resins nowadays have limitations in their clinical; Problems such as discoloration, abrasion, and polymerization shrinkage persist. The main advances made in its formulation focus on the continuous development of new compositions of resins.

[0006] Generally, resin-based composites comprise a resin matrix, reinforcing fibers, fiber-matrix interface coupling agents, and polymerization initiator system; however, the last two are usually incorporated in trace amounts (1 wt%). Resins are conventionally light-curable acrylate-based monomers, which represent one major influence on the final properties of filing composites. Light-curable resin-based composites are the common choice for patients and practitioners due to their superior aesthetics and easy handling and shaping properties. Therefore, they increasingly became popular in density.

[0007] Aromatic epoxy resins, particularly bisphenol-A diglycidyl ether (DGEBA) in combination with amine-based curing agents, represent the conventional two-component systems employed in the fabrication of laminated composite structures for orthotic and prosthetic applications. These epoxy systems are widely used in the production of prosthetic sockets and orthotic braces due to their mechanical strength, chemical resistance, and adhesive properties. However, several limitations are associated with these conventional two-component epoxy systems. Chief among them are the requirement for precise stoichiometric mixing of resin and hardener, limited working time (pot life), and a time-intensive curing process, which may require room temperature or elevated temperature post-curing cycles to achieve full mechanical performance. These factors not only complicate the manufacturing process but also introduce the potential for operator error, leading to suboptimal material properties and product variability.

[0008] US patent no. US20140239527A1 disclosed a light-curable resin composition suitable as a material for light-fabricating and capable of producing cured products with excellent mechanical strength and high heat resistance. Further disclosed is a process for molding a resin-based mold which provides superior molding dimensional precision and superb repetition durability. The resin composition contains a monomer component containing (A) 30-70 wt. % of a polyfunctional unsaturated monomer having a cyclic structure and (B) 70- 30 wt. % of a monofunctional unsaturated monomer having a cyclic structure of which the homopolymer has a glass transition temperature (Tg) of 70° C or higher; (C) a light-initiator; and (D) an inorganic filler having an average particle diameter or an average fiber length of 1-50 pm, wherein the ratio of the inorganic filler to 100 parts by volume of the monomer components and the light-initiator is 100-160 parts by volume, and the heat distortion temperature of the cured resin produced from the light-curable resin composition is 100° C or higher.

[0009] Bisphenol A glycidyl methacrylate (Bis-GMA) exhibits inherently high viscosity due to its rigid aromatic structure and extensive hydrogen bonding, which poses limitations on the incorporation of high filler loadings in composite formulations. This viscosity constraint can adversely affect processability, handling, and the overall mechanical performance of the final material.

[0010] The present invention provides a light-curable formulation comprising a cross linked methacrylate monomer characterized by a reduced acid value and lowered viscosity. The decreased acid content minimizes the potential for polymerization inhibition and enhances storage stability, while the reduced viscosity significantly improves processability, facilitates higher filler loading, and ensures superior wetting and dispersion of reinforcing agents. Collectively, these properties contribute to enhanced mechanical performance, better handling characteristics, and optimized curing behavior in light-activated composite systems.

[0011] SUMMARY OF THE INVENTION:

[0012] The main object the present invention to provide a light curable resin formulation comprises: a.) one or more cross linked methacrylate monomer present in amount of 5% to 90%w / w; b.) relative aliphatic initiator present in an amount of 10% to 30%; c) light initiator present in an amount of 0.1% to 10% w / t; d) thixotropic agents present in an amount of 0.5% to 25% wt.

[0013] Another object of the present invention is to provide a light-curable resin formulation wherein formula I is

[0014] Formula I wherein,

[0015] RHs selected from -2(C6H5CH3) C, -CH2(2C6H5), -C2H4, - (C2H4) C (CH3)2

[0016] R2is 2-methylprop-2-enoic acid

[0017] Yet another object of the present invention is to provide a light-curable resin formulation wherein, reactive aliphatic acrylate diluent. wherein,

[0018] R3can be -H or -CH3, and can also be an alkyl (C1-C12), cyclic (C3-C?), ester, halogen, ether, aryl, or amide group.

[0019] R4is an alkyl or aryl group, substituted or unsubstituted, ranging from Ci to C33. Yet another object of the present invention is to provide a light-curable resin formulation wherein the light initiator is selected from trimethylbenzoyl-diphenyl-phosphine oxide, camphorquinone, benzil, 1 -phenyl- 1, 2-propanedione.

[0020] Yet another object of the present invention is to provide a light-curable resin formulation wherein the thixotropic agent is selected from urea-modified diamine, silica, and alumina

[0021] Urea-modified diamine thixotropic agent wherein,

[0022] R5, -ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,4- butadiamne, 1-5-pentadiamine, 1,6-hexamethylenediamine, neopantadiamine;

[0023] R6- low end blocks, medium end blocks, and high-end blocks with various polarities; wherein, low end blocks are selected from Polybutadiene, ethylene-butylene, Polypropylene glycol, and Polyethylene;

[0024] Medium end blocks selected from styrene block, Polypropylene oxide, Poly(tetramethylene glycol), Polylactic Acid-Polyethylene;

[0025] High end blocks selected from Polystyrene, Polyisocyanates or Polyurethane, Polyamide, Polylactic Acid, Polycarbonate.

[0026] Yet another object of the present invention is to provide a synthesis of cross-linked methacrylate monomer (Formula I) comprising the following step;

[0027] (a) dissolve aromatic methacrylate monomer (Formula II) in high-boiling inert solvent at 25-30°C;

[0028] (b) slowly add epoxy monomer (Formula III) into the above monomer solution at 25-30°C;

[0029] (c) add organophosphine catalyst into the monomer solution at 25-30°C and slowly heat the solution at 90-95°C;

[0030] (d) maintain the monomer solution at 90-95°C for 4-6 hours; (e) cool the monomer solution at 25-30°C and distill out the solvent to get crosslinked methacrylate monomer (Formula I).

[0031] Formula II Formula III Formula I wherein,

[0032] R is selected from -H, -C2H4OH, -CH2(C6H5), - C2H4 (C6H5)

[0033] R1is selected from -2(C6H5CH3) C, -CH2(2C6H5), -C2H4, - (C2H4) C (CH3)2R2is 2-methylprop-2-enoic acid

[0034] Yet another object of the present invention is to provide a synthesis of cross-linked methacrylate monomer (Formula I) wherein aromatic methacrylate monomer (Formula II) is selected from benzyl 2-methylprop-2-enoate, 3 -phenylpropyl 2-methylprop-2-enoate, 2- methylprop-2-enoic acid, 2-hydroxyethyl 2-methylprop-2-enoate.

[0035] Yet another object of the present invention to provide as synthesis of cross-linked methacrylate monomer (Formula I) wherein epoxy monomer (Formula III) is selected from 2,2’-[methylenebis (3, l-phenyleneoxymethylene)]bis(oxirane), 2,2’ -[butane- 1, 4-diylbis (oxymethylene)]bis(oxirane),2,2’-[propane-2,2diylbis (3,lphenyleneoxymethylene)]bis(oxirane), 2,2’-[(2, 2-dimethylbutane-l, 4- diyl)bis(oxymethylene)]bis(oxirane).

[0036] Yet another object of the present invention is to provide a synthesis of cross-linked methacrylate monomer (Formula I) wherein a high-boiling inert solvent is selected from toluene, xylene, mesitylene, chlorobenzene, anisole, diphenyl ether, N-methylpyrrolidone, dimethyl sulfoxide.

[0037] Yet another object of the present invention is to provide a synthesis of cross-linked methacrylate monomer (Formula I) wherein organophosphine catalyst is selected from dimethylphenylphosphine, triphenylphosphine, tris (2, 4, 6-trimethoxyphenyl) phosphine, tributylphosphine, trimethylphosphine. Yet another object of the present invention is to provide a synthesis of cross-linked methacrylate monomer (Formula I) wherein the ratio between aromatic methacrylate monomer (Formula II) and epoxy monomer (Formula III) is 2: 1.

[0038] Further object of the present invention is to provide to process for the preparation of a light- curable resin formulation comprising the following steps:

[0039] (a) mix cross-linked methacrylate monomer (Formula I) and reactive aliphatic acrylate diluent under an inert atmosphere (under nitrogen);

[0040] (b) add the light initiator and stabilizer slowly into the base resin mixture under continuous stirring. Ensure uniform dispersion by maintaining for 30-40 minutes at 20-25°C;

[0041] (c) add thixotropic at 25-30°C into the above resin mixture and blend continuously until a homogeneous, final resin mixture is obtained.

[0042] Yet another object of the present invention is to provide a light-curable resin formulation with low acid value content and high purity.

[0043] Yet another object of the present invention is to provide a light-curable resin formulation to use in medical and orthopaedic products with minimal or no adverse environmental impact.

[0044] DETAILED DESCRIPTION OF THE INVENTION:

[0045] As used herein, the terms below have the meanings indicated.

[0046] The singular forms "a," "an," and "the" may refer to plural articles unless specifically stated otherwise.

[0047] The term "about," as used herein, is intended to qualify the numerical values which it modifies, denoting such a value as variable within a margin of error. When no particular margin of error, such as a standard deviation to a mean value given in a chart or table of data, is recited, the term "about" should be understood to mean that range which would encompass the recited value and the range which would be included by rounding up or down to that Figure as well, taking into account significant Figures. The present invention also relates to light curable resin formulation comprises a.) one or more cross-linked methacrylate monomer present in amount of 5% to 90%w / w; b.) relative aliphatic initiator present in an amount of 10% to 30%; c) light initiator present in an amount of 0.1% to 10% w / t; d) thixotropic agents present in an amount of 0.5% to 25% wt.

[0048] In the present invention, a cross-linked monomer is synthesized via an esterification reaction between an aromatic methacrylate monomer (Formula II) and an epoxy-functional monomer (Formula III), carried out in the presence of an organophosphine-based catalyst. This catalytic system facilitates the ring-opening of the epoxy group and subsequent ester bond formation with the methacrylate moiety, resulting in a multifunctional, polymerizable monomer suitable for high-performance thermoset applications.

[0049] The aromatic methacrylate monomer (Formula II), typically a bisphenol A (Bis-A) derivative, undergoes a catalytic reaction with the epoxy-functional monomer to yield a highly cross-linkable resin matrix. The resulting polymer network exhibits enhanced mechanical strength, thermal stability, and chemical resistance, attributable to the rigid aromatic backbone and dense cross-linked structure.

[0050] The synthesized cross-linked methacrylate monomer is subsequently blended with a reactive acrylate diluent, thixotropic agent, and various functional additives, including stabilizers, to formulate a homogeneous, application-ready resin system.

[0051] The synthesized cross-linked methacrylate monomer exhibits a low acid value and high chemical purity, characteristics essential for ensuring optimal stability, reduced reactivity with residual catalysts, and minimal interference with downstream curing processes. The low acid value contributes to improved hydrolytic stability and enhances the compatibility of the monomer with other resin components. Furthermore, the high purity of the monomer minimizes the presence of inhibitory or degradative by-products, which is particularly critical in applications demanding long-term performance and consistent polymerization behaviour.

[0052] Following synthesis, the methacrylate monomer is compounded with a reactive acrylate diluent to tailor the viscosity and reactivity of the formulation. The acrylate diluent acts as both a processing aid and a co-monomer, promoting efficient cross-linking during cure. Thixotropic agents are incorporated to impart shear-thinning behaviour, improving handling properties and application consistency, particularly in vertical or complex geometries. Additionally, functional additives such as stabilizers are included to inhibit premature polymerization and extend shelf life. The resulting formulation is a homogeneous, flow- optimized resin system engineered for high-performance curing under UV, thermal, or dualcure conditions, depending on end-use requirements.

[0053] The present invention provides a light curable resin formulation comprises: a. one or more cross-linked methacrylate monomers are present in an amount of 5% to 90% wt;

[0054] Formula I wherein,

[0055] RHs selected from -2(C6H5CH3) C, -CH2(2C6H5), -C2H4, - (C2H4) C (CH3)2

[0056] R2is 2-methylprop-2-enoic acid b. reactive aliphatic acrylate diluent present in amounts of 10% to 30% wt.; wherein,

[0057] R3can be -H or -CH3, and can also be an alkyl (C1-C12), cyclic (C3-C?), ester, halogen, ether, aryl, or amide group.

[0058] R4is an alkyl or aryl group, substituted or unsubstituted, ranging from Ci to

[0059] C33. c. light initiator present in an amount of 0.1% to 10% wt.; d. thixotropic agents present in an amount of 0.5% to 25% wt; Urea-modified diamine thixotropic agent wherein,

[0060] R5, -ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,4- butadiamne, 1-5-pentadiamine, 1,6-hexamethylenediamine, neopantadiamine; R6- low-end blocks, medium-end blocks, and high-end blocks with various polarities; wherein, low end blocks are selected from Polybutadiene, ethylene-butylene, Polypropylene glycol, and Polyethylene;

[0061] Medium end blocks selected from styrene block, Polypropylene oxide, Poly(tetramethylene glycol), Polylactic Acid-Polyethylene;

[0062] High end blocks selected from Polystyrene, Polyisocyanates or Polyurethane, Polyamide, Polylactic Acid, Polycarbonate.

[0063] Aliphatic acrylate diluents contain acrylate functional groups that participate in the polymerization and crosslinking reactions during curing. This leads to the formation of a more crosslinked polymer network, which enhances the resin's mechanical properties such as hardness, strength, and chemical resistance. The presence of these diluents can accelerate the curing process, reducing curing time while ensuring that the resin fully sets and achieves its desired performance.

[0064] In the present invention, reactive aliphatic acrylate diluent significantly lowers the viscosity of resin systems, making them more fluid and easier to handle during formulation, mixing, and application. This is particularly important in applications requiring smooth flow, such as casting, coating, and composites. By reducing the viscosity, these diluents help to ensure that the resin can fill intricate molds or cover complex surfaces without difficulty.

[0065] In the present invention, reactive aliphatic acrylate diluent compound(C) was selected from triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, and hexane diol dimethacrylates.

[0066] Light initiators in resin formulations for orthopaedic casts offer several distinct benefits that enhance both the processing and performance of the final product. Light initiators, typically light initiators, are compounds that, when exposed to specific wavelengths of light (usually UV or visible light), trigger the polymerization and curing of the resin.

[0067] In the present invention, light initiators allow for controlled and localized curing of the resin, which is particularly useful for orthopaedic casts. This enables the practitioner to directly control when and where the resin begins to set, allowing for more accurate application and finer detailing during the casting process. Curing only occurs when the resin is exposed to light, reducing the risk of premature setting and giving the practitioner more time to mold and adjust the cast to the desired shape before hardening.

[0068] In the present invention light initiator is selected from trimethylbenzoyl-diphenyl-phosphine oxide, camphorquinone, benzil, 1 -phenyl- 1, 2-propanedione.

[0069] Thixotropy is a very important property of adhesives in managing their flow properties during and after dispensing. For rapid dispensing, low viscosity, and high flow are required, while immediately after dispensing, reversion to low flow is important so that the adhesive is precisely placed and cured without any lateral or vertical movement. This occurs because of the non-Newtonian behaviour (thixotropy) of many filled adhesives whereby the shear force of screen printing or forcing the adhesive through apertures reduces its viscosity, but upon removal of the force, the material regains its original higher viscosity, preventing it from sagging or creeping until it can be fully cured. Thixotropic adhesives also allow for thicker, more controlled bond lines.

[0070] In the present invention, the incorporation of thixotropic agents into the resin formulation provides enhanced control over the material's rheological behaviour during application. These agents impart shear-thinning properties, allowing the resin to flow readily under applied force, such as during moulding or spreading, while rapidly recovering viscosity once the force is removed. This ensures that the resin maintains positional stability upon application to the cast area, minimizing the risk of dripping, sagging, or uncontrolled flow.

[0071] In the present invention, thixotropic agent behaviour is particularly advantageous in orthopaedic casting applications, where uniform distribution and dimensional stability of the resin are critical for effective immobilization and support of the injured limb. The ability of the resin to conform precisely to anatomical contours while resisting undesired movement post-application facilitates accurate mouldings and contributes to the mechanical integrity and therapeutic efficacy of the final cast structure.

[0072] In the present invention, the thixotropic characteristics of the resin formulation significantly mitigate the risk of excess material accumulation in unintended regions, such as pooling or runoff in recessed areas. This controlled deposition enhances application precision, reduces material waste, and ensures that only the necessary volume of resin is utilized to form a structurally sound and comfortable orthopaedic cast. The rapid viscosity recovery postapplication also minimizes the need for manual reworking or reshaping, ensuring consistent cast thickness and mechanical uniformity throughout the curing process.

[0073] In the present invention, the thixotropic agents are selected from urea-modified diamine, silica, and alumina.

[0074] Urea-modified diamine thixotropic agent wherein,

[0075] R5, -ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,4- butadiamne, 1-5-pentadiamine, 1,6-hexamethylenediamine, neopantadiamine; R6- low, medium, and high-end blocks with various polarities; wherein, low end blocks are selected from Polybutadiene, ethylene-butylene, Polypropylene glycol, and Polyethylene;

[0076] Medium end blocks selected from styrene block, Polypropylene oxide, Poly(tetramethylene glycol), Polylactic Acid-Polyethylene;

[0077] High end blocks selected from Polystyrene, Polyisocyanates, or Polyurethane, Polyamide, Polylactic Acid, Polycarbonate.

[0078] In resin formulations, low end block polymers, which typically have lower molecular weight, offer a unique set of benefits that contribute to the flexibility, flow properties, and processability of the resin. These low-end blocks, often characterized by their softness and low glass transition temperature (Tg), provide desirable characteristics for applications requiring elasticity, pliability, and ease of processing.

[0079] In the resin formulations, medium end block polymers, which typically have an intermediate molecular weight, play a key role in balancing the rigidity and flexibility of the final resin. These medium-end blocks typically exhibit a blend of the properties of both high-end and low-end blocks, resulting in resins with desirable characteristics for a wide range of applications.

[0080] In the resin formulations, high end block polymers which are typically rigid, high-molecular- weight segments, offer several benefits that can significantly improve the overall properties and performance of the resin system. These benefits are often related to the strength, durability, and stability of the resin, making them suitable for a variety of demanding applications. Here's a breakdown of the key benefits of high-end block polymers in resin formulations.

[0081] In the present invention, alumina as a thixotropic agent in resin formulations offers several key benefits, including enhanced flow control, improved suspension stability, and better mechanical properties and maintaining their viscosity during storage and application, and also providing ease of handling and consistent results. Alumina also contributes to better mechanical strength and abrasion resistance, making it a valuable additive in high- performance formulations.

[0082] In the present invention, silica (Si O2) is used as a thixotropic agent in resin formulations due to its excellent ability to modify the rheological properties of liquids, particularly their viscosity and flow behaviour. Silica, particularly fumed silica (or colloidal silica), is a fine- particle material with a high surface area that can significantly affect the flow characteristics of resins, adhesives, coatings, and other formulations. When used as a thixotropic agent, silica helps create a shear-thinning effect, meaning the material becomes more fluid when subjected to stress (e.g., mixing, brushing, or spraying), but it thickens when at rest, reducing flow and preventing dripping or sagging.

[0083] The present invention also provides synthesis of cross-linked methacrylate monomer (Formula I).

[0084] Formula II Formula III Formula I wherein,

[0085] R is selected from -H, -C2H4OH, -CH2(C6H5), - C2H4 (C6H5) R1is selected from -2(C6H5CH3) C, -CH2(2C6H5), -C2H4, - (C2H4) C (CH3)2

[0086] R2is 2-methylprop-2-enoic acid In the present invention, Compound A, Compound B, Compound C, and Compound D are also cross-linked methacrylate monomers, each synthesized to exhibit low acid values and reduced viscosities, thereby improving their compatibility and performance within the light- curable resin formulation. Further, the present invention also provides the synthesis of cross-linked methacrylate monomer (Formula I) which comprises the following steps:

[0087] Further, the present invention also provides a process for the preparation of light-curable resin formulation, which comprises the following steps:

[0088] In the present invention, Aromatic methacrylate monomers (Formula II) provide a variety of beneficial properties that enhance the performance of the final resin product. These monomers, which typically consist of an aromatic group (such as phenyl or benzyl) attached to a methacrylate functional group, contribute to the resin's mechanical strength, chemical resistance, and thermal stability. Their rigid aromatic structure increases the crosslinking density of the resin network, thereby improving the dimensional stability and resistance to deformation under stress.

[0089] In the present formulation, aromatic methacrylate monomers (Formula II) are used to increase hardness and tensile strength, making them ideal for structural applications where durability is critical. They also enhance the weathering resistance of the resin, improving its UV stability and preventing degradation from prolonged exposure to light and environmental factors. Additionally, these monomers contribute to the adhesion properties of the resin, improving bonding to various substrates.

[0090] In the present invention, aromatic methacrylate monomers (Formula II) are selected from benzyl 2-methylprop-2-enoate, 3 -phenylpropyl 2-methylprop-2-enoate, 2-methylprop-2-enoic acid, 2-hydroxyethyl 2-methylprop-2-enoate.

[0091] Epoxy monomers (Formula III) in the present resin formulations for orthopaedic casts provide several distinct benefits that enhance the overall performance, durability, and comfort of the cast. One of the primary advantages is their superior mechanical strength, which contributes to the rigidity and structural integrity of the cast. This ensures that the orthopaedic device provides optimal support and stabilization to the affected area, essential for effective healing and protection during the recovery process. The low shrinkage of epoxy -based resins during curing further contributes to a precise fit, improving the comfort and effectiveness of the cast.

[0092] Additionally, the chemical resistance of epoxy resins in the present invention makes them ideal for orthopaedic casts, as they are able to withstand exposure to moisture, sweat, and topical medications without degradation. This ensures the long-term durability of the cast, even under challenging conditions, without compromising its protective capabilities.

[0093] According to one embodiment, the epoxy monomers also offer thermal stability, enabling the cast to maintain its integrity even when exposed to temperature fluctuations, ensuring consistent support throughout the healing period. Furthermore, the ease of moulding and customization inherent in epoxy resin systems allows for the creation of casts with complex shapes, improving both the aesthetic appearance and functional fit.

[0094] In the present invention, epoxy monomers (Formula III) is selected from

[0095] 2, 2’-[methylenebis (3,l-phenyleneoxymethylene)]bis(oxirane),

[0096] 2,2’ -[butane- 1, 4-diylbis (oxymethylene)]bis(oxirane),

[0097] 2,2’-[propane-2,2-diylbis(3,lphenyleneoxymethylene)]bis(oxirane),

[0098] 2, 2’-[(2, 2-dimethylbutane-l, 4-diyl)bis(oxymethylene)]bis(oxirane). In the present invention, the organophosphine catalyst is employed to promote the reaction between an aromatic methacrylate monomer containing a carboxylic acid or hydroxyl group and an epoxy-functional monomer. The catalyst accelerates the ring-opening of the epoxide and facilitates the formation of ester linkages, yielding a structurally integrated, crosslinkable monomer system with improved functional uniformity. The use of organophosphine catalysts also offers advantages in terms of selectivity, low byproduct formation, and compatibility with sensitive functional groups such as methacrylate, which can be prone to premature polymerization under harsher catalytic conditions.

[0099] Moreover, organophosphine catalysts are generally thermally stable and can be employed in relatively low concentrations, minimizing contamination or interference with the final product’s performance characteristics. Their effectiveness in non-aqueous, solvent-free, or high-viscosity resin systems makes them especially well-suited for use in advanced polymer and composite material formulations, including those used in dental resins, structural adhesives, and orthopaedic casting systems.

[0100] In the present invention, organophosphine catalysts are selected from dimethylphenylphosphine, triphenylphosphine, tris (2, 4, 6-trimethoxyphenyl) phosphine, tributylphosphine, trimethylphosphine.

[0101] In the present invention, esterification reactions involving sensitive monomers such as epoxyfunctional acrylates or methacrylates, the choice of a high-boiling inert solvent is critical for maintaining system stability while ensuring efficient heat transfer and uniform dispersion of reactants and catalysts. These solvents allow the reaction to proceed at elevated temperatures, 90-95 °C, without degradation or side reactions, and they can often be removed post -reaction by vacuum distillation due to their favourable volatility profiles. Moreover, their chemical inertness ensures that they do not coordinate with catalysts, interfere with reaction intermediates, or initiate premature polymerization, which is especially important in formulations containing unsaturated monomers.

[0102] In the present invention, a high-boiling inert solvent is selected from toluene, xylene, mesitylene, chlorobenzene, anisole, diphenyl ether, N-methylpyrrolidone, dimethyl sulfoxide. In the present invention, completion of the reaction is confirmed by Fourier-transform infrared (FTIR) spectroscopy. The reaction is considered complete when the characteristic absorption band corresponding to the epoxide monomer disappears from the FTIR spectrum, indicating full conversion.

[0103] Example 1: Process for preparation of cross-linked methacrylate monomer Compound A (Formula I)

[0104] Prepare a solution of (50 g) benzyl 2-methylprop-2-enoate in a high-boiling inert (100ml) xylene at 25-30 °C under constant stirring. Add dropwise (40 g) 2, 2’-[methylenebis (3, 1- phenyleneoxymethylene)]bis(oxirane) into the monomer solution at 25-30°C to ensure uniform mixing. Add (0.5 g) triphenylphosphine into the reaction mixture at 25-30°C. The reaction mixture was then gradually heated to 90-95°C and maintained at this temperature for 4-6 hours under a nitrogen atmosphere to facilitate the cross-linking reaction. After reaction complies, the mixture was cooled to 25-30°C, and the solvent was removed by distillation under reduced pressure to get the cross-linked methacrylate monomer Compound A (Formula I).

[0105] Example 2: Process for preparation of cross-linked methacrylate monomer Compound B (Formula I)

[0106] Prepare a solution of (55 g) 3 -phenylpropyl 2-methylprop-2-enoate in a high-boiling inert (150ml) toluene at 25-30°C under constant stirring. Add dropwise (45 g) 2, 2’-[butane-l, 4- diylbis (oxymethylene)]bis(oxirane) into the monomer solution at 25-30°C to ensure uniform mixing. Add (0.25 g dimethylphenylphosphine into the reaction mixture at 25-30°C. The reaction mixture was then gradually heated to 90-95°C and maintained at this temperature for 4-6 hours under a nitrogen atmosphere to facilitate the cross-linking reaction. After reaction complies, the mixture was cooled to 25-30°C, and the solvent was removed by distillation under reduced pressure to get the cross-linked methacrylate monomer Compound B (Formula I).

[0107] Example 3: Process for preparation of cross-linked methacrylate monomer Compound C (Formula I)

[0108] Prepare a solution of (50 g) 2-methylprop-2-enoic acid in a high-boiling inert (100ml) N- methylpyrrolidone at 25-30 °C under constant stirring. Add dropwise (40 g) 2, 2’-[propane- 2, 2-diylbis (3,l-phenyleneoxymethylene)]bis(oxirane) into the monomer solution at 25- 30°C to ensure uniform mixing. Add (0.5 g) triphenylphosphine into the reaction mixture at 25-30°C. The reaction mixture was then gradually heated to 90-95 °C and maintained at this temperature for 4-6 hours under a nitrogen atmosphere to facilitate the cross-linking reaction. After reaction complies, the mixture was cooled to 25-30°C, and the solvent was removed by distillation under reduced pressure to get the cross-linked methacrylate monomer Compound C (Formula I).

[0109] Example 4: Process for preparation of cross-linked methacrylate monomer Compound D (Formula I)

[0110] Prepare a solution of (40 g) 2-hydroxyethyl 2-methylprop-2-enoate in a high-boiling inert (80ml) dimethyl sulfoxide at 25-30°C under constant stirring. Add dropwise (30 g) 2, 2’-[(2, 2-dimethylbutane-l, 4-diyl)bis(oxymethylene)]bis(oxirane) into the monomer solution at 25- 30°C to ensure uniform mixing. Add (0.25 g), trimethylphosphine into the reaction mixture at 25-30°C. The reaction mixture was then gradually heated to 90-95°C and maintained at this temperature for 4-6 hours under a nitrogen atmosphere to facilitate the cross-linking reaction. After reaction complies, the mixture was cooled to 25-30°C, and the solvent was removed by distillation under reduced pressure to get the cross-linked methacrylate monomer Compound D (Formula I).

[0111] Example 5: Process for preparing a formulation of a light-curable resin

[0112] 20% Compound A (Formula I) mixed with 10% ethylene glycol dimethacrylate under a nitrogen atmosphere. After achieving a uniform mixture, 0.1% trimethylbenzoyl-diphenyl- phosphine oxide and 0.5 g of BHT (butylated hydroxytoluene) were added slowly to the base resin mixture under continuous stirring. Maintain the reaction mass at 20-25°C for 30-40 minutes to ensure complete dissolution and homogeneity. Add 5% urea-modified diamide into the resin mixture at 25-30°C, and mixing was continued until a smooth, homogeneous, and light-curable resin composition was obtained.

[0113] Example 6: Process for preparing a formulation of a light-curable resin

[0114] 30% Compound B (Formula I) mixed with 15% triethylene glycol dimethacrylate under a nitrogen atmosphere. After achieving a uniform mixture, 0.5% camphorquinone and 0.5 g of butylated hydroxyanisole were added slowly to the base resin mixture under continuous stirring. Maintain the reaction mass at 20-25 °C for 30-40 minutes to ensure complete dissolution and homogeneity. Add 10% silica into the resin mixture at 25-30°C, and mixing was continued until a smooth, homogeneous, and light-curable resin composition was obtained.

[0115] Example 7: Process for preparing a formulation of a light-curable resin

[0116] 40% Compound C (Formula I) mixed with 20% 2-hydroxy ethyl methacrylate under a nitrogen atmosphere. After achieving a uniform mixture, 1.0% benzil and 0.5 g of hydroquinone, were added slowly to the base resin mixture under continuous stirring. Maintain the reaction mass at 20-25°C for 30-40 minutes to ensure complete dissolution and homogeneity. 20% urea-modified diamide was added to the resin mixture at 25-30°C, and mixing was continued until a smooth, homogeneous, and light-curable resin composition was obtained.

[0117] Example 8: Process for preparing a formulation of a light-curable resin

[0118] 50% Compound D (Formula I) mixed with 25% hexane diol dimethacrylates under a nitrogen atmosphere. After achieving a uniform mixture, 5% 1-phenyl-l, 2-propanedione and 0.5 g of quercetin were added slowly to the base resin mixture under continuous stirring. Maintain the reaction mass at 20-25°C for 30-40 minutes to ensure complete dissolution and homogeneity. Add 25% alumina into the resin mixture at 25-30°C, and mixing was continued until a smooth, homogeneous, and light-curable resin composition was obtained.

[0119] Example 9: Application of synthesized light-curable resin formulation in orthopaedic cast

[0120] The formulated resin is integrated into the orthopedic cast, which consists of a double-layered silicone rubber structure. The resin is enclosed between the top and bottom layers of the silicone rubber, ensuring containment and stability. During application, the cast is wrapped around the patient’s limb, and shaped as needed. Curing is initiated by exposure to visible or UV light, which activates the photoinitiator within the resin. This activation triggers rapid free-radical polymerization of the methacrylate and acrylate components, resulting in a rigid, durable orthopedic cast that hardens within minutes.

[0121] Table 1 : Analytical data of composition, like % Viscosity, Thickness of resin composition, and Comparison of resin composition with curing time

[0122] Table 2: Displays the viscosity of cross-linked methacrylate monomer at different temperatures

[0123] As per Table 1, the curing performance of the light-curable resin formulations was evaluated at a constant thickness of 7 mm and ambient temperature (24 °C) across multiple examples with similar high viscosities. The viscosity values for Examples 5 to 8 ranged narrowly from 235,797.40 to 235,798.70 cps, indicating consistent rheological behavior of the formulations. Correspondingly, the curing time increased incrementally from 8.5 seconds (Example 5) to 10 seconds (Example 8).

[0124] As shown in Table 2, the viscosity of the synthesized cross-linked methacrylate monomer resin demonstrates a strong dependence on temperature. At 24 °C, the resin exhibits a substantially high viscosity of 235,798.70 cps, characteristic of a highly viscous or semi-solid material under ambient conditions. In contrast, upon increasing the temperature to 55-60 °C, the viscosity markedly decreases to 2,402 cps, indicating significantly improved flowability. This pronounced reduction in viscosity with rising temperature confirms the thermoresponsive rheological behavior of the resin. Such a property is particularly advantageous for the processing, mixing, and application of light-curable formulations, where reduced viscosity at elevated temperatures facilitates efficient handling and homogeneity. Furthermore, the data support the applicability of the synthesized cross-linked methacrylate monomer resin in formulations that demand low viscosity during processing while maintaining structural integrity at room temperature.

[0125] The present invention offers a significant advancement in the synthesis of photo-curable resins by reducing reaction time, energy consumption, and production costs, while preserving the critical material properties required for medical-grade applications. Through the strategic use of high-efficiency light initiators, customized UV irradiation protocols, and solvent-free processing conditions, the polymerization of cross-linked methacrylate monomer is substantially accelerated, thereby minimizing thermal energy input and shortening the overall reaction duration. Furthermore, the integration of high-activity catalysts and microwave- assisted reaction techniques enhances the reaction kinetics, contributing to a marked decrease in energy demand. Importantly, these process optimizations do not adversely affect the mechanical strength, biocompatibility, or photo-curing performance of the resulting resin. As a result, the developed methodology ensures the scalable and reproducible production of light-curable resins with robust and reliable material characteristics, suitable for demanding medical and biomedical device applications.

Claims

CLAIMSWe Claim,1. A light curable resin formulation comprising; a) one or more cross-linked methacrylate monomers are present in an amount of 5% to 90% wt;Formula I wherein,RHs selected from -2(C6H5CH3) C, -CH2(2C6H5), -C2H4, - (C2H4) C (CH3)2R2is 2-methylprop-2-enoic acid b) reactive aliphatic acrylate diluent present in amounts of 10% to 30% wt.;wherein,R3can be -H or -CH3, and can also be an alkyl (C1-C12), cyclic (C3-C?), ester, halogen, ether, aryl, or amide group;R4is an alkyl or aryl group, substituted or unsubstituted, ranging from Ci to C33; c) light initiator presents in an amount of 0.1% to 10% wt; and d) thixotropic agents selected from Urea modified diamide, silica, and alumina present in an amount of 0.5% to 25% wt; wherein, the urea-modified diamine thixotropic agent isUrea-modified diamine thixotropic agentR5is -ethylenediamine, 1,2-propanediamine, 1,3-propanediamine, 1,4- butadiamne, 1-5-pentadiamine, 1,6-hexamethylenediamine, neopantadiamine;R6- low-end blocks, medium-end blocks, and high-end blocks with various polarities; wherein, low-end blocks are selected from Polybutadiene, ethylene-butylene, Polypropylene glycol, and Polyethylene;Medium end blocks selected from styrene block, Polypropylene oxide, Poly(tetramethylene glycol), Polylactic Acid-Polyethylene;High-end blocks selected from Polystyrene, Polyisocyanates, or Polyurethane, Polyamide, Polylactic Acid, Polycarbonate.

2. The light curable resin formulation as claimed in claim 1, wherein the reactive aliphatic acrylate diluent is selected from triethylene glycol dimethacrylate, ethylene glycol dimethacrylate, 2-hydroxyethyl methacrylate, and hexane diol dimethacrylates.

3. The light curable resin formulation as claimed in claim 1, wherein the light initiator is selected from trimethylbenzoyl-diphenyl-phosphine oxide, camphorquinone, benzil, 1 -phenyl- 1, 2-propanedione.

4. The light curable resin formulation as claimed in claim 1, where thixotropic agents are selected from Urea modified diamide, silica, and alumina.

5. A synthesis of cross-linked methacrylate monomer (Formula I) comprising the following steps;(a) dissolve aromatic methacrylate monomer (Formula II) in high-boiling inert solvent at 25-30°C;(b) slowly add epoxy monomer (Formula III) into the above monomer solution at 25-30°C;(c) add organophosphine catalyst into the monomer solution at 25-30°C and slowly heat the solution at 90-95°C;(d) maintain the monomer solution at 90-95°C for 4-6 hours;(e) cool the monomer solution at 25-30°C and distill out the solvent to get crosslinked methacrylate monomer (Formula I).Formula II Formula III Formula Iwherein,R is selected from -H, -C2H4OH, -CH2(C6H5), - C2H4 (C6H5)R1is selected from -2(C6H5CH3) C, -CH2(2C6H5), -C2H4, - (C2H4) C (CH3)2R2is 2-methylprop-2-enoic acid6. The process of light-curable resin formulation claimed in claim 5, wherein aromatic methacrylate monomer (Formula II) is selected from benzyl 2-methylprop-2-enoate, 3 -phenylpropyl 2-methylprop-2-enoate, 2-methylprop-2-enoic acid, 2 -hydroxy ethyl 2- methylprop-2-enoate.

7. The process of light-curable resin formulation claimed in claim 5, wherein epoxy monomer (Formula III) is selected from2,2’-[methylenebis (3, l-phenyleneoxymethylene)]bis(oxirane);2,2’ -[butane- 1, 4-diylbis (oxymethylene)]bis(oxirane);2,2’ -[propane-2, 2diylbis (3,lphenyleneoxymethylene)]bis(oxirane);2,2’ -[(2, 2-dimethylbutane-l, 4-diyl)bis(oxymethylene)]bis(oxirane).

8. The process of light-curable resin formulation claimed in claim 5, wherein high- boiling inert solvent is selected from toluene, xylene, mesitylene, chlorobenzene, anisole, diphenyl ether, N-methylpyrrolidone, dimethyl sulfoxide.

9. The process of light-curable resin formulation claimed in claim 5, wherein organophosphine catalyst is selected from dimethylphenylphosphine, triphenylphosphine, tris (2, 4, 6-trimethoxyphenyl) phosphine, tributylphosphine, trimethylphosphine.

10. The process of light-curable resin formulation claimed in claim 5, wherein the ratio between aromatic methacrylate monomer (Formula II) and epoxy monomer (Formula III) is 2: 1.

11. A process for the preparation of the light curable resin formulation comprises the following step:(a) mix cross-linked methacrylate monomer (Formula I) and reactive aliphatic acrylate diluent under an inert atmosphere (under nitrogen);(b) add the light initiator and stabilizer slowly into the base resin mixture under continuous stirring. Ensure uniform dispersion by maintaining for 30-40 minutes at 20-25°C;(c) add thixotropic at 25-30°C into the above resin mixture and blend continuously until a homogeneous, final resin mixture is obtained.

12. The process for the preparation of the light curable resin formulation claimed in claim 11, wherein the stabilizer is selected from butylated hydroxy anisole, butylated hydroxytoluene, hydroquinone, and quercetin.

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