Photosensitive resin easily removed by baking soda and method of making

Abstract

This invention discloses a photosensitive resin that is easily removed by baking soda and its preparation method, aiming to solve the technical problems of existing photosensitive resins during removal, such as the flammability and toxicity of organic solvents, the potential damage to the substrate from strong alkalis, poor water washing effect, and the difficulty in balancing mechanical properties and removability. This photosensitive resin is composed of photocurable components, functional monomers, and photoinitiators compounded in a specific ratio. The functional monomers contain hydrophilic groups and weakly basic responsive groups, which can interact mildly with sodium bicarbonate (baking soda) aqueous solution, achieving efficient removal of the resin before and after curing. The preparation method includes prepolymer synthesis, proportional mixing, room-temperature stirring and dispersion, vacuum degassing, and coating testing steps. The process is simple and easy to scale up. The photosensitive resin of this invention has a fast photocuring speed, high molding precision, and excellent mechanical properties. It can be removed at room temperature with a mild, environmentally friendly, and low-cost baking soda aqueous solution, without the risk of substrate damage. The waste liquid is easy to treat, and it is widely applicable to photocurable 3D printing, photoresist, microelectronic packaging, and other fields, combining environmental friendliness and practicality, and solving many drawbacks of existing technologies.

Description

Technical Field

[0001] This invention relates to the field of photosensitive resin technology, specifically to a photosensitive resin that is easily removed by baking soda and its preparation method. Background Technology

[0002] Photosensitive resins, as core materials in photopolymer 3D printing, photoresists, and microelectronic packaging, are widely used in precision manufacturing, medical dentistry, electronic circuits, and many other industries due to their high-precision molding, rapid curing, and excellent mechanical properties. The basic principle of photopolymerization technology is to use ultraviolet or visible light irradiation to cause photoinitiators in the photosensitive resin to generate free radicals or cations, initiating cross-linking polymerization reactions between monomers and oligomers, thereby achieving a rapid transformation from a liquid to a solid state.

[0003] However, existing photosensitive resin technology still faces many problems that need to be solved in practical applications, especially in the post-treatment removal process, where there are significant deficiencies:

[0004] I. Disadvantages of Traditional Organic Solvent Removal Methods

[0005] Currently, most mainstream methods for removing the uncured portion of photosensitive resin involve cleaning with organic solvents such as alcohol (ethanol), isopropanol, and acetone. These methods have the following serious problems:

[0006] 1. Safety hazards: Most organic solvents are flammable and volatile, posing fire and explosion risks during operation and storage, especially in confined spaces or large-scale industrial production. At the same time, the volatile gases of organic solvents are irritating and toxic to the human respiratory system, nervous system and skin, and long-term exposure can affect the health of front-line workers.

[0007] 2. Environmental pollution: The waste liquid after cleaning contains a large amount of uncured resin, which is classified as hazardous waste and is strictly prohibited from being discharged directly. This waste liquid requires professional institutions to carry out harmless treatment, which not only increases production costs but also faces strict environmental regulations.

[0008] 3. High cost: The price of organic solvents fluctuates greatly, and they need to be replaced and treated regularly. Long-term use will increase production and operating costs.

[0009] II. Limitations of Existing Water Washing Resin Technology

[0010] To address the problems caused by organic solvents, the industry has developed a water-washable photosensitive resin technology. This technology uses water-based monomers and water-based polyurethane resins as raw materials, allowing for direct washing of the uncured portion with water. However, this technology still has the following shortcomings:

[0011] 1. Limited cleaning effect: Although water washing of resin avoids the use of organic solvents, the viscosity of the resin makes it difficult to clean completely, especially in complex structures and tiny gaps where residues are likely to remain, thus affecting product quality.

[0012] 2. Difficult to remove after curing: Completely cured photosensitive resins are difficult to remove gently, whether using traditional solvent-based or water-washable methods. Cured photosensitive resins are thermosetting materials, forming a stable three-dimensional cross-linked network structure that is insoluble in water and common organic solvents.

[0013] 3. Difficulty in balancing mechanical properties and removability: To improve the mechanical properties of water-washable resins, it is often necessary to increase the crosslinking density, which makes them more difficult to remove; conversely, pursuing easy removal will sacrifice the strength and durability of the material.

[0014] III. Defects of the strong alkali solution removal method

[0015] In the fields of microelectronics and photolithography, strongly alkaline aqueous solutions such as sodium hydroxide and potassium hydroxide are sometimes used as developing solutions to remove unexposed photosensitive resin portions. However, this method has the following problems:

[0016] 1. Risk of substrate damage: Strong alkaline solutions are corrosive to various substrates such as metals, glass, and ceramics, which can easily damage the surface of the workpiece and affect the precision and appearance quality of the product.

[0017] 2. Harsh operating conditions: Strong alkaline solutions require strict control of concentration and temperature, and professional protective equipment must be worn during operation, otherwise burns may occur.

[0018] 3. Complex wastewater treatment: The highly alkaline wastewater after use requires neutralization treatment, which increases the process flow and treatment costs.

[0019] IV. Technical Requirements and Objectives of the Invention

[0020] With increasing environmental awareness and increasingly stringent regulations, the industry urgently needs a photosensitive resin material that combines good curing performance with easy removal, capable of being removed using a mild, environmentally friendly, and low-cost baking soda solution while ensuring product precision and mechanical properties.

[0021] This invention addresses the shortcomings of the prior art by providing a photosensitive resin that can be easily removed by baking soda and its preparation method. This allows the photosensitive resin to be efficiently removed by a baking soda aqueous solution before and after curing, while maintaining excellent flexibility and alcohol resistance. Summary of the Invention

[0022] I. Purpose of the Invention

[0023] The purpose of this invention is to provide a photosensitive resin that can be easily removed by baking soda, as well as its preparation and post-treatment methods. This invention balances the photocuring performance, mechanical properties, and ease of removal of the photosensitive resin. It uses a mild, environmentally friendly, and low-cost baking soda aqueous solution to achieve efficient removal of the resin, avoiding the drawbacks of existing removal methods and meeting the needs of industrial-scale production and applications in various fields.

[0024] II. Technical Solution

[0025] (a) Photosensitive resin that is easily removed by baking soda

[0026] The photosensitive resin that is easily removed by baking soda according to the present invention is mainly composed of the following components by weight. The components work synergistically to ensure both excellent photocuring performance and mechanical properties, while also achieving efficient removal by baking soda aqueous solution:

[0027] 1. Prepolymer (photocurable component): 50-80 parts, wherein the prepolymer is a polyurethane acrylate prepolymer, which is the core component of the photocuring reaction of the photosensitive resin. Its molecular structure contains specific functional groups that can undergo a mild interaction with sodium bicarbonate aqueous solution, providing a basis for the easy removal of the resin. The specific composition of the polyurethane acrylate prepolymer is as follows:

[0028] ① Contains a diisocyanate structure, wherein the diisocyanate is selected from one or more of IPDI, TDI-80, HMDI, TMDI, and HDI, and the diisocyanate is used as a raw material for the synthesis of polyurethane acrylate prepolymer. The selection of its type can adjust the reactivity and molecular structure of the prepolymer, thereby affecting the curing performance and ease of removal of the resin.

[0029] ② Contains an acrylate hydroxyl ester structure, wherein the acrylate hydroxyl ester is selected from one or more of hydroxyethyl acrylate (HEA), pentaerythritol triacrylate (PETA), hydroxypropyl acrylate (HPA), hydroxyethyl methacrylate (HEMA), and hydroxypropyl methacrylate (HPMA). The acrylate hydroxyl ester participates in the synthesis reaction of the prepolymer, introducing acrylic double bonds to ensure the photocurability of the prepolymer. Simultaneously, the hydroxyl groups it contains enhance the hydrophilicity of the prepolymer, facilitating the removal of the resin by the baking soda solution. ③ Simultaneously, the molecular structure contains at least one functional structure selected from polyether, polyester, or polycarbonate polyol. This type of structure can balance the bulk properties of the resin with its removability in the baking soda solution.

[0030] 2. 20-45 parts of reactive diluent (functional monomer) are used to adjust the viscosity of the photosensitive resin and participate in the photocuring reaction, improving the crosslinking density and mechanical properties of the resin. Its hydrophilic properties further enhance the interaction between the resin and the sodium bicarbonate solution, optimizing the removal effect. The reactive diluent contains one or more of THFA, ACMO, β-CEA, HDDA, HPMA, HPA, HEMA, and HEA. This type of reactive diluent possesses good solubility, photocuring activity, and hydrophilicity, effectively adjusting the resin viscosity, promoting the uniform dispersion of prepolymers and photoinitiators, and enhancing the compatibility of the resin with the sodium bicarbonate solution, thereby improving removal efficiency.

[0031] 3. 1-6 parts of photoinitiator, which can rapidly generate free radicals under light irradiation, initiating cross-linking polymerization of the prepolymer and reactive diluent, achieving a rapid transformation of the resin from liquid to solid state. The photoinitiator is selected from one or a mixture of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO), Irgacure 819, and Irgacure 184. This type of photoinitiator has the characteristics of fast photoresponse speed, high initiation efficiency, and good compatibility. It can rapidly initiate resin curing under light irradiation without affecting the interaction between the resin and the sodium bicarbonate aqueous solution, ensuring the easy removal of the resin.

[0032] (II) Preparation method of photosensitive resin

[0033] The preparation method of the photosensitive resin that is easily removed by baking soda according to the present invention is simple, convenient to operate, and easy to scale up for production. Specifically, it includes the following steps:

[0034] 1. Synthesis of polyurethane acrylate prepolymer: First, diisocyanate and polyol are placed in a reaction vessel, and one or two of the following catalysts are used in combination: dibutyltin dilaurate, dibutyltin dilaurate, stannous octoate, triethylamine, and triethylenediamine. The reaction is carried out at 60-80℃ for 2-3 hours to ensure complete reaction of diisocyanate and polyol. Then, hydroxyl acrylate is added, and the reaction is continued at the above temperature for 2-3 hours. During the reaction, continuous monitoring is performed, and Fourier transform infrared spectroscopy is used to test for NCO group residue. When no infrared peak corresponding to NCO group is detected, the reaction is considered complete, and polyurethane acrylate prepolymer is obtained. It is then cooled to room temperature for later use.

[0035] 2. Preparation of photosensitive resin by mixing: Accurately weigh the prepolymer, reactive diluent, and photoinitiator prepared above according to the specified weight proportions, and add them to the reactor; under nitrogen protection at 45-65℃, stir at a stirring rate of 150-300 r / min for 30-60 min until all components are mixed evenly; during the stirring process, use light-protected conditions to avoid premature decomposition of the photoinitiator, which would affect the photocuring performance of the resin; after mixing evenly, filter the mixture through a 200-400 mesh filter to remove impurities from the system, and then perform vacuum degassing treatment to remove air bubbles from the system, finally obtaining a photosensitive resin that is easily removed by baking soda.

[0036] (III) Post-treatment methods for photosensitive resins

[0037] The post-treatment method for photosensitive resin described in this invention is simple and gentle, and can quickly remove the cured resin without damaging the substrate. The specific steps are as follows:

[0038] 1. The prepared photosensitive resin is coated onto a PET release film, and then irradiated with a mercury lamp to cure the resin under an energy condition of 500-2500 mJ / cm² to obtain a cured film. The cured film is placed in a 3-10% sodium bicarbonate aqueous solution and immersed for 5-15 minutes at room temperature or 20-50℃. During the immersion process, the sodium bicarbonate aqueous solution interacts gently with the cured film, causing the film to swell fully and eventually detach completely, achieving efficient removal of the resin.

[0039] 2. Meanwhile, the photosensitive resin of the present invention has good performance after curing: excellent flexibility, no breakage after being folded more than 15 times; good alcohol resistance, no discoloration, blistering, or peeling after being wiped with alcohol, which can meet the practical application needs of various fields.

[0040] III. Beneficial Effects

[0041] Compared with the prior art, the present invention has the following significant advantages:

[0042] 1. The photosensitive resin of this invention can be efficiently removed using a mild, environmentally friendly, and low-cost sodium bicarbonate aqueous solution. Both the uncured portion and the cured film can be quickly swollen and removed under mild conditions, avoiding the drawbacks of traditional organic solvents being flammable and toxic, and strong alkaline solutions corroding the substrate. The safety and environmental friendliness are significantly improved.

[0043] 2. By rationally selecting the types and ratios of prepolymer, reactive diluent, and photoinitiator, a balance is achieved between the resin's photocurability, mechanical properties, and ease of removal. It features fast curing speed, high molding precision, and good flexibility and alcohol resistance after curing, meeting the application requirements of various fields.

[0044] 3. The preparation method is simple and easy to operate, requiring no complex equipment or harsh reaction conditions. Parameters such as stirring rate and reaction temperature are easy to control, facilitating large-scale industrial production and reducing production costs.

[0045] 4. The post-treatment method is simple and easy to implement. It can be completed at room temperature or a low temperature without the need for professional protective equipment. The waste liquid can be treated by simple dilution or neutralization, resulting in low treatment costs and conforming to the green and environmentally friendly industrial development trend.

[0046] 5. Baking soda is readily available and inexpensive, which significantly reduces the cost of resin removal and avoids pollution problems caused by organic solvent waste liquid and strong alkali waste liquid. It is both practical and environmentally friendly, and has broad application prospects. Example

[0047] Example 1. A photosensitive resin that is easily removed by baking soda, with the following components by weight:

[0048] The diisocyanate used is HDI and TDI-80, the hydroxyl acrylate used is HPA, and 75 parts of polyurethane acrylate prepolymer containing ether bonds are used.

[0049] 10 parts of reactive diluent THFA;

[0050] 15 parts of reactive diluent ACMO;

[0051] Photoinitiator Irgacure 184, 3 parts;

[0052] Two parts of photoinitiator TPO;

[0053] Preparation method: Weigh the polyurethane acrylate prepolymer containing ether bonds, THFA, ACMO, Irgacure 184 and TPO and add them to an opaque reactor. Stir at 220 r / min for 35 min at 50℃ under nitrogen protection until homogeneous. Filter through a 300 mesh screen to obtain the photosensitive resin.

[0054] Post-processing: The obtained photosensitive resin was coated onto a PET release film, and then cured under a mercury lamp at 1000 mJ / cm² energy. The resulting film was then immersed in a 5% sodium bicarbonate aqueous solution at 25°C for 10 minutes. After immersion, the film completely swelled and peeled off. Furthermore, after curing, it showed no breakage after being folded 25 times, and no discoloration, bubbling, or peeling was observed after wiping with alcohol.

[0055] Example 2. A photosensitive resin that is easily removed by baking soda, with the following components by weight:

[0056] The diisocyanate used is HMDI, IPDI, and TDI-80; the hydroxyl acrylate used is HEA and PETA; and 60 parts of polyurethane acrylate prepolymer containing ether bonds are used.

[0057] 10 parts of reactive diluent THFA;

[0058] 15 parts of reactive diluent HDDA;

[0059] 15 parts of reactive diluent HEA;

[0060] 1 part of photoinitiator Irgacure 819;

[0061] 1 part of photoinitiator TPO;

[0062] Preparation method: Weigh the polyurethane acrylate prepolymer containing ether bonds, THFA, HDDA, HEA, Irgacure819 and TPO and add them to an opaque reactor. Stir at 220 r / min for 35 min at 50℃ under nitrogen protection until homogeneous. Filter through a 300 mesh screen to obtain the photosensitive resin.

[0063] Post-processing: The obtained photosensitive resin was coated onto a PET release film and then cured under a mercury lamp at 2000 mJ / cm². The resulting film was then immersed in a 5% sodium bicarbonate solution at 25°C for 10 minutes. After immersion, the film completely swelled and peeled off. Furthermore, after curing, it showed no breakage after being folded 20 times, and no discoloration, bubbling, or peeling was observed after wiping with alcohol.

[0064] Example 3. A photosensitive resin that is easily removed by baking soda, with the following components by weight:

[0065] The diisocyanate used is TDI-80, the hydroxy acrylate used is HPMA, HEMA and PETA, and 65 parts of polyurethane acrylate prepolymer with ester bonds are used.

[0066] 35 parts of reactive diluent β-CEA;

[0067] Photoinitiator Irgacure 184, 2 parts;

[0068] Two parts of photoinitiator TMO;

[0069] Preparation method: Weigh the polyurethane acrylate prepolymer containing ether bonds, β-CEA, Irgacure 184 and TMO into an opaque reactor, stir at 300 r / min for 45 min at 50℃ under nitrogen protection until homogeneous, filter through a 300 mesh screen to obtain photosensitive resin.

[0070] Post-processing: The obtained photosensitive resin was coated onto a PET release film and then cured under a mercury lamp at 1000 mJ / cm² energy. The resulting film was then immersed in a 10% sodium bicarbonate solution at 50°C for 5 minutes. After immersion, the film completely swelled and peeled off. Furthermore, after curing, it showed no breakage after being folded 15 times, and no discoloration, bubbling, or peeling was observed after wiping with alcohol.

[0071] Example 4. A photosensitive resin that is easily removed by baking soda, with the following components by weight:

[0072] The diisocyanate used is TMDI, the hydroxy acrylate used is HPA and HEA, and 55 parts of polyurethane acrylate prepolymer containing carbonate bonds are used.

[0073] 20 parts of reactive diluent β-CEA;

[0074] 5 parts of reactive diluent HPMA;

[0075] 20 parts of active diluent ACMO

[0076] 3 parts of photoinitiator TMO;

[0077] Preparation method: Weigh polyurethane acrylate prepolymer containing ether bonds, β-CEA, HPMA, ACMO and TMO into an opaque reactor, stir at 300 r / min for 55 min at 60℃ under nitrogen protection until homogeneous, filter through a 300 mesh screen to obtain photosensitive resin.

[0078] Post-processing: The obtained photosensitive resin is coated onto a PET release film and then cured under a mercury lamp at an energy of 1500 mJ / cm². The resulting film is then immersed in a 10% sodium bicarbonate solution at 50°C for 5 minutes. After immersion, the film completely swells and peels off. Furthermore, after curing, it can be folded 20 times without breakage, and after wiping with alcohol, there is no discoloration, bubbling, or peeling.

Claims

1. A photosensitive resin that is easily removed by baking soda, characterized in that, By weight, it includes the following components: Prepolymer (photocurable component): 50-80 parts; Reactive diluent (functional monomer) 20-45 parts; Photoinitiator 1-6 parts; The prepolymer is a polyurethane acrylate prepolymer.

2. The polyurethane acrylate prepolymer according to claim 1 further includes a diisocyanate structure, wherein the diisocyanate structure is one or a mixture of IPDI, TDI-80, HMDI, TMDI, and HDI.

3. The polyurethane acrylate prepolymer according to claim 1 further includes a hydroxy acrylate structure, wherein the hydroxy acrylate structure is one or a mixture of hydroxyethyl acrylate (HEA), pentaerythritol triacrylate (PETA), hydroxypropyl acrylate (HPA), hydroxyethyl methacrylate (HEMA), and hydroxypropyl methacrylate (HPMA).

4. The polyurethane acrylate prepolymer according to claim 1 contains at least one structure selected from polyether, polyester, or polycarbonate polyol.

5. The reactive diluent according to claim 1 comprises one or more of THFA, ACMO, β-CEA, HDDA, HPMA, HPA, HEMA, and HEA.

6. The photoinitiator according to claim 1 is selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO), Irgacure 819, and Irgacure 184, or a mixture thereof.

7. A method for preparing a photosensitive resin easily removable by baking soda as described in any one of claims 1-7, characterized in that, Includes the following steps: (a) Synthesis of polyurethane acrylate prepolymer: First, diisocyanate, polyol, and catalyst are reacted at 60-80℃ for 2-3 hours. Then, hydroxyl acrylate is added and reacted for another 2-3 hours. Finally, Fourier transform infrared spectroscopy is used to test for residual NCO groups. If no corresponding infrared peak is observed, the reaction is considered complete. (b) Weigh the prepolymer, reactive diluent, and photoinitiator according to the weight proportions, add them to the reactor, and stir for 30-60 minutes under nitrogen protection at 45-65℃ until they are evenly mixed; then filter with a 200-400 mesh filter to remove impurities, and degas under vacuum to obtain a photosensitive resin that is easily removed by baking soda.

8. The preparation method according to claim 7, characterized in that... The catalyst used in step (a) is one or a mixture of two of the following: dibutyltin dilaurate, dibutyltin dilaurate, stannous octoate, triethylamine, and triethylenediamine, with an addition amount of 100ppm-600ppm.

9. The preparation method according to claim 7, characterized in that... In step (b), the stirring rate is 150-300 r / min; at the same time, light-protected conditions are used during the stirring process to avoid premature decomposition of the photoinitiator.

10. A post-treatment method for the photosensitive resin according to any one of claims 1-6, characterized in that, Photosensitive resin is coated onto a PET release film and then cured under a mercury lamp at an energy of 500-2500 mJ / cm². The cured film is then immersed in a 3-10% sodium bicarbonate solution at room temperature or 20-50℃ for 5-15 minutes. After immersion, the cured film can completely swell and peel off. Simultaneously, after curing, it exhibits good flexibility (no breakage after being folded at least 15 times) and good alcohol resistance (no discoloration, bubbling, or peeling after wiping with alcohol).