A low-viscosity high-heat-resistant sls photocuring 3D printing resin composition and a preparation method thereof

Abstract

The application discloses a low-viscosity high-heat-resistant SLA photocuring 3D printing resin composition and a preparation method thereof, which comprises the following components in proportion by weight: a cationic photocuring component selected from alicyclic epoxy resin, which provides a rigid skeleton and high heat resistance; a free radical photocuring component selected from an oligomer with an acrylate functional group, which provides cross-linking enhancement; an active diluent selected from a monofunctional or difunctional acrylate monomer; a free radical photoinitiator selected from a Norrish I type photoinitiator; a cationic photoinitiator selected from an aromatic sulfonium salt or an iodonium salt; a toughening modifier, which improves brittleness; and an auxiliary agent. The application belongs to the technical field of stereolithography photocuring 3D printing materials, and can have the following comprehensive performances: low viscosity, which is beneficial to rapid leveling and rapid curing to improve printing efficiency; high mechanical properties, which meet terminal use; and high heat distortion temperature, which adapts to high-temperature working conditions.

Description

Technical Field

[0001] This invention belongs to the field of stereolithography photopolymerization 3D printing materials technology, specifically relating to resin compositions for stereolithography 3D printing and their preparation methods. Background Technology

[0002] Stereolithography (SLA) was the first 3D printing technology to achieve commercial application. With its advantages of high forming accuracy, good surface quality, and ability to fabricate complex structures, it is widely used in medical devices, automotive industry, aerospace, precision molds and other fields.

[0003] However, existing SLA photosensitive resins still have the following technical defects, which restrict their promotion in engineering applications: (1) High viscosity affects printing efficiency and accuracy. Existing SLA photosensitive resins generally have a high viscosity, resulting in poor flowability and difficulty in quickly leveling the resin during printing. This affects the quality of interlayer bonding and molding accuracy, while also increasing the operating load on the equipment. Research shows that developing low-viscosity photosensitive resins is one of the key issues in SLA technology.

[0004] Currently, the viscosity of commercially available SLA resins at 25°C is typically in the range of 400-800 mPa·s, with some products having even higher viscosity, making it difficult to meet the needs of rapid printing.

[0005] (2) Insufficient mechanical properties limit end-use applications. Most photosensitive resins are brittle and prone to breakage after photocuring, which limits their application in many fields.

[0006] Currently, the tensile strength of commercially available SLA resins is typically between 30-56 MPa, and the flexural strength is mostly between 80-150 MPa, which is insufficient to meet the high strength requirements of engineering-grade functional components.

[0007] (3) Low heat distortion temperature and poor heat resistance The heat distortion temperature (HDT) of conventional SLA resins is generally low, usually in the range of 46-60 (0.45MPa), and they are prone to softening and deformation at high temperatures.

[0008] Although there are some high-temperature resistant SLA resin products on the market (HDT can reach 118-138℃), they often come at the cost of printing efficiency and toughness, making it difficult to meet the needs of fast printing and high mechanical properties.

[0009] (4) It is difficult to achieve both fast printing and high performance. SLA printing speed is limited by the curing speed of the resin, and increasing the amount of photoinitiator or using a highly active resin system often leads to increased shrinkage and brittleness.

[0010] Therefore, there is an urgent need to develop a low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition and its preparation method to solve the problems in the existing technology. Summary of the Invention

[0011] The purpose of this invention is to provide a low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition and its preparation method. This composition possesses comprehensive properties, including low viscosity for rapid leveling, rapid curing to improve printing efficiency, high mechanical properties to meet end-use requirements, and high heat distortion temperature to adapt to high-temperature conditions. It also has a simple structure and is easy to use, thus solving the problems mentioned in the background art, such as high viscosity, insufficient mechanical properties, low heat distortion temperature, and difficulty in achieving both rapid printing and high performance.

[0012] To achieve the above objectives, the present invention provides the following technical solution: A low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition comprises the following components by weight: 30-60 parts of cationic photocurable component, selected from alicyclic epoxy resin; 15-40 parts of free radical photocurable component, selected from oligomers with acrylate functional groups; 10-35 parts of reactive diluent, selected from monofunctional or difunctional acrylate monomers; 0.5-5 parts of free radical photoinitiator, selected from Norrish type I photoinitiators; 0.5-5 parts of a cationic photoinitiator, selected from aromatic thioonium salts or iodonium salts; Toughening modifier 1-10 parts; Additives: 0.1-3 parts; The resin composition has a viscosity of no more than 400 mPa·s at 25°C and a heat distortion temperature of no less than 77°C after curing. The cationic photocurable component, the free radical photocurable component, and the toughening modifier work together to achieve a balance between high strength and moderate toughness. The expansion effect of cationic ring-opening polymerization offsets the volume shrinkage of free radical polymerization to ensure dimensional accuracy.

[0013] By adopting the above technical solution, and by compounding cationic and free radical photocurable components and toughening modifiers, a balance is achieved between low viscosity, rapid curing, high strength, moderate toughness and high heat resistance, while the expansion effect is used to offset shrinkage and ensure dimensional accuracy.

[0014] As a further aspect of the present invention: the cationic photocurable component is selected from one or more of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate, bis(3,4-epoxycyclohexylmethyl)adipic acid ester, and 3-ethyl-3-oxabutane methanol.

[0015] By adopting the above technical solution, the cationic photocurable component is defined, and its characteristics of low ring-opening polymerization shrinkage and high crosslinking density are utilized to construct a rigid skeleton, thereby improving the heat resistance and dimensional stability of the cured product.

[0016] As a further aspect of the present invention: the free radical photocuring component is selected from one or more of epoxy acrylate, polyurethane acrylate, and polycarbonate acrylate.

[0017] By adopting the above technical solution, the free radical photocuring component is defined, and the rapid curing and cross-linking enhancement characteristics of multifunctional acrylates are utilized to provide the cured product with good mechanical properties and surface hardness.

[0018] As a further aspect of the present invention: the reactive diluent is selected from one or more of tetrahydrofuran acrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, acryloylmorpholine, and m-phenoxybenzyl acrylate.

[0019] By adopting the above technical solution, the reactive diluent is limited, effectively adjusting the viscosity of the resin system to meet printing requirements, and participating in curing and cross-linking to improve the overall cross-linking density of the system.

[0020] As a further aspect of the present invention: the free radical photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxycyclohexylphenyl ketone.

[0021] By adopting the above technical solution, a free radical photoinitiator is specified, which has high absorption efficiency for laser light sources of specific wavelengths, ensuring rapid and sufficient initiation of free radical polymerization reactions.

[0022] As a further aspect of the present invention: the cationic photoinitiator is selected from one or more of triarylthionium hexafluorophosphate, triarylthionium hexafluoroantimonate, and diphenyl-(4-phenylthio)phenylthiohexafluorophosphate.

[0023] By adopting the above technical solution, the cationic photoinitiator is limited to effectively initiate cationic ring-opening polymerization and form a hybrid curing network in combination with the free radical system.

[0024] As a further aspect of the present invention: the toughening modifier is selected from one or more of core-shell toughening modified resin, carboxyl-terminated liquid nitrile rubber, and hydroxyl-terminated liquid nitrile rubber.

[0025] By adopting the above technical solution, the toughening modifier is limited, and the elongation at break and impact resistance of the cured product are effectively improved and the brittleness is reduced without significantly increasing the viscosity and affecting the modulus.

[0026] As a further aspect of the present invention: the resin composition, after curing, has a tensile strength of not less than 60 MPa, a flexural strength of not less than 120 MPa, and a volume shrinkage rate of not more than 2.5%; the additives include leveling agents, defoamers, and polymerization inhibitors, specifically including polyether-modified silicone leveling agents, silicone defoamers, and hydroquinone polymerization inhibitors.

[0027] By adopting the above technical solution, the additives and key performance parameters were defined, the leveling, defoaming and storage properties of the resin were improved, and the final technical effect of low viscosity, high strength and high heat resistance of the cured product was clarified.

[0028] A method for preparing a low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition includes the following steps: S1: Weigh each component according to the weight percentages; S2: Add each component to a light-proof container and stir until homogeneous at room temperature to 50°C; S3: Vacuum degassing treatment yields a low-viscosity, high-heat-resistant SLA photopolymerizable 3D printing resin composition.

[0029] By adopting the above technical solution, it is ensured that the components are mixed uniformly under light-protected conditions and that air bubbles are effectively eliminated, thereby obtaining a stable resin suitable for 3D printing.

[0030] As a further aspect of the present invention: in step S2, the stirring speed is 300-500 rpm and the time is 1-3 hours; in step S3, the vacuum degree of vacuum degassing does not exceed 0.1 MPa and the time is 20-40 minutes.

[0031] By adopting the above technical solution, the specific parameters of the preparation process are defined, ensuring thorough mixing and degassing, and guaranteeing the final quality and printing applicability of the resin composition.

[0032] Compared with the prior art, the beneficial effects of the present invention are: 1. Through the optimized ratio of cationic-free radical hybrid system and reactive diluent, the resin composition of this invention has a viscosity of ≤400mPa·s at 25°C, which is comparable to commercially available industrial-grade SLA rapid printing resin (U-9100A, 350mPa·s) and significantly superior to conventional SLA resin. The low viscosity ensures rapid resin leveling during printing, shortens the printing interval between each layer, is suitable for high-speed doctor blade coating processes, and improves printing efficiency. 2. This invention forms a high-crosslink density interpenetrating network through free radical-cationic hybrid curing. The cationic component provides a rigid framework, the free radical component provides crosslinking reinforcement, and the toughening modifier improves brittleness. The three work synergistically to achieve a balance between high strength and moderate toughness. After curing, the tensile strength of the resin can reach 60-80 MPa (ASTM D638), and the flexural strength can reach 120-150 MPa (ASTM D790), reaching the level of commercially available high-performance SLA resins. 3. This invention endows the cured product with excellent heat resistance through the rigid structure of alicyclic epoxy resin. The heat distortion temperature (HDT, 1.82MPa) can reach 77-130℃, which is significantly better than conventional SLA resin (46-60℃) and close to the level of commercially available high-temperature resistant SLA resin (118-138℃). It is suitable for engineering applications such as automotive parts and electronic appliance housings that require high temperature resistance. 4. The photoinitiator system optimized for 355nm laser light sources in this invention exhibits high photosensitivity, with a critical exposure energy (Ec) ≤ 6mJ / cm². 2 With a curing depth (Dp) of less than 0.16mm, it can achieve full curing under low exposure, significantly shortening the single-layer exposure time and improving printing efficiency; 5. This invention effectively counteracts the volume shrinkage of free radical polymerization through the expansion effect of cationic ring-opening polymerization, with a curing shrinkage rate of ≤2.5%, ensuring the dimensional accuracy of printed parts and the shape retention of complex structures.

[0033] Other features and advantages of the present invention will be disclosed in detail in the following specific embodiments and accompanying drawings. Attached Figure Description

[0034] Figure 1 This is a schematic flowchart illustrating the steps of a method for preparing a low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition according to an embodiment of the present invention. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] In this embodiment of the invention, a low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition and its preparation method are described below. Figure 1 As shown, it comprises the following components by weight: The cationic photocurable component, selected from alicyclic epoxy resins, provides a rigid framework and high heat resistance; The free radical photocurable component, selected from oligomers with acrylate functional groups, provides crosslinking reinforcement; The reactive diluent is selected from monofunctional or difunctional acrylate monomers; Free radical photoinitiator, selected from Norrish type I photoinitiators; The cationic photoinitiator is selected from aromatic thioonium salts or iodonium salts; Toughening modifiers improve brittleness; Additives; Specifically, it includes the following: 1. Resin composition formulation The photopolymerizable 3D printing resin composition provided by this invention comprises the following components by weight:

[0037] The sum of the weight parts of each component is 100 parts.

[0038] 2. Cationic photocurable components It is selected from alicyclic epoxy resins or compounds containing epoxy groups. Alicyclic epoxy resins have the characteristics of low ring-opening polymerization shrinkage, high crosslinking density of cured products, high rigidity, and good heat resistance, and are key components for improving the heat distortion temperature and dimensional stability of resins.

[0039] Preferred options include, but are not limited to, one or more of the following: 3,4-Epoxycyclohexylmethyl-3,4-epoxycyclohexylcarboxylate (such as CY179, UVR-6105); Bis(3,4-epoxycyclohexylmethyl) adipate (e.g., UVR-6128); 3-Ethyl-3-oxabutane methanol; Itaconic acid-based epoxy resin (EIA) The epoxy equivalent of the alicyclic epoxy resin is preferably 130-200 g / eq, and the viscosity at 25°C is preferably 200-600 mPa·s.

[0040] 3. Free radical photocuring components The polymer is selected from oligomers containing (meth)acrylate functional groups, preferably multifunctional acrylates that combine rapid curing and crosslinking enhancement properties. The radical component provides rapid curing capability, complementing the cationic component to ensure printing efficiency.

[0041] Preferred options include, but are not limited to, one or more of the following: Epoxy acrylate (EA): Offers high hardness, high gloss, and rapid curing properties; Polyurethane acrylate (PUA): Offers good toughness and abrasion resistance; Polycarbonate acrylate: provides excellent resistance to damp heat and dimensional stability; Hyperbranched acrylates: offer excellent flexibility, adhesion and low shrinkage.

[0042] 4. Reactive diluent Acrylic monomers selected from low-viscosity monofunctional, difunctional, or polyfunctional monomers are used to adjust the viscosity of the resin system and participate in curing and crosslinking to increase the crosslinking density.

[0043] Preferred options include, but are not limited to, one or more of the following: Tetrahydrofuran acrylate (THFA); Tripropylene glycol diacrylate (TPGDA); 1,6-Hexanediol diacrylate (HDDA); Acryloylmorpholine (ACMO); m-Phenoxybenzyl acrylate; Pentaerythritol triacrylate (PETA); Trimethylolpropane triacrylate (TMPTA) The amount of reactive diluent added is controlled at 10-35 parts to ensure that the viscosity of the system meets the requirements of SLA printing (viscosity ≤400mPa·s at 25℃) without affecting the mechanical properties and heat resistance of the final cured product.

[0044] 5. Photoinitiator system To address the characteristics of the 355nm laser source in SLA equipment, a composite system of free radical photoinitiator and cationic photoinitiator was adopted: Free radical photoinitiator: selected from Norrish type I photoinitiators with high absorption efficiency at a wavelength of 355 nm, preferably including: 2,4,6-Trimethylbenzoyl-diphenylphosphine oxide (TPO); Phenylacetylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819); 2-Hydroxy-2-methyl-1-phenylpropanone (1173); 1-Hydroxycyclohexylphenyl ketone (184).

[0045] Cationic photoinitiators: selected from aromatic thioonium or iodonium salts, including: Triarylsulfonium hexafluorophosphate; Triarylsulfonium hexafluoroantimonate; Diphenyl-(4-phenylthio)phenylthiohexafluorophosphate (mixed salt 1176).

[0046] The weight ratio of free radical initiator to cationic initiator is preferably 1:0.5 to 1:2, and the total amount is controlled at 1-8 parts.

[0047] 6. Toughening modifier To address the issue of high brittleness caused by high crosslinking density, toughening modifiers are introduced to improve the resin's toughness and impact resistance. Preferred modifiers include: Core-shell toughened modified resin: does not affect modulus and glass transition temperature, and does not significantly increase viscosity; Carboxyl-terminated liquid nitrile butadiene rubber (CTBN): effectively improves elongation at break and impact strength.

[0048] The addition of toughening modifiers increases the elongation at break to the range of 3-8%, balancing high strength and moderate toughness.

[0049] 7. Additives These include leveling agents (such as BYK-373), defoamers (such as BYK-055), and polymerization inhibitors, which are used to improve the leveling properties, defoaming performance, and storage stability of resins.

[0050] This invention also discloses a method for preparing a low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition. Weigh the above components according to the weight proportions, place them in a light-proof container, and stir and mix them evenly at room temperature to 50°C (stirring speed 300-500 rpm, time 1-3 hours). Then, perform vacuum degassing treatment (vacuum degree ≤0.1MPa, time 20-40 minutes) or allow them to degas naturally to obtain a low viscosity, high heat resistance SLA photocurable 3D printing resin composition.

[0051] Example 1 This embodiment specifically includes the following:

[0052] Weigh each component according to the following parts by weight: Add the above components to a light-proof container and stir at 45°C and 400 rpm for 2 hours until the mixture is homogeneous. Then, perform vacuum degassing treatment for 30 minutes (vacuum degree ≤ 0.1 MPa) to obtain the resin composition.

[0053] Performance testing:

[0054] SLA-3D printing verification: The above resin composition was loaded into an industrial-grade SLA-3D printer (light source wavelength 355nm), with a scanning speed of 6m / s, laser power of 800mW, scanning spacing of 0.1mm, and a single-layer curing thickness of 50μm. Standard test models (including precision test pieces, tensile specimens, bending specimens, and heat deformation test strips) were printed. The printing process was smooth, without warping, interlayer delamination, or other problems. The printed parts had smooth surfaces and clear details. After cleaning and post-curing, the test performance of the printed parts was consistent with the above data.

[0055] Example 2 In this embodiment, the following specific steps are included: Weigh each component according to the following weight proportions:

[0056] The sample was prepared and tested according to the method in Example 1, and the results are as follows:

[0057] In this embodiment, polycarbonate acrylate is used to replace part of PUA, and a multifunctional reactive diluent is used, which further improves the heat resistance and makes it suitable for applications with higher temperature conditions.

[0058] Example 3 In this embodiment, the following specific steps are included: Weigh each component according to the following weight proportions:

[0059] The sample was prepared and tested according to the method in Example 1, and the results are as follows:

[0060] Comparative Example 1 The technical difference between this comparative example and Example 1 is that this example uses commercially available conventional SLA photosensitive resin and is tested using the same method:

[0061] As can be seen from the comparison, the resin viscosity of the present invention is reduced by 36%, the tensile strength is increased by 60%, the flexural strength is increased by 43%, and the heat distortion temperature is increased by 106%, and the overall performance is significantly better than that of conventional products.

[0062] Comparative Example 2 The technical feature that distinguishes this comparative example from Example 1 is that this example uses a pure free radical system SLA resin; A pure free radical system was prepared according to the following formula: 50 parts epoxy acrylate, 30 parts TPGDA, 10 parts TMPTA, 4 parts TPO, and 1843 parts. The system was prepared and tested according to the method in Example 1.

[0063] As can be seen from the comparison, the shrinkage rate of the pure free radical system without cationic components is significantly higher and the heat distortion temperature is lower, making it difficult to meet the requirements of high-precision heat-resistant applications.

[0064] This invention provides a low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition and its preparation method, which has comprehensive properties such as low viscosity for rapid leveling, rapid curing to improve printing efficiency, high mechanical properties to meet end-use requirements, and high heat distortion temperature to adapt to high-temperature working conditions.

[0065] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0066] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition, characterized in that, The following components are included by weight: 30-60 parts of cationic photocurable component, selected from alicyclic epoxy resin; 15-40 parts of free radical photocurable component, selected from oligomers with acrylate functional groups; 10-35 parts of reactive diluent, selected from monofunctional or difunctional acrylate monomers; 0.5-5 parts of free radical photoinitiator, selected from Norrish type I photoinitiators; 0.5-5 parts of a cationic photoinitiator, selected from aromatic thioonium salts or iodonium salts; Toughening modifier 1-10 parts; Additives: 0.1-3 parts; The resin composition has a viscosity of no more than 400 mPa·s at 25°C and a heat distortion temperature of no less than 77°C after curing.

2. The resin composition according to claim 1, characterized in that, The cationic photocurable component is selected from one or more of 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexylcarbamate, bis(3,4-epoxycyclohexylmethyl)adipic acid ester, and 3-ethyl-3-oxabutane methanol.

3. The resin composition according to claim 1, characterized in that, The free radical photocurable component is selected from one or more of epoxy acrylate, polyurethane acrylate, and polycarbonate acrylate.

4. The resin composition according to claim 1, characterized in that, The reactive diluent is selected from one or more of tetrahydrofuran acrylate, tripropylene glycol diacrylate, 1,6-hexanediol diacrylate, acryloylmorpholine, and m-phenoxybenzyl acrylate.

5. The resin composition according to claim 1, characterized in that, The free radical photoinitiator is selected from one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxycyclohexylphenyl ketone.

6. The resin composition according to claim 1, characterized in that, The cationic photoinitiator is selected from one or more of triarylthionium hexafluorophosphate, triarylthionium hexafluoroantimonate, and diphenyl-(4-phenylthio)phenylthiohexafluorophosphate.

7. The resin composition according to claim 1, characterized in that, The toughening modifier is selected from one or more of the following: core-shell toughening modified resin, carboxyl-terminated liquid nitrile rubber, and hydroxyl-terminated liquid nitrile rubber.

8. The resin composition according to claim 1, characterized in that, The resin composition, after curing, has a tensile strength of not less than 60 MPa, a flexural strength of not less than 120 MPa, and a volume shrinkage rate of not more than 2.5%.

9. A method for preparing a low-viscosity, high-heat-resistant SLA photocurable 3D printing resin composition as described in any one of claims 1 to 8, characterized in that, Includes the following steps: S1: Weigh each component according to the weight percentages; S2: Add each component to a light-proof container and stir until homogeneous at room temperature to 50°C; S3: Vacuum degassing treatment yields a low-viscosity, high-heat-resistant SLA photopolymerizable 3D printing resin composition.

10. The preparation method according to claim 9, characterized in that, In step S2, the stirring speed is 300-500 rpm and the time is 1-3 hours; in step S3, the vacuum degree of vacuum degassing does not exceed 0.1 MPa and the time is 20-40 minutes.

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