A photocurable 3D printing oriented acrylic-based liquid crystal photosensitive resin composition

Abstract

The application discloses a kind of light-curable 3D printing orientation acrylic-based liquid crystal photosensitive resin composition.The composition includes:0.1~20% small molecule liquid crystal,10~80% acrylic resin,0~25% polyethylene glycol dimethyl acrylate resin,0~25% alkoxylated acrylate,0~25% diluent,1~10% photoinitiator,0.1~5% defoaming agent,0~5% leveling agent and 0~5% antioxidant.The photosensitive resin composition is simple to prepare,uses light-curing 3D printing technology to fix small molecule rod-shaped liquid crystal during printing process and realizes light orientation,at this time small molecule liquid crystal is enhanced acrylic-based photosensitive resin due to its high modulus,excellent length-diameter ratio,preparation excellent acrylic-based liquid crystal photosensitive resin composition,while small molecule liquid crystal is simple in selection and synthesis strategy,avoid the problem of long production cycle and high cost in high polymer liquid crystal synthesis,has important significance for 3D printing application field.

Description

Technical Field

[0001] This invention relates to the preparation and application of photosensitive resins, and in particular to a photocurable 3D printing oriented acrylic liquid crystal photosensitive resin composition. Background Technology

[0002] With the rapid development of 3D printing technology, it is increasingly demonstrating its unique advantages over traditional manufacturing processes, including shorter manufacturing cycles and higher molding precision, and has been widely applied in various industries. Among them, photopolymer 3D printing resin is one of the earliest 3D printing technologies.

[0003] As a raw material for photopolymer 3D printing, photosensitive resin is generally composed of prepolymer, reactive diluent, photoinitiator, leveling agent, defoamer, toughening agent, crosslinking agent and various other additives.

[0004] Acrylic resins stand out among many photocurable resins due to their low price and are widely used in photocurable product systems. They also have their own advantages in terms of performance. Their curing speed is very fast, which is very beneficial for shortening the 3D printing time of models and improving work efficiency. They also perform well in terms of adhesion and chemical resistance. However, their viscosity before and after curing is high, and they are brittle after curing with low mechanical strength, which are also their significant performance defects.

[0005] Single-component UV-curable resins often cannot meet our industrial requirements, thus necessitating research into their modification. There are generally two common methods for modifying UV-curable resins. The first is direct chemical modification of the prepolymer, which requires the design and synthesis of prepolymer molecules, making it more challenging. However, the modified prepolymer exhibits higher stability, and the modification is more targeted. The second method involves blending, dispersing different types of additives and fillers to improve performance defects. This method is simple and quick, but the resulting product may suffer from uneven dispersion and inconsistent system composition, which can affect the performance of different parts after printing. Improving the dispersion problems caused by blending would be a better strategy.

[0006] Liquid crystals are a special structure between random liquids and three-dimensional ordered crystals. They exhibit both the fluidity of liquids and the anisotropy of crystals, thus possessing many excellent properties. Much current research focuses on liquid crystal polymers. Liquid crystal oligomers have attracted widespread attention due to their excellent high modulus and mechanical properties in photosensitive resin compositions. However, their production is costly, the synthesis process is slow, and it requires significant human and material resources. Therefore, there is an urgent need for a simple and convenient method to achieve the desired effect. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a photocurable 3D printing oriented acrylic-based liquid crystal photosensitive resin composition with good mechanical properties and excellent heat resistance. A small-molecule liquid crystal is blended with an acrylic ester-based photosensitive resin to prepare an acrylic-based resin-based liquid crystal photosensitive resin composition. This composition can be used in 405nm photocurable 3D printing, where the layer thickness is controlled by a computer program using photocurable 3D printing technology to achieve photo-oriented liquid crystal alignment.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows:

[0009] A photo-oriented acrylic liquid crystal photosensitive resin composition is prepared from the following components in the indicated weight percentages:

[0010]

[0011] Preferably, the small molecule liquid crystal has the structural formula shown in Formula I below:

[0012]

[0013] Wherein, R1 is one of hydrogen or alkyl, R2 is one of alkoxy, nitro, cyano, sulfonic acid or halogen, and E is one of alkyl, alkoxy, ester or amide or their homologues.

[0014] It is one of the formulas in II;

[0015]

[0016] Preferably, the acrylate resin is selected from at least one of aliphatic polyurethane acrylate oligomers, methacrylate oligomers, vinyl ester resins, and dimethacrylate urethane resins; the degree of polymerization of the polyethylene glycol dimethacrylate resin is 1 to 200; and the alkyl oxidized acrylate monomer is selected from at least one of propanetriol triacrylate oxypropanetriol ...

[0017] Preferably, the diluent is selected from at least one of styrene, acrylate diluents, hydroxy acrylate diluents, vinyl ether diluents, and cyclohexane diluents; the acrylate diluent is selected from at least one of methyl methacrylate, 1,6-hexanediol diacrylate, isobornyl acrylate, tetrahydrofuran acrylate, tripropylene glycol diacrylate, hexanediol diacrylate, bisphenol A diacrylate, trimethylolpropane triacrylate, pentaerythritol acrylate, isobornyl acrylate, and cyclotrimethylolpropane methyl acetal acrylate; the hydroxy acrylate diluent is selected from at least one of hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxyethyl acrylate; the vinyl ether diluent is selected from at least one of 4-hydroxybutyl vinyl ether and diethylene glycol divinyl ether; and the cyclohexane diluent is 4-vinylepoxycyclohexane.

[0018] Preferably, the photoinitiator is selected from at least one of acylphosphine oxide photoinitiators and aromatic ketone photoinitiators; the acylphosphine oxide photoinitiator is selected from at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide; the aromatic ketone photoinitiator is selected from at least one of 1-hydroxy-cyclohexylacetophenone, α,α-dimethyl-α-hydroxyacetophenone, p-isopropylphenyl-2-hydroxydimethylacetone-1, benzophenone, chlorobenzophenone, acrylated benzophenone, 4-phenylbenzophenone, 2-chlorothioxanthonone, isopropylthioxanthonone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, dimethylthioxanthonone, diethylthioxanthonone, dichlorothioxanthonone, and 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone.

[0019] Preferably, the defoamer is selected from at least one of silicone defoamers, mineral oil defoamers, polyether defoamers, and fatty alcohol defoamers.

[0020] Preferably, the leveling agent is selected from at least one of acrylic leveling agents, silicone leveling agents, and fluorocarbon leveling agents; the antioxidant is selected from at least one of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, phenyl tris(2,4-di-tert-butyl)phosphite, N,N′-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine, and 2,6-di-tert-butyl-4-methylphenol.

[0021] The acrylic-based liquid crystal photosensitive resin composition provided by this invention can be applied to 405nm photocuring 3D printing: the acrylic-based liquid crystal photosensitive resin composition is poured into the Form2 3D printer manufactured by Formlabs, Inc. in the United States, and then formed by computer modeling, drawing and printing.

[0022] By adopting the above technical solution, the present invention has the following beneficial effects compared with the prior art: The present invention introduces small molecule liquid crystals into acrylic photosensitive resins to prepare an acrylic-based liquid crystal photosensitive resin composition. This composition can retain the characteristics of acrylic resins, ensuring that the molded parts have good high temperature resistance and are suitable for high-end fields such as aerospace. At the same time, 3D printing technology is used to fix the rod-shaped liquid crystals during the molding process, and photo-orientation is achieved along the polarization direction. The high modulus and excellent aspect ratio of the liquid crystal molecules enhance the acrylic photosensitive resin. Attached Figure Description

[0023] Figure 1 This is a model printed by a 3D printer from the photo-oriented acrylic liquid crystal photosensitive resin composition prepared in Example 1 of this invention.

[0024] Figure 2 The stress-strain curves are obtained from tensile tests of strips printed with light parallel to and perpendicular to ultraviolet polarized light, based on the photo-oriented acrylic liquid crystal photosensitive resin composition prepared in Example 1 of this invention.

[0025] Figure 3 This is a POM image of the 3D printed product prepared by formula #2 in Example 1 after removing the liquid crystal.

[0026] Figure 4 This refers to the tensile strength of samples with different printing layer thicknesses obtained by printing with ultraviolet polarized light parallel to the photo-oriented acrylic photosensitive resin composition prepared in Example 1 of this invention.

[0027] Figure 5 This is a schematic diagram illustrating the liquid crystal enhancement principle of a photo-oriented acrylic liquid crystal photosensitive resin composition in the application of photocurable 3D printing. Detailed Implementation

[0028] The present invention will be further described below with reference to specific embodiments:

[0029] Example 1

[0030] A photo-oriented acrylic liquid crystal photosensitive resin composition, prepared from the following components in weight percentages:

[0031]

[0032]

[0033] The specific raw materials used in the embodiments of the present invention are as follows:

[0034] Small molecule liquid crystals are positive liquid crystals, including but not limited to one of the following liquid crystals, abbreviated as A-1, A-2 and A-3 respectively;

[0035]

[0036] Acrylic resins:

[0037] Aliphatic polyurethane acrylate 1: Purchased from Sartoma, product number CN9010, abbreviated as B-1;

[0038] Aliphatic polyurethane acrylate 2: Purchased from Sartoma, product number CN991, abbreviated as B-2;

[0039] Polyethylene glycol dimethacrylate resins:

[0040] Polyethylene glycol dimethacrylate resin 1: purchased from Sartoma, product number SR210, abbreviated as C-1;

[0041] Polyethylene glycol dimethacrylate resin 2: purchased from Sartoma, product number SR211, abbreviated as C-2;

[0042] Alkyl oxidized acrylate:

[0043] Pentaerythritol tetraacrylate ethoxylate, purchased from Sartoma, product number SR494, abbreviated as D-1;

[0044] Propylene glycerol triacrylate, purchased from Sartoma, product number SR9020, abbreviated as D-2;

[0045] Diluent:

[0046] Cyclotrimethylolpropane methyl acetal acrylate: purchased from Sartoma, product number SR351, abbreviated as E-1;

[0047] Hydroxypropyl methacrylate: purchased from Aladdin Reagent (Shanghai) Co., Ltd., abbreviated as E-2;

[0048] Hydroxyethyl methacrylate: purchased from Aladdin Reagent (Shanghai) Co., Ltd., abbreviated as E-3;

[0049] Photoinitiator:

[0050] 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide was purchased from Aladdin Reagent (Shanghai) Co., Ltd., product number photoinitiator TPO, abbreviated as F-1;

[0051] Phenylenol bis(2,4,6-trimethylbenzoyl)phosphine oxide: purchased from Aladdin Reagent (Shanghai) Co., Ltd., product number photoinitiator XBPO, abbreviated as F-2;

[0052] 1-Hydroxy-cyclohexyl-acetophenone: Purchased from Aladdin Reagent (Shanghai) Co., Ltd., product number photoinitiator 184, abbreviated as F-3;

[0053] Defoamer:

[0054] Silicone-based defoamer: purchased from BYK-088, abbreviated as G-1, from BYK Chemical AG, Germany;

[0055] Polyether defoamer: purchased from Guangdong Zhonglian Fine Chemical Co., Ltd., product number B-299, abbreviated as G-2;

[0056] Leveling agent:

[0057] Organosilicon leveling agent: purchased from Anhui Jiazhixinno Chemical Co., Ltd., product number WE-D5510, abbreviated as H-1;

[0058] Polyacrylic acid leveling agent: purchased from Anhui Jiazhi Xinno Chemical Co., Ltd., product number WE-D819, abbreviated as H-2;

[0059] Antioxidants:

[0060] 2,6-Di-tert-butyl-4-methylphenol: purchased from Aladdin Reagent (Shanghai) Co., Ltd., product number antioxidant BHT, abbreviated as I-1;

[0061] Pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenylpropionate): purchased from Guangzhou Kaiyin Chemical Co., Ltd., antioxidant 1010, abbreviated as I-2.

[0062] As shown in the above formula, the specific formulations are as shown in Table 1 for implementation formulas #1 to #4:

[0063] Table 1 Implementation Formulas for 1# to 4#

[0064]

[0065]

[0066] Formula #1 is the control group, which does not contain small molecule liquid crystals.

[0067] The preparation steps are as follows: Small molecule liquid crystal, acrylate resin, polyethylene glycol dimethacrylate resin, alkyl acrylate, and diluent are mixed and heated to 30-80°C. After stirring and mixing evenly, the mixture is cooled and then photoinitiator, defoamer, leveling agent, and antioxidant are added. After stirring until uniform, a milky white viscous liquid is obtained, which is the photo-oriented acrylic liquid crystal photosensitive resin composition described in this application.

[0068] The prepared photo-oriented acrylic liquid crystal photosensitive resin composition is poured into the Form2 3D printer manufactured by Formlabs, Inc. in the United States, and then formed by computer modeling, drawing and printing.

[0069] The photosensitive resin composition was evaluated by observing the appearance of the cured finished product based on the formulation described in Example 1. The results are as follows:

[0070] See Figure 1 It is a model printed by a 3D printer from the photo-oriented acrylic liquid crystal photosensitive resin composition prepared by formulation #2 in Example 1.

[0071] See Figure 2 These are the stress-strain curves of tensile tests on strips of the photo-oriented acrylic liquid crystal photosensitive resin composition prepared in Example 1, printed parallel to and perpendicular to ultraviolet polarized light. It can be seen that the tensile strengths of the liquid crystal / acrylic photosensitive resin compositions (2#, 3#, 4#) prepared in Example 1, parallel to the ultraviolet polarized light printing direction, are 121.2 MPa, 110.2 MPa, and 88.1 MPa, respectively, with elongations at break of 25.2%, 25.1%, and 24.2%, respectively, demonstrating excellent mechanical properties. In contrast, the tensile strength of the acrylic photosensitive resin (1#) is only 43.1 MPa, with an elongation at break of only 10.6%.

[0072] See Figure 3 This is a POM image of the 3D printed product prepared according to formulation #2 of Example 1 of this invention after removing the liquid crystal. During the printing process, the polymerization of photosensitive resin under ultraviolet laser irradiation is exothermic, and the resulting temperature field causes the liquid crystal molecules to orient. When the printing precision is 25 micrometers, the thickness of the printed layer is approximately the same as the length of the rod-shaped LC, and the molding time is short, so the LC also drives the surrounding photosensitive resin to orient together in the direction of light irradiation. Then, when the photosensitive resin polymerizes to obtain a polymer, it fixes the liquid crystal in one direction, resulting in polymer anisotropy. To prove that the polymer also undergoes orientation, we removed the liquid crystal from the 3D printed product with dichloromethane, leaving the polymer, and inspected the surface of the product using POM. The test results show that when the stage is rotated 360°, the phenomenon of alternating 4 bright and 4 dark images is observed, as shown in the image. Figure 3 The images shown are of bright and dark states. This indicates that the photosensitive resin also undergoes orientation during polymerization, forming an optically anisotropic structure similar to that of a liquid crystal.

[0073] join Figure 4This refers to the tensile strength of samples with different printing layer thicknesses obtained by printing the photo-oriented acrylic liquid crystal photosensitive resin composition prepared in Example 1 of this invention under ultraviolet polarized light. It can be seen that the tensile strength of the liquid crystal / acrylic photosensitive resin composition prepared in Example 1 varies with different printing layer thicknesses. The 25μm printing layer thickness exhibits the best tensile strength, while the 100μm printing layer thickness shows the lowest. The tensile strength of formulation #2 is the highest at 121.2MPa and the lowest at 29.1MPa.

[0074] join Figure 5 This is a schematic diagram illustrating the innovative liquid crystal enhancement principle of the photo-oriented acrylic liquid crystal photosensitive resin composition prepared in Example 1 of this invention in the application of photopolymerization 3D printing. The liquid crystal orientation of formulation #2 is quite strong, but due to the increased liquid crystal content, the "anchor points" provided by the photosensitive resin are insufficient to induce partial liquid crystal orientation, and the liquid crystal remains in droplet form. For the printed sample of formulation #4, the lower orientation degree leads to a significant decrease in tensile strength and modulus, which is detrimental to improving product strength. Furthermore, it was found that when the printing resolution increased to 50 micrometers and 100 micrometers, the mechanical properties of the product decreased. In particular, at a printing resolution of 100 micrometers, the mechanical properties of the product decreased significantly, exhibiting performance even worse than the product printed with the resin of formulation #1. Due to the long printing time and high polymerization temperature, the liquid crystals become disordered, forming spherical shapes above the orientation temperature and floating on the surface of the printed sample. However, after the photosensitive resin is converted into a polymer, these spherical liquid crystals are fixed on the surface of the sample and become microcrystalline structures after cooling, such as... Figure 5 As shown, the number of rod-shaped liquid crystals fixed varies with different layer thicknesses, resulting in different reinforcement effects from their oriented self-assembly. This invention combines reinforcement manufacturing technology with photosensitive resin materials to construct a simple and innovative solution.

[0075] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A photocurable 3D printing oriented acrylic liquid crystal photosensitive resin composition, characterized in that, It is prepared from the following components in the indicated mass percentages: Small molecule liquid crystal 0.1~20% Acrylic resins 10-80% Polyethylene glycol dimethacrylate resins 0~25% Alkyl oxidized acrylate 0~25% Diluent 0~25% Photoinitiator 1~10% Defoamer 0.1~5% Leveling agent 0~5% Antioxidant 0~5%; The structural formula of the small molecule liquid crystal is shown in Formula I: ； Wherein, R1 is one of hydrogen or alkyl, R2 is one of alkoxy, nitro, cyano, sulfonic acid or halogen, and E is one of alkyl, alkoxy, ester or amide. It is one of the formulas in II; ； The diluent is selected from at least one of styrene, acrylate diluents, vinyl ether diluents, and cyclohexane diluents; the acrylate diluent is selected from at least one of methyl methacrylate, 1,6-hexanediol diacrylate, isobornyl acrylate, tetrahydrofuran acrylate, tripropylene glycol diacrylate, hexanediol diacrylate, bisphenol A diacrylate, trimethylolpropane triacrylate, pentaerythritol acrylate, isobornyl acrylate, cyclotrimethylolpropane methyl acetal acrylate, hydroxyethyl methacrylate, hydroxypropyl methacrylate, and hydroxyethyl acrylate.

2. The photocurable 3D printing oriented acrylic liquid crystal photosensitive resin composition according to claim 1, characterized in that: The acrylate resin is selected from at least one of aliphatic polyurethane acrylate oligomers, methacrylate oligomers, vinyl ester resins, and dimethacrylate urethane resins; the degree of polymerization of the polyethylene glycol dimethacrylate resin is 1 to 200; the alkyl oxidized acrylate monomer is selected from at least one of propanetriol triacrylate oxypropanetriol ...

3. The photocurable 3D printing oriented acrylic liquid crystal photosensitive resin composition according to claim 1, characterized in that: The vinyl ether diluent is selected from at least one of 4-hydroxybutyl vinyl ether and diethylene glycol divinyl ether; the cyclohexane diluent is 4-vinylepoxycyclohexane.

4. The photocurable 3D printing oriented acrylic liquid crystal photosensitive resin composition according to claim 1, characterized in that: The photoinitiator is selected from at least one of acylphosphine oxide photoinitiators and aromatic ketone photoinitiators. The acylphosphine oxide photoinitiator is selected from at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide and 2,4,6-(trimethylbenzoyl)diphenylphosphine oxide. The aromatic ketone photoinitiator is selected from 1-hydroxy-cyclohexylacetophenone, α,α-dimethyl-α-hydroxyacetophenone, benzophenone, chlorobenzophenone, acrylated benzophenone, 4-phenylbenzophenone, 2-chlorothioxanthonone, isopropylthioxanthonone, and 2-hydroxy-2-methyl-1-phenyl-1-propane. At least one of the following: ketone, dimethylthionanone, diethylthionanone, dichlorothionanone, and 2-phenylbenzyl-2-dimethylamine-1-(4-morpholinobenzylphenyl)butanone.

5. The photocurable 3D printing oriented acrylic liquid crystal photosensitive resin composition according to claim 1, characterized in that: The defoamer is selected from at least one of the following: silicone defoamers, mineral oil defoamers, polyether defoamers, and fatty alcohol defoamers.

6. The photocurable 3D printing oriented acrylic liquid crystal photosensitive resin composition according to claim 1, characterized in that: The leveling agent is selected from at least one of acrylic leveling agents, silicone leveling agents, and fluorocarbon leveling agents; the antioxidant is selected from at least one of pentaerythritol tetrakis(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, phenyl tris(2,4-di-tert-butyl)phosphite, N,N′-bis-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl)hexamethylenediamine, and 2,6-di-tert-butyl-4-methylphenol.

7. A method for preparing a photocurable 3D printing oriented acrylic liquid crystal photosensitive resin composition according to any one of claims 1 to 6, characterized in that: Small molecule liquid crystal, acrylate resin, polyethylene glycol dimethacrylate resin, alkyl acrylate, and diluent are mixed and heated to 30~80℃. After stirring and mixing evenly, the mixture is cooled and then photoinitiator, defoamer, leveling agent, and antioxidant are added and stirred until uniform.

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