A light-curing 3D printing UV resin based on lactic acid, its preparation method and use

Abstract

The present invention discloses a light-curing 3D printing UV resin based on lactic acid, a preparation method thereof and an application thereof. The light-curing 3D printing UV resin based on lactic acid has a molecular structure of: , and the value of n is 0‑2. The light-curing 3D printing UV resin based on lactic acid is prepared by reacting lactic acid, bisphenol A epoxy resin and acrylic acid, wherein the molar ratio of lactic acid: bisphenol A epoxy resin: acrylic acid is (0.3-1): 1: 1. The light-curing 3D printing UV resin based on lactic acid is used to prepare lactic acid resin light-curing materials, and the prepared lactic acid resin light-curing materials are used for coatings or 3D printing. While ensuring the mechanical properties and chemical resistance of the lactic acid resin light-curing materials, the present invention significantly increases the amount of diluent monomer used, improves the operability of the light-curing materials, reduces costs, and increases the curing rate; it has high transparency; and can be applied to light-curing 3D printing to clearly print out the loaded objects. The synthesis method is simple, safe, easy to control, and low-cost.

Description

Technical Field

[0001] The present invention relates to a light-curing 3D printing UV resin based on lactic acid, a preparation method and application thereof, and belongs to the fields of green chemical industry and polymer materials. Background Art

[0002] 3D printing, formerly known as rapid prototyping (RP), leverages the principles of additive manufacturing (MIM, or AM) to rapidly fabricate parts of arbitrary complexity. Its fundamental principle is layer-by-layer fabrication, where material is added layer by layer to create a three-dimensional solid. Integrating the latest advances in computer technology, lasers, precision mechanics, micro-nano manufacturing, materials science, and control science, 3D printing can automatically and rapidly transform design concepts into physical prototypes with defined structural functions. This facilitates rapid evaluation, modification, and functional testing of product designs, effectively shortening product development cycles.

[0003] UV light-curing resins generally have a high viscosity, making them difficult to use as 3D printing materials. Therefore, light-curing diluents are needed as chemicals to reduce the viscosity of UV light-curing coatings. They can increase the fluidity and spreadability of the coating, thereby improving the quality of the coating. However, the current amount of light-curing diluents that can be added to 3D printing materials is very limited, reaching only 6-8% of the UV resin mass, and at most 10%. If the diluent monomer is further increased, its strength, adhesion and other properties will not meet the use requirements. Summary of the Invention

[0004] The present invention relates to a light-curing 3D printing UV resin based on lactic acid, a preparation method and an application thereof. The lactic acid resin light-curing material prepared by the light-curing 3D printing UV resin based on lactic acid of the present invention has a fast curing speed, good toughness and low shrinkage. While ensuring mechanical properties (such as strength and adhesion) and chemical resistance, the usage amount of diluent monomer is greatly increased to more than 50%, thereby improving the operability of the light-curing material and reducing costs. The light-curing material can be applied to light-curing 3D printing, thereby enabling the clear printing of loaded objects.

[0005] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0006] A light-curing 3D printing UV resin based on lactic acid, the molecular structure is:

[0007]

[0008] The value of n is 0-2.

[0009] The above-mentioned lactic acid-based light-curing 3D printing UV resin is prepared by reacting lactic acid, bisphenol A epoxy resin and acrylic acid, wherein the molar ratio of lactic acid: bisphenol A epoxy resin: acrylic acid is (0.3-1):1:1.

[0010] To ensure resin performance, the bisphenol A epoxy resin is at least one of E20, E35, E40, E42, E44, E51, and E54, preferably E44, E51, and E54, and more preferably E54.

[0011] The above-mentioned method for preparing the light-curing 3D printing UV resin based on lactic acid, under solvent-free conditions, uses p-hydroxyanisole as an inhibitor and triphenylphosphine as a catalyst, and heats lactic acid, bisphenol A epoxy resin and acrylic acid in the dark to react to prepare the light-curing 3D printing UV resin based on lactic acid.

[0012] As one specific implementation scheme, the above preparation method includes the following steps:

[0013] 1) mixing acrylic acid, bisphenol A epoxy resin, polymerization inhibitor p-hydroxyanisole, and catalyst triphenylphosphine uniformly, and reacting at 80-90° C. in the dark until the acid value AV is ≤1 to obtain an intermediate product;

[0014] 2) adding lactic acid to the intermediate product obtained in step 1), and reacting at 80-90° C. in the dark until the acid value AV is less than or equal to 3, to prepare a lactic acid light-curing UV resin.

[0015] In the above preparation method, when all the carboxyl groups of acrylic acid have reacted, the reaction of step 1) is completed; when all the carboxyl groups of lactic acid have reacted, the reaction of step 2) is completed.

[0016] The above method is simple, safe and easy to control.

[0017] In the above step 1), the reaction time is 3 to 8 hours; in the above step 2), the reaction time is 8 to 10 hours.

[0018] The above steps 1) and 2) are both carried out under the protection of nitrogen.

[0019] The dosage of the polymerization inhibitor p-hydroxyanisole accounts for 0.1% to 0.3% of the total mass of acrylic acid, bisphenol A epoxy resin and lactic acid, and the dosage of the catalyst triphenylphosphine accounts for 0.3% to 0.5% of the total mass of acrylic acid, bisphenol A epoxy resin and lactic acid.

[0020] The above-mentioned lactic acid-based light-curing 3D printing UV resin is used to prepare lactic acid resin light-curing materials, and the prepared lactic acid resin light-curing materials are used for coatings or 3D printing.

[0021] When used in coatings, the resulting product is a smooth, transparent, and highly adherent coating with excellent flexibility, including an impact resistance greater than 50 kg·cm and a flexibility ≤ 1 mm. The coating can adapt to bending of at least 1 mm without breaking. In terms of water resistance, even after 48 hours of immersion in water, the coating retains its original gloss, showing no signs of gloss loss, whitening, bubbles, or shedding.

[0022] The preparation method of the lactic acid resin photocurable material is as follows: a lactic acid-based photocurable 3D printing UV resin, an acrylate diluent monomer and a photoinitiator TPO are uniformly mixed, bubbles are removed under an environment of 20 to 30°C, and then the material is irradiated with ultraviolet light to form a lactic acid resin 3D printing photocurable material.

[0023] The mass dosage of the above-mentioned acrylate diluent monomer is 15-60% of the mass of the light-curing 3D printing UV resin based on lactic acid, and the mass dosage of the photoinitiator TPO is 1%-5% of the total mass of the light-curing 3D printing UV resin based on lactic acid and the acrylate diluent monomer.

[0024] The acrylate diluent monomer is at least one of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, 4-acryloylmorpholine or isobornyl acrylate, preferably isobornyl methacrylate.

[0025] The technologies not mentioned in this invention are all referred to the prior art.

[0026] The beneficial effects of the present invention are:

[0027] This lactic acid-based light-curing UV resin for 3D printing uses a bisphenol A epoxy resin compound. The epoxy ring opens under the action of a catalyst, reacting with the acrylic acid epoxy ring to produce an acrylic acid intermediate compound. This is then reacted with lactic acid to produce a modified epoxy resin. This resin effectively reduces viscosity and can be used in coatings or 3D printing. The resulting product cures quickly, exhibits excellent toughness, low shrinkage, high transparency, and excellent acid, alkali, and salt resistance. The synthesis method is simple, safe, easy to control, and low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a physical diagram of the preparation of the lactic acid light-curing 3D printing UV resin of the present invention;

[0029] Figure 2 This is the infrared spectrum of the lactic acid light-curing 3D printing UV resin of the present invention;

[0030] Figure 3 The UV images of the light-curing 3D printing UV resin of the present invention with different mass fractions of diluent monomer and lactic acid are shown;

[0031] Figure 4 The mechanical properties of the mixture of different mass fractions of diluents and lactic acid light-curing 3D printing UV resin of the present invention;

[0032] Figure 5 TG graphs of different mass fractions of diluent monomer and lactic acid light-curing 3D printing UV resin of the present invention;

[0033] Figure 6 This is a physical picture of the 3D printing of the lactic acid light-curing 3D printing UV resin of the present invention. DETAILED DESCRIPTION

[0034] In order to better understand the present invention, the content of the present invention is further illustrated below in conjunction with the examples, but the content of the present invention is not limited to the following examples.

[0035] Example 1

[0036] Acrylic acid (7.2 g, 0.1 mol), epoxy resin E54 (37.03 g, 0.1 mol), inhibitor 4-methoxyphenol (0.0885 g), and catalyst triphenylphosphine (0.1769 g) were added to a 250 mL three-necked flask, and the mixture was heated to 70° C. and stirred at a speed of 200 rad / min for 10 min to completely dissolve the inhibitor. The temperature was adjusted to 90° C. and the reaction was carried out in the dark. The acid value of the reaction was used to monitor the progress of the reaction. After 5 h of reaction, the acid value was less than 1 and no longer changed, thereby generating an intermediate product. Lactic acid (9 g, 0.1 mol) was added and the reaction was carried out at 90° C. in the dark (in the dark). The acid value of the reaction was used to monitor the progress of the reaction. After 10 h of reaction, the acid value no longer changed and was less than 3, thereby generating a lactic acid light-curing UV resin (light-curing 3D printing UV resin based on lactic acid) E54-LA-ACA. Figure 1 As shown, the above reactions were all carried out under the protection of nitrogen.

[0037] Figure 2 FT-IR spectra of the raw materials acrylic acid ACA, epoxy resin E54, lactic acid LA and the final product. The stretching vibration of -OH is at 3446cm -1 A broad peak was observed, and the characteristic peak of the epoxy group disappeared at 910 cm-1. In addition to the hydroxyl group contained in lactic acid, the epoxy ring opening will generate hydroxyl groups, indicating that the epoxy group is completely open. -1 The absorption peak of -C=O- indicates that the carboxylic acid has completely reacted with the epoxy group and the acid carbonyl group has been completely converted into an ester carbonyl group. The stretching vibration of the -C=C- bond is generally at 1695 cm -1 From the above, we can conclude that the compound synthesized in this experiment contains a -C=C- bond and does not contain an epoxy group. Its structure is:

[0038]

[0039] Example 2

[0040] Preparation of light-curable materials:

[0041] Accurately weigh 3.192 g of TPO photoinitiator using an analytical balance, add 53.2 g of lactic acid photocurable UV resin prepared in Example 1, add 26.6 g of isobornyl methacrylate (IBOA) diluent, heat to 50° C., stir thoroughly, mix well, pour into a polytetrafluoroethylene mold, remove bubbles at 20-30° C., and evenly coat on a corona-treated polypropylene film using a wire rod coater. The coating layer thickness is 10 μm. The coating is placed under a UV lamp for 2 seconds (UV lamp irradiation intensity is about 1036 mJ / cm 2 , distance 21cm), solidified to obtain E54-LA-ACA / IBOA50.

[0042] The prepared coating is not only smooth and transparent, but also has strong adhesion to the substrate, reaching level 0. In addition, the coating has excellent flexibility, impact resistance greater than 50kg·cm, flexibility ≤1mm, and can adapt to bending of at least 1 mm without breaking. In terms of water resistance, even after 48 hours of immersion in water, the coating still maintains its original gloss, without any signs of loss of gloss, whitening, bubbles or falling off. At the same time, the same method was used to add different mass fractions of the diluent monomer isobornyl methacrylate (IBOA) for comparison. UV spectroscopy tests were performed on diluent monomers with different mass fractions, such as Figure 3 As shown in the figure, the transparency is above 85%.

[0043] After solidification, the uniaxial tensile test was carried out to test its mechanical properties. Figure 4 As shown by Figure 4 It can be seen that the addition of 30% diluent monomer isobornyl methacrylate (IBOA) can effectively balance tensile strength and strain, showing better tensile strength. Therefore, it can be seen that the present application significantly increases the amount of diluent monomer, which can reach more than 30%, while still better balancing tensile strength (42Mpa) and elongation at break (up to 12%), while achieving level 0 adhesion, greatly improving the operability of the light-curable material. However, the existing diluent monomer can only reach 6-8% of the mass of UV resin, and at most only 10%. If the diluent monomer is further increased, the strength will decrease. If the amount of diluent monomer is too small, the operability of the material will deteriorate, increasing the difficulty of operation and thus affecting the quality. Moreover, reducing the amount of diluent monomer means increasing the amount of UV resin, which in turn increases the cost. Figure 3 and Figure 4In the figure, 10% means that the mass dosage of isobornyl methacrylate (IBOA) is 10% of the mass of the lactic acid photocurable UV resin, and the other similar expressions have similar meanings. TG tests were performed on diluent monomers with different mass fractions, such as Figure 5 shown.

[0044] Example 3

[0045] Testing the adhesion of light-curing materials on tinplate:

[0046] The preparation of the photocurable material refers to Example 2. As described in Example 2, the adhesion of the photocurable material to the plastic substrate can reach Level 0. In this example, the adhesion of the photocurable material to tinplate was tested. The photocurable material was attached to the tinplate with a coating thickness of 10μm. The adhesion of E54-LA-ACA / IBOA50 (the mass of IBOA is 50% of the mass of the lactic acid photocurable UV resin) reached Level 1. It can be seen that this photocurable material also has good adhesion to the metal substrate, enabling it to adhere well to the photocurable 3D printing platform.

[0047] Example 4

[0048] The following parameters were used for printing using the CREATY SKY, a stereolithography 3D printer from Shenzhen Chuangxiang 3D Technology Co., Ltd.: initial exposure 40s, light-off delay 4s, print exposure 2.2s, print rise height 7mm, motor speed 1mm / s, bottom exposure layer 3. The E54-LA-ACA / IBOA50 was able to clearly print complex objects on the tinplate 3D printing platform. Figure 6 .

[0049] Example 5

[0050] To conduct the chemical resistance test, first cut the light-curing material into small pieces of 2cm×2cm and measure their initial weight. Place these small pieces in a 10wt% H2S04 aqueous solution, a 10wt% NaOH aqueous solution, and a 3wt% NaCl aqueous solution, respectively, and soak them at room temperature for 48 hours. After the soaking is completed, take out the material blocks, wipe the surface solution with a clean cloth, and measure the weight again. By comparing the weight of the material before and after soaking, the mass retention rate of the material can be calculated. This ratio is used to evaluate the material's tolerance to acids, alkalis, and salts. The mass retention rate of the light-curing resin under these test conditions exceeds 99.9%, and the resin has excellent acid resistance, alkali resistance, and salt resistance.

[0051] Based on the description of the present invention, professionals in the relevant fields may make appropriate adjustments and modifications to the embodiments. Therefore, the scope of protection of the present invention should not be limited to the aforementioned embodiments, and some improvements and variations of the present invention should also be considered to be protected by the claims. In addition, although certain specific terms are used in this description, these terms are used for convenience of description only and do not impose any limitation on the scope of application of the present invention.

Claims

1. A method for preparing a light-curing 3D printing UV resin based on lactic acid, characterized in that: The steps include: 1) After uniformly mixing acrylic acid, bisphenol A epoxy resin, polymerization inhibitor p-hydroxyanisole and catalyst triphenylphosphine, react at 80-90°C in the dark until the acid value AV ≤ 1 to obtain an intermediate product; 2) adding lactic acid to the intermediate product obtained in step 1), and reacting at 80-90° C. in the dark until the acid value AV is ≤ 3, thereby preparing a lactic acid light-curing UV resin; The molar ratio of lactic acid: bisphenol A epoxy resin: acrylic acid is (0.3~1):1:1; The bisphenol A epoxy resin is at least one of E20, E35, E40, E42, E44, E51, and E54.

2. The preparation method according to claim 1, wherein: In step 1), the reaction time is 3 to 8 h; in step 2), the reaction time is 8 to 10 h.

3. The preparation method according to claim 1 or 2, wherein: Both step 1) and step 2) are reacted under the protection of nitrogen; the amount of the polymerization inhibitor p-hydroxyanisole is 0.1% to 0.3% of the total mass of acrylic acid, bisphenol A epoxy resin and lactic acid, and the amount of the catalyst triphenylphosphine is 0.3% to 0.5% of the total mass of acrylic acid, bisphenol A epoxy resin and lactic acid.

4. A use of a light-curable 3D printing UV resin based on lactic acid prepared by the preparation method according to any one of claims 1 to 3, characterized in that: Used to prepare lactic acid resin photocuring materials, and the prepared lactic acid resin photocuring materials are used for coatings or 3D printing.

5. The use according to claim 4, characterized in that: The preparation method of the lactic acid resin photocurable material is as follows: a lactic acid-based photocurable 3D printing UV resin, an acrylate diluent monomer and a photoinitiator TPO are uniformly mixed, bubbles are removed under an environment of 20-30°C, and then the mixture is irradiated with ultraviolet light to form a lactic acid resin 3D printing photocurable material.

6. The use according to claim 5, characterized in that: The mass amount of the acrylate diluent monomer is 15% to 60% of the mass of the light-curing 3D printing UV resin based on lactic acid, and the mass amount of the photoinitiator TPO is 1% to 5% of the total mass of the light-curing 3D printing UV resin based on lactic acid and the acrylate diluent monomer; the acrylate diluent monomer is at least one of 1,6-hexanediol diacrylate, tripropylene glycol diacrylate, trimethylolpropane triacrylate, 4-acryloylmorpholine or isobornyl acrylate.

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