A dual-curing 3D printing resin and its application method

Abstract

This invention discloses a dual-curing 3D printing resin, comprising an acrylate oligomer containing dynamic covalent bonds and a blocked isocyanate crosslinking agent. The acrylate oligomer containing dynamic covalent bonds is obtained by reacting an isocyanate-terminated oligomer with ethylene glycol acetoacetate methacrylate. The dual-curing 3D printing resin provided by this invention can have its internal molecular structure and crosslinking density altered through heat treatment after photocuring, and exhibits excellent stability, allowing for storage and use in single-component form.

Description

Technical Field

[0001] This invention relates to the field of polymer materials, specifically to a dual-curing 3D printing resin and its application method. Background Technology

[0002] Photopolymerization technology refers to the process where photoinitiators in liquid resin are activated under light, initiating polymerization and cross-linking reactions between molecules to form a solid. It offers advantages such as high efficiency, economy, and environmental friendliness. Photopolymerization 3D printing uses photosensitive resin as the main raw material, mapping planar layers of the target part (after slicing) onto the resin, curing and stacking them layer by layer to ultimately form the final product.

[0003] Typically, photosensitive resins mainly use acrylate or methacrylate compounds. To ensure molding rate and post-molding product strength (low strength affects printing yield), a high proportion of multifunctional acrylate or methacrylate compounds is usually used. This results in poor toughness of the product, affecting its use. Furthermore, simply using a combination of acrylate / methacrylate monomers and crosslinking agents is unlikely to yield products with good overall performance. The current common practice is to first prepare polyurethane acrylate or epoxy acrylate oligomers, then add reactive acrylate or methacrylate monomers and crosslinking agents to adjust the resin's viscosity and properties to meet application requirements. To achieve sufficiently superior material performance, it is necessary to increase the molecular weight of the polyurethane acrylate or epoxy acrylate oligomer and reduce the amount of reactive diluent. However, both of these factors increase the overall viscosity of the system, affecting its use. Chinese patents with application numbers 201910790012.1 and 202110198554.7 disclose a type of polyurethane / polyurea acrylate oligomer containing sterically hindered urea bonds in its molecular structure. These oligomers exhibit sterically hindered urea bonds that dissociate at high temperatures, re-exposing isocyanate groups. These groups can then react with moisture or the urea bonds in their own molecular structure, further increasing the molecular weight of the polyurethane / polyurea and forming an interpenetrating network system, thus improving the overall performance of the material. However, these sterically hindered urea bonds possess a certain degree of reactivity, making long-term storage and use in high humidity or high temperature (above 70°C) environments difficult. Summary of the Invention

[0004] The purpose of this invention is to provide a dual-curing 3D printing resin and its application method. After photocuring, the resin can undergo changes in its internal molecular structure and cross-linking density through heat treatment, and it has excellent stability. It can be stored and used in a single-component form.

[0005] The objective of this invention is achieved through the following technical approach:

[0006] A dual-curing 3D printing resin comprises an acrylate oligomer containing dynamic covalent bonds and a blocked isocyanate crosslinking agent. The acrylate oligomer containing dynamic covalent bonds is obtained by reacting an isocyanate-terminated oligomer with ethylene glycol acetoacetate methacrylate.

[0007]

[0008] The acrylate oligomer containing dynamic covalent bonds provided by this invention generates vinyl urethane through the reaction of isocyanate and acetoacetate. This chemical bond is a reversible dynamic bond that dissociates into an amino group and ketene under heating. The generated amino group can further react with a blocked isocyanate crosslinking agent that releases isocyanate groups upon deprotection at high temperatures to generate urea bonds, thereby achieving a rearrangement of the molecular and network structure and altering the material properties.

[0009]

[0010] Wherein, 1 is an acrylate network and 2 is a polyurethane network.

[0011] The preparation method of the acrylate oligomer containing dynamic covalent bonds is as follows:

[0012] 1) Mix polyol and polyisocyanate at 40-60℃ and stir for 3-6 hours to obtain isocyanate-terminated oligomers, wherein the molar ratio of isocyanate to hydroxyl group is greater than 1.

[0013] 2) Ethylene glycol acetoacetate methacrylate is added dropwise to the isocyanate-terminated oligomer at 60-80°C, and the mixture is stirred for 12-24 hours to obtain the acrylate oligomer containing dynamic covalent bonds.

[0014] Preferably, the polyol is selected from one or more of polyester polyols, polyether polyols, polycarbonate polyols, polyolefin polyols, or polyacrylate polyols.

[0015] Preferably, the polyisocyanate is selected from one or more of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), phenylmethylene diisocyanate (XDI), and dicyclohexylmethane diisocyanate (HMDI).

[0016] Preferably, the polyisocyanate obtained by removing the protecting group after heating the blocked isocyanate crosslinking agent is one or more combinations of hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), toluene diisocyanate (TDI), isophorone diisocyanate (IPDI), and HDI biuret.

[0017] To ensure good storage stability of the dual-curing 3D printing resin, the dissociation temperature of the blocked isocyanate crosslinking agent needs to be greater than 100°C, and the preferred grade of the blocked isocyanate crosslinking agent is... BI7982 BI7950, Dornet E402-80B.

[0018] Preferably, the content of the blocked isocyanate crosslinking agent satisfies the following condition: the molar amount of isocyanate groups contained in the blocked isocyanate crosslinking agent = the molar amount of acrylate oligomer containing dynamic covalent bonds * 2.

[0019] Preferably, the reactive diluent is a monofunctional or polyfunctional acrylate / methacrylate, and the specific type and amount of reactive diluent can be adjusted according to the required performance.

[0020] Preferably, the photoinitiator is selected from diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (TPO), 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (819), and 1-hydroxycyclohexylbenzophenone (184). Specifically, one or more combinations of photoinitiators need to be selected according to the wavelength of the curing light source.

[0021] The present invention also provides a method for applying the above-mentioned dual-curing 3D printing resin, the method comprising:

[0022] 1) The acrylate oligomer containing dynamic covalent bonds, the blocked isocyanate crosslinking agent, the reactive diluent, and the photoinitiator are mixed and then photocured.

[0023] 2) Perform heat treatment on the photocured sample. The heat treatment temperature is 120-160℃ and the heat treatment time is 3-6h.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: it has excellent photocuring performance, and its internal molecular structure and cross-linking density can be changed by heat treatment after photocuring. After heat treatment, the photocured 3D printing resin is transformed from a single acrylate network into an interpenetrating network structure of acrylate and polyurethane, which can significantly improve mechanical properties. At the same time, the dual-curing 3D printing resin provided by the present invention has excellent stability and can be stored and used in a single-component form. Attached Figure Description

[0025] Figure 1 The viscosity changes of the resins prepared in Examples 1-4 and Comparative Example 1 when stored in an open state at 60°C;

[0026] Figure 2 The viscosity changes of the resins prepared in Examples 1-4 and Comparative Example 1 when stored in a sealed environment at 60°C. Detailed Implementation

[0027] The present invention will be further described below with reference to specific embodiments. The following embodiments are not intended to be a simple limitation of the spirit of the present invention. Any simple changes or equivalent substitutions made based on the spirit of the present invention should fall within the scope of protection claimed by the present invention.

[0028] Example 1

[0029] 1. 1000g PTMG (Mw=1000) and 336.38g HDI were mixed evenly, and 1.13g dibutyltin dilaurate (DBTDL) was added. The mixture was stirred at 50℃ for 4h to obtain the isocyanate-terminated oligomer PTMG 1K-HDI.

[0030] 2. 428.44 g of ethylene glycol acetoacetate methacrylate (AAEMA) was slowly added dropwise to the above reaction system, and the mixture was stirred at 70°C for 12 h to obtain the acrylate oligomer PTMG 1K-HDI-AAEMA containing dynamic covalent bonds;

[0031] 3. Following Table 1, PTMG 1K-HDI-AAEMA, reactive diluent, and photoinitiator were mixed and photocured using a 405nm light source. The photocured samples were then subjected to post-heat treatment. The mechanical properties of the resin after heat treatment are shown in Table 1.

[0032] The mechanical properties of the resin after photocuring and before heat treatment are tensile strength of 1.2 MPa and elongation at break of 21%.

[0033] Table 1. Resin composition and mechanical properties in Example 1

[0034]

[0035] Example 2

[0036] 1.650g PTMG (Mw=650) and 444.56g IPDI were mixed evenly, and 0.82g dibutyltin dilaurate (DBTDL) was added. The mixture was stirred at 60℃ for 4h to obtain the isocyanate-terminated oligomer PTMG 650-IPDI.

[0037] 2. 428.44 g of ethylene glycol acetoacetate methacrylate (AAEMA) was slowly added dropwise to the above reaction system, and the mixture was stirred at 60°C for 24 h to obtain the acrylate oligomer PTMG 650-IPDI-AAEMA containing dynamic covalent bonds.

[0038] 3. Following Table 2, PTMG 1K-HDI-AAEMA, reactive diluent, and photoinitiator were mixed and photocured using a 405nm light source. The photocured samples were then subjected to post-heat treatment. The mechanical properties of the resin after heat treatment are shown in Table 2.

[0039] The mechanical properties of the resin after light curing and before heat treatment are tensile strength of 4.7 MPa and elongation at break of 12%.

[0040] Table 2 Resin composition and mechanical properties in Example 2

[0041]

[0042] Example 3

[0043] 1.530g PCL (Mw=530) and 336.38g HDI were mixed evenly, and 1.13g dibutyltin dilaurate (DBTDL) was added. The mixture was stirred at 50℃ for 6h to obtain the isocyanate-terminated oligomer PCL 530-HDI.

[0044] 2. 428.44 g of ethylene glycol acetoacetate methacrylate (AAEMA) was slowly added dropwise to the above reaction system, and the mixture was stirred at 80 °C for 12 h to obtain the acrylate oligomer PCL 530-HDI-AAEMA containing dynamic covalent bonds.

[0045] 3. Following Table 3, PTMG 1K-HDI-AAEMA, reactive diluent, and photoinitiator were mixed and photocured using a 405nm light source. The photocured samples were then subjected to post-heat treatment. The mechanical properties of the resin after heat treatment are shown in Table 3.

[0046] The mechanical properties of the resin after photocuring and before heat treatment are a tensile strength of 3.6 MPa and an elongation at break of 8%.

[0047] Table 3 Resin composition and mechanical properties in Example 3

[0048] PCL 530-HDI-AAEMA 800g Dornet E402-80B 711.28g IBOMA 200g DCPDA 30g TPO 15g Heat treatment process Heat treatment at 150℃ for 3 hours Tensile strength 35MPa Elongation at break 21％ Young's modulus 877MPa

[0049] Example 4

[0050] 1. 1000g PTMG (Mw=1000) and 348.32g TDI were mixed evenly, and 1.13g dibutyltin dilaurate (DBTDL) was added. The mixture was stirred at 60℃ for 5h to obtain the isocyanate-terminated oligomer PTMG 1K-TDI.

[0051] 2. 428.44 g of ethylene glycol acetoacetate methacrylate (AAEMA) was slowly added dropwise to the above reaction system, and the mixture was stirred at 80 °C for 18 h to obtain the acrylate oligomer PTMG 1K-TDI-AAEMA containing dynamic covalent bonds.

[0052] 3. According to Table 4, PTMG 1K-HDI-AAEMA, reactive diluent, and photoinitiator were mixed and photocured using a 405nm light source. The photocured samples were then subjected to heat post-treatment. The mechanical properties of the resin after heat treatment are shown in Table 4.

[0053] The mechanical properties of the resin after light curing and before heat treatment are tensile strength of 6.1 MPa and elongation at break of 45%.

[0054] Table 4 Resin composition and mechanical properties in Example 4

[0055]

[0056] Comparative Example 1

[0057] Referring to Embodiment 3 of Invention Patent CN113072678A

[0058] 1. Place 336.38g of HDI in a flask and stir. Add 2000g of polyetheramine D2000 dropwise through a constant pressure dropping funnel. After the addition is complete, stir the reaction at 50°C. Determine the reaction endpoint by the di-n-butylamine method to obtain the isocyanate-terminated intermediate.

[0059] 2. 370.54 g of 2-tert-butylaminoethyl methacrylate (TBEMA) was slowly added dropwise to the above intermediate product. After the addition was complete, 4 g of DBTDL was added, and the temperature was raised to 55°C and the reaction was continued for 3 h to obtain polyurea acrylate oligomer.

[0060] 3. Add 1 / 3 of the oligomer mass of isooctyl acrylate and 2% of the total mass of photoinitiator to obtain polyurea photocurable resin.

[0061] A certain amount of the photocurable resin from Examples 1-4 and the comparative example was placed in an oven at 60°C, either open or closed. After being removed and cooled to room temperature at regular intervals, the viscosity was measured. The viscosity change during open storage at 60°C is as follows: Figure 1 As shown, the viscosity change when stored in a sealed environment at 60°C is as follows: Figure 2 As shown. From Figure 1 and Figure 2 It can be seen that the dual-curing 3D printing resin provided by the present invention has excellent stability and can be stored and used in a single-component form.

[0062] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A dual-curing 3D printing resin, characterized in that, The dual-curing 3D printing resin comprises an acrylate oligomer with dynamic covalent bonds, a blocked isocyanate crosslinking agent, a reactive diluent, and a photoinitiator. The acrylate oligomer with dynamic covalent bonds is obtained by reacting an isocyanate-terminated oligomer with ethylene glycol acetoacetate methacrylate. ； The preparation method of the acrylate oligomer containing dynamic covalent bonds is as follows: 1) Mix polyol and polyisocyanate at 40-60℃ and stir for 3-6 hours to obtain isocyanate-terminated oligomers, wherein the molar ratio of isocyanate to hydroxyl group is greater than 1. 2) Ethylene glycol acetoacetate methacrylate is added dropwise to the isocyanate-terminated oligomer at 60-80 °C, and the mixture is stirred for 12-24 h to obtain the acrylate oligomer containing dynamic covalent bonds. The blocked isocyanate crosslinking agent is heated to remove the protecting group, yielding a polyisocyanate.

2. The dual-curing 3D printing resin according to claim 1, characterized in that, The polyol is selected from one or more of polyester polyols, polyether polyols, polycarbonate polyols, polyolefin polyols, or polyacrylate polyols. The polyisocyanate is selected from one or more of toluene diisocyanate, diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, phenylmethylene diisocyanate or dicyclohexylmethane diisocyanate.

3. The dual-curing 3D printing resin according to claim 1, characterized in that, The polyisocyanate obtained by removing the protecting group from the blocked isocyanate crosslinking agent after heating is one or more of hexamethylene diisocyanate, diphenylmethane diisocyanate, toluene diisocyanate, isophorone diisocyanate, or HDI biuret.

4. The dual-curing 3D printing resin according to claim 1, characterized in that, The content of the blocked isocyanate crosslinking agent satisfies the following condition: the molar amount of isocyanate groups contained in the blocked isocyanate crosslinking agent = the molar amount of acrylate oligomer containing dynamic covalent bonds * 2.

5. The dual-curing 3D printing resin according to claim 1, characterized in that, The reactive diluent is a monofunctional or polyfunctional (meth)acrylate.

6. The dual-curing 3D printing resin according to claim 1, characterized in that, The photoinitiator is selected from one or more of diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide, bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, or 1-hydroxycyclohexylbenzophenone.

7. A method for applying the dual-curing 3D printing resin according to any one of claims 1-6, characterized in that, The application method includes: 1) The acrylate oligomer containing dynamic covalent bonds, the blocked isocyanate crosslinking agent, the reactive diluent and the photoinitiator are mixed and then photocured. 2) Perform heat treatment on the photocured sample. The heat treatment temperature is 120-160℃ and the heat treatment time is 3-6h.

Images