Dual-curing 3D printing resin and application method thereof

Abstract

The invention discloses a dual-curing 3D printing resin, the dual-curing 3D printing resin comprises an acrylate oligomer containing a dynamic covalent bond and a blocked isocyanate cross-linking agent, and the acrylate oligomer containing the dynamic covalent bond is obtained by reacting an isocyanate-terminated oligomer with acetoacetic acid ethylene glycol methacrylate. The internal molecular structure and the crosslinking density of the dual-curing 3D printing resin can be changed through heat treatment after light curing, and the dual-curing 3D printing resin has excellent stability and can be stored and used in a single-component mode.

Description

Technical Field

[0001] The present invention relates to the field of polymer materials, and in particular to a dual-curing 3D printing resin and an application method thereof. Background Art

[0002] Photocuring technology refers to the process in which the photoinitiator contained in the liquid resin is activated under light to initiate polymerization and cross-linking reactions between molecules to form a solid. It has the advantages of high efficiency, economy, and environmental protection. Photocuring 3D printing is a process that uses photosensitive resin as the main raw material, maps the planar layer of the target part after slicing onto the resin, solidifies and stacks the layers, and finally forms the part.

[0003] Usually, photosensitive resins are mainly acrylate or methacrylate compounds. To ensure the molding rate and the strength of the product after molding (too low strength will affect the printing yield), there is generally a higher proportion of multifunctional acrylate or methacrylate compounds, which will lead to poor toughness of the product and affect the use. In addition, the combination of acrylate / methacrylate monomer and crosslinking agent is also difficult to obtain products with better comprehensive performance. The current common practice is to prepare polyurethane acrylate or epoxy acrylate oligomer first, then add active acrylate or methacrylate monomer and crosslinking agent, and adjust the viscosity and performance of the resin to meet the use requirements. In order to make the material have sufficiently excellent performance, it is necessary to increase the molecular weight of polyurethane acrylate or epoxy acrylate oligomer on the one hand, and reduce the amount of active diluent on the other hand, but both of them will cause the overall viscosity of the system to rise, affecting the use. Chinese patents with application numbers 201910790012.1 and 202110198554.7 disclose a class of polyurethane / polyurea acrylate oligomers containing large hindered urea bonds in their molecular structures. The large hindered urea bonds of these oligomers will dissociate at high temperatures, re-exposing the isocyanate groups, allowing them to react with water vapor or the urea bonds on their own molecular structures, further increasing the molecular weight of the polyurethane / polyurea, and forming an interpenetrating network system, thereby improving the overall performance of the material. However, this type of large hindered urea bond has a certain activity and is difficult to store and use for a long time in a high humidity or high temperature (greater than 70°C) environment. Summary of the invention

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

[0005] The invention objective of the present invention is achieved through the following technical route:

[0006] A dual-curing 3D printing resin, the dual-curing 3D printing resin comprising an acrylate oligomer containing a dynamic covalent bond and a blocked isocyanate crosslinker, wherein the acrylate oligomer containing a dynamic covalent bond is obtained by reacting an isocyanate-terminated oligomer with ethylene glycol acetoacetate methacrylate:

[0007]

[0008] The acrylate oligomer containing dynamic covalent bonds provided by the present invention generates vinyl carbamate through the reaction of isocyanate and acetoacetate. The chemical bond is a reversible dynamic bond, which will dissociate into amino group and vinyl ketone under heating. The generated amino group can further react with the blocked isocyanate cross-linking agent that releases the isocyanate group due to deprotection at high temperature to generate urea bond, thereby achieving rearrangement of the molecular and network structure and changing the material properties:

[0009]

[0010] Among them, 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) mixing the polyol and the polyisocyanate at 40-60° C. and stirring for reaction for 3-6 hours to obtain an isocyanate-terminated oligomer, wherein the molar ratio of isocyanate to hydroxyl is greater than 1;

[0013] 2) Add ethylene glycol acetoacetate and methacrylate dropwise into the isocyanate-terminated oligomer at 60-80° C., and stir to react 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 polyol, polyether polyol, polycarbonate polyol, polyolefin polyol or polyacrylate polyol;

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

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

[0017] In order to make the dual-curing 3D printing resin have better storage stability, the dissociation temperature of the blocked isocyanate cross-linking agent needs to be greater than 100°C, and the grade of the blocked isocyanate cross-linking agent is preferably BI7982, BI7950, Dornade 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 multifunctional acrylate / methacrylate, and the specific type and amount of the 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) phenyl phosphine oxide (819), 1-hydroxycyclohexyl phenyl ketone (184). Specifically, one or more combinations of corresponding photoinitiators need to be selected according to the wavelength of the curing light source.

[0021] The present invention also provides an application method of the dual-curing 3D printing resin, the application method comprising:

[0022] 1) mixing an acrylate oligomer containing a dynamic covalent bond, a blocked isocyanate crosslinking agent, a reactive diluent and a photoinitiator and then performing photocuring;

[0023] 2) The sample after light curing is subjected to heat post-treatment at a temperature of 120-160° C. and a heat treatment time of 3-6 hours.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: excellent photocuring performance, and the internal molecular structure and cross-linking density can be changed through 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 the 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 the form of a single component. BRIEF DESCRIPTION OF THE DRAWINGS

[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 state at 60°C. DETAILED DESCRIPTION

[0027] The content of the present invention is further explained below in conjunction with specific embodiments. The following embodiments are not simple limitations on the essential spirit of the present invention. Any simple changes or equivalent substitutions made based on the essential spirit of the present invention should fall within the scope of protection required by the present invention.

[0028] Example 1

[0029] 1.1000g PTMG (Mw=1000) was mixed with 336.38g HDI, and 1.13g dibutyltin dilaurate (DBTDL) was added. The mixture was stirred at 50°C for 4h to obtain an isocyanate-terminated oligomer PTMG 1K-HDI.

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

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

[0032] The mechanical properties of the resin after photocuring and before heat post-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] 1.650 g PTMG (Mw=650) and 444.56 g IPDI were mixed evenly, 0.82 g dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 60° C. for 4 h to obtain an isocyanate-terminated oligomer PTMG 650-IPDI;

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

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

[0039] Among them, the mechanical properties of the resin after light curing and before heat post-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] 1.530 g PCL (Mw = 530) and 336.38 g HDI were mixed evenly, 1.13 g dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 50 ° C for 6 h to obtain an isocyanate-terminated oligomer PCL 530-HDI;

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

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

[0046] The mechanical properties of the resin after photocuring and before thermal post-treatment are as follows: 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 Dornade E402-80B 711.28g IBOMA 200g DCPDA 30g TPO 15g Heat treatment process Heat treatment at 150℃ for 3h Tensile Strength 35MPa Elongation at break 21％ Young's modulus 877MPa

[0049] Example 4

[0050] 1.1000g PTMG (Mw=1000) was mixed evenly with 348.32g TDI, and 1.13g dibutyltin dilaurate (DBTDL) was added, and the mixture was stirred at 60°C for 5h to obtain an isocyanate-terminated oligomer PTMG 1K-TDI;

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

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

[0053] Among them, the mechanical properties of the resin after light curing and before heat post-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] Refer to Example 3 of invention patent CN113072678A

[0058] 1. Place 336.38 g of HDI in a flask and stir, add 2000 g of polyetheramine D2000 through a constant pressure dropping funnel, stir and react at 50°C after the addition is completed, and determine the reaction endpoint by the di-n-butylamine method to obtain an isocyanate-terminated intermediate product;

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

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

[0061] Take a certain amount of the photocurable resins in Examples 1-4 and the comparative example, place them in an oven at 60°C in an open or sealed form, take them out at regular intervals, cool them to room temperature, and measure the viscosity value: when stored in an open state at 60°C, the viscosity changes as follows: Figure 1 As shown, the viscosity changes when stored in a sealed state at 60°C. Figure 2 As shown. 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 the form of a single component.

[0062] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A dual-curing 3D printing resin, characterized in that: The dual-curing 3D printing resin includes an acrylate oligomer containing a dynamic covalent bond and a blocked isocyanate crosslinker, wherein the acrylate oligomer containing a dynamic covalent bond is obtained by reacting an isocyanate-terminated oligomer with ethylene glycol acetoacetate methacrylate:

2. The dual-curing 3D printing resin according to claim 1, characterized in that: The preparation method of the acrylate oligomer containing dynamic covalent bonds is as follows: 1) mixing the polyol and the polyisocyanate at 40-60° C. and stirring for reaction for 3-6 hours to obtain an isocyanate-terminated oligomer, wherein the molar ratio of isocyanate to hydroxyl is greater than 1; 2) Add ethylene glycol acetoacetate and methacrylate dropwise into the isocyanate-terminated oligomer at 60-80° C., and stir to react for 12-24 hours to obtain the acrylate oligomer containing dynamic covalent bonds.

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

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

5. 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 the acrylate oligomer containing dynamic covalent bonds*2.

6. The dual-curing 3D printing resin according to claim 1, characterized in that: The reactive diluent is a monofunctional or multifunctional acrylate / methacrylate.

7. 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) phenyl phosphine oxide or 1-hydroxycyclohexyl phenyl ketone.

8. A method for applying the dual-curing 3D printing resin according to any one of claims 1 to 7, characterized in that: The application method comprises: 1) mixing an acrylate oligomer containing a dynamic covalent bond, a blocked isocyanate crosslinking agent, a reactive diluent and a photoinitiator and then performing photocuring; 2) The sample after light curing is subjected to heat post-treatment at a temperature of 120-160° C. and a heat treatment time of 3-6 hours.

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