Reaction type closed diamine chain extender, dual-curing photosensitive resin, 3D printed part and preparation method

Abstract

The invention relates to a reaction type closed diamine chain extender, dual-curing photosensitive resin, a 3D printed part and a preparation method, the reaction type closed diamine chain extender is obtained through reaction of a diamine chain extender and a functional monomer, the functional monomer at least comprises a functional group A, a functional group B and a functional group C, the functional group A is an aldehyde group or a ketone group and is used for reacting with an amino group in the diamine chain extender; and a functional group B containing a photocurable unsaturated bond. The reactive closed diamine chain extender provided by the invention participates in a photocuring process, so that the strength of a material in a photocuring stage is improved, the product yield in a printing process is ensured, no by-product is generated during subsequent heat treatment, and the mechanical property of a final finished product is not influenced. The dual-curing photosensitive resin can be stably stored for a long time, the mechanical property of the material can be remarkably improved through the photocuring-heat treatment synergistic effect, and the dual-curing photosensitive resin can be used for photocuring 3D printing technologies such as sinking type SLA and pull-up type DLP and LCD at the same time.

Description

Technical Field

[0001] The present application relates to the technical field of polymer materials, and in particular to a reactive blocked diamine chain extender, a dual-curing photosensitive resin, a 3D printed part, and a preparation method. Background Art

[0002] Photocuring refers to the free radical polymerization and cross-linking reaction of photosensitive monomers and oligomers under light-induced curing. Due to its high efficiency, wide adaptability, economy, energy conservation, and environmental friendliness, photocuring technology is widely used in inks, adhesives, 3D printing, and other fields.

[0003] The core raw materials of photocurable resins typically include: 1) prepolymers (polyurethane acrylates, which provide high elasticity and impact resistance; epoxy acrylates, etc.), which directly determine the material's physical properties before and basic mechanical properties after photocuring; 2) reactive diluents (monofunctional or multifunctional acrylate monomers), the dosage of which not only determines the viscosity and mechanical properties of the cured material but also influences the photocuring reaction rate. 3) photoinitiators, the type and dosage of which directly determine the ability of the photosensitive resin to cure, affecting the degree of cure and the speed of photocuring. To increase the speed of photocurable 3D printing, multifunctional liquid raw materials are often used, which directly leads to brittleness of the printed material due to increased crosslinking density. Conventional toughening methods, such as increasing monomer molecular weight or introducing molecular design techniques such as multiple hydrogen bonds, also increase the material's viscosity and reduce its fluidity. Therefore, balancing resin fluidity, printing speed, and finished product performance has become a key technology driving the further development and application of 3D printing technology.

[0004] Carbon Corporation of the United States has proposed a dual-cure photosensitive resin (application number CN201680050991.1). The resulting material is a two-component material: one component is a polyurethane acrylate containing a large hindered urea bond, and the other is a polyol / polyamine chain extender. Before use, the two separately packaged components are mixed in a specific proportion and then cured with light or subjected to light-curing 3D printing. During post-treatment heating, the large hindered urea bonds break, exposing isocyanate groups. These react with free polyol / polyamine chain extenders in the system to produce polyurethane, thereby improving the material's toughness. Prolonged mixing of the polyol / polyamine with the resin will react with slowly dissociating isocyanate groups in the system; in addition, the polyol / polyamine will undergo Michael addition reactions with the terminal double bonds of the polyurethane acrylate. Both of these factors prevent the two components of the photosensitive resin from being directly mixed and stored, requiring them to be prepared immediately before 3D printing. At the same time, even if it is prepared for immediate use, the two components have a certain usage window period after being mixed together (spontaneously changing from liquid to solid), so the photosensitive resin cannot be used in industrial-grade sinking 3D printing processes that require a one-time feed of dozens or hundreds of kilograms of material.

[0005] Patent documents with application numbers CN201910790012.1 and CN202110198554.7 disclose two dual-cured polyurethane or polyurea acrylate oligomers. Both oligomers contain dissociable, large hindered urea bonds. After photocuring, the large hindered urea bonds dissociate during heat treatment, exposing isocyanate groups. However, the material systems of these two patents do not contain polyol / polyamine chain extenders, so the isocyanate groups exposed by dissociation react with urea bonds in the polymer chain structure or water in the heat treatment environment, thereby improving the material performance. Due to the lack of polyol / polyamine chain extenders, the dual-cured photosensitive resins in the above two patents are actually single-component materials, and their storage stability and 3D printing process window are very conducive to large-scale manufacturing. However, since the exposed isocyanate groups react with urea bonds in the polymer chain structure or water in the heat treatment environment, the performance adjustment range of the material is actually very limited, far inferior to that achieved by introducing polyol / polyamine chain extenders.

[0006] To address the contradiction between storage stability and the adjustable range of material properties, patent application CN202410823865.1 discloses a dual-curing photosensitive resin, its preparation method, and its application. The photosensitive resin raw materials include a polyurethane acrylate prepolymer containing a large hindered urea bond and a blocked diamine chain extender. Because the diamine chain extender is temporarily protected, it can coexist with the polyurethane acrylate prepolymer containing a large hindered urea bond for a long time and can be stored and used in a single-component form. After photocuring, through heat treatment, its molecular structure, crosslinking density, and other network structural characteristics are changed, forming an interpenetrating network and improving mechanical properties. However, the blocked diamine chain extender involved acts as a free inert component in the 3D printing process, resulting in a low gel content and poor mechanical properties of the printed products, affecting the printing yield. At the same time, during the heat treatment stage, the residual inorganic salts or gases generated after the blocked diamine chain extender is unblocked will also affect the final performance of the material. Summary of the Invention

[0007] The present application provides a diamine chain extender that can further improve the mechanical properties of photosensitive resins.

[0008] The present application provides a reactive blocked diamine chain extender, which is obtained by reacting a diamine chain extender with a functional monomer, wherein the functional monomer has at least: Functional group A is an aldehyde group or a ketone group, used to react with the amino group in the diamine chain extender; and Functional group B contains a photocurable unsaturated bond.

[0009] This application achieves the synergistic effect of dual photocuring and thermal curing reactions through the design of a reactive blocked diamine chain extender. This reactive blocked diamine chain extender participates in the free radical polymerization and crosslinking reaction of the photosensitive resin (polyurethane acrylate prepolymer and acrylate diluent) during the photocuring stage. This not only effectively improves the material strength and modulus during the photocuring printing stage, facilitating photocuring printing, but also prevents the escape of small molecules during the subsequent heat treatment stage. Furthermore, the resin system is stably stored as a single component (without the need to isolate the prepolymer and chain extender). During post-photocuring heat treatment, the isocyanate generated by the deblocking reaction continues to react with the amino group to form a polyurea interpenetrating network structure, without the generation of byproducts, significantly improving the material's mechanical properties.

[0010] Optionally, the unsaturated bond of the functional group B can undergo free radical polymerization, for example, the functional group B is selected from at least one of an acrylate group, a methacrylate group, an acrylamide group, and a methacrylamide group.

[0011] Optionally, the functional monomer is selected from at least one of diacetone acrylamide (DAA), acetoacetoxyethyl methacrylate (AAEMA), 4-formylbenzoic acid (2-methacryloyloxy)ethyl ester (FBEMA), and 4-formylbenzoic acid (2-acryloyloxy)ethyl ester (FBEA).

[0012] Optionally, the diamine chain extender (structural formula H2N-R-NH2, wherein R represents an aliphatic, alicyclic or aromatic group) is an aliphatic diamine, an alicyclic diamine or an aromatic diamine.

[0013] Optionally, the diamine chain extender is at least one of 4,4'-methylenebis(2-chloroaniline) (MOCA, structural formula), 4,4'-diaminodiphenylmethane (MDA, structural formula), p-phenylenediamine (PPDA, structural formula), p-phenylenediamine (structural formula), m-phenylenediamine, m-phenylenediamine and 4,4'-diaminodicyclohexylmethane (PACM, structural formula), and isophoronediamine (IPDA).

[0014] Optionally, the reaction equation of the diamine chain extender and diacetone acrylamide is as follows:

[0015] Optionally, the reaction equation of the diamine chain extender and acetoacetoxyethyl methacrylate is as follows:

[0016] Optionally, the reaction equation of the diamine chain extender and 4-formylbenzoic acid (2-methacryloyloxy) ethyl ester is as follows, wherein R1 is hydrogen or methyl:

[0017] The reactive blocked diamine chain extender of the present application will release amino groups under heating conditions (temperature greater than 100°C).

[0018] The present application also provides a dual-curing photosensitive resin, which includes the reactive blocked diamine chain extender described in the present application, a polyurethane acrylate prepolymer containing a large hindered urea bond, a reactive diluent, and a photoinitiator.

[0019] Optionally, the dual-curing photosensitive resin is composed of the reactive blocked diamine chain extender described in the present application, a polyurethane acrylate prepolymer containing a large hindered urea bond, a reactive diluent, and a photoinitiator.

[0020] The polyurethane acrylate prepolymer containing a large hindered urea bond temporarily protects the isocyanate group while providing a photocurable reactive group (acrylate); while the reactive blocked diamine chain extender temporarily protects the amino group while also providing a photocurable reactive group (acrylate).

[0021] During the UV-curing or UV-curable 3D printing stage, a polyurethane acrylate containing large sterically hindered urea bonds undergoes a free radical copolymerization reaction with a reactive blocked diamine chain extender to form a cross-linked network. Heat treatment of this product simultaneously releases the isocyanate and amino groups in the cross-linked network, which react to form a polyurea network. Blocking the diamine chain extender prevents the problem of conventional diamine chain extenders undergoing Michael addition reactions with acrylate groups in the polyurethane acrylate prepolymer during storage or use, which can render the resin material ineffective. Furthermore, because the diamine chain extender is reactively blocked, it avoids the low gel content and poor mechanical properties of printed products, which can result in low print yields, caused by the inability of conventional non-reactive blocked chain extenders to participate in the UV-curing process. Furthermore, residual UV-curing inerts or generated gases after heat treatment can affect material properties.

[0022] Optionally, the molar ratio of the reactive blocked diamine chain extender to the polyurethane acrylate prepolymer containing a large hindered urea bond is 1:1.

[0023] Optionally, the polyurethane acrylate prepolymer containing a large hindered urea bond releases an isocyanate group under heating conditions, and its structural formula is: .

[0024] Among them, the symbol " " does not represent a carbon chain. Its specific structure depends on the structure of the monomer raw materials (i.e., this segment is a polyurethane prepolymer, and its structure depends on the structures and feed ratio of the polyol and isocyanate. The details can be combined with the principle explanation below).

[0025] Optionally, the polyurethane acrylate prepolymer containing a large hindered urea bond is obtained by reacting a polyol, a polyisocyanate and tert-butylaminoethyl methacrylate, and the reaction formula is as follows:

[0026] Optionally, the relationship between the molar amounts of the polyol, polyisocyanate and tert-butylaminoethyl methacrylate is: n polyol×hydroxyl functionality+n tert-butylaminoethyl methacrylate=n polyisocyanate×isocyanate functionality, where n is a natural number not equal to 0.

[0027] Optionally, the reactive diluent is a monofunctional or multifunctional low-viscosity monomer of the acrylate or methacrylate type. The type and content of the reactive diluent can be adjusted according to the required mechanical properties. Preferably, the reactive diluent is one or more of EHA (isooctyl acrylate), PEGDA (polyethylene glycol diacrylate), IBOMA (isobornyl methacrylate), TMPTA (trimethylolpropane triacrylate), EHMA (isooctyl methacrylate), and THFA (tetrahydrofuran acrylate).

[0028] Optionally, the photoinitiator is a substance that can be cleaved under light of a specific wavelength to produce free radicals, thereby initiating double bond polymerization. In practical applications, a matching photoinitiator needs to be selected according to the wavelength of the light source used. For photocuring 3D printing, the wavelength of the light source commonly used is 355nm, 365nm, and 405nm. For example, the photoinitiator is preferably one or more of trimethylbenzoyl-diphenylphosphine oxide (TPO), bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide (819), and 1-hydroxycyclohexylphenyl ketone (184).

[0029] Optionally, the dual-curing photosensitive resin includes, in parts by weight: 40-60 parts of polyurethane acrylate prepolymer containing large hindered urea bonds; 10-30 parts of reactive blocked diamine chain extender; 20-40 parts of reactive diluent; Photoinitiator 0.5-5 parts.

[0030] Optionally, the dual-curing photosensitive resin includes, in parts by weight: 50 parts of polyurethane acrylate prepolymer containing large hindered urea bonds; 15-20 parts of reactive blocked diamine chain extender; 20-25 parts of reaction diluent; 1-2 parts of photoinitiator.

[0031] The present application also provides a method for preparing the dual-curing photosensitive resin, comprising stirring and uniformly mixing a reactive blocked diamine chain extender, a polyurethane acrylate prepolymer containing a large hindered urea bond, a reaction diluent and a photoinitiator to obtain the dual-curing photosensitive resin.

[0032] Optionally, stir to mix at room temperature.

[0033] The storage temperature of the dual-curing photosensitive resin prepared in the present application must be below the deblocking temperature of the polyurethane acrylate prepolymer with a large sterically hindered urea bond and the reactive blocked diamine chain extender.

[0034] Preferably, the storage temperature of the dual-cure photosensitive resin should be 20°C lower than the deblocking temperature of the urethane acrylate prepolymer with large hindered urea bonds and the blocked diamine chain extender. More preferably, the storage temperature should be 50°C lower than the deblocking temperature of the urethane acrylate prepolymer with large hindered urea bonds and the blocked diamine chain extender. For example, when the dual-cure photosensitive resin is stored in a sealed container at room temperature, the viscosity increase is less than 5% after 14 days and less than 10% after 28 days.

[0035] Optionally, the photocuring process of the dual-curing photosensitive resin is the copolymerization of a polyurethane acrylate prepolymer containing a large hindered urea bond and a reactive blocked diamine chain extender. Taking the reactive blocked diamine chain extender prepared by the diamine chain extender and ethyl acetoacetate methacrylate as an example, the chemical reaction is as follows:

[0036] Polyurethane acrylate prepolymer containing large hindered urea bonds +

[0037] Reactive blocked diamine chain extender copolymer ↓(after light curing)

[0038] Optionally, heat treatment is required after light curing to further improve the material properties. Two reactions occur during the heat treatment process, including the dissociation of the hindered urea bond in the polyurethane acrylate prepolymer containing a large hindered urea bond and the deblocking of the amino group in the reactive blocked diamine chain extender (Reaction A), and the reaction between the isocyanate and the amino group (Reaction B). The specific reaction equations are as follows:

[0039]

[0040] The reaction mechanism described above demonstrates that, after their respective deblocking steps, the reactive blocked diamine chain extender and the polyurethane acrylate prepolymer containing a bulky hindered urea bond react to form a polyurea, enhancing performance. Therefore, the molar ratio of the reactive blocked diamine chain extender to the blocked diisocyanate (polyurethane acrylate prepolymer containing a bulky hindered urea bond) in this photosensitive resin must meet certain requirements. Specifically, to ensure a sufficient reaction and optimal final material performance, the molar amount of the reactive blocked diamine chain extender should be equal to the molar amount of the polyurethane acrylate prepolymer containing a bulky hindered urea bond.

[0041] Optionally, the dual-curing photosensitive resin has a tensile strength of 18-35 MPa and an elongation at break of 85-342% after curing.

[0042] Optionally, the dual-curing photosensitive resin has a tensile strength of 25-35 MPa and an elongation at break of 85-150% after curing, making it more suitable for structural parts requiring high rigidity and load-bearing capacity.

[0043] Optionally, the dual-curing photosensitive resin has a tensile strength of 18-25 MPa and an elongation at break of 250-342% after curing, making it more suitable for parts requiring flexibility and impact resistance.

[0044] The present application also provides a 3D printed part, which is obtained by 3D printing using the dual-curing photosensitive resin described in the present application as a raw material.

[0045] This application does not directly and strictly limit the 3D method and specific equipment type. For example, it can be used for sinking SLA and top-pull DLP, LCD and other light-curing 3D printing.

[0046] This application also provides a method for preparing a 3D printed part, comprising: Step S100: providing the dual-curing photosensitive resin described in the present application, and performing light-curing 3D printing according to a preset shape to obtain a prefabricated part; Step S200: heating the preform to obtain the 3D printed part, wherein the preform is heated at a temperature of 100-140° C. for a time of 30 minutes to 12 hours.

[0047] Compared with the existing technology, this application has the following advantages and technical effects: (1) The reactive blocked diamine chain extender provided in this application participates in the photocuring process, thereby improving the strength of the material during the photocuring stage and ensuring the product yield during the printing process. In addition, there are no by-products during the subsequent heat treatment, which will not affect the mechanical properties of the final product.

[0048] (2) The present application obtains a photosensitive resin by uniformly mixing a polyurethane acrylate prepolymer having a large sterically hindered urea bond, a reactive blocked diamine chain extender, a reactive diluent, and a photoinitiator raw material, which can be stably stored for a long time.

[0049] (3) The mechanical properties of the material can be significantly improved through the synergistic effect of photocuring and heat treatment.

[0050] (4) The photosensitive resin provided in this application can be used for both sinking SLA and top-up DLP, LCD and other light-curing 3D printing technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0052] Figure 1 This is a graph showing the viscosity change of the photosensitive resin in Examples 1 to 4 of the present application when stored at room temperature and in a sealed condition; Figure 2 This is a graph showing the viscosity change of the photosensitive resin in Comparative Example 1 when stored at room temperature and in a sealed condition; Figure 3 This is a graph showing the viscosity change of the photosensitive resin in Comparative Example 2 when stored at room temperature and in a sealed condition; Figure 4 This is a flow chart of the preparation method of 3D printed parts in this application. DETAILED DESCRIPTION

[0053] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0054] Unless otherwise defined, all technical and scientific terms used in the specification of this application have the same meaning as commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in the specification of this application includes any and all combinations of one or more of the relevant listed items.

[0055] The embodiment of the present application provides a dual-curing photosensitive resin, the raw materials of which include a polyurethane acrylate prepolymer containing a large hindered urea bond and a reactive blocked diamine chain extender; Preparation of reactive blocked diamine chain extender: The reactive blocked diamine chain extender is obtained by reacting a diamine chain extender with one of diacetone acrylamide (DAA), acetoacetoxyethyl methacrylate (AAEMA), 4-formylbenzoic acid (2-methacryloyloxy)ethyl ester (FBEMA), and 4-formylbenzoic acid (2-acryloyloxy)ethyl ester (FBEA).

[0056] In a preferred embodiment of the present application, the diamine chain extender is an aliphatic diamine, an alicyclic diamine, or an aromatic diamine. More preferably, the diamine chain extender is at least one of the following: 4,4'-methylenebis(2-chloroaniline) (MOCA, structural formula is ), 4,4'-methylenediaminodiphenylmethane (MDA, structural formula is )、 p-phenylenediamine (PPDA, structural formula is )、 4,4'-Diaminodicyclohexylmethane (PACM, structural formula is ).

[0057] Taking 4,4'-diaminodiphenylmethane (MDA) and diacetone acrylamide (DAA) as an example, the reaction equation is:

[0058] The specific preparation steps of the reactive blocked diamine chain extender are as follows: 4,4'-Diaminodiphenylmethane and diacetone acrylamide were dissolved in dichloromethane at a molar ratio of 1:2 and stirred at room temperature for 12 h. During the reaction, the generated water was continuously removed. Finally, the solvent was removed by rotary evaporation to obtain the product, a reactive blocked diamine chain extender (MDA-DAA). The preparation and naming of the remaining reactive blocked diamine chain extender combinations were as described above.

[0059] The specific preparation steps of the polyurethane acrylate prepolymer containing large sterically hindered urea are as follows: (1) 1000 g PTMG (Mw = 1000) and 336.38 g HDI were mixed evenly, and 1.13 g dibutyltin dilaurate (DBTDL) was added. o C and stirred for 4 h to obtain isocyanate-terminated oligomer PTMG 1K-HDI; (2) 370.54 g of 2-tert-butylaminoethyl methacrylate (TBEMA) was slowly added dropwise to the above reaction system. o C and continued stirring for 3 h to obtain a polyurethane acrylate prepolymer PTMG 1K-HDI-TBEMA containing a large sterically hindered urea.

[0060] An embodiment of the present application also provides a method for preparing the dual-curing photosensitive resin, wherein the raw materials of the polyurethane acrylate prepolymer containing a large hindered urea bond, a blocked diamine chain extender, a reaction diluent and a photoinitiator are uniformly mixed to obtain the dual-curing photosensitive resin.

[0061] The technical solution of this application is further illustrated by examples below.

[0062] Example 1 PTMG 1K-HDI-TBEMA, reactive blocked diamine chain extender (MDA-DAA), EHA (isooctyl acrylate), PEGDA (polyethylene glycol diacrylate), and TPO (trimethylbenzoyl-diphenylphosphine oxide) were weighed according to the amounts listed in Table 1 and then mixed evenly to obtain a dual-cure photosensitive resin.

[0063] The dual-curing photosensitive resin prepared in Example 1 was photocured and then heat-treated at 120° C. for 8 h. The tensile strength, elongation at break, and Young's modulus of the obtained product were measured. The results are shown in Table 1.

[0064] Table 1 Amount of each raw material and performance test results in Example 1

[0065] Example 2 PTMG 1K-HDI-TBEMA, reactive blocked diamine chain extender (PPDA-AAEMA), IBOMA (isobornyl methacrylate), TMPTA (trimethylolpropane triacrylate), and TPO were weighed according to the amounts listed in Table 2 and then mixed evenly to obtain a dual-cure photosensitive resin.

[0066] The dual-curing photosensitive resin prepared in Example 2 was photocured and then heat-treated at 130° C. for 4 h. The tensile strength, elongation at break, and Young's modulus of the obtained product were measured. The results are shown in Table 2.

[0067] Table 2 Amounts of raw materials and performance test results in Example 2

[0068] Example 3 PTMG 1K-HDI-TBEMA, reactive blocked diamine chain extender (PACM-FBEMA), IBOMA (isobornyl methacrylate), TMPTA (trimethylolpropane triacrylate), and TPO were weighed according to the amounts listed in Table 2 and then mixed evenly to obtain a dual-cure photosensitive resin.

[0069] The dual-curing photosensitive resin prepared in Example 3 was photocured and then heat-treated at 100° C. for 30 min. The tensile strength, elongation at break, and Young's modulus of the obtained product were measured. The results are shown in Table 3.

[0070] Table 3 Amounts of raw materials and performance test results in Example 3

[0071] Example 4 PTMG 1K-HDI-TBEMA, reactive blocked diamine chain extender (PACM-DAA), EHMA (isooctyl methacrylate), TMPTA (trimethylolpropane triacrylate), and TPO were weighed according to the amounts listed in Table 4 and then mixed evenly to obtain a dual-cure photosensitive resin.

[0072] The dual-curing photosensitive resin prepared in Example 4 was photocured and then heat-treated at 130° C. for 6 h. The tensile strength, elongation at break, and Young's modulus of the obtained product were measured. The results are shown in Table 4.

[0073] Table 4 Amounts of raw materials and performance test results in Example 4

[0074] Comparative Example 1 Referring to patent application number CN202410823865.1, a diamine chain extender (structural formula H2N-R-NH2, where R represents an aliphatic, cycloaliphatic or aromatic group) reacts with an inorganic salt (MyXz) to obtain a bottom-blocked diamine chain extender. The reaction equation is as follows:

[0075] In Comparative Example 1, the diamine chain extender is MDA and the inorganic salt is sodium chloride.

[0076] The specific steps are as follows: a saturated aqueous solution of 4,4'-diaminodiphenylmethane and sodium chloride is placed in a small ball mill with cooling at a molar ratio of 3:1, ball milled for 7 hours, then washed twice with water, washed twice with chlorobenzene, dried, and then crushed with a jet mill to obtain the product, a blocked diamine chain extender (MDA-NaCl); The photosensitive resin obtained by replacing the equivalent amount of the reactive blocked diamine chain extender MDA-DAA in the dual-curing photosensitive resin of Example 1 of the present application with the blocked diamine chain extender MDA-NaCl prepared by the above reaction is recorded as Comparative Example 1. The specific formula is shown in Table 5.

[0077] Table 5 Amounts of raw materials in comparative example 1

[0078] Comparative Example 2 The photosensitive resin obtained by replacing an equivalent amount of the reactive blocked diamine chain extender in the dual-curing photosensitive resin of Example 1 of the present application with an unblocked diamine chain extender (i.e., replacing it with an equivalent molar amount of MDA) is recorded as Comparative Example 2. The specific formula is shown in Table 6.

[0079] Table 6 Amounts of raw materials in comparative example 2

[0080] Storage stability test The dual-curing photosensitive resins prepared in Examples 1-4, Comparative Examples 1 and 2 were stored at room temperature and in a sealed condition. The viscosity changes were as follows: Figure 1-3 As shown by Figure 1 It can be seen that all examples have good storage stability, which is because the active isocyanate groups and amino groups in the corresponding photosensitive resins are effectively protected.

[0081] Depend on Figure 2 It can be seen that although the diamine chain extender also provides effective protection, the affinity of the inorganic salt for water causes the water content in the resin to increase during long-term storage, and some slowly dissociated isocyanates react with water, resulting in a slightly larger increase in viscosity in Comparative Example 2 than in Examples 1-4.

[0082] Depend on Figure 3 It can be seen that when the diamine chain extender is not blocked and protected, the viscosity of the photosensitive resin will increase rapidly during storage, making it unusable. The reason is that the amino group of the diamine chain extender undergoes an addition reaction with other polyurethane acrylate polymers or double bonds in the reactive diluent in the photosensitive resin, thereby reducing its storage stability.

[0083] Gel content test A certain amount of the dual-cured photosensitive resin prepared in Examples 1-4 and Comparative Examples 1 and 2 was taken and weighed after photocuring, respectively, recorded as W0. Each sample was immersed in tetrahydrofuran, sealed, and placed at room temperature. The solvent was replaced every 6 hours for a total immersion time of 72 hours. Each sample was removed, the surface was rinsed with fresh solvent, and dried to constant weight in a 50°C vacuum drying oven. After cooling, it was weighed and recorded as W1. The gel content of each sample was calculated using the following formula:

[0084] In this application, the gel content of the photocured (printing stage) product is relatively high, and its mechanical properties are better, which can effectively improve the success rate of printing.

[0085] Mechanical properties testing The photosensitive resins of Example 1 and Comparative Examples 1 and 2 were photocured, and the tensile strength, elongation at break and Young's modulus of the obtained products were measured.

[0086] The specific results of gel content and mechanical properties are shown in Table 5 Table 5 Mechanical properties and gel content of samples after photocuring in Examples 1-4 and Comparative Examples 1 and 2

[0087] Table 5 illustrates that the polyurethane acrylate prepolymer and diamine chain extender MDA used in Example 1, Comparative Examples 1, and 2 are identical, differing only in the blocking method used for the MDA. Comparative Example 1 employs a non-reactive blocking method, while Comparative Example 2 employs no blocking method. The MDA in both examples is unable to participate in the cross-linking reaction of the polyurethane acrylate prepolymer during the photocuring stage, resulting in low modulus and strength of the resulting material. Low modulus and strength are detrimental to high-precision molding in photocuring printing, leading to reduced product yield during the actual printing process. The reactive blocked diamine chain extender described in this application effectively addresses this issue. It not only participates in the photocuring cross-linking reaction, effectively ensuring molding accuracy and product yield during the photocuring stage, but also enables a byproduct-free unblocking and chain extension reaction during the subsequent heat treatment process, thereby avoiding the effects of residual or dissipated conventional blocking agents on the mechanical properties of the material, ultimately resulting in a cured product with excellent overall performance.

[0088] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person skilled in the art may make various modifications and improvements without departing from the spirit of the present application, and such modifications and improvements are all within the scope of protection of the present application.

Claims

1. A reactive blocked diamine chain extender, characterized in that: Obtained by the reaction of a diamine chain extender and a functional monomer, wherein the functional monomer has at least: Functional group A is an aldehyde group or a ketone group, used to react with the amino group in the diamine chain extender; and Functional group B contains a photocurable unsaturated bond.

2. The reactive blocked diamine chain extender according to claim 1, characterized in that The functional group B is selected from at least one of an acrylate group, a methacrylate group, an acrylamide group, and a methacrylamide group.

3. The reactive blocked diamine chain extender according to claim 1, characterized in that The functional monomer is at least one selected from diacetone acrylamide, acetoacetoxyethyl methacrylate, 4-formylbenzoic acid (2-methacryloyloxy) ethyl ester, and 4-formylbenzoic acid (2-acryloyloxy) ethyl ester; The diamine chain extender is selected from at least one of 4,4'-methylenebis(2-chloroaniline), 4,4'-diaminodiphenylmethane, p-phenylenediamine, p-phenylenediamine, m-phenylenediamine, m-phenylenediamine, 4,4'-diaminodicyclohexylmethane, and isophoronediamine.

4. A dual-curing photosensitive resin, characterized in that: The dual-curing photosensitive resin comprises the reactive blocked diamine chain extender according to claim 1, a polyurethane acrylate prepolymer containing a large hindered urea bond, a reactive diluent and a photoinitiator.

5. The dual-curing photosensitive resin according to claim 4, characterized in that: In parts by weight, the dual-curing photosensitive resin comprises: 40-60 parts of polyurethane acrylate prepolymer containing large hindered urea bonds; 10-30 parts of reactive blocked diamine chain extender; 20-40 parts of reactive diluent; Photoinitiator 0.5-5 parts.

6. The dual-curing photosensitive resin according to claim 5, characterized in that: In parts by weight, the dual-curing photosensitive resin comprises: 50 parts of polyurethane acrylate prepolymer containing large hindered urea bonds; 15-20 parts of reactive blocked diamine chain extender; 20-25 parts of reaction diluent; 1-2 parts of photoinitiator.

7. The dual-curing photosensitive resin according to claim 4, characterized in that: The polyurethane acrylate prepolymer containing a large hindered urea bond has the following general structural formula: 。 8. The dual-curing photosensitive resin according to claim 4, characterized in that: The dual-curing photosensitive resin has a tensile strength of 18-35 MPa and an elongation at break of 85-342% after curing.

9. A 3D printed part, characterized in that: The dual-curing photosensitive resin described in any one of items 4 to 8 is used as a raw material and is obtained by 3D printing.

10. A method for preparing a 3D printed part, characterized in that: include: Step S100: providing the dual-curing photosensitive resin described in any one of items 4 to 8, and performing light-curing 3D printing according to a preset shape to obtain a prefabricated part; Step S200: heating the preform to obtain the 3D printed part, wherein the preform is heated at a temperature of 100-140° C. for a time of 30 minutes to 12 hours.

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