Reversibly and reactively blocked polyurethane prepolymer, polymerizable liquid, and 3D printing method

Abstract

The description of the present invention provides a reversibly and reactively blocked polyurethane prepolymer, a polymerizable liquid, and a 3D printing method. The reversibly and reactively blocked polyurethane prepolymer comprises a reactively blocking group, a polyurethane prepolymer, and an independent protecting group. The polymerizable liquid comprises at least one of the reversibly and reactively blocked polyurethane prepolymer, and / or at least one reversibly and reactively blocked polyisocyanate, wherein each reversibly and reactively blocked polyisocyanate comprises a reactively blocking group, a polyisocyanate, an independent protecting group, a reactive diluent, and a photoinitiator. The polymerizable liquid does not comprise an independent curing agent, thereby improving the overall stability of the polymerizable liquid.

Description

Reversibly capped reactive capped polyurethane prepolymer, polymerizable liquid and 3D printing method TECHNICAL FIELD

[0001] The present application relates to the technical field of 3D printing, in particular to a reversibly capped reactive capped polyurethane prepolymer, a polymerizable liquid and a 3D printing method. BACKGROUND

[0002] As an emerging additive manufacturing technology, 3D printing has been widely used in the fields of life and health, aerospace, automobiles, etc. Among many 3D printing technologies, light-curing 3D printing technology is widely promoted due to its low cost and high throughput.

[0003] Light-curing 3D printing technology is a technology that completes 3D printing through the curing of a polymerizable liquid under the irradiation of visible light or ultraviolet light. The polymerizable liquid can include various components, among which polyurethane, as a high molecular compound, has good chemical resistance, stability, resilience and excellent mechanical properties, and is widely used in polymerizable liquids. Light-curing 3D printing with polyurethane requires the additional introduction of a curing agent, and the introduction of the curing agent will affect the chain extension process of polyurethane. Therefore, if a high-performance polyurethane material is to be obtained, the molecular weight of the polyurethane prepolymer needs to be continuously expanded, but a larger molecular weight will result in a larger viscosity. Therefore, it is necessary to provide better materials and production methods to balance the molecular weight and viscosity of the polyurethane prepolymer to achieve better printing results. SUMMARY

[0004] The present application provides a reversibly capped reactive capped polyurethane prepolymer, a polymerizable liquid and a 3D printing method, so that the polymerizable liquid does not contain an independent curing agent, simplifying the printing process and improving the overall stability of the polymerizable liquid.

[0005] To achieve the above-mentioned purpose, the embodiments of the present application adopt the following technical solutions:

[0006] In a first aspect, the embodiments of the present application provide a reversibly capped reactive capped polyurethane prepolymer, which comprises a reactive capped group, a polyurethane prepolymer, and an independent protecting group.

[0007] According to some embodiments of the present application, the polyurethane prepolymer comprises at least one polyisocyanate oligomer.

[0008] According to some embodiments of the present application, the reversibly capped reactive capped polyurethane prepolymer comprises the structure of formula (A1) and (A2):

[0009] wherein R1, R2, R3, Z comprise independently selected hydrocarbyl groups; X, X1 comprise NH or O; B1 comprises the reactive capping group; B2 comprises the independent protecting group.

[0010] According to some embodiments of the application, the reactive capping group B1 comprises a reactive epoxy group, an alkenyl group, an alkynyl group, or a blocked thiol end group.

[0011] According to some embodiments of the application, the reactive capping group B1 comprises 2-(tert-butylamino)methyl acrylate.

[0012] According to some embodiments of the application, the independent protecting group B2 comprises a protecting group for an amino group or a hydroxyl group.

[0013] According to some embodiments of the application, the independent protecting group B2 comprises an imino group comprising a substituent resulting from the reaction of an aldehyde or a ketone with an amine.

[0014] According to some embodiments of the application, the reactive capping group B1 and the independent protecting group B2 each independently comprise a photocurable group.

[0015] According to some embodiments of the application, the photocurable group comprises an acrylate group or a methacrylate group.

[0016] In a second aspect, embodiments of the application provide a polymerizable liquid for 3D printing, comprising at least one reversibly capped reactive capping polyurethane prepolymer, each of the reversibly capped reactive capping polyurethane prepolymer comprising the reversibly capped reactive capping polyurethane prepolymer of any one of the above first aspect; and / or at least one reversibly capped reactive capping polyisocyanate, each of the reversibly capped reactive capping polyisocyanate comprising a reactive capping group, a polyisocyanate, and an independent protecting group; and a reactive diluent; and a photoinitiator, wherein the polymerizable liquid is free of an independent curing agent.

[0017] According to some embodiments of the application, the polyisocyanate comprises a diisocyanate.

[0018] According to some embodiments of the application, the reactive diluent comprises an acrylate, a methacrylate.

[0019] In a third aspect, embodiments of the present application provide a 3D printing method, comprising: providing a printing area, the printing area being defined by a build platform and a resin container comprising a forming surface; filling the printing area with the polymerizable liquid of any one of the second aspect described above; exposing the polymerizable liquid in the printing area to energy to solidify the polymerizable liquid into a solid printing intermediate having a shape substantially identical to that of a target printed object; and providing energy to the printing intermediate by heating, microwave radiation, or using other methods to form the target printed object.

[0020] According to some embodiments of the present application, the target printed object comprises a blend polymer of polyurethane and polyacrylate.

[0021] According to some embodiments of the present application, the target printed object comprises a copolymer of polyurethane and polyacrylate.

[0022] In summary, the present specification provides a reversibly blocked reactive blocked polyurethane prepolymer, a polymerizable liquid, and a 3D printing method. The reversibly blocked reactive blocked polyurethane prepolymer comprises a reactive blocking group, a polyurethane prepolymer, and an independent protecting group. The polymerizable liquid comprises at least one reversibly blocked reactive blocked polyurethane prepolymer described above, and / or at least one reversibly blocked reactive blocked polyisocyanate, each of which comprises a reactive blocking group, a polyisocyanate, and an independent protecting group, a reactive diluent, and a photoinitiator. The polymerizable liquid does not contain an independent curing agent, which on the one hand eliminates the step of adding an additional curing agent, simplifying the printing process, and on the other hand reduces the number of unstable components in the system, improving the overall stability of the polymerizable liquid. DETAILED DESCRIPTION

[0023] The following description provides specific applications and requirements of the present specification, which is intended to enable a person skilled in the art to manufacture and use the content of the present specification. Various modifications to the disclosed embodiments are apparent to those skilled in the art, and the general principles defined herein can be applied to other embodiments and applications without departing from the spirit and scope of the present specification. Therefore, the present specification is not limited to the embodiments shown, but is consistent with the widest scope of the claims.

[0024] In order to facilitate the understanding of the present specification, the present specification will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present specification are shown in the drawings. However, the present specification can be implemented in many different forms without departing from the core spirit of the present specification, and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present specification more thorough and comprehensive.

[0025] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. For example, singular forms "a", "an" and "the" are intended to mean one or more, unless the context clearly indicates otherwise. As used herein, the terms "including", "containing", and / or "comprising" mean that the integers, steps, operations, elements, and / or components associated with the system / method are present, but not excluding the presence of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0026] In the present application, the expression "X includes at least one of A, B, or C" means that X includes at least A, or X includes at least B, or X includes at least C. That is, X can include any combination of A, B, C, or any combination of A, B, C and other possible components / elements. The combination of A, B, C can be A, B, C, AB, AC, BC, or ABC.

[0027] In the present application, the terms "curing", "hardening" or "polymerization" all refer to the process of forming a three-dimensional polymer network from monomers, oligomers, prepolymers and / or polymers.

[0028] In a first aspect, the present specification provides a reversibly capped reactive capped polyurethane prepolymer. The use scenarios of the reversibly capped reactive capped polyurethane prepolymer can be various, including but not limited to the field of 3D printing. In some embodiments, the reversibly capped reactive capped polyurethane prepolymer can be used for coating and protective layer, so as to provide wear-resistant and anti-corrosion protection for metals or plastics. In some embodiments, the reversibly capped reactive capped polyurethane prepolymer can be used for chip packaging, so as to provide electrical insulation and physical protection for semiconductor chips. The use scenarios of the reversibly capped reactive capped polyurethane prepolymer in the present specification are not limited.

[0029] The reversibly capped reactive capped polyurethane prepolymer described in the present application comprises a reactive capping group, a polyurethane prepolymer, and an independent protecting group.

[0030] The reversibly capped reactive capped polyurethane prepolymer comprises the structure of formula (A1), (A2):

[0031] wherein R1, R2, R3, Z comprise independently selected hydrocarbyl groups; X, X1 comprise NH or O; B1 comprises the reactive endcapping group; B2 comprises the independent protecting group.

[0032] The polyurethane prepolymer can be the basis for the final polyurethane material, which determines the physical and chemical properties of the final product. The polyurethane prepolymer is prepared by the prepolymerization of a polyol and a polyisocyanate. The polyurethane prepolymer contains active isocyanate groups, which react with other active hydrogen containing components during the curing process to form a three-dimensional crosslinked network. The independent protecting group can be used to temporarily protect certain sensitive functional groups in the prepolymer to avoid unwanted side reactions during storage or processing.

[0033] The polyurethane prepolymer can comprise at least one polyisocyanate oligomer, i.e., the polyurethane prepolymer can comprise one polyisocyanate oligomer or a plurality of polyisocyanate oligomers. It is understood that the polyurethane prepolymer contains a plurality of isocyanate (-NCO) groups. Specifically, the polyurethane prepolymer comprises a polyisocyanate oligomer generated from the reaction of at least one polyisocyanate and at least one polyol. The polyisocyanate comprises a diisocyanate or a polyisocyanate compound having more than two isocyanate (-NCO) groups, i.e., the polyurethane prepolymer can comprise a polyurethane oligomer generated from the reaction of at least one diisocyanate or polyisocyanate and at least one polyol.

[0034] The polyurethane prepolymer can be a polyisocyanate oligomer generated from the reaction of a polyisocyanate and a polyol. During the above reaction, the polyisocyanate can comprise a diisocyanate or a polyisocyanate other than a diisocyanate. The polyisocyanate other than a diisocyanate can be a plurality, such as hexamethylene diisocyanate trimer (HDI trimer), isophorone diisocyanate trimer (IPDI trimer). Further, the diisocyanate can be a plurality, such as diisocyanate including but not limited to isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), methylene bis(phenyl isocyanate) (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), methylene bis-cyclohexyl isocyanate (HMDI).

[0035] The polyols can also be of various types, for example, the polyols include but are not limited to polyether polyols and polyester polyols, such as polytetramethylene glycol (PTMG). Because there are various types of diisocyanates, various types of polyisocyanates, and various types of polyols, there are also various types of polyurethane prepolymers formed from the reaction of diisocyanates or polyisocyanates and polyols. Thus, the polyurethane prepolymers can include at least one diisocyanate or at least one polyisocyanate oligomer formed from the reaction of at least one diisocyanate or at least one polyisocyanate and at least one polyol. For example, the polyurethane prepolymers can also include one polyisocyanate oligomer formed from the reaction of one diisocyanate or one polyisocyanate and one polyol, and another polyisocyanate oligomer formed from the reaction of another diisocyanate or another polyisocyanate and another polyol, and so on.

[0036] The reactive capping groups can increase the storage stability of the prepolymers, preventing them from reacting with moisture in the air in an uncured state. The reactive capping groups can be any group that can be removed by chemical reaction when needed. They are able to temporarily block the isocyanate groups, preventing them from reacting with water or other active hydrogen compounds. Once the curing reaction is needed, the reactive capping groups can be activated by heating or adding a specific deblocking agent, allowing them to release active isocyanate groups.

[0037] The reactive capping groups B1 can be used to reversibly block isocyanate (-NCO) groups. That is, the linkage between the reactive capping groups B1 and isocyanate (-NCO) groups is thermally unstable or otherwise unstable, so under unstable conditions, such a linkage will break, exposing the isocyanate group (-NCO), allowing it to freely react with other components. The reactive capping groups B1 can include blocking groups for isocyanate (-NCO) groups, including but not limited to: phenol, nonylphenol, pyridinol, oxime, thio-phenol, thiol, amide, cyclic amide, imide, imidazole, imidazoline, methyl ethyl ketone oxime (MEKO), alcohol, ε-caprolactam, pyrazole, triazole, amidine, hydroxylate, and the like.

[0038] In some embodiments, the reactive capping groups B1 can include a reactive end group, allowing the polyurethane prepolymers to be reversibly blocked. The reactive end groups included by the reactive capping groups B1 include but are not limited to blocking groups for epoxy, alkenyl, alkyl, alkynyl, or thiol end groups. For example, the reactive end group included by the reactive capping groups B1 is 2-(tert-butylamino)ethyl methacrylate (abbreviated as tBAEMA), having the following molecular formula:

[0039] In this example, the steric hindrance of the tert-butyl group makes the linkage between the blocking group and the isocyanate (-NCO) group unstable, and the linkage can break upon heating, thus allowing the isocyanate (-NCO) group to react with the curing agent or other components in the polymerizable liquid under heating conditions. In other examples, the reactive blocking group B1 can be tert-amyl methacrylate (TPAEMA), tert-hexyl methacrylate (THAEMA), tert-butyl methacrylate (TBAPMA), and mixtures thereof. Those skilled in the art can couple a (meth)acrylate group to the blocking group of the known isocyanate (-NCO) group described above.

[0040] The independent protecting group B2 can be used to temporarily protect certain sensitive functional groups in the prepolymer to avoid unwanted side reactions during storage or processing. In particular, the independent protecting group B2 can be a class of easily removable chemical groups that can be selectively removed under certain conditions (e.g., heating or using certain reagents). The presence of the protecting group helps to maintain the stability of the prepolymer during storage and transportation. Once the prepolymer is ready for the curing reaction, the protecting group is removed, thus releasing the originally protected functional group to participate in the subsequent chemical reactions. These components work together to allow the polyurethane prepolymer to remain stable for a long period of time and to initiate the curing reaction to form the desired final product when needed through simple chemical treatment.

[0041] The independent protecting group B2 includes the independent protecting group. In particular, the independent protecting group includes protecting groups for protecting amino groups or hydroxyl groups. The amino protecting group can include, but is not limited to, carbonyl groups, acyl groups, alkyl groups, and amino groups, and combinations thereof. In particular, the carbonyl group can include, but is not limited to, benzyloxycarbonyl (Cbz), tert-butyloxycarbonyl (Boc), pivaloyloxycarbonyl (Fmoc), allyloxycarbonyl (Alloc), trimethylsilylethoxycarbonyl (Teoc), meth(oxy)carbonyl, and combinations thereof. The acyl group can include, but is not limited to, phthaloyl (Pht), p-toluenesulfonyl (Tos), trifluoroacetyl (Tfa), and combinations thereof. The alkyl group can include, but is not limited to, trityl (Trt), 2,4-dimethoxybenzyl (Dmb), p-methoxybenzyl (PMB), benzyl (Bn), and combinations thereof. The amino group can include, but is not limited to, 1-chloroethylcarbamate, 4-methoxybenzenesulfonamide, acetamide, benzylamine, benzyloxy carbamate, formamide, methyl carbamate, trifluoroacetamide, and combinations thereof.

[0042] Hydroxyl protecting groups can include, but are not limited to, silyl ethers, benzyl ethers, substituted benzyl ethers, substituted methyl ethers, alkoxymethyl ethers, allyl ethers, aryl ethers, and combinations thereof. Among these, silyl ethers can include trimethylsilyl (TMS), tert-butyldimethylsilyl (TBDMS), tert-butyldiphenylsilyl (TBDPS), triisopropylsilyl (TIPS), and combinations thereof. Benzyl ethers (Bn) can include alkylhydroxy benzyl ethers, p-methoxybenzyl ether (PMB), trityl ethers, and combinations thereof. Alkoxymethyl ethers can include 2-tetrahydropyranyl ether (THP), methoxymethyl ether (MOM), a 2-ethoxyethyl ether (EE), 2-trimethylsilylethoxymethyl ether (SEM), and combinations thereof.

[0043] In some embodiments, hydroxyl protecting groups can also include, but are not limited to, acetyl, benzoyl, pivaloyl, acetate, benzoate, pivalate, and combinations thereof. In some embodiments, hydroxyl protecting groups can also include, but are not limited to, 2,2,2-trichloroethyl carbonate, 2-methoxyethoxymethyl ether, 2-naphthyl methyl ether, 4-methoxybenzyl ether, acetate, benzoate, benzyl ether, benzyloxy methyl acetal, ethoxyethyl acetal, methoxymethyl acetal, methoxypropyl acetal, methyl ether, tetrahydropyranyl acetal, triethylsilyl ether, triisopropylsilyl ether, trimethylsilyl ether, tert-butyldiphenylsilyl ether, acetylide, benzaldehyde acetal, carbonate, benzaldehyde acetal, di-tert-butyl dioxolane, and combinations thereof.

[0044] In some embodiments, the independent protecting group includes a protecting group for an amine or imine. In this case, it can include, but is not limited to, a carboxylic acid or anhydride group, an acid chloride group, an aldehyde group, or a ketone group.

[0045] The independent protecting group includes an imino group, the imino group including a substituent resulting from the reaction of an aldehyde with an amine, and the imino group including a substituent resulting from the reaction of a ketone with an amine. In some embodiments, the imino group is a substituent resulting from the reaction of acetaldehyde with ammonia. In some embodiments, the imino group is a substituent resulting from the reaction of benzaldehyde with ethylamine. In some embodiments, the imino group is a substituent resulting from the reaction of acetaldehyde with aniline.

[0046] In some embodiments, the reactive capping group B1 and the independent protecting group B2 can each independently include a photocurable group. Specifically, the reactive capping group B1 can include a photocurable group, the independent protecting group B2 can also include a photocurable group, and the presence or absence of a photocurable group in the reactive capping group B1 and the independent protecting group B2 is independent of each other. The photocurable group can include, but is not limited to, an acrylate group, a methacrylate group, an alkene group, an N-vinyl group, an acrylamide group, a methacrylamide group, a styrene group, an epoxy group, a thio group, a 1,3-diene group, a halo-vinyl group, an acrylonitrile group, a vinyl ester group, a maleimide group, a vinyl ether group, and combinations thereof. In some embodiments, the photocurable group can include an epoxy / amine group, an epoxy / hydroxyl group, an oxetane / amine group, an oxetane / alcohol group.

[0047] In a second aspect, the present specification provides a polymerizable liquid. The polymerizable liquid is suitable for use in a 3D printing scenario. The polymerizable liquid includes at least one reversibly capped, reactive capping polyurethane prepolymer, each of the reversibly capped, reactive capping polyurethane prepolymers including the reversibly capped, reactive capping polyurethane prepolymers of the first aspect described above, and / or at least one reversibly capped, reactive capping polyisocyanate, each of the reversibly capped, reactive capping polyisocyanates including a reactive capping group, a polyisocyanate, and an independent protecting group, and a reactive diluent, and a photoinitiator.

[0048] Specifically, in some embodiments, the polymerizable liquid can include at least one reversibly capped, reactive capping polyurethane prepolymer, a reactive diluent, and a photoinitiator. In some embodiments, the polymerizable liquid can include at least one reversibly capped, reactive capping polyisocyanate, a reactive diluent, and a photoinitiator. In some embodiments, the polymerizable liquid can include at least one reversibly capped, reactive capping polyurethane prepolymer, at least one reversibly capped, reactive capping polyisocyanate, a reactive diluent, and a photoinitiator.

[0049] The reversibly capped, reactive capping polyurethane prepolymers, as the main polymer matrix, provide the essential physical and chemical properties of the final product. The reversibly capped, reactive capping polyurethane prepolymers in the second aspect are from the first aspect. The reversibly capped, reactive capping polyurethane prepolymers provided in the second aspect and the reversibly capped, reactive capping polyurethane prepolymers provided in the second aspect are the same in composition and function, and are not repeated here.

[0050] When the polymerizable liquid includes a reversibly blocked reactive blocked polyisocyanate but does not contain a reversibly blocked reactive blocked polyurethane prepolymer, the reversibly blocked reactive blocked polyisocyanate and the above-mentioned reversibly blocked reactive blocked polyurethane prepolymer act similarly and can be the primary polymeric body, providing the essential physical and chemical properties of the final product. When the polymerizable liquid includes both a reversibly blocked reactive blocked polyisocyanate and a reversibly blocked reactive blocked polyurethane prepolymer, the reversibly blocked reactive blocked polyisocyanate can act as a crosslinker, enhancing the hardness and strength of the material by reacting with the polyurethane prepolymer or other active hydrogen atom containing compounds.

[0051] The reversibly blocked reactive blocked polyisocyanate can include a reactive blocking group, a polyisocyanate, and an independent protecting group. The following is the structure of the reversibly blocked reactive blocked polyisocyanate:

[0052] wherein R1, R2 are independently selected hydrocarbon groups; X, X1 are NH or O; B1 is the reactive blocking group; B2 is the independent protecting group.

[0053] The R1, R2, X, X 1、 B1, B2 are the same as R1, R2, X, X 1、 B1, B2 are the same as R1, R2, X, X

[0054] The polyisocyanate can be generated using a diamine or polyamine reacted with phosgene or other isocyanate precursors. The polyisocyanate can be of various types, such as hexamethylene diisocyanate trimer (HDI trimer), isophorone diisocyanate trimer (IPDI trimer). The polyisocyanate contains diisocyanates. The diisocyanates can be of various types, such as diisocyanates including but not limited to isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), methylene bis(phenyl isocyanate) (MDI), toluene diisocyanate (TDI), naphthalene diisocyanate (NDI), methylene bis-cyclohexyl isocyanate (HMDI).

[0055] The reactive diluent can reduce viscosity, facilitate processing and coating, and also participate in the curing reaction to become part of the final polymer. The reactive diluent is usually a low molecular weight compound that can participate in chemical reactions during the curing process. The reactive diluent can be a monomer, an oligomer, or a multifunctional compound, which reacts with the prepolymer and other ingredients during the curing process.

[0056] In some embodiments, the reactive diluent can be a photo-curable monomer or oligomer having a photo-curable group. In some embodiments, the photo-curable group can be a group that can undergo radical polymerization. In other embodiments, the photo-curable group can be a group that can undergo cationic polymerization. In some embodiments, the photo-curable monomer or oligomer can comprise acrylate, methacrylate, olefin, N-vinyl, vinyl amide, vinyl ether, vinyl ester, acrylamide, methacrylamide, styrene, acrylic acid, epoxy, thio, 1,3-diene, halovinyl, acrylonitrile, vinyl ester, maleimide, vinyl ether, and combinations of two or more of the foregoing. In some embodiments, the photo-curable monomer or oligomer can comprise epoxy / amine, epoxy / hydroxyl, oxetane / amine, oxetane / alcohol. The reactive diluent can reduce the viscosity of the photo-cured polymer network and copolymerize with the photo-curable component in the reversibly capped reactive blocked polyurethane prepolymer.

[0057] In some embodiments, the reactive diluent can have one or more than one functional group. Examples of the reactive diluent can include, but are not limited to, 1,3-propanediol diacrylate and 1,3-propanediol dimethacrylate, 1,4-butanediol diacrylate and 1,4-butanediol dimethacrylate, 1,5-pentanediol diacrylate and 1,5-pentanediol dimethacrylate, 1,6-hexanediol diacrylate and 1,6-hexanediol dimethacrylate, 1,7-heptanediol diacrylate and 1,7-heptanediol dimethacrylate, 1,8-octanediol diacrylate and 1,8-octanediol dimethacrylate, trimethylolpropane triol triacrylate and trimethylolpropane triol trimethacrylate, ethoxylated trimethylolpropane triol triacrylate and ethoxylated trimethylolpropane triol trimethacrylate, neopentyl glycol diacrylate and neopentyl glycol dimethacrylate, tripropylene glycol diacrylate and tripropylene glycol dimethacrylate, pentaerythritol triacrylate and pentaerythritol trimethacrylate, and the like. In some embodiments, the selection of certain reactive diluents or certain combinations of reactive diluents can increase the solubility of the photoinitiator used in the present application. In preferred embodiments, monomers with low functionality are suitable for increasing the solubility of the photoinitiator in powder form.

[0058] The photoinitiator can initiate the polymerization reaction under light conditions. When irradiated with light of a specific wavelength, the photoinitiator decomposes to generate active species such as free radicals or cations. These active species can initiate the polymerization reaction, promoting crosslinking between the prepolymer and the diluent. The choice of photoinitiator depends on the desired spectral range (UV or visible light) and reaction conditions.

[0059] In some embodiments, the wavelength of the light used to initiate the photocuring reaction is 405 nm, and in other embodiments, the wavelength of the light used to initiate the photocuring reaction is 385 nm. Photoinitiators can include, but are not limited to, benzoin ethyl ether, methyl benzoylformate, hydroxycyclohexyl phenyl ketone, phenyl bis(2,4,6-trimethylbenzoyl) phosphine oxide, thioxanthone, Irgacure 651, Irgacure 907, Darocur 2959, camphorquinone, a-ketoglutaric acid, or a mixture of the above.

[0060] In addition, it should be noted that the polymerizable liquid does not contain an independent curing agent, that is, when the components of the polymerizable liquid do not need to add an additional curing agent, the effect after adding the curing agent can be achieved. By adding components containing amine groups or amine group-substituted components to reversibly capped reaction-type capped polyurethane prepolymers, these components act as curing agents during the curing process and react with isocyanate groups in the prepolymer to form a crosslinked network.

[0061] The polymerizable liquid does not contain an independent curing agent, which on the one hand eliminates the step of adding an additional curing agent, simplifying the processing process, and on the other hand reduces the number of unstable components in the system, improving the overall stability of the liquid material. In addition, taking the 3D printing scenario as an example, when an additional curing agent is added to the polymerizable liquid, the small molecule curing agent is easily dissolved out during cleaning before heat treatment of the printed part, so that the ratio of polyurethane prepolymer and curing agent in the printed part is no longer the optimal ratio, affecting the mechanical properties of the printed part.

[0062] In a third aspect, the present specification provides a 3D printing method, which is suitable for a 3D printer using a light-curable 3D printing technology. The light-curable 3D printing technology mainly involves using a photosensitive resin or a liquid prepolymer to initiate a polymerization reaction by a photoinitiator under light, thereby curing to form a solid material. The light-curable 3D printing technology can be various, such as a stereolithography technology (SLA, Stereo Lithography Apparatus), a digital light processing technology (DLP, Digital Light Processing), a liquid crystal light curing technology (LCD, Liquid Crystal Display), a continuous liquid interface production technology (CLIP, Continuous Liquid Interface Production), or a micro-extrusion light curing technology (MJP, Micro Jetting), etc.

[0063] The 3D printing method can comprise the polymerizable liquid of the second aspect. The polymerizable liquid is placed in a material tank of a 3D printer, the target printing area is filled layer by layer with the polymerizable liquid, and after each layer of the polymerizable liquid is filled, the polymerizable liquid is irradiated with a light source to solidify until the printing is completed, thereby forming the target printed object.

[0064] Specifically, the 3D printing method comprises the following steps:

[0065] (a) providing a printing area defined by a build platform and a resin container comprising a forming surface;

[0066] (b) filling the printing area with the polymerizable liquid of any one of the second aspect;

[0067] (c) exposing the polymerizable liquid in the printing area to energy to solidify the polymerizable liquid into a solid printing intermediate substantially identical in shape to the target printed object;

[0068] (d) further processing the printing intermediate to form the target printed object.

[0069] Specifically, a build platform is prepared, which can be a fixed component of a 3D printer for carrying the object being printed. A material tank is prepared, which can be a transparent container for containing the polymerizable liquid described above. The printing area is defined by the build platform and the forming surface of the material tank.

[0070] Then, the printing area is filled with the polymerizable liquid described above. Specifically, the polymerizable liquid is poured into the material tank until the liquid covers the entire forming surface, ensuring that the liquid fills the printing area sufficiently for subsequent 3D printing operations.

[0071] Further, the polymerizable liquid is cured by light to form a solid printing intermediate substantially identical in shape to the target printed object. Specifically, a light source of a specific wavelength (usually ultraviolet or visible light) is used to irradiate the polymerizable liquid in the material tank. The light source irradiates layer by layer according to a predetermined pattern or model, so that the photoinitiator in the polymerizable liquid absorbs light energy and initiates polymerization. After each layer is cured, the build platform is lowered by a certain distance so that the next layer of polymerizable liquid is in contact with the light source and is cured. This process is repeated until the entire 3D model is printed. It can be understood that "visible light" refers to electromagnetic radiation with a wavelength of 400-700 nm, and "ultraviolet light" refers to electromagnetic radiation with a wavelength of 10-400 nm.

[0072] The printed intermediate is then cleaned. Specifically, once the 3D printing process is complete, the printed intermediate is removed from the vat. The printed piece is cleaned using a suitable solvent, typically alcohol or acetone, to remove surface residual uncured resin. Cleaning can be done by hand or using an ultrasonic cleaner. In some embodiments, the printed intermediate can also be directly moved to the next step without cleaning.

[0073] Finally, the printed intermediate is provided with energy, either by heating, microwave radiation, or using other methods, to form the target printed piece. Specifically, the printed intermediate is post-cured, which can be done by heating the printed piece in an oven, using microwave radiation, or using other forms of energy. The post-curing process can further strengthen the cross-linked structure, improving the hardness, durability, and stability of the printed piece. Suitable post-curing conditions (e.g., temperature, time) are determined to achieve the best results.

[0074] In some embodiments, the polymerizable liquid in the methods described herein comprises a blocked or reaction-type blocked polyurethane prepolymer in a range of 1% to 99% by weight and a blocked or reaction-type blocked curing agent in a range of 1% to 99% by weight.

[0075] In some embodiments, the printed intermediate is first generated by a first curing step of photocuring using a light-curable 3D printing technology. In some embodiments, the wavelength used to initiate photocuring is 405 nm, and in other embodiments, the wavelength used to initiate photocuring is 385 nm. Any photoinitiator that can initiate photocuring reaction with the light source used to initiate photocuring reaction can be used. In some embodiments, light with a wavelength longer than 400 nm is used to initiate photocuring, for example, using a 405 nm wavelength. In these embodiments, a photoinitiator is used to initiate light with a wavelength longer than 400 nm because the photoinitiator has a stronger absorption in the long wavelength UV range in the family of phosphine oxide photoinitiators.

[0076] After the printed intermediate is formed, the printed intermediate can optionally be cleaned and dried. In some embodiments, the cleaning solution can be aqueous, comprising water and a surfactant. In some embodiments, the water can be deionized water. Examples of surfactants can include, but are not limited to, anionic surfactants (e.g., sulfates, sulfonates, carboxylates, and phosphates), cationic surfactants, zwitterionic surfactants, nonionic surfactants, and the like, and combinations thereof. Common examples include, but are not limited to, sodium stearate, linear alkylbenzene sulfonate, lignin sulfonate, fatty alcohol ethoxylate, alkylphenol ethoxylate, and the like, and combinations thereof.

[0077] After the optional washing step, the printing intermediate is further cured to form the final target printed piece. The second step curing can be performed by heating, humidification, microwave irradiation, or other suitable energy source that can cause the cleavage of the blocking and protecting groups in the polymerizable liquid to initiate the second step curing. In some embodiments, the second step curing is thermal curing. In some embodiments, the thermal curing temperature is in the range of room temperature to 200 °C, and the thermal curing time can be in the range of 0.5 to 200 hours. In some embodiments, the second step curing can be heating under humidification conditions.

[0078] wherein, in some embodiments, the target printed piece comprises a blend of polyurethane and polyacrylate, and in some embodiments, the target printed piece comprises a copolymer of polyurethane and polyacrylate.

[0079] The following are specific embodiments designed in accordance with the above disclosure of the present disclosure. It is important to note that the following embodiments are merely for the purpose of illustrating the above disclosed reversibly end-capped reactive end-capped polyurethane prepolymer, polymerizable liquid, and 3D printing method, wherein the specific embodiments and parameters used are only one or a few of the numerous parameters and methods disclosed above. Those skilled in the art can understand that other specific embodiments not mentioned below are also within the scope of protection of the present disclosure.

[0080] Example 1: Synthesis of asymmetrically end-capped molecule A

[0081] An oil bath was preheated to 60 °C, 260 g of 3,3-dimethyl-4,4-diaminodicyclohexyl methane (DMDC) and 60 g of n-hexane were added into a reaction kettle, the oil bath was heated to 130 °C, and the stirring was started. Then 120 g of methyl isobutyl ketone (MIBK) was added dropwise while stirring vigorously. The generated water was removed by azeotropic distillation. The reaction was stopped when no water was distilled out after 9 h of reaction. The oil bath was cooled to 60 °C, and the n-hexane was distilled out under vacuum to obtain the yellowish oil product molecule A with a yield of 94%.

[0082] Example 2: Synthesis of asymmetrically end-capped prepolymer B

[0083] Into a 500 mL three-necked flask with overhead stirrer, nitrogen protection and thermometer, 200 g of anhydrous polytetramethylene glycol (PTMG2000) was added. Then 200 μL of catalyst dibutyltin dilaurate (DBTL) was added to the flask and stirred, and warmed to 70 °C. Next, 44.4 g of isophorone diisocyanate (IPDI) was added dropwise into the bottle, and reacted at 70 °C for 3 h. After 3 h, 100 ppm of hydroquinone was added. Subsequently, 18.5 g of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) was added dropwise, controlling the addition rate to be one drop per 5 seconds, while stirring vigorously. The reaction was continued at 70 °C for 5 hours to obtain a transparent liquid product, pre-polymer B.

[0084] Example 3: Synthesis of asymmetric end-capped pre-polymer C

[0085] Into a 2 L three-necked flask with overhead stirrer, nitrogen protection and thermometer, 429 g of pre-polymer B was added and warmed to 50 °C. 32 g of molecule A was dissolved in 500 g of ethyl acetate. Then the ethyl acetate solution of molecule A was added dropwise into the flask and stirred vigorously. The reaction was continued at 50 °C for 5 hours, and the ethyl acetate was removed by distillation to obtain a transparent liquid product, pre-polymer C.

[0086] Example 4: Photocuring 3D printing test using pre-polymer C of Example 3

[0087] The photoinitiator TPO was dissolved in 1,6-hexanediol dimethacrylate and polyethylene glycol (600) dimethacrylate (PEG(600)DMA), and then the pre-polymer C was added to the solution, and white paste was added. A rotor stirrer was used to stir for 30 min at 2000 r / min to obtain the desired 3D printing material. The viscosity of the photocuring 3D printing material was 3800 cps at room temperature. After 3 months of storage at room temperature, the viscosity was 4000 cps, only an increase of 2%, which proved good long-term storage stability. Using Anycubic Photon Mono X6Ks printer, a dog bone-shaped test sample was printed according to the size of ISO 37 No. 2 sample. After cleaning with IPA, the sample was tested for hardness according to ASTM D2240, and the hardness was 65A. The sample was placed in an environment of 25 °C and 80% humidity for 8 hours, and then heat cured at 120 °C for 8 hours. The tensile properties of the cured elastomer sample were tested with a CTM tensile tester according to ISO 37 standard. The tensile strength was 22 MPa, and the elongation at break was 410%.

[0088] wherein the weight parts of each component are as described in the following table:

[0089] Example 5: Synthesis of asymmetrically reactive end-capped molecule D

[0090] An oil bath was preheated to 60 °C, 260 g of 3,3-dimethyl-4,4-diaminodicyclohexyl methane (DMDC) and 60 g of n-hexane were added into a reaction kettle, the oil bath was heated to 100 °C, and the stirring was started. Then 198 g of 3,3-dimethyl-4-oxovaleric acid methacrylate was added dropwise while stirring vigorously. The generated water was removed by azeotropic distillation. The reaction was stopped when no water was distilled out after the reaction liquid was reacted for 12 h. The oil bath was cooled to 60 °C, and the n-hexane was distilled out under vacuum to obtain the yellowish oily product molecule D with a yield of 90%.

[0091] Example 6: Synthesis of asymmetrically end-capped prepolymer E

[0092] First, 429 g of prepolymer B was added into a 2 L three-necked flask with an overhead stirrer, nitrogen protection, and a thermometer, and the temperature was raised to 50 °C. 41.9 g of molecule D was dissolved in 500 g of ethyl acetate. Then the ethyl acetate solution of molecule D was added dropwise into the flask while stirring vigorously. The reaction was continued at 50 °C for 5 h to obtain the transparent liquid product prepolymer E.

[0093] Example 7: Photocuring 3D printing test using prepolymer E of Example 6

[0094] The photoinitiator TPO was dissolved in 1,6-hexanediol dimethacrylate and polyethylene glycol (600) dimethacrylate (PEG(600)DMA), and then prepolymer E was added to the solution, and white paste was added. A rotor stirrer was used to stir for 30 min at a speed of 2000 r / min to obtain the required 3D printing material. The viscosity of the photocuring 3D printing material was 3900 cps at room temperature. After being stored at room temperature for 3 months, the viscosity was 4000 cps, only increased by 2%, which proved that it had good long-term storage stability. Using Anycubic Photon Mono X6Ks printer, a dog bone-shaped test sample was printed according to the size of ISO 37 No. 2 sample. After being cleaned with IPA, the hardness of the sample was tested according to ASTM D2240, and the hardness was 68A. Compared with the results in Comparative Example 4, it shows that using the reactive end-capped prepolymer E can make the material have higher hardness after photocuring before thermal curing, which is more conducive to the stability of the printed structure during printing.

[0095] The sample was placed in an environment of 25 °C and 80% humidity for 8 h, and then heat cured at 120 °C for 8 h. The tensile properties of the cured elastomer sample were tested according to ISO 37 standard using a CTM tensile testing machine. The tensile strength was 20 MPa, and the elongation at break was 350%.

[0096] The weight parts of each component are as shown in the following table:

[0097] Example 8: Synthesis of amine-substituted PTMG-NH22000

[0098] PTMG2000200g was dissolved in 1 L of dichloromethane (CH2Cl2). Then 38 g of p-toluenesulfonyl chloride (TsCl) and 28 mL of triethylamine were added, and the mixture was stirred well and reacted at room temperature for 12 hours. Then the mixture was extracted with 1 mol / L dilute hydrochloric acid, and excess sodium carbonate was added to the organic phase and stirred well. After filtration, the filtrate was concentrated, and the concentrated filtrate was dropped into excess ethyl ether to obtain a white precipitate, which was suction filtered. Then the suction filtered material was dissolved in 100 mL of dichloromethane (CH2Cl2), and the insoluble material was filtered off, and then dropped into excess ethyl ether to obtain a white precipitate, which was suction filtered. The suction filtered material was vacuum dried for 24 hours to obtain 190 g of white PTMG-OTs, with a yield of 83%.

[0099] PTMG-OTs 17 g and 4.6 g of potassium phthalimide were dissolved in 150 mL of DMF, and reacted at 120°C for 6 hours. Then the DMF was evaporated under reduced pressure. Subsequently, 3.2 mL of hydrazine hydrate and 120 mL of anhydrous ethanol were added to the evaporated flask. The mixture was refluxed under nitrogen protection for 12 hours. The reaction solution was dropped into excess ethyl ether to obtain a white precipitate. The white precipitate was dissolved in 10 mL of dichloromethane (CH2Cl2), and the insoluble material was suction filtered. Then the filtrate was dropped into ethyl ether. Vacuum drying was performed for 24 hours to obtain 15.4 g of white precipitate, which was amine-substituted PTMG-NH22000.

[0100] Example 9: Synthesis of asymmetrically terminated prepolymer F

[0101] An oil bath was preheated to 60°C, 2000 g of PTMG-NH22000 and 600 g of n-hexane were added to a reaction kettle, the oil bath was warmed to 130°C, and stirring was started. Then 120 g of methyl isobutyl ketone (MIBK) was added dropwise while stirring vigorously. The generated water was removed by azeotropic distillation. After the reaction solution was reacted for 10 hours, the reaction was stopped when no water was distilled out. The oil bath was cooled to 60°C, and n-hexane was vacuum distilled to obtain an oil-like transparent product, prepolymer F, with a yield of 98%.

[0102] Example 10: Synthesis of asymmetrically terminated IPDI-tB

[0103] Into a 500 mL three-necked flask with overhead stirrer, nitrogen protection and thermometer, 44.4 g isophorone diisocyanate (IPDI) and 100 ppm hydroquinone were added. Then 200 μL of catalyst dibutyltin dilaurate (DBTL) was added to the flask and stirred, and warmed to 40 °C. Subsequently, 37 g of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) was added dropwise, controlling the speed of 1 drop per 5 seconds, while stirring vigorously. The reaction was continued at 40 °C for 5 hours to obtain a transparent liquid product IPDI-tB.

[0104] Example 11: Synthesis of asymmetrically capped prepolymer G

[0105] Into a 500 mL three-necked flask with overhead stirrer, nitrogen protection and thermometer, 200 g of prepolymer F and 100 ppm hydroquinone were added. Then 200 μL of catalyst dibutyltin dilaurate (DBTL) was added to the flask and stirred, and warmed to 40 °C. Subsequently, 40 g of IPDI-tB was added dropwise, controlling the speed of 1 drop per 5 seconds, while stirring vigorously. The reaction was continued at 40 °C for 5 hours to obtain a transparent product prepolymer G.

[0106] Example 12: Photocuring 3D printing test using prepolymer G of Example 11

[0107] The photoinitiator TPO was dissolved in 2-ethylhexyl acrylate and polyethylene glycol (600) dimethacrylate (PEG(600)DMA), and then prepolymer G was added to the solution, and white paste was added. A rotor stirrer was used to stir for 30 min at 2000 r / min to obtain the required 3D printing material. The viscosity of the photocuring 3D printing material was 3600 cps at room temperature. After 3 months of storage at room temperature, the viscosity was 3700 cps, only increased by 2%, which proved good long-term storage stability. Using Anycubic Photon Mono X6Ks printer, a dog bone-shaped test sample was printed according to the size of ISO 37 No. 2 sample. After cleaning with IPA, the sample was placed in an environment of 25 °C and 80% humidity for 8 hours, and then heat cured at 120 °C for 8 hours. The tensile properties of the cured elastomer sample were tested according to ISO 37 standard using a CTM tensile testing machine. The tensile strength was 23 MPa, and the elongation at break was 370%.

[0108] wherein the weight parts of each component are as described in the following table:

[0109] Example 13: Synthesis of asymmetrically capped molecule H

[0110] Into a 500 mL three necked flask with overhead stirrer, nitrogen protection and thermometer, 50.4 g of hexamethylene diisocyanate trimer (HDI trimer), 200 mL of ethyl acetate and 100 ppm of hydroquinone were added. Then 200 μL of catalyst dibutyltin dilaurate (DBTL) was added to the flask and stirred, and warmed to 40 °C. Subsequently 18.5 g of 2-(tert-butylamino)ethyl methacrylate (TBAEMA) was added dropwise, controlling the speed of addition to one drop per 5 seconds, while stirring vigorously. The reaction was continued at 40 °C for 5 hours, and the ethyl acetate solvent was distilled off. The transparent liquid product molecule H was obtained.

[0111] Example 14: Synthesis of asymmetrically capped prepolymer I

[0112] Into a 1 L three necked flask with overhead stirrer, nitrogen protection and thermometer, 400 g of prepolymer F and 100 ppm of hydroquinone were added. Then 200 μL of catalyst dibutyltin dilaurate (DBTL) was added to the flask and stirred, and warmed to 40 °C. Subsequently 68.9 g of molecule H was added dropwise, controlling the speed of addition to one drop per 5 seconds, while stirring vigorously. The reaction was continued at 40 °C for 5 hours, and the transparent product prepolymer I was obtained.

[0113] Example 15: Synthesis of asymmetrically capped molecule J

[0114] Into a 500 mL three necked flask with overhead stirrer, nitrogen protection and thermometer, 50.4 g of hexamethylene diisocyanate trimer (HDI trimer), 200 mL of ethyl acetate and 100 ppm of hydroquinone were added. Then 200 μL of catalyst dibutyltin dilaurate (DBTL) was added to the flask and stirred, and warmed to 40 °C. Subsequently 37 g of 2-methyl-2-propenoic acid-2-[(1,1-dimethylethyl)amino]ethyl ester (TBAEMA) was added dropwise, controlling the speed of addition to one drop per 5 seconds, while stirring vigorously. The reaction was continued at 40 °C for 5 hours, and the ethyl acetate solvent was distilled off. The transparent liquid product molecule J was obtained.

[0115] Example 16: Synthesis of asymmetrically capped prepolymer K

[0116] Into a 500 mL three necked flask with overhead stirrer, nitrogen protection and thermometer, 200 g of prepolymer F and 100 ppm of hydroquinone were added. Then 200 μL of catalyst dibutyltin dilaurate (DBTL) was added to the flask and stirred, and warmed to 40 °C. Subsequently 87.4 g of molecule J was added dropwise, controlling the speed of addition to one drop per 5 seconds, while stirring vigorously. The reaction was continued at 40 °C for 5 hours, and the transparent product prepolymer K was obtained.

[0117] Example 17: Photocuring 3D printing test using prepolymer I of Example 14 and prepolymer K of Example 16

[0118] Dissolve photoinitiator TPO in isobornyl methacrylate and polyethylene glycol (600) dimethacrylate (PEG(600)DMA), then add prepolymer I, prepolymer J to the solution, and add white paste. Stir with rotor stirrer for 30 min at 2000 r / min to obtain the desired 3D printing material. The photocuring 3D printing material has a viscosity of 5200 cps at room temperature. After 3 months of storage at room temperature, the viscosity is 5300 cps, only an increase of 2%, which proves good long-term storage stability. Using Anycubic Photon Mono X6Ks printer, print dog bone-shaped test bars according to ISO 37 No. 2 spline size. After cleaning with IPA, place the bars in an environment of 25°C and 80% humidity for 8 hours, then heat cure at 120°C for 8 hours. Test the tensile properties of the cured elastomer bars according to ISO 37 standard with CTM tensile tester. The tensile strength is 43 MPa and the elongation at break is 150%.

[0119] wherein the weight parts of each component are as described in the following table:

[0120] Example 18: Synthesis of asymmetric end-capped molecule L

[0121] Add 70 g of IPDI-tB in Example 10 and 100 ppm of p-benzoquinone to a 500 mL three-necked flask with an overhead stirrer, nitrogen protection and a thermometer. Then add 200 μL of catalyst dibutyltin dilaurate (DBTL) to the flask and stir, and warm up to 40°C. Then add 64 g of molecule A in Example 1 drop by drop, controlling the addition rate to be one drop every 5 seconds, while stirring vigorously. Continue to react at 40°C for 5 hours to obtain a transparent liquid product, molecule L.

[0122] Example 19: Photocuring 3D printing test using prepolymer G of Example 11 and molecule L of Example 18

[0123] The photoinitiator TPO was dissolved in 2-ethylhexyl acrylate and polyethylene glycol (600) dimethacrylate (PEG(600)DMA), then the prepolymer G, molecule L was added to the solution, and white paste was added. The desired 3D printing material was obtained by stirring with a rotor stirrer for 30 min at a speed of 2000 r / min. The viscosity of the photocured 3D printing material was 4000 cps at room temperature. After storage at room temperature for 3 months, the viscosity was 4100 cps, only increased by 2%, which proved that it had good long-term storage stability. Using Anycubic Photon Mono X6Ks printer, according to ISO 37 No. 2 sample size, dog bone-shaped test sample was printed. After cleaning with IPA, the sample was placed in an environment of 25°C and 80% humidity for 8 hours, and then heat cured at 120°C for 8 hours. The tensile properties of the cured elastomer sample were tested according to ISO 37 standard using a CTM tensile testing machine. The tensile strength was 28 MPa, and the elongation at break was 230%. Compared with the results of Comparative Example 12, it was proved that the mechanical properties of the material could be adjusted by adding molecule L to adjust the content of hard segment.

[0124] The weight parts of each component are as shown in the following table:

[0125] Example 20: Photocured 3D printing test using molecule L of Example 18

[0126] The photoinitiator TPO was dissolved in 2-ethylhexyl acrylate and polyethylene glycol (600) dimethacrylate (PEG(600)DMA), then the molecule L was added to the solution, and white paste was added. The desired 3D printing material was obtained by stirring with a rotor stirrer for 30 min at a speed of 2000 r / min. The viscosity of the photocured 3D printing material was 2000 cps at room temperature. After storage at room temperature for 3 months, the viscosity was 2050 cps, only increased by 2%, which proved that it had good long-term storage stability. Using Anycubic Photon Mono X6Ks printer, according to ASTM D638 No. 5 sample size, dog bone-shaped test sample was printed. After cleaning with IPA, the sample was placed in an environment of 25°C and 80% humidity for 8 hours, and then heat cured at 120°C for 8 hours. The tensile properties of the cured sample were tested according to ASTM D638 standard using a CTM tensile testing machine. The tensile strength was 54 MPa, and the elongation at break was 30%.

[0127] The weight parts of each component are as shown in the following table:

[0128] Example 21: Synthesis of asymmetric end-capped molecule M

[0129] Into a 500 mL three-necked flask with overhead stirrer, nitrogen protection and thermometer, 77.5 g of molecule J in Example 15 and 100 ppm of hydroquinone were added. Then 200 μL of catalyst dibutyltin dilaurate (DBTL) was added to the flask and stirred, and the temperature was raised to 40°C. Then 32 g of molecule A in Example 1 was added dropwise, controlling the addition rate to be one drop every 5 seconds, while stirring vigorously. The reaction was continued at 40°C for 5 hours to obtain a transparent liquid product molecule M.

[0130] Example 22: Photocuring 3D printing test using prepolymer I of Example 14 and prepolymer M of Example 21

[0131] The photoinitiator TPO was dissolved in isobornyl methacrylate and polyethylene glycol (600) dimethacrylate (PEG(600)DMA), and then prepolymer I, prepolymer J was added to the solution, and white paste was added. A rotor stirrer was used to stir for 30 min at 2000 r / min to obtain the required 3D printing material. The viscosity of the photocuring 3D printing material was 4900 cps at room temperature. After storage at room temperature for 3 months, the viscosity was 5000 cps, only increased by 2%, which proved good long-term storage stability. Using Anycubic Photon Mono X6Ks printer, the dog bone-shaped test sample was printed according to the size of ISO 37 No. 2 sample. After cleaning with IPA, the sample was placed in an environment of 25°C and 80% humidity for 8 hours, and then heat cured at 120°C for 8 hours. The tensile properties of the cured elastomer sample were tested according to ISO 37 standard using a CTM tensile testing machine. The tensile strength was 44 MPa, and the elongation at break was 120%.

[0132] wherein the weight parts of each component are as described in the following table:

[0133] Example 23: Photocuring 3D printing test using prepolymer G of Example 11

[0134] The photoinitiator TPO was dissolved in the prepolymer G and white paste was added. The desired 3D printing material was obtained by stirring for 30 min using a rotor stirrer at 2000 r / min. The viscosity of the photocurable 3D printing material was 13600 cps at room temperature. After 3 months of storage at room temperature, the viscosity was 13900 cps, only an increase of 2%, proving good long-term storage stability. Using Anycubic Photon Mono X6Ks printer, dog bone-shaped test samples were printed according to the size of ISO 37 No. 2 spline. Due to the addition of no reactive diluent, the viscosity of the material at room temperature is too large, and it needs to be heated to 50°C for printing. At this time, the viscosity of the material is 4100 cps. After reducing the IPA cleaning, the sample was placed in an environment of 25°C and 80% humidity for 8 hours, and then heat cured at 120°C for 8 hours. The tensile properties of the cured elastomer sample were tested according to ISO 37 standard using a CTM tensile testing machine. The tensile strength was 38 MPa, and the elongation at break was 670%.

[0135] wherein the weight parts of the components are as described in the following table:

[0136] In summary, the present specification provides a reversibly capped reactive capped polyurethane prepolymer, a polymerizable liquid and a 3D printing method. The reversibly capped reactive capped polyurethane prepolymer comprises a reactive capping group, a polyurethane prepolymer and an independent protecting group. The polymerizable liquid comprises at least one of the above-mentioned reversibly capped reactive capped polyurethane prepolymer, and / or at least one reversibly capped reactive capped polyisocyanate, each of the reversibly capped reactive capped polyisocyanate comprising a reactive capping group, a polyisocyanate and an independent protecting group, and a reactive diluent, and a photoinitiator. The polymerizable liquid does not contain an independent curing agent, on the one hand, it saves the step of adding an additional curing agent, simplifying the printing process, on the other hand, it reduces the number of unstable components in the system, and improves the overall stability of the polymerizable liquid.

[0137] The above describes particular embodiments of the present specification. Other embodiments are within the scope of the appended claims. In some cases, the acts or steps recited in the claims can be performed in an order other than as described in the embodiments and still achieve desirable results. Additionally, the processes depicted in the figures do not necessarily require the particular order or sequential order illustrated in order to achieve desirable results. In some embodiments, multitasking and parallel processing can be advantageous or possible.

[0138] In light of the foregoing disclosure, those skilled in the art will appreciate that the foregoing detailed description of the embodiments of the present application is made for the purpose of illustrating the general principles of the application and can not make reference to a particular system or method of the application that is preferably implemented and is at times referred to in a sending order. While specific embodiments of the application have been shown and described in detail to illustrate the application of the principles of the application, it will be understood that the application can be embodied differently without departing from such principles. The application is not limited to the details given herein but can be implemented with various alterations hereof within the scope of the application. Accordingly, while the application is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that it is not intended to limit the application to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the application as defined by the appended claims.

[0139] In addition, certain terminology has been used to describe embodiments of the application. For example, "one embodiment," "an embodiment" and / or "some embodiments" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the application. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment" or "in some embodiments" in various places throughout this specification are not necessarily referring to the same embodiment. Further, the particular features, structures or characteristics can be combined in any suitable manner on one or more embodiments without limitation.

[0140] It should be understood that throughout the foregoing description of embodiments of the application, use of terms such as "comprising" or "including" to describe various elements or components of the application are intended to be illustrative and not restrictive. Unless otherwise noted, terms such as "comprising" or "including" when used in reference to a list of elements or components to which the term applies, signify the inclusion of all elements or components of the list, and any other elements or components not explicitly identified in connection with the list. Thus, such terms specify the existence, but not the number, of intervening elements or components.

[0141] Each patent, patent application, publication of a patent application, and other material, for example articles, books, specifications, publications, documents, files, articles of manufacture, and the like which can be cited in the above specification to support the technical phrases described therein can be incorporated by reference for all purposes as if each were individually so denoted in the above specification. The entire contents of all of the above cited references, except to the extent any of the above cited references are inconsistent with the specification, publication, or document associated therewith, any same, or any prosecution history of any same which can have a limiting effect on the broadest possible scope of the claims, now or hereafter associated with this document. For example, if there is any inconsistency between the description, definition and / or use of a term associated with any of the incorporated material and the term, description, definition and / or use as used in this document, the term as used in this document is controlling.

[0142] Finally, it should be understood that the embodiments of the application disclosed herein are illustrative of the principles of the application. Other modifications can be employed which are within the scope of the description. Accordingly, the embodiments disclosed in the specification are intended to be illustrative only and not limiting of the scope of the application. As such, those skilled in the art can adopt alternative configurations to implement the application disclosed in the specification without departing from its scope. The embodiments disclosed in the specification are thus to be considered in all respects as illustrative and not restrictive, and the scope of the application to be given by the appended claims.

Claims

1. A reversibly capped reactive capped polyurethane prepolymer, characterized in that, comprising: a reactive capping group; a polyurethane prepolymer; and an independent protecting group.

2. The reversibly capped reactive capped polyurethane prepolymer of claim 1, wherein, The polyurethane prepolymer comprises at least one polyisocyanate oligomer.

3. The reversibly capped reactive capped polyurethane prepolymer of claim 1, wherein, The reversibly capped reactive capped polyurethane prepolymer includes the structure of formula (Al), (A2): wherein R1, R2, R3, Z comprise independently selected hydrocarbyl groups; X, X1 comprise NH or O; B1 comprises the reactive capping group; B2 comprises the independent protecting group.

4. The reversibly capped reactive capped polyurethane prepolymer of claim 1, wherein, The reactive capping group B1 comprises a reactive epoxy, alkenyl, alkynyl, or thiol end group blocking group.

5. The reversibly capped reactive capped polyurethane prepolymer of claim 4, wherein, The reactive capping group B1 comprises 2-(tert-butylamino)methyl ethyl acrylate.

6. The reversibly capped reactive capped polyurethane prepolymer of claim 1, wherein, The independent protecting group B2 comprises a protecting group for protecting an amino or hydroxyl group.

7. The reversibly capped reactive capped polyurethane prepolymer of claim 6, wherein, The independent protecting group B2 comprises an imino group for protecting an amine group, the imino group comprising a substituent formed from the reaction of an aldehyde or ketone with an amine.

8. The reversibly capped reactive capped polyurethane prepolymer of claim 1, wherein, The reactive capping group B1 and the independent protecting group B2 each independently comprise a photocurable group.

9. The reversibly capped reactive capped polyurethane prepolymer of claim 8, wherein, The photocurable group comprises an acrylate group or a methacrylate group.

10. A polymerizable liquid for 3D printing, characterized in that comprising: at least one reversibly capped, reactive capped polyurethane prepolymer, each of the reversibly capped, reactive capped polyurethane prepolymers comprising the reversibly capped, reactive capped polyurethane prepolymer of any one of claims 1-9; and / or at least one reversibly capped, reactive capped polyisocyanate, each of the reversibly capped, reactive capped polyisocyanates comprising a reactive capping group, a polyisocyanate, and an independent protecting group; and a reactive diluent; and a photoinitiator, wherein the polymerizable liquid is free of an independent curing agent.

11. The polymerizable liquid of claim 10, wherein, The polyisocyanate comprises a diisocyanate.

12. The polymerizable liquid of claim 10, wherein, The reactive diluent comprises an acrylate, a methacrylate.

13. A method of 3D printing, characterized in that, comprising: providing a print area, the print area defined by a build platform and a resin container comprising a forming surface; filling the print area with the polymerizable liquid of any one of claims 10-12; exposing the polymerizable liquid in the print area to energy, causing the polymerizable liquid to cure into a solid print intermediate substantially the same shape as a target print; and heating, microwave radiation, or using other methods to provide energy to the print intermediate to form the target print.

14. The 3D printing method according to claim 13, characterized in that, The target print comprises a blend polymer of polyurethane and polyacrylate.

15. The 3D printing method of claim 13, wherein, The target print comprises a copolymer of polyurethane and polyacrylate.

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