3D printing photosensitive resin based on modified cellulose nanofibrils and preparation method and application thereof

Abstract

The invention provides 3D printing photosensitive resin based on modified cellulose nanofibrils as well as a preparation method and application of the 3D printing photosensitive resin. The modified cellulose nanofibril is a cellulose nanofibril grafted with an acrylate group and an isocyanate chain segment; after the modified cellulose nanofibril is introduced into a 3D printing photosensitive resin system, the dispersity of the modified cellulose nanofibril in the photosensitive resin system can be improved, and the modified cellulose nanofibril can participate in a polymerization reaction of the photosensitive resin system, so that the 3D printing photosensitive resin system is endowed with better mechanical properties; the 3D printing product with higher precision, higher thermal deformation temperature and better mechanical property can be prepared.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocurable 3D printing resins, and particularly relates to a 3D printing photosensitive resin based on modified cellulose nanofibrils, a preparation method thereof, and an application thereof. Background Art

[0002] 3D printing technology is an additive manufacturing technology. Since it was proposed in the last century, it has attracted much attention from major industries. Its basic principle is to convert a three-dimensional digital model into a physical object. Specifically, it means decomposing the model file information output by software into a large number of slices, and finally completing the manufacture of the entire printed part by layer-by-layer scanning and printing. The development of 3D printing technology has a wide range of impacts on the global manufacturing, technology, medical, and aviation fields, etc.

[0003] However, most of the models obtained after the photocurable resin for 3D printing is printed and formed at present have problems such as low heat distortion temperature, low hardness, and high brittleness. Therefore, there is an urgent need to provide a new type of photocurable resin for 3D printing with good thermal stability and mechanical properties. Summary of the Invention

[0004] In order to solve the deficiencies in aspects such as high brittleness, low hardness, and low heat distortion temperature of the existing photocurable resin for 3D printing, the present invention provides a 3D printing photosensitive resin based on modified cellulose nanofibrils, a preparation method thereof, and an application thereof. The modified cellulose nanofibrils are cellulose nanofibrils grafted with acrylate groups and isocyanate segments; after the modified cellulose nanofibrils are introduced into the 3D printing photosensitive resin system, their dispersibility in the photosensitive resin system can be improved, and they can also participate in the polymerization reaction of the photosensitive resin system, endowing the 3D printing photosensitive resin system with better mechanical properties, and enabling the preparation of 3D printing products with higher precision, higher heat distortion temperature, and better mechanical properties.

[0005] Cellulose fibers with a nanofiber diameter or a nanofiber length are collectively referred to as cellulose nanofibers. According to different treatment methods, cellulose nanofibers can be divided into cellulose nanofibrils (CNF) and cellulose nanocrystals (CNC). Specifically, cellulose nanofibrils are long fibrous structures formed by the aggregation of many cellulose molecular chains, with a large aspect ratio. The diameter is generally in the range of dozens to hundreds of nanometers, and the length can reach the micron level, having a certain flexibility. It is obtained by mechanical treatment (such as high-pressure homogenization, grinding or microfluidics) combined with chemical / enzyme pretreatment to break the hydrogen bond network of cellulose fibers and separate nanofibrils. This process preserves the integrity of the fibers, including the crystalline region and the amorphous region. Cellulose nanocrystals are nanoscale crystal particles with a high degree of crystallinity extracted from cellulose, with a relatively regular shape, usually rod-shaped or needle-shaped. The length is generally several hundred nanometers, and the diameter is in the range of a few to dozens of nanometers. It is obtained by selectively degrading the amorphous region of cellulose through acid hydrolysis (such as sulfuric acid or hydrochloric acid) and only retaining short rod-shaped particles with a high degree of crystallinity.

[0006] The object of the present invention is achieved by the following technical solutions:

[0007] A modified cellulose nanofibril, wherein the raw materials for preparing the modified cellulose nanofibril include the following components:

[0008] Cellulose nanofibrils;

[0009] The reaction product of a diisocyanate compound and a mono-hydroxy (meth)acrylate compound;

[0010] Tertiary amine catalysts.

[0011] The present invention also provides a method for preparing the above-mentioned modified cellulose nanofibril, and the preparation method includes the following steps:

[0012] 1) Mix a diisocyanate compound, a mono-hydroxy (meth)acrylate compound and an organotin catalyst, react to prepare a compound with isocyanate and acrylate end groups;

[0013] 2) Mix cellulose nanofibrils and ethyl acetate, and perform azeotropic dehydration treatment on the cellulose nanofibrils by heating under reflux. After the azeotropic dehydration treatment is completed, add a tertiary amine catalyst and the compound with isocyanate and acrylate end groups prepared in step 1), react to prepare a modified cellulose nanofibril grafted with acrylate groups and isocyanate segments.

[0014] The present invention also provides a modified cellulose nanofibril prepared by the above method.

[0015] The present invention also provides a 3D printing photosensitive resin, and the preparation raw materials of the 3D printing photosensitive resin include the following components:

[0016] The above-mentioned modified cellulose nanofibrils;

[0017] Acrylate oligomer;

[0018] Acrylate monomer;

[0019] Photoinitiator.

[0020] The present invention also provides a preparation method of the above 3D printing photosensitive resin, and the method includes the following steps:

[0021] Mix the modified cellulose nanofibrils, acrylate oligomer, acrylate monomer, photoinitiator and optionally added or not added additives, and stir to prepare the 3D printing photosensitive resin.

[0022] The present invention also provides a 3D printed article, and the 3D printed article is prepared from the above 3D printing photosensitive resin.

[0023] Advantages of the present invention:

[0024] (1) The modified cellulose nanofibrils of the present invention are prepared by chemically modifying cellulose nanofibrils, reducing the content of original surface hydroxyl groups of cellulose nanofibrils, reducing the hydrophilicity and increasing the hydrophobicity of cellulose nanofibrils, thereby enhancing the water resistance of cellulose nanofibrils;

[0025] (2) After the modified cellulose nanofibrils of the present invention are added to the 3D printing photosensitive resin, the mechanical properties of the photosensitive resin system can be significantly improved, and the addition method is simple and easy to operate, which is beneficial to its use in the photosensitive resin system;

[0026] (3) The modified cellulose nanofibrils of the present invention include isocyanate segments, and the introduction of isocyanate segments can improve the thermal stability of the photosensitive resin system, greatly increasing the heat distortion temperature of the 3D printing photosensitive resin and the 3D printed article;

[0027] (4) The preparation raw material cellulose nanofibrils of the modified cellulose nanofibrils of the present invention are easily available and are a good environmental protection material, which is beneficial to protecting the environment and reducing resource consumption; at the same time, the content of hydroxyl groups on the surface of the modified cellulose nanofibrils is less, which can significantly inhibit the aggregation of cellulose nanofibrils and expand the application in organic systems and low-polarity systems. Description of the drawings

[0028] Figure 1 The electron microscope image of the modified cellulose nanofibrils prepared in Example 1 is shown.

[0029] Figure 2 Micrograph showing the modified cellulose nanofibrils prepared in Example 1.

[0030] Figure 3 Schematic diagram showing the 3D printed article incorporating the modified cellulose nanofibrils prepared in Example 11. Detailed Description of the Invention

[0031] <Modified Cellulose Nanofibrils>

[0032] As described above, the present invention provides a modified cellulose nanofibril, and the raw materials for preparing the modified cellulose nanofibril include the following components:

[0033] Cellulose nanofibrils;

[0034] Reaction product of a diisocyanate compound and a mono-hydroxy (meth)acrylate compound;

[0035] Tertiary amine catalyst.

[0036] According to an embodiment of the present invention, the raw materials for preparing the modified cellulose nanofibril include the following components in parts by mass:

[0037] Cellulose nanofibrils; 50 - 60 parts by mass;

[0038] Reaction product of a diisocyanate compound and a mono-hydroxy (meth)acrylate compound; 140 - 220 parts by mass;

[0039] Tertiary amine catalyst; 2.5 - 12 parts by mass.

[0040] According to an embodiment of the present invention, the raw materials for preparing the modified cellulose nanofibril include 50 parts by mass, 51 parts by mass, 52 parts by mass, 53 parts by mass, 54 parts by mass, 55 parts by mass, 56 parts by mass, 57 parts by mass, 58 parts by mass, 59 parts by mass or 60 parts by mass of cellulose nanofibrils.

[0041] According to an embodiment of the present invention, the raw materials for preparing the modified cellulose nanofibril include 140 parts by mass, 145 parts by mass, 150 parts by mass, 155 parts by mass, 160 parts by mass, 165 parts by mass, 170 parts by mass, 175 parts by mass, 180 parts by mass, 185 parts by mass, 190 parts by mass, 195 parts by mass, 200 parts by mass, 205 parts by mass, 210 parts by mass, 215 parts by mass, 220 parts by mass of the reaction product of a diisocyanate compound and a mono-hydroxy (meth)acrylate compound.

[0042] According to the embodiments of the present invention, the raw materials for preparing the modified cellulose nanofibrils include 2.5 parts by mass, 3 parts by mass, 3.5 parts by mass, 4 parts by mass, 4.5 parts by mass, 5 parts by mass, 5.5 parts by mass, 6 parts by mass, 7 parts by mass, 8 parts by mass, 9 parts by mass, 10 parts by mass, 11 parts by mass, and 12 parts by mass of tertiary amine catalysts.

[0043] <Reaction product of a diisocyanate compound and a monohydroxy(meth)acrylate compound>

[0044] According to the embodiments of the present invention, the raw materials for preparing the reaction product of the diisocyanate compound and the monohydroxy(meth)acrylate compound include the following components:

[0045] Diisocyanate compounds;

[0046] Monohydroxy(meth)acrylate compounds;

[0047] Organotin catalysts.

[0048] According to the embodiments of the present invention, the molar ratio of the diisocyanate compound to the monohydroxy(meth)acrylate compound is 1:1.

[0049] According to the embodiments of the present invention, the mass of the organotin catalyst is 0.1-1.0 wt% of the total mass of the diisocyanate compound and the monohydroxy(meth)acrylate compound, for example, 0.1 wt%, 0.2 wt%, 0.3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt%, 0.9 wt%, or 1 wt%.

[0050] <Diisocyanate compounds>

[0051] According to an embodiment of the present invention, the selection of the diisocyanate compound is not particularly limited and can be a diisocyanate compound known in the art; exemplarily, the diisocyanate compound is selected from at least one of 1,3-phenylene diisocyanate (b-1), 1,4-phenylene diisocyanate (b-2), 1-(chloromethyl)-2,4-diisocyanatobenzene (b-3), 4-methyl-m-phenylene diisocyanate 98 (CAS: 99741-73-8, b-4), 4-chloro-6-methyl-m-phenylene diisocyanate (b-5), 2,4-toluene diisocyanate (b-7), 2,5-toluene diisocyanate, 2,6-toluene diisocyanate (b-6), 3,3'-dimethoxy-4,4'-biphenyl diisocyanate (b-9), 4,4'-diphenylmethane diisocyanate, xylene diisocyanate, tetramethylxylene diisocyanate, isophorone diisocyanate (b-10), hexamethylene diisocyanate, tetramethylene diisocyanate, hydrogenated xylene diisocyanate, dodecamethylene diisocyanate, trimethylhexamethylene diisocyanate (b-8), dimethylhexamethylene diisocyanate, and 1,3-bis(isocyanatomethyl)-cyclohexane.

[0052] <monohydroxy (meth)acrylate compound>

[0053] According to an embodiment of the present invention, the selection of the monohydroxy (meth)acrylate compound is not particularly limited and can be a (meth)acrylate compound having a monohydroxy group known in the art, such as an acrylate compound having a monohydroxy group or a methacrylate compound having a monohydroxy group.

[0054] According to an embodiment of the present invention, the monohydroxy (meth)acrylate compound is selected from at least one of the compounds represented by Formula 1:

[0055]

[0056] In Formula 1, R is H or CH3; R' is an alkylene group.

[0057] According to an embodiment of the present invention, R' is an alkylene group containing 2 to 8 carbon atoms. Exemplarily, R' is an alkylene group containing 2, 3, 4, 5, 6, 7, or 8 carbon atoms.

[0058] According to an embodiment of the present invention, the mono-hydroxy (meth)acrylate compound is selected from at least one of 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl acrylate (HPA), 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate (4-HBA), 4-hydroxybutyl methacrylate (4-HBMA), 6-hydroxyhexyl acrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl acrylate, 8-hydroxyoctyl methacrylate, polyethylene glycol (200)-monoacrylate, polyethylene glycol (400)-monoacrylate, polypropylene glycol (400)-monoacrylate, caprolactone-modified 2-hydroxyethyl acrylate, phosphate ester 2-hydroxyethyl acrylate, silicone-modified 2-hydroxyethyl acrylate, fluorine-modified 2-hydroxyethyl acrylate, and 2-hydroxy-3-phenoxypropyl acrylate.

[0059] <Organotin catalysts>

[0060] According to an embodiment of the present invention, the organotin catalysts are selected from at least one of dibutyltin dilaurate, stannous octoate, dibutyltin diacetate, and dibutyltin dimaleate.

[0061] <Cellulose nanofibrils>

[0062] According to an embodiment of the present invention, the cellulose nanofibrils are unmodified cellulose nanofibrils.

[0063] According to an embodiment of the present invention, the cellulose nanofibrils can be obtained by purchasing through commercial channels or prepared by methods known in the art.

[0064] According to an embodiment of the present invention, the surface of the cellulose nanofibrils has hydroxyl groups, and the hydroxyl group content is 3-5 mmol / g.

[0065] According to an embodiment of the present invention, the length of the cellulose nanofibrils is in the micron scale; the diameter of the cellulose nanofibrils is 5-100 nm; the aspect ratio of the cellulose nanofibrils is 100-500.

[0066] <Tertiary amine catalysts>

[0067] According to an embodiment of the present invention, the tertiary amine catalyst is selected from at least one of triethylamine (TEA), N,N-dimethylcyclohexylamine (DMCHA), N,N-dimethylethanolamine (DMEA), triethylenediamine (TEDA / DABCO), N-methylmorpholine (NMM), N-ethylmorpholine (NEM), tetramethylethylenediamine (TMEDA), triethanolamine (TEOA), dimethylbenzylamine (DMBA), dimethylaminopropylamine (DMAPA), tributylamine (TBA), trioctylamine (TOA), N,N-dimethylaniline (DMA), triisopropanolamine (TIPA), bis(2-dimethylaminoethyl) ether (BDMAEE), 2,4,6-tris(dimethylaminomethyl)phenol (DMP-30), dimethylcyclohexylamine (DMCA), diethylethanolamine (DEEA), methyldiethanolamine (MDEA), and tris(2-hydroxypropyl)amine (THPA).

[0068] <Preparation method of modified cellulose nanofibrils>

[0069] The present invention also provides a preparation method of modified cellulose nanofibrils, and the preparation method includes the following steps:

[0070] 1) Mix a diisocyanate compound, a monohydroxy(meth)acrylate compound, and an organotin catalyst, and react to prepare a compound with isocyanate and acrylate at the end groups;

[0071] 2) Mix cellulose nanofibrils and ethyl acetate, and perform azeotropic dehydration treatment on the cellulose nanofibrils by heating under reflux. After the azeotropic dehydration treatment is completed, add a tertiary amine catalyst and the compound with isocyanate and acrylate at the end groups prepared in step 1), and react to prepare modified cellulose nanofibrils grafted with acrylate groups and isocyanate segments.

[0072] According to an embodiment of the present invention, in step 1), the molar ratio of the diisocyanate compound to the monohydroxy(meth)acrylate compound is 1:1.

[0073] According to an embodiment of the present invention, in step 1), the reaction time and the reaction temperature are not particularly limited as long as the reaction between the diisocyanate compound and the monohydroxy(meth)acrylate compound can be achieved; exemplarily, the reaction temperature is 40-60 °C; the reaction time is 5-6 hours.

[0074] According to an embodiment of the present invention, in step 2), the mass ratio of the cellulose nanofibrils to ethyl acetate is 50 - 60:80 - 200, for example, 55:100, 55:110, 55:120, 55:130, 55:140, 55:150, 55:160, 55:170, 55:180, 55:190.

[0075] According to an embodiment of the present invention, in step 2), the mixing is carried out at room temperature, the mixing time is 2 - 6 hours, and the mixing is carried out under stirring conditions.

[0076] According to an embodiment of the present invention, in step 2), the time for the azeotropic dehydration treatment is 3 - 8 hours; the temperature for the azeotropic dehydration treatment is 70 - 80 °C.

[0077] According to an embodiment of the present invention, in step 2), the mass ratio of the cellulose nanofibrils to the tertiary amine catalyst is 50 - 60:2.5 - 12.

[0078] According to an embodiment of the present invention, in step 2), the reaction temperature is 0 - 10 °C; controlling the reaction temperature within the range of 0 - 10 °C helps to reduce the formation of by-products. The reaction time is not particularly limited, and the reaction can be stopped until there is no isocyanate group in the reaction solution (detected by infrared spectroscopy); exemplarily, the reaction time is 4 - 6 hours.

[0079] According to an embodiment of the present invention, in step 2), the mass ratio of the cellulose nanofibrils to the compound with isocyanate and acrylate end groups prepared in step 1) is 50 - 60:140 - 220.

[0080] According to an embodiment of the present invention, the method further comprises the following steps:

[0081] 3) Purifying the modified cellulose nanofibrils prepared in step 2).

[0082] According to an embodiment of the present invention, in step 3), the purification treatment is to mix the modified cellulose nanofibrils prepared in step 2), n-butanol and acetone, stir evenly, add petroleum ether, continue stirring to obtain a white precipitate, remove the supernatant, and repeat the operation 3 - 6 times; the obtained solid is dried in vacuum to prepare modified cellulose nanofibrils with higher purity.

[0083] According to an embodiment of the present invention, in step 3), the purification treatment is to add 5-10 parts by weight of n-butanol and 10-20 parts by weight of acetone to 30-50 parts by weight of the modified cellulose nanofibrils prepared in step 2), stir and dissolve for 1-3 h, then add 30-70 parts by weight of petroleum ether, stir for 1-2 h to obtain a white precipitate, remove the supernatant, and repeat the operation 3-6 times; the obtained solid is vacuum dried for 24-48 h to prepare modified cellulose nanofibrils with higher purity.

[0084] <Modified cellulose nanofibrils>

[0085] The present invention also provides a modified cellulose nanofibril, which is prepared by the above method.

[0086] According to an embodiment of the present invention, the modified cellulose nanofibril is a reaction product of cellulose nanofibrils, diisocyanate compounds and mono-hydroxy (meth) acrylate compounds.

[0087] According to an embodiment of the present invention, the modified cellulose nanofibril is a reaction product of a reaction product of diisocyanate compounds and mono-hydroxy (meth) acrylate compounds and cellulose nanofibrils.

[0088] According to an embodiment of the present invention, acrylate groups and isocyanate segments are grafted on the surface of the modified cellulose nanofibril. The surface of the modified cellulose nanofibril has hydroxyl groups, and the hydroxyl content is 0.5-2 mmol / g.

[0089] According to an embodiment of the present invention, the length of the modified cellulose nanofibril is in the micron scale; the diameter of the modified cellulose nanofibril is 5-100 nm; the aspect ratio of the modified cellulose nanofibril is 100-500.

[0090] <3D printing photosensitive resin>

[0091] The present invention also provides a 3D printing photosensitive resin, and the preparation raw materials of the 3D printing photosensitive resin include the following components:

[0092] Modified cellulose nanofibrils;

[0093] Acrylate oligomer;

[0094] Acrylate monomer;

[0095] Photoinitiator.

[0096] According to an embodiment of the present invention, the preparation raw materials of the 3D printing photosensitive resin further include the following components:

[0097] Auxiliary agent.

[0098] According to an embodiment of the present invention, the modified cellulose nanofibrils are prepared by the above method.

[0099] According to an embodiment of the present invention, the acrylate oligomer is selected from one or a mixture of two or more of ethoxylated bisphenol A dimethacrylate, hexafunctional aliphatic urethane acrylate, difunctional aliphatic urethane acrylate, tetrafunctional polyester acrylate, and trifunctional aliphatic urethane acrylate.

[0100] According to an embodiment of the present invention, the acrylate monomer is selected from one or a mixture of two or more of polyurethane acrylate resin, acryloyl morpholine, ditrimethylolpropane tetraacrylate, trimethylolpropane triacrylate, and ethoxylated trimethylolpropane triacrylate.

[0101] According to an embodiment of the present invention, the photoinitiator is selected from one or a mixture of two or more of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, isopropylthioxanthone, and 1-hydroxycyclohexylphenyl ketone.

[0102] According to an embodiment of the present invention, the auxiliary agent is selected from one or more of a defoaming agent, a leveling agent, a matte agent, and the like.

[0103] According to an embodiment of the present invention, the defoaming agent may include silicone defoaming agents such as BASF FoamStar SI2240, FoamStar SI2292; WACKER 270C / 246C / 235C / 160C / 276C; Dow Corning DC-510, DC65; Momentive Silcolapse series; SIXIN BZ-5600, HT-916; polyether defoaming agents such as BASF Pluronic PE4300, PE6100; EVONIK TEGO843; Antifoam 793; Dow Ucon series, etc.

[0104] According to the embodiment of the present invention, the leveling agent may include BYK-306, BYK-333, BYK-358N, BYK-315, BYK-320; Deqian 435, 835; Haichuan Chemical HC-2020, N3250; Sixin Technology BZ-5600, HT-916, etc.

[0105] According to the embodiment of the present invention, the matte agent can be listed as Wanhua Chemical HT-300plus, 4616; Miki SM3107-X-60; Guangzhou Huisheng Silicon Material HS6; Guangzhou Houyou Trade HY-590; Nippon Kayaku KANEKAMP90; RB608; Guangzhou Lingwei Technology L-100, etc.

[0106] According to an embodiment of the present invention, the mass of the modified cellulose nanofibrils accounts for 3wt% - 60wt% of the total mass of the 3D printing photosensitive resin, for example, 3wt%, 5wt%, 6wt%, 8wt%, 10wt%, 12wt%, 15wt%, 16wt%, 18wt%, 20wt%, 22wt%, 25wt%, 26wt%, 28wt%, 30wt%, 32wt%, 35wt%, 36wt%, 38wt%, 40wt%, 42wt%, 45wt%, 46wt%, 48wt%, 50wt%, 52wt%, 55wt%, 56wt%, 58wt% or 60wt%.

[0107] According to an embodiment of the present invention, the mass of the acrylate oligomer accounts for 20wt% - 60wt% of the total mass of the 3D printing photosensitive resin, for example, 20wt%, 22wt%, 25wt%, 26wt%, 28wt%, 30wt%, 32wt%, 35wt%, 36wt%, 38wt%, 40wt%, 42wt%, 45wt%, 46wt%, 48wt%, 50wt%, 52wt%, 55wt%, 56wt%, 58wt% or 60wt%.

[0108] According to an embodiment of the present invention, the mass of the acrylate monomer accounts for 10wt% - 70wt% of the total mass of the 3D printing photosensitive resin, for example, 10wt%, 12wt%, 15wt%, 16wt%, 18wt%, 20wt%, 22wt%, 25wt%, 26wt%, 28wt%, 30wt%, 32wt%, 35wt%, 36wt%, 38wt%, 40wt%, 42wt%, 45wt%, 46wt%, 48wt%, 50wt%, 52wt%, 55wt%, 56wt%, 58wt%, 60wt%, 62wt%, 65wt%, 66wt%, 68wt% or 70wt%.

[0109] According to an embodiment of the present invention, the mass of the photoinitiator accounts for 0.05 wt% - 10 wt% of the total mass of the 3D printing photosensitive resin, for example, 0.05 wt%, 0.1 wt%, 0.2 wt%, 0.5 wt%, 0.6 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt%, 5 wt%, 6 wt%, 7 wt%, 8 wt%, 9 wt% or 10 wt%.

[0110] According to an embodiment of the present invention, the mass of the auxiliary agent accounts for 0 wt% - 5 wt% of the total mass of the 3D printing photosensitive resin, for example, 0.05 wt%, 0.1 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%, 3.5 wt%, 4 wt%, 4.5 wt% or 5 wt%.

[0111] <Preparation method of 3D printing photosensitive resin>

[0112] The present invention also provides a preparation method of a 3D printing photosensitive resin, and the method includes the following steps:

[0113] Mix modified cellulose nanofibrils, acrylate oligomer, acrylate monomer, photoinitiator and optionally added or not added auxiliary agent, and stir to prepare the 3D printing photosensitive resin.

[0114] According to an embodiment of the present invention, the stirring time is 2 - 12 hours; the stirring speed is 300 - 400 r / min; the stirring temperature is 20°C - 50°C.

[0115] According to an embodiment of the present invention, mix modified cellulose nanofibrils, acrylic oligomer, acrylate monomer, photoinitiator and auxiliary agent evenly according to a mass ratio of 3 - 60:20 - 60:10 - 70:0.05 - 10:0 - 5, and stir for 2 - 12 hours under the conditions of a temperature of 20°C - 50°C and a speed of 300 - 400 r / min after mixing evenly to prepare the 3D printing photosensitive resin.

[0116] <3D printed product>

[0117] The present invention also provides a 3D printed product, and the 3D printed product is prepared from the above 3D printing photosensitive resin.

[0118] According to an embodiment of the present invention, the 3D printed product is prepared after being printed by a 3D printer and secondarily cured for 5 min - 25 min with the above 3D printing photosensitive resin.

[0119] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only for exemplarily illustrating and explaining the present invention, and should not be construed as limiting the protection scope of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0120] Unless otherwise specified, the experimental methods used in the following embodiments are all conventional methods; unless otherwise specified, the reagents, materials, etc. used in the following embodiments can all be obtained from commercial channels.

[0121] The structures of the diisocyanate compounds used in the following embodiments are specifically shown as follows:

[0122]

[0123] Examples 1 - 10

[0124] S1: Weigh the diisocyanate compounds (specific selections are shown in Table 1) and dibutyltin dilaurate respectively, add them to acetone solvent, the stirring speed is 200 - 300 rpm, heat up to 50 °C, and then dropwise add the mono-hydroxy (meth)acrylate compounds (specific selections are shown in Table 1). The molar ratio of the diisocyanate compounds to the mono-hydroxy (meth)acrylate compounds is 1:1, and the addition amount of dibutyltin dilaurate is 0.5 wt% of the total mass of the reactants. Stir and react at 50 °C for 6 hours, stop the reaction, and prepare the intermediate product.

[0125] S2: Weigh 60 g of cellulose nanofibrils (manufacturer: Zhejiang Jinjiahao Green Nanomaterials Co., Ltd., grade: CNF-H4), add them to 80 g of ethyl acetate and stir to dissolve for 3 h, heat reflux for 4 h, after azeotropic dehydration is completed, cool to room temperature, then add 5 g of tertiary amine catalyst (specific selections are shown in Table 1), then cool to 0 - 10 °C, and then dropwise add 140 g of the intermediate product from step S1. Stir until the isocyanate groups in the reaction solution disappear as detected by infrared spectroscopy, and stop stirring to obtain the modified cellulose nanofibrils grafted with acrylate groups and isocyanate segments.

[0126] S3: Weigh 30 g of the modified cellulose nanofibrils from step S2, then add 5 g of n-butanol and 15 g of acetone, stir to dissolve for 2 h, quickly add them to 30 g of petroleum ether, and stir rapidly for 1 h to obtain white precipitates. Remove the supernatant, repeat 3 times, and the obtained solid is vacuum dried for 24 h to obtain pure modified cellulose nanofibrils.

[0127] Comparative Example 1

[0128] Other operations are the same as in Example 1, the difference is that:

[0129] S2: Weigh 60 g of cellulose nanofibrils, add them to 80 g of ethyl acetate, stir and dissolve for 3 h, heat under reflux for 4 h. After azeotropic dehydration is completed, cool to room temperature. Then add 5 g of tertiary amine catalyst (specific selection is shown in Table 1), heat to a constant temperature of 60 °C, and then dropwise add 140 g of the intermediate product from step S1. Stir until the isocyanate groups in the reaction solution disappear as detected by infrared spectroscopy, and then stop stirring to obtain modified cellulose nanofibrils grafted with acrylate groups and isocyanate segments.

[0130] Comparative Example 2

[0131] Other operations are the same as in Example 1, except that:

[0132] S2: Weigh 60 g of cellulose nanofibrils, add them to 80 g of ethyl acetate, stir and dissolve for 3 h, heat under reflux for 4 h. After azeotropic dehydration is completed, cool to room temperature. Then add 5 g of tertiary amine catalyst (specific selection is shown in Table 1), then cool to 0 - 10 °C, and then dropwise add 50 g of the intermediate product from step S1. Stir until the isocyanate groups in the reaction solution disappear as detected by infrared spectroscopy, and then stop stirring to obtain modified cellulose nanofibrils grafted with acrylate groups and isocyanate segments.

[0133] Comparative Example 3

[0134] S2: Weigh 60 g of cellulose nanofibrils, add them to 80 g of ethyl acetate, stir and dissolve for 3 h, heat under reflux for 4 h. After azeotropic dehydration is completed, cool to room temperature. Then add 5 g of tertiary amine catalyst (specific selection is shown in Table 1), then cool to 0 - 10 °C, and then dropwise add 300 g of the intermediate product from step S1. Stir until the isocyanate groups in the reaction solution disappear as detected by infrared spectroscopy, and then stop stirring to obtain modified cellulose nanofibrils grafted with acrylate groups and isocyanate segments.

[0135] The electron microscope images and microscope images of the modified cellulose nanofibrils prepared in Example 1 are as Figure 1 and Figure 2 shown. Among them, Figure 1 The electron microscope image is of a sample obtained by dispersing the modified cellulose nanofibrils in a photosensitive resin, then diluting with dichloromethane and drying. It can be seen from the electron microscope image that the modified cellulose nanofibrils can be well dispersed in the photosensitive resin without agglomeration, and a grid structure is naturally formed; it can be seen from the microscope image that when observing the modified cellulose nanofibrils under a microscope at a magnification of 200, it can be clearly seen that the attachments on the fiber chains are densely distributed on its surface. This indicates that the isocyanate groups have reacted with the cellulose nanofibrils, changing the surface morphology of the cellulose nanofibrils.

[0136] Table 1. Raw material table for preparing modified cellulose nanofibers in Examples 1 - 10 and Comparative Examples 1 - 3

[0137] Number Diisocyanate compound Mono-hydroxy(meth)acrylate compound Tertiary amine catalyst Example 1 b-1 2-Hydroxyethyl acrylate TEA Example 2 b-2 2-Hydroxyethyl methacrylate TEOA Example 3 b-3 4-Hydroxybutyl methacrylate DMCHA Example 4 b-4 6-Hydroxyhexyl acrylate TBA Example 5 b-5 2-Hydroxypropyl acrylate DMBA Example 6 b-6 Polyethylene glycol(200)-monoacrylate BDMAEE Example 7 b-7 2-Hydroxy-3-phenoxypropyl acrylate DMA Example 8 b-8 Siloxane-modified 2-hydroxyethyl acrylate MDEA Example 9 b-9 Caprolactone-modified 2-hydroxyethyl acrylate DMCA Example 10 b-10 4-Hydroxybutyl acrylate THPA Comparative Example 1 b-1 2-Hydroxyethyl acrylate TEA Comparative Example 2 b-1 2-Hydroxyethyl acrylate TEA Comparative Example 3 b-1 2-Hydroxyethyl acrylate TEA

[0138] Example 11

[0139] S1: Take 8 g of the pure modified cellulose nanofibrils prepared in Example 1 above and disperse them evenly in 50 g of acryloylmorpholine by stirring to form a uniform and stable dispersion;

[0140] S2: Dissolve and stir 12 g of ditrimethylolpropane tetraacrylate monomer, 7 g of polyurethane acrylate resin monomer, 18 g of hexa-functional aliphatic polyurethane acrylate oligomer, and 12 g of difunctional modified polyurethane acrylate oligomer under the conditions of a temperature of 20 - 30 °C and a rotation speed of 300 - 400 r / min until they are uniformly mixed;

[0141] S3: Uniformly disperse the dispersion prepared in step S1 into step S2, and add 0.4 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 0.4 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 0.1 g of isopropylthioxanthone, and 0.05 g of Dow Corning DC65, and continue stirring for 60 minutes to obtain a 3D printing photosensitive resin;

[0142] S4: Print a model with the 3D printing photosensitive resin prepared in step S3 using an LCD type 3D printer, and perform secondary curing at 20 °C for 15 min to obtain a 3D printed product.

[0143] Example 12

[0144] Other operations are the same as in Example 11, except that in step S1, take 8 g of the pure modified cellulose nanofibrils prepared in Example 2 above and disperse them evenly in 50 g of acryloylmorpholine by stirring to form a uniform and stable dispersion.

[0145] Example 13

[0146] Other operations are the same as in Example 11, except that in step S1, take 8 g of the pure modified cellulose nanofibrils prepared in Example 3 above and disperse them evenly in 50 g of acryloylmorpholine by stirring to form a uniform and stable dispersion; in step S3, also add 0.05 g of BYK333.

[0147] Comparative Example 4

[0148] S1: Dissolve and stir 50 g of acryloylmorpholine, 12 g of ditrimethylolpropane tetraacrylate monomer, 7 g of polyurethane acrylate resin monomer, 18 g of hexa-functional aliphatic polyurethane acrylate oligomer, and 12 g of difunctional modified polyurethane acrylate oligomer under the conditions of a temperature of 20 °C and a rotation speed of 400 r / min until they are uniformly mixed;

[0149] S2: Add 0.4 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 0.4 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, 0.1 g of isopropylthioxanthone, and 0.05 g of Dow Corning DC65 to the dispersion prepared in step S1, and continue stirring for 60 minutes to obtain a 3D printing photosensitive resin.

[0150] S3: Print a model with the 3D printing photosensitive resin prepared in step S2 using an LCD type 3D printer, and perform secondary curing at 20 °C for 15 minutes to obtain a 3D printed product.

[0151] Comparative Example 5

[0152] S1: Disperse 8 g of nanocrystalline cellulose (manufacturer: Cailu Biotech; grade: CNC-MH30N) into 50 g of acryloylmorpholine and stir evenly to prepare a homogeneous and stable dispersion.

[0153] S2: Dissolve and stir 12 g of ditrimethylolpropane tetraacrylate monomer, 7 g of polyurethane acrylate resin monomer, 18 g of hexafunctional aliphatic polyurethane acrylate oligomer, and 12 g of difunctional modified polyurethane acrylate oligomer under the conditions of a temperature of 20 °C and a rotation speed of 400 r / min until evenly mixed.

[0154] S3: Uniformly disperse the dispersion prepared in step S1 into step S2, and add 0.4 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 0.4 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 0.1 g of isopropylthioxanthone, and continue stirring for 60 minutes to obtain a 3D printing photosensitive resin.

[0155] S4: Print a model with the 3D printing photosensitive resin prepared in S3 using an LCD type 3D printer, and perform secondary curing at 20 °C for 15 minutes to obtain a 3D printed product.

[0156] Comparative Example 6

[0157] S1: Disperse 8 g of unmodified cellulose nanofibrils (manufacturer: Zhejiang Jinjiahao Green Nanomaterials Co., Ltd., grade: CNF-H4) into 50 g of acryloylmorpholine and stir evenly to prepare a homogeneous and stable dispersion.

[0158] S2: Dissolve and stir 12 g of ditrimethylolpropane tetraacrylate monomer, 7 g of polyurethane acrylate resin monomer, 18 g of hexafunctional aliphatic polyurethane acrylate oligomer, and 12 g of difunctional modified polyurethane acrylate oligomer under the conditions of a temperature of 20 °C and a rotation speed of 400 r / min until evenly mixed.

[0159] S3: Uniformly disperse the dispersion prepared in step S1 into step S2, and add 0.4 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 0.4 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, and 0.1 g of isopropylthioxanthone, and continue stirring for 60 minutes to obtain a 3D printing photosensitive resin.

[0160] S4: Print a model with the 3D printing photosensitive resin prepared in S3 through an LCD type 3D printer, and perform secondary curing at 20 °C for 15 min to obtain a 3D printed product.

[0161] Comparative Example 7

[0162] Other operations are the same as in Example 11, except that in step S1, 8 g of the pure modified cellulose nanofibrils prepared in the above Comparative Example 1 are dispersed into 50 g of acryloylmorpholine and stirred evenly to form a uniform and stable dispersion.

[0163] Comparative Example 8

[0164] Other operations are the same as in Example 11, except that in step S1, 8 g of the pure modified cellulose nanofibrils prepared in the above Comparative Example 2 are dispersed into 50 g of acryloylmorpholine and stirred evenly to form a uniform and stable dispersion.

[0165] Comparative Example 9

[0166] Other operations are the same as in Example 11, except that in step S1, 8 g of the pure modified cellulose nanofibrils prepared in the above Comparative Example 3 are dispersed into 50 g of acryloylmorpholine and stirred evenly to form a uniform and stable dispersion.

[0167] Print the photosensitive resins of the above examples and comparative examples into test specimens, and test their thermal stability (heat distortion temperature) and mechanical properties. The obtained data are shown in Table 2.

[0168] Table 2. Heat distortion temperature and mechanical properties of 3D printed models

[0169] Heat distortion temperature / °C Shore hardness / D Tensile strength / MPa Flexural strength / MPa Example 11 86 86 34 70.5 Example 12 88 90 35 64.3 Example 13 89 89 31 68.1 Comparative Example 4 65 55 20 50.5 Comparative Example 5 63 52 20 41.9 Comparative Example 6 64 54 22 42.1 Comparative Example 7 50 45 12 30.3 Comparative Example 8 69 52 21 51.5 Comparative Example 9 48 55 20 53.8

[0170] As can be seen from Table 2, after modifying the cellulose nanofibrils, the mechanical properties and thermal stability of the prepared photosensitive resin can be significantly improved.

[0171] In Comparative Example 4, no cellulose was added, only the photosensitive resin. In Comparative Examples 5-6, commercially available unmodified nanocrystalline cellulose and cellulose nanofibrils were added. From the test performance, the introduction of unmodified nanocrystalline cellulose and cellulose nanofibrils could not enhance the mechanical properties of the photosensitive resin, and the flexural strength even decreased. Compared with Examples 11-13, the thermal stability also deteriorated.

[0172] Comparative Examples 7-9 respectively added the modified cellulose nanofibrils prepared in Comparative Examples 1-3. After comparison with Examples 11-13, it was found that the modified cellulose nanofibrils of Comparative Example 1 had more reaction by-products due to the absence of low-temperature reaction during the preparation process, resulting in poor performance of the modified cellulose nanofibrils. After adding them to the photosensitive resin system (Comparative Example 7), not only did it not improve the performance of the photosensitive resin, but it also damaged the integrity of the photosensitive resin, making the overall performance of the test worse than that of Comparative Example 4 without adding cellulose. The modified cellulose nanofibrils of Comparative Example 2 had an excessive amount of remaining hydroxyl groups in the reaction system due to insufficient addition of compounds with isocyanate and acrylate end groups during the preparation process, resulting in the problem of agglomeration still existing in the prepared modified cellulose nanofibrils. After adding them to the photosensitive resin system (Comparative Example 8), they could not play a role in enhancing the mechanical properties and thermal stability. The modified cellulose nanofibrils of Comparative Example 3 had remaining isocyanate in the reaction system due to excessive addition of compounds with isocyanate and acrylate end groups during the preparation process. After adding them to the photosensitive resin system (Comparative Example 9), the thermal stability of the prepared photosensitive resin became poor, and at the same time, there was no improvement in the mechanical properties of the photosensitive resin.

[0173] In summary, it can be shown that the photosensitive resin added with the modified cellulose nanofibrils of the present application can significantly improve the tensile strength, Shore hardness, flexural strength and thermal stability. This is because after chemical modification of the cellulose nanofibrils, the hydrophobicity is increased, enabling them to not agglomerate in the photosensitive resin matrix; the reaction with isocyanate compounds also improves the dispersion uniformity, making it form a uniform network structure in the photosensitive resin matrix, and the thermal stability is also greatly enhanced.

[0174] The above describes the embodiments of the present invention. However, the present invention is not limited to the above embodiments. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A modified cellulose nanofiber, wherein, The raw materials for preparing the modified cellulose nanofibrils include the following components: Cellulose nanofibrils; The reaction product of a diisocyanate compound and a mono-hydroxy (meth)acrylate compound; Tertiary amine catalyst.

2. The modified cellulose nanofibrils according to claim 1, wherein, The raw materials for preparing the modified cellulose nanofibrils include the following components in parts by mass: Cellulose nanofibrils; 50 - 60 parts by mass; The reaction product of a diisocyanate compound and a mono-hydroxy (meth)acrylate compound; 140 - 220 parts by mass; Tertiary amine catalyst; 2.5 - 12 parts by mass. Preferably, the raw materials for preparing the reaction product of the diisocyanate compound and the mono-hydroxy (meth)acrylate compound include the following components: Diisocyanate compound; Mono-hydroxy (meth)acrylate compound; Organotin catalyst. Preferably, the molar ratio of the diisocyanate compound to the mono-hydroxy (meth)acrylate compound is 1:

1. Preferably, the mass of the organotin catalyst is 0.1 - 1.0 wt% of the total mass of the diisocyanate compound and the mono-hydroxy (meth)acrylate compound. Preferably, the mono-hydroxy (meth)acrylate compound is selected from at least one of the compounds shown in Formula 1: In Formula 1, R is H or CH3; R' is an alkylene group. Preferably, the mono-hydroxy (meth)acrylate compound is selected from at least one of 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl acrylate (HPA), 2-hydroxypropyl acrylate (HPA), 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate (4-HBA), 4-hydroxybutyl methacrylate (4-HBMA), 6-hydroxyhexyl acrylate, 6-hydroxyhexyl methacrylate, 8-hydroxyoctyl acrylate, 8-hydroxyoctyl methacrylate, polyethylene glycol (200)-monoacrylate, polyethylene glycol (400)-monoacrylate, polypropylene glycol (400)-monoacrylate, caprolactone-modified 2-hydroxyethyl acrylate, phosphate ester 2-hydroxyethyl acrylate, silicone-modified 2-hydroxyethyl acrylate, fluorine-modified 2-hydroxyethyl acrylate, and 2-hydroxy-3-phenoxypropyl acrylate. Preferably, the length of the cellulose nanofibrils is in the micron scale; the diameter of the cellulose nanofibrils is 5 - 100 nm; the aspect ratio of the cellulose nanofibrils is 100 - 500.

3. The method for preparing the modified cellulose nanofibrils according to claim 1 or 2, wherein the preparation method comprises the following steps: 1) Mix a diisocyanate compound, a mono-hydroxy (meth)acrylate compound, and an organotin catalyst, and react to prepare a compound with isocyanate and acrylate end groups; 2) Mix cellulose nanofibrils and ethyl acetate, and perform azeotropic dehydration treatment on the cellulose nanofibrils by heating under reflux. After the azeotropic dehydration treatment is completed, add a tertiary amine catalyst and the compound with isocyanate and acrylate end groups prepared in step 1), and react to prepare modified cellulose nanofibrils grafted with acrylate groups and isocyanate segments. Preferably, in step 2), the time of the azeotropic dehydration treatment is 3 - 8 hours; the temperature of the azeotropic dehydration treatment is 70 - 80 °C; the temperature of the reaction is 0 - 10 °C.

4. The preparation method according to claim 3, wherein, The method further includes the following steps: 3) Purify the modified cellulose nanofibrils prepared in step 2); The purification treatment is to mix the modified cellulose nanofibrils prepared in step 2), n-butanol and acetone, stir evenly, add petroleum ether, continue to stir to obtain a white precipitate, remove the supernatant, and repeat the operation 3 - 6 times; the obtained solid is dried under vacuum to prepare modified cellulose nanofibrils with higher purity.

5. A modified cellulose nanofibril, which is prepared by the method according to claim 3 or 4. Preferably, the surface of the modified cellulose nanofibril is grafted with acrylate groups and isocyanate segments. Preferably, the surface of the modified cellulose nanofibril has hydroxyl groups, and the hydroxyl group content is 0.5 - 2 mmol / g. Preferably, the length of the modified cellulose nanofibril is in the micron scale; the diameter of the modified cellulose nanofibril is 5 - 100 nm; the aspect ratio of the modified cellulose nanofibril is 100 - 500.

6. A 3D printing photosensitive resin, and the preparation raw materials of the 3D printing photosensitive resin include the following components: The modified cellulose nanofibril according to any one of claims 1 - 2 or 5; Acrylate oligomer; Acrylate monomer; Photoinitiator.

7. The 3D printing photosensitive resin according to claim 6, wherein, The acrylate oligomer is selected from one or a mixture of two or more of ethoxylated bisphenol A dimethacrylate, hexafunctional aliphatic polyurethane acrylate, difunctional aliphatic polyurethane acrylate, tetrafunctional polyester acrylate, trifunctional aliphatic polyurethane acrylate; The acrylate monomer is selected from one or a mixture of two or more of polyurethane acrylate resin, acryloylmorpholine, bis(trimethylolpropane) tetraacrylate, trimethylolpropane triacrylate, ethoxylated trimethylolpropane triacrylate; The photoinitiator is selected from one or a mixture of two or more of phenylbis(2,4,6 - trimethylbenzoyl)phosphine oxide, 2,4,6 - trimethylbenzoyl - diphenylphosphine oxide, isopropylthioxanthone, 1 - hydroxycyclohexyl phenyl ketone. Preferably, the preparation raw materials of the 3D printing photosensitive resin further include additives, and the additives are selected from one or more of defoamers, leveling agents, matting agents, etc.

8. The 3D printing photosensitive resin according to claim 6 or 7, wherein, The mass of the modified cellulose nanofibrils accounts for 3wt% - 60wt% of the total mass of the 3D printing photosensitive resin; the mass of the acrylate oligomer accounts for 20wt% - 60wt% of the total mass of the 3D printing photosensitive resin; the mass of the acrylate monomer accounts for 10wt% - 70wt% of the total mass of the 3D printing photosensitive resin; the mass of the photoinitiator accounts for 0.05wt% - 10wt% of the total mass of the 3D printing photosensitive resin.

9. The preparation method of the 3D printing photosensitive resin according to any one of claims 6 - 8, the method comprising the following steps: Mix the modified cellulose nanofibrils, acrylate oligomer, acrylate monomer, photoinitiator and optionally added or not added additives, and stir to obtain the 3D printing photosensitive resin. Preferably, the stirring time is 2 - 12 hours; the stirring speed is 300 - 400 r / min; the stirring temperature is 20°C - 50°C.

10. A 3D printed article, the 3D printed article is prepared from the 3D printing photosensitive resin according to any one of claims 6 - 8.

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