Preparation method of cellulose-based light-cured resin

Abstract

The invention discloses a preparation method of cellulose-based light-cured resin, and relates to a preparation method of light-cured resin. In order to solve the technical problems that an existing cellulose acetate butyrate photosensitization modification method is complex in reaction, harsh in condition and complex in purification process, the method comprises the steps that cellulose acetate butyrate, acryloyl chloride and a solvent are mixed to react, a modified product is directly obtained through aftertreatment, then the modified product is mixed with N, N-dimethylacrylamide and an initiator, and the photosensitization modification method for cellulose acetate butyrate is obtained. The cellulose-based light-cured resin is obtained. The modified resin disclosed by the invention is simple in synthesis, separation and purification steps and high in synthesis efficiency. The tensile strength of the cellulose-based light-cured resin after light curing is 55 MPa-70 MPa, the elongation at break is 6%-12%, and the cellulose-based light-cured resin can be used in the field of 3D printing.

Description

Technical Field

[0001] The invention belongs to the technical field of light-curing resin preparation, and particularly relates to a method for preparing a cellulose-based light-curing resin. Background Art

[0002] With the increasing global emphasis on sustainable development and environmentally friendly materials, traditional petroleum-based polymers are facing challenges such as resource shortages, environmental pollution, and non-degradability. Photocurable materials, due to their high efficiency, energy efficiency, and low VOC emissions, are gaining widespread application in coatings, 3D printing, electronic packaging, and other fields. However, current commercial photocurable resins (such as acrylates and epoxies) still rely heavily on non-renewable petrochemical raw materials and suffer from limited mechanical properties and difficulty in degradation and recycling, limiting their application in green manufacturing and high-value-added applications.

[0003] Cellulose acetate butyrate (CAB), a natural cellulose derivative, exhibits excellent film-forming properties, thermal stability, and processability. Its hydrophobicity, flexibility, and compatibility with other polymers can be manipulated through molecular design. However, traditional CAB materials lack photosensitivity and cannot be directly applied to photocuring technology. In recent years, researchers have endowed cellulose derivatives with photocurable properties through chemical modifications such as acrylation and maleic anhydride grafting. However, existing modification methods often require tedious pretreatment, multi-step functional group conversion, or high-cost catalysts, resulting in complex and difficult-to-control processes. Summary of the Invention

[0004] The present invention aims to solve the technical problems of the existing photosensitization modification method of cellulose acetate butyrate, such as complex reaction, harsh conditions and complex purification process, and proposes a method for preparing a cellulose-based light-curable resin. The method of the present invention is a one-step modification process. The synthesis diagram is shown in FIG. Figure 1 As shown, cellulose acetate butyrate (CAB), acryloyl chloride, and a solvent are mixed and reacted, and the modified product is directly obtained through post-treatment. This method avoids the intermediate separation and purification steps required in traditional multi-step synthesis, significantly improving synthesis efficiency. This method is simple, and the resulting modified CAB resin not only has rapid light-curing ability and adjustable mechanical properties, but also retains the renewable and biodegradable properties of natural cellulose.

[0005] The preparation method of the cellulose-based light-curable resin of the present invention is carried out according to the following steps:

[0006] 1. Mixing cellulose acetate butyrate (CAB), acryloyl chloride, a solvent, and a polymerization inhibitor under heating and an inert gas atmosphere, and stirring the mixture to react to obtain a crude product; wherein the solvent is ultra-dry tetrahydrofuran (THF) and ultra-dry triethylamine (Et3N);

[0007] 2. The crude product was centrifuged, rotary evaporated, washed, and freeze-dried to obtain cellulose acetate butyrate modified with acryloyl chloride, which was designated as CAB-g-Ac.

[0008] 3. First, weigh 3% to 40% of cellulose acetate butyrate modified with acryloyl chloride (CAB-g-Ac) and 60% to 97% of N,N-dimethylacrylamide (DMAA) by mass; then weigh a photoinitiator, wherein the mass of the photoinitiator is 0.5% to 7% of the total mass of cellulose acetate butyrate modified with acryloyl chloride and N,N-dimethylacrylamide; the cellulose acetate butyrate modified with acryloyl chloride, N,N-dimethylacrylamide (DMAA) and the photoinitiator are uniformly mixed to obtain a cellulose-based light-curing resin.

[0009] Furthermore, the mass ratio of cellulose acetate butyrate (CAB) to acryloyl chloride in step 1 is 1:(2-3).

[0010] Furthermore, the polymerization inhibitor in step 1 is hydroquinone, and the mass of hydroquinone is 0.1% to 1% of the total mass of cellulose acetate butyrate (CAB) and acryloyl chloride.

[0011] Furthermore, the mass ratio of cellulose acetate butyrate (CAB) described in step 1 to ultra-dry tetrahydrofuran is 1 g:(15-30) mL; the mass ratio of acryloyl chloride to ultra-dry triethylamine is 1:(1-1.5).

[0012] Furthermore, the specific preparation steps for the crude product in step 1 are as follows: cellulose acetate butyrate (CAB), ultra-dry tetrahydrofuran (THF), and a polymerization inhibitor are mixed at room temperature under an inert atmosphere and stirred at a speed of 100-1700 rpm for 30-50 minutes to obtain a clear, transparent solution; acryloyl chloride is then added dropwise to the clear solution at a temperature of 20-50°C under an inert atmosphere and stirred for 2-3 hours; finally, ultra-dry triethylamine (Et3N) is added dropwise at a temperature of 20-50°C under an inert atmosphere and stirred for 6-10 hours to obtain a crude product. In this step, the solvent is anhydrous to avoid side reactions induced by water or acid (such as hydrolysis of acryloyl chloride, cellulose degradation, or cross-linking). THF, a polar aprotic solvent, effectively dissolves cellulose acetate butyrate (CAB), forming a homogeneous reaction system. This allows the hydroxyl groups (-OH) on the CAB molecular chain to react more readily with the acyl groups (-COCl) of acryloyl chloride to form acrylate grafted products, improving grafting efficiency. The reaction of acryloyl chloride with CAB releases HCl, which is neutralized by Et3N, acting as a base, to form triethylamine hydrochloride (Et3N·HCl), preventing side reactions caused by HCl accumulation. The homogeneous environment of THF, combined with the acid-scavenging effect of Et3N, significantly improves grafting efficiency and product purity.

[0013] Furthermore, the centrifugation, rotary evaporation and washing treatment described in step 2 are specifically carried out according to the following steps: centrifugation at a rotation speed of 10000rpm~13000rpm, then rotary evaporation for 20min~40min, then washing with anhydrous ethanol until clear, and finally washing away excess alcohol with distilled water.

[0014] Furthermore, the photoinitiator in step three is photoinitiator 819, photoinitiator TPO or photoinitiator 1173.

[0015] The beneficial effects of the present invention are:

[0016] (1) The present invention utilizes a one-step modification process to graft acryloyl chloride onto cellulose acetate butyrate (CAB) to prepare acryloyl chloride-modified cellulose acetate butyrate (CAB-g-Ac) containing carbon-carbon double bonds. This allows the modified CAB to directly participate in the photocuring reaction as an oligomer, breaking through the application limitations of CAB and expanding its application in 3D printing. Furthermore, efficient acrylation modification of CAB can be achieved in a mild reaction system and under mild conditions. Compared with traditional CAB modification processes, this process greatly reduces the complexity of the process, improves reaction efficiency, reduces by-product generation, and ensures the controllability of the product structure.

[0017] (2) The cellulose-based photocurable resin prepared by the present invention has excellent mechanical properties. Its mechanical properties can be controlled by adjusting the proportions of the various components of the photosensitive resin and the photocuring conditions. When the oligomer content is 7% to 15%, its tensile strength can reach 55 MPa to 70 MPa, and its elongation at break can reach 6.8% to 12%. It has both rigidity and moderate toughness, and is suitable for 3D printed structural parts with high mechanical requirements.

[0018] (3) The double bond design of the CAB-g-Ac prepared by the present invention makes it a perfect match for UV curing systems, resulting in fast curing speed, high molding precision, smooth surface of the cured parts, strong interlayer bonding, and the ability to print complex structures. Furthermore, modified materials based on cellulose derivatives can partially replace petroleum-based resins, reducing environmental burdens and possessing excellent environmental benefits and social value.

[0019] (4) The present invention can flexibly control the strength and ductility of the photocurable resin by adjusting the CAB-g-Ac content and photocuring conditions to meet different application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Schematic diagram of the synthesis of CAB-g-Ac of the present invention;

[0021] Figure 21H NMR spectra of CAB-g-Ac and CAB prepared in Example 1;

[0022] Figure 3 FTIR spectra of CAB-g-Ac and CAB prepared in Example 1;

[0023] Figure 4 This is a photo of the cellulose-based light-curable resin prepared in Examples 1 to 5 after curing;

[0024] Figure 5 Graph showing the tensile properties of the cellulose-based photocurable resins prepared in Examples 1 to 5;

[0025] Figure 6 This is a sample image of the cellulose-based photocurable resin prepared in Example 1 printed in an LCD 3D printer. DETAILED DESCRIPTION

[0026] The beneficial effects of the present invention are demonstrated with the following examples.

[0027] Example 1: The preparation method of the cellulose-based light-curable resin of this embodiment is carried out according to the following steps:

[0028] 1. At room temperature and under a nitrogen atmosphere, 10 g of cellulose acetate butyrate (CAB), 250 mL of ultra-dry tetrahydrofuran, and 0.07 g of hydroquinone were mixed and stirred at 500 rpm for 40 min to obtain a clear and transparent solution. The temperature was then raised to 50°C, and 25 mL of acryloyl chloride was slowly added dropwise to the clear solution at a stirring speed of 1500 rpm under a nitrogen atmosphere, and the mixture was stirred for 2 h. The speed was then reduced to 800 rpm, and 45 mL of ultra-dry triethylamine was slowly added dropwise to the solution at a temperature of 50°C under a nitrogen atmosphere, and the mixture was stirred for 10 h to obtain a crude product.

[0029] 2. The crude product was centrifuged at 10,000 rpm, and the resulting supernatant was rotary evaporated and washed with anhydrous ethanol and distilled water until the solution turned light yellow. Finally, the solution was freeze-dried to obtain cellulose acetate butyrate modified with acryloyl chloride, denoted as CAB-g-Ac.

[0030] 3. Weigh 7% of cellulose acetate butyrate modified with acryloyl chloride (CAB-g-Ac) and 93% of N,N-dimethylacrylamide by mass; weigh 1% of the total mass of cellulose acetate butyrate modified with acryloyl chloride (CAB-g-Ac) and N,N-dimethylacrylamide as photoinitiator 819; mix the cellulose acetate butyrate modified with acryloyl chloride, N,N-dimethylacrylamide and photoinitiator 819, and then sonicate them with an ultrasonic disperser at room temperature for 10 minutes, and vacuum degas for 30 minutes to obtain a cellulose-based light-curing resin.

[0031] Example 2: This example differs from Example 1 in that step 3 is replaced by the following operation:

[0032] 3. Weigh 9% of cellulose acetate butyrate modified with acryloyl chloride and 91% of N,N-dimethylacrylamide by mass percentage; then weigh 1% of the total mass of cellulose acetate butyrate modified with acryloyl chloride CAB-g-Ac and N,N-dimethylacrylamide as photoinitiator 819; and mix the cellulose acetate butyrate modified with acryloyl chloride, N,N-dimethylacrylamide and photoinitiator 819, and then ultrasonicate them at room temperature for 10 minutes using an ultrasonic disperser, and vacuum degas for 40 minutes to obtain a cellulose-based light-curing resin.

[0033] Example 3: This example differs from Example 1 in that step 3 is replaced by the following operation:

[0034] 3. Weigh 11% of cellulose acetate butyrate modified with acryloyl chloride and 89% of N,N-dimethylacrylamide by mass percentage; then weigh 1% of the total mass of cellulose acetate butyrate modified with acryloyl chloride CAB-g-Ac and N,N-dimethylacrylamide as photoinitiator 819; mix the cellulose acetate butyrate modified with acryloyl chloride, N,N-dimethylacrylamide and photoinitiator 819, and then sonicate them with an ultrasonic disperser at room temperature for 5 minutes to 10 minutes, and vacuum degas for ≥30 minutes to obtain a cellulose-based light-curing resin.

[0035] Example 4: This example differs from Example 1 in that step 3 is replaced by the following operation:

[0036] 3. Weigh 13% of cellulose acetate butyrate modified with acryloyl chloride and 87% of N,N-dimethylacrylamide by mass percentage; then weigh 1% of the total mass of cellulose acetate butyrate modified with acryloyl chloride CAB-g-Ac and N,N-dimethylacrylamide as photoinitiator 819; mix the cellulose acetate butyrate modified with acryloyl chloride, N,N-dimethylacrylamide and photoinitiator 819, and then sonicate them with an ultrasonic disperser at room temperature for 10 minutes, and vacuum degas for 40 minutes to obtain a cellulose-based light-curing resin.

[0037] Example 5: This example differs from Example 1 in that step 3 is replaced by the following operation:

[0038] 3. Weigh 15% of cellulose acetate butyrate modified with acryloyl chloride and 85% of N,N-dimethylacrylamide by mass percentage; then weigh 1% of the total mass of cellulose acetate butyrate modified with acryloyl chloride CAB-g-Ac and N,N-dimethylacrylamide as photoinitiator 819; mix the cellulose acetate butyrate modified with acryloyl chloride, N,N-dimethylacrylamide and photoinitiator 819, and then sonicate them with an ultrasonic disperser at room temperature for 10 minutes, and vacuum degas for 40 minutes to obtain a cellulose-based light-curing resin.

[0039] The structure of the cellulose acetate butyrate CAB-g-Ac modified with acryloyl chloride obtained in step 2 of Example 1 was characterized and analyzed.

[0040] The structural characterization and quantitative analysis of cellulose acetate butyrate modified with acryloyl chloride (CAB-g-Ac) and unmodified cellulose acetate butyrate (CAB) were carried out by hydrogen nuclear magnetic resonance (¹H NMR). The test was carried out using a Bruker 400 MHz NMR spectrometer with CDCl3 as solvent. The results are shown in Figure 2. Figure 2 As shown. Triphenylphosphine (PPh3, δ = 7.0-8.0 ppm, 15 protons) was selected as the internal standard, and its integral value was set to 15.00. The characteristic double bond peak of the acryloyl group in cellulose acetate butyrate modified with acryloyl chloride appears in the δ = 5.6-6.7 ppm range, where =CH2 (5.6-6.7 ppm) and =CH- (6.0-6.7 ppm) correspond to two and one protons, respectively. The total integrated area of ​​the double bond protons was calculated to be 3.32 by integration. Combined with the molar number of the internal standard, the double bond content in the sample was calculated to be 0.8009 mmol / g. This result indicates that the acryloyl group was successfully grafted onto the CAB backbone, providing a quantitative basis for the subsequent functionalization of the material.

[0041] Then cross-validate it through FTIR test, the results are as follows Figure 3 As shown. Figure 3 It can be seen that CAB-g-Ac has a wavelength of 1630-1680 cm -1 A distinct absorption peak appeared within the wavelength range, attributed to the stretching vibration of the C=C double bond in the acryloyl group. Unmodified CAB showed no significant absorption within this wavenumber range, confirming that the peak was indeed derived from the grafted acryloyl group. The olefin proton signal observed at δ=5.5-6.5 ppm in H NMR further confirmed the successful introduction of the acryloyl group. The characteristic peak of the C=O ester bond in the infrared spectrum (approximately 1730 cm -1) remained present and showed no significant displacement, indicating that the modification process did not affect the original ester bond structure of the cellulose backbone. This result corroborates with the double bond content (0.8009 mmol / g) determined by quantitative NMR analysis, providing reliable structural characterization for the functionalization of the material.

[0042] The cellulose-based light-curable resins prepared in Examples 1 to 5 were cured and then subjected to mechanical property tests.

[0043] The cellulose-based light-curable resins prepared in Examples 1 to 5 were cast into 5B-type silicone dumbbell molds and irradiated under 405 nm wavelength ultraviolet light for 30s, 40s, 50s, 60s, and 70s for curing, respectively, to prepare standard tensile test pieces. Figure 4 The mechanical properties test was carried out according to GB / T 1040.2-2022 standard, and the results are shown in Table 1. Figure 5 shown.

[0044] Table 1 Mechanical test results

[0045]

[0046] From Table 1 and Figure 5 As can be seen, all specimens exhibited excellent tensile strength, exceeding 55 MPa. With increased UV irradiation time, the tensile strength exhibited a non-monotonic trend of "decline-rise-decline again," but the overall fluctuation was small (coefficient of variation <0.85). This is due to the fact that in the initial stage, the short curing time results in incomplete formation of the brittle network and weak inter-molecular forces. With increased curing time, the double bond conversion rate increases, the crosslinking density increases, and a more uniform three-dimensional network structure is formed, which increases the tensile strength. However, prolonged UV irradiation triggers the degradation of some chain segments and increases the brittleness of the material due to excessive crosslinking, thus reducing the tensile strength. The elongation at break is significantly affected by the CAB-g-Ac content and the irradiation time, and fluctuates to varying degrees, but generally remains above 6%, demonstrating good toughness. As the CAB-g-Ac content increases, its elongation at break generally shows a trend of first increasing and then decreasing. When the CAB-g-Ac content reaches 13%, the elongation at break reaches the highest value, and when the content is 15%, the elongation at break is at the lowest value. This is because the introduction of flexible cellulose chain segments enhances the mobility of the molecular chains, which increases the elongation at break. When the content reaches 15%, the excessively high cross-linking density restricts the slippage of the molecular chains, resulting in a slight decrease in elongation. At this time, the entire system becomes too viscous, which is not conducive to printing.

[0047] The cellulose-based photocurable resin prepared in Example 1 was placed in an LCD 3D printer to print a diamond lattice sample. The printing parameters are shown in Table 2 below. The photo of the printed diamond lattice sample is shown in Figure 6 The results show that cellulose-based photocurable resin can be successfully used in 3D printing.

[0048] Table 2 LCD 3D printing parameters

[0049]

[0050] The one-step modification process of the present invention can achieve efficient acrylation modification of CAB under mild conditions, and the light-curable resin prepared by the process can be successfully applied to 3D printing and has excellent mechanical properties.

Claims

1. A method for preparing a cellulose-based light-curable resin, characterized in that: The method proceeds as follows:

1. Mixing cellulose acetate butyrate, acryloyl chloride, a solvent, and a polymerization inhibitor under heating and an inert gas atmosphere, and stirring the mixture to react to obtain a crude product; wherein the solvent is ultra-dry tetrahydrofuran and ultra-dry triethylamine; 2. The crude product was centrifuged, rotary evaporated, washed, and freeze-dried to obtain cellulose acetate butyrate modified with acryloyl chloride, which was designated as CAB-g-Ac.

3. First, weigh 3% to 40% of cellulose acetate butyrate modified with acryloyl chloride and 60% to 97% of N,N-dimethylacrylamide by mass; then weigh a photoinitiator, wherein the mass of the photoinitiator is 0.5% to 7% of the total mass of the acryloyl chloride modified cellulose acetate butyrate and N,N-dimethylacrylamide; mix the acryloyl chloride modified cellulose acetate butyrate, N,N-dimethylacrylamide and the photoinitiator evenly to obtain a cellulose-based light-curing resin.

2. The method for preparing a cellulose-based light-curable resin according to claim 1, characterized in that: The mass ratio of cellulose acetate butyrate to acryloyl chloride described in step 1 is 1:(2-3).

3. The method for preparing a cellulose-based light-curable resin according to claim 1 or 2, characterized in that: The polymerization inhibitor described in step 1 is hydroquinone, and the mass of hydroquinone is 0.1% to 1% of the total mass of cellulose acetate butyrate and acryloyl chloride.

4. The method for preparing a cellulose-based light-curable resin according to claim 1 or 2, characterized in that: The mass ratio of the cellulose acetate butyrate described in step 1 to the volume of ultra-dry tetrahydrofuran is 1 g: (15-30) mL; the mass ratio of acryloyl chloride to ultra-dry triethylamine is 1: (1-1.5).

5. The method for preparing a cellulose-based light-curable resin according to claim 1 or 2, characterized in that: The specific preparation steps of the crude product in step 1 are: cellulose acetate butyrate, ultra-dry tetrahydrofuran and a polymerization inhibitor are mixed at room temperature and an inert gas atmosphere, and stirred at a rotation speed of 100 rpm to 1700 rpm for 30 minutes to 50 minutes to obtain a clear and transparent solution; then, acryloyl chloride is added dropwise to the clear solution at 20°C to 50°C and an inert gas atmosphere, and stirred for 2 hours to 3 hours; finally, ultra-dry triethylamine is added dropwise at a temperature of 20°C to 50°C and an inert gas atmosphere, and stirred for 6 hours to 10 hours to obtain a crude product.

6. The method for preparing a cellulose-based light-curable resin according to claim 1 or 2, characterized in that: The centrifugation, rotary evaporation and washing treatment described in step 2 are specifically carried out according to the following steps: centrifugation at a rotation speed of 10000rpm~13000rpm, then rotary evaporation for 20min~40min, then washing with anhydrous ethanol until clear, and finally washing away the alcohol with distilled water.

7. The method for preparing a cellulose-based light-curable resin according to claim 1 or 2, characterized in that: The photoinitiator described in step three is photoinitiator 819, photoinitiator TPO or photoinitiator 1173.

Images