A method for preparing starch-based 3D printing ink suitable for high printability

Abstract

The present invention discloses a method for preparing a starch-based 3D printing ink suitable for high printability, and belongs to the technical field of green printing materials. The present invention selects natural starch as raw material, and modifies the starch by methacrylic anhydride. The modified methacrylated starch can undergo self-crosslinking under ultraviolet light to form a network structure, and then compounded with natural starch and high-amylose starch to prepare a starch-based 3D printing ink with high printability. The ink has the characteristics of controllable photosensitivity, easy extrusion, and high formability, can be printed with high precision, is biodegradable, and uses non-toxic and pollution-free crosslinking agents and adhesives in the preparation process. It is a green material and can be safely used in biological tissue engineering. The present invention uses 3D printing technology, and can print the shape and size of printed products according to needs, which is convenient for personalized production. The printed products have high mechanical strength, high porosity and high biological stability, and have high application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of green printing materials, and in particular relates to a method for preparing a starch-based 3D printing ink suitable for high printability. Background Art

[0002] 3D printing, also known as additive manufacturing, is a new manufacturing technology driven by three-dimensional data models. It selectively and systematically accumulates materials under computer control to create the three-dimensional printed product. Currently, 3D printing technologies primarily include selective laser technology, hot melt extrusion, binder jetting, and inkjet printing. 3D printing technology is currently experiencing rapid development abroad, with numerous technological breakthroughs and application innovations achieved in recent years. In terms of materials, 3D printing technology now enables the printing of a wide variety of materials, with materials increasingly diversifying to include plastics, metals, ceramics, and food. This has greatly enhanced the functionality and diversity of printed products and enriched the application scenarios of 3D printing technology. 3D printing technology has also achieved significant advancements in the food and biotechnology fields, including: 3D printing technology can be customized to meet consumer needs and preferences, producing products with varying structural requirements; it can be used to add additional nutrients to meet specific nutritional requirements; and 3D printing technology can create specialized products with unique shapes and complex structures, enabling product redesign.

[0003] As an abundant, renewable, and low-cost natural biopolymer, starch is highly biocompatible, biodegradable, and its gelatinized form has a porous network structure. Its gelatinized and rheological properties make it a promising raw material for bio-3D printing. Starch 3D printing is an emerging technology with broad application prospects in the field of biodegradable materials. Researchers have improved starch's plasticity, rheological properties, and printing performance by adjusting its physical and chemical properties and combining it with other biodegradable polymers or additives. Common starch materials include corn starch and potato starch. Starch 3D printing uses various printing technologies, such as extrusion printing, photocuring printing, and powder sintering printing. Among them, extrusion printing is a more common method and is often divided into two operating methods: cooling printing and thermal printing. Cooling printing refers to heating the starch material to a gelatinized state, cooling and regenerating it, adding raw starch, and reheating it to the printing temperature, and stacking it layer by layer through an extruder to form a 3D printed object; thermal printing refers to heating the starch material to a gelatinized state, and stacking it layer by layer through an extruder at a high temperature to form a 3D printed object. Compared with cooling printing, thermal printing utilizes the low viscosity and strong fluidity of starch during gelatinization, making it more smoothly extruded from the nozzle, while saving cooling time and the cost of secondary heating. However, compared with cooling printing, thermal printing has the defects of short regeneration time and poor formability. Therefore, the present invention aims to develop a starch-based ink suitable for thermal printing. There has been extensive research into thermal 3D printing of starch, both domestically and internationally. Most studies have focused on improving the printing properties of specific starches through chemical modification or the addition of other substances. Foreign researchers have modified starch using a methacrylation reaction to produce methacrylated starch, which is then used for photocurable 3D printing using a DLP 3D printer. This method allows for intelligent and controllable 3D printing of starch, but it is associated with high equipment cost and complex operation, and it does not utilize the inherent gelatinization and regeneration properties of starch. Currently, starch 3D printing has diverse applications, including the preparation of scaffolds, drug delivery systems, and artificial tissues in the biomedical field; it can also be used in the food industry to achieve personalized food production; and it has applications in packaging, environmentally friendly materials, and textiles. However, starch 3D printing still faces challenges, such as improving printing accuracy, enhancing the mechanical properties of printed materials, and reducing costs. Future research directions include developing new starch materials, optimizing printing processes, and improving biodegradability.

[0004] Therefore, it is of great significance to develop a convenient method to prepare starch-based 3D printing ink with high printability for application in biological tissue engineering. Summary of the Invention

[0005] Starch is a potential raw material for 3D printing inks, but natural starch-based inks have problems such as difficulty in extrusion and poor formability. In addition, natural starch has a low amylose content and weak gel strength after regeneration. These defects have limited the application of starch in 3D printing to a certain extent.

[0006] In order to overcome one or more of the above-mentioned problems existing in the prior art, the present invention selects ordinary starch as the raw material for modification. After the starch is modified through a methacrylate reaction, a photoinitiator is introduced to enable it to obtain the ability of photocuring and cross-linking. It is then compounded with high-amylose starch. The gelatinization properties of natural starch, the high mechanical strength of high-amylose starch, and the photocross-linking properties of methacrylated starch are utilized to produce a starch-based ink that is easy to extrude and highly moldable.

[0007] The first object of the present invention is to provide a method for preparing a starch-based 3D printing ink with high printability, comprising the following steps:

[0008] (1) dissolving corn starch in dimethyl sulfoxide, heating and gelatinizing, and adding methacrylic anhydride and triethylamine;

[0009] (2) precipitating the solution obtained in step (1) in anhydrous ethanol, then washing with deionized water, repeating the precipitation and washing three times, and then freeze-drying to obtain methacrylated starch;

[0010] (3) mixing the methacrylated starch obtained in step (2) with the gelatinized high-amylose corn starch (amylose content > 70%) and ordinary starch, and adding phenyl dicarbamate as a photoinitiator to obtain a starch-based ink suitable for high-precision 3D printing;

[0011] In one embodiment of the present invention, the concentration of the corn starch in step (1) relative to the dimethyl sulfoxide solvent is 5.0 wt %; and the amount of methacrylic anhydride added relative to the corn starch is 5-10.0 wt %.

[0012] In one embodiment of the present invention, the heating gelatinization in step (1) is gelatinization at 95° C. for 30-45 minutes.

[0013] In one embodiment of the present invention, the amount of anhydrous ethanol used in step (2) is 5 times that of the starch solution obtained in step (1).

[0014] In one embodiment of the present invention, the concentration of the methacrylated starch in step (3) relative to water is 0.1-5.0 wt %.

[0015] In one embodiment of the present invention, the concentration of the high amylose corn starch in step (3) relative to water is 1-5.0 wt %.

[0016] In one embodiment of the present invention, the common starch in step (3) comprises one or more of cassava starch, corn starch, rice starch, wheat starch, and potato starch, and its concentration relative to water is 5.0-10.0 wt%.

[0017] In one embodiment of the present invention, the gelatinization of the high-amylose corn starch in step (3) is performed at 120° C. for 20-30 min, and the gelatinization of the common starch is performed at 95° C. for 30-45 min.

[0018] In one embodiment of the present invention, the concentration of the photoinitiator phenyl diurethane in step (3) relative to the methacrylated starch is 1 wt %.

[0019] In one embodiment of the present invention, the methacrylated starch, the gelatinized high-amylose corn starch and the common starch are mixed in a ratio of 1:(1-5):(1-5).

[0020] In one embodiment of the present invention, the uniform mixing in step (3) is performed by stirring and mixing at 95° C. for 10 minutes.

[0021] A second object of the present invention is to prepare a highly printable starch-based 3D printing ink using the method described herein.

[0022] The third object of the present invention is to provide a 3D printing method, which uses the highly printable starch-based 3D printing ink prepared by the method described in the present invention. During the printing process, the printed product is irradiated with ultraviolet light to solidify it, thereby obtaining a 3D printed product.

[0023] In one embodiment of the present invention, the 3D printing method has a printing temperature of 55-75° C. and a printing speed of 1-10 mm / min.

[0024] In one embodiment of the present invention, in the 3D printing method, the UV lamp irradiation wavelength is 365 nm and the irradiation time is 20 minutes.

[0025] A fourth object of the present invention is to provide an application of the highly printable starch-based 3D printing ink of the present invention in the field of 3D printing.

[0026] A fifth object of the present invention is to provide a 3D printed product, which is obtained by printing using the highly printable starch-based 3D printing ink of the present invention.

[0027] Advantages and effects of the present invention:

[0028] (1) The present invention uses natural starch as raw material, which is safe and non-toxic, is widely used in food processing and production, has achieved commercial production, has low production cost, and has broad application prospects in the field of biodegradable materials.

[0029] (2) The present invention selects high-amylose corn starch for compounding, and utilizes the high mechanical strength and low viscosity characteristics produced by increasing the amylose content to improve the extrudability and formability of starch-based ink.

[0030] (3) The present invention selects methacrylic anhydride to modify starch. The modified methacrylated starch can undergo self-crosslinking under ultraviolet light to form a network structure, has good biosafety, is safe and non-toxic, and is widely used in biological tissue engineering.

[0031] (4) The 3D printing ink prepared by the present invention has the characteristics of controllable light curing, easy extrusion, and high formability. It has high printability, can be printed with high precision, is biodegradable, and the preparation process does not use toxic and polluting cross-linking agents and adhesives. It is a green edible material and can be safely used in biological tissue engineering.

[0032] (5) The present invention uses 3D printing technology, which can print the shape and size of printed products according to needs, facilitating personalized production. The printed products have high mechanical strength, high porosity and high biological stability, and have high application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a photograph of the appearance of a starch-based cell culture scaffold obtained by printing the highly printable starch-based 3D printing ink prepared in Example 1.

[0034] Figure 2 This is a graph showing the change in storage modulus over time of starch-based 3D printing inks with different degrees of substitution prepared in Example 2.

[0035] Figure 3 This is a graph showing the change in storage modulus of corn starch-based 3D printing inks of different concentrations prepared in Example 3.

[0036] Figure 4 This is a graph showing the change in loss modulus of corn starch-based 3D printing inks of different concentrations prepared in Example 3.

[0037] Figure 5 This is a graph showing the change in regeneration viscosity of the light-curable 3D printing ink prepared in Example 5 as a function of temperature. DETAILED DESCRIPTION

[0038] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0039] Test method:

[0040] 1. Determination of viscosity of starch-based ink

[0041] The regeneration viscosity of the samples at 55-75℃ was measured using RVA-4500.

[0042] 2. Determination of rheological properties

[0043] The storage modulus and loss modulus of the samples before and after printing were measured using a DISCOVERY HR-3 rheometer.

[0044] 3. Determination of texture characteristics

[0045] The P / 20 probe in the TA.XT2i physical property analyzer was used to measure the cohesion, adhesiveness, elasticity and 50% compression hardness of the samples.

[0046] 4. Determination of contact angle and surface free energy

[0047] The contact angle and surface free energy of the samples were measured using an OCA-15EC video optical contact angle meter.

[0048] 5. Measurement of line width and center height of printed samples

[0049] The printed sample line width and center height of the samples were measured using a vernier caliper.

[0050] Example 1

[0051] A method for preparing a starch-based 3D printing ink with high printability comprises the following steps:

[0052] (1) A solution containing 5.0 wt% (relative to dimethyl sulfoxide) corn starch was gelatinized at 95°C for 30 min, and the solution was cooled to room temperature. 5.0 wt% methacrylic anhydride was then added dropwise using a syringe, followed by the slow addition of 0.5 ml of triethylamine as a nucleophilic catalyst. The final solution was allowed to stand at room temperature for 18 h, then precipitated in ethanol, dissolved in deionized water, and precipitated in ethanol twice. The final aqueous solution was freeze-dried to obtain methacrylated starch powder.

[0053] (2) gelatinizing an aqueous solution containing 5.0 wt% (relative to water) of corn starch at 95° C. for 30 min to obtain a starch gelatinized solution;

[0054] (3) gelatinizing an aqueous solution containing 5.0 wt% (relative to water) of high-amylose corn starch at 120° C. for 45 min, and stirring and heating (2) at 95° C. for 10 min until uniformly mixed to obtain a composite starch gelatinized solution;

[0055] (4) 5.0 wt% (relative to water) of methacrylated starch, 1 wt% (relative to methacrylated starch) of phenyl diurethane and the composite starch gelatinized solution of step (3) were stirred and heated at 95° C. for 10 min until uniformly mixed. The methacrylated starch, gelatinized high-amylose corn starch and corn starch were mixed in a ratio of 1:1:1 to prepare a starch-based 3D printing ink with high printability.

[0056] (5) The nozzle of the 3D printer is selected to be 0.6 mm, and the printing temperature and printing speed are set to 70°C. The gelatinized starch solution in (2) is added to the barrel and placed in the printer to balance the temperature for 10 minutes until the system temperature reaches 70°C. The 3D printer is operated for printing, and a UV lamp is used to irradiate the printing platform to obtain starch gel.

[0057] The morphology of the obtained starch-based cell culture scaffold is as follows Figure 1 ,from Figure 1 It can be seen from the surface: the printing effect is good, the texture is clear, and it has a complete appearance and structure.

[0058] Example 2

[0059] The addition amount of methacrylic anhydride in step (1) of Example 1 was adjusted to 6, 7, 8, and 10 wt %, while the other ingredients remained the same as in Example 1, to obtain a starch-based 3D printing ink with high printability.

[0060] The highly printable starch-based 3D printing inks obtained in Examples 1 and 2 were subjected to rheological property tests. The test results are as follows: Figure 2 As shown in the figure, with the increase of the amount of methacrylic anhydride added, the degree of substitution of methacrylated starch increases, the degree of chemical crosslinking under ultraviolet light excitation is enhanced, the storage modulus of starch-based ink is significantly improved, and the formability is significantly enhanced.

[0061] Example 3

[0062] The corn starch concentration in step (2) of Example 1 was adjusted to 6, 8, and 10 wt %, while the other conditions remained the same as in Example 1, to obtain a starch-based 3D printing ink with high printability.

[0063] The highly printable starch-based 3D printing inks obtained in Examples 1 and 3 were subjected to rheological property tests, and the test results are as follows Figure 3 、 Figure 4 As shown in the figure, starch concentration affects the smoothness and continuity of ink extrusion during the printing process and the formability of the printed product. High-concentration starch has good formability but difficult extrusion. Low-concentration starch has a smooth and continuous extrusion process, but the printed product has poor formability. As the starch concentration increases, the storage modulus and loss modulus of starch-based ink both increase.

[0064] Example 4

[0065] The addition amount of high-amylose corn starch in step (3) of Example 1 was adjusted to 1, 2, 3, and 4 wt %, while the other steps remained the same as in Example 1, thereby obtaining a starch-based 3D printing ink with high printability.

[0066] The highly printable starch-based 3D printing inks obtained in Examples 1 and 4 were used for 3D printing to obtain printed products, and the texture properties of the printed products were tested. The test results are shown in Table 1 below. The concentration of high-amylose corn starch mainly affects the formability of the printing process and the texture of the final printed product, such as the hardness. As the amount of high-amylose corn starch added increases, the formability and hardness are significantly enhanced.

[0067] Table 1 Printing quality structure with different addition amounts of high amylose corn starch

[0068]

[0069] Example 5

[0070] The printing temperature in step (5) of Example 1 was adjusted to 55, 60, 65, and 75° C., while the other temperatures remained the same as in Example 1, to obtain a starch-based 3D printing ink with high printability.

[0071] The highly printable starch-based 3D printing inks obtained in Examples 1 and 5 were subjected to a retrograde viscosity test. The test results are as follows: Figure 5 As shown in the figure, as the printing temperature increases, the regeneration viscosity of the printing ink decreases, especially in the range of 65℃-75℃, the regeneration viscosity decreases significantly. 3D printing ink should have a higher regeneration viscosity to achieve rapid molding during the printing process.

[0072] Comparative Example 1

[0073] The ink formula in Example 1 was adjusted to 15 wt % corn starch, without adding methacrylated starch and high-amylose corn starch, and the other formulas remained the same as in Example 1 to obtain a starch-based 3D printing ink.

[0074] Due to the low amylose content and high amylopectin content of corn starch, the starch ink has high viscosity and loss modulus, low storage modulus, uneven extrusion process and poor formability, and the precision of the resulting printed product is significantly lower than that of the printed product obtained in Example 1.

[0075] Comparative Example 2

[0076] The corn starch in step (1) of Example 1 was adjusted to cassava starch, and the ratio of methacrylated starch (modified cassava starch), gelatinized high-amylose corn starch, and corn starch was 1:1:1. Other conditions were the same as in Example 1 to obtain a starch-based 3D printing ink.

[0077] Due to the low content of amylose in cassava starch, it is not easy to be modified with methacrylate. After gelatinization, cassava starch has high viscosity, poor mechanical strength, difficulty in printing and extrusion, and poor formability, making it unsuitable for the preparation of light-curing 3D printing ink.

[0078] Comparative Example 3

[0079] The amount of methacrylic anhydride added in Example 1 was adjusted to 0 wt %, and the mixing ratio of methacrylated starch, gelatinized high-amylose corn starch, and corn starch was 1:1:1. Other conditions remained the same as in Example 1 to obtain a starch-based 3D printing ink.

[0080] Since methacrylic anhydride is not added, starch-based ink does not have photosensitive properties, cannot undergo chemical cross-linking under ultraviolet light, has no change in storage modulus, and cannot produce a photocuring effect.

[0081] Comparative Example 4

[0082] The composite starch formula in Example 1 was adjusted by not adding high-amylose corn starch, and the ratio of methacrylated starch to corn starch was 1:1. Other conditions remained the same as in Example 1 to obtain a starch-based 3D printing ink.

[0083] Since the addition of high-amylose corn starch increases the amylose content in starch-based ink, without the addition of high-amylose corn starch, the amylose content of starch-based ink decreases, the storage modulus decreases, and the formability deteriorates.

[0084] Comparative Example 5

[0085] The ink formula in Example 1 was adjusted to 15 wt % high-amylose corn starch, without adding methacrylated starch and ordinary corn starch, and the other formulas remained the same as in Example 1 to obtain a starch-based 3D printing ink.

[0086] Because high-amylose corn starch has a high amylose content and a low amylopectin content, the high-amylose corn starch ink has a high storage modulus, a low loss modulus, and a low viscosity. During the extrusion process, the ink lines cannot stick together to form complete continuous lines, the printing accuracy deteriorates, and it is easy to clog the nozzle, making it difficult to extrude smoothly.

[0087] Comparative Example 6

[0088] The composite starch formula in Example 1 was adjusted, corn starch was not added in step (2), the mixing ratio of methacrylated starch and gelatinized high-amylose corn starch was 1:1, and the other formulas were consistent with Example 1 to obtain a starch-based 3D printing ink.

[0089] Since methacrylated starch cannot produce structural gelatinization, and high-amylose corn starch has a high amylose content and a low amylopectin content, the starch-based ink has a low viscosity and cannot form complete and continuous lines, resulting in poor printing accuracy.

[0090] Comparative Example 7

[0091] The composite starch formula in Example 1 was adjusted, and only methacrylated starch was added in step (2), without compounding high-amylose corn starch and ordinary corn starch. Other formulas were kept consistent with Example 1 to obtain a starch-based 3D printing ink.

[0092] Since methacrylated starch cannot spontaneously produce structural gelatinization and cannot spontaneously produce adhesiveness through retrogradation, starch-based ink has low viscosity and cannot form complete and continuous lines, resulting in poor printing accuracy. After irradiation with ultraviolet light, methacrylated starch undergoes chemical cross-linking and its formability is enhanced.

[0093] Test Case

[0094] Test the relevant performance of comparative examples 1-7

[0095] The center height of the printed product is an important indicator for evaluating formability. The smaller the difference between the center height and the set height, the less collapse and better formability. The extrusion line width is a key indicator for evaluating printing accuracy. The ink expands and widens after being squeezed out of the nozzle. The smaller the line width expansion, the better the printing accuracy. Set the printer nozzle diameter to 0.8mm and the center height of the printed product to 20mm.

[0096] Contact angle and surface energy are important indicators for evaluating the printing accuracy of gel materials. The contact angle is a function of adhesion and cohesion. Strong adhesion and weak cohesion result in a hydrophilic surface, and the contact angle corresponds to a small strain. Surface free energy is related to material adhesion; higher surface free energy and higher surface adhesion contribute to maintaining dimensional stability of the printed sample. Materials with a surface free energy range of 28 to 42 mN / m are suitable for printing.

[0097] Table 2 Related performance test results of comparative examples 1-5

[0098]

[0099] Methacrylated starch has the property of crosslinking and curing under ultraviolet light of a specific wavelength, but its ability to spontaneously gel in the unexcited state is weak and it is not easy to spontaneously form a gel. High-amylose corn starch (amylose content >70%) has a high storage modulus and low loss modulus after gelatinization due to its high amylose content and low amylopectin content, which manifests as low viscosity, high mechanical strength of the gel, and good formability, but it is prone to clogging the nozzle and cannot be continuously and smoothly extruded. Ordinary corn starch has a moderate ratio of amylose to amylopectin and can spontaneously form a gel after gelatinization. Low-concentration corn starch solutions have low viscosity and smooth extrusion, but poor formability. High-concentration corn starch solutions have good formability, but are difficult to extrude and easily clog the nozzle. To overcome the above shortcomings, the present invention compounded ordinary corn starch, methacrylated starch, and high-amylose corn starch to produce a starch-based 3D printing ink, fully utilizing the properties of each component and improving the ink's printability.

Claims

1. A method for preparing a starch-based 3D printing ink with high printability, characterized in that The following steps are involved: (1) Dissolve corn starch in dimethyl sulfoxide, heat to gelatinize, and add methacrylic anhydride and triethylamine; (2) precipitating the solution obtained in step (1) in anhydrous ethanol, then washing with deionized water, repeating the precipitation and washing three times, and then freeze-drying to obtain methacrylated starch; (3) gelatinizing high-amylose corn starch and ordinary starch, and uniformly mixing an aqueous solution containing 0.1-5.0 wt% of methacrylated starch, the gelatinized high-amylose corn starch, and the gelatinized ordinary starch in proportion to obtain a starch-based ink suitable for high-precision 3D printing; The corn starch in step (1) has a concentration of 5.0 wt% relative to the dimethyl sulfoxide solvent; the amount of methacrylic anhydride added is 5-10.0 wt% relative to the corn starch; and the heating gelatinization is performed at 95°C for 30-45 min; The ratio of the methacrylated starch, gelatinized high-amylose corn starch and gelatinized common starch in step (3) is 1: (1-5): (1-5); The gelatinization of high-amylose corn starch in step (3) is to gelatinize 1-5.0 wt% of high-amylose corn starch in water at 120°C for 20-30 min, and the gelatinization of ordinary starch is to gelatinize 5.0-10.0 wt% of ordinary starch in water at 95°C for 30-45 min, and the uniform mixing is to stir and mix at 95°C for 10 min.

2. The method according to claim 1, characterized in that The amount of anhydrous ethanol used in step (2) is 5 times that of the starch solution obtained in step (1).

3. The method according to claim 1, characterized in that The common starch described in step (3) includes one or more of tapioca starch, corn starch, rice starch, wheat starch, and potato starch.

4. A starch-based 3D ink prepared according to any one of claims 1 to 3.

5. A 3D printing method, characterized in that: The ink according to claim 4 is used for printing, the 3D printing temperature is 55-75°C, the printing speed is 1-10 mm / min, and the printed product is cured by irradiating it with an ultraviolet lamp during the printing process. The ultraviolet lamp has an irradiation wavelength of 365 nm and an irradiation time of 20 min.

6. A 3D printed product, characterized in that: The printing method according to claim 5 is adopted.

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