In-situ foaming material for 3D printing and preparation method thereof

Abstract

The invention belongs to the technical field of 3D printing, and relates to an in-situ foaming material for 3D printing and a preparation method thereof.The in-situ foaming material is prepared from an acrylate oligomer, an acrylate monomer and a photoinitiator, the acrylate oligomer is monofunctional polyurethane acrylate, and the photoinitiator is a photoinitiator. The acrylate monomer is a monofunctional acrylate monomer which does not contain reactive hydrogen; wherein one end of the monofunctional polyurethane acrylate is an acrylate group, the other end of the monofunctional polyurethane acrylate is an isocyanate group, and the isocyanate group is subjected to in-situ foaming under a hydrothermal condition. According to the in-situ foaming material, the density of the material is remarkably reduced, meanwhile, good mechanical performance and functionality are kept, and the production requirement for environment friendliness is met.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, relates to a foaming material, and particularly relates to an in-situ foaming material for 3D printing and a preparation method thereof. Background Art

[0002] 3D printing foaming materials are a new type of material that combines additive manufacturing (3D printing) technology and foaming technology, and have the characteristics of light weight, porous structure, high strength, and high elasticity. By introducing gas during or after the printing process, such materials form foam bodies with complex internal structures, thereby significantly reducing the material density while maintaining good mechanical properties and functionality.

[0003] Due to the characteristics of light weight and high strength of 3D printing foaming materials, they show broad application potential in multiple fields. For example, in the aerospace field, such materials can be used to manufacture lightweight structural components; in the automotive industry, they can be used to produce shock-absorbing components; in the sports equipment field, such as shoe manufacturing, they can achieve a lighter, shock-absorbing effect. In addition, foaming materials are also applied in fields such as building insulation, medical scaffolds, and biomedical engineering.

[0004] Currently, the foaming methods of 3D printing foaming materials mainly include physical foaming and chemical foaming. Among them, physical foaming usually uses supercritical CO2 as a foaming agent, encapsulates the gas in the material under high pressure, and then releases the gas under lower pressure to make the material expand to form a foam structure. However, common foaming agents have low solubility in some cases and are extremely likely to have an adverse impact on the environment; chemical foaming relies on the decomposition products of foaming agents to generate gas, but this method usually involves the use of toxic substances and does not meet the production requirements of green environmental protection.

[0005] In addition, although foaming materials have a low density, their mechanical strength and durability after foaming are usually lower than those of solid materials. Especially under high-temperature or high-load conditions, the materials are prone to deformation or failure.

[0006] Therefore, how to provide a 3D printing foaming material that can significantly reduce the material density while maintaining good mechanical properties and functionality and taking into account the production requirements of green environmental protection has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0007] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an in-situ foaming material for 3D printing and a preparation method thereof. The in-situ foaming material can significantly reduce the material density while maintaining good mechanical properties and functionality and taking into account the production requirements of green environmental protection.

[0008] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0009] In a first aspect, the present invention provides an in-situ foaming material for 3D printing. The raw materials for preparing the in-situ foaming material include acrylate oligomer, acrylate monomer, and photoinitiator. The acrylate oligomer is a monofunctional polyurethane acrylate, and the acrylate monomer is a monofunctional acrylate monomer without active hydrogen.

[0010] Wherein, one end of the monofunctional polyurethane acrylate is an acrylate group, and the other end is an isocyanate group, and the isocyanate group undergoes in-situ foaming under hydrothermal conditions.

[0011] The in-situ foaming material provided by the present invention uses a monofunctional polyurethane acrylate and a monofunctional acrylate monomer without active hydrogen as raw materials. After photocuring, this monofunctional material forms a chain structure, which is beneficial to foaming expansion, thereby avoiding the three-dimensional network structure formed by multifunctional materials after photocuring from hindering the full expansion of bubbles, and effectively improving the foaming performance of the material.

[0012] In addition, one end of the monofunctional polyurethane acrylate used in the present invention is an acrylate group responsible for photocuring and forming, and the other end is an isocyanate group responsible for in-situ foaming under hydrothermal conditions, thereby further crosslinking and curing, significantly enhancing the mechanical strength and durability of the foaming material. This in-situ foaming characteristic avoids the use of blowing agents and meets the requirements of green and environmental protection production.

[0013] Preferably, the structural formula of the monofunctional polyurethane acrylate is:

[0014] Structural formula A:

[0015] And / or;

[0016] Structural formula B:

[0017] Wherein, R1 represents H and / or CH3, R2 represents the remaining structure after removing the -NCO group from the isocyanate, and R3 represents the remaining structure after removing the terminal H atom from the polyol.

[0018] Preferably, the isocyanate includes isophorone diisocyanate and / or toluene diisocyanate.

[0019] Preferably, the monofunctional acrylate monomer without active hydrogen includes any one or a combination of at least two of trimethylolpropane methylal acrylate, acryloylmorpholine, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, lauric acid acrylate, lauric acid methacrylate, 3,3,5-trimethylcyclohexyl acrylate, tert-butylcyclohexyl acrylate, ethoxyethoxyethyl acrylate, isobornyl acrylate or isobornyl methacrylate.

[0020] Preferably, the photoinitiator includes any one or a combination of at least two of α-dialkoxy-acetophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl phenyl ketone or diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide, and is further preferably diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide.

[0021] Preferably, based on parts by weight, the raw materials for preparing the in-situ foaming material include: 30-80 parts of monofunctional polyurethane acrylate; 20-65 parts of monofunctional acrylate monomer without active hydrogen; 0.5-8 parts of photoinitiator.

[0022] Preferably, the source of water in the hydrothermal condition includes water vapor and / or crystal water.

[0023] Among them, the crystal water is derived from adding a compound containing crystal water to the raw materials for preparation.

[0024] In a second aspect, the present invention provides a method for preparing an in-situ foaming material for 3D printing as described in the first aspect, and the preparation method includes the following steps:

[0025] (1) Prepare monofunctional polyurethane acrylate by an addition reaction;

[0026] (2) Mix monofunctional polyurethane acrylate, monofunctional acrylate monomer without active hydrogen and a photoinitiator for 3D printing, and obtain a solid material after photocuring;

[0027] (3) Subject the solid material to in-situ foaming under hydrothermal conditions to obtain an in-situ foaming material.

[0028] Preferably, when the monofunctional polyurethane acrylate is of structural formula A, the method of the addition reaction in step (1) is:

[0029] Mix 2-hydroxyethyl acrylate and bifunctional isocyanate in a molar ratio of 1:(1-1.05), and react at 40-60 °C for 4-6 h to obtain monofunctional polyurethane acrylate.

[0030] Alternatively, hydroxyethyl methacrylate and bifunctional isocyanate are mixed in a molar ratio of 1:(1 - 1.05) and reacted at 40 - 60 °C for 4 - 6 h to obtain monofunctional polyurethane acrylate.

[0031] Preferably, when the monofunctional polyurethane acrylate is of structural formula B, the addition reaction method in step (1) is as follows:

[0032] Bifunctional polyol and bifunctional isocyanate are mixed in a molar ratio of 1:(2 - 2.05) and reacted at 50 - 70 °C for 2 - 4 h. Then, the temperature is lowered to 40 - 60 °C, and hydroxyethyl acrylate or hydroxyethyl methacrylate is added and the reaction continues at 40 - 60 °C for 4 - 6 h to obtain monofunctional polyurethane acrylate.

[0033] Among them, the addition amount of the hydroxyethyl acrylate or hydroxyethyl methacrylate is 0.95 - 1 times the molar amount of the bifunctional polyol.

[0034] Preferably, the photocuring in step (2) uses ultraviolet light, and the energy density of the ultraviolet light is 10 - 200 mW / cm 2 .

[0035] Preferably, the photocuring time in step (2) is 5 - 60 min.

[0036] Preferably, the temperature of the hydrothermal condition in step (3) is 100 - 180 °C.

[0037] Preferably, the in-situ foaming time in step (3) is 30 - 60 min.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] (1) The in-situ foaming material provided by the present invention uses monofunctional polyurethane acrylate and monofunctional acrylate monomer without active hydrogen as raw materials. After photocuring, this monofunctional material forms a chain structure, which is beneficial to foaming and expansion, thus avoiding the three-dimensional network structure formed by the multifunctional material after photocuring from hindering the full expansion of bubbles, and effectively improving the foaming performance of the material.

[0040] (2) One end of the monofunctional polyurethane acrylate adopted by the present invention is an acrylate group, which is responsible for photocuring and forming, and the other end is an isocyanate group, which is responsible for in-situ foaming under hydrothermal conditions, thereby further crosslinking and curing, significantly enhancing the mechanical strength and durability of the foaming material. This in-situ foaming characteristic avoids the use of blowing agents, meeting the production requirements of green environmental protection. Description of the Drawings

[0041] Figure 11H NMR spectrum of the monofunctional polyurethane acrylate (structural formula A) provided in Example 1;

[0042] Figure 2 Photograph of the solid material provided in Example 1;

[0043] Figure 3 Photograph of the in-situ foamed material provided in Example 1. Detailed implementation manners

[0044] The technical solution of the present invention will be further described below through specific implementation manners. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0045] An in-situ foamed material for 3D printing is provided in an embodiment of the present invention. The raw materials for preparing the in-situ foamed material include an acrylate oligomer, an acrylate monomer, and a photoinitiator. The acrylate oligomer is a monofunctional polyurethane acrylate, and the acrylate monomer is a monofunctional acrylate monomer without active hydrogen.

[0046] Wherein, one end of the monofunctional polyurethane acrylate is an acrylate group, and the other end is an isocyanate group, and the isocyanate group undergoes in-situ foaming under hydrothermal conditions.

[0047] The in-situ foamed material provided by the present invention uses a monofunctional polyurethane acrylate and a monofunctional acrylate monomer without active hydrogen as raw materials. After photocuring, this monofunctional material forms a chain structure, which is beneficial to foaming and expansion, thereby avoiding the three-dimensional network structure formed by the multifunctional material after photocuring from hindering the full expansion of bubbles and effectively improving the foaming performance of the material.

[0048] In addition, one end of the monofunctional polyurethane acrylate used in the present invention is an acrylate group, which is responsible for photocuring and forming, and the other end is an isocyanate group, which is responsible for in-situ foaming under hydrothermal conditions and further crosslinking and curing, significantly enhancing the mechanical strength and durability of the foamed material. This in-situ foaming characteristic avoids the use of blowing agents and meets the requirements of green and environmental protection production.

[0049] In some embodiments, the structural formula of the monofunctional polyurethane acrylate is:

[0050] Structural formula A:

[0051] And / or;

[0052] Structural formula B:

[0053] Among them, R1 represents H and / or CH3, R2 represents the remaining structure after removing the -NCO group from the isocyanate, and R3 represents the remaining structure after removing the terminal H atom from the polyol.

[0054] Specifically, R2 represents the remaining structure after removing the -NCO group from the isocyanate, which can be, for example, isophorone, hexamethylene, dicyclohexylmethane, toluene, diphenylmethane, etc. The isocyanate is further preferably isophorone diisocyanate and / or toluene diisocyanate; R3 represents the remaining structure after removing the terminal H atom from the polyol. The polyol can be polypropylene glycol, polytetrahydrofuran ether glycol, poly-1,3-propanediol, polycaprolactone polyol, polycarbonate polyol, polyethylene adipate polyol, or polybutylene adipate polyol, etc.

[0055] As can be seen from the above structural formula, structural formula A is relatively simple, while structural formula B contains polyol, making its molecular structure more complex, thus forming a longer polymer chain and having more branched-chain structures. On the one hand, due to its simple structure, structural formula A is easier to control during the synthesis process, and the isocyanate content it contains is high, resulting in a high final foaming ratio and mechanical strength; on the other hand, due to its complex structure, structural formula B has a longer molecular chain and more branched chains, which helps to improve the toughness and durability of the material, and the complex structure also brings better chemical stability and thermal stability.

[0056] It can be seen that through the synergistic combination between structural formula A and structural formula B, the present invention well balances the comprehensive performance and cost control of the obtained foamed material.

[0057] In some embodiments, the monofunctional acrylate monomer without active hydrogen includes any one or a combination of at least two of trimethylolpropane formal acrylate, acryloylmorpholine, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, lauric acid acrylate, lauric acid methacrylate, 3,3,5-trimethylcyclohexyl acrylate, tert-butylcyclohexyl acrylate, ethoxyethoxyethyl acrylate, isobornyl acrylate, or isobornyl methacrylate.

[0058] The present invention strictly defines the specific types of the monofunctional acrylate monomer. Because during the photocuring process, each monomer molecule contains only one group that can participate in the reaction, the conversion rate is relatively high, which means that during the 3D printing process, more monomer molecules can participate in the photocuring reaction, thereby forming a stable polymer network and ultimately improving the curing efficiency of the material and the performance of the obtained product.

[0059] In addition, since the crosslinking density formed by the monofunctional acrylate monomer during the photocuring process is relatively low, its volume shrinkage rate is also relatively low, which helps to reduce the stress and deformation caused by volume change during the photocuring process, and ensures the dimensional accuracy and structural stability of the 3D printed parts.

[0060] Furthermore, the monofunctional acrylate monomer usually has a low viscosity, which is beneficial to improving the fluidity and coatability of the material during the 3D printing process, making the printing process smoother, fully filling the gaps between the printing layers, and improving the surface quality of the printed parts and the uniformity of the internal structure.

[0061] In some embodiments, the photoinitiator includes any one or a combination of at least two of α-dialkoxy-acetophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl phenyl ketone or diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide. Typical but non-limiting combinations include the combination of α-dialkoxy-acetophenone and 2-hydroxy-2-methyl-1-phenylpropanone, the combination of 2-hydroxy-2-methyl-1-phenylpropanone and 1-hydroxycyclohexyl phenyl ketone, or the combination of 1-hydroxycyclohexyl phenyl ketone and diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide. Further preferably, it is diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide.

[0062] In some embodiments, by weight, the raw materials for preparing the in-situ foaming material include: 30-80 parts of monofunctional polyurethane acrylate, such as 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts, 65 parts, 70 parts, 75 parts or 80 parts; 20-65 parts of monofunctional acrylate monomer without active hydrogen, such as 20 parts, 25 parts, 30 parts, 35 parts, 40 parts, 45 parts, 50 parts, 55 parts, 60 parts or 65 parts; 0.5-8 parts of photoinitiator, such as 0.5 parts, 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts or 8 parts, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0063] In some embodiments, the source of water in the hydrothermal conditions includes water vapor and / or crystal water.

[0064] Among them, the crystal water is derived from adding a compound containing crystal water to the raw materials for preparation, such as calcium sulfate dihydrate, potassium alum (commonly known as alum) or zinc sulfate heptahydrate, etc.

[0065] In the present invention, the compound containing crystal water removes crystal water in a high-temperature environment, and the obtained water undergoes in-situ foaming with the isocyanate group.

[0066] An embodiment of the present invention provides a method for preparing an in-situ foaming material for 3D printing according to any one of the above embodiments. The preparation method includes the following steps:

[0067] (1) Prepare monofunctional polyurethane acrylate by an addition reaction;

[0068] (2) Mix monofunctional polyurethane acrylate, monofunctional acrylate monomer without active hydrogen, and a photoinitiator for 3D printing, and obtain a solid material after photocuring;

[0069] (3) Subject the solid material to in-situ foaming under hydrothermal conditions to obtain an in-situ foaming material.

[0070] In some embodiments, the raw materials for the addition reaction in step (1) are hydroxyethyl acrylate and isocyanate, or hydroxyethyl acrylate, isocyanate, and polyol.

[0071] As mentioned above, the structural formula of the monofunctional polyurethane acrylate is divided into two types. When it is structural formula A, hydroxyethyl acrylate and isocyanate are used as the raw materials for the addition reaction. The specific reaction formula is:

[0072]

[0073] In the above case, the method for the addition reaction in step (1) is:

[0074] Mix hydroxyethyl acrylate and bifunctional isocyanate in a molar ratio of 1:(1 - 1.05), and react at 40 - 60 °C for 4 - 6 h to obtain monofunctional polyurethane acrylate.

[0075] Alternatively, mix hydroxyethyl methacrylate and bifunctional isocyanate in a molar ratio of 1:(1 - 1.05), and react at 40 - 60 °C for 4 - 6 h to obtain monofunctional polyurethane acrylate.

[0076] In some embodiments, the above molar ratio can be 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04, or 1:1.05, but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0077] When it is structural formula B, hydroxyethyl acrylate, isocyanate, and polyol are used as the raw materials for the addition reaction. The specific reaction formula is:

[0078]

[0079] In the above case, the method for the addition reaction in step (1) is:

[0080] Mix a difunctional polyol and a difunctional isocyanate in a molar ratio of 1:(2 - 2.05), react at 50 - 70 °C for 2 - 4 h, then cool down to 40 - 60 °C, add hydroxyethyl acrylate or hydroxyethyl methacrylate and continue to react at 40 - 60 °C for 4 - 6 h to obtain a monofunctional polyurethane acrylate.

[0081] In some embodiments, the above molar ratio can be 1:2, 1:2.01, 1:2.02, 1:2.03, 1:2.04 or 1:2.05, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0082] In some embodiments, the addition amount of the hydroxyethyl acrylate or hydroxyethyl methacrylate is 0.95 - 1 times the molar amount of the difunctional polyol. For example, it can be 0.95 times, 0.96 times, 0.97 times, 0.98 times, 0.99 times or 1 time, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0083] In some embodiments, the photocuring in step (2) uses ultraviolet light, and the energy density of the ultraviolet light is 10 - 200 mW / cm 2 , for example, it can be 10 mW / cm 2 , 20 mW / cm 2 , 40 mW / cm 2 , 60 mW / cm 2 , 80 mW / cm 2 , 100 mW / cm 2 , 120 mW / cm 2 , 140 mW / cm 2 , 160 mW / cm 2 , 180 mW / cm 2 or 200 mW / cm 2 , but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0084] In some embodiments, the photocuring time in step (2) is 5 - 60 min. For example, it can be 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, but is not limited to the listed values, and other unlisted values within this range are equally applicable.

[0085] Specifically, during the photocuring process, the reaction formula between the various materials is as follows:

[0086]

[0087] Or;

[0088]

[0089] Or;

[0090]

[0091] In some embodiments, the temperature of the hydrothermal conditions in step (3) is 100 - 180 °C, for example, it can be 100 °C, 110 °C, 120 °C, 130 °C, 140 °C, 150 °C, 160 °C, 170 °C or 180 °C, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0092] In some embodiments, the time for in-situ foaming in step (3) is 30 - 60 min, for example, it can be 30 min, 35 min, 40 min, 45 min, 50 min, 55 min or 60 min, but not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0093] Specifically, during the in-situ foaming process, the reaction of the solid material is as follows:

[0094]

[0095] Or;

[0096]

[0097] Or;

[0098]

[0099] The numerical ranges described in the present invention include not only the above-listed point values, but also any point values between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, the present invention does not exhaustively list the specific point values included in the described ranges.

[0100] Example 1

[0101] This example provides an in-situ foaming material for 3D printing and its preparation method. The preparation method includes the following steps:

[0102] (1) Prepare monofunctional polyurethane acrylate by an addition reaction, specifically:

[0103] (1.1) Add 1.02 mol of isophorone diisocyanate to a three-necked flask, heat it to 40 °C, and then slowly add 1 mol of hydroxyethyl acrylate dropwise while controlling the reaction temperature not to exceed 50 °C. After the addition of hydroxyethyl acrylate is complete, continue the reaction at 50 °C for 5 h to obtain a monofunctional polyurethane acrylate with the structural formula A and a content of more than 95 wt% (the HNMR spectrum is shown in Figure 1 ), and the relevant chemical formula is as follows:

[0104]

[0105] (1.2) Add 1 mol of polycaprolactone (molecular weight 1000) and 2.02 mol of isophorone diisocyanate to a three-necked flask, continue the reaction at 60 °C for 3 h, then cool it to 50 °C, and slowly add 0.98 mol of hydroxyethyl acrylate dropwise while controlling the reaction temperature not to exceed 50 °C. After the addition of hydroxyethyl acrylate is complete, continue the reaction at 50 °C for 5 h to obtain a monofunctional polyurethane acrylate with the structural formula B and a content of more than 95 wt%, and the relevant chemical formula is as follows:

[0106]

[0107]

[0108] In the above formula, R1 specifically refers to H, R2 specifically refers to isophorone, and R3 specifically refers to polycaprolactone.

[0109] (2) Mix the monofunctional polyurethane acrylates obtained in step (1) (30 parts of structural formula A and 30 parts of structural formula B), a monofunctional acrylate monomer without active hydrogen (36 parts of isobornyl acrylate), and a photoinitiator (4 parts of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide) for 3D printing (printer model: TAPS200). After taking out the model, wash it, and cure it with ultraviolet light with an energy density of 100 mW / cm 2 for 30 min to obtain a solid material (see Figure 2 ).

[0110] During the photocuring process, the reaction formula between the various materials is as follows:

[0111]

[0112] (3) Subject the solid material obtained in step (2) to in-situ foaming under hydrothermal conditions of 150 °C water vapor for 45 min, and then cool it to obtain an in-situ foamed material (see Figure 3 ).

[0113] During the in-situ foaming process, the reaction formula of the solid material is as follows:

[0114]

[0115] Example 2

[0116] This example provides an in-situ foaming material for 3D printing and a preparation method thereof. The preparation method includes the following steps:

[0117] (1) Prepare monofunctional polyurethane acrylate by an addition reaction, specifically:

[0118] Add 1.02 mol of toluene diisocyanate to a three-necked flask, heat to 40 °C, and then slowly dropwise add 1 mol of hydroxyethyl acrylate while controlling the reaction temperature not to exceed 50 °C. After the addition of hydroxyethyl acrylate is complete, continue the reaction at 50 °C for 5 h to obtain monofunctional polyurethane acrylate with the structural formula A and a content of more than 95 wt%. The relevant chemical formula is as follows:

[0119]

[0120] In the above formula, R1 specifically refers to H, and R2 specifically refers to toluene.

[0121] (2) Mix the monofunctional polyurethane acrylate obtained in step (1) (60 parts of structural formula A), monofunctional acrylate monomer without active hydrogen (36 parts of trimethylolpropane formal acrylate), and photoinitiator (4 parts of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide) for 3D printing (printer model: TAPS200). After taking out the model, wash it, and carry out photocuring for 45 min with ultraviolet light having an energy density of 100 mW / cm 2 to obtain a solid material.

[0122] During the photocuring process, the reaction formula between the various materials is as follows:

[0123]

[0124] (3) Subject the solid material obtained in step (2) to in-situ foaming under hydrothermal conditions of 150 °C steam for 60 min, and cool to obtain the in-situ foaming material.

[0125] During the in-situ foaming process, the reaction formula of the solid material is as follows:

[0126]

[0127] The morphologies of the solid material and the in-situ foaming material obtained in this example are similar to those in Example 1, so they will not be elaborated here.

[0128] Example 3

[0129] This example provides an in-situ foaming material for 3D printing and a preparation method thereof. The preparation method includes the following steps:

[0130] (1) Prepare monofunctional polyurethane acrylate by addition reaction, specifically as follows:

[0131] Add 1 mol of polypropylene glycol (molecular weight 2000) and 2.02 mol of isophorone diisocyanate to a three-necked flask, and react continuously at 60 °C for 3 h. Then cool down to 50 °C and slowly add dropwise 0.98 mol of hydroxyethyl acrylate, controlling the reaction temperature not to exceed 50 °C. After the addition of hydroxyethyl acrylate is completed, react continuously at 50 °C for 5 h to obtain monofunctional polyurethane acrylate with the structural formula B and a content of more than 95 wt%. The relevant chemical formula is as follows:

[0132]

[0133] In the above formula, R1 specifically refers to H, R2 specifically refers to isophorone, and R3 specifically refers to the remaining structure after removing the terminal H atom of polypropylene glycol.

[0134] (2) Mix the monofunctional polyurethane acrylate obtained in step (1) (60 parts of structural formula B), monofunctional acrylate monomer without active hydrogen (36 parts of isobornyl acrylate), and photoinitiator (4 parts of diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide) for 3D printing (printer model is TAPS200). After taking out the model, wash it, and carry out photocuring for 30 min with ultraviolet light having an energy density of 100 mW / cm 2 to obtain a solid material.

[0135] During the photocuring process, the reaction formula between the various materials is as follows:

[0136]

[0137] (3) Carry out in-situ foaming of the solid material obtained in step (2) under hydrothermal conditions of 100 °C steam for 30 min, and cool to obtain an in-situ foamed material.

[0138] During the in-situ foaming process, the reaction formula of the solid material is as follows:

[0139]

[0140] The morphologies of the solid material and the in-situ foamed material obtained in this example are similar to those in Example 1, so they will not be elaborated here.

[0141] Example 4

[0142] This embodiment provides an in-situ foaming material for 3D printing and its preparation method. Except that the hydrothermal conditions in step (3) are changed to: in step (2), 20 parts of calcium sulfate dihydrate are additionally mixed, and in step (3), instead of introducing water vapor, direct heating is carried out for in-situ foaming, the remaining steps and conditions are the same as those in Example 1, so they will not be elaborated here.

[0143] Example 5

[0144] This embodiment provides an in-situ foaming material for 3D printing and its preparation method. Except that the monofunctional acrylate monomer without active hydrogen described in step (2) is changed to tert-butylcyclohexyl acrylate in equal weight parts, the remaining steps and conditions are the same as those in Example 1, so they will not be elaborated here.

[0145] Example 6

[0146] This embodiment provides an in-situ foaming material for 3D printing and its preparation method. Except that the photoinitiator described in step (2) is changed to 1-hydroxycyclohexyl phenyl ketone in equal weight parts, the remaining steps and conditions are the same as those in Example 1, so they will not be elaborated here.

[0147] Comparative Example 1

[0148] This comparative example provides a foaming material for 3D printing and its preparation method. The preparation method includes the following steps:

[0149] (1) Mix 60 parts of polyurethane acrylate oligomer (brand CN996), 36 parts of isobornyl acrylate, 4 parts of diphenyl-(2,4,6-trimethylbenzoyl) phosphine oxide, and 8 parts of azodicarbonamide for 3D printing (printer model TAPS200). After taking out the model, wash it, and carry out photocuring for 30 min with ultraviolet light having an energy density of 100 mW / cm 2 to obtain a solid material.

[0150] (2) Foam the solid material obtained in step (1) under heating conditions of 180 °C for 45 min, and cool to obtain a foaming material.

[0151] Comparative Example 2

[0152] This comparative example provides a foaming material for 3D printing and its preparation method. Except that the monofunctional acrylate monomer without active hydrogen described in step (2) is replaced with a difunctional acrylate monomer (ethoxylated bisphenol A dimethacrylate) in equal weight parts, the remaining steps and conditions are the same as those in Example 1, so they will not be elaborated here.

[0153] Comparative Example 3

[0154] This comparative example provides a foaming material for 3D printing and its preparation method. Except that the monofunctional acrylate monomer without active hydrogen described in step (2) is replaced with an equal weight part of trifunctional acrylate monomer (ethoxylated trimethylolpropane triacrylate), the remaining steps and conditions are the same as those in Example 1, so they will not be elaborated here.

[0155] Performance Test

[0156] (1) Apparent density: Refer to the test method provided in "GB / T 6343 - 2009";

[0157] (2) Tensile strength: Refer to the test method provided in "GB / T 6344 - 2008";

[0158] (3) Rebound performance: Refer to the test method provided in "GB / T 6670 - 2008".

[0159] According to the above test methods, the solid materials and foaming materials obtained from Examples 1 - 6 and Comparative Examples 1 - 3 were tested respectively, and the relevant test results are shown in Table 1 below.

[0160] Table 1

[0161]

[0162] It can be seen that the in-situ foaming material provided by the present invention uses monofunctional polyurethane acrylate and monofunctional acrylate monomer without active hydrogen as raw materials. After photocuring, this monofunctional material forms a chain structure, which is beneficial to foaming and expansion, thus avoiding the three-dimensional network structure formed by multifunctional materials after photocuring from hindering the full expansion of bubbles, and effectively improving the foaming performance of the material.

[0163] In addition, one end of the monofunctional polyurethane acrylate used in the present invention is an acrylate group, which is responsible for photocuring and forming, and the other end is an isocyanate group, which is responsible for in-situ foaming under hydrothermal conditions, thereby further crosslinking and curing, significantly enhancing the mechanical strength and durability of the foaming material. This in-situ foaming characteristic avoids the use of blowing agents and meets the requirements of green and environmental protection production.

[0164] The above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and public scope of the present invention.

Claims

1. An in-situ foaming material for 3D printing, wherein the raw materials for preparing the in-situ foaming material include acrylate oligomer, acrylate monomer and photoinitiator, and are characterized in that, The acrylate oligomer is a monofunctional polyurethane acrylate, and the acrylate monomer is a monofunctional acrylate monomer without active hydrogen; Among them, one end of the monofunctional polyurethane acrylate is an acrylate group, and the other end is an isocyanate group, and the isocyanate group undergoes in-situ foaming under hydrothermal conditions.

2. The in-situ foaming material for 3D printing according to claim 1, characterized in that, The structural formula of the monofunctional polyurethane acrylate is: Structural formula A: and / or; Structural formula B: Among them, R1 represents H and / or CH3, R2 represents the remaining structure after removing the -NCO group from the isocyanate, and R3 represents the remaining structure after removing the terminal H atom from the polyol; Preferably, the isocyanate includes isophorone diisocyanate and / or toluene diisocyanate.

3. The in-situ foaming material for 3D printing according to claim 1 or 2, characterized in that The monofunctional acrylate monomer without active hydrogen includes any one or a combination of at least two of trimethylolpropane formal acrylate, acryloylmorpholine, tetrahydrofurfuryl acrylate, tetrahydrofurfuryl methacrylate, lauric acid acrylate, lauric acid methacrylate, 3,3,5-trimethylcyclohexyl acrylate, tert-butylcyclohexyl acrylate, ethoxyethoxyethyl acrylate, isobornyl acrylate or isobornyl methacrylate.

4. The in-situ foaming material for 3D printing according to claim 1, wherein The photoinitiator includes any one or a combination of at least two of α-dialkoxy-acetophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-hydroxycyclohexyl phenyl ketone or diphenyl-(2,4,6-trimethylbenzoyl)phosphine oxide.

5. The in-situ foaming material for 3D printing according to claim 1, characterized in that, By weight, the raw materials for preparing the in-situ foaming material include: 30-80 parts of monofunctional polyurethane acrylate; 20-65 parts of monofunctional acrylate monomer without active hydrogen; 0.5-8 parts of photoinitiator.

6. The in-situ foaming material for 3D printing according to claim 1, wherein, The source of water in the hydrothermal conditions includes water vapor and / or crystal water; Among them, the crystal water is derived from adding a compound containing crystal water to the raw materials for preparation.

7. A method for preparing an in-situ foaming material for 3D printing according to any one of claims 1-6, characterized in that, The preparation method includes the following steps: (1) Prepare monofunctional polyurethane acrylate by an addition reaction; (2) Mix the monofunctional polyurethane acrylate, the monofunctional acrylate monomer without active hydrogen and the photoinitiator for 3D printing, and obtain a solid material after photocuring; (3) Subject the solid material to in-situ foaming under hydrothermal conditions to obtain an in-situ foaming material.

8. The preparation method of the in-situ foaming material for 3D printing according to claim 7, characterized in that, When the monofunctional polyurethane acrylate is of structural formula A, the method of the addition reaction in step (1) is: Mix 2-hydroxyethyl acrylate and bifunctional isocyanate in a molar ratio of 1:(1-1.05), and react at 40-60 °C for 4-6 h to obtain monofunctional polyurethane acrylate; Or, mix 2-hydroxyethyl methacrylate and bifunctional isocyanate in a molar ratio of 1:(1-1.05), and react at 40-60 °C for 4-6 h to obtain monofunctional polyurethane acrylate.

9. According to the preparation method of the in-situ foaming material for 3D printing according to claim 7, when the monofunctional polyurethane acrylate is of structural formula B, the method of the addition reaction in step (1) is: Mix a difunctional polyol and a difunctional isocyanate in a molar ratio of 1:(2 - 2.05), react at 50 - 70 °C for 2 - 4 h, then cool down to 40 - 60 °C, add hydroxyethyl acrylate or hydroxyethyl methacrylate and continue to react at 40 - 60 °C for 4 - 6 h to obtain a monofunctional polyurethane acrylate; Among them, The addition amount of the hydroxyethyl acrylate or hydroxyethyl methacrylate is 0.95 - 1 times the molar amount of the difunctional polyol.

10. The method for preparing an in-situ foaming material for 3D printing according to claim 8 or 9, characterized in that, The photocuring in step (2) uses ultraviolet light, and the energy density of the ultraviolet light is 10-200 mW / cm 2 ; And / or, the photocuring time in step (2) is 5 - 60 min; And / or, the temperature of the hydrothermal condition in step (3) is 100 - 180 °C; And / or, the in-situ foaming time in step (3) is 30 - 60 min.

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