Silicone rubber foam material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of silicone rubber foam materials and 3D printing, and particularly relates to a silicone rubber foam material and a preparation method and application thereof. The silicon rubber foam material is prepared by virtue of a photocuring form and a chemical foaming method, and controllable foaming in the photocuring process is realized by ingeniously controlling the content and the use amount of reactive functional groups such as sulfydryl, vinyl, silicon hydrogen and hydroxyl; through the control, the preparation time of the silicone rubber foam material can be greatly shortened, the pore diameter can be controlled and adjusted, the prepared silicone rubber foam material has small and dense pores, and compared with an existing physical foaming method, the preparation method has the advantages of being simple and rapid in preparation process. The 3D technology is further expanded on the basis of photocuring, the processing means of the silicone rubber foam are enriched, customized customization and macroconfiguration design can be achieved, and the application field of the silicone rubber foam is further expanded.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicone rubber foam material and 3D printing thereof, and more specifically, relates to a silicone rubber foam material and a preparation method and application thereof. Background Art

[0002] Silicone rubber foam material is a porous polymer elastic material prepared by foaming silicone rubber. It has high thermal stability, good insulation, heat insulation and moisture resistance as well as excellent seismic performance. It is an ideal lightweight packaging material and can be used for various electronic components, instruments, meters, aircraft instrument wheels, filling materials for thermal insulation interlayers, floating materials in salt spray atmospheres, sealing materials, and filling, repair and lining materials for orthopedic surgery.

[0003] There are two types of foaming technologies for silicone rubber foam: dissolution pore formation and gas foaming. Dissolution pore formation technology is to mix water-soluble inorganic salts into silicone rubber compound, heat and vulcanize, and then dissolve the inorganic salts through a water washing process to obtain a through-hole silicone rubber foam material. The advantage of this technology is that the pore size, density and other parameters of silicone rubber foam materials can be controlled by controlling the type and amount of water-soluble inorganic salts. The disadvantage is that the water washing process produces a large amount of wastewater, which is seriously polluted, and it is impossible to prepare a closed-cell foam material. Gas foaming technology can be divided into physical foaming and chemical foaming. Physical foaming is achieved by the expansion of inert gas, the vaporization of low-boiling liquid or the filling and dissolution of particles. Chemical foaming is to blend a polymer with a chemical foaming agent or to produce gas through a reaction between two chemical groups. Among them, chemical foaming agents are most used in industries such as extrusion foaming processes because their use only requires a small modification of existing equipment. Compared with the use of chemical foaming agents, although physical foaming can induce a more uniform foam structure, its equipment requirements are high and the preparation process is cumbersome. Compared with physical foaming, chemical foaming has the advantages of simple process and high efficiency, but the process of chemical foaming is difficult to control. For example, Chinese patent application CN114752219A discloses a room temperature foaming silicone rubber foam material, which belongs to a heat curing foaming silicone rubber material. The foaming and curing processes in the preparation process are carried out in steps, and the curing process is achieved by adding hydrogen-containing silicone oil in the second step, which leads to a larger pore size of the obtained material (the appearance of the foam is taken by a camera, and obvious pores can be observed. If the pore size is less than 100μm, it is difficult to observe with the naked eye), and the foaming molding time is relatively long (1 to 10h).

[0004] Therefore, there is an urgent need to develop a silicone rubber foam material with uniform pores, a large number of pores and a short foaming molding time. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the defects and shortcomings of the silicone rubber foams prepared by the existing chemical foaming method, that is, most of the silicone rubber foams are macroporous silicone rubber foams with pore diameters greater than 100 μm, and the foaming rate of the chemical foaming is difficult to control, and it is impossible to obtain silicone rubber foam materials with uniform pores, a large number of pores, and a small pore diameter (less than 100 μm), and to provide a silicone rubber foam material with uniform pores, a large number of pores, and a short foaming molding time.

[0006] Another object of the present invention is to provide a method for preparing the silicone rubber foam material.

[0007] Another object of the present invention is to provide application of the silicone rubber foam material.

[0008] The above-mentioned purpose of the present invention is achieved through the following technical solutions:

[0009] The present invention protects a silicone rubber foam material, which comprises the following components by total mass percentage:

[0010] 40% to 50% pendant mercapto silicone oil;

[0011] 45% to 55% vinyl-terminated hydrogenated silicone oil;

[0012] 1% to 5% hydroxyl compounds;

[0013] 1% to 2% photoinitiator;

[0014] 0.5% to 2% platinum catalyst;

[0015] Wherein, the mercapto content of the pendant mercapto silicone oil is 0.5 to 2 mmol / g;

[0016] The vinyl content of the vinyl-terminated hydrogen-containing silicone oil is 0.3-0.8 mmol / g, and the hydrogen content is 8-11 mmol / g;

[0017] The hydroxyl-containing compound is one or more of an alcohol compound and a hydroxyl silicone oil;

[0018] The hydroxyl content of the hydroxy silicone oil is 0.6 to 1 mmol / g;

[0019] The alcohol compound is an alcohol compound with a boiling point greater than 90°C.

[0020] Aiming at the technical problem that most of the silicone rubber foams prepared by the existing chemical foaming method are macroporous silicone rubber foams with pore diameters greater than 100 μm, and the foaming rate of chemical foaming is difficult to control. The present invention controls the content and dosage of reactive functional groups (thiol, vinyl, silicon hydrogen and hydroxyl), which is different from the traditional platinum-catalyzed silicon hydrogen bond and carbon-carbon double bond silicon hydrogen addition curing, and uses the rapid curing of the mercapto-ene click reaction to limit the platinum-catalyzed silicon hydrogen bond and alcohol condensation dehydrogenation foaming, thereby limiting the aggregation and expansion of the pores, and obtaining a silicone rubber material with uniform pores, a large number of pores and a small pore diameter (less than 100 μm).

[0021] Furthermore, the side mercapto silicone oil is a polysiloxane containing a mercapto group on the side chain, and the terminal mercapto silicone oil is a polysiloxane containing a mercapto group on the main chain. If the terminal mercapto silicone oil is used, it is difficult to cure with the terminal vinyl hydrogen silicone oil to form a cross-linked network; for the content of mercapto in the mercapto silicone oil, too little will make it difficult to cure and form the bubbles, and too much will cause the curing rate to be inconsistent with the foaming rate, making it difficult to form small and dense bubbles.

[0022] Furthermore, the structural formula of the pendant mercapto silicone oil is:

[0023]

[0024] In the formula, m is selected from any integer in the range of 1 to 400, and n is selected from any integer in the range of 1 to 80.

[0025] Furthermore, the pendant mercapto silicone oil can be purchased from the market or prepared at home.

[0026] Further, as an optional method, the preparation method of the pendant mercapto silicone oil comprises the following steps:

[0027] Mix hexamethyldisiloxane, thiopropylmethyldimethoxysilane, organosilicon intermediate, acid catalyst and water, react fully at 60-90°C, and purify to obtain pendant mercapto silicone oil. The specific reaction equation is as follows:

[0028]

[0029] Furthermore, the organosilicon intermediate includes linear siloxane and cyclic siloxane.

[0030] Furthermore, the linear siloxane includes one or more of dimethyldimethoxysilane, methylphenyldimethoxysilane, diphenyldimethoxysilane, and aminopropyltrimethylsilane.

[0031] Furthermore, the cyclic siloxane includes one or more of octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trifluoropropylmethylcyclotrisiloxane, and tetramethyltetraphenylcyclotetrasiloxane.

[0032] Preferably, the organosilicon intermediate is octamethylcyclotetrasiloxane.

[0033] Furthermore, the acidic catalyst includes one or more of trifluoromethanesulfonic acid, hydrochloric acid, sulfuric acid, and cation exchange resin.

[0034] Furthermore, the cation exchange resin is a polymer compound containing a large number of strong acidic groups, such as sulfonic acid groups (-SO3H), etc. These groups can dissociate into hydrogen ions (H + ), thus showing strong acidity. Cation exchange resins play a catalytic role by donating protons or accepting electron pairs through their acidic groups.

[0035] Furthermore, the added amount of the acidic catalyst is 0.5% to 2% of the total weight of hexamethyldisiloxane, thiopropylmethyldimethoxysilane and the organosilicon intermediate.

[0036] Furthermore, the molar ratio of the hexamethyldisiloxane, thiopropylmethyldimethoxysilane and the organosilicon intermediate is 1:(10-50):(40-100).

[0037] Furthermore, the hexamethyldisiloxane is used as a capping agent, and the molar ratio of addition will affect the molecular weight of the polymer; the thiopropylmethyldimethoxysilane is used for grafting pendant mercapto groups, and the molar ratio of addition will affect the mercapto content of the pendant mercapto polysiloxane.

[0038] Furthermore, the molar ratio of the thiopropylmethyldimethoxysilane to water is 1:(0.5-1.5).

[0039] Furthermore, when the molar ratio of water to thiopropylmethyldimethoxysilane is small, the degree of hydrolysis of the organosilicon intermediate is insufficient, resulting in a low yield of pendant mercaptopolysiloxane; when the molar ratio of water to thiopropylmethyldimethoxysilane is large, the polymer is difficult to condense, resulting in insufficient molecular weight, thereby affecting subsequent cross-linking and curing.

[0040] Furthermore, the sufficient reaction time is 4 to 8 hours.

[0041] Furthermore, if the temperature of the full reaction is too low or the time is too short, the hydrolysis and condensation will be insufficient, resulting in poor thiol grafting effect; if the temperature of the full reaction is too high or the time is too long, the reaction will be too intense and gelation will easily occur. Under the conditions of the full reaction temperature of 60 to 90°C and the reaction time of 4 to 8 hours, a pendant mercapto polysiloxane with sufficient hydrolysis and condensation and good thiol grafting effect can be obtained.

[0042] Furthermore, the purification includes extraction, water removal and distillation.

[0043] Furthermore, the extraction is performed by dissolving the product with dichloromethane, adding water and ethanol, and then extracting 3 to 5 times.

[0044] Furthermore, the dehydration is performed by adding anhydrous magnesium sulfate after extraction.

[0045] Furthermore, the distillation is to remove excess solvent by distillation under reduced pressure at 60-80°C after removing water.

[0046] Specifically, the purification includes dissolving the product with dichloromethane and then adding appropriate amounts of water and ethanol to extract 3 to 5 times, adding anhydrous magnesium sulfate to remove water after extraction, and removing excess solvent by reduced pressure distillation at 60 to 80°C after removal of water.

[0047] Further, as an optional method for testing the thiol content, the following steps are included:

[0048] The Swiss Bruker AVANCE III 400MHz Superconducting Fourier NMR spectrometer was used. The measurement conditions were room temperature, the solvent was deuterated chloroform (CDCl3), and 1 The HNMR internal standard method can be used to test the mercapto content of the prepared pendant mercapto silicone oil.

[0049] Furthermore, the specific test method for the thiol content comprises the following steps:

[0050] At room temperature, with 1,4-dioxane as internal standard and CDCl3 as solvent, a certain amount of sample and 1,4-dioxane were weighed and mixed in CDCl3, tested after ultrasonic treatment for 20 minutes, and the thiol content was calculated.

[0051] Furthermore, the calculation formula of the sulfhydryl content (SC) is:

[0052]

[0053] The unit of SC is mmol·g -1 ; A is half of the absorption peak area of ​​-CH2- connected to -SH by mercaptopropyl; B is the peak area of ​​-CH2- in 1,4-dioxane; W i is the mass of the internal standard, in g; W s is the mass of the sample, in g; 8 is the number of protons in 1,4-dioxane; 88 is the relative molecular mass of 1,4-dioxane, in g·mol -1 .

[0054] Furthermore, the viscosity is tested by testing the dynamic viscosity value at 25° C. according to GB / T10247-□1988.

[0055] Furthermore, the pendant mercapto silicone oil has a mercapto content of 0.5 to 2 mmol / g and a viscosity of 3000 to 8000 mPa·s.

[0056] Preferably, the pendant mercapto silicone oil has a mercapto content of 0.8 to 1.2 mmol / g and a viscosity of 4000 to 6000 mPa·s.

[0057] Furthermore, the vinyl-terminated hydrogenated silicone oil is a polysiloxane containing hydrogen on the vinyl-terminated side chain. The pendant mercapto silicone oil and the polysiloxane can combine curing and foaming in the same raw material. Otherwise, additional vinyl silicone oil (vinyl silicone oil: a polysiloxane whose vinyl-terminated side chains are all methyl segments) needs to be added for curing, which will result in an unsatisfactory number and uniformity of bubbles. For the vinyl content of the vinyl-terminated hydrogenated silicone oil, too little will make it difficult to cure and form the bubbles or even no bubbles, while too much will cause the pore size to become larger and the number to become smaller.

[0058] Furthermore, the structural formula of the vinyl-terminated hydrogen-containing silicone oil is:

[0059]

[0060] In the formula, x is selected from any integer from 1 to 96, and y is selected from any integer from 1 to 16.

[0061] Further, as an optional method, the preparation method of the vinyl-terminated hydrogen-containing silicone oil comprises the following steps:

[0062] Divinyltetramethyldisiloxane, tetramethylcyclotetrasiloxane, organosilicon intermediate, acid catalyst and water are mixed, fully reacted at 50-70°C, and purified to obtain vinyl-terminated hydrogenated silicone oil. The specific reaction equation is as follows:

[0063]

[0064] Furthermore, the organosilicon intermediate includes linear siloxane and cyclic siloxane.

[0065] Furthermore, the linear siloxane includes one or more of dimethyldimethoxysilane, methylphenyldimethoxysilane, diphenyldimethoxysilane, and aminopropyltrimethylsilane.

[0066] Furthermore, the cyclic siloxane includes one or more of octamethylcyclotetrasiloxane, hexamethylcyclotrisiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, trifluoropropylmethylcyclotrisiloxane, and tetramethyltetraphenylcyclotetrasiloxane.

[0067] Preferably, the organosilicon intermediate is octamethylcyclotetrasiloxane.

[0068] Furthermore, the acidic catalyst includes one or more of trifluoromethanesulfonic acid, hydrochloric acid, sulfuric acid, and cation exchange resin.

[0069] Furthermore, the added amount of the acidic catalyst is 0.5% to 2% of the total weight of divinyltetramethyldisiloxane, tetramethylcyclotetrasiloxane and the organosilicon intermediate.

[0070] Furthermore, the molar ratio of divinyltetramethyldisiloxane, tetramethylcyclotetrasiloxane and the organosilicon intermediate is 1:(2-10):(1-4).

[0071] Furthermore, the divinyltetramethyldisiloxane is used as a capping agent, and the molar ratio of addition will affect the molecular weight and vinyl content of the polymer; the tetramethylcyclotetrasiloxane is used to introduce side active hydrogen, and the molar ratio of addition will affect the hydrogen content of the terminal vinyl hydrogen-containing polysiloxane.

[0072] Furthermore, the molar ratio of the tetramethylcyclotetrasiloxane to water is 1:(0.2-0.6).

[0073] Furthermore, when the molar ratio of water to tetramethylcyclotetrasiloxane is small, the tetramethylcyclotetrasiloxane and the organosilicon intermediate are easily hydrolyzed insufficiently, resulting in a low yield of the vinyl-terminated hydrogen-containing polysiloxane; when the molar ratio of water to tetramethylcyclotetrasiloxane is large, gelation is likely to occur.

[0074] Furthermore, the sufficient reaction time is 6 to 10 hours.

[0075] Furthermore, if the temperature of the full reaction is too low or the time is too short, the hydrolysis and condensation will be insufficient, resulting in poor grafting effect of the side active hydrogen; if the temperature of the full reaction is too high or the time is too long, the reaction will be too violent and gelation will easily occur. Under the conditions of the full reaction temperature of 50 to 70°C and the reaction time of 6 to 10 hours, a vinyl-terminated hydrogen-containing polysiloxane with sufficient hydrolysis and condensation and good side active hydrogen grafting effect can be obtained.

[0076] Furthermore, the purification includes extraction, water removal and distillation.

[0077] Furthermore, the extraction is performed by dissolving the product with dichloromethane, adding water and ethanol, and then extracting 3 to 5 times.

[0078] Furthermore, the dehydration is performed by adding anhydrous magnesium sulfate after extraction.

[0079] Furthermore, the distillation is to remove excess solvent by distillation under reduced pressure at 60-80°C after removing water.

[0080] Specifically, the purification includes dissolving the product with dichloromethane and then adding appropriate amounts of water and ethanol to extract 3 to 5 times, adding anhydrous magnesium sulfate to remove water after extraction, and removing excess solvent by reduced pressure distillation at 60 to 80°C after removal of water.

[0081] Furthermore, the test method for the hydrogen content of the vinyl-terminated hydrogen-containing silicone oil is the industry standard of the People's Republic of China HG / T 4658-2014.

[0082] Furthermore, the testing method for the vinyl content of the vinyl-terminated hydrogenated silicone oil is the National Standard of the People's Republic of China GB / T 43314-2023.

[0083] Preferably, the vinyl content of the vinyl-terminated hydrogen-containing silicone oil is 0.4 to 0.6 mmol / g, and the hydrogen content is 9 to 10 mmol / g.

[0084] Furthermore, the alcohol compound or hydroxy silicone oil is a small molecular weight hydroxy silicone oil with a high hydroxy content and a small molecular alcohol with a high boiling point (boiling point>90°C). For the hydroxy content of hydroxy silicone oil, too little will cause high viscosity of the system and poor dispersibility, resulting in poor foaming, while too high will cause polycondensation due to unstable raw materials, making it difficult to maintain a high hydroxy content; small molecular alcohols with low boiling points, such as ethanol, will evaporate under ultraviolet light irradiation, affecting the condensation dehydrogenation reaction of hydroxyl groups and silicon-hydrogen bonds, thereby affecting the foaming effect.

[0085] Furthermore, the boiling point > 90°C means that the boiling point is > 90°C under standard atmospheric pressure (101 kPa).

[0086] Preferably, the hydroxyl content of the hydroxy silicone oil is 0.8 to 0.9 mmol / g.

[0087] Preferably, the alcohol compound is an alcohol compound with a boiling point > 150°C.

[0088] Specifically, the alcohol compound includes one or more of n-propanol, ethylene glycol, and butanediol.

[0089] More preferably, the alcohol compound is ethylene glycol and / or butanediol.

[0090] Furthermore, the photoinitiators are all free radical photoinitiators available on the market, and the dosages thereof are the dosages commonly used in UV curing and 3D printing. Too much or too little has no significant effect on the silicone rubber foam.

[0091] Preferably, the photoinitiator is one or more of 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester (TPO-L), phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819), and 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide (TMO).

[0092] More preferably, the photoinitiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0093] Furthermore, the platinum catalysts are all platinum available on the market, and only a trace amount is needed, which can be dissolved and diluted using alkanes with higher boiling points such as 1,4-dioxane.

[0094] Furthermore, the platinum content of the platinum catalyst is 5 to 1000 ppm.

[0095] Furthermore, the platinum catalyst is selected from trimethylcyclopentadienylplatinum or platinum acetylacetonate.

[0096] The present invention provides a method for preparing the silicone rubber foam material, comprising the following steps:

[0097] S1. Evenly mix pendant mercapto silicone oil, terminal vinyl hydrogen silicone oil, hydroxyl-containing compound, photoinitiator and platinum catalyst to obtain a 3D printing silicone rubber precursor;

[0098] S2. Print the 3D printing silicone rubber precursor obtained in step S1, wash the finished product after printing, and perform a curing treatment under ultraviolet irradiation conditions to obtain a silicone rubber foam material.

[0099] The existing physical foaming method for preparing silicone rubber foam mostly adopts the supercritical carbon dioxide foaming method. This method has high equipment requirements and complex preparation methods, including pressurized dissolution blending and pressure relief foaming processes, which require 2 to 3 hours to solidify into foams; the existing chemical foaming method includes pre-vulcanization and post-curing processes, and it takes 2 to 3 hours to prepare silicone rubber foam. Compared with the above method, the photocuring preparation of silicone rubber foam in the present invention only requires 10 to 20 minutes of ultraviolet light irradiation, which greatly shortens the preparation time and saves energy. In addition, the present invention further expands to 3D printing technology based on photocuring preparation, enriching the processing methods of silicone rubber foam, enabling it to achieve customized customization and macro configuration design, and further expanding its application.

[0100] Furthermore, in step S2, the layer thickness in the printing is set to 50-150 μm, and the exposure time is 3-6 s, preferably 3 s.

[0101] Furthermore, in step S2, the wavelength of the ultraviolet irradiation is 350-420 nm.

[0102] Furthermore, in step S2, the light intensity of the ultraviolet irradiation is 1 to 20 mW / cm 2 .

[0103] Furthermore, in step S2, the curing time is 10 to 20 minutes.

[0104] Compared with the prior art, the present invention has the following beneficial effects: the present invention uses a photocuring form to prepare a silicone rubber foam material using a chemical foaming method, and achieves controllable foaming during the photocuring process by cleverly controlling the content and dosage of reactive functional groups such as mercapto, vinyl, silicon cyanide, and hydroxyl. This control can greatly shorten the preparation time of silicone rubber foam materials and controllably adjust the pore size. The pores of the silicone rubber foam material are small and dense, and compared with the existing physical foaming method, it has the advantages of simple and fast preparation process. The present invention further expands to 3D technology on the basis of photocuring, enriches the processing methods of silicone rubber foam, enables customized customization and macro configuration design, and further expands its applicable fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0105] Figure 1 This is the H NMR spectrum of the pendant mercapto silicone oil used in Example 1.

[0106] Figure 2 This is the H-NMR spectrum of the vinyl-terminated hydrogen-containing silicone oil used in Example 1.

[0107] Figure 3 These are SEM morphology images of cross-sectional cells of the silicone rubber foam prepared by 3D printing in Examples 1 to 8.

[0108] Figure 4 These are SEM morphology images of cross-sectional cells of the silicone rubber foam prepared by 3D printing in Comparative Examples 1 to 8.

[0109] Figure 5 This is a morphology of the cross-section of the pores of the silicone rubber foam prepared by 3D printing in Comparative Example 9, which was taken with an ordinary camera. DETAILED DESCRIPTION

[0110] The present invention is further described below in conjunction with the accompanying drawings and specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0111] Unless otherwise specified, the reagents and materials used in the following examples and comparative examples are commercially available or prepared by conventional methods.

[0112] Hydroxyl silicone oils with different hydroxyl contents were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0113] Vinyl silicone oil was purchased from Guangzhou Jucheng Zhaoye Organic Silicone Raw Materials Co., Ltd.;

[0114] Trimethylcyclopentadienyl platinum (platinum content 1000 ppm) was purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0115] Photoinitiator 819 was purchased from BASF AG, Germany.

[0116] Example 1 A photocurable 3D printing silicone rubber foam material

[0117] 1. Experimental Methods

[0118] (1) Preparation of pendant mercapto silicone oil

[0119] Weigh 1.86 g of hexamethyldisiloxane, 72.14 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 1.85 g of trifluoromethanesulfonic acid and 14.4 mL of water, mix well, and then react by hydrolysis condensation at 80 ° C for 6 hours to obtain the product. The product is dissolved in dichloromethane and then extracted three times with appropriate amounts of water and ethanol. After extraction, anhydrous magnesium sulfate is added to remove water. After dehydration, the excess solvent is removed by reduced pressure distillation at 70 ° C to obtain pendant mercapto silicone oil.

[0120] (2) Preparation of vinyl-terminated hydrogenated silicone oil

[0121] Weigh 20g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 60g of octamethylcyclotetrasiloxane, 1g of trifluoromethanesulfonic acid and 3.6mL of water, mix well, and then react by hydrolysis condensation at 60°C for 8h to obtain the product. Dissolve the product in dichloromethane and then add appropriate amount of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After dehydration, remove excess solvent by reduced pressure distillation at 70°C to obtain terminal vinyl hydrogenated silicone oil.

[0122] (3) Preparation of a photocurable 3D printing silicone rubber foam material

[0123] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0124] Specifically, 22.75g of pendant mercapto silicone oil, 25g of terminal vinyl hydrogen silicone oil, 1g of hydroxy silicone oil, 0.75g of photoinitiator 819, and 0.5g of trimethylcyclopentadiene platinum (platinum content of 1000ppm) were added to a black plastic jar in sequence and stirred evenly to obtain a photocurable 3D printable silicone rubber precursor. Pour it into the resin tank of the 3D printer. The 3D printing test was performed using a Shenzhen Vistech LCD-3D printer. The light source was a 405nm LED light source with a light intensity of 5mW / cm 2; The layer thickness was set to 100 μm and the exposure time was 3 s. After printing, the finished product was washed with ethanol to remove the uncured silicone rubber precursor. After removal, the finished product was post-cured in a 405 nm UV curing light box for 15 min to prepare a 3D printed product.

[0125] 2. Experimental results

[0126] The results of H NMR spectra of pendant mercapto silicone oil and terminal vinyl hydrogen silicone oil are as follows: Figure 1 , Figure 2 As shown, the chemical shift of each chemical bond is marked in the figure, among which the peak area corresponding to the CH3-Si bond in the two compounds is the largest, which is consistent with the molecular formula. Changing the thiol content or the vinyl content, the change in the nuclear magnetic hydrogen spectrum of the obtained side mercapto silicone oil or terminal vinyl hydrogen-containing silicone oil is very small, basically only the peak area changes, and the position of the peak remains unchanged. That is, the nuclear magnetic hydrogen spectrum of the side mercapto silicone oil with different thiol contents in other embodiments and comparative examples is basically the same as the nuclear magnetic hydrogen spectrum of the side mercapto silicone oil in Example 1; the nuclear magnetic hydrogen spectrum of the terminal vinyl hydrogen-containing silicone oil with different vinyl contents is the same.

[0127] SEM results are as follows Figure 3 As shown, the pore diameters of the obtained materials are all less than 1 μm, which is nanometer size, and the number of pores is large and uniform.

[0128] Example 2 A photocurable 3D printing silicone rubber foam material

[0129] 1. Experimental Methods

[0130] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 40% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 52% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 5% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1% photoinitiator 819; and 2% ultraviolet light-activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0131] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0132] 2. Experimental results

[0133] SEM results are as follows Figure 3 As shown, compared with Example 1, Example 2 increases the amount of hydroxy silicone oil and the amount of UV-activated platinum catalyst, which will make the foaming rate faster than that of Example 1 to a certain extent. The pore size of the obtained 3D printed silicone rubber foam material is still less than 1 μm, which is nanometer size, and the number of pores is large and uniform.

[0134] Example 3 A photocurable 3D printing silicone rubber foam material

[0135] 1. Experimental Methods

[0136] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 50% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 46.5% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 1% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 2% photoinitiator 819; and 0.5% ultraviolet light activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0137] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0138] 2. Experimental results

[0139] SEM results are as follows Figure 3 As shown, compared with Example 1, Example 3 increases the amount of side mercapto silicone oil and the amount of photoinitiator used in the cross-linking curing component, and the pore size of the obtained 3D printed silicone rubber foam material is less than 1 μm, which is nanometer size, and the number of pores is large and uniform.

[0140] Example 4 A photocurable 3D printing silicone rubber foam material

[0141] 1. Experimental Methods

[0142] (1) Preparation of pendant mercapto silicone oil

[0143] Weigh 1.63 g of hexamethyldisiloxane, 29.6 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 1.63 g of trifluoromethanesulfonic acid and 5.9 mL of water, mix well, and then react by hydrolysis condensation at 80 ° C for 6 hours to obtain the product. The product is dissolved in dichloromethane and then extracted three times with appropriate amounts of water and ethanol. After extraction, anhydrous magnesium sulfate is added to remove water. After dehydration, the excess solvent is removed by reduced pressure distillation at 70 ° C to obtain pendant mercapto silicone oil.

[0144] (2) Preparation of vinyl-terminated hydrogenated silicone oil

[0145] Weigh 10g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 54g of octamethylcyclotetrasiloxane, 0.92g of trifluoromethanesulfonic acid and 3.6mL of water, mix well, and then react by hydrolysis condensation at 60°C for 8h to obtain the product. Dissolve the product with dichloromethane and then add appropriate amount of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After dehydration, remove excess solvent by reduced pressure distillation at 70°C to obtain terminal vinyl hydrogenated silicone oil.

[0146] (3) Preparation of a curable 3D printing silicone rubber foam material

[0147] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 0.5 mmol / g, viscosity 8000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.3 mmol / g, hydrogen content 11 mmol / g); 2% hydroxy silicone oil (hydroxyl content 1 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light-activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0148] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0149] 2. Experimental results

[0150] SEM results are as follows Figure 3 As shown, compared with Example 1, Example 4 reduces the mercapto content and the vinyl content, increases the hydrogen content and the hydroxyl content, affects the matching degree of the curing rate and the foaming rate, and makes the pore size of the formed bubbles larger, becoming micron-sized bubbles, the pore size of the bubbles is less than 100 μm, and the number of bubbles is large, and it is still a silicone rubber foam material with good effect.

[0151] Example 5 A photocurable 3D printing silicone rubber foam material

[0152] 1. Experimental Methods

[0153] (1) Preparation of pendant mercapto silicone oil

[0154] Weigh 3.36g of hexamethyldisiloxane, 169.3g of thiopropylmethyldimethoxysilane, 296.62g of octamethylcyclotetrasiloxane, 2.35g of trifluoromethanesulfonic acid and 33.8mL of water, mix well, and then react by hydrolysis condensation at 80°C for 6h to obtain the product. Dissolve the product with dichloromethane and then add appropriate amount of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After removing water, remove excess solvent by reduced pressure distillation at 70°C to obtain pendant mercapto silicone oil.

[0155] (2) Preparation of vinyl-terminated hydrogenated silicone oil

[0156] Weigh 36g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 90g of octamethylcyclotetrasiloxane, 1.23g of trifluoromethanesulfonic acid and 3.6mL of water, mix well, and then react by hydrolysis condensation at 60°C for 8h to obtain the product. Dissolve the product with dichloromethane and then add appropriate amount of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After dehydration, remove excess solvent by reduced pressure distillation at 70°C to obtain terminal vinyl hydrogenated silicone oil.

[0157] (3) Preparation of a curable 3D printing silicone rubber foam material

[0158] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 2 mmol / g, viscosity 3000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.8 mmol / g, hydrogen content 8 mmol / g); 2% hydroxy silicone oil (hydroxyl content 0.6 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienyl platinum (platinum content 1000 ppm).

[0159] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0160] 2. Experimental results

[0161] SEM results are as follows Figure 3 As shown, compared with Example 1, Example 5 increases the mercapto content and vinyl content, reduces the hydrogen content and hydroxyl content, affects the matching degree of the curing rate and the foaming rate, and makes the pore size of the formed pores larger, becoming micron-sized pores. Compared with Example 4, the curing rate of Example 5 is faster and the foaming rate is slower. From the figure, it can be seen that the pore uniformity of Example 5 is better than that of Example 4.

[0162] Example 6 A photocurable 3D printing silicone rubber foam material

[0163] 1. Experimental Methods

[0164] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% ethylene glycol; 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienyl platinum (platinum content 1000 ppm).

[0165] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0166] 2. Experimental results

[0167] SEM results are as follows Figure 3 As shown, ethylene glycol is used instead of hydroxy silicone oil to prepare silicone rubber foam material. Since ethylene glycol is a small molecule alcohol, it is slightly inferior to hydroxy silicone oil in the silicone oil system, and its foaming effect is slightly worse than the system using hydroxy silicone oil, but it can still successfully prepare silicone rubber foam with micron-level pore diameter and a large number of pores.

[0168] Example 7 A photocurable 3D printing silicone rubber foam material

[0169] 1. Experimental Methods

[0170] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 40% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 52% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 5% ethylene glycol; 1% photoinitiator 819; and 2% ultraviolet light activated platinum catalyst trimethylcyclopentadienyl platinum (platinum content 1000 ppm).

[0171] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0172] 2. Experimental results

[0173] SEM results are as follows Figure 3 As shown, compared with Example 6, increasing the amount of small molecule alcohol and the amount of ultraviolet light activated platinum catalyst will, to a certain extent, make the foaming rate faster than that of Example 6. At the same time, more small molecule alcohols have poor compatibility with the silicone oil system and are more likely to agglomerate, so that the pore size of Example 7 is larger than that of Example 6, the number of pores is reduced, and an open cell phenomenon (the pores are connected) occurs. However, in general, it is still a silicone rubber foam with good uniformity, a large number of pores, and a micron-level pore size.

[0174] Example 8 A 3D printable silicone rubber foam material

[0175] 1. Experimental Methods

[0176] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 50% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 46.5% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 1% ethylene glycol; 2% photoinitiator 819; and 0.5% ultraviolet light activated platinum catalyst trimethylcyclopentadienyl platinum (platinum content 1000 ppm).

[0177] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0178] 2. Experimental results

[0179] SEM results are as follows Figure 3 As shown, compared with Example 6, the amount of side mercapto silicone oil and the amount of photoinitiator are increased, which will make the curing rate faster than that of Example 6 to a certain extent, which limits the aggregation and enlargement of the pores (referring to the process of several small bubbles gathering together to form a large bubble) to a certain extent, and can still prepare silicone rubber foam with good uniformity, a large number of pores and a pore size of micrometer level.

[0180] Comparative Example 1: A photocurable 3D printing silicone rubber foam material

[0181] 1. Experimental Methods

[0182] (1) Preparation of pendant mercapto silicone oil

[0183] Weigh 1.28g of hexamethyldisiloxane, 11.2g of thiopropylmethyldimethoxysilane, 296.62g of octamethylcyclotetrasiloxane, 1.55g of trifluoromethanesulfonic acid and 2.24mL of water, mix well, and then react by hydrolysis condensation at 80°C for 6h to obtain the product. The product is dissolved in dichloromethane and then extracted three times with appropriate amounts of water and ethanol. After extraction, anhydrous magnesium sulfate is added to remove water. After removal of water, excess solvent is removed by reduced pressure distillation at 70°C to obtain pendant mercapto silicone oil.

[0184] (2) Preparation of vinyl-terminated hydrogenated silicone oil

[0185] Weigh 20g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 60g of octamethylcyclotetrasiloxane, 1g of trifluoromethanesulfonic acid and 3.6mL of water, mix well, and then react by hydrolysis condensation at 60°C for 8h to obtain the product. Dissolve the product in dichloromethane and then add appropriate amount of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After dehydration, remove excess solvent by reduced pressure distillation at 70°C to obtain terminal vinyl hydrogenated silicone oil.

[0186] (3) Preparation of a curable 3D printing silicone rubber foam material

[0187] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 0.2 mmol / g, viscosity 10000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0188] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0189] 2. Experimental results

[0190] SEM results are as follows Figure 4 As shown in the figure, the cell diameter is less than 100 μm, but the number of cells is very small. This is because too low a mercapto content will cause a very poor match between the curing rate and the foaming rate. The slow curing rate and fast foaming rate will cause the cells to aggregate and grow, resulting in the material having too few cells, large and uneven pore diameters.

[0191] Comparative Example 2: A photocurable 3D printing silicone rubber foam material

[0192] 1. Experimental Methods

[0193] (1) Preparation of pendant mercapto silicone oil

[0194] Weigh 2.38g of hexamethyldisiloxane, 245.5g of thiopropylmethyldimethoxysilane, 296.62g of octamethylcyclotetrasiloxane, 2.72g of trifluoromethanesulfonic acid and 49mL of water, mix well, and then react by hydrolysis condensation at 80°C for 6h to obtain the product. The product is dissolved in dichloromethane and then extracted three times with appropriate amounts of water and ethanol. After extraction, anhydrous magnesium sulfate is added to remove water. After removal of water, excess solvent is removed by reduced pressure distillation at 70°C to obtain pendant mercapto silicone oil.

[0195] (2) Preparation of vinyl-terminated hydrogenated silicone oil

[0196] Weigh 20g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 60g of octamethylcyclotetrasiloxane, 1g of trifluoromethanesulfonic acid and 3.6mL of water, mix well, and then react by hydrolysis condensation at 60°C for 8h to obtain the product. Dissolve the product in dichloromethane and then add appropriate amount of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After dehydration, remove excess solvent by reduced pressure distillation at 70°C to obtain terminal vinyl hydrogenated silicone oil.

[0197] (3) Preparation of a curable 3D printing silicone rubber foam material

[0198] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 2.5 mmol / g, viscosity 1000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light-activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0199] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0200] 2. Experimental results

[0201] SEM results are as follows Figure 4 As shown in the figure, the pore diameter is less than 100 μm, but the number of pores is very small. This is because too high a mercapto content will cause a great mismatch between the curing rate and the foaming rate, making it difficult for the foaming component to foam, so that the resulting material has too few pores, with tiny pores in a small area and no pores in most areas.

[0202] Comparative Example 3: A photocurable 3D printing silicone rubber foam material

[0203] 1. Experimental Methods

[0204] (1) Preparation of pendant mercapto silicone oil

[0205] Weigh 1.86g of hexamethyldisiloxane, 72.14g of thiopropylmethyldimethoxysilane, 296.62g of octamethylcyclotetrasiloxane, 1.85g of trifluoromethanesulfonic acid and 14.4mL of water, mix well, and then subject to hydrolysis condensation reaction at 80°C for 6h to obtain the product. Dissolve the product in dichloromethane and then add appropriate amounts of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After removing water, remove excess solvent by reduced pressure distillation at 70°C to obtain pendant mercapto silicone oil.

[0206] (2) Preparation of vinyl-terminated hydrogenated silicone oil

[0207] Weigh 15g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 264g of octamethylcyclotetrasiloxane, 2g of trifluoromethanesulfonic acid and 3.6mL of water, mix well, and then react by hydrolysis condensation at 60°C for 8h to obtain the product. Dissolve the product with dichloromethane and then add appropriate amount of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After dehydration, remove excess solvent by reduced pressure distillation at 70°C to obtain terminal vinyl hydrogenated silicone oil.

[0208] (3) Preparation of a curable 3D printing silicone rubber foam material

[0209] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.2 mmol / g, hydrogen content 5 mmol / g); 2% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0210] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0211] 2. Experimental results

[0212] SEM results are as follows Figure 4 As shown in the figure, the cell diameter is less than 100 μm, but the number of cells is very small. This is because too low a hydrogen content will result in too few foaming components and insufficient foaming, so that the resulting material has too few cells and cells exist in a small area.

[0213] Comparative Example 4: A photocurable 3D printing silicone rubber foam material

[0214] 1. Experimental Methods

[0215] (1) Preparation of pendant mercapto silicone oil

[0216] Weigh 1.86 g of hexamethyldisiloxane, 72.14 g of thiopropylmethyldimethoxysilane, 296.62 g of octamethylcyclotetrasiloxane, 1.85 g of trifluoromethanesulfonic acid and 14.4 mL of water, mix well, and then react by hydrolysis condensation at 80 ° C for 6 hours to obtain the product. The product is dissolved in dichloromethane and then extracted three times with appropriate amounts of water and ethanol. After extraction, anhydrous magnesium sulfate is added to remove water. After dehydration, the excess solvent is removed by reduced pressure distillation at 70 ° C to obtain pendant mercapto silicone oil.

[0217] (2) Preparation of vinyl-terminated hydrogenated silicone oil

[0218] Weigh 30g of divinyltetramethyldisiloxane, 120.26g of tetramethylcyclotetrasiloxane, 16g of octamethylcyclotetrasiloxane, 0.83g of trifluoromethanesulfonic acid and 3.6mL of water, mix well, and then react by hydrolysis condensation at 60°C for 8h to obtain the product. Dissolve the product with dichloromethane and then add appropriate amount of water and ethanol to extract 3 times. After extraction, add anhydrous magnesium sulfate to remove water. After dehydration, remove excess solvent by reduced pressure distillation at 70°C to obtain terminal vinyl hydrogenated silicone oil.

[0219] (3) Preparation of a curable 3D printing silicone rubber foam material

[0220] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 1 mmol / g, hydrogen content 12 mmol / g); 2% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0221] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0222] 2. Experimental results

[0223] SEM results are as follows Figure 4 As shown in the figure, the pore diameters are all less than 100 μm, but the number of pores is very small. This is because too high a hydrogen content will make the foaming components too many and difficult to fully disperse and aggregate, so that the resulting material has too few pores and only large-diameter pores.

[0224] Comparative Example 5: A photocurable 3D printing silicone rubber foam material

[0225] 1. Experimental Methods

[0226] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% hydroxy silicone oil (hydroxyl content 0.3 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0227] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0228] 2. Experimental results

[0229] SEM results are as follows Figure 4 As shown in the figure, the pore diameters are all less than 100 μm, but the number of pores is very small. This is because too low a hydroxyl content will result in fewer foaming components and insufficient foaming, so that the resulting material has too few pores and pores exist in a small area.

[0230] In addition, hydroxy silicone oil with a hydroxyl content greater than 1 mmol / g is unstable and will self-condense to reduce the hydroxyl content, making it impossible to stably prepare 3D printing silicone rubber foam materials.

[0231] Comparative Example 6: A photocurable 3D printing silicone rubber foam material

[0232] 1. Experimental Methods

[0233] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 40% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 40% vinyl silicone oil (vinyl content 0.12 mmol / g, viscosity 5000 mPa·s); 15% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2.5% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light-activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0234] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0235] 2. Experimental results

[0236] SEM results are as follows Figure 4 As shown in the figure, there are almost no bubbles. This is because the addition of vinyl silicone oil for curing will reduce the amount of hydrogen silicone oil used and make it difficult to obtain the ideal number of bubbles.

[0237] Comparative Example 7: A photocurable 3D printing silicone rubber foam material

[0238] 1. Experimental Methods

[0239] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 35% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 60% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2.5% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0240] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0241] 2. Experimental results

[0242] SEM results are as follows Figure 4 As shown in the figure, the pore diameters are all less than 100 μm, and the number of pores is very small. This is because too low a dosage of side mercapto silicone oil will result in a very poor match between the curing rate and the foaming rate. The slow curing rate and fast foaming rate will cause the pores to aggregate and grow, resulting in the material having too few pores, large and uneven pore diameters.

[0243] Comparative Example 8: A photocurable 3D printing silicone rubber foam material

[0244] 1. Experimental Methods

[0245] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 60% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 35% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2.5% hydroxy silicone oil (hydroxyl content 0.9 mmol / g); 1.5% photoinitiator 819; and 1% ultraviolet light-activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0246] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0247] 2. Experimental results

[0248] SEM results are as follows Figure 4 As shown, there are almost no pores and many defects. This is because too high a dosage of side mercapto silicone oil will cause the curing rate and the foaming rate to be very mismatched, and the foaming component is difficult to foam, so that the resulting material has too few pores, with tiny pores in a small part of the area and no pores in most areas. Comparative Example 9 A photocurable 3D printing silicone rubber foam material

[0249] 1. Experimental Methods

[0250] A photocurable 3D printing silicone rubber foam material comprises the following components, calculated by total mass percentage: 45.5% side mercapto silicone oil (mercapto content 1 mmol / g, viscosity 5000 mPa·s); 50% terminal vinyl hydrogen-containing silicone oil (vinyl content 0.5 mmol / g, hydrogen content 10 mmol / g); 2% ethanol; 1.5% photoinitiator 819; and 1% ultraviolet light activated platinum catalyst trimethylcyclopentadienylplatinum (platinum content 1000 ppm).

[0251] Based on a total amount of 50 g, the raw materials of each component were weighed according to the above ratio, and a photocurable 3D printing silicone rubber foam material was prepared according to the method of Example 1.

[0252] 2. Experimental results

[0253] The pore results of the obtained material are as follows Figure 5 As shown (taken with an ordinary camera), ethanol is used instead of hydroxyl silicone oil to prepare silicone rubber foam material. Since ethanol is a small molecule alcohol and has a low boiling point (<80°C), it is easily volatilized by heat, which affects the condensation dehydrogenation reaction of hydroxyl groups and silicon-hydrogen bonds, resulting in its foaming effect being worse than that of the system using hydroxyl silicone oil, and only large-diameter bubbles exist.

[0254] As can be seen from the above, the side mercapto silicone oil used in the present invention is a polysiloxane containing a mercapto group on the side chain. If the end mercapto silicone oil is used, it is difficult to cure with the end vinyl hydrogen silicone oil to form a cross-linked network. Wherein for the content of mercapto in the mercapto silicone oil, if it is too little, it will cause the silicone rubber foam to be difficult to cure and form (Comparative Example 1); if it is too much, it will cause the curing speed to accelerate, causing the foaming process to be too restricted and difficult to form small and dense pores (Comparative Example 2); for the amount of side mercapto silicone oil, if it is too little, it will cause the pores to aggregate and become larger, resulting in too few pores, large and uneven pores (Comparative Example 7); if it is too much, it will be difficult to foam and the number of pores will be uneven (Comparative Example 8).

[0255] The vinyl-terminated hydrogenated silicone oil used in the present invention is a polysiloxane containing hydrogen on the vinyl-terminated side chain. Under the premise of using side mercapto silicone oil in the raw material, the polysiloxane cleverly concentrates the curing and foaming in the same raw material. If the vinyl-terminated hydrogenated silicone oil is not used, the additional addition of vinyl silicone oil is selected for curing (Comparative Example 6). On the one hand, it will lead to a reduction in the amount of hydrogenated silicone oil and it is difficult to obtain the ideal number of pores. On the other hand, it will lead to the cross-linking system being too complicated and dense and difficult to obtain uniform pores, and there may be uneven distribution of pores. Among them, for the vinyl content in the vinyl-terminated hydrogenated silicone oil, if it is too little, it will cause the silicone rubber foam to be difficult to cure and form, and there may be no pores (Comparative Example 3); if it is too much, it will lead to less mercapto silicone oil content, resulting in the foaming process not being sufficiently restricted, and it is difficult to form small and dense pores (Comparative Example 4).

[0256] The alcohol used in the present invention is a small molecular weight hydroxy silicone oil with a high hydroxy content and a small molecule alcohol with a high boiling point. If a hydroxy silicone oil with too low a hydroxy content is used, there are problems such as high system viscosity and poor dispersibility, which will lead to poor foaming effect (Comparative Example 5); while the hydroxy silicone oil with too high a hydroxy content has no effect on the foaming of silicone rubber, but there is a problem of unstable raw materials, self-condensation will occur, and it is difficult to maintain a high hydroxy content. If a small molecule alcohol with a low boiling point such as ethanol is used, it may be heated and volatilized during ultraviolet light irradiation, affecting the foaming effect (Comparative Example 9).

[0257] The photoinitiators used in the present invention are all free radical photoinitiators available on the market, and the dosage thereof is the dosage commonly used in ultraviolet light curing and 3D printing. Too much or too little will not have much effect on the silicone rubber foam.

[0258] The ultraviolet activated platinum used in the present invention is platinum available on the market. Since the amount added is small, an alkane with a high boiling point such as 1,4-dioxane is used to dissolve and dilute it into a mixture of 5 to 1000 ppm for easy weighing. Too little amount will lead to too slow foaming rate, which is difficult to match with the curing rate and causes poor foaming effect; too much amount will not have a particularly large impact on the foaming of silicone rubber foam, but will increase the cost.

[0259] In summary, the photocurable 3D printing silicone rubber foam material includes, by mass percentage, 40% to 50% of side mercapto silicone oil, 45% to 55% of terminal vinyl hydrogenated silicone oil, 1% to 5% of hydroxyl-containing compounds (hydroxyl silicone oil, n-propanol, ethylene glycol, butanediol), 1% to 2% of photoinitiator, and 0.5% to 2% of ultraviolet light activated platinum catalyst; wherein the mercapto content of the side mercapto silicone oil is 0.5 to 2 mmol / g; the vinyl content of the terminal vinyl hydrogenated silicone oil is 0.3 to 0.8 mmol / g, and the hydrogen content is 8 to 11 mmol / g; the hydroxyl-containing compound is one or more of alcohol compounds and hydroxyl silicone oil; the hydroxyl content of the hydroxyl silicone oil is 0.6 to 1 mmol / g; and the alcohol compound is an alcohol compound with a boiling point > 90°C. Only by following the above raw material ratio can a nano- or micron-sized photocurable silicone rubber foam material with good uniformity and a large number of pores be prepared.

[0260] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A silicone rubber foam material, characterized in that: Calculated by total mass percentage, it includes the following components: 40% to 50% pendant mercapto silicone oil; 45% to 55% vinyl-terminated hydrogenated silicone oil; 1% to 5% hydroxyl compounds; 1% to 2% photoinitiator; 0.5% to 2% platinum catalyst; Wherein, the mercapto content of the pendant mercapto silicone oil is 0.5 to 2 mmol / g; The vinyl content of the vinyl-terminated hydrogen-containing silicone oil is 0.3-0.8 mmol / g, and the hydrogen content is 8-11 mmol / g; The hydroxyl-containing compound is one or more of an alcohol compound and a hydroxyl silicone oil; The hydroxyl content of the hydroxy silicone oil is 0.6 to 1 mmol / g; The alcohol compound is an alcohol compound with a boiling point greater than 90°C.

2. The silicone rubber foam material according to claim 1, characterized in that: The structural formula of the pendant mercapto silicone oil is: In the formula, m is selected from any integer in the range of 1 to 400, and n is selected from any integer in the range of 1 to 80.

3. The silicone rubber foam material according to claim 1, characterized in that: The pendant mercapto silicone oil has a mercapto content of 0.8 to 1.2 mmol / g.

4. The silicone rubber foam material according to claim 1, characterized in that: The structural formula of the vinyl-terminated hydrogenated silicone oil is: In the formula, x is selected from any integer from 1 to 96, and y is selected from any integer from 1 to 16.

5. The silicone rubber foam material according to claim 1, characterized in that: The vinyl content of the vinyl-terminated hydrogen-containing silicone oil is 0.4-0.6 mmol / g, and the hydrogen content is 9-10 mmol / g.

6. The silicone rubber foam material according to claim 1, characterized in that: The hydroxyl content of the hydroxy silicone oil is 0.8-0.9 mmol / g.

7. The silicone rubber foam material according to claim 1, characterized in that: The photoinitiator is one or more of 2,4,6-trimethylbenzoylphenylphosphonic acid ethyl ester, phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, and 2,4,6-trimethylbenzoyl-di(p-tolyl)phosphine oxide.

8. The silicone rubber foam material according to claim 1, characterized in that: The platinum content of the platinum catalyst is 5 to 1000 ppm.

9. The method for preparing the silicone rubber foam material according to any one of claims 1 to 8, characterized in that: The steps include: S1. Evenly mix pendant mercapto silicone oil, terminal vinyl hydrogen silicone oil, hydroxyl-containing compound, photoinitiator and platinum catalyst to obtain a 3D printing silicone rubber precursor; S2. Print the 3D printing silicone rubber precursor obtained in step S1, wash the finished product after printing, and perform a curing treatment under ultraviolet irradiation conditions to obtain a silicone rubber foam material.

10. Use of the silicone rubber foam material according to any one of claims 1 to 8 in the preparation of shock-absorbing and buffering materials, sound-insulating materials, heat-insulating materials, sealing materials or filling materials.

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