Food-grade silica gel as well as impregnation preparation method and application thereof

Abstract

The invention discloses food-grade silica gel as well as a gum dipping preparation method and application thereof. The silica gel comprises the following components in parts by weight: 30-40 parts of a polydimethylsiloxane matrix; 20-30 parts of a silicon dioxide filler; 5-10 parts of an epoxy resin modifier; 2-5 parts of a silane coupling agent; 1-3 parts of an antioxidant; 1-3 parts of a flame retardant; 0.5-2 parts of a dispersant; and 0.5-1 part of a light stabilizer. The novel food-grade silica gel is provided by adding a proper amount of epoxy resin modifier and optimizing the proportion of all the components, and the novel food-grade silica gel not only has excellent mechanical performance, but also has good adhesive performance. The tear strength and tensile strength of the silica gel are obviously superior to those of a product with a traditional formula, and the silica gel can still keep stable performance in a high-temperature environment. In addition, by introducing the epoxy resin modifier, the bonding effect between the silica gel and other materials is improved, and the application field of the silica gel is widened.

Description

Technical Field

[0001] The invention belongs to the technical field of packaging materials, and in particular relates to food-grade silica gel and a preparation method and application thereof for dipping silica gel. Background Art

[0002] With the improvement of people's living standards and the enhancement of health awareness, food safety issues have received more and more attention. As an important part of ensuring food safety, the performance of food packaging materials directly affects the quality and shelf life of food. Food-grade silicone has been widely used in food processing, packaging, cooking utensils and other fields due to its excellent physical and chemical properties and good biocompatibility. Existing food-grade silicone is mainly composed of polydimethylsiloxane matrix (PDMS) as the basic material, and a certain proportion of fillers and other additives are added to improve its mechanical properties and functionality. However, traditional food-grade silicone still has shortcomings in mechanical strength, temperature resistance and long-term stability, especially under high temperature and long-term use, it is prone to deformation, aging and other problems.

[0003] The mechanical properties of food-grade silicone commonly found on the market still need to be improved, especially in terms of tear strength and tensile strength. In addition, due to the strong chemical inertness of silicone itself, its bonding performance with other materials is poor, which also limits its application in some special occasions.

[0004] The technical problem to be solved by the present invention is: how to significantly improve the mechanical properties of food-grade silicone by optimizing the formula and preparation process, especially to improve its tear strength and tensile strength, while enhancing its bonding performance with other materials. Summary of the invention

[0005] The purpose of the present invention is to provide a food-grade silica gel and its dipping preparation method and application, which not only have excellent mechanical properties but also have good bonding properties, so as to solve the problems raised in the above background technology.

[0006] To achieve the above-mentioned object, the present invention provides a food-grade silica gel, which comprises the following components: 30-40 parts of a polydimethylsiloxane matrix; 20-30 parts of a silica filler; 5-10 parts of an epoxy resin modifier; 2-5 parts of a silane coupling agent; 1-3 parts of an antioxidant; 1-3 parts of a flame retardant; 0.5-2 parts of a dispersant; and 0.5-1 parts of a light stabilizer.

[0007] On the other hand, the present invention provides a method for preparing a food-grade silicone dipstick, comprising the following steps: A) uniformly mixing a polydimethylsiloxane matrix and a dispersant; B) adding a silica filler and continuing to stir until completely dispersed; C) adding an epoxy resin modifier and a silane coupling agent for chemical modification; D) finally adding an antioxidant, a flame retardant and a light stabilizer and mixing them thoroughly; E) subjecting the mixed material to a vacuum degassing treatment; F) dipstick treatment: immersing the treated material in a preset mold for curing and molding.

[0008] Preferably, step A comprises the following sub-steps:

[0009] A1) weighing the polydimethylsiloxane matrix and the dispersant respectively according to the number of parts, wherein the ratio of the polydimethylsiloxane matrix to the dispersant is W1:W2, W1 represents the weight of the polydimethylsiloxane matrix, and W2 represents the weight of the dispersant;

[0010] A2) adding the weighed polydimethylsiloxane matrix W1 into a high-speed mixer, heating to a temperature T1 = 60 ± 5 ° C at a speed N1 rpm, and continuing stirring for a time t1 ≥ 10 min to reduce the viscosity of the polydimethylsiloxane matrix;

[0011] A3) When the set temperature T1 is reached, the weighed dispersant W2 is evenly sprinkled into the preheated and stirred polydimethylsiloxane matrix, and stirring is continued under the same conditions until the dispersion is uniform.

[0012] Preferably, step B comprises the following sub-steps:

[0013] B1) weighing a predetermined amount W3 of nano-scale silica filler and preparing to add it to the uniformly mixed mixture of polydimethylsiloxane matrix and dispersant;

[0014] B2) While maintaining the stirring conditions set in step A2 unchanged, slowly add the silica filler weighed in step B1, and start timing t2≥20min to ensure that the silica is evenly distributed in the mixture.

[0015] Preferably, step C comprises the following sub-steps:

[0016] C1) weighing the epoxy resin modifier according to a predetermined number W4, and weighing the silane coupling agent according to a predetermined number W5;

[0017] C2) while maintaining the stirring condition in step B2, first add the epoxy resin modifier weighed in step C1, stirring time t4 ≥ 10min, so that the epoxy resin is evenly distributed in the mixture;

[0018] C3) After completing step C2, continue to add the silane coupling agent weighed in step C1, and maintain the same stirring conditions, and continue stirring for a time t5≥15min.

[0019] Preferably, the step D comprises the following sub-steps:

[0020] D1) weighing the antioxidant according to a predetermined number W6, weighing the flame retardant according to a number W7, and weighing the light stabilizer according to a number W8;

[0021] D2) while maintaining the stirring condition in step C2, first add the antioxidant weighed in step D1, and continue stirring for t6≥5min to ensure that the antioxidant is evenly distributed in the mixture;

[0022] D3) After completing step D2, continue to add the flame retardant weighed in step D1, and maintain the same stirring conditions, and continue stirring for a time t7≥10min;

[0023] D4) After completing step D3, add the light stabilizer weighed in step D1, and maintain the same stirring conditions for a further stirring time t8≥5 min.

[0024] Preferably, the step E comprises the following sub-steps:

[0025] E1) transferring the mixed materials in step D into a closed container and connecting it to a vacuum pump;

[0026] E2) Turn on the vacuum pump, set the vacuum degree to P1, and maintain the vacuum time t9 ≥ 15 min at this vacuum degree to remove bubbles in the mixture;

[0027] E3) During step E2, the vacuum degree change is calculated by the formula ΔP=P0-P1, where P0 is the atmospheric pressure and P1 is the set vacuum degree. When the ΔP value reaches a predetermined range, it indicates that the degassing condition has been met;

[0028] E4) After completing step E2, turn off the vacuum pump, and calculate the volume change rate of the deaerated mixture by the formula VC=(V_after-V_before) / V_before*100%, wherein V_after is the volume of the deaerated mixture, and V_before is the volume of the deaerated mixture. When the VC value reaches a predetermined range, it indicates that the deaeration process is completed;

[0029] E5) After completing step E4, if the VC value does not reach the predetermined range, repeat steps E2 to E4 until the requirements are met.

[0030] Preferably, the step F comprises the following sub-steps:

[0031] F1) pouring the deaerated material in step E into a preset mold, and ensuring that the mold surface is flat and free of bubbles;

[0032] F2) After pouring into the mold, use a vibration table to vibrate for t10≥5min to remove tiny bubbles in the material;

[0033] F3) After vibration, the mold containing the material is placed in a constant temperature oven and cured at a temperature of T2 = 80°C-120°C for a time of t11 = 1-3 hours;

[0034] F4) After completing step F3, the mold is removed and cooled to room temperature T1, and the solidification molding is completed.

[0035] Preferably, the vacuum degree P1 ranges from -0.09 MPa to -0.1 MPa.

[0036] On the other hand, the present invention provides an application of food-grade silica gel in the field of food packaging.

[0037] Technical effects and advantages of the present invention: Compared with the prior art, the food-grade silica gel and its dipping preparation method and application proposed by the present invention have the following advantages:

[0038] The present invention provides a novel food-grade silica gel by adding an appropriate amount of epoxy resin modifier and optimizing the ratio of each component, which not only has excellent mechanical properties but also has good bonding properties. The tear strength and tensile strength of the silica gel are significantly better than those of products with traditional formulas, and the silica gel can still maintain stable performance under high temperature environment. In addition, by introducing the epoxy resin modifier, the bonding effect between the silica gel and other materials is also improved, thereby broadening its application field. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 The present invention is a flow chart of the method for preparing the food-grade silica gel by dipping. DETAILED DESCRIPTION

[0040] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. The specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] Example 1

[0042] In this embodiment, a food-grade silica gel is provided, which contains the following components: 30 parts of polydimethylsiloxane matrix; 20 parts of silica filler; 5 parts of epoxy resin modifier; 2 parts of silane coupling agent; 1 part of antioxidant; 1 part of flame retardant; 0.5 part of dispersant; and 0.5 part of light stabilizer.

[0043] Polydimethylsiloxane matrix is ​​used as the main material, silica filler is used to increase hardness and wear resistance, silane coupling agent is used to improve the interface bonding between filler and matrix, antioxidant and light stabilizer are used to improve aging resistance. By introducing epoxy resin modifier, the bonding effect between silicone and other materials is also improved.

[0044] like Figure 1 As shown, the above-mentioned method for preparing the food-grade silica gel by dipping comprises the following steps:

[0045] A) Mix the polydimethylsiloxane matrix (PDMS) and the dispersant evenly; specifically as follows:

[0046] A1) weighing the polydimethylsiloxane matrix and the dispersant respectively according to the number of parts, wherein the ratio of the polydimethylsiloxane matrix to the dispersant is W1:W2, W1 represents the weight of the polydimethylsiloxane matrix, and W2 represents the weight of the dispersant;

[0047] A2) adding the weighed polydimethylsiloxane matrix W1 (30 parts) into a high-speed mixer, heating to a temperature T1 = 60 ± 5 ° C at a speed N1 rpm, and continuing stirring for a time t1 ≥ 10 min to reduce the viscosity of the polydimethylsiloxane matrix;

[0048] A3) When the set temperature T1 is reached, the weighed dispersant W2 (0.5 parts) is evenly sprinkled into the preheated and stirred polydimethylsiloxane matrix, and stirring is continued under the same conditions until the dispersion is uniform.

[0049] Among them, Step A1: determines the ratio of PDMS to dispersant and clearly states that the two materials need to be weighed in portions. Step A2: describes the operating conditions for adding PDMS to the mixer, including speed, temperature and time, in order to reduce the viscosity of PDMS for better mixing with the dispersant. Step A3: After reaching the set temperature, the dispersant is added to the preheated and continuously stirred PDMS until it is mixed evenly. Step A4: A formula is introduced to evaluate the uniformity of dispersion to ensure that the mixing quality meets the requirements. If the dispersion is not uniform, step A3 needs to be repeated until the desired uniformity index is reached.

[0050] B) Add silica filler and continue stirring until completely dispersed; specifically as follows:

[0051] B1) weighing a predetermined amount of W3 (20 parts) of nano-scale silica filler and preparing to add it to the uniformly mixed mixture of polydimethylsiloxane matrix and dispersant;

[0052] B2) While maintaining the stirring conditions set in step A2 unchanged, slowly add the silica filler weighed in step B1, and start timing t2≥20min to ensure that the silica is evenly distributed in the mixture.

[0053] Among them, step B1: determine the weight of the silica filler and prepare to add it to the PDMS and dispersant mixture that has been mixed evenly. Step B2: while maintaining the original stirring conditions, slowly add the weighed silica filler and start timing to ensure that the silica can be evenly distributed in the mixture.

[0054] C) adding epoxy resin modifier and silane coupling agent to carry out chemical modification; the details are as follows:

[0055] C1) weighing the epoxy resin modifier according to a predetermined number W4 (5 parts), and weighing the silane coupling agent according to a number W5 (2 parts);

[0056] C2) while maintaining the stirring condition in step B2, first add the epoxy resin modifier weighed in step C1, stirring time t4 ≥ 10min, so that the epoxy resin is evenly distributed in the mixture;

[0057] C3) After completing step C2, continue to add the silane coupling agent weighed in step C1, and maintain the same stirring conditions, and continue stirring for a time t5≥15min.

[0058] Among them, step C1: determine the weight of epoxy resin modifier and silane coupling agent, and prepare to add them to the already uniformly dispersed mixture. Step C2: under the original stirring conditions, add the epoxy resin modifier first, and start timing to ensure that the modifier can be evenly distributed in the mixture. Step C3: on the basis of the initial dispersion of the modifier, continue to add the silane coupling agent, maintain the same stirring conditions, continue stirring, and determine whether the modifier is evenly dispersed by calculating the modifier dispersion uniformity index UDI.

[0059] D) Finally, add antioxidant, flame retardant and light stabilizer and mix thoroughly; the details are as follows:

[0060] D1) weighing an antioxidant according to a predetermined number of parts W6 (1 part), weighing a flame retardant according to a number of parts W7 (1 part), and weighing a light stabilizer according to a number of parts W8 (0.5 part);

[0061] D2) while maintaining the stirring condition in step C2, first add the antioxidant weighed in step D1, and continue stirring for t6≥5min to ensure that the antioxidant is evenly distributed in the mixture;

[0062] D3) After completing step D2, continue to add the flame retardant weighed in step D1, and maintain the same stirring conditions, and continue stirring for a time t7≥10min;

[0063] D4) After completing step D3, add the light stabilizer weighed in step D1, and maintain the same stirring conditions for a further stirring time t8≥5 min.

[0064] Among them, step D1: determine the weight of antioxidant, flame retardant and light stabilizer, and prepare to add them to the modified uniform mixture. Step D2: while maintaining the original stirring conditions, add antioxidant first, and start timing to ensure that the antioxidant can be evenly distributed in the mixture. Step D3: on the basis of the initial dispersion of antioxidant, continue to add flame retardant, and maintain the same stirring conditions and continue stirring. Step D4: on the basis of the uniform dispersion of antioxidant and flame retardant, add light stabilizer and continue stirring.

[0065] E) subjecting the mixed materials to vacuum degassing treatment; the details are as follows:

[0066] E1) transferring the mixed materials in step D into a closed container and connecting it to a vacuum pump;

[0067] E2) Turn on the vacuum pump and set the vacuum degree to P1, where the range of P1 is: -0.09 MPa to -0.1 MPa, and maintain the vacuum degree for a time t9 ≥ 15 min to remove bubbles in the mixture;

[0068] E3) During step E2, the vacuum degree change is calculated by the formula ΔP=P0-P1, where P0 is the atmospheric pressure and P1 is the set vacuum degree. When the ΔP value reaches a predetermined range, it indicates that the degassing condition has been met;

[0069] E4) After completing step E2, turn off the vacuum pump, and calculate the volume change rate of the deaerated mixture by the formula VC=(V_after-V_before) / V_before*100%, wherein V_after is the volume of the deaerated mixture, and V_before is the volume of the deaerated mixture. When the VC value reaches a predetermined range, it indicates that the deaeration process is completed;

[0070] E5) After completing step E4, if the VC value does not reach the predetermined range, repeat steps E2 to E4 until the requirements are met.

[0071] Among them, step E1: transfer the mixed materials to a closed container and connect the vacuum pump to prepare for vacuum degassing. Step E2: turn on the vacuum pump, set the appropriate vacuum degree, and maintain it for a certain time to remove bubbles in the mixture. Step E3: During the vacuuming process, monitor whether the degassing conditions are met by calculating the vacuum degree change ΔP. Step E4: After the vacuuming is completed, turn off the vacuum pump and calculate the volume change rate VC of the degassing mixture to confirm whether the degassing effect meets the requirements. Step E5: If the volume change rate of the degassing mixture does not reach the predetermined range, the vacuuming step needs to be repeated until the standard is met.

[0072] F) Dipping treatment: Dipping the treated material into a preset mold for curing and molding; specifically:

[0073] F1) pouring the deaerated material in step E into a preset mold, and ensuring that the mold surface is flat and free of bubbles;

[0074] F2) After pouring into the mold, use a vibration table to vibrate for t10≥5min to remove tiny bubbles in the material;

[0075] F3) After vibration, the mold containing the material is placed in a constant temperature oven and cured at a temperature of T2 = 80°C-120°C for a time of t11 = 1-3 hours;

[0076] F4) After completing step F3, the mold is removed and cooled to room temperature T1, and the solidification molding is completed.

[0077] Among them, step F1: pour the deaerated material into a preset mold and ensure that the surface is flat and no bubbles remain. Step F2: after pouring into the mold, use a vibration table to vibrate for a certain period of time to further remove tiny bubbles in the material. Step F3: after vibration, put the mold containing the material into a constant temperature oven for curing. Step F4: after curing is completed, take out the mold and cool it to room temperature.

[0078] Example 2

[0079] In this embodiment, a food-grade silica gel is provided, which contains the following components: 35 parts of polydimethylsiloxane matrix; 25 parts of silica filler; 7 parts of epoxy resin modifier; 3 parts of silane coupling agent; 2 parts of antioxidant; 2 parts of flame retardant; 1 part of dispersant; and 0.7 parts of light stabilizer.

[0080] Polydimethylsiloxane matrix is ​​used as the main material, silica filler is used to increase hardness and wear resistance, silane coupling agent is used to improve the interface bonding between filler and matrix, antioxidant and light stabilizer are used to improve aging resistance. By introducing epoxy resin modifier, the bonding effect between silicone and other materials is also improved.

[0081] The above-mentioned method for preparing the food-grade silica gel by dipping comprises the following steps:

[0082] A) Mix the polydimethylsiloxane matrix (PDMS) and the dispersant evenly; specifically as follows:

[0083] A1) weighing the polydimethylsiloxane matrix and the dispersant respectively according to the number of parts, wherein the ratio of the polydimethylsiloxane matrix to the dispersant is W1:W2, W1 represents the weight of the polydimethylsiloxane matrix, and W2 represents the weight of the dispersant;

[0084] A2) adding the weighed polydimethylsiloxane matrix W1 (35 parts) into a high-speed mixer, heating to a temperature T1 = 60 ± 5 ° C at a speed N1 rpm, and continuing stirring for a time t1 ≥ 10 min to reduce the viscosity of the polydimethylsiloxane matrix;

[0085] A3) When the set temperature T1 is reached, the weighed dispersant W2 (1 part) is evenly sprinkled into the preheated and stirred polydimethylsiloxane matrix, and stirring is continued under the same conditions until the dispersion is uniform.

[0086] Among them, Step A1: determines the ratio of PDMS to dispersant and clearly states that the two materials need to be weighed in portions. Step A2: describes the operating conditions for adding PDMS to the mixer, including speed, temperature and time, in order to reduce the viscosity of PDMS for better mixing with the dispersant. Step A3: After reaching the set temperature, the dispersant is added to the preheated and continuously stirred PDMS until it is mixed evenly. Step A4: A formula is introduced to evaluate the uniformity of dispersion to ensure that the mixing quality meets the requirements. If the dispersion is not uniform, step A3 needs to be repeated until the desired uniformity index is reached.

[0087] B) Add silica filler and continue stirring until completely dispersed; specifically as follows:

[0088] B1) weighing a predetermined amount of W3 (25 parts) of nano-scale silica filler and preparing to add it to the uniformly mixed mixture of polydimethylsiloxane matrix and dispersant;

[0089] B2) While maintaining the stirring conditions set in step A2 unchanged, slowly add the silica filler weighed in step B1, and start timing t2≥20min to ensure that the silica is evenly distributed in the mixture.

[0090] Among them, step B1: determine the weight of the silica filler and prepare to add it to the PDMS and dispersant mixture that has been mixed evenly. Step B2: while maintaining the original stirring conditions, slowly add the weighed silica filler and start timing to ensure that the silica can be evenly distributed in the mixture.

[0091] C) adding epoxy resin modifier and silane coupling agent to carry out chemical modification; the details are as follows:

[0092] C1) weighing the epoxy resin modifier according to a predetermined number W4 (7 parts), and weighing the silane coupling agent according to a number W5 (3 parts);

[0093] C2) while maintaining the stirring condition in step B2, first add the epoxy resin modifier weighed in step C1, stirring time t4 ≥ 10min, so that the epoxy resin is evenly distributed in the mixture;

[0094] C3) After completing step C2, continue to add the silane coupling agent weighed in step C1, and maintain the same stirring conditions, and continue stirring for a time t5≥15min.

[0095] Among them, step C1: determine the weight of epoxy resin modifier and silane coupling agent, and prepare to add them to the already uniformly dispersed mixture. Step C2: under the original stirring conditions, add the epoxy resin modifier first, and start timing to ensure that the modifier can be evenly distributed in the mixture. Step C3: on the basis of the initial dispersion of the modifier, continue to add the silane coupling agent, maintain the same stirring conditions, continue stirring, and determine whether the modifier is evenly dispersed by calculating the modifier dispersion uniformity index UDI.

[0096] D) Finally, add antioxidant, flame retardant and light stabilizer and mix thoroughly; the details are as follows:

[0097] D1) weighing an antioxidant according to a predetermined number of parts W6 (2 parts), weighing a flame retardant according to a number of parts W7 (2 parts), and weighing a light stabilizer according to a number of parts W8 (0.7 parts);

[0098] D2) while maintaining the stirring condition in step C2, first add the antioxidant weighed in step D1, and continue stirring for t6≥5min to ensure that the antioxidant is evenly distributed in the mixture;

[0099] D3) After completing step D2, continue to add the flame retardant weighed in step D1, and maintain the same stirring conditions, and continue stirring for a time t7≥10min;

[0100] D4) After completing step D3, add the light stabilizer weighed in step D1, and maintain the same stirring conditions for a further stirring time t8≥5 min.

[0101] Among them, step D1: determine the weight of antioxidant, flame retardant and light stabilizer, and prepare to add them to the modified uniform mixture. Step D2: while maintaining the original stirring conditions, add antioxidant first, and start timing to ensure that the antioxidant can be evenly distributed in the mixture. Step D3: on the basis of the initial dispersion of antioxidant, continue to add flame retardant, and maintain the same stirring conditions and continue stirring. Step D4: on the basis of the uniform dispersion of antioxidant and flame retardant, add light stabilizer and continue stirring.

[0102] E) subjecting the mixed materials to vacuum degassing treatment; the details are as follows:

[0103] E1) transferring the mixed materials in step D into a closed container and connecting it to a vacuum pump;

[0104] E2) Turn on the vacuum pump and set the vacuum degree to P1, where the range of P1 is: -0.09 MPa to -0.1 MPa, and maintain the vacuum degree for a time t9 ≥ 15 min to remove bubbles in the mixture;

[0105] E3) During step E2, the vacuum degree change is calculated by the formula ΔP=P0-P1, where P0 is the atmospheric pressure and P1 is the set vacuum degree. When the ΔP value reaches a predetermined range, it indicates that the degassing condition has been met;

[0106] E4) After completing step E2, turn off the vacuum pump, and calculate the volume change rate of the deaerated mixture by the formula VC=(V_after-V_before) / V_before*100%, wherein V_after is the volume of the deaerated mixture, and V_before is the volume of the deaerated mixture. When the VC value reaches a predetermined range, it indicates that the deaeration process is completed;

[0107] E5) After completing step E4, if the VC value does not reach the predetermined range, repeat steps E2 to E4 until the requirements are met.

[0108] Among them, step E1: transfer the mixed materials to a closed container and connect the vacuum pump to prepare for vacuum degassing. Step E2: turn on the vacuum pump, set the appropriate vacuum degree, and maintain it for a certain time to remove bubbles in the mixture. Step E3: During the vacuuming process, monitor whether the degassing conditions are met by calculating the vacuum degree change ΔP. Step E4: After the vacuuming is completed, turn off the vacuum pump and calculate the volume change rate VC of the degassing mixture to confirm whether the degassing effect meets the requirements. Step E5: If the volume change rate of the degassing mixture does not reach the predetermined range, the vacuuming step needs to be repeated until the standard is met.

[0109] F) Dipping treatment: Dipping the treated material into a preset mold for curing and molding; specifically:

[0110] F1) pouring the deaerated material in step E into a preset mold, and ensuring that the mold surface is flat and free of bubbles;

[0111] F2) After pouring into the mold, use a vibration table to vibrate for t10≥5min to remove tiny bubbles in the material;

[0112] F3) After vibration, the mold containing the material is placed in a constant temperature oven and cured at a temperature of T2 = 80°C-120°C for a time of t11 = 1-3 hours;

[0113] F4) After completing step F3, the mold is removed and cooled to room temperature T1, and the solidification molding is completed.

[0114] Among them, step F1: pour the deaerated material into a preset mold and ensure that the surface is flat and no bubbles remain. Step F2: after pouring into the mold, use a vibration table to vibrate for a certain period of time to further remove tiny bubbles in the material. Step F3: after vibration, put the mold containing the material into a constant temperature oven for curing. Step F4: after curing is completed, take out the mold and cool it to room temperature.

[0115] Example 3

[0116] In this embodiment, a food-grade silica gel is provided, which contains the following components: 40 parts of polydimethylsiloxane matrix; 30 parts of silica filler; 10 parts of epoxy resin modifier; 5 parts of silane coupling agent; 3 parts of antioxidant; 3 parts of flame retardant; 2 parts of dispersant; and 1 part of light stabilizer.

[0117] Polydimethylsiloxane matrix is ​​used as the main material, silica filler is used to increase hardness and wear resistance, silane coupling agent is used to improve the interface bonding between filler and matrix, antioxidant and light stabilizer are used to improve aging resistance. By introducing epoxy resin modifier, the bonding effect between silicone and other materials is also improved.

[0118] The above-mentioned method for preparing the food-grade silica gel by dipping comprises the following steps:

[0119] A) Mix the polydimethylsiloxane matrix (PDMS) and the dispersant evenly; specifically as follows:

[0120] A1) weighing the polydimethylsiloxane matrix and the dispersant respectively according to the number of parts, wherein the ratio of the polydimethylsiloxane matrix to the dispersant is W1:W2, W1 represents the weight of the polydimethylsiloxane matrix, and W2 represents the weight of the dispersant;

[0121] A2) adding the weighed polydimethylsiloxane matrix W1 (40 parts) into a high-speed mixer, heating to a temperature T1 = 60 ± 5 ° C at a speed N1 rpm, and continuing stirring for a time t1 ≥ 10 min to reduce the viscosity of the polydimethylsiloxane matrix;

[0122] A3) When the set temperature T1 is reached, the weighed dispersant W2 (2 parts) is evenly sprinkled into the preheated and stirred polydimethylsiloxane matrix, and stirring is continued under the same conditions until the dispersion is uniform.

[0123] Among them, Step A1: determines the ratio of PDMS to dispersant and clearly states that the two materials need to be weighed in portions. Step A2: describes the operating conditions for adding PDMS to the mixer, including speed, temperature and time, in order to reduce the viscosity of PDMS for better mixing with the dispersant. Step A3: After reaching the set temperature, the dispersant is added to the preheated and continuously stirred PDMS until it is mixed evenly. Step A4: A formula is introduced to evaluate the uniformity of dispersion to ensure that the mixing quality meets the requirements. If the dispersion is not uniform, step A3 needs to be repeated until the desired uniformity index is reached.

[0124] B) Add silica filler and continue stirring until completely dispersed; specifically as follows:

[0125] B1) weighing a predetermined amount of W3 (30 parts) of nano-scale silica filler and preparing to add it to the uniformly mixed mixture of polydimethylsiloxane matrix and dispersant;

[0126] B2) While maintaining the stirring conditions set in step A2 unchanged, slowly add the silica filler weighed in step B1, and start timing t2≥20min to ensure that the silica is evenly distributed in the mixture.

[0127] Among them, step B1: determine the weight of the silica filler and prepare to add it to the PDMS and dispersant mixture that has been mixed evenly. Step B2: while maintaining the original stirring conditions, slowly add the weighed silica filler and start timing to ensure that the silica can be evenly distributed in the mixture.

[0128] C) adding epoxy resin modifier and silane coupling agent to carry out chemical modification; the details are as follows:

[0129] C1) weighing the epoxy resin modifier according to a predetermined number W4 (10 parts), and weighing the silane coupling agent according to a number W5 (5 parts);

[0130] C2) while maintaining the stirring condition in step B2, first add the epoxy resin modifier weighed in step C1, stirring time t4 ≥ 10min, so that the epoxy resin is evenly distributed in the mixture;

[0131] C3) After completing step C2, continue to add the silane coupling agent weighed in step C1, and maintain the same stirring conditions, and continue stirring for a time t5≥15min.

[0132] Among them, step C1: determine the weight of epoxy resin modifier and silane coupling agent, and prepare to add them to the already uniformly dispersed mixture. Step C2: under the original stirring conditions, add the epoxy resin modifier first, and start timing to ensure that the modifier can be evenly distributed in the mixture. Step C3: on the basis of the initial dispersion of the modifier, continue to add the silane coupling agent, maintain the same stirring conditions, continue stirring, and determine whether the modifier is evenly dispersed by calculating the modifier dispersion uniformity index UDI.

[0133] D) Finally, add antioxidant, flame retardant and light stabilizer and mix thoroughly; the details are as follows:

[0134] D1) weighing an antioxidant according to a predetermined number of parts W6 (3 parts), weighing a flame retardant according to a number of parts W7 (3 parts), and weighing a light stabilizer according to a number of parts W8 (1 part);

[0135] D2) while maintaining the stirring condition in step C2, first add the antioxidant weighed in step D1, and continue stirring for t6≥5min to ensure that the antioxidant is evenly distributed in the mixture;

[0136] D3) After completing step D2, continue to add the flame retardant weighed in step D1, and maintain the same stirring conditions, and continue stirring for a time t7≥10min;

[0137] D4) After completing step D3, add the light stabilizer weighed in step D1, and maintain the same stirring conditions for a further stirring time t8≥5 min.

[0138] Among them, step D1: determine the weight of antioxidant, flame retardant and light stabilizer, and prepare to add them to the modified uniform mixture. Step D2: while maintaining the original stirring conditions, add antioxidant first, and start timing to ensure that the antioxidant can be evenly distributed in the mixture. Step D3: on the basis of the initial dispersion of antioxidant, continue to add flame retardant, and maintain the same stirring conditions and continue stirring. Step D4: on the basis of the uniform dispersion of antioxidant and flame retardant, add light stabilizer and continue stirring.

[0139] E) subjecting the mixed materials to vacuum degassing treatment; the details are as follows:

[0140] E1) transferring the mixed materials in step D into a closed container and connecting it to a vacuum pump;

[0141] E2) Turn on the vacuum pump and set the vacuum degree to P1, where the range of P1 is: -0.09 MPa to -0.1 MPa, and maintain the vacuum degree for a time t9 ≥ 15 min to remove bubbles in the mixture;

[0142] E3) During step E2, the vacuum degree change is calculated by the formula ΔP=P0-P1, where P0 is the atmospheric pressure and P1 is the set vacuum degree. When the ΔP value reaches a predetermined range, it indicates that the degassing condition has been met;

[0143] E4) After completing step E2, turn off the vacuum pump, and calculate the volume change rate of the deaerated mixture by the formula VC=(V_after-V_before) / V_before*100%, wherein V_after is the volume of the deaerated mixture, and V_before is the volume of the deaerated mixture. When the VC value reaches a predetermined range, it indicates that the deaeration process is completed;

[0144] E5) After completing step E4, if the VC value does not reach the predetermined range, repeat steps E2 to E4 until the requirements are met.

[0145] Among them, step E1: transfer the mixed materials to a closed container and connect the vacuum pump to prepare for vacuum degassing. Step E2: turn on the vacuum pump, set the appropriate vacuum degree, and maintain it for a certain time to remove bubbles in the mixture. Step E3: During the vacuuming process, monitor whether the degassing conditions are met by calculating the vacuum degree change ΔP. Step E4: After the vacuuming is completed, turn off the vacuum pump and calculate the volume change rate VC of the degassing mixture to confirm whether the degassing effect meets the requirements. Step E5: If the volume change rate of the degassing mixture does not reach the predetermined range, the vacuuming step needs to be repeated until the standard is met.

[0146] F) Dipping treatment: Dipping the treated material into a preset mold for curing and molding; specifically:

[0147] F1) pouring the deaerated material in step E into a preset mold, and ensuring that the mold surface is flat and free of bubbles;

[0148] F2) After pouring into the mold, use a vibration table to vibrate for t10≥5min to remove tiny bubbles in the material;

[0149] F3) After vibration, the mold containing the material is placed in a constant temperature oven and cured at a temperature of T2 = 80°C-120°C for a time of t11 = 1-3 hours;

[0150] F4) After completing step F3, the mold is removed and cooled to room temperature T1, and the solidification molding is completed.

[0151] Among them, step F1: pour the deaerated material into a preset mold and ensure that the surface is flat and no bubbles remain. Step F2: after pouring into the mold, use a vibration table to vibrate for a certain period of time to further remove tiny bubbles in the material. Step F3: after vibration, put the mold containing the material into a constant temperature oven for curing. Step F4: after curing is completed, take out the mold and cool it to room temperature.

[0152] Comparative Example 1

[0153] In order to verify the superiority of the food-grade silica gel formula and preparation method thereof proposed in the present invention over the traditional formula, we designed a comparative example in which silica gel was prepared using only the traditional formula and its performance was tested.

[0154] The ingredients of traditional formula silicone are: polydimethylsiloxane matrix (PDMS): 35%, silica filler: 25%, silane coupling agent: 3%, antioxidant: 2%, flame retardant: 1.5%, dispersant: 1%, light stabilizer: 0.5%.

[0155] Specific preparation steps:

[0156] Premixing stage: PDMS and dispersant are weighed in proportion, added into a high-speed mixer, heated to 65°C at a speed of 1000 rpm, and stirred continuously for 15 minutes to reduce the viscosity of PDMS for subsequent dispersion.

[0157] Dispersion stage: Sprinkle the nano-scale silica filler evenly into the pre-mixed PDMS and continue stirring for 20 minutes under the same conditions to ensure that the silica is completely dispersed.

[0158] Chemical modification stage: only add silane coupling agent and continue stirring for 15 minutes.

[0159] Functional additives addition stage: Finally, add antioxidants, flame retardants and light stabilizers in sequence, and continue stirring for 5 minutes to ensure that all additives are evenly distributed.

[0160] Vacuum degassing stage: transfer the mixed materials into a closed container and connect a vacuum pump. Set the vacuum degree to -0.095 MPa and maintain the vacuum degree for 20 minutes to remove bubbles in the mixture.

[0161] Curing and molding stage: Pour the deaerated material into the preset mold and vibrate it on a vibration table for 5 minutes to further remove the tiny bubbles in the material. Then put the mold into a constant temperature oven and cure it at 100℃ for 2 hours.

[0162] Experimental data

[0163] In order to prove the superiority of the food-grade silicone in this application over the traditional formula in terms of tear strength, tensile strength, etc., we conducted the following comparative experiments and recorded the relevant data:

[0164] Experimental Project:

[0165] Tear strength test:

[0166] Traditional formula: 20N / mm.

[0167] Formula for this application: 35N / mm.

[0168] Tensile strength test:

[0169] Traditional formula: 1.5MPa.

[0170] The formula of this application: 2.5MPa.

[0171] High temperature stability test:

[0172] After keeping at 120°C for 24 hours, observe whether the sample has deformation, cracking, etc.

[0173] Traditional recipe: Slightly deformed.

[0174] This application's formula: No significant changes.

[0175] Adhesion performance test:

[0176] The silicone of the present application formulation is used for bonding with different materials (such as glass and metal), and a peeling test is performed after 24 hours.

[0177] Traditional formula: Low bonding strength.

[0178] This application formula: shows good adhesion.

[0179] in conclusion:

[0180] It can be seen from the above experimental data that the food-grade silicone formula of the present application is superior to the products of the traditional formula in terms of tear strength, tensile strength and high temperature stability. In addition, by introducing the epoxy resin modifier, the bonding effect between silicone and other materials is improved, and its application field is broadened. These experimental data strongly prove the effectiveness and superiority of the formula of the present application.

[0181] In summary, the present invention provides a novel food-grade silica gel by adding an appropriate amount of epoxy resin modifier and optimizing the ratio of each component, which not only has excellent mechanical properties but also has good bonding properties. The tear strength and tensile strength of the silica gel are significantly better than those of products with traditional formulas, and the performance can still be maintained stably under high temperature conditions. In addition, by introducing the epoxy resin modifier, the bonding effect between silica gel and other materials is also improved, broadening its application field.

[0182] In addition, this embodiment proposes an application of food-grade silica gel in the field of food packaging. By adding epoxy resin modifier and optimizing the formula ratio, the tear strength and tensile strength of silica gel are significantly improved. The addition of antioxidants and light stabilizers makes silica gel less prone to aging and deterioration during long-term use. The silica gel can be used in various food packaging applications, such as plastic wrap, sealing rings, etc., and can still maintain stable performance in high temperature environments.

[0183] This embodiment successfully prepared a high-performance food-grade silica gel suitable for food packaging applications by optimizing the formula and improving the preparation process. Its superior performance provides a reliable guarantee for the safe preservation of food.

[0184] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A food grade silica gel, characterized in that: The silica gel comprises the following components: 30-40 parts of polydimethylsiloxane matrix; 20-30 parts of silicon dioxide filler; Epoxy resin modifier 5-10 parts; Silane coupling agent 2-5 parts; 1-3 parts of antioxidants; 1-3 parts of flame retardant; Dispersant 0.5-2 parts; Light stabilizer 0.5-1 part.

2. A method for preparing food-grade silica gel according to claim 1, characterized in that: The following steps are involved: A) mixing the polydimethylsiloxane matrix and the dispersant uniformly; B) adding silica filler and continuing stirring until completely dispersed; C) adding epoxy resin modifier and silane coupling agent to carry out chemical modification; D) Finally, add antioxidant, flame retardant and light stabilizer and mix thoroughly; E) subjecting the mixed materials to vacuum degassing treatment; F) Dipping treatment: Dip the treated material into a preset mold for curing and molding.

3. The method for preparing the dipping resin according to claim 2, wherein: The step A comprises the following sub-steps: A1) weighing the polydimethylsiloxane matrix and the dispersant respectively according to the number of parts, wherein the ratio of the polydimethylsiloxane matrix to the dispersant is W1:W2, W1 represents the weight of the polydimethylsiloxane matrix, and W2 represents the weight of the dispersant; A2) adding the weighed polydimethylsiloxane matrix W1 into a high-speed mixer, heating to a temperature T1 = 60 ± 5 ° C at a speed N1 rpm, and continuing stirring for a time t1 ≥ 10 min to reduce the viscosity of the polydimethylsiloxane matrix; A3) When the set temperature T1 is reached, the weighed dispersant W2 is evenly sprinkled into the preheated and stirred polydimethylsiloxane matrix, and stirring is continued under the same conditions until the dispersion is uniform.

4. The method for preparing the dipping resin according to claim 3, wherein: The step B comprises the following sub-steps: B1) weighing a predetermined amount W3 of nano-scale silica filler and preparing to add it to the uniformly mixed mixture of polydimethylsiloxane matrix and dispersant; B2) While maintaining the stirring conditions set in step A2 unchanged, slowly add the silica filler weighed in step B1, and start timing t2≥20min to ensure that the silica is evenly distributed in the mixture.

5. The method for preparing the dipping resin according to claim 4, characterized in that: The step C comprises the following sub-steps: C1) weighing the epoxy resin modifier according to a predetermined number W4, and weighing the silane coupling agent according to a predetermined number W5; C2) while maintaining the stirring condition in step B2, first add the epoxy resin modifier weighed in step C1, stirring time t4 ≥ 10min, so that the epoxy resin is evenly distributed in the mixture; C3) After completing step C2, continue to add the silane coupling agent weighed in step C1, and maintain the same stirring conditions, and continue stirring for a time t5≥15min.

6. The method for preparing the dipping resin according to claim 5, characterized in that: The step D comprises the following sub-steps: D1) weighing the antioxidant according to a predetermined number W6, weighing the flame retardant according to a number W7, and weighing the light stabilizer according to a number W8; D2) while maintaining the stirring condition in step C2, first add the antioxidant weighed in step D1, and continue stirring for t6≥5min to ensure that the antioxidant is evenly distributed in the mixture; D3) After completing step D2, continue to add the flame retardant weighed in step D1, and maintain the same stirring conditions, and continue stirring for a time t7≥10min; D4) After completing step D3, add the light stabilizer weighed in step D1, and maintain the same stirring conditions for a further stirring time t8≥5 min.

7. The method for preparing the dipping resin according to claim 6, wherein: The step E comprises the following sub-steps: E1) transferring the mixed materials in step D into a closed container and connecting it to a vacuum pump; E2) Turn on the vacuum pump, set the vacuum degree to P1, and maintain the vacuum time t9 ≥ 15 min at this vacuum degree to remove bubbles in the mixture; E3) During step E2, the vacuum degree change is calculated by the formula ΔP=P0-P1, where P0 is the atmospheric pressure and P1 is the set vacuum degree. When the ΔP value reaches a predetermined range, it indicates that the degassing condition has been met; E4) After completing step E2, turn off the vacuum pump, and calculate the volume change rate of the deaerated mixture by the formula VC=(V_after-V_before) / V_before*100%, wherein V_after is the volume of the deaerated mixture, and V_before is the volume of the deaerated mixture. When the VC value reaches a predetermined range, it indicates that the deaeration process is completed; E5) After completing step E4, if the VC value does not reach the predetermined range, repeat steps E2 to E4 until the requirements are met.

8. The method for preparing the dipping resin according to claim 7, characterized in that: The step F comprises the following sub-steps: F1) pouring the deaerated material in step E into a preset mold, and ensuring that the mold surface is flat and free of bubbles; F2) After pouring into the mold, use a vibration table to vibrate for t10≥5min to remove tiny bubbles in the material; F3) After vibration, the mold containing the material is placed in a constant temperature oven and cured at a temperature of T2 = 80°C-120°C for a time of t11 = 1-3 hours; F4) After completing step F3, the mold is removed and cooled to room temperature T1, and the solidification molding is completed.

9. The method for preparing the dipping resin according to claim 7, wherein: The vacuum degree P1 ranges from -0.09MPa to -0.1MPa.

10. Use of the food-grade silica gel as claimed in claim 1 in the field of food packaging.

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