Preparation method of low-heat vacuum volatile epoxy adhesive

Abstract

The invention discloses a preparation method of a low-heat vacuum volatile epoxy adhesive, which is characterized in that liquid epoxy resin is epoxy resin NPEL-128R; the diluent is a diluent 1, 6-hexanediol diglycidyl ether; the curing agent is a polyether amine curing agent D-230; the ratio of the mole number of epoxy in the epoxy resin NPEL-128R and the diluent 1, 6-hexanediol diglycidyl ether to the mole number of active hydrogen in the polyether amine curing agent D-230 is 1: 1, the epoxy and the curing agent component are subjected to addition and chain extension through ring opening in the addition curing process, and then the reaction continues to form a stable macromolecular network structure. The addition curing mode has a strict raw material proportion, and a stable and large polymer molecule can be obtained according to an equal mole number reaction. In the reaction process, the epoxy resin and the curing agent amine can participate in the addition reaction strictly according to the equal mole ratio, and the reaction produces a stable macromolecular structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of polymer materials, and particularly relates to a preparation method of a low-temperature vacuum volatile epoxy adhesive. Background Art

[0002] Epoxy resin materials have characteristics such as high strength and good electrical insulation, and are widely used in fields such as machinery, automobiles, electronic appliances, etc. With their penetration ability, they are used for structural bonding or insulation encapsulation. During the insulation encapsulation process, for vacuum-level applications and enclosed spaces such as submarine crew compartments, gases that can corrode electronic devices and harmful substances that are toxic to humans cannot be generated. In a vacuum environment, if there are unreacted low-molecular substances such as additives, impurities, and internally adsorbed gases or water vapor in the material, gas release will occur, which is a relatively common phenomenon, but it will have a great impact on the normal and stable operation of equipment in enclosed spaces. The outgassing of materials will affect the electrical, optical, and crystallinity of the materials, and cause the functions of sensitive devices to decrease or even fail. For the living environment in space, it may also affect life safety.

[0003] For a high-vacuum environment, if there is release of low-molecular substances, including a large amount of gas release such as water vapor, it will cause devices in the vacuum environment, including optical components, electronic components, etc., to be contaminated, and their optical systems, electronic control transmission, etc. will deteriorate, and in extreme cases, the functions will be severely damaged. Especially condensable volatiles will condense on the surface of components, causing problems such as contamination and corrosion of electronic components. And the amount of outgassing is also greater at higher temperatures because the vapor pressure and the rate of chemical reactions increase with temperature.

[0004] For adhesives used in a vacuum environment, the current specification for thermal vacuum outgassing is NASA 1124, which requires that at a temperature of 125 °C and a vacuum of 10 -5 Pa, after 24 hours, the total mass loss TML ≤ 1%, and the condensable volatile matter CVCM ≤ 0.1%.

[0005] Chinese Patent CN106147538A mixes epoxy resins with relatively low epoxy values such as E44, E51, and F51 with organic compounds having low viscosity and high boiling points, which can effectively reduce the viscosity of the combined system. Since high-boiling organic compounds are added, they will not volatilize under normal conditions, so as to achieve the purpose of reducing the viscosity of the combined system without increasing the VOC of the system. This method considers VOC at room temperature / atmospheric pressure, but does not consider volatilization under high temperature and vacuum conditions. And because there are unreacted inert diluents remaining in the cured system, they will volatilize under high temperature and vacuum conditions, failing to meet the requirements of low thermal vacuum volatilization.

[0006] Chinese Patent CN113717339A prepares a low-viscosity modified curing agent by subjecting hyperbranched polyamidoamine, organic amine, cardanol, and aldehyde monomers to a Mannich reaction, and then compounding it with liquid epoxy resin to obtain an adhesive with high tensile shear strength and low volatile content. By preparing hyperbranched polyamidoamine and introducing it into the amine curing agent through chemical modification, a low-viscosity hyperbranched polymer modified curing agent is prepared, and then compounded with liquid epoxy resin to obtain an adhesive with high tensile shear strength and low volatile content. This method only considers the volatile components in the curing agent and prepares a curing agent with a large molecular weight that is not prone to volatilization, having a certain anti-volatilization effect. However, it does not consider the influence of trace low-molecular substances and water vapor contained in the epoxy resin component, filler component, etc. It still cannot meet the requirement of low outgassing rate under long-term high-temperature conditions. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a method for preparing a low-heat vacuum volatile epoxy adhesive. By regulating aspects such as the selection of raw materials and the treatment of raw materials, not only does the reaction itself not produce low-molecular substances that are prone to volatilization, but there are also no residual small-molecular substances in the raw materials and reaction products, thus ensuring the low outgassing rate of the epoxy adhesive under heat vacuum.

[0008] The object of the present invention is achieved through the following technical solutions: A method for preparing a low-heat vacuum volatile epoxy adhesive, comprising the following steps:

[0009] 1) Capillary vacuum distillation: Respectively subject liquid epoxy resin, active epoxy diluent, and curing agent to capillary vacuum distillation to remove low-volatile substances, cool to room temperature to obtain refined raw materials, and take them out and seal them airtight for standby;

[0010] 2) Refine inorganic fillers: Respectively subject silica powder and talc powder to high-temperature heating and drying to remove residual and adsorbed water vapor, cool to room temperature to obtain refined inorganic fillers, and take them out and seal them airtight for standby;

[0011] 3) Prepare component A: Mix the refined liquid epoxy resin, active epoxy diluent, and silica powder described above to obtain component A;

[0012] 4) Prepare component B: Mix the refined curing agent, talc powder, and silica powder described above to obtain component B;

[0013] Comply component A and component B according to an equimolar ratio with a molar ratio of active reaction substances of 1:1 to obtain an epoxy adhesive; wherein, the active reaction substances in component A are liquid epoxy resin with epoxy groups and active epoxy diluent; the active reaction substances in component B are curing agents with active hydrogen.

[0014] In the present invention, the liquid epoxy resin is selected from the commercially available epoxy resin NPEL-128R, with an epoxy equivalent of 190 g / mol, and is purchased from Shenzhen Jiadida New Material Technology Co., Ltd.

[0015] In the present invention, the active diluent 1,6-hexanediol diglycidyl ether is selected from the commercially available diluent XY632, with an epoxy equivalent of 150 g / mol, and is purchased from Anhui Xinyuan Technology Co., Ltd.

[0016] In the present invention, the curing agent is selected from the commercially available polyetheramine curing agent D-230, with an active hydrogen equivalent of 61 g / mol, and is purchased from Dalian Liansheng Trading Co., Ltd.

[0017] Furthermore, in the step 3), the weight ratio of the liquid epoxy resin to the active epoxy diluent in component A is 100:4 to 15; the purpose of adding the diluent is to adjust the formulation viscosity to facilitate the application during use. Adding or not adding the diluent does not affect the thermal vacuum low-volatility effect of the present invention.

[0018] Furthermore, in the step 3), the mass ratio of the silica powder in component A accounts for 10 to 40% of the total weight of component A.

[0019] Furthermore, in the step 4), the mass ratio of the silica powder in component B accounts for 5 to 30% of the total weight of component B; the mass ratio of the talc powder accounts for 0 to 20% of the total weight of component B.

[0020] Furthermore, in the step 1), the capillary vacuum distillation of the liquid epoxy resin, active epoxy diluent or curing agent is completed through the following steps:

[0021] a. Add the raw material to be distilled into the distillation flask and set up the capillary vacuum distillation device;

[0022] b. After starting to heat to the set value, turn on the vacuum system. After the vacuum degree reaches the set value, open the capillary at this temperature and vacuum degree, and let the air in the capillary slowly enter the system. The bubbles enter the liquid surface one by one from the middle of the liquid, and then the low-molecular substances are distilled out under vacuum;

[0023] c. After the distillation is completed, cool to obtain the distilled raw material with low volatile substances removed, take it out and seal it for standby.

[0024] Among them, the vacuum degree of the capillary vacuum distillation of the liquid epoxy resin is -0.08 to -0.095 atm, the temperature is 120 to 150 °C, the capillary air intake speed is 10 to 20 bubbles per minute, and the capillary vacuum distillation time is 2 to 6 hours.

[0025] Among them, the vacuum degree of the capillary vacuum distillation of the active epoxy diluent is -0.08 to -0.095 atm, the temperature is 100 to 120 °C, the capillary air intake speed is 10 to 20 bubbles per minute, and the capillary vacuum distillation time is 2 to 6 hours.

[0026] Among them, the vacuum degree of the capillary vacuum distillation of the curing agent is -0.09 to -0.095 atm, the temperature is 100 to 120 °C, the capillary air intake speed is 10 to 20 bubbles per minute, and the capillary vacuum distillation time is 2 to 6 hours.

[0027] Further, in the step 2), the high-temperature heating and drying temperature of the silica powder and talc powder is 150 °C to 180 °C, and the drying time is 4 to 8 hours.

[0028] Advantages of the present invention:

[0029] 1. In the present invention, the liquid epoxy resin is epoxy resin NPEL-128R; the diluent is diluent 1,6-hexanediol diglycidyl ether; the curing agent is polyetheramine curing agent D-230; and the ratio of the epoxy mole number in the epoxy resin NPEL-128R and the diluent 1,6-hexanediol diglycidyl ether to the active hydrogen mole number in the polyetheramine curing agent D-230 is 1:1. Through the addition curing process, epoxy undergoes ring-opening and addition with the curing agent component, and then continues to react to form a stable macromolecular network structure. This addition curing method has strict raw material ratios. By reacting according to equimolar amounts, a stable large polymer molecule can be obtained. During the reaction process, both the epoxy resin and the curing agent amine can participate in the addition reaction, and react strictly according to the equimolar ratio to produce a stable macromolecular structure. No small molecules are generated during the reaction process, nor are there any residual low-molecular raw materials, ensuring that there are no low-boiling small molecules that are easily extractable remaining in the material. The total volatile matter TML of the adhesive prepared by the present invention is ≤1%, meeting the standard of the current specification NASA 1124 for thermal vacuum outgassing.

[0030] 2. In the present invention, the liquid epoxy resin, the active epoxy diluent, and the curing agent are removed of low-volatile substances by capillary vacuum distillation, and the refined raw materials are obtained after cooling to room temperature. According to the Clausius-Clapeyron equation, when the solution components change from one equilibrium state to another, the relationship between the change in saturated vapor pressure and the enthalpy change is as follows:

[0031]

[0032] Among them, R is the molar gas constant, T is the thermodynamic temperature; P0 is the vapor pressure before the bubbles escape in the capillary, and Pr is the vapor pressure after the bubbles escape in the capillary; The heat absorbed to vaporize 1 mole of liquid is called the molar enthalpy of vaporization of the liquid at that temperature; C E is the difference in integral constants before and after the bubble escapes;

[0033] Since the change in liquid-phase equilibrium is caused by the action of an external force field (the pressure difference inside and outside the capillary), it can be seen that under the condition of constant equilibrium temperature of the liquid system, the molar enthalpy of vaporization increases greatly due to multiple vaporizations, greatly improving the distillation separation efficiency.

[0034] 3. In the present invention, all raw materials are refined to control the low-molecular-weight volatiles during the preparation of raw materials and adhesive solutions.

[0035] 4. In the present invention, the epoxy resin NPEL-128R with high activity is selected because it has a lower viscosity, is not easy to crystallize, is convenient to use, has high activity, good adhesion to the substrate, and a lower price. In contrast, epoxy resins such as E-44 have a high viscosity, and E-20 is a solid, which are not convenient to use. Phenolic epoxy F-44 has a high viscosity and a higher price. NPEL-128R contains less low volatiles and is easy to achieve the purpose of low heat vacuum volatilization in the present invention;

[0036] The diluent is selected as 1,6-hexanediol diglycidyl ether. Based on its two active epoxy groups, it can participate in the curing with the curing agent in the present invention, will not form low-volatile residues, achieve the purpose of low heat vacuum volatilization, and has a good dilution effect, which is beneficial to the construction application of the formulated product. Correspondingly, if non-active diluents such as ethanol and toluene are selected as raw materials, although the dilution effect can be achieved, these materials do not participate in the reaction but are wrapped in the cured product as fillers and will escape under heating and vacuum conditions, failing to achieve the purpose of the invention;

[0037] The polyetheramine curing agent D-230 has a clear molecular structure. When used as the curing agent system of the present invention, it can be accurately metered according to the addition reaction, fully participates in the reaction under suitable conditions, has no residue, and is more likely to achieve the purpose of low heat vacuum volatilization in the present invention. In addition, polyetheramine D-230 has the characteristics of low viscosity and good adhesion, which is also beneficial to the application expansion of the formulated product. Correspondingly, although some mixed amine curing agents are inexpensive, their components are complex and there are materials with multiple active amine structures. Their different structures may have inconsistent curing conditions, some participate in the reaction while some have not started to react, which is likely to "freeze" their active groups in the reactants and cannot be fully cured, and it is also difficult to achieve the purpose of low heat vacuum volatilization in the present invention.

[0038] 5. The adhesive prepared in the present invention has high shear strength, excellent insulation, and low heat vacuum volatility after treatment, and can be used for bonding or encapsulation in a vacuum environment. Detailed implementation mode

[0039] The present invention will be further described in detail below in conjunction with embodiments, but the implementation manners of the present invention are not limited thereto.

[0040] Example 1

[0041] This example provides a preparation method of a low-heat vacuum volatile epoxy adhesive. The dosage of each raw material of component A and component B in this example is shown in Table 1:

[0042] Table 1 Dosage of each raw material of component A and component B in Example 1

[0043]

[0044] The epoxy adhesive is prepared by the following steps in this example:

[0045] 1) Capillary vacuum distillation: The liquid epoxy resin, active epoxy diluent and curing agent are respectively removed of low-volatile substances by capillary vacuum distillation, cooled to room temperature to obtain refined raw materials, and taken out and sealed for standby;

[0046] 2) Refine inorganic fillers. The silica powder and talc powder are respectively removed of residual and adsorbed water vapor by high-temperature heating and drying, cooled to room temperature to obtain refined inorganic fillers, and taken out and sealed for standby;

[0047] 3) Prepare component A. The refined liquid epoxy resin, active epoxy diluent and silica powder are mixed to obtain component A;

[0048] 4) Prepare component B. The refined curing agent, talc powder and silica powder are mixed to obtain component B;

[0049] The component A and component B are formulated according to the dosage of each raw material in Table 1 to obtain the epoxy adhesive;

[0050] Among them, in the step 1), the capillary vacuum distillation of the liquid epoxy resin, active epoxy diluent and curing agent is completed through the following steps:

[0051] a. Add the raw materials to be distilled into a three-necked flask and set up a capillary vacuum distillation device;

[0052] b. After starting to heat to the set value, turn on the vacuum system. After the vacuum degree reaches the set value, open the capillary at this temperature and vacuum degree, and let the air in the capillary slowly enter the system. The bubbles enter the liquid surface one by one from the middle of the liquid, and then the low-molecular substances are distilled out under vacuum;

[0053] c. After the distillation is completed, cool to obtain the distilled raw materials with low-volatile substances removed, take out and seal for standby.

[0054] Among them, the vacuum degree of the capillary vacuum distillation of the epoxy resin is -0.09 atm, the temperature is 150 °C, the capillary air intake speed is 15 bubbles / minute, and the capillary vacuum distillation time is 6 hours;

[0055] Among them, the vacuum degree of the capillary vacuum distillation of the diluent is -0.09 atm, the temperature is 120 °C, the capillary air intake speed is 15 bubbles / minute, and the capillary vacuum distillation time is 4 hours;

[0056] Among them, the vacuum degree of the capillary vacuum distillation of the curing agent is -0.093 atm, the temperature is 120 °C, the capillary air intake speed is 15 bubbles / minute, and the capillary vacuum distillation time is 4 hours;

[0057] In the step 2), the high-temperature heating and drying temperature of the silica powder and talc powder is 150 °C, and the drying time is 6 hours.

[0058] Example 2

[0059] Compared with Example 1, the difference in this example is that the dosage of each raw material of component A and component B in this example is shown in Table 2:

[0060] Table 2 Dosage of each raw material of component A and component B in Example 2

[0061]

[0062] In this example,

[0063] The vacuum degree of the capillary vacuum distillation of the epoxy resin is -0.095 atm, the temperature is 140 °C, the capillary air intake speed is 20 bubbles / minute, and the capillary vacuum distillation time is 4 hours;

[0064] Among them, the vacuum degree of the capillary vacuum distillation of the diluent is -0.095 atm, the temperature is 110 °C, the capillary air intake speed is 20 bubbles / minute, and the capillary vacuum distillation time is 6 hours;

[0065] Among them, the vacuum degree of the capillary vacuum distillation of the curing agent is -0.095 atm, the temperature is 110 °C, the capillary air intake speed is 20 bubbles / minute, and the capillary vacuum distillation time is 6 hours;

[0066] Among them, the high-temperature heating and drying temperature of the silica powder and talc powder is 180 °C, and the drying time is 8 hours;

[0067] The remaining steps are the same as those in Example 1.

[0068] Example 3

[0069] Compared with Example 1, this example is different in that the amounts of each raw material of Component A and Component B in this example are shown in Table 3:

[0070] Table 3 Amounts of Each Raw Material of Component A and Component B in Example 3

[0071]

[0072] In this example, the vacuum degree of the capillary vacuum distillation of the epoxy resin is -0.08 atm, the temperature is 120 °C, the capillary air intake speed is 10 bubbles per minute, and the capillary vacuum distillation time is 2 hours;

[0073] Among them, the vacuum degree of the capillary vacuum distillation of the diluent is -0.08 atm, the temperature is 100 °C, the capillary air intake speed is 10 bubbles per minute, and the capillary vacuum distillation time is 6 hours;

[0074] Among them, the vacuum degree of the capillary vacuum distillation of the curing agent is -0.09 atm, the temperature is 100 °C, the capillary air intake speed is 10 bubbles per minute, and the capillary vacuum distillation time is 2 hours;

[0075] Among them, the high-temperature heating and drying temperature of silica powder and talc powder is 170 °C, and the drying time is 4 hours;

[0076] The remaining steps are the same as those in Example 1.

[0077] Comparative Example 1

[0078] Compared with Example 1, this comparative example is different in that: the amounts of each raw material of Component A and Component B in this comparative example are shown in Table 4:

[0079] Table 4 Amounts of Each Raw Material of Component A and Component B in Comparative Example 1

[0080]

[0081]

[0082] This comparative example prepared an epoxy adhesive by the same method as in Example 1. This comparative example selected an epoxy resin different from that in Example 1. Since the epoxy resin EPLC-818S in this comparative example has a lower viscosity, the diluent can no longer be added. The curing agent used in this comparative example is polyamide, which has a higher viscosity compared with the curing agent D-230 in the example. The comparison of the raw material parameters between this example and those in Example 1 is shown in Table 5:

[0083] Table 5 Raw Material Parameters in Comparative Example 1 and Example 1

[0084]

[0085] In this comparative example, the viscosity of EPLC-818S is lower than that of NPEL-128R in the example, but the output is low, it is not easy to obtain, and the price is much higher. In Comparative Example 1, the properties after curing of the curing agent Aradur 140-3 are also good, but its viscosity is greater, it is not convenient to use, and at the same time its price is higher, which is not suitable for large-scale industrial production.

[0086] Comparative Example 2

[0087] The difference between this comparative example and Example 1 is that: the dosage of each raw material in Component A and Component B in this comparative example is shown in Table 6:

[0088] Table 6 Dosage of each raw material in Component A and Component B in Comparative Example 2

[0089]

[0090] The epoxy adhesive was prepared according to the same method as in Example 1. In this comparative example, the ratio of the epoxy mole number in Component A to the active hydrogen mole number in Component B is 1:1.3.

[0091] Comparative Example 3

[0092] In this comparative example, the types and dosages of each raw material in Component A and Component B are the same as those in Example 1. Compared with Example 1, the raw material refining step was deleted during the preparation of the epoxy adhesive, and the epoxy adhesive was prepared through the following steps:

[0093] 1) Prepare Component A, and mix liquid epoxy resin, active epoxy diluent and silica powder to obtain Component A;

[0094] 2) Prepare Component B, and mix the curing agent, talcum powder and silica powder to obtain Component B.

[0095] Comparative Example 4

[0096] In this comparative example, the types and dosages of each raw material in Component A and Component B are the same as those in Example 1. Compared with Example 1, during the preparation of the epoxy adhesive, the liquid epoxy resin, active epoxy diluent and curing agent were respectively removed of low volatile substances by conventional vacuum distillation instead of capillary vacuum distillation, and the remaining steps were the same as those in Example 1.

[0097] The epoxy adhesive was prepared through the following steps in this comparative example:

[0098] 1) Vacuum distillation: respectively remove the low volatile substances of the liquid epoxy resin, active epoxy diluent and curing agent by vacuum distillation, cool to room temperature to obtain refined raw materials, take out and seal them airtight for standby;

[0099] 2) Refined inorganic fillers: The silica powder and talcum powder are respectively dried by high-temperature heating to remove the residual and adsorbed water vapor, and then cooled to room temperature to obtain the refined inorganic fillers, which are taken out and sealed airtight for standby.

[0100] 3) Preparation of Component A: The refined liquid epoxy resin, active epoxy diluent and silica powder are mixed to obtain Component A.

[0101] 4) Preparation of Component B: The refined curing agent, talcum powder and silica powder are mixed to obtain Component B.

[0102] Components A and B are formulated according to the dosages of each raw material in Table 1 to obtain the epoxy adhesive.

[0103] Among them, in step 1), the vacuum distillation of the liquid epoxy resin, active epoxy diluent and curing agent is completed through the following steps:

[0104] a. Add the raw materials to be distilled into a three-necked flask and set up a vacuum distillation device.

[0105] b. After starting to heat to the set value, turn on the vacuum system. After the vacuum degree reaches the set value, start distillation.

[0106] c. After distillation is completed, cool to obtain the raw materials to be distilled with low volatiles removed, which are taken out and sealed airtight for standby.

[0107] Among them, the vacuum degree of the vacuum distillation of the epoxy resin is -0.09 atm, the temperature is 150 °C, and the time is 6 hours.

[0108] Among them, the vacuum degree of the vacuum distillation of the diluent is -0.09 atm, the temperature is 120 °C, and the vacuum distillation time is 4 hours.

[0109] Among them, the vacuum degree of the vacuum distillation of the curing agent is -0.093 atm, the temperature is 120 °C, and the distillation time is 4 hours.

[0110] In step 2), the high-temperature heating and drying temperature of the silica powder and talcum powder is 150 °C, and the drying time is 6 hours.

[0111] Performance test experiment

[0112] After mixing the Components A and B of the adhesives prepared in Examples 1 to 3 and Comparative Examples 1 to 4 above and curing them at 80 °C for 3 hours, the cured adhesives are obtained. The performance tests of the cured adhesives prepared in Examples 1 to 3 and Comparative Examples 1 to 4 are carried out, and the results are shown in Table 7, where TML is the total weight loss; CVCM is the collected volatile condensate.

[0113] In the present invention, the test standards for performance testing are QJ1558A - 2012 "Test Method for Volatile Performance of Materials under Vacuum Conditions" and Q / W776 - 98 "Gas Evolution Screening Method for Scrap Metal Materials Used in Satellites". The test conditions are as follows: the vacuum degree is better than 1×10 -3 Pa; the temperature of the sample being heated: 125 ± 1 °C; the temperature for collecting condensable volatiles: 25 ± 1 °C; the thermal vacuum time is 24 Hrs;

[0114] The specific test steps are as follows.

[0115] a. Pretreatment of the vacuum chamber and the sample chamber. Clean the vacuum chamber and the sample chamber with organic solvents, evacuate the air. When the pressure reaches 1×10 -4 Pa, heat the sample chamber to 150 ± 5 °C and keep it warm for 4 hours. Cool the sample chamber to room temperature and close the high - vacuum valve.

[0116] b. Cleaning of the empty boat and the collection plate. Place the sample boat in an environment with a temperature of 23 ± 2 °C and a relative humidity of 55 ± 10% for 24 hours. Bake the collection plate in a vacuum box with a pressure below 1 Pa and a minimum temperature of 125 °C for 16 hours. After baking, place the sample boat and the collection plate in a dry and miscellaneous silica gel drying tank for 24 hours.

[0117] c. Sample pretreatment. Take out the sample boat from the drying container, weigh it, add 100 - 300 mg of the sample, put it into a weighing bottle, and place it uncovered in a constant - temperature and constant - humidity box with a temperature of 23 ± 2 °C and a relative humidity of 55 ± 10% for 24 hours.

[0118] d. Take out the weighing bottle after covering it, weigh the sample boat containing the sample within 2 minutes at an ambient temperature of 23 ± 2 °C, and then put it back.

[0119] e. Put the sample boat containing the sample into the sample chamber. Place 3 specimens for each material, and randomly reserve 3 sample chambers with only empty sample boats. Tighten the end - cover of the sample chamber.

[0120] f. Take out the collection plate from the drying tank, weigh it, and then install it on the water - cooled base.

[0121] g. Evacuate the air. The time from atmospheric pressure to 7×10 -3 Pa should not exceed 1 hour, and at the same time, control the temperature of the collection plate to 25 ± 1 °C.

[0122] h. Heat the sample chamber. The temperature should reach 125 ± 1 °C within 1 hour and keep it warm for 24 hours.

[0123] i. Close the high - vacuum valve, stop heating the sample chamber, and fill the vacuum chamber with dry high - purity nitrogen with a purity not less than 99%. The pressure should be higher than atmospheric pressure by 1×10 4 ~3×10 4 Pa.

[0124] j. After the sample chamber cools down to 50 °C, turn off the cooling water of the collection plate, open the vacuum chamber, quickly place the sample boat containing the sample into the weighing bottle, uncover it, and put it into the drying tank. At the same time, put the collection plate into the drying tank. When the sample is close to room temperature, weigh the sample boat containing the sample, and then weigh the collection plate.

[0125] Table 7 Performance of the adhesives prepared in Examples 1-3 and Comparative Examples 1-4

[0126]

[0127]

[0128] As can be seen from Table 7, by using the method of the present invention, an adhesive meeting the requirements of low thermal vacuum volatilization can be prepared. Comparing Example 2 with Example 1, the amount of raw materials changes, the amount of diluent increases, and the filler decreases, resulting in a decrease in viscosity, which is suitable for uses such as bonding and encapsulation that require good fluidity with low viscosity; in Example 3, the filler increases and the viscosity becomes larger, which is suitable for bonding uses that require better gap filling ability.

[0129] In Comparative Example 1, different raw materials from those in the examples were used, and the treatment method proposed by the present invention was still adopted, and an adhesive with low thermal vacuum volatilization could still be prepared, but its cost was high and it was not suitable for industrial production; in Comparative Example 2, the raw materials were exactly the same as those in Example 1, and only the ratio of reactive groups was not in accordance with the 1:1 ratio proposed by the present invention. Although the raw material refining method proposed by the present invention was also adopted, the purpose of low thermal vacuum volatilization could not be achieved; in Comparative Example 3, the types, ratios, and molar ratios of active groups of the raw materials were exactly the same as those in Example 1, but the raw material refining treatment process of the present invention was not adopted, and the purpose of low thermal vacuum volatilization could not be achieved either; in Comparative Example 4, the same types, ratios, and equimolar ratios of active groups of the raw materials as those in Example 1 were used, but ordinary distillation was used for the liquid raw materials instead of capillary vacuum distillation. Compared with Comparative Example 3, the thermal vacuum volatility was improved, but the requirement of total volatile matter TML ≤ 1% could still not be achieved, and it did not meet the current standard of NASA 1124 for thermal vacuum outgassing regulations.

[0130] It can be understood that the present invention is described through some examples. Those skilled in the art know that without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and examples. In addition, under the teaching of the present invention, these features and examples can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific examples disclosed herein, and all examples falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A preparation method of a low-heat vacuum volatile epoxy adhesive, characterized in that: It includes the following steps: 1) Capillary vacuum distillation: Liquid epoxy resin, active epoxy diluent and curing agent are respectively removed of low volatile substances by capillary vacuum distillation, cooled to room temperature to obtain refined raw materials, taken out, sealed and reserved for use; 2) Refined inorganic fillers: Silicon micropowder and talcum powder are respectively removed of residual and adsorbed water vapor by high-temperature heating and drying, cooled to room temperature to obtain refined inorganic fillers, taken out, sealed and reserved for use; 3) Preparation of component A: The refined liquid epoxy resin, active epoxy diluent and silicon micropowder are mixed to obtain component A; 4) Preparation of component B: The refined curing agent, talcum powder and silicon micropowder are mixed to obtain component B; Components A and B are formulated in an equimolar ratio with the molar ratio of active reaction substances being 1:1 to obtain an epoxy adhesive; Among them, the active reaction substances in component A are liquid epoxy resin with epoxy groups and active epoxy diluent; the active reaction substances in component B are curing agents with active hydrogen; The liquid epoxy resin is selected from commercially available epoxy resin NPEL-128R with an epoxy equivalent of 190 g / mol; The active diluent is 1,6-hexanediol diglycidyl ether with an epoxy equivalent of 150 g / mol; The curing agent is selected from commercially available polyetheramine curing agent D-230 with an active hydrogen equivalent of 61 g / mol.

2. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 1, wherein: In the step 1), the capillary vacuum distillation of liquid epoxy resin, active epoxy diluent or curing agent is completed through the following steps: a. Add the raw material to be distilled into the distillation flask and set up the capillary vacuum distillation device; b. After starting to heat to the set value, turn on the vacuum system. After the vacuum degree reaches the set value, open the capillary at this temperature and vacuum degree, and let the air in the capillary slowly enter the system. The bubbles enter the liquid surface one by one from the middle of the liquid, and then the low-molecular substances are distilled out under vacuum; c. After the distillation is completed, cool to obtain the distilled raw material with low volatile substances removed, take out, seal and reserve for use.

3. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 2, wherein: The vacuum degree of the capillary vacuum distillation of the epoxy resin is -0.08 to -0.095 atm, the temperature is 120 to 150 °C, the capillary air intake speed is 10 to 20 bubbles per minute, and the capillary vacuum distillation time is 2 to 6 hours.

4. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 2, characterized in that: The vacuum degree of the capillary vacuum distillation of the diluent is -0.08 to -0.095 atm, the temperature is 100 to 120 °C, the capillary air intake speed is 10 to 20 bubbles per minute, and the capillary vacuum distillation time is 2 to 6 hours.

5. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 2, characterized in that: The vacuum degree of the capillary vacuum distillation of the curing agent is -0.09 to -0.095 atm, the temperature is 100 to 120 °C, the capillary air intake speed is 10 to 20 bubbles per minute, and the capillary vacuum distillation time is 2 to 6 hours.

6. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 1, characterized in that: In the step 2), the high-temperature heating and drying temperature of the silicon micropowder or talcum powder is 150 °C to 180 °C, and the drying time is 4 to 8 hours.

7. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 1, characterized in that: In the step 3), the weight ratio of the liquid epoxy resin to the active epoxy diluent in component A is 100:4 to 15.

8. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 1, characterized in that: In the step 3), the mass ratio of the silicon micropowder in component A accounts for 10 to 40% of the total weight of component A.

9. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 1, characterized in that: In the step 4), the mass proportion of silica powder in component B is 5-30% of the total weight of component B.

10. The preparation method of a low-heat vacuum volatile epoxy adhesive according to claim 1, characterized in that: In the step 4), the mass proportion of talcum powder is 0-20% of the total weight of component B.

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