Room temperature curing two-component sealant for microwave oven and preparation method and application thereof

Abstract

The application belongs to the technical field of high polymer sealing material, and particularly relates to a room-temperature curing two-component sealant for microwave ovens and a preparation method and application thereof. The sealant comprises component A and component B. The component A comprises hydroxyl-terminated polydimethylsiloxane, acid-resistant filler and moisture carrier. The component B comprises alkoxyl-terminated polydimethylsiloxane, acid-resistant filler, thixotropic filler, heat-resistant filler and auxiliary agent. The acid-resistant fillers in the component A and the component B are independently selected from at least one of the following: silicon powder with a particle size of 1-10 microns, nano-deposited barium sulfate and talc powder. The thixotropic filler is hydrophobic fumed white carbon black treated by silazane or alkoxysilane. The raw material components of the sealant are jointly added and interacted, so that the sealant has good high-temperature resistance and corrosion resistance, can be quickly cured, and the formed adhesive strip is in a semi-flowing state, the head and tail lap joints are well fused, and the aesthetic requirements of the microwave oven cavity can be met.

Description

Technical Field

[0001] This invention belongs to the field of polymer sealing materials technology, and specifically relates to a room temperature curing two-component sealant for microwave ovens, its preparation method, and its application. Background Technology

[0002] With the improvement of people's living standards and the acceleration of the pace of life, the popularity of microwave ovens in China has greatly increased. As an adhesive material for bonding the microwave oven cavity to the glass microcrystalline panel, sealant is indispensable. In microwave oven applications, high temperature resistance, acid and alkali corrosion resistance, and the aesthetic appearance of the adhesive strip at the junction of the cavity and the microcrystalline panel all place high demands on the performance of the sealant. Furthermore, the large-scale, automated, and efficient manufacturing of microwave ovens also places increasingly higher demands on the curing performance of the sealant; a faster curing speed is necessary to match the rapid turnover requirements of production lines.

[0003] Currently, the sealants used for bonding microwave oven cavities are mainly room-temperature curing single-component silicone sealants and addition-cure thermosetting silicone sealants. Single-component sealants, due to their curing mechanism, have a slow curing rate, generally requiring three to seven days to achieve initial curing and form a certain degree of adhesion, severely impacting the production efficiency of microwave oven manufacturing. Addition-cure thermosetting adhesives require significant equipment investment, such as constructing high-temperature drying tunnels, placing high demands on production space, capital investment, and subsequent energy costs. Furthermore, addition-cure silicone sealants, due to their poor self-adhesion, require matching primer or plasma equipment. Primer solvents generally contain harmful components such as toluene, negatively impacting environmental protection and production line structure.

[0004] Therefore, there is an urgent need to provide a room temperature curing two-component sealant for microwave ovens. This sealant can cure quickly, has good high temperature resistance and acid and alkali corrosion resistance, and the sealant strip formed is semi-flowing with good fusion at the joints. It can meet the aesthetic requirements of microwave oven cavities and is green and environmentally friendly, which is friendly to the environment and human body. Summary of the Invention

[0005] This invention aims to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions. This invention provides a room-temperature curing two-component sealant for microwave ovens. This sealant can cure rapidly and has good high-temperature resistance and acid / alkali corrosion resistance. The sealant forms a semi-flowing strip with good fusion at the joints, meeting the aesthetic requirements of microwave oven cavities. Furthermore, it is environmentally friendly and beneficial to both the environment and human health.

[0006] The inventive concept of this invention is as follows: Component A is obtained by adding hydroxyl-terminated polydimethylsiloxane, acid-resistant filler, and a moisture carrier; Component B is obtained by adding alkoxy-terminated polydimethylsiloxane, acid-resistant filler, thixotropic filler, heat-resistant filler, and additives. The combined addition and interaction of these components enable the sealant to possess excellent high-temperature resistance, acid and alkali corrosion resistance, rapid curing, and a semi-flowing adhesive strip with good fusion at the joints, meeting the aesthetic requirements of microwave oven cavities. This invention also adjusts the thixotropic properties, leveling properties, high-temperature resistance, and corrosion resistance of the sealant by compounding specific types and particle sizes of acid-resistant fillers, thixotropic fillers, and heat-resistant fillers. Furthermore, the addition of additives and a moisture carrier allows the sealant to cure rapidly, even completing curing in 10-30 minutes, significantly shortening the curing time.

[0007] Therefore, a first aspect of the present invention provides a room temperature curing two-component sealant for microwave ovens.

[0008] Specifically, a microwave oven room temperature curing two-component sealant includes component A and component B;

[0009] Component A includes: hydroxyl-terminated polydimethylsiloxane, acid-resistant filler, and moisture carrier;

[0010] Component B includes: alkoxy-terminated polydimethylsiloxane, acid-resistant filler, thixotropic filler, heat-resistant filler, and additives;

[0011] The acid-resistant fillers of component A and component B are each independently selected from at least one of silica micro powder, nano-precipitated barium sulfate, and talc powder, with a particle size of 1-10 μm.

[0012] The thixotropic filler is a hydrophobic fumed silica that has been surface-treated with silazane or alkoxysilane.

[0013] The heat-resistant filler is selected from at least one of cerium oxide, iron oxide red, zirconium oxide, and titanium dioxide;

[0014] The additives include crosslinking agents.

[0015] Specifically, the particle size of acid-resistant fillers needs to be within a certain range. If the particle size is too small, it is not easy to disperse, has high viscosity, and the finished product has particles. When applied to microwave ovens, the appearance is poor and it is difficult to meet the aesthetic requirements of the cavity. If the particle size is too large, it will affect the adhesion and mechanical properties of the sealant, such as the strength will be too low.

[0016] Specifically, hydrophobic fumed silica has fewer hydroxyl groups on its surface, reducing complex reactions with coupling agents, etc. In addition, compared with hydrophilic fumed silica, hydrophobic fumed silica has a relatively smaller impact on increasing the viscosity of the sealant when the same amount is added, thus avoiding excessively high viscosity that may affect construction.

[0017] Preferably, at 25°C, the viscosity of the hydroxyl-terminated polydimethylsiloxane is 1300-22000 mPa·s; and at 25°C, the viscosity of the alkoxy-terminated polydimethylsiloxane is 900-22000 mPa·s.

[0018] More preferably, at 25°C, the viscosity of the hydroxyl-terminated polydimethylsiloxane is 1500-20000 mPa·s; and at 25°C, the viscosity of the alkoxy-terminated polydimethylsiloxane is 1000-20000 mPa·s.

[0019] Preferably, the moisture carrier includes at least one of precipitated silica, molecular sieve, and activated carbon.

[0020] Preferably, the specific surface area of ​​the thixotropic filler is 110-440 m². 2 / g.

[0021] More preferably, the thixotropic filler has a specific surface area of ​​120-400 m². 2 / g.

[0022] Preferably, the additives also include coupling agents and catalysts.

[0023] Preferably, the crosslinking agent is selected from at least one of methyltrimethoxysilane, vinyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane, polymethyltriethoxysilane, vinyltriethoxysilane, 1,2-bis(trimethoxysilyl)ethane, tetraethoxysilane, tetrapropoxysilane, tetraethoxysilane oligomer, phenyltrimethoxysilane, methyltributylone oxime silane, vinyltributylone oxime silane, and tetrabutylone oxime silane.

[0024] Preferably, the coupling agent is selected from at least one of 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 2-aminoethyl-3-aminopropyltriethoxysilane, 3-diethylenetriaminopropylmethyldimethoxysilane, 3-diethylenetriaminopropyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, 3-(N-cyclohexylamino)propyltrimethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, and N,N-dimethyl-3-aminopropyltrimethoxysilane.

[0025] Preferably, the catalyst is selected from at least one of dibutyltin dilaurate, dioctyltin dilaurate, and dibutyltin diacetate.

[0026] Preferably, component A further includes a plasticizer, and component B further includes a coloring filler; and by weight, component A includes 100 parts of hydroxyl-terminated polydimethylsiloxane, 20-120 parts of acid-resistant filler, 1-5 parts of water carrier, and 0-10 parts of plasticizer; component B includes: 100 parts of alkoxy-terminated polydimethylsiloxane, 20-120 parts of acid-resistant filler, 1-6 parts of thixotropic filler, 5-15 parts of heat-resistant filler, 1-5 parts of coloring filler, 6-12 parts of crosslinking agent, 3-10 parts of coupling agent, and 0.1-1 parts of catalyst.

[0027] Preferably, the plasticizer is dimethyl silicone oil, and the viscosity of the plasticizer at 25°C is 90-1100 mPa·s.

[0028] More preferably, the viscosity of the plasticizer at 25°C is 100-1000 mPa·s.

[0029] Preferably, the coloring filler is selected from at least one of pigment carbon black and channel black.

[0030] Preferably, the volume ratio of component A to component B is 1:0.8-1.2.

[0031] More preferably, the volume ratio of component A to component B is 1:1.

[0032] A second aspect of the present invention provides a method for preparing the microwave oven room temperature curing two-component sealant described in the first aspect of the present invention.

[0033] Specifically, a method for preparing a microwave oven room temperature curing two-component sealant includes the following steps:

[0034] (1) Mix the raw materials of component A to obtain component A;

[0035] (2) Mix the raw materials of component B to obtain component B; component A and component B constitute the sealant.

[0036] Preferably, in step (1), the mixing is carried out under the condition of cooling water being introduced.

[0037] Preferably, in step (1), after mixing, the mixture is first stirred and dispersed; the revolution speed of the stirring and dispersion is 15-50Hz, the dispersion speed is 15-50Hz, and the stirring and dispersion time is 1-3h; then, the mixture is stirred for 8-22min under vacuum conditions to remove bubbles, and the vacuum degree of the vacuum conditions is -0.07 to -0.10MPa.

[0038] More preferably, in step (1), after mixing, the mixture is first stirred and dispersed; the revolution speed of the stirring and dispersion is 30-40Hz, the dispersion speed is 30-40Hz, and the stirring and dispersion time is 1.5-2.5h; then, the mixture is stirred for 10-20min under vacuum conditions to remove bubbles, and the vacuum degree of the vacuum conditions is -0.08 to -0.10MPa.

[0039] Preferably, in step (2), the alkoxy-terminated polydimethylsiloxane, acid-resistant filler, thixotropic filler, and heat-resistant filler are first mixed, and then an additive is added to obtain component B.

[0040] In a further preferred embodiment, in step (2), the alkoxy-terminated polydimethylsiloxane, acid-resistant filler, thixotropic filler, heat-resistant filler, and coloring filler are first mixed, and then an additive is added to obtain component B.

[0041] Preferably, in step (2), the mixture is first heated and stirred under vacuum to obtain a mixture, and then an additive is added to obtain component B.

[0042] Preferably, the vacuum degree of the vacuum condition is -0.07 to -0.10 MPa.

[0043] More preferably, the vacuum degree of the vacuum condition is -0.08 to -0.10 MPa.

[0044] Preferably, the heating temperature is 100-140℃, the revolution speed of the stirring and dispersing is 27-44Hz, the dispersion speed is 27-44Hz, and the stirring and dispersing time is 1-3h.

[0045] More preferably, the heating temperature is 110-130℃, the revolution speed of the stirring and dispersing is 30-40Hz, the dispersion speed is 30-40Hz, and the stirring and dispersing time is 1.5-2.5h.

[0046] Preferably, in step (2), the mixture is first cooled to below 45°C, then the additives are added, and the mixture is stirred and dispersed under cooling water and vacuum conditions to obtain component B.

[0047] Preferably, the vacuum degree of the vacuum condition is -0.07 to -0.10 MPa; the revolution speed of the stirring and dispersing is 16-25 Hz, the dispersion speed is 16-25 Hz, and the stirring and dispersing time is 18-65 min.

[0048] More preferably, the vacuum degree of the vacuum condition is -0.08 to -0.10 MPa; the revolution speed of the stirring and dispersing is 18-22 Hz, the dispersion speed is 18-22 Hz, and the stirring and dispersing time is 20-60 min.

[0049] Specifically, component A and component B are separately sealed and packaged, and can be mixed in a certain volume ratio before use.

[0050] A third aspect of the present invention provides an application of the room-temperature curing two-component sealant for microwave ovens described in the first aspect of the present invention in the field of electrical appliances.

[0051] Compared with the prior art, the beneficial effects of the technical solution provided by the present invention are as follows:

[0052] (1) The raw materials of components A and B of the sealant of the present invention are added together and interact with each other, so that the sealant has good high temperature resistance and acid and alkali corrosion resistance, can be cured quickly, and the formed strip is semi-flowing with good fusion at the joints, which can meet the aesthetic requirements of microwave oven cavity.

[0053] (2) The present invention also adjusts the thixotropic properties, leveling properties, high temperature resistance and acid and alkali corrosion resistance of the sealant by compounding specific types and particle sizes of acid-resistant fillers, thixotropic fillers and heat-resistant fillers.

[0054] (3) This invention does not contain any solvents with harmful components, making it green and environmentally friendly, and friendly to the environment and human body. In addition, due to its fast curing speed, it can improve production efficiency, thereby meeting the needs of large-scale, automated and efficient production. Detailed Implementation

[0055] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0056] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0057] Example 1

[0058] A microwave oven room temperature curing two-component sealant, comprising component A and component B;

[0059] By weight, component A comprises: 100 parts of hydroxyl-terminated polydimethylsiloxane with a viscosity of 1500 mPa·s at 25°C, 10 parts of dimethyl silicone oil with a viscosity of 100 mPa·s at 25°C, 120 parts of silica powder with a particle size of 1.5 μm, and 5 parts of precipitated silica.

[0060] By weight, component B comprises: 100 parts of alkoxy-terminated polydimethylsiloxane with a viscosity of 1000 mPa·s at 25°C; 120 parts of silica powder with a particle size of 10 μm; and a specific surface area of ​​400 m² / g. 2 / g of hydrophobic fumed silica 3 parts, cerium oxide 5 parts, pigment carbon black 5 parts, methyltrimethoxysilane 8 parts, 1,2-bis(trimethoxysilyl)ethane 4 parts, 2-aminoethyl-3-aminopropyltrimethoxysilane 3 parts, 3-diethylenetriaminepropyltrimethoxysilane 2 parts, and dibutyltin diacetate 0.1 parts.

[0061] A method for preparing a microwave oven room temperature curing two-component sealant includes the following steps:

[0062] (1) Under the condition of cooling water, a power mixer was used to mix and disperse hydroxyl-terminated polydimethylsiloxane, dimethyl silicone oil, silica powder with a particle size of 1.5 μm and precipitated silica in parts by weight. The stirring and dispersion speed was 30 Hz and the dispersion speed was 30 Hz. The stirring and dispersion time was 2 h. Then, a vacuum was turned on with a vacuum degree of -0.08 MPa and stirring was continued for 10 min to remove bubbles. Component A was obtained and sealed for storage.

[0063] (2) Using a power mixer, alkoxy-terminated polydimethylsiloxane, silica powder with a particle size of 10 μm, and a specific surface area of ​​400 m² are mixed. 2 Hydrophobic fumed silica, cerium oxide, and pigment carbon black were mixed in parts by weight, heated and dispersed under vacuum conditions (vacuum degree -0.08 MPa, heating temperature 110℃, stirring speed 30 Hz, dispersion speed 30 Hz, stirring and dispersion time 2 h) to obtain a mixture. After cooling the mixture to 40℃, methyltrimethoxysilane, 1,2-bis(trimethoxysilyl)ethane, 2-aminoethyl-3-aminopropyltrimethoxysilane, 3-diethylenetriaminepropyltrimethoxysilane, and dibutyltin diacetate were added to the mixture in parts by weight. Circulating cooling water was introduced, and vacuum was turned on for stirring and dispersion (vacuum degree -0.08 MPa, stirring speed 20 Hz, dispersion speed 20 Hz, stirring and dispersion time 20 min) to obtain component B, which was then sealed and stored.

[0064] Example 2

[0065] A microwave oven room temperature curing two-component sealant, comprising component A and component B;

[0066] By weight, component A includes: 100 parts of hydroxyl-terminated polydimethylsiloxane with a viscosity of 5000 mPa·s at 25°C, 5 parts of dimethyl silicone oil with a viscosity of 500 mPa·s at 25°C, 80 parts of silica powder with a particle size of 5 μm, and 2 parts of activated carbon.

[0067] By weight, component B comprises: 100 parts of alkoxy-terminated polydimethylsiloxane with a viscosity of 5000 mPa·s at 25°C, 50 parts of silica powder with a particle size of 3 μm, and a specific surface area of ​​170 m² / g. 2 / g of hydrophobic fumed silica 3.5 parts, cerium oxide 10 parts, pigment carbon black 3 parts, methyltrimethoxysilane 5 parts, 1,2-bis(trimethoxysilyl)ethane 2 parts, 3-aminopropyltrimethoxysilane 2 parts, 3-diethylenetriaminopropyltrimethoxysilane 1 part, 3-glycidylpropyltrimethoxysilane 2 parts, and dibutyltin dilaurate 0.3 parts.

[0068] A method for preparing a microwave oven room temperature curing two-component sealant includes the following steps:

[0069] (1) Under the condition of cooling water, a power mixer was used to mix and disperse hydroxyl-terminated polydimethylsiloxane, dimethyl silicone oil, silica powder with a particle size of 5μm and activated carbon according to the weight parts. The revolution speed of the stirring and dispersion was 35Hz, the dispersion speed was 35Hz, and the stirring and dispersion time was 2.5h. Then, the vacuum was turned on and the vacuum degree was -0.09MPa. Stirring was continued and the foam was removed for 15min to obtain component A, which was then sealed and stored.

[0070] (2) Using a power mixer, alkoxy-terminated polydimethylsiloxane, silica powder with a particle size of 3 μm, and a specific surface area of ​​170 m² are mixed. 2 / g of hydrophobic fumed silica, cerium oxide, and pigment carbon black were mixed in parts by weight, heated and stirred under vacuum conditions (vacuum degree -0.09 MPa, heating temperature 120℃, stirring speed 35 Hz, dispersion speed 35 Hz, stirring and dispersion time 2.5 h) to obtain a mixture. After cooling the mixture to 35℃, methyltrimethoxysilane, 1,2-bis(trimethoxysilyl)ethane, 3-aminopropyltrimethoxysilane, 3-diethylenetriaminopropyltrimethoxysilane, 3-glycidylpropyltrimethoxysilane, and dibutyltin dilaurate were added to the mixture in parts by weight. Circulating cooling water was introduced, and vacuum was turned on for stirring and dispersion (vacuum degree -0.09 MPa, stirring speed 18 Hz, dispersion speed 18 Hz, stirring and dispersion time 30 min) to obtain component B, which was then sealed and stored.

[0071] Example 3

[0072] A microwave oven room temperature curing two-component sealant, comprising component A and component B;

[0073] By weight, component A includes: 100 parts of hydroxyl-terminated polydimethylsiloxane with a viscosity of 5000 mPa·s at 25°C, 1 part of dimethyl silicone oil with a viscosity of 1000 mPa·s at 25°C, 100 parts of silica powder with a particle size of 3 μm, and 3 parts of molecular sieve.

[0074] By weight, component B comprises: 100 parts of alkoxy-terminated polydimethylsiloxane with a viscosity of 20000 mPa·s at 25°C; 80 parts of nano-precipitated barium sulfate with a particle size of 2 μm and a specific surface area of ​​150 m². 2 / g of hydrophobic fumed silica 1 part, cerium oxide 15 parts, pigment carbon black 4 parts, methyltrimethoxysilane 10 parts, 3-aminopropyltriethoxysilane 7 parts, 3-diethylenetriaminopropyltrimethoxysilane 3 parts, and dibutyltin dilaurate 0.5 parts.

[0075] A method for preparing a microwave oven room temperature curing two-component sealant includes the following steps:

[0076] (1) Under the condition of cooling water, a power mixer was used to mix and disperse hydroxyl-terminated polydimethylsiloxane, dimethyl silicone oil, silica powder with a particle size of 3μm and molecular sieve according to the weight parts. The revolution speed of the stirring and dispersion was 40Hz, the dispersion speed was 40Hz, and the stirring and dispersion time was 1.5h. Then the vacuum was turned on and the vacuum degree was -0.095MPa. Stirring was continued and the foam was removed for 20min to obtain component A, which was then sealed and stored.

[0077] (2) Using a power mixer, alkoxy-terminated polydimethylsiloxane, 2μm-sized nano-precipitated barium sulfate, and 150m² specific surface area were mixed. 2 / g of hydrophobic fumed silica, cerium oxide, and pigment carbon black were mixed in parts by weight, heated and stirred under vacuum conditions (vacuum degree -0.095MPa, heating temperature 130℃, stirring speed 40Hz, dispersion speed 40Hz, stirring and dispersion time 1.5h) to obtain a mixture. After cooling the mixture to 40℃, methyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-diethylenetriaminopropyltrimethoxysilane, and dibutyltin dilaurate were added to the mixture in parts by weight. Circulating cooling water was introduced, and vacuum was turned on for stirring and dispersion (vacuum degree -0.095MPa, stirring speed 20Hz, dispersion speed 20Hz, stirring and dispersion time 40min) to obtain component B, which was then sealed and stored.

[0078] Example 4

[0079] A microwave oven room temperature curing two-component sealant, comprising component A and component B;

[0080] By weight, component A includes: 100 parts of hydroxyl-terminated polydimethylsiloxane with a viscosity of 10000 mPa·s at 25°C, 3 parts of dimethyl silicone oil with a viscosity of 300 mPa·s at 25°C, 80 parts of silica powder with a particle size of 5 μm, and 5 parts of activated carbon.

[0081] By weight, component B comprises: 100 parts of alkoxy-terminated polydimethylsiloxane with a viscosity of 20000 mPa·s at 25°C; 60 parts of nano-precipitated barium sulfate with a particle size of 3 μm; and a specific surface area of ​​150 m² / g. 2 / g of hydrophobic fumed silica 2 parts, cerium oxide 8 parts, pigment carbon black 3 parts, methyltrimethoxysilane 12 parts, N,N-diethyl-3-aminopropyltrimethoxysilane 5 parts, 3-diethylenetriaminopropyltrimethoxysilane 2 parts, and dioctyltin dilaurate 1 part.

[0082] A method for preparing a microwave oven room temperature curing two-component sealant includes the following steps:

[0083] (1) Under the condition of cooling water, a power mixer was used to mix and disperse hydroxyl-terminated polydimethylsiloxane, dimethyl silicone oil, silica powder with a particle size of 5μm and activated carbon according to the weight parts. The revolution speed of the mixer was 35Hz, the dispersion speed was 35Hz, and the mixing and dispersion time was 2h. Then the vacuum was turned on with a vacuum degree of -0.09MPa, and the mixing was continued for 10min to degas the mixture and obtain component A, which was then sealed and stored.

[0084] (2) Using a power mixer, alkoxy-terminated polydimethylsiloxane, 3μm-sized nano-precipitated barium sulfate, and a specific surface area of ​​150m² are mixed. 2 / g of hydrophobic fumed silica, cerium oxide, and pigment carbon black were mixed in parts by weight, heated and stirred under vacuum conditions (vacuum degree -0.09MPa, heating temperature 120℃, stirring speed 35Hz, dispersion speed 35Hz, stirring and dispersion time 2h) to obtain a mixture. After cooling the mixture to 30℃, methyltrimethoxysilane, N,N-diethyl-3-aminopropyltrimethoxysilane, 3-diethylenetriaminopropyltrimethoxysilane, and dioctyltin dilaurate were added to the mixture in parts by weight. Circulating cooling water was introduced, and vacuum was turned on for stirring and dispersion (vacuum degree -0.09MPa, stirring speed 20Hz, dispersion speed 20Hz, stirring and dispersion time 50min) to obtain component B, which was then sealed and stored.

[0085] Example 5

[0086] A microwave oven room temperature curing two-component sealant, comprising component A and component B;

[0087] By weight, component A includes: 100 parts of hydroxyl-terminated polydimethylsiloxane with a viscosity of 20000 mPa·s at 25°C, 20 parts of silica powder with a particle size of 2 μm, and 2 parts of molecular sieve.

[0088] By weight, component B comprises: 100 parts of alkoxy-terminated polydimethylsiloxane with a viscosity of 20000 mPa·s at 25°C; 20 parts of silica powder with a particle size of 2 μm and a specific surface area of ​​350 m². 2 / g of hydrophobic fumed silica 6 parts, cerium oxide 6 parts, pigment carbon black 2 parts, polymethyltriethoxysilane 6 parts, 3-aminopropyltrimethoxysilane 3 parts, 3-diethylenetriaminopropyltrimethoxysilane 1 part, and dibutyltin dilaurate 0.35 parts.

[0089] A method for preparing a microwave oven room temperature curing two-component sealant includes the following steps:

[0090] (1) Under the condition of cooling water, a power mixer was used to mix and disperse 100 parts of hydroxyl-terminated polydimethylsiloxane, silica powder with a particle size of 2μm and molecular sieve according to the weight parts. The revolution speed of the stirring and dispersion was 38Hz, the dispersion speed was 38Hz, and the stirring and dispersion time was 2h. Then the vacuum was turned on and the vacuum degree was -0.08MPa. Stirring was continued and the foam was removed for 15min to obtain component A, which was then sealed and stored.

[0091] (2) Using a power mixer, alkoxy-terminated polydimethylsiloxane, silica powder with a particle size of 2 μm, and a specific surface area of ​​350 m² are mixed. 2 Hydrophobic fumed silica, cerium oxide, and pigment carbon black were mixed in parts by weight, heated and dispersed under vacuum conditions (vacuum degree -0.08 MPa, heating temperature 110℃, stirring speed 38 Hz, dispersion speed 38 Hz, stirring and dispersion time 2 h) to obtain a mixture. After cooling the mixture to 35℃, polymethyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-diethylenetriaminopropyltrimethoxysilane, and dibutyltin dilaurate were added to the mixture in parts by weight. Circulating cooling water was introduced, and vacuum was turned on for stirring and dispersion (vacuum degree -0.09 MPa, stirring speed 22 Hz, dispersion speed 22 Hz, stirring and dispersion time 40 min) to obtain component B, which was then sealed and stored.

[0092] Comparative Example 1

[0093] The only difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, component A is replaced with an equal amount of 80 nm nano-calcium carbonate to replace the 1.5 μm silica powder in Example 1; component B is replaced with an equal amount of 80 nm nano-calcium carbonate to replace the 10 μm silica powder in Example 1, and component B does not contain hydrophobic fumed silica; other components, contents, and preparation methods are the same as in Example 1.

[0094] Comparative Example 2

[0095] The only difference between Comparative Example 2 and Example 3 is that in Comparative Example 2, component A is replaced with an equal amount of 60 nm nano-calcium carbonate to replace the 3 μm silica powder in Example 3; in component B, 30 parts of 80 nm nano-calcium carbonate are replaced with 30 parts of 2 μm nano-precipitated barium sulfate in Example 3, and component B does not contain hydrophobic fumed silica; other components, contents, and preparation methods are the same as in Example 3.

[0096] Comparative Example 3

[0097] The only difference between Comparative Example 3 and Example 1 is that Comparative Example 3 uses an equal amount of hydrophilic fumed silica with the same specific surface area to replace the hydrophobic fumed silica in Example 1. Other components, contents and preparation methods are the same as in Example 1.

[0098] Performance testing

[0099] The A and B components of the microwave oven room temperature curing two-component sealant of Examples 1-5 and Comparative Examples 1-3 were packaged into a 400ml glue bottle with a volume ratio of 1:1. An 18-section mixing nozzle was installed on the top of the glue bottle. When using, the components were mixed and extruded at a volume ratio of 1:1, and relevant performance tests were conducted.

[0100] The performance test results of the room temperature curing two-component sealants for microwave ovens in Examples 1-5 and Comparative Examples 1-3 are shown in Table 1.

[0101] Table 1

[0102]

[0103] As shown in Table 1, the room temperature curing two-component sealant for microwave ovens in Examples 1-5 of this invention has a fast curing speed, good mechanical properties, high temperature resistance, acid and alkali corrosion resistance, and good adhesion to powder coatings. In addition, the sealant strip is semi-flowing, and the overlap at the ends is well fused, which can well meet the aesthetic requirements of microwave oven cavity.

[0104] As shown in Table 1, the sealant in Comparative Example 1 exhibits significantly worse high-temperature resistance and acid / alkali corrosion resistance than that in Example 1. Furthermore, the sealant strip formed is paste-like and lacks flowability, failing to meet the sealing performance and aesthetic requirements of the microwave oven cavity. This demonstrates that the addition of thixotropic fillers and specific types and particle sizes of acid-resistant fillers in this invention enables the sealant to possess excellent high-temperature resistance, acid / alkali corrosion resistance, and appearance properties.

[0105] The sealant in Comparative Example 2 exhibits inferior high-temperature resistance and acid / alkali corrosion resistance compared to Example 3. Furthermore, the sealant strip formed is paste-like with slight flowability, failing to adequately meet the sealing performance and aesthetic requirements of the microwave oven cavity. This demonstrates that the addition of thixotropic fillers and specific types and particle sizes of acid-resistant fillers in this invention enables the sealant to possess excellent high-temperature resistance, acid / alkali corrosion resistance, and appearance. Even partially replacing nano-precipitated barium sulfate with nano-calcium carbonate still affects the sealant's appearance and corrosion resistance.

[0106] The sealant in Comparative Example 3 has excessive fluidity and cannot form a paste-like adhesive strip, failing to meet the sealing performance and aesthetic requirements of the microwave oven cavity; furthermore, its high-temperature resistance is inferior to that of Example 1. This demonstrates that the use of hydrophobic fumed silica as a thixotropic filler in this invention has a significant impact on the appearance and high-temperature resistance of the sealant.

[0107] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A sealant, characterized by, The sealant comprises an A component and a B component; The A component comprises 100 parts of hydroxyl-terminated polydimethylsiloxane, 20-120 parts of acid-resistant filler, 1-5 parts of moisture carrier, and 0-10 parts of plasticizer, by weight; the B component comprises 100 parts of alkoxyl-terminated polydimethylsiloxane, 20-120 parts of acid-resistant filler, 1-6 parts of thixotropic filler, 5-15 parts of heat-resistant filler, 1-5 parts of colored filler, 6-12 parts of crosslinking agent, 3-10 parts of coupling agent, and 0.1-1 parts of catalyst. The acid-resistant fillers in the A component and the B component are independently selected from at least one of silicon powder with a particle size of 1-10 µm, nano-precipitated barium sulfate, and talc powder; The thixotropic filler is hydrophobic fumed silica treated with silazane or alkoxysilane; The heat-resistant filler is selected from at least one of cerium oxide, iron oxide red, zirconium oxide, and titanium dioxide; The moisture carrier comprises at least one of precipitated silica, molecular sieve, and activated carbon.

2. The sealant of claim 1, wherein The viscosity of the hydroxyl-terminated polydimethylsiloxane is 1300-22000 mPa·s at 25°C, and the viscosity of the alkoxyl-terminated polydimethylsiloxane is 900-22000 mPa·s at 25°C.

3. The sealant of claim 1, wherein The thixotropic filler has a specific surface area of 110-440 m 2 / g.

4. The sealant of claim 1, wherein The volume ratio of the A component to the B component is 1:0.8-1.

2.

5. Process for the preparation of the sealant according to any one of claims 1 to 4, characterized in that, The sealant comprises the following steps: (1) mixing the raw materials of the A component to obtain the A component; (2) mixing the raw materials of the B component to obtain the B component; the A component and the B component constitute the sealant.

6. The preparation method according to claim 5, characterized in that, In step (2), the alkoxyl-terminated polydimethylsiloxane, acid-resistant filler, thixotropic filler, and heat-resistant filler are mixed first, and then the crosslinking agent, coupling agent, and catalyst are added to obtain the B component.

7. Use of the sealant of any one of claims 1-4 in the field of electrical appliances.

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