Condensed type room-temperature moisture curing organic silicon sealant capable of resisting low temperature of 70 DEG C below zero and preparation method thereof

Abstract

The invention provides a condensed room-temperature moisture-cured organic silicon sealant resistant to low temperature of-70 DEG C and a preparation method thereof. The condensed room-temperature moisture-cured organic silicon sealant resistant to low temperature of-70 DEG C comprises the following components in percentage by weight: 20-90% of hydroxyl-terminated polydimethyldiethylsiloxane with the viscosity of 15-800St; 5 to 20% of trimethyl-terminated poly (dimethyl diethyl siloxane) with a viscosity of 1 to 10 St; 0-50% of a filler; 5-10% of a cross-linking agent; a proper amount of catalyst. According to the present invention, the hydroxyl-terminated polydimethyldiethylsiloxane and the trimethyl-terminated methyl ethyl siloxane are adopted as the raw materials, such that the prepared condensation type moisture curing organosilicon sealant can resist the low temperature of-70 DEG C or less, and can meet the requirements of the extremely low temperature weather on the earth on the organosilicon sealant;

Description

Technical Field

[0001] This application relates to the technical field of polysiloxanes, and particularly to a condensation-type room-temperature moisture-curing silicone sealant resistant to low temperatures of -70°C and a preparation method thereof. Background Art

[0002] At present, although the common condensation-type room-temperature moisture-curing polydimethylsiloxane silicone sealant can withstand high temperatures up to 150°C, or even above 200°C, its low-temperature resistance can only reach minus 60°C. At low temperatures below minus 60°C, the sealant may become brittle and hard, lose its elasticity, and cause seal failure. Summary of the Invention

[0003] The present invention aims to solve at least one of the technical problems existing in the prior art. For this purpose, the present invention provides a condensation-type room-temperature moisture-curing silicone sealant resistant to low temperatures of -70°C and a preparation method thereof. The technical solutions adopted include:

[0004] A condensation-type room-temperature moisture-curing silicone sealant resistant to low temperatures of -70°C, comprising, by weight percentage:

[0005] 20-90% of hydroxy-terminated polydimethyldiethylsiloxane with a viscosity of 15-800 St

[0006] 5-20% of trimethyl-terminated polydimethyldiethylsiloxane with a viscosity of 1-10 St

[0007] 0-50% of filler;

[0008] 3-8% of crosslinking agent;

[0009] 0.1-0.3% of catalyst.

[0010] As an optional embodiment of this application: The raw materials of the hydroxy-terminated polydimethyldiethylsiloxane with a viscosity of 15-800 St include, by weight percentage:

[0011]

[0012] As an optional embodiment of this application: The preparation method of the hydroxy-terminated polydimethyldiethylsiloxane with a viscosity of 15-800 St includes:

[0013] S1. Weigh the raw materials according to the formula;

[0014] S2. Put 2,2,4,4,6,6-hexaethylcyclotrisiloxane, cyclic dimethylsiloxane mixture, water and an alkali catalyst into a polymerization kettle for ring-opening polymerization reaction to obtain a high-molecular polysiloxane;

[0015] S3. Add water into the polymerization kettle, carry out hydrolysis rearrangement reaction at 150 - 170 °C, degrade to generate a polymer with a viscosity of 15 - 800 St, carry out neutralization, dehydration and removal of low-boiling components, and then cool to room temperature to obtain hydroxyl-terminated polydimethyldiethoxysiloxane with a viscosity of 15 - 800 St.

[0016] As an optional embodiment of the present application: The raw materials of trimethyl-terminated polydimethyldiethoxysiloxane dimethylethyl silicone oil with a viscosity of 1 - 10 St include by weight percentage:

[0017] 2,2,4,4,6,6 - hexaethylcyclotrisiloxane 10 - 100%

[0018] Cyclodimethylsiloxane 10 - 90%

[0019] Hexamethyldisiloxane 0.1 - 1%.

[0020] As an optional embodiment of the present application: The preparation method of trimethyl-terminated polydimethyldiethoxysiloxane with a viscosity of 1 - 10 St includes:

[0021] S1. Weigh the raw materials according to the formula;

[0022] S2. Mix 2,2,4,4,6,6 - hexaethylcyclotrisiloxane, cyclodimethylsiloxane and hexamethyldisiloxane evenly, and pump them into a vertical reaction tower containing perfluorosulfonic acid type cation exchange resin and cation exchange resin from the lower part under normal temperature and pressure to carry out ring-opening polymerization reaction. The residence time is 1 h. After carrying out low-boiling component removal and cooling the mixed product flowing out from the top of the vertical reaction tower to room temperature, trimethyl-terminated polydimethyldiethoxysiloxane with a viscosity of 1 - 10 St is obtained.

[0023] In the present application, a preparation method of a condensation-type room-temperature moisture-curing silicone sealant resistant to -70 °C low temperature is also proposed, including:

[0024] S1. Weigh the raw materials according to the formula;

[0025] S2. Carry out high-temperature vacuum kneading dehydration on different viscosity hydroxyl-terminated polydimethyldiethoxysiloxane and trimethyl-terminated polydimethyldiethoxysiloxane alone or after mixing with various fillers and reinforcing agents. The temperature during kneading is 130 - 150 °C, the vacuum degree is above 0.95, and the kneading time is 4 - 6 h to remove small molecules and moisture in the mixture;

[0026] S3. Put the kneaded material into a planetary stirring kettle, cool to room temperature, lower the lid of the planetary stirring kettle, close it tightly, and carry out vacuum degassing to above 0.95 under planetary stirring;

[0027] S4. Add a cross-linking agent and a catalyst into the degassed kneaded material, stir evenly, and carry out vacuum degassing to below 666 Pa.

[0028] S5. After deflation, raise the cover of the planetary mixer, pull out the mixing kettle, and use a charging machine to discharge and seal it to obtain a one-component condensation-type room-temperature moisture-curing silicone sealant.

[0029] Or a method for preparing a two-component condensation-type room-temperature moisture-curing silicone sealant resistant to low temperature of -70°C includes:

[0030] S1. Weigh the raw materials according to the formula.

[0031] S2. Mix the hydroxyl-terminated polydimethyldiethylsiloxane with different viscosities and the trimethyl-capped polydimethyldiethylsiloxane with different viscosities, or separately mix them with various fillers and reinforcing agents, and perform high-temperature vacuum kneading and dehydration. The temperature during kneading is 130 - 150°C, the vacuum degree is above 0.95, and the time is 1 - 3 h to remove small molecules and moisture in the mixture.

[0032] S3. Place the kneaded material in a planetary mixing kettle and cool it to room temperature, then use a charging machine to press it into a packaging barrel and seal it as component A.

[0033] S4. Mix the cross-linking agent and the catalyst evenly in a dry environment, and pour them into a packaging barrel and seal it as component B.

[0034] In the step of mixing the hydroxyl-terminated polydimethyldiethylsiloxane with different viscosities and the trimethyl-capped polydimethyldiethylsiloxane with different viscosities alone or with various fillers and reinforcing agents for high-temperature vacuum kneading and dehydration in this application, the silicone raw materials with different viscosities can be mixed first, then subjected to high-temperature vacuum kneading, and then mixed with fillers and reinforcing agents; or they can be mixed with fillers and reinforcing agents according to the formula and ratio respectively, then subjected to high-temperature vacuum kneading respectively, and then the kneaded materials are mixed.

[0035] Advantages of the present invention:

[0036] (1) By using hydroxyl-terminated polydimethyldiethylsiloxane and trimethyl-capped methyl ethyl silicone oil as raw materials, the prepared condensation-type moisture-curing silicone sealant has the performance of resisting -70°C, meeting the requirements of extremely low-temperature weather on the earth for silicone sealants.

[0037] (2) In the formula, the proportion of dimethylsiloxane chain segments is increased, reducing the cost of the sealant on the premise of still having good elasticity at -70°C.

[0038]

[0039] (3) The main chain of the condensation-type moisture-curing silicone sealant contains diethylsiloxane chain segments, having better elastic elongation rate, and can better meet the requirements of vibration resistance and high elasticity of silicone sealants in low-temperature environments. Specific embodiments

[0040] The terms used in the present invention, unless otherwise specified, generally have the meanings commonly understood by those of ordinary skill in the art.

[0041] The present invention will be further described in detail below with reference to specific examples and data. It should be understood that these examples are only for illustrative purposes and do not limit the scope of the present invention in any way.

[0042] In the following examples, various processes and methods not described in detail are conventional methods well known in the art. The materials, reagents, devices, instruments, equipment, etc. used in the following examples can be obtained from commercial sources unless otherwise specified.

[0043] Based on the condensation-type room-temperature moisture-curing silicone sealant resistant to -70°C low temperature and its preparation method proposed in this application, the following examples of this application are presented:

[0044] In this example, the raw materials of the hydroxyl-terminated polydimethyldiethylsiloxane with a viscosity of 15 - 800 St include, by weight percentage:

[0045]

[0046] Cyclodimethylsiloxane, also known as DMC, is a mixture of cyclic siloxanes such as D3, D4, and D5. The base catalyst is dimethyl silicone tetramethylammonium (commonly known as base gum), in which the content of (CH3)4NOH is about 3.9%.

[0047] Examples 1 - 3 of this application are proposed to prepare hydroxyl-terminated polydimethyldiethylsiloxane with a viscosity of 15 - 800 St. The raw material compositions of the hydroxyl-terminated polydimethyldiethylsiloxane in Examples 1 - 3 are shown in Table 1. The preparation methods of Examples 1 - 3 include:

[0048] S1. Weigh the raw materials according to the formula;

[0049] S2. Put 2,2,4,4,6,6 - hexaethylcyclotrisiloxane, cyclodimethylsiloxane mixture, water, and base catalyst into the polymerization kettle, and carry out ring-opening polymerization reaction to obtain high-molecular polysiloxane;

[0050] S3. Add water to the polymerization kettle, and carry out hydrolysis rearrangement reaction at 150 - 170°C to degrade and generate a polymer with a viscosity of 15 - 800 St,

[0051] S4. Put the hydroxyl-terminated polydimethyldiethylsiloxane with a viscosity of 15 - 800 St into the neutralization kettle, add a neutralizing agent (such as white carbon black or phosphoric acid polysiloxane solution), and process until the material is neutral;

[0052] S5. Inject dry nitrogen through a low tube and connect the vacuum system to remove low-molecular cyclic siloxanes and other volatile components from the product.

[0053] S6. After removing the volatile components, put the product into a cooling kettle, cool it to room temperature, and discharge to obtain hydroxy-terminated polydimethyldiethylsiloxane with a viscosity of 15 - 800 St.

[0054] Table 1

[0055]

[0056] In this example, the raw materials of trimethyl-terminated polydimethyldiethylsiloxane (methyl ethyl silicone oil) with a viscosity of 1 - 10 St include, by weight percentage:

[0057] 2,2,4,4,6,6 - hexaethylcyclotrisiloxane 10 - 90%

[0058] cyclodimethylsiloxane 10 - 90%

[0059] hexamethyldisiloxane 0.1 - 1.0%

[0060] Examples 4 - 6 of this application prepare trimethyl-terminated polydimethyldiethylsiloxane (methyl ethyl silicone oil) with a viscosity of 1 - 10 St. The raw material compositions of the trimethyl-terminated polydimethyldiethylsiloxane (methyl ethyl silicone oil) in Examples 4 - 6 are shown in Table 2. The preparation methods of Examples 4 - 6 include:

[0061] S1. Weigh the raw materials according to the formula.

[0062] S2. Mix 2,2,4,4,6,6 - hexaethylcyclotrisiloxane, cyclodimethylsiloxane, and hexamethyldisiloxane evenly, and pump them into a vertical reaction tower containing perfluorosulfonic acid type cation exchange resin and cation exchange resin from the lower part under normal temperature and pressure for ring-opening polymerization reaction. The residence time is 1 h, and send the mixed product flowing out from the top of the vertical reaction tower to an intermediate tank.

[0063] The catalytic speed of perfluorosulfonic acid type cation exchange resin is thirty times that of ordinary cation exchange resin, but the cost is expensive. By using perfluorosulfonic acid type cation exchange resin and cation exchange resin in combination, both the reaction speed is increased and the catalyst cost is controlled. The hexamethyldisiloxane is a kind of chain stopper or end-capping agent. The viscosity or molecular weight of trimethyl-terminated polydimethyldiethylsiloxane (methyl ethyl silicone oil) is related to the amount of the chain stopper hexamethyldisiloxane. The larger the amount of hexamethyldisiloxane, the smaller the viscosity or molecular weight.

[0064] S3. Pump the mixed product in the intermediate tank into the low-boiling-point removal column. After removing the low-boiling-point substances at 220°C and a vacuum degree higher than 0.95, put the bottom product of the low-boiling-point removal column into the cooling tank;

[0065] S4. Cool the bottom product in the cooling pipe until it is cooled to room temperature, and then discharge the material to obtain trimethyl-terminated polydimethyldiethylsiloxane (methyl ethyl silicone oil) with a viscosity of 1 - 10 St.

[0066] Table 2

[0067] Component Example 4 Example 5 Example 6 2,2,4,4,6,6-Hexaethylcyclotrisiloxane 19.9 45.5 79 Cyclic dimethylsiloxane (DMC) 80 50 20 Hexamethyldisiloxane 0.1 0.5 1.0

[0068] Based on the hydroxy-terminated polydimethyldiethylsiloxane with a viscosity of 15 - 800 St prepared in Examples 1 - 3 and the trimethyl-terminated polydimethyldiethylsiloxane (methyl ethyl silicone oil) with a viscosity of 1 - 10 St prepared in Examples 4 - 6, Examples 7 - 12 of the present application are now proposed;

[0069] The components of the condensation-type room-temperature moisture-curing silicone sealant in Examples 7 - 9 are shown in Table 3, and the preparation method includes:

[0070] S1. Weigh the raw materials according to the formula;

[0071] S2. Mix hydroxy-terminated polydimethyldiethylsiloxane with different viscosities and trimethyl-terminated methyl ethyl silane (methyl ethyl silicone oil) with various fillers and reinforcing agents in proportion, and then carry out high-temperature vacuum kneading for dehydration. The temperature during kneading is 130 - 150°C, the vacuum degree is above 0.95, and the time is 4 - 6 h to remove small molecules and moisture in the mixture;

[0072] S3. Put the kneaded material into a planetary stirring kettle, cool it to room temperature, lower the lid of the planetary stirring kettle, close it tightly, and carry out vacuum degassing to above 0.95 under planetary stirring;

[0073] S4. Add a cross-linking agent and a catalyst to the degassed kneaded material, stir evenly, and carry out vacuum degassing to above 0.95;

[0074] S5. After releasing the gas, raise the lid of the planetary stirrer, pull out the stirring kettle, and discharge and seal the material with a pressing machine to obtain a one-component condensation-type room-temperature moisture-curing silicone sealant.

[0075] Table 3

[0076]

[0077]

[0078] The organic titanium chelate catalyst described is a catalyst prepared by reacting a titanate with ethyl acetoacetate.

[0079] The one-component condensation type room-temperature moisture-curing silicone sealant prepared in Examples 7-9 was placed at room temperature. After the condensation type room-temperature moisture-curing silicone sealant contacted with moisture in the air and cured, the elastic elongation rate of the condensation type room-temperature moisture-curing silicone sealant in Example 7 was detected. Then, the cured condensation type room-temperature moisture-curing silicone sealant in Example 7 was placed in environments with temperatures of -40°C and -72°C for 24 hours respectively, and the elastic elongation rates of the cured condensation type room-temperature moisture-curing silicone sealant were detected respectively. The detection results are shown in Table 4.

[0080] Table 4

[0081] Temperature Elongation at break Room temperature >800％ -40℃ >600％ -72℃ >400％

[0082] According to the detection results in Table 4, it can be known that the cured condensation type room-temperature moisture-curing silicone sealant can meet the elastic requirements of silicone sealants such as building waterproof sealants, expansion joint sealants for expressways, expansion joint sealants for ballastless tracks of high-speed railways, and high-voltage cable insulation sealants in a low-temperature environment of -70°C.

[0083] The components of the two-component condensation type room-temperature moisture-curing silicone sealant in Examples 10-12 are shown in Table 5. The preparation method includes:

[0084] S1. Weigh the raw materials according to the formula.

[0085] S2. The hydroxyl-terminated polydimethyldiethylsiloxane with different viscosities and the trimethyl-terminated polydimethyldiethylsiloxane (methyl ethyl silicone oil) with different viscosities are separately mixed with various fillers and reinforcing agents in proportion and kneaded under high temperature and vacuum. The temperature during kneading is 130-150°C, the vacuum degree is above 0.95, and the time is 1-3 hours to remove small molecules and moisture in the mixture.

[0086] S3. The kneaded material is placed in a planetary stirring kettle and cooled to room temperature, and then pressed into a packaging barrel and sealed to be used as Component A.

[0087] S4. The cross-linking agent and the catalyst are mixed evenly in a dry environment and poured into a packaging barrel and sealed to be used as Component B.

[0088] Table 5

[0089]

[0090] The condensation type room temperature moisture-curing silicone sealant prepared in Examples 10 - 12 was mixed at a weight ratio of A component:B component in the ratio of 10:1 to 5:1, and then left at room temperature. After the condensation type room temperature moisture-curing silicone sealant contacted with moisture in the air and cured, the elastic elongation rate of the condensation type room temperature moisture-curing silicone sealant in Example 10 was detected. Then, the cured condensation type room temperature moisture-curing silicone sealant in Example 10 was placed in environments with temperatures of -40°C and -72°C for 24 hours respectively, and the elastic elongation rate of the cured condensation type room temperature moisture-curing silicone sealant was detected respectively. The detection results are shown in Table 6.

[0091] Table 6

[0092] Temperature Elongation at break Room temperature >400％ -40℃ >300％ -72℃ >200％

[0093] According to the detection results in Table 6, it can be known that the cured two-component condensation type room temperature moisture-curing silicone sealant can meet the elastic requirements of silicone sealants such as electronic three-proof glue, electronic insulating glue, and electrical sealant in a low-temperature environment of minus 70°C.

[0094] Of course, the present invention is not limited to the above embodiments. Those skilled in the art can make equivalent deformations or substitutions without departing from the spirit of the present invention, and these equivalent deformations and substitutions are all included within the scope defined by the claims of this application.

Claims

1. A condensation-type room temperature moisture curing silicone sealant resistant to -70°C low temperature, characterized in that: The percentage by weight includes: 20-95% of terminal hydroxyl polydimethyl diethyl siloxane with a viscosity of 15-800 St; 5-20% trimethyl terminated polydimethyl diethyl siloxane with a viscosity of 1-10 St; Filler 0~50%; Cross-linking agent 3-8%; Catalyst 0.1~0.3%.

2. The -70°C low temperature resistant condensation type room temperature moisture curing silicone sealant according to claim 1, characterized in that: The filler includes one, two or more of a reinforcing filler, a thermal conductive filler and a flame retardant filler.

3. The -70°C low temperature resistant condensation type room temperature moisture curing silicone sealant according to claim 2, characterized in that: The reinforcing filler includes one, two or more of heavy calcium carbonate, light calcium carbonate, nano calcium carbonate, white carbon black and fumed silica; The thermally conductive filler comprises aluminum oxide; The flame retardant filler includes one or both of aluminum hydroxide and magnesium hydroxide.

4. The -70°C low temperature resistant condensation type room temperature moisture curing silicone sealant according to claim 1, characterized in that: The crosslinking agent includes one or more of methyltrimethoxysilane, methyltriethoxysilane, dichloromethyltriethoxysilane, diethylaminomethyltriethoxysilane, methyltributylacetoximate silane, and phenyltributylacetoximate silane.

5. The -70°C low temperature resistant condensation type room temperature moisture curing silicone sealant according to claim 1, characterized in that: The raw materials of the terminal hydroxyl polydimethyl diethyl siloxane with a viscosity of 15 to 800 St include, by weight percentage:

6. The -70°C low temperature resistant condensation type room temperature moisture curing silicone sealant according to claim 5, characterized in that: The preparation method of terminal hydroxyl polydimethyl diethyl siloxane with a viscosity of 15 to 800 St comprises: S1. Weigh the raw materials according to the formula; S2, adding 2,2,4,4,6,6-hexaethylcyclotrisiloxane, a mixture of cyclodimethylsiloxane, water and an alkali catalyst into a polymerization kettle to carry out a ring-opening polymerization reaction to obtain a high molecular weight polysiloxane; S3. Add water into the polymerization kettle, carry out hydrolysis and rearrangement reaction at 150-170° C., degrade to generate a polymer with a viscosity of 15-800 St, neutralize, dehydrate and decompose, and cool to room temperature to obtain a hydroxy-terminated polydimethyldiethylsiloxane with a viscosity of 15-800 St.

7. The -70°C low temperature resistant condensation type room temperature moisture curing silicone sealant according to claim 1, characterized in that: The raw materials of trimethyl terminated polydimethyl diethyl siloxane dimethyl ethyl silicone oil with a viscosity of 1 to 10 St include, by weight percentage: 2,2,4,4,6,6-Hexaethylcyclotrisiloxane 10~100% Cyclodimethicone 10~90% Hexamethyldisiloxane 0.1~1%.

8. The -70°C low temperature resistant condensation type room temperature moisture curing silicone sealant according to claim 7, characterized in that: The preparation method of trimethyl terminated polydimethyl diethyl siloxane having a viscosity of 1 to 10 St comprises: S1. Weigh the raw materials according to the formula; S2. Evenly mix 2,2,4,4,6,6-hexaethylcyclotrisiloxane, cyclodimethylsiloxane and hexamethyldisiloxane, and pump them into a vertical reaction tower containing perfluorosulfonic acid type cation exchange resin and cation exchange resin at room temperature and pressure to carry out a ring-opening polymerization reaction with a residence time of 1 hour. Degassing the mixed product flowing out of the top of the vertical reaction tower and cooling it to room temperature to obtain trimethyl-terminated polydimethyldiethylsiloxane with a viscosity of 1 to 10St.

9. A method for preparing the -70°C low-temperature resistant condensation-type room-temperature moisture-curing silicone sealant according to any one of claims 1 to 8, characterized in that: include: S1. Weigh the raw materials according to the formula; S2. Mixing hydroxy-terminated polydimethyldiethylsiloxane with different viscosities and trimethyl-terminated polydimethyldiethylsiloxane alone or with various fillers and reinforcing agents, and then performing high-temperature vacuum kneading and dehydration. The kneading temperature is 130-150° C., the vacuum degree is above 0.95, and the kneading time is 4-6 hours to remove small molecules and moisture in the mixture; S3. Place the kneaded material into a planetary stirring kettle, cool it to room temperature, lower the lid of the planetary stirring kettle, close it tightly, and evacuate it to above 0.95 for degassing under planetary stirring; S4. Add a crosslinking agent and a catalyst to the degassed kneaded material, stir evenly, and evacuate to below 666 Pa for degassing; S5. After venting, raise the planetary mixer cover, pull out the mixing kettle, and use a press to discharge and seal the material to obtain a single-component condensation type room temperature moisture-curing silicone sealant.

10. A method for preparing the -70°C low temperature resistant two-component condensation type room temperature moisture curing silicone sealant according to any one of claims 1 to 8, characterized in that: S1. Weigh the raw materials according to the formula; S2. Mix hydroxy-terminated polydimethyldiethylsiloxane with different viscosities and trimethyl-terminated polydimethyldiethylsiloxane with different viscosities or mix them with various fillers and reinforcing agents respectively, and then perform high-temperature vacuum kneading and dehydration. The kneading temperature is 130-150°C, the vacuum degree is above 0.95, and the time is 1-3 hours to remove small molecules and moisture in the mixture. S3, put the kneaded material into a planetary stirring kettle and cool it to room temperature, and use a pressing machine to press it into a packaging barrel and seal it as component A. S4. Mix the cross-linking agent and the catalyst in a dry environment according to the proportion, pour them into a packaging barrel and seal them as component B.

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