Single-component polyurethane sealant as well as preparation method and application thereof

Abstract

The invention relates to a single-component polyurethane sealant as well as a preparation method and application thereof, and the single-component polyurethane sealant is prepared from the following raw materials in parts by mass: 25-50 parts of a polyurethane prepolymer, 30-60 parts of an inorganic filler, 0-5 parts of a tackifying aid, 5-10 parts of a thixotropic agent, 0-2 parts of a moisture scavenger and 0.01-1 part of a catalyst. The polyurethane prepolymer is prepared by reaction of polyester polyol, polyether polyol and isocyanate according to the mass ratio of (30-50): (20-30): (35-50). The single-component polyurethane sealant for sealing the gas meter has better thixotropy and higher curing speed, does not overflow in the construction process, has good solvent resistance, and can keep very small change rate of the mass change rate and the volume change rate after being soaked in a mixed solvent, so that the single-component polyurethane sealant can be used for sealing the gas meter. Good sealing performance can be maintained in the long-term use process.

Description

Technical Field

[0001] This invention relates to the field of polyurethane materials technology, specifically to a one-component polyurethane sealant, its preparation method, and its application. Background Technology

[0002] Gas meters (such as diaphragm gas meters, smart gas meters, and gas flow meters) are key metering devices in gas transmission and distribution systems. Their sealing performance directly affects the accuracy of gas metering, operational safety, and environmental protection. With the increasing proportion of natural gas consumption and the expansion of gas application scenarios (including residential, industrial, commercial, and vehicle applications), the sealing technology of gas meters faces higher requirements.

[0003] In the manufacturing and assembly of gas meters, sealants are widely used in various critical components such as sealing the meter housing (e.g., the contact surfaces of the upper and lower housings), sealing the connection between the gas outlet and the valve grille, and potting protection for internal electronic components. Currently available single-component polyurethane sealants mostly have long curing times, are prone to overflowing onto other parts during the tightening process, and have poor solvent resistance. Prolonged use may lead to adhesive and sealing failure, posing significant safety hazards. Therefore, developing a new type of sealant specifically for gas meters that can cure quickly, is less prone to overflow during application, and can withstand long-term corrosion from gas and its associated solvents is of great significance for improving the production efficiency, operational reliability, and service life of gas meters. Summary of the Invention

[0004] Based on the above description, the present invention provides a one-component polyurethane sealant, its preparation method and application, aiming to improve the solvent resistance of polyurethane sealants.

[0005] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: This invention provides a one-component polyurethane sealant, prepared from the following raw materials by weight: 25-50 parts of polyurethane prepolymer, 30-60 parts of inorganic filler, 0-5 parts of tackifying agent, 5-10 parts of thixotropic agent, 0-2 parts of dehydrating agent and 0.01-1 parts of catalyst; The polyurethane prepolymer is prepared by reacting polyester polyol, polyether polyol and isocyanate in a mass ratio of (30-50):(20-30):(35-50).

[0006] Furthermore, the polyester polyol includes at least one of polyethylene succinate and phthalic anhydride polyester polyol, wherein the molecular weight of the polyester polyol is 1000~3000 and the hydroxyl value is 50~100 mgKOH / g. The polyether polyol is a polyoxypropylene diol with a molecular weight of 1500~3000 and a hydroxyl value of 40~110 mgKOH / g. The isocyanate is at least one selected from toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0007] Furthermore, the inorganic filler is at least one of light calcium carbonate, nano-calcium carbonate, kaolin, and calcium oxide.

[0008] Furthermore, the tackifying agent includes at least one selected from 3-aminopropyltrimethylsilane, 3-aminopropyltriethylsilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0009] Furthermore, the thixotropic agent includes at least one of hydrophobic fumed silica and organobentonite.

[0010] Furthermore, the dehydrating agent includes oxazolidine dehydrating agent.

[0011] Furthermore, the catalyst is at least one selected from dibutyltin dilaurate, stannous octoate, bismorpholino diethyl ether, dimorpholino triethyl ether, triethylenediamine, and tetramethylenediamine.

[0012] This invention also proposes a method for preparing a single-component polyurethane sealant as described above, comprising: S1. Mix polyurethane prepolymer, inorganic filler, tackifier, thixotropic agent, dehydrating agent and catalyst under vacuum for 1-2 h to obtain polyurethane sealant.

[0013] Furthermore, step S1 is preceded by: S11. Heat polyester polyol and polyether polyol under vacuum to 115℃-125℃ to dehydrate for 20 min-40 min, cool to 55℃-65℃ and add isocyanate, heat to 75℃-80℃ and react for 2-4 hours, then degas under vacuum to obtain polyurethane prepolymer.

[0014] The present invention also proposes an application of a one-component polyurethane sealant in a gas meter, wherein the one-component polyurethane sealant includes the one-component polyurethane sealant as described above, or is prepared by the one-component polyurethane sealant preparation method described above.

[0015] Compared with the prior art, the technical solution of this application has the following beneficial technical effects: (1) In the technical solution of the present invention, by optimizing the composition of the polyurethane prepolymer and combining it with a high-efficiency catalyst system, the surface drying and hard drying time of the sealant is significantly shortened, which meets the process requirements for rapid positioning and efficient production in the assembly of gas instruments; the selected prepolymer with polyester / polyether polyol composite structure has both flexibility and chemical stability, combined with a dense cross-linked network structure, so that the cured adhesive layer has excellent resistance to hydrocarbons and trace sulfides that may exist in natural gas, and does not swell, crack or fail to bond during long-term use, thus ensuring the sealing reliability of the gas instrument under complex working conditions.

[0016] (2) The single-component polyurethane sealant for gas meter sealing of the present invention has better thixotropy and faster curing speed. It will not overflow during construction and has good solvent resistance. After being soaked in mixed solvent, the mass change rate and volume change rate of the sealant can be kept very small, and it can maintain good sealing performance during long-term use. Detailed Implementation

[0017] To facilitate understanding of this application, several embodiments will be described more fully below. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to make the disclosure of this application more thorough and complete.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0019] Gas meters (such as diaphragm gas meters, smart gas meters, and gas flow meters) are key metering devices in gas transmission and distribution systems. Their sealing performance directly affects the accuracy of gas metering, operational safety, and environmental protection. With the increasing proportion of natural gas consumption and the expansion of gas application scenarios (including residential, industrial, commercial, and vehicle applications), the sealing technology of gas meters faces higher requirements.

[0020] In the manufacturing and assembly of gas meters, sealants are widely used in various critical components such as sealing the meter housing (e.g., the contact surfaces of the upper and lower housings), sealing the connection between the gas outlet and the valve grille, and potting protection for internal electronic components. Currently available single-component polyurethane sealants mostly have long curing times, are prone to overflowing onto other parts during the tightening process, and have poor solvent resistance. Prolonged use may lead to adhesive and sealing failure, posing significant safety hazards. Therefore, developing a new type of sealant specifically for gas meters that can cure quickly, is less prone to overflow during application, and can withstand long-term corrosion from gas and its associated solvents is of great significance for improving the production efficiency, operational reliability, and service life of gas meters.

[0021] In view of this, the present invention provides a one-component polyurethane sealant, which is prepared from the following raw materials in parts by weight: 25-50 parts of polyurethane prepolymer, 30-60 parts of inorganic filler, 0-5 parts of tackifier, 5-10 parts of thixotropic agent, 0-2 parts of dehydrating agent and 0.01-1 parts of catalyst; The polyurethane prepolymer is prepared by reacting polyester polyol, polyether polyol and isocyanate in a mass ratio of (30-50):(20-30):(35-50).

[0022] In the technical solution of this invention, by optimizing the composition of the polyurethane prepolymer and combining it with a high-efficiency catalyst system, the surface drying and hard drying time of the sealant is significantly shortened, meeting the process requirements for rapid positioning and efficient production during the assembly of gas instruments. The selected polyester / polyether polyol composite prepolymer has both flexibility and chemical stability. Combined with a dense cross-linked network structure, the cured adhesive layer has excellent resistance to hydrocarbons and trace sulfides that may be present in natural gas. It does not swell, crack, or fail to bond during long-term use, ensuring the sealing reliability of the gas instrument under complex operating conditions.

[0023] The single-component polyurethane sealant for gas meter sealing of the present invention has better thixotropy and faster curing speed. It will not overflow during construction and has good solvent resistance. After being soaked in mixed solvents, the mass change rate and volume change rate of the sealant can remain very small, and it can maintain good sealing performance during long-term use.

[0024] Furthermore, the polyester polyol includes at least one of polyethylene succinate and phthalic anhydride polyester polyol, wherein the molecular weight of the polyester polyol is 1000~3000 and the hydroxyl value is 50~100 mgKOH / g. The polyether polyol is a polyoxypropylene diol with a molecular weight of 1500~3000 and a hydroxyl value of 40~110 mgKOH / g. The isocyanate is at least one selected from toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and polymethylene polyphenyl polyisocyanate.

[0025] In the technical solution of this invention, the polyester polyol is selected from polyethylene succinate and / or phthalic anhydride polyester polyol, with a molecular weight controlled at 1000~3000 and a hydroxyl value of 50~100 mgKOH / g. This ensures sufficient functional group density to form a dense cross-linked network while avoiding increased brittleness due to excessively low molecular weight or a dramatic increase in viscosity due to excessively high molecular weight. The polyether polyol is limited to polypropylene oxide diol (PPG), with a molecular weight of 1500~3000 and a hydroxyl value of 40~110 mgKOH / g. This provides appropriate cross-linking points while imparting good low-temperature flexibility and impact resistance to the adhesive layer, meeting the requirements of all-climate working conditions. The isocyanate component is selected from at least one of toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), and polymethylene polyphenyl polyisocyanate (PAPI), which can flexibly adjust the curing speed, hardness, and yellowing resistance according to the application scenario.

[0026] Furthermore, the inorganic filler is at least one of light calcium carbonate, nano-calcium carbonate, kaolin, and calcium oxide.

[0027] In the technical solution of this invention, calcium carbonate and kaolin have high specific surface area and lamellar / spherical microstructure, which can effectively construct a three-dimensional network structure, enhance the yield stress and thixotropic index of the colloid, and make the sealant "stand up" quickly after application without flowing. It is especially suitable for sealing construction on vertical surfaces or complex structures, and avoids the colloid overflowing into non-sealing areas due to gravity or assembly pressure. In addition to being a functional filler, calcium oxide can also react with trace amounts of moisture or acidic components in the environment, playing a role in in-situ drying and neutralizing corrosive media, delaying the aging of the sealing interface, and improving long-term sealing reliability.

[0028] Furthermore, the tackifying agent includes at least one selected from 3-aminopropyltrimethylsilane, 3-aminopropyltriethylsilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0029] In the technical solution of the present invention, by using the above-mentioned tackifier, molecular bridges can be constructed at the interface, which significantly enhances the initial adhesion of the sealant to various substrates and the retention rate after damp heat aging; wherein, silane tackifiers (such as 3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane) can generate silanol groups (Si-OH) after hydrolysis, which enhances the adhesion of the sealant to the surface of the substrate.

[0030] Furthermore, the thixotropic agent includes at least one of hydrophobic fumed silica and organobentonite.

[0031] In the technical solution of this invention, by employing the above-mentioned thixotropic agent, wherein the hydrophobic fumed silica has a high specific surface area and a three-dimensional network structure, and can form a strong hydrogen bond network in the polyurethane matrix; the organic bentonite constructs a thixotropic skeleton through the intercalation and stacking of layered silicate sheets in a polar system; thereby endowing the sealant with high yield stress and strong shear thinning properties, the colloid remains gel-like and does not flow under static conditions, and can stably adhere to vertical or inverted surfaces after dispensing; while the viscosity drops rapidly under shear force during assembly and pressing, making it easy to spread evenly and fill micro gaps.

[0032] Furthermore, the dehydrating agent includes oxazolidine dehydrating agent.

[0033] In the technical solution of this invention, by using oxazolidine dehydrating agent, stable hydroxyl compounds and inert byproducts can be rapidly reacted with water at room temperature, preferentially capturing free water in the system and protecting the -NCO groups to react orderly with environmental moisture after sizing, thereby ensuring that the curing process is controllable, dense, and free of pores.

[0034] Furthermore, the catalyst is at least one selected from dibutyltin dilaurate, stannous octoate, bismorpholino diethyl ether, dimorpholino triethyl ether, triethylenediamine, and tetramethylenediamine.

[0035] In the technical solution of the present invention, by using the above-mentioned catalyst, controllable, efficient and deep curing of single-component polyurethane sealant under different environmental conditions is achieved.

[0036] This invention also proposes a method for preparing a single-component polyurethane sealant as described above, comprising: S1. Mix polyurethane prepolymer, inorganic filler, tackifier, thixotropic agent, dehydrating agent and catalyst under vacuum for 1-2 h to obtain polyurethane sealant.

[0037] In the technical solution of this invention, all components are mixed under vacuum, effectively eliminating air entrained during stirring and trace amounts of moisture and volatile substances adsorbed in the raw materials, thus preventing the formation of microbubbles or cavities in the finished adhesive. This preparation method requires only one step of vacuum mixing, eliminating the need for high-temperature reactions, solvent recovery, or multi-stage feeding. The process is simple, energy-efficient, and environmentally friendly, and it is easy to achieve closed-loop and continuous production, aligning with the development direction of green and intelligent manufacturing.

[0038] Furthermore, step S1 is preceded by: S11. Heat polyester polyol and polyether polyol under vacuum to 115℃-125℃ to dehydrate for 20 min-40 min, cool to 55℃-65℃ and add isocyanate, heat to 75℃-80℃ and react for 2-4 hours, then degas under vacuum to obtain polyurethane prepolymer.

[0039] In the technical solution of this invention, a segmented temperature control strategy is adopted. Isocyanate is first added under mild conditions of 55℃-65℃ to avoid local charring or gelation caused by violent exothermic reactions, and then the temperature is raised to 75℃-80℃ to complete the reaction. This ensures complete reaction and avoids isocyanate self-polymerization caused by prolonged high-temperature heating. The resulting prepolymer has a light color, stable viscosity, and low free monomer residue, significantly improving its chemical stability during subsequent compounding and storage.

[0040] The present invention also proposes an application of a one-component polyurethane sealant in a gas meter, wherein the one-component polyurethane sealant includes the one-component polyurethane sealant as described above, or is prepared by the one-component polyurethane sealant preparation method described above.

[0041] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0042] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0043] Example 1 This embodiment provides a one-component polyurethane sealant, the preparation method of which is shown below: 1. Preparation of polyurethane prepolymer Prepare the raw materials according to the following proportions:

[0044] Among them, the molecular weight of polyethylene succinate is 1800, and the molecular weight of polypropylene glycol is 2000. 32 parts by weight of polyethylene succinate and 28 parts by weight of polypropylene glycol were added to a synthesis reactor. The mixture was heated to 120°C and vacuum dehydrated for 30 min. The temperature was then lowered to 60°C, and 40 parts by weight of diphenylmethane diisocyanate were added. The mixture was stirred and mixed evenly. The temperature was then raised to 75°C and kept at that temperature for 3 h. During this period, samples were taken regularly to monitor and detect the viscosity and isocyanate group content. When the viscosity was measured to be 28500±1500 mPa·s and the isocyanate group content was 10.77±0.5 wt%, vacuum degassing was performed. After degassing was completed, the mixture was cooled to room temperature and discharged to obtain polyurethane prepolymer A, which was then placed in a dry, sealed container for later use.

[0045] 2. Preparation of one-component polyurethane sealant Prepare the raw materials according to the following proportions:

[0046] 42.95 parts by weight of polyurethane prepolymer A, 46 parts by weight of light calcium carbonate, 3 parts by weight of 3-aminopropyltriethoxysilane, 7 parts by weight of organobentonite, 1 part by weight of oxazolidine dehydrating agent, and 0.05 parts by weight of dibutyltin dilaurate were added to a planetary mixer and stirred under vacuum for 1 hour. During stirring, the temperature was controlled below 50°C using a water-cooled mold temperature controller. After the reaction was completed, the vacuum was released with dry nitrogen, and the material was discharged to obtain a single-component polyurethane sealant with a solid content of 100 parts by weight, which was then placed in a sealed container.

[0047] Example 2 This embodiment provides a one-component polyurethane sealant, the preparation method of which is shown below: 1. Preparation of polyurethane prepolymer Prepare the raw materials according to the following proportions:

[0048] Among them, the molecular weight of polyethylene succinate is 1800, and the molecular weight of polypropylene glycol is 2500. 36 parts by weight of polyethylene succinate and 24 parts by weight of polypropylene glycol were added to a synthesis reactor. The mixture was heated to 120 °C, vacuum dehydrated for 30 min, cooled to 60 °C, and 40 parts by weight of diphenylmethane diisocyanate were added. The mixture was stirred and mixed evenly, and then heated to 75 °C and kept at that temperature for 3 h. During the reaction, the viscosity and isocyanate group content were monitored and tested at regular intervals. When the viscosity was measured to be 30500±1500 mPa·s and the isocyanate group content was 10.95±0.5 wt%, vacuum degassing was performed. After degassing was completed, the mixture was cooled to room temperature and discharged to obtain polyurethane prepolymer B, which was then placed in a dry, sealed container for later use.

[0049] 2. Preparation of one-component polyurethane sealant Prepare the raw materials according to the following proportions:

[0050] 40.95 parts by weight of polyurethane prepolymer A, 45 parts by weight of nano-calcium carbonate, 3 parts by weight of 3-aminopropyltrimethoxysilane, 10 parts by weight of organobentonite, 1 part by weight of oxazolidine dehydrating agent, and 0.05 parts by weight of stannous octoate were added to a planetary mixer and stirred under vacuum for 1 hour. During stirring, the temperature was controlled below 50°C using a water-cooled mold temperature controller. After the reaction was completed, the vacuum was released with dry nitrogen, and the material was discharged to obtain a single-component polyurethane sealant with a solid content of 100 parts by weight, which was then placed in a sealed container.

[0051] Example 3 This embodiment provides a one-component polyurethane sealant and its preparation method.

[0052] 1. Preparation of polyurethane prepolymer Prepare the raw materials according to the following proportions:

[0053] Among them, the molecular weight of polyethylene succinate is 1800, and the molecular weight of polypropylene glycol is 2700. 38 parts by weight of polyethylene succinate and 20 parts by weight of polypropylene glycol were added to a synthesis reactor. The mixture was heated to 120 °C and vacuum dehydrated for 30 min. The temperature was then lowered to 60 °C, and 42 parts by weight of diphenylmethane diisocyanate were added. The mixture was stirred and mixed evenly. The temperature was then raised to 75 °C and kept at that temperature for 3 h. During this period, samples were taken regularly to monitor and detect the viscosity and isocyanate group content. When the viscosity was measured to be 29800±1500 mPa·s and the isocyanate group content was 10.95±0.5 wt%, vacuum degassing was performed. After degassing was completed, the mixture was cooled to room temperature and discharged to obtain polyurethane prepolymer C, which was then placed in a dry, sealed container for later use.

[0054] 2. Preparation of one-component polyurethane sealant Prepare the raw materials according to the following proportions:

[0055] 45.95 parts by weight of polyurethane prepolymer C, 40 parts by weight of nano-calcium carbonate, 3 parts by weight of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, 10 parts by weight of hydrophobic fumed silica, 1 part by weight of oxazolidine dehydrating agent, and 0.05 parts by weight of bismorpholinodiethyl ether were added to a planetary mixer and stirred under vacuum for 1 hour. During stirring, the temperature was controlled below 50 °C using a water-cooled mold temperature controller. After the reaction was completed, the vacuum was released with dry nitrogen, and the material was discharged to obtain a single-component polyurethane sealant with a solid content of 100 parts by weight, which was then placed in a sealed container.

[0056] Comparative Example 1 This comparative example provides a one-component polyurethane sealant.

[0057] It includes most of the operating steps of Example 2, except that the polyethylene succinate used is replaced with polypropylene oxide-ethylene oxide copolyol, and the other components, amounts and preparation methods are the same as in Example 2.

[0058] Comparative Example 2 This comparative example provides a one-component polyurethane sealant.

[0059] It includes most of the operating steps of Example 2, except that the polyethylene succinate used is replaced with polyethylene adipate, while the other components, amounts, and preparation methods are the same as in Example 2.

[0060] Comparative Example 3 This comparative example provides a one-component polyurethane sealant.

[0061] It includes most of the steps of Example 2, except that the organic bentonite used is replaced with polyamide wax, while the other components, amounts and preparation methods are the same as in Example 2.

[0062] Comparative Example 4 This comparative example provides a one-component polyurethane sealant.

[0063] It includes most of the operational steps of Example 2, except that the weight fraction of the organic bentonite used is 3 parts, and the other components, amounts, and preparation methods are the same as in Example 2.

[0064] Performance testing The following performance tests were conducted on the one-component polyurethane sealants prepared in Examples 1-3 and Comparative Examples 1-4.

[0065] Curing speed: The curing speed of the single-component polyurethane sealant was tested according to the test method of curing speed in QC-T-1024-2015. The test temperature was 23±2℃ and the RH was 50±5%. Sealant overflow: For the sealant overflow test, refer to the actual application situation. Apply one-component polyurethane sealant evenly between the upper and lower housings of the gas instrument, accumulating about five layers. After the sample is cured in a constant temperature room (temperature 23±2℃, humidity 50±5%RH) for 8 hours, roll the edges together and observe the sealant overflow.

[0066] Volume and mass change rates: These were determined according to GB / T 6968-2011 standard. After curing the single-component polyurethane sealant sample under standard conditions for 168 hours, it was cut into 20 mm * 20 mm pieces, marked, weighed, and recorded. The pieces were then placed in a mixed solvent with a volume ratio of benzene:toluene:xylene:120# gasoline = 3:4:2:1. After 24 hours, the samples were removed, the surface solvent was absorbed with filter paper, and the samples were weighed. The mass and volume change rates were calculated based on the mass and volume before and after immersion.

[0067] Table 1 Performance test results of one-component polyurethane sealant

[0068] The performance test results of the one-component polyurethane sealants prepared in Examples 1-3 and Comparative Examples 1-4, as shown in Table 1, indicate that: 1. The single-component polyurethane sealants prepared in Examples 1-3 exhibit excellent curing speeds. After immersion in the mixed solvent, they show low volume and mass change rates and do not overflow during application, making them valuable in practical applications. 2. Compared with Example 2, Comparative Examples 1 and 2 showed a significant increase in both mass change rate and volume change rate, indicating that the solvent resistance of the sealant decreased. This suggests that the polyester polyol selected in this invention has good solvent resistance, which is related to the strong polarity of the ester group and the higher ester group density in polyethylene succinate.

[0069] 3. Compared with Example 2, Comparative Examples 3 and 4 showed a significant decrease in curing speed and obvious overflow during construction. This indicates that the thixotropic agent selected in this invention can significantly improve the thixotropy and curing speed of the single-component polyurethane sealant, effectively preventing overflow during actual construction.

[0070] In summary, this invention provides a one-component polyurethane sealant for sealing gas meters. It does not overflow during construction, exhibits good solvent resistance to benzene, toluene, xylene, and 120# gasoline, and maintains its sealing properties during long-term use.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0072] In summary, the technical solution of this application has the following beneficial technical effects: (1) In the technical solution of the present invention, by optimizing the composition of the polyurethane prepolymer and combining it with a high-efficiency catalyst system, the surface drying and hard drying time of the sealant is significantly shortened, which meets the process requirements for rapid positioning and efficient production in the assembly of gas instruments; the selected prepolymer with polyester / polyether polyol composite structure has both flexibility and chemical stability, combined with a dense cross-linked network structure, so that the cured adhesive layer has excellent resistance to hydrocarbons and trace sulfides that may exist in natural gas, and does not swell, crack or fail to bond during long-term use, thus ensuring the sealing reliability of the gas instrument under complex working conditions.

[0073] (2) The single-component polyurethane sealant for gas meter sealing of the present invention has better thixotropy and faster curing speed. It will not overflow during construction and has good solvent resistance. After being soaked in mixed solvent, the mass change rate and volume change rate of the sealant can be kept very small, and it can maintain good sealing performance during long-term use.

Claims

1. A one-component polyurethane sealant, characterized in that, It is prepared from the following raw materials by weight: 25-50 parts of polyurethane prepolymer, 30-60 parts of inorganic filler, 0-5 parts of tackifying agent, 5-10 parts of thixotropic agent, 0-2 parts of dehydrating agent and 0.01-1 parts of catalyst; The polyurethane prepolymer is prepared by reacting polyester polyol, polyether polyol and isocyanate in a mass ratio of (30-50):(20-30):(35-50).

2. The one-component polyurethane sealant according to claim 1, characterized in that, The polyester polyol includes at least one of polyethylene succinate and phthalic anhydride polyester polyol, wherein the molecular weight of the polyester polyol is 1000~3000 and the hydroxyl value is 50~100 mgKOH / g; The polyether polyol is a polyoxypropylene diol with a molecular weight of 1500~3000 and a hydroxyl value of 40~110 mgKOH / g. The isocyanate is at least one selected from toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and polymethylene polyphenyl polyisocyanate.

3. The one-component polyurethane sealant according to claim 1, characterized in that, The inorganic filler is at least one of light calcium carbonate, nano calcium carbonate, kaolin, and calcium oxide.

4. The one-component polyurethane sealant according to claim 1, characterized in that, The thickening agent includes at least one of 3-aminopropyltrimethylsilane, 3-aminopropyltriethylsilane, and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

5. The one-component polyurethane sealant according to claim 1, characterized in that, The thixotropic agent includes at least one of hydrophobic fumed silica and organobentonite.

6. The one-component polyurethane sealant according to claim 1, characterized in that, The dehydrating agent includes oxazolidine dehydrating agent.

7. The one-component polyurethane sealant according to claim 1, characterized in that, The catalyst is at least one selected from dibutyltin dilaurate, stannous octoate, bismorpholino diethyl ether, dimorpholino triethyl ether, triethylenediamine, and tetramethylenediamine.

8. A method for preparing a one-component polyurethane sealant as described in any one of claims 1 to 7, characterized in that, include: S1. Mix polyurethane prepolymer, inorganic filler, tackifier, thixotropic agent, dehydrating agent and catalyst under vacuum for 1-2 h to obtain polyurethane sealant.

9. The method for preparing the one-component polyurethane sealant according to claim 8, characterized in that, Step S1 is preceded by: S11. Heat polyester polyol and polyether polyol under vacuum to 115℃-125℃ to dehydrate for 20 min-40 min, cool to 55℃-65℃ and add isocyanate, heat to 75℃-80℃ and react for 2-4 hours, then degas under vacuum to obtain polyurethane prepolymer.

10. The application of a one-component polyurethane sealant in gas meters, characterized in that, The single-component polyurethane sealant includes the single-component polyurethane sealant as described in any one of claims 1 to 7, or is prepared according to the preparation method of the single-component polyurethane sealant as described in claim 8 or 9.

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