Polyurethane sealant for fault indicator and preparation method thereof

Abstract

The invention relates to the technical field of sealants, and discloses a polyurethane sealant for a fault indicator and a preparation method thereof. The polyurethane sealant is prepared by using a polyol as a soft segment and a diisocyanate as a hard segment, and is subjected to chain extension polymerization by a chain extender under the action of a catalyst to form a polyurethane pre-emulsion, which is then mixed with auxiliary materials such as a flame retardant, wherein the chain extender structure contains a large amount of long fatty hydrophobic chains, silicon-oxygen bonds and rigid pyrene rings. After the polyurethane is subjected to chain extension polymerization, these structures can be introduced into the polyurethane molecular chain, and the strong hydrophobicity of the long fatty hydrophobic chains, silicon-oxygen bonds and pyrene rings is utilized to improve the hydrophobic effect of the polyurethane molecular chain, and at the same time, the bonding strength of the polyurethane sealant can be effectively improved. The flame retardant is magnesium hydroxide with an isocyanate group modified on the surface, which can participate in the curing process of the polyurethane sealant, thereby achieving the effect of effectively improving the flame retardant performance of the polyurethane sealant by adding a small amount of it.

Description

Technical Field

[0001] The invention relates to the technical field of sealants, and in particular to a polyurethane sealant for a fault indicator and a preparation method thereof. Background Art

[0002] With the continuous development of science and technology, fault indicators have been widely used in various equipment and systems. Fault indicators are an important accessory for power equipment, widely used in power lines (overhead lines, cables and busbars) to indicate the location of fault currents. In order to ensure the stable operation of fault indicators in various harsh environments, it is crucial to choose a suitable sealant. Polyurethane sealant is a sealing material with excellent elasticity, wear resistance, high tensile strength, cold resistance and oil resistance. It is divided into two types: single component and two components. It has the characteristics of high tensile strength, excellent elasticity, wear resistance, oil resistance and cold resistance. Therefore, it is often used as a sealant for fault indicators. However, existing polyurethane sealants have some problems, such as insufficient adhesion, poor waterproof and moisture resistance, etc., which affect the service life and performance of fault indicators. Therefore, it has become an urgent need to develop a polyurethane sealant with excellent performance.

[0003] The invention patent with publication number CN114836164B discloses a silane-modified bio-based polyurethane waterproof sealant and a preparation method thereof. The sealant is endowed with good water-repellent, acid-base resistance and UV aging resistance by using a macromolecular diol or copolyester polyol containing a bio-based dimer nitrogen source, while also improving the mechanical properties of the sealant. Therefore, starting from the structure of the polyurethane and designing the soft and hard segment monomers, the various properties of the polyurethane sealant can be improved. Based on this, the present invention provides a polyurethane sealant having excellent bonding properties, waterproof and moisture-proof properties, etc., which can be directly used to make a fault indicator. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] In view of the deficiencies in the prior art, the present invention provides a polyurethane sealant for a fault indicator and a preparation method thereof.

[0006] (II) Technical solution

[0007] A method for preparing a polyurethane sealant for a fault indicator, the polyurethane sealant comprising the following raw materials measured in parts by weight: 15-30 parts of polyol, 10-15 parts of diisocyanate, 0.1-0.2 parts of catalyst, 2-3 parts of chain extender, 20-30 parts of ethyl acetate, 5-15 parts of plasticizer, 10-15 parts of flame retardant, 30-60 parts of filler, 0.1-0.2 parts of defoamer, and 0.2-0.5 parts of thixotropic agent;

[0008] The preparation method comprises the following steps:

[0009] The first step is to vacuum dehydrate the polyol at a temperature of 100-110°C, then cool it to 50-60°C, add diisocyanate, catalyst and ethyl acetate, stir mechanically after addition, control the temperature to 70-80°C, stir and react for 6-9h, then add the chain extender, after addition, keep warm and stir for 4-8h, cool and discharge, and obtain the polyurethane pre-emulsion;

[0010] The second step is to add plasticizer, flame retardant, filler and thixotropic agent into the polyurethane pre-emulsion, stir mechanically at a stirring rate of 300-500r / min to mix evenly, then continue to add defoaming agent, stir for 10-30 minutes, let it stand for defoaming, and then the polyurethane sealant can be obtained.

[0011] As a further embodiment of the present invention, the polyol is any one of polyoxypropylene polyol, polytetramethylene glycol or polyoxyethylene polyol; the diisocyanate is any one of toluene diisocyanate, isophorone diisocyanate or diphenylmethane diisocyanate; and the catalyst is any one of dibutyltin dilaurate, lead octoate or stannous octoate.

[0012] As a further embodiment of the present invention, the preparation method of the chain extender comprises the following steps:

[0013] Step A, stirring and mixing a chlorosilane compound and tetrahydrofuran to form a uniform reaction solution, then adding propylene oxide and triethylamine to the reaction solution, after the addition, introducing nitrogen protection, raising the temperature to 60-65° C., stirring at this temperature for 3-6 hours, evaporating and removing the solvent, collecting the product, and preparing a silane derivative;

[0014] Step B, adding silane derivatives, 1,6-pyrene dicarboxylic acid and N,N-dimethylformamide to a polymerization kettle, introducing nitrogen for protection, starting stirring, and waiting for a uniform solution to be formed, starting heating, maintaining the temperature at 80-90° C., and adding a phase transfer catalyst to the polymerization kettle. After the addition is completed, the mixture is stirred for 8-12 hours at a temperature maintained, the nitrogen is removed, the solvent is evaporated and removed, and the product is collected to obtain a chain extender.

[0015] As a further embodiment of the present invention, in step A, the chlorosilane compound is any one of dibutyldichlorosilane, dichlorodihexylsilane or dichlorodi-n-octylsilane.

[0016] As a further embodiment of the present invention, in step A, the molar ratio of the chlorosilane compound to glycidol is 1:2.

[0017] As a further embodiment of the present invention, in step B, the phase transfer catalyst is at least one of tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate or N,N-dimethylbenzylamine.

[0018] In the above technical scheme, chlorosilane compounds and glycidol are first used as reactants. Under the action of an acid-binding agent, the silicon-chloride groups and active hydroxyl substituents in each other's structures can undergo a substitution reaction to obtain a silane derivative containing two equivalents of epoxy substituents in the structure. Then, 1,6-pyrene dicarboxylic acid is used as a linker. Under the action of a phase transfer catalyst, the carboxyl substituents in its structure can undergo a continuous and uninterrupted ring-opening esterification reaction with the epoxy substituents in the structure of the silane derivative, thereby generating a block alternatingly connected macromolecular substance connected by ester bonds, namely a chain extender. Since a large number of hydroxyl substituents are generated in the ring-opening esterification process, these hydroxyl substituents can participate in the chain extension process of the polyurethane, thereby producing a chain extension polymerization effect.

[0019] As a further embodiment of the present invention, the preparation method of the flame retardant is as follows:

[0020] The magnesium hydroxide is ultrasonically dispersed in toluene to form a uniform dispersion, which is then placed in an ice bath environment. A surface modification agent is then added to the dispersion. After the addition is complete, the ice bath is removed and the dispersion is stirred at room temperature for 4-8 hours. The solid material is separated and washed and vacuum dried to obtain a flame retardant.

[0021] As a further embodiment of the present invention, the surface modification agent is any one of 5-isocyanate isopeptide chloride, 4-isocyanobenzoyl chloride or 3-isocyanatobenzoyl chloride.

[0022] In the above technical solution, a surface modification agent is used to modify the surface of magnesium hydroxide, and isocyanate groups are modified on the surface of magnesium hydroxide to prepare a flame retardant.

[0023] As a further embodiment of the present invention, the plasticizer is any one of phthalate, phosphate or benzoic acid glycol ester; the filler is any one of calcium carbonate, titanium dioxide, talc, carbon black or silicon dioxide; the defoamer is at least one of polyoxypropylene glycerol ether or pentaerythritol stearate; the thixotropic agent is any one of fumed silica, hydrogenated castor oil or bentonite.

[0024] A polyurethane sealant for a fault indicator is prepared by adopting the above preparation method.

[0025] (III) Beneficial technical effects

[0026] (1) The chain extender structure prepared by the present invention contains a large number of long fatty hydrophobic chains, siloxane bonds and rigid pyrene rings. After the polyurethane is subjected to chain extension polymerization, these structures can be introduced into the polyurethane molecular chain. The strong hydrophobicity of the long fatty hydrophobic chains, siloxane bonds and pyrene rings is utilized to improve the hydrophobic effect of the polyurethane molecular chain, so that the polyurethane sealant can form a super-hydrophobic surface after curing. At the same time, the chain extender structure contains a large number of hydroxyl substituents, so that the polyurethane molecular chain can present a cross-linked network structure, the structural density of the sealant is improved, and the penetration of water is effectively prevented, thereby improving the waterproof and moisture-proof performance of the polyurethane sealant. In addition, after the cross-linking density of the polyurethane molecular chain is improved, the cohesive energy increases, which is beneficial to improve the bonding strength of the polyurethane sealant.

[0027] (2) The present invention obtains a magnesium hydroxide-based flame retardant by surface modification of magnesium hydroxide and introduction of isocyanate functional groups on the surface thereof. Since the isocyanate functional groups can participate in the curing process of the polyurethane sealant, the interfacial compatibility between the magnesium hydroxide and the polyurethane can be greatly improved, and the magnesium hydroxide can be evenly dispersed in the polyurethane sealant, thereby achieving the effect of effectively improving the flame retardant properties of the polyurethane sealant by adding a small amount of the isocyanate functional groups. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for describing the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0029] Figure 1 Infrared analysis test chart of chain extender. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. Preferred embodiments of the present invention are given below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0031] Preparation Example 1

[0032] Preparation of chain extender:

[0033] Step A, 0.2 g of dichlorodihexylsilane and tetrahydrofuran were stirred and mixed to form a uniform reaction solution, and then 0.11 g of glycidol and 0.02 g of triethylamine were added to the reaction solution. After the addition was complete, nitrogen was introduced for protection, and the temperature was raised to 65° C., and the mixture was stirred for 4 hours at this temperature. The solvent was evaporated and removed, and the product was collected to prepare a silane derivative;

[0034] Step B, add 0.3g of silane derivative, 0.3g of 1,6-pyrene dicarboxylic acid and N,N-dimethylformamide to the polymerization kettle, introduce nitrogen for protection, start stirring, and wait until a uniform solution is formed, turn on heating, maintain the temperature at 90°C, and add 0.01g of tetrabutylammonium bromide to the polymerization kettle. After the addition, keep warm and stir for 9h, remove nitrogen, evaporate and remove the solvent, collect the product, and the chain extender can be obtained.

[0035] Figure 1 This is the infrared analysis test chart of the chain extender, where 3231cm -1 The characteristic absorption peak at 3000cm is the characteristic absorption peak of hydroxyl group. -1 ~3100cm -1 The characteristic absorption peak at 2800 cm is the characteristic absorption peak of carbon and hydrogen in the rigid pyrene ring structure. -1 ~3000cm -1 The characteristic absorption peak at 1749cm is the characteristic absorption peak of carbon and hydrogen in the methyl and methylene structures. -1 The characteristic absorption peak at 1029 cm is the characteristic absorption peak of the ester group C=O produced by the ring-opening esterification reaction. -1 The characteristic absorption peak that appears at is the Si-O characteristic absorption peak produced by the substitution reaction.

[0036] Preparation Example 2

[0037] Preparation of flame retardant:

[0038] 2.5 g of magnesium hydroxide was ultrasonically dispersed in toluene to form a uniform dispersion, which was then placed in an ice bath. 0.4 g of 3-isocyanatobenzoyl chloride was then added to the dispersion. After the addition was complete, the ice bath was removed and the mixture was stirred at room temperature for 6 hours. The solid material was separated and washed and vacuum dried to obtain a flame retardant.

[0039] Example 1

[0040] A polyurethane sealant for a fault indicator, comprising the following raw materials measured by weight: 15 parts of polyol, 10 parts of diisocyanate, 0.1 parts of dibutyltin dilaurate, 2 parts of chain extender, 20 parts of ethyl acetate, 5 parts of plasticizer, 10 parts of flame retardant, 30 parts of calcium carbonate, 0.1 parts of polyoxypropylene glycerol ether, and 0.2 parts of fumed silica;

[0041] The preparation method of the polyurethane sealant comprises the following steps:

[0042] The first step is to vacuum dehydrate the polyol at a temperature of 100°C, then cool it to 50°C, add diisocyanate, dibutyltin dilaurate and ethyl acetate, stir mechanically after addition, control the temperature to 70°C, stir and react for 6 hours, then add the chain extender, keep warm and stir for 4 hours, cool and discharge, and obtain the polyurethane pre-emulsion;

[0043] In the second step, plasticizer, flame retardant, calcium carbonate and fumed silica are added to the polyurethane pre-emulsion, and after being mechanically stirred and mixed at a stirring rate of 300r / min, polyoxypropylene glycerol ether is added, and after stirring for 10 minutes, the mixture is allowed to stand for defoaming to obtain the polyurethane sealant.

[0044] The polyol is polytetramethylene glycol with a number average molecular weight of 2000; the diisocyanate is isophorone diisocyanate; the preparation method of the chain extender is shown in Preparation Example 1; the plasticizer is dioctyl phthalate; the preparation method of the flame retardant is shown in Preparation Example 2, and the following are the same.

[0045] Example 2

[0046] A polyurethane sealant for a fault indicator, comprising the following raw materials measured by weight: 20 parts of polyol, 12 parts of diisocyanate, 0.1 parts of stannous octoate, 2.5 parts of chain extender, 25 parts of ethyl acetate, 10 parts of plasticizer, 12 parts of flame retardant, 50 parts of talc, 0.1 parts of pentaerythritol stearate, and 0.3 parts of bentonite;

[0047] The preparation method of the polyurethane sealant comprises the following steps:

[0048] The first step is to vacuum dehydrate the polyol at a temperature of 110°C, then cool it to 55°C, add diisocyanate, stannous octoate and ethyl acetate, stir mechanically after addition, control the temperature to 75°C, stir and react for 8 hours, then add the chain extender, keep warm and stir for 6 hours, cool and discharge, and obtain the polyurethane pre-emulsion;

[0049] In the second step, plasticizer, flame retardant, talcum powder and bentonite are added into the polyurethane pre-emulsion, and after being mechanically stirred and mixed evenly at a stirring rate of 400r / min, pentaerythritol stearate is added, and after stirring for 20 minutes, the mixture is allowed to stand for defoaming, and the polyurethane sealant is obtained.

[0050] Example 3

[0051] A polyurethane sealant for a fault indicator, comprising the following raw materials measured by weight: 30 parts of polyol, 15 parts of dibasic isocyanate, 0.2 parts of dibutyltin dilaurate, 3 parts of chain extender, 30 parts of ethyl acetate, 15 parts of plasticizer, 15 parts of flame retardant, 60 parts of carbon black, 0.2 parts of pentaerythritol stearate, and 0.5 parts of hydrogenated castor oil;

[0052] The preparation method of the polyurethane sealant comprises the following steps:

[0053] The first step is to vacuum dehydrate the polyol at a temperature of 110°C, then cool it to 60°C, add diisocyanate, dibutyltin dilaurate and ethyl acetate, stir mechanically after addition, control the temperature to 80°C, stir and react for 9 hours, then add the chain extender, keep warm and stir for 8 hours, cool and discharge, and obtain the polyurethane pre-emulsion;

[0054] In the second step, plasticizer, flame retardant, carbon black and hydrogenated castor oil are added into the polyurethane pre-emulsion, and after being uniformly mixed by mechanical stirring at a stirring rate of 500r / min, pentaerythritol stearate is added, and after stirring for 30 minutes, the mixture is allowed to stand for defoaming, and the polyurethane sealant is obtained.

[0055] Comparative Example 1

[0056] A polyurethane sealant for a fault indicator, comprising the following raw materials measured by weight: 20 parts of polyol, 12 parts of diisocyanate, 0.1 parts of stannous octoate, 2.5 parts of chain extender, 25 parts of ethyl acetate, 10 parts of plasticizer, 12 parts of magnesium hydroxide, 50 parts of talc, 0.1 parts of pentaerythritol stearate, and 0.3 parts of bentonite;

[0057] The preparation method of the polyurethane sealant comprises the following steps:

[0058] The first step is to vacuum dehydrate the polyol at a temperature of 110°C, then cool it to 55°C, add diisocyanate, stannous octoate and ethyl acetate, stir mechanically after addition, control the temperature to 75°C, stir and react for 8 hours, then add the chain extender, keep warm and stir for 6 hours, cool and discharge, and obtain the polyurethane pre-emulsion;

[0059] In the second step, plasticizer, magnesium hydroxide, talcum powder and bentonite are added into the polyurethane pre-emulsion, and after being mechanically stirred and mixed evenly at a stirring rate of 400r / min, pentaerythritol stearate is added, and after stirring for 20 minutes, the mixture is allowed to stand for defoaming, and the polyurethane sealant is obtained.

[0060] Comparative Example 2

[0061] A polyurethane sealant for a fault indicator, comprising the following raw materials measured by weight: 20 parts of polyol, 12 parts of diisocyanate, 0.1 parts of stannous octoate, 2.5 parts of a conventional chain extender, 25 parts of ethyl acetate, 10 parts of a plasticizer, 12 parts of a flame retardant, 50 parts of talc, 0.1 parts of pentaerythritol stearate, and 0.3 parts of bentonite;

[0062] The preparation method of the polyurethane sealant comprises the following steps:

[0063] The first step is to vacuum dehydrate the polyol at a temperature of 110°C, then cool it to 55°C, add diisocyanate, stannous octoate and ethyl acetate, stir mechanically after addition, control the temperature to 75°C, stir and react for 8 hours, then add a conventional chain extender, keep warm and stir for 6 hours, cool and discharge, and obtain a polyurethane pre-emulsion;

[0064] In the second step, plasticizer, flame retardant, talcum powder and bentonite are added into the polyurethane pre-emulsion, and after being mechanically stirred and mixed evenly at a stirring rate of 400r / min, pentaerythritol stearate is added, and after stirring for 20 minutes, the mixture is allowed to stand for defoaming, and the polyurethane sealant is obtained.

[0065] The conventional chain extender used in this comparative example is 2,2-dimethylolpropionic acid.

[0066] Test Case

[0067] The polyurethane sealants in the embodiments and comparative examples were made into test samples that met the specifications, and various performance tests were performed. The results are recorded in the following table:

[0068] 180° peel strength / N / 25mm Tensile strength / MPa Water contact angle / ° Oxygen index / % Example 1 4.5 29.8 151 29.4 Example 2 4.7 30.3 152 29.5 Example 3 4.5 30.1 151 29.4 Comparative Example 1 4.4 29.5 150 26.1 Comparative Example 2 3.2 25.7 114 29.1

[0069] Note: The 180° peel strength test method refers to the standard GB / T 2792-1998; the tensile strength test method is: the polyurethane sealant is made into a film sample with a thickness of 50μm, and the tensile performance test is carried out according to the standard GB / T528-2009; the water contact angle test method is: use a water contact angle meter to test the water contact angle of the film; the oxygen index test method refers to the standard GB / T 2406.2-2009.

[0070] Based on the ideal embodiment of the present invention, through the above description, relevant personnel can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the content in the specification, and the technical scope must be determined according to the scope of the claims.

Claims

1. A method for preparing a polyurethane sealant for a fault indicator, characterized in that: The polyurethane sealant includes the following raw materials measured by weight: 15-30 parts of polyol, 10-15 parts of diisocyanate, 0.1-0.2 parts of catalyst, 2-3 parts of chain extender, 20-30 parts of ethyl acetate, 5-15 parts of plasticizer, 10-15 parts of flame retardant, 30-60 parts of filler, 0.1-0.2 parts of defoamer, and 0.2-0.5 parts of thixotropic agent; The preparation method comprises the following steps: The first step is to vacuum dehydrate the polyol at a temperature of 100-110°C, then cool it to 50-60°C, add diisocyanate, catalyst and ethyl acetate, stir mechanically after addition, control the temperature to 70-80°C, stir and react for 6-9h, then add the chain extender, after addition, keep warm and stir for 4-8h, cool and discharge, and obtain the polyurethane pre-emulsion; The second step is to add plasticizer, flame retardant, filler and thixotropic agent into the polyurethane pre-emulsion, stir mechanically at a stirring rate of 300-500r / min to mix evenly, then continue to add defoaming agent, stir for 10-30 minutes, let it stand for defoaming, and then the polyurethane sealant can be obtained.

2. The method for preparing a polyurethane sealant for a fault indicator according to claim 1, characterized in that: The polyol is any one of polyoxypropylene polyol, polytetramethylene glycol or polyoxyethylene polyol; the diisocyanate is any one of toluene diisocyanate, isophorone diisocyanate or diphenylmethane diisocyanate; and the catalyst is any one of dibutyltin dilaurate, lead octoate or stannous octoate.

3. The method for preparing a polyurethane sealant for a fault indicator according to claim 1, characterized in that: The preparation method of the chain extender comprises the following steps: Step A, stirring and mixing a chlorosilane compound and tetrahydrofuran to form a uniform reaction solution, then adding propylene oxide and triethylamine to the reaction solution, after the addition, introducing nitrogen protection, raising the temperature to 60-65° C., stirring at this temperature for 3-6 hours, evaporating and removing the solvent, collecting the product, and preparing a silane derivative; Step B, adding silane derivatives, 1,6-pyrene dicarboxylic acid and N,N-dimethylformamide to a polymerization kettle, introducing nitrogen for protection, starting stirring, and waiting for a uniform solution to be formed, starting heating, maintaining the temperature at 80-90° C., and adding a phase transfer catalyst to the polymerization kettle. After the addition is completed, the mixture is stirred for 8-12 hours at a temperature maintained, the nitrogen is removed, the solvent is evaporated and removed, and the product is collected to obtain a chain extender.

4. The method for preparing a polyurethane sealant for a fault indicator according to claim 3, characterized in that: In step A, the chlorosilane compound is any one of dibutyldichlorosilane, dichlorodihexylsilane or dichlorodi-n-octylsilane.

5. The method for preparing a polyurethane sealant for a fault indicator according to claim 3, characterized in that: In step A, the molar ratio of the chlorosilane compound to glycidol is 1:

2.

6. The method for preparing a polyurethane sealant for a fault indicator according to claim 3, characterized in that: In step B, the phase transfer catalyst is at least one of tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate or N,N-dimethylbenzylamine.

7. The method for preparing a polyurethane sealant for a fault indicator according to claim 1, characterized in that: The preparation method of the flame retardant is as follows: The magnesium hydroxide is ultrasonically dispersed in toluene to form a uniform dispersion, which is then placed in an ice bath environment. A surface modification agent is then added to the dispersion. After the addition is complete, the ice bath is removed and the dispersion is stirred at room temperature for 4-8 hours. The solid material is separated and washed and vacuum dried to obtain a flame retardant.

8. The method for preparing a polyurethane sealant for a fault indicator according to claim 8, characterized in that: The surface modification agent is any one of 5-isocyanate isopeptide chloride, 4-isocyanobenzoyl chloride or 3-isocyanoxybenzoyl chloride.

9. The method for preparing a polyurethane sealant for a fault indicator according to claim 1, characterized in that: The plasticizer is any one of phthalate, phosphate or benzoic acid glycol ester; the filler is any one of calcium carbonate, titanium dioxide, talc, carbon black or silicon dioxide; the defoamer is at least one of polyoxypropylene glycerol ether or pentaerythritol stearate; the thixotropic agent is any one of fumed silica, hydrogenated castor oil or bentonite.

10. A polyurethane sealant for a fault indicator, characterized in that: The method is prepared according to claim 1.

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