Silane chain extender and its preparation method and application

Abstract

The present invention discloses a silane chain extender and its preparation method and application, belonging to the field of organic silicon technology. The structural formula of the silane chain extender is as follows:; The preparation method is: 1) Add aminosilane and solvent into a reaction bottle, connect a reflux condenser, add ketone compounds after heating, keep warm and react, and remove small molecules from the system; 2) After the reaction product of step 1) cools down, start to add isocyanate, and heat and react after the dripping is complete; 3) After the reaction product of step 2) cools down, add benzenesulfonic acid substances, and keep warm and react after the addition is complete, and finally obtain the silane chain extender. The present invention is applied to occasions with high elasticity requirements. The rubber strip is not easy to crack in an environment where expansion and contraction occur, and its performance can still be maintained for a long time.

Description

Technical Field

[0001] The invention belongs to the technical field of organic silicon, and specifically relates to a silane chain extender and a preparation method and application thereof. Background Art

[0002] Silicone sealant has excellent heat resistance, natural aging resistance, moisture resistance and air permeability, as well as excellent electrical properties and chemical inertness. It can maintain elasticity for a long time in a large temperature range, has a small shrinkage rate after curing, and has a wide bonding range. However, for some occasions with high elongation requirements, ordinary silicone glue cannot meet the requirements, so it is often necessary to add chain extenders to silicone glue to improve its elastic properties. Chain extenders contain highly active groups that can quickly react with 107 glue to generate macromolecular chains or prepolymers with more branched structures, reduce cross-linking density, and thus achieve the purpose of increasing elongation.

[0003] At present, the commonly used chain extenders in silicone rubber systems are dimethyldimethoxysilane, dimethyldiethoxysilane, dimethyldibutylketoxime silane, and methylvinyldibutylketoxime silane. The alkoxy type of these chain extenders has a low boiling point and is easily removed during the rubber making process, while the ketoxime type is not very effective. The more obvious effect is the amide type silane such as dimethylbis (N-methylacetylamino) silane and methylvinylbis (N-methylacetylamino) silane, but there are few such products on the market, and the cost is high and it is not easy to preserve. The chain extenders used in other systems are mostly isocyanate type, epoxy type and ester type. Isocyanate has the highest activity and the best effect, but these types have the problem of poor compatibility with silicone rubber systems and may migrate. Therefore, it is necessary to develop a silane chain extender containing highly active groups such as isocyanate, imine, alkoxy and good compatibility with silicone rubber systems. Summary of the invention

[0004] The present invention provides a silane chain extender and a preparation method and application thereof, which solves the problem that common silicone adhesive cannot meet the requirement for elongation and is applied to occasions with high elasticity requirements. In an environment where expansion and contraction occur, the adhesive strip is not easy to crack and can still maintain its performance for a long time.

[0005] The technical solution of the present invention is:

[0006] In the first aspect, a silane chain extender is disclosed, and its structural formula is as follows:

[0007] ;

[0008] Wherein R1 represents a methoxy group or an ethoxy group, R2 represents one of a methyl group, an ethyl group and H, R3 represents one of a trimethyl-1,6-hexamethylene group, a tetramethyl-isophthalimethylene group and a hexamethylene group, and R4 is a dodecyl group.

[0009] In a second aspect, a method for preparing the silane chain extender is disclosed, comprising the following steps:

[0010] 1) Add aminosilane and solvent into the reaction bottle, connect the reflux condenser, add ketone compound dropwise after heating, keep the temperature to react, and remove small molecules from the system;

[0011] 2) After the reaction product of step 1) is cooled down, isocyanate is added dropwise, and the temperature is raised to react after the addition is complete;

[0012] 3) After the reaction product of step 2) is cooled, benzenesulfonic acid is added dropwise, and the mixture is kept warm for reaction to finally obtain a silane chain extender.

[0013] Preferably, the molar ratio of the aminosilane, ketone compound, isocyanate and benzenesulfonic acid substance is 1: (0.8-1.0): (0.4-1.0): (0.05-0.15).

[0014] Preferably, the aminosilane is aminopropylmethyldimethoxysilane or aminopropylmethyldiethoxysilane; the solvent is a mixture of alcohol and amide, the alcohol is selected from one of methanol, ethanol and butanol, and the amide is dimethylformamide or dimethylacetamide.

[0015] Preferably, the ketone compound is a thiol-containing ketone substance, selected from one of 4-mercapto-2-butanone, 3-mercapto-2-butanone, 4-mercapto-2-pentanone and 3-mercapto-2-pentanone.

[0016] Preferably, in step 1), the temperature for dripping the ketone compound is 50-65° C., the dripping time is 30-50 min, and the reaction is kept warm for 4-6 h after the dripping is completed.

[0017] Preferably, the isocyanate is one of hexamethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate and tetramethyl-m-xylylene diisocyanate.

[0018] Preferably, in step 2), the temperature for dripping the isocyanate is 40-55° C., the dripping time is 40-60 min, and after the dripping is complete, the temperature is raised to 60-70° C. and the reaction is carried out for 3-5 h.

[0019] Preferably, the benzenesulfonic acid substance is dodecylbenzenesulfonic acid; the temperature for adding the benzenesulfonic acid substance in step 3) is 40-45°C, the adding time is 40-60min, and the reaction is completed for 3-4.5h.

[0020] In a third aspect, disclosed is the use of the silane chain extender prepared by the preparation method in the preparation of silicone rubber.

[0021] The raw materials of the present invention, aminosilane, ketone, and isocyanate are all highly active substances, especially aminosilane and isocyanate are very easy to react to form gel, and the reaction needs to be carried out in two steps. The first step is to react aminosilane and ketone to form imine, add solvent into the system and remove small molecules after the reaction is completed to prevent aminosilane from hydrolyzing and condensing due to moisture generated by the reaction, and then add isocyanate to react with mercapto groups. The reaction equations in each step are as follows:

[0022] Step 1)

[0023] ;

[0024] Step 2)

[0025] ;

[0026] Step 3)

[0027] Compared with the prior art, the present invention has the following beneficial effects:

[0028] (1) The present invention first prepares an imine silane through a Schiff base reaction to eliminate the active hydrogen of the aminosilane and prevent the amino group from reacting with isocyanate. Then, a high-activity silane is generated through an addition reaction between the mercapto group and the isocyanate. Finally, a benzenesulfonic acid substance is added to the isocyanate to generate a macromolecular chain extender, thereby avoiding the problem of poor compatibility between general additives and the silicone rubber system. Due to the presence of highly active groups such as amino ester, imine, and alkoxy, it is easy to react with 107 rubber to achieve the purpose of chain extension. The chain extender molecule contains a phenyl group with large steric hindrance and a long-chain hydrocarbon group in the structure of the benzenesulfonic acid substance, which reduces the crosslinking density of the silicone rubber and enables the prepared silicone rubber to have better tensile properties.

[0029] (2) The present invention is prepared by a two-step method, the reaction temperature is not high, the process is simple and easy to control. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is the infrared spectrum of the iminosilane generated in step 1) of Example 1 of the present invention.

[0031] Figure 2 This is an infrared spectrum of the isocyanate-containing iminosilane generated in step 2) of Example 1 of the present invention.

[0032] Figure 3 It is an infrared spectrum of the isocyanate generated in step 3) of Example 1 of the present invention. DETAILED DESCRIPTION

[0033] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0034] Example 1

[0035] This embodiment provides a silane chain extender, the structural formula of which is as follows:

[0036] ;

[0037] The preparation method of the silane chain extender is as follows:

[0038] 1) Add 38.27g aminopropylmethyldiethoxysilane, 20g dimethylformamide, and 20g ethanol into a 250mL three-necked flask, connect a reflux condenser, heat to 65°C, start to drop 23.64g 3-mercapto-2-pentanone, and let it drip for 50 minutes. React for 6 hours, then heat to 80°C and control the vacuum degree to -0.05MPa to remove small molecules from the system for 2 hours. The infrared spectrum of the generated iminosilane is as follows: Figure 1 As shown, 1100.75cm -1 The infrared peak of silicon-oxygen-carbon bond is 1069.74 cm -1 The infrared peak of silicon-oxygen-silicon bond is 2560.90 cm -1 The infrared peak of mercapto group is 1463.58cm -1 、1655.27cm -1 is the infrared peak of imine;

[0039] 2) After the above reactants are cooled to 40°C, 42.06 g of trimethyl-1,6-hexamethylene diisocyanate is added dropwise over 60 minutes, and then the temperature is raised to 70°C for 4 hours to generate an isocyanate-containing iminosilane. The infrared spectrum is as follows: Figure 2 As shown, 2261.57cm -1 is the infrared peak of isocyanate, 1681.22cm -1 It is the infrared peak of amino ester generated after partial reaction of isocyanate;

[0040] 3) After the reaction temperature drops to 40°C, 9.78 g of dodecylbenzenesulfonic acid is added dropwise over 40 minutes. The reaction is kept warm for 4 hours to finally obtain a silane chain extender. The infrared spectrum of the generated isocyanate is as follows: Figure 3 As shown, 1690.43cm -1 It is the infrared peak of amino ester, and the infrared peak of isocyanate group disappears.

[0041] Example 2

[0042] This embodiment provides a silane chain extender, the structural formula of which is as follows:

[0043] ;

[0044] 1) Add 32.66g aminopropylmethyldimethoxysilane, 15g dimethylformamide, and 20g ethanol into a 250mL three-necked flask, connect a reflux condenser, heat to 60°C, start to drop 23.64g 3-mercapto-2-pentanone, and let it drip for 50 minutes. React for 5 hours, then heat to 80°C and control the vacuum degree to -0.06MPa to remove small molecules from the system for 2 hours.

[0045] 2) After the above reactants are cooled to 40°C, 42.06 g of trimethyl-1,6-hexamethylene diisocyanate is added dropwise over 60 minutes, and then the temperature is raised to 60°C for reaction for 4 hours;

[0046] 3) After the reaction temperature drops to 45°C, 9.78 g of dodecylbenzenesulfonic acid is added dropwise over 40 minutes. The mixture is kept warm for 3.5 hours to obtain a silane chain extender.

[0047] Example 3

[0048] This embodiment provides a silane chain extender, the structural formula of which is as follows:

[0049] ;

[0050] 1) Add 38.27g aminopropylmethyldiethoxysilane, 20g dimethylacetamide, and 25g methanol into a 250mL three-necked flask, connect a reflux condenser, heat to 60°C, start to drop 18.91g 4-mercapto-2-pentanone, and finish dropping it within 40 minutes. React for 5 hours, then heat to 80°C and control the vacuum degree to -0.06MPa to remove small molecules from the system for 2 hours.

[0051] 2) After the above reactants are cooled to 40°C, 39.08 g of tetramethyl-m-xylylene diisocyanate is added dropwise over 60 minutes, and then the temperature is raised to 65°C for reaction for 5 hours;

[0052] 3) After the reaction temperature drops to 45°C, 6.52 g of dodecylbenzenesulfonic acid is added dropwise over 60 minutes. The mixture is kept warm for 4.5 hours to finally obtain a silane chain extender.

[0053] Example 4

[0054] This embodiment provides a silane chain extender, the structural formula of which is as follows:

[0055] ;

[0056] 1) Add 38.27g aminopropylmethyldiethoxysilane, 20g dimethylacetamide, and 15g butanol into a 250mL three-necked flask, connect a reflux condenser, heat to 50°C, start to drop 23.64g of 3-mercapto-2-pentanone, and finish dropping after 30 minutes. React for 4 hours, then heat to 80°C and control the vacuum degree to -0.05MPa to remove small molecules from the system for 2 hours;

[0057] 2) After the above reactants are cooled to 45°C, 16.82 g of hexamethylene diisocyanate is added dropwise over 40 minutes, and then the temperature is raised to 70°C for 4 hours;

[0058] 3) After the reaction temperature drops to 40°C, 6.52 g of dodecylbenzenesulfonic acid is added dropwise over 50 minutes. The mixture is kept warm for 4 hours to finally obtain a silane chain extender.

[0059] Example 5

[0060] This embodiment provides a silane chain extender, the structural formula of which is as follows:

[0061] ;

[0062] 1) Add 32.66g aminopropylmethyldimethoxysilane, 20g dimethylformamide, and 20g ethanol into a 250mL three-necked flask, connect a reflux condenser, heat to 65°C, start to drop 18.75g 4-mercapto-2-butanone, and let it drip for 40 minutes. React for 5 hours, then heat to 80°C and control the vacuum degree to -0.07MPa to remove small molecules from the system for 2 hours.

[0063] 2) After the above reactants are cooled to 45°C, 16.82 g of trimethyl-1,6-hexamethylene diisocyanate is added dropwise for 40 minutes, and then the temperature is raised to 65°C for reaction for 3 hours;

[0064] 3) After the reaction temperature drops to 42°C, 3.26 g of dodecylbenzenesulfonic acid is added dropwise over 40 minutes. The mixture is kept warm for 3 hours to finally obtain a silane chain extender.

[0065] Example 6

[0066] This embodiment provides a silane chain extender, the structural formula of which is as follows:

[0067] ;

[0068] 1) Add 32.66g aminopropylmethyldimethoxysilane, 15g dimethylformamide, and 15g butanol into a 250mL three-necked flask, connect a reflux condenser, heat to 60°C, and start to drop 16.66g of 3-mercapto-2-butanone. Add the mixture for 40 minutes, react for 4 hours, then heat to 80°C and control the vacuum degree to -0.05MPa to remove small molecules from the system for 2 hours;

[0069] 2) After the above reactants are cooled to 55°C, 24.43 g of tetramethyl meta-xylylene diisocyanate is added dropwise over 50 minutes, and then the temperature is raised to 70°C for reaction for 5 hours;

[0070] 3) After the reaction temperature drops to 45°C, 6.52 g of dodecylbenzenesulfonic acid is added dropwise over 60 minutes. The mixture is kept warm for 4.5 hours to finally obtain a silane chain extender.

[0071] Comparative Example 1

[0072] The preparation method of the chain extender is as follows:

[0073] 1) Add 38.27g aminopropylmethyldiethoxysilane, 20g dimethylformamide, and 20g ethanol into a 250mL three-necked flask, connect a reflux condenser, heat to 65°C, and start to drop 23.64g of 3-mercapto-2-pentanone. Add the mixture after 30 minutes. React for 5h, then heat to 80°C and control the vacuum degree to -0.05MPa to remove small molecules from the system for 2h.

[0074] 2) 42.06 g of trimethyl-1,6-hexamethylene diisocyanate was added dropwise over 50 minutes, and then the temperature was raised to 70°C for reaction for 4 hours. The system had a high viscosity and gradually gelled during the cooling process, making it impossible to carry out subsequent reactions. In this comparative example, there was no cooling treatment before entering step 2) after step 1), resulting in excessive viscosity of the system. The main reason was that the temperature during the addition process was too high, there were many side reactions, and some urea was generated. After the addition was completed, as the reaction time became longer and longer, more urea was generated and eventually gelled.

[0075] Comparative Example 2

[0076] Different from Example 1, the solvent "20 g dimethylformamide, 20 g ethanol" is replaced by "40 g dimethylformamide" in this comparative example, and the other reaction conditions and processes are the same as those in Example 1.

[0077] Comparative Example 3

[0078] Different from Example 1, small molecules are not removed in step 1) of this comparative example, and the other reaction conditions and processes are the same as those of Example 1. Since there is unremoved water in the system, it is gradually hydrolyzed and condensed during the reaction to eventually form a gel.

[0079] Comparative Example 4

[0080] Different from Example 1, step 1) of this comparative example is: 38.27g aminopropylmethyldiethoxysilane, 20g dimethylformamide, and 20g ethanol are added to a 250mL three-necked flask, connected to a reflux condenser, heated to 65°C, and 23.64g 3-mercapto-2-pentanone is directly added at one time, reacted for 5h, then heated to 80°C and controlled the vacuum degree to -0.05MPa, and small molecules of the system are removed for 2h, and the remaining reaction conditions and processes are the same as those of Example 1. The product has a large viscosity, and adding all the ketones at one time will result in a rapid reaction to produce more water, and the siloxane undergoes a large polycondensation to form a macromolecular chain compound.

[0081] Comparative Example 5

[0082] Different from Example 1, step 2) of this comparative example is: after the above reactants are cooled to 40°C, 42.06g of trimethyl-1,6-hexamethylene diisocyanate is added at one time, and then the temperature is raised to 70°C for reaction for 4h; the remaining reaction conditions and processes are the same as those of Example 1. The viscosity of the system gradually increases, and finally gels. The isocyanate reaction activity is very high, and it reacts quickly with active hydrogen when all is added to the system at one time to generate some urea, resulting in the increasing viscosity of the system and finally gelling.

[0083] Comparative Example 6

[0084] Different from Example 1, step 3) of this comparative example is: after the reaction temperature is cooled to 40°C, 9.78g of dodecylbenzenesulfonic acid is added at one time, and the reaction is kept warm for 4 hours to finally obtain a silane chain extender. The viscosity of the system gradually increases and finally gels. Direct addition to the reaction is highly exothermic, which promotes the occurrence of side reactions and finally makes the system gel.

[0085] Comparative Example 7

[0086] The preparation method of the chain extender is as follows:

[0087] 1) Add 38.27g aminopropylmethyldiethoxysilane, 20g dimethylformamide, and 20g ethanol into a 250mL three-necked flask, connect a reflux condenser, heat to 65°C, start to drop 23.64g 3-mercapto-2-pentanone, and finish dropping it within 50 minutes. React for 6 hours, then heat to 80°C and control the vacuum degree to -0.05MPa to remove small molecules from the system for 2 hours.

[0088] 2) After the above reactants are cooled to 40°C, 21.05 g of trimethyl-1,6-hexamethylene diisocyanate is added dropwise over 60 minutes, and then the temperature is raised to 70°C for 4 hours;

[0089] 3) After the reaction temperature drops to 40°C, add 3.26 g of dodecylbenzenesulfonic acid, add the mixture over 40 minutes, and keep the mixture warm for 4 hours to finally obtain a silane chain extender.

[0090] Examples 7-12 and Comparative Examples 8-10

[0091] The silane chain extenders prepared in Examples 1-6 and Comparative Examples 2, 4 and 7 were used to prepare ketoxime-type silicone rubber according to the formula in Table 1. The silane chain extenders prepared in Examples 1-6, Comparative Examples 2, 4 and 7 correspond to Examples 7-12 and Comparative Examples 8-10, respectively. The specific method is as follows: ① Put hydroxyl-terminated polydimethylsiloxane (abbreviated as 107), methyl silicone oil and calcium carbonate into a kneader, start stirring, heat to 140°C and disperse for 4 hours, and form a base material after cooling; ② Take 1 kg of the above base material into a planetary mixer, add methyl tributylidene oxime silane, vinyl tributylidene oxime silane, the chain extender prepared in Examples 1-6 or the silane chain extender prepared in Comparative Examples 2, 4 and 7, vacuum stir for 25 minutes, and then add dibutyltin dilaurate and vacuum stir for 25 minutes to discharge.

[0092] Table 1 Formulas for preparing silane chain extenders in Examples 1-6, Comparative Examples 2, 4 and 7

[0093]

[0094] Comparative Example 11

[0095] Different from Example 7, in this comparative example, no chain extender was added.

[0096] Comparative Example 12

[0097] Different from Example 7, in this comparative example, an equal amount of commercially available dibutyl ketoxime silane was added to replace the chain extender.

[0098] According to the standard GB / T14683-2017 "Silicone and modified silicone building sealants", the modules were prepared and the elastic elongation of Examples 7-12 and Comparative Examples 8-12 was tested. The results are shown in Table 2.

[0099] Table 2 Elastic elongation of Examples 7-12 and Comparative Examples 8-12

[0100]

[0101] Compared with Example 1, the amide solvent used in Comparative Example 2 has a higher boiling point and cannot be removed under the conditions of 80°C and -0.05MPa, and will remain in the product, which is equivalent to an increase in the amount of solvent, a decrease in the relative content of the chain extender, and a decrease in the elongation of the prepared silicone rubber;

[0102] Compared with Example 1, the alkoxy group in Comparative Example 4 was hydrolyzed to a greater extent, the product was polycondensed, and the alkoxy content was reduced. Comparative Example 7 produced less amino ester. The active group content of the products produced by both was relatively reduced, and the effect was reduced.

[0103] The elongation at break of the silicone rubber prepared in Comparative Example 11 without adding a chain extender is very low and cannot meet normal usage requirements.

[0104] In Comparative Example 12, a commercially available silicone adhesive chain extender, dibutyl ketoxime silane, is used, which can rapidly react with the hydroxyl group of 107 to extend the chain, but the effect is not very good. The present invention prepares an alkoxy-type macromolecular chain extender through a silane coupling agent, which solves the problem of easy detachment during adhesive preparation due to the low boiling point. The molecular chain contains active groups such as alkoxy and amino ester, which are easy to react with the hydroxyl groups in 107 and the filler. In addition, due to the presence of phenyl and long-chain alkyl groups, the steric hindrance of the sealant system is increased, resulting in a decrease in the crosslinking density, so that the silicone adhesive has a better elongation at break.

Claims

1. A silane chain extender, characterized in that: Its structural formula is as follows: ； Wherein R1 represents a methoxy group or an ethoxy group, R2 represents one of a methyl group, an ethyl group and H, R3 represents one of a trimethyl-1,6-hexamethylene group, a tetramethyl-isophthalimethylene group and a hexamethylene group, and R4 is a dodecyl group.

2. The method for preparing a silane chain extender according to claim 1, characterized in that: The following steps are involved: 1) Add aminosilane and solvent into the reaction bottle, connect the reflux condenser, add ketone compound dropwise after heating, keep the temperature to react, and remove small molecules from the system; 2) After the reaction product of step 1) is cooled down, isocyanate is added dropwise, and the temperature is raised to react after the addition is complete; 3) After the reaction product of step 2) is cooled, benzenesulfonic acid is added dropwise, and after the addition is completed, the temperature is kept for reaction to finally obtain a silane chain extender; The aminosilane is aminopropylmethyldimethoxysilane or aminopropylmethyldiethoxysilane; The solvent is a mixture of alcohol and amide, the alcohol is selected from one of methanol, ethanol and butanol, and the amide is dimethylformamide or dimethylacetamide; The ketone compound is one of 3-mercapto-2-butanone and 3-mercapto-2-pentanone; The isocyanate is one of hexamethylene diisocyanate, trimethyl-1,6-hexamethylene diisocyanate and tetramethyl meta-xylylene diisocyanate.

3. The method for preparing a silane chain extender according to claim 2, characterized in that: The molar ratio of the aminosilane, ketone compound, isocyanate and benzenesulfonic acid substance is 1: (0.8-1.0): (0.4-1.0): (0.05-0.15).

4. The method for preparing a silane chain extender according to claim 2, characterized in that: In step 1), the temperature for dropping the ketone compound is 50-65°C, the time for dropping is 30-50 minutes, and the reaction is kept warm for 4-6 hours after the dropping is completed.

5. The method for preparing a silane chain extender according to claim 2, characterized in that: In the step 2), the temperature for dripping isocyanate is 40-55° C., the dripping time is 40-60 min, and after the dripping is completed, the temperature is raised to 60-70° C. for reaction for 3-5 h.

6. The method for preparing a silane chain extender according to claim 2, characterized in that: The benzenesulfonic acid substance is dodecylbenzenesulfonic acid; the temperature for adding the benzenesulfonic acid substance in step 3) is 40-45°C, the adding time is 40-60min, and the reaction takes 3-4.5h after the addition.

7. Use of the silane chain extender prepared by the preparation method according to any one of claims 2 to 6 in the preparation of silicone rubber.

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