A neutral silicone sealant and its preparation method

Abstract

This invention relates to the field of polymer material manufacturing technology, and discloses a neutral silicone sealant and its preparation method. The neutral silicone sealant is prepared by first mixing hydroxyl-terminated polydimethylsiloxane, methyl-terminated polydimethylsiloxane, and calcium carbonate to form a base material, and then sequentially adding a ketoxime-type crosslinking agent, a catalyst, and an adhesion promoter under stirring and vacuum conditions. The adhesion promoter is prepared by adding silane A and p-toluenesulfonic acid dropwise with silane B under stirring at 65°C. Silane A and silane B represent methoxysilanes or ethoxysilanes with different substituents, respectively. This invention allows for the control of the tensile modulus, elongation, and other properties of the product by adjusting the composition of the adhesion promoter.

Description

Technical Field

[0001] This invention relates to the field of polymer material manufacturing technology, specifically to a neutral silicone sealant and its preparation method. Background Technology

[0002] Neutral silicone sealant possesses excellent adhesion and sealing properties, good temperature resistance, and good flexibility; it is mainly used for sealing gaps in doors and windows and in interior decoration projects. With the diversification of product applications, more demands are being placed on the tensile modulus, elongation, and other indicators of silicone sealant. Products with low modulus and high elongation are better suited to different application scenarios and are becoming the direction of product development.

[0003] Neutral silicone sealants, typically made from ketoxime-type silanes such as methyl tributanone oxime silane and vinyl tributanone oxime silane as crosslinking agents and reinforced with inorganic fillers such as calcium carbonate and silica powder, are currently the most widely used products on the market. To adjust different tensile modulus, elongation, and other indicators, difunctional crosslinking agents such as dimethyl dibutyl ketone oxime silane are usually added to the formulation to control the crosslinking density and achieve the target. However, the amount of difunctional crosslinking agent usually needs to account for more than 30% of the crosslinking agent to be effective (the target cannot be achieved when the amount added is small), and the price is high. Another solution is to add different proportions of plasticizers such as dimethyl silicone oil to adjust the indicators, but the introduction and large-scale addition of plasticizers will lead to contamination of the substrate.

[0004] Furthermore, both of the above methods also bring some production problems, such as the need for more production equipment and semi-finished product storage equipment to address the issues of various displacement capabilities, modulus, elongation, and other indicators. Therefore, how to prepare products with different tensile moduli and elongation by adjusting the content of a certain component while using fewer or no of the above two methods has become an urgent problem to be solved. Summary of the Invention

[0005] The first technical problem to be solved by the present invention is to provide a neutral silicone sealant that overcomes the problems caused by the use of difunctional crosslinking agents or dimethyl silicone oil in the prior art. The tensile modulus, elongation and other indicators of the product can be controlled by adjusting the composition of the adhesion promoter.

[0006] The second technical problem to be solved by the present invention is to provide a method for preparing a neutral silicone sealant.

[0007] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0008] A neutral silicone sealant, made from the following components in parts by weight:

[0009] Hydroxyl-terminated polydimethylsiloxane 300

[0010] 50% methyl-terminated polydimethylsiloxane

[0011] Calcium carbonate 650

[0012] Ketooxime-type crosslinking agent 55

[0013] Adhesion promoter 10

[0014] Catalyst 0.8;

[0015] The adhesion promoter was prepared by adding silane B dropwise to silane A and p-toluenesulfonic acid under stirring and at 65°C.

[0016] The general formula for silane A is:

[0017] ,

[0018] Where: R3 = H, NH2CH2CH2-; m = 0, 1; R 2 =CH3-, CH2CH3-;

[0019] The general formula for silane B is:

[0020] ,

[0021] Where: R4 = H, CH3-; n = 0, 1; R 3 =CH3-、CH2CH3-.

[0022] Preferably, the ketoxime-type crosslinking agent is one or a mixture of several of methyltributanone oxime silane, dimethyldibutylone oxime silane, vinyltributanone oxime silane, and tetrabutylone oxime silane.

[0023] Preferably, the ketoxime-type crosslinking agent is one or a mixture of methyltributanone oxime silane, vinyltributanone oxime silane, or methyltributanone oxime silane.

[0024] Preferably, the catalyst is at least one selected from dibutyltin dilaurate, dioctyltin dilaurate, stannous octoate, tetrabutyl titanate, tetraisobutyl titanate, and tetraisopropyl titanate.

[0025] Furthermore, the catalyst is dibutyltin dilaurate.

[0026] Preferably, the silane A is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane. Alkane; silane B is 3-(acryloyloxy)propyltrimethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, 3-(acryloyloxy)propylmethyldimethoxysilane, 3-(acryloyloxy)propylmethyldiethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane.

[0027] Furthermore, silane A is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and silane B is 3-methacryloyloxypropyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane.

[0028] Preferably, the amount of p-toluenesulfonic acid added is 50 ppm relative to the concentration of silane A, and the stirring speed is 180 revolutions per minute.

[0029] Preferably, the adhesion promoter is prepared by silane A and silane B in a molar ratio of 1:1.

[0030] Preferably, the adhesion promoter is a composition of silane A and silane B prepared in a molar ratio of 1:1.

[0031] Preferably, the adhesion promoter is a combination of the product prepared by silane A and silane B in a molar ratio of 1:1 and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

[0032] Preferably, the method for preparing the adhesion promoter is as follows:

[0033] S1. In a reaction vessel equipped with a mechanical stirrer, heating device, thermometer and dropping device, first use nitrogen to purge the air from the reaction vessel;

[0034] S2. After the air is exhausted, add silane A and p-toluenesulfonic acid (the concentration of p-toluenesulfonic acid relative to silane A is 50 ppm) sequentially under a mechanical stirring speed of 180 rpm; and add a measured amount of silane B (the molar ratio of silane A to silane B is 1:1) in a dropping device (maintaining atmospheric pressure).

[0035] S3. After silane A and p-toluenesulfonic acid are added, start heating. When the material temperature reaches 65°C, start slowly adding silane B. The addition time of silane B is 3 hours. During the addition process, the temperature rise of the material is controlled within 10°C. After the addition is completed, continue to keep the reaction at the final temperature for 2 hours.

[0036] S4. After the reaction is kept at a constant temperature for 2 hours, the material temperature is reduced to room temperature while stirring at a speed of 180 revolutions per minute to obtain the target adhesion promoter product.

[0037] A method for preparing a neutral silicone sealant includes the following steps:

[0038] a. Add hydroxyl-terminated polydimethylsiloxane, methyl-terminated polydimethylsiloxane, and calcium carbonate to a kneader in proportion, and vacuum mix and dehydrate at 110℃~150℃ for 2~4 hours. Then cool down to below 50℃ for later use. The resulting mixture is called the base material.

[0039] b. Transfer the base material obtained in step a into a glue-making machine, add ketoxime type crosslinking agent in proportion, and stir and mix for 30 minutes under vacuum degree ≤ -0.08Mpa and speed of 15-25 rpm;

[0040] c. Add the catalyst to the glue-making machine in step b according to the proportion and continue to stir and mix for 20 minutes under the conditions of vacuum degree ≤ -0.08Mpa and speed 15~25 rpm;

[0041] d. Add the adhesion promoter to the glue-making machine in step b according to the proportion, and continue to stir and mix for 20 minutes under the conditions of vacuum degree ≤ -0.08Mpa and speed 15~25 rpm; to obtain the neutral silicone sealant finished product.

[0042] Preferably, the reaction time in step a is 3 hours of vacuum mixing and dehydration at 130°C.

[0043] Preferably, the reaction conditions in steps b, c, and d are all 20 revolutions per minute.

[0044] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0045] This invention prepares a class of multifunctional, high-molecular-weight, and highly active silanes by combining aminosilanes and (meth)acryloyloxysilanes, which can be used as adhesion promoters for silicone sealants. Variations in the type of adhesion promoter can directly affect different tensile moduli, elongation, and other properties of silicone sealants. Furthermore, this adhesion promoter can be used alone or in combination with other silane coupling agents, effectively avoiding the problem of occupying multiple pieces of equipment caused by changing the amount of plasticizer to prepare various base materials in the prior art.

[0046] The adhesion promoter of the present invention has a simple preparation process, readily available raw materials, high product yield, and no waste discharge during the preparation process; the silicone sealant prepared thereby poses no risk of contamination to the substrate, has a small range of formula adjustment, and is cost-effective. Attached Figure Description

[0047] Figure 1 The infrared spectrum of 3-aminopropyltriethoxysilane in silane A;

[0048] Figure 2 The infrared spectrum of 3-methacryloyloxypropyltrimethoxysilane in silane B;

[0049] Figure 3 The infrared spectrum of G-34, the product of the reaction of 3-aminopropyltriethoxysilane and 3-methacryloyloxypropyltrimethoxysilane. Detailed Implementation

[0050] The technical solution of the present invention will be further described below with reference to embodiments:

[0051] This invention aims to demonstrate the effects of different combinations of adhesion promoters on the tensile modulus, elongation, and other properties of silicone sealants. Therefore, both the adhesion promoters and the silicone sealants were prepared under optimal conditions.

[0052] Example 1: Preparation of Adhesion Promoter

[0053] a. The general formula for silane A is:

[0054] ,

[0055] Where: R3 = H, NH2CH2CH2-; m = 0, 1; R 2 =CH3-, CH2CH3-;

[0056] The general formula for silane B is:

[0057] ,

[0058] Where: R4 = H, CH3-; n = 0, 1; R 3 =CH3-, CH2CH3-;

[0059] b. Preparation of adhesion promoters:

[0060] S1. In a reaction vessel equipped with a mechanical stirrer, heating device, thermometer and dropping device, first purge the air from the reactor with nitrogen;

[0061] S2. After the air is exhausted, add silane A and p-toluenesulfonic acid (the concentration of p-toluenesulfonic acid relative to silane A is 50 ppm) sequentially under a mechanical stirring speed of 180 rpm; and add a measured amount of silane B (the molar ratio of silane A to silane B is 1:1) in a dropping device (maintaining atmospheric pressure).

[0062] S3. After silane A and p-toluenesulfonic acid are added, start heating. When the material temperature reaches 65°C, start slowly adding silane B. The addition time of silane B is 3 hours. During the addition process, the temperature rise of the material is controlled within 10°C. After the addition is completed, continue to keep the reaction at the final temperature for 2 hours.

[0063] S4. After the reaction is kept at a constant temperature for 2 hours, the material temperature is reduced to room temperature while stirring at a speed of 180 revolutions per minute to obtain the target adhesion promoter product.

[0064] The reactions involved:

[0065]

[0066] In the formula, when R3=H, R1=NH; when R3=NH2CH2CH2, R1=NHCH2CH2NH;

[0067] Among them, silane A is 3-aminopropyltrimethoxysilane and 3-aminopropyltriethoxysilane (their infrared spectra are shown in [reference needed]). Figure 1 ), 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane;

[0068] Silane B consists of 3-(acryloyloxy)propyltrimethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, 3-(acryloyloxy)propylmethyldimethoxysilane, 3-(acryloyloxy)propylmethyldimethoxysilane, and 3-methacryloyloxypropyltrimethoxysilane (their infrared spectra are shown in [reference needed]). Figure 2 ), 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane.

[0069] Through the above reactions, a total of 64 products were obtained, named as follows: G-01 (adhesion promoter 01), G-02 to G-64 (among which, the infrared spectrum of product G-34 obtained by the reaction of 3-aminopropyltriethoxysilane and 3-methacryloyloxypropyltrimethoxysilane is shown in [reference needed]). Figure 3Through physicochemical property testing of the products (the adhesion promoter was dissolved in anhydrous ethanol at a mass concentration of 20% to prepare primer coatings, and the peel adhesion test was performed according to GB / T 13477.18 method, while a control test was conducted without the adhesion promoter as the primer coating), the performance indicators of each product meet market needs. The test results are shown in Table 1:

[0070] Table 1. Products and their performance indicators obtained from different combinations of silane A and silane B.

[0071]

[0072]

[0073]

[0074]

[0075]

[0076]

[0077]

[0078]

[0079]

[0080]

[0081]

[0082]

[0083] The prepared adhesion promoter caused cohesive failure in the bonding of anodized aluminum and cement mortar board, with a failure area ≥95% (the sealant used in this test consisted of 300g of hydroxyl-terminated polydimethylsiloxane at 80000mPa.s, 50g of methyl-terminated polydimethylsiloxane at 150mPa.s, 650g of calcium carbonate, 55g of methyl tributanone oxime silane, and 0.8g of dibutyltin dilaurate; the system did not contain the adhesion promoter). However, a comparative experiment was conducted using only the above sealant, without the adhesion promoter prepared in this invention, to prepare a primer. The results showed that the sealant caused cohesive failure of 21% and 15% of the bonding area of ​​anodized aluminum and cement mortar board, respectively.

[0084] Example 2: Preparation of Neutral Silicone Sealant

[0085] 300g of hydroxyl-terminated polydimethylsiloxane (80000mPa.s), 50g of methyl-terminated polydimethylsiloxane (150mPa.s), and 650g of calcium carbonate were added to a kneader and mixed and dehydrated under vacuum (≤-0.08Mpa) at 130℃ for 3 hours. The mixture was then cooled to below 50℃ to obtain a base material. The base material was transferred to a glue-making machine, and 55g of ketoxime-type crosslinking agent methyltributanone oxime silane was added and stirred and mixed under vacuum (≤-0.08Mpa) at 20 rpm for 30 minutes. 0.8g of catalyst dibutyltin dilaurate was added and stirred and mixed under vacuum (≤-0.08Mpa) at 20 rpm for 20 minutes. 10g of adhesion promoter G-34 obtained in Example 1 was added and stirred and mixed under vacuum (≤-0.08Mpa) at 20 rpm for 20 minutes to obtain silicone sealant product a.

[0086] Examples 3-5: Preparation of Neutral Silicone Sealants

[0087] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-34 is replaced with adhesion promoter G-37, adhesion promoter G-21 and adhesion promoter G-03 in sequence to obtain silicone sealant finished product b, silicone sealant finished product c and silicone sealant finished product d respectively.

[0088] Examples 6-9: Preparation of Neutral Silicone Sealants

[0089] The production process and material ratios are the same as in Example 2, except that the adhesion promoter G-34 is replaced sequentially with a mixture of G-34 and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a weight ratio of 2:1, a mixture of G-34 and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a weight ratio of 1:1, a mixture of G-34 and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane in a weight ratio of 1:2, and a mixture of G-34, G-21, and G-03 in a weight ratio of 1:1:1, to obtain silicone sealant finished products e, f, g, and h, respectively.

[0090] Comparative Example 1

[0091] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-34 is replaced with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to obtain the finished silicone sealant i.

[0092] Comparative Examples 2-4

[0093] The amount of methyl-terminated polydimethylsiloxane at 150 mPa·s was adjusted to 150 g, 200 g, and 250 g respectively. The amount of other components and the production process were the same as those in Comparative Example 1, and silicone sealant finished products j, k, and l were obtained respectively.

[0094] Comparative Examples 5-8

[0095] The process and material ratios are the same as in Comparative Example 1, except that the ketoxime-type crosslinking agent is successively replaced with a mixture of methyl tributanone oxime silane and dimethyl dibutyl ketone oxime silane in a weight ratio of 4:1, a mixture of methyl tributanone oxime silane and dimethyl dibutyl ketone oxime silane in a weight ratio of 2:1, a mixture of methyl tributanone oxime silane and dimethyl dibutyl ketone oxime silane in a weight ratio of 1:1, and a mixture of methyl tributanone oxime silane and dimethyl dibutyl ketone oxime silane in a weight ratio of 1:2, to obtain silicone sealant finished products m, n, o, and p, respectively.

[0096] Product testing results and analysis:

[0097] The above-mentioned silicone sealant products were placed in an environment of 23±2℃ and 50±5% relative humidity for 24 hours to prepare test specimens. The tensile modulus at 23℃ was tested according to GB / T 14683, 6.9; the elongation at break was tested according to GB / T 528 (Type 2 dumbbell-shaped specimen); and the staining was tested according to GB / T 13477.20 (Test Method B).

[0098] The tensile modulus test substrate was float glass, and the contamination test substrate was marble. The results are shown in Table 2.

[0099] Table 2 Performance analysis results of products obtained under different preparation conditions

[0100]

[0101] Note: The silicone sealant p did not fully cure within the specified test time, so the test data was invalid and therefore not recorded.

[0102] The results of Examples 2-9 show that the modulus and elongation of silicone sealant can be effectively adjusted by using the adhesion promoter prepared in this application or by mixing the adhesion promoter prepared in this application with a general-purpose silane. The silicone sealant does not contaminate the substrate, does not increase the cost burden, and saves the number of equipment and space.

[0103] The results of Comparative Examples 2-4 show that increasing the methyl-terminated polydimethylsiloxane silicone sealant significantly improves the modulus and elongation, but it can lead to substrate contamination.

[0104] The results of comparative examples 5-8 show that the modulus and elongation of silicone sealant were significantly adjusted by introducing a difunctional crosslinking agent. The proportion of the crosslinking agent used should not be too low, otherwise it will not be effective, while too much will cause curing problems in the silicone sealant.

[0105] It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. A neutral silicone sealant, characterized in that: It is made from the following components in parts by weight: Hydroxyl-terminated polydimethylsiloxane 300 50% methyl-terminated polydimethylsiloxane Calcium carbonate 650 Ketooxime-type crosslinking agent 55 Adhesion promoter 10 Catalyst 0.8; The adhesion promoter was prepared by adding silane B dropwise to silane A and p-toluenesulfonic acid under stirring and at 65°C. The general formula for silane A is: ， Where: R3 = H, NH2CH2CH2-; m = 0, 1; R 2 =CH3-, CH2CH3-; The general formula for silane B is: ， Where: R4 = H, CH3-; n = 0, 1; R 3 =CH3-、CH2CH3-.

2. The neutral silicone sealant according to claim 1, characterized in that: The silane A is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropylmethyldiethoxysilane; silicon Alkane B is 3-(acryloyloxy)propyltrimethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, 3-(acryloyloxy)propylmethyldimethoxysilane, 3-(acryloyloxy)propylmethyldiethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane, 3-methacryloyloxypropylmethyldimethoxysilane, 3-methacryloyloxypropylmethyldiethoxysilane.

3. The neutral silicone sealant according to claim 1, characterized in that: The silane A is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, and the silane B is 3-methacryloyloxypropyltrimethoxysilane, 3-(acryloyloxy)propyltrimethoxysilane.

4. The neutral silicone sealant according to claim 1, characterized in that: The adhesion promoter is prepared by silane A and silane B in a molar ratio of 1:

1.

5. The neutral silicone sealant according to claim 1, characterized in that: The adhesion promoter is a combination of the product prepared by silane A and silane B in a molar ratio of 1:1 and N-(2-aminoethyl)-3-aminopropyltrimethoxysilane.

6. The neutral silicone sealant according to claim 1, characterized in that: The adhesion promoter is prepared by: S1. In a reaction vessel equipped with a mechanical stirrer, heating device, thermometer and dropping device, first use nitrogen to purge the air from the reaction vessel; S2. After the air is exhausted, silane A and p-toluenesulfonic acid are added sequentially under a mechanical stirring speed of 180 revolutions per minute, wherein the concentration of p-toluenesulfonic acid relative to silane A is 50 ppm; and a measured amount of silane B is added to the dropping device, wherein the molar ratio of silane A to silane B is 1:

1. S3. After silane A and p-toluenesulfonic acid are added, start heating. When the material temperature reaches 65°C, start slowly adding silane B. The addition time of silane B is 3 hours. During the addition process, the temperature rise of the material is controlled within 10°C. After the addition is completed, continue to keep the reaction at the final temperature for 2 hours. S4. After the reaction is kept at a constant temperature for 2 hours, the material temperature is reduced to room temperature while stirring at a speed of 180 revolutions per minute to obtain the target adhesion promoter product.

7. The method for preparing a neutral silicone sealant as described in claim 1, characterized in that: Includes the following steps: a. Add hydroxyl-terminated polydimethylsiloxane, methyl-terminated polydimethylsiloxane, and calcium carbonate to a kneader in proportion, and vacuum mix and dehydrate at 110℃~150℃ for 2~4 hours. Then cool down to below 50℃ for later use. The resulting mixture is called the base material. b. Transfer the base material obtained in step a into a glue-making machine, add ketoxime type crosslinking agent in proportion, and stir and mix for 30 minutes under vacuum degree ≤ -0.08MPa and speed of 15-25 rpm; c. Add the catalyst to the glue-making machine in step b according to the proportion and continue to stir and mix for 20 minutes under the conditions of vacuum degree ≤ -0.08MPa and speed 15~25 rpm; d. Add the adhesion promoter to the glue-making machine in step b according to the proportion, and continue to stir and mix for 20 minutes under the conditions of vacuum degree ≤ -0.08MPa and speed 15~25 rpm; to obtain the neutral silicone sealant finished product.

8. The method for preparing a neutral silicone sealant according to claim 7, characterized in that: In step a, the reaction time is 3 hours of vacuum mixing and dehydration at 130°C. In steps b, c, and d, the reaction conditions are all 20 rpm.

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