A neutral silicone sealant and its preparation method

Abstract

This invention discloses a neutral silicone sealant and its preparation method, relating to the field of silicone sealant production technology. It comprises the following raw materials in parts by weight: 450 parts of hydroxyl-terminated polydimethylsiloxane, 400 parts of No. 3 white oil, 110 parts of fumed silica, 60 parts of a ketoxime-type crosslinking agent, 15 parts of an adhesion promoter, and 1.5 parts of a catalyst. The adhesion promoter has the general formula: [formula missing], where R1 is 0, -CH2CH2NH-, -CH2CH2NHCH2CH2NH-; R... 1 R2 is CH3−, CH2CH3−; R2 is H, CH3−; R 2 The compounds are CH3− and CH2CH3−. This effectively solves the curing problem of ketoxime-type neutral silicone sealants with fumed silica as the main filler under low temperature and low humidity conditions, and the prepared silicone sealant has excellent adhesion to most common substrates.

Description

Technical Field

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

[0002] Silicone sealant is one of the most common bonding and sealing materials in the construction industry. JGJ 133-2001 standard 6.1.3 stipulates that "when using silicone structural sealant to bond and fix components, the application of sealant should be carried out indoors at a temperature above 15℃ and below 30℃, a relative humidity above 50%, and in a clean and well-ventilated environment." This regulation has become a general construction condition in industry guidelines and specifications and has been extended to non-structural sealant products. Standards GB 16776 and GB / T14683 specify test conditions of 23±2℃ and 50±5% humidity.

[0003] However, the actual temperature and humidity environment during construction is more complex and difficult to control, especially in the low temperature and low humidity environment of northern winters. Conventional silicone sealants have a slow curing speed under low temperature and low humidity conditions and cannot achieve complete curing within the effective time to play a role in bonding, fixing and sealing, thus failing.

[0004] Among them, ketoxime-type neutral silicone sealants with fumed silica as the main filler are the most obvious. They cannot be fully cured within 7 days, and cannot be fully cured as time goes on, thus losing their bonding, fixing and sealing functions. Summary of the Invention

[0005] The first technical problem to be solved by this invention is to provide a neutral silicone sealant that cures quickly at low temperature and low humidity and has a good bonding, fixing and sealing effect, in order to address the shortcomings of the existing technology.

[0006] To solve the first technical problem mentioned above, the technical solution of the present invention is:

[0007] A neutral silicone sealant, characterized in that it comprises the following raw materials in parts by weight: 450 parts of hydroxyl-terminated polydimethylsiloxane, 400 parts of No. 3 white oil, 110 parts of fumed silica, 60 parts of ketoxime-type crosslinking agent, 15 parts of adhesion promoter, and 1.5 parts of catalyst, wherein the general formula of the adhesion promoter is: Where: R1 is absent, -CH2CH2NH-, -CH2CH2NHCH2CH2NH-; R 1 R2 is CH3- or CH2CH3-; R2 is H- or CH3-; R 2 It is CH3- or CH2CH3-.

[0008] Preferably, the adhesion promoter is obtained by reacting raw material A and raw material B, wherein the general formula of raw material A is: The general formula for raw material B is: .

[0009] Preferably, raw material A is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-(diethylenetriamine)propyltrimethoxysilane, 3-(diethylenetriamine)propyltriethoxysilane; raw material B is 3-(acryloyloxy)propyltrimethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, 3-methacryloyloxypropyltriethoxysilane.

[0010] More preferably, raw material A is 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, or 3-(diethylenetriamine)propyltrimethoxysilane, and raw material B is 3-methacryloyloxypropyltrimethoxysilane or 3-(acryloyloxy)propyltrimethoxysilane.

[0011] Preferably, the method for preparing the adhesion promoter includes the following steps:

[0012] S1. Nitrogen purging is performed in the reactor, and raw material A is added under stirring.

[0013] S2. When the reactor temperature is raised to 75°C, a mixture of raw material B and hydroquinone monomethyl ether is started to be added dropwise to the reactor under normal pressure. During the dropwise addition process, the temperature rise of the material is controlled within 10°C. The molar ratio of raw material A to raw material B is 1.05:1.

[0014] S3. After the addition is complete, continue the reaction at the final temperature for 2 hours. Then, while stirring, reduce the temperature of the vessel to room temperature within 1 hour to obtain the adhesion promoter.

[0015] Preferably, the stirring speed in steps S1 and S3 is 200 rpm, and the concentration of hydroquinone monomethyl ether relative to raw material B is 8 ppm.

[0016] The mixture of raw material B and hydroquinone monomethyl ether was added dropwise over a period of 2 hours.

[0017] Preferably, the adhesion promoter is one of the following: a single promoter, a composition of promoters, or a composition of promoter and 3-glycidyl etheroxypropyltrimethoxysilane.

[0018] 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.

[0019] Preferably, the catalyst is at least one selected from dibutyltin dilaurate, dioctyltin dilaurate, stannous octoate, tetrabutyl titanate, tetraisobutyl titanate, and tetraisopropyl titanate.

[0020] The second technical problem to be solved by the present invention is to provide a method for preparing a neutral silicone sealant, which, in view of the shortcomings of the prior art, has a fast curing speed and good bonding, fixing and sealing effect at low temperature and low humidity.

[0021] To solve the second technical problem mentioned above, the technical solution of the present invention is:

[0022] A method for preparing a neutral silicone sealant includes the following steps:

[0023] a. Add hydroxyl-terminated polydimethylsiloxane, No. 3 white oil, and ketoxime-type crosslinking agent to a dry planetary mixer, and mix for 30 min at a vacuum degree ≤ -0.08 MPa and a speed of 15-25 r / min.

[0024] b. Add fumed silica in two portions to the mixer in step a, and stir and mix for 15 min at 10-20 r / min under normal pressure and closed conditions; then continue stirring and mixing for 20 min under vacuum ≤ -0.08 MPa and 15-25 r / min conditions.

[0025] c. Add the catalyst in proportion to the mixer in step b, and continue stirring and mixing for 20 min under vacuum degree ≤ -0.08MPa and rotation speed of 15~25r / min;

[0026] d. Add the adhesion promoter to the mixer in step c according to the ratio, and continue to stir and mix for 20 minutes under the conditions of vacuum degree ≤ -0.08MPa and speed 15~25r / min; to obtain the neutral silicone sealant finished product.

[0027] Preferably, the stirring speed in steps a, b, c, and d is 20 r / min.

[0028] Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] 1. 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. This effectively solves the problem of curing ketoxime-type neutral silicone sealants with fumed silica as the main filler under low temperature and low humidity conditions. Furthermore, this adhesion promoter can be used alone or in combination with other silane coupling agents. The prepared silicone sealant exhibits excellent adhesion to most common substrates.

[0030] 2. 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 has a small range of formulation adjustments and reliable cost.

[0031] 3. The neutral silicone sealant of the present invention overcomes the curing defects of ketoxime-type neutral silicone sealants with fumed silica as the main filler in low temperature and low humidity environments. By adjusting the composition of the adhesion promoter, the curing speed of the product under low temperature and low humidity conditions can be accelerated, and it plays a role in bonding, fixing and sealing the substrate. The typical temperature and humidity values ​​are not lower than -10°C and not lower than 20%. Detailed Implementation

[0032] The present invention will be further illustrated below with reference to the embodiments.

[0033] This invention aims to demonstrate the influence of different combinations of adhesion promoters on the curing speed and adhesion to the substrate of silicone sealant under low temperature and low humidity conditions. Therefore, both the adhesion promoter and the silicone sealant are prepared under optimal preparation conditions. Example 1

[0034] Preparation of Adhesion Promoters

[0035] a. The general formula for raw material A is: Where: R1 is absent, -CH2CH2NH-, -CH2CH2NHCH2CH2NH-; R 1 CH3-, CH2CH3-;

[0036] The general formula for raw material B is: Where: R2 is H-, CH3-; R 2 It is CH3- or CH2CH3-.

[0037] b. Preparation of adhesion promoters:

[0038] 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;

[0039] S2. After the air is exhausted, add raw material A with a mechanical stirring speed of 200 rpm; and add a measured amount of raw material B and hydroquinone monomethyl ether (the concentration of hydroquinone monomethyl ether relative to silane B is 8 ppm) in the dropping device (maintaining normal pressure) (the molar ratio of raw material A to raw material B is 1.05:1).

[0040] S3. After raw material A is added, start heating. When the material temperature reaches 75°C, start slowly adding raw material B and hydroquinone monomethyl ether mixture. The addition time of raw material B and hydroquinone monomethyl ether mixture is 2 hours. During the addition process, the temperature rise range 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.

[0041] S4. After heat preservation, the material temperature is reduced to room temperature within 1 hour at a stirring speed of 200 rpm to obtain the target adhesion promoter product.

[0042] The reactions involved are: Wherein, silane A is 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane, N-(2-aminoethyl)-3-aminopropyltriethoxysilane, 3-(diethylenetriamine)propyltrimethoxysilane, and 3-(diethylenetriamine)propyltriethoxysilane; silane B is 3-(acryloyloxy)propyltrimethoxysilane, 3-(acryloyloxy)propyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and 3-methacryloyloxypropyltriethoxysilane.

[0043] Through the above reactions, a total of 24 products were obtained, named G-01 (Adhesion Accelerator 01), G-02 to G-24, respectively. The physicochemical properties of the products were tested (adhesion accelerators were dissolved in anhydrous ethanol at a mass concentration of 20% to prepare primers; peel adhesion was tested using GB / T 13477.18 method; the sealant used in this test consisted of 450g of 80000mPa.s hydroxyl-terminated polydimethylsiloxane, 400g of No. 3 white oil, 110g of fumed silica, 40g of methyl tributanone oxime silane, 20g of vinyl tributanone oxime silane, and 1.5g of dibutyltin dilaurate; the system did not contain adhesion accelerators). The performance indicators of each product met market requirements. The test results are shown in Table 1.

[0044] Table 1. Products and their performance indicators obtained from different combinations of raw materials A and B.

[0045]

[0046]

[0047] The adhesion promoter prepared in this invention causes cohesive failure in the bonding of float glass, anodized aluminum, acrylic-coated aluminum, and PVC plastic, with a failure area of ​​≥95%. In contrast, comparative experiments using only the aforementioned sealant without the adhesion promoter prepared in this invention to create a primer showed that the sealant caused cohesive failure areas of only 11%, 7%, 0%, and 0% in the bonding of float glass, anodized aluminum, acrylic-coated aluminum, and PVC plastic, respectively. Example 2

[0048] Preparation of neutral silicone sealant

[0049] 450g of hydroxyl-terminated polydimethylsiloxane (80000mPa·s), 400g of No. 3 white oil, 40g of methyl tributanone oxime silane, and 20g of vinyl tributanone oxime silane were added to a planetary mixer and stirred for 30 min at a vacuum of ≤-0.08MPa and a rotation speed of 20 r / min. 110g of fumed silica was added in two portions and stirred for 15 min at a normal pressure and sealed environment and a rotation speed of 20 r / min. Then, stirring was continued for 20 min at a vacuum of ≤-0.08MPa and a rotation speed of 20 r / min. 1.5g of dibutyltin dilaurate catalyst was added and stirred for 20 min at a vacuum of ≤-0.08MPa and a rotation speed of 20 r / min. 15g of adhesion promoter G-15 prepared in Example 1 was added and stirred for 20 min at a vacuum of ≤-0.08MPa and a rotation speed of 20 r / min. The resulting silicone sealant product a was obtained. Example 3

[0050] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-15 is replaced with the adhesion promoter G-02 to obtain the silicone sealant finished product b. Example 4

[0051] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-15 is replaced with the adhesion promoter G-14 to obtain the finished silicone sealant c. Example 5

[0052] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-15 is replaced with the adhesion promoter G-17 to obtain the finished silicone sealant d. Example 6

[0053] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-15 is replaced with a mixture of G-15 and 3-glycidyl etheroxypropyltrimethoxysilane mixed in a weight ratio of 2:1 to obtain the finished silicone sealant e. Example 7

[0054] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-15 is replaced with a mixture of G-15 and 3-glycidyl etheroxypropyltrimethoxysilane mixed in a weight ratio of 1:1 to obtain the finished silicone sealant f. Example 8

[0055] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-15 is replaced with a mixture of G-15, adhesion promoter G-06 and adhesion promoter G-09 mixed in a weight ratio of 1:1:1, to obtain the finished silicone sealant g. Comparative Example 1

[0056] The production process and material ratio are the same as in Example 2, except that the adhesion promoter G-15 is replaced with 3-aminopropyltriethoxysilane to obtain the finished silicone sealant h. Comparative Example 2

[0057] The process and material ratios are the same as those in Comparative Example 1, except that the adhesion promoter is replaced with N-(2-aminoethyl)-3-aminopropyltrimethoxysilane to obtain silicone sealant product i. Comparative Example 3

[0058] The process and material ratios are the same as those in Comparative Example 1, except that the adhesion promoter is replaced with 3-(diethylenetriamine)propyltrimethoxysilane to obtain the silicone sealant product j. Comparative Example 4

[0059] The process and material ratios are the same as those in Comparative Example 1, except that the adhesion promoter is replaced with 3-(acryloyloxy)propyltriethoxysilane to obtain the finished silicone sealant k. Comparative Example 5

[0060] The process and material ratios are the same as those in Comparative Example 1, except that the adhesion promoter is replaced with 3-methacryloyloxypropyltrimethoxysilane to obtain silicone sealant product 1. Comparative Example 6

[0061] The process and material ratios are the same as those in Comparative Example 1, except that the adhesion promoter is replaced with 3-glycidyl etheroxypropyltrimethoxysilane to obtain the finished silicone sealant m.

[0062] Product testing results and analysis:

[0063] The aforementioned silicone sealant products were placed in environments of 23℃ / 50%RH, 10℃ / 35%RH, 5℃ / 30%RH, 0℃ / 25%RH, and -5℃ / 20%RH for 24 hours before testing. Specimen preparation, curing, and testing were all conducted within these environments. The time required for complete curing of a 6mm diameter sealant strip, and the peel adhesion of the silicone sealant to float glass, anodized aluminum, acrylic-coated aluminum, and PVC plastic were recorded. Peel adhesion was tested according to GB / T 13477.18, with the difference being that 3mm thick specimens were prepared in a single batch and tested after curing in each environment for 7 days.

[0064] The results are shown in Tables 2 and 3:

[0065] Table 2: Complete curing time of 6mm adhesive strip

[0066]

[0067] Table 3: Peel-off adhesion of silicone sealant to substrates under different temperature and humidity conditions

[0068]

[0069] Among them: ① float glass, ② anodized aluminum, ③ acrylic sprayed aluminum, ④ PVC plastic; CF: bond cohesive failure; AF: bond interface failure.

[0070] The results of Examples 2-8 show that the use of the adhesion promoter prepared in this application, or the combination of the adhesion promoter prepared in this application and a general-purpose silane, can effectively solve the curing problem of ketoxime-type neutral silicone sealant with fumed silica as the main filler under low temperature and low humidity conditions, and has good adhesion performance to common substrates.

[0071] Based on the results of Comparative Examples 1 to 6, the silicone sealant prepared using aminopropyltrialkoxysilane as an adhesion promoter exhibited poor curing performance and poor adhesion to the substrate under low temperature and low humidity conditions. The silicone sealant prepared using acryloyloxytrialkoxysilane and 3-glycidyl etheroxypropyltrimethoxysilane as adhesion promoters showed good curing performance under low temperature and low humidity conditions, but poor adhesion to the substrate.

[0072] 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, The raw materials comprise the following parts by weight: 450 parts of hydroxyl-terminated polydimethylsiloxane, 400 parts of No. 3 white oil, 110 parts of fumed silica, 60 parts of ketoxime-type crosslinking agent, 15 parts of adhesion promoter, and 1.5 parts of catalyst. The general formula of the adhesion promoter is... Where: R1 is absent, -CH2CH2NH-, -CH2CH2NHCH2CH2NH-; R 1 R2 is CH3- or CH2CH3-; R2 is H, CH3-; R 2 CH3-, CH2CH3-; The adhesion promoter is obtained by reacting raw material A and raw material B, wherein raw material A has the general formula: The general formula for raw material B is: ; The method for preparing the adhesion promoter includes the following steps: S1. Nitrogen purging is performed in the reactor, and raw material A is added under stirring. S2. When the reactor temperature is raised to 75°C, a mixture of raw material B and hydroquinone monomethyl ether is started to be added dropwise to the reactor under normal pressure. During the dropwise addition process, the temperature rise of the material is controlled within 10°C. The molar ratio of raw material A to raw material B is 1.05:

1. S3. After the addition is complete, continue the reaction at the final temperature for 2 hours, and then reduce the temperature of the vessel to room temperature within 1 hour while stirring to obtain the adhesion promoter. The stirring speed in steps S1 and S3 is 200 rpm, and the concentration of hydroquinone monomethyl ether relative to raw material B is 8 ppm. The mixture of raw material B and hydroquinone monomethyl ether was added dropwise over a period of 2 hours.

2. The neutral silicone sealant as described in claim 1, characterized in that: 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.

3. The neutral silicone sealant as described in claim 1, characterized in that: The catalyst is at least one of dibutyltin dilaurate, dioctyltin dilaurate, stannous octoate, tetrabutyl titanate, tetraisobutyl titanate, and tetraisopropyl titanate.

4. A method for preparing a neutral silicone sealant as described in any one of claims 1-3, characterized in that, Includes the following steps: a. Add hydroxyl-terminated polydimethylsiloxane, No. 3 white oil, and ketoxime-type crosslinking agent to a dry planetary mixer, and mix for 30 min at a vacuum degree ≤ -0.08 MPa and a speed of 15-25 r / min. b. Add fumed silica in two portions to the mixer in step a, and stir and mix for 15 min at 10-20 r / min under normal pressure and closed conditions; then continue stirring and mixing for 20 min under vacuum ≤ -0.08 MPa and 15-25 r / min conditions. c. Add the catalyst in proportion to the mixer in step b, and continue stirring and mixing for 20 min under vacuum degree ≤ -0.08MPa and rotation speed of 15~25r / min; d. Add the adhesion promoter to the mixer in step c according to the ratio, and continue to stir and mix for 20 minutes under the conditions of vacuum degree ≤ -0.08MPa and speed 15~25r / min; to obtain the neutral silicone sealant finished product.

5. The method for preparing the neutral silicone sealant as described in claim 4, characterized in that: The stirring speed in steps a, b, c, and d is 20 r / min.

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