Low-corrosivity acidic silicone sealant and preparation method thereof

Abstract

The invention discloses a low-corrosivity acidic silicone sealant and a preparation method thereof, and belongs to the technical field of silicone sealants. The low-corrosivity acidic silicone sealant is prepared from the following raw materials in parts by weight: 200 to 230 parts of 107 glue, 60 to 200 parts of a plasticizer, 20 to 40 parts of fumed silica, 1 to 3 parts of an acid-binding agent, 0.2 to 0.5 part of a synergistic acid-binding agent, 2 to 5 parts of a composite pH regulator, 15 to 30 parts of a silane cross-linking agent and 0.01 to 0.2 part of a catalyst. The preparation method comprises the following steps: adding the 107 glue, the plasticizer and the silane cross-linking agent, vacuumizing, and uniformly stirring; adding fumed silica and an acid-binding agent, stirring at normal pressure for 5 minutes, scraping, continuously vacuumizing, and uniformly stirring; and finally, adding a catalyst, continuously stirring and vacuumizing, and uniformly mixing to prepare the acidic silicone sealant. The preparation method of the low-corrosivity acidic silicone sealant provided by the invention is simple, and the prepared acidic silicone sealant is high in curing speed, good in cohesiveness, high in strength and low in corrosivity, and can be applied to the field of metal bonding and sealing.

Description

TECHNICAL FIELD

[0001] The application relates to a chemical product, in particular to an acidic silicone sealant with the characteristics of fast curing speed, good adhesion, high strength and low corrosion and a preparation method thereof, and belongs to the technical field of silicone sealants. BACKGROUND

[0002] Acidic silicone sealant is the earliest type of silicone sealant, which has good adhesion, weather resistance, high and low temperature resistance and excellent vulcanization performance, and is widely used in the fields of building, electronics, automobiles and the like. However, since the acidic silicone sealant releases acidic substances such as acetic acid during the curing process, the acidic substances may corrode metal, concrete and other substrates, leading to problems such as sealing failure and substrate damage, thereby limiting the application of the acidic silicone sealant.

[0003] The Chinese patent with the application number CN201910089296.1 uses a tin-free catalyst (such as an organic titanium catalyst, an organic zirconium catalyst, etc.) to replace the traditional organic tin catalyst, which can significantly reduce the harm of the sealant to the human body and the environment, but still cannot solve the corrosion problem caused by the release of acetic acid during the curing process.

[0004] Both selecting a weakly acidic crosslinking agent to replace the traditional strongly acidic crosslinking agent and modifying the acidic crosslinking agent can reduce the corrosion of the sealant. For example, the patent CN201810030001.9 uses ethyltriacetoxy silane as the crosslinking agent and reduces the amount of the acidic crosslinking agent to reduce the release amount of acetic acid, and a small amount of aromatic ester is added to neutralize the irritating odor of acetic acid. However, ethyltriacetoxy silane still releases acetic acid during curing, and the addition of aromatic ester can only slightly alleviate the irritating odor, and cannot solve the corrosion problem caused by the release of acetic acid. The patent CN202210813470.4 modifies methyltriacetoxy silane with methanol or other alcohols, and then removes the generated acetic acid to prepare methylalkyloxy acetoxy silane. However, the patent mainly studies the problem of easy crystallization of the crosslinking agent, and does not further explore the change in corrosion of the product.

[0005] All the above methods are within the framework of “acidic silicone sealant”. The premise is that the hydrolysis of acetoxy groups to release acetic acid is necessary to achieve fast curing (condensation reaction), so any improvement can only be limited addition and subtraction in the “amount of acetic acid release”, and the corrosion problem of acetic acid to sensitive substrates (especially metal) cannot be completely solved. This leads to a dilemma in the industry for a long time: either accept corrosion and retain the advantages of fast curing and high adhesion, or give up the acidic system and switch to neutral glue with slow curing and usually weak adhesion. SUMMARY To solve the above problems, the application provides a low-corrosive acidic silicone sealant and a preparation method thereof, the low-corrosive acidic silicone sealant has fast curing speed, good adhesion, high strength and low corrosion, and can be used in the field of metal bonding and sealing; and the preparation method is simple and easy to implement. On the premise of keeping all the core performances (fast curing, high bonding strength and mature process) of traditional acidic silicone sealants, the release of acetic acid is controlled in real time from the reaction kinetics and chemical environment, so that the actual corrosion level of the sensitive metal substrate is achieved, and the application boundary of the acidic sealant is expanded to the precision metal sealing field which can only use neutral sealants in the past.

[0006] The technical scheme of the application is as follows: A low-corrosive acidic silicone sealant, according to weight parts, comprises the following raw materials: 107 glue 200-230 parts, plasticizer 60-200 parts, fumed white carbon black 20-40 parts, acid-binding agent 1-3 parts, synergistic acid-binding agent 0.2-0.5 parts, composite pH regulator 2-5 parts, silane crosslinking agent 15-30 parts, and catalyst 0.01-0.2 parts. Preferably, the viscosity of the 107 glue is one or more of 20,000 cP, 50,000 cP, 80,000 cP and 500,000 cP; further preferably, the viscosity of the 107 glue is a combination of 80,000 cP and 500,000 cP, and the ratio of the two is 1: (0.2-0.5).

[0007] Preferably, the plasticizer comprises one or more of 100 cP dimethyl silicone oil and No. 3 white oil.

[0008] Preferably, the fumed white carbon black is hydrophilic white carbon black with a specific surface area of 150-180 m 2 / g.

[0009] Preferably, the acid-binding agent comprises one or more of sodium carbonate, sodium bicarbonate, ammonium carbonate, ammonium bicarbonate, calcium carbonate, sodium acetate, potassium acetate, sodium methoxide or sodium ethoxide; preferably, the acid-binding agent is a mixture of sodium acetate and calcium carbonate, and the mass ratio of the two is 1: (0.5-1), and the synergistic acid-binding agent is acetylacetone.

[0010] Preferably, the composite pH regulator comprises one or more of sodium benzoate, ammonium benzoate, disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate or dipotassium phosphate; further preferably, the pH regulator is a combination of disodium hydrogen phosphate and sodium benzoate, and the mass ratio of the two is 1: (0.3-0.5).

[0011] Preferably, the silane crosslinking agent is one or more selected from methyltriacetoxysilane, ethyltriacetoxysilane, propyltriacetoxysilane, di-tert-butoxydiacetoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, tetramethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, and tetraethoxysilane; more preferably, the silane crosslinking agent is a composition of methyltriacetoxysilane, propyltriacetoxysilane, and methyltrimethoxysilane, with a ratio of 1:0.5 to 1:0.05 to 0.2; even more preferably, the methyltriacetoxysilane is a mixture of monomer and oligomer, with a monomer to oligomer ratio of 1:(0.25 to 0.75).

[0012] Preferably, the degree of polymerization of the oligomer is 2-3. If the proportion of oligomer and the degree of polymerization are too low, the acid reduction effect will be limited; if they are too high, the reactivity will decrease, which may affect the speed of deep curing and the compatibility with the system.

[0013] More preferably, the oligomer preparation process is as follows: a measured amount of methanol-water solution (5%-15% methanol concentration) is added dropwise to a methyltriacetoxysilane monomer, and the reaction is carried out at 30-50°C to obtain an oligomer with a degree of polymerization of 2-3. During the preparation of the oligomer, a small amount of alkoxy groups (such as methoxy or ethoxy groups) are introduced, and an alcohol is added to participate in the co-condensation during the partial hydrolysis and condensation of the monomer. This forms a mixed functional group of "acetoxy-alkoxy" within the oligomer molecule. This further reduces the theoretical acetic acid release of a single oligomer molecule and improves its compatibility with other alkoxysilanes in the formulation.

[0014] Preferably, the catalyst is dibutyltin diacetate.

[0015] Preferably, the method for preparing the low-corrosion acidic silicone sealant includes the following steps: S1. Add 107 glue, plasticizer, and silane crosslinking agent, vacuum, and stir evenly; S2. Add fumed silica, acid binder and synergistic acid binder, stir under normal pressure for 3-9 minutes, scrape the paddle, and continue to vacuum and stir evenly. S3. Add catalyst and composite pH adjuster, continue stirring and vacuuming, and after mixing, prepare acidic silicone sealant.

[0016] More preferably, in steps S1 to S3, the temperature of the vacuum stirring is controlled at 20 to 30 ℃, the time is 15 to 40 min, and the vacuum degree is -0.085 MPa to -0.098 MPa; in step S2, the fumed silica should be dried to remove water before being added, the drying temperature is 120 to 150 ℃, and the drying time is 2 to 4 h.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. The crosslinking agents used in this invention are methyltriacetoxysilane and propyltriacetoxysilane, both of which are mixtures of monomers and oligomers. The oligomers release less acetic acid than the monomers, and the overall acidity of the crosslinking agent is reduced. 2. The crosslinking agent used in this invention contains a small amount of methyltrimethoxysilane, which releases a small amount of methanol during curing, which helps to dilute the acetic acid concentration and reduce the corrosiveness of the silicone sealant to the environment or construction materials. 3. This invention incorporates a compound of sodium acetate and calcium carbonate as an acid-binding agent. The former further removes trace amounts of chloride ions remaining in the raw materials, preventing them from forming highly corrosive hydrogen chloride in acetic acid media; the latter continuously neutralizes the slowly released acetic acid in the later stages, thereby significantly reducing the corrosiveness of acidic silicone sealant. Acetylacetone is introduced as a synergistic acid-binding agent. Oligomers and crosslinking agents may contain trace amounts of catalytic metal ions (such as tin and titanium), which can exacerbate electrochemical corrosion in acidic environments. Acetylacetone can bind to these ions, eliminating this hidden corrosion-promoting factor and synergistically preventing corrosion with the acid-binding agent through different pathways.

[0018] 4. This invention, by adding a pH adjuster, can adsorb H+ ions from the ionization of acetic acid. + Ions reduce the acidity of silicone sealant, thereby significantly reducing the corrosiveness of acidic silicone sealant. Detailed Implementation

[0019] Example 1 Crosslinking agent oligomer pre-preparation: Under dry nitrogen protection, 0.05 parts of catalyst dibutyltin diacetate were added to 8 parts of methyltriacetoxysilane (MTAS) monomer, the temperature was raised to 45°C, and 0.45 parts of 5% methanol aqueous solution were slowly added dropwise. The reaction was kept at the temperature for 3 hours to obtain an oligomer mixture (MTAS-1) with a degree of polymerization of about 2.5.

[0020] Mixing of main rubber components: Add 107 rubber, plasticizer, MTAS, MTAS-1, propyltriacetoxysilane, and methyltrimethoxysilane to a planetary mixer and mix for 20 minutes at 25°C and -0.095 MPa vacuum. The proportions are shown in Table 1.

[0021] Dispersion of filler and acid binder: Add dried fumed silica, sodium acetate-calcium carbonate complex and acetylacetone, stir at normal pressure for 5 minutes, scrape the paddle, and then stir for 30 minutes under the same vacuum.

[0022] Final mixing and degassing: Add the composite pH adjuster and the remaining catalyst, stir for 15 minutes under a high vacuum of -0.098 MPa, and then discharge and fill.

[0023] Example 2: The only difference from Example 1 is that the crosslinking agent is 9.6 parts of MTAS and 2.4 parts of MTAS-1, and the ratio of monomer to oligomer is 1:0.25.

[0024] Example 3: The only difference from Example 1 is that the crosslinking agent is 7 parts MTAS and 5 parts MTAS-1, and the ratio of monomer to oligomer is 1:0.71.

[0025] Example 4: The only difference from Example 1 is that the sodium acetate-calcium carbonate complex is 2.5 parts and the composite pH adjuster is 2 parts.

[0026] Example 5: The only difference from Example 1 is that the sodium acetate-calcium carbonate complex is 1.5 parts and the composite pH adjuster is 4 parts.

[0027] Table 1 Dosage of each component in Examples 1-5

[0028] Comparative Example 1: The difference from Example 1 is that only MTAS monomers are used as crosslinking agents, and no acid binding agents, pH adjusters, etc. are added.

[0029] Comparative Example 2: The difference from Example 1 is that only MTAS monomers were used as crosslinking agents.

[0030] Comparative Example 3: The difference from Example 1 is that no acid-binding agent or pH adjuster was added.

[0031] Comparative Example 4: The difference from Example 1 is that no pH adjuster was added, and a single adjuster, disodium hydrogen phosphate, was used.

[0032] Comparative Example 5: The difference from Example 1 is that the degree of polymerization of the oligomer used reaches 4 to 5.

[0033] The dosage of each component in Comparative Examples 1 to 5 is shown in Table 2.

[0034] Table 2 Components of Comparative Examples 1-5

[0035] Detection and Analysis The curing speed, tensile strength, metal adhesion performance, and metal corrosion of the above-mentioned acidic silicone sealant were tested (the metal used was cold-rolled oriented silicon steel sheet that is not resistant to acetic acid corrosion).

[0036] Table 3 shows the performance test data of the acidic silicone sealants prepared in Examples 1-5 and Comparative Examples 1-5.

[0037] Table 3 Summary of Sample Performance Test Results

[0038] This invention resolves the technical contradiction between rapid curing and low corrosion resistance in acidic silicone sealants through the design of an oligomer and a dynamic two-stage buffer system. Compared to traditional acidic sealants (Comparative Example 1) and existing improved technologies (other comparative examples), this invention achieves a qualitative leap in the core indicator of corrosion resistance, while maintaining or even improving other key performance aspects. The examples and comparative examples together demonstrate the rationality and necessity of the parameter ranges regarding oligomer ratio, degree of polymerization, and buffer system composition specified in the claims; performance degrades when these ranges are exceeded (e.g., in Comparative Example 5).

Claims

1. A low-corrosion acidic silicone sealant, characterized in that, The raw materials include the following by weight: 200-230 parts of 107 glue, 60-200 parts of plasticizer, 20-40 parts of fumed silica, 1-3 parts of acid binder, 0.2-0.5 parts of synergistic acid binder, 2-5 parts of composite pH adjuster, 15-30 parts of silane crosslinking agent, and 0.01-0.2 parts of catalyst.

2. The low-corrosion acidic silicone sealant according to claim 1, characterized in that, The viscosity of the 107 adhesive is one or more of 20000 cP, 50000 cP, 80000 cP, and 500000 cP; preferably, the viscosity of the 107 adhesive is a combination of 80000 cP and 500000 cP, with a ratio of 1:(0.2~0.5).

3. The low-corrosion acidic silicone sealant according to claim 1, characterized in that, The plasticizers include one or more of 100cP dimethyl silicone oil and No. 3 white oil.

4. The low-corrosion acidic silicone sealant according to claim 1, characterized in that, The fumed silica mentioned is a hydrophilic silica with a specific surface area of ​​150-180 m². 2 / g.

5. The low-corrosion acidic silicone sealant according to claim 1, characterized in that, The acid-binding agent includes one or more of sodium carbonate, sodium bicarbonate, ammonium carbonate, calcium carbonate, sodium acetate, potassium acetate, sodium methoxide, or sodium ethoxide; preferably, the acid-binding agent is a mixture of sodium acetate and calcium carbonate in a mass ratio of 1:(0.5~1), the synergistic acid-binding agent is acetylacetone, and the catalyst is dibutyltin diacetate.

6. The low-corrosion acidic silicone sealant according to claim 1, characterized in that, The composite pH adjuster includes one or more of sodium benzoate, ammonium benzoate, disodium hydrogen phosphate, sodium dihydrogen phosphate, dipotassium hydrogen phosphate, or potassium dihydrogen phosphate. Preferably, the pH adjuster is a combination of disodium hydrogen phosphate and sodium benzoate, with a mass ratio of 1:(0.3~0.5).

7. The low-corrosion acidic silicone sealant according to claim 1, characterized in that, The silane crosslinking agent is one or more selected from methyltriacetoxysilane, ethyltriacetoxysilane, propyltriacetoxysilane, di-tert-butoxydiacetoxysilane, methyltrimethoxysilane, dimethyldiethoxysilane, tetramethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, and tetraethoxysilane; preferably, the silane crosslinking agent is a composition of methyltriacetoxysilane, propyltriacetoxysilane, and methyltrimethoxysilane, with a ratio of 1:0.5 to 1:0.05 to 0.2; more preferably, the methyltriacetoxysilane is a mixture of monomer and oligomer, with a monomer to oligomer ratio of 1:(0.25 to 0.75).

8. The low-corrosion acidic silicone sealant according to claim 7, characterized in that, The degree of polymerization of the oligomer is 2-3.

9. The low-corrosion acidic silicone sealant according to claim 8, characterized in that, The oligomer has a degree of polymerization of 2 to 3. The preparation process of the oligomer is as follows: a measured amount of methanol-water solution is added dropwise to methyltriacetoxysilane monomer, the methanol concentration is 5%-15%, and the reaction is carried out at 30-50℃ to obtain an oligomer with a degree of polymerization of 2 to 3.

10. The method for preparing the low-corrosion acidic silicone sealant according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Add 107 glue, plasticizer, and silane crosslinking agent, vacuum, and stir evenly; S2. Add fumed silica, acid binder and synergistic acid binder, stir under normal pressure for 3-9 minutes, scrape the paddle, and continue to vacuum and stir evenly. S3. Add catalyst and composite pH adjuster, continue stirring and vacuuming, and after mixing, prepare acidic silicone sealant. Preferably, in steps S1 to S3, the temperature of the vacuum stirring is controlled at 20 to 30 ℃, the time is 15 to 40 min, and the vacuum degree is -0.085 MPa to -0.098 MPa; In step S2, the fumed silica should be dried to remove moisture before being added. The drying temperature is 120~150℃ and the drying time is 2~4 h.

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