Silicone sealant and preparation method thereof

Abstract

The invention mainly relates to the technical field of adhesives, in particular to a silicone sealant. The flame-retardant silicone rubber is prepared from the following raw materials in parts by weight: 15 to 30 parts of hydroxyl-terminated polysiloxane, 10 to 15 parts of PET (Polyethylene Terephthalate) polyester, 5 to 10 parts of m-phthalic acid-5-sodium sulfonate, 2 to 5 parts of 3-sulfenyl-butantetraol, 5 to 8 parts of a cross-linking agent, 25 to 50 parts of a flame retardant, 10 to 30 parts of filler, 0.5 to 2 parts of a chain extender, 0.5 to 2 parts of a tackifier and 0.5 to 1 part of a catalyst. A-SOH sulfenyl group is introduced into 1, 3-sulfenyl-butantetraol, and a hydrophobic group is generated after the 1, 3-sulfenyl-butantetraol is combined with PET polyester, so that water is prevented from entering from fine holes in the surface of a product, better waterproof performance is obtained, silicon-containing components of the flame retardant are mutually crosslinked, a Si-O-Si network structure is formed in the sealant, and the flame retardant property is improved. And the decomposed product can help to prevent further occurrence of combustion, so that the flame-retardant effect is achieved. And the grafting of the silicon-containing group can greatly reduce the formation of tiny holes in the internal structure, so that the sealant has good waterproofness.

Description

Technical Field

[0001] The present invention relates to the technical field of adhesives, and particularly relates to a silicone sealant and a preparation method thereof. Background Art

[0002] As a new type of silicone elastomer, silicone sealant can crosslink and cure at room temperature. According to different packaging forms, silicone sealant can be divided into two categories: one-component and two-component. The use temperature of silicone sealant is -50~180°C. Since silicone sealant has good adhesiveness to a variety of substrates, can prevent dust and moisture from entering the interior of products, and has excellent electrical insulation, chemical stability, aging resistance and physiological inertness, etc., it is widely used in the industries of aerospace, automotive, construction and electronics. However, silicone sealant itself is flammable and will burn when encountering an open flame. In recent years, with the increasing application of sealant in buildings, once a fire occurs, it will inevitably cause serious property losses and casualties. Therefore, studying the flame retardant performance of sealant has become an important development trend. Flame retardant silicone sealant is a new type of flame retardant composite material. When encountering high temperature or flame, the flame retardant in the material will play a role and prevent the fire from spreading further. Flame retardant silicone sealant provides a new idea for the fire prevention and flame retardant problems of high-rise building glass curtain walls and other facilities. It can ensure the plugging and safety of buildings during a fire and win precious time for the evacuation of personnel.

[0003] The combustion of silicone sealant can be divided into three stages according to the development of time: heat accumulation, thermal decomposition and ignition combustion. (1) Heat accumulation: Silicone sealant will not soften and melt when it has not reached the thermal decomposition temperature. However, with the continuous accumulation of heat, a part of the heat will increase the internal energy of the polymer and continuously increase the temperature of the polymer, and another part of the heat will induce the scission of free radicals in the silicone sealant and accelerate the decomposition autocatalysis, thereby increasing the rate of thermal decomposition; (2) Thermal decomposition: The thermal decomposition process of silicone sealant can be divided into depolymerization reaction, elimination reaction, cyclization reaction and crosslinking reaction, etc. according to different structures and chemical compositions. When silicone sealant decomposes, the thermal decomposition occurring on the material surface is oxidative thermal decomposition, that is, oxygen participates in the decomposition process, while non-oxidative thermal decomposition will occur inside the material, and there is no oxygen participation in this process; (3) Ignition combustion: Under the action of heat transfer, a large amount of heat released by the combustion on the surface of silicone sealant intensifies the decomposition of the polymer. When the combustible substances generated by the decomposition are mixed with a certain proportion of air and reach the ignition point, combustion begins. At the same time, the flame will spread and propagate along the surface of the silicone sealant, thereby triggering a larger fire. Therefore, for flame retardant materials, controlling the spread of the flame is an important task for fire prevention and also an important basis for the design of flame retardant silicone sealant.

[0004] Chinese Patent No. 201510524661.9 discloses a new type of environmentally friendly flame-retardant silicone sealant and its preparation method, which includes the following components in parts by weight: 100 parts of α,ω-dihydroxy polydimethylsiloxane, 1-50 parts of polydimethylsiloxane, 5-150 parts of filler, 1-10 parts of phosphorus-silicon flame retardant, 1-15 parts of crosslinking agent, 0.1-3 parts of catalyst, and 0.5-4 parts of coupling agent. This invention uses a method of adding a new type of environmentally friendly flame retardant to prepare a de-alcohol type flame-retardant silicone sealant, which solves the problem of poor flame retardancy of de-alcohol type sealant products. The preparation process is simple, the loss during production is low, and the processing performance of the product is good.

[0005] Currently, commonly used flame retardants can generally be classified into five categories, namely: halogen-based flame retardants, organophosphorus flame retardants, intumescent flame retardants, inorganic flame retardants, silicon-based flame retardants, etc. Different types of flame retardants have different advantages and disadvantages. In actual use, generally only one flame retardant is rarely used. In actual applications, two or more flame retardants are often added to give full play to the advantages of different flame retardants, utilize the synergistic effect between flame retardants, play multiple flame retardant roles to improve the flame retardancy efficiency, reduce the total addition amount of flame retardants, reduce costs, and weaken the impact on the performance of the substrate itself. Silicone sealant itself is waterproof. However, when the flame retardant is added as an auxiliary agent, due to its poor compatibility with the sealant, more micropores will be formed. These micropores will affect the waterproofness of the sealant, causing water absorption and ultimately water seepage. Therefore, it is necessary to develop a flame retardant with better compatibility and apply it to silicone sealant to achieve better waterproofness. Summary of the Invention

[0006] In view of the deficiencies in the prior art, the present invention provides a silicone sealant and its preparation method, which solves the problem of insufficient waterproofness of the sealant in the prior art.

[0007] In the first aspect, the present invention provides a silicone sealant, which is composed of the following raw materials in parts by weight: 15-30 parts of terminal hydroxyl polydimethylsiloxane, 10-15 parts of PET polyester, 5-10 parts of sodium 5-sulfoisophthalate, 2-5 parts of 3-sulfino-butanetetrol, 5-8 parts of crosslinking agent, 25-50 parts of flame retardant, 10-30 parts of filler, 0.5-2 parts of chain extender, 0.5-2 parts of tackifier, and 0.5-1 part of catalyst.

[0008] Preferably, the flame retardant includes one of tris(2,3-dibromo)propyl borate or polyborosiloxane.

[0009] Preferably, the filler is one of fumed silica, quartz powder, or nano calcium carbonate.

[0010] Preferably, the crosslinking agent is one of methyltriacetoxysilane, methyltributanoneoxime silane, or methyltrimethoxysilane.

[0011] Preferably, the chain extender is one of dimethyldibutone oxime silane, methylvinyl dibutone oxime silane or methylvinyl diacetone oxime silane.

[0012] Preferably, the tackifier is one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane or γ-(2,3-epoxypropoxy)propyltrimethoxysilane.

[0013] Preferably, the catalyst is one of platinum-based catalysts, palladium-based catalysts or tin-based catalysts.

[0014] In a second aspect, the present invention also provides a method for preparing a silicone sealant, comprising the following steps:

[0015] A1. Knead the formula amount of hydroxyl-terminated polysiloxane and the flame retardant at room temperature, add the filler, heat up to 130-150 °C and vacuum knead and stir for 2-4 h to remove the moisture in the system, then cool to room temperature, grind evenly, and discharge to obtain the base rubber.

[0016] A2. Draw the base rubber in step A1 into a reaction kettle, vacuum stir to remove the moisture in the air, add PET polyester, then add sodium 5-sulfoisophthalate to the reaction kettle, keep the temperature at 240 °C and react for 2 hours, then add 3-sulfo group-butane tetrol, then add the crosslinking agent, chain extender, tackifier, catalyst, mix evenly, and remove the bubbles to obtain the silicone sealant product.

[0017] Further, the sodium 5-sulfoisophthalate is first made into a 40% wt esterification solution and then added to the reaction kettle.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention introduces PET polyester modified by sodium 5-sulfoisophthalate into the traditional sealant raw materials, which destroys the regular spatial configuration of polymer molecules, so as to have better interfacial compatibility, and can make various different flame retardants cooperate and combine more evenly. At the same time, the raw materials of the present invention also contain 3-sulfo group-butane tetrol, thus introducing -SOH sulfinic acid group, which generates hydrophobic groups after combining with PET polyester, so that the surface of the product at this time shows water resistance, thus avoiding water from entering through the fine holes on the product surface and obtaining better waterproof performance.

[0020] 2. The silicon-containing components of the flame retardant crosslink with each other to form a Si-O-Si network structure inside the sealant, preventing the volatilization of components during heating and finally degrading into SiO2, which remains in the carbon residue. In the boron-containing components, the O-C bond of the B-O-C bond breaks to form a borate structure, which can promote the generation of water vapor through a heat dissipation effect and finally degrade into B2O3, remaining in the carbon residue. These components can all help prevent the further occurrence of combustion, thus achieving a flame retardant effect. The nitrogen-containing groups can discharge non-combustible gases such as NH3, NO, and NO2 during the combustion process, which can dilute the oxygen and heat on the surface of the sealant and prevent the combustion of other combustible substances. Detailed implementation mode

[0021] The technical solutions in the present invention will be further described below in conjunction with embodiments.

[0022] Embodiment 1

[0023] A preparation method of a silicone sealant includes the following steps:

[0024] A1. Knead 4 kg of α,ω-dihydroxypolydimethylsiloxane and 2.5 kg of tris(2,3-dibromo)propyl borate as a flame retardant at room temperature, add 2 kg of nano calcium carbonate, raise the temperature to 140 °C and carry out vacuum kneading and stirring for 4 h to remove the moisture in the system, then cool to room temperature, grind evenly, and discharge to obtain the base glue;

[0025] A2. Vacuum stir the base glue in step A1 to remove the moisture in the air, then add 1.5 kg of PET polyester, and then add 0.5 kg of sodium 5-sulfoisophthalate to make a 40% wt esterification solution and add it to the reaction kettle. React at a temperature of 240 °C for 2 hours, then add 0.1 kg of 3-sulfonic acid group-butane tetrol, then add 1 kg of methyltriacetoxysilane and mix evenly. Then add 0.1 kg of dimethyldibutoxime-based silane, 0.1 kg of γ-aminopropyltrimethoxysilane, and 0.05 kg of stannous octoate, mix evenly, and remove the bubbles to obtain the silicone sealant product.

[0026] Embodiment 2

[0027] A preparation method of a silicone sealant includes the following steps:

[0028] A1. Knead 4 kg of α,ω-dihydroxypolydimethylsiloxane and 2.5 kg of polyborosiloxane at room temperature, add 2 kg of nano calcium carbonate, raise the temperature to 140 °C and carry out vacuum kneading and stirring for 4 h to remove the moisture in the system, then cool to room temperature, grind evenly, and discharge to obtain the base glue;

[0029] A2. Vacuum stir the base glue in step A1 to remove moisture in the air, then add 1.5 kg of PET polyester. Subsequently, make 0.5 kg of sodium 5-sulfoisophthalate into a 40% wt esterification solution and add it to the reaction kettle. React at a temperature of 240 °C for 2 hours, then add 0.1 kg of 3-sulfo group-butane tetrol, then add 1 kg of methyltriacetoxysilane and mix evenly. Then add 0.1 kg of dimethyldibutanone oxime silane, 0.1 kg of γ-aminopropyltrimethoxysilane, and 0.05 kg of stannous octoate. After mixing evenly, remove the bubbles to obtain the silicone sealant product.

[0030] Example 3

[0031] A preparation method of a silicone sealant, comprising the following steps:

[0032] A1. Knead 4 kg of α,ω-dihydroxypolydimethylsiloxane and 2.5 kg of polyborosiloxane at room temperature, add 2 kg of nano calcium carbonate, heat up and vacuum knead and stir at 140 °C for 4 h to remove moisture in the system, then cool to room temperature, grind evenly, and discharge to obtain the base glue;

[0033] A2. Vacuum stir the base glue in step A1 to remove moisture in the air, then add 1.5 kg of PET polyester. Subsequently, make 0.5 kg of sodium 5-sulfoisophthalate into a 40% wt esterification solution and add it to the reaction kettle. React at a temperature of 240 °C for 2 hours, then add 0.1 kg of 3-sulfo group-butane tetrol, then add 1 kg of methyltriacetoxysilane and mix evenly. Then add 0.1 kg of dimethyldibutanone oxime silane, 0.1 kg of γ-aminopropyltrimethoxysilane, and 0.05 kg of stannous octoate. After mixing evenly, remove the bubbles to obtain the silicone sealant product.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the purpose and scope of the technical solutions of the present invention, and they should all be covered by the scope of the claims of the present invention.

Claims

1. A silicone sealant, characterized in that: The invention is composed of the following raw materials in parts by weight: 15-30 parts of terminal hydroxyl polysiloxane, 10-15 parts of PET polyester, 5-10 parts of 5-sulfonated sodium isophthalate, 2-5 parts of 3-sulfonyl-butanetetrol, 5-8 parts of a crosslinking agent, 25-50 parts of a flame retardant, 10-30 parts of a filler, 0.5-2 parts of a chain extender, 0.5-2 parts of a tackifier and 0.5-1 parts of a catalyst.

2. The silicone sealant according to claim 1, characterized in that: The flame retardant includes one of tri(2,3-dibromo)propyl borate or polyborosiloxane.

3. The silicone sealant according to claim 1, characterized in that: The filler is one of white carbon black, quartz powder or nano calcium carbonate.

4. The silicone sealant according to claim 1, characterized in that: The crosslinking agent is one of methyltriacetoxysilane, methyltributylidene oxime silane and methyltrimethoxysilane.

5. The silicone sealant according to claim 1, characterized in that: The chain extender is one of dimethyl dibutyl ketone oxime silane, methyl vinyl dibutyl ketone oxime silane or methyl vinyl diacetone oxime silane.

6. The silicone sealant according to claim 1, characterized in that: The tackifier is one of γ-aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane or γ-(2,3-epoxypropyloxy)propyltrimethoxysilane.

7. The silicone sealant according to claim 1, characterized in that: The catalyst is one of a platinum catalyst, a palladium catalyst or a tin catalyst.

8. A method for preparing the silicone sealant according to any one of claims 1 to 7, characterized in that: The steps include: A1. Knead the formulated amount of terminal hydroxyl polysiloxane and flame retardant at room temperature, add filler, heat up to 130-150° C., knead and stir under vacuum for 2-4 hours, remove moisture from the system, then cool to room temperature, grind evenly, and obtain base rubber; A2. The base rubber in step A1 is pumped into a reactor, and the moisture in the air is removed by vacuum stirring. Then, PET polyester is added, and then sodium 5-sulfonisophthalate is added into the reactor. The reaction is maintained at 240° C. for 2 hours. Then, a cross-linking agent, a chain extender, a tackifier, and a catalyst are added. After mixing evenly, bubbles are removed to obtain a silicone sealant product.

9. The method for preparing silicone sealant according to claim 8, characterized in that: The 5-sodium sulfoisophthalate is first prepared into a 40%wt esterification liquid and then added into the reaction kettle.