Method for preparing organic silicon synthetic leather based on directional hydrolysis reaction type foaming agent

Abstract

The invention relates to a method for preparing organic silicon synthetic leather based on a directional hydrolysis reaction type foaming agent, and belongs to the field of organic silicon synthetic leather. The reactive foaming agent takes hydrated salt as an inner layer, nano silicon dioxide as a middle layer and alkyl isocyanate as an outer layer. In the heating and curing process of the organosilicon foaming layer slurry, water molecules released by heating of the inner-layer hydrated salt are directionally diffused from inside to outside and are preferentially subjected to hydrolysis reaction with the outer-layer alkyl isocyanate to generate carbon dioxide for foaming, so that the hydrolysis side reaction of the hydrogen-containing silicone oil is greatly reduced. Meanwhile, an amine intermediate generated by hydrolysis of alkyl isocyanate can be quickly condensed with surrounding alkyl isocyanate to generate urea, so that the poisoning risk of a platinum catalyst is reduced. The reactive foaming agent disclosed by the invention is good in dispersity in organic silicon foaming layer slurry, and foaming in a relatively wide temperature range of 80-130 DEG C can be realized; and residual nano silicon dioxide and hydrated salt decomposition products after foaming can be directly used as organic silicon synthetic leather filler.

Description

Technical Field

[0001] This invention relates to a method for preparing silicone synthetic leather based on a directional hydrolysis reaction foaming agent, belonging to the field of silicone synthetic leather. Background Technology

[0002] Silicone synthetic leather is a new generation of synthetic leather with a silicon-oxygen bond backbone, possessing excellent heat resistance, easy cleaning, and environmentally friendly and non-toxic properties. Silicone synthetic leather coatings are generally prepared from hydrogen-containing silicone oil and vinyl silicone oil through a hydrosilylation reaction. To improve the fullness, softness, and lightweight heat insulation properties of the silicone synthetic leather coating, foaming is often required. However, currently, there are relatively few foaming technologies suitable for silicone synthetic leather. Chinese patent CN111691193A discloses a foamed silicone synthetic leather and its preparation method. This method utilizes the hydrogen gas released from the reaction of hydrogen-containing silicone oil and hydroxyl silicone oil for foaming, achieving simultaneous cross-linking and foaming of the silicone synthetic leather.

[0003] In polyurethane foam materials, isocyanate is commonly used to generate carbon dioxide for foaming. This method is simple, low-cost, highly efficient, and produces uniformly distributed cells. However, this method is difficult to use directly for foaming silicone synthetic leather, mainly because: (1) Hydrogen-containing silicone oil undergoes hydrolysis with water under the action of a platinum catalyst, interfering with normal hydrosilylation; (2) The amine intermediate generated by isocyanate hydrolysis easily complexes with the platinum catalyst, leading to platinum catalyst poisoning. Although the amine intermediate can further react with isocyanate to generate urea, the platinum catalyst poisoning rate is often faster than the urea formation reaction. Therefore, although the isocyanate hydrolysis foaming method is simple and efficient, it cannot be directly used to prepare silicone synthetic leather. Summary of the Invention

[0004] This invention aims to overcome the shortcomings and deficiencies of existing technologies and provides a method for preparing organosilicon synthetic leather based on a directional hydrolysis reaction foaming agent. The method is characterized by the following synthesis steps and conditions, with all raw materials used being in parts by weight: (1) Add 8-10 parts of dehydrated nano silica and 12-18 parts of hydrated salt with a particle size of 500-600 nanometers to the reaction vessel, stir at 15-20℃ for 20-24 minutes, then add 120-220 parts of alkyl isocyanate to the reaction vessel, stir for 5-8 minutes to obtain a reactive foaming agent. (2) Mix 1-5 parts of the above-mentioned reactive foaming agent, 10-60 parts of hydrogen-containing silicone oil, 30-80 parts of vinyl silicone oil, 0.2-0.8 parts of platinum catalyst and 0.01-0.15 parts of inhibitor at 20-35°C to obtain organosilicon synthetic leather foaming layer slurry; (3) Mix 10-60 parts of hydrogen-containing silicone oil, 30-80 parts of vinyl silicone oil, 0.2-0.8 parts of platinum catalyst and 0.01-0.15 parts of inhibitor evenly to prepare organosilicon synthetic leather surface layer slurry; (4) Coat the surface of the release paper with a 0.05-0.1 mm thick silicone synthetic leather surface layer slurry, place it in an oven at 110-130℃ and heat and cure for 8-10 minutes, then coat the surface of the release paper with a 0.2-0.8 mm thick silicone synthetic leather foaming layer slurry, bond the base fabric, and then pass it through three ovens at 80-90℃, 110-120℃ and 130-135℃ in sequence, keeping it for 2-4 minutes, 8-10 minutes and 1-3 minutes respectively, and then peel off the release paper to obtain silicone synthetic leather; The above-mentioned hydrated salts are one or more of the following: sodium tetraborate decahydrate, magnesium sulfate heptahydrate, magnesium nitrate hexahydrate, sodium acetate trihydrate, and sodium carbonate monohydrate; The aforementioned alkyl isocyanates are one or more selected from octyl isocyanate, nonyl isocyanate, decyl isocyanate, undecyl isocyanate, dodecyl isocyanate, tridecyl isocyanate, and tetradecyl isocyanate. In the above-mentioned reactive foaming agent, the molar ratio of bound water to alkyl isocyanate is 1:2.22-2.40; The hydrogen content of the aforementioned hydrogen-containing silicone oil is 0.01-2.5 wt%; The vinyl content of the above-mentioned vinyl silicone oil is 0.01-2.5 wt%; The platinum catalyst mentioned above is one or more of the following: Speier catalyst, Karstedt catalyst, and Ashby catalyst; The above-mentioned inhibitors are one or more of ethynylisopropanol, ethynylbutanol, ethynylcyclopentanol, and ethynylcyclohexanol; The base fabric mentioned above is one or more of the following: non-woven fabric, woven fabric, knitted fabric, and microfiber fabric.

[0005] The core of this invention lies in the preparation of a directional hydrolysis-reactive foaming agent. The inner layer of this reactive foaming agent is a hydrated salt that releases water molecules upon heating. The middle layer is nano-silica rich in silanol groups, coated on the surface of the hydrated salt particles via hydrogen bonding. Its function is to isolate the hydrated salt from the alkyl isocyanate, preventing them from reacting at low temperatures. The outer layer is an alkyl isocyanate, where the isocyanate end groups are adsorbed onto the surface of the nano-silica via hydrogen bonding, while the alkyl chains are distributed outwards on the surface of the foaming agent, improving the compatibility of the foaming agent with the organosilicon foaming layer slurry and enhancing the dispersion uniformity of the foaming agent.

[0006] During the heating and curing process of the silicone foaming layer slurry, water molecules released from the inner layer hydrated salt diffuse directionally from the inside out, breaking through the intermediate layer and preferentially reacting with the outer layer alkyl isocyanate to generate carbon dioxide, which plays a foaming role, thus significantly reducing the hydrolysis side reaction of hydrogen-containing silicone oil. Simultaneously, since the alkyl isocyanate is concentrated on the outer layer of the foaming agent, the amine intermediates generated by its hydrolysis can rapidly condense with the surrounding alkyl isocyanates to form urea, significantly reducing the risk of amine-induced platinum catalyst poisoning. Furthermore, the reactivity of alkyl isocyanate with the silanol groups on the surface of nano-silica is much lower than its reactivity with water, and it does not interfere with the foaming process. Finally, the residual nano-silica and hydrated salt decomposition products after foaming can be directly used as fillers for silicone synthetic leather.

[0007] Experiments have shown that: (1) The molar ratio of bound water to alkyl isocyanate in hydrated salt should be controlled at 1:2.22-2.40. Too much bound water will trigger the hydrolysis side reaction of hydrogen-containing silicone oil, resulting in a decrease in the tensile strength of the foam layer (Comparative Example 1); too little bound water will lead to alkyl isocyanate residue, affecting the durability of synthetic leather; (2) The alkyl chain length of alkyl isocyanate should be limited to C8-C14. If the alkyl chain is too short, the compatibility between the foaming agent and the silicone foam layer slurry is poor, which will affect the dispersion effect of the foaming agent and lead to uneven foaming (Comparative Example 2); if the alkyl chain is too long, the compatibility with the silicone foam layer slurry is too strong, which will weaken the binding of hydrogen bonds to the isocyanate group, causing the alkyl isocyanate to detach from the foaming agent, resulting in a decrease in the foaming ratio, and increasing the risk of hydrolysis side reaction of hydrogen-containing silicone oil and poisoning of platinum catalyst, resulting in a decrease in the tensile strength of the foam layer (Comparative Example 3).

[0008] Compared with the prior art, the present invention has the following advantages: (1) It significantly reduces the risk of hydrolysis side reactions of hydrogen-containing silicone oil and poisoning of platinum catalyst; (2) The reactive foaming agent is easy to disperse in the silicone foaming layer slurry, and the resulting pores are evenly distributed; (3) By utilizing the differences in bound water content and decomposition temperature in different hydrated salts, foaming can be achieved in a wide temperature range of 80-130℃, with a foaming ratio of 1.5-4.0 times; (4) The residual nano silica and hydrated salt decomposition products after foaming can be directly used as fillers for silicone synthetic leather. Attached Figure Description

[0009] Figure 1 This is a schematic diagram of the structure of the reactive foaming agent involved in this invention. Detailed Implementation

[0010] The present invention will be specifically described below through embodiments, which are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above-described content.

[0011] Example 1: (1) Add 8 parts of dehydrated nano silica, 2 parts of sodium tetraborate decahydrate, 4 parts of magnesium nitrate hexahydrate and 10 parts of sodium acetate trihydrate, all with a particle size of 500 nm, to a reaction vessel and stir at 15°C for 20 minutes. Then add 38 parts of octyl isocyanate, 50 parts of decyl isocyanate and 42 parts of undecyl isocyanate to the reaction vessel and stir for 5 minutes to obtain a reactive foaming agent. (2) Mix 1.5 parts of the above-mentioned reactive foaming agent, 20 parts of hydrogen-containing silicone oil with a hydrogen content of 0.1 wt%, 50 parts of vinyl silicone oil with a vinyl content of 1.1 wt%, 0.35 parts of Speier catalyst and 0.05 parts of vinyl isopropanol evenly at a temperature below 35°C to prepare organosilicon synthetic leather foaming layer slurry. (3) Mix 25 parts of hydrogen-containing silicone oil with a hydrogen content of 0.4 wt%, 64 parts of vinyl silicone oil with a vinyl content of 2.5 wt%, 0.4 parts of Speier catalyst and 0.06 parts of ethynylcyclopentanol evenly to prepare organosilicon synthetic leather surface layer slurry; (4) Coat the surface of the release paper with a 0.05 mm thick silicone synthetic leather surface layer slurry, place it in an oven at 115℃ and heat for 10 minutes, then coat it with a 0.2 mm thick silicone synthetic leather foaming layer slurry, bond the non-woven fabric, and then pass it through three ovens at 80℃, 115℃ and 135℃ in sequence, keeping it for 4 minutes, 8 minutes and 3 minutes respectively, and then peel off the release paper to obtain silicone synthetic leather.

[0012] In Example 1 above, the molar ratio of bound water to alkyl isocyanate in the hydrated salt was 1:2.25; the resulting silicone synthetic leather foam layer had a foaming ratio of 1.7 times, a tensile strength of 2.8 MPa, and fine and uniformly distributed pores.

[0013] Example 2: (1) 10 parts of dehydrated nano silica, 2 parts of sodium tetraborate decahydrate, 10 parts of magnesium sulfate heptahydrate and 3 parts of sodium carbonate monohydrate with a particle size of 600 nm were added to the reaction vessel and stirred at 20°C for 24 minutes. Then, 52 parts of nonyl isocyanate, 48 parts of dodecyl isocyanate, 30 parts of dodecyl isocyanate and 42 parts of tetradecyl isocyanate were added to the reaction vessel and stirred for 8 minutes to obtain a reactive foaming agent. (2) Mix 5 parts of the above-mentioned reactive foaming agent, 27 parts of hydrogen-containing silicone oil with a hydrogen content of 0.06wt%, 55 parts of vinyl silicone oil with a vinyl content of 0.8wt%, 0.34 parts of Karstedt catalyst and 0.08 parts of ethynylbutanol evenly at a temperature below 35°C to prepare organosilicon synthetic leather foaming layer slurry. (3) Mix 15 parts of hydrogen-containing silicone oil with a hydrogen content of 0.4wt%, 80 parts of vinyl silicone oil with a vinyl content of 0.4wt%, 0.5 parts of Ashby catalyst and 0.1 parts of ethynylcyclohexanol evenly to prepare organosilicon synthetic leather surface layer slurry; (4) Coat the surface of the release paper with a 0.1 mm thick silicone synthetic leather surface layer slurry, place it in a 130℃ oven and heat for 8 minutes, then coat it with a 0.8 mm thick silicone synthetic leather foaming layer slurry, bond the knitted fabric, and then pass it through three ovens at 90℃, 120℃ and 130℃ in sequence, keeping it for 2 minutes, 10 minutes and 1 minute respectively, and then peel off the release paper to obtain silicone synthetic leather.

[0014] In Example 2 above, the molar ratio of bound water to alkyl isocyanate in the hydrated salt was 1:2.40; the resulting silicone synthetic leather foam layer had a foaming ratio of 4.0 times, a tensile strength of 0.7 MPa, and fine and uniformly distributed pores.

[0015] Comparative Example 1: (1) Add 8 parts of dehydrated nano silica, 2 parts of sodium tetraborate decahydrate, 4 parts of magnesium nitrate hexahydrate and 12 parts of sodium acetate trihydrate, all with a particle size of 500 nm, to a reaction vessel and stir at 15°C for 20 minutes. Then add 38 parts of octyl isocyanate, 50 parts of decyl isocyanate and 42 parts of undecyl isocyanate to the reaction vessel and stir for 5 minutes to obtain a reactive foaming agent. Steps (2), (3), and (4) are prepared according to the method in Example 1.

[0016] Compared with Example 1, the molar ratio of bound water to alkyl isocyanate in the hydrated salt of Comparative Example 1 was adjusted to 1:2.03, that is, the proportion of bound water in the foaming agent was excessive, which caused the hydrolysis side reaction of the hydrogen-containing silicone oil, and the tensile strength of the resulting silicone synthetic leather foam layer decreased to 2.0 MPa.

[0017] Comparative Example 2: (1) Add 8 parts of dehydrated nano silica, 2 parts of sodium tetraborate decahydrate, 4 parts of magnesium nitrate hexahydrate and 10 parts of sodium acetate trihydrate, all with a particle size of 500 nm, to a reaction vessel and stir at 15°C for 20 minutes. Then add 28 parts of butyl isocyanate, 35 parts of pentyl isocyanate and 23 parts of hexyl isocyanate to the reaction vessel and stir for 5 minutes to obtain a reactive foaming agent. Steps (2), (3), and (4) are prepared according to the method in Example 1.

[0018] Compared with Example 1, the isocyanate alkyl chain used in the foaming agent in Comparative Example 2 is too short (C4, C5, C6), resulting in poor dispersion of the foaming agent in the silicone foaming layer slurry. The resulting silicone synthetic leather has uneven cell distribution and cell merging.

[0019] Comparative Example 3: (1) Add 8 parts of dehydrated nano silica, 2 parts of sodium tetraborate decahydrate, 4 parts of magnesium nitrate hexahydrate and 10 parts of sodium acetate trihydrate, all with a particle size of 500 nm, to a reaction vessel and stir at 15°C for 20 minutes. Then add 120 parts of hexadecyl isocyanate and 95 parts of octadecyl isocyanate to the reaction vessel and stir for 5 minutes to obtain a reactive foaming agent. Steps (2), (3), and (4) are prepared according to the method in Example 1.

[0020] Compared with Example 1, the isocyanate alkyl chain used in the foaming agent of Comparative Example 3 was too long (C16, C18), which caused the foaming ratio of the silicone synthetic leather foam layer to drop to 1.2 times and the tensile strength to drop to 1.0 MPa.

Claims

1. A method for preparing organosilicon synthetic leather based on a directional hydrolysis reaction-type foaming agent, characterized in that... The synthesis steps and conditions of this method are as follows, and all parts of raw materials used are by weight: (1) Add 8-10 parts of dehydrated nano silica and 12-18 parts of hydrated salt with a particle size of 500-600 nanometers to the reaction vessel, stir at 15-20℃ for 20-24 minutes, then add 120-220 parts of alkyl isocyanate to the reaction vessel, stir for 5-8 minutes to obtain a reactive foaming agent. (2) Mix 1-5 parts of the above-mentioned reactive foaming agent, 10-60 parts of hydrogen-containing silicone oil, 30-80 parts of vinyl silicone oil, 0.2-0.8 parts of platinum catalyst and 0.01-0.15 parts of inhibitor at 20-35°C to obtain organosilicon synthetic leather foaming layer slurry; (3) Mix 10-60 parts of hydrogen-containing silicone oil, 30-80 parts of vinyl silicone oil, 0.2-0.8 parts of platinum catalyst and 0.01-0.15 parts of inhibitor evenly to prepare organosilicon synthetic leather surface layer slurry; (4) Coat the surface of the release paper with a 0.05-0.1 mm thick silicone synthetic leather surface layer slurry, place it in an oven at 110-130℃ and heat and cure for 8-10 minutes, then coat the surface of the release paper with a 0.2-0.8 mm thick silicone synthetic leather foaming layer slurry, bond the base fabric, and then pass it through three ovens at 80-90℃, 110-120℃ and 130-135℃ in sequence, keeping it for 2-4 minutes, 8-10 minutes and 1-3 minutes respectively, and then peel off the release paper to obtain silicone synthetic leather; The above-mentioned hydrated salts are one or more of the following: sodium tetraborate decahydrate, magnesium sulfate heptahydrate, magnesium nitrate hexahydrate, sodium acetate trihydrate, and sodium carbonate monohydrate; The aforementioned alkyl isocyanates are one or more selected from octyl isocyanate, nonyl isocyanate, decyl isocyanate, undecyl isocyanate, dodecyl isocyanate, tridecyl isocyanate, and tetradecyl isocyanate. In the above-mentioned reactive foaming agent, the molar ratio of bound water to alkyl isocyanate is 1:2.22-2.40; The hydrogen content of the aforementioned hydrogen-containing silicone oil is 0.01-2.5 wt%; The vinyl content of the above-mentioned vinyl silicone oil is 0.01-2.5 wt%; The platinum catalyst mentioned above is one or more of the following: Speier catalyst, Karstedt catalyst, and Ashby catalyst; The above-mentioned inhibitors are one or more of ethynylisopropanol, ethynylbutanol, ethynylcyclopentanol, and ethynylcyclohexanol; The base fabric mentioned above is one or more of the following: non-woven fabric, woven fabric, knitted fabric, and microfiber fabric.

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