Preparation method and application of a skin-friendly matte anti-slip flexible silicone

Abstract

The present invention relates to the technical field of silicone rubber, and discloses a preparation method and application of a skin-friendly matte anti-slip flexible silicone rubber. Methyl vinyl silicone rubber, phosphorus-silicon flame retardant, basic magnesium sulfate crystal, silica, and bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent are mixed and vulcanized to obtain the skin-friendly matte anti-slip flexible silicone rubber. The phosphorus-silicon flame retardant in the present invention can coat the surface of the basic magnesium sulfate crystal, enabling the basic magnesium sulfate crystal to be evenly dispersed in the silicone rubber material matrix, improving the tensile strength and elongation at break of the silicone rubber material. The basic magnesium sulfate crystal and the phosphorus-silicon flame retardant play a synergistic flame retardant role, improving the flame retardant performance of the silicone rubber material. The basic magnesium sulfate crystal can also act as a matting agent and an anti-slip agent, making the silicone rubber present a matte effect and improving the anti-slip performance.

Description

Technical Field

[0001] The present invention relates to the technical field of silicone rubber, and in particular to a preparation method and application of skin-friendly matte non-slip flexible silicone. Background Art

[0002] Silicone rubber, with its excellent elasticity, heat resistance, and aging resistance, is widely used in corrosion-resistant components and other electronic and electrical applications, daily necessities like silicone pillows and mattresses, and feminine products like bras and nipple covers. However, traditional silicone rubber suffers from shortcomings such as poor mechanical properties and poor surface hydrophilicity and skin-friendliness, which limit its practical application.

[0003] Basic magnesium sulfate crystals are a new type of inorganic fiber material with promising applications in polymer materials such as plastics and rubber. They can be used as a reinforcing agent, flame retardant, and matte agent to improve the mechanical strength and flame retardancy of the materials. Patent CN109370117B discloses a highly flame-retardant and aging-resistant fluororubber cable sheath material. Using fluororubber, acrylic rubber, EPDM rubber, benzyltriphenylphosphine chloride, white carbon black, and basic magnesium sulfate whiskers as raw materials, the resulting cable sheath material exhibits excellent flame retardancy, heat resistance, and aging resistance. However, this patent fails to improve the rubber material's hydrophilic and skin-friendly properties. Summary of the Invention

[0004] (1) Technical problems to be solved: The present invention provides a method for preparing a skin-friendly matte non-slip flexible silicone with high flame retardancy and good hydrophilicity.

[0005] (II) Technical Solution: A method for preparing a skin-friendly matte non-slip flexible silicone comprises the following steps:

[0006] Step S1, add acetonitrile and pentaerythritol diphosphate diphosphoryl chloride to a flask, heat to 80-85 ° C, stir, add triethylamine and acetonitrile solution containing bis (salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer dropwise, carry out polymerization reaction for 8-12 hours, filter after cooling, wash with acetonitrile and water in turn, add the product to methanol, add 120-140 g / L sodium hydroxide aqueous solution, heat to 80-90 ° C, hydrolyze for 6-8 hours, filter after cooling, wash with water, and dry to obtain a phosphorus silicon flame retardant.

[0007] Step S2: Add methyl vinyl silicone rubber, phosphorus silicon flame retardant, and basic magnesium sulfate crystals into an open mill for mixing, then add white carbon black, continue mixing, and finally add dipentadiene vulcanizing agent, vulcanize in a flat vulcanizer, cool and discharge the material to obtain a skin-friendly matte non-slip flexible silicone.

[0008] Preferably, in step S1, the molar ratio of pentaerythritol diphosphate dichlorophosphate (CAS No. 714-87-4), triethylamine, and bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer is 1:(1.8 - 2.2):(1 - 1.1).

[0009] Preferably, the preparation method of the bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer comprises the following steps: Add ethanol, bis(4-aminophenoxy)dimethylsilane (CAS No. 1223-16-1) with a molar ratio of 1:(2 - 2.1), and methyl 5-formylsalicylate (CAS No. 41489-76-3) to a flask, dropwise add glacial acetic acid, heat to 75 - 80 °C, react for 5 - 8 h, filter after cooling, wash with water, and recrystallize the product in acetonitrile to obtain the bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer.

[0010] Preferably, in step S2, the mass ratio of methyl vinyl silicone rubber, phosphorus-silicon flame retardant, basic magnesium sulfate crystal, fumed silica, and bis(2,5-dimethyl-2,5-di(t-butylperoxy)hexane) vulcanizing agent is 100:(15 - 30):(3 - 10):(10 - 20):(0.8 - 1.3).

[0011] Preferably, in step S2, the vulcanization temperature is 170 - 180 °C and the time is 10 - 20 min.

[0012] (III) Technical effects of the present invention: The present invention uses pentaerythritol diphosphate dichlorophosphate and bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer to carry out a polymerization reaction, and through hydrolysis with sodium hydroxide, a phosphorus-silicon flame retardant containing carboxylate groups is obtained. Then, it is kneaded and vulcanized with basic magnesium sulfate crystal, methyl vinyl silicone rubber, fumed silica, etc. to obtain a skin-friendly matte non-slip flexible silica gel.

[0013] The phosphorus-silicon flame retardant of the present invention contains a siloxane structural unit similar to that of methyl vinyl silicone rubber, so that the flame retardant has good compatibility with silicone rubber and does not affect the mechanical properties of the silicone material. Moreover, the phosphorus-silicon flame retardant contains a large number of hydrophilic carboxylate groups, which can increase the surface water contact angle of the silicone material and improve the surface hydrophilic and skin-friendly properties of the silicone material. At the same time, the phosphorus-silicon flame retardant contains a spirophosphate ester and a siloxane structure, forming a phosphorus-silicon flame retardant system and improving the flame retardant performance of the silicone material.

[0014] The phosphorus-silicon flame retardant of the present invention contains a carboxylate group, which can interact with the surface of basic magnesium sulfate crystals, enabling the phosphorus-silicon flame retardant to coat the surface of basic magnesium sulfate crystals. Due to the good compatibility between the phosphorus-silicon flame retardant and methyl vinyl silicone rubber, the basic magnesium sulfate crystals can be evenly dispersed in the silicone material matrix, playing a better reinforcing role and significantly improving the tensile strength and elongation at break of the silicone material. Moreover, the basic magnesium sulfate crystals and the phosphorus-silicon flame retardant play a synergistic flame retardant role, further improving the limiting oxygen index and vertical burning grade of the silicone material, showing better flame retardant performance.

[0015] The basic magnesium sulfate crystals of the present invention can also act as a matting agent and an anti-slip agent. The basic magnesium sulfate crystals are evenly distributed in the silicone material matrix, forming a fine concavo-convex structure on the surface, which can produce a strong light diffuse reflection effect, having a good matting effect, being conducive to reducing the gloss of the silicone surface, making the silicone present a matte finish, and the fine concavo-convex structure formed on the silicone surface is conducive to increasing the contact area and friction, improving the anti-slip and non-slip performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is the preparation reaction formula of bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer.

[0017] Figure 2 is the preparation reaction formula of the phosphorus-silicon flame retardant. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be further described in detail below with reference to specific embodiments, but the embodiments of the present invention are not limited thereto. For process parameters not specifically noted, conventional techniques can be referred to.

[0019] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0020] Methyl vinyl silicone rubber, Anhui Aiyota Silicone Oil Co., Ltd. Fumed silica, average particle size 3000 mesh, Guangzhou Yinuo Chemical Technology Co., Ltd.

[0021] Prepare basic magnesium sulfate whiskers according to the method in the journal "Journal of Chemical Industry and Engineering", Vol. 72, No. 6, 2021, "Controllable Preparation of Basic Magnesium Sulfate Whiskers and Influence Mechanisms of Different Ions".

[0022] Example 1:

[0023] (1) Add 400 mL of ethanol, 40 mmol of bis(4-aminophenoxy)dimethylsilane, and 80 mmol of methyl 5-formylsalicylate to a flask. Dropwise add 6 mL of glacial acetic acid, heat to 80 °C, and carry out a condensation reflux reaction for 5 h. After cooling, filter, wash with water, and recrystallize the product from acetonitrile to obtain the bis(salicylaldehyde methyl Schiff base)diphenylsiloxane monomer.

[0024] (2) Add 200 mL of acetonitrile and 50 mmol of pentaerythritol diphosphate dichloride to a flask. Heat to 85 °C, stir, and then dropwise add 100 mmol of triethylamine and 250 mL of an acetonitrile solution containing 50 mmol of bis(salicylaldehyde methyl Schiff base)diphenylsiloxane monomer. Carry out a polymerization reaction with condensation reflux for 8 h. After cooling, filter, and wash successively with acetonitrile and water. Add the product to 500 mL of methanol, add 400 mL of a 130 g / L sodium hydroxide aqueous solution, heat to 85 °C, and carry out hydrolysis for 8 h. After cooling, filter, wash with water, and dry to obtain the phosphorus-silicon flame retardant.

[0025] (3) Add 1000 g of methyl vinyl silicone rubber, 150 g of phosphorus-silicon flame retardant, and 30 g of basic magnesium sulfate crystals to an open mill for mixing. Then add 200 g of silica, continue mixing, and finally add 10 g of bis(2,5-dimethyl-2,5-di(t-butylperoxy)hexane) vulcanizing agent. Vulcanize at 170 °C for 30 min in a flat vulcanizer, cool, and discharge to obtain the skin-friendly matte anti-slip flexible silicone rubber.

[0026] Example 2:

[0027] (1) Add 400 mL of ethanol, 40 mmol of bis(4-aminophenoxy)dimethylsilane, and 84 mmol of methyl 5-formylsalicylate to a flask. Dropwise add 5 mL of glacial acetic acid, heat to 75 °C, and carry out a condensation reflux reaction for 8 h. After cooling, filter, wash with water, and recrystallize the product from acetonitrile to obtain the bis(salicylaldehyde methyl Schiff base)diphenylsiloxane monomer.

[0028] (2) Add 250 mL of acetonitrile and 50 mmol of pentaerythritol diphosphate dichloride to a flask. Heat to 80 °C, stir, and then dropwise add 90 mmol of triethylamine and 250 mL of an acetonitrile solution containing 55 mmol of bis(salicylaldehyde methyl Schiff base)diphenylsiloxane monomer. Carry out a polymerization reaction with condensation reflux for 12 h. After cooling, filter, and wash successively with acetonitrile and water. Add the product to 500 mL of methanol, add 500 mL of a 120 g / L sodium hydroxide aqueous solution, heat to 80 °C, and carry out hydrolysis for 8 h. After cooling, filter, wash with water, and dry to obtain the phosphorus-silicon flame retardant.

[0029] (3) Add 1000 g of methyl vinyl silicone rubber, 200 g of phosphorus-silicon flame retardant, and 50 g of basic magnesium sulfate crystal into an open mill for mixing. Then add 150 g of white carbon black and continue mixing. Finally, add 13 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent. Cure at 175 °C for 20 min in a flat vulcanizer, cool and discharge to obtain skin-friendly matte non-slip flexible silicone rubber.

[0030] Example 3:

[0031] (1) Add 250 mL of acetonitrile and 50 mmol of pentaerythritol diphosphate dichloride into a flask, heat to 80 °C, stir and then dropwise add 110 mmol of triethylamine and 250 mL of an acetonitrile solution containing 50 mmol of bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer (prepared in the same way as in Example 1). Carry out a polymerization reaction under reflux condensation for 12 h, cool and then filter, wash successively with acetonitrile and water. Add the product into 400 mL of methanol, add 400 mL of 140 g / L sodium hydroxide aqueous solution, heat to 85 °C, carry out hydrolysis for 8 h, cool and then filter, wash with water, and dry to obtain the phosphorus-silicon flame retardant.

[0032] (2) Add 1000 g of methyl vinyl silicone rubber, 250 g of phosphorus-silicon flame retardant, and 70 g of basic magnesium sulfate crystal into an open mill for mixing. Then add 150 g of white carbon black and continue mixing. Finally, add 8 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent. Cure at 180 °C for 20 min in a flat vulcanizer, cool and discharge to obtain skin-friendly matte non-slip flexible silicone rubber.

[0033] Example 4:

[0034] (1) Add 200 mL of acetonitrile and 50 mmol of pentaerythritol diphosphate dichloride into a flask, heat to 80 °C, stir and then dropwise add 100 mmol of triethylamine and 300 mL of an acetonitrile solution containing 55 mmol of bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer (prepared in the same way as in Example 1). Carry out a polymerization reaction under reflux condensation for 8 h, cool and then filter, wash successively with acetonitrile and water. Add the product into 500 mL of methanol, add 400 mL of 120 g / L sodium hydroxide aqueous solution, heat to 90 °C, carry out hydrolysis for 6 h, cool and then filter, wash with water, and dry to obtain the phosphorus-silicon flame retardant.

[0035] (2) Add 1000 g of methyl vinyl silicone rubber, 300 g of phosphorus-silicon flame retardant, and 100 g of basic magnesium sulfate crystal into an open mill for mixing. Then add 100 g of white carbon black and continue mixing. Finally, add 12 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent. Cure at 170 °C for 30 min in a flat vulcanizer, cool and discharge to obtain skin-friendly matte non-slip flexible silicone rubber.

[0036] Comparative Example 1:

[0037] (1) Add 1000 g of methyl vinyl silicone rubber and 200 g of silica to an open mill for mixing. Then add 10 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent. In a flat vulcanizer, cure at 170 °C for 30 min, cool and discharge to obtain skin-friendly matte non-slip flexible silicone rubber.

[0038] Comparative Example 2:

[0039] (1) Add 1000 g of methyl vinyl silicone rubber and 150 g of phosphorus-silicon flame retardant (prepared in the same way as in Example 1) to an open mill for mixing. Then add 200 g of silica and continue mixing. Finally, add 10 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent. In a flat vulcanizer, cure at 170 °C for 30 min, cool and discharge to obtain skin-friendly matte non-slip flexible silicone rubber.

[0040] Comparative Example 3:

[0041] (1) Add 1000 g of methyl vinyl silicone rubber and 30 g of basic magnesium sulfate crystal to an open mill for mixing. Then add 200 g of silica and continue mixing. Finally, add 10 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent. In a flat vulcanizer, cure at 170 °C for 30 min, cool and discharge to obtain skin-friendly matte non-slip flexible silicone rubber.

[0042] Comparative Example 4:

[0043] (1) Add 200 mL of acetonitrile and 50 mmol of pentaerythritol diphosphate dichloride to a flask, heat to 85 °C, stir and then dropwise add 100 mmol of triethylamine and 250 mL of an acetonitrile solution containing 50 mmol of bis(salicylaldehyde methyl Schiff base) diphenylsiloxane monomer (prepared in the same way as in Example 1). Carry out a polymerization reaction under reflux condensation for 8 h, cool and then filter, wash successively with acetonitrile and water, and dry to obtain a phosphorus-silicon flame retardant.

[0044] (2) Add 1000 g of methyl vinyl silicone rubber, 150 g of phosphorus-silicon flame retardant, and 30 g of basic magnesium sulfate crystal to an open mill for mixing. Then add 200 g of silica and continue mixing. Finally, add 10 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent. In a flat vulcanizer, cure at 170 °C for 30 min, cool and discharge to obtain skin-friendly matte non-slip flexible silicone rubber.

[0045] Comparative Example 5:

[0046] (1) Add 200 mL of acetonitrile and 50 mmol of pentaerythritol diphosphate dichloride to a flask, heat to 85 °C, stir and then dropwise add 100 mmol of triethylamine and 250 mL of an acetonitrile solution containing 50 mmol of hydroquinone. Carry out a polymerization reaction under reflux condensation for 8 h, cool and then filter, wash successively with acetonitrile and water, and dry to obtain a phosphorus-containing flame retardant.

[0047] (2) 1000 g of methyl vinyl silicone rubber, 150 g of phosphorus-containing flame retardant, and 30 g of basic magnesium sulfate crystal were added to an open mill for mixing. Then, 200 g of white carbon black was added and mixing continued. Finally, 10 g of bis(2,5-dimethyl-2,5-di(tert-butylperoxy)hexane) vulcanizing agent was added. It was vulcanized at 170 °C for 30 min in a flat vulcanizer, cooled, and discharged to obtain skin-friendly matte anti-slip flexible silicone rubber.

[0048] An optical contact lens tester was used to measure the water contact angle on the surface of the silicone rubber by the static contact angle measurement method.

[0049] The tensile properties of the silicone rubber were tested according to the standard of GB / T 528-2008.

[0050] The flame retardant properties of the silicone rubber were tested according to the standard of GB / T 10707-2008.

[0051] Table 1

[0052]

[0053] As can be seen from Table 1, the silicone rubber material of Comparative Example 1 has a large water contact angle, poor surface hydrophilicity, small tensile strength and elongation at break, poor mechanical properties, low limiting oxygen index, no rating for vertical burning, and poor flame retardancy.

[0054] In Comparative Example 2, a phosphorus-silicon flame retardant was added. It contains siloxane structural units similar to those of methyl vinyl silicone rubber, so that the flame retardant has good compatibility with the silicone rubber. When added to the silicone rubber matrix, it has little effect on the mechanical properties of the silicone rubber material and still has good tensile strength and elongation at break. Moreover, the phosphorus-silicon flame retardant contains a large number of hydrophilic sodium carboxylate groups, which can increase the surface water contact angle of the silicone rubber material, improve the surface hydrophilic and skin-friendly properties of the silicone rubber material. And the phosphorus-silicon flame retardant contains spirocyclic phosphate ester and siloxane structures, forming a phosphorus-silicon flame retardant system, improving the flame retardant properties of the silicone rubber material, increasing the limiting oxygen index, and the vertical burning rating reaching V-1 grade.

[0055] In Comparative Example 3, basic magnesium sulfate crystal was added. Its compatibility with methyl vinyl silicone rubber is poor and it is difficult to be evenly dispersed in the silicone rubber material matrix, so the reinforcing effect is not obvious and it cannot enhance the tensile strength and elongation at break of the silicone rubber material well.

[0056] In Examples 1-4, a phosphorus-silicon flame retardant and basic magnesium sulfate crystals were added. During the mixing process, the carboxylate groups contained in the phosphorus-silicon flame retardant could interact with the surface of the basic magnesium sulfate crystals, causing the phosphorus-silicon flame retardant to coat the surface of the basic magnesium sulfate crystals. Since the phosphorus-silicon flame retardant had good compatibility with methyl vinyl silicone rubber, the basic magnesium sulfate crystals could be evenly dispersed in the silicone material matrix, enabling the basic magnesium sulfate crystals to play a good reinforcing role and significantly improving the tensile strength and elongation at break of the silicone material. At the same time, the phosphorus-silicon flame retardant reduced the surface water contact angle of the silicone material and played a synergistic flame retardant role with the basic magnesium sulfate crystals, improving the limiting oxygen index and vertical burning grade of the silicone material, and showing better hydrophilic and skin-friendly properties and flame retardant properties.

[0057] In Comparative Example 4, the ester group of the phosphorus-silicon flame retardant was not hydrolyzed with sodium hydroxide and did not contain carboxylate groups, so it could not improve the hydrophilicity of the silicone material and could not interact with the surface of the basic magnesium sulfate crystals, making it difficult to effectively coat the surface of the basic magnesium sulfate crystals, resulting in poor dispersion of the basic magnesium sulfate crystals in the silicone material, poor reinforcing effect, and low tensile strength and elongation at break.

[0058] In Comparative Example 5, a phosphorus-containing flame retardant obtained by polymerizing pentaerythritol diphosphate dichloride and hydroquinone did not contain a siloxane structural unit and had poor compatibility with methyl vinyl silicone rubber, which had a great impact on the mechanical properties of the silicone material, and the tensile strength and elongation at break were significantly reduced.

Claims

1. A preparation method of skin-friendly matte anti-slip flexible silicone, characterized in that, The preparation method is as follows: Step S1: Add acetonitrile and pentaerythritol diphosphate dichloride into a flask, heat to the reaction temperature, stir and then dropwise add triethylamine and an acetonitrile solution containing bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer, carry out a polymerization reaction, filter after cooling, wash, add the product to methanol, add an aqueous sodium hydroxide solution, carry out hydrolysis, filter after cooling, wash, and dry to obtain a phosphorus-silicon flame retardant; Step S2: Add methyl vinyl silicone rubber, the phosphorus-silicon flame retardant prepared in Step S1, and basic magnesium sulfate crystals into an open mill for mixing, then add silica, continue mixing, and finally add bis(2,5-dimethyl-2,5-di(t-butylperoxy)hexane) vulcanizing agent, carry out vulcanization in a flat vulcanizer, cool and discharge to obtain a skin-friendly matte non-slip flexible silicone rubber; The preparation method of the bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer is as follows: Add ethanol, bis(4-aminophenoxy)dimethylsilane, and methyl 5-formylsalicylate into a flask, dropwise add glacial acetic acid, heat to 75 - 80 °C, react for 5 - 8 h, filter after cooling, wash with water, and recrystallize the product in acetonitrile to obtain the bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer; The molar ratio of the bis(4-aminophenoxy)dimethylsilane to methyl 5-formylsalicylate is 1:(2 - 2.1).

2. The preparation method of the skin-friendly matte non-slip flexible silicone according to claim 1, wherein In Step S1, the reaction temperature is 80 - 85 °C, and the polymerization reaction time is 8 - 12 h; the hydrolysis reaction temperature is 80 - 90 °C, and the time is 6 - 8 h.

3. The preparation method of the skin-friendly matte anti-slip flexible silicone according to claim 1, wherein In Step S1, the mass concentration of the aqueous sodium hydroxide solution is 120 - 140 g / L.

4. The preparation method of the skin-friendly matte non-slip flexible silicone according to claim 1, characterized in that, In Step S1, the molar ratio of pentaerythritol diphosphate dichloride, triethylamine, and bis(salicylaldehyde methyl ester Schiff base) diphenylsiloxane monomer is 1:(1.8 - 2.2):(1 - 1.1).

5. The preparation method of the skin-friendly matte anti-slip flexible silicone according to claim 1, characterized in that In Step S2, the mass ratio of methyl vinyl silicone rubber, phosphorus-silicon flame retardant, basic magnesium sulfate crystals, silica, and bis(2,5-dimethyl-2,5-di(t-butylperoxy)hexane) vulcanizing agent is 100:(15 - 30):(3 - 10):(10 - 20):(0.8 - 1.3).

6. The preparation method of the skin-friendly matte non-slip flexible silica gel according to claim 1, characterized in that, In Step S2, the vulcanization temperature is 170 - 180 °C, and the time is 10 - 20 min.

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