A method for preparing an organosilicon polyurethane emulsion for leather.

Abstract

The present invention relates to the technical field of leather finishing agents, and discloses a preparation method of a silicone polyurethane emulsion for leather. The present invention reacts polyether alcohol modified polysiloxane, isocyanate compound, chain extender, etc., and then adds distilled water, defoamer, thickener, to obtain a silicone polyurethane emulsion for leather. The side chain of its silicone polyurethane contains a large amount of hydrophilic polyether segments, has the effect of aqueous self-emulsification, good dispersibility in water, no stratification after emulsion storage, no sedimentation, and excellent storage stability. The polyether long chain segment introduced in the side chain of the silicone polyurethane undergoes molecular chain entanglement to form physical crosslinking, and a stable hydrogen bond network is formed between the polyether segments, which is conducive to improving the mechanical dimensional stability of the silicone polyurethane film, showing higher tensile strength and elongation at break, and the color fastness to friction also reaches 4-5 levels, with good friction resistance and high color fastness.

Description

Technical Field

[0001] The invention relates to the technical field of leather finishing agents, in particular to a method for preparing an organosilicon polyurethane emulsion for leather. Background Art

[0002] As a leather auxiliary, leather finishing agent mainly plays the role of protecting and beautifying the leather surface, and is divided into solvent-based finishing agent, water-based finishing agent, etc. Among them, water-based finishing agent does not contain organic solvents, is green and environmentally friendly, and has little damage to leather. According to the film-forming substance, it can be divided into polyurethane finishing agent, silicone finishing agent, acrylic resin finishing agent, etc. Among them, silicone polyurethane finishing agent has the characteristics of good water resistance and excellent wear resistance, and is widely used. The patent with announcement number CN115894851B discloses a method for preparing silicone-modified water-based polyurethane for leather finishing. The silicone-modified water-based polyurethane for leather finishing is prepared with dihydroxy polyether modified siloxane, isophorone diisocyanate, dimethylol propionic acid, and polyester diol as raw materials. The prepared silicone-modified water-based polyurethane for leather finishing has the characteristics of stable emulsion, low film water absorption, and excellent mechanical properties. However, the waterborne polyurethane needs to be supplemented with dimethylol propionic acid as a waterborne chain extender, and the preparation method of the dihydroxy polyether-modified siloxane is relatively complicated. The dihydroxy polyether as a reaction raw material has a special structure and is not easy to obtain. Summary of the invention

[0003] The technical problem solved by the invention is to provide a water-based self-emulsifying organic silicon polyurethane emulsion for leather with good mechanical properties.

[0004] The technical solution of the present invention is: a method for preparing a silicone polyurethane emulsion for leather:

[0005] (1) Add N,N-dimethylformamide, acetylene alcohol-modified polysiloxane, polyethylene glycol monomethyl ether thioglycolate and benzoin dimethyl ether into a flask, irradiate under ultraviolet light for reaction, remove N,N-dimethylformamide by reduced pressure distillation, wash with methanol, and dry to obtain polyether alcohol-modified polysiloxane.

[0006] (2) Add polyether alcohol modified polysiloxane, isocyanate compound and dibutyltin dilaurate into a flask, introduce nitrogen, heat to 75-85°C, react for 2.5-3h, then add acetone, reduce the temperature to 40-50°C, add chain extender 1,4-butanediol, react for 30-40min, remove acetone by vacuum distillation, add distilled water, defoamer and thickener, stir and mix well to obtain silicone polyurethane emulsion for leather.

[0007] Preferably, the mass ratio of acetylenic alcohol-modified polysiloxane, polyethylene glycol monomethyl ether thioglycolate, and benzoin dimethyl ether in (1) is 100:(42-48):(1.3-1.8).

[0008] Preferably, in (1), the central wavelength of the ultraviolet lamp is 365 nm, the total power of the ultraviolet lamp is 40-100 W, and the irradiation reaction time is 40-60 min.

[0009] Preferably, in (2), the mass ratio of polyether alcohol modified polysiloxane, isocyanate compound, dibutyltin dilaurate, chain extender, defoamer and thickener is 100:(14.4-19.2):(0.2-0.3):(7.6-8.2)(0.3-0.8):(1.3-2).

[0010] Preferably, the isocyanate compound is isophorone diisocyanate or toluene-2,4-diisocyanate.

[0011] Preferably, the preparation method of alkynol-modified polysiloxane is as follows: add terminal hydrogen silicone oil to a flask, introduce nitrogen, drop 3-butyn-1-ol, raise the temperature to 100-115°C, drop chloroplatinic acid-isopropanol solution, control the mass ratio of terminal hydrogen silicone oil, 3-butyn-1-ol, and chloroplatinic acid to be 100: (7.4-8.2): (0.006-0.007), react for 2-3h, distill under reduced pressure, add the product to water, stir and stand for stratification, separate and remove the aqueous phase, and dry the oil phase to obtain alkynol-modified polysiloxane. The reaction formula is:

[0012]

[0013] Beneficial effects of the present invention: The polyether alcohol modified polysiloxane of the present invention contains a polyether molecular chain, and after the double-terminal hydroxyl groups thereof are polymerized with the isocyanate compound, the side chains of the generated silicone polyurethane contain a large number of hydrophilic polyether segments, have the effect of aqueous self-emulsification, good dispersibility in water, the emulsion does not stratify or settle after storage, and has excellent storage stability.

[0014] The polyether long chain segments introduced into the side chains of the organosilicon polyurethane of the present invention cause molecular chain entanglement to form physical crosslinking, and at the same time, a stable hydrogen bond network is formed between the polyether chain segments, which is beneficial to improving the mechanical dimensional stability of the organosilicon polyurethane film, showing higher tensile strength and elongation at break, and at the same time, the friction resistance color fastness also reaches level 4-5, with good friction resistance and high color fastness. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is the preparation reaction formula of polyether alcohol modified polysiloxane. DETAILED DESCRIPTION

[0016] In order to make the purpose, technical solutions and advantages of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0017] Polyethylene glycol monomethyl ether thioglycolate was prepared according to the method of the document "Synthesis and Performance Research of Highly Adaptable Multi-branched Polycarboxylic Acid Water Reducer" in the journal "Bulletin of the Silicate Society", Vol. 38, No. 4, April 2019.

[0018] Add 10mmol polyethylene glycol monomethyl ether 400, 15mmol thioglycolic acid, and 48mg p-toluenesulfonic acid to a flask, stir and heat to 110°C, introduce nitrogen with water, react for 7 hours, and remove low-boiling substances by vacuum distillation to obtain polyethylene glycol monomethyl ether thioglycolate. The structural formula is .

[0019] The following hydrogen-terminated silicone oil, with an average molecular weight of 2000, was purchased from Jiangxi Better Silicon New Materials Co., Ltd. The thickener model is TT-936, purchased from Jinan Zhengyin Chemical Co., Ltd.

[0020] Example 1

[0021] (1) Add 50 g of terminal hydrogen silicone oil into a flask, introduce nitrogen, add 3.7 g of 3-butyn-1-ol dropwise, raise the temperature to 115°C, add 3 mL of isopropanol solution containing 3 mg of chloroplatinic acid dropwise, react for 2 h, and distill under reduced pressure. Add the product to water, stir and let stand to separate the layers, separate and remove the aqueous phase, and dry the oil phase to obtain acetylene alcohol-modified polysiloxane.

[0022] (2) 300 mL of N,N-dimethylformamide, 50 g of acetylenic alcohol-modified polysiloxane, 22.8 g of polyethylene glycol monomethyl ether thioglycolate, and 0.76 g of benzoin dimethyl ether were added into a flask, and the mixture was irradiated under an ultraviolet lamp with a central wavelength of 365 nm and a total power of 100 W for 40 min. After the reaction, N,N-dimethylformamide was removed by vacuum distillation, and the mixture was washed with methanol and dried to obtain a polyether alcohol-modified polysiloxane.

[0023] (3) Add 100 g of polyether alcohol modified polysiloxane, 19.2 g of isophorone diisocyanate, and 0.2 g of dibutyltin dilaurate into a flask, introduce nitrogen, heat to 80 °C, react for 3 h, then add acetone, lower the temperature to 40 °C, add 7.6 g of chain extender 1,4-butanediol, react for 40 min, remove acetone by reduced pressure distillation, add 130 mL of distilled water, 0.5 g of defoamer BYK024, and 1.5 g of thickener TT-936 from Zhengyin Chemical, stir and mix well to obtain a silicone polyurethane emulsion for leather.

[0024] Example 2

[0025] (1) Add 50 g of hydrogen-terminated silicone oil to a flask, introduce nitrogen, add 4.1 g of 3-butyn-1-ol dropwise, raise the temperature to 100°C, add 3 mL of an isopropanol solution containing 3.5 mg of chloroplatinic acid dropwise, react for 3 h, and distill under reduced pressure. Add the product to water, stir, and allow to stand to separate. Separate and remove the aqueous phase, and dry the oil phase to obtain an acetylene alcohol-modified polysiloxane.

[0026] (2) 400 mL of N,N-dimethylformamide, 50 g of acetylene alcohol-modified polysiloxane, 21 g of polyethylene glycol monomethyl ether thioglycolate, and 0.9 g of benzoin dimethyl ether were added into a flask, and the mixture was irradiated under an ultraviolet lamp with a central wavelength of 365 nm and a total power of 80 W for 40 min. After the reaction, N,N-dimethylformamide was removed by vacuum distillation, and the mixture was washed with methanol and dried to obtain a polyether alcohol-modified polysiloxane.

[0027] (3) Add 100 g of polyether alcohol modified polysiloxane, 14.4 g of toluene-2,4-diisocyanate, and 0.3 g of dibutyltin dilaurate into a flask, introduce nitrogen, heat to 85 °C, react for 2.5 h, then add acetone, lower the temperature to 50 °C, add 8.2 g of chain extender 1,4-butanediol, react for 30 min, remove acetone by vacuum distillation, add 150 mL of distilled water, 0.8 g of defoamer BYK024, and 2 g of thickener TT-936 from Zhengyin Chemical, stir and mix to obtain a silicone polyurethane emulsion for leather.

[0028] Example 3

[0029] (1) Add 50 g of terminal hydrogen silicone oil into a flask, introduce nitrogen, add 3.7 g of 3-butyn-1-ol dropwise, raise the temperature to 110°C, add 3 mL of isopropanol solution containing 3.5 mg of chloroplatinic acid dropwise, react for 2 h, and distill under reduced pressure. Add the product to water, stir and let stand to separate the layers, separate and remove the aqueous phase, and dry the oil phase to obtain acetylene alcohol-modified polysiloxane.

[0030] (2) 300 mL of N,N-dimethylformamide, 50 g of acetylene alcohol-modified polysiloxane, 24 g of polyethylene glycol monomethyl ether thioglycolate, and 0.65 g of benzoin dimethyl ether were added into a flask, and the mixture was irradiated under an ultraviolet lamp with a central wavelength of 365 nm and a total power of 40 W for 60 min. After the reaction, N,N-dimethylformamide was removed by vacuum distillation, and the mixture was washed with methanol and dried to obtain a polyether alcohol-modified polysiloxane.

[0031] (3) Add 100 g of polyether alcohol modified polysiloxane, 18.7 g of isophorone diisocyanate, and 0.27 g of dibutyltin dilaurate into a flask, introduce nitrogen, heat to 75 °C, react for 3 h, then add acetone, lower the temperature to 40 °C, add 8 g of chain extender 1,4-butanediol, react for 40 min, remove acetone by reduced pressure distillation, add 130 mL of distilled water, 0.3 g of defoamer BYK024, and 1.3 g of thickener TT-936 from Zhengyin Chemical, stir and mix to obtain a silicone polyurethane emulsion for leather.

[0032] Comparative Example 1

[0033] (1) 100 g of acetylene alcohol-modified polysiloxane (prepared according to the method of Example 1), 19.2 g of isophorone diisocyanate, and 0.2 g of dibutyltin dilaurate were added to a flask, nitrogen was introduced, and the mixture was heated to 80° C. and reacted for 3 h. Then, acetone was added, the temperature was lowered to 40° C., 7.6 g of chain extender 1,4-butanediol was added, and the mixture was reacted for 40 min. The acetone was removed by vacuum distillation, and 130 mL of distilled water, 0.5 g of defoamer BYK024, and 1.5 g of thickener TT-936 from Zhengyin Chemical were added. The mixture was stirred and mixed to obtain a silicone polyurethane emulsion for leather.

[0034] Comparative Example 2

[0035] (1) 70 g of acetylene alcohol-modified polysiloxane (prepared according to the method of Example 1), 30 g of polyethylene glycol 2000, 19.2 g of isophorone diisocyanate, and 0.2 g of dibutyltin dilaurate were added to a flask, nitrogen was introduced, and the mixture was heated to 80° C. for reaction for 3 h. Then, acetone was added, the temperature was lowered to 40° C., 7.6 g of chain extender 1,4-butanediol was added, and the mixture was reacted for 40 min. The acetone was removed by vacuum distillation, and 130 mL of distilled water, 0.5 g of defoamer BYK024, and 1.5 g of thickener TT-936 from Zhengyin Chemical were added. The mixture was stirred and mixed to obtain a silicone polyurethane emulsion for leather.

[0036] Comparative Example 3

[0037] (1) 100 g of acetylene alcohol-modified polysiloxane (prepared according to the method of Example 1), 19.2 g of isophorone diisocyanate, and 0.2 g of dibutyltin dilaurate were added to a flask, nitrogen was introduced, and the mixture was heated to 80° C. and reacted for 3 h. Then, acetone was added, the temperature was lowered to 40° C., 7.54 g of 2,2-dihydroxymethylpropionic acid was added, and the mixture was reacted for 60 min. 2.25 g of chain extender 1,4-butanediol was added, and the mixture was reacted for 40 min. Triethylamine was added for neutralization, and the acetone was removed by distillation under reduced pressure. 130 mL of distilled water, 0.5 g of defoamer BYK024, and 1.5 g of thickener TT-936 of Zhengyin Chemical were added, and the mixture was stirred and mixed to obtain a silicone polyurethane emulsion for leather.

[0038] Place the silicone polyurethane emulsion at room temperature for 30-120 days to observe the stability of the emulsion.

[0039] Table 1 Stability of silicone polyurethane emulsion

[0040]

[0041] After testing, the silicone polyurethane emulsions prepared in Examples 1-3 did not stratify or settle after being placed for 30-150 days, and had excellent dispersibility and stability. This was mainly because the polyether alcohol-modified polysiloxane contained polyether molecular chains, and after the double-terminal hydroxyl groups were polymerized with the isocyanate compound, a large number of hydrophilic polyether segments were introduced into the side chains of the silicone polyurethane. The silicone polyurethane had an aqueous self-emulsifying effect, had good dispersibility in water, and did not stratify or settle after the emulsion was stored.

[0042] In Comparative Example 1, the acetylene alcohol-modified polysiloxane does not contain a polyether molecular chain, and the side chain of the prepared silicone polyurethane does not contain a large amount of hydrophilic polyether segments, resulting in poor hydrophilicity and water dispersibility of the silicone polyurethane, lack of self-emulsification, and stratification and sedimentation after storage of the emulsion.

[0043] Comparative Example 2: Polyethylene glycol replaces acetylene alcohol-modified polysiloxane. The main chain of the prepared silicone polyurethane contains a hydrophilic polyether segment, has poor aqueous self-emulsification, poor dispersibility in water, and the emulsion is stratified and has sediment after storage.

[0044] In Comparative Example 3, 2,2-dihydroxymethylpropionic acid is used as a water-based chain extender to replace part of 1,4-butanediol in the chain extension reaction to prepare a silicone polyurethane side chain containing hydrophilic carboxyl groups. When stored for 30-60 days, the emulsion has good dispersibility, no stratification, and no sediment. However, after 150 days of storage, the emulsion stratifies, has a small amount of sediment, and the storage stability deteriorates.

[0045] The emulsion was poured into a mold and dried at 70°C for 24 h to prepare a film sample, and the tensile properties were tested according to the method of national standard GB / T 8949-2008.

[0046] Add 8 g of carbon black slurry to 100 mL of silicone polyurethane emulsion, stir and mix, and test the color fastness to rubbing according to the method of national standard GB / T 8949-2008.

[0047] Table 2

[0048]

[0049] After testing, compared with comparative examples 1-3, after the silicone polyurethane emulsions of embodiments 1-3 are cured and dried, the prepared silicone polyurethane films have greater tensile strength and elongation at break. This is mainly because the long polyether chain segments introduced in the side chains undergo molecular chain entanglement to form physical crosslinks, and at the same time, a stable hydrogen bond network is formed between the polyether segments, which is beneficial to improving the mechanical dimensional stability of the silicone polyurethane film, showing higher tensile strength and elongation at break. At the same time, the color fastness to friction also reaches level 4-5, with good friction resistance and high color fastness.

Claims

1. A method for preparing a silicone polyurethane emulsion for leather, characterized in that: The preparation method is: (1) Adding N,N-dimethylformamide, acetylene alcohol modified polysiloxane, polyethylene glycol monomethyl ether thioglycolate and benzoin dimethyl ether into a flask, irradiating the flask under ultraviolet light for reaction, distilling under reduced pressure, washing with methanol and drying to obtain polyether alcohol modified polysiloxane; (2) Add polyether alcohol modified polysiloxane, isocyanate compound and dibutyltin dilaurate into a flask, introduce nitrogen, heat to 75-85°C, react for 2.5-3h, then add acetone, lower the temperature to 40-50°C, add chain extender, react for 30-40min, remove acetone by vacuum distillation, add distilled water, defoamer and thickener, stir and mix to obtain silicone polyurethane emulsion for leather; The chain extender is 1,4-butanediol.

2. The method for preparing the silicone polyurethane emulsion for leather according to claim 1, characterized in that: The mass ratio of acetylenic alcohol modified polysiloxane, polyethylene glycol monomethyl ether thioglycolate and benzoin dimethyl ether in (1) is 100: (42-48): (1.3-1.8).

3. The method for preparing the silicone polyurethane emulsion for leather according to claim 1, characterized in that: The central wavelength of the ultraviolet lamp in (1) is 365 nm, the total power of the ultraviolet lamp is 40-100 W, and the irradiation reaction time is 40-60 min.

4. The method for preparing the silicone polyurethane emulsion for leather according to claim 1, characterized in that: The mass ratio of the polyether alcohol modified polysiloxane, isocyanate compound, dibutyltin dilaurate, chain extender, defoamer and thickener in (2) is 100: (14.4-19.2): (0.2-0.3): (7.6-8.2): (0.3-0.8): (1.3-2).

5. The method for preparing the silicone polyurethane emulsion for leather according to claim 4, characterized in that: The isocyanate compound is isophorone diisocyanate or toluene-2,4-diisocyanate.

6. The method for preparing the silicone polyurethane emulsion for leather according to claim 1, characterized in that: The preparation method of the acetylene alcohol modified polysiloxane is as follows: add terminal hydrogen silicone oil into a flask, introduce nitrogen, drop 3-butyn-1-ol, raise the temperature to 100-115° C., drop chloroplatinic acid-isopropanol solution, react for 2-3 hours, perform reduced pressure distillation, add the product into water, stir and stand to separate, separate and remove the water phase, and dry the oil phase to obtain the acetylene alcohol modified polysiloxane.

7. The method for preparing the silicone polyurethane emulsion for leather according to claim 6, characterized in that: The mass ratio of the hydrogen-terminated silicone oil, 3-butyn-1-ol and chloroplatinic acid is 100: (7.4-8.2): (0.006-0.007).

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