Waterborne polyurethane coating, preparation method and application of waterborne polyurethane coating in fabric

Abstract

The invention relates to the technical field of waterborne polyurethane coatings, and discloses a waterborne polyurethane coating, a preparation method and application of the waterborne polyurethane coating to fabric, and the preparation method of the coating comprises the steps that 2, 4, 6-trivinyl-2, 4, 6-trimethylcyclotrisiloxane serves as a core raw material, alkenyl functional group epoxidation and epoxy ring-opening reaction are sequentially carried out, and the waterborne polyurethane coating is obtained. Synthesizing a non-stearic acid organic silicon type self-crosslinking monomer or a stearic acid organic silicon type self-crosslinking monomer; a diisocyanate monomer reacts with polytetrahydrofuran ether glycol to prepare a prepolymer, a hydrophilic chain extender, a 1, 4-butanediol chain extender and the self-crosslinking monomer are subjected to a chain extension reaction, self-crosslinking type organic silicon modified waterborne polyurethane is synthesized, and the waterborne polyurethane coating is prepared after curing. The self-crosslinking organic silicon modified waterborne polyurethane, a thickening agent and a wetting agent are prepared into a coating agent, and a fabric prepared by a dry coating process has good water resistance and softness.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of water-based polyurethane coating technology, in particular to a water-based polyurethane coating, a preparation method and application thereof to fabrics. BACKGROUND

[0002] Coating finishing is a surface finishing technology that coats a layer of high molecular compound on the surface of various fabrics to form a film, so that the front and back of the fabric can have different functions. Coating glue is a high molecular compound for coating finishing. At present, the coating glue mainly uses polyacrylate, solvent-based polyurethane and water-dispersible polyurethane. Water-based polyurethane uses water as a dispersion medium, can meet the environmental protection requirements of no volatile organic compound emission, and has the advantages of safety, non-toxicity and no pollution. However, compared with solvent-based polyurethane, water-based polyurethane generally has the disadvantages of poor water resistance, poor solvent resistance, low initial adhesion and discontinuous film formation.

[0003] Research has found that in the application of fabric coating, the water resistance of water-based polyurethane can be improved by adding a crosslinking agent (such as a water-based polyurethane curing agent or an aziridine type crosslinking agent). However, such crosslinking agents have the problems of short service life, high toxicity, poor storage performance, and need to be mixed with coating agents before use, which is complicated and inconvenient to use. SUMMARY

[0004] The present application uses a self-developed non-stearate or stearate organosilicon type self-crosslinking monomer as a chain extender for preparing a self-crosslinking organosilicon modified water-based polyurethane emulsion, and uses the prepared self-crosslinking organosilicon modified water-based polyurethane emulsion for coating finishing of fabrics, so that the water resistance and softness of the finished fabrics are significantly improved.

[0005] To achieve the above-mentioned purpose, the present application adopts the following technical solutions: A water-based polyurethane coating is prepared by curing a self-crosslinking organosilicon modified water-based polyurethane emulsion. The raw material formula of the emulsion is: 30-50 parts by weight of polytetrahydrofuran ether diol, 20-30 parts by weight of diisocyanate monomer, 3-5 parts by weight of hydrophilic chain extender, 0.5-1.5 parts by weight of 1,4-butanediol chain extender, and 3-8 parts by weight of non-stearate organosilicon type self-crosslinking monomer or 10-20 parts by weight of stearate organosilicon type self-crosslinking monomer.

[0006] Preferably, the diisocyanate monomer is one of isophorone diisocyanate, toluene diisocyanate and hexamethylene diisocyanate.

[0007] Preferably, the Mn of the polytetrahydrofuran ether diol is 1000 or 2000.

[0008] Preferably, the hydrophilic chain extender is one of dimethylol propionic acid and dimethylol butyric acid.

[0009] Preferably, the thickness of the waterborne polyurethane coating is 0.3-0.5mm.

[0010] A preparation method of a waterborne polyurethane coating: a prepolymer is prepared from diisocyanate monomers and polytetrahydrofuran ether diols, chain extension is performed by a hydrophilic chain extender, 1,4-butanediol or a non-stearate organosilicon type self-crosslinking monomer or a stearate organosilicon type self-crosslinking monomer, a self-crosslinking type organosilicon modified waterborne polyurethane emulsion is prepared, and the emulsion is cured to obtain the waterborne polyurethane coating.

[0011] Preferably, the preparation method of the non-stearate organosilicon type self-crosslinking monomer is: under the action of glacial acetic acid, the alkenyl functional groups in 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane are oxidized into epoxy functional groups by hydrogen peroxide, and then the epoxy functional groups undergo ring-opening reaction under the catalysis of concentrated sulfuric acid to generate the non-stearate organosilicon type self-crosslinking monomer.

[0012] Preferably, the preparation method of the stearate organosilicon type self-crosslinking monomer is: under the action of glacial acetic acid, the alkenyl functional groups in 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane are oxidized into epoxy functional groups by hydrogen peroxide, and then the epoxy functional groups undergo epoxy-carboxyl ring-opening reaction with stearic acid to generate the stearate organosilicon type self-crosslinking monomer.

[0013] Preferably, the curing conditions of the waterborne polyurethane coating are: curing at 65-75℃ for 4-6min, and then curing at 110-130℃ for 4-6min.

[0014] The application method of the self-crosslinking type organosilicon modified waterborne polyurethane emulsion is: The self-crosslinking type organosilicon modified waterborne polyurethane emulsion, a thickening agent and a wetting agent are prepared into a waterborne polyurethane fabric coating agent, the coating agent is uniformly coated on the fabric by dry coating, and then the fabric is baked at 60-80℃ for 3-10min and then baked at 110-130℃ for 3-10min.

[0015] The present application has the following beneficial effects: 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is used as a core raw material, and then the alkenyl functional groups are sequentially epoxidized and ring-opening reacted to synthesize organosilicon type self-crosslinking monomers or stearate organosilicon type self-crosslinking monomers; Isophorone diisocyanate IPDI is reacted with polytetrahydrofuran ether diol to prepare a prepolymer, and a self-crosslinking type silicone modified waterborne polyurethane emulsion is synthesized by using dimethylol propionic acid (DMPA), 1,4-butanediol BDO and the silicone type self-crosslinking monomer as a chain extender. The self-crosslinking type silicone modified waterborne polyurethane emulsion, a thickening agent and a wetting agent are formulated into a waterborne polyurethane fabric coating agent. The coating agent is uniformly coated on the fabric by using a dry coating method to obtain a fabric which has a significant improvement in water resistance and softness. DETAILED DESCRIPTION

[0016] Example One

[0017] The silicone type self-crosslinking monomer is synthesized by oxidizing the alkenyl functional groups in 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane into epoxy functional groups under the action of hydrogen peroxide in the presence of glacial acetic acid, and then performing ring-opening reaction of the epoxy functional groups under the catalytic action of concentrated sulfuric acid to obtain the silicone type self-crosslinking monomer. The experimental steps of the silicone type self-crosslinking monomer are as follows: 3.1 g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is dissolved in 30 mL of chloroform, 20 mL of glacial acetic acid is added under nitrogen protection, the temperature of the system is increased to 70°C under stirring, 80 mL of 30% mass fraction of hydrogen peroxide is added dropwise, and the system is refluxed and condensed for 6 h. Then 5 drops of concentrated sulfuric acid is added, and the ring-opening reaction is carried out at room temperature for 3 h. The reaction solution is washed with sodium carbonate solution and deionized water in sequence until the pH is neutral. The solvent is removed by rotary evaporation to obtain the silicone type self-crosslinking monomer, which is a non-stearated silicone type self-crosslinking monomer. The chemical structural formula of the silicone type self-crosslinking monomer is as follows: ; The hydrogen nuclear magnetic resonance spectrum of the silicone type self-crosslinking monomer is as follows: 1 H NMR (DMSO-d6, 400 MHz) δ: 0.05 (s, 9H), 3.02-3.05 (t, 3H), 3.16-3.22 (m, 3H), 3.32-3.33 (d, 3H), 3.68-3.78 (m, 6H).

[0018] Example Two The stearated silicone type self-crosslinking monomer is synthesized by oxidizing the alkenyl functional groups in 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane into epoxy functional groups under the action of hydrogen peroxide in the presence of glacial acetic acid, and then performing epoxy-carboxyl ring-opening reaction of the epoxy functional groups with stearic acid to obtain the stearated silicone type self-crosslinking monomer. The experimental procedure of the stearic acid-modified silicone type self-crosslinking monomer is as follows: 3.1 g of 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is dissolved in 30 mL of chloroform, 20 mL of glacial acetic acid is added under nitrogen protection, the system temperature is increased to 70°C under stirring, 80 mL of 30% mass fraction of hydrogen peroxide is added dropwise, and the condensation reflux is carried out for 6 h, then 8.4 g of stearic acid is added, and the ring-opening reaction is carried out at 80°C for 3 h, the reaction solution is washed with sodium carbonate solution and deionized water in sequence until the pH is neutral, and the solvent is removed by rotary evaporation to prepare the stearic acid-modified silicone type self-crosslinking monomer; The chemical structural formula of the stearic acid-modified silicone type self-crosslinking monomer is as follows: ; The hydrogen nuclear magnetic resonance spectrum of the stearic acid-modified silicone type self-crosslinking monomer is as follows: 1 H NMR (DMSO-d6, 400 MHz) δ: 0.04 (s, 9H), 0.88-0.90 (t, 9H), 1.27-1.34 (m, 84H), 1.56-1.63 (m, 6H), 2.30-2.34 (t, 6H), 3.53-3.59 (m, 3H), 3.65-3.67 (d, 3H), 4.14-4.20 (m, 6H).

[0019] Example Three: The raw material formula of the self-crosslinking type silicone-modified waterborne polyurethane emulsion I is as follows: 40 parts by weight of polytetrahydrofuran ether glycol (Mn=2000, CAS number: 25190-06-1, Shandong Chentai Chemical Co., Ltd.); 25.4 parts by weight of isophorone diisocyanate; 4.6 parts of hydrophilic chain extender dimethylol propionic acid; 4.6 parts by weight of non-stearic acid-modified silicone type self-crosslinking monomer; 0.9 parts by weight of chain extender 1,4-butanediol; 3.5 parts by weight of triethylamine salting agent; 0.02 parts by weight of catalyst dibutyltin dimethylsilicate; 20 parts by weight of acetone; 200 parts by weight of deionized water; The preparation method of the self-crosslinking type silicone-modified waterborne polyurethane emulsion I is as follows: Under nitrogen protection, polytetrahydrofuran ether glycol and isophorone diisocyanate are added into a four-necked flask, stirred uniformly, reacted at a temperature of 80°C for 2h, dimethylol propionic acid and catalyst dibutyl tin dimethylsilicate are added, the temperature is raised to 85°C, and the reaction is continued for 2h, then the temperature is lowered to 60°C, non-stearic acidified silicone type self-crosslinking monomer, 1,4-butanediol and acetone are added, the temperature is maintained at 60°C, and the reaction is continued for 30min, then the temperature is lowered to room temperature, triethylamine is added for salting, neutralized for 15min, deionized water is added, and mechanical stirring is continued for 30min, and acetone is removed by reduced pressure distillation to prepare self-crosslinking type silicone modified waterborne polyurethane emulsion I; Self-crosslinking type silicone modified waterborne polyurethane emulsion II is prepared, which is only different from self-crosslinking type silicone modified waterborne polyurethane emulsion I in that 14.7 parts by weight of stearic acidified silicone type self-crosslinking monomer is used to replace 4.6 parts by weight of non-stearic acidified silicone type self-crosslinking monomer.

[0020] Example Four:

[0021] (1) The preparation method of waterborne polyurethane coating I is as follows: 100 parts by weight of self-crosslinking type silicone modified waterborne polyurethane emulsion I is uniformly scraped into a polytetrafluoroethylene plate, the film thickness is controlled to be 0.4mm, it is first dried at 70°C for 5min, then the temperature is continuously raised to 120°C for drying for 5min, the adhesive film is taken out and cooled to prepare waterborne polyurethane coating I.

[0022] (2) Waterborne polyurethane coating II is prepared, which is only different from waterborne polyurethane coating I in that self-crosslinking type silicone modified waterborne polyurethane emulsion II is used to replace self-crosslinking type silicone modified waterborne polyurethane emulsion I.

[0023] Performance test:

[0024] I. Mechanical property: the waterborne polyurethane coating is made into an elongated strip with a size of 10mm*70mm, then three test points are taken at the center of each sample to measure the thickness, and then the average value is taken, the sample is balanced for 24h under constant temperature and humidity conditions (T=20°C, RH=70%), then the breaking load value is measured on a universal material testing machine, the tensile speed is 250mm / min, and the tensile strength of the waterborne polyurethane coating is calculated according to the following formula: tensile strength (MPa)=breaking load value (N) / thickness of the film (mm) *width of the film (mm); The test results are shown in Table 1 below;

[0025] Example Five: Take the self-crosslinking type silicone modified waterborne polyurethane emulsion II as an example, the application experiment of the self-crosslinking type silicone modified waterborne polyurethane emulsion is carried out: 100 parts by weight of the self-crosslinking type silicone modified waterborne polyurethane emulsion II, 5 parts by weight of the thickening agent hydroxyethyl cellulose and 0.2 parts by weight of the wetting agent (model LUCRAMUL WT 100) are uniformly mixed to prepare a waterborne polyurethane fabric coating agent. The coating agent is directly and uniformly coated on pure cotton cloth (density of 133*72 g / m²) by dry coating, and then baked at 70°C for 5 min and baked at 120°C for 5 min to prepare a coated fabric.

[0026] Performance test:

[0027] I. Hydrostatic pressure resistance: According to the GB / T 4744-2013 “Textiles - Determination of water resistance - Hydrostatic pressure method” standard, the hydrostatic pressure resistance value of the coated fabric is tested. The test area is 100 cm 2 , and the pressure increasing rate is 600 mmH2O / min; II. Softness: The coated fabric is cut into a 25 mm x 200 mm sample, and the stiffness of the sample is tested by an electronic stiffness tester. The smaller the stiffness, the softer the hand feeling. The above test results are shown in Table 2 below:

[0028] Note: The difference between the comparative example and the self-crosslinking type silicone modified waterborne polyurethane emulsion II is that trimethylolpropane is used to replace the stearated silicone type self-crosslinking monomer, and the amount of substance of trimethylolpropane is controlled to be the same as that of the stearated silicone type self-crosslinking monomer. From the experimental results in Table 2, it can be seen that: The use of the self-crosslinking type silicone modified waterborne polyurethane emulsion II for coating finishing of pure cotton cloth has achieved significant technical effects in water resistance and softness of the prepared fabric.

Claims

1. An aqueous polyurethane coating, characterized in that, The water-based polyurethane coating is prepared by curing a self-crosslinking organosilicon modified water-based polyurethane emulsion, and the raw material formula of the emulsion is: 30-50 parts by weight of polytetrahydrofuran ether diol, 20-30 parts by weight of diisocyanate monomer, 3-5 parts by weight of hydrophilic chain extender, 0.5-1.5 parts by weight of 1,4-butanediol chain extender and 3-8 parts by weight of non-stearate organosilicon type self-crosslinking monomer or 10-20 parts by weight of stearate organosilicon type self-crosslinking monomer; The chemical structural formula of the non-stearate organosilicon type self-crosslinking monomer is: ； The chemical structural formula of the stearate organosilicon type self-crosslinking monomer is: 。 2. The aqueous polyurethane coating of claim 1, wherein, The diisocyanate monomer is one of isophorone diisocyanate, toluene diisocyanate and hexamethylene diisocyanate.

3. The aqueous polyurethane coating of claim 2, wherein, The Mn of the polytetrahydrofuran ether diol is 1000 or 2000.

4. The aqueous polyurethane coating of claim 3, wherein, The hydrophilic chain extender is one of dimethylol propanoic acid and dimethylol butanoic acid.

5. A waterborne polyurethane coating according to any one of claims 1 to 4, characterized in that, The thickness of the water-based polyurethane coating is 0.3-0.5 mm.

6. A process for the preparation of a waterborne polyurethane coating according to any one of claims 1 to 4, characterized in that, The preparation method is: a prepolymer is prepared by taking diisocyanate monomer and polytetrahydrofuran ether diol as raw materials, chain extension reaction is carried out by using hydrophilic chain extender, 1,4-butanediol or non-stearate organosilicon type self-crosslinking monomer or stearate organosilicon type self-crosslinking monomer, a self-crosslinking organosilicon modified water-based polyurethane emulsion is prepared, and the emulsion is cured to obtain a water-based polyurethane coating.

7. The method for preparing an aqueous polyurethane coating according to claim 6, characterized in that, The preparation method of the non-stearate organosilicon type self-crosslinking monomer is: under the action of glacial acetic acid, the alkenyl functional group in 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is oxidized into an epoxy functional group by hydrogen peroxide, and then the epoxy functional group undergoes ring-opening reaction under the catalysis of concentrated sulfuric acid to generate the non-stearate organosilicon type self-crosslinking monomer.

8. The method for preparing an aqueous polyurethane coating according to claim 6, characterized in that, The preparation method of the stearate organosilicon type self-crosslinking monomer is: under the action of glacial acetic acid, the alkenyl functional group in 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is oxidized into an epoxy functional group by hydrogen peroxide, and then the epoxy functional group undergoes epoxy-carboxyl ring-opening reaction with stearic acid to generate the stearate organosilicon type self-crosslinking monomer.

9. The method for preparing an aqueous polyurethane coating according to claim 6, characterized in that, The curing conditions of the water-based polyurethane coating are: curing at 65-75℃ for 4-6 min, and then curing at 110-130℃ for 4-6 min.

10. Use of a waterborne polyurethane coating according to any one of claims 1 to 4, characterized in that, The application method of the self-crosslinking organosilicon modified water-based polyurethane emulsion is: The self-crosslinking organosilicon modified water-based polyurethane emulsion, thickening agent and wetting agent are prepared into a water-based polyurethane fabric coating agent, the coating agent is uniformly coated on the fabric by using dry coating method, and then the fabric is baked at 60-80℃ for 3-10 min and baked at 110-130℃ for 3-10 min.

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