Aqueous polyurethane coating, method of preparation and use thereof on a fabric

Abstract

The present application relates to the technical fields of water-based polyurethane coating, and discloses a water-based polyurethane coating, a preparation method and application of the coating to fabrics, wherein the coating is prepared by taking 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane as a core raw material, and sequentially performing alkenyl functional group epoxidation and epoxy ring-opening reaction to synthesize non-stearated silicone type self-crosslinking monomers or stearated silicone type self-crosslinking monomers; a prepolymer is prepared by reacting diisocyanate monomers with polytetrahydrofuran ether glycol, and a self-crosslinking type silicone modified water-based polyurethane is synthesized by performing chain extension reaction on the self-crosslinking monomers, a hydrophilic chain extender and 1,4-butanediol chain extender, and a water-based polyurethane coating is prepared after curing. The self-crosslinking type silicone modified water-based polyurethane of the present application is formulated into a coating agent together with a thickening agent and a wetting agent, and the fabric prepared by 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 silicone type self-crosslinking monomer as a chain extender for preparing a self-crosslinking type silicone modified water-based polyurethane emulsion, and uses the prepared self-crosslinking type silicone modified water-based polyurethane emulsion for coating finishing of fabrics, so that the water resistance and softness of the finished fabric are significantly improved.

[0005] To achieve the above purpose, the present application adopts the following technical scheme:

[0006] A water-based polyurethane coating is prepared by curing a self-crosslinking type silicone 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 silicone type self-crosslinking monomer or 10-20 parts by weight of stearate silicone type self-crosslinking monomer.

[0007] Preferably, the diisocyanate monomer is one of isophorone diisocyanate, toluene diisocyanate and hexamethylene diisocyanate.

[0008] Preferably, the Mn of the polytetrahydrofuran ether diol is 1000 or 2000.

[0009] Preferably, the hydrophilic chain extender is one of dimethylol propanoic acid and dimethylol butanoic acid.

[0010] Preferably, the thickness of the waterborne polyurethane coating is 0.3-0.5mm.

[0011] 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.

[0012] 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.

[0013] 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.

[0014] 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.

[0015] The application method of the self-crosslinking type organosilicon modified waterborne polyurethane emulsion is:

[0016] 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.

[0017] The present application has the following beneficial effects:

[0018] 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane is used as a core raw material, and then epoxy functional groups are oxidized and ring-opening reactions are performed in sequence to synthesize organosilicon type self-crosslinking monomers or stearate organosilicon type self-crosslinking monomers;

[0019] 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 is formulated into a waterborne polyurethane fabric coating agent together with a thickening agent and a wetting agent, and 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

[0020] Example One

[0021] The silicone type self-crosslinking monomer is synthesized by oxidizing the alkenyl functional group in 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane into an epoxy functional group under the action of hydrogen peroxide in the presence of glacial acetic acid, and then generating the silicone type self-crosslinking monomer by ring-opening reaction of the epoxy functional group under the catalytic action of concentrated sulfuric acid;

[0022] 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 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 5 drops of concentrated sulfuric acid is added, and the ring-opening reaction is carried out for 3 h at room temperature. The reaction liquid 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 obtain the silicone type self-crosslinking monomer, which is a non-stearate silicone type self-crosslinking monomer;

[0023] The chemical structural formula of the silicone type self-crosslinking monomer is as follows:

[0024] ;

[0025] The hydrogen nuclear magnetic resonance spectrum of the silicone type self-crosslinking monomer is as follows:

[0026] 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).

[0027] Example Two

[0028] Synthesis of stearic acid-modified silicone type self-crosslinking monomer: 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 stearic acid-modified silicone type self-crosslinking monomer;

[0029] The experimental steps of the stearic acid-modified 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 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, then 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;

[0030] The chemical structural formula of the stearic acid-modified silicone type self-crosslinking monomer is as follows:

[0031] ;

[0032] The hydrogen nuclear magnetic resonance spectrum of the stearic acid-modified silicone type self-crosslinking monomer is as follows:

[0033] 1 H NMR(DMSO-d6, 400MHz) 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).

[0034] Example Three:

[0035] The raw material formula of the self-crosslinking type silicone-modified waterborne polyurethane emulsion I is as follows:

[0036] 40 parts by weight of polytetrahydrofuran ether diol (Mn=2000, CAS number: 25190-06-1, Shandong Chengtai Chemical Co., Ltd.);

[0037] 25.4 parts by weight of isophorone diisocyanate;

[0038] 4.6 parts of hydrophilic chain extender dimethylol propionic acid;

[0039] 4.6 parts by weight of non-stearic acid-modified silicone type self-crosslinking monomer;

[0040] 0.9 parts by weight of chain extender 1,4-butanediol;

[0041] 3.5 parts by weight of triethylamine salifying agent;

[0042] 0.02 parts by weight of catalyst dibutyltin dimuconate;

[0043] 20 parts by weight of acetone;

[0044] 200 parts by weight of deionized water;

[0045] The preparation method of the self-crosslinking type silicone modified waterborne polyurethane emulsion I is as follows:

[0046] Under the protection of nitrogen, polytetrahydrofuran ether diol and isophorone diisocyanate are added into a four-necked flask, stirred uniformly, reacted at a temperature of 80℃ for 2h, then 2-hydroxymethyl propionic acid and catalyst dibutyltin dimuconate are added, the temperature is raised to 85℃, and the reaction is continued for 2h, then the temperature is lowered to 60℃, non-stearated silicone type self-crosslinking monomer, 1,4-butanediol and acetone are added, the temperature is maintained at 60℃, and the reaction is continued for 30min, then the temperature is lowered to room temperature, triethylamine salifying agent is added, neutralized for 15min, deionized water is added, and mechanically stirred and dispersed for 30min, then acetone is removed by reduced pressure distillation, and the self-crosslinking type silicone modified waterborne polyurethane emulsion I is prepared;

[0047] The self-crosslinking type silicone modified waterborne polyurethane emulsion II is prepared, and the difference between the self-crosslinking type silicone modified waterborne polyurethane emulsion II and the self-crosslinking type silicone modified waterborne polyurethane emulsion I is that 14.7 parts by weight of stearated silicone type self-crosslinking monomer is used to replace 4.6 parts by weight of non-stearated silicone type self-crosslinking monomer.

[0048] Example Four:

[0049] (1) The preparation method of the waterborne polyurethane coating I is as follows:

[0050] 100 parts by weight of the 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℃ for 5min, then the temperature is continuously raised to 120℃ for drying for 5min, the adhesive film is taken out and cooled, and the waterborne polyurethane coating I is prepared.

[0051] (2) The waterborne polyurethane coating II is prepared, and the difference between the waterborne polyurethane coating II and the waterborne polyurethane coating I is that the self-crosslinking type silicone modified waterborne polyurethane emulsion II is used to replace the self-crosslinking type silicone modified waterborne polyurethane emulsion I.

[0052] Performance test:

[0053] I. Mechanical property: the waterborne polyurethane coating was made into an elongated strip of 10 mm x 70 mm, then the thickness of each sample at the center position was measured by taking three test points with a screw micrometer, and then the average value was taken. After the sample was balanced for 24 h under constant temperature and humidity conditions (T = 20℃, RH = 70%), the breaking load value was measured on a universal material testing machine, the tensile speed was 250 mm / min, and the tensile strength of the waterborne polyurethane coating was calculated according to the following formula: tensile strength (MPa) = breaking load value (N) / thickness of the film (mm) x width of the film (mm);

[0054] The above test results are shown in Table 1 below;

[0055]

[0056] Example Five:

[0057] Taking the self-crosslinking type organosilicon modified waterborne polyurethane emulsion II as an example, the application experiment of the self-crosslinking type organosilicon modified waterborne polyurethane emulsion was carried out:

[0058] 100 parts by weight of the self-crosslinking type organosilicon 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) were uniformly mixed to prepare a waterborne polyurethane fabric coating agent. The coating agent was directly and uniformly coated on pure cotton cloth (density of 133*72 g / m²) by dry coating, and then the coated fabric was prepared by baking at 70℃ for 5 min and then baking at 120℃ for 5 min.

[0059] Performance test:

[0060] I. Hydrostatic pressure resistance: according to the standard GB / T 4744-2013 "Textiles - Test and evaluation of water resistance - Hydrostatic pressure method", the hydrostatic pressure resistance value of the coated fabric was tested, the test area was 100 cm 2 , and the pressure increasing rate was 600 mmH2O / min;

[0061] II. Softness: the coated fabric was cut into a sample of 25 mm x 200 mm, and the stiffness of the sample was tested by an electronic stiffness tester. The smaller the stiffness, the softer the hand feeling;

[0062] The above test results are shown in Table 2 below;

[0063]

[0064] Note: the difference between the comparative example and the self-crosslinking type organosilicon modified waterborne polyurethane emulsion II is that trimethylolpropane is used to replace the stearated organosilicon type self-crosslinking monomer, and the amount of substance of trimethylolpropane is controlled to be the same as that of the stearated organosilicon type self-crosslinking monomer;

[0065] From the experimental results in Table 2, it can be seen that:

[0066] The self-crosslinking type silicone modified waterborne polyurethane emulsion II is used for coating finishing of pure cotton cloth, and the prepared fabric has achieved significant technical effects in water resistance and softness.

Claims

1. A waterborne polyurethane coating, characterized in that, The waterborne polyurethane coating is prepared by curing a self-crosslinking silicone-modified waterborne polyurethane emulsion. The raw material formulation 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-stearicated silicone self-crosslinking monomer or 10-20 parts by weight of stearicated silicone self-crosslinking monomer. The chemical structural formula of the non-stearicated organosilicon self-crosslinking monomer is: ； The chemical structural formula of stearic acid-modified organosilicon self-crosslinking monomer is: 。 2. The waterborne polyurethane coating according to claim 1, characterized in that, The diisocyanate monomer is one of isophorone diisocyanate, toluene diisocyanate, and hexamethylene diisocyanate.

3. The waterborne polyurethane coating according to claim 2, characterized in that, The polytetrahydrofuran ether diol has an Mn of 1000 or 2000.

4. The waterborne polyurethane coating according to claim 3, characterized in that, The hydrophilic chain extender is one of dimethylolpropionic acid and dimethylolbutyric acid.

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

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

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

8. The method for preparing an aqueous polyurethane coating according to claim 6, characterized in that, The method for preparing the stearic acid-modified organosilicon self-crosslinking monomer is as follows: under the action of glacial acetic acid, hydrogen peroxide oxidizes the alkenyl functional group in 2,4,6-trivinyl-2,4,6-trimethylcyclotrisiloxane into an epoxy functional group. Then, the epoxy functional group undergoes an epoxy-carboxyl ring-opening reaction with stearic acid to generate a stearic acid-modified organosilicon self-crosslinking monomer.

9. The method for preparing an aqueous polyurethane coating according to claim 6, characterized in that, The curing conditions for the waterborne polyurethane coating are: curing at 65-75℃ for 4-6 minutes, followed by curing at 110-130℃ for 4-6 minutes.

10. The application of a waterborne polyurethane coating according to any one of claims 1-4, characterized in that, The application method of self-crosslinking silicone-modified waterborne polyurethane emulsion is as follows: A waterborne polyurethane fabric coating agent is prepared by combining a self-crosslinking silicone-modified waterborne polyurethane emulsion, a thickener, and a wetting agent. The coating agent is then uniformly applied to the fabric using a dry coating method. The fabric is first baked at 60-80℃ for 3-10 minutes, and then baked at 110-130℃ for 3-10 minutes.

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