Preparation method of polyurethane acrylic resin finishing agent for improving fabric stiffness

Abstract

The invention relates to the technical field of finishing agents, and discloses a preparation method of a polyurethane acrylic resin finishing agent for improving fabric stiffness, polyether polyol, isophorone diisocyanate, a sodium hydroxysulfonate styrene monomer and the like are subjected to a reaction to obtain polyurethane acrylate. And then carrying out polymerization reaction with an acrylate monomer, a sodium hydroxysulfonate styrene monomer, azodiisobutyronitrile and the like to obtain the polyurethane acrylic resin finishing agent. The sodium hydroxysulfonate styrene monomer is simultaneously used as an end-capping reagent and a hard monomer, and after the prepared polyurethane acrylic resin finishing agent is used for finishing the cotton fabric, the stiffness of the cotton fabric is remarkably improved, and the bending deformation resistance of the cotton fabric is improved. Meanwhile, the finished cotton fabric still keeps relatively low water drop diffusion time and has very good hydrophilicity.

Description

Technical Field

[0001] The present invention relates to the technical field of finishing agents, and specifically to a preparation method of a polyurethane acrylate resin finishing agent for improving the stiffness of fabrics. Background Art

[0002] Stiffening agents are common fabric finishing agents that can improve the anti-bending deformation ability, heaviness, and stiff handfeel of fabrics, and are widely used in textiles such as cotton fabrics and polyester. Traditional stiffening agents include melamine resin, urea-formaldehyde resin, acrylic resin, etc. Polyurethane acrylate resin has excellent elasticity, softness, weather resistance, and mechanical strength, and is a fabric finishing agent with great development prospects.

[0003] By regulating the polymerization monomers, the prepared polyurethane acrylate resin finishing agent can improve the waterproof, oil-proof, wrinkle-resistant, antibacterial and other properties of fabrics. The invention patent with the publication number CN110607690B discloses a polyacrylate-polyurethane composite emulsion with anti-ultraviolet function and its preparation method and application. It mixes a water-soluble polyacrylate emulsion containing sodium lignosulfonate and a water-based polyurethane emulsion, and the obtained composite emulsion can improve the anti-ultraviolet and other properties of cotton fabrics, but the composite emulsion of this patent does not improve the stiffness of cotton fabrics. Summary of the Invention

[0004] Technical problem to be solved: Solve the problem that it is difficult for polyurethane finishing agents to effectively improve the stiffness and other properties of textiles such as cotton fabrics.

[0005] Technical solution: A preparation method of a polyurethane acrylate resin finishing agent for improving the stiffness of fabrics: (1) Add dry polyether polyol and isophorone diisocyanate to a reaction flask, introduce nitrogen, and carry out a prepolymerization reaction at 65 - 80°C for 2 - 3 h to generate an isocyanate-terminated polyurethane prepolymer; then add acetone, sodium hydroxystearate styrene monomer, and dibutyltin dilaurate, carry out a capping reaction for 40 - 60 min, and remove acetone by vacuum distillation to obtain polyurethane acrylate.

[0006] (2) Add deionized water, emulsifier, polyurethane acrylate, acrylate monomer, and sodium hydroxystearate styrene monomer to a reaction flask, shear and disperse, then introduce nitrogen, add azobisisobutyronitrile, carry out a polymerization reaction at 70 - 80°C for 6 - 8 h, add deionized water for dilution, and shear and disperse to obtain a polyurethane acrylate resin finishing agent for improving the stiffness of fabrics.

[0007] Preferably, in step (1), the molar ratio of polyether polyol, isophorone diisocyanate, sodium hydroxystearate styrene monomer, and dibutyltin dilaurate is 1:(2.6 - 2.8):(1.3 - 1.4):(0.014 - 0.018).

[0008] Preferably, the polyether polyol is polyethylene glycol or polypropylene glycol.

[0009] Preferably, in step (2), the mass ratio of polyurethane acrylate, emulsifier, acrylate monomer, sodium hydroxysulfonate styrene monomer, and azobisisobutyronitrile is 100: (7 - 10): (300 - 450): (80 - 140): (8 - 12).

[0010] Preferably, the acrylate monomer is any one or a combination of methyl acrylate, methyl methacrylate, butyl acrylate, and butyl methacrylate.

[0011] Preferably, the emulsifier is sodium dodecylbenzenesulfonate or sodium dodecyl sulfate.

[0012] Preferably, the preparation method of the sodium hydroxysulfonate styrene monomer is as follows: Add ethanol, deionized water, 3 - chloro - 2 - hydroxypropanesulfonic acid sodium with a molar ratio of (1 - 1.2):1, and sodium p - vinylbenzoate (CAS registration number: 77124 - 40 - 4) to the reaction flask, stir and react at 60 - 75 °C for 6 - 10 h. After vacuum distillation, add the product to deionized water, heat to volatilize, cool and crystallize to obtain the sodium hydroxysulfonate styrene monomer. The reaction formula is: .

[0013] The beneficial technical effects of the present invention: React the chlorine atom of 3 - chloro - 2 - hydroxypropanesulfonic acid sodium with the carboxylate group of sodium p - vinylbenzoate to obtain the sodium hydroxysulfonate styrene monomer, which contains a hydroxyl group and can be used as a capping agent to react with the terminal isocyanate of the polyurethane prepolymer, thereby introducing a sulfonate group and a polymerizable alkenyl group into the polyurethane molecular chain to obtain polyurethane acrylate.

[0014] The sodium hydroxysulfonate styrene monomer of the present invention can not only be used as a capping agent, but also contains a styrene structure and can be used as a hard monomer to replace conventional styrene, and polymerize with methyl methacrylate, butyl acrylate, etc. with polyurethane acrylate to obtain a polyurethane acrylate resin finishing agent. After finishing the cotton fabric, the stiffness of the cotton fabric is significantly improved, and the ability of the fabric to resist bending deformation is improved. And the polyurethane acrylate resin finishing agent contains a large number of hydroxyl groups and sulfonate groups, and has strong hydrogen bond and other interaction forces with the cotton fabric, so that the finishing agent adheres tightly and firmly to the fabric surface and is not easily eluted. After multiple washes, the cotton fabric still maintains a high stiffness and the ability to resist bending deformation.

[0015] The molecular chain of the polyurethane acrylate resin finishing agent of the present invention contains a large number of hydrophilic hydroxyl groups and sulfonate groups, and the finished cotton fabric still maintains a low water droplet diffusion time and has good hydrophilicity. Detailed Embodiments

[0016] In order to make the objectives, technical solutions and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below through embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0017] Embodiment 1 (1) Add 80 mL of ethanol, 30 mL of deionized water, 60 mmol of sodium 3-chloro-2-hydroxypropanesulfonate, and 60 mmol of sodium p-vinylbenzoate to a reaction flask, stir and react at 75 °C for 6 h. After vacuum distillation, add the product to deionized water, heat to volatilize, and cool to crystallize to obtain the styrene monomer of sodium hydroxysulfonate.

[0018] (2) Add 20 mmol of dry polyethylene glycol 1000 and 54 mmol of isophorone diisocyanate to a reaction flask, introduce nitrogen, and carry out a prepolymerization reaction at 70 °C for 3 h to generate an isocyanate-terminated polyurethane prepolymer; then add 10 mL of acetone, 27 mmol of the styrene monomer of sodium hydroxysulfonate, and 0.33 mmol of dibutyltin dilaurate, and carry out a capping reaction for 40 min. Remove acetone by vacuum distillation to obtain polyurethane acrylate.

[0019] (3) Add 160 mL of deionized water, 0.8 g of emulsifier sodium dodecylbenzenesulfonate, 10 g of polyurethane acrylate, 25 g of methyl methacrylate, 13 g of butyl acrylate, and 8 g of the styrene monomer of sodium hydroxysulfonate to a reaction flask. After shearing and dispersing, introduce nitrogen, add 1 g of azobisisobutyronitrile, and carry out a polymerization reaction at 80 °C for 6 h. Dilute with 960 mL of deionized water, shear and disperse to obtain a polyurethane acrylate resin finishing agent for improving the stiffness of fabrics.

[0020] Embodiment 2 (1) Add 80 mL of ethanol, 40 mL of deionized water, 72 mmol of sodium 3-chloro-2-hydroxypropanesulfonate, and 60 mmol of sodium p-vinylbenzoate to a reaction flask, stir and react at 60 °C for 10 h. After vacuum distillation, add the product to deionized water, heat to volatilize, and cool to crystallize to obtain the styrene monomer of sodium hydroxysulfonate.

[0021] (2) Add 20 mmol of dry polypropylene glycol 1000 and 56 mmol of isophorone diisocyanate to a reaction flask, introduce nitrogen, and carry out a prepolymerization reaction at 75 °C for 3 h to generate an isocyanate-terminated polyurethane prepolymer; then add 15 mL of acetone, 28 mmol of the styrene monomer of sodium hydroxysulfonate, and 0.36 mmol of dibutyltin dilaurate, and carry out a capping reaction for 60 min. Remove acetone by vacuum distillation to obtain polyurethane acrylate.

[0022] (3) Add 150 mL of deionized water, 0.7 g of emulsifier sodium dodecyl sulfate, 10 g of polyurethane acrylate, 19 g of methyl acrylate, 11 g of butyl methacrylate, and 10 g of sodium hydroxysulfonate styrene monomer into the reaction flask. After shear dispersion, introduce nitrogen gas, add 0.8 g of azobisisobutyronitrile, and carry out a polymerization reaction at 75 °C for 8 h. Then add 520 mL of deionized water for dilution and shear dispersion to obtain a polyurethane acrylate finishing agent for improving the stiffness of fabrics.

[0023] Example 3 (1) Prepare sodium hydroxysulfonate styrene monomer according to the method of Example 1.

[0024] (2) Add 20 mmol of dry polyethylene glycol 1000 and 52 mmol of isophorone diisocyanate into the reaction flask. Introduce nitrogen gas and carry out a prepolymerization reaction at 80 °C for 2 h to generate a terminal isocyanate polyurethane prepolymer; then add 10 mL of acetone, 26 mmol of sodium hydroxysulfonate styrene monomer, and 0.28 mmol of dibutyltin dilaurate, and carry out a capping reaction for 60 min. Remove acetone by vacuum distillation to obtain polyurethane acrylate.

[0025] (3) Add 180 mL of deionized water, 1 g of emulsifier sodium dodecyl sulfate, 10 g of polyurethane acrylate, 28 g of methyl acrylate, 17 g of butyl acrylate, and 12 g of sodium hydroxysulfonate styrene monomer into the reaction flask. After shear dispersion, introduce nitrogen gas, add 1.1 g of azobisisobutyronitrile, and carry out a polymerization reaction at 75 °C for 8 h. Then add 490 mL of deionized water for dilution and shear dispersion to obtain a polyurethane acrylate finishing agent for improving the stiffness of fabrics.

[0026] Example 4 (1) Prepare sodium hydroxysulfonate styrene monomer according to the method of Example 1.

[0027] (2) Add 20 mmol of dry polyethylene glycol 1000 and 56 mmol of isophorone diisocyanate into the reaction flask. Introduce nitrogen gas and carry out a prepolymerization reaction at 65 °C for 3 h to generate a terminal isocyanate polyurethane prepolymer; then add 15 mL of acetone, 28 mmol of sodium hydroxysulfonate styrene monomer, and 0.36 mmol of dibutyltin dilaurate, and carry out a capping reaction for 60 min. Remove acetone by vacuum distillation to obtain polyurethane acrylate.

[0028] (3) Add 170 mL of deionized water, 1 g of emulsifier sodium dodecylbenzenesulfonate, 10 g of polyurethane acrylate, 26 g of methyl methacrylate, 14 g of butyl acrylate, and 14 g of sodium hydroxysulfonate styrene monomer into the reaction flask. After shear dispersion, introduce nitrogen gas, add 1.2 g of azobisisobutyronitrile, and carry out a polymerization reaction at 70 °C for 8 h. Then add 360 mL of deionized water for dilution and shear dispersion to obtain a polyurethane acrylate finishing agent for improving the stiffness of fabrics.

[0029] Comparative Example 1 (1) Add 20 mmol of dry polyethylene glycol 1000 and 54 mmol of isophorone diisocyanate into the reaction flask. Introduce nitrogen gas and carry out a prepolymerization reaction at 70 °C for 3 h to form a terminal isocyanate polyurethane prepolymer; then add 10 mL of acetone, 27 mmol of hydroxyethyl acrylate, and 0.33 mmol of dibutyltin dilaurate, and carry out a capping reaction for 40 min. Distill off acetone under reduced pressure to obtain polyurethane acrylate.

[0030] (2) Add 160 mL of deionized water, 0.8 g of emulsifier sodium dodecylbenzenesulfonate, 10 g of polyurethane acrylate, 25 g of methyl methacrylate, 13 g of butyl acrylate, and 8 g of styrene into the reaction flask. After shear dispersion, introduce nitrogen gas, add 1 g of azobisisobutyronitrile, and carry out a polymerization reaction at 80 °C for 6 h. Then add 960 mL of deionized water for dilution and shear dispersion to obtain a polyurethane acrylate finishing agent for improving the stiffness of fabrics.

[0031] Comparative Example 2 (1) Prepare sodium hydroxysulfonate styrene monomer according to the method of Example 1.

[0032] (2) Add 20 mmol of dry polyethylene glycol 1000 and 54 mmol of isophorone diisocyanate into the reaction flask. Introduce nitrogen gas and carry out a prepolymerization reaction at 70 °C for 3 h to form a terminal isocyanate polyurethane prepolymer; then add 10 mL of acetone, 27 mmol of sodium hydroxysulfonate styrene monomer, and 0.33 mmol of dibutyltin dilaurate, and carry out a capping reaction for 40 min. Distill off acetone under reduced pressure to obtain polyurethane acrylate.

[0033] (3) Add 160 mL of deionized water, 0.8 g of emulsifier sodium dodecylbenzenesulfonate, 10 g of polyurethane acrylate, 25 g of methyl methacrylate, 13 g of butyl acrylate, and 8 g of styrene into the reaction flask. After shear dispersion, introduce nitrogen gas, add 1 g of azobisisobutyronitrile, and carry out a polymerization reaction at 80 °C for 6 h. Then add 960 mL of deionized water for dilution and shear dispersion to obtain a polyurethane acrylate finishing agent for improving the stiffness of fabrics.

[0034] Comparative Example 3 (1) Prepare the sodium hydroxysulfonate styrene monomer according to the method of Example 1.

[0035] (2) Add 20 mmol of dry polyethylene glycol 1000 and 54 mmol of isophorone diisocyanate into the reaction flask, introduce nitrogen, and carry out a prepolymerization reaction at 70 °C for 3 h to generate an isocyanate-terminated polyurethane prepolymer; then add 10 mL of acetone, 27 mmol of hydroxyethyl acrylate, and 0.33 mmol of dibutyltin dilaurate, and carry out a capping reaction for 40 min. Distill off the acetone under reduced pressure to obtain a polyurethane acrylate.

[0036] (3) Add 160 mL of deionized water, 0.8 g of emulsifier sodium dodecylbenzenesulfonate, 10 g of polyurethane acrylate, 25 g of methyl methacrylate, 13 g of butyl acrylate, and 8 g of sodium hydroxysulfonate styrene monomer into the reaction flask. After shearing and dispersing, introduce nitrogen, add 1 g of azobisisobutyronitrile, and carry out a polymerization reaction at 80 °C for 6 h. Dilute with 960 mL of deionized water, shear and disperse to obtain a polyurethane acrylate resin finishing agent for improving the stiffness of fabrics.

[0037] Comparative Example 4 (1) Prepare the sodium hydroxysulfonate styrene monomer according to the method of Example 1.

[0038] (2) Add 20 mmol of dry polyethylene glycol 1000 and 54 mmol of isophorone diisocyanate into the reaction flask, introduce nitrogen, and carry out a prepolymerization reaction at 70 °C for 3 h to generate an isocyanate-terminated polyurethane prepolymer; then add 10 mL of acetone, 27 mmol of sodium hydroxysulfonate styrene monomer, and 0.33 mmol of dibutyltin dilaurate, and carry out a capping reaction for 40 min. Distill off the acetone under reduced pressure to obtain a polyurethane acrylate.

[0039] (3) Add 160 mL of deionized water, 0.8 g of emulsifier sodium dodecylbenzenesulfonate, 10 g of polyurethane acrylate, 25 g of methyl methacrylate, 13 g of butyl acrylate, and 8 g of sodium 4-styrenesulfonate into the reaction flask. After shearing and dispersing, introduce nitrogen, add 1 g of azobisisobutyronitrile, and carry out a polymerization reaction at 80 °C for 6 h. Dilute with 960 mL of deionized water, shear and disperse to obtain a polyurethane acrylate resin finishing agent for improving the stiffness of fabrics.

[0040] Performance test of the finishing agent: Add cotton fabric into the finishing agent, with a liquor ratio of 1:20, carry out two-bath two-roll padding finishing, and the wet pick-up rate is 90%. Then pre-dry the cotton fabric at 80 °C for 4 min and cure it at 160 °C for 3 min. Wash it with water and dry it in the air to obtain the finished cotton fabric.

[0041] Use the cotton fabric without being treated with the finishing agent as the blank control sample.

[0042] Cut the cotton fabric into specimens of 20 cm × 2.5 cm, and test the stiffness A using a stiffness tester. Each group of specimens is tested 3 times, and the average value is taken.

[0043] Wash the cotton fabric 30 times according to the method of GB / T 8629-2017, and then test the stiffness A 1 . And calculate the stiffness retention rate. The stiffness retention rate = (A 1 / A) × 100%.

[0044] Table 1 Stiffness Performance Test

[0045] After testing, compared with the blank control sample of cotton fabric, in Examples 1-4, the polyurethane acrylate resin finishing agent was used to finish the cotton fabric. The stiffness of the cotton fabric reached 75.8-121.5 mm, showing good resistance to bending deformation. And after multiple washings, it still maintained a high stiffness with a low decline rate. This is mainly because sodium hydroxystearate styrene monomer was used as the capping agent and polymerization monomer, introducing a large number of hydroxyl and sulfonate groups into the molecular chain of the polyurethane acrylate resin. There are strong hydrogen bond and other interaction forces between the resin and the cotton fabric, making the finishing agent firmly adhere to the surface of the cotton fabric and not easy to be eluted, thus having a high stiffness retention rate.

[0046] Compared with Example 1, after the polyurethane acrylate resin finishing agent in Comparative Examples 1-4 was used to finish the cotton fabric, the stiffness of the cotton fabric also increased significantly. However, after multiple washings, the stiffness decreased to varying degrees with a low retention rate. In Comparative Example 1, mainly because 2-hydroxyethyl acrylate was used as the capping agent and styrene was used as the polymerization monomer, the prepared finishing agent did not contain hydroxyl and sulfonate groups, and the interaction force with the cotton fabric was relatively low, resulting in the finishing agent not firmly adhering to the fabric surface and being easily eluted, with a large decrease in stiffness. In Comparative Example 2, sodium hydroxystearate styrene monomer was used as the capping agent and styrene was used as the polymerization monomer. The prepared finishing agent had very few hydroxyl and sulfonate groups, and the interaction force between the finishing agent and the cotton fabric was relatively low, and the finishing agent was easily eluted, with a large decrease in stiffness. In Comparative Example 3, 2-hydroxyethyl acrylate (without sulfonate group) was used as the capping agent and sodium hydroxystearate styrene monomer was used as the polymerization monomer. The sulfonate group of the obtained polyurethane acrylate resin was slightly less than that in Example 1, resulting in a slightly lower stiffness retention rate than that in Example 1. In Comparative Example 4, 4-styrenesulfonic acid sodium (without hydroxyl) was used as the polymerization monomer, and the obtained polyurethane acrylate resin had very few hydroxyl groups, with a relatively low interaction force with the cotton fabric, and the finishing agent was easily eluted, with a large decrease in stiffness.

[0047] Test the hydrophilicity and water droplet diffusion time of cotton fabrics according to the method of AATCC 79-2010, test 5 times, and take the average value. The smaller the water droplet diffusion time, the better the hydrophilicity.

[0048] Table 2 Hydrophilicity Performance Test

[0049] After testing, in Examples 1-4, the cotton fabrics were finished with a polyurethane acrylate resin finishing agent. The molecular chain of the finishing agent contains a large number of hydrophilic hydroxyl groups and sodium sulfonate groups, so that the cotton fabrics still maintain a low water droplet diffusion time and have good hydrophilicity.

[0050] Compared with Example 1, the polyurethane acrylate resin finishing agent of Comparative Example 1 does not contain hydrophilic hydroxyl groups and sodium sulfonate groups, and the hydrophilicity of the cotton fabric after finishing becomes poor, and the water droplet diffusion time is very long. The polyurethane acrylate resin finishing agent of Comparative Example 2 has very few hydroxyl groups and sodium sulfonate groups, and the hydrophilicity of the cotton fabric after finishing becomes poor, and the water droplet diffusion time is very long. The polyurethane acrylate of Comparative Example 4 has very few hydroxyl groups, and its hydrophilicity is lower than that of Example 1, resulting in a relatively large water droplet diffusion time and poor hydrophilicity.

[0051] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a polyurethane acrylic resin finishing agent for improving fabric stiffness, characterized in that: The preparation method comprises the following steps: (1) Adding dry polyether polyol and isophorone diisocyanate into a reaction bottle, introducing nitrogen to carry out a prepolymerization reaction, then adding acetone, sodium hydroxysulfonate styrene monomer, and dibutyltin dilaurate to carry out a capping reaction, and removing the acetone by vacuum distillation to obtain polyurethane acrylate; (2) adding deionized water, emulsifier, polyurethane acrylate, acrylate monomer, sodium hydroxysulfonate styrene monomer into a reaction bottle, introducing nitrogen after shearing and dispersion, adding azobisisobutyronitrile, carrying out polymerization reaction, adding deionized water to dilute, shearing and dispersion, and obtaining a polyurethane acrylic resin finishing agent for improving the stiffness of the fabric; The structural formula of the sodium hydroxysulfonate styrene monomer is .

2. The method for preparing the polyurethane acrylic resin finishing agent for improving fabric stiffness according to claim 1, characterized in that: The molar ratio of the polyether polyol, isophorone diisocyanate, sodium hydroxysulfonate styrene monomer and dibutyltin dilaurate in the step (1) is 1:(2.6-2.8):(1.3-1.4):(0.014-0.018); the polyether polyol is polyethylene glycol or polypropylene glycol.

3. The method for preparing the polyurethane acrylic resin finishing agent for improving fabric stiffness according to claim 1, characterized in that: The temperature of the prepolymerization reaction in step (1) is 65-80°C, and the reaction time is 2-3h; the end-capping reaction time is 40-60min.

4. The method for preparing the polyurethane acrylic resin finishing agent for improving fabric stiffness according to claim 1, characterized in that: The mass ratio of polyurethane acrylate, emulsifier, acrylate monomer, sodium hydroxysulfonate styrene monomer and azobisisobutyronitrile in step (2) is 100: (7-10): (300-450): (80-140): (8-12).

5. The method for preparing the polyurethane acrylic resin finishing agent for improving fabric stiffness according to claim 1, characterized in that: The polymerization reaction temperature in step (2) is 70-80° C. and the reaction time is 6-8 hours.

6. The method for preparing the polyurethane acrylic resin finishing agent for improving fabric stiffness according to claim 4, characterized in that: The acrylic acid ester monomer is any one or a combination of methyl acrylate, methyl methacrylate, butyl acrylate and butyl methacrylate.

7. The method for preparing the polyurethane acrylic resin finishing agent for improving fabric stiffness according to claim 4, characterized in that: The emulsifier is sodium dodecylbenzene sulfonate or sodium dodecyl sulfate.

8. The method for preparing the polyurethane acrylic resin finishing agent for improving fabric stiffness according to claim 4, characterized in that: The preparation method of the sodium hydroxysulfonate styrene monomer comprises: adding ethanol, deionized water, sodium 3-chloro-2-hydroxypropanesulfonate and sodium p-vinylbenzoate into a reaction bottle, stirring and reacting at 60-75° C. for 6-10 hours, adding the product into deionized water after reduced pressure distillation, heating for volatilization, cooling for crystallization, and obtaining the sodium hydroxysulfonate styrene monomer.

9. The method for preparing the polyurethane acrylic resin finishing agent for improving fabric stiffness according to claim 8, characterized in that: The molar ratio of the sodium 3-chloro-2-hydroxypropanesulfonate to sodium p-vinylbenzoate is (1-1.2):1.

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