A water-based dyeing process for lacquered leather

Abstract

This invention relates to a water-based dyeing process for lacquered leather using natural lacquer, belonging to the technical field of leather dyeing and improvement of traditional techniques. The technical problem this invention aims to solve is the poor adhesion of existing mineral pigments to leather surfaces and the tendency for patterns to peel off. The key technical points of this invention include: firstly, pre-treating the leather surface; then preparing a lacquer layer on the pre-treated leather surface, formed by drying and curing natural lacquer at 20-30℃ and 60-80% relative humidity; next, preparing a natural plant-based paint solution and a mineral pigment dispersion; then, dripping the pigment dispersion onto the paint solution surface to draw the pattern; and finally, water-based dyeing of the lacquered leather surface by contacting the paint solution for 5-30 seconds; and finally, completing the color fixation process by drying at 20-30℃ and heat-fixing for 24-72 seconds. This invention significantly improves pigment adhesion by forming stable chemical bonds through the coordination complexation reaction between the phenolic hydroxyl groups of urushiol in the lacquer layer and the metal ions in the mineral pigments, achieving a color fastness of grade 4 or higher for both wet and dry rubbing. This invention is applicable to high-end leather goods, furniture, artworks, and home decorations.

Description

[0001] manual Technical Field This invention relates to a water-based dyeing process for lacquered leather using natural lacquer, belonging to the technical field of leather dyeing and improvement of traditional processes. Background Technology Leather dyeing technology has made significant progress. Currently, water-based marbling is mainly used on substrates such as paper and fabrics; its application on leather suffers from poor adhesion and patterns easily detaching. Some existing technologies use chemical thickeners or sugar alcohol solutions to pre-treat the leather to improve dyeing results, but these have drawbacks such as poor environmental friendliness and a stiffer feel. Another technology involves applying a resin layer to the leather surface before inkjet dyeing, but the bonding between the resin layer and mineral pigments relies mainly on physical adsorption, resulting in limited adhesion and requiring sophisticated equipment. In existing technologies, leather surface treatments often use synthetic resins such as polyurethane and acrylic as base coats. These synthetic resins have low surface energy and few active groups, and their bonding with mineral pigments mainly relies on physical adsorption, resulting in insufficient color fastness. Natural lacquer, on the other hand, contains active phenolic hydroxyl groups, which can undergo coordination complexation reactions with metal ions in mineral pigments to form chemical bonds, possessing a natural advantage in reactivity. However, its application in water marbling processes has not yet been reported. Lacquerware is a traditional Chinese craft. Natural lacquer possesses excellent film-forming properties and chemical stability. Its urushiol structure contains active phenolic hydroxyl groups, which can act as coordinating groups to undergo complexation reactions with metal ions. Combining lacquerware with water-based dyeing technology holds promise for solving the problem of poor adhesion of mineral pigments to leather surfaces, while simultaneously endowing leather with a unique luster and texture. Summary of the Invention The purpose of this invention is to provide a water-based dyeing process for lacquered leather using natural lacquer, which solves the problems of poor adhesion of mineral pigments to the leather surface and easy pattern detachment in the prior art. To achieve the above objectives, the present invention provides the following technical solution: A water-based dyeing process for lacquered leather includes the following steps: (1) Leather surface pretreatment: Clean and polish the leather surface until smooth, and control the moisture content to 15-25%; (2) Preparation of lacquer layer: Apply natural lacquer to the surface of the pretreated leather and dry and cure it at a temperature of 20-30℃ and a relative humidity of 60-80% to form a lacquer layer with a thickness of 0.1-0.5mm; The natural lacquer is mainly composed of urushiol (40-70%), laccase (about 10%), gum (3.5-9%), and water. Among them, the urushiol molecule contains a catechol structure (two adjacent phenolic hydroxyl groups). These phenolic hydroxyl groups act as coordinating groups and can undergo coordination complexation reactions with metal ions in mineral pigments to form stable six-membered ring chelates, thereby achieving chemical bonding and fixation of the pigment.

[0002] (3) Preparation of painting solution: Dissolve natural plant gum (selected from one or more of guar gum, gum arabic, and sodium alginate) in water to prepare a painting solution with a mass concentration of 0.5-3%, and add 0.1-0.5% surfactant; (4) Pigment dispersion: Mineral pigment powder and dispersant are mixed and ground at a mass ratio of 100:(1-5), and dispersed in an organic solvent to prepare a pigment suspension; (5) Water marbling: Pour the paint liquid prepared in step (3) into a flat-bottomed container, drop the pigment suspension prepared in step (4) onto the surface of the paint liquid, draw a pattern with a paint needle, and then place the lacquered leather obtained in step (2) with the lacquered side facing down onto the surface of the paint liquid, let it stand for 3-10 seconds and then lift it up. (6) Color fixing treatment: Dry the dyed leather at 20-30℃ and then fix it for 24-72 hours. Furthermore, the natural lacquer is one of raw lacquer or refined lacquer.

[0003] Furthermore, the mineral pigment is selected from one or more of 100 kinds, including cinnabar, azurite, malachite, realgar, orpiment, and ochre.

[0004] Furthermore, the dispersant is one of polyethylene glycol, polyvinylpyrrolidone, or sodium dodecyl sulfate.

[0005] Furthermore, the contact time with the paint in step (5) is 5-30 seconds.

[0006] Furthermore, in step (6), the heat fixation temperature is 20-30℃ and the time is 24-72 hours. This invention also protects lacquered leather water-dyed products obtained by the above process. Beneficial effects

[0007] 1. This invention pre-forms a lacquer layer on the leather surface, utilizing the phenolic hydroxyl groups of urushiol in natural lacquer to undergo a coordination complexation reaction with metal ions in mineral pigments, forming stable chemical bonds, which significantly improves the adhesion of pigments and achieves a color fastness of grade 4 or higher for dry and wet rubbing.

[0008] 2. The lacquer layer itself has excellent gloss and water resistance, giving the leather a unique texture, while providing a flat, moderately hydrophobic base for water marbling, making it easy to form patterns.

[0009] 3. Using natural plant gums as a thickener for the paint avoids the environmental pollution caused by chemical thickeners and has good compatibility with natural lacquer and mineral pigments.

[0010] 4. This process can create complex patterns such as multi-color gradients and ink wash on a single piece of leather, resulting in high added value for the products. It is suitable for high-end leather goods, furniture, art, and home decoration. Attached Figure Description

[0011] Figure 1 This is a flowchart of the water-based dyeing process for lacquered leather according to the present invention; Figure 2 This is a schematic diagram of the cross-sectional structure of the lacquered leather water-dyed product obtained by the present invention; Figure 3 The image shows the test results of the rubbing color fastness of the product prepared in Example 1. Detailed Implementation Example

[0012] (1) Take cowhide, clean the surface and polish it with 800-grit sandpaper, and control the moisture content to 20%; (2) Preparation of lacquer layer: Take natural lacquer (raw lacquer) with a urushiol content ≥50% and laccase activity ≥800 units / g, and apply it evenly to the pretreated leather surface at a coating amount of 100 g / m². Dry and cure for 48 hours at a temperature of 25℃ and a relative humidity of 80% to form a lacquer layer with a thickness of about 0.2 mm; (3) Pigment dispersion: Take 100 g of cinnabar mineral pigment powder, add 2 g of polyethylene glycol dispersant, grind evenly and disperse in 300 mL of turpentine oil to make a pigment suspension; (4) Preparation of painting solution: Prepare 5 L of 1.5% sodium alginate aqueous solution and add 0.3% ox bile as a surfactant; (5) Water marbling: Pour the paint solution into a water tank (area 4 m²), use a dropper to take 20 mL of pigment suspension and evenly drip it onto the surface of the paint solution, use a paint needle to draw cloud patterns, and place the lacquered leather (area 0.5 m²) with the lacquered side down in the paint solution for 15 seconds and then lift it up; (6) Color fixation treatment: After drying at 30℃, fix for 48 hours.

[0013] The resulting leather surface has clear patterns and natural cloud-like shading. According to GB / T 3920-2008, the dry rubbing color fastness is grade 4-5 and the wet rubbing color fastness is grade 4. Example

[0014] (1) Take sheep leather, clean the surface and polish it with 1000-grit sandpaper to control the moisture content to 18%; (2) Apply natural lacquer (refined lacquer) and dry and cure it for 48 hours at 28℃ and RH75% to form a 0.15mm lacquer layer; (3) Prepare a 2% sodium alginate aqueous solution, add 0.2% Tween-80 as a surfactant, and stir evenly to make a painting solution; (4) Azurite mineral pigment and polyvinylpyrrolidone are mixed and ground in a ratio of 100:3 and dispersed in ethanol to prepare a pigment suspension; (5) Pour the paint liquid into the tray, add the pigment suspension, draw the mountain and sea pattern with the paint needle, and then lift the lacquered leather with the lacquered side down after 20 seconds of contact with the paint liquid. (6) After drying at 30℃, fix for 48 hours. Comparative Example 1 The difference from Example 1 is that no lacquer layer was used; water-based dyeing was performed directly on the pre-treated leather. Results: Uneven pigment adhesion, wet rubbing color fastness of only 2-3, and the pattern visibly peeled off after wiping. Comparative Example 2 The difference from Example 1 is that sodium carboxymethyl cellulose was used instead of sodium alginate in the paint solution. Results: Pigment dispersion was slightly worse, pattern edge sharpness decreased, and the leather felt harder.

Claims

1. A water-based dyeing process for lacquered leather, characterized in that, Includes the following steps: (1) Leather surface pretreatment; (2) A lacquer layer is prepared on the surface of the pretreated leather, the lacquer layer being formed by drying and curing natural lacquer; (3) Prepare a painting solution, wherein the painting solution contains natural plant gum and water; (4) Preparation of mineral pigment dispersion; (5) Add mineral pigment dispersion to the surface of the paint liquid to form a pattern, and then dye the lacquered surface of the lacquered leather by contacting the surface of the paint liquid. (6) Color fixing treatment.

2. The process according to claim 1, characterized in that, The lacquer layer is formed by drying and curing natural lacquer at a temperature of 20-30℃ and a relative humidity of 60-80%, with a thickness of 0.1-0.5mm.

3. The process according to claim 1, characterized in that, The natural plant gum is selected from one or more of guar gum, gum arabic, and sodium alginate, and its mass concentration in the paint solution is 0.5-3%.

4. The process according to claim 1, characterized in that, The mineral pigments are selected from one or more of cinnabar, azurite, malachite, realgar, orpiment, and ochre.

5. The process according to claim 1, characterized in that, The contact time in step (5) is 5-30 seconds.

6. The process according to claim 1, characterized in that, The color-fixing treatment in step (6) includes drying at 20-30℃ and heat fixing for 24-72 hours.

7. A lacquered leather water-dyed product obtained by the process described in any one of claims 1-6.

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