CN118650997A - A digital positioning gold printing process - Google Patents

Abstract

The invention discloses a digital positioning gold printing process, comprising the following steps: S1 pre-treating fabric with a hydrophilic paste containing reactive activity; S2 printing gold with a screen printing method; S3 curing; S4 digital printing; S5 post-processing; the gold printing slurry contains surface modified flaky gold and silver powder with a specific morphology, the surface modified flaky gold and silver powder has higher bonding strength and oxidation resistance, and the visual effect has higher glossiness and brightness.

Description

A digital positioning gold printing process

Technical Field

The invention belongs to the field of printing technology, and in particular relates to a digital positioning gold printing technology.

Background Art

Gold printing technology refers to the technology of printing metal powder on fabrics, which can enhance the gloss and metallic feel of fabrics. At present, the use of gold printing technology has become an important process for increasing the visual effects and grades of clothing fabrics, curtain fabrics, sofa fabrics and various high-end fabrics. The gold and silver powder used for gold printing is usually a metal particle powder of 10 to 80 microns, so the gold printing paste usually has a high viscosity, and gold can usually only be printed by screen printing, which greatly limits the flexibility of printing. If you want to get a colorful print, you need to overprint different colors, which is complicated to operate and difficult to align, resulting in unclear patterns and low fineness.

On the other hand, the gold printing process also faces the problems of low bonding strength of gold and silver powders, easy oxidation and uneven distribution.

In view of this, the present invention is proposed.

Summary of the invention

The invention provides a digital positioning gold printing process, which can obtain a printed polyester fabric which has clear patterns and is firmly adhered and combines digital printing with gold stamping.

The present invention can be implemented like this:

A digital positioning gold printing process comprises the following steps:

Step S1: pre-treating the fabric with a hydrophilic paste, and then drying to obtain the pre-treated fabric;

Step S2: printing the gold printing paste on the pre-treated fabric by screen printing to obtain the gold printing fabric;

Step S3: solidifying the gold-printed fabric to obtain solidified gold-printed fabric;

Step S4: digitally printing the cured printed fabric to obtain a composite printed fabric.

Step S5: post-processing the composite printed fabric to obtain a finished fabric;

The hydrophilic paste contains a water-soluble vinyl resin; in some embodiments of the present invention, the vinyl resin can be selected from at least one of vinyl-modified polyvinyl alcohol, vinyl-modified polyethylene glycol, and vinyl-modified sodium alginate. Preferably, the vinyl content of the vinyl resin is 0.1 to 0.4 mmol/g.

In some embodiments of the present invention, the hydrophilic paste comprises the following components in percentage by mass: 1% to 5% of vinyl resin, 0.1% to 2% of surfactant, 0% to 15% of alkali agent, and the balance is water.

The method for preparing the vinyl resin is as follows: a polymer and methacrylic chloride are dissolved in a solvent to form a solution, and then the methacrylic chloride solution is distributed and added to the polymer solution, and the vinyl resin is obtained by stirring the reaction; wherein the polymer is selected from one of polyvinyl alcohol, polyethylene glycol, and sodium alginate; the solvent is selected from one of tetrahydrofuran, chloroform, and dichloromethane; and the stirring reaction refers to reacting at 25 to 50° C. and a stirring speed of 200 to 600 rpm for 3 to 20 hours.

In some embodiments of the present invention, the surfactant is a nonionic surfactant selected from one of alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and alkyl alcohol amide.

In some embodiments of the present invention, the alkaline agent is selected from at least one of urea, sodium carbonate, sodium hydroxide and potassium hydroxide.

The pretreatment described in step S1 refers to applying the hydrophilic slurry to the surface of the fabric by dipping, padding, coating or spraying; in some embodiments of the present invention, the fabric has a liquid carrying rate of 60% to 90% after pretreatment; in some embodiments of the present invention, the drying temperature is 80 to 100°C.

Textiles need to be pretreated during digital printing. On the one hand, due to the low viscosity of digital printing ink, when digital printing ink is directly sprayed on textiles, the wicking effect will cause the ink to quickly diffuse and penetrate after contacting the fabric, affecting the printing quality; on the other hand, it provides conditions for the coloring of the colorant on the fiber. For example, alkali needs to be added to the pretreatment paste of cotton fiber to provide conditions for the reaction of active dyes with fibers. For example, the polyester surface has poor affinity for ink, and a layer of hydrophilic paste needs to be applied to improve the fabric's water retention of ink.

The hydrophilic slurry provided by the present invention is added with vinyl resin, which is a type of hydrophilic high molecular polymer containing vinyl. The vinyl resin is used as a paste to pre-treat the cloth, which can prevent the ink droplets from spreading and has a good anti-bleeding effect, and can be removed by simple water washing in the post-processing stage. The vinyl in the vinyl resin is cross-linked with the light-curing adhesive in the glitter paste during the ultraviolet light curing stage, and the hydrophilic paste, gold and silver powder, and adhesive form a sandwich-like structure, and the hydrophilic paste is cross-linked with the adhesive to tightly fix the gold and silver powder therein, greatly improving the adhesion strength of the gold and silver powder.

The screen printing method described in step S2 includes: first preparing a printing screen according to the gold printing pattern, then applying the gold printing slurry to the pre-treated fabric through the hollowing of the printing screen by scraping with a scraper, and drying it naturally.

In some embodiments of the present invention, the printing screen has a mesh size of 80 to 120.

In some embodiments of the present invention, the gold printing paste in step S2 comprises the following components in percentage by mass: 60% to 70% glitter paste, 15% to 25% surface modified flaky gold and silver powder, and the remainder is water; preferably, the viscosity (25°C) of the gold printing paste is 150,000 to 200,000 mPa·s.

In some embodiments of the present invention, the glitter paste comprises the following components in percentage by mass: 40% to 60% of an acrylic adhesive, 2% to 5% of a defoaming agent, 0.5% to 1.2% of a thickener, and the remainder is water; preferably, the viscosity (25° C.) of the glitter paste is 8000 to 10000 mPa·s.

The surface modified flaky gold and silver powder has the following characteristics:

Feature ①: The size of powder particles is 300-1000 mesh;

Feature ②: The powder particles are flake-shaped, with an average aspect ratio of 8 to 50;

Feature ③: Surface chemical modification with L-cysteine and/or glutathione;

The aspect ratio refers to the ratio of the longest diagonal length of the plane with the largest powder particle area to the length perpendicular to the plane, which can be calculated by tracking the target and collecting data using an optical microscope.

In some embodiments of the present invention, the gold and silver powder is at least one of brass powder, bronze powder and aluminum powder.

Surface chemical modification with L-cysteine and/or glutathione refers to: ultrasonically dispersing gold and silver powder in a modifier solution, adjusting the pH to 5-11, sealing and ultrasonically reacting for 3-12 hours, washing the solid with water after solid-liquid separation, and drying at 30-50°C to obtain surface modified flaky gold and silver powder; the modifier is L-cysteine or glutathione.

In some embodiments of the present invention, the solution solvent of the modifier is water and/or alcohol; in some embodiments of the present invention, the concentration of the modifier solution is 3-9 g/L; in some embodiments of the present invention, the solid-liquid feed ratio of gold and silver powder to the modifier solution is 1 g:100 mL.

L-cysteine and glutathione have antioxidant effects. Specifically, the amine and carboxyl groups in them are reducing, providing hydrogen to capture oxygen free radicals, thereby achieving antioxidant effects. At the same time, the sulfhydryl groups on L-cysteine and glutathione can form metal-sulfur bonds with metal elements to coat the surface of gold and silver powders. On the one hand, they play an antioxidant role and prevent the gold and silver powders from being oxidized and darkening their luster; on the other hand, a large number of hydroxyl and carboxyl groups increase the hydration radius of the particles, which can effectively inhibit the agglomeration of gold and silver powders.

The gold printing paste used in the present invention adopts gold and silver powder with specific morphology, and the gold and silver powder is flaky particles with an aspect ratio of 8 to 30; the flaky particles have a larger surface area than spherical particles under the same volume. On the one hand, the larger the surface area, the higher the light reflectivity of the particles, and the obtained printing is more shiny and has a better visual effect; on the other hand, the larger the surface area, the larger the contact area between the powder and the substrate and the adhesive, which improves the adhesion fastness on the cloth and is not easy to wash off; furthermore, the flaky particles have a larger repose angle, which is conducive to improving the viscosity of the gold printing paste and reducing the use of thickeners.

The present invention uses the aspect ratio to describe the flake degree of the gold and silver powders. The aspect ratio of the gold and silver powders affects the fastness of printing, visual effects, and viscosity of the gold printing paste. However, if the aspect ratio is too large, the gold and silver powders will be severely agglomerated, the viscosity of the gold printing paste will be too high, and it will be difficult to mix evenly. If the aspect ratio is too small, that is, the closer it is to a spherical shape, the lower the bonding fastness of the gold and silver powders.

Furthermore, since the flaky gold and silver powders have a large surface area, resulting in a large surface energy, the powders are easy to agglomerate, so the powders need to be surface modified to improve the dispersibility of the powders. The present invention uses L-cysteine and/or glutathione to modify the surface of the powders, so that the surface of the powders contains a large number of hydrophilic groups, increases the hydration degree of the particles, thereby inhibiting the agglomeration of the particles, and the obtained gold and silver powders have good dispersibility.

The curing in step S3 includes one of thermal curing or UV curing, which can be selected according to the type of initiator in the acrylate adhesive; in some embodiments of the present invention, the thermal curing is baking at 130-160°C for 1-2 minutes; in some embodiments of the present invention, the wavelength of the UV curing is 300-500nm, and the irradiation time is 30s-1min.

The digital printing described in step S4 adopts a digital printing machine with an image positioning device, and the specific steps include: placing the solidified gold-printed fabric on the sample table, using the information recording device to capture image information of the solidified gold-printed fabric, obtaining the position, shape and distribution parameters of the fabric and the gold-printed pattern, and inputting the parameters into the computer to form a gold-printed template; comparing the gold-printed template with the design template containing the gold-printed pattern and the digital printing pattern, and then introducing the digital printing pattern into the gold-printed template, so that the position of the digital printing pattern matches and coincides with the position of the gold-printed pattern, and then spraying the digital printing pattern onto the solidified gold-printed fabric through the digital printing machine, so as to obtain a composite printed fabric.

The digital printing described in step S4 uses different inks according to different fabrics. In some embodiments of the present invention, the fabric is polyester, and the digital printing uses disperse dyes; in some embodiments of the present invention, the fabric is animal or plant fiber, and the digital printing uses reactive dyes, direct dyes, etc.; in some embodiments of the present invention, the fabric is polyester-cotton blended, and the digital printing can use a combination of disperse dyes and reactive dyes, or disperse dyes; in some embodiments of the present invention, the fabric is nylon, and the digital printing can use acid dyes, etc.

The prior art prepares printed fabrics containing both digital printing patterns and gold printing patterns, usually by first performing digital printing and then performing gold printing by screen printing. This method makes it difficult to align the plate during overprinting, and the plate alignment is often inaccurate, especially when printing long continuous patterns, the accuracy is poor, so that the gold printing and printing cannot be perfectly combined. The present invention first obtains the gold printing fabric, uses the image recognition positioning technology, takes the gold printing pattern as the positioning coordinate, and then performs digital positioning printing, which greatly improves the alignment accuracy of the gold printing and printing, and can obtain a composite printed fabric with clean contours and high matching degree.

The post-processing in step S5 adopts different post-processing methods according to the different fabrics and digital printing inks.

In some embodiments of the present invention, the fabric is polyester, disperse dyes are used for digital printing, and the post-processing steps are as follows: high-temperature steaming → reduction cleaning → water washing → drying.

The high temperature steaming refers to steaming in saturated steam at 102° C. and normal pressure, and the steaming time is 10 to 20 minutes.

The formula of the reduction cleaning is: 3g/L of hydrosulfur powder and 2g/L of caustic soda; the temperature of the reduction cleaning is 70-90°C, and the time is 20-40min.

In some embodiments of the present invention, the fabric is animal or plant fiber, and the digital printing uses reactive dyes and direct dyes. The post-processing steps are as follows: high-temperature steaming → washing → drying.

The present invention has the following advantages and beneficial effects:

(1) The present invention selects metal powders of specific particle shapes as gold and silver powders in the gold printing paste, so that the obtained gold printing pattern is more shiny, has better visual effects, has high adhesion strength on the cloth, and is not easy to wash off.

(2) The present invention uses L-cysteine and/or glutathione to modify the surface of gold and silver powder, and the obtained gold and silver powder has good antioxidant effect and good dispersibility.

(3) The process provided by the present invention first uses screen printing to print gold on the fabric and then performs digital printing, so that the obtained pattern has a clear outline and the position accuracy of the gold printing and the printing is high.

(4) The process provided by the present invention uses a reactive hydrophilic paste to pretreat the fabric. The paste can react chemically with the gold printing paste to improve the adhesion strength of the gold and silver powders. In addition, the paste provides a good anti-seepage effect for inkjet printing. The resulting digital printing pattern has a clear outline. The paste other than the gold printing pattern can also be removed by washing, and the resulting fabric has a good hand feel.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an infrared spectrum of the surface-modified flaky gold and silver powder prepared in Example 1.

DETAILED DESCRIPTION

The present invention is further described in detail below in conjunction with specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

EM-618 pigment printing thickener and silicone defoamer were purchased from Guangdong Yimei Chemical Technology Co., Ltd. Polyvinyl alcohol, polyethylene glycol, surfactant, and sodium alginate were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

Example 1

A digital positioning gold printing process comprises the following steps:

Step S1: pre-treating polyester (filament, 65 g/m ² , 484×346/7×7) with a hydrophilic paste in a dipping-and-rolling manner, and drying at 90° C. to obtain a pre-treated fabric;

The liquid carrying rate is 70%; the hydrophilic paste includes the following components: 3% vinyl-modified polyvinyl alcohol, 1.2% surfactant OP-10, and the balance is water.

The preparation method of vinyl-modified polyvinyl alcohol is as follows: polyvinyl alcohol (Mw=40000 g/mol) and methacryloyl chloride are dissolved in anhydrous tetrahydrofuran respectively, and then the methacryloyl chloride solution is added dropwise to the polyvinyl alcohol solution, the temperature is raised to 40°C, and the reaction is stirred at 400 rpm for 6 hours. After the reaction is completed, the solvent is evaporated to obtain vinyl-modified polyvinyl alcohol, and the vinyl content of the vinyl-modified polyvinyl alcohol is 0.22 mmol/g.

Step S2: firstly, preparing a printing screen according to the gold printing pattern, then applying the gold printing slurry on the pre-treated fabric through the printing screen, and drying it naturally to obtain the gold printing fabric;

Among them, the printing screen is 100 mesh.

The gold printing paste includes the following components: 65% glitter paste, 20% surface modified flaky gold and silver powder, and the balance is water; the viscosity of the gold printing paste (25° C.) is 186000 mPa·s.

The glitter paste includes the following components: 50% of acrylic adhesive (Dow PRIMAL TR407), 2% of silicone defoamer, 0.5% of thickener (EM-618), and the balance is water; the viscosity of the glitter paste (25° C.) is 9200 mPa·s.

Among them, the surface modified flaky gold and silver powder is a mixture of surface modified bronze powder, brass powder and aluminum powder; the surface modified flaky gold and silver powder is 300 mesh undersieve and 600 mesh oversieve, with an average aspect ratio of 22; the preparation method of the surface modified flaky gold and silver powder is as follows: ultrasonically disperse the gold and silver powder in a 6g/L L-cysteine aqueous solution according to a solid-liquid ratio of 1g:100mL, add sodium hydroxide to adjust the pH to 8, seal and conduct ultrasonic reaction for 6h, after solid-liquid separation, wash the solid with water, and dry the solid at 40°C to constant weight.

Step S3: The gold-printed fabric is placed in a heat oven at 150° C. for 2 minutes for curing to obtain a cured gold-printed fabric.

Step S4: placing the solidified gold-printed fabric on the sample table, turning on the image scanning device to scan the solidified gold-printed fabric, obtaining the position, shape and distribution parameters of the fabric and the gold-printed pattern, and inputting the parameters into the computer to form a gold-printed template; comparing the gold-printed template with the design template containing the gold-printed pattern and the digital printing pattern, and then introducing the digital printing pattern into the gold-printed template so that the position of the digital printing pattern matches and coincides with the position of the gold-printed pattern, and then spraying the digital printing pattern onto the solidified gold-printed fabric through a digital printing machine to obtain a composite printed fabric; digital printing uses disperse dye ink.

Step S5: Post-treatment, the composite printed fabric is placed in a steamer for steaming for 15 minutes, then placed in a reduction cleaning bath for cleaning for 30 minutes, washed with normal temperature water for 3 times after reduction cleaning, and dried at 80°C to obtain the finished fabric. The formula for reduction cleaning is: 3g/L of hydrosulfur powder, 2g/L of caustic soda, and the bath ratio is 1:10.

Figure 1 of the specification is an infrared spectrum of the prepared surface modified flaky gold and silver powder. The stretching vibration absorption peak of the Cu-S bond can be observed from the figure, and it is consistent with the simulated spectrum, indicating that L-cysteine is chemically bonded to the surface of the metal element.

Example 2

A digital positioning gold printing process comprises the following steps:

Step S1: pre-treating the cotton fabric with a hydrophilic paste in a dipping-padding manner, and drying at 90° C. to obtain a pre-treated fabric;

The liquid carrying rate is 60%; the hydrophilic paste includes the following components: 1.5% vinyl resin, 0.1% surfactant AEO-10, 8% urea, 3% sodium carbonate, and the balance is water. The vinyl resin is a mixture of vinyl-modified polyethylene glycol and vinyl-modified sodium alginate in a mass ratio of 1:1, and the vinyl content is 0.34.

The weight average molecular weight Mw of the polyethylene glycol in the vinyl-modified polyethylene glycol is 35000 g/mol. The preparation method of the vinyl-modified polyethylene glycol is the same as that in Example 1.

The specification of the sodium alginate in the vinyl-modified sodium alginate is ultra-high viscosity type II, 1% viscosity: 7000-10000 mPa.s. The preparation method of the vinyl-modified sodium alginate is the same as that in Example 1.

Step S2: firstly, preparing a printing screen according to the gold printing pattern, then applying the gold printing slurry on the pre-treated fabric through the printing screen, and drying it naturally to obtain the gold printing fabric;

Among them, the printing screen is 120 mesh.

The gold printing paste comprises the following components: 60% glitter paste, 15% surface modified flaky gold and silver powder, and the balance is water; the viscosity of the gold printing paste (25° C.) is 152000 mPa·s.

The glitter paste is the same as that in Example 1. The surface-modified flaky gold and silver powder is a mixture of surface-modified bronze powder, brass powder and aluminum powder; the surface-modified flaky gold and silver powder is a mixture of 300-mesh undersize and 1000-mesh oversize, with an average aspect ratio of 21; the preparation method of the surface-modified flaky gold and silver powder is the same as that in Example 1.

Step S3 is the same as that in Example 1.

The digital printing in step S4 uses reactive dye ink, and the rest is the same as in embodiment 1.

Step S5: post-treatment, placing the composite printed fabric in a steamer for steaming for 10 minutes, then washing it twice in room temperature water and once in 50°C water, with the bath ratio being 1:10, and finally drying it at 80°C to obtain the finished fabric.

Example 3

A digital positioning gold printing process comprises the following steps:

Step S1: pre-treating polyester fabric with a hydrophilic paste in a dipping-padding manner, and drying at 90° C. to obtain a pre-treated fabric;

The liquid carrying rate is 90%; the hydrophilic paste comprises the following components: 5% vinyl resin, 2% surfactant (cleaning agent 704), and the balance is water. The vinyl resin is vinyl-modified sodium alginate, the vinyl content is 0.11 mmol/g, the sodium alginate specification is ultra-high viscosity II type, 1% viscosity: 7000-10000 mPa.s, and the preparation method of vinyl-modified sodium alginate is the same as that of Example 1.

Step S2: firstly, preparing a printing screen according to the gold printing pattern, then applying the gold printing slurry on the pre-treated fabric through the printing screen, and drying it naturally to obtain the gold printing fabric;

Among them, the printing screen is 80 mesh.

The gold printing paste includes the following components: 70% glitter paste, 25% surface modified flaky gold and silver powder, and the balance is water; the viscosity of the gold printing paste (25° C.) is 189000 mPa·s.

The glitter paste is the same as that in Example 1. The surface-modified flaky gold and silver powder is a mixture of surface-modified bronze powder, brass powder and aluminum powder; the surface-modified flaky gold and silver powder is a mixture of 600-mesh undersize and 1000-mesh oversize, with an average aspect ratio of 22; the preparation method of the surface-modified flaky gold and silver powder is the same as that in Example 1.

Steps S3 to S5 are the same as those in Example 1.

Example 4

The difference from Example 1 is that the vinyl content of the vinyl-modified polyvinyl alcohol in the hydrophilic paste in step S1 is 0.14 mmol/g.

Example 5

The difference from Example 1 is that the vinyl content of the vinyl-modified polyvinyl alcohol in the hydrophilic paste in step S1 is 0.38 mmol/g.

Example 6

The difference from Example 1 is that the aspect ratio of the surface modified flaky gold and silver powder in the gold printing paste in step S2 is 8, and the viscosity (25° C.) of the obtained gold printing paste is 165000 mPa·s.

Example 7

The difference from Example 1 is that the aspect ratio of the surface modified flaky gold and silver powder in the gold printing paste in step S2 is 30, and the viscosity (25° C.) of the obtained gold printing paste is 182000 mPa·s.

Example 8

The difference from Example 1 is that the modifier of the surface-modified flaky gold and silver powder in the gold printing paste in step S2 is glutathione, the preparation method is the same as that in Example 1, and the viscosity (25°C) of the obtained gold printing paste is 183000 mPa·s.

Embodiment 9

The difference from Example 1 is that when preparing the surface-modified flaky gold and silver powder in the gold printing paste in step S2, the concentration of the modifier solution is 3 g/L.

Example 10

The difference from Example 1 is that when preparing the surface-modified flaky gold and silver powder in the gold printing paste in step S2, the concentration of the modifier solution is 9 g/L.

Comparative Example 1

The difference from Example 1 is that in step S1, the hydrophilic paste uses unmodified polyvinyl alcohol instead of vinyl-modified polyvinyl alcohol.

Comparative Example 2

The difference from Example 1 is that the aspect ratio of the surface modified flaky gold and silver powder in the gold printing paste in step S2 is 4, and the viscosity (25° C.) of the obtained gold printing paste is 151000 mPa·s.

Comparative Example 3

The difference from Example 1 is that the aspect ratio of the surface modified flaky gold and silver powder in the gold printing paste in step S2 is 38, and the viscosity (25° C.) of the obtained gold printing paste is 214000 mPa·s.

The viscosity of the gold printing paste is too high, making it difficult to use and resulting in poor printing uniformity.

Comparative Example 4

The difference from Example 1 is that in step S2, the gold printing paste uses flaky gold and silver powder that has not been surface modified instead of the flaky gold and silver powder that has been surface modified.

Comparative Example 5

The difference from Example 1 is that in step S2, the gold printing paste uses flaky gold and silver powder surface-modified with polyethylene glycol instead of flaky gold and silver powder surface-modified with L-cysteine. The preparation method of the flaky gold and silver powder surface-modified with polyethylene glycol is as follows: ultrasonically disperse the flaky gold and silver powder in a polyethylene glycol aqueous solution with a concentration of 6 g/L according to a solid-liquid ratio of 1 g:100 mL, separate the solid and liquid after ultrasonic reaction for 24 hours, and dry the solid at 40°C to constant weight.

Comparative Example 6

The difference from Example 1 is that the preparation method of the surface-modified flaky gold and silver powder used in the gold printing paste in step S2 is as follows: the gold and silver powder is ultrasonically dispersed in a 6 g/L L-cysteine aqueous solution at a solid-liquid ratio of 1 g:100 mL, and then sealed and ultrasonically reacted for 12 hours. After solid-liquid separation, the solid is dried at 40°C to constant weight.

Test Example 1: Gold powder aging test

The ordinary gold and silver powder or surface modified flaky gold and silver powder obtained in Examples 1, 6, 7 to 10 and Comparative Examples 2 to 5 were subjected to a gold powder aging test. Specifically, the sample to be tested was irradiated under ultraviolet light for 0, 6, and 24 hours, and then the glossiness of the powder was tested using a fixed angle (60°) light meter.

Table 1

From the results, it can be seen that the aspect ratio of the flaky gold and silver powder has a great influence on its glossiness. Specifically, the larger the aspect ratio, the larger the surface area of the gold and silver powder, so the higher the reflectivity of light, and the better the glossiness. In addition, Examples 1, 8 and Comparative Examples 4 and 5 show that surface modification with L-cysteine and glutathione has almost no effect on the glossiness of the gold and silver powder, while surface modification with polyethylene glycol reduces the glossiness of the gold and silver powder. The reason is that cysteine and glutathione are small molecular compounds that do not have film-forming properties, while polyethylene glycol is a polymer that forms a film on the surface of the powder particles and wraps them, thereby affecting their light reflection. The test results of Examples 1, 8, 9, and 10 show that the type and amount of the modifier have almost no effect on the glossiness of the gold and silver powder. After illumination, the glossiness of each sample decreases to varying degrees, because ultraviolet light accelerates the oxidation of the metal. Surface modification inhibits metal oxidation to varying degrees, and the L-cysteine and glutathione used in the present invention have a stronger effect on inhibiting metal oxidation than polyethylene glycol, and as the concentration of the modifier increases, the antioxidant properties of the obtained gold and silver powders are better. The reason is that the molecular structures of L-cysteine and glutathione contain a large amount of active hydrogen, which can be used as a reducing agent to react before peroxides or oxygen free radicals, thereby avoiding peroxides or oxygen free radicals attacking metal elements; while the molecular structure of polyethylene glycol has a low content of active hydrogen and a poor antioxidant effect. Example 1 is compared with Comparative Example 6. In Comparative Example 6, the modifier and the gold and silver powder are simply mixed by ultrasound without chemical reaction, so the amount of L-cysteine covering the surface of the gold and silver powder is small, so the antioxidant effect is poor and it is easy to wash out in the post-treatment process.

Test Example 2: Printing brightness test

The brightness of the gold-printed fabric without digital printing was tested by X-Rite i7800 colorimeter, using D65 light source and 10° observation angle. The "L*" value is used to represent the brightness of the gold-printed pattern. The brighter the printing, the brighter it is, and vice versa. The gold-printed pattern of each sample was tested 6 times in different parts, and the average value of the 6 tests was taken to obtain the printing brightness.

Test Example 3: Brightness persistence test

The cured gold-printed fabric that has not been digitally printed was placed in a steamer at 102°C for 4h, 8h, and 12h. The brightness value (L*t) at different placement times was tested according to the method of Test Example 1, and the brightness persistence was calculated based on the initial brightness value (L*0), brightness persistence = L*t ÷ L*0 × 100%.

Table 2

From the data in the table, it can be seen that the L* value of the embodiment is higher than that of the comparative example, indicating that the brightness of the printed fabric pattern obtained by using the gold printing paste and printing process of the present invention is significantly improved; the L* value of the embodiment is smaller than that of the comparative example when placed in a high temperature and high humidity environment for different times, indicating that the brightness and durability of the gold printing pattern are significantly improved after using the gold printing paste and printing process of the present invention. In addition, the brightness of the gold printing pattern is related to the aspect ratio of the surface modified gold and silver powder, and the gold printing pattern obtained by using L-cysteine and glutathione for surface modification is higher than that of polyethylene glycol, and the results are consistent with Test Example 1.

Test Example 3: Adhesion strength test

(1) A 2×2 cm piece of sealing tape is pasted on the surface of the gold-printed pattern. The area of the gold-printed pattern is larger than the area of the sealing tape. A 10 kg rectangular weight is placed on top of the tape and placed in a constant temperature and humidity chamber for 24 hours. The tape is then torn off and the bonding strength is evaluated based on the area of gold and silver powder adhered to the sealing tape. The evaluation criteria are: 0% ≤ gold and silver powder area ratio < 10% for Grade A, 10% ≤ gold and silver powder area ratio < 30% for Grade B, 30% ≤ gold and silver powder area ratio < 50% for Grade C, and gold and silver powder area ratio ≥ 50% for Grade D.

(2) The test shall be conducted in accordance with GB/T 420-2009 “Textiles - Tests for colour fastness - Colour fastness of pigment-dyed textiles to washing”.

Table 3

From the data in the table, it can be seen that the printed fabric obtained by using a hydrophilic paste with reactive activity has better bonding fastness than that obtained by using a hydrophilic paste without reactive activity (Comparative Example 1). In addition, when the aspect ratio of the flaky gold and silver powder is 4 (Comparative Example 2), the bonding fastness of the printed fabric decreases, because the larger the aspect ratio, the higher the flake degree of the gold and silver powder, and the larger its surface area, so the contact area with the binder or fabric is larger, and thus the fastness is higher; but the aspect ratio of the gold and silver powder cannot be too high. For example, in Comparative Example 3, although the glossiness of the gold and silver powder is high and the printed pattern of the obtained fabric is bright, the viscosity of the printing paste is high, which makes its fluidity poor and difficult to be evenly applied to the fabric surface. In addition, the larger the surface area, the lower the oxidation resistance of the gold and silver powder. In addition, from the test results of color fastness to scrubbing, it can be seen that the vinyl content in the vinyl resin in the hydrophilic paste has an impact on the color fastness to scrubbing of fabric printing. Specifically, the higher the vinyl content, the higher the color fastness. However, too high a vinyl content will lead to an excessive degree of cross-linking during curing and excessive stiffness of the pattern, affecting the feel.

The above contents are further detailed descriptions of the present invention in combination with specific preferred technical solutions, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For professionals and technicians in the technical field to which the present invention belongs, several simple deductions or substitutions can be made without departing from the concept of the present invention, which should be regarded as belonging to the protection scope of the present invention.

Claims (10)

1. The digital positioning gold stamping process is characterized by comprising the following steps of:

step S1: pretreating cloth by adopting hydrophilic paste, and then drying to obtain pretreated cloth;

step S2: printing gold printing slurry on the pretreated cloth by adopting a screen printing method to obtain a print Jin Buliao;

step S3: solidifying the gold-printed cloth to obtain a solidified stamp Jin Buliao;

Step S4: digital printing is carried out on the solidified printed cloth to obtain composite printed cloth;

step S5: post-processing the composite printed cloth to obtain a finished cloth;

the hydrophilic paste contains water-soluble vinyl resin;

The gold printing slurry contains surface modified flaky gold silver powder, and the surface modified flaky gold silver powder has the following characteristics: features ①: the size of the powder particles is 300-1000 meshes; features ②: the powder particles are flaky, and the average length-diameter ratio is 8-50; features ③: surface chemical modification of L-cysteine and/or glutathione; the aspect ratio is the ratio of the longest diagonal length of the plane with the largest powder particle area to the length in the direction perpendicular to the plane.

2. The digital positioning gold stamping process according to claim 1, wherein the hydrophilic paste in the step S1 comprises the following components in percentage by mass: 1 to 5 percent of vinyl resin, 0.1 to 2 percent of surfactant, 0 to 15 percent of alkaline agent and the balance of water; the vinyl resin can be at least one selected from vinyl modified polyvinyl alcohol, vinyl modified polyethylene glycol and vinyl modified sodium alginate.

3. The digital positioning gold stamping process according to any one of claims 1 or 2, wherein the vinyl content of the vinyl resin in the step S1 is 0.1-0.4 mmol/g.

4. The digital positioning gold stamping process according to claim 1, wherein the pretreatment in the step S1 is to apply hydrophilic sizing agent on the surface of cloth in a dipping, padding, coating or spraying mode, and the liquid carrying rate of the cloth is 60% -90%.

5. The digital positioning gold printing process according to claim 1, wherein the gold printing paste in the step S2 comprises the following components in percentage by mass: 60-70% of glitter pulp, 15-25% of surface modified flaky gold and silver powder and the balance of water.

6. The digital positioning gold printing process according to claim 5, wherein the gold wire paste in the step S2 comprises the following components in percentage by mass: 40-60% of acrylic adhesive, 2-5% of defoaming agent, 0.5-1.2% of thickening agent and the balance of water.

7. The digital positioning gold stamping process according to claim 5, wherein the viscosity of the gold stamping paste in the step S2 is 150000 ～ 200000 mPa.s at 25 ℃.

8. The digital positioning gold stamping process according to any one of claims 1 or 5, wherein the preparation method of the surface modified flaky gold and silver powder is as follows: dispersing gold and silver powder in a modifier solution by ultrasonic, regulating the pH value to 5-11, performing sealed ultrasonic reaction for 3-12 h, performing solid-liquid separation, cleaning the solid by water, and drying at 30-50 ℃ to obtain surface modified flake gold and silver powder; the modifier is L-cysteine or glutathione, and the solution solvent of the modifier is water or/and alcohol.

9. The digital positioning gold stamping process of claim 8, wherein the concentration of the modifier solution is 3-9 g/L; the solid-liquid feeding ratio of the gold silver powder to the modifier solution is 1g:100mL.

10. The digital positioning gold stamping process of claim 1, wherein the curing of step S3 comprises one of thermal curing or uv curing.