Gradient microcavity transfer paper structure for deep base color denim fabric and preparation method thereof

Abstract

The application discloses a gradient microcavity transfer paper structure for deep base color jean fabric, which comprises a substrate layer, a near-substrate layer, a transition layer and a far-substrate layer arranged from bottom to top; wherein the near-substrate layer, the transition layer and the far-substrate layer are all formed by mixing nano silicon dioxide, water-based polyurethane, PEG-PPG block copolymer, a dispersing agent and water and then solidifying; by controlling the component proportion of the far-substrate layer, the transition layer and the near-substrate layer, the average pore diameter of the three layers from top to bottom is formed to be gradiently decreased, ink drops are quickly absorbed and penetrated to the near-substrate layer from the far-substrate layer, the pores in the transition layer serve as a buffer, the micropores of the near-substrate layer slow down the migration of the ink, thereby prolonging the residence time of the ink in the near-substrate layer, avoiding reverse penetration, reducing the ink penetration rate, reducing the porosity deformation rate during calendering, and achieving good dark color covering effect.

Description

Technical Field

[0001] This invention relates to the field of textile materials, and more particularly to a gradient microcavity transfer paper structure for dark-colored denim fabric and its preparation method. Background Technology

[0002] Transfer paper is a type of paper with a printed pattern that can be transferred to other surfaces. Typically, the transfer is done face down, with the transfer paper pressed firmly against the second surface, and then the backing paper is peeled off to complete the pattern transfer.

[0003] Denim fabric, a pillar textile category with an annual global consumption exceeding 7 billion meters, boasts a market share of over 65% for its dark-colored products (especially INDIGO 14# standard dark blue). However, traditional transfer printing technology suffers from three structural defects: First, traditional homogeneous ink-absorbing layers (with pore sizes of 2-3μm) cannot effectively prevent pigment from seeping into dark denim fabrics, resulting in a large color difference between the white ink layer and the dark blue base fabric. This leads to ineffective dark-color coverage, far exceeding the industry threshold of color difference ΔE≤2.0, forcing companies to adopt a secondary printing process, drastically increasing costs and reducing production line efficiency. Second, ink bleeding is essentially a result of fluid dynamics imbalance. When the ink hydraulic pressure exceeds the capillary locking force (ΔP≈2.8kPa), ink bleeding easily occurs, causing blurred pattern edges and ink seeping into fiber gaps. Especially for light-colored gradient patterns, the ink bleeding width can reach 0.3-0.5mm, suppressing the industry average yield rate to 82%. Furthermore, the homogeneous ink-absorbing layer has low strength during calendering, and its pores are prone to deformation, thus affecting the subsequent ink absorption effect and reducing the yield of the ink-absorbing paper. Therefore, in order to solve the problems of poor dark-colored opacity, ink bleeding, and low yield caused by pore deformation in traditional transfer paper, there is an urgent need for a gradient microcavity transfer paper structure for dark-colored denim fabric with good dark-colored opacity, low ink bleeding rate, and low pore deformation rate, as well as its preparation method. Summary of the Invention

[0004] The objective of this invention is achieved through the following technical solution: A gradient microcavity transfer paper structure for dark-colored denim fabric includes a substrate layer, a near-substrate layer, a transition layer, and a far-substrate layer arranged from bottom to top. The near-substrate layer, transition layer, and far-substrate layer are all formed by curing a mixture of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant, and water. The average particle size of the nano-silica in the near-substrate layer is 0.15-0.18 μm, the crosslinking degree of the waterborne polyurethane is 90%, and the molecular weight of the PEG-PPG block copolymer is 800 g / mol. The mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant, and water is (52-58):(35-36):(8-13):5:100. The average particle size of the nano-silica in the transition layer is 0.8-1.0 μm, the crosslinking degree of the waterborne polyurethane is 75%, and the molecular weight of the PEG-PPG block copolymer is 2000 g / mol; the mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant, and water is 50:30:15:5:100; the average particle size of the nano-silica in the far substrate layer is 4.6-5.0 μm, the crosslinking degree of the waterborne polyurethane is 60%, the molecular weight of the PEG-PPG block copolymer is 4000 g / mol, and the mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant, and water is 45:25:20:5:100.

[0005] Preferably, the substrate layer is made of PET material.

[0006] Preferably, the dispersant is sodium polyacrylate.

[0007] Preferably, the substrate layer is corona treated.

[0008] Corona treatment of the substrate layer increases the surface tension of the substrate layer, providing a good foundation for adhesion in subsequent processes.

[0009] Preferably, the ratio of the average pore diameter of the far substrate layer to the average pore diameter of the near substrate layer is not less than 18:1.

[0010] By controlling the particle size ratio of nano-silica between the far substrate layer and the near substrate layer, the pore size ratio of the connecting channels between the far substrate layer and the near substrate layer can be controlled, thereby ensuring the pressure difference of capillary adhesion between the far substrate layer and the near substrate layer, thus preventing ink from back-seeping from the near substrate layer to the far substrate layer and reducing the ink seepage rate.

[0011] This invention also provides a method for preparing a gradient microcavity transfer paper structure for dark-colored denim fabric, comprising the following steps: S1. Biaxially oriented PET film is used as the substrate layer, and the substrate layer is subjected to corona treatment; S2. According to the composition of the near-substrate layer, transition layer and far-substrate layer, the corresponding nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant and water are mixed evenly and then degassed. S3. A three-chamber slot coater is used to simultaneously coat the near-substrate layer, transition layer and far-substrate layer on the substrate layer. The substrate layer, near-substrate layer, transition layer and far-substrate layer are distributed from bottom to top. After coating in step S4 and S3, cure with hot air at 80℃ for 30 seconds, then fix with infrared at 100℃ for 40 seconds, and then microwave at 130℃ for 50 seconds; finally, perform calendering.

[0012] The three-chamber slurry is extruded simultaneously. The viscosity of the slurry after mixing the components of the near-substrate layer, transition layer and original substrate layer is matched. The slurry of the three chambers is coated on the substrate layer at the same time, which has high coating efficiency. Then, through layer-by-layer curing from top to bottom, a transition zone is formed between the layers, which improves the interlayer bonding force and eliminates the interface peeling problem of traditional multi-layer coating.

[0013] Preferably, in step S3, the near-substrate layer forms a 10 μm wet coating under an extrusion pressure of 0.4 MPa; the transition layer forms a 15 μm wet coating under an extrusion pressure of 0.25 MPa; and the far-substrate layer forms an 80 μm wet coating under an extrusion pressure of 0.15 MPa.

[0014] Preferably, in step S1, the substrate layer thickness is 88-92 μm, the corona treatment voltage is 8-10 kV, and the treatment speed is 15 m / min.

[0015] Preferably, in step S4, the microwave power is 3kW, the microwave frequency is 2.45GHz, the linear pressure of the calendering process is 1.2MPa, the calendering roller temperature is 68-72℃, and the calendering speed is 8m / min.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention controls the composition ratio of the distal substrate layer, transition layer, and near substrate layer. The average pore size of each layer is dominated by the particle size, content, and packing method of nano-silica. The PEG-PPG block copolymer expands the gaps between nano-silica particles of corresponding sizes into interconnected channels, forming a gradient of decreasing average pore size across the three layers from top to bottom. Ink droplets in the distal substrate layer are rapidly adsorbed and penetrate to the near substrate layer by the large pores. The pores in the transition layer act as a buffer, and the micropores in the near substrate layer slow down the migration of the ink, thereby increasing the residence time of the ink in the near substrate layer. The capillary adsorption force on the ink in the micropores is much greater than that on the ink in the far substrate layer. Utilizing the difference in capillary adsorption force generated by the pore size gradient, a one-way valve effect is formed, forcing the ink to migrate from the far substrate layer to the near substrate layer, avoiding backflow problems and resulting in low ink penetration. The micropore size in the near substrate layer is smaller than the indigo pigment particle size in dark denim fabric, solving the problem of poor dark-colored coverage caused by indigo pigment seepage. The near substrate layer forms a rigid skeleton with high content of nano-silica and highly cross-linked polyurethane, which has strong structural strength and low pore deformation rate during calendering. Detailed Implementation

[0017] To make the technical problems solved by this invention, the technical solutions adopted, and the technical effects achieved clearer, the technical solutions of the embodiments of this invention will be described in further detail below. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention. Example

[0018] A gradient microcavity transfer paper structure for dark-colored denim fabric includes a substrate layer, a near-substrate layer, a transition layer, and a far-substrate layer arranged from bottom to top. The near-substrate layer, transition layer, and far-substrate layer are all formed by curing a mixture of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, sodium polyacrylate, and water. The average particle size of the nano-silica in the near-substrate layer is 0.18 μm, the crosslinking degree of the waterborne polyurethane is 90%, and the molecular weight of the PEG-PPG block copolymer is 800 g / mol. The nano-silica, waterborne polyurethane, and waterborne polyurethane in the near-substrate layer have an average particle size of 0.18 μm, the crosslinking degree of the waterborne polyurethane is 90%, and the molecular weight of the PEG-PPG block copolymer is 800 g / mol. The mass ratio of polyurethane, PEG-PPG block copolymer, sodium polyacrylate, and water is 55:35:10:5:100, and the viscosity after mixing is 3400-3600 cP; the average particle size of the nano-silica in the transition layer is 0.9 μm, the crosslinking degree of the waterborne polyurethane is 75%, and the molecular weight of the PEG-PPG block copolymer is 2000 g / mol; the mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, sodium polyacrylate, and water is 50:30:15:5:100. The viscosity after mixing is 1150-1250 cP; the average particle size of the nano-silica in the substrate layer is 4.8 μm, the crosslinking degree of the waterborne polyurethane is 60%, the molecular weight of the PEG-PPG block copolymer is 4000 g / mol, and the mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, sodium polyacrylate and water is 45:25:20:5:100, and the viscosity after mixing is 480-520 cP.

[0019] The substrate layer is made of PET material.

[0020] This embodiment also provides a method for preparing a gradient microcavity transfer paper structure for dark-colored denim fabric, including the following steps: S1. A biaxially oriented PET film is used as the substrate layer. The substrate layer is subjected to corona treatment. In step S1, the thickness of the substrate layer is 88-92μm, the corona treatment voltage is 8-10Kv, and the treatment speed is 15m / min.

[0021] S2. According to the composition of the near-substrate layer, transition layer and far-substrate layer, the corresponding nano-silica, waterborne polyurethane, PEG-PPG block copolymer, sodium polyacrylate and water are mixed evenly and then degassed. S3. Using a three-chamber slot coater, a near-substrate layer, a transition layer, and a far-substrate layer are simultaneously coated on the substrate layer. The substrate layer, near-substrate layer, transition layer, and far-substrate layer are distributed from bottom to top. In step S3, the near-substrate layer forms a 10μm wet coating under an extrusion pressure of 0.4MPa; the transition layer forms a 15μm wet coating under an extrusion pressure of 0.25MPa; and the far-substrate layer forms an 80μm wet coating under an extrusion pressure of 0.15MPa. After coating in step S4 and S3, cure with hot air at 80℃ for 30 seconds, then fix with infrared at 100℃ for 40 seconds, and then microwave at 130℃ for 50 seconds; finally, perform calendering.

[0022] In step S4, the microwave power is 3kW, the microwave frequency is 2.45GHz, the linear pressure of the calendering process is 1.2MPa, the calendering roller temperature is 68-72℃, and the calendering speed is 8m / min.

[0023] In this embodiment, mercury intrusion porosimetry is used to test the pore size of the near-substrate layer, transition layer and far-substrate layer. The steps are as follows: 1. Sample preparation: a 2cm×2cm sample is accurately cut from the transfer paper and dried at 105℃ for 2 hours to remove moisture.

[0024] 2. Sample loading: Place the sample into a dilatometer of known weight and evacuate to <6.7 Pa.

[0025] 3. Low pressure test: Measure the large pores (5-400μm) under a pressure of 0.0014-0.21 MPa.

[0026] 4. High pressure test: Measure the micropores (0.005-5μm) under pressure of 0.21-400 MPa.

[0027] The average pore diameter of the pores near the substrate layer was measured to be 0.2 μm, the average pore diameter of the pores in the transition layer was 1.0 μm, and the average pore diameter of the pores far from the substrate layer was 5.0 μm. Example

[0028] This embodiment is similar to Embodiment 1, except that the average particle size of the nano-silica near the substrate layer is 0.18 μm, the crosslinking degree of the waterborne polyurethane is 90%, and the molecular weight of the PEG-PPG block copolymer is 800 g / mol; the mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, sodium polyacrylate and water is 52:35:13:5:100, which expands the average pore size of the channels in the near substrate layer to 0.25 μm. Example

[0029] This embodiment is similar to Embodiment 1, except that the average particle size of the nano-silica near the substrate layer is 0.15 μm, the crosslinking degree of the waterborne polyurethane is 90%, and the molecular weight of the PEG-PPG block copolymer is 800 g / mol; the mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, sodium polyacrylate and water is 58:36:8:5:100; and the average pore size of the channels in the near substrate layer is reduced to 0.15 μm.

[0030] Comparative Example 1 This comparative example is similar to Example 1, except that the average particle size of the nano-silica near the substrate layer is 0.18 μm, the crosslinking degree of the waterborne polyurethane is 90%, and the molecular weight of the PEG-PPG block copolymer is 800 g / mol; the mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, sodium polyacrylate and water is 50:35:17:5:100, which expands the average pore size of the channels in the near substrate layer to 0.30 μm.

[0031] Comparative Example 2 This comparative example is similar to Example 1, except that the average particle size of the nano-silica near the substrate layer is 0.18 μm, the crosslinking degree of the waterborne polyurethane is 90%, and the molecular weight of the PEG-PPG block copolymer is 800 g / mol; the mass ratio of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, sodium polyacrylate and water is 45:35:22:5:100, which expands the average pore size of the channels in the near substrate layer to 0.80 μm.

[0032] The ink penetration rate of Examples 1-3 and Comparative Examples 1-2 was tested (AATCC 130) as follows: 1. Transfer a light gray gradient pattern (20% ink coverage).

[0033] 2. Cut the sample (5×5cm) and place it under a fiber optic analytical microscope (Keyence VHX-7000).

[0034] 3. Measure the width and area of ​​the ink penetration.

[0035] 4. Calculate the ink penetration rate: Ink penetration rate = (Ink penetration area / Total pattern area) × 100%.

[0036] Take the average of the three groups.

[0037] The measured ink penetration rate results are shown in Table 1.

[0038]

[0039] Therefore, when the ratio of the average pore size of the far substrate layer to the average pore size of the near substrate layer is greater than 20:1, the ink penetration rate is less than 5%.

[0040] Comparative Example 3 This comparative example is similar to the previous example, except that the comparative example has a homogeneous ink-absorbing layer without distinction between near-substrate layer, transition layer, and far-substrate layer. The ink-absorbing layer consists of nano-silica with an average particle size of 3.0 μm, waterborne polyurethane with a crosslinking degree of 75, PEG-PPG block copolymer, sodium polyacrylate, and water in a mass ratio of 55:35:15:5:100. The ink-absorbing layer is coated directly onto the substrate layer of the PET film and cured with hot air at 100°C. Other aspects are the same as in the previous example, and the final thickness of the transfer paper is the same as in Example 1.

[0041] The color difference ΔE, ink penetration rate, ink utilization rate, ink carrying capacity, porosity, and droplet residence time were tested for Example 1 and Comparative Example 3, respectively. Details are shown in Table 2.

[0042] Color difference ΔE test (ISO 2470), the steps are as follows: 1. Transfer the white pattern (10×10cm) to denim (L*=16.3).

[0043] 2. Measurement using a spectrophotometer (X-Rite i7): LAB values ​​(L1,a1,b1) in the white ink area LAB values ​​(L2, a2, b2) of the base fabric area.

[0044] 3. Calculation: ΔE=[(L1-L2) 2 +(a1-a2) 2 +(b1-b2) 2 ] 1 / 2 Take the average of 5 points.

[0045] The ink utilization rate test steps are as follows: 1. Ink marking: Add 0.01wt% yttrium aluminum garnet (YAG) phosphor (particle size 0.3μm).

[0046] 2. After transfer, scan the cross section using a laser confocal microscope (Leica TCS SP8): excitation wavelength: 488nm, emission wavelength: 530nm.

[0047] 3. Calculate the capture rate: Capture rate = Fluorescent signal amount in the ink absorption layer / Total fluorescent signal amount in the ink × 100%.

[0048] The ink carrying capacity test (ASTM D5402) procedure is as follows: 1. Weigh the dry weight m0 of the transfer paper (accuracy 0.1mg).

[0049] 2. Apply ink evenly (1mL / m²) and let stand for 30 seconds.

[0050] 3. Remove unabsorbed ink (air knife pressure 0.1MPa).

[0051] 4. Weigh the wet weight m1.

[0052] 5. Calculation: Load capacity = (m1-m0) / (ρ·A); ρ: ink density; A: effective ink absorption area of ​​the material (unit: cm²).

[0053] Pore ​​deformation rate testing method: Mercury intrusion porosimetry (ISO 15901); Equipment: Micromeritics AutoPore V; Pressure range: 0.1-400 MPa; Calculation: Deformation rate = (Vp - Va) / Vp × 100%; Vp: pore volume before calendering, Va: volume after calendering.

[0054] Ink droplet migration speed test: High-speed camera analysis was used; Equipment: Phantom VEO 710L (5000fps); Ink marking: 0.1% sodium fluorescein (λex=490nm); Measurement: The time difference from the ink droplet's contact with the surface to its disappearance was used to calculate the migration speed.

[0055]

[0056] The above embodiments are only some preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A gradient microcavity transfer paper structure for dark-colored denim fabric, characterized in that... The material comprises, from bottom to top, a substrate layer, a near-substrate layer, a transition layer, and a far-substrate layer; wherein the near-substrate layer, the transition layer, and the far-substrate layer are all formed by curing a mixture of nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant, and water; the average particle size of the nano-silica in the near-substrate layer is 0.15-0.18 μm, the degree of crosslinking of the waterborne polyurethane is 90%, and the molecular weight of the PEG-PPG block copolymer is 800 g / mol; the mass ratio of the nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant, and water is (52-58):(35-36):(8-13):5:100; the nano-silica in the transition layer... The average particle size of the silica is 0.8-1.1 μm, the degree of crosslinking of the waterborne polyurethane is 75%, and the molecular weight of the PEG-PPG block copolymer is 2000 g / mol; the mass ratio of the nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant, and water is 50:30:15:5:100; the average particle size of the nano-silica in the far substrate layer is 4.6-5.0 μm, the degree of crosslinking of the waterborne polyurethane is 60%, the molecular weight of the PEG-PPG block copolymer is 4000 g / mol, and the mass ratio of the nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant, and water is 45:25:20:5:

100.

2. The gradient microcavity transfer paper structure for dark-colored denim fabric according to claim 1, characterized in that, The substrate layer is made of PET material.

3. The gradient microcavity transfer paper structure for dark-colored denim fabric according to claim 2, characterized in that, The dispersant is sodium polyacrylate.

4. The gradient microcavity transfer paper structure for dark-colored denim fabric according to claim 3, characterized in that, The substrate layer is corona treated.

5. The gradient microcavity transfer paper structure for dark-colored denim fabric according to claim 4, characterized in that, The ratio of the average pore diameter of the far substrate layer to the average pore diameter of the near substrate layer is not less than 20:

1.

6. A method for preparing the gradient microcavity transfer paper structure for dark-colored denim fabric as described in claim 5, characterized in that... This includes the following steps: S1. A biaxially oriented PET film is used as the substrate layer, and the substrate layer is subjected to corona treatment. S2. According to the composition of the near-substrate layer, transition layer and far-substrate layer, the corresponding nano-silica, waterborne polyurethane, PEG-PPG block copolymer, dispersant and water are mixed evenly and then degassed. S3. A three-chamber slot coater is used to simultaneously coat the near-substrate layer, transition layer and far-substrate layer on the substrate layer, wherein the substrate layer, near-substrate layer, transition layer and far-substrate layer are distributed from bottom to top; After coating in step S4 and S3, cure with hot air at 80℃ for 30 seconds, then fix with infrared at 100℃ for 40 seconds, and then microwave at 130℃ for 50 seconds; finally, perform calendering.

7. The method for preparing the gradient microcavity transfer paper structure for dark-colored denim fabric according to claim 6, characterized in that, In step S3, the near-substrate layer forms a 10 μm wet coating under an extrusion pressure of 0.4 MPa; the transition layer forms a 15 μm wet coating under an extrusion pressure of 0.25 MPa; and the far-substrate layer forms an 80 μm wet coating under an extrusion pressure of 0.15 MPa.

8. The method for preparing the gradient microcavity transfer paper structure for dark-colored denim fabric according to claim 7, characterized in that, The substrate layer thickness in step S1 is 88-92 μm, the corona treatment voltage is 8-10 kV, and the treatment speed is 15 m / min.

9. The method for preparing the gradient microcavity transfer paper structure for dark-colored denim fabric according to claim 8, characterized in that, In step S4, the microwave power is 3kW, the microwave frequency is 2.45GHz, the linear pressure of the calendering process is 1.2MPa, the calendering roller temperature is 68-72℃, and the calendering speed is 8m / min.

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