Method for preparing DTF white ink by using sedimentation method

Abstract

The invention belongs to the technical field of ink preparation, and particularly relates to a method for preparing DTF white ink through a sedimentation method. In order to solve the problem that large-particle-size particles are not easy to remove in the prior art, the invention provides a method for preparing DTF white ink by using a sedimentation method, and the method comprises the steps of grinding and preparing white paste, preparing an ink solvent, preparing an ink crude product, settling the ink crude product, separating upper-layer ink, preparing a finished product and recycling lower-layer ink. According to the process designed by the invention, a sedimentation method is utilized, the time required for sedimentation of the white ink is determined by measuring the time for the 1000nm pigment particles to settle from the upper edge of a white ink sedimentation barrel to the boundary layer of the upper layer and the lower layer, and the upper layer and the lower layer of the settled white ink are separated, so that the pigment with the particle size of more than 1000nm can be fully removed; the problem that large-particle pigments are not easy to remove completely in the production of white ink is solved.

Description

Technical Field

[0001] The invention belongs to the technical field of ink preparation, and in particular relates to a method for preparing DTF white ink by using a sedimentation method. Background Art

[0002] DTF white ink ingredients include white pigment, dispersant, adhesive, surfactant, moisturizer, defoamer, etc., and the size of the dispersed particles of the white pigment is particularly important for the smoothness of the print head. Taking EPSON XP-600 and I3200 print heads as examples, the nozzle diameter of the nozzle is 20um. In theory, pigments with a particle size of less than 20um can pass through the nozzle. In fact, when the pigment particles pass through the nozzle and the internal pipeline of the nozzle, they will accumulate or adsorb to the pipe wall, affecting the ink passing through the pipeline, blocking the nozzle, and affecting the smoothness of printing. According to engineering practice, the smaller the pigment particle size, the better the fluidity of the ink. But the actual situation is that when the particle size of the white pigment in the white ink is less than 760nm, the reflectivity of the entire visible light spectrum will be reduced, resulting in a decrease in whiteness and a weakened covering effect. This is because the wavelength of visible light is 400-760nm. According to the Mie scattering theory, when the particle size exceeds the wavelength λ, the scattering is small, allowing white light to enter and exit. Therefore, controlling the white pigment particle size to be greater than 760nm is beneficial to maintaining the whiteness of the white ink.

[0003] In the process of ink production, the pigment particles obtained by grinding white slurry have a certain size distribution. If the pigment particle size obtained by grinding is too small, it will lack whiteness, and if the particle size is too large, it will affect the printing fluency. The best pigment particle size range is 760-1000nm, but the actual distribution of the pigment particle size is far beyond this range. Usually, the pigment particle size distribution is 400-3000nm. The ink production can only be completed by removing large-size pigment particles. The common method is to remove pigment particles larger than 1000nm through the filtering process from the ground white slurry or formulated ink, but it is difficult to remove pigment particles larger than 1000nm through the filtering process. The pore size of the filter membrane is also normally distributed. It is a common technical problem to selectively remove large-size particle pigments.

[0004] The white pigment in DTF ink is mostly titanium dioxide, with an original particle size of 190-250nm. With the assistance of a dispersant, the aggregated titanium dioxide is ground into a white slurry with a certain particle size distribution, and then mixed with a wetting agent, adhesive, moisturizer, defoamer, surfactant, water and other solvents to prepare white ink. Since the pigment particle size varies and is not uniform, and the particle size is distributed in a certain range, the large particle pigment in the ink is usually reduced through a filtration process. Since the filter mesh aperture size also has a certain distribution range, the pigment particle size of the filtered ink is difficult to be below 1000nm.

[0005] In the process of ink filtration, a filter membrane is required. The filter membranes for filtering particles with a size of 1000nm are mainly made of materials such as PP, nylon, polysulfone, and tetrafluoroethylene. Among them, the PP filter membrane has a low price, large capacity, but a wide pore size distribution. The other types are high in price, small in capacity, and narrow in pore size distribution, but the pore size still has a certain distribution. For example, the use of PP filter membrane cannot effectively remove large particles of pigments, while the use of the other filter membranes mentioned above can remove most of the large particles of pigments, but there are still some large particles of pigments left, and the filter membrane consumption is large, and the use cost is high.

[0006] There are also some methods for producing white ink in the prior art, such as US Patent: US2022 / 0135818AI, Chinese Patent: CN202110262679.1, Chinese Patent: CN202011449544.8, Chinese Patent: CN202410268111.4 and Chinese Patent: CN201911391487.X are all prior art about white ink. From the existing literature, all the process methods for producing white ink patents do not adopt sedimentation process to control the particle size of pigment particles therein. Some patents only mention filtering with PP filter membrane, such as CN202011449544.8. Controlling the maximum pigment particle size in the ink is very important for white ink, and the impact on the fluidity of the ink is more significant than that of color ink, which directly affects the quality of the ink.

[0007] The present invention adopts a sedimentation separation process which is different from the usual filtration process, which better solves the problem of controlling the particle size of large-particle pigments in white ink, ensuring that the particle size of pigments in white ink is no more than 1000nm, thereby ensuring the smoothness of white ink printing and maintaining the whiteness of the ink.

[0008] The present invention solves the problem of removing large-particle pigments from the above-mentioned ink, and adopts an economical and effective sedimentation process to replace the original filtering process to remove large-particle pigments. The process of the present invention is based on the theoretical and practical basis that large particles settle faster than small particles, and tests the time for 1000nm pigment particles in white ink to go from the upper edge of the sedimentation barrel to the boundary between the upper and lower layers. The white ink is placed in the sedimentation barrel. After a certain period of sedimentation, pigment particles larger than 1000nm will settle and gather in the lower layer of the sedimentation barrel, and the upper and lower layers of the ink are separated to obtain ink with pigments below 1000nm. At the same time, a part of the pigment particles smaller than 1000nm will also settle into the lower layer of ink, and then a certain amount of ink solvent is added to the lower layer of ink, and filtered with a PP filter membrane with a lower price and a larger capacity to remove the larger particle pigments therein, and the filtered part continues to prepare the next batch of ink, so that this part of the pigment particles smaller than 1000nm can be reused. Compared with the original filtration process, it not only saves the cost of the filter membrane, but also fully removes the pigment particles with a particle size greater than 1000nm that affect the fluidity of the ink, and achieves the production requirements of high-quality DTF white ink. The process of the invention improves the ink quality and reduces the ink production cost. Summary of the invention

[0009] The object of the present invention is to provide a method for preparing DTF white ink by sedimentation method in view of the above problems.

[0010] In order to achieve the above object, the present invention adopts the following technical solutions:

[0011] A method for preparing DTF white ink by sedimentation method, characterized in that it comprises the following steps:

[0012] Step 1: Grind and prepare white slurry. Add the white slurry raw materials containing water, dispersant and titanium dioxide into a stirring device, stir and disperse, and then transfer to a grinder for grinding until the maximum particle size of the solid particles in the slurry is less than 3000nm or the slurry can reach 10g / cm2 by filtering with a 3000nm nylon filter membrane. 2 When the filtration value is above 0.05, stop grinding and obtain white slurry;

[0013] Step 2: preparing the ink solvent, mixing the moisturizer, surfactant, defoamer, adhesive and water evenly to obtain the ink solvent;

[0014] Step 3: preparing a crude ink product, mixing and stirring the white slurry prepared in step 1 and the ink solvent prepared in step 2 to obtain a crude ink product;

[0015] Step 4: Settling of the crude ink product. Add the crude ink product prepared in step 3 into the settling barrel, measure the liquid level and viscosity of the crude ink product in the settling barrel, and control the liquid level to be 50-100 cm and the viscosity to be below 7 cp.

[0016] Step 5: The upper ink is separated and settled until the maximum particle size of the solid particles in the upper ink is less than 1000nm or the upper ink can reach 100g / cm by filtration with a 1000nm nylon filter membrane. 2 When the filtration value is above 0.04, use the liquid extraction tube to extract the upper layer of ink;

[0017] Step 6: Finished product preparation: filter the upper layer of ink using a filter, and then package it to obtain a white ink finished product.

[0018] In the above method for preparing DTF white ink by sedimentation method, the step of recycling the lower ink is also included:

[0019] After the upper ink is separated in step five, the lower ink remains. The ink solvent prepared in step two is added to the lower ink, filtered through a 1000nm PP filter membrane, and then mixed with the white slurry in step one and the ink solvent in step two to obtain a crude ink.

[0020] In the above method for preparing DTF white ink by sedimentation method, the volume ratio of the ink solvent to the lower layer ink is 1-2:10.

[0021] In the above-mentioned method for preparing DTF white ink by sedimentation method, in step 1, the white slurry raw material includes 10-15 parts by weight of dispersant, 40-45 parts by weight of titanium dioxide and 35-50 parts by weight of water.

[0022] In the above method for preparing DTF white ink by sedimentation method, in step 1, the stirring time for stirring and dispersing is 0.5-1h.

[0023] In the above-mentioned method for preparing DTF white ink by sedimentation method, in the step 1, the grinding temperature is 20-30° C., the rotation speed of the grinder is 400-600 r / min, the particle size of the grinding beads is 0.6-0.8 mm, and the grinding time is 3-5 h.

[0024] In the above-mentioned method for preparing DTF white ink by sedimentation method, in step 2, the ink solvent includes 10-20 parts by weight of a humectant, 1-5 parts by weight of a surfactant, 0.5-1 parts by weight of a defoaming agent, 10-30 parts by weight of an adhesive, and 20-30 parts by weight of water.

[0025] In the above-mentioned method for preparing DTF white ink by sedimentation method, in the step 3, the mass ratio of the added white slurry to the ink solvent is 1:4-6.

[0026] In the above method for preparing DTF white ink by sedimentation method, in step 5, the height of the liquid extraction tube from the outlet is 2-4 cm, and the sedimentation time is 20-30 days.

[0027] In the above method for preparing DTF white ink by sedimentation method, in step 6, the filter mesh is a stainless steel mesh with a pore size of 5 um, which can prevent aggregates, dust or other foreign particles on the container wall from being brought into the white ink before packaging.

[0028] Compared with the prior art, the advantages of the present invention are:

[0029] 1. The key to the present invention is to improve the original production technology in terms of method. The filtration technology can separate particles of a certain particle size, but due to the influence of the non-uniform scale of the pore size distribution of the filter membrane, which is a normal distribution, it cannot completely remove particles larger than 1000nm. The process designed by the present invention uses the sedimentation method to determine the time required for the white ink to settle by measuring the time for the 1000nm pigment particles to settle from the upper edge of the white ink sedimentation barrel to the upper and lower boundary layers. After the white ink is settled, the upper and lower layers are separated, and the pigments larger than 1000nm can be more fully removed, solving the problem that large-particle pigments are not easy to remove cleanly in the production of white ink.

[0030] 2. In order to make full use of the small particle pigments in the lower layer of white ink, the present invention designs a lower layer ink recycling process. The lower layer of white ink is appropriately diluted, and a low-cost PP filter membrane of 1000nm is used to filter out larger particles. The filtration is convenient and fast with low cost, avoiding the dead cycle of increasing accumulation of large particle pigments in the system, and ensuring that production can be carried out continuously and cyclically.

[0031] 3. The lower layer white ink recycling filtration of the present invention is different from the ink filtration in the prior art. The recycling of white ink does not require filtration accuracy, nor does it need to remove large particles of pigment, which will not affect the quality of the final white ink.

[0032] 4. The present invention is different from the existing filtration process using expensive nylon, polysulfone and tetrafluoroethylene membranes. The sedimentation method for producing DTF white ink not only has good effects but also saves production costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a flow chart of the present invention;

[0034] Figure 2 It is a schematic diagram of the structure of the sedimentation barrel;

[0035] In the figure: upper layer 1, lower layer 2, outlet 3, and liquid extraction pipe 4. DETAILED DESCRIPTION

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0037] The relevant terms involved in this invention are interpreted as follows:

[0038] Thermal transfer: A process whereby an image printed on a substrate is transferred to a material such as clothing by applying heat.

[0039] DTF process: It is a thermal transfer process that uses an inkjet printer to print DTF special ink on a DTF thermal transfer film (called DTF film), which is quickly solidified into a gel. After printing, polyurethane (TPU) and other hot melt adhesive powder are evenly sprinkled on the gel, and the TPU powder is dried and melted into a TPU thin layer. Finally, the image with the TPU thin layer is pressed on the transferred material such as clothing, and the DTF film is torn off to complete the entire DTF thermal transfer process.

[0040] DTF ink: Ink designed for DTF process, composed of five colors: magenta, yellow, cyan, black and white. In order to expand the color gamut, light magenta, light cyan, etc. can also be added.

[0041] White ink: It is the most important ink in DTF ink. It covers the entire image and plays the role of covering the base color of the transferred material and adhering the hot melt adhesive powder.

[0042] White slurry: refers to the addition of titanium dioxide into water containing dispersants and surfactants, and the high-speed grinding and dispersion by a grinder to form an aqueous dispersion of titanium dioxide aggregates with a certain particle size distribution, which is used to prepare white ink.

[0043] Ink solvent: refers to the mixture of other ingredients in the white ink formula before adding white paste.

[0044] Titanium dioxide: Titanium dioxide is a powder of titanium dioxide. Titanium dioxide mainly has rutile, anatase and other crystal forms. In white ink, rutile titanium dioxide crystals are generally used as silicon oxide and aluminum oxide coated particles. The particle size is usually 190-250nm. This type of product is very common in the market, such as Japanese Ishihara CR-50-2, CR-60-3, DuPont R960, R760, etc. The embodiments and comparative examples of the present invention all use Japanese Ishihara CR-50-2.

[0045] Dispersant: Dispersants used for titanium dioxide dispersion are mostly polyacrylic acid and polyurethane products, such as the common SN5040 dispersant, German BYK dispersant 190, British Lubrizol Solsperse8000, Zhejiang Chuanhua dispersant TF-DP1, etc. The examples and comparative examples of the present invention all use the Zhejiang Chuanhua dispersant TF-DP1.

[0046] Moisturizer: It can prevent the ink from drying up, especially at the nozzle orifice. The DTF white ink process also requires a moisturizer to adhere to the hot melt adhesive powder, so the moisturizer ratio is relatively large. Commonly used moisturizers include glycerol, ethylene glycol, diethylene glycol, triethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, etc. Glycerol is used in the embodiments and comparative examples of the present invention.

[0047] Surfactant: An additive that can adjust the surface tension of the ink to ensure that the surface tension of the white ink is 25-35mN / m to meet the process requirements. Commonly used surfactants mainly include silicones, acetylene glycols, and fatty alcohol polyoxyethylene ethers, such as BYK333, BYK349, Evonik Surfynol 440, 465, 485, Zhejiang Bailang Chemical AEO-4, AEO-9, etc. The embodiments and comparative examples of the present invention all use a 1:1 mixture of Zhejiang Bailang Chemical AEO-4 and Evonik Surfynol 485.

[0048] Defoamer: used to reduce and suppress foam in ink, commonly used are silicone defoamers, polyether defoamers, such as BYK021, BYK024, Dow DF-104, GP series domestic defoamers, etc. The examples and comparative examples of the present invention all use Dow DF-104.

[0049] Adhesive: It plays an important role in white ink, determines whether the white printing layer can form a gel, and also affects the structural fastness of the printing layer. Polyurethane emulsion is usually used as an adhesive, preferably polycarbonate polyurethane emulsion, such as Japan Mitsui W-6110. The embodiments and comparative examples of the present invention all use Japan Mitsui W-6110.

[0050] DTF film: a printing ink-absorbing material with a release function. In the DTF process, the DTF ink printed on the material can quickly solidify into a gel.

[0051] Filtration: It is a separation operation process, a method of removing larger solid particles in a fluid through a filter screen or filter membrane. The filtration in this patent refers to a method of removing solid particles in white ink through a filter membrane.

[0052] Sedimentation: When a dispersion containing solid particles is left stationary, large solid particles will settle to the lower layer of the liquid at a faster rate than small solid particles. After a period of time, the large solid particles will be concentrated in the lower layer or bottom layer of the liquid. This process is called sedimentation.

[0053] Filter membrane: It is a polymer material used to separate solid particles in filtration. The performance and price of filter membranes with different materials, structures and pore sizes vary. Among them, PP filter membrane is a cheap filter membrane made of polypropylene fiber filaments. Its pore size is normally distributed and the pore size distribution range is wide. It cannot accurately filter solid particles of a certain size, but it has a large filtration capacity and is not easy to clog. In addition, there are also filter membranes made of nylon, polysulfone, tetrafluoroethylene and other materials, which are produced through foaming and other technologies. The pore size distribution is narrower than that of PP filter membrane, but the pore size is still normally distributed, but the capacity is small and it is easy to clog.

[0054] Sedimentation barrel: Figure 2 As shown, the sedimentation barrel is an operating container for removing large-particle pigments in the process of the present invention, including an upper layer 1 and a lower layer 2. The bottom of the lower layer 2 has an outlet 3, and the lower layer ink containing more large-size particles after sedimentation is discharged from the outlet 3. There is an obliquely opened liquid extraction pipe 4 at a certain height from the outlet 3, and the upper layer ink after the large-size particles have been settled into the lower layer is discharged through the liquid extraction pipe 4. The overall barrel height is preferably 50-100cm, not too high or too low, because too high will increase the sedimentation time, and too low will reduce the separation accuracy of the upper and lower layers. The liquid extraction pipe in the sedimentation barrel is used to separate the upper and lower layers of ink.

[0055] Printing ink breakage rate: Under certain printing conditions, use a DTF printer to print ink. Each model of nozzle has a certain number of nozzle holes. Under normal circumstances, each nozzle hole can spray ink. As printing progresses, some nozzle holes will be blocked and can only be cleared through forced cleaning. After printing for a period of time, the blockage of the printing ink holes can be observed. At this time, the number of blocked holes / the number of unobstructed holes at the beginning of printing = the ink breakage rate. The ink printing smoothness can be judged based on the ink breakage rate.

[0056] Whiteness: The whiteness referred to in this patent is the whiteness of the white block printed by the DTF process under certain printing conditions, which is tested with a spectrophotometer after being dried at 130°C for 10 minutes. Certain printing conditions refer to the printing parameters set by the printer. Different parameter settings will result in different inkjet volumes and whiteness, so certain printing conditions must be set.

[0057] Example 1

[0058] This embodiment provides a method for preparing DTF white ink by sedimentation method, combined with Figure 1 As shown, the following steps are included:

[0059] Step 1: Grind to prepare white slurry, add a white slurry raw material containing 48 parts of water, 10 parts of dispersant, 2 parts of surfactant and 40 parts of titanium dioxide into a stirring device, stir and disperse for 1 hour, and then transfer to a grinding mechanism for grinding. The grinding temperature is 25°C, the speed of the grinder is 500r / min, and the particle size of the grinding beads is 0.7mm. After grinding for 4 hours, the particle size of the solid particles in the grinding liquid slurry is tested. When the maximum particle size of the solid particles is less than 3000nm, stop grinding immediately to obtain a white slurry;

[0060] Step 2: Preparation of ink solvent: 15 parts of moisturizer, 3 parts of surfactant, 0.8 parts of defoamer, 20 parts of adhesive and 25 parts of water are mixed evenly to obtain ink solvent;

[0061] Step 3: preparing a crude ink product, mixing the white slurry obtained in step 1 with the ink solvent obtained in step 2 at a mass ratio of 1:5 for 1 hour to obtain a crude ink product;

[0062] Step 4: Sedimentation of the crude ink product. Add the crude ink product prepared in step 3 into a sedimentation barrel. At 20°C, the viscosity of the crude ink product is 6cp and the liquid level is 50cm.

[0063] Step 5: Separate the upper ink layer and test the particle size of the upper ink layer. When the maximum particle size does not exceed 1000nm, it is qualified. Use a suction tube to extract the upper ink layer. The height of the suction tube from the outlet is 2cm. The sedimentation time is 25 days.

[0064] Step 6: recycling the lower ink. After the upper ink is separated in step 5, the remaining lower ink is added to the lower ink. The volume ratio of the ink solvent to the lower ink is 1:10. After stirring and mixing, the viscosity reaches below 7cp. If the viscosity exceeds 7cp, the above volume of ink solvent can be added again. The lower ink is filtered through a 1000nm PP filter membrane at a filtration pressure of 0.1MPa. The lower ink after removing most of the particles with a particle size of more than 1000nm is mixed with the white slurry in step 1 and the ink solvent in step 2 to obtain a crude ink product again.

[0065] Step 7: Finished product preparation: filter the upper ink through a filter net, and package it after filtration to obtain a white ink finished product. The filter net is a stainless steel net with a pore size of 5um.

[0066] Example 2

[0067] This embodiment provides a method for preparing DTF white ink by sedimentation method, combined with Figure 1 As shown, the following steps are included:

[0068] Step 1: Grind to prepare white slurry, add a white slurry raw material containing 39 parts of water, 15 parts of dispersant, 1 part of surfactant and 45 parts of titanium dioxide into a stirring device, stir and disperse for 1 hour, and then transfer to a grinding mechanism for grinding. The grinding temperature is 25°C, the speed of the grinder is 500r / min, and the particle size of the grinding beads is 0.7mm. After grinding for 4 hours, the particle size of the solid particles in the grinding liquid slurry is tested. When the maximum particle size of the solid particles is less than 3000nm, stop grinding immediately to obtain a white slurry;

[0069] Step 2: Preparation of ink solvent: 15 parts of moisturizer, 3 parts of surfactant, 0.8 parts of defoamer, 20 parts of adhesive and 25 parts of water are mixed evenly to obtain ink solvent;

[0070] Step 3: preparing a crude ink product, mixing the white slurry obtained in step 1 with the ink solvent obtained in step 2 at a mass ratio of 1:5 for 1 hour to obtain a crude ink product;

[0071] Step 4: Sedimentation of the crude ink product. The crude ink product prepared in step 3 is added into a sedimentation barrel. At 30°C, the viscosity of the crude ink product is 5.5 cp and the liquid level is 100 cm.

[0072] Step 5: Separate the upper ink layer and test the particle size of the upper ink layer. When the maximum particle size does not exceed 1000nm, it is qualified. Use a suction tube to extract the upper ink layer. The height of the suction tube from the outlet is 4cm. The sedimentation time is 20 days.

[0073] Step 6: recycling the lower ink. After the upper ink is separated in step 5, the remaining lower ink is added to the lower ink. The volume ratio of the ink solvent to the lower ink is 1:10. After stirring and mixing, the viscosity reaches below 7cp. If the viscosity exceeds 7cp, the above volume of ink solvent can be added again. The lower ink is filtered through a 1000nm PP filter membrane at a filtration pressure of 0.1MPa. The lower ink after removing most of the particles with a particle size of more than 1000nm is mixed with the white slurry in step 1 and the ink solvent in step 2 to obtain a crude ink product again.

[0074] Step 7: Finished product preparation: filter the upper ink through a filter net, and package it after filtration to obtain a white ink finished product. The filter net is a stainless steel net with a pore size of 5um.

[0075] Example 3

[0076] This embodiment provides a method for preparing DTF white ink by sedimentation method, combined with Figure 1 As shown, the following steps are included:

[0077] Step 1: Grind to prepare white slurry. Add the white slurry raw material containing 50 parts of water, 10 parts of dispersant and 40 parts of titanium dioxide into the stirring device, stir and disperse for 0.5 hours, and then transfer to the grinding mechanism for grinding. The grinding temperature is 20°C, the speed of the grinder is 400r / min, the particle size of the grinding beads is 0.6mm, and the grinding time is 3 hours, until the maximum particle size of the solid particles in the slurry is less than 3000nm or the slurry can reach 10g / cm by filtration with a 3000nm nylon filter membrane. 2 When the filtration value is above 0.05, stop grinding and obtain white slurry;

[0078] Step 2: Preparation of ink solvent: 20 parts of moisturizer, 1 part of surfactant, 0.5 parts of defoamer, 10 parts of adhesive and 20 parts of water are mixed evenly to obtain ink solvent;

[0079] Step 3: preparing a crude ink product, mixing the white slurry obtained in step 1 with the ink solvent obtained in step 2 at a mass ratio of 1:4 to obtain a crude ink product;

[0080] Step 4: Settling of the crude ink product. Add the crude ink product prepared in step 3 into the settling barrel, measure the liquid level and viscosity of the crude ink product in the settling barrel, and control the liquid level to be 50 cm and the viscosity to be 6 cp.

[0081] Step 5: The upper ink is separated and settled until the maximum particle size of the solid particles in the upper ink is less than 1000nm or the upper ink can reach 100g / cm by filtration with a 1000nm nylon filter membrane. 2 When the filtration value is above 0.05, the upper layer of ink is extracted by using a liquid extraction tube, the height of the liquid extraction tube from the outlet is 2 cm, and the sedimentation time is 20 days;

[0082] Step 6: recycling the lower ink. After the upper ink is separated in step 5, the lower ink remains. The ink solvent prepared in step 2 is added to the lower ink, wherein the volume ratio of the ink solvent to the lower ink is 1:10. After filtering through a 1000nm PP filter membrane, the lower ink is mixed with the white slurry in step 1 and the ink solvent in step 2 to obtain a crude ink product.

[0083] Step 7: Finished product preparation: filter the upper ink through a filter net, and package it after filtration to obtain a white ink finished product. The filter net is a stainless steel net with a pore size of 5um.

[0084] Example 4

[0085] This embodiment provides a method for preparing DTF white ink by sedimentation method, combined with Figure 1 As shown, the following steps are included:

[0086] Step 1: Grind to prepare white slurry. Add 35 parts of water, 15 parts of dispersant and 45 parts of titanium dioxide into a stirring device, stir and disperse for 1 hour, and then transfer to a grinding mechanism for grinding. The grinding temperature is 30°C, the speed of the grinder is 600r / min, the particle size of the grinding beads is 0.8mm, and the grinding time is 5 hours, until the maximum particle size of the solid particles in the slurry is less than 3000nm or the slurry can reach 10g / cm by filtration with a 3000nm nylon filter membrane. 2 When the filtration value is above 0.05, stop grinding and obtain white slurry;

[0087] Step 2: Preparation of ink solvent: 10 parts of moisturizer, 5 parts of surfactant, 1 part of defoamer, 30 parts of adhesive and 30 parts of water are mixed evenly to obtain ink solvent;

[0088] Step 3: preparing a crude ink product, mixing the white slurry obtained in step 1 with the ink solvent obtained in step 2 at a mass ratio of 1:6 to obtain a crude ink product;

[0089] Step 4: Settling of the crude ink product. Add the crude ink product prepared in step 3 into the settling barrel, measure the liquid level and viscosity of the crude ink product in the settling barrel, and control the liquid level to be 100 cm and the viscosity to be 7 cp.

[0090] Step 5: The upper ink is separated and settled until the maximum particle size of the solid particles in the upper ink is less than 1000nm or the upper ink can reach 100g / cm by filtration with a 1000nm nylon filter membrane. 2 When the filtration value is above 0.05, the upper layer of ink is extracted by using a liquid extraction tube, the height of the liquid extraction tube from the outlet is 4 cm, and the sedimentation time is 30 days;

[0091] Step 6: recycling the lower ink. After the upper ink is separated in step 5, the lower ink remains. The ink solvent prepared in step 2 is added to the lower ink, wherein the volume ratio of the ink solvent to the lower ink is 1:5. After filtering through a 1000nm PP filter membrane, the ink is mixed with the white slurry in step 1 and the ink solvent in step 2 to obtain a crude ink product.

[0092] Step 7: Finished product preparation: filter the upper ink through a filter net, and package it after filtration to obtain a white ink finished product. The filter net is a stainless steel net with a pore size of 5um.

[0093] Comparative Example 1

[0094] The sedimentation time in Example 1 was adjusted to obtain white ink products with different sedimentation times. The white ink products and the white ink products in Example 1 were tested for smoothness and whiteness. The inks with different sedimentation times were printed using a DTF printer with an EPSON XP-600 nozzle. The ink breakage rate after printing 10m of the image was tested. The printed layer was then dried at 130°C for 10 minutes and the whiteness was tested using a spectrophotometer. The results are shown in the following table:

[0095] Printing smoothness and whiteness at different times after settling in a settling bucket at 20℃ and 50cm height

[0096]

[0097] Comparative Example 2

[0098] The sedimentation time in Example 2 was adjusted to obtain white ink products with different sedimentation times. The white ink products and the white ink products in Example 2 were tested for smoothness and whiteness. The inks with different sedimentation times were printed using a DTF printer with an EPSON XP-600 nozzle. The ink breakage rate after printing an image for 10 m was tested. The printed layer was then dried at 130° C. for 10 minutes and then tested for whiteness using a spectrophotometer. The results are shown in the following table:

[0099] Printing smoothness and whiteness after settling for different time in a settling barrel at 30℃ and 100cm height

[0100]

[0101] Comparative Example 3

[0102] The finished white ink prepared in Example 2 is recorded as white ink 1;

[0103] 100 parts of the ink solvent prepared in Example 2 and 20 parts of the white slurry prepared in Example 2 were taken, stirred and mixed for 1 hour, and then directly filtered through a 1000 nm PP filter membrane to obtain white ink 2;

[0104] 100 parts of the ink solvent prepared in Example 2 and 20 parts of the white slurry prepared in Example 2 were taken, stirred and mixed for 1 hour, and then directly filtered through a 1000 nm PP filter membrane, and then re-filtered through a 1000 nm nylon filter membrane to obtain white ink 3;

[0105] The white slurry in Example 2 was deeply ground, and the maximum pigment particle size was tested to be less than 1000 nm. Then 100 parts of the ink solvent prepared in Example 2 were taken, 20 parts of the ground white slurry were added, and after stirring for 1 hour, the mixture was directly filtered through a 1000 nm PP filter membrane to obtain white ink 4.

[0106] Using a DTF printer with an EPSON XP-600 nozzle, set the same printing conditions, use white inks 1-4 to print, and use the same method as described in Comparative Example 1 to test the printing smoothness and whiteness of various white inks. The results are shown in the following table:

[0107]

[0108] The specific embodiments described herein are merely examples of the spirit of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in similar ways, but they will not deviate from the spirit of the present invention or exceed the scope defined by the appended claims.

[0109] Although the terms such as upper layer 1, lower layer 2, outlet 3, and liquid extraction tube 4 are used more frequently in this article, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional restrictions is contrary to the spirit of the present invention.

Claims

1. A method for preparing DTF white ink by sedimentation method, characterized in that: The following steps are involved: Step 1: Grind and prepare white slurry. Add the white slurry raw materials containing water, dispersant and titanium dioxide into a stirring device, stir and disperse, and then transfer to a grinder for grinding until the maximum particle size of the solid particles in the slurry is less than 3000nm or the slurry can reach 10g / cm2 by filtering with a 3000nm nylon filter membrane. 2 When the filtration value is above 0.05, stop grinding and obtain white slurry; Step 2: preparing the ink solvent, mixing the moisturizer, surfactant, defoamer, adhesive and water evenly to obtain the ink solvent; Step 3: preparing a crude ink product, mixing and stirring the white slurry prepared in step 1 and the ink solvent prepared in step 2 to obtain a crude ink product; Step 4: Settling of the crude ink product. Add the crude ink product prepared in step 3 into the settling barrel, measure the liquid level and viscosity of the crude ink product in the settling barrel, and control the liquid level to be 50-100 cm and the viscosity to be below 7 cp. Step 5: The upper ink is separated and settled until the maximum particle size of the solid particles in the upper ink is less than 1000nm or the upper ink can reach 100g / cm by filtration with a 1000nm nylon filter membrane. 2 When the filtration value is above 0.04, use the liquid extraction tube to extract the upper ink; Step 6: Finished product preparation: filter the upper layer of ink using a filter, and then package it to obtain a white ink finished product.

2. The method for preparing DTF white ink by sedimentation method according to claim 1, characterized in that: It also includes the steps of recycling the lower ink layer: After the upper ink is separated in step five, the lower ink remains. The ink solvent prepared in step two is added to the lower ink, filtered through a 1000nm PP filter membrane, and then mixed with the white slurry in step one and the ink solvent in step two to obtain a crude ink.

3. A method for preparing DTF white ink by sedimentation method according to claim 2, characterized in that: The volume ratio of the ink solvent to the lower layer ink is 1-2:

10.

4. The method for preparing DTF white ink by sedimentation method according to claim 1, characterized in that: In the step 1, the white slurry raw material includes 10-15 parts by weight of a dispersant, 40-45 parts by weight of titanium dioxide, and 35-50 parts by weight of water.

5. The method for preparing DTF white ink by sedimentation method according to claim 1, characterized in that: In the step 1, the stirring time for the stirring and dispersing is 0.5-1h.

6. The method for preparing DTF white ink by sedimentation method according to claim 1, characterized in that: In the step 1, the grinding temperature is 20-30° C., the rotation speed of the grinder is 400-600 r / min, the particle size of the grinding beads is 0.6-0.8 mm, and the grinding time is 3-5 h.

7. The method for preparing DTF white ink by sedimentation method according to claim 1, characterized in that: In the step 2, the ink solvent includes 10-20 parts by weight of a moisturizer, 1-5 parts by weight of a surfactant, 0.5-1 parts by weight of a defoamer, 10-30 parts by weight of an adhesive, and 20-30 parts by weight of water.

8. The method for preparing DTF white ink by sedimentation method according to claim 1, characterized in that: In the step three, the mass ratio of the added white slurry to the ink solvent is 1:4-6.

9. The method for preparing DTF white ink by sedimentation method according to claim 1, characterized in that: In the step 5, the height of the liquid extraction tube from the outlet is 2-4 cm, and the sedimentation time is 20-30 days.

10. The method for preparing DTF white ink by sedimentation method according to claim 1, characterized in that: In step six, the filter mesh is a stainless steel mesh with a pore size of 5 um.

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