A kind of cotton / lyocell blended fabric inkjet printing pretreatment agent and pretreatment method for directional regulation of ink drop spreading penetration

Abstract

This invention belongs to the field of textile dyeing and finishing technology, and particularly relates to a pretreatment agent and method for inkjet printing of cotton / lyocell blended fabrics with directional control of ink droplet spreading and penetration. This invention employs independently formulated components A and B, applied in layers to construct a hydrophilic-weakly hydrophobic bilayer interface on the fabric surface: the inner hydrophilic polymer creates an osmotic pressure difference, driving the ink droplets to fully penetrate longitudinally; the outer weakly hydrophobic polymer inhibits the lateral spreading of ink droplets; supplemented by surfactants, swelling agents, and crosslinking agents for synergistic regulation, it precisely adapts to the characteristics of cotton / lyocell bicomponent fibers, effectively solving problems in existing pretreatment technologies such as difficulty in simultaneously achieving anti-bleeding and deep penetration, easy bleeding, white showing, and color difference between the front and back sides. This invention achieves controllable ink droplet spreading diameter, clear printed patterns, excellent color fastness, a uniform and stable pretreatment agent system, simple application process, environmental friendliness, and compatibility with cotton / lyocell fabrics of any blend ratio, possessing good industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of textile dyeing and finishing technology, and particularly relates to a pretreatment agent and pretreatment method for inkjet printing of cotton / lyocell blended fabrics that allows for directional control of ink droplet spreading and penetration. Background Technology

[0002] Inkjet printing technology, with its advantages of short process flow, rich colors, fine patterns, and environmental friendliness and water conservation, has become the mainstream development direction in the textile printing industry, and its application is becoming increasingly widespread in industries such as clothing and home textiles. Cotton / lyocell blended fabrics are made by blending natural cotton fibers with regenerated lyocell cellulose fibers. They combine the moisture-wicking and skin-friendly properties of cotton fibers with the softness and smoothness of lyocell fibers, offering superior comfort compared to pure cotton fabrics. This makes them an important base material for high-end apparel and home textile fabrics.

[0003] However, there are significant differences in the surface hydrophilicity of cotton fiber and lyocell fiber. Lyocell fiber is significantly more hydrophilic than cotton fiber. After the two are blended, there are still many technical problems that need to be solved in the inkjet printing process. First, due to the difference in hydrophilicity and hydrophobicity between the two types of fibers, the spreading behavior of ink droplets when sprayed onto the surface of cotton / lyocell blended fabrics is difficult to synchronize, easily leading to problems such as uneven ink droplet distribution and reduced clarity of printed patterns. Second, cotton / lyocell blended fabrics have strong overall hydrophilicity, and ink droplets are easily driven by the capillary effect between fibers upon contact with the fabric, resulting in irregular lateral spreading and insufficient longitudinal penetration into the fabric. This ultimately leads to poor depth and weak three-dimensionality of the printed pattern, as well as insufficient dye fixation, resulting in low color fastness of the printed fabric. Finally, most existing pretreatment agents for inkjet printing of fabrics use anti-bleeding agents to block the capillary channels of fibers, simply inhibiting the lateral spreading of ink droplets. While this method hinders ink droplet penetration, it also significantly inhibits the longitudinal penetration of ink droplets into the fabric, failing to meet the dual requirements of anti-bleeding and penetration promotion. This easily leads to printing defects such as low color yield, floating color on the fabric surface, and white spots, seriously restricting the improvement of printing quality.

[0004] Currently, the research and development of pretreatment technology for inkjet printing of textiles mainly focuses on the single control of the lateral spread of ink droplets. For example, in existing public technologies, Chinese patent CN202010959197.7 discloses a method to improve the penetration effect of inkjet printing on cellulose fiber fabrics, using sodium alginate, modified plant gum, etc. as anti-permeability agents, which improves the printing penetration to a certain extent, but still does not solve the problem of not being able to simultaneously achieve anti-permeability and penetration promotion; Chinese patent CN202210440200.3 discloses a pretreatment agent for inkjet printing on pure cotton fabrics, using hydrophilic polymers such as propylene glycol alginate and hydroxyethyl methyl cellulose, which simplifies the paste-making process, but is only applicable to pure cotton fabrics and cannot meet the printing needs of cotton / lyocell blended fabrics; Chinese patent CN202210378357.8 discloses a pretreatment agent and treatment process for inkjet printing on cotton / polyamide fabrics, which uses alkaline and acidic environments to regulate dye fixation and improve the color depth of the fabric. This solution is only for cotton and polyamide fibers and does not involve the regulation of hydrophilic and hydrophobic differences in cotton / lyocell blended fabrics.

[0005] In summary, existing inkjet printing pretreatment technologies are mostly designed for single-fiber fabrics. For cotton / lyocell blended fabrics, there is a lack of pretreatment solutions that can directionally control the spreading and penetration behavior of ink droplets. This fails to address core technical issues such as uneven printing caused by the difference in hydrophilicity between the two fiber types, the difficulty in simultaneously achieving anti-bleeding and penetration-promoting effects, poor print three-dimensionality, and insufficient color fastness. Therefore, developing an inkjet printing pretreatment agent and method that can directionally control the lateral spreading and longitudinal penetration of ink droplets and is suitable for cotton / lyocell blended fabrics is of significant practical importance for improving the inkjet printing quality of cellulose blended fabrics and promoting the development of green printing and dyeing technologies. This is also the technical problem that this invention aims to solve. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the technical problem to be solved by this invention is to provide a pretreatment agent and pretreatment method for inkjet printing of cotton / lyocell blended fabrics that enables controllable ink droplet spreading diameter, sufficient longitudinal penetration, and effectively avoids printing and dyeing defects such as bleeding, white showing, and low color yield. This method also solves the problem of color difference between the front and back sides of blended fabrics, thereby obtaining clear printed patterns, excellent color fastness, a simple process, and is environmentally friendly.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a pretreatment agent for inkjet printing of cotton / lyocell blended fabrics with directional control of ink droplet spreading and penetration, wherein the pretreatment agent consists of two parts, component A and component B, which are independently formulated and applied in steps; component A, by mass parts, includes the following components: 1-10 parts of hydrophilic polymer, 0.1-1.0 parts of surfactant, 1-12 parts of swelling agent, 0.5-5 parts of alkali agent, and the balance being water; component B, by mass parts, includes the following components: 0.5-5 parts of weakly hydrophobic polymer, ... The crosslinking agent comprises 0.1-2.0 parts, with the remainder being water; the hydrophilic polymer is at least one or a combination of at least two of sodium alginate, propylene glycol alginate, guar gum, locust bean gum, and xanthan gum, and the surface energy dispersion component of the hydrophilic polymer after film formation is ≥40 mN / m; the weakly hydrophobic polymer is at least one or a combination of at least two of ethyl cellulose, cellulose acetate, methyl cellulose, hydroxypropyl methyl cellulose, propylene glycol alginate, and acetylated starch, and the surface energy dispersion component of the weakly hydrophobic polymer after film formation is 30-40 mN / m.

[0008] The aforementioned pretreatment agent for inkjet printing of cotton / lyocell blended fabrics with directional control of ink droplet spreading and penetration has the following properties at 25°C: pH value of component A and component B are both 4.0-6.5, viscosity is both 25-400 mPa·s, and surface tension is both 25-45 mN / m.

[0009] In the aforementioned pretreatment agent for inkjet printing of cotton / lyocell blended fabrics with directional control of ink droplet spreading and penetration, the mass percentage of solid particles with a particle size greater than 1 micrometer in each of components A and B is no higher than 0.1%.

[0010] The aforementioned pretreatment agent for inkjet printing of cotton / lyocell blended fabrics with directional control of ink droplet spreading and penetration, wherein the surfactant is at least one or a combination of at least two of the following: acetylenic glycol ethoxylate, polyether-modified polysiloxane, alkyl glycoside, acetylenic glycol block polyether, sodium dodecyl sulfate, and alkylphenol polyoxyethylene ether.

[0011] The aforementioned pretreatment agent for inkjet printing of cotton / lyocell blended fabrics with directional control of ink droplet spreading and penetration, wherein the crosslinking agent is at least one or a combination of at least two of the following: blocked isocyanate, polycarbodiimide, glyoxal, polyethylene glycol dimethacrylate, and dimethyloldihydroxyethylene urea; and the swelling agent is at least one or a combination of at least two of the following: urea, ethylene glycol, 1,2-propanediol, diethylene glycol, and polyethylene glycol 200.

[0012] The aforementioned pretreatment agent for inkjet printing of cotton / lyocell blended fabrics with directional control of ink droplet spreading and penetration, wherein the alkaline agent is at least one or a combination of at least two of sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide.

[0013] A pretreatment method for a cotton / lyocell blended fabric inkjet printing pretreatment agent that allows for directional control of ink droplet spreading and penetration, comprising the following steps: Pretreatment of the cotton / lyocell blended fabric with the aforementioned pretreatment agent, applying component A first, followed by component B.

[0014] (1) Apply the above component A to the surface of cotton / lyocell blended fabric by spraying or scraping, and dry; the liquid content of component A on the fabric surface is 50%-90%, the drying temperature is 80-120℃, and the drying time is 1-5 minutes.

[0015] (2) Apply the above component B to the surface of the fabric obtained in step (1) by spraying or scraping, and dry it; the liquid content of component B on the fabric surface is 50%-90%, the drying temperature is 80-120℃, and the drying time is 1-5 minutes.

[0016] (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is steamed, washed and dried in sequence to obtain the printed fabric.

[0017] In the above pretreatment method, in step (3), the temperature is controlled at 100℃-115℃ and the time is 12-20 minutes when steaming for color fixing; the water washing is done with room temperature water, and the washing is done 3 times, with each washing time being 5 minutes; the drying temperature is controlled at 80℃-120℃ and the drying time is 1-3 minutes.

[0018] The advantages of the pretreatment agent and method for inkjet printing of cotton / lyocell blended fabrics with directional control of ink droplet spreading and penetration in this invention are: This invention abandons the traditional single-impermeability approach of pretreatment agents, and based on the innovative concept of gradient interface control and unidirectional directional moisture conduction, it adopts a layered structure design to achieve precise decoupling control of the lateral spreading and vertical depth penetration of ink droplets. The overall control mechanism consists of three layers:

[0019] 1. Surface anti-seepage control: The outer layer is constructed with a weak hydrophobic polymer layer to form a "dynamic barrier" at the interface, which moderately increases the contact angle between ink droplets and fabric, effectively inhibits the lateral spread and diffusion of ink droplets along the fiber capillary network, avoids printing smudging and fuzzy edge defects from the source, and ensures the clarity and sharpness of the printed pattern edges.

[0020] 2. Inner layer directional penetration control: The inner layer is equipped with a hydrophilic polymer layer, which forms a stable hydrophilic-hydrophobic gradient with the outer layer, generating an osmotic pressure difference from the outside to the inside, driving ink droplets to break through the weak hydrophobic barrier of the surface layer, and realizing rapid and uniform vertical directional penetration of dye;

[0021] 3. Synergistic regulation of functional auxiliaries: The compounding of functional components such as surfactants, swelling agents, and crosslinking agents precisely matches the high-frequency jetting frequency of inkjet printing, optimizes the internal diffusion behavior of dyes in fibers, improves the interfacial bonding stability of the double-layer coating, adapts to the two-component fiber characteristics of cotton-lyocell blended fabrics, and effectively improves the technical problem of color difference between the front and back sides of the print.

[0022] This invention first constructs a hydrophilic-weakly hydrophobic dual-layer directional conditioning layer on the surface of cotton / lyocell blended fabrics. Relying on the synergistic effect of the osmotic pressure of the inner hydrophilic polymer and the outer weakly hydrophobic polymer, it simultaneously achieves inhibition of lateral ink droplet spreading and deep longitudinal penetration. This fundamentally solves the core problem in existing pretreatment technologies where it is difficult to simultaneously achieve anti-seepage and deep penetration, thus ensuring both high printing clarity and high dye fixation efficiency. Furthermore, this invention uses a specialized surfactant with low dynamic surface tension and a fast response rate, making it suitable for high-speed digital inkjet printing. The synergistic regulation of fiber surface energy by each component allows it to be adapted to cotton / lyocell fabrics with any blend ratio.

[0023] Furthermore, the functional auxiliaries and the double-layer interface structure work synergistically to significantly improve the wash and abrasion fastness of the print, without compromising the inherent moisture absorption, breathability, and softness of the fabric, thus balancing print functionality and wearing comfort. This pretreatment agent system is homogeneous and stable, exhibiting no agglomeration or precipitation. The application process is simple and easy, requiring no modification to existing digital printing equipment, and can directly achieve continuous industrial production, effectively reducing enterprise production costs. It possesses strong engineering practicality and industrial promotion value. Attached Figure Description

[0024] Figure 1 This is a comparison diagram of the longitudinal and latitudinal diffusion lengths of ink droplets under different pretreatment systems of this invention;

[0025] Figure 2 This is a comparison of the apparent clarity of inkjet printed patterns using different pretreatment systems of the present invention.

[0026] Figure 3 This diagram illustrates the effect of the double-layer pretreatment structure of the present invention on the regulation of ink droplet spreading and longitudinal penetration behavior.

[0027] Figure 4 This is a microscopic SEM image of the hydrophilic-weakly hydrophobic double-layer pretreated fabric of the present invention. Detailed Implementation

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] In this invention, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the device in its actual use or operating state, specifically the drawing directions in the accompanying drawings; while "inner" and "outer" refer to the outline of the device. Furthermore, in the description of this application, the term "comprising" means "including but not limited to". The terms first, second, third, etc., are used merely as illustrative purposes and do not impose numerical requirements or establish an order. The term "multiple" means "two or more".

[0030] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics, characterized by directional control of ink droplet spreading and penetration, comprises two parts, component A and component B, which are formulated independently and applied in stages. Component A, by weight, includes the following components: 1-10 parts of a hydrophilic polymer, 0.1-1.0 parts of a surfactant, 1-12 parts of a swelling agent, 0.5-5 parts of an alkali agent, with the balance being water. Component B, by weight, includes the following components: 0.5-5 parts of a weakly hydrophobic polymer, 0.1-2.0 parts of a crosslinking agent. The film contains 1 part water, with the remainder being water; the hydrophilic polymer is at least one or a combination of at least two of sodium alginate, propylene glycol alginate, guar gum, locust bean gum, and xanthan gum, and the surface energy dispersion component of the hydrophilic polymer after film formation is ≥40mN / m; the weakly hydrophobic polymer is at least one or a combination of at least two of ethyl cellulose, cellulose acetate, methyl cellulose, hydroxypropyl methyl cellulose, propylene glycol alginate, and acetylated starch, and the surface energy dispersion component of the weakly hydrophobic polymer after film formation is 30-40mN / m.

[0031] In this invention, at 25°C, the pH values ​​of components A and B are both 4.0-6.5, the viscosities are both 25-400 mPa·s, and the surface tensions are both 25-45 mN / m. Furthermore, the mass percentage of solid particles with a diameter greater than 1 micrometer in both components A and B is no higher than 0.1%.

[0032] The surfactant is at least one or a combination of at least two of the following: acetylenic glycol ethoxylate, polyether-modified polysiloxane, alkyl glycoside, acetylenic glycol block polyether, sodium dodecyl sulfate, and alkylphenol polyoxyethylene ether. The crosslinking agent is at least one or a combination of at least two of the following: blocked isocyanate, polycarbodiimide, glyoxal, polyethylene glycol dimethacrylate, and dimethyloldihydroxyvinyl urea. The swelling agent is at least one or a combination of at least two of the following: urea, ethylene glycol, 1,2-propanediol, diethylene glycol, and polyethylene glycol 200. The alkali agent is at least one or a combination of at least two of the following: sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide.

[0033] In this process, the hydrophilic polymer acts on the fabric-sizing interface, forming a film that anchors the entire layer to the fabric surface, controlling the penetration depth of ink droplets into the fabric. Surfactants are used to adjust the dynamic surface tension of the pretreatment agent to match the jetting frequency of inkjet printing droplets. Swelling agents cause the fiber and sizing coating to swell during steaming, forming channels and promoting dye diffusion into the fiber. Alkali agents are used to form chemical bonds between the fabric and the dye in the ink, improving print fastness. A weakly hydrophobic polymer coats the hydrophilic polymer layer, forming a transparent film on the fabric surface to control the spreading diameter of ink droplets. Crosslinking agents are used for bonding between the hydrophilic and weakly hydrophobic polymer layers, improving the stability of the sizing agent on the fabric surface.

[0034] A pretreatment method for a cotton / lyocell blended fabric inkjet printing pretreatment agent that allows for directional control of ink droplet spreading and penetration, comprising the following steps: Pretreatment of the cotton / lyocell blended fabric with the aforementioned pretreatment agent, applying component A first, followed by component B.

[0035] (1) Apply the above component A to the surface of cotton / lyocell blended fabric by spraying or scraping, and dry; the liquid content of component A on the fabric surface is 50%-90%, the drying temperature is 80-120℃, and the drying time is 1-5 minutes.

[0036] (2) Apply the above component B to the surface of the fabric obtained in step (1) by spraying or scraping, and dry it; the liquid content of component B on the fabric surface is 50%-90%, the drying temperature is 80-120℃, and the drying time is 1-5 minutes.

[0037] (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is subjected to steam fixing, washing and drying treatments in sequence to obtain the printed fabric. During steam fixing, the temperature is controlled at 100℃-115℃ and the time is 12-20 minutes. During washing, room temperature water is used for washing, and the fabric is washed 3 times, with each washing time being 5 minutes. During drying, the temperature is controlled at 80℃-120℃ and the drying time is 1-3 minutes.

[0038] The core advantage of this invention lies in the fact that, through the synergistic effect of its components, a hydrophilic / weakly hydrophobic dual-layer directional regulation system is constructed on the surface of cotton / lyocell blended fabrics, achieving precise control of ink droplet spreading and penetration. This fundamentally solves the technical problem of simultaneously achieving ink droplet spreading and penetration in existing technologies. Its mechanism of action and core advantages are as follows:

[0039] The mechanism of action of this invention can be summarized as three synergistic steps: "surface barrier, interfacial liquid absorption, and vertical flow guidance," achieving unidirectional moisture conduction and precise control of ink droplets on the fabric surface. A hydrophilic-hydrophobic gradient regulating layer is constructed on the surface of the cotton / lyocell blended fabric. A hydrophilic polymer forms the inner layer, and a weakly hydrophobic polymer covers the outer layer. The outer weakly hydrophobic polymer forms a transparent film, appropriately increasing the contact angle between the ink droplet and the fabric interface, constructing a "dynamic barrier," effectively inhibiting the lateral spread of ink droplets along the fiber capillaries, avoiding printing bleeding, and ensuring pattern clarity. The inner hydrophilic polymer is firmly anchored at the fabric-sizing interface, forming a hydrophilic-hydrophobic gradient with the outer layer, generating an osmotic pressure difference from the outside to the inside, driving the ink droplets to break through the surface barrier and quickly penetrate vertically.

[0040] This hydrophilic-hydrophobic gradient regulating layer enables directional control of ink droplet behavior in inkjet printing. Under the action of ink droplets with a volume of less than 5 μL, the spreading diameter on the fabric surface can be controlled within 9 mm, and the vertical penetration depth can reach 80% to 100% of the fabric thickness. The above mechanism endows the interface layer with the characteristics of "one-way conduction from the outside to the inside", realizing precise decoupling control of ink droplet spreading diameter and penetration depth, while taking into account both high printing clarity and efficient dye fixation.

[0041] The synergistic adaptation of each component further enhances the technical effect: the surfactant can adjust the dynamic surface tension of the pretreatment agent, precisely matching the high-frequency jetting requirements of inkjet printing (10-50kHz), avoiding ink droplet merging and splashing, and ensuring printing stability; the swelling agent can cause the fiber and the paste coating to swell during steaming, forming interconnected channels, which significantly promotes the diffusion of dye into the fiber interior; the alkali agent can promote the formation of stable chemical bonds between the fabric and the dye in the ink, greatly improving the printing fastness; the crosslinking agent achieves a strong bond between the hydrophilic polymer layer and the weakly hydrophobic polymer layer, effectively improving the adhesion stability of the paste on the fabric surface.

[0042] Furthermore, the components synergistically regulate the surface energy of cotton and lyocell fibers, effectively improving the color difference between the front and back of the blended fabric and adapting to cotton / lyocell blended fabrics of any proportion. The functional auxiliaries and the double-layer conditioning layer work together to enhance print fastness without compromising the fabric's moisture absorption, breathability, and other wearing properties. This invention features a simple process, stable performance, and requires no modification to existing digital printing equipment, demonstrating outstanding practicality and industrial application value.

[0043] The present application will be specifically described below through specific embodiments. The following embodiments are only some embodiments of the present application and are not intended to limit the present application.

[0044] Example 1

[0045] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics that allows for targeted control of ink droplet spreading and penetration, comprising two separately formulated components, A and B, with the following components by mass parts:

[0046] Component A: 1 part sodium alginate (hydrophilic polymer, surface energy dispersion component of 42mN / m after film formation), 0.1 part acetylacetonate ethoxylate (surfactant), 1 part urea (swelling agent), 0.5 part sodium hydroxide (alkali agent), and 87.4 parts deionized water; Preparation method of component A: Add each component to deionized water in sequence and stir at room temperature until completely dissolved to obtain component A.

[0047] Component B: 0.5 parts of ethyl cellulose (weakly hydrophobic polymer, surface energy dispersion component of 32mN / m after film formation), 0.1 parts of blocked isocyanate (crosslinking agent), and 99.4 parts of deionized water; Preparation method of component B: add each component to deionized water, stir and disperse evenly at room temperature to obtain component B.

[0048] Citric acid was used to adjust the pH of components A and B to 4.0 respectively. The pretreatment agent had a viscosity of 25 mPa·s and a surface tension of 25 mN / m at 25°C. The content of solid particles with a particle size greater than 1 micrometer in both components A and B was ≤0.1%.

[0049] The pretreatment method of this pretreatment agent includes the following steps:

[0050] (1) Apply the above component A to the surface of cotton / lyocell blended fabric (cotton fiber:lyocell fiber = 60:40) by spraying and dry; the liquid content of component A on the fabric surface is 50%, the drying temperature is 80℃, and the drying time is 5 minutes.

[0051] (2) Apply the above component B to the surface of the fabric obtained in step (1) by spraying and dry it; the liquid content of component B on the fabric surface is 50%, the drying temperature is 80°C, and the drying time is 5 minutes.

[0052] (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is subjected to steam fixing, washing and drying treatments in sequence to obtain the printed fabric. The steam fixing temperature is 100℃ and the time is 20 minutes; the washing is done with room temperature water for a total of 3 times, each time for 5 minutes; the drying temperature is 100℃ and the drying time is 3 minutes.

[0053] Example 2

[0054] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics that allows for targeted control of ink droplet spreading and penetration, comprising two separately formulated components, A and B, with the following components by mass parts:

[0055] Component A: 4 parts guar gum (hydrophilic polymer, surface energy dispersion component of 45 mN / m after film formation), 0.4 parts polyether modified polysiloxane (surfactant), 5 parts ethylene glycol (swelling agent), 2 parts sodium carbonate (alkali agent), and 88.6 parts deionized water; Preparation method of component A: Add each component to deionized water in sequence and stir at room temperature until completely dissolved to obtain component A.

[0056] Component B: 2 parts cellulose acetate (weakly hydrophobic polymer, surface energy dispersion component of 35mN / m after film formation), 0.8 parts polycarbodiimide (crosslinking agent), and 97.2 parts deionized water; Preparation method of component B: add each component to deionized water, stir and disperse evenly at room temperature to obtain component B.

[0057] Tartaric acid was used to adjust the pH of components A and B to 5.0 respectively. The pretreatment agent had a viscosity of 100 mPa·s and a surface tension of 30 mN / m at 25°C. The content of solid particles with a particle size greater than 1 micrometer in both components A and B was ≤0.1%.

[0058] The pretreatment method of this pretreatment agent includes the following steps:

[0059] (1) Apply the above component A to the surface of cotton / lyocell blended fabric (cotton fiber:lyocell fiber = 30:70) by scraping and dry; the liquid retention rate of component A on the fabric surface is 65%, the drying temperature is 90℃, and the drying time is 3 minutes.

[0060] (2) Apply the above component B to the surface of the fabric obtained in step (1) by scraping, and dry it; the liquid content of component B on the fabric surface is 65%, the drying temperature is 90°C, and the drying time is 3 minutes.

[0061] (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is subjected to steam fixing, washing and drying treatments in sequence to obtain the printed fabric. The steam fixing temperature is 105℃ and the time is 18 minutes; the washing is done with room temperature water for a total of 3 times, each time for 5 minutes; the drying temperature is 100℃ and the drying time is 3 minutes.

[0062] Example 3

[0063] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics that allows for targeted control of ink droplet spreading and penetration, comprising two separately formulated components, A and B, with the following components by mass parts:

[0064] Component A: 7 parts xanthan gum (hydrophilic polymer, surface energy dispersion component of 48 mN / m after film formation), 0.7 parts alkyl glycoside (surfactant), 8 parts 1,2-propanediol (swelling agent), 3.5 parts sodium bicarbonate (alkali agent), and 80.8 parts deionized water; Preparation method of component A: Add each component to deionized water in sequence and stir at room temperature until completely dissolved to obtain component A.

[0065] Component B: 3.5 parts of methylcellulose (weakly hydrophobic polymer, surface energy dispersion component of 38mN / m after film formation), 1.2 parts of glyoxal (crosslinking agent), and 95.3 parts of deionized water; Preparation method of component B: Add each component to deionized water, stir and disperse evenly at room temperature to obtain component B.

[0066] The pH values ​​of components A and B were adjusted to 5.5 using acetic acid. The pretreatment agent had a viscosity of 200 mPa·s and a surface tension of 35 mN / m at 25°C. The content of solid particles with a diameter greater than 1 micrometer in both components A and B was ≤0.1%.

[0067] The pretreatment method of this pretreatment agent includes the following steps:

[0068] (1) The above component A is applied to the surface of cotton / lyocell blended fabric (cotton fiber:lyocell fiber = 70:30) by spraying and then dried; the liquid content of component A on the fabric surface is 75%, the drying temperature is 100℃, and the drying time is 2 minutes.

[0069] (2) Apply the above component B to the surface of the fabric obtained in step (1) by spraying and dry it; the liquid content of component B on the fabric surface is 75%, the drying temperature is 100°C, and the drying time is 2 minutes.

[0070] (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is subjected to steam fixing, washing and drying treatments in sequence to obtain the printed fabric. The steam fixing temperature is 108℃ and the time is 18 minutes; the washing is done with room temperature water for a total of 3 times, each time for 5 minutes; the drying temperature is 100℃ and the drying time is 2 minutes.

[0071] Example 4

[0072] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics that allows for targeted control of ink droplet spreading and penetration, comprising two separately formulated components, A and B, with the following components by mass parts:

[0073] Component A: 10 parts of propylene glycol alginate (hydrophilic polymer, surface energy dispersion component of 41 mN / m after film formation), 1.0 part of acetylacetonate block polyether (surfactant), 12 parts of diethylene glycol (swelling agent), 5 parts of potassium hydroxide (alkali agent), and 72 parts of deionized water; Preparation method of component A: Add each component to deionized water in sequence and stir at room temperature until completely dissolved to obtain component A.

[0074] Component B: 5 parts acetylated starch (weakly hydrophobic polymer, surface energy dispersion component of 31mN / m after film formation), 2.0 parts polyethylene glycol dimethacrylate (crosslinking agent), and 93 parts deionized water; Preparation method of component B: Add each component to deionized water, stir and disperse evenly at room temperature to obtain component B.

[0075] Sodium citrate was used to adjust the pH of components A and B to 6.5 respectively. The pretreatment agent had a viscosity of 400 mPa·s and a surface tension of 45 mN / m at 25°C. The content of solid particles with a particle size greater than 1 micrometer in both components A and B was ≤0.1%.

[0076] The pretreatment method of this pretreatment agent includes the following steps:

[0077] (1) Apply the above component A to the surface of cotton / lyocell blended fabric (cotton fiber:lyocell fiber = 10:90) by scraping and dry; the liquid retention rate of component A on the fabric surface is 90%, the drying temperature is 120℃, and the drying time is 1 minute.

[0078] (2) Apply the above component B to the surface of the fabric obtained in step (1) by scraping, and dry it; the liquid rate of component B on the fabric surface is 90%, the drying temperature is 120°C, and the drying time is 1 minute.

[0079] (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is subjected to steam fixing, washing and drying treatments in sequence to obtain the printed fabric. The steam fixing temperature is 115℃ and the time is 12 minutes; the washing is done with room temperature water for a total of 3 times, each time for 5 minutes; the drying temperature is 100℃ and the drying time is 3 minutes.

[0080] Example 5

[0081] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics that allows for targeted control of ink droplet spreading and penetration, comprising two separately formulated components, A and B, with the following components by mass parts:

[0082] Component A: 3 parts of locust bean gum (hydrophilic polymer, surface energy dispersion component of 43mN / m after film formation), 0.3 parts of sodium dodecyl sulfate (surfactant), 4 parts of polyethylene glycol 200 (swelling agent), 1 part of sodium hydroxide (alkali agent), and 91.7 parts of deionized water; Preparation method of component A: Add each component to deionized water in sequence and stir at room temperature until completely dissolved to obtain component A.

[0083] Component B: 1.5 parts of propylene alginate (weakly hydrophobic polymer, with a surface energy dispersion component of 36 mN / m after film formation), 0.5 parts of dimethyloldihydroxyethylene urea (crosslinking agent), and 98 parts of deionized water; Preparation method of component B: Add each component to deionized water, stir and disperse evenly at room temperature to obtain component B.

[0084] Citric acid was used to adjust the pH of components A and B to 4.5 respectively. The pretreatment agent had a viscosity of 80 mPa·s and a surface tension of 28 mN / m at 25°C. The content of solid particles with a diameter greater than 1 micrometer in both components A and B was ≤0.1%.

[0085] The pretreatment method of this pretreatment agent includes the following steps:

[0086] (1) Apply the above component A to the surface of cotton / lyocell blended fabric (cotton fiber:lyocell fiber = 90:10) by scraping and dry; the liquid content of component A on the fabric surface is 60%, the drying temperature is 85℃, and the drying time is 4 minutes.

[0087] (2) Apply the above component B to the surface of the fabric obtained in step (1) by scraping, and dry it; the liquid content of component B on the fabric surface is 60%, the drying temperature is 85°C, and the drying time is 4 minutes.

[0088] (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is subjected to steam fixing, washing and drying treatments in sequence to obtain the printed fabric. The steam fixing temperature is 100℃ and the time is 20 minutes; the washing is done with room temperature water for a total of 3 times, each time for 5 minutes; the drying temperature is 80℃ and the drying time is 3 minutes.

[0089] Example 6

[0090] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics that allows for targeted control of ink droplet spreading and penetration, comprising two separately formulated components, A and B, with the following components by mass parts:

[0091] Component A: 6 parts of sodium alginate and guar gum compound (hydrophilic polymer, mass ratio 1:1, surface energy dispersion component after film formation 44mN / m), 0.6 parts of alkylphenol polyoxyethylene ether (surfactant), 7 parts of urea and ethylene glycol compound (swelling agent, mass ratio 2:1), 3 parts of sodium carbonate (alkali agent), and 83.4 parts of deionized water; Preparation method of component A: Add each component to deionized water in sequence and stir at room temperature until completely dissolved to obtain component A.

[0092] Component B: 4 parts of hydroxypropyl methylcellulose (weakly hydrophobic polymer, surface energy dispersion component of 39mN / m after film formation), 1.5 parts of blocked isocyanate and polycarbodiimide compound (crosslinking agent, mass ratio 1:1), and 94.5 parts of deionized water; Preparation method of component B: add each component to deionized water, stir and disperse evenly at room temperature to obtain component B.

[0093] Tartaric acid was used to adjust the pH of components A and B to 6.0 respectively. The pretreatment agent had a viscosity of 300 mPa·s and a surface tension of 40 mN / m at 25°C. The content of solid particles with a diameter greater than 1 micrometer in both components A and B was ≤0.1%.

[0094] The pretreatment method of this pretreatment agent includes the following steps:

[0095] (1) Apply the above component A to the surface of cotton / lyocell blended fabric (cotton fiber:lyocell fiber = 50:50) by scraping and dry; the liquid content of component A on the fabric surface is 80%, the drying temperature is 110℃, and the drying time is 1.5 minutes.

[0096] (2) Apply the above component B to the surface of the fabric obtained in step (1) by scraping, and dry it; the liquid content of component B on the fabric surface is 80%, the drying temperature is 110°C, and the drying time is 1.5 minutes.

[0097] (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is subjected to steam fixing, washing and drying treatments in sequence to obtain the printed fabric. The steam fixing temperature is 110℃ and the time is 12 minutes; the washing is done with room temperature water for a total of 3 times, each time for 5 minutes; the drying temperature is 100℃ and the drying time is 2 minutes.

[0098] Comparative Example 1

[0099] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics, capable of directional control of ink droplet spreading and penetration, comprises only a single polymer, an alkali agent, urea, and water; the components are as follows by weight:

[0100] Guar gum (a single polymer with a surface energy dispersion component of 45 mN / m after film formation) 4 parts, sodium carbonate (alkali agent) 2 parts, urea (swelling agent) 5 parts, deionized water 89 parts.

[0101] The pH of the pretreatment agent was adjusted to 5.0 using tartaric acid. The pretreatment agent had a viscosity of 95 mPa·s and a surface tension of 32 mN / m at 25°C. All the physicochemical parameters met the requirements for pretreatment of cotton / lyocell blended fabrics for inkjet printing.

[0102] The application process of the pretreatment agent and the fiber ratio of the cotton / lyocell blended fabric are consistent with those in Example 2 of this invention, so they will not be described again here.

[0103] Comparative Example 2

[0104] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics, capable of directional control of ink droplet spreading and penetration, comprises only a single polymer, an alkali agent, urea, and water; the components are as follows by weight:

[0105] 1 part sodium alginate (polymer, surface energy dispersion component after film formation 42mN / m), 0.5 parts sodium hydroxide (alkali agent), 1 part urea (swelling agent), and 97.5 parts deionized water.

[0106] The pH of the pretreatment agent was adjusted to 4.0 using citric acid. The pretreatment agent had a viscosity of 22 mPa·s and a surface tension of 26 mN / m at 25°C. All the physicochemical parameters met the requirements for pretreatment of cotton / lyocell blended fabrics for inkjet printing.

[0107] The method of using the above-mentioned pretreatment agent is exactly the same as that in Example 1 of the present invention, and will not be repeated here. The cotton / lyocell blended fabric used in this comparative example has a blending ratio of cotton fiber to lyocell fiber of 50:50.

[0108] Comparative Example 3

[0109] A pretreatment agent for inkjet printing on cotton / lyocell blended fabrics, capable of directional control of ink droplet spreading and penetration, comprises only a single polymer, an alkali agent, urea, and water; the components are as follows by weight:

[0110] 5 parts of hydroxypropyl methylcellulose (polymer, surface energy dispersion component after film formation 31mN / m), 5 parts of potassium hydroxide (alkali agent), 12 parts of urea (swelling agent), and 78 parts of deionized water.

[0111] The pH of the pretreatment agent was adjusted to 6.5 using sodium citrate. The pretreatment agent had a viscosity of 390 mPa·s and a surface tension of 44 mN / m at 25°C. All the physicochemical parameters met the requirements for pretreatment of cotton / lyocell blended fabrics for inkjet printing.

[0112] The application process of the pretreatment agent and the fiber ratio of the cotton / lyocell blended fabric are consistent with those in Example 4 of this invention, so they will not be described again here.

[0113] Performance testing and characterization:

[0114] 1. Analysis of color depth, anti-bleeding properties, and dye penetration properties of the treated fabric

[0115] This invention focuses on cotton / lyocell blended fabrics treated with inkjet printing. It conducts tests on color depth, anti-bleeding properties, and dye penetration performance to verify the regulatory effect of the pretreatment agent on the printing effect of cotton / lyocell blended fabrics. The K / S value is used to characterize the apparent color depth of the fabric; a higher K / S value indicates a deeper color and better dye uptake. The calculation formula is as follows:

[0116] K / S = (1-R)² / (2×R)

[0117] In the formula, K represents the light absorption coefficient of the fabric, S represents the scattering coefficient of the fabric, and R represents the reflectivity of the fabric at the maximum absorption wavelength.

[0118] Table 1 shows the colorimetric test results of cotton / lyocell blended fabrics under different pretreatment conditions after printing with red reactive dye ink.

[0119]

[0120] Analysis of the colorimetric test results in Table 1 shows that, compared to Comparative Examples 1-3, the cotton / lyocell blended fabric printing samples pretreated with the hydrophilic-weakly hydrophobic dual-layer directional adjustment layer of Examples 1-6 of this invention exhibit a significant decrease in lightness value (L*), reflecting a decrease in the apparent lightness of the printed area, an increase in color depth, and an enhancement in color intensity. In the CIE-Lab color space, the red color system is characterized by a positive a* value and a negative b* value. After pretreatment, the samples of this invention show an increase in the red-green hue value (a*) and an increase in the absolute value of the yellow-blue hue value (b*), effectively suppressing the interference of yellow stray light, improving the purity of the main red color in the print, and resulting in better color saturation. In addition, the overall color saturation (C*) of the samples in Examples 1-6 was improved and the hue angle (h°) range was more concentrated, indicating that the printed fabric had uniform and full color and better hue stability. The K / S value can intuitively characterize the apparent color depth of the fabric and the dye fixation efficiency. Among them, Example 6 had the highest K / S value, sufficient vertical dye penetration depth, the best dyeing and fixation performance, and the most significant anti-bleeding and directional moisture control effects.

[0121] 2. Analysis of Ink Droplet Diffusion Length Test Results (Warrior and Weft Directions)

[0122] The warp and weft diffusion lengths of ink droplets are core indicators for characterizing the anti-bleeding performance and pattern edge clarity of inkjet printing on fabrics. The shorter the diffusion length, the more significant the suppression of lateral ink droplet spreading and the higher the sharpness of the printed outline.

[0123] Depend on Figure 1 Test results show that compared with the single sodium alginate pretreatment system, the cotton / lyocell blended fabrics pretreated with the hydrophilic-weakly hydrophobic dual-layer directional adjustment layer of this invention exhibit significantly reduced ink droplet diffusion lengths in both the warp and weft directions. Specifically, the ink droplet diffusion length in the warp direction of the sodium alginate group was approximately 15.0 mm and in the weft direction, while the warp diffusion length after pretreatment with this invention decreased to approximately 7.5 mm and in the weft direction, respectively, representing a reduction of more than 40% in both directions.

[0124] The results confirm that the weakly hydrophobic polymer in the outer layer of the present invention can construct a dynamic barrier at the interface, effectively inhibiting the lateral spread of ink droplets along the fiber capillary network and improving printing penetration and edge burrs; the hydrophilic polymer in the inner layer forms an osmotic pressure difference, realizing the decoupling control of the inhibition of lateral ink droplet spread and the promotion of longitudinal penetration, significantly improving the sharpness and clarity of the printed pattern outline.

[0125] 3. Comparative Analysis of the Appearance Clarity of Inkjet Printed Patterns Using Different Pretreatment Systems

[0126] Depend on Figure 2 A comparison of the printed appearance shows that, compared with the single sodium alginate pretreatment system, the cotton / lyocell blended fabrics pretreated with the sodium alginate-guar gum-hydroxypropyl methylcellulose compound system have sharper and more regular inkjet printed lines with no obvious smudging, bleeding, or fuzzy edges. The sharpness and clarity of the pattern edges are significantly improved.

[0127] When pretreated with sodium alginate alone, ink droplets tend to spread laterally along the capillary network between fibers, causing blurred edges and bleeding of printed lines. However, the three-component compound system can construct a gradient interface control layer on the fabric surface. The weak hydrophobic component on the surface inhibits the lateral spread of ink droplets, while the hydrophilic component in the inner layer drives the dye to penetrate vertically and directionally, achieving decoupling control of spread and penetration. This effectively improves the printing bleed defects and enhances the pattern fineness and edge fidelity of digital printing.

[0128] 4. Analysis of the regulation of ink droplet spreading and longitudinal penetration behavior in a two-layer pretreatment system

[0129] Figure 3 The differences in the regulation of ink droplet spreading and penetration behavior were compared between a homogeneous bilayer hydrophilic structure (two layers of sodium alginate) and a hydrophilic-weakly hydrophobic gradient bilayer directional control layer.

[0130] Depend on Figure 3The test results show that when using two layers of homogeneous hydrophilic sodium alginate pretreatment, ink droplets spread irregularly over a large area on the front of the fabric, resulting in severe smudging at the printing edges. At the same time, the dye is unevenly dispersed on the reverse side, and the longitudinal penetration stability is poor. However, after using a hydrophilic-weakly hydrophobic bilayer structure constructed with sodium alginate as the bottom layer and hydroxypropyl methylcellulose as the top layer, the lateral spreading of ink droplets is significantly suppressed, the printing outline on the front is regular, and the dye can penetrate evenly and fully into the reverse side of the fabric, resulting in uniform color on both sides.

[0131] The above phenomena confirm the core mechanism of this invention: "surface barrier, interfacial liquid absorption, and vertical flow guidance." The top layer of weakly hydrophobic polymer constructs a dynamic interfacial barrier, inhibiting the lateral diffusion of ink droplets along the fiber capillary network; the bottom layer of hydrophilic polymer creates an osmotic pressure difference, driving the ink droplets to penetrate vertically in a directional manner. This achieves decoupling control between the inhibition of lateral ink droplet spreading and the depth of longitudinal penetration, endowing the fabric interface with unidirectional moisture-wicking properties. This system effectively solves the technical bottleneck of the difficulty in simultaneously achieving anti-seepage and deep penetration in traditional pretreatment, providing a reliable pretreatment solution for high-precision, high-color-gain digital inkjet printing of cotton / lyocell cellulose blended fabrics.

[0132] 5. Microscopic morphology analysis of hydrophilic-weakly hydrophobic bilayer pretreated fabric

[0133] Figure 4 These are scanning electron microscope (SEM) images at different magnifications of cotton / lyocell blended fabrics after a double-layer pretreatment consisting of a bottom layer of sodium alginate and a top layer of hydroxypropyl methylcellulose. Figure 4 (a) shows the overall warp and weft interlacing pattern of the fabric; Figure 4 (b) It can be clearly observed that the pretreated polymer forms a continuous and uniform film coating structure on the fiber surface, completely covering the fiber surface layer and constructing a stable hydrophilic-weakly hydrophobic gradient interface layer. Figure 4 (c) Further magnification reveals that the film layer on the fiber surface is dense and flat, with no obvious damage or agglomeration defects.

[0134] These morphological features directly confirm that the pretreatment agent of this invention can successfully construct a double-layer directional regulation film on the surface of cotton / lyocell fibers: the bottom layer of sodium alginate is firmly anchored on the surface of the fiber matrix, and the top layer of hydroxypropyl methylcellulose forms a continuous weakly hydrophobic surface layer. The two work together to construct an interface structure of "surface barrier - bottom liquid guide", which provides a microstructural basis for decoupling and controlling the lateral spreading and longitudinal directional penetration of ink droplets.

[0135] In summary, compared with the prior art, the present invention has the following outstanding advantages:

[0136] First, it achieves precise decoupling control of ink droplet spreading and penetration. This invention abandons the traditional single-barrier control approach and innovatively constructs a hydrophilic-weakly hydrophobic dual-layer gradient interface. Relying on the dynamic barrier on the surface to inhibit the lateral penetration of ink droplets, the osmotic pressure difference at the bottom layer drives the longitudinal directional penetration of dye. This solves the technical problem of simultaneously preventing penetration and promoting penetration in cotton / lyocell blended fabric printing, effectively improving printing clarity, apparent color depth, and dye fixation efficiency.

[0137] Secondly, it is adapted to high-speed digital printing production conditions. The formulation of a special surfactant with low dynamic surface tension and fast response rate precisely matches the needs of high-frequency inkjet printing, effectively preventing ink droplet merging and splattering, and ensuring a stable and controllable high-speed printing process.

[0138] Third, it solves the problem of color difference in printing on blended fabrics. The components work together to regulate the surface energy of cotton and lyocell fibers, balancing the spreading and penetration behavior of ink on different fibers, effectively improving the color difference between the front and back of the print, and can be adapted to cotton-lyocell fabrics with any blend ratio.

[0139] Fourth, it balances printing performance with fabric comfort. The double-layer interface structure bonds firmly to the fibers, significantly improving the print's wash and abrasion resistance, while maintaining the fabric's inherent moisture absorption, breathability, and softness.

[0140] Fifth, it has strong process adaptability and high industrial value. The pretreatment agent system is uniform and stable, without agglomeration or precipitation problems. The spraying / scraping process is simple, requiring no modification to existing printing equipment, enabling continuous production. It is green and environmentally friendly with controllable production costs, and has broad prospects for industrial promotion.

[0141] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should be protected by the present invention.

Claims

1. A pretreatment agent for inkjet printing of cotton / lyocell blended fabrics that allows for targeted control of ink droplet spreading and penetration, characterized in that: The pretreatment agent consists of two parts, component A and component B, which are independently formulated and applied in steps. Component A, by mass parts, includes the following components: 1-10 parts of hydrophilic polymer, 0.1-1.0 parts of surfactant, 1-12 parts of swelling agent, 0.5-5 parts of alkali agent, and the balance being water. Component B, by mass parts, includes the following components: 0.5-5 parts of weakly hydrophobic polymer, 0.1-2.0 parts of crosslinking agent, and the balance being water. The hydrophilic polymer is at least one or a combination of at least two of sodium alginate, propylene glycol alginate, guar gum, locust bean gum, and xanthan gum, and the surface energy dispersion component of the hydrophilic polymer after film formation is ≥40 mN / m; the weakly hydrophobic polymer is at least one or a combination of at least two of ethyl cellulose, cellulose acetate, methyl cellulose, hydroxypropyl methyl cellulose, propylene glycol alginate, and acetylated starch, and the surface energy dispersion component of the weakly hydrophobic polymer after film formation is 30-40 mN / m.

2. The cotton / lyocell blended fabric inkjet printing pretreatment agent for targeted control of ink droplet spreading and penetration according to claim 1, characterized in that: At 25°C, the pH values ​​of components A and B are both 4.0-6.5, the viscosity is both 25-400 mPa·s, and the surface tension is both 25-45 mN / m.

3. The cotton / lyocell blended fabric inkjet printing pretreatment agent for targeted control of ink droplet spreading and penetration according to claim 1, characterized in that: In both component A and component B, the mass percentage of solid particles with a diameter greater than 1 micrometer is no higher than 0.1%.

4. The cotton / lyocell blended fabric inkjet printing pretreatment agent for targeted control of ink droplet spreading and penetration according to claim 1, characterized in that: The surfactant is at least one or a combination of at least two of the following: acetylenic diol ethoxylate, polyether-modified polysiloxane, alkyl glycoside, acetylenic diol block polyether, sodium dodecyl sulfate, and alkylphenol polyoxyethylene ether.

5. The cotton / lyocell blended fabric inkjet printing pretreatment agent for targeted control of ink droplet spreading and penetration according to claim 1, characterized in that: The crosslinking agent is at least one or a combination of at least two of the following: blocked isocyanate, polycarbodiimide, glyoxal, polyethylene glycol dimethacrylate, and dimethyloldihydroxyvinyl urea; the swelling agent is at least one or a combination of at least two of the following: urea, ethylene glycol, 1,2-propanediol, diethylene glycol, and polyethylene glycol 200.

6. The cotton / lyocell blended fabric inkjet printing pretreatment agent for targeted control of ink droplet spreading and penetration according to claim 1, characterized in that: The alkaline agent is at least one or a combination of at least two of sodium hydroxide, sodium carbonate, sodium bicarbonate, and potassium hydroxide.

7. A pretreatment method for a cotton / lyocell blended fabric inkjet printing pretreatment agent that allows for directional control of ink droplet spreading and penetration, characterized in that, The pretreatment agent described in claim 1 is applied stepwise in the order of component A followed by component B, comprising the following steps: (1) Apply component A of claim 1 to the surface of cotton / lyocell blended fabric by spraying or scraping, and dry; the liquid content of component A on the fabric surface is 50%-90%, the drying temperature is 80-120℃, and the drying time is 1-5 minutes. (2) Apply component B of claim 1 to the surface of the fabric obtained in step (1) by spraying or scraping, and dry it; the liquid content of component B on the fabric surface is 50%-90%, the drying temperature is 80-120℃, and the drying time is 1-5 minutes. (3) The fabric obtained in step (2) is digitally inkjet printed using reactive dye ink. After printing, the fabric is steamed, washed and dried in sequence to obtain the printed fabric.

8. The pretreatment method according to claim 7, characterized in that: In step (3), during steam color fixing, the temperature is controlled at 100℃-115℃ and the time is 12-20 minutes; the water washing is done with room temperature water, and the washing is done 3 times, with each washing time being 5 minutes; during drying, the temperature is controlled at 80℃-120℃ and the drying time is 1-3 minutes.

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