Cationic acrylate emulsion for ink-absorbing coating and preparation method of cationic acrylate emulsion

Abstract

The invention discloses an ink-absorbing coating cationic acrylate emulsion and a preparation method thereof, and aims to solve the problems of poor water resistance, low ink-absorbing efficiency, insufficient emulsion stability and the like of the traditional acrylate emulsion. The emulsion is prepared by adopting a semi-continuous seed-core-shell polymerization process, and aluminum oxide nanoparticles are wrapped by the acrylate emulsion, so that the ink-absorbing coating is endowed with high porosity and a directional channel, and the ink-absorbing performance of the coating is improved; through a cationic reactive emulsifier, emulsifier molecules are covalently embedded into a polymer chain, and the water resistance of the coating is improved together with a constructed cross-linked network. The process is simple and environment-friendly, and the prepared coating has high ink absorbency, water resistance and mechanical stability and is suitable for the field of textile ink-jet printing.

Description

Technical Field

[0001] The invention belongs to the technical field of ink printing, and particularly relates to an ink-absorbing coating cationic acrylate emulsion and a preparation method thereof. Background Art

[0002] With the development of science and technology, inkjet printing technology has been widely used in the textile manufacturing industry. Ink-absorbing coating agents are a concept that has emerged with the development of inkjet printing technology. Ink-absorbing coating agents are mainly divided into two categories: inorganic ink-absorbing coating agents and organic ink-absorbing coating agents. Inorganic ink-absorbing coating agents mainly include silica, alumina, kaolin, and calcium carbonate. Organic ink-absorbing coating agents are diverse, including polyacrylates, polyurethanes, polyvinyl alcohol, starch, carboxymethyl cellulose, polyacrylamide, and polyvinyl pyrrolidone. Polyacrylates, especially acrylic emulsions, stand out among the many types of organic ink-absorbing coating agents due to their many excellent properties, such as film-forming properties, stability, weather resistance, water resistance, and chemical resistance. The ink-absorbing layer is the core functional layer for achieving precise printing and plays a vital role in the ink absorption performance, color vividness, and clarity of textile inkjet printing. Traditional acrylic emulsions have disadvantages such as poor water resistance, slow drying speed, and poor anti-blocking properties. Therefore, acrylic emulsions need to be modified, especially to improve their film-forming properties, stability, water resistance, and ink absorption properties, in order to obtain high-quality inkjet printing products.

[0003] There are many methods for modifying acrylic emulsions, such as introducing polyurethane, polyether segments or constructing core-shell structures, which can significantly improve their performance in the ink-absorbing layer of inkjet printing; improving the low-temperature brittleness and high-temperature stickiness problems by enhancing the flexibility of the molecular chain; using cross-linked networks and pore optimization design to increase ink absorption speed and fixation uniformity and reduce blooming; and enhancing water resistance and wear resistance by grafting hydrophobic groups or composite inorganic nanoparticles. The patent with publication number CN107236090A prepares a polyacrylate ink-absorbing quick-drying coating agent containing polyether segments. Although the polyether segments in the polyacrylate can improve the coating's absorption performance for water-soluble inks, the polyether segments are highly hydrophilic, especially in an environment with high humidity, which may aggravate the water absorption and swelling of the coating, resulting in reduced water resistance. At the same time, a specific proportion of anionic / non-ionic emulsifiers needs to be compounded. The patent uses two traditional non-reactive small molecule emulsifiers, sodium lauryl sulfate (SDS) and fatty alcohol polyoxyethylene ether (AEO-4). In the emulsion, the small molecule emulsifier is adsorbed on the surface of the emulsion particles by physical force. During the storage of the emulsion, it is easy to desorb from the surface, causing the emulsifier molecular layer around the latex particles to become thinner or disappear, making the emulsion stability worse, thereby affecting the stability of the product. In addition, the small molecule emulsifier easily migrates to the surface of the latex film, resulting in many problems such as slow film formation, poor water resistance, and poor adhesion. Summary of the Invention

[0004] Purpose of the invention: In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an ink-absorbing coating cationic acrylate emulsion and a preparation method thereof, using a reactive cationic emulsifier and a semi-continuous seed-core-shell polymerization process, with aluminum oxide as the core and acrylate monomers and functional monomers as the shell, aiming to develop an acrylate emulsion coating agent that has both ink absorbency and water resistance, while meeting green and environmental protection requirements and is suitable for textiles.

[0005] Technical solution: The present invention discloses a cationic acrylate emulsion for an ink-absorbing coating, which comprises a core phase, a shell phase, an emulsifier, and an initiator, wherein the core phase comprises inorganic nanoparticles accounting for 5 to 10 wt% of the monomer ratio; the shell phase comprises a soft monomer accounting for 50 to 60 wt% of the monomer ratio, a hard monomer accounting for 15 to 25 wt% of the monomer ratio, and a functional monomer accounting for 2 to 6 wt% of the monomer ratio; the emulsifier comprises a reactive cationic emulsifier accounting for 5 to 10 wt% of the monomer ratio and an auxiliary emulsifier accounting for 1 to 2 wt% of the monomer ratio; and the initiator accounts for 1 to 2 wt% of the monomer ratio.

[0006] Furthermore, as a preferred embodiment, the inorganic nanoparticles in the core phase are selected from one or more of aluminum oxide, silicon dioxide, titanium dioxide and zirconium dioxide.

[0007] Furthermore, as a preferred embodiment, the soft monomer in the shell phase is selected from one or more of butyl acrylate, ethyl acrylate, isooctyl acrylate and lauryl acrylate; the hard monomer is selected from one or more of methyl methacrylate, ethyl methacrylate, acrylonitrile and styrene; and the functional monomer is selected from one or more of acrylic acid, methacrylic acid, acrylamide, N-hydroxymethyl acrylamide, diacetone acrylamide and adipic acid dihydrazide.

[0008] Furthermore, as a preferred embodiment, the reactive cationic emulsifier in the emulsifier is selected from one or more of methacryloyloxyethyltrimethylammonium chloride (MAPTAC), vinylbenzyltrimethylammonium chloride (VBTAC) and acryloyloxyethyltrimethylammonium chloride (AETAC); the auxiliary emulsifier is selected from one or more of cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB).

[0009] Furthermore, as a preferred embodiment, the initiator is selected from one or more of azobisisobutyramidine hydrochloride (V-50), ammonium persulfate, potassium persulfate, and azobisisobutyronitrile.

[0010] The present invention also provides a method for preparing the above-mentioned cationic acrylate emulsion for ink-absorbing coating, comprising the following steps:

[0011] (1) Preparation of nanoparticle core dispersion:

[0012] A nanoparticle dispersion with a solid content of 40%, a cationic co-emulsifier and deionized water were mixed, ultrasonicated for 30-50 minutes, and the pH was adjusted to 4.5-5.0;

[0013] (2) Preparation of pre-emulsion:

[0014] The soft monomer, hard monomer, cross-linking monomer and reactive cationic emulsifier are mixed and sheared at high speed to form a uniform pre-emulsion;

[0015] (3) Core-shell emulsion polymerization:

[0016] Seed reaction: Add the nanoparticle dispersion prepared in step (1) to the reactor, remove oxygen with nitrogen, heat to 65°C, add 1 / 3 of the pre-emulsion and 1 / 2 of the initiator, stir and react for 1 hour to form nuclear seeds;

[0017] Shell coating: Add the remaining pre-emulsion and the remaining initiator to the reaction system at a uniform rate over 3-5 hours, raise the temperature to 75-85°C and keep it for 3-5 hours to ensure complete polymerization of the monomers;

[0018] (4) Post-processing:

[0019] The temperature was lowered to 35-40° C., the pH was adjusted to 6.5-7.0, the remaining deionized water was added for dilution, and the mixture was filtered to obtain an emulsion with a solid content of 40-45%.

[0020] Beneficial effects: (1) The present invention wraps the core-shell structure of inorganic nanoparticles with acrylic emulsion, giving the ink-absorbing layer high porosity and directional channels, allowing ink to pass through the pores between the nanoparticles, thereby improving the ink absorption performance of the ink-absorbing layer.

[0021] (2) The present invention adopts a cationic reactive emulsifier to covalently embed the emulsifier molecules into the polymer chain, thereby avoiding water resistance degradation caused by exposure of the hydrophilic groups, and jointly improving the water resistance of the ink-absorbing layer with the cross-linking system. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a transmission electron microscopy image of the cationic acrylate emulsion prepared according to the present invention. DETAILED DESCRIPTION

[0023] In order to better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with embodiments, the purpose of which is to understand the contents of the present invention in detail, rather than to limit the present invention.

[0024] Unless otherwise specified, the reagents and raw materials used in the examples and comparative examples of the present invention are commercially available.

[0025] Example 1:

[0026] The present embodiment describes an ink-absorbing coating cationic acrylate emulsion, wherein the core phase is selected from aluminum oxide nanoparticles; the soft monomer in the shell phase is selected from butyl acrylate, the hard monomer is selected from methyl methacrylate, and the functional monomer is selected from acrylic acid and diacetone acrylamide-adipic acid dihydrazide (DAAM-ADH) cross-linking system; the reactive cationic emulsifier in the emulsifier is selected from methacryloyloxyethyltrimethylammonium chloride (MAPTAC), and the auxiliary emulsifier is selected from cetyltrimethylammonium bromide (CTAB); and the initiator is selected from azobisisobutyramidine hydrochloride (V-50).

[0027] The specific preparation process is:

[0028] (1) Preparation of aluminum oxide core dispersion:

[0029] 16.25 parts of aluminum oxide dispersion (40% solid content), 1.6 parts of cationic auxiliary emulsifier CTAB and 10 parts of deionized water were mixed, ultrasonically treated for 30 minutes (300W, 40kHz), and the pH was adjusted to 4.5-5.0 with an appropriate amount of hydrochloric acid.

[0030] (2) Preparation of pre-emulsion:

[0031] 55.44 parts of butyl acrylate, 23.76 parts of methyl methacrylate (soft and hard monomer ratio is 7:3), 3.2 parts of acrylic acid, 1.6 parts of DAAM-ADH (DAAM:ADH=2:1) ​​system and 6.6 parts of reactive cationic emulsifier MAPTAC were mixed and sheared at high speed (8000 rpm, 15 minutes) to form a uniform pre-emulsion.

[0032] (3) Core-shell emulsion polymerization:

[0033] Seed reaction: Add the aluminum oxide dispersion prepared in step (1) to the reactor, pass nitrogen to deoxygenate, heat to 65°C, add 1 / 3 of the pre-emulsion and 0.65 parts of initiator V-50 (diluted with 50 parts of deionized water), stir and react for 1 hour to form nuclear seeds.

[0034] Shell coating: The remaining pre-emulsion and the remaining 0.65 parts of V-50 (diluted with 50 parts of deionized water) were uniformly added dropwise to the reaction system over 3 hours, and the temperature was raised to 75°C and kept for 3 hours to ensure complete polymerization of the monomers.

[0035] (4) Post-processing:

[0036] The temperature was lowered to 40° C., an appropriate amount of ammonia water was added to adjust the pH to 6.5-7.0, the remaining deionized water was added, and the mixture was filtered to obtain an emulsion with a solid content of about 45%.

[0037] Figure 1The transmission electron microscope image of the cationic acrylate emulsion prepared in this example shows that the particles are spherical and evenly dispersed without agglomeration or breakage, indicating that the process is stable during the preparation of the emulsion; the particles are gray of varying shades (dark in the center and light at the edges), wherein the aluminum oxide nanoparticles in the core layer are inorganic materials with high electron density, have strong electron beam scattering, and form a darker image, while the shell layer is an organic acrylate polymer with low electron density, weak scattering, and brighter image. It can be seen that the prepared emulsion has a core-shell structure of nano-aluminum oxide encapsulated by acrylate.

[0038] Example 2

[0039] This embodiment is basically the same as embodiment 1, except that the amount of cationic auxiliary emulsifier in the aluminum oxide core dispersion is reduced and the ultrasonic time is prolonged. Specifically, 1 part of CTAB is added and ultrasonic treatment is performed for 60 minutes (300W, 40kHz).

[0040] Example 3

[0041] This embodiment is basically the same as embodiment 1, except that the ratio of the soft and hard monomers in the pre-emulsion is changed, specifically, 59.4 parts of butyl acrylate and 19.8 parts of methyl methacrylate are added (the ratio of the soft and hard monomers is 3:1).

[0042] Comparative Example 1

[0043] Compared with Example 1, this comparative example differs in that the cationic emulsifiers MAPTAC and CTAB are replaced by anionic emulsifier sodium dodecyl sulfate (SDS), specifically, 1.6 parts of SDS are added to the alumina core dispersion and 6.6 parts of SDS are added to the pre-emulsion.

[0044] Comparative Example 2

[0045] Compared with Example 1, this comparative example is different in that the DAAM-ADH cross-linking system is replaced with acrylic acid in the pre-emulsion, specifically, 0 parts of the DAAM-ADH cross-linking system and 4.8 parts of acrylic acid are added.

[0046] Comparative Example 3

[0047] Compared with Example 1, the difference between this comparative example and Example 1 is that the amount of aluminum oxide nanoparticles added is increased, specifically, 37.5 parts (solid content 40%) of aluminum oxide dispersion is added.

[0048] Comparative Example 4

[0049] Compared with Example 1, this comparative example is different in that the aluminum oxide core dispersion liquid is not dispersed by ultrasound.

[0050] In order to verify the effect of the solution of the present invention, the emulsions and ink-absorbing coatings prepared in Examples 1-3 and Comparative Examples 1-4 were tested for emulsion stability, ink absorption and water resistance.

[0051] Table 1 Emulsions and ink-absorbing coating performance test data of Examples 1-3 and Comparative Examples 1-4

[0052]

[0053] As can be seen from the above table, the emulsion synthesized in Example 1 has better comprehensive performance. In Example 2, the ultrasonic dispersion time of the aluminum oxide dispersion is extended, and the stability of the emulsion is improved. In Example 3, the ratio of soft and hard monomers is adjusted from 7:3 to 3:1. Because butyl acrylate has a lower water absorption rate than methyl methacrylate, when the amount of butyl acrylate is increased, the water resistance of the coating is improved. In Comparative Example 1, the cationic emulsifiers MAPTAC and CTAB are replaced by the anionic emulsifier SDS. The synthesized emulsion is severely stratified. This is because the hydrophobic chain (C12 alkyl) of SDS is relatively short and cannot form a dense adsorption layer on the surface of aluminum oxide. CTAB can be adsorbed on the surface of aluminum oxide through the hydrophobic chain. MAPTAC and CTAB work together to further strengthen hydrophobic adsorption and enhance the stability of the emulsion. In Comparative Example 2, the DAAM-ADH cross-linking system was not used, resulting in insufficient hydrogen bonding and hydrophobic interaction between the polymer chains. Water easily penetrates the matrix, and the formed polymer chains are highly mobile. After curing, the porosity is reduced, and the ink diffusion path is also slightly obstructed, which ultimately leads to a decrease in the ink absorbency and water resistance of the coating. In Comparative Example 3, excessive aluminum oxide nanoparticles were added, and the particles agglomerated. The gravity sedimentation rate during centrifugation accelerated, and the dynamic equilibrium of the dispersed phase was destroyed, resulting in a decrease in the stability of the emulsion. In Comparative Example 4, the aluminum oxide dispersion was not ultrasonically treated, resulting in uneven dispersion, the formation of agglomerates, and a significant decrease in specific surface area, resulting in a decrease in emulsion stability. At the same time, the agglomerates were not tightly bonded to the polymer matrix interface, and water diffused along the weakly bonded interface to form a permeation channel, resulting in a decrease in the water resistance of the coating. The effective active sites (such as surface hydroxyl groups) in the coating were also reduced, resulting in a decrease in ink adsorption capacity.

[0054] The cationic acrylate emulsion for an ink-receptive coating described herein improves the ink absorbency of the ink-receptive coating by encapsulating inorganic nanoparticles in a core-shell structure. The cationic reactive emulsifier and crosslinking system synergistically enhance the water resistance of the coating. The prepared cationic acrylate emulsion combines excellent ink absorbency and water resistance while maintaining good stability. Furthermore, the emulsion is simple to prepare, safe, and environmentally friendly, making it suitable for use as an ink-receptive coating agent in inkjet printing on textiles.

[0055] The above is only an embodiment of the present invention and does not limit the scope of patent protection. Those skilled in the art can make non-substantial changes or substitutions based on the present invention and still fall within the scope of patent protection.

Claims

1. A cationic acrylate emulsion for ink-absorbing coating, characterized in that: The emulsion includes a core phase, a shell phase, an emulsifier and an initiator, wherein the core phase is inorganic nanoparticles accounting for 5 to 10 wt% of the monomer ratio; the shell phase is a soft monomer accounting for 50 to 60 wt% of the monomer ratio, a hard monomer accounting for 15 to 25 wt% of the monomer ratio and a functional monomer accounting for 2 to 6 wt% of the monomer ratio; the emulsifier is a reactive cationic emulsifier accounting for 5 to 10 wt% of the monomer ratio and an auxiliary emulsifier accounting for 1 to 2 wt% of the monomer ratio; and the initiator accounts for 1 to 2 wt% of the monomer ratio.

2. The cationic acrylate emulsion for ink-absorbing coating according to claim 1, characterized in that: The inorganic nanoparticles in the core phase are selected from one or more of aluminum oxide, silicon dioxide, titanium dioxide and zirconium dioxide.

3. The cationic acrylate emulsion for ink-absorbing coating according to claim 1, characterized in that: The soft monomer in the shell phase is selected from one or more of butyl acrylate, ethyl acrylate, isooctyl acrylate and lauryl acrylate; the hard monomer is selected from one or more of methyl methacrylate, ethyl methacrylate, acrylonitrile and styrene; and the functional monomer is selected from one or more of acrylic acid, methacrylic acid, acrylamide, N-hydroxymethyl acrylamide, diacetone acrylamide and adipic acid dihydrazide.

4. The cationic acrylate emulsion for ink-absorbing coating according to claim 1, characterized in that: The reactive cationic emulsifier in the emulsifier is selected from one or more of methacryloyloxyethyltrimethylammonium chloride (MAPTAC), vinylbenzyltrimethylammonium chloride (VBTAC) and acryloyloxyethyltrimethylammonium chloride (AETAC); the auxiliary emulsifier is selected from one or more of cetyltrimethylammonium bromide (CTAB), dodecyltrimethylammonium bromide (DTAB) and tetradecyltrimethylammonium bromide (TTAB).

5. The cationic acrylate emulsion for ink-absorbing coating according to claim 1, characterized in that: The initiator is selected from one or more of azobisisobutyramidine hydrochloride (V-50), ammonium persulfate, potassium persulfate, and azobisisobutyronitrile.

6. A method for preparing the cationic acrylate emulsion for ink-absorbing coating according to any one of claims 1 to 5, characterized in that The steps include: (1) Preparation of nanoparticle core dispersion: A nanoparticle dispersion with a solid content of 40%, a cationic co-emulsifier and deionized water were mixed, ultrasonicated for 30-50 minutes, and the pH was adjusted to 4.5-5.0; (2) Preparation of pre-emulsion: The soft monomer, hard monomer, cross-linking monomer and reactive cationic emulsifier are mixed and sheared at high speed to form a uniform pre-emulsion; (3) Core-shell emulsion polymerization: Seed reaction: Add the nanoparticle dispersion prepared in step (1) to the reactor, remove oxygen with nitrogen, heat to 65°C, add 1 / 3 of the pre-emulsion and 1 / 2 of the initiator, stir and react for 1 hour to form nuclear seeds; Shell coating: Add the remaining pre-emulsion and the remaining initiator to the reaction system at a uniform rate over 3-5 hours, raise the temperature to 75-85°C and keep it for 3-5 hours to ensure complete polymerization of the monomers; (4) Post-processing: The temperature was lowered to 35-40° C., the pH was adjusted to 6.5-7.0, the remaining deionized water was added for dilution, and the mixture was filtered to obtain an emulsion with a solid content of 40-45%.

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