Research Progress of Water-based Acrylic Resin for Ink (Chinese)

2. Emulsion acrylic resin

The emulsion polymerization process is basically a gap-type, semi-continuous, and continuous feed polymerization method in current industrial production. Gap type and semi-continuous type are currently the most commonly used methods in production. Proper feeding speed can ensure that the monomers participating in copolymerization can be polymerized in a molecularly designed manner, especially when functional monomers are polymerized. There are many types of emulsion-type acrylic resins. Due to the different composition of the emulsion particles, the physical and chemical properties are different. There are usually colloidal dispersions and conjunctival emulsions. The molecular weight of the colloidal dispersion is between 15,000 and 40,000, and the particle size is lower than the limit specified by the emulsion, so it is not a true emulsion. Despite this, it is often referred to as an emulsion. If the inorganic pigment formulation is used, the ink has poor stability, poor resistance, and low gloss. However, due to the large particle size of the colloid, it can be diluted with a large amount of water, which reduces the cost of the final ink. Membrane emulsions, because of their high molecular weight, have good oil resistance, water resistance, and gloss. It has good adhesion with non-absorbent printing materials, and due to low glass transition temperature leads to good film formation and resistance.

Emulsion polymerization usually adopts the seed polymerization process. The seed polymerization process is to prepare a polymer emulsion by pre-emulsion polymerization of a part of the monomers, and then use the emulsion as a seed, and then add the same or different types of monomers in the reaction system, so that the newly added The monomers continue to polymerize on the surface of the seed particles to form an emulsion. The operating core of this process is to strictly control the concentration of emulsifier. In the first step of seed polymerization, it is required to obtain seed emulsions with enough particles and small enough size:

In the second step of polymerization, the concentration of the emulsifier in the system must be strictly controlled so that no new micelles are present, so that the newly added monomer can only polymerize on the surface of the seed particles without generating new latex particles. The seed polymerization process has the following features:

1) In the process of continuous emulsion polymerization, if the seed polymerization process is adopted, the transient phenomenon can be overcome (transient phenomenon is an unsteady phenomenon caused by the change of the emulsifier concentration during the polymerization process):

2) The seed polymerization process can effectively control the diameter and distribution of latex particles.

Tang Jianxin et al. applied a seed polymerization process with azobisisobutyronitrile as an initiator and N,N2 dimethylethanolamine as a neutralizer, methyl methacrylate (or styrene), butyl acrylate, acrylic acid, and N2 methylol acrylamide quaternary monomer copolymerization reaction was used to synthesize dispersion resins and film-forming resins suitable for flexographic four-color overprinting aqueous inks.

Hu Lehui applied the step polymerization method of seed polymerization to synthesize a nucleus ö intermediate ö shell three-layer structure emulsion with methyl methacrylate, methacrylic acid, ethyl acrylate, and polyalkenyl unsaturated monomers. Ammonia water treatment at high temperature makes the middle layer of latex particles fully swell. After a certain optical effect, the emulsion will have good hiding after drying. The use of this emulsion formulated into water-based ink can be printed with colorful, full, good hiding power.

Cui Jinfeng obtains acrylic copolymer emulsion by free-radical polymerization of acrylic acid and its esters, methacrylic acid and its esters, and other olefinic monomers in an emulsifying system composed of an initiator, an emulsifier, and water, followed by a modified rosin resin solution. Compatible with composite resin. Water-based inks made from this composite resin are stored for a year without thinning and thickening. The aqueous ink has good printability, good "body bone", quick dryness, high gloss, and wear resistance and water resistance of the printing film.

SharmaMahendrak and others use the waterborne polyacrylic acid resin of CH2CR1COOR2 (R1=H or C1-8 alkyl, R2=C1-8 alkyl) as a monomer to form a water-based polyacrylic resin, and then add a polishing aid to produce a functional water-based ink. This water-based ink emits fluorescence when irradiated with ultraviolet light. Water-based inks made from this waterborne polyacrylic resin can be applied to paper, fabrics, films, plastics, wood, concrete, metals, and the like.

Su Shiaonuny et al.'s acrylic latex polymers polymerized with C4-8 alkyl acrylates, methacrylates, vinyl acrylates and methacrylic acid have high adhesion and can be applied to different substrates.

YoshidaMitsuo et al. Emulsion polymerized with acrylic acid, methacrylic ester, ethacrylic ester and butyl acrylate, and with 22 hydroxyethyl 2 methacrylate, polyhexene glycol ester, acrylate and styrene acrylic The ester polymerized emulsion is compounded into a composite resin and can maintain its viscosity at room temperature for 3 months. It has good resistance to hot water when used on tin foil.

Huang Zhihong et al. studied the flow of soap-free hydrosol formed from the copolymer of hydrophilic monomer acrylic acid and initiator benzoyl peroxide in the copolymerization of ternary acrylate (methyl methacrylate, butyl acrylate, and acrylic acid). Denaturation, stability, surface tension effects. Comparison of the copolymerization reaction conditions on the comprehensive effect of soap-free hydrosols on the performance of water-based inks, determine the synthesis conditions for acrylate copolymers suitable for cross-linked water-based inks, that is, acrylic acid 4%, benzoyl peroxide mass concentration It is 118×10-2göm. The copolymers were characterized by IR, NMR and GPC.