Microcapsule Screen Printing Process and Analysis of Common Problems

Abstract The basic characteristics and preparation methods of microcapsules are introduced. The application of microcapsule technology in the printing industry is analyzed, including pressure sensitive carbon paper making, home decoration printing, thermal printing, pressure sensitive printing, food packaging, transfer printing, and three-dimensional printing. etc. At the same time, the screen printing technology of microcapsules and some problems that should be paid attention to are discussed.

Key words microcapsule ink screen printing

Foreword

Microcapsule technology began its research work in the 1930s. First, the United States successfully developed carbonless copy paper based on the coacervation microcapsule technology. Microcapsule technology has developed rapidly since then. Has been extended to medicine, food, pesticides, feed, printing, coatings, adhesives, cosmetics, detergents, photographic materials, textiles and other industries. In particular, the use of microcapsule technology in the field of printing has produced many new processes, added new functions, and increased the added value of products. The research of this technology in China is still in its infancy.

1. Basic properties of microcapsules and their preparation

1.1 Basic characteristics of microcapsules

Microcapsule technology is a technology that uses a film-forming material to coat solids or liquids to form micro-particles. The substance enveloping the microcapsules is called a capsule core, and the capsule core can be solid or liquid or gas. The external film of the microcapsules formed by the film-forming material is called wall material. The wall material is a key part of the microcapsules. The commonly used wall film materials can be divided into two categories: one is extracted from natural substances, such as gelatin, Gum arabic, starch, bone glue protein, inorganic silicate, paraffin, ethyl cellulose, arabinose, etc.; the other is chemically synthesized, such as polyvinyl alcohol, polyethanol, polystyrene, polyamide, Polyurethanes, polyureas, polybutadienes, polyisoprenes, polysiloxanes, polyurethanes, epoxy resins, and the like. These different types and properties of the wall material, the use of different micro-capsule technology can produce different functions of the microcapsule production Lu heart and wall material dissolution properties must be different, such as water-soluble capsule heart can only use oil The (hydrophobic) wall material is coated, and the wall of the capsule may be a single layer structure or a multi-layer structure.

The size of the microcapsules is generally in the range of 2 to 200 μm, and can theoretically be made into microcapsules of 0.01 to 10 000 μm. The thickness of the capsule wall is generally in the range of 0.5-150 μm. The shape of the microcapsules: The microcapsules can take a variety of shapes, such as spherical, granular, kidney-shaped, grain-shaped, floc-like and lumpy.

1.2 Preparation of Microcapsules

Conventional microcapsules can be roughly classified into chemical methods, physicochemical methods, and physical methods in principle.

1.2.1 Chemical Methods

The microcapsule preparation technology based on chemical reaction mainly utilizes monomeric small molecules to generate a polymer film-forming material and encapsulates the core. Many synthetic polymers can be used in the polymerization of microcapsules. The main methods that are commonly used are: (1) interfacial polymerization methods, such as enzymatic or hemoglobin-containing polyamide microcapsules; (2) in-situ polymerization, For example, a bulk polystyrene capsule containing a dichlorobenzene plasticizer; (3) an orifice-coagulation bath method such as calcium alginate microcapsules containing a photographic emulsion.

1.2.2 Physical Chemistry Method

(1) Aqueous phase separation method: It has four types: (1) complex agglomerates such as gelatin-Arabic microcapsules containing pigments. 2 Single agglutination such as gelatin microcapsules containing rose oil. 3 Salt coagulation, for example, styrene-maleic anhydride copolymer microcapsules containing liquid paraffin. 4 By changing the pH of the aqueous system, the polymer is insoluble and precipitates. For example, a pyridine-acrylic acid copolymer microcapsule containing cod liver oil.

(2) Oil phase separation method: The organic solution of the polymer used for the microencapsulation medium. For example, polyvinyl chloride microcapsules containing cottonseed oil.

(3) Dry bath method: It is divided into a water bath drying method and an oil bath drying method. For example, enzyme-containing polystyrene microcapsules.

(4) Melt Dispersion and Condensation: This method can be divided into three types: microencapsulation in liquid medium, microencapsulation in gaseous medium, and microencapsulation in sharp hole forming. This method is particularly effective for microencapsulation of water-soluble materials and has certain practical value.

(5) Powder bed method: For example, CAP microcapsules containing vitamin B12. (to be continued)