Thixotropic Modulating Oil Formulation and Development (1)

1 Introduction

The varnish is mainly used for decals printing in the ceramic, glass and enamel industries. From the perspective of rheology, this type of varnish is divided into two kinds: rogue type and thixotropic type. The former is a Newtonian fluid, suitable for field printing; the latter is a non-Newtonian fluid, suitable for dot printing. There are in-depth studies on foreign-type and thixotropic inks, and there are also many patents. China has been developing and researching the rogue type of varnish for more than 20 years, and there has been no report on the development and research of thixotropic varnish. Thixotropic oils, such as Os4360 from Japan, Siebdruckoe L80820 from Degussa AG in Germany, and UN1263 from Medium in the UK, have thixotropic properties; ceramics have no carbon black marks after firing, and they have good adhesion; pigments have good dispersibility; suitable for dot-printing For 350 mesh / 100 line screen printing is not blocked network and so on. If you print fine pattern decals, you must use thixotropic varnish. In order to improve the grade of Chinese decals, thixotropic varnish was developed to meet the needs of decal paper printers.

2 Recipe design

2.1 film formation

The film forming material is a substance that forms an ink film and determines the properties of the ink film. It should be stable within the storage period, without obvious physical and chemical changes, but after the film is formed, the cured film layer should be quickly formed under the specified conditions. Film formers are generally natural oils, natural resins and synthetic resins. According to the requirements of the ceramic transfer printing on the ink, the acrylic resin was selected as the film forming material and the acrylic resin was prepared by the solution polymerization method. Acrylic resin used in many varieties of monomers, acrylic copolymers are usually used to improve the performance of the resin.

2.2 Solvent

Solvents are critical for the formation of the ink film. Correct use of the solvent can improve the physical properties of the ink film, such as gloss, compactness, and the like. Developing a solvent for varnish should dissolve the monomers and copolymers well to obtain a uniform acrylic resin solution. Solvents that dissolve acrylic monomers and polymers include aromatic hydrocarbons, chlorinated hydrocarbons, esters, ketones, and the like. Considering that the solvent of the thixotropic varnish is not easily volatilized before printing and the solvent is volatile after printing, the high-boiling solvent tetralin (SN), which has dual properties of aromatic hydrocarbons and alicyclic hydrocarbons, is used as the main solvent, esters and alcohol solvents. For auxiliary solvents. Mixed solvents can meet the performance requirements of thixotropic varnish.

2.3 Thickeners

The printing of the fine pattern requires that the varnish has thixotropy, and the thixotropy is mainly produced by adding a thickener. Commonly used thickeners include fumed silica and its complexes, carbon black, surface-treated light calcium carbonate, amine compounds, cellulose, synthetic resins, metal stearates and glyceryl stearate, etc. . Thickeners are used to make the thixotropy of the varnish, but there is no trace of carbon black on the ceramic (or enamel) products after decaling. For this purpose, glyceryl stearate was chosen as a thickener.

2.4 Initiators, Plasticizers, Defoamers

In the acrylic solution polymerization process, azos and peroxides can be used as initiators. Common initiators are azobisisobutyronitrile, benzoyl peroxide, cumene peroxide, isobutyl benzoate. Benzoyl peroxide (BPO) initiators are preferred.

In order to increase the flexibility of the ink film, a plasticizer should be added to the ink varnish system. Commonly used plasticizers are phthalates, epoxies, phosphate esters, paraffins, and the like. Dioctyl phthalate plasticizer is preferred.

In order to eliminate air bubbles generated during the production process of varnish and during screen printing, a small amount of defoamer should be added. Commonly used defoamers include n-octanol, sec-octanol, glycerin, isopropanol, isobutanol, tributyl phosphate and methyl silicone oil. Taking into account the development of varnish, alcohol defoamers are preferred.

(to be continued)