Development of Water-based Photocurable Materials (I)

1 Introduction

The traditional oil-based UV curing system still has a lot of deficiencies in terms of environmental protection, human health, process operation and membrane performance control, and the price is relatively expensive. One of the most interesting is the irritation and odor of the diluent monomer to human skin and eyes. The water-based photocuring system inherits and develops many advantages of the traditional UV curing technology and waterborne coating technology, and has emerged as a new type of photocuring system in recent years. It has the following advantages: Due to the use of the most inexpensive and safe water as a diluent, it is easy to adjust the viscosity, can achieve a monomer-free formula; convenient control of rheology, suitable for a variety of coating methods, in particular spraying is safe; no skin irritation Sex and odor; can avoid curing shrinkage caused by reactive diluents; can get a very thin coating, reduce costs; does not burn, safety; equipment, containers and other easy to clean.

2 Water-based photocurable resin

Water-based photocurable resins are soluble in water because of the presence of a certain number of strong hydrophilic groups in the polymer's molecular chain, such as carboxyl, hydroxyl, amino, ether, amide, and the like. However, these polar groups mostly form emulsions when they are mixed with water, and their carboxylates are partially soluble in water. Therefore, most water-soluble resins obtain water-solubility in the form of neutralized salt. In addition, the water-based UV-curable resin must be capable of undergoing photopolymerization in addition to water solubility. This requires that the resin made is a molecule with an unsaturated group, which is required to be able to cross-link with other unsaturated molecules under certain conditions, from liquid to solid coating. A method of introducing an acryloyl group, a methacryloyl group, or an allyl group is generally adopted so that the synthetic resin has an unsaturated group, so that photocuring can be performed under suitable conditions.

2.1 Water Dilutable Unsaturated Polyester Type

If maleic anhydride and glycerol are reacted, unsaturated groups and hydrophilic groups are introduced through maleic anhydride.

In addition, MJ Dvorchak et al. reported a non-ionic self-emulsifying WR-UPE as an allyl ether of a photo-curing group. Its design is as follows:

2.2 Water Dilutable Polyurethane Acrylic Prepolymers

This is the most studied system. There are mainly the following types: 2.2.1 The more common 2,2-dimethylolpropionic acid (DMPA) available as a component of the diol reacts with the diisocyanate, and the product is then acrylated. For example: PHStenson reported the design route as follows:

(to be continued)