When preparing a water-based paint formulation

Update:12-04-2018
Summary:

When preparing a water-based paint formulation, the cho […]

When preparing a water-based paint formulation, the choice of raw materials for the emulsion is the most important decision for the engineer. The main properties of the coating are determined by the resin. A wide variety of waterborne acrylate emulsions, including polystyrene-acrylate emulsions, are mixed on the market. The composition of different water-based acrylate resins has a great influence on the film-forming property and cost of the water-based paint. Here is a brief discussion of several influencing factors.

1. The main raw materials:

a. Styrene acrylic emulsion The main reason for introducing this monomer is that it can provide a higher glass transition temperature (Tg), thus increasing the hardness of the film formation; another reason is the cost. Styrene is used in a large amount in the packaging industry and is one of the most important and mature downstream products in the petroleum industry. Its price is low but it is greatly affected by the macro economy. However, the introduction of styrene, especially when the content is more than 15% of the total monomer amount, also brings about many negative effects on the film formability of the water-based paint. First, the styrene-containing polymer segments lack flexibility, and macroscopically, the water-based paint film is hard but not strong; and the benzene ring contained in styrene is an ultraviolet light absorber, and when the content of the monomer is high, UV light passes through the adjacent benzene ring and will have a shear reaction with the polymer chain, which will make the water-based paint film brittle, reduce the gloss, and reduce the service life. The structure of styrene also determines its affinity for many organic solvents. The solvent resistance of the paint film is also significantly different from other resins.

b. Acrylic monomers: There are many kinds of acrylic monomers, and their performance and price are very different. The most commonly used in China is butyl acrylate, which has the lowest cost of monomer modification, and is the monomer used by most emulsion manufacturers for supporting styrene to make inexpensive wall paint emulsions. Its function is to provide the flexibility of the waterborne paint film. Since the acrylate polymer backbone does not contain a group other than the ester group, the main chain and the ester group side chain have good flexibility, so that the water-based paint film lacks hardness. Although this type of polyacrylate emulsion is the choice of interior and exterior wall coatings, it is not sufficient for wood coatings with high hardness and toughness requirements.

c. Methacrylate monomers: Methacrylate monomers, which have taken a step up from the acrylate monomer. Due to the presence of more methyl groups in the main chain of the methacrylate polymer, its main chain mobility is limited, the main chain steel is enhanced, and the ester side chain provides flexibility, making the methacrylate single The body has the best balance of hardness and toughness. For example, polymethyl methacrylate (methyl methacrylate) is commonly known as plexiglass; methacrylate monomers are styrene-like due to the absence of benzene rings. The monomer has a distinct advantage over styrene in terms of resistance to UV erosion, durability, and solvent resistance.

In summary, manufacturers of water-based acrylate resins have many options for monomers, not only changing their types but also changing the relative proportions and components. When water-based paint manufacturers choose water-based acrylate emulsions, they should not only consider the empty concept vocabulary of “pure C” or “styrene-propylene”, but should measure the actual performance of waterborne acrylate resins and their formulations.