December 2013 Archives

(5) Polyester resin paint

Unsaturated polyester resin is a prepolymer with unsaturated acid base such as maleic anhydride and alcohol divalent such as ethylene glycol, propylene glycol. This dissolved in reactive monomers such as styrene monomer in a slight excess of the double bond equivalent is polyester resin paint.
For instance, by adding cobalt naphthenate peroxide as accelerator as a catalyst to polyester of ethylene glycol and maleic anhydride, insoluble paint coating is formed by reactive monomer bridge bonded in the double bond of maleic acid.
This is a two-component paint where a catalyst is mixed immediately before painting. In this case, the styrene monomer acts as a solvent that gives a fluidity to the paint, and becomes the paint coating element as a bridge bonding agent. Therefore, this paint is a non-solvent paint.
The polyester paint [1] can obtain thick coating just with a single application and there is no volatilization of the solvent, [2] has hard coating with good chemical resistance and wear resistance, [3] poor adhesion with large volumetric shrinkage when hardens, [4] paint coating is poor in elastic deformity and easily scratched, [5] significantly loses luster due to exposure.

(6) Polyurethane resin paint

This is the generic name of the paint with a urethane bond in the cured coating film, and there are roughly following 4 types of commercial urethane paints.

(1) Two-component polyurethane resin paint

When isocyanate compound solution with a large number of (-NCO) isocyanate group and polyester prepolymer solution with a large number of OH groups are mixed right before painting, OH groups and NCO groups bridge react and form urethane bonding.

(2) Polyurethane resin baked paint

A 1 component baking paint composed of polyester resin and alcoholic OH group blocked isocyanate component or NCO group blocked phenol, and is baked at 180℃. It is used on urethane enamel wire, and etc.

(3) Moisture curing polyurethane resin paint

The paint with the main component of prepolymer with toluene diisocyanate (TDI) bridged with alcohol of 2-3 valence. This paint forms mesh structure paint coating by a reaction of free NCO group and moisture within the air, after painting. It cures faster with the higher air moisture similar to lacquer, and is used for lacquer-ware for that reason.

(4) Oil modified polyurethane resin paint

Urethane alkyd resin or oil modified urethane is created by reacting toluene diisocyanate (TDI) and oil modified alkyd. Curing mechanism requires the addition of a drying agent the same as oil paint. It is used in woodworking paint.

(3) Alkyd resin paint

Alkyd resin paints are room temperature drying paints with alkyd resin which is based on substrates of polybasic acids such as phthalic anhydride and polyhydric alcohol (glycerin, etc.) ester modified with various oils or fatty acids as the main coating component.
For the purpose of improving the paint suitability, it may be modified with rosin, phenolic resins, silicone resins, epoxy resins, styrene monomer. Theses are called Modified Alkyd Resin Paints, and unmodified ones are called Oil Modified Alkyd Resin Paints or Pure Alkyd Resin Paints.
The characteristics of this type of paints are: [1] Strong coatings, good adhesion, good weatherability, [2] Good pigment dispersion thus good color, luster, color retention, [3] good density, [4] good water resistance, solvent resistance, heat resistance, [5] easy to use and economical, etc.
They are used in large quantities in all areas and dominates the field of practical use paints along with Amino Alkyd Paints mentioned next. They are used for construction applications (interior and exterior painting, construction materials, steel structure, equipment, etc.), marine vessels, automobiles, metal painting (large electrical appliances, machine and tools, farm implementation, etc.), and home use.

(4) Amino alkyd resin paint

Amino alkyd resin paints are baked paints with mixtures of alkyd resin and amino resin as the main coating component. For amino resin, butylated melamine or urea resin are widely used. During the baking process, the hardened coating is formed by OH group of alkyd resin and CH2OH group of amino resin making ether bonding.
The property of amino alkyd resin paints vary with the component resin types, mixture ratio, and baking conditions. For instance, the higher the resin concentration and baking temperature, the higher the coating crosslink density, hardness, chemical resistance will be.
The general characteristics of this type of paint are as shown below.
[1] Low temperature, short time baking are possible, [2] coating is hard and glossy, [3] little discoloration, good weatherability and chemical resistance, [4] good wear resistance and electrical property, flame resistant. As a shortcoming, if anything, they are not as good in adhesion and alkali resistance compared to epoxy, vinyl, acrylic resin paints.
They are widely used on applications, other than in-field paintings, as under and over coatings that can be baked on construction materials (sash, surface treated steel plates, etc.), automobiles, electrical material, machinery, metal furniture, office equipment, and other metal products.