With the re-emergence of solid wood furniture and the increasing proportion of wood materials in interior decoration materials, the demand for high-grade coatings for furniture and interior painting is also expanding, in order to obtain high-quality and high-quality decorative effects. Domestic high-grade coatings for wood are mainly polyurethane (PU) and polyester (PE). There are two major types of coatings in the national standard classification, which are very different in terms of category, composition, performance, application and curing mechanism. However, many users currently lack the necessary knowledge of the basic knowledge of coatings, especially the difference between polyester and polyurethane paint. What is more serious is that the coatings market generally refers to these two types of coatings as polyester. Paint, and even some products have no detailed description at all, and the sales staff is rarely trained professionally, which is very easy to cause users to purchase and can not purchase the required products; the painting construction can not be carried out correctly and smoothly, so it is difficult to ensure the finishing quality.
1 Problems to be aware of when purchasing paint
1.1 Before purchasing the paint, it is necessary to fully understand the main differences between polyester and polyurethane paint. The main difference between the two is shown in Table 1. When purchasing, ask the sales staff as much as possible whether the relevant properties of the purchased paint are consistent. Requirements and identification with reference to Table 1.
Project Coating Name Polyester Paint (PE) Polyurethane Paint (PU) Composition Base Unsaturated Polyester, Crosslinked Monomer Polyester, Acrylate, Polyether, Epoxy Resin (Hydroxy-OH-Containing Component) Additive or prepolymer of a poly-isocyanate group (either an isocyanate-NCO component or a component)
The group fraction is 3-4 components, and the 3-component is a non-wax type polyester lacquer 4 component which is a wax type polyester lacquer. Component one is a styrene solution (main agent) of unsaturated polyester; component two is an initiator (also known as curing agent, hardener, common name white water); component three is an accelerator (common name Lanshui) Component 4 is a 4% paraffin styrene solution. 1-3 components, there are one-component, two-component, the latter also has a thinner when adjusting the paint, the general paint ratio is: main agent: curing agent: thinner is 1:0.5-1:0.5-1.5
Classification PE is divided into air dry PE and anaerobic PE, anaerobic PE and wax type PE and non-wax type PE PU sub-component and two-component, one-component urethane oil and urethane alkyd. There are many types of PU, and the current market is mainly a two-component hydroxyl-curing PU.
Solvent styrene, etc. (ie solvent and film-forming substance) anhydrous xylene, anhydrous cyclohexanone or anhydrous butyl acetate solid content close to 100% 40-70%
Construction time limit (coating period, active period) 15-20min 4-8h
Curing conditions and mechanism Traditional anaerobic polyester needs oxygen curing (wax sealing method or wax sealing method), new air-drying polyester does not need to be oxygen-blockable, and unsaturated polyester and styrene are free under the action of initiator accelerator. The base polymerization reaction crosslinks and solidifies into a film. It can be dried at room temperature or at low temperature (50 °C). The solvent in the coating is volatilized, and an addition polymerization reaction occurs between the isocyanate-containing component and the hydroxyl group-containing component to form a film.
The sanitary conditions of the construction are solvent-free paints. Some of the solvents contained in the paint are copolymerized with the unsaturated polyester after the coating, and the common film formation is basically free of harmful gases. It is a solvent-based paint. It contains 30-60% organic solvent. It needs to be volatilized after coating. It pollutes the environment, is toxic and odorous, flammable and explosive. It needs to be ventilated and harmful substances (volatile organic compounds, benzene, toluene, xylene). TDI and heavy metals) Limited national standard "Limited harmful substances in interior decoration materials solvent-based coatings" GB18581-2001 has been clearly defined.
Dry schedule 30-40min
Polishing 6-10h
Dry>24h surface dry 15-20min
Polishing 3-4h
Hard work <24h
The re-coating interval can adopt the “wet-on-wet†process, that is, the surface dry coating can adopt the “wet-on-wet†process, that is, the surface dry coating performance, the paint film has excellent comprehensive physical and chemical properties and has the unique characteristics of solvent-free paint. Physical and chemical properties
Note: At present, 80% of China's furniture finishing PU, the “polyester paint†sold in the coatings market is mostly PU.
1.2 There are many varieties of polyester paints and polyurethane paints, such as putty, primer, top coat, varnish, colored paint, matt and bright, so users should purchase the corresponding varieties according to their needs.
2 Problems to be aware of during construction
2.1 The paint should be based on the length of the paint's active period to determine the amount of paint, so how much to use in the active period, the current use, now should not be too much, and strictly according to the ratio in the product description Provisioning.
2.2 When blending polyester paint, blue and white water can not be mixed directly, otherwise it will cause combustion and explosion, and can not be stored and transported together with acid or other flammable materials. White water cannot be mixed with acid drills, manganese, zinc, nickel and other salts. When preparing or coating polyurethane paint, it should not be in contact with water, acid, alkali or alcohol. In particular, the hardener should be sealed after opening and sealing to prevent moisture from entering.
2.3 Before finishing, the surface of the substrate should be treated flat and clean, and all kinds of dirt should be removed. The moisture content of the substrate should be appropriate (depending on the equilibrium moisture content of the product area, generally about 2% lower). When the paint is made of polyester paint, the primer should not be coated with shellac, and nitro, polyurethane and polyvinyl butyral can be used. When using polyurethane as a primer, it must be covered with polyester paint within 5h, otherwise it will affect the adhesion of the film.
2.4 Brushes, containers and tools used in construction should be cleaned with the corresponding solvent in time. The polyester paint can be washed with acetone or washing powder. When the polyurethane paint is applied, it should be cleaned with the matching diluent cyclohexanone or xylene.
2.5 Try to avoid coating the polyurethane paint in the rainy or summer high temperature and high humidity, winter low temperature and high humidity environment, otherwise, the coating film is easy to "white". If it is necessary to finish the application in the above environment, an appropriate amount of PU anti-whitening agent may be added to the lacquer, or the substrate to be coated may be appropriately heated to evaporate water vapor to prevent it.
2.6 When finishing PU paint, it should not be too thick for one finish, otherwise it will easily produce bubble pinholes. The recoating interval should be determined according to the instructions. The interval should not be too long. Otherwise, the cross-linking between the coatings is poor, and the adhesion is reduced. For the cured film, it needs to be sanded with a sandpaper or rubbed with a solvent before painting.
2.7 Painting construction is a harmful operation, and should pay attention to the labor protection of painters. Since May 1 this year, the implementation of the Law on Prevention and Control of Occupational Diseases has been carried out to improve the finishing environment and enhance the safety knowledge of workers in small-scale workshop furniture enterprises. Education, ensuring their physical and mental health, will play a catalytic role.
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