The surface treatment of wood products is by coating coating. Since wood contains resins, tannins, pigments, and moisture, they have an effect on the adhesion, drying, and decorative properties of the coating. In order to obtain a coating coating that is smooth and smooth, has a uniform color and excellent performance, the surface of the wood product is also pretreated before the coating coating treatment. The main processes of pretreatment include drying, deburring and the like.
1. Dry wood is porous, easy to absorb water and drain, and has the characteristics of shrinkage and swelling, which causes foaming, cracking and back-adhesion of the coating. Therefore, the new wood needs to be dried until the moisture content is 8% at 12%. Coating coating is carried out. There are two methods for drying wood: natural drying and low temperature drying.
2. Although the surface of deburring wood products is planed or polished, there are always residual surfaces of wood fibers that are not completely detached. Once they absorb moisture or solvent, they will wet and swell and sway their hands, and affect the uniformity of surface coloration. The coating leaves some uncolored white spots, so the burrs must be removed before the coating is coated. For general wood products, as long as several times of sanding, high-grade wood products can be treated as follows (1) The surface is brushed with a thin shellac varnish (shellac: alcohol = 1:71:8), so that the burr can not only It is erected and brittle, and it is easy to remove it by sanding. (2) Wipe the surface with a dampened cleaning rag to make the burrs swell and erect. After the surface is dry, polish it with fine sandpaper or old sandpaper. If you add some bone glue in the water, the effect is better. (3) Using the fire method, use a pen to brush a thin layer of alcohol and immediately use the fire. After the fire burr becomes hard and brittle, it is easy to sand and remove the net. This method is only suitable for the processing plane.
3. To remove the surface of wood products stained with dirt, oil stains, etc., sand the paper first, then use cotton yarn to rub the gasoline. If it is still clean, use a fine light planer to cut the surface. .
4. Goose rosin Most conifer wood contains turpentine. There are turpentine and rosin in the turpentine, and their presence affects the adhesion and color uniformity of the coated coating. In the case of high temperatures, turpentine will overflow from the wood, causing the coating to become sticky. The common method for removing turpentine is to wash with organic solvent, such as alcohol, turpentine, gasoline, toluene and acetone. It can also be washed with alkali, such as 5%6% sodium carbonate solution or 4% 5% caustic soda solution. The rosin is saponified and then scrubbed with a brush or sponge and hot water. After the surface is clean, brush 12 layers of shellac paint in the cleaning area to prevent the rosin from the inner layer of the wood from seeping out.
5. Bleaching a lot of wood contains natural pigments, such as mulberry, red sandalwood and other pigments with yellow, purple and red. The pigment of the wood sometimes needs to be preserved to serve as a decorative effect. If the wood product is to be painted in a light color or painted in any color unrelated to the color of the original material, the surface of the white product of the wood product is bleached. In general, bleaching is often carried out on a partially darker surface to achieve a consistent color on the surface of the wood prior to coating. There are many ways to bleach. Commonly used bleaching agents are a mixture of hydrogen peroxide (30% concentration) and ammonia water (25% concentration) (hydrogen peroxide: water: ammonia = 1: 1: 0.2) or sodium hydroxide solution (250 grams of sodium hydroxide dissolved in 500 grams of water) Or hydrogen peroxide, etc. When bleaching with a mixture of hydrogen peroxide and ammonia, if the veneer is bleached, the veneer can be fully bubbled in the mixture; if bleaching is applied to the entire surface, the solution can be applied to the surface of the wood until the surface is reached. When bleaching, clean the surface with a clean damp cloth; if it is partially bleached, to improve the bleaching effect, use a small group of clean cotton yarn to dip the bleach and press it on the area to be bleached. Keep bleach on the cotton yarn. When bleached with sodium hydroxide solution, the solution was applied to the surface of the wood, and after half an hour, it was coated with hydrogen peroxide. After the treatment, the surface of the wood is scrubbed with water, and the sodium hydroxide is neutralized with a weak acid (such as 1.2% acetic acid or oxalic acid) and then scrubbed with water. The above two methods have good effects on ash, eucalyptus, etc., and the surface after bleaching does not change color for many years.
6. Dyeing In order to obtain a wood surface with a beautiful texture and uniform color, wood products need to be dyed. Wood dyeing can generally be divided into two types: water color dyeing and wine color dyeing. The water color is an aqueous solution of the dye, and the wine color is an alcohol solution of the dye. It is preferable to use an acid dye for the preparation of water color, and the commercially available yellow and black powder is prepared by mixing several acid dyes. When dyeing with water color, the water volatilizes slowly, the dyeing is uniform, and the price is low, and the use is convenient. Its main disadvantage is that the water causes the wood to fluff and needs to be sanded to eliminate the fluffing phenomenon. It is preferred to use an alcohol-soluble base-based dye for the preparation of the wine color. Alcohol is made of alcohol as a solvent. It is volatile and does not wet the wood. It eliminates the fluffing of the wood surface and produces a vivid color. The disadvantage of wine color dyeing is that it is prone to uneven color tone. If dyeing with wine color, we can weigh 6 points of alcohol solution dye, 70 points of alcohol and 24 points of shellac varnish. After mixing evenly, dye by hand or spray. When dissolving the dye, whether it is water color dyeing or wine color dyeing, it is best to operate in a glass cup, ceramic pot or enamel pot. Do not use a metal container to avoid discoloration.
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