The manufacturing history of wood pencils in China has been nearly eighty years. Today, the annual output of pencils is the highest in the world, and it is a veritable pencil manufacturing country. However, the quality of the pencil is in the middle of the world, especially the appearance of the pencil (coating and appearance of the coating) is still far from the developed countries. Relative to the appearance of international famous brand pencils, it looks like plastic coating. The appearance of pencils in China is short-term and the fullness of gloss and fullness is good, but after a few months, the loss of light is produced, and the appearance of pencils is no longer the original light and fullness. It is. In order to improve the gloss and fullness of the appearance of the wood pencil, the author prevents the loss of light, and talks about the solution to the above problems from the aspect of pencil coating.
1. The closed lacquer wood contains a certain amount of water, which can absorb and volatilize water as the environment changes. Although the wood of the wood pencil has been denatured and coated with paint on the face, the insult of the wood has not disappeared. The pencil manufacturing process stipulates that the pencil must be painted for a certain period of time after it is made, otherwise quality problems will occur. Although the pencil has been painted, the current pencil primer (formulation and material) is not tightly sealed. As the moisture is absorbed, the wood fiber shrinks and the surface gap increases. The paint film sinks with the gap and the paint film sinks. This results in an uneven surface. Therefore, the gloss is lowered and the fullness is lowered, so that a resin having a large molecular weight, a small shrinkage ratio, good sealing property, and better resistance to moisture penetration is selected. This prevents the luster and fullness of the wooden pencil from falling.
2. The primer primer is generally a kind of paint with a relatively large amount of filler. Its function is to increase the fullness of the paint film on the one hand, and to fill the void portion of the wood surface, and increase the thickness of the paint film on the other hand. Improve the flatness of the surface and reduce the number of finishes. The pigment and filler of the primer also requires a certain fineness standard. When the surface area of ​​the pigment filler reaches a certain value, the shrinkage of the surface of the paint film after the paint is dried can be reduced, and the flatness of the surface of the sheath can be ensured.
3. Topcoat is the key material in the surface coating of wood pencils. The topcoat not only provides colorful colors for wood pencils, but also provides users with a beautiful enjoyment. For this purpose, the following requirements are imposed on the topcoat:
(a) The resins used in the topcoats should be very compatible with each other, and the solvent selected in the formulation should have two balances: solvent dissolution equilibrium and volatilization balance, so as to reduce the dryness of the paint film. The shrinkage rate ensures the smoothness of the surface of the paint film.
(b) The pigment used in the top coat must be ground to a certain fineness standard, and a system in which the pigment particles are dispersed and stabilized (stability during storage and workability at the time of coating) is obtained. If the pigment particles are unstable in dispersion, the pigment particles will coarsen as time goes by, which will destroy the coating performance and the smoothness of the surface of the pen, which directly leads to a decrease in gloss. It should be pointed out that even if the surface of the paint film is covered with varnish, the loss of gloss is generally not compensated, and floating color fading may occur.
(c) Use as little or no filler as possible in the topcoat because the filler has a certain matting effect on the paint (it only reduces the cost in the paint), so that although the film-forming substance in the topcoat is increased, However, the gloss of the surface of the paint film has a certain loss.
4. Varnish varnish is the most important coating in wood pencils. It provides a bright, mirror-like paint film on the one hand and a certain hardness on the other. The wear resistance and scratch resistance of the varnish are also a number of factors affecting the gloss. The gloss of the varnish is related to the flatness of the paint surface of the pen, and is related to the structural properties of the paint film molecules. To this end, the following requirements are imposed on the varnish:
(a) The resins used in the varnish should have good compatibility with each other and provide a certain hardness and transparency for the paint film.
(b) The solvent used in the varnish should have two balances: the equilibrium of dissolution and the balance of volatilization, so that the resin used is in a stable state of dissolution, and in the evaporation process of the solvent, the mixture of solvents always makes the resin The resin is in a stable system until the final evaporation of the solvent, and the various resins are smoothly leveled. In this way, the lacquer is always in a good stable state from the wet paint film to the dry film, and the gloss of the paint film is not lowered due to the precipitation of a certain resin in the varnish.
(c) Select suitable additives to increase the feel of the lacquer film, but also consider other processes after glazing, especially without affecting the recoatability of the film.
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