Main factors affecting the quality of impregnated laminated paper Particleboard

Main factors affecting the quality of impregnated laminated paper Particleboard

Melamine Particle BOard inspection ,checklist ,grading rules ,QC quality control ,manufacturing defects .

1. Main factors and control methods affecting the quality of impregnated laminated paper  particleboard.

The quality of melamine impregnated laminated paper veneered particleboard is mainly judged from two aspects: appearance quality and internal quality. Appearance quality is to observe the surface state to see whether there are defects on the surface. The intrinsic quality, i. e. physical and chemical properties, is determined by the physical and chemical test results of the resin layer cured on the surface.

1.1 Effect of Raw Materials on Decorated Particleboard

1.1.1 base paper

In order to ensure the quality of melamine impregnated paper, high quality decorative base paper must be used. The decorative base paper used in the current industry is generally divided into four categories: surface wear-resistant base paper, wood floor decorative base paper, furniture decorative base paper and floor balance base paper. Each kind of decorative base paper can be imported from abroad and produced domestically. Due to the restriction of low paper quality, ink, printing technology and other conditions, many decorative base paper has some defects, such as uneven density and unclear text. Therefore, in order to ensure the quality of melamine impregnated paper, the quality of decorative base paper has the following requirements:

()! The density is uniform and the fibers are of moderate thickness.

(2) The wet tensile strength conforms to the standard. The imported base paper is more than 9N and the domestic base paper is more than 4N.

(3) The surface is smooth, smooth, without wrinkles, pits, mosquitoes and other impurities.

(4) Clear texture without overlap.

(5) Uniform color, no color difference.

(6) The surface is dry without moisture absorption.

(7) Good ink, no obvious discoloration of hand touch, no obvious discoloration after impregnation.

Other quality indicators should meet the use requirements, and the use department should quantify the base paper. Thickness. Tensile strength. Smoothness, water absorption, air permeability, ash content. Photometric texture is clear, no overlap, moisture content and other indicators as well as printing quality are tested to meet their own needs. If the above indicators exist problems, they will cause quality defects such as bottom penetration, uneven thickness, uneven dipping, uneven glue loading, paper tearing and color difference of veneered particleboard. At present, according to the smoothness and smoothness of particleboard surface and the needs of customers, decorative base paper with a quantity of 80+-2g/m2 100+3g/m2 120+3g/m2 is generally used in production. No matter what kind of decorative base paper enters the production line, it must be strictly inspected according to the quality requirements of decorative base paper. Unqualified decorative base paper will not be allowed to flow into the production line.

Quality Control of 1.1.2 Melamine Adhesive

The quality of melamine gum is directly related to the quality of impregnated paper. Before mixing and using melamine gum, we should carefully check the performance indexes of melamine gum, such as PH value, viscosity, curing time and water dilution. It can be put into use under the conditions of ensuring the PH value of melamine gum = 9.2-9.7, viscosity = 15S-17S (temperature 20 C, 4 cups), curing time = 7-12 min, water dilution = 160-200.

Quality Control of 1.1.2.1 Additive

The type and amount of additives used vary with the variety of melamine impregnated paper produced. The additives include curing agent, demoulding agent and penetrating agent. In order to ensure the quality of melamine impregnated paper, high quality and qualified additives must be selected.

Quality Control of 1.1.3 Melamine Impregnated Paper Production

Impregnating resin is mainly a kind of geopolymer dissolved in water. The main resins used on the surface of impregnated paper are melamine formaldehyde resin adhesive and urea formaldehyde resin adhesive. Phenolic resin is called etc. In order to improve the properties of the resin, some modifiers and additives were added to the melamine formaldehyde resin adhesive. Curing time and solid content of impregnated resin adhesives. Viscosity and other indicators directly affect the curing speed of impregnated paper, and the length of curing time also directly affects the physical and chemical properties of decorative panels. Resin impregnation requires good impregnation, impregnated paper does not have uneven phenomenon, so the permeability of resin is good. If the permeability of the resin is not good, the base paper can not reach enough resin content, and it is difficult to absorb uniformly in the interior, resulting in uneven paper layer, which is easy to cause internal layering of the paper. At the same time, it will affect the thickness and surface quality of impregnated paper. Generally speaking, most manufacturers consider the economy and the use of secondary impregnation method, that is, decorative paper first impregnated with urea-formaldehyde resin adhesive, after osmotic drying, and then sprayed with melamine resin adhesive on the surface. The curing time of impregnated resin adhesives, technical indicators and the proportion of synthetic resins directly affect the physical and chemical properties of the panel, the glossiness and dimensional stability of the surface, as well as the production efficiency. The appearance defects are wet and dry flowers, surface pore, surface scratch and uneven gloss. The physical and chemical performance indicators are poor in water vapor resistance, pollution resistance, dry heat resistance and wear resistance.

The content of resin in 1.1.3.1 melamine impregnated paper is expressed by the weight ratio of resin to paper. The method is as follows: Take three to six samples of 100*100mm film paper and three to six same size base paper, weigh them respectively, and bake them in an oven at 160 2 C for 10 minutes (the base paper is baked at 120 20 min). Take them out and put them in a dryer for 5 minutes, and weigh them (accurate to 0.001 g). The resin content is calculated by the following formula

G=(G1-G2)/G2*100%

In formula G stands for resin content. G1 represents the weight (g) of the dried film paper and G2 represents the weight (g) of the dried base paper.

The resin content is about 50% or higher. Generally speaking, it depends on the type of product, the conditions of use and the actual production.

1.1.3.2 Volatile matter content: refers to the weight ratio of the volatile matter to the dry film paper. It includes water (free water, water formed during condensation), solvents, free components and low molecular weight substances. The method is as follows: take three pieces of plastic film paper pattern of 100 *100mm, weigh them on the balance (accurate to 0.001g), bake them in an oven at 160 2 C for 10mim, cool them in a dryer for 5min, weigh them quickly (accurate to 0.01g). Calculate as follows: W= (P1-P2)/P2 100%.

Formula: W represents the content of volatile matter (%). P1 represents the weight (g) before drying and P2 represents the weight (g) after drying.

In actual production, if the volatile content is high, it means that the pre-drying is not sufficient and the hygroscopicity is increased, so that the steam generated during hot pressing increases, which is easy to produce stratification, bulging, wet flowers, etc., which makes the gloss of the layout uneven. The main factors affecting the quality of impregnated laminated paper  particleboard produced by colleagues after hot pressing product surface shrinkage, its size changes greatly, easy to warp. The low content of volatile matter, the glossiness of particleboard surface decreased, and the bonding strength with the base material was poor. It was easy to produce dried flowers, and even more difficult to apply. The optimum value of volatiles should vary slightly according to the type of resin, roughly 4%-8%.

1.1.3.3 Fluidity of resin: When impregnated paper is hot pressed, the resin should melt and flow to form a continuous film. Liquidity is calculated by the following formula:

Liquidity%=(W-W0)/W*100%

In formula: W represents the weight (g) of film paper cut into 20 *20 cm cubic meters and 5-10 layers.

W0 represents the weight (g) of the sample after measuring W after hot pressing for 10 minutes at 150 and 15 kg/cm2, after completely removing the resin flowing out from the surrounding area.

The fluidity decreases with the increase of the molecular weight of the resin in impregnated paper, otherwise the opposite is true. In the case of high fluidity, film paper is easy to agglomerate and stick to metal pad. Low fluidity, uneven specific surface gloss, poor bonding with the base material, surface bonding strength is not up to the standard.

1.1.3.4. After the melamine impregnated paper is stored, impregnated and dried, it should be packed with DE plastic film immediately and sealed with adhesive tape. The temperature and humidity of the impregnated paper are 20-25 C and 45-65%. The storage time should not exceed three months in a relatively closed warehouse equipped with air conditioning. When using melamine impregnated paper, the principle of opening the warehouse with use should be adopted. For an incomplete impregnated paper, it should be immediately sealed and sent back to the warehouse for storage in order to prevent moisture absorption from causing the impregnated paper to stick together and can not be used, resulting in unnecessary losses.

Cause Analysis and Solution of Common Quality Problems of 1.1.4 Impregnated Paper

3.1 Glue Deficiency on the Surface of Impregnated Paper

3.1.1 The lack of glue on the surface of impregnated paper means that the surface of impregnated paper is one piece after impregnation and drying, and there is no glue or less glue in a large area. The reasons are as follows:

(1) Paper drying out of the air drying box in paragraph 1

(2) Insufficient glue on the rolls of the intermediate glue-coated mesh and no glue on them

(3) Foreign bodies on the middle scraper

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