1. Learn about hot melt adhesive for wood-based panel edge Banding
Guide: Hot melt adhesive for edge sealing is a kind of adhesive specially used for pasting artificial boards. It is an environment-friendly, solvent-free thermoplastic adhesive. When the hot melt adhesive is heated to a certain temperature, it changes from a solid state to a molten state. When it is coated on the surface of the wood-based panel substrate or edge Banding material, it cools down and becomes a solid state to bond the material with the substrate.
Hot melt adhesive for edge sealing is a kind of adhesive specially used for pasting artificial board. It is an environment-friendly, solvent-free thermoplastic adhesive. When the hot melt adhesive is heated to a certain temperature, it changes from a solid state to a molten state. When it is coated on the surface of the wood-based panel substrate or edge Banding material, it cools down and becomes a solid state to bond the material with the substrate. Since the late 1970s, hot melt adhesive began to enter the important wood industry for edge sealing, plywood core, board splicing, furniture tenoning, etc. Early hot melt adhesive equipment mainly relied on equipment from the United States, West Germany, Italy and other countries. With the maturity and stability of hot melt adhesive equipment in China, the selection and use of hot melt adhesive equipment suitable for the specific conditions of each furniture factory can not only improve the quality and grade of furniture, but also improve production efficiency, reduce the difficulty of panel repair and reduce the labor intensity of workers. 1、 Composition of hot melt adhesive Hot melt adhesive is a 100% solid thermoplastic macromolecular polymer. It does not need solvent in the process of processing and application, and is non-toxic and odorless. Its composition is roughly divided into high polymer, tackifier, viscosity control agent, antioxidant, heat stabilizer and filler. 1. Main material The main material of the edge sealing adhesive is thermoplastic resin or elastomer, which is the main component of the hot melt adhesive. According to different application intentions, the main materials used as hot melt adhesive mainly include ethylene and its copolymer, polyurethane, polyamide, polyester, polyolefin, styrene and its copolymer, in addition, polyvinyl alcohol, cellulose, polyvinyl butyral, etc. 2. Plasticizer tackifier refers to a generic term for a class of amorphous hot-melt polymers with a relative molecular weight of hundreds to thousands and a softening point of 60~150 ℃. Its main function is to reduce the melt viscosity of hot melt adhesive, improve the wettability and initial resistance of the adhesive after melting of hot melt adhesive, so as to increase the adhesive strength, improve the operating performance and reduce the cost. 3. Wax wax is also one of the main components of hot melt adhesive. Its role is to reduce the melt viscosity of hot melt adhesive, improve the fluidity, shorten the exposure time, improve the creep resistance, flexibility and melting speed, reduce the appearance of wire drawing, and avoid adhesive self adhesion; It can also reduce the cost of adhesive. However, the addition of wax will also reduce the cohesive strength and adhesive strength of hot melt adhesive. 4. Fillers are often used in the hot melt adhesive to reduce costs, reduce the volume reduction rate and excessive permeability after curing, improve the heat resistance and heat capacity of the edge Banding adhesive, and extend the operating time of the adhesive. The amount of filler is generally less than 15% (mass fraction). Too much filler will increase the viscosity of the adhesive too much and reduce the adhesion and resistance. 5. Plasticizer The addition of plasticizer in furniture edge sealant can reduce the melt viscosity, accelerate the melt speed, and improve the flexibility and cold resistance; Generally, the dosage shall not exceed 10% (mass fraction), and excessive dosage will reduce the heat resistance, cohesive strength and adhesive strength of the adhesive. 6. The function of antioxidant is to avoid the oxidation and differentiation of hot melt adhesive, and avoid adhesive degeneration and bond strength decline. It is generally believed that it is necessary to add antioxidant when the hot melt adhesive is heated at 180~230 ℃ for 10h or the composition used has poor thermal stability (such as paraffin wax, gum rosin, etc.). 2、 Selection of hot melt adhesive for edge Banding 1. The base material of hot melt adhesive for edge Banding can be divided into three categories according to the different base materials: (1) EVA (ethylene vinyl acetate copolymer resin) base material hot melt adhesive, which can be divided into two categories: filled and unfilled. (2) POL YAMIDE (polyamide) based hot melt adhesive, which has good heat resistance and fast curing characteristics, is mainly expensive. (3) HMPU (polyurethane) based hot melt adhesive, which is a kind of hot melt adhesive with the best performance, is the guarantee of high-quality plate edge Banding. It is expensive and requires special methods of use. 2. The viscosity of the edge sealing hot melt adhesive does not directly reflect the performance of the adhesive. In general, the higher the viscosity of the edge sealing hot melt adhesive, the better its initial adhesion strength, but the worse the coating performance. Low viscosity hot melt adhesive has smaller coating amount and better wetting property. Some hot-melt adhesives with low viscosity and fast curing speed may also have high initial adhesion strength. For the chipboard with poor quality, the hot melt adhesive with high viscosity should be used for edge sealing, because the high viscosity hot melt adhesive has poor fluidity and is not as easy to enter the pores at the edge of the chipboard as the low viscosity hot melt adhesive when applying glue, so that the hot melt adhesive can be fully applied at the edge of the board. 3. Density of edge sealing hot melt adhesive The density of edge sealing hot melt adhesive is generally 0.95-1.6g/cm3, and its density depends on the number of fillers (the more fillers, the greater the density). As a certain gluing area is required for sheet edge sealing, the gluing amount per unit length of unfilled hot melt adhesive with small density shall be less than that of filled hot melt adhesive. Moreover, due to the good Banding performance of the filler free hot melt adhesive, it is possible to achieve the same edge sealing effect, and the use amount of the filler free hot melt adhesive is less than that of the filler filled hot melt adhesive. In order to reduce the amount of gluing, the edge Banding machine must have a good gluing system. 4. The softening point and service temperature softening point of the edge Banding hot melt adhesive are indicators of the heat resistance of the edge Banding hot melt adhesive. The higher the softening point, the less easy the edge Banding hot melt adhesive is to melt. At the same time, softening point is also an important aspect to measure the temperature resistance of panel furniture. In Europe, there has been a set of testing methods for the heat resistance of panel edge banding, and a standard for the heat resistance of panel furniture has also been proposed. France, Germany, Italy and other countries have stopped large-scale production of low softening point hot melt adhesive for edge Banding, but domestic manufacturers (including Taiwan manufacturers) still produce and provide it to the domestic market, because domestic furniture manufacturers and consumers do not pay enough attention to the heat resistance of panel furniture, especially kitchen furniture. 3、 The opening time of the hot melt adhesive for edge banding refers to the time from the beginning of gluing to the time before the edge banding tape is pressed to the substrate. The opening time varies with the type of adhesive. The feeding speed and opening time of the edge banding machine are closely related, and both are very important in the selection and use of hot melt adhesive. For the fast feeding edge banding machine, the hot melt adhesive with short opening time must be selected, otherwise, the hot melt adhesive with long opening time shall be selected. For most manual edge banding machines, due to manual operation by workers, the opening time of the hot melt adhesive used is required to be long enough to facilitate edge banding of bending parts. For automatic or semi-automatic edge banding machines, as the end of the edge banding belt will be cut off, trimmed up and down and polished soon after the base material and edge banding belt are coated and pressed, the edge banding belt will undergo mechanical cutting force in these processes, so the hot melt adhesive is required to have a short opening time and a high initial adhesion strength. 4、 Use of hot melt adhesive for edge banding 1. The temperature during edge banding is affected by the temperature, so the temperature is a very important indicator in the edge banding process. Hot melt adhesive temperature, substrate temperature, edge Banding material temperature and working environment (workshop where the edge Banding machine is located) temperature are very important edge Banding parameters. The ambient temperature of the edge banding machine will affect the curing speed of the adhesive. In factories, edge sealing problems often occur in low temperature seasons. The reason is that the curing speed of hot melt adhesive is accelerated at low temperature, and the effective time of Banding is shortened. If the feeding speed of the edge banding machine cannot be changed (in most cases), the plates and edge banding materials must be preheated to ensure the edge banding quality. 2. Processing of edge Banding glue line After edge Banding, the glue line between the board and the edge Banding belt will have a negative impact on the appearance of panel furniture. Too much glue will make the glue line obvious, otherwise, it will reduce the edge sealing strength. For the discontinuous or uneven glue line, there are many reasons, and the following factors should be considered comprehensively: the cutting accuracy of the plate, and the edge of the plate must keep a 90 ° angle with its plane; Whether the pressure of the edge banding machine pressure roller is evenly distributed and appropriately sized, and the pressure direction should form a 90 ° angle with the plate edge; Check whether the gluing roller is intact, whether the hot melt glue is even on it, and whether the gluing amount is appropriate; The boards with sealed edges shall be kept in a clean place with less dust as far as possible. During the finishing process, the dirty things shall not contact with the glue line.
