The insulation felt is usually made of porous materials such as waste felt and cotton wool, and the methods of joining with the automobile body painted steel sheet are as follows: solvent type adhesive bonding method, pressure-sensitive adhesive method, foam hot melt adhesive bonding method, etc.
Using neoprene type adhesive and styrene butadiene rubber type adhesive to bond the thermal insulation felt is an early assembly method used in automobile manufacturing industry. Brush coating, roll coating or spray coating can be used for sizing. The general process requires that both sides of the thermal insulation felt and the painted steel plate of the car body should be coated separately, and the coating surface should be overlapped after the solvent is fully volatilized. The viscosity of the solvent type adhesive used should be larger, so as to prevent the adhesive liquid from penetrating into the fiber of felt and losing the adhesive ability on the surface. Because of the use of solvent adhesive, the smell is strong, and the air pollution in the construction site is serious, many automobile manufacturers began to use the way of precoating pressure-sensitive adhesive to bond the thermal insulation felt.
The advantages of precoating pressure-sensitive adhesive have been mentioned before and will not be repeated here. At present, many manufacturers in our country adopt this technology, such as the first automobile group company Hongqi car, FAW Volkswagen Co., Ltd. Jetta car, Shanghai Volkswagen Co., Ltd. Santana car and other thermal insulation felt are pre coated with pressure-sensitive adhesive on the back. The adhesive used for thermal insulation felt shall have good heat resistance, and maintain sufficient strength within the range of use temperature of the bonding surface to prevent falling off.
Now, foreign automobile manufacturers begin to use hot-melt pressure sensitive adhesives to bond heat insulation felt, and can be coated with foam hot melt glue machine. The so-called foam hot-melt glue machine is to mix the ordinary hot-melt adhesive with the inert gas such as nitrogen or carbon dioxide in the melting state and then spray on the back of the insulation felt, especially for the bonding of porous materials. Due to the foaming type, the volume of the adhesive can be expanded by 2-5 times, the amount of adhesive can be reduced by about 50% compared with the general adhesive, and the wetting effect of the adhesive can be improved, and the bonding strength can be increased. Using hot-melt adhesive to bond thermal insulation felt, the bonding speed is fast, and the cost is lower than precoating pressure-sensitive adhesive. Because this bonding method saves the anti sticking paper or isolation film needed in the packaging and transportation of the thermal insulation felt precoated with pressure-sensitive adhesive. Ford Motor Company, general motors and other manufacturers are using this method to bond the insulation wool