In recent years, the sticky tape (Velcro) has been widely used in human daily life, and its use in the market in recent years can be said to be full bloom. The most common application markets are packaging, such as automobile industry, windows and doors (screens), clothing, shoes, luggage, household goods, furniture, stationery, transportation tools, medical equipment, sports equipment, construction, etc.



Glue on straps can be easily sewn on most fabrics. However, for metal, glass, concrete, wood, ceramics, hard plastic and other objects that cannot be sewn, it is necessary to apply an additional layer of pressure-sensitive adhesive for bonding. Solvent based, water-based and hot-melt pressure-sensitive adhesive or double-sided adhesive tape can be applied to the buckle belt. However, due to the following advantages, hot melt pressure-sensitive adhesive has become a more popular adhesive.



Velcro hot melt adhesive



1、 Environmentally friendly



There is no solvent volatilization and waste water in the whole hot melt coating system.



2、 High thickness of pressure-sensitive adhesive coating



The typical coating thickness of the pressure sensitive adhesive for the buckle belt is 200-250 microns. It is difficult for solvent based or water-based adhesives to reach such a high thickness through one coating. The maximum coating thickness of hot melt pressure-sensitive adhesive on the buckle can easily reach 500 microns.



3、 Fast coating speed



Hot melt pressure-sensitive adhesive does not need a drying oven in the coating process of, but needs a series of cooling fans to cool and solidify the hot melt pressure-sensitive adhesive after gluing. Then immediately attach the release paper or film to the sticky adhesive layer surface.



4、 Coating width



The coating width can be adjusted randomly according to the width of the buckle belt or the longitudinal space can be coated with glue. In order to avoid glue leakage at the edges of both sides of the gluing surface, the gluing tape is usually applied to the die with a groove of precise width. The edges on both sides of the adhesive tape can remain 0.5-1mm wide without gluing. After most of the hot melt pressure-sensitive adhesive is coated on the back of the buckle belt, it is first covered with release paper or film and rolled into a drum for storage. Finally, it is cut into various sizes and shapes according to the actual needs of the market.



5、 Gluing method of hot melt pressure-sensitive adhesive for fastening belt



There are many ways to apply hot melt pressure-sensitive adhesive. No matter which way the adhesive is applied, the hot melt pressure-sensitive adhesive must first be heated into a molten state in the melt adhesive tank, and then the hot melt pressure-sensitive adhesive can be directly sprayed or transferred to the substrate or the adhesive by an appropriate gluing device.



The most commonly used gluing equipment are roller and die. In order to meet different processing equipment and individual special back gluing process, it is usually necessary to provide hot melt pressure-sensitive adhesive with different viscoelasticity. How to meet the special adhesive properties and workability of hot melt pressure-sensitive adhesive at the same time depends on the joint communication and cooperation between hot melt pressure-sensitive adhesive manufacturers, adhesives and users.



Generally, a wide range of thinness and consistency from 2000 to 20000 cps can be accepted with the back glue of the mouth mold. The roller back glue needs to have a lower dilute consistency range, usually below 10000cps. The hot-melt pressure-sensitive adhesive with low viscosity is easy to be coated, and the processing temperature can also be reduced moderately. It can also be applied to less heat-resistant substrates and release profiles, such as PE, PP film, etc.



However, the heat resistance of this kind of hot melt pressure-sensitive adhesive is usually relatively low. In recent years, there have been many newly developed thermoplastic polymer products that can be used to develop hot-melt pressure-sensitive adhesives with low dilute consistency and high heat resistance. The back glue surface of the fastener belt, whether hook belt (A) or hair belt (B), is quite rough. In order to obtain a flat adhesive surface, the hot melt pressure-sensitive adhesive can be applied by roller or the die can be directly pressed out of the back of the ribbon, and then covered with release paper or film.



The coating thickness is about 0.25mm (about 250 grams/square meter). If the roller is used for gluing, the gluing surface is usually uneven and cannot leave a blank on both sides of the gluing surface of the webbing. After gluing, it is easy to cause glue overflow on both sides of the webbing.



In addition, hot melt pressure-sensitive adhesive is constantly in contact with air in the open glue tank and sheared by the rotation of the roller, which will accelerate the deterioration of hot melt pressure-sensitive adhesive. In recent years, the gluing equipment of the gluing belt has been changed to the back glue of the mouth mold. They have the following advantages:



1) The hot melt pressure-sensitive adhesive is well anchored to prevent degumming;



2) The side can be left for gluing to avoid glue overflow on the side;



3) The adhesive surface is smooth, and the adhesive physical property is stable;



4) Closed glue melting tank, rubber tube and die equipment can slow down the aging speed of hot melt pressure-sensitive adhesive.




6、 Common Troubles in Glue Processing of Glue Belt Back



The troubles encountered during the processing and finishing of the back glue of the buckle belt are closely related to the viscoelasticity of the hot melt pressure-sensitive adhesive itself and the release paper or film selected. The following are the common problems and solutions of the adhesive tape back.



When the roller machine is applied with hot melt pressure sensitive adhesive, small bubbles appear in the hot melt pressure sensitive adhesive coating. During rotation, the roller will naturally bring air into the rubber groove and generate bubbles. After being sheared by scraper, large bubbles can be broken. While raising the operating temperature can reduce the thinness and consistency of the hot melt pressure-sensitive adhesive and release some bubbles, it may also cause the webbing to deform due to overheating. In addition, the ribbon and the PU sizing solution used by it are hygroscopic. When the webbing with high moisture content is used for backing, it may also release water vapor at the moment of high-temperature processing, resulting in small bubbles between the hot-melt pressure-sensitive adhesive and the interface of the webbing. The use of die gluing can prevent bubbles introduced in the hot melt pressure-sensitive adhesive by roller gluing.



When the back adhesive is applied to the release paper or film, the hot melt pressure-sensitive adhesive cannot be closely combined with the release paper or film. This phenomenon usually occurs in winter in low temperature operating environment. In the normal back glue procedure, when the hot melt pressure-sensitive adhesive is coated on the ribbon, the instant temperature is very high; In order to prevent the webbing from deformation, stretching and other problems due to overheating, the hot melt pressure-sensitive adhesive surface must be cooled immediately by fan blowing. However, when the temperature of the working environment is very low, the hot melt pressure-sensitive adhesive will quickly cool down after leaving the die.



When the temperature is low, turn off the cooling fan according to the situation. When the temperature is too low, a hot air gun shall be installed for insulation. Use hot melt pressure sensitive adhesive with better cold resistance. However, it must be considered whether the comprehensive adhesive properties still meet the market demand. It is difficult to punch the back glued buckle belt.