The method of vertically fixing short fibers (usually 0.03-0.5cm in length) onto a substrate coated with adhesive is called flocking. Electrostatic flocking is a processing technique that utilizes ionizing physical phenomena for surface flocking of objects. It is widely used in various industries due to its advantages such as high production efficiency, low cost, wide variety of designs and colors, and wide adaptability.
As the Spring Festival approaches, more and more New Year gift boxes are entering the production process. Flocking technology, as a decorative technique for high-end gift boxes, is widely used in the lining of gift boxes. Today, I will learn about flocking technology with you, hoping to help you better apply it~
01 Flocking process characteristics
1) Flocking principle
By utilizing the physical properties of charge equivalence, repulsion, and attraction, the villi are negatively charged. The object that needs to be flocked is placed at zero potential or grounded conditions, and the villi are attracted by the plant body at different potentials, accelerating vertically to the surface of the object that needs to be flocked. Due to the adhesive coating on the plant body, the villi are vertically adhered to the plant body.
2) Flocking method
Flocking machine assembly line type flocking: This flocking assembly line can achieve full automation from gluing, flocking, drying, and floating removal of items in one sample, such as flocking cloth, leather, paper, non-woven fabric, PVC, plastic sheets, sponges, various handicrafts, toys, automotive plastic parts, storage boxes, automotive sealant strips, decorative strips, plastic boxes, cardboard, calendars, couplets, New Year pictures, and packaging gift boxes for flocking printing.
Box type flocking: Make a flocking box according to the size and shape of the flocked product, place the flocking in the box, connect the power, and form a high-voltage electric field inside the flocking box. The flocked product is fed into the box from one end of the flocking box, and after three to five seconds, it is removed from the other end of the box after flocking, dried or air dried to form the finished product.
Sprinkler type flocking: Connect the power supply and output tens of thousands of volts of high-voltage static electricity generated by the flocking machine into the nozzle. The fuzz in the nozzle carries a negative charge, and then spray adhesive on the surface of the plant. Move the nozzle close to the flocked object, and the fuzz rises from the nozzle to the surface of the flocked object under the action of a high-voltage electric field, planting vertically on the surface of the object coated with adhesive.
3) Features of flocked fabric
Strong three-dimensional sense, bright colors, soft touch, luxurious and noble, luxurious and warm, lifelike image, non-toxic and odorless, thermal insulation and moisture-proof, friction resistant, flat and seamless.
02 Composition of flocking process system
1) Flocking machine
2) Fluff
Fluff is a key material for electrostatic flocking products, and the selection of fluff should be based on the appearance, style, and various physical properties required by the fluff product. At present, the main types are viscose and nylon short fibers, as well as acrylic, polyester, and leather short fibers. Fluff can be divided into two types according to its processing method: crushed fluff and cut fluff. Generally, the quality of crushed fluff is poor, and medium to high-end flocking products should choose high-quality cut fluff.
3) Adhesive
The combination of fuzz and substrate material is achieved through adhesive. Adhesive plays a crucial role in the internal quality of flocking products. It directly affects the friction fastness, feel, thickness and other performance of flocked products. Adhesives can also vary according to the requirements of different flocking products, considering economic and practical considerations.
4) Base cloth
Flocking substrate materials are very extensive, in addition to most current flocking textiles, there are also various materials such as plastic, leather, paper, wood, metal, etc
03 Flocking process flow
1) Feed
In order to achieve continuous production and improve production efficiency, it is necessary to evenly place the bottom fabric in the same direction into a pre prepared cart, and at the same time use a sewing machine to splice the joints. Before applying the flocking production line to the bottom fabric, the bottom fabric should be singed and ironed flat
2) Sizing
After pre-treatment, the bottom fabric is fed to the pulp table through the blooming roller at a certain rate (according to production needs) to provide a certain tension on the fabric surface, making it flat, and controlling the width of the bottom fabric. Then the operator applies the adhesive to the cloth surface, as the adhesive has a certain viscosity, it rotates along with the cloth surface and disperses evenly to the bottom surface.
Evenly extrude the adhesive through the gap between the scraper and the cloth surface, and then fix the bottom cloth to the needle holes on both sides of the flocking production line through the action of the brush plate and pressure plate to prevent the bottom cloth from shaking up and down and moving left and right. The automatic edge detection device detects whether the fabric surface is parallel to the working area and makes corresponding adjustments.
Pay attention to ensuring the cleanliness of the feeding roller under the scraper, and try not to apply adhesive to the surface of the roller as much as possible. At the same time, use a brush under the roller to clean the garbage on the surface of the roller, and use a scraper to remove moisture and adhesive from the surface of the roller. By adjusting the gap between the scraper and the feeding roller, the amount of adhesive applied can be adjusted to ensure the thickness of the final product and save costs.
3) Flocking
Put the prepared pile into the pile box and try to disperse the pile evenly without any pile formation. At the same time, the flocking machine feeds the coated fabric into the flocking area.
The upper plate (located under the hopper) is a plate shaped metal mesh frame, while the lower plate is a metal flat bracket covered with adhesive flocking cloth. The upper and lower plates are respectively connected to the positive and negative output terminals of the high-voltage electrostatic generator (usually tens of thousands of volts) with wires. The fuzz in the hopper evenly falls onto the negative electrode of the metal mesh with the rotation of the feeding shaft and the action of the brush.
Due to the contact between the fuzz and the negative electrode during the descent process, some of the fuzz is charged, causing it to be arranged in the direction of the electric field. At the same time, the fuzz polarizes in the electric field, with charges of the same polarity as the negative electrode concentrated at the end far away from the negative electrode, while positive charges are concentrated at the end near the negative electrode. When the fuzz contacts the negative electrode, due to the higher conductivity of the electrode than the fuzz, a certain conductive current is generated in the fiber, and the fuzz will generate a net negative charge, Make the fuzz have great straightness and flight ability in the electric field, and vertically drop onto the substrate coated with adhesive at a high speed, forming a beautiful velvet pattern. There is also an internal vibration device at the lower end of the bottom cloth, which allows the non firmly adhered fuzz on the cloth surface to detach from the cloth surface and enter the electrostatic field for secondary flocking.
The base fabric also needs to be flocked multiple times to achieve the required flocking density. In addition, the recycling bin under the bottom fabric will collect and recycle the scattered down under the flocking area to save production costs. After flocking, the fabric is sucked away by an air suction device to remove the floating hairs on the fabric surface. In this operation process, attention should be paid to the cleanliness of the process, especially the control of flying hairs.
The key to the quality of flocking is that the power of the high-voltage electrostatic generator must meet the technical requirements of the production line. The electrostatic generator is the heart of electrostatic flocking equipment, and there are two types: transistor high-voltage electrostatic generator and transformer direct boost electrostatic generator (divided into electronic tube rectification type and silicon pile rectification type), to ensure the generation of high and stable static voltage.
If the voltage is too low, the verticality of the villi is poor, and the bonding fastness decreases; If the voltage is too high, an electrostatic spark burning accident may occur. Generally, the output DC voltage is required to reach 20-100kV. The distance between the two plates is generally controlled within 10cm, and it is best to adjust the distance between the plates up and down. To supplement the insufficient static electricity, additional devices can be added.
4) Drying
After the flocking is completed, it enters the oven for drying.
Allow the glue to solidify and the fluff to be fixed on the base cloth. The temperature of the oven varies with the performance of the substrate and adhesive, as well as the amount of adhesive applied (usually above 100 ℃). And it needs to go through multiple hot boxes and undergo a certain period of drying, and the temperature of the oven needs to be gradually increased.
There are two layers of metal plates (heated by thermal oil) inside the oven, which are heated in the form of thermal convection. The oven is equipped with a suction device to timely absorb the evaporated water vapor from the fabric. Pay attention that if the drying temperature is too low and the time is too short, the drying effect cannot be achieved. Poor curing of the adhesive will reduce the wear resistance of the product; Too high a temperature can easily cause changes in the glossiness and texture of the fabric, and on the other hand, it can cause the adhesive to age and deteriorate, making it feel harder to handle.
After passing through the oven, the surface temperature of the fabric is relatively high and has undergone deformation. Therefore, a cooling tower composed of 4-6 cooling rollers is required for cooling treatment to reduce the temperature of the fabric. The cooling roller is filled with liquid circulating cooling water, which cools the fabric through heat transfer. In order to make both sides of the fabric neat and remove edge defects, it is necessary to cut the edges and remove the uneven edges on both sides.
5) Brush bristles
Although floating fluff is removed after flocking, there is still residual fluff in the gaps between the fluff. Generally, a brush is used to reverse the movement direction of the substrate and perform a brush cleaning. And use a hair dryer to collect the brushed down.
Feed the cloth produced by the drying process directly into the bristling machine for bristling treatment. The brush cleaning device is composed of a guide roller, a brush box, a vacuum cleaner, and a transmission device.
Among them, the guide roller is a device composed of a set of guide rollers arranged according to a specified position, which can enable the flocked fabric to be brushed and cleaned according to the specified process; The brush box is equipped with a high-speed brush roller, which can remove the remaining floating hairs on the flocking cloth surface during high-speed operation; A vacuum cleaner is used to collect the cleaned fuzz, and this device can adopt cyclone dust removal, bag dust removal, and other forms of dust removal; The brush box is connected to the vacuum cleaner through an induced draft fan; The transmission device is mainly driven by the guide roller, which can be connected to the guide roller chain of the drying and shaping machine to synchronize the speed with the drying and shaping machine. The transmission of the brush roller is separately driven by the motor through a triangular belt.
Finally, rolling can also be carried out, but for simulated leather fabrics, to ensure that there is no adhesion between the upper and lower layers of fabric during the rolling process, a layer of plastic film needs to be fed while forming the roll. Before rolling, the operator checks whether the fabric thickness meets the requirements and the uniformity of the fabric. If the thickness is too thick, the subsequent grinding process parameters need to be changed accordingly to meet the final requirements. At the same time, adjust the application amount of the adhesive in a timely manner to meet the specified requirements.
6) Organize
The purpose of post processing is to increase the added value of flocking products, mainly through deep processing such as inkjet, embossing, engraving, leather grinding, sand washing, ironing, and gilding, to achieve the desired visual feel effect of the product.
