The reason why PVC can be widely used in the building materials industry is two important reasons: First, the unique properties of PVC (rain, fire, antistatic, easy to form), and second, the low input and high output of PVC. So, why can PVC have the above two advantages? Let us find the answer from its production process.

The production process of PVC is not complicated. The ordinary production line generally consists of a rolling machine, a printing machine, a back coating machine and a cutting machine. The thickness is only produced by the direct motion stirring of the rolling machine, the roller rotation and the high temperature rolling. A film of 0.3 mm to 0.7 mm is produced at the same time and printed on the front side of the film by a printing machine, and a back coat is attached to the back side of the film by a back coater. Do not underestimate this layer of back coating, it is an important guarantee for the quality performance of PVC film. The back coating is made of special materials and is a high-energy affinity agent. It is because of this back coating that the PVC film can be tightly blended with the medium-density board or other sheets, and the glue is not opened for ten or even fifteen years. The biggest problem with ordinary veneers is that it can't solve the problem of film shedding. Since the entire production process is carried out at a high temperature (the temperature inside the rolling press reaches 220 degrees), the PVC film has high light resistance and fire resistance, and the quality of the PVC film is ensured. Of course, this is very demanding on production machines. Usually, the production cost of a production line is about 39 million marks, equivalent to about 160 million yuan. On the other hand, the production process of PVC film is quite simple, and the machine output is also very large. Therefore, PVC is actually a low-input, high-yield product.

Membrane pressure process:

Operating procedure

First, the use of film adhesive

Membrane rubber is a two-component adhesive with an activation temperature of about 60 °C. Storage environment temperature must be between 5 ° C and 30 ° C, below 5 ° C will cause flocculation. Plastic buckets should not be placed directly on the ground and should be placed on wooden pallets, especially during the winter months. The effective period of the film adhesive is not removed from the original packaging, and it is 6 months from the date of delivery.

Membrane pressure compound preparation ratio main agent: curing agent = 20:1, when the main agent is mixed with the curing agent, the main agent should be kept under stirring, and the curing agent is slowly added and stirred for at least 3 minutes. The amount of glue prepared each time should be guaranteed to be used within 4 hours. After the rubber is glued, the rubber bucket should be tightly closed.

Second, the glue injection process requirements

The order of spraying is end face → front line type → front side + line type → end face, the plane part can be sprayed once; the end face and the plane line type need to be sprayed twice.

The active time after mixing the main agent with the curing agent is 4-6 hours, and the glued workpiece should be processed within 4 hours to obtain the best bonding effect. Otherwise, the activation temperature needs to be raised due to the cross-linking reaction of the rubber. Although the gluing effect is good from the appearance, the temperature resistance has been significantly reduced, and if the secondary spray is applied, the rubber marks appear on the surface of the PVC.

After spraying, the surface is white and dry, and the hand is not sticky or dry. After drying, there is obvious film gloss drying time of 30-50 minutes (depending on the temperature, humidity and glue quality of the environment).

Commonly used fans are 1.5 to 2.0 meters away from the workpiece to align the workpiece to blow away the humid air to avoid PVC bubbling due to the high humidity of the workpiece.

In the winter, in order to increase the temperature of the workpiece, the workpiece can be heated to a temperature of 20-25 ° C in a small insulation room (the temperature is prohibited to exceed 35 ° C, otherwise the workpiece will be deformed). The spray should be carried out on a curtain machine at an air temperature of not less than 16 °C.

Glue operators should wear masks to protect the health of the operator.

Third, the use of film press silicone film

According to the characteristics of the workpiece line type (such as arc value, edge angle, width and depth of the line type, etc.), different thickness silicone membranes are selected.

Since the silicone film is often heated and stretched, its sag is increased, and it should be installed in time according to the degree of sagging of the silicone film to reduce the sag.

In order to prolong the service life of the silicone membrane and prevent the quality of the workpiece, the direction of the silicone membrane should be changed periodically, such as the front end of the front end and the left end of the right end.

If a hole or a short crack is formed in the corner of the silicone film, it can be repaired with a silicone gel and a film applicator. When repairing, use a flat weight to compact. After drying for 24 hours, the repaired area can be used normally with 240# sandpaper sand.

Fourth, the setting of process parameters

Membrane pressure workpiece spacing: narrow and long workpieces with a width less than 100mm, the workpiece spacing is not less than 80mm; workpieces with a width greater than 100mm, the workpiece spacing is not less than 60mm; the distance between the workpiece and the table frame is not less than 80mm. The horizontal and vertical spacing should be in a straight line to reduce the resistance to air flow.

Workpiece pad: The width and length of the pad should be 6-10mm smaller than the width and length of the workpiece. The corners around the upper surface of the pad should be rounded at a radius of 3mm-5mm or inverted at 3×45°C to ensure The air between the PVC and the workpiece is thoroughly pumped to achieve the effect that the PVC is firmly glued to the edge of the workpiece. The thickness of the backing plate should be about 3/4 of the thickness of the workpiece, which is one of the important measures to ensure that the PVC is not pulled white.

Set temperature: According to different PVC, the set temperature should be between 130 °C and 160 °C. The temperature of ordinary PVC (relative to high-gloss PVC) should be higher, and the high-gloss PVC should be lower (avoid the loss of light due to excessive temperature) ).

Set time: Preheating time should be between 30s and 50s (the color of PVC should be different, the preheating time should be different, the light color should be lengthened appropriately, the dark color should be shortened properly; the thick PVC should be lengthened appropriately, and the thin PVC should be appropriate Shorten), the vacuuming time should be about 8s, and the pressing time should be the warm-up time plus about 10-20s. The time to reach the set pressure should not be too long. It should be about 5s to ensure that the PVC and the substrate are quickly adhered when the end face of the workpiece reaches the activation temperature and does not excessively stretch the PVC on the workpiece.