Introduction and production of PVC SHEET
BRIEF INTRODUCTION OF PVC SHEET
According to the color can be divided into color film, slightly blue film, all kinds of color film;
According to the transparency is divided into transparent sheet, translucent sheet, Opaque Sheet;
According to the surface treatment can be divided into light sheet, Matte Sheet (thick and thin) , single, double paste film, Dumb White (black) ;
According to the grade can be divided into new material and ordinary new material;
According to the function can be divided into anti-static film and anti-ultraviolet Film;
Product Specifications: calendering line thickness 0.15 mm-0.55 mm, width ≤680 mm
Extrusion line: thickness 0.18 mm-3.0 mm, width ≤1300 mm
Product Features: extensive application, flame retardant self-extinguishing, high quality and low cost. Currently widely used in various tools, fishing gear, toys, electronics, medical packaging, clothing and other industries blister, carton, packaging, printing, business card printing and other fields. PVC material has good processing performance, low manufacturing cost, corrosion resistance, insulation and other good characteristics.
Processing flow of PVC SHEET
PVC Resin Conveying System → mixing process → high-speed Mixer → cooling high-speed mixer → extruder → two-roller open mill → calender → stripping → embossing roller → cooling roller thickness measuring device → take-up machine → finished product
Material Mixing: PVC Resin, stabilizer, internal lubricant into the high-speed mixer, stir to 80-90 °C, add processing AIDS, impact modifier, continue to heat up to 100-105 °C when adding lubricants, colorants. After mixing evenly (120 °C) , complete the mixing discharge to the cooling mixer. In the cooling mixer stir cooling to 40 °C when a discharge to the extruder hopper.
Barrel temperature 110-140 °C
Screw temperature 100-130 °C
This is the main plasticizing process, must ensure good plasticizing. The ideal condition is long strip shape, if is the ball shape hair sticks the matter to be disadvantageous exhausts, the product easy to produce the air bubble. If there is a powder for the process of plasticizing difficulties easy to appear crystal point.
Temperature 170-190 °c; roll gap 2-4 mm
Two to four roller feeding machine, sheet should be good plasticizing, surface bright without bubbles.
Temperature and speed of four-roller Machine
Roller 1:185-200 °C 8M / min
Roller 2:190-205 °c 9.5 m / min
Roller 3:195-210 °c 12 M / min
Roller 4:183-195 °c 12 M / min
Pe Wax is the main lubricant when the temperature rises to 100-105 °C. The quantity and quality of PE wax added with Paraffin and oxidized wax (OPE) are very important.
If the melting point of PE wax is too low and poor in quality, the lubricant will become unstable as the processing temperature rises There will be the phenomenon of migration precipitation, or even play a small effect of direct volatilization.
PVC calendered transparent sheet is one of the main varieties of rigid PVC, usually produced by Conical twin-screw extrusion.
1. YELLOWING PROBLEM
The causes and solutions are as follows:
First, PVC is inherently unstable. If it is a new PVC resin manufacturers, may be poor stability of PVC itself, you can change the PVC to try. However, even the brand name PVC that has been used may be caused by the PVC resin itself, because even different batches of PVC produced by the same manufacturer may have different quality.
PVC Resin has poor heat resistance and its melting temperature is close to the decomposition temperature Therefore, the choice of suspension loose type, high whiteness, proper viscosity, particle size is more uniform, good thermal stability, average molecular weight is basically the same, easy plasticization, short molding time of Resin. Sg-8 or TK-700 are usually used.
Second, there is not enough stabilizer
Third, the temperature controller problems, show the temperature is lower than the actual, high temperature will cause the decomposition of PVC, yellow. At this point need to re-check the alignment temperature controller. The method is very simple, use Mercury-in-glass thermometer to carry out the comparison. In the actual production, due to loose thermocouple, stick on the material and other reasons, will cause the temperature display temperature and the actual gap.
2. There are small air bubbles in the sheet
Reason for this:
1. Too much moisture in PVC raw materials, such as wet in summer rainy days, raw materials, that may not be moisture in the barrel full discharge, thermal expansion, and then the formation of bubbles in the sheet.
2. In addition, adjuvants may contain too much water.
To sum up, the solution can be adopted: Proper extension of the mixing time of the hot mixer, and the use of cooling mixer. Can effectively remove moisture from raw materials.
3. In the piece material crystal spot number exceeds the standard, also calls the fish eye
The common cause of crystal point is: Some PVC resin particles do not plastication, or plastication is not good. Reasons for the formation of PVC resin itself is not good quality. Under the condition of not changing PVC Resin, the solution is:
First, appropriately extend mixing time and improve the mixing temperature, promote the absorption of additives. And the use of high-quality Mixing Unit, the pre-plasticizing effect of mixing unit, is irreplaceable.
Second, the mixture of ingredients can be left for half a day or a day, let it mature, and then use.
Third, the setting temperature of the barrel can be appropriately increased, increase the screw speed, increase the head pressure, and further improve the plasticizing performance.
Fourth, in the formulation, we must be careful to choose the right auxiliaries, and the amount of auxiliaries, the current auxiliaries market more confusion, product quality varies greatly, it is necessary to carefully choose, in the price and performance to find a better balance.
REFERENCE FORMULA FOR PVC TRANSPARENT SHEET
PVC (SG-7 / 8)100, Organic Tin 0.8-1.2, ACR (TG-20)0.8, MBS 2-4, tg-600.8, tg-740.5, fluorescent whitening agent 0.002, ultramarine 0.001