Polyvinyl alcohol (PVA) is a kind of environmental protection material widely used, but because the melting point of partial alcoholysis material is 190 ℃, the decomposition point is 200 ℃, the melting point of complete alcoholysis material is 230 ℃, the decomposition point is 240 ℃, it is difficult to carry out thermoplastic processing, so it limits the play of its excellent performance. After years of efforts, the senior engineering and technical personnel of elkeme @ have successfully developed the melt thermoplastic polyvinyl alcohol resin through repeated tests, which has been put into large-scale production.
(1) Heat stability, the product softens when heated to 130-140 ℃, its properties hardly change, only the color turns yellow. When heated for a long time at 160 ℃, the color becomes darker; when it is above 200 ℃, it dehydrates in the molecule; when it is close to 300 ℃, it decomposes completely.
(2) Mechanical properties, can form a very strong, tear resistant film, wear resistance is very good, tensile strength is higher than general plastics;
(3) Oil resistance, acid and alkali resistance;
(4) Biodegradability is a kind of degradable material;
(5) It is hygienic, safe and nontoxic, and completely meets the requirements of environmental protection.
Plasticity and processability
The company's modified material series, on the basis of maintaining its own performance advantages described above, has developed a variety of products that can be mass-produced with proprietary innovative technology. Various profiles can be prepared by thermoplastic method.
Among them, the injection process conditions for injection molding products are:
Temperature: feed section temperature 100, barrel temperature 160-160-165, nozzle temperature 130 ℃, mold temperature normal temperature injection pressure: 50MPa
Injection speed: 35mm / S
Pressure maintaining pressure: 40MPa
Pressure maintaining speed: 30mm / S
Cooling time: 35S
Back pressure: 10MPa
Note: the injection molding process shall be adjusted according to the injection molding machine, and the above process conditions are only for reference.
Thermoplastic conditions: (normal temperature)
The single screw extruder with three-stage heating is adopted. The temperature of the first zone (feeding section) is generally set at about 15 ℃ lower than the melting temperature. The temperature of the second zone and the third zone (melting section) is 170 ~ 175 ℃, the die temperature is 145 ~ 150 ℃, the die gap is less than 1.0mm, and the single screw speed is 10 ~ 20rpm.
Note: first, set the temperature to the upper limit of the temperature, then observe the bubble condition, and properly adjust the melting temperature, so as to ensure complete plasticization without bubbles.
The thermoplastic conditions are: (high temperature)
The single screw extruder with three-stage heating is adopted. The temperature of the first zone (feeding section) is about 165 ℃, the temperature of the second zone and the third zone (melting section) is 170-180 ℃, the die temperature is 140-155 ℃, the die gap is less than 1.0mm, and the single screw speed is 10-20rpm.
Polyvinyl alcohol (PVA) blown granular material
1. Instant room temperature water-soluble blow molding granular material: used for blow molding the film with short dissolving time, such as the bead film of washing liquid, the film of pesticide bag, the film of aquatic product feed bag, etc.
2. General purpose room temperature water soluble blow molding granular material: it is used for blow molding of general-purpose film with certain strength and toughness, such as various corrosion-resistant water soluble packaging lining bags, laundry bags, bait bags, computer embroidery films, etc.
3. Medium and high temperature water-soluble blow molding granular material: used for blow molding film which is insoluble in normal temperature water. The water-soluble temperature of medium temperature water-soluble membrane is about 55 ℃, and that of high temperature water-soluble membrane is about 65 ℃. It is used for inner packing bag, artificial marble mold bag, high-grade clothing bag, supermarket shopping bag, etc.
