1、 Equipment process introduction:
Raw material accurate metering initial mixing plasticizing mixing cooling extruding plasticizing ASA raw material drying treatment extrusion plasticizing die compound sheet extrusion cooling shaping traction cutting conveying inspection finished product process layout diagram:
2、 Introduction to raw materials:
（1） PVC PVC is a kind of non-toxic, odorless white powder. The average molecular weight is 30000-100000, and the high molecular weight PVC can reach 250000. PVC began to soften at 65-85 ℃, slightly decomposed at 120-150 ℃, and completely decomposed at 200 ℃. It has good chemical stability, resistance to general acid and alkali corrosion, strong resistance to oxidants, reducing agents and strong acids, but it can be corroded by concentrated oxidizing acids such as concentrated sulfuric acid and concentrated nitric acid, and it is not suitable for contact with aromatic hydrocarbons and chlorinated hydrocarbons. Its main solvents are dichloroethane, cyclohexanone, tetrahydrofuran, etc. The biggest characteristic of PVC is flame retardant, so it is widely used as fireproof material. However, PVC will release hydrogen chloride and other toxic gases, such as dioxins, during combustion. The classification of soft and hard PVC is mainly related to the content of plasticizer. Generally speaking, 0-5 phr of plasticizer (based on 100 parts of PVC resin) is regarded as hard plastic; when the content of plasticizer is more than 25 phr, it is soft plastic. The loose resin produced by suspension method is commonly used in industry, commonly known as SG resin. Its structure is loose, the surface shape is irregular, and the cross-section transportation is porous network. Therefore, the plasticizer can be absorbed quickly and plasticized quickly. Suspension PVC can be divided into pvc-sgl and pvc-sg8. The smaller the number, the higher the degree of polymerization, the higher the molecular weight and strength. However, the more difficult the melt flow is, the more difficult the processing is (SG1 has the highest degree of polymerization, and SG8 has the smallest degree of polymerization). Specific selection, such as soft products, the general use of pvc-sgl, pvc-sg2, pvc-sg3, need to add a large number of plasticizers. And processing hard products, generally do not add or a small amount of plasticizer, so do hard products with pvc-sg4, pvc-sg5, pvc-sg6, pvc-sg7, pvc-sg8 resin.
（2） Calcium carbonate
Classification of calcium carbonate:
1. Heavy calcium carbonate
2. Light calcium carbonate
3. Activated calcium carbonate
4. Nano calcium
Heavy calcium carbonate and light calcium carbonate are mainly used in hard PVC products (plastic tiles, PVC profiles, etc.), which are mainly introduced here.
Brief introduction of heavy calcium carbonate:
Calcium carbonate, calcium carbonate, molecular formula: CaCO3, molecular weight 100.092
Properties of heavy calcium carbonate: white powder, colorless and tasteless. Stable in the air. Almost insoluble in water, insoluble in alcohol. In case of dilute acetic acid, dilute hydrochloric acid and dilute nitric acid, it will boil and dissolve. When heated to 898 ℃, it began to decompose into calcium oxide and carbon dioxide. Heavy calcium carbonate, referred to as heavy calcium, is made by grinding natural carbonate minerals such as calcite, marble and limestone. It is a commonly used powdery inorganic filler with high chemical purity, high inertia, not easy to chemical reaction, good thermal stability, no decomposition under 400 ℃, high whiteness, low oil absorption, low refractive index, soft, dry, no crystal water, low hardness, low abrasion value, non-toxic, tasteless, odorless, good dispersion and so on.
According to the needs of different particle size requirements of ordinary calcium carbonate, ultra-fine ground calcium carbonate, wet grinding ultra-fine calcium carbonate, superfine surface modified heavy calcium carbonate can be provided. [introduction] calcium carbonate is an important and widely used inorganic salt. Heavy calcium carbonate (GCC) is also called ground calcium carbonate (GCC) and kotamite in the United States. It is made by directly crushing natural calcite, limestone, chalk and shell by mechanical method. Because its settling volume (1.1-1.9 ml / g / g) is smaller than that of light calcium carbonate (2.4-2.8 ml / g), it is called heavy calcium carbonate. [production method] there are two production processes of heavy calcium carbonate. Dry process production process: firstly, calcite, limestone, chalk, shell, etc. transported from the quarry are manually selected to remove gangue; then, crusher is used to remove gangue
The limestone is roughly crushed and then crushed by Raymond (pendulum) grinding powder to obtain fine limestone powder. Finally, the grinding powder is graded by a classifier. The powder meeting the particle size requirements is stored in the warehouse as product packaging, otherwise it is returned to the mill for grinding again. Wet production process: firstly, dry fine powder is made into suspension liquid, which is further crushed in the mill. After dehydration and drying, ultrafine ground calcium carbonate is prepared.
The effect of heavy calcium carbonate is as follows
Heavy calcium carbonate, referred to as calcium carbonate, is a white powder made from high-quality calcite. Its main component is CaCO3. It is characterized by high whiteness, good purity, soft color and stable chemical composition. Therefore, the heavy calcium is a kind of good filler commonly used in industry. It is usually used as filler, and also widely used in artificial floor tile, rubber, plastic, papermaking, coating, paint, ink, cable, building supplies, food, medicine, textile, feed, toothpaste and other daily chemical industries. As a filler, it can increase the volume of products and reduce the production cost. When used in rubber, it can increase the volume of rubber, improve the processability of rubber, play the role of semi reinforcement or reinforcement, and adjust the hardness of rubber. The value of heavy calcium used in plastic industry: 400 mesh of heavy calcium carbonate powder for plastics plastic masterbatch and color masterbatch,
It is required that the whiteness remains unchanged after high temperature heating, the ore structure is large crystal calcite, the content of calcium carbonate is 99% and the whiteness is 95%. Calcium carbonate can play a role of skeleton in plastic products, which has a great effect on the dimensional stability of plastic products, and can also improve the hardness of products, and improve the surface gloss and surface smoothness of products, It can also replace expensive white pigments.
Brief introduction of light calcium carbonate:
Light calcium carbonate is also known as precipitated calcium carbonate PCC) is to produce lime (mainly composed of calcium oxide) and carbon dioxide by calcining limestone and other raw materials, then adding water to digest lime to produce lime milk (the main component is calcium hydroxide), and then carbon dioxide is added to carbonize lime milk to generate calcium carbonate precipitation. Finally, it is prepared by dehydration, drying and grinding, or the secondary decomposition reaction of sodium carbonate and calcium chloride is used to generate calcium carbonate precipitation, It is prepared by dehydration, drying and grinding. Because the settling volume of light calcium carbonate (2.4-2.8 ml / g) is larger than that of heavy calcium carbonate (1.1-1.4 ml / g), it is called light calcium carbonate. The chemical formula of calcium carbonate is CaCO3. Calcium carbonate reacts with all strong acids to form water and corresponding calcium salts (such as calcium chloride CaCl2) and emit carbon dioxide at the same time. At room temperature (25 ℃), the concentration product of calcium carbonate in water is 8.7 × 1029, the solubility is 0.0014, the pH value of calcium carbonate aqueous solution is 9.5-10.2, and the pH value of air saturated calcium carbonate aqueous solution is 8.0-8.6. Calcium carbonate is non-toxic, odorless and non irritant. It is usually white with a relative density of 2.7-2.9. The sedimentation volume of light calcium carbonate is more than 2.5ml/g, and the specific surface area is about 5m2 / g (it is tested by the BET method with the fully automatic F-Sorb 2400 specific surface area meter produced by Beijing Kingtech). Light calcium carbonate has fine particles, rough surface and large specific surface area, so its oil absorption value is high
About 60-90ml / 100g. The function of light calcium carbonate: it is widely used in papermaking, plastic, plastic film, chemical fiber, rubber, adhesive, sealant, daily chemical industry, cosmetics, building materials, coating, paint, ink, putty, sealing wax, putty, felt packaging, medicine, food (such as chewing gum, chocolate), feed, its role is: increase product volume, reduce costs, Improve processing properties (such as adjusting viscosity, rheological properties, vulcanization properties), improve dimensional stability, reinforcement or semi reinforcement, improve printing performance, and improve physical properties (such as heat resistance, extinction, wear resistance, flame retardancy, whiteness, glossiness).