At present, PVC Paste Resin has become an important product in the PVC industry. It has unique advantages in the application of soft products. At the same time, it also has the advantages of simple processing technology, less equipment, less investment, small plant area and quick effect. Therefore, it has been widely valued by PVC enterprises. With the continuous development of PVC paste Resin production technology, its product quality is gradually improved, and its application field is also expanding. The application of PVC paste resin in downstream industries includes the following aspects:
A large part of the early artificial leather was produced with PVC as raw material. In recent years, with the rise of Pu artificial leather (especially wet PU artificial leather), PVC artificial leather has gradually lost part of the market share, but Pvc Resin (especially PVC paste resin) still occupies an irreplaceable position in the field of foamed artificial leather (such as upper leather, luggage leather, seat leather, etc.). After China's accession to the WTO, the export of artificial leather has increased rapidly, and the demand for PVC paste resin has also increased year by year. Therefore, the application prospect of PVC paste resin in the field of artificial leather is still promising and worthy of attention. The areas with large production scale of artificial leather in China are Zhejiang, Hebei, Henan and Guangdong. The basic formula and technical points of PVC foamed artificial leather are as follows 1]2. The production method of PVC foamed artificial leather is indirect coating method. The circulating carrier mainly includes steel strip and release paper. Generally, it is coated for three times: the first time, a coating with small thickness (about 0.1mm) and no foaming agent can be coated to form a relatively wear-resistant surface layer; The second coating can be thicker (0.2 to 0.5mm) and contains a foaming agent to form a soft and elastic foam layer. Apply the adhesive layer without foaming agent with a thickness of about 0.1mm for the third time, and then stick the cloth base. By adopting the above method, a double-layer PVC foam artificial leather with a wearable and soft surface can be formed. The technological process is as follows: the carrier is coated with a surface layer, a dry, a cooling, a coating, a foaming layer, a gel, a cooling layer, a bonding layer, a cloth, a foam, a cooling, a stripping, a coil, and a surface treatment.
The paste viscosity of PVC paste resin used for surface layer shall be slightly higher and the degree of polymerization shall also be higher; PVC paste resin used for foaming layer should preferably use special materials; The degree of polymerization of PVC paste resin used for bonding layer shall be lower. DOP is the main Plasticizer. DOS can be added appropriately according to needs and uses to improve cold resistance, and chlorinated paraffin can be added to increase flame retardancy. In addition, antistatic agents, flame retardants, etc. can be added appropriately as needed.
The production process of indirect coating method has the following four characteristics.
(1) Because the cloth base can fit with the adhesive layer without tension, this method is particularly suitable when the cloth base is a knitted fabric with great flexibility or a non-woven fabric with low tensile strength.
(2) The surface of the product is flat and smooth, and is not affected by the cloth base. Therefore, artificial leather with better apparent quality can also be prepared by using coarse cloth with slightly poor quality.
Almost all the soft products in toy products are made of PVC paste resin. In recent years, with the further improvement of economic relations between China and Europe and the United States, Europe and the United States are becoming the largest exporter of Chinese toy products, and the export volume is increasing year by year. In addition, the production equipment investment of PVC toys is relatively small, the operation is simple, and driven by the benefits of good export, toy manufacturers are springing up, driving the market demand for PVC paste resin. The production methods of PVC toys mainly include rotational molding and lining molding. The production process, basic formula and technical points of these two molding methods are introduced below [2] shuoba.
1.2. I rotational molding
Rotational molding, also known as rotational molding, adds a certain amount of liquid or paste materials into the mold, melts and plasticizes the materials through the heating and vertical and horizontal rolling rotation of the mold, and evenly covers the whole surface of the mold cavity with the help of its own gravity. Hollow products can be obtained by demoulding after cooling and curing. The thickness of rotational molding products is more uniform than that of extrusion blow molding products, with less waste, and the products have almost no internal stress, so it is not easy to deform and sag. Rotational molding appeared in the late 1950s, mainly used in the production of toys, leather balls, bottles and cans. The mold used to produce toys by rotational molding method is usually the flap mold of aluminum or copper. The basic production process is as follows: ① add the prepared PVC paste into the mold whose cavity can be completely closed, and the mold is fixed on the machine that can rotate along two orthogonal (or several mutually perpendicular) axes at the same time. ② Close the mold. ③ The mold rotates in the hot air oven. The rotating speed of the main shaft is 5 ~ 20R / min, and the rotating speed of the secondary shaft is 20% ~ 100% of the main shaft, which can be adjusted according to the hot air temperature of the oven. With the rotation of the die, the paste is evenly distributed on the surface of the cavity and gradually melts. According to the properties of PVC paste, product thickness and molding temperature (the temperature of hot air in the oven), the required rotating speed and heating time are also different (generally 5 ~ 20min). ④ After the paste melts, put the mold into the water tank for cooling. After the product is finalized, open the mold and take it out. ⑤ The products produced shall be packed into the box after passing the inflation inspection. Pay attention to the following four points in production.
(1) The prepared PVC paste can only be used after vacuum defoaming.
(2) In the production process, the heating should not be too fast, otherwise the thickness of the product will be uneven.
(3) Increasing rotating speed can increase the fluidity of paste and improve the uniformity of products.
(4) Lower paste viscosity is beneficial to improve the uniformity of product thickness.
1.2.2 plastic lining molding
Enamel molding is also known as coating, molding or coating. The paste is poured into the pre heated mold (only in the negative mold). The paste close to the mold wall is heated by gelation, then the paste without gel is poured out, and the paste adhered to the mold is subjected to heat treatment (baking), and then the hollow product is obtained from the mold after cooling. The production process of plastic lining molding is as follows.
(1) The prepared and defoaming PVC paste is injected into the heated (about 130 ℃) mold (female mold).
(2) when the paste is completely filled with mold, stay for about 30S, then pour the paste back into the container. The paste adhered to the mold wall (thickness 1 to 2ram) has partially gel.
(3) Then put the mold into an oven at about 160 ℃ and heat it for 10 ~ 40min.
(4) Take out the mold, cool it to below 80 ℃ by air cooling or water cooling (immerse in water for 1 ~ 2min), and then take out the products from the mold.
Pay attention to the following three points in production.
(1) The prepared PVC paste can only be used after vacuum defoaming.
(2) When pouring paste into the mold, pay attention to keep the mold and paste clean, so that the whole mold cavity is wetted evenly by the paste. At the same time, the mold needs to be vibrated slightly to discharge the bubbles.
(3) The paste viscosity of the prepared paste shall be moderate, generally below 10Pa · s, so that the whole cavity surface can be fully wetted after pouring into the mold, and the fine concave convex or pattern on the product surface can be clearly displayed. If the paste viscosity is too large, it can not meet this requirement; If the paste viscosity is too low, the product thickness is too small, which is easy to leave small holes. Compared with lining molding, the accuracy of thickness and quality of rotational molding products is much better, but the equipment investment is also much higher.
