The common production methods of plastic sheet equipment are calendering, which is mainly used to produce pvc, PVDC and other sheets; The other is extrusion method, which is used to produce BOPS, EPS, PET, PP, HIPS and other sheets. The sheet mentioned in this paper mainly refers to the sheet used for thermoforming packaging products produced by the process of "extruder -T-head-three-roll calendering equipment-coiling". With the development of packaging sheet, domestic sheet machinery industry has continuously introduced advanced configuration and new machines. For more than ten years, sheet production and sheet machine manufacturing enterprises have cooperated with each other to launch the same products, which has also improved the overall development level of the plastic sheet industry. Advanced equipment configuration makes full use of new plate processing technology and new raw and auxiliary materials.
The gradual improvement of domestic film machinery manufacturing level has promoted the increase of domestic plastic film production enterprises and the diversification of film varieties, and also promoted the unprecedented prosperity of thermoforming packaging industry. The development of China's sheet machine industry generally has the following trends: First, the "vertical three-roll" sheet production line with a single "separate single screw extruder" tends to be saturated. Most domestic thermoforming enterprises have this type of sheet production line, which has made great contributions to the early occupation of the market, accumulation of funds and technical development. The sheets produced by HIPS can basically meet the production requirements, but the sheets produced by HIPS, especially HIPS sheets, can't produce satisfactory gloss, and the grade is low. This kind of sheet machine is quite mature in technology, easy to assemble, easy to buy parts, simple in configuration, simple in operation, cheap in price and low in maintenance cost, and has become a popular model. Fierce competition has forced some thin-plate machine manufacturers to turn to other products. For example, "Beijing Shengan" once focused on "the development of aluminum-plastic composite panels"; "Shantou Dacheng" is moving towards a higher-grade plate production line. There are also some manufacturers who have switched from film machine production to sheet processing, plastic cup manufacturing, plastic suction and other industries. This machine can be used to process PP, HIPS, PE egg trays, blister packaging sheets, etc. If air knife is used instead of calendering roller, thinner blister paper can be produced. However, at present, most of this equipment in China is not equipped with this device, which brings a lot of inconvenience to production enterprises and restricts the development of enterprises in the field of plate and molded products to some extent. 2. In the sheet production line with a single extruder, the first "electromagnetic dynamic extruder" in China has been successfully applied to the sheet production line. It has the advantages of energy saving, material saving, uniform plasticization, etc., and can produce a variety of materials with low price. This extruder with "China characteristics" should be vigorously promoted, continuously improved, equipped with advanced follow-up equipment and control system, and introduce our own advanced production line in China to the world, so as to get rid of the development state of always following others. For example, "Shantou David" has launched a number of such plate production lines to the market, and the market has responded well. 3. The sheet machine equipped with a single "exhaust-two-stage single screw extruder" is a new sheet production line promoted by equipment manufacturers to cooperate with "environmental protection". "Shantou Dacheng" and "Xi 'an Wanjie" have successfully trial-produced biodegradable sheets with starch content as high as 80% after many arduous tests and improvements. Many domestic enterprises have used "Xi 'an Wanjie" starch degradation materials to produce environmentally-friendly degradation sheets and thermoformed products on the "Shantou Dacheng" degradation sheet production line, and the prospects are promising. The sheet production line can be used to process highly filled PP/PE sheets, photo/biodegradable sheets and bio-starch degradable sheets. Domestic "degradable plastics" are not "fully degradable materials", but contain "plastics" to some extent. In addition, due to the proliferation of all kinds of "degradable materials", the existence of the phenomenon of confusing fish with pearls, the competition from "pulp molded products" and the impact of the resurgence of "foamed lunch boxes", the market situation of degradable thermoformed products is not optimistic. 4. In order to reduce the cost and grasp the market, enterprises producing degradable sheets have purchased granulation production lines and supplied their own "degradable sheet" production lines with "twin-screw granulation production lines". Shanghai Jinying, Xi An Wanjie, Xi An Maishikang and other plastic packaging companies all have their own "twin-screw granulation production line". We believe that the production technology of "degradable granular materials" in the market is mature and the price has dropped to a very low level. Enterprises that produce "degradable sheets" don't need to open their own granulation production lines, because many granulation production lines have insufficient tasks or even idle equipment. In addition, some sheet machine manufacturers are developing "twin-screw extrusion degradation sheet production line", aiming at canceling the intermediate procedure of "granulation" and directly producing sheets with the prepared powder, further reducing the production cost. Moreover, this "twin-screw extrusion sheet production line" can also process high-filled calcium-plastic degradation sheets and extrude PVC, PVDC and other sheets. 5.K-resin * * * mixed transparent KPS sheets tend to replace PP transparent sheets to manufacture disposable containers and bop and PVS sheets. Because BOPS and PVC sheets need special equipment to produce, most of BOPS and PVC sheets needed by general thermoforming enterprises are purchased. In addition, PVC scrap can not be used by enterprises themselves, and the recycling price is very low, which increases the production cost of enterprises. Another reason is that PVC recycled materials are easy to pollute other plastics, so special attention should be paid to production, which brings some trouble to production operation. KPS plate can be processed on the general extrusion plate production line, and the leftover materials can be used by enterprises themselves, which can increase their own plate output and reduce production costs. Therefore, some enterprises began to make transparent drinking cups with KPS sheets, which have good hardness and toughness, and also used KPS instead of PVC sheets as lids. KPS sheet is a mixture of k resin and GPPS resin. K resin is exclusively produced by Philip Chemical Company, and its price is gradually decreasing. It will be more likely to replace PP sheet, PVC sheet and BOPS sheet. Domestic equipment for producing PP sheets can also produce satisfactory KPS sheets. 6. "Multilayer composite extruded sheet" is favored by the market because of its special properties. The development of dairy and beverage industry requires more and more plastic cups. In addition to good appearance quality, transparency, brightness and hardness, it also requires long-term preservation function and shelf life, but single-layer sheet can not meet this requirement. The "multi-layer * * * extruded composite sheet" introduced by sheet manufacturers is not only the demand of the market, but also the need of product upgrading. Single-layer film machine has less investment, more competitors and low film price. Multi-layer composite plate production line has large investment, few competitors, good plate quality, high-grade thermoformed products and good market price. Another reason is that the production of composite extruded plastic sheets can eat more recycled materials and reduce costs.