Application of the hottest inorganic powder materi

2022-08-23
  • Detail

Application of inorganic powder materials in plastic films at present, at least 4million tons of inorganic powder materials are used in the production of plastic products as part of raw materials in China every year. Replacing some petroleum products with inorganic powder materials can save millions of tons of petroleum every year; On the other hand, for the generated plastic products, it is not only conducive to reducing the cost of raw materials, but also can improve some properties of plastic filling materials according to the predetermined direction, so as to improve the market competitiveness of plastic products

types and functions of commonly used inorganic powder materials

according to statistics, half of the 5million tons of products produced by more than 500 calcium carbonate manufacturers in China are sold to the plastic industry. In addition, talc powder, calcined kaolin, wollastonite powder and other inorganic powder materials are also widely used, and some even become an indispensable part of functional plastic materials

calcium carbonate

calcium carbonate is the inorganic powder filler that is most widely used and used in plastic processing. According to the statistics of calcium and magnesium branch of China Inorganic Salt Industry Association, the total amount of calcium carbonate used for plastic filling is more than 2 million tons every year, accounting for the largest share of various uses, about 50%

according to different processing methods, calcium carbonate is divided into light and heavy. Light calcium carbonate (hereinafter referred to as light calcium carbonate) is formed by calcination, digestion and carbonization of limestone, which has undergone chemical reactions, while heavy calcium carbonate is formed by grinding (dry or wet), with only changes in particle size and no chemical reaction process. At present, the calcium carbonate used in plastic film is 1250 mesh heavy calcium carbonate, which has been widely used in the production of PE packaging bags. It is affected by light transmittance in agricultural mulching film. Although it can be used, the addition amount is small

1) the fineness of heavy calcium has an obvious effect on the mechanical properties of PE film, as shown in Table 1

Table 1 Effect of weight fineness on the mechanical properties of PE film

2) the dispersion of calcium carbonate particles plays a decisive role in the performance of PE film

pe film manufacturers are very concerned about the amount of heavy calcium added, hoping that the more the amount is added, the better, but at the same time, the mechanical properties, aging resistance and light transmittance should not be greatly affected. In particular, how much calcium carbonate can be used in agricultural mulching film is a problem worthy of discussion. Baoji Yunpeng Plastic Technology Co., Ltd. has made beneficial exploration and achieved gratifying results. Table 2 lists the mechanical properties of pure LLDPE film and LLDPE film with 10%, 15%, 20% and 33% nano modified plastic composites produced by Yunpeng company respectively

Table 2 performance test results of Yunpeng nano modified plastic composite filled LLDPE film

from the data listed in Table 2, it can be seen that the LLDPE film with more than 10% to 33% nano modified plastic composite has little difference in various mechanical properties compared with pure LLDPE film. When the addition amount reaches 33%, that is, when the CaCO3 component in LLDPE film has accounted for 26.4%, its mechanical properties can still maintain a high level, especially the right angle tear strength is higher than that of pure LLDPE, which not only comprehensively exceeds the technical index of GB mulching film international premium products, but also is impossible for any CaCO3 filling masterbatch in the past

3) environmental effect of calcium carbonate - environmentally acceptable

"environmentally acceptable plastic" refers to a plastic that can comprehensively utilize environmental conditions and adapt to waste treatment methods, which can be degraded in the environment, composted or conducive to incineration and has less harm

calcium carbonate is an important component in the manufacturing process of environmentally acceptable plastics. The results showed that when the carbonyl index (an index indicating the degree of photodegradation) of the photodegradation film containing 30% heavy calcium reached a certain value during exposure, it was several days earlier than that of the photodegradation film without calcium carbonate, which was beneficial to environmental absorption. At the same time, the existence of calcium carbonate is very beneficial to the continuous degradation of PE film after landfilling, or to reducing the generation of harmful substances during incineration and protecting the incineration device. Compared with the degradable film added with starch, when calcium carbonate returns to nature, its CODcr value (used to measure the pollution degree of reducing substances in water) is 0, while the CODcr value of polyethylene film containing 15% starch is 96

talc powder

talc powder is a plastic filler second only to calcium carbonate, and its application amount in plastics is more than 200000 tons every year. With the further understanding of some physical and chemical properties of talc powder, its application scope and quantity are rapidly increasing

1) as a heat preservation agent for agricultural film, minerals containing silicon, such as mica, kaolin and talc, can block and shield infrared rays. Adding an appropriate amount of this mineral powder to the agricultural greenhouse film can improve the barrier of the plastic film to the infrared ray, so as to reduce the heat loss outside the greenhouse in the form of infrared radiation at night, and improve the heat preservation of the greenhouse

The research results of the Research Institute of light industrial plastics processing and application in the early 1990s show that:

① mica powder, kaolin, talc powder and light calcium carbonate have the same filling amount (similar fineness and surface treatment), and have similar effects on the mechanical properties of polyethylene films, among which the mechanical properties of films filled with kaolin and mica powder are better

② LDPE film pair filled with filler containing silicon μ M infrared ray barrier is obviously better than the inorganic filler without Si light calcium carbonate, while mica powder, kaolin and talc powder have similar infrared ray barrier

③ among the three fillers containing Si, the light transmittance of LDPE film filled with mica powder is the highest, which is close to that of pure LDPE plastic film, followed by kaolin and talc powder, but both are higher than that of calcium carbonate filled film

because talc powder is cheap and easy to operate, its light transmittance and infrared light barrier are not as good as mica powder and kaolin, but it can still maintain good light transmittance and improve its thermal insulation, so it has been widely used in agricultural plastic greenhouse films. At present, the amount of ultra-fine talc powder used by agricultural film manufacturers is 1% - 6% according to the variety of film (anti-aging film, double anti-aging film, multi-functional film, etc.)

2) as a nucleating agent, use

crystalline polymers such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyamide (PA), etc. during the cooling and shaping process after processing and melting, some macromolecules will be arranged in order, which is called crystallization

crystallization requires not only a certain temperature and cooling rate, but also nucleation, followed by crystal growth. Nucleating agent has two main functions: first, increasing the crystallization rate can ensure that the molten polymer solidifies more rapidly during the cooling process, so as to shorten the injection molding cycle and improve work efficiency; The second is that the average spherulite size decreases, the tensile strength, thermal deformation temperature and hardness are enhanced under the action of nucleating agent, and the transparency increases and the turbidity decreases

when talc is used as a nucleating agent for PE or PP, it is first required that the particles should be small. The smaller the particle size, the more the number of particles, which means the more crystallization centers. The more crystals are grown at the same time, the smaller the size of the crystal itself, and the better the performance of the whole material. At the same time, it is also required that the more thoroughly the stone powder is dispersed in the molten state, the better, and the less the agglomeration phenomenon is, the better

3) transparent filling masterbatch with talc powder as the main filler

although the use of calcium carbonate in plastic film can reduce the cost, when the amount is large, the transparency of the film will be greatly affected, causing some users' misunderstanding. In view of this situation, the transparent filling masterbatch has made significant improvements in the selection of fillers and processing technology, so that the transparency of PE film has been greatly improved. Table 3 and table 4 show the optical and mechanical properties of the film after adding 20% and 30% transparent masterbatch, respectively

Table 3 Effect of transparent masterbatch on the optical properties of HDPE film

Table 4 Effect of transparent masterbatch on the mechanical properties of HDPE film

calcined kaolin

because coal series kaolin contains combustible carbon and various forms of water (adsorbed water, crystalline water), when used as an additive for plastic film, it must be calcined first to realize dehydration, decarbonization, and the calcination process from black to white. When calcined at high temperature, minerals not only undergo dehydration and decarburization, but also may undergo various changes in the crystalline morphology of minerals. If the content of mullite phase is too high, due to the high hardness of mullite, it will cause serious wear and tear to the key components of plastic processing machinery and equipment - screw barrel and screw, resulting in the adverse consequences of reduced production efficiency and unstable product quality. In addition, the particle size and distribution, whiteness and price of calcined kaolin must also be taken seriously

98% of the wavelength of the light from the sun received on the earth is concentrated at 0 0 μ Within m, it is divided into ultraviolet light (0..4 μ m) Visible light (0..7 μ m) And infrared light (0.7 μ M above), of which the visible light for photosynthesis of crops during the day is the main form of sunlight transforming into heat energy on the earth. At night, 90% of the energy emitted from the earth's surface to the atmosphere is in the form of μ M of infrared radiation, with a peak value of μ m。 The greenhouse made of agricultural plastic film is mainly to make the temperature inside the shed much higher than that outside the shed, so that the crops can germinate and mature early, and the crops in the shed can still grow in cold seasons. Ordinary polyethylene film without infrared light barrier has poor barrier ability to infrared light, less than 25%. Therefore, although the sunlight passes through the greenhouse film in the daytime, and the energy is left in the greenhouse to be converted into heat energy, which increases the temperature in the greenhouse, at night, due to the poor barrier of the greenhouse film to infrared light, most of the heat will be lost outside the greenhouse in the form of radiation. Therefore, only the thickness of the greenhouse film can be increased, and this increase can not only improve the barrier property, but also can not be thickened indefinitely due to the cost limitation of the film. The only way is to add the substance that blocks the infrared light to the plastic film, so that when the infrared light radiates to the greenhouse film, it cannot penetrate the past, and then reflect back to the greenhouse, so as to achieve the effect of thermal insulation of the plastic greenhouse

pure polyethylene film (thickness 0..1mm) pair μ The infrared light transmittance in the wavelength range of M is 70% - 80%. By adding infrared light barrier, the infrared light transmittance can be reduced to less than 50%. Germany constab Polymer Chemical Co., Ltd. can reduce the infrared light transmittance to less than 25%; Polyethylene film filled with 0.05mm thick inorganic filler developed by Beijing Plastic Research Institute, μ The infrared transmittance in the M wavelength range can be reduced to 36%; Henan Jiaozuo No.1 plastic launched bio based material products in the fields of disposable tableware, hotel consumables, shopping bags and garbage bags, etc., using 0.05mm thick inorganic filler filled polyethylene film produced by the demonstration plant, μ The infrared transmittance in the M wavelength range can be reduced to 39%. Germany constab Polymer Chemical Co., Ltd. uses clay produced in China as raw material to make infrared light barrier masterbatch with the trade mark constab IR 0404 ID, and adds 7% to polyethylene film to make μ The infrared light transmittance in the range of M is reduced to less than 25%

after calcined coal series kaolin is added to polyethylene plastic, the mechanical properties of the filling system are better than talc powder or calcium carbonate filling system under the same conditions, as shown in Table 5

table 5 mechanical properties of polyethylene plastic film filled with different fillers

through the buckle shed experiment, it shows that compared with talc powder and calcium carbonate

Copyright © 2011 JIN SHI