Feasibility study on the production of the hottest

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Feasibility study on the production of transparent polypropylene and transparent nucleating agent (Part 2)

3.2 methods to improve the transparency of PP

according to the above principle, the morphological structure of PP can be controlled by the following methods to achieve the purposes of reducing crystallinity, controlling crystallization quality (including crystal form, spherulite content, crystal size, crystal regularity, etc.), reducing light scattering, etc

3.2.1 adding transparent agent

adding transparent modifier is to add some small molecular substances to PP to improve its light transmittance and refractive index. Experiments show that the amount of modifier added changes in a parabola with the light transmittance, mainly because when there are too many modifiers, the influence on the growth of crystallinity is greater than that of reducing the crystal size, but the light transmittance is reduced

3.2.2 transparent modification of polymer blending

transparent modification of polymer blending is to mix other resins into PP to achieve the purpose of translucency enhancement. Its principle is similar to that of nucleating agent. The blend also plays a role of heterogeneous nucleation and reduces the size of crystal

3.2.3 biaxial stretching transparent modification

biaxial stretching of PP film can destroy the original crystalline particles in the product through the forced stretching force, so that the crystal size in the product becomes smaller, thereby improving the light transmittance

3.2.4 control the processing conditions to improve the light transmittance

process condition control is also a very effective transparent modification method. Among them, processing temperature and cooling temperature are the two process conditions that have great influence

under the condition of ensuring that the polymer is in the molten state, the lower the processing temperature is, the more original crystal nuclei will remain in the melt, which acts as a nucleating agent, reducing the crystal size and improving the transparency

the lower the cooling temperature is, the faster the cooling is, and the melt quickly passes through the crystallization zone. The lower the crystallinity is, the smaller the spherulite size is, the more conducive to the improvement of transparency

in addition, the orientation during the molding process will increase the birefringence of the product, so it must be overcome

among the above methods of making its axis on a straight line as far as possible, adding transparent agent is the most effective method, because it has low technical difficulty, good flexibility, simple and easy to operate. This method has become the most commonly used and active method to improve the transparency of PP at present. Since the mid-1970s, Hamad, a Japanese, has found that adding a transparent agent to PP can improve its transparency and gloss, and that the translucent PP has high heat deformation temperature, rigidity and yield strength, fast crystallization speed and short processing cycle. Since then, this technology has been widely used all over the world, and the commercialization of transparent PP was realized in the early 1980s. Subsequently, many countries have produced PP resin with high transparency, high gloss, rigidity and excellent toughness by adding high-efficiency transparency agent. According to statistics, from 1991 to 1996, the growth rate of transparent PP products was 7% - 9% higher than that of conventional PP products. At present, almost all PP plants in the United States produce at least one brand of transparent polypropylene resin. In recent years, although it has been reported that targor, a joint company of BASF and Hoechst in Germany, uses metallocene catalysts to produce highly transparent PP resin (metocene x50081), and the transparent plastic film blowing machine industry is keeping up with the times, which is equivalent to PS, most manufacturers still use transparent agents to produce transparent PP, such as the highly transparent PP series (acclear) developed by Amoco polymer, It uses the transparent packaging technology of Milliken chemicals (using transparent agent)

It is more reasonable to use simple experimental settings; According to the literature, in recent years, many domestic and foreign enterprises have been quite active in the research and development of PP nucleating agents, and there are many varieties that have been commercialized. It can be divided into inorganic substances and organic substances. Inorganic nucleating agents are talc powder, calcium carbonate and other substances; Organic nucleating agents generally refer to low molecular weight organic compounds, mainly including fatty carboxylic acid metal soaps, sorbitol derivatives, aromatic carboxylic acid metal soaps and organic phosphates

inorganic nucleating agents are cheap and practical, but their effect on improving the transparency and surface gloss of PP is very poor, so they are not suitable for the production of high-end products; Among organic nucleating agents, the price of aromatic carboxylic acid metal soap is also low, which can improve the transparency of PP to a certain extent, but it has poor compatibility with PP and is easy to scale in plastic processing equipment. Sorbitol derivatives and organic phosphates with short service life can significantly improve the transparency of PP, so these nucleating agents are called nucleating transparent agents or transparent agents. Through comparison, sorbitol derivatives have better performance in improving the transparency of PP than organic phosphates, and have good compatibility with pp. the price of organic phosphates is high, and their dispersion in PP is poor, so they have certain limitations in practical application. Therefore, sorbitol derivatives have become a kind of PP nucleating transparency agent with the most active development, the most varieties and the largest production and sales at home and abroad

at present, the major transparent agent manufacturers in the world are Milliken (USA), new Japan Chemical (Japan), EC chemicals (Japan), Mitsui East Asia (Japan), Ciba (Switzerland), etc

the production and consumption of polypropylene in China are increasing year by year. In 1992, the domestic polypropylene production was 722kt/a, the import volume was 624kt/a, and the apparent consumption was 1240kt/A. By 1998, the domestic output of polypropylene was 2033kt/a, the import volume was 1544kt/a, and the apparent consumption was 3549kt/A. It is expected that the domestic demand for polypropylene will reach 6953kt by 2005. At present, the application of transparent polypropylene in China is only limited to films, sheets, cups, microwave cookers and a small amount of injection molded products. It is conservatively estimated that the national demand for transparent polypropylene in 2000 was 100kt/a, and the demand in 2005 is expected to be kt/A, that is, transparent polypropylene only accounts for 2.8% - 4.3% of the domestic demand for polypropylene. With the continuous expansion of the field of transparent polypropylene, it will further grow. If the addition amount is 0.4%, the domestic demand for transparent agent will be t/a by 2005. Therefore, the transparent agent has formed a market scale and has broad market prospects. However, the production scale of existing domestic devices is less than 100t/A. for example, Shanxi Chemical Research Institute and Hubei resin research institute are pilot production devices, and the output is far from meeting the domestic demand. The transparent additives used by manufacturers producing transparent PP are still mainly imported. To adapt to the rapid development of the plastic industry in the future, there is still a lot of work to be done in terms of product structure, internal quality and scale efficiency, In particular, the development and production of high-efficiency transparent agents in the future should become the focus of future development

5 Conclusion

the domestic transparent polypropylene market has started, and foreign manufacturers are doing everything possible to seize the domestic market. Therefore, we should seize the opportunity, increase the pace of production and development of domestic transparent PP, and further expand the application field of transparent polypropylene. At the same time, the transparency agent is very important to improve the transparency of polypropylene products. The production and sales of the transparency agent are booming in the polymer additives market. The product development and application technology research are also very active, and the market demand for the transparency agent is also rising. This is not only a huge challenge, but also a huge opportunity for Chinese enterprises, most of which rely on imports of the transparency agent. Therefore, it is of great significance to increase the pace of production and development of domestic transparent agents, rapidly develop efficient transparent additives, improve product quality and increase varieties. In addition, we should further expand its application fields and strive to form a large production capacity of transparent agent as soon as possible to meet the needs of users. In this way, we can not only realize the localization of PP transparent additive, reduce the production cost of enterprises, but also improve the product quality and market competitiveness of enterprises

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