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Development and application status of high fluidity polypropylene copolymer (I)

polypropylene injection molded products have been widely used in packaging, transportation, home appliances, automobiles, offices, daily consumer goods, medical products and other fields. In recent years, with the improvement of polypropylene (PP) production process, especially the improvement of new efficient catalyst and polymerization process, great progress has been made in the development and application of high fluidity polypropylene products

the use of high fluidity polypropylene can make the injection products easy to form and process, and reduce the injection defects and scrap rate. In the process of product processing and production, the processing temperature, injection pressure, clamping force, etc. can be reduced, so as to reduce energy consumption, shorten the molding cycle of products, and improve the output of products. In addition, due to the improved fluidity of the resin, the production of thin-walled products can be carried out and the use of raw materials can be reduced. This paper reviews the development and application status of high fluidity polypropylene copolymers at home and abroad

1 advantages of high fluidity copolymerized polypropylene

polypropylene products are divided into homopolymerization and copolymerization, and copolymerized polypropylene is divided into block copolymerized PP (PP-B) and random copolymerized PP (PP-R). Because copolypropylene improves the impact resistance of PP (especially the problem of low-temperature impact performance management, which can be thankless for free), and has better flexibility, its application field is broadened; High fluidity copolymerized PP has high flow rate and good physical properties, which can make the design of large-scale thin-walled injection products with complex structure feasible; In the production process, it can shorten the processing cycle, reduce the processing temperature, injection pressure and energy consumption, and has the advantages of good processing performance, easy mold filling and less product warpage and deformation

thin-walled food packaging containers with polypropylene resin injection mass of 56.78g and wall thickness of 0.036cm with melt flow rate of 35g/10min, 65g/10min and 100g/10min were selected respectively. It was found that the resin injection temperature with melt flow rate of 100g/10min was 210 ℃ (melt temperature was 220 ℃); The resin injection temperature of 65g/10min needs 228 ℃ (the melt temperature is 257 ℃); The injection temperature of 35g/10min resin needs to be as high as 282 ℃ (the melt temperature is 293 ℃). It can be seen that with the improvement of resin fluidity, the processing temperature is greatly reduced, and the reduction of temperature can reduce energy consumption for users

the improvement of fluidity can reduce the forming temperature and cooling time, and significantly reduce the forming cycle of products, so as to increase the huge market demand for products, as shown in Figure 1 (omitted). This advantage is the most attractive aspect for the wide application of high fluidity copolymerized PP. Generally, the cooling time is reduced by 30%, the whole molding cycle is shortened by 10%, and the molding cycle of high fluidity copolymer PP with melt flow rate of 65g/10min is reduced by 27% compared with the 35g/10min molding cycle, greatly improving the product output

the improvement of PP fluidity can reduce the mold cavity pressure, as shown in Figure 2 (omitted). Within the processing range of ℃, the injection pressure can be reduced by 20%-25% by replacing 35g/10min PP with high fluidity copolymer PP with melt flow rate of 100g/10min. Usually, the injection pressure is reduced by increasing the processing temperature, so as to reduce the deformation of the product. After selecting high fluidity copolymer PP, the processing temperature and injection pressure can be reduced, which can effectively inhibit the deformation of products and improve product quality, which is difficult for traditional polypropylene materials

the improvement of fluidity can improve the design and application of products, and can be used in the design of large thin-wall injection molded products with complex structure, making the design of products with large length thickness ratio (l/t) (such as 400/1) feasible. With the improvement of material fluidity, its spiral flow length increases, which can form products with large length thickness ratio. The development of high fluidity copolymer PP meets this need. The spiral flow length of resin with melt flow rate of 100g/10min is 15% higher than that of 65g/10min, and 30% higher than that of 35g/10m to solve the problem of microbial infection prevention and control of new aerospace materials as soon as possible (Fig. 3 is omitted); The length thickness ratio has also increased by 10% - 20% (Fig. 4 is omitted) (the test compares two kinds of food containers with a thickness of 0.36mm and 0.64mm). The increase of the length thickness ratio capacity makes the processing of thin-walled products easier, and develops to a thinner and larger aspect, saving materials; At the same time, with the improvement of fluidity, products with larger length thickness ratio can be obtained under lower injection pressure (Fig. 5 is omitted). This means that the market of plastic machinery enterprises in China will be more open. Manufacturers can use the existing equipment with limited injection pressure to produce more competitive products, and can easily realize multi cavity injection (low flow resin must be achieved by using higher pressure)

therefore, high flow copolymerized PP has great application advantages in improving product output, reducing production costs and forming large thin-walled products with complex structures

2Development and application status of high flow copolymerized PP abroad

as early as the early 1990s, some foreign polypropylene production enterprises successfully developed block copolymerized PP products with melt flow rate of g/10min. In the 21st century, several multinational polypropylene manufacturers in the world have developed ultra-high mobility PP copolymers, and successfully developed new ultra-high mobility copolymer PP products with a flow rate of g/10min. For example, the melt flow rate of sc973 from Basell is 100g/10min; The melt flow rate of sc917 is 65g/10min; The melt flow rate of sg853 is 55g/10min; The melt flow rate of pp7075p1 and pp7065p1 of Exxon is 100g/10min and 70g/10min respectively; The melt flow rate of dj360mo, bj380mo and bj355mo of Borealis is 60g/10min, 80g/10ndn and 100g/10min respectively; The melt flow rate of ax668 from Singapore TPC is 65g/10min; Atofina's ppc12712 melt flow rate is 70g/10min, and ppc10712 melt flow rate is 55g/10min; The melt flow rate of b1920 from Samsung, South Korea is 60g/10min B1970 melt flow rate is 100g/10min, etc. In addition to high fluidity, these products also have impact strength and good rigidity and toughness. It is mainly used for injection molding large-scale thin-walled products, such as injection molding household appliances, auto parts, industrial parts, office appliances, furniture and toys, which greatly promotes the large-scale thin-walled manufacturing industries such as automobiles, household products, food packaging, etc

the high fluidity PP copolymer with melt flow rate of 55g/10min produced by Montell company can be injected into 2.5kg daily packaging products. The original mold and pressure can be used to shorten the cooling time, so that the forming cycle can be shortened by 17%, the product quality can be reduced by 6%, and the total cost can be reduced by 15%

atofina's block copolymer PP with a melt flow rate of 35g/10min has special molecular structure and rubber composition, and has the characteristics of absorbing impact energy and good rigidity. For injection molding stackable packaging products, lower molding pressure (from 8Mpa to 6Mpa) and thinner wall thickness can be used, and the melting temperature of the material is reduced from 245 ℃ to 225 ℃, thus reducing energy consumption

Nordic chemical industry has developed a high flow copolymer PP resin bj356mo with a melt flow rate of 100g/10min, which can be used for injection molding ice cream packaging products with a length thickness ratio of 400:1

montell company directly produces various grades of PP resins with melt flow rates of 35g/10min, 55g/10min and 100g/10min in the polymerization reactor, which not only improves the processability of the resin (the processing cycle is reduced by 20%), but also has better low temperature toughness compared with the resin with poor processability. The injection products using this resin can compete with thermoformed PP and high impact polystyrene requiring good low temperature application performance

under the condition of keeping the rigidity and toughness unchanged, the fluidity of nx20167 copolymer PP product of targor company doubled (from 2..5g/10min to 5.5g/10min). This progress is also reflected in processed products. For example, the resin with a melt flow rate of 5g/10min was used in the production of larger loading pallets in Europe before 10a, and the resin with a melt flow rate of 12g/10min was used two or three years ago. Now advanced processing plants have adopted a resin with a melt flow rate of g/10min, and the increase of resin fluidity is not at the cost of the reduction of rigidity and toughness

with the development of catalyst and production technology as well as the development of supporting technology, the development and production of high flow copolymerized PP abroad has become a new development trend, and the melt flow rate is developing towards ultra-high direction, up to 120g/10min. The major companies have many varieties and brands of this series of products, and there are different products according to different applications, which can meet the needs of different application fields. Table 1, 2, 3, 4, 5, 6 and 7 show the product properties of high flow copolymer PP for injection molding produced by several major companies in the world

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