As the main raw material for masks, meltblown fabric has recently become increasingly expensive in China, reaching as high as the clouds. The market price of high melt index polypropylene (PP), the raw material for meltblown fabrics, has also skyrocketed, and the domestic petrochemical industry has sparked a wave of conversion to high melt index polypropylene materials.
By the way, it should be noted that real meltblown materials are biodegradable. The commonly used 2040 in the market is just ordinary PP material, and real PP meltblown materials are all modified. Currently, for small machines (modified extruders) on the market, using high fluidity meltblown materials is unstable. The larger the machine, the better the effect of using high melting value meltblown PP materials. The quality problems of small machines themselves account for a large part of the reasons. Regular meltblown fabric requires the use of 1500 melt finger special meltblown material, with the addition of polar masterbatch and polar process treatment to further improve filtration efficiency.
Today, the editor has compiled an article about the performance characteristics of modified PP meltblown materials, hoping to be helpful to everyone. If you want to produce meltblown fabrics that meet the national standards KN90, KN95, and KN99, you need to have an understanding of the entire production process, identify process omissions, and make up for them. First, let’s start with the melt blown raw materials.
High melting point refers to melt blown grade PP material
Manufacturing masks cannot do without spunbond fabric and meltblown fabric, both of which are high melting point PP materials after degradation. The higher the melt index of PP used to make meltblown fabric, the finer the fibers blown out, and the better the filtration performance of the resulting meltblown fabric. PP with low molecular weight and narrow molecular weight distribution is easier to produce fibers with good uniformity.
The raw material for producing S-layer (spunbond fabric) of masks is mainly high melt index PP with a melt index between 35-40, while the material for producing M-layer (meltblown fabric) is meltblown grade PP with a higher melt index (1500). The production of these two types of high melting point PP cannot be separated from a key raw material, which is organic peroxide degradation agent.
Due to the generally low melt index of ordinary PP, its flowability in the molten state is poor, which limits its application in certain fields. By adding organic peroxides to modify polypropylene, the melt index of PP can be increased, its molecular weight can be reduced, and the molecular weight distribution of PP can be narrowed, resulting in better flowability and higher drawing rate. Therefore, PP modified by organic peroxide degradation can be widely used in thin-walled injection molding and non-woven fabric fields.
Several peroxide degrading agents
Organic peroxides are Class 5.2 hazardous chemicals with very strict requirements for production, storage, transportation, and use. At present, there are only a few organic peroxides mainly used for PP degradation in China. Here are a few:
Di tert butyl peroxide (DTBP)
Its main characteristics are as follows:
Not approved by FDA for addition in PP, not recommended for production of food grade and sanitary grade products.
The flash point is only 6 ℃, and it is extremely sensitive to static electricity. 0.1MJ of energy is enough to ignite its vapor, making it easy to flash and explode at room temperature; Even with nitrogen protection, it can still flash and explode in environments above 55 ℃.
The conductivity coefficient is extremely low, making it easy to accumulate charges during the flow process.
DTBP was classified by the European Chemicals Agency (ECHA) in 2010 as a Level 3 inducing gene mutation substance and cannot be recommended for use as an additive in food contact and direct contact with human products, as there is a high risk of causing biotoxicity.
2,5-dimethyl-2,5-bis (tert butylperoxy) hexane (referred to as “101″)
This degradation agent is one of the earliest peroxides used in the field of PP degradation. Due to its suitable temperature range and high content of reactive oxygen species, as well as its FDA approval in the United States and BfR approval in Europe, it is still a widely used degradation agent in this field. Due to the high content of volatile compounds in its decomposition products, which are mostly volatile compounds with strong pungent odors, the resulting high melting point PP has a strong taste. Especially for meltblown materials used in mask production, the addition of large amounts of degradation agents can cause significant odor problems for downstream meltblown fabrics.
3,6,9-Triethyl-3,6,9-Trimethyl-1,4,7-Triperoxynonane (referred to as “301″)
Compared with other degradation agents, 301 has excellent safety performance and degradation efficiency, as well as extremely low odor, making it one of the preferred choices for degrading PP. Its advantages are as follows:
● Safer
The self accelerating decomposition temperature is 110 ℃, and the flash point is also as high as 74 ℃, which can effectively prevent the decomposition and flash ignition of the degradation agent during the feeding process. It is the safest peroxide product among known degradation agents.
● More efficient
Due to the presence of three peroxide bonds in a molecule, the addition of the same proportion of reactive oxygen species can provide more free radicals, effectively improving degradation efficiency.
Low odor
Compared with “Double 25″, the volatile compounds produced by its decomposition are only one tenth of those of other products, and the types of volatile compounds are mainly low odor esters, without irritating volatile compounds. Therefore, it can greatly reduce the odor of the product, which helps to develop high-end markets with strict odor requirements and increase the added value of the product. In addition, lower volatile compounds can also reduce the risk of degrading PP products during storage and transportation, thereby effectively improving safety.
Although DTBP is no longer recommended as a degradation agent for modified PP, there are still some domestic manufacturers using DTBP as a degradation agent to produce high melt index PP, which poses many safety risks in the production process and subsequent use areas. The resulting products also have serious odor problems, and there is a high risk of rejection or failure to pass testing when exported to the international market.
Dongguan Liansheng Non woven Technology Co., Ltd. was established in May 2020. It is a large-scale non-woven fabric production enterprise integrating research and development, production, and sales. It can produce various colors of PP spunbond non-woven fabrics with a width of less than 3.2 meters from 9 grams to 300 grams.
Post time: Nov-09-2024