Recently, a large number of small factories and mask factories have launched meltblown nonwoven fabric production equipment. Improvement from last month: I know post-electret process and I know that an electrostatic electret should be added, but problem is still there, I don't know. Adding 0.3% or 4%, high voltage electricity reaching 10KV or 20KV, choice of raw materials from different suppliers will have a big impact.
Seeing that filtration efficiency is improving step by step, it is nice to congratulate: Chinese are still smart and will always find free time. But choice is more important than hard work. This sentence can be used to describe companies that have recently launched melt blowing equipment. They may not know why their materials can never reach 99.97%, why data measured by themselves, and data sent to third parties for verification There is such a big difference why it is approved in China but blacklisted in foreign countries. (Currently, some third-party testing agencies in China are unreliable in issuing reports)￼
All kinds of test equipment, all kinds of dirty test data and low-quality defective materials can only be used for flat masks in accordance with GB15979-2002 "Hygiene standards for disposable sanitary ware", which has no requirements for filtration efficiency.
The test equipment with above test data has a relatively low detection accuracy, and there are big problems in detection methods. The particle counting method is suitable for low concentrations, but not for low dust generation. The smaller amount of dust particles, more filtration efficiency is distorted .
Some domestic test equipment may even deliberately increase filtration efficiency data when they leave factory, so you find your test data is so excellent, and then same material is tested on TSI 8130, why so many differences? TSI 8130 is a photometric test method, dust generation from salty particles alone can reach 17mg/m³, and dust generation from oily particles can reach 135mg/m³, and detection accuracy is even higher.
The above image is a test comparison of same filter material of same type, same block and same point in early 2018. 99.4% and 93.1% turned out to be same point of same material to low dust concentration of particle counting method equipment, repeated measurement of same point has no effect. If concentration of photometer method is too high, this operation not allowed), data is displayed on two different brands of filter equipment for performance testing, you will find that data from test equipment calibrated with 8130 will be more real than from other test equipment, although both are domestic.
Melt-blown materials without static electricity and purely physical filtration have same filtration efficiency for oil and salt (the CMD of oily particles is 0.185um, and CMD of salt is 0.075um. Some say their products can filter 0 particles, 1 µm To filter out 0.075 µm particles, first find out relationship between mean particle size (CMD), aerodynamic mean diameter (MMAD) and mean mass diameter).
Recently, many masks exported to foreign countries have encountered problems related to low filtration efficiency tests and lack of qualification. Of course, filtration efficiency of meltblown or filter materials cannot be equal to effectiveness of masks, which is due to ignorance of test standards, test equipment, test methods and sense of responsibility of experimenters.
Generally, traditional large-scale meltblown fabric materials do well with technology, for example, Grade 95 material (original 32LPM, H11, 8130) should be over 97.5%. Now new small manufacturers are using domestic testing equipment to achieve 95% filtration efficiency, and they are very satisfied. They do not test for aging and attenuation. The market of melt blowing industry is mixed, overall quality has dropped significantly compared to before epidemic, and it is easy to meet defective products and counterfeit products.
Many people in China believe that 95% of filtration efficiency of mask testing equipment is due to KN95 masks. 8130 equipment through some inappropriate means such as intermediary agencies to process qualified reports (this phenomenon is especially common during an epidemic). , there are a number of problems, such as quality of sent samples and quality of bulk products, and quality of masks during epidemic is generally better than before epidemic. many people in mask business are lay people.
GB2626-2006 KN95 stress test is different from EN149 FFP2 test, i.e. technical index of melt blown FFP2 material should be better than KN95/N95 material, but it is not. scares like a legendary difference (N95 is now on market 85, P2 current market price is 120-200), and continuation can be decided through distribution plan, because test conditions for FFP2 oil in EN149 are actually lower than test conditions for KP95 2626. The usual post-electret blowing process from melt is not competent, mainly reflected in finished mask, inhalation resistance is too large, and efficiency of oil load test is too low, and dolomite clogging of discarded mask is a random test).
Small workshops and small factories, which are new to meltblown production, have simple and crude equipment, and most of them have never been in contact with meltblown production, so it is difficult to produce high quality filter media at this stage, and it is necessary to ensure pretreatment process Stability final material, aging and attenuation of material and other issues. May is month when melt blown production line is most launched. Manufacturers with stable quality can grab tail and continue to make profits. Those who cannot produce good products can only be eliminated. Now there is no shortage of other products, besides melt blown fabric on market High quality The price of melt blown fabric continues to rise. ￼
The picture above shows imported meltblown materials from 3 different countries. After one year of regular storage, this month's 8130 test data shows that filtration performance is relatively stable, indicating high quality in meltblown industry in past. .
The old brand melt blown fabric factory has launched mask production line, and supply of high quality meltblown materials to market is getting smaller and smaller, forcing traditional mask factories to start melt blown fabric production line. It is said that famous mask factory spent 7 million euros to manufacture German melt-blown production line. The entire nation has gone from frying masks to blowing melt for entire nation. How long can this hype last? Besides meltblown, who will be next source of advertising for masks?
Remember that BFE is lowest filtration material and can be melt extruded using ground equipment. The theoretical data for two layers of BFE 99 of 25 grams cannot withstand loads of KN95/N95.
As price of high-quality melt-blown film continues to rise, many mask factories have turned their attention to relatively economical PTFE membranes and solved problem of poor filtration efficiency by increasing resistance, which has led to continued rise in membrane prices. PTFE membranes.
Although resistance of this type of membrane is high, it can be controlled within resistance range required by KN95/N95. I did not expect things that were eliminated by mask industry a few years ago to be revived due to epidemic, and there are not many companies that can do well. This is mainly reflected in process of compounding PTFE with substrates (spunbond, spunlace, hot air ), as well as in production process of masks, which are prone to holes and affect filtration efficiency. Of course, whether these two processes are well controlled or not depends on It is a matter of probability. Compared with melt blowing, which is usually increased by 20 times, there is still demand in market.
In next year, there will be a large number of problems with weakening of filtering efficiency of masks. The quality of masks will be carefully checked at home and abroad. From recent exposure of companies in different places, it can be seen that it is a new brand or a traditional mask factory, there will be substandard masks. The problem is that quality of masks in whole market has declined compared to before epidemic. In future, market for masks and filter materials , price war will begin in second half of year.
Source: Zhihu, Author: Zhou Liang