Recently, many companies have launched meltblown lines to meet the huge demand for masks. After the epidemic, a large part of these newly launched meltblown equipment will be shut down, especially small meltblown equipment, which cannot be expanded, devices that are difficult to transform other products, and devices whose quality is difficult to improve. And the remaining part, what else can we do besides the mask meltblown cloth? Here is a combination of "Spunbond and Meltblown Nonwovens Handbook" for everyone.

(1) Overview of Meltblown Nonwovens

Melt blown nonwovens are nonwovens manufactured by the Melt blown process, and also belong to the products directly manufactured by the melt spinning process. The process flow of meltblown nonwovens is shown in the figure.

Exxon Corporation of the United States started the research on meltblown technology in the 1960s, and obtained the first technology patent. This process is still the mainstream production process widely used in the meltblown nonwovens industry. .

The production process of melt-blown nonwoven fabrics is to use polymer chips with high melt index (referred to as MFI), after extrusion heating, melting into a high-temperature melt with good flow properties, and using high-temperature, high-speed hot air flow from the spray. The thin stream of melt sprayed from the silk plate is blown into very fine fibers, which are gathered into a fiber web on a receiving device (such as a web forming machine), and are bonded to each other into cloth by their own waste heat. We can take a look at the video of Yanshan Petrochemical's meltblown cloth production:

It has a short process flow (it only takes more than ten minutes from feeding material to forming a product), simple equipment (such as general production lines do not need equipment for consolidating fiber webs), and fine fibers (fiber diameter reaches micron level or even sub-nanometer level) ), product performance diversification and other characteristics.

Melt blowing is an important process for manufacturing fine filter materials and materials with high barrier properties. It is also a method for manufacturing nanomaterials, and it is a technology that is still developing rapidly. The first English letter of the melt-blown nonwoven process is "M", so the melt-blown fabric is also called "M", and the melt-blown system is also referred to as "M", sometimes called "MB" system. Generally, most of the independent meltblown nonwoven production lines have only one spinning system, and two or more meltblown systems can be configured in the production line according to market requirements to form MM or MMM production lines.

In the SMS production line, the MB system is an important system, which has a great impact on the applicability of the product (air permeability/barrier capacity). In order to improve the production capacity and product quality of the production line, a production line will be equipped with multiple MB system.

Since the molecular weight of the melt-blown fiber is small, the crystallization is insufficient, the orientation is not strong, and at the same time, there are fewer molecules under force, so the strength of the melt-blown fiber is low. However, the melt-blown fiber web is self-bonded into cloth by waste heat, and the main reason for its low strength is due to the low strength of the bonding points between the fibers and easy detachment, not the low fiber strength. Therefore, the breakage of the meltblown cloth is not the breakage of the fibers, but the breakage at the bonding point.

In order to overcome the characteristics of low strength and wear resistance of meltblown cloth, meltblown cloth is often compounded with spunbond cloth and needle punched cloth to make composite materials. To improve its comprehensive use effect. At present, the most widely used are SM and SMS composite materials combined with spunbond fabrics, SMS + breathable film + S composite materials, etc.

(2) Application of Meltblown Nonwovens

Meltblown nonwovens are mainly used as composite materials, filter materials, thermal insulation materials, sanitary products, oil-absorbing materials, cleaning cloths (wipes), battery separators, etc., and are widely used in medical and health care, automotive industry, filter materials, environmental protection and other fields.

In foreign countries, meltblown nonwovens are mainly used as two-step SMS materials and medical and sanitary materials and covering materials. In addition, wiping and absorbing materials, filtering and barrier materials are also important uses of meltblown cloths.

1. Medical protective equipment

Because the material compounded by meltblown cloth and spunbond cloth has high hydrostatic pressure resistance, good air permeability and filtration effect, especially the material compounded with membrane, has good barrier performance and filtration efficiency for non-oily particles up to more than 99%.

For example, medical protective clothing made of composite materials with a quantitative specification of 60-100g/m2 can effectively block microorganisms, particles and fluids, and has good resistance to viruses like SARS (45nm in size) and HIV (90nm in size). protective effect.

2. Materials for air filtration

The melt-blown composite material treated by electrostatic electret has low initial resistance, large dust holding capacity and high filtration efficiency when used for air filtration [under the flow rate of 32L/min, the filtration efficiency of 0.3μm particle size can reach 99.9 %, resistance is only 117.7Pa (12mm water column)] and other characteristics, widely used in electronic manufacturing, food, beverages, chemicals, airports, hotels and other places of air purification.