For masks, we just know that masks are hard to buy, but we do n’t know why, mainly because the supply of raw materials is in short supply. The shortage of raw materials has caused the price of masks to fluctuate repeatedly. So, how much do you know about non-woven fabrics and melt-blown fabrics? Popular science knowledge medical mask non-woven fabric classification, detailed explanation.
First of all, we should know that the scientific name of non-woven fabric is non-woven fabric, so the standard of non-woven fabric is mostly named after non-woven fabric. The non-woven fabrics used in the production of masks are mostly polypropylene spunbond non-woven fabrics and polyester non-woven fabrics.
With the outbreak of pneumonia caused by new coronaviruses, the demand for medical supplies has surged everywhere, and there are two main types of protective materials that are most needed: one is medical protective clothing and the other is medical masks. The raw material is non-woven fabric.
Non-woven fabrics are also called non-woven fabrics and non-woven fabrics. Traditional fabrics, whether they are woven or knitted, or other weaves, go through the fiber-spinning-weaving process, and non-woven fabrics do not require the process of spinning, hence the name. The non-woven fabric has no warp and weft, so it is very convenient to cut and sew, and it is light and easy to set. Non-woven fabrics break through the traditional textile principles, and have the characteristics of short process flow, fast production rate, high output, low cost, wide use, and many sources of raw materials.
The main process of non-woven fabrics is fiber web-consolidation-post-treatment. The types are mainly classified according to the method of consolidation web, mainly including spunbond, spunlace, dipping, needle punching, hot rolling, etc. The non-woven fabric in the mask is a spunlace non-woven fabric, which sprays a high-pressure micro-water stream onto one or more layers of fiber meshes to make the fibers entangle with each other, so that the fiber mesh is strengthened and has a certain strength.
In terms of environmental protection, the raw material used for most non-woven fabrics is polypropylene, and the raw material for plastic bags is polyethylene. Although the two substances have similar names, they are far from each other in chemical structure. The chemical molecular structure of polyethylene is quite stable and extremely difficult to degrade, so the plastic bag takes 300 years to decompose; and the chemical structure of polypropylene is not strong, and the molecular chain can be easily broken, which can be effectively degraded , And enter the next environmental cycle in a non-toxic form, generally the scraps of non-woven fabrics in the processing can also be recycled to make new non-woven fabrics, there will be no harm
The mask non-woven fabric is a surface made of pure cotton absorbent gauze or knitted fabric with various non-woven fabrics sandwiched in the middle. The mask non-woven fabric has good filtering effect and slightly poor air permeability. The varieties of mask non-woven fabric are non-woven material on the front and back, and filter paper in the middle, so that the filtering effect of the mask non-woven fabric is higher. Non-woven fabrics are moisture-proof, breathable, flexible, lightweight, non-combustible, easy to decompose, non-toxic and non-irritating, rich in color, inexpensive, and reusable. For example, polypropylene) pellets are used as raw materials, which are produced by a continuous one-step method of high temperature melting, spinning, spreading, and hot pressing. Non-woven fabrics do not have warp and weft threads. They are very convenient for cutting and sewing, and they are lightweight and easy to set.
The core material of non-woven fabrics for mask production is classified as industrial textiles, ranking third in the manufacture of textile surface materials, second only to woven and knitted fabrics. It is composed of oriented or random fibers. It has the appearance of cloth and certain cloth properties and is called non-woven fabric. Non-woven fabric is not made by interweaving and weaving together traditional yarns. Non-woven fabrics are made by directly bonding fibers through physical and chemical methods, so non-woven fabrics have no thread ends, unlike woven fabrics, which can be pulled out.
Raw materials for the production of non-woven fabrics: The fibers used in the production of non-woven fabrics are mainly polypropylene (PP), polyester (PET), nylon (PA), viscose, acrylic, ethylene (HDPE), chloroprene (PVC), and masterbatch. Wait.
Non-woven fabric process classification
1. Spunlace non-woven fabric
The spunlace process is to spray high-pressure micro-water flow onto one or more layers of fiber meshes to make the fibers entangle with each other, so that the fiber meshes can be strengthened and have a certain strength.
Features: Flexible entanglement, does not affect the original characteristics of the fiber, does not damage the fiber. The appearance is closer to traditional textiles. High strength and low fuzziness. High hygroscopicity, quick moisture absorption. Feel soft and drape. The appearance of the pattern is changeable. The production process is long and covers a large area. The equipment is complex, the energy consumption is large, and the water quality requirements are high.
Main applications: medical curtains, surgical gowns, surgical covers, medical dressing materials, wound dressings, medical gauze, aviation wipes, clothing lining cloths, coated base cloths, advanced rags for the electronics industry, cotton pads, wipes, masks Materials etc.
Spunbond non-woven fabric is after the polymer has been extruded and stretched to form continuous filaments, the filaments are laid into a net, and the fiber web is then subjected to self-bonding, thermal bonding, chemical bonding or mechanical reinforcement methods to make The web becomes nonwoven.
Features: The web consists of continuous filaments. Excellent tensile strength. There are many changes in the process, and various methods can be used for reinforcement. The range of filament fineness is wide.
Application: Polypropylene (PP): geotextile, tufted carpet base fabric, coated base fabric, medical materials, covering materials for disposable products, etc. Polyester (PET): filter materials, lining materials, tufted carpet base fabrics, agricultural materials, packaging materials, etc.
2. Meltblown nonwoven fabric
The process of melt-blown non-woven fabric: polymer feeding --- melt extrusion --- fiber formation --- fiber cooling --- netting --- reinforcement into cloth. High-speed hot air draws a thin stream of polymer melt extruded from the die orifice of the die, thereby forming ultra-fine fibers and condensing on the screen curtain or roller, relying on self-adhesive to become a nonwoven fabric, spinning principle. Features: The web is composed of very short and short fibers. The web has good uniformity and soft feel. Filtration performance and liquid absorption performance are good. The web strength is poor.
Application: filter materials, medical and health materials, clothing materials, battery separator materials, wiping materials.
3. Heat-sealed non-woven fabric:
Fibrous or powdery hot-melt adhesive reinforcement materials are added to the fiber web, and then the fiber web is heated, melted, cooled and consolidated into a cloth.
Features: surface bonding hot rolled surface is relatively smooth, point bonding hot rolled is relatively fluffy.
Application: Production of covering materials for baby diapers and feminine sanitary napkins, ointment base fabrics, clothing linings, masks, etc.
Pulp airlaid nonwoven fabric
The air-laid non-woven fabric can also be called dust-free paper and dry paper-making non-woven fabric. It uses air-laid technology to open the wood pulp fiber board into a single fiber state, and then uses the air-flow method to condense the fibers on the screen-forming curtain, and then strengthen the fiber into a cloth.
Features: good fluffiness, soft hand feeling, super moisture absorption performance.
Application: Medical hygiene materials, especially high-absorbency disposable hygiene products (such as diapers, sanitary napkins, wet facial towels, wipes, etc.).
4. Wet non-woven fabric
The wet non-woven fabric is to open the fiber raw materials in the aqueous medium into single fibers, and at the same time mix the different fiber raw materials to make a fiber suspension slurry, and the suspension slurry is sent to the web forming mechanism, and the fibers are netted under wet conditions Reinforced into cloth.
Features: High production speed, can reach 400m / min. Can make full use of short fibers. The fiber uniformity of the product is good. Large water consumption and high one-time investment.
Application: Special paper: dust / liquid filter paper, tea bags. Industrial use: filters, insulating materials, sound-absorbing materials. Medical use: medical backing, medical tape, surgical wrap material. Civil: wallpaper, etc.
5. Needle-punched non-woven fabric
Needle-punched non-woven fabric is a kind of dry method non-woven fabric. Needle-punched non-woven fabric uses the puncture effect of the needle to strengthen the fluffy web into a cloth.
Features: Flexible entanglement between fibers, with good dimensional stability and elasticity. Good permeability and filtration performance. It feels plump and fluffy. According to the requirements, we can manufacture various collection patterns or three-dimensional molding products.
Application: geotextile, geomembrane, halberd velvet cloth, speaker blanket, electric blanket cotton, embroidered cotton, clothing cotton, Christmas crafts, artificial leather base cloth, filter material special cloth.
6. Stitched non-woven fabric
Stitch-bonded non-woven fabric is a kind of dry-laid non-woven fabric. The stitch-bonded method is to use warp-knitted coil structure to web, yarn layer, non-woven material (such as plastic sheet, plastic thin metal foil, etc.) or their combination The body is reinforced to make a non-woven fabric.
Features: Durability, disposable. Insulated and conductive. Softness and stiffness. Fineness, swelling.
Application: clothing lining, flake, hard toe lining, heel lining, underwear, artificial deerskin, synthetic leather, warm shoe lining, cloth sole lining, etc.
7. Hydrophilic non-woven fabric
It is mainly used in the production of medical and hygienic materials to obtain a better feel and not to scratch the skin. For example, sanitary napkins and sanitary pads utilize the hydrophilic function of hydrophilic non-woven fabrics.
Features: Non-woven fabric has a certain ability to absorb moisture.
Application: medical supplies, sanitary care supplies, sanitary napkins, sanitary pads, etc.
Of course, because there is no clear standard, summing up the previous mask testing and non-woven testing experience, put forward several important testing indicators, namely the four major items of filtration efficiency, respiratory resistance, hygiene indicators, toxicology test.
1. Filtration efficiency
As we all know, filtration efficiency is a key indicator of mask quality assessment. This is also one of the important quality standards of non-woven fabrics, so referring to the relevant standards, we recommend that the bacterial filtration efficiency of mask non-woven fabrics should be no less than 95%, and the filtration efficiency of particles for non-oily particles is not less than 30%.
Second, respiratory resistance
Respiratory resistance, for people wearing masks, hinders the size of the breathing influence. Therefore, the non-woven breathing resistance of the mask determines the breathing comfort when wearing the mask. Here we recommend that the inhalation resistance should be ≤350Pa and the exhalation resistance should be ≤250Pa.
3. Health index
Hygiene index is naturally another important key index of non-woven masks. Here we recommend testing items mainly for initial contamination, total bacterial colonies, coliforms, pathogenic pyogenic bacteria, total fungal colonies, E. coli, Staphylococcus aureus, Candida albicans, ethylene oxide residues, etc.
4. Toxicology test
The skin irritation test is mainly a protective test for people who are allergic to some materials. Refer to the regulations in GB 15979. The mask non-woven skin irritation test is mainly to cut the sample of a suitable area in a transverse manner, soak it in physiological saline and stick it to the skin, and then cover it with a patch sticker for testing.
Warm reminder of Siyuan medical equipment: In addition to providing effective protection, the wearing of masks must also consider the comfort of the wearer, and it cannot bring about negative effects such as biological hazards. Generally speaking, the higher the protective performance of the mask, the greater the impact on comfort performance. When people wear masks to inhale, the masks have a certain resistance to the flow of air. When the inhalation resistance is too large, some people will feel dizzy, chest tightness and other uncomfortable conditions.
Different people have different industries and different physiques. Therefore, the requirements for the sealing, protection, comfort and adaptability of masks are also different. Some special groups, such as children, the elderly, people with respiratory diseases and cardiovascular diseases, should carefully choose the type of masks, on the premise of ensuring safety protection, to avoid accidents such as hypoxia and dizziness for a long time.
As an example of a common medical disposable mask, for the convenience of wearing, the common medical mask generally adopts rubber band ears. The face of the mask has two sides, there are several layers of wrinkles on the face, and there is a hard strip on the side. When wearing it, the stiff side is first on top, because the stiff strip can be used to pinch the bridge of the nose to ensure the tightness of the mask. Then the folds of the mask must be down, because if the folds are up, bacteria, viruses or dust will tend to stay in the folds. Be sure to wear the mask correctly and protect it!