Spunbond - the name of the technology of production of nonwoven material from polymer melt spunbond method. Often in the professional environment, the term "spunbond" also refers to material produced using the spunbond technology.
The essence of the spunbond method is as follows: the polymer melt is released through the spinnerets in the form of thin continuous filaments, which are then stretched out in the air flow and, laying on a moving conveyor, form a textile canvas. The threads on the formed web are subsequently sealed.
The binding of threads in a canvas can be done in several ways:
- chemical impregnation of threads with binders
- heat bonding on the calender
- hot air heat sealing
Fiber-forming polymers with a wide molecular-mass distribution, such as polypropylene, polyethylene terephthalate (polyester), polyamide, etc., are used as raw materials for the production of the spunbond material. in the canvas and provides a high production of fibers in recalculation per kilogram of raw materials.
The process of forming the canvas includes the following main steps:
- Preparation and supply of polymer raw materials to the melting device
- Polymer melt and melt filtration
- Melt feed to die set
- Fiber formation
- Aerodynamic drawing and cooling of the fibers with air
- Laying the fiber on the conveyor to form a canvas
- Calendering and winding material
Polymer granules enter the extruder, in which the melting process is carried out, after which the molten polymer is forced through special holes - dies, forming endless threads. The die is a metal plate with holes made of heat-resistant steel. Dies differ in the number of holes, their diameter and shape. The diameter of the holes in the die can vary from 250 to 1200 μm. The dies are located on a special dyed beam, while in the production of a more dense arrangement of fibers on the canvas is most often used several beams (usually two or three). Before laying on the conveyor, the threads go through a drawing stage - aerodynamically or mechanically.
The most widespread aerodynamic method of drawing, consisting in pulling the threads under the action of high-speed air coming from the ejector. In the process of stretching the threads are cooled, gaining strength. The cooled threads coming out of the ejector are placed on the conveyor; uniform and uniform distribution of the threads on the canvas is carried out with the help of special devices located in the ejector. The speed of the conveyor can vary, thereby achieving a different density of the material.
For fastening the formed web one of the following methods can be used:
- chemical impregnation of threads with binders
- heat bonding on the calender
- hot air heat bonding
The method of bonding the material determines the scope of its further use. The most common method of fastening threads in a canvas is thermal bonding on a calender used for cloths with a density of less than 150 g/m2. For denser cloths (over 150g/m2), the most frequently used needle-punching method of fastening. Thus, the range of possible spunbond densities varies from 15 to 600 g/m2.
At present, the improvement of technologies for the production of spunbond spunbond nonwovens follows the path of obtaining bicomponent (elementary fibers are obtained by coextrusion of two or more polymers) of materials combining the properties of the original polymers.
So, for example, SMS materials are very popular (“spanbond” - “meltblown” - “spanbond”).
“Meltblown” - meltblown technology implies the formation of fibers by blowing up molten polymer (spunbond-blown technology) with hot air directly onto the folding conveyor table.
In determining the suitability of non-woven materials "spunbond" for use in their respective industries, a comprehensive assessment of the material is carried out, which allows us to more accurately determine the behavior of the "spunbond" in operation. For this purpose, first of all, it is necessary to establish what impacts the material will be subjected to under operating conditions and what properties it must possess in order to meet the requirements imposed on it in connection with this. Thus, when evaluating a spunbond, its geometrical, physicomechanical and hygienic properties are guided.
- Geometric properties.
The thickness of the nonwoven material is determined by its purpose and method of production. The air permeability, stiffness, thermal insulation properties, etc., depend on the thickness of the nonwoven material.
The width of the nonwoven material is determined by the distance between its edges and varies widely - from 6 cm to 4 m and more. Spunbond is easy to cut, so many manufacturers cut spunbond non-woven fabric into widths demanded by consumers.
- Physical and mechanical properties.
The density of the material can vary from 10 g/m2 to 600 g/m2. Often, the density of the material determines the scope of application of spunbond, for example, a material with a density of 40 g/m2 can be used for sewing disposable clothing, and with a density of 200 g/m2 as a geotextile.
Abrasion and crushing resistance
Low electrical conductivity
High breaking load in dry and wet condition. Spunbond is an extremely durable material that can withstand heavy loads.
Resistance to high and low temperatures and weathering
Spunbond non-woven material is resistant to water, acids and alkalis, has low water absorption, does not rot and mold, which contributes to its long-term use.
It has frost resistance and can withstand low temperatures (-55°C) without changing the strength, with the introduction of special additives can acquire heat resistance up to 130°C.
The ability to uniform and deep staining. Spunbond is easily dyed to any color by adding special dyes to the polymer melt. In addition, on the finished products of spunbond can be applied images of any color. This property of a spanbond is widely demanded in light industry.
- Hygienic properties. Spunbond does not have the property to form toxic compounds in the air and wastewater in the presence of other substances and factors at ambient temperature
Due to the nature of the production and the versatility of the physicomechanical properties of non-woven materials spunbond and SMS, they are widely used in many industries and national economy. This feature must be taken into account not so much when building a product marketing system, as in assessing the possibility of market development.
According to the current trend in the market of non-woven materials such as Spunbond and SMS, it is accepted to consolidate the scope of application of these materials as follows:
- Agrotextiles, covering and mulching materials
- Material for hygienic productions
- Material for the manufacture of disposable clothing, including medical
- Basis for building membranes and waterproofing materials
- The material used in the light industry as fittings and packaging, including the manufacture of upholstered furniture, orthopedic mattresses, the manufacture of covers, bags, etc.
Agrotextiles - spunbond, used as a covering material in agriculture. Such a spunbond is obtained by the introduction into the melt of special ultraviolet stabilizers that prevent the process of destruction of polypropylene under the action of the sun's rays. White spunbond is used to harbor plants, black - for mulching the soil.
Production of feminine and child hygiene products
Material for the production of women's and children's hygiene (pads, diapers) - is used as one or more outer and inner layers in the product. It serves as a layer for retaining absorbent layers under the condition of passing moisture and air, in order to give anatomical shape to the products.
Non-woven material produced by technology Spunbond and SMS has several advantages when used in the manufacture of hygiene products:
- significant strength, allowing automatic lines to operate at high speeds
- cost due to the technological features of the simultaneous extrusion of fibers and the formation of the canvas, while lower energy costs of production (compared with the technology "Spunlace" and "Airlade")
Production of disposable clothing
In the production of disposable clothing around the world is widely used non-woven materials made using the technology Spunbond and SMS. This allows you to get sets or individual elements of protective clothing that has the desired properties and at the same time inexpensive to manufacture.
Products related to this segment of the nonwovens market are intended, first of all, for medical treatment and prevention facilities, beauty and treatment rooms. In addition to the medical and cosmetological industries, it is worth noting the widespread use of disposable clothing as protective clothing and clothing for various jobs. Nonwovens consumed in this market segment are represented by Spunbond and SMS in densities from 15 to 60 g/m2, and a wide range of colors.
Construction membranes - rolled or sheet materials used to protect buildings and structures, as well as their individual elements from the effects of climatic factors. Their use allows you to extend the service life of construction, finishing or insulation materials and reduce construction costs in terms of saving them.
Fittings and packaging materials
Furniture accessories - non-woven materials Spunbond, are used as a backup or protective material in the furniture industry, in garments or in materials that serve as the basis for the manufacture of covers, bags, substrates, bedspreads, etc.