1. Introduction
Polyvinyl alcohol (PVA), also known as PVOH, is a water-soluble polymer obtained from the alkali-catalyzed alcoholysis of polyvinyl acetate. Treatment agents, chemical fibers, emulsifiers, films, medical materials and construction of automotive modifications, its applications involve textiles, food, medicine, construction, wood processing, paper, printing, agriculture and metallurgy and other industries.
Foamed PVA is PVA cross-linked foam and molding of an environmentally friendly foam material. Foamed PVA has good water absorption and water retention properties: dry state, hard and good mechanical strength; wet state, such as natural sponge feel and elasticity, good softness, and dry and then Wet can still restore its softness. Foamed PVA also has certain wear resistance, heat resistance, chemical stability and good biocompatibility and other advantages, has been widely used in cleaning materials, filtration materials, medical materials, biological carrier materials and other fields. Foam PVA on the market is mainly made into a variety of sponge products, known as PVA sponge, some varieties have formed industrial production, such as PVA car wash cotton block, PVA cosmetic puff, etc., has a very good application prospects.
2. Analysis of industrialization of foamed PVA
Currently, PVA is mainly used in construction adhesives, textile pastes, adhesives, fibers, polyvinyl butyral (PVB), paper, biodegradable PVA films and other fields. adhesives, fibers, polyvinyl butyral (PVB), paper, biodegradable PVA films and other fields. Among them Construction adhesives are the first major application area, accounting for more than 40% of the total usage. The textile pulp and adhesive account for about 20% and 11% respectively.
2.1 Production process of foamed PVA
Foamed PVA is PVA as the main raw material, adding cross-linking agents, foaming agents, acid catalysts, surfactants and other substances, cross-linking foaming and molding of foaming materials. Foam PVA production process is usually equipped with stirring and temperature control device in the reactor, add PVA, water, cross-linking agent and acid catalyst and other substances, stirring to make it fully foaming reaction, and then poured into the mold heat preservation and curing, and finally stripped and cleaned to get foam products; or add chemical blowing agent (starch pore-forming agent) for foaming reaction, and then mold molding to get foam products. PVA is difficult to achieve continuous extrusion foam molding, mainly because its melting temperature and decomposition temperature is very close, many researchers have studied this, but is still in a small-scale experimental stage, to achieve industrialization The continuous extrusion of foamed PVA can effectively improve the production efficiency and The continuous extrusion of industrial foamed PVA can effectively improve the production efficiency and reduce the production cost, and will be more widely studied in the future.
2.2 Market analysis of foamed PVA
As countries pay more and more attention to environmental issues, in some areas, it has been clearly stipulated that the use of some environmentally polluting foam plastic products, such as disposable polystyrene lunch boxes have long been banned. Foamed PVA is a kind of polymer material that can biodegrade in the natural environment. The discarded products will not cause environmental pollution problems, and enterprises are increasingly concerned about its The development potential and market prospect are excellent because of the increasing concern of enterprises.
At present, the development momentum of domestic foamed PVA is good, and some kinds of products have formed a certain scale of industrial production, such products These products are mainly used in cleaning and medical fields, such as PVA absorbent stick, makeup Puff, medical dust-free cotton, etc. There is a wide range of foamed PVA products, which can be according to the need to process into different performance products, products in the form of more The products are mostly in the form of blocks, thick plates and tubes. The color of the product is generally white, but can be dyed with other colors as needed, and the color does not fade easily.
3 Applications of foamed PVA
The application of foamed PVA is closely related to its own performance. material for the open pore structure, has a super water absorption and water retention capacity, its water absorption can reach several times to dozens of times its own mass. The most outstanding feature of foamed PVA The most outstanding feature is the ultra-fast rate of liquid absorption and absorbent soft and delicate and rich The most striking feature of foamed PVA is its ultra-fast absorption rate and the soft and delicate nature of the absorbed liquid and the elasticity close to the muscle, thus being used in the medical field and will gradually replace gauze, medical cotton and other traditional supplies. At the same time, because its good mechanical strength and wear resistance, it can effectively resist It can effectively resist visible light and ultraviolet light.
3.1 Cleaning and beauty materials
Foam PVA with water immediately after the adsorption, good elasticity, soft surface, feel comfortable, high tensile strength and tear strength, non-toxic bacteria erosion, easy to clean after use, easy to operate, durable and wear-resistant, etc., and therefore is widely used as cleaning products for daily life, automotive supplies, electronics and telecommunications industry and other industries. Especially for semiconductors and other industries with high cleaning requirements, roller brushes and disc brushes made of foamed PVA play an important role in cleaning because they do not produce fine fibers.
3.2 Medical Materials
PVA foam is widely used in oral, ENT, gynecological, neurosurgery, etc. The main products are dust-free cotton (swabs), negative pressure drainage materials, wet cloth pharmaceutical substrates, cold dressing materials, hemostasis, stuffing sponges, etc. PVA medical sponges have replaced the traditional medical skim cotton, especially In ophthalmology, otorhinolaryngology and microsurgery, this type of medical sponge has become a must-use material. Through the control, according to the need to prepare material pore size of different medical sponge, such as medical-grade microporous and large pore PVA sponge, these materials have excellent hydrophilic, liquid absorption and blood absorption properties
PVA medical sponge is cured by cross-linking foam and does not contain fiber filaments or fiber heads, so there is no fiber shedding during use. During ophthalmic surgery, ENT surgery, neurosurgical craniotomy and thoracic cardiac surgery, there is no impact on wound healing due to fiber shedding. Depending on the clinical application, wound healing can also be facilitated by loading the sponge with appropriate excipients. At the same time, these sponges have good mechanical properties and can be processed into various shapes according to different surgical needs. In particular, the pike dart-shaped blood-absorbing sponges or sponge sticks used in microsurgery can quickly absorb fine bleeding and ensure error-free surgery.
3.3 Filtration Materials
Foamed PVA is used as an air filtration medium in the semiconductor, precision machinery and other industries with particularly high environmental requirements, as well as in air compressors, various engine suction chambers, and filter media for indoor air purification because of its flexibility, lack of fibers, strong water absorption and retention capacity, and lack of static electricity, etc. No fine lint is produced during use.
Foamed PVA can be used as a filter material for various oils, organic solvents and coatings. It is not only high infiltration efficiency but also can be washed and After washing, it can be used again and again.
3.4 Biological carrier materials
In recent years, with accelerated industrialization and continuous economic development, environmental pollution has become increasingly serious, and water pollution is an important part of the problem. The treatment of sewage not only can reduce and improve the water pollution environment, but also can make full use of limited water resources, how to deal with water pollution has become a hot research problem in recent years. Foam PVA has a large specific surface area, reasonable pore size distribution, from the surface to the internal formation of different dissolved oxygen gradients, very suitable for different requirements of aerobic, anaerobic microbial growth, its excellent bio affinity, mechanical properties and chemical stability is more conducive to maintain microorganisms in the reactor, as well as the cultivation of dominant genera, so foam PVA is used as immobilized carrier material in wastewater treatment has been It is widely used in wastewater treatment. Compared with existing fixed-bed and fluid-bed wastewater treatment processes, foamed PVA is more effective and has the advantages of low price, long life and no support.
4. Development Outlook
In summary, foamed PVA as an environmentally friendly foaming material, its production process is relatively mature, and the application range involves cleaning and beauty, medical, sewage treatment and other fields. Although the production process of foamed PVA is relatively mature, but the existing production process is more complex, the production cycle is long, the production efficiency is low, therefore, the realization of industrial foamed PVA continuous extrusion molding will be a hot spot for future research. At the same time, how to modify the foamed PVA, so that its preparation formula ratio, production process, product shape and other aspects more suitable for the requirements of cushioning liquid-absorbent packaging, will be the focus of the next research and development. In addition, it is of profound practical significance to continuously expand the application fields of this biodegradable foamed PVA material.