1. PVA Introduction
Polyvinyl alcohol (white powder for short) is a kind of water-soluble polymer with a wide range of applications, and its properties are between plastic and rubber. It has two major uses: non-fiber and non-fiber.
Because polyvinyl alcohol has unique strong adhesion, film flexibility, smoothness, oil resistance, solvent resistance, protective glue, gas barrier, wear-resistance, and special treatment Water resistance, in addition to fiber raw materials, but also widely used in the production of coatings, adhesives, paper processing agents, emulsifiers, dispersants, films, and other products.
It is widely used in textile, food, medicine, construction, wood processing, papermaking, printing, agriculture, iron and steel, polymer chemical industry, and other industries.
2. PVA Properties
Polyvinyl alcohol resin series products are white solid, the appearance is divided into floc, granule, and powder, non-toxic, tasteless, non-polluting, and can be dissolved in water of 80 to 90 degrees Celsius.
Its aqueous solution has good adhesion and film-forming ability, can withstand most organic solvents such as oils, lubricants, and hydrocarbons, and has chemical properties such as long-chain polyol esterification, etherification, acetalization, and so on.
3. PVA Applications
PVA is mainly used in the textile industry warp size, fabric finishing agent, vinylon fiber raw materials; building and decoration industry 107 glue, interior and exterior wall coatings, adhesives; chemical industry as polymeric emulsifier, dispersant and polyvinyl acetal, acetal, butyral resin; paper industry as paper binder; used in agriculture as soil improver, pesticide adhesion synergist and polyvinyl alcohol film.
It can also be used in daily cosmetics and high frequency quenchant.
4. PVA Usage
Polyvinyl alcohol resin series products can be dissolved in hot water below 95 °C, but due to the difference of degree of polymerization and alcoholysis, different alcoholysis methods have some differences in dissolution time and temperature. therefore, when using different brands of polyvinyl alcohol resins, the dissolution method and time need to be explored.
When dissolving, while stirring, this product can be slowly added to the cold water of about 20 °C to fully swell, disperse and escape volatile materials (do not directly dissolve the product in the water above 40 °C, in order to avoid enveloping and skin-soluble endogenesis), then heat up to about 95 °C to accelerate the dissolution, and keep for 2.5 hours until the solution no longer contains fine particles, and then after filtering impurities in 28 mesh stainless steel, it can be ready for standby.
The stirring speed is 70 to 100 rpm. When heating up, you can use jackets, water baths, and other indirect heating methods, or steam can be directly heated; however, do not use open fire direct heating, so as to avoid local overheating and decomposition, if there is no mixer, steam can be blown into the tangent direction to dissolve.
The concentration of the aqueous solution of polyvinyl alcohol resin series products is generally less than 12 to 14%; the concentration of aqueous solution of low alcoholysis polyvinyl alcohol resin products is generally about 20%.
The method to test whether this product is completely dissolved: take out a small amount of solution and add 1-2 drops of iodine. If a blue granular transparent body appears, it has not been completely dissolved. If the color can be diffused evenly, it has been completely dissolved.
Defoamer addition: in the configuration of aqueous solution, this product is not easy to foam, but a small amount of foam will be produced when the solution concentration is high and the rotational speed is fast. In order to restrain foam, defoamer can be added: 0.01-0.05% (based on PVA) of octanol, tributyl phosphate or 0.2-0.5% (based on PVA) silicone emulsion.
5. PVA Storage and Anticorrosion
If stored for a long time, the water of the aqueous solution will decay, but does not affect the performance of this product, at this time should add 0.01-0.05% (based on PVA) formaldehyde, salicylic acid or other preservatives.
Anti-rust: when storing with iron, a small amount of weak alkali should be added, and 0.02-0.05% (based on PVA) of sodium nitrite should be added when using copper, preferably in stainless steel and plastic containers.