1. Product Description
Polyvinyl alcohol (referred to as PVA) is the water-soluble resin after polymerization and alcoholysis by vinyl acetate. Featuring unique strong bonding, obdurability, smoothness, oil resistance, solvent resistance, gas interdiction, abrasion resistance, and protective colloid, as well as water resistance as being specially treated, PVA is widely used in such industries as textile, construction, paper, packaging, wood processing, agriculture, printing, polymer chemistry, ceramics, steel, electronics, electrolysis, and electroplating. PVA can be made into vinylon fiber after acetalation to be one kind of excellent synthetic fiber.
The Company is competent in mass production of PVA serial products in different specifications with the polymerization degree of 1700-2800 and alcoholysis degree of 88 ~ 99.9 (mol / mol) %. The products are featured by stable quality, high purity, low impurity, white chroma, high transparency, and steady viscosity. In addition to abundant supply of conventional varieties, it is able to develop and produce PVA products for other uses based on user needs.
2. Process Route and Product Performance Index
2.1 Process Route
With vinyl acetate as the monomer and azo-bis-isobutyronitrile as the initiator, the polyvinyl acetate intermediate is made by the method of solution polymerization, generated alcoholysis under the condition of alkaline catalyst, and then produced into PVA of various grades.
2.2 Product Performance Index
PVA is a colorless and odorless floccus, flake or granular solid. Due to the existence of numerous hydroxyls, PVA is easily soluble in water and soluble in hydroxy-contained organic compounds such as glycerol, ethylene glycol, acetic acid, acetaldehyde, and benzoic acid, but not soluble in the general organic solvents. When being heated to 130 ~ 140 ℃, PVA doesn’t change basically in nature, only yellowing; at 160 ℃ for a long time, PVA becomes darker; at 200 ℃, PVA intermolecular dehydration happens and the water solubility reduces; at 200 ℃ or higher, PVA intramolecular dehydration occurs; and close to 300 ℃, PVA is decomposed into water, acetic acid, acetaldehyde and crotonaldehyde. The packing proportion of PVA, dependent on the alcoholysis approach, is 0.2 ~ 0.27g/ml after the high-alkali alcoholysis and 0.42 ~ 0.52 g/ml after low alkali alcoholysis.
Product Usage and Application Notes (for reference only)
(1) Paper and Paper Converting
Water-soluble polymer is mainly applied as surface sizing agent, paint adhesive, and paper additive in the paper industry. The surface sizing agent was once made of starch pigment, and adhesive, casein. Polyvinyl alcohol is superior than casein in the adhesion to cellulose with strong film formation and excellent film toughness. Therefore, the demand for polyvinyl alcohol as paper processing agent is in rapid expansion. With the advancement of paper, the upsizing and high speed paper-making equipment, and the rationalization of packing method, the growing demand for polyvinyl alcohol is intensifying.
Mainly applied: (1) as paper adhesive; (2) as rewetting adhesive; (3) for paper surface sizing; (4) for paper paint coating; and (5) for paper making (paper internal sizing)
Applicable varieties: 24-99, 20-99, 17-88, etc.
(2) Plywood, Artificial Board, Wood Processing Industry
PVA can be used as denaturant for heat-curing resin, but mainly as adhesive for plywood, artificial board, and wood, e.g. urea, formaldehyde resin, melamine - formaldehyde resin.
The mix and match of PVA with formaldehyde resin or melamine - formaldehyde resin can increase slurry viscosity, shorten curing time, and have the strengths of fast curing, increased initial adhesion force, and shortened cooling time.
Usual Varieties: 17-99, 20-99, 24-99, etc.
(3) Emulsification Stabilizer
The primary reasons of PVA being applied for PVAC emulsion manufacture is that PVA has a very low surface tension, it can disperse VAC into fine particles in the water, and PVA is a good protective colloid to make PVAC particles in the polymerized colloidal state to form steady water emulsion but not agglomerate and degenerate. PVA models should be chosen for use in terms of the nature of finished products. The latex with the higher adhesive force in the initial production can take PVA after complete alcoholysis as the main body, e.g. 24-99, 18-99, 20-99, and 17-99. And the production of low-viscosity latex with high solid content can adopt the mixed use of PVA in low or high polymerization degree, e.g. 03-88, and 05-88 with 17-99.
(4) Building Industry
As cement and mortar additive, PVA can effectively increase the adhesion force and mobility of cement and mortar, slow down the drying time of cement surface, increase the coating adaptability, and prevent cement cracking. Simple to use, it is suitable for gluing walls, ceilings, and tiles, receiving good effect. PVA can also be applied as adhesive for profiled sheets, e.g. pre-cast slab and acoustic panel. Whatever the organic fibers (sugar, slag, wood chip) or inorganic materials, they can be matched with PVA for its efficient adhesive force and water-resistant property to be compressed and bonded into plates. PVA has good uses in coating. PVA aqueous solution, under the catalytic action of hydrochloric acid, is condensed with formaldehyde to be the water-resistance PVA formal polymer compound, which is extensively used as wall coating, dressing, and caulking of buildings. PVA coating has excellent weather resistance and waterproofness. When encountering with water, it won’t inflate and embrittle. And it is non-toxic, tasteless, and low in price. The traditional varieties in this area can only be used for manufacturing profiled sheet, and PVA with greater degree of polymerization like 20-99, 24-99 is often chosen in the coating area.
(5) PVA Film
PVA film offers incomparable unique advantages than the general polypropylene and PVC, such as non-static behavior, good light transmission, high transparency, good gloss, low oxygen permeability coefficient, and tough film. In this area the traditional varieties are not commonly used because 17-99 has too small viscosity. The insoluble film is regularly chosen from 20-99 and 24-99, and the water-soluble film, 17-95 and 17-88.
(6) Printing Industry
PVA film contains dichromate or cinnamate. After ultraviolet irradiation, some part of PVA is combined into insoluble complex salt with dichroma or is produced bridging action with cinnamate, dissolving in water. The film, with physical strength after heat treatment, can be used for printing plates. (7)Textile Industry
Functional PVA is the most efficient synthetic sizing agent. It has the advantages in warp size:
1. PVA film has excellent obdurability, smoothness, wear resistance, adhesion to fiber, and good sizing effect and it can improve the weave capacity of high-level textile in high-density fine yarn;
2. Thanks to the large cohesive force to fiber and good protective force, PVA can decrease the broken yarn frequency of fabric manufacturing silk and improve the weaving efficiency;
3. PVA serosity isn’t prone to spoilage and doesn’t change in viscosity after long-time heating. Therefore the sizing rate is controlled to be stable and hard size isn’t prone to occur;
4. The humidity of the textile mill to use starch slurry should be maintained at 80 ~ 85%, and that of PVA slurry, 70 ~ 75%. So it can improve the operating environment and work efficiency;
5. The applicable varieties to reduce destarch in the process of sizing and weaving and to maintain the clean plant are PVA, e.g. 20-95 and 17-95, with medium degree of polymerization and alcoholysis degree of 90 ~ 97 (mol / mol)%. (8) Vinylon Industry
Despite of the inferior performance in clothing than other synthetic fibers, vinylon can take place of cotton for the production of bedding, knitted underwear, decorative cloth, canvas, work clothes, fishnet, and curtain due to its moisture absorption and wear resistance. As vinylon has the fiber performances required for the industry such as high strength, low elongation, large modulus, acid and alkali resistance, and good weather resistance, as well as the excellent adhesion with rubber, the high-strength high-membrane vinylon can be used in place of asbestos.