Polyvinyl alcohol PVA 5-88 partially saponified

Application

The processing of polyvinyl alcohol in most applications occurs in the form of an aqueous solution. Tanks for its preparation should be made of corrosion-resistant material. First, the PVA, stirring, is poured into cold water and then heated in a water bath or when applying steam to +90°C - +95°C until completely dissolved.

To prevent film formation, the solution should be mixed while cooling. With temperature  increasing, the dissolution rate increases. With an increase in molecular weight (increase in viscosity of a 4% aqueous solution), the dissolution rate decreases. The dissolution process is also comes difficult when moving to high concentrations. Therefore, the preparation of a more concentrated, for example, 30% solution should be carried out at a temperature of +90°C - +95°C.

When mixing solutions of polyvinyl alcohols and during transportation, foam may forms in pipelines. An appropriate form of mixer, for example, an anchor type with a low speed or the exclusion of falling areas, will help prevent foaming. As an defoaming agent, it is possible to use n-octanol, tributyl phosphate, and others in an amount of 0.003-0.10%, relative to the solution.

With continuous storage of polyvinyl alcohol solutions, their viscosity can increase. The initial viscosity can be restored by heating and stirring.

It is recommended to prepare and store the PVA solution in clean containers.

Due to the some microorganisms possible resistance to the used preservatives, keep dissolving containers and bottling equipment (pipes, valves, hoses, etc.) clean. Films and deposits must be removed. In difficult cases, the preservative should be changed.

Under water influence, which acts as a plasticizer, the strength characteristics of PVA are significantly reduced. In water, the material disintegrates and instantly dissolves.

Polyvinyl alcohol in the granular form can form lumps when exposed to pressure and in the presence of moisture.

Under normal environmental conditions, PVA is non-toxic, however, when the temperature rises to + 180 ° C, it releases vapors of acetic acid, formaldehyde and carbon monoxide.

Combustible. It ignites from an external source of fire at a temperature of +205°C, and self-ignition occurs at a temperature of +344°C.

For the glue manufacturing, PVA solutions of up to 30% are used, depending on the viscosity requirements, if necessary, the solutions may contain additives of a preservative and antifoam agent.

The glue drying accelerates by adding alcohols or dispersing polymers. The drying temperature should be as low as possible and should not exceed +130°C, otherwise the activation of the dried layer worsens. The adhesive open exposure time depends on the grade of PVA used. The viscosity of a 4% PVA solution increasing is usually accompanied by a decrease in open exposure time.

10 g/m2 application of PVA 5-88  allows to obtain coatings with very good rewet properties.

Open exposure time is of great importance for manual or machine bonding of wood and paper. For a number of polymer dispersions, the addition of a PVA solution significantly increases the setting rate.