Applicable Products:Coresil Pucca Gum

The advantages of sodium silicate as an adhesive include:
  • Even spreading and contact
  • Good tackA set-rate controllable over wide limits
  • A set-rate controllable over wide limits
  • Formation of a permanent, strong & rigid bond, resistant to pilferage, vermin, heat and moderately moisture.

The more siliceous silicates (2.8-3.2 ratio) are particularly effective as adhesives or binders due to the higher content of polymeric silica. These products set quickly by removal of very small amounts of water, which converts them from a liquid to a solid.

Tube Winding

Silicate adhesives are widely used in the production of both spiral and convolute wound tubes. As a result of its controlled penetration of the paper, the silicate binds and anchors itself to the individual fibers, imparting greater strength to the tube.

Ready-to-use silicates are generally the most economical and efficient adhesives for tube winding.

Convolute wound tubes, used as fiber drums and cans, gain rigidity from silicate. For greater strength, it is economical to use silicates because they cost less per pound than the equivalent amount of paper fiber necessary for a comparable improvement in strength.

Paperboard Coating

Sodium silicate adds stiffness to paperboard and increases its resistance to moisture, fire, grease and vermin. Silicate may also be used on it's own as a greaseproofing agent.

Sodium silicate serves as a priming coat for the application of secondary materials such as paraffin, chlorinated naphthalenes, waxes, gums, nitrocellulose, lacquers and other paperboard coatings. Its fills the pores of the paperboard, makes the sheets less absorbent and as a result reduces the amount of of finishing coat required.

Coverage per 1000 square feet of paper varies from two pounds of the diluted silicate for light coatings, up to 30 pounds for heavy grease proof coatings.

Plywood/Corrugated Board

Silicate-protein adhesives have been used successfully for many years in the production of interior grade plywood. These adhesives are also used in bonding the top double-back liners in double-wall or triple-wall corrugated board. The silicateprotein combination is useful in producing wet-strength corrugated board that is preferred for cold storage packaging.

Laminating Metal Foil

Sodium Silicates are well-adapted for bonding aluminum and other metal foils to paper. silicate, used for this application, forms an adhesive bond by losing moisture into the paper laminate and by evaporation to the air. In order to obtain good adhesion, the foil should be clean and the silicate must wet the foil. Silicates give high bond strength, greater than that of the laminated materials. The foil or paper would be destroyed before the silicate bond.

Other lamination applications are wood to felt, mica sheets, cork, asbestos, and a variety of other fibers.

Case Sealing

For a number of years silicates have been used for sealing boxes. The silicate is picked up by the glue rolls of an automatic casesealing machine and spread in the flaps of the cases. As in other adhesive applications, the silicate sets by losing moisture to the paper and the air, thus forming a strong bond.

Latex Binder Extender

High ratio sodium silicate has been successfully incorporated into SBR latex formulations as a binder extender. Unlike pigment extenders of other fillers, sodium silicates aid the latex's ability to bind fillers. Silicate also eliminates the need for thickeners in certain adhesives, where the silicate's alkalinity is able to swell the latex polymer.

Some SBR based adhesives can be reformulated at a much lower cost by substituting silicate solids for latex solids. Silicate also increases heat resistance, hardness, and adhesion to some substrates.

Water Resistance

By themselves, silicate adhesives are not water proof. However, high temperature calcining, or reacting them with divalent metals (zinc, calcium and others) or soy protein additives, can make silicate adhesives water resistant. A starting point formula might look like this:

  • 14.5% Soya Protein
  • 3.0% Pearl Starch
  • 16.0% Silicates
  • 66.5% Water

This system has a shelf life of approximately 24 hours.
Heating a silicate film to 370'C will drive off all of the water and greatly reduce the tendency of the adhesive to pick up moisture.