Лако-красочные материалы — производство

As mentioned above, the base material of glutine glue is collagen, a high-molecular — weight protein that is insoluble in the unprocessed condition. Depending on its origin, collagen has different mechanical properties: skin collagen is highly elastic, while bone collagen is very hard. In order to obtain water-soluble glutine, calcium hydroxide is added to collagen, or water vapor is allowed to react, thereby breaking the crosslinks between the collagen chains and partly reducing the length of the chains. The solution is then mildly concentrated by evaporation in a vacuum at temperatures below 100 °C. The solidified glue broth is then cut into small plates, cubes or other small shapes, and these are dried to obtain a residual moisture content of 12-15%.

Shortly before application, the dry glue material (which may contain antibacterial agents) is remixed with water at a temperature of approximately 60 °C to generate a 35-50% solution with a viscosity of 500-2000 Pa-s. If the glue is slightly overheated (up to 100 °C) for a short period, its viscosity decreases and application is facilitated. The solution, which is usually applied at 60 °C, abruptly solidifies when it reaches 40 °C, after which the solid must undergo a final drying process. The addition of paraformaldehyde can generate a hot-setting system; here, crosslinking takes place and the final product has an increased resistance to water.

Owing to the rapid change in viscosity at 40 ° C and low application temperature, it may be difficult to replace glutine glues in very fast-bonding processes such as bookbinding.

Compared to other natural adhesives, glutine glues processed in the hot condition are noted for their high plasticity in the cured state. This is not the least of reasons why they are used for back bondings in bookbinding, and for wood composite materials which must be reshaped after bonding (see also Sections 8.4 and 8.5).