Adhesives use animal glue

The production process of hide glue mainly includes raw material pretreatment, extraction, and finished product manufacturing.

Raw material pretreatment

Remove fat, minerals, and other non-collagenous substances in raw materials (bone or skin). The main processes are degreasing, alkali treatment, and acid treatment. The raw material pretreatment process of industrial glue is relatively simple, but gelatin is higher. The pretreatment process is related to product variety and quality.
Extraction
First, the cross-linked hydrogen bonds or electrostatic bonds in the collagen contained in the raw material are broken under the action of hot water. Second is the hydrolytic fracture of covalent bonds, which causes the disintegration of collagen, and this action is called cleavage. After unfolding, soluble animal glue is produced. A dilute solution with a concentration of 3 ~ 8% (mostly 5 ~ 7%) was obtained by hot water extraction. For different products, the extraction steps and process conditions are different.

The finished product manufacturing

The finished product of animal glue is made from thin glue liquid, which is mainly through filtration, evaporation and concentration, gel-forming, and drying.
(1) Filtration: generally using plate and frame filter press, and use the cotton pulp board as the filter medium. This kind of equipment is cheaper, but filter cake clearing must be manually intermittent, this way suitable for small and medium-sized enterprises. Modern large filter production equipment uses the driving device consisting of the group, pressure cylinder, and centrifugal self-cleaning blade filter.
The filter blade is placed in the pressure cylinder, the inner side of each filter blade is connected with the hollow shaft, and the upper and lower are covered with a very fine metal wire mesh. Adding diatomite filter aid in advance to form a filter slurry, then pumping into the liquid pressure cylinder, filter aid on the filter leaf to form a filter medium layer. After a certain period of filtration operation, rotate the filter blade set to remove the filter residue and filter aid
together by centrifugal force.
(2) Evaporation and concentration: multi-effect tube or plate evaporator is generally carried out under reduced pressure. After evaporation, the concentration of the gel reached more than 20 ~ 25%.
(3) Gel forming: Use the drum or belt-type gel machine, so that the concentrated liquid glue cold can condense into irregular sheets or small particles. Another commonly used is the inner and outer tube cooler, which is a kind of tube-type equipment with a cooling jacket inside and outside.
The glue liquid flows through the middle annular gap under pressure, and the gap is also equipped with a rotating scraper. After cooling, the gel is pushed and squeezed by the scraper and fluid together through the porous plate at the exit, and the thin gel is extruded. So this equipment is also called extruding machine.

(4) Drying: using a drum dryer or long net belt dryer. Roller type is a clearance type operation, suitable for small and medium-sized enterprises. The long net belt type is continuous operation, suitable for large factories. After drying, the water content of the product is generally less than 16%. Some products need to be crushed and screened after drying to get the final product.

How to use Animal glue?

First use the same amount or slightly more water (the general glue ratio is 1 to 1.2-3, it is best to use warm water) to soak the glue for a few hours, let it soften, then heat it up to about 75 degrees, so it can be used as glue.
The proportion of glue should be determined according to the viscosity needed, such as lower viscosity is had when adding too much water, and higher viscosity is had when adding too small water. The temperature should not be too high when heating glue, the temperature exceeding 100 degrees will due to molecular degradation and viscosity decrease, glue aging deterioration.

The glue has trace precipitation in the process of use, so it is necessary to add water to the stirring side to adjust the viscosity and fluidity. Hot glue must be heated by bath heat method, do not directly use glue storage container heating. Glue can only be used under certain temperature conditions, therefore: when adding water while using, water temperature should be basically the same as the glue temperature, do not add cold water. Because the glue must be kept at a certain temperature (75 degrees ±10 degrees), the temperature will drop sharply after adding cold water, which will cause clumps and affect the bonding effect. When using glue, the speed of glue coating should be fast and uniform. Do not dip the glue too much at a time to cause uneven rubber layers, infiltration, joint adhesion, glue leakage, and other problems. Adjust the amount of water and rubber powder to the required viscosity, and coating use.

What other usage for animal glue?

First is used for match manufacturing, mainly using colloidal foaming to form pores, combined with an oxidizer, ignition agent, and filler, so that the instant ignition;
Second is as an adhesive, using its high strength, elasticity, and toughness, in the production of emery cloth, sandpaper, bonding wood, binding books, and used in gift boxes assembly lines, advanced Musical Instruments, furniture industry;
Third is electrolysis, where the addition of an electrolyte helps produce smooth, dense anode sedimentation, eliminating production losses;
Fourth is used for textiles, in the yarn bundle can form a film, so as to increase the toughness, strength, fiber smoothness, and elasticity, prevent fracture;
The fifth is for the manufacture of negative photosensitive corrosion film with dichromate;
Sixth is the extraction of hydrolyzed protein, used for additives;
Seventh is an important raw material for the production of paintball.

In short, animal glue or industrial gelatin is widely used in plate, furniture, matches, feed, packaging, paper making, textile, silk, printing and dyeing, printing, ceramics, petroleum, chemical, coating, metallurgy, and other industries of all kinds of products, including the main thickening, stabilization, coagulation, blending, polishing, sizing, solid glue, etc.