Why Is Charring Common During The Production Of Hot Melt Glue?

In the production of hot melt glue, it is common for materials to char, turn yellow, develop an off-odor, or have increased impurities. This not only affects the product's appearance but also leads to unstable viscosity, decreased coating performance, and even equipment blockage. The causes are usually not due to a single factor but rather the result of a combination of process and equipment design.

1. Localized overheating is the primary cause

Hot melt glue systems are extremely sensitive to temperature. Uneven temperature distribution within the equipment can easily lead to hot spots in localized areas.

Common causes include:

• Inadequate heating jacket design.
• Insufficient coverage of the stirring structure.
• Poor flowability of high-viscosity materials.

Localized overheating can cause premature thermal decomposition of resins or additives, leading to charring.

2. Insufficient mixing efficiency, creating dead corners

Hot melt glue is typically high-viscosity systems. If the mixer structure is incompatible with the material's characteristics, dead corners can easily form within the equipment.

The consequences are:

• Material remains in a localized area for an extended period.
• Continuous contact with the heated surface.
• Heat cannot be dissipated in time.

Materials that are heated for a long time are very prone to coking.

3. Insufficient temperature control accuracy or lagging control

Some production lines experience slow response or insufficient control accuracy in their temperature control systems, resulting in:

• Actual temperature exceeding the set value.
• Frequent temperature fluctuations.
• Excessively rapid heating rate.

For heat-sensitive hot melt glue systems, these factors significantly increase the risk of charring.

4. Material residence time in equipment is too long

In intermittent production, if:

• Incomplete discharge
• Complex equipment structure
• Frequent batch switching

The residual material will be repeatedly heated in a high-temperature environment, gradually carbonize, and eventually mix into the new batch of products.

5. Inadequate filtration and cleaning system

Once coking occurs, if:

• The filtration system is inadequate
• Cleaning is not timely

Coking particles will continuously circulate within the system, leading to a vicious cycle and affecting the quality of the entire batch of products.

The charring problem in hot melt glue production is essentially a result of an imbalance between temperature, time and mixing efficiency.

Through proper process design and equipment selection, the probability of charring can be significantly reduced, improving product stability and production efficiency without altering the formula.

JCT can provide solutions, from process design to equipment configuration for the entire production line, based on the process characteristics of different hot melt glue systems. These solutions cover the selection of reactors or sigma mixers, temperature control system design, optimization of discharge and filtration structures, and support for automation control. This helps customers improve product consistency and reduce coking while maintaining stable production.