In the refrigerator production process, polyurethane foaming is a key link to ensure thermal insulation performance and structural strength. If the problem of “slow foaming” occurs, it will not only affect the efficiency of the production line, but may also cause quality defects such as product appearance deformation and uneven foam cells. This article will systematically analyze the common reasons for slow refrigerator foaming from four aspects: raw material ratio, temperature control, process parameters and other potential factors, and provide corresponding solutions for reference by the majority of production technicians.
1. Raw material ratio problem
Insufficient proportion of B material (black material)
Insufficient amount of polyisocyanate will lead to lower concentration of reactants, slower reaction speed, and directly affect the foam generation rate.
Solution : calibrate the metering pump to ensure that B material is accurately injected according to the set proportion.
A material (white material) formula imbalance
If the tin catalyst is not added enough in the combined polyether, or the foaming agent content is low, it will also cause a slow foaming reaction.
Solution : Check the batch of raw material barrels and formula settings, and add catalyst or adjust the white material premix ratio if necessary.
2. Improper temperature control
When working in autumn and winter or in the early morning, if the ambient temperature is below 20℃, the chemical reaction will be significantly slowed down.
Solution
: Start the heating system of the plant, or increase the preheating treatment of raw materials and molds to maintain the on-site temperature between 20-30℃.
The mold or raw material temperature is insufficient.
If the mold temperature is lower than 40°C or the raw material is not heated by the constant temperature system, the raw material fluidity will be poor and the mixing efficiency will be low, thus prolonging the foaming time.
Solution :
- Ensure that the mold heating device operates normally and the temperature is stable at 40-50℃.
- Activate the raw material preheating system to keep the A/B material temperature in the range of 18-25℃.
3. Abnormal process parameters
Injection pressure imbalance
If the injection pressure difference between white material and black material exceeds 5 bar, it is easy to cause uneven mixing, backflow or equipment abnormality.
Solution : Check and adjust the pressure of the two lines to be basically consistent to ensure the mixing quality.
Insufficient aging time:
The foaming reaction requires a certain aging cycle. If the mold is demolded or cooled too early, the foam will not be completely formed.
Solution : According to the foam material system, appropriately extend the pressure holding time or aging cycle to ensure that the foaming reaction is fully completed.
Other potential factors
Raw material impurity contamination,
such as water, oil or impurities in the raw material, will cause reaction inhibition, and even produce bubbles and precipitation, slowing down the reaction speed.
Solution : Keep the raw material barrel sealed and moisture-proof, and regularly check the filtration system to prevent contamination.
Equipment failure or inadequate maintenance,
foaming gun mixing chamber blockage, metering pump aging, pipeline blockage, etc. will affect the raw material delivery and mixing efficiency.
Solution :
- Regularly maintain foaming equipment and clean mixing heads and filters;
- Replace aging pipes and seals to keep the equipment in good operating condition.
Conclusion
The slow foaming problem in refrigerators is often not caused by a single reason, but the result of multiple factors such as raw materials, equipment and process. When enterprises encounter related problems, they should conduct item-by-item investigations based on on-site data, starting from the four aspects of raw material quality, equipment status, environmental control and parameter settings, and make timely adjustments to ensure smooth production. If you need further technical support, please contact our engineering team.