[IWG Micro Classroom] Six common problems and solutions of PUR coating hot melt adhesive

With the rapid development of the national economy in recent years, the people have higher and higher requirements for the living environment and household items. With more and more types of substrates, in the field of woodworking adhesives, the market demand for PUR-coated hot melt adhesives has surged unprecedentedly, and the requirements for product performance have gradually increased.


As a leader in the global woodworking adhesive industry, IWG has always closely followed the international situation and industry development trend. Relying on the group's technological research and development advantages, the service experience of many leading customers and a strong product application system, IWG has successively developed a series of PUR coated hot melt adhesive products have been highly concerned by the market as soon as they were launched, and have been approved and trusted by many customers in a wide range of product applications.


IWG Yongte PUR coating hot melt adhesive performance characteristics

The main component of IWG Yongte PUR-resistant coating hot melt adhesive is isocyanate-terminated polyurethane prepolymer. The adhesion and toughness (elasticity) of PUR can be adjusted, and it has excellent adhesion strength, temperature resistance, chemical resistance and Aging resistance. It is suitable for PVC, PP film below 0.2mm, veneer, painted veneer and other finishing materials below 0.6mm. It is widely used in the coating process of MDF, solid wood, aluminum alloy, PVC, wood plastic, mud and other profiles.

As an important part of the production process, the coating process is enough to have a bad impact on the entire product. Therefore, in the process of use and production, we must pay great attention to any problems that arise, and have professional System-specific solutions. In view of this, IWG Yongte resistance has put forward reliable solutions for the six common problems in the use of PUR coating hot melt adhesives, and discussed with you.

After the PUR hot-melt adhesive is emptied, it is found that there are bubbles in the adhesive after continuous use for a period of time or after a period of inactivity, which affects the uniformity of scraping. Are there any bubbles in the hot-melt adhesive?
Reason analysis: The main reason is that there is a cavity in the plastic bucket, and the cold air outside will flow to the hot cavity.

solution

1. Replace the sealing ring of the rubber bucket.

2. Spread enough and evenly high temperature butter.

3. Remove the rubber around the sealing ring and the remaining rubber in the pressure plate.

4. Check whether there is a gap between the cylindrical hot-melt adhesive and the inner wall of the glue barrel (may be due to thermal expansion and contraction or the filling is not dense).

5. Check whether the aluminum foil packaging bag is wrinkled to form a gap due to the pressing down of the pressure plate. If there is, the aluminum foil at the folded part of the barrel should be tightly bonded (the upper hot-pressing plate melts the glue barrel).

After the PUR hot melt adhesive is discharged, the particle problem occurs continuously during the use process, which affects the appearance quality. Does the hot melt adhesive contain particle impurities?
Reason analysis: The particles come from colloids (in case of moisture) or from foreign objects, which need to be distinguished by a magnifying glass and a glass plate. Usually, the particles come from foreign objects.

solution

1. It is easy to contact moisture in the slit of the scraper head and in the cavity to form colloidal particles. After stopping working, use a cleaning agent that melts into a block to clean the scraper, apply high-temperature butter, and wrap it with aluminum foil after applying high-temperature butter. Before cleaning, use a cleaning solution and a feeler gauge to clean the scraper slit.

2. Due to the long-term use of the inner wall of the hose, there is carbonization and scaling of the rubber, residues of moisture curing, and carbon deposition of dust and wood chips. It is necessary to regularly use a cleaning agent to flush the hose and replace the hose and filter.

(200 mesh/inch, 0.075mm, 100 mesh/inch, 0.15mm).

3. PVC film attracts foreign dust and sawdust due to static electricity, which can be eliminated by using static electricity removal equipment.

4. The wood chips produced by high-speed friction between the veneer and the scraper are recommended to be replaced with high-quality or back-mounted veneers.

PVC film coated wood plastic or aluminum alloy, the peel strength after 5 minutes is poor, and the glue transfer on the substrate is not much, how to solve it?
Reason analysis: Usually the opening time is too short, resulting in insufficient wetting of the PUR hot melt adhesive to the substrate.

solution

1. Increase the ambient temperature, not lower than 18 ℃.

2. Turn on the substrate preheating device and control it at 35-45℃.

3. Open the corresponding hot air cylinder to extend the opening time of the glue.

4. The surface tension of the substrate is too low, and it is necessary to replace the substrate with high surface tension (not less than 34 dynes/cm) or do primer treatment.

5. Raise the operating temperature of the scraper, hose and bucket.

6. Appropriately increase the amount of glue.

7. Properly increase the production speed.

8. Replace the product with better wettability.

PVC film coated wood plastic or aluminum alloy, the peel strength after 5 minutes is acceptable, but after 16 hours the peel strength does not meet the requirements, how to solve it?
Reason analysis: This situation has a greater relationship with the surface tension of the material and the moisture curing speed of the hot melt adhesive.

solution

1. If most of the glue is transferred to the substrate, it is recommended to increase the surface tension of the PVC film, and a corona machine can be used.

2. Confirm whether there is any free plasticizer in the PVC film. It is recommended to store it in a cool and dry place without stacking the PVC film.

3. If most of the glue remains in the PVC film, it is recommended to increase the surface tension of the substrate, which can be treated with a corona machine or a primer.

4. Extend the curing time, especially in the environment of low temperature and low humidity.

5. Use a constant temperature and humidity room to maintain health.

6. Replace with products more suitable for such materials.

MDF coated with PVC film and MDF coated with veneer, the wood breaking rate after 5 minutes is less than 50%, how to solve it?
Reason analysis: Usually, the opening time is too short, resulting in insufficient wet penetration of PUR hot melt adhesive to MDF.

solution

1. Increase the ambient temperature, not lower than 18 ℃.

2. Turn on the substrate preheating device and control it at 35-45℃.

3. Open the corresponding hot air cylinder to extend the opening time of the glue.

4. Raise the operating temperature of the scraper, hose and bucket.

5. Appropriately increase the amount of glue.

6. Properly increase the production speed.

7. Replace the product with better wettability.

Within 5 minutes after PVC and veneer wrapping, the concave position in the sudden change and the final folding wrapping position will rebound immediately or gradually. How to solve it?
Cause analysis: Usually, the opening time is too short or too long, the pressing pressure is not enough, the pressing time is not enough, and the initial tack of the PUR hot melt adhesive is not enough.


solution

1. Use a hot air cylinder to soften the surface material and reduce the tension of rebound.

2. It is necessary to use a sharp and suitable pressure roller to increase the pressure, which is conducive to the wet penetration of the hot melt adhesive.

3. Increase the number of pressure rollers to increase the pressure time with a gradual change.

4. Use a cooling device and a hot air cylinder to control the appropriate opening time of the hot melt adhesive.

5. Appropriately reduce the operating temperature of the scraper, rubber hose and rubber bucket to improve the initial viscosity.

6. Appropriately increase the amount of glue.

7. Appropriately reduce the production speed.

8. Replace the product with better initial adhesion.

Special Note


IWG's full line of coating adhesive products specially developed for coating applications, covering a variety of different types of adhesives, suitable for a variety of applications, including contour coating of complex lines, as well as suitable for blade coating and roller coating Cloth contour wrap. Its wide range of equipment applicability can effectively improve production efficiency. The finished product has good temperature and humidity resistance, and meets F★★★★ and CARB PII standards, which is green and environmentally friendly.



1. For convenience in the future, use a specific mold to position the blank.

2. The proportion of adhesive should be precise, and the amount of glue should not be too large.

3. This product contains isocyanate, and protective gloves suitable for isocyanate should be worn. Goggles should be worn every time the product is used. Hardener must not come into contact with water or moisture.

4. The system must be cleaned before curing.

5. The cured glue can be treated as general non-hazardous waste.

6. The curing agent contains isocyanate and should be disposed of as hazardous waste.

7. After the mixed glue and curing agent are completely cured, they can be treated as general non-hazardous waste.