How to solve the problem of foaming and degumming when the technology is attached to PVC film and veneer?

Hello, Mr. Shen! I am a reader of "Asian Plates and Furniture", our company mainly produces panel furniture. The company has a contour coating machine that coats the substrate with a laminate of trim. The veneer profile is covered with an EVA hot melt. Later, I bought a second-hand contouring machine, which was coated with aluminum profiles and PVC and thin veneer. The adhesive was made of reactive hot melt adhesive. The PVC profile coating often has the disadvantages of foaming and insufficient adhesive force. The thin veneer profile coating often has the disadvantages of foaming and insufficient adhesive force after painting. Please help analyze the PVC profile coating, the thin veneer contour coating appears to cause foaming, and the adhesive force is not in place. What should you pay attention to in each step of the contour coating process? I hope that you can provide comments for reference. I wish you good business!

Mr. Wu Mr. Wu, thank you very much for your letter. Based on the information you provided on the phone, analyze the PVC profile coating and the thin veneer profile to cover the reason why the foaming glue is not in place. A brief description of what needs to be noted in each step of the contour wrapping process is as follows.

(1) Briefly explain the reasons for the blistering and insufficient adhesion of the EVA hot-melt adhesive veneer and the proposed improvement. 1. Contour-coated substrate quality: - The water content of the scrap aggregate is controlled at 10±2%. Too high a water content of the substrate will result in unstable adhesive strength. - Strictly control the quality of the substrate during the four-side planing process. There are serious shortcomings such as jumping knives, coarse knife marks, reverse lines, hoes, and gouging. Some blistering or glue will appear after the turf is coated. The force is not in place, the slight defect usually appears after the paint is painted (pictured)

2. Quality of thin veneer: - The moisture content of the thin veneer should be controlled at 10 ± 2%. If the moisture content is too high, the adhesive strength will be unstable or foaming. - Uneven thickness or too tight tolerance of the sliced veneer leads to unstable adhesive strength. Strict control confirms that the thickness of the veneer is stable. - Thin veneer composite back surface with water-based white latex, confirmed to meet the EU D3 standard, with appropriate water resistance, high temperature resistance and solvent resistance. - The thin veneer composite back gauge strictly controls the amount of glue applied, and the inspection confirms the defect of no penetration. The thin veneer composite backsheet penetrates the glue causing instability or foaming.

3. Selection of hot melt adhesive: - Select the appropriate heat according to the heating temperature range, the line speed of the glue, the viscosity of the glue, the range of the open time of the glue, the initial viscosity and the strength of the solvent resistance. Melt glue.

4. Concave cladding machine operation precautions: - According to the hot melt adhesive help book, confirm that the hot melt adhesive heating temperature is in place and stable, the heating temperature is too high and exceeds the highest temperature, causing the melt rubber to carbonize, resulting in insufficient glue force. The hot melt adhesive is carbonized, and the glue residue must be cleaned before the glue can be added to confirm the uniformity of the heating temperature of the glue residue without local carbonization. The amount of hot melt adhesive stored in the glue residue is kept at an appropriate stock. If too much glue is added, it will overflow the glue residue. The glue glue has too little influence on the flow rate of the glue pump, which will easily lead to carbonization of the hot melt adhesive (as shown in the figure).

- Pay attention to the maintenance of the glue applicator and confirm that there is no blockage and the amount of glue is evenly in place. - The upper and lower left and right press rolls of the contour wrapping machine are not damaged, the pressure of the press roll and the position setting are confirmed, and the surface of the veneer is confirmed to have no unbalanced tension. - The contour is covered and the surface temperature of the veneer must be checked to be approximately 55 ° C - 60 ° C. If the temperature is too high, the veneer will rebound and the corners will be peeled off. Under the premise that the line speed remains unchanged, an additional cooling fan is needed to help cool down, or the hot melt heating temperature is reset.

5. Finished paint: - Before the finished paint is put on the line, it must be strictly checked that there is no disadvantage that the glue is not in place. - Ordinary EVA hot melt adhesive is extremely weak against solvents, so try to avoid too thick when applying the first paint, and avoid excessive foaming and degumming. - If there is a process of grooving or milling, it can be better to move it after painting, and avoid excessive deposition of solvent in the tank to increase the probability of degumming. - It is recommended to test water-based paint to avoid the risk of foaming and degumming due to solvents.

(2) Using reactive hot melt adhesive, the substrate is changed to aluminum profile and thin veneer, PVC or artificial veneer for contour coating, the reasons for the foaming and poor adhesion of the finished product are improved. 1. Surface treatment of the substrate:- The aluminum profile must be subjected to a surface treatment prior to contour coating. - surface treatment agent is not in place (pictured)

Will cause the glue to be out of place. It is necessary to reset the coating amount of the surface treatment agent, but it is understood that the treatment agent is a transparent and colorless liquid, and it is difficult to find uneven coating amount when applying the treatment agent. It is recommended to require the supplier to add a fluorescent agent to the treatment agent. It is easy to confirm that the coating amount of each aluminum profile coating treatment agent is uniformly in place after inspection under a fluorescent lamp after coating the treatment agent. - Excessive application of the surface treatment agent, insufficient drying of the treatment agent will result in foaming of the contour coating (as shown).

 It is recommended to re-check the temperature of the heated hair dryer to confirm that the surface is properly dried.

2. The amount of glue applied is unstable: - the reaction type hot melt adhesive coating equipment is not cleaned, or the reactive hot melt adhesive package is damaged, resulting in local crust formation residue, and the glue residue is blocked in the glue dispenser (spray nozzle or scraper) Affect the unevenness of the cloth, resulting in the contour coating is not in place (as shown). Ensure that the reactive hot melt adhesive coating equipment is thoroughly cleaned, and the reactive hot melt adhesive is strictly inspected to confirm that the package is not damaged before use.

3. Reactive hot melt adhesive coating equipment maintenance: - If the wheel cover wrapper is scheduled to stop operating for more than three days, it is necessary to use the hot melt adhesive in the plastic bucket before parking, which is specially used for cleaning reactive hot melt. The wax coating equipment of the rubber coating equipment is confirmed to be thoroughly rinsed (as shown in the figure). Make sure that the next time you use the cloth, the cloth is even and stable. We need to pay attention to the different suppliers of reactive hot melt adhesives and contour coating machines. The maintenance details of the rubber coating equipment are not completely consistent. I hope that the above simple analysis and suggestions can help to improve some of the problems encountered in the coating of the corridor.

4. Have you encountered any problems when manufacturing or processing wood?

Please don't hesitate to ask Mr. Shen Yuxin immediately!

Mr. Shen Yuxin was born in Kuching, Sarawak, Malaysia in 1948. He graduated from the National Forest University of Taiwan in 1974. He graduated from the Taiwan Forestry Bureau after graduation. From 1975 to 1995, Mr. Shen worked in the wood processing and artificial board industries in Malaysia, Singapore and Kalimantan. He has worked as a engineering and technical personnel, production supervisor, production manager and general manager of production. Mr. Shen also joined the Asian Woodworking Group, a world-renowned chemical company, in 1996 as the Regional Technical Services Director.