Polyurethane adhesive with excessively high viscosity places specific requirements on the selection and application of glue spreaders (coating machines). It necessitates comprehensive consideration of equipment design, process control, and maintenance. The main requirements and considerations are as follows:

1. Requirements for the Adhesive Supply System

Type of Adhesive Pump**: Pumps with high pressure and strong conveying capacity, such as **gear pumps or screw pumps**, should be selected. Avoid using centrifugal pumps or diaphragm pumps, as they may be unable to handle high-viscosity fluids.

Pressure Range: The system must withstand high pressure (typically **≥10 bar**) to ensure stable delivery of the adhesive to the coating head.

Heating and Temperature Control: Polyurethane adhesive viscosity is sensitive to temperature. The supply system must be equipped with **heated pipelines and constant temperature devices** (e.g., hot water or oil circulation heating) to control the adhesive temperature within an appropriate range (e.g., 40-60°C), thereby reducing viscosity.

Adhesive Tank Design: The adhesive tank may require stirring or circulation devices to prevent sedimentation or stratification of the high-viscosity adhesive.

2. Design Requirements for the Coating Head

Slot Dimensions and Shape:

The slot opening of the coating head needs to be **widened** (e.g., 1-3 mm) to accommodate the flow of high-viscosity adhesive.

The slot shape should be optimized (e.g., "coat-hanger" or "T-type" die) to ensure uniform adhesive distribution.

Materials and Surface Treatment**: The interior walls require **high polishing** or anti-adhesive coatings (e.g., Teflon) to reduce adhesive buildup and clogging risks.

Adjustability: The gap and angle of the coating head opening should be adjustable to facilitate control of adhesive film thickness based on viscosity changes.

3. Control System and Process Parameters

Precise Temperature Control: The coating head and supply pipelines require independent temperature control, with a recommended precision within **±1°C**, to prevent local viscosity fluctuations.

Pressure and Flow Monitoring: The system must be equipped with **high-precision pressure sensors and flow meters** for real-time feedback and automatic adjustment of pump speed or valve opening.

- **Auxiliary Doctor Blade or Metering Roller: For extremely high-viscosity adhesives, a **doctor blade or roller coating device** can be added to assist in controlling adhesive layer thickness.

4. Cleaning and Maintenance

Quick Disassembly Design: Components such as the coating head and pipelines should be easy to disassemble for regular cleaning (high-viscosity adhesive is prone to residue and curing).

Solvent Circulation System: Equip with an automatic cleaning function to remove residual adhesive through solvent circulation.

Anti-Curing Measures**: Promptly flush with solvent or专用清洗剂 during shutdowns to prevent adhesive from curing and clogging inside the equipment.

5. Equipment Materials and Sealing

Corrosion and Wear-Resistant Materials: Components in contact with the adhesive should be made of **stainless steel (e.g., 304/316L) or hard alloys** to prevent wear and chemical corrosion.

High-Strength Sealing: Sealing components (e.g., O-rings, flange gaskets) must be pressure-resistant and solvent-resistant to prevent leaks under high pressure.

6. Safety and Environmental Considerations

Explosion-Proof Requirements: If solvent-based polyurethane adhesives or cleaning agents are used, the equipment must comply with **explosion-proof standards** (e.g., explosion-proof motors and electrical components).

Exhaust Gas Treatment: Heating may accelerate solvent evaporation, requiring local exhaust or waste gas collection devices.

7. Selection and Testing Recommendations

On-Site Testing**: Before selecting equipment, it is recommended to conduct **on-site flow tests** with the actual adhesive to verify pumping capacity, temperature control effectiveness, and coating uniformity.

Customized Design**: Fully communicate adhesive parameters (e.g., viscosity range, curing characteristics) with equipment suppliers and consider customizing专用淋胶机 if necessary.

By selecting glue spreaders specifically designed for high-viscosity fluids and strictly controlling process parameters such as temperature and pressure, issues like uneven coating and clogging caused by excessively high viscosity of polyurethane adhesive can be effectively resolved, ensuring production efficiency and product quality.