Hebei Shuangda | Deep analysis of two common problems of butyl rubber extrusion bubbles and adhesion

Butyl rubber is widely used in waterproof tape, hollow glass sealing, and damping products due to its excellent airtightness. In extrusion production, the most common pain points are internal bubbles, surface sticking of molds, and stacking adhesion of finished products, which directly increase the scrap rate and affect the sealing of the product.

01Bubbles and air holes appear on the extruded rubber strip (internal holes, surface bubbles)

Bubbles can directly damage the airtightness of butyl rubber, and the finished product is prone to water and air leakage, which is the primary production challenge.

　　PART.01

　　raw materialDamp (highest hair)

The storage environment for fillers (white carbon black, calcium carbonate) and raw rubber is humid, and the raw materials absorb moisture; During high-temperature extrusion, water vapor evaporates, forming permanent pores. The risk of clumping and outdoor storage of adhesive materials is extremely high.

　　PART.02

　　Feed wrapped in air

The manual feeding is intermittent, with large gaps between the rubber blocks, and air is carried into the screw; The feeding is unstable, and the gas carried by the melt cannot be discharged.

　　PART.03

　　Temperature parameter imbalance

Excessive temperature: Butyl rubber decomposes upon heating, producing volatile small molecule gases;

Low temperature: incomplete plasticization, poor flowability of the rubber material, and difficulty in releasing the trapped air.

　　PART.01

　　Raw material control

The rubber material is sealed and stored in the drying workshop; Moisture affected fillers should be dried at low temperatures in advance; Eliminate the use of damp, clumped old glue.

　　PART.02

　　Standardize feeding

Cut the rubber material neatly, feed continuously and evenly, and avoid intermittent feeding; Conditions permit the installation of a forced feeding device to reduce air entrapment.

　　PART.03

　　Refined temperature control

Adopting gradient segmented temperature control, following the principle that the head temperature is slightly higher than the barrel temperature; Temperature should be gradually adjusted, and it is forbidden to raise the temperature significantly at once.

02Two major adhesion issues: extrusion die adhesion and product stacking adhesion

Many factories cannot distinguish clearly: die adhesive belongs to extrusion process faults; The mutual adhesion of products after cooling belongs to the problem of later stage molding, and the handling method is completely different.

　　01Extrusion bonding mold (adhesive material sticking to the mold mouth, adhesive drawing, adhesive breakage)

Reason ① The temperature of the machine head/mouth mold is too high, and the rubber material is excessively softened; ② The Mooney viscosity of the formula is too low, and the flowability of the rubber material is too high; ③moldThe inner wall has insufficient smoothness and there are blind spots for adhesive accumulation; ④ The extrusion traction speed is not matched, and the rubber material stays at the mold mouth for too long.

Solution

Moderately lower the temperature of the machine head and mouth mold by 3-8 ℃ to reduce the melting and softening of the rubber material;

Formula fine-tuning: Adding a small amount of zinc stearate and polyethylene wax to enhance release properties;

Regular polishing and maintenance of molds, and regular cleaning of carbide deposits at the mold mouth;

Match the screw speed and traction speed to accelerate the detachment of the rubber strip from the mold.

　　02After cooling, the finished products adhere to each other (tape winding, tape stacking and sticking together)

Reason ① Insufficient cooling after extrusion, high residual heat inside the rubber strip, and continuous sticking on the surface; ② The formulation plasticizer precipitates, forming a viscous oil layer on the surface; ③ The winding tension is too high, and the rubber strip is tightly squeezed; High ambient temperature and poor ventilation.

Solution

Extend the length of the cooling section, fully air-cooled/water-cooled to ensure complete cooling of the gel before winding;

Optimize the formula and control the dosage of low molecular weight plasticizers; Can be paired with isolation film and isolation powder to assist in anti sticking;

Reduce winding tension, maintain ventilation during finished product storage, and avoid high-temperature and sealed stacking.

03Quick troubleshooting sequence

　　01Quick troubleshooting sequence

If any defects occur, investigate them in order to save debugging time:

Confirm if the raw materials are dry → 2 Check the actual temperature of each section (calibrate the temperature control probe) → 3 Observe whether the feeding is continuous and whether there is any curling air

Check if the mold head and exhaust port are blocked → 5 Adjust the screw speed and traction speed → 6 Determine whether it is sticking to the mold or stacking of finished products, and handle it accordingly

　　02summary

Extrusion bubbles and adhesion of butyl rubber are rarely caused by a single factor. Priority should be given to controlling the humidity and temperature curves of raw materials, followed by optimizing equipment exhaust and feeding methods; Continuously poor, combined with formula adjustment. Stable process parameters and standardized daily operations are the most effective ways to reduce waste rates.

If the equipment is old, the exhaust structure is inherently inadequate, and frequent debugging still cannot eliminate the fault, upgrading and optimizing the extrusion screw and head structure can solve the root problem from the hardware level.