Basic Requirements Of Position Glue
Moderate adhesive force.
If sticky force is too low, it will cause unstable of position glue,if sticky force is too high,it will tear the back sheet or underpants.
No residual glue.
There is no glue residue in the underpants after tearing.
Stable adhesive glue,Sanitary napkins can be stored for a long time.
Low temperature resistance.
Good adhesion can be maintained at low temperatures.
Light color, slight smell.
Strong adhesion for PE film.
Good thermal stability,not easily carbonized.
Pure component without impurities.
Low viscosity, easily coating.
Test Method For Adhesive Force of Position Glue
Initial peel strength before and after oxidation: prepare standard non woven, and then use a 2 kg rubber pressing roller presses it three times back and forth. In the case of 23°C, the 180° peel strength was tested at a speed of 300 mm / min. This indicator shows the positioning performance when the sanitary napkin is placed.
The heated and pressed peel strength before and after oxidation(TTP): bring 500g of the weight press on the standard non woven, and then into the 40°C oven for 2 hours,and then test the 180°peel strength after cooling down at 23°C temperature. This indicator shows positioning and tearing performances of the process of using sanitary napkins. TTP indicators is more important.
The Status Of Adhesive Force Of Position Glue
Most of sanitary napkins’ TTP between about 30-300gf/inch.
Width of gluing is about 2-4cm
The thickness of coating is about 15-50μm
There is a huge difference between the thickness of coating and peel strength. How should we choose?
The Best Adhesive Force Of Position Glue
Based on statistics, the best adhesive force of position glue TTP is between about 80-150 gf/inch.
Adhesive force too low will cause unstable of positioning.
Adhesive force too high will cause tear the back sheet or underpants.
The suitable width of coating is from about 2-4cm, could be divided into 1-3. The width of spreading should be more than about 3cm.
Several Factors Should Be Considered In Determining Thickness Of Position Glue
Adhesive force:the high viscous force of position glue can be scraped thinner properly.But not too lower, also should be consider the anti-oxidation and back sheet.
Anti-oxidation of position glue
The width of squeegee glue
The purity of back film
The hardness of embossed back film
The fluctuation of position glue machine
The results shows that the thicker the coating, the higher the adhesive force, as increasing deformation ability, expand the contact area.
The coating more thinner, the anti-oxidation more quickly, it have huge relation with glue type, basic materials and temperature of environment. The best suggestion is increase the thickness if coating, raise adhesive force, reduce the anti-oxidation.
The Relation Between CaCo3 Content And Thickness of PE film
Adding CaCo3 into PE film will reduce the strength of film, and the thickness of film must be reduced in order to keep the film weight unchanged. The results are below:
1.The tearing strength of PE film reduced greatly, it will cause back film are teared more easily.
2.The position glue accelerated anti-oxidation.
3.As the holes of breathable film and high filler dosage, its glue is especially rapid oxidation.
The Deeper Embossed Back Film Cause Coating More Thinner
Fluctuation For The Amount Of Outing Adhesive Per Equipment
The amount of glue produced by the viscose machine at different speed are inconstant.
The glue temperature changes, jams issues will also affect the amount of gum.
The above factors maybe cause the thickness of coating have fluctuation between 1-5 μm.
Conclusion And Suggestion
Confirm the thickness of coating must consider the adhesive force, anti-oxidation,content of back film,embossed depth of back film, width of coating and fluctuation of adhesive machine.
For most manufacturers, the thickness of coating controlled between 25-35 μm would be reliable.
The thickness of coating can be set at 20 μm, only when the filler of back film is very little, almost no embossing and the machine in very precise conditions.
For breathable film, position glue need increase the thickness of coating 5-10 μm to slow down the oxidation of adhesive.
Choose a good anti-oxidation of adhesive material is essential.