usually refers to its solid at room temperature, when heated to a certain temperature will melt into a viscous liquid, coated after wetting the adhesive, after pressing, cooling to room temperature in a few seconds to complete the bonding adhesive, and has a strong bonding effect.

EVA hot melt adhesive commonly used raw materials: EVA resin, viscosifying resin, wax, antioxidant, makeup filler. EVA hot melt glue common products: book binding glue, furniture edge sealing glue, packaging glue, mattress glue, banknote hot melt glue, toy hot melt glue, covering hot melt glue and so on.

With the wide application of EVA hot melt adhesive, a series of common problems are also generated:

1. Sticky in summer, brittle in winter;

2. Poor bonding strength to the substrate;

3. The viscosity used is too large or too small;

4. Drawing problems occur during use;

5. Soft and hard problems;

6. Curing speed problem;

7. The use of filler precipitation and other problems.

Looking at the above series of problems, do you resonate? For example, how do you solve the hot melt adhesive sticky in summer and brittle in winter? Microspectrum engineers will discuss with you how to solve these two problems from the perspective of formula adjustment.

First, hot melt adhesive summer sticky problem description

Summer, in the temperature of more than 40 бу C transportation and storage process, hot melt adhesive will soften and sticky because of the rise in temperature, colloids and colloids will bond together, increasing the difficulty of construction, affecting the use of effect.

Method 1

Surface treatment method (This method is suitable for the phenomenon of a small amount of glue bonded together)

(1) Add emulsified wax to the cold water tank before pelleting hot melt glue, the rubber strip is cooled in the cold water tank, the outer layer of the rubber will be covered with a layer of wax, the surface of the hot melt glue is smooth and dry after pelleting, and the rubber particles are not easy to stick.

(2) Add powder release agent after hot melt adhesive molding, and do surface treatment of hot melt adhesive.

Method 2

Change the type of viscosity regulator (Table 1)(applicable to the situation of adhesive area less than 1/3)

Table 1 Change the type of viscosity regulator

In the adjustment of formula, only 58 # paraffin wax is changed into 80 # microcrystalline wax, and the softening point is increased by 2 бц. The colloidal particles are sticky at 40 бу C. The

phenomenon is significantly reduced. Perhaps some technicians will suggest using polyethylene wax instead of paraffin, but if polyvinyl wax is added, the Tg of hot melt adhesive will increase a lot, and other properties of hot melt adhesive will also have a great impact.

Method 3

Change the composition and ratio of the formula (Table 2)(applicable to the phenomenon of large-area adhesion of hot melt adhesive)

Table 2 Change the composition and ratio of the formula adjustment

On the premise of ensuring the consistency and bonding strength of the formula, improve the hardness and softening point of the glue is the direction of the formula adjustment. The formulation changed the paraffin wax into microcrystalline wax, which improved the softening point and temperature resistance. The rosin glyceryl ester had higher temperature resistance than rosin and could improve the bonding strength of the adhesive. As far as the adjustment of EVA resin is concerned, EVA800 has high hardness and high softening point, but if only EVA910 is changed to EVA800, the viscosity of the glue will increase, so 15 parts of EVA910 are divided into 10 parts of EVA800 and 5 parts of EVA900.

Two, hot melt adhesive winter brittle problem description

Into the winter, EVA furniture edge sealing hot melt adhesive in good bonding PVC edge strip with the temperature drop, the adhesive layer will become brittle and hard, the edge strip pulling will crack phenomenon.

Method

Reduce the Tg of the hot melt adhesive, reduce the amount of wax used, reduce the hardness of the hot melt adhesive, and enhance the flexibility of the hot melt adhesive (add a small amount of plasticizer, add a small amount of SBS resin, etc.).

Table 3 is the adjustment of the formula of EVA hot melt adhesive to solve the problem of winter non-brittleness

Table 3 is the adjustment of the formula of EVA hot melt adhesive to solve the problem of winter non-brittleness. After adjustment, the plasticizer dioctyl phthalate is added to the adjusted formula, which improves the flexibility and low temperature resistance of the sample, but only increasing the plasticizer will reduce the cohesion and bond strength of the hot melt adhesive. Therefore, replace EVA810 with EVA800 and increase its content, and increase the bond strength by reducing the polyethylene wax content, replace C9 tree with C5/C9 copolymer resin with a softening point of 100 бц to reduce the softening point of the viscosifying resin, and add SBS with good low temperature resistance, The final formula is adjusted to meet the winter of no brittle and excellent performance of EVA hot melt adhesive.

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