Classification Of Solvent Based Adhesives For Footwear Industry In China

Uppers of the world

At present, there are basically 3 kinds of solvent adhesives in China's footwear industry, that is, CR glue, GCR glue and PU adhesive.

The proportion of 3 kinds of gum is about 30% of CR, 40% of GCR and 30% of PU.

Due to the lower cost of CR glue and GCR adhesive, the easier manufacture and the habit of people, the proportion of CR glue and GCR glue in our shoe adhesive is larger.

The solvent adhesive has the characteristics of simple manufacture, convenient use and high adhesion strength, and is well received by the footwear industry.

However, because it contains a lot of harmful volatile organic compounds, the life of the solvent adhesive will not be too long.

In the CR adhesive system, the ordinary CR gum contains about 30% of the toxic toluene, while the GCR gum is almost all aromatics.

Although PU gel is mostly used as a solvent with low toxicity ethyl acetate, its stimulation to the respiratory and nervous system of the human body should not be neglected.

It is for these reasons that many scientists and technicians in the world have paid much attention to the substitution of solvent glue.

As early as the mid 70s of last century, the former Soviet Union scholars developed the polyamide hot melt adhesive that adhered to the skin and skin. In 1992, the British scientists also introduced a reactive solventless paste.

However, due to many factors such as price, technology and equipment, these achievements have not been promoted.

Hot melt adhesives will be of great concern.

The first use of hot melt adhesive is used as adhesive.

Up to now, polyamide glue and polyester glue are still the main adhesive types in the stretching process.

The hot melt adhesive made of modified polyolefin based on the modified polyolefin in 80s by the shoe making Institute of China's light industry ministry has achieved good results in some factories.

At present, the use of adhesive is about 300t/a.

With the improvement of shoemaking mechanization, this kind of adhesive will develop.

At present, the glue used in China's footwear industry is imported from China, Taiwan, Italy and Germany.

Baotou is the second largest use of hot melt adhesive on shoes.

Baotou glue is mainly used for the production of some medium and low fashion shoes in Baotou, with an annual consumption of 800 to 1000t.

At present, there are two types of adhesive, one is polyamide type, the other is EVA type.

Taiwan and its wholly owned and joint venture factories in the mainland account for most of the market share.

The third use of hot melt adhesive on shoes is the hem of the upper part of the upper part (Beijing calls the edge).

Sipping gum was originally invented by BUSM company for polyamide.

The melting point of the adhesive is 120~150 degrees, the viscosity is less than 1500cP, and the curing speed is <1s.

Due to the limitation of machine accuracy, there are few factories in China, and it is possible to develop after joining WTO.

The fourth uses of hot melt adhesive are lining and heel.

In the past, the adhesive lining and shoe heels were mostly used as solvent glue, such as gasoline glue or neoprene, etc. now, because of the environmental protection needs, more latex is used in China.

The hot melt adhesive used for this purpose is massive, melting point is about 120 degrees, viscosity is <2000cP, adhesion force is more than 15N/cm, and EVA series are more varieties.

With the demand of environmental protection and efficiency, this aspect of application may develop in China.

The fifth use of hot melt adhesive is cloth compound.

Because of the high efficiency of compound cloth with hot melt adhesive, high shoe material, moisture resistance, anti-corrosion, good hygienic performance and environmental friendliness, the hot cloth is used to mix cloth and rubber shoes.

It has attracted the attention of many scientists that gluing the bottom with hot melt adhesive.

Its fast and pollution-free solvent is incomparable. However, practice has proved that its adhesion strength can not meet the needs of shoes.

To make the hot-melt adhesive reach the ideal degree of adhesion, we must start from two aspects: enhancing intermolecular force and rapid penetration function.

Water based adhesives and solventless adhesives -- the hopeful star of shoe glue

The water base glue of the shoe includes natural latex, synthetic latex and water dispersions of various kinds of polymers. The most used in Chinese shoe industry is natural latex and starch glue.

Water-based adhesives, as the least polluted rubber species, have attracted much attention with the development of social economy and the increasingly stringent requirements for the ecological environment.

Although it still has many shortcomings such as low adhesion strength, slow evaporation of water, long operation time, low efficiency, mucous membrane and so on, however, after all, the protection of human beings is the most important. Therefore, the application of water-based adhesives in shoemaking industry has gradually expanded over the years.

However, in order to make the water-based adhesives successfully used as the base glue, in addition to enhancing the adhesive property of the adhesive matrix itself, we must also solve the problem of permeability of the gum, and the effective penetration agent and thermal shock are all possible ways to consider.

The solvent-free adhesive, also known as reactive adhesive, is used to coat two surfaces of chemical reaction on the surface of the material that needs to be bonded. Then, under the condition of heat activation or other conditions, the components are closely contacted for chemical reaction, so as to achieve the purpose of cross-linking and adhesion.

For example, the shoe upper with polyester polyol prepolymer and the soles adhered to the isocyanate coating are tightly contacted under the conditions of thermal activation (or other substances activation) to form polyurethane, thereby forming strong adhesion.

This requires that the two reaction components have strong adhesion to their respective adhesives, and the reaction time, pressure, temperature and other technological factors are appropriate.

The reactive adhesive eliminates many processes such as polymerization, dissolution, evaporation and drying, so it has broad prospects for development.