The Latest Trend Of The Application Of Waterborne PU Adhesive In Shoemaking Industry

The use of harmless adhesive technology for harmless production has been widely advocated by the society. This is also a requirement of adapting to the development of today's society. It embodies the sense of social responsibility of enterprises.

When more and more shoemaking workers realize that they lack a safe and decent working environment, or they sacrifice their health for the necessities of life, they will not have much interest in shoemaking industry.

How to provide workers with a safe working environment has attracted more and more attention from the whole industry.

Bayer material technology introduced the green bonding technology to the shoemaking industry very early. Its waterborne PU adhesive is a harmless product to human beings and environment. The use of water-based adhesive can effectively avoid the poison caused by the abuse of solvent based adhesives and improve the sanitary condition of the working environment, which helps to improve and improve the image and competitiveness of the enterprise.

For China, which accounts for more than half of the world's shoe production, it will lead to a revolution in green production safety, which will enable more people to know how to avoid the harm of toxic chemicals, so that consumers and producers of shoes will have complete safety responsibilities.

The water-soluble glue is milky white emulsion, dried and infrared activation, without any color, pparent, and there will be no yellowing.

Bayer aqueous PU adhesives and neoprene CR adhesives can be applied to various bonding processes in shoe processing, such as shoe heel formation, molding, EVA/Phylon midsole, bottom processing, vamp sewing machines, rubber gluing and gluing.

The VOC (organic volatilization) is reduced to the greatest extent, thus avoiding physical damage to employees and damage to the surrounding environment.

The risk of solvents is due to the fact that most organic solvents are combustible, and most organic mixtures cause air pollution and smoke generation.

When the organic solvent is fully evaporated and the content in the air reaches a certain level, the volatile organic solvents will be ignited or exploded.

Therefore, when storing organic solvents, fire prevention is very important.

In addition, these volatile potential hazards can affect human health through eye contact, skin inhalation, mouth or nose inhalation.

The characteristics of common toxic solvents and their hazards to human body are listed below.

The adhesion of high strength polymer penetrated completely to the surface of the material, and even when the material was damaged, the adhesive surface remained intact.

The colorless liquid of aromatic aromatic smell quickly evaporates into the air or dissolves in small quantities in water.

High levels of benzene can cause death, which can cause drowsiness, dizziness, heartbeat, headache, convulsions, nervous disorders and mental confusion.

Long term exposure to benzene (365 days or longer) can cause bone marrow damage and lead to anemia or hemorrhagic disease, leading to impaired immune system and increased chance of infection. The human health protection department has identified benzene as a carcinogen.

Methylene chloride has a sweet smelling methylene chloride, also known as dichloromethane, which is often used as an industrial solvent and a paint remover.

A large amount of methylene chloride causes body wobble, dizziness, nausea, tingling and numbness in fingers, toes, and a small amount of poor coordination between eyes and hands.

WHO finds methylene chloride can cause cancer.

Toluene toluene is a colorless and pparent liquid with unique odour. Toluene can be obtained from crude oil extraction to gasoline.

Toluene can directly affect the nervous system. Even at low levels, it can cause fatigue, disorder, weakness, intoxication, frustration, nausea, loss of appetite, hearing loss and visual loss.

Inhalation of toluene in a short time and high dose can cause mild headache, dizziness, lethargy, or coma and death.

High doses of toluene also affect the kidneys, but studies on humans and animals show that toluene does not cause cancer.

The peel strength of waterborne PU adhesive (PUD) was compared with that of solvent PU adhesive on the surface of PVC.

Butanone butanone is a colorless liquid and has a pungent sour taste. Butanone is produced in large quantities, nearly half of which is consumed in paints and paints. It is easy to evaporate quickly into the air and can dissolve many substances.

Its cleaning function is used as a surface cleaner in glue.

The health effect of exposure to butanone is to stimulate the nasal cavity, throat, skin and eyes.

Single inhalation of butanone does not cause death, and the human health service has not put it in the list of carcinogens.

Acetone acetone is a colorless and pungent liquid.

Volatile, burning and soluble in water.

Acetone is used to make plastics, fibers, medicines and other chemicals, and also to dissolve other substances.

Inhalation of medium and high doses of acetone for a short time can cause irritation in the nose, throat, lungs and eyes.

In order to reduce the risk of ozone generation and reduce the risk of solvent, according to the European Union guidelines EUDirective1999/13/EC requirements for volatile organic solvent emissions, in terms of relevant footwear, the emission limit is determined to be less than 5T per year, and the total release limit (VOC) of all components is 25g/ double.

Moreover, the timetable for reducing the release of organic solvents has been determined. It is required to achieve 37.5g at the end of October this year, that is, 50% of the target release limit. At the end of October 2007, it is required to achieve the full target release limit (i.e. voc25g for each pair of shoes).

The present situation of rubber industry in China's shoemaking industry is a labor-intensive shoe making industry, and the solvent based adhesive for shoes is still in the leading position in China.

Moreover, female workers take the main role. Under the condition of volatile solvents, mental fatigue and sickness are more easily, which makes pregnant women and fetuses more dangerous. Most workers do not regularly check their bodies, and frequent overtime work makes the situation worse.

The whole industry is still generally in a bad working environment, coupled with the use of solvents, resulting in more serious occupational diseases often occur.

There are more than 2 thousand shoe factories and about 200000 workers in Fujian. There are nearly 800 molding lines and nearly 2000 family workshops, with a total output of 400 million pairs of sandals, sports shoes and casual shoes.

But solvent based glue is widely used in Fujian. About 30 thousand workers are exposed to harmful chemicals. Many workers suffering from occupational diseases can not afford the cost of treatment. The bad working environment is causing the loss of workers, and the shortage of labor is becoming more and more serious, resulting in a series of social problems.

Fujian is just an example.

In order to improve the working environment, some factories have increased investment, equipped with ventilation and ventilation devices, dust washing towers, tower conveyor belts, fireproof rubber floors, masks, carbonized masks and so on, but workers are still kept in toxic high volatile solvent release environment.

On the other hand, in order to reduce the pollution of toxic and irritant solvents, the allocation of ventilation systems and other facilities also brings high additional costs.

Compared with the improvement of the performance of waterborne adhesives and the development of the shoe industry, the use of a simple water-based system instead of solvent glue is indeed an optimal solution to remove those toxic, volatile and stimulating solvents.

Fortunately, Hongxing Erke recently introduced Bayer water adhesive technology in Fujian, which is the first local shoe factory to introduce the technology in the domestic industry.

With the intensification of competition in the footwear industry, especially the shoe products entering the international market, we will face all kinds of strict index requirements. Among them, environmentally friendly products will be more and more popular. I believe more and more domestic shoe companies will choose this environmental protection technology. The popularization and application of environmentally-friendly sole adhesives will be the trend of the times.

Waterborne PU adhesive and its application in the world the first PU dispersion adhesive developed in 1965, under the action of cross-linking agents, will have a very strong initial strength, and is applied to rubber outsole and shoemaking production.

Since the mid 90s of last century, the shoe making power countries have widely used and actively used water-based PU glue to produce sports shoes and casual leather shoes, and made positive contributions to the reduction of VOC in production and the advancement of advanced adhesive technology.

The performance of the water-borne PU/CR glue and the solvent PU/CR adhesive is different from that of the solvent PU/CR adhesive. The solid components that play the role of bonding are different in the distribution of solvent and water. In the solvent system, the polymer molecules are dissolved in the solvent, while in the aqueous system, the polymer particles are dispersed in the water. Therefore, the waterborne glue of the polymer has a higher solid content than the solvent adhesive.

Although the price of water gel is higher per kilogram, but because of its high solid content, the water gel of each pair of shoes is lower than that of the solvent glue, and only needs one time to brush.

Table 2 shows that the direct cost of using water based adhesive tape for each pair of shoes is the same as that of the solvent adhesive, or even lower.

The application of water-based adhesive in the bottom fitting process can reduce the coating steps. The performance of waterborne PU adhesive 1, the weatherability on canvas materials, the addition of 3% hardener aqueous PU glue and the addition of 3.75% hardener solvent glue as the control, the peeling strength is tested for 4 weeks.

Storage conditions are: temperature 70 C, relative humidity 95%.

Experiments show that peel strength has the same trend as time goes by, but the weatherability of waterborne adhesive is obviously better.

2, different types of leather and base materials were selected from two layers of leather, sheepskin and oil skin. The bottom materials were tested by SBR1, SBR2, TR and PVC respectively. It was found that the adhesive strength of two-component waterborne glue and two-component solvent adhesive varied with different materials.

3, the use of water-based adhesive in the bottom processing uses hardness A type 55 degree 3 degree rubber outsole and hardness C type 55 + 3 degrees EVA bottom as the bottom component.

Before the bottom assembly is the same as the traditional sizing process, we must first deal with the outsole. The rubber outsole will be rough and washed. The bottom edge of the EVA will be slightly rough, cleaned, and then dried by UV irradiation.

The current cleaning adopts ultrasonic water washing, which can greatly improve the labor efficiency and reduce the production cost.

It should be noted that the removal of the surface release agent after EVA bottom mold is essential, otherwise it will cause the phenomenon of adhesion.

The application of water-based adhesive at the bottom laminating process is similar to the traditional sizing method in the bottom gluing process, but it can be applied once.

Due to the difference of materials, it is recommended that the sole and middle sole be treated and dried.

The traditional way of pretreatment will not change because of the use of water-based adhesive. However, for different materials, appropriate treatment agents should be selected to achieve the best effect of bonding.

The pre drying temperature is basically set at 55 C, but it should be adjusted according to different materials.

Then the brushing process can be carried out. When the waterborne adhesive is applied to the bottom and the bottom, the surface of the coating should be uniform and as thin as possible.

After coating, the traditional oven can still be used without adding or changing the equipment.

But to slow down the speed of the conveyor belt so that the components are fully dried, the density of the components on the conveyor belt can be increased so that the output per unit time will not be affected.

After the universal press, it can be frozen and set. The conditions are: the temperature is set at 0-7 degrees, and the time is about 3-3.5 minutes.

After heat activation, the surface and the bottom are pressed together by the press, but the time is slightly longer than that of the solvent glue for 1-2 seconds.

4. How to improve the effect of waterborne adhesives? Stir mixing water-based adhesive to improve the adhesive effect of waterborne adhesive. When preparing water-based adhesive, pneumatic agitator is used, and the curing agent is added at the edge.

The stirring condition is: when the humidity is less than 90%, the hardener content is 5% and the stirring time is 300 seconds. When the humidity is above 90%, the hardener content is 6% and the stirring time is 300 seconds.

It should be noted that it should be as uniform as possible, stirring up and down, until there are small bubbles.

And the water gel should be used in 4 hours after mixing.

The material is rough and rubbed. It is very important to the adhesive force of the upper and the sole. Before the brush is applied, the leather surface needs to be rough and rough, and the leather surface can be worn off to achieve the best adhesive effect.

The test shows that the degree of roughness has great influence on the later tension.

After peeling slightly, the peeling strength of waterborne adhesive is lower than that of the peel after the standard roughing.

Other factors also include whether the use of treatment agents to pretreat and rough the bottom and leather surface, whether the coating is thin and uniform at the time of brushing and whether the drying is complete is also an important factor.

After the water gel is painted, it will dry for 3 minutes at 70-80 degrees, so that the water will evaporate and the particles dispersed into the material will be good.

In fact, the two parts of the surface and bottom are still activated by heating after drying, usually using infrared light, so that the PU glue can be extended.