PUR glue is a perfect binding method

There are many binding methods available today, such as PUR glue (Polyurethane Reactive-Polyurethane Reaction), EVA (ethylene vinyl acetate-Ethyl Acetate) Thermosol, PVA (Ethylene Polymer Acetate) Cooling Emulsion, different adhesive methods, in addition There are also various kinds of thread binding and so on. PUR appeared around 1989 and was first tested and applied on a manual binding system in North America. According to National Adhesives, which introduced PUR into the US book binding market, this binding process is mainly used by some high-quality books, annual reports, Used in catalogs and magazine publications.

Why use PUR?

Since its birth, PUR has been growing faster. In 1995, there were only 28 users in North America. By the end of 2002, more than 50 users were already using it. There are many reasons for PUR to replace commonly used hot sols, the most important of which is its super-adhesiveness and PUR process to make books fully unfold.

Adhesive

PUR has a very good effect on the treatment of surface coating, UV glazing film or paper products, which is mainly determined by the polar nature of the polyurethane molecule, which can be well combined with the surface coating layer to achieve high-quality adhesive Effect.

Changes in paper weight, different coatings and inks hardly affect the effect of PUR adhesives. The new PUR products can firmly bond various types of coated papers. It is said that the tensile force of paper using PUR is 40% -60% higher than that of ordinary adhesives.

For traditional adhesives, if the ink accidentally flows to the book binding line, it will affect the quality of the binding and cause binding failures. For the PUR process, these phenomena will not have any effect on the binding.

Super book spreading performance

The recommended thickness of PUR glue is 0.01 inches, which is much softer than the standard EVA hot melt. This performance allows PUR bound books to be spread out well without hand pressure. For some types of books, such as instruction manuals, instruction manuals, etc., it is very important to have good spreadability.

Other benefits

The other benefits of PUR binding are in

1. Cold and heat resistance

Books bound by PUR are not affected by temperature and can withstand temperatures ranging from 200 ° F to -40 ° F. These properties are very important for books and periodicals that exist in different temperature environments. According to statistics, after switching to PUR glue, customers ’complaints and complaints about the viscosity of the adhesive have been reduced a lot, and almost no.

2. Books do not wrinkle

The binding of horizontally threaded paper with standard hot melt will often wrinkle at the binding line of the book, and the lower binding temperature of PUR will not evaporate the water inside the paper at the spine, so it is not easy to wrinkle phenomenon. In addition, when PUR is cured, it also has certain ductility, which will not affect the fiber direction of the paper, so the paper will not wrinkle.

3. No gaps

Because the coating thickness of PUR is only half of the standard hot-sol coating thickness, it is unlikely that thick materials will accumulate at the cutter, and there will be no unevenness during cutting.

4. Fang Shuji

Since only a small amount of PUR is required to complete the binding, there will be no excess glue squeezed out when loading the book cover, so that the shape of the book spine is kept good.

5. Resistant to solvent attack

According to experts, PUR is currently the only binding material that resists solvent and oil erosion. The cured PUR material can penetrate into the oil and solvent used in printing, such as methyl ethyl ketone (MEK) and alcohol. These chemical reagents It has no effect on the PUR film. With traditional glue binding, some chemicals will slowly soften or even dissolve the hot melt adhesive film, which greatly reduces the effect of glue binding. [next]

Hardcover advantage

Binding companies engaged in binding hardcover or multi-volume books can more appreciate the advantages of PUR over ordinary wireless binding:

1. Cost savings vs. Smythe lock thread

For many years, the industry has usually used Smythe thread-locking, gluing, and rounding to produce round-back hardcover books. Before rounding, soft liquid glue was used for adhesion. After a survey of the European market, it was found that grinding the spine with the paste and then using PUR glue for adhesion can save at least 30% -40% of the cost.

2. Retaining power with roundness

Many hardcover books are rounded and ridged to add beauty and strength to the final product. The spine can be glued with PUR glue to get a very good roundness, and then the book can be rounded and ridged to get a good effect. When the PUR is cured, the book can maintain a circular state, and the endurance of the arc will be maintained to the greatest extent. For books and periodicals glued with hot melt, the roundness of the spine can easily be lost.

3. Application equipment

When applying PUR, special care should be taken to avoid premature or prolonged contact with air and cross-linking to avoid curing. Glue pots and closed extrusion systems are necessary equipment. Old-fashioned binding equipment can be transformed into high-end PUR binding after necessary transformation.

4. Glue pot

According to experts, the glue pot used by PUR can be a traditional glue pot or a special glue pot. Nordson company in OH, USA is a manufacturer of pre-melted glue containers and nozzle extruders. They have also developed some The single wheel device can be matched with the existing binding equipment. In the past few years, Korbus has also developed special glue pots for its binding equipment. Following this, Martini has also developed supporting PUR glue pots for some of the company ’s products, such as Corona, Acoro and Star binding equipment.

5. Closed extrusion system

Generally, the closed extrusion system is composed of a pre-melting device, a box and a connecting tube. It is precisely because of this piece of technology that limits the popularity and development of PUR binding technology. Many companies are working to improve this system.

The German Inatec Gmbh company has developed a new system that can be moved between the paper feeding device of the binding equipment and the cover station, extrude PUR to complete the gluing of the cover, and paste the cover on the book block. In this way, the paper material is easy to glue, so the effect is very good, and the spine after the cover is also very smooth. The pressure of the cover station determines the penetration effect of the PUR glue.

The latest technology developed by Nordson pumps PUR glue into a heated tube and then squeezes PUR to the lower end of each book. Since last year, three sets of this system have been installed in the United States and several sets are in use in Europe. The glue nozzle of this system can be opened and closed under control to control the flow of glue. This innovation can also always isolate the extrusion device from the air to avoid the waste of PUR. This is mainly because PUR will solidify when exposed to air for a long time.

Nordson's technology is best used on new or modified binding machines to achieve the most satisfactory results. Therefore, when the book block passes through the extrusion head, there is no need to change the height of the book holder and it is more stable. The pressure applied by the cover station ensures that the PUR penetrates into the spine.

It is recommended not to use PUR on older wireless binding equipment. The machine wears too much and the accuracy is difficult to guarantee.

Cost problem

One of the main problems of PUR is cost. Although the price of PUR is about three times that of ordinary hot melt, but the amount used is only half of ordinary hot melt. This number is quite important when considering the cost of the entire book. For example, a 8.5 × 11 inch book is about 1 inch thick. A normal hot melt will cost about 1.3 cents (assuming $ 1.35 per pound). Using PUR to glue the same book costs about 2 cents. Minute. A manager said that the cost of using PUR to increase is very insignificant, 100 books only increased by 70 cents, but using PUR can save a lot of attention and avoid many complaints.

Many PUR users did not choose to use hot melt because of this difference in cost. In addition, once you start using PUR, the operator can quickly become familiar with the equipment settings and produce high-quality products.

In terms of cost, maybe some users will mention that there is a cost of equipment modification when using PUR. Since the PUR is a 55-gallon drum (or a 5-gallon drum for small users), the binding equipment needs a device to transfer these materials to the glue pot or to the extrusion head, the most commonly used It is a container handling device. Such a device may cost between US $ 25,000 and US $ 50,000, while the application system costs an additional US $ 25,000-35,000. [next]

Productivity issues

The curing (drying) time is also a matter of general concern. Although the first-generation PUR process can be cut online, it must be done 24 hours after binding to ensure the strength and regularity of the book.

The second-generation PUR was developed in 1994, and can already be cut online, the thickness of the stack has increased, and it can be cut only 4 hours after binding.

The curing time of the third-generation PUR only takes 1 hour, although there is still a considerable amount of moisture in the paper. After cutting, you can pack it immediately. But this also has a certain negative effect. Because PUR can quickly reach the relative strength, the PUR in the glue pot becomes very heavy, which is more obvious in a humid environment.

Finally, the fourth-generation PUR is also very mature and thinner than the third-generation PUR, but has the same strength and can be stored for a longer period of time. The current generation has largely replaced the second and third generation of PUR, and is also well used in the latest extrusion systems.

Due to the fast drying speed of this new adhesive, the production efficiency has been significantly improved, and the flexibility of the enterprise has also been improved.

The future of PUR

PUR is widely used in medium-sized printing companies, and is mostly used for the binding of periodicals and annual reports. Since most of this type of work is coated paper or horizontal thread paper, there will be more and more users using PUR in the market. In addition, more and more publishers are also aware of the advantages of PUR technology, and are beginning to turn to this method to obtain better quality and product durability. Even some small businesses have begun to experiment with the PUR binding process.

Hardcover books are the main field of PUR binding in the future. Because the cost advantage of PUR binding covers is higher than Smythe lock thread, and the fourth-generation PUR technology can achieve online rounding, many hardcover book manufacturers have begun to carry out this technology. Research. The number of PUR applied to hardcover books will gradually increase, and people will more and more realize that this technology can save costs without sacrificing product quality.

Promote PUR to customers

Although printing companies and bookbinding factories are beginning to understand the benefits of using PUR, their customers may not be willing to use this more expensive adhesive. A commercial bookbinding factory in the United States discovered a way for customers to approve this process: they did an experiment for the client, bound the same book in two ways with EVA and PUR on a cold night, and then opened this in the morning Two books, found that the book bound with EVA has cracked, while the book bound with PUR is intact. Through a small experiment, customers were convinced of the application of this new process.

In addition, PUR is less sensitive to temperature. Suppose you put a book in a car in winter, or in summer, you can find that the book bound by the EVA method is damaged, but the PUR is not affected.

Why not spend a little more cost but get better product quality?

There are also some operations that require the use of PUR strong adhesives. For example, a book with a glossy surface and very smooth paper, the ink has penetrated into the binding line, and it has been die-cut and covered with a liquid film. At this time, PUR has become the only adhesive that strongly binds pages.

In summary, printing plants and bookbinding plants can perform multiple glue tests on an unknown paper material in order to achieve the best customer satisfaction and the least complaints. Some experts believe that testing should become a routine task and should satisfy every customer requirement as much as possible.