Improvement of glue head process

At present, our factory's large batch of teaching aids test paper series uses glue head technology to complete the binding work. The binding material is mainly polyvinyl acetate, commonly known as white latex. White latex is used to prevent the glue head of offset paper from sticking, and the current teaching auxiliary test paper uses coated paper as the cover. The cover and the book core together use white latex as the binder to glue the head, dry and divide the paper. After cutting and handing over to the user, the cover and the book core are easily loosened during the moving or flipping process, and the problem of poor adhesion occurs. We thought it was caused by the poor quality of the white latex. After changing the brands of white latex for testing, the problem could not be solved. Later, borrowing the experience of other factories, using tools to scratch the place where the glue head is needed, the cover of the book and the center of the book are not separated by the pulling force of the paper wool, but basically there is no solution to the problem, and the appearance is not beautiful, which is easy to hurt the hand. The teaching assistant test paper series is large in size, generally 16 or 3 open. It can not be carried out by using the existing wireless perfect binding equipment, and the user is not allowed to set the wire flat. In large-scale tasks, manually pasting the cover is not only time-consuming and time-consuming, but also unsightly. After observation, it is found that the traditional glue head can only form a glue film on the surface of the book back. If the glue material can enter the inside of the paper to form a side glue to achieve the effect of wireless glue binding, then the cover is naturally firm. After many experiments, the bonding materials and processes were improved to achieve the expected results.

1 Traditional glue head technology and principle analysis

The traditional glue head process flow: matching-cutting-applying adhesive material-drying-cost-cutting-cutting.

Principle analysis: The binding material used for the glue head when binding is mainly polyvinyl acetate, that is, white latex. For offset paper, because the surface of the offset paper is rougher than that of the coated paper, the offset paper is more easily wetted by the adhesive, and the bonding should be firm. Coated paper is a paper made by coating a layer of white paste on the base paper and then calendering it. The smoothness is high, and the binder is not easy to wet it or penetrate into the adhered material. Therefore, when using coated paper as the cover for binding, the cover and the book core are not adhered by the adhesive. The adhesive film formed on the back surface of the book after the adhesive is dried is adhered. The contact area of ​​the cover and the adhesive film is too small. Causes poor bonding. In addition, the adhesive film formed of polyvinyl acetate is poorly flexible after being thoroughly dried, and is easily brittle.

2 Improved process and principle analysis

Technological process: Matching-cutting-coating adhesive 1-drying-coating adhesive 2-drying-division-cutting.

Principle analysis: In the improved process, the choice of binder is very critical, the binder must be able to fully wet the surface of the material to be adhered. For the material to be bonded, the surface that is slightly rougher than the smooth surface can have a larger area of ​​contact with the adhesive; for the adhesive, it must ensure that the adhesive has good fluidity to make it All the places on the surface of the sticky object can be filled. The viscosity and concentration of the adhesive must have certain requirements. The thick adhesive has more solid content, less water, and greater cohesion. The strength of the adhesive is high. It is easy to set after drying, but its fluidity is poor and it is difficult to infiltrate the adhesive. The surface of the material is sticky, and it is not easy to penetrate into the interior of the material. Therefore, the thick adhesive is suitable for areas with a small bonding area but requiring a large bonding fastness. The thin binder has less solid content and more water, so it has good fluidity. It is easy to wet and penetrate into the material after being applied to the surface of the adhered object, but its cohesion is small, the viscosity is small, and the adhesion fastness is not strong enough. , So it is suitable for places with large bonding area.

3 Why use secondary coating binder

According to the analysis of the principle of the adhesive, the thin adhesive can penetrate into the adhered object, but the adhesion fastness is not strong enough; and the thick adhesive has poor fluidity and is not easy to penetrate into the adhered object. Therefore, the effect of firm adhesion cannot be achieved by applying the adhesive once. Therefore, the first time the adhesive is applied, it needs to be thinner to penetrate into the adherend, but the bonding strength is not enough. The second time, the thicker adhesive is applied to strengthen the adhesive strength.

4 Selection of binder

The selection of adhesive 1 and adhesive 2 are different. The purpose of applying the adhesive 1 is mainly to penetrate into the side glue to increase the area where the cover is bonded to the book block. The purpose of applying the adhesive 2 is mainly to form a large adhesive strength adhesive.

Binder 1 is a binder made of polyvinyl alcohol as the main raw material and some auxiliary agents. This is because the surface of the coated paper is smooth, and the polyvinyl alcohol has good film-forming properties and strong viscosity. After re-dissolution, the fluidity is very good, and it easily penetrates into the adherend.

The adhesive 2 is mainly white latex, and some additives can be added to increase its flexibility and adhesive strength. White latex tends to be brittle after drying, which is beneficial to the cost, but too much dilution is easy to precipitate, so it is not suitable for use as binder 1.

5 Matters needing attention in operation

The bound book is firmly bonded under a certain tension, and the cover and the heart of the book are not separated.

When applying adhesive material 1, do not stack the books too high. The books under the stack are too high and the pressure is too strong. The adhesive material is difficult to be completely absorbed, generally 25cm ~ 30cm high. Do not apply heavy materials to the books before applying the adhesive. The coating should be even. Make sure that each book can be fully absorbed. Finally, the adhesion between the cover and the center of the book will reach about 1mm ~ 2mm. The next process.

After the adhesive material 1 has been absorbed, the adhesive material 2 can be coated at this time. At this time, the heavy material is pressed on the top to prevent the adhesive material from infiltrating, and the cover is drawn when the cost is divided. The amount of adhesive material to be used should be moderate and even.

In order to meet the binding requirements, the process of applying the adhesive material twice is adopted, so that the drying time of the book is extended, and it generally takes 2 hours to perform the book division work. When the temperature is low, it may be longer. If the adhesive force of the glue has not been completely formed, the book is easy to separate the cover from the book core at this time; if the drying time is too long, it takes a certain force to separate the book from the book, and it is easy to separate the cover from the book core.

There are water and volatiles in the binder 1 and binder 2. Do not expose to the air for a long time, it will change the concentration of the ingredients and affect the quality. It is best to use as much as you want.

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