Adhesive production process analysis

I. Overview

The wireless glue-binding technology promoted and applied in recent years is a technological innovation for traditional flat-binding production. Polymer synthetic adhesives replace bone glue and paste. The unique “thermal-plastic-cold-solid” characteristic of hot-melt adhesives that occurs automatically with changes in temperature plays a key role in sewing and stapling that must be labored. Separating the binding of books and books from manual labor-intensive and extensive labor states, and embarking on a new stage of mechanization and automation.

Binding technology is the development of the chemical industry to the printing industry. Various dynamic variable factors flood the glue production process. With the advancement of printing technology and the continuous development of new polymer materials and blending polymerization processes, the physical and chemical changes of adhesive-adhesive hot melt adhesives are not only restricted by the operations of production personnel, but also due to the binding of objects, hot melt adhesives, and glue binding. Machines and other structures, their respective characteristics, and new changes under glued production conditions, coupled with environmental climate fluctuations, will have different applicability and effects. Inadequate understanding of the structure, characteristics, and changes of the basic elements involved in glue-binding production has only allowed glue-booking to pass yet. According to Bulletin No. 40 issued by the Printed Products Quality Supervision and Inspection Center of the Press and Publication Administration on February 1, 2001, the quality of the printing quality of the books printed in 1999 and the spring and autumn textbooks published by the 1999 Central Excellent Publishing House was checked. A total of 189 kinds of excellent publishers were sampled, among which 57 products from 21 publishers were unqualified products. It accounted for 30.16% of the total number of sample surveys. 16 provinces, autonomous regions, and municipalities directly sampled and sampled 8 to 23 kinds of textbooks, and 8 provinces, autonomous regions, and municipalities respectively had 1 to 5 varieties of substandard products. There are 358 types of random checks on this edition of the book. Except for Shanghai, there are 1 to 5 unqualified products in 15 other provinces and autonomous regions, accounting for 9.8% of the sample. This set of figures proves that the current problem of quality of glue binding is quite serious.

Changes in the structure, characteristics, and joint effects of the glue production elements—colloids (books, journals), adhesives (hot melts), adhesives (binders), through various surface phenomena Making scientific analysis, adopting correct measures, and adapting to the dynamic laws of change in its personality and commonality have become the rational basis for ensuring the quality of bookbinding. Combining production practice, conducting research on regularity exploration, and conducting extensive and in-depth exchanges on the current understanding, it will not only help increase the knowledge content in labor, improve the basic quality of the majority of glue production management personnel, but also enrich basic theories and Applying technology, we will continue to make new innovations to the glue-binding technology.

Second, the structure and characteristics of colloidal body (books, periodicals)

The structure of bookbinding (books and periodicals) is the joint action of cover, book block, text (including interlining, etc.), and linking material (hot-melt adhesive) on the binding (binder) mechanical force and heat. Next, produce a combination of physical and chemical changes.

As far as the binding body is concerned, the structure of its cover and book block inner text has the following characteristics:

1. Combination of different materials

2. Different materials have different characteristics

1 different major technical indicators;
2 different offset printing process, paper produces different changes.

The use of the ink control device, automatic register device, tension and edge position automatic control device, automatic paper splicing device, and printing quality measurement and control system affiliated with a modern offset press on the printing press has enabled “multi-color printing and high-efficiency” to be realized.

In order to adapt to the rapid development of printing technology, the paper industry uses a large number of chemical materials such as starch derivative adhesives and polymer coatings to improve the smoothness of the paper and other surface conditions. Increases the pull strength of the printing paper and decreases the ink absorption performance, so that the effect of ink transfer during the offset printing process is from small to large (≤0.32% to <0.4-0.5%), and the ultimate ink volume is limited by the amount of free ink. Large to small (3.60 to 3.68 g/m2 to 0.85 to 1.85 g/m2) in a good direction. The effect of different adhesive combinations on coating performance is shown in Table 3:

The main body of the paper is natural cellulose. Cellulose itself is a crystalline and amorphous compound composed of carbon, hydrogen, and oxygen. Pulps made from different plants have different pore volumes for different original papers. According to different uses, the surface of the base paper can be further coated with different levels of calendering. Due to the difference in the amount of coating and the moisture content of the paper, the printing papers have different compression rates and elastic recovery rates (see Table 4, Table 5, Table 6):

According to the scientific data in Table 1 to Table 6, we can rationally explain the high-quantity coated paper represented by coated paper from the aspects of tensile strength, tear strength, surface absorption performance, oil and water permeability. Cover paper, and low-quantity non-coated paper-based papers, such as letterpress papers and elementary and secondary school textbook papers, are responsible for different levels of powder dropping and hair loss in the printing process. After the offset printing, why the compression rate and moisture content of the book block are greater than the cover. It can also be said clearly that the book block text enters the bookbinding process under the condition of rough structure, high dust degree, and large moisture content.

Third, the adhesive material (hot melt adhesive) structure and characteristics

To achieve glue binding of books and magazines - hot melt adhesive, not only stick good book core, but also stick good cover; both to ensure that the initial state of the heating effect, but also to ensure that in high temperature, high humidity, low temperature, dry, etc. There are reliable and convenient long-term effects in a complex environment. From production operations to quality requirements, the main technical specifications of hot melt adhesives are summarized as viscosity (fluidity, permeability), strength, toughness, hardness, aging characteristics at high temperatures, low temperature resistance to cracking, curing time, density, etc. Aspects.

In order to ensure that the colloid has considerable cohesion and adhesion, the glue blending structure of the book hot melt adhesive is shown in Figure 1, and the composite material is shown in Table 7:

1. Fig.1 Structure of main adhesive resin, tackifier resin, adjustment material, anti-aging material selection, combination ratio, synthesis process and other factors, determine the effect of mixing the book glued hot melt adhesive itself molecules Force - Cohesion. The operation of the glue-binding production process is related to the physical interaction between the hot melt adhesive itself and the hot melt adhesive, the book block inner text, and the cover paper molecule; the hot-melt adhesive hydroxyl polar group, chemical bond and adhesive body The chemical bonding of the surface; and the glue binding mechanism of the glue-binding machine forces the adhesive to spread the mechanical force effect such as perfusion between the book blocks.

The main technical means of production operations focus on the stable control of the heating temperature of the colloids.
2. In order to guarantee the book fastness, the basic requirement for hot melt adhesives is the appropriate melt viscosity. Theoretically speaking, it has high viscosity, large cohesion and strong adhesive force. However, in actual operation, the viscosity is high and the fluidity is poor, which will reduce the wettability and permeability of the glue to the paper, resulting in the actual adhesiveness. For glue-bonded hot melt adhesives, viscosity and fluidity are contradictory to one another. The solution is generally to adjust the VA content of the primary adhesive resin to ensure that the adhesive has good adhesion, elongation, permeability, and weather resistance at an appropriate numerical position. Considering the glue-binding operation procedure, we also need to use glue-bonding resins that can maintain the bond strength of colloids after the production temperature is reduced to adjust the bonding performance of the primary adhesive resin. And through the addition of a low-melting-point adjusting material, the melt viscosity of the main tackifying resin and the tackifying resin are reduced and the working temperature is lowered, the fluidity and wettability of the colloid are improved, and the solidification rate is adjusted so that it has good operability. .

3. The co-mingling of the hot melt adhesive and the use during the glue binding operation are performed under heating. Thermal power is a prerequisite for the synthesis and use of hot melt adhesives. It is also an adjustment lever for the viscosity and fluidity of hot melt adhesives. At the same time, it is a catalytic factor for the performance and change of hot melt adhesives.

During the synthesis, the temperature is increased, and the strong heat accelerates the melting and blending of the material, resulting in uneven heat supply. This not only results in the trapping of materials in the low-temperature zone (difference in body color, or increase in sediment during use), but also forms a high-temperature region. Aging of the material (the color of the material darkens).

When the temperature is increased, the strong heat accelerates the melting of the colloid, improves the fluidity of the glue, and facilitates the coating and infiltration of the glue. At the same time, an excessively high temperature increases the evaporation of the regulating material, changes the original ratio combination, and prolongs the time that should be solidified. The tackifying resin also rapidly ages, the viscosity decreases, the color becomes darker, and the brittleness increases. (to be continued)