Use of hot melt adhesive in wireless binding

From the point of view of the process, similar to the lock-line paperback, this link is different only in the viscous setting. From the production efficiency point of view, the lock-thread flatpack is slightly improved. This kind of single-step processing, before and after the process of convergence of the process model in the production efficiency is difficult to have a new breakthrough, due to the semi-finished product in the process between the pile-up pauses and handling is inevitable, and repeated, the logistics speed is slow, according to a survey According to the data, the internal logistics transportation volume or handling capacity of processing enterprises, from single-process processing conditions, from raw materials to finished products, the traffic volume ratio is 1:30-60, and the speed ratio is 1:20-50 or more. Under the automatic line conditions, the traffic volume ratio was reduced to 1:10-30, and the speed ratio was increased to 1:10-20.

Wireless binding must change the single-step processing mode before it can greatly increase production efficiency and reduce labor intensity. To achieve this change, it is not simply to string together the individual machines and use a conveyor belt to form the connection relationship, but to organically combine them so that they can be combined to drive a complete machine or an automated production line.

In this case, new adhesive materials must be matched. The adhesive materials used for the bookbinding and the bookbinding of the book back saw groove are mostly made of polyvinyl acetate emulsion, because the rubber compound can be used directly, and plasticizers such as dibutyl ester can be added to solve the film brittleness. The problem is that polyvinyl alcohol is also used, mainly to reduce production costs. Polyvinyl acetate emulsion and polyvinyl alcohol are water-soluble adhesive materials. They are bonded by brushing, moisture evaporation, and drying of the conjunctiva. It takes a long time for the water to evaporate to dry the conjunctiva. Under summer conditions at room temperature, It takes at least one hour to dry completely, and it takes longer to dry in other seasons. If the use of electric baking, far infrared, high frequency, microwave radiation, can speed up the drying, but still can not match the speed of the engine, not to mention high frequency and microwave heating also take strict shielding measures to prevent the human body hurt.

With the rapid development of modern science and technology, new materials continue to emerge, and as many as thousands of adhesive materials are used in chemical products, categories continue to emerge, and as many as thousands of adhesive materials are used in chemical products, and categories are constantly increasing to accommodate various types. Different uses. EVA resin hot melt adhesive is a glue material for wireless binding and linking machine. It is a kind of solid material with no moisture and no solvent. When heated to the melting point, it changes from solid state to liquid state. As the temperature rises, Thick and dilute, with good fluidity, infiltration and permeability, when the temperature is lower than the melting point, it quickly turns into a solid, and has a certain degree of hardness and toughness, hot melt adhesive in the form of reversibility, in the melting point The above is a liquid, which is solid below the melting point, and completes the entire bonding process, which is much shorter than water evaporation and drying of the conjunctiva of the water-soluble adhesive material. The quick-fast-fast curing is the first major feature of the hot-melt adhesive.

Hot melt adhesive is a solid rubber material. It is very convenient for transportation, storage and use. First, it does not require an additive. It can be used as long as it is preheated and melted. It is not afraid of subversion during transportation and does not require sealing during storage.

The maximum melting temperature of hot-melt adhesives does not exceed 200°C, and there is no strong odor and smog-polluting environment. With these features, EVA resin-based hot-melt adhesives can fully meet the safe and efficient production of United Motors.

There are many kinds of hot melt adhesives. Different hot melt adhesives can be applied to different bonding targets in different environments. As one example, bitumen has a strong viscosity and toughness, and it can melt and disperse sand and gravel. Together, flattened by a roller.

Ethylene vinyl acetate is abbreviated as EVA, so this compound is also referred to as EVA hot melt adhesive. EVA resin is made by copolymerizing ethylene and vinyl acetate under high pressure. Adjusting the ratio of these two materials can change the molecular weight of EVA resin polymerization, and then change some properties of EVA hot melt adhesive to adapt to different temperatures in winter and summer. The purpose of use. EVA resin is the main component of EVA hot melt adhesive, accounting for about 50% of the total ratio, too much resin, high production cost, too little resin, easy to make the adhesive layer brittle, the right proportion of the resin, and even the low temperature of the hot melt adhesive. It can also maintain sufficient toughness and elasticity, and its mechanical strength is basically stable. EVA resin is the main component of hot melt adhesives, and it also has the main characteristics of hot melt adhesives. In order to adjust the fluidity, permeability, melting point, anti-oxidation ability and cost of EVA resin hot melt adhesive, an appropriate amount of a tackifier, a viscosity modifier, an antioxidant, and a filler are also required.

The main role of the tackifier is to improve the fluidity and wettability of the glue, and enhance the penetration of the paper fiber, so as to improve the adhesion force. Tackifiers include common rosins, hydrogenated rosins, polymerized rosins, modified rosins, rosin esters, and terpene resins, among which hydrogenated rosins, rosin esters, rosin hydrocarbons, and terpene resins play a major role in improving the fluidity of the rubber compound. Enhanced light, heat, low temperature, ozone stability, tackifiers accounted for 30% to 40% of the total ratio.

Viscosity modifiers include waxy materials such as stone vinegar, microcrystalline wax, and synthetic wax. Waxes have a low melting point and are used in hot-melt adhesives to reduce the melting point, but they mainly shorten the opening time and eliminate the phenomenon of spinning. Wax materials in the total ratio to be controlled within 25%, otherwise it will reduce the bond strength, causing the adhesive layer shrinkage, serious will seepage out of the cover, the formation of oil seepage phenomenon, affecting product quality.

In the use of hot-melt adhesives, glue is always maintained at 165 ~ 200 °C, easy to oxidative decomposition and deterioration, it is necessary to add antioxidants or heat stabilizers in the rubber compound, the amount of these materials is very small, a total of paper accounted for The total ratio of 0.1% to 1%.

EVA hot melt adhesive is a solid rubber material, the appearance of a small piece, before use, it must be preheated melting, preheating temperature should be set between 160 ~ 200 °C, preheating time of 1 to 2 hours. Since the softening point of the hot melt adhesive is approximately 100° C., the water bath jacket heating method cannot be used, and the high temperature oil bath jacket or the electric heating element must be used to integrally heat the plastic pan. When the preset temperature and time are reached, the hot melt adhesive has good fluidity.

The preheating melting temperature and the use temperature of hot melt adhesive are two completely different concepts; the use temperature is a set temperature according to the paper characteristics of the product, if the temperature is too high, although the glue has good fluidity and wettability. And permeability, but resin and adhesives will volatilize too much, open time is not enough or there is no open time, the back of the book block can not be infiltrated and penetrated, it will cause the book block adhesive is not solid, or even off page, serious It will also cause the cover to become sticky.

This situation mostly occurs in different paper situations, that is, different paper products require different setting temperatures. For example, the main text of the book block uses offset paper, letterpress paper, or newsprint paper. When the temperature is set at 170 to 175°C, the adhesive effect is the best, and the tensile value can reach 8kg/cm2 or more. When the set temperature is 180°C, The tensile value is reduced to 7.3 kg/cm2. When the set temperature is 155°C, the anti-scarf bookbinding is set at 170 to 175°C, which is the optimal setting temperature. This optimum temperature does not apply to coated paper. The same setting temperature, the tensile value of the coated paper is only 1.5 ~ 1.9kg/cm2, when the set temperature is increased to 195 °C, the tensile value can reach 4kg/c About m2. The reason is that the coating paper coating has too high thermal conductivity. It can quickly cool the hot melt adhesive, and its penetration and penetration are insufficient. Followed by the resin components have more volatility due to the increase of temperature, reducing the adhesive force, the thicker the coated paper, the more obvious this situation.

The setting temperature of the hot melt adhesive is set according to the change of the paper. While grasping the correct setting temperature of the hot melt adhesive, it is also necessary to grasp the opening time and the curing time. The so-called open time refers to the time after the back of the book is glued to the cover, and the adhesive must be in the prescribed time. Completed within. More than this time, the surface of the glue first cools the conjunctiva and becomes a kind of isolation medium, causing the phenomenon of tackiness. The open time of hot-melt adhesives varies according to their specifications. Generally, it takes 7-15 seconds for summer glue and 15-20 seconds for winter glue.

This characteristic does not have any adverse reactions when the machine is fast and does not stop. When the machine runs extremely slowly, or when it is stopped frequently, the response is obvious.

Curing time refers to the solidification of the book block and the cover. After cooling over a period of time, the glue liquid changes from a liquid state to a solid state. This time is referred to as the curing time. According to the type of the hot melt adhesive, the curing time is also different. For 3 to 5 minutes, when the machine is running extremely fast, it must be considered that the glue is fully cooled and solidified. Opening time and curing time are a pair of contradictions that must be taken into account. Only by properly handling these contradictions can we choose the normal operating speed.

summary
Stapling as a production process, including "packing" and "ordering" two processing content, the so-called "loading" refers to the decoration, packaging, assembly means, including the cover. The so-called "order" refers to the inner core pages of the series or linked. The two wireless binding processes of the book back saw slot and the book page punching only stay on the sticky link, so it can only be called glue binding. Hot melt adhesive linkage production line is extended to the binding processing, until the finished cutting, this is a complete line binding. Hot-melt adhesives wireless binding is a new device, and the new technology consisting of new materials is a major change that promotes binding processes for paperback books. Hot-melt adhesives wireless binding has played a big role in the production of books and journals. Similarly, it can also be applied to light-printed post-press processing. However, there is a premise that the processing party and the processing party are required to adapt to the hot-melt adhesive wireless binding. To understand, but also according to the characteristics of hot melt adhesives, municipalities to modify the design of commissioned parts, as little as possible to coated paper, for some fine color sheets, can be changed to light coated paper, slow down its thermal conductivity, for thick coated paper The product, as far as possible, is changed to a sewing thread.

Hot-melt adhesives wireless binding, although highly efficient and capable of adding quality products, has some limitations, so it is not all-powerful.