With the vigorous development of post-press binding technology, wireless gum as post-press binding technology is widely used in a binding manner, in its development. It is well known that wireless adhesive binding quality of the books in addition to the associated with the quality of the selected EVA hot melt adhesive, also with the work environment, paper, binding, materials and features of the equipment, process adjustments, the process conditions such as directly related to many factors. Typically, compressive strength of wireless glue order books through tensile test to test, the strength is higher, the compressive strength, the better. But what is how compressive strength test, test standard, has been plagued our problems. If too strict, standard will be set on a yoke, lead to production difficult; If the standards are too loose, and will cause serious quality problem such as pages, and bring incalculable economic losses.
1. The quality of EVA hot melt adhesive to the compressive strength
EVA hot melt adhesive for solid at room temperature, the heat can melt to a certain degree when to flow and has a certain viscosity liquid. EVA hot melt adhesive resin is the main ingredient, and resin is ethylene and vinyl acetate copolymerization under high pressure, and the main ingredients include EVA hot melt adhesive glue agent, viscosity conditioning agent and antioxidant, etc.
Among them, the resin is the main component of EVA hot melt adhesive of EVA hot melt adhesive by more than 50% of the total; Increases the adhesion agent is one of the main auxiliaries of EVA hot melt adhesive, and its main components in rosin matter or terpene resin, etc., main effect is to improve the liquidity of colloid and wettability, and thus improve the bond strength; Viscosity regulator is also one of the main auxiliaries of EVA hot melt adhesive, that contain mainly paraffin class material, is used to reduce the melt viscosity, increase liquidity, wettability, solidification speed regulation, in order to achieve the purpose of fast bond firm, otherwise, EVA hot melt adhesive viscosity is too big, not easy flow, difficult to infiltrate into the page, can not be fastened the pages; The addition of antioxidant to prevent EVA hot melt adhesive premature oxidation, metamorphism, the general selection against tert-butyl methyl phenol.
Wireless adhesive order books selected EVA hot melt adhesive bond strength and the quality is very important, so, EVA hot melt adhesive and wide use of tracking detection, EVA hot melt adhesive is a necessary link in the process of use. As is often the case, EVA hot melt adhesive curing time should be 7 ~ 13 seconds, the cooling time should be 2 minutes.
2. EVA hot melt adhesive temperature's influence on the compressive strength
EVA hot melt adhesive, temperature has a great influence on the compressive strength its gel temperature is too high, although the increased liquidity and permeability of colloid (loose), but the viscosity and the compressive strength will be decreased obviously; Conversely, gel temperature is too low, although colloid viscosity will rise (thick), but its liquidity, wettability and permeability can be decreased, at the same time, it will reduce the compressive strength of gel, viscous resistance, toughness, etc., can appear even after gel coated between the cover and book not bond or bond fragile phenomenon. EVA hot melt adhesive temperature, therefore, must be strictly controlled within the scope of a the best and appropriate, can achieve certain compressive strength requirements. Under normal circumstances, the softening point of EVA hot melt adhesive should be above 80 ℃, to attain to cohere the molten and the extent of the books, the heating temperature will rise to 130 ~ 180 ℃.
3. The paper texture and pasting temperature and the relationship between the compressive strength
Paper texture is different, the gluing temperature compressive strength and also will be different, and not just because the paper fiber is different, more important is because EVA hot melt adhesive curing, cooling speed is different in different paper. Light on coated paper, coated paper, book version of the paper, for example, because of inorganic substances contained in the coated paper to about 10 times higher than the book version of the paper and the inorganic materials with good thermal conductivity, can accelerate EVA hot melt adhesive curing and cooling speed, so EVA hot melt adhesive curing, cooling on coated paper, fastest in lightweight coated paper last time, in the book version of the paper to the slowest.
At 170 ℃ the gluing temperature as an example, the compressive strength of EVA hot melt adhesive on the book version of the uncoated paper can reach 8.83 N/cm, and on the coating of coated paper can only be 1.86 + / - 0.11 N/cm coated paper (65 g/m2) and 1.64 N/cm coated paper (100 g/m2). In coated paper on the compressive strength is so low, obviously can not meet the requirements of actual production, so need to improve on the gel strength and gel temperature. Pasting temperature during 180 ~ 190 ℃, compressive strength of EVA hot melt adhesive on the coated paper can reach 4.1 ~ 3.9 N/cm, should also be visible on the EVA hot melt adhesive glue temperature changes with paper of different texture. (Gold Printing Group)