At present, domestic paperback books and books are bound generally using wireless EVA hot-melt adhesive binding, EVA hot-melt adhesives used for raw material quality, ratio, production process, origin, brand, etc., performance, quality, price difference is also great. The author wanted to discuss some of the quality management aspects of the commonly used wireless EVA glue-binding process with industry peers.
1 How to choose EVA hot melt adhesive
1) Select EVA hot melt adhesive based on tensile strength and flexibility. With glue-bound books and periodicals, loose pages and page drops often occur during the open reading process, which is directly related to the low tensile strength and flexibility of hot melt adhesives. In the premise that the hot melt adhesive and the paper affinity (adhesive force) are sufficient, it must have high tensile strength and flexibility in order to ensure that the book is not easy to tear, break, and maintain a certain degree when reading books and periodicals. The degree of unfolding requires that the bookbinding strength index of the bound book be 0.5kg/cm or more.
2) Select EVA hot melt adhesive according to opening speed and curing speed. The open speed and curing speed of the hot melt adhesive directly affect the quality of the book. Especially for the high-speed linkage production line is very critical, if the opening speed and curing speed is too slow, the plastic seal will overflow when you hit the book, the book in the transfer process will produce back deformation, and will cause the book cover and the book block adhesive, wild glue wire Too much is not conducive to the high-speed production requirements of the linkage production line. If the hot melt adhesive with low tensile strength is used, the adhesive layer will be thick, which will cause the back of the book to be out of squareness, easy to stick the knife when cutting, the back of the book will be easily deformed, and unqualified products such as wrinkle and broken head will appear. For example, if the hot-melt adhesive with too fast curing speed is selected, stickiness will occur and the easy-to-open glue will bottom out, and if it is severe, it will cause the quality accident of degumming and page-off.
3) Select EVA hot melt adhesive according to melt viscosity. Hot melt adhesives only have a low melt viscosity to ensure good penetration of paper. This is very important for rubber staples, especially for some pages that use poor staple fiber and recycled pulp. . Excessively high melt viscosities increase the cost (such as special glue for coated paper), and too low melt viscosity can result in insufficient back gumming.
4) Select EVA hot melt adhesive based on thermal stability and durability. As the hot melt adhesive is recycled in the plastic pot or glue tank or heated for a long time, if the thermal stability of the hot melt adhesive is poor (that is, the anti-aging performance is poor), the color of the glue will be darkened, and the appearance of the book will be affected. When heavy, the surface of the skin crust, resulting in non-melting substances, so that the quality of the package greatly reduced. After aging test, the poor thermal stability of the glue will reduce the permeability of the pages of the book, affect the bond strength, and will produce smoke due to heating and gasification, not only increase the loss of hot melt adhesive, but also the formation of the operating environment Pollution. General requirements Gel pot operating temperature between 130 ~ 160 °C, continuous heating performance for 24h and the book is stable for 5 to 10 years, the quality of the package is not the same (this test requirements, currently only the industry, the company since There are no definite time limit requirements for national standards. It is one of the disadvantages of EVA hot-melt adhesives currently used, and it is also one of the reasons why PUR Adhesive can stand out in the binding processing of high-end products.)
5) Select EVA hot melt adhesive according to temperature suitability. High-quality hot melt adhesives should have good temperature adaptability. When the temperature is as low as -15°C, no adhesive layer cracking phenomenon can occur, so that the page can be opened and the page can be opened. When the temperature is up to 50°C, the adhesive layer cannot be softened by heat. , The page has a situation where the page is sticky. EVA hot melt adhesive temperature adaptability (embrittlement point ≤ -20 °C, soft point ≥ 70 °C) is also an important indicator that can be tested in the refrigerator and oven performance, qualified before use in batches, and in use During the process, maintain the proper test.
When using hot melt adhesives, first of all to ensure the quality and performance of hot melt adhesives, can not only consider the price level, after production trials, measure the actual use price and then buy. Make a decision by comparing tests. Good quality hot melt adhesive, book back adhesive layer thickness of 0.5 ~ 0.8mm to meet the quality requirements, the quality of the adhesive layer thickness to reach 1.2 ~ 1.5mm above, tensile strength is much lower than high-quality plastic. Good quality hot melt adhesive 1.5 ~ 20,000 yuan / ton, although the poor quality of hot melt adhesive price is 1.1 ~ 12,000 yuan / ton, but due to excessive use, the final calculation is also equivalent to 1.5 ~ 20,000 yuan / Tons of comprehensive economic losses, such as losses caused by aging consumption in use and losses due to unqualified quality such as loose-leaf pages or page-drops, longer production cycles, and lower reputation, tend to be even greater. Therefore, irrespective of actual production conditions, simply adopting low-cost, low-quality hot-melt adhesives from the point of view of price and one-sided use is actually much more expensive to use than good-quality hot-melt adhesives. This is particularly important in production management. Attention.
2 Prepress and printing are important processes for ensuring the quality of binding
1) Prepress process design
In the prepress process design should be fully considered, a reasonable arrangement for the post-press work and preparation, it can be said that the pre-press design arrangements are reasonable or not has determined the product's entire quality grade.
1 In order to reduce the stringing phenomenon that may occur during the process of bookbinding, the length of the cover may be 1 to 2 mm longer than the corresponding book block when the paper is suitable.
2 When there is no special fitting requirement for the book block layout, it should be designed as a folding method for the first time as much as possible to facilitate the construction of the binding and the quality of the book can be improved.
3 In order to adapt to the requirements of the binding, under the conditions allowed by the paper format, the width of the booklet width = 2mm + milling back size + 3mm bleeding. Such as 210 × 148mm finished book pages folded 216mm × 153mm, off the large version of 864mm × 612mm, completely suitable for flat and rotary press production binding books and publications requirements.
4 It is necessary to set up a complete and reasonable page and layout logo for post-press processing, and it should be suitable for the production requirements of manual and semi-automatic, fully linked production lines.
2) Printing requirements
1 Materials
● The cutting tolerance of white lithograph paper is ≤1mm, the skew tolerance is less than or equal to 1.5mm, and it is flattened and wide. The cut edges are neat and clean at an angle of 90° without burrs.
● The web used for rotation requires that the roll paper be tight and the paper roll be round. The weight of the specifications should be the same when printing on double paper.
● The printability of the paper must meet the requirements, and should be used with caution for paper that is soft, prone to water absorption elongation, easily deformed by heat, and is brittle.
2 Printing
● When printing on the machine, no matter the text or the cover must be printed according to the process requirements, the consistency of the entire book must be maintained before and after the specification. When printing rotary printing, consider flowering knife to vent the booklet folding, the tolerance of folding is less than or equal to 1.5mm, and at the same time, in order to facilitate the production process characteristics of binding, it is necessary to make the outer signature as short as possible within the inner signature. The thickness of the stencil on the inside of the book can be reduced, thereby reducing the chance of drawing and wild rubber.
● To control the balance of ink and ink to prevent excessive printing and deformation, if the printing is done by a sheet-fed machine, if the moisture is too large, the printed sheets will be uneven, easily deformed, and curled on both sides, thus affecting the folding machine construction.
● Use a rotary machine to print the positive postscripts. After the machine is placed, it is placed neatly and neatly on each layer. Generally, each board is ordered with 20 to 25 reams, placed for 4 to 8 hours. After the ink is completely dried, it is 500 to 800 sheets each. Shake it together, use a bundler, bind it with a pad of paper and send it to the binding process. Some high-performance commercial rotary machines are equipped with drying and signature stacking devices, which are not subject to the foregoing requirements. However, the final printed signatures must be bundled when they are sent for binding.
● If it is not possible to arrange the bookbinding when the workshop air humidity is high or within a short time, take measures such as covering the plastic cover to prevent moisture, to prevent the deformation of the signature, which is especially important for the normal operation of the semi-automatic and automatic production line. .
(to be continued)
