2. Adhesion and adaptability of EVA hot melt adhesive
In the production process, the adhesive strength of the hot melt adhesive changes with the heating temperature, the quality of the book block paper, the width and depth of the back-back milling, and the operating speed of the glue-binding equipment. Grasping these changing factors is extremely important for improving the adhesive strength and binding adaptability of hot melt adhesives.
(1) Heating temperature of hot melt adhesive
The softening point of the hot melt is generally within the range of 70 to 100°C. This temperature range is only the melting temperature of the glue. To make the hot melt glue capable of adhering to the book, the heating temperature must reach 150-180°C. According to foreign data, the glue on the ordinary book paper (press paper and newsprint paper) is glue-bonded. When the glue temperature is 170°C, the hot-melt adhesive's pull test value is 8.83±0.44N/cm. When the adhesive temperature rises to 180°C, the hot-melt adhesive's tensile test value will drop to 7.33±0.33N/cm. On the other hand, when the temperature of the glue drops to 155°C, the pull strength of the hot melt is only 5.22±0.25N/cm.
Thus, the heating temperature of the hot melt adhesive should not be too high or too low. If the temperature is too high, although the fluidity, wettability, and permeability of the glue are strengthened, the bond strength will decrease, which will affect the tensile strength of the glue. Conversely, if the temperature is too low, the viscosity will increase, but it will affect the fluidity of the glue, as well as the wettability and permeability of the book block and the tensile force of the glue, and may even fail to bond. Therefore, the heating temperature and the gluing temperature of the hot melt adhesive must be controlled within an optimal range.
(2) The relationship between the temperature of the book block paper and glue
The core of the book is different from the paper, and the gluing temperature of the hot melt adhesive should also be different. This is not only because the fiber properties of the paper are different, but more importantly, the thermal conductivity is different, that is, the cooling rate is different. Taking the thermal conductivity of coated paper (coating paper) and non-coated paper (topography paper) as an example, the former cools the glue faster than the latter. Because coated paper contains nearly 10 times more inorganic than non-coated paper, and inorganic materials have good thermal conductivity, the coated paper allows the hot melt to cool faster. The hot-melt adhesive pull test shows that if the sizing temperature is also 170°C, the uncoated paper can reach a pull value of 8.83±0.44N/cm, while the pull value of the coated paper can only reach 1.86±0.11N/cm (65g). /m2 coated paper) and 1.46±0.11 N/cm (100 g/m2 coated paper). Therefore, to improve the pull value of the hot melt adhesive on the coated paper, the gluing temperature must be increased. Practice has proved that the gluing temperature is generally about 195 °C. At this temperature, the pull value can reach 4.1 to 3.91 N/cm (The above data is extracted from foreign sources for reference only).
(3) Opening time and production operating speed of hot melt adhesive
During the use of hot-melt adhesives, there are two time variables that must be strictly controlled. One is the open time of the hot melt adhesive, and the other is the curing time.
The opening time means that the process of applying the hot melt adhesive to the adherend must be completed within the bonding time specified by the hot melt adhesive. Otherwise, the adhesive layer surface will be conjunctival beyond the specified time, so that the two adhesives cannot be adhered firmly. According to the type of hot melt adhesive, the opening time is also different, it can be 7 to 15 seconds, it can also be 15 to 20 seconds. After the two adherends are adhered within the specified time, they must be cooled for a certain period of time before they can be pressurized or turned. Otherwise, the adhesive force of the hot melt adhesive may be affected, and the product may be deformed or the pages may fall off. This cooling time is called the curing time. The curing time varies according to the model of the hot melt adhesive, and it has a length or a short time. The general curing time is 3 to 5 minutes.
The open time and curing time of the hot melt adhesive are closely related to the speed of the machine, especially the opening time. For example, if the opening time of the hot melt adhesive is 7 to 15 seconds, then the book block must be at the 15th after the milling and backing of the book block, starting from the application of the glue and until the cover is glued with the back of the book (without gauze and paper jam on the back of the book). Within seconds, the hot melt adhesive can achieve a good adhesive effect. If the machine runs slowly, the cover cannot be bonded within 15 seconds, and the bond between the cover and the back of the book is not strong and the bond strength is poor. Therefore, to determine the open time of hot melt adhesives, it is necessary to consider the normal operating speed of the glue-binding equipment.
In addition, it is necessary to grasp the curing time of the hot melt adhesive, because the glue is brushed to the back of the book, it will take 3 to 5 minutes before the basic curing. Before it has reached or nearly complete cure, the book cannot be cut and the page cannot be flipped. Otherwise, it will cause the back of the book cover bow wrinkles, book back deformation and book off and other ills. Therefore, if the interval between the book and the three-sided cutting process is shorter after the book is glued, you should try to extend the time so that the glue can be fully cured before cutting.
Hot melt adhesive precautions
(1) The hot melt adhesive can only be heated with the oil bath spacer or with a sealed hot plate. Never use open flame heating.
(2) After the hot melt adhesive is preheated with a preheating pot, it must be released into the rubberized glue bucket before it can be used. Therefore, the amount of glue in the preheated pan should be suitable. If too much is added, the adhesive can be repeatedly melted, and the colloid can easily be aged, which affects the adhesive force. Therefore, it is necessary to add less.
(3) In the hot melt adhesive opening time, complete the binding work of the book, if you encounter downtime or other failures, the books in the book folder brushing the end of plastic and not on the side of the plastic book, to remove timely to prevent the appearance of books The phenomenon of the core stalling on the rubber wheel.
(4) The temperature of the molten colloid must be strictly controlled within the use temperature range. It is necessary to prevent the temperature of the glue liquid from being too low, affect the flowability, wettability and permeability of the glue, and prevent the temperature from being too high, which will affect the viscosity of the glue. Causes problems such as aging of glue.
(5) The glue pan that melts the glue should be cleaned periodically. It is best to clean it twice a year to ensure that the glue pan is clean. Care should be taken when cleaning, do not use paraffin as a cleaning agent, because paraffin wax is flammable, there is a safety hazard, it is recommended to use a dedicated cleaning agent. In addition, the sensitivity of the temperature display must be ensured to ensure that the display temperature is reliable and accurate.
(6) After the hot-melt adhesive is melted, the adhesive temperature is between 100 and 180°C. If it is used improperly, the adhesive will stick to the skin and the skin will be burned. Therefore, when using hot melt adhesives, protective measures must be taken to ensure safety.
Correct use of hot melt adhesive
Proper use of hot melt adhesives can reduce many of the binding quality issues. The key to the correct use of hot-melt adhesives is to correctly grasp its use temperature. The following uses the products of the Wuxi Wanli Adhesive Materials Factory as an example to introduce the use of hot melt adhesives.
(1) Edge C-22
The use temperature is generally 120-130°C.
(2) Adhesive KG-6 (offset paper)
The use temperature is generally 150 to 170°C.
(3) Adhesive KG-8 (copper paper)
The use temperature is generally 160 ~ 180 °C.
(4) all kinds of plastic, adhesive
The operating temperature varies depending on the relationship between the operating temperature of the glue pan used in each machine and the operating speed of the machine, and the relationship with the ambient temperature change.
(5) If the adhesive is used at a higher temperature, it will cause too many stomata in the back of the book. If it is a damp paper, it will also cause short-back problems in the back of the book.
(6) The scraper wheel and the roller must be adjusted to the exact position. The first roller should be adjusted to be about 0.2mm lower than the second roller.
(7) The amount of hot melt adhesive in the plastic pot should be appropriate, and the amount of hot melt adhesive in the preheated pan should not exceed 160°C.
(8) Milling back, milling groove depth: offset paper to reach 1.2mm or more; coated paper to reach 1.5mm or more. Milling back, milling slotted knife should be adjusted well, the knife surface should be kept clean, the knife edge should be sharp, the paper scraps should be milled cleanly, the book book can't leave behind the milling paper. If there is paper residue behind the milling, it will affect the permeability of the hot melt adhesive, and the quality problems such as page dropout are likely to occur.
Source: Printing Technology
In the production process, the adhesive strength of the hot melt adhesive changes with the heating temperature, the quality of the book block paper, the width and depth of the back-back milling, and the operating speed of the glue-binding equipment. Grasping these changing factors is extremely important for improving the adhesive strength and binding adaptability of hot melt adhesives.
(1) Heating temperature of hot melt adhesive
The softening point of the hot melt is generally within the range of 70 to 100°C. This temperature range is only the melting temperature of the glue. To make the hot melt glue capable of adhering to the book, the heating temperature must reach 150-180°C. According to foreign data, the glue on the ordinary book paper (press paper and newsprint paper) is glue-bonded. When the glue temperature is 170°C, the hot-melt adhesive's pull test value is 8.83±0.44N/cm. When the adhesive temperature rises to 180°C, the hot-melt adhesive's tensile test value will drop to 7.33±0.33N/cm. On the other hand, when the temperature of the glue drops to 155°C, the pull strength of the hot melt is only 5.22±0.25N/cm.
Thus, the heating temperature of the hot melt adhesive should not be too high or too low. If the temperature is too high, although the fluidity, wettability, and permeability of the glue are strengthened, the bond strength will decrease, which will affect the tensile strength of the glue. Conversely, if the temperature is too low, the viscosity will increase, but it will affect the fluidity of the glue, as well as the wettability and permeability of the book block and the tensile force of the glue, and may even fail to bond. Therefore, the heating temperature and the gluing temperature of the hot melt adhesive must be controlled within an optimal range.
(2) The relationship between the temperature of the book block paper and glue
The core of the book is different from the paper, and the gluing temperature of the hot melt adhesive should also be different. This is not only because the fiber properties of the paper are different, but more importantly, the thermal conductivity is different, that is, the cooling rate is different. Taking the thermal conductivity of coated paper (coating paper) and non-coated paper (topography paper) as an example, the former cools the glue faster than the latter. Because coated paper contains nearly 10 times more inorganic than non-coated paper, and inorganic materials have good thermal conductivity, the coated paper allows the hot melt to cool faster. The hot-melt adhesive pull test shows that if the sizing temperature is also 170°C, the uncoated paper can reach a pull value of 8.83±0.44N/cm, while the pull value of the coated paper can only reach 1.86±0.11N/cm (65g). /m2 coated paper) and 1.46±0.11 N/cm (100 g/m2 coated paper). Therefore, to improve the pull value of the hot melt adhesive on the coated paper, the gluing temperature must be increased. Practice has proved that the gluing temperature is generally about 195 °C. At this temperature, the pull value can reach 4.1 to 3.91 N/cm (The above data is extracted from foreign sources for reference only).
(3) Opening time and production operating speed of hot melt adhesive
During the use of hot-melt adhesives, there are two time variables that must be strictly controlled. One is the open time of the hot melt adhesive, and the other is the curing time.
The opening time means that the process of applying the hot melt adhesive to the adherend must be completed within the bonding time specified by the hot melt adhesive. Otherwise, the adhesive layer surface will be conjunctival beyond the specified time, so that the two adhesives cannot be adhered firmly. According to the type of hot melt adhesive, the opening time is also different, it can be 7 to 15 seconds, it can also be 15 to 20 seconds. After the two adherends are adhered within the specified time, they must be cooled for a certain period of time before they can be pressurized or turned. Otherwise, the adhesive force of the hot melt adhesive may be affected, and the product may be deformed or the pages may fall off. This cooling time is called the curing time. The curing time varies according to the model of the hot melt adhesive, and it has a length or a short time. The general curing time is 3 to 5 minutes.
The open time and curing time of the hot melt adhesive are closely related to the speed of the machine, especially the opening time. For example, if the opening time of the hot melt adhesive is 7 to 15 seconds, then the book block must be at the 15th after the milling and backing of the book block, starting from the application of the glue and until the cover is glued with the back of the book (without gauze and paper jam on the back of the book). Within seconds, the hot melt adhesive can achieve a good adhesive effect. If the machine runs slowly, the cover cannot be bonded within 15 seconds, and the bond between the cover and the back of the book is not strong and the bond strength is poor. Therefore, to determine the open time of hot melt adhesives, it is necessary to consider the normal operating speed of the glue-binding equipment.
In addition, it is necessary to grasp the curing time of the hot melt adhesive, because the glue is brushed to the back of the book, it will take 3 to 5 minutes before the basic curing. Before it has reached or nearly complete cure, the book cannot be cut and the page cannot be flipped. Otherwise, it will cause the back of the book cover bow wrinkles, book back deformation and book off and other ills. Therefore, if the interval between the book and the three-sided cutting process is shorter after the book is glued, you should try to extend the time so that the glue can be fully cured before cutting.
Hot melt adhesive precautions
(1) The hot melt adhesive can only be heated with the oil bath spacer or with a sealed hot plate. Never use open flame heating.
(2) After the hot melt adhesive is preheated with a preheating pot, it must be released into the rubberized glue bucket before it can be used. Therefore, the amount of glue in the preheated pan should be suitable. If too much is added, the adhesive can be repeatedly melted, and the colloid can easily be aged, which affects the adhesive force. Therefore, it is necessary to add less.
(3) In the hot melt adhesive opening time, complete the binding work of the book, if you encounter downtime or other failures, the books in the book folder brushing the end of plastic and not on the side of the plastic book, to remove timely to prevent the appearance of books The phenomenon of the core stalling on the rubber wheel.
(4) The temperature of the molten colloid must be strictly controlled within the use temperature range. It is necessary to prevent the temperature of the glue liquid from being too low, affect the flowability, wettability and permeability of the glue, and prevent the temperature from being too high, which will affect the viscosity of the glue. Causes problems such as aging of glue.
(5) The glue pan that melts the glue should be cleaned periodically. It is best to clean it twice a year to ensure that the glue pan is clean. Care should be taken when cleaning, do not use paraffin as a cleaning agent, because paraffin wax is flammable, there is a safety hazard, it is recommended to use a dedicated cleaning agent. In addition, the sensitivity of the temperature display must be ensured to ensure that the display temperature is reliable and accurate.
(6) After the hot-melt adhesive is melted, the adhesive temperature is between 100 and 180°C. If it is used improperly, the adhesive will stick to the skin and the skin will be burned. Therefore, when using hot melt adhesives, protective measures must be taken to ensure safety.
Correct use of hot melt adhesive
Proper use of hot melt adhesives can reduce many of the binding quality issues. The key to the correct use of hot-melt adhesives is to correctly grasp its use temperature. The following uses the products of the Wuxi Wanli Adhesive Materials Factory as an example to introduce the use of hot melt adhesives.
(1) Edge C-22
The use temperature is generally 120-130°C.
(2) Adhesive KG-6 (offset paper)
The use temperature is generally 150 to 170°C.
(3) Adhesive KG-8 (copper paper)
The use temperature is generally 160 ~ 180 °C.
(4) all kinds of plastic, adhesive
The operating temperature varies depending on the relationship between the operating temperature of the glue pan used in each machine and the operating speed of the machine, and the relationship with the ambient temperature change.
(5) If the adhesive is used at a higher temperature, it will cause too many stomata in the back of the book. If it is a damp paper, it will also cause short-back problems in the back of the book.
(6) The scraper wheel and the roller must be adjusted to the exact position. The first roller should be adjusted to be about 0.2mm lower than the second roller.
(7) The amount of hot melt adhesive in the plastic pot should be appropriate, and the amount of hot melt adhesive in the preheated pan should not exceed 160°C.
(8) Milling back, milling groove depth: offset paper to reach 1.2mm or more; coated paper to reach 1.5mm or more. Milling back, milling slotted knife should be adjusted well, the knife surface should be kept clean, the knife edge should be sharp, the paper scraps should be milled cleanly, the book book can't leave behind the milling paper. If there is paper residue behind the milling, it will affect the permeability of the hot melt adhesive, and the quality problems such as page dropout are likely to occur.
Source: Printing Technology
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