The importance of paste quality in the production process of corrugated cardboard has been recognized by more and more carton manufacturers. Some people compare the glue to the "blood" of the cardboard production line. Because the quality of paste production directly affects the quality of cardboard and the speed of corrugated cardboard production line, which plays an absolute role in the quality of cardboard. Therefore, how to improve the quality of paste and how to use paste correctly and reasonably is very important. Relevant personnel must fully master the method of making paste and the ratio of raw materials, and timely adjust the gelatinization temperature and viscosity required for cardboard bonding, so as to enhance the strength of the cardboard, reduce losses, and reduce costs.
(1) Paste making process and operation method
The paste making process and related operating methods are the top priority. Because the improvement of paste quality and the correct and reasonable use of paste are the guarantee for producing high-quality corrugated cardboard. Of course, for the paste making process and related operations, each manufacturer is different and has a method suitable for its actual production situation. Next, we introduce one of the more ideal paste making processes.
1. Carrier
1). When the additive is used to make the paste, the amount of the carrier only accounts for 20% to 24% of the total amount. It will appear that the blade of the carrier tank mixer cannot hit the material in the tank, and the material cannot be fully mixed, affecting the effect. Therefore, the length of the shaft of the carrier agitator should be lengthened so that the blades extend into the material, or added to the main body in portions according to the amount of the second paste. However, due to the high viscosity of the carrier paste, it will inevitably cause inaccurate measurement;
2). The discharge valves of the carrier tank production and delivery are all 1.5`, about 2`, which makes the discharge too fast, and it is difficult to fully mix the carrier cooked slurry after adding it to the main body. The solution is to install 2`-1 / 2` on the discharge valve and reduce the diameter of the beam joint so that the diameter of the outlet is less than 15 mm, and it is appropriate to control the discharge time to about 8-12 minutes
3). According to the properties and preparation method of the carrier cooked pulp, if the paste has agglomeration and the discharge is too slow, the function of the carrier mixer motor should be increased, the shape and size of the mixer blade should be changed, and the installation stability of the carrier tank should be checked .
2. Subject
1). The main agitator is best to use a speed-regulating motor, with a control speed between 400 and 1400 rpm;
2). When the carrier cooked pulp is injected into the main body, the main body agitator should be in the stirring state, and the rotation speed is between 400 and 800 rpm;
3). After the carrier cooked slurry is injected into the main body, continue to stir for 15 minutes N20 minutes, the two must be fully mixed evenly.
3. Injection of additives
1). After the additive is weighed, the outlet of the container cannot be greater than 14 mm, and the injection time is basically controlled between 5 minutes and 10 minutes. The agitator must be in the stirring state when the additive is injected;
2). After the additive is injected into the main body, increase the stirring speed and continue to mix for 10 minutes to 20 minutes. If the mixing is still impermeable after 20 minutes, and the jelly appears in the paste, the mixing strength should be regarded as too low and the main motor must be replaced. If it is still unsatisfactory, the shape, angle and area of ​​the mixer mouth 10 should be modified to ensure that the force mouth is fully mixed with the paste in the boiling state;
3). Be sure to test the viscosity with a viscometer before applying glue on the machine.
4. Other
1). Don't try to extend the stirring time to achieve the viscosity requirement when the stirring is weak:
2). The amount of water injected into the carrier and body must be accurate;
3). Use the remaining glue that has not been used up (more than 12 hours). It should be poured into the storage tank or paste making tank and stirred for 5 minutes to 10 minutes. It is best to add 40% of the fresh paste and mix well;
4). Using additives, each factory should adjust the time and material ratio according to the conditions of its own enterprise and regional climate, paper tightness, water absorption, moisture content, etc. If the amount of starch is increased in summer, it should be reduced in winter.
(2) Realize the optimal efficiency of starch binder
Starch adhesives are used by more and more carton manufacturers due to their advantages of high bonding strength, high stiffness of cardboard, no moisture absorption and softening, no corrosion, no pollution, and low cost of use. However, the quality of the starch binder will still be unstable. The most critical process is the degree of oxidation. If the oxidation is too high, the viscosity of the adhesive is low, and the bonding strength is poor, which may cause poor adhesion of the cardboard. Insufficient oxidation, the viscosity of the adhesive is too high, can not be used on the machine, cardboard drying is slow, storage time is short, easy to skin and gel. Therefore, how to master the degree of oxidation is the key process for making adhesives.
The starch must be modified before it is formulated into a binder. The purpose of modification is to improve the adhesive force and fluidity of starch paste. After the unmodified starch is gelatinized, a thick paste is obtained. In order to prepare a "glue" with good flow properties, the starch must be modified. Modification methods include acid conversion method, enzyme conversion method, dextrinization method, etherification method, oxidation method and so on.
In the process of configuring the binder, when the bottom water temperature is 20 degrees Celsius, the amount of potassium permanganate should be controlled at 0.4kg-0.5kg per 25kg of corn starch.
(3) Analysis of possible problems and causes during the configuration process
The consumption of starch paste in the corrugated industry includes:
â—† Current process limitations;
â—† The speed range of corrugated board production line is too wide;
â—† As a "shock absorber" in the heating process, so that starch is used too much. The problems that too much starch may cause are:
â—† The cardboard is too soft and the moisture is too much;
â—† The thermal stress limits the production speed;
â—† Lamination of cardboard paste adhesive area;
â—† "Washboard" phenomenon-increase the difficulty of printing;
â—† After a long time, the cardboard warps;
â—† The product image is wrong.
â—† Low quality of maintenance work;
â—† Low quality of base paper;
â—† The steam supply is inconsistent;
â—† Insufficient training for operators
â—† Reduce profits.
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