Starch adhesives are generally used by carton manufacturers because of their superiority over silicate adhesives. Let's talk about the preparation and use of starch adhesives for your reference:
First, the preparation
(I) Preparation of raw materials and their main role
1, starch - the main adhesive material
It is insoluble in water, and it expands and gelatinizes as the temperature in the water rises. When it reacts with caustic soda solution, it is fully expanded and the viscosity increases.
Technical indicators: acidity, mesh number, spot, whiteness, protein content, water content.
Note: The protein content can not be too high, otherwise it is easy to produce foam and affect the quality of the adhesive.
2, water - solvent
Increase the fluidity of the adhesive, but pay attention to the water ratio.
3, soda ash - pasting agent
When dissolved in water, a certain amount of heat is released, and the aqueous solution and starch act to reduce the gelatinization temperature and increase the viscosity.
4, borax (Na2B4OT 10H2O) - crosslinker
When the solution is added to the main tank, the free acid (boric acid) is released, and the hydrogen bond binds to the starch adhesive to increase the firmness of the adhesive film and promote the adhesion of the adhesive.
Note: The amount must be controlled properly, too little, easy to penetrate, affect the strength of the box; too much, the adhesive is easy to gel, brittle, adhesive strength is affected.
(b) Preparation procedures and chemical principles
1. Preparation method
In the automatic production line of corrugated board, we generally use starch paste method (two-step method) to prepare starch adhesive. The process flow is as follows:
Preparation procedure:
The first step: Preparation of carrier starch (mature starch).
A. Place metered water in a carrier reaction vessel and heat to 55-60°C.
B. Put a certain amount of starch into the carrier reaction tank and stir while stirring.
C. After stirring evenly, the caustic soda solution with a certain concentration is added to the carrier tank three times, and stirring is continued for a certain period of time to obtain a beige-colored transparent paste, which is obtained by aging the starch (slurry paste).
The second step: the preparation of the main starch
A. Put a certain amount of water in the main reactor and heat to 30-35°C.
B. Put a certain amount of starch into the main reaction tank and stir while stirring.
C. After stirring evenly, dissolve the borax with hot water and add and stir for a certain period of time.
D. The "cured paste" prepared in the carrier is gradually added to the main tank and stirred while being added.
The third step: After the above “slurry paste†is mixed with the raw paste in the main tank, a translucent semi-cured adhesive is prepared, which is used for heat preservation in the storage tank and can be used for the machine table.
Note: (1) Must be fully stirred in the production process, otherwise it is easy to produce rubber block, block the pipe, affect the adhesive effect. (2) In the carrier tank must be made of "slurry paste", otherwise the initial viscosity of the adhesive will be affected and the adhesion will be affected.
2, the principle of adhesive bonding
The gelatinization process of starch is shown in the figure:
The starch granules are fully stirred under the action of a certain temperature water, and the surrounding moisture is gradually swollen under the catalysis of caustic soda, from several times expansion to tens of times, to the ultimate (gelatinization temperature), and with the increase of temperature, the starch granules It begins to collapse, and gradually disintegrates into small pieces. After soaking into the inner side of the tissue paper and core paper, it begins to adhere and requires a certain initial viscosity (mainly obtained by the action of caustic soda solution and borax solution), and the temperature rises. The moisture content of the starch granules evaporates, and is partially absorbed by the facial paper and the core paper, so that the initial viscosity is rapidly carried out. The adhesive-bonded inner paper, core paper, corrugated cardboard and noodle paper become a whole to achieve the purpose of bonding.
(to be continued)
First, the preparation
(I) Preparation of raw materials and their main role
1, starch - the main adhesive material
It is insoluble in water, and it expands and gelatinizes as the temperature in the water rises. When it reacts with caustic soda solution, it is fully expanded and the viscosity increases.
Technical indicators: acidity, mesh number, spot, whiteness, protein content, water content.
Note: The protein content can not be too high, otherwise it is easy to produce foam and affect the quality of the adhesive.
2, water - solvent
Increase the fluidity of the adhesive, but pay attention to the water ratio.
3, soda ash - pasting agent
When dissolved in water, a certain amount of heat is released, and the aqueous solution and starch act to reduce the gelatinization temperature and increase the viscosity.
4, borax (Na2B4OT 10H2O) - crosslinker
When the solution is added to the main tank, the free acid (boric acid) is released, and the hydrogen bond binds to the starch adhesive to increase the firmness of the adhesive film and promote the adhesion of the adhesive.
Note: The amount must be controlled properly, too little, easy to penetrate, affect the strength of the box; too much, the adhesive is easy to gel, brittle, adhesive strength is affected.
(b) Preparation procedures and chemical principles
1. Preparation method
In the automatic production line of corrugated board, we generally use starch paste method (two-step method) to prepare starch adhesive. The process flow is as follows:
Preparation procedure:
The first step: Preparation of carrier starch (mature starch).
A. Place metered water in a carrier reaction vessel and heat to 55-60°C.
B. Put a certain amount of starch into the carrier reaction tank and stir while stirring.
C. After stirring evenly, the caustic soda solution with a certain concentration is added to the carrier tank three times, and stirring is continued for a certain period of time to obtain a beige-colored transparent paste, which is obtained by aging the starch (slurry paste).
The second step: the preparation of the main starch
A. Put a certain amount of water in the main reactor and heat to 30-35°C.
B. Put a certain amount of starch into the main reaction tank and stir while stirring.
C. After stirring evenly, dissolve the borax with hot water and add and stir for a certain period of time.
D. The "cured paste" prepared in the carrier is gradually added to the main tank and stirred while being added.
The third step: After the above “slurry paste†is mixed with the raw paste in the main tank, a translucent semi-cured adhesive is prepared, which is used for heat preservation in the storage tank and can be used for the machine table.
Note: (1) Must be fully stirred in the production process, otherwise it is easy to produce rubber block, block the pipe, affect the adhesive effect. (2) In the carrier tank must be made of "slurry paste", otherwise the initial viscosity of the adhesive will be affected and the adhesion will be affected.
2, the principle of adhesive bonding
The gelatinization process of starch is shown in the figure:
The starch granules are fully stirred under the action of a certain temperature water, and the surrounding moisture is gradually swollen under the catalysis of caustic soda, from several times expansion to tens of times, to the ultimate (gelatinization temperature), and with the increase of temperature, the starch granules It begins to collapse, and gradually disintegrates into small pieces. After soaking into the inner side of the tissue paper and core paper, it begins to adhere and requires a certain initial viscosity (mainly obtained by the action of caustic soda solution and borax solution), and the temperature rises. The moisture content of the starch granules evaporates, and is partially absorbed by the facial paper and the core paper, so that the initial viscosity is rapidly carried out. The adhesive-bonded inner paper, core paper, corrugated cardboard and noodle paper become a whole to achieve the purpose of bonding.
(to be continued)
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