Overview of self-made adhesives in the hottest car

Overview of self-made adhesives in carton factory

starch adhesive is actually a raw additive, which is pumped to the corrugating machine and then applied to the corrugating peak. When it is in a raw state, it has no viscosity. Only when it is heated to a certain temperature on the paste line, it will become a strong and tough adhesive

water based adhesives are mainly used to dry or bond by absorbing water on the surface. The raw solid starch in the adhesive is gelatinized on the paste line to absorb water. The bonding time is from a few seconds to about a minute. Water is gradually absorbed by the surrounding air and paper fibers. This traditional adhesive is generally used in corrugated board production lines, which can immediately produce a strong bonding effect

in order to achieve satisfactory bonding effect, a slightly viscous suspension lotion containing pre gelatinized starch must be added to the starch and water lotion. This suspension lotion can suspend raw starch in water and prevent its sedimentation; Increasing the concentration is convenient for being put on the rubber roll and forming a paste film of appropriate thickness on the roll; Adjust the viscosity so that the paper fibers are properly wetted and initially adhered; Ensure that there is a large amount of water around the raw starch molecules, so that the starch can expand to the maximum extent and completely gelatinize when heated; Caustic soda must be added to adjust and control the gelatinization temperature of starch to the minimum

borax must be added to achieve satisfactory bonding effect, Make raw starch absorbed when heated "Relying on the newly expanded adhesive utilization and development laboratory in Bayer Shanghai polymer research and development center and the global innovation team that has been fully invested in scientific research projects, all the water available for absorption; make the starch produce appropriate viscosity and toughness during gelation; act as a buffer to prevent caustic soda from swelling part of raw starch under the lowest gelation temperature.

all manufacturers have specific paste formulas and have practiced for many years The experience found in must be strictly observed, and any deviation may lead to poor bonding and other quality problems. Regular starch adhesive is a mixture of water, raw starch, cooked paste, caustic soda, borax and formaldehyde, with an approximate proportion of 80% water; Starch 20% (including 85% raw starch and 15% cooked starch); Caustic soda (of total starch) 2..8%; Borax (of total starch) 2..2%, about 10 moles; Trace formaldehyde

the starch used by some carton factories in the United States is mostly corn starch. Some are untreated pure corn flour, while others have been chemically treated. In particular, the treated special starch has good stability, viscosity and excellent water containing properties. Some starches are powdery, while others are granular. The particles are just loose lumps surrounded by powder, which are used to prepare the whole batch of paste in the lower paste lees

some factories use specially treated corn starch to specially produce a single viscosity adhesive, with a gelatinization point of 61 ℃ and 63 ℃. Although the gelatinization point is low, the adhesive gelatinizes rapidly like the general double-sided machine paste. The viscosity is usually between 27 and 32 seconds. 680 gallons of paste with 500 kilograms of starch

after stirring in normal temperature water, the particles of starch disperse into emulsion, but they will not dissolve or absorb water. If you stop stirring, the starch will precipitate at the bottom and gradually form hard lumps. Once the hard lumps are formed, it is not so easy to disperse

starch dispersed in water begins to absorb water and expand when heated. Raw starch is used in the adhesive formula, which begins to swell at about 70 ℃. When the temperature rises to 90 ℃, the expansion is completed. The gelatinized starch is very viscous, and its degree depends on the amount of starch in the water

borax can also be divided into powder and granular, and fine-grained borax is the best. Borax can be divided into two levels according to strength. There are 10 water molecules in 10 moles of borax, which is called grade 10 water borax. Five moles of borax have five water molecules, which are called grade 5 water borax. The concentration of 5 moles of borax is higher. 0.35 kg of 5 moles of borax is equivalent to 0.454 kg of 10 moles of borax. If the same amount of two kinds of borax is used incorrectly, the consequences will be serious. If borax is added to raw starch and water lotion, and then the mixture is heated, the starch will expand rapidly after absorbing water, and become more viscous than when borax is not added. There is a certain limit to the amount of borax added, otherwise, it will affect the expansion of starch, the gelatinized paste will become brittle, and it will be in a powder state when dry

caustic soda can be used as long as it contains 76% sodium oxide and is of commercial grade without additives. It can be used as crumb, granular or flake. The composition is equivalent to 98% sodium hydroxide. Caustic soda will absorb water in the air and reduce its strength. Therefore, if the packaging barrel is damaged, it is not suitable to carry out supply side reform around market demand. After opening the end of the barrel to take materials, the end of the barrel should be closed immediately

caustic soda is a strong alkali, which can seriously burn the skin in dry state or dissolved in water. Wear a mask and rubber gloves when handling caustic soda, and prepare a bottle of vinegar at any time, so as to immediately deal with caustic soda contaminated skin. When caustic soda dissolves in water, it will smoke. Don't breathe the smoke. The smoke is toxic

adding caustic soda to the lotion of raw starch and water and heating the mixture can reduce the temperature of starch expansion and gelation. According to this feature, the amount of caustic soda added can be used to accurately control the temperature of starch expansion and gelation. However, too much addition will split the gelatinized particles, reduce the viscosity, and make the raw starch in the paste gelatinize in advance

formaldehyde is 37% aqueous solution, measured by the volume or wet weight specified in the formula. Formaldehyde is used in general adhesives to prevent corrosion. In some waterproof adhesive formulations, it is used as a chemical crosslinking agent. Wear protective equipment when handling formaldehyde, because formaldehyde has strong irritation to eyes and skin, and smoke must not be inhaled

Bayer resistant materials technology has 30 production bases and about 14200 employees around the world. The difference between water-resistant adhesives and ordinary adhesives is that they usually contain more raw starch, less caustic soda, and no or little borax. Of course, a certain amount of waterproof agent is added to water-resistant adhesives. There are many waterproof agents that can be used, all of which are water-soluble resins. After chemical cross-linking with formaldehyde, this kind of resin will become water-insoluble and water-resistant adhesive when heated on the paste line

at the same time, various sprockets on the electronic universal testing machine should be checked regularly, and the service life of most water-resistant adhesives has a certain limit. Some thicken gradually with the passage of time, even in the case of agitation. Some machines have good operation performance, but their water resistance is greatly reduced. Therefore, the adhesive must be used as soon as possible after it is prepared

precautions for improving the performance of waterproof paperboard are as follows:

1. The pH value of waterproof adhesive must be controlled within the specified limit

2. the coating must be heavier than the normal paste line

3. Try to use more heat energy when producing paperboard

4. the moisture content of tissue paper should not be too high

5. there must be more agitation, and the waterproof adhesive in the storage tank must be used as soon as possible

6. if the effect is still poor, the only remedy is to add more resin

(Zhu Wen)

source: Shanghai packaging