Buying Premium Carton Adhesives Note 2

5, different operating methods use different properties of the adhesive

According to different operating methods, the performance indicators of the adhesive used must also be different. Taking the snaking process as an example, the automatic squeegee has a high speed and therefore requires a lower viscosity of the adhesive and rapid drying. However, the manual squeezing speed is slow, and the viscosity of the adhesive is required to be slightly higher, and the drying speed cannot be too fast.

6, consider the binder storage period

When purchasing adhesives, the storage period should also be considered. Storage period refers to the time that the adhesive can maintain stable performance after storage under specified conditions. At the time of purchase, the minimum shelf life of the adhesive should be determined according to the production of the company. For general enterprises, the shelf life of adhesives should be more than one month.

7, the use of different state adhesives

At present, the common forms of adhesive on the market are emulsion, powder and solid. Emulsion glue can be used directly, but there are disadvantages such as high transportation costs, short storage period, and storage space. Powdered and solid adhesives need to be converted into emulsions before they are used in certain ways, but they have a long storage period. Save on transportation costs and storage space. Taking starch adhesives as an example, in the Pearl River Delta region, due to the dense carton manufacturers and developed transportation, most packaging companies purchase emulsion-like starch adhesives; in most regions in the Mainland, due to the scattered and relatively small scale of carton enterprises, Use powdered starch binders. Therefore, different forms of adhesives should be selected according to the specific conditions of the company during the procurement.

8. Requirements for adhesives for different uses

Different uses of paper products have different requirements for adhesives. General paper containers only require sufficient adhesive strength during storage and transportation. For food, cosmetics, and pharmaceutical packaging, in addition to adhesive strength requirements, the adhesive used must be odorless, Non-toxic, in line with national safety and health regulations and environmental protection requirements. Some ingredients in the adhesive, such as accelerators, plasticizers, anti-aging agents, etc., may transfer to the inner surface of the packaging material and contaminate the food, and therefore must be limited. In addition, the various resistances of the adhesives should also be investigated according to the specific use of the paper products, such as heat resistance, water resistance, chemical resistance, aging resistance, low temperature resistance, and the like.

9, the safety of adhesives

The environmental protection and safety of adhesives is also one of the factors that must be considered. Solvent-based adhesives use a large amount of organic solvents, which not only seriously pollute the environment, harm human health, but also cause fires. Therefore, it should be possible to search for water-based or solvent-free adhesives.

Second, how to determine the quality of adhesives

1, adhesive strength

The adhesive must first have sufficient adhesive strength to ensure that the adhesive does not affect the function of the paper product. To determine whether the bonding strength of the adhesive is acceptable, the two adhered materials can be torn along the adhesive interface. If it is found that the adhered material is damaged after tearing, it is proved that the adhesive strength is sufficient; if only the adhesive interface is separated, it indicates that Adhesive strength is insufficient. Sometimes the binder with poor performance will be debonded and the film will be brittle after being stored in high temperature or low temperature environment for a period of time. Therefore, it is necessary to perform high temperature thermal deformation and low temperature embrittlement experiments to determine whether the quality is reliable. The test method of high temperature heat change is to put the carton that has been completely cured at the bonding place in a constant temperature oven at 60° C. and bake it for 24 hours. After cooling, the hand taps the joint of the carton until it separates, and tears if adhered. It shows that the heat resistance of the adhesive is good. If the adhesive material is intact, only the bonding interface is disengaged, indicating that the heat resistance is enough; the low temperature embrittlement test method is to put the paperboard with the completely cured adhesive at -15°C. In the environment, it was frozen for 24 hours. The method of determination was the same as that of the high temperature thermal deformation test method.

2, drying speed

When choosing an adhesive, it must be measured whether the drying speed matches the bonding process. The general hand-bonding process is slower and requires a longer initial drying time, while the machine-bonding process is faster and requires a shorter initial drying time. For the whole time, the vast majority of cases require the sooner the better, so that we can enter the next process as soon as possible.

3, viscosity

Viscosity is the most important factor affecting the quality of adhesives. If the viscosity is too large, the coating is thick, the amount of glue is large, drying is slowed down, and the wetting and penetration of the adhesive on the surface of the adherend are also affected, thereby directly affecting the adhesive strength; if the viscosity is too low, the coating is applied. The layers are thin, dry quickly, and are prone to problems such as poor adhesion. Therefore, packaging companies must constantly check the viscosity to ensure that the bond strength is within the desired range. The ideal viscosity range for various adhesives is not the same, such as 50 ± 15 seconds for corrugated board adhesives, 50 ± 10 seconds for automatic paper glue, 70 ± 15 seconds for manual paper glue, and glue for stick boxes. It is 4000mPa.s—7000mPa.s and so on.

4, solid content

Solid content is also one of the important factors affecting the quality of adhesives. The higher the solids content, the stronger the adhesion and the faster the drying. In particular, for the corrugated board processing technology and the affixing process, the higher the solid content of the binder, the quicker the initial dry and dry time of the cardboard and the higher the production efficiency. Cardboard with a binder with a high solid content absorbs less water, and the cardboard produced has good hardness and is not easily warped and deformed. Therefore, under the same conditions of other technical indicators, high solid content will help improve production efficiency and maintain the quality of paper products.

5, PH value

Synthetic resin adhesives are mostly weakly acidic and do not produce negative effects on the bonding process and paper products. Yes, but water glass and starch binders are more basic. The high alkalinity not only causes corrosion to workers and equipment, but also sometimes corrodes the adherends, forms marks that affect the appearance, and reduces the moisture resistance of the paper products. Therefore, the impact of pH on the product must be taken into consideration when purchasing the adhesive.

For corrugated paperboard adhesives and other materials that require the purchase of starch, caustic soda, borax and other materials, the quality of the starch material should be strictly controlled. The water content of the starch should not be too high and should generally be maintained at 12% to 18%; the protein in the starch The content should not exceed 1%, and the content should be less than 0.5%. The most commonly used starches include corn starch and tapioca starch, corn starch binders are more prone to retrogradation, but strong adhesion; cassava starch binders are more stable, but the adhesion is not as good as corn starch binders. In the procurement of starch, may wish to do occasional testing of starch to ensure the quality of the adhesive.

(The author / Guan Guoping)