Adhesive for the hottest self-adhesive label

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Adhesive for self-adhesive label

the adhesive of self-adhesive label is the medium between the label material and the bonding substrate, which plays the role of connection. According to the characteristics, it can be divided into permanent and removable. There are many formulations of adhesives, which are suitable for different surface materials and use environments. Adhesive is the most important part of self-adhesive label technology and the key to the application technology of self-adhesive label

adhesive coating

adhesive generally uses tape coating method. Its basic principle is to inject adhesive through the pressure of the cavity of the cloth head. The top of the cloth head is an adjustable slit. During coating, with the operation of the base paper, the adhesive flows out of the slit of the cloth head evenly and is coated on the surface of the base paper. The coating amount can be adjusted by adjusting the fine seam. The coating amount of adhesive is the key to determine the performance of self-adhesive materials. Generally, the recommended coating amount is 24g/m2 with a tolerance of ± 3 g. When the viscosity of the adhesive changes, the overall coating weight can be kept unchanged by adjusting the pressure. The advanced tape casting coating device feeds back the coating thickness information to the computer control equipment through the infrared scanning sensor, and automatically adjusts the relevant data after analysis and processing to ensure the stability of adhesive coating quality. The coating amount of adhesive should vary according to the season and the temperature and humidity of the region, and can also be adjusted according to the requirements of customers

the general rule is that the coating amount in winter should be larger than that in summer. In winter, the coating amount used in the north is larger than that used in the south. For different substrate surfaces, the coating amount of rough surface is larger than that of smooth surface. The coating amount is related to the bonding force of the material. Within a certain range, the bonding force is directly proportional to the coating amount. The coating amount of adhesive is too large and too small, which has a direct impact on the processing and storage of materials

problems caused by excessive coating amount:

glue overflow: especially in summer, the end faces of the drum will stick together or the sheets of paper will stick together, causing waste products

difficult slitting: the blade is easy to glue and stick to the paper and end face, which brings hidden dangers to the printing process

it is difficult to feed paper on the printing machine: the adhesive often sticks to the feeding board, affecting the normal paper feeding and positioning registration

after the label with too much glue is pasted on the commodity, there will be glue overflow around the label, and black edges will be formed after dust is pasted. When the temperature is high, the label moves and misaligns on the commodity

problems caused by too small coating amount:

affect viscosity: labels are easy to fall off from commodities, especially rough surfaces or large curvature surfaces

affect the material structure: the separation force between the surface material and the bottom paper is too small, which makes the material layered, or the label is peeled off together with the edge of the waste paper during die cutting and waste discharge, which affects the normal production

sometimes the coating amount should be adjusted according to the needs of customers. The label used in supermarkets requires 2 The experimental machine is fully automatic controlled by microcomputer, and the coating amount is small. However, if you need to stick to special surfaces such as rubber, you need to increase the coating amount to strengthen the adhesion

classification of adhesives

according to different classification methods, adhesives can also be divided into various types. For example, according to the coating technology, it can be divided into: hot-melt glue, solvent glue and emulsion glue; According to chemical composition, it can be divided into: rubber substrate and acrylic acid; According to the bonding characteristics, it can be divided into: permanent and removable; According to the scope of application, it can be divided into general type, special adhesive type, medical type, low temperature type, high temperature type, etc

adhesive properties

initial viscosity: when the adhesive on the label contacts the substrate with a small pressure, the adhesion of the adhesive to the substrate is called the initial viscosity of the adhesive. After the label with high initial viscosity contacts the substrate, it immediately produces great adhesion, and it requires a certain force to remove the label. After the label with low initial viscosity contacts the surface of the substrate, the adhesion is very small, and the label is easy to be removed. Tensile test method and inclined rolling ball method can be used to determine the initial viscosity

final viscosity: when the adhesive penetrates into the surface of the substrate, the maximum adhesion that the label can get is called the final viscosity. Obtaining the maximum final viscosity depends on the strength of the adhesive, the roughness of the substrate surface, and the ambient temperature. The time to obtain the maximum viscosity after labeling is 2~24 hours. Generally speaking, there is no direct relationship between initial viscosity and final viscosity. Labels with higher initial viscosity do not necessarily have higher final viscosity

shear strength: shear strength is also known as stickiness. It is an index related to the cohesion of adhesives, indicating the softness of adhesives. Adhesives with low shear strength have a greater flow tendency, generally have a higher initial viscosity, and labels need greater tension to separate from the substrate. When the adhesive has high bonding strength, due to its high cohesion, it may have a low initial viscosity at this time, so it is easier to separate the label from the substrate

the flow degree of the adhesive not only affects its initial viscosity, but also determines the glue overflow around the label, and then affects the pollution and adhesion in the printing process. The paper feeding does not make an important contribution to the cause of China's rubber and plastic, packaging and other light industry, and the problem of double sheets. Therefore, the shear strength should be controlled within a certain range

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UV resistance: determine the adhesive's ability to not lose adhesion and change color under UV irradiation

solvent resistance: the adhesive solvent is applied in the environment with solvent and does not reduce the adhesion. Solvents include water, alcohol, solvents for petrochemical products, organic solvents, plasticizers, etc. These solvents exist in the application environment of the label or on the surface of the substrate

cold flow capacity: refers to the flow capacity of the adhesive under the condition of lower than normal temperature. Adhesives with good flow capacity are usually low-temperature or general-purpose adhesives

minimum labeling temperature: the minimum temperature of the substrate surface without losing its function. The lowest labeling temperature is determined by the "glass transition point" of the adhesive. Below the conversion point, the adhesive gradually crystallizes and hardens into a solid as the temperature decreases. The minimum labeling temperature of ordinary acrylic adhesives is 0 ℃, and the preferred minimum labeling temperature for rubber substrate adhesives with large load 5kn (1) 000kn and low frequency 0 (1) 0Hz is -25 ℃

application temperature range: refers to the temperature range in which the adhesive reaches the maximum adhesion without changing its characteristics after the label is used. For acrylic adhesives, the application temperature range is -20~120 ℃, and that for rubber substrates is -40~80 ℃. The application temperature range is the same as the surface material of the label. The surface condition of the substrate is related to the ambient temperature. Different adhesives have different application temperature ranges

permanent adhesive and removable adhesive

permanent adhesive refers to the adhesive that is difficult to peel the label as a whole without damaging the label surface. Such as self-adhesive labels and anti-counterfeiting labels for beer and most household chemicals

removable adhesive refers to the adhesive that can completely peel off the self-adhesive label and will not damage the bonded surface, such as the self-adhesive label on sunglasses

permanent and removable are actually only a relative concept. Permanent adhesives may become removable after a period of time, and removable adhesives may become permanent after a period of time. This is closely related to the performance of the adhesive, the condition of the bonding surface, the length of time and the environment of use. Finally, it should be defined through experiments

source: Shenzhen self-adhesive

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