The most popular self-adhesive label adhesive that

2022-07-24
  • Detail

Adhesive for self-adhesive labels

the adhesive for self-adhesive labels is the medium between the label material and the bonding substrate, playing the role of connection. The adhesive can be divided into permanent and removable according to its characteristics. The adhesive has a variety of formulas suitable for different surface materials and service 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

generally, tape coating method is used for adhesive. Its basic principle is to inject adhesive through the pressure in the cavity of the cloth head. The top of the cloth head is an adjustable slit. During coating, the adhesive flows out of the slit of the cloth head and is coated on the surface of the bottom paper with the operation of the bottom 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 3G. 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 adhesive force of the material. Within a certain range, the adhesive force is directly proportional to the coating amount. The coating amount of adhesive is too large or 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 reels will stick together or the sheets of paper will stick together, resulting in waste products

difficult slitting: the blade is easy to stick to the data error surface and end face of the paper pressure tester, which brings hidden dangers to the printing process

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

after a 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. Better service

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 the supermarket requires a small coating amount. However, if you need to stick to a special surface 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 adhesive, solvent adhesive and emulsion adhesive; According to the chemical composition, it can be divided into: rubber substrate and acrylic acid; It can be divided into permanent type and removable type according to bonding characteristics; According to the application scope, 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 a great adhesion. 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 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 can be obtained by the label 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. After labeling, it is expected to start mass production and sales in 2017; The time for obtaining the maximum viscosity at the same time is 2~24 hours. In general, there is no direct relationship between initial viscosity and final viscosity. Labels with a higher initial viscosity do not necessarily have a higher final viscosity

shear strength: shear strength is also known as stickiness. It is an index of adhesive cohesion and indicates the softness of adhesive. The adhesive with low shear strength has a greater flow tendency, generally has a higher initial viscosity, and the label separation from the substrate requires greater tension. When the adhesive has a 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, which in turn affects the problems of pollution, adhesion, adverse paper feeding and double sheets in the printing process. Therefore, the shear strength should be controlled within a certain range

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

solvent resistance: the ability of the adhesive solvent to be applied in the solvent environment without reducing 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. When the stress of Common Acrylic reaches a value, the minimum labeling temperature of adhesive is 0 ℃, and the minimum labeling temperature of rubber substrate adhesive 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 ℃. Apply surface materials with the same temperature range as 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 off the label as a whole without damaging the label surface. Such as self-adhesive labels and anti-counterfeiting labels for beer and most daily chemical products

removable adhesive refers to the adhesive that can completely peel off the self-adhesive label without damaging the bonded surface, such as the self-adhesive label on sunglasses

permanence and removability are actually a relative concept. The permanent adhesive may become removable after a period of time, and the removable adhesive 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 use environment. Finally, it should be defined by test

Copyright © 2011 JIN SHI