Also known as shrink labels. Currently commonly used materials are mainly PVC, PET, OPS three kinds, are transverse high shrinkage labeling, in the form of sleeve sleeve labeling; other small number of applications are OPP longitudinal shrinkage around the sticker labeling, as well as PLA biodegradable materials shrinkage sleeve labeling. Commonly used printing processes are gravure printing, flexographic printing, digital printing.

During the packaging, distribution and use of products, labels need to withstand the test of resistance to the contents, the test of the transportation environment on the label material, and the test of the customer's use process.

Influence of contents

When the contents are acidic, alkaline, or corrosive to the material, the risk of leakage during filling and the risk of leakage during use by the customer must be taken into account, resulting in damage to the label.

Therefore, we try our best to choose the material with better resistance to the content as the substrate of the label.

Transportation and use of the environmental impact of the relationship

From the shrinkage of the label before the transport environment on the label material constraints on the impact and the label shrinkage of the finished product after the transport of the label performance requirements of both to analyze.

Shrinkage before the main environmental temperature changes on the test of the material, if the label storage and transportation environment temperature exceeds 25 ℃, and there is no thermostatic control, it is relatively easy to cause the natural shrinkage of the label deformation, resulting in the inability to normal use.

Shrinkage in the transportation of mutual impact, wear and tear and final sales of containers and labels in the pre-heating treatment of the test of the material.

Heat shrink labels in addition to heat shrinkage, there is also a certain natural shrinkage phenomenon at room temperature. The so-called natural shrinkage that is, the material in the natural conditions of storage, the material will also occur to a certain degree of contraction.

The same material is mainly with the low-temperature (60 ℃ ~ 70 ℃) under the conditions of the shrinkage rate and the stability of the material itself has a lot to do with the low-temperature conditions, the greater the shrinkage rate of the natural shrinkage is more obvious.

In terms of material type, OPS has the largest natural shrinkage rate among several heat shrinkable labeling materials, followed by PVC, and PET is one of the materials with the smallest natural shrinkage rate.

Natural Shrinkage

There is a recommended method for evaluating natural shrinkage:

Same as the measurement of shrinkage rate, the test sample will be under the condition of constant temperature water bath at 30℃ or 40℃ for 7X24 hours continuously, and then observe the change of its shrinkage rate.

When the label needs to be transported over a long distance and time, as well as the product production cycle spanning a large time also need to properly consider the relationship between the impact of transportation and storage safety, such as can not be changed to choose the type of material, then in the high temperature season must be taken to take certain protective measures for distribution and storage.

Common storage conditions

The following two storage conditions are recommended for commonly used heat shrink labeling materials:

(1) Store at a constant temperature below 25°C and away from heat sources; (2) Keep out of direct sunlight.

For transportation can be based on the transport distance for a long time to make slightly flexible arrangements, for example: transport trips within 6 hours in the maximum temperature of 35 ℃ in the following high temperature season can be taken to the direct distribution of the evening delivery mode of transportation; the maximum temperature of 30 ~ 35 ℃ and the distance of more than 6 hours and the maximum temperature is higher than 35 ℃ or more, it is recommended to take the distribution of thermostatic box trucks.

In the labeling of storage links need to pay special attention to the temperature management of the constant temperature room, and the balance of the ambient temperature. From the above comparison chart can be clearly seen in the OPS sensitivity to ambient temperature, so in the storage link needs to be more concerned about the storage conditions of the OPS class labeling, such as in the constant temperature below 25 ℃ below the light-sheltered storage room, due to the refrigeration equipment placed in the wrong location or power is not enough to easily cause the regional differences in ambient temperatures, close to the refrigeration equipment temperature is low, far away from the regional temperature will be high, which also will This will also lead to obvious natural contraction of the label.

By the same token, when the production line from the thermostatic warehouse will be labeled to the production site to use, but also must pay attention to the site of the amount of spare labels to control the general recommendation not to exceed the amount of 4 hours, rather than to take a number of times less to lead, hard to lead the way of management of the hard to return, because the temperature of the production site will not usually be lower than the outside world of the natural conditions of the temperature. In the field of temporary spare labels stored in the location need to pay attention to stay away from some heat generating equipment (such as: high-power motors, heat shrink channels, steam pipes, etc.), and is strictly prohibited from being exposed to sunlight.

By the same token, when the production line from the thermostatic warehouse will be labeled to the production site to use, but also must pay attention to the site of the amount of spare labels to control the general recommendation not to exceed the amount of 4 hours, rather than to take a number of times less than the collar, diligently lead to the diligent way of management, because the production site of the temperature will not usually be lower than the outside world of the natural conditions of the temperature. In the field of temporary spare labels stored in the location need to pay attention to stay away from some heat generating equipment (such as: high-power motors, heat shrink channels, steam pipes, etc.), and is strictly prohibited from being exposed to sunlight.

Shrinkage after shaping in the finished product transportation and distribution links, due to the bumps in the transportation of the impact of the label will produce wear and tear and damage, which is also an important factor in the selection of materials must be considered in the design of the label. Material density and surface strength is different, its ability to resist wear and impact also varies greatly. In PVC, PET, OPS three commonly used labeling materials, PVC and PET surface strength is comparable, OPS is obviously much weaker. In order to overcome the shortcomings of the weak surface strength of OPS, we can make up for them by coating the surface with anti-injury varnish and improving the thickness of the substrate. The PET/OPS/PET co-extruded material was developed by combining the abrasion and impact resistance of PET with the good shrinkage properties of OPS.

The end customer use of special handling requirements for labeling performance. For example, in the winter dairy products, coffee drinks and other products that need to be heated, the surface of the heat shrink labeling film can withstand the test of preheating temperature is also a problem that designers should not be ignored. For example, PVC material in the 80 ℃ above the high temperature cooking for about 1 minute, the material will occur whitening phenomenon, that is, the transparent film becomes white, transparency will be significantly reduced; In addition, the OPS material in the second preheating is prone to overstretching and even the hole phenomenon, and PET in the resistance to high temperatures performs well.

The application of a small contraction label involved from the material, content, containers, equipment to the circulation of various processes, and in the actual industrialized production process of production efficiency, yield, automation and other aspects of the requirements of the label and the other elements of the match between the choice, so it is difficult to give a universal judging principle. But this is not completely out of the way, according to the labeling application scenarios we can make some sense of this idea. First of all, according to the characteristics of the container to determine the necessary conditions of the label (such as the maximum shrinkage rate, material resistance), combined with the specific needs of the product packaging to choose to match the sufficient conditions (such as channel equipment, storage and transportation conditions).