Release paper is used in many industries today. As a used person, it is not always possible to choose a suitable release paper. Today, Xiaobian will discuss with you some common problems already exist. For many years, there are already relatively reliable ways to prevent and resolve them. This section is dedicated to explaining the causes of these common problems and providing some advice to avoid or correct them.


1, film reverse transfer


When the adhesive is not on the correct side of the substrate, the film reverse transfer occurs; due to the peeling of the adhesive, unwinding may occur. The reverse transfer of the film may be caused by the following factors: adhesive bleed, uneven moisture content, improper winding tension, insufficient curing or release force of the release material is not wide enough.




2, foaming / blisters


Foaming is a phenomenon of damage on the surface of substrates, coatings, adhesive coatings, and the like. Foaming typically occurs when liquids such as water or organic solvents, or gases such as air, swell faster than the entire system is capable of dissipating its increased volume and pressure. For example, if the double-sided PEK release paper is heated to an excessively high temperature, the PE will soften, and when the vapor pressure of the moisture in the paper is sufficiently high, bubbles will form in the PE, also for releasing the pressure.


Foaming can be caused by the following reasons:


- overheating


- The penetration/dissipation of the liquid/vapor components of the system is limited


- Evaporation of solvent or water


The following practices can minimize bubbles:


- lower the maximum temperature


- Reduce heating rate


- Use a breathable, water permeable, release material


3, adhesion


When the layers of the release material are fused together, it is difficult to unwind without damaging the paper or using high unwinding tension, at which point adhesion has often occurred. Adhesion may only occur on a certain part of the paper such as the edge, or a whole sheet of paper, and can be caused by many different mechanisms.


- Insufficient curing of silicone oil


- uneven moisture content


- Excessive winding tension


- chemical pollution


- Insufficient release force


There are many different ways to prevent it:


- Increase the degree of cure


- Reduce environmental humidity and improve storage conditions


- Reduce tension by reducing press roll pressure, increasing winding tension taper or reducing torque


Many people also use noise as an indicator of adhesion. This method is very subjective and does not determine adhesion because of the inherent "slip" or "adsorption" properties of certain coatings.


4, delamination


Delamination means that the layers that are mechanically or chemically bonded together are separated at the interface. Delamination can occur at the interface of the PE with the paper or at the interface of the adhesive with the silicone oil.


Usually delamination is a problem with materials and interfaces. For example, delamination of PEK coated release paper is due to poor surface treatment before PE coating. The delamination of the adhesive may be due to the silicone oil being too easily peeled off.


Delamination may be caused by the following reasons:


- Improper flame or chemical surface treatment.


- Internal adhesion difference


- poor internal bond between fibers


- Improper release force of silicone oil coating (too light)


The delamination can be corrected by the following methods:


- Improve surface treatment


- Improve the internal bonding of the substrate


- Increase the release force of silicone oil coating


5, dimensional stability


Dimensional stability refers to the ability of a material to resist dimensional changes when exposed to external forces, such as moisture, high temperatures, or physical stress. All materials exhibit some dimensional changes when exposed to these external forces. The question is how to control the extent of the change to ensure that the quality of the product is not affected during processing and use.


For paper, the change in moisture profit and loss is a major problem. It can cause problems with curling of the paper, curling or flatness. The dimensional stability of paper is controlled by many factors. Among them are fiber type and percentage, degree of refining, adhesion between fibers, filler content, sizing type and amount, fiber orientation, drying process, sheet density and texture. Subsequent processing also affects the dimensional stability of the release paper.


Dimensional stability is also a factor in the release film. However, it is caused by thermal stress. Exposing the release film to a high temperature environment, especially under tension, may cause shrinkage, stretching, and even severe deformation.


Factors affecting dimensional stability are:


- Change in humidity


- Initial moisture content of the paper during production


- Percentage and type of pulp


- Paper drying process


- Fiber freeness


- Filler content


- Sheet density and construction




6, poor film and paper sag


When the tension of the substrate on the paper is uneven, the paper/film sagging is poor. Because the lengths of the incremental strips of the entire paper are not equal, different tensions occur.


Poor sag of the film and paper is a property that is produced during the processing of the substrate. The film can be cooled or minimized by cooling treatment.


The causes of poor sagging are as follows:


- uneven paper thickness


- Winding too tight


- Uneven thickness of surface winding


- Improper stretching


- improper drying


Corrective remedies include the following:


- Reduce thickness difference


- Rewinding using the slide axis mode


- Adjust the stretching device to obtain a uniform paper tension


- Reduce oven temperature gradient


7, flatness


Flatness is generally considered to be the ability of the release paper or finished structure to resist curling when humidity changes. This is fundamentally related to the dimensional stability of the release paper. However, other factors, such as improper tension during compounding, shrinkage of the facestock, exposure to high temperatures or roller settings, can cause curling or flatness problems.


The flatness can be optimized by the following methods:


- Use dimensionally stable release paper


- Suitable machine tension when compounding


- Minimize the shrinkage of the facestock


- Avoid exposure to high temperatures


8, moisture folds


Most of the paper is made from fiber pulp dispersed in water. Most of the water is removed during the manufacturing process. However, the paper retains the ability to absorb or dissipate large amounts of moisture during additional handling or storage. Water absorption often results in moisture wrinkling, particularly in the outer portion of a roll of paper or paper substrate product.


Kaolin coated paper, ultra-calendered kraft paper and PE coated paper will lose or absorb moisture during hot processing or storage if improperly packaged. Papers with low water content absorb moisture very quickly, often resulting in moisture wrinkles on the outer layer. Rewetting the paper after the thermal processing step will minimize the likelihood of wrinkles due to subsequent moisture uptake. Proper moisture-proof packaging and storage conditions are also important.


Moisture wrinkles can be caused by the following reasons:


- The paper is excessively dry during processing


- Prolonged exposure to low humidity


- Prolonged exposure to very high humidity environments


The following methods can minimize or even eliminate these effects:


- Rewind the paper roll after hot processing


- Control the storage environment and use moisture-proof packaging


9, scratches


Scratches are physical wear that occurs on the surface of the release material after contact with a relatively non-uniform material. Scratches occur when the line speed and surface finish do not match. As a result, the softer surface can be damaged, usually the surface of the coating or substrate. Scratches may also occur when the machine slides longitudinally or laterally due to uneven tension throughout the process. Appropriate roll alignment and tension control must be performed during processing.


Scratches are caused by the following reasons:


- Difference between line speed and substrate speed


- Large and rapid changes in surface topography


- Idler misalignment and tension setting error


Scratches can be eliminated by:


- Paper speed matches idler speed


- uniform surface topography


- Unify paper tension throughout the process


- Good machine benchmark


10, silicone oil transfer


Silicon oil transfer is the transfer of a silicone oil coating from one surface to another. This transfer is usually caused by the non-reactive component of the silicone oil coating or the insufficient curing of the silicone oil. Silicone oil transfer typically occurs on the back side of the substrate or on the surface of the adhesive. Transfer can be detected by changes in the surface energy of the back side of the substrate. The photoelectron spectroscopy test (ESCA) and subsequent adhesion testing of metal sheets is an additional method to determine the transfer of silicone oil to the adhesive.


Silicon oil transfer is caused by the following reasons:


- Insufficient curing of silicone oil


- Excessive or insufficient surface treatment


- Excessive winding pressure


- Non-reactive silicone polymer


The following methods can reduce silicone oil transfer:


- Enhance the curing level of silicone oil


- determine that the surface energy of the coating is sufficient; the surface energy level should not be too high


- Reduce the winding tension


11, static electricity


Electrostatic refers to the static charge that builds up on the surface of the substrate. They can be positive or negative.


When two different surfaces are separated (triboelectric effect), the charge is transferred from one surface to the other, thus generating static electricity. Pressure, friction, line speed, humidity, and surface smoothness all affect the magnitude of electron generation and transmission.


If static control equipment is not used during processing, the roll surface voltage can often exceed 50,000 volts. Corona discharge occurs at a potential level of 4000 volts or less based on the distance between the charges. Therefore, if the line potential does not drop to an acceptable level, there is a physical hazard to both the operator and the equipment. Corona discharge also affects the humidity and continuity of the coating. If it is coated with silicone oil, it will cause poor release.


Static electricity can be controlled by:


- The surface of the substrate is as close as possible to the static elimination device


- Increase humidity level (surface moisture)


- Use passive and air assisted ionization rods and blowers




12, folds


Pleats are defined as the lateral folding of the paper. Folding occurs because of uneven tension distribution and lateral edge misalignment failure. Typically, wrinkles are divided into hard folds and soft folds. The effect of wrinkles varies from application to application.


The main causes of wrinkles are:


- Insufficient tension in the transverse machine.


- Traction loss between paper and idler


- Machine benchmark difference


- Poor substrate sag


The corrective actions for the above problems are:


- Apply a stretch roll


- Improved edge guiding device to keep the paper even


- Check the machine reference, it is necessary to use optical alignment


How to choose a release paper


1. Characteristics of the products prepared: The tapes commonly used in China are Sanzhi of South Korea, Nitto of Japan, and M of the United States. Because different tapes have different glue characteristics. This determines that we should consider this aspect when choosing silicone paper.


2, cost: domestic and imported silicone oil paper is very different, generally speaking, the domestic silicone oil paper mouth beer is not very good. In particular, it is reflected in the tape of the Mi M and the tape of Nitto. It is often foggy or the release is too low, and it is not possible to tear the yellow silicone paper and the product very well. Only domestic silicone paper is definitely cheaper than imported. And there is a big price ratio. If you consider that the company's products are used for export, it is of course best to use imported silicone paper, which will be smoother in customs clearance. Due to the production equipment and production level of domestic silicone oil paper. It determines the instability of domestic silicone paper on some products, and the serious consequence is that it will cause waste of tape.


3, production procedures: The focus here is whether to stamp or cut, generally involves the thickness of silicone oil paper when stamping or cutting, because low-gram weight silicone oil release paper is not easy to break when used for stamping, of course, This is also related to the fragility of the base paper, which can tear the paper and the product apart during stamping or cutting. Can't achieve the ideal or the desired effect.


4. Usage: This is mainly reflected in the fact that some products only need to maintain the balance of the product during transportation, then it will require that the product and the silicone oil release paper are not easy to fall when combined.