Paper-plastic composite common faults and causes

Paper-plastic composite products require firm bonding, and the surface is clean, smooth, smooth, free from blistering, curling, loss of film, and film. There are many factors that affect the quality of composites, both objective and subjective. It relates to the environmental factors of the operation site (indoor temperature, humidity, dust, etc.) as well as the factors of the product itself (ink used, paper type, printing method, etc.), and adhesives and films used in combination with paper and plastic. As well as the process conditions, operation methods and laminating machine structure, technical performance, etc. have a close relationship, the need for comprehensive analysis.

First, the adhesive fastness of composite products

The factors affecting the bond fastness of composites are roughly: the adhesive strength of the adhesive itself, the adhesiveness of the adhesive and the film, the paper and the ink layer, the condition of the adhesive layer, and the operating conditions.

1. The adhesive strength of glue depends on the production process formula of the raw material machine for the glue, and the solid content of the adhesive film. Some products have good adhesion after being compounded, and release after a period of time, that is, the film is detached from the paper, separated by hand and peeled off, and even with a fingernail on the surface of the film, the crease film and the paper The face is peeled off, or the composite product is folded on the film surface, the film is peeled off from the paper surface in the crease, or the composite product is curled on the film surface, and the film is also released from the paper surface. These phenomena show that the adhesive force of the adhesive is ineffective due to the external natural conditions.

2. The effect of the affinity of the glue and the film on the composite fastness

The chemical structure of the composite polypropylene film itself does not have an active gene and is a non-polar substance. It has poor affinity for the glue and causes difficulties in the adhesion of the surface. Therefore, the film is subjected to corona treatment to make its surface product unsaturated double bond and carbon base, so that its surface energy has an active gene, and as a result, the surface roughness of the film is increased, which is favorable for the coating of the glue. The corona-treated film, a change in the nature of the film surface, is converted from a non-polar substance to a polar substance, which is advantageous to improve the affinity between the film and the adhesive. However, the corona-treated film has a period of time that will fade after a long period of time. The data is presented as 6 months. The failure of the membrane surface tension decreases, and the data is presented below 39 dyne/cm2. How to identify the inside of the film corona and corona treatment failure? Here are two methods.

(1) Use a fountain pen to write or scribing a film on the surface of the film. The surface on which the ink is easily stained is the corona treated surface. If the water does not shrink or beaded and it is not easily rubbed off, the corona treated surface has not failed.

(2) 38mn/m surface tension indicating agent: 54g of formamide and 46g of ethylene glycol ether were tested later. If the indicator does not shrink by itself within two seconds, the corona treatment is considered to be acceptable.

3. The effect of the affinity of glue and paper on the composite fastness.

Paper is a kind of porous material made by intertwining plant fibers. It fills the cavity and improves the water resistance of the paper by sizing to make up for the surface defects. In order to improve the smoothness and smoothness of the surface, a layer of paint is applied on the surface of the paper, which is formed by calendering or supercalendering.

There are many types of paper used in printed matters, and printed products such as white cardboard, coated paper and glass cardboard are generally used for laminating. To classify them, one type is the paper structure is relatively close, the surface is relatively flat, such as coated paper, cellophane. The other is a loose paper structure, rough surface, such as white paper. Its internal structure is similar to the first type, and its surface condition is near the first type. When the adhesive layer and the paper are compressed, the poor fastness of the surface of the paper is poor. The high point of the paper is combined with the glue, while the low blemish is not glued, and the glue layer is combined with the paper surface in point contact. For papers with high surface smoothness and high composite fastness, the adhesive layer and the paper surface are basically combined in point contact, and more glue is in contact with the paper surface. For structurally loose paper, the release paper is easily removed by the adhesive layer. Therefore, during the use process, the size of the glue should be adjusted according to the paper, so as to fill the unevenness of the surface of the paper and improve the adhesive fastness.

4. The effect of the affinity of glue and ink on the fastness of the composite

Water-based laminating adhesive not only adheres firmly to the film, but also adheres firmly to the paper and ink layers. The adhesive must adapt to these three different materials at the same time so that the film and the paper surface and the ink layer are both good. The combination together.

The affinity of glue and ink layers is more complex than glue and film, glue and paper. The ink used at present is basically a resin type. Ink tests a complex mixture of pigments, binders, and auxiliary materials to improve ink properties to suit printing requirements. The plain printing products generally use spot color inks to print. The color of the printed products has the size of the dots, which are juxtaposed and overlapped. The ink layer is thin, and the color of the embossed products is printed after being mixed with various colors and inks. The ink layer is thicker. From the ink layer structure, embossing is more complicated than plain printing. The internal structure of the printed ink layer, that is, the chemical properties of the ink is mainly related to the blistering phenomenon of the film. The black surface condition is related to the affinity of the glue, which is related to the fastness of the glue, as can be seen from the following points.

(1) The particles of the ink are large, that is, the particles of the pigment are large, and the age of the rubber and the ink layer is reasonably poor. Such as silver ink and gold ink, which aluminum powder, copper powder particles larger than the average ink particles much larger. It adheres to the surface of the ink layer in a granular form, and emits silver light or gold light obliquely by light. The adhesive layer is in contact with the silver ink and the gold ink layer in a point contact manner, resulting in poor adhesion and easy peeling. Domestically produced silver ink and gold ink particles are larger than the imported ones and they are even more pronounced. At the same time, for the combination of gold and silver inks, the water-based adhesive is a porous adhesive, which has a wetting effect on the ink and reflects the background color. Therefore, in the complex gold film should look at the background color.

(2) Prints with poor paper flatness cannot be filled with flat ink because of a thin layer of ink, so that the surface of the ink layer will be uneven with the situation. The ink on the plain print is thinner than the print, and the unevenness on the surface of the ink is more obvious. The adhesiveness of the glue and the ink layer of this composite product may be inferior.

(3) The high surface smoothness of the ink layer is also not conducive to the firm adhesion between the ink and the ink layer. Some prints have been left for a long time, and the surface of the film has crystallized to form a layer of vitreous. It is hard and smooth. The glue does not wet the affinity with each other, resulting in poor adhesion and severe separation. .

(4) A large picture of the ink layer, the affinity of the sizing layer and the ink layer is slightly worse than the paper, and it also affects the fastness of the bonding. Some full-size pictures of real or dot prints, all of the adhesive layers are in contact with the ink layer, and when the printed matter has large ink particles and uneven ink layers, the adhesive fastness is even worse. Therefore, when there is a full-size print composite, it is necessary to ensure the solid content of the adhesive layer and appropriately increase the thickness of the adhesive layer.

5. Effect of adhesive layer condition on composite fastness

The adhesive layer condition refers to the thickness and evenness of the adhesive layer. Obviously, the adhesive layer is good for the fastness of bonding. In the operation, it is necessary to keep the adhesive layer uniform, and the thickness of the adhesive layer should be grasped according to the actual situation. In principle, the thinnest glue layer is controlled on the premise that the composite product is firmly bonded.

(1) The effect of the thickness of the adhesive layer on the composite product

When the viscosity of the glue is constant, the thicker the adhesive layer and the more solid content, the higher the adhesive force, but the thicker the better. When the glue is too thick, the active ingredients in the glue cannot be played normally, which may easily result in a poor affinity between the paper and the ink, resulting in a poor effect of ink extraction.

(2) The effect of the uniformity of the adhesive layer on the composite fastness

If the adhesive layer is not uniform, there is an inconsistency in thickness and a difference in adhesive fastness will result. In the case where the adhesive layer does not vary uniformly, the adhesive fastness at the thin glue is poor, and the thick glue is relatively good. In the case where the adhesive layer is not uniformly varied, paper and ink will be separated from the thin glue.

(3) Causes of non-uniformity of adhesive layer

A: The adjustment of the gluing machine is correct or not.

B: Whether the gluing mechanism is damaged or not.

C: Is the machine running at a uniform speed?

Second, the composite surface has "snow"

Aqueous laminating machine and oil laminating machine, the working principle is not the same, water laminating machine belongs to low temperature, pressure (usually laminating film to the surface of the composite product without blistering aisle), while the oil laminating machine belongs to high temperature and high pressure.

1, as the print more and more exquisite, some designers to design a print propaganda novelty, resulting in print full or multiple spot color printing ink layer thickness. In order to prevent the printing surface from sticking, or to shorten the curing time of the film layer, the printing press operator uses a quick-drying oil, or increases the amount of ink, dry oil, and the amount of powder to be sprayed. It has brought great difficulties to filming. As a result, there are spots of snow after laminating of the printed matter. In case of laminating, it is required to wipe the powder or the alcohol on the surface of the printed matter.

2. The amount of glue is too small to cover the thicker surface of the printed matter.

3, laminating machine pressure roller pressure is too small to cause print and glue can not be fully integrated.

Third, the composite product curled uneven

1, the film tension is too large. When the tension during production is too large, the stress recovers after slitting, causing shrinkage.

2, the paper is too wet, the paper density is not enough

3, winding tension is too large to pull the film deformation.

4. The storage time after winding is too long. After the film and paper are compounded, the glue curing time is too long.

Fourth, the distance between the overlap of cardboard film at a large distance

1, the winding tension is too large film pull deformation.

2, pressure roller pressure is too small.

3, cardboard density is not enough deformation after absorption.

4. The speed of the lamination roller is inconsistent with the speed of the transfer board.

5. The film unwinding device is too tight and the film tension is too great.

Fifth, the composite product appears discolored

1, too much glue on the plastic tile.

2. The pH of the enamel tile is alkaline.

3. The moisture absorption of the plastic tile causes discoloration of the chemical reaction, causing it to fall off in severe cases.