PVC blister process common problems and solutions

Introduction to plastic absorption process

Blister is a kind of plastic processing technology, the main principle is the flat plastic sheet heated soft, vacuum adsorption on the surface of the mold, after cooling molding, widely used in plastic packaging, lighting, advertising, decoration and other industries.

Blister packaging products mainly include: blister. Tray. Blister box. Also belong to the said: vacuum hood. Blister, blister packaging equipment mainly package boast: blister forming machine. Punching machine. Sealing machine. The high frequency machine. Choosing machines. Packaging form the packing of the products can be divided into: plugins. Double blister card. Half a blister. Folded blister. Thirty percent 's shell, etc.

Blister process will be transparent plastic plate made specific protuberance of transparent plastic, cover on the surface of the product, protect and beautify the product, the ordinary plastic plate on the surface of a layer of solute material, making a solute the surface of the tray handle, used to improve the level of packaging products, the use of special process of modified materials blister tray, the material on the surface of the ohm resistance value is less than 10 of 11 times. IT is mainly used for electronic. IT products electrostatic tray.

The lowest cost of the mold used for plastic production is gypsum mold, followed by copper plating mold, and the most expensive is aluminum mold. The mold is drilled with holes, which are used for vacuum adsorption of hot plates to form plastic products.

We often talk about the blister, the use of plastic blister molding machine will be hot softening plastic sheet adsorption on the surface of the mold, cooling, forming a concave and convex plastic shape.

Blister cutting: blister packaging molding of plastic products, through the punching machine, the large sheet of material with a knife mold into a single product.

Folding edge: there is a kind of blister packaging called plug-in packaging, it is necessary to fold the three sides of the bubble shell to the back with a folding machine, so that in the next packaging process, the paper card is inserted into the folding edge, forming a card packaging.

Thermal sealing: it is a process of blister sealing. The paper card coated with blister oil and the bubble shell are also combined with the sealing machine to form the blister packaging.

High frequency sealing: a vacuum encapsulation in process with high Zhou Boji producing ultrasonic, blister and blister together, forming double blister packing, and high frequency sealing the difference is that ultrasound can not only seal PVC, PET, PETG material, also can seal PET materials, and is equipped with electromagnetic damage of packaging products, especially suitable for electronics packaging: shortcoming in ultrasonic sealing side only the interval of dot, and the general is the front cover side at a time.

Principle of PVC blister film: 

In the heating and softening process, PVC film is close to the MDF after glue spraying, and the air between the PVC film and MDF film is evacuated by vacuum, so that the PVC film is tightly pasted on the MDF by atmospheric pressure. This process is called vacuum blister film.

Characteristics of PVC blister film:

The adhesive used for vacuum blister film is vacuum blister plastic, which is mainly composed of waterborne polyurethane adhesive and mixed with other resins. In principle, hot melt adhesive and solvent adhesive can also be selected, but water-based adhesive is non-toxic, odorless, moderately priced and suitable for mechanized operation.

The biggest characteristic of this kind of craft is to need not spray paint again or coating, it is a kind of avoid lacquer craft. In addition, it can also be covered with concave and convex groove, curved surface edge, hollowing-out carving pieces, is not comparable to other processes.

Application of PVC blister film:

Vacuum blister film technology is widely used in computer table, speaker board, cabinet, door and furniture manufacturing, and a large number of applications in the automotive interior decoration processing and manufacturing.

Vacuum blister processing development is very fast, 45% of Japan's medium density fiberboard using vacuum blister coated; China's PVC composite processing of MDF has reached 30 million square meters, and the annual growth rate of more than 8%.

Vacuum suction plastic performance requirements:

Vacuum suction adopts spray sizing, so the viscosity of vacuum suction adhesive is required to be moderate, which can adapt to the changes of winter and summer weather and can achieve spray atomization. In addition, vacuum suction plastic also has the following characteristics:

(1) good flow ductility and no pitting on the surface after plasticizing.

(2) high solid content, fast drying.

(3) good initial viscosity, especially in the groove, the edge of the plastic suction is required to have a good initial viscosity.

(4) heat aging performance is good, at least at 60 ℃, 24 h after baking film no edge, no edge, no bubbles.

(5) low activation temperature, the use of waterborne polyurethane adhesive must have an activation temperature, activation temperature requirements within the scope of the 55 ~ 65 ℃, the temperature is too high, the PVC membrane perforation.

Common problems and solutions in PVC blister process 

Phenomenon 1: groove foaming 

Reason analysis:

1. The temperature or pressure does not meet the requirements, resulting in false suction;

2. Insufficient amount of glue, less amount of spraying or glue penetration of plate;

3. Insufficient preheating (softening PVC film) or plastic absorption time (molding time);

4. After the blister molding, withdraw the pressure before the temperature drops.

The glue itself is not heat-resistant enough. 

Solutions:

1. Increase temperature or vacuum;

2. Increase the sizing amount and select high-quality plates; 

3. Increase the preheating or molding time;

4. After the molding, cool to room temperature or slightly higher before withdrawing the vacuum.

5. Use with curing agent. 

Phenomenon 2: local foaming 

Reason analysis:

1. Uneven glue spraying results in a small amount of local glue and a decrease in bond strength; 

2. The problem of PVC film, PVC film contains plasticizer, in the case of aging or heat, plasticizer easy to surface migration, affecting the bond strength;

3. There is a problem with the heating pipe in the blister machine, resulting in uneven temperature.

Solutions:

1. Try to make the spray amount uniform; 

2. Use high-quality PVC film; 

3. Timely maintenance of equipment.

Phenomenon 3: edge can not absorb or shrink edge 

Reason analysis:

1. When plasticizing, the side temperature is low or the vacuum degree is insufficient;

2. Insufficient temperature resistance of glue;

3. After the blister molding, withdraw the pressure before the temperature drops.

Solutions:

1. Increase temperature or vacuum;

2. Use of curing agent;

3. After the molding, cool to room temperature or slightly higher before withdrawing the vacuum.

Phenomenon 4: blister product surface has pitting

Reason analysis: 

1. The size of the glue is large, the use of thin PVC film, easy to produce pitting, such pitting is characterized by uniform dispersion;

2. When used with curing agent, curing agent is not completely dispersed;

3. The surface of the plate is not treated clean, or after spraying glue, the workshop dust is large, stick on, this kind of pitting scattered very uneven, and different sizes;

4. Excessive viscosity of glue and uneven dispersion;

5. The viscosity of glue is too small or the solid content is low, resulting in the pilling of the plate, such pitting generally appears in the corner of the groove, into blocks.

6. The air pressure of the spray gun is not enough, and the atomization is not good.

7. The glue is not filtered (in this case, if it falls into the stolen goods or has conjunctival membrane, it should be filtered with a mesh).

Solutions:

1. Select glue with small particle size;

2. When the curing agent is added, the mixing time is prolonged to make the curing agent completely dispersed;

3. Clean the surface of the plate before spraying, and separate the spraying workshop;

4. Choose glue with suitable viscosity or high solid content;

5. After the glue is dried, it can be polished with fine sandpaper;

6. Increase vacuum degree and adjust atomization effect; 

7. Filter with a mesh when using. 

Phenomenon 5: local orange peel

Reason analysis:

1. Excessive spraying of local glue;

2. There is grease on the surface of the plate, causing shrinkage holes in the glue;

3. The curing agent is not completely dispersed, resulting in shrinkage cavity.

Solutions:

1. Spray proper amount of glue evenly;

2. Keep the surface of the plate clean;

3. Fully stir the curing agent to make it evenly dispersed.

Phenomenon 6: fold 

Reason analysis:

(1) the spacing between long and narrow workpieces is too small;

(2) edge angles around the upper surface of the backing plate are not chamfered;

(3) the horizontal and longitudinal spacing of the workpiece is not in a straight line, which increases the resistance of air flow;

(4) the temperature set is too high;

(5) it takes too long to reach the set pressure.

Phenomenon seven: PVC surface pull white

Reason analysis:

(1) the temperature set is too high;

(2) it takes too long to reach the set pressure;

(3) improper linestyle.

Phenomenon 8: the edge is not glued

Reason analysis:

(1) poor quality of glue; 

(2) the activation temperature of the glue is too high;

(3) the temperature of the equipment cannot reach the activation temperature required by the edge of the workpiece;

(4) improper workpiece pad;

(5) PVC back glue performance is not good or no back glue;

(6) the glue has expired or the storage is inconsistent with the requirements;

(7) leakage or improper glue spraying method.

Phenomenon 9: broken edge drops an Angle 

This kind of problem appears commonly, temperature appears too tall or low, time or length problem, adjust temperature and time can have ameliorative.

PVC blister film quality problems, should be in view of the above reasons to adjust the process or parameters and make a good record, do not adjust several process parameters or process at the same time, otherwise the real cause of quality problems will be difficult to identify, but also difficult to formulate and adjust the production environment process standards to provide objective basis.

 Phenomenon 10: poor adsorption

 Reason: a. the coating is too thin and uneven.

 B. Rough printing substrate and strong absorption.

 C. The absorbent oil is too thin and the absorbent force is insufficient.

 D. Insufficient temperature when heating and sealing.

 E. Influence of ink layer crystallization.

 F. The oil has deteriorated after being stored for too long.

 A. Adjust roller and coating amount.

 B. Replace the printing substrate or oil the substrate first.

 C. Replace the absorbent oil or increase the coating amount.

 D. Increase the temperature of sealing.

 E. Wipe the surface of the printed matter or dilute it with 5% lactic acid before applying the blister oil.

 F. Replace the absorbent oil.

 Phenomenon 11: grinding surface no luster

 Reason: a. the absorbent oil is too thin and the coating is too thin.

 B. Excessive dilution and too many non-participating solvents.

 C. High viscosity and flow adjustment.

 D. Low drying temperature and poor film forming quality.

Solution: a. increase the amount of coating.

 B. Try not to add dilution and use the original solution.

 C. Reduce the amount of coating.

 D. Appropriately raise the drying temperature.

[attachment] explanation of terms of postpress processing

1. Post-printing processing: in order to meet the requirements of use and improve the appearance quality after printing, a series of processing and manufacturing processes are carried out for the substrate.

2. Glazing: striation theory, the essence of printed matter glazing is glazing coating on the surface of printed matter leveling, through the coating leveling change paper surface gloss physical properties. 

3. Film covering: the process of covering the surface of printed matter with polymer film and applying adhesive to heat and pressure to make it stick together. 

4. Hot foil: the process of transferring metal foil or pigment foil to the surface of printed matter or other products by hot pressing.

5. Die cutting: the process of forming the steel blade into a mold or frame (or engraving the model with steel plate) and rolling and cutting the printed matter into a certain shape on the die cutting machine.

 6. Indentation: the use of steel wire, through the indentation, on paper or printed matter, or left for bending groove marks.

7. Concave and convex embossing: use Yin (concave), Yang (convex) mold, mechanical action to impose more than the elastic limit of the substrate of the presswork, so that the presswork form concave and convex three-dimensional effect of the processing process.

8. Layout heart: remove the white edges around the book into the layout, and the rest of the text and pictures are the layout heart, which is the effective area to accommodate the text and pictures.

9. Book center: the semi-finished product of the folded book stickers arranged according to their order.

10 spine :(and the back of the two edges and corners) that is, the surface of the book block and the back of the connection, but also hardcover books and periodicals before and after the shell and the back of the connection.

11 book back: also known as the back, refers to the book paste with glaze to be glued to the flush part.

12 floating mouth: the cover of the book block more than the edge called floating mouth.

13. Clogging cloth: also known as clogging cloth, rope head or flower cloth head, is a kind of cloth made by processing with line edges.

 14. Tiantou: the upper space of the book layout is called tiantou.

 15. Footer: the lower margin of the book layout is called footer.

 16. Front edge: also known as the edge or edge edge, refers to the position of the edge of the sewing seam relative to the edge of the hairline reading.

17. Bookbinding: close to the bookbinding space called bookbinding; The other side is called the incision.