1 Types of coating and process flow
According to different equipments and processes, coatings are divided into two categories, one is "coated film" and the other is "pre-coated film"; there are two types of sub-film and sub-film.
1.1 Instant film
Instant-coated film is a process that uses instant-coated film machine to stick film immediately with glue to carry out paper-plastic compounding. It is mainly produced by a coating film processing plant or a processing workshop, and the roll plastic film is coated with an adhesive according to needs, dried (slightly) compounded, and pressed to stick the paper film together to form a film product. That is, there are two types of film coating equipment: automatic and semi-automatic. The basic working principles are the same; the process flow mainly includes unwinding → sizing and coating → drying → compounding → slitting → product accumulation.
â‘ Unwinding â‘¡Glue coating A, roller reversal type; B, concave type; C, no blade roller extrusion; D, direct blade type.
â‘¢Dry A, evaporate; B, heat; C, remove the solvent.
â‘£Compound A, hot pressing roller; B, rubber pressure roller; C, pressure adjustment.
⑤Print input ⑥Recover and accumulate
1.2 Pre-coating film
The pre-coating film is a process of rewinding the plastic film on the plastic film in advance and then compounding it with paper prints. The pre-coated film is pre-coated by the pre-coated film processing plant according to the difference in the size of the application format. The glue is coated and rewinded, and then used by the factory to select and then compound with the printed paper.
The pre-coating film process flow is mainly pre-glue → roll up → glue coat (hanging type) → solidification and cooling → rewinding → slitting → rewinding → finished product packaging. Pre-coating machine: temperature adjustment → winding → paper feeding → heating → composite → slitting → automatic stacking → finished product.
There are three types of pre-coated film: thermal film, pressure sensitive film and special film. The binding is mainly used in two kinds of thermal film: BOPP, PET (the other is N nylon).
2 The "heat" of the coating film should "cool down"
In the past 10 years, the coating film has been popular all over the country, and the enthusiasm has reached an unmanageable level. Once the film coating equipment is installed everywhere; regardless of the hardcover, paperback, and saddle stitching of the cover of the book, no matter the paper quality This process is also increasingly used for surface decoration of printed matter. However, in these years, the quality problem of the binding film has not been resolved, so the economic losses caused by it have occurred from time to time; more importantly, the hazards caused by the coating film have not been fully understood. Below we briefly analyze the advantages and disadvantages of this process technology.
2.1 Seeing "profit" so I used "hot"
(1) Using instant film as the cover can protect the paper. After the film is coated, the service life of the cover (or the surface of the printed product) can be extended, especially for the students' textbooks, so the dosage is getting larger and larger.
(2) Imprints are not easily destroyed. After being coated with the instant coating film, it can increase the color effect and protect the color printed graphics without being worn. This is conducive to publishing house editors to make various art designs on the cover or printed surface according to their needs, so it also promotes the increase in usage.
(3) The production of coating film is beneficial. The production cost of the coating film in the cover film is low, easy to start, and profitable, and the enterprise can benefit.
The above three points make the instant coating film "hot", but the quality problems of the instant coating film and the impact on the binding quality, but few people pay attention to it, the following will further analyze this.
2.2 The quality problems of using instant coating film
The main problems with the covers and sheets after being coated with instant coating are:
The blistering, wrinkling, uneven bending, peeling and separation, and difficulty in storage, etc. These quality problems have not been solved for many years, and there are many reasons, such as:
â‘ The influence of different paper types.
â‘¡The influence of different ink colors.
â‘¢The influence of different climates.
â‘£The influence of environment and conditions.
⑤ Enterprises lack the influence of scientific management.
â‘¥ Influence of personnel quality.
2.3 Two major harms of coating film
The use of ready-to-coat films not only makes many quality problems difficult to solve, but more seriously, it has two major harms that cannot be tolerated.
â‘ Even if the coating film will cause white pollution A, the film cannot be corrupted in the air, and it is difficult to recycle and cause environmental pollution.
B. The coating film adhesive intervenes in harmful objects, which is harmful to people's health, and long-term use will seriously harm workers' bodies.
â‘¡ The coated paper cannot be recycled, wasting resources
At present, 80% of the sources of papermaking cellulose in China depend on the recovery of waste paper, including paper edge paper wool and so on. The amount of paper used in books, periodicals, etc. is very large. If we use a large number of coatings, especially coating materials, and can not separate the paper from the plastic film, then the coated waste paper and paper edge paper wool will not Recycling will bring incalculable losses to the country and actually waste resources.
The comparison of the advantages and disadvantages of the coating film is enough to prove that the "heat" of the coating film should be reduced to the point that it must be "cold".
3 Advantages of pre-coating film and future development trend
The advantages of pre-coated film compared with ready-to-coated film are:
(1) Less pollution, no harm to human body.
(2) There is no difference in paper properties that affects the quality.
(3) There is no difference in ink color that affects the coating effect.
(4) There is no influence of the use of adhesive with wireless perfect binding.
(5) The laminating machine with pre-coating film is easy to operate and easy to process.
(6) The graphics after processing are more beautiful and the effect is good.
(7) Basically eliminate wrinkles, bubbles, and shedding.
(8) It has a wide range of applications and can be used for lamination processing other than printed products.
In view of the above advantages of the pre-coating film and the current printing process can not get rid of the coating technology, it can be concluded that the pre-coating film will be the process technology for future development.
The pre-coating film began to be used in 1989, mainly used in European and American countries. Entering Asia in 1996, at the same time as entering Asia, Europe and the United States announced a ban on the use of ready-to-coat films, and changed to using pre-coating films. Japan has basically switched to pre-coated films, and other countries such as China, South Korea, and some countries in Southeast Asia are in the state of using both pre-coated films and pre-coated films. China has only officially started to use pre-coated films after 2000. The development situation tells us that the coating process will definitely be eliminated in a short time, and the pre-coating process technology will replace it. Once the pre-coating film is completely replaced by the pre-coating film, the immediate-coating film will be eliminated, which will eliminate a larger source of pollution for our country and the world.
Of course, there is still a process to eliminate the instant coating film. This process is the transformation of people's consciousness. As long as the harm of the instant coating film is recognized and the importance to the human environment protection, it will accelerate the change and make our print And the surface decoration technology of articles has been improved to a new historical stage, as soon as possible in line with international standards, and included in the ranks of the international advanced level.
In order to solve another problem of the film coating process as soon as possible, that is, there is no paper film separation device in China at present, the paper after the film is temporarily unable to realize paper recycling, we can take two methods for this, one is to seek foreign advanced technology; Second, according to the EVA hot melt adhesive used in the pre-coating film is a kind of re-adhesive adhesive material, as long as it is heated to the melting point, it can be separated and fallen off. Solve the worries brought by the laminating process, so that China's paper recycling rate reaches the international advanced indicators, creating a better tomorrow for mankind. The development of post-press technology will be a future of automation, diversification, informatization, digitization, and environmental protection. Let us work together and make more contributions to create this beautiful future.
4. Laminating process and equipment
The laminating process refers to the whole process of laminating pictures and photos, including film selection, film making, and cutting. It is mainly used for post-production of advertising pictures and wedding photos. The pictures covered with film have high anti-corrosion, waterproof, dustproof, anti-wrinkle and anti-ultraviolet erosion performance, which can produce strong three-dimensional sense and artistic appeal. The cold laminating machine is the main equipment to complete the laminating, and it is also the necessary supporting equipment for the computer inkjet machine and electrostatic photo machine. At present, the commonly used equipments for laminating are manual cold laminator, electric cold laminator, self-exposed film cold laminator, automatic cold and hot laminator, and there are also transfer equipment.
4.1 The effect of the coating process:
â‘ The protective film is covered on the picture to improve the strength of the picture and the wear resistance of the surface.
â‘¡Isolate the picture from the outside air to prevent deformation and cracking caused by corrosion, humidity and drying of corrosive gases in the atmosphere, fading and discoloration caused by rain erosion and ultraviolet radiation, and keep the bright color of the picture screen enduring and extended The picture shows the life.
â‘¢Put the picture on the display board or fabric surface to make a hangable advertising picture.
â‘£Lay a special mask or sheet on the picture to form a picture with special artistic effects such as bright light, matt, oil painting, virtual and three-dimensional.
4.2 Classification of laminating methods:
The coating process completed with various materials and equipment is divided into several categories according to the temperature and use of the raw materials (consumables) used. The following categories are introduced.
Cold mounting: The method of mounting the protective film on the surface of the picture by cold pressing at normal temperature is called cold mounting. There are single-sided mounting and double-sided mounting. In the operation method, there are also manual peeling and self-releasing membrane mounting. The cold mounting process has the characteristics of simple operation, good effect and low cost. At present, it is widely used in the post-production of advertising light boxes, engineering drawings and wedding photography.
Hot mounting: the mounting method of the dedicated hot film on the equipment heated to a certain temperature (about 100 ° C ~ 180 ° C) is called hot mounting, which can be divided into single-sided hot mounting and double-sided hot mounting, because of its light Good permeability and water resistance, good heat resistance and strong hardness, suitable for post-production of advertising pictures based on lights or other occasions. However, hot laminating equipment and consumables are relatively expensive, complicated to operate, consume large amounts of energy, and have high costs.
Similar to hot mounting, but generally miniaturized. At present, the largest specification plastic packaging equipment on the market is 24 inches, which is packaged by special plastic film heating. It is mainly used for packaging of documents, small-size pictures or documents.
Vacuum lamination is to use a special vacuum laminating machine to evacuate the film and the painting and set it at a certain temperature to complete the lamination. The operation method is complicated, the cost is high and the screen size is limited, but the mounting quality is very high and the screen texture is strong, which is suitable for photos.
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