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Paper-plastic composite packaging material is a composite material with paper as the basic structural material and combined with one or more film materials through one or more composite processes to form a certain function, which has high strength. It is one of the most popular packaging materials, and it is widely used in food, daily chemical, sanitary products and other industries. Usually, the film is made of BOPPPETCPPPE or the like, and the paper is made of refined composite paper.
Paper-plastic composite packaging materials can be said to be an environmentally friendly product that is harmless to the human body. It is different from traditional composite packaging materials and can be recycled. Consumers have higher recognition. This article will mainly introduce the production precautions and major failures and solutions of paper-plastic composite packaging materials.
Production precautions for paper-plastic composite packaging materials
1 paper selection considerations
At present, there are a wide variety of paper products on the market. There are dozens of categories depending on the application, process, etc., commonly used in the field of flexible packaging, such as kraft paper, white kraft paper, soft cotton paper, base paper, pearl paper, etc., from 25g/m2 to 80g. /m2 does not wait. Due to the wide variety of papers and different uses, the following points should be noted when using different papers.
(1) Generally speaking, the smooth surface of the paper is easier to adhere to the film, and the matte surface is difficult to adhere to the film. This is mainly due to the pitted phenomenon on the matte surface. If the bonding is very tight, the amount of glue must be increased. The adhesive fills these holes.
(2) Pay attention to the paper density. Some paper fibers are loose, and although the paper adheres well to the film during compounding, it is prone to delamination after heat sealing.
(3) paper moisture content also has a certain effect on the bonding effect. According to the author's personal experience, the paper moisture content should generally not exceed 0.4%. Some companies tend to put paper in the drying room for 1-2 days before production, which is a good method.
(4) Pay attention to the cleanliness of the paper surface. Some enterprises find that in the production process, sometimes the quality of several batches of products is very good, sometimes there will be stratification of individual batches of products, and there is no law, the stratification is irregular, and the number of stratification of each product is not regular. , completely randomly generated. After a long period of observation and testing, it was found that the surface of the paper was not clean enough. When there is dust and other debris on the surface of the paper, this place is a weak point. Once it is heat sealed here, it is prone to delamination.
2 precautions in the compound process
Solvent-free compounding is a relatively economical and environmentally friendly composite method that has been applied in more and more enterprises. When using a solventless composite method for composite paper-plastic composite packaging materials, attention should be paid to the type of adhesive and the amount of glue applied.
(1) Type of adhesive
Solvent-free adhesives are divided into one-component and two-component. One-component solvent-free adhesive requires moisture to crosslink and solidify. The moisture in the paper is just the curing reaction medium, and the molecular weight of the one-component solvent-free adhesive is large, and the viscosity after coating cooling is also large. Compared with the two-component solvent-free adhesive, it is not easy to be over-absorbed by the paper, and it is more suitable for the composite of paper-plastic composite packaging materials. The two-component solvent-free adhesive has a low viscosity, and is more easily absorbed by the capillary pores on the surface of the paper after the composite, and the surface is deficient, and the moisture in the paper consumes the curing agent, so that the adhesive layer is not dried. Therefore, a one-component solventless adhesive is usually used in paper-plastic solventless compounding.
(2) Glue amount
When sizing, the capillary pores of the paper fibers will absorb more liquid glue, and in the case of serious, there will be surface lack of glue and delamination. Usually, to make up for the amount of glue absorbed by the paper, it is necessary to increase the amount of glue, sometimes it needs to reach 3g/m2 or more. In addition, the sizing affects the color of the paper, which generally makes the paper darker, so we need to strictly control the amount of sizing during production. Generally, the amount of sizing can be minimized when the composite paper is smooth (according to the paper, it is controlled at 1.8 to 3.0 g/m2), and the inner layer can be appropriately increased in the amount of sizing. At the same time, the paper can be humidified in the compounding process to promote the rapid curing of the adhesive, which can reduce the influence of the sizing on the color change of the paper.
(3) details that should be noted
3.1 When sizing, the amount of sizing cannot be detected by the weight difference method, otherwise the measurement error will be caused due to the excessive deviation of the paper itself.
3.2 When the paper-plastic composite, the temperature of the composite roller should be slightly lower to reduce the fluidity of the adhesive layer, thereby reducing the amount of paper absorbed by the paper.
3.3 The air entering the storage tank should be dried and filtered.
3.4 The relative humidity of the environment should be less than 65% RH.
3.5 If the inner layer is composited on a dry laminating machine, the paper-plastic layer needs to be completely cured before proceeding.
Analysis of the causes of paper-plastic separation and solutions
Paper-plastic detachment is a kind of quality failure often occurs in paper-plastic composite packaging bags. Especially during production, transportation and storage, partial or overall delamination occurs easily in the edge and corner heat seals, and most of them are printed on the printing surface. Large products appear, especially in the case where the surface ink layer is thick and the adhesive is difficult to wet, diffuse, and penetrate, and the paper-plastic detachment phenomenon is more likely to occur. The phenomenon of paper-plastic detachment often coincides with the smoothness, uniformity, water content of the paper, the performance of the film, the thickness of the printed ink layer, the temperature and pressure of the paper-plastic composite, the production environment (sanitary conditions, temperature, relative humidity, etc.) )related. According to the specific conditions at the time of production, it can be treated according to specific measures.
1 Reason analysis
(1) Debonding in the middle of the paper, the film surface is 100% stuck with paper
This problem reflects the poor adhesion between the paper fibers, or the adhesion between the fibers is less than the adhesion of the film to the fibers on the surface of the paper.
(2) delaminating on the paper-plastic interface, and sticking paper on the surface of the film
This problem reflects that the thickness deviation of the paper is too large, the amount of glue is insufficient, or the composite pressure is too small (or the input air pressure changes greatly), or the composite temperature is low.
(3) delamination at the interface between ink and adhesive
This problem reflects poor heat resistance of the ink, or the temperature of the paper bag is too high, or the melting point of the heat seal film is too high, or the temperature deviation of the heat seal knife itself is too large.
(4) Stripping in the middle of the ink layer or delaminating between ink layers of different colors
This problem reflects ink whitening or poor ink quality, or the use of ink from different manufacturers for the same print, or poor drying of the ink.
2 solutions
(1) increase the amount of glue
If the amount of coating is insufficient due to the absorption of the adhesive by the paper and the printing ink, the paper is detached, and the amount of sizing should be appropriately increased to ensure the need for compounding.
(2) compounding after the printing ink is dry
When the ink layer is not dry or not dried, the residual solvent in the ink layer may consume part of the adhesive, resulting in insufficient use of the adhesive, which causes the adhesion between the paper and plastic to decrease, resulting in paper-paper detachment. In this case, the problem of paper-plastic detachment can be solved by compounding after the ink is dried.
(3) Improve compound temperature and pressure
When compounding, if the temperature and pressure are low, it may cause paper-plastic separation. The compound temperature and pressure should be increased appropriately.
(4) to ensure the surface tension of the film
The surface corona treatment strength is not enough or the surface tension of the film is insufficient due to the long storage time after the corona treatment on the surface of the film, which is also one of the important reasons for paper-paper detachment. When the paper-plastic detachment phenomenon occurs, the surface tension of the film should be tested first. If the surface tension is found to be insufficient, the film that meets the requirements should be replaced.
(5) Manual humidification when the air humidity is insufficient
Since the paper-plastic composite uses a one-component solvent-free adhesive, if the moisture in the air is insufficient, the paper-plastic detachment phenomenon may also occur. In this case, the humidity requirement of the single-component solvent-free adhesive processing process should be performed. Manual humidification treatment.
The development trend of paper-plastic composite packaging materials
The paper-plastic composite bag currently used has a certain moisture-proof property, which can prevent the articles in the package from being away from the mildew condition, and has good gas permeability, a certain abrasion resistance, is not easy to be damaged, and the product feels good and environmentally friendly. Well, it can be used for many times without deformation, and the fineness is high, and the novelty of appearance can be realized. In the market, not only Qiaoxi, three squirrels, herbaceous taste, good shop and other brand packaging use paper-plastic composite packaging materials, and the bowls of instant noodles manufacturers such as Master Kong, Uni-President, and Nissin are also paper-plastic structures. In the future, paper-plastic composite packaging materials will mainly develop in two aspects.
1 functional paper-plastic composite packaging material
Development from the ordinary four-side sealing bag to the stand-up pouch; development towards the insertion pocket and easy-to-tear zipper bag; development towards independent small packaging; development towards environmentally friendly packaging bags; mandatory establishment of traceability system, paper-plastic packaging bags will be One bag and one yard direction development.
2 low temperature sealing paper-plastic composite packaging material
In the future, packaging machinery requires simple and convenient equipment, saves energy, increases speed, and increases efficiency to meet the needs of modern high-volume packaging. The use of low-temperature sealing packaging materials is a necessary condition.
As the demand for packaging continues to increase, modern goods have placed more demands on packaging, which has greatly promoted the innovative development of packaging materials, from simple paper packaging to single-layer plastic packaging to paper. Plastic composite packaging materials. In the future, paper-plastic composite packaging materials will be developed in the direction of serialization, multi-function, high-performance, special functions, etc., showing a market situation of blooming flowers.