What is the difference between dry compounding and solvent-free compounding?

Dry composite is solvent-free composite is often seen in the production process of plastic packaging bags, these two composite methods have advantages and disadvantages, today we will compare and analyze for you.

Dry compound

Dry composite is a composite method in which the adhesive is evenly coated on the adhesive base film by roller loading, dried in the oven, and then pressed and bonded to the composite film at the composite part. Dry composite packaging film has a wide range of applications, excellent corrosion resistance to chemical media, and is mostly used for packaging containing alkali, spicy, oil and other strong corrosion contents, and is also suitable for cosmetics flavor, emulsifier and other ingredients, especially some packaging that requires high temperature cooking, which has advantages.

Compared with other composite processes, the dry compounding method has the following advantages:

(1) The available substrate surface is wide, can be plastic with plastic, can also be plastic with paper, plastic with metal and fabric, non-woven fabric, etc., even without plastic, paper with metal can also be composite;

(2) The fastness of the composite is relatively high, the peeling force between layers can reach 1000g/25mm wide or more, and high-grade packaging products can be produced, such as high temperature cooking bags;

(3) The thickness of each layer can be freely selected and accurately controlled;

(4) can be printed on the surface, can also be printed on the reverse;

(5) The production speed is fast, the general operating speed is 150-180㎡/0, and the fastest can reach more than 200m/g.

The disadvantages of dry compounding are:

(1) Composite requires the use of adhesives, there are residual solvent toxicity problems, therefore, dry composite packaging, especially the use of two-component polyurethane adhesive curing dry composite packaging can not be used in the North American and European markets, but can only be sold in Southeast Asia, Africa and other places. China and Japan, in line with national standards of dry products can be used for food and drug packaging, the health standard is the total amount of residual toxic ingredients ≤15mg/㎡ :

(2) Due to the use of a large number of solvent adhesives as composite adhesives, because of the environmental pollution of volatile organic solvents and flammable and explosive problems:

(3) Dry composite film because of the large amount of glue and high cost, the price is relatively expensive.

Solventless recombination

The difference between solvent-free composite packaging film and dry composite is that organic solvents are not used, which not only avoids the pollution caused by the volatilization of organic solvents to the environment, but also does not require the operating section of solvent volatilization and drying, directly reduces the production cost, and eliminates the impact of the composite substrate vulnerable to solvent and high temperature drying damage, so that the dimensional stability of the packaging film is better.

Solvent-free composite has the following advantages:

(1) Environmental protection. Because the adhesive does not contain solvents, it will not cause pollution to the environment due to solvent emissions. In addition, solvent-free equipment is much less noisy than solvent-based equipment because of its compact structure and reduced drying chambers. According to actual measurements, the noise of solvent-free composite equipment is generally between 70-75Db, and the solvent-based type is generally between 85-100Db.

(2) Low cost. In terms of equipment investment cost, due to the compact solvent-free composite equipment, the footprint is significantly smaller than that of solvent-based composite equipment, and the cost of the equipment is much lower than that of solvent-based equipment, and there is no need for solvent warehouse. In terms of energy cost, the motor power of solvent-free equipment is also tens of kilowatts less than that of solvent-based equipment.

(3) Health and safety. The solvent-free composite avoids residual solvent contamination of the contents or causes odor, makes food packaging safer and more assured, and the operation is safe, because there is no risk of fire and explosion due to the use of solvents, no explosion-proof measures are required.

(4) Product quality. Because the operating temperature is lower than the solvent type, the film will not be deformed at high temperature. At present, the substrate of ordinary composite films can be produced by solvent-free adhesives, and even composite films that can withstand high temperature cooking at 121℃ can be manufactured by this method.

Disadvantages of solvent-free composite:

The whole system should be heated and the coater should be insulated when the adhesive is coated. The application period of adhesive mixing is short, and the effective use time is not more than 30min; Products with heavy packaging, high medium resistance and ultra-high temperature sterilization are difficult to meet the requirements; Low initial viscosity, long curing time; High coating accuracy is required.

These two ways of composite packaging film have their own advantages, in the choice of which composite method, we must first refer to the nature of the packaging contents, weight and other elements, if they can not determine, you can also consult more experienced packaging bag manufacturers.