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The Advantage Of Solvent-Free Adhesives
1. Solvent-free adhesive is environmentally friendly
Solvent-free compound using solvent-free adhesive, neither volatilizes VOCs, nor produces any pungent odor, at the same time solves the problem of solvent residues in packaging, eliminates the organic solvent on the printing ink erosion, but also can realize clean production, is conducive to environmental protection.
2. Solvent-free adhesive saves energy
Solvent-free composite equipment does not need drying channel, reducing energy consumption. Moreover, in the later curing process, the curing temperature of solvent-free composite is basically the same as that of dry composite, so the energy consumption is relatively close.
3. Solvent-free adhesives are harmless
Because solvent-free adhesive does not contain organic solvent, there is no hidden danger of fire and explosion in the process of production, transportation, storage and use. There is no need for explosion-proof and thermal measures, and no need for storeroom for solvent storage. More importantly, there is no harm to the health of operators.
4. Solvent-free adhesives is Efficient
Using solvent-free adhesive compound speed is generally 250 ~ 350 m/min, the highest can even reach 400 ~ 500 m/min; The speed of solvent-based adhesive compound is generally 150 ~ 180 m/min; The rate of recombination with water-based adhesives is even lower.
5. Solvent-free adhesives cost lower
If the annual consumption of solvent-free adhesives is calculated as 20000 tons, then the consumption of solvent-based adhesives is 20000÷1.5×2.5 = 333333 tons (1.5g/m2 is the average amount of solvent-free adhesives, and 2.5g/m2 is the average amount of solvent-based adhesives). It can be seen that the use of solvent – free composite technology can greatly reduce the amount of adhesive. In addition, using solvent-free adhesive composite, coating cost per unit area is 0.026 ~ 0.052 CNY; Using solvent-based adhesive compound, the coating cost per unit area is 0.052 ~ 0.104 CNY; The coating cost per unit area is 0.076 ~ 0.090 CNY
Problems with universal solvent-free adhesives
At present, there are the following problems in the general solvent-free adhesive for flexible packaging compound.
(1) It has a great influence on the smoothness of PE film
When the solvent-free composite curing temperature is higher than 40℃, the solvent-free composite film with PE film (especially the structure with PE film thickness <45μm) has a great influence, and the friction coefficient is prone to increase significantly. This is mainly because the higher the curing temperature, the more intense the molecular movement of the smoothing agent in the PE film, easy to migrate to the adhesive layer and react with it and be consumed, eventually leading to the increase of the friction coefficient of the composite film.
(2) Aluminum coating transfer
Aluminized film, especially polyester aluminized film (VMPET), is prone to aluminized transfer during solvent-free recombination, resulting in insufficient peeling strength of the composite film.
(3) Solvent-free glue and ink phase dissolution
In the solvent – free compound process, sometimes there will be adhesive and ink phase solubilization, especially dye ink.
There are problems with cooking type solvent-free adhesives
At present, solvent-free adhesives used in cooking type packaging have some problems as follows :
(1) Poor temperature resistance
Most cooking packages require cooking at 121 ° C for 40 minutes. This is because the sterilization temperature of many flexible packaging enterprises is controlled in 118 ~ 120℃, so the highest temperature does not exceed 121℃, the use of 121℃ resistant to cooking solvent free adhesive will not appear quality problems. However, some flexible packaging enterprises will strictly control the sterilization temperature at 121℃, or in order to ensure product quality or even in accordance with the conditions greater than 121℃ sterilization, which requires cooking type solvent-free adhesive can withstand 125℃ or even higher temperature, in order to ensure that the composite product will not have quality problems.
(2) Solvent-free adhesives and ink matching problem
When cooking type solvent-free adhesive is used in transparent cooking packaging, the phenomenon of composite film stratification will not occur generally. But when the solven-free adhesive and ink matching is poor, it will cause the ink at the peel strength is significantly lower than the transparent and other ink at the peel strength, and the ink is more prone to stratification after cooking.
Other problem of laminating
1. Low peeling strength of aluminum foil composite
At present, the application of solvent-free adhesives in the solvent-free composite process of general films has been relatively mature, but for the solvent-free composite of aluminum foil, due to its insufficient peeling strength, can not meet the requirements of heavy packaging and cooking resistance, is still a bottleneck to be broken through.
2. Change the type of adhesive frequently
With the development of solvent-free composite technology, many adhesive suppliers have launched general solvent-free adhesives, cooking solvent-free adhesives, aluminum foil special solvent-free adhesives, low friction coefficient solvent-free adhesives, etc. Although the diversification of products can meet the composite requirements of different materials, However, flexible packaging enterprises should also frequently clean the glue equipment and composite equipment according to the different adhesives used in different composite materials, which is not only a waste of time, manpower and financial resources, but also low production efficiency.
The development trend of solvent-free adhesives
1. Functional solvent-free adhesive
Solvent-free adhesives should be developed to functional products, such as research and development resistance to benzene, toluene, xylene, esters, surfactants, content of less than 20% DMF organic solvent mixture, pesticides and other corrosion products.
2.UV curing solvent-free adhesive
UV consolidation solvent free adhesive in addition to curing speed, product transparency, high peel strength, finished adhesive softness, but also has the advantages of solvent free, non-toxic, non-corrosive, energy saving and environmental protection, can be used for plastic/plastic, plastic/paper, plastic/metal film and other materials of fast solvent free composite. At present, UV curing solvent-free adhesive has been developed, but still need to increase research and development efforts to introduce more mature products to the market.
