Two-component polyurethane adhesives will dominate the market

In the flexible packaging composite, the two-component polyurethane adhesive is a citron. In the dry compounding, the packaging using the two-component polyurethane adhesive is not only exquisite, but also not easy to be damaged during transportation, storage, and the like. Therefore, the use of two-component polyurethane adhesives for dry lamination has become the main technology for flexible packaging composites.

The two-component polyurethane adhesive uses ethyl acetate as the solvent and is therefore an ester-soluble polyurethane adhesive. With the rapid rise of other polyurethane-based, water-based, and solvent-free polyurethane adhesives, the polyurethane adhesive market for flexible packaging has increased unpredictable variables and difficult to control factors, then, two-component polyurethane adhesive What is the future of the agent? Will other polyurethane adhesives replace the two-component polyurethane adhesives?

Two-component polyurethane adhesive is still the mainstream product

development path

From the 1970s to the early 1980s, most of the common packaging compounds were made of one-component rubber adhesives, and high-grade packaging was made of two-component polyurethane adhesives. After the 1980s, the composites basically changed to two-component polyurethane adhesives as the leading compound, supplemented by extruded composite adhesives.

China's two-component polyurethane adhesive developed in the middle and late 80s of the last century. At that time, there were several adhesive factories and research institutes such as Zhejiang New Oriental, Beijing Chemical Research Institute, and Shanghai Lianyin, for research and development. With the advancement and development of technology, the quality of domestically produced two-component polyurethane adhesives has steadily increased, and prices have become lower and lower, gradually winning the majority of the domestic market.

Advantages of two-component polyurethane adhesives

The following advantages of the two-component polyurethane adhesive make it the leading product in the polyurethane adhesive market in the next 10 years.

(1) Good adhesion effect. High peel strength, suitable for a wide range of substrates, can be used for the composite of paper, PET, OPP, NY, PE, CPP and aluminum foil materials, with good composite quality and high composite strength.
(2) Excellent anti-media properties. Resistant to acid, alkali, oil, hot and various oxide, chemical corrosion.
(3) Good cold resistance and heat resistance. Many food packages require cryogenic preservation or sterilization at high temperatures from 121 to 135°C. Two-component polyurethane adhesives can maintain good peel strength under the above conditions.

Requirements

The main component of the two-component polyurethane adhesive is polycondensation with adipic acid and ethylene glycol as the main raw materials. The curing agent is made from toluene diisocyanate (TDI) and trimethylolpropane as the main raw material. It is worth noting that TDI will become toluenediamine (TDA) after hydrolysis at high temperatures, while TDA is a carcinogen.

After the compounding reaction of the polyurethane adhesive, there will remain very few isocyanates, and the isocyanate will transfer through the film into the food after high-temperature cooking and hydrolyze to generate TDA. Therefore, if the packaging is used improperly, the food has potential carcinogenic danger. . In response to this situation, the United States Food and Drug Administration (FDA) strictly prohibits the use of aromatic polyurethane adhesives in retort packaging. Although China, Japan, Europe and other countries and regions do not expressly prohibit the use of two-component polyurethane adhesives, there are certain restrictions on the content of TDA. The content of TDA required by our country must not exceed 0.004mg/L to reduce the potential harm in packaging.

Direction of development

As the solvent of the two-component polyurethane adhesive is ethyl acetate, while ethyl acetate is not completely environmentally friendly and flammable, the development direction of the ester-soluble polyurethane adhesive is high solid content and low viscosity. From the analysis of domestic production status and economic development trends, in the next 10 years, ester-soluble polyurethane adhesive will occupy about 70% market share of polyurethane adhesive.

Other adhesives cannot become alternatives

Alcohol-soluble polyurethane adhesives: Prospects are not optimistic Alcohol-soluble polyurethane adhesives have been developed in recent years as ethanol-based polyurethane adhesives. Alcohol-soluble polyurethane adhesives have the following advantages.

(1) Free isocyanate free monomer improves the operating environment.
(2) It is insensitive to moisture and improves the stability and adaptability of the adhesive.
(3) Industrial alcohol as a solvent reduces production costs.
(4) Excellent compatibility with alcohol-soluble polyurethane printing inks.
(5) Composite membrane products have low residual solvents.

However, the development of alcohol-soluble polyurethane adhesives is not optimistic because although alcohol-soluble polyurethane adhesives have taken a step forward in environmental protection, it is not strictly speaking an entirely environmentally friendly adhesive because Ethanol is also an organic solvent.

In addition, at present, alcohol-soluble polyurethane adhesives are only used in the compound packaging of common dry foods. With regard to the current technology and the properties of alcohol-soluble polyurethane adhesives, it is still unable to achieve the peeling of ester-soluble polyurethane adhesives. Strength and cooking performance. Therefore, the development prospect of alcohol-soluble polyurethane adhesives is not optimistic.

Waterborne polyurethane adhesives: high cost and energy consumption

Waterborne polyurethane adhesives are prepared by dispersing a polyurethane resin in water to form an emulsion or by splicing a polyurethane resin in a hydrophilic solution in an aqueous solution. Water-based polyurethane adhesives are non-flammable, non-toxic, non-toxic to the environment, and have wide applicability to the product. However, they are still inferior to ester-soluble polyurethane adhesives in terms of composite strength and weather resistance. Cooking technology is also a problem at present. Because of its long drying time, high energy consumption and cost, it cannot be further developed under the current situation of increasing energy resources.

Therefore, although water-based polyurethane adhesives have a certain space for development, due to cost and energy consumption, they cannot replace ester-soluble polyurethane adhesives in the next 10 years.

Solvent-Free Polyurethane Adhesives: Achieve Significant Growth After 10 Years In fact, solvent-free polyurethane adhesives are truly environmentally-friendly adhesives, and solvent-free adhesives have been widely used abroad. It has the following advantages.

(1) No pollution.
(2) Solvent evaporation drying process is not required, reducing energy consumption.
(3) Composite products are free of residual solvents and reduce the risk of fire during production.

Solvent-free polyurethane adhesives are suitable for all types of plastic composite packaging. They also have a good adhesive effect for aluminum foils. The resistance to high content and high temperature cooking performance can be similar to that of ester-soluble polyurethane adhesives, with high peel strength.

In summary, in the next 10 years, alcohol-soluble polyurethane adhesives will not be developed, and water-based polyurethane adhesives will still fail to compete with ester-soluble polyurethane adhesives; after 10 years, ester-soluble polyurethanes Adhesives will be gradually reduced, water-based adhesives have a certain space for development, and solvent-free polyurethane adhesives will gradually be widely promoted in China.

Source: Print World