Environmental Properties and Solutions for Polyurethane Raw Materials II

3. Self-skinning polyurethane foam

Self-skinning foams are much smaller than the above two types of foams. Its alternative routes are similar to those of rigid foams, namely HCFC (141b, 22), hydrocarbons (cyclopentane, etc.), and later HFCs (365mfc, etc.). It should be noted that 134a in HFC is a long-lived one, and its application on self-skinning foams is also earlier, but it is extremely inconvenient to use because it is gas (boiling point -26.5°C) at room temperature. Now that there are new types of HFCs (including blends of HFCs), it is of course ideal.

One alternative to self-skinning foams is water foaming. Different from the above-mentioned soft foam and hard cannon, in the conventional self-skinning foam production process, water is not used as a chemical foaming agent, because it is difficult to form a skin layer, and there are many technical difficulties. The environmental issues of CFCs have promoted the research of water foaming and self-crusting and have been successful. Although this product is different from the traditional skinned products (thinner skin), it has been applied in many ways.

As mentioned earlier, according to international conventions, developing countries allow a grace period in the progress of the substitution of CFCs. However, due to the acceleration of the process of economic globalization, China’s participation in the international economic division of labor and cooperation is accelerating, and the progress of replacing CFCs must also keep pace. Otherwise, it will face environmental barriers to trade, resulting in many related products (such as refrigerators, a variety of auto parts, etc.) can not be exported. Therefore, we must focus on the big things and speed up the progress of substitution.

three. Volatile organic compounds (VOCs)

There are many types of VOCs, and there are great differences in the degree of harm to the human body and the environment. Some potential hazards have not yet been fully understood and the situation is more complicated. In recent years, people have paid more and more attention to this issue. Polyurethane is closely related to VOC, and its environmental protection measures mainly include the following aspects:

1. Solvent-based product improvements

Many of polyurethane products are solvent-based, which is determined by the product's characteristics and construction requirements, such as coatings, finishes, adhesives, etc. Many organic solvents belong to VOC. Past safety and environmental protection measures are mainly to improve the local environment, that is, the operating environment and the use environment, including the use of less toxic solvents, reducing the amount of use, and improving ventilation.

Due to the rapid development of the global economy, the increase in the total volume of VOCs and the increasing severity of the situation have become more than just a partial environmental problem. It must be considered from its impact on the entire global environment and ecology, and applications should be minimized. In particular, the amount of emission is controlled. Solvent-based polyurethanes are of course limited. In this situation, waterborne polyurethanes have emerged and have been rapidly developed. Their application is increasing. This trend will continue and is an important direction for improvement.

2. Reduce the residual VOC in products

There are more or less volatile residues in polyurethane products, mainly auxiliaries (such as amine catalysts, etc.) that are not involved in the reaction and substances that are incompletely reacted. These substances are gradually released during use and pollute the environment. . Polyurethane products are used in public places, homes, and automobiles, making the problem even more serious. Therefore, reducing residual volatiles becomes an urgent task.

For this reason, in recent years, the automotive industry has formulated more stringent VOC release standards and improved the environmental protection threshold for PU interior parts. The polyurethane industry also responded positively and adopted a series of effective measures. A batch of raw materials with low volatility, low odor, and low atomization were successively launched, and some new technologies were successively researched and developed to make the situation significantly improved. It should be pointed out that all this has increased the cost. There are many polyurethane products that are subject to price and market factors and do not fully utilize these more environmentally friendly raw materials and new processes. This requires raising people's awareness of environmental protection and self-protection awareness, and formulating relevant standards and regulations so that people can use more environmentally friendly polyurethane products.

four. Recycling and reuse

At present, the output of polyurethanes in the world has reached more than 10 million t/a, which is quite impressive. The problem of recycling and reuse is even more pronounced. This issue is also a long-term concern in the industry. The first is the collection of scraps and waste products. This is a very complicated job. It must have regulations, regulations, organization, and economic leverage. In our country, the work in this area is still in the exploratory stage. It is necessary to constantly sum up experience and lessons and form a good way to improve the recovery rate of waste. However, there are many successful technologies and methods that can be used for reference and adoption. First, it is crushed to a certain size according to the kind of the recovered material, and then, it is molded by one of the following methods. One is mixing with a certain percentage of binders, compression, molding, and the other is thermoforming. Pulverized material can also be added as a filler to the formula. For thermoplastic recycling, it can be used alone or mixed with new materials, injection molding or extrusion molding. The other method, which belongs to the chemical method, includes hydrolysis, alcoholysis, alcohol amine treatment, etc. The polyol is recovered and reused. Among them, the alcoholysis of dihydric alcohols is a more mature method and has been applied in a certain scale. In addition, the combustion method, that is, blending with coal, etc., in an appropriate proportion and burning to generate heat energy, is also a method that is commonly used.

The environmental protection efforts of the polyurethane industry, in addition to the significant significance of environmental protection, are also an important aspect of the competition between such materials and other materials. In many fields of application, this rise and fall between various types of materials often occurs. In the near future, competition for environmental advantages among materials is a hot topic. Only by giving full play to the advantages of one kind of material, but also properly solving the problem of environmental protection, this kind of material can be generally accepted by people and can exist and develop.

(author/Hu Zhongwei)

Dalian Jin Lida Foam Co., Ltd.