On the greenization of plastic packaging

About green packaging, generally speaking, refers to the packaging that can protect human health and safety, reasonably utilize resources and energy, and does not harm the ecological environment during the entire process of design, production, use, circulation, and waste recycling and disposal. Specifically, packaging materials or containers are required to be recyclable, recyclable, or easily degraded in nature, and moderate packaging of the human body and the environment is not caused during the entire life cycle of the product. The most important meaning of green packaging is to protect the environment, but it also has the significance of resource regeneration.

Packaging materials should be non-toxic and harmless to humans and organisms. Packaging materials should not contain toxic elements, halogens, or heavy metals, or their contents should be controlled below relevant standards, and should not cause harm to the human body and the environment.

However, there are still some misunderstandings in the development of green packaging products in China. Green packaging is often understood as the greening of packaging products, and packaging products made from degradable materials are regarded as green packaging products, ignoring the environmental pollution generated during the production process. And waste of resources, ignore the impact of packaging products on human health and the reuse of packaging materials.

In fact, whether a packaging material is “green” requires its environmental impact from the entire life cycle of the product. For example, improper recycling of paper packaging may also have an adverse effect on the environment. Plastic packaging may become a green packaging product if it achieves goals such as reduction, recycling, and harmlessness. At present, even in developed countries that strictly implement green packaging, plastics are also the fastest-growing packaging materials. The main measure to reduce the environmental impact of plastics is to enhance recycling rather than a total ban.

According to the above requirements of green packaging, the packaging industry as a whole is undergoing a profound and green transformation in terms of design, material selection, and processing and use.

From the design perspective, green packaging design can effectively alleviate the dual pressure of resource crisis and pollution prevention and control.

For example, Japan stipulates that packaging raw materials or containers must not endanger human health, and should minimize the use of packaging materials that are difficult to degrade after they are discarded. The size of the packaging should be reduced as much as possible. The free volume in the container should not exceed 20% of the product volume. It also strives to adopt the simplest packaging method and even requires zero packaging efforts. From the above points of environmental protection, we can see that the focus of green packaging design should be on the beneficial to human health, prevention and control of pollution, and the close relationship between the reuse of resources, and its end result is still on the sustainable development of human society. on.

Green packaging material selection requirements:

The safety of packaging materials -- Basic materials should be given: Physical and chemical performance indicators: Technical parameters: Conformity with the relevant standards: The scope of use.
- Plastics, plastic matrix composites in the use of additives, adhesives should not produce toxic side effects.
- Adhesives, coatings and other auxiliary materials should be controlled according to the relevant standards volatile benzene, methanol and other harmful ingredients.
- Materials for food and pharmaceutical packaging should comply with relevant national regulations and be implemented in accordance with relevant standards.

The economics of packaging materials - Broad sources of raw materials: durable and easy to obtain.
-- The consumption of energy and resources in the production process is relatively small.
- The waste gas, waste water and waste residue produced in the production process can be recycled: it can be processed.
-- Variety of basic materials, serialization of models and standardization of specifications to meet the needs of the market.
- According to the standard or actual needs to develop and divide the grade and grade of the product to meet the user's choice.
-- Can use modern industrial technology to achieve large-scale production.
-- Deep processing of common raw materials to make them high-quality, multi-purpose materials.

Recycled (removable) properties of packaging materials -- The use of adhesives, coatings, printing inks, etc. should not affect the recycling of the main materials.
- Materials used in disposable containers should be degradable when they have no recycling value.
- The materials to be incinerated after recycling should not contain chlorine, fluorine, etc.

Based on the above principles, in the selection of materials, there is no need to use less or contain polymers that are harmful to the environment after incineration of the human body or waste, and the use of a single type of polymer or detachable coexistent materials is recommended to make packaging containers to facilitate the recycling of resins. Reuse; In the premise of meeting the packaging function, the selection of materials should minimize the amount of waste generated. Taking the film as an example, the trend is to reduce the weight of the packaging film. The key technology is the use of super toughness, thin processing and easy processing. The new raw materials such as bimodal HDPE, metallocene catalysts, polyolefins, and excellent barrier packaging materials, etc.; edible packaging film is based on natural edible substances (such as polysaccharides, proteins, etc.) as raw materials, through different molecules A film with a porous network structure formed by the interaction. Such as chitosan edible packaging film, corn protein packaging film, modified cellulose edible packaging film and composite edible packaging film, etc., edible film can be applied to the inner packaging of various ready-to-eat foods, in the food industry should Has a huge market; uses degradable packaging films, such as photodegradation, photo-oxygen biodegradation, high-starch content biodegradation, high-calcium carbonate-filled photo-oxygen degradation, full biodegradation, and water-soluble plastic packaging films to solve waste Recycling of packaging materials that are difficult to degrade will be difficult. Buried underground will destroy the soil structure. Incineration will also produce toxic gases that cause air pollution.

Greening in the process of packaging and processing, taking flexible packaging as an example, is mainly focused on cleaner production

Greening of composite film printing process

The printing ink of the composite film contains a large amount of volatile organic solvents, such as xylene, toluene, ethyl acetate, butanone and other low-boiling, highly volatile solvents. The aromatic hydrocarbons are toxic and flammable, and are the main environmental pollution. factor. In addition, the film printing usually uses gravure printing, and the speed is extremely high. It is necessary to use extremely fast-drying inks with high volatility, and external drying with electric power or infrared heating (drying process in gravure printing) is required to meet the requirement of high-speed printing non-stick. As a result, gravure exhaust emissions are large, making gravure printing particularly prominent in the environmental problems of all thin film printing processes.

The environmental issue of solvent in the gravure printing process has gained wide attention. The flexible packaging industry and related departments are improving the production process and related product emissions:

In order to reduce the overall amount of solvent, the development of high-concentration low-viscosity inks, even solvent-free solid inks are expected to reach the market in a few years;

Another effective way to solve the problem of harmful solvent contamination is the water-based printing ink of film packaging materials. Although water-based inks have attracted a lot of attention as an alternative system for benzene inks, the inks in packaging film printing are still water-based and have not yet reached a practical stage. The important reason is that the printing performance and quality still cannot reach the standard of solvent ink. Therefore, water-based inks are not yet fully capable of replacing benzene-based inks. However, alcohol-soluble inks that can be environmentally-accepted have also been effectively developed as the same contamination. Alcohol-soluble ink can effectively solve the health damage caused by benzene ink and the influence of solvent residue on the quality of packaged food. In many developed countries, this development has become a trend. In some countries, benzene inks are being eliminated and replaced by alcohol-soluble gravure inks. Alcohol-soluble inks are now used in the domestic gravure printing industry.

The greening of the composite processing process.

The main task is to develop and apply high-solids, low-viscosity composite adhesives. Using a high solids binder at the same coating weight can effectively reduce the amount of solvent used.

Previous two-component polyurethane adhesives, whose solid content of the main agent was 35% or 50%, have now been increased to 75% or 80%. Due to the characteristics of high solids and low viscosity, it is possible to use high solids content for high-speed composite machining.

The advantage of water-soluble binders is that water replaces organic solvents, there is no potential risk of combustion explosion, there is no pollution to the environment and the operator is poisonous, and the cost is low. However, such adhesives have poor coating properties, poor wetting of composite substrates, and poor adhesion. These factors, to a certain extent, limit the widespread use of water-based adhesives. Similar to the idea of ​​eco-friendly inks, people have developed alcohol-soluble polyurethane adhesives, but none of them have completely reached the level of solvent-based adhesives, so solvent-based polyurethane adhesives will still exist for a long time. Alcohol-soluble polyurethane adhesives will gradually occupy a certain market share because they meet the green environmental protection requirements and have the basic advantages of two-component, solvent-based polyurethane adhesives.

A new class of solvent-free adhesives has also been developed. They consist of two-component polyurethane adhesives. The main agent and curing agent have high viscosity at room temperature but still have fluidity and are semi-solid substances. When compounding is to be performed, the main agent and the curing agent are mixed in proportions, and the temperature is lowered until the viscosity is reduced to an appropriate level, and then applied to the substrate by an anilox roll having a heat insulating function. After coating, it is not necessary to heat and dry directly to compound with another substrate. The solvent-free composite process does not have the problem of exhaust emissions, and does not require heating blasts or exhaust air exhaust devices. The equipment is simple and energy consumption is reduced. The process flow is simple, the equipment covers a small area, the cost is reduced, resources are saved, and the environment is protected. Therefore, it will be the main direction for the development of composite processes in the future.

According to the successful experience of foreign developed countries, as long as we adhere to the principle of 5R1D, that is, under the premise of guaranteeing the packaging function, minimize the use of packaging materials, reduce the reuse of the packaging materials, and use the packaging materials as much as possible. Recycling is used for packaging, waste recycling is recycled as much as possible or recycled into useful materials, refuses to use non-environmentally friendly products, and degradable plastics are used for development. Waste packaging materials recycling network, the implementation of the development and use of biodegradable plastics and other comprehensive measures, will be able to minimize the harm of waste plastic packaging materials to the environment.

Source: Global Flexible Packaging Industry