Green packaging material category

1, repeated reuse and recycling of packaging materials

Repeated use of packaging, such as beer, beverages, soy sauce, vinegar and other packaging using glass bottles repeatedly. Sweden and other countries implemented repeated reuse of polyester PET bottles and PC bottles for more than 20 times. Wellman, the Netherlands, and Johnson, USA, have 100% recycled PET containers.

Recycling packaging, such as polyester bottles, can be regenerated in two ways after recycling. Physical methods are direct and thorough purification and comminution without any residual contaminants. The treated plastics are then used directly in recycled packaging containers. The chemical method means that after the recovered PET is pulverized and washed, the depolymerization agent, methanol water, ethylene glycol or diethylene glycol, etc. is used to depolymerize all the PET into monomers or partly depolymerize into oligomers after purification by the alkaline catalyst. The monomer or oligomer is re-polymerized into a recycled PET resin packaging material.

The repeated use and regeneration of packaging materials only prolongs the service life of plastics and other polymer materials as packaging materials. After reaching the end of its service life, it still faces the problems of waste disposal and environmental pollution.

2. Edible packaging materials

Edible packaging film. For decades, the familiar glutinous rice paper used for candy packaging and corn baking packaging cups for packaging ice cream are typical edible packaging.

Among the more mature synthetic packaging films is the pullulan resin that has been industrially produced in the 1970s. It is an odorless, odorless, amorphous, amorphous white powder that is non-ionic and non-reducing. Stabilized polysaccharide, because it is a polyglucose consisting of α-glucoside, is easily dissolved in water and can be used as a viscous, neutral, non-liquoring, non-gelatinized aqueous solution. Its 5% -10% aqueous solution can be made into a film with a thickness of 0.01mm by drying or hot pressing. This film is transparent, colorless, odorless, non-toxic, has toughness, high oil resistance, and can be eaten. Instrument packaging. Its gloss, strength, and folding resistance are all better than films made from high-chain starch.

Edible plastic wrap. As early as the 12th and 13th centuries, China used wax to apply orange and lemon to delay the weight loss of dehydration. Extend the shelf life of fruits and vegetables.

The commonly used edible plastic wrap has now been developed into a multi-component edible film made of a variety of bio-macromolecules (proteins and polysaccharides) and lipids with various functional properties. The composite membrane is mainly a stable emulsion formed by interactions between different molecules, and then dried to form a porous, transparent or translucent film of a three-dimensional network structure that volatilizes the solvent. This porous network structure makes The film has obvious water resistance and a certain selectable air permeability, so it has a broad application prospect in the food industry, especially in the preservation of fresh fruits and vegetables.

3, degradable materials

Degradable materials are plastics whose chemical structure changes in a specific environment that causes performance loss in a specific time. Degradable plastic packaging materials not only have the functions and characteristics of traditional plastics, but also can be split, degraded and reduced in the natural environment through the action of ultraviolet light in the sunlight or microorganisms in the soil and water after the service life is completed. Finally, they are non-toxic. The form re-enters the ecological environment and returns to nature.

The degradable plastics are mainly divided into synthetic photodegradable plastics, photodegradable plastics and biodegradable plastics added with photosensitizers, and multi-functional degradable plastics that are combined with various degradable plastics. According to the environmental conditions of degradable plastics, it can be divided into photodegradable plastics, biodegradable plastics (fully biodegradable plastics, partially biodegradable plastics), chemically degradable plastics (oxidative degradable plastics, water degradable plastics), and the above three kinds of degradable plastics. Composite degradable material.

Among the synthetic photodegradable plastics, the production of polyhydroxybutyrate (PHB) and polyhydroxyvalerate (PHV) is the largest. The annual production of Zeneca in the United Kingdom has reached 1000 tons. Their performance is similar to that of polyethylene and polypropylene. The price is About 10 times that of polyethylene. The degradation principle is that the polymer absorbs ultraviolet light to initiate the action, so that the bond energy is weakened, long chains are broken into lower molecular weight fragments, and physical properties are degraded. The lower molecular weight fragments are further oxidized in the air, generating radical chain scission and further degrading to carbon dioxide and water.

Adding a small amount of photosensitizer during plastic processing can make general plastics become photodegradable plastics. Because of the photo-initiating action of the photosensitizer and the photochemical reaction, a radical initiator is generated, so that the photodegradation process of the polymer can be accelerated. This method is simpler than the co-polymerization method and the cost is lower. The photodegradable plastics are mainly used as beverage bottles, shopping bags, garbage bags, and plastic films in foreign countries. The main research and development in China is for the use of plastic films. Fast food box. Because photodegradable plastics can only be degraded under sunlight irradiation conditions, they are highly restricted by geographical conditions and climatic conditions. To achieve accurate control, it is difficult to control and buried parts cannot be degraded. Therefore, large-scale applications are subject to certain limits.

Polymers based on petroleum as raw materials are difficult to be decomposed by ordinary microorganisms under natural conditions. Polymers and natural polymers synthesized from genes that are prone to hydrolysis have high biodegradability. Researches in China are based on the incomplete biodegradation of starch and polyolefin plastics. The degradation mechanism of such plastics is that starch granules are first attacked and consumed by fungi and bacteria, thereby weakening the strength of the plastics. At the same time, after the plastics are in contact with certain salts existing in the soil, peroxides are formed by self-oxidation and promote plastics. The polymer chains in the polymer break, they promote each other and complement each other, and the bacteria consume starch, which increases the surface area of ​​the plastic and facilitates auto-oxidative degradation. As time goes by, the polymer chain gradually breaks, shortens, and weakens the plastic strength until the molecular weight of the polymer is reduced to the extent that it can be metabolized by microorganisms.

Reproduced from: National Plastics Processing Industry Information Center