Green Packaging Materials Development Technology

Green packaging material is the key to the development of green packaging. Countries all over the world attach great importance and have achieved a series of important results. In order to enable the domestic packaging industry to understand the development of green packaging and better promote the development of green packaging in China, this article describes the progress of the development of green packaging materials, including recyclable or recycled packaging materials, lightweight, thin, and Fluorinated, high-performance packaging materials, biodegradable plastics, natural plant fiber packaging materials, edible packaging materials, agricultural packaging materials, nano packaging materials, genetic packaging materials, green packaging auxiliary materials and green packaging materials additives. Recyclable or Recyclable Packaging Materials Many countries in the world place emphasis on the development of reusable products, and through the deposit recovery system, beer, beverages, soy sauce, vinegar and other glass bottles or polyester bottles are used repeatedly. For example, Sweden and other countries have developed a sterilizing and washing technology to reuse PET beverage bottles and PE milk bottles for more than 20 times; recycling is a good way to solve solid waste, and it is also an effective way to solve the source of materials and mitigate environmental pollution. way. Plastic waste recycling technology includes direct recycling of raw materials, physical modification and recycling, chemical modification, recycling and other technologies. The physical method refers to directly purifying the recovered plastic after comminution and then directly to the production of the packaging container, or disintegrating and washing the polyester, and then placing the sandwich material in two layers of primary resin layers to form a multilayer PET packaging container; The method refers to the method of pulverizing and washing the recovered PET, depolymerizing the whole PET into monomer or partial depolymerization into oligomers by using a depolymerization agent such as methanol, water, ethylene glycol or diethylene glycol under the action of a basic catalyst, and purifying the PET after purification. The monomer or oligomer is re-polymerized into a recycled PET resin material.

After the glass and metal packaging containers are discarded, they are generally melted or remelted by remelting and used as raw materials. After the paper and paperboard are discarded, pulp is obtained after disintegration, desorption and bleaching to produce recycled paper. Degradable plastic packaging material

Currently, biodegradable polymers that have been identified have only biosynthetic fatty polyesters, such as PHB and PH-BV synthesized by fermentation, ether- and polyhydroxy-containing polymers such as starch and cellulose, and synthetics. Polyamides, polyurethanes, polymers containing ether bonds, and PVA. Among these polymer materials, polyurethanes, polyamides, polyesters, and PVA are good packaging materials and are widely used as packaging films, packaging containers, or tying materials. However, these types of fully degradable packaging materials are limited, and far from meeting the requirements of numerous packaging technologies and packaging protection performance. However, PHB, PHBV, and polyethers have low melting point and strength and are not very useful.

The incompletely degradable plastics (starch + PE type) blended with starches, also known as bio-disintegrating plastics, are materials that are rapidly researching and developing, have many industrialization results, and are expected to continue to reduce costs. In order to improve the compatibility of starch and polymer blends, it is necessary to modify the starch, and the surface of the modified starch granules is covered with an alkyl group, etc., which weakens the effect of hydrogen bonding, thereby increasing the compatibility with polyethylene, poly Compatibility of polymers such as vinyl alcohol.

The photodegradable material obtained by adding a photosensitizer can be obtained by adding a suitable photosensitizer to PE, PP or the like. The TPR green packaging material developed by Sweden's Filltec Co., Ltd. is composed of calcium carbonate and a polypropylene added with a photodecomposition agent. Its composition is very similar to the eggshell, almost harmless to the environment, and can be thermoformed, blow molded, Injection molding and extrusion molding, TPR smooth and smooth, different thickness of the film in the light of 4 - 18 months degradation into powder, is now used in butter, ice cream and other packaging.

Photodegradable packaging materials currently have the following problems: 1 The contradiction between the photodegradation rate and the photodegradable polymer performance. If the photodegradation rate is too fast, it is beneficial to the disposal of waste plastics, to beautify the environment and reduce pollution, but it is obviously detrimental to the performance and life. 2 The effect of photodegradation products on the ecological environment. If the photodegraded product can continue to be biodegraded, eventually becoming carbon or harmless to be absorbed by the microorganism, it is of course ideal. However, in fact, the copolymers of ethylene, propylene and vinyl ketone have very little biodegradability in the soil or underground water channels after photodegradation, and whether the photodegradation products are harmful to the ecological environment is also worth studying.

Currently, biological and light double-degradable plastics entering the market are mainly prepared by blending or grafting modified general-purpose polymers such as PE and PP with degradable polymers such as starch or cellulose. Induced photodegradation of photosensitizers has been studied and applied very actively in this field. Polyketones can be chemically modified with oxidizing agents such as hydrogen peroxide and peroxyacids, and oxidized into polymers containing both polyester and polyketone structure, and become packaging materials having both biodegradability and photodegradability. Edible packaging materials

Edible packaging materials are now widely used in food and pharmaceutical packaging. The raw materials of edible packaging materials mainly include lakes, proteins, plant fibers and other natural substances. Among the edible packaging materials made from corn, wheat, potatoes, beans, potatoes and other crops, the modification of corn starch into edible packaging materials is the most typical, and the processing technology and practical application are more mature. According to different additives, acid and alkali treatment, enzyme treatment or oxidation treatment method, the film can be made into film, and can also be extruded to form film clothing for small food, and can also be made into a cup that is both waterproof and oil-proof. And fast food boxes and so on. The use of protein to make edible packaging materials is divided into animal protein and vegetable protein. Animal protein is derived from animal skin, bone, cartilage tissue, etc. This type of edible material has very good strength, water resistance and oxygen permeability, and is particularly suitable for packaging of meat foods. Plant protein extracted from soybeans, etc., can be processed into a film and packaged, has good moisture and oxygen barrier properties, and has a certain degree of antibacterial properties, and is suitable for the packaging of fat-containing foods, not only improving the shelf life, but also maintaining the original flavor of oily foods.

Plant fiber edible packaging materials use agricultural and sideline products such as wheat bran, bean dregs, and marine plants such as seagrass and seaweed as main raw materials. Although the nutritional value of this type of material is not high, but many have the role of weight loss and health care, such as sodium alginate, it is not absorbed by the body, but it has blood sugar, regulate the role of the stomach, and can make cholesterol out of the body and have Slow down the effect of poisoning. The plant fibers can be made into various containers, and can be eaten together with the food after being cooked, or when used for packaging instant noodles seasoning, when the heat is applied, the water can be dissolved without disassembling. It can also produce fresh-keeping wrapping paper for fruits and vegetables. The edible material containing sodium alginate as a main component is impervious to fat and vegetable oil and is an excellent oil-resistant packaging material.

Edible packaging materials can also be made from edible shellfish such as shrimp and crab shells as the main raw material. Chitin can be extracted from chitosan under alkaline conditions. Chitosan has excellent film-forming properties after modification, and has good oil resistance, moisture barrier and transparency. This type of edible packaging material is now widely used in the packaging of fruits, bread, ice cream and other foods. Natural plant fiber packaging material

Paper made from wood pulp and straw pulp is the most widely used fiber packaging material. In recent years, some new types of green paper packaging products have been developed. The typical varieties are pulp molding and honeycomb paperboard products. Pulp moulding products use waste paper and plant fibres as raw materials. Molding machines use different moulds to shape certain shapes of products. It is a three-dimensional papermaking technology. Its products are used as substitutes for foamed plastic EPS products and are widely used. In tableware, poultry egg trays, fruit trays, industrial trays, food and medical device packaging. Honeycomb paperboard is composed of upper and lower two face papers and hexagonal honeycomb core paper. It has the advantages of light weight, high strength, high stiffness, good cushioning, heat insulation and sound insulation. It is used for wood replacement and EPS replacement. The ideal environmental protection material for cushioning pads.

In particular, natural plant fibers refer to natural fibers other than trees, such as bagasse, cotton stalks, husks, corn stalks, rice straw, wheat straw, and waste paper fibers. Natural plants are a source of abundant renewable resources. Natural resources. In recent years, a series of green packaging products have been developed using natural plant fibers such as reeds, rice straw, wheat straw, bagasse, and bamboo. Take bamboo as raw material, produce bamboo plastic packing box, wire bundle bamboo box, used for mechanical and electrical products and heavy machinery packaging; bamboo, straw and other plant fibers after high temperature sterilization pressed into a fiberboard, and then crushed, add padding Materials, adhesives, etc., after extrusion molding, can be made disposable fast food equipment, such as the expansion of the foam can also be made cushioning. Transgenic plant packaging materials

Although breakthroughs have been made in the research and development of biodegradable packaging materials using microbial fermentation, there are still low productivity, low temperature difference between melting point and degradation, slow crystallization rate, difficult processing, and high cost. Limitations and other issues. Therefore, the development of genetically modified plants to produce fatty polyesters PHB and PHAs has become a hot spot for the research and development of biodegradable plastics.

With the rapid development of plant genetic engineering, the production of PHB for microbial fermentation is expensive, and some large companies have successively developed PHB packaging materials using transgenic plants as reactors. The long-term goal set by the UK's ICI/Zeneca Seed Company is to introduce the pathway for bacterial biosynthesis of PHB into suitable crops for large-scale production of PHB/V packaging materials using transgenic plants; the Monsanto Company of the United States launched in 1996