First, the development of polylactic acid packaging materials
In April 2004, the American CollegeFarm brand candy used a biodegradable resin polylactic acid (PLA) NatureWorks natural material packaging film. This film has the same appearance and performance as a traditional candy packaging film (glassine or biaxially oriented polypropylene film) and has crystal transparency, excellent kink retention, printability, and strength, and has high barrier properties and is better Keep the sweet smell. At present, the company has a set of PLANatureWorks film in the high-speed kink packaging equipment, and the production capacity is to pack 1300 pieces of candy per minute.
In the chemical industry, the US company Carrick Dow Polymers has the world's largest corn-based polylactic acid brand. In cooperation with it, Mitsui Chemicals Corporation of Japan started to launch "RACEA" brand polylactic acid in April 2002. An artificial sprouts distribution company in Nakatsugawa City, Gifu Prefecture has started using "RACEA" polylactic acid as a new product packaging material from this month.
The Faerch Plastics Company of Denmark invented the use of polylactic acid as packaging material. The new product is suitable for packaging low-temperature fresh foods, including various pasta, meat and salads. Faerch's current packaging products include various trays and bottles. The original processing resins that can be heat sealed are PS, PP, and PET. Adopting this new product will put the company and its users at the front end of the packaging industry.
A German company successfully developed a green food cup with rapid natural decomposition using polylactic acid as a raw material, which has opened up a practical new way to solve the problem of degradation of disposable plastic packaging. The degradable material developed by the company belongs to the polyester polymer. The lactic acid can be extracted from sugar liquid fermented from sugar beet and undergo ring-opening polymerization to form polylactic acid.
In December 2002, the Japanese government introduced the “Bioengineering Strategy Outline†and other proposals to propose the use of biological raw materials instead of fossil raw materials for energy or products in order to prevent global warming. Increased consumer awareness of environmental protection has also encouraged companies to make full use of plastics made from plant raw materials.
Second, the advantages of polylactic acid packaging materials
Polylactic acid (PLA) is a new type of polyester material produced from organic acid lactic acid. It has advantages over existing plastic materials such as polyethylene, polypropylene, and polystyrene. It is defined by the industry as the most promising for the new century. New packaging materials are a star of environmental protection packaging materials. In the future, they will be expected to replace polyethylene, polypropylene, polystyrene and other materials for the packaging of plastic products. The application prospects are very broad.
As the basic raw material of polylactic acid is lactic acid, it is one of the body's inherent physiological substances, and it is non-toxic and harmless to the human body. Therefore, as an important raw material, polylactic acid can be processed into a variety of downstream products like thermoplastics such as polyvinyl chloride, polypropylene, and polystyrene, including films, bags, packaging boxes, food containers, and disposable snack boxes. Beverage bottles, low molecular weight polylactic acid for drug release packaging and other packaging materials.
Polylactic acid has good mechanical properties and physical properties, suitable for blow molding, thermoplastics and other processing methods, processing convenience. It can be used to process various plastic products, packaged foods, and fast food lunch boxes from industry to civilian use.
Polylactic acid has good moisture, grease and airtightness. The performance is stable at room temperature, but it will decompose automatically when the temperature is higher than 55°C or under the influence of oxygen and microorganisms. After use, it can be completely degraded by microorganisms in the natural world, eventually producing carbon dioxide and water, and not polluting the environment. This is very beneficial to the protection of the environment.
The decomposition of polylactic acid is divided into two stages: first, pure chemical hydrolysis into lactic acid monomer, and then the lactic acid monomer is decomposed into carbon dioxide and water by the action of microorganisms. The food cup made of polylactic acid can be completely decomposed in 60 days, and it truly achieves both ecological and economical effects.
Third, many agricultural and sideline products can be made of polylactic acid
The production of polylactic acid is based on lactic acid. Most of the traditional lactic acid fermentation uses starch-based raw materials. At present, the United States, France, Japan and other countries have developed and produced lactic acid by using corn, sugarcane, sugar beet, potato and other agricultural and sideline products as raw materials to produce lactic acid, and then produce polylactic acid. .
The process used by US LLC to make biodegradable plastics from corn is as follows: First, the corn is ground into powder, the starch is separated, and the original glucose is extracted from the starch. Then anaerobic fermentation of lactobacillus, the fermentation process with liquid caustic soda to generate lactic acid, fermentation broth after purification, using electrodialysis process, made up to 99.5% purity of L-lactic acid. The extracted lactic acid is then made into the final polymer, polylactic acid. The annual global output of 600 million tons of corn makes it the raw material of choice for biodegradable plastics.
PLA can be produced from lactic acid using two processes. One is direct polycondensation, that is, dehydration polycondensation using solvents under vacuum conditions. This method is simple, but the polymer obtained has a small molecular weight, generally less than 5,000. The other is a two-step method, also called non-solvent method, in which three lactic acid molecules self-polymerize to form lactide, and then undergo ring-opening polycondensation into PLA, so that a PLA with a higher molecular weight can be obtained. However, in this process, special catalysts and initiators must be selected; at the same time, lactide must be purified, otherwise it is difficult to obtain polymers with higher molecular weights, and inert gases are also used to prevent side reactions.
A U.S. institute has successfully developed a method to convert the scrapped potatoes after cheese production into glucose syrup, ferment them with bacteria into lactic acid fermentation liquor, and electrodialysis separation and heating to evaporate water to obtain polylactic acid that can be used for making films and coatings. As a fresh-keeping bag and in place of polyethylene and waterproof wax packaging materials.
On April 29, 2004, the French Danone Dairy Company produced a yoghurt box and cup made of lactic acid from sugar beets. This raw lactic acid can also be used to produce polylactic acid using the leftover lean sugar solution of the industrial sugar process, and the production cost is greatly reduced. The basic raw material that becomes a one-box (cup) after being mixed with minerals is sugar beet, which is first decomposed into monosaccharides, fermented to produce lactic acid, and then chemically polymerized lactic acid into a kind of light, strong material. (Text / Yang Yan)
Development and Application of Novel Green Packaging Material Polylactic Acid
May 04 08:06:35, 2024
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