Application of the hottest environmental friendly

2022-10-19
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Application of environmental friendly adhesives in packaging materials

under this topic, we need to talk about two major issues. The first question is what kind of adhesive is environmentally friendly and what is the connotation of environmentally friendly adhesive. The second is the application and characteristics of environmental friendly adhesives

what kind of adhesive is an environmental friendly adhesive? This should start with the historical change of using adhesives in packaging materials

flexible composite packaging materials refer to packaging films or bags made of various plastic films, paper, aluminum foil and other substrates, which are bonded together with adhesives. In China, the industry of manufacturing composite packaging materials by various methods is a sunrise industry that started in the mid-1970s, developed rapidly in the mid-1980s, and advanced rapidly after the 1990s. It has formed a complete industrial system so far. Among them, dry compounding method is the main method, and most of it is used in the packaging of food and drugs

one component solvent-based adhesives were first used in dry compounding in China. After the mid-1980s, ester soluble polyurethane adhesives were used, and have been widely used until now. Solvent free polyurethane adhesives appeared in the late 1990s, and water-based adhesives and alcohol soluble adhesives appeared at the beginning of this century. In recent years, solvent-free, water-based and alcohol soluble adhesives are collectively referred to as environmental friendly adhesives

which kind of adhesive is hygienic, safe and green? We have to analyze and describe them one by one, and compare them with the connotation of non-toxic and harmless, health and safety, environmental protection, resource conservation and energy consumption reduction, so as to get the answer

one component solvent-based adhesive

it is made of synthetic rubber as the base material, plus tackifier, antioxidant and stabilizer. It is made of organic solvent. Some products also contain benzene soluble, which is a bit like current pressure-sensitive adhesive. It can bond all substrates. It is affordable and easy to use. It was popular from the mid-1970s to the mid-1980s of the last century. However, the adhesive fastness is not high, it is not heat-resistant, water-resistant, and it is not resistant to the corrosion of media, especially the residual solubility, odor, toxicity, and the risk of flammability and explosion, which does not meet the requirements of health, safety, green and environmental protection. Therefore, it has been phased out since the mid-1980s and replaced by ester and soluble polyurethane adhesive proved by the company's research results

water-based adhesives

the water-based adhesives that have appeared in the past three or five years include water-based polyacrylates and water-based polyurethane

aqueous polyacrylate adhesive

it is copolymerized with acrylic acid, acrylate (methyl ester, maximum moving distance up to 40 cm, ethyl ester, butyl ester, hydroxyethyl ester, etc.) and methacrylate. In this system, there are not only two simple substances, acrylate copolymer and water, but also residual catalysts or their decomposition products, free radicals, emulsifiers, pH

saving agents, stabilizers, antifreeze agents, etc. At present, there is no definite conclusion whether these additives are hygienic and safe and harmless to human body. Moreover, when introducing the product performance and application technology, the enterprises providing such products also specially reminded that pure water should not be used to dilute, but must be diluted with the mixture of water and isopropanol after "hedging". We know that isopropanol is an organic solvent with a boiling point of 82.4 ℃. It is a flammable and explosive first-class flammable liquid. Isopropanol has a stronger physiological effect on human body than ethanol, and its toxicity, anesthesia and irritation to mucosa are also stronger than ethanol. The oral LD50 of rats is only 5840mg/kg body weight (13700mg/kg body weight for ethanol), which is only 43% of that of ethanol. It is also reported that long-term exposure to isopropanol will lead to nasal cancer. Since the mid-1980s, the abuse of isopropanol has been restricted. Therefore, such water-based polyacrylate adhesives cannot be called environmental friendly adhesives

water based polyurethane adhesive

it uses water instead of ethyl acetate, which is odorless, tasteless, non irritating, will not burn and explode, safe to use, and cheap, which is its advantage. However, to make water-based polyurethane adhesive, the substances contained in its system are as complex as water-based polyacrylate adhesive. These substances also have the problems of health and safety, green and environmental protection. If it is a two-component waterborne polyurethane, in the component containing - NCO group, the "capping agent" that protects the - NCO group from chemical reaction with active water molecules has greater health and safety problems. If phenolic compounds are used, its damage to human health is more obvious. In this way, it is difficult to say that waterborne polyurethane adhesives are environmentally friendly adhesives

alcohol soluble polyurethane adhesive

compared with the ester soluble polyurethane adhesive that has been used since the 1950s, it is exactly the same polyurethane in terms of its base material, except that the solvent used has been changed from ethyl acetate to alcohol

alcohol and ethyl acetate are both organic solvents, which also have the risk of flammability and explosion and the problem of air pollution. In recent six or seven years of research, it has been found that alcohol has a very serious damage to human health due to the combination of technology such as precursor design and repeated processing. It is more terrible than ethyl acetate to human health

alcohol has serious damage to human health. The reason is that alcohol (that is, ethanol) is oxidized under the action of oxidase after being inhaled into the body to produce acetaldehyde:

American scientists believe that acetaldehyde, like formaldehyde, is a carcinogenic substance, so ethanol is not non-toxic

in addition, it can be seen from the toxicity description in the 86 edition of solvent manual that compared with ethyl acetate, alcohol is more serious and severe than ethyl acetate in terms of the universality and severity of damage to human organs.

ethanol (i.e. alcohol) not only damages the central nervous system and paralyzes motor reflex, but also causes gastritis, dyspepsia, chronic liver disease, cirrhosis, and even pancreatic and heart diseases

ethyl acetate has anesthetic effect. Its vapor irritates eyes, skin and mucosa. High concentration vapor can cause liver and kidney congestion. If a large amount of ethyl acetate is continuously inhaled, acute pulmonary edema can occur

ester soluble polyurethane adhesive

with ethyl acetate as solvent, it only contains three simple substances: polyurethane resin, additives approved by FDA and ethyl acetate. It can even contain only two substances: polyurethane resin and ethyl acetate. It no longer contains other additives whose health and safety properties are unknown. It has been used in food and drug composites since the late 1950s and is still widely used today, In China, about 80% of composite materials are made with it

as far as the rubber itself is concerned, after five or six decades of practical testing, testing, research and long-term comprehensive and strict safety toxicological evaluation tests, it shows that this ester soluble polyurethane adhesive is hygienic and safe. Its LD50 is higher than 21500mg/kg body weight, and its MTD is also greater than 20000mg/kg body weight, far higher than the highest safety level of 15000mg/kg body weight - the data of this "non-toxic substance", Ethyl acetate used in ester soluble polyurethane adhesive is a flammable and explosive first-class flammable liquid, which has irritating effect on people, but does not cause much damage to human health. Therefore, the author believes that it is an adhesive product that meets the requirements of health, safety, green and environmental protection

solventless adhesives

solventless adhesives no longer contain any solvent media except rubber. They contain neither toxic, harmful or flammable and explosive organic solvents (benzene, alcohol or ester), nor water with large heat capacity and need to be dried with a large amount of heat energy. Therefore, the use of solventless adhesives does not have the problem of stimulation and toxicity to operators, and there is no danger of combustion and explosion, There will be no corrosion of mechanical equipment caused by water vapor, and there will be no problems of exhaust emission, air pollution and environmental damage. Its ingredients are only polyurethane and health and safety additives approved by FDA. It can even be as simple as polyurethane resin. There is no longer anything with uncertain health and safety performance. It is more reliable than ester soluble polyurethane adhesive, and it is more hygienic and safe if it is aliphatic

when using solvent-free adhesive, it does not need a huge heating, blowing and exhaust system, which is more energy-saving than water-soluble and ester soluble. The mechanical equipment is simpler and compact. Its composite starting speed is very high, up to 600 meters per minute, most of which are 400 ~ 480 meters, four to five times that of water-based adhesive and three to four times that of solvent-based adhesive, so the labor productivity is very high and the production cost is low. Since the solvent-free adhesive is 100% usable material, the glue amount per square meter area is small, generally no more than 2 grams, so resources are saved and the cost consumption of adhesive is lower

comparison results of various adhesives

considering the connotation of non-toxic and harmless to human body, no waste gas, friendly to the environment, non combustible and non explosive, reducing energy consumption, high-speed and high-yield, resource saving and so on, insoluble enterprises need to optimize the dosage form of processing machinery and equipment, and adhesives are truly "environmental friendly adhesives"

the ester soluble adhesive with ethyl acetate as solvent is hygienic, safe and relatively green

alcohol soluble polyurethane adhesive, because it contains a lot of alcohol and some additives whose health and safety are not reliable, it is difficult to say that it is a health, safety, green and environmental friendly adhesive

compared with alcohol soluble adhesives, water-based polyacrylate adhesives only have the advantages of non combustibility, non explosion, no stimulation and low price of water. However, in terms of health and safety and the dilution of the mixture of isopropanol and water, it is not quite consistent with the real health, safety and green environmental protection adhesives

single component pressure-sensitive adhesives, especially those containing benzene solvents, are not health, safety, green and environmental friendly adhesives

application and characteristics of environmental friendly adhesives in composites

solvent free polyurethane adhesives, whether aliphatic or aromatic, have two kinds of one component and two component

one component solventless polyurethane adhesive is a substance with the same molecular structure as the adhesive in one component solvent-based polyurethane adhesive, which is a polymer with polyisocyanate group (i.e., NCO) and a certain molecular weight:

one component solventless polyurethane adhesive is a product cured by wet steam crosslinking. In general, at least one of the composite substrates is a material with high water vapor transmission, such as paper, fabric, or the surface of the substrate absorbs more water, or it is humidified quantitatively (i.e. sprayed with water vapor) during compounding, so that the isocyanate group in the adhesive can be crosslinked and cured. However, when using this kind of adhesive, the humidification amount is difficult to control and the product quality is difficult to grasp. Therefore, similar to the dry compounding process, the two-component solventless polyurethane adhesive is the most widely used at present, while the single component one is rarely used

two component solventless polyurethane adhesive, like solvent-based two-component polyurethane adhesive, is divided into main agent and

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