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    Home > Coatings News > Paints and Coatings Market > Epoxy resin production process

    Epoxy resin production process

    • Last Update: 2020-06-19
    • Source: Internet
    • Author: User
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    < br / > 1Definition and development history < br / > 1.1 definition < br / > epoxy resin (epoxyresin) is a polymer prepolymer with two or more epoxy groups and aliphatic or aromatic groups as the main chain(some epoxies are also called epoxies without distinction because of their basic properties.)The typical structure of epoxy resin is: < br / > chemical name: bisphenol A diglycidyl ether < br / > English Name: diglycidyl ether of bisphenolA (abbreviated dgebpa) < br / > epoxy group is the characteristic group of epoxy resin, and its content is the most important index of this resinThere are three different ways to describe epoxy content< br / > epoxy equivalent refers to the mass of epoxy resin containing 1mol, and the epoxy equivalent of epoxy resin with low molecular weight (molecular weight) is 175-200g / molthe longer the chain segment between epoxy groups is, the higher the epoxy equivalent of high molecular weight epoxy resin isIf there is no branch in the resin chain segment, it is a linear molecule, and both ends of the chain segment are terminated by an epoxy group, then the epoxy equivalent will be half of the average molecular weight of the resinIt can be deduced that the molecular weight = epoxy equivalent × 2This formula is only applicable to the above ideal stateThe physical quantity of epoxy equivalent is often used in the United States, European countries, Japan and other countries< br / > epoxy value the amount (mole) of epoxy in every 100g of resinThis method is beneficial to the measurement and expression of the amount of curing agentBecause the amount of curing agent means the amount of curing agent added per 100g of epoxy resin (abbreviated as phr)The concept of epoxy value is adopted in China< br / > the mass fraction of epoxy group per 100g of resin (g)This physical quantity is commonly used by Russia and Eastern European countries The conversion formula between the three expressions is as follows: < br / > < br / > the molecular weight of epoxy group is 43 / mol < br / > the mass fraction of epoxy group = the molecular weight of epoxy group × the epoxy value < br / > < br / > epoxy resin is a kind of substance from liquid to solid It has almost no independent use value Generally, it has application value only when it reacts with curing agent to form three-dimensional network structure of insoluble and immiscible polymer Epoxy resin belongs to the category of thermosetting resin This kind of prepolymer changes into solidified product According to their uses, they are called epoxy coating, epoxy adhesive, epoxy laminate, epoxy resin casting material, etc < br / > 1.2 development history < br / > the invention of epoxy resin has gone through a quite long period, its industrial production and application is only nearly 40 years < br / > at the end of the 19th century and the beginning of the 20th century, two major discoveries opened the curtain of the invention of epoxy resin As far back as 1891, lindmann in Germany reacted with hydroquinone and epichlorohydrin to form resin like products In 1909, Russian chemist prileschajew found that the reaction of anisole peroxide with alkene can produce epoxy compounds These two chemical reactions are still the main way in the synthesis of epoxy resin < br / > in 1934, schlack polymerized the compounds containing more than one epoxy group with amines to prepare high polymer, which was published as a German patent In 1938, a number of patents published by Pierre Tan in Switzerland and S.O Greenlee in the United States revealed that bisphenol A and epichlorohydrin can be polycondensated to produce epoxy resin; the resin can be cured with organic polyamines or phthalic acid, and has excellent adhesion These research results prompted Devoe Raynolds to manufacture epoxy resin with industrial production value for the first time in 1947 Soon Ciba company in Switzerland, shell company in the United States and chemical company all started the industrial production and application development of epoxy resin By the early 1950s, epoxy resin had made a breakthrough in the fields of electrical insulation casting, anti-corrosion coating, metal bonding and other applications So epoxy resin as an industry has developed vigorously < br / > the development of epoxy resin in China started in 1956, and it was first successful in Shenyang and Shanghai Industrial production began in Shanghai in 1958 < br / > after more than 40 years' efforts, the production and application of epoxy resin in China has developed rapidly At present, there are more than 100 manufacturers With the increasing variety, output and quality of production, it is playing an increasingly important role in the construction of modernization However, compared with the world's advanced level in terms of production scale, product quality and variety, there is still a big gap In order to meet the needs of all walks of life for epoxy resin, we must use the leaping development mode to develop towards the six directions of "scale, high purification, refinement, specialization, serialization and functionalization" < br / > 2 The characteristics of epoxy resin < br / > the most common and representative variety of epoxy resin is bisphenol A diglycidyl ether, which is commonly known as bisphenol a type epoxy resin < br / > resin < br / > according to its chemical structure, it has the following characteristics: < br / > 2.1 high bonding strength and wide bonding area < br / > epoxy resin structure contains hydroxyl, ether bond and epoxy group with great activity, which make the molecule and adjacent interface of epoxy resin produce electromagnetic adsorption or chemical bond, In particular, the epoxy group can be crosslinked and polymerized under the action of curing agent to form macromolecules with three-dimensional network structure, which have certain cohesion Therefore, the adhesive of epoxy resin is particularly strong Except that PTFE, polypropylene and polyethylene can not be directly bonded with epoxy resin adhesive, most of the metal and non-metal have good adhesion, so it has the reputation of ten thousand adhesive The bonding strength of the adhesive with many non-metallic materials (glass, ceramics, wood) is often greater than the strength of the material itself, so it can be used in many stressed structural parts and is one of the main components of structural adhesive < br / > 2.2 low shrinkage < br / > the curing of epoxy resin mainly depends on the ring opening addition polymerization of epoxy group, so there is no low molecular substance in the curing process; the epoxy resin itself has secondary hydroxyl group, plus some residual hydroxyl groups derived from the curing of epoxy group, and their hydrogen bond association makes the molecular arrangement close, Therefore, the curing shrinkage of epoxy resin is one of the lowest thermosetting resins, generally 1% - 2% If proper filling is selected, the curing shrinkage can be reduced to 0.2% < br / > the low curing shrinkage of epoxy resin makes the size of processed products stable Small internal stress, not easy to crack Therefore, epoxy resin is widely used in the casting process < br / > 2.3 good stability < br / > as long as the epoxy resin does not contain acid, alkali, salt and other impurities, it is not easy to deteriorate If it is stored well (such as sealed, not affected by moisture, not exposed to high temperature), it can have a service life of 1 year, and it can still be used after 1 year if it passes the inspection < br / > after curing, the main chain of epoxy resin is ether bond, benzene ring and three-way cross-linking structure, which is dense and closed, so it is acid and alkali resistant and multi-media resistant < br / > 2.4 excellent electrical insulation < br / > the cured epoxy resin has low water absorption, no longer has active groups and free ions, so it has excellent electrical insulation < br / > 2.5 high mechanical strength < br / > the cured epoxy resin has strong cohesive force, but its molecular structure is compact, so its mechanical strength is relatively higher than that of phenolic resin and polyester resin < br / > 2.6 good processability < br / > the flexibility of epoxy resin formula components, the diversity of processing technology and product performance are rare in polymer materials < br / > before curing, the epoxy resin is thermoplastic, low molecular weight is liquid, medium and high molecular weight is solid Heating can reduce the viscosity of the resin In the temperature range above the softening point of the resin, epoxy resin and curing agent, other additives and fillers have good miscibility Because there is no release of low molecular substances in the curing process, it can be formed under atmospheric pressure, and no need to vent or change the pressure, so the operation is very convenient, and no need for excessively high technical equipment < br / > classification, properties and basic raw materials of epoxy resin < br / > 1 Classification of epoxy resin < br / > there are many kinds of epoxy resin There are two main classification methods: one is divided by chemical structure; the other is divided by form < br / > the former classification method is more scientific, while the latter one is also practical < br / > classified by chemical structure It is classified according to the chemical structure of epoxy group and the structure of epoxy group Therefore, epoxy resins can be roughly divided into the following categories: < br / > (1) glycidyletherins; (2) glycidyletherins; (3) glycidylamineresins; (4) ALICYCLIC EPOXIDES; (5) linear aliphatic epoxies (Alicyclicepoxides)。 < br / > the modified epoxy resin is classified according to the original matrix For example, organic (such as silicon, phosphorus) epoxy resin, polyurethane epoxy resin < br / > 2 The structure and properties of all kinds of epoxy resin < br / > 2.1 glycidyl ether type epoxy resin < br / > this kind of epoxy resin is made by polycondensation of polyphenol or polyol with epichlorohydrin The most representative is that the output of diglycidyl ether of bisphenol A (degbpa) accounts for more than 75% of the total epoxy resin in the world, and its application covers the whole field of national economy, so it is called universal epoxy resin < br / > 2.1.1 bisphenol A diglycidyl ether < br / > the most typical characteristics of the resin are as follows: < br / > (1) high bonding strength, wide bonding surface, which can be used to bond almost all materials except polyolefin; < br / > (2) low curing shrinkage, less than 2%, which is the smallest shrinkage in thermosetting resin; < br / > (3) good stability, When no curing agent is added, it can be placed for more than 1 year without deterioration; < br / > (4) it has good chemical resistance, acid and alkali resistance and many chemicals; < br / > (5) it has high mechanical strength and can be used as structural materials; < br / > (6) it has good electrical insulation and its general performance is better than polyester resin < br / > but it has the following disadvantages: < br / > (1) poor weather resistance, which will degrade under ultraviolet radiation, resulting in performance degradation and can not be used outdoors for a long time; < br / > (2) low impact strength; < br / > (3) not very high temperature resistant < br / > in addition to dgebpa, tetrabromobisphenol A diglycidyl ether has excellent flame retardancy due to the presence of bromine in its structure < br / > hydrogenated bisphenol A diglycidyl ether is prepared by the polycondensation reaction of alicyclic diol and epichlorohydrin which bisphenol A is hydrogenated Therefore, the cured product not only has the characteristics of bisphenol A diglycidyl ether, but also has the characteristics of weather resistance and ultraviolet radiation resistance, and the impact strength is better than the general alicyclic epoxide It is mainly used for casting and coating outdoor electrical appliances < br / > 2.1.2 bisphenol F diglycidyl ether < br / > has the basic properties of general epoxy resin, which is characterized by low viscosity and good fluidity Compared with the same molecular weight, its viscosity is about half of that of diglycidyl ether Therefore, it is suitable for low temperature applications, such as coating and adhesive for outdoor construction in winter, and raw materials for insulating impregnating paint < br / > bisphenol s epoxy resin has high viscosity and reactivity The thermal deformation temperature of the cured product is 40 ~ 60 ℃ higher than that of bisphenol A < br / > 2.1.3 aliphatic alcohol polyglycidyl ether < br / > polyoxyalkylene glycol diglycidylbutane structure formula is as follows: < br / > this resin takes long chain aliphatic chain as the main chain, the chain segment can rotate, showing excellent flexibility Its main purpose is to improve the brittleness of cured products of bisphenol A epoxy resin and linear phenolic resin However, if the dosage is too much, the heat resistance and resistance of the solidified product will be improved
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