Advances in the study of colorless transparent epoxy adhesives

China Paint Online News News
Li Mingkun 1, Yu Xinhai 1, Chen Jiwei 1, Liu Wanzhang 2 (1. Department of Applied Chemistry, Donghua University, Shanghai 201620; 2. Zhejiang Jinpeng Chemical Co., Ltd., Taizhou, Zhejiang 318050)
Summary: High transparency of colorless epoxy adhesives are mainly used in transparent materials and optical instruments and other industries. This paper focuses on the preparation methods of colorless transparent epoxy resins, curing agents and epoxy adhesives, as well as their development course and research status.
key words: colorless transparent, epoxy resin, adhesive
epoxy resin has a lot of excellent performance. Colorless transparent adhesives are commonly used for the bonding of transparent materials and light instruments due to their excellent light transmission and refractive index. In the field of optics, in particular the bonding of special components of optical instruments such as rangefinders, alferometers, telescopes, microscopes, projectors lenses and magnifying glasses, etc.; Therefore, colorless transparent epoxy adhesive has a very broad development prospects, for epoxy adhesive colorless transparency research has become a hot spot. This paper focuses on the research results of some well-transparent epoxy resins and curing agents, as well as colorless transparent epoxy gels.1. The purity of epoxy resin directly affects the transparency of epoxy adhesive
1.1 epoxy resin
as the most important component of epoxy adhesive. Taking the commonly used Bisphenol A epoxy resin as an example, the existing technology can make this kind of resin impurity content is very low, and the appearance can almost reach near colorless state, but the bisphenol A structure in the process of use by the photothermal action is easily oxidized to form a niobium base and yellowing, can add the appropriate amount of antioxidants and photothermal stabilizers to prevent and delay yellowing.1.2 Curing agents s5,6 s
Adipose polyamines and acid anhydride curing agents are the largest use of 2 types of curing agents, of which fat family polyamines are room temperature curing agents, its curing process Large heat release, resulting in local heating, accelerated yellowing, reduce gloss, the product brittle, heat and acid resistance are poor, and strong irritation, toxicity, but also easy to produce bleaching phenomenon, further reduce the transparency of epoxy curing. To this end, the raw amine needs to be modified. For example, replacing hydroxyalkyl on the N-atoms of amine can effectively reduce toxicity and improve its own color stability, to a certain extent, inhibit or delay yellowing in the curing process, and improve the transparency of epoxy adhesive. In addition, there are many modified methods: Michacl addition, amine methylation reaction, polyamine shrinking, sulphate shrinking, ecyclic compound addition, reaction with epoxy compounds, reaction with organic acids, reaction with organic acids, comelting mixed polyamines, etc.are mostly used to heat cured epoxy, usually in order to speed up the reaction speed of acid anhydride and epoxy resin, but also need to add the appropriate amount of promoter such as schoamine. In order to obtain a colorless transparent epoxy/acid curing system with good light transmission performance, acids with good weather resistance and saturated ring structure should be selected to avoid color change during heating curing process and long-term thermal use.1.3 Other additives
Other additives include promoter, toughener, thinner, stabilizer, plasticizer, filler, enhancer, coupled agent, flame retardant, de bubble inhibitor, etc. In addition to the color transparency of the additive itself affects the transparency of the adhesive, the color change in the process of use can not be ignored. For example, under the conditions of thermal oxygen and ultraviolet exposure, seramine promoter and pyrethroid promoter are yellowing, reducing adhesive transparency, so the right amount of antioxidants and UV absorbents need to be added. The existingtechnology can produce epoxy resins with very little impurity content and very pure and almost transparent epoxy
resins. The transparency of epoxy resins can be evaluated according to the epoxy color test method- Gardner color method, or the platinum-cobalt color method (i.e. Hazen method). The color measured by the Gardner color method increases and deepens with the color number, and the color color of pure water is measured by 1. Platinum-cobalt color method is also with the color value increase color deepening, color number 1 to 30 for colorless, 30 to 60 for almost colorless. As early as the 1980s, developed countries epoxy resin color has been able to control steadily below Gardnerl, the market product indicators are less than 1. In the 90's, the color of foreign epoxy resin has been much smaller than G1 near colorless transparent state, below Gardner 0.2. In this paper, the epoxy resin ≤1 or platinum-cobalt measurement≤60 is considered a colorless transparent epoxy resin.2.1 BPA colorless transparent epoxy resin
BIOL A epoxy resin also known as E epoxy resin, most of the epoxy resins currently used in this type. A wide range of products, good transparency of BPA type epoxy E-51, E-54, E-55 and so on. The more common view of the color-producing mechanism of BPA is that bisphenol A and possible impurities free phenol, bisphenol isomers oxidized into chlorine biochromic substances lead to the production of color. Such as isomers in BPA (2.2', 2.4') its reaction activity is less than the pair to replace BPA, the presence of such isomers, in the resin synthesis process may exist unreacted phenol hydroxyl, in the recovery of epoxy chloropropane, desolate and other post-treatment oxidation, so that the resin color darkening. Table 1 lists the color of some epoxy resins.Table 1 Some manufacturers at home and abroad E-type epoxy resin products 2.2 BPA F-type colorless transparent epoxy resin
BPA F-type epoxy resin for colorless or pale yellow liquid. Its adhesion, reactivity and BPA type is about the same, but its relative molecular quality is low, and therefore the viscosity is also low, can be used without or with less thinner, is a more environmentally friendly resin. NPEF-198 in South Asia, PY-306 in Ciba, Switzerland, JER4005P, JER4007P, JER4010P and other color numbers (G) ≤1, colorless transparency is excellent.2.3 Hydrogenated Bisphenol A colorless transparent epoxy resin
Bisphenol A epoxy resin also known as BPA H shrinking glyceros ether, its liquid product is a pale yellow transparent liquid. Is a small molecular mass, low viscosity, with good weather resistance, arc resistance and leakage trace resistance, especially suitable for outdoor epoxy resin. Such as Mitsubishi Chemical's YX8000, YX8034, YX8040, etc., the color number (G) ≤1.2.4 Other types of colorless transparent epoxy resin
1) 711 epoxy resin
i.e. tethydrobiphenylate double shrink glycerides, is a more transparent epoxy resin, inter-benzodiaxamine 50 degrees C curing 2h can be 85% of the light transmission rate of the product. Foreign brands are Epikote E-190, S-540, etc.2) Water-based epoxy resin
mainly include epoxy emulsion and water-soluble epoxy resin. The HTW-609, which has a solid content of 100% produced by Suzhou Sanjie special resin, is a transparent and uniform self-emulsified epoxy resin.
3. Colorless transparent curing agent
3.1 fatamine curing agent
fatamine curing agent has high reaction activity, can be quickly cured at room temperature, and heating can accelerate curing. Its application period is short, high heat when curing, easy to lead to poor gloss of the product. Fatty amine curing agent most of the alkaline, easy to produce the corresponding carbonate with CO, resulting in curing surface 2 al whitening, reduce product transparency. Colorless transparent fatty amine curing agents are diethylene triamide (DETA), 3-dimethylamphetamine (DMAPA), 3-dimethylamine (DEAPA), interphenylamine (MXDA), end amino polyether (ATPE), among which DMAPA, DEAPA, ATPE is a colorless transparent liquid, DETA and MXDA are colorless or pale yellow transparent liquid.3.2 lipocycamine curing agent
lipid cyclamine curing agent is a amine compound containing lipid ring structure, most of which are low viscosity liquid, low activity than fat amine curing agent, long application time, curing and heating is small, room temperature curing is not complete, need to heat up. However, the curing body has good heat resistance and flexibility, and the color is light and shiny. Colorless transparent curing agents have 1,3-2 (amomethyl) cyclohexane, 4,4'-dimethyl double 3-methyl cyclohexyl methane, TAC lipid cyclamine, 5618 curing agent, 5701 curing agent, etc., no color or pale yellow N-aminocetaminophen, isoframine diamine and so on.3.3 modified polyamine curing agent
adipose family polyamine curing agent because of the above shortcomings, it is not suitable for use alone, through the modified, increase strength and toughness, reduce toxicity to a wider range of new amine curing agents. Good transparency is: G-328 epoxy curing agent, does not produce albinism, TZ-500 phenolic amine curing agent, pure epoxy resin curing good transparency, β-hydroxyethyl amine, 593 curing agent.3.4 acidic curing agent
acidic curing agent is the earliest application, and is still an important category of epoxy curing agent, the dosage is second only to polyamine curing agent. The application period of acidic acid curing agent is long, most of the stimulation is small, the toxicity is low, the shrinkage rate is low, and the electrodynamic properties and electrical properties of epoxy gel are excellent. Compared with amine-type curing agent, high heat resistance, curing products are light, but not resistant to media especially alkali resistance, moisture and heat resistance is also poor. Well-transparent acidic curing agents are methyltephetyl phthalates (MeTHPA) (MeHHPA) (MNA-10 modified methylnadic acidic acids (MNA-10).3.5 polymer curing agent
some low-molecular polymers containing active groups such as -CHOH, -NH-、-2COOH, -NCO, -OH, -SH, etc. can also be used as curing agents for epoxy resins. These curing agents can be line phenolic resin, melamine formaldehyde resin, aniline-formaldehyde resin, inter-benzene formaldehyde resin, styrene-Malay acid copolymer resin (SMA), liquid polyurethane, polyester resin, polysulfur resin, sterol resin, etc. Because most of the above resins have good colorless transparency, the curing material obtained as epoxy curing agent is also good. 3.6 Polythionol curing agentalso known asbase curing agent, can be quickly cured at room temperature or low temperature. Multi-based curing agent is a colorless transparent fast curing epoxy adhesive in the application of the largest category, with a short curing time, high transparency advantages. Guangzhou Kawai electronic materials have used β--based propylene acid and gyroteanol reaction to make more meta-thiol esters, and then with E-51 epoxy resin heating expansion chain reaction to obtain colorless transparent, irritating odor light multi-base curing agent. Foreign polythionols are Capcure 3-800, Capcure 3830-81, CapcureLOF, Capcure40secHV, CapcureWR-6, Japan's E PomateQX-10, EpomateQX-11, EpomateQX-40, MP-2290, EH-316, EH-317, etc. 3.7 shamide curing agent
seramine-type curing agent is an anion polymerization type, also known as anion curing agent, is widely used as a promoter of acid anhydride and low-molecule polyamide-type curing agent. Its curing process heats up and cannot be used alone. Colorless transparent seramine curing agents are α-methyl methamphetamine, 2-methylamine (MPRD), triethanolamine (TEOA). Colorless or slightly yellow are pyridine (PRD), hexahydrodide (PPD), secondary ring (DBU), 596 curing agents (β,β'-dmhamethane Ethyl ethyl-4-methyl-1,3,2-triamcinoid boron hexa ring), adjacent hydroxypymphetamine (DMP-10) and pyrethyl methamphetamine (BDMA). 4. Colorless transparent epoxy adhesive
Morning Light Chemical Research Institute developed light transparent epoxy resin CGY-331 is a thermosolytic liquid resin, is a BPA type, it not only has the same epoxy resin E-51 all excellent performance, but also has a very light color, high transparency, small viscosity characteristics. The CGY-331 optical epoxy resin is nearly colorless and transparent with a colorless curing agent, and the transmission rate is similar to that of lycopic glass. Morning Light Chemical Research Institute with CGY-331 as the A component resin adhesive, respectively, with modified amine curing agent for the B components of the deployment of GHJ-01 (K), GHJ-01 (M), GHJ-02 and JN-791 optical epoxy. These products have low color, transparent, low toxicity, strong adhesion, high and low temperature resistance and other advantages. , Wang Zhong, etc., conducted field tests on the optical epoxy adhesive SEH-105 to comprehensively test its technical properties and field adaptability. The test results show that SEH-105 optical glue has better technical performance, transmission rate of more than 90%, subtle changes before and after aperture bonding, image quality is maintained well, the refractive index of the glue is close to the general optical glass, especially suitable for optical equipment manufacturing process of optical glue. And the field adaptability is strong, can be applied to the army optical equipment. Due to the shortcomings of slow curing rate and poor toughness persistence in room temperature curing epoxy adhesives, the high-strength structural glue and fast-fixing glue required by China's aviation and aerospace are almost entirely imported. To this end, Liu Xiaobo, such as the use of unsaturated polyester modified epoxy, homemade mixed amine-type curing agent and promoter and other parts developed a two-part room temperature fast solidified full transparent epoxy glue. The glue process has excellent performance, simple operation, with fast gel curing rate, low irritation, strong adhesion, long application period, anti-aging and other advantages, the quality level is comparable with similar products abroad, and the cost price is lower than similar products abroad. YuXinHai and so on, the use of E-51 epoxy resin as the main body of A, to home-made polysulfurization agent as part B, to obtain a colorless, transparent good epoxy / multibly adhesive, and this adhesive includes stretch shear strength, contact angle and surface energy, ultraviolet-visible light transmission rate, electrical properties, absorbent properties and other performance studies. Its room temperature curing stretch shear strength reached 12.1MPa, 70 degrees C viscosity of 8.84mPa.s, 2 surface can be 38.6mJ/m, the maximum pass rate of 91.5%, water absorption of 9.3%. With imported J-13 (E-5