Views: 0 Author: Site Editor Publish Time: 2023-08-13 Origin: Site
Characteristics and applications
Chloroprene rubber (CR) is the main raw material of chloroprene rubber adhesive, the adhesive can be cold cured at room temperature, the initial adhesive force is very large, the strength of the establishment of a rapid, high bonding strength, excellent overall performance, the use of a wide range of applications, able to bond rubber, leather, fabrics, leather, plastics, wood, paper, glass, ceramics, concrete, metal and many other materials, so the chloroprene rubber adhesive is also called Therefore, neoprene rubber adhesive also has the name of "universal adhesive". Neoprene rubber adhesive has a solvent-based, emulsion type and solvent-free liquid type, solvent-based is divided into mixed and graft type. Blends include pure CR adhesives and CR adhesives containing fillers, as well as resin-modified CR adhesives. Graft type is neoprene rubber and methyl methacrylate and other monomer solution graft copolymerization of the adhesive. At present, the solvent-based neoprene rubber adhesive is still the most used, measures should be taken to reduce toxic pollution, in line with environmental requirements.
First, mixed type neoprene rubber adhesive
Mixed neoprene rubber adhesive means that the neoprene rubber by mixing (or not mixing) dissolved in a mixture of solvents, adding resins, antioxidants, fillers and other additives.
Aging agent, filler and other additives into a one-component or two-component solvent-based adhesive.
1、 Characteristics
(1), the initial adhesive force, neoprene rubber is easy to crystallize, adhesive coating and drying stacking, it can be instantaneous crystallization plus with
Tackifier resin, showing a large initial adhesive force. (2), the strength of the establishment of fast, neoprene adhesives rely on their own crystallization and curing, CR crystallization speed, bonding immediately after the bond has sufficient bonding strength. (3), high bonding strength, high crystallinity of neoprene rubber, cohesion strength, and thus high bonding strength of CR adhesive. (4), good media resistance, oil resistance, water resistance, good chemical resistance. (5) The adhesive layer is soft, elastic and resistant to shock and vibration. (6), good durability, excellent light resistance, ozone resistance, atmospheric aging resistance, flame retardant. Rubber and steel bonding in the indoor 20 years after the bonding strength almost does not decline. (7), wide range of uses, metal and non-metallic materials have good adhesion, especially different materials bonded to each other, other rubber-based adhesives can not be compared. (8), easy to use, after drying glue, once the contact, immediate bonding without prolonged pressure, can be cured at outdoor temperature. (9), poor heat resistance, cold resistance is not good. (10), most of the solvent-based neoprene adhesive has a certain degree of toxicity and pollution.
Mixed neoprene adhesive is a very practical adhesive, widely used in industrial production and daily life. Especially It is widely used in industrial production and daily life, especially in shoe-making, furniture, construction, automobile and other industries with a large amount.
2.Composition
Mixed neoprene rubber consists of neoprene rubber, tackifying resin, metal oxides, solvents, antioxidants, fillers, accelerators,
Crosslinking agent and so on.
I. Chloroprene rubber
Chloroprene rubber, also known as polychloroprene, is 2-chloro-1,3 butadiene as the main raw material by emulsion polymerization and produced a kind of elastomer.
Elastomer. Chloroprene rubber is white or yellowish flake or tough solid, with reversible crystallinity, good adhesion, high tensile strength and elongation. Excellent aging, heat, oil and chemical resistance. Weather resistance and ozone aging resistance is second only to ethylene propylene rubber and butyl rubber. Heat resistance and nitrile rubber. Good resistance to inorganic acid and alkali corrosion. Has a certain degree of flame retardancy. Slightly worse heat resistance, electrical insulation is not good.
2, tackifying resin
Tackifier resin is an important component of solvent-based neoprene adhesive, which can improve cohesive strength, adhesive properties, heat resistance, water resistance and aging resistance.
Sex and aging resistance. Tackifier resins used are thermo-reactive alkyl phenolic resins, petroleum resins, terpene phenolic resins, terpene resins, rosin-modified phenolic resins, gumarone resins, rosin esters, poly a-methylstyrene and so on. Among them, tert-butylphenol formaldehyde resin (2402 resin) has the best effect. Tackifier resin has almost no effect on the crystallinity of neoprene rubber. Terpene phenolic resin is a non-reactive thermoplastic resin can extend the adhesive retention period, and make the adhesive layer soft, Gumarone resin will also make the neoprene adhesive
The gumarone resins also give a slight increase in the bond strength of neoprene adhesives. Chloroprene rubber AF is a carboxylic acid CR, with which the formulated adhesive bonding strength is established faster heat resistance, high delamination resistance, however, due to its reactivity, the viscosity of the adhesive in the storage process will rise, which is due to the crosslinking effect of magnesium oxide. Therefore, in the preparation of AF neoprene adhesive in order to obtain better viscosity stability and comprehensive performance must be added to a sufficient amount of 2402 resin, and magnesium oxide should be pre-reacted with the resin to generate chelates can prevent the magnesium oxide and hydroxyl direct reaction and increase the viscosity stability and heat resistance of the system.
3, metal oxides
Metal oxides in neoprene adhesives have four roles: acid absorber, anti-scorch agent, vulcanizing agent, resin reactant. Over time, neoprene rubber will release trace amounts of hydrogen chloride, can promote further decomposition of polymers, and will corrode metals and natural fibers, adding metal oxides can absorb hydrogen chloride to avoid degradation continues. The metal oxides generally used are mainly zinc oxide and magnesium oxide. Magnesium oxide has the function of absorbing acid, pre-reaction, anti-scorch, vulcanization, etc. It is an indispensable component of neoprene adhesive. Magnesium oxide and resin pre-reaction can improve the adhesive heat resistance and prevent delamination precipitation, magnesium oxide dosage on the pre-reaction effect and adhesive properties have an impact, with the magnesium oxide dosage increases, the high temperature strength increases, but the stability of the adhesive liquid is reduced. The addition of magnesium oxide can effectively accelerate the adhesive film to dry, and can greatly improve the initial bond strength, which may be due to calcined light magnesium oxide or active magnesium oxide. Light magnesium oxide is white amorphous powder, odorless and tasteless. Relative density 3. 58, melting point 28520C, boiling point 36000C in the air can gradually absorb carbon dioxide and water to generate basic magnesium carbonate . Zinc oxide added to the chloroprene adhesive can play a role in the absorption of acid, but that is a vulcanizing agent is not objective because the chloroprene adhesive is mostly outdoor temperature using the cold due to the chemical will not produce vulcanization, but also in the storage of the bottom of the precipitation. At the same time, zinc oxide can make the adhesive liquid become turbid, so that the adhesive film is sticky, seemingly dry non-dry, used for bonding polyurethane foam, zinc oxide will promote the aging of the material. Based on the above reasons can cancel the zinc oxide in fact, foreign electrical appliances with CR adhesive has not added zinc oxide, the glue is transparent and not layered. Without zinc oxide can also achieve the required bonding strength, but also to avoid burning of the adhesive refining, to prevent the adhesive in long-term storage
Produce gel and precipitation, and will not cause phase separation of the glue. If the neoprene adhesive bonding in high temperature use, add a small amount (1~3 copies) of ultra-fine active zinc oxide is beneficial.
4, antioxidant
In order to prevent the decomposition of rubber, enhance the aging resistance, prolong the service life, to maintain the durability of the bonded parts, it is necessary to add appropriate antioxidant. Used antioxidant D effect is very good but polluting and carcinogenic should be abandoned to ODA, RD, 264, etc. instead. Antioxidant 2246 can also be used, but will produce a discoloration phenomenon, in chlorinated solvents is light blue, blue to green changes in the latex is pink.
5, solvent
Solvent is a solvent-based neoprene adhesive indispensable high amount of components, the performance of the adhesive has an important impact. Chloroprene rubber solubility number of 9.2 ~ 9.4, soluble in benzene, toluene, dichloromethane, methylene chloride, methylene chloride, trichloromethane, 1, 1, 1-trichloroethane, carbon tetrachloride, trichloroethylene, butanone, etc., slightly soluble in cyclohexane, ethyl acetate, methyl acetate, isopropyl acetate, acetone, insoluble in n-alkane, n-heptane, n-heptane, solvent gasoline, isopropanol and so on. Undesirable solvents and non-solvents alone are not dissolved neoprene rubber, but through the appropriate proportion of mixing can also dissolve neoprene rubber. Solvent solubility of neoprene rubber, adhesive viscosity, viscosity stability, adhesive wetting, viscosity retention period, the initial adhesive force, drying speed, bond strength, storage stability, low temperature resistance, flammability, explosiveness, toxicity, contamination, adhesive cost, etc. have a great impact.
6, filler
Filler in the solvent-based neoprene adhesive is not used much, because the adhesive solvent dosage, low solid content, easy to precipitate, can not play the expected role. If superfine activated calcium carbonate is used, it may be more stable. And the use of ultrafine talcum powder, ultrafine silica, ultrafine aluminum silicate, ultrafine clay can only be maintained for a short period of time stable. And finally there will be precipitation.
7, crosslinking agent
Crosslinking agent, also known as curing agent, can accelerate the curing speed of neoprene rubber adhesive, improve bonding strength, heat resistance, water resistance, oil resistance, chemical resistance, aging resistance. Commonly used crosslinking agent for polyisocyanate, such as tetraisocyanate. Polyisocyanate crosslinking agent with high reactivity, add chloroprene adhesive 2~3h can be crosslinked gel, as a two-component adhesive, before the use of deployment, mixing and use immediately.
8, accelerator
Promoter is to promote vulcanization to improve heat resistance and add substances, such as vinylthiourea (NA-22), diethylthiourea (DE-TU), diphenylthiourea (promoter C), diaminodiphenylmethane, dosage of general 0.25 ~ 1 share. Some people found in the chloroprene adhesive by adding BRN-type vulcanizing black, can accelerate the vulcanization, adhesion is no less than polyisocyanate vulcanization system and toxicity is greatly reduced.