Rubber processing products plasticizer detailed
One. Petroleum plasticizer
It is one of the most used plasticizers in rubber processing. The plasticizing effect is good, the source is rich, and the cost is low. Petroleum plasticizers are prepared by selecting appropriate crude oil for atmospheric and vacuum distillation. The main varieties are operating oil, third-line oil, transformer oil, engine oil, light heavy oil, paraffin, petrolatum, asphalt and petroleum resin, among which the most commonly used is operating oil.
1. Classification of operating oil
The process oil is a high boiling fraction of petroleum and is composed of a complex hydrocarbon compound having a molecular weight of 300 to 600 and a broad molecular weight distribution. According to the main components of the oil, the operating oil can be divided into the following three types:
1 aromatic oil: mainly aromatic oil. The brown viscous liquid has the best compatibility with rubber, good processing performance and fast absorption speed. Applicable to natural rubber and a variety of synthetic rubber; the disadvantage is that it is polluting and should be used in dark rubber products.
2 naphthenic oil: mainly cycloalkane. Light yellow or transparent liquid, less compatible with rubber than aromatic oil, but less polluting than aromatic oil, suitable for NR and a variety of synthetic rubber.
3 paraffin oil: also known as paraffinic oil, mainly linear or branched paraffin. Colorless transparent liquid, low viscosity, poor compatibility with rubber, poor processing performance, slow absorption rate, mostly used in saturated rubber, low pollution or no pollution, suitable for use in light-colored rubber products.
2. Operating oil characteristics
(1) Operating oil viscosity The higher the viscosity of the oil, the more viscous the oil is, and the operating oil has an effect on the processing properties of the rubber compound and the physical properties of the vulcanized rubber. The operating oil with low viscosity has good lubricating effect and improved cold resistance, but the volatilization loss is large during processing. When the flash point is lower than 180 ° C, the volatilization loss is greater and special care should be taken.
The viscosity of the process oil has a lot to do with temperature. The viscosity is higher at low temperatures, so the properties of the oil have a great influence on the low temperature properties of the vulcanizate. The low temperature properties of the vulcanizate can be obtained by using a low viscosity (the kinematic viscosity at -18 ° C). improve. The viscosity of the high aromatic oil is more temperature dependent than the alkane oil.
The viscosity of the operating oil is related to the heat generation of the vulcanizate, and the rubber product using the high viscosity oil has a high heat generation. At the same viscosity, the aromatic oil has a low heat generation. The tensile strength and elongation increase as the viscosity of the oil increases, and the flexibility becomes better, but the tensile stress becomes smaller. Oils of the same viscosity, if added in equal volumes, give aromatics a higher elongation than saturated oils.
2) Relative density In the petroleum industry, the relative density at 60 ° C is usually measured. The relative density of rubber processing oils is important when the rubber product is sold by weight. Typically, the relative density of the aromatic oil is greater than the relative density of the alkane and naphthenic oils. Rubber processing oils are often sold by volume, while in rubber processing they are dosed by weight.
(3) Aniline point After adding 5-10 ml of aniline to the inner tube of the test tube, the same volume of the sample is added, and then heated from the lower portion until a uniform transparent solution appears. The temperature at this time is called the aniline point of the oil. The molecular structure of the aromatic hydrocarbon plasticizer is the closest to aniline, and it is easily soluble in it, so the aniline point is the lowest. The oil with low aniline point has good compatibility with the diene rubber, and is added in a large amount without blooming. On the contrary, oils with a high aniline point need to be miscible with the raw rubber at high temperatures, so that the surface is easily ejected when the temperature is lowered. The level of the operating oil aniline point is essentially a sign of the aromatic hydrocarbon content of the oil. In general, it is suitable to operate the oil aniline point in the range of 35 to 115 °C.
(4) Pour point (flow point) The pour point is the lowest temperature capable of maintaining flow and being able to pour. This property can be expressed as applicability to the process temperature of the article.
(5) Flash point is the temperature at which a mixture of sufficient vapor and air is released to ignite under standard test conditions. The flash point of the operating oil is directly related to the vulcanization, storage and fire prevention of the rubber, as well as the volatility of the operating oil.
(6) Neutralization value The neutralization value is a measure of the acidity of the operating oil, and the acidity can cause a significant delay in the vulcanization rate of the rubber. The neutralization value can be expressed as the number of milligrams of KOH required to neutralize the acid content of 1 gram of the operating oil.
In addition, the refractive index, appearance color, and volatile matter of the oil can also reflect the composition.
3. Effect of operating oil on rubber processing properties
(1) Impact on mixing
The absorption rate of rubber on oil is related to oil composition, viscosity and mixing conditions: low viscosity, high aromatic hydrocarbon content, high temperature and fast absorption. However, the amount of oil used is too large, so that the dispersion of carbon black in the rubber is deteriorated, and it must be added in batches. In addition, adding oil during mixing can reduce heat generation and reduce energy consumption.
(2) Influence on extrusion
Adding an appropriate amount of oil to the rubber compound can soften the rubber compound, and the surface of the semi-finished product is smooth, the extrusion expansion is small, and the extrusion speed is fast.
(3) Effect on vulcanization
As the amount of oil filled in the compound increases, the vulcanization rate tends to slow down. The addition of oil reduces the concentration of the vulcanizing agent and the accelerator in the rubber, and the vulcanization rate is slowed down.
The operating oil containing a large amount of aromatic oil has the function of promoting the scorching of the rubber and accelerating the vulcanization.
4. Operating characteristics of operating oil in several rubbers
(1) SBR: The aromatic hydrocarbon oil is the best, the tensile strength and elongation are increased, the tensile stress is lowered, and the vulcanized rubber has good flex resistance.
(2) BR: Due to the large amount of carbon black filled, the amount of operating oil is more, and the effect on performance is not significant.
(3) CR: The best choice is aromatic hydrocarbons, followed by naphthenic oils, and paraffin oils.
(4) NBR: Generally, no oil is used, and synthetic plasticizer is used.
(5) IIR: Use a low viscosity oil, a naphthenic oil or a paraffin oil, and no aromatic oil.
(6) EPDM: Generally, no aromatic oil is used, and paraffin oil and naphthenic oil are used.
two. Coal tar plasticizer
The main varieties are: coal tar, coumarone, coal pitch and RX-80 resin. It has good compatibility with rubber and can improve the aging resistance of rubber. The most commonly used is coumarone resin, which is both a plasticizer and a tackifier, and is particularly suitable for synthetic rubber.
1. Coal tar
Black viscous liquid, smelly, polluting, easy to mix into the rubber compound, can dissolve sulfur, prevent frosting, improve the aging resistance of the product, and increase the adhesion of SBR.
2. Gumalon resin
According to the degree of polymerization, the coumarone resin is divided into liquid coumarone resin and solid coumarone resin.
Liquid Gumalong: It has plasticizing and thickening effect, which is better than solid Gumalong, but it has low reinforcing property and is inconvenient to use.
Solid Gumalon: It has good compatibility with rubber, plasticizing, thickening and reinforcing. It helps to disperse carbon black, dissolve sulfur and stearic acid, prevent frosting, and improve rubber compound. The adhesive strength and the tensile strength and hardness of the vulcanizate are less than 15 parts.
According to the range of the softening point of the coumarone, its application is also different. Generally, the softening point is 5 to 30 °C, which is a viscous liquid. It belongs to the liquid coumarone, in synthetic rubber and natural rubber except styrene-butadiene rubber. Used as a regenerant for plasticizers, adhesives and recycled rubber; a viscous block-shaped coumarone with a softening point of 35-75 ° C, which can be used as a plasticizer, adhesive or auxiliary reinforcing agent; softening point is 75-135 The brittle solid coumarone resin at °C can be used as a plasticizer and a reinforcing agent.
3. RX-80 resin
It has high reactivity, can be plasticized, thickened and reinforced, and can also increase the gloss of color glue.
three. Pine tar plasticizer
Pine tar is a residual substance after dry distillation of pine roots and loosening to remove turpentine. The main varieties are pine tar, rosin, rosin oil, tall oil and so on. The most commonly used is pine tar, which can improve the adhesion and cold resistance of the rubber compound, help the dispersion of the compounding agent, delay the vulcanization, and have a large dynamic heat generation. Rosin is mostly used in glue and in combination with cloth.
four. Fatty oil plasticizer
Fatty oil plasticizers are fatty acids, ointments and others made from vegetable oils and animal oils.
Stearic acid: It can promote the dispersion of ZnO and carbon black in rubber, and is also an important vulcanization activator.
Ointment: There are black ointment and white ointment. The carbon black is easy to disperse, and is favorable for calendering and pressing. The surface of the semi-finished product is smooth, the shrinkage rate is small, and the stiffness is large, which can prevent blooming. It is easy to demould after vulcanization, but it will delay vulcanization when used in a large amount.
Others include glycerin, castor oil, soybean oil, zinc stearate, and the like.