Brominated butyl rubber (BIIR) is a modified product of IIR. The purpose of modification is to improve the activity of IIR, improve its compatibility with unsaturated rubber, improve the self-viscosity, cross-viscosity and co-crosslinking ability, and maintain the original characteristics of IIR.
IIR bromination not only increased the crosslinking position, but also enhanced the reactivity of the double bond.
This is because of the low bond energy of c-br bond and the high vulcanization reactivity of brominated butyl rubber, so it has faster vulcanization speed and stronger vulcanization adaptability, and it has better co-vulcanization performance with general rubber.
Compared with ordinary butyl rubber, brominated butyl rubber has the following characteristics :(1) high vulcanization rate;
(2) good compatibility with natural rubber and styrene butadiene rubber;
(3) improved bonding performance with natural rubber and styrene butadiene rubber;
(4) zno can be vulcanized separately (BIIR is the only elastomer that can be vulcanized solely with sulfur or zno), and the vulcanization methods are diversified;
(5) good heat resistance.
It is because of these advantages that brominated butyl rubber is gradually replacing normal butyl rubber in a variety of application fields, such as radial tire, bias tire, tire side, inner tube, container liner, medicine bottle stopper and machine liner and other industrial products.
Brominated butyl rubber is an irreplaceable raw material for tubeless tire and medical products.
Production method of 1 bromobutyl rubber
The preparation methods of BIIR include dry mixing bromination and solution bromination.
BIIR is prepared by hot mixing of n-brominated succinimide, dibromodimethyl glycosylurea or activated carbon adsorption bromide (mass fraction 0.312) with IIR in an open mill.
Solution bromination is a continuous process in which IIR is dissolved in a chlorinated hydrocarbon solvent and the bromine with a mass fraction of about 0.03 is re-introduced. The product quality is uniform and stable.
The optimum mass fraction of bromine in BIIR was 0.017-0.022.
Study on the application of butyl bromide
2.1 process requirements
Brominated butyl rubber has double bonds and bromine atoms in its molecular chain, so it can be vulcanized by many methods.
The mixing, rolling and extrusion processes of brominated butyl rubber are similar to those of normal butyl rubber with the same viscosity as Mooney. However, due to the rapid vulcanization rate of brominated butyl rubber and its easy scorch, the following conditions should be noted:
1. Mixing temperature.
Brominated butyl rubber mixing temperature exceeds 130 ℃, the coke burning dangerous, and the temperature is too high, rubber easily broken, bad result in rubber processing.
2. Brominated butyl rubber is corrosive to molds, so it is necessary to protect the molds during molding, such as using high-quality molds and coating protection, avoiding the use of water-based mold release agent and maintaining high temperature, avoiding repeated fluctuation of mold temperature.
2.2 mixture and blending system
The use of BIIR/IIR can improve the processing performance and physical properties of IIR, but also can shorten the curing time of IIR, and the interface adhesion of the adhesive is larger, and reduce the viscosity of the adhesive, improve the processing performance.
In addition, adding ordinary butyl rubber into brominated butyl rubber is also an important way to reduce production cost.
The combination of ordinary butyl rubber and brominated butyl rubber can improve the self-adhesion of the rubber material, and the process performance is good.
With the increase of the amount of brominated butyl rubber, the vulcanization rate was obviously accelerated, and the uv absorbance and the peroxide of the compound were improved gradually.
The change of butyl bromide content had no significant effect on the physical and mechanical properties and aging properties.
The vulcanization system of ordinary butyl rubber and brominated butyl rubber is sulfide with sulfur or morpholine.
2.2.2NR/BIIR combination system
Brominated butyl rubber can be combined with natural rubber in any proportion.
Brominated butyl rubber and natural rubber, vulcanization speed, can improve the natural rubber air tightness, improve its heat resistance, anti aging and resistance to a variety of chemical properties.
Natural rubber can improve the adhesion properties of brominated butyl rubber.
The largest amount of brominated butyl rubber in tire production is used in the formulation of airtight layer of tubeless tires.
Studies have been made on the comparison between the brominated butyl rubber and the brominated butyl rubber/natural rubber used as the gas-tight layer. The results show that the purpose of the combination of BIIR and NR is to improve the adhesion of the rubber, improve its physical properties and shorten its vulcanization time.
It has also been pointed out in the literature that BIIR and NR are blended instead of 100% using BIIR for the formulation of air tight layer. Another reason is the consideration of production cost and production process control.
However, it should be noted that, as BIIR and NR blend itself is difficult to achieve homogeneity in actual use, it will have an adverse impact on the performance of the rubber. In recent years, the development trend is to obtain low Mooney viscosity and easy to process 100%BIIR with no oil by mixing BIIR rubber and NR, so as to ensure the lowest permeability of air and water.
At present, the use of BIIR in the formula of airtight layer varies with different tire products. The products of well-known brands will adopt 100% BIIR or CIIR.
All steel tubelless radial tyres and high speed passenger tyres (e.g. V, Z) will be 100% BIIR or CIIR.
BIIR rubber mixed with NR will be used for radial tire with inner tube and passenger tire with lower speed class (such as S class and T class).
2.2.3EPDM/BIIR combination system
Brominated butyl rubber and epdm and use, can change the curing rate (as in brominated butyl rubber and rubber content increasing, the curing rate fell sharply, until a brominated butyl rubber content reaches 50%, then appear the opposite trend), to improve on this basis, the adhesion of the rubber and air tightness and damping characteristics, on the contrary, epdm can improve the brominated butyl rubber based adhesive material of low temperature brittleness, ozone resistance and heat resistance.
The main purpose of the combination of brominated butyl rubber and neoprene is to reduce the cost of the rubber based on brominated butyl rubber.
Like G and W neoprene, brominated butyl rubber can be cured with zinc oxide or sulphur.
Brominated butyl rubber has good heat and ozone resistance, compression resistance, permanent deformation resistance and anti-aging resistance, which are the same as chloroprene rubber.
2.2.5BIIR/NBR combination system
In brominated butyl rubber and nitrile rubber, to improve the sizing performance of resistance to oil, chemicals, improve the compression permanent deformation performance of products, but poorer physical and mechanical properties.
In combination with NBR, brominated NBR can also improve the low temperature flexibility, ozone resistance, ester resistance and ketone resistance of NBR, but the oil resistance and tensile strength are decreased.
2.2.6BR/BIIR combined system
The purpose of using butadiene bromide rubber and butadiene bromide rubber is to make use of good wet traction of butadiene bromide rubber and good wear resistance and low rolling resistance of butadiene bromide rubber to complement each other.
BR/BIIR blend rubber in the tread compound, white carbon black reinforcing, because of containing brominated butyl rubber tread rubber although have good wet tractional, but wearability is poor, one reason is the difference in the interaction between butyl rubber with carbon black, and through silane coupling, rubber and silica can greatly improve the interaction of butyl rubber and filler, get good reinforcing effect, add white in butadiene rubber tread rubber carbon black reinforcing brominated butyl rubber, tire surface glue three properties of wear resistance, tractional and rolling resistance are improved significantly.
2.3 regeneration of brominated butyl rubber
Brominated butyl rubber has good recycling function, which is one of the advantages of brominated butyl rubber.
The regeneration process of brominated butyl rubber is very simple, does not need to go through high temperature desulfurization and other complex processes, as long as certain plastic refining can be used, and with the original brominated butyl rubber mixed well.
Join the brominated butyl rubber reclaimed rubber with the increase of dosage of reclaimed rubber, gradually the decrease of the tensile strength and elongation can be increased, but the change is not a point clear, especially at 15% for the amount of reclaimed rubber, brominated butyl rubber keep good performance, and the aging properties of brominated butyl reclaimed rubber also does not have the too big effect.
In addition, the chemical properties of the product are not affected by the combination of the regenerated rubber and the original rubber.
2.4BIIR crosslinking process and mechanism
ScottPJ et al. studied the thermal stability of BIIR and small molecule model (BPMN), and found that the generalization and analysis of BPMN small molecule model was very close to the actual behavior of BIIR, which could be applied to the study of BIIR vulcanization mechanism.
When BIIR is at the curing temperature, isomerization will occur. The generation of isomerization is largely determined by the concentration of hydrogen bromide in the system. When hydrogen bromide is separated from BIIR, conjugated diene structure will be formed in the molecular chain of BIIR, which will be accompanied by isomerization.