Issue 50, 2013 - Research Progress on the Synthesis and Application of Bromobutyl Rubber

Research progress on the synthesis and application of brominated butyl rubber

□ Yan Feng

Bromide butyl rubber (BIIR) is a brominated copolymer of isobutylene-isoprene, which is an important modification product
of ordinary butyl rubber.
In addition to maintaining the low air tightness, high shock absorption, aging resistance, weather resistance, etc.
of ordinary butyl rubber, it also increases the advantages of fast vulcanization speed, good compatibility with natural rubber, styrene-butadiene rubber, etc.
, and is widely used in radial tires, bias tires, container lining, pharmaceutical corks and mechanical liners and other fields, and has a wide
range of development and utilization prospects.
In recent years, BIIR has made great strides
in the development of production and application technology.

First, the progress of synthesis technology

BIIR is very sensitive to temperature, and the bromine in BIIR will fall off at high temperatures, producing bromic acid to deteriorate product quality and corrode post-treatment and post-processing equipment
.
Therefore, the temperature of the twin screw dryer for post-treatment needs to be lower than 150 °C
.
In order to solve the contradiction between drying temperature and volatile content, ExxonMobil has developed twin-screw dryer filling nitrogen technology, which can control the temperature of the dryer at about 130 °C and maintain low volatile content
.

R.
Raisendis of Canadian Lancosus Ltd.
invented a method
for producing BIIR without water and without the addition of neutralizing agents.
The butyl rubber comprises at least 4.
1% (mol) of polyolefins, which, when a halode, can generate hydrohalide protonic acid
.
Therefore, there is no need to neutralize
with aqueous acids during the reaction.
BIIR is produced with a high content of external allyl bromide and a correspondingly low content of internal allyl bromide
.

Russian Yaraslav Research Institute Sergey S.
B.
Salnikov et al.
invented a method
for preparing BIIR.
It is characterized in the use of an initial butyl rubber solution containing water as a solution of butyl rubber dissolved in an inert solvent; Halogenation is carried out in two stages, after which phase separation is carried out and the lower layer of hydrogen halide aqueous solution is separated, and in the second stage, the water and halogen solution are sent to the partially halogenated butyl rubber solution, after which the phase is also separated and the water
is separated from the halobutyl rubber.

Zhang Yang of Beijing University of Chemical Technology et al.
prepared BIIR
by solution method.
The results show that the bromination process of butyl rubber is only within the first 1.
5min, and with the extension of the reaction time and the reaction under alkaline conditions, the molecular structure rearrangement occurs, that is, the transfer
from the bromo-secondary allyl structure to the more stable bromo-primary allyl structure.
Deng Zhengwei et al.
prepared BIIR by solution method, and the results showed that with the increase of pH value after neutralization reaction, the content of paraallyl bromide increased, while the content of primary allyl bromide decreased.
Mooney viscosity and relative molecular mass increase with pH and the relative molecular mass distribution narrows
.
Chen Jianfeng et al.
invented a method for preparing BIIR, the raw material butyl rubber solution and bromine solution are input into the enhanced mixing reactor in a certain proportion, the substitution reaction of bromine on allyl is carried out, the residence time of the material in the reactor is controlled, and then enters the stirring kettle to stop the reaction, and the product
is obtained after washing, adding stabilizer, flashing solvent, drying and other post-treatment.
The prepared BIIR product has a bromine content of 1.
0~2.
3 (wt%) and an unsaturation of 0.
6%~1.
6%, which greatly reduces the reaction residence time, greatly reduces the volume of the reactor and reduces the overall operating cost
.

Guo Wenli of Beijing Institute of Petrochemical Technology and others invented the process
of preparing butyl glue solution by solution method to directly produce halobutyl rubber.
In the mixed solvent of alkane and methyl chloride, under low temperature conditions, the solution butyl rubber was prepared by isobutylene and isoprene cation copolymerization; After the butyl glue solution is removed from methyl chloride and separated by sedimentation, the glue is halogenated to prepare halobutyl rubber
.

Second, the progress of applied research

Application progress is an important aspect of BIIR technology progress, which is mainly reflected in the preparation and application research of
composite materials.

Chen Gong et al.
of Shanghai Jiao Tong University invented a preparation method
of BIIR/montmorillonite nanocomposites.
Firstly, BIIR, montmorillonite, intercalation agent and coupling agent are added to the mixer for mixing at a processing temperature of 10~80 °C to obtain intercalated BIIR/montmorillonite mother compound; Then add vulcanizing active agent, accelerator and vulcanizing agent
.
In this process, the intercalation agent and BIIR molecules will undergo in-situ intercalation, so that the layer spacing of montmorillonite is significantly expanded, and the intercalated BIIR/montmorillonite compound is obtained
.
Finally, the compound is vulcanized at 150~190 °C to obtain an intercalated BIIR/montmorillonite nanocomposite
.
The invention process is simple, low cost, no need to organic modification of montmorillonite before mixing, and can improve the mechanical properties and chemical resistance of
BIIR.

Zang Yanan of Jiangsu Xuzhou Industrial Vocational and Technical College used dynamic vulcanization process to prepare PP/BIIR alloys, and studied the effects
of the mass ratio of PP and BIIR, the dosage of filling reinforcing agent attapulgite (AT) and maleic anhydride grafted polypropylene compatibilizer (PP-g-MAH) on the mechanical properties of the alloy 。 The results show that with the increase of BIIR, the hardness of PP/BIIR decreases, the tensile strength decreases, and the elongation at break and impact strength increase significantly.
When the mass ratio of PP to BIIR is 90:10 and the amount of AT is 5 parts, the performance of PP/BIIR alloy is the best; The addition of PP-g-MAH can improve the mechanical properties
of the alloy.

He Shaojian of Beijing University of Chemical Technology et al.
prepared clay/SBR/BIIR composites
.
The composite is an isolated nanocomposite, with BIIR as the continuous phase and SBR as the dispersed phase, and the clay is basically dispersed in the SBR dispersion phase.
The compatibility of BIIR and SBR is not good, and thermodynamically it is basically incompatible; Due to the barrier effect of clay on gas and the two-phase of the glue are island structures, the composite can maintain good air tightness
.

Lin Hao et al.
of Southwest University of Science and Technology prepared brominated butyl latex by solution emulsification, and nano-SiO2/BIIR composites
by emulsion blending.
The results show that the modified nano-SiO2 can be well dispersed in BIIR latex.
After vulcanization by coating molding, nano-SiO2/BIIR composites have good physical properties, and their elongationat break, tensile strength and tensile rupture stress have been greatly improved.
With a small amount of SiO2, the airtightness is significantly improved
.

Triangle Group Co.
, Ltd.
Gaoli et al.
prepared BIIR/natural rubber/organic montmorillonite (BIIR/NR/OMMT) nanocomposites
by mechanical mixing method.
The experimental results show that the OMMT sheet is uniformly dispersed in the rubber matrix in the form of peeling, and OMMT can significantly promote the rubber vulcanization reaction and strengthen
the cross-linking synchronization of BIIR and NR phases.

Xu Jianrong of East China University of Science and Technology et al.
prepared dynamic vulcanized BIIR/PP thermoplastic elastomer (TPV)
by mixing process.
The results show that when the processing temperature is 180 °C, the mechanical properties of TPV are good, and the rubber phase particles are uniformly dispersed in the
resin phase.
In the preparation process of TPV, when the vulcanization time is 10~12min, the crosslinking density of the rubber material tends to be stable, and the rubber material reaches complete vulcanization; At vulcanization for 3min, the blend completed the transition from BIIR and PP as the double continuous phase to BIIR as the dispersed phase and PP as the continuous phase.
With the extension of vulcanization time, the fluidity of TPV gradually increases
.

Third, new product development

ExxonMobil has developed brominated star-branched butyl rubber products, which are made by synthesizing star-branched butyl rubber using styrenic block copolymer as a branching agent
, and then by bromination.
The products have the characteristics of high strength, high hardness and easy processing, and can be used in the fields of
inner tubes, black and white sidewalls, compartments for houses, adhesives and sealants, and chewing gum.

Another new BIIR product that ExxonMobil has put on the market is the bromide isobutylene-p-methylstyrene copolymer (BIMS).

The preparation method of BIMS is: isobutylene and p-methyl styrene copolymerization to form a saturated copolymer backbone, and it has an irregular distribution of p-methyl styrene side groups
.
After polymerization, free radicals are brominated, and some substituted p-methylstyrene groups are brominated and converted into active benzyl bromide
with sulfidation ability and functionalization.
BIMS has two major characteristics in molecular structure: the molecular chain is completely saturated and contains highly active, functionalized benzyl bromide
.
Therefore, in addition to the excellent air tightness and damping of butyl rubber, it also shows better heat resistance, ozone resistance, weather resistance, and BIMS in tire compound can improve dynamic performance, reduce rolling resistance and improve wet slip resistance
.
The above properties improved
with the increase of bromolarity fraction in BIMS.
The biggest feature of BIMS is that it can be blended and modified with other polymers
.
In 2008, ExxonMobil launched a new variety of ExxcoreDVA resin blended and modified by BIMS and nylon (PA), which has higher strength, higher air tightness than BIIR, better heat resistance and weather resistance, and can be made into a 100 m film as the innerliner of the tire, which is only 1/10
of the innerliner of BIIR.
As a result, ExxcoreDVA resin can reduce the weight of tires and extend their service life
.

4.
Others

According to the structural characteristics of capillary rheometer, Xu Liangrui et al.
of Beijing University of Chemical Technology used to simulate the screw extrusion drying process of industrial production of BIIR, and synthesized BIIR
with bromine content and its microstructure meeting industrial requirements by solution method.
The results show that at a certain temperature, extending the residence time of the rubber in the barrel will reduce the bromine content, increase the content of structure I (non-brominated butyl rubber) and structure III (bromoprimal allyl), while the content of structure II (bromo-secondary allylyl) will decrease, and the temperature increase will exacerbate this trend
.
Li Yan et al.
used the thermal reversible properties of quaternary ammoniation reaction to replace traditional crosslinking agents with polymers containing tertiary amine functional groups to study the crosslinking activity of BIIR and the thermal reversibility of crosslinking
.
The results showed that the vulcanization temperature and vulcanization time had a significant effect on the gel content of crosslinked BIIR, and the crosslinker showed high crosslinking activity under the vulcanization conditions of 160°C×30 min.
Torque determination at different temperatures and plastic flow of secondary hot pressing at 190°C confirm the thermoplastic processability
of crosslinked BIIR.

Wang Dao, Beijing Research Institute of Chemical Industry, PetroChina, et al.
invented a comprehensive utilization method
for BIIR production wastewater.
Concentrate BIIR production wastewater so that the mass concentration of sodium bromide in wastewater is at least 10%; Mix the concentrated wastewater with chlorine-based fungicides, where chlorine-based fungicides are at least one of the chlorine-containing fungicides that produce hypochlorous acid in water; The above mixture is added to the industrial circulating cooling water, so that the concentration of sterilization active ingredients in the circulating cooling water is maintained at 0.
1~0.
5mg/L
in terms of residual chlorine.
Using this method, on the one hand, the sterilization effect of the circulating cooling water system can be strengthened; On the other hand, it can effectively use sodium bromide in wastewater, and at the same time, it can solve the problem that the high concentration of sodium bromide-containing wastewater generated in the BIIR production process is difficult to discharge, and does not produce secondary pollution
.