Issue 27/2013 - Progress in the production technology of rare earth isoprene rubber in China

Progress in the production technology of rare earth isoprene rubber in China

■ Yan Feng

Isoprene rubber (IR, referred to as isoprene rubber) is a synthetic rubber
prepared by solution polymerization of isoprene monomer under the action of a catalyst.
It has similar chemical composition, three-dimensional structure and mechanical properties to natural rubber, and is an important raw material to replace natural rubber in the manufacture of bus tires, bias tires, load radial tires, semi-steel cars and light truck radial tires, etc.
, which can be used alone or in combination with natural rubber or other synthetic rubber, and the application field is very wide
。 The synthesis of isoprene rubber by rare earth catalyst has high catalyst activity and less dosage than the titanium catalyst used in the traditional use; Low polymer gel content and low ash content; Short vulcanization processing time, good physical and mechanical properties and processing performance; The amount of "three wastes" is small; Continuous
polymerization can be carried out in production.
In recent years, the catalytic synthesis of isoprene rubber by rare earth has become a research and development hotspot in China and has made great progress
.

1 Synthesis catalyst

Cai Hongguang, president of the Chinese Academy of Sciences, developed a sulfonic acid rare earth catalyst
for polymerizing high cis-isoamyl rubber.
The catalyst is composed of neodymium besylate rare earth complexes and alkyl aluminum; The molar ratio of rare earth neodymium in the alkyl aluminum and neodymium besylate rare earth complexes is (15~40): 1
.
The sulfonic acid rare earth complex catalyst can obtain cis-1,4 structural content > 96.
0%, weight average molecular weight > 2.
2 million high
cis-earth isoprene rubber for isoprene polymerization.

Cui Dongmei, president of the Chinese Academy of Sciences, developed a rare earth catalyst and preparation method
for isoprene high cis-1,4-polymerization.
The catalyst is composed of
trivalent rare earth metal complexes and alkylation reagents.
There is no pollution and waste in the polymerization process, the process is simple and short, and the energy consumption is small
.
The average molecular weight of isoprene rubber obtained was 2.
97 million, the molecular weight distribution was less than 3.
0, the cis1,4- content was 95%~99.
5%, the tensile strength of raw rubber (23 °C) was 2.
0~3.
7MPa, the tensile stress of 300% vulcanized rubber was 10~18MPa, and the tensile strength (23 °C) was 25~28MPa
.

Wang Jiye of Qingdao Ecos New Materials Co.
, Ltd.
and others have developed rare earth catalysts
for isoprene rubber production.
The materials used for the preparation of rare earth catalysts include hexane solvent and neodymium naphthenate, sesquiethyl aluminum chloride and triisobutyl aluminum, the molar ratio (Nd: Cl: Al) is 1: (2~4):(10~20), the preparation and aging temperature are controlled between 0~40 °C, the aging concentration (in terms of Nd) is 0.
01~0.
05mol/L, and the aging time is controlled between
1~24 hours.

Cao Kun of Zhejiang University and others developed a method and catalyst
for the preparation of high cis-type polyisoprene rubber by gas phase polymerization.
The catalyst is composed of five components mixed, the first component is divided into rare earth compounds, and the second group is divided into any of alkyl aluminum, hydrogenated alkyl aluminum and alkyl aluminoxane; The third group is divided into any of alkyl chloride and alkyl aluminum chloride; The fourth group is divided into magnesium chloride, silica, carbon black or alumina; The fifth component is divided into any or a combination
of nano silica, nano carbon black, nano aluminum oxide, nano titanium dioxide, nano antimony trioxide, nano calcium carbonate, nano talc, and nano montmorillonite.
Isoprene and catalyst are polymerized in the gas phase at 40~70 °C for more than 30 minutes to obtain high cis-1,4-polyisoprene rubber particles
.

2 Synthesis process

Liu Naiqing of PetroChina Jilin Petrochemical Company and others have developed a wet agglomeration method
for rare earth isoamyl rubber.
The rubber hexane solution is preheated by steam, and is dispersed by the metering pump into the glue pretreatment device and circulating hot water, with a volume ratio of 1 :4, pressure 0.
3MPa, the obtained 90~95 °C glue suspension in a pulsating double fluid mode, through the nozzle with a thimble sprayed into the kettle; under the action of the stirring at the bottom of the kettle and the strong shear force of the steam, it is quickly dispersed in the condensed hot water at 90~95 °C, and the hexane and monomer in the glue are instantly vaporized to form uniform rubber particles, and under the action of the kettle top stirring and spiral baffle, the rubber particles are all dispersed in hot water and stay for 20~30min
.
The rubber particles are discharged tangentially at the mixing position at the bottom of the kettle in the direction of 30 degrees inclination, and hexane and monomer are discharged from the top of the kettle for condensation recovery
in the gas phase.

Li Yang of Dalian University of Technology et al.
have developed a class of rare earth catalytic system nitrogen-containing functionalized rare earth isoprene rubber, which is characterized by: weight average molecular weight is (1~120)×104; in terms of 100% of the total polymer, the content of bound styrene derivatives is 1%~50% (mass percentage, the same below), and the content of isoprene is 50%~99%.

The styrene derivative is selected from styrene containing a nitrogen atom substituent, and contains at least one tertiary amine group substituent
.

Zhu Han of Beijing University of Chemical Technology et al.
studied the chemical structure of chlorine-containing activator (CE) and alcohol (OH) and the effect
of triisobutylaluminum (Al) dosage on isoprene rubber.
The results showed that in the rare earth catalyzed isoprene polymerization reaction, a small amount of chlorocarboxylate ester and OH helped to improve the catalytic activity, reduce the molecular weight distribution and increase the cis-content, and the polymerization rate showed a first-order kinetic relationship with the monomer concentration, and the apparent growth activation energy was 69.
5kJ/mol
.
By adjusting the catalyst composition ratio and polymerization process conditions, cis-1,4-structure content of cis-isoprene rubber products
with a structure content of more than 98% can be prepared.

Tan Jinmiao of Yanshan Branch of Beijing Beijing North Chemical Institute of Sinopec used homogeneous neodymium catalysts to catalyze isoprene for solution polymerization
.
The experimental results show that the conversion
of isoprene increases with the increase of polymerization temperature, the mass concentration of isoprene and the dosage of homogeneous neodymium catalyst (Nd).
。 When polymerized at 50 °C, the mass concentration of isoprene was 102g/L, the dosage of homogeneous neodymium catalyst (the amount of Nd corresponding to 1g of isoprene) was 1.
60×10-6 mol/g, the conversion rate of isoprene was 96%, the Mooney viscosity of Nd-IR was 75±5, and the content of cis-1,4-isoprene structure was greater than 98%.
The vulcanization speed of Nd-IR raw rubber and compound rubber is fast, and the wear resistance and dynamic mechanical properties of Nd-IR after vulcanization are good
.

3 Production equipment

Liu Naiqing of PetroChina Jilin Petrochemical Company and others have developed a rare earth isoprene rubber wet coalescing device, which is characterized by: adding a primary condensing glue preparation kettle; Add glue preheater between glue metering pump and glue static mixer; Steam ports are added to the rubber water pipes between the condensing kettles; The first condenser glue nozzle is equipped with a thimble; The baffle in the first condenser and the second condenser are spiral
.

Yu Min of Qingdao Ecos New Materials Co.
, Ltd.
and others have developed a spiral stirring reactor, which replaces the full mixed flow type with a flat flow type without backmixing, which strengthens the polymerization reaction process and heat transfer process, significantly reduces the volume of the reactor, greatly reduces energy consumption, and improves
the polymer performance.
It is suitable for the production of polymers such as synthetic rubber, plastics and fibers by solution polymerization, especially for the synthesis of isoprene rubber and cis-butadiene rubber
in rare earth catalytic systems.

Luo Tianyun, High-tech Park, Dalian, Liaoning Province, has developed a one-step processing process of isoprene rubber post-treatment, which integrates the two processes of extrusion dehydration and expansion drying into a continuous processing process
.
This method simplifies the industrial production process of isoprene rubber, from the "two-step" post-treatment process to the "one-step" process; Reduce about 40% of equipment investment costs, reduce about 50% of floor space, reduce energy consumption by 27%, increase the output of single machine by more than 5%, reduce the labor intensity of workers, and have significant
economic benefits.

Dalian Tiansheng General Machinery Co.
, Ltd.
has developed a large-scale isoamyl rubber extrusion dehydration expansion drying integrated machine, which combines the extrusion dehydrator and the expansion dryer into one machine to complete the two operation processes
of extrusion dehydration and expansion drying of synthetic rubber.
The outstanding advantages are that the equipment investment cost can be greatly reduced, the energy consumption can be reduced and the floor space
can be reduced.

4 Applied Research

Yang Qing of Beijing University of Chemical Technology et al.
studied the effect of domestic rare earth IR and natural rubber (NR) on the performance of
rubber compounds.
The results showed that with the increase of IR dosage, the Mooney scorching time and positive vulcanization time (t90) of NR/IR rubber were gradually extended, and MH-ML gradually decreased.
The carbon black dispersion is unchanged, and the compatibility between IR and NR is good; The hardness and tear strength of Shaoer A type of vulcanized rubber gradually decreased, the 300% tensile stress and springback value showed a downward trend, the compression heat generation was reduced, and the flexural resistance was improved.
When the ratio of NR/IR is less than 50/50, the comprehensive performance of the rubber compound is better
.

Chen Jie, School of Chemical and Materials Engineering, Jilin University of Chemical Technology
, et al.
conducted research on the combined use of rare earth IR and NR.
The results show that the combination of 40 parts of IR in NR can not only extend the scorching time and improve the operation safety, but also improve the aging resistance, compression heat generation performance and dynamic cutting resistance of NR
.

Wu Xinxin of Qingdao University of Science and Technology et al.
studied the properties of domestic neodymium isoprene rubber (Nd-IR) and compared
it with NR and Russian titanium isoprene rubber (grade SKI-3).
The results show that the stress-strain curves of NR raw rubber and its carbon black compound have tensile-induced crystallization, but this phenomenon
does not occur in Nd-IR raw rubber and carbon black compound rubber.
The stress-strain curve of Nd-IR vulcanized rubber has a similar trend to that of NR and SKI-3, and when the strain is less than 600%, its stress is slightly greater than that of SKI-3
.
Compared with SKI-3, the physical properties of Nd-IR raw rubber and its carbon black compound and vulcanized rubber are not much
different.
Appropriately increasing the amount of accelerator can make the physical properties of Nd-IR vulcanized rubber similar to NR vulcanized rubber
.

In short, the research and development of production technology, equipment and application will provide favorable technical support
for the development of China's rare earth isoprene rubber industry.