Issue 41/2013 - Progress in nitrile rubber production technology in China

Progress in nitrile rubber production technology in China

□ Yan Feng

At present, the production of industrial nitrile butadiene rubber (NBR) mainly uses continuous or batch emulsion polymerization processes
.
In recent years, the technological progress of nitrile rubber industry in China is mainly reflected in the improvement of polymerization formula, improvement of polymerization process, development of new products and "wastewater" treatment
.

1.
Polymerization process and formula improvement

The important components in the emulsion polymerization system are initiators, emulsifiers, activators, regulators and antioxidants, etc.
, by adjusting the amount of these components in the formula, the polymerization reaction rate, monomer conversion rate, Mooney viscosity value, gel content, bound acrylonitrile amount, relative molecular mass and its distribution, mechanical properties and processing properties can
be effectively adjusted.

PetroChina Lanzhou Chemical Research Center Gui Qiang et al.
used the low-temperature emulsion polymerization method to determine the new emulsification system of N31 through the screening and compounding experiments of potassium oleate, rosin soap, sodium dodecylbenzenesulfonate, synthetic fatty acid potassium soap and other emulsifiers, with sodium dodecylbenzenesulfonate and potassium oleate as composite emulsifiers, the dosage ratio of the two is 2:1, and the total dosage of composite emulsifiers is 3.
2%.

。 At the same time, the polymerization formula and process conditions are optimized: the polymerization temperature is controlled at 7 °C before 60%, and the polymerization temperature is controlled at 4 °C after 60%; It is advisable to control the polymerization conversion rate below 86%, and the prepared nitrile rubber N31R has excellent
performance.

After replacing the pulling powder with sodium dodecylbenzenesulfonate, Zhu Jing et al.
of Lanzhou Chemical Industry Research Center of PetroChina investigated the effects
of the dosage and addition method of regulator butadiene on the synthesis and performance of thermal nitrile butadiene rubber (NBR) under the condition that other process conditions remained unchanged 。 The results showed that with the increase of the amount of regulator and the prolongation of polymerization time, the gel content, Mooney viscosity and average molecular weight of NBR decreased gradually, and the molecular structure did not change significantly.
When the regulator was added in 3 parts, the Mooney viscosity, gel content and average molecular weight of NBR decreased compared with 1 addition, and with the increase of the amount of regulator but, the tensile strength and 300% elongation stress of NBR vulcanized rubber decreased, and the elongation at break increased
.
The suitable total dosage of regulator is 0.
34~0.
36 parts
.

2.
Hydrogenated nitrile rubber

Hydrogenated nitrile butadiene rubber (HNBR) is obtained by selective hydrogenation of the double bond of the main chain of nitrile rubber, which not only maintains the original wear resistance and media resistance of nitrile rubber, but also improves the heat resistance, H2S resistance and O3 aging resistance, so that its comprehensive performance can be improved
.

Li Jinshan of PetroChina and others have developed a hydrogenation method
for nitrile rubber.
First dissolve nitrile rubber in organic solvent, and then hydrogenation under the condition of adding catalyst and stirring, which is characterized by first adding liquid nitrile rubber to the nitrile rubber to be hydrogenated, the amount of addition is 5%~20%, and then the solution of the above mixture is added to the hydrogenator, and the hydrogenation reaction is carried out at 40~100 °C and pressure 4.
0~9.
0MPa, and the reaction time is 2~12 hours
。 The advantage of this method is that the molecular weight distribution of hydrogenated product HNBR has bimodal characteristics, the molecular weight distribution is significantly widened, which effectively reduces the Mooney viscosity, improves the processing performance of HNBR, and has excellent
mechanical properties, compression set and hot air aging properties of the product.

Chenzhou Sun Art Platinum Co.
, Ltd.
Lei Dichen et al.
have developed a palladium-based catalyst for the synthesis of highly saturated nitrile rubber and a preparation method thereof
.
The method includes steps
such as infrared liquid production, vacuum adsorption, liquid phase reduction, washing and drying.
The nano-palladium-based catalyst prepared by the invention method, the average particle size of the active component palladium is 1~2nm, and the dispersion degree ≥ 40%.

Applied to the synthesis of highly saturated nitrile rubber, the hydrogenation rate of nitrile rubber is greater than 99.
5%, which has the advantages
of simple process, environmental protection and high efficiency, small particle size, narrow particle size distribution and good selectivity.

Haihua Hu of Lanzhou University of Technology et al.
used different grades of nitrile rubber N32 and N21 to add liquid nitrile rubber (LNBR) and free radical trap to prepare low Mooney viscosity hydrogenated nitrile rubber
。 The results show that with N32/N21/LNBR/free radical scavenger with mass ratios of 60/30/10/0.
3 and 40/50/10/0.
3 as the hydrogenation base glue, hydrogenated for 10h under the conditions of rhodium complex catalyst of 180×10-6, hydrogenation pressure of 7MPa and temperature of 80°C, hydrogenated nitrile rubber products
with hydrogenation degree greater than 90% and Mooney viscosity of 70~80 can be obtained.

Zhang Liqun of Beijing University of Chemical Technology and others developed a bimetallic catalytic hydrogenation method
of nitrile rubber.
Nitrile rubber was dissolved in xylene solvent and configured as glue, added to the high-pressure reactor, and then RhCl3 and Pt/C were put into the above high-pressure reactor according to the mass ratio of 100:1~1500:1; The temperature is 50~160 °C, the hydrogen pressure is 0.
5~5.
0MPa, and the reaction time is 1~24h for hydrogenation
.
This method greatly reduces the amount of catalyst, and the catalyst is directly added to the kettle for reaction, which does not have to be protected by nitrogen, which can effectively improve production efficiency and reduce costs
.

3.
Nitrile rubber sewage treatment

Nitrile rubber produces a large amount of wastewater during the synthesis process, which mainly contains incompletely reacted acrylonitrile, butadiene monomer and various additives, with complex composition, poor biochemistry, difficult treatment and great
harm to the environment.

He Lin et al.
of PetroChina Lanzhou Chemical Research Center used the Fe/C micro-electrolysis-Fenton combination process to treat nitrile rubber wastewater
。 The results show that in the microelectrolysis unit, Fe/C (mass ratio) is 3/1, the initial pH value is 2.
00~10.
00, and the reaction time is 1h.
In the Fenton unit, the total removal rate of chemical oxygen demand in nitrile rubber wastewater was more than 50%, and the total removal rate of acrylonitrile was more than 95
%, under the conditions of 2.
0mL/L of oxidant H2O2, 0.
2g/L of catalyst Fe2+, reaction temperature of 40°C and reaction time of 45 min.
Compared with the Fenton method alone, to achieve the same treatment effect, the dosage of H2O2 is reduced from 3.
0mL/L to 2.
0mL/L, and the dosage of Fe2+ is reduced from 0.
6g/L to 0.
2g/L
using the combination process.

Zhao Ying of Lanzhou Chemical Industry Research Center of PetroChina and others used the iron-carbon micro-electrolysis method to treat the pull-off powder wastewater discharged from the hard nitrile rubber unit, and carried out a pilot test
on the 1m3/h wastewater treatment plant 。 The results show that after the iron-carbon microelectrolysis reaction and catalytic oxidation reaction, the average mass concentration of pull-off powder in wastewater decreases from 767mg/L to 123mg/L, the average mass concentration of total suspended solids decreases from 376mg/L to 48mg/L, and the chemical oxygen demand (potassium dichromate method) decreases from 2862mg/L to 1490mg/L, which meets the effluent quality index
of the wastewater treatment device.

Ding Jian, School of Environmental and Municipal Engineering, Lanzhou Jiaotong University, used electrocoagulation to treat
nitrile rubber wastewater (COD is 800mg/L, pH value is 7~8).
The results show that under the optimal electrolysis conditions of voltage of 20V, reaction time of 25min and plate spacing of 1cm, the COD removal rate of wastewater can reach 51%.


Liang Fei of Jiangsu Provincial Key Laboratory of Resources and Environmental Information Engineering used chitosan as a coagulant to treat nitrile rubber wastewater
.
The experimental results showed that the dosage amount of chitosan was 100 mg/L, the pH value was 6, the stirring rate was 200r/min, the sedimentation time was 5min, the COD removal rate was 96.
7%, and the effluent COD was reduced to 276mg/L, which reached the national tertiary emission standard
.

4.
New product development

Fan Yongjiang of PetroChina and others have developed a preparation method
of microgel nitrile rubber.
The monomer composition is butadiene and acrylonitrile, and the amount of monomer added is 100 parts (according to the mass part, the same below); Butadiene 50~60 parts, acrylonitrile 40~50 parts; The emulsifier is a composite system of disproportioned potassium rosinate soap and potassium oleate soap, the dosage of emulsifier is 2.
5~6.
0 parts, the dosage ratio of disproportioned rosin potassium soap and potassium oleate soap is 3~8:1; the initiator is persulfate, the amount added is 0.
2~1.
0 parts; triethanolamine is 0.
1 part; the molecular weight regulator is molecular weight regulator butyl or alkyl mercaptan, the amount added is 0.
3~0.
7 parts, divided into equal amounts and added
in three batches 。 This method can produce nitrile rubber
with microgel content of 1%~10%, Mooney viscosity MS(1+4) 100 °C 40~65, tensile strength ≥ 27MPa and ≥ elongation at break.

Chen Jiming et al.
of PetroChina Lanzhou Petrochemical Company Research Institute used Bd, AN and AA as polymeric monomers, persulfate as initiators, and mercaptans
as molecular mass regulators 。 The results showed that persulfate was 0.
2~0.
3, mercaptan 5~6, emulsifier 3~3.
5, and the polymerization reaction temperature was (25±2) °C.
The detergent is not less than 90 °C tap water, the dosage is 1.
5 times that of the glue, and when the drying temperature is 110~130 °C, random carboxynitrile nitrile liquid rubber
with a molecular weight of 1400±200, a combined acrylonitrile mass fraction of 30%~35%, and a carboxyl value of 0.
5~1.
0mmol/g can be obtained.

Huangshan Hualan Technology Co.
, Ltd.
Chu Yinliang et al.
have developed a production method
of medium and high nitrile content cross-linked powder nitrile rubber.
Firstly, the synthesis of nitrile paste is carried out, and then the nitrile paste is condensed and isolated into powder, and finally dehydrated and dried to obtain
.
In the polymerization reaction stage, potassium carbonate was added as the buffer of the reaction, and a mixed solution of diethylhydroxylamine, hydroxylamine sulfate, potassium hydroxide and soft water was added as the composite terminator; In the isolation powder formation stage, WSL and DLTP are added as antioxidants, monovalent sodium salt and divalent magnesium salt or monovalent sodium salt and divalent calcium salt are used as coagulants, and the nitrile slurry is condensed and isolated into powder
at 30~75 °C.
The invention has a simple production process, easy to operate, low production cost, low energy consumption, and high conversion rate, which can reach more than 95%; Using a new composite terminator, Mooney is stable and has a good termination effect; The rubber powder is finer, which improves the dispersion during processing; The heat resistance of the product is very good and the wear resistance is good
.

5.
Miscellaneous

Zhang Hongxiang of Ningbo Shunze Rubber Co.
, Ltd.
and others have developed a nitrile rubber polymerization reaction initiator and activator feeding device to solve the defects
of the existing nitrile rubber initiator, activator and butadiene, acrylonitrile, etc.
at the same time that it is easy to cause heat exchanger blockage.
Zhang Hongxiang et al.
also developed an absorption device for butadiene exhaust gas produced by nitrile rubber production, which solved the problems
of complex structure, high treatment cost and high energy consumption of existing butadiene tail gas absorption devices.

Kong Shuguang of Shandong Qilu Petrochemical Engineering Co.
, Ltd.
and others have developed a nitrile rubber monomer recovery device, which can reduce the loss of monomer in the recycling process, improve the quality of recovered monomers, and reduce the impact
of monomer recycling on the quality of nitrile rubber products.

Huangshan Hualan Technology Co.
, Ltd.
Chu Yinliang and others developed a nitrile rubber initiator configuration device, which effectively solves the problem of rising storage temperature of initiator, prevents deterioration of initiator, improves the uniformity and stability of initiator feeding, greatly improves the stability rate of polymerization conversion rate, and avoids winter crystal precipitation being brought into the polymerization kettle to cause burst aggregation, eliminating potential safety hazards
.