SU1361153A1 - Method of controlling process of dewatering butadiene-nitrile and butadiene-styrene rubbers - Google Patents

Abstract

This invention relates to a process for dehydrating butadiene-nitrile and styrene-butadiene rubbers. Reduction of gelation and improvement of the physicomechanical properties of vulcanicates is achieved by fractional supply of antioxidant: 80-90% of it is fed into the latex proportionally to its consumption, taking into account the design, and the remaining 10-20% directly into the ganek drying unit. The amount of antioxidant supplied to the screw is adjusted by the temperature of the expander head, while increasing the temperature, the amount of antioxidant is increased, while decreasing the temperature is reduced. 2 tab., 3 Il. Q (L co o p & ate with

Description

The invention relates to the regulation of the process of dewatering synthetic rubbers in worm drying units and can be used in the petrochemical industry.

The purpose of the invention is to reduce the content of gel in rubber and to improve the physical and mechanical properties of the vulcanizate.

Fig. 1 shows the dependence of the gel content in SKN-40C rubber on the temperature of the expander head at a constant productivity of 2.8 t / h in dry rubber (when the antioxidant feeds into latex); Fig. 2 shows the dependence of the gel content in SKN-AOC rubber on the dosage of antioxidant P-23 to the screw machine; FIG. 3 is a flow chart for regulating the process of drying synthetic rubber.

The scheme for carrying out the proposed method comprises an antioxidant dispenser 1, a latex line 2, first 3 and second 4 coagulation devices, a concentrator 5 for separating serum, a washing tank 6, a concentrator 7 for separating water, an auger machine 8, an antioxidant supply line 9, line 10 additional input of antioxidant, line 11 for adjusting the second portion of antioxidant depending on temperature changes at the exit of the screw machine, flow rate 12 for supplying the antioxidant, temperature sensor 13 and thermocouple 14.

EXAMPLE 1 SKN-40C Butadiene Nitrile Rubber is obtained by emulsion copolymerization of butadiene with acrylonitrile using tertiary dodecylmercaptan as a modifier, and sodium alkyl sulfonate as an emulsifier. Before coagulation, the latex is filled with an antioxidant — a suspension of Naphtham-2 — in the amount of 2.5% for rubber. Then, LZ-7 plasticizer is added to the latex. the amount of 2% for rubber, the resulting chips are washed with water and dried in a screw machine at the temperature of the expander head.

The content of the gel in rubber is 5.5 wt.% Conditional tensile strength 29, JB MPa with a Defoe stiffness of 20.1 N

PRI mme R 2. Butadiene-nitrile rubber SKN-40C is obtained, as in Example 1, only 2.2% of Naphtam-2

it is introduced into latex, and 0.3% of antioxidant directly into a screw machine. The temperature of the expander head is maintained, as in Example 1.,

The content of the gel in rubber is 4% (Fig. 1), the relative tensile strength of 31.5 MPa with stiffness according to

Defoe 19.5 N.

I

Table

Serial process

100

8.0

Izvestny way

5.5

Offered

55.0

101.4

151.0

200,8

250,8

The results in the method of the inhibitor input on the content of the gel in the SKN-40С rubber (drying temperature 80 ° С, Naftam-2 content 2.5%).

From table 1 it follows that the optimal ratio of the quantities of inhibitors introduced into the latex and into the screw machine is 85:15. When feeding into a screw machine less than 10% of Naphtam-2, the content of the gel is almost at the control level. Increasing the amount of Naphtham-2 by more than 20% is impractical because the gel content does not change, but the amount of water introduced with the inhibitor in the form of a suspension into a screw machine increases, which is undesirable.

Example 3: SKN-40C butadiene nitrile rubber is prepared in the same manner as in Example 2, except that instead of Naff-i tama-2, antioxidant is introduced into latex.

 (2,4,6-tritretbutylphenol) in the amount of 1.5%, and 0.15% - directly into the screw machine. The temperature of the expander head is maintained at 160-165 0, the rubber load is maintained at 2.6 t / h, then increased to 2.8 t / h, and the temperature of the head is up to 170 ° C. At the same time, the amount of P-23 introduced into the screw machine is increased to 0.2%. Then the load is brought to 3 m / h, the temperature of the expander head is increased to 180 ° C, the amount of P-23 introduced into the screw machine is increased to 0.3%.

After each load change, a rubber sample is taken for gel content.

The results of the analysis: at temperature-20 asheena at. Rubber analyze

re-drying 165 C. with a productivity of 2.6 t / h, a dosage of P-23 equal to 0.15%, 1.91% gel is obtained; at a drying temperature of 170 ° C, a productivity of 2.8 t / h, a dosage of P-23 equal to 0.23%, a 1.87% gel is obtained; at a drying temperature of 180 ° C, a productivity of 3 t / h, a dosage of P-23 equal to 0.30%, 1.95% gel is obtained.

The data obtained show that with an increase in the temperature of the expander head, a simultaneous increase in the dosage of the antioxidant in the screw machine from 0.15 to 0.3% makes it possible to keep the gel content in rubber at the same level (2.0%) while

1.5

3.5

800

3, 27.829.3

575630

1.3 + 0

0.5

790

3.0

according to a known method, increasing the drying temperature from 160 to leads to an increase in the gel content from 1.5 to 4%.

PRI me R 4 (control). The styrene butadiene rubber SKS-30 ARKPN is obtained by copolymerization of butadiene and styrene according to a well-known recipe using a mixture of rosin rosin and synthetic fatty acids as an emulsifier. The resulting latex is charged with a non-darkening antioxidant AO-6 in the amount of 1.5% per rubber. The latex is coagulated according to a conventional scheme with sodium chloride and sulfuric acid, the resulting rubber crumb is dried in a laboratory screw.

on the content of the gel and physico-mechanical parameters. The results are presented in table 2.

PRI me R 5. Butadiene-styrene

The SKS-30 ARKPN curb is also prepared in the same way as in Example 1, only AO-6 is introduced as follows: 1.3% before the start of coagulation directly into the latex, and 0.3% into the loading cartridge of the auger machine. Drying temperature 190 and 200 C. Rubber analysis on the content of the gel and physico-mechanical properties.

The content of the gel and the physico-mechanical properties of the SKS-30 ARKPN rubber are shown in Table 2. Table 2

1.3 + 0.21.3 + 0.3

2.01.0

810800

3.13.0

28.0

28.9

600

610

Claims (1)

Invention Formula The method of regulating the dehydration process of butadiene-nitrile and styrene-butadiene rubbers by coagulating latex, pre-pressing moisture in the expeller and drying in a worm drying unit, characterized in that, in order to reduce gelation and improve the physical-mechanical indicator of vulcanizates, it is applied. supply of an antioxidant inhibitor. part of which in the amount of 80-90% is fed to the latex in proportion to its consumption with regard to concentration, and the second part in the amount of 10-20% is fed directly to the auger drying unit, correcting the input quantity by changing the temperature of the expander head, and with increasing temperature antioxidant inhibitor to the second point increase, and decrease with decreasing. 9.0 1.0 About 160 T & MP & Pa-tour foaoffftt ex-pa, .ra .. C Proct gel 3, a TO t.o  cios o.is ag Q, 2s 0,3 zv Doz “roL-a. QHmuaKcvda.na.4tuneKofyH) MQuivHy onakauguk f "A2 ± L Lnpaa and .five / 7/77 // 77tL. Editor N.Rogulich Compiled by O. Tigina Tehred M. Morgental Proofreader S. Shekmar Order 105 Circulation 438 Subscription VNIIPI USSR State Committee for inventions and discoveries 113035, Moscow, Zh-35, Raushsk nab., 4/5 Production and printing company, Uzhgorod, st. Project, 4