Method for coagulating ABS graft latex

文档序号：526365 发布日期：2021-06-01 浏览：27次中文

阅读说明：本技术 一种abs接枝胶乳的凝聚方法 (Method for coagulating ABS graft latex ) 是由孙一峰周兵黎源韩强赵以兵郑兵于 2021-01-18 设计创作，主要内容包括：本发明提供了一种ABS接枝胶乳凝聚方法。本发明采用1,2,4,5-苯四胺四盐酸盐和乙二胺四乙酸四钠凝聚体系,并结合“釜+管”串联连续凝聚工艺,提高了凝聚工艺稳定性以及所制备ABS接枝粉品质。该方法解决了ABS接枝胶乳凝聚过程中生产波动的问题,所制ABS接枝胶粉具有更窄的粒径分布、更小的安息角、更大的卡尔流动性指数,有利于提高后续的离心脱水、流化干燥、气体输送等工序的稳定性。(The invention provides an ABS graft latex coagulation method. The invention adopts a 1,2,4, 5-benzene tetramine tetrahydrochloride and ethylene diamine tetraacetic acid tetrasodium coacervation system, and combines a 'kettle + tube' series continuous coacervation process, thereby improving the stability of the coacervation process and the quality of the prepared ABS grafted powder. The method solves the problem of production fluctuation in the process of ABS graft latex agglomeration, and the prepared ABS graft rubber powder has narrower particle size distribution, smaller repose angle and larger Karl flow index, and is beneficial to improving the stability of subsequent procedures such as centrifugal dehydration, fluidized drying, gas conveying and the like.)

1. A process for the coagulation of ABS graft latex, characterized in that it comprises the following steps:

(1) adding ABS graft latex, deionized water and a coagulant into a coagulation kettle, and demulsifying and coagulating to obtain ABS graft powder slurry;

(2) introducing the ABS graft powder slurry into a tubular reactor, curing, cooling, filtering and drying to obtain ABS graft powder;

wherein, the coagulant in the step (1) is 1,2,4, 5-benzene tetramine tetrahydrochloride and/or ethylene diamine tetraacetic acid tetrasodium.

2. The coagulation method according to claim 1, wherein the feeding ratio of the coagulant to the ABS graft latex in step (1) is (0.5-5): 100;

and/or the solid content of the slurry in the step (1) is 20-27 percent based on the total mass of the slurry.

3. The coagulation method of claim 1, wherein the ABS graft latex of step (1) has a demulsification and coagulation temperature of 65-80 ℃;

and/or the linear velocity of the stirring blade end of the coagulation kettle in the step (1) is 1-7 m/s.

4. The coagulation method as claimed in claim 1, wherein the tubular reactor in the step (2) is a stepwise temperature-controlled maturation tubular reactor;

preferably, the tubular reactor in step (2) is equipped with combined mixing elements, preferably selected from one or more of SD, SY, SV, SX and SZ;

and/or, heating to the curing temperature at a fixed temperature rise rate in the step (2), and curing at a constant temperature;

preferably, the temperature rise rate in step (2) is 0.2-5 ℃/min;

preferably, the curing temperature in the step (2) is 85-98 ℃, and the constant-temperature curing time is 0.5-3 h.

5. The agglomeration method according to claim 1, wherein the particle diameter D50 of the ABS graft resin obtained in the step (2) is controlled to be 80 to 260. mu.m.

6. An ABS graft powder produced by the agglomeration method according to any one of claims 1 to 5.

7. The ABS graft powder of claim 6, wherein the particle size D50 of the ABS graft powder is 80-260 μm.

Technical Field

The invention belongs to the technical field of ABS resin, and particularly relates to a method for coagulating ABS graft latex.

Background

The ABS resin is produced by two processes of emulsion grafting-bulk SAN blending method and bulk method according to a synthetic route. The emulsion grafting-bulk SAN blending method can prepare ABS resin products with different impact resistance, glossiness and other properties by adjusting the blending ratio of the rear-stage double-screw blending process because the grafting powder and the SAN are produced respectively. As the emulsion grafting-bulk SAN blending method has the characteristics of flexible process and variable product types, almost 9-generation suppliers adopt the process to produce ABS.

The emulsion grafting-bulk SAN blending method adopts a two-step emulsion polymerization process to prepare 330-350nm grafted latex particles with a core-shell structure, wherein the core layer is polybutadiene rubber accounting for about 60% of the mass of the grafted latex particles, and the shell layer is grafted styrene-acrylonitrile copolymer, so as to provide two-phase bonding force for dispersed phase polybutadiene rubber and continuous phase SAN.

In order to facilitate the implementation of the subsequent blending process, the conventional process adopts an external acid/salt adding mode to coagulate the graft latex prepared by the two-step emulsion polymerization process into ABS graft powder with certain particle size distribution, generally, the coagulation procedure consists of two parts of low-temperature coagulation (about 75 ℃) and high-temperature curing (about 95 ℃), the most common method is a three-stage continuous kettle type reactor, the cured ABS graft powder slurry is centrifugally dehydrated after being cooled, and the prepared wet powder is sent into a nitrogen/air fluidized bed for drying and then used as an independent component for the double-screw blending production of ABS resin.

Usually, the average particle size of ABS graft powder has no clear requirement, but the fluctuation of the parameter in actual production has great influence on the stability of subsequent processes; for example, the small particle size of the grafted powder can cause the problems of blockage of a filter cake of a centrifuge, unqualified moisture content of wet powder, poor fluidization of a circulating fluidized bed dryer, loss of a large amount of fine powder, high possibility of dust explosion and the like. And the conditions of continuous coagulation kettle agglomeration and kettle solidification, fluidized bed fluidization, powder gas conveying, difficult material discharge of a bin and the like easily occur due to overlarge grafted powder particle diameter.

In respect of the kind of coagulant, H₂SO₄With MgSO₄Is the most common ABS latex coagulant, which inevitably remains in a small amount in the wet ABS powder in the centrifugal dehydration process, and both the strong oxidizing property of sulfuric acid and metal ions can generateThe problem of material degradation and yellowing in the subsequent fluidized drying and high-temperature blending extrusion processes is caused; finally, the quality of the finished resin is affected.

The phenomena are mentioned in part of documents (CN 1854162A; analysis of influence factors of ABS latex coagulation process, Sun Shichang, oil refining and chemical engineering, 2018, 29 (5): 30-32; measurement of ABS high rubber powder fluidity index-jet flow index and application discussion, smart, chemical engineering, 2019, 27 (6): 66-70), and can cause the production load fluctuation of a device under severe conditions, and the change of the diameter of grafted particles can cause the problems of double-screw mixing blanking and two-phase dispersion uniformity fluctuation, so that the batch stability of products is poor.

In order to improve the stability of the coagulation process, various ABS manufacturers invest a great deal of research work, such as CN1854162A, wherein ABS latex with high rubber content is easy to agglomerate at the coagulation process temperature of 70 ℃, the particle size distribution is wide, and the problems of dehydration and drying difficulty in the subsequent process are solved by adopting MgSO₄/HAc/CaCl₂/H₂SO₄One or more of the above-mentioned materials can be used as flocculant, and the flocculation temperature (40-45 deg.C) and stirring speed (200-260rpm) can be controlled so as to improve the grain size distribution effect of the coagulated powder.

The literature (analysis of the influence factors of the ABS latex coagulation process, Sun Shichang, oil refining and chemical engineering, 2018, 29 (5): 30-32) indicates that the water content of different latexes is directly related to the average particle size, and different forms of stirring can cause the shape difference of the coagulated particles. In terms of demulsification temperature, it is recommended to adopt a demulsification temperature of 70-75 ℃ to control the particle size distribution and bulk density of the grafted particles.

In a wider range, the problem exists in different degrees of emulsion polymerization demulsification and coagulation, and more patents are in the selection of coagulant type/complex coagulant and coagulation equipment. For example, patent CN105566514A adopts a complex coagulant (polyepichlorohydrin dimethylamine and cellulose derivative) containing no metal salts to perform a latex coagulation process of ternary integrated rubber, so as to improve the particle size distribution of coagulated rubber particles and reduce the corrosivity in the subsequent process. In patent CN1918194A, the latex is heated to a fixed temperature, and then polyethylene oxide and a coagulant are sequentially added to implement a coagulation process, so that the process has the effect of reducing the amount of micropowder and the moisture content of wet powder. Patent CN106133029B uses a special nozzle to spray the emulsion to be coagulated, into which the tackifier is added, into the coagulant solution to form a special coagulated body, and the coagulated body is pulverized again by a pulverizing pump to produce polymer particles with narrow particle size distribution.

In the aspect of the coagulation reactor, the tubular static mixer and the four-kettle series equipment are respectively used in patent CN102190741B and patent CN201825902U to improve the problems of short equipment cleaning period and poor powder product fluidity in the coagulation process.

It can be seen that the particle size distribution-production fluctuation of the graft latex coagulation process is a common problem, and although some domestic manufacturers make considerable effort to solve the problem, no guiding solution is formed, and the adjustment of the part of the process is still judged by the experience of field technicians.

Therefore, it is necessary to provide a method for controlling the particle size of the ABS graft powder in the agglomeration process, so that the method has universality and can obviously improve the process stability of continuous agglomeration-drying-blending production and the problem of product quality fluctuation.

Disclosure of Invention

The invention aims to provide a coagulation process method of ABS graft latex, which can conveniently and efficiently coagulate and prepare ABS graft powder, wherein the prepared ABS graft powder has narrower particle size distribution, and can obviously improve subsequent centrifugation, fluidized drying and powder gas transmission effects. Because the coagulated grafting powder has more uniform particle appearance and specific surface area and lower metal ion content, the dust explosion safety of the process, the oxidation resistance of the prepared grafting powder and the color phase of the finished ABS resin can be obviously improved after a proper antioxidant is selected.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a process for the coagulation of an ABS graft latex, said process comprising the steps of:

(1) adding ABS graft latex, deionized water and a coagulant into a coagulation kettle, and demulsifying and coagulating to obtain ABS graft powder slurry;

(2) introducing the ABS graft powder slurry into a tubular reactor, curing, cooling, filtering and drying to obtain ABS graft powder;

wherein, the coagulant in the step (1) is 1,2,4, 5-benzene tetramine tetrahydrochloride and/or ethylene diamine tetraacetic acid tetrasodium (EDTA tetrasodium).

According to the invention, when the problems of difficult regulation and control of the particle size distribution of ABS graft latex agglomeration and large production fluctuation are researched, the stability of the latex is found to be derived from the balance of buoyancy, gravity, electric double-layer repulsion force and Brownian motion, and when the coagulant is added into a system, the electric double-layer maintaining the stability of the emulsion is destroyed, so that demulsification and agglomeration are generated. Because the reaction process is a chemical equilibrium process, when the temperature rise rate is too high, the Brownian motion is strengthened, the latex double electron layer is coagulated under the condition that the latex double electron layer is not completely destroyed, the insufficiently destroyed double electron layer ions carry a large amount of water to wrap in the coagulates, and the apparent solid content and solid kettle occurrence probability of the system are rapidly increased. If the condensate is not cut and dispersed in time, the generation amount of large-particle-size rubber powder is also obviously increased, and the difficulty is brought to subsequent centrifugal dehydration, fluidized drying, gas conveying, blending and extrusion.

The invention innovatively adopts a mixed aqueous solution of 1,2,4, 5-benzene tetramine tetrahydrochloride and EDTA tetrasodium as a coagulation system, wherein the main coagulant 1,2,4, 5-benzene tetramine tetrahydrochloride has higher valence and ionic radius, and has better demulsification and coagulation effects on anionic surfactants such as potassium oleate and the like in ABS grafted latex. And the EDTA tetrasodium can also complex Fe (II) transition metal ions remained in the latex, so that the stability of the ABS rubber powder in subsequent fluidized drying, blending and extruding processes is improved.

In addition, the process of the invention also adopts a 'kettle-tube' series connection condensation mode, and can form a synergistic effect with the condensation system containing 1,2,4, 5-benzene tetramine tetrahydrochloride and EDTA tetrasodium, because the valence state of the condensation system is higher, a double electronic layer can be compressed in the demulsification process to reduce the water carrying condition of an ionic layer, the viscosity is reduced in the demulsification process in a condensation kettle, and MgSO (MgSO) can be effectively avoided₄/H₂SO₄The problem of large local viscosity and uneven shearing in the demulsification process of the conventional coagulant(ii) a And then, a tubular reactor provided with a mixing element is adopted for curing operation, the process retention time, the shearing strength and the heating rate are more consistent, the particle size distribution of rubber powder is narrower, the particle circularity and the surface smoothness are obviously improved, and the stability of subsequent procedures such as centrifugal dehydration, fluidized drying, gas conveying, mixing extrusion and the like is favorably improved.

In the invention, the feeding ratio of the coagulant in the step (1) to the ABS graft latex is (0.5-5): 100.

In the invention, the solid content of the slurry in the step (1) is 20-27% by mass of the total mass of the slurry.

In the invention, the demulsification and condensation temperature of the ABS graft latex in the step (1) is 65-80 ℃.

In the invention, the linear velocity of the stirring blade end of the coagulation kettle in the step (1) is 1-7 m/s.

In the invention, the tubular reactor in the step (2) is a sectional temperature-control curing tubular reactor; preferably, the tubular reactor in step (2) is equipped with combined mixing elements, preferably selected from one or more of SD, SY, SV, SX and SZ.

In the invention, in the step (2), the temperature is raised to the curing temperature at a fixed temperature rise rate, and the curing is carried out at a constant temperature; preferably, the temperature rise rate in step (2) is 0.2-5 ℃/min; preferably, the curing temperature in the step (2) is 85-98 ℃, and the constant-temperature curing time is 0.5-3 h.

In the invention, the particle diameter D50 of the ABS grafted resin prepared in the step (2) is controlled to be 80-260 μm. Because the graft powder has narrower particle size distribution, the conditions of kettle solidification caused by local uneven stirring of a coagulation kettle, water content difference of ABS graft powder caused by uneven fluidization, poor gas conveying fluidity of the graft powder, pipe blockage and bridging of the graft powder and the fluctuation of the performance of a resin product caused by unstable conveying in double-screw blending are not easy to generate in the processes of coagulation, drying and blending.

Another object of the present invention is to provide an ABS graft powder.

ABS graft powder is prepared by adopting the agglomeration method.

In the invention, the particle size D50 of the ABS graft powder is 80-260 μm.

In one embodiment, the prepared graft powder is blended with SAN in a fixed ratio to obtain ABS resin chips. The preparation process comprises the following steps:

and (3) drying: filtering the graft powder slurry obtained by coagulation by adopting a stainless steel filter cloth to obtain wet graft powder, and drying by adopting a fluidized bed dryer to obtain ABS graft powder;

blending: and adding SAN phase into a double-screw extruder for mixing, cooling and granulating to obtain ABS resin finished product slices.

In the present invention, the% are wt% unless otherwise specified.

Compared with the prior art, the invention has the beneficial effects that:

(1) the coagulation system does not contain transition metal ions which have obvious catalytic action on resin thermal degradation, and the added EDTA tetrasodium also has the function of complexing residual Fe (II) ions in the latex, so that the stability of the ABS rubber powder in subsequent fluidized drying, blending and extrusion processes can be obviously improved, and the product hue of the ABS grafted powder and the prepared ABS resin is improved.

(2) According to the scheme, a 'kettle + tube' series connection condensation process is adopted, the demulsification shear strength, the residence time and the temperature rise rate are effectively controlled, the prepared ABS grafted rubber powder has narrower particle size distribution (D5 is more than 50 mu m, D98 is less than 700 mu m), smaller repose angle (less than 28 degrees) and larger Carl fluidity index (more than 77), and the stability of subsequent procedures such as centrifugal dehydration, fluidized drying, gas conveying and the like is favorably improved.

Drawings

FIG. 1 is a flow chart of a continuous condensation process with a series of "kettle + tube";

FIG. 2 is a flow diagram of a three-kettle series continuous coagulation process of the prior art;

FIG. 3 is a particle size distribution diagram of the ABS graft powder obtained in example 1;

FIG. 4 is a particle size distribution diagram of the ABS graft powder prepared in comparative example 1;

FIG. 5 is a 3D photomicrograph of the ABS graft powder prepared in example 1;

FIG. 6 is a 3D photomicrograph of the ABS graft powder prepared in comparative example 1;

FIG. 7 is an electron micrograph of an ABS graft powder obtained in example 1;

FIG. 8 is an electron micrograph of an ABS graft powder obtained in comparative example 1;

FIG. 9 is a comparative graph of oven aging yellowing test of ABS graft powder prepared in example 1 and comparative example 1.

Detailed description of the preferred embodiments

The invention is further illustrated by the following examples and comparative examples, which, however, do not limit the scope of the invention as claimed.

Raw material specification:

raw materials/specification	Manufacturer of the product	Specification of
			ABS graft latex	Wanhua chemistry	345nm，41.9％
1,2,4, 5-benzenetetramine tetrahydrochloride	Sigma-aldrich	99％，AR
			Tetrasodium EDTA	Wujiang Yonghe fine chemical industry	99% technical grade
MgSO₄	Alpha Aisha	99.98％
			CaCl₂	NANJING CHEMICAL REAGENT Co.,Ltd.	99.98％
H₂SO₄	Laiyang Kangde chemical Co Ltd	500ml，AR，98％
			H₃PO₄	Alpha Aisha	99.98％
Hydrochloric acid	National Shanghai test	AR，31％

Experimental equipment:

the analysis method comprises the following steps:

particle size distribution: screening out large-particle-size rubber powder with the particle size of more than 1.2mm by using a 16-mesh screen, and weighing and recording the mass proportion of the large-particle-size rubber powder; taking 1g of the fine powder part, adding 3g of liquid detergent and 100g of water, stirring IKA at 300rpm for fully dispersing for 3-5min, testing the particle size distribution of the dispersed sample by adopting Dandongbeit betersize 2000LD, and recording the data of D10 and D50;

OIT: testing the oxidation induction period of the grafting powder according to GBT 19466.6-2009, and performing constant temperature method at 190 ℃;

aging and yellowing of the oven: loading the dried ABS grafted powder into a plurality of aluminum foil surface dishes, placing the aluminum foil surface dishes into a constant-temperature oven at 180 ℃, taking out samples at fixed time intervals, and observing the heated discoloration condition of the samples;

lab value: and performing product hue analysis by using a HunterLab UltraScan VIS color difference meter. In the test, the reflectance mode was used, and the sample was filled uniformly into a 50ml cuvette and calibrated using an instrument equipped with a white board and black light trap. And placing the cuvette after sample loading on a sample rack, starting testing, performing instrument testing for three times, taking an average value, rotating the cuvette by 180 degrees, and then testing again to obtain a sample value.

Karr flow index, angle of repose: testing the Carl flow index and the repose angle according to ASTM 6393-14;

powder morphology: observing the powder morphology by adopting a 3D microscope and an electron microscope;

the prepared ABS graft powder is mixed with SAN according to a fixed proportion, and ABS resin slices for performance test can be obtained.

Example 1

26kg of ABS graft latex (345nm, 41.9 percent of solid content) is taken, 109g of emulsion antioxidant (SF-50 LX in Shaoxing plastic industry, Zhejiang Shaoxing) is added, and IKA is adopted to mechanically stir and mix evenly for standby; 4890.3g of a mixed aqueous solution of 1,2,4, 5-benzene tetramine tetrahydrochloride and EDTA tetrasodium (wherein the concentration of the 1,2,4, 5-benzene tetramine tetrahydrochloride is 5 percent, and the concentration of the EDTA tetrasodium is 0.3 percent) is added with 12.68kg of deionized water and uniformly mixed for later use.

Performing nitrogen replacement on a kettle pipe series condensation reactor (shown in figure 1), heating the condensation reactor to the wall temperature of 80 ℃, starting stirring, adjusting the linear velocity of a stirring blade end to be 3m/s (640rpm), continuously introducing the prepared ABS graft latex and the mixed aqueous solution of 1,2,4, 5-benzene tetramine tetrahydrochloride and EDTA tetrasodium into the condensation reactor, establishing a liquid level, controlling the temperature in the condensation reactor to be 74 ℃, adjusting the flow of an outlet pump, curing the process temperature of different sections of a tubular reactor (filled with an SD type mixing element), meeting the requirement that the temperature rise rate of the material is 0.5 ℃/min, heating the material in the tubular reactor to 95 ℃, curing at constant temperature for 2 hours, and obtaining slurry with the solid content of 25% and flowing out of the reactor.

After the whole process is established and stably operated for 4 hours, the slurry is taken, is further cooled to the normal temperature, and is filtered by a stainless steel filter screen of 200 meshes, so that the wet-containing grafting powder is obtained. Drying at 70 deg.C for 1h with a fluidized bed dryer to obtain graft powder with water content of 0.76%.

The resulting graft powder was tested for a particle size distribution D5 of 62.79 μm, D50 of 157.1 μm, D98 of 640.4 μm, and >1.2mm particles of 1.7%.

The fluidity index of the graft powder was measured according to ASTM 6393-14, and the repose angle was 24.5 ℃ and the Karl flow index was 83.

The thermal stability of the graft powder was further characterized according to GBT 19466.6-2009 with an OIT of 24.7min and an L value of 91.54 and a b value of 1.23 as measured by a HunterLab UltraScan VIS color difference meter. BET of 0.46m in the specific surface area test²/g。

Fig. 3 is a particle size distribution diagram of the prepared ABS graft powder, fig. 5 is a 3D microscopic photograph, fig. 7 is an electron microscopic photograph, and fig. 9 is a comparative graph of oven aging yellowing.

Example 2

26kg of ABS graft latex (345nm, 41.9 percent of solid content) is taken, 109g of emulsion antioxidant (SF-50 LX in Shaoxing plastic industry, Zhejiang Shaoxing) is added, and IKA is adopted to mechanically stir and mix evenly for standby; 2445.2g of a mixed aqueous solution of 1,2,4, 5-benzene tetramine tetrahydrochloride and EDTA tetrasodium (wherein the concentration of the 1,2,4, 5-benzene tetramine tetrahydrochloride is 5 percent, and the concentration of the EDTA tetrasodium is 0.3 percent) is added with 14.45kg of deionized water and uniformly mixed for later use.

Performing nitrogen replacement on a kettle pipe series condensation reactor (shown in figure 1), heating the condensation reactor to the wall temperature of 86 ℃, starting stirring, adjusting the linear velocity of the stirring blade end to 7m/s, continuously introducing the prepared ABS graft latex and the mixed aqueous solution of 1,2,4, 5-benzene tetramine tetrahydrochloride and EDTA tetrasodium into the condensation reactor, establishing the liquid level, controlling the temperature in the condensation reactor to be 80 ℃, adjusting the flow of an outlet pump, curing the process temperature of different sections of a tubular reactor (internally provided with an SX type mixing element), meeting the requirement of the temperature rise rate of the material to be 5 ℃/min, heating the material in the tubular reactor to 92 ℃, curing at constant temperature for 3 hours, and obtaining slurry with the solid content of 27% and flowing out of the reactor.

The resulting graft powder was tested to have a particle size distribution D5 of 71.53 μm, D50 of 249.8 μm, D98 of 681 μm, and >1.2mm particles of 1.93%.

The fluidity index of the grafted powder was measured according to ASTM 6393-14, with a repose angle of 27.8 ℃ and a Carl flow index of 79.

The thermal stability of the graft powder was further characterized according to GBT 19466.6-2009 with an OIT of 23.5min and a HunterLab UltraScan VIS color difference meter measuring an L value of 90.69 and a b value of 1.76. BET of 0.42m in the specific surface area test²/g。

Example 3

26kg of ABS graft latex (345nm, 41.9 percent of solid content) is taken, 109g of emulsion antioxidant (SF-50 LX in Shaoxing plastic industry, Zhejiang Shaoxing) is added, and IKA is adopted to mechanically stir and mix evenly for standby; 24.45kg of a mixed aqueous solution of 1,2,4, 5-benzenetetraamine tetrahydrochloride and EDTA tetrasodium (wherein the concentration of the 1,2,4, 5-benzenetetraamine tetrahydrochloride is 5 percent, and the concentration of the EDTA tetrasodium is 0.3 percent) is added with 4.20kg of deionized water and uniformly mixed for later use.

Performing nitrogen replacement on a kettle pipe series condensation reactor (shown in figure 1), heating the condensation reactor to the wall temperature of 72 ℃, starting stirring, adjusting the linear velocity of the stirring blade end to be 1m/s, continuously introducing the prepared ABS graft latex and the mixed aqueous solution of 1,2,4, 5-benzene tetramine tetrahydrochloride and EDTA tetrasodium into the condensation reactor, establishing a liquid level, controlling the temperature in the condensation reactor to be 65 ℃, adjusting the flow of an outlet pump, curing the process temperature of different sections of a tubular reactor (a SY internal type mixing element), meeting the requirement of the temperature rise rate of the material to be 0.2 ℃/min, heating the material in the tubular reactor to 85 ℃, curing at constant temperature for 0.5h, and obtaining slurry with the solid content of 20% and flowing out of the reactor.

The resulting graft powder was tested for a particle size distribution D5 of 53.4 μm, D50 of 97.26 μm, D98 of 627.4 μm, >1.2mm particles of 0.39%.

The fluidity index of the grafted powder was measured according to ASTM 6393-14, with a repose angle of 21.7 ℃ and a Carl flow index of 86.

The thermal stability of the graft powder was further characterized according to GBT 19466.6-2009 with an OIT of 21.9min and a HunterLab UltraScan VIS color difference meter measuring an L value of 91.32 and a b value of 1.38. BET of 0.71m in the specific surface area test²/g。

Comparative example 1

The comparative example is the prior art, does not adopt the coagulant of the technical scheme of the invention, and does not adopt the 'kettle + tube' series continuous coagulation process of the technical scheme of the invention.

And (3) carrying out nitrogen replacement on the three-kettle continuous coagulation reactor (shown in figure 2), heating the first coagulation kettle to the wall temperature of 80 ℃, starting stirring, adjusting the stirring speed to 640rpm, continuously introducing the prepared ABS graft latex and magnesium sulfate aqueous solution into the coagulation kettle, controlling the internal temperature of the coagulation kettle to 74 ℃ after the liquid level is established, adjusting the flow rate of an outlet pump, heating the second coagulation kettle and the third coagulation kettle to the internal temperature of 95 ℃, and preparing slurry with the solid content of 25% and flowing out of the reactor.

The resulting graft powder was tested to have a particle size distribution D5 of 32.23 μm, D50 of 161 μm, D98 of 752 μm, and a particle size ratio of >1.2mm of 6.30%. The fluidity index of the graft powder was measured according to ASTM 6393-14, and the repose angle was 35.4 ℃ and the Karl flow index was 69.

The thermal stability of the graft powder was further characterized according to GBT 19466.6-2009 with an OIT of 17.3min and an L value of 88.73 and a b value of 5.46 as measured by a HunterLab UltraScan VIS color difference meter. BET of 0.85m in the specific surface area test²/g。

Fig. 4 is a particle size distribution diagram of the prepared ABS graft powder, fig. 6 is a 3D photomicrograph, fig. 8 is an electron micrograph, and fig. 9 is a comparative graph of oven aging yellowing.

Comparative example 2

The comparative example adopts the coagulant of the technical scheme of the invention, and does not adopt the 'kettle + tube' series continuous coagulation process of the technical scheme of the invention.

Taking 26kg of self-made ABS graft latex (345nm, solid content 41.9 percent), adding 109g of emulsion antioxidant, and mechanically stirring and mixing uniformly by adopting IKA for later use; 4890.3g of a mixed aqueous solution of 1,2,4, 5-benzene tetramine tetrahydrochloride and EDTA tetrasodium (wherein the concentration of the 1,2,4, 5-benzene tetramine tetrahydrochloride is 5 percent, and the concentration of the EDTA tetrasodium is 0.3 percent) is added with 12.68kg of deionized water and uniformly mixed for later use.

The resulting graft powder was tested for a particle size distribution D5 of 26.26 μm, D50 of 142.4 μm, D98 of 803 μm, and >1.2mm particles of 5.37%.

The fluidity index of the graft powder was measured according to ASTM 6393-14, and the repose angle was 33.8 ℃ and the Karl flow index was 71.

The thermal stability of the graft powder was further characterized by GBT 19466.6-2009 with an OIT of 18.3min and a HunterLab UltraScan VIS color difference meter test with an L value of 88.92 and a b value of 5.23. BET of 0.82m in the specific surface area test²/g。

Comparative example 3

The comparative example does not adopt the coagulant of the technical scheme of the invention, and adopts the 'kettle + tube' series continuous coagulation process of the technical scheme of the invention.

Performing nitrogen replacement on a kettle pipe series condensation reactor (shown in figure 1), heating the condensation reactor to the wall temperature of 80 ℃, starting stirring, adjusting the linear velocity of the stirring blade end to be 3m/s (640rpm), continuously introducing the prepared ABS graft latex and magnesium sulfate aqueous solution into the condensation reactor, establishing the liquid level, controlling the temperature in the condensation reactor to be 74 ℃, adjusting the flow of an outlet pump, curing the process temperature of different sections of a tubular reactor (filled with an SD type mixing element), meeting the requirement that the temperature rise rate of the material is 0.5 ℃/min, heating the material in the tubular reactor to 95 ℃, and curing at constant temperature for 2 hours to obtain slurry with the solid content of 25% and flowing out of the reactor.

The resulting graft powder was tested for a particle size distribution D5 of 30.16 μm, D50 of 168 μm, D98 of 831 μm, 3.94% for particles >1.2 mm.

The fluidity index of the grafted powder was measured according to ASTM 6393-14, with a repose angle of 36.9 ℃ and a Carl flow index of 67.

The thermal stability of the graft powder was further characterized according to GBT 19466.6-2009, which is OIT 19.1min, Hunthe L value of the terLab UltraScan VIS color difference meter is 89.23, and the b value is 4.38. BET of 0.89m in the specific surface area test²/g。

It can be seen from the above that the "kettle-tube" serial coagulation mode adopted by the invention can also form a synergistic effect with the coagulation system of 1,2,4, 5-benzene tetramine tetrahydrochloride/EDTA tetrasodium, and the ABS graft powder prepared by the invention has the characteristics of narrower particle size distribution, higher particle circularity, smooth surface and the like, thereby having better fluidity and oxidation resistance. In addition, the fine powder is obviously reduced, so that the loss amount in the fluidized drying process is reduced and the process safety is improved in the industrial implementation process.

It will be appreciated by those skilled in the art that modifications or adaptations to the invention may be made in light of the teachings of the present specification. Such modifications or adaptations are intended to be within the scope of the present invention as defined in the claims.

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Method for coagulating ABS graft latex

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