CN109942730B - Method for preparing brominated styrene-butadiene copolymer by heterogeneous oxidation - Google Patents
Method for preparing brominated styrene-butadiene copolymer by heterogeneous oxidation Download PDFInfo
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Abstract
The invention provides a method for preparing brominated styrene-butadiene copolymer by heterogeneous oxidation, which comprises the following main steps: (1) dissolving SBS with organic solvent, adding organic bromine ammonium salt water solution and methyl bromide inhibitor, dripping a small amount of acid catalyst to regulate pH value, adding metal oxidant, reacting at constant temperature, standing and layering; (2) washing and drying the layered organic phase at the lower layer; (3) adding solid acid catalyst and organic solution containing NBS into the dried organic phase, heating to 90-100 deg.c, refluxing for 1-2 hr, cooling, neutralizing free bromine with alkaline matter, precipitating with precipitant, filtering and drying to obtain brominated SBS product. The method has low production energy consumption, greatly reduces the discharge of three wastes, has high bromine content, high yield and good thermal stability, and is suitable for flame retardance of foamed rubber and plastic products such as foamed polyethylene, polypropylene, polystyrene and the like.
Description
Technical Field
The invention belongs to the technical field of synthesis of brominated flame retardants, and particularly relates to a method for preparing a brominated styrene-butadiene copolymer through heterogeneous oxidation.
Background
The brominated flame retardant has the advantages of high flame retardant efficiency, good heat resistance, capability of meeting the flame retardant requirements of various high polymer materials, sufficient raw material sources, low price and no great deterioration of the physical and mechanical properties of the base material, is incomparable with other flame retardants, is always favored by people, and is one of the flame retardants with the largest yield and the most extensive application in the current market. In all the flame retardants currently used in Polystyrene (PS) materials, Hexabromocyclododecane (HBCD) has good compatibility with PS resins, and the PS materials can have good flame retardant properties at a low addition level, and can maintain the thermal insulation properties and other physical properties of the PS materials to the maximum extent, thus being more widely used.
However, in recent years, extensive research and investigation have shown that hexabromocyclododecane has extremely strong toxicity accumulated in organisms, and it has been found that HBCD can diffuse into the environment through the processes of production, use and waste disposal, and that human beings as the end of the food chain absorb this substance from the environment, causing diseases in organs such as liver and thyroid gland or nerves. Aiming at the accumulation and toxicity of the hexabromocyclododecane in organisms, the substance is listed in a control list in the 'stockholm convention about persistent organic pollutants' held in 2013, hexabromocyclododecane is added to the 'catalogue of toxic chemicals strictly limiting import and export in China' in 2014 as a contracted country in China, and the forbidden requirement is also put forward for the hexabromocyclododecane to be used as a flame retardant in the 'green product evaluation technical requirement heat-insulating material' newly compiled in the current national standard, so that a substitute is required to be found for the hexabromocyclododecane, and the substitute can meet the requirement of environmental protection and the flame retardant performance of products.
In view of the above circumstances, a solution in the world is to actively research a halogen-free flame retardant, but the halogen-free flame retardant has low flame retardant efficiency, high addition amount, high price and high cost, and is generally used for products such as toys and clothes which are in close contact with human bodies, while the influence of the building material products on the product cost due to the high price is unacceptable, and the halogen-free flame retardant has poor flame retardant effect and cannot meet the requirement of the building material products on the flame retardant performance. Compared with the halogen-free flame retardant, the development of the macromolecular brominated flame retardant with low toxicity, good thermal stability, weather resistance and migration resistance by improving the molecular weight and the molecular structure is a more realistic solution. The high polymer base material has good compatibility, so the original physical and mechanical properties of the high polymer material can be maintained, and the high polymer material has no migration, good thermal stability, convenient processing and better durability.
Disclosure of Invention
Aiming at the technical problems mentioned in the background technology, the technical scheme of the invention provides a method for preparing brominated styrene-butadiene copolymer by heterogeneous oxidation, the method has low production energy consumption, greatly reduces the discharge of three wastes, and the obtained product has high bromine content, high yield and good thermal stability and is suitable for flame retardance of foamed rubber and plastic products such as foamed polyethylene, polypropylene, polystyrene and the like.
In order to solve the technical problems, the invention adopts the technical scheme that:
a method for preparing brominated styrene-butadiene copolymer by heterogeneous oxidation comprises the following main steps:
(1) dissolving SBS with organic solvent, adding organic bromine ammonium salt water solution, heating to 20-30 deg.C, adding methyl bromide inhibitor, dripping small amount of acidic catalyst to regulate pH value, adding metal oxidant, reacting at constant temperature for 3-5 hr, standing and layering;
(2) adding a certain volume of dilute alkali solution into the layered organic phase at the constant temperature of 20-30 ℃ to wash for 2-4 times, wherein the washing time is 0.5-1h each time to remove impurities, washing the organic phase with distilled water for several times, and drying with anhydrous calcium chloride solid;
(3) adding solid acid catalyst into the dried organic phase, adding organic solution containing NBS at 15-25 deg.c, heating to 90-100 deg.c for reflux for 1-2 hr, cooling, neutralizing free bromine with alkaline matter, precipitating with precipitant, filtering and drying to obtain brominated SBS product.
Wherein, the organic solvent for dissolving SBS in the step (1) is one or more of chloroform, tetrahydrofuran and dichloromethane, and the mass ratio of the organic solvent for dissolving SBS to SBS is 10-25: 1.
Wherein the organic bromine ammonium salt in the step (1) is one or a combination of more of tetraethyl ammonium bromide, tetrabutyl ammonium bromide, benzyl trimethyl ammonium bromide, benzyl triethyl ammonium bromide and dodecyl dimethyl benzyl ammonium bromide, the molar ratio of the organic bromine ammonium salt to the metal oxidant is 1.25-2:1, and the mass ratio of the organic bromine ammonium salt to the SBS is 3-11: 1.
Wherein the metal oxidant in the step (1) is any one or two of ammonium ceric nitrate and ammonium phosphomolybdate, and the mass ratio of the metal oxidant to the SBS is 5.5-18: 1.
Wherein, the methyl bromination inhibitor in the step (1) is any one or two of tin tetrachloride and titanium tetrachloride, and the amount of the methyl bromination inhibitor is 1 wt% -5 wt% of the SBS.
Wherein the acidic catalyst in the step (1) is one or more of citric acid, oxalic acid, acetic acid and silicic acid, and the dosage of the acidic catalyst is 1 wt% -10 wt% of the metal oxidant.
Wherein the dilute alkali solution in the step (2) is an aqueous solution with the mass fraction of 5% -10% of any one or more of sodium hydroxide, ammonia water, sodium carbonate and sodium bicarbonate, and the volume ratio of the dilute alkali solution to the washed organic phase is 1/3-1: 1.
Wherein, the solid acid catalyst in the step (3) consists of a metal solid phase carrier and protonic acid, and the metal solid phase carrier is Zr (OH)4、Co(OH)2The dosage of the metal solid phase carrier is 8-15 wt% of SBS, the protonic acid is one or more of sulfuric acid, hydrochloric acid and phosphoric acid, and the dosage of the protonic acid is 10-20 wt% of the metal solid phase carrier.
Wherein the organic solvent used in the organic solution containing NBS in the step (3) is one or two of carbon tetrachloride and dimethyl sulfoxide, the mass ratio of the organic solvent to the NBS in the organic solution containing NBS is 8-12:1, and the mass ratio of the NBS to SBS is 1-1.5: 1.
Wherein, the alkaline substance in the step (3) is any one or more of sodium thiosulfate, sodium hydroxide, sodium methoxide, sodium ethoxide, triethanolamine, sodium sulfite, hydrazine hydrate and ammonia water.
Wherein, the precipitant in the step (3) is any one or more of methanol, ethanol and isopropanol.
The invention has the following beneficial effects:
(1) the patent document CN201710655808 discloses a synthesis method of brominated SBS with high thermal stability, wherein hydrobromic acid which is a strong acid is used as a bromine agent, the bromine agent is a reagent with strong corrosivity, strong volatility and easy inhalation of toxicity, the bromine agent adopted in the scheme is an organic bromine ammonium salt, and the bromine agent is stable, safe and nontoxic, so that the production safety and operability in the scheme are better; metal ions in the water phase can be recycled, so that the environmental pollution is reduced, and the preparation cost of the product is reduced;
(2) compared with bromine as a brominating agent, the organic bromine ammonium salt is used as the brominating agent, the reaction condition is mild and easy to control, and the coordination of metal ions enables the bromine addition of double bonds to be more accurate, so that the product has high bromine content, high yield and better thermal stability
(3) The pH value is regulated and controlled by adopting an acid catalyst, the oxidability of metal ions is improved, the forming rate of bromide ions is ensured, and the yield and the quality of a product are ensured;
(4) solid protonic acid is used as a catalyst, and bromine is directionally and quantitatively substituted on main chain carbon of the styrene-butadiene polymer, so that all bromine elements are bonded on the main chain of the styrene-butadiene copolymer, and the thermal stability of the catalyst is better than that of bromine substituted on a benzene ring, so that the product has good compatibility with a polystyrene material, and the mechanical property of the added material is not negatively influenced;
(5) and the precipitant is adopted for precipitation, so that the product has high crystallization degree, high thermal stability and better and more stable product dispersibility.
Drawings
FIG. 1 is a schematic diagram of the process of the present invention, wherein styrene-butadiene copolymer (SBS) is used as a raw material to perform two reactions of double bond bromine addition and benzylic bromine substitution, wherein in the first step, under an acidic catalysis condition, a bromonium salt is obtained by using the oxidation of metal ions, and the bromonium salt is cleaved in an organic phase to form a bromine radical which is directionally reacted with the double bond addition in SBS; and in the second step, N-bromosuccinimide (NBS) is used as a brominating agent, and the directional and quantitative bromination of the benzyl position of the aliphatic chain is carried out under the catalysis of solid acid, so that the bromine conversion rate is improved.
FIG. 2 is a comparative analysis chart of the infrared spectra of SBS and brominated SBS; wherein (A) S(ii) a BS infrared spectrum; (B) brominated SBS infrared spectra; (A) SBS FTIR: characteristic peak of styrene (698 cm)-1And 756cm-1) 1, 2-vinyl characteristic peaks: 910cm-1And 1, 4 trans characteristic peaks: 966cm-1(ii) a (B) Brominated SBS FTIR: characteristic peak of styrene (698 cm)-1And 756cm-1) 1, 2-vinyl characteristic peaks: 908cm-1And 1, 4 trans characteristic peaks: 966cm-1Carbon-bromine bond characteristic peaks: 547cm-1(ii) a Characteristic peaks of carbon-bromine bond: 547cm-1The infrared region of the aliphatic carbon grafted with bromine proves the feasibility of addition and substitution of bromine on the main chain.
FIG. 3 is a chart comparing the nuclear magnetic resonance spectra of SBS and brominated SBS; wherein, (A) SBS nuclear magnetic resonance spectrogram; (B) brominated SBS nuclear magnetic resonance spectrogram; (A) SBS (CDCl)3)1HNMR: aromatic hydrogen (6.3-7.3ppm), olefinic hydrogen (1, 2-vinyl: 4.9-5.1 ppm; 1, 4-trans and 1, 4-cis: 5.3-5.5ppm), aliphatic hydrogen (0.5-2.5 ppm); (B) brominated SBS (CDCl)3)1HNMR: aromatic hydrogen (6.3-7.3ppm), bromo-hydrogen (3.7-4.3ppm) aliphatic hydrogen (0.5-2.5 ppm); the chemical displacement value of the carbon-carbon double bond on the SBS butadiene chain segment in the raw material is as follows: 1, 2-vinyl group: 4.9-5.1 ppm; 1, 4-trans and 1, 4-cis: 5.3-5.5 ppm; the chemical shift value of the carbon-carbon double bond disappears after the addition of the product bromine, which indicates that the double bond is added, and a new chemical shift value appears at 3.7-4.3ppm, and the new chemical shift value is determined as a hydrogen atom on the carbon-bromine bond through the comparison of a standard spectrogram, and simultaneously, the peak value of the product aliphatic hydrogen is obviously reduced compared with the peak value of SBS aliphatic hydrogen, which indicates that the substitution of the NBS on the main chain aliphatic hydrogen is very successful.
FIG. 4 is a thermogravimetric curve comparative analysis chart of SBS, a product synthesized by taking bromine as a bromine agent, a product synthesized by taking hydrobromic acid as a bromine agent and a product synthesized by taking organic bromine ammonium salt as a bromine agent according to the method in the patent document CN 201710655808; wherein (a) the thermogravimetric curve of SBS: the initial weight loss temperature is 377 ℃; (B) the thermogravimetric curve of the brominated SBS synthesized in the comparative example 4 by using bromine as a bromine agent is as follows: the initial weight loss temperature is 177 ℃; (C) thermogravimetric curves of brominated SBS synthesized in comparative example 2 according to the procedure in comparative document CN201710655808 with hydrobromic acid as the bromine agent: the initial weight loss temperature is 201 ℃; (D) thermogravimetric curves of brominated SBS synthesized in example 1 with organic bromine ammonium salt as bromine agent: the initial weight loss temperature was 233 ℃. Compared with the initial weight loss temperature of the raw material SBS, the initial weight loss temperature value of the brominated SBS is obviously reduced. However, the brominated SBS synthesized by using the organic bromine ammonium salt as the bromine agent has milder reaction conditions, and the oxidation of metal ions and the solid protonic acid as the catalyst ensure that the addition and the substitution of bromine are more accurate, compared with the brominated SBS synthesized by using hydrobromic acid and bromine as the bromine agent, the brominated SBS synthesized by using the organic bromine ammonium salt as the bromine agent has smaller damage to a polymer chain and more ordered molecular structure of the obtained product, so the initial weight loss temperature of the brominated SBS synthesized by using the organic bromine ammonium salt as the bromine agent is higher than that of the brominated SBS synthesized by using other reagents as the bromine agent, and the thermal stability is better. In the production process of the XPS plate, the production temperature range is generally 170-210 ℃, and compared with the production process, the brominated SBS obtained by using organic bromine ammonium salt as a bromine agent and through metal ion oxidation catalysis has stronger applicability.
Detailed Description
It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.
Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
Example 1
(1) Dissolving 10g of SBS by using 70ml of organic solvent chloroform, adding 180g of 45% tetraethylammonium bromide aqueous solution, heating to 25 ℃, adding 0.3g of stannic chloride, dropwise adding 4.8g of 50% citric acid aqueous solution serving as a catalyst, adding 154g of ceric ammonium nitrate, reacting at constant temperature for 3-5 hours after the addition is finished, and standing for layering;
(2) washing the layered organic phase of the lower layer with 50ml of 5% NaOH solution for 2-4 times at constant temperature of 25 ℃, wherein the washing time is 0.5-1h each time to remove impurities, washing the organic phase with 50ml of distilled water for several times, and drying the organic phase of the lower layer with anhydrous calcium chloride solid;
(3) adding 1g of Zr (OH) to the dried organic phase4And 0.2g of phosphoric acid, adding 80ml of dimethyl sulfoxide solution containing 10g of NBS at the temperature of 15-25 ℃, heating to 90-100 ℃, refluxing for 1-2 hours, cooling, neutralizing excess bromine with sodium hydroxide, precipitating under the action of ethanol, filtering and drying to obtain 33.75g of brominated SBS product.
Example 2
(1) Dissolving 10g of SBS by using 70ml of organic solvent chloroform, adding 180g of 45% tetraethylammonium bromide aqueous solution, heating to 25 ℃, adding 0.3g of stannic chloride, adding 154g of ceric ammonium nitrate, reacting at constant temperature for 3-5 hours after the addition is finished, and standing for layering;
(2) washing the layered organic phase of the lower layer with 50ml of 5% NaOH solution for 2-4 times at constant temperature of 25 ℃, wherein the washing time is 0.5-1h each time to remove impurities, washing the organic phase with 50ml of distilled water for several times, and drying the organic phase of the lower layer with anhydrous calcium chloride solid;
(3) adding 1g of Zr (OH) to the dried organic phase4And 0.2g of phosphoric acid, adding 80ml of dimethyl sulfoxide solution containing 10g of NBS at the temperature of 15-25 ℃, heating to 90-100 ℃, refluxing for 1-2 hours, cooling, neutralizing excess bromine with sodium hydroxide, precipitating under the action of ethanol, filtering and drying to obtain 17.58g of brominated SBS product.
Example 3
(1) Dissolving 10g of SBS by using 70ml of organic solvent chloroform, adding 180g of 45% tetraethylammonium bromide aqueous solution, heating to 25 ℃, adding 0.3g of stannic chloride, dropwise adding 4.8g of 50% sodium carbonate aqueous solution serving as a catalyst, adding 154g of ceric ammonium nitrate, reacting at constant temperature for 3-5 hours after the addition is finished, standing and layering;
(2) washing the layered organic phase of the lower layer with 50ml of 5% NaOH solution for 2-4 times at constant temperature of 25 ℃, wherein the washing time is 0.5-1h each time to remove impurities, washing the organic phase with 50ml of distilled water for several times, and drying the organic phase of the lower layer with anhydrous calcium chloride solid;
(3) adding 1g of Zr (OH) to the dried organic phase4And 0.2g of phosphoric acid, at a temperature of 15 ℃ to 25 ℃, 1 in0g NBS in 80ml carbon tetrachloride, heating to 90-100 deg.C, refluxing for 1-2 hours, cooling, neutralizing excess bromine with sodium hydroxide, precipitating under the action of ethanol, filtering, and drying to obtain 15.92g brominated SBS product.
Example 4
(1) Dissolving 10g of SBS by using 70ml of organic solvent chloroform, adding 180g of 45% tetraethylammonium bromide aqueous solution, heating to 25 ℃, adding 0.3g of stannic chloride, dropwise adding 4.8g of 50% citric acid aqueous solution serving as a catalyst, adding 154g of ceric ammonium nitrate, reacting at constant temperature for 3-5 hours after the addition is finished, and standing for layering;
(2) washing the layered organic phase of the lower layer with 50ml of 5% NaOH solution for 2-4 times at constant temperature of 25 ℃, wherein the washing time is 0.5-1h each time to remove impurities, washing the organic phase with 50ml of distilled water for several times, and drying the organic phase of the lower layer with anhydrous calcium chloride solid;
(3) adding the dried organic phase into 80ml dimethyl sulfoxide solution containing 10g NBS at the temperature of 15-25 ℃, heating to 90-100 ℃, refluxing for 1-2 hours, cooling, neutralizing excess bromine with sodium hydroxide, precipitating under the action of ethanol, filtering and drying to obtain 22.37g brominated SBS product.
Example 5
(1) Dissolving 15g of SBS in 210ml of organic solvent tetrahydrofuran, adding 130g of 45% benzyl trimethyl ammonium bromide aqueous solution, heating to 25 ℃, adding 0.15g of titanium tetrachloride, dropwise adding 5.9g of 50% oxalic acid aqueous solution serving as a catalyst, adding 260g of ammonium phosphomolybdate, reacting at constant temperature for 3-5 hours after the addition is finished, and standing for layering;
(2) washing the layered lower organic phase with 70ml 10% ammonia water at constant temperature of 25 deg.C for 2-4 times (0.5-1 hr for each time to remove impurities), washing the organic phase with 50ml distilled water for several times, and drying the lower organic phase with anhydrous calcium chloride solid;
(3) adding 1.5g Zr (OH) to the dried organic phase4And 0.15g hydrochloric acid, adding 135ml dimethyl sulfoxide solution containing 15g NBS at 15-25 deg.C, heating to 90-100 deg.C, refluxing for 1-2 hr, cooling, neutralizing excess bromine with triethanolamine, and dissolving in methanolPrecipitating under the action of alcohol, filtering and drying to obtain 51.45g of brominated SBS product.
Example 6
(1) Dissolving 20g of SBS by 300ml of organic solvent dichloromethane, adding 380g of 45% aqueous solution of benzyl triethyl ammonium bromide, heating to 25 ℃, adding 0.6g of stannic chloride, dropwise adding 21g of 38% aqueous solution of acetic acid as a catalyst, adding 260g of ceric ammonium nitrate, reacting at constant temperature for 3-5 hours after the addition is finished, and standing for layering;
(2) washing the layered organic phase of the lower layer with 100ml 10% sodium carbonate solution at constant temperature of 25 deg.C for 2-4 times, wherein the washing time is 0.5-1h to remove impurities, washing the organic phase with 100ml distilled water for several times, and drying the organic phase of the lower layer with anhydrous calcium chloride solid;
(3) the dried organic layer was added with 2g of Co (OH)2And 0.4g of sulfuric acid, adding 140ml of carbon tetrachloride solution containing 20g of NBS at the temperature of 15-25 ℃, heating to 90-100 ℃, refluxing for 1-2 hours, cooling, neutralizing excessive bromine with triethanolamine, precipitating under the action of ethanol, filtering and drying to obtain 63.74g of brominated SBS product.
Examples 1, 2, and 3 are comparative tests on the selection of catalysts in the first-step double bond addition reaction, and respectively select acid catalysis, non-catalysis, and basic catalysis, and under the same other reaction conditions, the yield of 3 examples is compared to find that the yield is highest, non-catalysis is inferior, and basic catalysis is lowest under acid catalysis, which indicates that the oxidation of metal ions is exerted to the maximum under acid conditions, thereby ensuring the formation rate of bromonium ions, and simultaneously, the double bond bromine is more favorably opened under acid conditions to form an electron-deficient state, and the bromonium anions approach and complete nucleophilic addition on double bonds. On the contrary, the alkaline catalysis has the effect of inhibiting the oxidability of metal ions, is not beneficial to the formation of the bromide onium ions and is also not beneficial to the opening of double bonds to finish nucleophilic addition; example 4 in comparison with example 1 except that no solid acid catalyst was added to assist the bromine substitution reaction of NBS, the solid acid was present to act as a support for the bromine cation to ensure stability of the bromine cation, i.e. to ensure the concentration of bromine cation that can participate in the reaction, and to make the benzylic hydrogen more reactive to favor electrophilic substitution of the bromine cation. Compared with the example 1, under the condition that the input proportions of SBS, organic bromine ammonium salt, metal oxidant and NBS brominating agent are the same, the output is basically increased according to the proportion under the condition of selecting and increasing the input quantity gradient, and the repeatability of the examples and the correctness of the input proportions of the raw materials and the catalysts are proved.
Comparative example 1
(1) Dissolving 10g of SBS by using 100g of organic solvent dichloroethane, adding into 10g of 50% hydrogen peroxide solution, adding 0.2g of tetrabutylammonium bromide and 0.1g of stannic chloride as catalysts, heating to 35-60 ℃, dropwise adding 30g of 50% hydrobromic acid aqueous solution, maintaining the reaction temperature at 50 ℃ after dropwise adding, reacting for 5h, cooling to room temperature, standing and layering;
(2) adding 0.2g of hydrogen peroxide and 0.2g of sodium methoxide into the layered lower organic layer, heating to 60 ℃, preserving the temperature for 2h, removing impurities, adding 100g of water, washing, standing for layering, and drying the lower organic layer by using calcium chloride solid;
(3) adding 1g of Zr (OH) to the dried organic phase4And 0.2g of phosphoric acid, adding 80ml of dimethyl sulfoxide solution containing 10g of NBS at the temperature of 15-25 ℃, heating to 90-100 ℃, refluxing for 1-2 hours, cooling, neutralizing excess bromine with sodium hydroxide, precipitating under the action of ethanol, filtering and drying to obtain 26.32g of brominated SBS product.
Comparative example 2
(1) Dissolving 10g of SBS by using 100g of organic solvent dichloroethane, adding into 10g of 50% hydrogen peroxide solution, adding 0.2g of tetrabutylammonium bromide and 0.1g of stannic chloride as catalysts, heating to 35-60 ℃, dropwise adding 30g of 50% hydrobromic acid aqueous solution, maintaining the reaction temperature at 50 ℃ after dropwise adding, reacting for 5h, cooling to room temperature, standing and layering;
(2) adding 0.2g of hydrogen peroxide and 0.2g of sodium methoxide into the layered lower organic layer, heating to 60 ℃, preserving the temperature for 2h, removing impurities, adding 100g of water, washing, standing for layering, and drying the lower organic layer by using calcium chloride solid;
(3) adding 0.3g of ferric trichloride and 0.1g of iodine as composite catalysts into the dried organic layer, controlling the reaction temperature to be 5-8 ℃, dropwise adding dichloroethane solution containing 24g of bromine chloride, neutralizing excess bromine by using ammonia water, heating to 100 ℃ under the action of water and 2 wt% of polyvinyl alcohol solution, distilling to remove the solvent, filtering and drying to obtain 24.85g of brominated SBS product.
Comparative example 3
(1) Dissolving 10g of SBS by using 70ml of organic solvent chloroform, adding 180g of 45% tetraethylammonium bromide aqueous solution, heating to 25 ℃, adding 0.3g of stannic chloride, dropwise adding 4.8g of 50% citric acid aqueous solution serving as a catalyst, adding 154g of ceric ammonium nitrate, reacting at constant temperature for 3-5 hours after the addition is finished, and standing for layering;
(2) washing the layered organic phase of the lower layer with 50ml of 5% NaOH solution for 2-4 times at constant temperature of 25 ℃, wherein the washing time is 0.5-1h each time to remove impurities, washing the organic phase with 50ml of distilled water for several times, and drying the organic phase of the lower layer with anhydrous calcium chloride solid;
(3) adding 0.3g of ferric trichloride and 0.1g of iodine as composite catalysts into the dried organic layer, controlling the reaction temperature to be 5-8 ℃, dropwise adding dichloroethane solution containing 24g of bromine chloride, neutralizing excess bromine by using ammonia water, heating to 100 ℃ under the action of water and 2 wt% of polyvinyl alcohol solution, distilling to remove the solvent, filtering and drying to obtain 28.71g of brominated SBS product.
Comparative example 4
(1) Dissolving 10g SBS in 70ml organic solvent chloroform, stirring at 0 deg.C in ice water bath, and slowly dripping 30.8ml bromine into the solution at 1d/2s speed;
(2) reacting for 2h at 0 ℃, heating to 25 ℃ for 1h, heating to 50 ℃ for 1h, heating to 75 ℃ for 2h, naturally cooling to room temperature, and keeping the temperature for 20 min; methanol is used as an anti-solvent for precipitation, and 35.25g of brominated SBS product is obtained after filtration and drying.
Compared with the example 1, the difference of the comparative example 1 is that the method for double bond bromine addition in the comparative example 1 is different, hydrogen peroxide is used as an oxidant in the comparative example 1, hydrobromic acid provides a bromine agent, and compared with organic bromine ammonium salt, the hydrobromic acid is strong in corrosivity, strong in volatility, easy to inhale and poison, namely unstable and unfavorable for reaction, and the poison has harm to human beings and the environment, so that the yield is low compared with the example 1. Example 2 was carried out completely according to the method of patent document CN201710655808, and it was found that the yield was lower than that of comparative example 1, indicating that using NBS as the brominating agent would make it easier to control the relationship between input and output, and the bromine band reaction is more accurate. In comparison with comparative example 1, the double bond bromine addition is carried out by the method of the present example, but bromine substitution is carried out by the method of patent document CN201710655808, it can be seen that the yield is lower than that of example 1, but higher than that of comparative example 1, and the yield is the highest in comparative examples 1, 2 and 3, which shows that the bromine addition reaction accounts for a heavier proportion of the bromine component in the product in the whole process, which is consistent with that of polybutadiene component in SBS which the proportion is 70%, and the double bond addition has two bromine added to the main chain and the bromine substitution is one substitution, and the addition reaction accounts for more important parts, so there is a comparison result of the product yields of comparative examples 1, 2 and 3. In comparative example 4, bromine is selected as a bromine agent, the yield is slightly higher than that of example 1, but because bromine has no selectivity on the bromination of SBS, partial hydrogen on benzene ring in the product can be replaced, so that the structure and the order of the product are damaged, the thermal stability of the flame retardant is affected, the thermal stability is reduced, and the bromine is not beneficial to being added and used in the production of foam materials such as XPS.
While one embodiment of the present invention has been described in detail, the description is only a preferred embodiment of the present invention and should not be taken as limiting the scope of the invention. All equivalent changes and modifications made within the scope of the present invention shall fall within the scope of the present invention.
Claims (8)
1. A method for preparing brominated styrene-butadiene copolymer by heterogeneous oxidation is characterized by comprising the following main steps:
(1) dissolving SBS with organic solvent, adding organic bromine ammonium salt water solution, heating to 20-30 deg.C, adding methyl bromide inhibitor, dripping small amount of acidic catalyst to regulate pH value, adding metal oxidant, reacting at constant temperature for 3-5 hr, standing and layering;
(2) adding a certain volume of dilute alkali solution into the layered organic phase at the constant temperature of 20-30 ℃ to wash for 2-4 times, wherein the washing time is 0.5-1h each time to remove impurities, washing the organic phase with distilled water for several times, and drying with anhydrous calcium chloride solid;
(3) adding a solid acid catalyst into the dried organic phase, adding an organic solution containing NBS at the temperature of 15-30 ℃, heating to 90-100 ℃, refluxing for 1-2 hours, cooling, neutralizing free bromine with an alkaline substance, precipitating under the action of a precipitator, filtering and drying to obtain a brominated SBS product;
the organic bromine ammonium salt in the step (1) is one or a combination of more of tetraethyl ammonium bromide, tetrabutyl ammonium bromide, benzyl trimethyl ammonium bromide, benzyl triethyl ammonium bromide and dodecyl dimethyl benzyl ammonium bromide, the molar ratio of the organic bromine ammonium salt to the metal oxidant is 1.25-2:1, and the mass ratio of the organic bromine ammonium salt to the SBS is 3-11: 1;
the metal oxidant in the step (1) is any one or two of ammonium ceric nitrate and ammonium phosphomolybdate, and the mass ratio of the metal oxidant to the SBS is 5.5-18: 1.
2. The method for preparing brominated styrene-butadiene copolymer through heterogeneous oxidation according to claim 1, wherein the organic solvent for dissolving SBS in the step (1) is any one or more of chloroform, tetrahydrofuran and dichloromethane, and the mass ratio of the organic solvent for dissolving SBS to SBS is 10-25: 1.
3. The method for preparing brominated styrene-butadiene copolymer through heterogeneous oxidation according to claim 1, wherein the methyl bromination inhibitor in the step (1) is any one or two of tin tetrachloride and titanium tetrachloride, and the amount of the methyl bromination inhibitor is 1-5 wt% of SBS.
4. The method for preparing brominated styrene-butadiene copolymer through heterogeneous oxidation according to claim 1, wherein the acidic catalyst in step (1) is any one or more of citric acid, oxalic acid, acetic acid and silicic acid, and the amount of the acidic catalyst is 1-10 wt% of the metal oxidant.
5. The method for preparing the brominated styrene-butadiene copolymer through heterogeneous oxidation according to claim 1, wherein the dilute alkali solution in the step (2) is an aqueous solution with the mass fraction of any one or more of sodium hydroxide, ammonia water, sodium carbonate and sodium bicarbonate being 5% -10%, and the volume ratio of the dilute alkali solution to the washed organic phase is 1/3-1: 1.
6. The method for preparing brominated styrene-butadiene copolymer through heterogeneous oxidation according to claim 1, wherein the solid acid catalyst in the step (3) consists of a metal solid phase carrier and protonic acid, and the metal solid phase carrier is Zr (OH)4、Co(OH)2The dosage of the metal solid phase carrier is 8-15 wt% of SBS, the protonic acid is one or more of sulfuric acid, hydrochloric acid and phosphoric acid, and the dosage of the protonic acid is 10-20 wt% of the metal solid phase carrier.
7. The method for preparing brominated styrene-butadiene copolymer through heterogeneous oxidation according to claim 1, wherein the organic solvent used in the NBS-containing organic solution in the step (3) is any one or two of carbon tetrachloride and dimethyl sulfoxide, the mass ratio of the organic solvent to the NBS in the NBS-containing organic solution is 8-12:1, and the mass ratio of the NBS to SBS is 1-1.5: 1.
8. The method for preparing brominated styrene-butadiene copolymer through heterogeneous oxidation according to claim 1, wherein the alkaline substance in the step (3) is any one or more of sodium thiosulfate, sodium hydroxide, sodium methoxide, sodium ethoxide, triethanolamine, sodium sulfite, hydrazine hydrate and ammonia water.
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