CN1884060A - Preparation method of expandable graphite with high initial expansion temperature - Google Patents

Abstract

The invention discloses a preparation method of expandable graphite with high initial expansion temperature. The invention adopts sealing agent and sulfuric acid mixed solution to soak natural flake graphite, adds oxidizing agent to react under constant stirring, and makes acidic graphite, and then adds reducing agent to decolorize, and goes through water washing to remove acid, aging, washing, drying and puffing The expansion volume is 250-260mL/g, the initial expansion temperature is 300±5°C, and the expandable graphite with pH=6-7 is prepared through the following procedures. The expandable graphite prepared by the present invention has a clean surface, does not contain acid and alkaline substances, has good fluidity, does not absorb moisture, is stable to air, can be used as a flame-retardant material for engineering plastics and rubber, and can be widely used In the fields of iron and steel, metallurgy, petroleum, chemical industry, machinery manufacturing and aerospace technology.

Description

Preparation method of expandable graphite with high initial expansion temperature

technical field

The invention relates to a preparation method of expandable graphite with a high initial expansion temperature, belonging to the technical field of material science.

Due to its good expandability, expandable graphite has high temperature resistance, radiation protection, heat insulation, lubrication, plasticity, chemical stability, flexibility, ductility, and sealing. It is widely used in steel, metallurgy, chemical industry, and machinery. Manufacturing and other fields. In particular, the application fields of expandable graphite with high initial expansion temperature are more extensive. The patent document of Chinese patent notification number CN1050340C discloses a technical scheme of "manufacturing method of sulfur-free expandable graphite", which is to immerse natural flake graphite in a mixed solution of 65-98% nitric acid and organic acid. Oxidation reaction, decolorization, water washing, and drying to obtain sulfur-free expandable graphite. The product obtained by this technical scheme can be further processed to obtain high-quality sealing materials. However, the initial expansion temperature of this expandable graphite is 150°C, so it cannot be used as a flame-retardant material for engineering plastics. In the prior art, the preparation method of expandable graphite with an initial expansion temperature of about 300° C. has not been reported yet.

Contents of the invention

The purpose of the present invention is to provide a method for preparing expandable graphite with high initial expansion temperature (300±5° C.), stable performance, and can be used as flame-retardant materials in the fields of engineering plastics and rubber.

The purpose of the present invention is achieved like this. Method of the present invention comprises the following steps:

(1) Oxidation sealing

Dissolving the sealing agent in sulfuric acid with a mass fraction of 80%-95%, then adding graphite and stirring evenly, the amount of sulfuric acid is 0.8-4 times the mass of graphite, and the amount of sealing agent is 0.005-0.26 times the mass of graphite; Afterwards, under continuous stirring, add an oxidant whose mass is 0.05-0.25 times the mass of graphite for reaction, the reaction time is 0.5-2 hours, and the reaction temperature is 5-40°C to obtain acidic graphite;

Wherein, the sealing agent used is selected from one of the following combinations: the combination of ferrous sulfate heptahydrate and sodium hexametaphosphate in a mass ratio of 1.0:2.5, the combination of anhydrous calcium chloride and sodium hexametaphosphate in a mass ratio of 1.0:2.0, the combination of seven The combination of ferrous sulfate hydrate and sodium pyrophosphate in a mass ratio of 1.0:2.0, the combination of anhydrous magnesium chloride and sodium pyrophosphate in a mass ratio of 1.0:2.0, the combination of anhydrous magnesium chloride and sodium hexametaphosphate in a mass ratio of 1.0:3.0, Anhydrous calcium chloride and sodium pyrophosphate are combined in a mass ratio of 1.0:2.7;

The oxidant used is selected from one of the following substances: potassium permanganate, potassium chlorate, ammonium peroxodisulfate;

(2) Decolorization

In the prepared acidic graphite, add water with a quality of 0.5-5 times of the graphite quality, add a decolorizer with a quality of 0.05-0.3 times of the graphite quality under constant stirring, decolorize for 15-50 minutes, and wash with water until the pH of the graphite surface = After 5-7 days, spin dry by centrifugation;

The decolorizing agent used is selected from one of the following substances: oxalic acid, formic acid, hydrogen peroxide, sodium nitrite;

(3) aging

The dried acid graphite is placed at 20-40°C and aged for 24-72 hours;

(4) washing

Wash the aged acidic graphite with water to pH = 6-7, and dry it by centrifugation;

(5) drying

Drying the dried graphite at 65-80°C until the mass fraction of water in the graphite is less than 1%, to obtain a high initial expansion temperature expandable graphite product;

(6) puffed

At 950°C, expand for 30 seconds, and measure the expansion volume of the expandable graphite product.

Compared with the prior art, the present invention has the following remarkable progress: 1, the expansion start temperature of the prepared expandable graphite is as high as 300 ± 5°C, and can be used as a flame-retardant material for materials such as engineering plastics and rubber; 2, its pH value = 6-7, the surface of the product is clean and does not contain acid and alkali substances; 3, the product has good fluidity, does not absorb moisture in the air, and is stable to the air; 4, the method has a simple process and is easy to realize industrial production.

Detailed ways

List specific examples below, the present invention is further described, and the graphite used in the given example is 50 order natural flake graphites.

Example 1

Dissolve 0.2g of ferrous sulfate heptahydrate and 0.5g of sodium hexametaphosphate in 27g of sulfuric acid solution with a mass fraction of 85%, add 10g of graphite with a mass fraction of carbon of 99%, and add 0.9g of Potassium permanganate was reacted for 50 minutes. After the reaction was completed, 30g of water and 1g of hydrogen peroxide with a mass fraction of 1g were added to the feed liquid, and the color was decolorized for 20 minutes under constant stirring, and the obtained acidic graphite was washed with water to the surface of the graphite. pH = 6, centrifugal drying; after aging at 20°C for 48 hours, wash with water again until the pH of the graphite surface = 6, centrifugal drying, and dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8% times So far, expandable graphite products have been obtained. At 950°C, puffed for 30 seconds, the measured expansion volume was 260mL/g, and the initial expansion temperature was 300°C.

Example 2

Dissolve 0.3g of anhydrous magnesium chloride and 0.6g of sodium pyrophosphate in 27g of sulfuric acid solution with a mass fraction of 85%, add 10g of graphite with a mass fraction of carbon of 99%, and add 0.9g of high Potassium manganate was reacted for 50 minutes. After the reaction was completed, 30 g of water and 1 g of hydrogen peroxide with a mass fraction of 30% were added to the feed liquid, and the color was decolorized for 20 minutes under constant stirring, and the obtained acidic graphite was washed with water until the graphite surface pH = 6, centrifugal drying; after aging at 20°C for 48 hours, wash again until the graphite surface pH = 6, centrifugal drying, and dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8%. Get expandable graphite products. At 950°C, puffed for 30 seconds, the measured expansion volume was 255mL/g, and the initial expansion temperature was 301°C.

Example 3

Dissolve 0.2g of ferrous sulfate heptahydrate and 0.5g of sodium hexametaphosphate in 29g of sulfuric acid solution with a mass fraction of 80%, add 10g of graphite with a mass fraction of carbon of 99%, and add 0.9g of Potassium permanganate was reacted for 50 minutes. After the reaction was completed, 30 g of water and 1 g of hydrogen peroxide with a mass fraction of 1 g were added to the feed liquid, and the color was decolorized for 20 minutes under constant stirring. The acidic graphite obtained was washed with water until the graphite Surface pH = 6, centrifugal drying; after aging at 20°C for 48 hours, wash with water again until the graphite surface pH = 7, centrifugal drying, and dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8% So far, expandable graphite products have been obtained. At 950°C, puffed for 30 seconds, the measured expansion volume was 265mL/g, and the initial expansion temperature was 295°C.

Example 4

Dissolve 0.25g of anhydrous calcium chloride and 0.5g of sodium hexametaphosphate in 25g of sulfuric acid solution with a mass fraction of 88%, add 10g of graphite with a mass fraction of carbon of 95%, and add 0.8 g of potassium permanganate was reacted for 60 minutes. After the reaction was completed, 40 g of water and 1.2 g of oxalic acid were added to the feed solution, and the color was decolorized for 30 minutes under constant stirring. The resulting acidic graphite was washed with water until the graphite surface pH=6, and centrifuged Drying; after aging at 25°C for 48 hours, wash with water again until the pH of the graphite surface is 6.2, and dry by centrifugation; dry the product at 75°C until the mass fraction of water in the expandable graphite is 0.8% to obtain expandable graphite finished product. At 950°C, puffed for 30 seconds, the measured expansion volume was 252mL/g, and the initial expansion temperature was 296°C.

Example 5

Dissolve 0.3g of ferrous sulfate heptahydrate and 0.6g of sodium pyrophosphate in 20g of sulfuric acid solution with a mass fraction of 95%, add 10g of graphite with a mass fraction of 95% of carbon, and add 0.9g of graphite at 25°C under constant stirring Potassium permanganate was reacted for 70 minutes. After the reaction was completed, 40g of water and 1.2g of oxalic acid were added to the feed liquid, and the color was decolorized for 30 minutes under constant stirring. The resulting acidic graphite was washed with water until the pH of the graphite surface was 6, and dried by centrifugation. , aged at 30°C for 70 hours, washed again until the pH of the graphite surface = 6, and dried by centrifugation; dried at 80°C until the mass fraction of water in the expandable graphite was 0.8%, and the finished expandable graphite was obtained. At 950°C, puffed for 30 seconds, the measured expansion volume was 255mL/g, and the initial expansion temperature was 305°C.

Example 6

Dissolve 0.3g of anhydrous magnesium chloride and 0.6g of sodium pyrophosphate in 27g of sulfuric acid solution with a mass fraction of 85%, add 10g of graphite with a mass fraction of carbon of 99%, and add 1.0g of potassium chlorate at 20°C under constant stirring React for 50 minutes. After the reaction is completed, the acidic graphite obtained is washed with water until the pH of the graphite surface=6, and dried by centrifugation; Dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8% to obtain a finished expandable graphite product. At 950°C, puffed for 30 seconds, the measured expansion volume was 245mL/g, and the initial expansion temperature was 302°C.

Example 7

Dissolve 0.2g of ferrous sulfate heptahydrate and 0.5g of sodium hexametaphosphate in 29g of sulfuric acid solution with a mass fraction of 80%, add 10g of graphite with a mass fraction of carbon of 99%, and add 2.0g of The ammonium peroxodisulfate was reacted for 60 minutes. After the reaction was completed, the acidic graphite obtained was washed with water until the pH of the graphite surface = 6, dried by centrifugation, aged at 20°C for 48 hours, and washed with water again until the pH of the graphite surface = 6. Centrifuge and dry, and dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8%, so as to obtain the finished expandable graphite. At 950°C, puffed for 30 seconds, the measured expansion volume was 260mL/g, and the initial expansion temperature was 298°C.

Example 8

Dissolve 0.2g of ferrous sulfate heptahydrate and 0.5g of sodium hexametaphosphate in 29g of sulfuric acid solution with a mass fraction of 80%, add 10g of graphite with a mass fraction of carbon of 99%, and add 0.9g of Potassium permanganate was reacted for 50 minutes. After the reaction was completed, 40 g of water and 1.3 g of oxalic acid were added to the feed liquid, and the color was decolorized for 20 minutes under constant stirring. Drying; after aging at 20°C for 48 hours, wash with water again until the pH of the graphite surface = 6, dry the product by centrifugal drying, and dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8%, and the finished expandable graphite is obtained . At 950°C, puffed for 30 seconds, the measured expansion volume was 260mL/g, and the initial expansion temperature was 297°C.

Example 9

Dissolve 0.2g of ferrous sulfate heptahydrate and 0.5g of sodium hexametaphosphate in 27g of sulfuric acid solution with a mass fraction of 85%, add 10g of graphite with a mass fraction of carbon of 99%, and add 0.9g of Potassium permanganate was reacted for 50 minutes. After the reaction was completed, 40 g of water and 1.0 g of sodium nitrite were added to the feed liquid, and the color was decolorized for 30 minutes under constant stirring. The acidic graphite obtained was washed with water until the pH of the graphite surface = 6 , centrifugal drying; after aging at 20°C for 48 hours, wash with water again until the pH of the graphite surface = 6.3, then centrifugally dry, and dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8%, DEK Expanded graphite finished product. At 950°C, puffed for 30 seconds, the measured expansion volume was 264mL/g, and the initial expansion temperature was 295°C.

Example 10

Dissolve 0.2g of anhydrous calcium chloride and 0.54g of sodium pyrophosphate in 27g of sulfuric acid solution with a mass fraction of 85%, add 10g of graphite with a mass fraction of carbon of 99%, and add 0.9g of graphite at 20°C under constant stirring Potassium permanganate was reacted for 60 minutes. After the reaction was completed, 30 g of water and 1 g of hydrogen peroxide with a mass fraction of 1 g were added to the feed solution, decolorized for 30 minutes under constant stirring, and the resulting acidic graphite was washed with water to the surface of the graphite. pH = 6, centrifugal drying; after aging at 20°C for 48 hours, wash with water again until the graphite surface pH = 6, centrifugal drying; dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8% , to obtain expandable graphite products. At 950°C, puffed for 30 seconds, the measured expansion volume was 267mL/g, and the initial expansion temperature was 298°C.

Example 11

0.3g of anhydrous magnesium chloride and 0.6g of sodium pyrophosphate are dissolved in 27g of sulfuric acid solution with a mass fraction of 85%, adding 10g of graphite with a mass fraction of carbon of 99%, at 20°C, adding 1.8g of super Ammonium disulfate was reacted for 60 minutes. After the reaction was completed, the obtained acidic graphite was washed with water until the pH of the graphite surface = 6, and dried by centrifugation; after aging at 20°C for 48 hours, it was washed with water again until the pH of the graphite surface = 6.8, and centrifuged. Drying, drying the product at 80°C until the mass fraction of water in the expandable graphite is 0.8%, to obtain the finished expandable graphite. At 950°C, puffed for 30 seconds, the measured expansion volume was 257mL/g, and the initial expansion temperature was 303°C.

Example 12

Dissolve 0.2g of anhydrous calcium chloride and 0.54g of sodium pyrophosphate in 27g of sulfuric acid solution with a mass fraction of 85%, add 10g of graphite with a mass fraction of carbon of 99%, and add 1.2g of The potassium chlorate was reacted for 60 minutes. After the reaction was completed, the acidic graphite obtained was washed with water until the pH of the graphite surface = 6, and dried by centrifugation; after aging at 20°C for 48 hours, it was washed with water again until the pH of the graphite surface = 7, and then dried by centrifugation. , drying the product at 80°C until the mass fraction of water in the expandable graphite is 0.8%, to obtain the finished expandable graphite. At 950°C, puffed for 30 seconds, the measured expansion volume was 259mL/g, and the initial expansion temperature was 300°C.

Example 13

Dissolve 0.2g of ferrous sulfate heptahydrate and 0.5g of sodium hexametaphosphate in 27g of sulfuric acid solution with a mass fraction of 85%, add 10g of graphite with a mass fraction of carbon of 99%, and add 0.9g of Potassium permanganate was reacted for 50 minutes. After the reaction was completed, 30 g of water and 1.5 g of formic acid were added to the feed liquid, and the color was decolorized for 25 minutes under constant stirring. Drying; after aging at 20°C for 48 hours, wash with water again until the pH of the graphite surface is 6.5, spin dry the product by centrifugal drying, and dry the product at 80°C until the mass fraction of water in the expandable graphite is 0.8% to obtain the finished expandable graphite . At 950°C, puffed for 30 seconds, the measured expansion volume was 267mL/g, and the initial expansion temperature was 303°C.

Claims (2)

1, Preparation of Expansible Graphite method is characterized in that it may further comprise the steps:

(1) oxidation sealing

It is that the sulfuric acid of 80%-95% dissolves that encapsulant is put into massfraction, add graphite then and stir, the vitriolic consumption be the graphite quality 0.8-4 doubly, the consumption of encapsulant be the graphite quality 0.005-0.26 doubly; Then, adding quality under constantly stirring is that graphite quality 0.05-0.25 oxygenant doubly reacts, and reaction times 0.5-2 hour, temperature of reaction was 5-40 ℃, made acid graphite;

Wherein, used encapsulant is selected one of following combination: ferrous sulfate and Sodium hexametaphosphate 99 are that combination in 1.0: 2.5, Calcium Chloride Powder Anhydrous and Sodium hexametaphosphate 99 are that combination in 1.0: 2.0, ferrous sulfate and trisodium phosphate are that combination in 1.0: 2.0, Magnesium Chloride Anhydrous and trisodium phosphate are that combination in 1.0: 2.0, Magnesium Chloride Anhydrous and Sodium hexametaphosphate 99 are that combination in 1.0: 3.0, Calcium Chloride Powder Anhydrous and trisodium phosphate are combination in 1.0: 2.7 with mass ratio with mass ratio with mass ratio with mass ratio with mass ratio with mass ratio;

Used oxygenant is one of following material: potassium permanganate, Potcrate, ammonium peroxydisulfate;

(2) decolouring

Adding quality in the acid graphite that makes is graphite quality 0.5-5 water doubly, and adding quality under constantly stirring is graphite quality 0.05-0.3 discoloring agent doubly, decolours 15-50 minute, washes to the pH=6-7 of graphite surface centrifuge dripping with water;

Used discoloring agent is selected one of following material: oxalic acid, formic acid, hydrogen peroxide, Sodium Nitrite;

(3) ageing

Acid graphite after the drying is 20-40 ℃ of placement, ageing 24-72 hour;

(4) washing

The acid graphite that ageing is good is washed with water to pH=6-7, centrifuge dripping;

(5) oven dry

Graphite after the drying is 65-80 ℃ of oven dry, to the graphite the massfraction of water less than 1%, the expansible black lead finished product;

(6) expanded

At 950 ℃, expanded 30 seconds, the allowance for expansion of survey expansible black lead product.

2,, it is characterized in that graphite is natural flake graphite in the step (1) by the described Preparation of Expansible Graphite method of claim.