CN108440731B - Preparation method of lignin-based intumescent flame retardant - Google Patents
Preparation method of lignin-based intumescent flame retardant Download PDFInfo
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- CN108440731B CN108440731B CN201810200344.5A CN201810200344A CN108440731B CN 108440731 B CN108440731 B CN 108440731B CN 201810200344 A CN201810200344 A CN 201810200344A CN 108440731 B CN108440731 B CN 108440731B
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- C08G12/00—Condensation polymers of aldehydes or ketones with only compounds containing hydrogen attached to nitrogen
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Abstract
The invention discloses a preparation method of a lignin-based intumescent flame retardant. Putting the alkaline lignin into sufficient water, heating up, adding melamine, stirring, heating up, dropwise adding a formaldehyde solution for reaction, dropwise adding a phytic acid solution according to a proportion, putting the product into a centrifuge for centrifugal operation, removing white precipitates, and then drying the residual liquid in a vacuum drying oven until the quality of the product is not changed any more. The flame retardant disclosed by the invention does not generate dense smoke and toxic, harmful and pungent odor gas during combustion, is environment-friendly, and simultaneously, the materials required for synthesizing the flame retardant are all renewable resources, the raw materials are easy to obtain and treat, and no burden is generated on the environment.
Description
Technical Field
The invention belongs to a preparation method of a flame retardant in the technical field of flame retardance, and particularly relates to a preparation method of a lignin-based intumescent flame retardant.
Background
With the development of scientific technology, petroleum-based polymers with low cost, high performance and environmental friendliness have attracted attention. Since the polymer industry of non-renewable resources such as petroleum has a poor prospect against the background of excessive global resource consumption and continuous environmental deterioration, people have turned their eyes to renewable resources. For example, the raw materials for preparing bio-based plastics such as polylactic acid and polybutylene succinate are derived from crops such as corn and beet, and the bio-based plastics have the excellent characteristics of high strength, high transparency, easy processing and forming, good biodegradation, compatibility and the like, and are widely applied to the fields of food packaging, textile and the like. However, these bio-based plastics are extremely flammable, and their limiting oxygen index is less than 20%, which greatly limits their applications in the fields of electronics, automobiles, ships, and the like. Therefore, it is extremely necessary and urgent to solve the problem of flammability of bio-based plastics and to improve the fire safety performance thereof.
The addition of the flame retardant is the simplest method for improving the flame retardant property of the bio-based plastic. At present, the halogen flame retardant which is developed relatively mature and occupies most of the market is gradually eliminated because the halogen flame retardant has high flame retardant efficiency but causes serious damage to the environment after combustion. Among various halogen-free flame retardants, phosphorus flame retardants are widely used because of their advantages of low smoke, low alcohol content, no corrosive gases, etc. Compared with the flame retardant containing phosphorus and nitrogen elements, the flame retardant containing phosphorus and nitrogen elements has lower toxicity and better thermal stability, and the phosphorus and nitrogen elements have a synergistic flame retardant effect. The flame retardant effect of an inorganic flame retardant on polylactic acid is researched by great congratulations (CN10172426A), a metal oxide mixture of zinc, potassium and lithium is smelted according to different proportions, and then is cooled and crushed to prepare glass powder, wherein the flame retardant property of the polylactic acid flame retardant material is not lower than V-2; jianming et al (Synthesis of flame retardant tris (diphenyl phosphate isocyanate) and application thereof in polyurethane vinegar. Plastic industry 2014,42(12): 103-; wang Huia (synthesis of novel single-component phosphorus-nitrogen intumescent flame retardant. chemical research 2010,21(1):32-35) synthesizes a novel single-component phosphorus-nitrogen intumescent flame retardant by taking neopentyl glycol, phosphorus oxychloride and benzimidazole derivatives as raw materials, and researches find that the flame retardant has higher thermal stability and char formation rate, and can effectively improve the melt-drip phenomenon of polyolefin to prevent the spread of fire; the Wangxinlong (CN104927061A) designs a high-molecular flame retardant containing a P-N bond, which is obtained by reacting 1, 3-propanediol bis (4-aminobenzoate) with phenyl dichlorophosphate, and the high-molecular flame retardant contains a plurality of benzene rings, so that the flame retardant effect is excellent, and the main chain contains a flexible chain segment, thereby being capable of being used as a nucleating agent and effectively improving the crystallinity of polylactic acid. However, although the flame retardant has excellent flame retardant performance, the synthetic raw materials of the flame retardant are mainly based on non-biodegradable and increasingly exhausted petrochemical resources, so that the flame retardant has the problem of biodegradability, and the large amount of the flame retardant can cause inestimable negative effects and burdens on the environment.
On the other hand, in nature, lignin is stored next to cellulose and is regenerated at a rate of about 500 million tons per year, and the pulping and papermaking industry processes about 1.4 million tons of cellulose from plants per year and produces about 5000 million tons of lignin as a by-product. However, so far, more than 95% of the separated lignin is burnt out or discharged into rivers after being concentrated, which not only causes great resource waste, but also pollutes the environment. Therefore, the preparation of the biodegradable lignin-based intumescent flame retardant has important social significance and economic value.
Disclosure of Invention
In order to improve the biodegradability of the intumescent flame retardant and reduce the environmental burden of the intumescent flame retardant, the invention provides a preparation method of a lignin-based intumescent flame retardant.
The technical solution for realizing the invention is as follows:
the intumescent flame retardant is prepared by reacting alkali lignin, melamine and formaldehyde and then mixing with phytic acid solution to form salt.
The preparation method comprises the following steps:
(1) putting the alkaline lignin into sufficient water, heating to 70 ℃, adding melamine, stirring for 5-10min, heating to 90 ℃, dropwise adding a formaldehyde solution, and reacting for 5-7 hours;
(2) then dropping phytic acid solution according to a proportion;
(3) the product was centrifuged in a centrifuge to remove the white precipitate, and the remaining liquid was dried in a vacuum oven at 80 ℃ for 12-36 hours until the product quality did not change.
And further grinding and crushing the product, and then placing the product into a ball mill for particle grinding to finally obtain the intumescent flame retardant containing phosphorus and nitrogen with excellent flame retardant property.
The obtained intumescent flame retardant is black powder.
The mass charge ratio of the melamine to the alkaline lignin to the formaldehyde is 1.6: 1: 0.6.
the mass feed ratio of the melamine to the phytic acid solution (the mass fraction of solute is 50 wt%) is 1: 1.746-1: 10.476.
and (2) finishing the dropwise addition of the formaldehyde solution in the step (1) within 1-2 h.
The sufficient amount of water in the step (1) refers to the water content of 60-80% of the total mass of the alkaline lignin and the water.
The synthetic preparation route of the invention is as follows:
(1) synthesis of Melamine modified Lignin
(2) Compounding synthesized melamine modified lignin and phytic acid into salt
The flame retardant of the invention contains phosphorus, nitrogen and other elements, has very strong flame retardant effect, does not contain halogen, and has extremely low influence on human body and environment.
The product formed by adding alkali lignin, melamine and formaldehyde to react and then mixing with the phytic acid solution has flame retardance, thermal stability and hydrolytic stability, and the melamine is introduced in the synthesis process in the molecular design process, so that the melamine is a six-membered ring structure, and the structure has extremely high thermal stability; the molecular structure of the lignin contains a benzene six-membered ring structure, and the structure is the same as melamine and has extremely strong thermal stability; the phytic acid in the molecule contains a large number of hydroxyl groups, and hydrogen bonds are formed with nitrogen and oxygen in the molecule in the hydrolysis process, so that the phytic acid has good thermal stability. The flame retardant provides a carbon source, a gas source and an acid source, and is rich in phosphorus and nitrogen elements, so that a considerable flame retardant effect can be achieved.
Compared with the prior art, the invention has the following advantages:
(1) the intumescent flame retardant disclosed by the invention does not contain halogen, is low in toxicity and does not generate harmful combustion products.
(2) The molecular structure of the intumescent flame retardant disclosed by the invention contains a six-membered ring, the thermal stability and the char formation are good, and the TGA test result shows that the product has high char formation rate and excellent flame retardant effect.
(3) The P element in the molecule is combined with other groups by P-C bonds or P ═ O bonds, so that the hydrolysis stability is high, and the flame retardant property is not easily reduced by decomposition and diffusion from the material in the use process of the material.
(4) The invention has the advantages of cheap and abundant raw materials and simple synthesis process, and is very suitable for industrial production.
(5) The raw materials of the invention are all renewable raw materials, and the synthesized flame retardant is degradable, so the influence on the environment is small.
Drawings
FIG. 1 is an infrared spectrum of the intumescent flame retardant of the present invention.
FIG. 2 thermogravimetric analysis (TGA) spectrum of the intumescent flame retardant of the invention in nitrogen.
Detailed Description
The invention is further illustrated by the following figures and examples.
The embodiment of the invention is as follows:
example 1:
putting 8.07g of alkali lignin into a 500ml three-necked bottle, adding 80g of deionized water, introducing condensed water, stirring, heating to 70 ℃, adding 12.906g of melamine into the system, and stirring for 10 min; the temperature is raised to 90 ℃, 13.08g of formaldehyde solution (37 wt%) is slowly dripped into a three-necked bottle, the dripping time is 1h, the temperature is maintained, and the reaction is carried out for 6 h. After the reaction, 20.88g of phytic acid solution (50 wt%) was added to the three-necked flask, filtered, and the residue was washed with deionized water 3 times, then dried, and placed in a vacuum oven at 80 ℃ for 24 hours. Grinding and crushing the product, and then putting the product into a ball mill for ball milling for 24 hours to finally obtain the intumescent flame retardant containing phosphorus and nitrogen elements.
Example 2:
putting 16.14 alkali lignin into a 500ml three-necked bottle, adding 160g of deionized water, introducing condensed water, stirring, heating to 70 ℃, adding 25.818g of melamine into the system, and stirring for 10 min; the temperature is raised to 90 ℃, 26.16g of formaldehyde solution (37 wt%) is slowly dripped into a three-necked bottle, the dripping time is 2h, the temperature is maintained, and the reaction is carried out for 7 h. After the reaction was completed, 83.52g of phytic acid solution (50 wt%) was added to a three-necked flask, filtered, and the residue was washed with deionized water 3 times, then dried, and placed in a vacuum oven at 80 ℃ for 24 hours. Grinding and crushing the product, and then putting the product into a ball mill for ball milling for 36 hours to finally obtain the intumescent flame retardant containing phosphorus and nitrogen elements.
Example 3:
putting 8.07g of alkali lignin into a three-neck flask, adding 80g of deionized water, introducing condensed water, stirring, heating to 70 ℃, adding 12.906g of melamine into the system, and stirring for 10 min; the temperature is raised to 90 ℃, 13.08g of formaldehyde solution (37 wt%) is slowly dripped into a three-necked bottle, the dripping time is 1h, the temperature is maintained, and the reaction is carried out for 6 h. After the reaction was completed, 41.76g of phytic acid solution (50 wt%) was added to a three-necked flask, filtered, and the residue was washed with deionized water 3 times, then dried, and placed in a vacuum oven at 80 ℃ for 24 hours. Grinding and crushing the product, and then putting the product into a ball mill for ball milling for 24 hours to finally obtain the intumescent flame retardant containing phosphorus and nitrogen elements.
Example 4:
putting 16.14 alkali lignin into a 500ml three-necked bottle, adding 160g of deionized water, introducing condensed water, stirring, heating to 70 ℃, adding 25.818g of melamine into the system, and stirring for 10 min; the temperature is raised to 90 ℃, 26.16g of formaldehyde solution (37 wt%) is slowly dripped into a three-necked bottle, the dripping time is 3h, the temperature is maintained, and the reaction is carried out for 8 h. After the reaction was completed, 83.52g of phytic acid solution (50 wt%) was added to a three-necked flask, filtered, and the residue was washed with deionized water 3 times, then dried, and placed in a vacuum oven at 80 ℃ for 36 hours. Grinding and crushing the product, and then putting the product into a ball mill for ball milling for 36 hours to finally obtain the intumescent flame retardant containing phosphorus and nitrogen elements.
Example 5:
putting 16.14 alkali lignin into a 500ml three-necked bottle, adding 160g of deionized water, introducing condensed water, stirring, heating to 70 ℃, adding 25.818g of melamine into the system, and stirring for 10 min; the temperature is raised to 90 ℃, 26.16g of formaldehyde solution (37 wt%) is slowly dripped into a three-necked bottle, the dripping time is 3h, the temperature is maintained, and the reaction is carried out for 6 h. After the reaction was completed, 83.52g of phytic acid solution (50 wt%) was added to a three-necked flask, filtered, and the residue was washed with deionized water 3 times, then dried, and placed in a vacuum oven at 80 ℃ for 36 hours. Grinding and crushing the product, and then putting the product into a ball mill for ball milling for 48 hours to finally obtain the intumescent flame retardant containing phosphorus and nitrogen elements.
The flame retardant product of example 1 of the present invention was tested by thermogravimetric analysis (TGA) to obtain an initial decomposition temperature (Tonset) and a char yield at 700 degrees, as shown in table 1 below:
TABLE 1 initial decomposition temperature (Tonset) and char yield at 700 ℃ of the alkaline lignin-based intumescent flame retardant of example 1 of the present invention
| Decomposition temperature | Amount of carbon residue | |
| Intumescent flame retardant | 203℃ | 37.73％ |
As can be seen from the above table, the initial decomposition temperature (T) of the alkali lignin-based intumescent flame retardant of the present inventiononset) The residual carbon content at 203 ℃ and 700 ℃ was 37.73%.
Elemental composition results obtained from elemental analysis testing of the flame retardant products of the various embodiments of the invention are as follows:
TABLE 2 elemental analysis test results for intumescent flame retardants of the present invention
| C | O | H | N | P | |
| Example 1 | 40.00％ | 38.11％ | 2.43％ | 7.57％ | 11.89％ |
| Example 2 | 39.83％ | 38.20％ | 3.66％ | 6.28％ | 12.03％ |
| Example 3 | 40.30％ | 37.91％ | 2.76％ | 7.29％ | 11.74％ |
| Example 4 | 40.01％ | 38.34％ | 1.92％ | 6.84％ | 12.89％ |
| Example 5 | 39.96％ | 38.15％ | 2.92％ | 7.06％ | 12.01％ |
As can be seen from the above table, the phosphorus content of the intumescent flame retardant of the invention is about 12% and the nitrogen content is about 7%.
FIG. 1 is an IR spectrum of an intumescent flame retardant of example 1 of the invention, from which it can be seen that it is at 3362cm-1Has obvious absorption peak, which indicates that the molecular structure of the flame retardant contains secondary amine structure (-NH) -, 1629cm-1、1151cm-1The absorption peaks indicate that the flame retardant contains structures of P ═ O and O ═ P-O-C respectively, and further illustrate that the actual reaction route is consistent with the designed reaction route.
FIG. 2 is a thermogravimetric analysis (TGA) spectrum of the intumescent flame retardant of the invention in nitrogen. The initial decomposition temperature (Tonset) and the amount of char at 700 degrees of the intumescent flame retardant prepared are shown.
Claims (5)
1. A preparation method of a lignin-based intumescent flame retardant is characterized by comprising the following steps:
(1) putting the alkaline lignin into sufficient water, heating to 70 ℃, adding melamine, stirring for 5-10min, heating to 90 ℃, dropwise adding a formaldehyde solution, and reacting for 5-7 hours;
the mass charge ratio of the melamine to the alkaline lignin to the formaldehyde is 1.6: 1: 0.6;
(2) then dropping phytic acid solution according to a proportion;
the mass feed ratio of the melamine to the phytic acid solution is 1: 1.746-1: 10.476, respectively;
(3) the product was centrifuged in a centrifuge to remove the white precipitate, and the remaining liquid was dried in a vacuum oven at 80 ℃ for 12-36 hours until the product quality did not change.
2. The method for preparing lignin-based intumescent flame retardant of claim 1, wherein: and further grinding and crushing the product, and then placing the product into a ball mill for particle grinding to finally obtain the intumescent flame retardant containing phosphorus and nitrogen with excellent flame retardant property.
3. The method for preparing lignin-based intumescent flame retardant of claim 2, wherein: the obtained intumescent flame retardant is black powder.
4. The method for preparing lignin-based intumescent flame retardant of claim 1, wherein: and (2) finishing the dropwise addition of the formaldehyde solution in the step (1) within 1-2 h.
5. The method for preparing lignin-based intumescent flame retardant of claim 1, wherein: the sufficient amount of water in the step (1) refers to the water content of 60-80% of the total mass of the alkaline lignin and the water.
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| CN110105626B (en) * | 2019-05-04 | 2021-02-26 | 武汉理工大学 | Supermolecular assembly modified ammonium polyphosphate and preparation method thereof |
| CN111848977A (en) * | 2020-08-06 | 2020-10-30 | 江南大学 | Modified lignin, preparation method and application thereof in toughening flame-retardant composite material |
| CN112143215A (en) * | 2020-10-16 | 2020-12-29 | 界首市宏达塑业有限公司 | High-flame-retardant polyurethane plastic particle and preparation method thereof |
| CN114874357B (en) * | 2022-06-28 | 2023-03-17 | 河北科技大学 | Hemicellulose-based intumescent flame retardant and preparation method thereof |
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| CN101735278A (en) * | 2009-12-09 | 2010-06-16 | 湖北兴发化工集团股份有限公司 | Method for synthesizing P-N-containing intumescent flame retardant |
| CN105504309A (en) * | 2015-12-31 | 2016-04-20 | 浙江农林大学 | Halogen-free flame retardant modified industrial lignin of wood-plastic section as well as preparation method and application |
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| WO2013165425A1 (en) * | 2012-05-03 | 2013-11-07 | Empire Technology Development Llc | Phosphonate-substituted lignin as a flame retardant |
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| CN101735278A (en) * | 2009-12-09 | 2010-06-16 | 湖北兴发化工集团股份有限公司 | Method for synthesizing P-N-containing intumescent flame retardant |
| CN105504309A (en) * | 2015-12-31 | 2016-04-20 | 浙江农林大学 | Halogen-free flame retardant modified industrial lignin of wood-plastic section as well as preparation method and application |
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