CN107245138A - A kind of preparation of lignin-base fire retardant and its application process - Google Patents

Abstract

The invention provides a preparation method of a lignin-based flame retardant and an application method thereof, and relates to the flame retardant. The flame retardant is prepared from the following raw materials: lignin, isocyanate, 9,10-dihydro-9-oxaphenanthrene-10-oxide (DOPO). The specific preparation method: first react lignin with isocyanate at a certain temperature; then react with DOPO at a certain temperature; finally, dry in a vacuum oven and pulverize to obtain. The flame retardant uses the hydroxyl group on the lignin to react with isocyanate, and the flame retardant contains a phosphate structure, which has an excellent flame retardant effect; the benzene ring structure contained in the lignin and DOPO can enhance the mechanical properties of the material. The invention also provides a preparation method of flame-retardant polyurethane. The method is to react polyol and isocyanate at a certain temperature until the system is viscous, add the above-mentioned phosphorus-containing lignin-based flame retardant and other additives, and then perform thermosetting molding; the obtained flame-retardant polyurethane can be used as an adhesive , coatings, foaming materials, flooring materials, etc.

Description

Preparation and application method of a lignin-based flame retardant

technical field

The invention belongs to the technical field of preparation and application of organic phosphine flame retardants, and in particular relates to the preparation of a phosphorus-containing lignin-based flame retardant and its application in polyurethane to prepare lignin-based flame-retardant polyurethane.

Background technique

Lignin is bound together with cellulose and hemicellulose to form the main support structure of plants. It is the second most abundant natural polymer material in the plant kingdom after cellulose and the only natural polymer material containing an aromatic ring structure. Lignin is a three-dimensional network polymer connected by carbon-carbon bonds and ether bonds with phenylpropane as the structural unit; according to the number and position of methoxy groups, it can be divided into p-hydroxyphenyl type (H), Guaiac-based (G) and syringyl-based (S). Due to its natural renewable, biodegradable, non-toxic and other advantages, lignin is derived from the by-product of the paper industry - industrial lignin has the advantage of low cost, and is used as an excellent biomass chemical raw material for comprehensive utilization of materials field has received extensive attention. At present, lignin has been widely used in the preparation of phenolic resin, polyurethane, epoxy resin and other materials, as a filler to modify fossil resource-based and bio-based polymer materials such as rubber, polyester, polyether, polyolefin, starch, protein, etc. .

The functional groups contained in lignin mainly include hydroxyl groups (alcohol hydroxyl groups and phenolic hydroxyl groups), carbonyl groups, methoxy groups, sulfonic acid groups, and the like. Among them, the hydroxyl group is a relatively large functional group in lignin, which plays an important role in the preparation of functional materials by lignin modification. For example, it can be used as a polyol modified polyurethane system, mainly based on the active hydroxyl group and isocyanate on lignin. Chemical reactions can occur in organic solvents; it can be used to prepare engineering plastics, elastomers, and various soft, semi-rigid, and rigid foam materials.

Polyurethane is generally a polymer compound containing urethane characteristic units in the main chain obtained by the interaction of dibasic or polybasic organic isocyanates and polyether/polyester polyol compounds. Depending on the structure and properties, it can be made into foam, rubber, synthetic leather, adhesives and coatings. Polyurethane has the advantages of temperature resistance, good processability, degradability, and good impact resistance. It is widely used in many fields such as automobiles, construction, electromechanical, aviation, medical treatment, and transportation. However, the limiting oxygen index of polyurethane is only about 17%, which is extremely flammable and will release a large amount of toxic smoke when burning, which has a great potential fire hazard. Therefore, the flame retardant research of polyurethane materials is a topic of great significance.

The flame retardant method of polymers includes adding flame retardants to polymers and connecting flame retardant elements such as silicon, phosphorus, nitrogen, etc. to the main chain or side chain of polymers through chemical reactions, so that the polymers have flame retardant properties. Traditional halogenated flame retardants have the advantages of good flame retardant effect, low addition amount, and little impact on the mechanical properties of materials. However, when halogenated flame retardants burn, they will release a large amount of toxic gases, which will cause great harm to human health and the environment. hazards, so halogenated flame retardants have been banned. Other flame retardants also include metal compound flame retardants, mainly aluminum hydroxide, magnesium hydroxide, calcium oxide, etc.; nitrogen-based flame retardants are mainly triazine compounds, including dicyandiamide, Guanidine salt, biurea, melamine and its salts, etc.; there are many types of phosphorus-based flame retardants, including phosphate esters, phosphazenes, phosphides, and phosphorus oxides. Intumescent flame retardants are currently a research hotspot. A typical intumescent flame retardant consists of three components, namely acid source, carbon source, and gas source. Acid source, also called dehydrating agent, dehydrates the surface of the material to generate acid during combustion, which can cross-link the carbon source and form a thermally stable carbon layer; gas source, also called blowing agent, generates non-flammable The gas can make the carbon source foam and expand; the carbon source, also known as a char-forming agent, is usually a multifunctional compound rich in carbon. At present, the most used acid source in the intumescent flame retardant system is APP; the gas source includes melamine, urea and synthetic new nitrogen-containing compounds, etc.; the carbon source includes pentaerythritol, cellulose, starch, lignin, etc.

9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is an organic phosphonate compound, which contains biphenyl and heterophenanthrene ring structures in its molecular structure. Organophosphorus compounds with a ring structure have higher thermal and chemical stability. And research in recent years has shown that DOPO and its derivatives, as a new type of environmentally friendly flame retardant, are not only halogen-free, low-toxic, smoke-free, but also highly efficient in flame retardancy. While improving the flame retardancy of polymer materials, it maintains the original mechanical properties of the materials, and can be used in fields such as plastics, coatings, and building materials. The DOPO structure contains active P-H bonds, which can react with unsaturated groups such as quinones, aldehydes, ketones, carbon-carbon double bonds, carbon-nitrogen double bonds and triple bonds, epoxy groups, etc., to generate various derivatives. Only heating is required, no catalyst is required, it is simple and fast.

Contents of the invention

The purpose of the present invention is to provide a preparation method of phosphorus-containing lignin-based flame retardant. The obtained flame retardant not only has excellent flame-retardant effect, but also has And it has good compatibility with polyurethane; in addition, the benzene ring contained in the lignin structure can also maintain or even improve the mechanical properties of polyurethane materials.

The invention provides a preparation and application method of a phosphorus-containing lignin-based flame retardant, including:

Step 1: first react lignin, isocyanate and N,N-dimethylformamide at a certain temperature for a period of time. Then heat up, add flame retardant intermediate 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) to the reaction system and react at a certain temperature to prepare phosphorus-containing wood Plain flame retardant.

Step 2: React polyol, isocyanate, and N,N-dimethylformamide at a certain temperature until the system is viscous, add the phosphorus-containing lignin-based flame retardant and other additives prepared in Step 1, and heat cure Molded to obtain flame retardant polyurethane.

The lignin is not particularly limited, and may be lignin of low purity in industrial grade or lignin of high purity; lignin itself may be organic solvent lignin, alkali lignin, or sulfonate lignin.

The isocyanate is not particularly limited, preferably toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isophorone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane Diisocyanate (HMDI), p-phenylene diisocyanate (PPDI), 1,4-cyclohexane diisocyanate (CHDI), xylylene diisocyanate (XDI), cyclohexane dimethylene diisocyanate (HXDI) , Trimethyl-1,6-hexamethylene diisocyanate (TMHDI), tetramethylene m-xylylene diisocyanate (TMXDI), 2,5(2,6)-bis(isocyanate)bicyclic [2.2.1] Heptane (NBDI), dimethylbiphenyl diisocyanate (TODI), methylcyclohexyl diisocyanate (HTDI), more preferably hexamethylene diisocyanate (HDI).

The polyol is not particularly limited, preferably polyester polyol, including polyethylene glycol (PEG), polypropylene glycol (PPG), polyethylene adipate glycol (PEA), polyethylene adipate diol Alcohol propylene glycol ester diol, polyethylene adipate diethylene glycol ester diol, polyethylene adipate diethylene glycol ester diol, poly-1,4-butylene adipate Diol, polyethylene adipate-1,4-butylene glycol ester diol, polyneopentyl adipate-1,6-hexanediol ester diol, polycastor oil adipate Alcohol, poly-ε-caprolactone diol, polycarbonate 1,6-hexyl alcohol ester diol, etc.; polyether polyol is preferably polyoxypropylene diol, polyoxypropylene triol, polyoxypropylene castor oil polyol Alcohol, polytetrahydrofuran diol, tetrahydrofuran-propylene oxide copolymerized diol, etc.; epoxy resin, including EP-12, EP-13, EP-16, EP-20, etc.; castor oil; acrylic resin; polyalkylene glycol, including Polybutadiene diol, polybutadiene acrylonitrile copolymerized diol. More preferred is polyethylene glycol (PEG).

The auxiliary agent for preparing lignin-based flame-retardant polyurethane, the curing agent included therein is not particularly limited, preferably including TDI dimer, TDI trimer, IPDI trimer, TDI-TMP adduct, HDI dimer Body, HDI trimer, HDI biuret, more preferably HDI trimer.

The catalyst for preparing lignin-based flame-retardant polyurethane is not particularly limited, and preferably includes tertiary amine catalysts: N,N-dimethylcyclohexylamine, bis(2-dimethylaminoethyl) ether, trimethylene bis Amine, N,N,N′,N′-Tetramethylethylene (or propane, butyl) diamine, N,N,N′,N″,N″-pentamethyldiethylenetriamine, Triethylamine, N,N-Dimethylbenzylamine, N,N-Dimethylhexadecylamine, Triethylenediamine, N-Ethylmorpholine, N-Methylmorpholine, N,N'- Diethylpiperazine, N,N'-diethyl-2-methylpiperazine, N,N'-bis-(α-hydroxypropyl)-2-methylpiperazine, N-2-hydroxypropyl dimethylmorpholine, triethanolamine, N,N-dimethylethanolamine, N,N'-lutidine; organotin catalysts, including dibutyltin dilaurate, stannous octoate, stannous oleate, Dibutyltin di-2-ethylhexanoate, Tributyltin chloride, Butyltin trichloride.

Beneficial effects of the present invention

(1) The present invention uses lignin, an industrial-grade organic solvent, to react the active hydroxyl groups on the lignin with isocyanate to generate carbamate groups, and at the same time select highly efficient flame-retardant phosphonate flame retardant intermediates 9 , 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO), using the highly reactive P-H in the DOPO structure to react with unsaturated groups to synthesize carbamate A structural flame retardant, which can improve the compatibility between the additive flame retardant and the matrix material when used in polyurethane, and ensure good interfacial compatibility while improving the flame retardancy of polyurethane.

(2) In order to avoid the incomplete reaction of lignin, the present invention first reacts lignin with isocyanate under heating conditions, then raises the temperature, and adds DOPO to make it react with unsaturated groups. The structure of the synthesized product was analyzed by Fourier transform infrared spectroscopy, and the results showed that the phosphorus-containing lignin-based flame retardant was successfully synthesized. The flame retardant not only improves the added value of industrial lignin, but also has a certain stability of the benzene ring structure of lignin itself, which can improve the mechanical properties of polyurethane materials.

(3) The present invention also prepares a lignin-based flame-retardant polyurethane, which has good flexibility and impact resistance, and is highly flame-retardant, and can be used as coatings, adhesives, foaming materials and flooring materials Wait.

Description of drawings

Fig. 1 FTIR charts of the phosphorus-containing lignin-based flame retardants in Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, Example 7, and Example 8.

The FTIR figure of flame-retardant polyurethane in Fig. 2 embodiment 1, embodiment 2, embodiment 3, embodiment 4.

detailed description

The invention provides a preparation and application method of a phosphorus-containing lignin-based flame retardant, including:

Step 1: First react lignin, isocyanate and N,N-dimethylformamide at a certain temperature for a certain period of time; then raise the temperature and add the flame retardant intermediate 9,10-dihydro-9-oxygen to the reaction system Hetero-10-phosphaphenanthrene-10-oxide (DOPO) is reacted at a certain temperature to prepare a phosphorus-containing lignin-based flame retardant.

Step 2: React polyol, isocyanate, and N,N-dimethylformamide at a certain temperature until the system is viscous, add the phosphorus-containing lignin-based flame retardant prepared in Step 1 and other additives, and heat-cure the molding , to obtain flame retardant polyurethane.

According to the present invention, lignin is dispersed in N,N-dimethylformamide (DMF), and then isocyanate is added to obtain the mixture, preferably reacted at 70-90°C until the system is viscous, and the reaction time is 8-40min, and then Raise the temperature to 120-130oC, add DOPO and continue the reaction for 10-40min to obtain a phosphorus-containing lignin-based flame retardant. The lignin is preferably organic solvent lignin; the reaction temperature and time are related to lignin content and P-H/NCO ratio.

According to the present invention, polyol, isocyanate, and N,N-dimethylformamide (DMF) are stirred and mixed uniformly, reacted at 50-70°C for 40-80min until the system becomes viscous, and 5-50% of the prepared Phosphorous lignin-based flame retardant and other additives are stirred evenly and then thermally cured to obtain lignin-based flame-retardant polyurethane.

The curing agent is not particularly limited, commercially available TDI dimer, TDI trimer, IPDI trimer, TDI-TMP adduct, HDI dimer, HDI trimer, HDI biuret, More preferred is HDI trimer. The catalyst is not particularly limited, and can be an organic tertiary amine catalyst and an organometallic compound; the DOPO is not particularly limited, and commercially available DOPO can be used; the solvent N,N-dimethylformamide (DMF) The amount of L is not particularly limited, as long as the lignin can be uniformly dispersed.

According to the present invention, to prepare lignin-based flame-retardant polyurethane, first disperse polyol in N,N-dimethylformamide, then add isocyanate, react at 50-70°C until the system is viscous, then add phosphorus-containing The lignin-based flame retardant and other additives are uniformly mixed, and heat-cured to obtain a flame-retardant polyurethane. The addition of phosphorus-containing lignin-based flame retardant is 5-50%; the additives include curing agents, catalysts, defoamers, leveling agents and other additives, without special requirements, and the addition amount is preferably 1% of the total mass of the system 1-10%.

The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments, in order to enable those skilled in the art to have a clearer understanding and understanding of the present application. The following specific examples should not be understood or interpreted as limiting the protection scope of the claims of the present application to any extent.

Comparative example 1

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 60°C for 60min, until the system is viscous, add 0.4g of defoamer, stir evenly, pour it on the tinplate sheet and the polytetrafluoroethylene mold, respectively, at room temperature, 40°C, 60°C , and cured at 80°C for 12 hours to obtain a flame-retardant polyurethane film PU1. The flexibility, adhesion, impact resistance and limiting oxygen index values of the polyurethane obtained in Comparative Example 1 are shown in Table 1.

Comparative example 2

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10.35g of toluene diisocyanate (TDI) into a 250ml three-neck flask, and stir until uniform. Put it in an oil bath, react at 50°C for 80 minutes, then add 0.4g of defoamer, stir evenly, pour it on a tinplate sheet and a polytetrafluoroethylene mold, and cure at room temperature, 40°C, 60°C, and 80°C respectively After 12 hours, a polyurethane film PU2 was obtained.

Example 1

(1) Preparation of phosphorus-containing lignin-based flame retardant

Weigh 1.36g of lignin, disperse it in 2ml of N,N-dimethylformamide (DMF), stir to disperse the lignin evenly, then add 4.2g of hexamethylene diisocyanate (HDI) and stir until it is evenly dispersed , put it into an oil bath at 80°C and keep stirring, react for 12 minutes until the system becomes viscous, set the oil bath temperature to 125°C, add 21.6g DOPO, continue stirring for 20 minutes until the system is viscous, take out the reaction product, and dry it at 80°C After 12 hours, it was pulverized to obtain phosphorus-containing lignin-based flame retardant L5-2, and its FTIR characterization results are shown in FIG. 1 .

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 60°C for 50 minutes until the system is viscous, add 3g of L5-2, stir until uniform, then add 0.8g of defoamer, stir until uniform, pour it on the tinplate sheet and the polytetrafluoroethylene mold respectively , and cured at 40°C, 60°C, and 80°C for 12 hours to obtain a flame-retardant polyurethane film PU15-L5-2. The FTIR characterization results of the flame-retardant polyurethane PU15-L5-2 obtained in Example 1 are shown in Figure 2, and its flexibility, adhesion, and impact resistance are shown in Table 1.

Example 2

(1) Preparation of phosphorus-containing lignin-based flame retardant

Weigh 1.43g of lignin and disperse it in 3ml of N,N-dimethylformamide (DMF). Stir to disperse the lignin evenly. Then add 5.55g of hexamethylene diisocyanate (HDI) and stir until dispersed. Evenly, put it in an oil bath at 80°C and keep stirring, react for 15 minutes until the system becomes viscous, set the temperature of the oil bath at 125°C, add 21.6g DOPO, continue stirring for 12 minutes until the system is viscous, take out the reaction product, and bake at 80°C Dry for 24 hours and pulverize to obtain phosphorus-containing lignin-based flame retardant L5-1.5, the FTIR characterization results of which are shown in Figure 1.

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 60°C for 50 minutes until the system is viscous, add 3g L5-1.5, stir until uniform, then add 0.6g HDI trimer, 0.8g defoamer, stir until uniform, pour them on the tinplate On the sheet and in the polytetrafluoroethylene mold, cure at room temperature, 40°C, 60°C, and 80°C for 12 hours, respectively, to obtain a flame-retardant polyurethane film PU15-L5-1.5. The FTIR characterization results of the flame-retardant polyurethane PU15-L5-1.5 obtained in Example 2 are shown in Figure 2, and its flexibility, adhesion, impact resistance, and limiting oxygen index values are shown in Table 1.

Example 3

(1) Preparation of phosphorus-containing lignin-based flame retardant

Weigh 1.58g of lignin and disperse it in 4ml of N,N-dimethylformamide (DMF). Stir to disperse the lignin evenly, then add 8.41g of hexamethylene diisocyanate (HDI) and stir until evenly dispersed. , placed in an oil bath at 80°C and continuously stirred, and reacted for 18 minutes. When the system becomes viscous, set the oil bath temperature to 120°C, add 21.6g DOPO, continue to react for 12 minutes and stir until the system is viscous, take out the reaction product, dry at 80°C for 20 hours, and pulverize to obtain phosphorus-containing lignin-based flame retardant L5- 1. The FTIR characterization results are shown in Figure 1.

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 60°C for 50 minutes until the system is viscous, add 3g L5-1, stir until uniform, then add 0.4g HDI trimer, 0.6g defoamer, stir until uniform, pour them on tinplate The flame-retardant polyurethane film PU15-L5-1 was obtained by curing at room temperature, 40°C, 60°C, and 80°C for 12 hours on the sheet and in the polytetrafluoroethylene mold. The FTIR characterization results of the flame-retardant polyurethane PU15-L5-1 obtained in Example 3 are shown in Figure 2, and its flexibility, adhesion, impact resistance, and limiting oxygen index values are shown in Table 1.

Example 4

(1) Preparation of phosphorus-containing lignin-based flame retardant

Weigh 2.02g of lignin and disperse it in 4ml of N,N-dimethylformamide (DMF). Stir to disperse the lignin evenly. Then add 16.8g of hexamethylene diisocyanate (HDI) and stir until dispersed. Evenly, put it into an oil bath at 80°C and keep stirring, and react for 40 minutes. When the system becomes viscous, set the temperature of the oil bath to 125°C, add 21.6g of DOPO, continue to stir and react for 10 minutes until the system is viscous, take out the reaction product, dry at 80°C for 15 hours, and pulverize to obtain phosphorus-containing lignin-based flame retardant L5 -0.5, the FTIR characterization results are shown in Figure 1.

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 60°C for 50 minutes until the system is viscous, add 3g L5-0.5, stir until uniform, then add 0.6g HDI trimer, 0.4g defoamer, stir until uniform, pour them on the tinplate respectively On the sheet and in the polytetrafluoroethylene mold, cure at room temperature, 40°C, 60°C, and 80°C for 12 hours, respectively, to obtain a flame-retardant polyurethane film PU15-L5-0.5. The FTIR characterization results of the flame-retardant polyurethane PU15-L5-0.5 obtained in Example 4 are shown in Figure 2, and its flexibility, adhesion, impact resistance, and limiting oxygen index values are shown in Table 1.

Example 5

(1) Preparation of phosphorus-containing lignin-based flame retardant

Weigh 2.87g of lignin, disperse it in 3ml of N,N-dimethylformamide (DMF), stir to make the lignin evenly dispersed, then add 4.2g of hexamethylene diisocyanate (HDI) and stir until dispersed Evenly, put it in an oil bath at 75°C and continue to stir, react for 16 minutes until the system becomes viscous, set the temperature of the oil bath to 120°C, add 21.6g DOPO, continue to stir for 25 minutes, and take out the reactant. Dry at 80°C for 18 hours and pulverize to obtain phosphorus-containing lignin-based flame retardant L10-2, the FTIR characterization results of which are shown in Figure 1.

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 50°C for 80 minutes until the system is viscous, add 4g L10-2, stir until uniform, then add 0.8g HDI trimer, 0.6g defoamer, stir until uniform, pour them on tinplate On the sheet and in the polytetrafluoroethylene mold, cure at room temperature, 40°C, 60°C, and 80°C for 12 hours, respectively, to obtain a flame-retardant polyurethane film PU20-L10-2.

Example 6

(1) Preparation of phosphorus-containing lignin-based flame retardant

Weigh 3.02g of lignin and disperse it in 3ml of N,N-dimethylformamide (DMF). Stir to disperse the lignin evenly, then add 5.55g of hexamethylene diisocyanate (HDI) and stir until evenly dispersed. , put it into an oil bath at 90°C and keep stirring, react for 13 minutes until the system becomes viscous, set the oil bath temperature to 130°C, add 21.6g DOPO, continue stirring for 12 minutes until the system becomes viscous, and take out the product. Dry at 85°C for 15 hours and pulverize to obtain phosphorus-containing lignin-based flame retardant L10-1.5. The FTIR characterization results are shown in Figure 1.

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 70°C for 40min until the system is viscous, add 10g L10-1.5, stir until uniform, then add 0.36g HDI trimer, 0.6g defoamer, 0.2g dibutyltin dilaurate , stirred until uniform, poured on a tinplate sheet and a polytetrafluoroethylene mold, and cured at room temperature, 40°C, 60°C, and 80°C for 12 hours to obtain a flame-retardant polyurethane film PU50-L10-1.5.

Example 7

(1) Preparation of phosphorus-containing lignin-based flame retardant

Take by weighing 4.55g lignin, disperse in 5ml of N,N-dimethylformamide (DMF), stirring is to make lignin disperse evenly, then add 4.2g hexamethylene diisocyanate (HDI) and, stir until Disperse evenly, put it in an oil bath at 80°C and keep stirring, react for 8 minutes until the system becomes viscous, set the temperature of the oil bath at 125°C, add 21.6g DOPO, continue stirring for 40 minutes until the system is viscous, and take out the reaction product. Drying at 80°C for 12 hours, and crushing, the phosphorus-containing lignin-based flame retardant L15-2 was obtained, and its FTIR characterization results are shown in Fig. 1 .

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 60°C for 60 minutes until the system is viscous, add 2g L15-2, stir until uniform, then add 0.42g HDI trimer, 0.7g defoamer, stir until uniform, pour them into tinplate On the sheet and in the polytetrafluoroethylene mold, cured at room temperature, 40°C, 60°C, and 80°C for 12 hours, respectively, to obtain a flame-retardant polyurethane film PU10-L15-2.

Example 8

(1) Preparation of phosphorus-containing lignin-based flame retardant

Weigh 4.79g of lignin and disperse it in 5ml of N,N-dimethylformamide (DMF). Stir to disperse the lignin evenly, then add 5.55g of hexamethylene diisocyanate (HDI) and stir until evenly dispersed. , placed in an oil bath at 70°C and continuously stirred, and reacted for 10 minutes. When the system becomes viscous, set the temperature of the oil bath to 125°C, add 21.6g of DOPO, continue to stir and react for 14 minutes until the system is viscous; take out the reaction product, dry it at 80°C for 18 hours, and crush it to obtain the phosphorus-containing lignin-based flame retardant L15- 1.5, and its FTIR characterization results are shown in Figure 1.

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 60°C for 55 minutes until the system is viscous, add 6g L15-1.5, stir until uniform, then add 0.6g HDI trimer, 1.0g defoamer, stir until uniform, pour them on the tinplate On the sheet and in the polytetrafluoroethylene mold, cure at room temperature, 40°C, 60°C, and 80°C for 12 hours, respectively, to obtain a flame-retardant polyurethane film PU30-L15-1.5.

Example 9

(1) Preparation of phosphorus-containing lignin-based flame retardant

Weigh 12.99g of lignin, disperse it in 12ml of N,N-dimethylformamide (DMF), stir to disperse the lignin evenly, then add 8.71g of toluene diisocyanate (TDI), stir until uniformly dispersed, put Put into an oil bath at 70°C and keep stirring, react for 25 minutes, react for 8 minutes, set the oil bath temperature to 120°C, then add 21.6g DOPO, continue stirring for 30 minutes until the system is viscous; take out the reaction product, and dry at 80°C for 24 hours , crushed to obtain phosphorus-containing lignin-based flame retardant L30T-1.

(2) Preparation of flame retardant polyurethane

Add 15ml of N,N-dimethylformamide (DMF), 10g of polyethylene glycol (PEG200), and 10g of hexamethylene diisocyanate (HDI) into a 250ml three-necked flask, and stir until uniform. Put it in an oil bath, react at 60°C for 50 minutes until the system is viscous, add 1g L30-1, stir until uniform, then add 0.6g HDI trimer, 1.0g defoamer, stir until uniform, pour them on the tinplate respectively On the sheet and in the polytetrafluoroethylene mold, cured at room temperature, 40°C, 60°C, and 80°C for 12 hours, respectively, to obtain a flame-retardant polyurethane film PU5-L30T-1.

Performance Testing

(1) Impact performance test: according to the standard of GB/T1732-93. Put the cured polyurethane film on the tinplate sheet facing up on the anvil, adjust the height of the heavy hammer of the CJQ-Ⅱ paint film impactor, and let the heavy hammer fall freely on the punch until the polyurethane film has no cracks, wrinkles and Peeling phenomenon, record the drop height of the weight.

(2) Oxygen index test: The standard is carried out according to the standard of GB/T 2406.2-2009. The composite material is made into a sample strip of 140mm×52mm×1mm, and it is measured with Shanfang M606 oxygen index meter. The sample holder is vertically clamped in a transparent combustion cylinder, and there is an upward flow of oxygen and nitrogen mixed in a certain proportion. . Light the upper end of the sample, observe the subsequent burning phenomenon, record the continuous burning time and increase the oxygen concentration until the sample burns slowly, record the oxygen index, measure 5 samples for each group, and calculate the average.

(3) Flexibility test: test according to the standard of GB/T 1731-93. Use both hands to put the cured polyurethane film on the tinplate sheet facing up, press it tightly on the rod shaft with a specified diameter, and use the strength of two thumbs to completely wrap the tinplate sheet around the rod shaft. After bending, until the polyurethane film does not produce damage such as texture, cracks or peeling off, record the minimum diameter of the rod shaft.

(4) Adhesion test: test according to the standard of GB/T 9286-1998. Put the cured polyurethane film on the tinplate sheet on a hard and straight table, use a single-edged cutting knife, make the knife perpendicular to the surface of the film and apply force evenly, the cutting distance is 1mm, draw 11 parallel lines; repeat the above steps, Draw the same number of parallel cutting lines that intersect with the original cutting line at 90° to form a grid. Pull out a section of adhesive tape, put the center point of the adhesive tape above the grid, and the direction is parallel to a set of cutting lines, then use your fingers to flatten the adhesive tape above the grid area, and stick it on Within 5 minutes of the adhesive tape, hold the dangling end of the adhesive tape and hold it as close to 60 as possible. Tear off the adhesive tape smoothly within 0.5-1.0 s, record the surface appearance of the cross cutting area where the peeling occurs, and analyze the experimental results.

Table 1 The present invention prepares the embodiment of polyurethane and the performance data of comparative example

Conclusion: From the data in Table 1, it can be seen that comparative example 1 is pure polyurethane without adding flame retardant, and its limiting oxygen index is only 17.1%, which is flammable. From its comparison with Example 1, Example 2, Example 3, and Example 4, it can be seen that the oxygen index of flame-retardant PU after adding the lignin-based flame retardant prepared by the present invention is significantly higher than that of pure PU. Improvement, in Example 1, when the flame retardant addition amount is 15%, its limiting oxygen index can reach 28.3%, indicating that the lignin-based flame retardant prepared by the present invention has played an obvious flame retardant effect. In addition, after the flame retardant prepared by the present invention is added to PU, the mechanical properties of PU can be significantly improved, the adhesion is improved from level 1 to level 0, and the impact resistance reaches more than 100 cm, which is better than PU.

From the comparison between Example 1, Example 2, Example 3, and Example 4, it can be seen that when the amount of lignin-based flame retardant added to the flame-retardant polyurethane is the same, the DOPO content in the lignin-based flame retardant increases. The larger the flame retardant effect is, the better it is, and it has almost no effect on its mechanical properties.

Therefore, the phosphorus-containing lignin-based flame retardant can not only increase the added value of industrial lignin, but also has the advantages of less dosage and good flame retardant effect, and has a good application prospect.

As shown in Figure 1, it is the infrared spectrogram of the phosphorus-containing lignin-based flame retardant synthesized by this patent, Example 1, Example 2, Example 3, Example 4, Example 5, Example 6, and Example 7 . It can be seen from the figure that the absorption peak at 3136cm-1 is attributed to the stretching vibration of benzene ring=C-H; the absorption peaks at 2940cm-1 and 2860cm-1 are attributed to the stretching vibration of CH2; the absorption peak at 1732cm-1 is The C=O stretching vibration of carbamate; the absorption peak at 1660 cm-1 is attributed to the vibration absorption of amide C=O; the absorption peak at 1199 cm-1 is attributed to the stretching vibration absorption of P=O.

Fig. 2 is the infrared spectrogram of the flame-retardant polyurethane material. It can be seen from the figure that the absorption peak at 3325 cm-1 belongs to the stretching vibration of hydrogen bonded N-H; the absorption peak near 1700 cm-1 is the C=O stretching vibration of carbamate; the absorption near 1660 cm-1 The peak is attributed to the vibration absorption of allophanate C=O; the absorption peak near 1247 cm-1 is attributed to the stretching vibration of C-O.

Claims (10)

1. A preparation and application method thereof of a phosphorus-containing lignin-based flame retardant, characterized in that, comprising: Step 1: First react lignin, isocyanate and N,N-dimethylformamide at a certain temperature for a certain period of time; then raise the temperature and add the flame retardant intermediate 9,10-dihydro-9-oxygen to the reaction system Hetero-10-phosphaphenanthrene-10-oxide (DOPO) is reacted at a certain temperature to prepare a phosphorus-containing lignin-based flame retardant; Step 2: React polyol, isocyanate, and N,N-dimethylformamide at a certain temperature until the system is viscous, add the phosphorus-containing lignin-based flame retardant prepared in Step 1 and other additives, and heat-cure the molding , to obtain flame retardant polyurethane. 2 . The preparation method of a phosphorus-containing lignin-based flame retardant according to claim 1 , wherein the source of lignin is alkali lignin, organic solvent lignin or sulfonate lignin. 3. the preparation method of a kind of phosphorus-containing lignin-based flame retardant according to claim 1, is characterized in that, described isocyanate is toluene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), isofluorine ketone diisocyanate (IPDI), hexamethylene diisocyanate (HDI), dicyclohexylmethane diisocyanate (HMDI), p-phenylene diisocyanate (PPDI), 1,4-cyclohexane diisocyanate (CHDI), benzene Dimethylene diisocyanate (XDI), cyclohexane dimethylene diisocyanate (HXDI), trimethyl-1,6-hexamethylene diisocyanate (TMHDI), tetramethylene isophthalylene diisocyanate (TMXDI), 2,5(2,6)-bis(isocyanate)bicyclo[2.2.1]heptane (NBDI), dimethylbiphenyl diisocyanate (TODI), methylcyclohexyl diisocyanate (HTDI). 4. The preparation method of a phosphorus-containing lignin-based flame retardant according to claim 1, wherein the mass fraction of lignin is 5-30 parts. 5. the preparation method of a kind of phosphorus-containing lignin-based flame retardant according to claim 1 is characterized in that, the mol ratio of the active reactive group P-H of DOPO and the active reactive group NCO of isocyanate is (0.5-2 ):1. 6 . The method for preparing a phosphorus-containing lignin-based flame retardant according to claim 1 , wherein the reaction temperature of the lignin and isocyanate is 70-90° C. 7 . The method for preparing a phosphorus-containing lignin-based flame retardant according to claim 1 , wherein the reaction temperature of DOPO is 120-130° C. 8. The preparation method of flame-retardant polyurethane according to claim 1, characterized in that, the phosphorus-containing lignin-based flame retardant with a mass fraction of 5-50% is added. 9. the preparation method of flame-retardant polyurethane according to claim 1 is characterized in that, described isocyanate is the same as claim 3, and polyol is polyester polyol, polyether polyol, epoxy resin, castor oil, acrylic acid Resin diol, the reaction temperature of the polyol and isocyanate is 50-70°C. 10. The auxiliary agent added to prepare flame-retardant polyurethane according to claim 1, including curing agent, catalyst, defoamer, leveling agent and the like.