1. The thiophosphonate-containing flame-retardant polyol is characterized by having the following structural general formula:

wherein R is- (CH)₂)₂-、-(CH₂)₃-、-CH₃CHCH₂-、-(CH₂)₄-、-(CH₂)₂CHCH₃-、-CH₃(CH₂)₂CH₃-one or more of (a) and (b).

2. A method of synthesizing a thiophosphonate-containing flame retardant polyol as claimed in claim 1, comprising the steps of:

placing a reactor added with dihydric alcohol, alkali and solvent in an ice water bath, then dropwise adding thiophosphoryl dichloride, stirring and reacting reaction liquid at the temperature of 0-100 ℃ for 1-24 hours after the addition is finished, and carrying out post-treatment on the reaction liquid to obtain a target product;

the reaction process is as follows:

HO-R-OH represents dihydric alcohol selected from one or more of ethylene glycol, 1, 3-propylene glycol, 1, 2-propylene glycol, 1, 4-butanediol, 1, 3-butanediol, and 2, 3-butanediol.

3. The method of synthesis according to claim 2, characterized in that:

the alkali is selected from one or more of triethylamine, tripropylamine, tributylamine, N-diisopropylethylamine, pyridine, imidazole, N-methylimidazole, sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide.

4. The method of synthesis according to claim 2, characterized in that:

the dihydric alcohol is one or more selected from ethylene glycol, 1, 3-propylene glycol, 1, 2-propylene glycol, 1, 4-butanediol, 1, 3-butanediol, and 2, 3-butanediol.

5. The method of synthesis according to claim 2, 3 or 4, characterized in that:

the molar ratio of the methylthio phosphonic dichloride to the dihydric alcohol is 1:1.01-1: 2; the molar ratio of the addition amount of the alkali to the methylthio phosphonic dichloride is 2.1:1-3: 1.

6. The method of synthesis according to claim 2, characterized in that:

the post-treatment steps are as follows: washing the reaction solution with dilute hydrochloric acid, saturated sodium bicarbonate solution and saturated sodium chloride solution in sequence, evaporating to dryness, drying with anhydrous sodium sulfate or magnesium sulfate, and drying in a vacuum oven at 25-100 ℃ for 1-24h to obtain the target product.

7. Use of a thiophosphonate-containing flame retardant polyol as claimed in claim 1, wherein:

the thiophosphonate-containing flame-retardant polyol partially replaces polyol in a polyurethane soft foam formula to prepare intrinsic flame-retardant polyurethane soft foam, or is compounded with other conventional flame retardants for use.

Technical Field

Polyurethane flexible foams are widely used as cushioning materials in furniture and automotive fields and as cushioning materials in packaging because of their excellent resilience. However, due to the high air permeability and high specific surface area brought by the high carbon and hydrogen content and low aromaticity in the soft foam matrix and the porous structure and the open pore characteristics of the soft foam matrix, the limit oxygen index of the polyurethane soft foam which is not subjected to flame retardant treatment is only 17.5 percent, and the polyurethane soft foam belongs to flammable materials. The furniture field has the largest market demand of polyurethane flexible foams in China, and the great fire safety hidden danger of residential buildings also exists due to the fact that a large amount of flammable polyurethane flexible foams are used. Therefore, the flame retardance of the soft foam is improved, the fire safety hidden danger of the soft foam is eliminated, the threat to life and property safety is reduced, and the method has great significance.

The flame retardant is added into the soft foam substrate, so that the flame retardance of the soft foam substrate can be effectively improved. However, the additive type flame-retardant flexible foam faces the problem that the flame retardant is migrated to cause the loss of flame retardancy in use. The reactive flame retardant containing hydroxyl in the molecular structure can be chemically bonded into a flexible polyurethane foam structure through the reaction with isocyanate groups, so that the intrinsic flame-retardant flexible foam is prepared. Compared with an additive flame retardant, the reactive flame retardant has good migration resistance, and can effectively avoid flame retardancy loss caused by migration of the flame retardant. Therefore, the development of the intrinsic flame-retardant polyurethane flexible foam has wide application prospect.

Disclosure of Invention

Aiming at the defects of poor migration and flame retardant durability of a flame retardant added into a polyurethane flexible foam, the invention provides a thiophosphonate-containing flame retardant polyol, a synthetic method thereof and application thereof in preparation of flame retardant polyurethane flexible foam. The synthesis of the flame-retardant polyol starts from methylthio phosphonic dichloride, the synthesis reaction is simple, the industrial implementation is convenient, and the flame-retardant polyol molecule contains phosphorus and sulfur flame-retardant elements, so that the flame-retardant polyol has the flame-retardant synergistic effect, high flame-retardant efficiency and wide application prospect. In addition, the flame-retardant polyol is liquid at normal temperature and is convenient to use in the foaming process of the polyurethane soft foam.

The thiophosphonate-containing flame-retardant polyol has the following structural general formula:

wherein R is- (CH)₂)₂–、–(CH₂)₃–、–CH₃CHCH₂–、–(CH₂)₄–、–(CH₂)₂CHCH₃–、–CH₃(CH₂)₂CH₃-and the like.

The invention relates to a method for synthesizing thiophosphonate-containing flame-retardant polyol, which comprises the following steps:

placing a reactor added with dihydric alcohol, alkali and solvent in an ice water bath, then dropwise adding thiophosphoryl dichloride, and after the addition is finished, stirring and reacting the reaction solution for 1-24 hours at the temperature of 0-100 ℃; and carrying out post-treatment on the reaction solution to obtain a target product.

The alkali is selected from one or more of triethylamine, tripropylamine, tributylamine, N-diisopropylethylamine, pyridine, imidazole, N-methylimidazole, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide and the like.

The solvent is selected from dichloromethane, trichloromethane, diethyl ether, etc.

The dihydric alcohol is one or more selected from ethylene glycol, 1, 3-propylene glycol, 1, 2-propylene glycol, 1, 4-butanediol, 1, 3-butanediol, 2, 3-butanediol, etc.

The molar ratio of the methylthio phosphonic dichloride to the dihydric alcohol is 1:1.01-1: 2; the molar ratio of the addition amount of the alkali to the methylthio phosphonic dichloride is 2.1:1-3: 1; the addition amount of the solvent is 5-20 times of the total mass of the reactants.

The post-treatment steps are as follows: washing the reaction solution with dilute hydrochloric acid, saturated sodium bicarbonate solution and saturated sodium chloride solution in sequence, evaporating to dryness, drying with anhydrous sodium sulfate or magnesium sulfate, and drying in a vacuum oven at 25-100 ℃ for 1-24h to obtain the target product.

Methylthiophosphonodichloride can be synthesized according to literature reported methods (Journal of the American Chemical Society, 1958; 80:3945-8) or purchased directly.

The reaction mechanism of the present invention is illustrated as follows:

the first step is as follows: under the catalysis of anhydrous aluminum chloride, the methyl phosphine dichloride is vulcanized by sulfur to generate the methyl thiophosphonyl dichloride.

The second step is that: and carrying out linear condensation polymerization on the methylthio phosphonic dichloride and dihydric alcohol to generate the thiophosphonate-containing flame-retardant polyhydric alcohol.

HO-R-OH represents dihydric alcohol, and is selected from one or more of ethylene glycol, 1, 3-propylene glycol, 1, 2-propylene glycol, 1, 4-butanediol, 1, 3-butanediol, 2, 3-butanediol, etc.

The thiophosphonate-containing flame-retardant polyol can partially replace the polyol in the formula of the polyurethane soft foam to prepare the intrinsic flame-retardant polyurethane soft foam, and can also be compounded with other flame retardants for use.

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

1. the thiophosphonate-containing flame-retardant polyol is liquid at room temperature, has proper viscosity and is convenient to use in the production process of polyurethane flexible foam.

2. The thiophosphonate-containing flame-retardant polyol molecule contains sulfur element, has the synergistic flame-retardant effect of phosphorus and sulfur, and has high flame-retardant efficiency.

3. The thiophosphonate-containing flame-retardant polyol molecule contains phosphorus-carbon bonds, is more resistant to hydrolysis, and is not easy to lose efficacy in the using process.

Detailed Description

The technical solution of the present invention is further illustrated by the following specific examples. Methylthiophosphonodichloride was synthesized according to the literature, the other starting materials were purchased directly.

Example 1:

12.8g (0.4mol) of sublimed sulphur were slowly added portionwise under nitrogen at room temperature to a three-necked flask containing 3.2g (0.024mol) of anhydrous aluminium chloride and 46.7g (0.4mol) of methyl phosphine dichloride. During this time, the temperature in the reaction flask was observed by a thermometer, and the reaction temperature was controlled to be between 35 and 45 ℃. After the addition was completed, the mixture was stirred overnight, and after the reaction was completed, the mixture was distilled under reduced pressure at 45 ℃ to obtain a colorless transparent liquid product.

Under an ice-water bath, 14.8g of methylthiophosphono dichloride was added dropwise to a three-necked flask containing 7.4g of ethylene glycol, 150mL of methylene chloride and 13.4g of triethylamine, and the dropping rate was controlled to ensure completion of the dropping within one hour. After the addition was complete, the ice bath was removed and the reaction was allowed to warm to room temperature and stirred overnight to complete the reaction. After completion of the reaction, triethylamine hydrochloride was removed by filtration, and then the filtrate was washed with 1M hydrochloric acid, a saturated sodium bicarbonate solution and a saturated sodium chloride solution in this order and dried over anhydrous magnesium sulfate. The dried filtrate was rotary evaporated to remove dichloromethane and finally dried in a vacuum oven at 80 ℃ for 24h to give a brown viscous liquid product with a yield of 80%. The product structure is shown below:

example 2:

14.8g of methylthiophosphonodichloride synthesized in example 1 was added dropwise to a three-necked flask containing 9.2g of 1, 3-propanediol, 150mL of dichloromethane and 13.4g of triethylamine in an ice-water bath, and the dropping rate was controlled to ensure completion of the dropping within one hour. After the addition was complete, the ice bath was removed and the reaction was allowed to warm to room temperature and stirred overnight to complete the reaction. After completion of the reaction, triethylamine hydrochloride was removed by filtration, and then the filtrate was washed with 1M hydrochloric acid, a saturated sodium bicarbonate solution and a saturated sodium chloride solution in this order and dried over anhydrous magnesium sulfate. The dried filtrate was rotary evaporated to remove dichloromethane and finally dried in a vacuum oven at 80 ℃ for 24h to give the product as a brown viscous liquid with a yield of 82%. The product structure is shown below:

example 3:

the thiophosphonate-containing flame-retardant polyol prepared in example 1 is used for partially replacing polyether polyol 330 according to 2.5%, 5% and 10% of the mass of polyether polyol 330 in the polyurethane soft foam formula, and is uniformly stirred together with polyether polyol 330, A33, dibutyltin dilaurate, silicone oil and water, then weighed TDI is added and is rapidly and uniformly stirred, when the mixed solution turns white, the mixed solution is poured into a mold, pre-foamed for 30 minutes, and then placed into an oven at 80 ℃ for curing for 24 hours. The formulations of the pure and intrinsic flame retardant polyurethane flexible foams are shown in Table 1.

TABLE 1 polyurethane Flexible foam (FPUF) formulation and flame retardancy

According to ISO 4589-1: 1996 and CALTB117-2000 standard (LOI and vertical burning test. after partial substitution of the polyether polyol by the polyol in example 1, the LOI of the soft foam rises and increases with increasing substitution, the LOI of the soft foam at 10% substitution can reach 23.5%.

Example 4:

the molecular structural formula of the reaction type flame retardant PDEO reported in the synthetic literature (Journal of Hazardous Materials, 2018; 360: 651- "660) is as follows:

the flame retardant is used for partially replacing polyether polyol 330 according to 10% of the mass of the polyether polyol 330 in the polyurethane flexible foam formula, the flame retardant is uniformly stirred with the polyether polyol 330, A33, dibutyltin dilaurate, silicone oil and water, then weighed TDI is added, the mixture is rapidly and uniformly stirred, when the mixed solution begins to turn white, the mixture is poured into a mold, pre-foamed for 30 minutes, and then the mixture is placed into an oven with the temperature of 80 ℃ and cured for 24 hours.

The limiting oxygen index of the flame-retardant polyurethane flexible foam is tested according to ISO 4589-1, and the result shows that the limiting oxygen index of the flexible foam can reach 23% at a substitution amount of 10%.

Compared with PDEO, the flame-retardant polyol modified polyurethane soft foam containing thiophosphonate synthesized by the invention has the synergistic effect of phosphine and sulfur flame retardance because the molecular structure contains P and S elements, so that the flame retardance of the polyurethane soft foam is better under the same substitution amount.