Flame-retardant degradable chain extender as well as preparation method and application thereof

Abstract

The preparation method comprises the following steps: dissolving pyrophosphoryl chloride and an alkali catalyst in a solvent, controlling the temperature of a reaction system to be 0 DEG C, dropwise adding hydroxybenzaldehyde under mechanical stirring, keeping the temperature at 0 DEG C, reacting for 2 hours, gradually heating to 30 DEG C, continuously reacting for 8-12 hours, after the reaction is finished, pouring a mixture into petroleum ether, and performing suction filtration, washing and drying to obtain the flame-retardant degradable chain extender. The preparation method comprises the following steps: dissolving a tetrafunctional aldehyde group intermediate into a solvent, precipitating, filtering and washing to obtain a tetrafunctional aldehyde group intermediate, dissolving the tetrafunctional aldehyde group intermediate and glycerol into the solvent, reacting under the action of an acid catalyst, cooling to room temperature, pouring a product into a 5% sodium bicarbonate aqueous solution, filtering, washing and drying in vacuum to obtain the flame-retardant degradable chain extender. The flame-retardant degradable chain extender is introduced into the formula, so that the polyurethane foam has excellent flame retardance and degradability at the same time.

Description

Technical Field

[0001] The invention belongs to the technical field of polyurethane foam, and specifically relates to a flame retardant and degradable chain extender and a preparation method and application thereof. Background Art

[0002] Polyurethane soft foam is a widely used polymer material, often used as home decoration, car seats, cushions and interior decoration parts. In recent years, with the rise of the new energy vehicle industry and people's increasing requirements for the quality of household products, the demand for high-quality polyurethane foam is increasing.

[0003] Although the porous structure of polyurethane foam makes it have low density and excellent damping function, it also shows high flammability. Its own oxygen index is only 14-18%, and it burns quickly, and produces a lot of heat and thick black smoke as well as toxic and harmful gases, which can easily cause serious loss of life and property. Therefore, it is of great significance to develop efficient and environmentally friendly flame-retardant polyurethane foam materials.

[0004] At present, there are two common methods for improving the flame retardant properties of polyurethane foam: one is to improve the flame retardant properties of polyurethane foam by adding external flame retardants. Common additive flame retardants include ammonium polyphosphate, aluminum hypophosphite, dimethyl methylphosphonate, triethyl phosphate, tri(2-chloroisopropyl) phosphate, etc. However, these additive flame retardants have problems such as low flame retardant efficiency, poor dispersibility and compatibility, and deterioration of the mechanical properties of the substrate. In addition, when stored for a long time, there are also problems with the precipitation and migration of flame retardants. Once the polyurethane foam directly contacts the human body, the dissolved and migrated flame retardants may even cause human harm.

[0005] The other is a reactive flame retardant, which uses covalent bonds to make polyurethane foam have intrinsic flame retardant properties from the perspective of molecular structure design. Specifically, some elements with flame retardant properties—nitrogen, phosphorus, and halogens—are introduced into the molecular segments of polyurethane foam. It can maintain the flame retardant effect for a long time without destroying the macroscopic structure of the polyurethane foam itself. In addition, since the flame retardant molecules participate in the polymerization process, there is no sedimentation and migration problem, so when the polyurethane foam comes into contact with the human body, it will no longer cause harm. However, with the large-scale use of polyurethane foam, whether it is additive flame retardant polyurethane foam or reactive flame retardant polyurethane foam, their pollution to the environment after disposal is becoming more and more serious.

[0006] Many waste polyurethane foams are not effectively recycled, and are mostly disposed of by incineration and landfill, which not only causes waste of resources and environmental pollution, but also requires companies to pay high disposal costs. Therefore, achieving flame retardancy and biodegradability of polyurethane foam plastics is one of the important issues in achieving green, low-carbon and circular development. Summary of the invention

[0007] Technical issues solved:

[0008] The present application aims at the deficiencies in the prior art and solves the current problems of high flammability, which can easily cause serious loss of life and property, low flame retardant efficiency, poor dispersibility and compatibility, and deterioration of the mechanical properties of the substrate. When stored for a long time, there are also problems of flame retardant sedimentation and migration. After being discarded, their pollution to the environment is becoming more and more serious. Incineration and landfill treatment not only cause waste of resources and environmental pollution, but also require enterprises to pay high processing costs and other technical problems. A flame retardant and degradable chain extender and its preparation method and application are provided, which can be linked to the molecular chain segments of polyurethane foam through covalent bonds, thereby effectively solving the flame retardant and degradable problems of polyurethane foam.

[0009] Technical solution:

[0010] To achieve the above objectives, this application is implemented through the following technical solutions:

[0011] A method for preparing a flame retardant and degradable chain extender comprises the following steps:

[0012] The first step is to dissolve pyrophosphoryl chloride and an alkali catalyst in a solvent, control the temperature of the reaction system to 0°C, control the mechanical stirring speed to 500-1000r / min, add hydroxybenzaldehyde dropwise, keep the temperature at 0°C for 2h, gradually raise the temperature to 30°C and continue the reaction for 8-12h. After the reaction is completed, pour the mixture into petroleum ether, precipitate, filter and wash to obtain a tetrafunctional aldehyde intermediate, and the molar ratio of pyrophosphoryl chloride, hydroxybenzaldehyde and alkali catalyst is 1.0:4.0-5.0:4.0-5.0;

[0013] Step 2: According to the mass volume ratio of tetrafunctional aldehyde intermediate: glycerol: solvent: acid catalyst = 53.04g: 38.68g:

[0014] 100mL:1.6g, dissolve the tetrafunctional aldehyde intermediate and propylene glycol in a solvent, react under the action of an acid catalyst, cool to room temperature, pour the product into a 5% sodium bicarbonate aqueous solution, filter, wash, and vacuum dry to obtain a flame retardant and degradable chain extender.

[0015] Furthermore, the first step hydroxybenzaldehyde is 3-hydroxybenzaldehyde or 4-hydroxybenzaldehyde; the base catalyst is one or more of triethylamine, pyridine, sodium acetate, sodium carbonate, potassium carbonate; and the solvent is N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide or chloroform.

[0016] Furthermore, in the first step, the solvent is chloroform and the base catalyst is triethylamine.

[0017] Furthermore, in the second step, the molar ratio of tetrafunctional aldehyde intermediate: propylene glycol is 1.0:4.1-5.0; the reaction temperature in the second step is 90-120°C, and the reaction time is 6-12h; the acid catalyst in the second step is one or more of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, and γ-Al2O3; and the solvent is N,N-dimethylformamide, N,N-dimethylacetamide or dimethyl sulfoxide.

[0018] Furthermore, the solvent in the second step is N,N-dimethylformamide.

[0019] A flame retardant and degradable chain extender prepared by any of the above preparation methods, wherein the molecular structure of the chain extender is as follows:

[0020]

[0021] The present application also discloses the use of a flame retardant and degradable chain extender in a flame retardant and degradable polyurethane foam, and a method for preparing the flame retardant and degradable polyurethane foam:

[0022] S1: Take 80-110 parts of polyether polyol, 30-90 parts of isocyanate, 0.05-4 parts of high-efficiency foam stabilizer, 0.5-5 parts of reactive composite catalyst, 0.5-5 parts of water and 0.01-20 parts of flame retardant and degradable chain extender according to the mass ratio;

[0023] S2: Mixing polyether polyol, flame retardant and degradable chain extender, high-efficiency foam stabilizer, reactive composite catalyst, water and isocyanate to prepare polymerization raw material;

[0024] S3, the polymer raw materials are pumped into the foaming machine through the pipeline, and the foaming machine head performs open continuous low-pressure flat foaming:

[0025] The polymer raw material is sprayed onto the landing plate of the foaming machine through the foaming nozzle of the foaming machine, and the flow rate of the material sprayed by the foaming nozzle is controlled at 60-400kg / min; a conveyor belt is arranged on the landing plate, and kraft paper is also laid on the conveyor belt. The foaming nozzle sprays the polymer raw material onto the kraft paper to form a flame retardant and degradable polyurethane foam, and the kraft paper moves forward with the conveyor belt at a speed of 1-8m / min, thereby driving the flame retardant and degradable polyurethane foam to move forward together, realizing foaming and conveying at the same time.

[0026] Furthermore, the polyether polyol is a trifunctional polyether; the isocyanate is toluene diisocyanate; the high-efficiency foam stabilizer is an organosilicon foam stabilizer or a polysiloxane-polyoxyolefin mosaic copolymer; and the reactive composite catalyst is a tin catalyst or an amine catalyst.

[0027] Furthermore, the trifunctional polyether is composed of a polyether polyol with a molecular weight of 5000 and a hydroxyl value of 35-39 and a polyether polyol with a molecular weight of 3000 and a hydroxyl value of 26-30.

[0028] Furthermore, the degradation steps of the flame retardant and degradable polyurethane foam are:

[0029] (1) immersing the flame-retardant and degradable polyurethane foam in an acidic mixed solvent to depolymerize and dissolve the polyurethane foam to obtain a uniform polyurethane foam solution; the acidic mixed solvent is a mixture of an organic solvent and an acid, the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, dichloromethane, and dimethyl sulfoxide, the acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, acetic acid, and citric acid, and the volume ratio of the organic solvent to the acid is 1.0-5.0:10.0-1.0; the immersion temperature is 50-80° C., and the immersion time is 1-6 hours;

[0030] (2) The polyurethane foam solution in step (1) is precipitated in a poor solvent, and a polyurethane prepolymer containing a terminal dihydroxyl functional group is precipitated from the solution, and then filtered and washed to obtain a solid polyurethane prepolymer containing a terminal dihydroxyl functional group; the filtrate is neutralized, evaporated, washed, and dried to obtain a tetrafunctional aldehyde intermediate; the poor solvent is one or more of water, methanol, ethyl acetate, n-hexane, and petroleum ether.

[0031] Principle explanation: pyrophosphoryl chloride is reacted with hydroxybenzaldehyde to obtain a tetrafunctional aldehyde intermediate, and then the tetrafunctional aldehyde intermediate is reacted with propylene glycol to form a cyclic acetal structure through an acetal reaction to obtain a flame retardant and degradable chain extender; the flame retardant and degradable chain extender used in the present invention is a tetrafunctional hydroxy compound, so it can be introduced into the chain segment of the polyurethane foam through foaming and polymerization reactions. Compared with traditional additive flame retardants, this method can maintain the flame retardant effect for a long time without destroying the macroscopic structure of the polyurethane foam itself, and because the flame retardant molecules participate in the foaming polymerization process, there are no sedimentation and migration problems. When the polyurethane foam comes into contact with the human body It will not cause harm and is safer; on the other hand, based on the dissociation ability of the cyclic acetal structure under acidic conditions and the swelling ability of the polymer chain in certain organic solvents, under the dual stimulation of specific organic solvents and acids, the polyurethane foam can be selectively depolymerized to regenerate a tetrafunctional aldehyde intermediate and a polyurethane prepolymer containing a dihydroxyl functional group at the end; the completely depolymerized solution is quickly purified through solution precipitation, filtration, evaporation, washing, and drying steps; the recovered tetrafunctional aldehyde intermediate I and the polyurethane prepolymer containing a dihydroxyl functional group at the end can be used to prepare new polyurethane foam again, thereby realizing the closed-loop recovery of polyurethane foam under mild conditions.

[0032] Beneficial effects:

[0033] The present application provides a flame retardant and degradable chain extender and a preparation method and application thereof, which have the following beneficial effects compared with the prior art:

[0034] 1. The present invention introduces a flame retardant and degradable chain extender into the formula, so that the polyurethane foam has excellent flame retardant and degradable properties;

[0035] 2. The flame retardant and degradable chain extender is linked to the chain segment of the polyurethane foam through foaming and polymerization reactions. This method can maintain the flame retardant effect for a long time without destroying the macroscopic structure of the polyurethane foam itself. Moreover, since the flame retardant molecules participate in the foaming and polymerization process, there is no sedimentation and migration problem. When the polyurethane foam comes into contact with the human body, it will not cause harm and is safer;

[0036] 3. For the flame-retardant polyurethane foam prepared by the present invention, the limiting oxygen index measured according to the national standard GB / T2406.2-2009 reaches up to 37.2%; at the same time, the flame retardant grade measured according to the UL94 flame retardant test method reaches V-0, and both indicators are better than the data in the currently disclosed technical solutions;

[0037] 4. The polyurethane foam of the present invention can be selectively depolymerized to regenerate a tetrafunctional aldehyde intermediate and a polyurethane prepolymer containing a dihydroxyl functional group at the end. The recovered tetrafunctional aldehyde intermediate I and the polyurethane prepolymer containing a dihydroxyl functional group at the end can be used to prepare new polyurethane foam, thereby realizing closed-loop recycling of polyurethane foam under mild conditions. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical scheme and advantages of the present invention more clear, the present invention is further described in detail below in conjunction with specific implementation methods. The following examples can enable technicians in this field to understand the present invention more comprehensively, but the present invention is not limited to the scope of the embodiments.

[0039] Density determination method: Determine the density of polyurethane soft foam material according to GB / T6343-2009 "Determination of apparent density of foam plastics and rubber". Place the polyurethane soft foam material in the environment (dryer) specified in the standard for at least 16 hours. After reaching a stable state, measure the size of the sample according to the provisions of GB / T6342-1996. Measure at least three times and calculate the average value as the final measurement result. Finally, the measured result is calculated according to ρ = (m / V) x 10 6 , calculate the apparent density of the foam. Where: ρ—apparent density, unit is kilograms per cubic meter (kg / m 3 ); m—mass of the sample, in grams (g); V—volume of the sample, in cubic millimeters (mm3 ).

[0040] Tensile strength and elongation at break determination: According to GB / T6344-2008 "Determination of tensile strength and elongation at break of flexible foam polymer materials", the tensile strength and elongation at break of the sample are tested.

[0041] Tensile strength: Measure the average thickness of each polyurethane soft foam material, and calculate the original cross-sectional area according to the average width and average thickness of the middle part of the punched specimen. S =(F / A)x10 3 Calculate the tensile strength of each specimen in kPa. Where: T S —Tensile strength, in kPa; F—maximum load, in N; A—average original cross-sectional area of ​​the specimen, in square millimeters (mm 2 ).

[0042] Elongation at break: press E b =[(L-L0) / L0]x100% to calculate the elongation at break of the soft foam material. Where: E b —Elongation at break, expressed in %; L—Gage length of the specimen at break, in millimeters (mm); L0—Original gauge length of the specimen, in millimeters (mm).

[0043] Hardness measurement: According to GB / T10807-2006 "Determination of hardness of soft foam polymer materials (indentation method)", the hardness of polyurethane soft foam material is measured.

[0044] Tear strength measurement: According to GB / T10808-2006 "Determination of tear strength of polymer porous elastic materials", the tear strength of the material is measured. Unfold the balanced sample, place it on the fixture of the testing machine, adjust it to a suitable position, and apply force to the sample. The tear strength of the polyurethane soft foam material is calculated according to R=F / d. In the formula: F—the maximum tear force value recorded on the experimental instrument, in Newton (N); d—the initial average thickness of the sample, in meters (m).

[0045] The limiting oxygen index of the sample in the present invention is tested according to the national standard GB / T2406.2-2009, using a critical oxygen index analyzer from Jiangsu Fellman Company, the instrument model is PX01005, and the sample size is 120mm×10mm×10mm.

[0046] Embodiment 1:

[0047] A method for preparing a flame retardant and degradable chain extender comprises the following steps:

[0048] Step 1: dissolve pyrophosphoryl chloride and alkaline catalyst triethylamine in chloroform solvent, control the temperature of the reaction system to 0°C, control the mechanical stirring speed to 500-1000r / min, add 4-hydroxybenzaldehyde dropwise, keep the temperature at 0°C for 2h, gradually increase the temperature to 30°C and continue the reaction for 8h, control the molar ratio of pyrophosphoryl chloride, 4-hydroxybenzaldehyde and triethylamine to 1.0:4.1:4.1, after the reaction is completed, pour the mixture into petroleum ether, precipitate, filter and wash to obtain a tetrafunctional aldehyde intermediate I, whose molecular formula is shown below;

[0049]

[0050] Step 2: Dissolve 53.04 g (0.1 mol) of tetrafunctional aldehyde intermediate I and 38.68 g (0.42 mol) of propylene glycol in 100 mL of N,N-dimethylformamide solvent, heat and reflux at 110 ° C for 12 h under the action of 1.6 g of acid catalyst phosphoric acid, and after cooling to room temperature, pour the product into 5% sodium bicarbonate aqueous solution, filter, wash, and vacuum dry to obtain a flame retardant and degradable chain extender, the molecular formula of which is as follows: Preparation method of flame retardant and degradable polyurethane foam:

[0051] S1: The raw materials of flame retardant and degradable polyurethane foam are prepared by weight: 75 parts of polyether polyol with a molecular weight of 5000 and a hydroxyl value of 35-39, 15 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 26-30, 45 parts of toluene diisocyanate, 2 parts of silicone foam stabilizer, 0.5 parts of amine catalyst, 2.5 parts of water and 20 parts of flame retardant and degradable chain extender;

[0052] S2: Mixing polyether polyol, flame retardant and degradable chain extender, high-efficiency foam stabilizer, reactive composite catalyst, water and isocyanate to prepare polymerization raw material;

[0053] S3, pumping the polymer raw material into the foaming machine through the pipeline, and performing open continuous low-pressure flat foaming by the foaming machine head: spraying the polymer raw material onto the landing plate of the foaming machine through the foaming nozzle of the foaming machine, and the flow rate of the material sprayed by the foaming nozzle is controlled at 60-400kg / min; a conveyor belt is arranged on the landing plate, and kraft paper is also laid on the conveyor belt. The foaming nozzle sprays the polymer raw material onto the kraft paper to form a flame retardant and degradable polyurethane foam, and the kraft paper moves forward with the conveyor belt at a speed of 1-8m / min, thereby driving the flame retardant and degradable polyurethane foam to move forward together, realizing foaming and conveying at the same time.

[0054] The degradable method of flame retardant degradable polyurethane foam comprises the following steps:

[0055] (1) immersing the flame-retardant and degradable polyurethane foam in an acidic mixed solvent to depolymerize and dissolve the polyurethane foam to obtain a uniform polyurethane foam solution; in the step (1), the acidic mixed solvent is a mixture of an organic solvent and an acid, the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, dichloromethane, and dimethyl sulfoxide, the acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, acetic acid, and citric acid, and the volume ratio of the organic solvent to the acid is 1.0-5.0:10.0-1.0; in the step (1), the immersion temperature is 50-80° C., and the immersion time is 1-6 hours;

[0056] (2) The polyurethane foam solution described in step (1) is precipitated in a poor solvent, and a polyurethane prepolymer containing a terminal dihydroxyl functional group is precipitated from the solution, and then filtered and washed to obtain a solid polyurethane prepolymer containing a terminal dihydroxyl functional group; the filtrate is neutralized, evaporated, washed, and dried to obtain a tetrafunctional aldehyde intermediate; the obtained polyurethane prepolymer containing a terminal dihydroxyl functional group and the tetrafunctional aldehyde intermediate can both be directly used for the preparation of new polyurethane foam, thereby realizing closed-loop recovery of polyurethane foam, and in step (2), the poor solvent is selected from one or more of water, methanol, ethyl acetate, n-hexane, and petroleum ether.

[0057] The flame retardant and degradable polyurethane foam prepared in Example 1 was ground into small particles, put into a mixed solution of N,N-dimethylformamide and concentrated hydrochloric acid (volume ratio of 6:4), stirred at 80°C for 6 hours, and the flame retardant and degradable polyurethane foam was depolymerized and completely dissolved in the mixed solution; the depolymerization solution was poured into petroleum ether for precipitation and filtering operations, and the obtained filter cake was washed and dried to obtain a polyurethane prepolymer containing terminal dihydroxy functionalization, with a recovery rate of about 89.3%; at the same time, the filtrate was neutralized and then evaporated to obtain a crude product, which was then washed with petroleum ether and vacuum dried to obtain a tetrafunctional aldehyde intermediate, with a recovery rate of about 87.6%; the flame retardant test of the flame retardant polyurethane foam showed excellent flame retardant properties, and the flame retardant grade tested by the UL94 method reached V-0 level, and the limiting oxygen index was 37.3%.

[0058] Example 2

[0059] The difference from Example 1 is that the ratio of the acidic mixed solvent in the degradation process of the flame retardant and degradable polyurethane foam is as follows: the volume ratio of N,N-dimethylformamide and concentrated hydrochloric acid is 5:5. The recovery rate of the obtained polyurethane prepolymer containing dihydroxyl functionalization at the end is about 92.1%; the recovery rate of the tetrafunctional aldehyde intermediate is about 90.4%. The flame retardant test of the flame retardant and degradable polyurethane foam shows excellent flame retardant properties. The flame retardant grade tested by the UL94 method reaches V-0 level, and the limiting oxygen index is 36.5%.

[0060] Embodiment 3:

[0061] A method for preparing a flame retardant and degradable chain extender comprises the following steps:

[0062] Step 1: dissolve pyrophosphoryl chloride and alkaline catalyst triethylamine in chloroform solvent, control the temperature of the reaction system to 0°C, control the mechanical stirring speed to 500-1000r / min, add 3-hydroxybenzaldehyde dropwise, keep the temperature at 0°C for 2h, gradually increase the temperature to 30°C and continue the reaction for 12h, control the molar ratio of pyrophosphoryl chloride, 3-hydroxybenzaldehyde and triethylamine to 1.0:4.2:4.2, after the reaction is completed, pour the mixture into petroleum ether, precipitate, filter and wash to obtain a tetrafunctional aldehyde intermediate I, whose molecular formula is shown below;

[0063]

[0064] Step 2: Dissolve 53.04 g (0.1 mol) of tetrafunctional aldehyde intermediate I and 38.68 g (0.42 mol) of propylene glycol in 100 mL of N,N-dimethylformamide solvent, heat and reflux at 110 ° C for 12 h under the action of 1.6 g of acid catalyst phosphoric acid, and after cooling to room temperature, pour the product into 5% sodium bicarbonate aqueous solution, filter, wash, and vacuum dry to obtain a flame retardant and degradable chain extender, the molecular formula of which is as follows:

[0065] Preparation method of flame retardant and degradable polyurethane foam:

[0066] S1: The raw materials of flame retardant and degradable polyurethane foam are prepared by weight: 75 parts of polyether polyol with a molecular weight of 5000 and a hydroxyl value of 35-39, 15 parts of polyether polyol with a molecular weight of 3000 and a hydroxyl value of 26-30, 45 parts of toluene diisocyanate, 2 parts of silicone foam stabilizer, 0.5 parts of amine catalyst, 2.5 parts of water and 20 parts of flame retardant and degradable chain extender;

[0067] S2: Mixing polyether polyol, flame retardant and degradable chain extender, high-efficiency foam stabilizer, reactive composite catalyst, water and isocyanate to prepare polymerization raw material;

[0068] S3, the polymer raw materials are pumped into the foaming machine through the pipeline, and the foaming machine head performs open continuous low-pressure flat foaming:

[0069] The polymer raw material is sprayed onto the landing plate of the foaming machine through the foaming nozzle of the foaming machine, and the flow rate of the material sprayed by the foaming nozzle is controlled at 60-400kg / min; a conveyor belt is arranged on the landing plate, and kraft paper is also laid on the conveyor belt. The foaming nozzle sprays the polymer raw material onto the kraft paper to form a flame retardant and degradable polyurethane foam, and the kraft paper moves forward with the conveyor belt at a speed of 1-8m / min, thereby driving the flame retardant and degradable polyurethane foam to move forward together, realizing foaming and conveying at the same time.

[0070] The flame retardant and degradable polyurethane foam was ground into small particles, placed in a mixed solution of N,N-dimethylformamide and concentrated hydrochloric acid (volume ratio of 6:4), stirred at 80℃ for 4 hours, and the flame retardant and degradable polyurethane foam was depolymerized and completely dissolved in the mixed solution. The depolymerized solution was poured into petroleum ether for precipitation and filtration. The obtained filter cake was washed and dried to obtain a polyurethane prepolymer containing dihydroxy functionalization at the end; at the same time, the filtrate was neutralized and evaporated to obtain a crude product, which was then washed with petroleum ether and vacuum dried to obtain a tetrafunctional aldehyde intermediate. The flame retardant test of the flame retardant polyurethane foam showed excellent flame retardant properties. The flame retardant grade of the UL94 method test reached V-0 level, and the limiting oxygen index was 37.1%.

[0071] Embodiment 4:

[0072] The difference from Example 3 is that the flame retardant and degradable polyurethane foam is composed of the following components in parts by weight: 80 parts of a polyether polyol having a molecular weight of 5000 and a hydroxyl value of 35-39, 20 parts of a polyether polyol having a molecular weight of 3000 and a hydroxyl value of 26-30, 10 parts of a flame retardant and degradable chain extender, 45 parts of toluene diisocyanate, 2 parts of an organosilicon foam stabilizer, 0.5 parts of an amine catalyst, and 2.5 parts of water.

[0073] The recovery rate of the obtained polyurethane prepolymer containing dihydroxyl functional groups at the end is about 85.8%, and the recovery rate of the tetrafunctional aldehyde intermediate is about 87.4%. The flame retardant test of the flame retardant and degradable polyurethane foam shows excellent flame retardant properties. The flame retardant grade tested by the UL94 method reaches V-0 level, and the limiting oxygen index is 31.6%.

[0074] Comparative Example 1:

[0075] The difference between this comparative example and Example 4 is that the polyurethane foam is composed of the following components in parts by weight: 90 parts of a polyether polyol having a molecular weight of 5000 and a hydroxyl value of 35-39, 20 parts of a polyether polyol having a molecular weight of 3000 and a hydroxyl value of 26-30, 45 parts of toluene diisocyanate, 2 parts of an organosilicon foam stabilizer, 0.5 parts of an amine catalyst, and 2.5 parts of water.

[0076] Comparative Example 2: Chinese patent CN118440388A discloses a high temperature resistant flame retardant polyurethane foam with self-repairing properties.

[0077] Comparative Example 3: A halogen-free flame-retardant polyurethane foam material disclosed in Chinese patent CN118290687A.

[0078] Comparative Example 4: The flame retardant polyurethane foam material disclosed in Chinese patent CN118256022A.

[0079] Comparative Example 5: Flame retardant polyurethane foam disclosed in Chinese patent CN117534828A.

[0080] Comparative Example 6: The flame retardant rigid polyurethane foam disclosed in Chinese patent CN117430780B.

[0081] Comparative Example 7: Flame retardant polyurethane foam disclosed in Chinese patent CN114854002B.

[0082] Comparative Example 8: Chinese patent CN117229473A discloses a high temperature resistant flame retardant polyurethane foam with self-repairing properties.

[0083] Table 1 Performance test results of polyurethane foams prepared in Examples 1 to 4 and Comparative Example 1

[0084]

[0085] Conclusion: The flame retardant and degradable chain extender is added to the polymerization raw material, and the alcohol hydroxyl group in the structure of the flame retardant and degradable chain extender is used to react with the isocyanate in the polymerization monomer, so that the flame retardant and degradable chain extender is linked to the molecular chain of the polyurethane foam through a covalent bond chain. Compared with the ordinary foam in Comparative Example 1, the density, hardness, tensile strength, elongation at break, tear strength, flame retardant properties, etc. are improved to a certain extent; By comparing Examples 3 and 4, it can be found that increasing the number of flame retardant and degradable chain extenders helps to improve the flame retardant effect of the foam.

[0086] The flame retardant polyurethane foams in Examples 1 to 4 were compared with those in Comparative Examples 2 to 8, as shown in Table 2.

[0087] Table 2 Comparison of flame retardant polyurethane foam properties in Examples 1 to 4 and Comparative Examples 2 to 8

[0088]

[0089]

[0090] Compared with Comparative Examples 2 to 8, the flame retardant polyurethane foam prepared by the present invention not only has a higher limiting oxygen index and a better flame retardant grade, but also can realize the degradation function under mild conditions, reduce environmental pollution, and realize the closed-loop recycling and reuse of raw materials. Compared with Comparative Examples 2 to 7, the flame retardant polyurethane foam prepared by the present invention introduces the flame retardant and degradable chain extender into the polyurethane foam structure through the action of covalent bonds, so that it has intrinsic flame retardant properties, completely overcoming the dissolution and migration of additive flame retardants during use and even human body damage. Compared with Comparative Example 8, although the flame retardant properties of polyurethane foam are achieved by reactive flame retardants, the flame retardant polyurethane foam prepared by the present invention has a higher limiting oxygen index and a better flame retardant grade.

[0091] The above description has fully disclosed the specific embodiments of the present invention. It should be pointed out that any changes made by those skilled in the art to the specific embodiments of the present invention do not deviate from the scope of the claims of the present invention. Accordingly, the scope of the claims of the present invention is not limited to the above specific embodiments.

Claims

1. A method for preparing a flame retardant and degradable chain extender, characterized in that: The specific steps are as follows: The first step: dissolving pyrophosphoryl chloride and an alkali catalyst in a solvent, controlling the temperature of the reaction system to 0°C, controlling the mechanical stirring speed to 500-1000 r / min, adding hydroxybenzaldehyde dropwise, maintaining the temperature at 0°C for 2 hours, gradually heating to 30°C and continuing the reaction for 8-12 hours. After the reaction is completed, pouring the mixture into petroleum ether, precipitating, filtering, and washing to obtain a tetrafunctional aldehyde intermediate, wherein the molar ratio of pyrophosphoryl chloride, hydroxybenzaldehyde, and alkali catalyst is 1.0:4.0-5.0:4.0-5.0; Step 2: According to the mass volume ratio of tetrafunctional aldehyde intermediate: propylene glycol: solvent: acid catalyst = 53.04 g: 38.68 g: 100 mL: 1.6 g, the tetrafunctional aldehyde intermediate and propylene glycol are dissolved in the solvent, reacted under the action of the acid catalyst, and after cooling to room temperature, the product is poured into a 5% sodium bicarbonate aqueous solution, filtered, washed, and vacuum dried to obtain a flame retardant and degradable chain extender.

2. The method for preparing a flame retardant and degradable chain extender according to claim 1, characterized in that: The first step hydroxybenzaldehyde is 3-hydroxybenzaldehyde or 4-hydroxybenzaldehyde; the base catalyst is one or more of triethylamine, pyridine, sodium acetate, sodium carbonate, potassium carbonate; the solvent is N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide or chloroform.

3. The method for preparing a flame retardant and degradable chain extender according to claim 2, characterized in that: In the first step, the solvent is chloroform and the base catalyst is triethylamine.

4. The method for preparing a flame retardant and degradable chain extender according to claim 1, characterized in that: In the second step, the molar ratio of tetrafunctional aldehyde intermediate: propylene glycol is 1.0:4.1-5.0; the reaction temperature in the second step is 90-120° C., and the reaction time is 6-12 hours; the acid catalyst in the second step is one or more of sulfuric acid, phosphoric acid, p-toluenesulfonic acid, and γ-Al2O3; and the solvent is N,N-dimethylformamide, N,N-dimethylacetamide or dimethyl sulfoxide.

5. The method for preparing a flame retardant and degradable chain extender according to claim 4, characterized in that: The solvent in the second step is N,N-dimethylformamide.

6. A flame retardant and degradable chain extender prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The molecular structure of the chain extender is shown below:

7. Use of the flame retardant and degradable chain extender according to claim 6 in flame retardant and degradable polyurethane foam, characterized in that: The preparation method of the flame retardant and degradable polyurethane foam: S1: Take 80-110 parts of polyether polyol, 30-90 parts of isocyanate, 0.05-4 parts of high-efficiency foam stabilizer, 0.5-5 parts of reactive composite catalyst, 0.5-5 parts of water and 0.01-20 parts of flame retardant and degradable chain extender according to the mass ratio; S2: Mixing polyether polyol, flame retardant and degradable chain extender, high-efficiency foam stabilizer, reactive composite catalyst, water and isocyanate to prepare polymerization raw material; S3, the polymer raw materials are pumped into the foaming machine through the pipeline, and the foaming machine head performs open continuous low-pressure flat foaming: The polymer raw material is sprayed onto the landing plate of the foaming machine through the foaming nozzle of the foaming machine, and the flow rate of the material sprayed by the foaming nozzle is controlled at 60-400kg / min; a conveyor belt is arranged on the landing plate, and kraft paper is also laid on the conveyor belt. The foaming nozzle sprays the polymer raw material onto the kraft paper to form a flame retardant and degradable polyurethane foam, and the kraft paper moves forward with the conveyor belt at a speed of 1-8m / min, thereby driving the flame retardant and degradable polyurethane foam to move forward together, realizing foaming and conveying at the same time.

8. The use according to claim 7, characterized in that: The polyether polyol is a trifunctional polyether; the isocyanate is toluene diisocyanate; the high-efficiency foam stabilizer is an organosilicon foam stabilizer or a polysiloxane-polyoxyolefin mosaic copolymer; The reactive composite catalyst is a tin catalyst or an amine catalyst.

9. The use according to claim 8, characterized in that: The trifunctional polyether is composed of a polyether polyol with a molecular weight of 5000 and a hydroxyl value of 35-39 and a polyether polyol with a molecular weight of 3000 and a hydroxyl value of 26-30.

10. The use according to claim 7, characterized in that: The degradation steps of the flame retardant and degradable polyurethane foam are: (1) immersing the flame-retardant and degradable polyurethane foam in an acidic mixed solvent to depolymerize and dissolve the polyurethane foam to obtain a uniform polyurethane foam solution; the acidic mixed solvent is a mixture of an organic solvent and an acid, the organic solvent is one or more of N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran, dichloromethane, and dimethyl sulfoxide, the acid is one or more of concentrated hydrochloric acid, concentrated sulfuric acid, acetic acid, and citric acid, and the volume ratio of the organic solvent to the acid is 1.0-5.0:10.0-1.0; the immersion temperature is 50-80° C., and the immersion time is 1-6 h; (2) The polyurethane foam solution in step (1) is precipitated in a poor solvent, and a polyurethane prepolymer containing a terminal dihydroxyl functional group is precipitated from the solution, and then filtered and washed to obtain a solid polyurethane prepolymer containing a terminal dihydroxyl functional group; the filtrate is neutralized, evaporated, washed, and dried to obtain a tetrafunctional aldehyde intermediate; the poor solvent is one or more of water, methanol, ethyl acetate, n-hexane, and petroleum ether.

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