Rigid polyurethane foam based on composite flame-retardant coating as well as preparation method and application of rigid polyurethane foam

Abstract

The invention belongs to the technical field of flame retardance of high polymer materials, and particularly relates to rigid polyurethane foam based on a composite flame-retardant coating as well as a preparation method and application of the rigid polyurethane foam. The method comprises the following steps: 1) preparing a rigid polyurethane foam base material by adopting a one-step foaming method; 2) taking an aqueous solution of polyvinyl alcohol as a base material, adding hydroxide, a ceramic flame retardant and expanded graphite as a composite flame retardant into the base material, and stirring at a high speed to form slurry; (3) uniformly coating the surface of a hard polyurethane foam base material with the slurry, and curing at room temperature to form an intumescent flame-retardant coating, so as to obtain the hard polyurethane foam. The hard polyurethane foam provided by the invention is high in flame-retardant grade and low in heat conductivity coefficient, and the formed coating is an intumescent ceramic carbon layer and is high in oxygen index.

Description

Technical Field

[0001] This invention belongs to the field of flame retardant polymer materials technology, specifically relating to a rigid polyurethane foam based on a composite flame retardant coating, its preparation method, and its application. Background Technology

[0002] Traditional additive flame retardants (such as phosphorus-based and halogen-based ones) have poor compatibility with rigid polyurethane foam matrices, easily leading to a decline in the material's mechanical properties (such as cracking and deformation). Surface treatment methods, through the application of flame-retardant coatings, can retain the characteristics of the substrate while improving fire resistance. In existing technologies, borates are widely used in flame-retardant systems due to their environmental friendliness and high thermal stability, while hydroxides exert their flame-retardant effect through endothermic decomposition. However, there are still technological gaps in the synergistic application of these two in coatings and in formulation optimization. Furthermore, in the traditional one-step preparation of rigid polyurethane foam, the dispersion uniformity of the blowing agent and flame retardant is insufficient, resulting in significant fluctuations in thermal conductivity.

[0003] Patent CN119505166A discloses a flame-retardant polyurethane composite material and its preparation process, relating to the field of polymer materials. In preparing the flame-retardant polyurethane composite material, this invention involves reacting tetramethyltetravinylcyclotetrasiloxane with DOPO to obtain phosphorus-modified cyclotetrasiloxane; then reacting lignin sequentially with 3-aminopropyldimethoxymethylsilane and phosphorus-modified cyclotetrasiloxane to obtain modified lignin microspheres; reacting 2,4-pentanedione, 1,5-dichloro with hydroxylamine hydrochloride to obtain a dioxime monomer; and then mixing isophorone diisocyanate, 1,4-butanediol, the dioxime monomer, N,N-dimethylhexylamine, modified lignin microspheres, and deionized water, pouring the mixture into a mold, and curing to obtain the flame-retardant polyurethane composite material.

[0004] The invention patent with announcement number CN119505336A discloses a polyurethane outer packaging material and its preparation method that uses molybdenum trioxide, ammonium polyphosphate, and organic silsesquioxane for synergistic flame retardancy. Belonging to the field of flame retardant material development, this invention achieves synergistic flame retardancy by adding molybdenum trioxide, ammonium polyphosphate, and organic silsesquioxane to a polyurethane flexible foam system. Flame-retardant polyurethane flexible foam is synthesized through a one-step foaming process. The resulting flame-retardant polyurethane flexible foam material exhibits extremely good flame retardant effects, with significant improvements in its limiting oxygen index, thermal stability, heat release rate and total heat release, smoke production rate and total smoke production, and char residue. Through the synergistic flame retardant effect of molybdenum trioxide, ammonium polyphosphate, and organic silsesquioxane, a polyurethane outer packaging material with outstanding flame retardant performance has been developed, showing excellent application prospects.

[0005] Chinese patent CN119286237A discloses a wear-resistant, flame-retardant, transparent polyurethane material and its preparation method. The material comprises the following components in parts by weight: polyurethane elastomer: 75-95.5 parts, dimethyl methylphosphonate: 2-15 parts, polycarbodiimide: 1-3 parts, tris(2-chloroethyl) phosphate quencher: 1-5 parts, and curing chain extender: 0.3-2 parts. The addition of DMMP flame retardant improves the flame-retardant properties of TPU. Modification of DMMP by adding polycarbodiimide reduces the activity of phosphorus groups and ester groups, thus solving the problem of DMMP flame retardant promoting TPU degradation and hydrolysis. Adding TCEP to the hydrolysis-resistant DMMP rapidly extinguishes the TPU flame, causing it to drip without flame. The synergistic effect of the modified DMMP and the curing chain extender solid-state chain extension of TPU further enhances its hydrolysis resistance and wear resistance.

[0006] To address the problems of poor compatibility between flame retardants and the substrate and insufficient coating uniformity in existing technologies, a surface coating technology based on polyvinyl alcohol and using hydroxide and zinc borate as composite flame retardant fillers is proposed. By optimizing the formulation and process, the flame retardant and thermal insulation properties of rigid polyurethane foam are synergistically improved. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a rigid polyurethane foam based on a composite flame-retardant coating, its preparation method, and its application.

[0008] The technical solution provided by this invention is as follows:

[0009] A method for preparing rigid polyurethane foam based on a composite flame-retardant coating includes the following steps:

[0010] 1) Rigid polyurethane foam substrate was prepared using a one-step foaming method;

[0011] 2) Using an aqueous solution of polyvinyl alcohol as a base material, hydroxide, ceramicized flame retardant and expanded graphite are added to the base material as a composite flame retardant, and the mixture is stirred at high speed to form a slurry;

[0012] 3) The slurry is uniformly coated onto the surface of the rigid polyurethane foam substrate and cured at room temperature to form an intumescent flame-retardant coating, thereby obtaining the rigid polyurethane foam.

[0013] In the above technical solution:

[0014] The working principle of the composite flame retardant coating is as follows: the molten glassy substance produced after the ceramic flame retardant burns melts and bonds the alumina and expanded carbon layer produced by combustion. The carbon layer is dense and forms a hard, flame-retardant protective layer that prevents the flame from burning inward.

[0015] The resulting rigid polyurethane foam has a high flame retardancy rating and low thermal conductivity. The coating it forms is an intumescent ceramic carbon layer with a high oxygen index.

[0016] Specifically, in step 1): 50-70 parts of rigid foam polyether polyol, 30-50 parts of rigid foam polyester polyol, 0.5-1.2 parts of water, 1-5 parts of HFC-245fa blowing agent, 0.5-1.5 parts of catalyst, and 1-3 parts of foam stabilizer are mixed evenly. 70-90 parts of 4,4-diphenylmethane diisocyanate are added and mixed rapidly until the system turns white. The mixture is then quickly injected into a mold for curing. After curing and demolding, a rigid polyurethane foam substrate is obtained.

[0017] Preferably, the rigid foam polyether polyol has a hydroxyl value of 250-400 mg KOH / g and a functionality of 6.

[0018] Preferably, the rigid foam polyester polyol has a hydroxyl value of 150-250 mg KOH / g and a functionality of 2.

[0019] Preferably, the catalyst is one or a mixture of PC-41 (CAS No. 15875-13-5) and T12 (CAS No. 77-58-7).

[0020] Preferably, the foam stabilizer is one or a mixture of TEGOSTAB® B8547, TEGOSTAB® B8534, and TEGOSTAB® B8465.

[0021] Specifically, in step 2): Dissolve 9-11 g of PVA in 80-100 mL of deionized water and stir at 75-85 ℃ for 1-3 h to form a homogeneous solution.

[0022] Specifically, in step 2):

[0023] The hydroxide is one or a mixture of magnesium hydroxide and aluminum hydroxide;

[0024] The ceramicized flame retardant is a low-melting-point glass powder with a melting point of 400-600℃;

[0025] The expanded graphite has a particle size of 100-200 mesh and an expansion ratio of 150-250 ml / g;

[0026] The mass ratio of hydroxide, ceramicized flame retardant, and expanded graphite is (3-4):(2-3):(0.5-1);

[0027] The ratio of composite flame retardant to base material is 30-50 wt%.

[0028] Specifically, in step 3):

[0029] The curing time is 18-30 hours, preferably 24 hours;

[0030] The thickness of the composite flame-retardant coating is 1-2 mm, preferably 1.5 mm.

[0031] The present invention also provides a rigid polyurethane foam with a composite coating flame retardant, which is prepared by the preparation method described above.

[0032] Specifically, the oxygen index of the composite flame-retardant coating is ≥30%.

[0033] The present invention also provides the application of the rigid polyurethane foam as a flame-retardant and heat-insulating material for flame retardancy and heat insulation of special equipment or building exteriors.

[0034] The rigid polyurethane foam provided by this invention has a high flame retardant rating and low thermal conductivity, and the coating it forms is an intumescent char layer with a high oxygen index.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] 1) By using a composite coating method, the flame retardancy problem of rigid polyurethane foam can be solved with a lower amount of flame retardant, resulting in a lower system cost. At the same time, it solves the problem of the decline in the physical properties of rigid polyurethane foam caused by directly adding flame retardants to rigid polyurethane foam.

[0037] 2) The composite flame retardant using hydroxide, ceramicized flame retardant and expanded graphite has a highly efficient synergistic flame retardant effect. In the initial stage of combustion, hydroxide can absorb heat and decompose to generate refractory alumina; expanded graphite can expand into a dense carbon layer after combustion, preventing oxygen from entering the inner polyurethane layer; low melting point glass powder ceramicized flame retardant can melt and solidify into a molten glass state at the high temperature generated by combustion, bonding the alumina generated by the decomposition of hydroxide and the expanded carbon layer of expanded graphite into a dense ceramic layer, which quickly prevents the flame from burning into the inner layer. Detailed Implementation

[0038] The principles and features of the present invention are described below. The embodiments given are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0039] Unless otherwise specified, the test methods used in the embodiments are conventional methods; unless otherwise specified, the materials and reagents used are commercially available.

[0040] Aluminum hydroxide is sourced from Weifang Wanfeng New Material Technology Co., Ltd.

[0041] The ceramicized flame retardant is CFR-2 from Anhui Yishitong Materials Technology Co., Ltd.

[0042] Expanded graphite comes from Changyi Senhui New Materials Co., Ltd.

[0043] The rigid foam polyether polyol is WANOL® R2490 from Wanhua Chemical.

[0044] The rigid foam polyester polyol is XCPA-195 from Asahikawa Chemical.

[0045] The thermal conductivity tests of the examples and comparative examples were performed according to GB / T10294; the oxygen index tests were performed according to GB / T2406.2, wherein the rigid polyurethane foam corresponding to the oxygen index test strip has a size of "100mm long, 10mm wide, and 10mm thick". A flame-retardant coating of the corresponding thickness was applied to the rigid foam strip of this size and cured before the oxygen index was tested; the combustion performance tests were performed according to GB / T8333, wherein the rigid polyurethane foam corresponding to the flame-retardant strip has a size of "254mm long, 19mm wide, and 19mm thick". A flame-retardant coating of the corresponding thickness was applied to the rigid foam strip of this size and cured before the combustion performance was tested. The residual mass percentage and afterflame time of the sample after combustion were recorded respectively.

[0046] Example 1

[0047] 1) Preparation of rigid polyurethane foam matrix

[0048] The one-step foaming method is adopted: 60g WANOL®R2490, 40g XCPA-195, 1g water, 4 parts HFC-245fa foaming agent, 0.8g PC-41, 0.2g T12, and 2.2g TEGOSTAB® B8547 are mixed evenly, 81g 4,4-diphenylmethane diisocyanate (MDI) is added and stirred rapidly until the system turns white. The mixture is then quickly poured into a mold and cured for 24 hours. After demolding, a rigid polyurethane foam substrate is obtained.

[0049] 2) Formulation and application of flame-retardant coatings

[0050] Base material preparation: 10 g PVA was dissolved in 90 mL of water and stirred at 80 °C for 2 h to form a homogeneous solution;

[0051] Flame retardant compounding: Add 40 wt% of aluminum hydroxide / ceramicized flame retardant CFR-2 / expanded graphite composite filler (mass ratio 3.5:2.4:0.8) per 100 g of total solution weight, and stir at high speed to form a slurry;

[0052] Coating process: The slurry is uniformly coated on the surface of rigid polyurethane foam and cured at room temperature for 24 hours to form a composite flame-retardant coating with a thickness of 1.3 mm.

[0053] Performance testing:

[0054] Oxygen index: 30.5%.

[0055] The thermal conductivity is 0.018 W / m·K.

[0056] Combustion performance: 99.1% of the sample remains by mass, and the afterflame time is 1.5s.

[0057] Example 2

[0058] 1) Preparation of rigid polyurethane foam matrix

[0059] The one-step foaming method is adopted: 50g WANOL®R2490, 50g XCPA-195, 0.6g water, 4.5 parts HFC-245fa foaming agent, 0.6g PC-41, 0.3g T12, and 2.5g TEGOSTAB® B8465 are mixed evenly, 84g 4,4-diphenylmethane diisocyanate (MDI) is added and stirred rapidly until the system turns white. The mixture is then quickly poured into a mold and cured for 24 hours. After demolding, a rigid polyurethane foam substrate is obtained.

[0060] 2) Formulation and application of flame-retardant coatings

[0061] Base material preparation: 10 g PVA was dissolved in 90 mL of water and stirred at 80 °C for 2 h to form a homogeneous solution;

[0062] Flame retardant compounding: Add 48 wt% of aluminum hydroxide / ceramicized flame retardant CFR-2 / expanded graphite composite filler (mass ratio 3.3:2.8:0.9) per 100 g of total solution weight, and stir at high speed to form a slurry;

[0063] Coating process: The slurry is uniformly coated on the surface of rigid polyurethane foam and cured at room temperature for 24 hours to form a composite flame-retardant coating with a thickness of 1.2 mm.

[0064] Performance testing:

[0065] Oxygen index: 31.4%.

[0066] The thermal conductivity is 0.017 W / m·K.

[0067] Combustion performance: 99.5% of the sample remains by mass, and the afterflame time is 1.2s.

[0068] Example 3

[0069] 1) Preparation of rigid polyurethane foam matrix

[0070] The one-step foaming method is adopted: 55g WANOL®R2490, 45g XCP-195, 1g water, 3.9 parts HFC-245fa foaming agent, 1.0g PC-41, 0.4g T12, and 2.7g TEGOSTAB® B8534 are mixed evenly, 89g 4,4-diphenylmethane diisocyanate (MDI) is added and stirred rapidly until the system turns white. The mixture is then quickly poured into a mold and cured for 24 hours. After demolding, a rigid polyurethane foam substrate is obtained.

[0071] 2) Formulation and application of flame-retardant coatings

[0072] Base material preparation: 10 g PVA was dissolved in 90 mL of water and stirred at 80 °C for 2 h to form a homogeneous solution;

[0073] Flame retardant compounding: Add 38wt% of aluminum hydroxide / ceramicized flame retardant CFR-2 / expanded graphite composite filler (mass ratio 3.7:2.4:0.8) per 100 g of total solution weight, and stir at high speed to form a slurry;

[0074] Coating process: The slurry is uniformly coated on the surface of rigid polyurethane foam and cured at room temperature for 24 hours to form a composite flame-retardant coating with a thickness of 1.4 mm.

[0075] Performance testing:

[0076] Oxygen index: 29.3%.

[0077] The thermal conductivity is 0.021 W / m·K.

[0078] Combustion performance: 99.3% of the sample remains by mass, and the afterflame time is 1.3s.

[0079] Comparative Example 1

[0080] Comparative Example 1 is based on Example 1, but with the composite flame-retardant coating without the ceramic flame retardant.

[0081] 1) Preparation of rigid polyurethane foam matrix

[0082] The one-step foaming method is adopted: 60g WANOL®R2490, 40g XCPA-195, 1g water, 4 parts HFC-245fa foaming agent, 0.8g PC-41, 0.2g T12, and 2.2g TEGOSTAB® B8547 are mixed evenly, 81g 4,4-diphenylmethane diisocyanate (MDI) is added and stirred rapidly until the system turns white. The mixture is then quickly poured into a mold and cured for 24 hours. After demolding, a rigid polyurethane foam substrate is obtained.

[0083] 2) Formulation and application of flame-retardant coatings

[0084] Base material preparation: 10 g PVA was dissolved in 90 mL of water and stirred at 80 °C for 2 h to form a homogeneous solution;

[0085] Flame retardant compounding: Add 40 wt% aluminum hydroxide / expanded graphite composite filler (mass ratio 3.5:0.8) per 100 g of total solution weight, and stir at high speed to form a slurry;

[0086] Coating process: The slurry is uniformly coated on the surface of rigid polyurethane foam and cured at room temperature for 24 hours to form a composite flame-retardant coating with a thickness of 1.3 mm.

[0087] Performance testing:

[0088] Oxygen index: 26.4%.

[0089] The thermal conductivity is 0.018 W / m·K.

[0090] Combustion performance: 92.4% of the sample remains by mass, and the afterflame time is 5.2 s.

[0091] Comparative Example 2

[0092] Comparative Example 2 is based on Example 2, but with the expanded graphite removed from the composite flame-retardant coating.

[0093] 1) Preparation of rigid polyurethane foam matrix

[0094] The one-step foaming method is adopted: 50g WANOL®R2490, 50g XCPA-195, 0.6g water, 4.5 parts HFC-245fa foaming agent, 0.6g PC-41, 0.3g T12, and 2.5g TEGOSTAB® B8465 are mixed evenly, 84g 4,4-diphenylmethane diisocyanate (MDI) is added and stirred rapidly until the system turns white. The mixture is then quickly poured into a mold and cured for 24 hours. After demolding, a rigid polyurethane foam substrate is obtained.

[0095] 2) Formulation and application of flame-retardant coatings

[0096] Base material preparation: 10 g PVA was dissolved in 90 mL of water and stirred at 80 °C for 2 h to form a homogeneous solution;

[0097] Flame retardant compounding: Add 48 wt% aluminum hydroxide / ceramicized flame retardant CFR-2 composite filler (mass ratio 3.3:2.8) per 100 g of total solution weight, and stir at high speed to form a slurry;

[0098] Coating process: The slurry is uniformly coated on the surface of rigid polyurethane foam and cured at room temperature for 24 hours to form a composite flame-retardant coating with a thickness of 1.2 mm.

[0099] Performance testing:

[0100] Oxygen index: 23.5%.

[0101] The thermal conductivity is 0.018 W / m·K.

[0102] Combustion performance: The residual mass percentage of the sample was 61.6%, and the afterflame time was 9.7s.

[0103] Based on the results of the examples and comparative examples, the composite flame-retardant coated rigid polyurethane foam prepared in Examples 1-3 has a high oxygen index, good flame-retardant performance, and the thermal conductivity of the material meets the application requirements. In Comparative Example 1, due to the lack of low-melting-point glass powder ceramicized flame retardant in the coating, the coating cannot melt and bond the alumina and expanded carbon layer produced during combustion due to the lack of molten glassy substances generated after the ceramicized flame retardant combustion. The carbon layer is loose and cannot form a hard protective layer, thus failing to prevent the flame from burning inward. In Comparative Example 2, due to the lack of expanded graphite, only a very thin molten glassy alumina layer can be generated during combustion, which cannot quickly generate a sufficiently thick and dense carbon layer, and therefore cannot prevent the flame from burning inward.

[0104] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A process for the production of rigid polyurethane foam based on a composite flame-retardant coating, characterized in that, The method comprises the following steps: 1) preparing a rigid polyurethane foam substrate by one-step foaming method; 2) using an aqueous solution of polyvinyl alcohol as a base, adding hydroxide, ceramic flame retardant and expanded graphite as a composite flame retardant to the base, and stirring at high speed to form a slurry; 3) uniformly coating the slurry on the surface of the rigid polyurethane foam substrate, curing at room temperature to form an intumescent flame-retardant coating, and obtaining the rigid polyurethane foam.

2. The method of producing rigid polyurethane foam based on a composite flame-retardant coating according to claim 1, characterized in that, In step 1), 50-70 parts of rigid foam polyether polyol, 30-50 parts of rigid foam polyester polyol, 0.5-1.2 parts of water, 1-5 parts of HFC-245fa foaming agent, 0.5-1.5 parts of catalyst, and 1-3 parts of foam stabilizer are uniformly mixed, 70-90 parts of 4,4-diphenyl methane diisocyanate is quickly mixed until the system turns white, and then quickly injected into a mold for curing, and after demolding, a rigid polyurethane foam substrate is obtained; The rigid foam polyether polyol has a hydroxyl value of 250-400 mgKOH / g and a functionality of 6; The rigid foam polyester polyol has a hydroxyl value of 150-250 mgKOH / g and a functionality of 2; The catalyst is one of PC-41 or T12 or a mixture of the two; The foam stabilizer is one or a mixture of more than one of TEGOSTAB® B8547, TEGOSTAB® B8534 or TEGOSTAB® B8465.

3. The method of making rigid polyurethane foam based on a composite flame- retardant coating according to claim 1, characterized in that, In step 2), 9-11 g of PVA is dissolved in 80-100 mL of deionized water, and stirred at 75-85 ℃ for 1-3 h to form a homogeneous solution.

4. The method of making rigid polyurethane foam based on a composite flame- retardant coating according to claim 1, characterized in that, In step 2): The hydroxide is one of magnesium hydroxide or aluminum hydroxide or a mixture of the two, and has a particle size of 3000-5000 mesh; The ceramic flame retardant is a low-melting-point glass powder with a melting point of 400-600 ℃; The expanded graphite has a particle size of 100-200 mesh and an expansion ratio of 150-250 ml / g; The mass ratio of hydroxide, ceramic flame retardant and expanded graphite is (3-4):(2-3):(0.5-1); The use amount ratio of the composite flame retardant to the base is 30-50 wt%.

5. The method of making rigid polyurethane foam based on a composite flame- retardant coating according to claim 1, characterized in that, In step 3): The curing time is 18-30 h; The thickness of the composite flame-retardant coating is 1-2 mm.

6. A rigid polyurethane foam based on a composite flame-retardant coating, characterized by: Prepared according to the preparation method of any one of claims 1 to 5.

7. The rigid polyurethane foam based on a composite flame-retardant coating according to claim 6, characterized in that: The oxygen index of the composite flame-retardant coating is ≥30%.

8. Use of a rigid polyurethane foam based on a composite flame-retardant coating according to claim 6 or 7, characterized in that: As a flame-retardant and thermal-insulating material.

9. Use of rigid polyurethane foam based on a composite flame-retardant coating according to claim 8, characterized in that: As a flame-retardant and thermal-insulating material for special equipment or buildings.