Bio-based polyurethane flame-retardant structural adhesive for rail transit and preparation method of bio-based polyurethane flame-retardant structural adhesive

Abstract

The invention discloses a bio-based polyurethane flame-retardant structural adhesive for rail transit and a preparation method thereof. The structural adhesive is prepared from a first component and a second component, wherein the first component comprises bio-based polyol, an organic-inorganic flame-retardant compound, a rare earth flame-retardant synergist, a chain extender, a coupling agent, a water removal agent, a defoaming agent, an adhesion promoter, a stabilizer and a catalyst, and the second component is isocyanate. The water resistance of the polyurethane is improved by adopting the hydrophobic bio-based polyol, and meanwhile, the organic and inorganic flame-retardant compound and the rare earth flame-retardant synergist are adopted to enable the polyurethane to form a non-combustible inorganic protective layer under the condition of high temperature or fire, so that the physical and mechanical properties of the material are improved; in addition, the polyurethane structural adhesive is endowed with excellent flame retardance and thermal stability. The bio-based polyurethane flame-retardant structural adhesive for rail transit has the advantages of high strength, good flame retardance, low smoke amount, wide application range and the like.

Description

Technical Field

[0001] The invention relates to the field of adhesives, and in particular to a bio-based polyurethane flame-retardant structural adhesive for rail transportation and a preparation method thereof. Background Art

[0002] Lightweight structure is the development trend of rail vehicle structure, which can reduce the weight of the vehicle body, thereby reducing vehicle energy consumption and achieving efficient power output. In modern trains, more and more components and parts are made of lightweight materials (such as fiber composite materials, plastics, foam materials, light metals or hybrid materials). When using lightweight materials, many traditional connection methods (such as bolting, riveting or welding) are not applicable, especially when using hybrid materials composed of multiple lightweight materials. This effect will be prominent. Innovative adhesive systems can precisely meet the requirements of various connections and provide a promising solution for the application of lightweight materials. Adhesives can firmly bond lightweight materials and traditional materials (such as steel or aluminum), and the resulting connections can withstand high loads. The average service life of rail vehicles is about 30 years, which places special requirements on the durability of adhesives; due to manufacturing technology, only cold-curing adhesives can be used, which must adapt to the high shear stress, peel stress and alternating stress in the railway field. With the increasing attention paid to carbon emissions internationally, the application fields of bio-based materials are becoming more and more extensive.

[0003] The rail transit field has strict requirements on the flame retardancy and smoke generation of materials. The use of inorganic flame retardants with less smoke generation and good thermal insulation performance is more effective. Patent CN107955576B discloses a high-strength flame-retardant polyurethane structural adhesive for high-speed rail passenger cars and a preparation method thereof. It uses a reactive phosphorus-based flame retardant dihydroxyethyl phosphate as a flame retardant component. Since the phosphorus-based flame retardant has low flame retardant efficiency and large smoke generation, it is difficult to meet the flame retardant standards for rail passenger cars. Patent CN104694068B discloses a halogen-free flame retardant two-component polyurethane adhesive for rail passenger cars and a preparation method thereof. It uses a low molecular weight phosphate flame retardant plasticizer and magnesium hydroxide and aluminum hydroxide inorganic flame retardants. The flame retardant grade reaches the FV-0 level, which can only meet the flame retardant level of indoor building interiors, and cannot meet the flame retardant requirements of materials in the rail transit field. Summary of the invention

[0004] The invention relates to the field of adhesives, and in particular to a bio-based polyurethane flame retardant structural adhesive for rail transit and a preparation method thereof, which solves the flame retardancy and smoke generation problems of the polyurethane structural adhesive for rail transit and contributes to the low carbon emission requirements of the material.

[0005] The technical solution of the present invention is as follows:

[0006] A bio-based polyurethane flame-retardant structural adhesive for rail transit and a preparation method thereof, characterized in that it is made of a first component and a second component as raw materials;

[0007] The first component includes the following components by mass: 100 parts of bio-based polyol, 10-20 parts of flame retardant compound, 1-5 parts of chain extender, 1-5 parts of rare earth flame retardant synergist, 0.2-2 parts of coupling agent, 1-5 parts of dehydrating agent, 1-5 parts of stabilizer, and 0.01-0.2 parts of catalyst;

[0008] The second component is isocyanate;

[0009] The second component is mixed with the first component at a molar ratio of NCO / OH=1.1-1.3:1.

[0010] The bio-based polyurethane flame-retardant structural adhesive for rail transit is characterized in that the bio-based polyol is a polyol prepared using castor oil or soybean oil as raw material.

[0011] The flame retardant composite comprises low melting point glass and at least one of triazine flame retardants, boron nitride and aluminum hypophosphite; the rare earth flame retardant synergist comprises rare earth metal oxide or rare earth metal complex, and the rare earth element is at least one of lanthanum or cerium.

[0012] The chain extender is selected from any one of 1,4-butanediol, glycerol, trimethylolpropane and sorbitol.

[0013] The coupling agent is any one of the silane coupling agents KH-560 and KH-550.

[0014] The dehydrating agent is any one of a liquid dehydrating agent and a solid dehydrating agent. The liquid dehydrating agent is Additive OF or Additive TI, and the solid dehydrating agent is calcium oxide or molecular sieve.

[0015] The stabilizer is one or a mixture of benzotriazole light stabilizers, salicylate light stabilizers, benzophenone light stabilizers, hindered amine light stabilizers, free radical chain blocking antioxidants and peroxide decomposition antioxidants.

[0016] The catalyst is an organic metal catalyst or a tertiary amine catalyst. The organic metal catalyst is one of dibutyltin dilaurate, stannous octoate and tetraisopropyl titanate; the tertiary amine catalyst is one of triethanolamine, triethylamine and triethylenetriamine.

[0017] The isocyanate is a mixture of polymeric isocyanate and isocyanate monomers, wherein the weight fraction ratio of polymeric isocyanate polymethylene polyphenyl polyisocyanate (P-MDI) to isocyanate monomer diphenylmethane diisocyanate (MDI) is 30:70-70:30.

[0018] A method for preparing a bio-based polyurethane flame-retardant structural adhesive for rail transit, the method comprising the following steps:

[0019] Step 1: drying a certain weight portion of the flame retardant composite and the rare earth flame retardant synergist in a vacuum oven at 110-120° C. for 4 hours, fully stirring and mixing with the coupling agent in proportion after cooling to room temperature, and then drying at 60-90° C. for 2-3 hours to obtain a coupling agent-modified flame retardant composite and a rare earth flame retardant synergist mixture;

[0020] Step 2: adding a certain weight portion of bio-based polyol and chain extender into a reaction kettle in proportion and heating to 100-120° C., stirring and dehydrating, and then cooling to below 60° C., and stirring and mixing with the coupling agent-modified flame retardant composite and rare earth flame retardant synergist mixture, dehydrating agent, stabilizer, and catalyst prepared in step 1 to obtain a first component;

[0021] Step 3: Mix the second component isocyanate with the first component obtained in step 2 at a molar ratio of NCO / OH=1.1~1.3:1 to obtain a bio-based polyurethane flame retardant structural adhesive.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following advantages:

[0023] 1. The present invention uses hydrophobic bio-based polyols to improve the water resistance and adhesion of polyurethane to substrates, and at the same time uses low-carbon and environmentally friendly materials to improve the competitiveness of rail transit products.

[0024] 2. The present invention adopts flame retardant composite and rare earth flame retardant synergist to enable polyurethane to form a non-combustible inorganic protective layer under high temperature or fire conditions, low melting point glass and not only improve the physical and mechanical properties of the material, but also endow the polyurethane structural adhesive with excellent flame retardancy and thermal stability through the flame retardant rare earth synergist, especially reducing the smoke emission, which is of great value to the safety of rail transit.

[0025] The bio-based polyurethane flame-retardant structural adhesive for rail transit described in the present invention has the advantages of high strength, good flame retardancy, low smoke emission, wide application range, etc. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution of the present invention will be clearly and completely described in conjunction with specific embodiments below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. The following embodiments are only used to illustrate the present invention and are not used to limit the scope of protection of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0028] Example

[0029] Example 1

[0030] 15 parts by weight of a flame retardant composite, including 6 parts by weight of low-melting glass SiO2-B2O3-TiO2, melting temperature 570-850°C, 1500 mesh), 5 parts by weight of aluminum hypophosphite, 4 parts by weight of triazine macromolecular carbon-forming foaming agent CFA935 (particle size 10-17 microns, decomposition temperature 280°C) and 1 part by weight of a rare earth flame retardant synergist (cerium oxide), are dried in a vacuum oven at 110°C for 4 hours, cooled to room temperature, and then fully stirred and mixed with 1.0 part by weight of a silane coupling agent KH560, and then dried at 80°C for 2 hours to obtain a coupling agent-modified flame retardant composite and a rare earth flame retardant synergist mixture;

[0031] 100 parts by weight of bio-based polyol (hydroxyl value of 170 mgKOH / g, derived from castor oil) and 3 parts by weight of chain extender (trimethylolpropane) are added into a reactor and heated to 110°C, vacuum dehydrated for 2 hours, and then cooled to 60°C, 15 parts by weight of coupling agent-modified flame retardant composite and rare earth flame retardant synergist, 3 parts by weight of dehydrating agent (Additive OF), 3 parts by weight of stabilizer (1.5 parts of Irganox1010, 1.5 parts of Tinuvin327), and 0.03 parts by weight of catalyst (triethylenetriamine) are stirred and mixed uniformly to obtain a first component;

[0032] The second component isocyanate (a mixture of Wanhua PM-200 and MDI-100LL in a ratio of 1:1 by weight) is mixed with the first component at a molar ratio of NCO / OH=1.2 to obtain a bio-based polyurethane flame retardant structural adhesive.

[0033] The adhesive was cured to prepare the specimens for mechanical and flame retardant property tests. The adhesive was used to bond aramid honeycomb / aluminum plates for composite rail transit and the peel strength was tested.

[0034] Example 2

[0035] 20 parts by weight of a flame retardant composite, including 8 parts by weight of low-melting glass SiO2-B2O3-TiO2, melting temperature 570-850°C, 1500 mesh), 6 parts by weight of aluminum hypophosphite, 6 parts by weight of triazine macromolecular carbon-forming foaming agent CFA935 (particle size 10-17 microns, decomposition temperature 280°C) and 2 parts by weight of a rare earth flame retardant synergist (lanthanum oxide) are dried in a vacuum oven at 110°C for 4 hours, cooled to room temperature, and then fully stirred and mixed with 1.5 parts by weight of a silane coupling agent KH~550, and then dried at 80°C for 2 hours to obtain a coupling agent-modified flame retardant composite and a rare earth flame retardant synergist;

[0036] 100 parts by weight of bio-based polyol (hydroxyl value of 120 mgKOH / g, derived from soybean oil) and 3 parts by weight of chain extender (trimethylolpropane) were added into a reactor and heated to 110°C, vacuum dehydrated for 2 hours, and then cooled to 60°C, 20 parts by weight of coupling agent modified flame retardant composite and rare earth flame retardant synergist, 3 parts by weight of dehydrating agent (Additive OF), 3 parts by weight of stabilizer (1.5 parts of Irganox1010, 1.5 parts of Tinuvin327), and 0.05 parts by weight of catalyst (dibutyltin dilaurate) were stirred and mixed uniformly to obtain a first component;

[0037] The second component isocyanate (a mixture of Wanhua PM-200 and MDI-100LL in a ratio of 1.5:1 by weight) is mixed with the first component at a molar ratio of NCO / OH=1.25 to obtain a bio-based polyurethane flame retardant structural adhesive.

[0038] The adhesive was cured to prepare the specimens for mechanical and flame retardant property tests. The adhesive was used to bond aluminum honeycomb / aluminum plate for composite rail transit and the peel strength was tested.

[0039] Example 3

[0040] 15 parts by weight of a flame retardant composite, including 6 parts by weight of low-melting glass SiO2-B2O3-Al2O3, melting temperature 650-900°C, 1500 mesh), 6 parts by weight of aluminum hypophosphite, 3 parts by weight of triazine macromolecular carbon-forming foaming agent CFA935 (particle size 10-17 microns, decomposition temperature 280°C) and 2 parts by weight of a rare earth flame retardant synergist (lanthanum oxide) are dried in a vacuum oven at 110°C for 4 hours, cooled to room temperature, and then fully stirred and mixed with 1.5 parts by weight of a silane coupling agent KH-560, and then dried at 80°C for 2 hours to obtain a coupling agent-modified flame retardant composite and a rare earth flame retardant synergist;

[0041] 100 parts by weight of bio-based polyol (hydroxyl value of 120 mgKOH / g, derived from soybean oil) and 3 parts by weight of chain extender (trimethylolpropane) were added into a reactor and heated to 110°C, vacuum dehydrated for 2 hours, and then cooled to 60°C, 15 parts by weight of coupling agent modified flame retardant composite and rare earth flame retardant synergist, 3 parts by weight of dehydrating agent (3A molecular sieve), 3 parts by weight of stabilizer (1.5 parts of Irganox1010, 1.5 parts of Tinuvin327), 0.05 parts by weight of catalyst (dibutyltin dilaurate) were stirred and mixed uniformly to obtain a first component;

[0042] The second component isocyanate (a mixture of Wanhua PM-200 and MDI-100LL in a ratio of 1:1 by weight) is mixed with the first component at a molar ratio of NCO / OH=1.20 to obtain a bio-based polyurethane flame retardant structural adhesive.

[0043] The adhesive was cured to prepare the specimens for mechanical and flame retardant property tests. The adhesive was used to bond aluminum honeycomb / aluminum plate for composite rail transit and the peel strength was tested.

[0044] Comparative Example 1

[0045] 100 parts by weight of bio-based polyol (hydroxyl value of 120 mgKOH / g, derived from soybean oil) and 3 parts by weight of chain extender (trimethylolpropane) were added into a reactor and heated to 110°C, vacuum dehydrated for 2 hours, then cooled to 60°C, 3 parts by weight of dehydrating agent (Additive OF), 3 parts by weight of stabilizer (1.5 parts of Irganox1010, 1.5 parts of Tinuvin327), and 0.05 parts by weight of catalyst (dibutyltin dilaurate) were stirred and mixed to obtain a first component;

[0046] The second component isocyanate (a mixture of Wanhua PM-200 and MDI-100LL in a ratio of 1:1 by weight) is mixed with the first component at a molar ratio of NCO / OH=1.20 to obtain a bio-based polyurethane structural adhesive.

[0047] The adhesive was cured to prepare the specimens for mechanical and flame retardant property tests. The adhesive was used to bond aluminum honeycomb / aluminum plate for composite rail transit and the peel strength was tested.

[0048] Comparative Example 2

[0049] 15 parts by weight of a flame retardant composite, including 6 parts by weight of low-melting glass SiO2-B2O3-Al2O3, melting temperature 650-900°C, 1500 mesh), 6 parts by weight of aluminum hypophosphite, and 3 parts by weight of a triazine macromolecular carbon-forming foaming agent CFA935 (particle size 10-17 microns, decomposition temperature 280°C) are dried in a vacuum oven at 110°C for 4 hours, cooled to room temperature, and then fully stirred and mixed with 1.5 parts by weight of a silane coupling agent KH-550, and then dried at 80°C for 2 hours to obtain a coupling agent-modified flame retardant composite and a rare earth flame retardant synergist;

[0050] 100 parts by weight of bio-based polyol (hydroxyl value of 120 mgKOH / g, derived from soybean oil) and 3 parts by weight of chain extender (trimethylolpropane) were added into a reactor and heated to 110°C, vacuum dehydrated for 2 hours, and then cooled to 60°C, 15 parts by weight of coupling agent modified flame retardant composite, 3 parts by weight of dehydrating agent (Additive OF), 3 parts by weight of stabilizer (1.5 parts of Irganox1010, 1.5 parts of Tinuvin327), and 0.05 parts by weight of catalyst (dibutyltin dilaurate) were stirred and mixed uniformly to obtain a first component;

[0051] The second component isocyanate (a mixture of Wanhua PM-200 and MDI-100LL in a ratio of 1:1 by weight) is mixed with the first component at a molar ratio of NCO / OH=1.20 to obtain a bio-based polyurethane flame retardant structural adhesive.

[0052] The adhesive was cured to prepare the specimens for mechanical and flame retardant property tests. The adhesive was used to bond aramid honeycomb / aluminum plates for composite rail transit and the peel strength was tested.

[0053] Performance Testing:

[0054] The shear strength is tested in accordance with GB / T 7124-2008 Determination of tensile shear strength of adhesives; the tensile strength and elongation at break are tested in accordance with GB / T 1040.3-2006 Test method for tensile properties of plastics; the flame retardancy is tested in accordance with TB / T3237-2010 Technical conditions for flame retardant interior materials for EMUs, GB / T2406.2-2009 Determination of combustion behavior of plastics by oxygen index method Part 2: Room temperature test, GB / T8323.2-2008 Plastics Smoke Generation Part 2: Single Chamber Test Method for Determination of Smoke Density and UIC564-2-1991 Fire Prevention and Firefighting Rules for Railway Passenger Cars or Similar Vehicles for International Combined Use.

[0055] The performances of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.

[0056] Table 1

[0057]

[0058] It can be seen from the examples, comparative examples and performance analysis in Table 1 that the present invention provides a bio-based polyurethane flame retardant structural adhesive for rail transit and a preparation method thereof, and the prepared polyurethane flame retardant structural adhesive has good mechanical properties and bonding strength, and high flame retardant performance, reaching Class A standards, and the limiting oxygen index is above 30. At the same time, due to the use of flame retardant composites and rare earth flame retardant synergists, the smoke density of the structure is very low, which fully meets the flame retardant technical requirements for interior materials for rail transit EMUs. In the comparative examples, there is no flame retardant effect without adding flame retardants and rare earth synergists, and the flame retardant effect of the structural adhesive with only flame retardants is poor, which cannot meet the flame retardant requirements of rail transit.

[0059] The above embodiments are only used to help understand the product, method and core concept of the present invention. It should be noted that, for ordinary technicians in this technical field, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the scope of protection of the claims of the present invention.

[0060] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A bio-based polyurethane flame retardant structural adhesive for rail transit, characterized in that: It is made of a first component and a second component as raw materials; The first component includes the following raw materials by mass: 100 parts of bio-based polyol, 10-20 parts of flame retardant compound, 1-5 parts of chain extender, 1-5 parts of rare earth flame retardant synergist, 0.2-2 parts of coupling agent, 1-5 parts of dehydrating agent, 1-5 parts of stabilizer, and 0.01-0.2 parts of catalyst; The second component is isocyanate; The second component is prepared by mixing and reacting with the first component according to a molar ratio of isocyanate functional group to hydroxyl functional group of NCO / OH = 1.1-1.3:

1.

2. The bio-based polyurethane flame retardant structural adhesive for rail transit according to claim 1, characterized in that: The bio-based polyol is a bio-based polyol prepared by using castor oil or soybean oil as a raw material.

3. The bio-based polyurethane flame retardant structural adhesive for rail transit according to claim 1, characterized in that: The flame retardant composite comprises low melting point glass and at least one of triazine flame retardants, boron nitride and aluminum hypophosphite; the rare earth flame retardant synergist comprises rare earth metal oxide or rare earth metal complex, and the rare earth element is at least one of lanthanum or cerium.

4. The bio-based polyurethane flame retardant structural adhesive for rail transit according to claim 1, characterized in that: The chain extender is selected from any one of 1,4-butanediol, glycerol, trimethylolpropane and sorbitol.

5. The bio-based polyurethane flame retardant structural adhesive for rail transit according to claim 1, characterized in that: The coupling agent is any one of the silane coupling agents KH560 and KH550.

6. The bio-based polyurethane flame retardant structural adhesive for rail transit according to claim 1, characterized in that: The dehydrating agent is any one of a liquid dehydrating agent and a solid dehydrating agent. The liquid dehydrating agent is Additive OF or Additive TI, and the solid dehydrating agent is calcium oxide or molecular sieve.

7. The bio-based polyurethane flame retardant structural adhesive for rail transit according to claim 1, characterized in that: The stabilizer is one or a mixture of benzotriazole light stabilizers, salicylate light stabilizers, benzophenone light stabilizers, hindered amine light stabilizers, free radical chain blocking antioxidants and peroxide decomposition antioxidants.

8. The bio-based polyurethane flame retardant structural adhesive for rail transit according to claim 1, characterized in that: The catalyst is an organic metal catalyst or a tertiary amine catalyst. The organic metal catalyst is one of dibutyltin dilaurate, stannous octoate and tetraisopropyl titanate; the tertiary amine catalyst is one of triethanolamine, triethylamine and triethylenetriamine.

9. The bio-based polyurethane flame retardant structural adhesive for rail transit according to claim 1, characterized in that: The isocyanate is a mixture of polymeric isocyanate and isocyanate monomers, wherein the weight fraction ratio of polymeric isocyanate polymethylene polyphenyl polyisocyanate (P-MDI) to isocyanate monomer diphenylmethane diisocyanate (MDI) is 30:70-70:

30.

10. The method for preparing a bio-based polyurethane flame-retardant structural adhesive for rail transit according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: Step 1: drying a certain weight portion of the flame retardant composite and the rare earth flame retardant synergist in a vacuum oven at 110-120° C. for 4 hours, cooling to room temperature, and then stirring and mixing with the coupling agent in proportion, and then drying at 60-90° C. for 2-3 hours to obtain a coupling agent-modified flame retardant composite and a rare earth flame retardant synergist mixture; Step 2: adding a certain weight portion of bio-based polyol and chain extender into a reaction kettle in proportion and heating to 100-120° C., stirring and dehydrating, and then cooling to below 60° C., and stirring and mixing with the coupling agent-modified flame retardant composite and rare earth flame retardant synergist mixture, dehydrating agent, stabilizer, and catalyst prepared in step 1 to obtain a first component; Step 3: Mix the second component isocyanate with the first component obtained in step 2 at a molar ratio of NCO / OH=1.1~1.3:1 to obtain a bio-based polyurethane flame retardant structural adhesive.

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