Bi-component bio-based flame-retardant polyurethane pouring sealant and preparation method thereof

Abstract

The invention belongs to the technical field of polyurethane adhesives, and particularly relates to a bi-component bio-based flame-retardant polyurethane pouring sealant and a preparation method thereof. The polyurethane adhesive is composed of a component A and a component B, and the molar ratio of hydroxyl in the component A to isocyanate groups in the component B is 1: (1-1.05); wherein the component A is prepared from the following raw materials in parts by weight: 44 to 55 parts of bio-based polyol I; 44 to 55 parts of bio-based polyol II; 1-2 parts of a cross-linking agent; 0.1 to 0.5 part of a catalyst; 1.0 to 3.0 parts of a defoaming agent; 0.1 to 0.5 part of a silane coupling agent; 0.5 to 1.0 part of a water removal agent; and the component B is modified isocyanate. According to the pouring sealant component A, bio-based raw materials such as castor oil and the like are synthesized into polyhydric alcohol with a comb-shaped structure, so that the hydrophobicity and the adhesion are improved; in the component B, nitrogen and phosphorus flame-retardant elements are introduced into modified isocyanate, so that intrinsic flame retardance is realized.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polyurethane adhesives, and particularly relates to a two-component bio-based flame-retardant polyurethane pouring sealant and a preparation method thereof. BACKGROUND

[0002] Pouring sealant is a key protective material for electronic components and precision equipment. Currently, the main products on the market mainly include three categories: epoxy resin pouring sealant, polyurethane pouring sealant and silicone pouring sealant. From the perspective of raw material supply, the core components of the above-mentioned traditional pouring sealants are mostly derived from the petrochemical industry chain, relying on non-renewable fossil resources. Not only are they significantly affected by fluctuations in crude oil prices, but they are also difficult to naturally degrade after being discarded. In the field of performance optimization, flame retardancy is one of the core performance indicators of pouring sealants. The existing technical solutions still mainly use additive flame retardants as the main implementation path, specifically by mixing inorganic flame retardants (such as magnesium hydroxide and aluminum hydroxide) or organic flame retardants (such as bromine-based and phosphorus-based compounds) into the matrix to improve the flame retardant effect. However, this technical route has inherent defects: on the one hand, flame retardants are prone to cause long-term flame retardant performance degradation of materials due to molecular migration, and even to contaminate surrounding components; on the other hand, a large amount of added flame retardants often damage the molecular chain structure of the matrix, thereby causing problems such as a decrease in mechanical strength, a deterioration in dielectric properties, and a deterioration in processing fluidity, which seriously restricts the promotion of pouring sealants in high-end application scenarios such as new energy vehicle electronics and aerospace precision devices.

[0003] Chinese Patent CN120118266A discloses a bio-based ultra-low water vapor transmission rate two-component polyurethane and a preparation method thereof. The bio-based raw material used is mainly modified castor oil, the bio-based proportion is low, and the biodegradability of the material is not explicitly shown. Chinese Patent CN120795858A discloses a bio-based two-component polyurethane transparent flame-retardant pouring sealant, a preparation method and application thereof. The material flame retardant performance is improved by adding phosphate ester flame retardants. The bio-based raw material used is mainly unmodified polyols such as castor oil and soybean oil, which have high acid value and high free fatty acid content, and will adversely affect the catalytic activity of the catalyst.

[0004] In order to break through the bottleneck of dependence on fossil resources and lack of environmental protection, the industry has gradually carried out research and development of bio-based pouring sealants. However, the related technology that takes into account flame retardant properties is still in its infancy, and a mature industrialization scheme has not yet been formed. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application aims to provide a two-component bio-based flame-retardant polyurethane pouring sealant, the A component of which uses bio-based raw materials such as castor oil, xylitol and amino acid as a starter to synthesize a polyol containing a bio-based segment; the polyol forms a comb structure by polymerization of epoxy hexane, which can improve the hydrophobicity and adhesion of the material; the B component introduces nitrogen and phosphorus flame-retardant elements into the molecular structure of modified isocyanate through a polymerization process, achieving intrinsic flame retardation, avoiding the problems of migration of flame retardants and hydrolysis of phosphorus-containing polyols, and improving the biodegradability of the material by introducing bio-based isocyanate. The finally obtained pouring sealant has excellent flame retardancy, hydrophobicity, adhesion and environmental friendliness.

[0006] Another object of the present application is to provide a preparation method of the two-component bio-based flame-retardant polyurethane pouring sealant.

[0007] The technical scheme adopted by the present application is as follows: The two-component bio-based flame-retardant polyurethane pouring sealant comprises A component and B component, and the molar ratio of hydroxyl groups in the A component to isocyanate groups in the B component is 1:(1-1.05); wherein the A component comprises the following raw materials in parts by weight: Bio-based polyol I: 44-55 parts; Bio-based polyol II: 44-55 parts; Crosslinking agent: 1-2 parts; Catalyst: 0.1-0.5 parts; Defoaming agent: 1.0-3.0 parts; Silane coupling agent: 0.1-0.5 parts; Water removal agent: 0.5-1.0 parts; The B component is modified isocyanate; The starter of the bio-based polyol I is amino acid, and the hydroxyl value is 278-282 mgKOH / g; The starter of the bio-based polyol II is castor oil and xylitol, and the hydroxyl value is 135-145 mgKOH / g; The modified isocyanate is prepared from a phosphorus-containing polyol, a flame retardant and a bio-based isocyanate.

[0008] The preparation method of the bio-based polyol I comprises the following steps: using amino acid as a starter, and catalyzing the polymerization reaction of epoxy hexane under the action of a phosphazene salt catalyst to obtain the bio-based polyol I; The amount of the phosphazene salt catalyst in the bio-based polyol I is 0.15-0.20 wt.% of the total amount of the starter and epoxy hexane.

[0009] The amino acid is alanine, which can be prepared by natural protein hydrolysis, microbial fermentation and the like, and is widely available.

[0010] The preparation method of the bio-based polyol II comprises the following steps: using castor oil and xylitol as starting agents in a molar ratio of 4.0: (0.9-1.1), and using phosphazene salt as a catalyst to catalyze the polymerization of epoxy hexane to prepare the bio-based polyol II. The amount of the phosphazene salt catalyst in the bio-based polyol II is 0.19-0.25 wt.% of the total amount of the starting agent and the epoxy hexane.

[0011] Both castor oil and xylitol are widely available bio-based raw materials. The former contains hydroxyl groups and unsaturated double bonds, and the latter is a five-membered alcohol structure with high hydroxyl group density. Using the two as a composite starting agent for polyol synthesis can significantly improve the functionality and reactivity of the product. The application of such bio-based polyols in the potting adhesive system can effectively improve the crosslinking density and structural integrity of the polyurethane network, thereby enhancing the mechanical strength, thermal stability and dimensional stability of the material.

[0012] The crosslinking agent is trimethylol phosphate.

[0013] The catalyst is Dabco ® T-120, purchased from Wincell.

[0014] The defoaming agent is BYK-066N, purchased from BYK-Chemie, Germany.

[0015] The silane coupling agent is KH-540.

[0016] The water removal agent is 3A molecular sieve.

[0017] The preparation method of the modified isocyanate comprises the following steps: mixing the phosphorus-containing polyol and the flame retardant, vacuum dehydrating at 100-110℃ and -0.09MPa until the water content is less than 500ppm, then cooling to below 60℃, adding bio-based isocyanate, and continuing to react at 70-80℃ until the -NCO content is 9.8-10.2wt.%, cooling, loading, and sealing with nitrogen to obtain the modified isocyanate; The molar ratio of the phosphorus-containing polyol, the flame retardant and the bio-based isocyanate is 4:1: (10.0-10.4). The phosphorus-containing polyol is Exolit OP560, purchased from Clariant; the flame retardant is pentaerythritol phosphate melamine salt, purchased from Sichuan Zhuoan New Material Technology Co., Ltd., which contains active hydrogen reaction groups and can react with isocyanate; and the bio-based isocyanate is L-lysine diisocyanate.

[0018] The preparation method of the two-component bio-based flame-retardant polyurethane potting adhesive comprises the following steps: (1) Mix the bio-based polyol I, bio-based polyol II, crosslinking agent, defoaming agent and water-removing agent, vacuum dehydrate at 100-110℃, -0.09MPa to moisture <500ppm, then cool to below 50℃, add silane coupling agent and catalyst, stir uniformly, cool, charge, seal with nitrogen, to obtain A component; (2) Mix A component and B component, stir at 25-35℃ for 10-15min until mixed uniformly, to obtain two-component bio-based flame-retardant polyurethane pouring sealant.

[0019] Compared with the prior art, the present application has the following advantages: (1) The bio-based polyol of A component in the present application is synthesized by using castor oil, xylitol, amino acid and other bio-based raw materials as starting agent, and by optimizing molecular weight design, the bio-based segment is introduced into the pouring sealant system, which effectively improves the biodegradability of the material; by using epoxy hexane as polymerization monomer, a product with comb-shaped molecular structure can be prepared, which significantly improves the hydrophobicity of the material; at the same time, the carboxyl in the molecular structure of amino acid and the ester group in the molecular structure of castor oil can synergistically improve the adhesion of the pouring sealant to the substrate; (2) B component in the present application is prepared by conventional polymerization reaction, by using the reaction of isocyanate and active hydrogen, nitrogen and phosphorus two flame-retardant elements are introduced into the molecular structure of modified isocyanate, which on the one hand realizes the intrinsic flame-retardant property of the material, and on the other hand effectively avoids the defect that the added flame-retardant agent is easy to migrate, and at the same time solves the problem of easy hydrolysis of phosphorus-containing polyol (hydrolysis of phosphorus-containing polyol will affect its storage stability and flame-retardant property); in addition, the use of bio-based isocyanate further improves the biodegradability of the material. DETAILED DESCRIPTION

[0020] The present application is further illustrated by the following examples, which do not limit the practice of the application.

[0021] The raw materials used in the examples are all conventional commercially available raw materials unless otherwise specified, and the process methods used in the examples are all conventional methods in the art unless otherwise specified.

[0022] Some of the raw materials used in the examples and comparative examples are described as follows: The preparation method of bio-based polyol I is as follows: 89g of alanine is used as starting agent, 510g of epoxy hexane is catalyzed to react under the action of 0.9g of phosphazene catalyst at 120℃, after sufficient reaction, bio-based polyol I is prepared by acid water neutralization, drying and adsorption purification treatment, and its hydroxyl value is 280mgKOH / g.

[0023] The preparation method of the bio-based polyol II is as follows: 31 g of xylitol and 752 g of castor oil are used as starting agents, 546 g of epoxy hexane is catalyzed to carry out polymerization reaction under the catalysis of 2.6 g of phosphazene catalyst at 120 DEG C, after sufficient reaction, the bio-based polyol II is prepared after acid water neutralization, drying and adsorption purification treatment, and the hydroxyl value is 145 mgKOH / g.

[0024] The preparation method of the modified isocyanate is as follows: 520 g of pentaerythritol phosphate melamine salt (PPMS, the number average molecular weight is 520 g / mol) and 1000 g of Exolit OP560 (the number average molecular weight is 250 g / mol) are added into a reaction kettle, vacuum dehydration is carried out at 105 DEG C and -0.09 MPa for 2 h until the moisture content is less than 500 ppm, then the temperature is reduced to 60 DEG C, 2050 g of L-lysine diisocyanate (the number average molecular weight is 198 g / mol) is added, and the reaction is continued at 80 DEG C for 2 h until the -NCO content is 10 wt.%, the temperature is reduced, the material is loaded, and nitrogen sealing is carried out, and the modified isocyanate is obtained.

[0025] The phosphazene catalyst is purchased from Shanghai Qike Fluorine Silicon Material Co., Ltd.

[0026] INOVOL C204 (hydroxyl value 280 mgKOH / g) is purchased from Shandong YINOWEI New Material Co., Ltd.

[0027] The glyceryl polyoxypropylene ether polyol is prepared by using glycerol as a starting agent, catalyzing propylene oxide to carry out polymerization reaction under the action of potassium hydroxide catalyst, after sufficient reaction, the glyceryl polyoxypropylene ether polyol is prepared after acid water neutralization, drying and adsorption purification treatment, and the hydroxyl value is 145 mgKOH / g.

[0028] Example 1 The two-component bio-based flame-retardant polyurethane pouring sealant is composed of component A and component B, and the molar ratio of the hydroxyl group in component A to the isocyanate group in component B is 1:1.05; wherein component A comprises the following raw materials in parts by weight: Bio-based polyol I: 55 parts; Bio-based polyol II: 44 parts; Trimethylol phosphate: 1 part; Dabco ® T-120: 0.1 part; BYK-066N: 3.0 parts; KH-540: 0.5 parts; 3A molecular sieve: 0.5 parts; Component B is 180.66 parts of modified isocyanate.

[0029] The preparation method of the two-component bio-based flame-retardant polyurethane pouring sealant comprises the following steps: (1) Mix bio-based polyol I, bio-based polyol II, trimethylol phosphate, BYK-066N and 3A molecular sieve, vacuum dehydrate at 105°C and -0.09 MPa until the moisture content is less than 500 ppm, then cool to 50°C, and add KH-540 and Dabco ® T-120, stir uniformly, cool, charge, and seal with nitrogen to obtain component A; (2) Mix component A with component B at 25°C and stir for 15 min until uniform, to obtain the two-component bio-based flame-retardant polyurethane pouring sealant.

[0030] Example 2 The two-component bio-based flame-retardant polyurethane pouring sealant is composed of component A and component B, and the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is 1:1.04; wherein component A comprises the following raw materials in parts by weight: Bio-based polyol I: 44 parts; Bio-based polyol II: 55 parts; Trimethylol phosphate: 1 part; Dabco ® T-120: 0.5 parts; BYK-066N: 2.0 parts; KH-540: 0.1 parts; 3A molecular sieve: 0.5 parts; Component B is 167.37 parts of modified isocyanate.

[0031] The preparation method of the two-component bio-based flame-retardant polyurethane pouring sealant is the same as that of Example 1.

[0032] Example 3 The two-component bio-based flame-retardant polyurethane pouring sealant is composed of component A and component B, and the molar ratio of hydroxyl groups in component A to isocyanate groups in component B is 1:1.01; wherein component A comprises the following raw materials in parts by weight: Bio-based polyol I: 49 parts; Bio-based polyol II: 49 parts; Trimethylol phosphate: 2 parts; Dabco ® T-120: 0.3 parts; BYK-066N: 1.0 parts; KH-540: 0.1 parts; 3A molecular sieve: 1.0 parts; Component B is 175.64 parts of modified isocyanate.

[0033] The preparation method of the two-component bio-based flame-retardant polyurethane pouring sealant is the same as that of Example 1.

[0034] Comparative Example 1 The difference from Example 3 is that in Component A, 49 parts by weight of INOVOL C204 is used instead of bio-based polyol I, and 49 parts by weight of glyceryl polyoxypropylene ether polyol is used instead of bio-based polyol II, the molar ratio of hydroxyl groups in Component A to isocyanate groups in Component B is controlled to be 1:1.01, and the others are the same as those in Example 3.

[0035] Comparative Example 2 The difference from Example 3 is that in Component B, 47.3 parts by weight of L-lysine diisocyanate is used instead of modified isocyanate, the molar ratio of hydroxyl groups in Component A to isocyanate groups in Component B is controlled to be 1:1.01, and the others are the same as those in Example 3.

[0036] The pouring sealants prepared in the examples and comparative examples are respectively tested for performance, and the testing methods are as follows: Cumulative biodegradation percentage is tested in accordance with GB / T 19276.1-2003.

[0037] 30-day water absorption is tested in accordance with GB / T 19250-2013.

[0038] Flame retardance (UL-94) is tested in accordance with UL 94-2023 Test for Flammability of Plastic Materials for Parts in Devices and Appliances.

[0039] Adhesion to substrate is tested in accordance with GB / T 2791-1995.

[0040] The test results are shown in Table 1.

[0041] Table 1 Performance test results

[0042] As can be seen from the above data in Table 1, the introduction of bio-based polyols into the crosslinked network structure of the pouring sealant can effectively improve the biodegradability of the material; the introduction of ester groups, carboxyl groups and urethane groups can enhance the adhesion of the pouring sealant to the substrate; and the introduction of reactive flame retardants can significantly improve the flame retardance of the material. The optimization of the above-mentioned performances can broaden the application scenarios of the pouring sealant.

Claims

1. A two-component bio-based flame-retardant polyurethane pour-in-place sealant, characterized in that, Consists of A component and B component, the molar ratio of hydroxyl in A component to isocyanate group in B component is 1: (1-1.05); wherein, A component includes the following raw materials in parts by weight: Bio-based polyol I: 44-55 parts; Bio-based polyol II: 44-55 parts; Crosslinking agent: 1-2 parts; Catalyst: 0.1-0.5 parts; Defoaming agent: 1.0-3.0 parts; Silane coupling agent: 0.1-0.5 parts; Water removal agent: 0.5-1.0 parts; B component is modified isocyanate; The starting agent of the bio-based polyol I is amino acid, and the hydroxyl value is 278-282 mgKOH / g; The starting agent of the bio-based polyol II is castor oil and xylitol, and the hydroxyl value is 135-145 mgKOH / g; The modified isocyanate is prepared from phosphorus-containing polyol, flame retardant and bio-based isocyanate.

2. The two-component bio-based flame-retardant polyurethane pour-in-place gasketing of claim 1, wherein, The preparation method of the bio-based polyol I comprises the following steps: taking amino acid as a starting agent, and catalyzing the polymerization reaction of epoxy hexane under the action of phosphazene salt catalyst to prepare bio-based polyol I; The amino acid is alanine; The amount of the phosphazene salt catalyst is 0.15-0.20 wt.% of the total amount of the starting agent and epoxy hexane.

3. The two-component bio-based flame retardant polyurethane pour-in-place gasketing of claim 1, wherein, The preparation method of the bio-based polyol II comprises the following steps: taking castor oil and xylitol with a molar ratio of 4.0: (0.9-1.1) as starting agents, and catalyzing the polymerization reaction of epoxy hexane under the action of phosphazene salt catalyst to prepare bio-based polyol II; The amount of the phosphazene salt catalyst is 0.19-0.25 wt.% of the total amount of the starting agent and epoxy hexane.

4. The two-component bio-based flame retardant polyurethane pour-in-place gasketing of claim 1, wherein, The crosslinking agent is trimethylol phosphate.

5. The two-component bio-based flame retardant polyurethane pour-in-place gasketing of claim 1, wherein, The catalyst is Dabco ® T-120.

6. The two-component bio-based flame retardant polyurethane pour-in-place gasketing of claim 1, wherein, The defoaming agent is BYK-066N.

7. The two-component bio-based flame retardant polyurethane pour-in-place gasketing of claim 1, wherein, The silane coupling agent is KH-540.

8. The two-component bio-based flame retardant polyurethane pour-in-place gasketing of claim 1, wherein, The water removal agent is 3A molecular sieve.

9. The two-component bio-based flame retardant polyurethane pour-in-place gasketing of claim 1, wherein, The preparation method of the modified isocyanate comprises the following steps: mixing phosphorus-containing polyol and flame retardant, vacuum dehydrating to moisture <500 ppm, then cooling to below 60℃, adding bio-based isocyanate, and continuing to react at 70-80℃ until the -NCO content is 9.8-10.2 wt.% to obtain the modified isocyanate; The molar ratio of the phosphorus-containing polyol, the flame retardant and the bio-based isocyanate is 4:1: (10.0-10.4); The phosphorus-containing polyol is Exolit OP560; the flame retardant is pentaerythritol phosphate melamine salt; and the bio-based isocyanate is L-lysine diisocyanate.

10. A process for the preparation of the two-component bio-based flame retardant polyurethane pour-in-place sealant according to any one of claims 1 to 9, characterized in that, Comprises the following steps: (1) mixing bio-based polyol I, bio-based polyol II, crosslinking agent, defoaming agent and water removal agent, vacuum dehydrating to moisture <500 ppm, then cooling to below 50℃, adding silane coupling agent and catalyst, and stirring uniformly to obtain A component; (2) mixing A component and B component, stirring at 25-35℃ for 10-15 min until uniformly mixed to obtain two-component bio-based flame-retardant polyurethane pouring sealant.

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