Heat-conducting flame-retardant polyurethane structural adhesive and preparation method thereof

Abstract

The invention provides a heat-conducting flame-retardant polyurethane structural adhesive, which comprises a component A and a component B. The component A comprises the following raw materials by mass: 23% of polyol, 74.5% of a heat-conducting filler and 2.5% of a first auxiliary agent. The component B is prepared from the following raw materials in percentage by mass: 24% of prepolymer, 74.5% of heat-conducting filler and 1.5% of second aid; the heat-conducting filler is obtained by compounding modified aluminum hydroxide, heavy calcium carbonate and hollow glass beads; the prepolymer is a dimer acid modified polyester polyol (MDI) prepolymer and a castor oil (MDI) prepolymer, and the MDI is CDMDI-100L (Code Dimethyl Diisocyanate). The CDMDI-100L is adopted as the raw material of the polyurethane structural adhesive, the CDMDI-100L is carbodiimide modified MDI, can react with polyhydric alcohols, and has lower toxicity than TDI, and the moldability of the polyurethane structural adhesive formed by the MDI is relatively good, so that the mechanical property of the polyurethane structural adhesive is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polyurethane structural adhesives, and specifically relates to a heat-conducting and flame-retardant polyurethane structural adhesive and a preparation method thereof. Background Art

[0002] With the rapid development of new energy vehicles, the demand for and performance requirements of automotive batteries are also getting higher and higher. However, the battery systems currently used in new energy vehicles all have problems such as short service life, serious decline in high and low temperature performance, and easy ignition after collision, which restricts their rapid development. In order to maintain the long-term stable use of automotive batteries, adhesives play a very important role inside the battery. They not only need to have a certain structural strength but also good heat-conducting performance. Polyurethane structural adhesives have the characteristics of wear resistance, water resistance, and solvent resistance as adhesives. However, the existing polyurethane structural adhesives have defects such as poor bonding performance and low mechanical strength. Summary of the Invention

[0003] The technical problem to be solved by the present invention is how to improve the bonding performance and mechanical strength of polyurethane structural adhesives.

[0004] The present invention solves the above technical problems through the following technical means:

[0005] In a first aspect of the present invention, a heat-conducting and flame-retardant polyurethane structural adhesive is provided, which includes component A and component B. Component A includes the following raw materials according to mass percentage: 23% of polyol, 74.5% of heat-conducting filler, and 2.5% of a first auxiliary agent; Component B includes the following raw materials according to mass percentage: 24% of prepolymer, 74.5% of heat-conducting filler, and 1.5% of a second auxiliary agent; The heat-conducting filler is obtained by compounding modified aluminum hydroxide, heavy calcium carbonate, and hollow glass microspheres; The prepolymer is a dimer acid-modified polyester polyol MDI prepolymer and a castor oil MDI prepolymer, and the MDI is CDMDI-100L.

[0006] Beneficial Effects: The present invention uses CDMDI-100L as a raw material for polyurethane structural adhesives. The CDMDI-100L is carbodiimide-modified MDI, which can react with polyol, and has lower toxicity than TDI. Moreover, the polyurethane structural adhesive formed by MDI has relatively good moldability, thereby improving the mechanical properties of polyurethane structural adhesives.

[0007] The thermal conductive filler used in the present invention is obtained by compounding multiple fillers. Among them, modified aluminum hydroxide can provide good thermal conductivity. However, if the filling amount of modified aluminum hydroxide is too large, the oil absorption value of the polyurethane structural adhesive will be relatively high, resulting in a relatively high viscosity in the preparation of component A and component B, making it not easy to disperse and store. By adding an appropriate amount of hollow glass microspheres in the present invention, not only can the dispersion performance of modified aluminum hydroxide in the polyurethane structural adhesive be improved, but also water resistance and chemical stability can be provided, and the volume cost can be reduced. Adding heavy calcium carbonate increases the strength, wear resistance and anti-aging of the polyurethane structural adhesive, and further reduces the cost.

[0008] Preferably, the polyol includes bisphenol A polyether polyol, dimer acid modified polyester polyol, castor oil, and castor oil modified polyol.

[0009] Beneficial effects: The polyol used in the present invention is obtained by compounding multiple polyols. Among them, modified castor oil polyol has a high hydroxyl value, high hardness, high reactivity, and can react with MDI to form urethane curing products, which have excellent mechanical properties, electrical properties and water resistance, etc.; the aromatic ring and carbon-oxygen chain structure in bisphenol A polyether polyol can endow the polyurethane structural adhesive with specific flexibility; castor oil, as the only natural vegetable oil containing hydroxyl groups, has the characteristics of low cost, and the polyurethane synthesized by reaction has a highly irregular structure and its crystallinity, which can improve the brittleness of highly cross-linked polyisocyanurate and endow the polyurethane structural adhesive with greater flexibility and reduce the modulus; dimer acid modified polyester polyol has excellent water resistance, outstanding ultraviolet light resistance, excellent antioxidant performance, good heat resistance, weather resistance, solvent resistance, and excellent cohesion, and can be miscible with most polyethers in any proportion.

[0010] Preferably, the first auxiliary agent includes a first water remover, a first thixotropic agent, a first dispersant and a catalyst; the second auxiliary agent includes a second water remover, a second dispersant and a second thixotropic agent.

[0011] Preferably, the first water remover is a modified molecular sieve water remover; the second water remover is methylbenzenesulfonyl isocyanate PTSI water remover.

[0012] Preferably, both the first thixotropic agent and the second thixotropic agent are hydrophobically modified fumed silica.

[0013] Preferably, both the first dispersant and the second dispersant are BYK-W 9010 wetting dispersants.

[0014] Preferably, the catalyst is a zinc-bismuth composite catalyst.

[0015] Preferably, the particle size D50 of the modified aluminum hydroxide is 50 μm, and D90 is 110 μm; the particle size D50 of the hollow glass microspheres is 45 μm, and D90 is 70 μm.

[0016] In the second aspect of the present invention, there is provided the above-mentioned method for preparing a thermally conductive and flame-retardant polyurethane structural adhesive, comprising the following steps:

[0017] S1 Place the polyol in a reaction kettle for heating and dehydration, and then successively add a thermally conductive filler and a first auxiliary agent and stir under vacuum to obtain component A;

[0018] S2 Place the prepolymer in a reaction kettle, successively add an electrically conductive filler and a second auxiliary agent, and stir under vacuum to obtain component B;

[0019] S3 Store component A and component B separately in an air-insulated manner according to a mass ratio of 1:1 to form a combination, thereby obtaining the polyurethane structural adhesive.

[0020] Preferably, the preparation method of the dimer acid-modified polyester polyol MDI prepolymer is as follows: Synthesize the dimer acid-modified polyester polyol MDI prepolymer by mixing MDI and the dimer acid-modified polyester polyol in a mass ratio of 3:2; the preparation method of the castor oil MDI prepolymer is as follows: Synthesize the castor oil MDI prepolymer by mixing MDI and castor oil in a mass ratio of 1:1.

[0021] Beneficial effects: The thermally conductive and flame-retardant polyurethane structural adhesive prepared by the present invention has excellent bonding performance and mechanical strength. Specific embodiments

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Apparently, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

[0023] The test materials and reagents used in the following embodiments can be obtained from commercial channels without special instructions.

[0024] For those not specifying specific techniques or conditions in the embodiments, they can all be carried out according to the techniques or conditions described in the literature in this field or according to the product specifications.

[0025] Some of the raw materials used in the embodiments are described as follows:

[0026] The bisphenol A polyether polyol has a model of BPA-3 and is supplied by Zibo Dexin Federal Chemical Industry Co., Ltd.;

[0027] The dimer acid-modified polyester polyol has a model of DA21 and is supplied by Shanghai Jingri New Materials Technology Co., Ltd.;

[0028] Castor oil, supplied by Nanjing Xinxu Industry and Trade Co., Ltd.

[0029] The castor oil-modified polyol has the model number A4105 and the supplier is Shanghai Jingri New Materials Technology Co., Ltd.;

[0030] The modified aluminum hydroxide has the model number JAZ-082 and the supplier is Guangdong Kinggoo New Materials Co., Ltd.;

[0031] The heavy calcium carbonate has the model number LD-200, its particle size is 8μm, and the supplier is Lida Ultrafine Industry (Suzhou) Co., Ltd.;

[0032] The hollow glass microspheres have the model number HS22K and the supplier is Zhengzhou Shenglaite Hollow Glass Microspheres New Materials Co., Ltd.;

[0033] The modified molecular sieve water remover has the model number G2055 and the supplier is Dalian Chuangge Technology Co., Ltd.;

[0034] The hydrophobic fumed silica has the model number KS-20SC and the supplier is Tokuyama Corporation, Japan;

[0035] The zinc-bismuth composite catalyst has the model number PC-02 and the supplier is Shanghai Zhengui New Materials Technology Co., Ltd.;

[0036] CDMDI-100L is carbodiimide-modified MDI and the supplier is Meizhou Fuxi Chemical Co., Ltd.

[0037] Example 1

[0038] This example provides a thermally conductive and flame-retardant polyurethane structural adhesive and its preparation method, which are as follows: It includes component A and component B. The component A prepares raw materials as follows: 6g of bisphenol A polyether polyol, 6g of dimer acid-modified polyester polyol, 6g of castor oil, 5g of castor oil-modified polyol, 60g of modified aluminum hydroxide, 10g of heavy calcium carbonate, 4.5g of hollow glass microspheres, 1.2g of modified molecular sieve water remover, 0.75g of hydrophobic fumed silica, 0.5g of BYK-W9010 wetting and dispersing agent, and 0.05g of zinc-bismuth composite catalyst.

[0039] Preparation of component A: Add the above-mentioned bisphenol A polyether polyol, dimer acid-modified polyester polyol, castor oil, and castor oil-modified polyol into the reaction kettle, heat up to 120°C for dehydration for 2 hours, cool down to 70°C, and then add modified aluminum hydroxide, heavy calcium carbonate, hollow glass microspheres, modified molecular sieve water remover, BYK-W 9010 wetting and dispersing agent, and zinc-bismuth composite catalyst in sequence, stir under vacuum for 20 minutes until uniform, and then add hydrophobic fumed silica and stir under vacuum for 30 minutes to disperse evenly to obtain component A.

[0040] The B component is prepared from the following raw materials: 6 g of dimer acid-modified polyester polyol MDI prepolymer, 18 g of castor oil MDI prepolymer, 60 g of modified aluminum hydroxide, 10 g of heavy calcium carbonate, 4.5 g of hollow glass microspheres, 0.5 g of BYK-W9010 wetting and dispersing agent, 0.5 g of methyl phenylsulfonyl isocyanate PTSI water scavenger, and 0.5 g of hydrophobic fumed silica. The MDI used is CDMDI-100L.

[0041] Preparation of the B component:

[0042] (1) Preparation of the dimer acid-modified polyester polyol MDI prepolymer: Synthesize the dimer acid-modified polyester polyol MDI prepolymer by mixing CDMDI-100L and dimer acid-modified polyester polyol at a mass ratio of 3:2. Specifically, add the dimer acid polyester polyol to the reaction kettle, heat it to 120 °C, stir under high temperature and vacuum for 2 h to dehydrate, and after cooling to 70 °C, add CDMDI-100L to the reaction kettle and stir under vacuum at 70 °C for 1.5 hours to obtain the dimer acid polyester polyol MDI prepolymer.

[0043] (2) Preparation of the castor oil MDI prepolymer: Synthesize the castor oil MDI prepolymer by mixing CDMDI-100L and castor oil at a mass ratio of 1:1. Specifically, add the castor oil to the reaction kettle, heat it to 120 °C, stir under high temperature and vacuum for 2 h to dehydrate, and after cooling to 70 °C, add CDMDI-100L to the reaction kettle and stir under vacuum at 70 °C for 1.5 hours to obtain the castor oil MDI prepolymer.

[0044] (3) Add the dimer acid polyester polyol MDI prepolymer and the castor oil MDI prepolymer to the reaction kettle, and then sequentially add modified aluminum hydroxide, heavy calcium carbonate, hollow glass microspheres, methyl phenylsulfonyl isocyanate PTSI water scavenger, and BYK-W9010 wetting and dispersing agent, stir under vacuum for 20 minutes until evenly mixed, and then add hydrophobic fumed silica and stir under vacuum for 30 minutes to disperse evenly to obtain the B component;

[0045] Preparation of the thermally conductive and flame-retardant polyurethane structural adhesive: Place the A component and the B component in a volume ratio of 1:1 in an independent airtight storage to form a combination, and mix them evenly during use to obtain the polyurethane structural adhesive.

[0046] In this example, the particle size D50 of the modified aluminum hydroxide used is 50 μm, and D90 is 110 μm; the particle size D50 of the hollow glass microspheres is 45 μm, and D90 is 70 μm.

[0047] Example 2

[0048] This embodiment provides a thermally conductive and flame-retardant polyurethane structural adhesive and its preparation method. The difference between this embodiment and Embodiment 1 is that: for the polyol in Component A, the polyol is specifically 10 g of bisphenol A polyether polyol, 4 g of dimer acid-modified polyester polyol, 5 g of castor oil, and 4 g of castor oil-modified polyol, and the others are the same.

[0049] Comparative Example 1

[0050] This comparative example provides a thermally conductive and flame-retardant polyurethane structural adhesive and its preparation method. The difference between this comparative example and Embodiment 1 is that: the thermally conductive filler is different, specifically 60 g of modified aluminum hydroxide and 14.5 g of hollow glass microspheres, and the others are the same.

[0051] Comparative Example 2

[0052] This comparative example provides a thermally conductive and flame-retardant polyurethane structural adhesive and its preparation method. The difference between this comparative example and Embodiment 1 is that: the bisphenol A polyether polyol in the polyol is replaced with castor oil, and the others are the same.

[0053] Comparative Example 3

[0054] This comparative example provides a thermally conductive and flame-retardant polyurethane structural adhesive and its preparation method. The difference between this comparative example and Embodiment 1 is that: the dimer acid-modified polyester polyol in the polyol is replaced with castor oil, and the others are the same.

[0055] Comparative Example 4

[0056] This comparative example provides a thermally conductive and flame-retardant polyurethane structural adhesive and its preparation method. The difference between this comparative example and Embodiment 1 is that: the castor oil-modified polyol in the polyol is replaced with castor oil, and the others are the same.

[0057] The storage period of the polyurethane structural adhesive is 6 months. The polyurethane structural adhesive prepared in this comparative example has too low viscosity of Component A due to the excessive use of castor oil with low viscosity, resulting in precipitation of the thermally conductive filler or precipitation of the polyol, affecting the use of the product.

[0058] Comparative Example 5

[0059] This comparative example provides a thermally conductive and flame-retardant polyurethane structural adhesive and its preparation method. The difference between this comparative example and Embodiment 1 is that: the thermally conductive filler is different, specifically 60 g of heavy calcium carbonate and 14.5 g of hollow glass microspheres, and the others are the same.

[0060] Comparative Example 6

[0061] This comparative example provides a thermally conductive and flame-retardant polyurethane structural adhesive and its preparation method. The difference between this comparative example and Embodiment 1 is that: CDMDI-100L in Component B is replaced with ordinary MDI solid.

[0062] Comparative Example 7

[0063] This comparative example provides a thermally conductive and flame - retardant polyurethane structural adhesive and its preparation method. The difference between this comparative example and Example 1 is that the hydrophobic fumed silica in components A and B is replaced by unmodified fumed silica.

[0064] Comparative Example 8

[0065] This comparative example provides a thermally conductive and flame - retardant polyurethane structural adhesive and its preparation method. The difference between this comparative example and Example 1 is that the polyol in component A is only 23 g of bisphenol A polyether polyol.

[0066] Experimental Example

[0067] The thermally conductive and flame - retardant polyurethane structural adhesives prepared in the examples and comparative examples were subjected to performance tests. The test standards and test methods for each item are as follows:

[0068] (1) Tensile strength and elongation at break: The test was carried out with reference to ATSTM D638 "Standard Test Method for Tensile Properties of Plastics". Three samples were tested for each example and comparative example, and the average value was finally obtained, as shown in Table 1 specifically.

[0069] (2) Shear strength: The test was carried out with reference to ASTM D1002 "Standard Test Method for Tensile Shear Strength of Adhesives (Rigid - to - Rigid)". Three samples were tested for each example and comparative example, and the average value was finally obtained, as shown in Table 1 specifically.

[0070] (3) Thermal conductivity: The test was carried out with reference to ASTM D5470 - 17 "Standard Test Method for Thermal Transmission Properties of Thermal Insulation Materials". Three samples were tested for each example and comparative example, and the average value was finally obtained, as shown in Table 1 specifically.

[0071] (4) Flame - retardant grade: The test was carried out with reference to the "UL94 Flame Retardant and Fire Prevention Standard". Three samples were tested for each example and comparative example, and the average value was finally obtained, as shown in Table 1 specifically.

[0072] Table 1

[0073]

[0074] According to the data in Table 1, through the data of Examples 1 - 2, Comparative Examples 2 - 4 and Comparative Example 8, Examples 1 and 2 use a compound polyol of bisphenol A polyether polyol, dimer acid - modified polyester polyol, castor oil and castor oil - modified polyol, and their mechanical properties and bonding properties are better than those of Comparative Examples 2 - 4 and Comparative Example 8. The mechanical properties of Comparative Examples 2 - 4 fluctuate too much, so the mechanical strength is low. The shear strength of Comparative Example 8 is low, resulting in low bonding performance.

[0075] From the comparison of the elongation at break between Examples 1-2 and Comparative Example 2, it can be seen that bisphenol A polyether polyol in the polyol can effectively improve the flexibility of the polyurethane structural adhesive; from the comparison of the shear strength between Examples 1-2 and Comparative Example 3, it can be seen that the dimer acid-modified polyester polyol in the polyol can enhance the bonding strength of the polyurethane structural adhesive; from the comparison between Examples 1-2 and Comparative Example 4, it can be seen that the castor oil-modified polyol in the polyol can increase the viscosity of the polyurethane structural adhesive, thereby making the thermal conductive filler disperse more evenly, so the processing performance of the polyurethane structural adhesive can be improved; from the comparison between Examples 1-2 and Comparative Example 8, it can be seen that using only bisphenol A polyether polyol cannot improve the bonding performance of the polyurethane structural adhesive.

[0076] From the comparison of the tensile strength between Examples 1-2 and Comparative Example 6, it can be seen that using ordinary MDI solid causes the viscosity of Component B to increase, resulting in uneven local curing of the polyurethane structural adhesive, indicating the effect of carbodiimide modification in reducing the viscosity (liquefaction) of MDI and improving the dispersion uniformity.

[0077] From the comparison of the thermal conductivity between Examples 1-2 and Comparative Examples 1 and 5, it can be seen that in Comparative Example 1, the proportion of hollow glass microspheres was increased, but the thermal conductivity of the polyurethane structural adhesive decreased, and the viscosity also decreased. Therefore, although hollow glass microspheres can improve the processability and reduce the settlement of thermal conductive fillers, the dosage needs to be controlled to maintain the thermal performance. In Comparative Example 5, the modified aluminum hydroxide was removed, although the cost was reduced, but the thermal conductivity of the polyurethane structural adhesive was further reduced. Therefore, it shows that heavy calcium carbonate cannot increase the thermal conductivity and can only be used as an auxiliary filler to increase the volume filling rate of the polyurethane structural adhesive.

[0078] From the comparison of the shear strength between Examples 1-2 and Comparative Example 7, it can be seen that the bonding performance of Examples 1-2 is better than that of Comparative Example 6. After the A component of Comparative Example 6 was stored for 3 months, thermal conductive filler settlement occurred, indicating that the hydrophobic modified thixotropic agent can effectively prevent the agglomeration and settlement of thermal conductive fillers by reducing the surface energy, ensuring long-term storage stability.

[0079] In summary, the present invention uses the compounded polyol, the compounded thermal conductive filler and CDMDI-100L to prepare a thermally conductive and flame-retardant polyurethane structural adhesive with good mechanical strength and bonding strength.

[0080] The above examples are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing examples, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing examples, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A thermally conductive and flame-retardant polyurethane structural adhesive, characterized in that, It includes Component A and Component B. Component A includes the following raw materials by mass percentage: 23% of polyol, 74.5% of heat-conducting filler, and 2.5% of the first auxiliary agent; Component B includes the following raw materials by mass percentage: 24% of prepolymer, 74.5% of heat-conducting filler, and 1.5% of the second auxiliary agent. The heat-conducting filler is obtained by compounding modified aluminum hydroxide, heavy calcium carbonate, and hollow glass microspheres. The prepolymer is dimer acid-modified polyester polyol MDI prepolymer and castor oil MDI prepolymer; the MDI is CDMDI-100L.

2. The thermally conductive and flame-retardant polyurethane structural adhesive according to claim 1, wherein The polyol includes bisphenol A polyether polyol, dimer acid-modified polyester polyol, castor oil, and castor oil-modified polyol.

3. The thermally conductive and flame-retardant polyurethane structural adhesive according to claim 1, wherein The first auxiliary agent includes the first water scavenger, the first thixotropic agent, the first dispersant, and the catalyst; the second auxiliary agent includes the second water scavenger, the second dispersant, and the second thixotropic agent.

4. The thermally conductive and flame-retardant polyurethane structural adhesive according to claim 3, wherein The first water scavenger is a modified molecular sieve water scavenger; the second water scavenger is methylbenzenesulfonyl isocyanate PTSI water scavenger.

5. The thermally conductive and flame-retardant polyurethane structural adhesive according to claim 3, wherein, The first thixotropic agent and the second thixotropic agent are both hydrophobically modified fumed silica.

6. The thermally conductive and flame-retardant polyurethane structural adhesive according to claim 3, wherein The first dispersant and the second dispersant are both BYK-W 9010 wetting dispersants.

7. The thermally conductive and flame-retardant polyurethane structural adhesive according to claim 3, wherein The catalyst is a zinc-bismuth composite catalyst.

8. The thermally conductive and flame-retardant polyurethane structural adhesive according to claim 1, wherein The particle size D50 of the modified aluminum hydroxide is 50 μm, and D90 is 110 μm; the particle size D50 of the hollow glass microspheres is 45 μm, and D90 is 70 μm.

9. The preparation method of the thermally conductive and flame-retardant polyurethane structural adhesive according to any one of claims 1-8, characterized in that, It includes the following steps: S1 Place the polyol in a reaction kettle for heating and dehydration, and then successively add the heat-conducting filler and the first auxiliary agent and stir under vacuum to obtain Component A. S2 Place the prepolymer in a reaction kettle, successively add the conductive filler and the second auxiliary agent, and stir under vacuum to obtain Component B. S3 Place Component A and Component B in a volume ratio of 1:1 in an independent air-insulated storage to form a combination, and mix them during use to obtain the polyurethane structural adhesive.

10. The preparation method of the thermally conductive and flame-retardant polyurethane structural adhesive according to claim 9, characterized in that, The preparation method of the dimer acid-modified polyester polyol MDI prepolymer is as follows: Synthesize the dimer acid-modified polyester polyol MDI prepolymer by mixing MDI and dimer acid-modified polyester polyol in a mass ratio of 3:2; the preparation method of the castor oil MDI prepolymer is as follows: Synthesize the castor oil MDI prepolymer by mixing MDI and castor oil in a mass ratio of 1:1.

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